bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved vector control strategy of linear induction motors for electromagnetic launch
Authors: Han Zhengqing , Xu Jin , Rui Wanzhi , Liu Liu
Published: February 2021

Due to the change of parameters caused by the dynamic longitudinal end effect, the operation characteristics of linear induction motors (LIMs) applied in an electromagnetic launch field are different from that of ordinary LIM. Due to the continuous increase of the LIM port voltage under high acceleration, the phase voltage is close to the inverter output limit. The conventional indirect field‐oriented control (IFOC) strategies of LIM based on the flux attenuation compensation or maximum thrust control cannot solve the problem well. Based on the LIM mathematical model, this study analyses the output thrust characteristics of the LIM and discusses different control methods. This study presents an improved vector control strategy. By dynamically adjusting the value of ‘k’ based on the moving speed of the LIM, the maximum thrust output is maintained at medium and low speeds, and the voltage rise of a motor port is restrained at high speed. The effectiveness of the proposed control method is verified by simulation and experiment. The method proposed in this study is helpful to broaden the application of the LIM in the higher speed field.
Enhanced power generation for total‐cross‐tied PV array using simulated annealing under partial shading conditions
Authors: Sai Krishna Gundluru , Moger Tukaram
Published: February 2021

Shade phenomena affect the PV module's power output, introduce multiple peak points in PV characteristics, and shorten the expected life cycle of the module. In order to prevent this issue, PV modules should reconfigure, namely, altering the electrical connections between PV modules based on the irradiance without changing their physical locations. As a result, the shading effects can distribute over the array and increase power output. This paper proposed a novel reconfiguration technique based on the simulated annealing algorithm to distribute shading impacts on 99 total‐cross‐tied (TCT) PV array. In this work, the proposed algorithm produces a reconfigured connection matrix for 99 TCT array that can minimize the current differences in each row and improve the power output. Various shading conditions have been taken to investigate the proposed technique by obtained global maximum power point (GMPP), current at GMPP, power loss, fill‐factor, and efficiency. Further, the performance of the proposed technique is validated with other existing reconfiguration methods under partial shadings. In comparison with existing methods, the result shows that the proposed simulated annealing enhanced the power generation of the TCT array under all shading patterns.
Assessment accuracy of power system frequency security with additional frequency controls in wind turbines
Authors: Steinkohl Joachim , Wang Xiongfei , Davari Pooya , Blaabjerg Frede
Published: February 2021

Power grids all over the world are nowadays facing high penetrations of renewable power generation. The converter‐based generation units play a major role in system behaviour and operation. Thereby, also the reliability of the power system is impacted in many different aspects. It has to be verified whether the frequency reliability assessment, which is often studied by simulations, is still accurate, every time a new control structure is considered. For this, the number of simulations should not be further increased if possible, in order to keep the computational efforts low. In this study, the authors verify that the assessment outcome will be accurate when the load duration curve (LDC) and wind power curve (WPC) of a system are described well enough. This is shown to be true for different frequency controls, implemented in wind power plants in the system. Besides, the effects of different LDCs and WPCs are analysed, as they can change over time. The used methodology is validated on the IEEE reliability test system (IEEE RTS).
Decoupling of high‐density, dual‐polarized, cross‐dipole arrays using broadband low‐profile composite isolator
Authors: Xiong Dong , Sun Xiaoshuai , Mu Dongmei , Li Mei , Tang Ming‐Chun
Published: February 2021

A low‐profile composite isolator (CI) for the decoupling of broadband, high‐density, dual‐polarized cross‐dipole arrays is introduced and investigated. The CI is composed of periodically resonant strips and a metallic wall, which are etched on both sides of a thin dielectric‐slab and vertically placed above the ground plane. The collaboration between the strips and the wall empowers the CI's broadband operation performance characteristics with low profile (0.16 λ0) and ultra‐thin thickness (0.0045 λ0). A two‐element cross‐dipole array loaded with CI is fabricated and tested to verify its decoupling effect. The two ±45°dual‐polarized cross‐dipole elements with impedance bandwidth of 45% (ranging from 1.7 to 2.7 GHz) are built with centre‐to‐centre distance of 0.45 λ0 (λ0 corresponds to free space wavelength at 1.7 GHz). The measured results, in good agreement with the simulation values, indicated that, after loading CI, the array witnessed 10 dB co‐polarized and 5 dB cross‐polarized isolation improvements while maintaining stable radiation patterns over the entire operational band, without increasing the overall array height.
A simple method for estimating the effectiveness of reactive power‐based low‐voltage ride‐through support of the distributed energy resources
Authors: Swandaru Akbar , Rotaru Mihai D. , Sykulski Jan K.
Published: February 2021

The increasing number of distributed energy resources (DERs) leads to the need for DER that can provide ancillary service, such as low‐voltage ride‐through (LVRT) voltage support. The support is made to improve the short‐term voltage stability in power systems. Recently, DER LVRT voltage support through reactive power regulation are becoming common. Designing LVRT voltage support is highly influenced by the accuracy of the modelling and the data needed. However, in some cases, the required modelling can challenge the computational complexity, effort, and required data. Nevertheless, modelling the systems through an oversimplification may result in inaccuracies and hypothetical solution. Thus, the best compromise between model accuracy and simplicity will alleviate the problem. The study presents a methodology for estimating the effectiveness of the support. Unlike the commonly computer‐assisted approach, such as the dynamic RMS simulation, the benefit of the methodology is on the computing process, which is much simpler since the dynamic DER modelling work is not needed, and the evaluation of the effectiveness can be achieved even when the grid information is incomplete. Its accuracy is validated against typical RMS simulation results obtained using PowerFactory DIgsilent software for well‐characterised networks.
Coordinated fuzzy logic‐based virtual inertia controller and frequency relay scheme for reliable operation of low‐inertia power system
Authors: Said Sayed M. , Aly Mokhtar , Hartmann Bálint , Mohamed Emad A.
Published: February 2021

Coordination between protection and control devices is crucial for maintaining continuous operation of power systems. Existing strategies suffer from improper coordination of control and protection devices. Moreover, high penetration levels of renewable energy sources result in lowering the overall power system inertia. Therefore, this paper presents a robust fuzzy‐logic control (FLC) method for superconducting magnetic energy storage (SMES) in low inertia power systems. The new proposed FLC enables robust and wide operating range for SMES compared to the widely employed controllers. The proposed FLC method and load frequency control are coordinated to emulate virtual inertia. In addition, a cooperate coordination between frequency relay and proposed controller is preserved to maintain reliable operation of low inertia power systems. To prove the effectiveness of proposed coordination strategy, it has been tested with considering different load and renewable energy sources (RESs) disturbances with varying inertia level of the selected case study. The results demonstrate that the proposed FLC method can achieve robust SMES operation as virtual inertia controller (VIC) at wide operating range. Moreover, cooperative operation of VIC and frequency protection is preserved using the proposed coordination strategy. The power system availability, frequency regulation, and dynamic stability are improved using the proposed method.
Analysis of an interleaved control scheme employed in split source inverter based grid‐tied photovoltaic systems
Authors: Nannam Hari Charan , Banerjee Atanu , Guerrero Josep M.
Published: February 2021

In conventional grid‐tied renewable energy applications, the dc–dc converter is inevitable. An increased cost, size, and reduced efficiency are the demerits of incorporating a dc–dc converter. A recently introduced split source inverter (SSI) is capable to perform both dc–dc as well as dcac at a time. The main attractive controllable feature of SSI is its modulation index. By utilizing this parameter, an interleaved control structure is proposed for the SSI in grid‐tied photovoltaic applications. The main objectives of the work are to track peak power and to maintain a stabilized voltage across the dc‐link capacitor at a variable load and grid disturbances. The proposed peak power controller performs two important actions: (i) the peak power is traced at all irradiance and (ii) generates a duty cycle to enhance the dc‐link capacitor voltage. The proposed scheme is essentially investigated with simulation. To validate experimentally, a 1 KW photovoltaic system is integrated into a grid‐tied 10 kVA SSI prototype. A Xilinx based Spartan field‐programmable gate array (FPGA) is used to provide a control algorithm for the SSI. Few case studies at different conditions are performed and investigated. Experimental and simulation results are presented to prove the robustness of the control strategy.
Reduced sensor operation and power quality improvement in grid‐tied doubly fed induction generator using composite and twin frequency generalised integrators
Authors: Das Souvik , Puchalapalli Sambasivaiah , Singh Bhim
Published: February 2021

This study presents a strategy involving a reduction in the stator current sensor count for control of power converters, in a doubly fed induction generator (DFIG)‐based wind energy conversion system (WECS). The reduced sensor vector control scheme is effectively used in lieu of the conventional vector control algorithm during sensor failure without any change in the overall control structure. This keeps the system operational in case of sensor failure. The reduced sensor scheme necessitates precise estimation of stator flux amplitude and an orientation angle, for control of power converters under all operating conditions. A composite generalised integrator phase‐locked loop is presented to estimate accurately the stator flux amplitude and orientation angle, even at operating system irregularities such as unbalanced voltages, lower‐order harmonics in the grid voltage, DC bias in sensing circuitry, and so forth, which otherwise lead to distortions in flux and orientation angle. The grid‐side converter control is based on a twin frequency improved second‐order generalised integrator. It enables fast and accurate power quality improvement in DFIG‐based WECS during load and grid abnormalities. A laboratory prototype is developed to validate the control of the system.
A range error reduction technique for positioning applications in sports
Authors: Waqar Adnan , Ahmad Iftekhar , Habibi Daryoush , Phung Quoc Viet
Published: February 2021

In recent times, ultra‐wideband (UWB)‐based positioning systems have become popular in sport performance monitoring. UWB positioning system uses time of arrival to calculate the range data between devices (i.e. anchors, tags), and then use trilateration algorithms to estimate position coordinates. In practical applications, non‐line‐of‐sight transmissions and multipath propagations lead to inaccurate range data and lower positioning accuracy. This paper introduces a range error minimisation algorithm to address this limitation of error in range data in UWB‐based positioning system. The proposed solution analyses the range error for each anchor and sequentially reduces this error based on the distance between each anchor and the tag. This ultimately contributes to higher positioning accuracies. The authors implemented the proposed algorithm in a hardware test‐bed, evaluating the positioning accuracy for an indoor sport. The proposed algorithm outperforms both the trilateration algorithm and a commercially used positioning algorithm by up to 50% and 25%, respectively.
Characterizing the dust content of disk substructures in TW Hydrae
Authors: Macías E. , Guerra-Alvarado O. , Carrasco-González C. , Ribas Á. , Espaillat C. C. , Huang J. , Andrews S. M.
Published: February 2021

Context. A key piece of information to understand the origin and role of protoplanetary disk substructures is their dust content. In particular, disk substructures associated with gas pressure bumps can work as dust traps, accumulating grains and reaching the necessary conditions to trigger the streaming instability.

Aims. In order to shed some light on the origin and role that disk substructures play in planet formation, we aim to characterize the dust content of substructures in the disk of TW Hya.

Methods. We present Atacama Large Millimeter Array (ALMA) observations of TW Hya at 3.1 mm with ~50 milliarcsecond resolution. These new data were combined with archival high angular resolution ALMA observations at 0.87, 1.3, and 2.1 mm. We analyze these multiwavelength data to infer a disk radial profile of the dust surface density, maximum particle size, and slope of the particle size distribution.

Results. Most previously known annular substructures in the disk of TW Hya are resolved at the four wavelengths. Inside the inner 3 au cavity, the 2.1 and 3.1 mm images show a compact source of free–free emission, likely associated with an ionized jet. Our multiwavelength analysis of the dust emission shows that the maximum particle size in the disk of TW Hya is >1 mm. The inner 20 au are completely optically thick at all four bands, which results in the data tracing different disk heights at different wavelengths. Coupled with the effects of dust settling, this prevents the derivation of accurate density and grain size estimates in these regions. At r > 20 au, we find evidence of the accumulation of large dust particles at the position of the bright rings, indicating that these are working as dust traps. The total dust mass in the disk is between 250 and 330 M⊕, which represents a gas-to-dust mass ratio between 50 and 70. Our mass measurement is a factor of 4.5–5.9 higher than the mass that one would estimate using the typical assumptions of large demographic surveys.

Conclusions. Our results indicate that the ring substructures in TW Hya are ideal locations to trigger the streaming instability and form new generations of planetesimals.
Hoinga: a supernova remnant discovered in the SRG/eROSITA All-Sky Survey eRASS1
Authors: Becker W. , Hurley-Walker N. , Weinberger Ch. , Nicastro L. , Mayer M. G. F. , Merloni A. , Sanders J.
Published: February 2021

Supernova remnants (SNRs) are observable for about (6−15) × 104yr before they fade into the Galactic interstellar medium. With a Galactic supernova rate of approximately two per century, we can expect to have of the order of 1200 SNRs in our Galaxy. However, only about 300 of them are known to date, with the majority having been discovered in Galactic plane radio surveys. Given that these SNRs represent the brightest tail of the distribution and are mostly located close to the plane, they are not representative of the complete sample. The launch of the Russian-German observatory SRG/eROSITA in July 2019 brought a promising new opportunity to explore the Universe. Here we report findings from the search for new SNRs in the eROSITA all-sky survey data which led to the detection of one of the largest SNRs discovered at wavelengths other than the radio: G249.5+24.5. This source is located at a relatively high Galactic latitude, where SNRs are not usually expected to be found. The remnant, ‘Hoinga’, has a diameter of about 4. °4 and shows a circular shaped morphology with diffuse X-ray emission filling almost the entire remnant. Spectral analysis of the remnant emission reveals that an APEC spectrum from collisionally ionised diffuse gas and a plane-parallel shock plasma model with non-equilibrium ionisation are both able to provide an adequate description of the data, suggesting a gas temperature of the order of kT = 0.1−0.02+0.02keV and an absorbing column density ofNH = 3.6−0.6+0.7 × 1020cm−2. Various X-ray point sources are found to be located within the remnant boundary but none seem to be associated with the remnant itself. Subsequent searches for a radio counterpart of the Hoinga remnant identified its radio emission in archival data from the Continuum HI Parkes All-Sky Survey and the 408-MHz ‘Haslam’ all-sky survey. The radio spectral indexα= −0.69 ± 0.08 obtained from these data definitely confirms the SNR nature of Hoinga. We also analysed INTEGRAL SPI data for fingerprints of44Ti emission, which is an ideal candidate with which to study nucleosynthesis imprinting in young SNRs. Although no44Ti emission from Hoinga was detected, we were able to set a 3σupper flux limit of 9.2 × 10−5ph cm−2s−1. From its size and X-ray and radio spectral properties we conclude that Hoinga is a middle-aged Vela-like SNR located at a distance of about twice that of the Vela SNR, i.e. at ~500 pc.
Towards a more complete sample of binary central stars of planetary nebulae with Gaia
Authors: Chornay N. , Walton N. A. , Jones D. , Boffin H. M. J. , Rejkuba M. , Wesson R.
Published: February 2021

Context. Many if not most planetary nebulae (PNe) are now thought to be the outcome of binary evolutionary scenarios. However, only a few percent of the PNe in the Milky Way are known to host binary systems. The high-precision repeated observing and long time baseline of Gaia make it well suited for detecting new close binaries through photometric variability.

Aims. We aim to find new close binary central stars of PNe (CSPNe) using data from the Gaia mission, building towards a statistically significant sample of post-common envelope, close binary CSPNe.

Methods. As the vast majority of Gaia sources do not have published epoch photometry, we used the uncertainty in the mean photometry as a proxy for determining the variability of our CSPN sample in the second Gaia data release. We derived a quantity that expresses the significance of the variability, and considered what is necessary to build a clean sample of genuine variable sources.

Results. Our selection recovers a large fraction of the known close binary CSPN population, while other CSPNe lying in the same region of the parameter space represent a promising set of targets for ground-based confirmatory follow-up observations. Gaia epoch photometry for four of the newly identified variable sources confirms that the variability is genuine and consistent with binarity.
« Mesurer » les couleurs
Authors: Hébert Mathieu
Published: February 2021

L’approche scientifique de la couleur a véritablement commencé au XIXe siècle et a conduit tout au long du XXe siècle, sous l’égide de la Commission Internationale de l’Eclairage (CIE), à l’établissement d’espaces de représentation normalisés reconnus dans le monde entier et à des recommandations pour la mesure physique. Bien que ces outils ne soient pas encore à même de rendre compte de nos sensations colorées dans les scènes les plus complexes de la vie quotidienne, ils permettent à de nombreux secteurs industriels d’affronter les exigences croissantes de leur marché en matière de gestion de la couleur.
Liebe Leserinnen und Leser
Authors: Buchner Helmut
Published: February 2021

die Klinische Neurophysiologie, Zeitschrift für Funktionsdiagnostik des Nervensystems, geht in ihren 52. Jahrgang. Das letzte und das vor uns stehende Jahr waren und werden anders als gewohnt, anders als gedacht und vielleicht noch anders als jetzt erwartet.
Ruheinseln schaffen – Ängsten trotzen
Authors: Freitag-Herse Barbara
Published: February 2021

Die Corona-Pandemie ist für die meisten Menschen eine echte Herausforderung. Das Infektionsrisiko und die Sorge um den Arbeitsplatz lösen bei vielen Angst aus. Als Führungskraft sind Sie besonders gefordert, wenn es darum geht, die Angst nicht das Handeln bestimmen zu lassen. Um das zu erreichen, gibt es ein paar einfache, aber wirkungsvolle Dinge, die Sie gemeinsam mit Ihren Mitarbeitenden tun können.
Schutzkleidung ja, aber nicht immer – MRSA
Authors: Mayer Luisa
Published: February 2021

Dass etwas unvorstellbar Kleines wie ein Bakterium oder ein Virus ganze Hundertschaften an Menschen lahm legen kann, wissen wir nicht erst seit Corona. Allerdings hat das Thema Krankheitserreger seitdem eine neue Dimension bekommen. Mit einer anderen Sorte Keim beschäftigte sich Ergotherapeutin Luisa Mayer: Sie entwickelte Handlungsempfehlungen zum Umgang mit Patienten mit MRSA.
Electrocardiographic Changes in Male and Female Amateur Marathon Runners: A Comparison Study
Authors: Lasocka Zofia , Dąbrowska-Kugacka Alicja , Kaleta Anna Maria , Lewicka-Potocka Zuzanna , Faran Anna , Szołkiewicz Ewa , Przybyłowski Krystian , Szołkiewicz Alicja , Daniluk Paulina , Raczak Grzegorz , Lewicka Ewa
Published: February 2021

Physical training is gaining popularity among amateurs. Males and females exhibit different cardiac adaptation to exercise. The aim of the study was to compare the incidence of electrocardiographic abnormalities before and after the marathon between sexes. 12-lead electrocardiogram was performed in 40 male (39±8 years) and 27 female (40±7 years) amateur runners: 2–3 weeks before (Stage 1) and immediately after (Stage 2) the marathon. Abnormalities in the resting (Stage 1) and exercise (Stage 2) electrocardiograms were compared between sexes. At rest left atrial enlargement was more frequent in females than males (48 vs. 20%; p<0.05). The incidence of right atrial enlargement was significantly more common at Stage 2 than 1, both in men (43 vs. 0%; p<0.001) and in women (48 vs. 4%; p=0.001). Significant increase of P-wave amplitude was found in male runners after the marathon (0.12±0.05 vs. 0.21±0.09 mV; p<0.001 Stage 1 vs. 2), but was absent in females. QTc prolongation was observed in both sexes, however to a higher degree in males (p<0.05 for the interaction stage and sex). Although both male and female amateur marathon runners exhibit abnormalities in resting and exercise electrocardiograms, men present more exercise-induced electrocardiographic changes, which might indicate a higher propensity for post-marathon arrhythmias. Electrocardiographic screening in amateurs should be considered.
Motorische Neurografie und Reflexstudien: Wegweiser der klinischen Elektrophysiologie
Authors: Bischoff Christian
Published: February 2021

Würdigung der Publikation: Electrophysiological studies of nerve and reflex activity in normal man I. Identification of certain reflexes in the electromyogram and the conduction velocity of peripheral nerve fibers
No Association of Plantar Aponeurosis Stiffness with Medial Longitudinal Arch Stiffness
Authors: Noro Hiroaki , Miyamoto Naokazu , Mitsukawa Naotoshi , Yanagiya Toshio
Published: February 2021

Lower stiffness of the medial longitudinal arch is reportedly a risk factor for lower leg disorders. The plantar aponeurosis is considered essential to maintaining the medial longitudinal arch. It is therefore expected that medial longitudinal arch stiffness is influenced by plantar aponeurosis stiffness. However, this has not been experimentally demonstrated. We examined the relationship between the plantar aponeurosis stiffness and medial longitudinal arch stiffness in humans in vivo. Thirty young subjects participated in this study. The navicular height and shear wave velocity (an index of stiffness) of the plantar aponeurosis were measured in supine and single-leg standing positions, using B-mode ultrasonography and shear wave elastography, respectively. The medial longitudinal arch stiffness was calculated based on body weight, foot length, and the difference in navicular height between the supine and single-leg standing conditions (i. e., navicular drop). Shear wave velocity of the plantar aponeurosis in the supine and single-leg standing positions was not significantly correlated to medial longitudinal arch stiffness (spine: r=−0.14, P=0.45 standing: r=−0.16, P=0.41). The findings suggest that the medial longitudinal arch stiffness would be strongly influenced by the stiffness of foot structures other than the plantar aponeurosis.
Synthesis of Multibromo-Substituted Quinolines by NBS-Mediated Cascade Electrophilic Bromination/Cyclization of N-(3-Phenylprop-2-ynyl)anilines
Authors: Yang Ruchun , Xiao Qiang , Deng Si , Ouyang Wenliang , Bai Jiang , Song Xian-Rong
Published: February 2021

A new and convenient protocol is presented here for the synthesis of 3,6,8-tribromoquinolines via cascade cyclization of N-(3-phenylprop-2-ynyl)anilines employing N-bromosuccinimide as an electrophile. The metal-free process is carried out under mild conditions and is compatible with a variety of substituents. The Sonogashira coupling reaction regioselectively occurs at position C-6 of the obtained products.
The Golden Hour Trauma Care
Authors: Babu Subbiah Venkatesh
Published: February 2021

Globally the road accidents had become a great burden and claiming lot of precious lives today. However, the initial treatment within the first hour of the injury indeed had proven the high chance of survival after the trauma. This article updates and signifies the systematic emergency approach and current principles in saving lives after injury.
Beware of Nihilism: Favorable Outcome despite Poor Admission Status in Posterior Circulation Aneurysms after Aneurysmal Subarachnoid Hemorrhage
Authors: Brawanski Nina , Kashefiolasl Sepide , Won Sae-Yeon , Berkefeld Joachim , Hattingen Elke , Senft Christian , Seifert Volker , Konczalla Juergen
Published: February 2021

Objective As shown in a previous study, aneurysm location seems to influence prognosis in patients with subarachnoid hemorrhage (SAH). We compared patients with ruptured aneurysms of anterior and posterior circulation, undergoing coil embolization, concerning differences in outcome and prognostic factors.

Methods Patients with SAH were entered into a prospectively collected database. We retrospectively identified 307 patients with aneurysms of the anterior circulation (anterior cerebral artery, carotid bifurcation, and middle cerebral artery) and 244 patients with aneurysms of the posterior circulation (aneurysms of the basilar artery, posterior inferior cerebellar artery, posterior communicating artery and posterior cerebral artery). All patients underwent coil embolization. The outcome was assessed using the modified Rankin Scale (mRS; favorable [mRS 0–2] vs. unfavorable [mRS 3–6]) 6 months after SAH.

Results In interventionally treated aneurysms of the anterior and posterior circulation, statistically significant risk factors for poor outcome were worse admission status and severe cerebral vasospasm. If compared with patients with ruptured aneurysms of the anterior circulation, patients with aneurysms of the posterior circulation had a significantly poorer admission status, and suffered significantly more often from an early hydrocephalus. Nonetheless, there were no differences in outcome or mortality rate between the two patient groups.

Conclusion Patients with a ruptured aneurysm of the posterior circulation suffer more often from an early hydrocephalus and have a significantly worse admission status, possibly related to the untreated hydrocephalus. Nonetheless, the outcome and the mortality rate were comparable between ruptured anterior and posterior circulation aneurysms, treated by coil embolisation. Therefore, despite the poorer admission status of patients with ruptured posterior circulation aneurysms, treatment of these patients should be considered.
Accuracy and Feasibility Analysis of SEEG Electrode Implantation using the VarioGuide Frameless Navigation System in Patients with Drug-Resistant Epilepsy
Authors: Song Shiwei , Dai Yihai , Chen Zhen , Shi Songsheng
Published: February 2021

Objective The objective of the study was to evaluate the feasibility and accuracy of frameless stereoelectroencephalography (SEEG) electrode implantation in patients with drug-resistant epilepsy using the VarioGuide system.

Methods The VarioGuide frameless navigation system was used to implant SEEG electrodes in patients with medically drug-resistant epilepsy. Demographic data, surgery duration, number of electrodes, and complications were retrospectively analyzed. Accuracy was compared by measuring the distance between the planned and actual electrode positions as determined by postoperative computed tomography images.

Results A total of 141 SEEG electrodes were implanted in 19 patients from May 2015 to December 2018 with an average of 7.42 (range: 4–10) leads per patient. The average entry point localization error (EPLE) was 1.96 ± 0.47 mm (range: 0.32–3.29) and average target point localization error (TPLE) was 2.47 ± 0.79 mm (range: 0.72–4.83). The average operating time per lead (OTPL) was 14.16 ± 2.68 minutes (range: 8.64–21.58). No complications occurred.

Conclusion The VarioGuide frameless navigation system can be an effective method for SEEG electrode implantation in patients with drug-resistant epilepsy, particularly when the electrodes are concentrated in a relatively small region and the number of implanted electrodes is small.
Pathological Spectrum of Dura-Based Nonmeningothelial Lesions: 5 Years' Experience from a Tertiary Care Centre
Authors: Rao Shilpa , Chandran Chitra , Konar Subhas , Mahadevan Anita , Santosh Vani , Nandeesh B N.
Published: February 2021

Introduction Nonmeningothelial lesions arising from the dura comprise a wide spectrum of pathologies ranging from neoplastic to infective etiologies. They have overlapping clinical and radiologic findings necessitating histopathological evaluation for the final diagnosis which in turn dictates management and prognosis. Therapeutic strategies are different for each of the lesion. There is scarcity of large case series detailing clinicopathological spectrum of dura-based nonmeningothelial lesions.

Materials and Methods In this study, we analyzed the neuropathological spectrum of dura-based nonmeningothelial lesions diagnosed over a period of 5 years in our tertiary care center.

Results There were 79 cases of dura-based nonmeningothelial lesions constituting 7.3% of all dura-based lesions (age range: 2–75 years; M:F = 2:3). Basal region was more frequently involved than the convexities. On histopathology, neoplastic lesions predominated (92.4%) and included in order of frequency solitary fibrous tumor/hemangiopericytoma (35.6%), gliomas (27.4%), metastasis (27.4%), mesenchymal tumors (4%), primitive neuroectodermal tumor (2.73%), and medulloblastoma (2.73%). Infective lesions were less frequent (7.6%), included fungal infections and Rosai-Dorfman disease.

Conclusion Awareness of the spectrum of nonmeningothelial dural lesions is useful for pathologists as well as the treating surgeon.
A Rare Case of Pulmonary Restrictive Syndrome after Liquid Silicone Injection: The Role of the Plastic Surgeon
Authors: Bonfirraro Pier Paolo , Sallam Davide , Verga Maurizio , Righi Bernardo , Mevio Gabriele , Codazzi Denis , Leone Francesco , Carminati Marcello
Published: February 2021

Despite being especially used in its solid form, silicone is still injected as a liquid filler for breast contouring in many countries. Here, we present a rare case of a woman with silicone pneumonitis and extended breast scarring after breast silicone injection. Because of evidence of a restrictive syndrome due to the thoracic extensive scarring tissue and the high demand of oxygen therapy, as jointly agreed with the pulmonologists, we decided to perform a surgical asportation of the scarring tissue and covering with microsurgical flap. We chose the deep inferior epigastric perforator flap mainly because of the large amount of skin that is possible to use, the good skin texture matching, and the possibility of double team working without changing patient’s position.
Psychiatric Assessment and Management of Clients Undergoing Cosmetic Surgery: Overview and Need for an Integrated Approach
Authors: Bascarane Sharmi , Kuppili Pooja P. , Menon Vikas
Published: February 2021

Background Psychiatric disorders are more common among people undergoing cosmetic procedures than the general population and evaluating mental health can be cumbersome for plastic surgeons. We aim to summarize the available literature in this regard and propose an integrated approach to psychiatric assessment and management of mental health issues among this group.

Methods Electronic search of MEDLINE, Google Scholar, and PsycINFO databases was done to identify relevant peer-reviewed English language articles from inception till April 2020. Generated abstracts were screened for their eligibility. Included articles were grouped according to their thematic focus under the following headings; prevalence of psychiatric morbidity among clients posted for cosmetic surgery, assessment tools, and management of psychiatric morbidity in relation to undergoing cosmetic surgery.

Results A total of 120 articles were reviewed. The prevalence of psychiatric disorder in patients undergoing cosmetic surgery was 4 to 57% for body dysmorphic disorder (BDD); the corresponding figures for depression, anxiety, and personality disorder were 4.8 to 25.8, 10.8 to 22, and 0 to 53%, respectively. A range of tools have been used to assess these disorders and specific measures are also available to assess clinical outcomes following surgery. Screening for these disorders is essential to prevent unnecessary surgical procedures, as well as to ensure timely management of the psychiatric comorbidity.

Conclusion Psychiatric morbidity is a common concomitant in cosmetic surgery. A structured and integrated approach to evaluation and management of psychiatric morbidity will help to optimize postsurgical outcomes.
Aggressive Pituitary Adenoma Not Fulfilling the New High-Risk Criteria with Progression after 18-Year Stable Clinical Course: Case Report
Authors: Kawaguchi Tomohiro , Ogawa Yoshikazu , Watanabe Mika , Tominaga Teiji
Published: February 2021

Background The World Health Organization (WHO) classification of tumors of the endocrine organs was revised in 2017. The term atypical adenoma is no longer recommended, and tumors with rapid growth, radiologic invasion, and high Ki-67 labeling index are defined as high-risk adenomas. In this article, we present the case of an aggressive pituitary adenoma not fulfilling the new high-risk criteria with extraordinary rapid progression after very long stable disease, and discuss the remaining problem of the new criteria in terms of a complicated balance between pathologic findings and clinical features.

Case Description A 67-year-old man was admitted with sellar tumor. Serum prolactin concentration was high at 4,552.2 ng/mL. Transsphenoidal surgery achieved subtotal removal. Histologic diagnosis was lactotroph cell adenoma, and Ki-67 labeling index was 2.6%. Postoperatively, magnetic resonance imaging revealed no evidence of tumor regrowth, but terguride or cabergoline administration was continued for slight hyperprolactinemia. Second surgery was performed 18 years after initial surgery because the tumor showed extraordinary rapid regrowth and hyperprolactinemia of 969 ng/mL. Histologic diagnosis was lactotroph cell adenoma with Ki-67 labeling index of 28.9% and positive immunoreactivity for p53. This case could be diagnosed as a high-risk adenoma from the beginning of treatment based on the WHO 2017 criteria, but the clinical course was unusually long and the indication of aggressive adjuvant therapy after initial surgery remained unsolved.

Conclusion Pathologic confirmation for the present definition would be expected to assess the cutoff between typical adenomas and aggressive tumors.
Putting the Pieces Back Together: Optimizing Function and Appearance after Orbital Surgery
Authors: Cockerham Kimberly , Laplant Jacquelyn
Published: February 2021

Objectives To describe medical and surgical options and techniques for functional and aesthetic abnormalities after orbital surgery and multidisciplinary approaches that include the orbit.

Design A review of current management options in outpatient clinics and ambulatory surgery centers with selected illustrative cases. The rationale for choosing specific medical and surgical interventions will be discussed with a focus on eyelid malposition and double vision.

Setting Outpatient clinics and ambulatory surgery centers.

Participants Patients with eyelid, orbital, eye muscle, and scalp contour abnormalities as a result of medical and surgical interventions for brain and/or orbital tumors.

Main Outcome Measures Descriptive outcomes.

Results A variety of medical and surgical options are available to optimize eyelid, orbit, extraocular muscle, and scalp structure and function.
3D Printing for Complex Cranial Surgery Education: Technical Overview and Preliminary Validation Study
Authors: Graffeo Christopher S , Perry Avital , Carlstrom Lucas P , Peris-Celda Maria , Alexander Amy , Dickens Hunter J , Holroyd Michael J , Driscoll Colin L W , Link Michael J , Morris Jonathan
Published: February 2021

Background 3D printing—also known as additive manufacturing—has a wide range of applications. Reproduction of low-cost, high-fidelity, disease- or patient-specific models presents a key developmental area in simulation and education research for complex cranial surgery.

Methods Using cadaveric dissections as source materials, skull base models were created, printed, and tested for educational value in teaching complex cranial approaches. In this pilot study, assessments were made on the value of 3D printed models demonstrating the retrosigmoid and posterior petrosectomy approaches. Models were assessed and tested in a small cohort of neurosurgery resident subjects (n = 3) using a series of 10 radiographic and 2 printed case examples, with efficacy determined via agreement survey and approach selection accuracy.

Results All subjects indicated agreement or strong agreement for all study endpoints that 3D printed models provided significant improvements in understanding of neuroanatomic relationships and principles of approach selection, as compared to 2D dissections or patient cross-sectional imaging alone. Models were not superior to in-person hands-on teaching. Mean approach selection accuracy was 90% (±13%) for 10 imaging-based cases, or 92% (±7%) overall. Trainees strongly agreed that approach decision-making was enhanced by adjunctive use of 3D models for both radiographic and printed cases.

Conclusion 3D printed models incorporating skull base approaches and/or pathologies provide a compelling addition to the complex cranial education armamentarium. Based on our preliminary analysis, 3D printed models offer substantial potential for pedagogical value as dissection guides, adjuncts to preoperative study and case preparation, or tools for approach selection training and evaluation.
Keyhole Endoscopic-Assisted Transcervical Approach to the Upper and Middle Retrostyloid Parapharyngeal Space: An Anatomic Feasibility Study
Authors: Eguiluz-Melendez Aldo , Torres-Bayona Sergio , Vega María Belen , Hernández-Hernández Vanessa , Wang Erik W. , Snyderman Carl H. , Gardner Paul A.
Published: February 2021

Objectives The aim of this study was to describe the anatomical nuances, feasibility, limitations, and surgical exposure of the parapharyngeal space (PPS) through a novel minimally invasive keyhole endoscopic-assisted transcervical approach (MIKET).

Design Descriptive cadaveric study.

Setting Microscopic and endoscopic high-quality images were taken comparing the MIKET approach with a conventional combined transmastoid infralabyrinthine transcervical approach.

Participants Five colored latex-injected specimens (10 sides).

Main Outcome Measures Qualitative anatomical descriptions in four surgical stages; quantitative and semiquantitative evaluation of relevant landmarks.

Results A 5 cm long inverted hockey stick incision was designed to access a corridor posterior to the parotid gland after independent mobilization of nuchal and cervical muscles to expose the retrostyloid PPS. The digastric branch of the facial nerve, which runs 16.5 mm over the anteromedial part of the posterior belly of the digastric muscle before piercing the parotid fascia, was used as a landmark to identify the main trunk of the facial nerve. MIKET corridor was superior to the crossing of the accessory nerve over the internal jugular vein within 17.3 mm from the jugular process. Further exposure of the occipital condyle, vertebral artery, and the jugular bulb was achieved.

Conclusion The novel MIKET approach provides in the cadaver straightforward access to the upper and middle retrostyloid PPS through a natural corridor without injuring important neurovascular structures. Our work sets the anatomical nuances and limitations that should guide future clinical studies to prove its efficacy and safety either as a stand-alone procedure or as an adjunct to other approaches, such as the endonasal endoscopic approach.
Anatomy and Biomechanics of the Posterior Cruciate Ligament
Authors: Lynch Thomas B. , Chahla Jorge , Nuelle Clayton W.
Published: February 2021

Posterior cruciate ligament (PCL) injuries are often encountered in the setting of other knee pathology and sometimes in isolation. A thorough understanding of the native PCL anatomy is crucial in the successful treatment of these injuries. The PCL consists of two independent bundles that function in a codominant relationship to perform the primary role of resisting posterior tibial translation relative to the femur. A secondary role of the PCL is to provide rotatory stability. The anterolateral (AL) bundle has a more vertical orientation when compared with the posteromedial (PM) bundle. The AL bundle has a more anterior origin than the PM bundle on the lateral wall of the medial femoral condyle. The tibial insertion of AL bundle on the PCL facet is medial and anterior to the PM bundle. The AL and PM bundles are 12-mm apart at the center of the femoral origins, while the tibial insertions are more tightly grouped. The different spatial orientation of the two bundles and large distance between the femoral centers is responsible for the codominance of the PCL bundles. The AL bundle is the dominant restraint to posterior tibial translation throughout midrange flexion, while the PM bundle is the primary restraint in extension and deep flexion. Biomechanical testing has shown independent reconstruction of the two bundles that better reproduces native knee biomechanics, while significant differences in clinical outcomes remain to be seen. Stress X-rays may play an important role in clinical decision-making process for operative versus nonoperative management of isolated PCL injuries. Strong understanding of PCL anatomy and biomechanics can aid surgical management.
How does internal governance affect banks’ financial stability? Empirical evidence from Egypt
Authors: Marie Mohamed , Kamel Hany , Elbendary Israa
Published: February 2021

This paper investigates whether internal governance mechanisms were associated with the financial stability of Egyptian banks over the period 2010–2019. To this end, a GMM regression analysis was employed using 252 firm-year observations. The results, in general, indicate that the level of banks’ financial stability is positively associated with board size, board meetings, and board gender. In contrast, the results show that board education and the ownership of shares by directors are negatively associated with banks’ financial stability. More interestingly, our results demonstrate that higher financial stability is significantly associated with lower board independence, the presence of CEO duality, and fewer audit committee meetings. These striking results can be attributed to the argument that the presence of independent directors on the board may reduce the CEO’s willingness to share information with board members, causing a high level of uncertainty in the decision-making process, which ultimately leads to a reduction in the financial stability of their bank.
Atomic-level charge transport mechanism in gate-tunable anti-ambipolar van der Waals heterojunctions
Authors: Wang Kuang-Chung , Valencia Daniel , Charles James , Henning Alex , Beck Megan E. , Sangwan Vinod K. , Lauhon Lincoln J. , Hersam Mark C. , Kubis Tillmann
Published: February 2021

van der Waals p–n heterojunctions using both 2D–2D and mixed-dimensional systems have shown anti-ambipolar behavior. Gate tunability in anti-ambipolar characteristics is obtained in special heterojunction geometries, such as self-aligned black phosphorus/MoS2 p–n heterojunctions. Although the device physics of anti-ambipolar characteristics has been investigated using finite-element or semi-classical device models, an atomic-level description has not yet been developed. This work models the interface physics with quantum transport including incoherent scattering and carrier recombination. Densities of electrons and holes are calculated in DFT-based maximally localized Wannier functions with 2% strain. Qualitative agreement with our experiments is found for both the anti-ambipolar (or Gaussian) behavior and the tunability of Gaussian function in a dual-gated geometry. Carrier recombination is found to determine the overall current density. The two gates control the recombination by regulating the density of electrons in MoS2 and holes in black phosphorus reaching the heterojunction area.
Heat transfer in binary polyatomic gas mixtures over the whole range of the gas rarefaction based on kinetic deterministic modeling
Authors: Tantos Christos , Varoutis Stylianos , Day Christian
Published: February 2021

In the present work, the problem of heat conduction through binary mixtures of non-vibrating polyatomic gases is studied over the whole range of the gas rarefaction in a deterministic manner. This is achieved by applying a recently proposed kinetic model, which takes into account the internal degrees of freedom of the gas molecules. The cross and self-collision frequencies are determined based on the thermal conductivity formulas proposed in the literature for the polyatomic gas mixtures. Numerical investigation is carried out for several binary mixtures consisting of linear and nonlinear gases in a wide range of all involved parameters. The validity of the present kinetic modeling is demonstrated by performing comparisons with the corresponding numerical and experimental data. Analytical solutions for the heat flux in the free molecular and hydrodynamic regimes are formulated showing excellent agreement with the numerical estimations. The effect of the internal degrees of freedom on the heat flux, as a function of the mole fraction, is also studied. The numerical results show that the relative deviation between monatomic and polyatomic heat fluxes varies linearly with the mole fraction when the difference between the molecular masses of the species is small. However, in the case of a mixture being composed of gases with quite different molecular masses, a nonlinear behavior is observed. It is clearly shown that the heat flux problem through polyatomic gas mixture cannot be captured by monatomic modeling. Furthermore, an approximate formula for the heat flux over the whole range of the Knudsen number is examined.