Effect of temperature programmes on protein crystallisation

Varying the temperature has been proven to be beneficial for improving the screening efficiency of protein crystallisation, and thus a crystallisation screening strategy based on this phenomenon can be developed. Such a temperature varying strategy can be applied in practical crystallisation screening, however, there are no guidelines for determining what temperature programme should be utilised. It is therefore necessary to investigate how the temperature programme affects the crystallisation process, so as to help people design a suitable temperature programme. For this purpose, we investigated the effect of temperature programmes on the protein crystallisation (lysozyme, proteinase K, and concanavalin A) that are characterised by different solubility behaviours with respect to temperature. Judging from the reproducibility studies of protein crystallisation with different temperature programmes, we recommend using linear temperature programmes for a moderate time period (24 to 48 h) and a large temperature range according to the properties of the proteins. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Tunneling injection temperature dependence in EEPROM cell

In this paper we propose a new model of the EEPROM tunnel capacitance that takes into account temperature dependence. For this purpose, non-quasi-static C(V) measurements are made in order to extract the tunnel capacity physical parameters. Temperature dependence of the interface state density occupation was evaluated. Simulation of surface potential with temperature variation was implemented. We propose a complete electrical simulation of tunnel capacitance with temperature dependence. Finally, temperature EEPROM cell working simulations are presented.     

Indentation response of glass with temperature

The mechanical response of different glasses to a Vickers indentor has been investigated between room temperature and T_g+50 °C. The permanent deformation, from which hardness is estimated, as well as the brittle fracture characteristics, allowing for an evaluation of the fracture toughness, were measured and analysed. Comparison between a standard float glass and advanced glasses such as chalcogenide (with mainly covalent bonding) and metallic glasses was made to get a more general insight into high temperature indentation behaviour. As temperature increases, the glass response becomes more and more time-dependent, and in the vicinity of T_g the permanent deformation was observed to increase rapidly for all glasses. Further, while the standard float glass showed an enhanced apparent toughness at elevated temperatures due to a brittle to ductile transition, almost no change in apparent toughness was revealed in the GeAsSe glass emphasizing the time-dependent response of glass at elevated temperature.     

Characteristic temperature of deformation of crystalline materials

Using the ceoncept of a characteristic deformation temperature, t^* (knee temperature), below which the PEIERLS -NABARRO stress becomes significant, some general regularities have been determined on the influence of temperature upon structural state and mechanical properties of crystalline materials. It is demonstrated that t^* represents a natural boundary between the intervals of warm and cold deformation. At the temperature t^*, the mechanisms of deformation, fracture, and recovery of properties in annealing vary significantly in the same manner for different crystals.     

The glass transition temperature versus the fictive temperature

A comparison of the values of the glass transition temperature (T_g) measured on cooling and the limiting fictive temperature measured on heating as a function of cooling rate is performed for a polystyrene sample using both capillary dilatometry and differential scanning calorimetry (DSC). The results from both techniques indicate that is systematically lower than T_g presumably due to the breadth of the relaxation on cooling. The Tool-Narayanaswamy-Moynihan (TNM) model is used to fit the experimental data from dilatometry and DSC in order to ascertain the origins of the higher value of T_g compared to .     

Analysis of the diameteral response of a czochralski crystal II. The melt temperature — furnace temperature relation

The paper is the second in a series which presentes results on the small-signal diametral response of a Czochralski crystal grown in a resistively heated furnace to variations in heater temperature and pull rate. Here it is shown that the small-signal bulk melt temperature variation is related to the small-signal furnace temperature variation via a first order linear differential equation.     

Lysozyme crystallization in a precision-controlled temperature gradient

The possibility to control the crystallization process of biomaterials by the temperature was examined by the mathematical simulation of lysozyme crystallization. The precision-temperature control with creation of a local temperature gradient in solution was demonstrated to allow the growth of lysozyme crystals with high structural perfection.     

Glassy states: Concentration glasses and temperature glasses compared

The behavior of glass-forming systems in the equilibrium state above the glass temperature is still a heavily investigated field. Surprisingly, the behavior of the glass itself is less widely investigated. Even less investigated is the behavior of glass-forming materials in which composition is changed. Here we look at the behavior of glasses after temperature-jumps and compare that behavior with that of glasses subjected to concentration-jumps. Moisture and carbon dioxide are used as the plasticizing environments. Surprisingly, the glass created by jumping (down) to a given final condition via a change in concentration is more stable than that formed by a change in temperature – this in spite of the external condition of temperature and chemical activity (RH or carbon dioxide pressure) being the same. Furthermore, the concentration glass under such conditions has a higher excess volume than the temperature glass and its response does not ‘merge’ with that of the temperature glass, hence, the concentration glass is not the same as a temperature hyperquenched glass.     

Calculation of temperature fields in a cylindrical heater system

A model for calculation of time dependent temperature fields in a cylindrical furnace used for crystal growth experiments is described. The comparison of the calculated and the experimental temperature profiles shows good agreement in the stationary case and the suitability of the model for the prediction of static temperature fields on the basis of given heating power distributions, and vice versa.     

Strain history effects at low temperature deformation

The work hardening coefficient of hep metals like Zn or Cd depends on the temperature even at very low temperatures. Additional information of the processes involved can be derived from specially designed annealing experiments. If deformed single crystals of Zn, Zn + 0.2 at.% Ga and Zn + 0.2 at.% Ag are annealed the work hardening increases. The amount of increase depends on deformation temperature and annealing time. The effects observed suggest that the work hardening is determined at least partly by the mobility of points defects.     

Growth of dendritic cobalt nanocrystals at room temperature

Dendritic cobalt nanocrystals have been synthesized by the reduction of Co²⁺ with hydrazine hydrate in ethanol via a room temperature solution synthetic route. The magnetic coercivity H_c of as-prepared cobalt dendrites came up to 500 Oe at room temperature. We chose different solvents to control the phases and morphologies of the cobalt products.     

Anomalous temperature dependence of sub-critical crack growth in silica glass

The effects of temperature, water vapor, and stress on the rate of sub-critical crack growth (SCG) in fused silica are reported. The crack velocity was measured using the double-cleavage-drilled compression method. In contrast to other inorganic oxide glasses, crack growth velocities (in region I) were found to decrease with increase in temperature. Hence a small temperature rise has the apparent effect of improving the mechanical strength of a stressed-glass part. Despite the anomalous temperature dependence, SCG in fused silica is still likely governed by the established water-enhanced stress-corrosion mechanism; another competing phenomenon is proposed to cause the observed temperature dependence. Measured crack velocities are described using an empirical model (for region I) and a mass-transport model limited by Knudsen diffusion (for region II).     

Electric twinning in quartz by temperature gradient

This paper presents a new method for obtaining electric twins in quartz crystal: thermal treatment in a temperature gradient at about 500 °C, that means under phase transition point. + 5X quartz crystal plates for resonators were used; a temperature gradient of 15–25 °C was applied for 4–5 hours along the Y axis (the place length). For + 5X resonators, the diminution of the resonant frequency and the increase of the inductance were plotted as a function of the level of twinning.     

Experimental measurement of temperature distribution across a loop-like heater

A new method for in situ measuring the temperature distribution of small loop-like heater for crystal growth in space is proposed. The existence of thermocouple and other attachment may cause the non-uniformity of the heater temperature distribution.     

Fictive temperature measurement of alumino-silicate glasses using IR spectroscopy

A simple IR reflection method was used in a previous study to determine the fictive temperature of silica glasses and a soda-lime glass. The IR method is based upon the fact that the silica structural band of a glass takes a unique wavenumber at a particular fictive temperature. When this method was applied to an alumino-silicate glass in this study, however, the IR reflection peak wavenumber of the glass surface was found to be strongly affected by the reaction of the glass with water vapor in the atmosphere. Still, it was possible to measure the fictive temperature of the alumino-silicate glass using IR spectroscopy by taking an IR reflection of the bulk sample after eliminating the surface layer affected by the reaction with water vapor. The IR peak wavenumber of the silica structural band decreased with increasing fictive temperature for the alumino-silicate glass, similar to silica glass.     

Thermoelectric monitoring of the interface temperature during Czochralski growth of InSb

A novel method of interface temperature detection is described in which the junction of the crystal and melt acts as the hot limb of a thermocouple. Theoretical analysis shows that although the method at present cannot measure absolute temperature, measurements of medium frequency (approximately 0.2 Hz) temperature variations can be very sensitive. This technique was applied during the growth of InSb, and temperature variations similar to those found by other workers using thermocouples in convectively unstable melts were detected.     

Prediction of maximum homogeneous nucleation temperature for crystallization of metallic glasses

A graphical method is used to find out the viscosity at any temperature between the melting temperature and glass transition temperature, which in turn is used to predict the temperature corresponding to the maximum in homogeneous nucleation rate. The present approach does not need any critical experimental data and the model predictions are very close to those experimentally measured in known metallic glasses. This model can be applied for both pure metals and glass forming alloys.     

Quantum effects in low temperature plastic deformation

A quantum mechanical calculation of the transition rate of a dislocation segment across an obstacle of finite width is performed. Compared with previous theories the achievement of the new treatment is that the finite compliance of the force distance profile is taken into account in the evaluation of the oscillatory modes. As a consequence, not only the DEBYE temperature of the dislocation line but also the obstacle compliance enters the transition rate and determines the temperature regime in which quantum effects become observable. Furthermore, the results of classical thermal activation theory that is valid at high temperatures are for the first time derived from first principles.     

AlAs-in-AlSb digital alloy superlattice morphology versus growth temperature

We report a systematic study of how growth temperature affects the quality of AlAs-in-AlSb digital alloy superlattices grown by molecular beam epitaxy for barrier layers in type-II W-structure infrared lasers. Using cross-sectional scanning tunneling microscopy to characterize the atomic-scale structure of the material, we find substantial differences in the superlattice morphology for growth temperatures between 435 and 540 °C. At lower growth temperatures, the AlAs forms three-dimensional clusters, with continuous structures threading through multiple periods of the superlattice. With increasing temperature, the morphology of the digitally doped AlAs layers consistently improves, with nearly perfect delta doping observed at the highest temperatures studied. The changes in the superlattice structure can be attributed primarily to the known temperature dependence of the AlSb growth front morphology, with secondary effects associated with anion-exchange at the interfaces and the different surface reconstructions on the two growth surfaces.     

On temperature dependence of Debye-Waller factor in V3Si in the temperature range from 8 to 293 K

The temperature dependence of the Debye-Waller factors of vanadium and silicon in V₃Si and that of the X-ray Debye temperature are obtained from the integral intensities of X-ray reflection measured at 11 temperatures ranging from 8 K to 293 K. It shown that the breaks on these curves are observed at T_br = 21.7 K. This fact allows to assume that the phase transition in this compound is accompanied by the rapid change of the atomic vibration frequencies.