Superfluid 4He quantum interference grating

We report the first observation of quantum interference from a grating structure consisting of four weak link junctions in superfluid 4He. We find that an interference grating can be implemented successfully in a superfluid matter wave interferometer to enhance its sensitivity while trading away some of its dynamic range. We also show that this type of device can be used to measure absolute quantum mechanical phase differences. The results demonstrate the robust nature of superfluid phase coherence arising from quantum mechanics on a macroscopic scale.     

Noninvasive spectral imaging of skin chromophores based on multiple regression analysis aided by Monte Carlo simulation

In order to visualize melanin and blood concentrations and oxygen saturation in human skin tissue, a simple imaging technique based on multispectral diffuse reflectance images acquired at six wavelengths (500, 520, 540, 560, 580 and 600 nm) was developed. The technique utilizes multiple regression analysis aided by Monte Carlo simulation for diffuse reflectance spectra. Using the absorbance spectrum as a response variable and the extinction coefficients of melanin, oxygenated hemoglobin, and deoxygenated hemoglobin as predictor variables, multiple regression analysis provides regression coefficients. Concentrations of melanin and total blood are then determined from the regression coefficients using conversion vectors that are deduced numerically in advance, while oxygen saturation is obtained directly from the regression coefficients. Experiments with a tissue-like agar gel phantom validated the method. In vivo experiments with human skin of the human hand during upper limb occlusion and of the inner forearm exposed to UV irradiation demonstrated the ability of the method to evaluate physiological reactions of human skin tissue.     

All optical microwave photonic filters with a round-trip configuration

We propose novel photonic microwave multi-tap filters using a section of Hi-Bi fiber in a round-trip configuration, together with their application in a 20 km single mode fiber (SMF) radio-over-fiber (RoF) link. We demonstrate for the first time that the effect of chromatic dispersion in these multi-tap filters can be reduced in an RoF link when a linearly chirped fiber Bragg grating (FBG) is adopted. This result can be used to combat radio frequency power fading in an RoF link. The configurations are free from optical coherent interference and phase noise. Measured results show 3-tap filters with notch rejections greater than 35 dB and suppression of the level of secondary sidelobes by adjusting a polarization controller. PACS 42.81.-I; 42.81.Gs; 07.50.Qx     

Seasonal variation in natural abundance of δ13C and 15N in Salicornia brachiata Roxb. populations from a coastal area of India

High and fluctuating salinity is characteristic for coastal salt marshes, which strongly affect the physiology of halophytes consequently resulting in changes in stable isotope distribution. The natural abundance of stable isotopes (δ¹³C and δ¹⁵N) of the halophyte plant Salicornia brachiata and physico-chemical characteristics of soils were analysed in order to investigate the relationship of stable isotope distribution in different populations in a growing period in the coastal area of Gujarat, India. Aboveground and belowground biomass of S. brachiata was collected from six different populations at five times (September 2014, November 2014, January 2015, March 2015 and May 2015). The δ¹³C values in aboveground (?30.8 to ?23.6?‰, average: ?26.6?±?0.4?‰) and belowground biomass (?30.0 to ?23.1?‰, average: ?26.3?±?0.4?‰) were similar. The δ¹³C values were positively correlated with soil salinity and Na concentration, and negatively correlated with soil mineral nitrogen. The δ¹⁵N values of aboveground (6.7–16.1?‰, average: 9.6?±?0.4?‰) were comparatively higher than belowground biomass (5.4–13.2?‰, average: 7.8?±?0.3?‰). The δ¹⁵N values were negatively correlated with soil available P. We conclude that the variation in δ¹³C values of S. brachiata was possibly caused by soil salinity (associated Na content) and N limitation which demonstrates the potential of δ¹³C as an indicator of stress in plants.     

Screening dependence superconducting state parameters of La100−CGaC binary metallic glasses

The screening dependence theoretical investigations of the superconducting state parameters (SSP) viz. electron-phonon coupling strength λ, Coulomb pseudopotential μ^*, transition temperature T_C, isotope effect exponent α and effective interaction strength N₀V of six binary La_100−CGa_C (C=16, 20, 22, 24, 26 and 28 at.%) metallic glasses have been reported using Ashcroft's empty core (EMC) model potential for the first time. Five local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) are used in the present investigation to study the screening influence on the aforesaid properties. The T_C obtained from H-local field correction function is found in qualitative agreement with available experimental data and show almost linear nature with the concentration (C) of ‘Ga’ element. A linear T_C equation is proposed by fitting the present outcomes for H-local field correction function, which is in conformity with other results for the experimental data. Also, the present results are found in qualitative agreement with other such earlier reported data, which confirms the superconducting phase in the metallic glasses.     

Benzylammonium-Mediated Formamidinium Lead Iodide Perovskite Phase Stabilization for Photovoltaics

There is an ongoing surge of interest in the use of formamidinium (FA) lead iodide perovskites in photovoltaics due to their exceptional optoelectronic properties. However, thermodynamic instability of the desired cubic perovskite (α-FAPbI₃) phase at ambient conditions leads to the formation of a yellow non-perovskite (δ-FAPbI₃) phase that compromises its utility. A stable α-FAPbI₃ perovskite phase is achieved by employing benzylammonium iodide (BzI) and the microscopic structure is elucidated by using solid-state NMR spectroscopy and X-ray scattering measurements. Perovskite solar cells based on the FAPbI₃(BzI)_0.25 composition achieve power conversion efficiencies exceeding 20%, which is accompanied by enhanced shelf-life and operational stability, maintaining 80% of the performance after one year at ambient conditions.     

Enhanced colorless and broadcast capable symmetrical 10-Gbps bidirectional transmission in WDM-PON using RSOA and EAM

Here we proposed a novel architecture of wavelength division multiplexed-passive optical network (WDM-PON) in which the downlink unicast data, broadcast data and uplink unicast data transmission is possible with the symmetric data rate of 10 Gbps. At remote node (RN) cyclic wavelength routing property of array waveguide grating (AWG) and power splitting capacity of power splitter is used in the architecture so that broadcast channel can be overlaid on downlink unicast channels. At ONU carriers sent from central office (CO) is reused for upstream data transmission with the help of integration of a reflective semiconductor amplifier (RSOA) and an electro-absorption modulator (EAM) so there is no need of extra laser sources at ONUs which makes them colorless. EAM can be operated at very high speed; a modulation bandwidth of tens of GHz can be achieved. Broadcast channel causes a limited interference with downlink and uplink unicast channels so it does not affect the system performance. Since each channel has different wavelength so NRZ data is used which eliminates expensive DPSK receivers and detection becomes very easy. Simulation is performed with all channels having data rate of 10 Gbps having acceptable performance.     

Estimating rainfall using machine learning strategies based on weather radar data

The precision of forecasting rainfall is vital owing to current world climate change. As deterministic weather forecasting models are usually time consuming, it becomes challenging to efficiently use this large volume of data in hand. Machine learning methods are already proven to be good replacement for traditional deterministic approaches in weather prediction. This paper presents an approach using recurrent neural networks (RNN) and long short term memory (LSTM) techniques to improve the rainfall forecast performance. This will be compared with the random forest classifier and XGBoost as well. The goal is to predict a set of hourly rainfall levels from sequences of weather radar measurements. Python libraries are utilized to forecast the time series data. The training set comprises of data from first 20 days of every month and the inference set data from the continuing days. This makes sure that both train and inference sets are more or less independent. The idea resides in implementing an end‐to‐end learning framework.     

An Approach for Microprobe Measurement and Modeling for Millimeter-Wave Application

This paper describes a simple method to check the performance of microprobe. The two-port S-parameters of the microprobe are determined by one-port S-parameters measurement using HP 8510XF Network Analyzer. Based on the measurement, an equivalent circuit model for the microprobe is presented and good agreement between the measurement results and modeling results is obtained.