Atambient Temperature Research Articles

Screening and partial purification of amylase from <i>Aspergillus Niger</i> isolated from deteriorated tomato (<i>Lycopersicon Esculentum</i> mill.) fruits

Amylases (EC 3.2.1.1) are cellwall degrading enzymes associated with the pathogenicity of microorganisms in the spoilage of tomato fruits. The use of amylase in many industries has made it very important to optimize production process to achieve maximum yields. Screening and partial purification of Amylase from Aspergillus niger isolated from tomato (Lycopersicon esculentum Mill.) fruits was studied. Amylase producing fungi were isolated from fresh tomatoes kept at ambient temperature (28±1˚C). Isolates were characterized on the basis of their morphological and cultural techniques. Partial purification of amylase was carried out by ammonium sulphate precipitation. The enzyme activity was determined and optimum conditions were obtained. The molecular weights of the crude and partially purified Amylase were determined by SDS PAGE method. A total of five isolates were obtained using basic screening technique for amylase activity, one of the isolates (Isolate code F2) exhibited maximum amylase activity. The fungi isolate code F2 was identified as Aspergillus niger. Optimum conditions for Amylase AMY F2 were ascertained at pH 6.0; temperature 30°C; substrate concentration of 0.3mg/ml, and time of heating of less than 10min. The molecular weights of the crude and partially purified Amylase AMY F2 were found to be 55kDa and 35kDa respectively by SDS PAGE method. Microorganisms had been an encouraging means of economical production of enzymes in large scale for the food and drug industry.

Viability of carabao (Bubalus bubalis carabanensis) epididymal sperm from post mortem testes in semen extender at refrigerated temperature

Post mortem epididymal sperm (ES) is an excellent source of germplasm for conservation of animal genetic resources. In this study, the viability of post mortem ES from carabao after collection at ambient temperature (AT) and after 24 hr and 48 hr of storage at refrigeration temperature (RT) were evaluated. ES were collected through slicing of epididymides from 7 carabaos. The mean ES volume was 0.4 ml with sperm concentration of 2.5×109 cells/ml. The mean percentage livability of fresh ES, after 24 hr and 48 hr of storage at RT were 81.93%, 65.93% and 43.7%, respectively. The mean percentage abnormalities of fresh ES, after 24 hr and 48 hr of storage at RT were 44.15%, 38.5% and 43.47%, respectively. The mean percentage motility of fresh ES, after 24 hr and 48 hr of storage at RT were 60.0%, 50.0% and 17.24%, respectively, after analysis through conventional means. Through CASA, the mean percentage motility was observed to be lower significantly at 26.12%, 37.94% and 18.32% for fresh ES, after 24 hr and 48 hr of storage at RT, respectively. The mean progressive motility of fresh ES, after 24 hr and 48 hr storage at RT were 10.02%, 16.47% and 10.87%, respectively. The results suggest that ES potential for use in fertilization studies remained viable when used immediately or after storage at RT for the first 24 hr.

Influence of surface morphology on fatigue behavior of metastable austenitic stainless steel AISI 347 at ambient temperature and 300°C

The effect of surface modification by cryogenic turning on fatigue behavior of metastable austenitic stainless steel AISI 347 was investigated in stress-controlled fatigue tests at ambient temperature (AT) and 300 °C in air. Five different surface morphologies were manufactured by the variation of turning parameters – with and without cryogenic CO2 snow cooling and feed velocity as well as by the application of polishing for reference surfaces with a very small surface roughness. For a comprehensive characterization of the surface and near surface morphology, X-ray diffraction investigations were performed. Three phases (γ-austenite, α-martensite and ε-martensite) were detected in the near-surface microstructure after cryogenic turning while after turning without cryogenic cooling the only microstructural constituent was γ-austenite. Moreover, residual stress state, micro hardness and surface roughness play an important role in surface morphology. The experimental data on the cyclic deformation behavior and stress-strain response of all surface morphologies are reported. Reference specimens with purely austenitic surface microstructure show the highest plastic strain amplitude during cyclic loading at both AT and 300°C. At elevated temperature these specimens achieved the shortest fatigue life. Martensitic surface layers induced by cryogenic turning result in the reduction of plastic strain amplitude during cyclic loading and significantly enhance fatigue life at both tested temperatures.

Use of Recycled Concrete Aggregate in High-Calcium Fly Ash Geopolymer Concrete

The comparison results of using crushed limestone (NA) and recycled concrete aggregates (RCA) as coarse aggregates in high-calcium fly ash geopolymer concrete with and without temperature curing are presented. Local river sand with a fineness modulus of 2.1, sodium hydroxide solution concentrations of 8, 12, and 16 Molar, and sodium silicate were used to produce geopolymer concrete (GC). The curing was separated in two conditions: the first was cured at ambient temperature (AT) and another was cured at temperature of 60°C for 48 hrs. (CT). The compressive strength, thermal conductivity, and ultra pulse velocity of GC were investigated at age 7 days. The results found that RCA could be use as coarse aggregate in GC. The thermal conductivity increased with the increasing of compressive strength. Curing at 60°C yielded compressive strength about 3 times higher than that of AT. However, both AT and CT curing, GC containing RCA had thermal conductivity and ultra pulse velocity lower than those of containing NA.

Investigations on performance and failure mechanisms of high temperature thermoplastic polymers as adhesives

Ability of high temperature thermoplastic polymers (TPs) to create strong bonds with metals provides an attractive solution to develop adhesives for harsh operating conditions. However, exploration of such TP based adhesives needs evaluation in desired operating temperature conditions along with understanding of failure mechanism which will serve as a platform for developing successive batches of composite adhesives or blends. In this work poly (ether sulphone) (PES), poly (ether ketone) PEK and poly (ether- ether ketone) PEEK were explored as adhesives for joining cold rolled steel lap joints. The lap joints were evaluated for bond performance at various temperatures. The adhesive-bond performance order differed at different temperatures. At ambient temperature (AT) it was as; PES>PEK>PEEK, while at higher temperatures PEK proved the best followed by PEEK. Micro-Raman spectroscopy (MRS) analysis of failed films was carried out to understand the failure mechanism as a function of thermal and mechanical stresses. Differential scanning calorimetry and scanning electron microscopy (SEM) of fractured films was carried out to understand the changes in crystallinity, thermal characteristics and failure mechanisms.

Light-Emitting Diodes Fabricated From Carbon Ions Implanted Into p-Type Silicon

Silicon-based light-emitting diodes (LEDs) are fabricated using p-type silicon implanted with C <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ions and postannealed at 1000 °C in flowing nitrogen. The ion implantation is carried out at ambient temperature (AT) and 400 °C to investigate the influence of high-temperature implantation on the luminescence of LEDs. Transmission electron microscopy shows a near-surface layer of amorphous silicon (a-Si) with nanoscale carbon-rich inclusions in both ambient and heated targets while an additional polycrystalline Si layer is observed in the heated target only. A Schottky diode is constructed from C <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -implanted Si (C:Si) with a semitransparent gold layer on the implanted surface and aluminum on the back of the target. Contact firing at 400 °C in flowing nitrogen is used to optimize diode performance. Turn-ON voltage is determined to be about 3 V for all devices. Electroluminescence (EL) spectra show visible orange-red emission indicating luminescence primarily due to a-Si and Si nanoparticles in the LEDs fabricated from C:Si implanted at AT. The high-temperature samples produced EL attributed to a-Si and porous silicon carbide.

Ecophysiological responses of two dominant subalpine tree species Betula albo-sinensis and Abies faxoniana to intra- and interspecific competition under elevated temperature

Seedlings of tree species Abies faxoniana and Betula albo-sinensis were grown under different competition regimes (single plant, monoculture or mixture) at ambient temperature (AT) and elevated temperature (ET) to evaluate the impact of inter- and intraspecific competition on photosynthesis capacity, N resorption efficiency, N uptake patterns, water use efficiency (foliar carbon isotope composition, δ13C) and root carbon reserve accumulation. Our results showed that ET did not have significant effects on relative height growth rate (RGRH), relative diameter growth rate (RGRD), chlorophyll fluorescence parameters (Fv/Fm, ΦPSII), light-saturated photosynthetic rate (A1400) and nitrogen uptake in A. faxoniana, but it significantly reduced the values of these parameters in B. albo-sinensis. On the other hand, RGRH of A. faxoniana was not influenced by intraspecific competition irrespective of temperature regimes, while in B. albo-sinensis intraspecific competition was severer under AT than under ET. Decreased photosynthetic capacity and reduced plant size detected in B. albo-sinensis under ET likely contribute to its low intraspecific competitive ability. However, we found positive effects of interspecific competition on A. faxoniana but negative effects on B. albo-sinensis under ET, as A. faxoniana exposed to interspecific competition showed higher RGRH, RGRD, A1400, chlorophyll fluorescence parameters, foliar δ13C, foliar N, and percentages of 15N-ammonium and 15N-nitrate recovery than did A. faxoniana exposed to intraspecific competition or no competition. The results indicate that A. faxoniana is a better competitor than B. albo-sinensis under ET. Further, A. faxoniana altered resource use patterns and had a high plasticity in its ammonium uptake in mixtures compared with monocultures under ET, while B. albo-sinensis did not change its N use pattern. In all, our results showed that high temperature stress tolerance (e.g., higher root carbon accumulation), high ability to keep carbon balance (e.g., higher water use efficiency, lower leaf respiration rate, higher Fv/Fm), as well as a better N acquisition ability make A. faxoniana a better competitor when compared to B. albo-sinensisg under ET.

Effect of polar additives on melt electrospinning of nonpolar polypropylene

Melt or solution electrospinning is an effective and direct technique for producing nanoscale fibers. Polypropylene (PP) cannot be easily dissolved at ambient temperature. Thus, it was commonly electrospun in melt state. However, compared with solution electrospun fibers, melt electrospun PP fibers are more uneven with bigger diameters. To remedy this problem, polar additives, namely, stearic acid and sodium stearate were added into pure PP. The effects of the additives were investigated. Results showed that contrasting to those of pure PP, the fiber diameter of PP with 8 wt% stearic acid decreased by 69.3 % (from 5.4 ?m to 1.6 ?m). The smallest fiber diameter was 600 nm and the smallest average fiber diameter was 1.8 ?m when the sodium stearate contents were 10 wt% and 8 wt%, respectively. The addition of polar compounds could alter not only the diameters of PP microfibers, but also the distribution of diameters, the processing current, and even the thermal properties of fibers. The microcosmic mechanisms for these changes were interpreted.

English

We report here the synthesis of phenyl(2 - phenyl - 2,3 - dihydro - 1H - perimidin - 2 - yl)methanone ( 2 ) by the condensation reaction between 1,8 - diaminonaphthalene ( 1 ) and benzil in equimolar ratio at ambient temperature. Further reaction of compound 2 with one equivalent of sodium borohydride at 0 oC resulted in quantitative conversion of ketone to corresponding alcohol, namely, phenyl(2 - phenyl - 2,3 - dihydro - 1H - perimidin - 2 - yl)methanol ( 3 ). The solid - state structures of both the compounds were established using single - crystal X - ray diffraction analysis. We probed, using quantum mechanics, the mechanism of formation of compound 2 through two of the most plausible routes and observed that it was more plausible that the first route, energy - wise, would result in product 2 . We also calculated the stabilization energy of intermolecular hydrogen bond ing, which leads to the formation of a dimer, which has already been observed in the solid - state structure of compound 3 .

Efficacy of Washing and Postharvest Treatments on Shelf Life and Quality of Oyster Mushroom

An experiment was conducted to study the efficacy of washing (control and 5% hydrogen peroxide) and post harvest treatments (control, hot water treatment, wrapping with unperforated and perforated plastic bags, wrapping with brown paper bag and wrapping with aluminum foil) on shelf life and quality of oyster mushroom. Postharvest treatments caused significant effects to influence weight loss, dry matter and protein contents, disease incidence and shelf life of mushroom. At the 7th day of storage, the highest weight loss (98.08%) was recorded in the untreated mushrooms, whereas the lowest weight loss (33.62%) was observed in mushrooms wrapped in unperforated plastic bag. Protein content was observed to be higher (28.98%) in mushrooms wrapped with unperforated plastic bag followed by perforated plastic bag (25.00%) at the 5th day of storage. Protein content declined dramatically in mushrooms held atambient conditions. The lowest protein content (2.97%) was recorded in the untreated mushrooms at the 7th day of storage. Unwashed mushrooms held atambient temperature had the highest incidence of disease. The longest shelf lifeof 6 days was recorded in mushrooms wrapped in unperforated plastic bag,whereas the shortest shelf life (3 days) was found in the untreated mushrooms.DOI: http://dx.doi.org/10.3329/pa.v21i1-2.16745 Progress. Agric. 21(1 &amp; 2): 21 - 29, 2010

Availability of soil nitrogen and phosphorus under elevated [CO2] and temperature in the Taihu Lake region, China

AbstractGlobal climate change affects the availability of soil nutrients, thereby influencing crop productivity. This study examined the effects of elevated [CO2] and temperature on the availability of soil N and P in a paddy field in the Taihu Lake region, China. Winter wheat (Triticum aestivum L.) was planted at two levels of atmospheric [CO2] (375 μmol L–1 ambient; 575 μmol L–1 elevated) and two temperature levels (ambient; ambient + 2°C). The results were as follows: Compared to ambient, the interaction effects of elevated [CO2] and temperature significantly decreased soil NH$ _4^+ $‐N contents by 20.3%, 20.6%, and 18.7% in the jointing, heading, and ripening stages (p &lt; 0.05), respectively, while soil NO3–‐N content had no clear variation trend under different [CO2] and temperature conditions. Elevated [CO2] significantly increased soil available P content by 14.3% in the jointing stage, and elevated temperature significantly decreased soil available P content by 18.8% in the jointing stage. Compared with ambient [CO2], elevated [CO2] significantly increased wheat biomass in jointing and heading stages (p &lt; 0.05). The positive effect of elevated [CO2] on wheat biomass was more significant at ambient temperature (AT) than at elevated temperature (ET) in the middle and late plant growth stages. These results explained that the availability of soil N and P varied under elevated [CO2] and temperature conditions. The application of N and P should be adjusted to meet the need of wheat plants after the wintering stage.

DEVELOPMENT AND VALIDATION OF RP-HPLC METHOD FOR THE ESTIMATION OFTRANDOLAPRIL AND VERAPAMIL IN COMBINED TABLET DOSAGE FORM

A reverse phase high performance liquid chromatographic method was developed and validated asper ICH guidelines for estimation of trandolapril and verapamil in combined tablet dosage form. Theseparation was obtained using a mobile phase consisting of acetonitrile and phosphate buffer adjustingpH to 3.0 in the ratio of 70:30 v/v and using Waters C18 (250 x 4.6 mm, 5 mcm) column maintained atambient temperature. The flow rate was 1.2 mL min-1 and UV detection was monitored at 215 nm. Theretention time (min) and linearity range (mcg mL-1) for trandolapril and verapamil were (5.12, 2.70) and(20-60, 20-60), respectively. The method validation results are within the acceptance criteria for precision,accuracy and linearity. The proposed method was found to be suitable for routine quality control ofmarketed formulation containing these APIs.

Synthesis of monodisperse silver nanoparticles for ink-jet printed flexible electronics

In this study, monodisperse silver nanoparticles were synthesized with anew reduction system consisting of adipoyl hydrazide and dextrose atambient temperature. By this facile and rapid approach, high concentrationmonodisperse silver nanoparticles were obtained on a large scale at lowprotectant/AgNO3 mass ratio which was highly beneficial to low cost and high conductivity. Based on thesynthesized monodisperse silver nanoparticles, conductive inks were prepared with water,ethanol and ethylene glycol as solvents, and were expected to be more environmentallyfriendly. A series of electrocircuits were fabricated by ink-jet printing silver nanoparticle inkon paper substrate with a commercial printer, and they had low resistivity in the range of9.18 × 10 − 8–8.76 × 10 − 8 Ω m after thermaltreatment at 160 °C for 30 min, which was about five times that of bulk silver (1.586 × 10 − 8 Ω m). Moreover, a radio frequency identification (RFID) antenna was fabricated by ink-jetprinting, and 6 m wireless identification was realized after an Alien higgs-3 chip wasmounted on the printed antenna by the flip-chip method. These flexible electrocircuitsproduced by ink-jet printing would have enormous potential for low cost electrodes andsensor devices.

ChemInform Abstract: Facile Synthesis of α-Amino Phosphonates in Water Using a Lewis Acid-Surfactant Combined Catalyst.

Three-component reactions of aldehydes, amines and triethyl phosphite were efficiently catalyzed by scandium tris(dodecyl sulfate) at ambient temperature in water to give various α-amino phosphonates in high yields.

Effects of storage temperature and humidity on shelf life and quality of African pear (Dacryodes edulis) fruits

The post harvest quality of African pear (Dacryodes edulis) fruits stored at ambient and refrigeration temperatures (300C, 100C and 50C) under the ambient vapour pressure and three relative humidities (65%, 75% and 81%) was studied. Results showed that the rates of growth of microorganisms, moisture loss, weight loss, browning and softening rates increased rapidly for all the African pear fruits stored atambient temperature (300C) in the four respective humidities. However, the quality losses as well as microbiological growths were drastically reduced when the fruits were stored at the lowest storage temperature (50C) and under three relative humidity regimes of 65%, 75% and81%. The African pear fruits stored at 50C under ambient vapour pressure have an average shelf life of 27days as against 31 days average recorded for those stored in 65%-81% relative humidity. Storage in this medium relative humidity (65%-81%) at refrigeration temperature of 100C extended the shelf life of African pear fruits to an average of 24 days as against 18 days which was recorded for pearsstored at the same refrigeration temperature at ambient vapour pressure.

Influence of Synthesis Condition on N&lt;sub&gt;2&lt;/sub&gt; Adsorption Characteristics of Anatase TiO&lt;sub&gt;2&lt;/sub&gt; Particles Prepared in an Aqueous Solution

TiO2 was crystallized to form particles in aqueous solutions containing ammonium hexafluorotitanate and boric acid. XRD diffraction patterns indicated they were in a single phase of anatase TiO2. TiO2 particles prepared at 90 °C exhibited N2 adsorption-desorption isotherms of type IV. BET specific surface area of the particles was estimated to 13 m2/g. On the other hand, TiO2 particles prepared at 50 °C exhibited N2 adsorption-desorption isotherms of type I. BET specific surface area of the particles was estimated to 168 m2/g. Crystal growth of TiO2 was strongly affected by synthesis temperature. Nano-sized pores or surface structure of TiO2 particles prepared at 50 °C would increase N2 adsorption volume to realize high BET specific surface area. Additionally, aqueous solution process described here had an advantage that TiO2 crystallized at ambient temperature. Anatase TiO2 was prepared without annealing at high temperature which caused aggregation of particles and disappearance of surface nanostructures. The particles with large surface area can be thus utilized for catalyst, cosmetic, photocatalyst, dye-sensitized solar cell or sensors.

Microstructure and Mechanical Properties of Al-0.5 at.% X (=Si, Ag, Mg) Alloys Highly Deformed by ARB Process

Effect of solid solution elements on microstructure evolution and mechanical properties was investigated using a high purity Al (purity 99.99%) and Al-0.5 at.% X ( X = Si, Ag, Mg ) alloys deformed by accumulative roll bonding (ARB) process up to 7 cycles (equivalent strain of 5.6) at ambient temperature. The ARB-processed high purity Al showed the equiaxed microstructure having mean grain size of 750 nm. On the other hand, the microstructure of the ARB-processed Al-0.5at.%X alloys showed lamellar boundary structures elongated along RD. The mean lamellar boundary spacing significantly differed depending on the alloying elements, which suggested that solute atoms had a significant effect on microstructure evolution. The difference in the grain size was regarded to be caused by the difference in recovery processes in the alloys. The tensile strength of the alloys increased with increasing the number of ARB cycles. In the Al-Si and Al-Ag alloys, the post-uniform elongation increased with increasing the number of the ARB cycles. On the other hand, the elongation of the Al-Mg hardly changed during the ARB process.

Water diffusion in a synthetic hectorite by neutron scattering—beyond the isotropictranslational model

A quasi-elastic neutron scattering study of water dynamics confined in a model clay system (a synthetichectorite with Na+ compensating counterions) is presented. The neutron spin echo (NSE) data obtained atambient temperature for the monohydrated and bihydrated hectorite powder areanalysed with the help of models taking into account the anisotropy of the system. Apowder-averaged two-dimensional (2D) diffusion model applied to the monohydrated stateyields a 2D diffusion coefficient in the plane of the clay layers () of 2.8 × 10−10 m2 s−1, where an isotropic analysis of the data would have underestimated the diffusion coefficientby approximately 25%. In the case of the bihydrated state, the analysis by amodel including a possible diffusion perpendicular to the clay layers () leads to a range of values for between 3.5 and 8.7 × 10−10 m2 s−1, depending on the ratio . We conclude that simple isotropic analysis can only give a rough estimate (order ofmagnitude) of the water dynamics in the medium.

Potential Benefits of Silicon Carbide Zener Diodes Used as Components of Intrinsically Safe Barriers

Zener diodes are widely used in electrical barriers to protect equipment operating in a potentially explosive atmosphere. Although normally not conducting, the zeners must have a high power rating so that their junction temperature meets safety factors when shunting the maximum fuse current. This often requires two or three lower voltage commercial zeners connected in series. Silicon carbide diodes have much higher thermal conductivity and maximum allowed junction temperature, so it should be possible to use one SiC zener in the place of two or three commercial diodes and/or allow use of higher fuse ratings. Low voltage SiC Zener diodes were fabricated and tested to evaluate potential benefits of their application as a component of intrinsically safe barriers. The diodes demonstrated mixed avalanche-tunnel breakdown at reverse bias voltages of 23 V with positive temperature coefficients of breakdown voltages of about 0.4 mV/°C. The diodes with mesa area of 4×10-4cm2 had maximum DC Zener current of 1.2 A and were capable of operating at ambient temperatures up to 500°C.

Fatigue Behaviour of Type 444 Stainless Steel at Elevated Temperatures

This paper describes the fatigue behaviour at elevated temperatures in a ferritic stainless steel, type 444. Test temperatures evaluated were ambient temperature, 673K and 773K in laboratory air. Fatigue strength decreased at elevated temperatures compared with at ambient temperature. At all temperatures, cracks were generated at the specimen surface due to cyclic slip deformation, but fractographic analysis revealed a brittle features in fracture surface near the crack initiation site at elevated temperatures. Cracks initiated earlier at elevated temperatures than at ambient temperature and subsequent small cracks grew faster at elevated temperatures even though the difference in elastic modulus was taken into account, indicating the decrease in crack initiation resistance and crack growth resistance. The observed decrease in both resistances was discussed in relation to the 748K(475C) embrittlement in ferritic stainless steels.