LIFE SUPPORT

Fifteen benefits of drinking water

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Only small amounts of air are needed to effect separation, e. Invertebrate animals have a great variety of liquids, cells, and modes of circulation, though many invertebrates have what is called an open system, in which fluid passes more or less freely throughout the tissues or defined areas of tissue. Some of its main actions relate to: Then they can be reused. Again blood is taken away from everything except large muscles used to fight or flee. I could not figure out how to do my own post without just hitting reply. Unfortunately, our bodies still react the same way to threats - real or imagined - even though, in a vast majority of cases, the stressor does not require us to fight or flee.

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After leaving the heart, the blood passes through a series of branching vessels of steadily decreasing diameter. The smallest branches, only a few micrometres there are about 25, micrometres in one inch in diameter, are the capillaries , which have thin walls through which the fluid part of the blood may pass to bathe the tissue cells. The capillaries also pick up metabolic end products and carry them into larger collecting vessels that eventually return the blood to the heart.

In vertebrates there are structural differences between the muscularly walled arteries, which carry the blood under high pressure from the heart, and the thinner walled veins , which return it at much reduced pressure.

Although such structural differences are less apparent in invertebrates, the terms artery and vein are used for vessels that carry blood from and to the heart, respectively. In the latter animals, the blood leaving the heart passes into a series of open spaces, called sinuses , where it bathes internal organs directly. Such a body cavity is called a hemocoel, a term that reflects the amalgamation of the blood system and the coelom.

To maintain optimum metabolism, all living cells require a suitable environment, which must be maintained within relatively narrow limits.

An appropriate gas phase i. Direct diffusion through the body surface supplies the necessary gases and nutrients for small organisms, but even some single-celled protozoa have a rudimentary circulatory system. Cyclosis in many ciliates carries food vacuoles—which form at the forward end of the gullet cytopharynx —on a more or less fixed route around the cell, while digestion occurs to a fixed point of discharge.

For most animal cells, the supply of oxygen is largely independent of the animal and therefore is a limiting factor in its metabolism and ultimately in its structure and distribution. The nutrient supply to the tissues, however, is controlled by the animal itself, and, because both major catabolic end products of metabolism—ammonia NH 3 and carbon dioxide CO 2 —are more soluble than oxygen O 2 in water and the aqueous phase of the body fluids, they tend not to limit metabolic rates. The diffusion rate of CO 2 is less than that of O 2 , but its solubility is 30 times that of oxygen.

This means that the amount of CO 2 diffusing is 26 times as high as for oxygen at the same temperature and pressure. The oxygen available to a cell depends on the concentration of oxygen in the external environment and the efficiency with which it is transported to the tissues. Dry air at atmospheric pressure contains about 21 percent oxygen, the percentage of which decreases with increasing altitude. Well-aerated water has the same percentage of oxygen as the surrounding air; however, the amount of dissolved oxygen is governed by temperature and the presence of other solutes.

For example, seawater contains 20 percent less oxygen than fresh water under the same conditions. The rate of diffusion depends on the shape and size of the diffusing molecule, the medium through which it diffuses, the concentration gradient, and the temperature. These physicochemical constraints imposed by gaseous diffusion have a relationship with animal respiration.

Investigations have suggested that a spherical organism larger than 0. Many invertebrates are small, with direct diffusion distances of less than 0. Considerably larger species, however, still survive without an internal circulatory system. A sphere represents the smallest possible ratio of surface area to volume; modifications in architecture, reduction of metabolic rate, or both may be exploited to allow size increase.

Sponges overcome the problem of oxygen supply and increase the chance of food capture by passing water through their many pores using ciliary action. The level of organization of sponges is that of a coordinated aggregation of largely independent cells with poorly defined tissues and no organ systems. The whole animal has a relatively massive surface area for gaseous exchange, and all cells are in direct contact with the passing water current. Among the eumetazoan multicellular animals the cnidarians sea anemones , corals , and jellyfish are diploblastic, the inner endoderm and outer ectoderm being separated by an acellular mesoglea.

Sea anemones and corals may also grow to considerable size and exhibit complex external structure that, again, has the effect of increasing surface area. Their fundamentally simple structure—with a gastrovascular cavity continuous with the external environmental water—allows both the endodermal and ectodermal cells of the body wall access to aerated water, permitting direct diffusion.

This arrangement is found in a number of other invertebrates, such as Ctenophora comb jellies , and is exploited further by jellyfish , which also show a rudimentary internal circulatory system. The thick, largely acellular, gelatinous bell of a large jellyfish may attain a diameter of 40 centimetres 16 inches or more. The gastrovascular cavity is modified to form a series of water-filled canals that ramify through the bell and extend from the central gastric pouches to a circular canal that follows the periphery of the umbrella.

Ciliary activity within the canals slowly passes food particles and water, taken in through the mouth, from the gastric pouches where digestion is initiated to other parts of the body. Ciliary activity is a relatively inefficient means of translocating fluids, and it may take up to half an hour to complete a circulatory cycle through even a small species. To compensate for the inefficiency of the circulation, the metabolic rate of the jellyfish is low, and organic matter makes up only a small proportion of the total body constituents.

The central mass of the umbrella may be a considerable distance from either the exumbrella surface or the canal system, and, while it contains some wandering amoeboid cells, its largely acellular nature means that its metabolic requirements are small. While ciliary respiratory currents are sufficient to supply the requirements of animals with simple epithelial tissues and low metabolic rates, most species whose bodies contain a number of organ systems require a more efficient circulatory system.

Many invertebrates and all vertebrates have a closed vascular system in which the circulatory fluid is totally confined within a series of vessels consisting of arteries, veins, and fine linking capillaries. Insects, most crustaceans, and many mollusks, however, have an open system in which the circulating fluid passes somewhat freely among the tissues before being collected and recirculated.

The distinction between open and closed circulatory systems may not be as great as was once thought; some crustaceans have vessels with dimensions similar to those of vertebrate capillaries before opening into tissue sinuses.

Compared with closed systems, open circulatory systems generally work at lower pressures, and the rate of fluid return to the heart is slower.

Blood distribution to individual organs is not regulated easily, and the open system is not as well-adapted for rapid response to change. The primary body cavity coelom of triploblastic multicellular organisms arises from the central mesoderm, which emerges from between the endoderm and ectoderm during embryonic development.

The fluid of the coelom containing free mesodermal cells constitutes the blood and lymph. The composition of blood varies between different organisms and within one organism at different stages during its circulation.

Essentially, however, the blood consists of an aqueous plasma containing sodium, potassium, calcium, magnesium, chloride, and sulfate ions; some trace elements; a number of amino acids; and possibly a protein known as a respiratory pigment. If present in invertebrates, the respiratory pigments are normally dissolved in the plasma and are not enclosed in blood cells. The constancy of the ionic constituents of blood and their similarity to seawater have been used by some scientists as evidence of a common origin for life in the sea.

In many marine invertebrates, such as echinoderms and some mollusks, the osmotic and ionic characteristics of the blood closely resemble those of seawater. Other aquatic, and all terrestrial, organisms, however, maintain blood concentrations that differ to some extent from their environments and thus have a greater potential range of habitats.

In addition to maintaining the overall stability of the internal environment, blood has a range of other functions. It is the major means of transport of nutrients, metabolites, excretory products, hormones, and gases, and it may provide the mechanical force for such diverse processes as hatching and molting in arthropods and burrowing in bivalve mollusks. Invertebrate blood may contain a number of cells hemocytes arising from the embryonic mesoderm.

Many different types of hemocytes have been described in different species, but they have been studied most extensively in insects, in which four major types and functions have been suggested: While the solubility of oxygen in blood plasma is adequate to supply the tissues of some relatively sedentary invertebrates, more active animals with increased oxygen demands require an additional oxygen carrier.

The oxygen carriers in blood take the form of metal -containing protein molecules that frequently are coloured and thus commonly known as respiratory pigments. The most widely distributed respiratory pigments are the red hemoglobins , which have been reported in all classes of vertebrates, in most invertebrate phyla, and even in some plants.

Hemoglobins consist of a variable number of subunits, each containing an iron—porphyrin group attached to a protein. The distribution of hemoglobins in just a few members of a phylum and in many different phyla argues that the hemoglobin type of molecule must have evolved many times with similar iron—porphyrin groups and different proteins.

The green chlorocruorins are also iron—porphyrin pigments and are found in the blood of a number of families of marine polychaete worms. There is a close resemblance between chlorocruorin and hemoglobin molecules, and a number of species of a genus, such as those of Serpula , contain both, while some closely related species exhibit an almost arbitrary distribution.

For example, Spirorbis borealis has chlorocruorin, S. The third iron-containing pigments, the hemerythrins , are violet. They differ structurally from both hemoglobin and chlorocruorin in having no porphyrin groups and containing three times as much iron, which is attached directly to the protein. Hemerythrins are restricted to a small number of animals, including some polychaete and sipunculid worms, the brachiopod Lingula , and some priapulids.

Hemocyanins are copper-containing respiratory pigments found in many mollusks some bivalves, many gastropods, and cephalopods and arthropods many crustaceans, some arachnids, and the horseshoe crab , Limulus.

They are colourless when deoxygenated but turn blue on oxygenation. The copper is bound directly to the protein, and oxygen combines reversibly in the proportion of one oxygen molecule to two copper atoms.

The presence of a respiratory pigment greatly increases the oxygen-carrying capacity of blood; invertebrate blood may contain up to 10 percent oxygen with the pigment, compared with about 0. All respiratory pigments become almost completely saturated with oxygen even at oxygen levels, or pressures, below those normally found in air or water.

The oxygen pressures at which the various pigments become saturated depend on their individual chemical characteristics and on such conditions as temperature, pH, and the presence of carbon dioxide. In addition to their direct transport role, respiratory pigments may temporarily store oxygen for use during periods of respiratory suspension or decreased oxygen availability hypoxia.

They may also act as buffers to prevent large blood pH fluctuations, and they may have an osmotic function that helps to reduce fluid loss from aquatic organisms whose internal hydrostatic pressure tends to force water out of the body.

All systems involving the consistent movement of circulating fluid require at least one repeating pump and, if flow is to be in one direction, usually some arrangement of valves to prevent backflow.

The simplest form of animal circulatory pump consists of a blood vessel down which passes a wave of muscular contraction, called peristalsis , that forces the enclosed blood in the direction of contraction. Valves may or may not be present. This type of heart is widely found among invertebrates, and there may be many pulsating vessels in a single individual.

In the earthworm, the main dorsal aligned along the back vessel contracts from posterior to anterior 15 to 20 times per minute, pumping blood toward the head. At the same time, the five paired segmental lateral side vessels, which branch from the dorsal vessel and link it to the ventral aligned along the bottom vessel, pulsate with their own independent rhythms.

Although unusual, it is possible for a peristaltic heart to reverse direction. After a series of contractions in one direction, the hearts of tunicates sea squirts gradually slow down and eventually stop.

After a pause the heart starts again, with reverse contractions pumping the blood in the opposite direction. An elaboration of the simple peristaltic heart is found in the tubular heart of most arthropods, in which part of the dorsal vessel is expanded to form one or more linearly arranged chambers with muscular walls.

The walls are perforated by pairs of lateral openings ostia that allow blood to flow into the heart from a large surrounding sinus, the pericardium.

The heart may be suspended by alary muscles, contraction of which expands the heart and increases blood flow into it. The direction of flow is controlled by valves arranged in front of the in-current ostia. Chambered hearts with valves and relatively thick muscular walls are less commonly found in invertebrates but do occur in some mollusks, especially cephalopods octopus and squid. Blood from the gills enters one to four auricles depending on the species and is passed back to the tissues by contraction of the ventricle.

The direction of flow is controlled by valves between the chambers. The filling and emptying of the heart are controlled by regular rhythmical contractions of the muscular wall.

In addition to the main systemic heart, many species have accessory booster hearts at critical points in the circulatory system. Cephalopods have special muscular dilations, the branchial hearts, that pump blood through the capillaries, and insects may have additional ampullar hearts at the points of attachment of many of their appendages.

The control of heart rhythm may be either myogenic originating within the heart muscle itself or neurogenic originating in nerve ganglia. The hearts of the invertebrate mollusks, like those of vertebrates, are myogenic. They are sensitive to pressure and fail to give maximum beats unless distended; the beats become stronger and more frequent with increasing blood pressure.

Although under experimental conditions acetylcholine a substance that transmits nerve impulses across a synapse inhibits molluscan heartbeat, indicating some stimulation of the heart muscle by the nervous system, cardiac muscle contraction will continue in excised hearts with no connection to the central nervous system. Tunicate hearts have two noninnervated, myogenic pacemakers , one at each end of the peristaltic pulsating vessel. Separately, each pacemaker causes a series of normal beats followed by a sequence of abnormal ones; together, they provide periodic reversals of blood flow.

The control of heartbeat in most other invertebrates is neurogenic, and one or more nerve ganglia with attendant nerve fibres control contraction. Removal of the ganglia stops the heart, and the administration of acetylcholine increases its rate.

Adult heart control may be neurogenic but not necessarily in all stages in the life cycle. The embryonic heart may show myogenic peristaltic contractions prior to innervation. Heart rate differs markedly among species and under different physiological states of a given individual. In general it is lower in sedentary or sluggish animals and faster in small ones. The rate increases with internal pressure but often reaches a plateau at optimal pressures. Oxygen availability and the presence of carbon dioxide affect the heart rate, and during periods of hypoxia the heart rate may decrease to almost a standstill to conserve oxygen stores.

The time it takes for blood to complete a single circulatory cycle is also highly variable but tends to be much longer in invertebrates than in vertebrates. For example, in isolation, the circulation rate in mammals is about 10 to 30 seconds, for crustaceans about one minute, for cockroaches five to six minutes, and for other insects almost 30 minutes. At the simplest levels of metazoan organization, where there are at most two cell layers, the tissues are arranged in sheets.

The necessity for a formal circulatory system does not exist, nor are the mesodermal tissues, normally forming one, present. The addition of the mesodermal layer allows greater complexity of organ development and introduces further problems in supplying all cells with their essential requirements.

Invertebrate phyla have developed a number of solutions to these problems; most but not all involve the development of a circulatory system: Among the acoelomate phyla, the members of Platyhelminthes flatworms have no body cavity, and the space between the gut and the body wall, when present, is filled with a spongy organ tissue of mesodermal cells through which tissue fluids may percolate.

Dorsoventral back to front flattening, ramifying gut ceca cavities open at one end , and, in the endoparasitic flatworm forms, glycolytic metabolic pathways which release metabolic energy in the absence of oxygen reduce diffusion distances and the need for oxygen and allow the trematodes and turbellarians of this phylum to maintain their normal metabolic rates in the absence of an independent circulatory system.

The greatly increased and specialized body surface of the cestodes tapeworms of this phylum has allowed them to dispense with the gut as well. Most of the other acoelomate invertebrate animals are small enough that direct diffusion constitutes the major means of internal transport.

One acoelomate phylum, Nemertea proboscis worms , contains the simplest animals possessing a true vascular system. In its basic form there may be only two vessels situated one on each side of the straight gut.

The vessels unite anteriorly by a cephalic space and posteriorly by an anal space lined by a thin membrane. The astronaut s enter the airlock, and the airlock pressure is reduced to They breath pure oxygen through masks for 60 minutes because the air in the airlock contains nitrogen. They then put on their space suits and do an EMU purge i. The air inside their suits is now also pure oxygen.

The airlock pressure is then brought back up to the normal They then do minutes of in-suit prebreath. Of those minutes, 50 of them are light-exercise minutes and 50 of them are resting minutes.

Thus "Slow Motion Hokey Pokey". Now they are ready to open the airlock and step into space. The innovation was the 50 minutes of exercise. Without it, the entire protocol takes twelve hours instead of one hour and fifty minutes. If the habitat module's pressure was 12 psi an astronaut could use an 8 psi space suit with no prebreathing required a pity such suits are currently beyond the state of the art , and for a 4.

In case of emergency, when there is no time for prebreathing, NASA helpfully directs the astronauts to gulp aspirin, so they can work in spite of the agonizing pain. Please note that most of the problem is due to the fact that soft space suits have a lower atmospheric pressure than the habitat module. So this can be avoided by using a hard space suit or space pod. All of the atmospheric controls will be on the life support deck. On a related note, forced ventilation in the spacecraft's lifesystem is not optional.

In free fall, the warm exhaled carbon dioxide will not rise away from your face. It will just collect in a cloud around your head until you pass out or suffocate. In the image above the blue dome shaped flame is an actual candle burning in free fall. And in Clarke's "Feathered Friend", he talks about the wisdom of using an animal sentinel to monitor atmospheric quality. Specifically by using the tried and true "canary in a coal mine" technique. I know most people like to tie little prayer flags and scarves and stuff to the air-vent to make sure it's working, but back home we use wind chimes.

You don't have to be looking at 'em to know they're working. They're not like the chimes they have back on Earth; these only have one note.

Most habs around Saturn do it that way — each compartment has a single note. That way, you can tell location of a faulty blower just by the change in the sound. And let me tell you, they are not optional. If you take a set down for anything other than maintenance on the air-vent in question, you can get arrested.

Of course they're loud! That's how you know they're working. But I know what you mean — when I first moved out to Titan, it took me a good month to get used to 'em. I was up all night most nights hearing chimes all over the hab ringing. It was like this constant drone with a few off notes every now and then to make sure you didn't relax. I complained to anybody who'd listen, which was nobody.

All I did was get myself a rep as another dumb groundhog fresh off the boat. The chimes didn't just bother me at night, either. In public spaces they make quiet conversation just about impossible.

And I just about failed my first semester in school from being distracted. Seriously, if I hadn't still been under Immigrant's Probation, I would have had to do a public service sentence.

As it was, I did have to take the Habitat Orientation class again — listening to the damned wind chimes the whole time. But let me tell you — They were absolutely right to bust me. They confiscated my ear buds when I got caught so I didn't have them during a weekend maintenance cycle on the hab. We were living in a retired Trans-Chronian, the kind they used to have before the River -class came out. The counter-spinning rings were always breaking down or getting fatigued or some damn thing, so we only had gravity maybe five days a week.

My little sisters loved it — I'd play catch with them, with the toddler standing in as the ball. Anyway, the apartment had only pair of rooms, and my parents got one and the girls the other. I slept in a bag in the living room and lived out of a foot locker. One night I woke up from a dead sleep with the uncontrollable feeling that something was wrong.

I couldn't put my finger out what it was, but the effect was disturbing. I figured that I was just having trouble sleeping from the wind chimes when I realized that was what was wrong — I wasn't hearing the chimes. A glance up told me that the chimes in the living room were still going, but I really didn't need it.

The sound of all the chimes in our apartment had gotten so far under my skin over the weeks we'd been living there that I pretty much figured out immediately which chimes had stopped. You guessed it — the girls' room. By the time I got in there they were both awake and holding hands while spinning like they teach you. My parents were in there a couple seconds after me, but only because they had farther to go.

Anyway, it was nothing much as vent problems go. A stuffed rabbit toy had gotten jammed into the fan — so the girls got grounded and had to do extra chores for a week.

They whined about it, and kids do, and then we all went back to bed. It took a me good while to go back to sleep after that. For all I my complaining about those annoying, distracting, aggravating wind chimes, if we didn't have 'em up that night my sisters would have never have woken up.

Yeah, Fireproof is another absolute classic from grand-master Hal Clement. And it hammers home a hard truth you can find in Lazarus Long's notebooks. On Terra, being ignorant shortens your lifespan. Being willfully ignorant is just asking for it. And being willfully ignorant in space means you are doing your darndest to cop a Darwin Award.

You don't just need a good education to get a job in space, you need so you don't die. Read how that moron saboteur Hart thinks education is a waste of time. Up to when his flaming body gets splattered all over the wall because he thinks he's so smart. He thinks Nah, I don't need no stinkin' physics and chemistry! That's the last thing that goes through his brain, besides the bulkhead. If Igno-Spy had ever had a high-school Science class he might have realized he was turning the inside of his jail cell into a freaking free-fall thermobaric weapon.

With him flicking his Bic at the fuse like Wile E. To conserve his oxygen supply, the curly-haired cadet had set the controls of his boat on a steady orbit around one of the larger asteroids and lay down quietly on the deck. One of the first lessons he had learned at Space Academy was, during an emergency in space when oxygen was low, to lie down and breath as slowly as possible.

And, if possible, to go to sleep. Sleep, under such conditions, served two purposes. While relaxed in sleep, the body used less oxygen and should help fail to arrive, the victim would slip into a suffocating unconsciousness, not knowing if and when death took the place of life. Unpleasant odors in the air is a problem, but there is not much one can do about it.

After all, you can't just open up a window to let in some fresh air, not in the vacuum of space. NASA carefully screens all materials, sealants, foods, and everything else to ensure that they do not emit noticeable odor in the pressurized habitat sections of spacecraft and space stations. Such odors can quickly become overpowering in such tight quarters. There's a fortune awaiting the man who invents a really good deodorizer for a spaceship. That's the one thing you can't fail to notice.

Oh, they try, I grant them that. The air goes through precipitators each time it is cycled; it is washed, it is perfumed, a precise fraction of ozone is added, and the new oxygen that is put in after the carbon dioxide is distilled out is as pure as a baby's mind; it has to be, for it is newly released as a by-product of the photosynthesis of living plants.

That air is so pure that it really ought to be voted a medal by the Society for the Suppression of Evil Thoughts. Besides that, a simply amazing amount of the crew's time is put into cleaning, polishing, washing, sterilizing - oh, they try! But nevertheless, even a new, extra-fare luxury liner like the Tricorn simply reeks of human sweat and ancient sin, with undefinable overtones of organic decay and unfortunate accidents and matters best forgotten.

Once I was with Daddy when a Martian tomb was being unsealed - and I found out why xenoarchaeologists always have gas masks handy. But a spaceship smells even worse than that tomb. It does no good to complain to the purser. He'll listen with professional sympathy and send a crewman around to spray your stateroom with something which I suspect merely deadens your nose for a while.

But his sympathy is not real, because the poor man simply cannot smell anything wrong himself. He has lived in ships for years; it is literally impossible for him to smell the unmistakable reek of a ship that has been lived in - and, besides, he knows that the air is pure; the ship's instruments show it. None of the professional spacers can smell it. But the purser and all of them are quite used to having passengers complain about the "unbearable stench" - so they pretend sympathy and go through the motions of correcting the matter.

Not that I complained. I was looking forward to having this ship eating out of my hand, and you don't accomplish that sort of coup by becoming known first thing as a complainer.

But other first-timers did, and I certainly understood why - in fact I began to have a glimmer of a doubt about my ambitions to become skipper of an explorer ship. But - Well, in about two days it seemed to me that they had managed to clean up the ship quite a bit, and shortly thereafter I stopped thinking about it. I began to understand why the ship's crew can't smell the things the passengers complain about. Their nervous systems simply cancel out the old familiar stinks - like a cybernetic skywatch canceling out and ignoring any object whose predicted orbit has previously been programmed into the machine.

But the odor is still there. I suspect that it sinks right into polished metal and can never be removed, short of scrapping the ship and melting it down. Thank goodness the human nervous system is endlessly adaptable. His hole was on the eighth level, off a residential tunnel a hundred meters wide with fifty meters of carefully cultivated green park running down the center.

The main corridor's vaulted ceiling was lit by recessed lights and painted a blue that Havelock assured him matched the Earth's summer sky. Living on the surface of a planet, mass sucking at every bone and muscle, and nothing but gravity to keep your air close, seemed like a fast path to crazy. The blue was nice, though. Some people followed Captain Shaddid's lead by perfuming their air.

Not always with coffee and cinnamon scents, of course. Havelock's hole smelled of baking bread. Others opted for floral scents or semipheromones. Candace, Miller's ex-wife, had preferred something called EarthLily, which had always made him think of the waste recycling levels.

These days, he left it at the vaguely astringent smell of the station itself. Recycled air that had passed through a million lungs. The circle of life on Ceres was so small you could see the curve. He liked it that way. Infinitely more serious than annoying odors are harmful atmospheric contaminants. They share the same problem that a spacecraft cannot open the windows to bring in some fresh air. But unlike odors, these can harm or kill.

Basic atmospheric monitors will keep an eye on the breathing mix inside the habitat module for oxygen and carbon dioxide levels. But prudent spacecraft will have monitors for carbon monoxide and other deadly gases, hooked up to strident alarms. In space no one can hear you scream, but in the habitat module's atmosphere everybody can hear that high-pitched squeaky wheel in the ventilator.

And there may be permanent hearing loss from loud noises, say, from rocket engines. As a point of reference, the normal ambient noise level on the International Space Station is 60 db.

Acoustic criteria are specified in terms of A-weighted sound level L A or equivalent A-weighted sound level L eq , where it is a specified time period, usually 8 or 24 hours.

The equivalent A-weighted sound level is defined as the constant sound level that, in a given situation and time period, conveys the same sound energy as the actual time varying A-weighted sound. The basic unit for these measurements is the decibel. Space station laboratory modules should have A-weighted sound levels not exceeding 55 dB a noise criterion curve of approximately 50 and reverberation times not exceeding 1.

These values should permit 95 percent intelligibility for sentences under conditions of normal vocal effort with the talker and the listener visible to each other.

Environments with A-weighted sound levels above 55 dB will require assistance for adequate speech communication. Designers of audiecommunication systems should recognize that the systems will amplify and distribute noise as well as speech signals to both intended and unintended listeners. Therefore, their use should be carefully controlled. For sleeping areas, background A-weighted sound levels below 45 dB are preferred, while levels up to 60 dB A are acceptable.

Brief noises or transients during continuous noise backgrounds are particularly disturbing to sleep. The probability of full behavioral awakening increases with increasing sound level of the transient. For transients with an L A of 60 dB, the probability of full behavioral awakening is about 0.

The risk for producing significant hearing loss is negligible in noise exposures to an L eq24 of 80 dB. A hearing conservation program similar to that described by the Occupational Safety and Health Administration should be initiated for exposures to an L eq8 of 85 dB or more. If acoustic requirements for acceptable speech communication, sleep, and hearing conservation are met, problems of annoyance and task disruption will be minimal.

Vibration criteria are specified for linear vibration in the Hz frequency range. To reduce the probability of motion sickness, it is recommended that acceleration not exceed 2.

Specific tasks requiring more stringent vibrational criteria should be analyzed on an individual basis. In the absence of appropriate information, these tasks should be simulated on earth to determine vibration sensitivity and required accuracy.

If head or finger control is required to an accuracy of 5mm rms or 2. Hypergolics hiss too, with a harsher metallic note, bangs and pings. Hydroxy rockets , they roar. Solid packs are similar, but rougher, with underlying stutters and clicks. You hear it with your bones. Hard burn, in the jargon, refers to the practice of injecting a limited supply of antiprotons into the exhaust of a fusion torch for short, high-power bursts.

Former astronaut Jay Buckey, now at Dartmouth Medical School in Hanover, New Hampshire, US, says that both temporary and permanent hearing loss were recorded after flights on the Soviet and Russian Salyut and Mir stations, even for stays as short as seven days. The lost hearing was usually at higher frequencies. The living quarters of the ISS are the Russian Zvezda module, which is the noisiest module on the station. NASA says the goal is for the working area to have noise levels at or below 60 decibels dB and sleep bunks to be 50dB.

At their peak several years ago, noise levels reached 72 to 78dB in the working area and 65 dB in the sleep stations.

Decibels are measured on a logarithmic scale, meaning, for example, that 60dB is 10 times louder than 50dB. NASA has worked to reduce the noise and its effect on the crew. By November , noise levels had been lowered to between 62 to 69dB in the work area and 55 to 60dB in the sleep compartments. Astronauts on the ISS used to have to wear ear plugs all day but are now only wear them for 2 to 3 hours per work day.

According to the US National Institutes of Health, however, noise levels below 80dB are unlikely to lead to hearing loss, even with prolonged exposure.

But while the primary cause of hearing loss in general is high noise levels, Buckey suggested in a paper in Aviation Space and Environmental Medicine that several other factors might contribute to the problem in space. Elevated intracranial pressure, higher carbon dioxide levels and atmospheric contaminants may make the inner ear more sensitive to noise, he says.

But there have been no studies yet to test these ideas. Buckey had designed a device to measure hearing loss of astronauts on the ISS, but his project was cancelled around the start of when NASA reduced funding for life sciences. Crews have installed fan vibration isolators and mufflers on fan outlets, and acoustic padding to wall panels. The current crew, Russian cosmonaut Pavel Vinogradov and US astronaut Jeff Williams, installed a sound-insulating cover on the Russian carbon dioxide removal system.

They also started adding acoustic padding near the Russian air conditioner. Future crews will swap out 30 to 40 fans with quieter versions. Meteors are probably nothing to worry about. On average a spacecraft will have to wait for a couple of million years to be hit by a meteor larger than a grain of sand. But if you insist, there are a couple of precautions one can take. First one can sheath the ship in a thin shell with a few inches of separation from the hull.

This "meteor bumper" aka " Whipple shield " will vaporize the smaller guys. For larger ones, use radar. It is surprisingly simple. For complicated reasons that I'm sure you can figure out for yourself, a meteor on a collision course will maintain a constant bearing it's a geometric matter of similar triangles.

So if the radar sees an object whose bearing doesn't change, but whose range is decreasing, it knows that You Have A Problem. This happens on Earth as well. If you are racing a freight train to cross an intersection, and the image of the front of the train stays on one spot on your windshield, you know that you and the engine will reach the intersection simultaneously. One can make an hard-wired link between the radar and the engines, but it might be a good idea to have it sound an alarm first.

This will give the crew a second to grab a hand-hold. You did install hand-holds on all the walls, didn't you? And require the crew to strap themselves into their bunks while sleeping. Having said that, Samuel Birchenough points out that anybody who has played the game Kerbal Space Program know that an object that is not on a fixed bearing can still hit you.

If your spacecraft and the other object are in orbit around a planet, the object's bearing will be constantly changing up to the last few kilometers before the collision. The moon, now visibly larger and almost painfully beautiful, hung in the same position in the sky, such that he had to let his gaze drop as he lay in the chair in order to return its stare. This bothered him for a moment -- how were they ever to reach the moon if the moon did not draw toward the point where they were aiming? It would not have bothered Morrie, trained as he was in a pilot's knowledge of collision bearings, interception courses, and the like.

But, since it appeared to run contrary to common sense, Art worried about it until he managed to visualize the situation somewhat thus: It was a simple matter of similar triangles, easy to see with a diagram but hard to keep straight in the head. The moon was speeding to their meeting place at about miles an hour, yet she would never change direction; she would simply grow and grow and grow until she filled the whole sky.

To guard against larger stuff Captain Yancey set up a meteor-watch much tighter than is usual in most parts of space. The only condition necessary for collision is that the other object hold a steady bearing-no fancy calculation is involved.

The only action necessary then to avoid collision is to change your own speed, any direction, any amount. This is perhaps the only case where theory of piloting is simple. Commander Miller put the cadets and the sublieutenants on a continuous heel-and-toe watch, scanning the meteor-guard 'scopes.

Even if the human being failed to note a steady bearing the radars would "see" it, for they were so rigged that, if a "blip" burned in at one spot on the screen, thereby showing a steady bearing, an alarm would sound- and the watch officer would cut in the jet, fast!

A more practical study of any such device shows that any extraneous object that does not change its aspect angle is necessarily on a collision course.

Ergo, any target that does not move causes the alarm to ring, and the autopilot to swerve aside. If the habitat module or space suit is punctured, all the air will start rushing out. Unless you and the other occupants want to experience first-hand all the many horrible ways that space kills you , you'd better patch that hole stat!

An instrument called a Manometer will register a sudden loss of pressure and trigger an alarm. Life support will start high-pressure flood of oxygen, and release some bubbles. The bubbles will rush to the breach, pointing them out to the crew. The crew will grab an emergency hull patch thoughtfully affixed near all external hull walls and seal the breach. The emergency hull patches are metal discs. They look like saucepan covers with a rubber flange around the edge.

They will handle a breach up to fifteen centimeters in diameter. Never slap them over the breach, place it on the hull next to the breach and slide it over. Once over the breach, air pressure will hold it in place until you can make more permanent repairs.

A more advanced alternative to bubbles are "plug-ups" or "tag-alongs". These are plastic bubbles full of helium and liquid sealing plastic. The helium is enough to give them neutral buoyancy, so they have no strong tendency to rise or sink. They fly to the breach, pop, and plug it with quick setting goo. Much to the relief of the crew caught in the same room with the breach when the automatic bulkheads slammed shut.

Holden froze, watching the blood pump from Shed's neck, then whip away like smoke into an exhaust fan.

The sounds of combat began to fade as the air was sucked out of the room. His ears throbbed and then hurt like someone had put ice picks in them. As he fought with his couch restraints, he glanced over at Alex. The pilot was yelling something, but it didn't carry through the thin air. Naomi and Amos had gotten out of their couches already, kicked off, and were flying across the room to the two holes.

Amos had a plastic dinner tray in one hand. Naomi, a white three-ring binder. Holden stared at them for the half second it took to understand what they were doing. The world narrowed, his peripheral vision all stars and darkness. By the time he'd gotten free, Amos and Naomi had already covered the holes with their makeshift patches.

The room was filled with a high-pitched whistle as the air tried to force its way out through the imperfect seals. Holden's sight began to return as the air pressure started to rise. He was panting hard, gasping for breath. Someone slowly turned the room's volume knob back up and Naomi's yells for help became audible.

She was pointing at a small red-and-yellow panel on the bulkhead near his crash couch. Years of shipboard training made a path through the anoxia and depressurization. Inside were a white first aid kit marked with the ancient red-cross symbol, half a dozen oxygen masks, and a sealed bag of hardened plastic disks attached to a glue gun.

He wasn't sure if her voice sounded distant because of the thin air or because the pressure drop had blown his eardrums. Holden yanked the gun free from the bag of patches and threw it at her. She ran a bead of instant sealing glue around the edge of her three-ring binder.

She tossed the gun to Amos, who caught it with an effortless backhand motion and put a seal around his dinner tray. The whistling stopped, replaced by the hiss of the atmosphere system as it labored to bring the pressure back up to normal. Little gas-filled plastic balls swarm into the compartment. They range from golf-ball to tennis-ball size. A new man, I decide. He's heard about the Commander. He's too anxious to look good.

He's concentrating too much. Doing his job one part at a time, with such thoroughness that he muffs the whole. The plug-ups will drift aimlessly throughout the patrol, and will soon fade into the background environment. No one will think about them unless the hull is breached. Then our lives could depend on them. They'll rush to the hole, carried by the escaping atmosphere. If the breach is small, they'll break trying to get through. A quick-setting, oxygen-sensitive goo coats their insides.

The cat scrambles after the nearest ball. He bats it around. It survives his attentions. He pretends a towering indifference. He's a master of that talent of the feline breed, of adopting a regal dignity in the face of failure, just in case somebody is watching. Breaches too big for the plug-ups probably wouldn't matter. We would be dead before we noticed them. Once a pressurized habitat module or space suit springs a leak in the vacuum of space, all the air starts howling out the hole escaping into the void.

Since people generally need air to breath or they die, there is an intense interest in how long it will take the air to go bye-bye.

Veteran rocketeers, vacationing on Terra, tend to have a momentary panic if they feel the wind. Their instincts tell them there is a hull breach.

You probably won't use this equation, but to calculate an approximate time it will take for all the air to totally escape:. If you want to get fancy and take the atmospheric temperature into account, use Fliegner's Formula equation from quote below:.

However, what we and the hapless people inside the breached compartment are more interested in is how long it takes the pressure to drop to the deadly level of anoxia, i. Remember if the compartment is using high pressure So if a posh passenger cabin of 15 cubic meters with high pressure has a 3 centimeter one inch diameter hole area 7.

So if it punches a perfect hole the same diameter as the bullet the hole will have a radius of 0. This will bring the 15 m 3 cabin down to anoxia in about seconds or The time will drop if the hole is more ragged or if there are multiple holes. Obviously each additional hole cuts the time in half.

Somebody in a space suit doesn't have that kind of time. The space suit uses low pressure. A hole a half-centimeter in diameter has a hole area of 1. As long as the suit's air tanks can keep up the loss the pressure won't drop. But once the tanks are empty, the pressure will drop to anoxia levels in a mere Does this mean that crewpeople in a combat spacecraft will do their fighting in space suits?

Probably not, for the same reason that crewpeople in combat submarines do not do their fighting while wearing scuba gear. The gear is bulky, confining, and tiring to wear. They will not wear it even though in both cases the vessel is surrounded by stuff you cannot breath. They may, however, wear partial-pressure suits or have emergency space suits handy. Those suits will only protect you for ten minutes or so, but in exchange you won't be hampered like you were wearing three sets of snow-suits simultaneously.

Instead, the ship's pressurized inhabitable section will be divided into individual sections by bulkheads, and the connecting airtight hatches will be shut. The air pressure might be lowered a bit. We do not see the room explosively decompress when the railgun projectile shoots through the Donnager's hull and wall. Except for the fact that air is being sucked out into "hard vacuum," everyone manages to stay in their seats.

This happens for a few reasons. The first is the hole, or constriction, is too small for all the air in the room to explosively leave the room. The second deals with the fact that air is made of atoms. Air escaping the hole in the hull to the vacuum of space leaves at approximately the speed of sound. As air molecules exit the hole, the remaining molecules have to "catch up.

All cars do not move together. One car slowly inches forward and then everyone follows. This means there is no explosive decompression unless the entire wall is suddenly removed. While the crew has some time to act, that time is very limited. Scientists and engineers have looked at the physics of constricted airflow for some time with regard to aircraft.

It is a very good idea to know what happens to an aircraft if a hole forms while in flight. Fliegner was one of the first engineers to look at this problem and was able to work out how much air leaves depending on the pressure inside a cabin and the size of a hole.

We know this as Fliegner's Formula:. As we expect, the air flow depends on the hole's area, cabin pressure and temperature. Of course, Fliegner's Formula is not that accurate. As the leak progresses, the pressure in the cabin drops and this also affects air flow through the hole. Have no fear, we can use the equation and a little physics to figure out the time it takes the pressure to drop to a certain level.

We have some new variables: Now that we have figured out the equation, we can model what happens inside the cabin and how much time the Canterbury crew have to act. While you would not necessarily die, you can fall unconscious.

We assume that the Canterbury crew can not help themselves and will eventually die as the cabin pressure decreases until all the air is sucked out to the vacuum. Maybe Shed is the lucky one here. While we do not have the exact dimensions of the room, we can make a few assumptions. Based on the body sizes of the crew, I assume the room is 10 meters by 10 meters by 5 meters or cubic meters in size.

If we plot the graph over time we see that the pressure drops to half its value where everyone has a little over a minute to plug up the holes. Assuming that everything happens in real-time, from the moment Sed loses his head to the second the holes are sealed, the crew manages to do seal the holes with some seconds to spare.

While the estimated size of the room may be larger than it really is, the point is The show definitely gets the science right and the urgency the crew must act to save their lives. It was just after reveille, "A" deck time, and I was standing by my bunk, making it up. I had my Scout uniform in my hands and was about to fold it up and put it under my pillow.

I still didn't wear it. None of the others had uniforms to wear to Scout meetings so I didn't wear mine. But I still kept it tucked away in my bunk. Suddenly I heard the goldarnest noise I ever heard in my life. It sounded like a rifle going off right by my ear, it sounded like a steel door being slammed, and it sounded like a giant tearing yards and yards of cloth, all at once.

Then I couldn't hear anything but a ringing in my ears and I was dazed. I shook my head and looked down and I was staring at a raw hole in the ship, almost between my feet and nearly as big as my fist. There was scorched insulation around it and in the middle of the hole I could see blackness—then a star whipped past and I realized that I was staring right out into space.

I don't remember thinking at all. I just wadded up my uniform, squatted down, and stuffed it in the hole. For a moment it seemed as if the suction would pull it on through the hole, then it jammed and stuck and didn't go any further. But we were still losing air.

I think that was the point at which I first realized that we were losing air and that we might be suffocated in vacuum. There was somebody yelling and screaming behind me that he was killed and alarm bells were going off all over the place. You couldn't hear yourself think. But man-made fertilisers provide only enough mineral substance to support basic plant life. Numerous trace minerals essential to human life do not get replenished.

Trace minerals do not exist by themselves but in relationship to one another. Too much of one trace element can lead to imbalances in others and most trace elements need to be in ionic form to be well absorbed in the small intestine. Therefore taking mineral supplements is not the answer. Only readily digestible minerals from natural food sources will provide optimum health and protection.

A typical plant makes its own food from raw materials and a typical animal eats its food. For plants, these raw materials include soil-based inorganic mineral salts. Soil-based mineral salts can be depleted through synthetic fertilisers, herbicides and pesticides, as well as repeatedly growing crops on the same soil.

This is why so many people are often unwittingly deficient in certain minerals especially those whose lifestyles deplete their bodily supplies faster and more often such as those on medications, those that drink alcohol regularly and those participating in high energy activates such as sports and dancing or those whose system is less able to absorb minerals due to illness or old age. Minerals taken as supplements are industrial chemicals made from processing rocks with one or more acids.

Humans were designed to eat food and to get their minerals from foods. Foods do not naturally contain minerals bound to substances such as picolinic acid, carbonates, oxides, phosphates, etc. When supplementation is required it should be in the form of natural foods only. Body cells receive the essential food elements through the blood stream. They must, therefore, be properly nourished with an adequate supply of all the essential minerals for the efficient functioning of the body.

They help maintain the volume of water necessary to life processes in the body. They help draw chemical substances into and out of the cells and they keep the blood and tissue fluid from becoming either too acidic or too alkaline. The importance of inorganic minerals, like organic vitamins, is illustrated by the fact that there are over 50, enzymes in the body which direct growth and energy and each enzyme has different minerals, vitamins and other chemicals associated with it.

Each of the essential food minerals does a specific job in the body and some of them do extra work, in teams, to keep body cells healthy and eliminate abnormal cells. Although as yet, it has not been discovered what the functions of some elements have in the human body, many of these elements are present and many have a purpose of some kind.

Those in blue are linked to their known functions, deficiencies, toxicity and natural food sources sections on this page. Minerals thus play a highly important role in every bodily function and are present in every human cell.

Although the amount needed may be small, without even the trace of the mineral, dysfunction is bound to occur at some level in the body. A zinc deficiency may show up in ridged fingernails with white spots. Lack of sulphur can cause lack-lustre hair and dull-looking skin. Less obvious deficiencies may surface as fatigue, irritability, loss of memory, nervousness, depression and weakness.

Minerals also interact with vitamins. Magnesium, for instance, must be present in the body for utilisation of B complex, vitamin C and vitamin E. Sulphur also works with the B complex vitamins. The body needs all the trace minerals in proper balance.

A constant lack of minerals in the body results in infection and disease and serious disorders of processes including diabetes, bone disorders, organ failures and cancer. For more information and natural sources see: Vitamin B complex Vitamin C Vitamin E Coffee, alcohol, excess refined salt, strenuous exercise, stress, sugar and many drugs can rob the body of minerals or make them ineffective.

Industrial pollutants cause toxic minerals to enter the body. Minerals at toxic levels also have the effect of destroying the usefulness of other vitamins and minerals. Exercise improves the activity of certain vitamins and minerals while stress and fatigue work against them.

Too much exercise, however, can cause deficiencies in minerals if they are not replaced. A well-balanced diet provides as abundance of minerals and vitamins. In refining cereals, grains, flour, salt and sugar, the food industry has robbed them of their natural vitamins and minerals. Some dietary sources of these nutrients are whole grains, cereals, bran and germ. It is the bran and germ which are removed in processing.

To obtain a balance of nutrients, it is , therefore, necessary to avoid refined and processed foods and consume far more organic whole fruit, herbs, legumes, nuts, sea foods, seeds, spices and vegetables which are an excellent source of minerals and vitamins. Electrolytes are the smallest of chemicals that are important for the cells in the body to function and allow the body to work. Electrolytes especially chloride, magnesium , potassium and sodium are critical in allowing cells to generate energy, maintain the stability of their walls and to function in general.

They generate electricity, contract muscles, move water and fluids within the body and participate in myriad other activities. The concentration of electrolytes in the body is controlled by a variety of hormones, most of which are manufactured in the kidney and the adrenal glands. Sensors in specialised kidney cells monitor the amount of sodium, potassium and water in the bloodstream.

Keeping electrolyte concentrations in balance also includes stimulating the thirst mechanism when the body gets dehydrated. Mineral water is a healthy alternative to tap water as it usually contains trace elements that are essential to human health. Depending upon it's source it can naturally contain minerals such as bicarbonate, calcium, fluoride, lithium, magnesium, potassium, silica, sodium and strontium.

Water from natural springs, wells and mountain lakes contains minerals which are in the rocks through which it flows and these minerals all have a purpose within the human body. Modern day farming techniques have leeched many minerals from the soil so non organic farmed food is often lacking in them, especially magnesium.

The best way to ingest the some of the minerals needed daily is through drinking mineral water, whether carbonated or still, everyday. Drinking mineral water is especially important for the elderly and those on medications which can force the body to expel essential minerals in the urine such as diuretics. Tap water has little mineral content except fluoride and chlorine which are added artificially and, in many developed countries, also contains traces of medications administered to humans such as hormone replacement drugs and the contraceptive pill.

Read about the dangers of drinking boiled or distilled water, why it is necessary to prevent heart attacks and signs of a deficiency of water in the body here: One IU is the biological equivalent of 0.

See also The A-Z of organic nutrients. Aluminium is a mineral, with the atomic number of Read more about Aluminium. S ource of aluminium. Arsenic is a heavy metal, with the atomic number of Read more about Arsenic. Apple juice, glues, pigments and wine. Milk and dairy products, beef, pork, poultry and cereal. Many water sources in the world have high levels of arsenic in them, both due to normal arsenic leaching out of the ground and from mining and industrial waste.

Arsenic is also often found in rice, which may be a potentially serious source of exposure in certain at-risk populations especially children. Barium is a mineral with the atomic number Read more about Barium. Natural sources of barium. See how bicarbonate can help reduce acidity in the body to treat and prevent many health disorders: Bismuth is a heavy metal similar to lead and arsenic. It is a mineral, with the atomic number Read more about Bismuth. Highest natural sources of bismuth.

Boron is a chemical element with the atomic number 5. Read more about Boron. Bromine has the atomic number of Read more about Bromine. Cadmium has the atomic number of Read more about Cadmium. S ources of cadmium. Tobacco and cannabis smoke. Cadmium is also a component of alloys, used in electrical materials and is present in burning coal, ceramics, dental materials, storage batteries and water pipes.

Caesium has the atomic number of Calcium has the atomic number of 20 and the human body needs calcium more than any other mineral. H ypercalcaemia occurs when there is high levels of calcium in the blood and muscles and can lead to irreversible kidney damage.

Taking high doses of vitamin D supplements can cause this. Hypocalcaemia is the medical term for low serum calcium levels in the blood. Read more about Calcium. Highest sources of calcium in milligrams per grams. Carbon is a chemical element with the atomic number 6 that is found in various compounds within the human body but not in its purest form.

Read more about Carbon. Chlorine is a chemical element with the atomic number of Read more about Chlorine. Chromium is a trace mineral element with the atomic number Read more about Chromium. Highest sources of chromium in micrograms per grams. Cobalt is a trace mineral element with the atomic number of Read more about Cobalt.

Natural sources of cobalt. Copper is a trace element with the atomic number of Read more about Copper.

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