The role of intermediate layers in the c-axis conductivity of layered superconductors

A simplified model of c axis transport in the high T_c superconductors is presented. Expressions are found for the c axis optical conductivity, the d.c. resistivity, and the c axis penetration depth. Within the framework of this model, the pseudogap in the optical conductivity arises naturally as a result of the layered band structure of the high T_c materials. We discuss the occurence of the pseudogap in terms of three parameters: a band gap Delta_{ps}, a temperature dependent scattering rate Gamma(T), and the strength of the interlayer coupling t_{perp}. We are also able to find analytic expressions for the d.c. conductivity and the low temperature penetration depth in terms of these three parameters. This work is an attempt to present a simple, unified picture of c axis properties in the high T_c cuprates.Comment: 3 pages, 2 figures, Proceedings of Spectroscopies of Novel Superconductors '97, To be published in J. Phys. Chem. Solid

The impact of physical conditions on network connectivity in wireless sensor network

In Wireless Sensor Networks, end-to-end routing paths need to be established when nodes want to communicate with the desired destination. For nodes assumed to be static, many routing protocols such as Directed Diffusion have been proposed to meet this requirement efficiently. The performance of such routing protocols is relative to the given network connectivity. This paper addresses mobile sensor nodes taking into account the diversity of scattered node density and investigates how physical conditions impact on network connectivity which in turn influences routing performance. Three analysis metrics: path availability, path duration, and interavailable path time are proposed to quantify the impact of different physical conditions on network connectivity. Simulation results show that the network connectivity varies significantly as a function of different physical conditions

An Alternative Interpretation of the Magnetic Penetration Depth Data on Pr(2-x)Ce(x)CuO(4-y) and La(2-x)Ce(x)CuO(4-y)

We have revisited the magnetic penetration depth data on the electron-doped cuprates Pr(2-x)Ce(x)CuO(4-y) and La(2-x)Ce(x)CuO(4-y). It is proposed that the transition between the nodal-gap-like and nodeless-gap-like behaviors upon electron-doping [see, e.g., M. Kim et al., Phys. Rev. Lett. 91, 87001 (2003)] can be due to a scattering of the quasiparticles in the d-wave superconducting state by an incipient or weak antiferromagnetic spin-density-wave. This conjecture is supported by the inelastic neutron scattering and angle-resolved photoemission experiments on some closely related electron-doped cuprates.Comment: 6 pages, 5 figure

The Application of RFID in Emergency Medicine

Recently natural disasters and man-made calamities happened very frequently in Taiwan, some of which caused hundreds of inhabitants died and injured. The most important thing that makes the emergency medical treatment system work effectively during these catastrophes is dependent on the accuracy and immediacy of the information among ambulances, hospitals, fire bureaus, public health bureaus or offices, and emergency executive centers. With this information, the medical system can arrange the resources efficiently. Radio frequency identification (RFID) is a kind of wireless technology that it uses radio frequency (RF) to identify target objects. The characteristics of RFID are its identification and orientation. Through tracing electronic signals, RFID is able to identify, orientate and trace patients or medical materials directly and continuously. Thus, RFID can help managers of medical institutions to promote emergency medical treatment quality, reduce medical mistakes effectively, and increase efficiency and effectiveness in hospitals. A series of emergency medical delivery applications that use 915MHz RFID rings is developed in this paper. Through the help of RFID, the paper integrates the information of the whole emergency medical supply chain, and establishes a new model of emergency medical activities to solve the problems of information blocking among different medical rescue units. By solving these problems, the new model can enhance the rescue quality, reduce the damage of the disaster and strengthen the patient-oriented emergency care system

Absence of anisotropic universal transport in YBCO

There exists significant in-plane anisotropy between $a$ and $b$ axis for various properties in YBCO. However recent thermal conductivity measurement by Chiao et al. which confirms previous microwave conductivity measurement by Zhang et al., shows no obvious anisotropy in the context of universal transport. We give a possible explanation of why the anisotropy is seen in most properties but not seen in the universal transport.Comment: 4 pages, 4 figure

Intake of meat mutagens and risk of prostate cancer in a cohort of U.S. health professionals

BACKGROUND: Evidence relating heterocyclic aromatic amines (HCA), associated with high-temperature cooking methods, to prostate cancer risk is inconsistent Methods: In a large US cohort study, intakes of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx) and a meat-derived mutagenicity index (MDM) were assessed using a cooking method questionnaire administered in 1996. Until 2010, 2,770 prostate cancer cases were observed among 26,030 participants. RESULTS: Intake of PhIP from red meat was statistically significantly associated with total prostate cancer risk (top vs. bottom quintile HR=1.18, 95% CI 1.03-1.35), but not other HCAs (MeIQx, 1.12, 0.98-1.27, PhIP from white meat, 1.07, 0.94-1.21, DiMeIQx, 1.09, 0.97-1.21) or MDM (1.13, 1.00-1.28). For high grade (Gleason sum 7 with pattern 4+3 and Gleason sum 8-10, n=483 cases) and advanced cancers (n=281), we only observed positive associations for PhIP from red meat (top vs. bottom quintile: high grade: HR=1.44, 95% CI 1.04-1.98, p-trend=0.03; advanced: HR=1.50, 95% 0.99-2.26; p-trend=0.12), but associations for advanced cancers did not reach statistical significance. Observed associations remained similar after adjustment for total, unprocessed or processed red meat intake. CONCLUSION: Observed positive associations between PhIP intake from red meat and prostate cancer, particularly high-grade and possibly also advanced prostate cancer need to be confirmed in other studies. IMPACT: Results do not provide strong evidence that HCAs increase risk of prostate cancers

Effect of microstructures on the electron-phonon interaction in the disordered metals Pd60_{60}Ag40_{40}

Using the weak-localization method, we have measured the electron-phonon scattering times $\tau_{ep}$ in Pd$_{60}$Ag$_{40}$ thick films prepared by DC- and RF-sputtering deposition techniques. In both series of samples, we find an anomalous $1/\tau_{ep} \propto T^2\ell$ temperature and disorder dependence, where $\ell$ is the electron elastic mean free path. This anomalous behavior cannot be explained in terms of the current concepts for the electron-phonon interaction in impure conductors. Our result also reveals that the strength of the electron-phonon coupling is much stronger in the DC than RF sputtered films, suggesting that the electron-phonon interaction not only is sensitive to the total level of disorder but also is sensitive to the microscopic quality of the disorder.Comment: accepted for publication in Phys. Rev.

Heisenberg exchange enhancement by orbital relaxation in cuprate compounds

We calculate the Heisenberg exchange J in the quasi-2D antiferromagnetic cuprates La2CuO4, YBa2Cu3O6, Nd2CuO4 and Sr2CuO2Cl2. We apply all-electron (MC)SCF and non-orthogonal CI calculations to [Cu2O11]18-, [Cu2O9]14-, [Cu2O7]10- and [Cu2O7Cl4]14- clusters in a model charge embedding. The (MC)SCF triplet and singlet ground states are well characterized by Cu2+ (dx2-y2) and O2-. The antiferromagnetic exchange is strongly enhanced by admixing relaxed (MC)SCF triplet and singlet excited states, in which a single electron is transferred from the central O ion to Cu. We ascribe this effect to orbital relaxation in the charge transfer component of the wave function. Close agreement with experiment is obtained.Comment: publishe

Real-time visualization of a sparse parametric mixture model for BTF rendering

Bidirectional Texture Functions (BTF) allow high quality visualization of real world materials exhibiting complex appearance and details that can not be faithfully represented using simpler analytical or parametric representations. Accurate representations of such materials require huge amounts of data, hindering real time rendering. BTFs compress the raw original data, constituting a compromise between visual quality and rendering time. This paper presents an implementation of a state of the art BTF representation on the GPU, allowing interactive high fidelity visualization of complex geometric models textured with multiple BTFs. Scalability with respect to the geometric complexity, amount of lights and number of BTFs is also studied.Fundação para a Ciência e Tecnologi

Measurement of the Intrinsic Radiopurity of Cs-137/U-235/U-238/Th-232 in CsI(Tl) Crystal Scintillators

The inorganic crystal scintillator CsI(Tl) has been used for low energy neutrino and Dark Matter experiments, where the intrinsic radiopurity is an issue of major importance. Low-background data were taken with a CsI(Tl) crystal array at the Kuo-Sheng Reactor Neutrino Laboratory. The pulse shape discrimination capabilities of the crystal, as well as the temporal and spatial correlations of the events, provide powerful means of measuring the intrinsic radiopurity of Cs-137 as well as the U-235, U-238 and Th-232 series. The event selection algorithms are described, with which the decay half-lives of Po-218, Po-214, Rn-220, Po-216 and Po-212 were derived. The measurements of the contamination levels, their concentration gradients with the crystal growth axis, and the uniformity among different crystal samples, are reported. The radiopurity in the U-238 and Th-232 series are comparable to those of the best reported in other crystal scintillators. Significant improvements in measurement sensitivities were achieved, similar to those from dedicated massive liquid scintillator detector. This analysis also provides in situ measurements of the detector performance parameters, such as spatial resolution, quenching factors, and data acquisition dead time.Comment: 28 pages, 12 figure