Multiscale models of angiogenesis

This article aims to promote integration of angiogenesis-related models, both integration of the work described herein and many other existing and future models. Integration of molecular mechanisms with cell- and organ- level models allows investigators to study angiogenesis from perspectives in time and space that were once unattainable. As new tools develop for the systematic validation, integration, visualization, and adaptation of these models, the field of angiogenesis heralds an era where modeling becomes an essential component of rigorous experimental design and therapeutic advances.     

Velocity slip,chemical reaction,and suction/injection effects on two-dimensional unsteady MHD mass transfer flow over a stretching surface in the presence of thermal radiation and viscous dissipation

The purpose of this study is to analyze the impact of velocity slip, chemical reaction, and suction/injection on two-dimensional mass transfer effects on unsteady MHD flow over a stretching surface in the presence of thermal radiation and viscous dissipation. The governing time-dependent nonlinear partial differential equations are transformed into nonlinear ordinary differential equations by using similarity transformations. The converted equations are solved using the numerical technique with the help of Keller-Box method. The effect of nondimensional variables is studied and graphically illustrated on velocity, temperature, concentration, friction factor, Nusselt number, and Sherwood number. Concentration and temperature profiles are enhanced and the contrasting pattern for velocity profiles as increasing the velocity slip and magnetic parameter. The concentration profile is diminished as the Schmidt number (Sc) and chemical reaction (C_r) increase. The concentration, velocity, and temperature profiles display a reversal pattern, as the suction and unsteady parameter (A) increase. The findings of this study are very well-acknowledged with current research.     

Flexible polymer microtubes and microchannels via electrospinning

Here we report an approach to fabricate flexible polymer self standing films embedded with continuous aligned microtubes/microchannels via electrospinning. The scheme is to wash the electrospun fibers selectively to form either microtubes/microchannels. Optical microscope (OM) and Scanning electron microscope images are evident for the well aligned microtubes and microchannels respectively with a diameter of ~ 8 μm and a length of ~ 4 cm. Meniscus of tetrahydrofuran in the microtubes can be observed explicitly in the OM images. Mutually perpendicular microtubes are also fabricated on a polymer film. Angular distribution of aligned microstructures indicates the standard deviation is not more than 1°. These tubes/channels can be potential for tissue engineering as they could provide a directional template for the growth when a biodegradable polymer such as Poly(vinylalcohol) is used.     

An effective heuristic for flow shop problems with total flow time as criterion

This research studies on application of genetic algorithms for flow shop problems with total flowtime as the criterion. There is still very little research focusing on total flow time for flow shop problems. We develop a genetic algorithm based heuristic for the problems, and use an integer programming model and an existing heuristic to evaluate the efficiency of the genetic algorithm based heuristic. We generate a set of problems with different numbers of machines, different numbers of jobs, and solve ten of each of the problems using the integer programming model, the existing heuristic, and the genetic algorithm based heuristic, respectively. The results are very encouraging and appear to indicate the genetic algorithms are efficient approaches for flow shop problems.     

Stability of two-layered fluid flows in an inclined channel

A linear stability analysis of two-layer fluid flows in an inclined channel geometry has been carried out. The onset of flow transitions and the spatio-temporal characteristics of secondary flows produced by the flow instabilities have been examined. The effects of density and viscosity stratifications and surface tension on flow structures also have been investigated at various values of Froude numbers (channel inclinations). Multi-domain Chebyshev–Tau spectral methods along with MATLAB QZ eigenvalue solver are used to determine the whole spectrum of the eigenvalues and associated eigenfunctions. The neutral stability diagrams and stability boundaries are constructed for various values of flow parameters. The onset of flow transitions and flow structures predicted by linear stability analysis are compared against experimental results and they agree reasonably well. The results presented in the present paper imply that the shear mode of flow transitions is the one likely to be identified in experiments.     

Combined buoyancy and viscous effects in liquid–liquid flows in a vertical pipe

This paper presents experimental and numerical results of interfacial dynamics of liquid–liquid flows when an immiscible core liquid is introduced into a continuous liquid flow. The fully developed flow model predicts multiple solutions of the jet diameter over a range of dimensionless numbers: flow rate ratio, viscosity ratio, Bond and Capillary numbers. Experiments have been carried out using Polyethylene Glycol (PEG) and Canola oil to investigate the realizability of the three possible solutions predicted by the fully developed flow model. The measured values of inner fluid radii agree very well with the lower branch of the three branched solution while deviating from the top branch beyond a critical flow ratio value. This deviation is attributed to the fact that the flow develops a non-axisymmetric solution at this critical point. Computational fluid dynamics simulations have also been performed to examine the developing core annular flow and to compare the analytical solution results of liquid jet radius. The results predicted by numerical simulations agree very well with both the lower and upper branches of solution predicted by the analytical theory.     

Sequential bad data analysis in state estimation using orthogonaltransformations

The sequential identification of multiple bad data in power system state estimation using orthogonal transformations is described. The method involves iteratively building a list of suspect bad data based on their normalized residuals. The measurements are then analyzed for their estimated errors, and the suspect list is pruned to reveal the bad data. Valid measurements are then returned to the system for completing the solution. As part of this development, a new method of computing and updating the residual covariance matrix is also presented. Test results on the IEEE 30-bus system are presented     

Crosslinkable coupling agents: Synthesis and use for modification of interfaces in polymer blends

A novel coupling agent containing 2-oxazoline and 2-oxazinone as well as hydrosilane moieties has been prepared by hydrosilylation of the corresponding allyl ether containing precursor with a methylhydrosiloxane-dimethylsiloxane copolymer. This hydrosiloxane containing coupling agent, termed as SCA, was characterized by ¹H NMR and its crosslinkability was proven by DSC. SCA was used for the modification of the interfaces in heterogeneous polymer blends. In a model blend system based on mono-carboxylic acid terminated polystyrene (PS-COOH) and mono-amino terminated poly(methyl methacrylate) (PMMA-NH₂) the 2-oxazoline and 2-oxazinone units of SCA can selectively react with the carboxylic groups or amino groups, respectively. The remaining hydrosilane units partially crosslink under the used mixing conditions.The morphology of the three-component blends prepared by melt mixing was evaluated. SCA is immiscible with the polymers and forms its own phase. The expected location of the SCA at the interface between the polymers was proven only in an annealed, strongly phase separated blend. Overall the effect of the compatibilizer on the morphology is very small. Neither the domain size nor the composition for phase inversion are significantly affected in this blend system by the presence of SCA.     

Ionizing radiation tolerance and low-frequency noise degradation inUHV/CVD SiGe HBT's

The effect of ionizing radiation on both the electrical and 1/f noise characteristics of advanced UHV/CVD SiGe HBT's is reported for the first time. Only minor degradation in the current-voltage characteristics of both SiGe HBT's and Si BJT's is observed after total radiation dose exposure of 2.0 Mrad(Si) of gamma-radiation. The observed immunity to ionizing radiation exposure suggests that these SiGe HBT's are well suited for many applications requiring radiation tolerance. We have also observed the appearance of ionizing-radiation-induced generation-recombination (G/R) noise in some of these SiGe HBT's     

Bed of Nails—100- $mu$m-Pitch Wafer-Level Interconnections Process

The rapid advances in integrated chip (IC) design and fabrication continue to challenge electronic packaging technology, in terms of fine pitch, high performance, low cost, and reliability. Demand for higher input/output (I/O) count per IC chip increases as the IC chip fabrication technology is continuously moving towards nano ICs with feature size less than 90 nm. As micro systems continue to move towards high speed and microminiaturization technologies, stringent electrical and mechanical properties are required. To meet the above requirements, chip-to-substrate interconnection technologies with less than 100-mum pitch are required. Currently, the coefficient of thermal expansion (CTE) mismatch between the Si chip and the substrate serves as the biggest bottleneck issue in conventional chip to substrate interconnections technology, which becomes even more critical as the pitch of the interconnects is reduces. Further, the assembly yield of such fine-pitch interconnections also serves as one of the biggest challenges. Bed-of-nails (BoN) interconnects show great potential in meeting some of these requirements for next-generation packaging. In the present study, BoN interconnects prepared by a novel process called copper column wafer-level packaging is presented. The BoN interconnect technology is being developed to meet fine pitch of 100 mum and high-density interconnections. These BoN interconnects are demonstrated by designing a test chip of 10times10mm²size with 3338 I/Os and fabricated using an optimized process. The board-level reliability tests performed under temperature cycling in the range of -40degC to 125degC show promising results.