Search

Xanthan is a biopolymer produced by Xanthomonas bacteria which is widely used in many industries such as food and oil. In this work, three Xanthomonas strains (X. citri/NIGEB-88, X. citri/NIGEB-386 and X. citri/NIGEB-K37) were used to evaluate their industrial potential to produce xanthan gum in whey medium. Bacteria growth rate, viscosity, biomass, dry weigh of produced xanthan and β-galactosidase activity were studied during the fermentation process and the presence of β-galactosidase genes was assessed by PCR technique. Strain NIGEB-386 had the best ability to utilize lactose in the whey medium. The highest amount of xanthan production and viscosity were 22.7 g/l and 2066.6 mPa·s, respectively. The presence of six β-galactosidase genes in strains NIGEB-386 and NIGEB-K37 was confirmed. The pyruvate and acetyl contents in xanthan gum were 2.1 and 0.29 %, respectively. Fourier-transform infrared spectroscopy analysis determined the position of the functional groups in the structure of the fermentation product. In whey medium, the performance of both NIGEB-386 and NIGEB-K37 strains were better than the X. campestris. The findings showed that Xanthomonas citri/NIGEB-386 is suitable for industrial production of xanthan using cheese whey as a low-cost medium.

Non-host resistance (NHR) is a plant defense system against the majority of microbial pathogens. Blumeria graminis f. sp. hordei (Bgh), is an obligate biotrophic ascomycete fungal pathogen that can grow and reproduce only on living cells of wild or domesticated barley (Hordeum sp.).‎ In this study, the expression pattern of eight defense-related genes including NPR1, PR2, PR5, PR1-2, Lipase, LTP, PAL and POX was assessed in bread wheat (Triticum aestivum cv. Darya) against the powdery mildew fungus Bgh. Hydrogen peroxide (H2O2) activity in leaf tissues was also detected histochemically with 3,3-diaminobenzidine (DAB) staining. Result showed that in response to virulence agent, Bgh spores, papillae and hypersensitive response (HR) were formed in the 53.9 and 40.1% of infected area, respectively while in the rest of the infected area (6%) spores were not germinated. According to the histochemical analysis, the wheat NHR against Bgh belongs to type IІ NHR and display a multi-layered feature including wax composition, pre-formed barriers, papilla formation, hypersensitive response. According to results of expression analysis, the Pox, PR5 and PR1-2 expression level were clearly upregulated 24 hours post inoculation (hpi) and LTP was identified as an early signaling response to Bgh. In this study NPR1 was down regulated during all given time points, thus we suggested that salicylic acid (SA) signaling pathway may be mediated by a NPR1-independent mechanism(s) in wheat-Bgh interaction. The coordinated induction of a set of so-called systemic acquired resistance (SAR) genes including POX, PR1-2 and PR5 was observed in wheat-Bgh interaction. Expression pattern of defense-related genes at the wheat-Bgh interaction can be taken as an indication of their functional relevance at different time points of tissue infection.

One of the significant concerns in the MTDC systems is that voltage source converters (VSCs) do not hit their limits in the post-contingency conditions. Converters outage, DC line disconnection, and changeable output power of wind farms are the most common threats in these systems. Therefore, their destructive impact on neighboring AC systems should be minimized as much as possible. The fixed droop control is a better choice than others to deal with this, although it also has some limitations. Accordingly, a novel centralized droop-based control strategy considering N-1 contingency is proposed in this paper. It prevents converters from exceeding their limits while causes optimal power sharing and minimum DC link voltage deviation immediately, without secondary control layer. It also utilizes maximum wind power without curtailment. These properties improve the performance of the MTDC system in post-contingency conditions. The effectiveness of the proposed control method is validated by simulation of a 4-terminal VSC-MTDC system in MATLAB/Simulink R2016a.

This paper aims at developing an aeroelastic model for the instability analysis of supersonic thick fins. To this aim the modal analysis technique is used for the structural dynamics modelling of a fin with a general structure. An unsteady aerodynamic model is applied based on the shock/expansion analysis over the flat surfaces of the fin along with local application of the piston theory. Assuming a supersonic fin with an arbitrary polygonal cross-section, thickness and initial angle-of-attack, the steady flow properties (e.g. Mach number, density and temperature) are calculated over the flat surfaces of the fin. Then, assuming small amplitude vibrations, the generalised aerodynamic forces are obtained in terms of the structural modal coordinates. Using the obtained model, the effect of thickness, initial angle-of-attack, taper ratio and sweep angle on the aerodynamic derivatives and aeroelastic stability of the fin are studied which show their remarkable effects on the instability Mach number and its type. Specially, the presented results show that increasing the fin thickness dramatically diminishes the stability margin mainly at low angles of attack. Also a sharp decrease of the divergence Mach number is observed by increasing the fin’s incidence angle.

Objective The aim of this study was to compare the effect of 6% hydroxyl ethyl starch solution with 4% gelatin and Ringer’s solutions on the haemodynamic stability of patients after coronary artery bypass graft (CABG) surgery and immediately after discontinuation of cardiopulmonary bypass (CPB). Methods This was a randomised, double-blind clinical trial of 92 patients who were candidates for on-pump CABG. After discontinuation of CPB, all patients were transferred to the intensive care unit (ICU) and divided randomly into three groups. The first group received Ringer’s solution, the second group 4% gelatin, and the third 6% hydroxyl ethyl starch (HES) solution (Voluven). Haemodynamic parameters such as heart rate, mean arterial pressure, systolic blood pressure, diastolic blood pressure, central venous pressure, cardiac output and the presence of arrhythmias were documented. Results The volume needed for maintaining normal blood pressure and central venous pressure in the range of 10–14 mmHg was less in the HES group than in the other groups. The volume was similar however in the gelatin and Ringer’s groups in the first 24 hours after surgery. Urinary output in the first four and 24 hours after surgery were significantly higher in the HES group than in the other two groups. Mean creatinine levels were significantly lower in the HES group. Conclusion HES (6%) had a better volume-expanding effect than gelatin (4%) and Ringer’s solutions, and its short-term effects on renal function were also better than gelatin and Ringer’s solutions.

Reactive oxygen species (ROS) derived from molecular oxygen under biotic and abiotic stress such as salinity which have deleterious effects on cell metabolism. The toxic effect of ROS counteract by enzymatic as well as non-enzymatic antioxidant system. Superoxide dismutase (SOD) has a potential role for elimination of ROS. Halophytes respond to salt stress at different levels and can be a model for increasing salt tolerance in crop plants. Thus salt tolerance gene isolation and cloning of gene as well as subsequent transformation are first step for sensitive crop improvement. Aeluropus littoralis is a halophyte plant from poaceae family can be as a beneficial plant with high potential for creal breeding. There was no report on isolation of SOD gene from A. littoralis and little genomic study of this plant carried out. In this study a novel gene from A. littoralis isolated. This gene amplified by reverse transcription-PCR and cloned in E. coli pTZ57R/T cloning vector. The AlSOD gene sequence contained 456bp and the deduced transcripts encoding 152 amino acids shared a high homology with those putative CuZnSOD of higher plants like Zea mays and Oryza sativa.

In this paper, we present the modeling of a non-invasive electromagnetic sensor for the measurement glycaemia. The model is based on a bio-impedance measurement. First, we optimized the dimensions of the sensor’s parameters that can influence on measurement. Second, we investigated the influence of the dielectric parameters on the conductivity and its impact on the measurement of glycaemia. Results from this study demonstrate that the variation of the sensor impedance depends on the resistance and the inductance, which depend on the conductivity. The sensitivity of the output and input signal ratio strongly depends on the conductivity of the medium under investigation. Maximum conductivity at the resonance frequency was demonstrated.

The bulk free-radical polymerization of styrene was carried out on a spinning disc reactor (SDR) with prepolymer feeds previously prepared in a stirred batch reactor at 70°C. The SDR significantly enhanced the reaction rate when the conversion of the prepolymer feed was about 50%. There was an optimal disc rotation speed, that is, 1500 rpm, at which the conversion enhancement was maximized. Increasing the disc rotation speed up to 1500 rpm increased the conversion, but a further increase beyond this speed caused the conversion enhancement to decrease. This behavior could be attributed to the dual effect of the disc speed (controlling both the residence time and the effective radial mixing of the reaction media) on the disc. On the other hand, the multipass disc feeding mode was used as an approach to increase the residence time and evolution of the conversion of the reacting mixture in the SDR. Surprisingly, a maximum conversion change of about 40% was achieved for a prepolymer feed of 50% after three passes across the rotating disc. Furthermore, the effect of multipass disc feeding on the molecular characteristics of the SDR products was investigated. In comparison with the results obtained at a feed conversion of 30%, the weight-average molecular weight, the z-average molecular weight, and the polydispersity index of the three-pass SDR products prepared with a 50% feed conversion at a rotation speed of 1500 rpm were lower than those of the one-pass products. This behavior could be attributed to probable chain scission of long polymer chains as a result of the high shear and elongation forces that arose on the disc surface. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

In order to determine zinc and catalase content of seminal plasma in the buffalo and to study their associations with the semen characteristics, 54 semen samples were collected from 10 buffalo bulls; semen volume and sperm concentration, gross and progressive motility and viability were evaluated, seminal plasma was then harvested by centrifugation and its zinc content was estimated by atomic absorption spectrophotometer and its catalase activity determined by using a commercial kit. The zinc content of the seminal plasma (Mean +/- SEM) was recorded as 154.40 +/- 1.74 mg L(-1), while, the mean catalase value was 32.00 +/- 0.42 U mL(-1). The mean zinc values was highly correlated with sperm progressive motility and viability and with catalase values (p = 0.000 for all) and also was associated with gross motility (p = 0.020) and negatively with abnormal morphology (p = 0.049). The catalase values were highly associated with sperm progressive motility, viability and zinc content (p = 0.000 for all) and was associated with sperm gross motility (p = 0.024). For further clarification of these correlations, the samples were categorized in three groups of excellent (Ex, >90% motile, n = 33), good (Go, 80-89% motile, n = 15) and moderate (Mo

Reactive oxygen species (ROS) derived from molecular oxygen under biotic and abiotic stress such as salinity which have deleterious effects on cell metabolism. The toxic effect of ROS counteract by enzymatic as well as non-enzymatic antioxidant system. Superoxide dismutase (SOD) has a potential role for elimination of ROS. Halophytes respond to salt stress at different levels and can be a model for increasing salt tolerance in crop plants. Thus salt tolerance gene isolation and cloning of gene as well as subsequent transformation are first step for sensitive crop improvement. Aeluropus littoralis is a halophyte plant from poaceae family can be as a beneficial plant with high potential for creal breeding. There was no report on isolation of SOD gene from A. littoralis and little genomic study of this plant carried out. In this study a novel gene from A. littoralis isolated. This gene amplified by reverse transcription-PCR and cloned in E. coli pTZ57R/T cloning vector. The AlSOD gene sequence contained 456 bp and the deduced transcripts encoding 152 amino acids shared a high homology with those putative CuZnSOD of higher plants like Zea mays and Oryza sativa.

Adaptive resource allocation including the allocation of subcarrier, bit and power in orthogonal frequency division multiple access (OFDMA) system, can significantly improve spectral efficiency, increase capacity, and reduce power consumption. The resource allocation in an OFDMA system is normally modeled as a combinatorial optimization problem involving a nonlinear objective with nonlinear constraints. This leads to high computation complexity that is only solvable online. In this paper we first develop a nonlinear optimization model of OFDMA resource allocation that incorporates not only the throughput constraint but also the delay constraint. We then find an equivalent linear formulation to this optimization problem to facilitate analysis. Moreover, we develop a heuristic approximation algorithm to provide a close solution to the equivalent linear programming problem. The heuristic algorithm is efficient enough for on-line adaptive resource allocation. Simulation results show that the heuristic solution can achieve almost same capacity but with less computation complexity.

This study aims at investigation of the resonance frequencies of carbon nanopeapods constructed by a single wall carbon nanotube and encapsulated buckyball molecules ( C 60). A nanopeapod can be used as a nanoscale variable frequency beam resonator according to the number and positions of the encapsulated fullerenes. Using the molecular structural mechanics method the covalence bonds are simulated by equivalent beam elements and the van der Waal interactions between the buckyballs and nanotube are modeled as linear springs. Also, an equivalent beam model is proposed for the nanopeapod with sectional properties which are obtained by the molecular structural mechanics model. The beam-like modes of free vibrations are obtained using both models and the effect of position and number of buckyballs on the resonance frequencies are investigated.

Papillomas are the most common laryngeal tumors of infancy and childhood (1–7). Children are more prone to this affliction than adults, particularly if the papillomas are multiple. The sex incidence is roughly equal, with a slight male predominance. The lesions are more likely to recur after removal if the patient is under the age of sixteen years. Most investigators (8) feel it is impossible to detect histologic differences between papillomas removed from a child and those removed from an adult or between single and multiple papillomas. Hoarseness is the most common, and usually the first, symptom of this disorder. The only other consistent symptom is respiratory distress occasioned by obstruction caused by the papillomas. Both symptoms depend upon the extent and location of the lesions. The primary treatment of these tumors is surgical removal. A single removal effects a permanent cure in the majority of cases, although recurrences are common and should be treated in the same manner as the original lesi...