281 research outputs found
Entanglement entropy in gauge theories and the holographic principle for electric strings
We consider quantum entanglement between gauge fields in some region of space
A and its complement B. It is argued that the Hilbert space of physical states
of gauge theories cannot be decomposed into a direct product of Hilbert spaces
of states localized in A and B. The reason is that elementary excitations in
gauge theories - electric strings - are associated with closed loops rather
than points in space, and there are closed loops which belong both to A and B.
Direct product structure and hence the reduction procedure with respect to the
fields in B can only be defined if the Hilbert space of physical states is
extended by including the states of electric strings which can open on the
boundary of A. The positions of string endpoints on this boundary are the
additional degrees of freedom which also contribute to the entanglement
entropy. We explicitly demonstrate this for the three-dimensional Z2 lattice
gauge theory both numerically and using a simple trial ground state wave
function. The entanglement entropy appears to be saturated almost completely by
the entropy of string endpoints, thus reminding of a ``holographic principle''
in quantum gravity and AdS/CFT correspondence.Comment: 6 pages RevTeX, 5 figure
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Evaluating recruitment methods of patients with advanced cancer: a pragmatic opportunistic comparison
YesBackground: Recruitment of patients with advanced cancer into studies is challenging.
Objective: To evaluate recruitment methods in a study of pharmacist-led cancer pain medicines consultations and produce recommendations for future studies.
Method: Two methods of recruitment were employed: 1) community-based (general practitioner computer search, identification by general practitioner, community pharmacist or district nurse and hospital outpatient list search), and 2) hospice-based (in and outpatient list search). Patients identified in method 1 were invited by post and in method 2 were invited face-to-face. Information was designed in collaboration with patients and carers.
Results: 128 patients were identified (85 from the community and 43 from the hospice), 47 met the inclusion criteria. Twenty-three agreed to take part and 19 completed the study, 17 of whom were already under specialist palliative care. Recruitment rates were 7% for community-based methods and 40% for hospice. The recruitment methods differed in intensity of resource use. Recruitment via letter and a lack of engagement by healthcare professionals were found to be barriers. Facilitators included the researcher having personal involvement in recruitment.
Conclusion: The overall recruitment rate was in line with other studies for this patient cohort. Attempts to identify and engage patients through community-based postal contact were less effective than where personal contact with patients was both possible and occurred. Methods were less successful at recruiting patients who were not already engaged with hospice services.Programme Grants for Applied Research. Grant Number: RP-PG-0610-1011
Uniqueness and Nondegeneracy of Ground States for in
We prove uniqueness of ground state solutions for the
nonlinear equation in , where
and for and for . Here denotes the fractional Laplacian
in one dimension. In particular, we generalize (by completely different
techniques) the specific uniqueness result obtained by Amick and Toland for
and in [Acta Math., \textbf{167} (1991), 107--126]. As a
technical key result in this paper, we show that the associated linearized
operator is nondegenerate;
i.\,e., its kernel satisfies .
This result about proves a spectral assumption, which plays a central
role for the stability of solitary waves and blowup analysis for nonlinear
dispersive PDEs with fractional Laplacians, such as the generalized
Benjamin-Ono (BO) and Benjamin-Bona-Mahony (BBM) water wave equations.Comment: 45 page
What is the extent of potentially avoidable admissions amongst hospital inpatients with palliative care needs?
Background: There is clear evidence that the full range of services required to support people dying at home are far from being implemented, either in England or elsewhere. No studies to date have attempted to identify the proportion of hospital admissions that could have been avoided amongst patients with palliative care needs, given existing and current local services. This study aimed to examine the extent of potentially avoidable admissions amongst hospital patients with palliative care needs.
Methods: A cross sectional survey of palliative care needs was undertaken in two acute hospitals in England. Appropriateness of admission was assessed by two Palliative Medicine Consultants using the following data collected from case notes: reasons for admission; diagnosis and co-morbidities; age and living arrangements; time and route of admission; medical and nursing plan on admission; specialist palliative care involvement; and evidence of cognitive impairment.
Results: A total of 1359 inpatients were present in the two hospitals at the time of the census. Of the 654
consenting patients/consultees, complete case note data were collected for 580 patients; the analysis in this paper relates to these 580 patients. Amongst 208 patients meeting diagnostic and prognostic criteria for palliative care need in two acute settings in England, only 6.7% were identified as ‘potentially avoidable’ hospitalisations. These patients had a median age of 84. Half of the patients lived in residential or nursing homes and it was concluded that most could have received care in this setting in place of hospital.
Conclusion: Our findings challenge assumptions that, within the existing configuration of palliative and end of life health and social care services, patients with palliative care needs experience a high level of potentially avoidable hospitalisations.
Keywords: Palliative care needs, End of life, Avoidable admissions, Inappropriate admissions, Survey, Acute hospita
Update on biomarkers in neuromyelitis optica
Neuromyelitis optica (NMO) (and NMO spectrum disorder) is an autoimmune inflammatory disease of the CNS primarily affecting spinal cord and optic nerves. Reliable and sensitive biomarkers for onset, relapse, and progression in NMO are urgently needed because of the heterogeneous clinical presentation, severity of neurologic disability following relapses, and variability of therapeutic response. Detecting aquaporin-4 (AQP4) antibodies (AQP4-IgG or NMO-IgG) in serum supports the diagnosis of seropositive NMO. However, whether AQP4-IgG levels correlate with disease activity, severity, response to therapy, or long-term outcomes is unclear. Moreover, biomarkers for patients with seronegative NMO have yet to be defined and validated. Collaborative international studies hold great promise for establishing and validating biomarkers that are useful in therapeutic trials and clinical management. In this review, we discuss known and potential biomarkers for NMO
Quantitative Treatment of Decoherence
We outline different approaches to define and quantify decoherence. We argue
that a measure based on a properly defined norm of deviation of the density
matrix is appropriate for quantifying decoherence in quantum registers. For a
semiconductor double quantum dot qubit, evaluation of this measure is reviewed.
For a general class of decoherence processes, including those occurring in
semiconductor qubits, we argue that this measure is additive: It scales
linearly with the number of qubits.Comment: Revised version, 26 pages, in LaTeX, 3 EPS figure
Dust Devil Tracks
Dust devils that leave dark- or light-toned tracks are common on Mars and they can also be found on the Earth’s surface. Dust devil tracks (hereinafter DDTs) are ephemeral surface features with mostly sub-annual lifetimes. Regarding their size, DDT widths can range between ∼1 m and ∼1 km, depending on the diameter of dust devil that created the track, and DDT lengths range from a few tens of meters to several kilometers, limited by the duration and horizontal ground speed of dust devils. DDTs can be classified into three main types based on their morphology and albedo in contrast to their surroundings; all are found on both planets: (a) dark continuous DDTs, (b) dark cycloidal DDTs, and (c) bright DDTs. Dark continuous DDTs are the most common type on Mars. They are characterized by their relatively homogenous and continuous low albedo surface tracks. Based on terrestrial and martian in situ studies, these DDTs most likely form when surficial dust layers are removed to expose larger-grained substrate material (coarse sands of ≥500 μm in diameter). The exposure of larger-grained materials changes the photometric properties of the surface; hence leading to lower albedo tracks because grain size is photometrically inversely proportional to the surface reflectance. However, although not observed so far, compositional differences (i.e., color differences) might also lead to albedo contrasts when dust is removed to expose substrate materials with mineralogical differences. For dark continuous DDTs, albedo drop measurements are around 2.5 % in the wavelength range of 550–850 nm on Mars and around 0.5 % in the wavelength range from 300–1100 nm on Earth. The removal of an equivalent layer thickness around 1 μm is sufficient for the formation of visible dark continuous DDTs on Mars and Earth. The next type of DDTs, dark cycloidal DDTs, are characterized by their low albedo pattern of overlapping scallops. Terrestrial in situ studies imply that they are formed when sand-sized material that is eroded from the outer vortex area of a dust devil is redeposited in annular patterns in the central vortex region. This type of DDT can also be found in on Mars in orbital image data, and although in situ studies are lacking, terrestrial analog studies, laboratory work, and numerical modeling suggest they have the same formation mechanism as those on Earth. Finally, bright DDTs are characterized by their continuous track pattern and high albedo compared to their undisturbed surroundings. They are found on both planets, but to date they have only been analyzed in situ on Earth. Here, the destruction of aggregates of dust, silt and sand by dust devils leads to smooth surfaces in contrast to the undisturbed rough surfaces surrounding the track. The resulting change in photometric properties occurs because the smoother surfaces have a higher reflectance compared to the surrounding rough surface, leading to bright DDTs. On Mars, the destruction of surficial dust-aggregates may also lead to bright DDTs. However, higher reflective surfaces may be produced by other formation mechanisms, such as dust compaction by passing dust devils, as this may also cause changes in photometric properties. On Mars, DDTs in general are found at all elevations and on a global scale, except on the permanent polar caps. DDT maximum areal densities occur during spring and summer in both hemispheres produced by an increase in dust devil activity caused by maximum insolation. Regionally, dust devil densities vary spatially likely controlled by changes in dust cover thicknesses and substrate materials. This variability makes it difficult to infer dust devil activity from DDT frequencies. Furthermore, only a fraction of dust devils leave tracks. However, DDTs can be used as proxies for dust devil lifetimes and wind directions and speeds, and they can also be used to predict lander or rover solar panel clearing events. Overall, the high DDT frequency in many areas on Mars leads to drastic albedo changes that affect large-scale weather patterns
Colliders and Cosmology
Dark matter in variations of constrained minimal supersymmetric standard
models will be discussed. Particular attention will be given to the comparison
between accelerator and direct detection constraints.Comment: Submitted for the SUSY07 proceedings, 15 pages, LaTex, 26 eps figure
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