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Lin Wang, Xuefeng Shi, Yaqian Wu, Jian Zhang, Yuejun Zhu, Jinben Wang
A novel supramolecular hydrogel was designed and constructed by molecular self-assembly of a cationic gemini surfactant, 1,3-bis(N,N-dimethyl-N-cetylammonium)-2-propylacrylate dibromide (AGC16), and an anionic aromatic compound, trisodium 1,3,6-naphthalenetrisulfonate (NTS). Owing to its unique structure, the hydrogel (abbreviated as AGC16/NTS) has the potential to be used as a multifunctional drug delivery system. The structure and properties of AGC16/NTS were characterized by rheological measurements, differential scanning calorimetry, variable-temperature 1H nuclear magnetic resonance, ultraviolet-visible spectroscopy, variable-temperature fluorescence emission spectroscopy, cryogenic scanning electron microscopy, transmission electron microscopy and X-ray diffraction methods...
January 15, 2018: Soft Matter
Mingjun Xia, Shipeng Shen, Jun Lu, Young Sun, R K Li
Magnetic cooling technology based on magnetocaloric effect (MCE) has attracted great interest in obtaining extreme low temperature, e. g. for space exploration. Here we grew a new gadolinium-rich orthoborate K3Li3Gd7(BO3)9 (1) as a promising cryogenic magnetic coolant. It exhibits complicated three dimensional framework constructed from BO3 groups and gadolinium-oxygen chains. The Gd-O chain consists of two types of clusters of Gd3O20 and Gd3O19 interconncetion by Gd(4)O8 polyhydron. Thanks to its high gadolinium concentration, a large -Sm for 1 was obtained as 56...
January 15, 2018: Chemistry: a European Journal
V Gayathri Devi, Amit Sircar, Deepak Yadav, Jayraj Parmar
In the fusion fuel cycle, the accurate analysis and understanding of the chemical composition of any gas mixture is of great importance for the efficient design of a tritium extraction and purification system or any tritium handling system. Methods like laser Raman spectroscopy and gas chromatography with thermal conductivity detector have been considered for hydrogen isotopes analyses in fuel cycles. Gas chromatography with a cryogenic separation column has been used for the analysis of hydrogen isotopes gas mixtures in general due to its high reliability and ease of operation...
January 12, 2018: Journal of Separation Science
Michael A Becker, Roman Vaxenburg, Georgian Nedelcu, Peter C Sercel, Andrew Shabaev, Michael J Mehl, John G Michopoulos, Samuel G Lambrakos, Noam Bernstein, John L Lyons, Thilo Stöferle, Rainer F Mahrt, Maksym V Kovalenko, David J Norris, Gabriele Rainò, Alexander L Efros
Nanostructured semiconductors emit light from electronic states known as excitons. For organic materials, Hund's rules state that the lowest-energy exciton is a poorly emitting triplet state. For inorganic semiconductors, similar rules predict an analogue of this triplet state known as the 'dark exciton'. Because dark excitons release photons slowly, hindering emission from inorganic nanostructures, materials that disobey these rules have been sought. However, despite considerable experimental and theoretical efforts, no inorganic semiconductors have been identified in which the lowest exciton is bright...
January 10, 2018: Nature
Alexander Löhner, Richard Cogdell, Jürgen Köhler
As the electronic energies of the chromophores in a pigment-protein complex are imposed by the geometrical structure of the protein, this allows the spectral information obtained to be compared with predictions derived from structural models. Thereby, the single-molecule approach is particularly suited for the elucidation of specific, distinctive spectral features that are key for a particular model structure, and that would not be observable in ensemble-averaged spectra due to the heterogeneity of the biological objects...
January 2018: Journal of the Royal Society, Interface
Kai Fan, Min Zhang, Arun S Mujumdar
Microwave heating has been applied in the drying of high-value solids as it affords a number of advantages, including shorter drying time and better product quality. Freeze-drying at cryogenic temperature and extremely low pressure provides the advantage of high product quality, but at very high capital and operating costs due partly to very long drying time. Freeze-drying coupled with a microwave heat source speeds up the drying rate and yields good quality products provided the operating unit is designed and operated to achieve the potential for an absence of hot spot developments...
January 10, 2018: Critical Reviews in Food Science and Nutrition
Keishi Suga, Yoko Otsuka, Yukihiro Okamoto, Hiroshi Umakoshi
Aqueous dispersions of oleic acid (OA) and those modified with 1-oleoylglycerol (monoolein, MO) form various kinds of self-assembled structures: micelles, vesicles, oil-in-water (O/W) emulsions, hexagonal phases, and dispersed cubic phases. Conventionally, these self-assembled structures have been characterized using cryogenic transmission electron microscopy or X-ray diffraction spectroscopy. However, these methodologies require specialized treatments before they can be used, which may lead to the self-assemblies not adopting their true equilibrium state...
January 8, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Zhuang Wu, Ruijuan Feng, Jian Xu, Yan Lu, Bo Lu, Tao Yang, Gernot Frenking, Tarek Trabelsi, Joseph S Francisco, Xiaoqing Zeng
An exotic ternary S, N, O heterocumulene OSNSO in syn-syn (A) and syn-anti (B) conformations has been generated in the gas phase through flash vacuum pyrolysis of CF3S(O)NSO at 700 K. Upon visible light irradiation (570±20 or 532 nm), both conformers A and B, isolated in cryogenic matrices (N2, Ne, Ar, and Kr, < 30 K), convert to a higher-energy anti-anti conformer (C). The reverse conformational transformation occurs either through S-N bond rotation (C to A and B) under the visible light irradiation (400±20 nm) at 2...
January 6, 2018: Journal of the American Chemical Society
Abhinav S Raman, Huiyong Li, Y C Chiew
Supercritical oxygen, a cryogenic fluid, is widely used as an oxidizer in jet propulsion systems and is therefore of paramount importance in gaining physical insights into processes such as transcritical and supercritical vaporization. It is well established in the scientific literature that the supercritical state is not homogeneous but, in fact, can be demarcated into regions with liquid-like and vapor-like properties, separated by the "Widom line." In this study, we identified the Widom line for oxygen, constituted by the loci of the extrema of thermodynamic response functions (heat capacity, volumetric thermal expansion coefficient, and isothermal compressibility) in the supercritical region, via atomistic molecular dynamics simulations...
January 7, 2018: Journal of Chemical Physics
Jiusheng Ren, Changchun Song, Aixin Hou, Yanyu Song, Xiaoyan Zhu, Grace Ann Cagle
Diurnal freeze-thaw cycles (FTCs) occur in the spring and autumn in boreal wetlands as soil temperatures rise above freezing during the day and fall below freezing at night. A surge in methane emissions from these systems is frequently documented during spring FTCs, accounting for a large portion of annual emissions. In boreal wetlands, methane is produced as a result of syntrophic microbial processes, mediated by a consortium of fermenting bacteria and methanogenic archaea. Further research is needed to determine whether FTCs enhance microbial metabolism related to methane production through the cryogenic decomposition of soil organic matter...
January 3, 2018: Science of the Total Environment
Benjamin T Diroll, Peijun Guo, Richard D Schaller
Methylammonium (MA) and formamidinium (FA) lead halides are widely studied for their potential as low-cost, high-performance optoelectronic materials. Here, we present measurements of visible and IR absorption, steady state, and time-resolved photoluminescence from 300 K to cryogenic temperatures. Whereas FAPbI3 nanocrystals (NCs) are found to behave in a very similar manner to reported bulk behavior, colloidal nanocrystals of MAPbI3 show a departure from the low-temperature optical behavior of the bulk material...
January 5, 2018: Nano Letters
Takayuki Iwasaki, Yoshiyuki Miyamoto, Takashi Taniguchi, Petr Siyushev, Mathias H Metsch, Fedor Jelezko, Mutsuko Hatano
Tin-vacancy (Sn-V) color centers were created in diamond via ion implantation and subsequent high-temperature annealing up to 2100 °C at 7.7 GPa. The first-principles calculation suggested that a large atom of tin can be incorporated into a diamond lattice with a split-vacancy configuration, in which a tin atom sits on an interstitial site with two neighboring vacancies. The Sn-V center showed a sharp zero phonon line at 619 nm at room temperature. This line split into four peaks at cryogenic temperatures, with a larger ground state splitting (∼850  GHz) than that of color centers based on other group-IV elements, i...
December 22, 2017: Physical Review Letters
Andrei Zholud, Ryan Freeman, Rongxing Cao, Ajit Srivastava, Sergei Urazhdin
We utilize a nanoscale magnetic spin-valve structure to demonstrate that current-induced magnetization fluctuations at cryogenic temperatures result predominantly from the quantum fluctuations enhanced by the spin transfer effect. The demonstrated spin transfer due to quantum magnetization fluctuations is distinguished from the previously established current-induced effects by a nonsmooth piecewise-linear dependence of the fluctuation intensity on current. It can be driven not only by the directional flows of spin-polarized electrons, but also by their thermal motion and by scattering of unpolarized electrons...
December 22, 2017: Physical Review Letters
Laura F Pinelo, Elsbeth R Klotz, William R Wonderly, Leif Oscar Paulson, Sharon C Kettwich, Jan Kubelka, David Todd Anderson
Complexes of lithium atoms with ethylene have been identified as potential hydrogen storage materials. As a Li atom approaches an ethylene molecule two distinct low lying electronic states are established; one is the 2A1 electronic state (for C2v geometries) that is repulsive but supports a shallow van der Waals well and correlates with the Li 2s atomic state and the second is a 2B2 electronic state that correlates with the Li 2p atomic orbital and is a strongly bound charge transfer state. Only the 2B2 charge transfer state would be advantageous for hydrogen storage because the strong electric dipole created in the Li-(C2H4) complex due to charge transfer can bind molecular hydrogen through dipole-induced dipole and dipole-quadrupole electrostatic interactions...
January 4, 2018: Journal of Physical Chemistry. A
Jana Broecker, Takefumi Morizumi, Wei-Lin Ou, Viviane Klingel, Anling Kuo, David J Kissick, Andrii Ishchenko, Ming-Yue Lee, Shenglan Xu, Oleg Makarov, Vadim Cherezov, Craig M Ogata, Oliver P Ernst
Protein crystallography has significantly advanced in recent years, with in situ data collection, in which crystals are placed in the X-ray beam within their growth medium, being a major point of focus. In situ methods eliminate the need to harvest crystals, a previously unavoidable drawback, particularly for often small membrane-protein crystals. Here, we present a protocol for the high-throughput in situ X-ray screening of and data collection from soluble and membrane-protein crystals at room temperature (20-25°C) and under cryogenic conditions...
February 2018: Nature Protocols
Timothy A Cross
In this issue of Structure, Baker et al. (2018) take advantage of recent technological breakthroughs in solid-state NMR spectroscopy and electron cryogenic tomography to characterize structural and functional differences between reconstituted YidC in E. coli lipids and YidC as overexpressed in the E. coli inner cellular membrane.
January 2, 2018: Structure
M Giulbudagian, G Yealland, S Hönzke, A Edlich, B Geisendörfer, B Kleuser, S Hedtrich, M Calderón
Topical administration permits targeted, sustained delivery of therapeutics to human skin. Delivery to the skin, however, is typically limited to lipophilic molecules with molecular weight of < 500 Da, capable of crossing the stratum corneum. Nevertheless, there are indications protein delivery may be possible in barrier deficient skin, a condition found in several inflammatory skin diseases such as psoriasis, using novel nanocarrier systems. METHODS: Water in water thermo-nanoprecipitation; dynamic light scattering; zeta potential measurement; nanoparticle tracking analysis; atomic force microscopy; cryogenic transmission electron microscopy; UV absorption; centrifugal separation membranes; bicinchoninic acid assay; circular dichroism; TNFα binding ELISA; inflammatory skin equivalent construction; human skin biopsies; immunohistochemistry; fluorescence microscopy; western blot; monocyte derived Langerhans cells; ELISA Results: Here, we report the novel synthesis of thermoresponsive nanogels (tNG) and the stable encapsulation of the anti-TNFα fusion protein etanercept (ETR) (~150 kDa) without alteration to its structure, as well as temperature triggered release from the tNGs...
2018: Theranostics
Palash V Acharya, Vaibhav Bahadur
This article reviews the fundamental interfacial mechanisms underlying electrofreezing (promotion of ice nucleation via the application of an electric field). Electrofreezing has been an active research topic for many decades, with applications in food preservation, cryopreservation, cryogenics and ice formation. There is substantial literature detailing experimental and simulations-based studies, which aim to understand the complex mechanisms underlying accelerated ice nucleation in the presence of electric fields and electrical charge...
December 8, 2017: Advances in Colloid and Interface Science
M Wiesel, G Birkl, M S Ebrahimi, A Martin, W Quint, N Stallkamp, M Vogel
We have conceived, built, and operated a cryogenic Penning trap with an electrically conducting yet optically transparent solid electrode. The trap, dedicated to spectroscopy and imaging of confined particles under large solid angles, is of "half-open" design with one open endcap and one closed endcap that mainly consists of a glass window coated with a highly transparent conductive layer. This arrangement allows for the trapping of externally or internally produced particles and yields flexible access for optical excitation and efficient light collection from the trapping region...
December 2017: Review of Scientific Instruments
Owen M Wilkin, Neil Harris, John F Rooms, Emma L Dixon, Adam J Bridgeman, Nigel Andrew Young
The interaction of FeBr2, CoBr2, NiBr2 and ZnBr2 with Ne, Ar, Kr, Xe, CH4 and N2 matrices has been investigated using IR, electronic absorption and X-ray absorption spectroscopies, as well as DFT calculations. ZnBr2 is linear in all the matrices. NiBr2 is linear in all but N2 matrices where it is severely bent. For FeBr2 and CoBr2 there is a more gradual change, with evidence of non-linearity in Xe and CH4 matrices as well as N2. In the N2 matrices the presence of νNN modes blue shifted from the "free" N2 values indicates the presence of physisorbed species, and the magnitude of the blue-shift correlates with the shift in the ν3 mode of the metal dibromide...
December 28, 2017: Journal of Physical Chemistry. A
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