Parallel force measurement with a polymeric microbeam array using an optical microscope and micromanipulator

An image analysis method and its validation are presented for tracking the displacements of parallel mechanical force sensors. Force is measured using a combination of beam theory, optical microscopy, and image analysis. The primary instrument is a calibrated polymeric microbeam array mounted on a micromanipulator with the intended purpose of measuring traction forces on cell cultures or cell arrays. One application is the testing of hypotheses involving cellular mechanotransduction mechanisms. An Otsu-based image analysis code calculates displacement and force on cellular or other soft structures by using edge detection and image subtraction on digitally captured optical microscopy images. Forces as small as 250+/-50 nN and as great as 25+/-2.5 microN may be applied and measured upon as few as one or as many as hundreds of structures in parallel. A validation of the method is provided by comparing results from a rigid glass surface and a compliant polymeric surface.     

Modeling of heat and mass transfer in accelerator targets during postulated accidents

The modeling of thermal-chemical behavior of targets used in accelerator applications is an important part of safety analysis. Tungsten is considered as a target material to produce tritium in a linear proton accelerator. The prediction of the chemical reactivity of tungsten in a steam flow at high temperatures is the most important part of a safety analysis of target design. The oxidation and volatilization of tungsten in steam at high temperatures is a complex phenomenon that involves various mechanisms (depending on the temperature), steam pressure, and steam velocity. A simple diffusion model that considers chemical equilibrium at the reaction interface and effective diffusion thickness, including the boundary and oxide layers, is proposed for predicting the volatilization rate. The proposed simple model predicts the available data reasonably well. The proposed model is implemented into a computer program that is developed to predict the radiological releases during postulated loss-of-coolant accidents (LOCAs). The computer program models heat production, heat transfer, and oxidation reactions in the multiple radiation enclosures representing the accelerator target elements. It treats each element of the radiation enclosures as a lumped control volume, or heat structure. Each heat structure may generate or lose heat by conduction, convection, or radiation and is subject to mass loss as a result of oxidation, melting, and volatilization. Postulated beyond-design-basis LOCAs are simulated with this computer program for the accelerator-production-of-tritium target. Sample calculations demonstrate oxidation/volatilization model capabilities and sensitivity to the assumptions selected.     

0.35 μm CMOS T/R Switch for 2.4 GHz Short Range Wireless Applications

This paper describes the design and implementation of a transmit/receive switch for 2.4 GHz ISM band applications. The T/R switch is implemented in a 0.35 m bulk CMOS process and it occupies 150 m · 170 m of die area. A parasitic MOSFET model including bulk resistance is used to optimize the physical dimensions of the transistors with regard to insertion loss and isolation. The measured insertion loss is 1.3 dB without port matching. Simulations using measured s-parameters indicate that an insertion loss of 0.8 dB can be obtained with a conjugate match. The measured isolation is 42 dB and the maximum transmit power is 16 dBm.     

UTRA/FDD RF Transceiver Requirements

Unified RF requirements are derived for an UMTS Terrestrial RadioAccess/Frequency Division Duplex (UTRA/FDD) compliant mobile transceiver. Aset of transceiver requirements are proposed with consideration to systemissues including duplex aspects. From these design-compatible requirements areproposed for each functional block in the transceiver.     

Transcriptional Profiling of Cardiac Cells Links Age-Dependent Changes in Acetyl-CoA Signaling to Chromatin Modifications

Metabolism has emerged as a regulator of core stem cell properties such as proliferation, survival, self-renewal, and multilineage potential. Metabolites serve as secondary messengers, fine-tuning signaling pathways in response to microenvironment alterations. Studies show a role for central metabolite acetyl-CoA in the regulation of chromatin state through changes in histone acetylation. Nevertheless, metabolic regulators of chromatin remodeling in cardiac cells in response to increasing biological age remains unknown. Previously, we identified novel cardiac-derived stem-like cells (CTSCs) that exhibit increased functional properties in the neonatal heart (nCTSC). These cells are linked to a unique metabolism which is altered with CTSC aging (aCTSC). Here, we present an in-depth, RNA-sequencing-based (RNA-Seq) bioinformatic with cluster analysis that details a distinct epigenome present in nCTSCs but not in aCTSCs. Gene Ontology (GO) and pathway enrichment reveal biological processes, including metabolism, gene regulation enriched in nCTSCs, and STRING analysis that identifies a network of genes related to acetyl-CoA that can potentially influence chromatin remodeling. Additional validation by Western blot and qRT-PCR shows increased acetyl-CoA signaling and histone acetylation in nCTSCs compared to aCTSCs. In conclusion, our data reveal that the link between metabolism and histone acetylation in cardiac cells is altered with the aging of the cardiac tissue.     

Development of a specially tailored local drug delivery system for the prevention of fibrosis after insertion of cochlear implants into the inner ear

A cochlear implant (CI)-associated local drug delivery system based on dexamethasone (DMS) was developed with the purpose to inhibit the growth of fibrotic tissue which influences the signal transmission from the CI to the neurons of the inner ear. For the realization of a targeted DMS delivery the following concepts were combined: modification of the silicone-based electrode carrier by incorporation of DMS and a DMS-containing polymeric coating chemically attached on the surface of the electrode carrier. It was demonstrated that the coated CI showed a high coating stability in a simulated implantation procedure. The in vitro drug release studies in a quasi-stationary model revealed a faster DMS release in the initial phase originating from the DMS-containing coatings and then a lower and sustained DMS release originating from the DMS-loaded silicone carrier. The performed in vitro biocompatibility study confirmed that the released DMS was non-toxic for cultured spiral ganglion cells.     

Mathematical treatment of the kinetics of binding protein dependent transport systems reveals that both the substrate loaded and unloaded binding proteins interact with the membrane components

Binding-protein-dependent transport systems in Gram-negative bacteria are multicomponent systems in which a soluble periplasmic binding protein of high substrate binding affinity establishes the major substrate recognition site. Usually, there are two membrane proteins which are thought to interact with the substrate loaded form of the binding protein to allow transport of substrate to occur. Transport is against the concentration gradient and needs energization by an ATP hydrolyzing polypeptide. Overall transport is considered mainly unidirectional owing to the high energy of ATP hydrolysis coupled to transport. We dissected the overall transport process into three individual steps: (i) reversible binding of substrate to the binding protein; (ii) reversible binding of the binding protein to the membrane components forming the translocation complex; (iii) irreversible transport of substrate through the membrane and dissociation of the binding protein from the complex. Two models were considered. In the first, only the substrate-loaded binding protein interacts with the membrane components, while in the second model both the loaded and the unloaded form of the binding protein interact with the membrane components. The mathematical analysis of the second model revealed that the substrate concentration KM at half-maximal rate of transport approaches KD of the binding protein when the last step of transport becomes low and when the concentration of binding protein in the periplasm becomes large. This is usually observed in real systems. Under the same conditions, in model 1 KM approaches zero and is hence considerably smaller than KD. This has never been observed in any real system. In addition, the dependence of the overall rate of transport on the concentration of binding protein in the periplasm follows a sigmoidal curve only when model 2 is considered. The sigmoidal behavior becomes more pronounced when the substrate concentration is low and it is less pronounced when the last step in overall transport is low. This phenomenon has been observed with the Escherichia coli maltose transport system. Thus, at least for the maltose transport system, it seems likely that both the loaded and the unloaded forms of the binding protein interact with the membrane components. We propose that this should generally be considered in binding-protein-dependent transport systems.     

Development of a screening test based on isothermal calorimetry for determination of self‐heating potential of biomass pellets

For the risk for spontaneous combustion in storage of biomass pellets to be assessed, it is important to know how prone the fuel is to self‐heating. There are traditional methods that are used to determine self‐heating characteristics of fuels, eg, basket heating tests. The results from basket heating tests indirectly give the reactivity from a series of tests at high temperatures. This paper presents a sensitive screening test procedure for biomass pellets using isothermal calorimetry for direct measurement of the heat production rate at typical bulk storage temperatures. This method can be used to directly compare the reactivity of different batches of biomass pellets. The results could be used, eg, by storage security managers to gain better knowledge of their fuels propensity for self‐heating and thereby for safer storage. A large number of tests have been performed to develop the test procedure presented. Different parameters, such as temperature, type of the test sample (powder/crushed or pellets), mass of test sample, and preheating time, have been varied. Furthermore, gas concentrations in the sample ampoule have been measured before and after some tests to study the oxygen consumption and the formation of CO and CO₂. Three different types of pellets with different characteristics were tested to assess the variation in behaviour. Based on these tests, a screening test procedure is presented with a test temperature of 60°C, a sample size of 4 g, a 15‐minute preheating period at the test temperature, and 24‐hour test duration.     

Analysis of the torsion angle distribution of poly(vinylidene fluoride) in the melt

Analysis of the torsion angle distribution of poly(vinylidene fluoride) (PVDF) structures at temperatures above its melting point is addressed by combining first principles methods, atomistic simulations and laboratory experiments. Amorphous, α- and β-conformations of PVDF structures have been considered. The results from the atomistic simulations as well as the experiments show that there is a larger probability of the PVDF torsions to be near ±180° at temperatures above the melting point, which is associated more with the β-conformation than the α-conformation.