The redox reactions occurring in the Li-S battery positive electrode conceal various and critical electrocatalytic processes, which strongly influence the performances of this electrochemical energy ...storage system. Here, we report the development of a single-dispersed molecular cluster catalyst composite comprising of a polyoxometalate framework (Co
(PW
O
)
) and multilayer reduced graphene oxide. Due to the interfacial charge transfer and exposure of unsaturated cobalt sites, the composite demonstrates efficient polysulfides adsorption and reduced activation energy for polysulfides conversion, thus serving as a bifunctional electrocatalyst. When tested in full Li-S coin cell configuration, the composite allows for a long-term Li-S battery cycling with a capacity fading of 0.015% per cycle after 1000 cycles at 2 C (i.e., 3.36 A g
). An areal capacity of 4.55 mAh cm
is also achieved with a sulfur loading of 5.6 mg cm
and E/S ratio of 4.5 μL mg
. Moreover, Li-S single-electrode pouch cells tested with the bifunctional electrocatalyst demonstrate a specific capacity of about 800 mAh g
at a sulfur loading of 3.6 mg cm
for 100 cycles at 0.2 C (i.e., 336 mA g
) with E/S ratio of 5 μL mg
.
The prevalence of HIV among men who have sex with men (MSM) has become a significant public health challenge. The aim was to comprehensively estimate the national prevalence of HIV among MSM and its ...time trends through a large-scale systematic analysis.
Systematic search of Cochrane Library, PubMed, EMBASE, CNKI, VIP, and Wanfang Data databases without language restriction for studies on the prevalence of HIV among MSM published before Dec.31, 2018. Studies were eligible for inclusion if they were published in the peer-reviewed literature and used validated assessment methods to assess the prevalence of HIV among MSM. Estimates were pooled using random-effects analysis.
Data were extracted from 355 cross-sectional studies (571,328 individuals) covered 59 cities from 30 provinces and municipalities of China. The overall national prevalence of HIV among MSM from 2001 to 2018 was estimated to be 5.7% (95% CI: 5.4-6.1%), with high between-study heterogeneity (I
= 98.0%, P < 0.001). Our study showed an increased tendency in the HIV prevalence as time progressed by meta-regression analysis (I
= 95.9%, P < 0.0001). HIV prevalence was the highest in those aged 50 years and older with HIV prevalence of 19.3% (95%CI: 13.1-27.4%, N = 13). HIV was more prevalent in the illiterate population (16.8%), than in those who had received an education. Although the internet was a major venue for Chinese MSM seeking male sex partners (35.6, 95%CI: 32.3-39.9%, N = 101), seeking MSM in bathhouses/saunas had the highest associated prevalence of HIV (13.4, 95%CI: 10.3-17.1%, N = 22). The HIV prevalence among MSM varied by location: compared with other regions in China, HIV was highly prevalent among MSM in the southwest (10.7, 95%CI: 9.3-12.2%, N = 91). Compared to participants who sometimes or always used condoms, participants who had never used a condom in the past 6 months had a higher risk of HIV infection, with odds ratios of 0.1 (95%CI: 0.08-0.14).
Our analysis provided reliable estimates of China's HIV burden among MSM, which appears to present an increasing national public health challenge. Effective government responses are needed to address this challenge and include the implementation of HIV prevention.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
DNA methylation is a heritable epigenetic mark, enabling stable but reversible gene repression. In mammalian cells, DNA methyltransferases (DNMTs) are responsible for modifying cytosine to ...5-methylcytosine (5mC), which can be further oxidized by the TET dioxygenases to ultimately cause DNA demethylation. However, the genome-wide cooperation and functions of these two families of proteins, especially at large under-methylated regions, called canyons, remain largely unknown.
Here we demonstrate that DNMT3A and TET1 function in a complementary and competitive manner in mouse embryonic stem cells to mediate proper epigenetic landscapes and gene expression. The longer isoform of DNMT3A, DNMT3A1, exhibits significant enrichment at distal promoters and canyon edges, but is excluded from proximal promoters and canyons where TET1 shows prominent binding. Deletion of Tet1 increases DNMT3A1 binding capacity at and around genes with wild-type TET1 binding. However, deletion of Dnmt3a has a minor effect on TET1 binding on chromatin, indicating that TET1 may limit DNA methylation partially by protecting its targets from DNMT3A and establishing boundaries for DNA methylation. Local CpG density may determine their complementary binding patterns and therefore that the methylation landscape is encoded in the DNA sequence. Furthermore, DNMT3A and TET1 impact histone modifications which in turn regulate gene expression. In particular, they regulate Polycomb Repressive Complex 2 (PRC2)-mediated H3K27me3 enrichment to constrain gene expression from bivalent promoters.
We conclude that DNMT3A and TET1 regulate the epigenome and gene expression at specific targets via their functional interplay.
Polyoxometalates (POMs) are a series of molecular metal oxide clusters, which span the two domains of solutes and solid metal oxides. The unique characters of POMs in structure, geometry, and ...adjustable redox properties have attracted widespread attention in functional material synthesis, catalysis, electronic devices, and electrochemical energy storage and conversion. This review is focused on the links between the intrinsic charge carrier behaviors of POMs from a chemistry‐oriented view and their recent ground‐breaking developments in related areas. First, the advantageous charge transfer behaviors of POMs in molecular‐level electronic devices are summarized. Solar‐driven, thermal‐driven, and electrochemical‐driven charge carrier behaviors of POMs in energy generation, conversion and storage systems are also discussed. Finally, present challenges and fundamental insights are discussed as to the advanced design of functional systems based upon POM building blocks for their possible emerging application areas.
The links between the intrinsic charge‐carrier behaviors of polyoxometalates (POMs) from a chemistry‐oriented view are discussed and their recent ground‐breaking developments in related areas, including molecular‐level electronic devices, solar‐driven, thermally driven, and electrochemically driven energy generation, conversion, and storage systems are reviewed. Finally, present challenges and the fundamental insights for advanced design and self‐assembly of POM building blocks are also discussed.
Hydrogen is seen as a sustainable fuel of the future, yet the vast majority of global hydrogen production comes from the reformation of fossil fuels. Electrolytic water splitting using proton ...exchange membrane electrolysers (PEMEs) provides a pathway to sustainable hydrogen production through coupling to renewable energy sources, but can suffer from gas crossover at low current densities and high operating pressures, causing explosive gas mixtures and decreasing cell lifetimes. Here we demonstrate the application of a highly stable, organic electron-coupled proton buffer (ECPB) which allows the decoupling of hydrogen and oxygen production during water splitting. By merging concepts from redox flow battery and PEM electrolysis research, we have built a hybrid electrolyser device capable of decoupling the gas evolution reactions during water splitting. The device improves on both gas purity and operational safety, while still working at industrially relevant, high current density. Anthraquinone-2,7-disulfonic acid was used as an organic redox mediator in this two-step process, producing H
at current densities of up to 3.71 A cm
at 2.00 V, extending the concept of the ECPB.
A new class of axially chiral styrene‐based thiourea tertiary amine catalysts, which have unique characteristics such as an efficient synthetic route, multiple chiral elements, and multiple ...activating groups, has been rationally designed. These new chiral catalysts have proven to be efficient organocatalysts, enabling the chemo‐, diastereo‐, and enantioselective (2+4) cyclization of 2‐benzothiazolimines with homophthalic anhydrides in good yields (up to 96 %) with excellent stereoselectivities (all >95:5 dr, up to 98 % ee). More importantly, theoretical calculations elucidated the important role of an axially chiral styrene moiety in controlling both the reactivity and enantioselectivity. This work not only represents the first design of styrene‐based chiral thiourea tertiary amine catalysts and the first catalytic asymmetric (2+4) cyclization of 2‐benzothiazolimines, but also gives an in‐depth understanding of axially chiral styrene‐based organocatalysts.
A new class of axially chiral styrene‐based organocatalysts has been rationally designed. They enable the chemo‐, diastereo‐ and enantioselective (2+4) cyclization of 2‐benzothiazolimines. This work represents the first design of styrene‐based chiral thiourea tertiary amine catalysts and the first catalytic asymmetric (2+4) cyclization of 2‐benzothiazolimines, and it gives an in‐depth understanding of axially chiral styrene‐based organocatalysts.
Thermal C-C bond cleavage reactions allow the construction of structurally diverse molecular skeletons via predictable and efficient bond reorganizations. Visible light photoredox-catalyzed ...radical-mediated C-C bond cleavage reactions have recently emerged as a powerful alternative method for overcoming the thermodynamic and kinetic barrier of C-C bond cleavage in diverse molecular scaffolds. In recent years, a plethora of elegant and useful reactions have been invented, and the products are sometimes otherwise inaccessible by classic thermal reactions. Considering the great influence and synthetic potential of these reactions, we provide a summary of the state of art visible light-driven radical-mediated C-C bond cleavage/functionalization strategies with a specific emphasis on the working models. We hoped that this review will be useful for medicinal and synthetic organic chemists and will inspire further reaction development in this interesting area.
Interaction solutions between lump and soliton are analytical exact solutions to nonlinear partial differential equations. The explicit expressions of the interaction solutions are of value for ...analysis of the interacting mechanism. We analyze the one-lump-multi-stripe and one-lump-multi-soliton solutions to nonlinear partial differential equations via Hirota bilinear forms. The one-lump-multi-stripe solutions are generated from the combined solution of quadratic functions and
N
exponential functions, while the one-lump-multi-soliton solutions from the combined solution of quadratic functions and
N
hyperbolic cosine functions. Within the context of the derivation of the lump solution and soliton solution, necessary and sufficient conditions are presented for the two types of interaction solutions, respectively, based on the combined solutions to the associated bilinear equations. Applications are made for a (2+1)-dimensional generalized KdV equation, the (2+1)-dimensional NNV system and the (2+1)-dimensional Ito equation.
The polyoxovanadate cluster Li7V15O36(CO3) is shown to be an active cathode material in Li‐ion batteries, delivering a capacity of 250 mA h g−1 at 50 mA g−1 and 140 mA h g−1 at 10 A g−1. Li‐ion ...diffusion is rapid in this material and gives rise to an impressive maximum power density output of 25.7 kW kg−1 (55 kW L−1).
With the changing lifestyle and the acceleration of aging in the Chinese population, the incidence and mortality of colorectal cancer (CRC) have risen in the last decades. On the contrary, the ...incidence and mortality of CRC have continued to decline in the USA since the 1980s, which is mainly attributed to early screening and standardized diagnosis and treatment. Rectal cancer accounts for the largest proportion of CRC in China, and its treatment regimens are complex. At present, surgical treatment is still the most important treatment for rectal cancer. Since the first Chinese guideline for diagnosis and treatment of CRC was issued in 2010, the fourth version has been revised in 2020. These guidelines have greatly promoted the standardization and internationalization of CRC diagnosis and treatment in China. And with the development of comprehensive treatment methods such as neoadjuvant chemoradiotherapy, targeted therapy, and immunotherapy, the post-operative quality of life and prognosis of patients with rectal cancer have improved. We believe that the inflection point of the rising incidence and mortality of rectal cancer will appear in the near future in China. This article reviewed the current status and research progress on surgical therapy of rectal cancer in China.
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