New Distances to Four Supernova Remnants

Object: Distances are found for four supernova remnants without previous distance measurements. H I spectra and H I channel maps are used to determine the maximum velocity of H I absorption for the four Supernova Remnants (SNRs). Method: We examined 13CO emission spectra and channel maps to look for possible molecular gas associated with each SNR, but did not find any. Result: The resulting distances for the SNRs are 3.5 ± 0.2 kpc (G24.7+0.6), 4.7 ± 0.3 kpc (G29.6+0.1), 4.1 ± 0.5 kpc (G41.5+0.4) and 4.5 ± 0 .4 - 9.0 ± 0.4 kpc (G57.2+0.8).

An Analytical Theory of Hall-Effect Devices with Three Contacts

Object:Vertical Hall-effect devices (VHalls) and split-drain MAG-FETs often have three contacts and a single mirror symmetry. We discuss the Equivalent Resistor Circuit (ERC) at small magnetic field, relate it to the electrical degrees of freedom, and compare it to traditional Hall plates with four contacts.Methods:In contrast to devices with four contacts, it is not possible to determine the sheet resistance of devices with three contacts by electrical measurements like the one of van der Pauw. However, for both types of devices, the output voltage over input current depends only on resistances of the ERC, the sheet resistance, and the Hall angle, irrespective of the exact shape of the devices and the size of the contacts.Result:This allows one to explore the maximum Signal-to-Noise Ratio (SNR) in a very general sense without consideration of any specific device geometry. It is shown how VHalls with all three contacts on the top face of the Hall tub can have electrical symmetry with maximum SNR.

Step-by-step Evolution of Young’s Double-slit Interference Fringes Using Boundary Diffraction Wave Theory

Present work reports formation of Young’s double-slit interference fringes using the Young's own theory of diffraction called the theory of boundary diffraction wave. Theory demands that double-slit interference fringes are generated due to superposition of boundary diffraction waves originating from the edges of the slits due to their physical interaction with the incident light. The theoretical development is further verified with the experimental observations.

Performance Analysis of an Optical System Using Dispersion Compensation Fiber & Linearly Chirped Apodized Fiber Bragg Grating

In this paper, a proposal for analyzing the performance of an optical system by using dispersion compensation fiber (DCF) and linear chirped apodized fiber Bragg grating (FBG) has been put forth. Both systems have three different schemes pre, post and symmetrical. Various parameters used for this analysis are input power, distance & input bit rate. Performance is analyzed in terms of Q factor, Bit Error Rate (BER) and Eye Diagram. It is found that use of FBG as a dispersion compensating element gives better system performance as compared to DCF.

Constraints on the Active and Sterile Neutrino Masses from Beta-Ray Spectra: Past, Present and Future1

Although neutrinos are probably the most abundant fermions of the universe their mass is not yet known. Oscillation experiments have proven that at least one of the neutrino mass states hasmi> 0.05 eV while various interpretations of cosmological observations yielded an upper limit for the sum of neutrino masses ∑mi< (0.14 ‒ 1.7) eV. The searches for the yet unobserved 0νββ decay result in an effective neutrino massmββ< (0.2 ‒ 0.7) eV. The analyses of measured tritium β-spectra provide an upper limit for the effective electron neutrino massm(ve) < 2 eV. In this review, we summarize the experience of two generations of β-ray spectroscopists who improved the upper limit ofm(ve) by three orders of magnitude. We describe important steps in the development of radioactive sources and electron spectrometers, and recapitulate the lessons from now-disproved claims for the neutrino mass of 30 eV and the 17 keV neutrino with an admixture larger than 0.03%. We also pay attention to new experimental approaches and searches for hypothetical sterile neutrinos.

Study of Optical Constants of ZnO Dispersed PC/PMMA Blend Nanocomposites

Present research work deals with the optical study of Zinc Oxide (ZnO) dispersed Polycarbonate/Polymethylmethacrylate (PC/PMMA) blend nanocomposites. ZnO nanoparticles have been prepared by simple chemical route and their average size has been confirmed by Transmission Electron Microscopy (TEM). The average particle size of the nanoparticles has been found to be ~11 nm. Formation of PC/PMMA blend nanocomposites has been confirmed by means of X-ray Diffraction (XRD). Absorption spectra, recorded using UV-Visible spectrophotometer, have been used to determine optical constants such as band gap, extinction coefficient, refractive index and real & imaginary part of dielectric constant. It has been found that band gap decreases as ZnO wt% increases in the blend nanocomposites. Lowest band gap has been found for PC25%/PMMA75% with ZnO 3 wt% blend nanocomposite. Increase in refractive index has also been found with increasing ZnO content. These types of blend nanocomposites have applications in UV-shielding and wave guide technologies.

Experimental Simulation of the Behaviour of Diagnostic First Mirrors Fabricated of Different Metals for ITER Conditions

In the experimental fusion reactor ITER, the plasma-facing component of each optical and/or laser diagnostic needs to be based on reflective optics with at least one mirror (first mirror) facing the thermonuclear plasma. The different kinds of radiation emanating from the burning plasma (neutrons, neutral atoms, electromagnetic radiation) create hostile operating conditions for the first mirrors. Therefore, a special program has been set up under the ITER framework aimed at solving the first mirror problem. This paper will review the main results in this field that have been obtained in the Institute of Plasma Physics, National Science Center “Kharkov Institute of Physics and Technology” (in many cases in cooperation with groups of other countries, as indicated in corresponding parts of the manuscript) during long-term investigations directed to find a solution of this problem,i.e., to find a material and accompanying precautions in order to satisfy the requirements for first mirrors. The main efforts were devoted to finding solutions to overcome the impact of the most severe deteriorating factors resulting in degradation of the optical properties of mirrors: sputtering by charge exchange atoms and deposition of contaminants. The obtained results are focused on: the effects of long term sputtering on mirror specimens fabricated from different metals with different structures (polycrystals, single crystals, metal film on metal substrates, amorphous), the effects of contaminating film and the possible protection to avoid of its appearance, the role of chemical processes for some metal mirrors, and the choice of material of laser mirrors.

A Numerical Analysis for Optimizing the Gratings Length and Coupling Coefficient for High Reflectivity and Low Cavity Loss in Fiber Grating Fabry-Perot Laser Model

The effects of gratings length (kLFG) and amplitude coupling (Co) coefficients on the effective reflectivity (Reff) and the total cavity loss (αtot) of an external cavity laser source (ECLS) based fiber Bragg gratings (FBGs) are numerically analyzed for designing a laser source operating in strong feedback regime (Regime V). In this study, FBG is used as a wavelength selective element to control the properties of the laser output by controlling the fiber gratings reflectivity level. The study is performed by modifying full analytical expressions for the Reff and the αtot based on laser coupled-wave equations. Results show that Reff is strongly dependent on kLg and Co. Also, it is found that αtot has been reduced significantly with increasing Co, especially at high value for kLG (kLFG> 1.5).