bluuebunny/crossref_metadata_2025 huggingface dataset:
Graph‐based iterative measurement‐denoising and radio‐map generation for semi‐supervised indoor localisation
Authors: Fallah Maryam , Pourahmadi Vahid
Published: February 2018

This study considers the problem of indoor localisation in which the authors try to generate the radio map of the environment based on both labelled and unlabelled measurements (i.e. measurements with and without information about the location that they have been collected). In such problems, the method that has been used for radio‐map generation as well as the quality of the measurements (the received signal strength from different environment's WiFi Access Points) are very critical in the overall accuracy of the generated radio map. In this study, they apply two of the well‐known graph‐based signal processing schemes (namely iterative least square reconstruction and graph‐based label propagation) for polishing the input data, determining the outliers and radio‐map generation. Experimental results show the superior performance of the proposed method compared to previous schemes.
Various skewing arrangements and relative position of dual rotor of an axial fluxinduction motor, modelling and performance evaluation
Authors: Nobahari Amin , Darabi Ahmad , Hassannia Amir
Published: February 2018

Using a dual air‐gap structure in a disc‐type motor is an effective solution to eliminate undesirable axial force between stator and rotor, by which higher power density can be achieved, too. Furthermore, some of the performance characteristics such as pulsating torque may be improved greatly by adjusting the existing extra selective design parameters in a dual air‐gap motor. Accordingly, in this study, a widespread design consideration is carried out on rotor skewing arrangements of a dual rotor (DR) axial flux induction motor with the aim of pulsating torque reduction. The studied scenarios include when the slots of both rotors are skewed exactly similar with different skew angles, the slots of both rotors are skewed similarly but in the opposite directions and the slots of both rotors are not skewed but one rotor is mounted on the shaft by some shift angle relative to the other. The last one is introduced as an alternative to skewed rotors, which is easily executable in small and large size motors with DR topology. Moreover, an algorithm is proposed to determine the appropriate shift angle. Three‐dimensional time stepping finite element analysis is employed in all cases for verification.
Three‐phase current injection method for mitigating turn‐to‐turn short‐circuit fault in concentrated‐winding permanent magnet aircraft starter generator
Authors: Jiang Yunyi , Zhang Zhuoran , Jiang Wenying , Geng Weiwei , Huang Jian
Published: February 2018

Fractional‐slot concentrated‐winding (FSCW) permanent magnet synchronous machines, which are characterised with high power density, fault tolerance and wide constant‐power speed range, are gaining more and more attention in the aircraft starter generator (SG) systems. Nevertheless, the short‐circuit (SC) fault, especially the turn‐to‐turn SC fault, is the obstruct crux in aviation applications. This study is aimed to demonstrate the feasibility of FSCW permanent magnet SG (PMSG) in dealing with turn‐to‐turn SC fault. The law of FSCW‐PMSG SC fault is analysed and verified by finite‐element analysis (FEA), including the influence on turn‐to‐turn SC current by the number of the shorted turns and the coil position in the slot. The three‐phase current injection control is employed to mitigate the SC fault in PMSG when a turn‐to‐turn SC fault occurs. A 24‐slot, 16‐pole FSCW‐PMSG with spoke‐type rotor topology is designed to confirm the ability of inhibiting turn‐to‐turn SC current without the risk of irreversible demagnetisation. Both FEA and experimental results are presented, verifying the effectiveness of the three‐phase current injection control in restraining the turn‐to‐turn SC current for FSCW PMSG in an acceptable range.
Understanding DC‐side high‐frequency resonance in MMC‐HVDC system
Authors: Li Chang , Li Yong , Cao Yijia , Zhu Hongqi , Rehtanz Christian , Häger Ulf
Published: February 2018

Instability on direct‐current (DC)‐side resonance occurs if the connected converters interact with the DC network. In this study, a single‐input–single‐output transfer function is built to investigate the DC‐side resonance of modular multilevel converter‐based high‐voltage DC (MMC‐HVDC) system. The small signal model is developed for the DC‐side resonance of an MMC‐HVDC system. Furthermore, the system can be separated into two subsystems, i.e. H (s) and G (s). This study shows that both amplitudes of H (s), i.e. Abs [H (s)] and resonance peak of G (s) affect the encirclement radius of the Nyquist curve, and the encirclement radius reaches the largest at the resonance frequency. More importantly, the power transfer capability is restricted by the DC‐side resonance since the more transmitted power leads to larger Abs [H (s)]. The impedance model is verified by both time‐domain simulations and frequency responses imposed by impedance frequency scan in power systems computer‐aided design/electro‐magnetic transient design and control. Besides, an active damping control approach is introduced to suppress the resonance on DC side.
Simulation–optimisation framework for City Logistics: an application on multimodal last‐mile delivery
Authors: Perboli Guido , Rosano Mariangela , Saint‐Guillain Michael , Rizzo Pietro
Published: February 2018

City Logistics has attracted considerable interest from the operations research and logistics communities during past decades. It resulted in a broad variety of promising approaches from different fields of combinatorial optimisation. However, research on urban freight transportation is currently slowing down due to two different lacks, limiting the exploratory capacity and compromise the technology transfer to the industry. First, the majority of the instances in the literature are based on the generalisation of classical instances, often not created for urban applications, or on artificial data, i.e. data not coming from any historical or empirical datasets. Thus, the validation of models and methods becomes more difficult, being the results not directly compared with real or realistic settings. Second, even when some data sources become available, there is no standard way to mixing data gathered from different sources and, from them, generate new instances for urban applications. This study aims to overcome these issues, proposing a simulation–optimisation framework for building instances and assess operational settings. To illustrate the usefulness of the framework, the authors conduct a case study, in order to evaluate the impact of multimodal delivery options to face the demand from e‐commerce, in an urban context as Turin (Italy).
Multidisciplinary collaborative optimisation‐based scenarios decoupling dynamic economic dispatch with wind power
Authors: Xie Min , Luo Wenhao , Cheng Peijun , Ke Shaojia , Ji Xiang , Liu Mingbo
Published: February 2018

Multidisciplinary collaborative optimisation (MCO) is an effective theory to solve the design optimisation problems of complex systems. Here, power‐system day‐ahead dynamic economic dispatch with integrated wind power is studied. The MCO method is introduced to decouple the scenarios and collaboratively optimise the multiple scenarios to deal with the uncertainty of wind‐power generation. Based on this, the dynamic economic‐dispatch problem is divided into a system‐level model and multiple subdisciplinary optimisation models for the forecasting and error scenarios. A dynamic relaxation algorithm is then introduced to solve the system‐level optimisation model. The decoupled subdisciplinary models for the error scenarios are solved by a grid‐computation tool in parallel, which greatly improves computational efficiency. Finally, the established model and its corresponding solution method are applied to a 10‐machine, 39‐bus test system. It is shown that the proposed MCO‐based dynamic economic dispatching method performs much better in high‐dimensional scenarios, which are the inherent limitations of the traditional centralised multi‐scenario method.
Asymmetric emission of the [OIII]λ5007 profile in narrow-line Seyfert 1 galaxies
Authors: Schmidt E. O. , Oio G. A. , Ferreiro D. , Vega L. , Weidmann W.
Published: February 2018

Context. Many active galactic nuclei (AGN) and particularly narrow-line Seyfert 1 (NLS1) galaxies, usually exhibit blueshifts and blue wings in several emission lines, which are mainly associated with outflows and strong winds. Although there is no clear evidence of the physical origin of the [OIII] blue wings, it has been suggested that they could be emitted from the inner parts of the narrow-line region (NLR).

Aims. In order to study the radial velocity difference between the narrow component of Hβ and the core component of [OIII]λ5007 and the asymmetric emission of this forbidden line, we investigate a sample of NLS1 galaxies. One of the aims of this paper is to analyze the blue wings of the [OIII] 5007 profiles and their relation with the central engine.

Methods. We have obtained and studied medium-resolution spectra (190 km s−1 FWHM at Hβ) of a sample of 28 NLS1 galaxies in the optical range 4300–5200 Å. We performed Gaussian decomposition to the Hβ and [OIII]λλ 4959,5007 emission profiles in order to study the distinct components of these lines.

Results. A new blue outlier galaxy is found, in which the center of the core component of [OIII] is blueshifted by 405 km s−1 relative to the center of the narrow component of Hβ line. We confirmed a previously known correlation between the blueshift and the full width half maximum (FWHM) of the core component of [OIII]λ5007 line. We also corroborated the correlation between the latter and the velocity of the centroid of the blue wing. On the other hand, by studying the radial velocity difference between the blue end of the asymmetric emission and the centroid of the core component of [OIII], we found a correlation between it and the central black hole mass and, therefore, with the luminosity of the broad component of Hβ. Finally, we found a moderate correlation between the luminosity of the [OIII] blue wing and the black hole mass.

Conclusions. These results suggest that the asymmetric emission of the [OIII] lines is related to the central engine, not only through the black hole but also in the intensity of the AGN, which is in agreement with previous results.
One-Pot Synthesis of 1-Monosubstituted 1,2,3-Triazoles from Propargyl Alcohol
Authors: Chen Zhen , Han Chunmei , Dong Suping , Zhang Wensheng
Published: February 2018

A one-pot synthesis of 1-monosubstituted-1,2,3-triazoles from propargyl alcohol and various aryl azides was achieved. This simple method provides concise and efficient access to various 1-monosubstituted 1,2,3-triazole derivatives through a three-step one-pot ­sequence in good to excellent yields.
Short Synthesis of Phenylpropanoid Glycosides Calceolarioside A and Syringalide B
Authors: Judeh Zaher , Khong Duc
Published: February 2018

An efficient and practical three-step synthesis of phenylpropanoid glycosides calceolarioside A and syringalide B in >62% overall yield is disclosed. The key step involves the chemoselective and regio­selective direct O-4 cinnamoylation of unprotected 2-phenylethyl-β-d-glucosides with cinnamic anhydrides using a chiral 4-pyrrolidinopyridine organocatalyst. This approach serves as a model for the short synthesis of phenylpropanoid glycosides acylated at O-4 without protection/deprotection steps.
Regioselective Approach to 5-Carboxy-1,2,3-triazoles Based on Palladium-Catalyzed Carbonylation
Authors: Latyshev Gennadij , Kotovshchikov Yury , Beletskaya Irina , Lukashev Nikolay
Published: February 2018

A regioselective two-step approach to 5-carboxy-1,2,3-triazoles based on palladium-catalyzed carbonylation has been developed. The protocol utilizes readily available 5-iodotriazoles as starting materials. The obtained products were used in the syntheses of fused heterocycles as well as derivatization of the steroidal hormone cortexolone­.
Efficient Biginelli Synthesis of 2-Aminodihydropyrimidines under Microwave Irradiation
Authors: Felluga Fulvia , Benedetti Fabio , Berti Federico , Drioli Sara , Regini Giorgia
Published: February 2018

A practical and general method for the Biginelli cyclocondensation of guanidine with aldehydes and β-dicarbonyl compounds is described and illustrated with the synthesis of a set of 26 functionalized 2-amino-3,4-dihydropyrimidines. The simple protocol involves the ­microwave-mediated reaction of a twofold excess of guanidine hydrochloride with the required reaction partners in an alcohol at 120 °C. Yields are generally good, with short reaction times and a simple workup. The scope is considerably wider than that of similar reactions ­carried out under conventional heating.
Exploring Data Quality Management within Clinical Trials
Authors: Houston Lauren , Probst Yasmine , Yu Ping , Martin Allison
Published: February 2018

Background Clinical trials are an important research method for improving medical knowledge and patient care. Multiple international and national guidelines stipulate the need for data quality and assurance. Many strategies and interventions are developed to reduce error in trials, including standard operating procedures, personnel training, data monitoring, and design of case report forms. However, guidelines are nonspecific in the nature and extent of necessary methods.

Objective This article gathers information about current data quality tools and procedures used within Australian clinical trial sites, with the aim to develop standard data quality monitoring procedures to ensure data integrity.

Methods Relevant information about data quality management methods and procedures, error levels, data monitoring, staff training, and development were collected. Staff members from 142 clinical trials listed on the National Health and Medical Research Council (NHMRC) clinical trials Web site were invited to complete a short self-reported semiquantitative anonymous online survey.

Results Twenty (14%) clinical trials completed the survey. Results from the survey indicate that procedures to ensure data quality varies among clinical trial sites. Centralized monitoring (65%) was the most common procedure to ensure high-quality data. Ten (50%) trials reported having a data management plan in place and two sites utilized an error acceptance level to minimize discrepancy, set at <5% and 5 to 10%, respectively. The quantity of data variables checked (10–100%), the frequency of visits (once-a-month to annually), and types of variables (100%, critical data or critical and noncritical data audits) for data monitoring varied among respondents. The average time spent on staff training per person was 11.58 hours over a 12-month period and the type of training was diverse.

Conclusion Clinical trial sites are implementing ad hoc methods pragmatically to ensure data quality. Findings highlight the necessity for further research into “standard practice” focusing on developing and implementing publicly available data quality monitoring procedures.
Diet, Microbiome and Multiple Sclerosis
Authors: Haghikia Aiden , Linker Ralf
Published: February 2018

During recent years, research into the causes of multiple sclerosis (MS), especially in the field of genetic risks of this disease, has made immense advances, thanks to new molecular biology techniques and large consortia. However, the functional relevance of disease-associated risk gene variants remains unclear, and representing about one-third of the overall risk compared to environmental risk factors, plays a smaller role. Thus, the further identification and, where appropriate, prevention of environmental risks is currently the focus of research. Here recently, risk factors for MS have been shown which are closely related to Western diet and lifestyle, such as high consumption of salt and cigarette smoking. In addition, the human gut continues to be the focus of research: with its large surface, the gut offers immense opportunities for interaction between intestinal bacteria, food and their metabolic products, as well as the immune system associated with the gut. In the present paper, we summarize the findings of the constantly growing research field dealing with the gut, nutrition and MS, and discuss how these findings, as shown recently for fatty acids, could have translational-therapeutic potential.
Usefulness of cholangioscopic-guided mapping biopsy using SpyGlass DS for preoperative evaluation of extrahepatic cholangiocarcinoma: a pilot study
Authors: Ogawa Takahisa , Ito Kei , Koshita Shinsuke , Kanno Yoshihide , Masu Kaori , Kusunose Hiroaki , Sakai Toshitaka , Murabayashi Toji , Hasegawa Sho , Noda Yutaka
Published: February 2018

Background and study aims Evaluation of longitudinal tumor extent is indispensable for curative surgical treatment of extrahepatic cholangiocarcinoma. The aim of this study was to evaluate the usefulness and feasibility of cholangioscopic-guided mapping biopsy using a newly developed peroral digital cholangioscope, SpyGlass DS (SpyDS), for preoperative evaluation of extrahepatic cholangiocarcinoma.

Patients and methods Thirteen patients (mean age, 75 years; male 10, female 3) with extrahepatic cholangiocarcinoma who underwent cholangioscopic-guided mapping biopsy using SpyDS for preoperative evaluation were included in this study. Successful cholangioscopic-guided mapping biopsy was defined as the acquisition of specimens sufficient for histopathological diagnosis.

Results The mean number of biopsies was 5 per patient. The overall success rate for cholangioscopic-guided mapping biopsy was 88 % (59/67). The success rate for cholangioscopic-guided mapping biopsy from the confluence of the right and left hepatic ducts was 89 %, that from the B4 confluence was 93 %, that from the confluence of the right anterior and right posterior segmental ducts was 86 %, that from the intrapancreatic common bile duct was 67 %, and that from the main lesion was 100 %. The overall diagnostic accuracy of longitudinal tumor extent at the hepatic side, the duodenal side and overall by cholangioscopic findings and mapping biopsy, was 88 % (7/8), 88 % (7/8) and 88 % (7/8), respectively. Assessment according to location of the main lesion revealed that diagnostic accuracy in the patients with distal bile duct carcinoma was 100 % (5/5) and that in patients with perihilar bile duct carcinoma was 66 % (2/3). Complications after the procedure did not occur in any patients.

Conclusions Cholangioscopic-guided mapping biopsy using SpyDS is thought to be feasible for preoperative evaluation of extrahepatic cholangiocarcinoma.
Operative Therapie der weiblichen Inkontinenz
Authors: Zugor Vahudin , Akbarov Ilgar , Karapanos Leonidas , Heidenreich Axel
Published: February 2018

Die weibliche Belastungsinkontinenz stellt ein weit verbreitetes Problem dar. So sind in Deutschland etwa 4 – 5 Millionen Frauen davon betroffen. Die Zahl von Patientinnen wird aufgrund der demografischen Entwicklung in Zukunft weiter steigen. Auch muss aufgrund der Tabuisierung des Themas von einer hohen Dunkelziffer an betroffenen Patientinnen ausgegangen werden. Die weibliche Harninkontinenz wird von der International Continence Society (ICS) als jeder unwillkürliche Urinverlust bezeichnet, der objektiv nachweisbar ist und zudem zu sozialer Beeinträchtigung führt.

Voraussetzung für eine erfolgreiche Behandlung ist eine gründliche urologische Untersuchung zur Evaluation der Art und der Ursache der Inkontinenz. Hierzu sind neben einer gezielten Anamnese der genauen Art der Inkontinenzsymptome und einer körperlichen Untersuchung des Genitalbereiches ggf. auch weiterführende Ultraschall- und Röntgenuntersuchungen der Blase notwendig. Ebenfalls können zur Evaluation der Blasenfunktion eine urodynamische Untersuchung sowie eine Zystoskopie zur Diagnostik notwendig sein.

Die Therapieoptionen der Belastungsinkontinenz beinhalten zuerst konservative Maßnahmen wie eine Gewichtsreduktion und eine physiotherapeutische Beübung des Beckenbodens, weitere Möglichkeiten sind eine Elektrostimulation, Konus- sowie Pessar-Therapien und bei Bedarf eine lokale Östrogenisierung in der Postmenopause oder auch ein medikamentöser Therapieversuch mit Serotonin-Noradrenalin-Rezeptoren-Inhibitor (Duloxetin). Bei Versagen der konservativen Therapieoptionen sollte eine operative Therapie mit den Patientinnen besprochen werden.

Neben aufwendigen offen-operativen Verfahren der früheren Jahrzehnte wie der Kolposuspension oder der Faszienzügelplastiken haben sich in den letzten Jahrzehnten zunehmend minimal-invasive Techniken etabliert, die einfach und schnell durchführbar sind sowie wenig belastend für die Patientinnen und die Belastungsinkontinenz zuverlässig und nachhaltig therapieren. Die spannungsfreien, mitturethralen Schlingen können mittlerweile als etablierte und weitverbreitete Techniken in der Behandlung der Belastungsinkontinenz bezeichnet werden. Die Implantation eines artifiziellen Sphinkters hat sich als sichere und verlässliche Methode zur Behandlung der weiblichen Belastungsinkontinenz höheren Grades und unterschiedlicher Ätiologie erwiesen, bleibt aktuell aber Spezialfällen vorbehalten.
OCT Angiography of the Central Macular Capillary Network in Glaucoma Patients and Healthy Controls
Authors: Müller Olena , Todorova Margarita G. , Schlote Torsten
Published: February 2018

Purpose We aimed to investigate central macular microvasculature by optical coherence tomography angiography (OCTA) and to analyse its relation to alterations in classical parameters of optical coherence tomography (OCT) in glaucoma patients.

Methods Using OCTA (Avanti incl. AngioVue; Optovue, Inc., Fremont, CA), the superficial flow (SF) and the superficial non-flow (SNF) area of the macula, as well as the S-ETDRS (based on Early Treatment Diabetic Retinopathy charts). and S-grid vessel density (zones 1 – 9) of the macula, were evaluated in 27 glaucoma patients (49 eyes) and compared to those of 27 age-matched healthy controls (50 eyes; p = 0.253). The interactions between OCTA parameters representing macular microvasculature and classical OCT measurements of the circumpapillary retinal nerve fibre layer (RNFL) and macular ganglion cells (mGCC) were analysed within groups (linear mixed-effects model).

Results SF, SNF, and S-ETDRS vessel density exhibited no significant difference between the glaucoma and control groups (all p ≥ 0.158). However, within the glaucoma group, decreased RNFL and mGCC thickness correlated significantly with decreased S-ETDRS density (zones 1; 2 – 9, p ≤ 0.033). The same held true for the interactions between the RNFL and mGCC thickness with S-grid density (zones 1 – 3; 6 – 9; p ≤ 0.033). For perimetric glaucoma patients, subgroup analyses demonstrated significantly reduced density maps of superficial foveal flow as well as significant interactions between OCT and OCTA parameters; this was not the case within the preperimetric group.

Conclusions Even if the central macular microvasculature, as measured by SF and SNF, is found preserved in glaucoma, the strong positive relation between the central microvascular and structural changes in OCTA and OCT indicates that there are alterations in central macular microvasculature in subclinical glaucoma.
Anreicherung eines GKV-Datensatzes mit amtlichen Todesursachen über einen Abgleich mit dem Epidemiologischen Krebsregister Nordrhein-Westfalen: Machbarkeitsstudie und Methodenvergleich
Authors: Langner Ingo , Krieg Volker , Heidinger Oliver , Hense Hans Werner , Zeeb Hajo
Published: February 2018

Ziel der Studie Für die Evaluation von Krebsvorsorgeprogrammen stellen Daten der Gesetzlichen Krankenversicherung (GKV) eine wichtige Datenquelle dar, die jedoch nicht die benötigten Daten zum genauen Sterbedatum und zur Todesursache enthält. Diese Studie sollte prüfen, ob eine diesbezügliche Anreicherung individueller GKV-Daten über einen Abgleich mit einer geeigneten externen Datenquelle erfolgen kann.

Methodik In der pharmako-epidemiologischen Forschungsdatenbank GePaRD identifizierten wir eine Versichertenstichprobe von 25 528 Frauen, die laut den Angaben in GePaRD im Zeitraum 2006–2013 verstorben waren und ihren Wohnsitz in Nordrhein-Westfalen (NRW) hatten. Datum und Ursache des Todes aller Einwohner von NRW seit 2005 liegen im Epidemiologischen Krebsregister von NRW vor. In Kooperation mit 2 gesetzlichen Krankenkassen wurde mit einem probabilistischen bzw. deterministischen Abgleichverfahren versucht, jeder Verstorbenen der Stichprobe einen Todesfall aus NRW und damit eine Todesursache zuzuordnen.

Ergebnisse Für 94,72% der Verstorbenen der Versichertenstichprobe konnte probabilistisch und für 93,36% deterministisch ein Todesfall aus NRW zugeordnet werden.

Schlussfolgerung Das probabilistische und das deterministische Verfahren erreichten vergleichbar hohe Trefferquoten. Nicht erfolgte Zuordnungen sind vermutlich größtenteils auf Fehler bei der Erfassung der Personendaten zurückzuführen. Aufgrund des geringeren technischen Aufwands erscheint das deterministische Verfahren als die Methode der Wahl für die Anreicherung von GKV-Daten mit amtlichen Todesursachen aus geeigneten externen Datenquellen.
Antral Follicle Diameter Variance Within Each Ovary May Be A Predictor For Poor Response In Cases With Normal Ovarian Reserve
Authors: Sanverdi Ilhan , Ozkaya Enis , Kucur Suna , Bilen Dilsat , Eken Meryem , Bilgic Bulent
Published: February 2018

Objectives To determine the predictive value of antral follicle diameter variance within each ovary for ovarian response in cases with normal ovarian reserve tests.

Methods This is a prospective observational study. One hundred and thirty nine infertile women who underwent ART in IVF-ICSI unit of Zeynep Kamil women and children’s Health Training and research hospital between January 2017 to June 2017 were recruited. Blood samples were collected on day 2/day 3 for assessment of serum FSH and estradiol. Trans-vaginal sonography was done for antral follicle count. During antral follicle count, in order to determine antral follicle diameter variance, diameters of the largest and smallest follicles were recorded. Variance was calculated by subtracting the smallest diameter from the largest one. Following ovarian stimulation with antagonist protocol, poor response was determined in cases with total oocyte number≤3. Ovarian reserve tests and antral follicle diameter variance were utilized to predict cases with poor response in women with normal ovarian reserve.

Results Antral follicle diameter variance both in right (AUC=0.737, P<0.001) and left (AUC=0.651, P<0.05) ovaries significantly predicted poor ovarian response. Variance>3.5 mm was found to have 75% sensitivity to predict poor response. Basal serum FSH with estradiol levels and AFC failed to predict poor response (P>0.05). Other significant predictors for poor response were day 5 estradiol level and estradiol level at trigger day (P<0.05). In multivariate regression analysis, both AFC and antral follicle diameter variance in the right ovary were found to be significantly associated with clinical pregnancy, on the other hand peak estradiol concentration and antral follicle diameter variance in the right ovary were significantly associated with poor response.

Conclusion Antral follicle diameter variance may be utilized to predict poor ovarian response in cases with normal ovarian reserve.
Feasibility of a Single Contrast Bolus High-Pitch Pulmonary CT Angiography Protocol Followed by Low-Dose Retrospectively ECG-Gated Cardiac CT in Patients with Suspected Pulmonary Embolism
Authors: Schäfer Julia , Haubenreisser Holger , Meyer Mathias , Grüttner Joachim , Walter Thomas , Borggrefe Martin , Schoepf Joseph , Nance John , Schönberg Stefan , Henzler Thomas
Published: February 2018

Introduction To prospectively evaluate the feasibility of single contrast bolus high-pitch CT pulmonary angiography (CTPA) subsequently followed by low-dose retrospectively ECG-gated cardiac CT (4D-cCT) in patients with suspected pulmonary embolism (PE) to accurately evaluate right ventricular (RV) function.

Materials and Methods 62 patients (33 female, age 65.1 ± 17.5 years) underwent high-pitch CTPA examination with 80cc of iodinated contrast material. 5 s after the end of the high-pitch CTPA study, a low-dose retrospectively ECG-gated cardiac CT examination was automatically started. The volume CT dose index (CTDI vol) and dose length product (DLP) were recorded in all patients and the effective dose was calculated. For the assessment of image quality, attenuation was measured as Hounsfield units (HUs) within various regions of interest (ROIs). These ROIs were used to calculate the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). Subjective image quality was assessed using a five-point Likert scale. On 4D-cCT, the ejection fraction of both ventricles (RVEF, LVEF) as well as the ratio of RVEF and LVEF (RVEF/LVEF) was assessed. The statistical difference of all parameters between the PE and non-PE group was calculated.

Results The mean effective radiation dose was 4.22 ± 2.05 mSv. Attenuation measurements on CTPA showed the highest attenuation values in the main pulmonary artery (442.01 ± 187.64). On 4D-cCT attenuation values were highest in the descending aorta (560.59 ± 208.81). The CNR and SNR values on CTPA were highest within the main pulmonary artery (CNR = 12.43 ± 4.57; SNR = 15.14 ± 4.90). On 4D-cCT images, the highest SNR and CNR could be measured in the descending aorta (CNR = 10.26 ± 5.57; SNR = 10.86 ± 5.17). The mean LVEF was 60.73 %± 14.65 %, and the mean RVEF was 44.90 %± 9.54 %. The mean RVEF/LVEF was 0.79 ± 0.29. There was no significant difference between the PE and non-PE group for either of the parameters.

Conclusion The investigated combined CTPA and 4D-cCT protocol is feasible using a single contrast bolus and allows the evaluation of RV function in patients with suspected PE. Further studies have to evaluate the additional value of this protocol regarding risk stratification in patients with PE.

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Glass-like stress relaxation of a permanent gelatin network as a signature of pretransitional helix-coil fluctuations
Authors: Caroli Christiane , Ronsin Olivier , Lemaître Anaël
Published: February 2018

The stress response of permanently crosslinked gelatin gels was recently observed to display glass-like features, namely, a stretched-exponential behavior terminated by an exponential decay, the characteristic time scales of which increase dramatically with decreasing temperature. This phenomenon is studied here using a model of flexible polymer gel network where relaxation proceeds via elementary monomer exchanges between helix and coil segments. The relaxation dynamics of a full network simulation is found to be nearly identical to that of a model of independent strands, which shows that for flexible polymer gels in the range of elastic moduli of interest, both strand contour length disorder and elastic couplings are irrelevant. We thus focus on the independent strand model and find it not only to explain the observed functional form of the stress relaxation curves but also to yield predictions that match very satisfactorily the experimental measurements of final relaxation time and total stress drop. The system under study thus constitutes a rare case where the origin of glass-like behavior can be unambiguously identified, namely, as the signature of the enhancement of helix content fluctuations when approaching from above the mean-field helix-coil transition of strands.
Optically adjustable valley Hall current in single-layer transition metal dichalcogenides
Authors: Sengupta Parijat , Pavlidis Dimitris , Shi Junxia
Published: February 2018

The illumination of a single-layer transition metal dichalcogenide with an elliptically polarized light beam is shown to give rise to a differential rate of inter-band carrier excitation between the valence and conduction states around the valley edges, K and K′. This rate with a linear dependence on the beam ellipticity and inverse of the optical gap manifests as an asymmetric Fermi distribution between the valleys or a non-equilibrium population which under an external field and a Berry curvature induced anomalous velocity, results in an externally tunable finite valley Hall current. Surface imperfections that influence the excitation rates are included through the self-consistent Born approximation. Further, we describe applications centered around circular dichroism, quantum computing, and spin torque via optically excited spin currents within the framework of the suggested formalism. A closing summary points to the possibility of extending the calculations to composite charged particles like trions. The role of the substrate in renormalizing the fundamental band gap and moderating the valley Hall current is also discussed.
Expedite random structure searching using objects from Wyckoff positions
Authors: Wang Shu-Wei , Hsing Cheng-Rong , Wei Ching-Ming
Published: February 2018

Random structure searching has been proved to be a powerful approach to search and find the global minimum and the metastable structures. A true random sampling is in principle needed yet it would be highly time-consuming and/or practically impossible to find the global minimum for the complicated systems in their high-dimensional configuration space. Thus the implementations of reasonable constraints, such as adopting system symmetries to reduce the independent dimension in structural space and/or imposing chemical information to reach and relax into low-energy regions, are the most essential issues in the approach. In this paper, we propose the concept of “object” which is either an atom or composed of a set of atoms (such as molecules or carbonates) carrying a symmetry defined by one of the Wyckoff positions of space group and through this process it allows the searching of global minimum for a complicated system to be confined in a greatly reduced structural space and becomes accessible in practice. We examined several representative materials, including Cd3As2 crystal, solid methanol, high-pressure carbonates (FeCO3), and Si(111)-7 × 7 reconstructed surface, to demonstrate the power and the advantages of using “object” concept in random structure searching.
Influence of dust particles on DC glow discharge plasma
Authors: Liang Yonggan , Yuan Chengxun , Li Hui , Tian Ruihuan , Wu Jian , Kudryavtsev A. A. , Zhou Zhongxiang , Tian Hao
Published: February 2018

The effect of dust particles on DC glow discharge plasma parameters is studied numerically through the development of a self-consistent model based on the extended fluid approach. The orbital motion limited theory and collision enhanced collection approximation are employed to describe the charging processes of dust particles with various sizes and densities. The uniform distribution of dust particles in plasma and the instantaneous charging process were assumed during simulations. The influence of dust particle size rd and density Nd on gas discharge and dust particle parameters is investigated systematically. It is shown that the plasma parameters can be affected obviously by the dust particles. The increase in the values of rd and Nd leads to the decrease in the dust particle charge number, electron, and ion density. Meanwhile, the appearance of dust particles leads to an obvious increase in the averaged plasma electric field and electron temperature to sustain the discharge in the dust region. The dust particles are proven to be a very efficient way to artificially manipulate gas discharge parameters.
Spatially dependent carrier dynamics in single InGaN/GaN core-shell microrod by time-resolved cathodoluminescence
Authors: Liu W. , Mounir C. , Rossbach G. , Schimpke T. , Avramescu A. , Lugauer H.-J. , Strassburg M. , Schwarz U. , Deveaud B. , Jacopin G.
Published: February 2018

The optical properties of InGaN/GaN core-shell microrods are studied by time-resolved cathodoluminescence. Probing the carrier dynamics along the length of the rod from 4 to 300 K enables us to decompose radiative (τr) and non-radiative (τnr) lifetimes. At 300 K, τnr decreases from 500 at the bottom of the rod to 150 ps at its top. This variation results from an increased In-content in the upper part of the rod that causes a higher density of point defects. We further observe that thanks to the use of nonpolar m-plane growth, τr remains below 1.5 ns up to room temperature even with a thick active layer, which is promising for pushing the onset of the efficiency droop to higher current densities.
Force feedback effects on single molecule hopping and pulling experiments
Authors: Rico-Pasto M. , Pastor I. , Ritort F.
Published: February 2018

Single-molecule experiments with optical tweezers have become an important tool to study the properties and mechanisms of biological systems, such as cells and nucleic acids. In particular, force unzipping experiments have been used to extract the thermodynamics and kinetics of folding and unfolding reactions. In hopping experiments, a molecule executes transitions between the unfolded and folded states at a preset value of the force [constant force mode (CFM) under force feedback] or trap position [passive mode (PM) without feedback] and the force-dependent kinetic rates extracted from the lifetime of each state (CFM) and the rupture force distributions (PM) using the Bell-Evans model. However, hopping experiments in the CFM are known to overestimate molecular distances and folding free energies for fast transitions compared to the response time of the feedback. In contrast, kinetic rate measurements from pulling experiments have been mostly done in the PM while the CFM is seldom implemented in pulling protocols. Here, we carry out hopping and pulling experiments in a short DNA hairpin in the PM and CFM at three different temperatures (6 °C, 25 °C, and 45 °C) exhibiting largely varying kinetic rates. As expected, we find that equilibrium hopping experiments in the CFM and PM perform well at 6 °C (where kinetics are slow), whereas the CFM overestimates molecular parameters at 45 °C (where kinetics are fast). In contrast, nonequilibrium pulling experiments perform well in both modes at all temperatures. This demonstrates that the same kind of feedback algorithm in the CFM leads to more reliable determination of the folding reaction parameters in irreversible pulling experiments.
The regimes of twin-fluid jet-in-crossflow at atmospheric and jet-engine operating conditions
Authors: Tan Zu Puayen , Bibik Oleksandr , Shcherbik Dmitriy , Zinn Ben T. , Patel Nayan
Published: February 2018

The “Twin-Fluid Jet-in-Crossflow (TF-JICF)” is a nascent variation of the classical JICF, in which a liquid jet is co-injected with an annular sleeve of gas into a gaseous crossflow. Jet-engine designers are interested in using TF-JICF for liquid-fuel injection and atomization in the next-generation combustors because it is expected to minimize combustor-damaging auto-ignition and fuel-coking tendencies. However, experimental data of TF-JICF are sparse. Furthermore, a widely accepted TF-JICF model that correlates the spray’s penetration to the combined liquid-gas momentum-flux ratio (Jeff) is increasingly showing discrepancy with emerging results, suggesting a gap in the current understanding of TF-JICF. This paper describes an investigation that addressed the gap by experimentally characterizing the TF-JICF produced by a single injector across wide ranges of operating conditions (i.e., jet-A injectant, crossflow of air, crossflow Weber number = 175-1050, crossflow pressure Pcf = 1.8-9.5 atm, momentum-flux ratio J = 5-40, and air-nozzle dP = 0%-150% of Pcf). These covered the conditions previously used to develop the Jeff model, recently reported conditions that produced Jeff discrepancies, and high-pressure conditions found in jet-engines. Dye-based shadowgraph was used to acquire high-resolution (13.52 μm/pixel) images of the TF-JICF, which revealed wide-ranging characteristics such as the disrupted Rayleigh-Taylor jet instabilities, air-induced jet corrugations, spray-bifurcations, and prompt-atomization. Analyses of the data showed that contrary to the literature, the TF-JICF’s penetration is not monotonically related to Jeff. A new conceptual framework for TF-JICF is proposed, where the flow configuration is composed of four regimes, each having different penetration trends, spray structures, and underlying mechanisms.
Electronic structure, defect formation energy, and photovoltaic properties of wurtzite-derived CuGaO2
Authors: Okumura H. , Sato K. , Kakeshita T.
Published: February 2018

Wurtzite-derived CuGaO2 (β-CuGaO2) is a recently synthesized oxide and expected as a candidate material for photovoltaic solar cells. In this paper, we propose computational material design concerning β-CuGaO2 based on the first-principles calculations. We perform hybrid calculations by using the VASP code. It is predicted that β-CuGaO2 has a direct bandgap (Eg = 1.56 eV), which is nearly optimal for high efficiency solar cells. The calculated formation energy of Cu vacancy (VCu) is very small and can be negative depending on the Fermi level. This result reasonably explains the observed p-type conduction in this material. As for the n-type doping, Cd doping could be suitable; however, VCu formation needs to be repressed in order to realize n-type β-CuGaO2. It is also shown that halogen impurities are not suitable for n-type β-CuGaO2 because of their large formation energy. Band alignment between β-CuGaO2 and ZnO is predicted to be type-II, leading to a suggestion of photovoltaic device based on the heterojunction.
A portable extruder for in situ wide angle x-ray scattering study on multi-dimensional flow field induced crystallization of polymer
Authors: Chang Jiarui , Wang Zhen , Tang Xiaoliang , Tian Fucheng , Ye Ke , Li Liangbin
Published: February 2018

We have designed and constructed a portable extruder with a rotatable mandrel, which can be employed to study the multi-dimensional flow field (MDFF) induced crystallization of polymer combined with in situ wide angle x-ray scattering (WAXS). With the piston driving the melt sample to flow along the channel, a direct axial shear field is achieved. At the same time, the central mandrel keeps rotating under a stable speed, providing the sample with an additional circumferential shear field. By presetting different proportions of the two shear fields, namely, axial and circumferential, various flow states of the sample can be obtained, which makes it capable of investigating the effects of MDFF on polymer crystallization. We have performed an in situ WAXS experiment of MDFF induced crystallization of isotactic polypropylene based on the portable extruder at the beam line BL16B in Shanghai Synchrotron Radiation Facility. The rheological and structural information is collected simultaneously, which manifests the viability of the portable extruder on regulating MDFF and can provide guidance for polymer processing.
A classical density functional theory for the asymmetric restricted primitive model of ionic liquids
Authors: Lu Hongduo , Nordholm Sture , Woodward Clifford E. , Forsman Jan
Published: February 2018

A new three-parameter (valency, ion size, and charge asymmetry) model, the asymmetric restricted primitive model (ARPM) of ionic liquids, has recently been proposed. Given that ionic liquids generally are composed of monovalent species, the ARPM effectively reduces to a two-parameter model. Monte Carlo (MC) simulations have demonstrated that the ARPM is able to reproduce key properties of room temperature ionic liquids (RTILs) in bulk and at charged surfaces. The relatively modest complexity of the model raises the possibility, which is explored here, that a classical density functional theory (DFT) could resolve its properties. This is relevant because it might generate great improvements in terms of both numerical efficiency and understanding in the continued research of RTILs and their applications. In this report, a DFT for rod-like molecules is proposed as an approximate theoretical tool for an ARPM fluid. Borrowing data on the ion pair fraction from a single bulk simulation, the ARPM is modelled as a mixture of dissociated ions and connected ion pairs. We have specifically studied an ARPM where the hard-sphere diameter is 5 Å, with the charge located 1 Å from the hard-sphere centre. We focus on fluid structure and electrochemical behaviour of this ARPM fluid, into which a model electrode is immersed. The latter is modelled as a perfect conductor, and surface polarization is handled by the method of image charges. Approximate methods, which were developed in an earlier study, to take image interactions into account, are also incorporated in the DFT. We make direct numerical comparisons between DFT predictions and corresponding simulation data. The DFT theory is implemented both in the normal mean field form with respect to the electrostatic interactions and in a correlated form based on hole formation by both steric repulsions and ion-ion Coulomb interactions. The results clearly show that ion-ion correlations play a very important role in the screening of the charged surfaces by our ARPM ionic liquid. We have studied electrostatic potentials and ion density profiles as well the differential capacitance. The mean-field DFT fails to reproduce these properties, but the inclusion of ion-ion correlation by a simple approximate treatment yields quite reasonable agreement with the corresponding simulation results. An interesting finding is that there appears to be a surface phase transition at relatively low surface charge which is readily explored by DFT, but seen also in the MC simulations at somewhat higher asymmetry.
Note: Development of a multichannel magnetic probe array for magnetohydrodynamic activity studies in Sino-United Spherical Tokamak
Authors: Zhong H. , Tan Y. , Gao Z.
Published: February 2018

A 30-channel movable magnetic probe radial array measuring the poloidal magnetic field’s time derivative Ḃθ has been developed and installed on the Sino-United Spherical Tokamak to investigate the magnetohydrodynamic (MHD) activities in ohmic discharges. The probe array consists of thirty identical commercial chip inductors mounted on a slim printed circuit board and shielded by a customized quartz tube of 14 mm in outer diameter. With the application of instrumentation amplifiers, the system exhibits a good signal to noise ratio and the measured vertical field spatial distribution agrees well with the simulation result. The measured spatial and temporal distribution of Ḃθ during the MHD activities exhibits a clear phase reversal layer, which is a direct proof of tearing mode and provides a reliable indication of the magnetic island chain position.