bluuebunny/crossref_metadata_2025 huggingface dataset:
Real colloidal quantum dot structures revealed by high resolution analytical electron microscopy
Authors: McBride James R. , Rosenthal Sandra J.
Published: October 2019

The development of bright and photostable colloidal quantum dots has been a truly interdisciplinary feat. Designing a specific composition of core and shell materials and then producing the desired nanoarchitecture through chemical routes require a blend of physical and inorganic chemistry, solid-state physics, and materials science. In a battle to separate charge carriers from a surface wrought with defect states, complex shell structures with precisely specified gradient compositions have been engineered, producing nanosized emitters with exceptional stability and color purity. However, much of the success has resided in II-VI materials, such as CdSe, and progress is only just being made on cadmium-free quantum dots. This perspective will discuss the primary challenges in engineering colloidal quantum dots and highlight how the advent of advanced analytical electron microscopy is revealing the structure-function relationships of these complex systems.
Stepped care mental health service in Australian primary care: codesign and feasibility study
Authors: Anderson Josephine , O'Moore Kathleen , Faraj Mariam , Proudfoot Judith
Published: October 2019

Objective
In 2015, the Australian Government introduced several mental health reforms, including the requirement that Primary Health Networks (PHNs) provide stepped care services for Australians with mental health needs such as anxiety and depression. This paper reports on the development and feasibility study of StepCare, an online stepped mental healthcare service in general practice that screens patients, provides immediate feedback to patients and general practitioners (GPs), transmits stepped treatment recommendations to GPs and monitors patients’ progress, including notification of deterioration.

Methods
The present codesign and feasibility study in one PHN examined: (1) the acceptability and feasibility of StepCare to GPs, practice staff and patients; (2) the impact of StepCare on clinical practice; and (3) the barriers to and facilitators of implementation.

Results
Thirty-two GPs, 22 practice staff and 418 patients participated in the study. Overall, patients, practice staff and GPs found StepCare acceptable and feasible, commending its privacy, the mental health screening, monitoring and feedback. They also made suggestions for service improvements. GPs reported that StepCare helped with their identification and management of patients with common mental health issues.

Conclusions
Preliminary data suggest that StepCare may be acceptable and feasible in Australian general practice, helping GPs identify and manage common mental health problems in their patients. The study provides implications for policy and practice, and points the way to future translational research into stepped mental health care.

What is known about the topic?
Depression and anxiety are common illnesses in primary care and GPs are ideally placed to implement stepped care approaches enabling early detection and accessible, effective care.

What does this paper add?
Developed in and for general practice, StepCare is the first fully integrated stepped approach to primary mental health care in Australia. As a first step in a translational research program evaluating the effectiveness of StepCare, this paper reports data regarding the feasibility and acceptability of the service.

What are the implications for practitioners?
Integrated into the workflow of general practice, StepCare is an online service that helps GPs detect new cases of depression and anxiety, provide evidence-based stepped care treatments and monitor patients’ progress.
Evidence for behavioural interventions addressing condom use fit and feel issues to improve condom use: a systematic review
Authors: Anstee Sydney , Shepherd Jonathan , Graham Cynthia A. , Stone Nicole , Brown Katherine , Newby Katie , Ingham Roger
Published: October 2019

Continuing high rates of sexually transmissible infections (STIs) in many countries highlight the need to identify effective behavioural interventions. Consistent and correct use of male condoms is a key strategy for the prevention of STIs. However, some men report problems with condom fit (e.g. the size and shape of the condom) and feel (e.g. tightness, irritation, sensitivity), which inhibits their use. We conducted a systematic review to identify existing interventions addressing condom use fit and feel problems. We searched electronic databases for peer-reviewed articles and searched reference lists of retrieved studies. Five studies met the inclusion criteria. These were generally small-scale pilot studies evaluating behavioural interventions to promote safer sex with men aged under 30 years, addressing, among other things, barriers to condom use relating to fit and feel. There were significant increases in the reported use of condoms, including condom use with no errors and problems. Improvements in some condom use mediators were reported, such as condom use self-efficacy, knowledge, intentions and condom use experience. There were mixed findings in terms of the ability of interventions to reduce STI acquisition. Behavioural interventions addressing condom fit and feel are promising in terms of effectiveness but require further evaluation.
Glia-derived exosomal miR-274 targets Sprouty in trachea and synaptic boutons to modulate growth and responses to hypoxia
Authors: Tsai Yi-Wei , Sung Hsin-Ho , Li Jian-Chiuan , Yeh Chun-Yen , Chen Pei-Yi , Cheng Ying-Ju , Chen Chun-Hong , Tsai Yu-Chen , Chien Cheng-Ting
Published: October 2019

Significance

Our study provides significant advances in the understanding of circulating exosomal microRNA (miRNA) in animals. Circulating exosomal miRNAs mediate communication among tissues and organs. In glia, mature miR-274 is produced and secreted to the circulating hemolymph to target the recipient cells, neurons, and tracheal cells. We also identified the target gene
sty
whose expression is down-regulated by miR-274 in the target/recipient cells. Downregulation of Sty leads to upregulation of MAPK signaling, thereby promoting the growth of synaptic boutons and tracheal branches. Thus, glia-derived miR-274 might be deemed a “gliotransmitter” to mediate communication with neurons and tracheal cells. The modulation of tracheal branches by glial-derived miR-274 is also crucial for fine-tuning larval behavior in response to hypoxia.
Structure of a Tc holotoxin pore provides insights into the translocation mechanism
Authors: Roderer Daniel , Hofnagel Oliver , Benz Roland , Raunser Stefan
Published: October 2019

Tc toxins are modular toxin systems of insect and human pathogenic bacteria. They are composed of a 1.4-MDa pentameric membrane translocator (TcA) and a 250-kDa cocoon (TcB and TcC) encapsulating the 30-kDa toxic enzyme (C terminus of TcC). Binding of Tc toxins to target cells and a pH shift trigger the conformational transition from the soluble prepore state to the membrane-embedded pore. Subsequently, the toxic enzyme is translocated and released into the cytoplasm. A high-resolution structure of a holotoxin embedded in membranes is missing, leaving open the question of whether TcB-TcC has an influence on the conformational transition of TcA. Here we show in atomic detail a fully assembled 1.7-MDa Tc holotoxin complex from
Photorhabdus luminescens
in the membrane. We find that the 5 TcA protomers conformationally adapt to fit around the cocoon during the prepore-to-pore transition. The architecture of the Tc toxin complex allows TcB-TcC to bind to an already membrane-embedded TcA pore to form a holotoxin. Importantly, assembly of the holotoxin at the membrane results in spontaneous translocation of the toxic enzyme, indicating that this process is not driven by a proton gradient or other energy source. Mammalian lipids with zwitterionic head groups are preferred over other lipids for the integration of Tc toxins. In a nontoxic Tc toxin variant, we can visualize part of the translocating toxic enzyme, which transiently interacts with alternating negative charges and hydrophobic stretches of the translocation channel, providing insights into the mechanism of action of Tc toxins.
Hydrodynamics of random-organizing hyperuniform fluids
Authors: Lei Qun-Li , Ni Ran
Published: October 2019

Significance

Recently, an exotic hyperuniform fluid state was found in a number of nonequilibrium systems, which shows the promise for fabrication of novel lifelike functional materials capable of self-healing and self-adapting. However, the general mechanism of fluidic hyperuniformity (HU) and its fundamental difference from equilibrium fluids remain unclear, which hinders the rational design of nonequilibrium hyperuniform fluids. In this work, we propose a nonequilibrium hard-sphere model of hyperuniform fluids and formulate a full hydrodynamic description based on the generalized Navier–Stokes equations. Our theory reveals the mechanism of fluidic HU in a simple and intuitive way, which is confirmed by simulating a realistic active spinner system.
Timing and specificity of cotranslational nascent protein modification in bacteria
Authors: Yang Chien-I , Hsieh Hao-Hsuan , Shan Shu-ou
Published: October 2019

The nascent polypeptide exit site of the ribosome is a crowded environment where multiple ribosome-associated protein biogenesis factors (RPBs) compete for the nascent polypeptide to influence their localization, folding, or quality control. Here we address how N-terminal methionine excision (NME), a ubiquitous process crucial for the maturation of over 50% of the bacterial proteome, occurs in a timely and selective manner in this crowded environment. In bacteria, NME is mediated by 2 essential enzymes, peptide deformylase (PDF) and methionine aminopeptidase (MAP). We show that the reaction of MAP on ribosome-bound nascent chains approaches diffusion-limited rates, allowing immediate methionine excision of optimal substrates after deformylation. Specificity is achieved by kinetic competition of NME with translation elongation and by regulation from other RPBs, which selectively narrow the processing time window for suboptimal substrates. A mathematical model derived from the data accurately predicts cotranslational NME efficiency in the cytosol. Our results demonstrate how a fundamental enzymatic activity is reshaped by its associated macromolecular environment to optimize both efficiency and selectivity, and provides a platform to study other cotranslational protein biogenesis pathways.
Single-nucleotide control of tRNA folding cooperativity under near-cellular conditions
Authors: Leamy Kathleen A. , Yamagami Ryota , Yennawar Neela H. , Bevilacqua Philip C.
Published: October 2019

Significance

RNA structures control many essential functions of life, including gene expression, protein synthesis, and development. To perform these functions, RNAs often adopt complex tertiary folds. Here, we study the thermodynamics of late-transcriptional folding of eukaryotic and prokaryotic tRNAs. In near-cellular conditions, tRNAs gain folding cooperativity only when nearly all nucleotides in the acceptor stem are transcribed. Furthermore, the native 5′ and 3′ extensions in the precursor do not affect the folding pathway. Therefore, tRNA folding cooperativity is controlled by a single nucleotide under near-cellular conditions.
The Dragoman and the Scholar: Two Polish Translations of Saʿdi’sGolestān
Authors: Kłagisz Mateusz M. , Rusek-Kowalska Renata
Published: October 2019

This article discusses two Polish translations of Saʿdi’sGolestān, prepared by Samuel Otwinowski and Wojciech Biberstein-Kazimirski (alias Albert Kazimirski de Biberstein) and published in 1879 and 1876 respectively. Though edited at the end of the nineteenth century, Otwinowski's translation had been originally completed in the first half of the seventeenth century and is assumed to be the first one or one of the very first renderings of Saʿdi's work into a European language. The question that remains unresolved is whether or not Otwinowski's translation, despite being unpublished, was known to seventeenth- and eighteenth-century Polish poets. One can find some stories and motifs “picked” from Saʿdi’sGolestānin their poetry, but they seem more likely to have been influenced by non-Polish renderings. This article describes the different translation strategies adopted by the two translators, the literarily gifted dragoman Otwinowski and the nineteenth-century philologist Biberstein Kazimirski.
Molecular doping of blue phosphorene: a first-principles investigation
Authors: Sun Minglei , Tang Wencheng , Li Song , Chou Jyh-Pin , Hu Alice , Schwingenschlögl Udo
Published: October 2019

Using first-principles calculations, we show that p-doped blue phosphorene can be obtained by molecular doping with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) and 1,3,4,5,7,8-hexafluorotetracyanonaphthoquinodimethane (F6-TNAP), whereas n-doped blue phosphorene can be realized by doping with tetrathiafulvalene (TTF) and cyclooctadecanonaene (CCO). Moreover, the doping gap can be effectively modulated in each case by applying an external perpendicular electric field. The optical absorption of blue phosphorene can be considerably enhanced in a broad spectral range through the adsorption of CCO, F4-TCNQ, and F6-TNAP molecules, suggesting potential of the doped materials in the field of renewable energy.
Dosimetric performance of the Elekta Unity MR-linac system: 2D and 3D dosimetry in anthropomorphic inhomogeneous geometry
Authors: Pappas E , Kalaitzakis G , Boursianis T , Zoros E , Zourari K , Pappas E P , Makris D , Seimenis I , Efstathopoulos E , Maris T G
Published: October 2019

Following the clinical introduction of the Elekta Unity MR-linac, there is an urgent need for development of dosimetry protocols and tools, not affected by the presence of a magnetic field. This work presents a benchmarking methodology comprising 2D/3D passive dosimetry and involving on-couch adaptive treatment planning, a unique step in MR-linac workflows.

Two identical commercially available 3D-printed head phantoms (featuring realistic bone anatomy and MR/CT contrast) were employed. One phantom incorporated a film dosimetry insert, while the second was filled with polymer gel. Gel dose-response characteristics were evaluated under the Unity irradiation and read-out conditions, using vials and a cubic container filled with gel from the same batch.

Treatment plan for the head phantoms involved a hypothetical large C-shape brain lesion, partly surrounding the brainstem. An IMRT step-and-shoot 7-beam plan was employed. Pre-treatment on-couch MR-images were acquired in order for the treatment planning system to calculate the virtual couch shifts and perform adaptive planning. Absolute 2D and relative 3D measurements were compared against calculations related to both adapted and original plans. Real-time dose accumulation monitoring in the gel-filled phantom was also performed.

Results from the vials and cubic container suggest that gel dose-response is linear in the dose range investigated and signal integrity is mature at the read-out timings considered. Head phantom 2D and 3D measurements agreed well with calculations with 3D gamma index passing rates above 90% in all cases, even with the most stringent criteria used (2 mm/2%). By exploiting the 3D information provided by the gel, comparison also involved DVHs, dose-volume and plan quality metrics, which also reflected the agreement between adapted and delivered plans within  ±4%. No considerable discrepancies were detected between adapted and original plans.

A novel methodology was developed and implemented, suitable for QA procedures in Unity. TPS calculations were validated within the experimental uncertainties involved.
Interactions of magnetized plasma flows in pulsed-power driven experiments
Authors: Suttle L G , Burdiak G C , Cheung C L , Clayson T , Halliday J W D , Hare J D , Rusli S , Russell D R , Tubman E R , Ciardi A , Loureiro N F , Li J , Frank A , Lebedev S V
Published: October 2019

A supersonic flow of magnetized plasma is produced by the application of a 1 MA-peak, 500 ns current pulse to a cylindrical arrangement of parallel wires, known as an inverse wire array. The plasma flow is produced by the J × B acceleration of the ablated wire material, and a magnetic field of several Tesla is embedded at source by the driving current. This setup has been used for a variety of experiments investigating the interactions of magnetized plasma flows. In experiments designed to investigate magnetic reconnection, the collision of counter-streaming flows, carrying oppositely directed magnetic fields, leads to the formation of a reconnection layer in which we observe ions reaching temperatures much greater than predicted by classical heating mechanisms. The breakup of this layer under the plasmoid instability is dependent on the properties of the inflowing plasma, which can be controlled by the choice of the wire array material. In other experiments, magnetized shocks were formed by placing obstacles in the path of the magnetized plasma flow. The pile-up of magnetic flux in front of a conducting obstacle produces a magnetic precursor acting on upstream electrons at the distance of the ion inertial length. This precursor subsequently develops into a steep density transition via ion-electron fluid decoupling. Obstacles which possess a strong private magnetic field affect the upstream flow over a much greater distance, providing an extended bow shock structure. In the region surrounding the obstacle the magnetic pressure holds off the flow, forming a void of plasma material, analogous to the magnetopause around planetary bodies with self-generated magnetic fields.
Cosmology data analysis challenges and opportunities in the LSST sky survey
Authors: Anthony Tyson J
Published: October 2019

Fueled by advances in software, microelectronics, and large optics fabrication, a new type of sky survey will soon begin. In a relentless campaign of 15 second exposures with a 3 gigapixel camera, the Large Synoptic Survey Telescope will cover the sky deeply every week for ten years. LSST will chart billions of remote galaxies, providing multiple probes of the mysterious Dark Matter and Dark Energy. Multiple probes of the effects of dark energy over an unprecedented volume of the universe will allow us to measure how dark energy behaves over time to high precision. Hundreds of petabytes of high dimensional complex data will be mined and compared with Exascale simulations. After reviewing the LSST project, I will describe some of the computational challenges and opportunities.
Principal component analysis of the magnetic transition in the three-dimensional Fermi-Hubbard model
Authors: Khatami Ehsan
Published: October 2019

Machine learning techniques have been widely used in the study of strongly correlated systems in recent years. Here, we review some applications to classical and quantum many-body systems and present results from an unsupervised machine learning technique, the principal component analysis, employed to identify the finite-temperature phase transition of the three-dimensional Fermi-Hubbard model to the antiferromagnetically ordered state. We find that this linear method can capture the phase transition as well as other more complicated and nonlinear counterparts.
Learning Materials Properties from Orbital Interactions
Authors: Pham Tien-Lam , Dang Tran-Thai , Nguyen Van-Doan , Kino Hiori , Miyake Takashi , Dam Hieu-Chi
Published: October 2019

Orbital field matrix (OFM) descriptors were developed with an emphasis on atomic orbitals for representing material structures in datasets of multi-element compounds. The descriptors were based on atomic valence shell electrons and their coordination. In addition to original OFM and OFM1 which is OFM with a column representing information on the center atom, in this work, we present another version, named OFM0, which is OFM1 without information on atomic distances, for predicting the properties of unoptimized structures. We focus on formation energy and phase stability of crystalline systems, while the atomization energy is examined for molecules. With the emphasis on the ability to identify materials with similar properties, here, the applicabilities of OFM, OFM1, and OFM0 are systematically examined with decision tree (DT) regression, random forest (RF) regression, and kernel ridge regression (KRR). We show that the family of OFM descriptors are highly capable to build predictive models for the properties of solids and molecules. The accuracy of a DT and a forest of trees (RF) is comparable to that of the KRR models. The KRR with a Laplacian kernel estimated by OFM1 yields the most accurate predictions, with the formation energy, phase stability, and atomization energy having mean absolute errors (MAEs) of 0.072 eV/atom, 0.059 eV/atom, and 6.74 kcal/mol, respectively. The OFM0 without atomic distances also yields acceptable predictions with respective MAEs of 0.090 eV/atom, 0.069 eV/atom, and 7.77 kcal/mol. The results imply that our descriptors are highly useful to find similar materials.
A Comparison of Medium-Sized Basis Sets for the Prediction of Geometries, Vibrational Frequencies, Infrared Intensities and Raman Activities for Water
Authors: Ferrari Brian C. , Bennett Chris J.
Published: October 2019

Optimized geometries, vibrational frequencies, as well as infrared intensities and Raman activities were calculated for water (H2O) utilizing popular quantum mechanical approaches. Here, density functional theory (DFT) calculations were performed using the B3LYP (Becke, three-parameter, Lee-Yang-Parr) functional, as well asab initiocalculations using second-order Møller-Plesset (MP2) perturbation theory and coupled-cluster with single, double and perturbative triple excitations [CCSD(T)] levels of theory were used. We assess and benchmark the performance of 69 different atomic orbital basis sets including various popular families of medium-sized basis sets typically of two to four zeta quality and differing levels of augmentation by polar and diffuse functions. The basis sets range from the commonly adopted Pople-style (6-31G & 6-311G), Dunning’s correlation consistent (cc-pV(n+d)Z & aug-cc-pV(n+d)Z, as well as Truhlar’s calendar variations, Jensen’s polarization consistent (pc-n & aug-pc-n), Ahlrichs (def2-…), Sapporo’s and Karlsruches as well as atomic natural orbitals (ANOs) such as NASA Ames (ANOn), Neese-style, and Roos-style. We also compare several basis sets specifically designed to calculate vibrational and electronic properties, including the Sadlej-pVTZ (and LPol-X families), as well as SNS families of Barone. The results are compared to experimental values where available, or calculations performed with 5 or 6 zeta-level (e.g., cc-pV6Z). The performance of each family of basis sets is discussed in terms of their accuracy (and pitfalls), as well as computational resource scaling and efficiency. The Def2 basis family performs very well overall, yielding more accurate results with lower runtimes than traditional basis sets. ‘May’ basis sets also provide accurate predictions of vibrational frequencies at significantly lower costs. Raman activities can be accurately calculated using MP2 under harmonic approximation with several ‘spectroscopic’ families performing well.
A Brief History of Strukturbericht Symbols and Other Crystallographic Classification Schemes
Authors: Mehl Michael J.
Published: October 2019

In 1913, x-ray crystallography was first used to determine the crystal structure of diamond. Since that time hundreds of thousands, if not millions, of crystal structures have been determined. Published structures require critical review and indexing to make them easily available to other researchers. One of the first systems for doing this was Strukturbericht (Structure Reports), published in Germany from 1931-1943 and covering research from 1913-1939, and now best known for the Strukturbericht symbols which label common crystal structures. A comprehensive history of Strukturbericht has not been written. This brief report sketches the early history of Strukturbericht, as well as its post-World War II successor publications, handbooks, and online resources.
DCA++ project: Sustainable and scalable development of a high-performance research code
Authors: Hähner U R , Balduzzi G , Doak P W , Maier T A , Solcà R , Schulthess T C
Published: October 2019

Scientific discoveries across all fields, from physics to biology, are increasingly driven by computer simulations. At the same time, the computational demand of many problems necessitates large-scale calculations on high-performance supercomputers. Developing and maintaining the underlying codes, however, has become a challenging task due to a combination of factors. Leadership computer systems require massive parallelism, while their architectures are diversifying. New sophisticated algorithms are continuously developed and have to be implemented efficiently for such complex systems. Finally, the multidisciplinary nature of modern science involves large, changing teams to work on a given codebase. Using the example of the DCA++ project, a highly scalable and efficient research code to solve quantum many-body problems, we explore how computational science can overcome these challenges by adopting modern software engineering approaches. We present our principles for scientific software development and describe concrete practices to meet them, adapted from agile software development frameworks.
Free energy profiles of lipid translocation across pure POPC and POPC/CHOL bilayer: all-atom molecular dynamics study
Authors: Saito Hiroaki , Morishita Tetsuya , Mizukami Taku , Nishiyama Ken-ichi , Kawaguchi Kazutomo , Nagao Hidemi
Published: October 2019

All-atom molecular dynamics (MD) simulations of pure 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayer and POPC bilayer containing cholesterol (POPC/CHOL) with CHARMM36 force field were carried out to investigate the effects of CHOL on structure and lipid translocation across the membranes. We calculated the potential mean force (PMF) profiles for translocation of POPC and CHOL along the pure POPC and the POPC/CHOL bilayer normal by umbrella sampling method. The obtained PMF profile of the POPC translocation was in good agreement with that of the previous MD study, showing that the estimated PMF profiles with the CHARMM36 force field should be reasonable. We found that the PMF peak appears slightly beyond the bilayer center. The CHOL effects on the PMF profile of POPC translocation were clearly observed; the free energy barrier for the flip-flop of lipid increased and, the energy for the desorption of lipid decreased. These changes in the PMF profile should be responsible for the tight packing of the POPC/CHOL bilayer. The PMF profiles for the CHOL translocation showed that the free energy barriers at the bilayer center were sufficiently smaller than those of POPC translocation, indicating that the CHOL can easily flip over compared to the POPC in the membrane. In the case of PMF of CHOL translocation in the POPC/CHOL system, while the PMF energy in the hydrophobic core region was higher than that of the pure POPC bilayer, the free energy difference at bilayer center was small.
On the carbuncle instability of the HLLE-type solvers
Authors: Shen Zhijun , Ren Jian , Cui Xia
Published: October 2019

The carbuncle phenomenon is a numerical instability that affects the numerical capturing of shock waves when low-dissipative upwind scheme is used. This paper investigates shock instabilities of the HLLE-type methods for the Euler equations under the strong shock interaction, where the HLLE-type methods include the HLLE, HLLC, HLLEM, HLLCM and HLLEC Riemann solvers with specific wavespeed estimates. Based on a matrix stability analysis for two dimensional steady shocks, a new factor to influence carbuncle phenomenon is pointed out and the choice of the signal velocity plays an important role. A numerical flux function with wave velocity estimates which can crisply resolve shocks seems to be vulnerable to the shock anomalies even if the numerical fluxes to be regarded to be free from the carbuncle phenomenon. A suggestion to the choice of the wave speed is proposed when calculating strong shock wave problems.
On the geometric structures in evolutionary games on square and triangular lattices
Authors: Burovski Evgeni , Malyutin Aleksandr , Shchur Lev
Published: October 2019

We study a model of a spatial evolutionary game, based on the Prisoner’s dilemma for two regular arrangements of players, on a square lattice and on a triangular lattice. We analyze steady state distributions of players which evolve from irregular, random initial configurations. We find significant differences between the square and triangular lattice, and we characterize the geometric structures which emerge on the triangular lattice.
A Brief Review on Canonical Loop Quantum Gravity: The Kinematical Part
Authors: Zen Freddy Permana , Ariwahjoedi Seramika
Published: October 2019

In this article, we briefly review the kinematical part of canonical loop quantum gravity. This article starts with tetradic formulation of gravity both in the covariant approach and canonical approach. The next step is to introduce Ashtekar new variables and to apply the Dirac canonical quantization procedure of gravity. By the holonomy representation, one obtains the loop representation of quantum gravity.
Matter perturbation in coupled scalar field cosmology
Authors: Mulki F A M , Wulandari H
Published: October 2019

A universe containing a coupled scalar field would have different dynamical evolution compared to uncoupled cases. Significant differences are expected to emerge during matter dominated era, where scalar field density mimics how matter density evolves, by becoming subdominant. Analysis of the dynamics was investigated both analytically and numerically through phase plane method, and we obtained two attractor solutions which are compatible to a late time cosmic acceleration as the ending of matter dominated era. Ordinary scalar field triggers an acceleration with stable attractor solution which converges to ωϕ
= ωeff
≈ −1. Whereas, phantom scalar field allows negative values for its own energy (ωeff
˂ −1 and Ωϕ ˂ 0); however this is not stable, therefore it will be caught by attractor solution which is stable to ωϕ
= ωeff
≈ −1. In addition, we found cosmological parameters generated from both analytical and numerical calculations, i.e. ωϕ
, Ωϕ and ωeff
, by assuming a flat universe. The existence of a coupling constant Q between scalar field and matter induces different structure growth compared to uncoupled cases and standard cold dark matter (CDM) model. During matter dominated era, ordinary scalar field induces growth of structures so that it becomes faster than the standard model does, whereas phantom scalar field slows down the growth of structures. During scalar field dominated era (far in the future), we obtained that formed structures or density contrasts will decay in a similar way as in uncoupled cases, whereas following phantom scenario, the decay of formed structures occurs faster and more significant. This result is associated to background dynamics which shows that big rip will be the relevant fate of our universe.
Multiwavelength analysis of nearby ultraluminous x-ray sources (ULXs) and their environment
Authors: Vierdayanti K , Khairunnisa S A , Wulandari H
Published: October 2019

Ultraluminous X-ray sources (ULXs) are known as extragalactic point-like X-ray sources with luminosities considerably in excess of the maximum luminosity of a 10 solar mass accreting black hole. X-ray spectra of ULXs have been investigated in many previous studies. However, sparse observations render it more difficult to convincingly distinguish between two competing scenarios, i.e. sub-critical accreting intermediate-mass black hole and super-critical accreting stellar remnant black hole. Here, we report our investigation of a sample of nearby ULXs, as well as their host galaxies, in order to get a more complete understanding of their nature. Multiwavelength analysis was applied to study these ULXs. From X-ray study, we found that most ULXs in our sample do exhibit spectral variability in which higher energy X-ray predominates the spectra as the source becomes brighter. We also compiled some properties of the host galaxies, as a proxy of ULX environment. We found that ULXs in our sample can neither be exclusively associated with a certain type of morphology, nor with high nuclear activity. We also found that 12 out of 19 ULXs reside in host galaxies with star formation rate of less than 1 solar mass per year.
Low Energy Theorem for Kaon Photoproduction
Authors: Sakinah S. , Clymton S. , Mart T.
Published: October 2019

We study the Low Energy Theorem (LET) for kaon photoproduction at threshold region. To this end we expand the transition amplitude in terms of the kaon mass and the averaged mass of nucleon and Λ-hyperon. The background amplitudes are obtained from the appropriate Feynman diagrams. The amplitudes have been so far expanded up to the 3th order.
Theoretical Study of Unconventional Plasmon Generation by Solving Finite-Size 3D Hubbard Model within Mean Field Approximation
Authors: Prakasa Dedi , Majidi Muhammad Aziz
Published: October 2019

Recent experimental study on Strontium Niobate Oxide system has revealed unconventional plasmons generated due to confinement by oxygen planes. A phenomenological model accompanied the experimental data on that report has suggested that the confined electrons behave as harmonic oscillators. These motivate us to further study the effect of space confinement to the electrons on the formation of unconventional plasmons theoretically. For this purpose, we propose a method of modeling the generation of the unconventional plasmons in a finite system. The dynamics of correlated electrons in this confined system is described using finite-size 3D Hubbard model that is solved within mean field approximation. We study a hypothetical cubic system that consists of 5x5x5 single-orbital atoms. The calculation is done with and without incorporating the on-site Coulomb repulsion. We also consider both restricted and unrestricted mean field treatments to the calculation. Our dielectric function results show that for restricted mean field with U = 0 eV and unrestricted mean field with U ≤ 2 eV, the system is metal and only two and four unconventional plasmons found respectively. While, for U > 2 eV, it becomes insulator and shows more emergence of unconventional plasmons.
Drop of Spin Polarization of Half Metal due to Interfacial Spin Mixing
Authors: Cahaya Adam B. , Majidi M. A.
Published: October 2019

Half metal is a ferromagnetic metal that act as a conductor to electrons with of one spin orientation, while act as an insulator for the opposite spin. Because of this high spin-dependent property, half metals are widely studied in spiritroriics area. This property can be represented by the spin polarization P = (G↑ — G↓
) / (G↑ + G↓
) of its spin-dependent conductances G↑,↓. The value of P of an ideal half metal is 1. However, the value of P is reduced when it is attached to other material. We study how the spin current generations that occurs at the interface of half metal and normal metal reduces the value P. At the interface of a half metal and a normal metal a spin current can be pumped from the ferromagnetic layer to the normal metal. This spin pumping effect is characterized by spin-mixing conductance, which represents the magnitude of the generated spin current due to the mixing of electrons with spin up and down. By analyzing the coupling of spin and electric currents in the interface of half metal and normal metal, we show that the spin mixing strongly influences the spin-dependent transport near the interface, and therefore reduces the spin polarization of the half metal.
Three Dimensional Numerical Modeling of Current and Temperature Distribution in the Estuary of Palu River
Authors: Lutfi Mohammad
Published: October 2019

Three dimensional numerical model of current and temperature distribution in the estuary of Palu river was discussed in this article. The simulation was conducted using estuary coastal ocean model and sediment transport (ECOMSED) and geographical information system (GIS). The first simulation was conducted by assuming no discharge and the second simulation using combination of tidal and river discharge. The first simulation runs smoothly, where the results revealed that the tidal current velocity on the horizontal and vertical cross sections for one tidal cycle ranged from 0 m/s to 0.03 m/s. Whereas a run time error occurred during the second simulation due to the calculation of nonliniear advection term parameter in momentum equation. The error problem could be solved by imposing a low river discharge data into the model. The visual appearance of current circulation at the river mouth, calculated surface elevation, and temperature distribution on the horizontal and vertical cross sections revealed a good agreement with the primary and secondary data.
The quality of the machined surface of an aluminum alloy depending on the cutting depth variation
Authors: Țîțu A M , Pop A B
Published: October 2019

The surface quality study of the cutting processes is a very current and complex subject, which approached in variously specialized researches. This paper is a continuation of our previous research. The primary objective of this paper is to track the evolution of the surface roughness measured longitudinally on the feed motion direction in the end-milling process of an aluminum alloy used in the aerospace industry. The active experiment is the research method used to achieve the proposed objective. The cutting regime adapted to carrying out the necessary experiments supposes a constant cutting speed, while the cutting depth varies with different values. Obtaining the experimental data did possibly using the roughness tester as a measuring device. The obtained measurements were used to determine the surface quality evolution in the various situations of the cutting regimes resulting from the combination of the process parameters considered in the analysis. The experimental study is very complex and carried in an industrial organization that focuses on the aerospace industry. Through this original research that was carried out in the smallest details, a series of comparative graphs of the surface roughness evolution performed under the cutting depth variation, which led to a package of conclusions to have taken into consideration.
Examination of the influence of cutting conditions on nano-metric face milling using MD models
Authors: Karkalos N E , Markopoulos A P
Published: October 2019

Machining is indispensable in the manufacturing sector for a wide variety of products. In the last years, the field of micro- and nano-scale manufacturing attracted a lot of interest, especially in high-end industries such as the biomedical and electronics industries. In order to improve the efficiency of these processes and understand the various underlying phenomena, it is important to develop relevant theoretical models. However, methods such as the Finite Element Method (FEM), which are well-established in the macro- or micro-scale level are not appropriate for creating models of nano-scale processes, as they treat the materials as continua. For that reason, the Molecular Dynamics (MD) method is usually used for simulations of nano-metric machining processes such as nano-milling. In the present study, a MD model of nano-milling is created and an investigation regarding the effect of cutting conditions such as feed rate and cutting speed on cutting forces, temperature and subsurface damage is conducted.
Effect of cooling condition over surface quality in turning of aluminium alloy 6082-T6
Authors: Beșliu I , Tamașag I
Published: October 2019

Cutting fluids play an important role in machining operations helping reduce friction, workpiece heating, tool wear and also with chips detachment and evacuation. The usage of cutting fluids also have a number of drawbacks that are related with the environmental threats and costs. Dry matching and MQL-minimum quantity of liquid seem to be promising solutions for these problems. But these solutions are not feasible under all machining applications. The present paper purpose is to investigate the effect of cutting and cooling conditions over surface quality in aluminium alloy 6082-T6 turning operations.
Experimental research of tool axis inclination angle influence upon surface roughness in ball-nose end milling of polyetheretherketones (Tecapeek natural)-Part I
Authors: Paşca I , Lobonţiu M , Bǎnicǎ M , Tǎmaş I
Published: October 2019

In order to find solutions for different medical applications like implants and reconstructions in clinical dentistry, orthopaedic or spinal implants, the polyetheretherketones have achieved a remarkable application because of their properties. The polyetherketone materials combine excellent wear resistance with very good mechanical properties, even under thermal load. Because of these qualities it is used also in different applications in automotive, aerospace and food industry. For each application, no matter if the process to obtain different shape is extrusion, injection moulding or machining by turning or milling, the surface roughness value is critical. For pieces with complex surfaces some finishing operations are necessary. The ball nose end milling process is recommended in this case because of its versatility. In ball nose end milling process the influence of tool axis inclination angle has a big influence upon surface roughness value. In this way theoretical studies are required in order to establish the influence of this parameter upon effective cutting speed. Also, experimental research method was needed in order to establish the quality of surface in terms of surface roughness. The experimental research results establish the most favourable values of inclination angle for Tecapeek-natural material in comparison with C45 material.
The in-plane compression performance of hierarchical honeycomb additive manufactured structures
Authors: Mansour M T , Tsongas K , Tzetzis D. , Antoniadis A.
Published: October 2019

Fused Deposition Modelling (FDM) is a simple additive manufacturing (AM) technology utilising fine filament extrusion of mainly thermoplastic materials to build 3D objects layer by layer. The focus of this paper is firstly to design hierarchical honeycombs and secondly to fabricate such structures using FDM with polylactic acid (PLA). The manufactured hierarchical honeycombs were tested under compression. The compression performance of the hierarchical honeycombs was assessed also with finite element analysis and the results were compared with the experimental derived properties in order to elucidate the mechanical behaviour of such honeycomb AM structures. The results reveal that for the 2nd order hierarchy of honeycombs the stiffness and the strength are increased in comparison with the 0th and the 1st hierarchies.
Research on manufacturing of pyramidal frustum parts using single point incremental forming process
Authors: Nasulea D , Oancea G
Published: October 2019

The incremental sheet metal forming is a flexible “die-less” process used to manufacture sheet metal parts in cold pressing domain. Especially talking about single point incremental forming, it is a process which does not require a special die to allow the sheet metal forming. To implement this process, a fixing device and a simple rounded tool are needed. The paper presents some research on the influence of a support plate upon the parts dimensional precision. Because, the main advantage of single point incremental forming process is the flexibility, in experiments, a fixing device that it was initial designed for incremental deformation of frustum cone parts, is used to deform pyramidal frustum parts. Different configurations of pyramidal frustum parts are simulated using a finite element method and a special software tool named TMPG, to check if the sheet material, deep drawing steel DC05, can be deformed without fracture. The manufactured parts are measured using a 3D scanner, and a comparison with the 3D CAD models of the original parts is made.
Continuously pulsed electric field treatment chamber modelling and design
Authors: Shorstkii I , Sosnin M , Khudyakov D
Published: October 2019

The perspectives of pulsed electric field (PEF) application for rheological changes in plant materials and treatment chamber design are considered in current paper. By using some mathematical tools and experiments data, viscosity of transporting plant materials confirms proposed Bingham rheological model assumption. Experimental studies have shown the presence of structure formation in material supplied to the treatment chamber channel. An effect of PEF treatment, with changes of material structure and increasing of material plastic viscosity from 0.117 to 0.159 Pa·s for samples after treatment by a field strength of E = 8 kV/cm and the number of pulses n = 300 was found. Obtained results of pulsed electric fields application in continuously material flow can be used in pulsed electric fields technologies, equipment design and help to determine cost efficiency of treatment in industrial application.
Numerical simulation of Friction Stir Welding of three dissimilar aluminium alloys
Authors: Boșneag A , Constantin M A , Nitu E L
Published: October 2019

FSW process is increasingly required in industrial environment. This innovative process has a lot of advantages: can be performed without melting of material, uses a non-consumable tool, performed good mechanical properties, can weld dissimilar materials and have a low environmental influence. On the other hand, FSW process has several disadvantages: an excessive tool wear, weld speeds slower, expensive equipment and limitations for high melting temperature materials. To achieve the expected results during industrial applications, welding process behaviour must be properly understood. The Finite Element Simulation is a technique which would help to understand the process variation during the welding and the result could be used to notice the effect of process parameters on weld quality. In this study an attempt is made to develop a FE model using ABAQUS V6.13/Explicit with help of CEL formulation, Johnson-Cook material law and Coulomb’s Law of friction. The model will obtain a perspective on circumstance of processing before carrying out the welding process, would predict the effect of input process parameters on outputs parameters like: temperature. The simulation results are used to obtain the optimized process parameters. Numerical model validation is performed by comparing the value of temperatures from FE simulation with the experimentally recorded temperatures.
Study on the diamond’s role in manufacturing engineering and in energy
Authors: Grosse E Bauer
Published: October 2019

Due to its outstanding properties, diamond is considered as an advanced material that generates innovation in various applications belonging to many fields. A very short literature overview is proposed about its role in manufacturing engineering and in energy with a focus on some recent discoveries.