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Absolute zero environments

If such spillage does not happen in a controlled, near-absolute zero environment, the BEC will simply vaporize back into a gas and disappear. Near-absolute zero temperatures do not exist in nature and are difficult to create in the laboratory. But it can be done. [Pg.70]

All matter above absolute zero (-456.7°F) emits electromagnetic radiation. The exact process is a complex quantum physics phenomena. How much heat an object radiates is determined by the temperature of the object, the temperature of the surrounding environment, and the object s emissivity factor. [Pg.404]

The reaction entropy ACS is a result of the different opportunities of the species to save thermal energy between the absolute zero level of temperature and the temperature level of the reactor. Concerning the energy balance of a fuel cell (Figure 2.1), the heat <2FCrev has to be transferred reversibly from the fuel cell to the environment. 0FCrev is defined as a positive value if the reversible change in entropy is... [Pg.16]

Today, 473 million billion seconds after the big bang, the temperature of the universe has dropped to three degrees above absolute zero. Embedded in this frigid environment are galactic systems distributed across the far reaches of the observable universe. Each galaxy consists of stars and dust clouds. Each star, each dust cloud in each and every galaxy consists of about 90 percent hydrogen atoms and 9 percent helium atoms. Because of this composition, established approximately 15 billion years (or 473 million billion seconds) ago, the stars twinkle and the Sun shines. [Pg.9]

The temperature in deep space is close to absolute zero, which presents thermal challenges for the astronauts who do space walks. Propose a design for the clothing of the astronauts that will be most suitable for the thermal environment in space. Defend the selections in your design. [Pg.235]

The name zero-point energy is used for the energy of a system in its lowest stationary state because the system in thermodynamic equilibrium with its environment at a temperature approaching the absolute zero would be in this stationary state. The zero-point energy is of considerable importance in many statistical-mechanical and thermodynamic discussions. The existence of zero-point energy is correlated with the uncertainty principle (Chap. XV),... [Pg.73]

Helium (He) is produced by cryogenically distilling natural gas. Helium has a low boiling point and will liquefy only under high pressure. Liquid helium, therefore, is used to cool environments to very low temperatures. This can be important for scientific applications where temperatures close to absolute zero are required helium s freezing point is only 4 °C warmer than absolute zero. For comparison, water freezes at 273.15 °C warmer than absolute zero. [Pg.204]

Let us finally consider more closely the definition of the reduced temperature T (16.7.7). The occurrence of the factor q in the denominator is quite understandable. An increase of q increases the number of first neighbours and therefore the average potential energy of the r-mer. The reduced temperature which depends on the ratio of thermal energy to potential energy is decreased. On the other hand a decrease of c means a decrease of entropy and acts in the same way as a decrease of the temperature T. An extreme case is cjq -> 0. The polymer molecule becomes then independent of the thermod3mamic state of its environment because it has no external degrees of freedom to interact with it. We may say that in this case the polymer molecule remains at absolute zero whatever the macroscopic temperature. [Pg.337]

In practice this means that for an atom in any environment of symmetry lower than spherical, an absolute direction exists and fixes the direction of z. As a working rule it follows that only one of the three degenerate p-states (pz) can be specified in real form. Other p-states in the system cannot be located more closely than to a plane perpendicular to z, with orbital angular momentum quantum numbers m = 1. Non-zero implies circulating charge and non-zero kinetic energy. [Pg.84]

Quantum yield values measured in solution may not necessarily apply to polymer films, the usual environment for practical application of this photochemistry. McKean et al. have adapted the indicator dye method to the measurement of quantum yields for Bronsted acid photogeneration in poly-(4-tert-butoxycarbonyloxystyrene) [20], As with the solution photochemistry of diphenyliodonium salts [71], an inverse dependence of quantum yield on exposure intensity was observed absolute quantum yields from 0.26 to 0.40 were measured at 254 nm, which extrapolate to approximately 0.45 at zero intensity, comparable to the value estimated by Dektar and Hacker [82b] in solution. McKean et al. [20b] note that similar quantum yields in solution and polymer films below Tg have also been reported for photo-Fries rearrangements [84] and photodissociation of diacyl peroxides [85]. [Pg.330]

Often, our interest will lie not so much in the actual structure of a particular molecule or molecular fragment in a particular environment as in the details of how this molecule or fragment deviates from some reference structure with the same atomic connectedness or constitution. Insofar as we can usually ignore the absolute position and orientation of our molecule, comparisons of this kind are most conveniently made in terms of internal coordinates. The distortion can be expressed in terms of a total displacement vector D = pj, where the d/s are displacements along some set of basis vectors pj. The only difference to the internal coordinates described in the previous section is that for deformation coordinates the displacements dj are defined to be zero for the reference structure. This could be an observed structure, or a calculated one, or an idealized, more symmetric version of the structure we are interested in. [Pg.21]

A majority of safety professionals accept the premise that absolute safety, a zero risk state, is not attainable. But, some safety practitioners profess that only a risk-free environment is acceptable. Consider these two examples. [Pg.272]

Water content is defined as the amount of water lost by a food when it reaches the true equilibrium against zero water vapor pressure. From this definition arises a quantification method of water content called the absolute reference method, a determination that is only possible in specialized laboratories. The food industry only uses practical reference methods, calibrated against the absolute reference method. Moreover, water content standards are not available because a product s water content depends on the humidity and temperature of the environment, which makes participating in intercomparison exercises between laboratories essential for detecting possible experimental errors. [Pg.1485]

The safety of a process can be achieved by inherent (internal) and external means. Inherent safety focuses on the intrinsic properties of a process and attempts to design out hazards rather than trying to control hazards through the application of external protective systems. Inherently safer processes rely on chemistry and physics (properties of materials, quantity of hazardous materials) instead of control systems (interlocks, alarms, procedures) to protect workers, property, and the environment. It would be inappropriate to talk about an inherendy safe process, as an absolute definition of safe is difficult to achieve in this context since risk cannot be reduced to zero. However, one can talk about a process or chemical being inherently safer than other(s). For instance, water can be an extremely hazardous chemical under certain conditions (e.g., floods), but in the context of a chemical process, water is an inherently safer solvent than other chemicals. Trevor Kletz has postulated some basic principles of inherent safety [79,80] that process systems engineers can follow when designing or retrofitting chemical processes. Kletz s inherent safety principles can be summarized as follows ... [Pg.369]

Pressmes can be measured in environments from the near vacuum of space to more than 1,400 megapascals (MPa) and from steady state to frequencies greater than 100,000 cycles per second. Sensors that measure with respect to zero pressure or absolute vacuum are called absolute pressure sensors, whereas those that measure with respect to some other reference pressure are called gauge pressure sensors. Vented gauge sensors have the reference side open to the atmosphere so that the pressure reading is with respect to atmospheric pressure. Sealed gauges report pressure with respect to a constant reference pressure. [Pg.170]


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See also in sourсe #XX -- [ Pg.69 , Pg.73 ]




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