1,489 research outputs found
Singular measures in circle dynamics
Critical circle homeomorphisms have an invariant measure totally singular
with respect to the Lebesgue measure. We prove that singularities of the
invariant measure are of Holder type. The Hausdorff dimension of the invariant
measure is less than 1 but greater than 0
Bilateral superficial ulnar artery with high origin from the axillary artery: its anatomy and clinical significance
The superficial ulnar artery (SUA) is a rare anatomical variant that usually arises either in the axilla or the arm and runs a superficial course in the forearm, enters the hand, and participates in the formation of superficial palmar arch. During the routine dissection of cadavers in the department of anatomy, whilst preparing the specimen for medical students, an unusual bilateral branch of the axillary artery was found in one of the cadavers: a rare variant of the artery known as SUA, which originates from the 2nd part of the axillary arteries of
both sides. The SUA is a known anatomical variant, but the bilateral high origin from the 2nd part of the axillary artery is extremely unusual. Its occurrence is of great clinical importance to the surgical and radiological departments
Multifractal Scaling, Geometrical Diversity, and Hierarchical Structure in the Cool Interstellar Medium
Multifractal scaling (MFS) refers to structures that can be described as a
collection of interwoven fractal subsets which exhibit power-law spatial
scaling behavior with a range of scaling exponents (concentration, or
singularity, strengths) and dimensions. The existence of MFS implies an
underlying multiplicative (or hierarchical, or cascade) process. Panoramic
column density images of several nearby star- forming cloud complexes,
constructed from IRAS data and justified in an appendix, are shown to exhibit
such multifractal scaling, which we interpret as indirect but quantitative
evidence for nested hierarchical structure. The relation between the dimensions
of the subsets and their concentration strengths (the "multifractal spectrum'')
appears to satisfactorily order the observed regions in terms of the mixture of
geometries present: strong point-like concentrations, line- like filaments or
fronts, and space-filling diffuse structures. This multifractal spectrum is a
global property of the regions studied, and does not rely on any operational
definition of "clouds.'' The range of forms of the multifractal spectrum among
the regions studied implies that the column density structures do not form a
universality class, in contrast to indications for velocity and passive scalar
fields in incompressible turbulence, providing another indication that the
physics of highly compressible interstellar gas dynamics differs fundamentally
from incompressible turbulence. (Abstract truncated)Comment: 27 pages, (LaTeX), 13 figures, 1 table, submitted to Astrophysical
Journa
Clinical outcomes post transition to adult services in young adults with perinatally acquired HIV infection: mortality, retention in care, and viral suppression
OBJECTIVE: Adolescence is the only age group globally where HIV associated mortality is rising, with poorer outcomes at all stages of the care cascade compared to adults. We examined post-transition outcomes for young adults living with perinatal HIV (YAPaHIV). DESIGN: Retrospective cohort analysis. SETTING: A tertiary Youth Friendly Service (YFS) London, UK. PARTICIPANTS: 180 YAPaHIV registered between 01.01.06 and 31.12.17 contributed 921 person-years of follow up post-transition to adult services. INTERVENTION: YFS with multidisciplinary care and walk-in access. MAIN OUTCOME MEASURES: mortality, morbidity, retention in care, antiretroviral (ART) uptake and HIV-viral load (HIV-VL) suppression. Crude incidence rates (CIR) are reported per 1000 person-years. RESULTS: Of 180 youth registered; 4 (2.2%) died, 14 (7.8%) transferred care and 4 (2.2%) were lost to follow up. For the 158 retained in care the median age was 22.9 years (IQR 20.3-25.4), 56% were female, 85% Black African, with a median length of follow up in adult care of 5.5 years (IQR 2.9-7.3). 157 (99.4%) ever received an ART prescription, 127/157 (81%) with a latest HIV-VL < 200 copies RNA/ml, median CD4 count of 626 cells/ul (IQR 441-820). The all-cause mortality was 4.3/1000 person-years (95% CI 1.2 - 11.1), ten fold the aged-matched UK HIV-negative population (0.43/1000 person-years (95% CI 0.41 - 0.44). Post-transition, 17/180 (9.4%) developed a new AIDS diagnosis; CIR 18.5/1000 person-years (95% CI 10.8 - 29.6). CONCLUSION: Whilst this youth-friendly multi-disciplinary service achieved high engagement and coverage of suppressive ART, mortality remains markedly increased compared to the general UK population
Rheological Behavior of Aqueous Suspensions of Laponite: New Insights into the Ageing Phenomena
In this paper, ageing behavior of suspensions of laponite with varying salt
concentration is investigated using rheological tools. It is observed that the
ageing is accompanied by an increase in the complex viscosity. The succeeding
creep experiments performed at various ages showed damped oscillations in the
strain. The characteristic time-scale of the damped oscillations, retardation
time, showed a prominent decrease with the age of the system. However, this
dependence weakens with an increase in the salt concentration, which is known
to change microstructure of the system from glass-like to gel-like. We
postulate that a decrease in the retardation time can be represented as a
decrease in the viscosity (friction) of the dissipative environment surrounding
the arrested entities that opposes elastic deformation of the system. We
believe that ageing in colloidal glass leads to a greater ordering that
enhances relative spacing between the constituents thereby reducing the
frictional resistance. However, since a gel state is inherently different in
structure (fractal network) than that of a glass (disordered), ageing in the
same does not induce ordering. Consequently, we observe inverse dependence of
retardation time on age becoming weaker with an increase in the salt
concentration. We analyze these results from a perspective of ageing dynamics
of both glass state and gel state of laponite suspensions.Comment: 27 Pages, 12 figure
Multifractal burst in the spatio-temporal dynamics of jerky flow
The collective behavior of dislocations in jerky flow is studied in Al-Mg
polycrystalline samples subjected to constant strain rate tests. Complementary
dynamical, statistical and multifractal analyses are carried out on the
stress-time series recorded during jerky flow to characterize the distinct
spatio-temporal dynamical regimes. It is shown that the hopping type B and the
propagating type A bands correspond to chaotic and self-organized critical
states respectively. The crossover between these types of bands is identified
by a large spread in the multifractal spectrum. These results are interpreted
on the basis of competing scales and mechanisms.Comment: 4 pages, 6 figures To be published in Phys. Rev. Lett. (2001
Flow induced by a sphere settling in an aging yield-stress fluid
We have studied the flow induced by a macroscopic spherical particle settling
in a Laponite suspension that exhibits a yield-stress, thixotropy and
shear-thinning. We show that the fluid thixotropy (or aging) induces an
increase with time of both the apparent yield stress and shear-thinning
properties but also a breaking of the flow fore-aft symmetry predicted in
Hershel-Bulkley fluids (yield-stress, shear-thinning fluids with no
thixotropy). We have also varied the stress exerted by the particles on the
fluid by using particles of different densities. Although the stresses exerted
by the particles are of the same order of magnitude, the velocity field
presents utterly different features: whereas the flow around the lighter
particle shows a confinement similar to the one observed in shear-thinning
fluids, the wake of the heavier particle is characterized by an upward motion
of the fluid ("negative wake"), whatever the fluid's age. We compare the
features of this negative wake to the one observed in viscoelastic
shear-thinning fluids (polymeric or micelle solutions). Although the flows
around the two particles strongly differ, their settling behaviors display no
apparent difference which constitutes an intriguing result and evidences the
complexity of the dependence of the drag factor on flow field
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