Effects of Plasma Nitriding on Microstructure and Tribological Properties of CoCrMo Alloy Implant Materials

##正## Medical forged CoCrMo alloy was treated by plasma nitriding process.The microstructures were characterized by 3Dprofiler,SEM and XRD.The tribological properties were investigated under lubrication of 25% bovine serum solution.Resultsshow that plasma nitriding is a promising process to produce thick,hard,and more wear resistant layers on the surface of CoCrMoalloy.All nitrided samples showed an important increase in the surface hardness due to the formation of harder CrN andCr_2N phases with compact nano-crystalline structures.The typical hardness values of HV_(0.05) increased almost two times thanuntreated one.Under bovine serum lubrication,at low nitriding temperature the Coefficient of Friction (COF) of nitrided samplewas lower than that of untreated sample,but at high nitriding temperature the COF was almost the same as the untreated one.Compared with the untreated sample,the nitrided samples showed lower wear rates and higher wear resistance under differentnitriding temperatures.The adhesive wear is the main mechanism for untreated CoCrMo alloy and the wear mechanisms ofnitrided ones are the fatigue wear and slight adhesive wear.It is concluded that the improvement of wear resistance is ascribed tothe hard nitride formation of CrN and Cr_2N phases at the nitrided surfaces.     

Anodization of aluminum and silicon in plasma of a non-self-sustained glow discharge

The results of anodization of aluminum and silicon in an oxygen plasma are presented. The plasma was generated by a non-self-sustained glow discharge with a hollow cathode excited by an electron beam at the oxygen pressure of 20 Pa. The density of the current flowing through the anodized specimen did not exceed 1.5 mA/cm², and its temperature was 200–250°C. Continuous Al₂O₃ and SiO₂ films were formed on the aluminum and silicon surfaces. The growth rate of the oxide layers was 150–200 nm/h for Al₂O₃ and 400–800 nm/h for SiO₂.     

Wear Resistance and Non-Magnetic Layer Formation on 316L Implant Material with Plasma Nitriding

In this study, the applicability of plasma nitriding treatment in the production of non-magnetic and corrosion resistant layer on 316L stainless steel implant material was investigated. 316L stainless steel substrates were plasma nitrided at temperatures of 350 ℃, 375 ℃, 400 ℃, 425 ℃ and 450 ℃ for 2 h in a gas mixture of 50% N2-50% H2, respectively. It was determined that the treatment temperature is the most important factor on the properties of the corrosion resistant layer of 316L stainless steel. The results show that s-phase formed at the temperatures under 400 ℃, and at the temperatures above 400 ℃, instead of s-phase, CrN and y＇-Fe4N phases were observed in the modified layer. The electrical resistivity and surface roughness of the modified layer increase with treatment temperature. Under 400 ℃ the corrosion resistance increased with the temperature, above 400 ℃ it decreased with the increase in treatment temperature. It was analyzed that the electrical resistivity and the soft （ideal） ferro- magnetic properties of 316L stainless steel increased with treatment temperature during nitriding treatment. Also, plasma ni- triding at low temperatures provided magnetic behavior close to the ideal untreated 316L stainless steel.     

Monitoring the Changes of Chemical Properties of Rice Straw–Derived Biochars Modified by Different Oxidizing Agents and Their Adsorptive Performance for Organics

Biochar derived from agricultural biomass waste is increasingly recognized as a multifunctional material for various applications according to its characteristics. In this study, rice straw–derived biochars were produced at different temperatures (550, 650, 750°C), then they were modified by using different oxidizing agents, including KOH, HNO₃, H₂SO₄, H₂O₂, and KMnO_4. The influence of carbonization temperature and the oxidizing agent's nature on the surface chemistry was investigated. Fourier transform infrared (FTIR) analysis detected lactone, carbonyl, quinone or conjugated quinone, carboxyl-carbonate structure, and alcohol groups in most of the oxidized samples. Modified biochars have low pH values compared with their parent biochars. This is due to the fact that most treatments of biochar increase the acidic functional groups on the surface. Modified biochars presented greater capacities for adsorption of organic species of different molecular sizes such as iodine, phenol, and methylene blue from solutions. Such behavior proves that the most important surface properties of these biochars affecting their solution adsorption behavior are their acidity/alkalinity and hydrophilicity.     

Effects of Menstrual Cycle and Room Temperature on Color Preference

This study investigated the effects of menstrual cycle on color preference in nine normally menstruating female subjects. They were instructed to choose their preferred color out of 45 Munsell hues every 5 min at ambient temperatures (T _a) of 28°C (630-800 h), from 28°C to 23°C (800-900 h) and at 23°C (900-930 h). Warmer color hues were preferred during the luteal phase than the follicular phase at 28°C, while there did not exist any significant differences at other T _as. The findings that a preference for warmer colors occurred in the luteal phase at 28°C is discussed in terms of the load error between actual core temperature and its setpoint.     

Stabilization by glutaraldehyde of high-rate electron transport in isolated chloroplasts

Treatment of isolated chloroplasts with glutaraldehyde affects their ability to photoreduce artificial electron acceptors. The remaining rate of O₂ evolution approaches zero with methyl viologen, is low with ferricyanide, but nearly normal with lipophilic Photosystem II acceptors, like oxidized p-phenylenediamine and oxidized diaminodurene. Since Photosystem I donor reactions are also affected, a specific site of inhibition of electron transport to Photosystem I is indicated. At the same time, glutaraldehyde prolongs the longevity of the chloroplasts stored in dark. In control samples the half-life of Photosystem II activity varied between 5 days at 4 °C and 1 day at 25 °C. Glutaraldehyde treatment increased these half times approx. 3-fold. The glutaraldehyde doses required to induce inhibition and stabilization were very similar.     

Moderate hypothermia suppressed excessive generation of superoxide anion radical and inflammatory reactions in blood and liver in heatstroke: Laboratory study in rats

Abstract

The study was performed to demonstrate superoxide radical (O₂·–) generation, systemic inflammation and liver injury caused by heatstroke and to reveal suppressive effects of moderate hypothermia. Heatstroke was defined as achieving pharyngeal temperature of 40°C with arterial pressure reduction. Heatstroke rats were divided to four groups by the temperature after the onset; 40°C, 37°C, 32°C and sham-treated with 37°C. O₂·– current was measured continuously in the right atrium using an electrochemical O₂·– senor. The O₂·– current increased in all groups except for the sham-treated group during the induction. After the onset of heatstroke, the O₂·– current was suppressed with temperature-dependency. Plasma and liver high-mobility group box 1, intercellular adhesion molecule-1, plasma aspartate aminotransferase and alanine aminotransferase were also suppressed with the suppression of O₂·– generation. Therefore, excessive O₂·– generation might be a key factor in heatstroke and the suppression with moderate hypothermia would be a therapeutic modality.     

Effects of short-term heat stress on oxidative damage and responses of antioxidant system in Lilium longiflorum

This paper aims to determine the changes in reactive oxygen species (ROS) and the responses of the lily (Lilium longiflorum L.) antioxidant system to short-term high temperatures. Plants were exposed to three levels of heat stress (37°C, 42°C, 47°C) for 10 h when hydrogen peroxide (H₂O₂) and superoxide (O₂⁻) production rate along with membrane injury indexes, and changes in antioxidants were measured. Compared with the control (20°C), electrolyte leakage and MDA concentration varied slightly after 10 h at 37°C and 42°C, while increased significantly at 47°C. During 10 h at 37°C and 42°C, antioxidant enzyme activities, such as SOD, POD, CAT, APX and GR, were stimulated and antioxidants (AsA and GSH concentrations) maintained high levels, which resulted in low levels of O₂⁻ and H₂O₂ concentration. However, after 10 h at 47°C, SOD, APX, GR activities and GSH concentration were similar to the controls, while POD, CAT activities and AsA concentration decreased significantly as compared with the control, concomitant with significant increase in O₂⁻ and H₂O₂ concentrations. In addition, such heat-induced effects on antioxidant enzymes were also confirmed by SOD and POD isoform, as Cu/ZnSOD maintained high stability under heat stress and the intensity of POD isoforms reduced with the duration of heat stress, especially at 47°C. It is concluded that in lily plants, the oxidative damage induced by heat stress was related to the changes in antioxidant enzyme activities and antioxidants.     

Effect of low-temperature stress on abscisic acid,jasmonates, and polyamines in apples

The effect of low temperatures on polyamines, jasmonates, abscisic acid (ABA), and antioxidant activities was investigated in apple fruitlets. Although endogenous ABA concentrations were not significantly different between untreated control fruit kept at −2°C and those kept at 20°C, endogenous jasmonic acid (JA), putrescine, and spermidin concentrations at −2°C were generally higher than those at 20°C. Endogenous ABA concentrations increased in n-propyl dihydrojasmonate (PDJ)—or spermine-treated fruit in comparison to the untreated control at 20 and −2°C. The applications of PDJ or spermine decreased low-temperature injuries such as splitting and spotting in fruit. Although the IC₅₀ of 1,1-diphenil-2-pycrylhydrazyl (DPPH)-radical scavenging activities was not significantly different among the treatments, the IC₅₀ of O₂ ⁻-scavenging activities in PDJ-treated or Spm-treated fruit at 5 days after the low-temperature treatment was lower than in the untreated control at 20 and −2°C. The expression of MdCHS increased in Spm-treated fruit. The concentrations of ascorbic acid, catechin, chlorogenic acid, epi-catechin, and phloridzin in Spm-treated fruit were higher than in the untreated control at −2 or 20°C. These facts suggest that ABA, jasmonates and polyamines may be associated with low-temperature stress tolerance in apple fruitlets.     

Stability of (1R,2S)-(-)-Ephedrine hydrochloride in Candida albicans-inoculated urine and blood samples

The stability of drugs in biological evidence during collection and storage is of particular concern in forensic investigations. Microbes in the samples and other elements are an essential component of these investigations. In the current study, the HPLC method was used to examine the stability of (1R, 2S)-(-)-Ephedrine hydrochloride in plasma and urine samples inoculated with C. albicans after storage at 37 °C for 48 h and −20 °C for six months. In the stability experiment, MIC_50% of (1R, 2S)-(-)-Ephedrine hydrochloride was applied according to MIC and MFC that were determined in this work. This drug had MIC and MFC of 50 and 100 ppm, respectively. In HPLC analysis, the standard (1R, 2S)-(-)-Ephedrine hydrochloride had a retention time of 1.63 and was used to identify this drug in samples that had or had not been exposed to C. albicans. The findings demonstrated that within 48 h at 37 °C, C. albicans had an impact on the drug concentration (10% and more than 15%, respectively, were lost in plasma and urine samples inoculated with C. albicans). In plasma samples, the drug content remained stable at −20 °C for three months, although it degraded in urine samples after one month. In plasma and urine samples, the concentration reduction had surpassed 70% and 50% by the sixth month, respectively. The results of this investigation show that C. albicans can change the stability of (1R, 2S)-(-)-Ephedrine hydrochloride in plasma and urine samples that contain MIC_50% of Ephedrine hydrochloride.     

The effect of a post-harvest heat-treatment on the storage behaviour of Cox's Orange Pippin apple fruits

Samples from a wide range of commercially grown Cox's Orange Pippin apple fruits were immersed in water at 45° C. for 10 min. to control rotting due to Gloeosporium spp. In two seasons the incidence of rotting following storage for 19 weeks at 3·3° C. (38° F.) was reduced to about 40% of the level in the untreated samples. However, there was a marked increase in the incidence of breakdown and core flush in the treated fruit, particularly when stored in a controlled atmosphere of 5% CO₂, 3 % O₂. A similar but less severe increase in the incidence of breakdown was also recorded in the second season in treated fruit stored in 2% O₂ (with continuous removal of CO₂). The treated fruit tended to develop a more yellow ground colour and softened more rapidly during storage in 5% CO₂, 3% O₂. It is concluded that the treatment advances fruit senescence and that the increased incidence of physiological disorders is likely to limit the use of this method for the control of Gloeosporium rotting in English-grown Cox apples.     

Pasting properties of a heat-moisture treated canna starch in relation to its structural characteristics

Native and moistened canna starches (moisture contents of 15%, 18%, 20%, 22%, and 25%) were heat treated at 100 °C for 16 h. Heat-moisture treatment (HMT) did not alter the shape or size of starch granules. Heat-treated starches showed lower paste viscosity, more stable paste (with no breakdown) and noticeable decrease in setback value compared to untreated native starch. These changes were more obvious when the starch samples contained more moisture. Starch gel morphology investigated by I₂ staining revealed that the granules of untreated native canna starch were completely ruptured, whereas those of HMT22% and HMT25% samples remained in granular form. These gel morphologies were correlated and provided the information to explain the pasting behaviors of treated and untreated canna starches. Shifts of gelatinization endotherms towards higher temperatures (1–8 °C) with broadened peaks following the moisture contents in starch samples were found after HMT. Amylose leaching of treated samples tended to be lower when the moisture content of the samples increased. HMT did not alter crystalline type of canna starch (B-type), but with increase of the moisture, slight reduction of a peak at 5.7° and a fusion of doublet at 22° and 24° were observed.     

Bioleaching of Heavy Metal Polluted Sediment: Influence of Temperature and Oxygen (Part 1)

A remediation process for heavy metal polluted sediment has previously been developed in which the heavy metals are removed from the sediment by solid‐bed bioleaching using elemental sulfur (S⁰): the added S⁰ is oxidized by the indigenous microbes to sulfuric acid that dissolves the heavy metals which are finally extracted by percolating water. In this process, the temperature is a factor crucially affecting the rate of S⁰ oxidation and metal solubilization. Here, the effect of temperature on the kinetics of S⁰ oxidation has been studied: oxidized Weiße Elster River sediment (dredged near Leipzig, Germany) was mixed with 2 % S⁰, suspended in water and then leached at various temperatures. The higher the temperature was, the faster the S⁰ oxidized, and the more rapid the pH decreased. But temperatures above 35 °C slowed down S⁰ oxidation, and temperatures above 45 °C let the process – after a short period of acidification to pH 4.5 – stagnate. The latter may be explained by the presence of both neutrophilic to less acidophilic thermotolerant bacteria and acidophilic thermosensitive bacteria. Within 42 days, nearly complete S⁰ oxidation and maximum heavy metal solubilization only occurred at 30 to 45 °C. The measured pH(t) courses were used to model the rate of S⁰ oxidation depending on the temperature using an extended Arrhenius equation. Since molecular oxygen is another factor highly influencing the activity of S⁰‐oxidizing bacteria, the effect of dissolved O₂ (controlled by the O₂ content in the gas supplied) on S⁰ oxidation was studied in suspension: the indigenous S⁰‐oxidizing bacteria reacted quite tolerant to low O₂ concentrations; the rate of S⁰ oxidation – measured as the specific O₂ consumption – was not affected until the O₂ content of the suspension was below 0.05 mg/L, i.e., the S⁰‐oxidizing bacteria showed a high affinity to O₂ with a half‐saturation constant of about 0.01 mg/L. Stoichiometric coefficients describing the relationship between the mass of S⁰, O₂ and CO₂ consumed are scarcely available. The growth of S⁰‐oxidizing, obligate aerobic, autotrophic bacteria was, therefore, stoichiometrically balanced (by using a yield coefficient of Y_X/S = 0.146 g cells/g S⁰, calculated with data from the literature): 24.14 S⁰ + 29.21 O₂ + 27.14 H₂O + 5 CO₂ + NO₃^–→ C₅H₇O₂N + 24.14 SO₄^2– + 47.28 H⁺, which resulted in Y = 1.21 g O₂/g S⁰ and Y = 0.28 g CO₂/g S⁰.     

Effect of heat stress on superoxide anion production in native and crossbred cattle under in vitro whole blood culture model

Impact of global warming on the dairy industry has gained attention due to huge economic losses through low production and fertility caused by heat stress. Exposure to hyperthermia provokes a series of complex responses in mammals which are been related to morphological and physiological alterations including the production of reactive oxygen species (ROS). A quantitative spectrophotometric based nitroblue tetrazolium (NBT) reduction assay was used to estimate the superoxide anion (•O₂⁻) level in heat stressed (at 42 °C) whole blood cultures of native and crossbred bulls (Sahiwal and Frieswal), in vitro. The breed effect in the kinetics of •O₂⁻ production at different time periods of continual heat stress was analyzed by repeated measures ANOVA. Comparison between different time periods in reference to 37 °C was analyzed by paired t-test. The •O₂⁻ level was significantly different (p < 0.05) between cells at 37 °C and 42 °C at different periods of incubation. Kinetics study showed increment of •O₂⁻ production on the acute phase of stress followed by a reduction in both Sahiwal and Frieswal breeds. In Sahiwal breed, the inflated superoxide level continued abated till 4 h and raised again at 6 h, while in Frieswal •O₂⁻ level reverted to raise sooner with in 2 h of incubation itself. Contrarily, kinetic of •O₂⁻ level in plasma showed a significant reduction (p < 0.001) at 30 min of 42 °C incubation followed by increment of •O₂⁻ level. Further, the breed variation was significant (p < 0.05) and a significant high reduction of •O₂⁻ level was observed in Sahiwal breed. Our finding indicates that, a better and longer •O₂⁻ production homeostasis and higher plasma scavenging ability of native breed may be one of the reasons for the higher thermal tolerance of these breeds in tropical climate.     

Effect of annealing on down‐conversion properties of monoclinic Gd2O3:Er3+ nanophosphors

Erbium‐doped nano‐sized Gd₂O₃ phosphor was prepared by a solution combustion method in the presence of urea as a fuel. The phosphor was characterized by X‐ray diffractometry (XRD), Fourier transform infra‐red spectroscopy, energy dispersive X‐ray analysis (EDX) and transmission electron microscopy (TEM). The results of the XRD shows that the phosphor has a monoclinic phase, which was further confirmed by the TEM results. Particle size was calculated by the Debye–Scherrer formula. The erbium‐doped Gd₂O₃ nanophosphor was revealed to have good down‐conversion (DC) properties and the intensity of phosphor could be modified by annealing. The effects of annealing at 900°C on the particle size and luminescence properties were studied and compared with freshly prepared Gd₂O₃:Er³⁺ nanoparticles. The average particle sizes were calculated as 8 and 20 nm for the freshly prepared samples and samples annealed at 900°C for 1 h, respectively. The results show that both freshly prepared and annealed Gd₂O₃:Er³⁺ have monoclinic structure. Copyright © 2014 John Wiley & Sons, Ltd.     

Chemoenzymatic epoxidation of citronellol catalyzed by lipases

The chemoenzymatic epoxidation of a terpene alcohol, citronellol, is reported. Some experimental conditions, such as the use of lipases from different sources, oxidizing agents (H₂O₂ or urea–hydrogen peroxide, UHP), reaction time, acyl donor type (C6–C16), temperature (15–40 °C) and the influence of organic media, were evaluated. In most cases, citronellol oxide 2 or the ester citronellol oxide 3 were obtained. Depending on the reaction conditions, high yields of products 2 or 3 were obtained (>99%). CAL-B was the most effective catalyst in this reaction. For epoxide 2, the highest yields of 80% and 77% were obtained at 20 °C and 25 °C, respectively, using UHP as an oxidizing agent and octanoic acid as an acyl donor. The organic medium appears to be one of the most important parameters in the reaction. Using chloroform or dichloromethane, product 2 was obtained at a >99% yield after 24 h. When different mixtures consisting of varied organic solvents and an imidazolium-based ionic liquid (IL) were used, the results were dependent on both the solvent and IL counter-ion (18–75%).     

Thermoluminescence properties of annealed natural quartz after beta irradiation

Here we investigated the effects of annealing, heating rate and fading (after annealing at 800 °C) on the thermoluminescence (TL) glow curves of natural quartz (NQ). All of the samples were annealed at different temperatures between 100 °C and 800 °C and then irradiated with a beta dose of about 34 Gray (Gy), in order to determine the effects of annealing treatments on TL peaks of natural quartz. TL glow curves of the samples were recorded. It was observed that the intensities of TL peaks were strongly sensitive to annealing temperatures at 800 °C. The heating rate and fading effect of TL peaks of natural quartz were examined for the annealed samples at 800 °C for 30 min. It was observed that the intensities of the TL peaks were differently affected from heating rate and fading. Additionally, TL kinetic parameters (activation energy, frequency factor and order of kinetics) of all peaks were determined for annealed samples using a computerized glow curve deconvolution (CGCD) method and Mathematica software. Copyright © 2016 John Wiley & Sons, Ltd.     

Optimization of ultraviolet ozone treatment process for improvement of polycaprolactone (PCL) microcarrier performance

Growing cells on microcarriers may have overcome the limitation of conventional cell culture system. However, the surface functionality of certain polymeric microcarriers for effective cell attachment and growth remains a challenge. Polycaprolactone (PCL), a biodegradable polymer has received considerable attention due to its good mechanical properties and degradation rate. The drawback is the non-polar hydrocarbon moiety which makes it not readily suitable for cell attachment. This report concerns the modification of PCL microcarrier surface (introduction of functional oxygen groups) using ultraviolet irradiation and ozone (UV/O₃) system and investigation of the effects of ozone concentration, the amount of PCL and exposure time; where the optimum conditions were found to be at 60,110.52 ppm, 5.5 g PCL and 60 min, respectively. The optimum concentration of carboxyl group (COOH) absorbed on the surface was 1495.92 nmol/g and the amount of gelatin immobilized was 320 ± 0.9 µg/g on UV/O₃ treated microcarriers as compared to the untreated (26.83 ± 3 µg/g) microcarriers. The absorption of functional oxygen groups on the surface and the immobilized gelatin was confirmed with the attenuated total reflectance Fourier transformed infrared spectroscopy (ATR-FTIR) and the enhancement of hydrophilicity of the surface was confirmed using water contact angle measurement which decreased (86.93°–49.34°) after UV/O₃ treatment and subsequently after immobilization of gelatin. The attachment and growth kinetics for HaCaT skin keratinocyte cells showed that adhesion occurred much more rapidly for oxidized surfaces and gelatin immobilized surface as compared to untreated PCL.     

Temperature shift-induced changes in the antioxidant enzyme system of cyanobacteriumSynechocystis PCC 6803

The 24 h effect of low (20°C) and high (43°C) temperature on the antioxidant enzyme activities and lipid peroxidation was investigated in intact cells of the cyanobacteriumSynechocystis PCC 6803 grown at 36°C. At low temperature treated cells, the superoxide dismutase, catalase and glutathione peroxidase activities were significantly higher and the protein content lower than in high temperature treated cells. The increase of hydroxyl free radical level and malonyldialdehyde formation, when algal cells were exposed to low temperature, were due to the stimulated production of superoxide radicals O₂ ⁻ and hydrogen peroxide (H₂O₂).     

The density-dependency of dark- and low-background radiation effects on water and water solution properties

The effects of dark -(Ev = 0 lux) and low-background radiation (BGR), where R < 1μRongen/h, on physicochemical properties (specific electrical conductivity, heat fusion, hydrogen peroxide (H₂O₂), and oxygen contents) of distilled water (DW) and physiological solution (PS) at 4°C and 18°C were studied. The incubation of DW and PS samples in dark and in low BGR (under dark) medium at 4°C and 18°C brings to changes of their physicochemical properties compared with DW and PS samples incubated in light and normal BGR condition (Ev = 500–550 lux and R = 17 μRoentgen/h). The observed changes of DW and PS properties depended on their initial temperature, density and ionic composition. It is suggested that water molecules dissociation and ions hydration are sensitive to illumination and BGR. Therefore, the cell-bathing medium can be considered as a messenger through which direct and non direct (by modulating of others factors-induced effects) influences of illumination and BGR on cell metabolism are realized.