bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative Study of Student-Led Objective Tutorials versus Traditional Tutorials in Undergraduate Pharmacology Teaching in an Indian Medical School
Authors: Adiga Manoor Narasimha Sachidananda , Acharya Swathi , Holla Rajendra
Published: March 2020

Introduction The drawback of conventional tutorials (CTs) stresses the need for a tutorial with more active participation from students. Student-led objective tutorial provides an opportunity for active learning and makes student responsible. Hence, the effectiveness of student-led objective tutorial (SLOT) with CT in teaching pharmacology for II MBBS students was evaluated in this study.

Materials and Methods In this study, 157 students were divided into three groups and further allocated to SLOT and CT subgroup equally. The effectiveness of the tutorial was evaluated objectively by comparing pretest and posttest scores as well as mean scores.

Results Pretest and posttest scores in SLOT were 3.343 ± 1.347 versus 4.8750 ± 1.750 and in CT were 3.2500 ± 1.690 versus 4.5781 ± 1.883, both type of the tutorials have shown the statistically significant improvement in the scores. The mean score in the SLOT group was 13.6711 ± 3.47712 compared with 12.1842 ± 3.50128 in the CT group showing statistically significantly (U = 2171.50, p = 0.008) higher score in SLOT. Feedback regarding the type of tutorial indicating SLOT was better and preferred among the students compared with CT. It is more interesting, helps in active learning of the subject, and encourages student to participate actively in learning process.

Conclusion SLOT and CT both improve the learning pharmacology in II MBBS students; however, SLOT being an innovative method will help in active participation of students and increases the focus of the student on particular topic in teaching.
Multi-field dependence responses and their micro-structure analysis in YBa2Cu3O7−x-based second-generation coated conductors with different protective layers by Nd-laser irradiations
Authors: Guan Mingzhi , Xin Canjie , Wu Wei , Yao Qinggao , Ma Lizhen
Published: March 2020

High-temperature superconductors (HTS) are materials that hold great promise for future particle-accelerator plants. YBa2Cu3O7-x-based (YBCO) second-generation coated conductor coils can produce the intense field needed for ion confinement. Such coils can act as a radiation resistance magnet when exposed to radiation, and therefore, it is essential to better understand irradiation responses and defect creation in YBCO superconductors. The influence of laser or ion irradiation on the electrical characteristics of HTS has been studied previously; however, most results remain ambiguous and inconsistent. Degradation of or incremental changes in the critical current of the HTS tap are currently only observed and explained via irradiation dose. The relation between irradiation defects and macro-multi-field responses has yet to be established for YBCO tapes, for magnet design and operation. In this study, YBCO (2 G HTS) taps with Ag, Cu–Ag, and Cu protective cap layers were selected as targets of Nd-laser irradiation, at varying power. Irradiation defects were formed in YBCO taps, and irradiation dose was monitored as a function of superconducting properties and mechanical behaviors. The critical current and its N-values eventually degrade under intense Nd-laser irradiation, and the mechanical behavior of YBCO tapes shows nonlinear features after irradiation. Scanning electron microscopy and x-ray energy-dispersive spectrometry were applied to investigate the micro-defect changes that occurred in the taps after each Nd-laser irradiation dose. Micro-structural observations showed that the protective layers were critical for radiation resistance in YBCO taps. Furthermore, the macro-stress dependence of the critical current field was measured before and after Nd-laser irradiation to establish the relationship with micro-defect morphology by Nd-laser irradiation.
Generation of large-volume high-pressure plasma by spatiotemporal control of space charge
Authors: Dhali Shirshak K.
Published: March 2020

Any attempt to scale pressure and volume of nonthermal plasma usually leads to instabilities due to the formation of localized space charge. The control of the plasma is limited by the discharge geometry, type of excitation, and gas composition. This article explores the possibility of controlling the space charge in a discharge with a spatially and temporally varying electric field. It is shown that a phase-staggered sinusoidal excitation to a set of conformal azimuthal electrodes in a cylindrical geometry leads to a traveling electric field. Simulations show that in space charge dominated transport, the charged species are dispersed both in the radial and azimuthal directions. This will lead to better control of the space charge and stable discharges near atmospheric pressures.
Simulations demonstrate droplets climbing
Authors: Bandari Anashe
Published: March 2020

Droplets on a vibrating surface climb by swaying and spreading
Evaluating the use of thermal imaging cameras to monitor the endangered greater bilby at Astrebla Downs National Park
Authors: Augusteyn John , Pople Anthony , Rich Maree
Published: March 2020

Spotlight surveys are widely used to monitor arid-zone-dwelling species such as the greater bilby (Macrotis lagotis). These surveys require a sufficient sample size to adequately model detection probability. Adequate sample sizes can be difficult to obtain for low-density populations and for species that avoid light and or have poor eyeshine like the bilby. Abundance estimates based on burrow counts can be problematic because of the variable relationship between the number of burrows used and bilby abundance. In 2013, feral predators devastated a Queensland bilby population and a method was required that could locate and monitor the remaining bilbies. We report on a study that compared density estimates derived from spotlighting and thermal cameras. Bilbies were surveyed annually over three years, using spotlights and thermal cameras on different nights but using the same transects to compare the methods. On average, thermal cameras detected twice the number of bilbies per kilometre surveyed than spotlighting. Despite this difference in the number of bilbies detected, density estimates (bilbies km−2) were similar (thermal camera versus spotlight: 0.6 versus 0.2 (2014), 3.4 versus 3.4 (2015) and 4.8 versus 3.3 (2016)). Nevertheless, the larger sample size obtained using thermal cameras gave greater confidence in modelling detection probability.
The Case for Methyl Group Precession Accompanying Torsional Motion
Authors: Gascooke Jason R. , Lawrance Warren D.
Published: March 2020

For molecules containing a methyl group, high precision fits of rotational line data (microwave spectra) that encompass several torsional states require considerably more constants than are required in comparable rigid molecules. Many of these additional terms are ‘torsion-rotation interaction’ terms, but their precise physical meaning is unclear. In this paper, we explore the physical origins of many of these additional terms in the case where the methyl group is attached to a planar frame. We show that torsion-vibration coupling, which has been observed in toluene and several substituted toluenes, provides the dominant contribution to a number of the torsion-rotation constants in toluene. It is further demonstrated that this coupling is intimately related to precession of the methyl group. A number of the constants required in the high resolution fits of rotational line data are shown to arise as a natural consequence of methyl precession. By considering several molecules whose rotational line spectra have been fit to high precision, we demonstrate that the experimental evidence is consistent with the occurrence of methyl group precession. Quantum chemistry calculations of the optimised molecular structures at key torsional angles provide further evidence that methyl precession occurs. There is both a torsional angle dependent tilt of the Cmethyl-frame bond and of the methyl group principal rotation axis relative to the Cmethyl-frame bond.
Ephemeral effects of El Niño–Southern Oscillation events on an eastern tropical Pacific coral community
Authors: Cruz-García R. , Rodríguez-Troncoso A. P. , Rodríguez-Zaragoza F. A. , Mayfield A. , Cupul-Magaña A. L.
Published: March 2020

Coral-reef ecosystems of the central Mexican Pacific have been routinely affected by both moderate and severe El Niño–Southern Oscillation (ENSO) events over the past 20 years. Such conditions are associated with abnormally high (1997–1998, 2002–2003, 2009–2010, and 2015–2016; ‘El Niño’) and low (1999–2000, 2008–2009, and 2010–2011; ‘La Niña’) seawater temperatures. Because few studies have documented how ENSO events affect both corals and key coral competitors such as macroalgae, we evaluated the short- and long-term changes in the cover of three reef coral genera, namely, Pocillopora, Pavona and Porites, as well as four coral competitors, namely, macroalgae, turf algae, coralline algae (CCA) and sponges, over a multi-year period that encapsulated two strong ENSO events: the 2010–2011 La Niña and the 2015–2016 El Niño. Such temperature anomalies caused a short-lived decrease in coral cover, alongside a concomitant increase in CCA. The communities eventually returned to their coral-dominated states within several months of the ENSO events, suggesting that these reef habitats can recover from such episodes of anomalous seawater temperatures.
Stability of H
3
O at extreme conditions and implications for the magnetic fields of Uranus and Neptune
Authors: Huang Peihao , Liu Hanyu , Lv Jian , Li Quan , Long Chunhong , Wang Yanchao , Chen Changfeng , Hemley Russell J. , Ma Yanming
Published: March 2020

Significance

Understanding the interior structure and dynamics of outer Solar System planets in terms of their component materials is a major scientific challenge. A highly intriguing case concerns the anomalous nondipolar and nonaxisymmetric magnetic fields of Uranus and Neptune. A thin-shell dynamo model has been shown to capture observed phenomena but leaves unexplained its origin and materials basis. We report extensive theoretical calculations that indicate the stability of trihydrogen oxide (H
3
O) in solid, superionic, and fluid metallic states at the deep interior conditions of these planets. The fluid metallic phase is stable in a thin-shell zone near their cores and exhibits the properties required to produce the observed enigmatic magnetic fields. These findings have implications for other planets, including related exoplanets.
Detecting language change
Authors: Calude Andreea S. , Harper Sally , Miller Steven , Whaanga Hemi
Published: March 2020

The borrowing of words from one language into another is most likely as ancient as language itself. While ample linguistic attention has focused on various linguistic contact scenarios in which words from one language enter productive use into another, their aim has been largely restricted to documenting the words which are borrowed, their frequency, and other situation-specific information. In this paper, we propose new methods for studying loanwords, namely a combination of statistical testing techniques which can be used together to increase knowledge in this area. We illustrate these tools with a case-study of loanwords from an indigenous language (Māori) into a world dominant language (New Zealand English). Using a topic-constrained newspaper corpus in conjunction with quantitative methods, we explore the use of loanwords diachronically and analyse variation in loanword use across newspapers and across writers.
Storytelling and stance-taking in group interaction
Authors: Peplow David
Published: March 2020

This paper looks at two highly prevalent actions in naturally-occurring talk: stance-taking and storytelling. Stance-taking and storytelling have been shown to co-occur often (e.g.Siromaa, 2012), and this is especially the case in reading group talk, a discursive environment in which speakers are engaged in the joint enterprise of assessing the meaning and quality of a shared object: a written narrative text (e.g. a novel). Insights from conversation analysis and dialogic syntax are used to analyse interactional data from several reading group meetings, with a focus on the types of storytelling that are found in this talk, the relationship between the various stories told in sequence in the talk – including the relationship between the written narrative text and the spoken narratives, and the ways in which stance-taking and storytelling are intertwined.
Group field theory and holographic tensor networks: dynamical corrections to the Ryu–Takayanagi formula
Authors: Chirco Goffredo , Goeßmann Alex , Oriti Daniele , Zhang Mingyi
Published: March 2020

We introduce a generalised class of (symmetric) random tensor network states in the framework of group field theory. In this setting, we compute the Rényi entropy for a generic bipartite state via a mapping to the partition function of a topological 3D BF theory, realised as a simple interacting group field theory. The expectation value of the entanglement entropy is calculated by an expansion into stranded Feynman graphs and is shown to be captured by a Ryu–Takayanagi formula. For the simple case of a 3D BF theory, we can prove the linear corrections, given by a polynomial perturbation of the Gaussian measure, to be negligible for a broad class of networks.
Attosecond transient absorption of a continuum threshold
Authors: Birk Paul , Stooß Veit , Hartmann Maximilian , Borisova Gergana D , Blättermann Alexander , Heldt Tobias , Bartschat Klaus , Ott Christian , Pfeifer Thomas
Published: March 2020

The laser-field-modified dipole response of the first ionization threshold of helium is studied by means of attosecond transient absorption spectroscopy. We resolve light-induced time-dependent structures in the photoabsorption spectrum both below and above the ionization threshold. By comparing the measured results to a quantum-dynamical model, we isolate the contributions of the unbound electron to these structures. They originate from light-induced couplings of near-threshold bound and continuum states and light-induced energy shifts of the free electron. The ponderomotive energy, at low laser intensities, is identified as a good approximation for the perturbed continuum response.
Perceptible exciton-to-trion conversion and signature of defect mediated vibronic modes and spin relaxation in nanoscale WS2 exposed to γ-rays
Authors: Sarmah Hemanga Jyoti , Mohanta Dambarudhar , Saha Abhijit
Published: March 2020

In this work, we report manifested optical, optoelectronic and spin–spin relaxation features of a few layered tungsten disulphide (WS2) nanosheets subjected to energetic γ-photons (∼1.3 MeV) emitted from a Co60 source. Upon intense irradiation (dose = 96 kGy), a slight departure from the pure hexagonal phase was realized with the introduction of the trigonal phase at large. Moreover, in the Raman spectra, as a consequence of the radiation-induced effect, an apparent improvement of the E-to-A mode intensity and a reduction in phonon lifetimes have been realized, with the latter being dependent on the linewidths. The emergence of the new peak (D) maxima observable at ∼406 cm−1 in the Raman spectra and ∼680 nm in the photoluminescence (PL) spectra can be attributed to the introduction of defect centres owing to realization of sulphur vacancies (V
S) in the irradiated nanoscale WS2. Additionally, neutral exciton to charged exciton (trion) conversion is anticipated in the overall PL characteristics. The PL decay dynamics, while following bi-exponential trends, have revealed ample improvement in both the fast parameter (0.39 ± 0.01 ns to 1.88 ± 0.03 ns) and the slow parameter (2.36 ± 0.03 ns to 12.1 ± 0.4 ns) after γ-impact. We attribute this to the finite band gap expansion and the incorporation of new localized states within the gap, respectively. A declining exciton annihilation rate is also witnessed. The isotropic nature of the electron paramagnetic resonance spectra as a consequence of γ-exposure would essentially characterize a uniform distribution of the paramagnetic species in the system, while predicting a three-fold improvement of relative spin density at 96 kGy. Exploring defect dynamics and spin dynamics in 2D nanoscale systems does not only strengthen fundamental insight but can also offer ample scope for designing suitable components in the areas of miniaturized optoelectronic and spintronic devices.
Nano-bridged nanosphere lithography
Authors: Luo Lingpeng , Akinoglu Eser Metin , Wu Lihua , Dodge Tyler , Wang Xin , Zhou Guofu , Naughton Michael J , Kempa Krzysztof , Giersig Michael
Published: March 2020

We develop nano-bridged nanosphere lithography (NB-NSL), a modification to the widely used conventional nanosphere lithography (NSL). Nano-bridges between polystyrene (PS) spheres of a pristine NSL template are controllably formed in a two-step process: (i) spin-coating of a dilute styrene solution on top of the template, followed by (ii) oxygen plasma etching of the template. We show that the nanobridge dimensions can be precisely tuned by controlling the pre-processing conditions and the plasma etching time. The resulting lithography templates feature control over the shape and size of the apertures, which determine the morphology of the final nano-island arrays after material deposition and template removal. The unique advantage of NB-NSL is that PS particle templates based on a single PS particle diameter can be utilized for the fabrication of a variation of nano-island shapes and sizes, whereas conventional NSL yields only bowtie-shaped nano-islands, with their size being predetermined by the PS particle diameter of the template.
A holistic system approach for short range passenger aircraft with cryogenic propulsion system
Authors: Boll Martin , Corduan Matthias , Biser Stefan , Filipenko Mykhaylo , Pham Quoc Huang , Schlachter Sonja , Rostek Peter , Noe Mathias
Published: March 2020

Currently, hybrid-electric aircraft are under investigation as one possible solution to reduce the emissions of the aviation industry according to Flightpath 2050 of the European Union. To meet the drive train's requirements on low mass while aiming for highest efficiency, superconducting technologies are regarded as a key enabling technology for drive train powers of several tens of megawatts. Within the German nationally funded project TELOS an exemplary mission profile and the physical measures of a 220-passenger aircraft are used to derive the requirements for a cryogenic-cooled serial hybrid-electric propulsion system. To optimize the total system performance, we subsequently evaluated the superconducting and cryogenic-cooled components by using computationally fast, analytical models. This approach allows quantifying the system performance by using component technologies being available today. In particular, the system performance of geared drive to direct drive propulsion units are compared and the influence of the DC bus voltage and the electric frequencies of the AC circuits on the mass and the efficiency of the drive trains are analysed.
Dynamic loss of HTS field windings in rotating electric machines
Authors: Kails Kevin , Zhang Hongye , Machura Philip , Mueller Markus , Li Quan
Published: March 2020

High-temperature superconducting (HTS) coated conductors (CCs) are frequently applied under complex electromagnetic fields to develop powerful, compact and efficient rotating electric machines. In such electric machines, field windings constructed by HTS CCs are adopted to increase the magnetic loading of the machines. The HTS field windings work with DC currents and due to the time-varying magnetic field environment, dynamic losses occur. In addition to the AC magnetic field, there is a large DC background field, which is caused by the self-field of the HTS field windings. This paper investigates the dynamic loss in HTS CCs using an H-formulation based numerical model for a wide range of combined DC and AC magnetic fields under various load conditions, and two different methods have been used for calculating dynamic loss. The results show that a DC background field plays a vital role to accurately predict the dynamic losses in HTS CCs. A DC background field of 75 mT can triple the dynamic loss as compared to only applying an AC magnetic field. In addition, the theoretical definition for the dynamic region for the case of solely an AC field has been found inapplicable in the case of a DC background field. Finally, a case study is done based on our double claw pole power generator to estimate the dynamic loss in an actual rotating machine, which was found to be 13.3 W. A low dynamic loss was achieved through the generator field winding design, which prevents high magnetic field fluctuations in the winding, since it is located at a distance from the air gap and armature coils. Furthermore, the rotational speed is very low and hence the resultant magnetic field frequency is low as well.
Ultracold ions wake in dusty plasmas
Authors: Sundar Sita , Moldabekov Zhandos A
Published: March 2020

Motivated by the recent experimental realization of ultracold dusty plasma (2019 Sci. Rep. 9 3261), we present the results of particle-in-cell simulation with Monte-Carlo-collisions for wake behind a dust particle due to focusing of ions at superfluid helium temperature (∼2 K). Dynamical screening (wakefield) defines structural and dynamical properties of charged dust particles in plasmas such as phase transition, crystal formation, vibration modes (waves) etc. Here, we delineate in detail the dependence of wake strength on the streaming velocity of ions and on the ion-neutral charge exchange collision frequency (neutrals density) in the ultracold dusty plasma. Lowering the temperature to ultracold level leads to a wake pattern behind a dust particle that completely differs from the wake at normal conditions. For wide range of parameters, most remarkable features of the wakefield are (i) the formation of wake pattern with two maxima split in transverse to ion flow direction in the downstream area, (ii) pronounced inverse V shape of the wakefield closely resembling the wake in quark-gluon plasma and dense quantum plasma (warm dense matter), and (iii) the inter-dust attraction region in transverse direction. The latter shows that molecule-like interaction between dust particles is realized in ultracold dusty plasmas. These observations show a fundamental difference of ultracold dusty plasma physics from well studied complex plasmas at normal conditions.
Extending qubit coherence by adaptive quantum environment learning
Authors: Scerri Eleanor , Gauger Erik M , Bonato Cristian
Published: March 2020

Decoherence, resulting from unwanted interaction between a qubit and its environment, poses a serious challenge towards the development of quantum technologies. Recently, researchers have started analysing how real-time Hamiltonian learning approaches, based on estimating the qubit state faster than the environmental fluctuations, can be used to counteract decoherence. In this work, we investigate how the back-action of the quantum measurements used in the learning process can be harnessed to extend qubit coherence. We propose an adaptive protocol that, by learning the qubit environment, narrows down the distribution of possible environment states. While the outcomes of quantum measurements are random, we show that real-time adaptation of measurement settings (based on previous outcomes) allows a deterministic decrease of the width of the bath distribution, and hence an increase of the qubit coherence. We numerically simulate the performance of the protocol for the electronic spin of a nitrogen-vacancy centre in diamond subject to a dilute bath of 13C nuclear spin, finding a considerable improvement over the performance of non-adaptive strategies.
Extracellular voltage thresholds for maximizing information extraction in primate auditory cortex: implications for a brain computer interface
Authors: Bigelow James , Malone Brian J
Published: March 2020

Objective. Research by Oby (2016 J. Neural. Eng.
13 036009) demonstrated that the optimal threshold for extracting information from visual and motor cortices may differ from the optimal threshold for identifying single neurons via spike sorting methods. The optimal threshold for extracting information from auditory cortex has yet to be identified, nor has the optimal temporal scale for representing auditory cortical activity. Here, we describe a procedure to jointly optimize the extracellular threshold and bin size with respect to the decoding accuracy achieved by a linear classifier for a diverse set of auditory stimuli. Approach. We used linear multichannel arrays to record extracellular neural activity from the auditory cortex of awake squirrel monkeys passively listening to both simple and complex sounds. We executed a grid search of the coordinate space defined by the voltage threshold (in units of standard deviation) and the bin size (in units of milliseconds), and computed decoding accuracy at each point. Main results. The optimal threshold for information extraction was consistently near two standard deviations below the voltage trace mean, which falls significantly below the range of three to five standard deviations typically used as inputs to spike sorting algorithms in basic research and in brain-computer interface (BCI) applications. The optimal binwidth was minimized at the optimal voltage threshold, particularly for acoustic stimuli dominated by temporally dynamic features, indicating that permissive thresholding permits readout of cortical responses with temporal precision on the order of a few milliseconds. Significance. The improvements in decoding accuracy we observed for optimal readout parameters suggest that standard thresholding methods substantially underestimate the information present in auditory cortical spiking patterns. The fact that optimal thresholds were relatively low indicates that local populations of cortical neurons exhibit high temporal coherence that could be leveraged in service of future auditory BCI applications.
Surface modification of PLA scaffold using radio frequency (RF) nitrogen plasma in tissue engineering application
Authors: Mohsenimehr Soad , Khani Mohammad Reza , Fani Nesa , Baghaban Eslaminejad Mohammad Reza , Shokri Babak , Ghassami Amirreza
Published: March 2020

In this study, two models of flat film and three-dimensional porous structure made by 3D printing (scaffolding) of poly lactic acid polymer (PLA) were processed by radio frequency (RF; 13.56 MHz) low-pressure nitrogen, nitrogen/oxygen and nitrogen/hydrogen plasma to improve surface properties requested in tissue engineering. Samples were treated at different RF power (80–150 w) and time processing was 90 s. Optical emission spectroscopy was used to identify the species in plasma. A significant change in hydrophilicity and surface energy measured by contact angle was observed. Aging effect on the wettability of PLA films at two different temperatures was examined. The result showed that the samples, kept at low temperature, have not changed significantly. Morphology and surface roughness were studied by Atomic force microscopy. Chemical components at the surface were investigated by x-ray photoelectron spectroscopy (XPS). Mechanical and thermal effect on the 3D scaffold PLA were carried out by tension test and thermogravimetric analysis respectively to indicate the effects of RF plasma treatment on the samples. The structural order, interconnectivity, and scale of the scaffold holes have been recorded by an optical microscope. Surface treatment by plasma increased biocompatibility of PLA samples without any toxicity. Cell adhesion on scaffolds was approved through MTT and scanning electron microscope (SEM) analysis. MTT essay show there was significant different between N2/O2 (1:1) group than control sample. Plasma surface treatment is a convenient method to reach a perfect substrate with desired hydrophilicity for attaching cells.
Enhancement of temperature coefficient of resistance (TCR) and magnetoresistance (MR) of La0.67–xRExCa0.33MnO3 (x = 0, 0.1; RE = Gd, Nd, Sm) system via rare-earth substitution
Authors: Pal Anand , Nagaraja B S , Rachana K J , Supriya K V , Kekuda Dhananjaya , Rao Ashok , Li Chia-Ruei , Kuo Yung-Kang
Published: March 2020

We investigated the influence of 10% substitution of rare-earth (RE) elements on the crystallographic, transport, and magnetic properties of La0.67–x
RE
x
Ca0.33MnO3(RE = Nd, Sm, and Gd, x = 0.0, 0.1) manganite perovskite compounds. The bulk polycrystalline samples were synthesized using solid-state reaction method. The phase purity and crystal structure of studied samples were confirmed by room temperature X-ray diffraction followed by the Rietveld refinement analysis. A high temperature insulator to low temperature metal phase transition is observed in electrical transport measurement. We observed an enhancement in the temperature coefficient of resistance (TCR) and magnetoresistance (MR) by partially substituting La with RE ions. The maximum TCR ≈ 22% and MR ≈ 96% are observed in Gd doped sample. The magnetic transition temperature, T

c
, decreases from ∼254 K for the pristine sample to about ∼165 K for the Gd-doped sample. Our analysis of electrical and thermal transport data shows that the Small Polaron Hopping (SPH) is predominant at high temperatures conduction mechanism, whereas at low temperatures mechanism is dominated by electron-magnon scattering. The high temperature insulator paramagnetic phase to low temperature metallic ferromagnetic phase transitions are also observed in thermal conductivity and specific heat.
Microstructure evolution and mechanical properties of friction stir processed TiC/7085Al nanocomposites
Authors: Zhou Dongshuai , Wang Jian , Lu Yalin , Bai Zhihao
Published: March 2020

In this paper, homogeneously dispersed TiC nanoparticles and fine-grained composite was successfully achieved by friction stir processing (FSP) of in situ 0.5 wt.% TiC/7085Al nanocomposites with different rotational speed. The effects of the rotational speed on the microstructures and tensile properties were investigated. Experimental results showed that the stir zone (SZ) exhibited equiaxed recrystallized grains with fine size and a high fraction of high-angle grain boundaries (HAGBs) caused by dynamic recrystallization (DRX). Moreover, the tensile strength and elongation of the friction stir processed (FSPed) composite were significantly improved compared with the base composite. With the rotational speed of 1000 rpm, the composite has the smallest grain size and the optimum mechanical properties. The average grain size decreased to 1.61 μm, the yield strength (YS), ultimate tensile strength (UTS) and elongation reached to 345 MPa, 429 MPa and 17.8%, respectively.
Head stabilization in small vertebrates that run at high frequencies with a sprawled posture
Authors: Jorissen Cas , Paillet Eric , Scholliers Jan , Aerts Peter , Goyens Jana
Published: March 2020

Small animals face a large challenge when running. A stable head is key to maintenance of a stable gaze and a good sense of self-motion and spatial awareness. However, trunk undulations caused by the cyclic limb movements result in involuntary head movements. Hence, the head needs to be stabilized. Humans are capable of stabilizing their head up to 2–3 Hz, but small animals run at cycle frequencies that are up to six times higher. We wondered how natural selection has adapted their head stabilization control. We observed that the relative contributions of vision, on the one hand, and vestibular perception and proprioception, on the other hand, remain the same when lizards undergo fast or slow body undulations in an experimental set-up. Lizards also maintain a short phase lag at both low and high undulation frequencies. Hence, we found no indication that they use a different control mechanism at high frequencies. Instead, head stabilization probably remains possible owing to faster reflex pathways and a lower head inertia. Hence, the intrinsic physical and neurological characteristics of lizards seem to be sufficient to enable head stabilization at high frequencies, obviating the need for evolutionary adaptation of the control pathways. These properties are not unique to lizards and might, therefore, also facilitate head stabilization at high frequencies in other small, fast animals.
Cognitive load amplifies Parkinson’s tremor through excitatory network influences onto the thalamus
Authors: Dirkx Michiel F , Zach Heidemarie , van Nuland Annelies J , Bloem Bastiaan R , Toni Ivan , Helmich Rick C
Published: March 2020

Parkinson’s tremor is related to cerebral activity in both the basal ganglia and a cerebello-thalamo-cortical circuit. It is a common clinical observation that tremor markedly increases during cognitive load (such as mental arithmetic), leading to serious disability. Previous research has shown that this tremor amplification is associated with reduced efficacy of dopaminergic treatment. Understanding the mechanisms of tremor amplification and its relation to catecholamines might help to better control this symptom with a targeted therapy. We reasoned that, during cognitive load, tremor amplification might result from modulatory influences onto the cerebello-thalamo-cortical circuit controlling tremor amplitude, from the ascending arousal system (bottom-up), a cognitive control network (top-down), or their combination. We have tested these hypotheses by measuring concurrent EMG and functional MRI in 33 patients with tremulous Parkinson’s disease, OFF medication, during alternating periods of rest and cognitive load (mental arithmetic). Simultaneous heart rate and pupil diameter recordings indexed activity of the arousal system (which includes noradrenergic afferences). As expected, tremor amplitude correlated with activity in a cerebello-thalamo-cortical circuit; and cognitive load increased tremor amplitude, pupil diameter, heart rate, and cerebral activity in a cognitive control network distributed over fronto-parietal cortex, insula, thalamus and anterior cingulate cortex. The novel finding, obtained through network analyses, indicates that cognitive load influences tremor by increasing activity in the cerebello-thalamo-cortical circuit in two different ways: by stimulating thalamic activity, likely through the ascending arousal system (given that this modulation correlated with changes in pupil diameter), and by strengthening connectivity between the cognitive control network and the cerebello-thalamo-cortical circuit. We conclude that both the bottom-up arousal system and a top-down cognitive control network amplify tremor when a Parkinson’s patient experiences cognitive load. Interventions aimed at attenuating noradrenergic activity or cognitive demands may help to reduce Parkinson’s tremor.
Thinking fast or slow? Functional magnetic resonance imaging reveals stronger connectivity when experienced neurologists diagnose ambiguous cases
Authors: van den Berg Berry , de Bruin Anique B H , Marsman Jan-Bernard C , Lorist Monicque M , Schmidt Henk G , Aleman André , Snoek Jos W
Published: March 2020

For ∼40 years, thinking about reasoning has been dominated by dual-process theories. This model, consisting of two distinct types of human reasoning, one fast and effortless and the other slow and deliberate, has also been applied to medical diagnosis. Medical experts are trained to diagnose patients based on their symptoms. When symptoms are prototypical for a certain diagnosis, practitioners may rely on fast, recognition-based reasoning. However, if they are confronted with ambiguous clinical information slower, analytical reasoning is required. To examine the neural underpinnings of these two hypothesized forms of reasoning, 16 highly experienced clinical neurologists were asked to diagnose two types of medical cases, straightforward and ambiguous cases, while functional magnetic resonance imaging was being recorded. Compared with reading control sentences, diagnosing cases resulted in increased activation in brain areas typically found to be active during reasoning such as the caudate nucleus and frontal and parietal cortical regions. In addition, we found vast increased activity in the cerebellum. Regarding the activation differences between the two types of reasoning, no pronounced differences were observed in terms of regional activation. Notable differences were observed, though, in functional connectivity: cases containing ambiguous information showed stronger connectivity between specific regions in the frontal, parietal and temporal cortex in addition to the cerebellum. Based on these results, we propose that the higher demands in terms of controlled cognitive processing during analytical medical reasoning may be subserved by stronger communication between key regions for detecting and resolving uncertainty.
Measurement of Serum Neuron-Specific Enolase in Neuroblastoma: Is There a Clinical Role?
Authors: Ferraro Simona , Braga Federica , Luksch Roberto , Terenziani Monica , Caruso Simone , Panteghini Mauro
Published: March 2020

BACKGROUND

The measurement of neuron-specific enolase (NSE) in serum is frequently requested for diagnosis, risk stratification, and treatment monitoring of neuroblastoma (NB) in the pediatric population. However, authoritative clinical practice guidelines advise about the poor diagnostic performance of NSE.

Content

We critically appraised the available literature evaluating the diagnostic and prognostic value of NSE in the management of NB, paying special attention to the definition of appropriate threshold levels. In addition, we discuss the interfering conditions causing artifactual increases of NSE concentrations in serum and potentially influencing the clinical evaluation of patients with suspected NB.

No definitive evidence supports the use of serum NSE for diagnosis and monitoring of NB. The risk of obtaining false-positive NSE results associated with confounders (e.g., sample hemolysis) and other pathophysiologic conditions (e.g., inflammation) is remarkable and hampers the diagnostic value of this test. NSE may be helpful to define the risk of death of patients with NB, mainly in the advanced stages of disease. However, further studies validating currently marketed immunoassays and defining threshold values useful for this scope are warranted.
Variations in incidence of venous thromboembolism in low-, middle-, and high-income countries
Authors: Siegal Deborah M , Eikelboom John W , Lee Shun Fu , Rangarajan Sumathy , Bosch Jackie , Zhu Jun , Yusuf Salim ,   the Venous Thromboembolism Collaboration
Published: March 2020

Aims

To examine the rates of venous thromboembolism (VTE) in high-income, upper middle-income, and lower middle/low-income countries (World Bank Classification).

Methods and results

We examined the rates of VTE in high-income, upper middle-income, and lower middle/low-income countries (World Bank Classification) in a cohort derived from four prospective international studies (PURE, HOPE-3, ORIGIN, and COMPASS). The primary outcome was a composite of pulmonary embolism, deep vein thrombosis, and thrombophlebitis. We calculated age- and sex-standardized incidence rates (per 1000 person-years) and used a Cox frailty model adjusted for covariates to examine associations between the incidence of VTE and country income level. A total of 215 307 individuals (1.5 million person-years of follow-up) from high-income (n = 60 403), upper middle-income (n = 42 066), and lower middle/low-income (n = 112 838) countries were included. The age- and sex-standardized incidence rates of VTE per 1000 person-years in high-, upper middle-, and lower middle/low-income countries were 0.87, 0.25, and 0.06, respectively. After adjusting for age, body mass index (BMI), smoking, antiplatelet therapy, anticoagulant therapy, education level, ethnicity, and incident cancer diagnosis or hospitalization, individuals from high-income and upper middle-income countries had a significantly higher risk of VTE than those from lower middle/low-income countries [hazard ratio (HR) 3.57, 95% confidence interval (CI) 2.40–5.30 and HR 2.27, 95% CI 1.59–3.23, respectively]. The effect of country income level on VTE risk was markedly stronger in people with a lower BMI, hypertension, diabetes, non-White ethnicity, and higher education.

Conclusion

The rates of VTE are substantially higher in high-income than in low-income countries. The factors underlying the increased VTE risk in higher-income countries remain unknown.
The remodelling index risk stratifies patients with hypertensive left ventricular hypertrophy
Authors: Le Thu-Thao , Lim Vanessa , Ibrahim Rositaa , Teo Muh-Tyng , Bryant Jennifer , Ang Briana , Su Boyang , Aw Tar-Choon , Lee Chi-Hang , Bax Jeroen , Cook Stuart , Chin Calvin W L
Published: March 2020

Aims 

Hypertensive left ventricular hypertrophy (LVH) is associated with increased cardiovascular events. We previously developed the remodelling index (RI) that incorporated left ventricular (LV) volume and wall-thickness in a single measure of advanced hypertrophy in hypertensive patients. This study examined the prognostic potential of the RI in reference to contemporary LVH classifications.

Methods and results 

Cardiovascular magnetic resonance was performed in 400 asymptomatic hypertensive patients. The newly derived RI (EDV3t, where EDV is LV end-diastolic volume and t is the maximal wall thickness across 16 myocardial segments) stratified hypertensive patients: no LVH, LVH with normal RI (LVHNormal-RI), and LVH with low RI (LVHLow-RI). The primary outcome was a composite of all-cause mortality, acute coronary syndromes, strokes, and decompensated heart failure. LVHLow-RI was associated with increased LV mass index, fibrosis burden, impaired myocardial function and elevated biochemical markers of myocardial injury (high-sensitive cardiac troponin I), and wall stress. Over 18.3 ± 7.0 months (601.3 patient-years), 14 adverse events occurred (2.2 events/100 patient-years). Patients with LVHLow-RI had more than a five-fold increase in adverse events compared to those with LVHNormal-RI (11.6 events/100 patient-years vs. 2.0 events/100 patient-years, respectively; log-rank P < 0.001). The RI provided incremental prognostic value over and above a model consisting of clinical variables, LVH and concentricity; and predicted adverse events independent of clinical variables, LVH, and other prognostic markers. Concentric and eccentric LVH were associated with adverse prognosis (log-rank P = 0.62) that was similar to the natural history of hypertensive LVH (5.1 events/100 patient-years).

Conclusion 

The RI provides prognostic value that improves risk stratification of hypertensive LVH.
Long-term adaptive versus maladaptive remodelling of the pulmonary autograft after the Ross operation
Authors: Yacoub Magdi H , Tsang Victor , Sarathchandra Padmini , Jensen Hanna , Hughes Sian , Latif Najma
Published: March 2020

OBJECTIVES

Following the Ross operation, the pulmonary autograft undergoes structural changes (remodelling). We sought to determine the extent, nature and possible determinants of long-term remodelling in the different components of the pulmonary autograft.

METHODS

Ten pulmonary autografts and 12 normal control valves (6 pulmonary and 6 aortic) were examined by conventional histology, immunocytochemistry and electron microscopy. The structural changes were quantified by morphometry.

RESULTS

The leaflets from free-standing root replacement valves demonstrated thickening to levels comparable to the normal aortic leaflets, largely due to the addition of a thin layer of ‘neointima’ formed of radial elastic fibres, collagen bundles and glycoaminoglycans, on the ventricular aspect of the leaflets. The leaflets of valves from sub-coronary implantation demonstrated a significantly thicker fibroelastic layer on the ventricularis and calcium deposition in the fibrosa. The media of the explanted valves showed increased number of lamellar units to levels comparable to normal aortic roots. Electron microscopy of valves inserted as free-standing roots showed increased organization into continuous layers. However, intralamellar components showed varying degrees of ‘disorganization’ in comparison to those in the normal aortic media. In addition, there was a marked increase in the number of vasa vasorum with thickened arteriolar wall in the outer media and adventitia.

CONCLUSIONS

Following the Ross operation, in the very long term, all components of the autograft showed varying degrees of remodelling, which was judged to be largely adaptive. Defining the type, determinants and possible functional effects of remodelling could help in understanding and optimizing the results of the Ross operation.
Investigation of the roles of AgrA and σB regulators in Listeria monocytogenes adaptation to roots and soil
Authors: Marinho Catarina M , Garmyn Dominique , Gal Laurent , Brunhede Maja Z , O'Byrne Conor , Piveteau Pascal
Published: March 2020

Little is known about the regulatory mechanisms that ensure the survival of the food-borne bacterial pathogen Listeria monocytogenes in the telluric environment and on roots. Earlier studies have suggested a regulatory overlap between the Agr cell–cell communication system and the general stress response regulator σB. Here, we investigated the contribution of these two systems to root colonisation and survival in sterilised and biotic soil. The ability to colonise the roots of the grass Festuca arundinacea was significantly compromised in the double mutant (∆agrA∆sigB). In sterile soil at 25°C, a significant defect was observed in the double mutant, suggesting some synergy between these systems. However, growth was observed and similar population dynamics were shown in the parental strain, ΔagrA and ΔsigB mutants. In biotic soil at 25°C, viability of the parental strain declined steadily over a two-week period highlighting the challenging nature of live soil environments. Inactivation of the two systems further decreased survival. The synergistic effect of Agr and σB was stronger in biotic soil. Transcriptional analysis confirmed the expected effects of the mutations on known Agr- and σB-dependent genes. Data highlight the important role that these global regulatory systems play in the natural ecology of this pathogen.
Challenging the charge balance hypothesis: reconsidering buffer effect and reuptake of previously excreted organic acids by Penicillium ochrochloron
Authors: Artmann D J , Vrabl P , Gianordoli R , Burgstaller W
Published: March 2020

Penicillium ochrochloron was used in the past for the leaching of zinc from a zinc oxide containing filter dust via excreted organic acids. Organic acid excretion by P. ochrochloron was stimulated by the addition of an extracellular buffer (2-(N-Morpholino)ethanesulfonic acid, MES; or zinc oxide, ZnO: ZnO + 2 H+ → Zn2+ + H2O). It was tested if the buffer stimulated excretion of organic acid anions is due to the necessity of an anion efflux across the plasma membrane to maintain electroneutrality by balancing the excretion of protons by the H+-ATPase. This charge balance hypothesis was previously postulated for P. ochrochloron. Two strains of P. ochrochloron were studied, which differed in growth parameters and amount of excreted organic acids. From the results, it was concluded that charge balance at the plasma membrane is not the main reason for organic acid excretion in these two strains of P. ochrochloron. Furthermore, the phenomenon of reuptake of excreted organic acids in the presence of about 100 mM of glucose is confirmed. It is suggested that the equilibrium between extracellular and intracellular organic acid anions may be maintained passively by a facilitated diffusion transporter.