The mass diagnosis of ankylostome infestation. (Part I)

n/

Improving access to jobs via effective public transportation : a planning framwork for mobility in San Juan

Thesis (M.C.P. and S.M.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 1999.Includes bibliographical references (leaves 167-176).The research couples accessibility models and demographic analyses to evaluate a modern interpretation of the spatial mismatch hypothesis as it applies to Boston, Massachusetts and San Juan, Puerto Rico. In relation to San Juan's new rapid rail line, Tren Urbano, the research evaluates alternative transportation services and land-use policies based on their ability to help welfare recipients and low-income workers reach employment. Empirical results show that concentrated poverty severely reduces low-income workers' job accessibility by forcing them to compete more intensely with one another for a limited supply of employment. In addition, results from Boston show that some aspect of race contributes very strongly to isolating low income workers, thereby creating relatively vast areas of highly concentrated poverty. Results from both cities indicate that employment concentrates toward the metropolitan center and that public transportation helps level the economic "playing field" for disadvantaged workers by enabling them to compete more effectively for employment outside low-income enclaves. In Boston, a city-to-suburb residential relocation program would be ineffective and might even reduce low-income families' quality of life by separating them from the social networks, services, densities of opportunity and transportation options available to them within the city. Rather, improving key transportation services seems to have a much greater potential for success. In San Juan, Tren Urbano will improve the physical job accessibility of all workers, though its social and geographic distribution of benefits will be inherently uneven. Tren Urbano will assist low-income workers living in outlying areas to reach jobs in the central city. Conversely, workers living near major employment centers will experience slight declines in their job accessibility as a result of increased competition. Welfare recipients, meanwhile, will experience an easier time reaching job locations but a slightly harder time gaining employment. The research identifies five key bus routes in San Juan, recommends adjustments to them, and proposes three specific cross-town services. It also recommends simple extensions of two existing routes, to serve roughly 30% of presently transit-isolated recipient households. Finally, policies that encourage residential relocation to Tren Urbano station areas from outlying regions have the greatest potential for improving individual recipients' access to jobs.by Clayton H. Lane.M.C.P.and S.M

The Importance of Winter Dinoflagellate Blooms in Chesapeake Bay—a Missing Link in Bay Productivity

It is widely assumed that phytoplankton abundance and productivity decline during temperate winters because of low irradiance and temperatures. However, winter phytoplankton blooms commonly occur in temperate estuaries, but they are often undocumented because of reduced water quality monitoring in winter. The small body of in situ work that has been done on winter blooms suggests they can be of enormous consequence to ecosystems. However, because monitoring is often reduced or stopped altogether during winter, it is unclear how widespread these blooms are or how long they can last. We analyzed an over 30-year record of monthly phytoplankton monitoring samples along with ad hoc sampling throughout Chesapeake Bay to assess the distributions of two common winter bloom species, Heterocapsa rotundata and Heterocapsa steinii, and the environmental conditions associated with these blooms. The long-term monitoring data revealed that H. rotundata blooms occur within a narrow salinity range (7–12) and potentially have different triggers depending upon the nutrient status of waters affected. The ad hoc sampling confirmed the occurrence of H. steinii blooms in the lower Chesapeake Bay, despite the lack of evidence for them from monthly monitoring data. Together, our findings demonstrate that winter blooms routinely occur in numerous locations throughout Chesapeake Bay and can last up to a month. Our findings suggest that while winter blooms are a staple of the Bay’s annual phytoplankton community, there are major data gaps reporting their occurrence highlighting the need for more frequent monitoring to understand factors promoting these blooms and their consequences on ecosystem productivity

On continuum driven winds from rotating stars

We study the dynamics of continuum driven winds from rotating stars, and develop an approximate analytical model. We then discuss the evolution of stellar angular momentum, and show that just above the Eddington limit, the winds are sufficiently concentrated towards the poles to spin up the star. A twin-lobe structure of the ejected nebula is seen to be a generic consequence of critical rotation. We find that if the pressure in such stars is sufficiently dominated by radiation, an equatorial ejection of mass will occur during eruptions. These results are then applied to {\eta}-Carinae. We show that if it began its life with a high enough angular momentum, the present day wind could have driven the star towards critical rotation, if it is the dominant mode of mass loss. We find that the shape and size of the Homunculus nebula, as given by our model, agree with recent observations. Moreover, the contraction expected due to the sudden increase in luminosity at the onset of the Great Eruption explains the equatorial "skirt" as well.Comment: 8 pages, 4 figure

Exploring the approximate number system in Sotos syndrome: insights from a dot comparison task

Background Sotos syndrome is a congenital overgrowth condition associated with intellectual disability and an uneven cognitive profile. Previous research has established that individuals with Sotos syndrome have relatively poor mathematical ability, but domain‐specific numeracy skills have not been explored within this population. This study investigated the approximate number system (ANS) in Sotos syndrome. Method A dot comparison task was administered to 20 participants with Sotos syndrome (mean age in years = 18.43, SD = 9.29). Performance was compared to a chronological agematched typically developing control group (n = 25) and a mental age‐matched Williams syndrome group (n = 24). Results The Sotos group did not display an ANS deficit overall when compared to chronological agematched control participants. However, for trials where the size of the individual dots and the envelope area were negatively correlated with the total number of dots (incongruent trials), the Sotos group were less accurate than the typically developing group but more accurate than the Williams syndrome group, suggesting an inhibitory control deficit. Better accuracy on incongruent trials, but not congruent trials, was associated with higher quantitative reasoning ability for participants with Sotos syndrome. Conclusion Overall, the findings suggest that ANS acuity is not impaired in Sotos syndrome but that numerical difficulties may be associated with an inhibitory control deficit for individuals with Sotos syndrome

Melting and differentiation of early-formed asteroids: The perspective from high precision oxygen isotope studies

A number of distinct methodologies are available for determining the oxygen isotope composition of minerals and rocks, these include laser-assisted fluorination, secondary ion mass spectrometry (SIMS)and UV laser ablation. In this review we focus on laser-assisted fluorination, which currently achieves the highest levels of precision available for oxygen isotope analysis. In particular, we examine how results using this method have furthered our understanding of early-formed differentiated meteorites. Due to its rapid reaction times and low blank levels, laser-assisted fluorination has now largely superseded the conventional externally-heated Ni “bomb” technique for bulk analysis. Unlike UV laser ablation and SIMS analysis, laser-assisted fluorination is not capable of focused spot analysis. While laser fluorination is now a mature technology, further analytical improvements are possible via refinements to the construction of sample chambers, clean-up lines and the use of ultra-high resolution mass spectrometers. High-precision oxygen isotope analysis has proved to be a particularly powerful technique for investigating the formation and evolution of early-formed differentiated asteroids and has provided unique insights into the interrelationships between various groups of achondrites. A clear example of this is seenin samples that lie close to the terrestrial fractionation line (TFL). Based on the data from conventional oxygen isotope analysis, it was suggested that the main-group pallasites, the howardite eucrite diogenite suite (HEDs) and mesosiderites could all be derived from a single common parent body. However,high precision analysis demonstrates that main-group pallasites have a Δ17O composition that is fully resolvable from that of the HEDs and mesosiderites, indicating the involvement of at least two parent bodies. The range of Δ17O values exhibited by an achondrite group provides a useful means of assessing the extent to which their parent body underwent melting and isotopic homogenization. Oxygen isotope analysis can also highlight relationships between ungrouped achondrites and the more well-populated groups. A clear example of this is the proposed link between the evolved GRA 06128/9 meteorites and the brachinites. The evidence from oxygen isotopes, in conjunction with that from other techniques, indicates that we have samples from approximately 110 asteroidal parent bodies (∼60 irons, ∼35 achondrites and stony-iron, and ∼15 chondrites) in our global meteorite collection. However, compared to the likely size of the original protoplanetary asteroid population, this is an extremely low value. In addition, almost all of the differentiated samples (achondrites, stony-iron and irons) are derived from parent bodies that were highly disrupted early in their evolution. High-precision oxygen isotope analysis of achondrites provides some important insights into the origin of mass-independent variation in the early Solar System. In particular, the evidence from various primitive achondrite groups indicates that both the slope 1 (Y&R) and CCAM lines are of primordial significance. Δ17O differences between water ice and silicate-rich solids were probably the initial source of the slope 1 anomaly. These phases most likely acquired their isotopic composition as a result of UV photo-dissociation of CO that took place either in the early solar nebula or precursor giant molecular cloud. Such small-scale isotopic heterogeneities were propagated into larger-sized bodies, such as asteroids and planets, as a result of early Solar System processes, including dehydration, aqueous alteration,melting and collisional interactions

MOCVD of ultra-thin PV solar cell devices using a pyrite based p-i-n structure

Ultra-thin photovoltaic (PV) devices were produced by atmospheric pressure metal organic chemical vapour deposition (AP-MOCVD) incorporating a highly absorbing intermediate sulphurised FeSₓ layer into a CdS/CdTe structure. X ray diffraction (XRD) confirmed a transitional phase change to pyrite FeS₂ after post growth sulphur (S) annealing of the FeSₓ layer between 400⁰C and 500⁰C. Devices using a superstrate configuration incorporating a sulphurised or non sulphurised FeSₓ layer were compared to p-n devices with only a CdS/CdTe structure. Devices with sulphurised FeSₓ layers performed least efficiently, even though pyrite fractions were present. Rutherford back scattering (RBS) confirmed deterioration of the CdS/FeSₓ interface due to S inter-diffusion during the annealing process

Compilation and R-matrix analysis of Big Bang nuclear reaction rates

We use the R-matrix theory to fit low-energy data on nuclear reactions involved in Big Bang nucleosynthesis. A special attention is paid to the rate uncertainties which are evaluated on statistical grounds. We provide S factors and reaction rates in tabular and graphical formats.Comment: 40 pages, accepted for publication at ADNDT, web site at http://pntpm3.ulb.ac.be/bigban

Magnetic separation of algae genetically modified for increased intracellular iron uptake

a b s t r a c t Algae were investigated in the past as a potential source of biofuel and other useful chemical derivatives. Magnetic separation of algae by iron oxide nanoparticle binding to cells has been proposed by others for dewatering of cellular mass prior to lipid extraction. We have investigated feasibility of magnetic separation based on the presence of natural iron stores in the cell, such as the ferritin in Auxenochlorella protothecoides (A. protothecoides) strains. The A. protothecoides cell constructs were tested for inserted genes and for increased intracellular iron concentration by inductively coupled plasma atomic absorption (ICP-AA). They were grown in Sueoka's modified high salt media with added vitamin B1 and increasing concentration of soluble iron compound (FeCl 3 EDTA, from 1 Â to 8 Â compared to baseline). The cell magnetic separation conditions were tested using a thin rectangular flow channel pressed against interpolar gaps of a permanent magnet forming a separation system of a well-defined fluid flow and magnetic fringing field geometry (up to 2.2 T and 1000 T/m) dubbed "magnetic deposition microscopy", or MDM. The presence of magnetic cells in suspension was detected by formation of characteristic deposition bands at the edges of the magnet interpolar gaps, amenable to optical scanning and microscopic examination. The results demonstrated increasing cellular Fe uptake with increasing Fe concentration in the culture media in wild type strain and in selected genetically-modified constructs, leading to magnetic separation without magnetic particle binding. The throughput in this study is not sufficient for an economical scale harvest