bluuebunny/crossref_metadata_2025 huggingface dataset:
Stability radius formulation of Lσ ‐gain in positive stabilisation of regular and time‐delay systems
Authors: Shafai Bahram , Naghnaeian Mohammad , Chen Jie
Published: June 2019

This study initially considers the relationship between stability radius and ‐gain of linear time‐invariant positive systems. The ‐, ‐, and ‐gains of an asymptotically stable positive system are characterised in terms of stability radii and useful bounds are derived. The authors show that the structured perturbation of a stable matrix can be regarded as a closed‐loop system with uncertainty structure represented by the unknown static output feedback. This makes it possible to relate the ‐gains in terms of closed‐form expression available for stability radii of Metzler matrices. The authors generalise the above connection for positive‐delay systems as well. Performance characterisation and computation of ‐gains are also given based on linear programming for and linear matrix inequality (LMI) for . The importance of this characterisation becomes evident when state feedback controllers are designed for regular and time‐delay systems with positivity constraints. In particular, they show that positive stabilisation with maximum stability radius for the case of can be considered as an ‐gain minimisation, which can be solved by LMI. This inherently achieves the performance criterion and establishes a link to the reported iterative convex optimisation approaches that have been developed for the cases of and . A significant result of this study is the derivation of bounds for ‐gains and the unique commonality among the optimal state feedback gain matrices in obtaining ‐gains of the stabilised system.
Design of unknown input fractional order proportional–integral observer for fractional order singular systems with application to actuator fault diagnosis
Authors: Pourdadashi Komachali Fateme , Shafiee Masoud , Darouach Mohamed
Published: June 2019

This study proposes the design of an unknown input fractional order proportional–integral observer for fault diagnosis of linear fractional order singular (FOS) systems. The considered system is rectangular in general form. The necessary and sufficient conditions for the existence of the proposed observer are derived, and a systematic design approach is presented. The proposed observer is non‐singular, and uses only the original coefficient matrices to estimate the norm‐bounded actuator faults. Also, the unknown input appearing in measurement is considered and the effects of unknown inputs are decoupled from observer dynamics. By introducing a continuous frequency distributed model and using indirect Lyapunov approach, the convergence conditions of the proposed observer are derived in terms of linear matrix inequalities. Furthermore, for a class of non‐linear FOS systems with both output disturbances and input uncertainties, a non‐linear observer is developed based on the proposed design approach. The existence and convergence of this observer are proved. Finally, the effectiveness of the proposed method is illustrated via two examples.
Relaxed hybrid consensus ADMM for distributed convex optimisation with coupling constraints
Authors: Olama Alireza , Bastianello Nicola , Mendes Paulo R.C. , Camponogara Eduardo
Published: June 2019

In this study, the solution of a convex distributed optimisation problem with a global coupling inequality constraint is considered. By using the Lagrange duality framework, the problem is transformed into a distributed consensus optimisation problem and then based on the recently proposed Hybrid Alternating Direction Method of Multipliers (H‐ADMM), which merges distributed and centralised optimisation concepts problems, a novel distributed algorithm is developed. In particular, the authors offer a reformulation of the original H‐ADMM in an operator theoretical framework, which exploits the known relationship between ADMM and Douglas–Rachford splitting. In addition, the authors' formulation allows us to generalise the H‐ADMM by including a relaxation constant, not present in the original design of the algorithm. Moreover, an adaptive penalty parameter selection scheme that consistently improves the practical convergence properties of the algorithm is proposed. Finally, the convergence results of the proposed algorithm are discussed and moreover, in order to present the effectiveness and the major capabilities of the proposed algorithm in off‐line and on‐line scenarios, distributed quadratic programming and distributed model predictive control problems are considered in the simulation section.
Distributed iterative learning coordination control for leader–follower uncertain non‐linear multi‐agent systems with input saturation
Authors: Yang Nana , Li Junmin
Published: June 2019

In this study, the fully distributed adaptive iterative learning coordination control of the uncertain non‐linear leader–follower multi‐agent systems with input saturation is studied. Under the alignment initial condition and Lyapunov theory, a novel adaptive distributed control protocol with a fully saturated parameter learning law is designed. Despite the existence of input saturation, the global perfect consensus tracking can be realised over a finite time interval. Besides, the consensus tracking problem is extended to the formation control problem as well. Ultimately, the validity of theoretical analysis of this study is shown by two examples.
Robust fixed‐time synchronisation of non‐identical nodes in complex networks under input non‐linearities
Authors: Shirkavand Mehrdad , Pourgholi Mahdi , Yazdizadeh Alireza
Published: June 2019

In this study, a novel global fixed‐time synchronisation of uncertain complex dynamical networks including nonidentical nodes in the presence of unknown disturbances under input non‐linearity constraint is investigated. First, in order to achieve the fixed‐time synchronisation of network with unknown disturbances, a novel sliding manifold is established. The fixed‐time stability of both the reaching and sliding modes are proved based upon the Lyapunov stability theorem. The notable feature of the proposed control is that the fixed convergence time of both reaching and sliding modes can be tuned to the desired values by selecting the designable parameters in advance. Finally, five numerical experiments are presented to demonstrate the validity of the obtained results as well as the practicability of the proposed methods.
Multi‐model switching‐based fault tolerant control for planar robot manipulators
Authors: Meng Yajun , Yang Hao , Jiang Bin
Published: June 2019

This study addresses the fault‐tolerant tracking control issue for a class of planar manipulators with various actuator and sensor faults. Firstly, a set of linear models are constructed to approximate the original non‐linear model at the different joint angular positions, which explicitly reveal the coupling effects among sub‐manipulators. Secondly, a family of decentralised fault‐tolerant controllers are proposed with each one being related to one linear model respectively, which does not require the information exchange among sub‐manipulators and thus lightens the communication burden. Finally, a switching law is proposed among controllers such that the system remains stable in the presence of controller switching. An example of a three‐link planar robot manipulator is taken to illustrate the effectiveness of the proposed methods.
Enhancing the performance of DFIG variable speed wind turbine using a parallel integrated capacitor and modified modulated braking resistor
Authors: Okedu Kenneth E.
Published: June 2019

Wind energy has a dilute, unpredicted nature; hence, it creates a challenge for effective and well managed operation of wind turbines connected to the grid network. There is a mandatory requirement for wind turbines to fulfil standard grid codes for stability control. In this study, a new scheme consisting of a parallel connected capacitor with the DC‐link scheme of the doubly fed induction generator (DFIG) wind turbine is proposed. Scenarios of integrating different sizes of the parallel capacitor at the grid side converter of the DFIG were investigated, in order to know the optimum size for the better transient performance of the wind generator. For effective comparative study, the same constant wind speed was used for the considered scenarios in the investigation of the wind generator transient performance. The presented results in power system computer design and electromagnetic transient including DC show that the proposed parallel capacitor based DC‐link scheme power converter improves the grid voltage response and the variables of the wind generator during a severe grid fault condition. Furthermore, a proposed modulated series dynamic braking resistor (MSDBR) was used to improve the overall performance of the capacitor scheme. The results of the proposed MSDBR were compared to the traditional scheme.
Enhancement of transmission characteristics for the antenna system printed on silicon wafer substrate by using FSS‐based coplanar parallel reflector
Authors: Yang Shuhui , Chen Yinchao , Lu Guizhen , Li Bin , Wang Ling , Zeng Dongdong
Published: June 2019

Here, a silicon‐substrate‐based four element antenna system is investigated by using a coplanar frequency selective surface (FSS) as a novel parallel reflector to improve radiation and transmission characteristics of the antennas. The four antennas are arranged around the square FSS, and one of the antennas is used as the transmitting element, while the other three as the receiving ones. It is found that, owing to the stopband filtering and the linearly changing reflection phase of the designed coplanar FSS, the gain and directivity of the transmitting antenna have been greatly improved, and that the antenna system transmission coefficients, including S21, S31 and S41, have been significantly increased. Two types of the antenna systems have been designed and fabricated on a P‐type silicon wafer substrate for the cases with and without a coplanar FSS reflector. The measured S‐parameters are essentially consistent with those simulated. In comparison with the case without the FSS, the transmission coefficients of S21, S31 and S41 for the system with the FSS have been increased about 6.42, 5.97 and 5.89 dB at the center frequency of 5.42 GHz, respectively. Furthermore, the proposed coplanar FSS exhibits distinct advantage of low‐profile compared to the conventional vertical FSS reflector.
Probing the initial conditions of high-mass star formation
Authors: Zhang Chuan-Peng , Csengeri Timea , Wyrowski Friedrich , Li Guang-Xing , Pillai Thushara , Menten Karl M. , Hatchell Jennifer , Thompson Mark A. , Pestalozzi Michele R.
Published: June 2019

Context. Fragmentation and feedback are two important processes during the early phases of star formation.

Aims. Massive clumps tend to fragment into clusters of cores and condensations, some of which form high-mass stars. In this work, we study the structure of massive clumps at different scales, analyze the fragmentation process, and investigate the possibility that star formation is triggered by nearby H ii regions.

Methods. We present a high angular resolution study of a sample of massive proto-cluster clumps G18.17, G18.21, G23.97N, G23.98, G23.44, G23.97S, G25.38, and G25.71. Combining infrared data at 4.5, 8.0, 24, and 70 μm, we use a few arcsecond resolution, radiometer and millimeter inteferometric data taken at 1.3 cm, 3.5 mm, 1.3 mm, and 870 μm to study their fragmentation and evolution. Our sample is unique in the sense that all the clumps have neighboring H ii regions. Taking advantage of that, we tested triggered star formation using a novel method where we study the alignment of the center of mass traced by dust emission at multiple scales.

Results. The eight massive clumps, identified based on single-dish observations, have masses ranging from 228 to 2279 M⊙ within an effective radius of Reff ~ 0.5 pc. We detect compact structures towards six out of the eight clumps. The brightest compact structures within infrared bright clumps are typically associated with embedded compact radio continuum sources. The smaller scale structures of Reff ~ 0.02 pc observed within each clump are mostly gravitationally bound and massive enough to form at least a B3-B0 type star. Many condensations have masses larger than 8 M⊙ at a small scale of Reff ~ 0.02 pc. We find that the two infrared quiet clumps with the lowest mass and lowest surface density with <300 M⊙ do not host any compact sources, calling into question their ability to form high-mass stars. Although the clumps are mostly infrared quiet, the dynamical movements are active at clump scale (~1 pc).

Conclusions. We studied the spatial distribution of the gas conditions detected at different scales. For some sources we find hints of external triggering, whereas for others we find no significant pattern that indicates triggering is dynamically unimportant. This probably indicates that the different clumps go through different evolutionary paths. In this respect, studies with larger samples are highly desired.
Mass transfer on a nuclear timescale in models of supergiant and ultra-luminous X-ray binaries
Authors: Quast M. , Langer N. , Tauris T. M.
Published: June 2019

Context. The origin and number of the Galactic supergiant X-ray binaries is currently not well understood. They consist of an evolved massive star and a neutron star or black-hole companion. X-rays are thought to be generated from the accretion of wind material donated by the supergiant, while mass transfer due to Roche-lobe overflow is mostly disregarded because the high mass ratios of these systems are thought to render this process unstable.

Aims. We investigate how the proximity of supergiant donor stars to the Eddington limit, and their advanced evolutionary stage, may influence the evolution of massive and ultra-luminous X-ray binaries with supergiant donor stars (SGXBs and ULXs).

Methods. We constructed models of massive stars with different internal hydrogen and helium gradients (H/He gradients) and different hydrogen-rich envelope masses, and exposed them to slow mass-loss to probe the response of the stellar radius. In addition, we computed the corresponding Roche-lobe overflow mass-transfer evolution with our detailed binary stellar evolution code, approximating the compact objects as point masses.

Results. We find that a H/He gradient in the layers beneath the surface, as it is likely present in the well-studied donor stars of observed SGBXs, can enable mass transfer in SGXBs on a nuclear timescale with a black-hole or a neutron star accretor, even for mass ratios in excess of 20. In our binary evolution models, the donor stars rapidly decrease their thermal equilibrium radius and can therefore cope with the inevitably strong orbital contraction imposed by the high mass ratio. We find that the orbital period derivatives of our models agree well with empirical values. We argue that the SGXB phase may be preceded by a common-envelope evolution. The envelope inflation near the Eddington limit means that this mechanism more likely occurs at high metallicity.

Conclusion. Our results open a new perspective for understanding that SGBXs are numerous in our Galaxy and are almost completely absent in the Small Magellanic Cloud. Our results may also offer a way to find more ULX systems, to detect mass transfer on nuclear timescales in ULX systems even with neutron star accretors, and shed new light on the origin of the strong B-field in these neutron stars.
A NuSTAR view of powerful γ-ray loud blazars
Authors: Ghisellini G. , Perri M. , Costamante L. , Tagliaferri G. , Sbarrato T. , Campitiello S. , Madejski G. , Tavecchio F. , Ghirlanda G.
Published: June 2019

We observed three blazars at z >  2 with the NuSTAR satellite. These were detected in the γ-rays by Fermi/LAT and in the soft X-rays, but have not yet been observed above 10 keV. The flux and slope of their X-ray continuum, together with Fermi/LAT data allows us to estimate their total electromagnetic output and peak frequency. For some of them we were able to study the source in different states, and investigate the main cause of the different observed spectral energy distribution. We then collected all blazars at redshifts greater than 2 observed by NuSTAR, and confirm that these hard and luminous X-ray blazars are among the most powerful persistent sources in the Universe. We confirm the relation between the jet power and the disk luminosity, extending it at the high-energy end.
Global mapping of lunar refractory elements: multivariate regression vs. machine learning
Authors: Bhatt M. , Wöhler C. , Grumpe A. , Hasebe N. , Naito M.
Published: June 2019

Context.The quantitative estimation of elemental concentrations at the spatial resolution of hyperspectral near-infrared (NIR) images of the lunar surface is an important tool for understanding the processes relevant for the origin and evolution of the Moon.

Aims.We aim to map the abundances of the elements Fe, Ca, and Mg at a typical accuracy of about 1 wt.% at the spatial resolution of the Moon Mineralogy Mapper (M3) instrument on-board Chandrayaan-1 lunar mission.

Methods.The NIR reflectance of the lunar regolith is an integrated response to the presence of refractory elements and soil alteration processes. Our approach was to define a combination of spectral parameters that are robust with respect to the effects of soil maturity. We calibrated the spectral parameters with respect to elemental abundances measured by the Lunar Prospector Gamma Ray Spectrometer (LP GRS) and the Kaguya GRS (KGRS). For this purpose, we compared a classical multivariate linear regression (MLR) approach and the machine learning based support vector regression (SVR) technique applied to M3global observations.

Results.The M3-based global elemental maps are consistent in distribution and range with the LP GRS and KGRS elemental maps and do not show artifacts in immature areas such as small fresh craters. The results derived using MLR and SVR are compared to sample-based ground truth data of the Apollo and Luna sample-return sites, where the root-mean-square deviations obtained by the two regression models are similar.

Conclusions.The main advantage of the proposed new algorithm is its ability to minimize artifacts due to space-weathering effects. The elemental maps of Mg and Ca provide additional information and reveal structures not always visible in the Fe map. The global elemental abundance maps derived for the fully calibrated M3observations might thus serve as important tools to investigate the lunar geology and evolution.
Study on the Construction Mode of Ecological and Sustainable Rain Flood in New Urban Area of China
Authors: Kang Caixia , Lu Qing , Zhang Zhiheng , Zhao Qian , Nan Huihui
Published: June 2019

In the background of the urbanization process has exceeded 58% of China and expansion of the construction land expansion, as a future appropriate residential development and ahead of the key area of urban rain flood management, this research expounds the new cities and new district how to follow the principle of ecological priority in different application field, and how to use land for urban green space and ecological protection for elastic development and rain flood management. The study of the new cities’ eco-rain flood management model is of great significance for the governance and sustainable development of urban diseases in China.By combining natural ways with artificial measures, planning is carried out in advance.On the premise of ensuring the safety of urban drainage and waterlogging prevention, the accumulation, infiltration and purification of rainwater in urban areas can be realized to the maximum extent, and the utilization of rainwater resources and ecological environment protection can be promoted in new cities. To make plan ahead,to avoid the problems of rain and flood in existing urban areas, and improve the livable quality of new cities greatly.New ways of thinking and construction guidance are proposed for ecological livable construction and flexible rain flood management of new urban areas in China.
Guidelines for the Stable Development of Public Bus Transport in the City of Sofia
Authors: Tzvetkova Svetla
Published: June 2019

The stable development of public bus transport includes the improvement of the social, economic and ecological aspects of its activity or increasing its social effectiveness through improving the quality of offered transport services, reducing energy consumption, using energy sources more effectively and reducing the harmful effects on the environment. Public bus transport is the most commonly used type of ground transport in the city of Sofia; in recent years, unfortunately, the quality of its services has dropped and its harmful influence on the environment has grown. This is primarily caused by obsolete vehicles and the lack of adequate measures for improving its social and economic effectiveness. The present article substantiates the necessity for its future stable development and outlines the measures for improving the quality of the transport services it offers as well as reducing harmful emissions. In order to support the study’s topicality, it should also be pointed out that similar goals and objectives set in the Declaration for reducing harmful emissions, creating conditions for the use of renewable energy and attracting green investments, which Sofia joined during the World Conference for Climate Change held in Paris in December 2015.
The identification problem solution of the ventilation system model based on static pressure
Authors: Boykov Dmitriy V. , Dekterev Aleksandr A.
Published: June 2019

A pressure method to solve the problem of flow distribution in a pipeline system based on the static pressure use was proposed in the study. A modification of the identification method to search for the local resistance coefficients of the ventilation system sites was provided. Static pressure and flow rate as identifying values were used in the developed approach. The applicability of the identification method for local resistance of the gas removal system to be found was shown.
Gas pipeline infrastructure and economic growth of Russian regions: panel cointegration analysis
Authors: Belinsky Alexander
Published: June 2019

The Russian gas supply system is one of the largest infrastructures in the world. It is continuing to develop at a high rate. Modern methodological approaches and software allow to investigate the relationship between the development of energy infrastructure and economic dynamics of the regions. This paper proposes a methodological approach to the evaluation of the relationship “development of gas distribution systems – economic growth”. The evaluation is based on the concept of cointegration and an error-correction models. This approach identifies both long-run and short-run components of this relationship. In this paper we aim to estimate the relationship using annual data of 17 Central Russia regions for the period 1998-2017. The results indicate that this relationship is statistically significant. It allows to apply proposed approach and the obtained estimates to the problems of analysis and forecasting of the domestic gas market.
Optimization of development schemes for group water supply systems under uncertainty of prospective water consumption
Authors: Chupin Roman V. , Pham Minh Ngoc , Chupin Viktor R.
Published: June 2019

In recent years, in the Russian cities there has been a decrease about 15-30% the total volume of water consumed and the specific indicator of water consumption per resident. However, this phenomenon is not taken into account in the SP 31.13330.2012, therefore the values of specific water consumption do not correspond to the modern level of sanitary equipment of the buildings and water consumption, which can not be the same for all cities and towns in Russia. Using the standard values of the design loads indicated in this code can lead to a significant increase in the cost of the project and operating costs. Their correction is necessary taking into account the assessment and forecast of the actual values of specific water consumption. This requires appropriate research and updating of specific water consumption standards for the design and reconstruction water supply and sewerage systems. The article describes the parameter justification method for the designed water supply systems under uncertainty of the prospective values of specific water consumption. The technique is based on the fuzzy sets theory and decision-making methodology under uncertainty of the initial information. This technique allows you to make decisions based on the minimum values of investment risks.
Study of the measurements placement problem for planning of the optimal experiment
Authors: Grebneva Oksana A.
Published: June 2019

Both in Russia and abroad, there are works that are devoted to the problem of optimal placement of measuring devices, which are evidenced by the current literature. The proposed methods are not universal, that does not allow them to be directly used for different types of pipeline systems. In addition, the developed algorithms does not guarantee a global solution. In this regard, there is a demand for solving the problem of optimal placement of measuring devices for pipeline systems. At the same time, not only the number and accuracy of measuring devices, but also their composition and placement locations are important. In this paper, a mathematical formulation of the problem of optimal placement of measuring devices is given, methods for its solution are proposed. The numerical example shows the effectiveness of the proposed method of optimal placement of measuring devices, which allows to get a global solution for a previously known finite number of steps.
Problems and technologies of remote access to unified information space of urban pipeline systems
Authors: Alekseev Alexander , Mikhailovsky Egor
Published: June 2019

The paper presents the experience of applying modern information technologies while operating the urban pipeline systems. Consideration is given to the main problems interfering with ensuring the efficient modes of pipeline systems operation that are caused by uncertainty and inconsistency of information on the actual condition of the system that, in turn, are originated by different technological factors. The paper also pays attention to the lack of continuity, inconsistency and duplication of data in different software packages (accounting, billing, resources planning and management, geo-information systems, SAPR, SCADA, digital models of pipeline systems, etc.) used by companies, which complicates operation of pipeline systems. The paper discusses advantages of development and introduction of unified information space in a company, related problems of its updating, and methods of remote access to it. Causes originating this problem are analyzed and ways for its solution are searched for from the standpoint of the latest information technologies. For solving this problem the authors propose specialized software that implies active use of wireless communication channels, mobile devices, etc. This mobile information package is briefly described as a prototype intended for remote access to unified information space of a company and to a digital model of the pipeline system in particular using mobile communication devices. Considered are the advantages of this development and scenarios of its application.
Materials, properties, manufacturing methods and cutting performance of innovative ceramic cutting tools − a review
Authors: Grigoriev Sergey N. , Fedorov Sergey V. , Hamdy Khaled
Published: June 2019

For mechanical machining the quality of cutting-tool materials is one of the most significant issues that need to be addressed. Enhancement of cutting tool performance may be achieved through the use of modern composition ceramic cutting tools This may be enabled through surface treatment, and also hot pressing and spark plasma sintering – the two main processes used for manufacturing such tools. In this article the advantages and disadvantages of the technologies and processes involved are analyzed and compared to identify the most appropriate methods for creating ceramic cutting-tools. In parallel the latest improvements in ceramic cutting-tool materials are reviewed. The paper shows that the choice of ceramic cutting tools is a quite complex process with a number of important factors to be taken into account.
Primary Therapy of Early Breast Cancer: Evidence, Controversies, Consensus
Authors: Untch Michael , Thomssen Christoph , Bauerfeind Ingo , Braun Michael , Brucker Sara Y. , Felberbaum Ricardo , Hagemann Friederike , Haidinger Renate , Hönig Arnd , Huober Jens , Jackisch Christian , Kolberg Hans-Christian , Kolberg-Liedtke Cornelia , Kühn Thorsten , Lüftner Diana , Maass Nicolai , Reimer Toralf , Schneeweiss Andreas , Schumacher-Wulf Eva , Schütz Florian , Thill Marc , Wuerstlein Rachel , Fasching Peter A. , Harbeck Nadia
Published: June 2019

The results of the international St. Gallen Consensus Conference for the treatment of patients with primary breast cancer were discussed this year by a working group of leading breast cancer experts in view of the therapy recommendations for everyday clinical practice in Germany. Three of the breast cancer experts are also members of this yearʼs St. Gallen panel. The comparison of the St. Gallen recommendations with the annually updated treatment recommendations of the AGO 2019 as well as the S3 guideline is useful, since the recommendations of the St. Gallen panel represent the opinions of experts from various countries and disciplines. The recommendations of the S3 guideline and AGO are based on evidence-based research of the literature. This yearʼs 16th St. Gallen conference featured the motto “Magnitude of clinical benefit”. In addition to the evidence-based data, each therapeutic decision must also undergo a benefit/risk assessment of the patientʼs individual situation and be discussed with the patient.
Cerebroplacental and Uterine Doppler Indices in Pregnancies Complicated by Congenital Heart Disease of the Fetus
Authors: Graupner Oliver , Koch Jessica , Enzensberger Christian , Götte Malena , Wolter Aline , Müller Vera , Kawecki Andreea , Herrmann Johannes , Axt-Fliedner Roland
Published: June 2019

Purpose Children with congenital heart disease (CHD) are known to have impaired neurodevelopment possibly influenced by altered cerebroplacental hemodynamics antenatally. We compared fetomaternal Doppler patterns in different CHD groups with published normative values during gestation.

Materials and Methods Retrospective cohort study consisting of 248 CHD fetuses. Subgroups were generated according to the expected ascending aorta oxygen saturation: low portion of high oxygenated umbilical venous (UV) blood (group 1: n = 108), intermediate portion of UV blood due to intracardiac mixing with oxygen poor systemic blood (group 2: n = 103), high (group 3: n = 13) and low portion of UV blood without mixing of blood (group 4: n = 24). Doppler examination included umbilical artery and middle cerebral artery pulsatility index (UA-PI, MCA-PI), cerebroplacental ratio (CPR) and mean uterine artery (mUtA) PI. For mean comparisons at different gestational ages (GA), estimated marginal means from regression models are reported for GA 22 weeks (wks), GA 30 wks and GA 38 wks.

Results Z-score transformed values of MCA-PI (zMCA-PI) were significantly lower in group 1 compared to all other subgroups at GA 30 wks (p < 0.05). At 38 wks, group 1 had significantly lower values of zMCA-PI and zCPR compared to groups 2 and 4. Group 1 fetuses showed a significant association between zMCA-PI and zCPR (negative) and GA as well as zmUtA-PI (positive) and GA compared to reference values.

Conclusion Our data confirm that CHD fetuses have a higher rate of cerebral redistribution in the third trimester. Changes in Doppler patterns were mainly observed in CHD with a low portion of UV blood in the ascending aorta.
The Impact of Fetal Anomalies on Contemporary Labor Patterns
Authors: McCormick Anna C. , McIntosh Jennifer J. , Gao Weihua , Hibbard Judith U. , Cruz Meredith O.
Published: June 2019

Objective To compare labor patterns in pregnancies affected by fetal anomalies to low-risk singletons.

Study Design Labor data from the Consortium on Safe Labor, a multicenter retrospective study from 19 U.S. hospitals, including 98,674 low-risk singletons compared with 6,343 pregnancies with fetal anomalies were analyzed. Repeated-measures analysis constructed mean labor curves by parity, gestational age, and presence of fetal anomaly in women who reached full dilation. Interval-censored regression analysis adjusted for covariables was used to determine the median traverse times for labor progression.

Results Labor curves for all groups indicated slower labor progress for patients with fetal anomalies. The most significant trends in median traverse times were observed in the preterm nulliparous and term multiparous groups. The median traverse times from 4 cm to complete dilation in the preterm nulliparous control versus anomaly groups were 5.0 and 5.4 hours (p < 0.0001).

Conclusion Labor proceeds at a slower rate in pregnancies affected by anomalies.
Correction of Biapical Tibial Deformity by True Spherical Osteotomy, Modified Circular External Skeletal Fixation and Distraction Osteogenesis
Authors: Walmsley Darby , Fitzpatrick Noel , Black Cameron
Published: June 2019

Objectives The aim of this study was to describe a case of biapical tibial deformity as a result of premature distal physeal closure corrected by true spherical osteotomy, circular external skeletal fixation and distraction osteogenesis.

Methods A 6-month-old male Labrador Retriever was presented for the evaluation and treatment of angular limb deformity of the left pelvic limb, with radiography and computed tomography revealing a multiplanar, biapical, compensatory tibial growth deformity, with marked distal tibial recurvatum and varus. A true spherical osteotomy was performed at the distal tibial centre of rotation of angulation (CORA), allowing for correction of the deformity in three planes, with a transverse osteotomy performed at the most proximal CORA. A circular external skeletal fixator was applied and distraction osteogenesis performed at the transverse osteotomy. Latency, distraction osteogenesis, and consolidation were performed over a 113-day period.

Results At frame removal, tibial length discrepancy improved from 16.8% to 0.6% and frontal plane varus angulation improvement from 20° to 5°, when compared with the contralateral limb. Long-term evaluation revealed a satisfactory clinical and cosmetic outcome, judged by the clinician and owners, with force plate analysed symmetry index of the pelvic limb within reported normal limits.

Clinical significance To our knowledge this is the first case report illustrating the value of true spherical osteotomy for the treatment of an angular limb deformity when performed in combination with distraction osteogenesis in a canine pelvic limb.
Can the geometry of all-atom protein trajectories be reconstructed from the knowledge of C
α
time evolution? A study of peptide plane O and side chain Cβ atoms
Authors: Liu Jiaojiao , Dai Jin , He Jianfeng , Peng Xubiao , Niemi Antti J.
Published: June 2019

We inquire to what extent can the geometry of protein peptide plane and side chain atoms be reconstructed from the knowledge of Cα time evolution. Due to the lack of experimental data, we analyze all atom molecular dynamics trajectories from the Anton supercomputer, and for clarity, we limit our attention to the peptide plane O atoms and side chain Cβ atoms. We reconstruct their positions using four different approaches. Three of these are the publicly available reconstruction programs Pulchra, Remo, and Scwrl4. The fourth, Statistical Method, builds entirely on the statistical analysis of Protein Data Bank structures. All four methods place the O and Cβ atoms accurately along the Anton trajectories; the Statistical Method gives results that are closest to the Anton data. The results suggest that when a protein moves under physiological conditions, its all atom structures can be reconstructed with high accuracy from the knowledge of the Cα atom positions. This can help to better understand and improve all atom force fields, and advance reconstruction and refinement methods for reduced protein structures. The results provide impetus for the development of effective coarse grained force fields in terms of reduced coordinates.
The microscopic Einstein-de Haas effect
Authors: Wells T. , Horsfield A. P. , Foulkes W. M. C. , Dudarev S. L.
Published: June 2019

The Einstein-de Haas (EdH) effect, where the spin angular momentum of electrons is transferred to the mechanical angular momentum of atoms, was established experimentally in 1915. While a semiclassical explanation of the effect exists, modern electronic structure methods have not yet been applied to model the phenomenon. In this paper, we investigate its microscopic origins by means of a noncollinear tight-binding model of an O2 dimer, which includes the effects of spin-orbit coupling, coupling to an external magnetic field, and vector Stoner exchange. By varying an external magnetic field in the presence of spin-orbit coupling, a torque can be generated on the dimer, validating the presence of the EdH effect. The avoided energy level crossings and the rate of change of magnetic field determine the evolution of the spin. We also find that the torque exerted on the nuclei by the electrons in a time-varying B field is not only due to the EdH effect. The other contributions arise from field-induced changes in the electronic orbital angular momentum and from the direct action of the Faraday electric field associated with the time-varying magnetic field.
Laser-cooling with an intermediate electronic state: Theoretical prediction on bismuth hydride
Authors: Yuan Xiang , Guo Hui-Jie , Wang Yu-Min , Xue Jian-Lei , Xu Hai-Feng , Yan Bing
Published: June 2019

The possibility of laser cooling of bismuth hydride (BiH) molecules has been investigated based on high-level ab initio calculations by considering the core-valence and the spin-orbit coupling (SOC) effects. The potential energy curves of the 12 Λ-S states as well as the 25 Ω states that split from them via SOC are obtained by multireference configuration interaction plus the Davidson correction. The properties of b-X transition are investigated. Based on our calculations, we show that the transition between Ω states b0+–X10+ of BiH is a possible candidate for laser cooling, with consideration of the intermediate Ω state X21. An optical cycling scheme is proposed by utilizing four lasers at wavelengths around 471 and 601 nm with 5400 cycles for photon absorption/emission and a sub-microkelvin temperature. Our study should shed some light on searching for possible molecular candidates for laser cooling with the existence of an intermediate electronic state.
Enhanced thermoelectric performance of a simple method prepared polycrystalline SnSe optimized by spark plasma sintering
Authors: Zhang Q. K. , Ning S. T. , Qi N. , Chen Z. Q. , Tang X. F. , Chen Z. Y.
Published: June 2019

In this study, polycrystalline SnSe was synthesized via a rapid, cost-effective, and large-scale synthesis route. The obtained SnSe powders were pressed into pellets via spark plasma sintering (SPS) at different temperatures. Powder X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) were used to characterize the crystal structures and morphology of the SnSe samples. The XRD results indicate that the orientation factors increase monotonously with the increase of sintering temperature. The FESEM images show that sintering temperatures have no obvious influence on the particle size. Positron annihilation measurements indicate that vacancy defects exist in all the sintered SnSe samples, and they recover gradually with increasing sintering temperatures. These vacancy defects are responsible for the lower lattice thermal conductivity in samples sintered at lower temperatures. The electrical conductivity, power factor, thermal conductivity, and figure of merit ZT show nearly the same variation trend, which increases initially with the increasing sintering temperature up to 550 °C then decreases with further increase of the sintering temperature, which is possibly due to slight oxidation of SnSe. A maximum ZT value of ∼0.47 at 430 °C was achieved for the 550 °C sintered sample, which is higher than those reported for undoped polycrystalline SnSe around this temperature. Thus, we provide a simple, energy-saving, and effective method to synthesize polycrystalline SnSe in large quantities, and SPS is an effective method to optimize thermoelectric performance.
Effect of OH groups on the polyamorphic transition of polyol aqueous solutions
Authors: Suzuki Yoshiharu
Published: June 2019

Polyamorphic transition in water is expected to occur at low temperatures and high pressures. Recently, the polyamorphic transitions of polyol aqueous solutions were examined under pressure at low temperatures, and the location of their liquid-liquid critical points was estimated experimentally. The addition of polyol solute in water induces the shift of polyamorphic transition pressure toward the lower pressure side. Here, by comparing the polyamorphic transition of various polyol aqueous solutions, especially by comparing those of dilute 1,2-propanediol and dilute 1,3-propanediol aqueous solutions, it is clarified that the OH-groups in the polyol molecule efficiently affect the polyamorphic behavior of solvent water. This suggests that the hydrogen bonding interaction between solvent water and polyol solute relates closely to the polyamorphic behavior of solvent water such as the stabilization of high-density-amorph-like solvent water induced by the presence of polyol solute. In addition, the effect of CH3 groups in the 1,2-propanediol molecule seems to be opposite to the effect of OH groups. These results have important implications for the understandings of low-temperature phenomena of aqueous solutions, for example, hydration, segregation, phase separation, folding/unfolding of macromolecules, glass forming, and nucleation of crystalline ice Ih.
Exploring conductivity in ex-situ doped Si thin films as thickness approaches 5 nm
Authors: MacHale John , Meaney Fintan , Kennedy Noel , Eaton Luke , Mirabelli Gioele , White Mary , Thomas Kevin , Pelucchi Emanuele , Petersen Dirch Hjorth , Lin Rong , Petkov Nikolay , Connolly James , Hatem Chris , Gity Farzan , Ansari Lida , Long Brenda , Duffy Ray
Published: June 2019

Silicon (Si) has been scaled below 10 nm in multigate and silicon-on-insulator (SOI) device technologies, but clearly Si thickness cannot be reduced indefinitely, as we will run out of atoms eventually. As thickness approaches 5 nm, surfaces and interfaces will significantly impact the electrical behavior of Si, and surface physics cannot be discounted. Below that, bulk material properties will be altered considerably in the few-monolayer limit. One of the most basic defining properties of a semiconductor is its conductivity. To improve conductivity, while inducing a channel by appropriate biasing, it is necessary to define an accurate impurity doping strategy to reduce parasitic resistance. In this paper, we investigated the changing electrical conductivity of SOI films as a function of the Si thickness, in the range of 3–66 nm. SOI films were ex situ doped using three different approaches: liquid/vapor phase monolayer doping of phosphorus using allyldiphenylphosphine, gas-phase doping of arsenic using arsine (AsH3), and room-temperature beam-line ion implantation of phosphorus. The circular transfer length method and micro-four-point probe measurements were used to determine the resistivity of the Si films, mitigating the contribution from contact resistance. The resistivity of the Si films was observed to increase with decreasing Si film thickness below 20 nm, with a dramatic increase observed for a Si thickness at 4.5 nm. This may drastically impact the number of parallel conduction paths (i.e., nanowires) required in gate-all-around devices. Density functional theory modeling indicates that the surface of the Si film with a thickness of 4.5 nm is energetically more favorable for the dopant atom compared to the core of the film.
Transition from glow-like to streamer-like discharge in atmospheric pressure dielectric barrier discharge controlled by variable dielectric surface layer permittivity
Authors: Yao Congwei , Chen Sile , Xu Guimin , Chang Zhengshi , Mu Haibao , Sun Anbang , Zhang Guan-Jun
Published: June 2019

Atmospheric pressure dielectric barrier discharge (DBD) has abundant application fields, and the influence of the barrier material on DBD characteristics has been the research focus in recent years. In this work, a two-dimensional fluid model is built to investigate the effects of the barrier dielectric surface layer with different permittivity distribution on DBD, including electric parameters, electron distribution, and surface charge evolution. It is demonstrated that higher dielectric permittivity can affect DBD by enhancing the electric field Espace of space charge and weakening electric field Esurf of the surface charge and have a more obvious influence on Esurf, which can make DBD transform from glowlike discharge to streamerlike discharge. The dielectric surface layer with linear distribution of permittivity is introduced in DBD, changing the discharge appearance and discharge channel forming sequence. This work may provide some theoretical experiences for the application of a functionally graded material as a barrier dielectric in DBD.
Intermediate range O–O correlations in supercooled water down to 235 K
Authors: Pathak Harshad , Späh Alexander , Kim Kyung Hwan , Tsironi Ifigeneia , Mariedahl Daniel , Blanco Maria , Huotari Simo , Honkimäki Veijo , Nilsson Anders
Published: June 2019

Wide angle x-ray scattering of supercooled water down to 234.8 K was studied using high energy x rays at the European Synchrotron Radiation Facility. The oxygen-oxygen pair distribution function (PDF) was calculated from the scattering pattern out to the 5th peak at an intermolecular distance, r ≈ 11 Å. We observe that the 4th peak and the 5th peak in the PDF increase in height upon supercooling. We also observe that the 4th peak position (r4) shifts to shorter distances upon supercooling consistent with previous studies, but we see a more rapid change at the lowest temperature. The running oxygen-oxygen coordination number is calculated for 5 different temperatures, and an isosbestic point at riso = 3.31 ± 0.05 Å was found corresponding to a coordination number of 4.39 ± 0.15. The comparison of the PDF of the coldest water with that of amorphous ice shows distinct differences. We propose that there are 5-member pentamer rings in low density liquid-like structures giving rise to the sharp correlations at r ≈ 9 Å and r ≈ 11 Å.
A scalable algorithm of numerical real-time path integral for quantum dissipative systems
Authors: Sato Yoshihiro
Published: June 2019

Numerical real-time path integration has been a practical method to study a quantum system under the influence of its environment. Performing the path integral computations, however, is a resource-demanding task in general, and implementing it is less straightforward with modern hardware architectures of massively parallel platforms. In this article, a numerical algorithm based on the quasiadiabatic propagator path integral scheme is proposed and shown to scale for systems with large size. As a case study of performance, the quantum dynamics of excitation energy transfer in the Fenna-Matthews-Olson complex is discussed, employing a vibronic model in which the system size can be varied simply by adding vibrational excitations.