bluuebunny/crossref_metadata_2025 huggingface dataset:
Cache allocation optimisation of user relationship group based on reinforcement learning
Authors: Xuan Duo , Chen Jian , Yan Hang , Lv Lu
Published: February 2021

In order to alleviate network congestion and reduce request delay, device‐to‐device caching technology will be an important part of modern communication networks. People always browse the Internet for things they are interested in. However, different people have different points of interest. Therefore, how to choose a suitable cache node when people share content is a challenge. In this study, an optimal cache node selection algorithm based on virtual delay is proposed, where the multi‐armed bandit model is used to obtain optimised cache decision based on the interest differences of users. Each candidate user may become a cache node, and the algorithm selects the user who minimises the overall delay as the node. When multiple candidate users exist, it is necessary to cooperate between multiple candidate users whose cache space is limited in order to maximise the cache hit rate. However, since each candidate user acts as a cache node has a defferent service efficiency for different requests from surrounding users, it is necessary to effectively distinguish cooperative cache users. This study proposes a master–slave node cooperative cache model based on the optimal cache node selection. The experimental results confirm that the proposed schemes achieve lower overall delay performance.
Techno‐economic model of fibre‐to‐the‐home as 5G fronthaul: evaluation of capital expenditures
Authors: Asgarirad Mohammadreza , Nejati Jahromi Mansour , Dana Arash
Published: February 2021

Fibre optics is the best solution for the deployment of 5G fronthaul, but it is expensive and time‐consuming. The use of a common fibre access network for fixed and mobile services results in cost reduction, quality of experience improvement, and synergy and convergence of the resources. Accordingly, in this study, a practical dual‐purpose techno‐economic model (FTTx + 5G) was introduced to evaluate its Capital Expenditures (CAPEX). Some technical, financial, and geographical data were also used for computation and comparing the costs in different situations by the integer linear programming method.
Hybrid machine learning detection for orbital angular momentum over turbulent MISO wireless channel
Authors: ElHelaly Alaa , Kafafy Mai , Mehanna Ahmed H. , Khairy Mohamed M.
Published: February 2021

This work proposes a machine learning detection scheme for wireless orbital angular momentum (OAM) communication systems. The new scheme works for single‐input–single‐output (SISO) and multiple‐input–single‐output (MISO) wireless communication between the transmitter and the receiver. The transmitter encodes its data in OAM modes which are constructed using Laguerre–Gaussian beam form. The transmitted beams travel through a wireless channel with weak to medium turbulence strength and they arrive at random positions on the same receiver area. The authors proposed detection scheme allows the reception of multiple overlapping beams without prior knowledge of beams centre positions. The proposed scheme uses a novel technique of receiver segmentation and space filtering along with neural network to decode the received beams. Simulations show the detection efficiency and the enhanced performance of their proposed scheme for the SISO case and the MISO case with 2, 4, and 16 beams.
MMSE‐based secure precoding in two‐way relaying systems
Authors: Long Hang , Xiang Wei , Zhang Luyuan , Huang Li
Published: February 2021

In this study, secure communications in a two‐way relaying wiretap system with a silent eavesdropper are studied. Under the assumption that the channel state information relating to the eavesdropper is unknown at legitimate nodes, the precoding vectors at the two source nodes are jointly designed to decrease the wiretap capacity at the eavesdropper. The derived relationship between the two precoding vectors is partially similar in nature to the linear minimum mean squared error (MMSE) equaliser. An iterative process is proposed to jointly achieve two precoding vectors, and its convergence is proved. Simulation results are presented to demonstrate that the proposed MMSE‐based precoding algorithm can be used for source nodes with any number of antennas, and outperforms its conventional zero‐forcing‐ and matched‐filter‐based counterparts. Signal leakage from the relay node to the eavesdropper is nearly completely suppressed by the proposed precoding design.
3DEOR: an opportunity routing protocol using evidence theory appropriate for 3D urban environments in VANETs
Authors: Bozorgzadeh Elham , Barati Hamid , Barati Ali
Published: February 2021

The vehicular ad hoc network (VANET) is a promising technology to improve the comfort and safety of passengers, roads and urban traffic. Applications applied to VANETs require efficient routing protocols. Urban environments include tunnels, subways, overpasses, and multilevel highways, which indicate the multilevel information environment and specific conditions of radio channel dissemination. In this paper proposed a three‐dimensional (3D) evidence theory based, opportunistic routing protocol, called 3DEOR, which address the above issues using a new hybrid criterion called PAL. The PAL criterion includes three metrics of packet delivery probability to compensate for unreliable dissemination environments, packet advancement appropriated to 3D environments to reduce the number of hop counts and level to improve link connectivity. Prioritise the relay set members based on the new criteria to select the best relay node. In cases where there is no certainty, the evidence theory can be a good choice for combining the three metrics of the PAL criterion. The simulation results show the superiority of the proposed protocol over the 3D link state aware geographic opportunistic (3DLSGO) and 3D greedy perimeter stateless routing (3DGPSR) protocols in network performance indices such as packet delivery rate, end‐to‐end delay and average hop count.
Performance analysis of adaptive combining based hybrid FSO/RF terrestrial communication
Authors: Siddharth Mokkapati , Shah Suyash , Vishwakarma Narendra , Swaminathan R
Published: February 2021

This study deals with the performance analysis of adaptive combining‐based hybrid free‐space optics (FSO)/radio‐frequency (RF) system in a terrestrial communication scenario with and without pointing errors. Here, outage probability and average symbol error rate (SER) are used as the performance metrics. Adaptive combining is a switching scheme in which the FSO link is active throughout, whereas the RF link is activated based on the transmission reliability of the FSO link and maximal‐ratio‐combining (MRC) of RF and FSO links is performed at the destination. The small‐scale fading in RF and atmospheric turbulence induced fading in FSO links have been characterised by Nakagami‐m and Gamma–Gamma distributions, respectively. In addition, the radial displacement between the beam centre and detector centre, which induces pointing errors, is modelled using Rayleigh distribution. The exact closed form expressions for the outage and average SER have been derived along with their corresponding asymptotic expressions. Diversity gain of the system has also been determined using the asymptotic expressions. Further, the variation in the performance of the system has been analysed with respect to various parameters including link distance, fading severity parameter, average signal‐to‐noise of the RF link, and the pointing errors parameter.
Energy management strategy for solid‐state transformer‐based solar charging station for electric vehicles in smart grids
Authors: Zand Mohammad , Nasab Morteza Azimi , Sanjeevikumar Padmanaban , Maroti Pandav Kiran , Holm‐Nielsen Jens Bo
Published: February 2021

This study introduces a type of solid‐state transformer (SST) for solar power station design and an energy management strategy (EMS) for the SST. The purpose of this study is to design a real efficient EMS for the photovoltaic‐assisted charging station in smart grid ancillary services and apply the optimal decision method. Also, the energy bound calculation (EBC) model is proposed to find the upper and lower bounds of flexible sources. Also, taking into account the EBC results and the power order from the aggregator, a charge power allocation algorithm is designed to distribute the power of flexible electric vehicles (EVs). With the help of a case study and laboratory analysis, the proposed EMS strategy is effective in real‐time energy management and is suitable for practical applications. The obtained results show the stable performance in the calculation of the energy range and real‐time power allocation which improves the efficiency of the photovoltaic‐based charging station. Also, the SST improves the operation of charge stations for supplying the sustaining power.
Response of a grid forming wind farm to system events, and the impact of external and internal damping
Authors: Roscoe Andrew , Knueppel Thyge , Da Silva Ricardo , Brogan Paul , Gutierrez Isaac , Elliott Douglas , Perez Campion Juan‐Carlos
Published: February 2021

Following from smaller‐scale investigations of grid‐forming converter control applied to wind turbines in 2017–2018, this study describes a much larger trial involving an entire wind farm, owned and operated by ScottishPower Renewables. To the authors’ knowledge, this was the first UK converter‐connected wind farm to operate in grid‐forming mode, and the largest in the world to date. The 23‐turbine, 69 MW farm ran in the grid‐forming mode for 6 weeks, exploring inertia contributions between H = 0.2 s and H = 8 s. A number of unscheduled frequency disturbances occurred due to interconnector, combined cycle gas turbine (CCGT) and other trips, to which un‐curtailed turbines were able to respond. In addition, several deliberate tests were carried out. The turbines were able to provide a stable and appropriate response at relatively high inertia levels to the frequency events commonly occurring today. The captured responses stimulated a debate as to whether external damping power might be required in a grid‐forming converter, or whether internal damping is sufficient to allow stable and robust power‐sharing with parallel devices in all grid event scenarios. Analysis in this study suggests that, practically, internal damping is probably appropriate, and that any deficiency in external damping power can be more than mitigated by reactance and/or droop‐slope response‐time management in the grid‐forming converters.
Determination of optimal location of FACTS device to improve integration rate of wind energy in presence of MBPSS regulator
Authors: Dhouib Bilel , Alaas Zuhair , Kahouli Omar , Haj Abdallah Hsan
Published: February 2021

This study aims to improve oscillation damping and the rate of integration of wind energy into the grid. To this end, this study focuses on selecting the optimal location of flexible alternating current transmission system (FACTS) devices, such as the static synchronous series compensator, the static synchronous parallel compensator, and the unified power flow controller (UPFC). This study proposes new methods to determine the optimal locations of FACTS devices in the transmission system. To further improve power oscillation damping and the rate of integration of wind energy, FACTS devices were combined with a multiband power system stabiliser (MBPSS) at each synchronous machine. The MBPSS is an advanced power system damping controller that offers clear advantages over conventional power system stabilisers in the damping of low‐frequency oscillatory modes. A comparative study was performed on the two‐zone, four‐machine (Kundur) multi‐machine test network containing a wind farm to select the best combination of FACTS devices with the MBPSS. The results indicate that a combination of UPFC with MBPSS is favourable in terms of improving stability and increasing the rate of integration of wind energy into the grid.
Hierarchical coordination strategy for three‐phase MV and LV distribution networks with high‐penetration residential PV units
Authors: Tang Wei , Cai Yongxiang , Zhang Lu , Zhang Bo , Wang Zhaoqi , Fu Yu , Xiao Xiaobing
Published: February 2021

This paper presents a hierarchical coordination method to improve operation conditions between the medium‐voltage distribution network (MVDN) and low‐voltage distribution networks (LVDN) considering high‐level residential PV units integrating LV distribution networks. It addresses the following issues: (i) rapid power fluctuations and unbalance caused by high‐level residential PV units passes to the MV distribution network via the point of common coupling (PCC) and thus increase operation challenges; (ii) power fluctuations, voltage violations and unbalance simultaneously happens in the LVDNs. A hierarchical coordination structure the MVDN and LVDN is proposed. In the MV level, a centralized dispatch method based on three‐phase optimal power flow is developed in the timescale of minutes to minimize the power losses, unbalance and PCC adjustments, which are achieved by regulating energy storage systems (ESSs) and PV inverters in the LV level. In the LV level, a distributed control model based on a consensus algorithm is proposed in the timescale of seconds to track the reference active (or reactive) power at the PCC given by the MV level and mitigate its fluctuations. Simulations studies are performed to verify the proposed method.
Modeling the nonaxisymmetric structure in the HD 163296 disk with planet-disk interaction
Authors: Rodenkirch P. J. , Rometsch T. , Dullemond C. P. , Weber P. , Kley W.
Published: February 2021

Context. High-resolution ALMA observations such as the DSHARP campaign have revealed a variety of rich substructures in numerous protoplanetary disks. These structures consist of rings, gaps, and asymmetric features. It has been debated whether planets can be accounted for among these substructures in the dust continuum. Characterizing the origin of asymmetries, as seen in HD 163296, might lead to a better understanding of planet formation and the underlying physical parameters of the system.

Aims. We test the possibility that the formation of the crescent-shaped asymmetry in the HD 163296 disk can be attributed to planet-disk interaction. The goal is to obtain constraints on planet masses, eccentricities, and disk viscosities. Furthermore, we test the reproducibility of the two prominent rings in the HD 163296 disk at 67 and 100 au.

Methods. We performed two-dimensional, multi-fluid, hydrodynamical simulations with the FARGO3D code, including three embedded planets in the setup. Dust is described via the pressureless fluid approach and distributed over eight size bins. The resulting grids were post-processed with the radiative transfer code RADMC-3D and CASA software to model the synthetic observations.

Results. We find that the crescent-shaped asymmetry can be qualitatively modeled with a Jupiter mass planet at a radial distance of 48 au. Dust is trapped in the trailing Lagrange point L5, preferably, with a mass of between 10 and 15 earth masses. The observation of such a feature constrains the level of viscosity and planetary mass. Increased values of eccentricity of the innermost Jupiter mass planet negatively impacts the stability of the crescent-shaped feature and does not reproduce the observed radial proximity to the first prominent ring in the system. Generally, a low level of viscosity (α ≤ 2 × 10−3) is necessary to allow for the existence of such a feature. Including dust feedback in the leading point, L4, can dominantly capture dust for dust grains with an initial Stokes number ≤ 3.6 × 10−2. In the synthetic ALMA observation of the model with dust feedback, two crescent-shaped features are visible. The observational results suggest a negligible effect on the part of dust feedback since only one such feature has been detected so far. The dust-to-gas ratio may thus be overestimated in the models. Additionally, the planet mass growth time scale does not strongly affect the formation of such asymmetries in the co-orbital region.
Helioseismological determination of the subsurface spatial spectrum of solar convection: Demonstration using numerical simulations
Authors: Böning Vincent G. A. , Birch Aaron C. , Gizon Laurent , Duvall Thomas L.
Published: February 2021

Context. Understanding convection is important in stellar physics, for example, when it is an input in stellar evolution models. Helioseismic estimates of convective flow amplitudes in deeper regions of the solar interior disagree by orders of magnitude among themselves and with simulations.

Aims. We aim to assess the validity of an existing upper limit of solar convective flow amplitudes at a depth of 0.96 solar radii obtained using time-distance helioseismology and several simplifying assumptions.

Methods. We generated synthetic observations for convective flow fields from a magnetohydrodynamic simulation (MURaM) using travel-time sensitivity functions and a noise model. We compared the estimates of the flow amplitude with the actual value of the flow.

Results. For the scales of interest (ℓ < 100), we find that the current procedure for obtaining an upper limit gives the correct order of magnitude of the flow for the given flow fields. We also show that this estimate is not an upper limit in a strict sense because it underestimates the flow amplitude at the largest scales by a factor of about two because the scale dependence of the signal-to-noise ratio has to be taken into account. After correcting for this and after taking the dependence of the measurements on direction in Fourier space into account, we show that the obtained estimate is indeed an upper limit.

Conclusions. We conclude that time-distance helioseismology is able to correctly estimate the order of magnitude (or an upper limit) of solar convective flows in the deeper interior when the vertical correlation function of the different flow components is known and the scale dependence of the signal-to-noise ratio is taken into account. We suggest that future work should include information from different target depths to better separate the effect of near-surface flows from those at greater depths. In addition, the measurements are sensitive to all three flow directions, which should be taken into account.
Measuring the ratio of the gas and dust emission radii of protoplanetary disks in the Lupus star-forming region
Authors: Sanchis E. , Testi L. , Natta A. , Facchini S. , Manara C. F. , Miotello A. , Ercolano B. , Henning Th. , Preibisch T. , Carpenter J. M. , de Gregorio-Monsalvo I. , Jayawardhana R. , Lopez C. , Mužić K. , Pascucci I. , Santamaría-Miranda A. , van Terwisga S. , Williams J. P.
Published: February 2021

We performed a comprehensive demographic study of the CO extent relative to dust of the disk population in the Lupus clouds in order to find indications of dust evolution and possible correlations with other disk properties. We increased the number of disks of the region with measured RCO and Rdust from observations with the Atacama Large Millimeter/submillimeter Array to 42, based on the gas emission in the 12CO J = 2−1 rotational transition and large dust grains emission at ~0.89 mm. The CO integrated emission map is modeled with an elliptical Gaussian or Nuker function, depending on the quantified residuals; the continuum is fit to a Nuker profile from interferometric modeling. The CO and dust sizes, namely the radii enclosing a certain fraction of the respective total flux (e.g., R68%), are inferred from the modeling. The CO emission is more extended than the dust continuum, with a R68%CO/R68%dust median value of 2.5, for the entire population and for a subsample with high completeness. Six disks, around 15% of the Lupus disk population, have a size ratio above 4. Based on thermo-chemical modeling, this value can only be explained if the disk has undergone grain growth and radial drift. These disks do not have unusual properties, and their properties spread across the population’s ranges of stellar mass (M⋆), disk mass (Mdisk), CO and dust sizes (RCO, Rdust), and mass accretion of the entire population. We searched for correlations between the size ratio and M⋆, Mdisk, RCO, and Rdust: only a weak monotonic anticorrelation with the Rdust is found, which would imply that dust evolution is more prominent in more compact dusty disks. The lack of strong correlations is remarkable: the sample covers a wide range of stellar and disk properties, and the majority of the disks have very similar size ratios. This result suggests that the bulk of the disk population may behave alike and be in a similar evolutionary stage, independent of the stellar and disk properties. These results should be further investigated, since the optical depth difference between CO and dust continuum might play a major role in the observed size ratios of the population. Lastly, we find a monotonic correlation between the CO flux and the CO size. The results for the majority of the disks are consistent with optically thick emission and an average CO temperature of around 30 K; however, the exact value of the temperature is difficult to constrain.
Editorial
Authors: Tausche Anne-Kathrin
Published: February 2021

Sehr geehrte Damen und Herren, liebe Kolleginnen und Kollegen in der Rheumatologie,

im vorliegenden Schwerpunktheft soll es im Wesentlichen um ganz verschiedene Aspekte der Kristallarthritis Gicht gehen.
Robustly High Hippocampal BDNF levels under Acute Stress in Mice Lacking the Full-length p75 Neurotrophin Receptor
Authors: Dunay Ildiko Rita , Hellweg Rainer , Schott Björn H. , Kronenberg Golo , Schmidt Ulrike , Düsedau Henning P. , Ehrentraut Stefanie , Geisel Olga , von Bohlen und Halbach Oliver , Gass Peter
Published: February 2021

Background Brain-derived neurotrophic factor (BDNF) exerts its effects on neural plasticity via 2 distinct receptor types, the tyrosine kinase TrkB and the p75 neurotrophin receptor (p75NTR). The latter can promote inflammation and cell death while TrkB is critically involved in plasticity and memory, particularly in the hippocampus. Acute and chronic stress have been associated with suppression of hippocampal BDNF expression and impaired hippocampal plasticity. We hypothesized that p75NTR might be involved in the hippocampal stress response, in particular in stress-induced BDNF suppression, which might be accompanied by increased neuroinflammation.

Method We assessed hippocampal BDNF protein concentrations in wild-type mice compared that in mice lacking the long form of the p75NTR (p75NTRExIII−/−) with or without prior exposure to a 1-hour restraint stress challenge. Hippocampal BDNF concentrations were measured using an optimized ELISA. Furthermore, whole-brain mRNA expression of pro-inflammatory interleukin-6 (Il6) was assessed with RT-PCR.

Results Deletion of full-length p75NTR was associated with higher hippocampal BDNF protein concentration in the stress condition, suggesting persistently high hippocampal BDNF levels in p75NTR-deficient mice, even under stress. Stress elicited increased whole-brain Il6 mRNA expression irrespective of genotype; however, p75NTRExIII−/− mice showed elevated baseline Il6 expression and thus a lower relative increase.

Conclusions Our results provide evidence for a role of p75NTR signaling in the regulation of hippocampal BDNF levels, particularly under stress. Furthermore, p75NTR signaling modulates baseline but not stress-related Il6 gene expression in mice. Our findings implicate p75NTR signaling as a potential pathomechanism in BDNF-dependent modulation of risk for neuropsychiatric disorders.
Photochemical Synthesis of 4H-Thieno[3,2-c]chromene and Their Optical Properties
Authors: Fisyuk Alexander S. , Ulyankin Evgeny B. , Bogza Yulia P. , Kostyuchenko Anastasia S. , Chernenko Sergey A. , Samsonenko Anna L. , Shatsauskas Anton L. , Yurpalov Vyacheslav L.
Published: February 2021

4-{[(2-Iodoaryl)oxy]methyl}thiophene-2-carbaldehydes and 5-iodo-4-(aryloxymethyl)thiophene-2-carbaldehydes were obtained by the reaction of phenols with 4-(chloromethyl)thiophene-2-carbaldehyde or its 5-iodo analogue, respectively. These products underwent ring closure upon irradiation with UV light (254 nm) to form the corresponding 4H-thieno[3,2-c]chromene-2-carbaldehydes in high yield. The formation of intermediate radical species was detected by EPR spectroscopy. Comparative analysis of ring-closure methods showed that photochemical cyclization of 5-iodo-4-(aryloxymethyl)thiophene-2-carbaldehyde is superior to Pd-catalyzed intramolecular arylation. A series of substituted 4H-thieno[3,2-c]chromene-2-carbaldehydes were synthesized by the photochemical cyclization of the corresponding precursors, and the photophysical properties of the products were studied. The 4H-thieno[3,2-c]chromene-2-carbaldehydes can be used as covert marking pigments.
Mapping Meta-Therapy in Voice Interventions onto the Rehabilitation Treatment Specification System
Authors: Helou Leah B. , Gartner-Schmidt Jackie L. , Hapner Edie R. , Schneider Sarah L. , Van Stan Jarrad H.
Published: February 2021

Meta-therapy refers to the clinical dialogue via which direct and indirect voice treatments are introduced and discussed, and which helps build a useful conceptual framework for voice therapy. Meta-therapy was idiosyncratically defined in previous work. However, the current colloquial narrative of meta-therapy is not standardized or specific enough to be reliably taught, rigorously studied, or clinically delivered with high fidelity. Therefore, this article uses a standard framework (the Rehabilitation Treatment Specification System or RTSS) to further articulate and operationalize meta-therapy in vocal rehabilitation. Meta-therapy's conceptual framework generally aligns with the RTSS's treatment theory and associated concepts; e.g., the treatment component and its underlying ingredients, mechanisms of action, and target. Because the treatment theories in meta-therapy most frequently involve mechanisms of action related to information processing, they primarily map onto the RTSS's Representations treatment components. The treatment targets in meta-therapy are often focused on changes in the patient's cognitions, knowledge, beliefs, attitudes, intentions, and/or awareness regarding voice-related modifications. The ingredients in meta-therapy are frequently clinician actions conveying information with the goal of appropriately shaping the patient's mental representations, and are delivered with verbal cues, stories, analogies, etc. This manuscript provides specific examples of how meta-therapy is applied in clinical voice practice. Considerations for future investigation of meta-therapy are proposed.
The Pulmonary Embolism Response Team: Why and How?
Authors: Channick Richard N.
Published: February 2021

Treatment of patients with intermediate and high-risk pulmonary embolism (PE) is a controversial area. Many therapeutic options exist, and deciding on appropriate treatment can be difficult. In addition, multiple specialties are often involved in the care of PE patients. To better organize the response to serious PE patients, several hospitals and academic centers throughout the world have created pulmonary embolism response teams (PERTs). The goal of a PERT is to have a single multidisciplinary team of experts in thromboembolic disease, who can respond rapidly to patients with acute PE, and offer consultation and implementation of the full spectrum of therapeutic options. PERT teams were modeled after rapid response teams and are meant to generate a prompt, patient-specific plan for patients with PE without having to consult multiple individual specialists. Data are emerging demonstrating the value of PERTs in reducing hospital length of stay and, possibly, patient outcomes.
Individuals Age Determination from Human Dental Pulp Through DNA Analysis by PCR
Authors: Tejasvi M.L. Avinash , CK Anulekha Avinash , Reddy E. Rajendra , Kulkarni Pavan , Bhayya Harsha , Kugaji Manohar S.
Published: February 2021

Objectives Age estimation in forensic odontology is having a great importance in recent times because of the request by court or other government authorities so that immigrants whose real age is unknown should not suffer unfair disadvantages because of their supposed age, and so that all legal procedures to which an individual's age is relevant can be properly followed.

Purpose The present study was planned to be conducted on pulp tissue and dental hard tissues derived from individuals for DNA isolation and age determination .

Materials and Methods The present study was an experimental single-blinded study consisting of 30 extracted teeth categorized into three groups as follows: Group A: 10 to 20 years, Group B: 21 to 30 years, Group C: 31 to 40 years. DNA was isolated from the pulp of each tooth and quantitative polymerase chain reaction (qPCR) for calculating telomere length was performed.

Results With increase in age, the length of telomere gets shortened which will be helpful in analyzing the age of the person when morphological and biological remnants are not available except the tooth.

Conclusion The present study found that estimation of human age based on the relative TL measured by the real-time quantitative PCR may be a useful method for age prediction, especially when there is no morphologic information in the biological sample. This is the first study to accesses the age of a person by telomere length using dental pulp.
Vein Grafting in Microsurgical Lower Extremity Reconstruction: Outcome Analysis of Primary versus Secondary Salvage Procedures
Authors: Gazyakan Emre , Xiong Lingyun , Sun Jiaming , Kneser Ulrich , Hirche Christoph
Published: February 2021

Background Many microsurgeons fear high complication rates and free flap loss when vein grafting is necessary to restore blood flow at the recipient site. The aims of this study were to comparatively analyze surgical outcomes of interposition vein grafts (VG) in microsurgical primary lower extremity reconstruction and secondary salvage procedures.

Methods A retrospective study was conducted on 58 patients undergoing free flap transfers with vein grafting for primary lower extremity reconstruction (cohort 1) and secondary salvage procedures (cohort 2) between 2002 and 2016. A matched-pair analysis of both cohorts and 58 non-VG flaps was performed. Patient data, preoperative conditions, flap and vein graft characteristics, postoperative outcomes such as flap failure, thrombosis, and wound complications were analyzed.

Results A total of 726 free flap transfers were performed. In total, 36 primary reconstructions (5%) utilized 41 interposition VG (cohort 1). Postoperative vascular compromise was observed in 65 free flaps (9%). In total, 22 out of 65 secondary salvage procedures (33.8%) utilized 26 interposition VG (cohort 2). Two total flap losses occurred in each cohort (5.6 vs. 9.1%; p = 0.63). Postoperative complications were observed in 38.9% of free flaps in cohort 1 and 72.7% in cohort 2 (p = 0.01). Takeback for microvascular compromise was comparable in both cohorts (19.4 vs. 22.7%; p = 0.75). Microvascular complications occurred more often in cohort 2 (22.7%) than in cohort 1 (8.3%; p = 0.28). Lower extremity salvage rates were high among both cohorts (94.4 vs. 90.9%; p = 0.63). Matched-pair analysis did not show any relevant differences on takebacks and flap loss (p = 0.32 and p = 1.0).

Conclusion In complex lower extremity reconstructions, VG can be performed with acceptable complication rates and outcomes in primary and especially in salvage cases. With careful planning and a consistent surgical protocol, VG can provide reliable success rates in limb salvage.
The Chimeric Gracilis and Profunda Artery Perforator Flap: Characterizing This Novel Flap Configuration with Angiography and a Cadaveric Model
Authors: Hammond Jacob B. , Teven Chad M. , Flug Jonathan A. , Jokerst Clint E. , Howarth Ashley L. , Shrout Max A. , Laitinen Marko A. , Foley Brittany M. , Kruger Erwin A. , Casey William J. , Rebecca Alanna M.
Published: February 2021

Background A chimerically configured gracilis and profunda artery perforator (PAP) flap is highly prevalent based on recent computed tomography (CT)-imaging data. The purpose of this study is to further characterize the vascular anatomy of this novel flap configuration and determine the feasibility of flap dissection.

Methods To characterize flap arterial anatomy, lower extremity CT angiograms performed from 2011 to 2018 were retrospectively reviewed. To characterize venous anatomy and determine the feasibility of flap harvest, the lower extremities of cadavers were evaluated.

Results A total of 974 lower extremity CT angiograms and 32 cadavers were included for the assessment. Of the 974 CT angiograms, majority (966, 99%) were bilateral studies, yielding a total of 1,940 lower extremities (right-lower-extremity = 970 and left-lower-extremity = 970) for radiographic evaluation. On CT angiography, a chimerically configured gracilis and PAP flap was found in 51% of patients (n = 494/974). By laterality, chimeric anatomy was present in 26% of right lower extremities (n = 254/970) and 25% of left lower extremities (n = 240/970); bilateral chimeric anatomy was found in 12% (n = 112/966) of patients. Average length of the common arterial pedicle feeding both gracilis and PAP flap perforasomes was 31.1 ± 16.5 mm (range = 2.0–95.0 mm) with an average diameter of 2.8 ± 0.7 mm (range = 1.3–8.8 mm).

A total of 15 cadavers exhibited chimeric anatomy with intact, conjoined arteries and veins allowing for anatomical tracing from the profunda femoris to the distal branches within the tissues of the medial thigh. Dissection and isolation of the common pedicle and distal vessels was feasible with minimal disruption of adjacent tissues. Chimeric flap venous anatomy was favorable, with vena commitante adjacent to the common pedicle in all specimens.

Conclusion Dissection of a chimeric medial thigh flap consisting of both gracilis and PAP flap tissues is feasible in a cadaveric model. The vascular anatomy of this potential flap appears suitable for future utilization in a clinical setting.
The U.S. National Trend for Retinopathy of Prematurity
Authors: Aly Hany , Othman Hasan F. , Munster Chelsea , Das Anirudha , Sears Jonathan
Published: February 2021

Objective The use of supplemental oxygen in premature infants is essential for survival. However, its use has been associated with unintended complications. The restricted use of oxygen is associated with increased mortality and necrotizing enterocolitis (NEC), whereas its liberal use is associated with increased risk for retinopathy of prematurity (ROP). Although there is no clear consensus on the acceptable oxygen saturation range, clinicians have recently become more liberal with the use of oxygen. We aim to assess (1) the national trends for ROP in very low birth weight preterm infants, and (2) the associated trends in mortality, NEC, intraventricular hemorrhage (IVH), and length of hospital stay (LOS).

Study Design We analyzed deidentified patient data from the National Inpatient Sample (NIS) of the Healthcare Cost and Utilization Project (HCUP) from 2002 to 2017. All infants with gestational age ≤32 weeks and birth weight <1,500 g were included. Trends in ROP, severe ROP, mortality, NEC, IVH, severe IVH, and LOS were analyzed using Jonckheere–Terpstra test.

Results A total of 818,945 neonates were included in the study. The overall mortality was 16.2% and the prevalence of ROP was 17.5%. There was a significant trend for increased ROP over the years (p < 0.001). Severe ROP was also significantly increased (p < 0.001). This was associated with a significant trend for increased median LOS in survived infants (p < 0.001). Mortality was significantly decreased (p < 0.001), whereas NEC and severe NEC did not change over time (p = 0.222 and p = 0.412, respectively).

Conclusion There is a national trend for increased ROP and severe ROP over the 16 years of the study period. This trend was associated with a significant increase in the LOS in survived infants without change in NEC.

Key Points
Suspected Acute Pulmonary Embolism: Gestalt, Scoring Systems, and Artificial Intelligence
Authors: Douillet Delphine , Roy Pierre-Marie , Penaloza Andrea
Published: February 2021

Pulmonary embolism (PE) remains a diagnostic challenge in 2021. As the pathology is potentially fatal and signs and symptoms are nonspecific, further investigations are classically required. Based on the Bayesian approach, clinical probability became the keystone of the diagnostic strategy to rule out PE in the case of a negative testing. Several clinical probability assessment methods are validated: gestalt, the Wells score, or the revised Geneva score. While the debate persists as to the best way to assess clinical probability, its assessment allows for the good interpretation of the investigation results and therefore directs the correct diagnostic strategy. The wide availability of computed tomography pulmonary angiography (CTPA) resulted in a major increase in investigations with a moderate increase in diagnosis, without any notable improvement in patient outcomes. This leads to a new challenge for PE diagnosis which is the limitation of the number of testing for suspected PE. We review different strategies recently developed to achieve this goal. The last challenge concerns the implementation in clinical practice. Two approaches are developed: simplification of the strategies versus the use of digital support tools allowing more sophisticated strategies. Artificial intelligence with machine-learning algorithms will probably be a future tool to guide the physician in this complex approach concerning acute PE suspicion.
Single- and Multimarker Genome-Wide Scans Evidence Novel Genetic Risk Modifiers for Venous Thromboembolism
Authors: Herrera-Rivero Marisol , Stoll Monika , Hegenbarth Jana-Charlotte , Rühle Frank , Limperger Verena , Junker Ralf , Franke André , Hoffmann Per , Shneyder Maria , Stach Michael , Nowak-Göttl Ulrike
Published: February 2021

Previous genome-wide association studies (GWASs) have established several susceptibility genes for venous thromboembolism (VTE) and suggested many others. However, a large proportion of the genetic variance in VTE remains unexplained. Here, we report genome-wide single- and multimarker as well as gene-level associations with VTE in 964 cases and 899 healthy controls of European ancestry. We report 19 loci at the genome-wide level of association (p ≤ 5 × 10−8). Our results add to the strong support for the association of genetic variants in F5, NME7, ABO, and FGA with VTE, and identify several loci that have not been previously associated with VTE. Altogether, our novel findings suggest that 20 susceptibility genes for VTE were newly discovered by our study. These genes may impact the production and prothrombotic functions of platelets, endothelial cells, and white and red blood cells. Moreover, the majority of these genes have been previously associated with cardiovascular diseases and/or risk factors for VTE. Future studies are warranted to validate our findings and to investigate the shared genetic architecture with susceptibility factors for other cardiovascular diseases impacting VTE risk.
Acidic Region Residues 1680–1684 in the A3 Domain of Factor VIII Contain a Thrombin-Interactive Site Responsible for Proteolytic Cleavage at Arg1689
Authors: Nakajima Yuto , Minami Hiroaki , Nogami Keiji
Published: February 2021

Factor VIII (FVIII) is activated by thrombin-catalyzed cleavage at Arg372, Arg740, and Arg1689. Our previous studies suggested that thrombin interacted with the FVIII C2 domain specific for cleavage at Arg1689. An alternative report demonstrated, however, that a recombinant (r)FVIII mutant lacking the C2 domain retained >50% cofactor activity, indicating the presence of other thrombin-interactive site(s) associated with cleavage at Arg1689. We have focused, therefore, on the A3 acidic region of FVIII, similar to the hirugen sequence specific for thrombin interaction (54–65 residues). Two synthetic peptides, spanning residues 1659–1669 with sulfated Tyr1664 and residues 1675–1685 with sulfated Try1680, inhibited thrombin-catalyzed FVIII activation and cleavage at Arg1689. Treatment with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide to cross-link thrombin with either peptide showed possible contributions of both 1664–1666 and 1683–1684 residues for thrombin interaction. Thrombin-catalyzed activation and cleavage at Arg1689 in the alanine-substituted rFVIII mutants within 1663–1666 residues were similar to those of wild type (WT). Similar studies of 1680–1684 residues, however, demonstrated that activation and cleavage by thrombin of the FVIII mutant with Y1680A or D1683A/E1684A, in particular, were severely or moderately reduced to 20 to 30% or 60 to 70% of WT, respectively. Surface plasmon resonance-based analysis revealed that thrombin interacted with both Y1680A and D1683A/E1684A mutants with approximately sixfold weaker affinities of WT. Cleavage at Arg1689 in the isolated light-chain fragments from both mutants was similarly depressed, independently of the heavy-chain subunit. In conclusion, the 1680–1684 residues containing sulfated Tyr1680 in the A3 acidic region also contribute to a thrombin-interactive site responsible for FVIII activation through cleavage at Arg1689.
Understanding the buffering effect of social media use on anxiety during the COVID-19 pandemic lockdown
Authors: Marzouki Yousri , Aldossari Fatimah Salem , Veltri Giuseppe A.
Published: February 2021

During the COVID-19 outbreak, lockdown measures have been deployed worldwide. In the wake of these measures, internet and social media use has reached unprecedented peaks. We hypothesize that social media can, in the context of the pandemic, be a placeholder for collective resilient processes modulated by cognitive and emotional components. An online survey (N = 1408) using a cross-sectional design was carried out over nine weeks from the beginning of March 2020 to the end of May 2020. The triangulation via SEM statistical modeling, text mining, and sentiment, discriminant, and entropy analyses revealed the granular functional role of social media use in promoting a positive perception towards stressors during the pandemic. This study provides an empirically tested theoretical framework to understand the evolution of buffering mechanisms of social media use as a result of collective resilience. Recommendations on social media use for future lockdown scenarios were provided.
A built-in coil system attached to the inside walls of a magnetically shielded room for generating an ultra-high magnetic field homogeneity
Authors: Liu Tianhao , Schnabel Allard , Voigt Jens , Kilian Wolfgang , Sun Zhiyin , Li Liyi , Trahms Lutz
Published: February 2021

The homogeneity of the magnetic field generated by a coil inside a magnetic shield is essential for many applications, such as ultra-low field nuclear magnetic resonance or spin precession experiments. In the course of upgrading the Berlin Magnetically Shielded Room (BMSR-2) with a new inserted Permalloy layer of side length 2.87 m, we designed a built-in coil consisting of four identical square windings attached to its inside walls. The spacings of the four windings were optimized using a recently developed semi-analytic model and finite element analysis. The result reveals a strong dependence of the field homogeneity on the asymmetric placement of the inner two windings and on the chosen material permeability value μs. However, our model calculations also show that these experimental variations can be counterbalanced by an adjustment of the inner winding positions in the millimeter range. Superconducting quantum interference device-based measurements yield for our implementation after fine adjustments of a single winding position a maximum field change of less than 10 pT for a total field of B0 = 2.3 µT within a 10 cm region along the coil axis, which is already better than the residual field of the upgraded BMSR-2.1 after degaussing. Measurements of free spin precession decay signals of polarized Xe129 nuclei show that the transverse relaxation time for the used cell is not limited by the inhomogeneity of the new built-in coil system.
AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors (MISHEMTs) using plasma deposited BN as gate dielectric
Authors: Yang Tsung-Han , Brown Jesse , Fu Kai , Zhou Jingan , Hatch Kevin , Yang Chen , Montes Jossue , Qi Xin , Fu Houqiang , Nemanich Robert J. , Zhao Yuji
Published: February 2021

AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors (MISHEMTs) were fabricated on Si substrates with a 10 nm boron nitride (BN) layer as a gate dielectric deposited by electron cyclotron resonance microwave plasma chemical vapor deposition. The material characterization of the BN/GaN interface was investigated by X-ray photoelectric spectroscopy (XPS) and UV photoelectron spectroscopy. The BN bandgap from the B1s XPS energy loss is ∼5 eV consistent with sp2 bonding. The MISHEMTs exhibit a low off-state current of 1 × 10−8 mA/mm, a high on/off current ratio of 109, a threshold voltage of −2.76 V, a maximum transconductance of 32 mS/mm at a gate voltage of −2.1 V and a drain voltage of 1 V, a subthreshold swing of 69.1 mV/dec, and an on-resistance of 12.75 Ω·mm. The interface state density (Dit) is estimated to be less than 8.49 × 1011 cm−2 eV−1. Gate leakage current mechanisms were investigated by temperature-dependent current–voltage measurements from 300 K to 500 K. The maximum breakdown electric field is no less than 8.4 MV/cm. Poole–Frenkel emission and Fowler–Nordheim tunneling are indicated as the dominant mechanisms of the gate leakage through the BN gate dielectric at low and high electric fields, respectively.
Radiation-enhanced dual-inverted bowlers antenna for high-power mesoband system
Authors: Li Qiwei , Tie Weihao , Sun Jing , Fang Jinyong , Ding Jun
Published: February 2021

We propose a novel radiation-enhanced dual-inverted bowlers antenna to pursue a maximal radiated electric field (E-field). Based on increasing the stored energy and the high-frequency component of the excitation pulse, the new structure significantly improves the radiation performance without increasing the generator output voltage or antenna size. Computer simulations show that the radiated E-field increases by a factor of 2.7 relative to the same sized conventional biconical antenna. Under a charge voltage of 300 kV, the experimental far-field voltage is 110 kV (22 kV/m at 5 m) and the voltage gain is 0.37. This voltage gain is an improvement of at least 23% over typical biconical antennas. This work brings new opportunities to improve the radiation performance of high-power mesoband systems.
Properties of states on Weyl algebra with variable multiplication law
Authors: Ługiewicz Piotr , Jakóbczyk Lech , Frydryszak Andrzej
Published: February 2021

We consider possible quantum effects for infinite systems implied by variations of the multiplication law in the algebra of observables. Using the algebraic formulation of quantum theory, we study the behavior of states ω under changes in the defining relations of the canonical commutation relations (CCR-algebra). These defining relations of the multiplication law depend explicitly on the symplectic form σ, which encodes commutation relations of canonical field operators. We consider the change in this form given by simple rescaling of σ by a positive parameter h. We analyze to what extent changes in h preserve the original state space (this gives restrictions on the admissible changes in the scaling parameter h) and which properties have original quantum states ω as states on the new algebra. We answer such questions for the quasi-free states. We show that any universally invariant state can be interpreted as a convex combination of Fock states with different values of constant h. The second important class of states we study is the KMS-state; here, the rescaling alters in a nontrivial way the relevant dynamics. We also show that it is possible to go beyond the limits restricting the changes in h, but then one has to restrict the CCR-algebra to a subalgebra.