Internal silicon laser processing with picosecond double pulses.

Abstract. A series of studies were conducted using dual energy X-ray absorptiometry (DXA) to measure energy and protein deposition in pigs. In an initial validation study DXA was compared directly with slaughter analysis as a method for measuring energy deposition in pigs. During growth from 30 to 60 kg the mean value for carcass energy deposition measured by DXA was 251 MJ compared to 249 MJ by chemical analysis (R2=0.94). Subsequently it was shown that both compensatory growth and the addition of ractopamine to the diet resulted in an improvement in efficiency of protein deposition (PE), however, ractopamine also resulted in a reduction in the efficiency of energy deposition (kg). Another study was conducted to compare the efficiency of utilization of dietary energy and protein by control and IGF-I transgenic pigs in response to dietary conjugated linoleic acid (CLA). Addition of CLA to the diet resulted in a reduction in kg, though there was no difference in kg based on genotype or sex. The PE was higher (P<0.05) in the IGF-I transgenic pigs. DXA was also used to assess energy deposition in pigs that were either homozygous stress non-sensitive (NN), heterozygous (Nn) or homozygous stress sensitive (nn). During growth from 30 to 60 kg or 60 to 90 kg there were no differences in the efficiency of either energy or protein deposition. In conclusion, DXA can be used to replace the comparative slaughter technique for measuring energy and protein deposition in pigs, thus this approach is useful for identifying differences in energy and protein deposition in pigs of different genotypes or when subjected to various dietary treatments.

The article is devoted to experimental and numerical studies of the efficiency of microwave energy deposition into a supersonic flow around the blunt cylinder at different Mach numbers. Identical conditions for energy deposition have been kept in the experiments, thus allowing to evaluate the pure effect of varying Mach number on the pressure drop. Euler equations are solved numerically to model the corresponding unsteady flow compressed gas. The results of numerical simulations are compared to the data obtained from the physical experiments. It is shown that the momentum, which the body receives during interaction of the gas domain modified by microwave discharge with a shock layer before the body, increases almost linearly with rising of Mach number and the efficiency of energy deposition also rises.

Dichroic ratios in polarized Fourier transform infrared for nonaxial symmetry of beta-sheet structures

The effect of light polarization on the interband transition spectra of zigzag carbon nanotubes and its diameter dependence

In this work, we have systematically investigated the polarization and distance effect of Ag-NPs double sphere to localized surface plasmon resonance (LSPR) using metallic nanoparticles simulation based on boundary element approximation. Two way polarizations were applied to Ag-NPs double sphere, in parallel and perpendicular polarizations. LSPR profile generally shifted to red-shift as the diameter of Ag-NPs increased both in parallel and perpendicular polarizations. Concerning the polarization direction, we have found that LSPR shifted to blue-shift as the distance of Ag-NPs double sphere increased in parallel polarization, while LSPR shifted to red-shift in perpendicular polarization. The phenomenon can be explained by the dipole-dipole coupling interaction between Ag-NPs double sphere. The results showed that the LPSR profile was not only affected by the diameter size and the distance of Ag-NPs double sphere but also by the polarization direction.

Advances in ultrashort laser pulse technology have recently generated several new applications in fields as diverse as laser processing, medical and bio-optics, opto-electronics, etc. However, ultrashort-pulse lasers require quiet laboratory environments and water cooling which prevents their use for practical applications. Spectroscopic applications also require a wavelengthtunable ultrashort pulses. The tuning range, however, is generally limited by the gain bandwidth of the laser. Since these pulses are generated with wavelength conversion using nonlinear crystals and mechanical tuning, it is difficult to generate wideband tunable pulses. Of significant interest is the recent development of compact ultrashort-pulse fiber lasers. Since these lasers consist of fiber-optic devices, they produce stable pulses and water cooling is not required. Fiber lasers are also maintenance-free and can work wherever there is electricity. The wavelength of the output pulses, however, can only be changed within the gain bandwidth of the fiber amplifier and the bandwidth is less than 100nm. In our work, we investigate all-fiber wideband utrashort-pulse sources based on ultrashort-pulse fiber lasers and study nonlinear effects in optical fibers. Specialty fibers, such as highly nonlinear fibers and photonic crystal fibers, were recently developed. Their characteristics are determined by their structure and they have demonstrated high energy density and dispersion tunability. Using ultrashort-pulse lasers and suitable specialty fibers, we can generate ultrawideband optical spectra, referred to as a super continuum. All-fiber super-continuum sources have also been reported. However, their noise level is generally high and the super continuum is characterized by excessive fine structure. To date, no practical Figure 1. Optical spectra of wavelength-tunable soliton pulses that were generated through nonlinear effects. As the fiber input power is increased, the center wavelength is continuously red-shifted. We can tune the wavelength from 1.55 to 2.0μm.

Optical properties of α-, β-, γ-, and 6,6,12-graphyne structures: First-principle calculations

We show spectacular and different effect of the sequential and simultaneous writing of two perpendicularly polarized ultrashort laser pulse trains on profile and magnitude of induced optical retardation inside fused silica glass. Clear birefringence was observed in the region exposed to linearly polarized pulse train radiation. It found out that the induced birefringence is erasable. It means that, when the sample is irradiated again with pulse train having perpendicular polarization, the induced birefringence is vanished and can be totally erased by optimizing the pulse energy. However, in a simultaneous writing approach, a contradictory result was observed. When the glass substrates were simultaneously (i.e. with an accuracy better than the pulse duration) exposed to two beams with perpendicular polarization the induced birefringence not only remained but also enhanced. Discussion and study on the results of interaction of polarized single ultrashort laser pulse and sequential laser beams (which spatially overlapped) having different polarizations and also change of energy ratio of simultaneously writing pulse trains helps us to analyze different results of the simultaneous interaction of two orthogonally polarized ultrashort laser pulse trains with transparent material. Our results provide pieces of evidence for further understanding the physical mechanism of creation of the birefringence using ultrashort laser pulses. Additionally, they provide the ability to manipulate the transient electron dynamics to control the profile and tailor of the induced birefringence.

We have investigated lattice disordering of cupper oxide (Cu2O) and copper nitride (Cu3N) films induced by high- and low-energy ion impact, knowing that the effects of electronic excitation and elastic collision play roles by these ions, respectively. For high-energy ion impact, degradation of X-ray diffraction (XRD) intensity per ion fluence or lattice disordering cross-section (YXD) fits to the power-law: YXD = (BXDSe)NXD, with Se and BXD being the electronic stopping power and a constant. For Cu2O and Cu3N, NXD is obtained to be 2.42 and 1.75, and BXD is 0.223 and 0.54 (kev/nm)−1. It appears that for low-energy ion impact, YXD is nearly proportional to the nuclear stopping power (Sn). The efficiency of energy deposition, YXD/Se, as well as Ysp/Se, is compared with YXD/Sn, as well as Ysp/Sn. The efficiency ratio RXD = (YXD/Se)/(YXD/Sn) is evaluated to be ~0.1 and ~0.2 at Se = 15 keV/nm for Cu2O and Cu3N, meaning that the efficiency of electronic energy deposition is smaller than that of nuclear energy deposition. Rsp = (Ysp/Se)/(Ysp/Sn) is evaluated to be 0.46 for Cu2O and 0.7 for Cu3N at Se = 15 keV/nm.

The dissociation dynamics of trans-azomethane upon excitation to the S,(n, pi) state with a total energy of 93 kcalmol-1 is investigated using femtosecond-resolved mass spectrometry in a molecular beam. The transient signal shows an opposite pump-probe excitation feature for the UV (307 nm) and the visible (615 nm) pulses at the perpendicular polarization in comparison with the signal obtained at the parallel polarization: The one-photon symmetry-forbidden process excited by the UV pulse is dominant at the perpendicular polarization, whereas the two-photon symmetry-allowed process initiated by the visible pulse prevails at the parallel polarization. At the perpendicular polarization, we found that the two C-N bonds of the molecule break in a stepwise manner, that is, the first C-N bond breaks in approximately 70 fs followed by the second one in approximately 100 fs, with the intermediate characterized. At the parallel polarization, the first C-N bond cleavage was found to occur in 100 fs with the intensity of the symmetry-allowed transition being one order of magnitude greater than the intensity of the symmetry-forbidden transition at the perpendicular polarization. Theoretical calculations using time-dependent density functional theory (TDDFT) and the complete active space self-consistent field (CASSCF) method have been carried out to characterize the potential energy surface for the ground state, the low-lying excited states, and the cationic ground state at various levels of theory. Combining the experimental and theoretical results, we identified the elementary steps in the mechanism. The initial driving force of the ultrafast bond-breaking process of trans-azomethane (at the perpendicular polarization) is due to the CNNC torsional motion initiated by the vibronic coupling through an intensity-borrowing mechanism for the symmetry-forbidden n-pi transition. Following this torsional motion and the associated molecular symmetry breaking, an S0/S1 conical intersection (CI) can be reached at a torsional angle of 93.1 degrees (predicted at the CASSCF(8.7)/cc-pVDZ level of theory). Funneling through the S0/S1, CI could activate the asymmetric C-N stretching motion, which is the key motion for the consecutive C-N bond breakages on the femtosecond time scale.

Current-driven domain wall dynamics is studied theoretically in the spin-valve nanostrips with parallel, perpendicular and tilted polarizers by Lagrangian formalism. In this description, the Slonczewski and field-like spin-transfer torques act as a Coulomb-type dissipation and an effective magnetic field, respectively. Considering a Walker profile, the wall behavior is governed by the dynamic equations about the center position, the out-of-plane angle, and the width of walls. It is found that the wall precesses after the steady motion breaks down for the parallel polarizer. The field-like spin-transfer torque favors a rapid increase of the steady velocity. The average velocity in the precession is nearly proportional to the current density. On the other hand, there is no precession for the perpendicular and tilted polarizers. Under the perpendicular polarizer, the wall stops when increasing current density. Moreover, there exist hysteresis and tri-stability for a large spin polarization. Under the tilted polarizer, it can be observed hysteretic, linear and nonlinear dependence of the wall velocity on the increasing current density. In the hysteresis, the wall experiences a switching of polarity or a reversal of motion.

Ultrafast transit-time measurement of leaves

Problem. The article is part of the authors' research in the field of road construction using GPR technologies. Ensuring a certain level of pavement reliability on highways requires the development of methods and means for continuous information acquisition and processing in real time, taking into account the parameters of structural heterogeneity, heterogeneity of physical and mechanical parameters of structures, as well as their changes over time. The solution of this problem is limited by the complexity of tasks of obtaining and interpreting the data of subsurface sensing and the associated errors in determining the parameters of structures, imperfection of methods of flaw detection of structures with subsurface inhomogeneities, multifactorial tasks of estimation of physical and mechanical parameters of multicomponent materials. Goal. Improving the accuracy and reliability of determining the boundaries of layers of non-rigid pavement structure, which have a low level of electrodynamic contrast due to interpenetration of layer materials or changes in their physical and mechanical properties. The solution of this problem is connected with the development of a method of obtaining reflected GPR signals and the improvement of algorithms for their processing. Methodology. The development of methods for the analysis of the electromagnetic field with a variable state of polarization makes it possible to assess the localization of violations of the integrity of the pavement structure at a qualitatively new level and allows the positioning of small inclusions even with a slight contrast in the dielectric constant. The proposed method of recording the reflection of an ultra-wideband GPR pulse signal at different polarizations is implemented by measuring the reflected signal from a metal sheet at oblique incidence and parallel polarization, recording the reflected pulse at perpendicular polarization, followed by measuring the reflection coefficient from the structure of the nonrigid pavement under study at parallel and perpendicular polarization. The electrophysical parameter recovery procedure is based on the solution of inverse scattering problems and ensures the accuracy of determining the low-contrast boundaries of the pavement structure and increases the accuracy of positioning subsurface heterogeneities. GPR signal processing algorithms are based on procedures for analyzing their polarization state, which allows determining the geometric parameters of subsurface heterogeneities. Practical value. The combination of the obtained results increases the accuracy and reliability of the results of GPR diagnosis and assessment of the condition of non-rigid pavement based on the most complete and reliable information about the subsu

The radiative response of antenna structures highly depends upon the extinction efficiency of the structures and the major parameter for the optimization of nanoantenna designs. To optimize the radiative response of the plasmonic antenna design, i.e., the oblique scattering of the THz radiation form, graphene‐coated gold (Au) nanowires have been studied. The present work provides a universal solution for the graphene‐coated cylindrical geometries. The optical conductivity of graphene has been modeled by the use of Kubo formalism, while the analytical modeling of the gold (Au) is done by employing Drude’s model. The Jacobi–Anger expansion method has been adopted for the transformation of electromagnetic fields in terms of series of cylindrical waves and has been modeled in terms of cylindrical vector wave functions (CVWFs). The analytical formulation has been presented for both polarizations, i.e., parallel polarization (TM) and perpendicular polarization (TE). The unknown scattering coefficients have been calculated by applying impedance boundary conditions at graphene‐gold nanowire interface. The analytical and numerical results have been computed for extinction efficiency (Qext) under parallel and perpendicular polarization states. The Qext under different parameters of graphene, diameter of metallic nanowire (R) and angle of incidence θi, has been computed. It is reported that the graphene‐coated Au nanorod supports the localized surface plasmon resonance (LSPR) under perpendicular polarization at a high THz frequency range. The surface plasmon resonance can be actively controlled under suitable parameters, i.e., graphene parameters, core size, and angle of incidence. The numerical results reveal that the radiative response of the plasmonic structures can be tuned actively from THz to Far‐IR frequency range under appropriate parameters. The provided results have potential applications in subwavelength devices and plasmonic antenna designs.

Lidar profiling of atmospheric aerosols and clouds in the lower atmosphere has been in progress at the Indian Institute of Tropical Meteorology (IITM), Pune (18°32′N, 73°52′E, 559 m MSL), India, for more than two decades. To enlarge the scope of these studies, an eye-safe new portable dual polarization micropulse lidar (DPMPL) has been developed and installed at this station. The system utilizes a diode-pumped solid-state (DPSS) neodymium–yttrium–aluminum–garnet (Nd:YAG) laser second harmonic, with either parallel polarization or alternate parallel and perpendicular polarization, as a transmitter and a Schmidt–Cassegrain telescope, with a high-speed detection and data acquisition and processing system, as a receiver. This online system in real-time mode provides backscatter intensity profiles up to about 75 km at every minute in both parallel and perpendicular polarization channels, corresponding to each state of polarization of the transmitted laser radiation. Thus, this versatile lidar system is expected to play a vital role not only in atmospheric aerosol and cloud physics research and environmental monitoring but also in weather and climate modeling studies of the impact of radiative forcing on the earth–atmosphere radiation balance and hydrological cycle. This paper provides a detailed description of Asia’s only lidar facility and presents initial observations of space–time variations of boundary layer structure from experiments carried out during winter 2005/06.