Se-Jin Lee was elected member to the National Academy of Sciences on 28 April 2012. Dr Lee is responsible for the discovery of myostatin, a critical regulator of skeletal muscle mass and function. He ...also determined the primary binding receptor for myostatin, and has characterized additional transforming growth factor-β family members acting in this pathway.
This article explores the contention that the concentration of women in certain jobs that accommodate parenting can help explain both occupational gender segregation and the lower wages received by ...women employed full time. Evidence from the 1977 Quality of Employment Survey shows that the combination of both schedule flexibility and ease of job performance most clearly reduces job-family conflict for parents. However, mothers employed over 30 hours a week are not more likely to be in jobs with those characteristics, nor are predominantly female jobs in general likely to possess that cluster of characteristics shown to reduce job-family conflict.
The suprachiasmatic nuclei (SCN) express the highly polysialylated form of the neural cell adhesion molecule (NCAM) that has been proposed to promote plasticity in the adult brain. To investigate a ...role for NCAM in SCN circadian clock function, we examined the daily locomotor rhythm of mice homozygous for a mutation, Ncamtm1Cwr, which results in deletion of the NCAM-180 isoform that in brain carries polysialic acid (PSA). Mutant mice entrained well to a 12 hr light/dark cycle but exhibited a significantly shortened free-running period and longer activity duration under constant darkness (DD) than did wild-type mice. By the third week of DD treatment, circadian rhythmicity in the mutant was abolished. Immunocytochemical analyses of the mutant SCN revealed an abnormal number and distribution of vasoactive intestinal polypeptide-producing neurons, suggesting a developmental effect of the mutant phenotype; however, a direct physiological effect of the mutation on clock function was indicated by the fact that removal of PSA from adult wild-type SCN by microinjection of endoneuraminidase shortened the free-running period to a similar extent as in the mutant. Together, these data indicate critical roles for NCAM and PSA in the development and physiology of the mammalian SCN circadian clock.
The neglected issue of using profit efficiency for the best-practice benchmarking of UK universities is explored to see whether this supports the policy stance of encouraging more specialized ...university production. The article also investigates whether nonparametric modelling with financial ratios, in contrast to nonparametric modelling based on the prices and quantities of each university's inputs and outputs, can yield ready insights into this profit efficiency issue. The empirical results, using two new approaches, confirm that more specialized university production yields relatively higher performance on average than less specialized production. The results also highlight certain advantages of financial ratios modelling.
Double-diffusive finger convection is studied experimentally in a transparent Hele-Shaw
cell for a two-solute system. A less dense sucrose solution is layered on top
of a more dense salt solution ...using a laminar flow technique, and convective motion
is followed photographically from the static state. We systematically increase solute
concentrations from dilute to the solubility limit of the salt solution while maintaining
a fixed buoyancy ratio of approximately 1.08. Across the 14 experiments conducted,
the convective motion shows considerable variation in both structure and time scale.
We find that new finger pairs form continuously within a finger generation zone where
complexity increases with Rayleigh number, reaches a peak, and then decreases for
highly concentrated solutions. The vertical fnger length scale grows linearly in time
across the full concentration range. The vertical finger velocity also increases linearly
with Rayleigh number, but as the concentrations increase, deviation from linearity and
asymmetrical convection occur. The horizontal length scale grows as a power law in
time with the exponent constant over most of the range; again, deviations are observed
for highly concentrated solutions. The observed deviations at high concentrations are
attributed to the increasing nonlinearity in the governing equations as the solutions
approach their solubility limits. There, the fluid properties become functions of
solute concentration and vary significantly within the experimental fields suppressing
structural complexity, imparting asymmetry to the convective motion, and influencing
emergent vertical and horizontal length scales and their growth.
Understanding of single‐phase and multiphase flow and transport in fractures can be greatly enhanced through experimentation in transparent systems (analogs or replicas) where light transmission ...techniques yield quantitative measurements of aperture, solute concentration, and phase saturation fields. Here we quantify aperture field measurement error and demonstrate the influence of this error on the results of flow and transport simulations (hypothesized experimental results) through saturated and partially saturated fractures. We find that precision and accuracy can be balanced to greatly improve the technique and present a measurement protocol to obtain a minimum error field. Simulation results show an increased sensitivity to error as we move from flow to transport and from saturated to partially saturated conditions. Significant sensitivity under partially saturated conditions results in differences in channeling and multiple‐peaked breakthrough curves. These results emphasize the critical importance of defining and minimizing error for studies of flow and transport in single fractures.
The cause of acquired immunodeficiency syndrome (AIDS) dementia, which is a frequent late manifestation of human immunodeficiency virus (HIV) infection, is unknown but radiological and pathological ...studies have implicated alterations in subcortical white matter. To investigate the pathological basis of these white matter abnormalities, we performed an immunocytochemical and histological analysis of subcortical white matter from AIDS patients with and without dementia, from pre-AIDS patients (asymptomatic HIV-seropositive patients), and from HIV-seronegative control subjects. Reduced intensity of Luxol fast blue staining, designated "diffuse myelin pallor," was detected in 8 of 15 AIDS dementia patients, 3 of 13 AIDS nondemented patients, and none of the pre-AIDS patients (n = 2) or control subjects (n = 9). In contrast to Luxol fast blue staining, sections stained immunocytochemically for myelin proteins did not show decreased staining intensities in regions of diffuse myelin pallor. In addition, neither demyelinated axons nor active demyelination were detected in light and electron micrographs of subcortical white matter from brains of patients with AIDS dementia. An increase in the number of perivascular macrophages and hypertrophy of astrocytes and microglia occurred in brain sections from HIV-infected patients. These changes were not specific to dementia or regions of diffuse myelin pallor and they occurred in both gray and white matter. In contrast to the lack of myelin pathology in AIDS dementia brains, significant accumulations of serum proteins in white matter glia were detected in the brains of 12 of 12 patients with AIDS dementia and 6 of 12 AIDS patients without dementia. Serum protein-immunopositive cortical neurons were detected in the frontal cortex of 11 of 12 patients with AIDS dementia and 3 of 12 nondemented AIDS patients. Seronegative control subjects showed minimal serum protein immunoreactivity in both cortex and white matter. We conclude therefore that alterations in the blood-brain barrier and not demyelination contribute to the development of AIDS dementia.
We reconceptualize “macro” modified invasion percolation (MMIP) at the near pore (NP) scale and apply it to simulate the nonwetting phase invasion experiments of Glass et al. 2000 conducted in ...macroheterogeneous porous media. For experiments where viscous forces were nonnegligible, we redefine the total pore filling pressure to include viscous losses within the invading phase as well as the viscous influence to decrease randomness imposed by capillary forces at the front. NP MMIP exhibits the complex invasion order seen experimentally with characteristic alternations between periods of gravity‐stabilized and destabilized invasion growth controlled by capillary barriers. The breaching of these barriers and subsequent pore‐scale fingering of the nonwetting phase is represented extremely well, as is the saturation field evolution and total volume invaded.
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