4,126 research outputs found
Universality in edge-source diffusion dynamics
We show that in edge-source diffusion dynamics the integrated concentration
N(t) has a universal dependence with a characteristic time-scale tau=(A/P)^2
pi/(4D), where D is the diffusion constant while A and P are the
cross-sectional area and perimeter of the domain, respectively. For the
short-time dynamics we find a universal square-root asymptotic dependence
N(t)=N0 sqrt(t/tau) while in the long-time dynamics N(t) saturates
exponentially at N0. The exponential saturation is a general feature while the
associated coefficients are weakly geometry dependent.Comment: 4 pages including 4 figures. Minor changes. Accepted for PR
Slow-light enhanced optical detection in liquid-infiltrated photonic crystals
Slow-light enhanced optical detection in liquid-infiltrated photonic crystals
is theoretically studied. Using a scattering-matrix approach and the
Wigner-Smith delay time concept, we show that optical absorbance benefits both
from slow-light phenomena as well as a high filling factor of the energy
residing in the liquid. Utilizing strongly dispersive photonic crystal
structures, we numerically demonstrate how liquid-infiltrated photonic crystals
facilitate enhanced light-matter interactions, by potentially up to an order of
magnitude. The proposed concept provides strong opportunities for improving
existing miniaturized absorbance cells for optical detection in lab-on-a-chip
systems.Comment: Paper accepted for the "Special Issue OWTNM 2007" edited by A.
Lavrinenko and P. J. Robert
Reexamination of Hagen-Poiseuille flow: shape-dependence of the hydraulic resistance in microchannels
We consider pressure-driven, steady state Poiseuille flow in straight
channels with various cross-sectional shapes: elliptic, rectangular,
triangular, and harmonic-perturbed circles. A given shape is characterized by
its perimeter P and area A which are combined into the dimensionless
compactness number C = P^2/A, while the hydraulic resistance is characterized
by the well-known dimensionless geometrical correction factor alpha. We find
that alpha depends linearly on C, which points out C as a single dimensionless
measure characterizing flow properties as well as the strength and
effectiveness of surface-related phenomena central to lab-on-a-chip
applications. This measure also provides a simple way to evaluate the hydraulic
resistance for the various shapes.Comment: 4 pages including 3 figures. Revised title, as publishe
Strontium Exchange Characteristics of Soils from the Ogotoruk Creek Watershed in Alaska
Author Institution: Department of Agronomy, Ohio Agricultural Experiment Station, and The Ohio State University, Columbus 1
Transport coefficients for electrolytes in arbitrarily shaped nano and micro-fluidic channels
We consider laminar flow of incompressible electrolytes in long, straight
channels driven by pressure and electro-osmosis. We use a Hilbert space
eigenfunction expansion to address the general problem of an arbitrary cross
section and obtain general results in linear-response theory for the hydraulic
and electrical transport coefficients which satisfy Onsager relations. In the
limit of non-overlapping Debye layers the transport coefficients are simply
expressed in terms of parameters of the electrolyte as well as the geometrical
correction factor for the Hagen-Poiseuille part of the problem. In particular,
we consider the limits of thin non-overlapping as well as strongly overlapping
Debye layers, respectively, and calculate the corrections to the hydraulic
resistance due to electro-hydrodynamic interactions.Comment: 13 pages including 4 figures and 1 table. Typos corrected. Accepted
for NJ
Revitalizing the Retail Trade Sector in Rural Communities: Experiences of 13 North Dakota Towns
Community/Rural/Urban Development,
Low-loss criterion and effective area considerations for photonic crystal fibers
We study the class of endlessly single-mode all-silica photonic crystal
fibers with a triangular air-hole cladding. We consider the sensibility to
longitudinal nonuniformities and the consequences and limitations for realizing
low-loss large-mode area photonic crystal fibers. We also discuss the
dominating scattering mechanism and experimentally we confirm that both macro
and micro-bending can be the limiting factor.Comment: Accepted for Journal of Optics A - Pure and Applied Optic
Ptychographic X-ray computed tomography of extended colloidal networks in food emulsions
As a main structural level in colloidal food materials, extended colloidal
networks are important for texture and rheology. By obtaining the 3D
microstructure of the network, macroscopic mechanical properties of the
material can be inferred. However, this approach is hampered by the lack of
suitable non-destructive 3D imaging techniques with submicron resolution.
We present results of quantitative ptychographic X-ray computed tomography
applied to a palm kernel oil based oil-in-water emulsion. The measurements were
carried out at ambient pressure and temperature. The 3D structure of the
extended colloidal network of fat globules was obtained with a resolution of
around 300 nm. Through image analysis of the network structure, the fat globule
size distribution was computed and compared to previous findings. In further
support, the reconstructed electron density values were within 4% of reference
values.Comment: 19 pages, 4 figures, to be published in Food Structur
Bayesian Error Estimation in Density Functional Theory
We present a practical scheme for performing error estimates for Density
Functional Theory calculations. The approach which is based on ideas from
Bayesian statistics involves creating an ensemble of exchange-correlation
functionals by comparing with an experimental database of binding energies for
molecules and solids. Fluctuations within the ensemble can then be used to
estimate errors relative to experiment on calculated quantities like binding
energies, bond lengths, and vibrational frequencies. It is demonstrated that
the error bars on energy differences may vary by orders of magnitude for
different systems in good agreement with existing experience.Comment: 5 pages, 3 figure
Early motor developmental milestones and level of neuroticism in young adulthood:a 23-year follow-up study of the Copenhagen Perinatal Cohort
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