Different Temperatures For Various Durations Research Articles

Survival of murine norovirus and hepatitis A virus in bottled drinking water, strawberries, and oysters

The survival of murine norovirus (MNV) and hepatitis A virus (HAV) in bottled drinking water, strawberries, and oysters stored at different temperatures for various durations was investigated. In drinking water, over 6.4 and 1.6 log 10 plaque-forming units (PFU/mL) reductions of viable MNV and HAV were observed after 20 days of incubation at 35 °C. After 160 days of incubation at 20 °C, there was a sharp decrease in the MNV (>6.4 log 10 PFU/mL) and HAV (>2.9 log 10 PFU/mL) load but only a slight reduction at 4 °C. In fresh strawberry, the MNV and HAV titers reduced by 1.0 and 0.9 log 10 PFU/g after incubation for 2 days at 25 °C, by 0.85 and 1.22 log 10 PFU/g after 3 days of incubation at 15 °C, and by 0.7 and 1.1 log 10 PFU/g after 7 days of incubation at 4 °C, respectively. After 3 days of incubation at 4, 15, and 25 °C in oyster reductions of over 0.3, 0.4, and 0.6 log 10 PFU/mL in the MNV load and 0.16, 0.28, and 0.52 log 10 PFU/mL in the HAV load were observed, respectively. Even though, survival of the two viruses fluctuated with temperature and food commodity. Therefore, our results indicate that major enteric foodborne viruses such as MNV and HAV can survive for long periods, with only a partial reduction in their titers. Owing to the persistence of foodborne viruses, preventive measures need to be taken to prevent food contamination. • MNV and HAV survival in drinking water, strawberries, and oysters was investigated. • MNV and HAV survivability varies with temperature and food type. • Enteric foodborne viruses can persist for a long time at 4 °C. • Study results could lay the foundation for the development of food hazard assessment models.

Linking chemical to rheological properties of asphalt binder with oxidative aging effect

ABSTRACT This study aimed to establish the chemical-rheological property relationships of asphalt binders subjected to oxidative aging. Five asphalt binders were aged in the oven at several different temperatures for various durations. The chemical characteristic in terms of carbonyl index and rheological characteristic in terms of complex shear modulus and phase angle. The aged asphalt binders were measured using the Fourier Transform infrared spectroscopy (FTIR) and Dynamic Shear Rheometer (DSR) techniques, respectively. During oxidative aging process, the carbonyl index was predicted using the Glover’s aging kinetic model. Crossover frequency and rheological index generated from the aging mastercurves, correlates well with the carbonyl index of asphalt binders, and the correlations are independent of aging temperature and time. Christensen-Anderson model is used in combination with crossover frequency-carbonyl index and rheological index-carbonyl index relationships to predict complex shear modulus and phase angle master curves of the binder with respect to aging.

Microstructure evolution, grain morphology variation and mechanical property change of Cu-Sn intermetallic joints subjected to high-temperature aging

In this work, the aging treatment was carried out on full Cu3Sn joints at different temperatures for various durations, the microstructure evolution, grain morphology variation and mechanical property change of joints were investigated. The temperature effects on the growth rate and grain morphology of Cu41Sn11 phase were found: The complete transformation from Cu3Sn phase to Cu41Sn11 phase in joints needed 300h at 400°C, but 4h at 500°C. The Cu41Sn11 phase formed at 400°C consisted of columnar grains with an average width of 23.5μm, while the Cu41Sn11 phase formed at 500°C consisted columnar grains with an average width of 8.5μm. The average hardness and shear strength values of the Cu41Sn11 joints formed at 400°C were 432.5HV and 62MPa, while the joints formed at 500°C exhibited higher hardness and shear strength (451.5HV and 65MPa). Besides, the Cu41Sn11 joint was found to exhibit a combination of transgranular and intergranular fracture during shear test.

Impacts of the annealing profile on AIC thin film solar cell characteristics fabricated by magnetron sputtering

Two different layer orders of p-Si/Al (as structure #1) and Al/p-Si (as structure #2) thin films were deposited on n-type mono-crystalline Silicon wafer and quartz glass by magnetron sputtering at 200 °C. The fabricated films were annealed at different temperatures for various durations. Then, they were analyzed by XRD, Raman and SEM methods. According to XRD results the largest grain size of both structures was smaller than 20 nm. The Raman spectra of the samples annealed at 1000 °C determined a crystallization ratio of 98% and 75% of structures #1 and #2 respectively. SEM images confirmed that the crystallization happened for structure #1 at lower temperatures than for structure #2. The impact of annealing on electrical and photovoltaic performance of the samples were studied after the fabrication of metal contact by sputtering of a few hundred nanometers of aluminium. The highest measured Voc were 360 and 402 mV, and the best Jsc were 2.2 and 0.12 mA/cm2, for structure #1 and #2 respectively.

W/Cu thin film infrared reflector for TiNxOy based selective solar absorber with high thermal stability

The W/Cu thin film structure is deposited by magnetron sputtering to form the infrared reflector for the TiNxOy based selective solar absorber (SSA) that can be used in the low- and middle-temperature applications. The structural, chemical, and optical properties of the SSA layers that experienced thermal annealing at different temperatures for various durations have been investigated with the characterization techniques, including X-ray photoelectron spectroscopy, X-ray diffraction, atomic force microscopy, spectroscopic ellipsometry, and spectrophotometry. Without a W layer, the reflectance in both visible and infrared ranges of the SSA increases as a result of the crystallization of the Cu layer at elevated temperatures. With a W layer with appropriate film thickness, the increase of the reflectance in the visible range can be suppressed to maintain a high solar absorptance, whereas a high infrared reflectance can be maintained to achieve a low thermal emittance. It is shown that for the SiO2-TiNxOy-W-Cu-Glass SSA with a 15 nm W thin film, thermal annealing can significantly reduce the thermal emittance to a low value (e.g., 4.4% at the temperature of 400 °C for annealing at 400 °C for 6 h), whereas the solar absorptance can be maintained at a high value (e.g., 92.2% for the annealing at 400 °C for 6 h).

Effect of SrO addition on the growth behavior of ZrO2–3Y2O3 precursor powders synthesized by a coprecipitation process

Effect of SrO addition on the crystalline growth behavior of ZrO2–3Y2O3 precursor powders using a coprecipitation process has been studied. Zirconium nitrate (Zr(NO3)4·xH2O), yttrium nitrate (Y(NO3)3·6H2O) and strontium nitrate (Sr(NO3)2) were used as the initial materials. Crystalline growth behavior was investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), nano beam electron diffraction (NBED) and high-resolution TEM (HRTEM). The XRD results showed the ZrO2–3Y2O3–xSrO only contained single phase of tetragonal ZrO2 (t-ZrO2) when the precursor powders were calcined at different temperatures for various durations. The crystallite size increased from 22.91 to 27.44nm when the ZrO2–3Y2O3–1SrO precursor powders after calcination at 823K from 15 to 120min. The activation energy values obtained are 9.98, 9.04 and 7.43kJ/mol for SrO addition amount of 1, 2 and 3mol%, respectively, and the kinetics equations of t-ZrO2 crystalline growth with SrO addition are also expressed as follows: D1SrO2=6.00×t0.13exp(−9.98×103RT),D2SrO2=6.02×t0.11exp(−9.04×103RT) and D3SrO2=6.13×t0.10exp(−7.43×103RT) with SrO content for 1, 2 and 3mol%, respectively, for 15≤t≤120min and 773≤T≤923K.

The mechanism of foaming and thermal conductivity of glasses foamed with MnO2

We prepare foam glass from cathode ray tube (CRT) panels using MnO2 as foaming agent at different temperatures for various durations. The reduction of MnO2 to Mn2O3 leads to formation of O2 gas, and hence, causes initial foaming. The Mn2O3 particles dissolve into the glass melt and subsequently reduce, causing further formation of O2 gas and foaming of the glass melt. Increasing the treatment temperature and time enhances foam expansion, Mn2O3 dissolution, and lowers the closed porosity. Once the foam reaches a percolated stage, the foam continues to grow. This is caused by nucleation of new bubbles and subsequent growth. We discuss evolution of pore morphology in terms of pore number density, pore size and closed porosity. The thermal conductivity of the foam glasses is linearly dependent on density. The heat transfer mechanism is revealed by comparing the experimental data with structural data and analytical models. We show that the effect of pore size, presence of crystal inclusions and degree of closed porosity do not affect the overall thermal conductivity.

Characterization of the effects of three Lactobacillus species on the function of chicken macrophages

Lactobacillus acidophilus, Lactobacillus reuteri and Lactobacillus salivarius can influence the adaptive immune responses in chickens but vary in their ability to do so. The present study attempted to identify how these three bacteria alter the innate immune system. A chicken macrophage cell line, MQ-NCSU, was co-cultured with the three live Lactobacillus species, alone or in combination, grown at different temperatures for various durations of time. Late exponential growth phase bacteria were more immunostimulatory, while bacterial growth temperature had little effect. L. acidophilus and L. salivarius significantly increased nitric oxide (NO) production and phagocytosis, while L. reuteri did not. In fact, L reuteri was shown to inhibit NO production of macrophages when co-cultured with the other bacteria or when cells were pre-treated with LPS. The results demonstrate a possible molecular mechanism for the immunomodulatory effects of L. acidophilus and L. salivarius, and a unique immunomodulatory ability of L. reuteri.

Growth behavior of nanosized ceria powders prepared by coprecipitation routes

Abstract Nanosized ceria (CeO 2 ) powders were obtained by coprecipitation routes of cerium nitrate hexahydrate [Ce(NO 3 ) 3 ·6H 2 O]. The growth behavior of the nanosized CeO 2 powders was investigated by X-ray diffraction, transmission electron microscopy and selected area electron diffraction. The XRD results showed that the dried precursor powders contained a single crystalline phase of CeO 2 , and only a single phase of CeO 2 appeared when the dried precursor powders were calcined at different temperatures for various durations. Moreover, the crystallite size of CeO 2 increased on increasing the calcination temperature and duration. The kinetics equation of the nanosized CeO 2 powders grown between 673 and 1273 K for various durations is described as D t − D 0 = k t m exp ( − 56.42 × 10 3 / R T ) where k =7.5×10 −1 and m =0.20 when t ≤360 min and 673 K≤ T ≤873 K; k =8.46 and m =0.43 when 5 min≤ t ≤30 min and 1073 K≤ T ≤1273 K; and k =3.17×10 and m =0.03 when 30 min≤ t ≤360 min and 1073 K≤ T ≤1273 K.

Formation of aluminide phases on electrodeposited nanocrystalline nickel

The formation and growth of aluminide phases during pack cementation of electrodeposited nanocrystalline (NC) nickel were investigated and compared with microcrystalline (MC) nickel. MC and electrodeposited NC samples were aluminized at different temperatures for various durations. The microstructure of aluminized specimens was studied by means of SEM and XRD methods. The results showed that the aluminizing time needed for the onset of formation of aluminide phases on NC samples was shorter than MC specimens at all investigated aluminizing temperatures. The aluminide coating formed on MC samples always consisted of Al 3Ni 2 single layer, whereas the coating formed on NC nickel was Al 3Ni 2 single layer or Al 3Ni–Al 3Ni 2 double layers depending on aluminizing time and temperature.

On the uniform elongation of cast Al–7%Si–0.6%Mg (A357) alloys

Continuously cast A357 alloy specimens that are essentially free from structural defects, such as oxide bifilms and porosity, were artificially aged at three different temperatures for various durations. The stress–strain curves of 90 specimens were analyzed. It was determined that in A357: (i) nonuniform elongation can be up to 38% of total elongation, (ii) nonuniform elongation can be as high as 5%, (iii) for the same yield strength, uniform elongation is a lower fraction of the total elongation in the overaged specimens than in the underaged, (iv) the strain-hardening exponent, n, of the Ludwik–Hollomon equation changes linearly with yield strength in underaged and overaged conditions, (v) n provides a poor estimate of the uniform elongation, and (vi) the Voce equation estimates the uniform elongation accurately.

σ phase dissolution in duplex stainless steel at elevated temperature studied by thermal analysis

The redissolution of σ phase to ferrite in duplex stainless steel (DSS) in high temperature range was studied by differential thermal analysis (DTA) and scanning electron microscopy. DSS samples were aged at different temperatures for various durations. The conditions were chosen such that all the ferrite transformed to σ phase. Subsequent DTA measurements revealed that the onset temperature T s and the peak temperature T p for sigma dissolution strongly depend on the initial distribution and the morphology of σ phase. This correlation between the DTA characteristic temperatures and prior ageing temperatures may be used for temperature indication purposes in applications involving hostile environments.

Microstructural Evolution in Niobium-Based Alloys

Nb-Ti-Cr-Si-Al-X alloys have been considered as candidate materials for high-temperature structural applications in aero engines. Using a multicomponent approach, attempts are being made to obtain good strength with adequate oxidation resistance at the expected operating temperatures (∼1073 through 1273 K) in these alloys. In the microstructure of these alloys, which essentially consist of the silicide phase distributed in the bcc β matrix, the presence or absence of the Laves phase can bring about considerable changes in the mechanical properties. The present article reports on the instability observed in the β phase and also on the formation of the Laves phase in the β matrix. The extent of the chemical separation and elements responsible for this separation has been determined. Different morphologies of the Laves phase have been obtained by aging at different temperatures for various durations and the structure, chemistry, and volume fraction of these phases have been determined.

Effects of annealing temperature and heat-treatment duration on electrical properties of sol–gel derived indium-tin-oxide thin films

Transparent indium tin oxide (ITO) thin films have been deposited by the dip-coating process on silica substrates using solutions of 2,4-pentanedione, ethanol, indium and tin salts. The films have been first dried in air at 260 °C for 10 min and then annealed in a reducing atmosphere at different temperatures for various durations. The resistivity of ITO layers was found to decrease with increasing the metal concentration of the starting solution or the annealing temperature. Hence, by adjusting both metal concentration in the coating solution and heat-treatment, resistivities lower than 5 × 10 − 3 Ω cm for an annealing temperature of 550 °C and lower than 2 × 10 − 2 Ω cm for an annealing temperature of 300 °C, were obtained. These results are correlated with the density and the size of ITO grains in the films.

Factors Affecting the Mechanical Properties of Cu/Electroless Ni-P/Sn-3.5Ag Solder Joints

ABSTRACTThis work investigates the factors that affect the mechanical properties of Cu/electroless Ni-P/Sn-3.5Ag solder joints. For the investigation, solder joints were tensile tested after solid-state aging at different temperatures for various durations. Several factors, such as the growth of interfacial compounds (IFCs), Ni3Sn4 morphology, the accumulation of spalled Ni3Sn4 intermetallic particles at the solder/Ni3Sn4 interface, and the formation of Kirkendall voids at the Ni3P/Cu interface, are found to deteriorate the mechanical properties of the joints. Among all these factors, the formation of a layer of Kirkendall voids at the Ni3P/Cu interface, which is a result of Cu diffusion from the interface, causes the most severe decrease in tensile strength with a brittle fracture at the Ni3P/Cu interface. This layer of Kirkendall voids remains the main cause of brittle failure even after the transformation of the Ni3P layer into a Ni-Sn-P layer.

Effect of duration and temperature of sample preservation on the result of peripheral blood CD4+ and CD8+ T lymphocyte count in HIV/AIDS patients

By analyzing the CD4+ and CD8+ T lymphocyte count of whole blood from HIV/AIDS patients, which were stored at different temperatures for various durations, the authors studied the ideal preserving condition for whole blood and processed, in a purpose of guaranteeing the accuracy of clinical testing of CD4+ and CD8+ T lymphocyte count. Blood from 34 HIV carriers/AIDS patients, were kept at 4 degrees C for 2, 24, 48, or 72 h, and tested for CD4+ and CD8+ T lymphocyte count using cytometric analysis. Part of the blood was processed, and kept at degrees C or room temperature for 2, 24, 48, or 72 h, then tested for CD4+ and CD8+ T lymphocyte count. The results were compared statistically in parallel. Whole blood and processed samples preserved at degrees C showed no statistical difference in CD4+ T lymphocyte count among different preserving durations (P greater than 0.05), but CD8+ T lymphocyte counts were significantly different at 72 h (P less than 0.05). Processed samples at 72 h were significantly different in CD4+ T lymphocyte count(P less than 0.05), and significantly different in CD8+ T lymphocyte count at 24 h (P less than 0.05). At room temperature, samples at different duration were not significantly different in CD4+ T lymphocyte count, but significantly different in CD8+ T lymphocyte count at 48 and 72 h (P less than 0.05). There were stable results for performing analysis of the CD4+ and CD8+ T lymphocyte count of the anticoagulated blood within 48 h. At room temperature, there were stable results for performing the analysis of CD4+ and CD8+ T lymphocyte count of processed samples within 24 h. Between 24 h and 48 h, although CD4+ count was stable, CD8+ count showed significant changes, so the ratio of CD4 to CD8 changed accordingly.

Relationship between indentation size effect and material properties in the microhardness measurement of some cobalt-based alloys

The load dependence of the Vickers microhardness of some cobalt-based alloys subjected to heat treatment at different temperatures for various durations, investigated using Hanemann’s method and a PMT-3 hardness tester, has been discussed. The experimental results show that: (1) the indentation size effect is best revealed by the proportional specimen resistance model of Li and Bradt, and (2) the plot of the ratio of indentation load P to indentation diagonal d against d for a sample exhibits two different slopes b with a transition in the slopes occurring at an indentation diagonal d lying between 9 and 20μm. Analysis of the results revealed that: (1) the origin of indentation size effect is associated with the processes of relaxation of indentation stresses, (2) the load-dependent quantity a and load-independent quantity b for cobalt-based alloys are intimately connected with the grain size and defect structure of the alloys, and the grain-size dependence of their microhardness qualitatively agrees with the modified Hall–Petch relation, (3) in the range of high indentation loads the microhardness of cobalt-based alloys, as determined by using the proportional specimen resistance model, is practically independent of the applied load, and (4) the origin of a critical indentation diagonal dc*≈15μm, when a change in the slope of the plot of a against b occurs, is associated with the value of indentation diagonal d when frictional resistance begins to contribute to the values of a.

Synthesis of Bulk β-FeSi2 Crystal

The feasibility of adopting two methods to synthesizing the bulk crystal of β-FeSi2 was examined: one involving two-step Bridgmann growth with a three-zone furnace and another involving melting growth with a single zone furnace. As-grown iron disilicides were annealed in the furnaces at different temperatures for various durations. Experimental results indicate that a larger β-FeSi2 crystal can be obtained using the two-step fast Bridgmann growth method with post-annealing at 1073 K for 300 h. Fast cooling and adding some copper impurities to the raw materials were found to promote the growth of β-FeSi2. The iron disilicide crystal, with a large contribution from the β phase, supported a higher thermoelectric power. A thermoelectric power of 450 µV/K was obtained at 300–900 K for the sample with copper doping. The energy band gap of β-FeSi2 samples was about 0.82–0.88 eV, determined by measuring the temperature-dependent resistivity.

Adsorbate-induced faceting of high-index semiconductor surfaces: antimony adsorbed on Ge(103)

Scanning tunneling microscopy, low-energy electron diffraction and reflection high-energy electron diffraction were used to monitor changes in the morphology of Ge(103) surfaces after adsorption of antimony and annealing at different temperatures for various durations. After deposition of Sb at room temperature, the Sb-covered Ge(103) surface breaks up on annealing into small irregular pyramids, which coalesce and form more regular quasi-one-dimensional `hill-and-valley' structures bounded by reconstructed {113} facets. The average periodicity of the structures approaches a constant maximum value in the nanometer range. The symmetry of the substrate with respect to the facets constrains the formation of single domain nanostructures.

Fourier transform infrared study of porous silicon dipped into Cr3+ solution

We have measured Fourier transform infrared (FTIR) spectra of Cr3+ immersed porous silicon after annealing at different temperatures. After dipping porous silicon into Cr3+ solution, three additional peaks appear at 807, 886, and 940 cm−1 in the FTIR spectrum. When annealed in nitrogen at different temperatures for various durations, the peak at 807 cm−1 remains almost unchanged, the height of peak 886 cm−1 decreases gradually, while the peak at 940 cm−1 disappears quickly. This decay process occurs much faster at higher annealing temperature. These FTIR features reflect the surface chemistry change after immersed into Cr3+ solution.