655 research outputs found
Diversity in the Heartland of America: The Impact on Human Development in Indiana
This article is the third in a series of studies measuring the impact of cultural diversity on human development. We disaggregate cultural diversity into three components: ethnicity, language, and religion. The first study examined the impact of diversity internationally. We found that countries are worse off with greater diversity, especially religious diversity; however, we found that more-prosperous countries with strong institutions benefited from increased diversity. We concluded that strong institutions are essential to maximize the benefits of diversity while mitigating the associated costs. The second study examined the impact of diversity within the United States, where institutional strength was assumed to be relatively great and similar between states. We found an overall negative impact from diversity. Ethnic diversity was negatively associated with human development, while religious and language diversity had a positive impact. We concluded that in the United States, there is more tolerance for religious and language differences compared to ethnic differences. In this third study, we examine the impact of diversity within the state of Indiana. As with our national results, we find a generally negative relationship between human development and diversity. Ethnic diversity has a negative impact, while religious and language diversity are generally positive influences. Strong political and legal institutions may not be sufficient to extract net benefits from diversity if social attitudes that guide behavior are not supportive. The results suggest that net benefits from diversity in Indiana may depend on improvement of social attitudes and in commitment to social services that support historically disadvantaged minority groups
A New Measurement of Cosmic Ray Composition at the Knee
The Dual Imaging Cerenkov Experiment (DICE) was designed and operated for
making elemental composition measurements of cosmic rays near the knee of the
spectrum at several PeV. Here we present the first results using this
experiment from the measurement of the average location of the depth of shower
maximum, , in the atmosphere as a function of particle energy. The value
of near the instrument threshold of ~0.1 PeV is consistent with
expectations from previous direct measurements. At higher energies there is
little change in composition up to ~5 PeV. Above this energy is deeper
than expected for a constant elemental composition implying the overall
elemental composition is becoming lighter above the knee region. These results
disagree with the idea that cosmic rays should become on average heavier above
the knee. Instead they suggest a transition to a qualitatively different
population of particles above 5 PeV.Comment: 7 pages, LaTeX, two eps figures, aas2pp4.sty and epsf.sty included,
accepted by Ap.J. Let
On the invariant causal characterization of singularities in spherically symmetric spacetimes
The causal character of singularities is often studied in relation to the
existence of naked singularities and the subsequent possible violation of the
cosmic censorship conjecture. Generally one constructs a model in the framework
of General Relativity described in some specific coordinates and finds an ad
hoc procedure to analyze the character of the singularity. In this article we
show that the causal character of the zero-areal-radius (R=0) singularity in
spherically symmetric models is related with some specific invariants. In this
way, if some assumptions are satisfied, one can ascertain the causal character
of the singularity algorithmically through the computation of these invariants
and, therefore, independently of the coordinates used in the model.Comment: A misprint corrected in Theor. 4.1 /Cor. 4.
Complementing T Cells’ Functions: Bringing in Metabolism Matters
Components of the complement system act directly on T cells to alter conventional and regulatory T cell subsets. In this issue of Immunity, Kolev, Dimeloe, Le Friec et al. (2015) provide evidence of a mechanism by which the complement stimulates sustained mTORC1 activation and regulates cellular metabolism
A lipopolysaccharide-induced DNA-binding protein for a class II gene in B cells is distinct from NF-kappa B
Class II (Ia) major histocompatibility complex molecules are cell surface proteins normally expressed by a limited subset of cells of the immune system. These molecules regulate the activation of T cells and are required for the presentation of antigens and the initiation of immune responses. The expression of Ia in B cells is determined by both the developmental stage of the B cell and by certain external stimuli. It has been demonstrated previously that treatment of B cells with lipopolysaccharide (LPS) results in increased surface expression of Ia protein. However, we have confirmed that LPS treatment results in a significant decrease in mRNA encoding the Ia proteins which persists for at least 18 h. Within the upstream regulatory region of A alpha k, an NF-kappa B-like binding site is present. We have identified an LPS-induced DNA-binding protein in extracts from athymic mice whose spleens consist predominantly of B cells. Binding activity is present in low levels in unstimulated spleen cells and is increased by LPS treatment. This protein binds to two sites in a regulatory region of the Ia A alpha k gene, one of which contains the NF-kappa B-like binding site. DNA fragments containing these sites cross-compete for protein binding. Analysis by DNase I footprinting identified a target binding sequence, named the LPS-responsive element. Although this target sequence contains an NF-kappa B-like binding site, competition with a mutant oligonucleotide demonstrated that bases critical for NF-kappa B binding are not required for binding of the LPS-inducible protein. Therefore, we hypothesized that this inducible protein represents a new mediator of LPS action, distinct from NF-kappa B, and may be one mechanism to account for the decrease in mRNA encoding the Ia proteins
Universal families and quantum control in infinite dimensions
In a topological space, a family of continuous mappings is called universal
if its action, in at least one element of the space, is dense. If the mappings
are unitary or trace-preserving completely positive, the notion of universality
is closely related to the notion of controllability in either closed or open
quantum systems. Quantum controllability in infinite dimensions is discussed in
this setting and minimal generators are found for full control universal
families. Some of the requirements of the operators needed for control in
infinite dimensions follow from the properties of the infinite unitary group.
Hence, a brief discussed of this group and their appropriate mathematical
spaces is also included.Comment: 9 pages Late
On the cyclically fully commutative elements of Coxeter groups
Let W be an arbitrary Coxeter group. If two elements have expressions that are cyclic shifts of each other (as words), then they are conjugate (as group elements) in W. We say that w is cyclically fully commutative (CFC) if every cyclic shift of any reduced expression for w is fully commutative (i.e., avoids long braid relations). These generalize Coxeter elements in that their reduced expressions can be described combinatorially by acyclic directed graphs, and cyclically shifting corresponds to source-to-sink conversions. In this paper, we explore the combinatorics of the CFC elements and enumerate them in all Coxeter groups. Additionally, we characterize precisely which CFC elements have the property that powers of them remain fully commutative, via the presence of a simple combinatorial feature called a band. This allows us to give necessary and sufficient conditions for a CFC element w to be logarithmic, that is, ℓ(wk)=k⋅ℓ(w) for all k≥1, for a large class of Coxeter groups that includes all affine Weyl groups and simply laced Coxeter groups. Finally, we give a simple non-CFC element that fails to be logarithmic under these conditions
Depth of maximum of extensive air showers and cosmic ray composition above 10**17 eV in the geometrical multichain model of nuclei interactions
The depth of maximum for extensive air showers measured by Fly's Eye and
Yakutsk experiments is analysed. The analysis depends on the hadronic
interaction model that determine cascade development. The novel feature found
in the cascading process for nucleus-nucleus collisions at high energies leads
to a fast increase of the inelasticity in heavy nuclei interactions without
changing the hadron-hadron interaction properties. This effects the development
of the extensive air showers initiated by heavy primaries. The detailed
calculations were performed using the recently developed geometrical multichain
model and the CORSIKA simulation code. The agreement with data on average depth
of shower maxima, the falling slope of the maxima distribution, and these
distribution widths are found for the very heavy cosmic ray mass spectrum
(slightly heavier than expected in the diffusion model at about 3*10**17 eV and
similar to the Fly's Eye composition at this energy).Comment: 11pp (9 eps figures
Temporal dynamics of aquatic communities and implications for pond conservation
Conservation through the protection of particular habitats is predicated on the assumption that the conservation value of those habitats is stable. We test this assumption for ponds by investigating temporal variation in macroinvertebrate and macrophyte communities over a 10-year period in northwest England. We surveyed 51 ponds in northern England in 1995/6 and again in 2006, identifying all macrophytes (167 species) and all macroinvertebrates (221 species, excluding Diptera) to species. The alpha-diversity, beta-diversity and conservation value of these ponds were compared between surveys. We find that invertebrate species richness increased from an average of 29. 5 species to 39. 8 species between surveys. Invertebrate gamma-diversity also increased between the two surveys from 181 species to 201 species. However, this increase in diversity was accompanied by a decrease in beta-diversity. Plant alpha-, beta and gamma-diversity remained approximately constant between the two periods. However, increased proportions of grass species and a complete loss of charophytes suggests that the communities are undergoing succession. Conservation value was not correlated between sampling periods in either plants or invertebrates. This was confirmed by comparing ponds that had been disturbed with those that had no history of disturbance to demonstrate that levels of correlation between surveys were approximately equal in each group of ponds. This study has three important conservation implications: (i) a pond with high diversity or high conservation value may not remain that way and so it is unwise to base pond conservation measures upon protecting currently-speciose habitats; (ii) maximising pond gamma-diversity requires a combination of late and early succession ponds, especially for invertebrates; and (iii) invertebrate and plant communities in ponds may require different management strategies if succession occurs at varying rates in the two groups
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