On the way to becoming an adult in urban America: Similarities and differences between men and women
Year of Dissertation:
2011
The term emerging adulthood coined by Jeffrey Arnett (2004), attempts to describe the tumultuous lives of individuals in their 20's. Emerging adults in western society are characterized as postponing adult commitments and responsibilities while completing their extended education, trying out and then establishing careers and exploring relationships (Arnett, 2000, 479).
Representations of Colorism in the Jamaican Culture and the Practice of Skin Bleaching
Author:
Christopher Charles
Year of Dissertation:
2010
Advisor:
William Cross Jr.
This study deconstructs the images that influence Jamaicans to bleach their skin. Social representation theory (SRT) is used to pinpoint the origins of colorism and then trace its entrenchment in the culture and communications. SRT theorems say (1) the social images have a history; (2) these images are diffused and become embedded in the culture; (3) people use these images to understand their environment and create identities; (4) over time, repeated social exchanges become institutionalized culture; and (5) the images in the culture can be easily triggered and overheard in conversations. History data was collected from colonial and contemporary newspapers; the diffusion data was collected from popular songs, poems, and a novel; identity data was collected from interviews; institutionalization data was captured from participant observation of skin bleaching vendor-customer transactions; dialogic data was collected from a focus group interview. The findings are that the complexion consensus is a historical continuum in old and new newspapers. Colorism is contested in reggae and dancehall songs and literary works. The repeated vendor-customer exchanges reveal that skin bleaching is an established cultural practice. Participants use colorism to define themselves which influences them to bleach their skin. Colorism was heard in participants' conversations about race and skin bleaching. The results suggest that the complexion consensus is a hegemonic representation which influences the beliefs and behavior of the skin bleachers in Jamaica.
The Molecular Beam Epitaxy Growth and Characterization of Znx'Cd(1-x')Se/ZnxCdyMg(1-x-y)Se-InP Quantum Cascade Structures Designed for Operation in the 3 - 5 µm Range
Year of Dissertation:
2010
Advisor:
Dr. Maria Tamargo
The quantum cascade (QC) laser has captured the interest of researchers for almost three decades. In the early stages, researchers were very interested in proving the QC concept1 proposed by Kazarinov and Suris in 1971. This new concept gave researchers hope that very bulky energy inefficient infra-red (IR) lasers would be replaced with ones that are very compact, tunable and portable. Since the proposal of the QC laser concept and its first demonstration by researchers at Bell Laboratories2 in 1994, this technology has progressed to the point where it is now finding commercial applications in a variety of areas such as military counter measures, free space telecommunications, infra-red imaging and chemical spectroscopy.3-5 The success of this technology can be attributed to the coming of age of the techniques of molecular beam epitaxy (MBE) semiconductor growth and bandgap engineering.6,7
STRUCTURAL STUDIES OF BIOPOLYMERS USING COMPUTER SIMULATIONS, OPTICAL AND MAGNETIC SPECTROSCOPY
Author:
Subhasish Chatterjee
Year of Dissertation:
2009
Biopolymers are essential components of numerous natural and synthetic macromolecular assemblies. In the present study, the structural properties of biopolymers ranging from fungal melanins to synthetic nucleic acids were investigated using spectroscopic methods and theoretical modeling. (1) Computational modeling and molecular dynamics simulations were used to study the structural properties of a short single-stranded (ss) DNA. The dependence of the conformational stability and flexibility of the ssDNA on the thermodynamic conditions of the system was demonstrated. (2) Time-resolved fluorescence spectroscopy involving an organic donor-quencher pair was utilized to study the conformational properties of Y-shaped DNA. Results highlighted the different distances between the arms of the Y-DNA and indicated the overall structural stability of the Y-DNA system. Time-resolved fluorescence techniques were applied to investigate the distance dependence of the non-radiative energy transfer process between an organic donor (fluorescein) and a gold nanoparticle quencher connected by double stranded (ds) DNA. (3) Synthesis of phospholipid-conjugated gold nanoparticles and their self-assembly onto an aqueous subphase were tested. The resulting lipid-capped nanoparticles were characterized by optical methods such as UV-Vis absorption spectroscopy and dynamic light scattering. The effects of bio-functionalization on the size of biotin-capped gold nanoparticles were investigated using optical techniques. (4) Solid-state nuclear magnetic resonance (NMR) spectroscopy was utilized to elucidate the structural characteristics of fungal melanins. Various spinning speeds, temperatures, magnetic field strengths, and isotopic labels were utilized with 1D and 2D 13C MAS NMR, revealing distinctive structural fingerprints of the fungal melanins generated biosynthetically with L-dopa, methyldopa, epinephrine, and norepinephrine. These pigments exhibited differences in their aromatic and aliphatic structures and probable biosynthetic pathways, and it was possible to delineate proximities between particular melanin and membrane-related molecular groups.
STRUCTURAL AND BIOCHEMICAL CHARACTERIZATION OF RHOMBOID INTRAMEMBRANE PROTEASES
Year of Dissertation:
2011
Intramembrane proteases are involved in multiple biological processes including cell growth and development, and apoptosis. There is no conservancy between hydrosoluble and membrane proteases. However, the catalytic residues and surrounding amino acids are absolutely conserved, suggesting that they both protein families share catalytic mechanisms but with two remarkable differences. (1) The ability of intramembrane proteases to cleave their substrates in the hydrophobic interior of the lipid bilayer, and (2) to do so in regions where the substrate displays a-helical conformation. D. melanogaster rhomboid-1 cleaves within the transmembrane domain region of epidermic growth factor receptor (EGFR) ligands Gurken, Keren and Spitz, resulting in their extracellular export. We designed substrate chimeras in which the transmembrane and cytoplasmic regions of Gurken, Keren and Spitz were preserved, while their EGFR ligand ectodomain was replaced by maltose binding protein. In vitro activity assays in detergent using purified components showed that rhomboid-1, H. sapiens RHBDL2, P. aeruginosa PA3086 and E. coli GlpG display comparable activity against these substrate chimeras. Mass spectrometry analysis of the N-terminal reaction product identified a single cleavage site after Ala138 for the Spitz chimeras, after Ala122 for the Keren chimeras, and after Ala245 for the Gurken chimeras that was identical for all rhomboids tested, suggesting a conservation of proteolytic profiles among prokaryotic and eukaryotic rhomboids. The identified cleavage site was located towards the N-terminal end of the transmembrane domain of each substrate. Positions that were sensitive to alanine scanning were further studied by introducing additional mutations to show that aside of ala in position P1, amino acids with low-helical propensities are necessary in the positions P2 and P1'. Finally, a bulky hydrophobic residue with a high helical propensity is important in P2' position to control the location of cleavage. We also carried out structural work and solved the N-terminal domain of Rhomboid and showed it displays high-affinity for membranes. Our work is put in a more general context by comparison with other intramembrane proteases and future work to unravel the mechanism of substrate binding and unwinding is also discussed.
Lidar Calibration
Year of Dissertation:
2009
Owing to its inherent low gain detection of the 1064nm channel and a negligible molecular return from the atmosphere, a boundary condition for the retrieval of optical data by inversion cannot be assumed with high confidence as for the other channels in the multiwavelength Mie lidar. It is therefore necessary to evaluate the calibration constant for the channel. Two methods of calibration are studied and compared. One method is calibration by high or low clouds. The other method is calibration by a ceilometer which is itself calibrated and co-located at the lidar site. The results are compared with the aerosol optical depth measured by a calibrated sun photometer co-located at the same site as part of the AERONET network at CCNY. In the latter method, all three instruments are located at the same site, there is no issue of atmospheric differences when comparing data but it makes calibration dependent on that of other instruments. Clouds are a natural and frequent occurrence but the lidar system may change between cloud appearances. Both methods have their merits and shortcomings.
Conflict-free coloring
Author:
Panagiotis Cheilaris
Year of Dissertation:
2009
Graph and hypergraph colorings constitute an important subject in
Parental Involvement of Chronically Ill Mothers and Its Impact on the Child's Education
Year of Dissertation:
2009
Program:
Educational Psychology
This study examined how maternal chronic illnesses may affect children's academic functioning through parental involvement. Levels of maternal demands of illness were measured in order to see if they affect the levels of parental involvement and children's grades. Four research questions are addressed in this study. Do the maternal demands of illness affect children's educational achievement? Do the maternal demands of illness impact the extent of parental involvement? Does parental involvement of mothers with chronic illness influence their children's academic achievement? Does positive parental involvement mediate or moderate the impact of maternal chronic illness on children's educational performance? One hundred fifty mothers diagnosed with Multiple Sclerosis (MS), diabetes, cancer, HIV/AIDS, Myelodysplasic Syndrome, and Fibromyalgia and with a child in middle school or high school (aged 10-18) participating in this study were recruited from national organizations, clinics, and social support groups serving patients with chronic illnesses. Participants completed a 184-item questionnaire that was composed of measures of 1) parent demographic information, 2) parent medical information, 3) child demographic information, 4) Demands of Illness Inventory (DOII), 5) parental self-efficacy, 6) parental educational aspirations, 7) grade expectations, 8) school contact and participation, 9) Parent Involvement in School Interview, 10) home supervision, and 11) children's educational outcomes. Each participant was compensated ten dollars for completing the questionnaire. Overall, the results suggest that the majority of students of mothers with chronic illness were able to function adequately in terms of academic achievement. However, children's academic functioning may be at risk when their mothers experienced high levels of illness demands as a result of their chronic illness. Children's grades were found negatively related to levels of demands of illness their mothers experienced. This study also revealed that levels of demands of illness imposed on the mothers with chronic illness and disruption in normal family functioning were negatively related to parental self-efficacy in helping their children succeed in education. Moreover, this study found that parental self-efficacy mediated the effects of maternal demands of illness on children's academic achievement. Children of chronically ill mothers with higher academic efficacy tended to do better academically than those of mothers with lower levels of efficacy. Finally, among different forms of parental involvement, parental educational aspirations and grade expectations were positively related to children's educational performance in terms of grades.
RESIDENTIAL RELOCATION CHOICE AND CONSEQUENT BEHAVIORAL CHANGE
Year of Dissertation:
2009
Transit-oriented developments with the goal of reducing dependency on the automobile have been observed nationwide. The implicit hypothesis behind these developments is that where one lives would affect his or her consequent activity and travel behavior. Many questions remain despite decades of research in residential location choice and activity and travel behavior. In residential location choice literature, previous studies have modeled residential location choices as static ones, with no memory of the past. In addition, few studies have modeled the spatial correlation between alternative locations, although they may exist in reality. In activity and travel behavior literature, most studies implicitly assume that behavioral changes are instantaneous, despite the recognition that a behavioral change in response to an external trigger may take time to occur, due to various types of constraints one may face. This dissertation will introduce a residential relocation model that addresses spatial correlation and accounts for the influence of the prior residential location on one's current preference. Furthermore, I will examine how a change in the built environment (spurred by a change in residence) can affect the response lag generated by a significant change in the time people allocate to discretionary activities and travel.
I. The RCM Approach Towards 1,6-methano-bridged[12] & [14]Annulenes and their Bisdehydro-derivatives II. 1,5-bisdehydro[10]Annulene Revisited
Year of Dissertation:
2010
Part I of my dissertation presents a new efficient synthesis of 3,4-benzo-1,6-methano[12]annulene (3). This novel synthetic approach involves a grignard addition to 3,4-benzo-cycloheptatriene-1,6-dialdehyde followed by a ring closing olefin metathesis (RCM) reaction giving the bridged 12-menber ring of 3,4-benzo-1,6-methano[12]annulene (3) was obstained in six steps and an overall yield 44%. This allowed the complete structural and spectroscopic characterization as a paratropic ethano-bridged benzo[12]annulene with a 28% reduction of the paramagnetic ring current relative to the non-benzannulated molecule. A careful comparison of the 1H NMR of (3) with its 9,10-dihydro derivative (104) suggests an extended paratropic 16π system. The RCM approach is general and thus formally presents a 6 steps route to the parent 1,6-methano[12]annulene, previously reported by E. Vogel et al. Combination of cis-selective Wittig reaction of (36) with the ylide derived from 4-bromo-1-butene followed by RCM reaction yielded the 9,12-dihydro-3,4-benzo-1,6-methano[14]annulene (35). Attempts to convert this molecular in to the expectedly diatropic 14π system did not succeed so far. In course of this investigation, an efficient synthesis for 3,4-benzo-1,6-ethynylcycloheptatriene was developed. Diketone (37) obtained through Jones oxidation of the diasteromeric alcohols (26) was converted into the 3,4-benzo-1,6-methano-7,12-bis(dibromomethylene)-8,11-dihydro[12]annulene (38). Treatment of this molecule with two moles of n-butyllithium did not yield the anticipated diacetylene (39). From diketone (37) a series of 7,12-disubstituted bridged [12]annulene can be synthesized, this illustrating the generality of this approach.