Collective excitations and low temperature transport properties of bismuth

We examine the influence of collective excitations on the transport properties (resistivity, magneto- optical conductivity) for semimetals, focusing on the case of bismuth. We show, using an RPA approximation, that the properties of the system are drastically affected by the presence of an acoustic plasmon mode, consequence of the presence of two types of carriers (electrons and holes) in this system. We found a crossover temperature T* separating two different regimes of transport. At high temperatures T > T* we show that Baber scattering explains quantitatively the DC resistivity experiments, while at low temperatures T < T* interactions of the carriers with this collective mode lead to a T^5 behavior of the resistivity. We examine other consequences of the presence of this mode, and in particular predict a two plasmon edge feature in the magneto-optical conductivity. We compare our results with the experimental findings on bismuth. We discuss the limitations and extensions of our results beyond the RPA approximation, and examine the case of other semimetals such as graphite or 1T-TiSe_2

Effects of Charge and Substituent on the S∙∙∙N Chalcogen Bond

Neutral complexes containing a S···N chalcogen bond are compared with similar systems in which a positive charge has been added to the S-containing electron acceptor, using high-level ab initio calculations. The effects on both XS···N and XS+···N bonds are evaluated for a range of different substituents X = CH3, CF3, NH2, NO2, OH, Cl, and F, using NH3 as the common electron donor. The binding energy of XMeS···NH3 varies between 2.3 and 4.3 kcal/mol, with the strongest interaction occurring for X = F. The binding is strengthened by a factor of 2–10 in charged XH2S+···NH3 complexes, reaching a maximum of 37 kcal/mol for X = F. The binding is weakened to some degree when the H atoms are replaced by methyl groups in XMe2S+···NH3. The source of the interaction in the charged systems, like their neutral counterparts, is derived from a charge transfer from the N lone pair into the σ*(SX) antibonding orbital, supplemented by a strong electrostatic and smaller dispersion component. The binding is also derived from small contributions from a CH···N H-bond involving the methyl groups, which is most notable in the weaker complexes

Increasing time delay from presentation until surgical referral for hepatobiliary malignancies

AbstractBackgroundStudies have shown that delayed treatment of several non-hepatobiliary (HB) malignancies is associated with adverse effects on disease progression and survival. Delayed treatment of HB malignancies has not been thoroughly investigated.MethodsWe performed a retrospective institutional review of patients referred to the Hepatobiliary Surgery Service at Beth Israel Deaconess Medical Center (BIDMC) for hepatobiliary malignancies from 2002 to 2008. Primary outcomes included the time delays (TD) in patient workup. Secondary outcomes were reasons for delay as well as disparities in TD based on demographic factors.ResultsMultivariate-adjusted linear regression showed a significant trend of increasing time from presentation until referral to a HB surgeon over the 7-year period (P= 0.001). There were no differences in TD by gender, age or education level. Multivariate-adjusted linear regression showed a significant trend of increasing number of imaging tests performed prior to referral [computerized tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET) and ultrasound and endoscopic ultrasound (US/EUS)] (P < 0.001). Multivariate-adjusted linear regression in resectable patients showed a significant difference in overall length of survival in those with a TD1 > 30 days compared with those with a TD1 (TD from presentation until referral) <30 days (P= 0.042).ConclusionsDelays were associated with an increase in imaging studies and delays adversely affect survival in resected patients. Referring physicians are encouraged to expedite the evaluation and early referral of all patients to an HB surgeon for evaluation and treatment

Bauhinia proteinase inhibitor-based synthetic fluorogenic substrates for enzymes isolated from insect midgut and caterpillar bristles

Bauhinia ungulata factor Xa inhibitor (BuXI) inactivates factor Xa and LOPAP, a prothrombin activator proteinase isolated from the venom of Lonomia obliqua caterpillar bristles. the reactive site of the enzyme inhibitor interaction was explored to design specific substrates for both enzymes. Methionine is crucial for LOPAP and factor Xa substrate interaction, since the change of both Met residues in the substrates abolished the hydrolysis. Synthetic substrates containing the sequence around the reactive site of BbKI, a plasma kallikrein inhibitor, were shown to be specific for trypsin hydrolysis. Therefore, these substrates may be an alternative in studies aiming at a characterization of trypsinlike enzyme activities, especially nonmammalian enzymes.Universidade Federal de São Paulo, Sch Med, Dept Biochem, BR-04044020 São Paulo, BrazilUniversidade Federal de São Paulo, Sch Med, Dept Biophys, BR-04044020 São Paulo, BrazilUniv São Paulo, Dept Biochem, Inst Chem, BR-05508900 São Paulo, BrazilInst Butantan, BR-05503900 São Paulo, BrazilUniversidade Federal de São Paulo, Sch Med, Dept Biochem, BR-04044020 São Paulo, BrazilUniversidade Federal de São Paulo, Sch Med, Dept Biophys, BR-04044020 São Paulo, BrazilWeb of Scienc

Assessment of a circular powered stapler for creation of anastomosis in left-sided colorectal surgery: a prospective cohort study.

BACKGROUND Circular staplers perform a critical function for creation of anastomoses in colorectal surgeries. Powered stapling systems allow for reduced force required by surgeons to fire the device and may provide advantages for creating a secure anastomosis. The objective of this study was to evaluate the clinical performance of a novel circular powered stapler in a post-market setting, during left-sided colectomy procedures. MATERIALS AND METHODS Consecutive subjects underwent left-sided colorectal resections that included anastomosis performed with the ECHELON CIRCULAR™ Powered Stapler (ECP). The primary endpoint was the frequency in which a stapler performance issue was observed. Secondary endpoints included evaluation of ease of use of the device via a surgeon satisfaction questionnaire, and monitoring/recording of procedure-related adverse events (AEs). RESULTS A total of 168 anastomoses were performed with the ECP. Surgical approaches included robotic-assisted (n= 74, 44.0%), laparoscopic (n=71, 42.3%), open (n=20, 11.9%), and hand-assisted minimally invasive (n=3, 1.8%) procedures. There were 22 occurrences of device performance issues in 20 (11.9%) subjects during surgery. No positive intraoperative leak tests were observed, and only 1 issue was related to a procedure-related AE or surgical complication, which was an instance of incomplete surgical donut necessitating re-anastomosis. Postoperative anastomotic leaks were experienced in 4 (2.4%) subjects. Clavien-Dindo classification of all AEs indicated that 92.0% were Grades I or II. Participating surgeons rated the ECP as easier to use compared to previously used manual circular staplers in 85.7% of procedures. CONCLUSION The circular powered stapler exhibited few clinically relevant performance issues, an overall favorable safety profile, and ease of use for creation of left-sided colon anastomoses