Candida tropicalis BPU1, a novel isolate from the rumen of the Malabari goat,is a dual producer of biosurfactant and polyhydroxybutyrate

This unique study reports a new strain (BPU1) of Candida tropicalis isolated from the rumen of the Malabari goat, showing dual production of biosurfactant and polyhydroxybutyrate. C. tropicalis strain BPU1, a facultative anaerobe, was tuned to become an aerobe in specially designed flask, the Benjamin flask. The puffy circular colonies were smooth, white‐to‐cream in colour, with pseudo‐filaments. The strain fermented glucose, sucrose, maltose and dextrose, but not lactose and cellulose. It assimilated (NH₄)₂SO₄, peptone, glycine and arginine, but not NaNO₃, as the nitrogen source. Interestingly, it utilized groundnut oil (up to 0.3%) in a specially designed basal mineral salt medium (BSM). Its capability for dual production of a biosurfactant and a polyhydroxybutyarate (PHB) was explored by various methods from the BSM–oil medium. Extracted biosurfactant from 6 day‐old culture was biochemically characterized as a complex of lipid and carbohydrate with an R_f value of 0.88 by thin layer chromatography. Its PHB production was confirmed by specific staining methods with Nile blue sulphate, Sudan black B and Sudan 3. Briefly, this first‐ever report gives ample physical evidence for the dual production of a glycolipid (biosurfactant) and PHB by C. tropicalis strain BPU1 on a specially designed medium, which would open up elaborate research on this yeast. Copyright © 2013 John Wiley & Sons, Ltd.     

Integration of functional reliability analysis with hardware reliability: An application to safety grade decay heat removal system of Indian 500 MWe PFBR

A passive system can fail either due to classical mechanical failure of components, referred to as hardware failure, or due to the failure of physical phenomena to fulfill the intended function, referred to as functional failure. In this paper a methodology is discussed for the integration of these two kinds of unreliability and applied to evaluate the integrated failure probability of the passive decay heat removal system of Indian 500 MWe prototype fast breeder reactor (PFBR). The probability of occurrence of various system hardware configurations is evaluated using the fault tree method and functional failure probabilities on the corresponding configurations are determined based on the overall approach reported in the reliability methods for passive system (RMPS) project. The variation of functional reliability with time, which is coupled to the probability of occurrence of various hardware system configurations is studied and incorporated in the integrated reliability analysis. It is observed that this consideration of the dependence of functional reliability on time will give significant advantages on system reliability. The integrated reliability analysis is also explained using an event tree. The impact of the provision for forced circulation in the primary circuit on functional reliability is also studied with this procedure and it is found that the forced circulation capability helps to bring down the total decay heat removal failure probability by lowering the peak temperatures after the reactor shut down.     

Novel ceramic substrates for high Tc superconductors

A group of complex perovskite oxides REBa₂NbO₆ (RE=La and Dy) have been synthesized and developed for their use as substrates for both YBa₂Cu₃O_7-δ and Bi(2223) superconductors. These materials have a complex cubic perovskite (A₂BB′O₆) structure with lattice constants,a=8·48?8·60 Å. REBa₂NbO₆ did not show any phase transition in the temperature range 30–1300°C. The thermal expansion coefficient, thermal diffusivity and thermal conductivity values of REBa₂NbO₆ are favourable for their use as substrates for highT _c superconductors. The dielectric constant and loss factor of REBa₂NbO₆ are in a range suitable for their use as substrates for microwave applications. Both YBa₂Cu₃O_7-δ and Bi(2223) superconductors did not show any detectable chemical reaction with REBa₂NbO₆ even under extreme processing conditions. Dip coated YBa₂Cu₃O_7-δ thick films on polycrystalline REBa₂NbO₆ substrate gave aT _c(0) of 92 K and a current density of ～1·1×10⁴ A/cm² and Bi(2223) thick film on polycrystalline REBa₂NbO₆ substrate gave aT _c(0) of 110 K and a current density of ～ 4×10³ A/cm² at 77 K and zero magnetic field. A laser ablated YBa₂Cu₃O_7-δ thin film deposited on polycrystalline REBa₂NbO₆ substrate gave aT _c(0) of 90 K and a current density of ～5×10⁵ A/cm².     

Error compensation in machine tools — a review: Part II: thermal errors

Accuracy of machined components is one of the most critical considerations for any manufacturer. Many key factors like cutting tools and machining conditions, resolution of the machine tool, the type of workpiece etc., play an important role. However, once these are decided upon, the consistent performance of the machine tool depends upon its ability to accurately position the tool tip vis-à-vis the required workpiece dimension. This task is greatly constrained by errors either built into the machine or occurring on a periodic basis on account of temperature changes or variation in cutting forces. The three major types of error are geometric, thermal and cutting-force induced errors. Geometric errors make up the major part of the inaccuracy of a machine tool, the error caused by cutting forces depending on the type of tool and workpiece and the cutting conditions adopted. This part of the paper attempts to review the work done in analysing the various sources of geometric errors that are usually encountered on machine tools and the methods of elimination or compensation employed in these machines. A brief study of cutting-force induced errors and other errors is also made towards the end of this paper.     

Gastropathy caused by nonsteroidal anti-inflammatory agents

Nonsteroidal anti-inflammatory drugs (NSAID) are widely used in current clinical practice. Several gastric lesions occur as a side effect. This review paper describes the spectrum of gastric lesions, its pathogenesis, prevalence and incidence as well as clinical data, common risk factors, treatment and the prophylaxis of NSAID gastric toxicity.     

Lower bounds for the trace of the solution of the discretealgebraic Riccati equation

Two lower bounds for the trace of the solution of the discrete algebraic Riccati equation (DARE) are presented. It is shown that in many cases, these trace bounds are tighter than those in the literature and greater than the trace of the state weighting matrix even when the system matrix is singular. The results are illustrated by an example     

Tracking and contour error control in CNC servo systems

The dynamic response of a machine tool is a complex interaction of several factors that includes the basic design of the machine as well as the capability and performance of the corresponding axis servo system. In terms of the performance of the servo system, tracking and contour errors are two important aspects that significantly affect the machine tool. Extensive research has been conducted over the last several decades into the study of these error components. A number of different approaches have been proposed by various researchers that attempt to effectively address this problem. This paper attempts to study the work that has been carried out in minimising tracking and contour errors in CNC machine tools.     

Performance analysis of customer access to an ISDN

A simple analytical model has been developed to quantify the performance encountered by voice and data traffic during customer access to an ISDN. This enables a direct comparison of traffic capabilities of various proposed implementation schemes currently under consideration by telecommunications administrations.     

Adaptive iso-planar tool path generation for machining of free-form surfaces

The iso-planar (Cartesian) tool path generation method has been used for several decades. However, it suffers an inherent drawback: in the region where the direction of the surface normal is close to that of the parallel intersecting planes, the intersecting plane intervals have to be reduced because of the influence of surface slopes. This causes redundant tool paths in the associated flatter regions and results in lower machining efficiency. This paper presents an algorithm that overcomes the disadvantage of the iso-planar method while keeping its advantages of robustness and simplicity. In this algorithm, the concept of isophote is applied to partition the surface into different regions. In each region the tool path side steps are adaptive to the surface features. Therefore redundant tool paths are avoided. By applying the region-by-region or global-local machining strategy, the machining efficiency is increased.     

Optimal Sublogarithmic Time Parallel Algorithms on Rooted Forests

The problem of finding a sublogarithmic time optimal parallel algorithm for 3 -colouring rooted forests has been open for long. We settle this problem by obtaining an O(( log log n) log ^* ( log ^* n)) time optimal parallel algorithm on a TOLERANT Concurrent Read Concurrent Write (CRCW) Parallel Random Access Machine (PRAM). Furthermore, we show that if f(n) is the running time of the best known algorithm for 3 -colouring a rooted forest on a COMMON or TOLERANT CRCW PRAM, a fractional independent set of the rooted forest can be found in O(f(n)) time with the same number of processors, on the same model. Using these results, it is shown that decomposable top-down algebraic computation and, hence, depth computation (ranking), 2 -colouring and prefix summation on rooted forests can be done in O( log n) optimal time on a TOLERANT CRCW PRAM. These algorithms have been obtained by proving a result of independent interest, one concerning the self-simulation property of TOLERANT: an N -processor TOLERANT CRCW PRAM that uses an address space of size O(N) only, can be simulated on an n -processor TOLERANT PRAM in O(N/n) time, with no asymptotic increase in space or cost, when n=O(N/ log log N) . Received May 20, 1997; revised June 15, 1998.