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https://www.readbyqxmd.com/read/28241579/direct-diode-pumped-ti-sapphire-ultrafast-regenerative-amplifier-system
#1
Sterling Backus, Matt Kirchner, Randy Lemons, David Schmidt, Charles Durfee, Margaret Murnane, Henry Kapteyn
We report on a direct diode-pumped Ti:sapphire ultrafast regenerative amplifier laser system producing multi-μJ energies with a repetition rate from 50 to 250 kHz. By combining cryogenic cooling of Ti:sapphire with high brightness fiber-coupled 450nm laser diodes, we for the first time demonstrate a power-scalable CW-pumped architecture that can be directly applied to demanding ultrafast applications such as coherent high-harmonic EUV generation without any complex post-amplification pulse compression. Initial results promise a new era for Ti:sapphire amplifiers not only for ultrafast laser applications, but also for tunable CW sources...
February 20, 2017: Optics Express
https://www.readbyqxmd.com/read/28237331/an-optimized-method-for-cryogenic-storage-of-xenopus-sperm-to-maximise-the-effectiveness-of-research-using-genetically-altered-frogs
#2
Esther Pearl, Sean Morrow, Anna Noble, Adelaide Lerebours, Marko Horb, Matthew Guille
Cryogenic storage of sperm from genetically altered Xenopus improves cost effectiveness and animal welfare associated with their use in research; currently it is routine for X. tropicalis but not reliable for X. laevis. Here we compare directly the three published protocols for Xenopus sperm freeze-thaw and determine whether sperm storage temperature, method of testes maceration and delays in the freezing protocols affect successful fertilisation and embryo development in X. laevis. We conclude that the protocol is robust and that the variability observed in fertilisation rates is due to differences between individuals...
April 1, 2017: Theriogenology
https://www.readbyqxmd.com/read/28236790/multi-scale-characterization-of-thermoresponsive-dendritic-elastin-like-peptides
#3
Mingjun Zhou, Yulia Shmidov, John B Matson, Ronit Bitton
Elastin like peptides (ELPs)-polypeptides based on the protein elastin-are used widely as thermoresponsive components in biomaterials due to the presence of a sharp soluble-to-insoluble phase change at a characteristic transition temperature (Tt). While linear ELPs have been thoroughly studied, few investigations into branched ELPs have been carried out. Using lysine amino acids as branching and terminal units with 1-3 pentameric repeats between each branch, ELP dendrimers were prepared by solid-phase peptide synthesis with molecular weights as high as 14kDa...
February 16, 2017: Colloids and Surfaces. B, Biointerfaces
https://www.readbyqxmd.com/read/28231148/potential-use-of-gamma-irradiated-ethnic-ready-to-eat-foods-to-improve-the-nutritional-status-of-landslide-victims
#4
REVIEW
Zubaidah Irawati Koenari, Carmen M Siagian, Bona Simanungkalit, Asti Nilatany, Indra Mustika Pratama, Deudeu Lasmawati, Cecep M Nurcahya
The safety and high quality of ethnic ready-to-eat foods as a source of nourishment and food supplies chain to the remote areas become particularly important. Consuming healthy and balanced nutritional foods means eating better quality foods in proper quantities. Such foods can be developed through a preservation technique by using ionizing radiation. Although implementation of the technology for certain foodstuffs has been implemented in some countries, application of the process to a complete set of meals for selected target groups is still very limited...
July 26, 2016: Foods (Basel, Switzerland)
https://www.readbyqxmd.com/read/28228169/characterization-of-sulfur-and-nanostructured-sulfur-battery-cathodes-in-electron-microscopy-without-sublimation-artifacts
#5
Barnaby D A Levin, Michael J Zachman, Jörg G Werner, Ritu Sahore, Kayla X Nguyen, Yimo Han, Baoquan Xie, Lin Ma, Lynden A Archer, Emmanuel P Giannelis, Ulrich Wiesner, Lena F Kourkoutis, David A Muller
Lithium sulfur (Li-S) batteries have the potential to provide higher energy storage density at lower cost than conventional lithium ion batteries. A key challenge for Li-S batteries is the loss of sulfur to the electrolyte during cycling. This loss can be mitigated by sequestering the sulfur in nanostructured carbon-sulfur composites. The nanoscale characterization of the sulfur distribution within these complex nanostructured electrodes is normally performed by electron microscopy, but sulfur sublimates and redistributes in the high-vacuum conditions of conventional electron microscopes...
February 2017: Microscopy and Microanalysis
https://www.readbyqxmd.com/read/28219400/alleviation-of-secondary-brain-injury-posttraumatic-inflammation-and-brain-edema-formation-by-inhibition-of-factor-xiia
#6
Sarah Hopp, Marc W Nolte, Christian Stetter, Christoph Kleinschnitz, Anna-Leena Sirén, Christiane Albert-Weissenberger
BACKGROUND: Traumatic brain injury (TBI) is a devastating neurological condition and a frequent cause of permanent disability. Posttraumatic inflammation and brain edema formation, two pathological key events contributing to secondary brain injury, are mediated by the contact-kinin system. Activation of this pathway in the plasma is triggered by activated factor XII. Hence, we set out to study in detail the influence of activated factor XII on the abovementioned pathophysiological features of TBI...
February 20, 2017: Journal of Neuroinflammation
https://www.readbyqxmd.com/read/28218750/quaternary-contact-in-the-initial-interaction-of-cd4-with-the-hiv-1-envelope-trimer
#7
Qingbo Liu, Priyamvada Acharya, Michael A Dolan, Peng Zhang, Christina Guzzo, Jacky Lu, Alice Kwon, Deepali Gururani, Huiyi Miao, Tatsiana Bylund, Gwo-Yu Chuang, Aliaksandr Druz, Tongqing Zhou, William J Rice, Christoph Wigge, Bridget Carragher, Clinton S Potter, Peter D Kwong, Paolo Lusso
Binding of the gp120 envelope (Env) glycoprotein to the CD4 receptor is the first step in the HIV-1 infectious cycle. Although the CD4-binding site has been extensively characterized, the initial receptor interaction has been difficult to study because of major CD4-induced structural rearrangements. Here we used cryogenic electron microscopy (cryo-EM) to visualize the initial contact of CD4 with the HIV-1 Env trimer at 6.8-Å resolution. A single CD4 molecule is embraced by a quaternary HIV-1-Env surface formed by coalescence of the previously defined CD4-contact region with a second CD4-binding site (CD4-BS2) in the inner domain of a neighboring gp120 protomer...
February 20, 2017: Nature Structural & Molecular Biology
https://www.readbyqxmd.com/read/28217785/surfactant-free-microemulsions-of-1-butyl-3-methylimidazolium-hexafluorophosphate-propylamine-nitrate-and-water
#8
Jie Xu, Huanhuan Deng, Yunlei Fu, Yuquan Chen, Jing Zhang, Wanguo Hou
Generally, surfactants (or amphiphiles) are believed to be necessary components of microemulsions. However, it has been demonstrated that, in the absence of traditional surfactants, microemulsions can also form from a ternary system of two immiscible fluids (i.e., oil and water phases) and an amphi-solvent, but the current understanding of such surfactant-free microemulsions (SFMEs) is very limited. Herein, we report an SFME consisting of the hydrophobic ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6), the protic IL propylamine nitrate (PAN), and water, in which bmimPF6 and PAN are used as the oil phase and the amphi-solvent, respectively...
February 20, 2017: Soft Matter
https://www.readbyqxmd.com/read/28212663/isolation-of-primary-microglia-from-the-human-post-mortem-brain-effects-of-ante-and-post-mortem-variables
#9
Mark R Mizee, Suzanne S M Miedema, Marlijn van der Poel, Adelia, Karianne G Schuurman, Miriam E van Strien, Jeroen Melief, Joost Smolders, Debbie A Hendrickx, Kirstin M Heutinck, Jörg Hamann, Inge Huitinga
Microglia are key players in the central nervous system in health and disease. Much pioneering research on microglia function has been carried out in vivo with the use of genetic animal models. However, to fully understand the role of microglia in neurological and psychiatric disorders, it is crucial to study primary human microglia from brain donors. We have developed a rapid procedure for the isolation of pure human microglia from autopsy tissue using density gradient centrifugation followed by CD11b-specific cell selection...
February 17, 2017: Acta Neuropathologica Communications
https://www.readbyqxmd.com/read/28212035/ultrafast-time-resolved-x-ray-absorption-spectroscopy-of-ferrioxalate-photolysis-with-a-laser-plasma-x-ray-source-and-microcalorimeter-array
#10
Galen C O'Neil, Luis Miaja-Avila, Young Il Joe, Bradley K Alpert, Mahalingam Balasubramanian, D M Sagar, William Doriese, Joseph W Fowler, Wilfred K Fullagar, Ning Chen, Gene C Hilton, Ralph Jimenez, Bruce Ravel, Carl D Reintsema, Dan R Schmidt, Kevin L Silverman, Daniel S Swetz, Jens Uhlig, Joel N Ullom
The detailed pathways of photoactivity on ultrafast time scales are a topic of contemporary interest. Using a tabletop apparatus based on a laser plasma X-ray source and an array of cryogenic microcalorimeter X-ray detectors, we measured a transient X-ray absorption spectrum during the ferrioxalate photoreduction reaction. With these high-efficiency detectors, we observe the Fe K edge move to lower energies and the amplitude of the extended X-ray absorption fine structure reduce, consistent with a photoreduction mechanism in which electron transfer precedes disassociation...
February 22, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28199220/critical-analysis-of-soft-point-contact-andreev-reflection-spectra-between-superconducting-films-and-pressed-in
#11
Pradnya Parab, Prashant Chauhan, H Muthurajan, Sangita Bose
We present a critical analysis of an alternative technique of point contact Andreev reflection (PCAR) spectroscopy used to extract energy resolved information of superconductors which is based on making 'soft-contacts' between superconductors and indium. This technique is not sensitive to mechanical vibrations and hence can be used in a cryogen free platform increasing its accessibility to users having no access to cryogenic liquids. Through our experiments on large number of superconducting films we show that the PCAR spectra below the T c of In show sub-harmonic gap structures consistent with the theory of multiple Andreev reflection (MAR) and a zero bias conductance (ZBC) anomaly associated with the Josephson supercurrent...
February 15, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28198845/picosecond-kilohertz-class-cryogenically-cooled-multistage-yb-doped-chirped-pulse-amplifier
#12
F X Morrissey, T Y Fan, D E Miller, D Rand
A multistage cryogenic chirped pulse amplifier has been developed, utilizing two different Yb-doped gain materials in subsequent amplifier stages. A Yb:GSAG regenerative amplifier followed by a Yb:YAG power amplifier is able to deliver pulses with a broader bandwidth than a system using only one of these two gain media throughout. We demonstrate 90 mJ of pulse energy (113 W of average power) uncompressed and 67 mJ (84 W of average power) compressed at 1.25 kHz pulse repetition frequency, 3.0 ps FWHM Gaussian pulse width, and near-diffraction-limited (M<sup>2</sup><1...
February 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28197783/freezing-nitrogen-ethanol-composite-may-be-a-viable-approach-for-cryotherapy-of-human-giant-cell-tumor-of-bone
#13
Po-Kuei Wu, Cheng-Fong Chen, Jir-You Wang, Paul Chih-Hsueh Chen, Ming-Chau Chang, Shih-Chieh Hung, Wei-Ming Chen
BACKGROUND: Liquid nitrogen has been used as adjuvant cryotherapy for treating giant cell tumor (GCT) of bone. However, the liquid phase and ultrafreezing (-196° C) properties increase the risk of damage to the adjacent tissues and may lead to perioperative complications. A novel semisolid cryogen, freezing nitrogen ethanol composite, might mitigate these shortcomings because of less-extreme freezing. We therefore wished to evaluate freezing nitrogen ethanol composite as a coolant to determine its properties in tumor cryoablation...
February 14, 2017: Clinical Orthopaedics and related Research
https://www.readbyqxmd.com/read/28177622/photoinduced-reductive-elimination-of-h2-from-the-nitrogenase-dihydride-janus-state-involves-a-femo-cofactor-h2-intermediate
#14
Dmitriy Lukoyanov, Nimesh Khadka, Dennis R Dean, Simone Raugei, Lance C Seefeldt, Brian M Hoffman
N2 reduction by nitrogenase involves the accumulation of four reducing equivalents at the active site FeMo-cofactor to form a state with two [Fe-H-Fe] bridging hydrides (denoted E4(4H), the Janus intermediate), and we recently demonstrated that the enzyme is activated to cleave the N≡N triple bond by the reductive elimination (re) of H2 from this state. We are exploring a photochemical approach to obtaining atomic-level details of the re activation process. We have shown that, when E4(4H) at cryogenic temperatures is subjected to 450 nm irradiation in an EPR cavity, it cleanly undergoes photoinduced re of H2 to give a reactive doubly reduced intermediate, denoted E4(2H)*, which corresponds to the intermediate that would form if thermal dissociative re loss of H2 preceded N2 binding...
February 20, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28177030/infrared-spectroscopic-study-of-absorption-and-separation-of-co-using-copper-i-containing-ionic-liquids
#15
Stephen E Repper, Anthony Haynes, Evert J Ditzel, Glenn J Sunley
Absorption of carbon monoxide by copper(i)-containing ionic liquids, [Cnmim][CuX2] (Cnmim = 1-alkyl-3-methylimidazolium, n = 2, 4, 6, X = Cl, Br, I) has been investigated using in situ high pressure infrared spectroscopy. For each liquid, observation of a ν(CO) band in the region 2075-2090 cm(-1) indicates the formation of copper(i) monocarbonyl complexes, assigned as [Cu(CO)X2](-). The rate of growth and equilibrium intensity of the ν(CO) absorption is dependent on applied CO pressure. Binding of CO is reversible such that complete desorption occurs rapidly on heating above 100 °C and the liquids are robust over multiple gas absorption/desorption cycles...
February 8, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28170156/micelles-versus-ribbons-how-congeners-drive-the-self-assembly-of-acidic-sophorolipid-biosurfactants
#16
Prabhu Dhasaiyan, Patrick Le Griel, Sophie Roelants, Emile Redant, Inge N A Van Bogaert, Sylvain Prevost, B L V Prasad, Niki Baccile
Sophorolipids (SLs), a class of microbially derived biosurfactants, are reported by different research groups to have different self-assembled structures (either micelles or giant ribbons) under the same conditions. Here we explore the reasons behind these contradictory results and attribute these differences to the role of specific congeners that are present in minute quantities. We show that a sample composed of a majority of oleic acid (C18:1) sophorolipid in the presence of only 0.5 % (or more) of congeners with stearic acid (C18:0) or linoleic acid (C18:2) results in the formation of micelles that are stable over long periods of time...
February 7, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28157867/wavelength-tuning-in-cryogenically-cooled-lasers-based-on-er-doped-orthovanadates
#17
Nikolay Ter-Gabrielyan, Viktor Fromzel
Continuous tuning between 1590 and 1612 nm has been demonstrated in cryogenically cooled lasers with composite active media consisting of Er:YVO<sub>4</sub>, Er:LuVO<sub>4</sub>, and Er:GdVO<sub>4</sub> crystals resonantly pumped by a fiber-coupled laser diode emitting at 1529 nm. Wavelength tuning was implemented using an intracavity single-plate birefringent filter.
January 20, 2017: Applied Optics
https://www.readbyqxmd.com/read/28154426/a-new-experiment-for-investigating-evaporation-and-condensation-of-cryogenic-propellants
#18
K Bellur, E F Médici, M Kulshreshtha, V Konduru, D Tyrewala, A Tamilarasan, J McQuillen, J Leao, D S Hussey, D L Jacobson, J Scherschligt, J C Hermanson, C K Choi, J S Allen
Passive and active technologies have been used to control propellant boil-off, but the current state of understanding of cryogenic evaporation and condensation in microgravity is insufficient for designing large cryogenic depots critical to the long-term space exploration missions. One of the key factors limiting the ability to design such systems is the uncertainty in the accommodation coefficients (evaporation and condensation), which are inputs for kinetic modeling of phase change. A novel, combined experimental and computational approach is being used to determine the accommodation coefficients for liquid hydrogen and liquid methane...
March 2016: Cryogenics
https://www.readbyqxmd.com/read/28151688/structural-insights-into-a-hemoglobin-albumin-cluster-in-aqueous-medium
#19
Ryuichi Shinohara, Taiga Yamada, Boris Schade, Christoph Böttcher, Takaaki Sato, Natsuhiko Sugimura, Toshimichi Shibue, Teruyuki Komatsu
A hemoglobin (Hb) wrapped covalently by three human serum albumins (HSAs) is a triangular protein cluster designed as an artificial O2-carrier and red blood cell substitute. We report the structural insights into this Hb-HSA3 cluster in aqueous medium revealed by 3D reconstruction based on cryogenic transmission electron microscopy (cryo-TEM) data and small-angle X-ray scattering (SAXS) measurements. Cryo-TEM observations showed individual particles with approximately 15 nm diameter in the vitrified ice layer...
February 6, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28151674/electrostatic-asymmetry-in-the-reaction-center-of-photosystem-ii
#20
Frank Müh, Melanie Plöckinger, Thomas Renger
The exciton Hamiltonian of the chlorophyll (Chl) and pheophytin (Pheo) pigments in the reaction center (RC) of photosystem II is computed based on recent crystal structures by using the Poisson-Boltzmann/quantum-chemical method. Computed site energies largely confirm a previous model inferred from fits of optical spectra, in which ChlD1 has the lowest site energy, while that of PheoD1 is higher than that of PheoD2. The latter assignment has been challenged recently under reference to mutagenesis experiments...
February 7, 2017: Journal of Physical Chemistry Letters
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