bluuebunny/crossref_metadata_2025 huggingface dataset:
Temporal partitioning of cardiac metabolism by the cardiomyocyte circadian clock
Authors: Young Martin E.
Published: October 2016

New Findings

What is the topic of this review?

This review highlights temporal partitioning of cardiac metabolism by the cardiomyocyte circadian clock.

What advances does it highlight?

Advances include: 1) cardiac glucose utilization peaks during the active period to meet increased energetic demands at this time; 2) synthesis of glycogen and triglyceride peak in the heart during the latter half of the active period, likely in anticipation of the upcoming sleep/fasting period; and 3) protein turnover increases in the heart at the beginning of the sleep phase, probably to promote growth and repair at this time.

Cell‐autonomous circadian clocks have emerged as crucial mediators of 24 h rhythms in cellular processes. In doing so, these molecular timekeepers confer the selective advantage of anticipation, allowing cells and organs to prepare for stimuli and stresses before their onset. The heart is subjected to dramatic fluctuations in energetic demand and nutrient supply in association with sleep–wake and fasting–feeding cycles. Recent studies suggest that the cardiomyocyte circadian clock orchestrates daily rhythms in both oxidative and non‐oxidative glucose and fatty acid metabolism, as well as protein turnover. Here, I review this evidence and discuss whether disruption of these rhythms can contribute to cardiovascular disease.
Analysis of the Staggered and Fixed Cavitation Phenomenon Observed in Centrifugal Pumps Employing a Gap Drainage Impeller
Authors: Zhu Bing , Chen Hongxun
Published: October 2016

Previous work has shown that the employment of a gap drainage impeller in a centrifugal pump can improve the pump's hydraulic performance and cavitation resistance. However, during experiments, an unconventional cavitation phenomenon has been observed in the form of a staggered pair of fixed impeller flow tunnels. For the purpose of understanding the factors involved with this unconventional phenomenon, the present study analyzes the cavitation formation and evolution processes using numerical and experimental methods. A scalable detached eddy simulation (SDES) method was employed to address unsteady turbulent flow. First, the method was validated by comparing the performance data and liquid water velocity distributions obtained by calculation and experiment in the absence of cavitation. Then, numerical simulations of the cavitation flow field were conducted under a flow discharge condition one-half that of the optimum value. Within a particular range of cavitation numbers, the calculated results are found to reproduce the unconventional cavitation phenomenon observed in the experiments. The formation mechanism involves a combination of many factors such as impeller geometry, inflow discharge condition, and cavitation number. As for a certain geometry, the formation and evolution processes can generally be analyzed and explained according to the influence of the attack angle, which is affected by variations in the allocated flow discharge and cavitation volume in each impeller tunnel. The jet flow through the gap between the main and vice blades also contributes to the formation of this phenomenon.
Effect of the Matrix and Reinforcement Sizes on the Microstructure, the Physical and Mechanical Properties of Al-SiC Composites
Authors: Salem M. A. , El-Batanony I. G. , Ghanem M. , Abd ElAal Mohamed Ibrahim
Published: October 2016

Different Al-SiC metal matrix composites (MMCs) with a different matrix, reinforcement sizes, and volume fractions were fabricated using ball milling (BM) and powder metallurgy (PM) techniques. Al and Al-SiC composites with different volume fractions were milled for 120 h. Then, the Al and Al-SiC composites were pressed under 125 MPa and finally sintered at 450 °C. Moreover, microsize and combination between micro and nano sizes Al-SiC samples were prepared by the same way. The effect of the Al matrix, SiC reinforcement sizes and the SiC volume fraction on the microstructure evolution, physical and mechanical properties of the produced composites was investigated. The BM and powder metallurgy techniques followed by sintering produce fully dense Al-SiC composite samples with different matrix and reinforcement sizes. The SiC particle size was observed to have a higher effect on the thermal conductivity, electrical resistivity, and microhardness of the produced composites than that of the SiC volume fraction. The decreasing of the Al and SiC particle sizes and increasing of the SiC volume fraction deteriorate the physical properties. On the other hand, the microhardness was enhanced with the decreasing of the Al, SiC particle sizes and the increasing of the SiC volume fraction.
Uniform scattering and attenuation of acoustically sorted ultrasound contrast agents: Modeling and experiments
Authors: Segers Tim , de Jong Nico , Versluis Michel
Published: October 2016

The sensitivity and efficiency in contrast-enhanced ultrasound imaging and therapy can potentially be increased by the use of resonant monodisperse bubbles. However, bubbles of the same size may respond differently to ultrasound due to differences in their phospholipid shell. In an acoustic bubble sorting chip, resonant bubbles can be separated from the polydisperse agent. Here, a sample of acoustically sorted bubbles is characterized by measuring scattering and attenuation simultaneously using narrowband acoustic pulses at peak negative pressures of 10, 25, and 50 kPa over a 0.7–5.5 MHz frequency range. A second sample is characterized by attenuation measurements at acoustic pressures ranging from 5 to 75 kPa in steps of 2.5 kPa. Scattering and attenuation coefficients were modeled by integration over the pressure and frequency dependent response of all bubbles located within the non-uniform acoustic characterization beam. For all driving pressures and frequencies employed here, the coefficients could be modeled using a single and unique set of shell parameters confirming that acoustically sorted bubbles provide a uniform acoustic response. Moreover, it is shown that it is crucial to include the pressure distribution of the acoustic characterization beam in the modeling to accurately determine shell parameters of non-linearly oscillating bubbles.
Life without Division: Physiology of Escherichia coli FtsZ-Deprived Filaments
Authors: Sánchez-Gorostiaga Alicia , Palacios Pilar , Martínez-Arteaga Rocío , Sánchez Manuel , Casanova Mercedes , Vicente Miguel
Published: October 2016

When deprived of FtsZ,
Escherichia coli
cells (VIP205) grown in liquid form long nonseptated filaments due to their inability to assemble an FtsZ ring and their failure to recruit subsequent divisome components. These filaments fail to produce colonies on solid medium, in which synthesis of FtsZ is induced, upon being diluted by a factor greater than 4. However, once the initial FtsZ levels are recovered in liquid culture, they resume division, and their plating efficiency returns to normal. The potential septation sites generated in the FtsZ-deprived filaments are not annihilated, and once sufficient FtsZ is accumulated, they all become active and divide to produce cells of normal length. FtsZ-deprived cells accumulate defects in their physiology, including an abnormally high number of unsegregated nucleoids that may result from the misplacement of FtsK. Their membrane integrity becomes compromised and the amount of membrane proteins, such as FtsK and ZipA, increases. FtsZ-deprived cells also show an altered expression pattern, namely, transcription of several genes responding to DNA damage increases, whereas transcription of some ribosomal or global transcriptional regulators decreases. We propose that the changes caused by the depletion of FtsZ, besides stopping division, weaken the cell, diminishing its resiliency to minor challenges, such as dilution stress.

IMPORTANCE
Our results suggest a role for FtsZ, in addition to its already known effect in the constriction of
E. coli
, in protecting the nondividing cells against minor stress. This protection can even be exerted when an inactive FtsZ is produced, but it is lost when the protein is altogether absent. These results have implications in fields like synthetic biology or antimicrobial discovery. The construction of synthetic divisomes in the test tube may need to preserve unsuspected roles, such as this newly found FtsZ property, to guarantee the stability of artificial containers. Whereas the effects on viability caused by inhibiting the activity of FtsZ may be partly overcome by filamentation, the absence of FtsZ is not tolerated by
E. coli
, an observation that may help in the design of effective antimicrobial compounds.
Order effects in high stakes undergraduate examinations: an analysis of 5 years of administrative data in one UK medical school
Authors: Burt Jenni , Abel Gary , Barclay Matt , Evans Robert , Benson John , Gurnell Mark
Published: October 2016

Objective

To investigate the association between student performance in undergraduate objective structured clinical examinations (OSCEs) and the examination schedule to which they were assigned to undertake these examinations.

Design

Analysis of routinely collected data.

Setting

One UK medical school.

Participants

2331 OSCEs of 3 different types (obstetrics OSCE, paediatrics OSCE and simulated clinical encounter examination OSCE) between 2009 and 2013. Students were not quarantined between examinations.

Outcomes

(1) Pass rates by day examination started, (2) pass rates by day station undertaken and (3) mean scores by day examination started.

Results

We found no evidence that pass rates differed according to the day on which the examination was started by a candidate in any of the examinations considered (p>0.1 for all). There was evidence (p=0.013) that students were more likely to pass individual stations on the second day of the paediatrics OSCE (OR 1.27, 95% CI 1.05 to 1.54). In the cases of the simulated clinical encounter examination and the obstetrics and gynaecology OSCEs, there was no (p=0.42) or very weak evidence (p=0.099), respectively, of any such variation in the probability of passing individual stations according to the day they were attempted. There was no evidence that mean scores varied by day apart from the paediatric OSCE, where slightly higher scores were achieved on the second day of the examination.

Conclusions

There is little evidence that different examination schedules have a consistent effect on pass rates or mean scores: students starting the examinations later were not consistently more or less likely to pass or score more highly than those starting earlier. The practice of quarantining students to prevent communication with (and subsequent unfair advantage for) subsequent examination cohorts is unlikely to be required.
Evaluation of California's Armed and Prohibited Persons System: study protocol for a cluster-randomised trial
Authors: Wintemute Garen J , Beckett Laurel , Kass Philip H , Tancredi Daniel , Studdert David , Pierce Glenn , Braga Anthony A , Wright Mona A , Cerdá Magdalena
Published: October 2016

Background and objective

Too little is known about the effectiveness of efforts to prevent firearm violence. Our objective is to evaluate California's Armed and Prohibited Persons System (APPS), a law enforcement intervention that seeks to recover firearms from individuals who purchased them legally but subsequently became prohibited from having access to firearms. Prohibitions usually arise from events suggesting an increased risk for future violence.

Design and study population

This group-randomised trial involves approximately 20 000 APPS-eligible individuals in 1041 communities. Randomisation was performed at the community level, to early or later intervention (Group 1 and Group 2, respectively) with stratification by region, population and violent crime rate.

Methods

APPS is being implemented by the California Department of Justice. The principal outcome measure is the incidence of arrest for a firearm-related or violent crime. Primary analysis will be on an intention-to-treat basis, comparing individuals in Group 1 and Group 2 communities. Analyses will focus on time to event, using proportional hazards regression with adjustment for the clustered nature of the data and incorporating individual- and community-level characteristics. Secondary analyses will examine the effect of the intervention on an as treated basis, effects on subgroups, and effects on community-wide measures such as crime rates.

Discussion

APPS may have a significant impact on risk for future violence among members of its target population. The findings of this study will likely be generalisable and have clear implications for violence prevention policy and practice.

Trial registration number

NCT02318732.
Prognostic relevance of epithelial–mesenchymal transition and proliferation in surgically treated primary parotid gland cancer
Authors: Busch Alina , Bauer Larissa , Wardelmann Eva , Rudack Claudia , Grünewald Inga , Stenner Markus
Published: October 2016

Aims

Cancer of the major salivary glands comprises a morphologically diverse group of rare tumours of largely unknown cause. Epithelial–mesenchymal transition (EMT) has been shown to play a significant prognostic role in various human cancers. The aim was to assess the expression of EMT markers in different histological subtypes of parotid gland cancer (PGC) and analyse their prognostic value.

Methods

We examined 94 PGC samples (13 histological subtypes) for the expression of MIB-1, epithelial cadherin (E-cadherin), β-catenin, vimentin and cytokeratin 8/18 (CK8/18) by means of immunohistochemistry. The experimental findings were correlated with clinicopathological and survival parameters.

Results

We detected all analysed EMT and proliferation markers in specifically different constellations within the examined histological subtypes of PGC. We found high epithelial marker expressions (CK8/18, E-cadherin, membranous β-catenin) only in a distinct variety of carcinomas. A high proliferation rate (high MIB-1 expression) as well as a combination of high CK8/18 and low vimentin expression was associated with a significantly worse survival.

Conclusions

Our findings indicate that activation of the EMT pathway is a relevant explanation for tumour progression in individual histological subtypes of malignant parotid gland lesions, but by far not in all. Evidence of EMT activation in PGC cannot be seen as an isolated prognostic factor.
Predictors of poor outcome among children with heterotaxy syndrome: a retrospective review
Authors: McGovern Eiméar , Kelleher Eoin , Potts James E , O'Brien John , Walsh Kevin , Nolke Lars , McMahon Colin J
Published: October 2016

Objective

To determine predictors of poor outcome in patients with heterotaxy syndrome.

Methods

A retrospective review of children with heterotaxy syndrome, in a single tertiary paediatric cardiology centre, was conducted between 1 January 1997 and 1 January 2014 to determine predictors of poor outcome. Poor outcome was defined as death, cardiac transplantation or New York Heart Association (NYHA) functional class III or IV.

Results

There were 35 patients diagnosed with heterotaxy syndrome, 17 of whom were diagnosed antenatally. 22 patients had right atrial isomerism and 13 had left atrial isomerism. The median age of postnatal diagnosis was 2.5 days old (1 day to 19 months). 12 patients had a poor outcome; 6 patients died, 1 underwent cardiac transplantation and 5 had an NYHA functional class of >III. 5 patients had a biventricular repair and the remaining 30 had a univentricular repair. Type of atrial isomerism, univentricular or biventricular anatomy, severity of atrioventricular valve regurgitation or ventricular dysfunction, obstructed pulmonary venous return, occurrence of arrhythmia and presence of pulmonary atresia did not predict poor outcome. Fetal diagnosis also did not confer a survival advantage. The median duration of follow-up in this cohort was 65 months (2 days to 16.8 years).

Conclusions

Survival for patients with heterotaxy syndrome was 83% over a median follow-up of 65 months. 34% of patients had a poor outcome. None of the variables studied were predictive of death, transplantation or NYHA classification III or IV.
Timing of fracture fixation from an Intensive Care Unit perspective: the obstacles to early fracture fixation
Authors: Thomson Lauren Elizabeth , Fry Nicola , Jackson Richard
Published: October 2016

Trauma is one of the leading causes of death worldwide, with road traffic accidents being the leading cause of death in the age group of 15–29 years However, with modern advances in management and the introduction of specialised trauma centres, more and more are surviving severe and life-threatening trauma. The ideal timing of fracture fixation has been the subject of debate for a number of decades. There is evidence to suggest that fracture fixation in the patient with polytrauma is best achieved early on to reduce the incidence of morbidity and mortality, with damage control surgery in the more appropriate option in those patients who are haemodynamically unstable. However, early fracture fixation is not always possible, and the focus of this article is to review the common contributing factors resulting in delayed fixation. For the purpose of this discussion, we will consider all trauma as a single entity, taking into account that each type of fixation has its own complications, which are outside the scope of this article.
Relative effects of biotic and abiotic factors during early life history on recruitment dynamics: a case study
Authors: Zhang Fan , Reid Kevin B. , Nudds Thomas D.
Published: October 2016

The relative effects of biotic and abiotic factors, and the life-history stages upon which they act to affect fish recruitment, vary among species and ecosystems. We compared the effects of spawning stock biomass, and factors operating at early-term (encompassing the egg, yolk-sac larval, and first few days of swim-up larval stages), middle-term (including the swim-up larval and pelagic juvenile stages), and late-term (over the benthic juvenile stage) on recruitment by yellow perch (Perca flavescens) in the western basin of Lake Erie between 1999 and 2013. Variation of recruitment was mainly driven by middle-term effects. Then, abiotic factors, such as warming rate and wind speed, more strongly affected recruitment than did biotic factors. Among middle-term biotic factors, the top-down effect of yearling walleye (Sander vitreus) abundance was stronger than the bottom-up effect of zooplankton abundance. Similar to marine species, physical processes appear to strongly affect recruitment dynamics of Lake Erie yellow perch over its pelagic larval and juvenile stages, demonstrating the importance of physical and biological processes in understanding fish population dynamics in large lakes.
Clarification on the early history of neutrino experiments
Authors: Shi Yu
Published: October 2016

Clarification is made on the early history of experiments on neutrinos. Especially, it is noted that the work of Reines and Cowan had nothing to do with Pontecorvo, as stated in some documents. Some other related history of neutrino physics is also briefly reviewed.
Is the Fulling–Davies–Unruh effect valid for the case of an atom coupled to quantum electromagnetic field?
Authors: Zhou Wenting
Published: October 2016

We study, from the viewpoint of a co-accelerated observer, the average rate of change of atomic energy for an atom in uniform acceleration and coupled to quantum electromagnetic field at a thermal state with an arbitrary temperature T. We show that only when the temperature of the thermal state in the co-accelerated frame is assumed to be the Fulling–Davies–Unruh (FDU) temperature, T = a/2[Formula: see text], can the average rate of change of atomic energy in a local inertial frame be recovered, which exemplifies the equivalence between the Minkowski vacuum and a thermal bath of Rindler particles. This conclusion is verified to be valid not only in a free spacetime, but also in a spacetime with a boundary.
The calibration and the monitoring/alarm system
Authors: Cappella F. , Caracciolo V. , Cerulli R. , Bussolotti A. , Mattei A.
Published: October 2016

Two important parts of the DAMA/LIBRA setup are the calibration system and the monitoring/alarm system. The calibration system allows to perform detector calibrations without changing the running condition of the experiment; the monitoring/alarm system allows to record several parameters to control the running status and its stability.

In this paper, we will describe the two system reporting some related obtained results.
Other rare processes with DAMA/LIBRA
Authors: Di Marco A. , Cappella F. , Cerulli R.
Published: October 2016

DAMA/NaI and DAMA/LIBRA data have allowed the study of several rare processes. In this paper, the results obtained for internal pair production in [Formula: see text]Am [Formula: see text] decay, charge not conserving electron capture in [Formula: see text]I and possible processes violating the Pauli Exclusion Principle are briefly discussed.
Towards the next and far future
Authors: Bernabei R. , Belli P. , Incicchitti A. , Cerulli R. , Dai C. J. , Ma X. H.
Published: October 2016

The DAMA project has realized and is developing many experiments in the field of Dark Matter direct detection, and in the search for many other rare processes by developing and using a wide choice of low background scintillators at the Laboratori Nazionali del Gran Sasso (LNGS) of the I.N.F.N. Thus, DAMA covers from pioneer to future aspects and can offer many other new results in the future.
Connected Car
Authors: Coppola Riccardo , Morisio Maurizio
Published: October 2016

The connected car—a vehicle capable of accessing to the Internet, of communicating with smart devices as well as other cars and road infrastructures, and of collecting real-time data from multiple sources—is likely to play a fundamental role in the foreseeable Internet Of Things. In a context ruled by very strong competitive forces, a significant amount of car manufacturers and software and hardware developers have already embraced the challenge of providing innovative solutions for new-generation vehicles. Today’s cars are asked to relieve drivers from the most stressful operations needed for driving, providing them with interesting and updated entertainment functions. In the meantime, they have to comply with the increasingly stringent standards about safety and reliability. The aim of this article is to provide an overview of the possibilities offered by connected functionalities on cars and the associated technological issues and problems, as well as to enumerate the currently available hardware and software solutions and their main features.
Shoot4U
Authors: Ouyang Jiannan , Lange John R. , Zheng Haoqiang
Published: October 2016

Virtual Machine based approaches to workload consolidation, as seen in IaaS cloud as well as datacenter platforms, have long had to contend with performance degradation caused by synchronization primitives inside the guest environments. These primitives can be affected by virtual CPU preemptions by the host scheduler that can introduce delays that are orders of magnitude longer than those primitives were designed for. While a significant amount of work has focused on the behavior of spinlock primitives as a source of these performance issues, spinlocks do not represent the entirety of synchronization mechanisms that are susceptible to scheduling issues when running in a virtualized environment. In this paper we address the virtualized performance issues introduced by TLB shootdown operations. Our profiling study, based on the PARSEC benchmark suite, has shown that up to 64% of a VM's CPU time can be spent on TLB shootdown operations under certain workloads. In order to address this problem, we present a paravirtual TLB shootdown scheme named Shoot4U. Shoot4U completely eliminates TLB shootdown preemptions by invalidating guest TLB entries from the VMM and allowing guest TLB shootdown operations to complete without waiting for remote virtual CPUs to be scheduled. Our performance evaluation using the PARSEC benchmark suite demonstrates that Shoot4U can reduce benchmark runtime by up to 85% compared an unmodified Linux kernel, and up to 44% over a state-of-the-art paravirtual TLB shootdown scheme.
Building a KVM-based Hypervisor for a Heterogeneous System Architecture Compliant System
Authors: Huang Yu-Ju , Wu Hsuan-Heng , Chung Yeh-Ching , Hsu Wei-Chung
Published: October 2016

Heterogeneous System Architecture (HSA) is an archi-tecture developed by the HSA foundation aiming at reduc-ing programmability barriers as well as improving commu-nication efficiency for heterogeneous computing. For ex-ample, HSA allows heterogeneous computing devices to share the same virtual address space. This feature allows programmers to bypass explicit data copying between devices, as was required in the past. HSA features such as job dispatching through user level queues and memory based signaling help to reduce communication latency between the host and other computing devices. While the new features in HSA enable more efficient heterogeneous computing, they also introduce new chal-lenges to system virtualization, especially in memory virtu-alization and I/O virtualization. This work investigates the issues involved in HSA virtualization and implements a KVM-based hypervisor that supports the main features of HSA inside guest operating systems. Furthermore, this work shows that with the newly introduced hypervisor for HSA, system resources in HSA-compliant AMD Kaveri can be effectively shared between multiple guest operating sys-tems.
The nom Profit-Maximizing Operating System
Authors: Ben-Yehuda Muli , Agmon Ben-Yehuda Orna , Tsafrir Dan
Published: October 2016

In the near future, cloud providers will sell their users virtual machines with CPU, memory, network, and storage resources whose prices constantly change according to market-driven supply and demand conditions. Running traditional operating systems in these virtual machines is a poor fit: traditional operating systems are not aware of changing resource prices and their sole aim is to maximize performance with no consideration of costs. Consequently, they yield low profits.

We present nom, a profit-maximizing operating system designed for cloud computing platforms with dynamic resource prices. Applications running on nom aim to maximize profits by optimizing simultaneously for performance and resource costs. The nom kernel provides them with direct access to the underlying hardware and full control over their private software stacks. Since nom applications know there is no single ``best'' software stack, they adapt their stacks' behavior on the fly according to the current price of available resources and their private utility from them, which differs between applications. We show that in addition to achieving up to 3.9x better throughput and up to 9.1x better latency, nom applications yield up to 11.1x higher profits when compared with the same applications running on Linux and OSv.
Leveraging Managed Runtime Systems to Build, Analyze, and Optimize Memory Graphs
Authors: Smith Rebecca , Rixner Scott
Published: October 2016

Optimizing memory management is a major challenge of embedded systems programming, as memory is scarce. Further, embedded systems often have heterogeneous memory architectures, complicating the task of memory allocation during both compilation and migration. However, new opportunities for addressing these challenges have been created by the recent emergence of managed runtimes for embedded systems. By imposing structure on memory, these systems have opened the doors for new techniques for analyzing and optimizing memory usage within embedded systems. This paper presents GEM (Graphs of Embedded Memory), a tool which capitalizes on the structure that managed runtime systems provide in order to build memory graphs which facilitate memory analysis and optimization. At GEM's core are a set of fundamental graph transformations which can be layered to support a wide range of use cases, including interactive memory visualization, de-duplication of objects and code, compilation for heterogeneous memory architectures, and transparent migration. Moreover, since the same underlying infrastructure supports all of these orthogonal functionalities, they can easily be applied together to complement each other.
Nonalcoholic Steatohepatitis
Authors: Suzuki Ayako , Diehl Anna Mae
Published: October 2016

Nonalcoholic steatohepatitis (NASH) has become a major cause of cirrhosis and liver-related deaths worldwide. NASH is strongly associated with obesity and the metabolic syndrome, conditions that cause lipid accumulation in hepatocytes (hepatic steatosis). It is not well understood why some, but not other, individuals with hepatic steatosis develop NASH. The factors that determine whether or not NASH progresses to cirrhosis are also unclear. This review summarizes key components of NASH pathogenesis and discusses how inherent and acquired variations in regulation of these processes impact the risk for NASH and NASH cirrhosis.
Is Most Published Research Really False?
Authors: Leek Jeffrey T. , Jager Leah R.
Published: October 2016

There has been an increasing concern in both the scientific and lay communities that most published medical findings are false. But what does it mean to be false? Here we describe the range of definitions of false discoveries in the scientific literature. We summarize the philosophical, statistical, and experimental evidence for each type of false discovery. We discuss common underpinning problems with the scientific and data analytic practices and point to tools and behaviors that can be implemented to reduce the problems with published scientific results.
A Realistic 3D Model of Mediator Supercapacitors in Micrometer Level
Authors: Wang Yuchen , Zhang Chen , Qiao Xiaoyao , Zhou Xiangyang
Published: October 2016

A 3-D microscopic model is set up for studying the roles of different components in mediator supercapacitor. In the model, mediator clusters are interfacing with active carbon, carbon fibers, and polymer electrolyte. Different conductivities, capacities, and mechanical properties were assigned to different components. Computational analyses were conducted using COMSOL Multiphysics. Hotspots appear around mediator clusters because of current concentration around them during charging/discharging. Further minimization of the mediator clusters will help mitigate this issue. Total capacitance of mediator supercapacitor increases exponentially when mediator capacitance and activated carbon capacitance reaches critical values. In addition, the mediator supercapacitor stores more charge with higher electrolyte conductivity. When applied pressure is high, stress concentrates around carbon fibers which cause the destruction of polymer electrolyte.
Lithium-Ion Capacitor Based on Electrodes Constructed Via Electrostatic Spray Deposition
Authors: Agrawal Richa , Chen Chunhui , Dages Samantha , Wang Chunlei
Published: October 2016

Conventional Electrochemical double-layer capacitors (EDLCs) are well suited as power devices that can provide large bursts of energy in short time periods. However, their relatively poor energy densities hinder their application in devices that require a simultaneous supply of both high energy and high power. In the wake of addressing this shortcoming of EDLCs, the concept of hybridization of lithium-ion batteries (LIBs) and EDLCs has gained significant scientific interest in past few years. Such a device, generally referred to as the “lithium-ion capacitor” typically utilizes a lithium intercalating electrode along with a fast charging capacitor electrode in a lithium-containing electrolyte. Herein we have constructed a lithium ion capacitor comprising a Li4Ti5O12 –TiO2 (LTO-TiO2) anode and a graphene and carbon nanotube (G-CNT) composite cathode using electrostatic spray deposition (ESD). The morphology and material properties were studied using scanning and transmission electron microscopy and X-ray diffraction studies, respectively. Electrochemical characterization was thereafter carried out for both the half cells as well as full cells.
Binder-Free Freestanding Flexible Si Nanoparticles-Multi-Walled Carbon Nanotubes Composite Anodes for Li-Ion Batteries
Authors: Yao Kang , Zheng Jim P. , Liang Richard
Published: October 2016

Binder-free freestanding flexible Si nanoparticles-multi-walled carbon nanotubes (SiNPs-MWNTs) composite paper anodes have been prepared by simple, inexpensive, and scalable approach of ultra-sonication and pressure filtration. The 3D network of MWNTs forms a continuous conductive pathway within the composite structure, which ensures sufficient electrical conductivity, holds the particles together, and alleviates volume expansion of Si. Through control of Si/C weight ratio, we found out the SiNPs-MWNTs electrode with 3:2 Si/C ratio exhibits the optimal balance between high capacity of SiNPs and high conductivity and structural stabilization quality of MWNTs, leading to high rate capability as well as specific capacity and cycle performance superior to conventional slurry-cast SiNPs anode using binder and Cu current collector. After 100 cycles, the electrode retains capacity of 1170 mAh/g at 100 mA/g. The freestanding feature of our electrode eliminates the non-active mass, which is promising for enhanced capacity and energy density of Li-ion cells.
X-ray Tomographic Investigation of Water Distribution in Polymer Electrolyte Membrane Fuel Cells with Different Gas Diffusion Media
Authors: Alrwashdeh Saad Sabe' , Markötter Henning , Haußmann Jan , Scholta Joachim , Hilger André , Manke Ingo
Published: October 2016

In this study, water transport in polymer electrolyte membrane fuel cells (PEMFCs) is investigated by synchrotron X-ray tomography. The measurement technique is used to reveal the relationship between the structure of the gas diffusion media (GDM) and the water distribution. It is shown how the water distribution and transport is visualized and quantitatively analyzed. We present investigations on three different GDM: A GDM with a modified microporous layer (MPL), a thick GDM with limited back diffusion and a reference material.
Computational Simulation of Thermal and Chemical Phenomena for Honeycomb-Structured Catalytic Reforming Reactor
Authors: Raoufi Arman , Kapadia Sagar , Newman James C.
Published: October 2016

A fully coupled numerical model for solid and fluid phases is developed to investigate the performance of catalytic reforming reactors. The transport of mass, momentum, energy and species in a reforming reactor are simultaneously solved using a three dimensional fully implicit unstructured finite volume approach. The nonlinear system of equations is solved by Newton’s method. Eight gas-phase species (CH4, CO2, H2O, N2, O2, CO, OH and H2) are considered for the simulation. The surface chemistry is modeled by detailed reaction mechanisms including 38 heterogeneous reactions with 20 surface-adsorbed species for rhodium catalyst and solved using the mean-field approximation model to obtain the surface convergence and reaction rates. The numerical results are compared with the experimental data and good agreement is observed. The simulation is performed for two different honeycomb-structured reactors. The governing equations for fluid and solid regions of the monolith are simultaneously solved with considering the catalytic combustion at their interface. The performance of the reforming reactor is numerically studied.
Ionic Conductivity and Stability of the Lithium Aluminum Germanium Phosphate
Authors: Cui Yuantao , Rohde Magnus , Reichmann Thomas Ludwig , Mahmoud Morsi M , Ziebert Carlos , Seifert Hans Jürgen
Published: October 2016

Lithium aluminum germanium phosphate (LAGP) solid state electrolytes with different compositions were synthesized and then heat-treated at different temperatures. The ionic conductivity of the prepared samples was studied. Lithium ion cells using LAGP as solid state electrolyte were assembled and tested. The stability of the prepared LAGP samples was investigated.
New Nitrogen-Doped Graphene/MOF-modified catalyst for Fuel Cell Systems
Authors: Zhuang Shiqiang , Lei Lin , Nunna Bharathbabu , Lee Eon Soo
Published: October 2016

Metal-organic frameworks (MOFs), which have advantages such as large surface area and high porosity, are recently investigated as a component of electrochemical catalysts to enhance the catalytic performance. But the influences of MOFs on the properties of catalysts such as surface structure, local structure of active sites, catalytic activity, and selectivity are still under investigation. This research is focused on the new MOF-modified nitrogen-doped graphene (N-G/MOF) catalyst, which is expected to have better ORR activity than N-G catalysts, for PEM fuel cell systems. The primary research objective is to understand the catalytic reaction mechanism of the N-G/MOF. It also includes the study of the physical structure & chemical composition of the N-G/MOF and their influence on the ORR activity and selectivity. The experimental efforts to realize this objective include the controllable synthesis of the N-G/MOF, imaging of the microstructure, analyzing the chemical bonding distribution of active sites, and the electrochemical characterization at the acid electrolyte.
Phase Diagram Approach to Study Acid and Water Uptake of Polybenzimidazole-Type Membranes for Fuel Cells
Authors: Conti Fosca , Bertasi Federico , Wackerl Juergen , Dams Pierre , Di Noto Vito , Lehnert Werner , Korte Carsten
Published: October 2016

Polybenzimidazole (PBI) membranes doped with phosphoric acid are the most commonly used materials for high-temperature polymer electrolyte fuel cells. Despite this fact, only little is known on the chemical equilibria of the species inside the membrane as a function of the composition of the ternary system PBI - H3PO4 - H2O. This includes details on the condensation equilibria, leading to the formation of diphosphoric acid and higher homologues species and on the proton transfer processes, i.e. on the dominant conduction mechanisms. As a first step to understand the thermodynamic equilibria in the ternary system PBI - H3PO4 - H2O the phase diagrams for two different polymers, poly(2,2’-(m-phenylene)-5,5’-bibenzimidazole) (m-PBI) and the recent commercially available Fumapem AM-55, were evaluated from own and from experimental data found in literature. Miscibility gaps are identified and equilibrium lines separating one- and two-phase fields in the diagrams are estimated.
Enhanced Conversion and Storage of Solar Energy Using TiO2 Nanobelts in an All-Vanadium Photoelectrochemical Storage Cell
Authors: Shen Yi , Wei Zi , Liu Dong , Liu Fuqiang
Published: October 2016

Application of nanostructured materials in electrochemical and photoelectrochemical devices could yield a dramatic improvement in energy storage, conversion, and generation efficiency because they dramatically alter the surface reaction rates and charge transport throughout the materials. In this work, one-dimensional TiO2 nanobelts have been explored as photocatalyst in an all-vanadium photoelectrochemical storage cell to achieve efficient solar energy storage. Results show that photocurrent of the all-vanadium storage cell has been significantly improved after additional step of heat-treatment of the photoelectrode, in comparison to that using conventional P25 TiO2. It is proposed that this observed improvement in photocurrent is due to the connected network as a result of improved bonding between TiO2 nanobelts after prolonged heat treatment.
Investigation of the Effect of Electrolyte Velocity on Mass Transport in Porous Electrodes Utilizing a Symmetric Cell
Authors: You Xin , Ye Qiang , Cheng Ping
Published: October 2016

A symmetric cell using Fe2+/Fe3+ as a redox couple at both sides was fabricated to investigate the impact of electrolyte velocity on mass transport in porous electrodes. Polarization behaviors were measured at different velocities ranging from 1.7 to 20 mm s-1. The significant mass transport loss is observed at velocities lower than 5 mm s-1 even though the reactant stoichiometry is high enough. Starting from the lowest velocity of 1.7 mm s-1, the improvement of cell performance with the increase of velocity is initially significant, which becomes minor as the velocity reaches a high value above 10 mm s-1. According to the experimental results, velocities lower than 5 mm s-1 should be avoided in designing flow batteries to prevent significant mass transport loss, while those higher than 20 mm s-1 are not recommended because the slight benefit might be overweighed by the increment of pumping loss.
Evaluation of Si-Based Cells and the Importance of Scale-up
Authors: Karulkar Mohan , Wen Hao , Kudla Robert , Blaser Rachel
Published: October 2016

Automotive target metrics, which include specific and volumetric energy and power densities, are difficult to assess for many bench-scale materials. Thus, in order to identify the most promising technologies for future EV applications, it is crucial that researchers pursue scale-up to, in the least, a “pilot fab” scale that enables larger format cells and more relevant metric assessment. Several key processing differences have emerged during Ford’s scale-up operations involving advanced lithium ion battery research, affecting every fabrication step, including mixing, coating, drying, calendaring, and cell assembly. Processing, in turn, affects key electrode characteristics like slurry formulation, active loading, density, adhesion, uniformity, and repeatability. In every case, scale-up improves processing and the associated electrode characteristics. Certain metrics are also very challenging to measure at small scales, including energy and power densities, effects of cell abuse, calendar life, electrolyte consumption, and volume expansion. This is detailed further with a silicon anode case study.
Potentiodynamic Polarization and Potentiostatic Polarization Behaviors for Iron in Sulfuric Acid Solution with or without a Magnetic Field
Authors: Li Hongjuan , Xiong Qi , Xiao Qian , Chen Zhen , Peng Hao , Lu Zhanpeng
Published: October 2016

The effect of a magnetic field on the cathodic reaction of iron in a sulfuric acid solution is studied. Potentiodynamic polarization curves with or without a 0.4 T magnetic field and potentiostatic polarizations under the intermittent imposing or withdrawing of the magnetic field are used to determine the magnetic field effect on hydrogen evolution reaction(HER). The current density in the Tafel region of the cathodic polarization curve at 0.4T magnetic field is higher than that at 0T. When the iron electrode has been polarized potentiostatically in the cathodic Tafel region after many cycles of imposing and withdrawing the magnetic field, imposing the magnetic field finally causes a decrease of the current and withdrawing the magnetic field causes an increase of the current. If the magnetic field had been applied at the start of the polarization, withdrawing the magnetic field causes a sudden decrease of the current density. The effect of magnetic field on cathodic hydrogen evolution is dependent on the cathodic polarization mode and the test sequence.
Electrochemical Behaviors of Various Alloys in Ferric Sulfate Solution
Authors: Xiao Qian , Chen Junjie , Peng Hao , Chen Zhen , Lu Zhanpeng
Published: October 2016

The effects of alloying elements on the electrochemical behaviors in ferric sulfate solution at 25 oC were investigated using A508III low alloy steel, pure Fe, Cr, Ni, 316L SS, 430 SS and Alloy 690. The electrochemical behaviors of A508III steel and iron are similar, showing no active-passivation transition on the anodic polarization curves and no mass-transport-controlled region on the cathodic polarization curves. Active-passivation transition appears on the anodic polarization curves of 316L and 430 steel. Mass-transport-controlled region appears on the cathodic polarization curves of the alloys with certain contents of Cr and Ni. Certain contents of Cr and Ni in alloys increases the open circuit potential, decreases the current density, and increases the electrochemical impedance spectroscopy value. A higher Cr content results in a higher EIS value.
Effects of H2s and pH on Tafel Slopes in Electrochemical Corrosion of High Strength Carbon Steel S-135 in Alkaline Brines
Authors: Feng Ruishu , Beck Justin , Ziomek-Moroz Margaret , Lvov Serguei N.
Published: October 2016

Effects of H2S and pH on electrochemical corrosion of high-strength low-alloy carbon steel, Grade S-135, were investigated through Tafel slopes. Linear sweep voltammetry (LSV) was conducted in 5 %wt. NaCl solutions of pH 7.9, 10.7, and 12.4 with four H2S partial pressures (p
H2S) ranging from 0 to 69 kPa at 85 oC after 60 hours of exposure. Anodic limiting current was observed without H2S, but disappeared at higher p
H2S. Cathodic LSV plots did not show limiting currents, suggesting that H2O was the main reactant for the hydrogen evolution reaction at high pH. Both anodic and cathodic currents increased at 69 kPa p
H2S compared to 0 kPa. Electrochemical reaction mechanisms were discussed based on anodic and cathodic Tafel slopes. The Tafel slopes from LSV were generally larger than those obtained from electrochemical frequency modulation. Different Tafel slopes could result in a discrepancy in corrosion rate by a factor of 5.
Effect of Process Parameters on the Corrosion Resistance Properties of PEO Coatings Produced on AZ31B Magnesium Alloy
Authors: Savguira Yuri , Ni Qing , Sobrinho Pedro H. , North Tom H. , Thorpe Steven J.
Published: October 2016

Plasma electrolytic oxidation (PEO) can reduce the corrosion susceptibility of Mg alloys by producing a protective oxide layer. The present investigation examined the influence of PEO processing parameters on the corrosion resistance of the resulting coatings. Changes in the oxidation time, applied current density, and electrolyte temperature were shown to alter the thickness of the coating as well as its phase composition. Increasing the coating time was found to increase the thickness and uniformity of the coating. Application of a greater current density was found to increase the thickness of the outer layer, resulting in a more porous structure with reduced corrosion resistance. Elevating the temperature of the electrolyte resulted in partial dissolution of the coating, producing a thinner coating than that produced in an electrolyte at a lower temperature. The resistance to corrosion initiation was considered to be related to through-film pores in the coating, via electrochemical impedance modelling.
Environmental Aspects of Using Metal Organic Frameworks as Adsorbents in Natural Gas Storage Systems
Authors: Abd Elhamid Mahmoud Hassan , Dailly Anne , Cai Mei
Published: October 2016

This work is in direct support of GM’s ongoing effort in developing transformational technologies to reduce the barriers of onboard Natural Gas mass adoption. Alternative NG storage technologies seek to bypass the pressure and thermal challenges of traditional storage technologies by utilizing the chemical and physical properties of certain solid materials to store gas. While the gas adsorption/desorption properties, thermodynamics and kinetics of the adsorbent materials have been evaluated in depth there is, to our knowledge, no report of the compatibility of the same materials with the pressure vessel liner at (P, T) operating conditions. The stability of the benchmark Metal Organic Framework, Cu3BTC2, in the presence of Natural Gas contaminants and its impact on the metallic tank liner material has been investigated and will be addressed in this report.