1,560 research outputs found
Single-Atom Gating of Quantum State Superpositions
The ultimate miniaturization of electronic devices will likely require local
and coherent control of single electronic wavefunctions. Wavefunctions exist
within both physical real space and an abstract state space with a simple
geometric interpretation: this state space--or Hilbert space--is spanned by
mutually orthogonal state vectors corresponding to the quantized degrees of
freedom of the real-space system. Measurement of superpositions is akin to
accessing the direction of a vector in Hilbert space, determining an angle of
rotation equivalent to quantum phase. Here we show that an individual atom
inside a designed quantum corral can control this angle, producing arbitrary
coherent superpositions of spatial quantum states. Using scanning tunnelling
microscopy and nanostructures assembled atom-by-atom we demonstrate how single
spins and quantum mirages can be harnessed to image the superposition of two
electronic states. We also present a straightforward method to determine the
atom path enacting phase rotations between any desired state vectors. A single
atom thus becomes a real space handle for an abstract Hilbert space, providing
a simple technique for coherent quantum state manipulation at the spatial limit
of condensed matter.Comment: Published online 6 April 2008 in Nature Physics; 17 page manuscript
(including 4 figures) + 3 page supplement (including 2 figures);
supplementary movies available at http://mota.stanford.ed
The two rival concepts of devotional leisure: Towards an understanding of Twenty-First Century human creativity and the possibility of freedom
The starting point of this article is that the ultimate objective of sociology so far as the study
of leisure is concerned should be with understanding the ways in which twenty-first century
modern men and women attempt to reconcile the demands of individuality and community
(aka freedom and security) by focusing on what they choose to do when they can do anything
at all. The first introductory part sets up the rest of the article by offering a brief critique of
the sociology of leisure which operates with the somewhat startling assertion that in modern
societies leisure is largely consumerist in orientation and that as a result freedom is a fiction.
Counteracting this assertion with a startling one of its own it is subsequently argued that the
twentieth century interregnum saw modernity radically revise its modernity which led to a
transformation in the power of human agency and emergence of the insistent voice ‘I too am
in individual’. Taking as its starting point Peter Sloterdijk’s reading of Nietzsche’s imperative
to ‘Become who you are’ articulated passionately in his book You must change your life
(2013), the second part of the article argues that in the twenty-first century terms like
authentic leisure and consumerist leisure, work and leisure are not antithetical to one another,
and there is a radical need to rethink how people give meaning and order to their lives though
their leisure pursuits. Here the article explores the relationship between Sloterdijk’s concept
of anthropotechnics, the art of living and leisure. The next part of the article fleshes out the
theory of devotional leisure which is one part of a more embracing project set out in the book
Re-imagining leisure studies (Blackshaw 2017). Here the article explores two contrasting
ways of understanding devotional leisure practice, namely ‘devotional leisure’ and
‘performative leisure’ by drawing respectively on the examples of surfing and car cruising.
The article concludes with an attempt to reconcile these two seemingly contradictory forms
of devotional leisure practice with a discussion of urban exploration, speculating that their
uniqueness to one another is never absolute, and the more you perceive their particularity, the
more you understand their double nature, as simultaneously aspects of a third endeavour
Fluid biomarkers in frontotemporal dementia: past, present and future
The frontotemporal dementia (FTD) spectrum of neurodegenerative disorders includes a heterogeneous group of conditions. However, following on from a series of important molecular studies in the early 2000s, major advances have now been made in the understanding of the pathological and genetic underpinnings of the disease. In turn, alongside the development of novel methodologies for measuring proteins and other molecules in biological fluids, the last 10 years have seen a huge increase in biomarker studies within FTD. This recent past has focused on attempting to develop markers that will help differentiate FTD from other dementias (particularly Alzheimer’s disease (AD)), as well as from non-neurodegenerative conditions such as primary psychiatric disorders. While cerebrospinal fluid, and more recently blood, markers of AD have been successfully developed, specific markers identifying primary tauopathies or TDP-43 proteinopathies are still lacking. More focus at the moment has been on non-specific markers of neurodegeneration, and in particular, multiple studies of neurofilament light chain have highlighted its importance as a diagnostic, prognostic and staging marker of FTD. As clinical trials get under way in specific genetic forms of FTD, measures of progranulin and dipeptide repeat proteins in biofluids have become important potential measures of therapeutic response. However, understanding of whether drugs restore cellular function will also be important, and studies of key pathophysiological processes, including neuroinflammation, lysosomal function and synaptic health, are also now becoming more common. There is much still to learn in the fluid biomarker field in FTD, but the creation of large multinational cohorts is facilitating better powered studies and will pave the way for larger omics studies, including proteomics, metabolomics and lipidomics, as well as investigations of multimodal biomarker combinations across fluids, brain imaging and other domains. Here we provide an overview of the past, present and future of fluid biomarkers within the FTD field
Does the road to happiness depend on the retirement decision? Evidence from Italy
This study estimates the causal effect of retirement decision on well-being in Italy. To do so, the authors exploit the exogenous variation provided by the changes in the eligibility criteria for pensions that were enacted in Italy in 1995 (Dini’s law) and in 1997 (Prodi’s law, from the names of the prime ministers at the time of their introduction). A sizeable and positive impact of retirement decision is found on satisfaction with leisure time and on frequency of meeting friends. Furthermore, the results are generalized, allowing for the estimation of different moments from different data sources
The effectiveness of extra corporeal shock wave therapy for plantar heel pain: a systematic review and meta-analysis
BACKGROUND: There is considerable controversy regarding the effectiveness of extracorporeal shock wave therapy in the management of plantar heel pain. Our aim was to conduct a systematic review of randomised controlled trials to investigate the effectiveness of extracorporeal shock wave therapy and to produce a precise estimate of the likely benefits of this therapy. METHODS: We conducted a systematic review of all randomised controlled trials (RCTs) identified from the Cochrane Controlled trials register, MEDLINE, EMBASE and CINAHL from 1966 until September 2004. We included randomised trials which evaluated extracorporeal shock wave therapy used to treat plantar heel pain. Trials comparing extra corporeal shock wave therapy with placebo or different doses of extra corporeal shock wave therapy were considered for inclusion in the review. We independently applied the inclusion and exclusion criteria to each identified randomised controlled trial, extracted data and assessed the methodological quality of each trial. RESULTS: Six RCTs (n = 897) permitted a pooled estimate of effectiveness based on pain scores collected using 10 cm visual analogue scales for morning pain. The estimated weighted mean difference was 0.42 (95% confidence interval 0.02 to 0.83) representing less than 0.5 cm on a visual analogue scale. There was no evidence of heterogeneity and a fixed effects model was used. CONCLUSION: A meta-analysis of data from six randomised-controlled trials that included a total of 897 patients was statistically significant in favour of extracorporeal shock wave therapy for the treatment of plantar heel pain but the effect size was very small. A sensitivity analysis including only high quality trials did not detect a statistically significant effect
Somatic mutations in exocrine pancreatic tumors: association with patient survival.
KRAS mutations are major factors involved in initiation and maintenance of pancreatic tumors. The impact of different mutations on patient survival has not been clearly defined. We screened tumors from 171 pancreatic cancer patients for mutations in KRAS and CDKN2A genes. Mutations in KRAS were detected in 134 tumors, with 131 in codon 12 and only 3 in codon 61. The GGT>GAT (G12D) was the most frequent mutation and was present in 60% (80/134). Deletions and mutations in CDKN2A were detected in 43 tumors. Analysis showed that KRAS mutations were associated with reduced patient survival in both malignant exocrine and ductal adenocarcinomas (PDAC). Patients with PDACs that had KRAS mutations showed a median survival of 17 months compared to 30 months for those without mutations (log-rank P = 0.07) with a multivariate hazard ratio (HR) of 2.19 (95%CI 1.09-4.42). The patients with G12D mutation showed a median survival of 16 months (log-rank-test P = 0.03) and an associated multivariate HR 2.42 (95%CI 1.14-2.67). Although, the association of survival in PDAC patients with CDKN2A aberrations in tumors was not statistically significant, the sub-group of patients with concomitant KRAS mutations and CDKN2A alterations in tumors were associated with a median survival of 13.5 months compared to 22 months without mutation (log-rank-test P = 0.02) and a corresponding HR of 3.07 (95%CI 1.33-7.10). Our results are indicative of an association between mutational status and survival in PDAC patients, which if confirmed in subsequent studies can have potential clinical application
The priB Gene of Klebsiella pneumoniae Encodes a 104-Amino Acid Protein That Is Similar in Structure and Function to Escherichia coli PriB
Primosome protein PriB is a single-stranded DNA-binding protein that serves as an accessory factor for PriA helicase-catalyzed origin-independent reinitiation of DNA replication in bacteria. A recent report describes the identification of a novel PriB protein in Klebsiella pneumoniae that is significantly shorter than most sequenced PriB homologs. The K. pneumoniae PriB protein is proposed to comprise 55 amino acid residues, in contrast to E. coli PriB which comprises 104 amino acid residues and has a length that is typical of most sequenced PriB homologs. Here, we report results of a sequence analysis that suggests that the priB gene of K. pneumoniae encodes a 104-amino acid PriB protein, akin to its E. coli counterpart. Furthermore, we have cloned the K. pneumoniae priB gene and purified the 104-amino acid K. pneumoniae PriB protein. Gel filtration experiments reveal that the K. pneumoniae PriB protein is a dimer, and equilibrium DNA binding experiments demonstrate that K. pneumoniae PriB's single-stranded DNA-binding activity is similar to that of E. coli PriB. These results indicate that the PriB homolog of K. pneumoniae is similar in structure and in function to that of E. coli
How Did the Gene Become a Chemical Compound? The Ontology of the Gene and the Patenting of DNA
Long-Range Rapidity Correlations in Heavy Ion Collisions at Strong Coupling from AdS/CFT
We use AdS/CFT correspondence to study two-particle correlations in heavy ion
collisions at strong coupling. Modeling the colliding heavy ions by shock waves
on the gravity side, we observe that at early times after the collision there
are long-range rapidity correlations present in the two-point functions for the
glueball and the energy-momentum tensor operators. We estimate rapidity
correlations at later times by assuming that the evolution of the system is
governed by ideal Bjorken hydrodynamics, and find that glueball correlations in
this state are suppressed at large rapidity intervals, suggesting that
late-time medium dynamics can not "wash out" the long-range rapidity
correlations that were formed at early times. These results may provide an
insight on the nature of the "ridge" correlations observed in heavy ion
collision experiments at RHIC and LHC, and in proton-proton collisions at LHC.Comment: 32 pages, 2 figures; v2: typos corrected, references adde
The impact on neonatal mortality of shifting childbirth services among levels of hospitals: Taiwan's experience
<p>Abstract</p> <p>Background</p> <p>There is considerable discussion surrounding whether advanced hospitals provide better childbirth care than local community hospitals. This study examines the effect of shifting childbirth services from advanced hospitals (i.e., medical centers and regional hospitals) to local community hospitals (i.e., clinics and district hospitals). The sample population was tracked over a seven-year period, which includes the four months of the 2003 severe acute respiratory syndrome (SARS) epidemic in Taiwan. During the SARS epidemic, pregnant women avoided using maternity services in advanced hospitals. Concerns have been raised about maintaining the quality of maternity care with increased demands on childbirth services in local community hospitals. In this study, we analyzed the impact of shifting maternity services among hospitals of different levels on neonatal mortality and maternal deaths.</p> <p>Methods</p> <p>A population-based study was conducted using data from Taiwan's National Health Insurance annual statistics of monthly county neonatal morality rates. Based on a pre-SARS sample from January 1998 to December 2002, we estimated a linear regression model which included "trend," a continuous variable representing the effect of yearly changes, and two binary variables, "month" and "county," controlling for seasonal and county-specific effects. With the estimated coefficients, we obtained predicted neonatal mortality rates for each county-month. We compared the differences between observed mortality rates of the SARS period and predicted rates to examine whether the shifting in maternity services during the SARS epidemic significantly affected neonatal mortality rates.</p> <p>Results</p> <p>With an analysis of a total of 1,848 observations between 1998 and 2004, an insignificantly negative mean of standardized predicted errors during the SARS period was found. The result of a sub-sample containing areas with advanced hospitals showed a significant negative mean of standardized predicted errors during the SARS period. These findings indicate that despite increased use of local community hospitals, neonatal mortality during the SARS epidemic did not increase, and even decreased in areas with advanced hospitals.</p> <p>Conclusion</p> <p>An increased use of maternity services in local community hospitals occurred during the SARS epidemic in Taiwan. However, we observed no increase in neonatal and maternity mortality associated with these increased demands on local community hospitals.</p
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