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https://www.readbyqxmd.com/read/28454172/are-optical-fibers-really-uniform-measurement-of-refractive-index-on-a-centimeter-scale
#1
Sébastien Loranger, Raman Kashyap
Many applications of optical fiber, such as specialized fiber Bragg gratings (FBGs), require high uniformity of a fiber's refractive index (RI) along its length. We show here that the mode effective index of most fibers is not constant, even on a short length scale. To help improve fiber manufacturing and selection, we demonstrate a technique for characterizing a meter length single-mode optical fiber's effective RI over a centimeter scale with a precision of 3×10<sup>-6</sup> RI units (RIUs) and an absolute accuracy of 2×10<sup>-4</sup> RIU...
May 1, 2017: Optics Letters
https://www.readbyqxmd.com/read/28454170/origin-and-suppression-of-parasitic-signals-in-kagom%C3%A3-lattice-hollow-core-fibers-used-for-srs-microscopy-and-endoscopy
#2
Alberto Lombardini, Esben Ravn Andresen, Alexandre Kudlinski, Ingo Rimke, Hervé Rigneault
Hollow core fibers are considered as promising candidates to deliver intense temporally overlapping picosecond pulses in applications such as stimulated Raman scattering (SRS) microscopy and endoscopy because of their inherent low nonlinearity compared to solid-core silica fibers. Here we demonstrate that, contrary to prior assumptions, parasitic signals are generated in Kagomé lattice hollow core fibers. We identify the origin of the parasitic signals as an interplay between the Kerr nonlinearity of air and frequency-dependent fiber losses...
May 1, 2017: Optics Letters
https://www.readbyqxmd.com/read/28454152/88-conversion-efficiency-with-an-atomic-spin-wave-mediated-mode-selection
#3
Jinxian Guo, L Q Chen, Peiyu Yang, Zhengjun Li, Yuan Wu, Xiaotian Feng, Chun-Hua Yuan, Z Y Ou, Weiping Zhang
In studying quantum correlation and quantum memory of continuous variables of light fields and atoms, a crucial step is the retrieval of the quantum fields by converting an atomic spin wave to light, and retrieval efficiency is a crucial parameter. In this Letter, we implement a double-pass Raman scheme in Rb87 by incorporating coherent feedback. We find that the transfer efficiency from an atomic spin wave, which is generated from a Raman process in a high gain regime, to light fields is enhanced by the double-pass scheme as compared to the commonly used single-pass scheme...
May 1, 2017: Optics Letters
https://www.readbyqxmd.com/read/28454151/high-power-frequency-comb-source-tunable-from-2-7-to-4-2%C3%A2-%C3%A2-%C3%AE-m-based-on-difference-frequency-generation-pumped-by-an-yb-doped-fiber-laser
#4
Grzegorz Soboń, Tadeusz Martynkien, Paweł Mergo, Lucile Rutkowski, Aleksandra Foltynowicz
We demonstrate a broadband mid-infrared (MIR) frequency comb source based on difference frequency generation (DFG) in periodically poled lithium niobate crystal. MIR radiation is obtained via mixing of the output of a 125 MHz repetition rate Yb-doped fiber laser with Raman-shifted solitons generated from the same source in a highly nonlinear fiber. The resulting idler is tunable in the range of 2.7-4.2 μm, with average output power reaching 237 mW and pulses as short as 115 fs. The coherence of the MIR comb is confirmed by spectral interferometry and heterodyne beat measurements...
May 1, 2017: Optics Letters
https://www.readbyqxmd.com/read/28454142/in-situ-sers-monitoring-of-plasmonic-nano-dopants-during-photopolymerization
#5
Ruoping Li, Yanmeng Li, Junhe Han, Mingju Huang
The motion of the plasmonic nano-dopant in photopolymers was monitored in situ and in real time using the surface-enhanced Raman scattering (SERS) technique. Here an Au@MBA@Ag (core-molecule-shell) nanoparticle colloid was synthesized to act as the nano-dopant and adsorbed 4-mercaptobenzoic acid (MBA) between the Au cells and Ag shells as the internal standard. The changes of the MBA signal closely reflect the motion of nanoparticles, since the MBA signal itself has time stability. Experimental data indicate that the optimized concentration of the nano-dopant can be obtained based on the peak intensity change of MBA at 1583  cm<sup>-1</sup>...
May 1, 2017: Optics Letters
https://www.readbyqxmd.com/read/28454138/programmable-single-pixel-based-broadband-stimulated-raman-scattering
#6
Pascal Berto, Camille Scotté, Frédéric Galland, Hervè Rigneault, Hilton B de Aguiar
We report a simple add-on for broadband stimulated Raman scattering (SRS) microscopes to enable fast and programmable spectroscopy acquisition. It comprises a conventional dispersive spectrometer layout incorporating a fast digital micromirror device (DMD). The approach is validated by acquiring SRS spectra of standard chemicals. We demonstrate a DMD's advantage in broadband SRS by showing higher signal-to-noise ratio using a multiplexed Hadamard spectral basis and compressive sensing detection. Our results apply to a variety of frequency-domain pump-probe spectroscopy...
May 1, 2017: Optics Letters
https://www.readbyqxmd.com/read/28454077/comparison-of-ftir-atr-and-raman-spectroscopy-in-determination-of-vldl-triglycerides-in-blood-serum-with-pls-regression
#7
Adam Oleszko, Jadwiga Hartwich, Anna Wójtowicz, Marlena Gąsior-Głogowska, Hubert Huras, Małgorzata Komorowska
Hypertriglyceridemia, related with triglyceride (TG) in plasma above 1.7mmol/L is one of the cardiovascular risk factors. Very low density lipoproteins (VLDL) are the main TG carriers. Despite being time consuming, demanding well-qualified staff and expensive instrumentation, ultracentrifugation technique still remains the gold standard for the VLDL isolation. Therefore faster and simpler method of VLDL-TG determination is needed. Vibrational spectroscopy, including FT-IR and Raman, is widely used technique in lipid and protein research...
April 18, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28454073/low-temperature-raman-spectra-of-the-2-%C3%AE-methylbenzylamino-5-nitropyridine-crystal
#8
G S Pinheiro, M N G Ferreira Júnior, A O Dos Santos, P T C Freire, J A Lima, C E S Nogueira, L P Cardoso, J N Sherwood, C M R Remédios
The polar organic 2-(α-methylbenzylamino)-5-nitropyridine crystal (MBANP) has been studied by Raman spectroscopy at low temperatures (from 300 to 10K). The effect of temperature change on the vibrational spectrum is discussed with the aid of DFT calculations. The behavior of the Raman spectra indicates that MBANP molecules present a different conformation at low temperatures associated with the rotation of the phenyl and pyridine rings. Temperature-dependent X-ray measurements and differential scanning calorimetry (DSC) analysis were utilized as complementary techniques to investigate the structural stability of MBANP crystal...
April 20, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28453968/association-of-altered-collagen-content-and-lysyl-oxidase-expression-in-degenerative-mitral-valve-disease
#9
K-Raman Purushothaman, Meerarani Purushothaman, Irene C Turnbull, David H Adams, Anelechi Anyanwu, Prakash Krishnan, Annapoorna Kini, Samin K Sharma, William N O'Connor, Pedro R Moreno
BACKGROUND: Collagen cross-linking is mediated by lysyl oxidase (LOX) enzyme in the extracellular matrix (ECM) of mitral valve leaflets. Alterations in collagen content and LOX protein expression in the ECM of degenerative mitral valve may enhance leaflet expansion and disease severity. METHODS: Twenty posterior degenerative mitral valve leaflets from patients with severe mitral regurgitation were obtained at surgery. Five normal posterior mitral valve leaflets procured during autopsy served as controls...
April 12, 2017: Cardiovascular Pathology: the Official Journal of the Society for Cardiovascular Pathology
https://www.readbyqxmd.com/read/28453432/multiregional-radiogenomic-assessment-of-prostate-microenvironments-with-multiparametric-mr-imaging-and-dna-whole-exome-sequencing-of-prostate-glands-with-adenocarcinoma
#10
Neema Jamshidi, Daniel J Margolis, Steven Raman, Jiaoti Huang, Robert E Reiter, Michael D Kuo
Purpose To assess the underlying genomic variation of prostate gland microenvironments of patients with prostate adenocarcinoma in the context of colocalized multiparametric magnetic resonance (MR) imaging and histopathologic assessment of normal and abnormal regions by using whole-exome sequencing. Materials and Methods Six patients with prostate adenocarcinoma who underwent robotic prostatectomy with whole-mount preservation of the prostate were identified, which enabled spatial mapping between preoperative multiparametric MR imaging and the gland...
April 28, 2017: Radiology
https://www.readbyqxmd.com/read/28449325/electrosynthesis-of-bifunctional-ws3-x-rgo-hybrid-for-her-and-orr-electrocatalysis
#11
Martin Pumera
We combined the desirable properties of tungsten sulfide and reduced graphene oxide (rGO) and fabricated the hybrid materials through simultaneous electrochemical reduction and synthesis, as a versatile and environmentally benign alternative to conventional fabrication techniques. We synthesised a mixed WS2/WS3 film-like material (WS3-x) directly onto GO-modified glassy carbon electrodes via cyclic voltammetry (CV) and the resultant hybrid materials (WS3-x/rGO) were thoroughly characterised using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) as well as Raman spectroscopy...
April 27, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28448887/macro-raman-spectroscopy-for-bulk-composition-and-homogeneity-analysis-of-multi-component-pharmaceutical-powders
#12
Hui Wang, David Barona, Sulayman Oladepo, Lisa Williams, Susan Hoe, David Lechuga-Ballesteros, Reinhard Vehring
A new macro-Raman system equipped with a motorized translational sample stage and low-frequency shift capabilities was developed for bulk composition and homogeneity analysis of multi-component pharmaceutical powders. Different sampling methods including single spot and scanning measurement were compared. It was found that increasing sample volumes significantly improved the precision of quantitative composition analysis, especially for poorly mixed powders. The multi-pass cavity of the macro-Raman system increased effective sample volumes by 20 times from the sample volume defined by the collection optics, i...
April 23, 2017: Journal of Pharmaceutical and Biomedical Analysis
https://www.readbyqxmd.com/read/28448402/left-atrium-measurements-via-computed-tomography-pulmonary-angiogram-as-a-predictor-of-diastolic-dysfunction
#13
Adam N Lick, Raman Danrad, David L Smith, Matthew R Lammi
PURPOSE: Left atrium (LA) enlargement on echocardiography may be an indicator of diastolic dysfunction (DD). It is not well known if computed tomography pulmonary angiography (CTPA) can detect DD. METHODS: A total of 127 patients who underwent both CTPA and echo within 48 hours were analyzed retrospectively. Left atrium diameters from CTPA were correlated with echo and evaluated against degrees of DD. Computed tomography pulmonary angiography pulmonary artery (PA)/aorta ratio was analyzed as a tool to detect pulmonary hypertension...
April 26, 2017: Journal of Computer Assisted Tomography
https://www.readbyqxmd.com/read/28448046/a-novel-technique-for-raman-analysis-of-highly-radioactive-samples-using-any-standard-micro-raman-spectrometer
#14
Jean-Yves Colle, Mohamed Naji, Mark Sierig, Dario Manara
A novel approach for the Raman measurement of nuclear materials is reported in this paper. It consists of the enclosure of the radioactive sample in a tight capsule that isolates the material from the atmosphere. The capsule can optionally be filled with a chosen gas pressurized up to 20 bars. The micro-Raman measurement is performed through an optical-grade quartz window. This technique permits accurate Raman measurements with no need for the spectrometer to be enclosed in an alpha-tight containment. It therefore allows the use of all options of the Raman spectrometer, like multi-wavelength laser excitation, different polarizations, and single or triple spectrometer modes...
April 12, 2017: Journal of Visualized Experiments: JoVE
https://www.readbyqxmd.com/read/28447704/influence-of-dopants-on-the-impermeability-of-graphene
#15
S S K Mallineni, D W Boukhvalov, I S Zhidkov, A I Kukharenko, A I Slesarev, A F Zatsepin, S O Cholakh, A M Rao, S M Serkiz, S Bhattacharya, E Z Kurmaev, R Podila
Graphene has attracted much attention as an impermeable membrane and a protective coating against oxidation. While many theoretical studies have shown that defect-free graphene is impermeable, in reality graphene inevitably has defects in the form of grain boundaries and vacancies. Here, we study the effects of N-dopants on the impermeability of few-layered graphene (FLG) grown on copper using chemical vapor deposition. The grain boundaries in FLG have minimal impact on their permeability to oxygen as they do not provide a continuous channel for gas transport due to high tortuosity...
April 27, 2017: Nanoscale
https://www.readbyqxmd.com/read/28447698/anisotropic-metal-nanoparticles-for-surface-enhanced-raman-scattering
#16
Javier Reguera, Judith Langer, Dorleta Jiménez de Aberasturi, Luis M Liz-Marzán
The optimization of the enhancement of Raman scattering by plasmonic effects is largely determined by the properties of the enhancing substrates. The main parameters behind this effect are related to the morphology of plasmonic nanoparticles and their relative distribution within the substrate. We focus this tutorial review on the effects of nanoparticle morphology, for the particular case of anisotropic metal nanoparticles. Anisotropy in silver and gold nanoparticles offers the possibility to tailor their plasmonic properties and intrinsic electromagnetic "hotspots"...
April 27, 2017: Chemical Society Reviews
https://www.readbyqxmd.com/read/28447677/investigation-of-easy-plane-magnetic-anisotropy-in-p-ligand-square-pyramidal-co-ii-single-ion-magnets
#17
Amit Kumar Mondal, Jesús Jover, Eliseo Ruiz, Sanjit Konar
In this work we report two pentacoordinated Co(II)-P4X1 Single Ion Magnets (SIMs) based on P-donor ligands. The tetradentate ligand tris[2-(diphenylphosphino)ethyl]phosphine allows the obtention of the isostructural square pyramidal [Co(PP3)Cl]·ClO4 (1) and [Co(PP3)Br]·ClO4 (2) complexes. Consistent theoretical and experimental studies indicate that these complexes have a high spin (S = 3/2) ground state and suggest that the relaxation dynamics is governed by ground state quantum tunneling, whereas its temperature dependence is directed by optical or acoustic Raman processes...
April 27, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28447129/comparison-between-non-invasive-methods-used-on-paintings-by-goya-and-his-contemporaries-hyperspectral-imaging-vs-point-by-point-spectroscopic-analysis
#18
Floréal Daniel, Aurélie Mounier, Josefina Pérez-Arantegui, Carlos Pardos, Nagore Prieto-Taboada, Silvia Fdez-Ortiz de Vallejuelo, Kepa Castro
The development of non-invasive techniques for the characterization of pigments is crucial in order to preserve the integrity of the artwork. In this sense, the usefulness of hyperspectral imaging was demonstrated. It allows pigment characterization of the whole painting. However, it also sometimes requires the complementation of other point-by-point techniques. In the present article, the advantages of hyperspectral imaging over point-by-point spectroscopic analysis were evaluated. For that purpose, three paintings were analysed by hyperspectral imaging, handheld X-ray fluorescence and handheld Raman spectroscopy in order to determine the best non-invasive technique for pigment identifications...
April 26, 2017: Analytical and Bioanalytical Chemistry
https://www.readbyqxmd.com/read/28447119/maxillary-sinus-lift-with-beta-tricalcium-phosphate-%C3%AE-tcp-in-edentulous-patients-a-nanotomographic-and-raman-study
#19
Florence Pascaretti-Grizon, Bernard Guillaume, Lisa Terranova, Baptiste Arbez, Hélène Libouban, Daniel Chappard
Sinus lift elevation restores bone mass at the maxilla in edentulate patients before the placement of dental implants. It consists of opening the lateral side of the sinus and grafting beta-tricalcium phosphate granules (β-TCP) under the olfactory membrane. Bone biopsies were obtained in five patients after 60 weeks. They were embedded undecalcified in poly(methyl methacrylate) (pMMA); blocks were analyzed by nanocomputed tomography (nanoCT); specific areas were studied by Raman microspectroscopy. Remnants of β-TCP were osseointegrated and covered with mineralized bone; osteoid tissue was also filling the inner porosity...
April 26, 2017: Calcified Tissue International
https://www.readbyqxmd.com/read/28446900/bioactive-molecule-from-streptomyces-sp-mitigates-mdr-klebsiella-pneumoniae-in-zebrafish-infection-model
#20
Lalitha Cheepurupalli, Thiagarajan Raman, Sudarshan S Rathore, Jayapradha Ramakrishnan
The emergence and spread of multi-drug resistant (MDR) especially carbapenem-resistant Klebsiella pneumoniae is a major emerging threat to public health, leading to excess in mortality rate as high as 50-86%. MDR K. pneumoniae manifests all broad mechanisms of drug resistance, hence development of new drugs to treat MDR K. pneumoniae infection has become a more relevant question in the scientific community. In the present study a potential Streptomyces sp. ASK2 was isolated from rhizosphere soil of medicinal plant...
2017: Frontiers in Microbiology
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