13,382 research outputs found
Islands in the Gap: Intertwined Transport and Localization in Structurally Complex Materials
Localized waves in disordered one-dimensional materials have been studied for
decades, including white-noise and correlated disorder, as well as
quasi-periodic disorder. How these wave phenomena relate to those in
crystalline (periodic ordered) materials---arguably the better understood
setting---has been a mystery ever since Anderson discovered disorder-induced
localization. Nonetheless, together these revolutionized materials science and
technology and led to new physics far beyond the solid state. We introduce a
broad family of structurally complex materials---chaotic crystals---that
interpolate between these organizational extremes---systematically spanning
periodic structures and random disorder. Within the family one can tune the
degree of disorder to sweep through an intermediate structurally disordered
region between two periodic lattices. This reveals new transport and
localization phenomena reflected in a rich array of energy-dependent
localization degree and density of states. In particular, strong localization
is observed even with a very low degree of disorder. Moreover, markedly
enhanced localization and delocalization coexist in a very narrow range of
energies. Most notably, beyond the simply smoothed bands found in previous
disorder studies, islands of transport emerge in band gaps and sharp band
boundaries persist in the presence of substantial disorder. Finally, the family
of materials comes with rather direct specifications of how to assemble the
requisite material organizations.Comment: 7 pages, 3 figures, supplementary material;
http://csc.ucdavis.edu/~cmg/compmech/pubs/talisdm.ht
-meson in nuclear matter
The -nucleon (N) interactions are deduced from the heavy baryon
chiral perturbation theory up to the next-to-leading-order terms. Combining the
relativistic mean-field theory for nucleon system, we have studied the
in-medium properties of -meson. We find that all the elastic scattering
N interactions come from the next-to-leading-order terms. The N
sigma term is found to be about 280130 MeV. The off-shell terms are also
important to the in-medium properties of -meson. On application of the
latest determination of the N scattering length, the ratio of
-meson effective mass to its vacuum value is near , while
the optical potential is about MeV, at the normal nuclear density.Comment: 8 pages, 3 figures, to appear in PRC, many modification
Effect of the Kondo correlation on thermopower in a Quantum Dot
In this paper we study the thermopower of a quantum dot connected to two
leads in the presence of Kondo correlation by employing a modified second-order
perturbation scheme at nonequilibrium. A simple scheme, Ng's ansatz [Phys. Rev.
Lett. {\bf 76}, 487 (1996)], is adopted to calculate nonequilibrium
distribution Green's function and its validity is further checked with regard
to the Onsager relation. Numerical results demonstrate that the sign of the
thermopower can be changed by tuning the energy level of the quantum dot,
leading to a oscillatory behavior with a suppressed magnitude due to the Kondo
effect. We also calculate the thermal conductance of the system, and find that
the Wiedemann-Franz law is obeyed at low temperature but violated with
increasing temperature, corresponding to emerging and quenching of the Kondo
effect.Comment: 6 pages, 4 figures; accepted for publication in J Phys.: Condensed
Matte
Vertical distributions of non-methane hydrocarbons and halocarbons in the lower troposphere over northeast China
Vertical distributions of air pollutants are crucial for understanding the key processes of atmospheric transport and for evaluating chemical transport models. In this paper, we present measurements of non-methane hydrocarbons (NMHCs) and halocarbons obtained from an intensive aircraft study over northeast (NE) China in summer 2007. Most compounds exhibited a typical negative profile of decreasing mixing ratios with increasing altitude, although the gradients differed with different species. Three regional plumes with enhanced VOC mixing ratios were discerned and characterized. An aged plume transported from the northern part of the densely populated North China Plain (NCP; i.e. Beijing-Tianjin area) showed relatively higher levels of HCFC-22, 1,2-dichloroethane (1,2-DCE) and toluene. In comparison, the plume originating from Korea had higher abundances of CFC-12, tetrachloroethene (C2Cl4) and methyl chloride (CH3Cl), while regional air masses from NE China contained more abundant light alkanes. By comparing these results with the earlier PEM-West B (1994) and TRACE-P (2001) aircraft measurements, continuing declining trends were derived for methyl chloroform (CH3CCl3), tetrachloromethane (CCl4) and C2Cl4 over the greater China-northwestern Pacific region, indicating the accomplishment of China in reducing these compounds under the Montreal protocol. However, the study also provided evidence for the continuing emissions of several halocarbons in China in 2007, such as CFCs (mainly from materials in stock) and HCFCs. © 2011 Elsevier Ltd
Improved preservation effects of litchi fruit by combining chitosan coating with ascorbic acid treatment during postharvest storage
Pericarp browning and aril decay of litchi fruits shorten post-harvest storage and thus reduce market value. Effects of chitosan coating and ascorbic acid (AsA) on litchi fruits storage were investigated in this paper. Based on the fact that AsA increases anti-oxidation capacity and chitosan inhibitsdehydration and microbial attack, the novel strategies of combining chitosan with AsA treatment were developed to improve litchi storability. By treating harvest fruits with 40 mmol/l AsA and 1.0% (w/v) chitosan solution, parameters of browning index and relative leakage rate and activities of polyphenol oxidase (PPO) and peroxidase (POD) in pericarp were markedly lowered in treated fruits. Moreover, increased activities of super oxide dismutase (SOD) and catalase (CAT) and contents of AsA andglutathione were observed in pulp of treated fruit, thus leading to lowered contents of hydrogen peroxide (H2O2) and malondialdehyde (MDA). Correspondingly, total soluble solids, soluble sugar and titratable acidity were significantly increased and thus lowered decay rate was achieved. It was suggested that chitosan and AsA play active roles in inhibiting pericarp browning, dehydration and microbial attack and maintaining membrane integrity, thus improved litchi storability being achieved
Nuclear pairing reduction due to rotation and blocking
Nuclear pairing gaps of normally deformed and superdeformed nuclei are
investigated using the particle-number conserving (PNC) formalism for the
cranked shell model, in which the blocking effects are treated exactly. Both
rotational frequency -dependence and seniority (number of unpaired
particles) -dependence of the pairing gap are
investigated. For the ground-state bands of even-even nuclei, PNC calculations
show that in general decreases with increasing , but
the -dependence is much weaker than that calculated by the
number-projected Hartree-Fock-Bogolyubov approach. For the multiquasiparticle
bands (seniority ), the pairing gaps keep almost -independent.
As a function of the seniority , the bandhead pairing gaps
decrease slowly with increasing . Even for
the highest seniority bands identified so far,
remains greater than 70% of
.Comment: 15 pages, 5 figure
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