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high harmonic generation

Mohamad Hamieh, Kokoo Dorkenoo, Gregory Taupier, Yves Henry, David Halley
We investigate the second harmonic generation (SHG) signal in strained Cr2O3 clusters. We show that the SHG signal generated by nanometric Cr2O3 clusters embedded in MgO varies under an applied electric field, at room temperature. The variation of the intensity follows a Langevin law as a function of the electric field, which is consistent with a super-paraelectric clusters assembly. This reveals the presence of a weak spontaneous electric dipole in Cr2O3 when in the shape of highly strained epitaxial clusters, whereas this material does not posses any permanent electric dipole in the bulk phase...
March 24, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Jaroslav Vacek, Hana Vonkova, Roman Gabrhelík
We conducted a feasibility study for matching children (N = 2571, average age 12 years, 50.4% female) and their parents (N = 1931, average age 41 years, 83.3% female) represented by an anonymous self-generated identification code (SGIC) and assessed its methodological properties. We used a nine-character SGIC with the children and a mirrored version of the same code with the parents. The average overall error rate in generating the SGIC was 9.7% (4.0% in the parents and 13.9% in the children). We were able to link a total of 1765 parents' and children's codes uniquely (94...
March 24, 2017: Prevention Science: the Official Journal of the Society for Prevention Research
Yang Han, Shutao Wang, Thomas Payen, Elisa Konofagou
The successful clinical application of high intensity focused ultrasound (HIFU) ablation depends on reliable monitoring of the lesion formation. Harmonic motion imaging guided focused ultrasound (HMIgFUS) is an ultrasound-based elasticity imaging technique, which monitors HIFU ablation based on the stiffness change of the tissue instead of the echo intensity change in conventional B-mode monitoring, rendering it potentially more sensitive to lesion development. Our group has shown that predicting the lesion location based on the radiation force-excited region is feasible during HMIgFUS...
March 21, 2017: Physics in Medicine and Biology
Martin K Schmitt, Oliver Janka, Oliver Niehaus, Thomas Dresselhaus, Rainer Pöttgen, Florian Pielnhofer, Richard Weihrich, Maria Krzhizhanovskaya, Stanislav Filatov, Rimma Bubnova, Lkhamsuren Bayarjargal, Björn Winkler, Robert Glaum, Hubert Huppertz
γ-NiB4O7 was synthesized in a high-pressure/high-temperature experiment at 5 GPa and 900 °C. The single-crystal structure analysis yielded the following results: space group P6522 (No. 179), a = 425.6(2), c = 3490.5(2) pm, V = 0.5475(2) nm(3), Z = 6, and Flack parameter x = -0.010(5). Second harmonic generation measurements confirmed the acentric crystal structure. Furthermore, γ-NiB4O7 was characterized via vibrational as well as single-crystal electronic absorption spectroscopy, magnetic measurements, high-temperature X-ray diffraction, differential scanning calorimetry, and thermogravimetry...
March 21, 2017: Inorganic Chemistry
Jean Lebacq, Jean Schoentgen, Giovanna Cantarella, Franz Thomas Bruss, Claudia Manfredi, Philippe DeJonckere
PURPOSE: Smartphone technology provides new opportunities for recording standardized voice samples of patients and transmitting the audio files to the voice laboratory. This drastically improves the achievement of baseline designs, used in research on efficiency of voice treatments. However, the basic requirement is the suitability of smartphones for recording and digitizing pathologic voices (mainly characterized by period perturbations and noise) without significant distortion. In a previous article, this was tested using realistic synthesized deviant voice samples (/a:/) with three precisely known levels of jitter and of noise in all combinations...
March 17, 2017: Journal of Voice: Official Journal of the Voice Foundation
Kenta Shimamoto, Saumya Mukherjee, Sebastian Manz, Jonathan S White, Morgan Trassin, Michel Kenzelmann, Laurent Chapon, Thomas Lippert, Manfred Fiebig, Christof W Schneider, Christof Niedermayer
A current challenge in the field of magnetoelectric multiferroics is to identify systems that allow a controlled tuning of states displaying distinct magnetoelectric responses. Here we show that the multiferroic ground state of the archetypal multiferroic TbMnO3 is dramatically modified by epitaxial strain. Neutron diffraction reveals that in highly strained films the magnetic order changes from the bulk-like incommensurate bc-cycloidal structure to commensurate magnetic order. Concomitant with the modification of the magnetic ground state, optical second-harmonic generation (SHG) and electric measurements show an enormous increase of the ferroelectric polarization, and a change in its direction from along the c- to the a-axis...
March 20, 2017: Scientific Reports
Giuseppe Licari, Lukasz Cwiklik, Pavel Jungwirth, Eric Vauthey
The adsorption of a DNA fluorescent probe belonging to the thiazole orange family at the dodecane/water and dodecane/phospholipid/water interfaces has been investigated using a combination of surface-second harmonic generation (SSHG) and all-atomistic molecular dynamics (MD) simulations. Both approaches point to a high affinity of the cationic dye for the dodecane/water interface with a Gibbs free energy of adsorption of the order of -45 kJ/mol. Similar affinity was observed with a monolayer of negatively charged DPPG (1,2-dipalmitoyl-sn-glycero-3-phospho-rac-(1-glycerol)) lipids...
March 17, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Renee J Tran, Krystal L Sly, John C Conboy
Surface second harmonic generation (SHG) is a coherent, nonlinear optical technique that is well suited for investigations of biomolecular interactions at interfaces. SHG is surface specific due to the intrinsic symmetry constraints on the nonlinear process, providing a distinct analytical advantage over linear spectroscopic methods, such as fluorescence and UV-Visible absorbance spectroscopies. SHG has the ability to detect low concentrations of analytes, such as proteins, peptides, and small molecules, due to its high sensitivity, and the second harmonic response can be enhanced through the use of target molecules that are resonant with the incident (ω) and/or second harmonic (2ω) frequencies...
March 16, 2017: Annual Review of Analytical Chemistry
Kevin F Lee, Xiaoyan Ding, T J Hammond, M E Fermann, G Vampa, P B Corkum
High harmonic generation in solids presents the possibility for bringing attosecond techniques to semiconductors and a simple source for frequency comb spectroscopy in the vacuum ultraviolet. We generate up to the seventh harmonic of a Tm fiber laser by focusing in silicon or zinc oxide. The harmonics are strong and stable, with no indication of material damage. Calculations show the potential for generating nineteenth harmonic photons at 12 eV photons of energy.
March 15, 2017: Optics Letters
Toshihiko Shibanuma, Gustavo Grinblat, Pablo Albella, Stefan A Maier
High refractive index dielectric nanoantennas are expected to become key elements for nonlinear nano-optics applications due to their large nonlinearities, low energy losses and ability to produce high electric field enhancements in relatively large nanoscale volumes. In this work, we show that the nonlinear response from a high-index dielectric nanoantenna can be significantly improved by adding a metallic component to build metal-dielectric hybrid nanostructures. We demonstrate that the plasmonic resonance of a Au nanoring can boost the anapole mode supported by a Si nanodisk, strongly enhancing the electric field inside the large third-order susceptibility dielectric...
March 13, 2017: Nano Letters
Nicolas Tancogne-Dejean, Oliver D Mücke, Franz X Kärtner, Angel Rubio
An accurate analytic model describing the microscopic mechanism of high-harmonic generation (HHG) in solids is derived. Extensive first-principles simulations within a time-dependent density-functional framework corroborate the conclusions of the model. Our results reveal that (i) the emitted HHG spectra are highly anisotropic and laser-polarization dependent even for cubic crystals; (ii) the harmonic emission is enhanced by the inhomogeneity of the electron-nuclei potential; the yield is increased for heavier atoms; and (iii) the cutoff photon energy is driver-wavelength independent...
February 24, 2017: Physical Review Letters
Alex Turpin, Laura Rego, Antonio Picón, Julio San Román, Carlos Hernández-García
We investigate theoretically the generation of extreme-ultraviolet (EUV) beams carrying fractional orbital angular momentum. To this end, we drive high-order harmonic generation with infrared conical refraction (CR) beams. We show that the high-order harmonic beams emitted in the EUV/soft x-ray regime preserve the characteristic signatures of the driving beam, namely ringlike transverse intensity profile and CR-like polarization distribution. As a result, through orbital and spin angular momentum conservation, harmonic beams are emitted with fractional orbital angular momentum, and they can be synthesized into structured attosecond helical beams -or "structured attosecond light springs"- with rotating linear polarization along the azimuth...
March 10, 2017: Scientific Reports
John P Veluchamy, María Delso-Vallejo, Nina Kok, Fenna Bohme, Ruth Seggewiss-Bernhardt, Hans J van der Vliet, Tanja D de Gruijl, Volker Huppert, Jan Spanholtz
Advancements in multi-colour fluorescence activated cell sorting (FACS) panel warrant harmonized procedures to obtain comparable data between various laboratories. The intensifying clinical exploration of Natural Killer (NK) cell-based immunotherapy demands standardized and harmonized NK cell FACS panels and acquisition protocols. Eight colour FACS panels were designed to study human NK cell phenotype and function within peripheral blood mononuclear cells (PBMC). The panels were designed around fixed backbone markers and channels, covering antigens for non-NK lineage exclusion (CD3, TCRγδ, CD19, CD14, SYTOX(®) Blue) and NK cell selection (CD45, CD56, CD16), complemented with variable drop-in markers/channels to study NK cell phenotype (NKG2A, NKG2C, NKG2D and KIR2D) or NK cell function and activation (CD25, NKp44 and CD107a)...
March 10, 2017: Scientific Reports
Xu Jia, Shenghui Liao, Xuanchu Duan, Wanqiu Zheng, Beiji Zou
Purpose. This study examined the influence of anisotropic material for human sclera. Method. First, the individual geometry of patient-specific sclera was reproduced from a laser scan. Then, high quality finite element modeling of individual sclera was performed using a convenient automatic hexahedral mesh generator based on harmonic field and integrated with anisotropic material assignment function. Finally, comparison experiments were designed to investigate the effects of anisotropy on finite element modeling of sclera biomechanics...
2017: BioMed Research International
Patrik K Johansson, Patrick Koelsch
The optical properties of amyloid fibers are often distinct from those of the source protein in its non-fibrillar form. These differences can be utilized for label-free imaging or characterization of such structures, which is particularly important for understanding amyloid fiber related diseases such as Alzheimer's and Parkinson's disease. We demonstrate that two amyloid forming proteins, insulin and β-lactoglobulin (β-LG), show intrinsic fluorescence with emission spectra that are dependent on the excitation wavelength...
February 1, 2017: Biomedical Optics Express
Anton Autere, Christopher R Ryder, Antti Säynätjoki, Lasse Karvonen, Babak Amirsolaimani, Robert A Norwood, Nasser Peyghambarian, Khanh Kieu, Harri Lipsanen, Mark C Hersam, Zhipei Sun
Black phosphorus (BP) is a layered semiconductor that recently has been the subject of intense research due to its novel electrical and optical properties, which compare favorably to those of graphene and the transition metal dichalcogenides. In particular, BP has a direct bandgap that is thickness-dependent and highly anisotropic, making BP an interesting material for nanoscale optical and optoelectronic applications. Here, we present a study of the anisotropic third-harmonic generation (THG) in exfoliated BP using a fast scanning multiphoton characterization method...
March 13, 2017: Journal of Physical Chemistry Letters
A Aadhi, Varun Sharma, N Apurv Chaitanya, G K Samanta
We report a high power ultrafast Airy beam source producing femtosecond pulses at multi-gigahertz (GHz) repetition rate (RR). Based on intra-cavity cubic phase modulation of an optical parametric oscillator (OPO) designed in high harmonic cavity configuration synchronous to a femtosecond Yb-fiber laser operating at 78 MHz, we have produced ultrafast 2D Airy beam at multi-GHz repetition rate through the fractional increment in the cavity length. While small (<1 mm) crystals are used in femtosecond OPOs to take the advantage of broad phase-matching bandwidth, here, we have exploited the extended phase-matching bandwidth of a 50-mm long Magnesium-oxide doped periodically poled LiNbO3 (MgO:PPLN) crystal for efficient generation of ultrafast Airy beam and broadband mid-IR radiation...
March 6, 2017: Scientific Reports
Emmanuel Cherin, Johan M Melis, Raymond W Bourdeau, Melissa Yin, Dennis M Kochmann, F Stuart Foster, Mikhail G Shapiro
Gas vesicles (GVs) are a new and unique class of biologically derived ultrasound contrast agents with sub-micron size whose acoustic properties have not been fully elucidated. In this study, we investigated the acoustic collapse pressure and behavior of Halobacterium salinarum gas vesicles at transmit center frequencies ranging from 12.5 to 27.5 MHz. The acoustic collapse pressure was found to be above 550 kPa at all frequencies, nine-fold higher than the critical pressure observed under hydrostatic conditions...
March 1, 2017: Ultrasound in Medicine & Biology
Jian-Ping Wu, Benjamin John Swift, Thomas Becker, Andrew Squelch, Allan Wang, Yong-Chang Zheng, Xuelin Zhao, Jiake Xu, Wei Xue, Minghao Zheng, David Lloyd, Thomas Brett Kirk
Knowledge of the collagen structure of an Achilles tendon is critical to comprehend the physiology, biomechanics, homeostasis and remodelling of the tissue. Despite intensive studies, there are still uncertainties regarding the microstructure. The majority of studies have examined the longitudinally arranged collagen fibrils as they are primarily attributed to the principal tensile strength of the tendon. Few studies have considered the structural integrity of the entire three-dimensional (3D) collagen meshwork, and how the longitudinal collagen fibrils are integrated as a strong unit in a 3D domain to provide the tendons with the essential tensile properties...
March 2, 2017: Journal of Microscopy
S A Smirnova, O A Yastrebov
The authors interpret forensic expertology as a synthetic science and propose the models for the training of professionals in the field of forensic medical expertise. They provide a rationale for the realization of such systematic training in the framework of the model of the three-level system based at the educational institutions of higher professional education. Characteristic features of the existing standards of professional training in the sphere of forensic medical expertise are considered with special reference to the organization of education of future forensic medical experts based at the many-level programs adopted in the Russian University of People's Friendship...
2017: Sudebno-meditsinskaia Ekspertiza
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