Crystal Growth and Property Tuning of Layered Magnetic Topological Semimetals

The demand for energy-efficient devices has been growing rapidly due to the need for data-driven technologies and the global energy crisis. As device size approaches the atomic scale, the miniaturization of electronic devices may stop in the near future unless fundamentally new materials or device concepts are developed. The emergent topological materials with exotic properties show remarkable robustness against crystal lattice defects, which are promising for next-generation technology. These materials host exotic properties such as high mobility, large magnetoresistance, chiral anomaly, and surface Fermi arcs, etc. Among various topological materials, the ZrSiS-family materials exhibit two types of Dirac states, which provide opportunities to tune topological states by varying different parameters. The magnetic version of ZrSiS-family compounds, LnSbTe (Ln = lanthanide), hosts inherent magnetism, providing a novel platform to study the interplay between magnetism and exotic quantum states.With this motivation, this research is focused on the synthesis of single-crystal and characterization of previously unexplored magnetic topological nodal line semimetals LnSbTe. The compounds NdSbTe and SmSbTe exhibit antiferromagnetic ground states and enhanced electronic correlations. The magnetization and heat capacity measurements suggest the possible existence of magnetic frustration in tetragonally crystallized SmSbTe. Furthermore, the evolution of electronic and magnetic properties was studied with varying composition

Block Copolymer Nanostructures for Inorganic Oxide Nanopatterning

Self-assembled nature of block copolymer (BCP) makes them ideal for emerging technologies in nanometer scale. The micro phase separation between two or more dissimilar polymer blocks of BCP leads to uniform periodic nanostructures of different domains of dimension in the range of 5-100 nm, good for the development of emerging microelectronic and optoelectronics devices. Molecular weight and chain architecture of each blocks govern the morphology evolution; gives different structure like spherical, micelles, lamellae, cylindrical, gyroid etc. The morphology evolution of BCP nanostructure also depends on different external factors as well. In the first work of this thesis, three external factors temperature, BCP thickness and brush layer which influences microphase separation and orientation of the BCP have been varied to study their influence on a cylinder forming BCP poly (styrene-block-methyl methacrylate (PS-b-PMMA). The well-organized periodic nanostructure of BCPs can be used as template to make inorganic nanopattern. In this work, titanium dioxide (TiO2) with unique structural and functional properties has been selected as inorganic material. In the second and third work of this thesis, I have used the same cylinder forming PS-b-PMMA as a template to deposit TiO2 nanodots using two different inorganic deposition methods. In the second work, room temperature pulse laser deposition (PLD) and in the third work wet chemical method were used to deposit TiO2 nanodots. Scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDS), x-ray diffraction (XRD), and photoluminescence (PL) were used to characterize BCP and TiO2 nanostructures

Impact of climate change on agricultural production in Chitwan district, Nepal

Forskningen bak denne masteravhandlingen ble gjennomført i Chitwan-distriktet i Nepal og hadde som mål å undersøke effekten av klimaendringer på landbruket der. Klimaendringer har påvirket landbruket over hele verden. Nepal, som jordbruksland, står overfor flere problemer på grunn av de pågående endringene. Nøkkelfaktorer som påvirker matproduksjonen er temperatur, nedbør, jordkvalitet og bøndenes evne til å tilpasse seg til nye situasjoner. Klimaendringene har endret disse parameterne og det skaper mange problem for landbrukssektoren i Nepal. Forskningen er utført for å undersøke effektene av klimaendringer på produksjonen av mat, men også på bøndenes daglige liv; deres økonomi og deres tanker rundt de endringer som skjer. Forskningen involverte en undersøkelse av 80 hushold for å samle inn primærdata som deretter ble analysert med kjikvadratstester. 26 prosent av husholdene indikerte at risplantingssesongen hadde begynte tidligere, og 30 prosent antydet at de skulle endre dyrkingen til senere i sesongen. Innhøstingstiden antas å komme tidligere enn før ifølge 30 prosent av bøndene. Et stort problem ble identifisert i risproduksjonen, hvor 42,5 prosent av bøndene rapporterte at risavlingene har gått ned sammenlignet med tidligere år. Videre ble klimadata fra Chitwan-området analysert ved bruk av regresjonsanalyser, dette for å finne eventuelle trender de seneste 20 år. Gjennomsnittlig maksimum- og minimumstemperatur viste en årlig reduksjon på henholdsvis 0,028°C og 0,0377°C, mens den årlige nedbørstrenden viste en reduksjon med 21,75 mm per år men med stor variasjon fra år til år. Avslutningsvis er en korrelasjonsanalyser brukt for å undersøke sammenhengen mellom klimadata og produksjonsstatistikk. Klimaendringene har direkte påvirket livet til bønder som er avhengige av avlingene sine for å overleve. Omtrent 94 % av bøndene tok i bruk skadedyrbekjempelse som et tilpasningstiltak. Bønder rapporterte om økende problem med plante- og insektsykdommer ved bruk av vekster med høy avkastning. Til tross for disse utfordringene, har forskning vist at bøndene er villige til å gjøre endringer i sin praksis for å tilpasse seg klimaendringene. Dette viser at beslutningstakere må holde fokus på klimaendringsstrategier og oppmuntre til forskning og utvikling på disse områdeneThis research was conducted in the Chitwan district of Nepal to determine the effect of climate change on agriculture. Climate change has affected agriculture worldwide. Nepal being an agricultural country is facing several problems due to ongoing climate change. Key factors affecting food production are temperature, rainfall, soil quality, and farmers’ ability to adapt to the situation. Climate change has disturbed these parameters which are creating numerous problems in the agriculture sector of Nepal. This research is performed to determine the effects on the production but also the life of farmers, their economic situation, and their perceptions of what is going on. The research involved a household survey to collect primary data that was then analyzed with the Chi-square test. 26% indicated that the rice planting season had changed to earlier, and 30 percent indicated that they should shift cultivation to later in the season. Harvest time is believed to be ahead of before according to 30 percent of farmers. A major problem has been identified in the rice crop, with 42.5 percent of farmers reporting that rice yields have declined compared to previous years. Further, the climate data are analyzed with the implementation of a regression model. Trend analysis of annual average maximum and minimum temperature shows a minute reduction of temperature (2000-2021) by 0.028° C and 0.0377° C respectively whereas the annual rainfall trend also shows a reduction by 21.75mm per year. Finally, the correlation model is accommodated to examine the relationship between the climate data and production statistics. Climate change has directly affected the lives of farmers who depend on their crops for their livelihood. About 94% of farmers used pest management practices as an adaptation measure. Farmers report a growing problem of plant and insect diseases when using high-yielding crops. Despite these challenges, research has shown that farmers are willing to make changes in their practices to adapt to climate change. This shows that policymakers need to stay focused on climate change strategies and encourage research and development on these approaches.

High-resolution hyperfine spectroscopy of excited states using electromagnetically-induced transparency

We use the phenomenon of electromagnetically-induced transparency in a three-level atomic system for hyperfine spectroscopy of upper states that are not directly coupled to the ground state. The three levels form a ladder system: the probe laser couples the ground state to the lower excited state, while the control laser couples the two upper states. As the frequency of the control laser is scanned, the probe absorption shows transparency peaks whenever the control laser is resonant with a hyperfine level of the upper state. As an illustration of the technique, we measure hyperfine structure in the $7S_{1/2}$ states of $^{85}$Rb and $^{87}$Rb, and obtain an improvement of more than an order of magnitude over previous values.Comment: 7 pages, 6 figure

Quinolines and Related Compounds as Potential Antimalarials

Various 4-and 8-aminoquinoline derivatives having different substituents in the side chain and in the nucleus have been discussed in respect of their antimalarial activity and tolerance dosages. The effect of the incorporation of different moieties e.g. piperazine, piperidine and quinoline itself has also been highlighted. Certain quinoline quinones and benzoquinones as effective antimalarial agents have also been described

The proposed Nepal-China trans-border railway in Nepal’s collective imagination

Nepal-China relations have been amicable since the establishment of diplomatic ties in 1955. Consequently, the image of China in Nepal’s collective imagination has remained positive. This imagination reached new heights when China welcomed the promulgation of Nepal's new constitution in September 2015, while India, opposed to the promulgation, imposed an embargo. The Indian embargo not only undermined Nepali sovereignty by disapproving of the contents of the new constitution, but also compelled Nepal to think about lessening its dependency on India. The most obvious route was to expand trans-border connectivity with China. In March 2016, Nepal and China inked a ‘historic’ trade deal aiming to expand trans-border connectivity including a much-hyped trans-border railway link. Drawing broad public support, the deal had the effect of revitalising Nepali aspirations of coming out of an ‘India-locked’ trade and transit. This article examines opposing voices regarding the significance of this shift. On the one hand, there are those that embrace expansion of Nepal-China cross-border railway connectivity. Here, hopes are that railway connectivity will shift Nepal’s destiny away from dependence on India. On the other hand, many are wary that such a project is unaffordable, technically difficult, and most importantly, it plays into China’s interests in South Asian sub-regional geopolitics

Generalized H-fold sumset and Subsequence sum

Let $A$ and $H$ be nonempty finite sets of integers and positive integers, respectively. The generalized $H$-fold sumset, denoted by $H^{(r)}A$, is the union of the sumsets $h^{(r)}A$ for $h\in H$ where, the sumset $h^{(r)}A$ is the set of all integers that can be represented as a sum of $h$ elements from $A$ with no summand in the representation appearing more than $r$ times. In this paper, we find the optimal lower bound for the cardinality of $H^{(r)}A$, i.e., for $|H^{(r)}A|$ and the structure of the underlying sets $A$ and $H$ when $|H^{(r)}A|$ is equal to the optimal lower bound in the cases $A$ contains only positive integers and $A$ contains only nonnegative integers. This generalizes recent results of Bhanja. Furthermore, with a particular set $H$, since $H^{(r)}A$ generalizes subsequence sum and hence subset sum, we get several results of subsequence sums and subset sums as special cases.Comment: To be appear in C. R. Math. Acad. Sci. Paris, 25 page