13,124 research outputs found
A least squares method for the reduction of free-oscillation data
Least squares determination of frequency, damping ratio, amplitude, and phase angle from free oscillation dat
Crossover from weak localization to weak antilocalization in a disordered microbridge
We calculate the weak localization correction in the double crossover to
broken time-reversal and spin-rotational symmetry for a disordered microbridge
or a short disordered wire using a scattering-matrix approach. Whereas the
correction has universal limiting values in the three basic symmetry classes,
the functional form of the magnetoconductance is affected by eventual
non-homogeneities in the microbridge.Comment: 5 pages, RevTeX; 2 figure
When the going gets rough – studying the effect of surface roughness on the adhesive abilities of tree frogs
Tree frogs need to adhere to surfaces of various roughnesses in their natural habitats; these include bark, leaves and rocks. Rough
surfaces can alter the effectiveness of their toe pads, due to factors such as a change of real contact area and abrasion of the pad
epithelium. Here, we tested the effect of surface roughness on the attachment abilities of the tree frog Litoria caerulea. This was
done by testing shear and adhesive forces on artificial surfaces with controlled roughness, both on single toe pads and whole animal
scales. It was shown that frogs can stick 2–3 times better on small scale roughnesses (3–6 µm asperities), producing higher adhesive
and frictional forces, but relatively poorly on the larger scale roughnesses tested (58.5–562.5 µm asperities). Our experiments
suggested that, on such surfaces, the pads secrete insufficient fluid to fill the space under the pad, leaving air pockets that would
significantly reduce the Laplace pressure component of capillarity. Therefore, we measured how well the adhesive toe pad would
conform to spherical asperities of known sizes using interference reflection microscopy. Based on experiments where the conformation
of the pad to individual asperities was examined microscopically, our calculations indicate that the pad epithelium has a low
elastic modulus, making it highly deformable
The optical variability of the narrow line Seyfert 1 galaxy IRAS 13224-3809
We report on a short optical monitoring programme of the narrow-line Seyfert
1 Galaxy IRAS 13224-3809. Previous X-ray observations of this object have shown
persistent giant variability. The degree of variability at other wavelengths
may then be used to constrain the conditions and emission processes within the
nucleus. Optical variability is expected if the electron population responsible
for the soft X-ray emission is changing rapidly and Compton-upscattering
infrared photons in the nucleus, or if the mechanism responsible for X-ray
emission causes all the emission processes to vary together. We find that there
is no significant optical variability with a firm upper limit of 2 per cent and
conclude that the primary soft X-ray emission region produces little of the
observed optical emission. The X-ray and optical emission regions must be
physically distinct and any reprocessing of X-rays into the optical waveband
occurs some distance from the nucleus. The lack of optical variability
indicates that the energy density of infrared radiation in the nucleus is at
most equal to that of the ultraviolet radiation since little is upscattered
into the optical waveband. The extremely large X-ray variability of IRAS
13224-3809 may be explained by relativistic boosting of more modest variations.
Although such boosting enhances X-ray variability over optical variability,
this only partially explains the lack of optical variability.Comment: 5 pages with 8 postscript figures. Accepted for publication in MNRA
Monte Carlo direct simulation technique user's manual
User manual for Monte Carlo direct simulation techniqu
Implications of new measurements of O-16 + p + C-12,13, N-14,15 for the abundances of C, N isotopes at the cosmic ray source
The fragmentation of a 225 MeV/n O-16 beam was investigated at the Bevalac. Preliminary cross sections for mass = 13, 14, 15 fragments are used to constrain the nuclear excitation functions employed in galactic propagation calculations. Comparison to cosmic ray isotonic data at low energies shows that in the cosmic ray source C-13/C approximately 2% and N-14/0=3-6%. No source abundance of N-15 is required with the current experimental results
Active Galaxies and Cluster Gas
Two lines of evidence indicate that active galaxies, principally radio
galaxies, have heated the diffuse hot gas in clusters. The first is the general
need for additional heating to explain the steepness of the X-ray
luminosity--temperature relation in clusters, the second is to solve the
cooling flow problem in cluster cores. The inner core of many clusters is
radiating energy as X-rays on a timescale much shorter than its likely age.
Although the temperature in this region drops by a factor of about 3 from that
of the surrounding gas, little evidence is found for gas much cooler than that.
Some form of heating appears to be taking place, probably by energy transported
outward from the central accreting black hole or radio source. How that energy
heats the gas depends on poorly understood transport properties (conductivity
and viscosity) of the intracluster medium. Viscous heating is discussed as a
possibility. Such heating processes have consequences for the truncation of the
luminosity function of massive galaxies.Comment: 14 pages, 16 fig, Feb 2004 talk for Phil Trans Roy So
Using Intervention Mapping to Develop an Efficacious Multicomponent Systems-Based Intervention to Increase Human Papillomavirus (HPV) Vaccination in a Large Urban Pediatric Clinic Network
Background: The CDC recommends HPV vaccine for all adolescents to prevent cervical, anal, oropharyngeal, vaginal, vulvar, and penile cancers, and genital warts. HPV vaccine rates currently fall short of national vaccination goals. Despite evidence-based strategies with demonstrated efficacy to increase HPV vaccination rates, adoption and implementation of these strategies within clinics is lacking. The Adolescent Vaccination Program (AVP) is a multicomponent systems-based intervention designed to implement five evidence-based strategies within primary care pediatric practices. The AVP has demonstrated efficacy in increasing HPV vaccine initiation and completion among adolescents 10-17 years of age. The purpose of this paper is to describe the application of Intervention Mapping (IM) toward the development, implementation, and formative evaluation of the clinic-based AVP prototype. Methods: Intervention Mapping (IM) guided the development of the Adolescent Vaccination Program (AVP). Deliverables comprised: a logic model of the problem (IM Step 1); matrices of behavior change objectives (IM Step 2); a program planning document comprising scope, sequence, theory-based methods, and practical strategies (IM Step 3); functional AVP component prototypes (IM Step 4); and plans for implementation (IM Step 5) and evaluation (IM Step 6). Results: The AVP consists of six evidence-based strategies implemented in a successful sequenced roll-out that (1) established immunization champions in each clinic, (2) disseminated provider assessment and feedback reports with data-informed vaccination goals, (3) provided continued medical and nursing education (with ethics credit) on HPV, HPV vaccination, message bundling, and responding to parent hesitancy, (4) electronic health record cues to providers on patient eligibility, and (5) patient reminders for HPV vaccine initiation and completion. Conclusions: IM provided a logical and systematic approach to developing and evaluating a multicomponent systems-based intervention to increase HPV vaccination rates among adolescents in pediatric clinics
Pretransitional behavior in a water-DDAB-5CB microemulsion close to the demixing transition. Evidence for intermicellar attraction mediated by paranematic fluctuations
We present a study of a water-in-oil microemulsion in which surfactant coated
water nanodroplets are dispersed in the isotropic phase of the thermotropic
liquid crystal 5CB. As the temperature is lowered below the isotropic to
nematic phase transition of pure 5CB, the system displays a demixing transition
leading to a coexistence of a droplet rich isotropic phase with a droplet poor
nematic. The transition is anticipated, in the high T side, by increasing
pretransitional fluctuations in 5CB molecular orientation and in the
nanodroplet concentration. The observed phase behavior supports the notion that
the nanosized droplets, while large enough for their statistical behavior to be
probed via light scattering, are also small enough to act as impurities,
disturbing the local orientational ordering of the liquid crystal and thus
experiencing pretransitional attractive interaction mediated by paranematic
fluctuations. The pretransitional behavior, together with the topology of the
phase diagram, can be understood on the basis of a diluted Lebwohl-Lasher model
which describes the nanodroplets simply as holes in the liquid crystal.Comment: 64 pages, 16 figures, J. Chem. Phys. in pres
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