Field-Assisted DC-Pulsed Cathodes for next generation light sources and accelerators

International audienceThe scope of that contribution is to present the challenges of the next particle sources for accelerators. It is admitted that emittance near Interaction Point (IP) is strongly dominated by the emittance of the low power source. To minimize theBremstrahlung effects in the Interaction Point (IP), we also need extremely low emittance bunches, ultra high brillance, very low charges sub fC, near depopulated attosecond electronic bunches. These produced bunches should fit the entrances of Dielectric Laser Accelerators (DLA) and Laser Plasma Accelerators (LPA).A 20kV DC pulsed sub nanosecond Field Emission Array source with extremely low emittance is considered in order to obtain such results. Firstly, we will describe the DC-pulsed experimental source by blocks. Following that, we will raise more general problems induced by DC-pulsed configuration: thermal transient behaviour of nanostructures, enhancement of plasmons coupling in relation to nanostructured networks, then fast prototyping of cathode geometry will be undertaken using different models. These cathodes are to be fabricated at Orsay.We present the method of curvilinear coordinate calculus, adapted to major classes of nanostructured tips. We define 3 major classes of 3D analytical profiles to emulate experimental conditions (multi-segment, quadratic and exponential one) and apply curvilinear analytical Maxwellsolving to find electrostatic potential around the profile. Our method is concurrent to T-splines for instance, but it is expected to converge faster. Cathode physics will be modelled integrating different phenomenons: photo/thermal/field/emission... Results will be compared to electromagnetic simulations with CST and Astra tools. To conclude, we shall then evaluate the emittance performances planned for a 20keV cathodic source, and its acceptance to the next stages, with the help of some electrostatic focusing. Numerous experimental and theoretical aspects are to be solved

Rapid Mapping of Zebrafish Mutations With SNPs and Oligonucleotide Microarrays

Large-scale genetic screens in zebrafish have identified thousands of mutations in hundreds of essential genes. The genetic mapping of these mutations is necessary to link DNA sequences to the gene functions defined by mutant phenotypes.Here, we report two advances that will accelerate the mapping of zebrafish mutations: (1) The construction of a first generation single nucleotide polymorphism (SNP) map of the zebrafish genome comprising 2035 SNPs and 178 small insertions/deletions, and (2) the development of a method for mapping mutations in which hundreds of SNPs can be scored in parallel with an oligonucleotide microarray.We have demonstrated the utility of the microarray technique in crosses with haploid and diploid embryos by mapping two known mutations to their previously identified locations.We have also used this approach to localize four previously unmapped mutations.We expect that mapping with SNPs and oligonucleotide microarrays will accelerate the molecular analysis of zebrafish mutations

Psychopathological Features in Alzheimer's Disease: Course and Relationship with Cognitive Status

OBJECTIVES: To examine the course, clinical correlates, and relationship between cognitive status and psychopathological features in patients with probable Alzheimer's disease (AD) followed over a 5-year period. DESIGN: Cohort study with follow-up of 5 years. SETTING: Patients were recruited at three sites: 91 patients at Columbia Medical Center, 84 at Johns Hopkins School of Medicine, and 61 at Massachusetts General Hospital. PARTICIPANTS: Patients diagnosed with probable AD (n = 236) enrolled in a longitudinal study (Predictors study). MEASUREMENTS: Wandering/agitation, physical aggression, hallucinations, and delusions were evaluated at 6-month intervals using the Columbia Scale for Psychopathology in Alzheimer's Disease. Descriptive analyses were used to provide estimates of prevalence and course of psychopathological features. General estimating equations determined the odds of having any of the four psychopathological behaviors as a function of cognitive status. Markov analyses provided 6-month transition probabilities for psychopathological behaviors given patients' cognitive status and the presence or absence of such behaviors in the previous evaluation. RESULTS: For wandering/agitation, prevalence (39-57%) and persistence increased as a function of time and decrement in cognitive status. Physical aggression was less prevalent (6-22%) and increased as a function of cognitive decline but tended to persist only in the more severely impaired patients. Delusions (34-49%) reached a peak at the second year and then declined. The odds of delusions were maximal with intermediate decline but remained persistent regardless of cognitive status. Hallucinations, despite some fluctuations, were relatively stable during the follow-up period (8-17%) and moderately persistent. CONCLUSION: Psychopathological features, particularly wandering/agitation and delusions, in AD were common throughout the disease course. The natural history and persistence of the four psychopathological features varied. These findings provide important information to clinicians and caregivers regarding the course, predictability, and possible treatment of psychopathological behaviors in patients with probable AD

Axion searches with the EDELWEISS-II experiment

We present new constraints on the couplings of axions and more generic axion-like particles using data from the EDELWEISS-II experiment. The EDELWEISS experiment, located at the Underground Laboratory of Modane, primarily aims at the direct detection of WIMPs using germanium bolometers. It is also sensitive to the low-energy electron recoils that would be induced by solar or dark matter axions. Using a total exposure of up to 448 kg.d, we searched for axion-induced electron recoils down to 2.5 keV within four scenarios involving different hypotheses on the origin and couplings of axions. We set a 95% CL limit on the coupling to photons $g_{A\gamma}<2.13\times 10^{-9}$ GeV$^{-1}$ in a mass range not fully covered by axion helioscopes. We also constrain the coupling to electrons, $g_{Ae} < 2.56\times 10^{-11}$, similar to the more indirect solar neutrino bound. Finally we place a limit on $g_{Ae}\times g_{AN}^{\rm eff}<4.70 \times 10^{-17}$, where $g_{AN}^{\rm eff}$ is the effective axion-nucleon coupling for $^{57}$Fe. Combining these results we fully exclude the mass range $0.91\,{\rm eV}<m_A<80$ keV for DFSZ axions and $5.73\,{\rm eV}<m_A<40$ keV for KSVZ axions

Background studies for the EDELWEISS dark matter experiment

The EDELWEISS-II collaboration has completed a direct search for WIMP dark matter using cryogenic Ge detectors (400 g each) and 384 kg$\times$days of effective exposure. A cross-section of $4.4 \times 10^{-8}$ pb is excluded at 90% C.L. for a WIMP mass of 85 GeV. The next phase, EDELWEISS-III, aims to probe spin-independent WIMP-nucleon cross-sections down to a few $\times10^{-9}$ pb. We present here the study of gamma and neutron background coming from radioactive decays in the set-up and shielding materials. We have carried out Monte Carlo simulations for the completed EDELWEISS-II setup with GEANT4 and normalised the expected background rates to the measured radioactivity levels (or their upper limits) of all materials and components. The expected gamma-ray event rate in EDELWEISS-II at 20-200 keV agrees with the observed rate of 82 events/kg/day within the uncertainties in the measured concentrations. The calculated neutron rate from radioactivity of 1.0-3.1 events (90% C.L.) at 20-200 keV in the EDELWEISS-II data together with the expected upper limit on the misidentified gamma-ray events ($\le0.9$), surface betas ($\le0.3$), and muon-induced neutrons ($\le0.7$), do not contradict 5 observed events in nuclear recoil band. We have then extended the simulation framework to the EDELWEISS-III configuration with 800 g crystals, better material purity and additional neutron shielding inside the cryostat. The gamma-ray and neutron backgrounds in 24 kg fiducial mass of EDELWEISS-III have been calculated as 14-44 events/kg/day and 0.7-1.4 events per year, respectively. The results of the background studies performed in the present work have helped to select better purity components and improve shielding in EDELWEISS-III to further reduce the expected rate of background events in the next phase of the experiment.Comment: 15 pages, 9 figures, to be published in Astroparticle Physic

Motoric Cognitive Risk Syndrome: Multicountry Prevalence and Dementia Risk

OBJECTIVES: Our objective is to report prevalence of motoric cognitive risk syndrome (MCR), a newly described predementia syndrome characterized by slow gait and cognitive complaints, in multiple countries, and its association with dementia risk. METHODS: Pooled MCR prevalence analysis of individual data from 26,802 adults without dementia and disability aged 60 years and older from 22 cohorts from 17 countries. We also examined risk of incident cognitive impairment (Mini-Mental State Examination decline ≥4 points) and dementia associated with MCR in 4,812 individuals without dementia with baseline Mini-Mental State Examination scores ≥25 from 4 prospective cohort studies using Cox models adjusted for potential confounders. RESULTS: At baseline, 2,808 of the 26,802 participants met MCR criteria. Pooled MCR prevalence was 9.7% (95% confidence interval [CI] 8.2%-11.2%). MCR prevalence was higher with older age but there were no sex differences. MCR predicted risk of developing incident cognitive impairment in the pooled sample (adjusted hazard ratio [aHR] 2.0, 95% CI 1.7-2.4); aHRs were 1.5 to 2.7 in the individual cohorts. MCR also predicted dementia in the pooled sample (aHR 1.9, 95% CI 1.5-2.3). The results persisted even after excluding participants with possible cognitive impairment, accounting for early dementia, and diagnostic overlap with other predementia syndromes. CONCLUSION: MCR is common in older adults, and is a strong and early risk factor for cognitive decline. This clinical approach can be easily applied to identify high-risk seniors in a wide variety of settings

Quantitative description of temperature induced self-aggregation thermograms determined by differential scanning calorimetry

A novel thermodynamic approach for the description of differential scanning calorimetry (DSC) experiments on self-aggregating systems is derived and presented. The method is based on a mass action model where temperature dependence of aggregation numbers is considered. The validity of the model was confirmed by describing the aggregation behavior of poly(ethylene oxide)-poly(propylene oxide) block copolymers, which are well-known to exhibit a strong temperature dependence. The quantitative description of the thermograms could be performed without any discrepancy between calorimetric and van 't Hoff enthalpies, and moreover, the aggregation numbers obtained from the best fit of the DSC experiments are in good agreement with those obtained by light scattering experiments corroborating the assumptions done in the derivation of the new model

Dual-task costs while walking increase in old age for some, but not for other tasks: an experimental study of healthy young and elderly persons

<p>Abstract</p> <p>Background</p> <p>It has been suggested in the past that the ability to walk while concurrently engaging in a second task deteriorates in old age, and that this deficit is related to the high incidence of falls in the elderly. However, previous studies provided inconsistent findings about the existence of such an age-related dual-task deficit (ARD). In an effort to explain this inconsistency, we explored whether ARD while walking emerges for some, but not for other types of task.</p> <p>Methods</p> <p>Healthy young and elderly subjects were tested under five different combinations of a walking and a non-walking task. The results were analysed jointly with those of a previous study from our lab, such that a total of 13 task combinations were evaluated. For each task combination and subject, we calculated the mean dual-task costs across both constituent tasks, and quantified ARD as the difference between those costs in elderly and in young subjects.</p> <p>Results</p> <p>An analysis of covariance yielded no significant effects of obstacle presence and overall task difficulty on ARD, but a highly significant effect of visual demand: non-walking tasks which required ongoing visual observation led to ARD of more than 8%, while those without such requirements led to near-zero ARD. We therefore concluded that the visual demand of the non-walking task is critical for the emergence of ARD while walking.</p> <p>Conclusion</p> <p>Combinations of walking and concurrent visual observation, which are common in everyday life, may contribute towards disturbed gait and falls during daily activities in old age. Prevention and rehabilitation programs for seniors should therefore include training of such combinations.</p