Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 127
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Inflammation ; 2020 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-32462546

RESUMO

Sepsis, a systemic inflammatory response mediated by excessive production of diverse inflammatory cytokines, remains the vital cause of morality in the intensive care unit (ICU). TLR4-MD2 (toll-like receptor 4-myeloid differentiation factor 2) complex activated by LPS serves as an effective target to decrease the inflammation during sepsis. In this study, we evaluated the effects of a new small molecule Z20 structural based on (2S, 3R, 4S)-chromene-3-carboxamide on LPS-induced sepsis in mice. We found Z20 markedly improved the survival rate and attenuated the multiply organs injury after LPS administration in mice. In addition, Z20 significantly alleviated organ inflammation as characterized by diminished inflammatory factors expression in vivo. Furthermore, by employing surface plasmon resonance (SPR) experiment, we identified that TLR4-MD2 complex was the potential target for Z20. Finally, we performed the safety assessment experiment to confirm the safety of Z20 in vivo. In conclusion, Z20, as a potential TLR4-MD2 inhibitor, effectively attenuated LPS-induced organ injury and inflammation.

2.
Chin J Integr Med ; 2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-32240476

RESUMO

OBJECTIVE: To evaluate the effectiveness and safety of Chinese herbal external umbilicus treatment with Modified Dinggui Powder (, MDGP) in patients with chronic nonbacterial prostatitis (CNP). METHODS: A randomized, double-blind, placebo-controlled clinical trial was conducted among 72 patients with CNP. Participants were randomly allocated to a treatment group and a placebo group using computer software in a 1:1 ratio, and received either MDGP external umbilicus treatment (MDGP group, 36 cases) or placebo control groupl (36 cases) at acupoints Shenque (CV 8), twice a week for 4 weeks. In addtion, patients all received herbal medicine treatment twice a day for 4 weeks. The primary outcomes was the US National Institutes of Health Chronic Prostatitis Symptom Scores Index (NIH-CPSI) with a questionnaire at weeks 2 and 4. The secondary outcomes including prostatic fluid examination (white blood cells and lecithin bodies), the clinical efficacy evaluation, and the adverse events were also assessed during the entire trial. RESULTS: The NIH-CPSI scores regarding pain or discomfort scores showed greater improvement in the MDGP group than placebo control group at weeks 2 (P0.001) and week 4 (P0.004), respectively. NIH-CPSI scores of symptom severity, total scores, the amount of leukocytes number in the prostatic fifluid in the MDGP group were significantly improved (P<0.05). There was no statistical difference in the urinary symptoms, quality of life, lecithin and other scores between two groups (P>0.05). The clinical effective rate was 73.53% (25/34) in the MDGP group, which was significally higher than the placebo control group with 48.39% (25/31, P<0.05). Patients were blinded successfully, and no serious adverse effects were found during the trial. CONCLUSION: A 4-week course of umbilicus treatment with modified Dinggui Powder seems to relieve pain and symptom severity effectively and increase the amount of leukocytes number in patients with CNP (Trial registration No. ChiCTR1800014687).

3.
Environ Sci Technol ; 54(10): 5973-5979, 2020 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-32343120

RESUMO

The oxidation of nitric oxide to nitrogen dioxide by hydroperoxy (HO2) and organic peroxy radicals (RO2) is responsible for the chemical net ozone production in the troposphere and for the regeneration of hydroxyl radicals, the most important oxidant in the atmosphere. In Summer 2014, a field campaign was conducted in the North China Plain, where increasingly severe ozone pollution has been experienced in the last years. Chemical conditions in the campaign were representative for this area. Radical and trace gas concentrations were measured, allowing for calculating the turnover rates of gas-phase radical reactions. Therefore, the importance of heterogeneous HO2 uptake on aerosol could be experimentally determined. HO2 uptake could have suppressed ozone formation at that time because of the competition with gas-phase reactions that produce ozone. The successful reduction of the aerosol load in the North China Plain in the last years could have led to a significant decrease of HO2 loss on particles, so that ozone-forming reactions could have gained importance in the last years. However, the analysis of the measured radical budget in this campaign shows that HO2 aerosol uptake did not impact radical chemistry for chemical conditions in 2014. Therefore, reduced HO2 uptake on aerosol since then is likely not the reason for the increasing number of ozone pollution events in the North China Plain, contradicting conclusions made from model calculations reported in the literature.

4.
J Am Chem Soc ; 142(12): 5702-5708, 2020 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-32118414

RESUMO

Electrochemical conversion of nitrate (NO3-) into ammonia (NH3) recycles nitrogen and offers a route to the production of NH3, which is more valuable than dinitrogen gas. However, today's development of NO3- electroreduction remains hindered by the lack of a mechanistic picture of how catalyst structure may be tuned to enhance catalytic activity. Here we demonstrate enhanced NO3- reduction reaction (NO3-RR) performance on Cu50Ni50 alloy catalysts, including a 0.12 V upshift in the half-wave potential and a 6-fold increase in activity compared to those obtained with pure Cu at 0 V vs reversible hydrogen electrode (RHE). Ni alloying enables tuning of the Cu d-band center and modulates the adsorption energies of intermediates such as *NO3-, *NO2, and *NH2. Using density functional theory calculations, we identify a NO3-RR-to-NH3 pathway and offer an adsorption energy-activity relationship for the CuNi alloy system. This correlation between catalyst electronic structure and NO3-RR activity offers a design platform for further development of NO3-RR catalysts.

5.
Opt Lett ; 45(3): 660-663, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-32004277

RESUMO

The three-dimensional (3D) precision measurement of subsurface defects (SSDs) remains a long-term, critical, and urgent challenge in advanced manufacturing technology. In this study, we present a 3D dark-field confocal microscopy technique with complementary illumination and detection apertures to detect the SSD in ultraprecise optical components, which are widely employed at laser fusion facilities. Under an annular illumination generated using a pair of axicons, the specular reflected beam from the surface can be blocked by a diaphragm placed in the detection path, while the scattered beam from the SSD can be effectively collected by the detector. Both surface topography and subsurface defects distribution can be measured simultaneously by this method. We constructed a dark-field confocal microscope that could readily detect the SSD 60 µm beneath the surface in neodymium glass. Furthermore, the 3D volume distributions of the SSD were also reconstructed.

7.
Nat Commun ; 11(1): 129, 2020 01 08.
Artigo em Inglês | MEDLINE | ID: mdl-31913268

RESUMO

Land use policies have turned southern China into one of the most intensively managed forest regions in the world, with actions maximizing forest cover on soils with marginal agricultural potential while concurrently increasing livelihoods and mitigating climate change. Based on satellite observations, here we show that diverse land use changes in southern China have increased standing aboveground carbon stocks by 0.11 ± 0.05 Pg C y-1 during 2002-2017. Most of this regional carbon sink was contributed by newly established forests (32%), while forests already existing contributed 24%. Forest growth in harvested forest areas contributed 16% and non-forest areas contributed 28% to the carbon sink, while timber harvest was tripled. Soil moisture declined significantly in 8% of the area. We demonstrate that land management in southern China has been removing an amount of carbon equivalent to 33% of regional fossil CO2 emissions during the last 6 years, but forest growth saturation, land competition for food production and soil-water depletion challenge the longevity of this carbon sink service.

8.
Proc Natl Acad Sci U S A ; 117(3): 1788-1798, 2020 01 21.
Artigo em Inglês | MEDLINE | ID: mdl-31911476

RESUMO

The lipid dependence of the nicotinic acetylcholine receptor from the Torpedo electric organ has long been recognized, and one of the most consistent experimental observations is that, when reconstituted in membranes formed by zwitterionic phospholipids alone, exposure to agonist fails to elicit ion-flux activity. More recently, it has been suggested that the bacterial homolog ELIC (Erwinia chrysanthemi ligand-gated ion channel) has a similar lipid sensitivity. As a first step toward the elucidation of the structural basis of this phenomenon, we solved the structures of ELIC embedded in palmitoyl-oleoyl-phosphatidylcholine- (POPC-) only nanodiscs in both the unliganded (4.1-Å resolution) and agonist-bound (3.3 Å) states using single-particle cryoelectron microscopy. Comparison of the two structural models revealed that the largest differences occur at the level of loop C-at the agonist-binding sites-and the loops at the interface between the extracellular and transmembrane domains (ECD and TMD, respectively). On the other hand, the transmembrane pore is occluded in a remarkably similar manner in both structures. A straightforward interpretation of these findings is that POPC-only membranes frustrate the ECD-TMD coupling in such a way that the "conformational wave" of liganded-receptor gating takes place in the ECD and the interfacial M2-M3 linker but fails to penetrate the membrane and propagate into the TMD. Furthermore, analysis of the structural models and molecular simulations suggested that the higher affinity for agonists characteristic of the open- and desensitized-channel conformations results, at least in part, from the tighter confinement of the ligand to its binding site; this limits the ligand's fluctuations, and thus delays its escape into bulk solvent.


Assuntos
Microscopia Crioeletrônica , Canais Iônicos de Abertura Ativada por Ligante/química , Canais Iônicos de Abertura Ativada por Ligante/metabolismo , Fosfatidilcolinas/química , Fosfatidilcolinas/metabolismo , Animais , Sítios de Ligação , Ligantes , Modelos Moleculares , Conformação Molecular , Ligação Proteica , Domínios Proteicos , Receptores Nicotínicos/metabolismo , Torpedo
9.
Nature ; 577(7791): 509-513, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31747679

RESUMO

The electrocatalytic reduction of carbon dioxide, powered by renewable electricity, to produce valuable fuels and feedstocks provides a sustainable and carbon-neutral approach to the storage of energy produced by intermittent renewable sources1. However, the highly selective generation of economically desirable products such as ethylene from the carbon dioxide reduction reaction (CO2RR) remains a challenge2. Tuning the stabilities of intermediates to favour a desired reaction pathway can improve selectivity3-5, and this has recently been explored for the reaction on copper by controlling morphology6, grain boundaries7, facets8, oxidation state9 and dopants10. Unfortunately, the Faradaic efficiency for ethylene is still low in neutral media (60 per cent at a partial current density of 7 milliamperes per square centimetre in the best catalyst reported so far9), resulting in a low energy efficiency. Here we present a molecular tuning strategy-the functionalization of the surface of electrocatalysts with organic molecules-that stabilizes intermediates for more selective CO2RR to ethylene. Using electrochemical, operando/in situ spectroscopic and computational studies, we investigate the influence of a library of molecules, derived by electro-dimerization of arylpyridiniums11, adsorbed on copper. We find that the adhered molecules improve the stabilization of an 'atop-bound' CO intermediate (that is, an intermediate bound to a single copper atom), thereby favouring further reduction to ethylene. As a result of this strategy, we report the CO2RR to ethylene with a Faradaic efficiency of 72 per cent at a partial current density of 230 milliamperes per square centimetre in a liquid-electrolyte flow cell in a neutral medium. We report stable ethylene electrosynthesis for 190 hours in a system based on a membrane-electrode assembly that provides a full-cell energy efficiency of 20 per cent. We anticipate that this may be generalized to enable molecular strategies to complement heterogeneous catalysts by stabilizing intermediates through local molecular tuning.

10.
Behav Brain Res ; 379: 112342, 2020 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-31705920

RESUMO

Post-traumatic stress disorder (PTSD) is a chronic and disabling condition arising after exposure to a severe traumatic event, which affects approximately eight percent of the population. The underlying neurobiology of PTSD, however, has only been partially understood. The exploration of fear memory and its extinction has been the subject to increase our understanding of PTSD. Our previous studies have already found that adolescent mice exhibited impaired fear memory extinction with accompanied depressive-like behaviors. Considering the relationship between ketamine and its rapid antidepressant function, we hypothesis that ketamine can facilitate the fear memory extinction so as to exhibit an antidepressant effects. In this study, to evaluate our hypothesis, we intraperitoneal (i.p.) injection of ketamine in adolescent mice and found that ketamine exhibited a rapid antidepressant effect and facilitated the fear memory extinction. Moreover, ketamine can also reverse the accompanied depressive-like behaviors and restore long-term potentiation (LTP) induction in extinction process, which involved the presynaptic mechanism. Our results suggest that ketamine exhibited an antidepressant effect in FST and facilitated the fear memory extinction via presynaptic-mediated synaptic plasticity, which may provide new strategy for treatment of PTSD.

11.
Artigo em Inglês | MEDLINE | ID: mdl-31863899

RESUMO

OBJECTIVES: Ceftazidime-avibactam (CAZ-AVI) is a novel synthetic ß-lactamase inhibitor combination. Although the combination has been available clinically for only a few years, cases of resistance to CAZ-AVI have already been reported. METHODS: In the present review, we summarized the distribution of CAZ-AVI-resistant strains and the possible resistance mechanisms. RESULTS: There are no significant differences in CAZ-AVI resistance rates across different regions. CAZ-AVI maintains good activity against Gram-negative bacteria, especially Enterobacteriaceae. Pseudomonas aeruginosa is less susceptible to CAZ-AVI compared with Enterobacteriaceae, with a resistance rate ranging from 2.9% to 18%. The resistance to CAZ-AVI exceeds 50% in Acinetobacter baumannii. Higher resistance rate to CAZ-AVI is associated with carbapenem resistance. Moreover, ß-lactamase related amino acid substitutions are the main mechanism leading to CAZ-AVI resistance. Membrane protein amino acid substitutions and efflux pumps also play important roles in CAZ-AVI resistance. CONCLUSION: In order to maintain its efficacy, CAZ-AVI should not be used for pathogens that are naturally resistant to it. For CAZ-AVI-resistant strains, other effective antibacterial agents or CAZ-AVI in combination with other antibacterial agents should be considered.

12.
Nat Commun ; 10(1): 5814, 2019 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-31862886

RESUMO

Producing liquid fuels such as ethanol from CO2, H2O, and renewable electricity offers a route to store sustainable energy. The search for efficient electrocatalysts for the CO2 reduction reaction relies on tuning the adsorption strength of carbonaceous intermediates. Here, we report a complementary approach in which we utilize hydroxide and oxide doping of a catalyst surface to tune the adsorbed hydrogen on Cu. Density functional theory studies indicate that this doping accelerates water dissociation and changes the hydrogen adsorption energy on Cu. We synthesize and investigate a suite of metal-hydroxide-interface-doped-Cu catalysts, and find that the most efficient, Ce(OH)x-doped-Cu, exhibits an ethanol Faradaic efficiency of 43% and a partial current density of 128 mA cm-2. Mechanistic studies, wherein we combine investigation of hydrogen evolution performance with the results of operando Raman spectroscopy, show that adsorbed hydrogen hydrogenates surface *HCCOH, a key intermediate whose fate determines branching to ethanol versus ethylene.

13.
Sensors (Basel) ; 19(23)2019 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-31779164

RESUMO

The ultrasonic guided wave-based structural damage diagnosis method has broad application prospects in different fields. However, some environmental factors such as temperature and loads will significantly affect the monitoring results. In this paper, a reference matching-based temperature compensation for ultrasonic guided wave signals is proposed to eliminate the effect of temperature. Firstly, the guided wave signals measured at different temperatures are used as reference signals to establish the relationship between the features of the reference signals and temperature. Then the matching algorithm based on Gabor function is used to establish the relationship between the amplitude influence coefficient obtained by the reference signal and the corresponding temperature. Finally, through these two relationships, the values of the phase and amplitude influence coefficients of the guided wave signals at other temperatures are obtained in a way of interpolation in order to reconstruct the compensation signals at the temperature. The effect of temperature on the amplitude and phase of the guided wave signal is eliminated. The proposed temperature compensation method is featured such that the compensation performance can be improved by multiple iteration compensation of the residual signal. The ultrasonic guided wave test results at different temperatures show that the first iterative compensation of the proposed method can achieve compensation within the temperature range greater than 7 °C, and the compensation within the temperature range greater than 18 °C can be achieved after three iterations.

14.
Nat Commun ; 10(1): 5186, 2019 11 29.
Artigo em Inglês | MEDLINE | ID: mdl-31780655

RESUMO

The electroreduction of C1 feedgas to high-energy-density fuels provides an attractive avenue to the storage of renewable electricity. Much progress has been made to improve selectivity to C1 and C2 products, however, the selectivity to desirable high-energy-density C3 products remains relatively low. We reason that C3 electrosynthesis relies on a higher-order reaction pathway that requires the formation of multiple carbon-carbon (C-C) bonds, and thus pursue a strategy explicitly designed to couple C2 with C1 intermediates. We develop an approach wherein neighboring copper atoms having distinct electronic structures interact with two adsorbates to catalyze an asymmetric reaction. We achieve a record n-propanol Faradaic efficiency (FE) of (33 ± 1)% with a conversion rate of (4.5 ± 0.1) mA cm-2, and a record n-propanol cathodic energy conversion efficiency (EEcathodic half-cell) of 21%. The FE and EEcathodic half-cell represent a 1.3× improvement relative to previously-published CO-to-n-propanol electroreduction reports.

15.
Polymers (Basel) ; 11(11)2019 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-31726740

RESUMO

An effective approach to the fabrication of progressive epoxy nanocomposites by the incorporation of hydroxyl-terminated dendrimers functionalized graphene oxide (GO-TCT-Tris) is reported. The relationship between surface grafting, chemical construction, morphology, dispersion, and interfacial interaction as well as the corresponding mechanical properties of the composites were studied in detail. It was shown that hydroxyl-terminated triazine derivatives have been resoundingly bonded onto the GO surface through covalent bonding, which effectively improved the dispersion and compatibility of GO sheets in epoxy resin. The tensile and flexural tests manifested that the GO-TCT-Tris/epoxy composites exhibited greater tensile/flexural strength and modulus than either the pure epoxy or the GO/epoxy composites. For GO-TCT-Tris (0.10 wt%)/epoxy composite, the tensile strength and elastic modulus increased from 63 ± 4 to 89 ± 6 MPa (41.27%) and from 2.8 ± 0.1 to 3.6 ± 0.2 GPa (28.57%), and the flexural strength and modulus increased from 106 ± 5 to 158 ± 6 MPa (49.06%) and from 3.0 ± 0.1 to 3.5 ± 0.2 GPa (16.67%), respectively, compared to the pure epoxy matrix. Moreover, the fractographic analysis also illustrated the ameliorative interfacial interaction between GO-TCT-Tris and epoxy matrix.

16.
J Obstet Gynaecol Res ; 45(12): 2307-2317, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31608558

RESUMO

This study aimed to conduct a comprehensive analysis of clinical studies on acupuncture treatment for breast cancer-related lymphedema (BCRL), so as to explore the efficacy and safety of acupuncture treatment and provide evidence for the clinical decision-making. Public databases, mainly including China Academic Journals Full-text Database, Database of Chinese Sci-Tech Journal, Wanfang, PubMed, Embase and the Cochrane Library, from the establishment of databases to December 2018 were searched for randomized controlled trials (RCT) of acupuncture for BCRL. Clinical RCT on the treatment of BCRL with acupuncture combined with drugs or functional exercise were enrolled for the analysis. Bias risk and quality were assessed by two investigators according to the Cochrane Handbook 5.1.0 standard, and the Revman 5.3 software was used for meta-analysis. A total of 13 studies were enrolled, comprising 747 patients (377 in the treatment group and 370 in the control group). The results of meta-analysis showed that acupuncture intervention could improve the total effective rate for the treatment of BCRL (odds ratio = 4.62; 95% confidence interval 2.61-8.17). Recent studies suggest that acupuncture therapy can alleviate the upper limb swelling and improve the subjective pain and discomfort in patients with BCRL, regardless of the control intervention used. However, the number of high-quality RCT is low. Moreover, most of the studies adopted inconsistent efficacy indicators. Hence, additional blinded, large-sample, randomized, well-controlled studies with objective and uniform efficacy indicators are needed, especially in China, to confirm the findings.

17.
Zhongguo Gu Shang ; 32(8): 696-700, 2019 Aug 25.
Artigo em Chinês | MEDLINE | ID: mdl-31533378

RESUMO

OBJECTIVE: To explore long-term outcomes of Chiari osteotomy for Legg-Calvé-Perthes disease in children with type Catterall III or IV, and to analyze clinical effect of osteotomy angle on clinical and radiographic results. METHODS: From March 2005 to July 2013, 26 children with Legg-Calvé-Perthes disease with type Catterall III or IV were treated by Chiari osteotomy, including 17 males and 9 females, aged from 4 to 13 years old with an average of (8.9±2.6) years old. Children were divided into low osteotomy angle group and high osteotomy angle group. according to osteotomy angle. There were 10 children in low osteotomy angle group with an osteotomy angle of 10 degrees, including 8 boys and 2 girls, aged from 4 to 13 years old with an average of (9.2±3.3) years old; while there were 16 children in high osteotomy angle group with an osteotomy angle of 15 degress, including 9 boys and 7 girls, aged from 6 to 12 years old with an average of (8.8±2.1) years old. HHS score before operation and at the latest follow-up were recorded to observe clinical results. CE angle of hip joint, acetabular index, Sharp angle, Shenton's line continuity, femoral head coverage, acetabular depth ratio were recorded to compare radiographic results. Stulberg classification was analyzed to compare reshaping ability of femoral head. RESULTS: Twenty-six children were followed up for 4.5 to 12.0 years with an average of (7.9±1.8) years. All incisions were healed at stage I for 10 to 14 days, with an average of(12.3±1.1) days. No inflammation, skin necrosis and injury of vessel and nerve occurred. All osteotomies achieved bone union for 8 to 13 weeks, with an average of(9.8±1.4) weeks. HHS score increased from 75.8±6.5 before operation to 93.5±2.5 at the latest follow-up in low osteotomy angle group(P<0.05), and form 77.6±6.2 to 97.8±1.6 in high osteotomy angle group (P<0.05). HHS score of high osteotomy angle group at the latest follow-up was higher than that of low osteotomy angle group (P<0.05). The acetabular index decreased from (10.1±2.5)° before operation to (4.5±1.3)° at the latest follow-up in low osteotomy angle group (P<0.05), and from (10.7±3.3)° before operation to (2.0±1.1)° in high osteotomy angle group (P<0.05). The acetabular index of high osteotomy angle group at the latest followup was better than low osteotomy angle group(P<0.05). There was no significant difference in CE angle, Sharp angle, Shenton's continuity, femoral head coverage, acetabular depth ratio between two groups. According to Stulberg classification, the femoral head reshaping ability in high osteotomy angle group was better than that of low osteotomy angle group(P<0.05). CONCLUSIONS: Chiari osteotomy with 15° for Legg-Calvé-Perthes disease in children with type Catterall III or IV could effectively decrease index of acetabulum, and helpful for femoral head reshaping ability, then in further improve clinical effects.


Assuntos
Cabeça do Fêmur , Osteotomia , Acetábulo , Adolescente , Criança , Pré-Escolar , Feminino , Articulação do Quadril , Humanos , Inflamação , Masculino , Resultado do Tratamento
18.
Sci Total Environ ; 693: 133580, 2019 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-31376754

RESUMO

Heterogeneous reactions of N2O5, O3, OH, ClONO2, HOCl, ClNO2, and NO2, with chlorine-containing particles are incorporated in the Community Multiscale Air Quality (CMAQ) model to evaluate the impact of heterogeneous reactions of reactive chlorine species on ozone and free radicals. Changes of summertime ozone and free radical concentrations due to the additional heterogeneous reactions in north China were quantified. These heterogeneous reactions increased the O3, OH, HO2 and RO2 concentrations by up to 20%, 28%, 36% and 48% for some regions in the Beijing-Tianjin-Hebei (BTH) area. These areas typically have a larger amount of NOx emissions and a lower VOC/NOx ratio. The zero-out method evaluates that the photolysis of ClNO2 and Cl2 are the major contributors (42.4% and 57.6%, respectively) to atmospheric Cl in the early morning hours but the photolysis of Cl2 is the only significant contributor after 10:00 am. The results highlight that heterogeneous reactions of reactive chlorine species are important to atmospheric ozone and free-radical formation. Our study also suggests that the on-going NOx emission controls in the NCP region with a goal to reduce both O3 and secondary nitrate can also have the co-benefit of reducing the formation Cl from ClNO2 and Cl2, which may also lead to lower secondary organic aerosol formation and thus the control of summertime PM2.5 in the region.

19.
Nature ; 573(7775): 546-552, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31461748

RESUMO

The αß T cell receptor (TCR), in association with the CD3γε-CD3δε-CD3ζζ signalling hexamer, is the primary determinant of T cell development and activation, and of immune responses to foreign antigens. The mechanism of assembly of the TCR-CD3 complex remains unknown. Here we report a cryo-electron microscopy structure of human TCRαß in complex with the CD3 hexamer at 3.7 Å resolution. The structure contains the complete extracellular domains and all the transmembrane helices of TCR-CD3. The octameric TCR-CD3 complex is assembled with 1:1:1:1 stoichiometry of TCRαß:CD3γε:CD3δε:CD3ζζ. Assembly of the extracellular domains of TCR-CD3 is mediated by the constant domains and connecting peptides of TCRαß that pack against CD3γε-CD3δε, forming a trimer-like structure proximal to the plasma membrane. The transmembrane segment of the CD3 complex adopts a barrel-like structure formed by interaction of the two transmembrane helices of CD3ζζ with those of CD3γε and CD3δε. Insertion of the transmembrane helices of TCRαß into the barrel-like structure via both hydrophobic and ionic interactions results in transmembrane assembly of the TCR-CD3 complex. Together, our data reveal the structural basis for TCR-CD3 complex assembly, providing clues to TCR triggering and a foundation for rational design of immunotherapies that target the complex.

20.
Environ Pollut ; 253: 207-220, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31310871

RESUMO

Characterizing the vertical distribution of aerosol optical properties is crucial to reduce the uncertainty in quantifying the radiative forcing and climate effects of aerosols. The analysis of four-year (2007-2010) Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) lidar measurements revealed the existence of tropospheric aerosol layers associated with the Asian summer monsoon. The measurements of five typical aerosol optical and microphysical parameters were used to explore the properties, spatial/vertical distributions, annual evolution of tropopause aerosols over the South Asia region. Results extracted from various latitude-height and longitude-height cross sections of aerosol extinction coefficient at 532 and 1064 nm, backscatter coefficient at 532 nm, and depolarization ratio at 532 nm demonstrated that a large amount of aerosols vertically extended up to the tropopause (12 km) during the monsoon season over the north Arabian Sea, India, north Bay of Bengal, and equatorial Indian Ocean, finally reaching the southeast of the Tibetan Plateau. Convective transport associated with Asian summer monsoon is an important factor controlling the vertical distribution of tropopause aerosols. The evolution of aerosol scattering ratio at 532 nm indicated that from equatorial Indian Ocean to South Asia, there exists an upward tilting and ascending structure of the aerosols layer during the monsoon season, which typically indicates enhanced aerosols over the Asian monsoon region. Information on aerosol size distribution and detailed composition are needed for better understanding the nature and origin of this aerosol layer. Enhancement of the tropopause aerosols should be considered in the future studies in evaluating the regional or global climate systems. Further satellite observations of aerosols and in-situ observations are also urgently needed to diagnose this aerosol layer, which likely originate from anthropogenic emissions.


Assuntos
Aerossóis/análise , Poluentes Atmosféricos/análise , Monitoramento Ambiental/métodos , Ásia , Atmosfera/química , Clima , Índia , Oceano Índico , Estações do Ano
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA