Effect of manganese doping on the size effect of lead zirconate titanate thin films and the extrinsic nature of dead layers

We have investigated the size effect in lead zirconate titanate (PZT) thin films with a range of manganese (Mn) doping concentrations. We found that the size effect in the conventional Pt/PZT/Pt thin-film capacitors could be systematically reduced and almost completely eliminated by increasing Mn doping concentration. The interfacial layer at the electrode-film interface appears to disappear almost entirely for the PZT films with 2% Mn doping levels, confirmed by the fits using the conventional in-series capacitor model. Our work indicates that the size effect in ferroelectrics is extrinsic in nature, supporting the work by Saad et al. Other implications of our results have also been discussed. By comparing a variety of experimental studies in the literature we propose a scenario that the dead layer between PZT (or barium strontium titanate, BST) and metal electrodes such as Pt and Au might have a defective pyrochlore/fluorite structure (possibly with a small portion of ferroelectric perovskite phase).Comment: 21 pages, 6 figure

Duality in Off-Shell Electromagnetism

In this paper, we examine the Dirac monopole in the framework of Off-Shell Electromagnetism, the five dimensional U(1) gauge theory associated with Stueckelberg-Schrodinger relativistic quantum theory. After reviewing the Dirac model in four dimensions, we show that the structure of the five dimensional theory prevents a natural generalization of the Dirac monopole, since the theory is not symmetric under duality transformations. It is shown that the duality symmetry can be restored by generalizing the electromagnetic field strength to an element of a Clifford algebra. Nevertheless, the generalized framework does not permit us to recover the phenomenological (or conventional) absence of magnetic monopoles.Comment: 18 page

Solutions for certain classes of Riccati differential equation

We derive some analytic closed-form solutions for a class of Riccati equation y'(x)-\lambda_0(x)y(x)\pm y^2(x)=\pm s_0(x), where \lambda_0(x), s_0(x) are C^{\infty}-functions. We show that if \delta_n=\lambda_n s_{n-1}-\lambda_{n-1}s_n=0, where \lambda_{n}= \lambda_{n-1}^\prime+s_{n-1}+\lambda_0\lambda_{n-1} and s_{n}=s_{n-1}^\prime+s_0\lambda_{k-1}, n=1,2,..., then The Riccati equation has a solution given by y(x)=\mp s_{n-1}(x)/\lambda_{n-1}(x). Extension to the generalized Riccati equation y'(x)+P(x)y(x)+Q(x)y^2(x)=R(x) is also investigated.Comment: 10 page

Clustered bottlenecks in mRNA translation and protein synthesis

We construct an algorithm that generates large, band-diagonal transition matrices for a totally asymmetric exclusion process (TASEP) with local hopping rate inhomogeneities. The matrices are diagonalized numerically to find steady-state currents of TASEPs with local variations in hopping rate. The results are then used to investigate clustering of slow codons along mRNA. Ribosome density profiles near neighboring clusters of slow codons interact, enhancing suppression of ribosome throughput when such bottlenecks are closely spaced. Increasing the slow codon cluster size, beyond $\approx 3-4$, does not significantly reduce ribosome current. Our results are verified by extensive Monte-Carlo simulations and provide a biologically-motivated explanation for the experimentally-observed clustering of low-usage codons

Linear response strength functions with iterative Arnoldi diagonalization

We report on an implementation of a new method to calculate RPA strength functions with iterative non-hermitian Arnoldi diagonalization method, which does not explicitly calculate and store the RPA matrix. We discuss the treatment of spurious modes, numerical stability, and how the method scales as the used model space is enlarged. We perform the particle-hole RPA benchmark calculations for double magic nucleus 132Sn and compare the resulting electromagnetic strength functions against those obtained within the standard RPA.Comment: 9 RevTeX pages, 11 figures, submitted to Physical Review

Strain Gradients in Epitaxial Ferroelectrics

X-ray analysis of ferroelectric thin layers of Ba1/2Sr1/2TiO3 with different thickness reveals the presence of internal strain gradients across the film thickness and allows us to propose a functional form for the internal strain profile. We use this to calculate the direct influence of strain gradient, through flexoelectric coupling, on the degradation of the ferroelectric properties of thin films with decreasing thickness, in excellent agreement with the observed behaviour. This work highlights the link between strain relaxation and strain gradients in epitaxial films, and shows the pressing need to avoid strain gradients in order to obtain thin ferroelectrics with bulk-like properties.Comment: 4 pages, 3 embedded figures (1 color), revTex

Low-Cost Compact Integrated Rectenna for Implantable Medical Receivers

This work describes a novel fully integrated rectenna circuit using tunnelling-based devices for implanted medical devices. An ASPAT (Asymmetric Spacer Layer Tunnel Diode) was used as the active rectifier due to its high non-linearity and temperature insensitivity features. A miniaturized geometry rectenna ( 1×5 mm 2 ) with improved matching characteristics was demonstrated, by integrating a Cockcroft-Walton rectifier with an L-shaped planar folded antenna structure operating at ISM frequency bands. The circuit performance was experimentally explored at various separation distance between transmitter and receiver units. For a 5cm transmission set-up, the rectenna with a single-stage rectifier delivered 0.8V output at 20dBm transmit power. An extended doubler configuration exhibited enhanced performance when multiple stages are used, is predicted to reach 0.24mW output power at 23dBm transmit power and yielding ~1.6V output voltage with an efficiency of 0.12%. These findings can assist in compensating for the degraded antenna gain attributed to the extremely small effective-radiating area of 0.04λ . Furthermore, the ability of controlling the antenna input impedance helps in circumventing the requirement for a matching circuitry thereby offering further reduction in chip size.UWIPOM2 project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 857654

Impact of nitrogen regime on fatty acid profiles of Desmodesmus quadricaudatus and Chlorella sp. and ability to produce biofuel

Abstract Microalgae have emerged as one of the most promising sources for fatty acid production. Since the various fatty acid profiles (chain length, degree of unsaturation, and branching of the chain) of the different sources influence biodiesel fuel properties, it is important to possess data on how the presence of NaNO3 as nitrogen source can influence the profile of produced fatty acids from algae. The fatty acid profiles of Desmodesmus quadricaudatus and Chlorella sp. were detected in pure batch cultures experiments. BG-11 nitrogen free medium and the medium contained 1.5 g NaNO3 l−1 were used in this investigation. At late stationary growth phase in nitrogen free medium, Chlorella sp. produced 58.39% saturated fatty acids and 41.60% unsaturated fatty acids. While in medium contained 1.5 g NaNO3 l−1Chlorella sp. produced 62.08% saturated fatty acids and 37.92% unsaturated fatty acids. In nitrogen free medium D. quadricaudatus produced 66.92% saturated fatty acids and 33.07% unsaturated fatty acids. While in cultures contained 1.5 g NaNO3 l−1D. quadricaudatus produced 51.62% saturated fatty acids and 48.37% unsaturated fatty acids. The fatty acid profile of Chlorella sp. and D. quadricaudatus that isolated from Egyptian water body and grown in nitrogen free medium may be suitable for biodiesel production. The results discussed and compared to fatty acid profiles produced by other algal species

Assessment of rock slope stability and structurally controlled failures along Samma escarpment road, Asir Region (Saudi Arabia)

Samma escarpment road is located in Asir Region, Saudi Arabia. It is located NW of Abha city. This escarpment road represents a major corridor in the area which connects different cities and touristic resorts in the region. It is descended from Sudah plateau at about 2700 m above sea level (asl) toward Wadi al Aws at about 1500 m asl. The total length of the road section is about 8 km which is passing through a highly mountainous area characterized by a complex geological and structural elements. This road has been exposed to frequent slope failures from time to time due to various factors such as intense rain storms, different geological and structural elements (weak rocks, shear zones, and faults), road characteristics (different horizontal/vertical curvatures and narrow road section), and human activities (uncontrolled rock cuts). Many sliding events have been documented along this escarpment road, particularly during and following rainstorms. The purpose of this paper is to evaluate the geology and structures by applying the rock mass rating (RMR) and slope stability (structurally controlled failures) along the Samma escarpment road. The stability analysis was performed using two Dips and RockPack III programs with the help of RocLab software. The Summa escarpment rock cuts were classified into 51 stations which were investigated in detail. Results indicated that most rock stations are poor quality, and 31, 32, and 41 stations are stable, 4, 6, and 7 stations are marginally stable, and 16, 13, and 3 stations are potentially unstable due to planar, wedge, and toppling failures, respectively. Finally, different recommendations and remediation methods were suggested as mitigation measures