Hg Vapor Pressure Research Articles

High pressure reflux technique for growth of Hg 1-xCd xTe crystals

A high pressure reflux technique has been used to grow Hg 1−xCd xTe alloy crystals under controlled Hg pressures up to 80 atm. Refluxing is obtained by combining a high pressure of inert gas and a negative temperature gradient over the charge of volatile materials, making it possible to contain the charge without high-temperature seals or liquid encapsulation. The continuous evaporation and condensation process results in the separation of the inert gas and vapor species at a well-defined interface where gas and vapor have the same pressure. For Hgin1-xCd xTe crystal growth, the pressure of the inert gas at the reflux interface is adjusted to correspond to the Hg vapor pressure required to maintain stoichiometry in the charge during solidification and crystal growth. Large-diameter (up to 2.5 cm), high-quality Hgin1-xCd xTe crystals with x up to 0.60 have been grown by the technique in a high-pressure furnace. Carrier concentrations below 10 15 cm -3 and electron mobilities in excess of 10 5 cm 2/V-sec have been obtained at 77 K in annealed n-type Hg 0.80Cd 0.20Te. Background-limited photoconductive infrared detectors for to μm spectral region have been fabricated from this n-type material. High-performance short-wavelength (2 to 5 μm) photovoltaic detectors have been fabricated from as-grown p-type material by In ion implantation.

Electrons and holes in HgTe and Hg 0.82Cd 0.18Te with controlled deviations from stoichiometry

The deviations from the stoichiometric composition of HgTe and Hg 0.82Cd 0.18Te crystals have been controlled by heat treatment under Hg vapor pressure. The magnetic field dependence of the Hall coefficient always shows the presence of two different sets of electrons and one set of holes. A low mobility electron is shown to belong to the conduction band. Vapor pressure dependence of hole concentration in HgTe shows that the concentration of nonstoichiometric defects decreases with increasing Hg vapor pressure, but the hole concentration is always higher than the electron concentration. In the case of Hg 0.82Cd 0.18Te, the electron concentration exceeds the hole concentration at high Hg vapor pressures. The dependence of the conduction band electron mobility in HgTe upon carrier density shows that the scattering by holes and impurities is predominant. In Hg 0.82Cd 0.18Te, however, optical phonon scattering is dominant when the deviation from stoichiometry is small and the effect of residual impurities can be neglected, and scattering by holes is dominant when the hole concentration is over 10 17 cm 3 .

Flight of the salt marsh Tabanidae (Diptera), Tabanus nigrovittatus, Chrysops atlanticus and C. fuliginosus: correlation with temperature, light, moisture and wind velocity.

The flight activities of the greenhead fly, Tabanus nigrovittatus Macquart (collected by traps), and deer flies, Chrysops atlanticus Peehuman and Chrysops fuliginosus Wiedemann (both collected by netting from a human), were measured in the field and correlated with the environmental conditions during the collection periods. The highest number of T. nigrovittatus were correlated with intermediate light intensity (40,000 lux), temperatures around 25°C and no wind. C. atlanticus was most active at relatively low light intensity (5000 lux), high tempteratures (30°C) and air moisture equivalent to 8 mm Hg vapor pressure deficit. The greatest activity of C. fuliginosus was correlated with high levels of light (100,000 lux). Graphs are presented for both actual and predicted levels of flight activity for the significantly correlated values of light, VPD, temperature and wind for each species.

Electrons and holes in HgTe and Hg 0.82Cd 0.18Te with controlled deviations from stoichiometry

Abstract The deviations from the stoichiometric composition of HgTe and Hg 0.82 Cd 0.18 Te crystals have been controlled by heat treatment under Hg vapor pressure. The magnetic field dependence of the Hall coefficient always shows the presence of two different sets of electrons and one set of holes. A low mobility electron is shown to belong to the conduction band. Vapor pressure dependence of hole concentration in HgTe shows that the concentration of nonstoichiometric defects decreases with increasing Hg vapor pressure, but the hole concentration is always higher than the electron concentration. In the case of Hg 0.82 Cd 0.18 Te, the electron concentration exceeds the hole concentration at high Hg vapor pressures. The dependence of the conduction band electron mobility in HgTe upon carrier density shows that the scattering by holes and impurities is predominant. In Hg 0.82 Cd 0.18 Te, however, optical phonon scattering is dominant when the deviation from stoichiometry is small and the effect of residual impurities can be neglected, and scattering by holes is dominant when the hole concentration is over 10 17 cm 3 .

Determination of mercury vapor pressure over amalgams from weight loss data.

AbstractMercury vapor pressure over clinically used amalgams, as well as the individual phases composing dental amalgam, has been determined from weight loss data using Langmuir's time averaged weight loss technique. The results show that the Hg vapor pressure of 38.2 × 10−6 torr over the pure γ1 (Ag2Hg3) phase is more than an order of magnitude greater than that over the remaining amalgams considered: β1, α1, γ2, Ag‐Sn amalgams, True Dentalloy amalgams, Au‐containing amalgams, and Dispersalloy amalgams.

Interaction of Environmental Variables on Growth and Development of Honey Mesquite

The influence of soil and aerial environments on the growth and development of honey mesquite (Prosopis juliflora [Swartz] DC. var. glandulosa [Torr.] Cockerell) was studied under controlled environment conditions. Either low soil temperature (13 C) or cool aerial environments (11-25 C) retarded shoot growth; however, maximum shoot growth occurred as a result of an interaction of optimum soil temperature (29 C) and moderate aerial environment (20.9 mm Hg vapor pressure deficit). The efficiency of shoot growth with respect to water use is maximum at 29 C soil temperature and with a vapor pressure deficit regime of 7.3 mm Hg, the latter being well below the optimum aerial environment for maximum growth.

Flight of the eye gnat, Hippelates pusio (Diptera: chloropidae): effect of temperature, light, moisture and wind velocity.

The flight activity, based on collections from humans, of Hippelates Pusio eye gnats was measured under varying field conditions. Thresholds for flight were 17°C, 0.25 mm Hg vapor pressure deficit (VPD), 5.38 milliphots (5 ft-c) of light and wind velocity below 67 m/min. Graphs are presented for flight activity at various values of temperature, light, VPD, and wind velocity.

EFFECTS OF HIGH TEMPERATURE AND VAPOR PRESSURE DEFICIT ON EUROPEAN PINE SHOOT MOTH, RHYACIONIA BUOLIANA (LEPIDOPTERA: OLETHREUTIDAE), EGG PRODUCTION AND SURVIVAL

AbstractFecundity and egg survival had inverse linear relationships with increasing evaporation potentials expressed as vapor pressure deficits. With an increase of vapor pressure deficit from 4 to 24 mm Mg at a favorable temperature of 25.5 °C, mean fecundity could be reduced from 130 to 51 eggs and egg survival from 90% to 20%. Optimal laboratory physical conditions for egg production consisted of a low evaporation rate of less than 9 mm Hg vapor pressure deficit but short of a saturated atmosphere at a room temperature of 25.5 °C. One hour daily exposure of eggs to high temperatures up to 39 °C did not cause a significant increase in egg mortality. In the field there was no difference in fecundity of females between plots in damp western Washington and dry central Oregon (pine region). Egg mortality was always higher at the central Oregon plot, presumably because of higher evaporation rates. Since high vapor pressure deficits are common occurrences during the growing season in most of the pine region, it is possible this factor could limit Rhyacionia buoliana populations in some of these areas.

Die Aktivitätskoeffizienten des Hg im Indiumamalgam beim Übergang von der festen zur flüssigen Phase / The activity coefficients of hg in in-amalgams at the solid-liquid phase transition

Abstract By 2537 Å resonance absorption the temperature dependency of mercury partial pressure of dif­ferent In-amalgams is measured. - The Hg-concentrations of the investigated amalgams are 1.9 - 20 atomic per cent. The temperature interval is 30 -160 °C. In the solid + liquid two-phase region the activity coefficient of mercury is strongly diminuted with growing temperature. For tem­peratures higher than 130 °C the Hg-vapour pressure in the two-phase region falls with growing temperature. With the help of a generalized Clausius-Clapeyron formula for a three phase system with two components the mercury vapour pressure in the liquid + solid two-phase region is calculated. There is a good agreement with our experimental results

The Influence of Cataphoresis Upon the Noise Temperature of F8T5 Lamps

Fluorescent lamps were once used as standard noise sources for microwave measurements. Because of unpredictable noise output, they were abandoned in favor of pure-gas discharge tubes. It is shown that the unpredictability resulted from changes in Hg vapor pressure which were indirectly caused by cataphoretic pumping of the Hg ions. Data are presented which give excess noise as a function of discharge current and as a function of bulb temperature. These data were obtained for normal and abnormal lamps at 147 MHz.

Some Population Parameters for the Grain Mite, Acarus siro1,2,3,4

Two laboratory populations of A. siro L. (Acarina: Acaridae), were maintained at 15°C and 1.33- and 4.00-mm Hg vapor pressure deficit. Egg hatch, survival, and developmental time of immatures, and survival and fecundity of adult females were observed and recorded at 2-day intervals from egg to death of the adults. Life tables are presented for each population. Net production per generation, intrinsic rates of natural increase, and stable-age distribution are calculated and presented for each population.

A Psychrometer System for Micrometeorology Profile Determination

Abstract An aspirated psychrometer system using thermopiled copper-constantan sensors is described. Field data are presented showing temperature and humidity profiles obtained over a turf crop by nine self-contained units mounted on a 6 m mast. Temperature and humidity can be determined with accuracies of 0.025C and 0.15 mm Hg vapor pressure. The units are relatively inexpensive and easy to fabricate. The wet-bulb element, a porous ceramic cup supplied with a continuous column of water from a reservoir, provides more reliable and less critical operation than the conventional cotton-wick elements.

The evaporation of water from Helix aspersa. IV. Loss from the mantle of the inactive snail.

ABSTRACT Data is presented which suggest that inactive specimens of Helix aspersa are able to regulate evaporative water loss from the mantle. Evaporation is reduced following the cessation of glandular extrusion, by the concentration of solutes in partially dehydrated superficial mucus. Methods are described for determining vapour pressure gradients across living and freshly killed mantle tissue and for calculating permeabilities. Osmotic permeability measurements using isolated and intact body wall were made. The permeability of regulating mantle tissue was 0·039 mg./cm.2/hr. per mm. Hg vapour pressure difference. Living body wall and freshly killed mantle were at least forty times more permeable to water. Low permeability seems to be a unique property of living mantle tissue.

Simple Procedure for Measurement of Hg Vapor Pressure of Amalgams

A simple, relatively accurate method for determining the Hg vapor pressure of amalgams at elevated temperatures is described. The transmission of 2537 Å radiation through an evacuated quartz optical cell containing the amalgam is compared with that of a similar cell containing only Hg, using a spectroradiometer. After plotting log transmission vs 1/T °K for each of the cells, the Hg vapor pressure of the amalgam is found by determining the temperature at which the Hg cell shows the same transmission as the amalgam, and reference to a table of Hg vapor pressure vs temperature.

763. Basic principles of the entrainment method and measurements of Hg vapour pressure with a continuous method: N G Schmahl et al, Z Physik Chem, (Frankfurt), 46 (3/4), 1965, 160–182, (in German)

763. Basic principles of the entrainment method and measurements of Hg vapour pressure with a continuous method: N G Schmahl et al, Z Physik Chem, (Frankfurt), 46 (3/4), 1965, 160–182, (in German)

Effect of Artificial Light, Temperature, and Humidity on Physiological Response of Dairy Bulls

Reproductive and physiological responses of 12 mature dairy bulls were measured under varying artificial incandescent illumination, temperature, and humidity conditions. Bulls in Group I were housed in one-half of a large barn (control), and Group II in the remaining half of the barn, with the addition of incandescent light. Bulls in Group III were housed in an environmental control chamber maintained at 64F, 15mm Hg vapor pressure (humidity) and controlled incandescent light. Significant differences (P<0.01) in favor of the bulls exposed to artificial light were attained for initial progressive motility of spermatozoa, morphologically abnormal spermatozoa, livability (72 hr) of spermatozoa, methylene blue reduction time (modified), and percentage of shippable ejaculates. However, no significant differences were attained for concentration of spermatozoa and volume of semen.The serum protein-bound iodine level declined slightly during the period with 15 hr of light and was essentially equal during the periods with 14 and 16 hr of light. Bulls exposed to artificial light exhibited a significant (P<0.01) decrease in respiration rate as compared with the control. However, there were no significant differences among groups in body temperatures.

Relaxationszeiten f�r die Umorientierung von Quecksilberatomen im metastabilen 63 P 2-Zustand durch St��e

From the linewidth of the radiofrequency resonance between the Zeeman levels of the 63 P 2 state the lifetimeT m of the metastable Hg atoms in a certain magnetic sublevel was derived as a function of the Hg vapour pressure. The lifetime of the metastable stateT(63 P 2) was determined under the same experimental conditions by optical absorption measurements. In the pressure range from 2·10−3 to 2.4·10−2 mm HgT(63 P 2) was longer thanT m by one to two orders of magnitude. This result means thatT m is only dependent on disorienting collisions and is practically not affected by the collisional destruction of the metastable state. ThusT m is the relaxation time for the disorientation of the metastable atoms by collisions. The pressure dependence of the relaxation time indicates that the disorientation is achieved by two-body collisions with ground state Hg atoms. The disorientation cross section was found to be (2.1±0.2)·10−14 cm2.

Effect of vapor pressure on physiologic strain and body heat storage.

Physiologic strain, in terms of body heat storage, and other physiologic responses were measured and compared in two series of heat stress experiments performed on human subjects exposed to different ambient vapor pressures. One group of 75 experiments conducted on 5 healthy nonacclimatized male subjects exposed 5 times each to 38, 54, and 71 C at 10 mm Hg vapor pressure was compared with a series of 81 experiments performed on 10 similar subjects exposed 1–6 times each to 38, 41, and 54 C at 20 mm Hg vapor pressure. Subjects were sitting and wore 1.0 clo insulation. The data show relation between body heat storage and a) the modified Craig index of physiologic strain; b) over-all sweat rate; c) evaporative rate; d) sweat-evaporative ratio; e) mean skin and rectal temperatures; and f) change of heart rate at the respective vapor pressure levels. Statistically significant correlation between sweat-evaporative ratio and over-all sweat rate with body heat storage is shown. Use of the over-all sweat response as a physiologic strain index is suggested. Submitted on August 14, 1962

Seminal degeneration in the ram and its relation to the temperature of the scrotum.

Summary. The semen collected from twelve Merino rams was examined before and after they were exposed during 3 days to two 6-hr periods in a climate room at 40·5° C, 8·5 mm Hg vapour pressure and 40·5° C, 31·5 mm Hg, respectively. Semen of decreased quality was collected from all the rams after this treatment. The change varied markedly in severity and duration and was related to the rise of the temperature of the subcutaneous tissue of the scrotum measured during the climate-room treatment and not to changes in rectal or flank-skin temperatures. The first ejaculate containing abnormal spermatozoa was collected 13 to 21 days after the treatment, and the concentration and total content of fructose in the semen of all rams started to rise at this time. The three rams which were most severely affected suffered a seminal degeneration which lasted for 35 to 39 days. After recovery from the first experiment, the same rams were divided into three groups of four. Two groups were exposed to the same heat treatments as before and the third group stood in the climate room for 12 hr at 21° C and 6·8 mm Hg vapour pressure. Water at 17 to 19° C was circulated around the scrotum of one group of rams exposed to heat and of the group in the thermo-neutral environment. Only the rams exposed to heat without their scrota cooled in this way produced semen of inferior quality. It was concluded that under the conditions of these experiments, the efficiency of the heat-dissipating properties of the scrotum alone decided the magnitude of the adverse effects of short periods of raised air temperature on the quality of the semen produced by Merino rams.

Ignition of a Thermionic Cathode Arc

Ignition of a thermionic cathode discharge in mercury vapor at the low applied potential of 2.4 V is shown to be the result of a potential minimum in space 0.8 V below the cathode, and of a favorable contact potential difference. Good emitters require more voltage to fire than high work function cathodes. Using an argon buffer gas at about 3.5 mm Hg pressure, ignition is easiest with an added Hg vapor pressure of 1.85 mm. Adequate pressure is required because of the two-stage ionization which produces ignition. This process applies also to the noble gases, and requires that ignition cannot occur with electron energy less than half the ionization potential.