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Confined Spaces

Julien Ramade, Léon Marcel Andriambariarijaona, Violette Steinmetz, Nicolas Goubet, Laurent Legrand, Thierry Barisien, Frédérick Bernardot, Christophe Testelin, Emmanuel Lhuillier, Alberto Bramati, Maria Chamarro
All inorganic CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) belong to the novel class of confined metal-halide perovskites which are currently arousing enthusiasm and stimulating huge activity across several fields of optoelectronics due to outstanding properties. A deep knowledge of the band-edge excitonic properties of these materials is thus crucial to further optimize their performances. Here, high-resolution photoluminescence (PL) spectroscopy of single bromide-based NCs reveals the exciton fine structure in the form of sharp peaks that are linearly polarized and grouped in doublets or triplets, which directly mirror the adopted crystalline structure, tetragonal (D4h symmetry) or orthorhombic (D2h symmetry)...
March 21, 2018: Nanoscale
S Hu, K Gopinadhan, A Rakowski, M Neek-Amal, T Heine, I V Grigorieva, S J Haigh, F M Peeters, A K Geim, M Lozada-Hidalgo
Atoms start behaving as waves rather than classical particles if confined in spaces commensurate with their de Broglie wavelength. At room temperature this length is only about one ångström even for the lightest atom, hydrogen. This restricts quantum-confinement phenomena for atomic species to the realm of very low temperatures1-5 . Here, we show that van der Waals gaps between atomic planes of layered crystals provide ångström-size channels that make quantum confinement of protons apparent even at room temperature...
March 19, 2018: Nature Nanotechnology
Kazuhiro Yanagi, Ryotaro Okada, Yota Ichinose, Yohei Yomogida, Fumiya Katsutani, Weilu Gao, Junichiro Kono
Confined electrons collectively oscillate in response to light, resulting in a plasmon resonance whose frequency is determined by the electron density and the size and shape of the confinement structure. Plasmons in metallic particles typically occur in the classical regime where the characteristic quantum level spacing is negligibly small compared to the plasma frequency. In doped semiconductor quantum wells, quantum plasmon excitations can be observed, where the quantization energy exceeds the plasma frequency...
March 16, 2018: Nature Communications
Chiho Watanabe, Miho Yanagisawa
Micrometric membrane confinements and macromolecular crowding of cytoplasm are key factors that regulate molecular diffusion in live cells. Previous studies have shown that macromolecular crowding delays molecular diffusion. However, the effect of cell-size confinement on diffusion in the crowding environment is yet to be elucidated. Using fluorescence correlation spectroscopy (FCS), we analyzed protein diffusion in microdroplets containing polymer solution covered with lipid membranes that mimic cells. As a result, we found that a synergistic condition of crowding and micrometric confinement results in accelerated protein diffusion on a sub-millisecond time scale...
March 15, 2018: Physical Chemistry Chemical Physics: PCCP
Ganhua Xie, Pei Li, Zhiju Zhao, Zhongpeng Zhu, Xiang-Yu Kong, Zhen Zhang, Kai Xiao, Liping Wen, Lei Jiang
Water wetting behavior in nano-confined environments plays an important role in mass transport and signal trans-mission of organisms. It is valuable and challengeable to investigate how water behaves in such a nanometer-scale with external stimuli, in particular with electric field and light. Unfortunately, the mechanism of hydrophobic reaction inside the nano-spaces is still obscure and lacks of experimental supporting for the current electric-field- or photo-responsive nanochannels which suffer from fragility or monofunctionality...
March 15, 2018: Journal of the American Chemical Society
Lars Borchardt, Mirian Elizabeth Casco, Joaquin Silvestre-Albero
Methane hydrate inheres the great potential to be a nature-inspired alternative for chemical energy storage, since it allows to store large amounts of methane in a dense solid phase. The embedment of methane hydrate in the confined environment of porous materials can be capitalized for potential applications as its physico-chemical properties such as the formation kinetics or pressure and temperature stability are significantly changed as compared to the bulk system. We review this topic from a materials scientific perspective by considering porous carbons, silica, clays, zeolites, and polymers as host structure for methane hydrate formation...
March 14, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Xu Wang, Yinchu Ma, Xing Sheng, Yucai Wang, Hangxun Xu
Extensive efforts have been devoted to synthesizing photothermal agents (PTAs) that are active in the first near-infrared (NIR) region (650~950 nm). However, PTAs for photothermal therapy (PTT) in the second NIR window (1000~1350 nm) are still rare. Here, we show that two-dimensional ultrathin polypyrrole (PPy) nanosheets prepared via a novel space-confined synthesis method could exhibit unique broadband absorption with a large extinction coefficient of 27.8 L g-1 cm-1 at 1064 nm and can be used as an efficient PTA in the second NIR window...
March 12, 2018: Nano Letters
Majid Malboubi, Asier Jayo, Maddy Parsons, Guillaume Charras
Cell migration plays a key role in many physiological and pathological conditions during which cells migrate primarily in the 3D environments formed by tissues. Microfluidics enables the design of simple devices that can mimic in a highly controlled manner the geometry and dimensions of the interstices encountered by cells in the body. Here we describe the design, fabrication, and implementation of an array of channels with a range of cross sections to investigate migration of cells and cell clusters through confined spaces...
2018: Methods in Molecular Biology
Bian Liu, Kui Kai Lau, Linxin Li, Caroline Lovelock, Ming Liu, Wilhelm Kuker, Peter M Rothwell
BACKGROUND AND PURPOSE: It has been hypothesized that cerebral small vessel disease (SVD) and chronic renal impairment may be part of a multisystem small-vessel disorder, but their association may simply be as a result of shared risk factors (eg, hypertension) rather than to a systemic susceptibility to premature SVD. However, most previous studies were hospital based, most had inadequate adjustment for hypertension, many were confined to patients with lacunar stroke, and none stratified by age...
March 9, 2018: Stroke; a Journal of Cerebral Circulation
Qingqing Wang, Fangxu Yang, Yu Zhang, Mingxi Chen, Xiaotao Zhang, Shengbin Lei, Rongjin Li, Wenping Hu
Two-dimensional molecular crystals (2DMCs) are promising candidate for flexible and large-area electronics. Their large-area production requires both low nuclei density and 2D crystal growth mode. As an emerging type of material, their large-area production remains a case-by-case practice. Here we present a general, efficient strategy for large-area 2DMCs. The method grows crystals on water surface to minimize the density of nuclei. By control-ling the interfacial tension of the water/solution system with a phase transfer surfactant, the spreading area of the solvent increases tens of times, leading to the space-confined 2D growth of molecular crystals...
March 9, 2018: Journal of the American Chemical Society
Robert K Katzschmann, Brandon Araki, Daniela Rus
This paper presents ALVU (Array of Lidars and Vibrotactile Units), a contactless, intuitive, hands-free, and discreet wearable device that allows visually impaired users to detect low- and high-hanging obstacles, as well as physical boundaries in their immediate environment. The solution allows for safe local navigation in both confined and open spaces by enabling the user to distinguish free space from obstacles. The device presented is composed of two parts: a sensor belt and a haptic strap. The sensor belt is an array of time-of-flight distance sensors worn around the front of a user's waist, and the pulses of infrared light provide reliable and accurate measurements of the distances between the user and surrounding obstacles or surfaces...
March 2018: IEEE Transactions on Neural Systems and Rehabilitation Engineering
Alexandra Battaglia-Mayer, Roberto Caminiti
Eye-hand coordination lies at the core of our daily actions and interactions with objects and people around us, and is central to understanding how the brain creates internal models of the action space and generates movement within it. Eye-hand coordination remains a very complex and elusive problem, which is further complicated by its distributed representation in the brain. In fact, evolution did not confine such a crucial function to a single area, but rather assigned it to several distributed cortical and subcortical systems, where encoding mechanisms can satisfy multiple demands and the consequences of lesions are less disruptive...
2018: Handbook of Clinical Neurology
Zhengli Hu, Zi-Yuan Li, Yi-Lun Ying, Junji Zhang, Chan Cao, Yi-Tao Long, He Tian
Identification of the configuration for the photoresponsive oligonucleotide plays an important role in the ingenious design of DNA nanomolecules and nanodevices. Due to the limited resolution and sensitivity of present methods, it remains a challenge to determine the accurate configuration of photoresponsive oligonucleotides, much less a precise description of their photo-conversion process. Here, we used an aerolysin (AeL) nanopore-based confined space for real-time determination and quantification of the absolute cis/ trans configuration of each azobenzene-modified oligonucleotide (Azo-ODN) with a single molecule resolution...
March 8, 2018: Analytical Chemistry
Han Zhao, Pei Miao, Mohammad H Teimourpour, Simon Malzard, Ramy El-Ganainy, Henning Schomerus, Liang Feng
Topological physics provides a robust framework for strategically controlling wave confinement and propagation dynamics. However, current implementations have been restricted to the limited design parameter space defined by passive topological structures. Active systems provide a more general framework where different fundamental symmetry paradigms, such as those arising from non-Hermiticity and nonlinear interaction, can generate a new landscape for topological physics and its applications. Here, we bridge this gap and present an experimental investigation of an active topological photonic system, demonstrating a topological hybrid silicon microlaser array respecting the charge-conjugation symmetry...
March 7, 2018: Nature Communications
Seonhee Lee, Changdeuck Bae, Jubok Lee, Subin Lee, Sang Ho Oh, Jeongyong Kim, Gyeong-Su Park, Hyun Suk Jung, Hyunjung Shin
Gold is known as the most noblest metal with only face-centered cubic (fcc) structure in ambient conditions. Here, stable hexagonal non-close-packed (ncp) gold nanowires (NWs), having a diameter of about 50 nm and aspect ratios of well over 400, are reported. Au NWs are grown in the confined system of nanotubular TiO2 arrays via photoelectrochemical reduction of HAuCl4 precursors. Some of the resulting Au NWs are proved to have sixfold rotational symmetry, observed by transmission electron microscopy tilting experiments...
March 7, 2018: Advanced Materials
Duanduan Wan, Sharon C Glotzer
We calculate the configurational entropy of hard particles confined in a cavity using Monte Carlo integration. Multiple combinations of particle and cavity shapes are considered. For small numbers of particles N, we show that the entropy decreases monotonically with increasing cavity aspect ratio, regardless of particle shape. As N increases, we find ordered regions of high and low particle density, with the highest density near the boundary for all particle and cavity shape combinations. Our findings provide insights relevant to engineering particles in confined spaces, entropic barriers, and systems with depletion interactions...
March 7, 2018: Soft Matter
Doyoon Kim, Byeongdu Lee, Stavros Thomopoulos, Young-Shin Jun
Mineralization of collagen is critical for the mechanical functions of bones and teeth. Calcium phosphate nucleation in collagenous structures follows distinctly different patterns in highly confined gap regions (nanoscale confinement) than in less confined extrafibrillar spaces (microscale confinement). Although the mechanism(s) driving these differences are still largely unknown, differences in the free energy for nucleation may explain these two mineralization behaviors. Here, we report on experimentally obtained nucleation energy barriers to intra- and extrafibrillar mineralization, using in situ X-ray scattering observations and classical nucleation theory...
March 6, 2018: Nature Communications
Kara A Moser, Lixin Zhang, Ian Spicknall, Nikolay P Braykov, Karen Levy, Carl F Marrs, Betsy Foxman, Gabriel Trueba, William Cevallos, Jason Goldstick, James Trostle, Joseph N S Eisenberg
Small-scale production poultry operations are increasingly common worldwide. To investigate how these operations influence antimicrobial resistance and mobile genetic elements (MGEs), Escherichia coli isolates were sampled from small-scale production birds (raised in confined spaces with antibiotics in feed), household birds (no movement constraints; fed on scraps), and humans associated with these birds in rural Ecuador (2010-2012). Isolates were screened for genes associated with MGEs as well as phenotypic resistance to 12 antibiotics...
March 1, 2018: American Journal of Epidemiology
Fei Gao, Li Zhang, Chao Yu, Xinwen Yan, Shaowen Zhang, Xiaofang Li
Chromium-based metal-organic framework (MOF) Cr-MIL-100/101 activated by activator and aluminum trialkyl compound serve as unique, highly efficient heterogeneous single-site catalysts for the controlled polymerization of isoprene, which not only exhibit quasi-living nature in isoprene polymerization but also unprecedentedly switch from cyclic to cis-1,4-selectivity depending on the activator used to yield low molecular weight cyclic PIPs or extremely high molecular weight cis-1,4-PIPs. Such heterogeneous Cr-MOF catalysts can be recycled approximately five times...
March 5, 2018: Macromolecular Rapid Communications
Jaime Moreno-García, Teresa García-Martínez, Juan C Mauricio, Juan Moreno
Yeast immobilization is defined as the physical confinement of intact cells to a region of space with conservation of biological activity. The use of these methodologies for alcoholic fermentation (AF) offers many advantages over the use of the conventional free yeast cell method and different immobilization systems have been proposed so far for different applications, like winemaking. The most studied methods for yeast immobilization include the use of natural supports (e.g., fruit pieces), organic supports (e...
2018: Frontiers in Microbiology
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