Pulse-Tube Refrigeration

1964 ◽  
Vol 86 (3) ◽  
pp. 264-268 ◽  
Author(s):  
W. E. Gifford ◽  
R. C. Longsworth
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
Room Temperature ◽  
Experimental Models ◽  
Pulse Tube ◽  
Thomson Effect ◽  
Test Results ◽  
Simple Effect ◽  
Very Low Temperature ◽  
Moving Parts

A very simple effect makes it possible to construct very low temperature refrigerators without the use of low temperature moving parts or the Joule-Thomson effect. The effect, which occurs in many places and is frequently ignored, is described in detail, along with means for using it to build refrigerators capable of achieving low temperatures. A description of experimental models and test results is also included. A temperature 218 deg F below room temperature has been achieved.

scholarly journals The behaviour of visual purple at low temperature

1941 ◽  
Vol 179 (977) ◽  
pp. 151-159 ◽  
Keyword(s):  
Aqueous Solution ◽  
Low Temperature ◽  
Low Temperatures ◽  
Room Temperature ◽  
Absorption Curve ◽  
Quantum Yields

Visual purple is soluble and stable in a mixture of glycerol and water (3:1). At room temperature the spectrum of such a solution is identical with that of the aqueous solution. At — 73° C the peak of the absorption curve is higher and narrower than at room temperature, and it is shifted towards longer waves. The product of photodecomposition at — 73° C has a spectrum in ­ dependent of pH and is at low temperatures thermostable and photostable, but at room temperature it decomposes therm ally to indicator yellow. The primary product appears to be identical with transient orange. The quantum yields of the photoreaction at low and at room temperature are of the same order.

Compressive Plasticity of Zr-Based Bulk Metallic Glass at Low Temperature

2012 ◽  
Vol 443-444 ◽  
pp. 583-586
Author(s):  
Ya Juan Sun ◽  
Ri Ga Wu ◽  
Hong Jing Wang
Keyword(s):  
Mechanical Properties ◽  
Low Temperature ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Low Temperatures ◽  
Room Temperature ◽  
Shear Bands ◽  
Strain Curve ◽  
Testing Temperature ◽  
Stress Strain Curve

The mechanical properties of a new Zr-based bulk metallic glass at low temperatures were investigated. The results indicate that the fracture strength increases significantly (4.9%) and the global plasticity increases somewhat when testing temperature is lowered to 123K. The stress-strain curve of the sample deformed exhibits more serrations and smaller stress drop due to formation of more shear bands at low temperature than at room temperature.

scholarly journals THE INFLUENCE OF TEMPERATURE ON THE ACTION OF STRYCHNIN IN FROGS

1913 ◽  
Vol 18 (3) ◽  
pp. 300-309 ◽  
Author(s):  
Thomas Stotesbury Githens
Keyword(s):  
Low Temperature ◽  
High Temperatures ◽  
Low Temperatures ◽  
Room Temperature ◽  
Drug Action ◽  
The State ◽  
Great Caution ◽  
Influence Of Temperature ◽  
Influence Of Temperature On

In order to establish the influence of temperature upon the effect of varying doses of strychnin injected into frogs, the animals must be kept under observation for several days and at various definite degrees of temperature. Statements that the animal was kept "cold," "at room temperature," or "warm" are insufficient. With a certain dose tetanus may result constantly at 30° C. yet never appear at 21° C., and either of these temperatures might be described as warm, when compared to a room temperature of 15° C. Furthermore an animal may apparently fail to respond in the cold to an injection of certain doses of strychnin and yet be found in tetanic convulsions the next day. That an animal may have late, long lasting, or strong tetanus while kept at such a low temperature as 5° C. after an injection of a dose of strychnin smaller than 0.01 of a milligram per frog emphasizes the fact that great caution must be exercised in formulating laws as to the influence of temperature on drug action. The main results of this investigation may be summarized as follows: Doses of strychnin amounting to 0.0006 of a milligram per gram of frog will cause tetanus at all temperatures between 5° C. and 30° C., although at low temperatures the tetanus may appear late. A dose of 0.0003 of a milligram per gram of frog will frequently produce tetanus at 5° C. as well as at 30° or 27° C., but may nevertheless fail to produce any reaction at such an intermediary temperature as 21° C. Smaller doses, 0.0002 of a milligram per gram, will cause tetanus in the cold but not at high temperatures. It may be stated in general that in frogs kept at low temperatures the tetanic state sets in later, continues longer, and each tetanic attack is of longer duration, while in the interval between the attacks the state of tonus is higher and the animals are more irritable than when they are kept at higher temperatures.

INVESTIGATIONS OF PERMEABILITY, DIAPAUSE, AND HATCHING IN THE EGGS OF THE MOSQUITO AEDES HEXODONTUS DYAR

1958 ◽  
Vol 36 (4) ◽  
pp. 541-554 ◽  
Author(s):  
W. E. Beckel
Keyword(s):  
Low Temperature ◽  
Sodium Hypochlorite ◽  
Water Loss ◽  
Low Temperatures ◽  
Room Temperature ◽  
Early Embryo ◽  
Adult Mosquito ◽  
Egg Cell ◽  
Distilled Water ◽  
Exposure To Cold

Methods for collection in the laboratory of many thousands of eggs from field-collected, blood-fed females are described. Also a way of separating fertile from infertile eggs is outlined. When the eggs are laid they are white but begin to darken within one-half hour. The darkening did not occur when the egg cell or early embryo was killed.Two changes in permeability in the prediapause stage of the eggs of Aedcs hexodontus were observed. The first took place as the chorion changed from white to black. The egg lost and gained water easily when first laid but resisted water loss and uptake as the chorion darkened. However, a complete waterproofing did not result. With the formation of the transparent cuticle a further change in permeability occurred. The egg lost hardly any water even when exposed to extreme desiccation and what little water was lost was regained very slowly. However, the cuticle, with the chorion removed in sodium hypochlorite, was quite permeable. The impermeability of the chorion and cuticle combination must result from the bonding between the two and this bonding must be disrupted by the dechorionation.To study the obligate diapause that occurs in the late embryogeny of the mosquito egg the effect of making water available to the embryo, of light, and of low temperature was studied. Diapause was not broken when water was available to the embryo, nor did alternate periods of light and dark at room temperature or at lower temperatures disrupt the diapause. To test the influence of cold the temperature of 1° and −3 °C. were used to simulate the temperatures in the field. The low temperatures were found to terminate the diapause but the numbers of eggs hatching did not steadily increase with an increase in the time of exposure to cold. No clue has as yet been discovered to explain these results. A hatching infusion of decaying adult mosquito bodies in distilled water was found to give more hatching than did distilled water alone. The mechanism of the hatching stimulus is not known.

Primary Defects in n-Type Irradiated Germanium: A First-Principles Investigation

2007 ◽  
Vol 131-133 ◽  
pp. 253-258 ◽  
Author(s):  
A. Carvalho ◽  
R. Jones ◽  
C. Janke ◽  
Sven Öberg ◽  
Patrick R. Briddon
Keyword(s):  
Low Temperature ◽  
Point Defects ◽  
Electron Irradiation ◽  
First Principles ◽  
Low Temperatures ◽  
Damage Evolution ◽  
Room Temperature ◽  
Temperature Electron ◽  
Conductivity Loss

The properties of point defects introduced by low temperature electron irradiation of germanium are investigated by first-principles modeling. Close Frenkel pairs, including the metastable fourfold coordinated defect, are modelled and their stability is discussed. It is found that damage evolution upon annealing below room temperature can be consistently explained with the formation of correlated interstitial-vacancy pairs if the charge-dependent properties of the vacancy and self-interstitial are taken into account. We propose that Frenkel pairs can trap up to two electrons and are responsible for conductivity loss in n-type Ge at low temperatures.

Laser Crystallized Polysilicon TFT'S Using LPCVD, PECVD and PVD Silicon Channel Materials-A Comparative Study

1999 ◽  
Vol 557 ◽  
Author(s):  
R.T. Fulks ◽  
J. B. Boyce ◽  
J. Ho ◽  
G. A. Davis ◽  
V. Aebi
Keyword(s):  
Low Temperature ◽  
Field Effect ◽  
Room Temperature ◽  
Laser Energy ◽  
Laser Crystallization ◽  
Drain Bias ◽  
Excimer Laser Crystallization ◽  
Laser Anneal ◽  
Active Channel ◽  
Very Low Temperature

AbstractIn this work polysilicon TFI's were fabricated by excimer laser crystallization of active channel silicon which was deposited by three different methods: I) LPCVD at 550 °C; 2) PECVD at 225 °C; and 3) PVD at room temperature. CMOS devices were produced with the same low temperature (less than 600 °C) top gate process and the laser anneal condition was optimized for the material type and thickness. For PECVD material a pre-anneal step of 450 °C for 1 hour was required before crystallization to avoid bubbling and ablation due to hydrogen evolution, but no such anneal was required for either LPCVD or PVD material due to their low hydrogen and Ar content. For 50 nm films, laser energy densities were typically in the range of 300-400 miJ/cm2. Excellent device results were obtained for both LPCVD and PECVD material with n-channel field effect mobilities greater than 100 cm2/Vs and on/off ratios greater than 108 at 5 V drain bias. Good results were also obtained for PVD films that can be further improved by optimizing deposition and anneal conditions. In moving toward very low temperature polysilicon processing (less than 230 °C) both PECVD and PVD channel films appear to be viable candidates.

THE EFFECT OF ELECTRICAL STIMULATION AT LOW TEMPERATURES ON THE LARVAE OF PHOCANEMA DECIPIENS

1961 ◽  
Vol 39 (1) ◽  
pp. 35-42 ◽  
Author(s):  
Clare Bradley
Keyword(s):  
Electrical Stimulation ◽  
Low Temperature ◽  
Low Temperatures ◽  
Room Temperature ◽  
Morphological Changes ◽  
Neuromuscular System ◽  
Anodal Stimulation ◽  
Rhythmical Activity ◽  
Cathodal Stimulation

Observations were made on the effect of low temperatures (down to 0° C) on the response of Phocanema to external polarizing stimuli. The response to anodal stimulation (contraction) was not affected by a fall in temperature. The response to a cathodal stimulus varied with the temperature, and whereas at room temperature the response was a relaxation, at low temperatures it was either a contraction or it was blocked altogether. Storage of the worm at low temperature for several hours had a similar effect. In some cases spontaneous rhythmical activity ceased as the temperature fell; this effect was shown to be independent of the effect of low temperature on the response to cathodal stimulation. No associated morphological changes in the neuromuscular system were observed.

Accurate charge densities in days — use of synchrotrons, image plates and very low temperatures

1999 ◽  
Vol 55 (3) ◽  
pp. 363-374 ◽  
Author(s):  
B. B. Iversen ◽  
F. K. Larsen ◽  
A. A. Pinkerton ◽  
A. Martin ◽  
A. Darovsky ◽  
...  
Keyword(s):  
Low Temperature ◽  
Electron Density ◽  
Diffraction Data ◽  
Low Temperatures ◽  
Systematic Errors ◽  
Reciprocal Space ◽  
Synchrotron Source ◽  
X Ray ◽  
Single Temperature ◽  
Very Low Temperature

Extensive synchrotron (28 K) and conventional sealed-tube (9 K) X-ray diffraction data have been collected on tetrakis(dimethylphosphinodithioato-S,S′)thorium(IV), [Th(S2PMe2)4]. The use of very low temperatures, well below those obtained with liquid-nitrogen cooling, is crucial for the accuracy of the data. This is due to minimization of temperature-dependent systematic errors such as TDS and anharmonicity, and extension and intensification of the data in reciprocal space. Comparison of structural parameters derived separately from the sealed-tube data and the synchrotron data shows good agreement. The synchrotron data are markedly superior when comparing refinement residuals, standard uncertainties (s.u.'s) of the data and s.u.'s of the derived parameters. However, the study suggests that there are still small uncorrected systematic errors in the data. The very large extent [(\sin\theta/\lambda)max = 1.77 Å−1] of the synchrotron data and the very low temperature at which they were collected makes it possible to separate anharmonic effects from electron-deformation effects even with only an X-ray data set at a single temperature. The electron density shows a large polarization of the outer Th core of d-type symmetry. This deformation is successfully modelled with contracted multipolar functions, which are only slightly correlated with anharmonic expansions in reciprocal space when using the full extent of the data. In the data collection more than a factor of 100 in speed is gained by use of image-plate area detectors at the synchrotron source compared with conventional sequential measurements. Thus accurate, very low temperature synchrotron-radiation diffraction data can now be measured within days, which makes electron-density studies of compounds beyond the first transition series more frequently within reach.

Ultrasonic measurements in liquid helium

1953 ◽  
Vol 220 (1140) ◽  
pp. 116-132 ◽  
Keyword(s):  
Low Temperature ◽  
Liquid Helium ◽  
Low Temperatures ◽  
Relaxation Effect ◽  
Recent Theory ◽  
Normal Boiling Point ◽  
Velocity Measurements ◽  
Ultrasonic Measurements ◽  
Very High ◽  
Very Low Temperature

Measurements have been made of the velocity and absorption of ordinary sound in liquid helium at frequencies of 2, 6 and 12 Mc/s, over the temperature range from the normal boiling-point down to 0-85° K. The accuracy of the velocity measurements has been increased above that reported in an earlier paper, and the temperature and frequency ranges of those measurements have been extended. Particular attention has been paid to the attenuation in the neighbourhood of the A-point and in the very low temperature region. The attenuation is found to be very high near the A-point and at low temperatures, and is proportional to w2 between 1-2°K and the A-point. At lower temperatures a change in the frequency dependence is observed, indicating the presence of a relaxation effect. The significance of these results is discussed in relation to a recent theory of Khalatnikov.

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