Climate change adaptation and recovery from climate hazards: microeconometric evidence from rural Bangladesh

This thesis addresses two important issues of environmental and resource economics: how agricultural households adapt to climate change (CC) and how the households recover from climate hazards. Chapter 1 attempts to enunciate the perspective of the overall research and the rationale for researching on Bangladesh. It summarizes the global evidences of CC and disaster, their impacts, vulnerabilities in agriculture sector, significance of adaptation and poverty impact of disaster. Chapter 2 examines whether crop choice is affected by CC and the extent to which households switch their crops in response to the CC scenarios. It finds that crop choice is climate-sensitive and a shift in crop choices will take place in Bangladesh in response to CC scenarios. This research also finds that crop choice will be more sensitive to change in temperature than change in rainfall. Chapter 3 examines the effect of CC on crop diversification and the households’ response to CC scenarios. It finds that crop diversity is climate sensitive and this diversity in different locations varies with climatic conditions. Effects of rainfall scenarios on crop diversity are much lower compared to the effects of temperature. Chapter 4 investigates the impact of cyclone on consumption and income dynamics in a quasi-experimental setting and finds that low income people are more sensitive of their asset loss to income generation compared to the high income people, and disaster causes income loss, but, people show their resilience in accelerating higher income growth compared to the non-affected areas. Chapter 5 examines poverty group dynamics in the post-shock period and the existence of a poverty trap in the cyclone affected coastal region of Bangladesh. It finds that asset loss or asset holding impacts the dynamism of the poverty groups and poverty traps exists at low levels of income in the disaster affected areas compared to the unaffected areas

Spherical and Rod-shaped Gold Nanoparticles for Surface Enhanced Raman Spectroscopy

Raman Spectroscopy offers an in-situ, rapid, and non-destructive characterization tool for chemical analysis of diverse samples with no or minimal preparation. However, due to the inherent weak signal of conventional Raman spectroscopy, surface plasmon resonance features of noble metal nanoparticles have been utilized to conduct Surface Enhanced Raman Spectroscopy (SERS) in detecting trace label contaminants in foods and foodstuffs. In this effort, we synthesized gold nanoparticles (AuNPs) by reduction of chloroauric acid (HAuCl4) with sodium citrate dehydrate. We prepared different sizes of AuNPs at a fixed temperature (100 oC) but with varying pHs of 4 and 8. The as-synthesized AuNPs were characterized by UV-Vis spectroscopy, dynamic light scattering (DLS), and Field Emission Scanning Electron Microscopy (FE-SEM). FE-SEM micrographs revealed spherical AuNPs with an average diameter of approx. 55 nm and rod-shaped AuNPs with an average length of approx. 170 nm for sample synthesis at pH 8 and 4, respectively. The effectiveness of the as-prepared AuNPs for SERS is tested by detecting Rhodamine 6G diluted at a trace level. This study suggests that plasmonic nanoparticles coupled with SERS have great potential for broad applications in detecting other trace amounts of hazardous chemicals in foods and foodstuffs.Comment: 4 pages, 5 figure

Probing ultrafast dynamics of solid-density plasma generated by high-contrast intense laser pulses

We present ultrafast dynamics of solid-density plasma created by high-contrast (picosecond contrast ∼10-9), high-intensity (∼4 × 1018 W/cm2) laser pulses using time-resolved pump-probe Doppler spectrometry. Experiments show a rapid rise in blue-shift at early time delay (2-4.3 ps) followed by a rapid fall (4.3-8.3 ps) and then a slow rise in blue-shift at later time delays (>8.3 ps). Simulations show that the early-time observations, specifically the absence of any red-shifting of the reflected probe, can only be reproduced if the front surface is unperturbed by the laser pre-pulse at the moment that the high intensity pulse arrives. A flexible diagnostic which is capable of diagnosing the presence of low-levels of pre-plasma formation would be useful for potential applications in laser-produced proton and ion production, such as cancer therapy and security imaging

Collimated hot electron generation from sub-wavelength grating target irradiated by a femtosecond laser pulse of relativistic intensity

We investigate the production of hot electrons from the interaction of relativistically intense ($I> 10^{18} W/cm^{2}$) ultra-short (25 fs) laser pulses with sub-wavelength grating target. We measure the hot electron angular distribution and energy spectra for grating target and compare them with those from a planar mirror target. We observe that hot electrons are emitted in a collimated beam along the specular direction of the grating target. From the measured electron energy spectra we see electron temperature for grating is higher than the mirror, suggesting a higher electron yield and hence a stronger coupling with the laser. We performed numerical simulations which are in good agreement with experimental results, offer insights into the acceleration mechanism by resulting electric and magnetic fields. Such collimated fast electron beams have a wide range of applications in applied and fundamental science.Comment: 6 figure

Generation of a strong reverse shock wave in the interaction of a high-contrast high-intensity femtosecond laser pulse with a silicon target

We present ultrafast pump-probe reflectivity and Doppler spectrometry of a silicon target at relativistic laser intensity. We observe an unexpected rise in reflectivity to a peak approximately9 ps after the main pulse interaction with the target. This occurs after the reflectivity has fallen off from the initially high “plasma-mirror” phase. Simultaneously measured time-dependent Doppler shift data show an increase in the blue shift at the same time. Numerical simulations show that the aforementioned trends in the experimental measurements correspond to a strong shock wave propagating back toward the laser. The relativistic laser-plasma interaction indirectly heats the cool-dense (ne 10^23 cm^-3 and Te ~10eV) target material adjacent to the corona, by hot electron induced return current heating, raising its temperature to around 150eV and causing it to explode violently. The increase in reflectivity is caused by the transient steepening of the plasma density gradient at the probe critical surface due to this explosive behavior

Imaging an isolated water molecule with an attosecond electron wave packet

We use laser-induced electron diffraction (LIED) to self-image the molecular structure of an isolated water molecular ion using its own retuning attosecond electron wave packet (EWP). Using LIED’s sub-femtosecond and picometre spatio-temporal resolution imaging capabilities, we observe the symmetric stretching of the O-H and H-H internuclear distances with increasing laser field strength.Postprint (published version

Ultrafast imaging of the Renner-Teller effect in a field-dressed molecule

We present experimental results of linear-to-bent transition of field-dressed molecules, mediated by Renner-Teller effect. Using the state-of-the-art laser-induced electron diffraction (LIED) technique, we image a bent and symmetrically stretched carbon disulfide (CS2) molecule populating an excited electronic state under the influence of strong laser field. Our findings are well-supported by ab initio quantum mechanical calculations.Peer ReviewedPostprint (published version

Tracking ultrafast dynamics of intense shock generation and breakout at target rear

We report upon the picosecond plasma dynamics at the rear surface of a thin aluminium foil (of either 5.5 um or 12 um thickness) excited by high contrast (picosecond intensity contrast of 10^10), 800 nm, femtosecond pulses at an intensity of 3 x 10^19 W/cm2. We employ ultrafast pump-probe reflectometry using a second harmonic probe (400 nm) interacting with the rear surface of the target. A rise in the probe reflectivity 30 picoseconds after the pump pulse interaction reveals the breakout of a shock wave at the target rear surface which reflects the 400 nm probe pulse. Simulations using the ZEPHYROS hybrid particle-in-cell code were performed to understand the heating of the target under the influence of the high intensity laser pulse, and the temperature profile was then passed to the radiation-hydrodynamics simulation code HYADES in order to model the shock wave propagation in the target. A good agreement was found between the calculations and experimental results