Current-voltage behavior of AlGaAs/InGaAs pHEMT structures and the effect of optical illumination

Various pseudomorphic High Electron Mobility Transistor (pHEMT) structures of AlGaAs/InGaAs alloys have been observed their current-voltage behavior. The tungsten probes were used for a measurement the structures by ramping the voltage from −5 to 5 V and measure the electrical current. Measurement was carried out at room temperature and also under optical illumination. From the measurement, the electrical current was found to increase as the increase of Al content in the AlGaAs alloys layer in the pHEMT structure. This phenomenon was supported by the decrease of sheet resistance as obtained from Hall effect measurement. Under visible light illumination, the current-voltage behavior of pHEMT structure was observed to vary as the light power density was varied for 0, 25 and 55 μW/cm.     

Enzymatic interesterification of structured lipids containing conjugated linoleic acid with palm stearin for possible margarine production

Structured lipids containing conjugated linoleic acid as a functional ingredient were blended with palm stearin in the ratios of 30 : 70, 40 : 60, 50 : 50, 60 : 40 and 70 : 30 (wt/wt). The blends were subjected to enzymatic interesterification by Candida antarctica lipase. After interesterification of the blends, changes in the physical properties of the products, including lower melting points and solid fat contents along with different melting behaviors, were evidenced. Analysis of triacylglycerols (TAG) of the interesterified blends showed a decrease in the concentration of high‐melting TAG. X‐ray diffraction analysis revealed, that all the reacted blends were predominantly in the β' crystal form. The mixture could be used for the formulation of margarines or other, similar products.     

Fluoroscopy-based 3-D reconstruction of femoral bone cement: a new approach for revision total hip replacement

In revision total hip replacement the removal of the distal femoral bone cement can be a time consuming and risky operation due to the difficulty in determining the three-dimensional (3-D) boundary of the cement. We present a new approach to reconstruct the bone cement volume by using just a small number of calibrated multiplanar X-ray images. The modular system design allows the surgeon to react intraoperatively to problems arising during the individual situation. When encountering problems during conventional cement removal, the system can be used on demand to acquire a few calibrated X-ray images. After a semi-automatic segmentation and 3-D reconstruction of the cement with a deformable model, the system guides the surgeon through a free-hand navigated or robot-assisted cement removal. The experimental evaluation using plastic test implants cemented into anatomic specimen of human femoral bone has shown the potential of this method with a maximal error of 1.2 mm (0.5 mm RMS) for the distal cement based on just 4-5 multiplanar X-ray images. A first test of the complete system, comparing the 3-D-reconstruction with a computed tompgraphy data set, confirmed these results with a mean error about 1 mm.     

Improvements in the cell-free production of functional antibodies using cell extract from protease-deficient Escherichia coli mutant

Expression of a functional antibody fragment (Fab) using an Escherichia coli cell-free expression system has been reported previously [Jiang et al., FEBS Lett., 514, 290-294 (2002)]. The low yield of the synthesized antibody, however, limits the usefulness of the cell-free expression system, partly due to the degradation of product by endogenous proteases from the E. coli extract. To determine which proteases are responsible for the degradation, we compared the expression of a 6D9 Fab fragment under conditions whereby several protease inhibitors were added into the cell-free system. The addition of serine protease inhibitor increased the amount of the Fab fragment, indicating that serine proteases caused the antibody degradation. Therefore, several serine protease-deficient mutants of E. coli BW25113 were constructed by targeted homologous recombination. The use of extract from a double protease-deficient mutant (DeltadegP-ompT) significantly increased the amount and antigen-binding activities of an anti-HSA scFv and a 6D9 Fab fragment. These results suggest that the DegP- and OmpT-deleted mutant is a useful source of S30 extract for the production or screening of antibodies using the cell-free expression system.     

Sharing Malaysian experience with the development of biotechnology-derived food crops

Biotechnology-derived food crops are currently being developed in Malaysia mainly for disease resistance and improved post harvest quality. The modern biotechnology approach is adopted because of its potential to overcome constraints faced by conventional breeding techniques. Research on the development of biotechnology-derived papaya, pineapple, chili, passion fruit, and citrus is currently under way. Biotechnology-derived papaya developed for resistance to papaya ringspot virus (PRSV) and improved postharvest qualities is at the field evaluation stage. Pineapple developed for resistance to fruit black heart disorder is also being evaluated for proof-of-concept. Other biotechnology-derived food crops are at early stages of gene cloning and transformation. Activities and products involving biotechnology-derived crops will be fully regulated in the near future under the Malaysian Biosafety Law. At present they are governed only by guidelines formulated by the Genetic Modification Advisory Committee (GMAC), Malaysia. Commercialization of biotechnology-derived crops involves steps that require GMAC approval for all field evaluations and food-safety assessments before the products are placed on the market. Public acceptance of the biotechnology product is another important factor for successful commercialization. Understanding of biotechnology is generally low among Malaysians, which may lead to low acceptance of biotechnology-derived products. Initiatives are being taken by local organizations to improve public awareness and acceptance of biotechnology. Future research on plant biotechnology will focus on the development of nutritionally enhanced biotechnology-derived food crops that can provide more benefits to consumers.     

Network formation involving epoxide and carboxyl groups

Summary The base catalyzed reaction between epoxide and carboxyl groups was studied using a simple model system phenylglycidyl ether-caproic acid in the presence of triethylamine. The reaction was investigated by mass spectrometry and GPC which provide an overall qualitative and quantitative survey of all the forming reaction products. The addition esterification is followed by etherification and condensation esterification and the main reaction product, monoester, is disproportionated yielding diester and diol. In a polyfunctional system, the latter reaction may cause splitting of the polymer chain and formation of new crosslinks.     

Phytochemical composition of the essential oils from three Apiaceae species and their antibacterial effects on food-borne pathogens

Essential oils (EOs) of three Apiaceae species, including Bunium persicum, Cuminum cyminum and Carum copticum, extracted by hydrodistillation, were analyzed by gas chromatography (GC) and GC/mass spectrometry. The main components of EOs of B. persicum were γ-terpinene (44.2%), cuminaldehyde (16.9%), γ-terpinen-7-al (10.5%), and ρ-cymene (8%). The major constituents of Cu. cyminum were cuminaldehyde (30.2%), ρ-cymene (14.1%), γ-terpinene (12.8%), and safranal (9.4%), while those of Ca. copticum were thymol (48.4%), ρ-cymene (21.8%) and γ-terpinene (21.3%). The antibacterial effects of the EOs were assessed on several food-borne pathogens, namely Staphylococcus aureus, Bacillus cereus, Escherichia coli O157:H7, Salmonella enteritidis, and Listeria monocytogenes. The ranges of minimum inhibitory concentration (MIC) of the oils were 0.03–0.5, 0.18–3.0, and 0.37–3.0 mg/ml, respectively, for Ca. copticum, B. persicum and Cu. cyminum. Moreover, the combination of B. persicum and Cu. cyminum EOs confirmed synergistic and additive activities against the pathogens.     

Antimicrobial effectiveness of oregano and sage essential oils incorporated into whey protein films or cellulose‐based filter paper

BACKGROUND: In this study the antimicrobial effectiveness of oregano and sage essential oils (EOs) incorporated into two different matrices, whey protein isolate (WPI) and cellulose‐based filter paper, was analysed. RESULTS: Antimicrobial properties of WPI‐based films containing oregano and sage EOs were tested against Listeria innocua, Staphylococcus aureus and Salmonella enteritidis. Oregano EO showed antimicrobial activity against all three micro‐organisms. The highest inhibition zones were against L. innocua. However, sage EO did not show antimicrobial activity against any of the micro‐organisms. Antimicrobial activity was confirmed for both EOs using cellulose‐based filter paper as supporting matrix, although it was significantly more intense for oregano EO. Inhibition surfaces were significantly greater when compared with those of the WPI films. This finding is likely due to the higher porosity and diffusivity of the active compounds in the filter paper. CONCLUSION: The interactions between the EOs and the films have a critical effect on the diffusivity of the active compounds and therefore on the final antimicrobial activity. As a result, to obtain active edible films, it is necessary to find the equilibrium point between the nature and concentration of the active compounds in the EO and the formulation of the film. Copyright © 2010 Society of Chemical Industry     

Megalanthine,a Bioactive Sesquiterpenoid from <Emphasis Type="Italic">Heliotropium megalanthum</Emphasis>, its Degradation Products and their Bioactivities

The new bioactive sesquiterpenoid (3R,6E)-2,6,10-trimethyl-3-(3-p-hydroxyphenylpropanoyloxy)-dodeca-6,11-diene-2,10-diol, named megalanthine, was isolated from the resinous exudates of Heliotropium megalanthum. The degradation products of this compound were identified. Several plant-defensive properties (insecticidal, antifungal, and phytotoxic) were evaluated after obtaining positive results in a preliminary etiolated wheat coleoptile bioassay. This bioassay showed the need to have both the phenolic and sesquiterpene moieties of the natural product present to achieve a biological effect. This result was confirmed in phytotoxicity bioassays. Megalanthine was ruled out as a significant plant–plant defense agent because of its lack of stability. The positive results recorded in the antifungal and antifeedant tests suggest, however, that this chemical is relevant in several ecological interactions involving H. megalanthum.     

Electrochemical Formation of Polypyrrole-carboxymethylcellulose Conducting Polymer Composite Films

1.IntroductionConjugated polymers such as polypyrrole(PPY),polyaniline,polythiophene and polyphenylene etc.whichexhibit significant level of electrical conductivity andhence are termed as conducting polymers,have gotversatile promising applications in the field of energystorage[1],sensors[2],electronic and optical devices[3]andso on.Many researches have been conducted to pro-duce composites or blends of conducting polymer filmswith some insulating polymers in order to overcome thedrawbacks su…