Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 59
Filtrar
1.
Parasit Vectors ; 15(1): 130, 2022 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-35413937

RESUMO

BACKGROUND: The fast-declining clinical efficacy of dihydroartemisinin-piperaquine (DHA-PPQ) in Cambodia is a warning of the underlying westward dissemination of piperaquine resistance in the Greater Mekong Subregion (GMS). Mutations in the Plasmodium falciparum Kelch 13-propeller (PfK13) and the P. falciparum chloroquine resistance transporter (PfCRT), as well as plasmepsin 2/3 gene amplification, have been discovered as molecular markers for predicting DHA-PPQ treatment failure. Determining whether these genetic variations of P. falciparum are linked to DHA-PPQ resistance is critical, especially along the China-Myanmar (CM) border, where PPQ has been utilized for decades. METHODS: A total of 173 P. falciparum samples of dried blood spots (DBS) were collected along the CM border between 2007 and 2010, the Thailand-Cambodia (TC) border between 2009 and 2013, and the Thailand-Myanmar (TM) border between 2012 and 2014. PCR and sequencing were used to identified PfCRT mutations, while qPCR was used to determine the copy number of plasmepsin 2/3. The prevalence of DHA-PPQ resistance in three locations was investigated using data paired with K13 mutations. RESULTS: Three fragments of the pfcrt gene were amplified for all 173 samples, and seven SNPs were identified (M74I, N75E/D, K76T, H97L, I218F, A220S, I356L). No new PfCRT mutations conferring resistance to PPQ (T93S, H97Y, F145I, M343L, and G353V) were discovered, except for one mutant I218F identified in the TM border (2.27%, 1/44). Additionally, mutant H97L was found in the TC, TM, and CM borders at 3.57% (1/28), 6.82% (3/44), and 1% (1/101), respectively. A substantial K13 C580Y variant prevalence was found in the TC and TM border, accounting for 64.29% (18/28) and 43.18% (19/44), respectively, while only 1% (1/101) was found in the CM border. The K13 F446I variant was only identified and found to reach a high level (28.71%, 29/101) in the CM border. Furthermore, 10.71% (3/28) of TC isolates and 2.27% (1/44) of TM isolates carried more than one copy of plasmepsin 2/3 and K13 C580Y variant, while no plasmepsin 2/3 amplification was identified in the CM isolates. CONCLUSIONS: Compared with the P. falciparum samples collected from the TC and TM borders, fewer parasites carried plasmepsin 2/3 amplification and novel PfCRT variants, while more parasites carried predominant K13 mutations at position F446I, in the CM border. Clear evidence of DHA-PPQ resistance associated with candidate markers was not found in this border region suggesting a further evaluation of these markers and continuous surveillance is warranted.


Assuntos
Antimaláricos , Artemisininas , Malária Falciparum , Antimaláricos/farmacologia , Antimaláricos/uso terapêutico , Artemisininas/farmacologia , Artemisininas/uso terapêutico , Biomarcadores , Camboja , Cloroquina/farmacologia , Resistência a Medicamentos/genética , Humanos , Malária Falciparum/parasitologia , Proteínas de Membrana Transportadoras/genética , Mianmar , Piperazinas , Plasmodium falciparum , Proteínas de Protozoários/genética , Proteínas de Protozoários/metabolismo , Quinolinas , Tailândia
2.
Curr Biol ; 32(7): R307-R308, 2022 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-35413253

RESUMO

Respiratory syncytial virus (RSV) is an enveloped non-segmented negative sense RNA virus that belongs to Orthopneumovirus genus of the Pneumoviridae family in the order Mononegavirales. The virus is the leading cause of severe respiratory disease in children under two years of age and is responsible for substantial disease burden in infants and elder people in both developed and developing countries1,2. RSV is only known to circulate among humans, though it was first isolated from chimpanzees3. The virus can experimentally infect mice, rats, cotton rats, ferrets, and hamsters, but does not naturally circulate in these animal populations4. We found that Malayan pangolins (Manis javanica) were naturally infected with RSVs that have 99.4-99.8% genomic identity with strains circulating in humans. Phylogenetic analyses revealed that five RSVs in pangolins were RSV-A ON1 and seven were RSV-B BA genotypes, both of which are currently prevalent in humans worldwide. These findings suggest that humans might transmit their viruses to endangered wildlife.


Assuntos
Infecções por Vírus Respiratório Sincicial , Vírus Sincicial Respiratório Humano , Idoso , Animais , Furões , Genótipo , Humanos , Lactente , Camundongos , Pangolins , Filogenia , Infecções por Vírus Respiratório Sincicial/veterinária , Vírus Sincicial Respiratório Humano/genética
3.
BMC Infect Dis ; 22(1): 332, 2022 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-35379167

RESUMO

BACKGROUND: The current surveillance system only focuses on notifiable infectious diseases in China. The arrival of the big-data era provides us a chance to elaborate on the full spectrum of infectious diseases. METHODS: In this population-based observational study, we used multiple health-related data extracted from the Shandong Multi-Center Healthcare Big Data Platform from January 2013 to June 2017 to estimate the incidence density and describe the epidemiological characteristics and dynamics of various infectious diseases in a population of 3,987,573 individuals in Shandong province, China. RESULTS: In total, 106,289 cases of 130 infectious diseases were diagnosed among the population, with an incidence density (ID) of 694.86 per 100,000 person-years. Besides 73,801 cases of 35 notifiable infectious diseases, 32,488 cases of 95 non-notifiable infectious diseases were identified. The overall ID continuously increased from 364.81 per 100,000 person-years in 2013 to 1071.80 per 100,000 person-years in 2017 (χ2 test for trend, P < 0.0001). Urban areas had a significantly higher ID than rural areas, with a relative risk of 1.25 (95% CI 1.23-1.27). Adolescents aged 10-19 years had the highest ID of varicella, women aged 20-39 years had significantly higher IDs of syphilis and trichomoniasis, and people aged ≥ 60 years had significantly higher IDs of zoster and viral conjunctivitis (all P < 0.05). CONCLUSIONS: Infectious diseases remain a substantial public health problem, and non-notifiable diseases should not be neglected. Multi-source-based big data are beneficial to better understand the profile and dynamics of infectious diseases.


Assuntos
Doenças Transmissíveis , Sífilis , Adolescente , Adulto , Big Data , Criança , China/epidemiologia , Doenças Transmissíveis/epidemiologia , Feminino , Humanos , Incidência , Pessoa de Meia-Idade , Adulto Jovem
5.
SLAS Technol ; 27(1): 76-84, 2022 02.
Artigo em Inglês | MEDLINE | ID: mdl-35058205

RESUMO

The advent of deep-learning has set new standards in an array of image translation applications. At present, the use of these methods often requires computer programming experience. Non-commercial programs with graphical interface usually do not allow users to fully customize their deep-learning pipeline. Therefore, our primary objective is to provide a simple graphical interface that allows researchers with no programming experience to easily create, train, and evaluate custom deep-learning models for image translation. We also aimed to test the applicability of our tool in CT image semantic segmentation and noise reduction. DeepImageTranslator was implemented using the Tkinter library, the standard Python interface to the Tk graphical user interface toolkit; backend computations were implemented using data augmentation packages such as Pillow, Numpy, OpenCV, Augmentor, Tensorflow, and Keras libraries. Convolutional neural networks (CNNs) were trained using DeepImageTranslator. The effects of data augmentation, deep-supervision, and sample size on model accuracy were also systematically assessed. The DeepImageTranslator a simple tool that allows users to customize all aspects of their deep-learning pipeline, including the CNN, training optimizer, loss function, and the types of training image augmentation scheme. We showed that DeepImageTranslator can be used to achieve state-of-the-art accuracy and generalizability in semantic segmentation and noise reduction. Highly accurate 3D segmentation models for body composition can be obtained using training sample sizes as small as 17 images. In conclusion, an open-source deep-learning tool for accurate image translation with a user-friendly graphical interface was presented and evaluated. This standalone software can be downloaded at: https://sourceforge.net/projects/deepimagetranslator/.


Assuntos
Aprendizado Profundo , Processamento de Imagem Assistida por Computador/métodos , Redes Neurais de Computação , Software , Tomografia Computadorizada por Raios X
6.
Endocr Rev ; 43(1): 35-60, 2022 01 12.
Artigo em Inglês | MEDLINE | ID: mdl-34100954

RESUMO

The obesity pandemic increasingly causes morbidity and mortality from type 2 diabetes, cardiovascular diseases and many other chronic diseases. Fat cell size (FCS) predicts numerous obesity-related complications such as lipid dysmetabolism, ectopic fat accumulation, insulin resistance, and cardiovascular disorders. Nevertheless, the scarcity of systematic literature reviews on this subject is compounded by the use of different methods by which FCS measurements are determined and reported. In this paper, we provide a systematic review of the current literature on the relationship between adipocyte hypertrophy and obesity-related glucose and lipid dysmetabolism, ectopic fat accumulation, and cardiovascular disorders. We also review the numerous mechanistic origins of adipocyte hypertrophy and its relationship with metabolic dysregulation, including changes in adipogenesis, cell senescence, collagen deposition, systemic inflammation, adipokine secretion, and energy balance. To quantify the effect of different FCS measurement methods, we performed statistical analyses across published data while controlling for body mass index, age, and sex.


Assuntos
Doenças Cardiovasculares , Diabetes Mellitus Tipo 2 , Resistência à Insulina , Adipócitos , Doenças Cardiovasculares/etiologia , Tamanho Celular , Diabetes Mellitus Tipo 2/complicações , Humanos , Hipertrofia/complicações , Lipídeos , Obesidade/complicações
7.
Small Methods ; 5(5): e2001250, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-34928103

RESUMO

It is desirable for a sustainable society that the production and utilization of renewable materials are net-zero in terms of carbon emissions. Carbon materials with emerging applications in CO2 utilization, renewable energy storage and conversion, and biomedicine have attracted much attention both academically and industrially. However, the preparation process of some new carbon materials suffers from energy consumption and environmental pollution issues. Therefore, the development of low-cost, scalable, industrially and economically attractive, sustainable carbon material preparation methods are required. In this regard, the use of biomass and its derivatives as a precursor of carbon materials is a major feature of sustainability. Recent advances in the synthetic strategy of sustainable carbon materials and their emerging applications are summarized in this short review. Emphasis is made on the discussion of the original intentions and various sustainable strategies for producing sustainable carbon materials. This review provides basic insights and significant guidelines for the further design of sustainable carbon materials and their emerging applications in catalysis and the biomedical field.

8.
Angew Chem Int Ed Engl ; 60(29): 16085-16092, 2021 Jul 12.
Artigo em Inglês | MEDLINE | ID: mdl-33963658

RESUMO

To avoid the energy-consuming step of direct N≡N bond cleavage, photocatalytic N2 fixation undergoing the associative pathways has been developed for mild-condition operation. However, it is a fundamental yet challenging task to gain comprehensive understanding on how the associative pathways (i.e., alternating vs. distal) are influenced and altered by the fine structure of catalysts, which eventually holds the key to significantly promote the practical implementation. Herein, we introduce Fe dopants into TiO2 nanofibers to stabilize oxygen vacancies and simultaneously tune their local electronic structure. The combination of in situ characterizations with first-principles simulations reveals that the modulation of local electronic structure by Fe dopants turns the hydrogenation of N2 from associative alternating pathway to associative distal pathway. This work provides fresh hints for rationally controlling the reaction pathways toward efficient photocatalytic nitrogen fixation.

9.
Am J Physiol Endocrinol Metab ; 320(6): E1093-E1106, 2021 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-33870714

RESUMO

The mechanism of increased postprandial nonesterified fatty acid (NEFA) appearance in the circulation in impaired glucose tolerance (IGT) is due to increased adipose tissue lipolysis but could also be contributed to by reduced adipose tissue (AT) dietary fatty acid (DFA) trapping and increased "spillover" into the circulation. Thirty-one subjects with IGT (14 women, 17 men) and 29 with normal glucose tolerance (NGT, 15 women, 14 men) underwent a meal test with oral and intravenous palmitate tracers and the oral [18F]-fluoro-thia-heptadecanoic acid positron emission tomography method. Postprandial palmitate appearance (Rapalmitate) was higher in IGT versus NGT (P < 0.001), driven exclusively by Rapalmitate from obesity-associated increase in intracellular lipolysis (P = 0.01), as Rapalmitate from DFA spillover was not different between the groups (P = 0.19) and visceral AT DFA trapping was even higher in IGT versus NGT (P = 0.02). Plasma glycerol appearance was lower in IGT (P = 0.01), driven down by insulin resistance and increased insulin secretion. Thus, we found higher AT DFA trapping, limiting spillover to lean organs and in part offsetting the increase in Rapalmitate from intracellular lipolysis. Whether similar findings occur in frank diabetes, a condition also characterized by insulin resistance but relative insulin deficiency, requires further investigation (Clinicaltrials.gov: NCT04088344, NCT02808182).NEW & NOTEWORTHY We found higher adipose tissue dietary fatty acid trapping, limiting spillover to lean organs, that in part offsets the increase in appearance rate of palmitate from intracellular lipolysis in prediabetes. These results point to the adaptive nature of adipose tissue trapping and dietary fatty acid spillover as a protective mechanism against excess obesity-related palmitate appearance rate from intracellular adipose tissue lipolysis.


Assuntos
Tecido Adiposo/metabolismo , Gorduras na Dieta/farmacocinética , Ácidos Graxos não Esterificados/metabolismo , Período Pós-Prandial/fisiologia , Estado Pré-Diabético/metabolismo , Adulto , Idoso , Ácidos Graxos/farmacocinética , Feminino , Intolerância à Glucose/metabolismo , Humanos , Resistência à Insulina/fisiologia , Lipólise/fisiologia , Masculino , Pessoa de Meia-Idade
10.
Artigo em Inglês | MEDLINE | ID: mdl-33673163

RESUMO

Western countries are experiencing surges in COVID-19 cases and deaths due to increasing public transportation during holiday seasons. This study aimed to explore whether mainland China will face an epidemic rebound during the Spring Festival holiday, when millions of Chinese people travel across the country, and investigate which nucleic acid testing (NAT) strategy is optimal to contain the epidemic. A microsimulation model was used to simulate SARS-CoV-2 transmission among railway travelers and evaluated the effects of various NAT strategies. An extended susceptible-exposed-infectious-recovered (SEIR) model was built to forecast local transmission during the Spring Festival period under different scenarios of testing strategies. The total number of infections, testing burden, and medical expenditure were calculated to devise an optimal strategy during the Spring Festival travel rush. Assuming the daily incidence of 20 per 10 million persons, our model simulated that there would be 97 active infections on the day of travel among 10 million railway passengers without NAT and symptom screening. Pre-travel testing could reduce the number of active infections. Compared with no NAT, testing passengers from risk tier 2-4 regions 3 days before travelling could significantly reduce the risk of transmission, and it is more economical and efficient than testing for all passengers.


Assuntos
Teste de Ácido Nucleico para COVID-19 , COVID-19/diagnóstico , Férias e Feriados , Viagem , COVID-19/transmissão , China/epidemiologia , Simulação por Computador , Humanos , Estações do Ano
11.
J Med Entomol ; 58(3): 1363-1369, 2021 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-33399212

RESUMO

Spotted fever group rickettsiae, mainly maintained and transmitted by ticks, are important etiological agents of (re)emerging zoonotic diseases worldwide. It is of great significance to investigate spotted fever group rickettsiae in ticks in different areas for the prevention and control of rickettsioses. In this study, a total of 305 ticks were collected from wild and domestic animals in Chongqing, Guizhou, Yunnan, and Guangxi provinces of southwestern China during 2017-2019 and examined for the presence of spotted fever group rickettsiae by PCR with primers targeting the partial gltA, ompA, rrs, and htrA genes. Results showed that two spotted fever group rickettsiae species, including the pathogenic Candidatus Rickettsia jingxinensis (Rickettsiales: Rickettsiaceae) and a potential novel species Rickettsia sp. sw (Rickettsiales: Rickettsiaceae), were identified. The Ca. R. jingxinensis sequences were recovered from Rhipicephalus microplus (Ixodida: Ixodidae) and Haemaphysalis longicornis (Ixodida: Ixodidae) ticks and phylogenetically clustered with previous Ca. R. jingxinensis, Ca. R. longicornii (Rickettsiales: Rickettsiaceae), and Rickettsia sp. XY118 (Rickettsiales: Rickettsiaceae) strains. Rickettsia sp. sw was detected in Amblyomma geoemydae (Ixodida: Ixodidae) and Rh. microplus. Interestingly, as far as we know, this was the first report of Rickettsia (Rickettsiales: Rickettsiaceae) in A. geoemydae. Phylogenetic analyses indicated that this potential novel species was closely related to R. aeschlimannii (Rickettsiales: Rickettsiaceae) with gltA and ompA genes and grouped in a cluster composed of R. montanensis (Rickettsiales: Rickettsiaceae), R. raoultii (Rickettsiales: Rickettsiaceae), R. aeschlimannii, R. massiliae (Rickettsiales: Rickettsiaceae), and R. rhipicephali (Rickettsiales: Rickettsiaceae) with htrA, while formed a separate clade with rrs. The pathogenicity of Rickettsia sp. sw should be further confirmed. These results expand the knowledge of the geographical distribution and vector distribution of spotted fever group rickettsiae in China and are useful for assessing the potential public health risk.


Assuntos
Ixodidae/microbiologia , Rickettsia/isolamento & purificação , Animais , Animais Domésticos/parasitologia , Animais Selvagens/parasitologia , China , Feminino , Masculino , Ninfa/crescimento & desenvolvimento , Ninfa/microbiologia , Rhipicephalus/microbiologia , Rickettsiose do Grupo da Febre Maculosa/transmissão
12.
Chem Asian J ; 16(6): 678-689, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33453068

RESUMO

CO2 is the main component of greenhouse gases and also an important carbon source. The hydrogenation of CO2 to methane using Ni-based catalysts can not only alleviate CO2 emissions but also obtain useful fuels. However, Ni-based catalysts face one major problem of the sintering of Ni nanoparticles in the process of CO2 methanation. Thus, this work has synthesized a series of efficient and robust nickel silicate catalysts (NiPS-X) with different nickel content derived from nickel phyllosilicate by the hydrothermal method. It was found that the Ni loading plays a critical role in the structure and catalytic performance of the NiPS-X catalysts. The catalytic performance gradually increases with the increase of Ni loading. In particular, the highly dispersed NiPS-1.6 catalyst with a high Ni loading of 34.3 wt% could obtain the CO2 conversion greater than 80%, and the methane selectivity was close to 100% for 48 h at 330 °C and the GHSV of 40,000 mL g-1 h-1 . The excellent catalytic property can be assigned to the high dispersion of Ni nanoparticles and the strong interaction between the active component and the carrier, which is derived from a unique layered silicate structure with lots of nickel phyllosilicate and a large number of Lewis acid sites.

13.
Small ; 17(9): e1906250, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-32406190

RESUMO

Heterogeneous hydrogenation reactions are of great importance for chemical upgrading and synthesis, but still face the challenges of controlling selectivity and long-term stability. To improve the catalytic performance, many hydrogenation reactions utilize special yolk/core-shell nanoreactors (YCSNs) with unique architectures and advantageous properties. This work presents the developmental and technological challenges in the preparation of YCSNs that are potentially useful for hydrogenation reactions, and provides a summary of the properties of these materials. The work also addresses the scientific challenges in applications of these YCSNs in various gas and liquid-phase hydrogenation reactions. The catalyst structures, catalytic performance, structure-performance relationships, reaction mechanisms, and unsolved problems are discussed too. Also, a brief outlook and opportunities for future research in this field are presented. This work on the advancements in YCSNs might inspire the creation of new materials with desired structures for achieving maximal hydrogenation performances.


Assuntos
Nanotecnologia , Catálise , Hidrogenação
14.
Vector Borne Zoonotic Dis ; 21(3): 162-171, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33347789

RESUMO

Background: Tick-borne bacteria and protozoa can cause a variety of human and animal diseases in China. It is of great importance to monitor the prevalence and dynamic variation of these pathogens in ticks in ever-changing natural and social environment. Materials and Methods: Ticks were collected from Heilongjiang and Jilin provinces of northeastern China during 2018-2019 followed by morphological identification. The presence of Rickettsia spp., Anaplasma spp., Ehrlichia spp., Borrelia spp., Babesia spp., and Theileria spp. was examined by PCR and Sanger sequencing. The obtained sequences were subjected to phylogenetic analysis through Mega 7.0. Statistical analysis was performed using SPSS 24.0. Results: A total of 250 ticks from 5 species of 3 genera were collected. Ixodes and Haemaphysalis ticks carried more species of pathogens than Dermacentor, and the pathogens detected in Haemaphysalis japonica varied significantly among different sampling sites. The infection rates of Rickettsia spp., Anaplasma spp., Ehrlichia spp., Borrelia spp., Babesia spp., and Theileria spp. were 41.2%, 0, 2.0%, 7.2%, 1.2%, and 7.2%, respectively. Twelve pathogens were identified, among which Rickettsia raoultii (29.6%), Candidatus Rickettsia tarasevichiae (9.2%), and Theileria equi (4.4%) were the three most common ones. Rickettsia had its dominant vector, that is, R. raoultii had high infection rates in Dermacentor nuttalli and Dermacentor silvarum, Ca. R. tarasevichiae in Ixodes persulcatus, and Rickettsia heilongjiangensis in H. japonica. Interestingly, unclassified species were observed, including a Rickettsia sp., an Ehrlichia sp., a Borrelia sp., and a Babesia sp. Coinfections with different pathogens were identified in 9.2% of all tested ticks, with I. persulcatus most likely to be coinfected (23.8%) and Rickettsia spp. and Borrelia spp. as the most common combination (16.7%). Conclusions: The results of this study reflect high diversity and complexity of pathogens in ticks, which are useful for designing more targeted and effective control measures for tick-borne diseases in China.


Assuntos
Ixodes , Rickettsia , Doenças Transmitidas por Carrapatos , Animais , China/epidemiologia , Filogenia , Prevalência , Rickettsia/genética , Doenças Transmitidas por Carrapatos/epidemiologia , Doenças Transmitidas por Carrapatos/veterinária
16.
J Glob Health ; 10(2): 020513, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33312506

RESUMO

BACKGROUND: The COVID-19 pandemic is challenging the public health response system worldwide, especially in poverty-stricken, war-torn, and least developed countries (LDCs). METHODS: We characterized the epidemiological features and spread dynamics of COVID-19 in Niger, quantified the effective reproduction number (Rt ), evaluated the impact of public health control measures, and estimated the disease burden. RESULTS: As of 4 July 2020, COVID-19 has affected 29 communes of Niger with 1093 confirmed cases, among whom 741 (67.8%) were males. Of them 89 cases died, resulting in a case fatality rate (CFR) of 8.1%. Both attack rates and CFRs were increased with age (P < 0.0001). Health care workers accounted for 12.8% cases. Among the reported cases, 39.3% were isolated and treated at home, and 42.3% were asymptomatic. 74.6% cases were clustered in Niamey, the capital of Niger. The Rt fluctuated in correlation to control measures at different outbreak stages. After the authorities initiated the national response and implemented the strictest control measures, Rt quickly dropped to below the epidemic threshold (<1), and maintained low level afterward. The national disability-adjusted life years attributable to COVID-19 was 1267.38 years in total, of which years of life lost accounted for over 99.1%. CONCLUSIONS: Classic public health control measures such as prohibition of public gatherings, travelling ban, contact tracing, and isolation and quarantine at home, are proved to be effective to contain the outbreak in Niger, and provide guidance for controlling the ongoing COVID-19 pandemic in LDCs.


Assuntos
COVID-19/epidemiologia , COVID-19/prevenção & controle , Controle de Doenças Transmissíveis/organização & administração , Adulto , Países em Desenvolvimento , Feminino , Pessoal de Saúde , Humanos , Masculino , Pessoa de Meia-Idade , Níger/epidemiologia , Pandemias , SARS-CoV-2 , Fatores Socioeconômicos
17.
Artigo em Inglês | MEDLINE | ID: mdl-33169978

RESUMO

Exploration of a new nonlinear optical (NLO)-active functional motif is important in the rational design of promising infrared (IR) NLO materials. Compared with typical tetrahedral MQ4 (M = IIB, III, IV metals; Q = S, Se) motifs, MQ3 (M = As, Sb) pyramids favor high second-harmonic generation (SHG) efficiency while frequently hindering phase matching (PM) because of excessively large optical anisotropy. The surfactant-thermal method was first adopted to achieve PM in MQ3-containing systems and synthesize mixed covalent-ionic IR NLO materials. Two new thioarsenates of AMnAs3S6 (A = Cs, Rb) exhibiting strong PM SHG efficiencies comparable to commercial AGS and laser-induced damage thresholds of one order higher than AGS were obtained. The [As3S6]3- unit in their structures is an unprecedented NLO-active functional motif, which can be useful in designing new IR NLO compounds with large SHG efficiency. In addition, the surfactant-thermal method provides a new general strategy for synthesizing new IR NLO materials.

18.
Dalton Trans ; 49(46): 16954-16961, 2020 Dec 08.
Artigo em Inglês | MEDLINE | ID: mdl-33188664

RESUMO

Three novel polyoxometalate (POM) clusters of K10Na10[Dy3(H2O)6Ni(H2O)(W3O11)(B-α-SbW9O33)3]·(H2O)45 (1), (NH4)5K4Na8[Dy3(H2O)6SbV(H2O)(W3O11)(B-α-SbW9O33)3]·(H2O)50 (2), and (NH4)9Na[Ni2(H2O)6(WO2)2(B-ß-SbW9O33)2]·(H2O)24 (3) were successfully obtained using the same precursor under different ionic strength conditions. Structural analysis showed that compounds 1-3 possess discrepant structural characteristics in 1 M KCl, 1 M NH4Cl, and saturated NH4Cl, respectively. Among them, 2 is the first reported lanthanide cluster including both Sb3+ and Sb5+ in POM derivatives. Furthermore, the analysis of ac magnetic data proved that 1 and 2 embodied dramatic field-induced slow magnetic relaxation, and the effective barrier of 2 was estimated as Ueff/KB = 21.10 K based on the Orbach process. It was found that the structure and magnetic properties of POM materials can be regulated using an effective and satisfactory ionic strength-controlled strategy.

19.
BMJ Open ; 10(10): e043411, 2020 10 15.
Artigo em Inglês | MEDLINE | ID: mdl-33060093

RESUMO

OBJECTIVE: To compare the epidemiological characteristics and transmission dynamics in relation to interventions against the COVID-19 and severe acute respiratory syndrome (SARS) outbreak in mainland China. DESIGN: Comparative study based on a unique data set of COVID-19 and SARS. SETTING: Outbreak in mainland China. PARTICIPANTS: The final database included 82 858 confirmed cases of COVID-19 and 5327 cases of SARS. METHODS: We brought together all existing data sources and integrated them into a comprehensive data set. Individual information on age, sex, occupation, residence location, date of illness onset, date of diagnosis and clinical outcome was extracted. Control measures deployed in mainland China were collected. We compared the epidemiological and spatial characteristics of COVID-19 and SARS. We estimated the effective reproduction number to explore differences in transmission dynamics and intervention effects. RESULTS: Compared with SARS, COVID-19 affected more extensive areas (1668 vs 230 counties) within a shorter time (101 vs 193 days) and had higher attack rate (61.8 vs 4.0 per million persons). The COVID-19 outbreak had only one epidemic peak and one epicentre (Hubei Province), while the SARS outbreak resulted in two peaks and two epicentres (Guangdong Province and Beijing). SARS-CoV-2 was more likely to infect older people (median age of 52 years), while SARS-CoV tended to infect young adults (median age of 34 years). The case fatality rate (CFR) of either disease increased with age, but the CFR of COVID-19 was significantly lower than that of SARS (5.6% vs 6.4%). The trajectory of effective reproduction number dynamically changed in relation to interventions, which fell below 1 within 2 months for COVID-19 and within 5.5 months for SARS. CONCLUSIONS: China has taken more prompt and effective responses to combat COVID-19 by learning lessons from SARS, providing us with some epidemiological clues to control the ongoing COVID-19 pandemic worldwide.


Assuntos
Betacoronavirus , Infecções por Coronavirus/epidemiologia , Pandemias , Pneumonia Viral/epidemiologia , Vigilância da População/métodos , Adulto , COVID-19 , China/epidemiologia , Surtos de Doenças , Feminino , Humanos , Incidência , Masculino , Pessoa de Meia-Idade , SARS-CoV-2 , Taxa de Sobrevida/tendências , Adulto Jovem
20.
Int J Hyg Environ Health ; 230: 113610, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32896785

RESUMO

The ongoing pandemic of 2019 novel coronavirus disease (COVID-19) is challenging global public health response system. We aim to identify the risk factors for the transmission of COVID-19 using data on mainland China. We estimated attack rate (AR) at county level. Logistic regression was used to explore the role of transportation in the nationwide spread. Generalized additive model and stratified linear mixed-effects model were developed to identify the effects of multiple meteorological factors on local transmission. The ARs in affected counties ranged from 0.6 to 9750.4 per million persons, with a median of 8.8. The counties being intersected by railways, freeways, national highways or having airports had significantly higher risk for COVID-19 with adjusted odds ratios (ORs) of 1.40 (p = 0.001), 2.07 (p < 0.001), 1.31 (p = 0.04), and 1.70 (p < 0.001), respectively. The higher AR of COVID-19 was significantly associated with lower average temperature, moderate cumulative precipitation and higher wind speed. Significant pairwise interactions were found among above three meteorological factors with higher risk of COVID-19 under low temperature and moderate precipitation. Warm areas can also be in higher risk of the disease with the increasing wind speed. In conclusion, transportation and meteorological factors may play important roles in the transmission of COVID-19 in mainland China, and could be integrated in consideration by public health alarm systems to better prevent the disease.


Assuntos
COVID-19 , Humanos , Conceitos Meteorológicos , Pandemias , SARS-CoV-2 , Temperatura
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...