bluuebunny/crossref_metadata_2025 huggingface dataset:
Review: Fluid biomarkers for frontotemporal dementias
Authors: Zetterberg H. , van Swieten J. C. , Boxer A. L. , Rohrer J. D.
Published: November 2018

Frontotemporal dementias (FTDs) are clinically, genetically and pathologically heterogeneous neurodegenerative disorders that affect the frontal and anterior temporal lobes of the brain. They are relatively common causes of young‐onset dementia and usually present with behavioural disturbance (behavioural variant FTD) or language impairment (primary progressive aphasia), but there is also overlap with motor neurone disease and the atypical parkinsonian disorders, corticobasal syndrome and progressive supranuclear palsy. At post mortem, neuronal inclusions containing tau, TDP‐43 or infrequently FUS protein are seen in most cases. However, a poor correlation between clinical syndrome and underlying pathology means that it is difficult to diagnose the underlying molecular basis using clinical criteria. At this point, biomarkers for the underlying pathology come into play. This paper provides a brief update on fluid biomarkers for FTDs that may be useful to dissect the underlying molecular changes in patients presenting with signs of frontal and/or temporal lobe dysfunction. The hope is that such biomarkers, together with genetics and imaging, would be useful in clinical trials of novel drug candidates directed against specific pathologies and, in the long run, helpful in clinical practice to select the most appropriate treatment at the right dose for individual patients.
Measuring the effects of bronchial thermoplasty using oscillometry
Authors: Langton David , Ing Alvin , Sha Joy , Bennetts Kim , Hersch Nicole , Kwok McKinny , Plummer Virginia , Thien Francis , Farah Claude
Published: November 2018

Background and objective

Bronchial thermoplasty (BT) has been consistently shown to reduce symptoms, exacerbations and the need for reliever medication in patients with severe asthma. Paradoxically, no consistent improvement in spirometry has been demonstrated. It has been suggested that this is due to a reduction in peripheral resistance in small airways, not captured by spirometry. Therefore, in this study, we evaluate the response to BT using oscillometry.

Methods

A total of 43 patients with severe asthma from two centres were evaluated at baseline, 6 weeks and 6 months post BT, using spirometry, plethysmography and oscillometry, in addition to medication usage, exacerbation frequency and the Asthma Control Questionnaire (5‐item version) (ACQ‐5).

Results

The mean age was 58.4 ± 11.2 years, forced expiratory volume in 1 s (FEV1) 55.5 ± 20.1% predicted, forced expiratory ratio 53.0 ± 14.5% and FEV1 response to salbutamol was 14.0 ± 14.5%. Following BT, the group responded to treatment with an improvement in ACQ‐5 from 2.9 ± 0.9 at baseline to 1.7 ± 1.1 at 6 months (P < 0.005). There was an 81% reduction in exacerbation frequency (P < 0.001) and 50% of patients were weaned completely from maintenance oral corticosteroids. No changes after treatment were observed in spirometry but the residual volume reduced from 147 ± 38% to 139 ± 39% predicted (P < 0.01). Baseline oscillometry demonstrated high levels of resistance at 5 Hz with normal resistance at 20 Hz, indicating resistance in the small airways was elevated, but no changes were observed in any oscillometry parameter after BT treatment.

Conclusion

Lung impedance measured with oscillometry did not change following BT despite marked clinical improvements in patients with severe asthma.
Liquid media regulated growth of cinnamon nanoparticles: Absorption and emission traits
Authors: Salim Ali Aqeel , Ghoshal Sib Krishna , Suan Lau Pik , Bidin Noriah , Hamzah Khaidzir , Duralim Maisarah , Bakhtiar Hazri
Published: November 2018

Customized cinnamon-based nanostructures are of great demand for broad arrays of nanomedical, biomedical and photocatalytic purposes. Conventional methods for cinnamon nanomaterials production with desirable optical absorption and emission properties are still limited. This communication elucidates the role of growth media (liquid ethanol and methanol) in controlling the optical qualities of cinnamon nanoparticles (CNPs). Such CNPs of varied morphologies were prepared using pulsed laser ablation in liquid (PLAL) technique (a simple, an inexpensive, and an eco-friendly approach). In the PLAL process, clean cinnamon sticks (as target material purchased from supermarket) were ablated via Q-switched Nd:YAG laser pulse of wavelength 532 nm operated at optimum fluence of 5.73 J/cm2. As-synthesized CNPs were characterized at room temperature using ultraviolet-visible (UV-Vis) absorption and photoluminescence (PL) emission spectroscopy. Uniformly dispersed high purity colloidal CNPs with narrow size distribution was achieved. The UV-Vis absorption and the PL spectra of CNPs revealed prominent peaks. These observed distinctive absorption and emission traits of studied CNPs were ascribed to the effects of oxygen deficiency, quantum confinement, crystal defects and existence of cinnamaldehyde compounds. In short, the nucleation and growth of CNPs was significantly sensitive to the chemical character of liquid suspension that provided a favorable thermodynamic condition via entropy driven free energy minimization. It was demonstrated that the structural, morphological, physical, optical properties of such CNPs can be tailored by intuitively selecting the liquid growth media. This disclosure affirmed that the present systematic approach can constitute a basis for the large-scale production of CNPs effective for widespread applications.
Extraction of β-sitosterol from Swietenia mahagoni seeds by using supercritical carbon dioxide (SC-CO2) extraction
Authors: Md Norodin Nur Salsabila , Md Salleh Liza , Machmudah Siti , Mustafa Nik Musaadah , Hartati Hartati , Ismail Ramdan
Published: November 2018

This work investigates the effect of supercritical carbon dioxide (SC-CO2) extraction conditions (pressure and temperature) on the oil yield and β-sitosterol content extracted from Swietenia mahagoni seeds by using response surface methodology (RSM). The experimental data obtained were fitted to a second-order polynomial model and the obtained oil yields were 1.49-14.45%, while β-sitosterol content obtained were 3.12-9.20 mg/g. The best conditions within the ranges studied were 30 MPa and 40°C to extract β-sitosterol in the highest amount. The present findings show that S. mahagoni seeds extract has a high concentration of β-sitosterol.
The effect of dynamic vulcanization on the morphological and mechanical properties of the toughened poly (lactic acid)/epoxidized natural rubber
Authors: Abdullah Nur Amira Sahirah , Mohamad Zurina
Published: November 2018

Poly (lactic acid)/epoxidized natural rubber (PLA/ENR) was prepared by using counter-rotating twin-screw extruder. For dynamic vulcanization process, ENR was compounded with 3 phr of N, N’-m-phenylenebismaleimide (HVA-2) as a crosslinking agent. The aim of this study is to determine the effect of unvulcanized and dynamically vulcanized of ENR on the properties of PLA/ENR blend. The blending of PLA with ENR was prepared with the various composition of ENR (0 wt% to 30 wt%). The morphology and mechanical properties of the blends were investigated by using scanning electron microscope (SEM), tensile test, and impact test. The unvulcanized blend produced a co-continuous morphology of PLA and ENR and the dynamically vulcanized blend shows the dispersed ENR rubber particles in PLA continuous matrix.  For both systems, the tensile strength value was dropped with the increasing amount of ENR content. The impact strength of both systems shows the maximum value at 20 wt% of ENR content. However, dynamically vulcanized PLA/ENR blend shows a better tensile strength and impact strength value as compared with unvulcanized blend.
Study on the effect of spinning conditions on the performance of PSf/PVP ultrafiltration hollow fiber membrane
Authors: Mansur Sumarni , Othman Mohd Hafiz Dzarfan , Ismail Ahmad Fauzi , Zainol Abidin Muhammad Nidzhom , Said Noresah , Sean Goh Pei , Hasbullah Hasrinah , Sheikh Abdul Kadir Siti Hamimah , Kamal Fatmawati
Published: November 2018

Asymmetric, porous ultrafiltration polysulfone (PSf) hollow fiber membranes were fabricated via the dry-wet phase inversion spinning technique specifically for haemodialysis membrane. The objective was to discover the suitable spinning condition for the fabrication of ultrafiltration hollow fiber membrane with desired sponge-like structure. During haemodialysis procedure, uremic toxins such as urea and creatinine range from size 10,000-55,000 Da needs to be excreted out from the blood. While, proteins such as albumin (66,000 Da) need to be retained. The physical structure or morphology of a fabricated membrane is a major concern in determining the efficiency of a dialysis membrane. Different type of membrane morphology will give a different result in term of its permeability and clearance efficiency. The phase inversion spinning technique is suitable in producing ultrafiltation (UF) membrane where the average pore size of the fabricated membrane is in the range of 0.001 – 0.1 µm. However, there is many factors need to be controlled and manipulated in the phase inversion technique. In this study, the effect of the PVP on membrane pore size and performances were analysed. The contact angle measurement was measured to determine the hydrophilicity of the fibers. The hydrophilic polymer is favorable to avoid fouling and increase its biocompatibility. Furthermore, the diameter of the hollow fibers was determined using a scanning electron microscope (SEM). The effects of different morphology of the hollow fibers on the performance of the membranes were evaluated by pure water flux and BSA rejection. Both techniques were tested using permeation flux system. Based on the results obtained, it is found that the finger-like macrovoids in PSf hollow fiber membranes were suppressed by adding 8% PVP (Mw of 360 kDa) into the spinning dope solution as the result of a drastic increase in dope viscosity. On top of that, fiber spun with 8% PVP show more porous structure which contribute to higher permeability of the membrane. The result of this study can benefit to the membrane field of research especially in membrane technology for haemodialysis application.
Lyapunov Sliding-Mode Observers With Application for Active Magnetic Bearing Operated With Zero-Bias Flux
Authors: Mystkowski Arkadiusz
Published: November 2018

This study deals with sliding-mode nonlinear observers for a flux-controlled active magnetic bearing (AMB) operated with zero-bias flux. The Lyapunov sliding-mode observer (LSMO) feedback designs are performed for the nonlinear AMB dynamics due to control voltage saturation. The nonlinear observers are designed to estimate the magnetic flux and rotor mass velocity. The observer designs are incorporated in equivalence implementation of the nonlinear state-feedback controller. The main design tools such as sliding-mode control, Lyapunov-based control are used in this framework. The proposed observers are verified by means of numerical simulations, and stability and effectiveness of the proposed observer-based feedback designs are shown.
Characterization of New Nonstoichiometric Ferroelectric (Li0.95Cu0.15)Ta0.76Nb0.19O3 and Comparative Study With (Li0.95Cu0.15)Ta0.57Nb0.38O3 as Photocatalysts in Microbial Fuel Cells
Authors: Louki S. , Touach N. , Benzaouak A. , Ortiz-Martínez V. M. , Salar-García M. J. , Hernández-Fernández F. J. , de los Ríos A. P. , El Mahi M. , Lotfi E. M.
Published: November 2018

This work investigates the photocatalytic activity of new ferroelectric material with formula (Li0.95Cu0.15)Ta0.76Nb0.19O3 (LT76) in a single chamber microbial fuel cell (MFC) and compares its performance with the similar photocatalyst (Li0.95Cu0.15)Ta0.57Nb0.38O3 (LT57). The photocatalysts LT76 and LT57 were synthesized by ceramic route under the same conditions, with the same starting materials. The ratio Ta/Nb was fixed at 4.0 and 1.5 for LT76 and LT57, respectively. These phases were characterized by different techniques including X-ray diffraction (XRD), transmission electronic microscopy (TEM), particle size distribution (PSD), differential scanning calorimetry (DSC), and ultraviolet (UV)–visible (Vis). The new photocatalyst LT76 presents specific surface area of 0.791 m2/g and Curie temperature of 1197 °C. The photocatalytic efficiency of this material is assessed in terms of wastewater treatment and electricity generation by power density and removal rate of chemical oxygen demand (COD) in the presence of a light source. The values of maximum power density and COD removal were 19.77 mW/m3 and 93%, respectively, for LT76.
Experimental Analysis of Cavitation Phenomena on Kaplan Turbine Blades Using Flow Visualization
Authors: Podnar Andrej , Dular Matevž , Širok Brane , Hočevar Marko
Published: November 2018

In this study, a comparison of two different Kaplan turbine runners with differently shaped turbine blades was performed. The two turbines differed in the selection of the hydrofoil, the main hydrofoil parameters of which had been modified including, the position of maximum thickness and curvature and the inlet edge radius. Both turbines (unmodified and modified hydrofoils) were tested on a rig designed for low pressure model turbine acceptance tests. The effect of blade shape on cavitation inception, development, and intensity was demonstrated using computer aided visualization. Visualization was performed on the suction side of Kaplan runner blade where the shape of the blade determines cavitation inception and development. The modified Kaplan turbine reduced the cavitation phenomena, and as a result, both turbine performance and output increased for the selected operating points. This demonstrates that choosing the right turbine blade shape is key for optimal turbine performance.
Computational Fluid Dynamics Flow Simulations in Discrete Element Method-Resolved Packed Beds
Authors: Zhang Joanna , Shotorban Babak , Bayyuk Sami , Zhang Sijun
Published: November 2018

This paper presents computational simulations of flows in packed beds and compares the computational pressure-drop results with those given by the Ergun correlation. The computational methodology used in this work follows the combined discrete element method (DEM) and computational fluid dynamics (CFD) technique. DEM is used to predict the locations and packing structure of the particles in the bed, while CFD is used to predict the flow field in the void space surrounding the packed particles. The computational results obtained for irregular packed beds show that the local packing-structure parameters have significant effects not only on the local velocity and pressure fields but also on macroscopic quantities, such as the average pressure gradient along the length of the packed column. The computational results also show that classical correlations based on averaged values, such as the Ergun correlation, have poor predictive accuracy for macroscopic variations along a packed column, and this is mainly because such correlations do not account for local packing-structure parameters. The computational results confirm the existence of sections with linear variation of macroscopic parameters along the length of the packed column, and this leads to the conclusion that accurate results from DEM-CFD methods on shortened columns can be extrapolated to full-length columns. Moreover, it was found that unlike regularly packed beds, the predicted pressure for randomly packed beds experiences an apparent strong recovery near the downstream end of the packed bed, and then experiences a strong dip down to the plateau leading to the exit pressure.
Multiphase Sloshing and Interfacial Wave Interaction With a Baffle and a Submersed Block
Authors: Kargbo Obai , Xue Mi-An , Zheng Jinhai
Published: November 2018

A numerical model of a rectangular tank containing a layered liquid is modeled for studying layered sloshing wave. The Arbitrary Lagrangian Eulerian method is used to track the development for both the interfacial and free surface of the fluid domain. A series of cases are simulated for baffled and unbaffled sloshing with various excitation frequencies and various baffle configurations. A case containing a submerged block is also simulated to observe the interfacial wave interaction with the block structure and to observe how the position and size of the block affect the interfacial wave in a fluid. Velocity screenshots are analyzed for observing the velocity distribution in the layers and to observe the behavior of the interfacial layer for baffled and unbaffled tank cases. A fast Fourier transform spectral analysis of the layered liquid sloshing time series for both the interfacial layer and free surface layer is presented to observe the energy in the fluid layers as well as to observe the dominant peak frequency for both the layers.
Theoretical and Applied Insights on Pistons Buckling According to DNV Regulation
Authors: Fantuzzi Nicholas , Borgia Fabio
Published: November 2018

Pistons are fundamental structural elements in any engineering practices such as mechanical, civil, aerospace, and offshore engineering. Their strength strongly depends on buckling load, and such information is a major requirement in the design process. Euler's linear buckling equation is the most common and most used model in design. It is well suited for linear elastic members without geometrical imperfections and nonlinear behavior. Several analytical and experimental investigations of typical hydraulic cylinders have been carried out through the years but most of the available standards still use a linear approach with many simplifications. Pistons are slender beams with not-uniform cross section, which need a stronger effort than the classical Euler's approach. The present paper aims to discuss limitations of current DNV standards for piston design in offshore technologies when compared to classical numerical approaches and reference results provided by the existing literature.
The Influence of Thermal Oxidation Parameters on Structural, Friction, and Wear Characteristics of Oxide Layers Produced on the Surface of Ti–6Al–7Nb Alloy
Authors: Aniołek Krzysztof , Barylski Adrian , Kupka Marian , Tylka Joanna
Published: November 2018

The effects of thermal oxidation of a biomedical titanium alloy (Ti–6Al–7Nb) on its morphology, structure, mechanical properties, and sliding friction and wear against alumina were investigated. It was found that at 600 °C, the surface of the alloy was characterized with a thin inhomogeneous oxide scale. Increasing the temperature of oxidation to 700 °C and 800 °C allowed obtaining homogeneous layers, which fully covered the examined surfaces. By contrast, the oxide scale obtained at 800 °C was composed of big oxide particles with a developed surface. Thermal oxidation process allows a fourfold increase in the hardness of Ti–6Al–7Nb alloy. It was shown that the oxide scale on the examined alloy efficiently enhances its resistance to sliding wear against alumina.
Numerical Study of the Flow Condition of the Hydrodynamic Levitated Mechanical Micropump
Authors: Wu Ruikang , Lan Wei , Yu Xingjian , Shu Weicheng , Wang Meng , Luo Xiaobing
Published: November 2018

Active liquid cooling is one of the most efficient and promising strategy for extreme thermal issues. As is the power source of the active liquid cooling system, a reliable and powerful micropump is urgently needed. In this study, we numerically studied the fluid flow of a hydrodynamic levitated micropump, considering the fluid flow in the motor. We found that the load capacity of the journal bearing is not influenced by the pump fluid flow. However, the pressure distribution of the journal bearing results in the dissymmetric pressure distribution in the spiral groove bearing, leading to worse stability of the axial levitation performance. The axial suspension force is at least 1.0N with the liquid film thickness of 15μm and is sufficient for the rotor with weight of 30g to be stably levitated in the fluid. Owing to the pressure difference inside the pump, the balance point of the rotor should be lower than the theoretical design when the micropump is operating.
Rack-Level Study of Hybrid Cooled Servers Using Warm Water Cooling With Variable Pumping for Centralized Coolant System
Authors: Sahini Manasa , Kshirsagar Chinmay , McGinn Patrick , Agonafer Dereje
Published: November 2018

As global demand for data centers grows, so does the size and load placed on data centers, leading constraints on power and space available to the operator. Cooling power consumption is a major part of the data center energy usage. Liquid cooling technology has emerged as a viable solution in the process of optimization of the energy consumed per performance unit. In this data center rack level evaluation, 2OU (Open U) hybrid (liquid+air) cooled web servers are tested to observe the effects of warm water cooling on the server component temperatures, IT power and cooling power. The study discusses the importance of variable speed pumping in a centralized coolant configuration system.

The cooling setup includes a mini rack capable of housing up to eleven hybrid cooled web servers and two heat exchangers that exhaust the heat dissipated from the servers to the environment (the test rig data center room). The centralized configuration has two redundant pumps placed in series with heat exchanger at the rack. Each server is equipped with two passive (i.e. no active pump) cold plates for cooling the CPUs while rests of the components are air cooled. Synthetic stress load has been generated on each server using stress-testing tools. Pumps in the servers are separately powered using an external power supply. The pump speed is proportional to the voltage across the armature [1]. The pump rpm has been recorded with input voltages ranging from 11V to 17V. The servers are tested for higher inlet temperatures ranging from 25°C to 45°C which falls within the ASHRAE liquid cooled envelope W4 [2]. Variable pumping has been achieved by using different input voltages at respective inlet temperatures.
Analysis of Thermal Properties of Power Multifinger HEMT Devices
Authors: Chvála Aleš , Szobolovszký Robert , Kováč Jaroslav , Florovič Martin , Marek Juraj , Černaj Luboš , Príbytný Patrik , Donoval Daniel , Kováč Jaroslav , Delage Sylvain Laurent , Jacquet Jean-Claude
Published: November 2018

In this paper, several methods suitable for real time on-chip temperature measurements of power AlGaN/GaN based high-electron mobility transistor (HEMT) grown on SiC substrate are presented. The measurement of temperature distribution on HEMT surface using Raman spectroscopy is presented. We have deployed a temperature measurement approach utilizing electrical I-V characteristics of the neighboring Schottky diode under different dissipated power of the transistor heat source. These methods are verified by measurements with micro thermistors. The results show that these methods have a potential for HEMT analysis in thermal management. The features and limitations of the proposed methods are discussed. The thermal parameters of materials used in the device are extracted from temperature distribution in the structure with the support of 3-D device thermal simulation. The thermal analysis of the multifinger power HEMT is performed. The effects of the structure design and fabrication processes from semiconductor layers, metallization, and packaging up to cooling solutions are investigated. The analysis of thermal behavior can help during design and optimization of power HEMT.
Next Gen Test-Vehicle to Simulate Thermal Load for IoT FPGA Applications
Authors: Parameswaran Suresh , Refai-Ahmed Gamal , Ramalingam Suresh , Ang Boon
Published: November 2018

As semiconductor device feature size scales and circuit performance increases, power dissipation and thermal management are becoming very important. Attention to thermal considerations is required throughout the chip development cycle from preliminary architecture planning to deployment on customer board and beyond. This paper describes a versatile thermal test vehicle that can be used to address these requirements. We discuss the architecture and implementation of a specially designed test-vehicle chip, followed by its operation. The programmability and flexibility of this vehicle will be highlighted. In addition, we cover other usage of this vehicle which includes modelling of chip-level thermal behavior with different floorplan, simulating thermal loads in IoT FPGA applications, cross-calibrating thermal numerical simulators with measured silicon data and evaluating the thermal impact of different package form-factor / material (such as thermal interface material) and cooling solutions.

The abovementioned chip was fabricated using 0.18um technology and assembled in a flip-chip package. The reminder of this evaluation system is a simple, inexpensive tester from which a software is run to program the chip and to measure the spatial & temporal temperature values. Measured thermal data from different use cases are presented in this paper.
Improving Energy Efficiency in Data Centers by Controlling Task Distribution and Cooling
Authors: Nakajo Yusuke , Athavale Jayati , Yoda Minami , Joshi Yogendra , Nishi Hiroaki
Published: November 2018

The rapid growth in cloud computing, the Internet of Things (IoT), and data processing via Machine Learning (ML), have greatly increased our need for computing resources. Given this rapid growth, it is expected that data centers will consume more and more of our global energy supply. Improving their energy efficiency is therefore crucial. One of the biggest sources of energy consumption is the energy required to cool the data centers, and ensure that the servers stay within their intended operating temperature range. Indeed, about 40% of a data center’s total power consumption is for air conditioning[1].

Here, we study how the server air inlet and outlet, as well as the CPU, temperatures depend upon server loads typical of real Internet Protocol (IP) traces. The trace data used here are from Google clusters and include the times, job and task ID, as well as the number and usage of CPU cores. The resulting IT loads are distributed using standard load-balancing methods such as Round Robin (RR) and the CPU utilization method.

Experiments are conducted in the Data Center Laboratory (DCL) at the Georgia Institute of Technology to monitor the server outlet air temperature, as well as real-time CPU temperatures for servers at different heights within the rack. Server temperatures were measured by on-line temperature monitoring with Xbee, Raspberry PI, Arduino, and hot-wire anemometers. Given that the temperature response varies with server position, in part due to spatial variations in the cooling airflow over the rack inlet and the server fan speeds, a new load-balancing approach that accounts for spatially varying temperature response within a rack is tested and validated in this paper.
Thermal Interface Materials Enhanced by Micro and Nanostructures
Authors: Lu Mei-Chien
Published: November 2018

Thermal Interface materials are crucial elements for packaging of power electronics. In particular, development of high temperature lead free die-attach thermal interface materials for silicon carbide wide bandgap power electronics is a challenge. Failures of power electronics package modules often occur at die-attach areas. Among major options, sintered silver shows advantages in ease of applications. Cost, reliability, and integration are concerns for technology implementation. The current study first discusses issues and status reported in literatures. Then it focuses on cost reduction and improvement of sintered silver using enhancement structures at micro and nano scales. A few design architectures are analyzed by finite element methods. The feasibility of strengthening edges and corners is also assessed. The downside of potential increase of unfavorable stresses to accelerate void coalescence would be discussed in conjunction with design concept of power electronics package modules for paths of solutions in the form of integrated module systems.
Assessment of Damage Progression in Automotive Electronics Assemblies Subjected to Temperature and Vibration
Authors: Lall Pradeep , Thomas Tony
Published: November 2018

Electronics in automotive underhood environments is used for a number of safety critical functions. Reliable continued operation of electronic safety systems without catastrophic failure is important for safe operation of the vehicle. There is need for prognostication methods, which can be integrated, with on-board sensors for assessment of accrued damage and impending failure. In this paper, leadfree electronic assemblies consisting of daisy-chained parts have been subjected to high temperature vibration at 5g and 155°C. Spectrogram has been used to identify the emergence of new low frequency components with damage progression in electronic assemblies. Principal component analysis has been used to reduce the dimensionality of large data-sets and identify patterns without the loss of features that signify damage progression and impending failure. Variance of the principal components of the instantaneous frequency has been shown to exhibit an increasing trend during the initial damage progression, attaining a maximum value and decreasing prior to failure. The unique behavior of the instantaneous frequency over the period of vibration can be used as a health-monitoring feature for identifying the impending failures in automotive electronics. Further, damage progression has been studied using Empirical Mode Decomposition (EMD) technique in order to decompose the signals into Independent Mode Functions (IMF). The IMF’s were investigated based on their kurtosis values and a reconstructed strain signal was formulated with all IMF’s greater than a kurtosis value of three. PCA analysis on the reconstructed strain signal gave better patterns that can be used for prognostication of the life of the components.
Orientation Effects in Two-Phase Microgap Flow
Authors: Robinson Franklin L. , Bar-Cohen Avram
Published: November 2018

The high power density of emerging electronic devices is driving the transition from remote cooling, which relies on conduction and spreading, to embedded cooling, which extracts dissipated heat on-site. Two-phase microgap coolers employ the forced flow of dielectric fluids undergoing phase change in a heated channel within or between devices. Such coolers must work reliably in all orientations for a variety of applications (e.g., vehicle-based equipment), as well as in microgravity and high-g for other applications (e.g., spacecraft and aircraft). The lack of acceptable models and correlations for orientation- and gravity-independent operation has limited the use of two-phase coolers in such applications. Previous research has revealed that gravitational acceleration plays a diminishing role in establishing flow regimes and transport rates as the channel size shrinks, but there is considerable variation among the proposed microscale criteria and limited research on two-phase flows in low aspect ratio microgap channels. Reliable criteria for achieving orientation- and gravity-independent flow boiling would enable emerging systems to exploit this thermal management technique and streamline the technology development process.

As a first step toward understanding the effect of gravity on two-phase microgap flow and transport, in the present effort the authors have studied the effect of evaporator orientation and mass flux on near-saturated flow boiling of HFE7100 in a 1.01 mm tall by 13.0 mm wide by 12.7 mm long microgap channel. Orientation-independence, defined as achieving similar critical heat fluxes, heat transfer coefficients, and flow regimes across evaporator orientations, was achieved for mass fluxes of 400 kg/m2-s and greater. The present results are compared to published criteria for achieving gravity-independence.
A Novel Activated Carbon Enabled Steam Generation System Under Simulated Solar Light
Authors: Mishra Ashreet , Nnanna A. G. Agwu
Published: November 2018

A number of studies on CNT, Au and Ag solar enabled steam generation with potential application in water purification, distillation and sterilization of medical equipment. The key challenge with these nanoparticles is cost of production hence limiting its wide application for clean water production. This work for the first time, reports on activated carbon enabled steam generation hence addressing the cost limitations of metallic nanoparticles. Activated carbon has high solar absorptivity at various wavelengths of visible light under low concentration.

Experiments were carried out using activated carbon and CNT nanofluids and polyurethane membrane with immobilized activated carbon and CNT. A simulated solar light of 1 KW ∼1 Sun was used. The rate of evaporation, temporal and spatial evolution of bulk temperature in the water were monitored automatically and recorded for further data reductions. Parametric studies of the effect of nanoparticle concentration, water quality and salinity were performed. Experimental evidence showed that activated carbon has potential. We reported for the first time that optimal activated carbon concentration for maximum steam generation is 60 % vol. We also obtained a 160 % increase in steam production rate at 60 % concentration of activated carbon when compared with D.I water.
Nanoindentation Measurements of the Mechanical Properties of Individual Phases Within Lead Free Solder Joints Subjected to Isothermal Aging
Authors: Fahim Abdullah , Ahmed Sudan , Suhling Jeffrey C. , Lall Pradeep
Published: November 2018

Exposure of lead free solder joints to high temperature isothermal aging conditions leads to microstructure evolution, which mainly includes coarsening of the intermetallic (IMC) phases. In our previous work, it was found that the coarsening of IMCs led to degradation of the overall mechanical properties of the SAC solder composite consisting of β-Sn matrix and IMC particles. However, it is not known whether the isothermal aging changes properties of the individual β-Sn and IMC phases, which could also be affecting to the overall degradation of properties.

In this study, the aging induced variations of the mechanical properties of the β-Sn phase, and of Sn-Cu IMC particles in SAC solder joints have been explored using nanoindentation. SAC solder joints extracted from SuperBGA (SBGA) packages were aged for different time intervals (0, 1, 5, 10 days) at T = 125 °C. Nanoindentation test samples were prepared by cross sectioning the solder joints, and then molding them in epoxy and polishing them to prepare the joint surfaces for nanoindentation. Multiple β-Sn grains were identified in joints using optical polarized microscopy and IMCs were also observed. Individual β-Sn grains and IMC particles were then indented at room temperature to measure their mechanical properties (elastic modulus and hardness) and time dependent creep deformations. Properties measured at different aging time were then compared to explore aging induced degradations of the individual phases. The properties of the individual phases did not show significant degradation. Thus, IMC coarsening is the primary reason for the degradation of bulk solder joint properties, and changes of the properties of the individual phases making up the lead free solder material are negligible.
The Effects of Temperature, Strain Rate, and Aging on the Poisson’s Ratio of SAC Lead Free Solders
Authors: Hassan K. M. Rafidh , Alam Mohammad S. , Basit Munshi , Suhling Jeffrey C. , Lall Pradeep
Published: November 2018

In this study, we have conducted a combined numerical and experimental study on the Poisson’s ratio of SAC lead free solders. The Poisson’s ratio (PR) is one of the basic mechanical properties used in many material constitutive models. Although often not measured, it is important property in many finite element method (FEM) calculations. The value of the Poisson’s ratio of SAC lead free solders is relatively unexplored compared to other material properties, and for FEA simulations it is typically assumed to be v = 0.3. In the current work, we have shown the effects of the chosen value of the solder joint Poisson’s ratio on the finite element results for BGA components subjected to thermal cycling. In the finite element models, the reliability predictions were based on the Morrow-Darveaux energy-based fatigue model. Several sizes (5, 10, 15 mm) of PBGA components with SAC305 solder joints with 0.4 and 0.8 mm spacing were modeled. The packages were subjected to a time dependent cyclic temperature distribution from −40 to 125 °C. The package assemblies were assumed to be in a stress-free state at 25 °C (room temperature), with no residual stresses induced in the manufacturing process. The simulation results have demonstrated that for specified range of Poisson’s ratio values of 0.15 < v < 0.40, the solder Plastic Work varied over 20% and the Predicted Reliability Varied over 50%.

To determine the actual Poisson’s ratio experimentally, uniaxial tensile stress-strain tests were carried out on SAC305 (96.5Sn3.0Ag0.5Cu) specimens using a micro tension/torsion testing machine with two strain rates (0.0001, and 0.00001 (sec−1)), four testing temperatures (T = 25, 50, 75, 100 °C), and several durations of prior aging at T = 125 °C. Deformations and strains in axial and transverse directions were measured using strain gages with automatic data acquisition from LabVIEW software. The recorded transverse strain vs. axial strain data were then fit with a linear regression analysis to determine the Poisson’s ratio values. A test matrix of experiments was developed to study the effects of temperature, strain rate, alloy composition, and solidification cooling profile on the value of solder Poisson’s ratio. The Poisson’s ratio was found to increase with increasing temperature, and decrease with increasing strain rate. Using a slower solidification cooling profile led to an increase in the solder Poisson’s ratio value. Finally, the microstructural coarsening that occurs during isothermal aging lead to an increase in the Poisson’s ratio.
Impact of Internal Design on the Efficiency of IT Equipment in a Hot Aisle Containment System: An Experimental Study
Authors: Khalili Sadegh , Alissa Husam , Nemati Kourosh , Seymour Mark , Curtis Robert , Moss David , Sammakia Bahgat
Published: November 2018

There are various designs for segregating hot and cold air in data centers such as cold aisle containment (CAC), hot aisle containment (HAC), and chimney exhaust rack. These containment systems have different characteristics and impose various conditions on the information technology equipment (ITE). One common issue in HAC systems is the pressure buildup inside the HAC (known as backpressure). Backpressure also can be present in CAC systems in case of airflow imbalances. Hot air recirculation, limited cooling airflow rate in servers, and reversed flow through ITE with weaker fan systems (e.g. network switches) are some known consequences of backpressure. Currently there is a lack of experimental data on the interdependency between overall performance of ITE and its internal design when a backpressure is imposed on ITE. In this paper, three commercial 2-rack unit (RU) servers with different internal designs from various generations and performance levels are tested and analyzed under various environmental conditions. Smoke tests and thermal imaging are implemented to study the airflow patterns inside the tested equipment. In addition, the impact leak of hot air into ITE on the fan speed and the power consumption of ITE is studied. Furthermore, the cause of the discrepancy between measured inlet temperatures by internal intelligent platform management interface (IPMI) and external sensors is investigated. It is found that arrangement of fans, segregation of space upstream and downstream of fans, leakage paths, location of sensors of baseboard management controller (BMC) and presence of backpressure can have a significant impact on ITE power and cooling efficiency.
Comparison of Evaporation and Condensation Characteristics Among Three Enhanced Tubes
Authors: Shen Kunrong , Sun Zhichuan , Yan Xiaolong , Li Wei , Kukulka David J. , Zhou Jianxin , Luan Deyu , He Yan , Zhang Bin
Published: November 2018

With the current ozone depletion and global warming issues, it is critical to develop systems with better heat transfer performance and nontoxic refrigerants. An experimental investigation was performed to evaluate convective condensation and evaporation heat transfer characteristics using R410A at low mass fluxes. Experiments were conducted in a 12.0-mm O.D. horizontal smooth tube, and three enhanced tubes: 2EHT1 tube, 2EHT2 tube and 1EHT1 tube (O.D. 12.7 mm), with different sizes and shapes of dimple/protrusion and petal arrays.

Refrigerant inlet quality varied in this study. Single phase experiment was conducted before the two-phase flow measurement. In-tube evaporation measurements of R410A were reported for saturation temperature at 6°C with vapor quality in the range of 0.2 to 0.9, and mass flux varied from 60 to 200 kg/m2s. Condensation tests were performed at saturation temperature of 45°C, vapor quality of 0.9 to 0.2, and mass flux of 60 to 260 kg/m2s.

For evaporation with mass flux less than 200 kg/m2s, heat transfer coefficient of the 2EHT2 tube, 2EHT1 tube and 1EHT1 tube were greater than the experimental HTC (heat transfer coefficient) of smooth tube results by an average factor of 1.71, 1.69 and 1.87, respectively. Pressure drop in the 2EHT2 tube was 5% higher than the 2EHT1 tube and 1EHT1 tube. For condensation, when mass flux was less than 200 kg/m2s, the 1EHT1 tube showed obvious enhancement in heat transfer coefficient, while the pressure drop in the 1EHT1 tube was slightly 3–5% higher than that of the 2EHT1 tube and the 2EHT2 tube. In conclusion, for mass flux below 200 kg/m2s, the 1EHT1 tube presented the best heat transfer performance among others with R410A as the refrigerant.
Landing Stiffness Between Individuals With and Without a History of Low Back Pain
Authors: Sutherlin Mark A. , Mangum L. Colby , Russell Shawn , Saliba Susan , Hertel Jay , Hart Joe M.
Published: November 2018

Context:Reduced spinal stabilization, delayed onset of muscle activation, and increased knee joint stiffness have been reported in individuals with a history of low back pain (LBP). Biomechanical adaptations resulting from LBP may increase the risk for future injury due to suboptimal loading of the lower-extremity or lumbar spine. Assessing landing mechanics in these individuals could help identify which structures might be susceptible to future injury.Objective:To compare vertical and joint stiffness of the lower-extremity and lumbar spine between individuals with and without a previous history of LBP.Design:Cross-sectional study.Setting:Research laboratory.Participants:There were 45 participants (24 without a previous history of LBP—age 23 [8] y, height 169.0 [8.5] cm, mass 69.8 [13.8] kg; 21 with a previous history of LBP—age 25[9] y, height 170.0 [8.0] cm, mass 70.2 [11.8] kg).Interventions:Single-limb landing trials on the dominant and nondominant limb from a 30-cm box.Main Outcome Measures:Vertical stiffness and joint stiffness of the ankle, knee, hip, and lumbar spine.Results:Individuals with a previous history of LBP had lower vertical stiffness (P = .04), but not joint stiffness measures compared with those without a previous history of LBP (P > .05). Overall females had lower vertical (P = .01), ankle (P = .02), and hip stiffness (P = .04) compared with males among all participants. Males with a previous history of LBP had lower vertical stiffness compared with males without a previous history LBP (P = .01). Among all individuals without a previous history of LBP, females had lower vertical (P < .01) and ankle stiffness measures (P = .04) compared with males.Conclusions:Landing stiffness may differ among males and females and a previous history of LBP. Comparisons between individuals with and without previous LBP should be considered when assessing landing strategies, and future research should focus on how LBP impacts landing mechanics.
GlcNAc De-
N
-Acetylase from the Hyperthermophilic Archaeon
Sulfolobus solfataricus
Authors: Iacono Roberta , Strazzulli Andrea , Maurelli Luisa , Curci Nicola , Casillo Angela , Corsaro Maria Michela , Moracci Marco , Cobucci-Ponzano Beatrice
Published: November 2018

In this study, a preliminary screening of cellular extracts of
S. solfataricus
allowed the identification of an α-
N
-acetylglucosaminidase activity. However, the characterization of the corresponding recombinant enzyme revealed a novel GlcNAc de-
N
-acetylase, which, in cooperation with the α-glucosidase, catalyzed the hydrolysis of O-α-GlcNAc glycosides. In addition, we show that the product of a gene flanking the one encoding the de-
N
-acetylase is a putative glycosyltransferase, suggesting the involvement of the two enzymes in the metabolism of GlcNAc. The discovery and functional analysis of novel enzymatic activities involved in the modification of this essential sugar represent a powerful strategy to shed light on the physiology and metabolism of
Archaea
.
Recessive Host Range Mutants and Unsusceptible Cells That Inactivate Virions without Genome Penetration: Ecological and Technical Implications
Authors: Roznowski Aaron P. , Young Robert J. , Love Samuel D. , Andromita Avenetti A. , Guzman Vanessa A. , Wilch Margaret H. , Block Ava , McGill Anne , Lavelle Martine , Romanova Anastasia , Sekiguchi Aimi , Wang Meixiao , Burch April D. , Fane Bentley A.
Published: November 2018

To expand host range, viruses must interact with unsusceptible host cell surfaces, which could be detrimental. As observed in this study, virions were inactivated without genome penetration. This may be advantageous to potential new hosts, culling the viral population from which an expanded host range mutant could emerge. When identified, altered host range mutations were recessive. Accordingly, isolation required populations generated in low-MOI environments. However, in laboratory settings, viral propagation includes high-MOI conditions. Typically, infected cultures incubate until all cells produce progeny. Thus, coinfections dominate later replication cycles, masking recessive host range expansion phenotypes. This may have impacted similar studies with other viruses. Last, structural and genetic data could be used to predict site-directed mutant phenotypes, which may broaden the classic antireceptor definition to include interfaces between capsid complexes.
Challenges and opportunities for antibiotic stewardship among preterm infants
Authors: Mukhopadhyay Sagori , Sengupta Shaon , Puopolo Karen M
Published: November 2018

Antibiotic stewardship programmes aim to optimise antimicrobial use to prevent the emergence of resistance species and protect patients from the side effects of unnecessary medication. The high incidence of systemic infection and associated mortality from these infections leads neonatal providers to frequently initiate antibiotic therapy and make empiric antibiotic courses one of the main contributors of antibiotic use in the neonatal units. Yet, premature infants are also at risk for acute life-threatening complications associated with antibiotic use such as necrotising enterocolitis and for long-term morbidities such as asthma. In this review, we discuss specific aspects of antibiotic use in the very low birthweight preterm infants, with a focus on empiric use, that provide opportunities for stewardship practice. We discuss strategies to risk-stratify antibiotic initiation for the risk of early-onset sepsis, optimise empiric therapy duration and antibiotic choice in late-onset sepsis, and standardise decisions for stopping empiric therapy. Lastly, review the evolving role of biomarkers in antibiotic stewardship.