bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Transcutaneous Vagus Nerve Stimulation in Dysphagia After Lateral Medullary Infarction: A Case Report
Authors: Yuan Ying , Wang Jie , Wu Dongyu , Zhang Dahua , Song Weiqun
Published: September 2019

Purpose

Severe dysphagia with weak pharyngeal peristalsis after dorsal lateral medullary infarction (LMI) requires long-term tube feeding. However, no study is currently available on therapeutic effectiveness in severe dysphagia caused by nuclear damage of vagus nerve after dorsal LMI. The purpose of the present investigation was to explore the potential of transcutaneous vagus nerve stimulation (tVNS) to improve severe dysphagia with weak pharyngeal peristalsis after dorsal LMI.

Method

We assessed the efficacy of 6-week tVNS in a 28-year-old woman presented with persisting severe dysphagia after dorsal LMI who had been on nasogastric feeding for 6 months. tVNS was applied for 20 min twice a day, 5 days a week, for 6 weeks. The outcome measures included saliva spitted, Swallow Function Scoring System, Functional Oral Intake Scale, Clinical Assessment of Dysphagia With Wallenberg Syndrome, Yale Pharyngeal Residue Severity Rating Scale, and upper esophagus X-ray examination.

Results

After tVNS, the patient was advanced to a full oral diet without head rotation or spitting. No saliva residue was found in the valleculae and pyriform sinuses. Contrast medium freely passed through the upper esophageal sphincter.

Conclusion

Our findings suggest that tVNS might provide a useful means for recovery of severe dysphagia with weak pharyngeal peristalsis after dorsal LMI.

Supplemental Material

https://doi.org/10.23641/asha.9755438
Economic and ecological sustainability of the thermal building envelope: a cross-European perspective
Authors: Gauer Tillman , Kurzrock Björn-Martin
Published: September 2019

The building sector is crucial to reach the goals of common climate agreements. This paper contrasts three approaches to reduce emissions from typical residential buildings in Central Europe: the instalment of electric heat pumps (eHP), a thicker insulation of the thermal envelope and the encumbrance of a carbon tax. The use of less carbon intense fuels allows major savings of GHG emissions. An insulation thickness of 30 cm leads to GHG emission savings of 8% against a thickness of just 12 cm, while total cost savings (LCC) remain negligible. The introduction of a carbon tax of up to 250 €/t-CO2-eq. does not necessarily result in a reduction of GHG emissions due to increased costs of construction. It was further found that the focus of legal building regulations on heating demand is sufficient for now but needs to be revised as carbon intensities continue to decrease. The heating then reduces its share of the GHG emissions from 85 to 55% for typical residential buildings. The paper closes with a general expression of the lifecycle costs of a building which is dependent on the factors above.
Compact wooden roofs with smart vapour barriers – effect of wooden joists on drying of built-in moisture
Authors: Geving Stig , Olsen Tom-Andre
Published: September 2019

The application of a smart vapour barrier in compact wood frame roofs has been investigated. The study was performed using a laboratory setup for small roof elements, exposed to a typical Nordic summer climate and a high level of built-in moisture. The concept of this study was to investigate how various types of wooden joists and their hygroscopic properties influenced the inward drying and moisture distribution within the elements. The results were compared to previous studies with similar roof elements without wooden joists. The results showed that the type and size of wooden joist influenced both the drying speed and the moisture level and distribution within the elements.
Impact of radiation on hygrothermal behavior of ventilated cavity wall
Authors: Colinart Thibaut , Bendouma Mathieu , Glouannec Patrick
Published: September 2019

This work deals with the performance of a high school building renovated with prefabricated ventilated façade elements through a field experimental study under oceanic climate. Temperature, relative humidity and heat flux were measured at different points of the renovated façade and are analyzed as function of the exterior boundary conditions. The measured data are compared to numerical results. For this purpose, two models are considered: an energy balance is made for the cladding, while a heat and moisture transfer model is solved within the insulation materials. In this study, particular attention is paid in the influence of the radiative exchanges in short and long wavelengths on the hygrothermal behavior of the retrofitted wall.
Analysis of building energy upgrade technologies for implementing the dual energy efficiency and demand response scheme for non-residential buildings
Authors: Macías Olga , Noyé Sarah , Tellado Nagore , Torrens Ignacio , De Agustín Pablo , Tsagkrasoulis Dimosthenis , Bucur Mircea , Southernwood Jo
Published: September 2019

The continuous growth of renewable energy and the transition to a more de-centralised electricity generation adds significant complexity to balance power supply and demand in the grid. These imbalances are partially compensated by demand response programs, which represent a new business opportunity in the building sector, especially for ESCOs. Including demand response to their traditional energy efficiency-based business model adds an additional revenue stream that could potentially shorten payback periods of energy renovation projects. This paper introduces this new dual-services business model, and evaluates the potential suitability of HVAC, generation and storage technologies to ensure proposed energy efficiency and flexibility goals.
Efficiency and area demand of multi-layer ground heat exchanger using phase change of water
Authors: Hirsch Hauke , Petzold Hans , Grunewald John
Published: September 2019

We conducted numerical simulations of a heat pump system connected to a horizontal ground heat exchanger (HGHX), using a coupling of the hygro-thermal simulation software DELPHIN with Modelica. The aim was to study the influence of different HGHX sizes and assemblies as well as the impact of passive cooling on the systems efficiency. We found that the required ground area could be reduced by up to 70 % compared to the recommendation of German standard when the pipes are placed in multiple layers. Passive cooling is possible but has a negligible effect on the systems efficiency.
Evaluation of heat transfer in humidification phenomena – Comparison between infrared thermography and numerical simulation
Authors: Barreira Eva , Almeida Ricardo M.S.F. , Pereira Miguel
Published: September 2019

Infrared thermography (IRT) is a non-destructive testing technology used to assess the performance of buildings. As a diagnosis tool for retrofit and conservation of buildings it helps understanding the anomalies by allowing “seeing” their causes in a non-invasive manner. However, in most cases, the interpretation of the results (thermal images) is mainly qualitative, restraining and, eventually, pointing to incorrect conclusions. Using numerical tools that contribute to the quantitative interpretation of IRT applications is therefore a step forward in this field. The main objective of this work is the evaluation of heat transfer in humidification phenomena by comparing the results of 2D hygrothermal simulation with thermal images. Thermal images were taken to a lightweight concrete specimen during a 24-hours partial immersion period. The humidification of the specimen was simulated using WUFI 2D. The best way to deal with the liquid water level in contact with the bottom of the specimen was deeply analysed. The comparison of the simulation with the results of IRT showed that the program tends to overestimate the phenomena of heat transfer (water rise and evaporation on the surface), as the water level reached in the simulation was consistently higher than the one obtained in the thermal images.
Freeze-thaw risk in solid masonry: are moisture reference years able to represent real climate conditions?
Authors: Vandemeulebroucke Isabeau , Caluwaerts Steven , Van Den Bossche Nathan
Published: September 2019

Today, there is no consensus on the selection method of representative exterior boundary conditions when performing HAM (Heat Air Moisture) simulations on building envelopes. Many existing methods to select moisture reference years (MRY) fail to provide an acceptable validation in terms of quantified risk assessment. Although new methods have been suggested during the past few years, the influence of several parameters on the selection of “critical years” in long-term datasets still needs to be assessed. The objective of this paper is to validate the application of MRY’s to evaluate freeze-thaw risk in retrofitted solid masonry. Furthermore, the influence of the chosen wall assembly, damage criterion, preconditioning and start date of the evaluation period on the ranking of critical years is assessed, using a 31-year meteorological dataset of Brussels. Results indicate that for a given wall assembly and freeze-thaw criterion, as well as a smart start date of the evaluated period, single year simulations entail a similar ranking of critical years as the corresponding year in the 31-year simulation. The number of critical freeze-thaw cycles only varies between 0 - 2 cycles (0 - 2.9%). However, changing the wall assembly and damage criterion, alters the top 5 ranking of critical years substantially.
Centrifuge experiments for the determination of the moisture storage and transport properties in the overhygroscopic range
Authors: Vereecken Evy , Roels Staf , Janssen Hans
Published: September 2019

This study explores the potential of a centrifuge experiment for hygric property determination. In this method, a core sample is placed in a tube which is spun at different rotational speeds to create a distribution of moisture contents and capillary pressures. This way, a simultaneous determination of the moisture retention curve and moisture permeability curve is possible. Measurements performed in the petroleum industry and in soil science already showed the technique to be an appropriate substitute for the pressure plate method. In building physics, the potential of the centrifuge method is currently still unexplored. Therefore, in this study, preliminary desorption measurements on brick samples are performed. To infer the moisture retention curve, an approximate data analysis method is applied. This approach is compared to a more sophisticated parameter estimation technique, which is also used to infer the moisture permeability curve. From a theoretical point of view, the centrifuge method allows a simultaneous determination of the moisture storage and transport properties of building materials. In practice, however, experimental inaccuracies make the experimental results unusable for a reliable determination of the moisture transport properties.
Characterization of the diffusivity function through water-uptake tests
Authors: Bianchi Janetti Michele , Janssen Hans
Published: September 2019

A method is proposed to determine the moisture diffusivity of capillary active materials by means of water-uptake tests performed with different initial water contents. The method is based on an analytical approach, in which the diffusivity is approximated as a multiple step function of the water content. Contrary to other well-established techniques, the method proposed here requires neither the knowledge of the water content distribution in the absorbing sample, nor the application of numerical simulations. Experiments are carried out on calcium silicate samples.
Parametric assessment of a building active façade by means of a combined metallic sandwich panel with an unglazed solar collector
Authors: Elguezabal Peru , Lopez Alex , Blanco Jesús María , Chica José Antonio
Published: September 2019

The building sector has a poor performance in terms of energy efficiency and is looking for alternatives to reduce the use of fossil fuels on building use stage. Renewables are unlimited and solar thermal energy is a technology with a demonstrated potential. The façade is a key element able to harness renewable energy coming from the sun becoming in an Active Solar Thermal Façade (ASTF). The main purpose of this study is the development of a parametric study using a numerical model to analyze the behavior of an unglazed solar collector. Thus, evaluating different design and meteorological parameters to show their influence on the heat transfer and the efficiency. The study shows that solar irradiation and mass flow are the most influential on thermal difference. However, for the efficiency ambient temperature and inlet temperature both are the most influencing ones. In brief, a set of parameters have a significant influence on the behavior of the ASTF that are fully governed by environmental conditions. Nevertheless, there are some other parameters that can be controlled during the operation. The challenge is to make a continuous configuration of this adaptable values depending on the external situation to achieve a higher performance for the ASTF.
Experimental field-trial design to investigate the effects of a defective internal vapour layer on timber frame wall constructions including initial findings
Authors: Corcoran Lee , Duffy Prof Aidan
Published: September 2019

Hygrothermal analysis in multi-layered building components is becoming common practice. Low energy design criteria demands an increase in thermal and airtightness requirements resulting in more complicated building envelope designs to accommodate the necessary insulation and airtightness layers. Furthermore, in many cases materials are being chosen based solely on their thermal characteristics without fully considering other properties and this may lead to unintentional interstitial moisture-related problems. Much progress has been made in developing tools for undertaking hygrothermal simulations; however, there are on-going questions regarding how best to model imperfections and defects accurately using these software packages. Results of simulation models carried out in accordance with the new WTA guideline have been reported in literature as encouraging and confirming practical experience. Further verification of these simplified methods is therefore essential, including investigations of the relationship between model assumptions and typical defects in different construction types. Therefore, there is a need for specific field experiments and laboratory tests which gather the data necessary to validate and/or calibrate these models under a wider range of constructions types, defect types and climates. This paper describes the experimental design and fabrication of a full-scale timber frame test house that has been developed to assess the impact of a common defect in the internal vapour control/airtightness barrier, along with initial data results and findings. The data obtained will be used to validate existing commercial hygrothermal models and investigate different parameters and methods for modelling these vapour barrier defects.
Suitability of time domain reflectometry (TDR) for moisture content monitoring in historic building walls
Authors: Stingl Freitas Teresa , Guimarães Ana Sofia , Freitas Vasco Peixoto de
Published: September 2019

Measuring moisture content in building materials is crucial for the correct diagnosis of buildings pathologies, for the adoption of appropriate intervention measures and for the efficiency evaluation of the treatment solutions applied. There are several different techniques available to measure and monitoring the moisture content in building materials. However, it still remains a great challenge to perform those studies in historical buildings, since minor-destructive techniques are required. Furthermore, if continuous moisture content readings in space are desired, in order to study the moisture transfer phenomenon along the wall thickness, the challenge is even greater. The TDR technique is a relatively new method for measurement of moisture content in building materials with a set of unexplored potentialities capable of satisfying the two mentioned requirements. In this paper, the suitability of the TDR technique to obtain continuous cross-section moisture content profiles has started to be tested on two limestone prototype walls. Each wall was equipped with four TDR probes, designed practically with the same length of the wall thickness and placed at different heights. All the necessary equipment, installation steps, and difficulties are here presented. The preliminary results suggest that the TDR technique is suitable for moisture content monitoring in consolidated porous building materials.
Hygric parameters of cement-lime plasters modified by superabsorbent polymers
Authors: Kočí Jan , Begaly Akbota , Fořt Jan
Published: September 2019

Moisture level significantly affects durability of constructions, their thermal performance and quality of indoor air. As the building envelopes are subjected to the effect of changing weather conditions from the exterior and numerous sources of water vapor from interior, the proper design may significantly increase the performance of the construction. In this paper, modified plasters with different amount of super absorbent polymers (SAP) are analyzed in the laboratory conditions in terms of their hygric and mechanical properties. The results showed that addition of SAP in the plasters may be promising for the utilization in building envelopes composition. However, the exact amount of SAP is crucial as the results revealed that if more that 1% of SAP is added to the plasters, the poor mechanical properties may exclude the plasters from real applications.
Evaluation of mould growth risks due to air leakage through air cavity of the building walls
Authors: Dang Xinyuan , Hokoi Shuichi , Li Yonghui , Xia Changchang , Yan Ma
Published: September 2019

Mould growth causes damage and poses high risk to a large number of existing buildings and their users. Air leakage through air cavity of the building walls, such as gaps between walls and some pipes penetrating the walls, produces obvious hygrothermal exchange, altering the temperature and humidity distribution of the walls. It would promote condensation and mould growth. Air cavity are common on the walls of existing buildings. In order to make a quantitative analysis on the mould growth risks due to air leakage through air cavity, an office room in an existing building in Nanjing, China was selected and hygrothermometers were arranged indoor and outdoor for monitoring. The measured results showed the room was in high temperature and relative humidity from June to early September. Two-dimensional hygrothermal simulation was made to investigate the hygrothermal conditions of the walls with air cavity, using the measured data as boundary conditions and validation for the numerical simulation. Mould growth risks under these situations were estimated.
Experimental determination of length changes of autoclaved aerated concrete during the freeze-thaw cycle
Authors: Sovják Radoslav , Maděra Jiří
Published: September 2019

The aim of the paper is an experimental determination of the longitudinal expansion of autoclaved aerated concrete (AAC) during the freeze-thaw cycle. Longitudinal changes were measured with lasers and the surface temperature was measured using an infrared temperature gauge. The temperature distribution over the sample was verified by a numerical calculation.
The urban heat island effect on frost damage of natural building stones.
Authors: Guilbert Daphne , De Kock Tim , Caluwaerts Steven , Cnudde Veerle , Calle Klaas , Van Den Bossche Nathan
Published: September 2019

Climate plays a major role in the weathering of building stones. This study specifically investigates the influence of the urban heat island (UHI) in Ghent, Belgium, on freeze-thaw (F-T) weathering of natural building stones and their hydrophobic equivalent. Climatic analysis of data of two places in and around Ghent indicates higher temperatures and lower wind speeds in the city center. This leads to a reduced number of F-T cycles and a lower wind-driven load. Hygrothermal modelling of a natural building stone, Savonnières limestone, is performed for the urban and rural climate of Ghent on the untreated limestone and on the treated limestone to assess the freeze-thaw risk inside these materials. Urban climate has a mitigating effect on the potential frost risk in natural building stones as a result of the urban heat island. Additionally, the application of a water repellent product reduces the potential frost risk even more, since the water density in the stone is reduced.
Experimental investigation of frost induced damage of cement mortar
Authors: Wieczorek Alicja , Koniorczyk Marcin , Grabowska Kalina
Published: September 2019

Questions connected to influence of frost degradation on microstructure and physical properties of water saturated cement mortars and their resistance to cyclic water freezing are the objectives of research. The main aim of the investigation is to analyze the ice-induced deterioration of cement mortars with different water/cement ratios (w/c=0.50 and 0.40) in a accelerated durability tests. The changes of pore size distribution and water absorption coefficient are investigated by means of mercury intrusion porosimetry and capillary absorption test. Additionally, the analysis of the impact of drying temperature (40°C, 60°C, 80°C and 105°C) on the microstructure is introduced.The performed tests enabled to estimate that the destruction of the cement matrix and the range of observed changes depend on the initial pore size distribution and their volume in the cement matrix. It is also established that the increase of transport properties is correlated with the change of pore size distribution. The obtained results allow to conclude a decrease of content of small pores (up to 150nm) and increase of larger pores for mortar with w/c=0.50. Application of superplasticizer, which resulting in reduction of water to cement ratio up to 0.40, allows to obtained resistant to 150 frost cycles cement mortar.
Open Ankle Dislocation without Associated Malleolar Fracture on a Trampoline. A Case Report
Authors: Hagebusch Paul , Neun Oliver , Gramlich Yves , Schweigkofler Uwe , Hoffmann Reinhard
Published: September 2019

Dislocation of the ankle without fracture is very uncommon. There are only few reports in the international literature. Up to now approximately 80 cases are published. The risk of hyperflexion and -inversion of the ankle seems high on a trampoline. A multiple of the jumperʼs body-weight projects delayed on the upper ankle joint while dipping in the trampoline-sheet. Reduction should be performed as fast as possible to ensure a good clinical outcome. Imaging via MRI and CT scan allows a detailed evaluation of the injury severity. The decision for further treatment should be based on the findings in the MRI and CT scans. Reconstructing the medial and lateral capsular ligaments can be necessary. With a consequent treatment algorithm a good functional outcome can be achieved. In our case we documented a post-traumatic AOFAS score of 87/100 six months after the injury without an instability of the upper or lower ankle joint. Propioreceptive reflex and pronator training as well as taping seem to be useful before and during trampoline sports.
Parasitic Infections
Authors: Khubchandani Indru T. , Bub David S.
Published: September 2019

Parasitic infections of the gastrointestinal tract are a cause of morbidity to millions of individuals worldwide. These parasites are endemic in underdeveloped countries with poor sanitation allowing for spread through contaminated water supplies. While much is known about these parasites, the cutaneous manifestations caused by infection are infrequently reported in the literature. The deposition of the parasites into the perianal region often leads to significant skin irritation. Cutaneous findings vary from a mild pruritus ani to a macular rash to even severe perianal ulceration. This article discusses the perianal cutaneous findings caused by the parasitic illnesses, amebiasis, schistosomiasis, Enterobius vermicularis, strongyloidiasis, and cutaneous larva migrans, as well as their respective management.
Early Antibiotic Prophylaxis Prior to Bypass Surgery Improves Tissue Penetration
Authors: Andreas Martin , Zeitlinger Markus , Shabanian Shiva , Wisser Wilfried , Thell Rainer , Edlinger-Stanger Maximilian , Maier-Salamon Alexandra , Jaeger Walter , Kocher Alfred , Laufer Guenther , Hiesmayr Joerg-Michael , Hutschala Doris
Published: September 2019

Background We previously identified preparation of the internal mammary artery as a risk factor significantly impairing antibiotic tissue penetration into the presternal subcutaneous tissue. We, therefore, adapted our dosing schema regarding preoperative timing to overcome this risk factor.

Methods Eight patients who underwent coronary artery bypass grafting with a left internal mammary artery and vein grafts were included in this clinical trial. Cefazolin (4 g) was administered twice (3 hours and 1 hour) prior to skin incision and once during skin closure (2 g). Antibiotic concentrations were measured with subcutaneous microdialysis probes on both sternal sides. Results were directly compared with the previously published patient cohort receiving the standard schema (4 g cefazolin prior to skin incision and 2 g during closure).

Results All patients (7 male, 1 female, 69 ± 7 years, 26.3 ± 3.9 kg/m2) survived the perioperative period. Mean area under the curve on the right and left sternal side was 117.0 ± 92.5 μg/mL and 114.5 ± 83.2 μg/mL, respectively (p = 0.95). This was well above the previously measured mean peak tissue concentrations without early preoperative antibiotic administration on the side of mammary artery harvesting (52.4 ± 48.5 μg/mL vs. 13.1 ± 5.8 μg/mL; p = 0.039). The %fT > minimal inhibitory concentration (MIC) for Staphylococcus epidermidis and Staphylococcus aureus during the first 10 hours in presternal tissue was ≥ 70% but did not differ compared with standard schema.

Conclusions Early, additional preoperative administration of cefazolin was able to significantly increase peak tissue concentrations during surgery compared with the standard protocol. No difference, however, could be achieved in the percentage of time during which the concentration exceeded the MIC.
Review of Bladder Pain and Referred T12–L2 Input as One Etiology for Interstitial Cystitis
Authors: Dellon A. Lee , Herati Amin S.
Published: September 2019

Background The etiology of interstitial cystitis (IC)/bladder pain syndrome (BPS) remains a mystery. Based on two patients, whose IC/BPS was relieved by resection of injured iliohypogastric (IH) and ilioinguinal (II) nerves, injured by endoscopic prostatectomy in the first patient and a stretch/traction injury in the second patient, a referred pain pathway is hypothesized that can be applied to patients with IC/BPS and previous abdominal wall surgery/injury.

Methods The known neurophysiology of bladder function was reviewed as were the pathways for accepted referred pain syndromes.

Results Perception of bladder filling occurs by impulses generated from stretch receptors in the bladder wall, traveling along visceral afferent fibers that enter the thoracolumbar spinal cord at T12, L1, and L2, the same location as the sympathetic outflow to the viscera and the same location as some of the visceral afferents from the bladder. The II and IH nerves originate from T12, L1, and sometimes L2 somatic, dorsal root ganglia. It is hypothesized that somatic afferent pain impulses, from the lower abdominal wall, are misinterpreted as visceral afferent impulses from the bladder, giving rise to the urinary frequency and urgency of IC/BPS. Resecting injured cutaneous afferents (II and IH) permitted long-term IC/BPS relief in the first patient for 59 months and in the second patient for 30 months. Neural inputs from the sacral visceral afferents and sacral somatic afferents did not appear to be involved in this referred pain pathway.

Conclusion Nerve blocks of the T12 -L2 spinal nerves in patients with bladder pain who also have had abdominal wall surgery/injury may identify IC/BPS patients for whom resection of the II and IH nerves may prove beneficial in obtaining lasting IC/BPS relief.
In Vivo Kinematics of Bicruciate-Retaining Total Knee Arthroplasty with Anatomical Articular Surface under High-Flexion Conditions
Authors: Kono Kenichi , Inui Hiroshi , Tomita Tetsuya , Yamazaki Takaharu , Taketomi Shuji , Tanaka Sakae
Published: September 2019

Bicruciate-retaining total knee arthroplasty (BCR-TKA) recreates normal knee movement by preserving the anterior cruciate and posterior cruciate ligaments. However, in vivo kinematics of BCR-TKA with the anatomical articular surface remains unknown. The objective of this study was to evaluate in vivo kinematics of BCR-TKA with the anatomical articular surface during high-flexion activities. For this purpose, 17 knees after BCR-TKA with an anatomical articular surface were examined. Under fluoroscopy, each patient performed squatting and cross-legged sitting motions. To estimate the spatial position and orientation of the knee, a two-dimensional or three-dimensional registration technique was used. Rotation, varus-valgus angle, and anteroposterior translation of medial and lateral contact points of the femoral component relative to the tibial component were evaluated in each flexion angle. The results showed that from 80 to 110° of flexion, the femoral external rotation during squatting was significantly larger than that during cross-legged sitting. At maximum flexion, the knees during sitting indicated significantly more varus alignment than during squatting. During squatting, a medial pivot pattern was observed from minimum flexion to 10° flexion, with no significant movement beyond 10° of flexion. Conversely, during cross-legged sitting, no significant movement was detected from minimum flexion to 60° of flexion, with a medial pivot beyond 60° of flexion. Therefore, the knees showed relatively normal kinematics after BCR-TKA with an anatomical articular surface; however, it varied during high-flexion activities depending on the activity.
Studies of electrical and magnetic properties across the Verwey transition in epitaxial magnetite thin films
Authors: Singh Amit V. , Srivastava Abhishek , Mohammadi Jamileh Beik , Regmi Sudhir , Bhat Usha , Datta Ranjan , Mewes Tim , Gupta Arunava
Published: September 2019

The magnetic and transport properties of magnetite (Fe3O4) films grown on isostructural substrates (MgAl2O4, MgGa2O4, and CoGa2O4), with varying degrees of lattice mismatches (3.8%, −1.4%, and −0.8%, respectively), have been investigated. A significant reduction in the density of antiphase boundary defects is observed for the Fe3O4 films grown under optimal process conditions on smaller lattice mismatch substrates (MgGa2O4 and CoGa2O4) as compared to MgAl2O4. Correspondingly, films on these substrates show much improved magnetic properties and sharper transition in the resistance values at the Verwey transition. Room temperature magnetic hysteresis and ferromagnetic resonance measurement studies indicate the presence of uniaxial magnetic anisotropy induced by substrate-induced strain in the film. Temperature-dependent transport measurements confirm that film thickness has a larger effect on the sharpness of the Verwey transition temperature than the degree of lattice mismatch with substrates.
Cooling of a levitated nanoparticle with digital parametric feedback
Authors: Zheng Yu , Guo Guang-Can , Sun Fang-Wen
Published: September 2019

The motion control of a levitated nanoparticle plays a central role in optical levitation for fundamental studies and practical applications. Here, we presented digital parametric feedback cooling based on square wave modulation by switching trapping laser intensity between two levels. The effects of the modulation depth and modulation signal phase on the cooling result were investigated in detail. Using such a digital parametric feedback method, the center-of-mass temperature of all three motional degrees of freedom can be cooled to dozens of millikelvin. The flexibility and agility of the digital feedback control pave the way for a variety of motion control modes.
Arc discharges during disruptions in the T-10 tokamak
Authors: Savrukhin P. V. , Shestakov E. A.
Published: September 2019

Arc discharges are considered as a possible mechanism determining transition from relatively slow growth of the magnetohydrodynamic (MHD) perturbations to thermal quench (minor disruption) and subsequent transition to the major disruption with current collapse in the T-10 tokamak. The effect of the arc discharges is evaluated using analysis of the fast-scale (0.2–1.5 MHz) electromagnetic oscillations measured by movable magnetic and electric probes located near the plasma boundary at multiple positions inside the vacuum vessel and by postoperational inspection of the in-vessel components. Experiments using a special “arc” probe with castellated surface stimulating arc discharges indicated that transition to the major disruption is associated with enhanced electron emission from the plasma facing components. The role of the arcs is confirmed in experiments with initiation of the currents in the peripheral plasma using biasing (Ub ∼ 0–400 V) between the rail limiter and the movable tungsten electrode. Experiments indicated that critical surface current density is required for the arc initiation. The radial decay rate and frequencies of the electromagnetic oscillations measured in the T-10 experiments are found to be similar to the ones during arc discharges at the laboratory bench. Present experiments in the T-10 tokamak indicate that arc discharges could determine plasma-wall interaction during growth of the MHD modes and disruptions.
Dielectric nanoantennas to manipulate solid-state light
emission
Authors: Bidault Sébastien , Mivelle Mathieu , Bonod Nicolas
Published: September 2019

Thanks to their enhanced and confined optical near-fields, broadband subwavelength resonators have the ability to enhance the spontaneous emission rate and brightness of solid-state emitters at room temperature. Over the last few years, high-index dielectrics have emerged as an alternative platform to plasmonic materials in order to design nanoresonators/optical nanoantennas with low ohmic losses. In particular, the excitation of electric and magnetic multipolar modes in dielectric resonators provides numerous degrees of freedom to manipulate the directivity and radiative decay rates of electric or magnetic quantum emitters. We review recent theoretical and experimental applications of dielectric nanoantennas to enhance or control decay rates of both electric and magnetic emitters but also to manipulate their radiation pattern through the coherent excitation of electric and magnetic modes; before discussing perspectives of this emerging field.
Polarization modulation effect of BeO on AlGaN/GaN high-electron-mobility transistors
Authors: Wang Weijie , Lee Seung Min , Pouladi Sara , Chen Jie , Shervin Shahab , Yoon Seonno , Yum Jung Hwan , Larsen Eric S. , Bielawski Christopher W. , Chatterjee Bikramjit , Choi Sukwon , Oh Jungwoo , Ryou Jae-Hyun
Published: September 2019

We investigate the polarization modulation effect of a single-crystalline BeO layer on AlGaN/GaN high-electron-mobility transistors (HEMTs). The BeO layer with macroscopic polarization on top of the AlGaN barrier layer increases the 2-dimensional electron gas density in the triangular quantum well (QW) at the interface of the AlGaN/GaN heterostructure. Electronic band bending of BeO and a deeper triangular QW observed from the simulated conduction band profile indicate that the BeO layer can modify the polarization field at the AlGaN/GaN interface. A ∼20-nm-thick single-crystalline BeO thin film is grown on AlGaN/GaN HEMTs by atomic-layer deposition. Room-temperature and variable-temperature Hall-effect measurements confirm that the HEMT with BeO forms a channel with a 14% increase of the sheet carrier concentration as compared with a conventional HEMT. An improved output performance is also observed in the I-V characteristics which confirms the polarization modulation effect of the BeO layer.
Efficient formulation of full configuration interaction quantum Monte Carlo in a spin eigenbasis via the graphical unitary group approach
Authors: Dobrautz Werner , Smart Simon D. , Alavi Ali
Published: September 2019

We provide a spin-adapted formulation of the Full Configuration Interaction Quantum Monte Carlo (FCIQMC) algorithm, based on the Graphical Unitary Group Approach (GUGA), which enables the exploitation of SU(2) symmetry within this stochastic framework. Random excitation generation and matrix element calculation on the Shavitt graph of GUGA can be efficiently implemented via a biasing procedure on the branching diagram. The use of a spin-pure basis explicitly resolves the different spin-sectors and ensures that the stochastically sampled wavefunction is an eigenfunction of the total spin operator S^2. The method allows for the calculation of states with low or intermediate spin in systems dominated by Hund’s first rule, which are otherwise generally inaccessible. Furthermore, in systems with small spin gaps, the new methodology enables much more rapid convergence with respect to walker number and simulation time. Some illustrative applications of the GUGA-FCIQMC method are provided: computation of the 2F − 4F spin gap of the cobalt atom in large basis sets, achieving chemical accuracy to experiment, and the Σg+1, Σg+3, Σg+5, and Σg+7 spin-gaps of the stretched N2 molecule, an archetypal strongly correlated system.
Characterization of Ge ions implantation in Sb2Te3 thin films for high speed phase change memory application
Authors: Zhang Xin , Zhang Zhonghua , Song Sannian , Zheng Qianqian , Yu Wenlei , Zheng Wanting , Zhu Xiuwei , Shao Hehong , Zhang Juan , Chen Liangliang
Published: September 2019

Ge ion implantation is adopted for doping of Sb2Te3 thin films and modifying the amorphous to crystal transition kinetics. The crystallization temperatures, crystallization activation energies of crystallization, and thermal stability improve with the Ge dose increasing from 5 × 1015 to 3.0 × 1016 Ge-ions/cm2. In the case of 1.0 × 1016 Ge-ions/cm2 dose, GexSb2Te3 phase change material exhibits a higher crystallization temperature (∼180 °C), a larger crystallization activation energy (∼3.7 eV), and a better data retention ability (∼102 °C for 10 years) in comparison with Ge2Sb2Te5. A reversible switching between Set and Reset can be realized by an electric pulse width as short as 10 ns for GexSb2Te3 based phase change memory.
Numerical evaluation of hydrogen outgassing from copper electrodes with mitigation based on a tungsten capping layer
Authors: Acharjee J. , Joshi R. P.
Published: September 2019

Outgassing remains a pertinent issue for high power applications and is exacerbated by the high field driven, localized heating environments commonly encountered. Here, molecular dynamics simulations are performed for a simple model-based assessment of outgassing from electrodes. Our results of temperature dependent diffusion coefficients for hydrogen in copper agree well with experimental reports over a wide range spanning 300 K to 1330 K. Separate results are also obtained for transport of hydrogen to ascertain whether a grain-boundary would facilitate channeled transport or work to impede flow by clustering the gas atoms. Finally, the use of a tungsten overlayer on copper is evaluated as a material-based strategy for mitigating outgassing. It is demonstrated that a few monolayers of tungsten coating on the outer surface can be effective in significantly reducing outdiffusion at 700 K.
Broadband near-perfect absorption of low-frequency sound by subwavelength metasurface
Authors: Long Houyou , Shao Chen , Liu Chen , Cheng Ying , Liu Xiaojun
Published: September 2019

The emerging absorptive metasurface relies on arrays of structured meta-atoms with various geometries for customized sound localization, which can significantly enhance the energy dissipation. However, most of the existing absorbers are for given frequencies at an optimal incident angle. This limitation on the working frequency and incident angle remains a challenging obstacle for their practical applications, in addition to the perfect absorptance demand. Guided by the causality principle, a physical model is established in which the absorptive properties of such systems can be fully controlled by two simple parameters (i.e., leakage factor and loss factor) which are dictated by the geometrical properties of the underlying structures. We demonstrate a subwavelength metasurface absorber which shows near-perfect absorptance (at 95%) in a broad frequency regime from 228 Hz to 319 Hz (wavelength λ from 12.6 to 9.0 times thickness) and even allows 93% reduction with a large incident angle of 60°. We prove that this broadband near-perfect absorption behavior stems from the tunable damping conditions, which can be achieved by coupling an ordinary ultrathin surface sponge coating with an artificial underdamped multiband absorptive system. From the view of the causality principle, the subwavelength near-perfect absorptions originate from the finite working bandwidth. As the research premise, we also demonstrate a λ/21.7-thick, 16.7%-filling ratio ultrasparse absorber with unity absorptance by modulating the displacements between uniformly sized coiled space resonators. The paradigm may pave the way for versatile devices in noise remediation engineering.
Atlas of the medium frequency waves in the ion-electron two-fluid plasma
Authors: Huang Y. C. , Lyu L. H.
Published: September 2019

Medium-frequency waves in the ion-electron two-fluid plasma with frequencies between the electron gyrofrequency and the ion gyrofrequency are studied. The dispersion relations and the Friedrichs diagrams of the group velocities are plotted with color-coded electric-field information. The group-velocity distributions and the properties of the electric fields can help us explain the observed dynamic spectra of waves when the waves are generated by a localized broadband disturbance. Possible sources of such disturbances are explored. One of them is the magnetic trapped energetic electrons with pitch angles greater than 70°. The dynamic spectra of the waves generated by these energetic electrons are ray-angle dependent. For the ray angle greater than 2°, the dynamic spectra of the rising-tone quasielectromagnetic chorus waves are characterized by a frequency gap near half of the electron gyrofrequency. The dynamic spectra of the rising tone chorus waves without the frequency gap can only be found when either the ray angle is less than 2° or when the lower-band chorus waves are quasielectrostatic. Lightning from the neutral atmosphere provides another type of localized disturbance. Depending on the magnetic latitude, lightning can result in two types of falling-tone electromagnetic whistler waves. One of them is the low-k⊥ whistler waves with highly field-aligned phase velocity and group velocity. The other is the high-k⊥ whistler waves with highly field-aligned group velocity but with phase velocity almost perpendicular to the background magnetic field. The results of this study will provide a road map for future studies of the waves in this frequency range.
Thermal boundary resistance measurement and analysis across SiC/SiO2 interface
Authors: Deng Shichen , Xiao Chengdi , Yuan Jiale , Ma Dengke , Li Junhui , Yang Nuo , He Hu
Published: September 2019

Silicon Carbide (SiC) is a typical material for third-generation semiconductors. The thermal boundary resistance (TBR) of the 4H-SiC/SiO2 interface was investigated by both experimental measurements and theoretical calculations. The structure of 4H-SiC/SiO2 was characterized by using transmission electron microscopy and X-ray diffraction. The TBR was found to be 8.11 × 10−8 m2K/W at 298 K by the 3ω method. Furthermore, the diffuse mismatch model was employed to predict the TBR of different interfaces, which is in good agreement with measurements. Heat transport behavior based on the phonon scattering perspective was also discussed to understand the variations of TBR across different interfaces. Besides, the intrinsic thermal conductivity of SiO2 thin films (200–1500 nm in thickness) on 4H-SiC substrates was measured by the 3ω procedure, to be 1.42 W/m K at 298 K. It is believed the presented results could provide useful insights into the thermal management and heat dissipation for SiC devices.
First-principles study of bandgap bowing in BGaN alloys
Authors: Turiansky Mark E. , Shen Jimmy-Xuan , Wickramaratne Darshana , Van de Walle Chris G.
Published: September 2019

III-nitride alloys continue to drive advances in electronic and optoelectronic devices. Recently, boron-containing nitride alloys have been explored with the goal of expanding the range of applications. Using first-principles calculations with a hybrid functional, we study the electronic structure of wurtzite BGaN alloys. Strong bandgap bowing is observed, with a concentration-dependent bowing parameter. Due to the strong bandgap bowing, the fundamental bandgap in strain-free alloys is effectively unchanged for the lowest B concentrations. A crossover from a direct to an indirect bandgap occurs for B concentrations greater than 50%.
An inverse analysis for contact conductance at the charge/mold interface during pressurized loading of melt-cast explosives
Authors: Ni Lei , Zhang Xiangrong , Zhou Lin , Zhu Daoli
Published: September 2019

The basic safety requirement for explosive charges is their charge quality. Increasing the casting pressure can significantly reduce the solidification/cooling time and improve the charge quality of melt-cast explosives, but the mechanism underlying the former reduction is yet to be revealed. This study uses a simplified formulation of inverse analysis (namely, the conjugate gradient method with an adjoint equation) to estimate the contact conductance at the charge/mold interface with the help of experimentally determined temperatures. The method is described in detail and verified by comparing the estimated contact conductance with the exact value using simulated measurement temperatures, thereby demonstrating the effectiveness of the method. Combining this method with the experimentally determined temperatures, the mechanism underlying the reduction in the solidification/cooling time with the increase in casting pressure is revealed.
Development of a Faraday cup fast ion loss detector for keV beam ions
Authors: Lazerson Samuel A. , Ellis Robert , Freeman Chris , Ilagan Jessica , Wang Tianyao , Shao Lin , Allen Nicole , Gates David , Neilson Hutch
Published: September 2019

The development and testing of a Faraday cup fast-ion loss detector capable of measuring sub 100 keV particles is documented. Such measurement capabilities play an important role in the assessment of particle confinement of nuclear fusion experiments. The detector is manufactured using thin-film deposition techniques, building upon previous work using discrete foils. This new manufacturing method allows the form factor of the sensor to become that of essentially a microchip. Analysis of the diagnostic response is performed using Monte-Carlo particle simulations. These simulations show peaks in the detector response at 40 and 70 keV. The sensor is then tested in a tunable linear accelerator capable of accelerating protons from 20 to 120 keV. The detector response was found to be well matched to simulations. Improvements to the design to facilitate robustness are discussed.