Metal-Insulator Transition in Variably Doped (Bi1-xSbx)2Se3 Nanosheets

Topological insulators are novel quantum materials with metallic surface transport, but insulating bulk behavior. Often, topological insulators are dominated by bulk contributions due to defect induced bulk carriers, making it difficult to isolate the more interesting surface transport characteristics. Here, we report the synthesis and characterization of nanosheets of topological insulator Bi2Se3 with variable Sb-doping level to control the electron carrier density and surface transport behavior. (Bi1-xSbx)2Se3 thin films of thickness less than 10 nm are prepared by epitaxial growth on mica substrates in a vapor transport setup. The introduction of Sb in Bi2Se3 effectively suppresses the room temperature electron density from ~4 \times 10^13/cm^2 in pure Bi2Se3 (x = 0) to ~2 \times 10^12/cm^2 in (Bi1-xSbx)2Se3 at x ~0.15, while maintaining the metallic transport behavior. At x > ~0.20, a metal-insulator transition (MIT) is observed indicating that the system has transformed into an insulator in which the metallic surface conduction is blocked. In agreement with the observed MIT, Raman spectroscopy reveals the emergence of vibrational modes arising from Sb-Sb and Sb-Se bonds at high Sb concentrations, confirming the appearance of Sb2Se3 crystal structure in the sample. These results suggest that nanostructured chalcogenide films with controlled doping can be a tunable platform for fundamental studies and electronic applications of topological insulator systems.Comment: accepted for publication in Nanoscale. See http://gaogroup.case.edu/index.php/Publications for related papers from our la

Management of postoperative ileus: focus on alvimopan

Postoperative ileus (POI) is a transient loss of coordinated peristalsis precipitated by surgery and exacerbated by opioid pain medication. Ileus causes a variety of symptoms including bloating, pain, nausea, and vomiting, but particularly delays tolerance of oral diet and liquids. Thus POI is a primary determinant of hospital stay after surgery. ‘Fast-track’ recovery protocols, opioid sparing analgesia, and laparoscopic surgery reduce but do not eliminate postoperative ileus. Alvimopan is a mu opioid receptor antagonist that blocks the effects of opioids on the intestine, while not interfering with their centrally mediated analgesic effect. Several large randomized clinical trials have demonstrated that alvimopan accelerates the return of gastrointestinal function after surgery and subsequent hospital discharge by approximately 20 hours after elective open segmental colectomy. However, it has not been tested in patients undergoing laparoscopic surgery and is less effective in patients receiving nonsteroidal anti-inflammatory agents in a narcotic sparing postoperative pain control regimen. Safety concerns seen with chronic low dose administration of alvimopan for opioid bowel dysfunction have not been noted with its acute use for POI

Alvimopan for the Management of Postoperative Ileus After Bowel Resection: Characterization of Clinical Benefit by Pooled Responder Analysis

BACKGROUND: A pooled post hoc responder analysis was performed to assess the clinical benefit of alvimopan, a peripherally acting mu-opioid receptor (PAM-OR) antagonist, for the management of postoperative ileus after bowel resection. METHODS: Adult patients who underwent laparotomy for bowel resection scheduled for opioid-based intravenous patient-controlled analgesia received oral alvimopan or placebo preoperatively and twice daily postoperatively until hospital discharge or for 7 postoperative days. The proportion of responders and numbers needed to treat (NNT) were examined on postoperative days (POD) 3-8 for GI-2 recovery (first bowel movement, toleration of solid food) and hospital discharge order (DCO) written. RESULTS: Alvimopan significantly increased the proportion of patients with GI-2 recovery and DCO written by each POD (P \u3c 0.001 for all). More patients who received alvimopan achieved GI-2 recovery on or before POD 5 (alvimopan, 80%; placebo, 66%) and DCO written before POD 7 (alvimopan, 87%; placebo, 72%), with corresponding NNTs equal to 7. CONCLUSIONS: On each POD analyzed, alvimopan significantly increased the proportion of patients who achieved GI-2 recovery and DCO written versus placebo and was associated with relatively low NNTs. The results of these analyses provide additional characterization and support for the overall clinical benefit of alvimopan in patients undergoing bowel resection

Observation of Low Energy Raman Modes in Twisted Bilayer Graphene

Two new Raman modes below 100 cm^-1 are observed in twisted bilayer graphene grown by chemical vapor deposition. The two modes are observed in a small range of twisting angle at which the intensity of the G Raman peak is strongly enhanced, indicating that these low energy modes and the G Raman mode share the same resonance enhancement mechanism, as a function of twisting angle. The 94 cm^-1 mode (measured with a 532 nm laser excitation) is assigned to the fundamental layer breathing vibration (ZO (prime) mode) mediated by the twisted bilayer graphene lattice, which lacks long-range translational symmetry. The dependence of this modes frequency and linewidth on the rotational angle can be explained by the double resonance Raman process which is different from the previously-identified Raman processes activated by twisted bilayer graphene superlattice. The dependence also reveals the strong impact of electronic-band overlaps of the two graphene layers. Another new mode at 52 cm^-1, not observed previously in the bilayer graphene system, is tentatively attributed to a torsion mode in which the bottom and top graphene layers rotate out-of-phase in the plane.Comment: 12 pages, 5 figures, 14 supp. figures (accepted by Nano Lett

Preoperative Rectal Cancer Management: Wide International Practice Makes Outcome Comparison Challenging: Reply

In a letter to the editor Dr. Hottenrott provides valuable comments on our survey describing international preoperative rectal cancer management. In our opinion, three key messages are derived from our survey: First, most surgeons agree to neoadjuvant treatment when there is an increased risk of finding histologically positive circumferential margins. In addition, we found more than 40 other indications for neoadjuvant treatment (see our Table 4). This emphasizes the need for an international agreement, as different indications for neoadjuvant treatment will select noncomparable groups of patients in outcome studies. Second, we have shown (see our Table 6) that multidisciplinary team (MDT) meetings significantly influence several important decisions in preoperative rectal cancer management. Interestingly, centers with regular MDT have a higher rate of using magnetic resonance imaging (MRI) (Odds Ratio [OR] = 3.62) and consider a threatened circumferential resection margin (CRM) as indication for neoadjuvant treatment (OR = 5.67). We believe that MDT improves preoperative management of rectal cancer by increasing adherence to national guidelines. Similar discussions in international rectal cancer societies are needed aiming towards an international consensus statement. Finally, our survey revealed sparse use (35% of all cases) of MRI. The goal for the radiologic examination in rectal cancer is to explore the tumor’s relation to nearby anatomical structures. This evaluation will conclude with TNM staging, important for chemoradiotheraphy, surgical treatment, and prognosis. Magnetic resonance imaging has a central role in this evaluation and should be the first choice radiologic modality. Not only is MRI crucial in detection of TNM stage but also plays a central role in determination of the tumor’s distance to the mesorectal fascia and the CRM. Magnetic resonance imaging has moderate sensitivity on T1 and T2 tumors, and should be supplemented with rectal ultrasound

Attenuated CSF-1R signalling drives cerebrovascular pathology

Cerebrovascular pathologies occur in up to 80% of cases of Alzheimer's disease; however, the underlying mechanisms that lead to perivascular pathology and accompanying blood-brain barrier (BBB) disruption are still not fully understood. We have identified previously unreported mutations in colony stimulating factor-1 receptor (CSF-1R) in an ultra-rare autosomal dominant condition termed adult-onset leucoencephalopathy with axonal spheroids and pigmented glia (ALSP). Cerebrovascular pathologies such as cerebral amyloid angiopathy (CAA) and perivascular p-Tau were some of the primary neuropathological features of this condition. We have identified two families with different dominant acting alleles with variants located in the kinase region of the CSF-1R gene, which confer a lack of kinase activity and signalling. The protein product of this gene acts as the receptor for 2 cognate ligands, namely colony stimulating factor-1 (CSF-1) and interleukin-34 (IL-34). Here, we show that depletion in CSF-1R signalling induces BBB disruption and decreases the phagocytic capacity of peripheral macrophages but not microglia. CSF-1R signalling appears to be critical for macrophage and microglial activation, and macrophage localisation to amyloid appears reduced following the induction of Csf-1r heterozygosity in macrophages. Finally, we show that endothelial/microglial crosstalk and concomitant attenuation of CSF-1R signalling causes re-modelling of BBB-associated tight junctions and suggest that regulating BBB integrity and systemic macrophage recruitment to the brain may be therapeutically relevant in ALSP and other Alzheimer's-like dementias

Complications, Not Minimally Invasive Surgical Technique, Are Associated with Increased Cost after Esophagectomy

Background. Minimally invasive esophagectomy (MIE) techniques offer similar oncological and surgical outcomes to open methods. The effects of MIE on hospital costs are not well documented. Methods. We reviewed the electronic records of patients who underwent esophagectomy at a single academic institution between January 2012 and December 2014. Esophagectomy techniques were grouped into open, hybrid, MIE, and transhiatal (THE) esophagectomy. Univariate and multivariate analyses were performed to assess the impact of surgery on total hospital cost after esophagectomy. Results. 80 patients were identified: 11 THE, 11 open, 41 hybrid, and 17 MIE. Median total cost of the hospitalization was $31,375 and was similar between surgical technique groups. MIE was associated with higher intraoperative costs, but not total hospital cost. Multivariable analysis revealed that the presence of a complication, increased age, American Society of Anesthesiologists class IV (ASA4), and preoperative coronary artery disease (CAD) were associated with significantly increased cost. Conclusions. Despite the association of MIE with higher operation costs, the total hospital cost was not different between surgical technique groups. Postoperative complications and severe preoperative comorbidities are significant drivers of hospital cost associated with esophagectomy. Surgeons should choose technique based on clinical factors, rather than cost implications

Correction: Cocaine- and stress-primed reinstatement of drug-associated memories elicit differential behavioral and frontostriatal circuit activity patterns via recruitment of L-type Ca2+ channels

Correction to: "Cocaine- and stress-primed reinstatement of drug-associated memories elicit differential behavioral and frontostriatal circuit activity patterns via recruitment of L-type Ca2+ channels