In-band label extractor based on Cascaded Si ring resonators enabling 160 Gb/s optical packet switching modules

Photonic integration of optical packet switching modules is crucial to compete with existing electronic switching fabrics in large data center networks. The approach of coding the forwarding packet information in an in-band label enables a spectral-efficient and scalable way of building low-latency large port count modular optical packet switching architecture. We demonstrate the error-free operation of the four in-band label extraction from 160 Gb/s optical data packets based on photonic integrated silicon-on- insulator ring resonators. Four low-loss cascaded ring resonators using the quasi-TM mode are used as narrowband filters to ensure the detection of four optical labels as well as the error-free forwarding of the payload at limited power penalty. Due to the low-loss and less-confined optical quasi-TM mode the resonators can be very narrowband and have low insertion loss. The effect of the bandwidth of the four ring resonators on the quality of the payload is investigated. We show that using four rings with 3dB bandwidth of 21 pm and only an insertion loss of 3 dB, the distortion on the payload is limited (< 1.5 dB power penalty), even when the resonances are placed very close to the packet's central wavelength. We also investigate the optical power requirements for error-free detection of the label as function of their spectral position relative to the center of the payload. The successful in-band positioning of the labels makes this component very scalable in amount of labels

An upper limit on the contribution of accreting white dwarfs to the type Ia supernova rate

There is wide agreement that Type Ia supernovae (used as standard candles for cosmology) are associated with the thermonuclear explosions of white dwarf stars. The nuclear runaway that leads to the explosion could start in a white dwarf gradually accumulating matter from a companion star until it reaches the Chandrasekhar limit, or could be triggered by the merger of two white dwarfs in a compact binary system. The X-ray signatures of these two possible paths are very different. Whereas no strong electromagnetic emission is expected in the merger scenario until shortly before the supernova, the white dwarf accreting material from the normal star becomes a source of copious X-rays for ~1e7 yr before the explosion. This offers a means of determining which path dominates. Here we report that the observed X-ray flux from six nearby elliptical galaxies and galaxy bulges is a factor of ~30-50 less than predicted in the accretion scenario, based upon an estimate of the supernova rate from their K-band luminosities. We conclude that no more than ~5 per cent of Type Ia supernovae in early type galaxies can be produced by white dwarfs in accreting binary systems, unless their progenitors are much younger than the bulk of the stellar population in these galaxies, or explosions of sub-Chandrasekhar white dwarfs make a significant contribution to the supernova rate.Comment: 10 pages, 1 tabl

Mapping the structural organization of the brain in conduct disorder: replication of findings in two independent samples.

BACKGROUND: Neuroimaging methods that allow researchers to investigate structural covariance between brain regions are increasingly being used to study psychiatric disorders. Structural covariance analyses are particularly well suited for studying disorders with putative neurodevelopmental origins as they appear sensitive to changes in the synchronized maturation of different brain regions. We assessed interregional correlations in cortical thickness as a measure of structural covariance, and applied this method to investigate the coordinated development of different brain regions in conduct disorder (CD). We also assessed whether structural covariance measures could differentiate between the childhood-onset (CO-CD) and adolescence-onset (AO-CD) subtypes of CD, which may differ in terms of etiology and adult outcomes. METHODS: We examined interregional correlations in cortical thickness in male youths with CO-CD or AO-CD relative to healthy controls (HCs) in two independent datasets. The age range in the Cambridge sample was 16-21 years (mean: 18.0), whereas the age range of the Southampton sample was 13-18 years (mean: 16.7). We used FreeSurfer to perform segmentations and applied structural covariance methods to the resulting parcellations. RESULTS: In both samples, CO-CD participants displayed a strikingly higher number of significant cross-cortical correlations compared to HC or AO-CD participants, whereas AO-CD participants presented fewer significant correlations than HCs. Group differences in the strength of the interregional correlations were observed in both samples, and each set of results remained significant when controlling for IQ and comorbid attention-deficit/hyperactivity disorder symptoms. CONCLUSIONS: This study provides new evidence for quantitative differences in structural brain organization between the CO-CD and AO-CD subtypes, and supports the hypothesis that both subtypes of CD have neurodevelopmental origins.This research was funded by Wellcome Trust grant 083140 (Fairchild, Goodyer), Medical Research Council project U.1055.02.001.00001.01 (Calder), an Adventure in Research grant from Southampton University (Fairchild), a PhD studentship from Southampton University (Sully), and the Betty Behrens Research Fellowship at Clare Hall, Cambridge University (Passamonti).This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1111/jcpp.1258

Cognitive reserve in granulin-related frontotemporal dementia: from preclinical to clinical stages

OBJECTIVE Consistent with the cognitive reserve hypothesis, higher education and occupation attainments may help persons with neurodegenerative dementias to better withstand neuropathology before developing cognitive impairment. We tested here the cognitive reserve hypothesis in patients with frontotemporal dementia (FTD), with or without pathogenetic granulin mutations (GRN+ and GRN-), and in presymptomatic GRN mutation carriers (aGRN+). METHODS Education and occupation attainments were assessed and combined to define Reserve Index (RI) in 32 FTD patients, i.e. 12 GRN+ and 20 GRN-, and in 17 aGRN+. Changes in functional connectivity were estimated by resting state fMRI, focusing on the salience network (SN), executive network (EN) and bilateral frontoparietal networks (FPNs). Cognitive status was measured by FTD-modified Clinical Dementia Rating Scale. RESULTS In FTD patients higher level of premorbid cognitive reserve was associated with reduced connectivity within the SN and the EN. EN was more involved in FTD patients without GRN mutations, while SN was more affected in GRN pathology. In aGRN+, cognitive reserve was associated with reduced SN. CONCLUSIONS This study suggests that cognitive reserve modulates functional connectivity in patients with FTD, even in monogenic disease. In GRN inherited FTD, cognitive reserve mechanisms operate even in presymptomatic to clinical stages

Surgical treatment of aortobronchial fistula after thoracic endograft failure

Endovascular stent grafting has been recently considered as a less invasive alternative to either medical therapy or open surgical treatment for many patients with descending thoracic aortic disease. Late complications are rarely described in literature. Herein, we described the occurrence of an aorto-bronchial fistula and a retro-A dissection in a 73-year-old man after stent-grafting for a penetrating atherosclerotic ulcer (PAU) of the descending thoracic aorta and the successful surgical technique adopted in order to remove the stent-graft

Decay of correlations for maps with uniformly contracting fibers and logarithm law for singular hyperbolic attractors

We consider two dimensional maps preserving a foliation which is uniformly contracting and a one dimensional associated quotient map having exponential convergence to equilibrium (iterates of Lebesgue measure converge exponentially fast to physical measure). We prove that these maps have exponential decay of correlations over a large class of observables. We use this result to deduce exponential decay of correlations for the Poincare maps of a large class of singular hyperbolic flows. From this we deduce logarithm laws for these flows.Comment: 39 pages; 03 figures; proof of Theorem 1 corrected; many typos corrected; improvements on the statements and comments suggested by a referee. Keywords: singular flows, singular-hyperbolic attractor, exponential decay of correlations, exact dimensionality, logarithm la

AGUIA: autonomous graphical user interface assembly for clinical trials semantic data services

<p>Abstract</p> <p>Background</p> <p>AGUIA is a front-end web application originally developed to manage clinical, demographic and biomolecular patient data collected during clinical trials at MD Anderson Cancer Center. The diversity of methods involved in patient screening and sample processing generates a variety of data types that require a resource-oriented architecture to capture the associations between the heterogeneous data elements. AGUIA uses a semantic web formalism, resource description framework (RDF), and a bottom-up design of knowledge bases that employ the S3DB tool as the starting point for the client's interface assembly.</p> <p>Methods</p> <p>The data web service, S3DB, meets the necessary requirements of generating the RDF and of explicitly distinguishing the description of the domain from its instantiation, while allowing for continuous editing of both. Furthermore, it uses an HTTP-REST protocol, has a SPARQL endpoint, and has open source availability in the public domain, which facilitates the development and dissemination of this application. However, S3DB alone does not address the issue of representing content in a form that makes sense for domain experts.</p> <p>Results</p> <p>We identified an autonomous set of descriptors, the GBox, that provides user and domain specifications for the graphical user interface. This was achieved by identifying a formalism that makes use of an RDF schema to enable the automatic assembly of graphical user interfaces in a meaningful manner while using only resources native to the client web browser (JavaScript interpreter, document object model). We defined a generalized RDF model such that changes in the graphic descriptors are automatically and immediately (locally) reflected into the configuration of the client's interface application.</p> <p>Conclusions</p> <p>The design patterns identified for the GBox benefit from and reflect the specific requirements of interacting with data generated by clinical trials, and they contain clues for a general purpose solution to the challenge of having interfaces automatically assembled for multiple and volatile views of a domain. By coding AGUIA in JavaScript, for which all browsers include a native interpreter, a solution was found that assembles interfaces that are meaningful to the particular user, and which are also ubiquitous and lightweight, allowing the computational load to be carried by the client's machine.</p

The Global Groundwater Crisis

Groundwater depletion the world over poses a far greater threat to global water security than is currently acknowledged

The relationship between chronic type III acromioclavicular joint dislocation and cervical spine pain

<p>Abstract</p> <p>Background</p> <p>This study was aimed at evaluating whether or not patients with chronic type III acromioclavicular dislocation develop cervical spine pain and degenerative changes more frequently than normal subjects.</p> <p>Methods</p> <p>The cervical spine of 34 patients with chronic type III AC dislocation was radiographically evaluated. Osteophytosis presence was registered and the narrowing of the intervertebral disc and cervical lordosis were evaluated. Subjective cervical symptoms were investigated using the Northwick Park Neck Pain Questionnaire (NPQ). One-hundred healthy volunteers were recruited as a control group.</p> <p>Results</p> <p>The rate and distribution of osteophytosis and narrowed intervertebral disc were similar in both of the groups. Patients with chronic AC dislocation had a lower value of cervical lordosis. NPQ score was 17.3% in patients with AC separation (100% = the worst result) and 2.2% in the control group (p < 0.05). An inverse significant nonparametric correlation was found between the NPQ value and the lordosis degree in the AC dislocation group (p = 0.001) wheras results were not correlated (p = 0.27) in the control group.</p> <p>Conclusions</p> <p>Our study shows that chronic type III AC dislocation does not interfere with osteophytes formation or intervertebral disc narrowing, but that it may predispose cervical hypolordosis. The higher average NPQ values were observed in patients with chronic AC dislocation, especially in those that developed cervical hypolordosis.</p

A Comprehensive Analysis of Electric Dipole Moment Constraints on CP-violating Phases in the MSSM

We analyze the constraints placed on individual, flavor diagonal CP-violating phases in the minimal supersymmetric extension of the Standard Model (MSSM) by current experimental bounds on the electric dipole moments (EDMs) of the neutron, Thallium, and Mercury atoms. We identify the four CP-violating phases that are individually highly constrained by current EDM bounds, and we explore how these phases and correlations among them are constrained by current EDM limits. We also analyze the prospective implications of the next generation of EDM experiments. We point out that all other CP-violating phases in the MSSM are not nearly as tightly constrained by limits on the size of EDMs. We emphasize that a rich set of phenomenological consequences is potentially associated with these generically large EDM-allowed phases, ranging from B physics, electroweak baryogenesis, and signals of CP-violation at the CERN Large Hadron Collider and at future linear colliders. Our numerical study takes into account the complete set of contributions from one- and two-loop EDMs of the electron and quarks, one- and two-loop Chromo-EDMs of quarks, the Weinberg 3-gluon operator, and dominant 4-fermion CP-odd operator contributions, including contributions which are both included and not included yet in the CPsuperH2.0 package. We also introduce an open-source numerical package, 2LEDM, which provides the complete set of two-loop electroweak diagrams contributing to the electric dipole moments of leptons and quarks.Comment: 23 pages, 11 figures; v2: references added, minor change