Spontaneous Valley Polarization of Interacting Carriers in a Monolayer Semiconductor.

We report magnetoabsorption spectroscopy of gated WSe_{2} monolayers in high magnetic fields up to 60 T. When doped with a 2D Fermi sea of mobile holes, well-resolved sequences of optical transitions are observed in both σ^{±} circular polarizations, which unambiguously and separately indicate the number of filled Landau levels (LLs) in both K and K^{'} valleys. This reveals the interaction-enhanced valley Zeeman energy, which is found to be highly tunable with hole density p. We exploit this tunability to align the LLs in K and K^{'}, and find that the 2D hole gas becomes unstable against small changes in LL filling and can spontaneously valley polarize. These results cannot be understood within a single-particle picture, highlighting the importance of exchange interactions in determining the ground state of 2D carriers in monolayer semiconductors.

[Artificial intelligence in general and visceral surgery]. / Künstliche Intelligenz in der Allgemein- und Viszeralchirurgie.

Artificial intelligence procedures will find special fields of application also in general and visceral surgery. These will not only be limited to intraoperative surgical applications but also extend to perioperative processes, education and training as well as to future scientific developments. Major impulses are to be expected in decision support systems, cognitive collaborative interventional environments and in evidence-based knowledge acquisition models; however, the implementation into the daily practice not only requires profound insights into the field of informatics and computer science but also a comprehensive knowledge of the surgical domain. Accordingly, the future implementation of artificial intelligence in surgery requires a new culture of collaboration between surgeons and researchers/computer scientists.

[Digitalization in surgery : What surgeons currently think and know about it-results of an online survey]. / Digitalisierung in der Chirurgie : Was Chirurgen darüber denken und was sie wissen ­ Ergebnisse einer Onlineumfrage.

BACKGROUND: The digitalization process is currently on everyone's lips and sweeping changes in the field of public health and especially in surgery are to be expected within the next few years. Besides general issues, such as electronic health records and medical information systems, artificial intelligence, robotics and model-based surgery will decisively impact on the daily routine. In order to provide the necessary knowledge base, to point out related risks and chances and also to define fields of action for surgery, the German Society of Surgery commissioned a position paper on digitalization. A first appraisal in form of an online survey is the subject of this article. METHODS: This article is based on an online survey of the members of the German Society of Surgery and selected members of other related societies. The survey asked for the members' personal assessment concerning different aspects of the digitalization process and the respective state of knowledge as well as the impact on the field of surgery. RESULTS: A total of 296 members contributed to this survey. According to their assessment, digitalization in surgery is currently associated with terms such as electronic health records and medical information systems but they also assume a relevant influence on their own activities and on the fields of interventional medicine and surgery. A relevant need for improvement of the current state of knowledge was highlighted, not only for general aspects of digitalization but also for surgically relevant issues in particular. The vast majority of interviewed members saw digitalization more as a chance for improvement than as a risk factor. CONCLUSION: According to the views of interviewed members of the German Society of Surgery the process of digital transformation will significantly impact the field of surgery. All those involved should feel responsible to contribute to and guide this process in order to maintain the surgically inherent requirements and to protect patient safety. The position paper on digitalization can serve as a basis and should define concrete recommendations for action. In the sense of an academic approach the new possibilities should be critically evaluated with respect to suitability and should be exclusively confined to applications that are beneficial to ourselves and to our patients.

Revealing exciton masses and dielectric properties of monolayer semiconductors with high magnetic fields.

In semiconductor physics, many essential optoelectronic material parameters can be experimentally revealed via optical spectroscopy in sufficiently large magnetic fields. For monolayer transition-metal dichalcogenide semiconductors, this field scale is substantial-tens of teslas or more-due to heavy carrier masses and huge exciton binding energies. Here we report absorption spectroscopy of monolayer [Formula: see text], and [Formula: see text] in very high magnetic fields to 91 T. We follow the diamagnetic shifts and valley Zeeman splittings of not only the exciton's [Formula: see text] ground state but also its excited [Formula: see text] Rydberg states. This provides a direct experimental measure of the effective (reduced) exciton masses and dielectric properties. Exciton binding energies, exciton radii, and free-particle bandgaps are also determined. The measured exciton masses are heavier than theoretically predicted, especially for Mo-based monolayers. These results provide essential and quantitative parameters for the rational design of opto-electronic van der Waals heterostructures incorporating 2D semiconductors.

Scaling law for excitons in 2D perovskite quantum wells.

Ruddlesden-Popper halide perovskites are 2D solution-processed quantum wells with a general formula A2A'n-1M n X3n+1, where optoelectronic properties can be tuned by varying the perovskite layer thickness (n-value), and have recently emerged as efficient semiconductors with technologically relevant stability. However, fundamental questions concerning the nature of optical resonances (excitons or free carriers) and the exciton reduced mass, and their scaling with quantum well thickness, which are critical for designing efficient optoelectronic devices, remain unresolved. Here, using optical spectroscopy and 60-Tesla magneto-absorption supported by modeling, we unambiguously demonstrate that the optical resonances arise from tightly bound excitons with both exciton reduced masses and binding energies decreasing, respectively, from 0.221 m0 to 0.186 m0 and from 470 meV to 125 meV with increasing thickness from n equals 1 to 5. Based on this study we propose a general scaling law to determine the binding energy of excitons in perovskite quantum wells of any layer thickness.

Magnetooptics of Exciton Rydberg States in a Monolayer Semiconductor.

We report 65 T magnetoabsorption spectroscopy of exciton Rydberg states in the archetypal monolayer semiconductor WSe_{2}. The strongly field-dependent and distinct energy shifts of the 2s, 3s, and 4s excited neutral excitons permits their unambiguous identification and allows for quantitative comparison with leading theoretical models. Both the sizes (via low-field diamagnetic shifts) and the energies of the ns exciton states agree remarkably well with detailed numerical simulations using the nonhydrogenic screened Keldysh potential for 2D semiconductors. Moreover, at the highest magnetic fields, the nearly linear diamagnetic shifts of the weakly bound 3s and 4s excitons provide a direct experimental measure of the exciton's reduced mass m_{r}=0.20±0.01m_{0}.

Terahertz Dynamics of a Topologically Protected State: Quantum Hall Effect Plateaus near the Cyclotron Resonance of a Two-Dimensional Electron Gas.

We measure the Hall conductivity of a two-dimensional electron gas formed at a GaAs/AlGaAs heterojunction in the terahertz regime close to the cyclotron resonance frequency using highly sensitive Faraday rotation measurements. The sample is electrically gated, allowing the electron density to be changed continuously by more than a factor of 3. We observe clear plateaulike and steplike features in the Faraday rotation angle vs electron density and magnetic field (Landau-level filling factor) even at fields or frequencies very close to cyclotron resonance absorption. These features are the high frequency manifestation of quantum Hall plateaus-a signature of topologically protected edge states. We observe both odd and even filling factor plateaus and explore the temperature dependence of these plateaus. Although dynamical scaling theory begins to break down in the frequency region of our measurements, we find good agreement with theory.

[Discharge and transfer management]. / Entlassungs- und Überleitungsmanagement.

The demographic changes together with the increasingly shorter duration of hospital stays are leading to changes in the current health care systems. Not least due to statutory requirement for an assured access to post-hospital health care, the discharge or, respectively, medical transfer management accordingly represent an increasingly important component of hospital routine and should thus help to avoid health-care gaps in the post-hospital periods.A successful discharge management is characterised by the interdisciplinary cooperation of several professions. It is thus necessary to understand as such the issues at stake and the differing concepts. A successful discharge management ensures the success of surgical treatment and in the meantime has also emerged as a showcase for the respective department of hospital. In future it will only be possible to combine high quality medicine with economic interests and competitiveness with the help of a qualitatively high class discharge or, respectively, medical transfer management. The present article is intended to provide an overview of the possible concepts in the files of discharge/medical transfer management and also to illustrate the steps and structures necessary for the successful discharge of the patient.

A 45-year-old female with hypokalemic rhabdomyolysis due to VIP-producing composite pheochromocytoma.

The watery diarrhea, hypokalemia and achlorhydria (WHDA) syndrome due to vasoactive intestinal polypeptide (VIP)-producing extra-pancreatic tumors is rare. We report on a 45-year-old woman who suffered from persistent secretory diarrhea for six years and who was admitted to hospital with complaints of muscular weakness and myalgia. Biochemical testing revealed pronounced rhabdomyolysis due to severe hypokalemia. Gastrointestinal evaluation of long-standing diarrhea including endoscopy of the upper and lower gastrointestinal tract and the small intestine did not show any pathologies. An abdominal computed tomography scan revealed a mass of 4 × 5 cm in the left adrenal gland demonstrating a strong uptake in the 123I-labelled metaiodobenzylguanidine scintigraphy. Plasma levels of chromogranin A, calcitonin, parathormone, basal renin and most prominently VIP were increased in line with a increased 24 hour urinary secretion of noradrenaline, dopamine, normetanephrine and vanillymandelic acid. A WDHA (watery diarrhea, hypokalaemia, achlorhydria) syndrome with hypokalemic rhabdomyolysis due to a VIP-producing adrenal tumor was diagnosed that was removed surgically. The histological evaluation demonstrated a composite pheochromocytoma. Diarrhea stopped immediately after surgery together with a normalization of laboratory parameters. In conclusion, this case report focuses on the rare clinical presentation of secretory diarrhea and electrolyte disturbances in combination with hypokalemic rhabdomyolysis which was caused by a VIP-producing composite pheochromocytoma.

Dynamic magnetic resonance angiography for localization of hyperfunctioning parathyroid glands in the reoperative neck.

OBJECTIVES: To evaluate the use of dynamic magnetic resonance angiography for localization of hyperfunctioning parathyroid glands in the reoperative neck. METHODS: We retrospectively evaluated the head-neck MRIs of 30 patients with a history of hyperparathyroidism, prior head-neck surgery, and intraoperative proven adenomas. The protocol included conventional imaging with T2-weighted STIR sequences, T1w axial and coronal prior to and after contrast media administration, and dynamic magnetic resonance angiography. We compared the results from MRI, dynamic magnetic resonance angiography with 99m-Tc-Sestamibi with intraoperative findings as the gold standard. RESULTS: In conventional MRI 19/30 true positives were detected with a sensitivity and specificity of 63.3% and 100%, respectively. However, by adding dynamic magnetic resonance angiography the detection rate increased to 28/30 true positives. Based on intraoperative findings, the sensitivity and specificity of dynamic magnetic resonance angiography were 93.3% and 100%, respectively. 99m-Tc-Sestamibi detected 24/30 true positives, sensitivity was 80%. CONCLUSION: The diagnostic value of MRI including dynamic magnetic resonance angiography is superior to MRI alone and superior to that of 99m-Tc-Sestamibi in the diagnostic workup of hyperfunctioning parathyroid glands when compared against intraoperative findings.

Polarization modulation time-domain terahertz polarimetry.

We present high precision measurements of polarization rotations in the frequency range from 0.1 to 2.5 THz using a polarization modulation technique. A motorized stage rotates a polarizer at ~ 80 Hz, and the resulting modulation of the polarization is measured by a lock-in technique. We achieve an accuracy of 0.050° (900 µrad) and a precision of 0.02° (350 µrad) for small rotation angles. A detailed mathematical description of the technique is presented, showing its ability to fully characterize elliptical polarizations from 0.1 to 2.5 THz.

Terahertz response and colossal Kerr rotation from the surface states of the topological insulator Bi2Se3.

We report the THz response of thin films of the topological insulator Bi2Se3. At low frequencies, transport is essentially thickness independent showing the dominant contribution of the surface electrons. Despite their extended exposure to ambient conditions, these surfaces exhibit robust properties including narrow, almost thickness-independent Drude peaks, and an unprecedentedly large polarization rotation of linearly polarized light reflected in an applied magnetic field. This Kerr rotation can be as large as 65° and can be explained by a cyclotron resonance effect of the surface states.

A syngeneic orthotopic murine model of pancreatic adenocarcinoma in the C57/BL6 mouse using the Panc02 and 6606PDA cell lines.

BACKGROUND/AIMS: To develop a clinically relevant immunocompetent murine model to study pancreatic cancer using two different syngeneic pancreatic cancer cell lines and to assess MRI for its applicability in this model. METHODS: Two cell lines, 6606PDA and Panc02, were employed for the experiments. Cell proliferation and migration were monitored in vitro. Matrigel™ was tested for its role in tumor induction. Tumor cell growth was assessed after orthotopic injection of tumor cells into the pancreatic head of C57/BL6 mice by MRI and histology. RESULTS: Proliferation and migration of Panc02 were significantly faster than those of 6606PDA. Matrigel did not affect tumor growth/migration but prevented tumor cell spread after injection thus avoiding undesired peritoneal tumor growth. MRI could reliably monitor longitudinal tumor growth in both cell lines: Panc02 had a more irregular finger-like growth, and 6606PDA grew more spherically. Both tumors showed local invasiveness. Histologically, Panc02 showed a sarcoma-like undifferentiated growth pattern, whereas 6606PDA displayed a moderately differentiated glandular tumor growth. Panc02 mice had a significantly shorter (28 days) survival than 6606PDA mice (50 days). CONCLUSION: This model closely mimics human pancreatic cancer. MRI was invaluable for longitudinal monitoring of tumor growth thus reducing the number of mice required. Employing two different cell lines, this model can be used for various treatment and imaging studies.

[Rare cause of hypercalcemia]. / Seltene Differenzialdiagnose einer schweren Hyperkalzämie.

We report a 47-year-old women who presented to her general practitioner and our hospital with weight loss of unknown etiology. Eight years previously she had undergone a hemithyroidectomy for nodular goiter with one cold nodule. Laboratory results revealed hypercalcemia, evidence of primary hyperparathyroidism and computer tomography of the thorax showed bilateral pulmonary metastasis. After undergoing CT-guided biopsy of a metastasis, histology revealed an endocrine primary tumor with low parathyroid hormone expression. In view of the history, clinical and biochemical findings we diagnosed a recently metastasized functioning parathyroid carcinoma, which eight years previously has been labeled as a benign atypical thyroid adenoma. The patient underwent surgical resection of all detected metastases. Afterwards the serum calcium and parathyroid hormone levels normalized. Parathyroid carcinoma is an uncommon tumor. In the absence of pathognomonic diagnostic criteria a definitive pathological diagnosis of parathyroid carcinoma often is not possible. The treatment of parathyroid carcinoma is essentially surgical. Patients with parathyroid carcinoma mostly die from uncontrollable hypercalcemia rather than from other tumor-related complications.

[Atypical vascular supply from the coeliac trunk. Recurrent bleeding from a duodenal ulcer]. / Atypische Gefässversorgung aus dem Truncus coeliacus. Rezidivblutung aus einem Ulcus duodeni.

Hemorrhagic duodenal ulcers should primarily be controlled by endoscopy. In cases of recurrent bleeding or if bleeding cannot be controlled endoscopically, open surgery is the gold standard. Rarely, atypical origin of arteries or additional atypical arteries may lead to further unexpected hemorrhagic recurrences and angiography with surgical intervention is the treatment of choice. In this article a rare case of an atypical visceral artery connecting the coeliac trunk and the gastroduodenal artery leading to recurrent bleeding from a duodenal ulcer is presented.

[Laser-induced thermotherapy (LITT) of tumors of the liver in central location: results and complications]. / Laserinduzierte Thermotherapie (LITT) von Lebertumoren in zentraler Lokalisation: Ergebnisse und Komplikationen.

PURPOSE: To investigate whether laser-induced thermotherapy (LITT) for tumors of the liver in central location is a sufficient and safe therapeutic option. MATERIAL AND METHODS: According to predefined criteria, 23 of 136 patients were chosen to be treated with LITT because of malignant liver tumors. At the time of the first LITT, the patients had 28 central tumors (27 metastases, one HCC), which were treated in 34 sessions with 64 laser applications and had a clinical and imaging follow-up every 3 months. RESULTS: The primary effectiveness rate was 74.1% and the secondary effectiveness rate 82.1%. The mortality rate was 0%. Major complications occurred in one patient (hemorrhagic pleural effusion), while minor complications occurred in 10 patients. During the median follow-up of 20 months (range 3-57 months), local tumor progression developed in 22% of the tumors. The effectiveness rate was 78.6%, 71.4% and 64.3% after 3, 6 and 9 months. The median survival was 46.0 months (95% confidence interval: 28.6-47.1 months). CONCLUSION: In our patients, complications and ablation rate of laser-induced thermotherapy for central liver tumors do not differ from those in peripheral location as described in the literature.

Significantly increased levels of mannose-binding lectin (MBL) in rheumatic heart disease: a beneficial role for MBL deficiency.

Although mannose-binding lectin (MBL) is known to be involved in the primary defense against microorganisms, there are emerging lines of evidence for an active proinflammatory role for MBL in different chronic diseases. In this study we determined the circulating levels of MBL in patients with rheumatic heart disease (RHD). A total of 100 patients (77 women, 23 men; mean age 45.8 +/- 11 years, range 19-76 years) with chronic RHD, and a previous diagnosis of rheumatic fever, were studied. Transthoracic echocardiography was performed in all patients to evaluate valvular heart disease. Ninety-nine healthy individuals matched for age, sex and ethnic origin were included as controls. MBL concentration was measured by enzyme-linked immunosorbent assay and C3 and C4 levels by turbidimetry. MBL levels were significantly higher in patients with RHD than in healthy subjects (mean +/- SEM: 3036.2 +/- 298.9 ng/ml versus 1942.6 +/- 185.5 ng/ml, P <0.003). In addition, MBL deficiency was more prevalent in controls (17.1%) than in patients (9% P <0.09). Concentrations of C4 were within the normal range (22.7 +/- 0.8 mg/dl, normal: 10.0-40.0 mg/dl), while C3 concentrations were found to be elevated (109.2 +/- 3.6 mg/dl, normal: 50.0-90.0 mg/dl). No correlation was observed between serum MBL levels and valve area or the type of surgical procedure. The significantly elevated circulating MBL levels in patients with RHD together with the greater prevalence of MBL deficiency in controls suggest that MBL may cause undesirable complement activation contributing to the pathogenesis of RHD.

[Surgical therapy of lung metastases-indications, technique, results]. / Die chirurgische Therapie der Lungenmetastasen-Indikationen, Techniken und Ergebnisse.

Due to the absence of established guidelines for the surgical treatment of lung metastases, informational prognostic factors such as: initial primary tumor, length of disease-free interval and number of lung metastases, can be derived from extensive, retrospective patient analyses and thereby serve as a directive in the development of a therapeutic course of treatment. The ultimate surgical goal is a complete, yet, parenchymal-sparing tumor resection. Regardless of primary tumor type, the 5-year survival rate for resected patients varies between 26 and 53%. Controversy still remains as to whether lung metastases should be removed either via open thoracotomy, or under video thoracoscopic conditions. Independent of surgical approach, thoracic surgical operations are associated with very low rates of morbidity as well as mortality even in patients of advanced age.

[Chronic pancreatitis. Diagnosis and treatment]. / Chronische Pankreatitis. Diagnostik und Therapie.

Chronic pancreatitis is characterized by periodic episodes of inflammation and loss of exocrine and endocrine function of the pancreas. Hereditary pancreatitis is an autosomal dominant disorder with an 80% penetrance, is associated with recurrent episodes of pancreatitis starting in early childhood and correlated to an increased risk of pancreatic cancer. The pathogenesis of chronic and hereditary pancreatitis is not yet fully understood. Patients suffering from chronic pancreatitis present with belt-like abdominal pain, weight loss, and often diabetes mellitus. The diagnosis is made by a combination of imaging procedures such as ultrasound and endoscopic retrograde cholangiopancreatography and exocrine and endocrine function tests. Therapy is restricted to symptom control. Approximately 30-60% of all patients develop disease-associated complications such as persistent pain, strictures of the common bile duct, or pancreatic duct stones which require either interventional or surgical treatment.