401 research outputs found
The Good Temp
[Excerpt] The story of the explosion of temporary employment and the challenge to the permanent employment contract in the last half of the twentieth century has been told many times. Researchers from\u27\u27a variety of academic disciplines have written about it, as have activists who organize to help American workers maintain a decent standard of living and a modicum of dignity, and policy analysts who fear the degradation of the employment relationship that seems to be a foregone implication of temporary work. They have focused on different units of analysis: workers who desire permanent jobs but can\u27t find them, workers who have lost out as companies have downsized and restructured, businesses and their myriad reasons for using temporary workers as a solution to their profitability and competition problems, and the temporary help service industry (THS) itself.
The Good Temp takes a different tack to explain these developments in labor market institutions and behaviors. Specifically, we look at how the THS industry in the United States reinvented temporary work in the second half of the twentieth century and examine how individual THS agencies continue to manufacture and market this reinvented product—the good temporary worker—today. It is a customized, historically specific make and model whose marketability rested on two selling points: that temporary employment could be a viable alternative to permanent employment and that the workers on whom the system of temporary employment relations depends could be as good as permanent workers and sometimes better. The historical and social construction of the good temp, we show, was embedded in THS-industry profitmaking strategies and relied on the diffusion of new norms about what constituted acceptable employment practice. Now entrenched, these norms underpin our current employment relations in the United States which many, if not most, of us experience as precarious and contingent, even when we have so-called permanent jobs
The diameter of the set of boundary slopes of a knot
Let K be a tame knot with irreducible exterior M(K) in a closed, connected,
orientable 3--manifold Sigma such that pi_1(Sigma) is cyclic. If infinity is
not a strict boundary slope, then the diameter of the set of strict boundary
slopes of K, denoted d_K, is a numerical invariant of K. We show that either
(i) d_K >= 2 or (ii) K is a generalized iterated torus knot. The proof combines
results from Culler and Shalen [Comment. Math. Helv. 74 (1999) 530-547] with a
result about the effect of cabling on boundary slopes.Comment: This is the version published by Algebraic & Geometric Topology on 29
August 200
Electroweak superpartner production at 13.6 TeV with Resummino
Due to the greater experimental precision expected from the currently ongoing
LHC Run 3, equally accurate theoretical predictions are essential. We update
the documentation of the Resummino package, a program dedicated to precision
cross section calculations for the production of a pair of sleptons,
electroweakinos, and leptons in the presence of extra gauge bosons, and for the
production of an associated electroweakino-squark or electroweakino-gluino
pair. We detail different additions that have been released since the initial
version of the program a decade ago, and then use the code to investigate the
impact of threshold resummation corrections at the
next-to-next-to-leading-logarithmic accuracy. As an illustration of the code we
consider the production of pairs of electroweakinos and sleptons at the LHC for
centre-of-mass energies ranging up to 13.6 TeV and in simplified model
scenarios. We find slightly increased total cross section values, accompanied
by a significant decrease of the associated theoretical uncertainties.
Furthermore, we explore the dependence of the results on the squark masses.Comment: 30 pages, 5 figure
Thin Melanoma with Nodal Involvement: Analysis of Demographic, Pathologic, and Treatment Factors with Regard to Prognosis.
BACKGROUND: Although only a small proportion of thin melanomas result in lymph node metastasis, the abundance of these lesions results in a relatively large absolute number of patients with a diagnosis of nodal metastases, determined by either sentinel lymph node (SLN) biopsy or clinical nodal recurrence (CNR).
METHODS: Independent cohorts with thin melanoma and either SLN metastasis or CNR were identified at two melanoma referral centers. At both centers, SLN metastasis patients were included. At center 1, the CNR cohort included patients with initial negative clinical nodal evaluation followed by CNR. At center 2, the CNR cohort was restricted to those presenting in the era before the use of SLN biopsy. Uni- and multivariable analyses of melanoma-specific survival (MSS) were performed.
RESULTS: At center 1, 427 CNR patients were compared with 91 SLN+ patients. The 5- and 10-year survival rates in the SLN group were respectively 88 and 84 % compared with 72 and 49 % in the CNR group (p \u3c 0.0001). The multivariate analysis showed age older than 50 years (hazard ratio [HR] 1.5; 95 % confidence interval [CI] 1.2-1.9), present ulceration (HR 1.9; 95 % CI 1.2-2.9), unknown ulceration (HR 1.6; 95 % CI 1.3-2.1), truncal site (HR 1.6; 95 % CI 1.2-2.2), and CNR (HR 3.3; 95 % CI 1.8-6.0) to be associated significantly with decreased MSS (p \u3c 0.01 for each). The center 2 cohort demonstrated remarkably similar findings, with a 5-year MSS of 88 % in the SLN (n = 29) group and 76 % in the CNR group (n = 39, p = 0.09).
CONCLUSION: Patients with nodal metastases from thin melanomas have a substantial risk of melanoma death. This risk is lower among patients whose disease is discovered by SLN biopsy rather than CNR
Quantum key distribution with entangled photons generated on demand by a quantum dot
Quantum key distribution-exchanging a random secret key relying on a quantum mechanical resource-is the core feature of secure quantum networks. Entanglement-based protocols offer additional layers of security and scale favorably with quantum repeaters, but the stringent requirements set on the photon source have made their use situational so far. Semiconductor-based quantum emitters are a promising solution in this scenario, ensuring on-demand generation of near-unity-fidelity entangled photons with record-low multiphoton emission, the latter feature countering some of the best eavesdropping attacks. Here, we use a coherently driven quantum dot to experimentally demonstrate a modified Ekert quantum key distribution protocol with two quantum channel approaches: both a 250-m-long single-mode fiber and in free space, connecting two buildings within the campus of Sapienza University in Rome. Our field study highlights that quantum-dot entangled photon sources are ready to go beyond laboratory experiments, thus opening the way to real-life quantum communication
Intramural Duodenal Haematoma after Endoscopic Biopsy: Case Report and Review of the Literature
The development of intramural duodenal haematoma (IDH) after small bowel biopsy is an unusual lesion and has only been reported in 18 children. Coagulopathy, thrombocytopenia and some special features of duodenal anatomy, e.g. relatively fixed position in the retroperitoneum and numerous submucosal blood vessels, have been suggested as a cause for IDH. The typical clinical presentation of IDH is severe abdominal pain and vomiting due to duodenal obstruction. In addition, it is often associated with pancreatitis and cholestasis. Diagnosis is confirmed using imaging techniques such as ultrasound, magnetic resonance imaging or computed tomography and upper intestinal series. Once diagnosis is confirmed and intestinal perforation excluded, conservative treatment with nasogastric tube and parenteral nutrition is sufficient. We present a case of massive IDH following endoscopic grasp forceps biopsy in a 5-year-old girl without bleeding disorder or other risk for IDH, which caused duodenal obstruction and mild pancreatitis and resolved within 2 weeks of conservative management. Since duodenal biopsies have become the common way to evaluate children or adults for suspected enteropathy, the occurrence of this complication is likely to increase. In conclusion, the review of the literature points out the risk for IDH especially in children with a history of bone marrow transplantation or leukaemia
Signatures of the Optical Stark Effect on Entangled Photon Pairs from Resonantly-Pumped Quantum Dots
Two-photon resonant excitation of the biexciton-exciton cascade in a quantum
dot generates highly polarization-entangled photon pairs in a
near-deterministic way. However, there are still open questions on the ultimate
level of achievable entanglement. Here, we observe the impact of the
laser-induced AC-Stark effect on the spectral emission features and on
entanglement. A shorter emission time, longer laser pulse duration, and higher
pump power all result in lower values of concurrence. Nonetheless, additional
contributions are still required to fully account for the observed below-unity
concurrence.Comment: 7 pages, 3 figure
A multipair-free source of entangled photons in the solid state
Unwanted multiphoton emission commonly reduces the degree of entanglement of
photons generated by non-classical light sources and, in turn, hampers their
exploitation in quantum information science and technology. Quantum emitters
have the potential to overcome this hurdle but, so far, the effect of
multiphoton emission on the quality of entanglement has never been addressed in
detail. Here, we tackle this challenge using photon pairs from a
resonantly-driven quantum dot and comparing quantum state tomography and
second-order coherence measurements as a function of the excitation power. We
observe that the relative (absolute) multiphoton emission probability is as low
as () at the maximum
source brightness, values that lead to a negligible effect on the degree of
entanglement. In stark contrast with probabilistic sources of entangled
photons, we also demonstrate that the multiphoton emission probability and the
degree of entanglement remain practically unchanged against the excitation
power for multiple Rabi cycles, despite we clearly observe oscillations in the
second-order coherence measurements. Our results, explained by a theoretical
model that we develop to estimate the actual multiphoton contribution in the
two-photon density matrix, highlight that quantum dots can be regarded as a
multipair-free source of entangled photons in the solid state
Genomic patterns in the widespread Eurasian lynx shaped by Late Quaternary climatic fluctuations and anthropogenic impacts.
Disentangling the contribution of long-term evolutionary processes and recent anthropogenic impacts to current genetic patterns of wildlife species is key for assessing genetic risks and designing conservation strategies. Here, we used 80 whole nuclear genomes and 96 mitogenomes from populations of the Eurasian lynx covering a range of conservation statuses, climatic zones and subspecies across Eurasia to infer the demographic history, reconstruct genetic patterns and discuss the influence of long-term isolation and/or more recent human-driven changes. Our results show that Eurasian lynx populations shared a common history until 100 kya, when Asian and European populations started to diverge and both entered a period of continuous and widespread decline, with western populations, except Kirov, maintaining lower effective sizes than eastern populations. Population declines and increased isolation in more recent times likely drove the genetic differentiation between geographically and ecologically close westernmost European populations. By contrast, and despite the wide range of habitats covered, populations are quite homogeneous genetically across the Asian range, showing a pattern of isolation by distance and providing little genetic support for the several proposed subspecies. Mitogenomic and nuclear divergences and population declines starting during the Late Pleistocene can be mostly attributed to climatic fluctuations and early human influence, but the widespread and sustained decline since the Holocene is more probably the consequence of anthropogenic impacts which intensified during the last centuries, especially in western Europe. Genetic erosion in isolated European populations and lack of evidence for long-term isolation argue for the restoration of lost population connectivity
A source of entangled photons based on a cavity-enhanced and strain-tuned GaAs quantum dot
A quantum-light source that delivers photons with a high brightness and a
high degree of entanglement is fundamental for the development of efficient
entanglement-based quantum-key distribution systems. Among all possible
candidates, epitaxial quantum dots are currently emerging as one of the
brightest sources of highly entangled photons. However, the optimization of
both brightness and entanglement currently requires different technologies that
are difficult to combine in a scalable manner. In this work, we overcome this
challenge by developing a novel device consisting of a quantum dot embedded in
a circular Bragg resonator, in turn, integrated onto a micromachined
piezoelectric actuator. The resonator engineers the light-matter interaction to
empower extraction efficiencies up to 0.69(4). Simultaneously, the actuator
manipulates strain fields that tune the quantum dot for the generation of
entangled photons with fidelities up to 0.96(1). This hybrid technology has the
potential to overcome the limitations of the key rates that plague current
approaches to entanglement-based quantum key distribution and
entanglement-based quantum networks. Introductio
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