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Vito Rizzi, Davide Vurro, Tiziana Placido, Paola Fini, Andrea Petrella, Paola Semeraro, Pinalysa Cosma
The stability of Chlorophyll a in water during prolonged exposure, at room temperature, to a neon lamp has been investigated by means of UV-vis and fluorescence spectroscopies. In addition, the Chlorophyll a (photo)stability evaluation in presence of suitable carriers has been performed in order to investigate its reactivity under the same conditions, for possible and future applications in Antimicrobial Photodynamic Therapy. Cetyltrimethylammonium chloride was chosen to solubilize Chlorophyll a in water. While, cetyltrimethylammonium chloride-capped gold nanoparticles offer a great opportunity because combine the Chlorophyll a action, used as a photosensitizer in Antimicrobial Photodynamic Therapy, with gold nanoparticles effect used in photothermal therapy...
November 9, 2017: Colloids and Surfaces. B, Biointerfaces
A Kortyna, A J Samin, T A Miller, D J Nesbitt
Highly reactive benzyl radicals are generated by electron dissociative attachment to benzyl chloride doped into a neon-hydrogen-helium discharge and immediately cooled to Trot = 15 K in a high density, supersonic slit expansion environment. The sub-Doppler spectra are fit to an asymmetric-top rotational Hamiltonian, thereby yielding spectroscopic constants for the ground (v = 0) and first excited (v = 1, ν3, ν4) vibrational levels of the ground electronic state. The rotational constants obtained for the ground state are in good agreement with previous laser induced fluorescence measurements (LIF), with vibrational band origins (ν3 = 3073...
November 3, 2017: Physical Chemistry Chemical Physics: PCCP
M Isinger, R J Squibb, D Busto, S Zhong, A Harth, D Kroon, S Nandi, C L Arnold, M Miranda, J M Dahlström, E Lindroth, R Feifel, M Gisselbrecht, A L'Huillier
Ultrafast processes in matter, such as the electron emission after light absorption, can now be studied using ultrashort light pulses of attosecond duration (10(-18) seconds) in the extreme ultraviolet spectral range. The lack of spectral resolution due to the use of short light pulses has raised issues in the interpretation of the experimental results and the comparison with theoretical calculations. We determine photoionization time delays in neon atoms over a 40-electron volt energy range with an interferometric technique combining high temporal and spectral resolution...
November 17, 2017: Science
Ruirui Zhao, Ding Wang, Yu Zhao, Yuxin Leng, Ruxin Li
A method of temporally compressing picosecond pulses is proposed. To increase the spectral broadening, two picosecond pulses at different central wavelengths are overlapped spatiotemporally to induce a modulation on the intensity envelope, thus leading to a high temporal intensity gradient. The combined pulse is then coupled into a gas-filled hollow-core fiber (HCF) to broaden the spectrum through nonlinear propagation. After that the pulse can be compressed by chirp compensation. This method is demonstrated numerically with two 1-ps/5-mJ pulses centered at 1053- and 1064-nm, respectively, which are coupled into a 250-μm-inner-diameter, 1-m-long HCF filled with 5-bar neon...
October 30, 2017: Optics Express
Wenjie Yu, Lester Andrews, Xuefeng Wang
Laser ablated Be atoms, cations and electrons were reacted with F2, ClF, Cl2, NF3, CCl4, CF2Cl2, HCl, DCl, and SiCl4 diluted in noble gases. The major products were the dihalides BeF2, BeClF, BeCl2 and the hydride chloride HBeCl whose identities were confirmed by comparison with previous evaporative work, deuterium substitution, and vibrational frequency calculations. The matrix isolated BeF molecule fundamental frequency is higher and the BeCl frequency is lower than determined for the gas phase molecules, respectively...
November 1, 2017: Journal of Physical Chemistry. A
Eliza L Congdon, Miriam A Novack, Neon Brooks, Naureen Hemani-Lopez, Lucy O'Keefe, Susan Goldin-Meadow
When teachers gesture during instruction, children retain and generalize what they are taught (Goldin-Meadow, 2014). But why does gesture have such a powerful effect on learning? Previous research shows that children learn most from a math lesson when teachers present one problem-solving strategy in speech while simultaneously presenting a different, but complementary, strategy in gesture (Singer & Goldin-Meadow, 2005). One possibility is that gesture is powerful in this context because it presents information simultaneously with speech...
August 2017: Learning and Instruction
Yu Zhao, Ding Wang, Ruirui Zhao, Yuxin Leng
The compression of high-energy, radially polarized pulses in a gas-filled hollow-core fiber (HCF) is theoretically studied. The simulation results indicate that a 40-fs input pulse can be compressed to a full-width at half-maximum of less than 9 fs when the pulse energy reaches 7.0 mJ with a transmission efficiency of more than 67% after propagating through a 1-m-long, 500-μm diameter HCF filled with neon. Furthermore, the spatio-temporal intensity distributions of the compressed pulses with different initial input energies are studied, and the numerical results indicate that the spatio-temporal intensity distributions are more uniform for lower input pulse energies...
August 21, 2017: Optics Express
Satoru Muramatsu, Xuan Wu, Mohua Chen, Mingfei Zhou, Tatsuya Tsukuda
Infrared spectroscopy and density functional theory calculations showed that the gold complexes [CH3-Au-I] and [(CH3)2-Au-I2], in which one and two CH3I molecule(s), respectively, are oxidatively adsorbed on the Au atoms, are formed in a solid neon matrix via reactions between laser-ablated gold atoms and CH3I. Global reaction route mapping calculations revealed that the heights of the activation barriers for the sequential oxidative additions to produce [CH3-Au-I] and [(CH3)2-Au-I2] are 0.53 and 1.00 eV, respectively, suggesting that the reactions proceed via electronically excited states...
October 31, 2017: Journal of Physical Chemistry. A
Phoebe C M Williams, David Isaacs, James A Berkley
Antimicrobial resistance is an important threat to international health. Therapeutic guidelines for empirical treatment of common life-threatening infections depend on available information regarding microbial aetiology and antimicrobial susceptibility, but sub-Saharan Africa lacks diagnostic capacity and antimicrobial resistance surveillance. We systematically reviewed studies of antimicrobial resistance among children in sub-Saharan Africa since 2005. 18 of 1075 articles reviewed met inclusion criteria, providing data from 67 451 invasive bacterial isolates from inconsistently defined populations in predominantly urban tertiary settings...
October 9, 2017: Lancet Infectious Diseases
Tobias Fahleson, Patrick Norman
The second-order nonlinear (or cubic) response function is derived from the Ehrenfest theorem with inclusion made of the finite lifetimes of the excited states, representing the extension of the derivation of the quadratic response function in the same framework [P. Norman et al., J. Chem. Phys. 123, 194103 (2005)]. The resulting damped response functions are physically sound and converging also in near-resonance and resonance regions of the spectrum. Being an accurate approximation for small complex frequencies (defined as the sum of an optical frequency and an imaginary damping parameter), the polynomial expansion of the complex cubic response function in terms of the said frequencies is presented and used to validate the program implementation...
October 14, 2017: Journal of Chemical Physics
Han-Yuan Liu, Wei-Liang Chen, Christopher K Ober, Susan Daniel
Reconstituted supported lipid bilayers (SLB) are widely used as in vitro cell-surface models because they are compatible with a variety of surface-based analytical techniques. However, one of the challenges of using SLBs as a model of the cell surface is the limited complexity in membrane composition, including the incorporation of transmembrane proteins and lipid diversity that may impact the activity of those proteins. Additionally, it is challenging to preserve the transmembrane protein native orientation, function, and mobility in SLBs...
October 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Richard Behringer, Marina Gertsenstein, Kristina Vintersten Nagy, Andras Nagy
Mouse embryonic fibroblasts can be reprogrammed to embryonic stem (ES) cell-like pluripotent stem cells by the forced expression of four transcription factors-OCT4, SOX2, KLF4, and c-MYC. The piggyBac transposon system has proven effective as a vehicle for the delivery of transgenes into fibroblasts and for successful reprogramming to induced pluripotent stem (iPS) cells. This protocol is designed for use with the Neon electroporation system. It can be adapted to other types of electroporation systems.
October 3, 2017: Cold Spring Harbor Protocols
Nicholas D Embleton, Chris Hp Van Den Akker
No abstract text is available yet for this article.
September 27, 2017: Archives of Disease in Childhood. Fetal and Neonatal Edition
V K Saini, P Kumar, K K Sarangpani, S K Dixit, S V Nakhe
Development of a demountable and see-through hollow cathode (HC) discharge lamp suitable for optogalvanic (OG) spectroscopy is described. The design of the HC lamp is simple, compact, and inexpensive. Lithium, investigated rarely by the OG method, is selected for cathode material as its isotopes are important for nuclear industry. The HC lamp is characterized electrically and optically for discharge oscillations free OG effect. Strong OG signals of lithium as well as neon (as buffer gas) are produced precisely upon copper vapor laser pumped tunable dye laser irradiation...
September 2017: Review of Scientific Instruments
C J E Straatsma, M I Fabrikant, G E Douberly, H J Lewandowski
Cryogenic buffer-gas beam sources are capable of producing intense beams of a wide variety of molecules and have a number of advantages over traditional supersonic expansion sources. In this work, we report on a neon matrix isolation study of carbon clusters produced with a cryogenic buffer-gas beam source. Carbon clusters created by laser ablation of graphite are trapped in a neon matrix and detected with a Fourier-transform infrared spectrometer in the spectral range 4000-1000 cm(-1). Through a study of carbon cluster production as a function of various system parameters, we characterize the behavior of the buffer-gas beam source and find that approximately 10(11)-10(12) of each cluster is produced with each pulse of the ablation laser...
September 28, 2017: Journal of Chemical Physics
Tsveta Miteva, Sévan Kazandjian, Přemysl Kolorenč, Petra Votavová, Nicolas Sisourat
Inner-valence ionized states of atoms and molecules live shorter if these species are embedded in an environment due to the possibility for ultrafast deexcitation known as interatomic Coulombic decay (ICD). In this Letter we show that the lifetime of these ICD active states decreases further when a bridge atom is in proximity to the two interacting monomers. This novel mechanism, termed superexchange ICD, is an electronic correlation effect driven by the efficient energy transfer via virtual states of the bridge atom...
August 25, 2017: Physical Review Letters
D Iablonskyi, K Ueda, K L Ishikawa, A S Kheifets, P Carpeggiani, M Reduzzi, H Ahmadi, A Comby, G Sansone, T Csizmadia, S Kuehn, E Ovcharenko, T Mazza, M Meyer, A Fischer, C Callegari, O Plekan, P Finetti, E Allaria, E Ferrari, E Roussel, D Gauthier, L Giannessi, K C Prince
Single-photon laser-enabled Auger decay (spLEAD) is predicted theoretically [B. Cooper and V. Averbukh, Phys. Rev. Lett. 111, 083004 (2013)PRLTAO0031-900710.1103/PhysRevLett.111.083004] and here we report its first experimental observation in neon. Using coherent, bichromatic free-electron laser pulses, we detect the process and coherently control the angular distribution of the emitted electrons by varying the phase difference between the two laser fields. Since spLEAD is highly sensitive to electron correlation, this is a promising method for probing both correlation and ultrafast hole migration in more complex systems...
August 18, 2017: Physical Review Letters
T Bryk, F A Gorelli, I Mryglod, G Ruocco, M Santoro, T Scopigno
The "Frenkel line" (FL), the thermodynamic locus where the time for a particle to move by its size equals the shortest transverse oscillation period, has been proposed as a boundary between recently discovered liquid-like and gas-like regions in supercritical fluids. We report a simulation study of isothermal supercritical neon in a range of densities intersecting the FL. Specifically, structural properties and single-particle and collective dynamics are scrutinized to unveil the onset of any anomalous behavior at the FL...
September 29, 2017: Journal of Physical Chemistry Letters
Vladimir E Ivanov, Anna M Usacheva, Anatoly V Chernikov, Vadim I Bruskov, Sergey V Gudkov
It was demonstrated that low-intensity radiation of helium-neon (He-Ne) laser at 632.8nm, which leads to the transition of oxygen to a singlet state, causes the formation of reactive oxygen species (ROS) - hydrogen peroxide, hydroxyl and superoxide (hydroperoxide) radicals - in aqueous solutions. The oxygen effect - dependence of hydrogen peroxide formation on the concentration of molecular oxygen - was shown, and the participation of singlet oxygen, hydroxyl radicals and superoxide (hydroperoxide) radicals in this process was testified...
September 14, 2017: Journal of Photochemistry and Photobiology. B, Biology
Jiwen Jian, Wei Li, Xuan Wu, Mingfei Zhou
The organo-boron species formed from the reactions of boron atoms with acetylene in solid neon are investigated using matrix isolation infrared spectroscopy with isotopic substitutions as well as quantum chemical calculations. Besides the previously reported single C-H bond activation species, a cyclic-HBC2BH diboron species is formed via double C-H bond activation of acetylene. It is characterized to have a closed-shell singlet ground state with planar D2h symmetry. Bonding analysis indicates that it is a doubly aromatic species involving two delocalized σ electrons and two delocalized π electrons...
June 1, 2017: Chemical Science
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