Lidar sensing of ship wakes

Detection of ship wakes is utterly important for ship traffic monitoring, security of sea borders, etc. Among standard detection methods there are radar and acoustic sensing, photographing, hyperspectral measurements, and water sample analysis. However, these methods are hardly suitable for detecting wakes of light high-speed boats. An alternative is optical methods, in particular laser remote sensing. In this work, laboratory experiments on laser remote sensing of water perturbed by a propeller rotating at up to 20 000 rpm are described. A long (over 5 h) decrease in the integral of the band of OH stretching vibrations inH2Omolecules in the Raman scattering spectrum and a blueshift of theOHband center by 2.5 to 3 cm?1 are demonstrated.     

Laser induced breakdown spectroscopy for multielement analysis of powdered materials used in additive technologies

Additive manufacturing technologies utilizing metal parts production with layer by layer printing are of high demand for different fields of science and technology. Analytical chemistry is challenged to provide multielemental quantitative analysis of any metal powders within a few minutes and onsite to fulfil the requirements for high quality metal parts production. Powder materials utilized in additive technologies were quantitatively analyzed by laser induced breakdown spectroscopy for the first time. Laser induced breakdown spectroscopy mapping of loose metal powder attached to the double-sided adhesive tape provided high reproducibility of measurements even for powder mixtures with large difference of particles densities (tungsten carbide particles in nickel alloy powder). Laser induced breakdown spectroscopy analytical capabilities were estimated for tungsten and carbon analysis by calibration curve construction and accuracy estimation by leave-one-out cross-validation procedure. Laser induced breakdown spectroscopy and X-ray fluorescence spectroscopy techniques comparison revealed better results for laser induced breakdown spectroscopy analysis. Improved accuracy of analysis and capability to quantify light elements (carbon, etc.) demonstrated the potential of laser induced breakdown spectroscopy as a promising technique for express onsite multielement analysis of powder materials utilized in additive technologies.     

Search for the Decay K L0-->pi0nu nu[over

We performed a search for the K L0-->pi0nu nu[over] decay at the KEK 12-GeV proton synchrotron. No candidate events were observed. An upper limit on the branching ratio for the decay was set to be 6.7 x 10(-8) at the 90% confidence level.     

Searches for rare and forbidden neutral decays of η mesons at the GAMS-4π facility

Searches for rare and forbidden neutral decays of η mesons are performed at the GAMS-4π facility. A charge-exchange reaction at an initial momentum of 32.5 GeV/c was used as a source of 3.7 × 10⁶ η mesons. The following upper limits are established at a 90% confidence level: Br(η → 3γ) < 1.6 × 10^?4, Br(η → 4γ) < 2.8 × 10^?4, Br(η → π⁰π⁰) < 3.5 × 10^?4, Br(η → π⁰π⁰γ) < 1.7 × 10^?3, Br(η → π⁰π⁰γγ) < 4.0 × 10^?3, Br(η → 3π⁰γ) < 2.4 × 10^?4, and Br(η → 4π⁰) < 2.0 × 10^?5.     

Observation of the f 2(1525) resonance in the ηη system produced in K − p interactions at a momentum of 32.5 GeV/c

The reaction K ^? p → ηη(Λ/Σ⁰) at a momentum of 32.5 GeV/c was studied for the first time. The experiment was performed by using the GAMS-4π spectrometer at the 70-GeV accelerator of the Institute for High Energy Physics (IHEP, Protvino). The f ₂(1525) resonance was observed in the effective-mass spectrum of the ηη system at a low background level. The cross section for f ₂(1525) production was measured. The branching ratio for f ₂(1525)-meson decay to ηη and K $\bar K$ was found to be R = 0.119 ± 0.015(stat.) ± 0.036(syst.), which is in agreement with the world-average value.     

Ultracompact Fluorescence Lidar Based on a Diode Laser (405 nm, 150 mW) for Remote Sensing of Waterbodies and the Underlying Surface from Unmanned Aerial Vehicles

Doklady Physics - We report on developing an ultracompact (～300 g) fluorescence lidar based on a diode laser (405 nm, 150 mW) and a diffraction spectrometer equipped with a linear photodiode...     

Raman Spectroscopy Diagnostics of the Local Time Profile of an Ultrasound Beam in Water

JETP Letters - It has been demonstrated for the first time that pulsed laser Raman spectroscopy can be used for diagnostics of a local acoustic pressure profile with a peak pressure drop of 50 MPa...     

Structure and Composition of Insulin Fibril Surfaces Probed by TERS

Amyloid fibrils associated with many neurodegenerative diseases are the most intriguing targets of modern structural biology. Significant knowledge has been accumulated about the morphology and fibril-core structure recently. However, no conventional methods could probe the fibril surface despite its significant role in the biological activity. Tip-enhanced Raman spectroscopy (TERS) offers a unique opportunity to characterize the surface structure of an individual fibril due to a high depth and lateral spatial resolution of the method in the nanometer range. Herein, TERS is utilized for characterizing the secondary structure and amino acid residue composition of the surface of insulin fibrils. It was found that the surface is strongly heterogeneous and consists of clusters with various protein conformations. More than 30% of the fibril surface is dominated by β-sheet secondary structure, further developing Dobson's model of amyloid fibrils (Jimenez et al. Proc. Natl. Acad. Sci. U.S.A. 2002 , 99 , 9196 - 9201 ). The propensity of various amino acids to be on the fibril surface and specific surface secondary structure elements were evaluated. β-sheet areas are rich in cysteine and aromatic amino acids, such as phenylalanine and tyrosine, whereas proline was found only in α-helical and unordered protein clusters. In addition, we showed that carboxyl, amino, and imino groups are nearly equally distributed over β-sheet and α-helix/unordered regions. Overall, this study provides valuable new information about the structure and composition of the insulin fibril surface and demonstrates the power of TERS for fibril characterization.     

Spontaneous inter-conversion of insulin fibril chirality

Amyloid fibrils are associated with many neurodegenerative diseases and are considered to be the energetically most favorable form of proteins. Here we report that a small pH change initiates spontaneous transformation of insulin fibrils from one polymorph to another. As a result, fibril supramolecular chirality overturns both accompanying morphological and structural changes.