The Relative Occupational Success of Blacks and Whites

macroeconomics, occupational success

What Every Teacher Should Know about Joe Crosswhite

The authors discuss the life and legacy of Dr. F. Joe Crosswhite, a mathematics educator whose work has had a profound impact on the lives of countless students and colleagues.  As NCTM president (1984-86), F. Joe Crosswhite oversaw the approval of the basic design and initial financing for what became the Curriculum and Evaluation Standards for School Mathematics.  Crosswhite also made significant contributions to the influential Second International Mathematics and Science Study. He played a seminal role in the development of the Mathematical Sciences Education Board and chaired the Conference Board of the Mathematical Sciences

Issues in the reporting of epidemiological studies: a survey of recent practice.

OBJECTIVES: To review current practice in the analysis and reporting of epidemiological research and to identify limitations. DESIGN: Examination of articles published in January 2001 that investigated associations between risk factors/exposure variables and disease events/measures in individuals. SETTING: Eligible English language journals including all major epidemiological journals, all major general medical journals, and the two leading journals in cardiovascular disease and cancer. MAIN OUTCOME MEASURE: Each article was evaluated with a standard proforma. RESULTS: We found 73 articles in observational epidemiology; most were either cohort or case-control studies. Most studies looked at cancer and cardiovascular disease, even after we excluded specialty journals. Quantitative exposure variables predominated, which were mostly analysed as ordered categories but with little consistency or explanation regarding choice of categories. Sample selection, participant refusal, and data quality received insufficient attention in many articles. Statistical analyses commonly used odds ratios (38 articles) and hazard/rate ratios (23), with some inconsistent use of terminology. Confidence intervals were reported in most studies (68), though use of P values was less common (38). Few articles explained their choice of confounding variables; many performed subgroup analyses claiming an effect modifier, though interaction tests were rare. Several investigated multiple associations between exposure and outcome, increasing the likelihood of false positive claims. There was evidence of publication bias. CONCLUSIONS: This survey raises concerns regarding inadequacies in the analysis and reporting of epidemiological publications in mainstream journals

Human central nervous system (CNS) ApoE isoforms are increased by age, differentially altered by amyloidosis, and relative amounts reversed in the CNS compared with plasma

The risk of Alzheimer's disease (AD) is highly dependent on apolipoprotein-E (apoE) genotype. The reasons for apoE isoform-selective risk are uncertain; however, both the amounts and structure of human apoE isoforms have been hypothesized to lead to amyloidosis increasing the risk for AD. To address the hypothesis that amounts of apoE isoforms are different in the human CNS, we developed a novel isoform-specific method to accurately quantify apoE isoforms in clinically relevant samples. The method utilizes an antibody-free enrichment step and isotope-labeled physiologically relevant lipoprotein particle standards produced by immortalized astrocytes. We applied this method to a cohort of well characterized clinical samples and observed the following findings. The apoE isoform amounts are not different in cerebrospinal fluid (CSF) from young normal controls, suggesting that the amount of apoE isoforms is not the reason for risk of amyloidosis prior to the onset of advanced age. We did, however, observe an age-related increase in both apoE isoforms. In contrast to normal aging, the presence of amyloid increased apoE3, whereas apoE4 was unchanged or decreased. Importantly, for heterozygotes, the apoE4/apoE3 isoform ratio was increased in the CNS, although the reverse was true in the periphery. Finally, CSF apoE levels, but not plasma apoE levels, correlated with CSF β-amyloid levels. Collectively, these findings support the hypothesis that CNS and peripheral apoE are separate pools and differentially regulated. Furthermore, these results suggest that apoE mechanisms for the risk of amyloidosis and AD are related to an interaction between apoE, aging, and the amount of amyloid burden

Comparative evaluation of pebble-bed and prismatic fueled high-temperature gas-cooled reactors

A comparative evaluation has been performed of the HTGR and the Federal Republic of Germany's Pebble Bed Reactor (PBR) for potential commercial applications in the US. The evaluation considered two reactor sizes (1000 and 3000 MW(t)) and three process applications (steam cycle, direct cycle, and process heat, with outlet coolant temperatures of 750, 850, and 950/sup 0/C, respectively). The primary criterion for the comparison was the levelized (15-year) cost of producing electricity or process heat. Emphasis was placed on the cost impact of differences between the prismatic-type HTGR core, which requires periodic refuelings during reactor shutdowns, and the pebble bed PBR core, which is refueled continuously during reactor operations. Detailed studies of key technical issues using reference HTGR and PBR designs revealed that two cost components contributing to the levelized power costs are higher for the PBR: capital costs and operation and maintenance costs. A third cost component, associated with nonavailability penalties, tended to be higher for the PBR except for the process heat application, for which there is a large uncertainty in the HTGR nonavailability penalty at the 950/sup 0/C outlet coolant temperature. A fourth cost component, fuel cycle costs, is lower for the PBR, but not sufficiently lower to offset the capital cost component. Thus the HTGR appears to be slightly superior to the PBR in economic performance. Because of the advanced development of the HTGR concept, large HTGRs could also be commercialized in the US with lower R and D costs and shorter lead times than could large PBRs. It is recommended that the US gas-cooled thermal reactor program continue giving primary support to the HTGR, while also maintaining its cooperative PBR program with FRG

Drivers of Iron Cycling in Sediments of the sub-Antarctic Island South Georgia

Sediments of sub-Antarctic islands have been proposed to be important contributors to natural iron fertilization in the Southern Ocean [1, 2]. This potential contribution depends on biogeochemical processes within the sediment that may result in an iron benthic flux, most likely related to the degradation of organic matter (OM). Yet, the OM degradation pathways vary strongly among different sedimentary settings. We elucidate the role of environmental factors on the prevailing biogeochemical pathways and reaction rates at three contrasting sites of South Georgia, using comprehensive solid-phase and pore-water analyses, as well as transportreaction modelling. Samples were obtained along a transect from a glacial fjord towards the shelf during cruise ANTXXIX/ 4 of RV POLARSTERN in 2013. Oxygen penetration depth at all sites is <1 cm. Sediments recovered within the fjord are dominated by dissimilatory iron reduction (DIR) and show very high dissolved Fe2+ concentrations of up to 760 μM, while sulfide was not detected. In addition, Fe reduction below the sulfate/methane transition was observed. High input of reactive iron phases, possibly enhanced by bioturbation and bubble ebullition, appear to favour DIR as the dominant metabolic process for OM degradation in the basin like fjord. Shelf sediments outside the fjord are sulfidic throughout, with H2S formed primarily by anaerobic oxidation of methane. The conversion of Fe oxides into Fe sulfides significantly alters the initial sediment composition along the shelf, and impact the availability of iron to the water column. OM is of marine origin at all three sites (C:N~7), indicating that Fe oxide availability and reactivity rather than the carbon source determine whether iron or sulfate reduction dominantes. [1] Moore & Braucher (2008) Biogeosciences 5, 631-656. [2] Borrione et al., (2014) Biogeosciences 11, 1981–2001

Ecological fitness and strategies of adaptation of Bartonella species to their hosts and vectors

Bartonella spp. are facultative intracellular bacteria that cause characteristic hostrestricted hemotropic infections in mammals and are typically transmitted by blood-sucking arthropods. In the mammalian reservoir, these bacteria initially infect a yet unrecognized primary niche, which seeds organisms into the blood stream leading to the establishment of a long-lasting intra-erythrocytic bacteremia as the hall-mark of infection. Bacterial type IV secretion systems, which are supra-molecular transporters ancestrally related to bacterial conjugation systems, represent crucial pathogenicity factors that have contributed to a radial expansion of the Bartonella lineage in nature by facilitating adaptation to unique mammalian hosts. On the molecular level, the type IV secretion system VirB/VirD4 is known to translocate a cocktail of different effector proteins into host cells, which subvert multiple cellular functions to the benefit of the infecting pathogen. Furthermore, bacterial adhesins mediate a critical, early step in the pathogenesis of the bartonellae by binding to extracellular matrix components of host cells, which leads to firm bacterial adhesion to the cell surface as a prerequisite for the efficient translocation of type IV secretion effector proteins. The best-studied adhesins in bartonellae are the orthologous trimeric autotransporter adhesins, BadA in Bartonella henselae and the Vomp family in Bartonella quintana. Genetic diversity and strain variability also appear to enhance the ability of bartonellae to invade not only specific reservoir hosts, but also accidental hosts, as shown for B. henselae. Bartonellae have been identified in many different blood-sucking arthropods, in which they are typically found to cause extracellular infections of the mid-gut epithelium. Adaptation to specific vectors and reservoirs seems to be a common strategy of bartonellae for transmission and host diversity. However, knowledge regarding arthropod specificity/res