An analysis and optimisation of the geometrical inaccuracy due to wire lag phenomenon in WEDM

An extensive study of the wire lag phenomenon in Wire-cut Electrical Discharge Machining (WEDM) has been carried out and the trend of variation of the geometrical inaccuracy caused due to wire lag with various machine control parameters has been established in this paper. In an extremely complicated machining process like Wire-cut EDM, which is governed by as many as ten control factors, it is very difficult to select the best parametric combination for a particular situation arising out of customer requirements. In the present research study, all the machine control parameters are considered simultaneously for the machining operation which comprised a rough cut followed by a trim cut. The objective of the study has been to carry out an experimental investigation based on the Taguchi method involving thirteen control factors with three levels for an orthogonal array L₂₇ (3¹³). The main influencing factors are determined for given machining criteria, such as: average cutting speed, surface finish characteristic and geometrical inaccuracy caused due to wire lag. Also, the optimum parametric settings for different machining situations have been found out and reported in the paper.     

Long-range correlation properties of coding and noncoding DNA sequences: GenBank analysis

An open question in computational molecular biology is whether long-range correlations are present in both coding and noncoding DNA or only in the latter. To answer this question, we consider all 33301 coding and all 29453 noncoding eukaryotic sequences--each of length larger than 512 base pairs (bp)--in the present release of the GenBank to dtermine whether there is any statistically significant distinction in their long-range correlation properties. Standard fast Fourier transform (FFT) analysis indicates that coding sequences have practically no correlations in the range from 10 bp to 100 bp (spectral exponent beta=0.00 +/- 0.04, where the uncertainty is two standard deviations). In contrast, for noncoding sequences, the average value of the spectral exponent beta is positive (0.16 +/- 0.05) which unambiguously shows the presence of long-range correlations. We also separately analyze the 874 coding and the 1157 noncoding sequences that have more than 4096 bp and find a larger region of power-law behavior. We calculate the probability that these two data sets (coding and noncoding) were drawn from the same distribution and we find that it is less than 10(-10). We obtain independent confirmation of these findings using the method of detrended fluctuation analysis (DFA), which is designed to treat sequences with statistical heterogeneity, such as DNA's known mosaic structure ("patchiness") arising from the nonstationarity of nucleotide concentration. The near-perfect agreement between the two independent analysis methods, FFT and DFA, increases the confidence in the reliability of our conclusion.     

Experimental investigations in powder mixed electric discharge machining of Ti–35Nb–7Ta–5Zrβ-titanium alloy

The present research is the first type of study in which the application of powder mixed electrical discharge machining (PMEDM) for the machining of β-phase titanium (β-Ti) alloy has been proposed. β-Ti alloys are new range of titanium alloys, which has a wide-spread application in dental, orthopedics, shape memory, and stents. The aim of the present study is to fabricate submicro- and nanoscale topography by PMEDM process to enhance the biocompatibility without affecting machining efficiency. The effect of Si powder concentration along with pulse current and duration on the surface and machining characteristics has been investigated. A significant decrease in surface crack density on the machined surface with 4 g/l Si powder concentration was observed. When β-Ti alloy was modified at 15 A pulse current, longer pulse interval with 8 g/l concentration of Si powder particles, the interconnected surface porosities with pore size 200–500 nm was observed. Moreover, at Si powder concentrations of 2 g/l and 4 g/l, the recast layer thickness is 8 µm and 2–3 µm, respectively. Elemental mapping analysis confirmed that PMEDM also generated carbides and oxides enriched surface, a favorable surface chemistry to enhance the biocompatibility of β-Ti alloy. Furthermore, PMEDM also enhances the machining performance by improving material removal rate and reducing tool wear rate.     

Self-nanoemulsifying drug delivery system of docosahexanoic acid: development,in vitro,in vivo characterization

Context: Docosahexanoic acid (DHA) is an essential omega-3 fatty acid for normal brain development and its use has increased considerably in recent years.

Objective: The aim of this study is to develop and evaluate self-nanoemulsifying drug delivery systems (SNEDDS) of DHA for improved palatability, dispersibility and bioavailability.

Methods: The SNEDDS were prepared and evaluated for miscibility, employing different combinations of olive oil and soyabean oil as oil phase, Span 80, Span 20, soya phosphatidylcholine, Labrafil M 1944 CS as surfactants while Tween 80, PEG 400, Cremophor RH40 and propylene glycol as cosurfactants. Thermodynamically stable SNEDDS were characterized for dispersibility, self-emulsification time, droplet size, zeta potential along with sensory analysis. The optimized formulation was subjected to ex vivo and in vivo evaluation such as intestinal permeability, memory performance test, brain concentration and histopathology studies.

Results: The optimized SNEDDS formulation showed emulsification time of 27?±?4.7?s with droplet size of 17.6?±?3.5?nm and zeta potential of??37.6?±?0.5?mV. Intestinal absorption study depicted 18.3%, 21.5%, 41.5%, 98.7% absorption of DHA with SNEDDS-based formulation in comparison to 8.2%, 15.1%, 28.8%, 46.1% absorption of DHA with oil-based marketed formulation after 0.5, 1, 2 and 4?h. DHA concentration in brain homogenate was found to be increased to 2.6-fold in comparison to DHA-marketed formulation. This could be ascribed to enhanced dispersibility and bioavailability of DHA from nanosized formulation.

Conclusion: The developed formulation led to enhanced dispersibility and bioavailability of DHA due to the formation of nanodroplets.     

Exploring the genetic and environmental etiology of high general cognitive ability in fourteen- to thirty-six-month-old twins

Two definitions of normality ("isolated" or "correlated") are considered. The boundaries of "isolated" normality were determined by a statistical procedure, whereas the "correlated" approach was related to a clinical or predictive definition. In the latter case, the biological variations were considered abnormal if they implied a hazard with some significant future ailment as a risk factor. In this pragmatic approach, the upper limit of normal/abnormal variations is the point beyond which medical strategy is related to the most expected benefit when applied to a definite population or to an individual patient. The capacity of a diagnostic test to discriminate between patients with a defined risk and those without risk depends strictly on the value of the parameter chosen. In medical care for the prevention of vascular complications in diabetic patients or with foetal risks in pregnant women, the limits of the so-called normal range of glycaemia and other parameters should be determined according to the objective of the preventive and/or therapeutic measures to be prescribed.     

Changing patterns of localization of the tobacco mosaic virus movement protein and replicase to the endoplasmic reticulum and microtubules during infection

Tobacco mosaic virus (TMV) derivatives that encode movement protein (MP) as a fusion to the green fluorescent protein (MP:GFP) were used in combination with antibody staining to identify host cell components to which MP and replicase accumulate in cells of infected Nicotiana benthamiana leaves and in infected BY-2 protoplasts. MP:GFP and replicase colocalized to the endoplasmic reticulum (ER; especially the cortical ER) and were present in large, irregularly shaped, ER-derived structures that may represent "viral factories." The ER-derived structures required an intact cytoskeleton, and microtubules appeared to redistribute MP:GFP from these sites during late stages of infection. In leaves, MP:GFP accumulated in plasmodesmata, whereas in protoplasts, the MP:GFP was targeted to distinct, punctate sites near the plasma membrane. Treating protoplasts with cytochalasin D and brefeldin A at the time of inoculation prevented the accumulation of MP:GFP at these sites. It is proposed that the punctate sites anchor the cortical ER to plasma membrane and are related to sites at which plasmodesmata form in walled cells. Hairlike structures containing MP:GFP appeared on the surface of some of the infected protoplasts and are reminiscent of similar structures induced by other plant viruses. We present a model that postulates the role of the ER and cytoskeleton in targeting the MP and viral ribonucleoprotein from sites of virus synthesis to the plasmodesmata through which infection is spread.     

An integrated source transcoding and congestion control paradigmfor video streaming in the Internet

In this work we present an end-to-end optimized video streaming system comprising of synergistic interaction between a source packetization strategy and an efficient and responsive, TCP-friendly congestion control protocol [Linear Increase Multiplicative Decrease with History (LIMD/H)]. The proposed source packetization scheme transforms a scalable/layered video bitstream so as to provide graceful resilience to network packet drops. The congestion control mechanism provides low variation in transmission rate in steady state and at the same time is reactive and provably TCP-friendly. While the two constituent algorithms identified above are novel in their own right, a key aspect of this work is the integration of these algorithms in a simple yet effective framework. This “application-transport” layer interaction approach is used to maximize the expected delivered video quality at the receiver. The integrated framework allows our system to gracefully tolerate and quickly react to sudden changes in the available connection capacity due to the onset of congestion, as verified in our simulations     

Lattice Boltzmann method simulation of electroosmotic stirring in a microscale cavity

The suitable surface modification of microfluidic channels can enable a neutral electrolyte solution to develop an electric double layer (EDL). The ions contained within the EDL can be moved by applying an external electric field, inducing electroosmotic flows (EOFs) that results in associated stirring. This provides a solution for the rapid mixing required for many microfluidic applications. We have investigated EOFs generated by applying a steady electric field across a square cavity that has homogenous electric potentials along its walls. The flowfield is simulated using the lattice Boltzmann method. The extent of mixing is characterized for different electrode configurations and electric field strengths. We find that rapid mixing can be achieved by using this simple configuration which increases with increasing electric field strength. The mixing time for water-soluble organic molecules can be decreased by four orders of magnitude by suitable choice of wall zeta potential and electric field. We dedicate this paper to the memory of our colleagues Professors Kevin Granata and Liviu Librescu who fell tragically on April 16, 2007 while answering their call to serve higher education. They continue to inspire us. AM gratefully acknowledges support from Jadavpur University under the World Bank funded Technical Education Quality Improvement Programme of the Government of India and the hospitality of the Virginia Tech ESM Department where he conducted a portion of this work.     

Turnover of inositol polyphosphate pyrophosphates in pancreatoma cells

There is little information concerning the intracellular function of inositol 1,3,4,5,6-pentakis- and hexakisphosphate, despite their being the most abundant inositol polyphosphates. Current opinions that they play passive roles as antioxidants (Graf, E., Mahoney, J. R., Bryant, R. G., and Eaton, J. W. (1987) J. Biol. Chem. 259, 3620-3624) or "housekeeping" molecules (Berridge, M. J., and Irvine, R. F. (1989) Nature 341, 197-205) arises from belief in their metabolic lethargy. However, we have discovered that cell homogenates, incubated with 5 mM fluoride and 5 mM ATP, converted both inositol hexakisphosphate (Km = 2 +/- 0.5 microM, Vmax = 9 +/- 2 pmol/mg of protein/min) and inositol 1,3,4,5,6-pentakisphosphate (Km = 13 +/- 4 microM, Vmax = 11 +/- 5 pmol/mg of protein/min) to more polar products. These reactions were also observed in intact cells treated with 0.5-20 mM fluoride, and the precursor/product relationships were confirmed by comparing the effects of fluoride on cells differentially labeled with [3H]inositol in either short-term or pulse-chase protocols. The novel products were determined to be inositol pyrophosphates because of their relatively specific hydrolysis by tobacco pyrophosphatase and alkaline phosphatase. The pyrophosphates were metabolized rapidly by cell homogenates back to their pentakisphosphate and hexakisphosphate precursors. This endogenous pyrophosphatase activity was inhibited by up to 99% by 5 mM fluoride in vitro. In intact cells incubated with 10 mM fluoride, about 20% of the inositol 1,3,4,5,6-pentakisphosphate pool, and 50% of the inositol hexakisphosphate pool were each converted to pyrophosphate derivatives within 1 h.     

Distributed video coding in wireless sensor networks

This paper addresses the important aspect of compressing and transmitting video signals generated by wireless broadband networks while heeding the architectural demands imposed by these networks in terms of energy constraints as well as the channel uncertainty related to the wireless communication medium. Driven by the need to develop light, robust, energy-efficient, and low delay video delivery schemes, a distributed video coding based framework dubbed PRISM is introduced. PRISM addresses the wireless video sensor network requirements far more effectively than current state-of-the-art standards like MPEG. This paper focuses on the case of a single video camera and use it as a platform to describe the theoretical principles and practical aspects underlying distributed video coding.