bluuebunny/crossref_metadata_2025 huggingface dataset:
Predicting pathology on small bowel capsule endoscopy: a good FIT
Authors: Judge Ciaran , Tighe Donal , Barry Lillian , O’Neill Julie , Wong Jenny , Shahin Amir , Moran Neil , Stack Roisin , Hussey Mary , Breslin Niall , O’Connor Anthony , Ryan Barbara , Buckley Martin , McNamara Deirde
Published: October 2019

Background and study aims Small bowel capsule endoscopy [SBCE) has an established role in investigating suspected small bowel bleeding [SSBB). Identification of a biomarker to predict pathology would maximize utility of this valuable diagnostic modality. This study aimed to investigate if fecal immunochemical test [FIT) could predict likelihood of small bowel pathology on SBCE.

Patients and methods Patients referred for SBCE to investigate anaemia or suspected small bowel bleeding were prospectively recruited. All patients had negative upper and lower endoscopy prior to referral. A FIT ≥ 45 ug Hb/g was considered positive. SBCE was positive if a potential source of SSBB was identified. The primary endpoint was correlation between FIT and positive SBCE. Secondary endpoints were correlation between anemia and SBCE and a combination of anemia plus FIT and SBCE.

Results Fifty-one patients were included in the final study cohort. 29.4 % had a positive FIT, 33.3 % were anemic, and 25.5 % patients had significant SBCE findings. There was a statistically significant association between positive FIT and pathology on SBCE (OR 12, 95 % CI [2.8 – 51.9), P = 0.001). Sensitivity and specificity of positive FIT in predicting SBCE findings were 69 % and 84 %, respectively. A normal Hb had an NPV of 83 % (OR 0.30, P = 0.09). Combining Hb and FIT was statistically significant in predicting pathology on SBCE (OR 9.14, 67 % PPV, 82 % NPV, P = 0.025).

Conclusion FIT ≥ 45 ug Hb/g is a useful tool in predicting small bowel pathology on SBCE. Use of this biomarker alone, or in combination with serum haemoglobin, has value as a screening tool and may help to better triage patients referred for SBCE.
Upstream and downstream revenue of upper gastrointestinal endoscopic ultrasound determined with an episode-of-care approach
Authors: Maeng Daniel , Wall Beth , Hassen Dina , Diehl David L.
Published: October 2019

Background and study aims Upper gastrointestinal endoscopic ultrasound (EUS) has clinical advantages that can lead to improved patient outcome. This study seeks to characterize and quantify the upstream and downstream healthcare utilizations and revenues.

Patients and methods A retrospective claims data analysis of upper gastrointestinal EUS procedures was conducted at a large health system. Types of care and total revenues associated with each episode of care were characterized by descriptive statistics. Comparisons were made between patients who had Medicare Advantage and commercial plans as well as those with and without cancer diagnoses during the downstream period.

Results A total of 436 cases were identified. The most frequent downstream healthcare utilizations consisted of radiology (31 %), pathology services (28 %), and high-revenue services including chemotherapy and inpatient admissions. The most common upstream utilizations included radiology (18 %) and lab services (22 %). Average total downstream revenue was $ 34 231 (95 %CI: $ 28 561 – $ 39 901) per case, and average total upstream revenue was $4373 (95 %CI: $3227 – $ 5519). Average total revenue per case did not differ significantly between Medicare Advantage and commercial plan members. However, patients who were diagnosed with cancer at or immediately following EUS (20 %) were associated with significantly higher total revenue compared to those without cancer diagnosis (P < 0.0001).

Conclusions This episode-of-care approach to quantifying the revenue impact of upper gastrointestinal EUS to the providers suggests there are substantial downstream as well as upstream revenues associated with upper gastrointestinal EUS procedures, driven by patients who are diagnosed with cancer by the EUS procedures and subsequently require oncologic care.
Gibt es einen negativen Nacht- oder Wochenendeffekt auf den
kindlichen postnatalen Zustand bei Frauen mit
Migrationshintergrund?
Authors: David Matthias , Henrich Wolfgang , Schlembach Dietmar , Lanowska Malgorzata , Razum Oliver , Breckenkamp Jürgen
Published: October 2019

Fragestellung Ist bei Frauen mit Migrationshintergrund (MH)
(=Proxy-Variable für erhöhtes Risiko
kultureller/sprachlicher Kommunikationsprobleme) die neonatale
Morbidität außerhalb der Regelarbeitszeit
erhöht?

Methoden Datenerhebung an 3 Berliner Geburtskliniken mit
Fragebogenset (soziodemografische, Versorgungsaspekten, Migration);
Ergänzung durch Mutterpassangaben und Klinik-Perinataldaten.
Surrogatmarker für kindliche Morbidität: Apgar-,
Nabelschnur-pH-Wert, Verlegung in eine Kinderklinik. Deskriptive und
logistische Regressions-Analysen wurden durchgeführt.

Ergebnisse Datensätze von 2014 Migrantinnen der 1., 771
Frauen der 2. Generation, 2564 Frauen ohne MH wurden einbezogen, darunter
39,7% sog. Tagesgeburten (Montag – Freitag, jeweils
7:00–18:00 Uhr). In 2 Modellen wurde für die beiden
Proxy-Parameter der kindlichen Morbidität der Einfluss der
Geburtszeit und verschiedener anderer Parameter überprüft.
Die Chancen für ungünstige Apgar- oder Nabelschnur-pH-Werte
waren z. B. bei einer Geburt in den Abend- und Nachtstunden, am
Wochenende und an Feiertagen (OR 1,84; 95% CI 1,23–2,76;
p=0,003), bei vaginal-operativen Geburten (OR 3,36; 95% CI
2,07–5,46, p<0,001) oder einer sekundären Sectio (OR
1,94; 95 CI 1,28–2,96, p=0,002) erhöht, nicht aber
bei einem MH der Gebärenden.

Zusammenfassung Gebärende mit MH werden trotz
möglicher interkultureller und sprachlicher Kommunikationsprobleme
unabhängig von Tageszeit und Wochentag ebenso gut versorgt wie
Schwangere ohne MH.
Diabetic Neuropathy
Authors: Zakin Elina , Abrams Rory , Simpson David M.
Published: October 2019

Diabetes mellitus is becoming increasingly common worldwide. As this occurs, there will be an increase in the prevalence of known comorbidities from this disorder of glucose metabolism. One of the most disabling adverse comorbidities is diabetic neuropathy. The most common neuropathic manifestation is distal symmetric polyneuropathy, which can lead to sensory disturbances, including diminished protective sense, making patients prone to foot injuries. However, focal, multifocal, and autonomic neuropathies are also common. Diabetic nerve pain and Charcot osteoarthropathy are advanced neuropathic conditions that portend a severe deterioration in quality of life. To combat these symptoms, along with glycemic control and establishment of health care systems to educate and support patients with the complexities of diabetes, there are pharmacologic remedies to ameliorate the neurologic symptoms. Several guidelines and review boards generally recommend the use of tricyclic antidepressants, serotonin/norepinephrine-reuptake inhibitors, α-2-delta ligands, and anticonvulsants as medications to improve painful diabetic neuropathy and quality of life.
Neuropathy of Connective Tissue Diseases and Other Systemic Diseases
Authors: Jin Peter H. , Shin Susan C.
Published: October 2019

Peripheral neuropathy is associated with numerous systemic diseases. It is often the heralding finding, which can lead to earlier diagnoses and better outcomes. An understanding of the epidemiology and clinical features of these diseases is paramount to their diagnosis and management. This article will focus on neuropathy associated with connective tissue diseases, monoclonal gammopathies, paraneoplastic disorders, medications including chemotherapeutic agents, nutritional deficiencies, alcohol, and toxins.
Peripheral Neuropathies in Infectious Diseases
Authors: Anand Pria , Kharal G. Abbas , Reda Haatem , Venna Nagagopal
Published: October 2019

Peripheral nerve disorders may be the presenting manifestation of a systemic infection, and early recognition of these syndromes is essential for prompt diagnosis and treatment. Mechanisms associated with infectious disorders of the peripheral nerve are often complex and multiple, with secondary inflammation, direct infectious invasion of nerves, and toxicities of antimicrobial medications playing a role. Here, we provide a complete review of the most common infectious pathogens that can affect the peripheral nerves.
Synthesis of Enantioenriched Tetra-ortho-3,3′-substituted Biaryls by Small-Molecule-Catalyzed Noncanonical Polyketide Cyclizations
Authors: Witzig Reto M. , Sparr Christof
Published: October 2019

The arene-forming aldol condensation is a fundamental reaction in the biosynthesis of aromatic polyketides. Precisely controlled by the polyketide synthases, the highly reactive poly-β-carbonyl substrates are diverged into numerous aromatic natural products by selective cyclization reactions; a fascinating biosynthetic strategy that sparked our interest to investigate atroposelective aldol condensations. In this Account, we contextualize and highlight the ability of small-molecule catalysts to selectively convert noncanonical hexacarbonyl substrates in a double arene-forming aldol condensation resulting in the atroposelective synthesis of tetra-ortho-3,3′-substituted biaryls. The hexacarbonyl substrates were obtained by a fourfold ozonolysis enabling a late-stage introduction of all carbonyl functions in one step. Secondary amine catalysts capable of forming an extended hydrogen-bonding network triggered the noncanonical polyketide cyclization in order to form valuable biaryls in high yields and with stereocontrol of up to 98:2 er.

1 Biosynthesis of Aromatic Polyketides

2 Rotationally Restricted Aromatic Polyketides

3 3,3′-Substituted Binaphthalenes in Catalysis

4 Stereoselective Synthesis of Atropisomers

5 Synthesis of Enantioenriched Tetra-ortho-3,3′-Substituted Biaryls by the Atroposelective Arene-Forming Aldol Condensation

6 Conclusion
Laboratory Evaluation of Peripheral Neuropathy
Authors: Lau K.H. Vincent
Published: October 2019

Peripheral neuropathy is a common neurological disorder, with high prevalence especially in the aged population. The general evaluative approach is to first identify the type of peripheral neuropathy prior to investigating for a possible underlying etiology, which is an increasingly important endeavor, as many causes of peripheral neuropathy are now recognized as treatable. To this end, laboratory testing plays an important adjunctive role to a detailed history and examination. This review will discuss possible diagnostic laboratory testing pathways for different types of peripheral neuropathy, with the goal of minimizing costs and false-positive results while maximizing the likelihood of identifying a potentially reversible etiology.
Common Entrapment Neuropathies
Authors: Malek Elia , Salameh Johnny S.
Published: October 2019

Entrapment neuropathies are defined as compression of peripheral nerves due to known or unknown causes. The high incidence and variety of presentations require a comprehensive knowledge of these conditions, especially in neurology and orthopedic surgery clinical practices. Detailed knowledge of topographic anatomy, clinical manifestations, and appropriate use of electrophysiological studies with selective addition of neuromuscular ultrasonography are needed to establish an early and accurate diagnosis to advice patients and provide them with a comprehensive treatment plan. In this article, we discuss the most common forms of entrapment neuropathies in the upper and lower extremities.
Guillain–Barre Syndrome
Authors: Malek Elia , Salameh Johnny
Published: October 2019

Guillain–Barre syndrome (GBS) is the leading cause of acute paralysis that can potentially affect all of the human population. GBS is believed to be an immune-mediated disease, possibly triggered by a recent infection, and driven by an immune attack targeting the peripheral nervous system. GBS can be divided into several subtypes depending on the phenotype, pathophysiology, and neurophysiological features. Unfortunately, morbidity and mortality rates are still high despite the current understanding of the pathophysiology and available treatment options. Additional research is still needed to shed more light into the pathogenesis for a better understanding and treatment of this condition.
A Clinician's Approach to Peripheral Neuropathy
Authors: Siao Peter , Kaku Michelle
Published: October 2019

Peripheral neuropathies are a group of disorders that affect the peripheral nervous system, for which hundreds of etiologies have been identified. This article presents a stepwise approach to the evaluation and workup of peripheral neuropathy, which starts with a detailed history of symptoms, family and occupational history, and a neurological as well as general physical exam. Pattern recognition of various neuropathies can help to build a differential diagnosis based on the presentation. Such patterns include acute versus chronic, primary demyelinating versus axonal, hereditary versus acquired, asymmetric versus symmetric, presence of facial palsies, sensory or motor predominant, and presence of prominent autonomic symptoms. Early categorization of the type of neuropathy can help focus the workup for peripheral neuropathy. Nerve conduction studies and electromyography (NCS/EMG) is the primary diagnostic tool in the evaluation of patients with large-fiber polyneuropathy. One of the most important roles of NCS/EMG is to help categorize polyneuropathy as primary axonal versus primary demyelinating. The finding of a primary demyelinating polyneuropathy narrows the differential diagnosis of polyneuropathy dramatically and increases the chances of finding a treatable etiology. Laboratory workup includes serum studies and potentially cerebrospinal fluid, genetic studies, immunological markers, and fat pad biopsy for select patients. Skin biopsy may be used to assess intraepidermal nerve fiber density if small-fiber neuropathy is suspected, and nerve biopsy may be useful in select cases. In recent years, magnetic resonance imaging and neuromuscular ultrasound have also shown promise in the evaluation of peripheral neuropathy. Identification of the etiology of neuropathy is crucial and often time-sensitive, as an increasing number of causes are now reversible or treatable.
Chin Reshaping in Profileplasty: Augmentative and Reductive Strategies
Authors: Eppley Barry L.
Published: October 2019

After studying this article, the reader should be able to understand how various implants, osteotomies, and reductive tissue techniques affect the aesthetic outcomes of chin reshaping surgery. The roles of standard versus custom chin implants, the operative steps and indications for a bony genioplasty and the techniques for chin reduction are described with emphasis on proper patient selection and avoiding their common complications.
Vitamin D Deficiency and Its Response to Supplementation as “Stoss Therapy” in Children with Cyanotic Congenital Heart Disease Undergoing Open Heart Surgery
Authors: Sahu Manoj Kumar , Bipin Chalattil , Niraghatam Harsha Vardhan , Karanjkar Ameya , Singh Sarvesh Pal , Rajashekar Palleti , Ramakrishnan Lakshmy , Devagourou V. , Upadhyay Ashish Datt , Choudhary Shiv Kumar
Published: October 2019

Background Data from many studies suggest that patients with congenital heart disease are vitamin D (vitD) deficient. Following cardiac surgery as a result of intraoperative institution of cardiopulmonary bypass (CPB), serum vitD levels become even low. This may affect postoperative convalescence in terms of mechanical ventilation, inotropic support, infection, and so forth.

Objective We intended to study the prevalence of vitD deficiency pre and post cardiac surgery and the effect of vitD supplementation (stoss therapy) on postoperative convalescence of the children with tetralogy of Fallot (TOF) undergoing intracardiac repair (ICR).

Methodology In this randomized controlled trial (RCT), 60 children younger than 18 years with TOF and serum vitD levels < 20ng/dL were randomized into two groups. The study group received vitD supplementation as “stoss therapy” at 10,000 units/kg body weight. All these children underwent ICR with CPB. Demographic data, preoperative, intraoperative, and postoperative variables were compared between the study and the control groups.

Results Prevalence of severe vitD deficiency was 93.1%. When compared with the control group, study group showed higher serum vitD levels in the immediate preoperative period (p = 0.001), postoperative period following CPB (p = 0.012), and on the first postoperative day (p = 0.003). No statistically significant difference was observed in postoperative mechanical ventilation (p = 0.35), intensive care unit (ICU) stay (p = 0.15), and inotropic duration (p = 0.19).

Conclusion Children with TOF are highly deficient of vitD, its level falls further after CPB, and supplementing vitD preoperatively does not influence postoperative recovery pattern. Supplementation of vitD as “stoss therapy” was useful in raising the serum levels before and after cardiac surgery.
A Thrombin-Activatable Factor X Variant Corrects Hemostasis in a Mouse Model for Hemophilia A
Authors: Muczynski Vincent , Verhenne Sebastien , Casari Caterina , Chérel Ghislaine , Panicot-Dubois Laurence , Gueguen Paul , Trossaert Marc , Dubois Christophe , Lenting Peter J. , Denis Cécile V. , Christophe Olivier D.
Published: October 2019

Engineered recombinant factor X (FX) variants represent a promising strategy to bypass the tenase complex and restore hemostasis in hemophilia patients. Previously, a thrombin-activatable FX variant with fibrinopeptide-A replacing the activation peptide (FX-delAP/FpA) has been described in this regard. Here we show that FX-delAP/FpA is characterized by a sixfold shorter circulatory half-life compared with wild-type FX, limiting its therapeutical applicability. We therefore designed a variant in which the FpA sequence is inserted C-terminal to the FX activation peptide (FX/FpA). FX/FpA displayed a similar survival to wt-FX in clearance experiments and could be converted into FX by thrombin and other activating agents. In in vitro assays, FX/FpA efficiently restored thrombin generation in hemophilia A and hemophilia B plasmas, even in the presence of inhibitory antibodies. Expression following hydrodynamic gene transfer of FX/FpA restored thrombus formation in FVIII-deficient mice in a laser-induced injury model as well as hemostasis in a tail-clip bleeding model. Hemostasis after tail transection in FVIII-deficient mice was also corrected at 5 and 90 minutes after injection of purified FX/FpA. Our data indicate that FX/FpA represents a potential tenase-bypassing agent for the treatment of hemophilia patients with or without inhibitors.
Extra-axial Cerebellopontine Angle Adult Medulloblastoma: An Unusual Presentation at an Unusual Site
Authors: Ratha Vishwaraj , Karmarkar Vikram S. , Deopujari Chandrashekhar E.
Published: October 2019

Medulloblastoma is a rare adult primary brain tumor and its presence in the cerebellopontine angle (CPA) constitutes an even rarer site for origin. There are only 40 reported cases of CPA medulloblastoma in the literature, with most being intra-axial and occurring in the pediatric population. Extra-axial CPA medulloblastoma in adults are extremely rare and only 10 adult cases have been reported in world literature.We report a rare case of primary extra-axial CPA medulloblastoma occurring in an adult. We review the literature for such an unusual presentation of medulloblastoma in adults and discuss its appropriate clinico-radiological features along with its possible pathogenesis and surgical management.With increasing reporting of such tumors, CPA region, medulloblastoma should be considered a differential diagnosis of intra-axial or extra-axial CPA tumor, as their further management and prognosis differ significantly. Adjuvant radiotherapy and combined chemotherapy regimen should be added to the postoperative management.
Foramen Magnum Meningioma: Microsurgical Endoscopic-Controlled Resection via a Lateral Suboccipital Retrocondylar Approach with Preservation of Posterior Arch of Atlas Integrity
Authors: Bassiouni Hischam
Published: October 2019

Objective Surgical treatment of foramen magnum (FM) meningiomas is challenging due to proximity of the tumor to critical neurovascular structures, namely, the lower brainstem/upper cervical cord, vertebral artery, PICA, and lower cranial nerves. Controversies in microsurgical resection of meningiomas in this location include the necessity for condyle drilling and the need for vertebral artery mobilization. However, a laminectomy or hemilaminectomy of the C1 posterior arch is usually routinely performed. We herein present microsurgical, endoscopic-controlled resection of a FM meningioma via a posterolateral retrocondylar suboccipital craniotomy with preservation of the integrity of the posterior arch of the atlas.

Setting Our patient, a 57-year-old patient, suffered from right-sided hemiparesis due to a right-sided ventrolateral FM meningioma compromising the medulla oblongata and upper cervical cord. The tumor at the craniocervical junction was resected through a posterolateral suboccipital retrocondylar craniotomy.

Results Radical resection of the FM meningioma was accomplished via a lateral suboccipital retrocondylar craniotomy with preservation of posterior arch of atlas integrity. The postoperative course was uneventful with full preservation of neurological function. Preoperative hemiparesis subsided completely after surgery.

Conclusion Anterior-laterally located FM meningiomas can be safely and completely resected via a suboccipital retrocondylar craniotomy. A laminectomy or hemilaminectomy of the posterior arch of C1 is not routinely required for complete and safe resection of these tumors at the craniocervical junction. Neuroendoscopy is beneficial for control of complete tumor resection.

The link to the video can be found at: https://youtu.be/DBk6qoJ6OzQ.
Factors Complicating Discharge to Home following Total Knee Arthroplasty—A Single Institution Initiative
Authors: Issa Kimona , Kurowicki Jennifer , Novack Thomas A. , Pierce Todd P. , Festa Anthony , Scillia Anthony J. , McInerney Vincent K.
Published: October 2019

Recently, with the Medicare bundled payments initiative for total knee arthroplasty (TKA), there has been a move by many institutions to further streamline costs associated with the entire operative and perioperative process. One of these cost-saving strategies has been to favor discharging patients to home with outpatient services as opposed to discharging to the relatively more expensive rehabilitation facilities. Our aim was to determine the success of a teaching institute's initiative in discharging patients to home instead of a rehabilitation facility. Specifically, we evaluated if there were differences in discharge disposition based off of (1) surgeon/patient preference, (2) length of stay, (3) demographics, and (4) postoperative complications. A retrospective review of all patients who had a TKA from 2015 to 2017 at a single teaching institution was performed and assessed discharge to home or to a rehabilitation facility. If they were not discharged to home, we evaluated why that did not happen, stratified the reason they were discharged to a rehabilitation facility into four groups based on (1) physician and occupational health team assessment, (2) patient preference, (3) physician preference, and (4) family or caretaker preference. A total of 229 patients were enrolled in this initiative, with 107 patients (47%) discharged to home with outpatient physical therapy services and 122 (53%) discharged to a rehabilitation facility. Of these, 35 patients (29%) went to these facilities because of physician and occupational health team assessment. However, 31 (25%) patients were due to patient preference, 32 (26%) were because of surgeon's preference, and 24 (20%) were not discharged to home because of family or caretaker preference. There were no differences in length of stay, gender, or complication rates between cohorts. Many patients can be safely discharged to home following TKA at a community teaching institution; however, there continues to be a strong prejudice by patients, physicians, and caretakers to be discharged to a rehabilitation facility despite the home discharge initiative.
Nonlinear control of air-feed system for proton exchange membrane fuel cell with auxiliary power battery
Authors: Zhang Fan , Ma Yan , Zhu Tianlin , Chen Hong
Published: October 2019

This paper proposes a novel nonlinear controller of the air-feed system for a polymer electrolyte membrane (PEM) fuel cell with an auxiliary power battery. To improve the fast response of the air-feed system, we designed a PEM fuel cell hybrid system, wherein the PEM fuel cell supplies the primary power for the load demand, and the buffered power battery satisfies the additional power requirement. A power coordination strategy is presented to distribute dynamically varying load power demand to the PEM fuel cell and battery. A reduced third-order nonlinear model is used to analyze the nonlinear characteristics of the air-feed system. Next, to improve the tracking performance of the oxygen excess ratio, a triple-step nonlinear controller is designed through the affinelike air-feed system model, and the stability of closed-loop system is guaranteed by the Lyapunov-based technique. Subsequently, the effectiveness of the power coordination strategy and controller is validated by some simulation comparisons. The simulation results indicate that the proposed approach performs better than the proportional-integral-derivative (PID) controller and the triple-step controller for a PEM fuel cell system without an auxiliary battery.
Ion acceleration in laser generated megatesla magnetic vortex
Authors: Park J. , Bulanov S. S. , Bin J. , Ji Q. , Steinke S. , Vay J.-L. , Geddes C. G. R. , Schroeder C. B. , Leemans W. P. , Schenkel T. , Esarey E.
Published: October 2019

Magnetic Vortex Acceleration (MVA) from near critical density targets is one of the promising schemes of laser-driven ion acceleration. 3D particle-in-cell simulations are used to explore a more extensive laser-target parameter space than previously reported in the literature as well as to study the laser pulse coupling to the target, the structure of the fields, and the properties of the accelerated ion beam in the MVA scheme. The efficiency of acceleration depends on the coupling of the laser energy to the self-generated channel in the target. The accelerated proton beams demonstrate a high level of collimation with achromatic angular divergence, and carry a significant amount of charge. For petawatt-class lasers, this acceleration regime provides a favorable scaling of the maximum ion energy with the laser power for the optimized interaction parameters. The megatesla-level magnetic fields generated by the laser-driven coaxial plasma structure in the target are a prerequisite for accelerating protons to the energy of several hundred mega-electron-volts.
Influence of nonradiative Auger process in the lanthanide complexes lifetime near interfaces in organic light-emitting diode structures
Authors: Pereira Alessandra , Conte Gilmar , Faceto Angelo D. , Nunes Luis A. O. , Quirino Welber G. , Legnani Cristiano , Gallardo Hugo , Cremona Marco , Bechtold Ivan H. , Guimarães Francisco E. G.
Published: October 2019

The low efficiency of organic light-emitting diodes based on lanthanide complexes is generally attributed to the triplet-triplet annihilation processes in the regime of high concentration of excited states caused by their long lifetimes and optical losses near the interfaces of multilayer device structures. Despite the enormous effort to synthesize short-lived complexes and minimize the optical losses in the interfaces, it remains insufficient in understanding the exciton recombination processes that reduce the lifetime of these complexes. Herein, we investigated the influence of the exciton recombination processes on a Tb complex (Tb-C) lifetime in the regime of a highly excited state concentration as a function of the distance between the carrier layer and the interface by using a typical organic light-emitting diode structure. Our results show that a 10 nm-thick Alq3 layer decreases the exciton lifetime of the Tb-C, increasing approximately by 16 times the spontaneous emission decay rate of triplet exciton. The effects of interference and optical losses at the metallic interface contribute actively to the modulation of the emission intensity and lifetime decay. However, these effects alone do not explain the significant increase in the emission decay rate. The nonradiative Auger process at the Alq3/Tb-C interface seems to be largely accountable for the Tb-C lifetime reduction as the energy released by the terbium ion occurs by the excitation of an adjacent electron at higher energy. Furthermore, we propose a simple theoretical model to explain the observed effects. These results can provide a new approach to reduce the lanthanide complexes’ lifetime through the Auger electron process near the interface and thus improve the performance of organic light-emitting diodes.
Crystallographic orientation-dependent piezoelectric response in BaTiO3 thin films and the domain evolution under different temperatures
Authors: Zhu Zhe , Li Chao
Published: October 2019

The effects of crystallographic orientation on the domain structures and piezoelectric response of BaTiO3 (BTO) thin films were investigated by piezoresponse force microscopy (PFM) systematically. It is found that the domain structures of BTO films are obviously orientation dependent, and the (111) oriented BTO film shows the best piezoelectric properties. Therefore, the nanoscale polydomain switchings within valid single grains of the BTO(111) thin film were observed by PFM under different temperatures. According to the switching process, the a1/a2c, r/a2c, and a1c/r polydomain states were specially introduced into the theoretical model to describe the temperature-induced polydomain switchings of the BTO(111) thin film. The misfit strain-temperature phase diagram was simulated to present the a1/a2c-r/a2c-a1c/r-p domain switching, which corresponds with the threshold temperature of domain switchings obtained from the experimental results of the BTO(111) thin film.
Dominant ZA phonons and thermal carriers in HfS2
Authors: Peng Jie , Najmaei Sina , Dubey Madan , Chung Peter W.
Published: October 2019

Through a systematic study of HfS2 based on density functional theory calculations using the quasiharmonic approximation, we show that out-of-plane ZA phonons alone are responsible for 80% of the thermal transport—both in-plane and out-of-plane. The calculations determine the temperature-dependent structural, phonon, and thermal properties in HfS2. The cause is the uncommonly strong interlayer van der Waals interaction relative to its in-plane interaction. The highly anisotropic interactions also give rise to a combination of effects including anisotropic phonon group velocities, a large ZA-optical phonon gap, and a vanishing Grüneisen parameter in ZA modes that leads to large phonon lifetimes. In turn, these enable other unusual properties. HfS2 can have either a negative (T<40 K) or positive (T>40 K) temperature-dependent thermal expansion coefficient and an exceptionally large LO-TO splitting.
Manipulation of exciton and trion quasiparticles in monolayer WS2 via charge transfer
Authors: Gaur Anand P. S. , Rivera Adriana M. , Dash Saroj P. , Dey Sandwip , Katiyar Ram S. , Sahoo Satyaprakash
Published: October 2019

Charge doping in transition metal dichalcogenide is currently a subject of high importance for future electronic and optoelectronic applications. Here, we demonstrate chemical doping in the CVD-grown monolayer (1L) of WS2 by a few commonly used laboratory solvents by investigating the room temperature photoluminescence (PL). The appearance of distinct trionic emission in the PL spectra and quenched PL intensities suggests n-type doping in WS2. The temperature-dependent PL spectra of the doped 1L-WS2 reveal a significant enhancement of trions emission intensity over the excitonic emission at low temperature, indicating the stability of trion at low temperature. The temperature-dependent exciton-trion population dynamic has been modeled using the law of mass action of trion formation. These results shed light on the solution-based chemical doping in 1L-WS2 and its profound effect on the photoluminescence which is essential for the control of optical and electrical properties for optoelectronic applications.
On structural and dynamical factors determining the integrated basin instability of power-grid nodes
Authors: Kim Heetae , Lee Mi Jin , Lee Sang Hoon , Son Seung-Woo
Published: October 2019

In electric power systems delivering alternating current, it is essential to maintain its synchrony of the phase with the rated frequency. The synchronization stability that quantifies how well the power-grid system recovers its synchrony against perturbation depends on various factors. As an intrinsic factor that we can design and control, the transmission capacity of the power grid affects the synchronization stability. Therefore, the transition pattern of the synchronization stability with the different levels of transmission capacity against external perturbation provides the stereoscopic perspective to understand the synchronization behavior of power grids. In this study, we extensively investigate the factors affecting the synchronization stability transition by using the concept of basin stability as a function of the transmission capacity. For a systematic approach, we introduce the integrated basin instability, which literally adds up the instability values as the transmission capacity increases. We first take simple 5-node motifs as a case study of building blocks of power grids, and a more realistic IEEE 24-bus model to highlight the complexity of decisive factors. We find that both structural properties such as gate keepers in network topology and dynamical properties such as large power input/output at nodes cause synchronization instability. The results suggest that evenly distributed power generation and avoidance of bottlenecks can improve the overall synchronization stability of power-grid systems.
Electrical resistance of metal contact to Bi2Te3 based thermoelectric legs
Authors: Vikhor L. M. , Anatychuk L. I. , Gorskyi P. V.
Published: October 2019

The theoretical aspects of evaluating the electrical resistance of a thermoelectric leg–metal contact are considered. A physical model of such a contact and methods for calculating the main components of the contact resistivity, namely, the resistivity of the interfacial layer and the resistivity related to the transfer of charge carriers through a potential barrier at the boundary between a material of the thermoelectric leg and a metal, are proposed. The contact resistivity for thermoelectric legs made of Bi2Te3 based materials with deposited antidiffusion nickel layers is calculated. It was established that the contact resistivity in such thermoelements reaches a value from 0.25 × 10−6 to 2.5 × 10−6 Ω cm2 and depends on the temperature and interfacial layer thickness. It is demonstrated that the findings are in good agreement with the known experimental values of contact resistivity.
Theoretical model of excitonic luminescence and its application to the study of fine structure and exciton dynamics in ZnO
Authors: Zhou N. , Hu B. C. , Zhang Q. Y. , Ma C. Y. , Hao S. Z.
Published: October 2019

By solving the continuity equation of excitons under steady excitation, a theoretical model for the excitonic luminescence of semiconductors was developed taking into account the exciton diffusion and surface recombination. The theoretical model was used to analyze the photoluminescence (PL) spectra of ZnO obtained from the bulk single-crystal samples with and without surface passivation, showing that the nonradiative recombination on the surface is an important channel of losing excitons, thus substantially reducing the PL quantum efficiency of excitons at room temperature. In addition, the surface recombination was found to have impacts on the fine structure of excitonic luminescence at low temperature. Using the theoretical model, the diffusion length of excitons at room temperature was estimated and found to be different from sample to sample, strongly depending on the sample processing. The theoretical model was demonstrated to be capable of accurately fitting the temperature-dependent PL intensity of passivated samples and showed that the exciton diffusion has significant impacts on the dynamics of excitonic luminescence at high temperature.
Scalable microplasma array for argon metastable lasing medium
Authors: Kim Hyunjun , Hopwood Jeffrey
Published: October 2019

Optically pumped rare gas laser systems require a lasing medium of high density metastable atoms. A scalable two-dimensional array of quarter-wave resonators produces high microwave electric fields suitable for generating a dense gas of argon 1s5 states. This resonator array is immersed within an evacuated waveguide in order to create a volume of plasma in a relatively wide discharge gap (13 mm) at argon-helium pressures up to 100 Torr using 30 W of continuous microwave power at 2.3 GHz. Spatial density profiles of argon 1s5 states are measured using diode laser absorption spectroscopy with 0.5 mm resolution. The region of argon 1s5 states is mapped in the discharge and shown to have an estimated density in excess of 1×1018m−3 within a volume of 11.6×3.2×0.8mm3.
Size-dependent toughness and strength in defective 3C-SiC nanowires
Authors: Ma Ling , Hao Tengyuan , Hossain Zubaer M.
Published: October 2019

This paper presents an atomistic understanding of effective toughness and strength in defective 3C-SiC nanowires of different diameters. We consider a set of high-symmetry vacancy defect clusters and employ a combination of density functional theory and molecular dynamics simulations to calculate stress in the nanowires, using an energy-based approach that does not require use of any macroscopic geometric information of the nanowire. Our results suggest that for defect-free nanowires, cracks nucleate from one of the corners of the hexagonal cross section, whereas for defective nanowires—regardless of the size of the defect core—cracks nucleate from the edge of the defect core. With increasing diameter, both strength and toughness increase in defective or defect-free nanowires. Furthermore, defects alter the size-dependent effective toughness and strength of the nanowire: the larger the size of the defect, the stronger the size-dependence of effective toughness and strength. A single vacancy in a 8.0 nm diameter nanowire reduces effective toughness and strength by around 16.5% and 3.4%, respectively. As diameter approaches ∞, effective stiffness approaches the bulk behavior—whereas neither strength nor toughness approaches the behavior of the bulk. This is primarily because of the presence of the surface and associated sustained stress-localization in the nanowire. Effective toughness and strength are, therefore, controlled by the local critical events and not by the macroscopic features of the nanowire. Additionally, both toughness and strength decrease nonlinearly with increasing temperature due to thermal softening of the material—and this thermal softening is, however, weakly dependent on the size of the defective regime.
gFORC: A graphics processing unit accelerated first-order reversal-curve calculator
Authors: Groß Felix , Martínez-García José Carlos , Ilse Sven Erik , Schütz Gisela , Goering Eberhard , Rivas Montserrat , Gräfe Joachim
Published: October 2019

First-order reversal-curves have proven to be an indispensable characterization tool for physics as well as for geology. However, the conventional evaluation algorithm requires a lot of computational effort for a comparable easy task to overcome measurement noise. In this work, we present a new evaluation approach, which exploits the diversity of Fourier space to not only speed up the calculation by a factor of 1000 but also move away from the conventional smoothing factor toward real field resolution. By comparing the baseline resolution of the new and the old algorithm, we are able to deduce an analytical equation that converts the smoothing factor into field resolution, making the old and new algorithm comparable. We find excellent agreement not only for various systems of increasing complexity but also over a large range of smoothing factors. The achieved speedup enables us to calculate a large number of first-order reversal-curve diagrams with increasing smoothing factor allowing for an autocorrelation approach to find a hard criterion for the optimum smoothing factor. This previously computational prohibitive evaluation of first-order reversal-curves solves the problem of over- and undersmoothing by increasing general readability and preventing information destruction.
Magnetocaloric effect near room temperature in quintenary and sextenary Heusler alloys
Authors: White B. D. , Barabash R. I. , Barabash O. M. , Jeon I. , Maple M. B.
Published: October 2019

An inverse magnetocaloric effect is studied in Ni2Mn1+xX1−x-type Heusler alloys. Principally known for their shape-memory properties, these alloys also exhibit significant entropy and temperature changes (ΔS and ΔTAd, respectively) under adiabatic conditions when a modest magnetic field is applied. We investigated the impact on magnetocaloric properties of introducing substantial chemical disorder on the X-site (X=Si,Ga,In), of replacing Ni with nonmagnetic Ag, and of replacing a small amount of Mn with Gd. While a reduction in ΔS is observed in the first two cases, we observe a significant enhancement of ΔS when a small amount of Gd is substituted for Mn. A thermodynamic analysis was conducted using magnetization and heat capacity data to estimate adiabatic temperature changes in the range of ΔTAd≃ −1 to −3 K for a 5 T magnetic field. Several alloys characterized in this study exhibit these respectable ΔTAd values near room temperature, making them potentially viable candidates for magnetic refrigeration applications.
Interaction between water and carbon nanostructures: How good are current density functional approximations?
Authors: Brandenburg Jan Gerit , Zen Andrea , Alfè Dario , Michaelides Angelos
Published: October 2019

Due to their current and future technological applications, including realization of water filters and desalination membranes, water adsorption on graphitic sp2-bonded carbon is of overwhelming interest. However, these systems are notoriously challenging to model, even for electronic structure methods such as density functional theory (DFT), because of the crucial role played by London dispersion forces and noncovalent interactions, in general. Recent efforts have established reference quality interactions of several carbon nanostructures interacting with water. Here, we compile a new benchmark set (dubbed WaC18), which includes a single water molecule interacting with a broad range of carbon structures and various bulk (3D) and two-dimensional (2D) ice polymorphs. The performance of 28 approaches, including semilocal exchange-correlation functionals, nonlocal (Fock) exchange contributions, and long-range van der Waals (vdW) treatments, is tested by computing the deviations from the reference interaction energies. The calculated mean absolute deviations on the WaC18 set depend crucially on the DFT approach, ranging from 135 meV for local density approximation (LDA) to 12 meV for PBE0-D4. We find that modern vdW corrections to DFT significantly improve over their precursors. Within the 28 tested approaches, we identify the best performing within the functional classes of generalized gradient approximated (GGA), meta-GGA, vdW-DF, and hybrid DF, which are BLYP-D4, TPSS-D4, rev-vdW-DF2, and PBE0-D4, respectively.
Determination of the saturation length and study of its effects in optical gain measurements of organic semiconductors using the variable stripe length method
Authors: Wilke Hans , Hoinka Nicolai M. , Kusserow Thomas , Fuhrmann-Lieker Thomas , Hillmer Hartmut
Published: October 2019

Three indicators for the determination of the saturation length limiting the validity of the variable stripe length method are presented. Depending on the maximum stripe length being used for the nonlinear fit, the resulting modal gain, its confidence interval, and the spectral full width at half maximum vary and give clear indications on the saturation length. Exemplarily, a blend of organic semiconducting spiro-compounds has been measured to present the importance of this length and demonstrate its determination. Subsequently, the optical modal gain is calculated with consideration of the saturation length. Both the saturation length and modal gain are shown to be dependent on the pump energy but result in a constant gain-length product of 2.2 ± 0.2, independent of the pump energy. Additionally, spectral gain profiles for different pump energies are presented with a maximum net modal gain of (128±4) cm−1 found at (2.98±0.09) mJ/cm2.
Evidence of polyamorphic transitions during densified SiO2 glass annealing
Authors: Cornet Antoine , Martinet Christine , Martinez Valérie , de Ligny Dominique
Published: October 2019

In situ X-ray scattering monitoring is carried out during temperature annealing on different densified SiO2 glasses. Density fluctuations and intermediate range coherence from X-ray scattering (small-angle X-ray scattering) and diffraction (wide angle X-ray scattering) evidence a maximum in their evolution at the same relaxation time. These extrema confirm the existence of an intermediate transitory disordered state between the two more ordered high and low density amorphous states. We propose that the existence of this transitory state confirms the existence of two mega basins in the energy landscape and therefore an amorphous-amorphous transition. Including older Raman results, we show that this intermediate disorder state implies similar mechanisms at all length scales from a few angstroms to 5 nm.
Highly flexible superconducting films with metal-decorated composite 2D materials
Authors: Ronseaux Pauline , Othmen Riadh , Kalita Dipankar , Han Zheng , Marty Laëtitia , Bendiab Nedjma , Renard Julien , Bouchiat Vincent
Published: October 2019

Graphene forms an ideal platform to realize macroscopic hybrid materials by direct physisorption of electronically-active adsorbates on top of the high-mobility bidimensional (2D) gas of charge carriers. Here, we demonstrate a novel composite multilayer based on a thin polymer film covered with a monolayer of CVD graphene on top of which a thin layer of tin is evaporated. The metal film shows dewetting and forms a self-organized network of metal nanodots electronically coupled to the graphene. The resulting macroscopic multilayered structure is a highly flexible, stable, and processable composite 2D material that exhibits tunable superconductivity at low temperature. The superconducting properties of the macroscopic composite extend over the full sample size (several square centimeters) and are comparable to the ones of a mesoscopic array of Josephson junctions prepared with similar materials. It provides an upscaling of the concept that is useful for flexible electronics.