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Ying-Feng Hsu, Yu-Hsun Chen, Chih-Wei Chang
We performed comprehensive studies on the photoluminescence properties of the carbon dots prepared from citric acid (C-dots(CA)) and citric acid + ethylenediamine (C-dots(CA+EDA)). The cryogenic experiment confirmed that the excitation dependent fluorescence and the spectral relaxation dynamics of the C-dots are associated with the presence of multiple emissive states/species in the C-dots instead of solvation dynamics. Moreover, we also compared the size of the C-dots estimated from the TEM/AFM images and fluorescence anisotropy methods...
October 24, 2016: Physical Chemistry Chemical Physics: PCCP
Norihiko L Okamoto, Shu Fujimoto, Yuki Kambara, Marino Kawamura, Zhenghao M T Chen, Hirotaka Matsunoshita, Katsushi Tanaka, Haruyuki Inui, Easo P George
High-entropy alloys (HEAs) comprise a novel class of scientifically and technologically interesting materials. Among these, equatomic CrMnFeCoNi with the face-centered cubic (FCC) structure is noteworthy because its ductility and strength increase with decreasing temperature while maintaining outstanding fracture toughness at cryogenic temperatures. Here we report for the first time by single-crystal micropillar compression that its bulk room temperature critical resolved shear stress (CRSS) is ~33-43 MPa, ~10 times higher than that of pure nickel...
October 24, 2016: Scientific Reports
Sujan K Sarkar, Onyinye Osisioma, William L Karney, Manabu Abe, Anna D Gudmundsdottir
Photolysis of 3-azido-1-indenone (1) with a light-emitting diode (LED, λ= 405 nm) or mercury arc lamp (Pyrex) resulted in the formation of heterodimer 3 in excellent yield, through dimerization of triplet vinylnitrene (3)2. At ambient temperature, vinylnitrene (3)2 (λmax at 340 and 480 nm) was detected directly with laser flash photolysis of vinyl azide 1. The vinylnitrene intermediate was also characterized directly with IR and ESR spectroscopy in cryogenic matrices. The ESR spectrum of vinylnitrene (3)2 yielded a zero-field splitting parameter |D/hc| of 0...
October 22, 2016: Journal of the American Chemical Society
Nurettin Sahiner, Selin Sagbas, Mehtap Sahiner, Coskun Silan
Super porous poly(2-hydroxy ethyl methacrylate) (p(HEMA)) cryogel was successfully synthesized by using polyethylene glycol diacrylate (p(EGDA)) crosslinker under cryogenic conditions. Poly(Tannic acid) (p(TA)) macro-, micro-, and nanoparticles prepared from a natural polyphenol, tannic acid (TA), were embedded into p(HEMA) cryogel networks to obtain composite p(TA) particle-embedded p(HEMA) cryogel. Different size ranges of spherical p(TA) particles, 2000-500μm, 500-200μm, 200-20μm, and 20-0.5μm size, were included in the cryogel network and illustrated by digital camera, optic microscope, and SEM images of the microgel-cryogel network...
January 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
Terrence R Tiersch, William T Monroe
Development of devices through design, prototyping, testing, and fabrication is especially necessary for enhancement of research and eventual application in cryobiology. The advent of 3-dimensional printing offers unique opportunities for this process, given that the materials involved are suitable for use in cryogenic temperatures. We report herein that 3-D printing with polylactic acid (PLA) thermoplastic is ideally suited for cryobiology device development. Devices that are designed and standardized in open-source fashion can be electronically distributed and created locally on increasingly affordable 3-D printers, and can accelerate cryobiology findings and improve reproducibility of results...
October 18, 2016: Cryobiology
P H Kim, B D Hauer, C Doolin, F Souris, J P Davis
Reducing the moment of inertia improves the sensitivity of a mechanically based torque sensor, the parallel of reducing the mass of a force sensor, yet the correspondingly small displacements can be difficult to measure. To resolve this, we incorporate cavity optomechanics, which involves co-localizing an optical and mechanical resonance. With the resulting enhanced readout, cavity-optomechanical torque sensors are now limited only by thermal noise. Further progress requires thermalizing such sensors to low temperatures, where sensitivity limitations are instead imposed by quantum noise...
October 20, 2016: Nature Communications
Ivan Kozyryev, Louis Baum, Kyle Matsuda, John M Doyle
An experimentally feasible strategy for direct laser cooling of polyatomic molecules with six or more atoms is presented. Our approach relies on the attachment of a metal atom to a complex molecule, where it acts as an active photon cycling site. We describe a laser cooling scheme for alkaline earth monoalkoxide free radicals taking advantageof the phase space compression of a cryogenic buffer-gas beam. Possible applications are presented including laser cooling of chiral molecules and slowing of molecular beams using coherent photon processes...
October 19, 2016: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Petra Edlund, Heikki Takala, Elin Claesson, Léocadie Henry, Robert Dods, Heli Lehtivuori, Matthijs Panman, Kanupriya Pande, Thomas White, Takanori Nakane, Oskar Berntsson, Emil Gustavsson, Petra Båth, Vaibhav Modi, Shatabdi Roy-Chowdhury, James Zook, Peter Berntsen, Suraj Pandey, Ishwor Poudyal, Jason Tenboer, Christopher Kupitz, Anton Barty, Petra Fromme, Jake D Koralek, Tomoyuki Tanaka, John Spence, Mengning Liang, Mark S Hunter, Sebastien Boutet, Eriko Nango, Keith Moffat, Gerrit Groenhof, Janne Ihalainen, Emina A Stojković, Marius Schmidt, Sebastian Westenhoff
Phytochromes are a family of photoreceptors that control light responses of plants, fungi and bacteria. A sequence of structural changes, which is not yet fully understood, leads to activation of an output domain. Time-resolved serial femtosecond crystallography (SFX) can potentially shine light on these conformational changes. Here we report the room temperature crystal structure of the chromophore-binding domains of the Deinococcus radiodurans phytochrome at 2.1 Å resolution. The structure was obtained by serial femtosecond X-ray crystallography from microcrystals at an X-ray free electron laser...
October 19, 2016: Scientific Reports
S Saeidpour, S B Lohan, M Anske, M Unbehauen, E Fleige, R Haag, M C Meinke, R Bittl, C Teutloff
The skin and especially the stratum corneum (SC) act as a barrier and protect epidermal cells and thus the whole body against xenobiotica of the external environment. Topical skin treatment requires an efficient drug delivery system (DDS). Polymer-based nanocarriers represent novel transport vehicles for dermal application of drugs. In this study dendritic core-multishell (CMS) nanoparticles were investigated as promising candidates. CMS were loaded with a drug (analogue) and were applied to penetration studies of skin...
October 15, 2016: European Journal of Pharmaceutics and Biopharmaceutics
Ching-Yu Chou, Minglee Chu, Chi-Fon Chang, Tsunai Yu, Tai-Huang Huang, Dimitris Sakellariou
Field-dependent NMR studies of bio-molecular systems using a sample shuttling hardware operating on a high-field NMR apparatus have provided valuable structural and dynamic information. We have recently published a design of a compact sample transportation device, called "field-cycler", which was installed in a commercial spectrometer and which provided highly precise positioning and stability during high speed shuttling. In this communication, we demonstrate the first use of a sample shuttling device on a commercial high field standard bore NMR spectrometer, equipped with a commercial triple resonance cryogenically cooled NMR probe...
October 15, 2016: Journal of Biomolecular NMR
David A Riehm, David J Rokke, Prakash G Paul, Han Seung Lee, Brent S Vizanko, Alon V McCormick
Lecithin-rich mixtures of the nontoxic surfactants lecithin and Tween 80 are effective marine oil spill dispersants, but produce much higher oil-water interfacial tension than other, comparably effective dispersants. This suggests interfacial phenomena other than interfacial tension influence lecithin-Tween 80 dispersants' effectiveness. The interface between seawater and dispersant-crude oil mixtures was studied using light microscopy, cryogenic scanning electron microscopy, and droplet coalescence tests. Lecithin:Tween 80 ratio was varied from 100:0 to 0:100 and wt% dispersant in the oil was varied from 1...
October 5, 2016: Journal of Colloid and Interface Science
Y Chen, Kevin K Lehmann, Y Peng, L M Pratt, J R White, S B Cadieux, B Sherwood Lollar, G Lacrampe-Couloume, T C Onstott
In this study, near-infrared continuous wave cavity ring-down spectroscopy was applied to the measurement of the δ(2)H of methane (CH4). The cavity ring-down spectrometer (CRDS) system consisted of multiple DFB laser diodes to optimize selection of spectral line pairs. By rapidly switching measurements between spectral line peaks and the baseline regions, the long-term instrumental drift was minimized, substantially increasing measurement precision. The CRDS system coupled with a cryogenic pre-concentrator measured the δ(2)H of terrestrial atmospheric CH4 from 3 standard liters of air with a precision of ±1...
October 2016: Astrobiology
Lei Song, Johannes Kästner
Investigating how formamide forms in the interstellar medium is a hot topic in astrochemistry, which can contribute to our understanding of the origin of life on Earth. We have constructed a QM/MM model to simulate the hydrogenation of isocyanic acid on amorphous solid water surfaces to form formamide. The binding energy of HNCO on the ASW surface varies significantly between different binding sites, we found values between ∼0 and 100 kJ mol(-1). The barrier for the hydrogenation reaction is almost independent of the binding energy, though...
October 12, 2016: Physical Chemistry Chemical Physics: PCCP
Bolin Liao, A A Maznev, Keith A Nelson, Gang Chen
There is a growing interest in the mode-by-mode understanding of electron and phonon transport for improving energy conversion technologies, such as thermoelectrics and photovoltaics. Whereas remarkable progress has been made in probing phonon-phonon interactions, it has been a challenge to directly measure electron-phonon interactions at the single-mode level, especially their effect on phonon transport above cryogenic temperatures. Here we use three-pulse photoacoustic spectroscopy to investigate the damping of a single sub-terahertz coherent phonon mode by free charge carriers in silicon at room temperature...
October 12, 2016: Nature Communications
Andrea D Merg, Jennifer C Boatz, Abhishek Mandal, Gongpu Zhao, Soumitra Mokashi-Punekar, Chong Liu, Xianting Wang, Peijun Zhang, Patrick C A van der Wel, Nathaniel L Rosi
Chiral nanoparticle assemblies are an interesting class of materials whose chiroptical properties make them attractive for a variety of applications. Here, C18-(PEPAu(M-ox))2 (PEPAu(M-ox) = AYSSGAPPM(ox)PPF) is shown to direct the assembly of single-helical gold nanoparticle superstructures that exhibit exceptionally strong chiroptical activity at the plasmon frequency with absolute g-factor values up to 0.04. Transmission electron microscopy (TEM) and cryogenic electron tomography (cryo-ET) results indicate that the single helices have a periodic pitch of approximately 100 nm and consist of oblong gold nanoparticles...
October 11, 2016: Journal of the American Chemical Society
Yaser Kashcooli, Keunhan Park, Arijit Bose, Michael Lewis Greenfield, Geoffrey D Bothun
Layer-by-layer deposition of polyelectrolytes (PEs) onto self-assembled liposomes represents an alternative to PE deposition on solid particles for the formation of hollow nanoscale capsules. This work examines how competition between PE-liposome and inter-PE interactions drives the structure and colloidal stability of layersomes. Unlike solid particles, liposomes respond to adsorbed material through lipid reorganization and changes in size and shape. This responsive nature could yield new types of layered PE structures...
October 10, 2016: Biomacromolecules
Matias R Fagiani, Harald Knorke, Tim K Esser, Nadja Heine, Conrad T Wolke, Sandy Gewinner, Wieland Schöllkopf, Marie-Pierre Gaigeot, Riccardo Spezia, Mark A Johnson, Knut R Asmis
We use cryogenic ion trap vibrational spectroscopy to study the structure of the protonated water pentamer, H(+)(H2O)5, and its fully deuterated isotopologue, D(+)(D2O)5, over nearly the complete infrared spectral range (220-4000 cm(-1)) in combination with harmonic and anharmonic electronic structure calculations as well as RRKM modelling. Isomer-selective IR-IR double-resonance measurements on the H(+)(H2O)5 isotopologue establish that the spectrum is due to a single constitutional isomer, thus discounting the recent analysis of the band pattern in the context of two isomers based on AIMD simulations 〈W...
September 29, 2016: Physical Chemistry Chemical Physics: PCCP
Leïla Zerkoune, Sylviane Lesieur, Jean-Luc Putaux, Luc Choisnard, Annabelle Gèze, Denis Wouessidjewe, Borislav Angelov, Corinne Vebert-Nardin, James Doutch, Angelina Angelova
Soft mesoporous hierarchically structured particles were created by the self-assembly of an amphiphilic deep cavitand cyclodextrin βCD-nC10 (degree of substitution n = 7.3), with a nanocavity grafted by multiple alkyl (C10) chains on the secondary face of the βCD macrocycle through enzymatic biotransesterification, and the nonlamellar lipid monoolein (MO). The effect of the non-ionic dispersing agent polysorbate 80 (P80) on the liquid crystalline organization of the nanocarriers and their stability was studied in the context of vesicle-to-cubosome transition...
September 13, 2016: Soft Matter
Sonia Álvarez-Barcia, Marie-Sophie Russ, Jan Meisner, Johannes Kästner
The title reaction is involved in the formation of ammonia in the interstellar medium. We have calculated thermal rates including atom tunnelling using different rate theories. Canonical variational theory with microcanonically optimised multidimensional tunnelling was used for bimolecular rates, modelling the gas-phase reaction and also a surface-catalysed reaction of the Eley-Rideal type. Instanton theory provided unimolecular rates, which model the Langmuir-Hinshelwood type surface reaction. The potential energy was calculated on the CCSD(T)-F12 level of theory on the fly...
September 29, 2016: Faraday Discussions
R Alonso-Mori, K Asa, U Bergmann, A S Brewster, R Chatterjee, J K Cooper, H M Frei, F D Fuller, E Goggins, S Gul, H Fukuzawa, D Iablonskyi, M Ibrahim, T Katayama, T Kroll, Y Kumagai, B A McClure, J Messinger, K Motomura, K Nagaya, T Nishiyama, C Saracini, Y Sato, N K Sauter, D Sokaras, T Takanashi, T Togashi, K Ueda, W W Weare, T-C Weng, M Yabashi, V K Yachandra, I D Young, A Zouni, J F Kern, J Yano
The ultra-bright femtosecond X-ray pulses provided by X-ray Free Electron Lasers (XFELs) open capabilities for studying the structure and dynamics of a wide variety of biological and inorganic systems beyond what is possible at synchrotron sources. Although the structure and chemistry at the catalytic sites have been studied intensively in both biological and inorganic systems, a full understanding of the atomic-scale chemistry requires new approaches beyond the steady state X-ray crystallography and X-ray spectroscopy at cryogenic temperatures...
September 14, 2016: Faraday Discussions
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