Negative to Positive Magnetoresistance transition in Functionalization of Carbon nanotube and Polyaniline Composite

Electrical resistivity and magnetoresistance(MR) in polyaniline(PANI) with carbon nanotube(CNT) and functionalized carbon nanotube(fCNT) composites have been studied for different weight percentage down to the temperature 4.2K and up to magnetic field 5T. Resistivity increases significantly in composite at low temperature due to functionalization of CNT compare to only CNT. Interestingly transition from negative to positive magnetoresistance has been observed for 10wt% of composite as the effect of disorder is more in fCNT/PANI. This result depicts that the MR has strong dependency on disorder in the composite system. The transition of MR has been explained in the basis of polaron-bipolaron model. The long range Coulomb interaction between two polarons screened by disorder in the composite of fCNT/PANI, increases the effective on-site Coulomb repulsion energy to form bipolaron which leads to change the sign of MR from negative to positive.Comment: 5 pages, 8 figures; typos adde

Tuning spin one channel to exotic orbital two-channel Kondo effect in ferrimagnetic composites of LaNiO3 and CoFe2O4

We report the tuning from spin one channel (1CK) to orbital two-channel Kondo (2CK) effect by varying CoFe2O4 (CFO) content in the composites with LaNiO3 (LNO) along with the presence of ferrimagnetism. Although there is no signature of resistivity upturn in case of pure LNO, all the composites exhibit a distinct upturn in the temperature range 30-80 K. For composite with lower percentage of CFO (10 %), the electron spin plays the key role in the emergence of resistivity upturn which is affected by external magnetic field. On the other hand, when the CFO content is increased (15%), the upturn shows strong robustness against high magnetic field (14 T) and a crossover in temperature variation from lnT to T^1/2 at the Kondo temperature, indicating the appearance of orbital 2CK effect. The orbital 2CK effect is originated due to the scattering of conduction electrons from the structural two-level systems which is created at the interfaces between the two phases (LNO and CFO) of different crystal structures as well as inside the crystal planes. A negative magnetoresistance (MR) is observed at low temperature (< 30 K) for composites containing both lower (10 %) and higher percentage (15 %) of CFO. We have analyzed the negative MR using Khosla and Fisher semi-empirical model based on spin dependent scattering of conduction electrons from localized spins.Comment: 14 pages including supplementary materials and 12 figure

Reproductive Health Challenges and Coping Strategies: A Study of Female Construction Workers in India

Reproductive Health (RH) is a key area of focus which can lead towards an overall empowerment of women. Better RH positively contributes in the process of human development and augments the socio-economic welfare of the population. Safe motherhood is a crucial aspect of reproductive health services. Adequate utilization of health care services during pregnancy and delivery ensures a healthy mother. With the rapid increase in construction sector, the number of female construction workers is growing. Prolonged working hours, strenuous work and unhealthy environment exposure among the female workers is making them more vulnerable to the health issues such as lower abdominal pain, irregular periods, prolapsed uterus, miscarriages, reproductive tract infections (RTIs) and sexually transmitted diseases(STDs).This study aims:(i) to explore the various problems related to reproductive health faced by the women workers in the construction sites;(ii) to examine the health seeking behaviour and coping strategies for various reproductive health problems; (iii) to assess the impact of workplace culture on RH problems and; (iv) to explore the impact of women’s autonomy and experience of domestic violence on their RH decision making. The study was confined to the major construction sites present in the city of Bhubaneswar, Odisha. A total of 288 sampled respondents were randomly selected from ten different construction sites of the city. The key finding indicates that the prevalence of RTIs/STIs morbidity is widely present among women in the age group of 15-49 years. The nature of harassment reported was more of verbal by nature than physical or sexual. Among the respondents (81%) of women workers reported that generally contractor shouts at them and the behavior is also same towards the other workers also. Moreover, the female workers feel that they do not get sufficient leave while unwell as they have to join the work to sustain their family. Unwillingness to seek treatment, cultural stigmatization was quoted to be the major reasons for not availing health care facilities by these workers. Women’s experiences of different forms of domestic violence leading to several levels of emotional and physical trauma were found to significantly diminish their antenatal health. Moreover, availability of social protection mechanism among these female construction workers to a large extent can solve the issue of unmet needs of RH. The findings of the present study will help in addressing the challenges faced by the female construction workers and to cater the growing healthcare needs of this segment of the populatio

Effect of LaNiO3 on the impedance and dielectric properties of CoFe2O4: a high temperature study

In this article, we report the impedance and dielectric properties of the nanocomposites comprising of CoFe2O4 (CFO) and LaNiO3 (LNO) with varying LNO content (0, 5, 10 and 15%) in the temperature range from 35 degrees C-400 degrees C. The impedance and modulus spectroscopy show the non-Debye type dielectric relaxation behaviour of the grain and grain boundary separately in pure CFO with an additional relaxation in the composite with 15% LNO, arising from the electrode polarization. Mostly the grain boundary of the composites is affected by the presence of LNO as its activation energy in the composite with 15% LNO is reduced by similar to 0.2-eV compared to pure CFO, whereas that of the grain remains similar. The dielectric constant increases consistently with increasing LNO content in the composites owing to the Maxwell-Wagner-Sillar type polarization effect between the interfaces of LNO and CFO. The dielectric constant manifests a negative value in both pure CFO and the composite with 15% LNO at all temperatures in the frequency of hundreds of MHz which is explained by the interband transition. The ac conductivity of pure CFO reveals short range and orientational hopping inside the grains and across the grain boundary, respectively. However, in the composite with 15% LNO, the reduced activation energy assists the charge carriers for short range hopping across the grain boundary while the conductivity inside the grain remains unaffected

Polydimethylsiloxane-multiwalled carbon nanotube composite as a metamaterial

Negative permittivity is an exceptional property of metamaterials, which makes them unique class of artificial materials with numerous applications ranging from cloaking to wave filters. In this paper we report about the PDMS (Polydimethylsiloxane)-MWcnt (Multi wall carbon nano tube) composite beyond percolation, as a metamaterial with high negative permittivity. Percolated composite showed high negative permittivity of -2376.62 at 2541.401 Hz and low tangent loss of -0.065 at 1 MHz. The conductivity spectra followed Jonscher's power law, indicating hopping conduction for composites below percolation threshold. Beyond percolation, networking between the MWcnts formed large number of conductive paths resulting in free electron conduction. The impedance studies showed the capacitive-inductive transition in the percolated composite with inductive phase exhibiting negative permittivity. (C) 2017 Elsevier B.V. All rights reserved

Influence of orbital two-channel Kondo effect on anomalous Hall effect in ferrimagnetic composites of LaNiO3 and CoFe2O4

In this report, we have investigated the magnetoresistance (MR) and Hall effect of the ferrimagnetic composites containing LaNiO3 and CoFe2O4 (CFO) (with CFO content 15% and 20%) which exhibit orbital two-channel Kondo (2CK) effect and therefore pronounced resistivity upturn at low temperature. Both composites manifest a negative to positive crossover in MR with increasing temperature. The MR is described by the Khosla and Fisher model of spin fluctuations scattering of conduction electrons and the two-band theory based on hybridized p-d sub-bands. The Hall resistivity of the composites consists of both ordinary and anomalous part. The negative sign of the ordinary Hall coefficient suggests electrons as the dominating charge carriers. The coefficient of anomalous Hall resistivity (R-S) follows the scaling relation (R-S = a rho(xx) + b rho(2)(xx)) with longitudinal resistivity (rho(xx)) at high temperature above the resistivity upturn. However, at low temperature R-S shows non-monotonous behaviour and deviates from the scaling relation where orbital 2CK effect takes place. More detailed study below the resistivity upturn of the composite with 20% CFO reveals that this deviation occurs around the Kondo temperature. This breakdown of scaling relation around the Kondo temperature indicates the possible influence of orbital 2CK on the anomalous Hall effect

Tuning magnetoresistance and electrical resistivity by enhancing localization length in polyaniline and carbon nanotube composites

We report low temperature electrical resistivity and magnetoresistance (MR) measurements of conducting polyaniline (PANI) and multiwalled-carbon nanotube (MWCNT) composites. We have used an in-situ oxidative polymerization method to synthesize hydrochloric acid-doped PANI composites with MWCNT weight percentages of 0, 5, 10 and 15. The temperature dependence of resistivity is studied from room temperature to 4.2K and analysed by a Mott variable range hopping (VRH) model. The resistivity increases from 1.1 x 10 -3 m at 300K to 65.75 m at 4.2 K, almost four orders of the magnitude change with temperature for pure PANI. Whereas the PANI composite with 15% MWCNTs shows less variation from 4.6x10 -4 to 3.5x10 -2 m. The huge change in resistivity is due to the localization of charge carriers in the presence of disorder. At 4.2K MR shows transition from positive to negative with higher MWCNT loading. Samples with 5 and 10% MWCNTs show positive MR, whereas the 15% MWCNT loaded sample shows negative MR. The positive and negative MR are discussed in terms of the wave function shrinkage effect and quantum interference effect on VRH conduction

Field emission properties and strong localization effect in conduction mechanism of nanostructured perovskite LaNiO3

We report the potential field emission of highly conducting metallic perovskite lanthanum nickelate (LaNiO3) from the nanostructured pyramidal and whisker shaped tips as electron emitters. Nano particles of lanthanum nickelate (LNO) were prepared by sol-gel route. Structural and morphological studies have been carried out. Field emission of LNO exhibited high emission current density, J = 3.37 mA/cm(2) at a low threshold electric field, E-th = 16.91 V/mu m, obeying Fowler-Nordheim tunneling. The DC electrical resistivity exhibited upturn at 11.6K indicating localization of electron at low temperature. Magnetoresistance measurement at different temperatures confirmed strong localization in nanostructured LNO obeying Anderson localization effect at low temperature. Published by AIP Publishing

Sensing metrics of a dual-cavity single-gate MOSHEMT

This paper presents the simulation study of the impact of dielectric modulation on the characteristics of a single-gate single-cavity and a single-gate dual-cavity AlGaN/GaN heterostructure for biomolecule detection. The drain current, which is used as a sensing metric to carry out the device’s sensitivity analysis, is affected by dependent variables, such as cavity design, various biomolecules, and charges. The drain current sensitivity with HfO2 as the gate dielectric has been found to be 0.22 for cavity length of 40 nm each which decreased by 23% and 41% when cavity lengths are 30 nm and 25 nm, respectively. For 75%, 50%, and 25% fill percentage, the drain current sensitivity is observed to be 3.19, 0.75, and 0.54, respectively, establishing the applicability of the device for biosensing applications