bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrodynamics of active particles confined in a periodically tapered channel
Authors: Dhar A. , Burada P. S. , Sekhar G. P. Raja
Published: October 2020

Active particles in diverse circumstances encounter confined channels with asymmetric bounding walls. In the present work, employing the squirmer model, we analyze the trajectory of a single and a pair of active particles in a two-dimensional periodically tapered channel with asymmetric bounding walls through a combined analytical-numerical approach. Assuming Stokes equations for the flow inside the channel, both puller and pusher types of squirmers are treated. We illustrate through phase diagrams how for different projection angles of the squirmer the associated swimming trajectories are non-trivially altered for various tapering angles of the channel. The phase diagram characterizes the trajectory of the squirmer as trapped or escaped depending on these angles. It is observed that for a fixed projection angle, the swimmer exhibits a transition in the swimming state at a critical tapering of the channel. Correspondingly, the combination of the projection and tapering angles may serve as a control mechanism guiding the swimmer for relevant applications in micro-fluidic systems. We further investigate the stability of the individual squirmer trajectory in the presence of a second squirmer, which hints at the development of parallel or coordinated swimming motion inside the channel. The results indicate that the tapering of the channel acts as a decisive parameter in the mutual attraction or repulsion and navigates the collective swimming state of the squirmers.
Capillary-fed, thin film evaporation devices
Authors: Vaartstra Geoffrey , Zhang Lenan , Lu Zhengmao , Díaz-Marín Carlos D. , Grossman Jeffrey C. , Wang Evelyn N.
Published: October 2020

Evaporation plays a critical role in a range of technologies that power and sustain our society. Wicks are widely used as passive, capillary-fed evaporators, attracting much interest since these devices are highly efficient, compact, and thermally stable. While wick-based evaporators can be further improved with advanced materials and fabrication techniques, modeling of heat and mass transport at the device level is vital for guiding these innovations. In this perspective, we present the design and optimization of capillary-fed, thin film evaporation devices through a heat and mass transfer lens. This modeling framework can guide future research into materials innovations, fabrication of novel architectures, and systems design/optimization for next generation, high-performance wick-based evaporators. Furthermore, we describe specific challenges and opportunities for the fundamental understanding of evaporation physics. Finally, we apply our modeling framework to the analysis of two important applications—solar vapor generation and electronics cooling devices.
Electron Landau damping of kinetic Alfvén waves in simulated magnetosheath turbulence
Authors: Horvath Sarah A. , Howes Gregory G. , McCubbin Andrew J.
Published: October 2020

Turbulence is thought to play a role in the heating of the solar wind plasma, though many questions remain to be solved regarding the exact nature of the mechanisms driving this process in the heliosphere. In particular, the physics of the collisionless interactions between particles and turbulent electromagnetic fields in the kinetic dissipation range of the turbulent cascade remains incompletely understood. A recent analysis of an interval of Magnetospheric Multiscale (MMS) observations has used the field–particle correlation technique to demonstrate that electron Landau damping is involved in the dissipation of turbulence in the Earth's magnetosheath. Motivated by this discovery, we perform a high-resolution gyrokinetic numerical simulation of the turbulence in the MMS interval to investigate the role of electron Landau damping in the dissipation of turbulent energy. We employ the field–particle correlation technique on our simulation data, compare our results to the known velocity–space signatures of Landau damping outside the dissipation range, and evaluate the net electron energization. We find qualitative agreement between the numerical and observational results for some key aspects of the energization and speculate on the nature of disagreements in light of experimental factors, such as differences in resolution, and of developing insights into the nature of field–particle interactions in the presence of dispersive kinetic Alfvén waves.
Enhancement of spin Hall conductivity in W–Ta alloy
Authors: Kim Jun-Young , Han Dong-Soo , Vafaee Mehran , Jaiswal Samridh , Lee Kyujoon , Jakob Gerhard , Kläui Mathias
Published: October 2020

Generating pure spin currents via the spin Hall effect in heavy metals has been an active topic of research in the last decade. In order to reduce the energy required to efficiently switch neighboring ferromagnetic layers for applications, one should not only increase the charge-to-spin conversion efficiency but also decrease the longitudinal resistivity of the heavy metal. In this work, we investigate the spin Hall conductivity in W1-xTax/CoFeB/MgO (x = 0–0.2) using spin torque ferromagnetic resonance measurements. Alloying W with Ta leads to a factor of two change in both the damping-like effective spin Hall angle (from −0.15 to −0.3) and longitudinal resistivity (60–120 μΩ cm). At a 11% Ta concentration, a remarkably high spin Hall angle value of –0.3 is achieved with a low longitudinal resistivity of 100 μΩ cm, which could lead to a very low power consumption for this W-based alloy. This work demonstrates that sputter-deposited W–Ta alloys could be a promising material for power-efficient spin current generation.
Viscous dissipated hybrid nanoliquid flow with Darcy–Forchheimer and forced convection over a moving thin needle
Authors: Gul Taza , Rahman Junaid ur , Bilal Muhammad , Saeed Anwar , Alghamdi Wajdi , Mukhtar Safyan , Alrabaiah Hussam , Bonyah Ebenezer
Published: October 2020

The study of hybrid nanoliquid can help achieve innumerable advanced features that make heat and mass transmission more convenient, such as in hybrid-powered engines, pharmaceutical processes, microelectronics, domestic refrigerators, engine cooling, and so on. The intention behind this work is to escalate the performance of water based hybrid nanoliquid containing magnetic ferrite and CNTs. The viscous dissipated convective flow of hybrid nanoliquid passing over a horizontal moving thin needle is scrutinized. The nonlinear structure of the differential equations is transfigured into dimensionless ordinary differential equations, making use of Karman’s scaling. The results are deciphered via manipulating the homotopy analysis method. The physical entities out-turn on velocity, concentration, and the temperature profile are sketched and discussed in brief. The numerical outcomes are the skin friction, Nusselt number, and Sherwood number. It is perceived that the design of the needle including its size and shape strongly affects the thermal characteristics and fluid velocity. The energy and flow boundary layers of both CNTs and Fe3O4 are significantly diminished with the increase in the needle size. The uses of CNT + Fe3O4/H2O are more dominant for the enactment of thermo physical characteristics of carrier fluids associated with iron oxide nanomaterials.
Tearing mode analysis in electron magnetohydrodynamics with pressure gradient
Authors: Guo Wenping , Liu Dongjian , Wang Xiaogang , Wang Jiaqi
Published: October 2020

A two-dimensional three-component (2D/3C) electron magnetohydrodynamic (EMHD) model is implemented to investigate the linear behavior of collisionless tearing modes in slab geometry. Owing to nonuniformity of thermal pressure and plasma density, the electron diamagnetic drift and Biermann battery effects are involved. The linear structures, growth rate, and real frequency are analyzed with a thin current sheet in the electron inertia scale. The ratio of the electron current to the total current in equilibrium can notably promote the growth of the tearing mode in EMHD. More numerical results then show that the effect of the pressure gradient on the tearing mode is dependent on the plasma beta, stabilizing the mode in a low enough beta limit but destabilizing it with the higher beta. The frequency of the mode caused by the pressure gradient is found to be increasing with it. The Biermann battery effect slightly stabilizes the tearing mode in low beta plasma but is indicated to be significant in much higher beta conditions.
A constitutive hemorheological model addressing both the deformability and aggregation of red blood cells
Authors: Stephanou Pavlos S.
Published: October 2020

Red blood cells (RBCs) in physiological conditions are capable of deforming and aggregating. However, both deformation and aggregation are seldom considered together when modeling the rheological behavior of blood. This is particularly important since each mechanism is dominant under specific conditions. To address this void, we herein propose a new model that accounts for the deformability of red blood cells, by modeling them as deformed droplets with a constant volume, and of their aggregation, by properly characterizing the network formed by red blood cells under small shear rates. To derive the model, we employ non-equilibrium thermodynamics that allows us to consistently couple the two mechanisms and guarantees model admissibility with the thermodynamic laws. Relative to our previous model, which addresses the rheological behavior of non-aggregating deformable red blood cells, one additional structural variable, λ, to properly characterize the network formed by RBCs, and another additional parameter, ε, that quantifies the relative importance between the regeneration/buildup and flow-induced breakup of the network, are considered here. The new model predicts a yield shear stress, in accord with experimental data, but also predicts non-vanishing yield normal stresses. Although no rheological measurements of yield normal stresses of blood have been reported in the literature, the recent measurement of yield normal stresses of other yield stress fluids indicates their potential existence in blood as well. We show that the new model is in complete accord with the experimental rheological behavior of normal blood in both steady-state and transient (step-change in shear-rate) simple shear.
Statistical learning of NMR tensors from 2D isotropic/anisotropic correlation nuclear magnetic resonance spectra
Authors: Srivastava Deepansh J. , Grandinetti Philip J.
Published: October 2020

Many linear inversion problems involving Fredholm integrals of the first kind are frequently encountered in the field of magnetic resonance. One important application is the direct inversion of a solid-state nuclear magnetic resonance (NMR) spectrum containing multiple overlapping anisotropic subspectra to obtain a distribution of the tensor parameters. Because of the ill-conditioned nature of this inverse problem, we investigate the use of the truncated singular value decomposition and the smooth least absolute shrinkage and selection operator based regularization methods, which (a) stabilize the solution and (b) promote sparsity and smoothness in the solution. We also propose an unambiguous representation for the anisotropy parameters using a piecewise polar coordinate system to minimize rank deficiency in the inversion kernel. To obtain the optimum tensor parameter distribution, we implement the k-fold cross-validation, a statistical learning method, to determine the hyperparameters of the regularized inverse problem. In this article, we provide the details of the linear-inversion method along with numerous illustrative applications on purely anisotropic NMR spectra, both synthetic and experimental two-dimensional spectra correlating the isotropic and anisotropic frequencies.
Asymptotic behavior of the average local ionization energy in finite basis sets
Authors: El-Samman Amer M. , Staroverov Viktor N.
Published: October 2020

The average local ionization energy (ALIE) has important applications in several areas of electronic structure theory. Theoretically, the ALIE should asymptotically approach the first vertical ionization energy (IE) of the system, as implied by the rate of exponential decay of the electron density; for one-determinantal wavefunctions, this IE is the negative of the highest-occupied orbital energy. In practice, finite-basis-set representations of the ALIE exhibit seemingly irregular and sometimes dramatic deviations from the expected asymptotic behavior. We analyze the long-range behavior of the ALIE in finite basis sets and explain the puzzling observations. The findings have implications for practical calculations of the ALIE, the construction of Kohn–Sham potentials from wavefunctions and electron densities, and basis-set development.
Unraveling intra-aggregate structural disorder using single-molecule spectroscopy
Authors: Kunsel T. , Löhner A. , Mayo J. J. , Köhler J. , Jansen T. L. C. , Knoester J.
Published: October 2020

Structural disorder within self-assembled molecular aggregates may have strong effects on their optical functionality. Such disorder, however, is hard to explore using standard ensemble measurements. In this paper, we report on the characterization of intra-aggregate structural disorder through a linewidth analysis of fluorescence excitation experiments on individual zinc-chlorin (ZnChl) nanotubular molecular aggregates. Recent experiments suggest an anomaly in the linewidths of the two absorption bands that dominate the spectra: the higher-energy bands on average show a smaller linewidth than the lower-energy bands. This anomaly is explored in this paper by analyzing and modeling the correlation of the two linewidths for each aggregate. We exploit a Frenkel exciton model to show that the experimentally observed correlation of linewidths and other statistical properties of the single-aggregate spectra can be explained from small variations of the molecular orientations within individual aggregates.
Low temperature homoepitaxy of (010)
β
-Ga2O3 by metalorganic vapor phase epitaxy: Expanding the growth window
Authors: Bhattacharyya Arkka , Ranga Praneeth , Roy Saurav , Ogle Jonathan , Whittaker-Brooks Luisa , Krishnamoorthy Sriram
Published: October 2020

In this work, we report on the growth of high-mobility β-Ga2O3 homoepitaxial thin films grown at a temperature much lower than the conventional growth temperature window for metalorganic vapor phase epitaxy. Low-temperature β-Ga2O3 thin films grown at 600 °C on Fe-doped (010) bulk substrates exhibit remarkable crystalline quality, which is evident from the measured room temperature Hall mobility of 186 cm2/V s for the unintentionally doped films. N-type doping is achieved by using Si as a dopant, and a controllable doping in the range of 2 × 1016–2 × 1019 cm−3 is studied. Si incorporation and activation is studied by comparing the silicon concentration from secondary ion mass spectroscopy and the electron concentration from temperature-dependent Hall measurements. The films exhibit high purity (low C and H concentrations) with a very low concentration of compensating acceptors (2 × 1015 cm−3) even at this growth temperature. Additionally, an abrupt doping profile with a forward decay of ∼ 5 nm/dec (10 times improvement compared to what is observed for thin films grown at 810 °C) is demonstrated by growing at a lower temperature.
Trapping of multiple H atoms at the Ga(1) vacancy in
β
-Ga2O3
Authors: Fowler W. Beall , Stavola Michael , Qin Ying , Weiser Philip
Published: October 2020

Recent suggestions that hydrogen incorporation at the Ga(1) vacancy in β-Ga2O3 may have an impact on its electronic properties have led us to extend our earlier work on these defects. While our previous work provides strong evidence for one, two, and perhaps three or four H trapped into the shifted vacancy configurations introduced by Varley and Kyrtsos, the apparent experimental absence of several H trapped in the unshifted configuration is puzzling. While a structure of two hydrogen atoms trapped in the unshifted configuration is not favored energetically, structures of three or four hydrogens in the unshifted configuration are favored. We suggest that these structures are absent because there are no available pathways for the system to reach them by sequentially trapped H and, therefore, that three- or four-hydrogen defects will occur only in the shifted vacancy configurations.
Forward and backward stimulated Brillouin scattering in aqueous suspension of SiO2 spherical nanoparticles
Authors: Gorelik V. S. , Bunkin A. F. , Davydov M. A. , Fedorov A. N. , Pershin S. M. , Pyatyshev A. Yu. , Wu Mengyuan
Published: October 2020

Both backward and forward directed Stimulated Brillouin Light Scattering (SBLS) are observed in an aqueous suspension of SiO2 nanoparticles with diameters of 100 and 200 nm by using for excitation a second harmonic (λ = 532 nm, 10 ns) of a single (∼0.005 cm−1) mode YAG:Nd3+ laser. Both backward and forward directed SBLS are characterized by a low beam divergence and typically for a water Stokes shift of ≈0.25 cm−1. The microscopic explanation of forward directed SBLS in an aqueous suspension of SiO2 spherical nanoparticles is proposed.
Private versus public? Examining hospital use by a privately insured population in New South Wales, Australia, using data linkage
Authors: Khoo Joanna , Hasan Helen , Eagar Kathy
Published: October 2020

ObjectiveTo examine hospital use characteristics of a privately insured cohort including hospital setting (public or private), declared insurance status and category of services received during hospital admission.
MethodsThe study population consisted of 14276 people with membership of a private health insurance (PHI) fund in New South Wales, Australia. The final study cohort included 9004 people with at least one hospital admission over a 6-year period from 1 January 2010 to 31 December 2015. PHI claims data were linked with public hospital records from a Local Health District. Hospital utilisation measures include number of admissions and length of stay. Measures were categorised by hospital user group (public only, private only or both), declared insurance status (PHI or public patient), type of service and admission case weight.
ResultsThe study finds that despite having PHI, 40% of people receive services exclusively in a public hospital in the 6-year study period. Additionally, only 62% of overnight hospital admissions for the study population are claimed on PHI. There are differences in hospital utilisation for medical- and surgical-related admissions. Seventy percent of people with a medical admission receive services only in public hospitals, but a similar proportion of people (66%) receive services only in private hospitals for surgical admissions.
ConclusionsPeople with PHI make considerable use of public hospitals both as a public and a private patient. For this privately insured cohort, public hospitals are more frequently used for medical-related admissions and also for more resource-intensive admissions compared with private hospitals.
What is known about the topic?There are multiple government incentives to encourage people to take out PHI policies in Australia. Although PHI is closely associated with private hospital utilisation, people with PHI can still use public hospitals as either a public patient, in which the service is fully government-funded, or as a private patient in which PHI contributes funding towards the cost of hospital admissions.
What does this paper add?This study provides the first analysis of hospital utilisation of a privately insured cohort in Australia that reports on the interaction between public and private hospital use and declared insurance status, including utilisation differences based on service type.
What are the implications for practitioners?Although there are financial incentives offered by the Australian Government to encourage uptake of PHI, the study findings show that people with PHI still make considerable use of public hospitals both as a public and private patient. Future policy reforms relating to the regulation of PHI in Australia should consider the nuanced differences in the way people with PHI use public and private hospitals to optimise resource allocation.
Subpopulations of extracellular vesicles from human metastatic melanoma tissue identified by quantitative proteomics after optimized isolation
Authors: Crescitelli Rossella , Lässer Cecilia , Jang Su Chul , Cvjetkovic Aleksander , Malmhäll Carina , Karimi Nasibeh , Höög Johanna L. , Johansson Iva , Fuchs Johannes , Thorsell Annika , Gho Yong Song , Olofsson Bagge R. , Lötvall Jan
Published: October 2020

The majority of extracellular vesicle (EV) studies conducted to date have been performed on cell lines with little knowledge on how well these represent the characteristics of EVs in vivo. The aim of this study was to establish a method to isolate and categorize subpopulations of EVs isolated directly from tumour tissue. First we established an isolation protocol for subpopulations of EVs from metastatic melanoma tissue, which included enzymatic treatment (collagenase D and DNase). Small and large EVs were isolated with differential ultracentrifugation, and these were further separated into high and low‐density (HD and LD) fractions. All EV subpopulations were then analysed in depth using electron microscopy, Bioanalyzer®, nanoparticle tracking analysis, and quantitative mass spectrometry analysis. Subpopulations of EVs with distinct size, morphology, and RNA and protein cargo could be isolated from the metastatic melanoma tissue. LD EVs showed an RNA profile with the presence of 18S and 28S ribosomal subunits. In contrast, HD EVs had RNA profiles with small or no peaks for ribosomal RNA subunits. Quantitative proteomics showed that several proteins such as flotillin‐1 were enriched in both large and small LD EVs, while ADAM10 were exclusively enriched in small LD EVs. In contrast, mitofilin was enriched only in the large EVs. We conclude that enzymatic treatments improve EV isolation from dense fibrotic tissue without any apparent effect on molecular or morphological characteristics. By providing a detailed categorization of several subpopulations of EVs isolated directly from tumour tissues, we might better understand the function of EVs in tumour biology and their possible use in biomarker discovery.
Conflict reterritorialisation: Shifting group boundaries in the diaspora during the armed conflict in the ‘homeland’
Authors: Voytiv Sofiya
Published: October 2020

Research on wars, including the ethnicised armed conflicts, has focused on the territorial dimension of war, and direct and indirect actors involved therein. This paper uses concepts of deterritorialisation and reterritorialisation to explore if the symbols, narratives, and attitudes of war in the ‘homeland’ can be embedded into the ethnic boundary-making processes and shift them according to the situation in the ‘homeland’ in the diasporic setting. I focus on the Ukrainian-Russian conflict, and interview Ukrainians and Russians from Ukraine living in Sweden. I find that attitudes toward the conflict can become intertwined with subjective ethnic identification of the Self and the Other, shifting ethnic boundary-making processes in alliance with the conflict ‘back home.’
Gravitational waves in higher order teleparallel gravity
Authors: Capozziello Salvatore , Capriolo Maurizio , Caso Loredana
Published: October 2020

The teleparallel equivalent of higher order Lagrangians like L
□R
= −R + a
0
R
2 + a
1
R□R can be obtained by means of the boundary term B = 2∇
μ

T

μ
. In this perspective, we derive the field equations in presence of matter for higher-order teleparallel gravity considering, in particular, sixth-order theories where the □ operator is linearly included. In the weak field approximation, gravitational wave solutions for these theories are derived. Three states of polarization are found: the two standard + and × polarizations, namely 2-helicity massless transverse tensor polarizations, and a 0-helicity massive, with partly transverse and partly longitudinal scalar polarization. Moreover, these gravitational waves (GWs) exhibit four oscillation modes related to four degrees of freedom: the two classical + and × tensor modes of frequency ω
1, related to the standard Einstein waves with

k

1

2

=
0

; two mixed longitudinal-transverse scalar modes for each frequencies ω
2 and ω
3, related to two different 4-wave vectors,

k

2

2

=

M

2

2

and

k

3

2

=

M

3

2

. The four degrees of freedom are the amplitudes of each individual mode, i.e.

ϵ

̂

(

+

)

ω

1

,

ϵ

̂

(

×

)

ω

1

,

B

̂

2

k

, and

B

̂

3

k

. To describe a general teleparallel gravity model of order (2p + 2), we used the teleparallel Lagrangian

L

□

k

T

neq

=
e

T
+

a

0

T

2

+

∑

k
=
1

p

a

k

T

□

k

T

which demonstrates to be not equivalent to

L

□

k

R

=

−
g

R
+

∑

k
=
0

p

a

k

R

□

k

R

. By varying its action, the related field equations in the presence of matter are derived. Hence we obtain the GWs for these teleparallel gravity models, i.e.

L

□

k

T

neq

, that are exactly the Einstein GWs as in f(T) teleparallel gravity. In conclusion, the boundary term B generates extra polarizations and additional modes beyond the standard ones. In particular B
2 and B□B terms generate both the additional scalar polarization and the extra scalar modes.
A discussion regarding the duration of motion in a non-uniform gravitational field
Authors: Kontomaris S V , Malamou A
Published: October 2020

Assume that an object is thrown vertically from a planet’s surface with a low velocity. Using basic kinematics theory, it is easy to calculate the duration of the motion. In this type of problem, the acceleration due to gravity is considered to be uniform, because the motion is taking place near the planet’s surface. By contrast, if we assume that an object is launched vertically from a planet’s surface at its escape velocity, how much time does it take for the object to cover a specific distance? In addition, is it possible to find a simplified way to calculate the duration of the motion or to derive the equations of motion in a non-uniform gravitational field? In this paper, we provide a simplified analysis that can be used to answer these questions.
Pulse length effects on autoionizing states under the influence of intense SASE XUV fields
Authors: Aufleger L , Friebel P , Rupprecht P , Magunia A , Ding T , Rebholz M , Hartmann M , Stooß V , Ott C , Pfeifer T
Published: October 2020

The Fano absorption line shape of an autoionizing state encodes information on its internal atomic structure and dynamics. When driven near-resonantly with intense extreme ultraviolet (XUV) electric fields, the absorption profile can be deliberately modified, including observable changes of both the line-shape asymmetry and strength of the resonance, revealing information on the underlying dynamics of the system in response to such external driving. We report on the influence of the XUV pulse parameters at high intensity that can be achieved with a free-electron laser (FEL) with statistically broadened spectra based on self-amplified spontaneous emission (SASE). More specifically, the impact of the FEL pulse duration is studied for the example of the doubly excited 2s2p resonance in helium, where line-shape modifications have been measured with XUV transient absorption spectroscopy in Fraunhofer-type transmission geometry. A computational few-level-model provides insight into the impact of different average pulse durations of the stochastic FEL pulses. These findings are supported by measurements performed at the Free-Electron Laser in Hamburg (FLASH) and provide further insight into XUV strong-coupling dynamics of resonant transitions driven by intense high-frequency FEL sources.
Fast iron oxide-induced low-field magnetic resonance imaging
Authors: Rodriguez Gonzalo G , Erro Eustaquio M , Anoardo Esteban
Published: October 2020

Dynamic images acquired by proton fast field-cycling magnetic resonance imaging are presented for the first time. Image contrast mediated by superparamagnetic iron oxide nanoparticles and weighted by the spin-lattice (T1) relaxation time, and both spin-lattice and spin-spin (T2) relaxation times, are discussed. Image acquisition and processing within 8 s is allowed for real-time recording of exemplary physical situations evolving in a compatible time-scale. Two simple examples are shown with the corresponding videos assembled by sequencing the acquired images. Fast iron oxide-induced low-field magnetic resonance imaging (MRI) constitutes the first step in the development of field-cycling functional MRI for biomedical and physical applications.
Hybrid functional investigation of band offsets for non-polar, Ga-polar and Al-polar interfaces in GaN/AlN heterojunction
Authors: Kaewmeechai Chaiyawat , Laosiritaworn Yongyut , Jaroenjittichai Atchara Punya
Published: October 2020

We investigated band alignment of non-polar and polar GaN/AlN heterojunction by using density functional theory with the Heyd–Scuseria–Ernzerhof hybrid functional. In the heterojunction model, AlN was considered as a substrate while strained GaN was grown on top. The deformation potential of GaN, were included to calculate the unstrained band offsets. For polar heterojunction, the artificial effects from an undesired interface was removed by using vacuum insertion and dipole correction. We found that the unstrained valence band offsets (VBOs) are 0.92 eV, 1.23 eV and 1.09 eV for non-polar, Ga-polar and Al-polar interfaces respectively. The variation of VBOs can be explained from the difference in both deformation and dipole potential at the interfaces. Moreover, the additional energy shift of polar VBO from non-polar VBO were extracted as 0.33 eV from considering the effect of spontaneous polarization.
Person-specific calibration of a partial body counter used for individualised Am241 skull measurements
Authors: Nogueira P , Rühm W
Published: October 2020

Incorporation of bone seeking alpha-emitting radionuclides such as 241Am are of special concern, due to the potential of alpha particles to damage the extremely radiation-sensitive bone marrow. In the case of an internal contamination with 241Am, direct in vivo measurements using Gamma-detectors are typically used to quantify the incorporated activity. Such detectors need to be calibrated with an anatomical phantom, for example of the skull, of known 241Am activity that reproduces the anatomy of the measured individual as closely as possible. Any difference in anatomy and material composition between phantom and individual will bias the estimation of the incorporated activity. Consequently, in this work the impact of the most important anatomical parameters on detection efficiency of one of the germanium detectors of the Helmholtz Center Munich (HMGU) partial body counter were systematically studied. For that a detailed model of the germanium detector was implemented in the Monte Carlo codes GEANT4 and MCNPX. To simulate the detector efficiency, various skull voxel phantoms were used. By changing the phantom dimensions and geometry the impact of parameters such as shape and size of the skull, thickness of tissue covering the skull bone, distribution of 241Am across the scull and within the skull bone matrix, on the detector efficiency was studied. Approaches to correct for these parameters were specifically developed for three physical skull phantoms for which Voxel phantoms were available: Case 102 USTUR phantom, Max-06 phantom, BfS phantom. Based on the impact of each parameter, correction factors for an ‘individual-specific’ calibration were calculated and applied to a real 241Am contamination case reported in 2014. It was found that the incorporated 241Am activity measured with the HMGU partial body counter was about twice as large as that estimated when using the BfS skull phantom without applying any correction factor for person-specific parameters. It is concluded that the approach developed in the present study should in the future be applied routinely for skull phantom measurements, because it allows for a considerably improved reconstruction of incorporated 241Am using partial body counters.
Antibacterial activity of biogenic silver and gold nanoparticles synthesized from Salvia africana-lutea and Sutherlandia frutescens
Authors: Dube Phumuzile , Meyer Samantha , Madiehe Abram , Meyer Mervin
Published: October 2020

Nanoparticles (NPs) synthesized using various chemical and physical methods are often cytotoxic which restricts their use in biomedical applications. In contrast, metallic biogenic NPs synthesized using biological systems such as plant extracts are said to be safer and their production more cost effective. NPs synthesized from plants with known medicinal properties can potentially have similar bioactivities as these plants. It has been shown that Salvia africana-lutea (SAL) and Sutherlandia frutescens (SF) have antibacterial activities. This study used water extracts of SAL and SF to produce biogenic silver NPs (AgNPs) and gold NPs (AuNPs). The antibacterial activity of AgNPs and AuNPs was tested against two pathogens (Staphylococcus epidermidis and P. aeruginosa). NP synthesis was optimized by varying the synthesis conditions which include synthesis time and temperature, plant extract concentration, silver nitrate (AgNO3) concentration and sodium tetrachloroaurate (III) dihydrate (NaAuCl4 · 2H2O) concentration. The NPs were characterized using Ultraviolet-visible (UV–vis) spectroscopy, dynamic light scattering, high-resolution transmission electron microscopy (HR-TEM), and Fourier transform infrared (FT-IR) spectroscopy. SAL was able to synthesize both Ag (SAL AgNP) and Au (SAL AuNP) nanoparticles, whilst SF synthesized Ag (SF AgNP) nanoparticles only. The absorbance spectra revealed the characteristic surface plasmon resonance peak between 400–500 nm and 500–600 nm for AgNP and AuNP, respectively. HR-TEM displayed the presence of spherical and polygon shaped nanoparticles with varying sizes whilst the Energy Dispersive x-ray spectra and selected area diffraction pattern confirmed the successful synthesis of the AgNPs and AuNPs by displaying the characteristic crystalline nature, optical adsorption peaks and lattice fringes. FT-IR spectroscopy was employed to identify the functional groups involved in the NP synthesis. The microtitre plate method was employed to determine the minimum inhibitory concentration (MIC) of the NPs and the extracts. The water extracts and SAL AuNP did not have significant antibacterial activity, while SAL AgNP and SF AgNP displayed high antibacterial activity. In conclusion, the data generated suggests that SAL and SF could be used for the efficient synthesis of antibacterial biogenic nanoparticles.
In silico design, building and gas adsorption of nano-porous graphene scaffolds
Authors: Bellucci Luca , Delfino Francesco , Tozzini Valentina
Published: October 2020

Graphene-based nano-porous materials (GNM) are potentially useful for all those applications needing a large specific surface area (SSA), typical of the bidimensional graphene, yet realized in the bulk dimensionality. Such applications include for instance gas storage and sorting, catalysis and electrochemical energy storage. While a reasonable control of the structure is achieved in micro-porous materials by using nano-micro particles as templates, the controlled production or even characterization of GNMs with porosity strictly at the nano-scale still raises issues. These are usually produced using dispersion of nano-flakes as precursors resulting in little control on the final structure, which in turn reflects in problems in the structural model building for computer simulations. In this work, we describe a strategy to build models for these materials with predetermined structural properties (SSA, density, porosity), which exploits molecular dynamics simulations, Monte Carlo methods and machine learning algorithms. Our strategy is inspired by the real synthesis process: starting from randomly distributed flakes, we include defects, perforation, structure deformation and edge saturation on the fly, and, after structural refinement, we obtain realistic models, with given structural features. We find relationships between the structural characteristics and size distributions of the starting flake suspension and the final structure, which can give indications for more efficient synthesis routes. We subsequently give a full characterization of the models versus H2 adsorption, from which we extract quantitative relationship between the structural parameters and the gravimetric density. Our results quantitatively clarify the role of surfaces and edges relative amount in determining the H2 adsorption, and suggest strategies to overcome the inherent physical limitations of these materials as adsorbers. We implemented the model building and analysis procedures in software tools, freely available upon request.
Magnetite nanoparticle anchored graphene cathode enhances microbial electrosynthesis of polyhydroxybutyrate by Rhodopseudomonas palustris TIE-1
Authors: Rengasamy Karthikeyan , Ranaivoarisoa Tahina , Bai Wei , Bose Arpita
Published: October 2020

Microbial electrosynthesis (MES) is an emerging technology that can convert carbon dioxide (CO2) into value-added organic carbon compounds using electrons supplied from a cathode. However, MES is affected by low product formation due to limited extracellular electron uptake by microbes. Herein, a novel cathode was developed from chemically synthesized magnetite nanoparticles and reduced graphene oxide nanocomposite (rGO-MNPs). This nanocomposite was electrochemically deposited on carbon felt (CF/rGO-MNPs), and the modified material was used as a cathode for MES production. The bioplastic, polyhydroxybutyrate (PHB) produced by Rhodopseudomonas palustris TIE-1 (TIE-1), was measured from reactors with modified and unmodified cathodes. Results demonstrate that the magnetite nanoparticle anchored graphene cathode (CF/rGO-MNPs) exhibited higher PHB production (91.31 ± 0.9 mg l−1). This is ∼4.2 times higher than unmodified carbon felt (CF), and 20 times higher than previously reported using graphite. This modified cathode enhanced electron uptake to −11.7 ± 0.1 μA cm−2, ∼5 times higher than CF cathode (−2.3 ± 0.08 μA cm−2). The faradaic efficiency of the modified cathode was ∼2 times higher than the unmodified cathode. Electrochemical analysis and scanning electron microscopy suggest that rGO-MNPs facilitated electron uptake and improved PHB production by TIE-1. Overall, the nanocomposite (rGO-MNPs) cathode modification enhances MES efficiency.
Ion temperature measurements in a tokamak using active neutral particle analyzers diagnostics
Authors: Bakharev N N , Chernyshev F V , Gusev V K , Kiselev E O , Kurskiev G S , Larionova M M , Melnik A D , Minaev V B , Mironov M I , Miroshnikov I V , Petrov Yu V , Sakharov N V , Shchegolev P B , Skrekel O M , Telnova A Yu , Tukhmeneva E A , Varfolomeev V I
Published: October 2020

Active ion temperature measurement in the core plasma of a tokamak using active neutral particle analyzers (NPA) diagnostics is considered. Two approaches for local ion temperature reconstruction are reviewed: semi-analytical and iterative. A semi-analytical approach allows the calculation of ion temperature using simple expression, while a more complex iterative approach provides more flexibility. Problems associated with active NPA measurements and their possible solutions are discussed. An example of the core ion temperature profile reconstruction in the compact spherical tokamak Globus-M2 using both approaches is shown. Problems associated with active ion temperature measurements in a compact reactor and possible solutions are considered.
A gravity model and network analysis of household food sharing in Zambia
Authors: von Gnechten Rachel , Wang Junren , Konar Megan , Baylis Kathy , Anderson Patrese , Giroux Stacey , Jackson Nicole D , Evans Thomas
Published: October 2020

Food sharing is an important part of smallholder food systems and can help households to buffer food security shocks. Household food sharing is the smallest scale food exchange system, yet we do not understand how it compares with food exchange networks at other spatial scales. To this end, we collect information on bilateral household food sharing in two villages in Zambia with approximately 50 households each. We observed seasonal fluctuations for the density of the food sharing. To our knowledge, we are the first to show that the gravity model of trade is applicable to household food sharing. Additionally, sharing networks exhibit the same statistical properties as food exchanges in other locations and at different spatial scales. Specifically, maize exchanges (in mass) follow the Gamma distribution and the relationship between household mass flux and connectivity follows a power law distribution. This work sheds light on household food sharing in rainfed agricultural systems and suggests common underlying mechanisms of food exchange systems across spatial scales and geographies.
Comparative study on cutting performance of plain and coated carbide inserts in CNC turning of EN9 steel
Authors: Chauhan Sachin , Kumar Rajeev
Published: October 2020

The present work deals with comparative study on cutting performance of plain carbide and coated carbide inserts in turning of EN9 steel. The design of experiments (DOE) was done using response surface methodology (RSM) technique. The cutting parameters were spindle speed, feed and depth of cut (DOC). The combined interactions of cutting parameters on surface roughness, flank wear and crater wear were analyzed. The crater and flank wear were observed using machine vision system. This work is concentrated on building up a mathematical relation between cutting parameters and output responses. Analysis of variance (ANOVA) was used for checking the adequacy of the model. The relation between input factors and the response parameters are determined using a cubic regression model. The optimization was done using desirability ramp plots. The main motive behind this research is to compare the performance of plain and coated carbide tool and analyzing which tool performs better and to optimize the cutting parameters for high quality and cost reduction. It was concluded from this research that at optimized speed, feed and DOC the coated carbide tool is suitable for turning of EN9 steel. The tool wear observed on coated carbide tool was less than plain carbide tool. The coated carbide tool showed a slight improvement in results as compared to the plain carbide tool.
Changes in the Price of Alcohol and Effect on Youth Drinking and in Different Socio-Economic Groups
Authors: Trolldal Björn , Landberg Jonas , Ramstedt Mats
Published: October 2020

Aims

Many studies have shown that changes in alcohol prices have a significant effect on total sales. However, few studies have focused on youth, particularly in different socioeconomic groups. This study examined the effect of changes in the price of alcohol on consumption levels and binge drinking among 15 to 16 year old students in Sweden, both overall, among boys and girls, as well as within different socioeconomic groups.

Methods

Data on consumption were retrieved from a representative survey of students aged 15-16, conducted annually between 1989 and 2017. Time series analysis employed an autoregressive integrated moving average model (ARIMA). Two types of price data were used: the official price at the retail stores, and the mean price of the ten cheapest beverages in each category. The mean aggregate annual income per Swedish household was included as a control variable.

The variable used to measure the socioeconomic status was the proportion of the ninth-grade students at each school, who had at least one parent with an education higher than upper secondary school.

Results

The students' alcohol consumption levels and binge drinking were not significantly affected by price changes during the study period; this was true both for the group as a whole, and among subgroups of boys or girls or of different socioeconomic status. Results were similar regardless of which type of price data variable was used in the analyses.

Conclusion

Neither average nor minimum price of alcohol had a significant impact on the development of youth drinking in Sweden during the study period.
Context-dependent trait covariances: how plasticity shapes behavioral syndromes
Authors: Mitchell David J , Houslay Thomas M
Published: October 2020

The study of behavioral syndromes aims to understand among-individual correlations of behavior, yielding insights into the ecological factors and proximate constraints that shape behavior. In parallel, interest has been growing in behavioral plasticity, with results commonly showing that animals vary in their behavioral response to environmental change. These two phenomena are inextricably linked—behavioral syndromes describe cross-trait or cross-context correlations, while variation in behavioral plasticity describes variation in response to changing context. However, they are often discussed separately, with plasticity analyses typically considering a single trait (univariate) across environments, while behavioral trait correlations are studied as multiple traits (multivariate) under one environmental context. Here, we argue that such separation represents a missed opportunity to integrate these concepts. Through observations of multiple traits while manipulating environmental conditions, we can quantify how the environment shapes behavioral correlations, thus quantifying how phenotypes are differentially constrained or integrated under different environmental conditions. Two analytical options exist which enable us to evaluate the context dependence of behavioral syndromes—multivariate reaction norms and character state models. These models are largely two sides of the same coin, but through careful interpretation we can use either to shift our focus to test how the contextual environment shapes trait covariances.
Supervised clustering of high-dimensional data using regularized mixture modeling
Authors: Chang Wennan , Wan Changlin , Zang Yong , Zhang Chi , Cao Sha
Published: October 2020

Identifying relationships between genetic variations and their clinical presentations has been challenged by the heterogeneous causes of a disease. It is imperative to unveil the relationship between the high-dimensional genetic manifestations and the clinical presentations, while taking into account the possible heterogeneity of the study subjects.We proposed a novel supervised clustering algorithm using penalized mixture regression model, called component-wise sparse mixture regression (CSMR), to deal with the challenges in studying the heterogeneous relationships between high-dimensional genetic features and a phenotype. The algorithm was adapted from the classification expectation maximization algorithm, which offers a novel supervised solution to the clustering problem, with substantial improvement on both the computational efficiency and biological interpretability. Experimental evaluation on simulated benchmark datasets demonstrated that the CSMR can accurately identify the subspaces on which subset of features are explanatory to the response variables, and it outperformed the baseline methods. Application of CSMR on a drug sensitivity dataset again demonstrated the superior performance of CSMR over the others, where CSMR is powerful in recapitulating the distinct subgroups hidden in the pool of cell lines with regards to their coping mechanisms to different drugs. CSMR represents a big data analysis tool with the potential to resolve the complexity of translating the clinical representations of the disease to the real causes underpinning it. We believe that it will bring new understanding to the molecular basis of a disease and could be of special relevance in the growing field of personalized medicine.