Doctor of Philosophy

dissertationIn this work, we focused on the magnetic field effect in organic films and devices, including organic light emitting diodes (OLEDs) and organic photovoltaic (OPV) cells. We measured magnetic field effect (MFE) such as magnetoconductance (MC) and magneto-electroluminescence (MEL) in OLEDs based on several π-conjugated polymers and small molecules for fields B∼2mT. Magnetic field effect (MFE) measured on three isotopes of Poly (dioctyloxy) phenylenevinylene (DOO-PPV) showed that both regular and ultra-small effects are isotope dependent. This indicates that MFE response in OLED is mainly due to the hyperfine interaction (HFI). We also performed spectroscopy of the MFE including magneto-photoinduced absorption (MPA) and magneto-photoluminescence (MPL) at steady state conditions in several systems. This includes pristine Poly[2-methoxy-5-(2-ethylhexyl-oxy)-1,4-phenylene-vinylene] (MEH-PPV) films, MEH-PPV films subjected to prolonged illumination, and MEH-PPV/[6,6]-Phenyl C61 butyric acid methyl ester (PCBM) blend, as well as annealed and pristine C60 thin films. For comparison, we also measured MC and MEL in organic diodes based on the same materials. By directly comparing the MPA and MPL responses in films to MC and MEL in organic diodes based on the same active layers, we are able to relate the MFE in organic diodes to the spin densities of the excitations formed in the device, regardless of whether they are formed by photon absorption or carrier injection from the electrodes. We also studied magneto-photocurrent (MPC) and power conversion efficiency (PCE) of a 'standard' Poly (3-hexylthiophene)/PCBM device at various Galvinoxyl radical wt%. We found that the MPC reduction with Galvinoxyl wt% follows the same trend as that of the PCE enhancement. In addition, we also measured the MPC response of a series of OPV cells. We attribute the observed broad MPC to short-lived charge transfer complex species, where spin mixing is caused by the difference, Δg of the donor/acceptor g factors; whereas narrow MPC is due to HFI within long-lived polaron-pairs

Phase Transitions and Magnetoresistance in Ni50Mn50−xInx Heusler Alloys

The phase transitions and magnetoresistance in polycrystalline ferromagnetic Ni50Mn50−xInx (15 ≤ x ≤ 16.2) Heusler alloys were studied through ac susceptibility, magnetization, thermal expansion, and resistivity measurements in the temperature interval of 5–400 K. The temperatures of the martensitic transformations were found to be strongly dependent on In concentration and on the strength of the applied external magnetic field. We observed large magnetoresistance (MR) Δρ/ρo ≈ −80% for x = 16 at T ≈ 125 K and Δρ/ρo ≈ −56% for x = 15 at T ≈ 309 K for ΔH = 5 T. In addition to large MR, the Ni50Mn50−xInx system exhibits ferromagnetic shape-memory effect and a large magnetic entropy change. Hence this system has potential to be a multifunctional applied material

Zirconium modified pomegranate peel for efficient removal of arsenite from water

We developed a novel biosorbent based on zirconium-modified pomegranate peel (SPP@Zr) for efficient arsenic (As(III)) removal from water. SEM, EDX, XRD, and FTIR were used to characterize the prepared biosorbent. The batch adsorption method was used to evaluate the adsorption viability of biosorbents for the removal of As(III) from water. The EDX analysis of saponified pomegranate peels (SPP) before and after Zr (IV) loading demonstrated that ion exchange was the preferred metal loading technique. As (III) adsorption is very pH-dependent, with the maximum adsorption occurring at pH 8.0. The maximum As(III) adsorption capacity of SPP@Zr was found to be 82.0 mg/g. According to isotherm and kinetic modeling studies, the experimental results fitted well with the Langmuir isotherm and pseudo-second-order kinetic modeling. The spent biosorbent may be easily regenerated and reused using an alkaline solution. Hence, SPP@Zr is proving to be a promising biosorbent for uptake of As (III) from water. BIBECHANA 19 (2022)1-1

Zirconium modified pomegranate peel for efficient removal of arsenite from water

We developed a novel biosorbent based on zirconium-modified pomegranate peel (SPP@Zr) for efficient arsenic (As(III)) removal from water. SEM, EDX, XRD, and FTIR were used to characterize the prepared biosorbent. The batch adsorption method was used to evaluate the adsorption viability of biosorbents for the removal of As(III) from water. The EDX analysis of saponified pomegranate peels (SPP) before and after Zr (IV) loading demonstrated that ion exchange was the preferred metal loading technique. As (III) adsorption is very pH-dependent, with the maximum adsorption occurring at pH 8.0. The maximum As(III) adsorption capacity of SPP@Zr was found to be 82.0 mg/g. According to isotherm and kinetic modeling studies, the experimental results fitted well with the Langmuir isotherm and pseudo-second-order kinetic modeling. The spent biosorbent may be easily regenerated and reused using an alkaline solution. Hence, SPP@Zr is proving to be a promising biosorbent for uptake of As (III) from water. BIBECHANA 19 (2022)1-1

Deixis in Kusunda

This paper examines the different categories of demonstrative deixis in Kusunda, a language isolate of western Nepal. Our corpus, based on naturalistic data evidences a much wider range of contrasts than is attested in earlier, elicitation based work. We show that while there is no evidence for any linguistic encoding of the relative directions left and right, nor of the absolute directions north-south-east-west, the spatial deictics are rich in differentiation of the vertical dimension, with both absolute height and relative height encoded, and elaborated on in complex constructions; some locative terms are also used for temporal reference. Unusually, the proximal range is more highly elaborated than the distal range, though the distal categories show overlap into the pronominal system

Evidence and stance in Kusunda

Kusunda has been described in sketch form (Watters et al. 2006), but a number of morphemic and syntactic structures remain unclear. In particular, the Watters et al. description was based on elicited materials, resulting in confusion about some morphemes. Following the collection of a naturalistic corpus we discuss the function of two verbal suffixes with interesting uses

Negotiation and normalization in Kusunda

Negative structures are generally assumed to be maximally accessible for verbal predicates, as evidenced by the requirement in many languages that nonverbal predicates be supported by a verb when negated. Indeed, the term ‘standard negation’ is used to refer to the negation of a declarative verbal clause, and yet this is at best highly restricted in Kusunda. We discuss the mood and nomi- nalizing strategies that are employed to escape from the restrictions imposed by such a system.

The structural and magnetic properties of Ni2Mn1-xBxGa Heusler alloys

The influence of the substitution of manganese by boron on the crystal structure and magnetic properties of Ni2Mn1-xBxGa Heusler alloys with 0≤x≤0.5 has been investigated using X-ray diffraction, thermal expansion, resistivity, and magnetization measurements. The samples with concentrations x\u3c0.25 were found to be of single phase and belonged to the cubic L21 crystal structure at room temperature. Crystal cell parameters of the alloys decreased from 5.830 to 5.825 Å with increasing boron concentration (x) from 0 to 0.25. The alloys were ferromagnetically ordered at 5 K and the saturation magnetization decreased with increasing boron concentration. The ferromagnetic ordering and structural transition temperatures for 0≤x≤0.3 have been observed and the phase (x-T) diagram of the Ni2Mn1-xBxGa system was constructed. The phase (x-T) diagram indicates that the ground state of Ni2Mn1-xBxGa alloys belongs to ferromagnetic martensitic, premartensitic, and austenitic phases in x≤0.12, 0.1