Enhanced Thermal Stability of W‐Ni‐Al2O3 Cermet‐Based Spectrally Selective Solar Absorbers with Tungsten Infrared Reflectors

Solar thermal technologies such as solar hot water and concentrated solar power trough systems rely on spectrally selective solar absorbers. These solar absorbers are designed to efficiently absorb the sunlight while suppressing re‐emission of infrared radiation at elevated temperatures. Efforts for the development of such solar absorbers must not only be devoted to their spectral selectivity but also to their thermal stability for high temperature applications. Here, selective solar absorbers based on two cermet layers are fabricated on mechanically polished stainless steel substrates using a magnetron sputtering technique. The targeted operating temperature is 500–600 °C. A detrimental change in the morphology, phase, and optical properties is observed if the cermet layers are deposited on a stainless steel substrate with a thin nickel adhesion layer, which is due to the diffusion of iron atoms from the stainless steel into the cermet layer forming a FeWO₄ phase. In order to improve thermal stability and reduce the infrared emittance, tungsten is found to be a good candidate for the infrared reflector layer due to its excellent thermal stability and low infrared emittance. A stable solar absorptance of ≈0.90 is demonstrated, with a total hemispherical emittance of 0.15 at 500 °C.     

An electrochemical method for functionalization of a 316L stainless steel surface being used as a stent in coronary surgery: irreversible immobilization of fibronectin for the enhancement of endothelial cell attachment

An electrochemistry-based method for the formation of functionalized alkanethiol layers on a 316L stainless steel surface was developed. The method was efficient in forming a very stable, irreversibly-attached COOH-terminated (mercaptoundecanoic acid) surface layer. This layer was used as a ‘linker’ to immobilize the extracellular matrix protein fibronectin to the 316L stainless steel surface. Fibronectin was irreversibly attached to the surface and, unlike physisorbed fibronectin, resisted detachment more in aggressive 0.1 M NaOH under sonication. The fibronectin-modified 316L stainless steel surface was more biocompatible towards attachment of endothelial cells than a bare (unmodified) 316L stainless steel surface, yielding a 25% improvement in cell density.     

Bactericidal Activity of Copper and Niobium–Alloyed Austenitic Stainless Steel

Biofouling and microbiologically influenced corrosion are processes of material deterioration that originate from the attachment of microorganisms as quickly as the material is immersed in a nonsterile environment. Stainless steels, despite their wide use in different industries and as appliances and implant materials, do not possess inherent antimicrobial properties. Changes in hygiene legislation and increased public awareness of product quality makes it necessary to devise control methods that inhibit biofilm formation or to act at an early stage of the biofouling process and provide the release of antimicrobial compounds on a sustainable basis and at effective level. These antibacterial stainless steels may find a wide range of applications in fields, such as kitchen appliances, medical equipment, home electronics, and tools and hardware. The purpose of this study was to obtain antibacterial stainless steel and thus mitigate the microbial colonization and bacterial infection. Copper is known as an antibacterial agent; in contrast, niobium has been demonstrated to improve the antimicrobial effect of copper by stimulating the formation of precipitated copper particles and its distribution in the matrix of the stainless steel. Thus, we obtained slides of 3.8% copper and 0.1% niobium alloyed stainless steel; subjected them to three different heat treatment protocols (550°C, 700°C, and 800°C for 100, 200, 300, and 400 hours); and determined their antimicrobial activities by using different initial bacterial cell densities and suspending solutions to apply the bacteria to the stainless steels. The bacterial strain used in these experiments was Escherichia coli CCM 4517. The best antimicrobial effects were observed in the slides of stainless steel treated at 700°C and 800°C using an initial cell density of approximately 10⁵ cells ml⁻¹ and phosphate-buffered saline as the solution in which the bacteria came into contact with copper and niobium–containing steel.     

Impact of biological factors on the ennoblement of stainless steel in Baltic seawater

Open circuit potentials of stainless steels increased when immersed in the Baltic Sea. The ennoblement potential was +200 mV_sce in 40 to 50 days when sea water temperature was below 52°C and +300–400 mV_sce within <40 days at around 102°C. Ennoblement occurred in a laboratory ecosystem at 232°C in 20 to 30 days, and at 262°C in <20 days, but no ennoblement occurred at A322°C within 40 days. By the time the ennoblement was complete, compact microcolonies covered 1–10% of the steel surface. Nutrient enrichment of Baltic Sea water by twofold above the natural levels increased microbial growth but attenuated open circuit potential increase of the stainless steels. Exposure of the ennobled stainless steels to similar levels of nutrients did not reverse the already developed open circuit potentials. Attenuation of the ennobling response of the stainless steels by increases of temperature and eutrophication suggests a role for microorganisms which is crucial for the electrochemical behaviour of steels in brackish Baltic Sea water. Journal of Industrial Microbiology & Biotechnology (2000) 24, 410–420. Received 02 November 1999/ Accepted in revised form 24 March 2000     

Effect of temperature and some common metals on the stability of volatile anaesthetic–Entonox mixtures

Thermal stability of pressurised ready-to-use volatile liquid anaesthetic mixtures (halothane, isoflurane and enflurane) in Entonox (commercially available premixed 50% N₂O, 50% O₂ mixture) were investigated at temperatures of 20, 258, 400, 503 and 602°C on glass, stainless steel, copper and aluminium by gas chromatography and GC–MS. It was found that most of the decomposition products formed were halogenated compounds and the observed thermal stabilities in glass, stainless steel and copper allowed a thermal treatment up to 250°C without any decomposition problem. Aluminium was found to be the most effective metal at causing decomposition of the anaesthetic mixtures even at lower temperatures.     

Effect of photosynthetic biofilms on the open‐circuit potential of stainless steel

Periodic illumination of photosynthetic biofilms on AISI* 316L stainless steel resulted in evolution of oxygen (1–7 mg.1^‐1) and a corresponding increase in open circuit potential (E_corr) from 2 to 15 mV. The change in E^ depended on the interval of illumination. When the dark cycle began, elevation in potential was followed by an immediate drop. Illumination did not affect E_corr in sterile systems or in systems that contained only nonphotosynthetic eubacteria. Radiated heat from illumination accounted for changes of 4 to 5°C in temperature which, in the absence of oxygen production, should decrease dissolved oxygen by 0.75 mgl^‐1 and decrease E_corr by 1 mV. Positive shifts of E_corr induced by periodic illumination of photosynthetic biofilms are primarily the result of oxygen production.     

Recrystallization and modification of the stainless-steel surface relief under photonic heat load in powerful plasma discharges

Targets made of ITER-grade 316L(N)-IG stainless steel and Russian-grade 12Cr18Ni10Ti stainless steel with a close composition were exposed at the QSPA-T plasma gun to plasma photonic radiation pulses simulating conditions of disruption mitigation in ITER. After a large number of pulses, modification of the stainless-steel surface was observed, such as the formation of a wavy structure, irregular roughness, and cracks on the target surface. X-ray and optic microscopic analyses of targets revealed changes in the orientation and dimensions of crystallites (grains) over a depth of up to 20 μm for 316L(N)-IG stainless steel after 200 pulses and up to 40 μm for 12Cr18Ni10Ti stainless steel after 50 pulses, which is significantly larger than the depth of the layer melted in one pulse (～10 μm). In a series of 200 tests of ITER-grade 316L(N)-IG ITER stainless steel, a linear increase in the height of irregularity (roughness) with increasing number of pulses at a rate of up to ～1 μm per pulse was observed. No alteration in the chemical composition of the stainless-steel surface in the series of tests was revealed. A model is developed that describes the formation of wavy irregularities on the melted metal surface with allowance for the nonlinear stage of instability of the melted layer with a vapor/plasma flow above it. A decisive factor in this case is the viscous flow of the melted metal from the troughs to tops of the wavy structure. The model predicts saturation of the growth of the wavy structure when its amplitude becomes comparable with its wavelength. Approaches to describing the observed stochastic relief and roughness of the stainless-steel surface formed in the series of tests are considered. The recurrence of the melting-solidification process in which mechanisms of the hill growth compete with the spreading of the material from the hills can result in the formation of a stochastic relief.     

Effect of Crystal Orientation and Conduction Band Grading of Absorber on Efficiency of Cu(In,Ga)Se2 Solar Cells Grown on Flexible Polyimide Foil at Low Temperature

Flexible Cu(In,Ga)Se₂ (CIGS) solar cells are developed on polyimide (PI) foil by using a three‐stage co‐evaporation method. To deposit CIGS on a PI substrate, low temperature deposition process (below 440 °C) is investigated. By optimizing the three‐stage process, power conversion efficiency (PCE) values of 12.1% and 13.6% are obtained at maximum process temperatures of 400 °C and 440 °C, respectively (without anti‐reflection coating). The CIGS absorber deposited at 400 °C is grown with (220)/(204) rather than (112) as its dominant growth orientation, accompanied by highly homogeneous crystal structure and phases. Admittance spectroscopy reveals that the defect levels were lower in the CIGS absorber with (220)/(204) dominant growth orientation, which could have contributed to the PCE of 12.1%. The CIGS solar cell deposited at a temperature of 440 °C exhibits worse defect characteristics compared to that fabricated at 400 °C. However, the CIGS solar cell fabricated below 440 °C exhibited marginal double‐grading of Ga/(Ga + In) in the absorber layer, which resulted in an improved PCE of 13.6%. This result implies that at a temperature below 440 °C, the double‐grading of Ga/(Ga + In) is the more dominant factor causing the PCE improvement above 13%.     

Water stress preconditioning and cotton root pressure-flux relationships

Summary A model was developed to describe interactive effects of exposure time and treatment on thermostability of excisedIllicium parviflorum Michx. root cell membranes using electrolyte leakage (L_c) procedures. Roots were moved from 25°C to treatment temperatures between 35°C and 60°C for 30 to 300 min. A sigmoidal response described L_c increases with increasing temperature at selected time exposures and the lethal exposure time decreased exponentially as temperature increased. The lethal temperature (52.0±1.1°C) for a 15 min exposure using this technique was comparable to the critical temperature (52.2±1.2°C) when roots were exposed to gradually increasing temperatures (4°C per h). Total protein content of roots began to decrease as temperatures increased from 35 to 40°C and the temperature corresponding to 50% reduction in total proteins was 49.1±2.2°C.     

Production of alkanes (C7–C29) from different part of poplar tree via direct deoxy-liquefaction

Poplar leaves, poplar bark and poplar wood were deoxy-liquefied directly in an air-proof stainless steel reactor at different temperatures. The oils from leaves at 350 °C, from bark at 400 °C and from wood at 450 °C, at which the liquid product yields were the maximum, were analyzed by GC–MS. The oils obtained from three parts of poplar tree were quite different from each other in the relative contents of their compositions. The oil from leaves was rich in hydrocarbons (alkanes: C₇–C₂₉; aromatics) and poor in phenolics, while oil from wood was rich in phenolics and poor in hydrocarbons. The oil from bark was moderate. Relative contents of hydrocarbons in the leaves oil were as high as 60.01% but decreased to 29.71% in bark oil and 11.43% in wood oil. GC analysis of gases and FT-IR, GC–MS and elemental analysis of oils were performed in this study.     

Cultural Conditions and Some Properties of the Lipase of Humicola lanuginosa S-38

The cultural conditions for the production of thermostable lipase by a thermophilic fungus Humicola lanuginosa S-38 were investigated. The optimal cultural conditions to obtain the maximum yield of thermostable lipase with a 600-liter stainless steel fermentor were as follows: optimal medium- 2.0% soluble starch, 5.0% corn steep liquor, 0.2% K₂HPO₄, 0.1% MgSO₄·7H₂O, 0.5% CaCO₃, 0.5% soybean oil, 0.005% deforming agent (Adecanol LG-109); optimal fermentation conditions- temperature 45°C; rate of agitation 300 rpm; initial pH 7.0; rate of aeration 1/1 volume per volume of medium per minute. The optimal pH of the crude lipase preparation for the hydrolysis of the polyvinyl alcohol-emulsified olive oil was 8.0 and the optimal temperature was 60°C. It retained 100% of activity with the heat treatment at 60°C for 2 hr, but at 70°C for 20 min only 35% activity retained.     

ADAPTATION OF PHOTOSYNTHESIS IN LAMINARIA SACCHARINA (PHAEOPHYTA) TO CHANGES IN GROWTH TEMPERATURE1

The effect of growth temperature on photosynthetic metabolism was studied in the kelp Laminaria saccharina (L.) Lamour. Photosynthesis was subject to phenotypic adaptation, with almost constant photosynthetic rates being achieved at growth temperatures between 0 and 20° C. This response involved: (1) an inverse relationship between growth temperature and photosynthetic capacity, (2) a reduction in the Q₁₀ value for photosynthesis of L. saccharina grown at 0 and 5° C compared with 10, 15 and 20° C grown sporophytes, and (3) an acquired tolerance of photosynthesis to temperatures between 15–25° C (which inhibited photosynthesis in 0 and 5° C grown L. saccharina) in sporophytes grown at 10, 15 and 20° C. The physiological basis of these adaptations is discussed in terms of observed changes in activities and kinetics of the Calvin cycle enzyme ribulose-1, 5-bisphosphate carboxylase (oxygenase) and efficiency of light harvesting-electron transport systems.     

Physiological Responses of Apple Trees to Supraoptimal Root Temperature

Ungrafted apple rootstocks were grown in sand cultures at constant root temperatures between 20°C to 40°C. Temperatures of 30°C and above reduced root and shoot growth. Serious damage to the leaves occurred at 35°C and above. The O₂ consumption, CO₂ evolution and respiratory quotient (RQ) of the roots showed maximum values at 35°C. Different rootstock cultivars varied greatly in their susceptibility to damage by supraoptimal root temperatures apparently due to anaerobic respiration. The more susceptible ones differed from resistant types in the larger amount of ethanol they accumulated in their roots at supraoptimal root temperature, and the more severe reduction in the malic acid content of the roots at such temperature. Acetaldehyde was also found in roots and leaves at supraoptimal root temperatures, whereas the organic acid content of the leaves tended to decrease. Supraoptimal root temperature also caused a reduction of cytokinins in both roots and leaves accompanied by a reduction in the leaf chlorophyll content. This could be prevented by the application of kinetin or benzyladenine to the leaves. In a short experiment a rise in root temperature up to 40°C caused an increase in transpiration and a decrease in the resistance of the leaves to the passage of water vapor, whereas in prolonged experiments transpiration reached a maximum and leaf resistance a minimum at 30°C. The leaf water potential increased also with increasing root temperature. Leaf temperature increased with increasing root temperature, irrespective of increasing or decreasing transpiration rates.     

Life from the ashes: survival of dry bacterial spores after very high temperature exposure

We found that spores of Bacillus amyloliquefaciens rank amongst the most resistant to high temperatures with a maximum dry heat tolerance determined at 420 °C. We found that this extreme heat resistance was also maintained after several generations suggesting that the DNA was able to replicate after exposure to these temperatures. Nonetheless, amplifying the bacterial DNA using BOXA1R and (GTG)₅ primers was unsuccessful immediately after extreme heating, but was successful after incubation of the heated then cooled spores. Moreover, enzymes such as amylases and proteases were active directly after heating and spore regeneration, indicating that DNA coding for these enzymes were not degraded at these temperatures. Our results suggest that extensive DNA damage may occur in spores of B. amyloliquefaciens directly after an extreme heat shock. However, the successful germination of spores after inoculation and incubation indicates that these spores could have a very effective DNA repair mechanism, most likely protein-based, able to function after exposure to temperatures up to 420 °C. Therefore, we propose that B. amyloliquefaciens is one of the most heat resistant life forms known to science and can be used as a model organism for studying heat resistance and DNA repair. Furthermore, the extremely high temperature resistivity of these spores has exceptional consequences for general methodology, such as the use of dry heat sterilization and, therefore, virtually all studies in the broad area of high temperature biology.

     

In Vitro Electrochemical Corrosion and Cell Viability Studies on Nickel-Free Stainless Steel Orthopedic Implants

The corrosion and cell viability behaviors of nanostructured, nickel-free stainless steel implants were studied and compared with AISI 316L. The electrochemical studies were conducted by potentiodynamic polarization and electrochemical impedance spectroscopic measurements in a simulated body fluid. Cytocompatibility was also evaluated by the adhesion behavior of adult human stem cells on the surface of the samples. According to the results, the electrochemical behavior is affected by a compromise among the specimen''s structural characteristics, comprising composition, density, and grain size. The cell viability is interpreted by considering the results of the electrochemical impedance spectroscopic experiments.     

Cold tolerance characteristics of Korean population of potato tuber moth,Phthorimaea operculella (Zeller), (Lepidoptera: Gelechiidae)

Potato tuber moth (PTM), Phthorimaea operculella (Zeller), (Lepidoptera: Gelechiidae) is an invasive insect pest damaging solanaceous crops. We measured the supercooling point (SCP) and survival at low temperature of different development stages to determine which would be capable of overwintering in the Korean climate and adapting to low temperatures. The SCP ranges from ?23.8°C of the egg to ?16.8 of fourth instar larvae (L4). After short periods of low temperature acclimation in L3 (third instar larva), L4 and prepupae, only the prepupal stage showed a significant lowered SCP from ?20.78 to ?22.37°C. When exposed to different subzero temperature for two hours the egg turned out to be the most cold tolerant stage showing LT₅₀ of ?21.7°C followed by the pupal stage with ?15.89°C. One hundred percent mortality was observed when the larvae or adults were exposed to temperatures below ?15.1°C even for a period as short as 2 h. The results suggest that PTM pupae and egg would be the main overwintering stage in Korea where winter temperature does not drop below ?15°C.     

Effect of high temperature on active oxygen species,senescence and photosynthetic properties in cucumber leaves

To gain a physiological understanding of the effects of high temperatures on cucumber (Cucumis sativus L.), we subjected seedlings to heat treatment at daytime temperatures of 28 °C, 32 °C, and 36 °C for 7 h a day for 30 days. The amount of active oxygen species, indicators of senescence, and photosynthetic properties in the second and third leaves were determined at the start of temperature treatment and on the 15th and 30th days of treatment. The amount of active oxygen species superoxide in leaves was greatest in the high temperature zones on the 15th day of treatment, and the amount of hydrogen peroxide was greatest in the high temperature zones on both the 15th and 30th days of treatment. The reduction in the amount of protein and the increase in the amount of malondialdehyde, both indicators of senescence, were greatest in the high temperature zones on both the 15th and 30th days of treatment, and the amount of chlorophyll was lowest in the 36 °C zone on the 15th day, and lower in the high temperature zones on the 30th day. It is clear from these results that a large amount of active oxygen species is generated and accumulated in the leaves at high temperatures, and senescence is significantly accelerated. The photosynthetic properties of stomatal conductance, sub-stomatal CO₂ concentration, and transpiration rate were at the same level on both the 15th and 30th days of treatment in all three temperature treatment zones. No significant difference was seen in the net photosynthesis rate between the 28 °C and 32 °C zones, was lower in the 36 °C zone than the 32 °C zone on the 15th day, and lowest in the 36 °C zone on the 30th day. CO₂ intake and water absorption are only mildly affected by high temperatures, and the reduction in net photosynthesis rate due to the 36 °C high temperature stress suggests that the large amount of active oxygen species induces inhibition of photosynthesis and damage to the mechanism of photosynthesis.     

Quantifying the heterogeneous heat response of Escherichia coli under dynamic temperatures

Aims: Non‐sigmoid growth curves of Escherichia coli obtained at constant temperatures near the maximum growth temperature (T_max) were previously explained by the coexistence of two subpopulations, i.e. a stress‐sensitive and a stress‐resistant subpopulation. Mathematical simulations with a heterogeneous model support this hypothesis for static experiments at 45°C. In this article, the behaviour of E. coli, when subjected to a linearly increasing temperature crossing T_max, is studied. Methods and Results: Subpopulation dynamics are studied by culturing E. coli K12 MG1655 in brain heart infusion broth in a bioreactor. The slowly increasing temperature (°C h^?1) starting from 42°C results in growth up to 60°C, a temperature significantly higher than the known T_max. Given some additional presumptions, mathematical simulations with the heterogeneous model can describe the dynamic experiments rather well. Conclusions: This study further confirms the existence of a stress‐resistant subpopulation and reveals the unexpected growth of E. coli at temperatures significantly higher than T_max. Significance and Impact of the Study: The growth of the small stress‐resistant subpopulation at unexpectedly high temperatures asks for a revision of currently applied models in food safety and food quality strategies.     

A renewable energy source — hydrocarbon gases resulting from pyrolysis of the marine nanoplanktonic alga Emiliania huxleyi

The marine coccolithophore, Emiliania huxleyi, grown in the laboratory was subjected to vacuum pyrolysis at various temperatures from 100 to 500 °C. The highest yield of pyrolytic gases (183 mL g⁻¹ dry cells) was obtained at 400 °C. The amount of total hydrocarbon gas produced at 400 °C was 129 mL, about 10 times higher than at 300 °C. CH₄ was the major component at the high gas-production stage (400–500 °C). The great increase in hydrocarbon gases at 400 °C was accompanied by a marked decrease in liquid saturates and aromatics. The results indicate that the liquid hydrocarbons (oil) produced by pyrolysis at lower temperature is a direct source for the formation of the hydrocarbon gases. Due to its large potential for the production of biomass and hydrocarbons with low energy input, E. huxleyi is suggested as one of candidates for the production of renewable fuels. This revised version was published online in July 2006 with corrections to the Cover Date.     

Physiological responses of Opuntia ficus-indica to growth temperature

The influences of various day/night air temperatures on net CO₂ uptake and nocturnal acid accumulation were determined for Opuntia ficus-indica, complementing previous studies on the water relations and responses to photosynthetically active radiation (PAR) for this widely cultivated cactus. As for other Crassulacean acid metabolism (CAM) plants, net nocturnal CO₂ uptake had a relatively low optimal temperature, ranging from 11°C for plants grown at day/night air temperatures of 10°C/0°C to 23°C at 45°C/35°C. Stomatal opening, which occurred essentially only at night and was measured by changes in water vapor conductance, progressively decreased as the measurement temperature was raised. The CO₂ residual conductance, which describes chlorenchyma properties, had a temperature optimum a few degrees higher than the optimum for net CO₂ uptake at all growth temperatures. Nocturnal CO₂ uptake and acid accumulation summed over the whole night were maximal for growth temperatures near 25°C/15°C, CO₂ uptake decreasing more rapidly than acid accumulation as the growth temperature was raised. At day/night air temperatures that led to substantial nocturnal acid accumulation (25°C/15°C.). 90% saturation of acid accumulation required a higher total daily PAR than at non-optimal growth temperatures (10°C/0°C and 35°C/25°C). Also, the optimal temperature of net CO₂ uptake shifted downward when the plants were under drought conditions at all three growth temperatures tested, possibly reflecting an increased fractional importance of respiration at the higher temperatures during drought. Thus, water status, ambient PAR, and growth temperatures must all be considered when predicting the temperature response of gas exchange for O. ficus-indica and presumably for other CAM plants.