713 research outputs found
Partitioning of on-demand electron pairs
We demonstrate the high fidelity splitting of electron pairs emitted on
demand from a dynamic quantum dot by an electronic beam splitter. The fidelity
of pair splitting is inferred from the coincidence of arrival in two detector
paths probed by a measurement of the partitioning noise. The emission
characteristic of the on-demand electron source is tunable from electrons being
partitioned equally and independently to electron pairs being split with a
fidelity of 90%. For low beam splitter transmittance we further find evidence
of pair bunching violating statistical expectations for independent fermions
Public Availability of Published Research Data in High-Impact Journals
BACKGROUND: There is increasing interest to make primary data from published research publicly available. We aimed to assess the current status of making research data available in highly-cited journals across the scientific literature. METHODS AND RESULTS: We reviewed the first 10 original research papers of 2009 published in the 50 original research journals with the highest impact factor. For each journal we documented the policies related to public availability and sharing of data. Of the 50 journals, 44 (88%) had a statement in their instructions to authors related to public availability and sharing of data. However, there was wide variation in journal requirements, ranging from requiring the sharing of all primary data related to the research to just including a statement in the published manuscript that data can be available on request. Of the 500 assessed papers, 149 (30%) were not subject to any data availability policy. Of the remaining 351 papers that were covered by some data availability policy, 208 papers (59%) did not fully adhere to the data availability instructions of the journals they were published in, most commonly (73%) by not publicly depositing microarray data. The other 143 papers that adhered to the data availability instructions did so by publicly depositing only the specific data type as required, making a statement of willingness to share, or actually sharing all the primary data. Overall, only 47 papers (9%) deposited full primary raw data online. None of the 149 papers not subject to data availability policies made their full primary data publicly available. CONCLUSION: A substantial proportion of original research papers published in high-impact journals are either not subject to any data availability policies, or do not adhere to the data availability instructions in their respective journals. This empiric evaluation highlights opportunities for improvement
Altered Cerebellar-Cerebral Functional Connectivity in Geriatric Depression
Although volumetric and activation changes in the cerebellum have frequently been reported in studies on major depression, its role in the neural mechanism of depression remains unclear. To understand how the cerebellum may relate to affective and cognitive dysfunction in depression, we investigated the resting-state functional connectivity between cerebellar regions and the cerebral cortex in samples of patients with geriatric depression (nā=ā11) and healthy controls (nā=ā18). Seed-based connectivity analyses were conducted using seeds from cerebellum regions previously identified as being involved in the executive, default-mode, affective-limbic, and motor networks. The results revealed that, compared with controls, individuals with depression show reduced functional connectivity between several cerebellum seed regions, specifically those in the executive and affective-limbic networks with the ventromedial prefrontal cortex (vmPFC) and increased functional connectivity between the motor-related cerebellum seed regions with the putamen and motor cortex. We further investigated whether the altered functional connectivity in depressed patients was associated with cognitive function and severity of depression. A positive correlation was found between the Crus IIāvmPFC connectivity and performance on the Hopkins Verbal Learning Test-Revised delayed memory recall. Additionally, the vermisāposterior cinglate cortex (PCC) connectivity was positively correlated with depression severity. Our results suggest that cerebellumāvmPFC coupling may be related to cognitive function whereas cerebellumāPCC coupling may be related to emotion processing in geriatric depression
Cosmic Ray Anomalies from the MSSM?
The recent positron excess in cosmic rays (CR) observed by the PAMELA
satellite may be a signal for dark matter (DM) annihilation. When these
measurements are combined with those from FERMI on the total () flux
and from PAMELA itself on the ratio, these and other results are
difficult to reconcile with traditional models of DM, including the
conventional mSUGRA version of Supersymmetry even if boosts as large as
are allowed. In this paper, we combine the results of a previously
obtained scan over a more general 19-parameter subspace of the MSSM with a
corresponding scan over astrophysical parameters that describe the propagation
of CR. We then ascertain whether or not a good fit to this CR data can be
obtained with relatively small boost factors while simultaneously satisfying
the additional constraints arising from gamma ray data. We find that a specific
subclass of MSSM models where the LSP is mostly pure bino and annihilates
almost exclusively into pairs comes very close to satisfying these
requirements. The lightest in this set of models is found to be
relatively close in mass to the LSP and is in some cases the nLSP. These models
lead to a significant improvement in the overall fit to the data by an amount
dof in comparison to the best fit without Supersymmetry
while employing boosts . The implications of these models for future
experiments are discussed.Comment: 57 pages, 31 figures, references adde
The heteronomy of choice architecture
Choice architecture is heralded as a policy approach that does not coercively reduce freedom of choice. Still we might worry that this approach fails to respect individual choice because it subversively manipulates individuals, thus contravening their personal autonomy. In this article I address two arguments to this effect. First, I deny that choice architecture is necessarily heteronomous. I explain the reasons we have for avoiding heteronomous policy-making and offer a set of four conditions for non-heteronomy. I then provide examples of nudges that meet these conditions. I argue that these policies are capable of respecting and promoting personal autonomy, and show this claim to be true across contrasting conceptions of autonomy. Second, I deny that choice architecture is disrespectful because it is epistemically paternalistic. This critique appears to loom large even against non-heteronomous nudges. However, I argue that while some of these policies may exhibit epistemically paternalistic tendencies, these tendencies do not necessarily undermine personal autonomy. Thus, if we are to find such policies objectionable, we cannot do so on the grounds of respect for autonomy
PrEP (HIV pre-exposure prophylaxis) and its possibilities for clinical practice
In this article, we reflect on the possibilities that PrEP (HIV pre-exposure prophylaxis) raises for HIV specialist clinicians. Often neglected, yet a direct participant at the intersection of a complex tension within public health debates on how to reduce HIV transmission and the sexual sociability of individuals, we reflect on current thinking of health practitioners involved in the day-to-day practice of prescribing PrEP. Drawing on interviews with practitioners in the context of UK sexual health and HIV specialist medicine, while bearing in mind neoliberal critiques and process studies of medical science, we propose that PrEP invites the possibility for reconstituting approaches to sex and risk
Informing research priorities for immature sea turtles through expert elicitation
This is the final version. Available from Inter Research via the DOI in this record.āÆAlthough sea turtles have received substantial focus worldwide, research on the immature life stages is still relatively limited. The latter is of particular importance, given that a large proportion of sea turtle populations comprises immature individuals. We set out to identify knowledge gaps and identify the main barriers hindering research in this field. We analyzed the perceptions of sea turtle experts through an online survey which gathered their opinions on the current state of affairs on immature sea turtle research, including species and regions in need of further study, priority research questions, and barriers that have interfered with the advancement of research. Our gap analysis indicates that studies on immature leatherback Dermochelys coriacea and hawksbill Eretmochelys imbricata turtles are lacking, as are studies on all species based in the Indian, South Pacific, and South Atlantic Oceans. Experts also perceived that studies in population ecology, namely on survivorship and demography, and habitat use/behavior, are needed to advance the state of knowledge on immature sea turtles. Our survey findings indicate the need for more interdisciplinary research, collaborative efforts (e.g. data-sharing, joint field activities), and improved communication among researchers, funding bodies, stakeholders, and decision-makers
Complications and reoperations of the SB CharitƩ lumbar disc prosthesis: experience in 75 patients
Artificial disc prosthesis show fair to good short- and mid-term results. Long-term results are becoming apparent now, however, the incidence of late complications with this procedure remain poorly understood. In this report we will analyse late complications and discuss our experiences with salvage operations in patients with persistent pain after SB CharitĆ© disc prosthesis implantation. Seventy-five patients with persistent leg and back pain after insertion of an artificial disc prosthesis were enrolled in the study. In this negative selection frequently occurring late-complications were subsidence, wear, adjacent disc degeneration, facet joint degeneration and migration. In 15 patients we performed a posterior fusion without disc removal, and in 22 patients we removed 26 prostheses and performed a posterior and anterior fusion. The visual analogue scale (VAS) and Oswestry were examined before the salvage operation and after a follow-up period of at least 1Ā year, which is not yet available in all patients. The VAS and Oswestry decreased in the posterior group (nĀ =Ā 10) respectively from 8.0 (SD 0.9) to 6.3 (SD 2.1) and from 57.0 (SD 17.0) to 44.6 (SD 20.4); and in the disc removal group (nĀ =Ā 14) respectively from 8.0 (SD 0.9) to 5.6 (SD 2.7) and from 56.3 (SD 14.0) to 43.0 (SD 20.7). Serious late complications may occur following total disc replacement. Removal of the SB CharitĆ© artificial disc is feasible but with inherent risks. Removal of the disc prosthesis gives slightly better results than posterior fusion alone after a follow-up of at least 1Ā year
Clumps and streams in the local dark matter distribution
In cold dark matter cosmological models, structures form and grow by merging
of smaller units. Numerical simulations have shown that such merging is
incomplete; the inner cores of halos survive and orbit as "subhalos" within
their hosts. Here we report a simulation that resolves such substructure even
in the very inner regions of the Galactic halo. We find hundreds of very
concentrated dark matter clumps surviving near the solar circle, as well as
numerous cold streams. The simulation reveals the fractal nature of dark matter
clustering: Isolated halos and subhalos contain the same relative amount of
substructure and both have cuspy inner density profiles. The inner mass and
phase-space densities of subhalos match those of recently discovered faint,
dark matter-dominated dwarf satellite galaxies and the overall amount of
substructure can explain the anomalous flux ratios seen in strong gravitational
lenses. Subhalos boost gamma-ray production from dark matter annihilation, by
factors of 4-15, relative to smooth galactic models. Local cosmic ray
production is also enhanced, typically by a factor 1.4, but by more than a
factor of ten in one percent of locations lying sufficiently close to a large
subhalo. These estimates assume that gravitational effects of baryons on dark
matter substructure are small.Comment: 14 pages, 5 figures, to appear in Nature, includes supplementary
information. Full version of Figure 1 available at
http://www.ucolick.org/~diemand/vl2/fig1.pn
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