1,541 research outputs found
The Wheel of Servitude: Black Forced Labor after Slavery
Emancipation brought an end to many of the evils of slavery, but it did not do away with involuntary servitude in the South. Even during Reconstruction, state legislatures passed laws that bound laborers to the landowner with a nearly unbreakable tie—which still chains many a rural black to what a 1914 Supreme Court ruling called an “ever-turning wheel of servitude.”
Daniel Novak shows how federal, state, and local regulations combined in an undisguised effort to keep southern agriculture supplied with black labor. A freedman who did not immediately enter into a labor contract was subject to arrest as a vagrant. Once a contract was agreed upon, it was a criminal offense for a laborer to fail to carry it out, no matter how unfair the terms might be.
If, as was almost inevitable, the freedman fell into debt to the landowner, he could be kept in service until repayment-and exorbitant interest rates and judicious bookkeeping could often postpone that day indefinitely. Novak traces the sporadic efforts of the federal government to do away with this kind of peonage. In studying the details of the legal basis for peonage in the South, he breaks new ground. The institution has aroused surprisingly little interest in the past; this compelling account should do much to establish that peonage is one of the most severe and widespread violations of civil rights in the nation.
Daniel Novak is assistant professor of political science at State University of New York, Buffalo.https://uknowledge.uky.edu/upk_african_american_studies/1015/thumbnail.jp
Expression of selected pathway-marker genes in human urothelial cells exposed chronically to a non-cytotoxic concentration of monomethylarsonous acid
AbstractBladder cancer has been associated with chronic arsenic exposure. Monomethylarsonous acid [MMA(III)] is a metabolite of inorganic arsenic and has been shown to transform an immortalized urothelial cell line (UROtsa) at concentrations 20-fold less than arsenite. MMA(III) was used as a model arsenical to examine the mechanisms of arsenical-induced transformation of urothelium. A previous microarray analysis revealed only minor changes in gene expression at 1 and 2 months of chronic exposure to MMA(III), contrasting with substantial changes observed at 3 months of exposure. To address the lack of information between 2 and 3 months of exposure (the critical period of transformation), the expression of select pathway marker genes was measured by PCR array analysis on a weekly basis. Cell proliferation rate, anchorage-independent growth, and tumorigenicity in SCID mice were also assessed to determine the early, persistent phenotypic changes and their association with the changes in expression of these selected marker genes. A very similar pattern of alterations in these genes was observed when compared to the microarray results, and suggested that early perturbations in cell signaling cascades, immunological pathways, cytokine expression, and MAPK pathway are particularly important in driving malignant transformation. These results showed a strong association between the acquired phenotypic changes that occurred as early as 1–2 months of chronic MMA(III) exposure, and the observed gene expression pattern that is indicative of the earliest stages in carcinogenesis
Spin Tunneling and Phonon-assisted Relaxation in Mn12-acetate
We present a comprehensive theory of the magnetization relaxation in a
Mn12-acetate crystal in the high-temperature regime (T>1 K), which is based on
phonon-assisted spin tunneling induced by quartic magnetic anisotropy and weak
transverse magnetic fields. The overall relaxation rate as function of the
longitudinal magnetic field is calculated and shown to agree well with
experimental data including all resonance peaks measured so far. The Lorentzian
shape of the resonances, which we obtain via a generalized master equation that
includes spin tunneling, is also in good agreement with recent data. We derive
a general formula for the tunnel splitting energy of these resonances. We show
that fourth-order diagonal terms in the Hamiltonian lead to satellite peaks. A
derivation of the effective linewidth of a resonance peak is given and shown to
agree well with experimental data. In addition, previously unknown spin-phonon
coupling constants are calculated explicitly. The values obtained for these
constants and for the sound velocity are also in good agreement with recent
data. We show that the spin relaxation in Mn12-acetate takes place via several
transition paths of comparable weight. These transition paths are expressed in
terms of intermediate relaxation times, which are calculated and which can be
tested experimentally.Comment: 18 pages, 22 EPS figures, REVTe
On spontaneous scalarization
We study in the physical frame the phenomenon of spontaneous scalarization
that occurs in scalar-tensor theories of gravity for compact objects. We
discuss the fact that the phenomenon occurs exactly in the regime where the
Newtonian analysis indicates it should not. Finally we discuss the way the
phenomenon depends on the equation of state used to describe the nuclear
matter.Comment: 41 pages, RevTex, 10 ps figures, submitted to Phys. Rev.
Accounting for autocorrelation in multi-drug resistant tuberculosis predictors using a set of parsimonious orthogonal eigenvectors aggregated in geographic space
Spatial autocorrelation is problematic for classical hierarchical cluster detection tests commonly used in multidrug
resistant tuberculosis (MDR-TB) analyses as considerable random error can occur. Therefore, when MDR-TB clusters
are spatially autocorrelated the assumption that the clusters are independently random is invalid. In this research, a
product moment correlation coefficient (i.e. the Moran’s coefficient) was used to quantify local spatial variation in multiple
clinical and environmental predictor variables sampled in San Juan de Lurigancho, Lima, Peru. Initially, QuickBird
(spatial resolution = 0.61 m) data, encompassing visible bands and the near infra-red bands, were selected to synthesize
images of land cover attributes of the study site. Data of residential addresses of individual patients with smear-positive
MDR-TB were geocoded, prevalence rates calculated and then digitally overlaid onto the satellite data within a 2 km
buffer of 31 georeferenced health centres, using a 10 m2 grid-based algorithm. Geographical information system (GIS)-
gridded measurements of each health centre were generated based on preliminary base maps of the georeferenced data
aggregated to block groups and census tracts within each buffered area. A three-dimensional model of the study site was
constructed based on a digital elevation model (DEM) to determine terrain covariates associated with the sampled MDRTB
covariates. Pearson’s correlation was used to evaluate the linear relationship between the DEM and the sampled
MDR-TB data. A SAS/GIS® module was then used to calculate univariate statistics and to perform linear and non-linear
regression analyses using the sampled predictor variables. The estimates generated from a global autocorrelation
analyses were then spatially decomposed into empirical orthogonal bases, using a negative binomial regression with a
non-homogeneous mean. Results of the DEM analyses indicated a statistically non-significant, linear relationship
between georeferenced health centres and the sampled covariate elevation. The data exhibited positive spatial autocorrelation
and the decomposition of Moran’s coefficient into uncorrelated, orthogonal map pattern components which
revealed global spatial heterogeneities necessary to capture latent autocorrelation in the MDR-TB model. It was thus
shown that Poisson regression analyses and spatial eigenvector mapping can elucidate the mechanics of MDR-TB transmission
by prioritizing clinical and environmental-sampled predictor variables for identifying high risk populations
Physical signatures of discontinuities of the time-dependent exchange-correlation potential
The exact exchange-correlation (XC) potential in time-dependent
density-functional theory (TDDFT) is known to develop steps and discontinuities
upon change of the particle number in spatially confined regions or isolated
subsystems. We demonstrate that the self-interaction corrected adiabatic
local-density approximation for the XC potential has this property, using the
example of electron loss of a model quantum well system. We then study the
influence of the XC potential discontinuity in a real-time simulation of a
dissociation process of an asymmetric double quantum well system, and show that
it dramatically affects the population of the resulting isolated single quantum
wells. This indicates the importance of a proper account of the discontinuities
in TDDFT descriptions of ionization, dissociation or charge transfer processes.Comment: 17 pages, 6 figure
The linear multiplet and ectoplasm
In the framework of the superconformal tensor calculus for 4D N=2
supergravity, locally supersymmetric actions are often constructed using the
linear multiplet. We provide a superform formulation for the linear multiplet
and derive the corresponding action functional using the ectoplasm method (also
known as the superform approach to the construction of supersymmetric
invariants). We propose a new locally supersymmetric action which makes use of
a deformed linear multiplet. The novel feature of this multiplet is that it
corresponds to the case of a gauged central charge using a one-form potential
not annihilated by the central charge (unlike the standard N=2 vector
multiplet). Such a gauge one-form can be chosen to describe a variant nonlinear
vector-tensor multiplet. As a byproduct of our construction, we also find a
variant realization of the tensor multiplet in supergravity where one of the
auxiliaries is replaced by the field strength of a gauge three-form.Comment: 31 pages; v3: minor corrections and typos fixed, version to appear in
JHE
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