Artificial Graphene Spin Polarized Electrode for Magnetic Tunnel Junctions.

2D materials offer the ability to expose their electronic structure to manipulations by a proximity effect. This could be harnessed to craft properties of 2D interfaces and van der Waals heterostructures in devices and quantum materials. We explore the possibility to create an artificial spin polarized electrode from graphene through proximity interaction with a ferromagnetic insulator to be used in a magnetic tunnel junction (MTJ). Ferromagnetic insulator/graphene artificial electrodes were fabricated and integrated in MTJs based on spin analyzers. Evidence of the emergence of spin polarization in proximitized graphene layers was observed through the occurrence of tunnel magnetoresistance. We deduced a spin dependent splitting of graphene's Dirac band structure (∼15 meV) induced by the proximity effect, potentially leading to full spin polarization and opening the way to gating. The extracted spin signals illustrate the potential of 2D quantum materials based on proximity effects to craft spintronics functionalities, from vertical MTJs memory cells to logic circuits.

Clinical Trials in Hepatopancreatobiliary Surgery: Assessing Trial Characteristics, Early Discontinuation, Result Reporting, and Publication.

BACKGROUND: Hepatopancreaticobiliary (HPB) diseases carry high morbidity despite efforts aimed at their reduction. An assessment of their trial characteristics is paramount to determine trial design adequacy and highlight areas for improvement. As such, the aim of this study is to assess HPB surgery trial characteristics, summarize logistic, financial, and practical reasons behind early discontinuation, and propose potential interventions to prevent this in the future. METHODS: All clinical trials investigating HPB surgery registered on ClinicalTrials.gov from October 1st, 2007 (inclusive), to April 20th, 2021 (inclusive), were examined. Trial characteristics were collected including, but not limited to, study phase, duration, patient enrollment size, location, and study design. Peer-reviewed publications associated with the selected trials were also assessed to determine outcome reporting. RESULTS: A total of 1776 clinical trials conducted in 43 countries were identified, the majority of which were conducted in the USA. Of these trials, 32% were reported as "completed" whereas 12% were "discontinued." The most common cause of trial discontinuation was low accrual, which was reported in 37% of terminated studies. These resulted in 413 published studies. Most trials had multiple assignment, randomized, or open-label designs. Treatment was the most common study objective (73%) with pharmacological therapy being the most commonly studied intervention. CONCLUSIONS: The main reasons for early discontinuation of clinical trials in HPB surgery are poor patient recruitment and inadequate funding. Improved trial design, recruitment strategies and increased funding are needed to prevent trial discontinuation and increase publication rates of HPB surgery clinical trials.

Distribution of international medical graduates across USA surgical training programs: a descriptive cross-sectional study.

BACKGROUND: International medical graduates (IMGs) have been a critical part of the USA healthcare in the past 30 years, especially in small rural and poor counties. However, little to no publications are present on the distribution of these IMGs across general surgery residency programs. METHODS: All freely accessible information on current residents in accredited general surgery residency programs within the USA with at least a 5-year history was explored for IMGs in the current roster using the AMA residency and fellowship database in 2020. Demographic and geographic data were summarized. RESULTS: A total of 230 general surgery residency program were included. Programs were distributed among 46 (92%) states. Of a total 6304 categorical general surgery residents, 573 (9%) were IMGs. Florida (USA) had the highest total number of current IMG general surgery residents with 64. The highest percentage of current IMG residents was found in Maryland (USA) with 31%. IMGs obtained their medical degrees from 76 different countries worldwide. Grenada was the country with the highest origin of IMGs with 77 residents. Central/North America had the highest origin of IMGs with 217 (38%). CONCLUSIONS: IMGs make up a small portion of current general surgery residents in USA programs. Some states host more IMGs than others. Particular countries have contributed more IMGs than others. More research is needed to the challenges facing IMGs and come up with novel solutions for them.

Preoperative MELD score predicts adverse outcomes following gastrectomy: An ACS NSQIP analysis.

BACKGROUND: The Model End-Stage Liver Disease (MELD) has been widely used to predict the mortality and morbidity of various surgical procedures. We aimed to assess the impact of preoperative MELD score on adverse 30-day postoperative outcomes following gastrectomy. METHODS: Patients who underwent elective, non-emergent gastrectomy were identified from the ACS NSQIP 2014-2019 database. Patients were categorized according to a calculated MELD score. The primary outcomes of this study were the 30-day overall complications and major complication rates following gastrectomy. RESULTS: Compared to MELD <11, patients with MELD ≥11 had significantly higher rates of mortality, any complication, and major complication. MELD score ≥11 was significantly associated with any complication (OR 1.73, p = 0.011) and major complications (1.85, p = 0.014) on multivariate analysis. CONCLUSIONS: MELD score ≥11 was associated with poorer outcomes in patients undergoing gastrectomy compared to lower MELD scores.

Robotic pancreas surgery: an overview of history and update on technique, outcomes, and financials.

The use robotics in surgery is gaining momentum. This approach holds substantial promise in pancreas surgery. Robotic surgery for pancreatic lesions and malignancies has become well accepted and is expanding to more and more center annually. The number of centers using robotics in pancreatic surgery is rapidly increasing. The most studied robotic pancreas surgeries are pancreaticoduodenectomy and distal pancreatectomy. Most studies are in their early phases, but they report that robotic pancreas surgery is safe feasible. Robotic pancreas surgery offers several advantages over open and laparoscopic techniques. Data regarding costs of robotics versus conventional techniques is still lacking. Robotic pancreas surgery is still in its early stages. It holds promise to become the new surgical standard for pancreatic resections in the future, however, more research is still needed to establish its safety, cost effectiveness and efficacy in providing the best outcomes.

Rashba-Type Dzyaloshinskii-Moriya Interaction, Perpendicular Magnetic Anisotropy, and Skyrmion States at 2D Materials/Co Interfaces.

We report a significant Dzyaloshinskii-Moriya interaction (DMI) and perpendicular magnetic anisotropy (PMA) at interfaces comprising hexagonal boron nitride (h-BN) and Co. By comparing the behavior of these phenomena at graphene/Co and h-BN/Co interfaces, it is found that the DMI in the latter increases as a function of Co thickness and beyond three monolayers stabilizes with 1 order of magnitude larger values compared to those at graphene/Co, where the DMI shows opposite decreasing behavior. Meanwhile, the PMA for both systems shows similar trends with larger values for graphene/Co and no significant variations for all thickness ranges of Co. Furthermore, using micromagnetic simulations we demonstrate that such significant DMI and PMA values remaining stable over a large range of Co thickness give rise to the formation of skyrmions with small applied external fields. These findings open up further possibilities toward integrating two-dimensional (2D) materials in spin-orbitronics devices.

Mass casualty management during a pandemic surge: The American University of Beirut Medical Center experience.

Mass casualty incidents can be devastating events associated with a large number of fatalities, morbidities, and long-lasting sequelae. The negative outcomes can be further amplified if the incident occurred during a pandemic surge, such as what occurred in Beirut, Lebanon with the August 4, 2020 Beirut Port explosion. To decrease the mortality and morbidity and avoid inefficiency, management depends on having an established coordinated multidisciplinary approach from transport and triage to emergency department care and in-hospital management. In this article, the mass casualty management and the impact of the coronavirus disease 2019 pandemic will be discussed based on the American University of Beirut Medical Center experience.

Current-Driven Domain Wall Dynamics in Ferrimagnetic Nickel-Doped Mn4N Films: Very Large Domain Wall Velocities and Reversal of Motion Direction across the Magnetic Compensation Point.

Spin-transfer torque (STT) and spin-orbit torque (SOT) are spintronic phenomena allowing magnetization manipulation using electrical currents. Beyond their fundamental interest, they allow developing new classes of magnetic memories and logic devices, in particular based on domain wall (DW) motion. In this work, we report the study of STT-driven DW motion in ferrimagnetic manganese nickel nitride (Mn4-xNixN) films, in which magnetization and angular momentum compensation can be obtained by the fine adjustment of the Ni content. Large domain wall velocities, approaching 3000 m/s, are measured for Ni compositions close to the angular momentum compensation point. The reversal of the DW motion direction, observed when the compensation composition is crossed, is related to the change of direction of the angular momentum with respect to that of the spin polarization. This is confirmed by the results of ab initio band structure calculations.

Comparison of the Oxygenation Factor and the Oxygenation Ratio in Subjects With ARDS.

BACKGROUND: The oxygenation ratio (ie, [Formula: see text]/[Formula: see text]) remains the most commonly used index for assessing oxygenation and disease severity in patients with acute ARDS. However, the oxygenation ratio does not account for mechanical ventilation settings. We hypothesized that the oxygenation factor (ie, oxygenation ratio/mean airway pressure) is superior to the oxygenation ratio in reflecting oxygenation in patients with ARDS and results in a different classification of ARDS severity. METHODS: In 150 subjects with ARDS (50 severe, 50 moderate, and 50 mild), arterial blood gas, mean airway pressure, static lung compliance, driving pressure, and mechanical power were obtained. The oxygenation ratio and the oxygenation factor were then calculated. Receiver operating characteristic curves were constructed for oxygenation ratio and oxygenation factor at lung compliance > 40 mL/cm H2O, driving pressure < 15 cm H2O, and mechanical power < 17 J/min, thresholds that are known to predict survival in patients with ARDS. Subjects were reclassified for ARDS severity on the basis of the oxygenation factor and compared to classification on the basis of the oxygenation ratio. RESULTS: Areas under the receiver operating characteristic curves for the oxygenation factor were significantly higher than for the oxygenation ratio. Reclassification of ARDS severity using the oxygenation factor did not affect subjects classified as having severe ARDS per the oxygenation ratio. However, 52% of subjects with moderate ARDS per the oxygenation ratio criteria were reclassified as either severe (25 subjects) or mild ARDS (1 subject) on the basis of oxygenation factor criteria. Also, 54% of subjects with mild ARDS per the oxygenation ratio criteria were reclassified as severe (4 subjects), moderate (21 subjects), or non-ARDS (2 subjects) on the basis of oxygenation factor criteria. CONCLUSIONS: The oxygenation factor was a superior ARDS oxygenation index compared to the oxygenation ratio and should be considered as a substitute criteria for classification of the severity of ARDS. (ClinicalTrials.gov registration NCT03946189.).

Splenic Artery Aneurysm (SAA) Rupture in Pregnancy: A Case Report of a Rare but Life-Threatening Obstetrical Complication.

This is the case of a 38 year-old Lebanese woman G2P1, history of previous cesarean section, presenting at 30+5 weeks of gestation with acute left-sided flank pain and a two-day history of chills and dysuria. In light of the clinical presentation, the patient was initially diagnosed with pyelonephritis and managed accordingly; however, her clinical status deteriorated with worsening hypotension and lethargy despite resuscitative measures and a normal abdominal ultrasound. Failure to revive the patient eventually led to a cardiac arrest for which a peri-mortem cesarean section was performed at bedside. Upon abdominal entry, an actively-bleeding ruptured splenic artery aneurysm (SAA) was identified, for which massive transfusion protocol was activated, and the patient was transferred to the operating room. The patient had a complicated postoperative course, the fetus was stillborn, and she was discharged home after 6 months of hospital stay. In view of the high mortality and morbidity associated with ruptured SAA in pregnancy, early recognition and prompt intervention are crucial for maternal and fetal benefit.

Large esophageal schwannoma: En-bloc resection with primary closure by esophagoplasty.

BACKGROUND: Gastrointestinal schwannomas are submucosal tumors accounting for 2-7% of mesenchymal gastro-intestinal neoplasms; the stomach being the most common site. Esophageal schwannomas are more frequent in women, and are usually located in the upper to mid portion. Dysphagia is the main presenting symptom. A definitive diagnosis requires confirmation by histopathological and immunohistochemical studies. CASE PRESENTATION: A 50-year-old healthy lady, presented with gradual increasing onset of dyspnea, with minimal dysphagia to solid food, over a period of several years. Enhanced CT scan of the chest revealed a well-defined soft tissue mass arising from the proximal third of the esophagus, measuring 7.8 × 5.4 x 10.5 cm. Esophagogastric endoscopy with ultrasonography showed an elevated, smooth surface lesion, arising from the submucosal layer of the esophagus, with a hypervascular mucosa. Enucleation of this large tumor, with preservation of the overlying mucosa, was difficult to accomplish due to its large size. Making use of a dilated proximal esophageal segment, total en-bloc excision of the mass rendered a 15 cm esophagotomy gap, which was easily closed, in two layers, without affecting the overall caliber thus achieving a good esophagoplasty result. Histologically, abundance of spindle-shaped cells with positive S-100 proteins, confirmed the diagnosis of esophageal schwannoma. CONCLUSION: Variations in mesenchymal gastrointestinal tumors is vast, rendering diagnosis by radiology alone difficult. As such, characteristic histologic and immunostaining features are cornerstones in precise diagnosis of esophageal schwannomas. Despite being rare in incidence, symptomatic esophageal schwannoma lesions can be excised entirely, with low rate of recurrence and favorable overall outcomes.

Establishing an ECMO program in a developing country: challenges and lessons learned.

AIM: The ECMO (extracorporeal membrane oxygenation) Program at the American University of Beirut Medical Center was established in November 2015 as the first program serving adult and pediatric population in a low-resource setting. The aim of the study is to describe the challenges faced during the establishment of the program and factors leading to its success. METHODS: The program establishment is described. The preparation phase, included the strategic, financial, and clinical planning by administration, nursing, and a multidisciplinary team of physicians. The training and education phase included all the involved nurses, perfusionists, and physicians. Concerns were heard from various stakeholders, and the challenges were analyzed and discussed. RESULTS: The preparation committee chose the adequate equipment, responded to the concerns, defined roles and responsibilities through credentialing and privileging, wrote policies and protocols, and established a strategy to decide for the ECMO indication. Selected team of nurses, physicians, and perfusionists are identified and trained locally, and abroad. A full-time ECMO physician was recruited to launch the program. Twelve patients (6 adults, 3 children, and 3 neonates) were supported by ECMO, for cardiac and respiratory indications. Eleven patients were supported by veno-arterial ECMO, and 1 patient (a neonate) with veno-venous ECMO. Overall, 75% survived to decannulation and 41% survived to discharge. CONCLUSION: With limited human and financial resources, new ECMO centers need to carefully establish selection criteria that may differ from those used in developed countries. Indications should be discussed on a case by case basis, taking into account clinical, social, and financial issues. This experience might help other institutions in developing countries to build their own program despite financial and human limitations.

Penetrating shrapnel injury to the chest presenting as a delayed tracheoesophageal fistula (TEF). A case report.

Tracheo-esophageal fistulae (TEF) due to trauma are rare. We report a case of a delayed TEF caused by a shrapnel from a blast. A 25-year-old male was admitted to the hospital after sustaining a blast injury. A contrast CT scan of the chest and neck revealed the presence of metallic shrapnel in close proximity to the tracheo-esophageal groove at the level of the thoracic inlet. Bronchoscopy revealed 0.5 cm tear in the membranous trachea while esophagoscopy and contrast swallow were normal. Coughs after starting fluid intake triggered a repeat endoscopy that showed a large TEF at 22 cm from the incisors. He underwent surgical repair through a collar incision and limited sternotomy. The TEF extended for 2 cm. The esophagus was repaired in two layers, the membranous trachea was sutured primarily, and an interposition strap muscle flap was placed. A contrast swallow on postoperative day 7 revealed the presence of a small leak into the trachea that was treated conservatively. Traumatic TEF are rare and should be suspected in patients with injuries to proximal structures. Delay in diagnosis and appropriate management can conceivably lead to death.

Predicting Conversion from Laparoscopic to Open Cholecystectomy: A Single Institution Retrospective Study.

BACKGROUND: Laparoscopic cholecystectomy (LC) is the standard surgical treatment for benign gallbladder disease. Nevertheless, conversion to open cholecystectomy (OC) is needed in some cases. The aim of this study is to calculate our institutional conversion rate and to identify the variables that are implicated in increasing the risk of conversion (LC-OC). MATERIALS AND METHODS: We carried out a retrospective study of all cases of LC performed at the American University of Beirut Medical Center between 2000 and 2015. Each (LC-OC) case was randomly matched to a laparoscopically completed case by the same consultant within the same year of practice, as the LC-OC case, in a 1:5 ratio. Forty-eight parameters were compared between the two study groups. RESULTS: Forty-eight out of 4668 LC were converted to OC over the 15-year study period; the conversion rate in our study was 1.03%. The variables that were found to be most predictive of conversion were male gender, advanced age, prior history of laparotomy, especially in the setting of prior gunshot wound, a history of restrictive or constrictive lung disease and anemia (Hb < 9 g/dl). The most common intraoperative reasons for conversion were perceived difficult anatomy or obscured view secondary to severe adhesions or significant inflammation. Patients who were in the LC-OC arm had a longer length of hospital stay. CONCLUSION: Advance age, male gender, significant comorbidities and history of prior laparotomies have a high risk of conversion. Patients with these risk factors should be counseled for the possibility of conversion to open surgery preoperatively. Further research is needed to determine whether these high risks patients should be operated on by surgeons with more extensive experience in minimal invasive surgery.

Intestinal obstruction caused by a strangulating adnexa: a rare complication of ovarian sparing hysterectomy.

Intestinal obstruction caused by a remnant fallopian tube from previous hysterectomy is a rare entity that has been reported once in the literature. We report the case of a 61-year-old woman who presented with both small and large bowel obstructions caused by a strangulating remnant fallopian tube. She had an ovarian sparing hysterectomy 16 years ago and was diagnosed with antiphospholipid syndrome. Our case report will discuss the clinical presentation, imaging and outcome of the patient. It will also briefly tackle other rare causes of bowel obstruction.

Small Bowel Obstruction Secondary to a Metamucil Bezoar: Case Report and Review of the Literature.

Bezoar-induced small bowel obstruction is a rare entity. It should be highly suspected in patients with gastric hypomotility disorders, psychiatric conditions, prior abdominal or bariatric surgery, or improper intake of medication. Their diagnosis is quite challenging and surgical exploration remains the best treatment of choice to ensure the viability of the small bowel tissue and relieve the obstruction. This is a case of a 48-year-old female with no previous abdominal surgery who presented with acute abdominal pain. The patient's history was remarkable for the daily ingestion of 1.5 teaspoons of Metamucil with minimal amount of water. Computed tomography scan demonstrated dilated small bowel loops and a transition zone at the level of the mid jejunum. On laparoscopy, the patient was found to have a hard mass in the mid jejunum amenable to gentle fragmentation and breakdown. Metamucil bezoars are due to the solidification of psyllium-based substances in the gastrointestinal tract. The usual management of small bowel obstruction induced by a bezoar is exploratory laparotomy with enterotomy and primary anastomosis. Laparoscopic intervention has gained popularity among surgeons with good outcome and lower morbidity. In this unusual case, the small bowel obstruction induced by the Metamucil bezoar was safely treated with laparoscopic fragmentation alone.

Pancreaticoduodenal Artery Aneurysm Associated with Celiac Trunk Stenosis: Case Illustration and Literature Review.

Pancreaticoduodenal artery aneurysms (PDA) are rare visceral aneurysms. Celiac trunk stenosis represents a common attributable aetiology for those aneurysms. Therefore, an alternative treatment approach, which differs from those isolated aneurysms, is recommended. We hereby present a 77-year-old male patient who was admitted with sudden onset of severe abdominal pain and significant drop in haemoglobin, occurring within a 24-hour interval. Contrast-enhanced computed tomography revealed a ruptured visceral aneurysm arising from the anterior branch of the inferior pancreaticoduodenal artery. A severe stenosis was also noted at the take-off of the celiac trunk. Selective catheterization of the supplying branch of the superior mesenteric artery, followed by coil embolization of the aneurysm, was performed, resulting in cessation of flow within the aneurysm, with preservation of the posterior branch, supplying the celiac territory. PDAs are usually asymptomatic and discovered incidentally at rupture. The risk of rupture is independent of the aneurysmal size and is associated with a 50% mortality rate. The consensus on coping with aneurysms is to treat them whenever they are discovered. Selective angiography followed by coil embolization represents a less invasive, and frequently definitive, approach than surgery. The risk for ischemia mandates that the celiac territory must not be compromised after embolization.

Perforated Duodenal Diverticulum Treated Conservatively: Another Two Successful Cases.

Diverticula of the duodenum proceed those of the colon in respect to frequency of location. Incidence at times of autopsy ranges from 15 to 23%. Despite the fact that more than 90% of duodenal diverticulum cases are asymptomatic, complications if they do occur can be calamitous. Perforation is one of these rare complications. Surgical intervention has always been the mainstay for symptomatic/complicated duodenal diverticula, but with the advancement of imaging, medical treatment, and proper intensive observation, conservative treatment came forth. We hereby present two cases of duodenal diverticula, complicated by perforation and fistulization into the retroperitoneal cavity, both treated conservatively by Taylor's approach of upper gastrointestinal tract perforation. Review of other cases of duodenal diverticulum perforation has also been presented.