Collective cell guidance by cooperative intercellular forces

Cells comprising a tissue migrate as part of a collective. How collective processes are coordinated over large multi-cellular assemblies has remained unclear, however, because mechanical stresses exerted at cell-cell junctions have not been accessible experimentally. We report here maps of these stresses within and between cells comprising a monolayer. Within the cell sheet there arise unanticipated fluctuations of mechanical stress that are severe, emerge spontaneously, and ripple across the monolayer. Within that stress landscape, local cellular migrations follow local orientations of maximal principal stress. Migrations of both endothelial and epithelial monolayers conform to this behaviour, as do breast cancer cell lines before but not after the epithelial-mesenchymal transition. Collective migration in these diverse systems is seen to be governed by a simple but unifying physiological principle: neighbouring cells join forces to transmit appreciable normal stress across the cell-cell junction, but migrate along orientations of minimal intercellular shear stress.     

Detection of vesicoureteral reflux using microwave radiometry-system characterization with tissue phantoms

Microwave (MW) radiometry is proposed for passive monitoring of kidney temperature to detect vesicoureteral reflux (VUR) of urine that is externally heated by a MW hyperthermia device and thereafter reflows from the bladder to kidneys during reflux. Here, we characterize in tissue-mimicking phantoms the performance of a 1.375 GHz radiometry system connected to an electromagnetically (EM) shielded microstrip log spiral antenna optimized for VUR detection. Phantom EM properties are characterized using a coaxial dielectric probe and network analyzer (NA). Power reflection and receive patterns of the antenna are measured in layered tissue phantom. Receiver spectral measurements are used to assess EM shielding provided by a metal cup surrounding the antenna. Radiometer and fiberoptic temperature data are recorded for varying volumes (10-30 mL) and temperaturesg (40-46°C) of the urine phantom at 35 mm depth surrounded by 36.5°C muscle phantom. Directional receive pattern with about 5% power spectral density at 35 mm target depth and better than -10 dB return loss from tissue load are measured for the antenna. Antenna measurements demonstrate no deterioration in power reception and effective EM shielding in the presence of the metal cup. Radiometry power measurements are in excellent agreement with the temperature of the kidney phantom. Laboratory testing of the radiometry system in temperature-controlled phantoms supports the feasibility of passive kidney thermometry for VUR detection.     

Synthesis,characterization and corrosion protection properties of poly(N-vinyl carbazole-co-glycidyl methacrylate) coatings on low nickel stainless steel

Methacrylate based copolymers are considered as one of the best organic coating materials for anticorrosive application. Poly(N-vinyl carbazole-co-glycidyl methacrylate) have been synthesized by free radical solution polymerization technique from different mole ratios of N-vinyl carbazole (N-Vc) and glycidyl methacrylate (GMA) and characterized using Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (¹H NMR and ¹³C NMR). Thermal analyses of the poly(N-Vc-co-GMA) were performed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The number average molecular weight (M_n) of different compositions of the same was determined by gel permeation chromatography (GPC). The corrosion performances of low nickel stainless steel specimens coated with different composition of copolymers were investigated in 1 M H₂SO₄ using potentiodynamic polarization, electrochemical impedance spectroscopic (EIS) method, scanning electron microscopic (SEM) and energy dispersive X-ray analysis (EDAX). Poly(N-Vc-co-GMA) have been provided in order to achieve adherent, low permeability to aggressive ions as well as environmentally favored good anticorrosive coating. Electrochemical corrosion test and surface analysis results clearly showed that poly(N-Vc-co-GMA) coatings served as a stable host matrix on low nickel stainless steel against corrosion. It was also observed that the coatings of poly(N-Vc-co-GMA) with equal mole ratio of N-Vc and GMA exhibited the best corrosion resistance among all combinations.     

Hydroxyapatite coating on selectively passivated and sensitively polymer-protected surgical grade stainless steel

Surgical grade stainless steel (316L SS) is a widely used implant material in orthopedic surgeries. However, the release of metallic ions evidenced from the 316L SS implants in vivo conditions is a big challenge. In order to minimize the release of metallic ions, coating the 316L SS implant with a biocompatible material like hydroxyapatite [HAP, Ca₁₀(PO₄)₆(OH)₂] is one of the suitable methods. In this paper, the hydroxyapatite coating on borate passivated through poly-ortho-phenylenediamine (PoPD)-coated 316L SS by a dip coating method has been reported. The coatings were characterized by electrochemical techniques such as potentiodynamic polarization, electrochemical impedance spectroscopy, and cyclic voltammetry. Surface characterization studies of the coatings such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were also carried out. The leach out characteristics of the coatings was determined at the impressed potential. The mechanical property of the coatings was evaluated by Vicker’s microhardness test. The Cr-rich passive film formed underneath the PoPD layer showed a higher protective efficiency. The ability to form apatite on the post-passivated PoPD-coated 316L SS specimen was examined by immersing it in the simulated body fluid. The enhanced corrosion resistivity of the HAP coating on the post-passivated PoPD-coated 316L SS was due to an effective barrier of PoPD followed by the passive film underneath the PoPD.     

Transport properties of copper indium aluminum selenide thin films deposited by successive Ionic layer adsorption and reaction

Cu(InAl)Se₂ (CIAS) thin films have been prepared by successive ionic layer adsorption and reaction (SILAR) technique on well-cleaned glass substrates. The structure, composition, morphology, optical, electrical, and Hall effect studies of prepared thin films have been studied. X-ray diffraction studies confirmed the polycrystalline nature of the thin films with a chalcopyrite structure. Scanning electron microscopy studies revealed that the morphology of the prepared films was smooth, dense, uniform, and granular. Composition of various constituents such as Cu, In, Al, and Se in the CIAS films has been determined from energy dispersive x-ray analysis. Optical properties have been studied in detail from the transmittance spectra in the visible and near infrared region and the optical transition has been found to be direct and allowed with the band gap of around 1.16–1.50 eV. Electrical analysis helps to identify that in high temperature region the conductivity is attributed due to thermal excitation of the charge carriers from grain boundaries to the neutral region of the grains. Transport properties of CIAS thin films have been studied in the temperature range 298–398 K and the transport parameters are evaluated and reported in this paper in detail.     

Investigations on microstructural and optical properties of CdS films fabricated by a low-cost,simplified spray technique using perfume atomizer for solar cell applications

Good quality CdS films were fabricated by employing a simplified spray pyrolysis technique using perfume atomizer. CdS films have been deposited from aqueous solutions of sulphur and cadmium, keeping the molar concentrations of S:Cd = 0.01:0.01, 0.02:0.02, 0.04:0.04 and 0.06:0.06 in the starting solutions. The structural studies reveal that the S:Cd concentration has a strong influence on the microstructural characteristics of the sprayed CdS films. It was found that there is a transition in the preferred orientation from (0 0 2) plane to (1 0 1) plane when S:Cd molar concentration increases. The SEM images depict that the films are uniform and homogeneous. All the films have high optical transmittance (>80%) in the visible range. The optical band gap values are found to be in the range of 2.46–2.52 eV. CdS films fabricated by this simple and economic spray technique without using any carrier gas are found to be good in structural and optical properties which are desirable for photovoltaic applications. Hence, this simplified version of spray technique can be considered as an economic alternative to conventional spray pyrolysis (using carrier gas), for the mass production of low-cost, large area CdS coatings for solar cell applications.     

Experimental study on the plastic deformation and densification characteristics of some sintered and heat treated low alloy powder metallurgy steels

Sintered low alloy steels containing the alloying elements molybdenum, copper and titanium were synthesised through powder metallurgy route from mixed elemental powders to yield the compositions: Fe–0.5% C, Fe–0.5% C–2% Cu, Fe–0.5% C–2% Mo and Fe–0.5% C–2% Cu–2% Mo–2% Ti. Green cylindrical compacts were made using a 1000 kN hydraulic press using suitable cylindrical die-punch combination. The ceramic coated cylindrical preforms were sintered at 1000 ± 10 °C in a muffle furnace for a period of 120 min. After sintering, the preforms were subjected to different heat treatment processes, namely, heating to 900 °C, soaking for 60 min and quenching in air or oil or cooled inside the furnace. The heat treated preforms were subject to axial upsetting deformations, at various applied loads and their densification behaviours were compared. The influence of various heat treatment processes on deformation and densification of the alloys was studied and correlated with their microstructures. The plain carbon steel preforms were observed to respond well to the three heat treatment cycles by way of exhibiting the highest levels of densification and plastic deformation. However, both alloy addition and heat treatment have led to a reduction in densification and deformation of the alloy steel preforms. Presence of titanium carbide particulates in the microstructure of the Ti-alloyed steel has played a significant role in reducing the densification as well as deformation. The basic ferritic–pearlitic microstructure of Fe–0.5% C steel has essentially promoted the largest deformation levels coupled with higher densification.     

A constrained binary knapsack approximation for shortest path network interdiction

A modified shortest path network interdiction model is approximated in this work by a constrained binary knapsack which uses aggregated arc maximum flow as the objective function coefficient. In the modified shortest path network interdiction problem, an attacker selects a path of highest non-detection probability on a network with multiple origins and multiple available targets. A defender allocates a limited number of resources within the geographic region of the network to reduce the maximum network non-detection probability between all origin-target pairs by reducing arc non-detection probabilities and where path non-detection probability is modeled as a product of all arc non-detection probabilities on that path. Traditional decomposition methods to solve the shortest path network interdiction problem are sensitive to problem size and network/regional complexity. The goal of this paper is to develop a method for approximating the regional allocation of defense resources that maintains accuracy while reducing both computational effort and the sensitivity of computation time to network/regional properties. Statistical and spatial analysis methods are utilized to verify approximation performance of the knapsack method in two real-world networks.