1,785 research outputs found
Berry's Phase in the Presence of a Dissipative Medium
We consider the spin 1/2 model coupled to a slowly varying magnetic field in
the presence of a weak damping represented by a Lindblad-form operators. We
show that Berry's geometrical phase remains unaltered by the two dissipation
mechanism considered. Dissipation effects are twofold: a shrinking in the
modulus of the Bloch's vector, which characterizes coherence loss and a time
dependent (dissipation related) precession angle. We show that the line
broadening of the Fourier transformation of the components of magnetization is
only due to the presence of dissipation.Comment: 19 pages, 2 figure
Adiabatic Approximation in the Density Matrix Approach: Non-Degenerate Systems
We study the adiabatic limit in the density matrix approach for a quantum
system coupled to a weakly dissipative medium. The energy spectrum of the
quantum model is supposed to be non-degenerate. In the absence of dissipation,
the geometric phases for periodic Hamiltonians obtained previously by M.V.
Berry are recovered in the present approach. We determine the necessary
condition satisfied by the coefficients of the linear expansion of the
non-unitary part of the Liouvillian in order to the imaginary phases acquired
by the elements of the density matrix, due to dissipative effects, be
geometric. The results derived are model-independent. We apply them to spin 1/2
model coupled to reservoir at thermodynamic equilibrium.Comment: 24 pages (new version), accepted for publication in Physica
Pressures generated during corneal wound hydration
CorrespondenceMichelle T. Sun, Megan Wood, WengOnn Chan, Robert Casso
Effect of magnetic and non-magnetic impurities on highly anisotropic superconductivity
We generalize Abrikosov-Gor'kov solution of the problem of weakly coupled
superconductor with impurities on the case of a multiband superconductor with
arbitrary interband order parameter anisotropy, including interband sign
reversal of the order parameter. The solution is given in terms of the
effective (renormalized) coupling matrix and describes not only
suppression but also renormalization of the superconducting gap basically at
all temperatures. In many limiting cases we find analytical solutions for the
critical temperature suppression. We illustrate our results by numerical
calculations for two-band model systems.Comment: 18 pages (12pt) RevTeX, 4 postscript figure
Phase transition from a to superconductor
We study the phase transition from a to
superconductor using the tight-binding model of two-dimensional cuprates. As
the temperature is lowered past the critical temperature , first a superconducting phase is created. With further reduction of
temperature, the phase is created at temperature
. We study the temperature dependencies of the order parameter,
specific heat and spin susceptibility in these mixed-angular-momentum states on
square lattice and on a lattice with orthorhombic distortion. The
above-mentioned phase transitions are identified by two jumps in specific heat
at and .Comment: Latex file, 5 pages, 6 postscript figures, Accepted in Physical
Review
Interplay of superexchange and orbital degeneracy in Cr-doped LaMnO3
We report on structural, magnetic and Electron Spin Resonance (ESR)
investigations in the manganite system LaMn_{1-x}Cr_{x}O_{3} (x<=0.5). Upon
Cr-doping we observe a reduction of the Jahn-Teller distortion yielding less
distorted orthorhombic structures. A transition from the Jahn-Teller distorted
O' to the pseudocubic O phase occurs between 0.3<x<0.4. A clear connection
between this transition and the doping dependence of the magnetic and ESR
properties has been observed. The effective moments determined by ESR seem
reduced with respect to the spin-only value of both Mn^{3+} and Cr^{3+} ions
Changing trends in glaucoma surgery within Australia
Background: Limited data are available on glaucoma surgical trends in Australia. Methods: Nationwide study of glaucoma surgery in Australia over 17-year period from 2001 to 2018. The Australian Institute of Health, Welfare and Ageing hospitalisation database was used to review age- and gender-specific trends in glaucoma surgeries from 2001 to 2018 in Australian public and private hospitals. Results: Although there was an increase in the absolute number of trabeculectomy procedures from 2926 to 3244 over the 17-year study period, this represented a decline in the age-standardised and gender-standardised number of trabeculectomy procedures from 15.1 to 13.2 procedures per 100 000 persons. However, during this same period, there was a dramatic increase in the number of glaucoma drainage devices (GDD) from 119 to 3262 procedures, representing an age-standardised and gender-standardised increase from 0.6 to 13.3 procedures per 100 000 persons. Negative binomial regression analysis revealed a decrease in trabeculectomy procedures of 1.1% per year, while there was increase in GDD insertions of 16.3% per year (p60 years, compared with stable or increasing rates in younger age groups. GDD insertion rates demonstrated a progressively greater increase in older compared with younger age groups. Conclusion: Our findings demonstrate changing trends in the surgical management of advanced glaucoma in Australia, likely reflecting updated evidence regarding the role of GDD surgeries.Michelle T Sun, Reema Madike, Sonia Huang, Cassie Cameron, Dinesh Selva, Robert J Casson, Christopher X Won
QND measurements for future gravitational-wave detectors
Second-generation interferometric gravitational-wave detectors will be
operating at the Standard Quantum Limit, a sensitivity limitation set by the
trade off between measurement accuracy and quantum back action, which is
governed by the Heisenberg Uncertainty Principle. We review several schemes
that allows the quantum noise of interferometers to surpass the Standard
Quantum Limit significantly over a broad frequency band. Such schemes may be an
important component of the design of third-generation detectors.Comment: 22 pages, 6 figures, 1 table; In version 2, more tutorial information
on quantum noise in GW interferometer and several new items into Reference
list were adde
Epidermis recreation in spongy-like hydrogels: New opportunities to explore epidermis-like analogues
[Excerpt] On the road to successfully achieving skin regeneration, 3D matrices/scaffolds that provide the adequate physico-chemical and biological cues to recreate the ideal healing environment are believed to be a key element [1], [2] and [3].
Numerous polymeric matrices derived from both natural [4] and [5] and synthetic [6], [7] and [8] sources have been used as cellular supports; nowadays, fewer matrices are simple carriers, and more and more are ECM analogues that can actively participate in the healing process. Therefore, the attractive characteristics of hydrogels, such as high water content, tunable elasticity and facilitated mass transportation, have made them excellent materials to mimic cells’ native environment [9]. Moreover, their hygroscopic nature [10] and possibility of attaining soft tissues-like mechanical properties mean they have potential for exploitation as wound healing promoters [11], [12], [13] and [14]. Nonetheless, hydrogels lack natural cell adhesion sites [15], which limits the maximization of their potential in the recreation of the cell niche. This issue has been tackled through the use of a range of sophisticated approaches to decorate the hydrogels with adhesion sequences such as arginine-glycine-aspartic acid (RGD) derived from fibronectin [16], [17] and [18], and tyrosine-isoleucine-glycine-serine-arginine (YIGSR) derived from laminin [18] and [19], which not only aim to modulate cell adhesion, but also influencing cell fate and survival [18]. Nonetheless, its widespread use is still limited by significant costs associated with the use of recombinant bioactive molecules
Weak magnetism and non-Fermi liquids near heavy-fermion critical points
This paper is concerned with the weak-moment magnetism in heavy-fermion
materials and its relation to the non-Fermi liquid physics observed near the
transition to the Fermi liquid. We explore the hypothesis that the primary
fluctuations responsible for the non-Fermi liquid physics are those associated
with the destruction of the large Fermi surface of the Fermi liquid. Magnetism
is suggested to be a low-energy instability of the resulting small Fermi
surface state. A concrete realization of this picture is provided by a
fractionalized Fermi liquid state which has a small Fermi surface of conduction
electrons, but also has other exotic excitations with interactions described by
a gauge theory in its deconfined phase. Of particular interest is a
three-dimensional fractionalized Fermi liquid with a spinon Fermi surface and a
U(1) gauge structure. A direct second-order transition from this state to the
conventional Fermi liquid is possible and involves a jump in the electron Fermi
surface volume. The critical point displays non-Fermi liquid behavior. A
magnetic phase may develop from a spin density wave instability of the spinon
Fermi surface. This exotic magnetic metal may have a weak ordered moment
although the local moments do not participate in the Fermi surface.
Experimental signatures of this phase and implications for heavy-fermion
systems are discussed.Comment: 20 pages, 8 figures; (v2) includes expanded discussion and solution
of quantum Boltzmann equatio
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