Nonequilibrium brittle fracture propagation: Steady state, oscillations and intermittency

A minimal model is constructed for two-dimensional fracture propagation. The heterogeneous process zone is presumed to suppress stress relaxation rate, leading to non-quasistatic behavior. Using the Yoffe solution, I construct and solve a dynamical equation for the tip stress. I discuss a generic tip velocity response to local stress and find that noise-free propagation is either at steady state or oscillatory, depending only on one material parameter. Noise gives rise to intermittency and quasi-periodicity. The theory explains the velocity oscillations and the complicated behavior seen in polymeric and amorphous brittle materials. I suggest experimental verifications and new connections between velocity measurements and material properties.Comment: To appear in Phys. Rev. Lett., 6 pages, self-contained TeX file, 3 postscript figures upon request from author at [email protected] or [email protected], http://cnls-www.lanl.gov/homepages/rafi/rafindex.htm

Status of the HIE-ISOLDE project at CERN

The HIE-ISOLDE project represents a major upgrade of the ISOLDE nuclear facility with a mandate to significantly improve the quality and increase the intensity and energy of radioactive nuclear beams produced at CERN. The project will expand the experimental nuclear physics programme at ISOLDE by focusing on an upgrade of the existing Radioactive ion beam EXperiment (REX) linac with a 40 MV superconducting linac comprising thirty-two niobium-on-copper sputter-coated quarter-wave resonators housed in six cryomodules. The new linac will raise the energy of post-accelerated beams from 3 MeV/u to over 10 MeV/u. The upgrade will be staged to first deliver beam energies of 5.5 MeV/u using two high-$\beta$ cryomodules placed downstream of REX, before the energy variable section of the existing linac is replaced with two low-$\beta$ cryomodules and two additional high-$\beta$ cryomodules are installed to attain over 10 MeV/u with full energy variability above 0.45 MeV/u. An overview of the project including a status summary of the different R&D activities and the schedule will outlined.Comment: 7 pages, 12 figures, submitted to the Heavy Ion Accelerator Technology conference (HIAT) 2012, in Chicag

Rates of Response to Atogepant for Migraine Prophylaxis Among Adults: A Secondary Analysis of a Randomized Clinical Trial

Migraine; Atogepant; AdultsMigraña; Atogepant; AdultosMigranya; Atogepant; AdultsImportance Some patients with migraine, particularly those in primary care, require effective, well-tolerated, migraine-specific oral preventive treatments. Objective To examine the efficacy of atogepant, an oral, small-molecule, calcitonin gene–related peptide receptor antagonist, using 4 levels of mean monthly migraine-day (MMD) responder rates. Design, Setting, and Participants This secondary analysis of a phase 3, double-blind, placebo-controlled randomized clinical trial evaluated the efficacy and safety of atogepant for the preventive treatment of migraine from December 14, 2018, to June 19, 2020, in adults with 4 to 14 migraine-days per month at 128 sites in the US. Interventions Patients were administered 10 mg of atogepant (n = 222), 30 mg of atogepant (n = 230), 60 mg of atogepant (n = 235), or placebo (n = 223) once daily in a 1:1:1:1 ratio for 12 weeks. Main Outcomes and Measures These analyses evaluated treatment responder rates, defined as participants achieving 50% or greater (α-controlled, secondary end point) and 25% or greater, 75% or greater, and 100% (prespecified additional end points) reductions in mean MMDs during the 12-week blinded treatment period. Results Of 902 participants (mean [SD] age, 41.6 [12.3] years; 801 [88.8%] female; 752 [83.4%] White; 825 [91.5%] non-Hispanic), 873 were included in the modified intention-to-treat population (placebo, 214; 10 mg of atogepant, 214; 30 mg of atogepant, 223; and 60 mg of atogepant, 222). For the secondary end point, a 50% or greater reduction in the 12-week mean of MMDs was achieved by 119 of 214 participants (55.6%) treated with 10 mg of atogepant (odds ratio, 3.1; 95% CI, 2.1-4.6), 131 of 223 participants (58.7%) treated with 30 mg atogepant (odds ratio, 3.5; 95% CI, 2.4-5.3), 135 of 222 participants (60.8%) treated with 60 mg of atogepant (odds ratio, 3.8; 95% CI, 2.6-5.7), and 62 of 214 participants (29.0%) given placebo (P < .001). The numbers of participants who reported a 25% or greater reduction in the 12-week mean of MMDs were 157 of 214 (73.4%) for 10 mg of atogepant, 172 of 223 (77.1%) for 30 mg of atogepant, and 180 of 222 (81.1%) for 60 mg of atogepant vs 126 of 214 (58.9%) for placebo (P < .002). The numbers of participants who reported a 75% or greater reduction in mean MMDs were 65 of 214 (30.4%) for 10 mg of atogepant, 66 of 223 (29.6%) for 30 mg of atogepant, and 84 of 222 (37.8%) for 60 mg of atogepant compared with 23 of 214 (10.7%) for placebo (P < .001). The numbers of participants reporting 100% reduction in mean MMDs were 17 of 214 (7.9%) for 10 mg of atogepant (P = .004), 11 of 223 (4.9%) for 30 mg of atogepant (P = .02), and 17 of 222 (7.7%) for 60 mg of atogepant (P = .003) compared with 2 of 214 (0.9%) for placebo. Conclusions and Relevance At all doses, atogepant was effective during the 12-week double-blind treatment period beginning in the first 4 weeks, as evidenced by significant reductions in mean MMDs at every responder threshold level. Higher atogepant doses appeared to produce the greatest responder rates, which can guide clinicians in individualizing starting doses

HIGH EXCITATION ENERGY STRUCTURES IN HEAVY ION COLLISIONS ON A208Pb TARGET

Energy spectra of fragments from the 36Ar +208Pb reaction at 11 MeV/n and 20Ne + 208Pb reaction at 30 MeV/n were measured using a time of flight spectrometer. Structures ranging up to 130 MeV excitation energy are observed in the inelastic spectra. These structures are shown to be due to an excitation of the208Pb target nucleus

Standardized test outcomes for students engaged in inquiry-based science curricula in the context of urban reform

Considerable effort has been made over the past decade to address the needs of learners in large urban districts through scaleable reform initiatives. We examine the effects of a multifaceted scaling reform that focuses on supporting standards based science teaching in urban middle schools. The effort was one component of a systemic reform effort in the Detroit Public Schools, and was centered on highly specified and developed project-based inquiry science units supported by aligned professional development and learning technologies. Two cohorts of 7th and 8th graders that participated in the project units are compared with the remainder of the district population, using results from the high-stakes state standardized test in science. Both the initial and scaled up cohorts show increases in science content understanding and process skills over their peers, and significantly higher pass rates on the statewide test. The relative gains occur up to a year and a half after participation in the curriculum, and show little attenuation with in the second cohort when scaling occurred and the number of teachers involved increased. The effect of participation in units at different grade levels is independent and cumulative, with higher levels of participation associated with similarly higher achievement scores. Examination of results by gender reveals that the curriculum effort succeeds in reducing the gender gap in achievement experienced by urban African-American boys. These findings demonstrate that standards-based, inquiry science curriculum can lead to standardized achievement test gains in historically underserved urban students, when the curriculum is highly specified, developed, and aligned with professional development and administrative support. © 2008 Wiley Periodicals, Inc. J Res Sci Teach 45: 922–939, 2008Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/61206/1/20248_ftp.pd

Probing the 6He halo structure with elastic and inelastic proton scattering

Proton elastic scattering and inelastic scattering to the first excited state of 6He have been measured over a wide angular range using a 40.9A MeV 6He beam. The data have been analyzed with a fully microscopic model of proton-nucleus scattering using 6He wave functions generated from large space shell model calculations. The inelastic scattering data show a remarkable sensitivity to the halo structure of 6He.Comment: 9 pages, 3 figures. RevTeX. Replaced figure 3 with updated figur

Structure of unbound neutron-rich 9^{9}He studied using single-neutron transfer

The 8He(d,p) reaction was studied in inverse kinematics at 15.4A MeV using the MUST2 Si-CsI array in order to shed light on the level structure of 9He. The well known 16O(d,p)17O reaction, performed here in reverse kinematics, was used as a test to validate the experimental methods. The 9He missing mass spectrum was deduced from the kinetic energies and emission angles of the recoiling protons. Several structures were observed above the neutron-emission threshold and the angular distributions were used to deduce the multipolarity of the transitions. This work confirms that the ground state of 9He is located very close to the neutron threshold of 8He and supports the occurrence of parity inversion in 9He.Comment: Exp\'erience GANIL/SPIRAL1/MUST

The Role of Friction in Compaction and Segregation of Granular Materials

We investigate the role of friction in compaction and segregation of granular materials by combining Edwards' thermodynamic hypothesis with a simple mechanical model and mean-field based geometrical calculations. Systems of single species with large friction coefficients are found to compact less. Binary mixtures of grains differing in frictional properties are found to segregate at high compactivities, in contrary to granular mixtures differing in size, which segregate at low compactivities. A phase diagram for segregation vs. friction coefficients of the two species is generated. Finally, the characteristics of segregation are related directly to the volume fraction without the explicit use of the yet unclear notion of compactivity.Comment: 9 pages, 6 figures, submitted to Phys. Rev.

Transport properties of heterogeneous materials derived from Gaussian random fields: Bounds and Simulation

We investigate the effective conductivity ($\sigma_e$) of a class of amorphous media defined by the level-cut of a Gaussian random field. The three point solid-solid correlation function is derived and utilised in the evaluation of the Beran-Milton bounds. Simulations are used to calculate $\sigma_e$ for a variety of fields and volume fractions at several different conductivity contrasts. Relatively large differences in $\sigma_e$ are observed between the Gaussian media and the identical overlapping sphere model used previously as a `model' amorphous medium. In contrast $\sigma_e$ shows little variability between different Gaussian media.Comment: 15 pages, 14 figure