281 research outputs found
Giant Kerr nonlinearities in Circuit-QED
The very small size of optical nonlinearities places wide ranging
restrictions on the types of novel physics one can explore. For an ensemble of
multi-level systems one can synthesize a large effective optical nonlinearity
using quantum coherence effects but such non-linearities are technically
extremely challenging to demonstrate at the single atom level. In this work we
describe how a single artificial multi-level Cooper Pair Box molecule,
interacting with a superconducting microwave coplanar waveguide resonator, when
suitably driven, can generate extremely large optical nonlinearities at
microwave frequencies, with no associated absorption. We describe how the giant
self-Kerr effect can be detected by measuring the second-order correlation
function and quadrature squeezing spectrum.Comment: 4 pages, 4 figures, 1 table; version accepted by PRL edito
Quantum walks with tuneable self-avoidance in one dimension
Quantum walks exhibit many unique characteristics compared to classical random walks. In the classical setting, self-avoiding random walks have been studied as a variation on the usual classical random walk. Here the walker has memory of its previous locations and preferentially avoids stepping back to locations where it has previously resided. Classical self-avoiding random walks have found numerous algorithmic applications, most notably in the modelling of protein folding. We consider the analogous problem in the quantum setting - a quantum walk in one dimension with tunable levels of self-avoidance. We complement a quantum walk with a memory register that records where the walker has previously resided. The walker is then able to avoid returning back to previously visited sites or apply more general memory conditioned operations to control the walk. We characterise this walk by examining the variance of the walker's distribution against time, the standard metric for quantifying how quantum or classical a walk is. We parameterise the strength of the memory recording and the strength of the memory back-action on the walker, and investigate their effect on the dynamics of the walk. We find that by manipulating these parameters, which dictate the degree of self-avoidance, the walk can be made to reproduce ideal quantum or classical random walk statistics, or a plethora of more elaborate diffusive phenomena. In some parameter regimes we observe a close correspondence between classical self-avoiding random walks and the quantum self-avoiding walk
Neuropsychological function in college students with and without posttraumatic stress disorder
Novel mechanism of C/EBPbeta (NF-M) transcriptional control: activation through derepression
Phosphorylation of transcription factors is regarded as a major mechanism to control their activity in regulation of gene expression. C/EBP beta is a transcription factor that becomes activated after phosphorylation to induce genes involved in inflammation, acute-phase response, cytokine expression, cell growth, and differentiation. The chicken homolog NF-M collaborates with Myb and various kinase oncogenes in normal myeloid differentiation as well as in the leukemic transformation of myelomonocytic cells. Here, we examined the structure of NF-M and its mechanism of activation. We show that NF-M is a repressed transcription factor with concealed activation potential. Derepressed NF-M exhibits enhanced transcriptional efficacy in reporter assays. More importantly, NF-M activates resident chromatin-embedded, myelomonocyte-specific target genes, even in heterologous cell types such as fibroblasts or erythroblasts. We identified two regions within NF-M that act to repress trans-activation. Repression is abolished by deletion of these regions, activation of signal transduction kinases including v-erbB, polyoma middle T, ras and mil/raf, or point mutation of a critical phosphorylation site for MAP kinases. We provide evidence that phosphorylation plays a unique role to derepress rather than to enhance the trans-activation domain as a novel mechanism to regulate gene expression by NF-M/C/EBP beta
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Artificial intelligence approaches to predicting and detecting cognitive decline in older adults: A conceptual review.
Preserving cognition and mental capacity is critical to aging with autonomy. Early detection of pathological cognitive decline facilitates the greatest impact of restorative or preventative treatments. Artificial Intelligence (AI) in healthcare is the use of computational algorithms that mimic human cognitive functions to analyze complex medical data. AI technologies like machine learning (ML) support the integration of biological, psychological, and social factors when approaching diagnosis, prognosis, and treatment of disease. This paper serves to acquaint clinicians and other stakeholders with the use, benefits, and limitations of AI for predicting, diagnosing, and classifying mild and major neurocognitive impairments, by providing a conceptual overview of this topic with emphasis on the features explored and AI techniques employed. We present studies that fell into six categories of features used for these purposes: (1) sociodemographics; (2) clinical and psychometric assessments; (3) neuroimaging and neurophysiology; (4) electronic health records and claims; (5) novel assessments (e.g., sensors for digital data); and (6) genomics/other omics. For each category we provide examples of AI approaches, including supervised and unsupervised ML, deep learning, and natural language processing. AI technology, still nascent in healthcare, has great potential to transform the way we diagnose and treat patients with neurocognitive disorders
The Utility of the Timed Up-and-Go Test in Predicting Cognitive Performance: A Cross-Sectional Study of Independent Living Adults in a Retirement Community.
Physical, emotional, and cognitive changes are well documented in aging populations. We administered a comprehensive battery of mental and physical health measures and the Montreal Cognitive Assessment (MoCA; a cognitive screening tool) to 93 independently living older adults (OAs) residing in a Continuing Care Senior Housing Community. Performance on the Timed Up-and-Go (TUG) test (a measure of functional mobility) correlated more strongly with the MoCA total score than did measures of aging, psychiatric symptoms, sleep, and both self-report and objective physical health. Furthermore, it was associated with MoCA Attention, Language, Memory, and Visuospatial/Executive subscales. The MoCA-TUG relationship remained significant after controlling for demographic and physical/mental health measures. Given that the TUG explained significantly more variance in broad cognitive performance than a comprehensive battery of additional physical and mental health tests, it may function as a multimodal measure of health in OAs, capturing physical changes and correlating with cognitive measures
Phase-Space Decoherence: a comparison between Consistent Histories and Environment Induced Superselection
We examine the decoherence properties of a quantum open system as modeled by
a quantum optical system in the Markov regime. We look for decoherence in both
the Environment Induced Superselection (EIS) and Consistent Histories (CH)
frameworks. We propose a general measure of the coherence of the reduced
density matrix and find that EIS decoherence occurs in a number of bases for
this model. The degree of ``diagonality'' achieved increases with bath
temperature. We evaluate the Decoherence Functional of Consistent Histories for
coarse grained phase space two-time projected histories. Using the measures
proposed by Dowker and Halliwell we find that the consistency of the histories
improves with increasing bath temperature, time and final grain size and
decreases with initial grain size. The peaking increases with increasing grain
size and decreases with increasing bath temperature. Adopting the above
proposed measure of ``coherence'' to the Decoherence Functional gives similar
results. The results agree in general with expectations while the anomalous
dependence of the consistency on the initial grain size is discussed.Comment: 27 pages, 5 postscript figs in uuencoded compressed tar format
Replaced: definition of special character for the complex number
‘They’re more like ordinary stroppy British women’: Attitudes and expectations of maternity care professionals to UK-born ethnic minority women
Objective To explore the attitudes and expectations of maternity care professionals to UK-born ethnic minority mothers. Methods Qualitative in-depth interviews with 30 professionals from eight NHS maternity units in England that provide services for large proportions of women of black Caribbean, black African, Indian, Pakistani and Irish descent. Results All the professionals reported providing care to both UK-born and migrant mothers from ethnic minorities. Most of them felt that they could differentiate between UK-born and migrant mothers based mainly on language fluency and accent. ‘Westernized dress’ and ‘freedom’ were also cited as indicators. Overall, professionals found it easier to provide services to UK-born mothers and felt that their needs were more like those of white English mothers than those of migrant mothers. UK-born mothers were generally thought to be assertive and expressive, and in control of care-related decision-making whereas some South Asian Muslim women were thought to be constrained by family influences. Preconceived ideas about ethnic minority mothers' tolerance of pain in labour, use of pharmacological pain relief measures and mode of delivery were recurring themes. Women's education and social class were felt to be major influences on the uptake of maternity care, regardless of ethnicity.
Conclusions Professionals appeared to equate the needs of UK-born ethnic minority women with those of white English women. Overall, this has positive implications for care provision. Despite this, specific behavioural expectations and unconscious stereotypical views were evident and have the potential to affect clinical practice
Two-photon quantum walks in an elliptical direct-write waveguide array
Integrated optics provides an ideal test bed for the emulation of quantum
systems via continuous-time quantum walks. Here we study the evolution of
two-photon states in an elliptic array of waveguides. We characterise the
photonic chip via coherent-light tomography and use the results to predict
distinct differences between temporally indistinguishable and distinguishable
two-photon inputs which we then compare with experimental observations. Our
work highlights the feasibility for emulation of coherent quantum phenomena in
three-dimensional waveguide structures.Comment: 8 pages, 7 figure
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