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https://www.readbyqxmd.com/read/28548509/ultrafast-reversal-of-the-ferroelectric-polarization
#1
R Mankowsky, A von Hoegen, M Först, A Cavalleri
We report on the demonstration of ultrafast optical reversal of the ferroelectric polarization in LiNbO_{3}. Rather than driving the ferroelectric mode directly, we couple to it indirectly by resonant excitation of an auxiliary high-frequency phonon mode with femtosecond midinfrared pulses. Because of strong anharmonic coupling between these modes, the atoms are directionally displaced along the ferroelectric mode and the polarization is transiently reversed, as revealed by time-resolved, phase-sensitive, second-harmonic generation...
May 12, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28547763/new-approaches-towards-the-understanding-of-integral-membrane-proteins-a-structural-perspective-on-g-protein-coupled-receptors
#2
REVIEW
Reinhard Grisshammer
Three-dimensional structure determination of integral membrane proteins has advanced in unprecedented detail our understanding of mechanistic events of how ion channels, transporters, receptors and enzymes function. This exciting progress required a tremendous amount of methods development, as exemplified here with G protein-coupled receptors (GPCRs): Optimizing the production of GPCRs in recombinant hosts; increasing the probability of crystal formation using high-affinity ligands, nanobodies, and minimal G proteins for co-crystallization, thus stabilizing receptors into one conformation; using the T4 lysozyme technology and other fusion partners to promote crystal contacts; advancing crystallization methods including the development of novel detergents, and miniaturization and automation of the lipidic cubic phase crystallization method; the concept of conformational thermostabilization of GPCRs; and developing microfocus X-ray synchrotron technologies to analyze small GPCR crystals...
May 25, 2017: Protein Science: a Publication of the Protein Society
https://www.readbyqxmd.com/read/28546559/mapping-few-femtosecond-slices-of-ultra-relativistic-electron-bunches
#3
Tim Plath, Christoph Lechner, Velizar Miltchev, Philipp Amstutz, Nagitha Ekanayake, Leslie Lamberto Lazzarino, Theophilos Maltezopoulos, Jörn Bödewadt, Tim Laarmann, Jörg Roßbach
Free-electron lasers are unique sources of intense and ultra-short x-ray pulses that led to major scientific breakthroughs across disciplines from matter to materials and life sciences. The essential element of these devices are micrometer-sized electron bunches with high peak currents, low energy spread, and low emittance. Advanced FEL concepts such as seeded amplifiers rely on the capability of analyzing and controlling the electron beam properties with few-femtosecond time resolution. One major challenge is to extract tomographic slice parameters instead of projected electron beam properties...
May 25, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28546151/comparison-of-intraocular-pressure-during-the-application-of-a-liquid-patient-interface-femto-ldv-z8-for-femtosecond-laser-assisted-cataract-surgery-using-two-different-vacuum-levels
#4
Martina Ebner, Siegfried Mariacher, Kai Januschowski, Katrin Boden, Anna-Maria Seuthe, Peter Szurman, Karl Thomas Boden
BACKGROUND: To evaluate intraocular pressure (IOP) using the application of a novel liquid patient interface for femtosecond laser-assisted cataract surgery with the FEMTO LDV Z8. METHODS: IOP was evaluated in enucleated porcine eyes prior, during and after the application of the Femto LDV Z8 liquid patient interface (Ziemer Ophthalmic Systems, Switzerland) using intracameral cannulation (n=20), intravitreal cannulation (n=20), rebound tonometry (n=20) and indentation tonometry (n=20)...
May 25, 2017: British Journal of Ophthalmology
https://www.readbyqxmd.com/read/28544745/fs-laser-ablation-of-teeth-is-temperature-limited-and-provides-information-about-the-ablated-components
#5
Rebeca Ferraz de Menezes, Catherine Malinda Harvey, Marleny Elizabeth Márquez de Martínez Gerbi, Zachary J Smith, Dan Smith, Juan C Ivaldi, Alton Phillips, James W Chan, Sebastian Wachsmann-Hogiu
The goal of this work is to investigate the thermal effects of femtosecond laser (fs-laser) ablation for the removal of carious dental tissue. Additional studies identify different tooth tissues through femtosecond laser induced breakdown spectroscopy (fsLIBS) for the development of a feedback loop that could be utilized during ablation in a clinical setting. Scanning Election Microscope (SEM) images reveal that minimal morphological damages are incurred at repetition rates below the carbonization threshold of each tooth tissue...
May 24, 2017: Journal of Biophotonics
https://www.readbyqxmd.com/read/28541674/effect-of-conjugation-length-on-photoinduced-charge-transfer-in-%C3%AF-conjugated-oligomer-acceptor-dyads
#6
Junlin Jiang, Amani A Alsam, Shanshan Wang, Shawkat M Aly, Zhenxing Pan, Omar F Mohammed, Kirk S Schanze
A series of -conjugated oligomer-acceptor dyads were synthesized that feature oligo(phenylene ethynylene) (OPE) conjugated backbones end-capped with a naphthalene diimide (NDI) acceptor. The OPE segments vary in length from 4 to 8 phenylene ethynene units (PEn-NDI, where n = 4, 6 and 8). Fluorescence and transient absorption spectroscopy reveals that intramolecular OPE NDI charge transfer dominates the deactivation of excited states of the PEn-NDI oligomers. Both charge separation (CS) and charge recombination (CR) are strongly exothermic (G0CS ~ -1...
May 25, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28540717/imaging-laser-triggered-drug-release-from-gold-nanocages-with-transient-absorption-lifetime-microscopy-talm
#7
Yongkui Xu, Qi Liu, Ruoyu He, Xianchong Miao, Minbiao Ji
Nanoparticles have shown promise in loading and delivering drugs for targeted therapy. Many progresses have been made in the design, synthesis and modification of nanoparticles to fulfill such goals. However, realizing targeted intracellular delivery and controlled release of drugs remain challenging, partly due to the lack of reliable tools to detect the drug releasing process. In this paper, we applied femtosecond laser pulses to trigger the explosion of gold nanocages (AuNCs) and controlled the intracellular release of loaded AlPcS molecules for photodynamic therapy (PDT)...
May 25, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28540469/a-3d-microfluidic-perfusion-system-made-from-glass-for-multiparametric-analysis-of-stimulus-secretioncoupling-in-pancreatic-islets
#8
Torben Schulze, Kai Mattern, Eike Früh, Lars Hecht, Ingo Rustenbeck, Andreas Dietzel
Microfluidic perfusion systems (MPS) are well suited to perform multiparametric measurements with small amounts of tissue to function as an Organ on Chip device (OOC). Such microphysiolgical characterization is particularly valuable in research on the stimulus-secretion-coupling of pancreatic islets. Pancreatic islets are fully functional competent mini-organs, which serve as fuel sensors and transduce metabolic activity into rates of hormone secretion. To enable the simultaneous measurement of fluorescence and oxygen consumption we designed a microfluidic perfusion system from borosilicate glass by 3D femtosecond laser ablation...
September 2017: Biomedical Microdevices
https://www.readbyqxmd.com/read/28540082/a-meta-analysis-comparing-postoperative-complications-and-outcomes-of-femtosecond-laser-assisted-cataract-surgery-versus-conventional-phacoemulsification-for-cataract
#9
REVIEW
Zi Ye, Zhaohui Li, Shouzhi He
Objective. This meta-analysis aimed to compare the outcomes and postoperative complications between femtosecond laser-assisted cataract surgery (FLACS) and conventional phacoemulsification cataract surgery (CPCS). Methods. Bibliographic databases, including PubMed, Embase, and Cochrane library, were systematically searched for references on or before September 2015 regarding the outcomes and complications by FLACS or CPCS. Data on corneal endothelial cell loss, uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive outcomes, and postoperative complications were retrieved...
2017: Journal of Ophthalmology
https://www.readbyqxmd.com/read/28539633/ultrashort-vortex-from-a-gaussian-pulse-an-achromatic-interferometric-approach
#10
Dinesh N Naik, Nabil A Saad, D Narayana Rao, Nirmal K Viswanathan
The more than a century old Sagnac interferometer is put to first of its kind use to generate an achromatic single-charge vortex equivalent to a Laguerre-Gaussian beam possessing orbital angular momentum (OAM). The interference of counter-propagating polychromatic Gaussian beams of beam waist ωλ with correlated linear phase (ϕ 0  ≥ 0.025 λ) and lateral shear (y 0  ≥ 0.05 ωλ) in orthogonal directions is shown to create a vortex phase distribution around the null interference. Using a wavelength-tunable continuous-wave laser the entire range of visible wavelengths is shown to satisfy the condition for vortex generation to achieve a highly stable white-light vortex with excellent propagation integrity...
May 24, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28537270/coherent-structural-trapping-through-wave-packet-dispersion-during-photoinduced-spin-state-switching
#11
Henrik T Lemke, Kasper S Kjær, Robert Hartsock, Tim B van Driel, Matthieu Chollet, James M Glownia, Sanghoon Song, Diling Zhu, Elisabetta Pace, Samir F Matar, Martin M Nielsen, Maurizio Benfatto, Kelly J Gaffney, Eric Collet, Marco Cammarata
The description of ultrafast nonadiabatic chemical dynamics during molecular photo-transformations remains challenging because electronic and nuclear configurations impact each other and cannot be treated independently. Here we gain experimental insights, beyond the Born-Oppenheimer approximation, into the light-induced spin-state trapping dynamics of the prototypical [Fe(bpy)3](2+) compound by time-resolved X-ray absorption spectroscopy at sub-30-femtosecond resolution and high signal-to-noise ratio. The electronic decay from the initial optically excited electronic state towards the high spin state is distinguished from the structural trapping dynamics, which launches a coherent oscillating wave packet (265 fs period), clearly identified as molecular breathing...
May 24, 2017: Nature Communications
https://www.readbyqxmd.com/read/28535670/ultrafast-spectroscopy-reveals-electron-transfer-cascade-that-improves-hydrogen-evolution-with-carbon-nitride-photocatalysts
#12
Kathryn L Corp, Cody W Schlenker
Solar hydrogen generation from water represents a compelling component of a future sustainable energy portfolio. Recently, chemically-robust heptazine-based polymers known as graphitic carbon nitrides (g-C3N4) have emerged as promising photocatalysts for hydrogen evolution using visible light while withstanding harsh chemical environments. However, since g-C3N4 electron transfer dynamics are poorly understood, rational design rules for improving activity remain unclear. Here, we use visible and near-infrared femtosecond transient absorption (TA) spectroscopy to reveal an electron transfer cascade that correlates with a near-doubling in photocatalytic activity from 2050 µmol h(-1)g(-1) to 3810 µmol h(-1)g(-1) when we infuse a suspension of bulk g-C3N4 with 10% mass loading of chemically exfoliated carbon nitride...
May 23, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28534917/charge-stabilizing-tris-triphenylamine-zinc-porphyrin-carbon-nanotube-hybrids-synthesis-characterization-and-excited-state-charge-transfer-studies
#13
Luis M Arellano, Myriam Barrejón, Habtom B Gobeze, María J Gómez-Escalonilla, José Luis G Fierro, Francis D'Souza, Fernando Langa
Functionalization of single-walled (SWCNTs) and double-walled carbon nanotubes (DWCNTs) with a charge stabilizing zinc porphyrin functionalized with triphenylamine entities has been accomplished. The synthetic approach involved the reaction of tris-(triphenylamine)porphyrinato zinc(ii) with iodobenzene functionalized nanotubes through a Sonogashira C-C cross coupling reaction under microwave irradiation conditions. Evidence of covalent functionalization and the extent of functionalization was obtained from systematic studies carried out by AFM, TGA, XPS and Raman spectroscopy techniques...
May 23, 2017: Nanoscale
https://www.readbyqxmd.com/read/28534584/composition-dependent-electronic-energy-relaxation-dynamics-of-metal-domains-as-revealed-by-bimetallic-au144-xagx-sc8h9-60-monolayer-protected-clusters
#14
Hongjun Zheng, Marcus A Tofanelli, Christopher J Ackerson, Kenneth L Knappenberger
We examined the electronic relaxation dynamics for mono and bimetallic Au144-xAgx(SC8H9)60 monolayer-protected clusters (MPCs) using femtosecond time-resolved transient extinction spectroscopy. MPCs provide compositionally well-defined model systems for structure-specific determination of nanoscale electronic properties. Based on pulse-energy-dependent transient extinction data, we quantified electron-phonon coupling constants for three distinct Au144-xAgx(SC8H9)60 MPC samples, where x = 0, 0 < x < 30, and x ∼ 30, as Gx=0 = (1...
May 23, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28532941/cataract-surgery-practices-in-the-united-states-veterans-health-administration
#15
Annika G Havnaer, Paul B Greenberg, Glenn C Cockerham, Melissa A Clark, Amy Chomsky
PURPOSE: To describe current cataract surgery practices within the United States Veterans Health Administration (VHA). SETTING: Veterans Health Administration hospitals in the U.S. DESIGN: Retrospective data analysis. METHODS: An initial e-mail containing a link to an anonymous 32-question survey of cataract surgery practices was sent to participants in May 2016. Two reminder e-mails were sent to nonresponders 1 week and 2 weeks after the initial survey was sent; the remaining nonresponders were called twice over a 2-week period...
April 2017: Journal of Cataract and Refractive Surgery
https://www.readbyqxmd.com/read/28532934/effects-of-topical-ketorolac-tromethamine-0-45-on-intraoperative-miosis-and-prostaglandin-e2-release-during-femtosecond-laser-assisted-cataract-surgery
#16
Jong Hwa Jun, Young-Sik Yoo, Sung A Lim, Choun-Ki Joo
PURPOSE: To determine the effects of topical 0.45% ketorolac tromethamine on intraoperative miosis and prostaglandin E2 (PGE2) release during femtosecond laser-assisted cataract surgery. SETTING: Seoul St. Mary's Hospital, Seoul, Korea. DESIGN: Prospective case series. METHODS: The study comprised the following 3 groups: conventional cataract surgery without topical NSAIDs (conventional group); femtosecond laser-assisted cataract surgery with preoperative topical ketorolac tromethamine 0...
April 2017: Journal of Cataract and Refractive Surgery
https://www.readbyqxmd.com/read/28532933/clinical-outcomes-of-femtosecond-laser-assisted-cataract-surgery-versus-conventional-phacoemulsification-surgery-for-hard-nuclear-cataracts
#17
Xinyi Chen, Yinhui Yu, Xiaohui Song, Yanan Zhu, Wei Wang, Ke Yao
PURPOSE: To compare the outcomes between femtosecond laser-assisted cataract surgery (femtosecond group) and conventional phacoemulsification cataract surgery (conventional group) in patients with hard nuclear cataract. SETTING: Eye Center, Second Affiliated Hospital of School of Medicine, Zhejiang University, Hangzhou, China. DESIGN: Prospective consecutive nonrandomized comparative cohort study. METHODS: According to the Emery-Little classification, cataract patients with a grade 4 or 5 hard nuclei were assigned to 1 of the 2 groups...
April 2017: Journal of Cataract and Refractive Surgery
https://www.readbyqxmd.com/read/28532932/intereye-comparison-of-femtosecond-laser-assisted-cataract-surgery-capsulotomy-and-manual-capsulorhexis-edge%C3%A2-strength
#18
Thomas Chan, Ushasree Pattamatta, Mark Butlin, Kerrie Meades, Chandra Bala
PURPOSE: To compare the breaking force required to tear the explanted capsule after femtosecond laser-assisted cataract surgery in the worse eye and manual cataract surgery in the contralateral eye. SETTING: Personaleyes, Sydney, Australia. DESIGN: Prospective nonrandomized case study. METHOD: Patients with bilateral cataract had femtosecond laser-assisted cataract surgery with the Lensx laser in the eye with worse vision and manual cataract surgery in the contralateral eye...
April 2017: Journal of Cataract and Refractive Surgery
https://www.readbyqxmd.com/read/28532925/does-femtosecond-laser-assisted-cataract-surgery-improve-corneal-endothelial-safety-the-debate-and-conundrum
#19
EDITORIAL
David F Chang
No abstract text is available yet for this article.
April 2017: Journal of Cataract and Refractive Surgery
https://www.readbyqxmd.com/read/28530741/thionine-graphene-oxide-covalent-hybrid-and-its-interaction-with-light
#20
Ewelina Krzyszkowska, Justyna Walkowiak-Kulikowska, Sven Stienen, Aleksandra Wojcik
Graphene oxide sheets (GO) were covalently functionalized with thionine molecules. The obtained hybrid material, Th-GO, was characterized by means of scanning electron microscopy (SEM), Auger electron spectroscopy (AES), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. Subsequently, the interaction of light with the free dye molecules and with dye molecules bound to the graphene oxide sheets was probed via UV-Vis spectroscopy, fluorescence spectroscopy and femtosecond pump-probe spectroscopy...
May 22, 2017: Physical Chemistry Chemical Physics: PCCP
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