重组大肠杆菌利用醋酸及乳酸为碳源合成PHB

以廉价的工业副产物醋酸及乳酸为碳源,对产PHB重组大肠杆菌进行培养,考察醋酸及乳酸的添加对重组大肠杆菌生长及PHB产量的影响。将来自Cupriavidusnecator的PHB合成操纵子phaCAB基因簇克隆至pBAD载体,得到产PHB菌株BL21＿pBAD＿phaCAB,以阿拉伯糖为诱导剂,在大肠杆菌中进行重组表达。分别使用LB及M9培养基,对重组菌株BL21＿pBAD＿phaCAB进行培养,研究其生长速度及PHB产量,探索产PHB重组大肠杆菌最适培养基。以添加0.04 g/L乳酸、1.2 g/L乳酸、0.02 g/L醋酸、0.6 g/L醋酸、0.04 g/L乳酸+0.02g/L醋酸、1.2g/L乳酸+0.4g/L醋酸的M9培养基(均含2 g/L葡萄糖)为实验组,以M9培养基(含2g/L葡萄糖)为对照组,考察醋酸及乳酸的添加对重组大肠杆菌生长及PHB产量的影响。分别取第6,12,24和36小时的培养液,分析其葡萄糖、醋酸及乳酸含量的变化。结果表明,低氮型M9培养基更适合产PHB重组大肠杆菌在低糖培养环境中生长。在葡萄糖消耗殆尽后,大肠杆菌能够以醋酸及乳酸为碳源进行代谢,因此在培养基中...     

Preparation and characterization of doubly substituted microwave absorbing material by sol-gel technique for super high frequency applications

Rare earth Dy~(3+)and divalent Mn~(2+)elements substituting W-type hexagonal ferrites Ba_(1-x)Dy_xZn_2Fe_(16-y)Mn_yO_(27)(x=0,0.02,0.06,0.1 and y=0,0.1,0.3,0.5)were prepared by sol-gel method.The thermo-gravimetric analysis(TGA)and differential scanning calorimetry(DSC)was carried out to find the temperature at which single phase can be obtained.XRD patterns indicate the presence of the single phase for all the synthesized samples with the absence of any extra peak due to unreacted material and secondary phases.The occurrence of absorption bands at low wave numbers(563 and 446 cm~(-1)),can be assigned to the stretching vibration of metal and oxygen ions in FTIR spectra,which also confirms the single hexagonal phase for prepared material.The grains are of platelet like structure,which enhances the microwave absorption properties of hexagonal ferrites.The synthesized material exhibits the minimum reflection loss of-20.9 dB at 11.8 GHz frequency,which reflects the applications of this material in super high frequency devices.The microwave conductivity of the material increases with frequency.     

Bioactivity analysis of the Ta (V) doped SiO2–CaO–Na2O–P2O5 ceramics prepared by solid state sintering method

The main objective of the study was to control the degradation rate of material at a higher degradation rate improving the chemical stability of the material. Ta is known to have good chemical resistance, biocompatibility and show no adverse biological response. In the present study, SiO2–Na2O–CaO–P2O5 bioceramics with different Ta2O5 contents was prepared by solid state sintering method at 1000 °C. The as-sintered ceramics were subjected to immersion studies in stimulated body fluid (SBF) for 21 days under static condition and characterized by XRD, FTIR, SEM, and AAS. The findings of the research indicate that the addition of Ta2O5 controlled degradability, and all samples showed sufficient bioactivity.     

Reduced bit low power VLSI architectures for motion estimation

Low power and real time very large scale integration(VLSI) architectures of motion estimation(ME) algorithms for mobile devices and applications are presented.The power reduction is achieved by devising a novel correction recovery mechanism based on algorithms which allow the use of reduced bit sum of absolute difference(RBSAD) metric for calculating matching error and conversion to full resolution sum of absolute difference(SAD) metric whenever necessary.Parallel and pipelined architectures for high throughput of full search ME corresponding to both the full resolution SAD and the generalized RBSAD algorithm are synthesized using Xilinx Synthesis Tools(XST),where the ME designs based on reduced bit(RB) algorithms demonstrate the reduction in power consumption up to 45% and/or the reduction in area up to 38%.     

Concentration and temperature dependence of viscosity of uranium solutions in H2O and 3mol／L HNO3

Viscosities of uranium solutions in H2O and 3mol/L HNO3 medium were measured by Ubbelhode flow viscometer in the concentration range of 0.5%-3.0% from 10℃ to 30℃ at 5℃ interval.Viscosity data were interpreted in terms of an empirical equation;η=aoexp(boM coM^2).Values of coefficients ao, bo and Co were calculated for all the three systems studied. Flow activation energies and thermodynamic parameters were also evaluated.     

Structural and dielectric study of nano-crystalline single phase Sn1−xNixS (xNi=0–10%) showing room temperature ferromagnetism

SnS is a promising Ⅳ-Ⅵ semiconductor,which is very less explored for diluted magnetic semiconducting and dielectric applications.In this study,the Ni doping(x_(Ni)=0-10mol%) effects on SnS host lattice were investigated.A simple and low cost co-precipitation technique was employed to grow Ni doped SnS powders.The X-ray diffraction confirmed single phase orthorhombic structure with a nano-crystalline nature that was further verified through the surface structure observed by scanning electron microscopy.Near edge x-ray absorption fine structure spectroscopy revealed a shift in the Ni absorption edge towards higher energy,depicting the formation of Ni~(+3) oxidation state.The impedance measurements,in the frequency range 1 kHz to 20 MHz,depict that owing to the excellent sensitivity to the electromagnetic radiations at the low energy,the Ni doped SnS finds potential applications in various energy related devices.Vibrating sample magnetometer measurements have elucidated room temperature ferromagnetism,which depicts potential memory device applications.     

Effects of drug-polymer dispersions on solubility and <Emphasis Type="Italic">in vitro</Emphasis> diffusion of artemisinin across a polydimethylsiloxane membrane

Artemisinin(ART) is a sesquiterpene lactone with an endo-peroxide bridge that is thought to be responsible for its antimalarial activity.It has low oral bioavailability because of aqueous insolubility,which leads to local toxicity at the site of aggregation.The present work focused on increasing its solubility and evaluating its permeation across a model membrane to mimic transdermal delivery that bypasses the hepatic metabolism.For this purpose,physical mixtures(PM),solid dispersions(SD) and lyophilized dispersions(LD) with different drug-polymer ratios(1:0.5,1:1,1:2,1:4 and 1:9) were prepared using the hydrophilic polymer polyvinylpyrrolidone(PVP).Drug-polymer dispersions were characterized using X-ray diffraction(XRD) and Fourier transform infrared spectroscopy(FTIR).Solubility was measured in three solvents:de-ionized water,phosphate buffered saline(PBS) and methanol.The toluene-water partition coefficient was evaluated and compared with the literature and calculated logP values.In vitro diffusion of ART was studied across a polydimethylsiloxane membrane from a saturated solution of drug-polymer dispersions.XRD patterns showed a gradual decrease in crystallinity of ART with increasing polymer concentration,while FTIR confirmed no interactions between ART and PVP.Solubility was increased up to 4-,5-and 8-fold for LD in water,PBS and methanol,respectively.The logP for toluene-water was 2.65 ± 0.3,which is in good agreement with literature and calculated logP values.Permeation was enhanced,which is attributed to the decrease in crystallinity and increase in wettability of the drug.The ART flux was significantly higher than that of pure ART(0.12 ± 0.01) with increasing PVP concentration for SD and LD formulations.In conclusion,drug-polymer dispersions with PVP improve the pharmaceutical properties of ART in the order LD>SD>PM.     

Effect of oxygen content on the structural and optical properties of ZnO films grown by atmospheric pressure MOCVD

Atmospheric pressure MOCVD was used to deposit ZnO layers on sapphire and homoepitaxial template under different oxygen flow rates.Oxygen content affects the lattice constant value and texture coefficient of the films as evidenced by the θ-2θ peaks position and their intensity.Films deposited at lower oxygen flow rate possess higher value of strain and stresses.ZnO films deposited at high oxygen flow rates show intense UV emissions while samples prepared under oxygen deficient conditions exhibited defect related emission along with UV luminescence.The results are compared to the ZnO films deposited homoepitaxially on annealed ZnO samples.The data obtained suggest that ZnO stoichiometry is responsible for the structural and optical quality of ZnO films.