Advances in thermoelectric materials research He, Jian; Tritt, Terry M.
Science (American Association for the Advancement of Science),
09/2017, Volume:
357, Issue:
6358
Journal Article
Peer reviewed
High-performance thermoelectric materials lie at the heart of thermoelectrics, the simplest technology applicable to direct thermal-to-electrical energy conversion. In its recent 60-year history, the ...field of thermoelectric materials research has stalled several times, but each time it was rejuvenated by new paradigms. This article reviews several potentially paradigm-changing mechanisms enabled by defects, size effects, critical phenomena, anharmonicity, and the spin degree of freedom. These mechanisms decouple the otherwise adversely interdependent physical quantities toward higher material performance. We also briefly discuss a number of promising materials, advanced material synthesis and preparation techniques, and new opportunities. The renewable energy landscape will be reshaped if the current trend in thermoelectric materials research is sustained into the foreseeable future.
DNA methylation is an important epigenetic mark involved in diverse biological processes. In plants, DNA methylation can be established through the RNA-directed DNA methylation pathway, an RNA ...interference pathway for transcriptional gene silencing （TGS）, which requires 24-nt small interfering RNAs. In mammals, de novo DNA methylation occurs primarily at two developmental stages： during early embryogenesis and during gametogenesis. While it is not clear whether establishment of DNA methylation patterns in mammals involves RNA interference in general, de novo DNA methylation and suppression of transposons in germ cells require 24-32-nt piwi-interacting small RNAs. DNA methylation status is dynamically regulated by DNA methylation and demethylation reactions. In plants, active DNA demethylation relies on the repressor of silencing 1 family of bifunctional DNA glycosylases, which remove the 5-methylcytosine base and then cleave the DNA backbone at the abasic site, initiating a base excision repair （BER） pathway. In animals, multiple mechanisms of active DNA demethylation have been proposed, including a deaminase- and DNA glycosylase-initiated BER pathway. New information concerning the effects of various histone modifications on the establishment and maintenance of DNA methylation has broadened our understanding of the regulation of DNA methylation. The function of DNA methylation in plants and animals is also discussed in this review.
During the outbreak of coronavirus disease 2019 (COVID-19), consistent and considerable differences in disease severity and mortality rate of patients treated in Hubei province compared to those in ...other parts of China have been observed. We sought to compare the clinical characteristics and outcomes of patients being treated inside and outside Hubei province, and explore the factors underlying these differences.
Collaborating with the National Health Commission, we established a retrospective cohort to study hospitalised COVID-19 cases in China. Clinical characteristics, the rate of severe events and deaths, and the time to critical illness (invasive ventilation or intensive care unit admission or death) were compared between patients within and outside Hubei. The impact of Wuhan-related exposure (a presumed key factor that drove the severe situation in Hubei, as Wuhan is the epicentre as well the administrative centre of Hubei province) and the duration between symptom onset and admission on prognosis were also determined.
At the data cut-off (31 January 2020), 1590 cases from 575 hospitals in 31 provincial administrative regions were collected (core cohort). The overall rate of severe cases and mortality was 16.0% and 3.2%, respectively. Patients in Hubei (predominantly with Wuhan-related exposure, 597 (92.3%) out of 647) were older (mean age 49.7
44.9 years), had more cases with comorbidity (32.9%
19.7%), higher symptomatic burden, abnormal radiologic manifestations and, especially, a longer waiting time between symptom onset and admission (5.7
4.5 days) compared with patients outside Hubei. Patients in Hubei (severe event rate 23.0%
11.1%, death rate 7.3%
0.3%, HR (95% CI) for critical illness 1.59 (1.05-2.41)) have a poorer prognosis compared with patients outside Hubei after adjusting for age and comorbidity. However, among patients outside Hubei, the duration from symptom onset to hospitalisation (mean 4.4
4.7 days) and prognosis (HR (95%) 0.84 (0.40-1.80)) were similar between patients with or without Wuhan-related exposure. In the overall population, the waiting time, but neither treated in Hubei nor Wuhan-related exposure, remained an independent prognostic factor (HR (95%) 1.05 (1.01-1.08)).
There were more severe cases and poorer outcomes for COVID-19 patients treated in Hubei, which might be attributed to the prolonged duration of symptom onset to hospitalisation in the epicentre. Future studies to determine the reason for delaying hospitalisation are warranted.
To present the 12-month prevalence of DSM-IV major depressive disorder (MDD) and severe MDD; to examine sociodemographic correlates and comorbidity; and to describe impairment and service use.
Data ...are from the National Comorbidity Survey-Adolescent Supplement (NCS-A), a nationally representative survey of 10,123 adolescents aged 13 to 18 years that assesses DSM-IV disorders using the Composite International Diagnostic Interview (CIDI) Version 3.0. One parent or surrogate of each participating adolescent was also asked to complete a self-administered questionnaire.
Lifetime and 12-month prevalence of MDD were 11.0% and 7.5%, respectively. The corresponding rates of severe MDD were 3.0% and 2.3%. The prevalence of MDD increased significantly across adolescence, with markedly greater increases among females than among males. Most cases of MDD were associated with psychiatric comorbidity and severe role impairment, and a substantial minority reported suicidality. The prevalence of severe MDD was about one-fourth of that of all MDD cases; estimates of impairment and clinical correlates were of 2- to 5-fold greater magnitude for severe versus mild/moderate depression, with markedly higher rates for suicidal thoughts and behaviors. Treatment in any form was received by the majority of adolescents with 12-month DSM-IV MDD (60.4%), but only a minority received treatment that was disorder-specific or from the mental health sector.
Findings underscore the important public health significance of depression among US adolescents and the urgent need to improve screening and treatment access in this population.
Hypertension has been recognized as one of the highest risk factors for cardiovascular diseases. Anti-hypertension agent screening and development has been recognized as a pharmaceutical therapy ...approach for the cardiovascular diseases treatment. Many kinds of traditional Chinese medicines, such as pine needle, have been used for the treatment of hypertension for a long time, but the bioactive ingredients which responsible for their therapeutic effectiveness are remain unclear. Therefore, screening bioactive chemicals in natural sources is still the most straightforward strategy for novel Angiotensin-converting enzyme inhibitor (ACEi)-based anti-hypertension agents discovery. In this study, we demonstrated a bioactivity-guided fractionation strategy for identifying bioactive fractions and chemicals from pine needle based on LC/MS assay as well as elucidating their mechanisms of pharmacological activity. And we found out the compound in pine needle extracts being ACE-inhibitory active is catechin. When ACE activity was assayed in rat tissue membranes, it was observed that catechin demonstrate ACE inhibition in kidney, lung and testes tissue. All these presents catechin in pine needle could be a potential cardiovascular medicine.
Chest CT is thought to be sensitive but less specific in diagnosing the 2019 coronavirus disease (COVID-19). The diagnostic value of CT is unclear. We aimed to compare the performance of CT and ...initial RT-PCR for clinically suspected COVID-19 patients outside the epicentre—Wuhan, China.
Patients clinically suspected of COVID-19 infection who underwent initial RT-PCR and chest CT at the same time were retrospectively enrolled. Two radiologists with specific training reviewed the CT images independently and final diagnoses of the presence or absence of COVID-19 was reached by consensus. With serial RT-PCR as reference standard, the performance of initial RT-PCR and chest CT was analysed. A strategy of combining initial RT-PCR and chest CT was analysed to study the additional benefit.
82 patients admitted to hospital between Jan 10, 2020 to Feb 28, 2020 were enrolled. 34 COVID-19 and 48 non-COVID-19 patients were identified by serial RT-PCR. The sensitivity, specificity was 79% (27/34) and 100% (48/48) for initial RT-PCR and 77% (26/34) and 96% (46/48) for chest CT. The image readers had a good interobserver agreement with Cohen's kappa of 0.69. No statistical difference was found in the diagnostic performance between initial RT-PCR and chest CT. The comprehensive strategy had a higher sensitivity of 94% (32/34).
Initial RT-PCR and chest CT had comparable diagnostic performance in identification of suspected COVID-19 patients outside the epidemic center. To compensate potential risk of false-negative PCR, chest CT should be applied for clinically suspected patients with negative initial RT-PCR.
•Well trained radiologist has good specificity for COVID-19 in clinical setting.•Sensitivity of CT for suspected COVID-19 is lower than those in the epidemic center.•Chest CT may compensate false-negative initial RT-PCR.•Chest CT should be applied with RT-PCR for clinically suspected COVID-19, especially when initial RT-PCR is negative.
Chiral secondary alcohols play an important role in pharmaceutical, agrochemical, and chemical industries. In recent years, impressive steps forward have been achieved towards biocatalytic ketone ...reduction as a green and useful access to enantiopure alcohols. An increasing number of novel and robust enzymes are now accessible as a result of the ongoing progress in genomics, screening and evolution technologies, while process engineering provides further success in areas of biocatalytic reduction in meeting synthetic challenges. The versatile platform of these techniques and strategies offers the possibility to apply high substrate loading and thus to overcome the limitation of low volumetric productivity of usual enzymatic processes which is the bottleneck for their practical application. In addition, the integration of bioreduction with other enzymatic or chemical steps allows the efficient synthesis of more complex chiral products.
Biocatalytic cascade reactions using isolated stereoselective enzymes or whole cells in one‐pot processes lead to value‐added chiral products in a single workup. The concept has been restricted ...mainly to starting materials and intermediate products that are accepted by the respective wild‐type enzymes. In the present study, we exploited directed evolution as a means to create E. coli whole cells for regio‐ and stereoselective cascade sequences that are not possible using man‐made catalysts. The approach is illustrated using P450‐BM3 in combination with appropriate alcohol dehydrogenases as catalysts in either two‐, three‐, or four‐step cascade reactions starting from cyclohexane, cyclohexanol, or cyclohexanone, respectively, leading to either (R,R)‐, (S,S)‐, or meso‐cyclohexane‐1,2‐diol. The one‐pot conversion of cyclohexane into (R)‐ or (S)‐2‐hydroxycyclohexanone in the absence of ADH is also described.
Four steps in one pot: E. coli cells harboring P450‐BM3 mutants and appropriate alcohol dehydrogenases were obtained by directed evolution. Such cells enable one‐pot cascade reactions of cyclohexane with selective formation of all three stereoisomeric cyclohexane‐1,2‐diols.
Critical patients with the coronavirus disease 2019 (COVID-19), even those whose nucleic acid test results had turned negative and those receiving maximal medical support, have been noted to progress ...to irreversible fatal respiratory failure. Lung transplantation (LT) as the sole therapy for end-stage pulmonary fibrosis related to acute respiratory distress syndrome has been considered as the ultimate rescue therapy for these patients.
From February 10 to March 10, 2020, three male patients were urgently assessed and listed for transplantation. After conducting a full ethical review and after obtaining assent from the family of the patients, we performed three LT procedures for COVID-19 patients with illness durations of more than one month and extremely high sequential organ failure assessment scores.
Two of the three recipients survived post-LT and started participating in a rehabilitation program. Pearls of the LT team collaboration and perioperative logistics were summarized and continually improved. The pathological results of the explanted lungs were concordant with the critical clinical manifestation, and provided insight towards better understanding of the disease. Government health affair systems, virology detection tools, and modern communication technology all play key roles towards the survival of the patients and their rehabilitation.
LT can be performed in end-stage patients with respiratory failure due to COVID-19-related pulmonary fibrosis. If confirmed positive-turned-negative virology status without organ dysfunction that could contraindicate LT, LT provided the final option for these patients to avoid certain death, with proper protection of transplant surgeons and medical staffs. By ensuring instant seamless care for both patients and medical teams, the goal of reducing the mortality rate and salvaging the lives of patients with COVID-19 can be attained.
This paper presents an experimental study on the compressive behavior of ultra-high performance concrete (UHPC) confined with fiber-reinforced polymer (FRP) composites. A total of 18 cylindrical ...specimens were prepared from UHPC containing 2.5% of micro steel fibers by volume, among which 6 were unconfined and 12 were confined with carbon FRP (CFRP). They were tested to investigate the experimental compressive behavior of unconfined or CFRP-confined UHPC. The external confinement was provided by two to six plies of CFRP wraps with the confinement ratio ranging from 0.11 to 0.54. The test results obtained from this study were presented and compared with those from existing studies on unconfined and FRP-confined UHPC specimens in the form of concrete-filled FRP tubes or FRP-wrapped cylinders. Predictive equations were proposed for the compressive strength and ultimate strain of FRP-confined UHPC, based on the interpretation of test results from the present study and from the existing literature. An existing stress–strain model for FRP-confined conventional concrete has been recalibrated for FRP-confined UHPC. While the recalibrated model predicted the test results of FRP-confined UHPC reasonably well, the inadequacy of a parabolic curve for describing the stress–strain relationship of unconfined UHPC is noticed, as a result of the higher strength and more brittle behaviour of UHPC in compression.
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