bluuebunny/crossref_metadata_2025 huggingface dataset:
A Computational Investigation of Piston Bowl Geometry and Injector Spray Pattern Effects on Gasoline Compression Ignition in a Heavy-Duty Diesel Engine
Authors: Zhang Yu , Pei Yuanjiang , Tang Meng , Traver Michael
Published: December 2019

This study computationally investigates the potential of utilizing gasoline compression ignition (GCI) in a heavy-duty diesel engine to address a future ultra-low tailpipe NOx standard of 0.027 g/kWh while achieving high fuel efficiency.

By conducting closed-cycle, full-geometry, 3-D computational fluid dynamics (CFD) combustion simulations, the effects of piston bowl geometry, injector spray pattern, and swirl ratio (SR) were investigated for a market gasoline. The simulations were performed at 1375 rpm over a load range from 5 to 15 bar BMEP. The engine compression ratio (CR) was increased from 15.7 used in previous work to 16.5 for this study. Two piston bowl concepts were studied with Design 1 attained by simply scaling from the baseline 15.7 CR piston bowl, and Design 2 exploring a wider and shallower combustion chamber design.

The simulation results predicted that through a combination of the wider and shallower piston bowl design, a 14-hole injector spray pattern, and a swirl ratio of 1, Design 2 would lead to a 2–7% indicated specific fuel consumption (ISFC) improvement over the baseline by reducing the spray-wall interactions and lowering the in-cylinder heat transfer loss. Design 1 (10-hole and SR2) showed a more moderate ISFC reduction of 1–4% by increasing CR and the number of nozzle holes. The predicted fuel efficiency benefit of Design 2 was found to be more pronounced at low to medium loads.
Twin-Peak Heat Release Phenomenon Inside a Heavy-Duty Diesel Engine Retrofitted to Natural-Gas Spark Ignition
Authors: Liu Jinlong , Dumitrescu Cosmin E. , Ulishney Christopher
Published: December 2019

Existing compression ignition engines can be modified to spark ignition configuration to increase the use of natural gas in the heavy-duty transportation sector. A better understanding of the premixed natural gas combustion inside the original diesel chamber (i.e., flat-head-and-bowl-in-piston) will help improve the conversion process and therefore accelerate the diesel engine conversion. Previous studies indicated that the burning process in such engines is a two-stage combustion with a fast burning inside the bowl and a slower burning inside the squish. This paper used experimental and numerical results to investigate the combustion process at a more advanced spark timing representative of ultra-lean medium-load operation, which placed most of the combustion inside the compression stroke. At such operating conditions, the high turbulence intensity inside the squish region accelerated the flame propagation inside the squish region to the point that the burn inside the bowl separated less from that inside the squish region. However, several individual cycles produced a double-peak energy-release with the peak locations closer to the only one heat release peak seen in the average cycle. Moreover, RANS CFD simulations indicated that the time at which the flame entered the squish region was near the peak location of the energy-release process for the conditions investigated here. As a result, the data suggests that the double-peak seen in the apparent heat release rate was the result of the cycle-by-cycle variation in the flame propagation.
A Computational Investigation of the Impact of Multiple Injection Strategies on Combustion Efficiency in Diesel-Natural Gas Dual Fuel Low Temperature Combustion Engine
Authors: Bartolucci Lorenzo , Cordiner Stefano , Mulone Vincenzo , Krishnan Sundar R. , Srinivasan Kalyan K.
Published: December 2019

Dual fuel diesel-methane low temperature combustion (LTC) has been investigated by various research groups, showing high potential for emissions reduction (especially oxides of nitrogen (NOx) and particulate matter (PM)) without adversely affecting fuel conversion efficiency in comparison with conventional diesel combustion.

However, when operated at low load conditions, dual fuel LTC typically exhibit poor combustion efficiencies. This behavior is mainly due to low bulk gas temperatures under lean conditions, resulting in unacceptably high carbon monoxide (CO) and unburned hydrocarbon (UHC) emissions. A feasible and rather innovative solution may be to split the pilot injection of liquid fuel into two injection pulses, with the second pilot injection supporting the methane combustion once the process is initiated by the first one.

In this work, diesel-methane dual fuel LTC is investigated numerically in a single-cylinder heavy-duty engine operating at 5 bar brake mean effective pressure (BMEP) at 85% and 75% percentage of energy substitution (PES) by methane (taken as a natural gas surrogate). A multidimensional model is first validated in comparison with experimental data obtained on the same single-cylinder engine for early single pilot diesel injection at 310 CAD and 500 bar rail pressure. With the single pilot injection case as baseline, the effects of multiple pilot injections and different rail pressures on combustion emissions are investigated, again showing good agreement with experimental data.

Apparent heat release rate and cylinder pressure histories as well as combustion efficiency trends are correctly captured by the numerical model. Results prove that higher rail pressures yield reductions of HC and CO by 90% and 75%, respectively, at the expense of NOx emissions, which increase by ∼30% from baseline. Furthermore, it is shown that post-injection during the expansion stroke does not support the stable development of the combustion front as the combustion process is confined close to the diesel spray core.
Analysis of a 5-Stroke Engine With a Two-Zone Equilibrium Combustion Products Model
Authors: Stuart Kurt , Yan Terry , Mathias James
Published: December 2019

A 5-stroke engine was analyzed using an improved 2-zone combustion model utilizing an equilibrium combustion model to calculate the gas properties in each zone. The flows of inlet, exhaust, and transfer port are handled using quasi-steady 1-D flow models. Heat transfer in the transfer port is also considered. The results are reported as indicated thermal efficiency and power output over a range of operating points and design characteristics, including engine RPM, compression ratio, overall expansion ratio, expansion cylinder clearance volume, and transfer port volume. It was found that the transfer port volume had a significant effect on the overall indicated thermal efficiency. The results were compared with those of a baseline 4-stroke engine. The 5-stroke engine with a compression ratio of 9:1, and an overall expansion ratio of 27:1 achieves a peak indicated thermal efficiency of 47%, representing a 6% increase over the baseline 4-stroke engine with the same compression ratio.
RCCI Investigations With n-Butanol and ULSD
Authors: Soloiu Valentin , Carapia Cesar E. , Wiley Justin T. , Moncada Jose , Gaubert Remi , Knowles Aliyah , Ilie Marcel , Rahman Mosfequr
Published: December 2019

The focus of this study is to reduce harmful NOx and soot emissions of a compression ignition (CI) engine using reactivity-controlled compression ignition (RCCI) with n-Butanol. RCCI was achieved with the port fuel injection (PFI) of a low reactivity fuel, n-butanol, and a direct injection (DI) of the highly reactive fuel ULSD #2 (Ultra Low Sulfur Diesel) into the combustion chamber. The reactivity, ID, and CD where determined using a Constant Volume Combustion Chamber (CVCC) where ID for n-butanol was found to be 15 times slower than ULSD. The emissions and combustion analysis was conducted at 1500 RPM at an experimental low engine load of 4 bar IMEP; the baseline for emissions comparison was conducted using conventional diesel combustion (CDC) with an injection timing of 16° BTDC at a rail pressure of 800 bar. RCCI was conducted utilizing 75% by mass PFI of n-butanol with 25% ULSD DI, showed a simultaneous reduction of both NOx and soot emissions at a rate of 96.2% and 98.7% respectively albeit with an increase in UHC emissions by a factor of 5. Ringing Intensity was also significantly reduced for Bu75ULSD25 (RCCI Experiment) with a reduction of 62.1% from CDC.
Characteristics of Diesel Spray With Varying Injection Rate
Authors: Naruemon Intarat , Liu Long , Liu Dai , Ma Xiuzhen
Published: December 2019

Multiple-injection is an effective injection strategy in order to control the advanced combustion processes in diesel engines. However, because of the multiple-injection application, cause the duration of each injection is shortened, such as the pilot injection and post-injection. The short injection duration results in a very short quasi-steady injection process so that the ramping-up and ramping-down injection processes occupied a much larger scale during the injection. As a result, this circumstance of the spray evolution not been fully understood. To investigate the diesel spray propagation with varying injection rate, visual experiments and numerical simulation analyses on diesel spray were performed. The penetrations of diesel sprays with short injection duration were obtained by reflected shadowgraphy in a combustion chamber’s constant-volume with the multi-hole injector. The diesel spray with varying injection rates was modeled by using CONVERGE CFD software and the model was calibrated and validated by the experimental data. Then diagnosed the spray characteristics including spray penetration, Sauter means diameter, as well as fuel concentration distribution, were analyzed with different injection quantities and injection rate shapes. The spray mixing analysis included that after the end-of-injection in order to consider the low-temperature combustion phenomenon. The shape of the improved injection rate in the fuel mixture considered in the case of injection ending before or after the ignition time was summarized for different conditions.
Effect of Ambient Pressure on the Behavior of Single-Component Fuels in a Gasoline Multi-Hole Injector
Authors: Nocivelli Lorenzo , Yan Junhao , Saha Kaushik , Magnotti Gina M. , Lee Chia-Fon , Som Sibendu
Published: December 2019

The injection characteristics of neat ethanol and pure iso-octane are studied under different ambient pressure and temperature conditions. Injection under flash-boiling conditions can enhance liquid atomization and evaporation, providing the possibility of improvement in the fuel/air mixing. These super-heated conditions often introduce phenomena that are not taken into account in the standard modeling of sprays for engine applications. The present work proposes a numerical investigation of the behavior of Engine Combustion Network’s 8-hole spray-G injector, starting at the subcooled nominal condition and reducing the ambient pressure at constant low temperature to reach the flare flash-boiling condition. To initialize the properties of the injected fuel, the flow in the nozzle is simulated with a Eulerian approach, handling the two phases with a mixture model and the phase change, due to cavitation and flash boiling, with the Homogenous Relaxation Model. A map of the mixture’s kinematic and thermal behavior is obtained at the interface between the injector and the chamber to initialize the Lagrangian simulations. A literature-based vaporization model is implemented to obtain the proper description of the characteristic features of a multi-hole spray under super-heated conditions, like plume-plume interaction. The numerical representation of the spray is validated in terms of penetration and radial spreading on DBI images, reproducing the light attenuation profiles caused by the presence of the liquid spray. Simulations show that coupled nozzle flow and spray calculations capture the spray morphology and shape better compared to calculations performed without considering the nozzle flow simulation details, especially under flare flash conditions.
Design of Passive Two-Phase Thermosyphons for Server Cooling
Authors: Amalfi Raffaele L. , Marcinichen Jackson B. , Thome John R. , Cataldo Filippo
Published: December 2019

The main objective of this paper is to utilize an improved version of the simulator presented at InterPACK 2017 to design a thermosyphon system for energy-efficient heat removal from 2-U servers used in high-power datacenters. Currently, between 25% and 45% of the total energy consumption of a datacenter (this number does not include the energy required to drive the fans at the server-level) is dedicated to cooling, and with a predicted annual growth rate of about 15% (or higher) coupled with the plan of building numerous new datacenters to handle the “big data” storage and processing demands of emerging 5G networks, artificial intelligence, electrical vehicles, etc., the development of novel, high efficiency cooling technologies becomes extremely important for curbing the use of energy in datacenters.

Notably, going from air cooling to two-phase cooling, not only enables the possibility to handle the ever higher heat fluxes and heat loads of new servers, but it also provides an energy-efficient solution to be implemented for all servers of a datacenter to reduce the total energy consumption of the entire cooling system. In that light, a pseudo-chip with a footprint area of 4 × 4 cm2 and a maximum power dissipation of 300 W (corresponding heat flux of about 19 W/cm2), will be assumed as a target design for our novel thermosyphon-based cooling system. The simulator will be first validated against an independent database and then used to find the optimal design of the chip’s thermosyphon. The results demonstrate the capability of this simulator to model all of the thermosyphon’s components (evaporator, condenser, riser and downcomer) together with overall thermal performance and creation of operational maps. Additionally, the simulator is used here to design two types of passive two-phase systems, an air- and a liquid-cooled thermosyphon, which will be compared in terms of thermal-hydraulic performance. Finally, the simulator will be used to perform a sensitivity analysis on the secondary coolant side conditions (inlet temperature and mass flow rate) to evaluate their effect on the system performance.
Thermal Analysis of 3D ICs With TSVs Placement Optimization
Authors: Ren Zongqing , Alqahtani Ayed , Bagherzadeh Nader , Lee Jaeho
Published: December 2019

While 3D integrated circuits (3D ICs) offer a great enhancement in performance, the increased power density, nonuniform power distribution and high thermal resistance pose significant thermal management challenges. Thermal through-silicon-vias (TTSVs) are TSVs that do not carry signal but facilitate heat transfer across stacked dies. The use of TTSVs occupies extra space and extends the distance between IC blocks leading to an increase in signal delay. The trade-offs between the temperature and wirelength are evident in the TTSV placement. In this paper, we propose a hierarchical approach to optimize the floorplan of a 3D Nehalem-based multicore processor. The floorplan of a single core is optimized using simulated annealing (SA)-based algorithm and the floorplan of the entire 3D IC is generated based on the symmetric operation. Our simulation results show that the peak temperature decreases with the TTSV area overhead and the wirelength strongly depends on the TTSV placement. Compared to the SA-optimized floorplan with no TTSVs, the SA-optimized floorplans with TTSV offer 6–15 °C more reduction in peak temperature while keeping the wirelength increase from 10 % to 40 % at 2–20 % TTSV area overheads. We also evaluate the effects of anisotropic thermal transport in TTSVs and show that the lateral thermal conductivity of TTSV has a significant impact on the peak temperature of 3D ICs.
Effects of Cooling Architecture and PCB Layout Co-Design on the Concurrent Thermal and Electrical Performance of an On-Board Electric Vehicle Charger
Authors: Tayyara Omri , Gupta Kshitij , Da Silva Carlos , Nasr Miad , Assadi Amir , Trescases Olivier , Amon Cristina H.
Published: December 2019

Significant advances are needed to optimize the charging speed, reliability, safety, and cost of today’s conservatively designed electric vehicle charging systems. The design and optimization of these novel engineering systems require concurrent consideration of thermal and electrical phenomena, as well as component- and system-level dynamics and control to guarantee reliable continuous operation, scalability, and minimum footprint. This work addresses the concurrent thermal and electrical design constraints in a high-density, on-board, bi-directional charger (referred to as power-hub) with vehicle-to-grid (V2G), grid-to-vehicle (G2V), vehicle-to-house (V2H) and vehicle-to-vehicle (V2V) power transfer capabilities. The electrical design of this charger consists of dc-dc and dc-ac power stages connected in series. The power-stage circuits are implemented on a Printed Circuit Board (PCB) with 16 surface-mount Silicon Carbide (SiC) MOSFETs, three inductors and one transformer. The main goal of this work is to investigate the interplay between the cooling architecture and the PCB layout, and the corresponding impact on the heat dissipation and parasitic inductance. This work compares the performance of three prototypes of this multifunctional charger using multi-physics simulations and experimental tests.
Design, Analysis and Comparison of Insulated Metal Substrates for High Power Wide-Bandgap Power Modules
Authors: Gurpinar Emre , Ozpineci Burak , Chowdhury Shajjad
Published: December 2019

In this technical paper, design, analysis and comparison of insulated metal substrates for high power wide-bandgap semiconductor-based power modules is discussed. The paper starts with technical description and discussion of state-of-the-art direct bonded copper substrates with different ceramic insulators such as AlN, Al2O3 and Si3N4. This is followed by introduction of insulated metal substrates, material properties and options on each layer, and design approach for high power applications. The properties of dielectric thickness, and impact on power handling capability of the substrate are discussed. Insulated metal substrate design approach for SiC MOSFET based power modules is presented. Finite element analysis-based characterization and comparison of different designs including steady-state and transient thermal response is presented. The results show that IMS is a promising alternative to DBC in high power modules with improved transient thermal performance. IMS provides flexible building structure with multi-layer stacking options and variable thicknesses at different layers.
Optimal Design and Modeling of Server Cabinets With In-Row Coolers and Air Conditioning Units in a Modular Data Center
Authors: Chowdhury Uschas , Hendrix Walter , Craft Thomas , James Willis , Sutaria Ankit , Agonafer Dereje
Published: December 2019

In a data center, electronic equipment such as server and switches dissipate heat and the corresponding cooling systems contribute to typically 25–35% of total energy consumption. The heat load continues to increase as there is a greater need for miniaturization and convergence. In 2014, data centers in the U.S. consumed an estimated 70 billion kWh, representing about 1.8% of total U.S. electricity consumption. Based on current trend estimates, U.S. data centers are projected to consume approximately 73 billion kWh in 2020 [1]. Many research and strategies are adopted to minimize energy cost. The recommended dry bulb temperature for long-term operation and reliability for air cooling is between 18–27°C and the largest allowable inlet temperature range to operate at is between 5°C and 45°C with American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) enabling much broader allowable zones) [2]. But understanding a proper cooling system is very important especially for thermal management of IT equipment with high heat loads such as 1U or 2U multi-core, high-end servers and blade servers which provide more computing per watt. Many problems like high inlet temperature due to the mixing of hot air with cold air, local hot spots, lower system reliability, increased failure, and downtime may occur. Among many other approaches to managing high-density racks, in-row coolers are used in between racks to provide cold air and minimize local hot spots. This paper describes a computational study being performed by applying in-row coolers for different rack power configuration with and without aisle containment. The power, as well as the number of racks, are varied to study the effect of raised inlet temperature for the IT equipment in a Computational Fluid Dynamics (CFD) model developed in 6SigmaRoom with the help of built-in library items. A comparative analysis is also performed for a typical small-sized non-raised facility to investigate the efficacy and limitations of in-row coolers in thermal management of IT equipment with variation in rack heat load and containment. Several other aspects like a parametric study of variable opening areas of duct between racks and in-row coolers, the variation of operating flow rate and failure scenarios are also studied to find proper flow distribution, uniformity of outlet temperature and predict better performance, energy savings and reliability. The results are presented for general guidance for flexible and quick installation and safe operation of in-row coolers to improve thermal efficiency.
Impact of Immersion Cooling on Thermo-Mechanical Properties of PCB’s and Reliability of Electronic Packages
Authors: Ramdas Shrinath , Rajmane Pavan , Chauhan Tushar , Misrak Abel , Agonafer Dereje
Published: December 2019

Immersion cooling is highly efficient thermal management technique and can potentially be used for thermal management of high-density data. However, to use this as a viable cooling technique, the effect of dielectric coolants on the reliability of server components needs to be evaluated. Previous work reported contradicting findings for Young’s modulus of PCBs, providing motivation for this work. This study focuses on effect of immersion cooling on the mechanical properties of printed circuit board (PCB) and its impact on reliability of electronic packages. Changes in thermo-mechanical properties like Young’s modulus (E), Glass transition temperature (Tg), of PCB and its layers due to aging in dielectric coolant are studied. Two types of PCBs using different material namely 370HR and 185HR are studied. To characterize Young’s modulus and Tg dynamic mechanical analyzer (DMA) is used. Major finding is Young’s modulus is decreasing for PCBs after immersion in dielectric coolant which is likely to increase reliability of electronics package.
Evolution of Anand Parameters With Elevated Temperature Aging for SAC Leadfree Alloys
Authors: Lall Pradeep , Yadav Vikas , Suhling Jeff , Locker David
Published: December 2019

Electronic components in downhole oil drilling and gas industry applications, automotive and avionics may exposed to high temperatures (> 150°C) and high strain rates (1–100 per sec) during storage, operation and handling which can contribute to the failures of electronics devices. Temperatures in these applications can exceed 200°C, which is closed to melting point for SAC alloys. The microstructure for lead free solder alloys constantly evolves when subjected to thermal aging for sustained periods with accompanying degradation in mechanical properties of solder alloys. In this paper, evolution of microstructure and Anand parameters for unaged and aged SAC (SAC105 and SAC-Q) lead free solder alloys at high strain rates has been investigated induced due to thermal aging. The microstructure of the SAC solder is studied using scanning electron microscopy (SEM) for different strain rate and elevating temperature. The thermal aged leadfree SAC solder alloys specimen has been tested at high strain rates (10–75 per sec) at elevated temperatures of (25°C–200°C). The SAC leadfree solder samples were subjected to isothermal aging at 50°C up to 1-year before testing. To describe the material constitutive behavior, Anand Viscoplastic model has been used. Effect of thermal aging on Anand parameters has been investigated. In order to verify the accuracy of the model, the computed Anand parameters have been used to simulate the uniaxial tensile test. FEA based method has been used to simulate the drop events using Anand constitutive model. Hysteresis loop and Plastic work density has been computed from FEA.
CFD Analysis of Thermal Shadowing and Optimization of Heatsinks in 3rd Generation Open Compute Server for Single-Phase Immersion Cooling
Authors: Shah Jimil M. , Dandamudi Ravya , Bhatt Chinmay , Rachamreddy Pranavi , Bansode Pratik , Agonafer Dereje
Published: December 2019

In today’s networking world, utilization of servers and data centers has been increasing significantly. Increasing demand of processing and storage of data causes a corresponding increase in power density of servers. The data center energy efficiency largely depends on thermal management of servers. Currently, air cooling is the most widely used thermal management technology in data centers. However, air cooling has started to reach its limits due to high-powered processors. To overcome these limitations of air cooling in data centers, liquid immersion cooling methods using different dielectric fluids can be a viable option. Thermal shadowing is an effect in which temperature of a cooling medium increases by carrying heat from one source and results in decreasing its heat carrying capacity due to reduction in the temperature difference between the maximum junction temperature of successive heat sink and incoming fluid. Thermal Shadowing is a challenge for both air and low velocity oil flow cooling. In this study, the impact of thermal shadowing in a third-generation open compute server using different dielectric fluids is compared. The heat sink is a critical part for cooling effectiveness at server level. This work also provides an efficient range of heat sinks with computational modelling of third generation open compute server. Optimization of heat sink can allow to cool high-power density servers effectively for single-phase immersion cooling applications. A parametric study is conducted, and significant savings in the volume of a heat sink have been reported.
Detection and assessment of hypernasality in repaired cleft palate speech using vocal tract and residual features
Authors: Dubey Akhilesh Kumar , Prasanna S. R. Mahadeva , Dandapat S.
Published: December 2019

The presence of hypernasality in repaired cleft palate (CP) speech is a consequence of velopharyngeal insufficiency. The coupling of the nasal tract with the oral tract adds nasal formant and antiformant pairs in the hypernasal speech spectrum. This addition deviates the spectral and linear prediction (LP) residual characteristics of hypernasal speech compared to normal speech. In this work, the vocal tract constriction feature, peak to side-lobe ratio feature, and spectral moment features augmented by low-order cepstral coefficients are used to capture the spectral and residual deviations for hypernasality detection. The first feature captures the lower-frequencies prominence in speech due to the presence of nasal formants, the second feature captures the undesirable signal components in the residual signal due to the nasal antiformants, and the third feature captures the information about formants and antiformants in the spectrum along with the spectral envelope. The combination of three features gives normal versus hypernasal speech detection accuracies of 87.76%, 91.13%, and 93.70% for /a/, /i/, and /u/ vowels, respectively, and hypernasality severity detection accuracies of 80.13% and 81.25% for /i/ and /u/ vowels, respectively. The speech data are collected from 30 control normal and 30 repaired CP children between the ages of 7 and 12.
Sound production mechanisms of audible nasal emission during the sibilant /s/
Authors: Sundström Elias , Oren Liran
Published: December 2019

Audible nasal emission is a speech disorder that involves undesired sound generated by airflow into the nasal cavity during production of oral sounds. This disorder is associated with small-to-medium sized velopharyngeal openings. These openings induce turbulence in the nasal cavity, which in turn produces sound. The purpose of this study is to examine the aeroacoustic mechanisms that generate turbulent sound during production of a sibilant /s/ with and without a small opening of the velopharyngeal valve. The models are based on two pediatric subjects who were diagnosed with severe audible nasal emission. The geometries were delineated from computed tomography scans taken while the subjects were sustaining a sibilant sound. Large eddy simulation with the Ffowcs Williams and Hawkings analogy was used to predict the flow behavior and its acoustic characterization. It shows that the majority of the acoustic energy is produced by surface loading, which is related to dipole sources that resonate in the nasal cavity. The quadrupole source term that is associated with the unsteady shear layers is seen to be less significant. It also shows that closure of the velopharyngeal valve changes the far-field spectrum significantly because aeroacoustic mechanisms in the nasal cavity are eliminated.
Lipopolysaccharide Stimulates the Growth of Bacteria That Contribute to Ruminal Acidosis
Authors: Dai Xiaoxia , Hackmann Timothy J. , Lobo Richard R. , Faciola Antonio P.
Published: December 2019

Gram-negative bacteria contain lipopolysaccharide (LPS) coating their thin peptidoglycan cell wall. The presence of LPS has been suggested to be associated with a metabolic disorder of cattle—ruminal acidosis—through affecting ruminal bacteria. Ruminal acidosis could reduce feed intake and milk production and increase the incidence of diarrhea, milk fat depression, liver abscesses, and laminitis. However, how LPS affects bacteria associated with ruminal acidosis has not been studied. In this study, we investigated how LPS affects the growth of ruminal bacteria by pure cultures, including those that contribute to acidosis, and the functional genes of ruminal bacteria. Thus, this work serves to further our understanding of the roles of LPS in the pathogenesis of ruminal acidosis, as well as providing information that may be useful for the prevention of ruminal acidosis and reducetion of economic losses for farmers.
Relationship between the Gut Microbiome and Energy/Nutrient Intake in a Confined Bioregenerative Life Support System
Authors: Chen Juanjuan , Wang Qi , Hao Zikai , Li Zhongxia , Sahu Sunil Kumar , Liu Hong , Xiao Liang
Published: December 2019

The gut microbiome shows individual specificity and is affected by sex, environment, and diet; gut microbiome imbalance is related to cancer, cardiovascular diseases, and autoimmune diseases. Astronauts are faced with a challenging environment and limited diet in outer space. Recent studies indicate that the gut microbiome is altered in space simulators and space, but what happens to intestinal microorganisms when astronauts cohabitate in a self-sufficient ecosystem in which they plant and cook food is unclear. Bioregenerative life support systems (BLSSs) are ideal devices to investigate the above issues because they are closed and self-sufficient. Four healthy Chinese subjects cohabitated in a confined BLSS for 60 days, during which their physical parameters and energy/nutrient intake were recorded. We performed a metagenome-wide association study (MWAS) on 55 shotgun-sequenced fecal samples longitudinally obtained from the subjects. Alterations occurred in the gut microbial composition and function, and their relationships with energy/nutrient intake were explored.
The Metabolite Repair Enzyme Phosphoglycolate Phosphatase Regulates Central Carbon Metabolism and Fosmidomycin Sensitivity in Plasmodium falciparum
Authors: Dumont Laure , Richardson Mark B. , van der Peet Phillip , Marapana Danushka S. , Triglia Tony , Dixon Matthew W. A. , Cowman Alan F. , Williams Spencer J. , Tilley Leann , McConville Malcolm J. , Cobbold Simon A.
Published: December 2019

The malaria parasite has a voracious appetite, requiring large amounts of glucose and nutrients for its rapid growth and proliferation inside human red blood cells. The host cell is resource rich, but this is a double-edged sword; nutrient excess can lead to undesirable metabolic reactions and harmful by-products. Here, we demonstrate that the parasite possesses a metabolite repair enzyme (PGP) that suppresses harmful metabolic by-products (via substrate dephosphorylation) and allows the parasite to maintain central carbon metabolism. Loss of PGP leads to the accumulation of two damaged metabolites and causes a domino effect of metabolic dysregulation. Accumulation of one damaged metabolite inhibits an essential enzyme in the pentose phosphate pathway, leading to substrate accumulation and secondary inhibition of glycolysis. This work highlights how the parasite coordinates metabolic flux by eliminating harmful metabolic by-products to ensure rapid proliferation in its resource-rich niche.
Integrative Activity of Mating Loci, Environmentally Responsive Genes, and Secondary Metabolism Pathways during Sexual Development of Chaetomium globosum
Authors: Wang Zheng , López-Giráldez Francesc , Wang Junrui , Trail Frances , Townsend Jeffrey P.
Published: December 2019

Fungal diversity has amazed evolutionary biologists for decades. One societally important aspect of this diversity manifests in traits that enable pathogenicity. The opportunistic pathogen
Chaetomium globosum
is well adapted to a high-humidity environment and produces numerous secondary metabolites that defend it from predation. Many of these chemicals can threaten human health. Understanding the phases of the
C. globosum
life cycle in which these products are made enables better control and even utilization of this fungus. Among its intriguing traits is that it both is self-fertile and lacks any means of propagule-based asexual reproduction. By profiling genome-wide gene expression across the process of sexual reproduction in
C. globosum
and comparing it to genome-wide gene expression in the model filamentous fungus
N. crassa
and other closely related fungi, we revealed associations among mating-type genes, sexual developmental genes, sexual incompatibility regulators, environmentally responsive genes, and secondary metabolic pathways.
Forming sulfate- and REE-rich fluids in the presence of quartz
Authors: Cui Hao , Zhong Richen , Xie Yuling , Yuan Xueyin , Liu Weihua , Brugger Joël , Yu Chang
Published: December 2019

The presence of sulfate-rich fluids in natural magmatic hydrothermal systems and some carbonatite-related rare earth element (REE) deposits is paradoxical, because sulfate salts are known for their retrograde solubility, implying that they should be insoluble in high-temperature geofluids. Here, we show that the presence of quartz can significantly change the dissolution behavior of Na2SO4, leading to the formation of extremely sulfate-rich fluids (at least 42.8 wt% Na2SO4) at temperatures >∼330 °C. The elevated Na2SO4 solubility results from prograde dissolution of immiscible sulfate melt, the water-saturated solidus of which decreases from ≥∼450 °C in the binary Na2SO4-H2O system to ∼270 °C in the presence of silica. This implies that sulfate-rich fluids should be common in quartz-saturated crustal environments. Furthermore, we found that the sulfate-rich fluid is a highly effective medium for Nd mobilization. Thermodynamic modeling predicts that sulfate ions are more effective in complexing REE(III) than chloride ions. This reinforces the idea that REEs can be transported as sulfate complexes in sulfate-rich fluids, providing an alternative to the current REE transport paradigm, wherein chloride complexing accounts for REE solubility in ore fluids.
How do undergraduate nursing students learn in the hospital setting? A scoping review of conceptualisations, operationalisations and learning activities
Authors: Stoffels Malou , Peerdeman Saskia M , Daelmans Hester E M , Ket Johannes C F , Kusurkar Rashmi A
Published: December 2019

Objectives

Although clinical learning is pivotal for nursing education, the learning process itself and the terminology to address this topic remain underexposed in the literature. This study aimed to examine how concepts equivalent to ‘learning in practice’ are used and operationalised and which learning activities are reported in the nursing education literature. The final aim was to propose terminology for future studies.

Design

The scoping framework proposed by Arksey and O’Malley was used to answer the research questions and address gaps in the literature. Two systematic searches were conducted in PubMed, EBSCO/ERIC and EBSCO/CINAHL between May and September 2018: first, to identify concepts equivalent to ‘learning in practice’ and, second, to find studies operationalising these concepts. Eligible articles were studies that examined the regular learning of undergraduate nursing students in the hospital setting. Conceptualisations, theoretical frameworks and operationalisations were mapped descriptively. Results relating to how students learn were synthesised using thematic analysis. Quality assessment was performed using the Critical Appraisal Skills Programme checklist.

Results

From 9360 abstracts, 17 articles were included. Five studies adopted a general, yet not explained, synonym for learning in practice, and the other approaches focused on the social, unplanned or active nature of learning. All studies used a qualitative approach. The small number of studies and medium study quality hampered a thorough comparison of concepts. The synthesis of results revealed five types of learning activities, acknowledged by an expert panel, in which autonomy, interactions and cognitive processing were central themes.

Conclusions

Both theoretical approaches and learning activities of the current body of research fit into experiential learning theories, which can be used to guide and improve future studies. Gaps in the literature include formal and informal components of learning, the relation between learning and learning outcomes and the interplay between behaviour and cognitive processing.
Simultaneous resection of the primary tumour and liver metastases after conversion chemotherapy versus standard therapy in pancreatic cancer with liver oligometastasis: protocol of a multicentre, prospective, randomised phase III control trial (CSPAC-1)
Authors: Wei Miaoyan , Shi Si , Hua Jie , Xu Jin , Yu Xianjun
Published: December 2019

Introduction

Approximately 50% of pancreatic ductal adenocarcinoma (PDAC) patients are diagnosed with distant metastasis, especially liver metastasis. The current standard treatment for these stage IV patients is palliative chemotherapy. There is increasing agreement that synchronous PDAC and liver metastasis resection may benefit highly selected patients. Thus, the Chinese Study Group for Pancreatic Cancer (CSPAC)−1 trial is being launched to establish a strategy for selecting PDAC patients with liver oligometastases who may benefit from synchronous resection after conversion chemotherapy.

Methods and analysis

In this study, liver oligometastasis is defined as no more than three metastatic lesions irrespective of their distribution within the liver lobes. The trial contains two steps. In the first step, 1000 to 1200 needle biopsy-confirmed PDAC patients with liver oligometastases are eligible for inclusion. Candidates will receive first-line chemotherapy. The RECIST V.1.1 criteria combined with tumour markers will be applied to evaluate the tumour response to chemotherapy every two cycles. Pancreatic cancer and hepatic metastasis resectability will be identified by multidisciplinary teams. Approximately 300 patients who meet our criteria will enter the second step and be randomly assigned at a 1:1 ratio to simultaneous resection of the primary pancreatic cancer lesion and liver oligometastases if no extensive metastatic sites are found during surgery or standard chemotherapy. Postoperative chemotherapy is recommended, and regimen selection should be based on the preoperative chemotherapy regimen. The primary endpoint is real overall survival (from enrolment to death). This study was activated in July 2018 and is expected to complete accrual within 5 years.

Ethics and dissemination

This trial has been approved by the Clinical Research Ethics Committee of Fudan University Shanghai Cancer Centre. Written informed consent will be obtained from all participants. Serious adverse events will be reported. Trial results will be submitted for peer-reviewed publication.

Trial registration number

NCT03398291; Pre-results.
Relationship between visual acuity and muscle mass in the Korean older population: a cross-sectional study using Korean National Health and Nutrition Examination Survey
Authors: Moon Ji Hyun , Oh Yun Hwan , Kong Mi Hee , Kim Hyeon Ju
Published: December 2019

Objectives

We aimed to assess the effects of visual acuity on muscle mass, which is an important indicator of health in older populations.

Design

Pooled-sample cross-sectional study.

Setting

Nationally representative population survey data.

Participants

The present study analysed men aged 65 years or older who participated in the Korea National Health and Nutrition Examination Survey (KNHANES, 2008–2011).

Primary and secondary outcome measures

Muscle mass was measured by dual-energy X-ray absorptiometry scan, and low muscle mass was defined as appendicular skeletal mass divided by height squared (kg/m2) <6.43 kg/m2 (lowest quintile of the older population in KNHANES, 2008–2011). Visual acuity was evaluated based on best-corrected visual acuity of the better eye.

Results

Of the 1733 participants, 89.9% had good visual acuity. After adjusting for age, the height-adjusted appendicular skeletal muscle mass values were 7.16 and 7.00 kg/m2 in the good and poor vision groups, respectively (p=0.042). According to our criterion for low muscle mass, the prevalence of low muscle mass was 16.4% and 34.7% in the good and poor vision groups, respectively. After adjusting for age, smoking status, alcohol consumption status, frequency of physical activity, educational level, the status of basic livelihood recipient and history of stroke, the poor visual acuity group had higher odds of low muscle mass than the good visual acuity group (OR=1.60; 95% CI 1.02 to 2.50; p=0.040).

Conclusions

Older men with decreased visual acuity have low muscle mass. Poor vision might be an indicator of low muscle mass.
Benzodiazepines for cancer dyspnoea: a nationwide survey of palliative care physicians
Authors: Matsuda Yoshinobu , Matsunuma Ryo , Suzuki Kozue , Mori Masanori , Watanabe Hiroaki , Yamaguchi Takashi
Published: December 2019

Objectives

It is unclear whether patients with non-specific dyspnoea are suitable candidates for studies investigating the effectiveness of benzodiazepines against dyspnoea. The objective of this survey was to investigate suitable subjects for studies of benzodiazepines for cancer dyspnoea.

Methods

A nationwide questionnaire survey was conducted among 536 Japanese-certified palliative care physicians. We randomly selected 268 physicians and inquired about their approach to dyspnoea management in patients with cancer, with and without anxiety, as follows: (1) Administration of a benzodiazepine. (2) Administration or titration of an opioid. We also asked them to consider their approach in the following situations: (1) Opioid-naïve. (2) Low-to-moderate baseline opioid dose. (3) High baseline opioid dose. We assessed the use of specific benzodiazepines separately.

Results

Overall, 192 physicians responded to the questionnaire (71.6%). For patients without anxiety, the proportion of participants reporting that they frequently or very frequently ‘administer a benzodiazepine’ increased with baseline opioid dose (opioid-naïve: 5.2%, low-to-moderate: 11.5%, high: 26.0%). The proportion of participants reporting that they frequently or very frequently ‘administer or titrate an opioid’ decreased with baseline opioid dose (opioid-naïve: 83.3%, low-to-moderate: 73.4%, high: 41.1%). The pattern was similar for patients with anxiety, although more respondents said they prescribe benzodiazepine for these patients (naïve: 22.4%, low-to-moderate: 34.4%, high: 45.8%) and fewer prescribed an opioid. Alprazolam and lorazepam are frequently used.

Conclusion

Patients with anxiety or receiving a high baseline opioid dose could be potential candidates for future studies investigating the effectiveness of benzodiazepines against cancer dyspnoea.
Discriminating hypothalamic oligomenorrhea/amenorrhea from hyperandrogenic oligomenorrhea/amenorrhea in exercising women
Authors: Koltun Kristen J. , Williams Nancy I. , Scheid Jennifer L. , De Souza Mary Jane
Published: December 2019

The mechanism underlying oligo/amenorrhea in exercising women is often presumed as hypothalamic inhibition secondary to energy deficiency; however, hyperandrogenism may provide an alternative mechanism in some exercising women. Our purpose was to compare reproductive, metabolic, and androgen profiles of exercising women with eumenorrheic, ovulatory menstrual cycles (n = 91), oligo/amenorrhea without evidence of hyperandrogenism (Oligo/Amen; n = 83), and oligo/amenorrhea with evidence of hyperandrogenism (Oligo/Amen-HA; n = 17), and determine the prevalence of oligo/amenorrhea with evidence of hyperandrogenism in exercising women. Self-reported menstrual history and quantification of daily estrogen and progesterone urinary metabolites determined reproductive status. Resting energy expenditure, body composition, and metabolic hormone concentrations determined metabolic status. Serum androgens and calculated free androgen index (FAI) determined androgen status. Groups were similar in age (22.4 ± 0.3 years), height (165.1 ± 0.5 cm), resting energy expenditure (1198.4 ± 12.0 kcal/day), and total triiodothyronine (85.0 ± 1.5 ng/dL) concentration. Oligo/Amen-HA had greater weight (60.0 ± 1.6, 56.1 ± 0.7 kg), body mass index (22.3 ± 0.4, 20.6 ± 0.2 kg/m2), percentage body fat (27.3% ± 1.4%, 24.4% ± 0.6%), fat mass (16.2 ± 1.0, 13.8 ± 0.4 kg), insulin (5.8 ± 0.7, 4.2 ± 0.3 μIU/mL), leptin (12.2 ± 2.3, 6.6 ± 0.7 ng/mL), FAI (6.1 ± 0.3, 1.7 ± 0.1), and luteinizing hormone/follicle-stimulating hormone (1.9 ± 0.3, 1.3 ± 0.2) compared with Oligo/Amen, respectively. In our sample, 17% of those with oligo/amenorrhea had concurrent hyperandrogenism. This study supports that oligo/amenorrhea in some exercising women is related to hyperandrogenism.

Novelty Caution must be utilized when discriminating hypothalamic oligo/amenorrhea from hyperandrogenic oligo/amenorrhea. In our sample, 17% of those with presumed hypothalamic oligo/amenorrhea had concurrent hyperandrogenism. Exercise and/or mild energy deficiency may be protective against developing severe hyperandrogenic symptoms.