Seminars

Luminosity gap transients are stellar explosions whose peak luminosities lie between those of classical novae and core-collapse supernovae. In this thesis, I investigated one particularly intriguing example, AT 2019krl. My work included multi-wavelength and spectroscopic analyses, together with a study of its progenitor system. On examination, recent HST images showed that AT 2019krl faded beyond its progenitor magnitude. This implies that the explosion must have been terminal, either an electron-capture supernova (ECSN) or a failed supernova. However, both hypotheses contain inconsistencies. The magnitude and light curve of AT 2019krl were consistent with expectations for a failed supernova; however, the progenitor mass is incompatible with such an event. While the progenitor mass fell within the predicted range for an ECSN, the transient was notably fainter than expected for this class. Regardless of the exact explosion mechanism, we know that AT 2019krl was a terminal explosion with an absolute magnitude a factor of 10 fainter than any previous known examples. I also conducted a study on the environments of intermediate-luminosity red transients (ILRTS), a subclass of luminosity gap transients. The magnitudes of the stellar populations surrounding 10 ILRTs were matched to stellar evolution models, allowing their ages to be determined. I found that the ages of ILRT progenitors are systemically older than those of Type II core-collapse supernovae. This indicates that ILRTs originate from stars less massive than the 9M⊙ required for iron core-collapse, and are consistent with ECSNe.

Proteins in cells function within crowded, dynamic, and heterogeneous environments, yet they are often studied in isolation under idealized conditions. Understanding how these complex surroundings shape protein dynamics, organization, and function requires approaches that connect molecular details to collective biological function. In this seminar, I will outline recent work aimed at modelling biomolecular systems with increasing biological and structural complexity. Topics will include integrating experimental observables and machine-learning-derived data into coarse-grained MD simulations, the interplay between the local membrane environment and the dynamics and activity of respiratory Complex I, the membrane-driven formation of respiratory supercomplexes, predictive modelling of liquid–liquid phase separation in mixtures of intrinsically disordered and folded proteins, and emerging insights into the structure and cargo organization of bacterial microcompartments.

Antimicrobial resistance (AMR) has intensified research efforts towards the development of innovative methods and technologies to suppress the spread of infectious pathogens facilitated by high-touch surfaces. To this aim, various morphologies of zinc oxide (ZnO) nanostructures have been developed as efficient antimicrobial surfaces by tuning their wettability and surface chemistry. The surfaces with structures such as flowers, needles, and fibers coated with ionic liquids cause a drastic impairment of bacterial cells on them. The coating has been stabilized by using a polymer. The bactericidal activity has been quantified by observing the bacterial growth through spot assay and colony-forming unit (CFU) analysis. The molecular mechanism of impaired growth of bacteria due to ionic liquids has been investigated by quantifying the assembly of the molecules in lipid membranes that mimic the bacterial membrane. Synchrotron based X-ray reflectivity (XRR) and grazing incidence X-ray diffraction (GIXD) have provided the structural deformation in the membrane caused by these molecules. The ionic liquids, commonly known as green solvents, are found to be emerging coating materials to develop advanced antimicrobial surfaces.

PhD Defense.

Abstract:  Herbig Ae/Be stars constitute a fascinating bridge between low-mass and high-mass star formation. This talk present findings of the inner disk around these stars in order to characterise their environment using high-resolution optical and near-infrared spectroscopy. In a first project, the inner disk of the Herbig Ae star HD 141569 is studied with HI lines, showing that the disk is very compact, constrained within few stellar radii, and reaching very close to the star. This infers significant constraints on the nature of the disk winds around the star, and it's mass accretion mode. In a second project, the forbidden emission around a large sample of Herbig Ae/Be stars is studied. The results show a significant discrepancy to the emission from young low-mass stars, and shed light on the disk dispersal mechanisms around young intermediade-mass stars.