Single fiber colorless symmetric WDM-PON architecture using time interleaved remodulation technique for mitigating Rayleigh backscattering resilience

A time interleaved differential phase shift keying (DPSK) remodulation technique is proposed to mitigate the effect of Rayleigh backscattering (RBS)-induced noise in a single fiber colorless wavelength-division-multiplexing passive optical network (WDM-PON). In order to achieve a cost effective optical network unit (ONU) solution without dedicated laser sources for upstream signals to provide optimum symmetric capacity in a colorless WDM-PON, remodulation becomes the core attraction. Also as the performance of colorless WDM-PON systems suffers from the transmission impairments due to RBS, it is mitigated by using this remodulation scheme. Simulation results show that downstream and upstream signals achieve the error-free performance at 10 Gbit/s with negligible penalty, and enhance the tolerance to RBS-induced noise over a 25 km single-mode fiber.     

A frequency reconfigurable MIMO antenna with agile feedline for cognitive radio applications

A novel frequency agile multiple‐input‐multiple‐output (MIMO) patch antenna based on a reconfigurable feedline is proposed. The proposed antenna structure has two hexagonal‐shaped patch antenna elements. A defected ground structure having hexagonal shape is included in the ground plane to make the design compact and improve isolation among antenna elements. Further compactness is achieved using reactive loading. Frequency reconfigurability is realized by employing varactor diodes in the microstrip feedline. The proposed antenna achieves a frequency reconfigurable band with wide tuning range from 1.42 to 2.27 GHz with good gain and efficiency. Furthermore, an envelope correlation coefficient value of less than 0.2 and minimum isolation of 12 dB was achieved, displaying good MIMO performance. The presented antenna has a planar, low profile design with compact size of 100 × 50 mm². Thus, frequency agility, wide range tuning, compactness, and planar structure of the proposed antenna design make it suitable for modern wireless handheld devices particularly in cognitive radio applications.     

Hydrogarnet-type cubic crystals in polymer-modified mortars

Polymer-modified mortars (PMMs) using recently developed redispersible polymer powders and aqueous polymer dispersions have become popular construction materials in the world, particularly for finishing and repairing works, because of their excellent performance and durability. In order to develop usable models of structure-property relationships for such systems, the authors have focussed their studies on the microscopic level because such aspects still need more information. In this context, they have already reported their detailed observations on the formation of Ca(OH)₂, AFt, AFm, hollow tubules, and hollow crystals in PMMs (1–5). However, studies on hydrogarnet-type cubic crystals in PMMs were not available by that time.

The purpose of this paper is to establish morphologically the formation of hydrogarnet-type cubic crystals in PMMs.     

Selective Electroanalytical Method for the Determination of Roxarsone in Poultry Feed and Litter

An extremely sensitive and selective voltammetric method was developed for the determination of roxarsone (ROX) at a newly modified carbon paste microelectrode in Britton–Robinson buffer (BRB) at pH 2.0. The electrode is based on a disposable plastic pipette tip filled with carbon paste based on a mixture of graphite powder and Amberlite XAD-4 (5:1, w/w). The experimental parameters, such as pH, type of the buffer, mode of voltammetry, accumulation potential, accumulation time, and stirring rate were optimized. The reduction peak current dependences were linear for the concentration of ROX from 2.0 to 100 μM. The method showed reproducible results with RSD (n?=?11) of <2.0 %. The limit of detection (LOD) and limit of quantification (LOQ) were 0.53 and 1.76 μM, respectively. ROX showed that there was no apparent surface passivation indicating the suitability of the modified electrode for ROX detection. The developed method was successfully applied for the determination of ROX in poultry feed and poultry litter collected from various localities of Hyderabad.     

Microscopic investigations and pharmacognostic techniques for the standardization of Caralluma edulis (Edgew.) Benth. ex Hook.f.

Herbal medicines frequently suffer with quality controversies because of similar species or varieties. This often leads to sophistication or admixture of the crude drug as they share various look alike physical features. Commercially, stalks of Caralluma edulis are commonly adulterated with other species because of their analogous morphology. In the present research, the microscopic standardization of the drug was performed by structural, histological, and anatomical features. Pharmacognostical characterization was carried out by physicochemical (moisture content, swelling index, pH value, ash values, and extractive values) and fluorescence analysis. The chemical characterization by UV–Visible, Fourier transform infrared spectroscopy, and high‐performance liquid chromatography was also performed that disclosed the chief phytoconstituents of the herbal drug. The above mentioned constraints, being reported for the first time in C. edulis, are substantial in establishing the microscopic and pharmacopoeial standards for future identification and authentication.     

Highly sensitive spectrometric method for determination of hydroquinone in skin lightening creams: application in cosmetics

A highly sensitive, simpler, faster and economical UV/visible spectrophotometric method has been established for the estimation of hydroquinone (HQ) in dilute organic matrices. The method is based on using ammonium meta‐vanadate as an oxidizing catalyst for conversion of HQ to p‐benzoquinone (BQ) in the presence of oxygen. As a result of higher absorption of UV light by BQ than by HQ, its signal has been utilized for determining HQ at the trace level. The effect of various parameters such as amount of oxidizing agent, stability time, temperature, acids and bases, solvents and interference by various compounds has been studied upon the absorption of BQ as HQ. Under optimized conditions, Beer’s Law was obeyed in the range of 0.025–2.00 μg ml^?1 HQ at 245.5 nm using 1 : 1 (V/V) 2‐propanol/water system with a lower detection limit of 7 ng ml^?1 and linear regression coefficient of 0.9998. Relative standard deviation of 1.5% was observed for 0.5 μg ml^?1 HQ solution (n = 11). The newly developed method has been successfully applied to diluted samples of various skin lightening creams for free HQ determination at the trace level. Comparison of the results obtained by the proposed method with those by a previously reported method proved its validity.     

On-chip electrostatic discharge protection for CMOS gas sensor systems-on-a-chip (SoC)

An on-chip electrostatic discharge (ESD) protection scheme is demonstrated for an emerging technology of microelectromechanical systems (MEMS)-based embedded sensor (ES) system-on-a-chip (SoC). The ESD protection scheme is implemented using ground-referenced multifinger thyristor-type devices optimized for (1) the input/output (I/O) protection, (2) the power supply clamp, and (3) the internal sensors’ electrodes during the micromachining process. The ESD structure developed demonstrates a leakage current below 10⁻¹⁰ A, high on-state conductance, and high level of human body model (HBM) immunity.     

Microhotplate Temperature Sensor Calibration and BIST

In this paper we describe a novel long-term microhotplate temperature sensor calibration technique suitable for Built-In Self Test (BIST). The microhotplate thermal resistance (thermal efficiency) and the thermal voltage from an integrated platinum-rhodium thermocouple were calibrated against a freshly calibrated four-wire polysilicon microhotplate-heater temperature sensor (heater) that is not stable over long periods of time when exposed to higher temperatures. To stress the microhotplate, its temperature was raised to around 400 °C and held there for days. The heater was then recalibrated as a temperature sensor, and microhotplate temperature measurements were made based on the fresh calibration of the heater, the first calibration of the heater, the microhotplate thermal resistance, and the thermocouple voltage. This procedure was repeated 10 times over a period of 80 days. The results show that the heater calibration drifted substantially during the period of the test while the microhotplate thermal resistance and the thermocouple-voltage remained stable to within about plus or minus 1 °C over the same period. Therefore, the combination of a microhotplate heater-temperature sensor and either the microhotplate thermal resistance or an integrated thin film platinum-rhodium thermocouple can be used to provide a stable, calibrated, microhotplate-temperature sensor, and the combination of the three sensor is suitable for implementing BIST functionality. Alternatively, if a stable microhotplate-heater temperature sensor is available, such as a properly annealed platinum heater-temperature sensor, then the thermal resistance of the microhotplate and the electrical resistance of the platinum heater will be sufficient to implement BIST. It is also shown that aluminum- and polysilicon-based temperature sensors, which are not stable enough for measuring high microhotplate temperatures (>220 °C) without impractically frequent recalibration, can be used to measure the silicon substrate temperature if never exposed to temperatures above about 220 °C.