Some studies on Lorentz transformation matrix in non-cartesian co-ordinate system

The Lorentz matrices for transformation of co-ordinates in Cartesian system are presented for the cases when the relative velocity between two reference frames is along X , Y and Z axes. The general form of the matrix for transformation of co-ordinates from unprimed to primed frame has been deduced in case of Cartesian co-ordinate system with the help of the above matrices. This matrix has not been transformed to the cases of cylindrical and spherical polar co-ordinates due to the fact that the calculations are cumbersome and lengthy. Hence, considering the relative velocity between two frames along a co-ordinate axis the transformation matrix has been found out for cylindrical and spherical co-ordinates

Evaluation of cervical smear in high risk women

Background: Objectives of current study were (i) To find out the pattern of cervical smear in females having risk factors. (ii) To observe the relationship between abnormal cervical smear with high risk factors.Methods:A cross-sectional descriptive study was carried out in the department of obstetrics and gynecology, Guwahati medical college & hospital from July 2009 to August 2010 with the help of Pathology department. 200 women attending gynecological OPD with associated risk factors were selected at random. Detailed history, demographic information, contraceptive history and coital history were taken. Smear was taken from endocervix with the help of Ayer’s spatula or cytobrush.Results:Out of 200 cases, in 110 (55%) the smear was reported negative for malignancy. 73(36.5%) had an inflammatory smear, 11 (5.5%) had CIN, 1(0.5%) had malignancy and 5(2.5%) the smear was inadequate for cytological examination. In the study mean age of Cervical Intraepithelial Neoplasia (CIN) was 42.64 ± 6.34 years. Low socio-economic status, high parity & the use of oral contraceptive pills were major risk factors.  Conclusion:Cervical smear should be routinely used as a reliable diagnostic aid for early detection carcinoma cervix especially in high risk cases. The need of the hour is to create awareness and easy accessibility to proper screening.

Synthetic and structural investigation of ZnO nano-rods, hydrothermally grown over Au coated optical fiber for evanescent field-based detection of aqueous ammonia

We present the fabrication of modified clad optical fiber coated with ZnO nanorod over Au thin film to be served as ammonia gas sensor. The deposited material ZnO synthesized by hydrothermal process and modified clad fiber is coated by Autoclave technique. The as-synthesized materials are characterized by XRD, XPS, FTIR, Raman spectra and its hexagonal nanorods morphology was checked by FESEM. The ZnO coated over Au thin film fiber is found to be a good candidate towards ammonia sensing. The developed sesnor exihibted sensitivity (%) ~ 0.638 of ammonia gas at room temperature

Generation of dark pulses in a bismuth tellurite based mode-locked erbium-doped fiber laser

We report on the formation of dark pulses in a highly nonlinear fiber laser passively mode-locked by a Bistmuth Tellurite (Bi2Te3) based SA. The SA was fabricated by embedding Bi2Te3 powder into polyvinyl alcohol (PVA) film by a solution casting technique. By inserting the SA into an EDFL cavity, stable mode-locked operation was achieved at 1592.68 nm with the maximum pulse energy up to 2.38 nJ by adjusting polarization controller. The laser operated at pulse repetition frequency of 1.0 MHz with a pulse width of 215 ns. These results suggested that Bi2Te3 could be developed as an effective SA for mode-locked dark pulses generation in a highly nonlinear cavity

Detection of Ammonia Gas Molecules in Aqueous Medium by Using Nanostructured Ag-Doped ZnO Thin Layer Deposited on Modified Clad Optical Fiber

The synthesis of Ag-doped ZnO nanorod employing hydrothermal process over modified cladd optical fiber is reported. The developed material is characterized using X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), and Brunauer-Emmett-Teller (BET)analysis to evaluate the morphology and the nature of nanorod formed. The initial performance of the coated modified clad optical fiber toward detection of ammonia gas in aqueous solution is also presented. The sensing performance revealed that the developed material possess improved sensitivity toward ammonia gas at room temperature compared to Ag doped nanowires containing optical fiber sensor

Bismuth-doped hafnia-yttria-alumina-silica based fiber: spectral characterization in NIR to mid-IR

We report an experimental analysis of new hafnia-yttria-alumina-silica glass based fiber doped with bismuth (Bi), with absorption/fluorescence spectra along with resonant-absorption saturation, fluorescence lifetime, and gain, all adherent to Bi-related active centers (BACs), being measured at laser-diode excitation @ 908, 976, 1069, and 1120 nm, matching the NIR BACs' band. The found spectral laws reveal the optimal on excitation wavelength fluorescence, resonant-absorption bleaching, and gain capacities of the fiber, useful for applications at diode pumping. Besides, we report, for the first time to the best of our knowledge, a new resonant-absorption band of BACs in mid-IR (similar to 2.1 mu m) in the fiber, effectively bleached under the action of low-power in-band excitation, and provide the reasons for its association with co-doping the fiber with hafnium. (C) 2017 Optical Society of Americ

Wideband and flat gain series erbium doped fiber amplifier using hybrid active fiber with backward pumping distribution technique

A modern wideband and flat gain erbium-doped fiber amplifier (EDFA) is suggested and accomplished, by employing a recently fabricated hafnia-bismuth-erbium doped fiber (HB-EDF) and zirconia-erbium doped fiber (Zr-EDF) as a hybrid active fiber. The performance of the proposed EDFA is examined in both forward and backward pumping schemes, using 0.5m long HB-EDF and 4m long Zr-EDF in series structure to fulfill a wideband amplification that cover C- and L-telecommunication bands, respectively. At the optimumlaser diodes powers, the backward pumping amplifier attained a gain flatness of 14.6dB with the maximum gain variation of±1.8dB, throughout a wide bandwidth of 70nm, that is from 1530nm to 1600nm. The noise figure fluctuates from 4.3dB to 7.9dB within the gain flatness band. Using the backward pumping distribution technique, the proposed amplifier demonstrates not only an efficient performance, but also a cost reduction since only one laser diode is utilized to pump two stages

Er3+-Doped Nanoengineered Yttria-Stabilized Zirconia Alumino-Silicate Fiber for Efficient CW and Mode-Locked Laser Operation

We report on the development of efficient continuous wave (CW) and mode-locked ring fiber lasers utilizing an Er3+-doped nanoengineered yttria-stabilized zirconia alumino (YSZA)-silicate fiber as the gain element. With the proper design of the material composition, the YSZA fiber host presents superior features to eliminate the Er3+ cluster effects and enhance the radiative emission over commercial silica fibers, thus significantly increasing the fiber laser efficiencies. Through cavity analysis and optimization, we successfully demonstrate a 975-nm pumped single-mode Er3+-doped CW YSZA-silicate fiber laser with a slope efficiency of 43%, which is corresponding to the quantum efficiency of 69%. Because of the special dispersion property of the Er3+-doped YSZA-silicate fiber, we are able to build a stable soliton mode-locked 1565-nm fiber laser with 3.2-nJ pulse energy, 644-fs pulsewidth, and 4.96-kW peak power

Q-Switched Hafnium Bismuth Erbium-Doped Fiber Laser With Bismuth (Iii) Telluride Based Saturable Absorber

In this work, we fabricated the Bismuth (III) Telluride (Bi2Te3) based saturable absorber (SA) by embedding the material into polyvinyl Alcohol (PVA) film. By incorporating the film inside laser cavity with a homemade Hafnium Bismuth Erbium-doped fiber (HBEDF) as a gain medium, a stable Q-switched fiber laser was generated to operate at 1532 nm region. The repetition rate of the laser was tunable from 41.1 to 61.0 kHz while corresponding pulse width shrinks from 9.46 to 5.48 mu s as the 980 nm pump power rises from 69 to 122 mW. The maximum pulse energy was 31.5 nJ. To the best of our knowledge, this is the first report on the Q-switched fiber laser using n relatively short length of HBEDF as the gain medium

Evaluation of the performance of high phosphorous with germanium codoped multimode optical fiber for use as a radiation sensor at low dose rates

We propose a GeO(2)-P(2)O(5)-codoped step index multimode (SIMM) fiber having a core diameter of around 50 mu m with numerical aperture of around 0.21-0.22. The proposed SIMM fiber shows excellent linear radiation response behavior with sensitivity of around 0.69-0.97 dB/m/100 rad at a 505 nm wavelength within the dose rate range of 10-100 rad/h, as well as very low recovery at room temperature using a (60)Co gamma radiation source. This enables its practical application in fiber optic personal dosimeters for measurement of low dose gamma radiation. (C) 2011 Optical Society of Americ