Substrate Resistance Research Articles

Freeze-thaw decellularization of the trabecular meshwork in an ex vivo eye perfusion model.

ObjectiveThe trabecular meshwork (TM) is the primary substrate of outflow resistance in glaucomatous eyes. Repopulating diseased TM with fresh, functional TM cells might be a viable therapeutic approach. Decellularized TM scaffolds have previously been produced by ablating cells with suicide gene therapy or saponin, which risks incomplete cell removal or dissolution of the extracellular matrix, respectively. We hypothesized that improved trabecular meshwork cell ablation would result from freeze-thaw cycles compared to chemical treatment.Materials and MethodsWe obtained 24 porcine eyes from a local abattoir, dissected and mounted them in an anterior segment perfusion within two hours of sacrifice. Intraocular pressure (IOP) was recorded continuously by a pressure transducer system. After 72 h of IOP stabilization, eight eyes were assigned to freeze-thaw (F) ablation (−80 °C × 2), to 0.02% saponin (S) treatment, or the control group (C), respectively. The TM was transduced with an eGFP expressing feline immunodeficiency viral (FIV) vector and tracked via fluorescent microscopy to confirm ablation. Following treatment, the eyes were perfused with standard tissue culture media for 180 h. TM histology was assessed by hematoxylin and eosin staining. TM viability was evaluated by a calcein AM/propidium iodide (PI) assay. The TM extracellular matrix was stained with Picro Sirius Red. We measured IOP and modeled it with a linear mixed effects model using a B-spline function of time with five degrees of freedom.ResultsF and S experienced a similar IOP reduction of 30% from baseline (P = 0.64). IOP reduction of about 30% occurred in F within 24 h and in S within 48 h. Live visualization of eGFP demonstrated that F conferred a complete ablation of all TM cells and only a partial ablation in S. Histological analysis and Picro Sirius staining confirmed that no TM cells survived in F while the extracellular matrix remained. The viability assay showed very low PI and no calcein staining in F in contrast to many PI-labeled, dead TM cells and calcein-labeled viable TM cells in S.ConclusionWe developed a rapid TM ablation method that uses cyclic freezing that is free of biological or chemical agents and able to produce a decellularized TM scaffold with preserved TM extracellular matrix in an organotypic perfusion culture.

Control of base-excited dynamical systems through piezoelectric energy harvesting absorber

The spring-mass absorber usually offers a good control to dynamical systems under direct base excitations for a specific value of the excitation frequency. As the vibrational energy of a primary dynamical system is transferred to the absorber, it gets dissipated. In this study, this energy is no longer dissipated but converted to available electrical power by designing efficient energy harvesters. A novel design of a piezoelectric beam installed inside an elastically-mounted dynamical system undergoing base excitations is considered. A design is carried out in order to determine the properties and dimensions of the energy harvester with the constraint of simultaneously decreasing the oscillating amplitudes of the primary dynamical system and increasing the harvested power of the energy harvesting absorber. An analytical model for the coupled system is constructed using Euler–Lagrange principle and Galerkin discretization. Different strategies for controlling the primary structure displacement and enhancing the harvested power as functions of the electrical load resistance and thickness of the beam substrate are performed. The linear polynomial approximation of the system’s key parameters as a function of the beam’s substrate thickness is first carried out. Then, the gradient method is applied to determine the adequate values of the electrical load resistance and thickness of the substrate under the constraints of minimizing the amplitudes of the primary structure or maximizing the levels of the harvested power. After that, an iterative strategy is considered in order to simultaneously minimize the amplitudes of the primary structure and maximize the levels of the harvested power as functions of the thickness of the substrate and electrical load resistance. In addition to harmonic excitations, the coupled system subjected to a white noise is explored. Through this analysis, the load resistance and thickness of the substrate of the piezoelectric energy harvester are determined. It is shown that, in addition to efficiently control the oscillating amplitudes of the primary structure, broadband resonance regions can take place and hence high levels of the harvested power are obtained.

Mechanism of host substrate acetylation by a YopJ family effector.

Yersinia outer protein J (YopJ) family of bacterial effectors depends on a novel acetyltransferase domain to acetylate signaling proteins from plant and animal hosts. However, the underlying mechanism is unclear. Here, we report the crystal structures of PopP2, a YopJ effector produced by the plant pathogen Ralstonia solanacearum, in complex with inositol hexaphosphate (IP6), acetyl-coenzyme A (AcCoA), and/or substrate RRS1-RWRKY. PopP2 recognizes the WRKYGQK motif of RRS1-RWRKY to position a targeted lysine in the active site for acetylation. Importantly, the PopP2 – RRS1-RWRKY association is allosterically regulated by IP6 binding, suggestive of a previously unidentified role of the eukaryote-specific cofactor in substrate interaction. Furthermore, we provide evidence for the reaction intermediate of PopP2-mediated acetylation, an acetyl-cysteine covalent adduct, lending direct support to the “Ping-Pong”-like catalytic mechanism proposed for YopJ effectors. Together, our study provides critical mechanistic insights into the virulence activity of YopJ class of acetyltransferases.

Measuring thermal substrate resistance and impact on the characterization of thermoelectric modules

Different characterization methods for measuring Seebeck, electrical resistance, thermal conductance, and ZT of thermoelectrics modules for power generation applications found in literature have produced different results. These differences exist even when the methods use the same module on the same test equipment using the same temperatures across the module. We develop a model that accounts for the thermal resistance of the module substrate and contact resistance and do simulations to show that by accounting for the thermal substrate resistance the observed experimental differences can be accounted for. Based on the model, we develop two new test approaches for determining the thermal substrate resistance and provide means for properly interpreting results from four common thermoelectric characterization methods. We apply the correction to experimental data to demonstrate consistent results for measured module parameters regardless of testing approach used.

Electrospray as a suitable technique for manufacturing carbon-based devices

We demonstrate here that electrospray is a technique suitable for deposition carbon-based materials. It is versatile enough to be used with graphene oxide (GO), reduced graphene oxide (rGO) and carbon nanofibers (CNF), obtained by chemical methods. A detailed analysis of the effects of the dispersion properties and the main process parameters (voltage and flow rate) on the deposits quality is presented. Rigid and flexible substrates have been coated with good geometry control under ambient conditions. Thickness of GO films onto silicon substrates, optical transmittance of rGO onto fluoride doped tin oxide (FTO) coated glass substrate and electrical resistance of both, rGO and CNF films onto flexible polyamide have been correlated with deposition time. As an example of application, the manufacture of carbon nanofibers gas sensing devices deposited onto a ceramic platform and flexible polyimide by means of electrospray technique are shown.

Measurement of Thickness of High-Resistivity Substrate by Photoconduction Enhanced Capacitance Displacement Sensor

Capacitive displacement sensors provide non-contact, extreme resolution, and absolute accuracy thickness measurements. However, if the resistivity of a target substrate is within 105-107 ohm-cm, an uncertainty will appear in the thickness measurement. The common solution is to adjust the resistivity to be outside the range that causes the measurement uncertainty by implanting dopants and followed by an activation anneal, but this will unavoidably lead to changes in the material properties and morphology. Here, we exploit the photoconductive effect to generate sufficient high amount of electron-hole pairs, thereby temporarily decreasing the resistivity and thus enabling the capacitive displacement sensor to accurately measure the thickness at nanoscale resolution. After the measurement is complete, the resistivity of the substrate will return to its original status. The photoconductive effect can be simply induced via laser irradiation at the sensing point, which narrows or eliminates the gap in the measurement range of capacitive sensors to include high-resistivity substrate.

The Effects of Film Thickness and Substrate Resistivity on Corrosion of Iron Thin Films

This study investigated the corrosion behavior of Fe films with different thicknesses in NaCl solution. It has been reported that nanocrystalline metal thin films are more corrosion resistant than their coarser bulk counterparts, but the effect of thickness is not well characterized. Polarization curves were generated for three iron thin films with thicknesses of 10, 20, and 100 nm and bulk iron in aerated 3.5 wt% NaCl solution at 24 ˚C. All films were deposited on silica substrates, and 20 and 100 nm films were also deposited on silica substrates with a Pt conductive under-layer. The resistivity/conductivity of the samples were measured using a four point probe, and the effects of film and substrate resistivity on corrosion were addressed by comparing polarization curves of thin films with and without the Pt conductive layer. The extent of film corrosion was spatially varied and the variation in localized electrochemical response was measured using scanning vibrating electrode technique (SVET). The corroded films were also characterized by optical microscopy.

Multistereocenter-Containing Cyclopentanoids from Ynamides via Oxazolidinone-Controlled Nazarov Cyclization.

Achieving ready-enantioselective access to multistereocenter-containing cyclopentyl rings is an area of great significance to organic synthesis. In this work, we describe a general protocol for accessing multistereocenter-containing cyclopentanoids from simple N-alkynyloxazolidinones (Ox-ynamides). This protocol involves conversion of Ox-ynamides into Ox-activated divinyl and aryl vinyl ketones that undergo facile Nazarov cyclization with excellent chemo-, regio-, and stereocontrol. The Ox auxiliary directs all aspects of reactivity and selectivity, both in the electrocyclization and in the subsequent transformations of the resulting oxyallyl intermediate. Stereoinduction in the electrocyclization results from a "coupled-torque" mechanism in which rotation of the Ox group, driven by increasing orbital overlap of the nitrogen lone pair with the incipient oxyallyl cation, is coupled with the rotation of the termini of the pentadienyl cation, favoring a particular direction of conrotatory ring closure (torquoselectivity). The associated lone-pair stabilization of the transition state by Ox promotes cyclization of traditionally resistant substrates, broadening the scope of this asymmetric Nazarov cyclization. The Ox group also facilitates the stereo- and regioselective incorporation of nucleophiles (Nu) and dienes, giving more complex, multistereocenter containing cyclopentanoids. Finally, the Ox group is readily removed and recovered or can be converted into other amine functionalities.

Characterization of the newly isolated ω-oxidizing yeast Candida sorbophila DS02 and its potential applications in long-chain dicarboxylic acid production.

α, ω-Dicarboxylic acids (DCAs) are multipurpose chemicals widely used in polymers, perfumes, plasticizers, lubricants, and adhesives. The biotransformation of DCAs from alkanes and fatty acids by microorganisms has attracted recent interest, since synthesis via chemical oxidation causes problems in terms of the environment and safety. We isolated an ω-oxidizing yeast from a wastewater disposal facility of a petrochemical factory by chemostat enrichment culture. The haploid strain identified as Candida sorbophila DS02 grew on glucose and dodecane, exhibiting greater cell shrinkage on the latter. In flask cultures with mixed alkanes (C10-16) and fatty acid methyl esters (C10-16), DS02 used mixed alkanes simultaneously unlike Candida tropicalis and Yarrowia lipolytica and showed high substrate resistance. In flask cultures with acrylic acid-a known inhibitor of β-oxidation-DS02 produced 0.28g/l dodecanedioic acid (DDDA) from dodecane, similar to wild-type C. tropicalis ATCC 20336. In fed-batch fermentation, DS02 produced 9.87g/l DDDA, which was 5.7-fold higher than wild-type C. tropicalis. These results suggest that C. sorbophila strain DS02 has potential applications for the large-scale production of DCA.

First results on the ATLAS HL-LHC H35DEMO prototype

This article presents the first measured results from the H35DEMO pixel demonstrator. The H35DEMO is a prototype ASIC in the 0.35 μm High Voltage-CMOS (HV-CMOS) process from ams aimed at proving that HV-CMOS sensor technologies are suitable as tracking detectors for the ATLAS High Luminosity-LHC (HL-LHC) upgrade. The prototype was fabricated in an engineering run, in which wafers with four different substrate resistivities, ranging from the standard value of 20 Ω ⋅ cm to a high value of 1 kΩ ⋅ cm, were used to increase the depletion region of the sensor. The prototype includes four large area matrices and a few test structures. New experimental set-ups have been developed to measure the ASIC with radioactive sources and laser beams. The experimental set-ups and the measured results obtained will be discussed in this article.

Ferroelastic strain control of multiple nonvolatile resistance tuning in SrRuO3/PMN-PT(111) multiferroic heterostructures

The electric-field-tunable resistance switching in elastically coupled SrRuO3 thin films grown on (111)-oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 ferroelectric-crystal substrates has been investigated. During the ferroelectric poling process, the resistance evolution tracks the electric-field-induced in-plane strain of the film efficiently, revealing strain but not the electrostatic charge-mediated coupling mechanism. Using 109° and 71° ferroelastic domain switching of the substrate, multiple reversible and nonvolatile resistance states can be achieved at room temperature, which is closely related to the relative proportion of in-plane polarization vectors and induced distinct in-plane strain states after domain switching. Our findings provide an approach to elucidate electrically driven domain switching dynamics and design energy efficient, high-density spintronic memory devices.

PO-0759: Validation of the influence of M512 substrate resistivity on sensitivity degradation of radiation

PO-0759: Validation of the influence of M512 substrate resistivity on sensitivity degradation of radiation

Measurement of Thickness of High-Resistivity Substrate By Photoconduction Enhanced Capacitance Displacement Sensor

Capacitive displacement sensors can offer non-contact, extreme resolution, and absolute accuracy thickness measurements. However, for general capacitive displacenent sensors, if the resistivity of a target substrate is within 105-107 ohm-cm, a measurement uncertainty will occur in the thickness measurement. The measnurement uncentration may be several microon meters. The common solution is to adjust the resistivity to be outside the range that causes the measurement uncertainty by implanting dopants and followed by an activation anneal, but this will unavoidably lead to changes in the material properties and morphology. Here, we exploit the photoconductive effect to generate sufficient high amount of electron-hole pairs, thereby temporarily decreasing the resistivity and thus enabling the capacitive displacement sensor to accurately measure the thickness at nanoscale resolution. After the measurement is complete, the resistivity of the substrate will return to its original status. The photoconductive effect can be simply induced via laser irradiation at the sensing point, which narrows or eliminates the gap in the measurement range of capacitive sensors to include high-resistivity substrates.

The Effect of Film Thickness and Substrate Resistivity on Corrosion of Fe Thin Films

This study investigated the corrosion behavior of Fe films with different thickness in NaCl solution. It has been reported that nanocrystalline metal thin films are more corrosion resistant than their coarser or bulk counterparts, but the effect of thickness is not well characterized. Polarization curves were measured for three iron thin film with thicknesses of 10, 20, and 100 nm and bulk iron in aerated 3.5 wt% NaCl solution at 24 ˚C. Each film thickness was deposited on silica substrates, and 20 and 100 nm films were also deposited on silica substrates with a Pt conductive layer. The resistivity/conductivity of the samples were measured using four point resistivity measurement, and the effect of film and substrate resistivity on corrosion was addressed by comparing polarization curves of thin films with and without the platinum conduction layer. The extent of film corrosion was spatially varied and the variation in localized electrochemical response was measured using scanning vibrating electrode technique. The corroded films were also characterized by SEM.

Static and Dynamic Magnetization Investigation in Permalloy Electrodeposited onto High Resistive N-Type Silicon Substrates

The present study reports on the development of permalloy thin films obtained by electrodeposition onto low-doped n-type silicon substrates. While changing from non-percolated clusters into percolated thin films upon increasing the electrodeposition time, the static and dynamic magnetic properties of the as-obtained structures were investigated. We found the experimental magnetic results to be in very good agreement with the simulations performed by solving the Landau-Lifshitz for the dynamics of the magnetic moment. For short electrodeposition times we found the static and dynamic magnetization behavior of the as-formed nanoclusters evidencing vortex magnetization with random chirality and polarization, which is explained in terms of dipolar interaction minimization. Indeed, it is herein emphasized that recent applications of ferromagnetic materials in silicon-based spintronic devices, such as logic and bipolar magnetic transistors and magnetic memories, have revived the possible utilization of low cost and simple electrodeposition techniques for the development of these upcoming hetero-nanostructured devices.

A novel diamond-like carbon film

In this work, we fabricate a novel DLC film through shortening the deposition periods. The novel DLC film included F and Si doped multi-layer structure, and a silicon interlayer that is able to reduce internal stress, improve the bonding and adhesion, and bridge the film and substrate. This work mainly focused on discussing the cause of the corrosion behavior of the novel DLC film. Corrosion resistance is assessed by potentiodynamic polarization tests in 3.5wt.% NaCl solution. The corrosion test results show that the novel DLC film exhibits good adhesion to Ti alloy substrate and good resistance to corrosion.

Indoor Light Enhanced Photocatalytic Ultra-Thin Films on Flexible Non-Heat Resistant Substrates Reducing Bacterial Infection Risks

Photocatalytic antibacterial sol-gel coated substrates have been reported to kill bacteria under light or in the dark. These coatings showed non-uniform distribution, poor adhesion to the substrate and short effective lifetime as antibacterial surfaces. These serious limitations to the performance/stability retard the potential application of antibacterial films on a wide range of surfaces in hospital facilities and public places. Here, the preparation, testing and performance of flexible ultra-thin films prepared by direct current magnetron sputtering (DCMS) at different energies are reviewed. This review reports the recent advancements in the preparation of highly adhesive photocatalytic coatings prepared by up to date sputtering technology: High Power Impulse Magnetron Sputtering (HIPIMS). These latter films demonstrated an accelerated antibacterial capability compared to thicker films prepared by DCMS leading to materials saving. Nanoparticulates of Ti and Cu have been shown during the last decades to possess high oxidative redox potentials leading to bacterial inactivation kinetics in the minute range. In the case of TiO2CuOx films, the kinetics of abatement of Escherichia coli (E. coli) and methicillin resistant Staphylococcus aureus (MRSA) were enhanced under indoor visible light and were perceived to occur within few minutes. Oligodynamic effect was seen to be responsible for bacterial inactivation by the small amount of released material in the dark and/or under light as detected by inductively-coupled plasma mass spectrometry (ICP-MS). The spectral absorbance (detected by Diffuse Reflectance Spectroscopy (DRS)) was also seen to slightly shift to the visible region based on the preparation method.

Thin large area vertical Schottky barrier diamond diodes with low on-resistance made by ion-beam assisted lift-off technique

We designed and made 15μm large area vertical Schottky barrier diamond diodes with resulting substrate thickness of about 1μm. The ion-beam assisted lift-off technique was successfully used to separate 5×5mm2 active two-layered structure from ballast HPHT diamond substrate. The fabricated diodes had <6mΩ∗cm2 (0.03Ω) on-resistance at room temperature and 3mΩ∗cm2 (0.015Ω) at 200°C fixed temperature of the diode case. A removal of large ballast substrate resistance results in a significant drop of on-state voltage, power losses and, therefore, increasing of diode efficiency. An additional technology step of sacrificial layer formation by ion implantation did not cause a considerable degradation of diode reverse characteristics. As a result, the room-temperature Baliga's figure of merit of the fabricated thin diodes is more than ten times higher comparing to earlier made thick diodes with a drift layer of the same thickness and boron content. 20A maximum forward DC current and <2V voltage drop were measured at fixed case temperatures in the range from 0°C to 200°C using an active heat sink.

Effect of Anode Shape on Uniformity of Electrodeposition onto Resistive Substrates

This work is devoted to the theoretical study of the effect of anode shape, insulating shields, the exchange current density and operating conditions on the uniformity of metal layer deposited onto the resistive cathode. Laplace’s equation for the potential in the electrolyte solution, Poisson’s equation for the potential in the resistive cathode, and the equation of metal thickness evolution were used as the mathematical model. The numerical solution was performed using the boundary element and finite element methods. The possibilities for controlling the distribution of deposit thickness over the cathode surface are demonstrated by the example of metal deposition onto an annulus workpiece. The use of the anode of the calculated shape enabled us to obtain a deposit of uniform thickness over almost the entire workpiece surface except for the very edges, where the deposit was thicker. The application of shields designed in the work enabled us to eliminate this drawback.

Design, fabrication, characterization of micromachined capacitive shunt switches with low actuation voltages and low temperature packaging

This paper reports the design, fabrication, electrical characterization and packaging of micromachined shunt capacitive switch with low actuation voltage. These switches are fabricated on a low resistive silicon substrate using only a four mask surface micromachining process. The co-planar waveguide is patterned using chrome/gold layer. Positive photoresist S1813 is used as the sacrificial layer. The top beam membrane is made of gold. The membranes are released through a wet release process through Piranha solution. Supercritical point drying tools were used for the top beam release after wet etching to provide anti-stiction. The switches are 300 µm long with 10 μm holes on the top membrane to lower both residual stress and pull-in voltages. These switches exhibit low actuation voltages in the range of 5.5–6.4 V. The RF characterization shows that these switches have low insertion loss and high isolation in the frequency range of interest. The packaging was carried out using commercially available surface mount style RF packages. However, the whole packaging process is performed under low temperature in order to free the MEMS structures of thermally induced stress which otherwise would affect the performance of the switch. The adhesion of the die to the bottom package is excellent and is tested by die shear test. The packaged switch has passed the non-destructive pull test.