Larger Cell Area Research Articles

Oligomerization Dynamics of Cell Surface Receptors in Living Cells by Total Internal Reflection Fluorescence Microscopy Combined with Number and Brightness Analysis.

Despite the importance and ubiquity of receptor oligomerization, few methods are applicable for detecting clustering events and measuring the degree of clustering. Here, we describe an imaging approach to determine the average oligomeric state of mEGFP-tagged-receptor homocomplexes in the membrane of living cells. The protocol is based on Total Internal Reflection Fluorescence (TIRF) microscopy combined with Number and Brightness (N&B) analysis. N&B is a method similar to fluorescence-correlation spectroscopy (FCS) and photon counting histogram (PCH), which are based on the statistical analysis of the fluctuations of the fluorescence intensity of fluorophores diffusing in and out of an illumination volume during an observation time. In particular, N&B is a simplification of PCH to obtain information on the average number of proteins in oligomeric mixtures. The intensity fluctuation amplitudes are described by the molecular brightness of the fluorophore and the average number of fluorophores within the illumination volume. Thus, N&B considers only the first and second moments of the amplitude distribution, namely, the mean intensity and the variance. This is, at the same time, the strength and the weakness of the method. Because only two moments are considered, N&B cannot determine the molar fraction of unknown oligomers in a mixture, but it only estimates the average oligomerization state of the mixture. Nevertheless, it can be applied to relatively small time series (compared to other moment methods) of images of live cells on a pixel-by-pixel basis, simply by monitoring the time fluctuations of the fluorescence intensity. It reduces the effective time-per-pixel to a few microseconds, allowing acquisition in the time range of seconds to milliseconds, which is necessary for fast oligomerization kinetics. Finally, large cell areas as well as sub-cellular compartments can be explored.

A 28-nm 320-Kb TCAM Macro Using Split-Controlled Single-Load 14T Cell and Triple-Margin Voltage Sense Amplifier

Ternary content-addressable memory (TCAM) is limited by large cell area, high search power, significant active-mode leakage current, and a tradeoff between search speed and signal margin on the match-line (ML). In this paper, we developed a split-controlled single-load 14T (SCSL-14T) TCAM cell and a triple-margin voltage sense amplifier (TM-VSA) to achieve the following: 1) compact cell area; 2) lower search delay and search energy; 3) reduced current leakage in standby and active modes; and 4) tolerance for small sensing margin. A testchip with 320-Kb 14T-TCAM macro was fabricated using a 28-nm CMOS logic process and modified compact foundry six-transistor (6T) cell. The proposed macro achieved search delay of only 710 ps and 0.422 fJ/bit/search.

Histological characteristics of accessory adrenal glands of rabbits with different types of autonomous tonus

For the purposes of the adrenal gland’s study, 27 four months old male rabbits (Oryctolagus cuniculus) of Termond White breed were selected. Based on electrocardiography and variation pulsometry results, three types of autonomous tonus were determined in animals: sympathicotonia (ST), normotonia (NT) and parasympathicotonia (PS), which formed the basis for the division of animals into three groups. All rabbits were subjected to euthanasia and histological preparations were made from their adrenal glands. Apart from the main adrenal gland, accessory adrenal gland was detected in five purposes animals, including three ST rabbits, one NT rabbit and one PS rabbit. Also, four accessory adrenal glands were revealed in one ST rabbit simultaneously. In fact, these accessory adrenal glands became the main object of the further morphological research. The obtained historical indicators accessory adrenal glands were compared to the ones from various animal groups (CT with NT and CT with PS), as well as to the indicators of the main adrenal gland in each group. Statistical analysis of the received data was performed only in the group of ST animals. Accessory adrenal gland of ST rabbits is represented by two zones: zona glomerulosa and zona fasciculata, the area of which is 52% and 48% respectively. In PS and NT rabbits, the glands are formed by zona glomerulosa only. Investigating the accessory adrenal gland’s cellular component, it was found that NT rabbits have the largest cell area in zona glomerulosa, while PS rabbits have the smallest one. At the same time, the area of nucleus has the largest values in ST animals and the smallest ones in PS animals likewise. Сomparing zona glomerulosa and zona fasciculata in ST rabbits, it was found that cell size differs significantly, while the area of nucleus is almost identical. The nuclear-cytoplasmic ratio in zona glomerulosa cells is the largest for PS rabbits. The smallest ratio values were detected among the NT rabbits. Obviously, ST rabbits occupy an intermediate position. Unlike the main adrenal gland, the cells of accessory adrenal gland are of a smaller size and а denser location of cells in all groups of animals. The conducted studies allow concluding that the typological features of the autonomous tonus affect the morphology of accessory adrenal gland.

Multinucleation of Incubated Cells and Their Morphological Differences Compared to Mononuclear Cells.

Some cells cultured in vitro have multiple nuclei. Since cultured cells are used in various fields of science, including tissue engineering, the nature of the multinucleated cells must be determined. However, multinucleated cells are not frequently observed. In this study, a method to efficiently obtain multinucleated cells was established and their morphological properties were investigated. Initially, we established conditions to quickly and easily generate multinucleated cells by seeding a Xenopus tadpole epithelium tissue-derived cell line (XTC-YF) on less and more hydrophilic dishes, and incubating the cultures with medium supplemented with or without Y-27632—a ROCK inhibitor—to reduce cell contractility. Notably, 88% of the cells cultured on a less hydrophilic dish in medium supplemented with Y-27632 became multinucleate 48 h after seeding, whereas less than 5% of cells cultured under other conditions exhibited this morphology. Some cells showed an odd number (three and five) of cell nuclei 72 h after seeding. Multinucleated cells displayed a significantly smaller nuclear area, larger cell area, and smaller nuclear circularity. As changes in the morphology of the cells correlated with their functions, the proposed method would help researchers understand the functions of multinucleated cells.

Substrate Viscosity Dictates Cellular Response

Cells respond to and are regulated by the mechanical properties of the substrate to which they are attached. Previous studies have shown that cells can generate larger forces on stiffer substrates, driving extracellular matrix assembly and increasing the substrate stiffness. In vitro models of fibrotic tissue focus on increasing the elastic modulus of the polymer substrate. However, this approach ignores the viscoelastic nature of fibrotic tissue. Recent research has suggested that as fibrotic tissue matures, the matrix transitions from one with a high viscosity to one that is more purely elastic. In this work, we investigate mechanosensitive effects of viscoelasticity using single and dual blends of poly (dimethyl siloxane) (PDMS) formulations with tunable viscous and elastic properties. We found that 3T3 fibroblast cells on a substrate with higher viscosity have larger cell area, but assemble less fibronectin. To elucidate the mechanism of altered viscosity, we simulated a modification of the Chan-Odde motor-clutch model, representing the substrate as a viscoelastic spring-dashpot system instead of a purely spring element. The viscoelastic model shows that cells are sensitive to changes in substrate viscosity, switching from a “frictional slippage” to “load and fail” regime. Our experiments and simulations demonstrate that the viscous component of underlying substrates plays a larger role in cell functionality than previously expected. This may be key in exploring the dynamics of and potential treatments for fibrosis.

Ferroelectric random access memory with high electric properties and high production yield realized by employing an AlOx underlying layer of Pt bottom electrode for a La-doped lead zirconate titanate capacitor

Although ferroelectric random access memory (FRAM) has superior electric properties, its downside is that it has a relatively larger cell area in comparison other non-volatile memories. We tried to apply TiOx, and AlOx to an underlying layer (TiOx-UL, AlOx-UL) instead of our previously used Ti underlying layer (Ti-UL) for the La-doped lead zirconate titanate (PLZT) capacitor to obtain a high polarization value aiming to a lowering cell area. The failed bit ratio of the FRAM with TiOx-UL was found to be higher than that with AlOx-UL even though polarization values of the PLZT capacitor with both underlying layers are almost the same and much higher than that with Ti-UL. It is strongly suggested that the imprint induced in PLZT by charged defect is a main cause of bit failure by fail-bit analysis. X-ray diffraction and atomic force microscopy observations shows that charged defect density in PLZT over TiOx-UL is possibly higher than that in PLZT over AlOx-UL due to surface roughness of underlying layers.

Asymmetric Polyoxometalate Electrolytes for Redox Flow Batteries

Electrochemical storage of energy is a valuable asset for the integration of intermittent renewable energy sources such as wind and solar power. Redox flow batteries (RFBs) are the only type of battery in which the energy content and the power output can be scaled independently, offering flexibility for applications from frequency regulation and load levelling. The energy in a RFB is stored in dissolved redox shuttles of its electrolytes which offers many intrinsic advantages for grid scale energy storage: (1) Independent scalability of energy and power content because the volume of the tanks and the size of the electrodes can be chosen independently. (2) Degradation of RFBs is be limited because the electrodes do not undergo conversion or intercalation reactions, instead they only serve as electron sink or reservoir. (3) To a certain degree RFBs are chemistry-agnostic, one battery cell can be run with various redox electrochemistries.However, while the advantages of the flow battery concept are undisputed, there is no agreement on the best (electro-)chemistry yet. The champion of the metal chemistries is the all-vanadium redox flow battery (VRFB)1. Utilizing four oxidation states of vanadium (V2+,V3+,VO2+,VO2 +) this cell chemistry has the main advantage that cross-over of species from one half-cell through the separator into the other half-cell does not lead to a chemical contamination and can be rebalanced electrochemically. The main drawbacks of the VRFB are the sluggish kinetics of the V2+/V3+ and the VO2+/VO2 + redox reactions which limit the current density and therefore the power density2. Organic redox couples can be low cost and made from abundant elements, and they offer greater variability than metallic redox couples due to their tuneable structure3. A great number of organic redox couples were presented in recent years, with capital cost of metallic RFB chemistries being the main driver for their development. As most studies have been restricted to laboratory cell operation, insights into scale-up with larger cell areas and bigger electrolyte volumes and long-term cycling are currently not available3. We have proposed a new class of redox electrolyte which combines the tuneability of organic molecules with the stability of metal ions: Polyoxometalates (POMs) functioning as nanostructured electron carriers 4. Employing electrochemistry and in-situ 51V NMR, we show that POMs exhibit four main advantages for the use as electrolyte in a RFB: (1) POMs do not permeate cation exchange membranes because they are large anions. This prevents cross-over and thereby self-discharge and capacity fade. (2) POMs exhibit facile redox kinetics with electron transfer constants four orders of magnitude faster than V2+/V3+ and VO2+/VO2 +. This can enable high current densities. (3) POMs undergo multi-electron redox reactions which increases the capacity per molecule. (4) The investigated POMs are soluble and stable. The catholyte species even spontaneously reassembles when destroyed by adverse solvent conditions.In flow battery studies the theoretical capacity (10.7 Ah L-1) could be achieved under operating conditions. The cell showed a capacity fade of 0.16% per cycle when the cell was cycled for 14 days with current densities from 30 to 60mA cm-2. Avenues to improve the redox electrochemistry of the POMs and the battery will be discussed. References (1) Rychcik, M.; Skyllas-Kazacos, S. J. Power Sources 1987, 19, 45–54.(2) Friedl, J.; Stimming, U. Electrochim. Acta 2017, 227, 235–245.(3) Leung, P.; Shah, A. A.; Sanz, L.; Flox, C.; Morante, J. R.; Xu, Q.; Mohamed, M. R.; Ponce de León, C.; Walsh, F. C. J. Power Sources 2017, 360, 243–283.(4) Friedl, J.; Bauer, C.; Al-Oweini, R.; Yu, D.; Kortz, U.; Hoster, H.; Stimming, U. In 222nd MEeting of the ECS; 2012.

Low-Temperature Soft-Cover Deposition of Uniform Large-Scale Perovskite Films for High-Performance Solar Cells.

Large-scale high-quality perovskite thin films are crucial to produce high-performance perovskite solar cells. However, for perovskite films fabricated by solvent-rich processes, film uniformity can be prevented by convection during thermal evaporation of the solvent. Here, a scalable low-temperature soft-cover deposition (LT-SCD) method is presented, where the thermal convection-induced defects in perovskite films are eliminated through a strategy of surface tension relaxation. Compact, homogeneous, and convection-induced-defects-free perovskite films are obtained on an area of 12 cm2 , which enables a power conversion efficiency (PCE) of 15.5% on a solar cell with an area of 5 cm2 . This is the highest efficiency at this large cell area. A PCE of 15.3% is also obtained on a flexible perovskite solar cell deposited on the polyethylene terephthalate substrate owing to the advantage of presented low-temperature processing. Hence, the present LT-SCD technology provides a new non-spin-coating route to the deposition of large-area uniform perovskite films for both rigid and flexible perovskite devices.

A 3T1R Nonvolatile TCAM Using MLC ReRAM for Frequent-Off Instant-On Filters in IoT and Big-Data Processing

Existing nonvolatile ternary content-addressable-memory (nvTCAM) suffers from limited word-length (WDL), large write-energy ( $E_{W})$ and search-energy ( $E_{S})$ , and large cell area (A). This paper develops a 3T1R nvTCAM cell using a single multiple-level cell (MLC)-resistive RAM (ReRAM) device to achieve long WDL, lower $E_{W}$ and $E_{S}$ , and reduced cell area. Two peripheral control schemes were developed, dual-replica-row self-timed and invalid-entry power consumption suppression (IEPCS), for the suppression of dc current in 3T1R nvTCAM cells in order to reduce $E_{S}$ . Two versions of the IEPCS scheme were developed (basic and charge-recycle-controlled) to alter the tradeoff between area overhead and power consumption in the updating of invalid-bits. A $128~\text {b} \times 64$ b 3T1R nvTCAM macro was fabricated using back-end-of-line ReRAM under 90-nm CMOS process. The fabricated MLC-based 3T1R nvTCAM macro achieved sub-1-ns search-delay and sub-6-ns wake-up time with supply voltage of 1 V and WDL = 64 b.

English

The present study assessed the response of physiological and anatomical characteristics of four widely cultivated fragrant Rosa species. Water analysis showed that all minerals and chemicals were in permissible level in canal water and treated wastewater, whereas untreated wastewater contained higher EC, biological oxygen demand (BOD), chemical oxygen demand (COD) and heavy metals like Cd, Co, Cu, Pb. There was considerable variations among different Rosa species regarding response to wastewater irrigations. Under treated wastewater, R. bourboniana showed highest photosynthetic rate, high transpiration rate and maximum chlorophyll contents than other Rosa species whereas stomatal conductance of R. Gruss-anTeplitz was highest under treated wastewater. Leaf anatomical characteristics showed that R. Gruss-an-Teplitz under untreated wastewater showed large cortical cell area, vascular bundle area, large spongy cell area and thick midrib while large epidermal thickness of R. centifolia was recorded under treated wastewater. Large palisade cell and phloem area and thick leaves (lamina) were found in R. damascena under treated wastewater while large metaxylem area of R. bourboniana in untreated wastewater. The study showed that treated wastewater was most suitable and desirable irrigation treatment than canal water and untreated wastewater while R. bourboniana and R. Gruss-an-Teplitz was dominant Rosa species regarding physiological characteristics, while all species showed great diversity in leaf tissue architecture under treated and untreated wastewater. © 2016 Friends Science Publishers

Co-solvent effect on microwave-assisted Cu2ZnSnS4 nanoparticles synthesis for thin film solar cell

Cu2ZnSnS4 (CZTS) nanoparticles (NPs) were prepared in a one-step microwave-assisted synthesis using a mixture of trioctylphosphine oxide (TOPO) and oleylamine (OLA) as solvent. The reaction medium was optimized by varying the TOPO and OLA ratios to control the CZTS NPs formation. The synthesized CZTS NPs were characterized by X-ray diffraction, Raman spectroscopy, UV–vis spectroscopy, and transmission electron microscopy techniques. High quality CZTS NPs with composition of Cu1.8Zn1.4SnS3.6, optimum size distribution in the range of 22±4nm and band gap of around 1.5eV were obtained using microwave assisted synthesis method with OLA:TOPO (1:1) as co-solvent. In the microwave assisted process, the reaction temperature and time has been reduced significantly to 165°C and 10min respectively, as compared with other wet chemical solvothermal hot injection/ surfactant based methods. Finally, CZTSSe solar cell fabricated from the selenized microwave-assisted CZTS NPs yielded an efficiency of 4.48%; therefore, the low cost of synthesis of this high quality CZTS NPs ink and the capability of spraying for large solar cell area is very attractive.

Chinese herbal medicine enhances sexual function and c-Fos/nNOS expression in the nucleus accumbens of orchidectomized rats

ObjectiveTo determine whether the central nervous system is involved in the effect of Chinese herbal medicine on sexual function recovery in orchidectomized rats. MethodsOrchidectomized rats were administered intragastrically with a decoction of “kidney-nourishing” Chinese herbal medicine once per day for 28 days. Accessory genital organ weight, plasma testosterone, and mating behavior were investigated. The expression of c-Fos and neuronal nitric oxide synthase (nNOS) in neuronal cells in the nucleus accumbens (NAc) was analyzed by immunohistochemistry. ResultsThere was a decrease in accessory genital organ weight, plasma testosterone, and sexual behavior, as well as a low number of c-Fos-positive cells and a large nNOS-positive cell area in orchidectomized rats. Administration of the herbal medicine increased accessory genital organ weight, testosterone level, mating behavior, and c-Fos-positive cell number, while it decreased the nNOS-positive cell area in orchidectomized rats. ConclusionAn increase of plasma testosterone after administration of “kidney-nourishing” herbal medicine might contribute to the elevated sexual function and activity in orchidectomized rats. In addition, a central nervous system mechanism, such as the functional alteration of NAc, might be involved.

Characterization of local Al‐contacts by light beam induced current measurements and their verification by 2D simulation using flexPDE

In recent years the relevance of passivated emitter and rear contact solar cells for industrial application increased due to significantly higher cell efficiencies compared to full area back surface field solar cells. However, the formation of local Al contacts is particularly sensitive to the manufacturing process parameters. Under non‐optimized conditions, the eutectic in local Al contacts is missing and so‐called voids are formed. So far, their impact onto the electrical parameters of the solar cells is not fully understood, mainly because of their difficult spatially resolved detection. Within this work the application of scanning acoustic microscopy circumvents this difficulty and allows a classification of local contacts in terms of “voids” or “filled contacts” on large cell area. The passivation quality of the BSF in the local contacts is investigated in detail through the local internal quantum efficiency (IQE) measured by light beam induced current (LBIC). It is found that there is a large spreading for the IQE values, attributed to a variation in BSF layer thickness. In addition, LBIC measurements of voids are fitted by 2D simulations, according to a detailed modelling of the surface recombination velocities (SRV) in local contacts. The final model is based on a non‐uniform SRV in the void's vicinity, attributed to laser damage close to the interface. It is demonstrated that the electrical parameters of the solar cell are affected by voids only when their surface is not sufficiently passivated by a local BSF.

Thickness sensing of nerve cells on double-layered hydrophobic polymer networks with distinct mechanical properties

Event Abstract Back to Event Thickness sensing of nerve cells on double-layered hydrophobic polymer networks with distinct mechanical properties Lei Cai1 and Shanfeng Wang1, 2 1 The University of Tennessee, Knoxville, Department of Materials Science and Engineering, United States 2 The University of Tennessee, Knoxville, Institute of Biomedical Engineering, United States Rat Schwann cell precursor line (SpL201) cells with the glial nature were used to demonstrate the dependence of cell spreading and proliferation on the coating thickness of two-layer substrates. Besides the better support of SpL201 cells on stiffer substrate, the effective stiffness cells can respond depended on the coating thickness. A critical coating thickness was required to completely screen the influence from the base layer and this value was higher for the softer top layer. Two poly(ε-caprolactone) triacrylates (PCLTAs), PCLTA2k and PCLTA20k, were named after their number-average molecular weight of 2030 and 20020 g mol-1, respectively. Each substrate consisted of a top thin film layer and a base layer using either of these two PCLTAs[1]. Different thicknesses for the top thin film layer have been achieved on the base layer. PCLTA2k and 20k were used in this study because of their distinct mechanical properties at 37°C after crosslinking. Crosslinked PCLTA2k was amorphous and soft with a tensile modulus of 4.8 ± 0.5 MPa, while crosslinked PCLTA20k was semi-crystalline and stiff with a much higher tensile modulus of 193 ± 16 MPa[2]. SpL201 cell images on these two-layer polymer substrates at day 7 post-seeding are shown in Figure 1. Distinct cell proliferation was found for the substrates with different mechanical properties and coating thicknesses. Stiff crosslinked PCLTA20k was found to support SpL201 cell proliferation much better than soft crosslinked PCLTA2k. Much more cells were well spread on crosslinked PCLTA20k as the base material. As the thickness of soft PCLTA2k top layer increased, the cell number decreased gradually. When the PCLTA2k film was sufficiently thick, cells showed a similar density to that on pure PCLTA2k network. An opposite trend for SpL201 cell proliferation was demonstrated in the mirror system with soft PCLTA2k network as the base material. Cell spreading was shown in Figure 2. Two trends were clearly demonstrated on the two-layer substrates of distinct crosslinked PCLTAs. SpL201 cells could spread more with larger cell areas on the stiffer substrates of crosslinked PCLTA20k than on crosslinked PCLTA2k. Cell area did not differ significantly from the base material when the coating thickness was 870 nm for crosslinked PCLTA2k and 170 nm for crosslinked PCLTA20k. When the top layer became thicker, cell area gradually increased or decreased asymptotically to the value on the bulk form of the coating material. The critical coating thickness that could block the influence of the base material was ~2 µm for soft crosslinked PCLTA2k and ~5 µm for stiff crosslinked PCLTA20k. It indicated that the mechanical stiffness of the top layer could influence the critical coating thickness for cells to be able to sense. Figure 1. Fluorescence cell images for actin filaments (stained with RP, red) and nuclei (stained with DAPI, blue) at day 7 on the top layer of crosslinked PCLTA2k and 20k with different thicknesses covering the base layer of crosslinked PCLTA20k and 2k, respectively. Scale bar of 200 µm is applicable to all. Figure 2. Cell area of SpL201 cells at day 1 on the thin films of PCLTA2k and 20k with different thickness on a base layer of crosslinked PCLTA20k and 2k, respectively. Conclusions: We have used two PCLTAs with distinct mechanical properties to fabricate a series of substrates consisting of a top thin layer with controlled thickness from one PCLTA and a base layer of bulk networks from the other. The mirror systems demonstrated the roles of both thickness and stiffness of the top layer in mechanosensing of SpL201 cells. The stiffer substrate of crosslinked PCLTA20k could support both cell spreading and proliferation better than crosslinked PCLTA2k. A critical coating thickness for screening the effect of the base layer was higher for the softer network of crosslinked PCLTA2k, compared with crosslinked PCLTA20k.

Eggs with larger accessory structures are more likely to be fertilized in both low and high sperm concentrations in Styela plicata (Ascidiaceae)

The evolution of egg size has been intensively studied due to its influence on both fecundity and offspring performance. In marine broadcast spawners, egg size influences the probability of sperm–egg collision, and therefore, egg size can also influence fertilization success, depending on the local concentration of sperm. Many broadcast-spawning species have egg accessory structures that are thought to be a cheap means of altering egg size, but their influence on fertilization remains controversial. To determine the relative influences of ovicell size and follicle cell size on fertilization success in the ascidian Styela plicata, the size distribution of eggs that were not successfully fertilized in both high and low sperm concentrations was compared to that of unfertilized controls. At high sperm concentrations, a greater proportion of eggs with smaller ovicells were fertilized, resulting in smaller larvae hatching from this treatment. Eggs with a large follicle cell area relative to ovicell area were preferentially fertilized in both high and low sperm concentration treatments. Hence, follicle cells do not eliminate selection on ovicell size at fertilization in S. plicata. Furthermore, follicle cells appear to increase fertilization success across a range of sperm concentrations by performing different functions in each environment—increasing the target size of eggs in low-sperm concentrations and presumably reducing polyspermy in high sperm concentrations.

Atmospheric Plasma-Sprayed Metal-Supported Solid Oxide Fuel Cells with Varying Cathode Microstructures

Metal-supported solid oxide fuel cells (SOFCs) use less expensive materials than traditional anode-supported or electrolyte-supported SOFCs. The active layers of a metal-supported SOFC can be manufactured by plasma spraying without the need for high-temperature sintering. Plasma spraying is a rapid-fabrication process that is scalable for large cell areas and for mass production. Porous ferritic stainless steel (Sanergy HT, Sandvik, Sweden) supports were manufactured from powders by pressing and sintering pellets. The active cell layers consisted of a composite nickel - yttria-stabilized zirconia (YSZ) anode, a YSZ electrolyte, and a La0.6­Sr0.4Co0.2Fe0.8O3-δ (LSCF) – Ce0.8Sm0.2O1.9 (SDC) cathode. Plasma spraying produces unique microstructures, as the cell layers are built up by the rapid solidification of molten (or semi-molten) splats. These microstructures were tailored by adjusting the plasma spray process parameters and the ingredients in the feedstock. Dense electrolytes were made using a high-power plasma, a very high torch pass speed (to minimize the plasma heat impulse to the substrate), and a feedstock consisting of YSZ suspended in a mixture of water, ethanol, and ethylene glycol. Cathodes with four different microstructures were produced by varying the plasma spray parameters and mixing carbon or starch-based pore forming agents into the ceramic feedstock powders. Resultant microstructures are shown in Figure 1. Electrochemical performances of metal-supported button cells with varying cathode microstructures were measured. At 750°C, the cells had open circuit potentials of up to 1.057 V and peak power densities as high as 562 mW/cm². Electrochemical impedance spectra were measured at an operating point of 0.7 V, varying the cathode gas with different air-nitrogen mixtures. With 100% air as the cathode gas, the lowest cell polarization resistance was 0.29 Ωcm² at 750°C. Equivalent circuit modeling was performed to analyse how the cathode microstructure affected the cell performance. Figure 1

In-Operando Neutron Radiography Studies of Polymer Electrolyte Membrane Water Electrolyzers

Polymer Electrolyte Membrane Water Electrolysis (PEMWE) is increasingly attracting interest from academia and industry as it offers an option for storing renewable energy from sources such as wind or solar [1]. Further, electrolysis is considered one of the few available pathways to achieve a 100% renewable electricity supply [2]. In PEMWE, water is typically supplied via flow channels and distributed across the catalyst layer through a porous transport layer (PTL). Gas evolution occurs at the catalyst layer, and the gas is transported back through the PTL and discharged into the flow channels where it is then transported out of the cell as a two-phase mixture with the feed water. This evolution of oxygen and hydrogen in the surrounding water leads to distinct two-phase flow phenomena, which are investigated in this study in-operando inside operating PEMWE cells using synchrotron X-ray radiography as well as neutron radiography. In the past, both methods have allowed to visualize processes inside operating fuel cells, elucidating water management issues [3], the formation of liquid water, its accumulation rate and transport in polymer electrolyte membrane fuel cells (PEFC) [4], as well as the carbon dioxide evolution in liquid fed direct methanol fuel cells (DMFC) [5]. PEM water electrolysis systems are currently scaled to the megawatt range, necessitating an increase of the active area of an individual cell. This scale-up goes along with challenges concerning media distribution on large cell areas. Information about the oxygen saturation and distribution inside the PTL at different points of operation but also at different locations a large area PTL is therefore of special interest. In this work, operating PEMWE cells are examined using synchrotron X-ray radiography at BESSY II and using neutron radiography at BER II (both Helmholtz-Zentrum Berlin). In both setups, a synchrotron X-ray beam or a neutron beam is directed at the running cell, and the attenuation dependence of the beam on the elements inside the cell allows visualizing the processes occurring inside the cells. Both methods are to a certain degree complimentary – the synchrotron radiography setup allows inspecting small areas of some mm² with a spatial resolution of a few µm, while the neutron radiography allows inspecting areas of several cm² with a spatial resolution of lower than 100µm. The especially strong neutron attenuation in hydrogen offers the possibility to visualize the gas/water distribution on large areas, while the comparably low neutron attenuation in metals allows using a typical cell setup with only minor adjustments. The PEMWE cells examined using neutron radiography contained different PTLs, which were compared in terms of the gas/water distribution under different operating conditions. On the anode side, an additional injection of oxygen from the bottom of the cell was used to simulate the effects occurring in a scaled cell exhibiting a larger area. This setup allowed examining the dynamics in the transport and quantifying the distribution along the cell area. In the PEMWE cells examined using synchrotron radiography, oscillations in the gas bubble discharge from the PTL into the flow channel were investigated in terms of their frequency and the gas discharge volumes. Furthermore, the implications of this on the gas transport within the PTL are discussed, and the number of gas bubble discharge sites is correlated with the current density. Thereby it is demonstrated that both synchrotron X-ray and neutron radiography represent valuable tools to study transport processes and to gain insights into the gas-water distribution inside running PEMWE cells. These results pose important implications for the design of cell components with facilitated gas removal, for the modeling of two-phase flow in PEMWE cells and for the modeling of mass transport losses in PEMWE.

The Histone Methyltransferase Setd8 Represses Gata2 Expression and Regulates Erythroid Maturation

The maturation of a committed erythroid progenitor to a functional red blood cell is a complex process that involves significant changes in gene expression during a time of rapid cell division and nuclear condensation. Posttranslational modifications of histone proteins are critical determinates of erythroid gene expression, however the histone modifications required to execute the erythroid-specific transcriptional program during maturation are incompletely understood. Setd8 is the sole histone methyltransferase in mammals capable of generating mono-methylated histone H4 lysine 20 (H4K20me1). Setd8 and H4K20me1 are transcriptional regulators that also play an important role in mediating nuclear condensation, cell cycle progression and response to DNA damage (Beck, Genes Dev 2012). Setd8 is expressed throughout the maturation of murine and human erythroid cells (Kingsley et al, Blood 2012; An et al, Blood 2014), and erythroid precursors have significantly higher levels of Setd8 expression than any other cell- or tissue- type (biogps.org), suggesting that Setd8 may have an erythroid-specific function. Data regarding the function of Setd8 in erythroid cells is limited; with the only published study to date linking Setd8 to Gata1-mediated repression (DeVilbiss, PNAS 2013). We hypothesize that mono-methylation of H4K20 by Setd8 is a critical mediator of transcriptional repression during erythroid maturation.To test this hypothesis, lentiviral mediated shRNA was utilized to generate stable knockdown of Setd8 in extensively self-renewing erythroblasts (ESREs). ESREs are a well-characterized, non-transformed model of erythroid maturation (Getman et al, Exp Hematol 2014), which are cultured from yolk sac or fetal liver. Once the culture is established, ESREs self-renew extensively at the proerythroblast stage, without losing the ability to mature and enucleate in approximately three days (England et al, Blood 2012). Knockdown of Setd8 was confirmed at the mRNA (~70% knockdown) and protein level (~50% knockdown), and persisted throughout maturation. Setd8 knockdown did not alter ESRE proliferation or viability, or result in accumulation of DNA damage. As expected, Setd8 knockdown was associated with a significant decline in H4K20me1 compared to scramble controls. Setd8 knockdown resulted in a significant delay in hemoglobin accumulation as determined by benzidine staining. Setd8 knockdown also significantly impaired several facets of erythroid maturation, resulting in larger cell area, persistent kit expression, incomplete nuclear condensation, and lower rates of enucleation than control cells.To delineate the molecular mechanisms underlying these abnormalities in erythroid maturation, global gene expression was analyzed by RNA-seq in biological replicates of Setd8 knockdown and scramble samples. CuffDiff was used for differential expression analyses. 1149 genes were differentially expressed (p-value<10-3, False Discovery Rate<0.01). Consistent with the repressor function of Setd8, 780 genes were upregulated (including Gata2) and 369 genes were downregulated (including Setd8, Pklr, Alad, Tfrc, and Hbb-b1.) The top three networks identified by Ingenuity Pathway Analyses of the differentially expressed genes were Hematologic Development and Disease, Hereditary Disorder, and Cell Signaling/DNA Recombination and Repair. The increased Gata2 expression was validated using qPCR in independent Setd8 knockdown cultures.Gata2 is a critical regulator of the balance between maturation and self-renewal in hematopoietic stem and progenitor cells, and Gata2 overexpression is sufficient to impair erythroid maturation (Ikonomi et al, Exp Hematol 2000). The Gata2 gene has both general (1G) and hematopoietic specific (1S) promoters, as well as several well-characterized enhancers that control its spatial and temporal expression (Grass et al, MCB 2006). Chromatin Immunoprecipitation experiments demonstrated Setd8 occupancy at the Gata2 1S promoter and at the critical +9.5 enhancer. Knockdown of Setd8 resulted in loss of Setd8 occupancy in the Gata2 locus and an increase in histone H4 acetylation at the Gata2 1S promoter. Taken together, these results indicate that Setd8 is an important transcriptional regulator of erythroid cells and suggest that Setd8 facilitates erythroid maturation by repressing Gata2 expression. DisclosuresNo relevant conflicts of interest to declare.

A QoS control scheme using dynamic window size control for wide area ubiquitous wireless network

This paper describes a quality‐of‐service (QoS) control scheme for a wide‐area ubiquitous wireless network which is designed to accommodate many wireless terminals (WTs), such as sensors and actuators, in a large cell area. The purpose of this paper is to establish a QoS control scheme in a medium access control (MAC) layer that can hold the transmission delay of high‐priority class traffic within a predefined value regardless of how much low‐priority class traffic there is. Several QoS control schemes for wireless communication use have been proposed. However, in the wide‐area ubiquitous wireless network, an access point (AP) accommodates many WTs and the AP traffic volume often drastically changes. Therefore, conventional schemes sometimes cannot control the QoS of high‐priority traffic. To solve this problem, we propose a QoS control scheme that calculates a suitable initial back‐off window size of random access for each QoS class by using equations derived from a Markov chain behavior model. The proposed scheme adjusts the window size so as to prevent increased transmission delay of high‐priority traffic. The scheme's performance is clarified by computer simulation. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

A Sub-0.3 V Area-Efficient L-Shaped 7T SRAM With Read Bitline Swing Expansion Schemes Based on Boosted Read-Bitline, Asymmetric-V$_{\rm TH}$ Read-Port, and Offset Cell VDD Biasing Techniques

In previous SRAM designs, reducing minimum operating voltage (VDDmin) inevitably resulted in devices with a large cell area (A). This work proposes an L-shaped 7T cell (L7T) and read-bitline (RBL) swing expansion scheme (RBL-EXPD) to minimize A <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">*</sub> VDDmin for low-voltage applications. This L7T features an area-efficient cell layout and a read-disturb free decoupled 1T read port (RP) capable of providing a wide space for write margin improvement. The RBL-EXPD employs (1) boosted RBL (BRBL), (2) 1T-RP with asymmetric-V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</sub> , (AV-1TRP) and (3) offset cell-VDD biasing (OFS-CVDD) to expand RBL swing in both the upward and downward directions securing both `High' and `Low' sensing margins. A 65 nm 256-row 32 Kb L7T SRAM macro-fabricated using BRBL and AVTH-RP achieved a 260 mV VDDmin. The resulting A <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">*</sub> VDDmin is ~50% lower than that of conventional 8T SRAM devices.