Supervised learning and frequency domain averaging-based adaptive channel estimation scheme for filterbank multicarrier with offset quadrature amplitude modulation

Filterbank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) is an attractive alternative to the orthogonal frequency division multiplexing (OFDM) modulation technique. In comparison with OFDM, the FBMC-OQAM signal has better spectral confinement and higher spectral efficiency and tolerance to synchronization errors, primarily due to per-subcarrier filtering using a frequency-time localized prototype filter. However, the filtering process introduces intrinsic interference among the symbols and complicates channel estimation (CE). An efficient way to improve the CE in FBMC-OQAM is using a technique known as windowed frequency domain averaging (FDA); however, it requires a priori knowledge of the window length parameter which is set based on the channel's frequency selectivity (FS). As the channel's FS is not fixed and not a priori known, we propose a k-nearest neighbor-based machine learning algorithm to classify the FS and decide on the FDA's window length. A comparative theoretical analysis of the mean-squared error (MSE) is performed to prove the proposed CE scheme's effectiveness, validated through extensive simulations. The adaptive CE scheme is shown to yield a reduction in CE-MSE and improved bit error rates compared with the popular preamble-based CE schemes for FBMC-OQAM, without a priori knowledge of channel's frequency selectivity.     

C60 Concentration Influence on MEH-PPV:C60 Bulk Heterojunction-Based Schottky Devices

We have investigated the effect of C60 concentration on the performance of poly[2-methoxy-5-(2′-ethylhexoxy-p-phenylene vinylene] (MEH-PPV):C60 blend-based Schottky barrier-based devices. Incorporation of C60 in MEH-PPV leads to a red shift and the reduction of intensity in MEH-PPV absorption spectra. The appearance of a C60 characteristic band in the Raman spectra of the composites indicates the presence of C60 in the blends. A FESEM study reveals that the addition of C60 significantly modifies the surface morphology of the blend films. However, higher concentrations (>?5 wt.%) results in agglomeration of C60 particles. Dark I–V measurements allow us to extract various diode parameters including barrier height, ideality factor, and saturation current. Profound variations have been observed in the dominant charge carrier transport mechanism for different C60 concentrations. A photoresponse study demonstrates the enhancement in the photocurrent with the increase in the C60 concentration up to 5 wt.%. Beyond this concentration, agglomeration impedes exciton dissociation and charge transport, which results in a decrease in the photocurrent. Finally, an impedance spectroscopy analysis has been extensively carried out to estimate the internal device parameters, such as junction resistance, capacitance and carrier lifetime. The correlation between these parameters and I–V curves has been established.     

Potentiometric studies of N,N′-Bis(2-dimethylaminoethyl)-N,N′-dimethyl-9,10 anthracenedimethanamine as a chemical sensing material for Zn(II) ions

A liquid membrane based Zn²⁺ ion selective electrode containing N,N′-Bis(2-dimethylaminoethyl)-N,N′-dimethyl-9,10 anthracenedimethanamine (Bis(TMEDA) anthracene) (I) as ionophore has been prepared and characterized. The membrane comprises of PVC, ionophore and plasticizer in the ratio of 33:2:65, respectively. It showed the best response in terms of detection limit (1.5 × 10^− 6 M) and working concentration range (1.0 × 10^− 5 M to 1.0 × 10^− 1 M) with Nernstian response towards Zn²⁺ ions. The electrode responds within 15 s of coming in contact with the solution. The potential response remains almost unchanged over a pH range of 3.0 to 7.5. The electrode can be used for at least 3 months without any considerable alteration in its response behavior. The proposed electrode revealed good selectivity towards Zn²⁺ ions over a number of alkali, alkaline earth, transition metals and some other heavy metal ions. The electrode has been used as an indicator electrode in the potentiometric titration of Zn²⁺ with EDTA. The proposed electrode also detected Zn²⁺ ions from real life samples.     

Preventive effects of diallyl sulfide on 7,12-dimethylbenz[a]anthracene induced DNA alkylation damage in mouse skin

Mutations that occur through DNA strand breaks are the prerequisites for the development of tumors, which ultimately leads to various genetic disorders including cancer. A number of naturally occurring compounds including certain dietary constituents play an important role in causation and prevention of a number of genetic diseases. Diallyl sulfide (DAS), a volatile organosulfur compound present in garlic has been shown to possess various pharmacological effects including cancer preventive properties. Now we are reporting the antimutagenic properties of DAS on 7,12- dimethylbenz[a]anthracene (DMBA), a carcinogenic polycyclic aromatic hydrocarbon, induced DNA strand breaks in mouse skin, using an alkaline unwinding assay. DAS (2.5-10 mg/kg body-weight) was applied topically, prior and post to DMBA (5 mg/kg body-weight) at the sampling time of 24, 48, 72 and 96 h. DAS application resulted in a significant (p < 0.001) protection in DMBA-induced DNA strand breaks. The pre-treatment of DAS (10 mg/kg body-weight) showed 68.35% protection and post-treatment showed 59.49% protection, at an intermittent period of 48 h, against DMBA-induced DNA strand breakage. These findings suggest that DAS can effectively check the mutations induced by environmental toxicants.     

Micromechanical characteristics of flux-grown SmAlO<Subscript>3</Subscript> single crystal

Results on mechanical characterization of flux-grown samarium aluminate (SmAlO₃) crystals in the load range from 0.098 to 0.98 N are reported. The variation of microhardness with applied load is found to be nonlinear and is explained by using the Hays–Kendall law. The applicability of the Hays–Kendall law leads to the load-independent value of hardness. The indentations are associated with cracks only at higher loads (over 0.686 N) and the cracks developed are Palmqvist’s in nature. The hardness results and the indentation-induced cracking yield the value of fracture toughness (K_c ), brittleness index (B_i ), and yield strength (σ_Y ) for SmAlO₃ crystal.