Effect Of Sample Temperature Research Articles

Enhanced Gold Nanoparticle Mobility in Thermoresponsive Hydrogels Caused by Localized Light-to-Heat Conversion, Leading to a Superdiffusive Particle Transport

We study the local mobility of light-absorbing gold nanoparticles in a thermoresponsive poly-N-isopropylacrylamide hydrogel by laser light scattering. On the basis of the effect of sample temperature, gold particle size, and laser power on the time dependence of scattered intensity fluctuations, we conclude that the movement of the nanoparticles is stimulated by localized light-to-heat conversion and a corresponding change in the structure of the gel. A slowing down and decay in amplitude of these scattered fluctuations with sample irradiation time are interpreted as an outward migration or superdiffusion of the gold nanoparticles from the heated scattering volume to colder regions of the hydrogel, explained by a local change in the mesh structure within the heated parts of the thermoresponsive hydrogel and a corresponding gradient in nanoparticle mobility.

Temperature dependent current–voltage characteristics of the Cd/CdO/n–Si/Au–Sb structure

In this study, this is the first time, it has been employed Successive Ionic Layer Adsorption and Reaction (SILAR) method in order to prepare Cd/CdO/n–Si/Au–Sb sandwich structure. The sample temperature effect on the current–voltage ( I– V) characteristics of Cd/CdO/n–Si/Au–Sb structure has been investigated in a wide temperature range by steps of 20 K. The parameters such as barrier height, ideality factor and series resistance of this structure have been calculated from the forward bias I– V characteristics as a function of sample temperature. With a decreasing temperature, a decreasing in the apparent barrier height ( Φ b 0) , an increasing in the ideality factor ( n) and a nonlinearity in the activation energy plot have been seen. The experimental values of barrier height and ideality factor for this device have been calculated as 0.871 eV and 1.787 at 300 K and 0.436 eV and 2.221 at 80 K, respectively. These abnormal behaviors can be explain by the barrier inhomogeneities at the metal–semiconductor ( M– S) interface. From the temperature dependent I– V characteristics of the Cd/CdO/n–Si/Au–Sb sandwich structure, Φ ¯ b 0 and A ∗ are calculated as 0.790 and 1.160 eV, and 153.90 and 188.42 A/cm 2 K 2, respectively, by using ln ( I 0 / T 2 ) - q 2 σ s 2 / 2 k 2 T 2 vs . 1 /T plot for the two temperature regions. Deviation of experimental values of A ∗ from known value for n–Si has been attributed to the spatial inhomogeneous barrier heights and potential fluctuations at the interface that consist of low and high barrier areas.

Structural effects of shot-peening in bulk metallic glasses

Shot-peening induces surface compressive stresses in bulk metallic glass components, improving their plasticity. Structural changes in the peened surface of fully glassy and partially crystalline Zr 55Al 10Cu 30Ni 5 are studied by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. An earlier study is extended by examining the effect of sample temperature. While fully glassy samples show no phase change under peening, partially crystalline samples show either amorphization or crystallization depending on temperature. Peening can induce very large stored energy in metallic glasses rendering them susceptible to crystallization below room temperature, a result which may be relevant for improving the plasticity of these materials.

Effect of sample temperature on laser-induced breakdown spectroscopy

The effect of initial sample temperature on spectral emission of laser-induced plasma has been investigated. The plasma has been produced on aluminum alloy surface at ambient air pressure. The sample has been uniformly heated by a heating element up to 150 °C. The spectral emission of aluminum at different initial sample temperature and gate delay times has been measured. A simple model has been improved in order to compare the analytical and experimental results. An increase in sample temperature leads to an increase in the area under spectral line profiles. The results suggest that increasing the sample temperature can improve the limits of detection (LOD).

INVESTIGATIONS OF THE INDENTATION-INDUCED CRYSTALLOGRAPHIC PHASE CHANGES IN SILICON USING RAMAN SPECTROSCOPY

Raman spectroscopy, which is a non-destructive technique, has been used to investigate the effect of sample temperature on indentation-induced crystallographic phase transitions in crystalline silicon and amorphous silicon films deposited on a sapphire crystal. It has been shown that in both types of sample, whereas 300 K Vickers diamond indentations lead to the transformation to the Si -II phase during indenter loading on the crystalline and amorphous samples, there is no such transformation in either sample when it is cooled down to 77 K. An explanation of the experimental results has been provided using the pressure–temperature phase diagram of silicon.

Effect of sample temperature on the indentation-induced phase transitions in crystalline silicon

Using four-terminal in-situ dc electrical resistance measurements and Raman spectra of residual Vickers indentations in single crystals of Si (100), it has been shown that the sample temperature, in the range of 150 to 300 K, at which a Vickers diamond indentation is made, has a strong influence on the occurrence of indentation-induced phase transitions within the plastically deformed zone around the indentation. A consistent explanation of the experimental results, based on an existing theoretical pressure-temperature phase diagram of silicon, has been provided.

Use of Near-Infrared Spectroscopy for Monitoring Fermentation in a Corn Dry Grind Ethanol Process

The objective of this study was to determine suitability of near-infrared (NIR) spectroscopy to predict various fermentation quality indicators such as ethanol, total soluble sugars, fermentable sugars, glucose, maltose, maltotriose, glycerol, and organic acids in the fermentation broth for a corn dry grind process. Effects of sample temperature on spectral absorption were identified and related to loadings of principal component scores. Partial least squares 1 (PLS1) calibration models were built on spectra obtained from a 5 mm pathlength transmission accessory and from a 0.5 mm transflectance accessory. Prediction results from calibration on both accessories were compared. Lactic acid and acetic acid were present at very low levels and did not appear to separate from the other fermentation constituents for the given pathlength and concentrations observed. External validation for ethanol had RMSEP values of 1.5% v/v, the larger portion of which was contributed by a large bias of 1.4% v/v, while the SEP (indicating precision of the model) was 0.6% v/v with two factors. External validation for total soluble sugars had RMSEP values of 1.5% v/v, the larger portion of which was contributed by the SEP with a value of 1.4% v/v, while the bias was 0.5% v/v with two factors. The RPD values obtained from the external validation for ethanol and total soluble sugars were 6.0 and 5.0, respectively. Total soluble sugar calibration had low RMSEP and high RPD values, while fermentable sugars, glucose, maltose, maltotriose, and glycerol had high RMSEP values and low RPD values. High RPD and low RMSEP values for both ethanol and total soluble sugar prediction validated the suitability of the near-infrared spectroscopy for monitoring of the fermentation process.

On-Line Determination of the Molar Ratio between Methanol and Isobutylene in Feedstock of a Methyl Tertiary Butyl Ether Production Plant Using Near-Infrared Spectroscopy

The molar ratio between methanol and isobutylene (MRMI) is very important to the operation of methyl tertiary butyl ether (MTBE) production units. A new on-line near-infrared (NIR) analytical system was integrated for monitoring the MRMI in real time and was successfully applied in a rubber plant. Calibration models for methanol and isobutylene were established using partial least squares (PLS). The sample temperature effect on the performance of the models is discussed. The MRMI is calculated by methanol content and isobutylene content predicted by NIR. A large benefit has been obtained by the user through controlling the operation of the unit according to the monitoring of the MRMI of the feedstock in real time.

CATHODOLUMINESCENCE AND THERMOLUMINESCENCE STUDIES OF CLAY MINERALS

Cathodoluminescence (CL) measurements of clay minerals were performed at both room temperature and low temperature. Panchromatic CL images of kaolinite and dickite show blue emission at room temperature. Their CL spectra exhibit an intense broad band peak at around 375 nm. This emission band related to radiation induced defect centers (RID) disappears at low temperature. Effect of sample temperature on CL intensity of kaolinite and dickite can not be interpreted on the basis of a temperature quenching theory. In halloysite, serpentine minerals, sericite and sepiolite, the intensity of a broad band between 400 and 450 nm is higher at low temperature than at room temperature. CL spectra of serpentine minerals are characterized by a broad band centered at 720 nm, which can be assigned to Fe 3+ impurity center. Natural TL glow curve of sepiolite presents two glow peaks around at 210 and 260°C in the high temperature region, of which intensities are weak. This implies that it is rather a possibility of applying TL of sepiolite to the dating. The other minerals show no emission in natural TL measurements. X-ray induced TL of kaolin minerals exhibit intense several TL glow peaks below room temperature. Serpentine minerals have glow curves with a relative large peak between 70 and 90°C. Sericite, montmorillonite and sepiolite show a combination of emission peaks in their TL glow curves, while their intensities are weak compared to kaolin and serpentine minerals. Clay minerals might have characteristic TL related to their crystal structure.

The effect of sample temperature on instrumental and sensory properties of mashed potato products

SummaryThe effect of sample temperature on texture, firmness and the sensory attributes of fresh and frozen/thawed natural and commercial mashed potatoes was studied. Scanning electron microscopy was used to obtain information on the structure of potato cells and how this is affected by processing. Various parameters were measured and were found to increase at 55 °C, these changes could be related to gelatinisation of the starch remaining in the products. In natural mashed potato, texture profile analysis (TPA) and firmness parameters were lower in the processed than in the fresh samples, indicating a weakening of the structure; this was confirmed by photomicrographs. In commercial mashed potato, TPA parameters measured at 55 and 65 °C and firmness parameters measured at 25 °C were higher in the processed samples, indicating enhanced structural strength; this was confirmed by photomicrographs. Firmness per gram of product was the best instrumental parameter for measuring texture in these products. The results of the different analyses indicated that 55 °C was the preferred temperature for consumption of mashed potatoes.

Effects of sample temperature in femtosecond single-pulse laser-induced breakdown spectroscopy.

As much as tenfold atomic emission enhancements have been observed in experiments combining nanosecond (ns) and femtosecond (fs) laser pulses in an orthogonal dual-pulse configuration for laser-induced breakdown spectroscopy (ns-fs orthogonal dual-pulse LIBS). In the examination of one of several potential sources of these atomic emission enhancements (sample heating by a ns air spark), minor reductions in atomic emission and as much as 15-fold improvements in mass removal have been observed for fs single-pulse LIBS of heated brass and aluminum samples. These results suggest that, although material removal with a high-powered, ultrashort fs pulse is temperature dependent, sample heating by the ns air spark is not the source of the atomic emission enhancements observed in ns-fs orthogonal dual-pulse LIBS.

Rheological behaviour of fresh and frozen potato puree in steady and dynamic shear at different temperatures

Rheological behaviour of natural and commercial potato purees was studied in steady and dynamic shear conditions at sample temperatures ranging from 25–65 °C. Both types of puree were frozen-then-thawed to determine how changes occurring in their structure affected their rheological behaviour. All of the purees presented shear-thinning behaviour with yield stress. Dynamic shear data revealed weak gel-like behaviour in the purees: magnitudes of G′ were higher than those of G″, and both increased with frequency. For fresh natural puree and fresh and frozen/thawed commercial puree, the frequency dependence of G′ increased, and the frequency dependence of G″ decreased with sample temperature. Processing weakened the structure of natural puree but resulted in a coarsely aggregated structure in commercial puree. The effect of sample temperature on dynamic parameters was more significant in processed than in fresh purees. The Cox-Merz rule was not applicable to the steady and dynamic shear data on all of the purees. For fresh natural puree, the two types of data conformed to the use of shift factor on frequency, and therefore for this product it would be possible to estimate steady shear data from dynamic shear data, and vice versa. For fresh commercial puree, the relationship between steady and dynamic shear data was non-linear. In both processed purees, the linearity or otherwise of the relationship between viscosities was dependent on sample temperature.

Oxidation Properties of Hydrogen-Terminated Si(001) Surfaces Following Use of a Hyperthermal Broad Atomic Oxygen Beam at Low Temperatures

The oxidation properties of an H-terminated Si(001) surface following the use of a hyperthermal broad atomic oxygen beam have been studied at low temperatures. Effects of sample temperature, flux and energy of the impinging atomic oxygen on the oxidation of silicon were investigated by X-ray photoelectron spectroscopy. It was confirmed that oxide growth at the surface was achieved even at room temperature and the oxide thickness reached a terminal thickness of a few nanometers depending upon the oxidation conditions. The oxidation process was divided into two stages: the fast oxidation stage and the subsequent slow oxidation stage. It was also confirmed that the reaction yield of atomic oxygen with Si increased with increasing translational energy. The characteristic feature of beam oxidation was explained by the effect of energy accommodation from the impinging oxygen atom to the surface silicon atom.

Investigation into the effects of indium, and the purity of precursor materials on the scintillation yield of cerium-doped heavy metal fluoride glasses for electromagnetic calorimetry in particle physics

The properties of heavy metal fluoride glasses have been investigated to assess the potential for using these materials to construct electromagnetic calorimeters for particle physics. We report here on measurements of scintillation yield, transmission and decay time, on large blocks of CeF 3-doped HfF 4-based glasses. The effects of sample temperature, the addition of Ce and In, ZrF 4 concentrations, and different HfF 4 feedstocks, have also been studied. The samples were excited by a high energy proton beam and the associated scintillation yield and time structure was measured. The optical transmission of the samples was measured. It was observed that by comparing the time dependence of scintillation yield with optical transmission, the relative contributions of quenching and absorption in reducing optical yield could be separated. It was concluded that variations in HfF 4 feedstock purity can be a dominant factor in determining affective scintillation yield of large glass samples.

Structural analysis of nanocrystalline SiC thin films grown on silicon by ECR plasma CVD

Wide bandgap emitters on crystalline substrates are an active area of research for use in heterojunction silicon solar cells. We have deposited high conductivity SiC containing large concentrations of β-SiC crystallites. The effect of sample temperature and gas concentrations on the stoichiometry of the material has been investigated. Depending on process parameters, we find these films consist of varying concentrations of β -SiC crystallites, amorphous silicon, amorphous silicon carbide alloys and C C phases. The contribution of these material features to high and low conductivity in these films is assessed here. In order to facilitate this analysis we have used elastic recoil detection analysis (ERDA) and secondary ion mass spectrometry (SIMS) for atomic concentrations. Raman spectroscopy has been used for the detection of amorphous silicon, amorphous SiC and carbon based phases in the films. X-ray diffractometry has also been used to determine the crystallinity. The results from these techniques are correlated with film properties.

Accuracy and precision of the portable StatPal II and the laboratory-based NOVA stat profile 1 for measurement of pH, P(CO2), and P(O2) in equine blood.

To investigate the accuracy and precision of the portable, battery-powered StatPal II and the laboratory-based NOVA StatProfile 1 blood gas and pH analyzers for use in analysis of equine blood. Patient sample comparison and whole blood tonometry. Patient sample comparison: 125 arterial or venous blood samples from 49 healthy, awake, or anesthetized horses or ponies. Tonometry: venous blood samples from 11 healthy Thoroughbred horses. Arterial and venous blood taken from awake and anesthetized equine patients was placed in an ice-water bath, then analyzed within 30 minutes of collection. Bias and limits of agreement between analyzers in measurement of pH, P(CO2), and P(O2) were calculated according to the method of Bland and Altman. Tonometry, using analyzed gases with a range of P(O2) of 28 to 286 mm Hg and P(CO2) of 21 to 85 mm Hg, was performed on equine whole blood or blood with abnormally high (55%) or low (20%) hematocrit. Samples were introduced directly from the tonometer into the analyzers. Inaccuracy (% of target value) and imprecision (coefficient of variation) were determined for each instrument. In addition, results of analysis of blood samples introduced into the analyzers at 36 degrees C, 0 to 3 degrees C, and 22 degrees C were compared. In the patient sample comparisons, bias between analyzers (StatPal-NOVA) for measurement of P(O2) less than 60 mm Hg was -0.33+/-6.2 mm Hg (x +/-2 SD) and for P(O2) between 60 and 110 mm Hg bias was -1.48+/-9.2 mm Hg. Bias was 46.5+/-67 mm Hg (significantly different from bias at the lower P(O2) levels) for measurement of P(O2) values of 111 to 505 mm Hg, and at P(O2) values greater than 110 mm Hg, bias increased with increasing P(O2). During the course of the study, a significant shift in bias between instruments occurred for P(CO2) and pH measurement, coincident with a change of P(CO2) and pH electrodes in the NOVA and use of a new lot of StatPal sensors. Bias (StatPal-NOVA) for P(CO2) before and after the electrode change was -3.74+/-4.2 and -0.88+/-6.8 mm Hg, and bias for pH before and after the electrode change was 0.026+/-0.034 and -0.024+/-0.038. The change in bias was significant (P<.05). In the whole blood tonometry trials, mean recovered values of P(CO2) and P(O2) from blood with a normal hematocrit ranged from 94% to 109% of target values for StatPal and from 98% to 107% for NOVA. Imprecision ranged from 3.3% to 5.3% for StatPal and from 2.2% to 4.3% for NOVA. With extremes of hematocrit (55% and 20%), StatPal's mean recovered P(CO2) values were 115% and 112% of the target value of 21 mm Hg, whereas NOVA's recovered P(CO2) values were similar to those recovered from samples with normal hematocrit. Introduction of cold blood samples (0 to 3 degrees C) into StatPal resulted in P(CO2) readings that were approximately 2 mm Hg lower than those of 22 degrees C and 36 degrees C samples (P<.05). No other effects of sample temperature were found for either instrument. StatPal and NOVA are of similar accuracy and demonstrate acceptable precision for measurement of P(CO2) and P(O2) in equine blood with values in the normal arterial and venous range. Mean recovered values during tonometry differed by as much as 10% between instruments, indicating that they should not be used interchangeably for a single patient or for a group of subjects in a research setting. The StatPal is a portable blood gas analyzer of acceptable accuracy and precision, for clinical or investigational work in horses.

Infrared laser ablation and atomic emission spectrometry of stainless steel at high temperatures

Laser-induced breakdown spectrometry has been evaluated at high temperatures for stainless steel samples. A Q-switched Nd:YAG laser operating at 1064 nm was used to create a microplasma on an AISI 304L stainless steel sample placed inside a laboratory oven. The steel sample was 51.5 cm away from the focusing lens. The temperature of the samples ranged from 25 to 1200 °C. The plasma light was collected by means of a fiber optic bundle, spectrally resolved and then detected by a CCD camera. The effects of sample temperature in the formation of a laser-induced plasma have been studied in terms of its spectral features as well as the morphology of the ablated craters in air at atmospheric pressure. A noticeable dependence of signal emission intensity on sample temperature has been found. Depth profiling of stainless steel samples for several temperature conditions was performed. Results have revealed changes in the superficial composition at temperatures above 600 °C due to the formation of a slag layer of variable thickness, mainly composed of chromium, iron and manganese oxides.

Influence of Sample Temperature on Reflectance Photometry and Electrochemical Glucometer Measurements

A study was conducted to determine the influence of sample temperature on manual reflectance photometers, automatic reflectance photometers, and electrochemical glucometers. Aqueous and blood-based control solutions were tested at temperatures ranging from 25 to 44 degrees C. With the Accu-Chek 3, One Touch, and Satellite G glucometers, multiple glucose determinations were performed on each sample. The results indicate that the manual reflectance photometry glucometer is prominently influenced by variation in sample temperature. The effect of sample temperature is greatest at high glucose levels. Caution may be required in the interpretation of manual reflectance photometry glucometer measurements in febrile or hypothermic diabetic patients.

Effect of sample temperature on the irradiation effects of energetic particles in the YBCO system

16O ions at 75 MeV incident energy have been used to study the irradiation effects on the normal state resistance variation with fluence. The studies conducted include the measurement of resistance variation with dose due to the ion used. The samples were the bulk sintered pellets of YBa 2Cu 3O 7 − x maintained at normal temperature ( T ∼ 300 K) and low temperature ( T ∼ 100 K). In the case of a sample irradiated at normal temperature there is a continuous decrease in resistance with dose, while in the other case there is a minimal change in the resistance vs fluence curve. These experimental results reveal that the sample temperature has a special effect on the damage mechanism.

Artificial weathering procedures for plastics glazing materials

Transparent or translucent plastics glazing materials are of light weight, tough, easily formed into complex shapes and transmit light well. This useful combination of properties allows widespread use in construction, for example as rooflights. However, the plastics used are more susceptible to degradation by weathering than the traditionally used glass, notably the combined effects of ultraviolet light, heat and moisture. Complete inhibition of degradation is not possible but the general world trend to an increase in the use of plastics in external applications has led to the development of many new products which improve stability and increase component service life. However, examples of unacceptable durability have been seen in practice, particularly when high operating temperatures in sunlight occur. Hence the need for reliable artificial weathering tests to assess proposed combinations of plastics glazing materials in a reasonably short time. The procedures described in this paper take account of the revisions currently proposed in ISO/TC61 for ISO 4892: Plastics — Methods of Exposure to Laboratory Light Sources, including Part 2: Xenon Arc Sources and Part 3: Fluorescent uv Lamps. In conducting these tests particular consideration is given to the control and effects of sample temperature. Test procedures are assessed for their degradative effects on commercial glazing materials of polyvinylchloride, acrylic and polycarbonate, including examples of surface-coated and thermoformed sheets. Procedures based on xenon arc sources appear to be most generally applicable because the full solar wavelength range is needed to promote the effects observed in practice. The method of mounting strongly influences the temperature of transparent test pieces and thus the test results, enabling the temperature sensitivity of materials and products to be investigated.