bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Performance and Flow Field Study of Centrifugal Compressor With Supercritical Carbon-Dioxide (SCO2)
Authors: Kumar Hemant , Mistry Chetan S.
Published: January 2020

The Supercritical carbon-dioxide Brayton cycle main attraction is due to the Supercritical characteristic of the working fluid, carbon-dioxide (SCO2). Some of the advantages of using SCO2 are relatively low turbine inlet temperature, the compression work will be low, and the system will be compact due to the variation of thermodynamic properties (like density, and specific heat ratio) of SCO2 near the critical point. SCO2 behave more like liquid when its state is near the critical point (Total Pressure = 7.39 MPa, Total Temperature = 305 K), operating compressor inlet near critical point can minimize compression work.

For present study the centrifugal compressor was designed to operate at 75,000 rpm with pressure ratio (P.R) = 1.8 and mass flow rate = 3.53 kg/s as available from Sandai report. Meanline design for centrifugal compressor with SCO2 properties was done. The blade geometry was developed using commercial CAD Ansys Bladegen. The flow domain was meshed using Ansys TurboGrid. ANSYS CFX was used as a solver for present numerical study. The thermodynamic properties of SCO2 were imported from the ANSYS flow material library using SCO2.RPG [NIST thermal physics properties of fluid system]. In order to ensure the change in flow physics the mesh independence study was also conducted.

The present paper discuss about the performance and flow field study targeting different mass flow rates as exit boundary condition. The comparison of overall performance (Pressure Ratio, the Blade loading, Stage efficiency and Density variation) was done with three different mass flow rates. The designed and simulated centrifugal compressor meets the designed pressure rise requirement. The variation of mass flow rate on performance of centrifugal compressor was tend to be similar to conventional centrifugal compressor. The paper discusses about the effect of variation in density, specific heat ratio and pressure of SCO2 with different mass flow outlet condition. The performance map of numerical study were validated with experiment results and found in good agreement with experimental results. The change in flow properties within the rotor flow passage are found to be interesting and very informative for future such centrifugal compressor design for special application of SCO2 Brayton cycle. 80% mass flow rate has given better results in terms of aerodynamic performance. Abrupt change in thermodynamic properties was observed near impeller inlet region. Strong density variations are observed at compressor inlet.
Multi-Point Optimization of a Centrifugal Compressor Stage
Authors: Ramachandran Dhinagaran , Mayandi Balamurugan , George Libin , A. Vasudevan Chaithanya , Garigipati Ranjith
Published: January 2020

Turbocharger has a paramount influence on the performance of an internal combustion. Improved emission requirements have led to complex after treatment systems, which add pressure drop to the air management system. One of the ways to mitigate negative effects of pressure drop is to improve turbocharger efficiency. The scope of performance improvement for a typical turbocharger majorly lies on the modification of compressor wheel, turbine wheel, volutes etc. The major challenges in compressor wheel modification include setting the right major geometrical dimensions, considering compressor operability at different application requirements, design cycle time and the cost of computation. Present study is about evolving an effective optimization methodology, which comprises of parametrization of compressor stage at preliminary design stage and optimization of the chosen parameters through coupling one dimensional flow analysis tool with a robust optimization tool. The parameters were chosen based on their influence on overall efficiency and pressure ratio at different mass flows and varying engine rotational speeds. Surrogate models have been used to choose the optimal designs from the preliminary design space as per requirement and optimized designs were analyzed further for verification. Final validation has been carried out using a 3D RANS code.
Model Order Identification of Combustion Instability Using Lipschitz Indices
Authors: Harris Salil , Sinha Aniruddha , Kumar Sudarshan
Published: January 2020

Gas turbine combustors employing lean premixed combustion are prone to combustion instability. Combustion instability, if unchecked, will have deleterious effects to the combustor and hence needs to be controlled. Active control methods are preferred to obtain better off-design performance. The effectiveness of active control methods is dependent on the quality of controller which in-turn depends on the quality of model. In the present work, an input-output model structure, where the output of the system at the current instant is modelled as a nonlinear function of delayed inputs and outputs is chosen. As there are infinite possibilities for representation of nonlinear functions, all parameters in the model structure like time delay between input and output, number of delayed input and output terms and the appropriate form of nonlinear function can be obtained only iteratively. However, prior knowledge of delay and number of delayed inputs and outputs reduces the computational intensity. To this end, the present work utilizes the method of Lipschitz indices to obtain the number of delayed inputs and outputs.
The Effect of Temperature on Formability of AA6061-T6 Alloy Material Under Stretching Operation
Authors: Raman Goud R. , Rachala Aryan
Published: January 2020

Forming process is one of the most promising techniques in sheet metal forming process in which flat sheet is converted into desired component. Formability analysis has to be carried out in order to obtain successful forming components. In this paper the effect of temperature on formability of AA6061-T6 alloy material was estimated by conducting stretch forming operations on one mm AA6061-T6 alloy material sheets at different temperatures. The range of specimen sizes wastaken from 110 mm × 20 mm to 110 mm × 110mm of AA6061-T6 alloy material for experimentation. The experiments were conducted on the sheet metal forming setupat temperatures RT (250C), 1000C and 2000C.The obtained results were compared with the finite element analysis. The data extracted by the simulation results was well matched with the experimentation results.
Experimental and Numerical Investigations of Thermal Hydraulic Performance in Ribbed Channel for Combustor Liner
Authors: Bihari Divya , Bokade Sanjay
Published: January 2020

The present study assess the thermal hydraulic performance of V-shaped, W-shaped and 2W-shaped ribs in a rectangular channel with an aspect ratio of 6:1. The rib-roughened copper plates were located at the bottom of the channel to simulate the backside wall cooling of gas turbine combustor liners. The rib height-to-hydraulic diameter ratio (e/Dh) was 0.05834 and the rib pitch-to-height ratio (P/e) was 10 for all the cases. The experiments were carried out at the Reynolds numbers ranging from 32000 to 72000. A steady state heat transfer measurement method is used to investigate the heat transfer enhancement of ribbed wall against a smooth wall. Pressure taps were located at two stream-wise locations in channel walls to measure the pressure loss. To validate the understanding of experimental data, all the rib configurations were investigated numerically using ANSYS FLUENT. A low Reynolds number k-ε turbulence model was used to predict the heat transfer in the channel. The results show that the 2W ribs have the highest heat transfer and pressure loss characteristics in channel. It gives around 1.4–1.6 times increase in average Nusselt number and 2.7–3.3 times increase in friction factor as compare to smooth plate. Among all the cases V ribs obtained lowest heat transfer and pressure loss characteristics. Furthermore, both heat transfer enhancement and pressure loss increases with increasing Reynolds number.
Numerical Study of Vortices and Their Interactions in the Passage of Rotor Blade With Tip Gap
Authors: Rawat Sachin Singh , Prasad B. V. S. S. S.
Published: January 2020

A detailed three-dimensional steady-state numerical investigation using ANSYS CFX-18.2 on a high-pressure turbine blade with linear cascade is done for tip leakage flow of an axial gas turbine. Stationary casing with a fixed blade having tip gap is considered for the present study. There is leakage flow from the pressure side to the suction side of the blade which consecutively rolls up in the passage and forms the tip leakage vortex. The formation of vortices and their interaction with each other inside the passage is complex which makes experimental investigation difficult. The effect of tip gap size, off-design incidence angles, outlet Mach number, pitch size and flow path (stagger angle) are several parameters considered during the present study. The strength of tip leakage vortex and the vortex formed inside the gap is maximum. The losses are compared in terms of total pressure loss coefficient. The deviation of the flow direction is measured in terms of yaw angle distribution. Among various turbulence model available in CFX 18.2 the BSL k-ω turbulence model shows the most reliable results with experimental data. The results are compared with the base model without the tip gap. This investigation incites a better design of the blade tip with a precise reduction in losses.
Experimental Investigation of Solar Still With Varying Pressure
Authors: Sinhmar Harender , Bhati Jitendra , Bhati Ritanshu
Published: January 2020

The shortage for the pure water exists in many developing countries like India even though three fourth of the earth is sheltered by water. The main reason behind this is the unplanned growth of industry and uncontrolled growth of population. In this context, solar still may serve as an efficient solution for addressing pure water shortage in hot climatic areas facing scarcity of water. Solar still is a very simple device that can be used for converting the available non-potable water into potable water. Various water purifiers based on solar energy have been proposed in literature but most of them are having low water output. This paper presents a novel method of a solar water purifier operating under vacuum to enhance its productivity. An experimental investigation of a scaled model has been carried out and it was observed that productivity of solar still increases with decrease in pressure inside the still.
Comparison of Atomization Characteristics of Jet A-1 and Alternative Aviation Fuels Using High-Speed Imaging Technique
Authors: Kumar Manish , Karmakar Srinibas
Published: January 2020

Environmental pollution from gas turbine engines is becoming a serious concern recently because of the steep growth in the aviation sector globally. Therefore, potential alternative fuels which can partially or fully replace fossil-based jet fuel are getting significant attention. However, the search for suitable candidate fuels which can fulfill the requirement in terms of fuel properties and combustion performance is continuing. The present study deals with an experimental investigation of atomization characteristics of Jet A-1, butanol, and butyl butyrate in quiescent atmospheric air. A high-speed imaging technique has been adopted to make a comparison of ligament breakup characteristics and droplet formation of these alternative biofuels with that of Jet A-1. Various fuel properties, including density, viscosity, and surface tension, are compared. An effort is made to understand how the variation in fuel properties influences the atomization mechanism of each fuel. The surface tension seems to be similar for these three fuels with a slight variation in density. However, there is a significant variation in viscosity. Viscosity appears to play a major role in the difference observed in ligament length and droplet formation. Due to the higher viscosity of butanol, the droplet formation seems to be delayed compared to Jet A-1, whereas the lower viscosity of butyl butyrate promotes faster droplet formation. The effect of blending of these biofuels with Jet A-1 on atomization characteristics will be compared with that of Jet A-1.
Investigation of Performance of Fins Geometry on a Vertical Cylinder
Authors: Yadav Nagendra P. , Srivastava Ayush
Published: January 2020

This paper focuses the prediction of the performance of fins having different geometry on a vertical cylinder in natural convection heat transfer. The extensive experimental investigations are performed for different geometrical profile of fins. The hollow cylindrical base having the same fins on their periphery with variable numbers 6 to 18. The temperature measurement was done at different location on the base of cylindrical surface as well as on the surface of the fins. The temperature behaviors for various fins are discussed with power. The measurement was done after justification of the steady state. The temperature is decreases with measurement location from base to tip of fin. As per the variation of base temperature and thermal resistance, semiconvex profile of fin is better than other geometry of fin. The Nusselt number is higher at low power input and less number of fins. The variation in temperature for different power inputs and geometry of fin and the numbers of fin help us to design fins which can be used up in advanced semiconductors in the newest technology because the cooling of those devices is a major challenge to the industries and researchers.
Investigations on the Effect of Bearing Clearance in Turbocharger Fully Floating Hydro-Dynamic Bearing System
Authors: Chandrasekaran Lokesh , Selvaraj Praveen Kumar , Vengala Prasanth R. , Arthanarisamy Subramani D.
Published: January 2020

Turbocharger technology helps in achieving reduced emissions, increased performance and downsizing of automobile engines. The rotor system of the TC is supported with the help of hydrodynamic fully/ rotating floating ring (RFRB) bearing systems. Hydro-dynamic bearing systems are more sensitive to inner and outer clearances. The possibility of maintaining nominal clearance in the mass produced turbocharger is limited to manufacturing capabilities and constrains. The inner and outer bearing clearances are always in the controlled range. This range creates four different combination of clearances which need to be validated to ensure safe shaft motion, which incurs huge development & testing cost and time. In hot gas stand, using NVH Data Acquisition System (DAQ) with frequency analyzers and eddy current displacement sensors, rotor shaft motion behavior was studied for the nominal bearing clearances. Numerical simulation model was created for the nominal clearances case. In numerical simulations, multi-body dynamics (MBD) of flexible rotor and housing structures are coupled with Elasto-hydrodynamics (EHD) of the inner and outer oil films. The energy equation is considered for calculation of oil film temperature in EHD using thermal boundary conditions obtained from 3D FE simulation. Simulation and tested results are compared and correlated. With this validated simulation methodology, investigation is conducted for the four different combination of clearances and results are discussed in this paper.
Time Dependent Low Velocity Impact Response of Turbomachinery Blade Made of Porous Exponential FGM
Authors: Das Apurba , Agarwal Gopal , Inaba Kazuaki , Karmakar Amit
Published: January 2020

This study presents transient dynamic response of porous and non-porous exponential functionally graded (E-FGM) conical shells subjected to low velocity single and multiple impact. Hertzian contact law in modified form considering permanent indentation is used to calculate the impact response parameters. For finite element formulation eight-noded isoparametric shell element having five degrees of freedom per node is used. The dynamic equations for the low velocity impact problems are solved by Newmark’s time integration scheme. Parametric studies in terms of contact force, initial velocity of impactor, impactor displacement and shell displacement for Stainless Steel-Silicon Nitrite porous and non-porous conical shells (idealized as rotating turbo-machinery blade) under low velocity single and multiple impact are analyzed. Twist angle has significant effect on contact force but has marginal effect on contact duration. Contact force for perfect (porosity free) case is higher than that of porous one and the contact forces are found to decrease with higher porosity factor. Even porous FG conical shell is predicting lower contact force and higher shell displacement than that of uneven porous FG conical shell for a given porosity factor.
Simultaneity in cylindrical spacetime
Authors: Lee Chunghyoung
Published: January 2020

In cylindrical spacetime which is flat like Minkowski spacetime but is spatially closed, two twins can part and reunite, while none of them go through any acceleration. Still, the twins are aged differently upon their reunion (except for some special occasions). The key to understanding what happens in cylindrical spacetime lies in clock synchrony. In cylindrical spacetime, the Round-trip Axiom (that two light signals sent simultaneously in opposite directions along a closed path return simultaneously) fails to hold, and so distant clocks cannot be consistently synchronized following the standard procedure proposed by Einstein except for those under some privileged motion. We propose an alternative method of synchrony utilizing the one-way speed of light traveling around the universe, which can be measured with one clock and varies from inertial frame to inertial frame. This alternative synchrony renders simultaneity not relative but absolute and makes it possible to consistently describe both the local and global phenomena in cylindrical spacetime.
Composite cores and tamper yield: Lesser-known aspects of Manhattan Project fission bombs
Authors: Reed B. Cameron
Published: January 2020

This paper examines the physics of two lesser-known aspects of the nuclear weapons produced in the Manhattan Project: The idea of constructing weapons with so-called composite cores (that is, ones which would have comprised combinations of uranium and plutonium), and the fact that some 30% of the plutonium-fueled Fat Man yield was due to fissions in the uranium-238 tamper of that weapon, fissions induced by high-energy neutrons liberated by fissions in the plutonium core. Simple models of both issues give results in reasonable accord with available data.
Implementation of the two-dimensional electrostatic particle-in-cell method
Authors: Rodríguez-Patiño D. F. , Ramírez S. , Salcedo-Gallo J. S. , Hoyos J. H. , Restrepo-Parra E.
Published: January 2020

We provide a guide to implementing the particle-in-cell algorithm, which is useful for simulating diverse phenomena in plasmas. We focus on two-dimensional systems which have vector fields with three Cartesian components but depend only on two spatial coordinates. We describe the algorithm in detail, including particle-to-grid interpolation, the fast Fourier transform, the Boris algorithm, and the use of dimensionless units. As an example, we discuss a simulation of the two-stream instability, which occurs in a plasma system composed of two counter-streaming electrons and an ion background at rest.
Conceptual difficulties in interpreting the real image of an object
Authors: Mitrović Mićo M. , Misailović Branislava M. , Maksimović Biljana Z. , Žekić Andrijana A.
Published: January 2020

This work was conducted to investigate the understanding of the concept of real image observation among students and teachers of physics. We studied the implications of inadequate explanation of the role of the eyes in the observation of the real and virtual images of an object and in understanding the laws of geometrical optics. The eyes have been given a far more significant role in the observation of virtual images than that of real images in the majority of textbooks for students at all levels of the educational system, from primary school to university level. This leads to several incorrect conclusions about the possibility of observing real images using the eyes. To correct this mistaken perception, this work suggests ways of explaining the role of the eye in real and virtual image observation in textbooks for students of different ages and at all levels.
Analytic error control methods for efficient rotation in dynamic binaural rendering of Ambisonics
Authors: Magariyachi Tetsu , Mitsufuji Yuki
Published: January 2020

Dynamic binaural rendering of Ambisonics considering head movements gives a highly realistic sensation to listeners owing to the precise localization and the presence of dynamic cues. Dealing with a head movement is often achieved in the spherical harmonic domain by multiplying Ambisonic signals by a Wigner D-matrix (WDM) with the aim of rotating signals in the opposite direction to the head movement. However, for a vertical rotation, the system requires an enormous computational cost owing to the structure of the WDM, whose number of block diagonal elements increases with the spherical harmonic order of Ambisonics. In this paper, a method is introduced to reduce the computational cost related to the vertical rotation by approximating a WDM with a banded WDM generated from the truncated sum of a power series expression of the WDM. By using an analytically derived upper bound of the approximation error, two methods are devised to determine the minimum bandwidth which archives the maximum computational cost reduction under the user-preferred threshold. The experimental results show that there is a trade-off between the approximation error and the computational cost and that these methods are applicable to the use case of interest, i.e., dynamic binaural rendering of Ambisonics.
Rethinking chemistry for a circular economy
Authors: Kümmerer Klaus , Clark James H. , Zuin Vânia G.
Published: January 2020

Chemical complexity complicates product recycling and manufacturing sustainability
Hyperviscosity-related splenic infarction, gastrointestinal ischaemia–reperfusion injury and transient dysarthria in a patient with distributive shock due to idiopathic systemic capillary leak syndrome (Clarkson’s syndrome)
Authors: van Erven Jelle Alexander , Schrama Jolanda , Castelijn Daan Albert Robertus
Published: January 2020

Clarkson’s syndrome, also known as idiopathic systemic capillary leak syndrome, is characterised by vascular hyperpermeability resulting in intravascular hypovolaemia and shock. A clinician should consider the diagnosis if other causes of shock, for example, sepsis and anaphylaxis, are ruled out and concomitant hyperviscosity is not caused by a myeloproliferative disease. Here, we describe a patient presenting with severe plasma leakage and assumable blood hyperviscosity leading to splenic infarction, gastrointestinal ischaemia–reperfusion syndrome and transient dysarthria. Our patient was first suspected of polycythaemia vera and phlebotomies were performed. Awareness of this syndrome and subsequent correct treatment is essential to prevent complications and to reduce mortality. As in our patient, most patients with Clarkson’s syndrome have a monoclonal gammopathy, light-chain-type kappa. Prophylactic treatment with intravenous immunoglobulin (IVIg) is advised to prevent recurrence of capillary leak. Our patient did not suffer from another symptomatic episode after starting IVIg.
Literature review: technological interventions and their impact on quality of life for people living with dementia
Authors: Sanders David , Scott Philip
Published: January 2020

Objectives

Rapid technology-driven innovation in the healthcare sector has led to an increasing ability to effectively respond to health challenges. However, the cognitive challenges faced by a person with dementia exacerbate the difficulty of designing enduring technological dementia care solutions. Despite this, and in the absence of a cure, facilitating well-being and improved quality of life becomes pivotal for those living with dementia and their caregivers. This review aimed to identify and consolidate the provision of technological solutions for dementia care, and how these are perceived to impact the quality of life of a person with dementia.

Methods

Articles and journals were identified using keywords including those relating to quality of life, assistive technologies and technology adoption and acceptance. Greater priority was given to resources published after 2010 due to the speed of technological advancement, and peer-reviewed articles were preferred.

Results

91 resources were identified, with 38 contributing to the final review. In addition to multiple quality of life measurement tools, the literature identified a large variety of solutions that fell into three categories: those used ‘by’, ‘with’ or ‘on’ a person with dementia.

Conclusions

This review concludes that the ‘one size fits all’ approach to many solutions reflects the lack of supporting evidence, negatively impacting trust in their usefulness among caregivers and their subsequent adoption rates. This could be attributed to limited involvement of people with dementia in studies of effectiveness and adoption. Additional research is recommended to further consolidate research on quality of life and to understand the individuality and progression of dementia and its influence on dementia care solutions.
Physical activity and exercise in youth mental health promotion: a scoping review
Authors: Pascoe Michaela , Bailey Alan P , Craike Melinda , Carter Tim , Patten Rhiannon , Stepto Nigel , Parker Alexandra
Published: January 2020

Background/Aim

This scoping review examined the breadth and outcomes of controlled trials testing the effect of physical activity and exercise interventions across all mental health outcomes for mental health promotion and indicated prevention studies in young people.

Methods

The literature search was conducted using ‘Evidence Finder’.

Results

Thirty publications were included. Available evidence suggested that interventions of varying intensity may lead to a reduction in depression symptoms and that moderate-to-vigorous-intensity and light-intensity interventions may reduce anxiety symptoms. Effects of physical activity/exercise interventions on additional mental health outcomes were also shown; however, the number of studies was small, indicating a limited evidence base. Robust research regarding the effects of physical activity/exercise on mental health promotion and as an indicated prevention strategy in young people is lacking.

Conclusion

The available evidence suggests that physical activity/exercise is a promising mental health promotion and early intervention strategy and warrants further investigation.
Campylobacter prevalence and risk factors associated with exceeding allowable limits in poultry slaughterhouses in Spain
Authors: Sevilla‐Navarro Sandra , Marin Clara , Cortés Verónica , García Cristina , Catalá‐Gregori Pablo
Published: January 2020

Background

Campylobacter is the main pathogen involved in zoonotic gastrointestinal diseases. In 2018, European Regulation 2017/1495 on Campylobacter in broiler carcases came into force. In this context, the aim of the study was to assess the potential risk factors associated with exceeding the 1000 cfu/g (colony‐forming units per gram) limit set by the EC in several slaughterhouses in Spain.

Methods

Data relating to 12 factors were collected using questionnaires. Samples were collected from 12 Spanish abattoirs in June, July and August 2017 (n=1725) and were analysed following the ISO 10272‐2:2006 method.

Results

The proportion of Campylobacter‐positive samples was 23.7 per cent (n=409). Analysis of flock age (41–50 days) revealed a significantly increased odds ratio (OR) in Campylobacter enumeration (OR=7.41). Moreover, scalding temperature (51.9°C–54°C) was positively associated with an increase in OR (OR=2.75). Time in transit to slaughter for 1–1.5 hours showed a significant decrease in OR (OR=0.25), while time in transit for more than two hours showed an increase in OR (OR=4.44). With regard to carcase weight, a weight of 3.21–3.58 kg showed a decrease in OR (OR=0.01).

Conclusion

The outcomes of this study suggest that although most chickens are contaminated by the bacterium, the prevalence of those exceeding the 1000 cfu/g limit is not so high as thought.
A review of possible pathways of marine microplastics transport in the ocean
Authors: Li Yanfang , Zhang Hua , Tang Cheng
Published: January 2020

Marine microplastics pollution has been a new challenge to marine environmental protection. The research results have shown that microplastics exist everywhere in the ocean. However, understanding of the transport of microplastics in the ocean, including coastal zones, is not clear. This paper provides a holistic overview of the modelling of microplastic transportation. The transport processes are complex, including surface drifting, vertical mixing, beaching, and settling. Besides the dynamic conditions of oceans, the transportation of microplastics is influenced by their physical characteristics, such as size, shape, and density. For buoyant particles, a Lagrange track model is used to simulate the surface drift process, considering current, windage effect, and Stokes drift. It is difficult to observe the vertical mixing process of microplastics because of their small size (<5 mm), therefore the parameters of the vertical mixing process in the model are still less known. Large accumulation of microplastics in sediments may be a result of settlement and entrainment. Also, biofilm formation can increase their density and thus, deposition. Considering sedimentation of microplastics is somewhat different from sediment deposition, some primary parameters (e.g., diffusivity, Stokes-drift, settling rate, biofouling rate) are required in future studies to better understand the transport of marine microplastics.
Weyl’s unified field theory: Perspectives for a new approach
Authors: Sanomiya T. A. T. , Lobo I. , Formiga J. B. , Romero C.
Published: January 2020

We revisit Weyl’s unified field theory, which arose in 1918, shortly after general relativity was discovered. As is well known, in order to extend the program of geometrization of physics started by Einstein to include the electromagnetic field, H. Weyl developed a new geometry which constitutes a kind of generalization of Riemannian geometry. However, despite its mathematical elegance and beauty, a serious objection was made by Einstein, who considered Weyl’s theory not suitable as a physical theory since it seemed to lead to the prediction of a not yet observed effect, the so-called “second clock effect”. In this paper, our aim is to discuss Weyl’s proposal anew and examine its consistency and completeness as a physical theory. Finally, we propose new directions and possible conceptual changes in the original work. We believe that in this way we could perhaps be led to a rich and interesting new modified gravity theory.
A combinatorial description of dual defects of toric varieties
Authors: Furukawa Katsuhisa , Ito Atsushi
Published: January 2020

From a finite set in a lattice, we can define a toric variety embedded in a projective space. In this paper, we give a combinatorial description of the dual defect of the toric variety using the structure of the finite set as a Cayley sum with suitable conditions. We also interpret the description geometrically.
Multiple positive solutions for nonlocal elliptic problems involving the Hardy potential and concave–convex nonlinearities
Authors: Shakerian Shaya
Published: January 2020

In this paper, we study the existence and multiplicity of solutions for the following fractional problem involving the Hardy potential and concave–convex nonlinearities: [Formula: see text]

where [Formula: see text] is a smooth bounded domain in [Formula: see text] containing [Formula: see text] in its interior, and [Formula: see text] with [Formula: see text] which may change sign in [Formula: see text]. We use the variational methods and the Nehari manifold decomposition to prove that this problem has at least two positive solutions for [Formula: see text] sufficiently small. The variational approach requires that [Formula: see text] [Formula: see text] [Formula: see text], and [Formula: see text], the latter being the best fractional Hardy constant on [Formula: see text].
Understanding the Role of Graphene in Hydrated Layered V-Oxide Based Cathodes for Rechargeable Aqueous Zn-Ion Batteries
Authors: Wu Tao , Zhu Kaiyue , Huang Kevin
Published: January 2020

Graphene is commonly used as a performance enhancer for batteries. Other than increasing the electronic conductivity, however, additional performance beneficial mechanisms remain unclear. Herein, we report a combined experimental and theoretical study on the role of graphene nanoplate (GN) in a high-capacity aqueous-ZIB cathode hydrated Ca0.67V8O20 (CaVO). The experimental results reveal that the GN does improve the interfacial charge transfer kinetics and affect the stability and capacity of the cathode without changing the bulk property of the cathode. The theoretical results suggest that GN helps enhance Zn-adsorption on the interface, which increases the Zn-coverage and thus promotes faster kinetics.
Maximum Closeness Centrality k-Clubs: A Study of Dock-Less Bike Sharing
Authors: Rahim Taleqani Ali , Vogiatzis Chrysafis , Hough Jill
Published: January 2020

In this work, we investigate a new paradigm for dock-less bike sharing. Recently, it has become essential to accommodate connected and free-floating bicycles in modern bike-sharing operations. This change comes with an increase in the coordination cost, as bicycles are no longer checked in and out from bike-sharing stations that are fully equipped to handle the volume of requests; instead, bicycles can be checked in and out from virtually anywhere. In this paper, we propose a new framework for combining traditional bike stations with locations that can serve as free-floating bike-sharing stations. The framework we propose here focuses on identifying highly centralized k-clubs (i.e., connected subgraphs of restricted diameter). The restricted diameter reduces coordination costs as dock-less bicycles can only be found in specific locations. In addition, we use closeness centrality as this metric allows for quick access to dock-less bike sharing while, at the same time, optimizing the reach of service to bikers/customers. For the proposed problem, we first derive its computational complexity and show that it is NP-hard (by reduction from the 3-SATISFIABILITY problem), and then provide an integer programming formulation. Due to its computational complexity, the problem cannot be solved exactly in a large-scale setting, as is such of an urban area. Hence, we provide a greedy heuristic approach that is shown to run in reasonable computational time. We also provide the presentation and analysis of a case study in two cities of the state of North Dakota: Casselton and Fargo. Our work concludes with the cost-benefit analysis of both models (docked vs. dockless) to suggest the potential advantages of the proposed model.
Prevalence of Mental Distress and Associated Factors among Samara University Students, Northeast Ethiopia
Authors: Tesfaye Kelemu Robel , Bayray Kahsay Alemayehu , Ahmed Kedir Y.
Published: January 2020

Background. Empirical findings have indicated that higher institution students experience a higher prevalence of mental distress compared to the general population. Understanding the magnitude and associated factors of mental distress in university students would be helpful to practitioners and policymakers in Ethiopia. The aim of the present study was to examine the prevalence and associated factors of mental distress among Samara university students, Northeast Ethiopia. Methods. Institution based cross-sectional study design was conducted in Samara university from December to June 2018. A simple random sampling technique was employed to select the study participants. Self-Reporting Questionnaire-20 (SRQ-20) was used to measure the mental distress of students. Multivariable logistic regression modeling was used to examine the association between sociodemographic and psychosocial factors with the mental distress of students. Results. The proportion of students with mental distress were found to be 53.2% (95% confidence interval [CI]: 48.0%, 58.0%). Female students were more likely to be mentally distressed compared to male students (adjusted odds ratio [AOR]: 4.66; 95% CI: 2.81, 7.71). Ever khat use (AOR: 3.09; 95% CI: 1.74, 5.50) and poor sleep quality (AOR: 2.23; 95% CI: 1.12, 3.66) were significantly associated with mental distress of students. Conclusion. Our study indicates that the proportion of mental distress was found to be higher among Samara university students as compared to previously published studies in Ethiopia. Female students, ever khat users and those with poor sleep quality were associated with mental distress. There is a need for evidence-based interventional strategies such as self-help measures, sleep hygiene and peer support, as well as professional mental health services as part of student health services that would be helpful to reduce the burden of mental distress of students.
Cardiac Inotropes Offer Protection of Renal Function in Patients with Kidney Transplantation
Authors: Guo Ning , Wang Zehua , Bow Laurine M. , Cui Xianquan , Zhang Luwei , Xian Wanhua , Sun Huaibin , Tian Jun
Published: January 2020

Introduction: Impaired cardiac function is one of the most concomitant symptoms in patients with kidney failure after long-term dialysis. In addition, the preservation of adequate perfusion pressure to the graft plays a significant role in the intraoperative management during kidney transplantation, but the use of positive inotropic drugs in kidney transplant patients has been studied less. We investigated the protective effects of renal function by means of cardiac inotropes in kidney transplant patients. Methods: Eighty-nine patients that received kidney transplantation between April 2014 and December 2016 at Qilu Hospital were included and randomly divided into the treatment group receiving levosimendan and a control group. All kidney recipients received ABO-compatible donors. A poor outcome was defined as one of the following: delayed graft function, graft hemorrhage, or nephrectomy. Results: The treatment group had a better composite outcome and the level of neutrophil gelatinase-associated lipocalin was also lower than in the control group. Conclusion: Inotropic drugs may play a protective role in renal function in kidney transplantation.
A Stent for Every Stone? Prestenting Habits and Outcomes from a German Multicenter Prospective Study on the Benchmarks of Ureteroroscopic Stone Treatment (BUSTER)
Authors: Werthemann Peter , Weikert Steffen , Enzmann Thomas , Schostak Martin , Lebentrau Steffen
Published: January 2020

Introduction: Previous studies have shown that prestenting in ureterorenoscopic stone removal (URS) is carried out more frequently in Germany than in other countries. Objective: This investigation evaluated the impact of high prestenting rates on outcomes as well as the influence of stone characteristics and treatment habits on prestenting. Methods: The dataset from the BUSTER observational study was used. Patient and stone characteristics, as well as treatment outcomes, were analyzed for 307 cases from 14 urological clinics in Germany. Results: The overall prestenting rate was 70.0%. Prestenting rates were significantly higher for renal stones than ureteric stones (84.6 vs. 60.6%, p < 0.0001). Compared to the unstented cases, prestenting for renal stones improved stone-free rates (73.2 vs. 11.1%, p < 0.0001) and increased the rate of completely lesion-free URS (45.4 vs. 16.7%, p = 0.034) while reducing the rate of poststenting (from 100 to 80.8%, p = 0.041). None of these effects could be demonstrated when prestenting for ureteric stones. Prestenting rates were less variable for renal stones (57–100%) than for ureteric stones (0–100%, p < 0.01). Conclusions: This study confirms the benefits of prestenting in URS for renal stones but not for ureteric stones. There were considerable differences in prestenting rates between the participating clinics.
Commercially Available Gene Expression Assays as Predictive Tools for Adjuvant Radiotherapy? A Critical Review
Authors: Krug David , Baumann René , Budach Wilfried , Duma Marciana Nona , Dunst Jürgen , Feyer Petra , Fietkau Rainer , Haase Wulf , Harms Wolfgang , Hehr Thomas , Piroth Marc D. , Sedlmayer Felix , Souchon Rainer , Wenz Frederik , Sauer Rolf ,   Breast Cancer Expert Panel of the German Society of Radiation Oncology (DEGRO)
Published: January 2020

Background: Gene expression assays are increasingly used for decision-making regarding adjuvant chemotherapy in patients with hormone receptor-positive, HER2-negative breast cancer. There are some clinical situations in which there is also a need for better prognostic and predictive markers to better estimate the amount of benefit from adjuvant radiotherapy. The rising availability of gene expression analyses prompts the question whether their results can also be used to guide clinical decisions regarding adjuvant radiation. Summary: Multiple studies suggest a correlation between results from gene expression assays and locoregional recurrence rates. Only few publications addressed the predictive value of results from gene expression analysis for the role of adjuvant radiotherapy in different settings. Key Messages: To date, the available evidence on the possible predictive value of gene expression assays for radiotherapy does not support their inclusion into the decision-making process for adjuvant radiation. This is due to methodological weaknesses and limitations regarding patient selection, the nonrandomized design of all studies in terms of radiotherapy use, and limited availability of tissue from prospective trials. Thus, utilization of the present knowledge for clinical indication of radiotherapy should be very cautious.
Mosaic Small Supernumerary Marker Chromosome Derived from Five Discontinuous Regions of Chromosome 8 in a Patient with Neutropenia and Oral Aphthous Ulcer
Authors: Altıner Şule , Yürür Kutlay Nüket , Ilgın Ruhi Hatice
Published: January 2020

Small supernumerary marker chromosomes (sSMCs) are characterized as additional centric chromosome fragments which are too small to be classified by cytogenetic banding alone and smaller than or equal to the size of chromosome 20 of the same metaphase spread. Here, we report a patient who presented with slight neutropenia and oral aphthous ulcers. A mosaic de novo sSMC, which originated from 5 discontinuous regions of chromosome 8, was detected in the patient. Formation of the sSMC(8) can probably be explained by a multi-step process beginning with maternal meiotic nondisjunction, followed by post-zygotic anaphase lag, and resulting in chromothripsis. Chromothripsis is a chromosomal rearrangement which occurs by breakage of one or more chromosomes leading to a fusion of surviving chromosome pieces. This case is a good example for emphasizing the importance of conventional karyotyping from PHA-induced peripheral blood lymphocytes and examining tissues other than bone marrow in patients with inconsistent genotype and phenotype.
Programação dinâmica aplicada à redução de custos nas compras de vacinas de um hospital
Authors: Cechin Rafaela Boeira , Biasuz Rodrigo , Falavigna Asdrubal , Corso Leandro Luís
Published: January 2020

Uma organização não depende somente do quanto ela fatura com seus produtos e serviços, mas também do quanto ela gasta, por isso, redução de custos é tão importante, podendo até ser o diferencial para uma empresa se manter no mercado. Este artigo apresenta um estudo de caso de Programação Dinâmica aplicada a compras de vacina em um hospital, a fim de otimizar a maneira que é realizada as compras e reduzir seus custos. Para isso, foram coletadas informações relacionadas a aquisição da mercadoria e estoque. O resultado obtido com o modelo de otimização foi comparado com o cenário atual do hospital, e foi observada uma possível redução de 5,57%, representando quase R$ 100.000,00.
Impedância pulmonar como novo marcador de fisioterapia respiratória em adultos com distúrbios ventilatórios obstrutivos
Authors: Santos Dyovana Silva Dos , Spitznagel Andressa Schenkel , Branco Karolini Reis , Donadio Márcio Vinícius Fagundes , Schivinski Camila Isabel Santos , Schiwe Daniele , Heinzmann Filho João Paulo
Published: January 2020

Modelo do estudo: Revisão sistemática.

Objetivo: Avaliar se os recursos de fisioterapia respiratória modificam a impedância pulmonar avaliada pelas técnicas de oscilações forçadas (TOF’s) em adultos com distúrbios ventilatórios obstrutivos. Método: Trata-se de uma revisão sistemática conduzida nas bases de dados PubMed, Scielo, Lilacs e PEDro, utilizando-se a seguinte estratégia de busca: Obstructive pulmonary disease OR chronic obstructive pulmonary disease OR COPD OR Bronchiectasis OR Bronchial diseases OR Cystic fibrosis OR mucoviscidosis AND impulse oscillometry OR forced oscillation techniques AND physical therapy OR physiotherapy AND Airway Resistance. Resultados: De um total de 216 artigos, apenas 3 foram incluídos. As amostras totalizaram 64 participantes, incluindo adultos com fibrose cística (FC), doença pulmonar obstrutiva crônica (DPOC) e bronquiectasias. Dois estudos utilizaram o flutter® e um realizou drenagem autógena. A impedância pulmonar foi avaliada em duas pesquisas pelo sistema de oscilometria de impulso (IOS) e em um pela TOF modificada (TOF-m). Houve redução da resistência em várias frequências, sendo que as mais frequentes foram a resistência total (3/3), a resistência central (2/3) e a periférica (2/3). Além disso, a reatância pulmonar apresentou resultados conflitantes. Conclusão: Evidenciou-se que os recursos fisioterapêuticos utilizados para remoção de secreções das vias aéreas modificam a impedância pulmonar avaliada pelas TOF’s em adultos com DVO, sendo a resistência total das vias aéreas o parâmetro com maior ganho terapêutico.
Diagnóstico intraoperatório de paraganglioma retroperitoneal em massa abdominal
Authors: Macêdo Anna Flávia Magalhães Castrillon De , Silva Camila Fernandes Álvares Da , Gomes Ricardo da Silva , Silva Evandro Oliveira , Coutinho Sandra Lucia Branco Mendes
Published: January 2020

Modelo do estudo: relato de caso; Importância do Problema: O presente relato de caso tem como objetivo relatar o caso de paciente do sexo masculino, 40 anos, com quadro de dor em região lombar esquerda há seis meses, sem massas palpáveis e sem achados de massas retroperitoneais à Ultrassonografia de abdome. A investigação diagnóstica constatou, através de Tomografia Computadorizada de abdome, imagem de lesão retroperitoneal acoplada medialmente à artéria aorta, com suposto diagnóstico de Sarcoma Retroperitoneal e, por conseguinte, indicação de tratamento cirúrgico. Durante o período intraoperatório, o paciente apresentou sintomas adrenérgicos, que cessaram após a ressecção completa da lesão e ligadura de parte das aderências do tumor ao retroperitônio. A biópsia evidenciou se tratar de um Paraganglioma Retroperitoneal. A partir do estudo de caso supracitado, é possível perceber a importância de incluir o Paraganglioma como diagnóstico diferencial de tumores retroperitoneais, em consequência de sua raridade, difícil diagnóstico e importância clínica. Comentários: Os Paragangliomas, frequentemente chamados de feocromocitomas extra-adrenais, são tumores raros, na sua maioria benignos, produtores de catecolaminas, com origem em células provenientes do Sistema Nervoso Autônomo e das células da crista neural.1 A sintomatologia clássica desses tumores, em função da capacidade secretora, inclui palpitações, cefaleias e diaforese, associados a Hipertensão Arterial (HTA).