Spin-orbit-coupling induced lateral spin transport from first principles

Everything digital is currently stored in data centres on magnetic hard disk drives which are accessed at will using a magnetic read head. The spinning disks and moving read heads in the hard disks imply slow access time and high-power consumption making data centres giant sponges for electricity. At the same time, semiconductor based storage suffers from thermal dissipation with miniaturization on top of data leakage and high cost. The ideal memory for data storage would be cost-effective, non-volatile, fast and consume less power, combining desirable features of both magnetic and semiconductor storage technology. To this end, the field of “spintronics" promises a new direction towards efficient data storage using magnetic memories. The impetus for the research that has gone into realizing this thesis was fuelled by uncertainties in the reported spin transport parameters and the gap between phenomenological models and experiments in (spin)transport phenomena. The aim of the thesis is to resolve some of the uncertainties by pushing our computational capabilities in investigating microscopic details of transport. Furthermore, I attempt to improve upon existing models of interpretation or prediction used in experiments and application. I studied a number of topics in the field of electronic spin transport in transition metals. Because of their partially filled d-bands and complex Fermi surfaces with spin-orbit coupling, transition metals are rich in spin phenomena that have potential for spintronics applications. Using a density functional theory-based scattering approach, I studied the generation and diffusion of spin currents in non-magnetic 5d and ferromagnetic 3d transition metals. By including thermal disorder, I presented realistic calculations for these metals. I next studied lateral transport in finite size geometries that are encountered in spintronics experiments. This form the last three chapters of the thesis. The main focus of the thesis has been on the determination of the two most important spin-orbit coupling related spin transport properties, the spin flip diffusion length and the spin Hall angle

Protein-Poly(amino acid) Nanocore–Shell Mediated Synthesis of Branched Gold Nanostructures for Computed Tomographic Imaging and Photothermal Therapy of Cancer

Anisotropic noble metal nanoparticles especially branched gold nanoparticles with a large absorption cross-section and high molar extinction coefficient have promising applications in biomedical field. However, sophisticated and cumbersome methodologies of synthesis along with toxic precursors pose serious concern for its use. Herein, we report the synthesis of branched gold nanostructures from protein (albumin) nanoparticles by a simple reduction method. Albumin nanoparticles were synthesized by a modified desolvation technique with poly-l-arginine (cationic poly amino acid) substituting the conventional toxic cross-linker, glutaraldehyde. <i>In silico</i> molecular docking was carried out to study the interaction of poly-l-arginine with albumin which revealed its binding to Pocket 1B of the A-chain of albumin. The poly-l-arginine-albumin core–shell nanoparticles of ∼100 nm in size served as a base for attachment of gold ions and its reduction to form 140 nm sized branched gold nanostructures conjugated with glutathione. These gold nanostructures exhibited near-infrared absorption λ_max at 800 nm with extreme compatibility toward non cancerous (NIH 3T3), oral epithelial carcinoma (KB) cell lines, and human blood (red blood cells, platelets, and coagulation mechanisms) even up to a high concentration of 250 μg/mL. These structures demonstrated superior computed tomographic (CT) contrast ability and marked photothermal cytotoxicity on KB cells. This study reports for the first time a method to develop blood and cell compatible branched gold nanostructures from protein nanoparticles as a dual CT diagnostic and photothermal therapeutic agent

Rapid, One-Pot, Protein-Mediated Green Synthesis of Gold Nanostars for Computed Tomographic Imaging and Photothermal Therapy of Cancer

Plasmonic nanostructures such as gold nanostars have immense prospects in the biomedical field. However, toxic precursors and complex methodologies of synthesis are the major obstacles to their application. This study hence makes use of a protein macromolecule (albumin) to synthesize gold nanostars by a simple reduction method. The formation of an anisotropic morphology of gold using albumin was determined to be a pH-dependent process. The net positive charge of the protein at pH below its isoelectric point facilitated the attachment of chloroaurate ions, which were subsequently reduced to gold atoms. Furthermore, the stretching of the α-helices of albumin at low pH and its transformation to the β-sheet conformer favored the oriented growth of the gold nanostructures to yield a star-shaped morphology. Additionally, the non-toxic and ligand binding characteristics of the albumin endowed the gold nanostars with stability, functionality, as well as biocompatibility. The albumin-derived gold nanostars exhibited enhanced computed tomographic (CT) contrast, photothermal activity, and compatibility toward cells and human blood. This study thus puts forth, for the first time, a rapid, one-pot methodology for developing gold nanostars using protein and demonstrates the application of the resulting gold nanostars as a dual CT diagnostic and photothermal therapeutic agent

Chemodiversity in flowers of Tanacetum vulgare has consequences on a florivorous beetle

Sasidharan R, Brokate L, Eilers EJ, Müller C. Chemodiversity in flowers of Tanacetum vulgare has consequences on a florivorous beetle. Plant Biology. 2023;25(7):1071-1082.- The chemical composition of plant individuals can vary, leading to high intraspecific chemodiversity. Diversity of floral chemistry may impact the responses of flower-feeding insects. - Tanacetum vulgare plants vary significantly in their leaf terpenoid composition, forming distinct chemotypes. We investigated the composition of terpenoids and nutrients of flower heads and pollen in plants belonging to three chemotypes – dominated either by β-thujone (BThu), artemisia ketone (Keto) or a mixture of (Z)-myroxide, santolina triene, and artemisyl acetate (Myrox) – using different analytical platforms. We tested the effects of these differences on preferences, weight gain and performance of adults of the shining flower beetle, Olibrus aeneus. - The terpenoid composition and diversity of flower heads and pollen significantly differed among individuals belonging to the above chemotypes, while total concentrations of pollen terpenoids, sugars, amino acids, and lipids did not differ. Beetles preferred BThu over the Myrox chemotype in both olfactory and contact choice assays, while the Keto chemotype was marginally repellent according to olfactory assays. The beetles gained the least weight within 48 h and their initial mortality was highest when feeding exclusively on floral tissues of the Myrox chemotype. Short-term weight gain and long-term performance were highest when feeding on the BThu chemotype. - In conclusion, the beetles showed chemotype-specific responses towards different T. vulgare chemotypes, which may be attributed to the terpenoid composition in flower heads and pollen rather than to differences in nutrient profiles. Both richness and overall diversity are important factors when determining chemodiversity of individual plants and their consequences on interacting insects

Nonlinear Synchronization Of Biceps And Triceps Muscles During Maximum Voluntary Contraction

The objective of this pilot study was to explore nonlinear synchronization of biceps and triceps muscles during maximum voluntary contraction (MVC) protocol for biceps muscles. Generalized synchronization indexes (S-, H-, and N-index) were utilized to explore synchronization and interdependence of bivariate biceps and triceps time series data. It was found that the more robust H- and N-index were able to distinguish the dynamical changes in three stages (pre-MVC, MVC, and post- MVC) of MVC protocol. According to the H- and N-index values, synchronization between biceps and triceps muscles was more pronounced in pre and post-MVC stage than in MVC. ANOVA analyses confirmed the significant difference (p \u3c 0.01) of those index values between pre-, MVC, and post-MVC stages. A linear synchronization measure, cross-correlation, was utilized that failed to capture any synchronization patterns between biceps and triceps muscles. It is argued that that nonlinear synchronization indexes could provide useful insight to the synergistic muscle activities and their relationships with respect to the task, posture control and stability

Floral volatiles evoke partially similar responses in both florivores and pollinators and are correlated with non-volatile reward chemicals

Sasidharan R, Junker RR, Eilers EJ, Müller C. Floral volatiles evoke partially similar responses in both florivores and pollinators and are correlated with non-volatile reward chemicals. Annals of Botany. 2023.**Background** Plants often use floral displays to attract mutualists and prevent antagonist attacks. Chemical displays detectable from a distance include attractive or repellent floral volatile organic compounds (FVOCs). Locally, visitors perceive contact chemicals including nutrients but also deterrent or toxic constituents of pollen and nectar. FVOC and pollen chemical composition may vary intra- and interspecifically. For certain pollinator and florivore species, responses towards these compounds are studied in specific plant systems; yet we lack a synthesis of general patterns comparing these two groups and insights into potential correlations between FVOC and pollen chemodiversity. **Scope** We reviewed how FVOCs and non-volatile floral chemical displays, i.e., pollen nutrients and toxins, vary in composition and affect the detection and behaviour of insect visitors. Moreover, we used meta-analyses to evaluate the detection of and responses towards FVOCs by pollinators vs. florivores within the same plant genera. We also tested whether the chemodiversity of FVOCs, pollen nutrients and toxins are correlated and hence mutually informative. **Key Results** According to available data, florivores could detect more FVOCs than pollinators. Frequently tested FVOCs were often reported as pollinator-attractive and florivore-repellent. Among FVOCs tested on both visitor groups, there were a higher number of attractive than repellent compounds. FVOC and pollen toxin richness correlated negatively, indicating trade-offs, while a marginal positive correlation between pollen protein amount and toxin richness was observed. **Conclusions** Plants face critical trade-offs, as floral chemicals mediate similar information to both mutualists and antagonists, particularly through attractive, and fewer repellent, FVOCs. Furthermore, florivores may detect more FVOCs, whose richness is correlated to reward chemical richness. FVOC chemodiversity is potentially informative of reward traits. To better understand the ecological processes shaping floral chemical displays, more research is needed on floral antagonists of diverse plant species, and on the role of floral chemodiversity towards visitor responses