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Diastereoselective synthesis and conformational analysis of (2R)- and (2S)-fluorostatines : an approach based on organocatalytic fluorination of a chiral aldehyde
No full textStereoselectively fluorinated analogues of the amino acid statine have been efficiently synthesized. The key step is an organocatalytic electrophilic fluorination of a chiral β-oxygenated aldehyde, which provided a test of both diastereoselectivity and chemoselectivity. The target statine analogues were found to adopt unique conformations influenced by the fluorine gauche effect, rendering them potentially valuable building blocks for incorporation into bioactive peptides.4 page(s
Mercury(II) selective sensors based on AlGaN/GaN transistors
No full textThis work presents the first polymer approach to detect metal ions using AlGaN/GaN transistor-based sensor. The sensor utilised an AlGaN/GaN high electron mobility transistor-type structure by functionalising the gate area with a polyvinyl chloride (PVC) based ion selective membrane. Sensors based on this technology are portable, robust and typically highly sensitive to the target analyte; in this case Hg²⁺. This sensor showed a rapid and stable response when it was introduced to solutions of varying Hg²⁺ concentrations. At pH 2.8 in a 10⁻²M KNO₃ ion buffer, a detection limit below 10⁻⁸M and a linear response range between 10⁻⁸ M-10⁻⁴ M were achieved. This detection limit is an order of magnitude lower than the reported detection limit of 10⁻⁷M for thioglycolic acid monolayer functionalised AlGaN/GaN HEMT devices. Detection limits of approximately 10⁻⁷M and 10⁻⁶M in 10⁻²M Cd(NO₃)₂ and 10⁻²M Pb(NO₃)₂ ion buffers were also achieved, respectively. Furthermore, we show that the apparent gate response was near-Nernstian under various conditions. X-ray photoelectron spectroscopy (XPS) experiments confirmed that the sensing membrane is reversible after being exposed to Hg²⁺ solution and rinsed with deionised water. The success of this study precedes the development of this technology in selectively sensing multiple ions in water with use of the appropriate polymer based membranes on arrays of devices.7 page(s
Auditing and assurance : a case studies approach
No full textAuditing and assurance: a case studies approach provides challenging, practical cases for auditing students at both the undergraduate and postgraduate level. The revised 6th edition incorporates key revisions to existing and new auditing standards as of December 2015. The most significant changes to auditing standards since the 6th edition was published in 2014 are in the areas of audit reporting and addressing disclosures in the audit of financial statements. Auditing and assurance: a case studies approach also offers extensive new online support materials for both students and lecturers, including a comprehensive teaching guide for instructors.310 page(s)Revised 6th editio
Satellite based estimates underestimate the effect of CO₂ fertilization on net primary productivity
No full text2 page(s
Complication-effectiveness analysis for brain arteriovenous malformation surgery : a prospective cohort study
No full textBackground: Intervention for brain arteriovenous malformations (bAVMs) should aim at treatment that is safe and effective. Objective: To analyze a prospective database to derive the probability of neurological deficit and adjust this risk for effectively treated bAVMs (complication-effectiveness analysis [CEA]). Methods: First, we calculated the percentage of surgical complications leading to a modified Rankin Scale >1 at 12 months after surgery for each Spetzler-Ponce class (SPC). Second, we performed a sensitivity analysis of these results by including bAVMs not undergoing surgery, to correct for bias. Third, we established the long-term cumulative incidence of freedom from recurrence from Kaplan-Meier analysis. Finally, we combined the results to calculate the risk of surgery per effective treatment in a complication-effectiveness analysis. Results: Seven hundred seventy-nine patients underwent 641 microsurgical resections. Complications of surgery leading to a modified Rankin Scale >1 at 12 months occurred in 1.4% (95% confidence interval [CI]: 0.5-3.3), 20% (95% CI: 15-26), and 41% (95% CI: 30-52) of SPC A, SPC B, and SPC C, respectively. The cumulative 9-year freedom from recurrence was 97% for SPC A and 92% for other bAVMs. The 9-year CEA risk was 1.4% (credible range: 0.5%-3.4%) for SPC A, 22% to 24% (credible range: 16%-31%) for SPC B, and 45% to 63% (credible range: 33%-73%) for SPC C bAVM. Conclusion: CEA presents the treatment outcome in the context of efficacy and provides a basis for comparing outcomes from techniques with different times to elimination of the bAVM.11 page(s
Axioms for information leakage
No full textQuantitative information flow aims to assess and control the leakage of sensitive information by computer systems. A key insight in this area is that no single leakage measure is appropriate in all operational scenarios, as a result, many leakage measures have been proposed, with many different properties. To clarify this complex situation, this paper studies information leakage axiomatically, showing important dependencies among different axioms. It also establishes a completeness result about the g-leakage family, showing that any leakage measure satisfying certain intuitively-reasonable properties can be expressed as a g-leakage.16 page(s
Bone remodeling during pregnancy and post-partum assessed by metal lead levels and isotopic concentrations
No full textBone remodeling is normally evaluated using bone turnover markers/indices as indicators of bone resorption and formation. However, during pregnancy and post-partum, there have been inconsistent results between and within biomarkers for bone formation and resorption. These differences may relate to pregnancy-related changes in metabolism and/or hemodilution altering measured marker levels. An alternative approach to evaluating bone remodeling is to use the metal lead (Pb) concentrations and Pb isotopic compositions in blood. These measurements can also provide information on the amount of Pb that is mobilized from the maternal skeleton. Despite some similarities with accepted bone turnover markers, the Pb data demonstrate increased bone resorption throughout pregnancy that further continues post-partum independent of length of breast-feeding, dietary intake and resumption of menses. Furthermore the isotopic measurements are not affected by hemodilution. These data confirm calcium balance studies that indicate increased bone resorption throughout pregnancy and lactation. They also indicate potentially major public health implications of the transfer of maternal Pb burden to the fetus and new born.12 page(s
From biological cilia to artificial flow sensors : biomimetic soft polymer nanosensors with high sensing performance
No full textWe report the development of a new class of miniature all-polymer flow sensors that closely mimic the intricate morphology of the mechanosensory ciliary bundles in biological hair cells. An artificial ciliary bundle is achieved by fabricating bundled polydimethylsiloxane (PDMS) micro-pillars with graded heights and electrospinning polyvinylidenefluoride (PVDF) piezoelectric nanofiber tip links. The piezoelectric nature of a single nanofiber tip link is confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Rheology and nanoindentation experiments are used to ensure that the viscous properties of the hyaluronic acid (HA)-based hydrogel are close to the biological cupula. A dome-shaped HA hydrogel cupula that encapsulates the artificial hair cell bundle is formed through precision drop-casting and swelling processes. Fluid drag force actuates the hydrogel cupula and deflects the micro-pillar bundle, stretching the nanofibers and generating electric charges. Functioning with principles analogous to the hair bundles, the sensors achieve a sensitivity and threshold detection limit of 300 mV/(m/s) and 8 μm/s, respectively. These self-powered, sensitive, flexible, biocompatibale and miniaturized sensors can find extensive applications in navigation and maneuvering of underwater robots, artificial hearing systems, biomedical and microfluidic devices.13 page(s
Mediastinal micro-vessels clipping during lymph node dissection may contribute to reduce postoperative pleural drainage
No full textBackground: Postoperative pleural drainage markedly influences the length of postoperative stay and financial costs of medical care. The aim of this study is to retrospectively investigate potentially predisposing factors related to pleural drainage after curative thoracic surgery and to explore the impact of mediastinal micro-vessels clipping on pleural drainage control after lymph node dissection. Methods: From February 2012 to November 2013, 322 consecutive cases of operable non-small cell lung cancers (NSCLC) undergoing lobectomy and mediastinal lymph node dissection with or without application of clipping were collected. Total and daily postoperative pleural drainage were recorded. Propensity score matching (1:2) was applied to balance variables potentially impacting pleural drainage between group clip and group control. Analyses were performed to compare drainage volume, duration of chest tube and postoperative hospital stay between the two groups. Variables linked with pleural drainage in whole cohort were assessed using multivariable logistic regression analysis. Results: Propensity score matching resulted in 197 patients (matched cohort). Baseline patient characteristics were matched between two groups. Group clip showed less cumulative drainage volume (P=0.020), shorter duration of chest tube (P=0.031) and postoperative hospital stay (P=0.022) compared with group control. Risk factors significantly associated with high-output drainage in multivariable logistic regression analysis were being male, age >60 years, bilobectomy/sleeve lobectomy, pleural adhesion, the application of clip applier, duration of operation ≥220 minutes and chylothorax (P<0.05). Conclusions: This study suggests that mediastinal micro-vessels clipping during lymph node dissection may reduce postoperative pleural drainage and thus shorten hospital stay.7 page(s
Modular multiplication using the core function in the residue number system
No full textModular multiplication can be performed in the residue number system (RNS) using a type of Montgomery reduction. This paper presents an alternative in which RNS modular multiplication are performed by using the core function. All of the intermediate calculations use short wordlength operations within the RNS. This work contributes to the long wordlength modular multiplication operation Z = A × B mod M, the basis of many DSPs and public-key cryptosystems.16 page(s