Negligible Effect Of Temperature Research Articles

Effect of calcium hydroxide on pasting, thermal, and water‐adsorption behavior, and the flow properties of nixtamalized corn flour

AbstractNixtamalized corn flour (NCF) has gained favor worldwide due to the growing popularity of Mexican cuisine. This research evaluates the effect of the amount of calcium hydroxide (Ca(OH)2) employed during the nixtamalization on the water‐adsorption, thermodynamic, and flow properties of NCF. In addition, NCF pasting and thermal properties were evaluated to relate bulk‐powder properties to wet‐dispersion conditions. Ca(OH)2 amounts of 1.5 and 2.0% induced higher ash and calcium content as well as lower fat and protein content. Also, pasting properties and gelatinization enthalpy (ΔHgel) values, in addition to yellowish NCF, were related to Ca(OH)2 concentration. With the independence of the Ca(OH)2 amounts employed, no important differences in the equilibrium's moisture content, as well as a negligible effect of temperature on adsorption behavior, were observed. For prepared NCF, the moisture content corresponding to minimum integral entropy was not observed within the range of the aw analyzed; thus, GAB parameters are more reliable for suggesting the storage conditions. NCF with a low amount of Ca(OH)2 exhibited higher values of mean caking strength (≈1.81 N) and cohesiveness index (≈13.99 × 10−5 N m g−1), in addition to higher resistance to flow. Therefore, the amount of Ca(OH)2 positively influenced flow properties, whereas wet‐dispersion properties such as lower maximal peak viscosity and ΔHgel values were obtained.Practical applicationsThis study contributes useful information to the manufacturers of NCF concerning the amount of Ca(OH)2 needed to obtain NCF with desirable physical properties while attempting to affect thermal and pasting properties to a lesser extent. In addition, this study characterizes and provides the adequate amount of Ca(OH)2 employed the during the nixtamalization process to improve the flowability of NCF in industry during handling. Finally, the absence of a moisture content corresponding to minimum integral‐adsorption entropy provides clarification for NCF producers regarding the long‐term storage stability of NCF.

Diffusion of CO2 across the Mesophyll-Bundle Sheath Cell Interface in a C4 Plant with Genetically Reduced PEP Carboxylase Activity.

Phosphoenolpyruvate carboxylase (PEPC), localized to the cytosol of the mesophyll cell, catalyzes the first carboxylation step of the C4 photosynthetic pathway. Here, we used RNA interference to target the cytosolic photosynthetic PEPC isoform in Setaria viridis and isolated independent transformants with very low PEPC activities. These plants required high ambient CO2 concentrations for growth, consistent with the essential role of PEPC in C4 photosynthesis. The combination of estimating direct CO2 fixation by the bundle sheath using gas-exchange measurements and modeling C4 photosynthesis with low PEPC activity allowed the calculation of bundle sheath conductance to CO2 diffusion (gbs ) in the progeny of these plants. Measurements made at a range of temperatures suggested no or negligible effect of temperature on gbs depending on the technique used to calculate gbs Anatomical measurements revealed that plants with reduced PEPC activity had reduced cell wall thickness and increased plasmodesmata (PD) density at the mesophyll-bundle sheath (M-BS) cell interface, whereas we observed little difference in these parameters at the mesophyll-mesophyll cell interface. The increased PD density at the M-BS interface was largely driven by an increase in the number of PD pit fields (cluster of PDs) rather than an increase in PD per pit field or the size of pit fields. The correlation of gbs with bundle sheath surface area per leaf area and PD area per M-BS area showed that these parameters and cell wall thickness are important determinants of gbs It is intriguing to speculate that PD development is responsive to changes in C4 photosynthetic flux.

Flexural fatigue life prediction of CFRP-Nomex honeycomb sandwich beams

Long-term flexural fatigue life of composite sandwich beams consisting of plain weave carbon 3K-70P/epoxy (CFRP) faceplates and Nomex honeycomb core is studied using time–temperature superposition principle (TTSP) by extending our previous study on laminates [Composites Part B: Engineering (19):539-547, 2016]. Considering negligible effect of temperature on the honeycomb core performance, time-temperature shift factors (TTSF) of the sandwich beams is assumed to be same as that of the CFRP faceplates. Hence, TTSFs are taken from previous laminates study. Constant strain rate (CSR) experiments at various temperatures and strain rates are conducted to construct the CSR master curve, followed by prediction and validation of creep strength master curve. Flexural fatigue tests were then conducted at various temperatures and load levels to construct S-N curves at respective temperatures. Finally, fatigue strength master curve is constructed. Within experimental scatter, predicted fatigue behavior at any given (a) frequency and (b) load ratio is confirmed to be in reasonable agreement with the experimental measurements.

Impact of Environmental Stressors on the Performance of Backyard Poultry

The present study was conducted to determine the effect of different climatic parameters on production performance of Vanaraja poultry birds under deep litter system of rearing. The experiment was carried out at the hatchery unit of Bihar Veterinary College, Patna. A total of 129 birds were used for the study. Different climatic parameters such as temperature, relative humidity and temperature–humidity index were studied. Based upon average daily dry and wet bulb temperatures, temperature–humidity index values of the shed were calculated. The evaluation of egg production rate and external and internal egg quality traits at different climatic parameters was carried out. The overall average temperature, relative humidity, temperature–humidity index in different months of Bihar ranged from 16.67 ± 0.23 to 33.08 ± 0.28, from 46.60 ± 2.40 to 90.20 ± 1.12 and from 64.84 ± 0.30 to 85.94 ± 0.38, respectively. Egg production, fertility, hatchability on total egg set and on fertile egg set was significantly lower at the temperature–humidity index range from 85.53 ± 0.18 to 85.94 ± 0.38 (May–August). temperature–humidity index values inside the shed in the month of May–August suggested that the birds were in stress during the experiment. However, there was negligible effect of temperature–humidity index on egg quality. It was concluded that during the extremes of temperature–humidity index (>85) the performance of the Vanaraja birds in terms of egg production was less.

Absorption of CO2 from natural gas using different amino acid salt solutions and regeneration using hollow fiber membrane contactors

Natural gas consists primarily of methane but it also contains considerable amounts of contaminating compounds mainly carbon dioxide (CO2). In the present work, the absorption/Stripping performance of four different amino acid salt (AAS) aqueous solutions was compared with MEA and NaOH solutions by using homemade PVDF hollow fiber gas–liquid membrane contactor modules. Compared to MEA, AAS have enhanced CO2 absorption/stripping performance. The experimental results show that the absorption performance can be enhanced by increasing liquid flow rate. However, the gas flow rate has negative effect on the removal efficiency although flux increases. Furthermore, it has been observed that AAS shows negligible effect of temperature on absorption performance. To improve the stripping performance, enhanced CO2 desorption (based on pH-shift) was studied by using asymmetric solutions of AAS. Higher molar ratios of amino acid shows better stripping and reduced absorption performance because lower pH shifts the CO2 reaction equilibrium towards the release of CO2. Also it has been observed AAS solutions have lower potential of membrane wetting due to its high surface tension. Further it has been proved AAS solutions have good recyclability.

Flower wastes as a low-cost adsorbent for the removal of acid blue 9

This paper describes the use of flower wastes (carnation, rose and daisy) as a potential, alternative and low-cost adsorbent for the removal of Acid Blue 9 (AB9). The best conditions to achieve an efficient adsorption were evaluated in a batch process. With an acidic pH of 2.0, a removal exceeding 90% was obtained using concentrations of AB9 of 15.0 mgL-1 and a dosage of adsorbent of 4.0 gL-1. The equilibrium of the process was modeled using the Langmuir and Freundlich isotherms, obtaining a better fit with the latter one. Kinetic studies indicated a better fit of the process to a pseudo-second order model and negligible effect of temperature. In addition, the bromatological characterization of the adsorbent is shown.

High-temperature bioleaching of nickel sulfides: thermodynamic and kinetic implications

The effect of temperature on nickel sulfide bioleaching was studied in the presence of mesophile ( Acidithiobacillus ferrooxidans) and moderate thermophile ( Sulfobacillus thermosulfidooxidans) strains and the results were discussed in terms of sulfide dissolution thermodynamics (Eh–pH diagrams) and kinetics (cyclic voltammetry). It was observed that in the pH range 1.8–2.0 the highest nickel dissolution was achieved which reached 50% for mesophiles and over 80% for moderate thermophiles. External ferrous iron addition had no effect on the metal dissolution at 34 °C, but adversely affected nickel leaching at higher temperatures. The best outcomes were accomplished with low FeSO 4 additions (2.5 g/L) at 50 °C. Pyrrhotite dissolution avoided the need for external iron addition, providing Fe 2+ concentrations as high as 7 g/L during bioleaching, which supports bacterial growth. Eh–pH diagrams for pentlandite and pyrrhotite show a negligible effect of temperature on the stability field of each sulfide whilst cyclic voltammetry indicated that temperature has the strongest influence on pyrrhotite oxidation. The latter along with a rapid increase in solution potential (Eh) explains the higher and faster extraction observed with S. thermosulfidooxidans.

Grb2 adaptor undergoes conformational change upon dimerization

Grb2 is an adaptor protein that couples activated receptor tyrosine kinases to downstream effector molecules such as Ras and Akt. Despite being a central player in mitogenic signaling and a target for therapeutic intervention, the role of Grb2 oligomerization in cellular signaling is not well understood. Here, using the techniques of size-exclusion chromatography, mass spectrometry, analytical ultra-centrifugation and isothermal titration calorimetry, we demonstrate that Grb2 exists in monomer–dimer equilibrium in solution and that the dissociation of dimer into monomers is entropically-driven without an unfavorable enthalpic change at physiological temperatures. Our data indicate that enthalpy and entropy of dimer dissociation are highly temperature-dependent and largely compensate each other resulting in negligible effect of temperature on the overall free energy. From the plot of enthalpy change versus temperature, the magnitude of heat capacity change derived is much smaller than that expected from the rather large molecular surfaces becoming solvent-occluded upon Grb2 dimerization, implying that Grb2 monomers undergo conformational rearrangement upon dimerization. 3D structural models of Grb2 dimer and monomers suggest strongly that such conformational rearrangement upon dimerization may arise from domain swapping. Taken together, our study provides novel insights into the role of Grb2 as an adaptor in cellular signaling circuitry and how Grb2 dimerization may impart high fidelity in signal transduction as well as lead to rapid signal amplification upon receptor stimulation.

Coupling of folding and DNA-binding in the bZIP domains of Jun–Fos heterodimeric transcription factor

In response to mitogenic stimuli, the heterodimeric transcription factor Jun–Fos binds to the promoters of a diverse array of genes involved in critical cellular responses such as cell growth and proliferation, cell cycle regulation, embryogenic development and cancer. In so doing, Jun–Fos heterodimer regulates gene expression central to physiology and pathology of the cell in a specific and timely manner. Here, using the technique of isothermal titration calorimetry (ITC), we report detailed thermodynamics of the bZIP domains of Jun–Fos heterodimer to synthetic dsDNA oligos containing the TRE and CRE consensus promoter elements. Our data suggest that binding of the bZIP domains to both TRE and CRE is under enthalpic control and accompanied by entropic penalty at physiological temperatures. Although the bZIP domains bind to both TRE and CRE with very similar affinities, the enthalpic contributions to the free energy of binding to CRE are more favorable than TRE, while the entropic penalty to the free energy of binding to TRE is smaller than CRE. Despite such differences in their thermodynamic signatures, enthalpy and entropy of binding of the bZIP domains to both TRE and CRE are highly temperature-dependent and largely compensate each other resulting in negligible effect of temperature on the free energy of binding. From the plot of enthalpy change versus temperature, the magnitude of heat capacity change determined is much larger than that expected from the direct association of bZIP domains with DNA. This observation is interpreted to suggest that the basic regions in the bZIP domains are largely unstructured in the absence of DNA and only become structured upon interaction with DNA in a coupled folding and binding manner. Our new findings are rationalized in the context of 3D structural models of bZIP domains of Jun–Fos heterodimer in complex with dsDNA oligos containing the TRE and CRE consensus sequences. Taken together, our study demonstrates that enthalpy is the major driving force for a key protein–DNA interaction pertinent to cellular signaling and that protein–DNA interactions with similar binding affinities may be accompanied by differential thermodynamic signatures. Our data corroborate the notion that the DNA-induced protein structural changes are a general feature of the bZIP family of transcription factors.

Investigations on arsenic(V) removal by modified calcined bauxite

The present study suggests a solution to the real life problem of arsenic poisoning of potable ground water by examining the use of calcined bauxite, a locally available adsorbent in a modified form, for arsenic(V) scavenging. This adsorbent (modified calcined bauxite, MCB) exhibited excellent As(V) removal (99–100%) over a wide range of pH ∼ 2–8 in batch studies. In the neutral pH range (pH ∼ 7), the intensity of adsorption increased from 0.099 to 1.37 mg g −1 corresponding to initial As(V) concentrations of 0.5–8 mg l −1 with a dose of 5 g l −1 within 3 h. The sorption kinetics was found to follow the pseudo-second order model. The Langmuir, Freundlich and Dubinin–Radushkevich models were tried to represent the equilibrium data of As(V) adsorption. The removal of As(V) can be best modeled using Langmuir isotherm which renders the maximum adsorption capacity as 1.566 mg g −1. The sorption process was almost unaffected by temperature variations. During sorption, no appreciable ionic effects except from SO 4 2− and EDTA complex were observed from the background ions Ca 2+, Fe 3+, Cl −, NO 3 −, PO 4 3− and F −. The most distinguishing characteristic was the pH of the effluent within the drinking water range of 6–7.5. The column study results show that at a sorbent bed depth of 10 cm and feed flow rate of 8 ml min −1, the MCB media was capable of treating 8.16 l (260 bed volumes) of As(V) spiked water ( C 0 = 2 mg l −1) before breakthrough. The values of adsorption rate coefficient ( K) and adsorption capacity coefficient ( N) are calculated using Logit method of column design and were found to be 0.2467 l mg −1 h −1 and 865.85 mg l −1, respectively. The XRD data analysis describes chemical combinations of the sorption mechanism. The consistency in arsenic sorption over a wide pH range, availability and adaptability in the local environment, excellent sorption potential, least interference from most of the anions, negligible temperature effects and quality of the treated water makes it an ideal choice for arsenic removal.

Effect of temperature and salt on the phase behavior of nonionic and mixed nonionic–ionic microemulsions with fish-tail diagrams

The phase behavior of Brij-56/1-butanol/n-heptane/water is investigated at 30 °C with α [weight fraction of oil in (oil + water)] =0.5, wherein a 2̲→3→2¯ phase transition occurs with increasing W1 (weight fraction of 1-butanol in total amphiphile) at low X (weight fraction of both the amphiphiles in the mixture) and a 2̲→1→2¯ phase transition occurs at higher X. Addition of an ionic surfactant, sodium dodecylbenzene sulfonate, destroys the three-phase body and decreases the solubilization capacity of the system at different δ (weight fraction of ionic surfactant in total surfactant). A three-phase body appears at α=0.25, but not at α=0.75 for the single system. No three-phase body appears with the mixed system at either α value. Increased temperature increases the solubilization capacity of the Brij-56 system; on the other hand, a negligible effect of temperature on the Brij-56/SDBS mixed system has been observed. Addition of salt (NaCl) produces a three-phase body for both single and mixed systems and increases their solubilization capacities. The monomeric solubility of 1-butanol in oil (S1) and at the interface (S1s) has been calculated using the equation hydrophile–lipophile balance plane for both singles- and mixed-surfactant systems. These parameters have been utilized to explain the increase in solubilization capacity of these systems in the presence of NaCl.

The influence of the mode of enzyme preparation on enzymatic enantioselectivity in organic solvents and its temperature dependence

The enantioselectivities of subtilisin Carlsberg and Rhizomucor miehei lipase in organic solvents are found to strongly depend on the method by which the enzymes are prepared. For the transesterification between sec-phenethyl alcohol and vinyl butyrate in dioxane at 7 degrees C, the enantioselectivity of subtilisin precipitated with isopropanol is more than twice that of the enzyme prepared by lyophilization from aqueous buffer. Furthermore, the temperature dependence of the enantioselectivity is influenced by the mode of enzyme preparation. For example, in the aforementioned process the enantioselectivities of subtilisin lyophilized from aqueous buffer and crosslinked subtilisin crystals increase when the temperature is raised from 7 to 45 degrees C. In contrast, the enantioselectivities decrease with temperature for the enzyme precipitated from aqueous solution with acetone or isopropanol and for the enzymatic hydrolysis in water. The temperature dependence of the enantioselectivity of subtilisin lyophilized from buffer is markedly affected by the solvent: In acetonitrile and nitromethane the enzyme is more enantioselective at higher temperatures, while negligible temperature effects have been found in tetrahydrofuran and pyridine. Lyophilized lipase exhibits striking temperature dependencies of its enantioselectivity in dioxane, acetonitrile, and nitromethane, while showing almost none in pyridine, triethylamine, and tetrahydrofuran. The results underscore the importance of the mode of enzyme recovery on enantioselectivity and its temperature dependence in enzymatic reactions in organic solvents (in contrast to those in water). (c) 1996 John Wiley & Sons, Inc.

Wheat Development as Affected by Radiation at Two Temperatures

A wheat cultivar (Condor) was grown in two experiments (thermal regimes 18/13 and 21/16°C) under low (298 μE m-2: s-1) radiation regimes during either an early phase from seedling emergence to terminal spikelet initiation (S2), a late phase from terminal spikelet initiation to anthesis (S2), or for the full period from seedling emergence to anthesis (S12), or high (560 μE m-2s-1) radiation throughout the growing period (S12) to determine whether developmental events are affected by radiation. The main developmental events considered in this study were the timing of terminal spikelet initiation and anthesis, the final number of leaf and spikelet primordia initiated in the apex and the rate of leaf appearance. Number of grains per spike and culm height were also measured. The duration of each phenophase was not affected by radiation intensity. Temperature affected the rate of wheat development, but the acceleration of development due to temperature during the seedling emergence - terminal spikelet initiation phase only slightly reduced (from 24.8 to 23.2 days). Differences in time from terminal spikelet initiation to anthesis were greater than in the earlier phases, having been the duration reduced from 24.6 to 20.0 days due to high temperature. Associated with the lack of effect of radiation on phasic development and the negligible effect of temperature on the duration of the early phases of development, final Leaf number was practically unchanged in this study by either the radiation level or the growing temperature. Thus, radiation did not affect the rate of leaf initiation. The number of spikelets was affected by neither the treatments nor the thermal environment. The rates of leaf appearance were accelerated by temperature. Radiation, on the other hand, did not significantly alter the rates of leaf appearance in any of the treatments. As expected from many sources in the literature, the number of grains per spike was significantly affected by radiation during the phase from terminal spikelet initiation to anthesis. Due to the lack of significant effects of radiation on the developmental patterns of wheat, the changes in number of grains per spike were due to changes in the number of grains born in each spikelet. The results of the present study were compared with others available in the literature on the effects (or lack of them) of radiation and CO2 concentration on phasic development, plastochron and phyllochron in wheat to reach the general conclusion that the rate of developmental events in wheat, in contrast to other plants, is almost completely independent of the availability of assimilates, with a possible exception for the Equatorial latitudes.

Temperature dependence of the symmetry factor in electrode kinetics

Facts concerning the variation of β with temperature are reviewed. Former models do not explain them. Models examined concern (A) double layer changes with temperature; (B) electrode kinetic effects. As temperature increases, water molecule aggregates dissociate and expand the double layer. Hence, ιβ/ι T = 2 × 10 −4 K −1. As the bias potential increases, the double layer constricts: the consequent effect on β is shown to be negligible. If a non-aqueous solution contains a trace of water, the water occupancy of the double layer will depend on temperature. Reasonable parameter assumptions show this effect to give ιβ/ι T ≅ −1 × 10 −3. Examination of the frequency factor in equations, which relate electron transfer rate to the interfacial field show this factor to give ιβ/ι T ≅ −1 × 10 −4. The electrokinetic potential varies with temperature and gives ιβ/ι T ≅ 2.5 × 10 −4. Quantum mechanical barrier penetration by protons gives about −2 × 10 −4 for ιβ/ι T; and non-adiabaticity ca. 1.7 × 10 −4. Experimental values of ιβ/ι T are in the region of 1.5 × 10 −3. If the solution is of one component, the present theory accounts for about one quarter of the effect. The two component concept allows an explanation of about 90% of the data. The model allows good interpretation of the variation of the pre-exponential factor with temperature for hydrogen solution and oxygen reduction and serves well to interpret the negligible effect of temperature of β for redox reactions.

Aluminium Uptake by Excised Roots of Cabbage, Lettuce and Kikuyu Grass

Uptake of aluminium by excised roots of cabbage, lettuce, kikuyu grass and by a weakly acidic cation exchange resin was studied. The role of metabolism was also investigated, using a range of temperatures and a metabolic inhibitor. The time course of uptake had two phases: an initial rapid phase of about 60 min duration for all species and a slower accumulation phase that was pronounced for cabbage and lettuce and almost absent for kikuyu grass. During the initial phase, calcium was exchanged by aluminium. A small fraction of the aluminium taken up by excised roots could not be desorbed by dilute buffer; this was thought to result from irreversible binding of aluminium directly to exchange sites. Evidence is also presented for a third component for aluminium uptake involving diffusion through the plasmalemma. The non-metabolic nature of the entire uptake process was confirmed by the negligible effect of temperature (1-30°C) and enhancement by 2,4-dinitrophenol on the rate of uptake. Aluminium uptake at pH 4.2 exceeded that at pH 4.0, probably due to the lowering of net charge density of aluminium ions as pH is increased.