Pure-state quantum trajectories for general non-Markovian systems do not exist

Since the first derivation of non-Markovian stochastic Schr\"odinger equations, their interpretation has been contentious. In a recent Letter [Phys. Rev. Lett. 100, 080401 (2008)], Di\'osi claimed to prove that they generate "true single system trajectories [conditioned on] continuous measurement". In this Letter we show that his proof is fundamentally flawed: the solution to his non-Markovian stochastic Schr\"odinger equation at any particular time can be interpreted as a conditioned state, but joining up these solutions as a trajectory creates a fiction.Comment: 4 page

Completely Positive Maps and Classical Correlations

We expand the set of initial states of a system and its environment that are known to guarantee completely positive reduced dynamics for the system when the combined state evolves unitarily. We characterize the correlations in the initial state in terms of its quantum discord [H. Ollivier and W. H. Zurek, Phys. Rev. Lett. 88, 017901 (2001)]. We prove that initial states that have only classical correlations lead to completely positive reduced dynamics. The induced maps can be not completely positive when quantum correlations including, but not limited to, entanglement are present. We outline the implications of our results to quantum process tomography experiments.Comment: 4 pages, 1 figur

Quantum measurements in continuous time, non Markovian evolutions and feedback

In this article we reconsider a version of quantum trajectory theory based on the stochastic Schr\"odinger equation with stochastic coefficients, which was mathematically introduced in the '90s, and we develop it in order to describe the non Markovian evolution of a quantum system continuously measured and controlled thanks to a measurement based feedback. Indeed, realistic descriptions of a feedback loop have to include delay and thus need a non Markovian theory. The theory allows to put together non Markovian evolutions and measurements in continuous time in agreement with the modern axiomatic formulation of quantum mechanics. To illustrate the possibilities of such a theory, we apply it to a two-level atom stimulated by a laser. We introduce closed loop control too, via the stimulating laser, with the aim to enhance the "squeezing" of the emitted light, or other typical quantum properties. Note that here we change the point of view with respect to the usual applications of control theory. In our model the "system" is the two-level atom, but we do not want to control its state, to bring the atom to a final target state. Our aim is to control the "Mandel $Q$-parameter" and the spectrum of the emitted light; in particular the spectrum is not a property at a single time, but involves a long interval of times (a Fourier transform of the autocorrelation function of the observed output is needed).Comment: Latex, 19 pages, 3 figures; added references and "Conclusions"; expanded explanations. To appear in Phil. Trans. R. Soc.

Operational approach to open dynamics and quantifying initial correlations

A central aim of physics is to describe the dynamics of physical systems. Schrodinger's equation does this for isolated quantum systems. Describing the time evolution of a quantum system that interacts with its environment, in its most general form, has proved to be difficult because the dynamics is dependent on the state of the environment and the correlations with it. For discrete processes, such as quantum gates or chemical reactions, quantum process tomography provides the complete description of the dynamics, provided that the initial states of the system and the environment are independent of each other. However, many physical systems are correlated with the environment at the beginning of the experiment. Here, we give a prescription of quantum process tomography that yields the complete description of the dynamics of the system even when the initial correlations are present. Surprisingly, our method also gives quantitative expressions for the initial correlation.Comment: Completely re-written for clarity of presentation. 15 pages and 2 figure

No evidence that herpes zoster is associated with increased risk of dementia diagnosis.

OBJECTIVE: To investigate whether herpes zoster (HZ) was associated with subsequent increased risk of dementia diagnosis. METHODS: We conducted a historical cohort study using primary care electronic health records from the Clinical Practice Research Datalink in the United Kingdom. Individuals with incident HZ aged ≥40 years from 2000 to 2017 were matched with up to four individuals without HZ by age, sex, primary care practise and calendar time. The primary outcome was a new diagnosis of all-cause dementia. We used the Cox proportional hazards regression adjusting for demographic, lifestyle and clinical confounders to assess any association between HZ and dementia. We investigated interactions with sex, frailty index and antiviral treatment and conducted various sensitivity analyses. RESULTS: The cohort comprised 177,144 individuals with HZ and 706,901 matched unexposed individuals (median age 65 years (IQR 55.1-75.0), 40% male) followed for a median duration of 4.6 years (IQR 2.0-8.1). In total, 26,585 (3%) patients had an incident dementia diagnosis recorded and 113,056 patients died (12.8%). HZ was associated with a small reduction in dementia diagnosis (adjusted HR 0.92 (95% CI 0.89-0.95)), occurring predominantly in frail individuals and females. For patients who were fit (578,115, 65%), no association was seen (adjusted HR 0.97, 95% CI 0.92-1.02). There was no association between HZ and a composite outcome of dementia or death (adjusted HR 1.00, 95% CI 0.99-1.02). Dementia risk did not vary by prescription of antiviral agents. Sensitivity analyses showed consistent results. INTERPRETATION: HZ was not associated with increased dementia diagnosis in a UK primary care-based cohort

A positioning pillow to improve lumbar puncture success rate in paediatric haematology-oncology patients: a randomized controlled trial

<p>Abstract</p> <p>Background</p> <p>Lumbar punctures (LPs) are common in children with cancer. Although pain management during the lumbar puncture has been well standardized, dealing with stress and anxiety is not well addressed yet. Our objective was to evaluate the potential improvement of the LP success rate using a positioning pillow, to ensure maximum lumbar flexion, and allow paravertebral muscles to relax, in children who are awake, with either conscious sedation or no sedation.</p> <p>Methods</p> <p>Children aged 2–18 years undergoing LP were randomly assigned to a positioning pillow or no intervention. The primary outcome was the rate of success, i.e. achieving the LP (sampling or injection) at the first attempt, without bleeding (RBC < 50/mm³). The secondary outcomes included: the child's pain, assessed by a self-administered visual analogical scales (VAS) for children over 6 years of age; the parents' and caregivers' perception of the child's pain; the satisfaction of the children, the parents, the caregivers and the physician. The child's cooperation and the occurrence of post-LP syndrome were also evaluated.</p> <p>Results</p> <p>124 children (62 in each group) were included. The LP pillow tended to increase the success rate of LPs (67% vs. 57%, p = 0.23), and decreased the post-LP syndromes (15% vs. 24%, p = 0.17) but the differences were not statistically significant. In children over 6-year of age (n = 72), the rate of success was significantly higher in the pillow group (58.5% vs. 41.5%, p = 0.031), with a tendency to feel less pain (median VAS 25 vs. 15 mm, p = 0.39) and being more satisfied (84.4% vs. 75.0%, p = 0.34).</p> <p>Conclusion</p> <p>Overall results do not demonstrate a benefit in using this pillow for lumbar punctures. This study results also suggest a benefit in the sub group of children over 6-year of age; this result needs confirmation.</p> <p>Trial Registration</p> <p>The trial was registered with Clinical Trials.gov (number NCT00775112).</p

Social media and protest mobilization: evidence from the Tunisian revolution

This article explores how social media acted as a catalyst for protest mobilization during the Tunisian revolution in late 2010 and early 2011. Using evidence from protests we argue that social media acted as an important resource for popular mobilization against the Ben Ali regime. Drawing on insights from “resource mobilization theory”, we show that social media (1) allowed a “digital elite” to break the national media blackout through brokering information for mainstream media; (2) provided a basis for intergroup collaboration for a large “cycle of protest”; (3) reported event magnitudes that raised the perception of success for potential free riders, and (4) provided additional “emotional mobilization” through depicting the worst atrocities associated with the regime’s response to the protests. These findings are based on background talks with Tunisian bloggers and digital activists and a revealed preference survey conducted among a sample of Tunisian internet users (February–May 2012)

A multidisciplinary systematic literature review on frailty: Overview of the methodology used by the Canadian Initiative on Frailty and Aging

<p>Abstract</p> <p>Background</p> <p>Over the past two decades, there has been a substantial growth in the body of literature on frailty in older persons. However, there is no consensus on its definition or the criteria used to identify frailty. In response to this lack of consensus, the Canadian Initiative on Frailty and Aging carried out a set of systematic reviews of the literature in ten areas of frailty research: biological basis; social basis; prevalence; risk factors; impact; identification; prevention and management; environment and technology; health services; health and social policy. This paper describes the methodology that was developed for the systematic reviews.</p> <p>Methods</p> <p>A Central Coordination Group (CCG) was responsible for developing the methodology. This involved the development of search strategies and keywords, article selection processes, quality assessment tools, and guidelines for the synthesis of results. Each review was conducted by two experts in the content area, with the assistance of methodologists and statisticians from the CCG.</p> <p>Results</p> <p>Conducting a series of systematic literature reviews involving a range of disciplines on a concept that does not have a universally accepted definition posed several conceptual and methodological challenges. The most important conceptual challenge was determining what would qualify as literature on frailty. The methodological challenges arose from our goal of structuring a consistent methodology for reviewing literature from diverse fields of research. At the outset, certain methodological guidelines were deemed essential to ensure the validity of all the reviews. Nevertheless, it was equally important to permit flexibility in the application of the proposed methodology to capture the essence of frailty research within the given fields.</p> <p>Conclusion</p> <p>The results of these reviews allowed us to establish the status of current knowledge on frailty and promote collaboration between disciplines. Conducting systematic literature reviews in health science that involve multiple disciplines is a mechanism to facilitate interdisciplinary collaboration and a more integrated understanding of health. This initiative highlighted the need for further methodological development in the performance of multidisciplinary systematic reviews.</p

Crystal Structure of the PIM2 Kinase in Complex with an Organoruthenium Inhibitor

BACKGROUND: The serine/threonine kinase PIM2 is highly expressed in human leukemia and lymphomas and has been shown to positively regulate survival and proliferation of tumor cells. Its diverse ATP site makes PIM2 a promising target for the development of anticancer agents. To date our knowledge of catalytic domain structures of the PIM kinase family is limited to PIM1 which has been extensively studied and which shares about 50% sequence identity with PIM2. PRINCIPAL FINDINGS: Here we determined the crystal structure of PIM2 in complex with an organoruthenium complex (inhibition in sub-nanomolar level). Due to its extraordinary shape complementarity this stable organometallic compound is a highly potent inhibitor of PIM kinases. SIGNIFICANCE: The structure of PIM2 revealed several differences to PIM1 which may be explored further to generate isoform selective inhibitors. It has also demonstrated how an organometallic inhibitor can be adapted to the binding site of protein kinases to generate highly potent inhibitors. ENHANCED VERSION: This article can also be viewed as an enhanced version in which the text of the article is integrated with interactive 3D representations and animated transitions. Please note that a web plugin is required to access this enhanced functionality. Instructions for the installation and use of the web plugin are available in Text S1

Behavioral responses to short periods of lowered gravitational force in blind goldfish

(1) The movements of blind goldfish flown in an aircraft through vertical flight patterns show a consistent correlation with the varying g loads as recorded by a g meter.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43344/1/11084_2004_Article_BF00924246.pd