2,363 research outputs found
Equivalent Circuit Modeling of the Dielectric Loaded Microwave Biosensor
This article describes the modeling of biological tissues at microwave frequency using equivalent lumped elements. A microwave biosensor based on microstrip ring resonator (MRR), that has been utilized previously for meat quality evaluation is used for this purpose. For the first time, the ring-resonator loaded with the lossy and high permittivity dielectric material, such as; biological tissue, in a partial overlay configuration is analyzed. The equivalent circuit modeling of the structure is then performed to identify the effect of overlay thickness on the resonance frequency. Finally, the relationship of an overlay thickness with the corresponding RC values of the meat equivalent circuit is established. Simulated, calculated and measured results are then compared for validation. Results are well agreed while the observed discrepancy is in acceptable limit
A Novel Dielectric Anomaly in Cuprates and Nickelates: Signature of an Electronic Glassy State
The low-frequency dielectric response of hole-doped insulators
La_{2}Cu_{1-x}Li_{x}O_{4} and La_{2-x}Sr_{x}NiO_{4} shows a large dielectric
constant \epsilon ^{'} at high temperature and a step-like drop by a factor of
100 at a material-dependent low temperature T_{f}. T_{f} increases with
frequency and the dielectric response shows universal scaling in a Cole-Cole
plot, suggesting that a charge glass state is realized both in the cuprates and
in the nickelates.Comment: 5 pages, 4 figure
Suppression of Antiferromagnetic Order by Light Hole Doping in La_2Cu_{1-x}Li_xO_4: A ^{139}La NQR Study
^{139}La nuclear quadrupole resonance measurements in lightly doped
La_2Cu_{1-x}Li_xO_4 have been performed to reveal the dependence of the
magnetic properties of the antiferromagnetic CuO_2 planes on the character of
the doped holes and their interactions with the dopant. A detailed study shows
that the magnetic properties are remarkably insensitive to the character of the
dopant impurity. This indicates that the added holes form previously
unrecognized collective structures.Comment: 4 pages, 3 figures. Slightly modified version, as accepted for
publication in Physical Review Letter
COVID-19 Related Mobility Reduction: Heterogenous Effects on Sleep and Physical Activity Rhythms
Mobility restrictions imposed to suppress coronavirus transmission can alter
physical activity (PA) and sleep patterns. Characterization of response
heterogeneity and their underlying reasons may assist in tailoring customized
interventions. We obtained wearable data covering baseline, incremental
movement restriction and lockdown periods from 1824 city-dwelling, working
adults aged 21 to 40 years, incorporating 206,381 nights of sleep and 334,038
days of PA. Four distinct rest activity rhythms (RARs) were identified using
k-means clustering of participants' temporally distributed step counts.
Hierarchical clustering of the proportion of time spent in each of these RAR
revealed 4 groups who expressed different mixtures of RAR profiles before and
during the lockdown. Substantial but asymmetric delays in bedtime and waketime
resulted in a 24 min increase in weekday sleep duration with no loss in sleep
efficiency. Resting heart rate declined 2 bpm. PA dropped an average of 38%. 4
groups with different compositions of RAR profiles were found. Three were
better able to maintain PA and weekday/weekend differentiation during lockdown.
The least active group comprising 51 percent of the sample, were younger and
predominantly singles. Habitually less active already, this group showed the
greatest reduction in PA during lockdown with little weekday/weekend
differences. Among different mobility restrictions, removal of habitual social
cues by lockdown had the largest effect on PA and sleep. Sleep and resting
heart rate unexpectedly improved. RAR evaluation uncovered heterogeneity of
responses to lockdown and can identify characteristics of persons at risk of
decline in health and wellbeing.Comment: 30 pages, 3 main figures, 3 tables, 4 supplementary figure
Magnetic Incommensurability in Doped Mott Insulator
In this paper we explore the incommensurate spatial modulation of spin-spin
correlations as the intrinsic property of the doped Mott insulator, described
by the model. We show that such an incommensurability is a direct
manifestation of the phase string effect introduced by doped holes in both one-
and two-dimensional cases. The magnetic incommensurate peaks of dynamic spin
susceptibility in momentum space are in agreement with the neutron-scattering
measurement of cuprate superconductors in both position and doping dependence.
In particular, this incommensurate structure can naturally reconcile the
neutron-scattering and NMR experiments of cuprates.Comment: 12 pages (RevTex), five postscript figure
Vibronic coupling and band gap trends in CuGeO3 nanorods
We measured the optical response of CuGeO3 nanorods in order to reveal size effects on the electronic properties. The vibronically activated d-to-d color band excitations are activated by the 131 and 478 cm−1 phonons, with the relative contribution of the lower frequency O-Cu-O bending mode increasing with decreasing size until it dominates the process. We also uncover trends in the direct band gap, with the charge transfer edge hardening with decreasing size. These findings advance the understanding of size effects in low-dimensional copper oxides
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