Development of Portable Diffuse Optical Spectroscopic Systems For Treatment Monitoring

The goal of this dissertation is to demonstrate the utility of portable, small-scale diffuse optical spectroscopic (DOS) systems for the diagnosis and treatment monitoring of various diseases. These systems employ near-infrared light (wavelength range of 650nm to 950nm) to probe human tissue and are sensitive to changes in scattering and absorption properties of tissues. The absorption is mainly influenced by the components of blood, namely oxy- and deoxy-hemoglobin (HbO2 and Hb) and parameters that can be derived from them (e.g. total hemoglobin concentration [THb] and oxygen saturation, StO2). Therefore, I focused on diseases in which these parameters change, which includes vascular diseases such as Peripheral Atrial Disease (PAD) and Infantile Hemangiomas (IH) as well as musculoskeletal autoimmune diseases such as Rheumatoid Arthritis (RA). In each of these specific diseases, current monitoring techniques are limited by their sensitivity to disease progression or simply do not exist as a quantitative metric. As part of this project, I first designed and built a wireless handheld DOS device (WHDD) that can perform DOS measurements at various tissue depths. This device was used in a 15-patient pilot study for infantile hemangiomas (IH) to differentiate diseased skin from normal skin and monitor the vascular changes during intervention. In another study, I compare the ultra-small form- factor WHDD’s ability to monitor synovitis and disease progression during a patient’s treatment of RA against the capabilities of a proven frequency domain optical tomographic (FDOT) system that has shown to differentiate patients with and without RA. Learning from clinical utility of the WHDD from these two studies, I adapted the WHDD technology to develop a compact multi- channel DOS measurement system to monitor perfusion changes in the lower extremities before and after surgical intervention for patients with peripheral artery disease (PAD). Using this multi- channel system, which we called the vascular optical spectroscopic measurement (VOSM) system, our group conducted a 20-subject pilot study to quantify its ability to monitor blood perfusion before and after revascularization of stenotic arteries in the lower extremities. This proof-of- concept study demonstrated how DOS may help vascular surgeons perform revascularization procedures in the operating room and assists in post-operative treatment monitoring of vascular diseases

The Cost of Free Assistance: Why Low-Income Individuals Do Not Access Food Pantries

Non-governmental free food assistance is available to many lowincome Americans through food pantries. However, most do not use this assistance, even though it can be worth over $2,000 per year. Survey research suggests concrete barriers, such as lack of information, account for non-use. In contrast, qualitative studies focus on the role of cultural factors, such as stigma. Drawing on interviews with 53 low-income individuals in San Francisco who did not use food pantries, we reconcile these findings by illustrating how the two types of barriers are connected. Reasons for non-use such as need, information, long lines, and food quality were rooted in respondents\u27 subjective understandings of those for whom the service was intended, those perceived to use the service, and the service\u27s respect for the community. Increasing nonprofit service utilization requires attention to how potential users relate seemingly objective barriers to subjective interpretations

Forward Modeling of Double Neutron Stars: Insights from Highly-Offset Short Gamma-Ray Bursts

We present a detailed analysis of two well-localized, highly offset short gamma-ray bursts---GRB~070809 and GRB~090515---investigating the kinematic evolution of their progenitors from compact object formation until merger. Calibrating to observations of their most probable host galaxies, we construct semi-analytic galactic models that account for star formation history and galaxy growth over time. We pair detailed kinematic evolution with compact binary population modeling to infer viable post-supernova velocities and inspiral times. By populating binary tracers according to the star formation history of the host and kinematically evolving their post-supernova trajectories through the time-dependent galactic potential, we find that systems matching the observed offsets of the bursts require post-supernova systemic velocities of hundreds of kilometers per second. Marginalizing over uncertainties in the stellar mass--halo mass relation, we find that the second-born neutron star in the GRB~070809 and GRB~090515 progenitor systems received a natal kick of $\gtrsim 200~\mathrm{km\,s}^{-1}$ at the 78\% and 91\% credible levels, respectively. Applying our analysis to the full catalog of localized short gamma-ray bursts will provide unique constraints on their progenitors and help unravel the selection effects inherent to observing transients that are highly offset with respect to their hosts.Comment: 18 pages, 7 figures, 1 table. ApJ, in pres

The Systemic Perspective Approach (SPA) – a multi-cultural model for workplace counseling in the Singapore context

Organisations today face the challenge of managing the expectations of a culturally diverse workforce as a result of globalisation. Singaporean organisations, both governmental and private, face the same challenge due to the prevailing influx of foreign talents and transnational migrant workers in the last decade. There is a growing need to consider both diversity and multi-cultural issues in the workplace to ensure an effective management of their culturally diverse workforce. Multi-cultural and diversity issues when not aligned with workplace norms and culture may lead to interpersonal conflicts, challenges in adjusting to organisational culture, poor work performances and maligned communication styles. Organisations are turning to workplace counsellors and Employee Assistance Program (EAP) to support their employees in mitigating these issues so as to improve corporate organisational behaviour (OB) initiatives like employee engagement, motivation and work performance. Counselling in the context of multi-culturalism needs to consider not just ethnic and cultural factors but diversity issues such as age, gender, ability, religion, language, socio-economic status and issues, political factors, sexual orientation and the global environment. Both the client and the counsellor bring their unique personal cultural identities into the counselling process. Since one’s personal cultural identity is influenced and shaped by these cultural and diversity issues, the counselling process is a multi-cultural interaction. In order to develop more effective therapeutic alliance with culturally diverse clients, counsellors then need to consider multi-cultural competencies as part of their core professional competencies. A multi-cultural approach would enable practitioners to be more culturally sensitive by becoming aware of their faulty assumptions, stereotyping tendencies, biases and prejudices, and adopt more culturally appropriate interventions as existing western-style therapeutic approaches may not be adequately contextualised for application in non-western contexts. In this thesis, the Systemic Perspective Approach (SPA), considers both culture and diversity issues framed by its eight dimensions that include physical, mindset, affect, philosophy, ethnicity, social, political/economics and globalisation. Each of these dimensions of the workplace system is undergirded by their own defined values, beliefs, norms and culture (VBNC). The SPA model explores how each dimension of the system may inter-relate with each other and their underlying VBNC’s within the context of a problem experienced by the client being counselled. In this regard, the SPA model helps provide a multi-dimensional and holistic framework for counselling and also a framework to help develop awareness, knowledge and skills related to multi-cultural competencies. It is proposed to have significant practice value in an increasingly cultural diverse workplace. This study investigates the SPA model as applied to the 'Dads for Life' survey project sponsored by the Singapore Government. The programme was implemented across organisations nationally and yielded valid responses to the survey. Multi-variate statistical analysis was conducted to (a) determine the validity and reliability of the survey instrument and items and (b) to determine the relationships between variables relevant to the Singapore workforce. The conceptual model underpinning this study classified the eight dimensions as independent variables. The VBNCs of each dimension was then classified as dependent variables and justified by existing theory. The findings of this statistical analysis research demonstrated the statistical significance of the relationships between the independent and dependent variables (eight dimensions and the VBNCs). The findings support the applicability of the model within the workplace counselling context and is a valid and reliable instrument for measurement of the dimension / VBNC constructs. Numerous limitations of the study are addressed including the need for further validation of the model. Future research is suggested to further develop the potential of this model to contribute in areas of policy development, human resources management, social services sector improvement and most of all, in support of professional advocacy

Reliability analysis of a passive cooling system using a response surface with an application to the Flexible Conversion Ratio Reactor

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2008.Page 128 blank. Cataloged from PDF version of thesis.Includes bibliographical references (p. 50-52).A comprehensive risk-informed methodology for passive safety system design and performance assessment is presented and demonstrated on the Flexible Conversion Ratio Reactor (FCRR). First, the methodology provides a framework for risk-informed design decisions and as an example two design options for a decay heat removal system are assessed and quantitatively compared. Next, the reliability of the system is assessed by quantifying the uncertainties related to system performance and propagating these uncertainties through a response surface using Monte Carlo simulation. Finally, a sensitivity study is performed to measure the relative effects of each parameter and to identify ways to maintain, improve, and monitor system performance.by Christopher J. Fong.S.M

Neural Underpinnings of Distortions in the Experience of Time Across Senses

Auditory signals (A) are perceived as lasting longer than visual signals (V) of the same physical duration when they are compared together. Despite considerable debate about how this illusion arises psychologically, the neural underpinnings have not been studied. We used functional magnetic resonance imaging (fMRI) to investigate the neural bases of audiovisual temporal distortions and more generally, intersensory timing. Adults underwent fMRI while judging the relative duration of successively presented standard interval–comparison interval (CI) pairs, which were unimodal (A–A, V–V) or crossmodal (V–A, A–V). Mechanisms of time dilation and compression were identified by comparing the two crossmodal pairs. Mechanisms of intersensory timing were identified by comparing the unimodal and crossmodal conditions. The behavioral results showed that auditory CIs were perceived as lasting longer than visual CIs. There were three novel fMRI results. First, time dilation and compression were distinguished by differential activation of higher-sensory areas (superior temporal, posterior insula, middle occipital), which typically showed stronger effective connectivity when time was dilated (V–A). Second, when time was compressed (A–V) activation was greater in frontal cognitive-control centers, which guide decision making. These areas did not exhibit effective connectivity. Third, intrasensory timing was distinguished from intersensory timing partly by decreased striatal and increased superior parietal activation. These regions showed stronger connectivity with visual, memory, and cognitive-control centers during intersensory timing. Altogether, the results indicate that time dilation and compression arise from the connectivity strength of higher-sensory systems with other areas. Conversely, more extensive network interactions are needed with core timing (striatum) and attention (superior parietal) centers to integrate time codes for intersensory signals

Genome-scale metabolic analysis of Clostridium thermocellum for bioethanol production

<p>Abstract</p> <p>Background</p> <p>Microorganisms possess diverse metabolic capabilities that can potentially be leveraged for efficient production of biofuels. <it>Clostridium thermocellum </it>(ATCC 27405) is a thermophilic anaerobe that is both cellulolytic and ethanologenic, meaning that it can directly use the plant sugar, cellulose, and biochemically convert it to ethanol. A major challenge in using microorganisms for chemical production is the need to modify the organism to increase production efficiency. The process of properly engineering an organism is typically arduous.</p> <p>Results</p> <p>Here we present a genome-scale model of <it>C. thermocellum </it>metabolism, <it>i</it>SR432, for the purpose of establishing a computational tool to study the metabolic network of <it>C. thermocellum </it>and facilitate efforts to engineer <it>C. thermocellum </it>for biofuel production. The model consists of 577 reactions involving 525 intracellular metabolites, 432 genes, and a proteomic-based representation of a cellulosome. The process of constructing this metabolic model led to suggested annotation refinements for 27 genes and identification of areas of metabolism requiring further study. The accuracy of the <it>i</it>SR432 model was tested using experimental growth and by-product secretion data for growth on cellobiose and fructose. Analysis using this model captures the relationship between the reduction-oxidation state of the cell and ethanol secretion and allowed for prediction of gene deletions and environmental conditions that would increase ethanol production.</p> <p>Conclusions</p> <p>By incorporating genomic sequence data, network topology, and experimental measurements of enzyme activities and metabolite fluxes, we have generated a model that is reasonably accurate at predicting the cellular phenotype of <it>C. thermocellum </it>and establish a strong foundation for rational strain design. In addition, we are able to draw some important conclusions regarding the underlying metabolic mechanisms for observed behaviors of <it>C. thermocellum </it>and highlight remaining gaps in the existing genome annotations.</p

A new and unusual LBV-like outburst from a Wolf–Rayet star in the outskirts of M33

MCA-1B (also called UIT003) is a luminous hot star in the western outskirts of M33, classified over 20 yr ago with a spectral type of Ofpe/WN9 and identified then as a candidate luminous blue variable (LBV). Palomar Transient Factory data reveal that this star brightened in 2010, with a light curve resembling that of the classic LBV star AF And in M31. Other Ofpe/WN9 stars have erupted as LBVs, but MCA-1B was unusual because it remained hot. It showed a WN-type spectrum throughout its eruption, whereas LBVs usually get much cooler. MCA-1B showed an almost four-fold increase in bolometric luminosity and a doubling of its radius, but its temperature stayed ≳29 kK. As it faded, it shifted to even hotter temperatures, exhibiting a WN7/WN8-type spectrum, and doubling its wind speed. MCA-1B is reminiscent of some supernova impostors, and its location resembles the isolated environment of SN 2009ip. It is most similar to HD 5980 (in the Small Magellanic Cloud) and GR 290 (also in M33). Whereas these two LBVs exhibited B-type spectra in eruption, MCA-1B is the first clear case where a Wolf–Rayet (WR) spectrum persisted at all times. Together, MCA-1B, HD 5980, and GR 290 constitute a class of WN-type LBVs, distinct from S Doradus LBVs. They are most interesting in the context of LBVs at low metallicity, a possible post-LBV/WR transition in binaries, and as likely Type Ibn supernova progenitors

SN2013fs and SN2013fr: Exploring the circumstellar-material diversity in Type II supernovae

We present photometry and spectroscopy of SN2013fs and SN2013fr in the first 100 days post-explosion. Both objects showed transient, relatively narrow H$\alpha$ emission lines characteristic of SNeIIn, but later resembled normal SNeII-P or SNeII-L, indicative of fleeting interaction with circumstellar material (CSM). SN2013fs was discovered within 8hr of explosion. Its light curve exhibits a plateau, with spectra revealing strong CSM interaction at early times. It is a less luminous version of the transitional SNIIn PTF11iqb, further demonstrating a continuum of CSM interaction intensity between SNeII-P and IIn. It requires dense CSM within 6.5$\times$10$^{14}$~cm of the progenitor, from a phase of advanced pre-SN mass loss shortly before explosion. Spectropolarimetry of SN2013fs shows little continuum polarization, but noticeable line polarization during the plateau phase. SN2013fr morphed from a SNIIn at early times to a SNII-L. After the first epoch its narrow lines probably arose from host-galaxy emission, but the bright, narrow H$\alpha$ emission at early times may be intrinsic. As for SN2013fs, this would point to a short-lived phase of strong CSM interaction if proven to be intrinsic, suggesting a continuum between SNeIIn and II-L. It is a low-velocity SNII-L, like SN2009kr but more luminous. SN2013fr also developed an IR excess at later times, due to warm CSM dust that require a more sustained phase of strong pre-SN mass loss.Comment: MNRAS accepted. 28 pages, 23 figures, 8 table