10,748 research outputs found

    A taxonomic revision of Camptocerus Dejean (Coleoptera: Curculionidae: Scolytinae)

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    The Neotropical ambrosia beetle genus Camptocerus Dejean was revised. Monophyly of the genus was tested using 66 morphological characters in a cladistic analysis. Camptocerus was recovered as monophyletic and 31 species were recognized. Six new synonyms were discovered: C. auricomus Blandford 1896 (= C. striatulus Hagedorn 1905), C. inoblitus (Schedl) 1939 (= C. morio (Schedl) 1952), C. niger (Fabricius) 1801 (= C. tectus Eggers 1943), C. opacicollis (Eggers) 1929 (= C. infidelis Wood 1969; = C. uniseriatus Schedl 1972), C. suturalis (Fabricius) 1801 (= C. cinctus Chapuis 1869). Two species were removed from synonymy: C. charpentierae Schedl and C. hirtipennis Schedl. Twelve new species of Camptocerus were described: C. coccoformus (Brazil, Ecuador), C. distinctus (Ecuador), C. doleae (Ecuador), C. igniculus (Brazil), C. mallopterus (Ecuador), C. noel (widely distributed across Amazonia), C. petrovi (Ecuador), C. pilifrons (Ecuador), C. pseudoangustior (widely distributed across Amazonia), C. satyrus (Brazil), C. unicornus (Brazil) and C. zucca (Ecuador). Lectotypes are here designated for the following species: Camptocerus auricomus Blandford, Camptocerus squammiger Chapuis, Hylesinus gibbus Fabricius, Hylesinus suturalis Fabricius, Hylesinus fasciatus Fabricius. A key, diagnosis, distribution, host records and images were provided for each species

    A two-step approach to achieve secondary amide transamidation enabled by nickel catalysis.

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    A long-standing challenge in synthetic chemistry is the development of the transamidation reaction. This process, which involves the conversion of one amide to another, is typically plagued by unfavourable kinetic and thermodynamic factors. Although some advances have been made with regard to the transamidation of primary amide substrates, secondary amide transamidation has remained elusive. Here we present a simple two-step approach that allows for the elusive overall transformation to take place using non-precious metal catalysis. The methodology proceeds under exceptionally mild reaction conditions and is tolerant of amino-acid-derived nucleophiles. In addition to overcoming the classic problem of secondary amide transamidation, our studies expand the growing repertoire of new transformations mediated by base metal catalysis

    Improved self-gain in deep submicrometer strained silicon-germanium pMOSFETs with HfSiOx/TiSiN gate stacks

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    The self-gain of surface channel compressively strained SiGe pMOSFETs with HfSiOx/TiSiN gate stacks is investigated for a range of gate lengths down to 55 nm. There is 125% and 700% enhancement in the self-gain of SiGe pMOSFETs compared with the Si control at 100 nm and 55 nm lithographic gate lengths, respectively. This improvement in the self-gain of the SiGe devices is due to 80% hole mobility enhancement compared with the Si control and improved electrostatic integrity in the SiGe devices due to less boron diffusion into the channel. At 55 nm gate length, the SiGe pMOSFETs show 50% less drain induced barrier lowering compared with the Si control devices. Electrical measurements show that the SiGe devices have larger effective channel lengths. It is shown that the enhancement in the self-gain of the SiGe devices compared with the Si control increases as the gate length is reduced thereby making SiGe pMOSFETs with HfSiOx/TiSiN gate stacks an excellent candidate for analog/mixed-signal applications

    Impaired contextual modulation of memories in PTSD: an fMRI and psychophysiological study of extinction retention and fear renewal

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    Post-traumatic stress disorder (PTSD) patients display pervasive fear memories, expressed indiscriminately. Proposed mechanisms include enhanced fear learning and impaired extinction or extinction recall. Documented extinction recall deficits and failure to use safety signals could result from general failure to use contextual information, a hippocampus-dependent process. This can be probed by adding a renewal phase to standard conditioning and extinction paradigms. Human subjects with PTSD and combat controls were conditioned (skin conductance response), extinguished, and tested for extinction retention and renewal in a scanner (fMRI). Fear conditioning (light paired with shock) occurred in one context, followed by extinction in another, to create danger and safety contexts. The next day, the extinguished conditioned stimulus (CS+E) was re-presented to assess extinction recall (safety context) and fear renewal (danger context). PTSD patients showed impaired extinction recall, with increased skin conductance and heightened amygdala activity to the extinguished CS+ in the safety context. However, they also showed impaired fear renewal; in the danger context, they had less skin conductance response to CS+E and lower activity in amygdala and ventral-medial prefrontal cortex compared with combat controls. Control subjects displayed appropriate contextual modulation of memory recall, with extinction (safety) memory prevailing in the safety context, and fear memory prevailing in the danger context. PTSD patients could not use safety context to sustain suppression of extinguished fear memory, but they also less effectively used danger context to enhance fear. They did not display globally enhanced fear expression, but rather showed a globally diminished capacity to use contextual information to modulate fear expression

    The impact of self-heating and SiGe strain-relaxed buffer thickness on the analog performance of strained Si nMOSFETs

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    The impact of the thickness of the silicon–germanium strain-relaxed buffer (SiGe SRB) on the analog performance of strained Si nMOSFETs is investigated. The negative drain conductance caused by self-heating at high power levels leads to negative self-gain which can cause anomalous circuit behavior like non-linear phase shifts. Using AC and DC measurements, it is shown that reducing the SRB thickness improves the analog design space and performance by minimizing self-heating. The range of terminal voltages that leverage positive self-gain in 0.1 μm strained Si MOSFETs fabricated on 425 nm SiGe SRBs is increased by over 100% compared with strained Si devices fabricated on conventional SiGe SRBs 4 μm thick. Strained Si nMOSFETs fabricated on thin SiGe SRBs also show 45% improvement in the self-gain compared with the Si control as well as 25% enhancement in the on-state performance compared with the strained Si nMOSFETs on the 4 μm SiGe SRB. The extracted thermal resistance is 50% lower in the strained Si device on the thin SiGe SRB corresponding to a 30% reduction in the temperature rise compared with the device fabricated on the 4 μm SiGe SRB. Comparisons between the maximum drain voltages for positive self-gain in the strained Si devices and the ITRS projections of supply-voltage scaling show that reducing the thickness of the SiGe SRB would be necessary for future technology nodes

    Understanding meal patterns: definitions, methodology and impact on nutrient intake and diet quality

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    Traditionally, nutrition research has focused on individual nutrients, and more recently dietary patterns. However, there has been relatively little focus on dietary intake at the level of a \u27meal\u27. The purpose of the present paper was to review the literature on adults\u27 meal patterns, including how meal patterns have previously been defined and their associations with nutrient intakes and diet quality. For this narrative literature review, a comprehensive search of electronic databases was undertaken to identify studies in adults aged ≥  19 years that have investigated meal patterns and their association with nutrient intakes and/or diet quality. To date, different approaches have been used to define meals with little investigation of how these definitions influence the characterisation of meal patterns. This review identified thirty-four and fourteen studies that have examined associations between adults\u27 meals patterns, nutrient intakes and diet quality, respectively. Most studies defined meals using a participant-identified approach, but varied in the additional criteria used to determine individual meals, snacks and/or eating occasions. Studies also varied in the types of meal patterns, nutrients and diet quality indicators examined. The most consistent finding was an inverse association between skipping breakfast and diet quality. No consistent association was found for other meal patterns, and little research has examined how meal timing is associated with diet quality. In conclusion, an understanding of the influence of different meal definitions on the characterisation of meal patterns will facilitate the interpretation of the existing literature, and may provide guidance on the most appropriate definitions to use

    Examining variations in prescribing safety in UK general practice: cross sectional study using the Clinical Practice Research Datalink

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    Study question: What is the prevalence of different types of potentially hazardous prescribing in general practice in the United Kingdom, and what is the variation between practices? Methods: A cross sectional study included all adult patients potentially at risk of a prescribing or monitoring error defined by a combination of diagnoses and prescriptions in 526 general practices contributing to the Clinical Practice Research Datalink (CPRD) up to 1 April 2013. Primary outcomes were the prevalence of potentially hazardous prescriptions of anticoagulants, anti-platelets, NSAIDs, β blockers, glitazones, metformin, digoxin, antipsychotics, combined hormonal contraceptives, and oestrogens and monitoring by blood test less frequently than recommended for patients with repeated prescriptions of angiotensin converting enzyme inhibitors and loop diuretics, amiodarone, methotrexate, lithium, or warfarin. Study answer and limitations: 49 927 of 949 552 patients at risk triggered at least one prescribing indicator (5.26%, 95% confidence interval 5.21% to 5.30%) and 21 501 of 182 721 (11.8%, 11.6% to 11.9%) triggered at least one monitoring indicator. The prevalence of different types of potentially hazardous prescribing ranged from almost zero to 10.2%, and for inadequate monitoring ranged from 10.4% to 41.9%. Older patients and those prescribed multiple repeat medications had significantly higher risks of triggering a prescribing indicator whereas younger patients with fewer repeat prescriptions had significantly higher risk of triggering a monitoring indicator. There was high variation between practices for some indicators. Though prescribing safety indicators describe prescribing patterns that can increase the risk of harm to the patient and should generally be avoided, there will always be exceptions where the indicator is clinically justified. Furthermore there is the possibility that some information is not captured by CPRD for some practices—for example, INR results in patients receiving warfarin. What this study adds: The high prevalence for certain indicators emphasises existing prescribing risks and the need for their appropriate consideration within primary care, particularly for older patients and those taking multiple medications. The high variation between practices indicates potential for improvement through targeted practice level intervention. Funding, competing interests, data sharing: National Institute for Health Research through the Greater Manchester Primary Care Patient Safety Translational Research Centre (grant No GMPSTRC-2012-1). Data from CPRD cannot be shared because of licensing restrictions
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