9,950 research outputs found
Migration in Arctic Alaska: Empirical Evidence of the Stepping Stones Hypothesis
This paper explores hypotheses of hierarchical migration using data from the Alaskan Arctic. We focus on migration of Iñupiat people, who are indigenous to the region, and explore the role of income and subsistence harvests on migration. To test related hypotheses we use confidential micro-data from the US Census Bureau’s 2000 Decennial Census of Population and Income and generate migration probabilities using a mixed multinomial and conditional logit model. Our findings are broadly consistent with Ravenstein’s (1885) early hypothesis of step-wise migration; we find evidence of step-wise migration, both up and down an urban and rural hierarchy. We also find that where migrants choose to live is a function of place, personal, and household characteristics.Migration, Hierarchical Migration, Rural to Urban Migration, Arctic Alaska
Searching for Dark Photons with Maverick Top Partners
In this paper, we present a model in which an up-type vector-like quark (VLQ)
is charged under a new gauge force which kinetically mixes with the SM
hypercharge. The gauge boson of the is the dark photon, .
Traditional searches for VLQs rely on decays into Standard Model electroweak
bosons or Higgs. However, since no evidence for VLQs has been found at
the Large Hadron Collider (LHC), it is imperative to search for other novel
signatures of VLQs beyond their traditional decays. As we will show, if the
dark photon is much less massive than the Standard Model electroweak sector,
, for the large majority of the allowed parameter space
the VLQ predominately decays into the dark photon and the dark Higgs that
breaks the . That is, this VLQ is a `maverick top partner' with
nontraditional decays. One of the appeals of this scenario is that pair
production of the VLQ at the LHC occurs through the strong force and the rate
is determined by the gauge structure. Hence, the production of the dark photon
at the LHC only depends on the strong force and is largely independent of the
small kinetic mixing with hypercharge. This scenario provides a robust
framework to search for a light dark sector via searches for heavy colored
particles at the LHC.Comment: 40 pages and 11 figure
Virus–Bacteria Interactions: Implications and Potential for the Applied and Agricultural Sciences
Eukaryotic virus–bacteria interactions have recently become an emerging topic of study due to multiple significant examples related to human pathogens of clinical interest. However, such omnipresent and likely important interactions for viruses and bacteria relevant to the applied and agricultural sciences have not been reviewed or compiled. The fundamental basis of this review is that these interactions have importance and deserve more investigation, as numerous potential consequences and applications arising from their discovery are relevant to the applied sciences. The purpose of this review is to highlight and summarize eukaryotic virus–bacteria findings in the food/water, horticultural, and animal sciences. In many cases in the agricultural sciences, mechanistic understandings of the effects of virus–bacteria interactions remain unstudied, and many studies solely focus on co-infections of bacterial and viral pathogens. Given recent findings relative to human viral pathogens, further research related to virus–bacteria interactions would likely result in numerous discoveries and beneficial applications
Conductance fluctuations at the integer quantum Hall plateau transition
We study numerically conductance fluctuations near the integer quantum Hall
effect plateau transition. The system is presumed to be in a mesoscopic regime,
with phase coherence length comparable to the system size. We focus on a
two-terminal conductance G for square samples, considering both periodic and
open boundary conditions transverse to the current. At the plateau transition,
G is broadly distributed, with a distribution function close to uniform on the
interval between zero and one in units of e^2/h. Our results are consistent
with a recent experiment by Cobden and Kogan on a mesoscopic quantum Hall
effect sample.Comment: minor changes, 5 pages LaTex, 7 postscript figures included using
epsf; to be published Phys. Rev. B 55 (1997
Comparing Offline Decoding Performance in Physiologically Defined Neuronal Classes
Objective: Recently, several studies have documented the presence of a bimodal distribution of spike waveform widths in primary motor cortex. Although narrow and wide spiking neurons, corresponding to the two modes of the distribution, exhibit different response properties, it remains unknown if these differences give rise to differential decoding performance between these two classes of cells. Approach: We used a Gaussian mixture model to classify neurons into narrow and wide physiological classes. Using similar-size, random samples of neurons from these two physiological classes, we trained offline decoding models to predict a variety of movement features. We compared offline decoding performance between these two physiologically defined populations of cells. Main results: We found that narrow spiking neural ensembles decode motor parameters better than wide spiking neural ensembles including kinematics, kinetics, and muscle activity. Significance: These findings suggest that the utility of neural ensembles in brain machine interfaces may be predicted from their spike waveform widths
Mechanism for Fine-Grained Software Controlled Core Dumps
We present a mechanism to generate a minidump file that will only include the exact memory an application wants when the application receives a fatal signal – the application itself can write a file in valid ELF CORE file format
The endothelium solves problems that endothelial cells do not know exist
The endothelium is the single layer of cells that lines the entire cardiovascular system and that regulates vascular tone and blood-tissue exchange, recruits blood cells, modulates blood clotting and determines the formation of new blood vessels. To control each function, the endothelium uses a remarkable sensory capability to continuously monitor vanishingly small changes in the concentration of many simultaneously arriving extracellular activators that each provide cues to physiological state. Here, we suggest that the extraordinary sensory capabilities of the endothelium does not come from single cells but from the combined activity of a large number of endothelial cells. Each cell has a limited, but distinctive, sensory capacity and shares information with neighbours so that sensing is distributed among cells. Communication of information among connected cells provides a system-level sensing substantially greater than the capabilities of any single cell and, as a collective, the endothelium solves sensory problems too complex for any single cell
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