bluuebunny/crossref_metadata_2025 huggingface dataset:
Using power-consuming materials for volume damping of thin-walled structural elements
Authors: Mironov Vladimir , Ogorelkov Dmitriy , Lukashuk Olga
Published: November 2019

Using low-modulus foam materials of lower density leads to significantly higher protection of personnel (from noise and harmful vibrations) and structures (from corrosion), while only slightly increasing the weight of an object. But the main intended purpose of such a filler which is capable of actively absorbing the energy of vibrations caused by external dynamic forces is to reduce their number and amplitude. To achieve a similar effect, the building industry and aircraft construction have a long and successful history of utilizing three-layer plates and shells coated with a thin foam material. Theoretical studies, supported by experiments, make one come to the conclusion that volume damping of such elements has quite a low efficiency. The goal of the research was to preliminarily estimate how appropriate it is to use artificial low-modulus elastic materials to damp thin-walled elements of metal structures. It was achieved by running computational experiments in Solid Works software environment and plotting, on the basis of the experiments, vibrograms of damped vibrations of a cantilever beam. The results obtained during the testing showed that the volume damping using a foam material could be an efficient tool for damping free vibrations of a metal structure affected by bending.
Improvement of road traffic management system on the basis of mathematical and simulation modeling
Authors: Lomakin Denis , Bodrov Andrei , Kulev Maksim , Kulev Andrei
Published: November 2019

A mathematical model of the “Driver-Vehicle-Road-Environment” system is substantiated in the form of a multidimensional random process with a large number of components based on a structural approach which is a basic algorithm for subsequent modeling of traffic flows on a road network.
Construction of a specialized control system for brush machine and rounding the cutting edges of a metal cutting tool
Authors: Nikishechkin Petr , Grigoriev Nikita , Chervonnova Nadezhda
Published: November 2019

The basic aspects of preparing a cutting tool for applying wear-resistant coatings to it, in particular, the use of brush technology to round its cutting edges, are investigated. A structural model for constructing a specialized brush machine control system has been developed and the basic aspects of its development have been determined.
Formation of Cr-Zr gradient layer by magnetron sputtering and ion mixing
Authors: Kashkarov Egor B. , Sidelev Dmitrii V. , Rombaeva Maya R. , Kudiiarov Viktor N. , Lomygin Anton
Published: November 2019

The gradient Cr-Zr layer was formed onto Zr-1Nb substrate by magnetron sputtering of chromium and zirconium targets and ion mixing (Ar+ with 25 keV). The distribution of Cr and Zr elements in the deposited coatings was measured by using a glow discharge optical emission spectroscopy. The optimal ion fluence onto the substrate was 8×1019 ion/m2. At higher ion dose, the intensive sputtering of the deposited coating was observed.
Thermal stability of the carbon fibers with SiO2coating
Authors: Gallyamova Rida , Galyshev Sergei , Musin Fanil , Dokichev Vladimir
Published: November 2019

This paper presents the results of a study of silicon dioxide coating deposited on the surface of carbon fiber by the sol-gel method. The effect of the viscosity of the prepared sol-gel solution and the oxidizing properties at elevated temperatures obtained by SiO2coatings were studied. It was found that the kinematic viscosity of the sol-gel solution does not change for 72 hours. An increase in viscosity leads to the formation of colloidal particles, which degrades the quality of the coatings.Studies have shown that in the temperature range 600-800 °C, the quality of uncoated fibers degrade, but the SiO2coating well protects the fiber surface and significantly slows down the rate of destruction.
The cleaning process model of diesel fuel in an electric field
Authors: Abramov Alexander , Morozov Alexander , Koshkina Anastasia , Petryakov Sergey , Nuretdinova Julia
Published: November 2019

The authors of the article carried out the analysis of the failure causes of diesel engine types 4Ч 110/125 and 4ЧН 110/125. As a result of this analysis it was found that the highest percentage of failures occurred in the high-pressure fuel pump and nozzle. The procedure of the electric cleaning process of diesel fuel in an electric field is also considered in the article. A mathematical model of the electric cleaning process of diesel fuel in an electric field has been obtained and the boundaries of the initial parameters of the electric field have been determined.
Loads of road vehicles during piggyback transportation
Authors: Tsyganov Aleksandr
Published: November 2019

The impact of rail transportation on road vehicles that are placed in flatcars is considered in the article. The features of piggyback transportation and the dynamic forces acting on road vehicles in railway rolling stock are determined. The change dependences of the values of dynamic forces for different masses of road vehicles in the longitudinal and transverse directions are established. It is concluded that road vehicles that are used in regular piggyback transportation will experience significant dynamic loads of structural elements, which requires monitoring of their technical condition. Consequently, the infrastructure of piggyback terminals that load and unload road vehicles onto railway rolling stock should include the availability of automobile service facilities.
Development of a method for the determination and registration of unauthorized data transmission channels at industrial manufactories
Authors: Kovalev Ilya , Babin Michael , Nikishechkin Petr
Published: November 2019

The problem of industrial espionage is very common in the modern world. Existing complex systems are difficult to configure and turnkey solutions are created from integrator firms. In many enterprises, both industrial and civilian, wireless is a less secure area. The proposed solution, which is used as an addition to existing security systems, is able to detect not only created networks with the usual parameters, but also detect hidden data networks and signal unregistered wireless data networks to send information to a special server. The paper presents the architecture of the hardware-software complex, presents the first prototype and conducts test tests.
The providing durability of the movable square-sided spline joints by electromechanical treatment of the working surfaces
Authors: Morozov Alexander , Fedotov Gennady , Fedorova Lilia , Musharapov Damir , Khabieva Lilia
Published: November 2019

The article deals with the operating conditions and causes of loss of performance of movable involute splines joints. In order to ensure the durability of the movable involute splines joints, an effective method of hardening the working surfaces of the splined hub by electromechanical treatment is proposed. The influence of the current on the change of microstructure and microhardness in the electromechanical processing of the working surfaces of the spline bushing was determined. The obtained results of the comparative wear testing of samples involute splines joints depending on the time of testing. It is established that the use of electromechanical processing of the working surfaces of involute splines joints allows reducing the time of their running-in and increasing the wear resistance of the movable joints up to 2 ... 2.5 times.
Phosphate coatings as a way to protect steel reinforcement from corrosion
Authors: Fedosov Sergey , Roumyantseva Varvara , Konovalova Viktoriya
Published: November 2019

Phosphate coatings are successfully applied as a method of protecting steel products and structures from corrosion. Phosphate coatings mechanically prevent the entry of aggressive particles, such as chloride ions, to the surface of steel reinforcement. The parameters of corrosion rate of reinforcing steel in aggressive environment are determined by graphical method. The analysis of corrosion diagrams allows us to judge the effect of protective phosphate coatings on the kinetics of the corrosion process of steel reinforcement in environments of varying degrees of aggressiveness. The tests of the protective properties of phosphate coatings by contact corrosion method show that films with a finer crystal structure, as in modified phosphate coatings, are more resistant to anodic dissolution of steel. In parallel to determination of iron ions content in solutions the potential of steel reinforcement samples was measured. In samples protected by phosphate films, the potential change is not as sharp as in samples without coating, and the “dilution” of steel is slower. The study of anodic behavior of steel reinforcement of reinforced concrete, experimental study of the mass transfer mechanism of electrolyte supply to the surface of reinforced steel allow to develop practical recommendations to improve corrosion resistance and ensure the durability of reinforced concrete building materials.
Modeling of the high-strength clinker-free binder structure
Authors: Petropavlovskaya Victoria , Novichenkova Tatiana , Petropavlovskii Kirill , Buryanov Аleksandr
Published: November 2019

Modern approaches in materials science should provide a solution to the problems of energy and resource conservation. They are also called upon to develop a line of directed synthesis of composites that possess the required parameters over the entire spectrum of properties. In order to obtain a high-strength structure of a clinker-free binder, the possibility of obtaining it on the basis of natural gypsum stone is considered. As is known, the strength of crystallization structures by adhesion in contact and the number of contacts is determined. To optimize the internal structure of a high-strength clinker-free binder, to obtain the maximum number of contacts and increase their strength, the possibilities of geometric topological approaches were used. When solving such problems, the geometric parameters and organization levels of the structures of disperse systems allow topology to be described. The fundamental possibility of obtaining a high-strength composite structure through the prism of the formation of a dispersed system with a maximum number of phase contacts between crystals of calcium sulfate dihydrate is considered. The granulometric composition of gypsum stone must meet the requirements (principles) of hardening, physical-chemical model and type of structure. Therefore, in the work, the possibility of obtaining high binder strength by optimizing it in accordance with the model was studied. mixtures of two powders with different average particle sizes were used. This increases efficiency and improves the properties of the binder.
Experimental research method when developing a mathematical model for calculating cutting speed in the course of turning steels with a coated tool
Authors: Tikhonova Zhanna , Frolov Evgeniy , Krainev Dmitriy , Plotnikov Alexander
Published: November 2019

The article is devoted to the description of the experimental research method when developing a mathematical model for calculating the cutting speed based on information from the cutting zone obtained during the test run in the process of turning using steel coated tools as an example. This paper also presents the results of an experimental study which prove the effectiveness of applying the obtained mathematical dependence.
Simulation and research of cylindrical broach structures stress-strain state in solidworks system
Authors: Lukina Svetlana , Yakovleva Anna , Zimovets Olga
Published: November 2019

The authors considered a methodology for the automated design of cylindrical broach structures consisting of the following stages: forming a 3D-parametric geometrical broach image, assessing a broach structure stress-strain state during operation. The paper presents the results of software implementation of the algorithm for forming a broach structure parametric model from 3D-geometrical prototypes in the system Solidworks. To assess a stress-strain state of tools with the numerical method of finite elements in Solidworks Simulation, the authors formed an analytical design model taking into account strain of geometric prototypes. A series of numerical experiments was aimed at researching a stress-strain state of broach teeth under cutting forces action. According to the results of numerical experiments, by means of the least square method the authors obtained analytical expressions to estimate the influence of geometrical and design parameters of the broach teeth structure on elastic displacements of cutting edges vertice and equivalent stresses of the most loaded teeth components. The authors developed recommendations on the change of the teeth section parameters allowing for the extension of the broach structure operation life and reducing the tool life consumption for the batch of parts.
Electro-slag heating of parts surfaces by welding of protective coatings by the method of immersion
Authors: Fedyaev Vladimir , Osipov Petr , Belyaev Alexey , Sirotkina Liliya
Published: November 2019

One of the effective methods of surfacing protective coatings on large areas, as well as the formation of permanent joints is the method of immersion (dipping) of parts into the melt. In order to increase the productivity of this method, the quality of surfacing is proposed to heat the work surfaces of the parts with an electroslag method. The rational regimes for its realization are determined by calculation. A mathematical model is proposed for heating the contacting layers of a solid body, slag and melt, taking into account the Joule heat released during the passage of an electric current. The corresponding problem is solved numerically with the help of the method of finite differences. The results are discussed, practical recommendations are presented.
Sialolithiasis: aktuelle Diagnostik und Therapie
Authors: Wolf Gregor , Langer Christine , Wittekindt Claus
Published: November 2019

Die Sialolithiasis als eine der häufigsten Speicheldrüsenerkrankungen betrifft die Glandula submandibularis im Vergleich zur Glandula parotis deutlich häufiger. Im Verlauf der Erkrankung kommt es in vielen Fällen zu rezidivierenden Sialadenitiden. Durch verbesserte Diagnostik besteht neben der Submandibulektomie auch die Möglichkeit einer drüsenerhaltenden Therapie, z. B. mittels Miniaturendoskopie (Sialendoskopie).
Tonsillektomie bei Erwachsenen medizinisch und ökonomisch sinnvoll
Authors: Sesterhenn Andreas
Published: November 2019

Tzelnick S et al. Long-Term Outcomes of Tonsillectomy for Recurrent Tonsillitis in Adults. Laryngoscope 2019; 9999: 1–4. doi:10.1002/lary.27928

Ein Cochrane Review von 2014 beantwortete die Frage nach der Effektivität von Tonsillektomien bei Erwachsenen nicht abschließend, sprach aber für einen positiven Einfluss auf die Lebensqualität. Die retrospektive Studie aus Israel belegt nun eine deutliche Reduktion der Tonsillitis-Episoden und der Gesundheitskosten.
Empfehlungen zur Früherkennung, Risikoreduktion, Überwachung und Therapie bei Patienten mit Lynch-Syndrom
Authors: Hüneburg Robert , Aretz Stefan , Büttner Reinhard , Daum Severin , Engel Christoph , Fechner Guido , Habermann Jens K. , Heling Dominik , Hoffmann Katrin , Holinski-Feder Elke , Kloor Matthias , von Knebel-Döberitz Magnus , Loeffler Markus , Möslein Gabriela , Perne Claudia , Redler Silke , Rieß Olaf , Schmiegel Wolff , Seufferlein Thomas , Siebers-Renelt Ulrike , Steinke-Lange Verena , Tecklenburg Johanna , Vangala Deepak , Vilz Tim , Weitz Jürgen , Wiedenmann Bertram , Strassburg Christian P , Nattermann Jacob
Published: November 2019

Einleitung Das Lynch-Syndrom (LS) ist die häufigste Form des erblichen Darmkrebses und verursacht ca. 3 % aller kolorektalen Karzinome (KRK). Ursächlich ist eine pathogene Sequenzvariante in einem Mismatch-Reparaturgen (MLH1, MSH2, MSH6, PMS2, EPCAM). Nach aktueller Schätzung ist ca. eine von 300 Personen Anlageträger für LS (ca. 300 000 Mutationsträger/Deutschland). Anlageträger haben ein erhöhtes Lebenszeitrisiko für ein KRK mit einer kumulativen Inzidenz von 15 bis 46 % bis zum 75. Lebensjahr. Weiterhin ist auch das Risiko für extrakolonische Tumoren wie Endometrium-, Dünndarm-, Magen-, Urothel- und andere Karzinome erhöht.

Methoden Das Deutsche Konsortium Familiärer Darmkrebs besteht aus 14 universitären Zentren in Deutschland. Das Ziel des Konsortiums ist es, geeignete Vorsorgeprogramme zu entwickeln und zu evaluieren, damit diese später in die allgemeine Patientenversorgung übernommen werden können. Wir haben aktuell die Empfehlung zur klinischen Betreuung von LS-Patienten überarbeitet.

Ergebnis Eine Koloskopie sollte ab dem 25. Lebensjahr alle 12–24 Monate erfolgen. Bei Diagnose eines KRK ist eine onkologische Resektion notwendig, eine Kolektomie mit ileorektaler Anastomose sollte individuell mit dem Patienten besprochen werden. Das Lebenszeitrisiko für ein Magenkarzinom liegt bei 0,2–13 %. Im Rahmen der endoskopischen Überwachung können signifikant mehr Magenkarzinome in früheren Tumorstadien entdeckt werden im Vergleich zur symptomgetriggerten Endoskopie. Das Lebenszeitrisiko für ein Dünndarmkarzinom liegt bei 4–8 %. Dünndarmkarzinome treten zur Hälfte im Duodenum auf, in 10 % der Fälle vor dem 35. Lebensjahr. Eine ÖGD sollte deshalb ab dem 25. Lebensjahr alle 12–36 Monate erfolgen.

Schlussfolgerung Die Früherkennung, Vorsorge und Behandlung von kolonischen und extrakolonischen Karzinomen bei Patienten mit LS reduziert die Mortalität und Morbidität, ist aber komplex und in verschiedenen Aspekten noch nicht umfassend evaluiert. Weitere gen- und geschlechtsspezifische Vorsorgeempfehlungen sind wünschenswert und sollen in prospektiven Studien evaluiert werden.
Akzeptanz des therapeutischen fäkalen Mikrobiomtransfers bei Patienten mit chronisch entzündlichen Darmerkrankungen: Ergebnisse einer fragebogenbasierten Erhebung an einer universitären Spezialambulanz
Authors: Schulte Lucas-Alexander , Schäfer Annika , Steding Katja , Rauschek Lena , Klaus Jochen
Published: November 2019

Zusammenfasung

Gestützt von einer wachsenden Fülle an klinischen Daten, gerät der fäkale Mikrobiomtransfer (FMT) zunehmend in den therapeutischen Fokus bei chronisch entzündlichen Darmerkrankungen. Die Bewertung dieses therapeutischen Ansatzes ist in vielerlei Hinsicht ambivalent, da die klinische Evidenz teils widersprüchlich ist und Wirkung sowie Nebenwirkung dieser bisher nicht völlig zu standardisierenden Therapie unsicher sind. Hinzu kommt die fragliche Akzeptanz des Verfahrens bei den Patienten. Wir führten eine fragebogenbasierte Umfrage an 302 Patienten mit Colitis ulcerosa oder Morbus Crohn an unserer spezialisierten Hochschulambulanz für chronisch entzündliche Darmerkrankungen durch, um abzuschätzen, wie hoch die Akzeptanz des fäkalen Mikrobiomtransfers bei diesen Patienten ist und welche Faktoren für eine eventuell ablehnende Haltung relevant sind. Unsere Ergebnisse weisen darauf hin, dass die Akzeptanz der FMT mit dem Informationsgrad des Patienten zusammenhängen könnte (68 % Befürworter bei Vorkenntnis des Verfahrens vs. 30 % bei Unkenntnis, p < 0,001), was einen Ansatzpunkt für eine ärztliche Intervention böte. Die als am wichtigsten eingestuften Bedenken gegen eine FMT waren Sorgen vor einer Infektionsübertragung (Rang 1: 98 Stimmen). Die Methode, die die höchste Akzeptanz bei den Befragten erreichte, war die Gabe als orale Kapsel (44 % der Befragten).
Frequency and clinical presentation of alveolar and cystic echinococcosis in a tertiary medical center in Germany 2004–2018: lessons from a low-prevalence area
Authors: Karlas Thomas , Reinhardt Fabian , Blank Valentin , Lippmann Norman , Seehofer Daniel , Lübbert Christoph
Published: November 2019

Introduction The prevalence of alveolar echinococcosis (AE) and cystic echinococcosis (CE) in Germany is increasing. The number of cases in northern and eastern regions is low, so there is little experience with regard to diagnosis and therapy.

Objectives The objective of this paper was to evaluate the management of suspected and/or diagnosed echinococcosis at a university center in a low-prevalence region.

Methods All the patients at the Leipzig University Hospital between 2004 and 2018 who had been serologically examined for echinococci were included in a retrospective cohort study. Clinical course, imaging, histology, therapeutic characteristics, relevant comorbidities and risk factors for AE and CE were evaluated. A time-staggered prevalence estimation, as well as sensitivity and specificity calculations for the serological tests, were performed.

Results A total of 382 patients were enrolled, with 11 AE and 7 CE cases identified. The mean prevalence rate of AE in this cohort was 2.9 % and that of CE was 1.8 %. Among the patients, 56 % had known risk factors for AE and CE. The serological tests showed a sensitivity of 86 % and a specificity of 91 %. Two patients with false-negative serology were diagnosed by biopsy. All CE and 5 AE patients (45 %) were operated on. Six AE patients received long-term treatment with albendazole.

Conclusions AE and CE are rare diseases in the greater Leipzig region; however, case numbers are on the rise. Due to favorable factors such as the escalation of migration, a further increase is expected. Diagnosis and therapy are challenging and should be supported by specialists (experienced infectiologists, imaging experts and skilled hepatobiliary surgeons) who should be integrated in a German network.
Novel Neonatal Umbilical Catheter Protection and Stabilization Device in In vitro Model of Catheterized Human Umbilical Cords: Effect of Material and Venting on Bacterial Colonization
Authors: Wood Lauren S. Y. , Fuerch Janene H. , Dambkowski Carl L. , Chehab Eric F. , Torres Shivani , Shih Joseph D. , Venook Ross , Wall James K.
Published: November 2019

Objective Umbilical central lines deliver life-saving medications and nutrition for neonates; however, complications associated with umbilical catheters (UCs) occur more frequently than in adults with central lines (i.e., line migration, systemic infection). We have developed a device for neonatal UC protection and stabilization to reduce catheter exposure to bacteria compared with the standard of care: “goal post” tape configuration. This study analyzes the effect of device venting and material on bacterial load of human umbilical cords in vitro.

Study Design Catheters were inserted into human umbilical cord segments in vitro, secured with plastic or silicone vented prototype versus tape, and levels of bacterial colonization were compared between groups after 7 days of incubation.

Results Nonvented plastic prototype showed increased bacterial load compared with goal post (p = 0.04). Colonization was comparable between the goal post and all vented plastic prototypes (p ≥ 0.30) and when compared with the vented silicone device (p = 1).

Conclusion A novel silicone device does not increase external bacterial colonization compared with the current standard of care for line securement, and may provide a safe, convenient alternative to standard adhesive tape for UC stabilization. Future studies are anticipated to establish safety in vivo, alongside benefits such as migration and infection reduction.
G6PD Deficiency Prevalence as a Cause of Neonatal Jaundice in a Neonatal Ward in Dohuk, Iraq
Authors: Eissa Adil Abozaid , Haji Bijar Ali , Al-Doski Adnan Anwar
Published: November 2019

Objective The current study initiated to address the effect of glucose-6-phosphate dehydrogenase (G6PD) deficiency on the pathogenesis and the severity of neonatal hyperbilirubinemia (NHB).

Study Design A total of 100 newborns with moderate to severe indirect hyperbilirubinemia and 50 normal neonates without hyperbilirubinemia had been enrolled in the current case–control study. All enrolled neonates had been tested for ABO and Rh(D) blood grouping, Total serum bilirubin measurement, complete blood count, morphology, reticulocyte counts, direct Coombs' test, and G6PD enzyme assay.

Results From all enrolled hyperbilirubinemic neonates, 16% were G6PD deficient and this displays a statistically significant difference in comparison to controls (only 6% were G6PD deficient). Also, significant difference was found in the level of serum indirect bilirubin among G6PD-deficient neonate in comparison to G6PD nondeficient neonates which had contributed significantly to the difference in the duration of phototherapy and hospitalization among deficient neonate. Despite this, no significant difference found in the onset of presentation, reticulocytes count, and age of neonates between the two groups (G6PD-deficient and G6PD nondeficient neonates).

Conclusion The current study augments the etiological role of G6PD in the causation and severity of NHB in the region; however, in the absence of significant difference in the reticulocytes and the hemoglobin level, the underlying mechanism cannot be backed to the excess hemolysis alone.
Low Fetal Fraction and Birth Weight in Women with Negative First-Trimester Cell-Free DNA Screening
Authors: Clapp Mark A. , Berry Margaret , Shook Lydia L. , Roberts Penelope S. , Goldfarb Ilona T. , Bernstein Sarah N.
Published: November 2019

Objective To determine the association between low fetal fraction and birth weight among women with a negative cell-free DNA (cfDNA) result for common aneuploidies in the first trimester.

Study Design This is a retrospective cohort of women who delivered a singleton between July 2016 and June 2018 at a single institution and had normal cfDNA testing in the first trimester. The primary variable of interest was “low fetal fraction,” which was defined as fetal fractions less than 5th percentile among all fetal fractions in the cohort (fetal fraction < 5.34%). The primary outcomes were birth weight ≤ 5th and ≤ 10th percentiles. Multivariable logistic regressions assessed for the association between low fetal fraction and birth weight.

Results A total of 7,478 women delivered a singleton at ≥24 weeks' gestation, of which 2,387 (32%) underwent genetic screening through cfDNA; the majority were in the first trimester (n = 2,052 [86%]). 2,035 met the inclusion criteria. Birth weight ≤ 5th percentile was significantly higher in the low fetal fraction group (6.9 vs. 3.2%; p = 0.04). A low fetal fraction was associated with higher odds of an infant with a low birth weight: adjusted odds ratio (aOR) of 2.32 (95% CI 1.15–4.67) for birth weight ≤ 10th percentile (p = 0.02) and aOR of 3.73 (95% CI 1.40–9.03) for birth weight ≤ 5th percentile (p = 0.004).

Conclusion Low fetal fractions of ≤ 5th percentile were associated with an increased risk of birth weights ≤ 5th and ≤ 10th percentiles in women with negative cfDNA screening in the first trimester. Future work is needed to further investigate this relationship and to determine the potential clinical implications, such as third-trimester screening for growth restriction in women with low fetal fractions and negative cfDNA screening results.
Enhanced upper critical field in Co-doped Ba122 superconductors by lattice defect tuning
Authors: Tokuta Shinnosuke , Yamamoto Akiyasu
Published: November 2019

Nanoscale defects in superconductors play a dominant role in enhancing superconducting properties through electron scattering, modulation of coherence length, and correlation with quantized magnetic flux. For iron-based superconductors (IBSCs) that are expected to be employed in high-field magnetic applications, a fundamental question is whether such defects develop an upper critical field (Hc2) similar to that of conventional BCS-type superconductors. Herein, we report the first demonstration of a significantly improved Hc2 in a 122-phase IBSC by introducing defects through high-energy milling. Co-doped Ba122 polycrystalline bulk samples [Ba(Fe, Co)2As2] were prepared by sintering powder which was partially mechanically alloyed through high-energy milling. A remarkable increase in the full-width at half maximum of X-ray powder diffraction peaks, anomalous shrinkage in the a-axis, and elongation in the c-axis were observed. When lattice defects are introduced into the grains, the semiconductor behavior of the electric resistivity at a low temperature (T < 100 K), a slight decrease in transition temperature (Tc), an upturn of Hc2(T) near Tc, and a large increase in the Hc2(T) slope were observed. The slope of Hc2(T) increased approximately by 50%, i.e., from 4 to 6 T/K, and exceeded that of single crystals and thin films. Defect engineering through high-energy milling is expected to facilitate new methods for the designing and tuning of Hc2 in 122-phase IBSCs.
Energy storage properties of polyimide/BaTiO3 nanocomposite films and their breakdown mechanism in a wide content range
Authors: Ru Jiasheng , Min Daomin , Lanagan Michael , Li Shengtao , Chen George
Published: November 2019

Polyimide (PI) has excellent dielectric properties with superior thermal stability, and it is considered as a promising polymer dielectric for energy storage capacitors. Here, we studied the energy storage properties of PI composite films with BaTiO3 (BT) nanoparticles in a wide content range. Benefiting from the high breakdown strength (520 kV/mm), the nanocomposite filled with 0.05 wt. % of BT exhibits an increased energy density of 4.51 J/cm3 at room temperature and keeps a good thermal stability (3.22 J/cm3 at 100 °C). Additionally, trap properties of the nanocomposites and their effect on breakdown strength were studied by thermally stimulated depolarization current. It was found that the dominant trap parameter on breakdown strength variation, with the increase in the BT content, is correlated with deep traps, deep and shallow traps especially their depths, and shallow trap density. Then, a physical quantity of average trap depth was introduced, the value of which decreases from 0.81 eV to 0.44 eV as the BT content increases to 50 wt. %, and a clear correspondence was discovered between the average trap depth and breakdown strength.
Radial variation of electron temperature gradient in a double plasma laboratory device
Authors: Alex Prince , Sanyasi A. K. , Srivastav Prabhakar , Srivastava P. K. , Sugandhi R. , Awasthi L. M.
Published: November 2019

Radial control of the electron temperature gradient is demonstrated in a double plasma device by making use of segmented grid biasing. The plasma produced in the source region is allowed to diffuse into the target region through a single grid as well as through the cassette of multiple grid assembly, under different grid bias conditions. Both electron heating and cooling are observed radially at one location in the target region when a single grid is used. The electrons are cooled down to a temperature of 3.3 eV from 5.1 eV when the grid bias is raised from −25 to 0 V. Similarly, during heating, the electron temperature increases from 4.8 to 7.3 eV when the grid bias is varied between 0 and +20 V. Two different transparencies of grids, 45% transparency (mess-size, m = 0.8 mm ∼ λDe) and 75% transparency (mess-size, m = 2.4 mm > λDe), are used, where the value of λDe ≈ 0.8 mm. The obtained electron energy distribution function suggests that a grid with less transparency is more effective in cooling the electrons because of insignificant energetic electron–neutral collisions in the target region as a sheath in the close vicinity of grid allows only the high energetic electrons to pass through it. The higher transparent grid, on the other hand, produces electron heating as it exerts a negligible influence on the free flow of accelerated high energy electrons to target plasma due to insignificant thermalization. We expanded this concept and, for novelty, applied it to a radially segmented grid assembly of electrically isolated grids, for effectively charging different plasma regions with differently various potentials for exerting a radial control on electron temperature. The results obtained show that a significantly sharp electron temperature gradient is obtained with a typical gradient scale length of LTe∼10 cm in the target plasma region. The outcome of this study may be useful both in plasma processing applications and for studying plasma turbulence in unmagnetized plasmas.
On a center-of-mass system of coordinates for symmetric classical and quantum many-body problems
Authors: Amorim Érik
Published: November 2019

In the context of classical or quantum many-body problems involving identical bodies, a linear change of coordinates can be constructed with the properties that it includes the center-of-mass as one of the new coordinates and preserves the inherent permutation symmetry of both the Hamiltonian and the admissible states. This has advantages over the usual system of Jacobi coordinates in the study of many-body problems for which permutation symmetry of the bodies plays an important role. This paper contains the details of the construction of this system and the proof that these properties uniquely determine it up to trivial modifications. Examples of applications to both classical and quantum problems are explored, including a generalization to problems involving groups of different species of bodies.
Controlling energy distribution of fast ions and X-ray emission via target reliefs in ultrafast and relativistic laser plasma interaction
Authors: Andreev A. A. , Sedov M. V. , Platonov K. Y. , Lübcke A. , Schnürer M.
Published: November 2019

Secondary emission from laser produced plasma is governed by the electron distribution function. Therefore, its control is of utmost importance to steer the emission, e.g., of ultrashort bursts of high energy photons and ions for decisive application. Maximum gain is achieved if the laser light absorption by plasma is also maximized. In our theoretical analysis including comparison to recent experiments, we follow this route and study how the energy is transferred from a short laser pulse to the energy of fast ions and X-rays. We make use of ion and K-α emissions, which respond differently to branches of the electron distribution function when we optimize the laser light absorption via structuring of the target surface. Our investigation comprises laser intensities up to 5 × 1020 W/cm2 produced with femtosecond near infrared laser pulses and titanium foil targets of a few micrometer thicknesses. In particular, we reveal an energy relaxation process of hot electrons, which determines the observed laser intensity dependence of secondary emission and points to the benefit of target surface structuring in different optimization scenarios.
Design and characterization of a compact magnetic shield for ultracold atomic gas experiments
Authors: Farolfi A. , Trypogeorgos D. , Colzi G. , Fava E. , Lamporesi G. , Ferrari G.
Published: November 2019

We report on the design, construction, and performance of a compact magnetic shield that facilitates a controlled, low-noise environment for experiments with ultracold atomic gases. The shield was designed to passively attenuate external slowly varying magnetic fields while allowing for ample optical access. The geometry, number of layers, and choice of materials were optimized using extensive finite-element numerical simulations. The measured performance of the shield is in good agreement with the simulations. From measurements of the spin coherence of an ultracold atomic ensemble, we demonstrate a residual field noise of 2.6 μG and a suppression of external dc magnetic fields by more than five orders of magnitude.
A reflective acoustic meta-diffuser based on the coding meta-surface
Authors: Cao Wen Kang , Wu Li Ting , Zhang Cheng , Ke Jun Chen , Cheng Qiang , Cui Tie Jun
Published: November 2019

The acoustic coding metasurfaces have attracted much attention recently for their unique and flexible control of wavefronts by arranging the binary elements in special sequences with antiphase responses. In this paper, we investigate the application of coding metasurfaces to manipulate the scattering features found under plane-wave illumination. Different coding strategies are considered to realize multibeam generation and construct meta-diffusers that can disperse incoming energy in various directions, leading to considerable suppression of acoustic waves traveling in specular directions. Both simulated and measured results demonstrate the powerful capability of wave manipulation by the coding metasurfaces, offering a new method for noise control in the future.
On the virtual level of two-body interactions and applications to three-body systems in higher dimensions
Authors: Barth Simon , Bitter Andreas
Published: November 2019

We consider a system of three particles in dimension d = 4 interacting via short-range potentials, where the two-body Hamiltonians have a resonance at the bottom of the essential spectrum. We prove that the three-body Hamiltonian can only admit a finite number of eigenvalues. This is in contrast to the case of three-dimensional bosons and two-dimensional fermions, where the existence of resonances leads to the infiniteness of the discrete spectrum.
Magnetically tunable random lasing from polymer dispersed liquid crystal doped ferromagnetic nanoparticles in capillary
Authors: Dai H. T. , Gao M. N. , Xue Y. X. , Xiao A. X. , Ahmad A. , Mohamed Z. , Liu C. L. , Lu Q. , Feng S. Z.
Published: November 2019

In this paper, magnetically tunable random lasing from a polymer dispersed liquid crystal (PDLC) in a capillary was achieved by means of doping with magnetic nanoparticles (MNPs). We experimentally explored the effects of the concentration of MNPs and the amplitude and direction of the magnetic field on the emission properties of random lasing, such as threshold, envelope of the emission spectrum, and intensities. The related mechanism was also investigated theoretically. Experimental results also showed that weakly tuned effects appeared from the sample with a polymer or pure liquid crystal (LC) doped with MNPs in comparison with PDLCs. Our research would provide an additional way to achieve tunable compact LC-based lasers.
Inference of chemical reaction networks based on concentration profiles using an optimization framework
Authors: Langary Damoun , Nikoloski Zoran
Published: November 2019

Understanding the structure of reaction networks along with the underlying kinetics that lead to particular concentration readouts of the participating components is the first step toward optimization and control of (bio-)chemical processes. Yet, solutions to the problem of inferring the structure of reaction networks, i.e., characterizing the stoichiometry of the participating reactions provided concentration profiles of the participating components, remain elusive. Here, we present an approach to infer the stoichiometric subspace of a chemical reaction network from steady-state concentration data profiles obtained from a continuous isothermal reactor. The subsequent problem of finding reactions consistent with the observed subspace is cast as a series of mixed-integer linear programs whose solution generates potential reaction vectors together with a measure of their likelihood. We demonstrate the efficiency and applicability of the proposed approach using data obtained from synthetic reaction networks and from a well-established biological model for the Calvin-Benson cycle. Furthermore, we investigate the effect of missing information, in the form of unmeasured species or insufficient diversity within the data set, on the ability to accurately reconstruct the network reactions. The proposed framework is, in principle, applicable to many other reaction systems, thus providing future extensions to understanding reaction networks guiding chemical reactors and complex biological mixtures.
Flow structures in transitional and turbulent boundary layers
Authors: Lee Cunbiao , Jiang Xianyang
Published: November 2019

The basic problems of transition in both incompressible and compressible boundary layers are reviewed. Flow structures in low-speed transitional and developed turbulent boundary layers are presented, together with almost all of the physical mechanisms that have been proposed for their formation. Comparisons of different descriptions of the same flow structures are discussed as objectively as possible. The importance of basic structure such as solitonlike coherent structure is addressed. For compressible flows, the receptivity and instability of boundary layer are reviewed, including the effect of different parameters on the transition. Finally, the principle of aerodynamic heating of hypersonic boundary layer is presented.
Tracer transport in attractive and repulsive supercooled liquids and glasses
Authors: Roberts Ryan C. , Poling-Skutvik Ryan , Conrad Jacinta C. , Palmer Jeremy C.
Published: November 2019

The transport of small penetrants through disordered materials with glassy dynamics is encountered in applications ranging from drug delivery to chemical separations. Nonetheless, understanding the influence of the matrix structure and fluctuations on penetrant motions remains a persistent challenge. Here, we use event-driven molecular dynamics to investigate the transport of small, hard-sphere tracers embedded in matrices of square-well particles. Short-range attractions between matrix particles give rise to reentrant dynamics in the supercooled regime, in which the liquid’s relaxation time increases dramatically upon heating or cooling. Heating results in a “repulsive” supercooled liquid where relaxations are frustrated by steric interactions between particles, whereas cooling produces an “attractive” liquid in which relaxations are hindered by long-lived interparticle bonds. Further cooling or heating, or compression, of the supercooled liquids results in the formation of distinct glasses. Our study reveals that tracer transport in these supercooled liquids and glasses is influenced by the matrix structure and dynamics. The relative importance of each factor varies between matrices and is examined in detail by analyzing particle mean-square displacements, caging behavior, and trajectories sampled from the isoconfigurational ensemble. We identify features of tracer dynamics that reveal the spatial and temporal heterogeneity of the matrices and show that matrix arrest is insufficient to localize tracers.
Swelling of polydimethylsiloxane in toluene solutions on electromagnetic resonance of metamaterials
Authors: Chiang Wei-Fan , Silalahi Harry Miyosi , Liu Yuan-Ming , Lin Yan-Shou , Chang Tsung-Hao , Lee Chia-Rong , Huang Chia-Yi
Published: November 2019

A simple method for detecting organic solutions with a similar refractive index using metamaterials that are deposited on polydimethylsiloxane (PDMS) films is proposed. Pure toluene is diluted with pure alcohol for making up toluene solutions with concentrations of 0.5 wt. % and 1.0 wt. %. The experimental results from terahertz time-domain spectroscopy depict that pure alcohol and the toluene solutions have a similar refractive index in the terahertz region. The spectra of the metamaterials that are exposed to the toluene solutions are redshifted from that of the metamaterial that is exposed to pure alcohol, and the resonance frequencies of the metamaterials decrease with the increase in the concentrations of the toluene solutions. This result arises from the fact that the swelling of the PDMS films in the toluene solutions extends the arms of the split ring resonators, changing the dimensions of the metamaterials. The minimum detectable concentration of the metamaterials is less than 0.5 wt. % when they are exposed to the toluene solutions. The metamaterials deposited on the PDMS films can detect the organic solutions with a similar refractive index, and so they have the potential to sense organic gases with low concentrations.
A model of gas desorption and radiation during initial high voltage conditioning in vacuum
Authors: Diamond William T.
Published: November 2019

Large quantities of gas are desorbed from the anode electrode during initial high-voltage conditioning of broad-area electrodes in a vacuum, equivalent to many monolayers and consist mostly of neutral molecules with an ionic component of a few percent. The ions are accelerated to the cathode, producing secondary electrons from the cathode and x-rays. There is still no reasonable explanation of these phenomena. Experiments have been performed to try to understand the source of the gas and radiation by using a residual gas analyzer to examine the desorption products from copper electrodes during initial high-voltage conditioning. The desorption products produced during initial high-voltage conditioning were then compared with those from thermal desorption of the same electrodes and surface preparation as they were heated in vacuum to about 600 °C, both with and without a high electric field present. Thermal desorption with an applied field showed a significant difference in the desorption spectrum compared with no applied field and produced a modest source of radiation that did not appear to be produced by field emission. At electrode temperatures beyond 450 °C, radiation production increased exponentially with temperature, likely produced by surface ionization of minor contaminants with a low ionization potential. These observations have been used as input to propose that the radiation and gas desorption observed during initial high-voltage conditioning is initiated by surface ionization from the many projections with high field enhancement factors on the anode surface.
MolSpin—Flexible and extensible general spin dynamics software
Authors: Nielsen Claus , Solov’yov Ilia A.
Published: November 2019

Magnetic field effects have been measured in various processes involving radical pairs, and such magnetic field effects have provided the basis for a popular hypothesis of magnetoreception in migratory song birds. The spin dynamics of radical pairs exposed to radiofrequency radiation have also been associated with changes in the production of reactive oxygen species within a biological cell, an effect that is potentially harmful. In order to investigate such phenomena theoretically, one needs to employ complex computations which rely on solving stochastic differential equations, which may appear significantly different for slightly different problems relying on spin dynamics. To avoid creating a manifold of specialized tools for various spin chemistry problems, MolSpin has been crafted as general software to handle spin systems of varied complexity. In particular, it permits solving the Liouville-von Neumann equation to obtain the time-evolution of the spin density operator, calculate quantum yields, allows us to utilize semiclassical methods, enables calculation of energy levels in an arbitrary spin system, and predicts resonance frequencies. MolSpin is designed with a high emphasis on extensibility that makes it easy to implement new or extend existing functionality.
Hybrid spin-superconducting quantum circuit mediated by deterministically prepared entangled photonic states
Authors: Mathieson Kayleigh , Bhattacharyya Somnath
Published: November 2019

In hybrid quantum systems, a controllable coupling can be obtained by mediating the interactions with dynamically introduced photons. We propose a hybrid quantum architecture consisting of two nitrogen vacancy center ensembles coupled to a tunable flux qubit, which is contained on the transmission line of a multimode nonlinear superconducting coplanar waveguide resonator with an appended Josephson mixing device. We discuss the use of entangled propagating microwaves photons, which through our nonlinear wave-mixing procedure are made into macroscopically distinct quantum states. We use these states to steer the system and show that, with further amplification, we can create a similar photonic state, which has a more distinct reduction of its uncertainty. Furthermore, we show that all of this leads to a lengthened coherence time, a reasonable fidelity that decays to 0.94 and then later increases upward to stabilize at 0.6, as well as a strengthened entanglement.