bluuebunny/crossref_metadata_2025 huggingface dataset:
Swirling Flame Combustion of Heavy Fuel Oil: Effect of Fuel Sulfur Content
Authors: Pei Xinyan , Abdul Jameel Abdul Gani , Chen Chaoqin , AlGhamdi Ibrahim A. , AlAhmadi Kamal , AlBarakati Eid , Saxena Saumitra , Roberts William L.
Published: October 2020

In the present work, an experimental investigation on the effect of sulfur content in heavy fuel oil (HFO) on the gaseous emissions under swirling flame conditions was carried out. The sulfur content in HFO was varied by blending with ultra-low sulfur diesel and four fuel samples containing 3.15, 2.80, 1.97, and 0.52% sulfur (by mass) were prepared. Pure asphaltenes were added to the blends to ensure that the asphaltene content in the fuel remained the same. The fuels were then fired in a high-swirl stabilized, turbulent spray flame. The combustion performance of the fuels was evaluated by measuring flame temperature distribution, gaseous emissions (SOx, NOx, CO, CO2, and flue gas pH), and particulate matter (PM) emissions (morphology, composition, and pH). The results showed a significant reduction in the SO2 emissions and acidity of the flue gas when the sulfur content in the fuel was reduced, as expected. The reduction was more than would be expected based on sulfur content, however. For example, the flue gas SO2 concentration reduced from 620 ppm to 48 ppm when the sulfur content in the fuel was reduced from 3.15 to 0.52% (by mass). Sulfur balance calculations indicate that nearly 97.5% of the sulfur in the fuel translates into gaseous emissions and the remaining 2.5% appears in PM emissions. Ninety-five percent of the gaseous sulfur emissions are SO2, whereas the rest appears as SO3. Varying the sulfur content in the fuel did not have a major impact on the flame temperature distribution or NOx emissions. The morphologies and the size distribution of the PM also did not change significantly with the sulfur content as the asphaltenes content of the fuels remained the same.
Co-Simulation: Error Estimation and Macro-Step Size Control
Authors: Meyer T. , Kraft J. , Schweizer B.
Published: October 2020

Efficiency and accuracy of a co-simulation may considerably be increased by using a variable communication-time grid. Therefore, an error estimator for controlling the macro-step size is required. Here, error estimators are derived and investigated for explicit and implicit co-simulation approaches. The paper focuses on mechanical co-simulation models. The basic results may, however, also be applied to arbitrary, non-mechanical co-simulation models.
Heat Transfer in Composite Spheroids
Authors: Alassar Rajai
Published: October 2020

Heat transfer from a composite prolate spheroid under the third-type boundary condition is investigated using a Legendre series expansion. The model is verified against published data on cooling boiled eggs and also against the asymptotic solution of a composite sphere. The impact of Biot number on the heat transfer in spheroids with realistic dimensions and properties, such as eggs and olives, is investigated. The results are also presented for varying conductivity ratios and fractional volume of the inner part of the spheroid.
On the Steady-State Workpiece Flow Mechanism and Force Prediction Considering Piled-Up Effect and Dead Metal Zone Formation
Authors: Hu Cheng , Zhang Weiwei , Zhuang Kejia , Zhou Jinming , Ding Han
Published: October 2020

The manufacturing of miniaturized components is indispensable in modern industries, where the uncut chip thickness (UCT) inevitably falls into a comparable magnitude with the tool edge radius. Under such circumstances, the ploughing phenomenon between workpiece and tool becomes predominant, followed by the notable formation of dead metal zone (DMZ) and piled-up chip. Although extensive models have been developed, the critical material flow status in such microscale is still confusing and controversial. In this study, a novel material separation model is proposed for the demonstration of workpiece flow mechanism around the tool edge radius. First, four critical positions of workpiece material separation are determined, including three points characterizing the DMZ pattern and one inside considered as stagnation point. The normal and shear stresses as well as friction factors along the entire contact region are clarified based on slip-line theory. It is found that the friction coefficient varies symmetrically about the stagnation point inside DMZ and remains constant for the rest. Then, an analytical force prediction model is developed with Johnson–Cook constitutive model, involving calibrated functions of chip-tool contact length and cutting temperature. The assumed tribology condition and morphologies of material separation including DMZ are clearly observed and verified through various finite element (FE) simulations. Finally, comparisons of cutting forces from cutting experiments and predicted results are adopted for the validation of the predictive model.
Analytical and Numerical Prediction of Springback of SS/Al-Alloy Cladded Sheet in V-Bending
Authors: Sharma Pankaj Kumar , Gautam Vijay , Agrawal Atul Kumar
Published: October 2020

The present work deals with the development of an analytical model incorporating the effects of anisotropy and strain hardening to predict the springback in V-bending of two-ply sheet metal using a punch profile radius of 15 mm and included a bend angle of 90 deg. In the analytical model, the total bending moment is determined from resulting bending stresses for two different layers arranged in parallel planes one above the other and a new radius of curvature after springback is determined by applying a negative bending moment. The two-ply sheet composed of layers of AA1050 and SS430 is characterized for its tensile properties to be used in analytical and numerical models for prediction of springback. To study the effect of each layer during bending operation, two possible cases of sheet placements during bending and springback are studied; i.e., in the first case, the inner layer is of AA1050 while the SS430 layer is the outer layer whereas in the second case it is opposite. In all the cases of springback experiments when the outer layer is of SS430, the springback values are higher than the values obtained with the specimens when the inner layer is of SS430. This could be attributed to the higher tensile strength of the stainless steel layer and the higher bending radius experienced by it. The springback behaviors are also analyzed by simulations using Hill's anisotropic yield criterion in abaqus software. The springback results obtained by simulations and analytical models are in good agreement in general; however, in some cases, discrepancy of more than 15% is observed in the analytical results when compared with the experimental results.
Reliability Analysis and Random Vibration of Nonlinear Systems Using the Adjoint Method and Projected Differentiation
Authors: Papadimitriou Dimitrios , Mourelatos Zissimos P. , Hu Zhen
Published: October 2020

This paper proposes a new methodology for time-dependent reliability and random vibrations of nonlinear vibratory systems using a combination of a time-dependent adjoint variable (AV) method and a projected differentiation (PD) method. The proposed approach is called AV-PD. The vibratory system is excited by stationary Gaussian or non-Gaussian input random processes. A Karhunen–Loeve (KL) expansion expresses each input random process in terms of standard normal random variables. The nonlinear equations of motion (EOM) are linearized using a Taylor expansion using the first-order derivatives of the output with respect to the input KL random variables. An adjoint approach obtains the output derivatives accurately and efficiently requiring the solution of as many sets of EOM as the number of outputs of interest, independently of the number of KL random variables. The proposed PD method then computes the autocorrelation function of each output process at an additional cost of solving as many sets of EOM as the number of outputs of interest, independently of the time horizon (simulation time). A time-dependent reliability analysis is finally performed using a KL expansion of the output processes and Monte Carlo simulation (MCS). The number of solutions of the EOM scales only with the number of output random processes which is commonly much smaller than the number of input KL random variables. The efficiency and accuracy of the proposed approach is demonstrated using a four degree-of-freedom (DOF) half-car vibratory problem.
A Dynamically Balanced Kinematically Redundant Planar Parallel Robot
Authors: Baron Nicholas , Philippides Andrew , Rojas Nicolas
Published: October 2020

A dynamically balanced robotic manipulator does not exert forces or moments onto the base on which it is fixed; this can be important for the performance of parallel robots as they are able to move at very high speeds, albeit usually have a reduced workspace. In recent years, kinematically redundant architectures have been proposed to mitigate the workspace limitations of parallel manipulators and increase their rotational capabilities; however, dynamically balanced versions of these architectures have not yet been presented. In this paper, a dynamically balanced kinematically redundant planar parallel architecture is introduced. The manipulator is composed of parallelogram linkages that reduce the number of counter rotary elements required to moment balance the mechanism. The balancing conditions are derived, and the balancing parameters are optimized using Lagrange multipliers, such that the total mass and inertia of the system is minimized. The elimination of the shaking forces and moments is then verified via a simulation in the multi-body dynamic simulation software msc adams.
Development of a Multi-Cable-Driven Continuum Robot Controlled by Parallel Platforms
Authors: Chen Xinbo , Yao Jiantao , Li Tong , Li Haili , Zhou Pan , Xu Yundou , Zhao Yongsheng
Published: October 2020

Cable-driven continuum robots exhibit excellent capabilities in the unstructured environment due to their inherent compliance and dexterity. To improve the reliability and load capacity of continuum robots, increasing the number of cables is often used in the control of continuum robots. However, the number of actuators will increase with the cables. To tackle this challenge, this work proposes a method for increasing the number of cables without increasing actuators in a continuum robot through parallel platforms. The parallel platforms are used to control all the cables in the continuum robot and can be separated from the continuum robot to enable the remote drive of a manipulation arm by using the cable-tube structure. The manipulation arm is composed of several independent bending modules in series, which can be configured freely according to the demand of degrees-of-freedom. Further, each bending module is controlled independently by a parallel platform, which can avoid the mutual interference between the cables of one bending module and another one, improve the position accuracy and simplify the control difficulty of the manipulation arm. To evaluate the proposed method, this work develops a prototype of six-cable-driven continuum robot controlled by 3RPS parallel platforms and presents some basic kinematic models to describe its function, and then an experimental work characterizing its performance. Experimental results illustrated the importance of increasing the number of cables, the rationality of kinematic models of the continuum robot, and the feasibility of controlling multiple cables by a parallel platform.
Analysis of Burnett Stresses and Entropy Generation for Pressure-Driven Plane Poiseuille Flow
Authors: Yadav Upendra , Agrawal Amit
Published: October 2020

In this paper, we undertake an analytical study of stresses (augmented and Onsager–Burnett) and entropy generation for the plane Poiseuille flow problem, and their variation with Knudsen number. The gas flow is assumed to be 2D laminar, fully developed, compressible, and isothermal; these assumptions make the problem amenable to analytical treatment. The variation of stresses and entropy generation has been analyzed over a large range of Knudsen number. The magnitude of stresses and entropy generation at a particular position in the channel has been considered. It is found that the augmented and OBurnett normal stresses are of opposite signs to the corresponding Navier–Stokes stresses, while the magnitude of the net normal stress increases with Knudsen number. The magnitude of the augmented Burnett shear stress is insignificant as compared to the augmented Burnett normal stresses. A close match between the augmented and OBurnett normal stresses has been found at low Knudsen number. However, an opposite variation has been observed between the augmented and Onsager shear stresses at high Knudsen number. A good comparison of the normalized mass flow rate with the reported value in the literature helps to validate our analysis. A minimum in the variation of normalized entropy generation against the Knudsen number (Kn) is observed at Kn close to unity, and is being reported for the first time. The magnitude of net entropy generation from the summation of Navier–Stokes and augmented Burnett stresses is found to be positive, even in the transition regime of gas flow. Further, an appearance of minimum or maximum in normalized net shear stress versus Knudsen number, depending upon the lateral position in the microchannel, has also been observed. Altogether, this analysis supports the validity of the Navier–Stokes equation with modified constitutive expression, even for higher Knudsen numbers. Moreover, the significant terms of Burnett stress are pointed out by the analysis, which can help in developing reduced-order model for these equations.
Experimental and Numerical Analysis of Gas Premix Turbulent Flames Stabilized in a Swirl Burner With Central Bluff Body
Authors: Biagioli Fernando , Innocenti Alessandro , Terhaar Steffen , Marchione Teresa
Published: October 2020

Lean premixed gas turbulent flames stabilized in the flow generated by an industrial swirl burner with a central bluff body are experimentally found to behave bistable. This bistable behavior, which can be triggered via a small change in some of the controlling parameters, for example, the bulk equivalence ratio, consists in a rather sudden transition of the flame from completely lifted to well attached to the bluff body. This has impact on combustion dynamics, emissions, and pressure losses. While several experimental investigations exist on this topic, numerical analysis is limited. This work is therefore also of numerical nature, with a twofold scope: (a) simulation and validation with experiments of the bistable flame behavior via computational fluid dynamics (CFD) in the form of large eddy simulation (LES) and (b) analysis of CFD results to shed light on the flame stabilization properties. LES results, in case of the lifted flame, show that the vortex core is sharply precessing at a given frequency. Phase averaging these results at the frequency of precession clearly indicates a counterintuitive and unexpected presence of reverse flow going all the way through the flame apex and the bluff body tip. The counterintuitive presence of a lifted flame is explained here in terms of the phase averaged data, which show that the flame apex is not placed at the center of the spinning reverse flow region. It is instead slightly shifted radially outward where the axial velocity recovers to low positive values of the order of the turbulent burning rate. A simple one-dimensional flame stabilization model is applied to explain this peculiar flame behavior. This model provides first an estimation of the flame radius of curvature in terms of axial velocity and turbulence quantities. This radius is therefore used to determine the total flux of reactants into the flame, given by an axial convection and radial diffusion contributions. Subsequently, the possibility of the flame positioned at the center of the vortex is excluded based on the balance between this flux and the turbulent burning rate. A clear explanation of the mechanism leading to the sudden flame jump has instead not been identified and only some hypotheses are provided.
Aero Engine Concepts Beyond 2030: Part 1—The Steam Injecting and Recovering Aero Engine
Authors: Schmitz Oliver , Klingels Hermann , Kufner Petra
Published: October 2020

Recognizing the attention currently devoted to the environmental impact of aviation, this three-part publication series introduces two new aircraft propulsion concepts for the timeframe beyond 2030. This first part focuses on the steam injecting and recovering aero engine (SIRA) concept. Exhaust heat generated steam is injected into the combustion chamber. By use of a condenser, installed behind the steam generator, the water is recovered from the exhaust gas–steam mixture. Both lead to a noticeable increase in specific power compared to a conventional gas turbine and, foremost, to a significant increase in thermodynamic efficiency. The proposed concept is expected to reduce fuel burn and carbon dioxide (CO2) emissions by about 15% and nitrogen oxides (NOx) formation can be almost completely avoided compared to state-of-the-art engines of the same technology level. Moreover, the described concept has the potential to drastically reduce or even avoid the formation of condensation trails. Thus, the SIRA concept operated with sustainable aviation fuels offers the potential for climate-neutral aviation. Based on consistent thermodynamic descriptions, preliminary designs and initial performance studies, the potentials of the concepts are analyzed. Complementarily, a detailed discussion on concrete engineering solutions considers the implementation into aircraft. Finally, the impact on emissions is outlined.
Resolving self-limiting growth in silicon nitride plasma enhanced atomic layer deposition with tris-dimethylamino silane precursor
Authors: Muneshwar Triratna , Cadien Ken
Published: October 2020

Self-limiting character of the involved surface reactions is essential for highly uniform and conformal growth in atomic layer deposition (ALD). However, the poor conformal coverage (<75%) that is often reported with silicon nitride (SiNx) plasma enhanced ALD (PEALD) processes using metalorganic Si-precursors is confounding. In this article, we report our study of the SiNx PEALD process using the tris-dimethylamino silane (3DMAS) precursor and forming gas (5% H2–95% N2) reactant plasma. For the substrate temperature (Tsub) range of 50 °C ≤ Tsub ≤ 150 °C, growth per cycle (GPC) for SiNx deposition was found to approach saturation at 0.034 ± 0.001 nm/cycle though higher Tsub required longer 3DMAS exposures (tA) for saturation. However, for Tsub > 150 °C, SiNx GPC was seen to increase with tA, indicating nonself-limiting growth from potential chemical vapor deposition-like side reactions emerging at higher temperatures. The refractive index (n) of 2.097 ± 0.003 at 2 eV with an optical bandgap of ∼1.7 eV determined from in situ spectroscopic ellipsometry measurements, and peaks s1 and n1 with ΔBE = 295.42 eV in Si2p and N1s XPS spectra measured on the capped SiNx sample were found to agree with the optical constants and chemical characteristics reported for the silicon nitride material. SiNx films deposited at Tsub = 250 °C (nonself-limiting) were found to be more resistant to ambient oxidation as compared to SiNx PEALD films grown at Tsub = 100 °C. Although an entire 30 nm thick SiNx PEALD film was oxidized after an unavoidable long ambient exposure, a cross-sectional transmission electron microscope image showed a conformal coverage of 95%–98% in a 3D trench structure with an aspect ratio of 4.5. Furthermore, higher resistance to ambient oxidation in plasma treated of SiNx PEALD films demonstrates a potential of postgrowth treatments to improve desirable material properties without resorting to high-temperature processes.
Reliability of Change-of-Direction Economy in Soccer Players
Authors: Dolci Filippo , Kilding Andrew E. , Spiteri Tania , Chivers Paola , Piggott Ben , Maiorana Andrew , Hart Nicolas H.
Published: October 2020

Purpose: To evaluate the reliability of new change-of-direction-economy tests (assessing energetic efficiency when performing continuous shuttle runs) compared with common running-economy tests in soccer players Methods: Sixteen subelite, male soccer players were recruited to perform a testing battery involving running economy (RE), 10-m shuttle-running economy (SRE10), and 20-m shuttle-running economy (SRE20) at 8.4 km·h−1 mean speed on 2 different days within 48 hours. SRE10 and SRE20 consisted of continuous shuttle runs interspersed with 180° directional changes. During the RE, SRE20, and SRE10 tests, respiratory exchange ratio and oxygen uptake were collected and used to calculate the movement-economy values over any running condition as oxygen cost and energetic cost. The secondary variables (carbon dioxide production, heart rate, minute ventilation, and blood lactate) were also monitored during all tests. Results: Depending on expression (oxygen cost or energetic cost), reliability was established for RE (CV: 5.5%–5.8%; ICC = .77–.88), SRE10 (CV: 3.5%–3.8%; ICC = .78–.96), and SRE20 (CV: 3.5%–3.8%; ICC = .66–.94). All secondary physiological variables reported good reliability (CV < 10%), except for blood lactate (CV < 35.8). The RE, SRE10, and SRE20 tests show good reliability in soccer players, whereas blood lactate has the highest variability among physiological variables during the economy tests. Conclusion: The assessment of change-of-direction economy through performing 20- and 10-m shuttle runs is reliable and can be applied to evaluate soccer players’ energetic movement efficiency under more soccer-specific running conditions.
Is There a Decrease in the Acromiohumeral Distance Among Recreational Overhead Athletes With Rotator Cuff–Related Shoulder Pain?
Authors: de Oliveira Fábio Carlos Lucas , Ager Amanda L. , Roy Jean-Sébastien
Published: October 2020

Context:Recreational overhead athletes are exposed to high overload, which increases the risk of shoulder injuries. Reduction of the acromiohumeral distance (AHD) is often associated with rotator cuff–related shoulder pain (RCRSP) among the general population. However, the AHD of symptomatic shoulders of recreational athletes has not yet been compared with their asymptomatic shoulders.Objective:To compare the AHD of a symptomatic to asymptomatic shoulder at rest (0°) and 60° abduction. To establish the relationship between AHD, pain, and functional limitations of recreational athletes with RCRSP.Design:Cross-sectional study.Setting:University laboratory.Participants:A total of 45 recreational overhead athletes with RCRSP were examined.Main Outcome Measures:The AHD was measured by ultrasonography at 0° and 60° abduction (angles). Shoulder pain was assessed using a numeric pain scale, whereas functional limitations were assessed using the The Disabilities of the Arm, Shoulder, and Hand questionnaire. Differences in the between-shoulders condition (symptomatic and asymptomatic) were determined using 2-way analysis of variance for repeated measures. A Pearson correlation established the relationship between AHD, pain, and functional limitations.Results:No angles × shoulder condition interactions (P = .776) nor shoulder condition effects (P = .087) were detected, suggesting no significant differences (P > .05) between asymptomatic and symptomatic shoulders in the AHD at 0° or 60°. The AHD at 60° reduced significantly compared with 0° (3.05 [1.36] mm [2.77–3.33], angle effects:P < .001). The AHD at 0° and 60° was not correlated with pain or functional limitations (−.205 ≤ r ≤ .210, .167 ≤ P ≤ .585).Conclusions:The AHD of recreational athletes is not decreased in symptomatic shoulders compared with asymptomatic shoulders. Reduction of the AHD in symptomatic shoulders is not associated with an increase in pain or functional limitations of recreational athletes with RCRSP.
U.S. funds new fleet of probes to explore ocean biogeochemistry
Authors: Voosen Paul
Published: October 2020

Drifting Argo floats will track oxygen loss from global warming and the oceans' ability to soak up carbon.
How an immunologist pivoted to tackle COVID-19
Authors: Couzin-Frankel Jennifer
Published: October 2020

For Akiko Iwasaki, the pandemic has brought new research priorities—and new urgency.
Physical traits of cancer
Authors: Nia Hadi T. , Munn Lance L. , Jain Rakesh K.
Published: October 2020

Physical traits of cancer

The biological and physical properties of tumors contribute to their growth and to treatment outcome. Although intense research efforts have helped to delineate cancer biology, the physics of cancer has only emerged in relatively recent times as a key area of research. Nia
et al.
reviewed the physical features that are common to tumors and that limit successful treatment: solid stresses, interstitial fluid pressure, stiffness (rigidity), and architecture and organization of tumor constituents. The authors provide a conceptual framework and discuss the origins of these distinct physical traits of cancer and how they enable and synergize with aberrant cancer biology to fuel cancer initiation, progression, immune evasion, and treatment resistance.

Science
, this issue p.
eaaz0868
Receptor kinase module targets PIN-dependent auxin transport during canalization
Authors: Hajný Jakub , Prát Tomáš , Rydza Nikola , Rodriguez Lesia , Tan Shutang , Verstraeten Inge , Domjan David , Mazur Ewa , Smakowska-Luzan Elwira , Smet Wouter , Mor Eliana , Nolf Jonah , Yang BaoJun , Grunewald Wim , Molnár Gergely , Belkhadir Youssef , De Rybel Bert , Friml Jiří
Published: October 2020

Hormone-guided self-organization

Auxin signals travel through pathways in developing or regenerating plant tissues to guide tissue formation. Hajný
et al.
now show that an auxin-regulated receptor in turn regulates phosphorylation and thus subcellular localization of an auxin transporter. Through this signaling pathway, auxin builds the pathways through which it is transported, guiding development as it goes.

Science
, this issue p.
550
A complex phenotype in salmon controlled by a simple change in migratory timing
Authors: Thompson Neil F. , Anderson Eric C. , Clemento Anthony J. , Campbell Matthew A. , Pearse Devon E. , Hearsey James W. , Kinziger Andrew P. , Garza John Carlos
Published: October 2020

Unexpectedly simple

Chinook salmon are known to return to spawn at two distinct times of the year: spring and fall. Individuals that return during these times have generally been referred to as parts of distinct groups, or ecotypes, with traits specific to their timing and presumed divergence being caused by the lack of interbreeding. By looking at genomes across fish from both runs, Thompsonet al.found that a single genomic region of interest was nearly perfectly associated with run timing but not with other traits such as maturity and fat reserves (see the Perspective by McKinney). Further, they conclude that the region operates as a Mendelian trait, with assortment dictating run timing and associated phenotypes being caused by the migration environment rather than genetics.

Science, this issue p.609; see also p.526
Political sectarianism in America
Authors: Finkel Eli J. , Bail Christopher A. , Cikara Mina , Ditto Peter H. , Iyengar Shanto , Klar Samara , Mason Lilliana , McGrath Mary C. , Nyhan Brendan , Rand David G. , Skitka Linda J. , Tucker Joshua A. , Van Bavel Jay J. , Wang Cynthia S. , Druckman James N.
Published: October 2020

A poisonous cocktail of othering, aversion, and moralization poses a threat to democracy
Of dogs and men
Authors: Pavlidis Pavlos , Somel Mehmet
Published: October 2020

Ancient genomes reveal the common history of human and dog
Evolution of Colistin Resistance in the Klebsiella pneumoniae Complex Follows Multiple Evolutionary Trajectories with Variable Effects on Fitness and Virulence Characteristics
Authors: Janssen Axel B. , Doorduijn Dennis J. , Mills Grant , Rogers Malbert R. C. , Bonten Marc J. M. , Rooijakkers Suzan H. M. , Willems Rob J. L. , Bengoechea Jose A. , van Schaik Willem
Published: October 2020

The increasing prevalence of multidrug-resistant
Klebsiella pneumoniae
has led to a resurgence in the use of colistin as a last-resort drug. Colistin is a cationic antibiotic that selectively acts on Gram-negative bacteria through electrostatic interactions with anionic phosphate groups of the lipid A moiety of lipopolysaccharides (LPSs). Colistin resistance in
K. pneumoniae
is mediated through loss of these phosphate groups, their modification by cationic groups, and by the hydroxylation of acyl groups of lipid A.
Molecular Evidence for an Active Microbial Methane Cycle in Subsurface Serpentinite-Hosted Groundwaters in the Samail Ophiolite, Oman
Authors: Kraus Emily A. , Nothaft Daniel , Stamps Blake W. , Rempfert Kaitlin R. , Ellison Eric T. , Matter Juerg M. , Templeton Alexis S. , Boyd Eric S. , Spear John R.
Published: October 2020

Serpentinization of ultramafic rock can generate conditions favorable for microbial methane (CH
4
) cycling, including the abiotic production of hydrogen (H
2
) and possibly CH
4
. Systems of low-temperature serpentinization are geobiological targets due to their potential to harbor microbial life and ubiquity throughout Earth’s history. Biomass in fracture waters collected from the Samail Ophiolite of Oman, a system undergoing modern serpentinization, yielded DNA and RNA signatures indicative of active microbial methanogenesis and methanotrophy. Intriguingly, transcripts for proteins involved in methanogenesis were most abundant in the most highly reacted waters that have hyperalkaline pH and elevated concentrations of H
2
and CH
4
. These findings suggest active biological methane cycling in serpentinite-hosted aquifers, even under extreme conditions of high pH and carbon limitation. These observations underscore the potential for microbial activity to influence the isotopic composition of CH
4
in these systems, which is information that could help in identifying biosignatures of microbial activity on other planets.
Human Noroviruses Attach to Intestinal Tissues of a Broad Range of Animal Species
Authors: Villabruna Nele , Schapendonk Claudia M. E. , Aron Georgina I. , Koopmans Marion P. G. , de Graaf Miranda
Published: October 2020

Noroviruses are a major cause of acute gastroenteritis in humans. New norovirus variants and recombinants (re)emerge regularly in the human population. From animal experiments and surveillance studies, it has become clear that at least seven animal models are susceptible to infection with human strains and that domesticated and wild animals shed human noroviruses in their feces. As virus attachment is an important first step for infection, we used a novel method utilizing FITC-labeled VLPs to test for norovirus attachment to intestinal tissues of potential animal hosts. We further characterized these tissues with regard to their HBGA expression, a well-studied norovirus susceptibility factor in humans. We found attachment of several human strains to a variety of animal species independent of their HBGA phenotype. This supports the hypothesis that human strains could reside in an animal reservoir.
Clumped isotope thermometry of modern and fossil snail shells from the Himalayan-Tibetan Plateau: Implications for paleoclimate and paleoelevation reconstructions
Authors: Wang Yang , Passey Benjamin , Roy Rupsa , Deng Tao , Jiang Shijun , Hannold Chance , Wang Xiaoming , Lochner Eric , Tripati Aradhna
Published: October 2020

Carbonate clumped isotope thermometry has been applied to fossil mollusk shells from Tibet to reconstruct the paleoclimate and paleoelevation of the region. However, inferred paleoelevation and climatic conditions from this proxy are inconsistent with paleontological evidence. Here, we report new clumped isotope data from both modern and fossil (5–4 Ma) freshwater mollusk shells with the results of X-ray diffraction (XRD) analyses of fossil shells from the Himalayan-Tibetan Plateau. Although all of the fossil shells analyzed in this study appeared pristine based on visual inspection, XRD data reveal that more than half of these apparently “pristine” fossil shells contain trace amounts of calcite. Clumped isotope temperatures derived from the fossil shells display a large range of variation (>22 °C). Among the fossil shells analyzed, those containing traces of calcite have yielded temperatures that are on average ∼10 °C lower than those with no detectable calcite from the same strata. These observations suggest that clumped isotope alteration can occur in aragonite shells in low-temperature environments and even in shells with no visible signs of alteration that contain only traces of calcite. The temperatures derived from fossil shells with no detectable calcite are on average 4 °C higher than those derived from modern shells, indicating that southwest Tibet was warmer 4–5 Ma than today. After accounting for temperature change due to global cooling, the difference in clumped isotope temperatures between pristine fossil shells and modern shells suggests that the paleoelevation of the southwestern Tibetan Plateau in the Pliocene was similar to its present-day elevation.
Clear cell chondrosarcoma of proximal femur: a rare entity with diagnostic dilemma
Authors: Pruthi Manish , Virk Jagandeep Singh , Sharma Anila , Mahawar Vivek
Published: October 2020

Clear cell chondrosarcoma is an extremely rare malignant neoplasm. The rarity and slow-growing nature of this tumour often lead to prolonged symptoms and also initial misdiagnosis with benign lesions such as chondroblastoma. It can also be confused with avascular necrosis of the femoral head when the lesion is located in the femoral head, as was in the case we report. The patient was kept on observation and conservative treatment for almost 9 years before the correct diagnosis and appropriate treatment. Wide local resection with negative margins forms the mainstay of treatment since intralesional procedures predispose to high local recurrence rate. A prolonged follow-up is recommended since late local recurrences and metastases are common.
Treatments and outcomes of untreated cerebral cavernous malformations in China: study protocol of a nationwide multicentre prospective cohort study
Authors: Lin Fuxin , He Qiu , Gao Zhuyu , Yu Lianghong , Wang Dengliang , Zheng Shufa , Lin Yuanxiang , Kang Dezhi
Published: October 2020

Introduction

The treatment decision and long-term outcomes of previously untreated cerebral cavernous malformation (U-CCM) are still controversial. Therefore, we are conducting a nationwide multicentre prospective registry study in China to determine the natural history and effect of surgical treatment on long-term outcomes in Chinese people with U-CCM.

Methods and analysis

This study was started on 1 January 2018 and is currently ongoing. It is a cohort follow-up study across a 5-year period. Patients will be followed up for at least 3 years after inception. Patients with U-CCM will be enrolled from 24 Grade III, level A hospitals distributed all over China. The cohort size is estimated to be 1200 patients. Patients are registered in surgically treated group and conservatively treated group. Clinical characteristics, radiology information and laboratory data are prospectively collected using an electronic case report form through an electronic data capture system. The primary outcome of this study is poor clinical outcome at the last follow-up (modified Rankin Scale score >2 lasting at least 1 year). The secondary outcome includes symptomatic haemorrhage, drug refractory epilepsy, focal neurological deficits, morbidity and all-cause mortality during follow-up. Univariate and multivariate regression analysis will be performed to determine the risk factors for poor outcomes in all patients, and to estimate the effect of surgery. Life tables, Kaplan-Meier estimates, log-rank test and proportional hazards Cox regression will be used to analyse the follow-up data of conservatively treated patients to determine the natural history of U-CCM. Initial presentation and location of U-CCM are prespecified subgroup factors.

Ethics and dissemination

The study protocol and informed consent form have been reviewed and approved by the Research Ethical Committee of First Affiliated Hospital of Fujian Medical University (FAHFMU-2018-003).

Written informed consent will be obtained from each adult participant or from the guardian of each paediatric participant. The final results will be published in peer-reviewed journals.

Trial registration number

NCT03467295.
Standard echocardiography versus handheld echocardiography for the detection of subclinical rheumatic heart disease: a systematic review and meta-analysis of diagnostic accuracy
Authors: Telford Lisa Helen , Abdullahi Leila Hussein , Ochodo Eleanor Atieno , Zuhlke Liesl Joanna , Engel Mark Emmanuel
Published: October 2020

Objective

To summarise the accuracy of handheld echocardiography (HAND) which, if shown to be sufficiently similar to that of standard echocardiography (STAND), could usher in a new age of rheumatic heart disease (RHD) screening in endemic areas.

Design

Systematic review and meta-analysis.

Data sources

PubMed, Scopus, EBSCOHost and ISI Web of Science were initially searched on 27 September 2017 and again on 3 March 2020 for studies published from 2012 onwards.

Eligibility criteria

Studies assessing the accuracy of HAND compared with STAND when performed by an experienced cardiologist in conjunction with the 2012 World Heart Federation criteria among populations of children and adolescents living in endemic areas were included.

Data extraction and synthesis

Two reviewers independently extracted data and assessed the methodological quality of included studies against review-specific Quality Assessment of Diagnostic Accuracy Studies (QUADAS)-2 criteria. A meta-analysis using the hierarchical summary receiver operating characteristic model was conducted to produce summary results of sensitivity and specificity. Forest plots and scatter plots in receiver operating characteristic space in combination with subgroup analyses were used to investigate heterogeneity. Publication bias was not investigated.

Results

Six studies (N=4208) were included in the analysis. For any RHD detection, the pooled results from six studies were as follows: sensitivity: 81.56% (95% CI 76.52% to 86.61%) and specificity: 89.75% (84.48% to 95.01%). Meta-analytical results from five of the six included studies were as follows: sensitivity: 91.06% (80.46% to 100%) and specificity: 91.96% (85.57% to 98.36%) for the detection of definite RHD only and sensitivity: 62.01% (31.80% to 92.22%) and specificity: 82.33% (65.15% to 99.52%) for the detection of borderline RHD only.

Conclusions

HAND displayed good accuracy for detecting definite RHD only and modest accuracy for detecting any RHD but demonstrated poor accuracy for the detection of borderline RHD alone. Findings from this review provide some evidence for the potential of HAND to increase access to echocardiographic screening for RHD in resource-limited and remote settings; however, further research into feasibility and cost-effectiveness of wide-scale screening is still needed.

PROSPERO registration number

CRD42016051261.
Association between medical students’ prior experiences and perceptions of formal online education developed in response to COVID-19: a cross-sectional study in China
Authors: Wang Cixiao , Xie A’na , Wang Weimin , Wu Hongbin
Published: October 2020

Objectives

(1) Understanding the characteristics of online learning experiences of Chinese undergraduate medical students; (2) Investigating students’ perceptions of ongoing online education developed in response to COVID-19 and (3) Exploring how prior online learning experiences are associated with students’ perceptions.

Design

Students’ familiarity with online learning modes and corresponding perceived usefulness (PU) according to their previous experiences were investigated using an online survey. The survey also collected data on students’ perceptions through their evaluation of and satisfaction with current online learning.

Setting

In response to the educational challenges created by COVID-19, medical schools in China have adopted formal online courses for students.

Participants

The questionnaire was sent to 225 329 students, of whom 52.38% (118 080/225 329) replied, with valid data available for 44.18% (99 559/225 329).

Methods

Pearson correlations and t-tests were used to examine the relationship between familiarity and PU. Multiple linear regression and logistic regression analyses were used to determine the impact of prior learning experiences and its interactions with gender, area, learning phase and academic performance on students’ perceptions.

Results

Students’ PU had a significant positive correlation with their familiarity with online learning modes (p<0.01). Students’ evaluation of and satisfaction with their current online education were positively associated with their familiarity (β=0.46, 95% CI 0.45 to 0.48, p<0.01; OR 1.14, 95% CI 1.13 to 1.14, p<0.01) with and PU (β=3.11, 95% CI 2.92 to 3.30, p<0.01; OR 2.55, 95% CI 2.37 to 2.75, p<0.01) of online learning. Moreover, the higher the students’ learning phases, the lower the associations between PU and students’ evaluation of and satisfaction with ongoing online education.

Conclusions

Medical students in China have experiences with various online learning modes. Prior learning experiences are positively associated with students’ evaluation of and satisfaction with current online education. Higher learning phases, in which clinical practices are crucial, and high academic performance led to lower evaluation and satisfaction scores.
Addition of aprepitant improves acute emesis control in children and adolescents receiving induction chemotherapy for acute myeloid leukaemia: a randomised, open-label trial
Authors: Sharma Atul , Ganguly Shuvadeep , C Santosh Kumar , Pillai Ashwati S , Dhawan Deepa , Sreenivas Vishnubhatla , Bakhshi Sameer
Published: October 2020

Objectives

More than 50% patients develop emesis during induction therapy for acute myeloid leukaemia (AML). The addition of aprepitant for emesis control in children receiving induction for AML have not been explored.

Methods

A single-institutional randomised, open-label trial (NCT02979548) was conducted where children between 5 and 18 years with the diagnosis of AML being planned for 3+7 induction regimen were included. All study participants received ondansetron (0.15 mg/kg) every 8 hours for 8 days starting 30 min prior to chemotherapy. Children belonging to aprepitant group additionally received aprepitant capsules (15–40 kg=days 1–3, 80 mg; >40 kg=day 1, 125 mg and days 2–3, 80 mg) starting from 1 hour prior to chemotherapy. The proportion of patients with complete response (CR) in chemotherapy induced vomiting (CIV) in acute phase (day 1–8), delayed phase (day 9–13), overall and initial 96 hours were recorded along with severity of vomiting and adverse effects.

Results

Total 78 children were randomised (Aprepitant group: 37 and control group: 41). The proportion of patients with CR in CIV was significantly higher in Aprepitant group in acute phase (p=0.007), overall phase (p=0.007) and in initial 96 hours (p<0.001) but it was not different in delayed phase (p=0.07). The first episode of vomiting was also significantly delayed in aprepitant group (p=0.02). Adverse effect profile was similar in two groups.

Conclusion

Aprepitant significantly improves emesis control in children receiving induction therapy for AML, especially in acute phase and should be routinely incorporated as part of antiemetic prophylaxis.

Trial registration number

The study was registered at ClinicalTrials.gov (NCT02979548).
Diagnostic performance of morning serum cortisol as an alternative to short synacthen test for the assessment of adrenal reserve; a retrospective study
Authors: Kumar Rajeev , Carr Peter , Wassif Ws
Published: October 2020

Objective

The short synacthen test (SST) is widely used across the UK to assess adrenal reserve. The main objective of our study was to determine the morning serum cortisol level that will predict adrenal insufficiency (AI) thus reducing our reliance on SST.

Design

This was a single centre retrospective study of 393 SST tests measuring 0 and 60 min cortisol levels after administration of 250 μg of synacthen (synthetic ACTH).

Patients and methods

All the SST tests for patients suspected of primary or secondary AI between April 2016 and October 2018 were included in this study. We used serum to determine circulating cortisol by a newer generation competitive electrochemiluminescence immunoassay (ECLIA) (Roche Diagnostics). A post-ACTH cortisol response of ≥420 nmol/L at 60 min was considered adequate to rule out AI. The data were analysed to ascertain the relationship between 0 min and 60 min serum cortisol.

Results

A total of 393 SST results were included in this study. Overall, a total of 332 (84.5%) subjects achieved sufficient serum cortisol level at 60 min, while 61 subjects (15.5%) showed insufficient response. Using the logistic regression, we determined that a morning basal serum cortisol level of ≥354 nmol/L was able to predict normal adrenal function with 100% sensitivity. We were unable to find a lower cut-off value below which SST will not be required. By using this proposed cut-off point, approximately 37% of the SSTs tests could be avoided.

Conclusions

Basal morning serum cortisol can be safely used as a first step in the evaluation of patients with suspected AI. This will enhance the number of patients being screened for this condition.
Spicules and skeletons: mantle musculature of two species of dorid nudibranchs (Gastropoda: Nudibranchia: Doridina)
Authors: Penney B.K. , Sigwart J.D. , Parkinson D.Y.
Published: October 2020

Molluscs often possess complex calcified elements in addition to the shell, but how these elements function and relate to other tissues is often poorly understood. Dorid nudibranchs typically possess innumerable calcareous spicules arranged in complex networks. To describe how these spicules interact with muscles and connective tissue, we reconstructed tomographic digital models using serial sections and synchrotron micro-computed tomography. In two species with dramatically different spicule network morphologies, musculature was divided into a dorsal layer of crossed fibres, a ventral layer of branching radial fibres, and scattered dorsoventral fibres in between. These two species differed in the size of their dorsal tubercles, which was reflected in the organization of dorsal musculature, and in the amount and organization of connective tissue. In Platydoris sanguinea Bergh, 1905, dense mats of spicules sandwiched a layer of connective tissue with fewer spicules and muscle insertions only onto the ventral spicules. In Cadlina luteomarginata MacFarland, 1966, thick tracts of spicules are surrounded by a sheath of connective tissue. Muscles surround and insert into the dorsal tubercle spicule layer. Thus, both species appear to use the spicule network for muscle antagonism and transfer of motion, but the different arrangement of elements suggests that they use this skeleton in quite different ways.