bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Analysis of Heat Exchangers Used in a Liquid Piston Compressor Using a One-Dimensional Model With an Embedded Two-Dimensional Submodel
Authors: Zhang Chao , Wieberdink Jacob , Simon Terrence W. , Li Perry Y. , Van de Ven James , Loth Eric
Published: August 2016

The present study presents a one-dimensional liquid-piston compressor model with an embedded two-dimensional submodel. The submodel is for calculating heat conduction across a representative internal plate of a porous heat exchanger matrix within the compression space. The liquid-piston compressor is used for Compressed Air Energy Storage (CAES). Porous-media-type heat exchangers are inserted in the compressor to absorb heat from air as it is compressed. Compression without heat transfer typically results in a temperature rise of a gas and a drop in efficiency, for the elevated temperature leads to wasted thermal energy, due to cooling during subsequent cooling back to ambient temperature. The use of heat exchangers can reduce the air temperature rise during the compression period.

A typical numerical model of a heat exchanger is a one-dimensional simplification of the two-energy-equation porous media model. The present authors proposed a one-dimensional model that incorporates the Volume of Fluid (VOF) method for application to the two-phase flow, liquid piston compressor with exchanger inserts. Important to calculating temperature distributions in both the solid and fluid components of the mixture is heat transfer between the two, which depends on the local temperature values, geometry, and the velocity of fluid through the matrix. In the one-dimensional model, although the axial temperatures vary, the solid is treated as having a uniform temperature distribution across the plate at any axial location. This may be in line with the physics of flow in most heat exchangers, especially when the exchangers are made of metal with high thermal conductivity. However, it must be noted that for application to CAES, the gas temperature in the compression chamber rises rapidly during compression and the core of the solid wall may heat up to a different temperature than that of the surface, depending on the geometry, solid material of the exchanger and fluid flow situation. Therefore, a new, one-dimensional model with embedded two-dimensional submodel is developed to consider two-dimensional heat conduction in a representative solid plate. The VOF concept is used in the model to handle the moving liquid-gas interface (liquid piston).

The model gives accurate solutions of temperature distributions in the liquid piston compression chamber. Six different heat exchangers with different length scales and different materials are simulated and compared.
Parametric Study of Showerhead Film Cooling Performance on a Gas Turbine Blade
Authors: Urquiza G. , Davalos J. O. , Garcia J. C. , Castro L. , Rodríguez J. A. , Basurto-Pensado M. A. , De Santiago O. C.
Published: August 2016

Gas turbine power and efficiency have direct relation with inlet gas temperature. However, high gas temperature could cause thermal damage to gas turbine blade material. Gas turbine blade could be cooled using the so-called film cooling technique which is necessary to ensure blade material integrity. In film cooling, air from compressor is injected through internal blade ducts. The air leaves the internal ducts through holes placed on blade surface, creating a cooling film on the blade surface. Operating conditions and hole geometrical factors can influence the cooling effectiveness. Several investigations have been conducted related to film cooling in order to study its behavior under different conditions. Due to its complexity, many studies replace blade geometry for flat plates. A better approximation to realistic results could be obtained by modeling the blade geometry with cooling holes. In this work, influence of geometrical parameters on cooling effectiveness under different operating conditions, like blowing ratio and angular velocity, is studied by means of numerical analysis using a commercial CFD code. The object of study is a typical showerhead configuration at mid-span of the tested blade, with three rows of cooling holes. In order to reduce computational cost, an algorithm was implemented to generate blade geometries and grids, performing numerical analyses and computing results in an automatic way, based on selected parameters. The algorithm could be used in optimization process to reduce the effort used in the construction geometries. The results show the effects of change geometrical parameters on cooling effectiveness. Additionally, changes on cooling flow direction are observed at high angular velocities.
Computational Assessment of Inlet Turbulence on Boundary Layer Development and Momentum/Thermal Wakes for High Pressure Turbine Nozzle and Blade
Authors: Kopriva James E. , Laskowski Gregory M. , Sheikhi M. Reza H.
Published: August 2016

A series of systematic computational studies have been conducted for transonic HPT nozzles and blades to evaluate the impact of free stream turbulence on boundary layer growth and downstream wake mixing. Transition modeling is first compared to measurements for an uncooled nozzle. The computational results are compared against measurements of loading, HTC, and wake predictions. The approach is then applied to a cooled trail-edge nozzle. The added complexity of cooling flow injection at the trail-edge showed an increase in deviation between the SST Transition model predictions and wake measurement. By applying a scale resolve model (WALE LES), wake mixing predictions are found within 1% of measurement. Finally, the computational approach is extended to a coupled uncooled nozzle/blade stage analysis. Given the favorable results for an uncooled nozzle using the SST transition model, preliminary assessment of boundary layer impact on HTC and the overall stage loss was made for the nozzle/blade stage design.
Numerical Investigation of the Onset of Steady Natural Convection in a Square Cavity Partially Filled With a Single Porous Block
Authors: Daroz Vinicius , Junqueira Silvio L. M. , Franco Admilson T. , Lage José L.
Published: August 2016

The critical Rayleigh number at the onset of natural convection within a square cavity filled with a centralized porous block was investigated. The porous medium is modeled by using the heterogeneous model and the governing equations are solved for each phase separately. The thermal gradient is applied from the bottom to the top horizontal walls while the vertical walls are kept adiabatic. The amount of solid within the cavity was kept constant by fixing both external and internal porosity in 36% and 40%, respectively. The equations are solved using the Finite Volume Method and the interpolation scheme for the convective terms is the Hybrid Scheme. For the pressure-velocity coupling, the SIMPLEC method is used. The effects on the conductive-convective regime transition, reads critical Rayleigh Number, characterized by the average Nusselt number and the heatlines contour plot, was investigated by varying the Rayleigh number and the porous block permeability. The results show that the so called critical Rayleigh number is affected by the block permeability. As the permeability decreases, the flow tends to recirculate around the block being squeezed against the cavity walls and therefore, more susceptible to viscous effects. A correlation to the critical Rayleigh number is presented as a function of the agglomerate permeability showing that the higher the permeability the lower the amount of energy required to trigger the convection.
Enhanced Passive Thermal Management of Grid-Scale Power Routers Utilizing Ionic Wind
Authors: Gallandat Noris , Mayor J. Rhett
Published: August 2016

This paper presents a numerical model assessing the potential of ionic wind as a heat transfer enhancement method for the cooling of grid distribution assets. Distribution scale power routers (13–37 kV, 1–10 MW) have stringent requirements regarding lifetime and reliability, so that any cooling technique involving moving parts such as fans or pumps are not viable. Increasing the air flow — and thereby enhancing heat transfer — through Corona discharge could be an attractive solution to the thermal design of such devices. In this work, the geometry of a rectangular, vertical channel with a corona electrode at the entrance is considered. The multiphysics problem is characterized by a set of four differential equations: the Poisson equation for the electric field and conservation equations for electric charges, momentum and energy. The electrodynamics part of the problem is solved using a finite difference approximation (FDA). Solutions for the potential, electric field and free charge density are presented for a rectangular control volume with mixed boundary conditions.
Analytical Modeling of Dual-Loop Single Phase Thermosiphons for Power Electronics Cooling
Authors: Hesse Danielle L. , Mayor J. Rhett , Semidey S. Andrew
Published: August 2016

This paper presents a dual-loop single-phase thermosiphon for power electronics cooling. This design will be incorporated into a compact dynamic phase angle regulator that will facilitate power routing and reduce line losses on the power grid. The power router utilizes power electronics that reject heat to a planar area, or cold plate, which must be cooled by an entirely passive system to comply with the minimum 30 year mean time between failures consistent with grid reliability requirements. This design will include a secondary-loop cooling path that utilizes the cooling oil already present in the transformer to also cool the power router. An analytical multi-physics thermosiphon model is developed that couples existing fluid dynamic and heat transfer correlations to create a description of the steady state operation of a specific dual-loop thermosiphon design. The ultimate goal of this model will be to optimize critical geometries in the thermosiphon design.
Convective Cooling in the Transitional Rarefied Flow Regime
Authors: Strongrich Andrew D. , Alexeenko Alina A.
Published: August 2016

Convective heat transfer in the transitional rarefied flow regime is evaluated both numerically using the ES-BGK collision model and experimentally for freely suspended silicon beams. Results are compared to both empirically derived continuum correlations as well as analytical free-molecule solutions, demonstrating a monotonic nonlinear transition between the two regimes. Both horizontal and vertical orientations were explored in an effort to evaluate the potential influence of buoyancy on heat transfer performance. Results demonstrate that such effects are largely insignificant for transitional rarefied flows and convective thermal dissipation is instead driven by thermal creep phenomena.
Development of a Multi-Loop Flow and Heat Transfer Facility for Advanced Nuclear Reactor Thermal Hydraulic and Hybrid Energy System Studies
Authors: O’Brien James E. , Sabharwall Piyush , Yoon SuJong
Published: August 2016

A new high-temperature multi-fluid, multi-loop test facility for advanced nuclear applications is under development at the Idaho National Laboratory. The facility will include three flow loops: high-temperature helium, molten salt, and steam/water. Molten salts have been identified as excellent candidate heat transport fluids for primary or secondary coolant loops, supporting advanced high temperature and small modular reactors (SMRs). Details of some of the design aspects and challenges of this facility, which is currently in the conceptual design phase, are discussed. A preliminary design configuration will be presented, with the required characteristics of the various components. The loop will utilize advanced high-temperature compact printed-circuit heat exchangers (PCHEs) operating at prototypic intermediate heat exchanger (IHX) conditions. The initial configuration will include a high-temperature (750°C), high-pressure (7 MPa) helium loop thermally integrated with a molten fluoride salt (KF-ZrF4) flow loop operating at low pressure (0.2 MPa) at a temperature of ∼450°C. Experiment design challenges include identification of suitable materials and components that will withstand the required loop operating conditions. Corrosion and high temperature creep behavior are major considerations. The facility will include a thermal energy storage capability designed to support scaled process heat delivery for a variety of hybrid energy systems and grid stabilization strategies. Experimental results obtained from this research will also provide important data for code verification and validation (V&V) related to these systems.
Study of Convective Heat Transfer for Turbulent Flow of Nanofluids Through Corrugated Channels
Authors: Noor Shafi , Ehsan M. Monjurul , Mayeed Mohammed S. , Islam A. K. M. Sadrul
Published: August 2016

Numerical study of turbulent heat transfer of nanofluid through a corrugated channel is presented. The finite volume method is used to solve the transport equation for the momentum, energy and turbulence quantities adopting a single phase approach. The corrugated channels are sine-shaped, V-shaped and rectangular shaped with amplitude (a/H) and wave length (λ/H) of 0.15 and 1 respectively. Three different nano-particles such as aluminum oxide (Al2O3), Copper (Cu) and titanium dioxide (TiO2) with different volume fraction (1%, 3% and 5%) using water as the base fluid are analyzed for a range of Reynolds number from 2000 to 14,000 with constant heat flux at the corrugated walls. Realizable k-ε turbulence model with enhanced wall treatment is considered. For all three geometries, average Nusselt number for the corrugated section is obtained. The result reveals that increasing the Reynolds number and volume fraction of nanoparticle in the base fluid has an effect of increasing the heat transfer rate. The sine shaped channel gives a better heat transfer enhancement compared to other two geometries up to Re = 8200 for 3% volume fraction of Al2O3-water nanofluid. At Reynolds number higher than this, rectangular shaped corrugated channel gives better heat transfer rate. Among the nano-particles, Al2O3 gives a higher heat transfer rate in all three corrugated channels. The enhancement of heat transfer is about 10.5% to 50.15% compared to water for the flow of Al2O3-water nanofluid through sine wave channel depending on the Reynolds number and volume fraction.
Experimental Investigation of a Flat-Plate Oscillating Heat Pipe With Modified Evaporator and Condenser
Authors: Rhodes M. J. , Taylor M. R. , Monroe J. G. , Thompson S. M.
Published: August 2016

The thermal performance of a flat-plate oscillating heat pipe (FP-OHP) - with modified evaporator and condenser was experimentally investigated during high heat flux conditions. The copper FP-OHP (101.6 × 101.6 × 3.18 mm3) possessed two inter-connected layers of 1.02 mm2 square channels with the evaporator and condenser possessing two parallel, 0.25 × 0.51 mm2 square microchannels. The microchannels were integrated to enhance evaporation and condensation heat transfer to improve the FP-OHP’s ability to transport high heat flux. The FP-OHP was oriented vertically and locally heated with a 14.52 cm2 heating block at its base and cooled with a water block that provided either: 20 °C, 40 °C, or 60 °C operating temperatures. A FP-OHP without embedded microchannels was also investigated for baseline performance comparison. Both FP-OHPs were filled with Novec HFE-7200 (3M) working fluid at a filling ratio of approximately 80% by volume. The maximum temperature of each FP-OHP was recorded versus time for various heat inputs for the investigated operating temperatures. The results indicate that the integrated microchannels enhance the FP-OHP’s thermal performance for all operating temperatures. At 20 °C, 40 °C, and 60 °C, the microchannel-embedded evaporator and condenser dissipated 80 W, 65 W, and 55 W more than the baseline control with a minimum thermal resistance of 0.219 °C/W, 0.205 °C/W, and 0.170 °C/W, respectively — corresponding to a percent enhancement on-the-order of 25%. This percent enhancement increased with operating temperature. It has also been shown that Novec HFE-7200 allows the FP-OHP to start at relatively lower heat inputs — as low as 35 W, demonstrating that this working fluid can enhance heat transfer even at lower heat flux applications.
Forced and Mixing Convection Analysis of Discrete Heated Porous Convergent Channel
Authors: Ghorab Mohamed G.
Published: August 2016

The paper presents a numerical investigation of forced and mixing convection heat transfer and flow analysis of a passive heat exchanger inside clear (non-porous) and partially porous channels at different outlet area. Four discrete heat sources with uniform heat flux are simulated on the bottom wall of the channel. FORTRAN CFD code was developed and used to solve non-dimensional the governing equations for the fluid and porous media using finite volume method. The flow field and thermal analysis inside the channel are investigated across a wide range of Reynolds number (50 ≤ Re ≤ 300), Darcy number (10−2 ≤ Da ≤ 10−6), Richardson number (0 ≤ Ri ≤ 100) for 0.71 Prandtl number. The results show that the heat exchanger with partially porous convergent channel provides superior heat source cooling which leads to develop the macro and microelectronic devices.
Dynamic Control of Radiative Surface Properties With Origami-Inspired Design
Authors: Mulford Rydge B. , Christensen Luke M. , Jones Matthew R. , Iverson Brian D.
Published: August 2016

Thermal management systems for space equipment commonly utilize static solutions such as insulation, optical coatings or reflective mirrors. The simplicity of static systems is advantageous, but the inability to adapt to environmental changes leads to systems designed for extreme conditions. Active control of radiative surface properties would increase the operational capabilities of spacecraft thermal management systems. This study investigates a dynamic solution that allows for real-time control of radiative surface properties based on origami-inspired designs. The extent to which the absorptivity and emissivity of a surface may be varied is demonstrated experimentally. Linear actuation of origami-based structures provides the avenue to alternating between flat and cavity-like surface geometries where the number of reflections, and hence the radiative surface properties are controlled. Flat and folded aluminum foil samples were alternately irradiated with a blackbody emitter at 1000 °C then shielded from the radiation source while the transient temperature was recorded using thermocouples and an IR camera. Thermal models relating the apparent absorptivity of the radiation shield to the time-dependent surface temperature are presented, and methods to invert these models are described. Preliminary results show a significant increase in irradiated steady state temperature for a high fold density as compared to unfolded configurations of the same thickness and material. These results indicate that origami-inspired designs have the potential to provide dynamic control of the apparent absorptivity of radiation shields and surfaces.
Total Temperature Measurement of Gas Flow in Micro-Tube With Constant Wall Temperature
Authors: Matsushita Seiryu , Nakamura Taiki , Hong Chungpyo , Asako Yutaka
Published: August 2016

This paper describes experimental results on total temperature measurement of nitrogen micro-jet from micro-tubes outlet measured for the wide range from unchoked to choked flow. The experiments were preformed for a stainless micro-tube of 523.2 μm in diameter whose temperature difference between the wall and inlet was maintained at 2, 5 and 10 K by circulating water around the micro-tube, respectively. The gas flows out to the atmospheric condition. A thermally insulated tube of foamed polystyrene with six baffles fabricated by the companion paper (IMECE-36965) where the gas velocity reduces and the kinetic energy is converted into the thermal energy, was attached to the outlet of the micro-tube. The inner diameter of the polystyrene tube is 22 mm. The baffles are equally spaced and the intervals of the baffles tested are 5 and 10 mm to investigate the effect of the interval of the baffle on the reduction of the gas velocity. The gas temperature measured by thermocouples at locations of baffles is considered as total temperature. The measured total temperature is higher than the wall temperature and increases with increasing the stagnation pressure (Reynolds number) for unchoked flow since the additional heat transfer from the wall to the gas near the micro-tube outlet caused by the temperature fall due to the energy conversion into the kinetic energy. It decreases in the insulated tube for chocked flow since Joule-Thomson effect is dominant in the insulated tube. The measured total temperatures are compared with results obtained by numerical computations.
Modeling of the Thermal Characteristics of an Eccentric Multi-Stage Inverse Jet Diffusion Flame Burner
Authors: Amin Sherif , Emara Ahmed , Hussien Adel , Shabaka Ibrahim
Published: August 2016

The objective of this paper is to study the effect of eccentricity on the thermal characteristics and flow field of a triple-concentric free jet burner. The investigation concerns three values of eccentricity (1.25, 1.88, and 2.5 times the inner-jet diameter); and in addition to the normal centric jet (no eccentricity). Prediction of the reacting flow characteristics and the planar flow visualization for all burners’ configurations is simulated with the CFD k-ε turbulence of “ANSYS-CFX”. In addition, the finite rate and eddy dissipation model is utilized to simulate the interaction between the chemical reaction and turbulence. The temperature, velocity and turbulence intensity are investigated to simulate the thermal-structure interaction. The results are obtained at a constant momentum rate. It showed significant changes in the coherent structures shed from the annular jets. By increasing the eccentricity, the maximum temperature will be attained more rapidly than centric case. In addition, the mixing point become nearer the burner rim, which increased the flame size and shifted the flame structure.
Effect of Uncertainties in Physical Properties on Mixed Convection Along a Rotating Vertical Slender Cylinder With Nanofluids
Authors: Rana Puneet , Kumar Lokendra
Published: August 2016

The present investigation is aimed to study the effects of uncertainties in physical properties on predicting mixed convection alumina-water nanofluid flow and heat transfer characteristics along a rotating vertical slender cylinder. For this purpose, the different models for thermal conductivity and dynamic viscosity which takes into account the effects of particle size, particle volume fraction, nanolayer conductivity and temperature on the steady boundary layer are applied. The transformed set of coupled non-linear partial differential equations for the single phase nanofluid model is solved by robust Finite Element Method. The influence of various pertinent parameters on velocity profile, temperature profile and on Nusselt number are shown graphically. Excellent validation of the present numerical results has been achieved with earlier published results. It is also found that the Nusselt number increases nonlinearly with the increase of nanoparticle loading for the KKL model which correlates strongly with experimental findings.
An Investigation of Methane Combustion in a Rectangular Shaped Meso Chamber
Authors: Ahmed Mahbub , Zhang Cheng , McKay Scott , Shirsat Vivek , Khan Jobaidur
Published: August 2016

Hydrocarbon-based miniature power generators are promising any many application since hydrocarbon based fuels have higher power densities compared to conventional lithium batteries. A 40mm long meso-combustor of two different configurations, two-inlet and three-inlet, were used to investigate the combustion of methane in the meso-chamber. A non-premixed combustion of methane and oxygen was simulated numerically using a steady laminar flamelet model. The mesh generation and the CFD simulation were performed using ANSYS FLUENT software. A a finite volume approach was used for the simulation. The fuel-oxidizer mixing, thermal behavior and fuel burning efficiency were studied. An adequate mixing that supports the combustion was observed in certain locations. The exhaust gas was analyzed experimentally. The temperature distributions were also observed to predict the flame locations. According to the numerical analysis it was apparent that the flame would be anchored in the well mixed regions of the chamber the flames were found to be attached in two distinct locations. One in the upstream zone and the other one in the downstream zone. Another important finding was that the fuel lean condition produced higher efficiency than the fuel rich condition.
Horton-Rogers-Lapwood Convection in a Binary Nanofluid Saturated Rotating Porous Layer
Authors: Agarwal Shilpi , Rana Puneet
Published: August 2016

Double-diffusive convection in a horizontal rotating porous medium layer saturated by a nanofluid, for the case when the base fluid of the nanofluid is itself a binary fluid such as salty water, is studied. The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis, while the Brinkman model is used for the porous medium. The Rayleigh numbers’ for stationary and oscillatory convection have been obtained in terms of various non-dimensional parameters. Several results are obtained as limiting cases of the present study.
Application of the MSMD Framework in the Simulation of Battery Packs
Authors: Li Genong , Li Shaoping , Cao Jing
Published: August 2016

Lithium-ion battery has been widely used in electric vehicles (EVs). Battery’s performance, life and safety are of great engineering importance. Using simulation tools, battery’s electric performance and thermal behavior can be computed to provide useful information in the design of a battery pack and its thermal management system.

The muti-scale muti-dimensional (MSMD) methodology has been proven to be very effective in the simulation of battery at the battery’s geometry dimension scale. The method has been demonstrated in the literature for a single battery cell simulation. However, in the EV applications, battery packs where individual battery is connected in series and/or parallel are often used to provide the required power input during a real driving cycle. In this paper the MSMD methodology is extended to the battery pack simulation.
Water Droplet Vaporization on Superhydrophilic Nanostructured Surfaces at High and Low Superheat
Authors: Padilla Jorge , Carey Van P.
Published: August 2016

This paper summarizes results of an experimental exploration of heat transfer during vaporization of a water droplet deposited on a superhydrophilic nanostructured surface at high and low superheat conditions. The superhydrophilic surface is composed of a vast array of zinc oxide (ZnO) nanostructures grown by hydrothermal synthesis on a smooth copper substrate. The individual nanostructures are randomly-oriented and have a mean diameter of about 400 nm, a mean length of 2 μm and a mean centerline spacing of about 700 nm. The macroscopic wetting characteristics of the surface were measured and scanning electron microscope imaging was used to document the nanoscale features of the surface before and after the experiments. These surfaces typically exhibited water contact angles less than 5 degrees. In single droplet deposition experiments at atmospheric pressure, a high-speed video camera was used to document the droplet-surface interaction, and the heat transfer coefficients were simultaneously determined from thermal measurements in the test apparatus. At low superheat levels (10–20°C), droplets spread rapidly over the heated surface when deposited. For these conditions, no bubble nucleation was observed, and we nevertheless observed extremely high heat transfer coefficients resulting from rapid evaporation of the thin liquid film formed by the spreading droplet. At high wall superheat levels, the vaporization process exhibited Leidenfrost droplet vaporization. The extreme wetting for these surfaces resulted in extremely high Leidenfrost transition temperatures. The results document a trend of increasing Leidenfrost temperature with decreasing contact angle, which is consistent with earlier studies. The results of this study are compared with early work in this area and the implications for applications are discussed.
Heat Transfer Characteristics of Longitudinal Perforated and Unperforated Ribs Under Impingement Jets
Authors: Caliskan Sinan
Published: August 2016

Impingement heat transfer is considered as heat transfer enhancement technique. Impinging jets are used in many applications where high heat transfer rates are required. An experimental study was conducted to investigate heat transfer under impingement of a multiple circular jet array with longitudinal perforated rib surfaces (LPRS) and longitudinal solid rib surfaces (LSRS). Heat transfer results were obtained using an infrared thermal imaging technique. The equipment for the experiments consist of blower, frequency controller, plenum section, impinging jet plate, Dantec 2D LDA system, 3-D traverse system, an infrared thermal imaging system, and LabVIEW software system. In order to generate the impinging jets, circular sharp-edged holes are used. A 3×5 array of jets is issued from the nozzles through the orifice plate. Fifteen in-line jet-nozzles are equally spaced over the orifice plate with the jet diameter (d) of 5mm. The impingement section is open on all four sides providing free outflow of the spent air. The heat transfer results of the rib surfaces are compared with those of a smooth plate. Best heat transfer performance was obtained with the LPRS arrangements.
Intense pulsed light annealing of copper zinc tin sulfide nanocrystal coatings
Authors: Williams Bryce A. , Smeaton Michelle A. , Holgate Collin S. , Trejo Nancy D. , Francis Lorraine F. , Aydil Eray S.
Published: August 2016

A promising method for forming the absorber layer in copper zinc tin sulfide [Cu2ZnSnS4 (CZTS)] thin film solar cells is thermal annealing of coatings cast from dispersions of CZTS nanocrystals. Intense pulsed light (IPL) annealing utilizing xenon flash lamps is a potential high-throughput, low-cost, roll-to-roll manufacturing compatible alternative to thermal annealing in conventional furnaces. The authors studied the effects of flash energy density (3.9–11.6 J/cm2) and number of flashes (1–400) during IPL annealing on the microstructure of CZTS nanocrystal coatings cast on molybdenum-coated soda lime glass substrates (Mo-coated SLG). The annealed coatings exhibited cracks with two distinct linear crack densities, 0.01 and 0.2 μm−1, depending on the flash intensity and total number of flashes. Low density cracking (0.01 μm−1, ∼1 crack per 100 μm) is caused by decomposition of CZTS at the Mo-coating interface. Vapor decomposition products at the interface cause blisters as they escape the coating. Residual decomposition products within the blisters were imaged using confocal Raman spectroscopy. In support of this hypothesis, replacing the Mo-coated SLG substrate with quartz eliminated blistering and low-density cracking. High density cracking is caused by rapid thermal expansion and contraction of the coating constricted on the substrate as it is heated and cooled during IPL annealing. Finite element modeling showed that CZTS coatings on low thermal diffusivity materials (i.e., SLG) underwent significant differential heating with respect to the substrate with rapid rises and falls of the coating temperature as the flash is turned on and off, possibly causing a build-up of tensile stress within the coating prompting cracking. Use of a high thermal diffusivity substrate, such as a molybdenum foil (Mo foil), reduces this differential heating and eliminates the high-density cracking. IPL annealing in presence of sulfur vapor prevented both low- and high-density cracking as well as blistering. However, grain growth was limited even after annealing with 400 flashes. This lack of grain growth is attributed to a difficulty of maintaining high sulfur vapor pressure and absence of alkali metal impurities when Mo foil substrates are used.
Interface state density and dielectric properties of Au/n-GaP Schottky diode
Authors: Shiwakoti Nagendra , Bobby Achamma , Antony Bobby , Asokan Kandasami
Published: August 2016

The temperature and frequency dependent capacitance and conductance measurements of Au/n-GaP Schottky diode were carried out in the 200–400 K and 1 kHz–1 MHz range, under different bias voltages. The obtained interface state density (Nss) and the carrier life time (τ) were evaluated from the measured data. The values of Nss and τ depend strongly on the applied voltage and temperature. The effect of the interface states of the device under different conditions was also analyzed. The series resistance (Rs) of the device was evaluated under different frequencies and temperature conditions using Nicollian and Goetzberger method. The dielectric parameters like dielectric constant (ε′), dielectric loss (ε″), loss tangent (tan δ), and ac electric conductivity (σac) were analyzed under complex permittivity (ε*) formalism. The variations of ε′ and ε″ with frequency and temperature are attributed to the interfacial polarization and the temperature induced restructuring and reordering of interface state density. The activation energy of the interface states shows three different linear regions corresponding to activation energy values of 0.013, 0.034, and 0.061 eV.
Quantitative human cell encyclopedia
Authors: Andrews Brenda J. , Walhout A. J. Marian , Iyengar Ravi ,   The Human Cells Project Working Group
Published: August 2016

Quantitative cataloging of molecular entities in human cells will enable a better understanding of human physiology.
Science Signaling
Podcast for 30 August 2016: Human arginine methylome
Authors: Nielsen Michael L. , VanHook Annalisa M.
Published: August 2016

The human arginine methylome reveals the extent and importance of this posttranslational modification.
Paper of note in
Science
Authors: VanHook Annalisa M.
Published: August 2016

This week’s article shows how hypoxia controls activity of the kinase Akt.
A lock that cuts its own key
Authors: VanHook Annalisa M.
Published: August 2016

DWARF14 is a strigolactone receptor that hydrolyzes its ligand but remains covalently bound to one of the reaction products.
PDAC puts its neighbors to work
Authors: Ferrarelli Leslie K.
Published: August 2016

Mitochondria in pancreatic tumor cells use alanine released by pancreatic stellate cells undergoing autophagy in the nutrient-poor microenvironment.
Plasmid with Colistin Resistance Gene
mcr-1
in Extended-Spectrum-β-Lactamase-Producing Escherichia coli Strains Isolated from Pig Slurry in Estonia
Authors: Brauer Age , Telling Kaidi , Laht Mailis , Kalmus Piret , Lutsar Irja , Remm Maido , Kisand Veljo , Tenson Tanel
Published: August 2016

A plasmid carrying the colistin resistance gene
mcr-1
was isolated from a pig slurry sample in Estonia. The gene was present on a 33,311-bp plasmid of the IncX4 group.
mcr-1
is the only antibiotic resistance gene on the plasmid, with the other genes mainly coding for proteins involved in conjugative DNA transfer (
taxA
,
taxB
,
taxC
,
trbM
, and the
pilX
operon). The plasmid pESTMCR was present in three phylogenetically very different
Escherichia coli
strains, suggesting that it has high potential for horizontal transfer.
Complex Class 1 Integron Carrying
qnrB62
and
bla
VIM-2
in a Citrobacter freundii Clinical Isolate
Authors: Lee Jae Jin , Kim Mi-Na , Park Kwang Seung , Lee Jung Hun , Karim Asad Mustafa , Park Moonhee , Kim Ji Hwan , Lee Sang Hee
Published: August 2016

The coexistence of
qnrB62
and
bla
VIM-2
was detected in a
Citrobacter
clinical isolate. The reduced fluoroquinolone susceptibility is attributable to
qnrB62
, mutations of quinolone-resistance-determining regions, and an efflux pump or pumps. The genetic context surrounding chromosomal
qnrB62
was a novel complex class 1 integron (In1184::IS
CR1
::
qnrB62
) containing a unique gene array (
bla
VIM-2
-
aacA4′-8
-
gucD
). An 18-nucleotide deletion at the 3′ end of the
pspA
gene [
pspA
(Δ
18
)], upstream of
qnrB62
, and an inverted repeat region (IRR2) were detected in In1184::IS
CR1
::
qnrB62
, indicating past transposition events.
Clinical Features and Risk Factors for Development of Breakthrough Gram-Negative Bacteremia during Carbapenem Therapy
Authors: Lee Ji-Yong , Kang Cheol-In , Ko Jae-Hoon , Lee Woo Joo , Seok Hye-Ri , Park Ga Eun , Cho Sun Young , Ha Young Eun , Chung Doo Ryeon , Lee Nam Yong , Peck Kyong Ran , Song Jae-Hoon
Published: August 2016

With the increasing use of carbapenems, carbapenem-resistant Gram-negative bacteria have become a major concern in health care-associated infections. The present study was performed to evaluate the clinical and microbiological features of breakthrough Gram-negative bacteremia (GNB) during carbapenem therapy and to assess risk factors for development of breakthrough GNB. A case-control study was performed at a tertiary hospital from 2005 to 2014. Case patients were defined as individuals whose blood cultures grew Gram-negative bacteria while the patients were receiving carbapenems for at least 48 h before breakthrough GNB. Age-, sex-, and date-matched controls were selected from patients who received carbapenem for at least 48 h and did not develop breakthrough GNB during carbapenem treatment. A total of 101 cases of breakthrough GNB were identified and compared to 100 controls. The causative microorganisms for breakthrough GNB were
Stenotrophomonas maltophilia
(
n
= 33),
Acinetobacter baumannii
(
n
= 32),
Pseudomonas aeruginosa
(
n
= 21), and others (
n
= 15). Approximately 90% of
S. maltophilia
isolates were susceptible to levofloxacin and trimethoprim-sulfamethoxazole. The most common infection types were primary bacteremia (38.6%) and respiratory infections (35.6%). More than half of the patients died within a week after bacteremia, and the 30-day mortality rate was 70.3%. In a multivariate analysis, a longer hospital stay, hematologic malignancy, persistent neutropenia, immunosuppressant use, and previous colonization by causative microorganisms were significantly associated with breakthrough GNB. Our data suggest that
S. maltophilia
,
A. baumannii
, and
P. aeruginosa
are the major pathogens of breakthrough GNB during carbapenem therapy, in association with a longer hospital stay, hematologic malignancy, persistent neutropenia, immunosuppressant use, and previous colonization.
Molecular Characterization of Extended-Spectrum-Cephalosporin-Resistant Enterobacteriaceae from Wild Kelp Gulls in South America
Authors: Liakopoulos Apostolos , Olsen Björn , Geurts Yvon , Artursson Karin , Berg Charlotte , Mevius Dik J. , Bonnedahl Jonas
Published: August 2016

Extended-spectrum-cephalosporin-resistant
Enterobacteriaceae
are a public health concern due to limited treatment options. Here, we report on the occurrence and the molecular characteristics of extended-spectrum-cephalosporin-resistant
Enterobacteriaceae
recovered from wild birds (kelp gulls). Our results revealed kelp gulls as a reservoir of various extended-spectrum cephalosporinase genes associated with different genetic platforms. In addition, we report for the first time the presence of a known epidemic clone of
Salmonella enterica
serotype Heidelberg (JF6X01.0326/XbaI.1966) among wild birds.
Distinct Effects of T-705 (Favipiravir) and Ribavirin on Influenza Virus Replication and Viral RNA Synthesis
Authors: Vanderlinden Evelien , Vrancken Bram , Van Houdt Jeroen , Rajwanshi Vivek K. , Gillemot Sarah , Andrei Graciela , Lemey Philippe , Naesens Lieve
Published: August 2016

T-705 (favipiravir) is a new antiviral agent in advanced clinical development for influenza therapy. It is supposed to act as an alternative substrate for the viral polymerase, causing inhibition of viral RNA synthesis or virus mutagenesis. These mechanisms were also proposed for ribavirin, an established and broad antiviral drug that shares structural similarity with T-705. We here performed a comparative analysis of the effects of T-705 and ribavirin on influenza virus and host cell functions. Influenza virus-infected cell cultures were exposed to T-705 or ribavirin during single or serial virus passaging. The effects on viral RNA synthesis and infectious virus yield were determined and mutations appearing in the viral genome were detected by whole-genome virus sequencing. In addition, the cellular nucleotide pools as well as direct inhibition of the viral polymerase enzyme were quantified. We demonstrate that the anti-influenza virus effect of ribavirin is based on IMP dehydrogenase inhibition, which results in fast and profound GTP depletion and an imbalance in the nucleotide pools. In contrast, T-705 acts as a potent and GTP-competitive inhibitor of the viral polymerase. In infected cells, viral RNA synthesis is completely inhibited by T-705 or ribavirin at ≥50 μM, whereas exposure to lower drug concentrations induces formation of noninfectious particles and accumulation of random point mutations in the viral genome. This mutagenic effect is 2-fold higher for T-705 than for ribavirin. Hence, T-705 and ribavirin both act as purine pseudobases but profoundly differ with regard to the mechanism behind their antiviral and mutagenic effects on influenza virus.
Metabolomic Profiling of the Malaria Box Reveals Antimalarial Target Pathways
Authors: Allman Erik L. , Painter Heather J. , Samra Jasmeet , Carrasquilla Manuela , Llinás Manuel
Published: August 2016

The threat of widespread drug resistance to frontline antimalarials has renewed the urgency for identifying inexpensive chemotherapeutic compounds that are effective against
Plasmodium falciparum
, the parasite species responsible for the greatest number of malaria-related deaths worldwide. To aid in the fight against malaria, a recent extensive screening campaign has generated thousands of lead compounds with low micromolar activity against blood stage parasites. A subset of these leads has been compiled by the Medicines for Malaria Venture (MMV) into a collection of structurally diverse compounds known as the MMV Malaria Box. Currently, little is known regarding the activity of these Malaria Box compounds on parasite metabolism during intraerythrocytic development, and a majority of the targets for these drugs have yet to be defined. Here we interrogated the
in vitro
metabolic effects of 189 drugs (including 169 of the drug-like compounds from the Malaria Box) using ultra-high-performance liquid chromatography–mass spectrometry (UHPLC-MS). The resulting metabolic fingerprints provide information on the parasite biochemical pathways affected by pharmacologic intervention and offer a critical blueprint for selecting and advancing lead compounds as next-generation antimalarial drugs. Our results reveal several major classes of metabolic disruption, which allow us to predict the mode of action (MoA) for many of the Malaria Box compounds. We anticipate that future combination therapies will be greatly informed by these results, allowing for the selection of appropriate drug combinations that simultaneously target multiple metabolic pathways, with the aim of eliminating malaria and forestalling the expansion of drug-resistant parasites in the field.
Metabolomics-Based Screening of the Malaria Box Reveals both Novel and Established Mechanisms of Action
Authors: Creek Darren J. , Chua Hwa H. , Cobbold Simon A. , Nijagal Brunda , MacRae James I. , Dickerman Benjamin K. , Gilson Paul R. , Ralph Stuart A. , McConville Malcolm J.
Published: August 2016

High-throughput phenotypic screening of chemical libraries has resulted in the identification of thousands of compounds with potent antimalarial activity, although in most cases, the mechanism(s) of action of these compounds remains unknown. Here we have investigated the mode of action of 90 antimalarial compounds derived from the Malaria Box collection using high-coverage, untargeted metabolomics analysis. Approximately half of the tested compounds induced significant metabolic perturbations in
in vitro
cultures of
Plasmodium falciparum
. In most cases, the metabolic profiles were highly correlated with known antimalarials, in particular artemisinin, the 4-aminoquinolines, or atovaquone. Select Malaria Box compounds also induced changes in intermediates in essential metabolic pathways, such as isoprenoid biosynthesis (i.e., 2-C-methyl-
d
-erythritol 2,4-cyclodiphosphate) and linolenic acid metabolism (i.e., traumatic acid). This study provides a comprehensive database of the metabolic perturbations induced by chemically diverse inhibitors and highlights the utility of metabolomics for triaging new lead compounds and defining specific modes of action, which will assist with the development and optimization of new antimalarial drugs.
Prevalence of Quinolone Resistance in Enterobacteriaceae from Sierra Leone and the Detection of
qnrB
Pseudogenes and Modified LexA Binding Sites
Authors: Leski Tomasz A. , Stockelman Michael G. , Bangura Umaru , Chae Daniel , Ansumana Rashid , Stenger David A. , Vora Gary J. , Taitt Chris R.
Published: August 2016

A collection of 74
Enterobacteriaceae
isolates found in Bo, Sierra Leone, were tested for quinolone antibiotic susceptibility and resistance mechanisms. The majority of isolates (62%) were resistant to quinolones, and 61% harbored chromosomal
gyrA
and/or
parC
mutations. Plasmid-mediated quinolone resistance genes were ubiquitous, with
qnrB
and
aac(6′)-Ib-cr
being the most prevalent. Mutated LexA binding sites were found in all
qnrB1
genes, and truncated
qnrB
pseudogenes were found in the majority of
Citrobacter
isolates.
CovR Regulates Streptococcus mutans Susceptibility To Complement Immunity and Survival in Blood
Authors: Alves Lívia A. , Nomura Ryota , Mariano Flávia S. , Harth-Chu Erika N. , Stipp Rafael N. , Nakano Kazuhiko , Mattos-Graner Renata O.
Published: August 2016

Streptococcus mutans
, a major pathogen of dental caries, may promote systemic infections after accessing the bloodstream from oral niches. In this study, we investigate pathways of complement immunity against
S. mutans
and show that the orphan regulator CovR (CovR

Sm

) modulates susceptibility to complement opsonization and survival in blood.
S. mutans
blood isolates showed reduced susceptibility to C3b deposition compared to oral isolates. Reduced expression of

covR
Sm

in blood strains was associated with increased transcription of CovR

Sm

-repressed genes required for
S. mutans
interactions with glucans (
gbpC
,
gbpB
, and
epsC
), sucrose-derived exopolysaccharides (EPS). Consistently, blood strains showed an increased capacity to bind glucan
in vitro
. Deletion of

covR
Sm

in strain UA159 (UAcov) impaired C3b deposition and binding to serum IgG and C-reactive protein (CRP) as well as phagocytosis through C3b/iC3b receptors and killing by neutrophils. Opposite effects were observed in mutants of
gbpC
,
epsC
, or
gtfBCD
(required for glucan synthesis). C3b deposition on UA159 was abolished in C1q-depleted serum, implying that the classical pathway is essential for complement activation on
S. mutans
. Growth in sucrose-containing medium impaired the binding of C3b and IgG to UA159, UAcov, and blood isolates but had absent or reduced effects on C3b deposition in
gtfBCD
,
gbpC
, and
epsC
mutants. UAcov further showed increased
ex vivo
survival in human blood in an EPS-dependent way. Consistently, reduced survival was observed for the
gbpC
and
epsC
mutants. Finally, UAcov showed an increased ability to cause bacteremia in a rat model. These results reveal that CovR

Sm

modulates systemic virulence by regulating functions affecting
S. mutans
susceptibility to complement opsonization.