276 research outputs found
Orthogonal measurements are {\it almost} sufficient for quantum discord of two qubits
The common use in literature of orthogonal measurements in obtaining quantum
discord for two-qubit states is discussed and compared with more general
measurements. We prove the optimality of orthogonal measurements for rank 2
states. While for rank 3 and 4 mixed states they are not optimal, we present
strong numerical evidence showing that they give the correct quantum discord up
to minimal corrections. Based on the connection, through purification with an
ancilla, between discord and entanglement of formation (EoF), we give a tight
upper bound for the EoF of a mixed state of rank 2, given by an
optimal decomposition of 2 elements. We also provide an alternative way to
compute the quantum discord for two qubits based on the Bloch vectors of the
state.Comment: EPL 96, 40005 (2011
Negativity and quantum discord in Davies environments
We investigate the time evolution of negativity and quantum discord for a
pair of non-interacting qubits with one being weakly coupled to a decohering
Davies--type Markovian environment. At initial time of preparation, the qubits
are prepared in one of the maximally entangled pure Bell states. In the
limiting case of pure decoherence (i.e. pure dephasing), both, the quantum
discord and negativity decay to zero in the long time limit. In presence of a
manifest dissipative dynamics, the entanglement negativity undergoes a sudden
death at finite time while the quantum discord relaxes continuously to zero
with increasing time. We find that in dephasing environments the decay of the
negativity is more propitious with increasing time; in contrast, the evolving
decay of the quantum discord proceeds weaker for dissipative environments.
Particularly, the slowest decay of the quantum discord emerges when the energy
relaxation time matches the dephasing time.Comment: submitted for publicatio
Parents' postnatal depressive symptoms and their children's academic attainment at 16 years: Pathways of risk transmission
This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record.The aim of the study was to examine whether parentsâ increased postnatal depressive symptoms predicted
childrenâs academic attainment over time, and whether the parent-child relationship, childrenâs prior
academic attainment and mental health mediated this association.
We conducted secondary analyses on the Avon Longitudinal Study of Parents and Children data (12,607
mothers, 9,456 fathers). Each parent completed the Edinburgh-Postnatal Depression Scale at 8 weeks after
the childâs birth (predictor) and a questionnaire about the mother-child and father-child relationship at 7
years and 1 month (mediator). The childrenâs mental health problems were assessed with the teacher version
of the Strengths and Difficulties Questionnaire at 10-11 years (mediator). We used data on the childrenâs
academic attainment on UK Key Stage 1 (5-7 years; mediator) and Key Stage 4 (General Certificate of
Secondary Education (GCSE)16 years) (outcome). We adjusted for the parentsâ education, and child gender
and cognitive ability.
The results revealed that parentsâ depressive symptoms at 8 weeks predicted lower academic performance in
children at 16 years. Mothersâ postnatal depressive symptoms had an indirect effect through childrenâs
mental health problems on academic outcomes at 16 years via negative mother-child relationship, and prior
academic attainment. There was a significant negative indirect effect of fathersâ postnatal depressive
symptoms on academic attainment at 16 years via negative father-child relationship on child mental health.
The findings suggest that the family environment (parental mental health and parent-child relationship) and
childrenâs mental health should be potential targets for support programmes for children of depressed
parents.Medical Research Council (MRC)Wellcome Trus
Creation and manipulation of entanglement in spin chains far from equilibrium
We investigate creation, manipulation, and steering of entanglement in spin
chains from the viewpoint of quantum communication between distant parties. We
demonstrate how global parametric driving of the spin-spin coupling and/or
local time-dependent Zeeman fields produce a large amount of entanglement
between the first and the last spin of the chain. This occurs whenever the
driving frequency meets a resonance condition, identified as "entanglement
resonance". Our approach marks a promising step towards an efficient quantum
state transfer or teleportation in solid state system. Following the reasoning
of Zueco et al. [1], we propose generation and routing of multipartite
entangled states by use of symmetric tree-like structures of spin chains.
Furthermore, we study the effect of decoherence on the resulting spin
entanglement between the corresponding terminal spins.Comment: 10 pages, 8 figure
Cardiovascular Risk in Early Psychosis: Relationship with Inflammation and Clinical Features 6 Months after Diagnosis
Background: We aimed to investigate the state of cardiovascular risk/protection factors in early psychosis patients.
Methods: A total 119 subjects were recruited during the first year after their first episode of psychosis. Eighty-five of these subjects were followed during the next 6 months. Cardiovascular risk/protection factors were measured in plasma and co-variated by sociodemographic/clinical characteristics. Multiple linear regression models detected the change of each biological marker from baseline to follow-up in relation to clinical scales, antipsychotic medication, and pro-/antiinflammatory mediators.
Results: Glycosylated hemoglobin is a state biomarker in first episode of psychosis follow-up patients and inversely correlated to the Global Assessment of Functioning scale. We found opposite alterations in the levels of VCAM-1 and E-selectin in first episode of psychosis baseline conditions compared with control that were absent in the first episode of psychosis follow-up group. Adiponectin levels decreased in a continuum in both pathological time points studied. E-Selectin plasma levels were inversely related to total antipsychotic equivalents and adiponectin levels inversely co-related to the Global Assessment of Functioning scale. Finally, adiponectin levels were directly related to antiinflammatory nuclear receptor PPARy expression in first episode of psychosis baseline conditions and to proinflammatory nuclear factor nuclear factor kB activity in follow-up conditions, respectively.
Conclusions: Our results support the need for integrating cardiovascular healthcare very early after the first episode of psychosis
Sustained Gq-Protein Signaling Disrupts Striatal Circuits via JNK
International audienceThe dorsal striatum is a major input structure of the basal ganglia and plays a key role in the control of vital processes such as motor behavior, cognition, and motivation. The functionality of striatal neurons is tightly controlled by various metabotropic receptors. Whereas the G s /G i-protein-dependent tuning of striatal neurons is fairly well known, the precise impact and underlying mechanism of G q-protein-dependent signals remain poorly understood. Here, using different experimental approaches, especially designer receptor exclusively activated by designer drug (DREADD) chemogenetic technology, we found that sustained activation of G q-protein signaling impairs the functionality of striatal neurons and we unveil the precise molecular mechanism underlying this process: a phospholipase C/Ca 2ĎŠ /proline-rich tyrosine kinase 2/cJun N-terminal kinase pathway. Moreover, engagement of this intracellular signaling route was functionally active in the mouse dorsal striatum in vivo, as proven by the disruption of neuronal integrity and behavioral tasks. To analyze this effect anatomically, we manipulated G q-protein-dependent signaling selectively in neurons belonging to the direct or indirect striatal pathway. Acute G q-protein activation in direct-pathway or indirect-pathway neurons produced an enhancement or a decrease, respectively , of activity-dependent parameters. In contrast, sustained G q-protein activation impaired the functionality of direct-pathway and indirect-pathway neurons and disrupted the behavioral performance and electroencephalography-related activity tasks controlled by either anatomical framework. Collectively, these findings define the molecular mechanism and functional relevance of G q-protein-driven signals in striatal circuits under normal and overactivated states
Geometric measure of quantum discord and the geometry of a class of two-qubit states
We investigate the geometric picture of the level surfaces of quantum
entanglement and geometric measure of quantum discord (GMQD) of a class of
X-states, respectively. This pictorial approach provides us a direct
understanding of the structure of entanglement and GMQD. The dynamic evolution
of GMQD under two typical kinds of quantum decoherence channels is also
investigated. It is shown that there exists a class of initial states for which
the GMQD is not destroyed by decoherence in a finite time interval.
Furthermore, we establish a factorization law between the initial and final
GMQD, which allows us to infer the evolution of entanglement under the
influences of the environment.Comment: 10 pages, 4 figures, comments are welcom
Benchmarking the performance of a low-cost Magnetic Resonance Control System at multiple sites in the open MaRCoS community
Purpose: To describe the current properties and capabilities of an
open-source hardware and software package that is being developed by many sites
internationally with the aim of providing an inexpensive yet flexible platform
for low-cost MRI. Methods: This paper describes three different setups from 50
to 360 mT in different settings, all of which used the MaRCoS console for
acquiring data, and different types of software interfaces (custom-built GUI or
PulSeq overlay) to acquire the data. Results: Images are presented from both
phantoms and in vivo from healthy volunteers to demonstrate the image quality
that can be obtained from the MaRCoS hardware/software interfaced to different
low-field magnets. Conclusions: The results presented here show that a number
of different sequences commonly used in the clinic can be programmed into an
open-source system relatively quickly and easily, and can produce good quality
images even at this early stage of development. Both the hardware and software
will continue to develop, and it is an aim of this paper to encourage other
groups to join this international consortium.Comment: 9 pages, 10 figures, comments welcom
Portable magnetic resonance imaging of patients indoors, outdoors and at home
Mobile medical imaging devices are invaluable for clinical diagnostic
purposes both in and outside healthcare institutions. Among the various imaging
modalities, only a few are readily portable. Magnetic resonance imaging (MRI),
the gold standard for numerous healthcare conditions, does not traditionally
belong to this group. Recently, low-field MRI start-up companies have
demonstrated the first decisive steps towards portability within medical
facilities, but these are so far incompatible with more demanding use cases
such as in remote and developing regions, sports facilities and events, medical
and military camps, or home healthcare. Here we present in vivo images taken
with a light, home-made, low-field extremity MRI scanner outside the controlled
environment provided by medical facilities. To demonstrate the true portability
of the system and benchmark its performance in various relevant scenarios, we
have acquired images of a volunteer's knee in: i) an MRI physics laboratory;
ii) an office room; iii) outside a campus building, connected to a nearby power
outlet; iv) in open air, powered from a small fuel-based generator; and v) at
the volunteer's home. All images have been acquired within clinically viable
times, and signal-to-noise ratios (SNR) and tissue contrast suffice for 2D and
3D reconstructions with diagnostic value, with comparable overall image quality
across all five situations. Furthermore, the volunteer carries a fixation
metallic implant screwed to the femur, which leads to strong artifacts in
standard clinical systems but appears sharp in our low-field acquisitions.
Altogether, this work opens a path towards highly accessible MRI under
circumstances previously unrealistic.Comment: 17 pages, 4 figures, comments welcom
A pilot clinical study of Î9-tetrahydrocannabinol in patients with recurrent glioblastoma multiforme
Î9-Tetrahydrocannabinol (THC) and other cannabinoids inhibit tumour growth and angiogenesis in animal models, so their potential application as antitumoral drugs has been suggested. However, the antitumoral effect of cannabinoids has never been tested in humans. Here we report the first clinical study aimed at assessing cannabinoid antitumoral action, specifically a pilot phase I trial in which nine patients with recurrent glioblastoma multiforme were administered THC intratumoraly. The patients had previously failed standard therapy (surgery and radiotherapy) and had clear evidence of tumour progression. The primary end point of the study was to determine the safety of intracranial THC administration. We also evaluated THC action on the length of survival and various tumour-cell parameters. A dose escalation regimen for THC administration was assessed. Cannabinoid delivery was safe and could be achieved without overt psychoactive effects. Median survival of the cohort from the beginning of cannabinoid administration was 24 weeks (95% confidence interval: 15â33). Î9-Tetrahydrocannabinol inhibited tumour-cell proliferation in vitro and decreased tumour-cell Ki67 immunostaining when administered to two patients. The fair safety profile of THC, together with its possible antiproliferative action on tumour cells reported here and in other studies, may set the basis for future trials aimed at evaluating the potential antitumoral activity of cannabinoids
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