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The Poisson’s ratio is a fundamental mechanical property that relates the resulting lateral strain to applied axial strain. Although this value can theoretically be negative, it is positive for nearly all materials, though negative values have been observed in so-called auxetic structures. However, nearly all auxetic materials are bulk materials whose microstructure has been specifically engineered to generate a negative Poisson’s ratio. Here we report using first-principles calculations the existence of a negative Poisson’s ratio in a single-layer, two-dimensional material, black phosphorus. In contrast to engineered bulk auxetics, this behaviour is intrinsic for single-layer black phosphorus, and originates from its puckered structure, where the pucker can be regarded as a re-entrant structure that is comprised of two coupled orthogonal hinges. As a result of this atomic structure, a negative Poisson’s ratio is observed in the out-of-plane direction under uniaxial deformation in the direction parallel to the pucker. Auxetic materials display a negative Poisson’s ratio and are usually observed in engineered structures. Here, the authors observe intrinsic auxetic behaviour in unmodified two-dimensional black phosphorous by first-principles calculations, with the auxetic behaviour resulting from its puckered structure.

Resistance change under mechanical stimuli arouses mass operational heat, damaging the performance, lifetime, and reliability of stretchable electronic devices, therefore rapid thermal heat dissipating is necessary. Here we report a stretchable strain sensor with outstanding thermal management. Besides a high stretchability and sensitivity testified by human motion monitoring, as well as long-term durability, an enhanced thermal conductivity from the casted thermoplastic polyurethane-boron nitride nanosheets layer helps rapid heat transmission to the environments, while the porous electrospun fibrous thermoplastic polyurethane membrane leads to thermal insulation. A 32% drop of the real time saturated temperature is achieved. For the first time we in-situ investigated the dynamic operational temperature fluctuation of stretchable electronics under repeating stretching-releasing processes. Finally, cytotoxicity test confirms that the nanofillers are tightly restricted in the nanocomposites, making it harmless to human health. All the results prove it an excellent candidate for the next-generation of wearable devices. Though stretchable strain sensors are attractive for next-generation applications due to their high sensitivity, heat generated in these devices limits their reliability. Here, the authors report boron nitride nanosheet-based stretchable strain sensors with enhanced thermal management.

أصدرت مؤسسة بيت الحكمة للاستثمارات الثقافية، النسخة العربية من السلسلة الموسوعية الأولى من نوعها باللغة العربية \"ثقافة وفنون الخطوط الصينية\" والمترجمة عن اللغة الصينية من إصدار دار نشر هوبي التعليمية بالصين، وتعد سلسلة \"ثقافة وفنون الخطوط الصينية\" المحتوى المعرفي الأكثر شمولا، والأول من نوعه بالعربية عن ثقافة الخط الصيني، الذي هو أحد روافد الثقافة الصينية وأحد فنون الكتابة الممتدة لخمسة آلاف عام، وتشتمل السلسلة الموسوعية على دراسات حول تاريخ الخطوط القديمة وأنواعها وفنون كتابتها، كما تضم المعارف الخاصة بأنواع الخطوط وسماتها وتاريخها، بل وبأدوات الكتابة ومراحل تطورها، وتمثل الخطوط الصينية أحد أبرز عناصر الثقافة الصينية التقليدية، بل وأحد أهم الفنون الصينية التراثية التي كانت ولا تزال سمة أساسية لثقافة الكتابة الصينية على مر العصور، والتي هي جزء لا يتجزأ من تراث البشرية.

MicroRNA targets are often recognized through pairing between the miRNA seed region and complementary sites within target mRNAs, but not all of these canonical sites are equally effective, and both computational and in vivo UV-crosslinking approaches suggest that many mRNAs are targeted through non-canonical interactions. Here, we show that recently reported non-canonical sites do not mediate repression despite binding the miRNA, which indicates that the vast majority of functional sites are canonical. Accordingly, we developed an improved quantitative model of canonical targeting, using a compendium of experimental datasets that we pre-processed to minimize confounding biases. This model, which considers site type and another 14 features to predict the most effectively targeted mRNAs, performed significantly better than existing models and was as informative as the best high-throughput in vivo crosslinking approaches. It drives the latest version of TargetScan (v7.0; targetscan.org), thereby providing a valuable resource for placing miRNAs into gene-regulatory networks. Proteins are built by using the information contained in molecules of messenger RNA (mRNA). Cells have several ways of controlling the amounts of different proteins they make. For example, a so-called ‘microRNA’ molecule can bind to an mRNA molecule to cause it to be more rapidly degraded and less efficiently used, thereby reducing the amount of protein built from that mRNA. Indeed, microRNAs are thought to help control the amount of protein made from most human genes, and biologists are working to predict the amount of control imparted by each microRNA on each of its mRNA targets. All RNA molecules are made up of a sequence of bases, each commonly known by a single letter—‘A’, ‘U’, ‘C’ or ‘G’. These bases can each pair up with one specific other base—‘A’ pairs with ‘U’, and ‘C’ pairs with ‘G’. To direct the repression of an mRNA molecule, a region of the microRNA known as a ‘seed’ binds to a complementary sequence in the target mRNA. ‘Canonical sites’ are regions in the mRNA that contain the exact sequence of partner bases for the bases in the microRNA seed. Some canonical sites are more effective at mRNA control than others. ‘Non-canonical sites’ also exist in which the pairing between the microRNA seed and mRNA does not completely match. Previous work has suggested that many non-canonical sites can also control mRNA degradation and usage. Agarwal et al. first used large experimental datasets from many sources to investigate microRNA activity in more detail. As expected, when mRNAs had canonical sites that matched the microRNA, mRNA levels and usage tended to drop. However, no effect was observed when the mRNAs only had recently identified non-canonical sites. This suggests that microRNAs primarily bind to canonical sites to control protein production. Based on these results, Agarwal et al. further developed a statistical model that predicts the effects of microRNAs binding to canonical sites. The updated model considers 14 different features of the microRNA, microRNA site, or mRNA—including the mRNA sequence around the site—to predict which sites within mRNAs are most effectively targeted by microRNAs. Tests showed that Agarwal et al.'s model was as good as experimental approaches at identifying the effective target sites, and was better than existing computational models. The model has been used to power the latest version of a freely available resource called TargetScan, and so could prove a valuable resource for researchers investigating the many important roles of microRNAs in controlling protein production.

في قرية فاولا وتشوانغ أراد السيد قاو العثور على زوج لابنته الصغرى ولكن الأمر انتهى به الشيطان الخنزير ودعا السيد قاو الكثيرين لإخضاع الشيطان لكنهم فشلوا. وعندما سمع سان تسائخ والقرد أثناء رحلتهما إلى الغرب أن هناك شيطانا في القرية، تطوع الفرد للمساعدة، والتقى بالشيطان الخنزير وحاربه ولحق به إلى كيفه. أدرك الشيطان الخنزير أن سان تسانغ والقرد في رحلة لإحضار الكتب المقدسة، فأخبر القرد أنه كان ينتظرهما بعدما تلقى تعليمات من قوان بن. لكن القرد لم يصدقه فطلب منه أن يحرق كهفه ثم سيأخذه لمقابلة سان تسانغ فك سان تسانغ وثاق الشيطان الخنزير واتخذه تلميذا ثانيا له. واتضح أن الشيطان الخنزير كان قائدا في السماء ولكنه نفي إلى العالم الأرضي لسوء سلوكه، ومنحته قوان بن اسم وو ننغ ثم منحه سان تسانغ اسم \"با جیه\".

We propose a scheme for realizing exact parity-time ( P T ) antisymmetry of complex susceptibility in a wide range of probe detuning by considering a one-dimensional lattice of cold atoms driven into the simplest three-level Λ configuration. This is attained by modulating the intensity of a standing-wave coupling field with a proper phase shift to counteract the product of a single-photon detuning and a two-photon detuning. Such a dynamically controlled P T -antisymmetric lattice supports the integration of a few nontrivial scattering behaviors including unidirectional light reflectionless, asymmetric perfect absorption, and directional signal quenching. These behaviors, depending in particular on atomic densities and lattice lengths, facilitate the on-demand realization of unidirectional or bidirectional photon transport blockade.

Electrochemical catalytic reductive cross couplings are powerful and sustainable methods to construct C−C bonds by using electron as the clean reductant. However, activated substrates are used in most cases. Herein, we report a general and practical electro-reductive Ni-catalytic system, realizing the electrocatalytic carboxylation of unactivated aryl chlorides and alkyl bromides with CO 2 . A variety of unactivated aryl bromides, iodides and sulfonates can also undergo such a reaction smoothly. Notably, we also realize the catalytic electrochemical carboxylation of aryl (pseudo)halides with CO 2 avoiding the use of sacrificial electrodes. Moreover, this sustainable and economic strategy with electron as the clean reductant features mild conditions, inexpensive catalyst, safe and cheap electrodes, good functional group tolerance and broad substrate scope. Mechanistic investigations indicate that the reaction might proceed via oxidative addition of aryl halides to Ni(0) complex, the reduction of aryl-Ni(II) adduct to the Ni(I) species and following carboxylation with CO 2 . Electrochemistry is a promising approach to make existing chemical protocols milder, but many simple transformations of feedstocks are still out of reach. Here, the authors transform unactivated aryl and alkyl (pseudo)halides into carboxylic acids, via nickel catalysis and electricity, using atmospheric CO 2 as the carbon source.