136 research outputs found

    Rapid Characterization of Local Shape Memory Properties Through Indentation

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    Shape memory alloys (SMAs) have the ability to show large recoverable shape changes upon temperature, stress or magnetic field cycling. Their shape memory, material and magnetic properties (e.g. transformation temperatures, strain, saturation magnetization and strength) determine their prospects for applications from small-scale microelectromechanical systems to large scale aerospace and biomedical systems. It should be noted that properties of SMAs are highly temperature dependent. Generally, the conventional mechanical characterization methods (e.g, tension, compression, and torsion) are used on bulk samples of SMAs to determine those properties. In this article, it will be shown that indentation technique can be used as an alternative rapid method to determine some of the important shape memory properties of SMAs. Indentation response of a high-temperature NiTiHf alloy was determined as a function of temperature. A clear relationship between the work recoverable ratio and transformation temperatures, superelastic and plastic behavior was observed. This work shows that indentation response can be used to measure local superelasticity response, determine phase transformation temperatures and reveal the temperature intervals of the deformation mechanisms of shape memory alloys

    Ubiquitin carboxyl-terminal hydrolases are required for period maintenance of the circadian clock at high temperature in Arabidopsis

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    Protein ubiquitylation participates in a number of essential cellular processes including signal transduction and transcription, often by initiating the degradation of specific substrates through the 26S proteasome. Within the ubiquitin-proteasome system, deubiquitylating enzymes (DUBs) not only help generate and maintain the supply of free ubiquitin monomers, they also directly control functions and activities of specific target proteins by modulating the pool of ubiquitylated species. Ubiquitin carboxyl-terminal hydrolases (UCHs) belong to an enzymatic subclass of DUBs, and are represented by three members in Arabidopsis, UCH1, UCH2 and UCH3. UCH1 and UCH2 influence auxin-dependent developmental pathways in Arabidopsis through their deubiquitylation activities, whereas biological and enzymatic functions of UCH3 remain unclear. Here, we demonstrate that Arabidopsis UCH3 acts to maintain the period of the circadian clock at high temperatures redundantly with UCH1 and UCH2. Whereas single uch1, uch2 and uch3 mutants have weak circadian phenotypes, the triple uch mutant displays a drastic lengthening of period at high temperatures that is more extreme than the uch1 uch2 double mutant. UCH3 also possesses a broad deubiquitylation activity against a range of substrates that link ubiquitin via peptide and isopeptide linkages. While the protein target(s) of UCH1-3 are not yet known, we propose that these DUBs act on one or more factors that control period length of the circadian clock through removal of their bound ubiquitin moieties, thus ensuring that the clock oscillates with a proper period even at elevated temperature

    Mining the bitter melon (momordica charantia l.) seed transcriptome by 454 analysis of non-normalized and normalized cDNA populations for conjugated fatty acid metabolism-related genes

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    Abstract Background Seeds of Momordica charantia (bitter melon) produce high levels of eleostearic acid, an unusual conjugated fatty acid with industrial value. Deep sequencing of non-normalized and normalized cDNAs from developing bitter melon seeds was conducted to uncover key genes required for biotechnological transfer of conjugated fatty acid production to existing oilseed crops. It is expected that these studies will also provide basic information regarding the metabolism of other high-value novel fatty acids. Results Deep sequencing using 454 technology with non-normalized and normalized cDNA libraries prepared from bitter melon seeds at 18 DAP resulted in the identification of transcripts for the vast majority of known genes involved in fatty acid and triacylglycerol biosynthesis. The non-normalized library provided a transcriptome profile of the early stage in seed development that highlighted the abundance of transcripts for genes encoding seed storage proteins as well as for a number of genes for lipid metabolism-associated polypeptides, including Δ12 oleic acid desaturases and fatty acid conjugases, class 3 lipases, acyl-carrier protein, and acyl-CoA binding protein. Normalization of cDNA by use of a duplex-specific nuclease method not only increased the overall discovery of genes from developing bitter melon seeds, but also resulted in the identification of 345 contigs with homology to 189 known lipid genes in Arabidopsis. These included candidate genes for eleostearic acid metabolism such as diacylglycerol acyltransferase 1 and 2, and a phospholipid:diacylglycerol acyltransferase 1-related enzyme. Transcripts were also identified for a novel FAD2 gene encoding a functional Δ12 oleic acid desaturase with potential implications for eleostearic acid biosynthesis. Conclusions 454 deep sequencing, particularly with normalized cDNA populations, was an effective method for mining of genes associated with eleostearic acid metabolism in developing bitter melon seeds. The transcriptomic data presented provide a resource for the study of novel fatty acid metabolism and for the biotechnological production of conjugated fatty acids and possibly other novel fatty acids in established oilseed crops.</p

    Self-Similar Random Process and Chaotic Behavior In Serrated Flow of High Entropy Alloys

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    The statistical and dynamic analyses of the serrated-flow behavior in the nanoindentation of a high-entropy alloy, Al0.5CoCrCuFeNi, at various holding times and temperatures, are performed to reveal the hidden order associated with the seemingly-irregular intermittent flow. Two distinct types of dynamics are identified in the high-entropy alloy, which are based on the chaotic time-series, approximate entropy, fractal dimension, and Hurst exponent. The dynamic plastic behavior at both room temperature and 200 °C exhibits a positive Lyapunov exponent, suggesting that the underlying dynamics is chaotic. The fractal dimension of the indentation depth increases with the increase of temperature, and there is an inflection at the holding time of 10 s at the same temperature. A large fractal dimension suggests the concurrent nucleation of a large number of slip bands. In particular, for the indentation with the holding time of 10 s at room temperature, the slip process evolves as a self-similar random process with a weak negative correlation similar to a random walk

    Promoting routine syphilis screening among men who have sex with men in China: study protocol for a randomised controlled trial of syphilis self-testing and lottery incentive.

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    BACKGROUND: Men who have sex with men (MSM) bear a high burden of syphilis infection. Expanding syphilis testing to improve timely diagnosis and treatment is critical to improve syphilis control. However, syphilis testing rates remain low among MSM, particularly in low- and middle-income countries. We describe the protocol for a randomised controlled trial (RCT) to assess whether provision of syphilis self-testing services can increase the uptake of syphilis testing among MSM in China. METHODS: Four hundred forty-four high-risk MSM will be recruited online and randomized in a 1:1:1 ratio to (1) standard syphilis self-testing arm; (2) a self-testing arm program enhanced with crowdsourcing and a lottery-based incentive, and (3) a standard of care (control). Self-testing services include a free syphilis self-test kit through the mail at monthly intervals. Participants in the lottery incentive arm will additionally receive health promotion materials generated from an open crowdsourcing contest and be given a lottery draw with a 10% chance to win 100 RMB (approximately 15 US Dollars) upon confirmed completion of syphilis testing. Syphilis self-test kits have step-by-step instructions and an instructional video. This is a non-blinded, open-label, parallel RCT. Participants in each arm will be followed-up at three and 6 months through WeChat (a social media app like Facebook messenger). Confirmation of syphilis self-test use will be determined by requiring participants to submit a photo of the used test kit to study staff via secure data messaging. Both self-testing and facility-based testing will be ascertained by sending a secure photographic image of the completed kit through an existing digital platform. The primary outcome is the proportion of participants who tested for syphilis in the past 3 months. DISCUSSION: Findings from this study will provide much needed insight on the impact of syphilis self-testing on promoting routine syphilis screening among MSM. The findings will also contribute to our understanding of the safety, effectiveness and acceptability of syphilis self-testing. These findings will have important implications for self-testing policy, both in China and internationally. TRIAL REGISTRATION: ChiCTR1900022409 (10 April, 2019)

    Stages of syphilis in South China – a multilevel analysis of early diagnosis

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    Abstract Background Early diagnosis of syphilis and timely treatment can effectively reduce ongoing syphilis transmission and morbidity. We examined the factors associated with the early diagnosis of syphilis to inform syphilis screening strategic planning. Methods In an observational study, we analyzed reported syphilis cases in Guangdong Province, China (from 2014 to mid-2015) accessed from the national case-based surveillance system. We categorized primary and secondary syphilis cases as early diagnosis and categorized latent and tertiary syphilis as delayed diagnosis. Univariate analyses and multivariable logistic regressions were performed to identify the factors associated with early diagnosis. We also examined the factors associated with early diagnosis at the individual and city levels in multilevel logistic regression models with cases nested by city (n = 21), adjusted for age at diagnosis and gender. Results Among 83,944 diagnosed syphilis cases, 22% were early diagnoses. The city-level early diagnosis rate ranged from 7 to 46%, consistent with substantial geographic variation as shown in the multilevel model. Early diagnosis was associated with cases presenting to specialist clinics for screening, being male and attaining higher education level. Cases received syphilis testing in institutions and hospitals, and diagnosed in hospitals were less likely to be in early diagnosis. At the city-level, cases living in a city equipped with more hospitals per capita were less likely to be early diagnosis. Conclusions To enhance early diagnosis of syphilis, city-specific syphilis screening strategies with a mix of passive and client/provider-initiated testing might be a useful approach

    Distribution of reported syphilis cases in South China: spatiotemporal analysis.

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    There was a varied spatial distribution of reported syphilis cases across cities in South China. This study aims to identify and describe spatiotemporal clusters of primary and secondary syphilis (P/S) cases in this region. Reported syphilis cases in Guangdong Province, China, from January 2014 to June 2015 were collected from the national centralized reporting system. Spatiotemporal clusters of P/S were identified and cross-validated by calculating local Moran's I, performing hotspot analysis (Getis-Ord Gi*), and constructing a discrete Poisson model in SaTScan. Reported cases within and outside the clusters were compared by bivariable and multivariable logistic regression. Out of 17,691 reported P/S cases, 11% were in the identified spatiotemporal clusters. The monthly P/S notification rate (per 100,000 persons) ranged between 0.6 and 1. The identified clusters were located in 14, out of 126, counties in eight, out of 21, cities. Cases of older age, living in rural area and taking self-initiated syphilis test were more likely to be in the clusters. Some areas bore a greater burden of P/S in Guangdong Province. Routine spatiotemporal analysis of P/S cases may be useful for enhancing syphilis control programs by strategic location-based service planning

    Two-phase exhumation along major shear zones in the SE Tibetan Plateau in the late Cenozoic

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    Three continent-scale shear zones are arguably the most outstanding structural features in the southeastern Tibetan Plateau, and therefore, their tectonic and landscape evolution have significant implications for understanding the history and mechanisms of intracontinental mountain building and plateau growth. This study presents low-temperature thermochronology from the Gaoligong and Chongshan shear zones (GLSZ and CSSZ) and quantitative analyses of fluvial longitudinal profiles of tributaries in the Salween drainage, which lies between the shear zones. Apatite and zircon (U-Th)/He data reveal a two-stage exhumation history for both shear zones: rapid and prominent cooling in the middle Miocene followed by a second, lower magnitude cooling event in the late Miocene to early Pliocene. Ductile transpressional shearing is inferred to have caused the first cooling, continuing until ~11\ua0Ma. The northward migration of the tectonic events along the Mogok metamorphic belt and GLSZ and synchronous dextral displacement along the Jiali fault indicate the dominant role of the north advancing eastern Himalayan syntaxis on the surrounding structures. Increased river incision is identified in the middle Salween drainage, leading to two-segment river profiles and further exhumation along the GLSZ and CSSZ. The tributary transient response could result from temporal changes in uplift or adjustments of the trunk channel to climatic change. Furthermore, glaciers play an important role in shaping the landscape of the upper reaches of catchments in the northern segment of the shear zones. Different drivers for the two exhumation events may reflect distinct stages of plateau growth characterized by different crustal deformation patterns

    Rapid increase of gonorrhoea cases in Guangdong Province, China, 2014-2017: a review of surveillance data.

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    OBJECTIVES: An increased trend in the number of reported gonorrhoea cases has been observed between 2014 and 2017 in China. This study aims to describe the reported epidemic of gonorrhoea and potential driving forces in Guangdong Province, China. DESIGN: A review of surveillance data. PARTICIPANTS: Three different sources of data from Guangdong Province were analysed: gonorrhoea cases reported to the Chinese sexually transmitted infections (STI) case report system (CRS); a clinic-based retrospective study conducted to collect information on annual gonorrhoea screening coverage and data from the Guangdong governmental sentinel surveillance network (SSN) to examine the gonorrhoea prevalence among males attending STI clinics. OUTCOME MEASURES: Reported incidence of gonorrhoea, number of reported gonorrhoea cases, number of screening tests for gonorrhoea and gonorrhoea prevalence. RESULTS: The STI CRS data showed that the reported incidence of gonorrhoea has increased rapidly from 15.7 cases per 100 000 population in 2014 to 27.3 cases per 100 000 in 2017 in Guangdong (p<0.001). Regions with a reported incidence of gonorrhoea cases of more than 10 cases per 100 000 expanded from 7 cities in 2014 to 13 cities in 2017. The SSN data showed that the gonorrhoea prevalence among males attending STI clinics increased from 2.7% in 2015 to 3.6% in 2017 (p=0.14). The retrospective study showed that the increased rate of screening for gonorrhoea between 2014 and 2017 was 35.0%, which was much lower than the increased rate of the number of reported gonorrhoea cases (123.3%). CONCLUSIONS: The number of gonococcal infections is rapidly rising in Guangdong, China. Expanded screening coverage, use of more sensitive diagnostics and increase of gonorrhoea prevalence are three potential contributors to the epidemic. Additional targeted intervention strategies are necessary in the future to control the epidemic
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