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1.
The power to survive prolonged exposure to low temperatures is possessed by various enzymes, including those producing hydrolysis of fats, of carbohydrates, and of proteins, those concerned in biochemical oxidations and reductions, the clotting enzymes and that of alcoholic fermentation. The enzymes retained their catalytic power after exposure, either in situ or in solution in vitro, to temperatures varying from a few degrees above 0° C. to the temperature of liquid air (?180° to ?191° C.). The shortest periods of holding, invariably less that one day and usually less than one hour, were at the temperature of liquid air. The longest period of holding was eighty-nine months at a temperature of ?9.4° to ?12.2° C.The activity of certain of these enzymes, including rennin, zymase, and those hydrolyzing fats, carbohydrates, and proteins, has been studied at low temperatures, varying from that of an ice-box to one of ?9° to ?12° C. While the enzymes produced autolytic digestion or acted on artificial media at these temperatures, the velocity of the reaction was always lessened to a considerable degree.  相似文献   

2.
BackgroundRemoval of dyes from wastewater by microorganisms through adsorption, degradation, or accumulation has been investigated. Biological methods used for dye treatment are generally always effective and environmentally friendly. In this study, biosorption of the Fast Black K salt azo dye by the bacterium Rhodopseudomonas palustris 51ATA was studied spectrophotometrically, at various pH (2–10), temperatures (25°C, 35°C, and 45°C) and dye concentrations (25–400 mg L-1).ResultsThe bacterial strain showed extremely good dye-removing potential at various dye concentrations. IR studies at different temperatures showed that the dye was adsorbed on the bacterial surface at lower temperatures. Characteristics of the adsorption process were investigated by Scatchard analysis at 25°C and 35°C. Scatchard analysis of the equilibrium binding data for the dye on this bacterium gave rise to linear plots, indicating that the Langmuir model could be applied. The regression coefficients obtained for the dye from the Freundlich and Langmuir models were significant and divergence from the Scatchard plot was observed.ConclusionThe adsorption behavior of the dye on this bacterium was expressed by the Langmuir, Freundlich, and Temkin isotherms. The adsorption data with respect to various temperatures provided an excellent fit to the Freundlich isotherm. However, when the Langmuir and Temkin isotherm models were applied to these data, a good fit was only obtained for the dye at lower temperatures, thus indicating that the biosorption ability of R. palustris 51ATA is dependent on temperature, pH, and dye concentration.How to cite: Öztürk A, Bayol E, Abdullah MI. Characterization of the biosorption of fast black azo dye K salt by the bacterium Rhodopseudomonas palustris 51ATA strain. Electron J Biotechnol 2020;46. https://doi.org/10.1016/j.ejbt.2020.05.002.  相似文献   

3.
1960年至2007年汾河流域气温年际和季节性变化特征分析   总被引：7，自引：3，他引：4  
刘宇峰  孙虎  原志华 《资源科学》2011,33(3):489-496
运用线性倾向分析、滑动平均法、Mann-Kendall法等数理分析方法,对山西省汾河流域19个气象站1960年-2007年的逐月气温资料进行了分析。研究表明:自1960年以来,汾河流域年平均气温、平均最高和最低气温均呈波动变化趋势,并有升高趋势,递增率分别为0.32℃/10a、0.13℃/10a和0.50℃/10a。同时,气温年较差呈减小趋势,近48年的气温年较差递减率为0.37℃/10a。此外,年平均气温、平均最高和最低气温发生趋暖突变的时间分别是1993年、1996年、1981年,且近15年是流域年平均气温发生上升的主要时段。气候趋暖还表现出在冬季气温的递增速率最大的特点。流域南北年均气温变化的区域差异并不是很明显,但就各区域的季节变化而言,春冬两季的年均气温变化则表现出明显的区域差异。  相似文献   

4.
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5.
Using the velocity analyzer of Zartman with improved technique the combined velocity spectrum of Bi atoms and Bi2 molecules was obtained at 827°, 851°, 875°, 899°, 922°, 947° C. From the spectral distribution curves the relative abundance of Bi atoms and Bi2 molecules in the beams at the above temperatures could be determined to 1 per cent. The vapor pressure curve of Bi was obtained experimentally by the method of effusion and the values so obtained were combined with the degree of dissociation of the vapor as computed from the beams to give the heat of dissociation. The heat of dissociation was computed from the data, assuming the pressure to be given by the temperature of the crucible Tc. In calculating the heat of dissociation, the equilibrium temperature was taken as that of the slit chamber Ts which was 24° above Tc. The results of these calculations plotted with log10Kp as ordinates against 1Ts give a straight line whose slope yields the value of the heat of dissociation as 77,100±1200 calories. The curves for the distribution of velocities observed and computed on the assumption of a given ratio of Bi atoms to Bi2 molecules in the beam were compared in an attempt to test the law of distribution of velocities. On the high velocity side agreement in two curves was obtained within the limits of experimental accuracy. On the low velocity side important deviations were noted of such a sort that the observed curves below a velocity α2, (α is the most probable velocity) gave more molecules than the theory demanded. Other deviations were observed on some of the runs taken with a fourth slit in which a deficiency of molecules was observed between velocities of .75α and α2. This deviation was probably due to a warping of the fourth slit carriage due to heat. The nature of the variation at velocities less than α2 indicated the presence of molecules of greater mass than Bi2 in the beam and at the lower temperatures a distinct peak corresponding to Bi8 molecules was observed which were present to less than 2 per cent. The vapor pressure curve for Bi was determined by least square reduction of the observed points to be given by log10 P = ? 52.23 × 195.26T + 8.56 between 1100° and 1220° abs. It lies very close to the extrapolated curve given in the International Critical Tables.  相似文献   

6.
BackgroundXylanases and β-d-xylosidases are the most important enzymes responsible for the degradation of xylan, the second main constituent of plant cell walls.ResultsIn this study, the main extracellular xylanase (XYL I) and β-xylosidase (BXYL I) from the fungus Penicillium janczewskii were purified, characterized and applied for the hydrolysis of different substrates. Their molecular weights under denaturing and non-denaturing conditions were, respectively, 30.4 and 23.6 kDa for XYL I, and 100 and 200 kDa for BXYL I, indicating that the latter is homodimeric. XYL I is highly glycosylated (78%) with optimal activity in pH 6.0 at 65°C, while BXYL I presented lower sugar content (10.5%) and optimal activity in pH 5.0 at 75°C. The half-lives of XYL I at 55, 60 and 65°C were 125, 16 and 6 min, respectively. At 60°C, BXYL I retained almost 100% of the activity after 6 h. NH4+, Na+, DTT and β-mercaptoethanol stimulated XYL I, while activation of BXYL I was not observed. Interestingly, XYL I was only partially inhibited by Hg2 +, while BXYL I was completely inhibited. Xylobiose, xylotriose and larger xylooligosaccharides were the main products from xylan hydrolysis by XYL I. BXYL I hydrolyzed xylobiose and larger xylooligosaccharides with no activity against xylans.ConclusionThe enzymes act synergistically in the degradation of xylans, and present industrial characteristics especially in relation to optimal activity at high temperatures, prolonged stability of BXYL I at 60°C, and stability of XYL I in wide pH range.  相似文献   

7.
Not many years ago it was quite generally believed that iron was unable to follow rapid magnetic changes. Experiments which showed an apparent decrease in the permeability of the iron with an increase in the frequency of the magnetic cycle furnished a basis for a theory that iron was magnetically sluggish. Further and more accurate experiments proved, however, that the effects which had previously been ascribed to a peculiarity of the material were in reality caused by eddy currents in the sample. Theoretical calculations were made which demostrated that eddy currents in an iron test piece increased as the square of the frequency and that for even the lower frequencies it was necessary to use quite thin laminations in magnetic circuits in order to eliminate deleterious effects. Furthermore, it was found that due to eddy currents and the magnetic properties of iron, the magnetization in high frequency fields was confined to a thin surface layer of the piece. This “Magnetic Skin Effect” reduced the cross section of the iron which was magnetically active even though the laminations were extremely thin. Careful experimental measurements compared with theoretical calculations proved that the real permeability of iron remained unchanged at frequencies up to about 106 and that previous results had been is serious error due to neglect of the factors mentioned. This fact having been established, efforts were made to see what practical use could be made of iron in high frequency work and to that end some extensive experimental investigations of the saturation curves and core losses were made upon specimens laminated as thinly as was commercially practicable. The resulting data have furnished a basis for design.It is a demostrated fact that the permeability of all metals is unity for the magnetic cycles imposed upon them by heat and light waves. In the region between frequencies of about 106, where the true permeability of iron is practically the same as at zero frequency, and frequencies of about 1010 where the true permeability of iron approaches unity, the experimental values of μ decrease smoothly with the frequency. What happens to μ in the range of frequencies between the lingest heat waves and the shortest Hertzian waves which have yet been made is a question which has many interesting features but which has not yet yielded to the experimenter.  相似文献   

8.
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9.
We have carried out a geometrical analysis which applies to that type of cosmic ray deflection experiment in which an extended region of magnetic field lies between the lower two of three or more Geiger-Mueller counters arranged in line for counting coincident discharges. It is apparent that charged particles of sufficiently low energy will be deviated away from the last counter and that the counting rate will therefore be reduced by application of the field. This paper presents a method for computing what proportion of electrons of a given energy will be eliminated by application of the field. The method is extended to include a constant loss of energy per unit path length as the particle traverses an iron core. The results of the experiments of Curtiss and of Mott-Smith are interpreted in the light of these calculations. Curtiss' result could be explained if all rays were electrons of 4 × 108 volts energy. One may conclude from his observation that if all the radiation consists of positive or negative electrons, the fraction between 2 × 107 volts and 1.5 × 108 volts is less than 30 per cent. of the total above 2 × 107, and that the fraction between 2 × 107 and 109 is greater than 30 per cent. A comparison of Curtiss' and Mott-Smith's experiments yields no reason for doubting the correctness of using the magnetic induction B when computing the deflection within iron. Nor does it necessarily sustain this procedure. An experiment by W. F. G. Swann and the writer is at present under way for the purpose of securing, if possible, more conclusive evidence on this point.  相似文献   

10.
This paper outlines the cathode characteristics of thoria which lead to its selection in certain cases where the barium-strontium oxide cathode is unsuitable. Dependable values of pulsed thermionic emission of 4 amps/cm.2 at 1600° C. and 14 or 15 amps/cm.2 at 1800° C. are available.The decay of emission with time is much less rapid than with barium-strontium oxides, the time constants being of the order of one-tenth of 1 second. Maximum d-c. emission, that is, equilibrium emission after decay, is found to be between 1 and 5 amps/cm.2. Although when compared to barium-strontium oxide the activation phenomena are not prominent, it is found that the same essential pattern exists. For use in pulsed applications the life of a thoria coated cathode is determined by its evaporation rate. At 1800° C. where 14 amps/cm.2 is available the coating disappears at the rate of 1 mil thickness in about 300 hours.  相似文献   

11.
The goal of this study was to determine the stability of Total Prostrate Specific antigen (PSA-T) and Free Prostrate Specific Antigen (PSA-F) in archival serum stored at 4°C and −20°C and subjected to temperature shift due to interruption in power supply. Our study showed that PSA-T was stable up to 285 days and PSA-F was stable for 158 days under these conditions. Since power supply interruption is an unavoidable problem in developing nations, our study has implication on the validity of measurement of PSA-T and PSA-F in serum that was not properly stored due to emergency situations and for certain types of retrospective studies.  相似文献   

12.
DNA samples from a family (parents and a son) with hereditary persistence of fetal hemoglobin (HPFH) condition were subjected to amplification of a 1.214 kbp DNA fragment from β-globin gene using polymerase chain reaction (PCR). The aim of this study was to identify the type of HPFH i.e. deletional or non deletional. Non deletional type of HPFH was identified in two samples and moreover, these samples were found to be associated with 619bp β°-thalassemia deletion. This is the first report on the association of non deletional HPFH with 619bp β°-thalassemia deletion.  相似文献   

13.
BackgroundLipases are used in detergent industries to minimise the use of phosphate-based chemicals in detergent formulations. The use of lipase in household laundry reduces environmental pollution and enhances the ability of detergent to remove tough oil or grease stains.ResultsA lipase-producing indigenous Bacillus subtilis strain [accession no. KT985358] was isolated from the foothills of Trikuta mountain in Jammu and Kashmir, India. The lipase (BSK-L) produced by this strain expressed alkali and thermotolerance. Lipase has an optimal activity at pH 8.0 and temperature 37°C, whereas it is stable at pH 6.0–9.0 and showed active lipolytic activity at temperatures 30 to 60°C. Furthermore, lipase activity was found to be stimulated in the presence of the metal ions Mn2 +, K+, Zn2 +, Fe2 + and Ca2 +. This lipase was resistant to surfactants, oxidising agents and commercial detergents, suggesting it as a potential candidate for detergent formulation. BSK-L displayed noticeable capability to remove oil stains when used in different washing solutions containing buffer, lipase and commercial detergent. The maximum olive oil removal percentage obtained was 68% when the optimum detergent concentration (Fena) was 0.3%. The oil removal percentage from olive oil-soiled cotton fabric increased with 40 U/mL of lipase.ConclusionsThis BSK-L enzyme has the potential for removing oil stains by developing a pre-soaked solution for detergent formulation and was compatible with surfactants, oxidising agents and commercial detergents.  相似文献   

14.
文章介绍了太阳系和太阳系外行星冰冻圈。太阳系各行星和卫星的表面温度差异很大,它们的冰冻圈发育各不相同。水星和月球的两极陨石坑的永久阴影区中可能有水冰存在。金星太热,表面既没有液态水,也不可能有水冰存在。火星两极存在永久性冰帽,包括水冰和干冰(固态CO2)。在太阳系雪线之外,存在很多冰卫星和富含水的矮行星,它们的主要是由水冰组成的;在极低的温度下,水冰甚至比地球上的岩石还要坚硬,并成为这些星体的壳层。除了水冰,其他易挥发组分如CO2、CH4、N2、CO等在极低温度下都会凝固为冰,形成不同于水冰的冰冻圈。因此,行星冰冻圈具有与地球冰冻圈迥然不同的丰富多样性。对行星冰冻圈的研究有助于我们扩大视野,更深入地理解地球冰冻圈,也将有助于我们理解太阳系的形成、地球水分的来源、地球深时古气候环境和生命演化,以及开展未来的系外生命探测。  相似文献   

15.
The problem of calculating the resonance frequency and power pulsation of a synchronous motor direct connected to reciprocating apparatus is comparatively easy, provided the machine is operated from an infinite system, i.e., a system having constant voltage and frequency.In this paper a method is developed for calculating the resonance frequency of two synchronous machines electrically in parallel. It is also shown that in a system of n machines in parallel, there are (n - I) resonance frequencies. A general method of calculating these is given. Systems of three and four machines are treated as special examples of the general case. The theory is also given for calculating the actual power pulsations which occur in systems of two and three synchronous machines connected to reciprocating apparatus. With some approximation the theory is extended to four machines and a general method for n machines is suggested.Simple methods of calculating the correct sizes of flywheels necessary for the successful parallel operation of engine-driven generators are given. These are calculated directly from a knowledge of the resonance frequencies involved.In general the thesis is a mathematical treatment of the phenomena which occur in connection with hunting of synchronous machines, electrically in parallel and direct connected to reciprocating apparatus. Specific problems have been treated and illustrative examples presented which make quite clear not only the nature and causes of hunting, but also the methods of overcoming it.  相似文献   

16.
针对分时操作系统,依据任务执行时间提出系统性能损失作为性能参数,定义最佳节能条件并推出最佳节能频率的计算公式;进而重点论述为实现分时操作系统中的频率管理模块,在系统频率为离散值的前提下,如何对最佳节能频率进行有效近似;最后利用实现了频率管理模块的Linux,实验验证了最佳节能频率以及对其实现的正确性和有效性,而所增加的系统开销仅为3.63%.  相似文献   

17.
BackgroundSulphur-oxidizing microorganisms are widely used in the biofiltration of total reduced sulphur compounds (odorous and neurotoxic) produced by industries such as the cellulose and petrochemical industries, which include high-temperature process steps. Some hyperthermophilic microorganisms have the capability to oxidize these compounds at high temperatures (> 60°C), and archaea of this group, for example, Sulfolobus metallicus, are commonly used in biofiltration technology.ResultsIn this study, a hyperthermophilic sulphur-oxidizing strain of archaea was isolated from a hot spring (Chillán, Chile) and designated as M1. It was identified as archaea of the genus Sulfolobus (99% homology with S. solfataricus 16S rDNA). Biofilms of this culture grown on polyethylene rings showed an elemental sulphur oxidation rate of 95.15 ± 15.39 mg S l-1 d-1, higher than the rate exhibited by the biofilm of the sulphur-oxidizing archaea S. metallicus (56.8 ± 10.91 mg l-1 d-1).ConclusionsThe results suggest that the culture M1 is useful for the biofiltration of total reduced sulphur gases at high temperatures and for other biotechnological applications.  相似文献   

18.
The present preliminary study was performed to find out stability of total prostate specific antigen (PSA) and free prostate specific antigen (FPSA) in serum of healthy males as well as in patients of benign and malignant disorders of prostate at various freezing and nonfreezing temperatures and at different duration of time. The results of our study indicated long-term stability of both the analytes in frozen serum. Serum total and free PSA were stable only for three to four days in regular refrigerators in unfrozen states. Clotted blood kept at room temperature (25°C–30°C) did not cause change in concentrations of both the analytes for twenty four hours.  相似文献   

19.
Since ammonia, when added to the dye bath in preparing bathed plates, increases the sensitizing action of the dye, its action on commercial plates was investigated.In the course of the work three methods of sensitometry were used. Of these, one was used as a first qualitative test; the second, the spectrograph method, was used to study the effect of the ammonia on the sensitivity of the plate to each wave-length; the third, the Hurter and Driffield method, gives the absolute value of the speed of the plate.It was found that by bathing commercial panchromatic plates in a solution of 25 c.c. ethyl-alcohol, 75 c.c. water, and 3 c.c. of strong ammonia water (20 per cent. NH3) for four minutes at 18° C. and drying rapidly, the speed to white light is increased 100 per cent. in nearly all cases, and the sensitivity in the red. extended one hundred or more Ångström units. The speed in the red is increased, in many cases, 400 per cent. If the plates be bathed without the alcohol (100 c.c. water, 312 c.c. ammonia water) the speed is still more increased, but the plates should be used immediately after drying.Ordinary plates do not have their sensitivity appreciably changed. Most brands of orthochromatic plates are not improved, although one, the Cramer Trichromatic, showed the same increase as the panchromatic plate.  相似文献   

20.
In an alternating current servomechanism, the error is proportional to the modulation envelope of a modulated-carrier error signal. It is shown in part I that for stability and fidelity of the servo, it is highly desirable that the effect of the controller includes a proportional-derivative action on the modulation envelope. This action may be obtained with various forms of RC networks, including the parallel “T,” bridge “T,” and Wien Bridge forms.This part contains detailed design procedures and tables of values for the various types of proportional-derivative networks. Several forms of parallel “T” networks arise from the fact that there are five independent time constants in the network, while in order to realize the desired transfer characteristic it is necessary to impose only four conditions. It is indicated how the remaining degree of freedom may be used to obtain the most suitable input and output impedances for the source and load impedances with which the parallel “T” is to be used. The derivations for the parallel “T” formulae are given in an Appendix.Tolerance requirements on the components of parallel “T” and bridge “T” networks are derived. If ±1 per cent components are used at 60 cycles, the resonant frequency will lie between 56.4 and 63.6 cycles, and the notch width (rejection band width) will be within ±0.99 cps. of the correct value. In order to guarantee that the phase shift at 60 cycles is within ±10°, the percentage deviation of each part must be less than (9.0Tdω0), where ω0 is the carrier angular frequency, Td the derivative time constant.  相似文献   

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