bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on joint detection of fabricated concrete shear wall based on percussion method
Authors: Song Bo , Li Jian , Wang Man sheng
Published: April 2019

The knock detection method is one of the non-destructive testing methods for assembly prefabricated components. The knocker is used to knock on the concrete prefabricated components to be tested. The internal conditions of the tested components can be judged by analyzing the time-domain and frequency-domain diagrams of the knocker. In this paper, the impact of the change of the knock point on the detection is studied by using the knock detection experiment. It is found that the location of the knock point has a great influence on the detection. With the change of the position of the knock point, the peak frequency in the spectrum obtained by the detection changes correspondingly. According to the frequency information corresponding to the peak value in the spectrum, the depth of the void to the knock surface can be calculated.
(IM-)Material flow analysis for system innovation
Authors: Allais Romain , Gobert Julie
Published: April 2019

Current assessment tools are mainly disciplinary and support the assessment of material flows in terms of environmental impacts or economical flows, for example. These tools provide helpful quantitative information for system (re)-design but do not explicitly question the value creation factors and their embeddedness in a specific socio-spatial context. This article underlines that innovation for sustainability requires more complexity and a system and multidisciplinary approach. A dynamic material and immaterial resource flows model coupled with extended scorecard to support both the analysis and structuration of territorial projects may be of great support to better understand, qualify and quantify the different kinds of resources revealed, mobilized or denied during a project. This communication focuses on the model development and the cross-fertilization of industrial, sociological and geographical disciplines for system transition analysis. Even if this model is still under development, it appears to strengthen strategic analysis, as it enables both the representation of the tangibles and intangible assets mobilized during the emergence and structuration of territorial projects (e.g. business model transition to functional economy) and sustainability assessment of existing projects (e.g. industrial and territorial ecology projects).
Optimal inventory management and order book modeling
Authors: Baradel Nicolas , Bouchard Bruno , Evangelista David , Mounjid Othmane
Published: April 2019

We model the behavior of three agent classes acting dynamically in a limit order book of a financial asset. Namely, we consider market makers (MM), high-frequency trading (HFT) firms, and institutional brokers (IB). Given a prior dynamic of the order book, similar to the one considered in the Queue-Reactive models [12, 18, 19], the MM and the HFT define their trading strategy by optimizing the expected utility of terminal wealth, while the IB has a prescheduled task to sell or buy many shares of the considered asset. We derive the variational partial differential equations that characterize the value functions of the MM and HFT and explain how almost optimal control can be deduced from them. We then provide a first illustration of the interactions that can take place between these different market participants by simulating the dynamic of an order book in which each of them plays his own (optimal) strategy.
Statistical and probabilistic modeling of a cloud of particles coupled with a turbulent fluid
Authors: Goudenège Ludovic , Larat Adam , Llobell Julie , Massot Marc , Mercier David , Thomine Olivier , Vié Aymeric
Published: April 2019

This paper exposes a novel exploratory formalism, the end goal of which is the numerical simulation of the dynamics of a cloud of particles weakly or strongly coupled with a turbulent fluid. Given the large panel of expertise of the list of authors, the content of this paper scans a wide range of connex notions, from the physics of turbulence to the rigorous definition of stochastic processes. Our approach is to develop reduced-order models for the dynamics of both carrying and carried phases which remain consistant within this formalism, and to set up a numerical process to validate these models. The novelties of this paper lie in the gathering of a large panel of mathematical and physical definitions and results within a common framework and an agreed vocabulary (sections 1 and 2), and in some preliminary results and achievements within this context, section 3. While the first three sections have been simplified to the context of a gas field providing that the disperse phase only retrieves energy through drag, the fourth section opens this study to the more complex situation when the disperse phase interacts with the continuous phase as well, in an energy conservative manner. This will allow us to expose the perspectives of the project and to conclude.
The impact of the rise of using solar energy in GCC countries
Authors: Alnaser N.W. , Alnaser W.E.
Published: April 2019

The research and the prototype projects in the GCC countries were in place since 1970's which first was started in Kuwait, followed by Saudi Arabia in the 1980's, United Arab Emirates in the 1990's, Bahrain, Oman and Qatar in 21 centuries. Now all GCC countries had conducted, relatively, large project in solar and wind energy, especially Kuwait (currently about 70 MW among a plan of 2000 MW by 2030), UAE (currently about 300 MW among a plan of 2500 MW by 2030) and Saudi Arabia (with an ambitious renewable energy target of 3450 MW by 2020 with a further 6000 GW envisioned by 2023 and to 200 000 MW by 2030). Such an acceleration in the use of solar and wind energy would have an impact. Major impacts are: (1) Major reduction in the solar electricity prices in the region; (2) More investors in renewable energy business; (3) Rise of innovative design of houses to utilize its structure in installation and integration of renewable energy devices; (4) Rise of many service and maintenance of solar technology companies; (5) Establishment of new academic programs and courses in solar and other renewable energy technologies in the higher education institute and technical organizations; (6) More concern and studies on disturbances to the main grid due to solar connection; (7) Major reduction in carbon footprint per capita in GCC countries; (8) Use of more efficient and low consumption household and industrial devices; (9) Boost in battery industry for solar electricity storage.
Pankreaskarzinom 2018 – reif für personalisierte Therapiekonzepte?
Authors: Simon Ole , Beyer Georg , Mahajan Ujjwal , Mayerle Julia
Published: April 2019

Epidemiologie Die 5-Jahres-Überlebensrate (5-JÜR) aller Pankreaskarzinompatienten liegt mit rund 6 % sehr niedrig und die potenziell kurative Operation ist nur bei 15 – 20 % der Erkrankten möglich. Durch häufigeren Einsatz und Kombination systemischer Chemotherapeutika konnte in den letzten Jahren eine verbesserte Lebenserwartung erreicht werden.

Resektables Stadium Nach vollständiger operativer Resektion eines Pankreaskarzinoms trägt eine adjuvante Chemotherapie zur Verlängerung des Gesamtüberlebens bei. Mittel der Wahl sind Gemcitabin oder 5-Fluorouracil (5-FU) und Folinsäure (FS). Kürzlich konnte für die Kombination aus Gemcitabin und Capecitabin (Gem-Cap) eine signifikante Verlängerung des Gesamtüberlebens im Vergleich zur Gemcitabin-Monotherapie gezeigt werden. Für den Einsatz einer adjuvanten Radiochemotherapie gibt es derzeit keine Empfehlung.

Borderline-resektables Stadium Eine neoadjuvante Therapie hat bei Pankreaskarzinomen außerhalb klinischer Studien keinen Stellenwert. Eine Ausnahme stellen borderline-resektable Pankreaskarzinome dar.

Fortgeschrittenes Stadium (M1) Patienten mit fortgeschrittenem oder metastasiertem Pankreaskarzinom profitieren von einer Chemotherapie. Für Patienten mit gutem ECOG-Status konnte kürzlich in 2 Phase-III-Studien eine signifikante Lebenszeitverlängerung durch die Kombination aus Gemcitabin plus nab-Paclitaxel (Gem-Nab) sowie durch das Kombinationsschema aus Folinsäure, 5-FU, Irinotecan und Oxaliplatin (FOLFIRINOX) gezeigt werden. In der Zweitlinie steht nanoliposomales Irinotecan oder Oxaliplatin kombiniert mit 5FU/FS (OFF) zur Verfügung.

Personalisierte Therapien Die molekulare Charakterisierung des Pankreaskarzinoms hat Fortschritte gemacht und bietet schon heute Ansätze zur personalisierten Medizin. Bei gutem ECOG-Status sollte vor Zweitlinientherapie eine MSI-H/dMMR-Analyse erfolgen, um den möglichen Einsatz einer Checkpoint-Inhibitor-Therapie zu evaluieren. Bei BRCA-Mutationen kann die Gabe von PARP-Inhibitoren vielversprechend sein.
A Regioselective Approach to C3-Aroylcoumarins via Cobalt-Catalyzed­ C(sp2)–H Activation Carbonylation of Coumarins
Authors: Pashazadeh Rahim , Rajai-Daryasarei Saideh , Mirzaei Siyavash , Soheilizad Mehdi , Ansari Samira , Shabanian Meisam
Published: April 2019

A new cobalt-catalyzed C–H bond activation of coumarins with aryl halides or pseudohalides and carbon monoxide insertion to give various 3-aroylcoumarin derivatives is described. It is the first time that CO as C1 feedstock is used as the coupling partners in cobalt-catalyzed regioselective coumarin C–H functionalization reactions. Upon activation with manganese powder, the Co catalyzes the C–H bond activation carbonylation reactions of aryl iodides, bromides, and even triflates under mild conditions, providing the regioselective aroylated products in moderate to good yields.
Practical Synthesis of Chiral N-Heterocyclic Carbene Triazolium Salts Containing a Hydroxy Functional Handle
Authors: Dhayalan Vasudevan , Mal Kanchan , Milo Anat
Published: April 2019

A library of functionalized chiral pyrrolidine-based N-heterocyclic carbene triazolium salts containing a hydroxy handle is prepared from readily accessible chiral (S)-pyroglutamic acid in eight steps. This improved synthetic protocol affords increased yields for known structures and 18 new NHCs are prepared by this method. The presence of a hydroxy handle offers potential for further functionalization and for non-covalent control over catalytic reactions in which the NHCs can serve as organocatalysts or ligands for organometallic catalysis.
Treating the Lips and Its Anatomical Correlate in Respect to Vascular Compromise
Authors: Ghannam Sahar , Sattler Sonja , Frank Konstantin , Freytag David , Webb Katherine , Devineni Aditya , Cotofana Sebastian
Published: April 2019

Treating the lips to increase facial attractiveness and youthfulness is challenging when trying to consider ethnic differences in an increasingly more diverse society. Multiple injection techniques are currently available for treating lip contour and volume, but a validation in the cadaveric model under the aspects of safety has not been performed yet. The injection techniques presented in this study are based on the experience and personal selection of the authors. The authors have assessed, treated, and evaluated for more than 20 years patients from the Middle East and Central Europe. Cadaveric verification was performed for each of the presented techniques to identify the positioning of the injected product inside the lips and its relation to the superior/inferior labial arteries. The results of the anatomic analyses revealed that in 58.3% of the performed injections, the product was placed close to the superior/inferior labial arteries. In 60.0% of the cases, applications using a needle placed the injected product in endangered locations, whereas 57.1% of the cases using cannulas placed the product in endangered locations (i.e., in the vicinity of the superior/inferior labial arteries). This anatomic study revealed that injected material into the lips is frequently placed in close proximity to labial arteries representing a high risk for intra-arterial applications, leading to tissue loss (necrosis) and potential end-arterial embolism (potential blindness). Nevertheless, treatment of the lips should be a multistep approach focusing first on the far (upper and middle face) and close (labiomandibular and labiomental) perioral regions.
Decreasing Incidence of Postoperative Ileus Following Total Hip Arthroplasty: A 17-Year Retrospective Review of 31,619 Total Hip Replacements at One Institution
Authors: Nguyen Bob , Bono Olivia J. , Bono James V.
Published: April 2019

Ileus following total hip arthroplasty (THA) is a clinically and financially significant postoperative complication that has not been extensively described in the orthopaedic joint literature. Ileus has been found to occur in 0.7 to 4.0% of patients after total joint arthroplasty and as high as 5.6% in patients after revision THA.1,2,3 In a 17-year period (2001 Fiscal Year through 2017 Fiscal Year) at one institution, the authors found an incidence of 0.674% (213/31619) following THA. In addition, the incidence of ileus following THA has drastically declined over this 17-year period, from 1.822% (19/1043) in 2001 to 0.099% (3/3036) in 2017. This decrease may be attributed to a reduction in narcotic use postoperatively, earlier ambulation following surgery, and reduction in length of hospital stay. Though postoperative ileus is not yet a preventable complication, recognition of risk factors may permit earlier intervention to ameliorate some of the morbidity associated with this condition.
Relationship between Third Molar Agenesis and Other Dental Anomalies
Authors: Gulati Stuti , Singla Divya , Mittal Sanjay , Bhullar Mandeep , Aggarwal Isha , Sharma Abhishek
Published: April 2019

Objective The purpose of this study was to find the prevalence of dental abnormalities in patients with third molar agenesis, and a comparison was made for the prevalence of those anomalies within the north Indian natives.

Materials and Methods Pretreatment records of 518 patients were collected. Out of 518 patients whose records were analyzed, 472 patient records were selected on the basis of inclusion and exclusion standards. Panoramic radiographs and dental casts were analyzed in patients who had an absence of at least one third molar in which absence of any other tooth, presence of supernumerary teeth, presence of impacted canines, and peg-shaped lateral incisors were further assessed. The prevalence of these anomalies was compared with a randomly selected group of patients with presence of third molars that served as controls. Statistical analysis was done using the chi-square test (p < 0.05) and odds ratio.

Results The incidence of third molar nondevelopment was found to be 19.2%. The presence of other anomalies was 39.5% in patients with third molar nondevelopment, and difference was statistically significant. The occurrence of impacted canines in patients with absence of third molars was 22%, and presence of third molars was 6.6%. The presence of other dental anomalies, that is, supernumerary teeth and tooth agenesis, was 7.7% in the agenesis group, which was also higher than that in the control group (3.3%) but was not statistically significant. The incidence of peg-shaped lateral incisors was similar in both the groups.

Conclusion Impacted canines and total dental anomalies are more often related with absence of third molars than with the presence of third molars.
A Novel Frameshift Mutation Associated with Hurler's Syndrome: A Case Report
Authors: Kamranjam Mana , Hosseini Seyedeh Maryam , Alaei Mohammadreza
Published: April 2019

Mucopolysaccharidosis 1 (MPS1) is a rare inherited lysosomal storage disorder resulting from the absence or reduction of lysosomal alpha-l-iduronidase due to mutations in the IDUA gene. Three major clinical manifestations have been established including Hurler's or severe type (OMIM 607914), Hurler–Scheie or intermediate type (MIM 607914) and Scheie's or attenuated type (MIM 607016). In the present study, a patient whose disease was diagnosed by biochemical and enzymatic assay was studied in our laboratory. Molecular analysis implemented by PCR-sequencing of all 14 exons and exon–intron junctions confirmed a novel deleterious mutation in a homozygous state. The result of this study has broadened the genotypic spectrum of MPS1 patients, assisting in a more effective approach for carrier testing and counseling.
Comparison of the mechanical strength of a monolayer of silver nanoparticles both in the freestanding state and on a soft substrate
Authors: Wang Pangpang , Ryuzaki Sou , Gao Lumei , Shinohara Shuhei , Saito Noboru , Okamoto Koichi , Tamada Kaoru , Yamada Sunao
Published: April 2019

A 7-nm-thick monolayer comprising myristate-capped silver nanoparticles (AgNPs) was fabricated by first drop casting an AgNP solution on the surface of a 10–100 μl water drop placed on a solid substrate. With the natural evaporation of the water, a monolayer slowly descended onto the substrate, the latter containing an array of 2.5-μm-diameter and 200-nm-deep holes, and finally formed circular freestanding monolayers in the holes. Nanoindentation measurement based on atomic force microscopy was carried out on the circular freestanding monolayer at its center, and the extending and retracting force–indentation curves were recorded to analyze further the mechanical properties of the monolayer. The force–indentation curves were evidently nonlinear, and so a two-term continuum-mechanics theory was used to interpret the results. By fitting the force–indentation curves using a two-term equation, the prestress and Young’s modulus of the freestanding AgNP monolayer were obtained as approximately 0.05 N/m and several gigapascals, respectively, which are consistent with the results reported in the literature. For comparison, we also studied the mechanical responses of AgNP monolayers and bilayers on a soft polydimethylsiloxane (PDMS) substrate by using nanoindentation. Because the AgNP monolayer was stiffer than the PDMS substrate, it was possible to measure the mechanical response of the former despite it being only 7 nm thick. The mechanical strength of the freestanding AgNP monolayers was considered to be dominated by the attractive interactions between the interdigitated hydrocarbon chains of the myristate.
Two-dimensional self-assembly and electrical properties of the donor-acceptor tetrathiafulvalene-polychlorotriphenylmethyl radical on graphite substrates
Authors: Guasch Judith , Crivillers Núria , Souto Manuel , Ratera Imma , Rovira Concepció , Samorì Paolo , Veciana Jaume
Published: April 2019

The electron donor-acceptor tetrathiafulvalene-polychlorotriphenylmethyl (PTM) radical dyad, which shows a strong interplay between intra- and intermolecular charge transfer processes in solution, has been deposited by drop-casting on highly oriented pyrolytic graphite substrates, and its self-assembled structure has been investigated. Conducting atomic force microscopy revealed that the presence of a PTM radical in the molecules enhances the electrical conduction by almost two orders of magnitude and that this enhancement occurs in spite of the poor molecular orientation control achieved with drop-casting. Moreover, the study also reveals that the presence of a tetrathiafulvalene subunit in the deposited molecules can result in slightly asymmetric I-V curves.
Fast magnetic reconnection and the ideal evolution of a magnetic field
Authors: Boozer Allen H.
Published: April 2019

Regardless of how small non-ideal effects may be, phenomena associated with changes in magnetic field line connections are frequently observed to occur on an Alfvénic time scale. Since it is mathematically impossible for magnetic field line connections to change when non-ideal effects are identically zero, an ideal evolution must naturally lead to states of unbound sensitivity to non-ideal effects. That such an evolution is natural is demonstrated by the use of Lagrangian coordinates based on the flow velocity of the magnetic field lines. The Lagrangian representation of an evolving magnetic field is highly constrained when neither the magnetic field strength nor the forces exerted by the magnetic field increase exponentially with time. The development of a state of fast reconnection consistent with these constraints (1) requires a three-dimensional evolution, (2) has an exponentially increasing sensitivity to non-ideal effects, and (3) has a parallel current density, which lies in exponentially thinning but exponentially widening ribbons, with a magnitude that is limited to a slow growth. The implication is that exponential growth in sensitivity is the cause of fast magnetic reconnection when non-ideal effects are sufficiently small. The growth of the non-ideal effect of the resistivity multiplied by the parallel current density is far too slow to be competitive.
Enhanced laser-driven ion acceleration from a low-density-PMMA coated metal-foil
Authors: Kumar Manoj , Lee Kitae , Kim Ha-Na , Ryu Woo-Je , Park Seong Hee , Jeong Young Uk
Published: April 2019

Strong enhancement in proton energy was investigated from a two-dimensional particle-in-cell simulation where an ultraintense laser pulse irradiates a 2-μm thick metal foil coated with a low density, 1-μm thick PMMA (polymethylmathacrylate - C5H8O2) on the rear surface. The reduction of PMMA density effectively increases resistivity of hot electrons, which results in the generation of a strong electrostatic field at the metal-PMMA interface in addition to the sheath electrostatic field at the PMMA-vacuum boundary. The interaction of each proton beam accelerated by the two electrostatic fields leads to the enhancement of energy for the protons originated from the PMMA-vacuum side. With a laser intensity of 1×1020 W/cm2, maximum proton energy of 80 MeV was investigated with a modulation in energy spectrum, which is 2.2 times higher than those from a metal-contamination layer target or a metal-high density PMMA target. It is also interesting that there is an energy peak around 18 MeV, which is caused by an interaction with heavier ions.
PageRank as a collective variable to study complex chemical transformations and their energy landscapes
Authors: Zhou Tiecheng , Martinez-Baez Ernesto , Schenter Gregory , Clark Aurora E.
Published: April 2019

A reduced set of reaction coordinates is often employed in chemistry to describe the collective change between reactants and products within the context of rare event theories and the exploration of energy landscapes. Yet selecting the proper collective variable becomes increasingly challenging as the systems under study become more complex. Recent advancement of new descriptions of collective molecular coordinates has included graph-theoretical metrics, including social permutation invariant and PageRank (PR) coordinates, based upon the network of interactions about molecules and atoms within a system. Herein we continue the development of PR by (1) presenting a new formulation that is continuous along a reaction path, (2) illustrating that the fluctuations in PR are demonstrative of the fundamental motions of the atoms/molecules, and (3) providing the analytical derivatives with respect to atomic coordinates. The latter is subsequently combined with a harmonic bias to create the potential of mean force (PMF). As an example, we first consider the transformation of tetrahedral [Al(OH)4](aq)− to octahedral [Al(OH)4(H2O)2](aq)− using the PR PMF. Second, we explore the interchange of contact ion pair and solvent separated ion pairs of aqueous Na⋯OH, where the distance-biased PMF is projected onto PR space. In turn, this reveals where solvent rearrangement has the most impact upon the reaction pathway.
Phonon modes and photonic excitation transitions of MoS2 induced by top-deposited graphene revealed by Raman spectroscopy and photoluminescence
Authors: Cao Yan , Wang Zhijun , Bian Qi , Cheng Zhengwang , Shao Zhibin , Zhang Zongyuan , Sun Haigen , Zhang Xin , Li Shaojian , Gedeon Habakubaho , Liu Lijun , Wang Xina , Yuan Hui , Pan Minghu
Published: April 2019

Although the MoS2/graphene 2D stack achieved a lot of attention in recent research on 2D semiconductor devices, the interface interaction between perfect MoS2 and graphene and its effects on the electronic properties are rarely studied. Here, we report our recent studies on Raman spectroscopy and photoluminescence of the MoS2/graphene heterostructure. A nearly perfect interface between these two materials was achieved with a dry transfer and forming gas annealing. Raman spectroscopy of the heterostructure shows that the strong interface interaction leads to blue-shifts of Raman modes in MoS2 and graphene. Moreover, indicated by the photoluminescene of the heterostructure, the photon excitation and electronic dynamics of MoS2 are significantly influenced by the additional graphene layer on top. Our results reveal that the interface of heterostructures plays an important role in determining the physical properties, and it is better to view the heterostructure as a newly emerging material rather than a simple physical combination of the two materials.
Scattering strength dependence of terahertz random lasers
Authors: Schoenhuber S. , Wenclawiak M. , Kainz M. A. , Limbacher B. , Andrews A. M. , Detz H. , Strasser G. , Darmo J. , Unterrainer K.
Published: April 2019

Random lasing operation requires an active region, a gain medium that supports multiple scattering, and, especially for integrated optoelectronic devices, a nonresonant outcoupling mechanism over a continuous spectrum. For broadband operation, the resonator geometry must provide frequency nonselective, strong feedback over a large bandwidth. The feedback mechanism by multiple scattering in terahertz semiconductor random lasers and the bandwidth of such cavities are presented and discussed. We demonstrate the influence of shape and scattering strength of the scatterers on the lasing process and determine the bandwidth of such resonator structures. We use passive resonator structures to prove that the feedback as well as the outcoupling is frequency independent over a large bandwidth.
Low temperature excitonic spectroscopy study of mechano-synthesized hybrid perovskite
Authors: Sadhukhan Priyabrata , Pradhan Anway , Mukherjee Suman , Sengupta Payal , Roy Atanu , Bhunia Satyaban , Das Sachindranath
Published: April 2019

Photo-physical properties of mechano-chemically synthesized organic-inorganic hybrid perovskites have been investigated. CH3NH3PbBr3 nano-particles were prepared using the wet ball milling technique. Three emission peaks have been observed using low temperature photoluminescence spectroscopy. We assign these peaks to originate from free excitonic (FE) and bound excitonic emission and impurity level transition. FE peak energy increases linearly with temperature and a lattice phase change (orthorhombic to cubic) induces a sudden lateral shift after 110 K. However, the simultaneous presence of two phases has not been observed in this case. Greater activation energy is found in the mechano-chemically synthesized material rather than reported solution processed samples which indicates higher excitonic stability.
Design and analysis of polarization independent conformal wideband metamaterial absorber using resistor loaded sector shaped resonators
Authors: Kalraiya Sachin , Chaudhary Raghvendra Kumar , Abdalla Mahmoud A.
Published: April 2019

A polarization independent conformal wideband metamaterial absorber has been proposed in this study. The proposed absorber unit cell consists of a circle and a slotted sector, loaded with four lumped resistors between them to improve the absorption bandwidth. Measured and simulated results exhibit more than 90% absorption in the frequency band from 3.90 GHz to 10.5 GHz under the normal incidence angle, and the fractional bandwidth is 91.6%. The proposed absorber is polarization independent due to the symmetrical nature. The absorber unit cell is compact in configuration with a unit cell size of 0.16 λo × 0.16 λo, where λo is the wavelength at 3.9 GHz and the substrate thickness is 0.098 λo. Once the proposed absorber is wrapped on the cylindrical surface, it shows good absorptivity in the absorption frequency band. The effects of many designed parameters have been studied to understand the performance of the wideband absorber. To recognize the absorption phenomenon of the absorber, normalized impedance, electric field distribution, and surface current density have been demonstrated. Finally, the proposed conformal absorber fabricated and measured the absorption for flat and curved surfaces, which exhibits good agreement between the simulated and the experimental results.
Interface conductance modal analysis of a crystalline Si-amorphous SiO2 interface
Authors: Gordiz Kiarash , Muraleedharan Murali Gopal , Henry Asegun
Published: April 2019

We studied the modal contributions to heat conduction across an interface between crystalline Si and amorphous SiO2, using the interface conductance modal analysis (ICMA) method. Our results show that >70% of the thermal interface conductance (TIC) arises from the extended modes. Using ICMA, we could also determine the contribution of interfacial modes to the TIC. Interestingly, we observed that although the number of these modes is <5% of all modes, interfacial modes contribute significantly to the TIC (>15%). Such an observation shows the non-negligible role of localized modes in facilitating heat conduction across systems with interfaces between dissimilar materials, specifically in a system that is straightforward to fabricate and study experimentally. Our observations suggest that neglecting the contribution of localized modes would be an oversimplification of the actual mechanisms at play. Determining the individual mode contributions is therefore of vital importance, since these values are directly utilized in predicting the temperature dependent TIC, which is important to silicon on insulator technologies with a myriad of applications within microelectronics and optoelectronics.
Analysis of plastic strain-enhanced diffusivity in nanocrystalline iron by atomistic simulation
Authors: Mohammadzadeh Roghayeh
Published: April 2019

Plastic deformation may affect bulk diffusion in nanocrystalline materials by altering the rates of point defect production and annihilation. In the present work, a detailed analysis of this phenomenon is given by a series of molecular dynamics (MD) simulations to clarify the effect of preplastic strain on the diffusivity of iron atoms. The embedded atom method interatomic potential was used to perform MD simulations. The self-diffusion coefficient of iron atoms in unstrained and prestrained samples was measured over temperatures ranging from 600 to 1000 K and at total strains of 5%–20%. The results reveal that the diffusivity is indeed enhanced as a result of plastic straining, especially at low temperatures. The calculated diffusion coefficient of iron atoms in the prestrained samples is 10–80 times higher than that in the unstrained samples. The atomic structure analysis results indicated that the generation of excess vacancies and unstructured region by preplastic deformation contributes to the enhancement of self-diffusion under plastic straining conditions. At low temperatures, preplastic straining has a considerable effect in the peak shifting and broadening of the radial distribution function, which probably lowers the activation barrier height for diffusion.
Comparative study of catalyst-induced doping and metal incorporation in silicon nanowires
Authors: Šilhavík Martin , Müller Martin , Stuchlík Jiří , Stuchlíková Ha , Klementová Mariana , Kočka Jan , Fejfar Antonín , Červenka Jiří
Published: April 2019

Foreign atoms incorporated into the crystal structure of a semiconductor have profound effects on the electronic structure and charge transport in the material, particularly in nanoscale systems. Here, we demonstrate that catalyst-induced doping of silicon nanowires (SiNWs) can be used as an effective way for controlling dopant density and electrical conductivity in SiNWs, allowing the construction of p-n junctions. We investigate and compare metal incorporation and charge transport in SiNWs grown by six different metal catalysts (In, Sn, Bi, Ga, Pb, and Au) in plasma-enhanced chemical vapor deposition. The distribution of the catalytic metals within SiNWs was mapped by scanning transmission electron microscopy using high-angle annular dark-field imaging. The metals are either homogenously distributed or segregated in clusters on the surface or in the core of the nanowires, depending on the metal catalyst used. Each of the metal catalysts is found to play a unique role in the charge transport of SiNWs. Sn, Pb, and Au yield semiconducting SiNWs, Ga and In produce p-type self-doped SiNWs, and Bi catalyzes n-type self-doped SiNWs. A combination of these different nanowires may provide a bottom-up growth strategy for fabrication of different nanowire-based electronic components.
Fragmentation and slow autoneutralization of isolated negative molecular ions of phthalocyanine and tetraphenylporphyrin
Authors: Khatymov Rustem V. , Muftakhov Mars V. , Tuktarov Renat F. , Raitman Oleg A. , Shokurov Alexander V. , Pankratyev Evgeniy Yu.
Published: April 2019

Macrocyclic tetrapyrrolic compounds, such as naturally occurring or artificial porphyrins and phthalocyanines, have unique and highly attractive properties for applications in medicine and technology. The interaction of free-base phthalocyanine (H2Pc) and tetraphenylporphyrin (H2TPP) molecules with low-energy (0–15 eV) electrons was studied in vacuo by means of negative ion resonant electron capture mass spectrometry. Close similarities in formation and decay of negative ions of these compounds were revealed. Efficient formation of long-lived molecular negative ions (MNIs) was observed in the incident electron energy range of 0–8 eV, unprecedentedly wide for organic compounds and comparable to the range characteristic to carbon atomic clusters, fullerenes. Experiments testify to the strong persistence of MNIs of both compounds to dissociative decay, isomerization, and electron autodetachment. Lifetimes of MNIs as a function of incident electron energy were measured and it was concluded that the isolated anions may retain additional electrons in a time scale of up to hundreds of seconds at standard temperature due to the high adiabatic electron affinity of these large molecules. For the representatives of dyes and photochromic compounds comprehensively studied in terms of interaction with light, the present work highlights yet another unique property of these molecules, namely the capability to attach and durably retain an additional electron of low, pre-ionization energy.
Supercavitation phenomenon research of projectiles passing through density change area
Authors: Fan Chunyong , Li Zengliang , Khoo B. C. , Du Mingchao
Published: April 2019

The past research on the supercavity flow mostly focused on the homogeneous fluid medium, ignoring the influence of the sudden change of the medium density. We present results from numerical study of moving projectile passing density change zone, both from low-density zone to high-density zone and from high-density to low-density. Particular attention is given to the cavity variation when projectile voyaging through different liquid density areas. And the influence of the cavitation number on the cavity variation is also studied. Research results show that there is a ‘diameter shrinkage’ phenomenon when the projectile moving pass the density jump area. The location of ‘diameter shrinkage’ is relative to the density change model: moving from high density side to low, it appears at the interface of liquids; while moving from low density side to high side, it occurs at low density side not the interface. And the degree of ‘necking’ have something to do with the density difference of two sides. However the effect of cavitation number is much complex, the ‘necking’ phenomenon at the interface showed disorder maybe due to the sample limit, but the re-development of the cavity after passing through the interface showing obvious regularity with the cavitation number.
Pulsed-laser epitaxy of topological insulator Bi2Te3 thin films
Authors: Liao Zhaoliang , Brahlek Matthew , Ok Jong Mok , Nuckols Lauren , Sharma Yogesh , Lu Qiyang , Zhang Yanwen , Lee Ho Nyung
Published: April 2019

Determining optimized conditions necessary to achieve high-quality films by pulsed laser deposition (PLD) for materials with multiple volatile elements is challenging. In this work, we present the optimized growth of epitaxial films of the topological insulator Bi2Te3 on Al2O3 (0001) substrates using PLD. It is found that the key to maximize film quality requires balanced control of the Ar background pressure (PAr) and growth temperature (TG). Within a narrow window (200 ≤ PAr < 350 mTorr and 300 ≤ TG < 350 °C), we find that Bi2Te3 thin films are flat, stoichiometric, and of the highest crystalline quality. This is a result of balancing the kinetics of ablated species in the PLD plume and the bulk thermodynamics of Bi2Te3. This work demonstrates that a careful optimization of the growth parameters can enable PLD to successfully grow multielemental materials containing volatile constituents.
A machine learning approach for automated fine-tuning of semiconductor spin qubits
Authors: Teske Julian D. , Humpohl Simon Sebastian , Otten René , Bethke Patrick , Cerfontaine Pascal , Dedden Jonas , Ludwig Arne , Wieck Andreas D. , Bluhm Hendrik
Published: April 2019

While spin qubits based on gate-defined quantum dots have demonstrated very favorable properties for quantum computing, one remaining hurdle is the need to tune each of them into a good operating regime by adjusting the voltages applied to electrostatic gates. The automation of these tuning procedures is a necessary requirement for the operation of a quantum processor based on gate-defined quantum dots, which is yet to be fully addressed. We present an algorithm for the automated fine-tuning of quantum dots and demonstrate its performance on a semiconductor singlet-triplet qubit in GaAs. The algorithm employs a Kalman filter based on Bayesian statistics to estimate the gradients of the target parameters as a function of gate voltages, thus learning the system response. The algorithm's design is focused on the reduction of the number of required measurements. We experimentally demonstrate the ability to change the operation regime of the qubit within 3–5 iterations, corresponding to 10–15 min of lab-time.
Swarm intelligence inspired cooperation promotion and symmetry breaking in interdependent networked game
Authors: Liu Yishun , Yang Chunhua , Huang Keke , Wang Zhen
Published: April 2019

The evolution of a cooperative strategy on multilayer networks is arousing increasing concern. Most of the previous studies assumed that agents can only choose cooperation or defection when interacting with their partners, whereas the actual provisions in real world scenarios might not be discrete, but rather continuous. Furthermore, in evolutionary game, agents often make use of their memory which keeps the most successful strategy in the past, as well as the best current strategy gained by their directed neighbors, to find the best available strategies. Inspired by these observations, we study the impact of the particle swarm optimization (PSO) algorithm on the evolution of cooperation on interdependent networks in the continuous version of spatial prisoner’s dilemma games. Following extensive simulations of this setup, we can observe that the introduction of the PSO mechanism on the interdependent networks can promote cooperation strongly, regardless of the network coupling strength. In addition, we find that the increment of coupling strength is more suitable for the propagation of cooperation. More interestingly, we find that when the coupling strength is relatively large, a spontaneous symmetry breaking phenomenon of cooperation occurs between the interdependent networks. To interpret the symmetry breaking phenomenon, we investigate the asynchronous expansion of heterogeneous strategy couples between different networks. Since this work takes cooperation from a more elaborate perspective, we believe that it may provide a deep understanding of the evolution of cooperation in social networks.
Radiative lifetime of boron-bound excitons in diamond
Authors: Kubo Yoshiki , Temgoua Solange , Issaoui Riadh , Barjon Julien , Naka Nobuko
Published: April 2019

We report the ultraviolet absorption of boron-bound excitons at low temperature in a single crystal of diamond grown by chemical vapor deposition. The no-phonon (NP) and phonon-assisted lines are identified by comparison with cathodoluminescence. The oscillator strength of the NP lines was found to be 3.0 × 10−5 based on the measured absorption cross-section. This value is discussed in terms of the scaling law known for doped silicon, where the oscillator strength varies proportionally to Eloc2.5, with Eloc being the localization energy of excitons on acceptors. More importantly, we also could assess the oscillator strength of the dominant transverse optical phonon-assisted transition, which is found to be equal to 1.2×10−3. The associated radiative lifetime for the boron-bound exciton is 1.8 μs, which is much longer than the non-radiative Auger lifetime that governs its decay.
New fine structure of red luminescence in ZnO observed under exciton resonance excitation
Authors: Zhou N. , Hu B. C. , Zhang Q. Y. , Ma C. Y. , Hao S. Z.
Published: April 2019

A new fine structure of red luminescence (RL) was observed in unintentionally doped ZnO at low temperature. The new RL was demonstrated to be different from the one assigned to Fe3+ center by Heitz et al and visible only under the excitation of light capable of generating excitons. The RL can be extremely enhanced at the incident frequency in resonance with the donor exciton and the intensities of some adjacent lines separated by ∼4 meV are thermally populated with the increase in temperature. The new structured RL was studied in the terms of photoluminescence (PL) and PL excitation spectra and the origin was discussed taking into account the internal transitions of transition metal elements, structure defects, and native point defects. There is a great possibility that the new structured RL arises from the excited states converted from bound excitons, for example, the excitons or the electron and hole pairs bounded by the donor and acceptor pairs (DAPs) of O and Zn vacancies, because the binding energy determined by the equation of DAP fluorescence is highly in accordance with the theoretic values reported in the literature.
Investigating the complex interaction between polymer brush grafted surface in the approach-sliding using atomic modeling method
Authors: Han Xuesong
Published: April 2019

Polymer brush has already been widely used to modify the surface property while there is little research about the interaction between polymer-bearing surfaces at atomic scale. The complex multibody interaction among atoms makes it difficult to characterize the microscopic dynamic process using continuum mechanics. Molecular dynamics method has already been justified to be an efficient theoretical toolkit for investigating the complex dynamic behavior at atomic scale. Friction interface modified by polymer brush in confined space and the corresponding effect are investigated using parallel molecular dynamics simulation method. It is shown that some chains stretch along the direction of flow while others shrink inside the brush resulted by the normal compression. The normal force quickly increases when two end-grafted surfaces are brought into contact while the shear force keeps smaller under the same circumstances. The friction coefficient between polymer brush grafted surfaces is gradually decreased with the increasing of sliding speed which means polymer brush can dramatically improve working conditions. The components of the chains prefer to repel each other as much as possible and weaken interactions among them by stretching away and thus reducing the entropy of the chain.
A study on the reversibility of electric response induced by second sound in superfluid helium
Authors: van Woensel Jean-Paul , Yayama Hideki
Published: April 2019

The reversibility of the electric response induced by second sound in helium II, the so-called “reverse effect”, was examined. Two different cylindrical cavities were used to provide a different direction of the electric field and to check the significance of the interruption of longitudinal flow from the copper mesh electrode. The ability to reproduce the normal electric response induced by second sound was verified and compared with a previously performed experiment. No indications of the reverse effect were found. The results show that the reverse effect was absent or within a lower limit of the measurement in the order of nano-volts regardless of temperature.
Critical temperature of the superconducting transition of individual phases of multiphase bismuth cuprates after cooling in a magnetic field to a temperature of 77 K
Authors: Chigvinadze J. G. , Ashimov S. M. , Acrivos J. V. , Gulamova D. D.
Published: April 2019

Using a highly sensitive torsional vibration technique, the authors have determined the critical temperatures of the superconducting transition (Tc) of individual phases of multiphase cuprates [Bi1.7Pb0.3Sr2Ca(n-1)CunOy (n = 2–30)] in a constant external magnetic field (H) in the temperature range of 77 to 270 K. It has been found that oscillation damping peaks are more pronounced when a sample is rapidly cooled in an external magnetic field (FC) to a temperature of 77 K and then is slowly warmed to room temperature. An increase in the time of sample exposure to a magnetic field at 77 K leads to a rise in the temperature Tc of different phases, and to an increase in the intensity of a signal corresponding to high-temperature phases with Tc > 240 K. Structural studies have shown that with increasing sample exposure time at 77 K, as a result of sample compression an increase in stress concentration at grain boundaries appears to increase defect density and to enhance the pinning of Abrikosov vortices, i.e. creates new (additional) conditions for their “freezing” during the field cooling (FC) procedure. It has been established that in samples of the Bi1.7Pb0.3Sr2Ca(n-1)CunOy (n = 2–30) series, the critical temperature Tc increases from 107 K to ≥ 240 K with an increase in n.
Punishing and toxic neighborhood environments independently predict the intergenerational social mobility of black and white children
Authors: Manduca Robert , Sampson Robert J.
Published: April 2019

Significance

Growing up in neighborhoods with concentrated violence, incarceration, and lead exposure predicts lower intergenerational income mobility and higher adult incarceration of poor black males, after accounting for commonly studied factors such as concentrated poverty and racial composition. Similar patterns emerge for the income mobility of poor white children and teenage birth among both poor black and poor white girls. In Chicago, harsh environments are also racially segregated, with little overlap in exposure rates for blacks and whites: virtually all majority black Census tracts are more exposed to hazards than any majority white tracts. This large difference in exposure rates plausibly accounts for a substantial portion of racial disparities in intergenerational inequality (20–60%).