Ultrafast nonlinearities of minibands in metallodielectric Bragg resonators

The nonlinear properties of metallodielectric DBRs are investigated via optical pump-probe techniques using a widely tunable, dual-colour, high-repetition rate, ultrafast setup. As a consequence of the Bragg-arranged multilayers, the electric field penetrates to different depths of the nanostructure at different excitation resonances, strongly enhancing the intrinsic nonlinear response of the metal in comparison with bulk films. The analyzed spectral response of these structures reveals how their nonlinear behavior is dominated by the pump-induced modification of the metal dielectric function. Fitting the simulated changes of the optical resonances using transfer-matrix methods matches experiment well, and shows the key effects of the spectral dependence of the spatial mode profiles.

Small aperture evanescent-mode waveguide antenna matched using distributed coupled resonators

Presented is a design methodology which permits the application of distributed coupled resonator bandpass filter principles to form wideband small-aperture evanescent-mode waveguide antenna designs. This approach permits matching of the complex antenna aperture admittance of an evanescent-mode open-ended waveguide to a real impedance generator, and thereby to a coaxial feed probe. A simulated reflection coefficient of < - 10 dB was obtained over a bandwidth of 20%, from 2.0-2.45 GHz, in a 2.58 GHz cutoff waveguide. Dielectric-filled propagating waveguide and air-filled evanescent-mode waveguide sections are used to form the resonators/coupling elements of the antenna's coupled resonator matching sections. Simulated realised gain variation from 3.4-5.0 dBi is observed across the bandwidth. The antenna's maximum aperture dimension is < 0.47 wavelength at the upper operating frequency and so it is suitable for use in a wide angle scanning phased array.

The Split in Stalin's Secretariat, 1939-1948

The question of the relationship between the Party and the State is crucial for understanding Soviet political system. Jonathan Harris goes to the heart of the matter by examining two principal views about the Communist Party’s role in Soviet society during the late 1930s and 1940s. Drawing on a meticulous analysis of the main party publications during this period, the author reconstructs the main battle lines between Georgii Malenkov and Andrei Zhdanov, the two antagonists of the book.
The book provides a very detailed and extensive analysis of the debates about Party's role in Soviet system as it appeared in the official press. However, without a much needed discussion of the 1948 reform of the Party apparatus and use of archival sources, there are few arguments which were not already present in the original article by Jonathan Harris published in 1976.

Compact filters using metal-dielectric inserts

A novel filter based on e-plane metal-dielectric insert in rectangular waveguide is proposed. Properties of the structure containing metallic septa, C- and I-shaped resonators placed in waveguide are investigated. Pseudo-elliptic cross-coupled filter with direct source-load coupling is designed, simulated and fabricated. Experimental results are presented to prove feasibility of the filter. Significant size reduction is achieved.

Preparation, Characterisation And Microwave Dielectric Properties Of Anbn-1o3n (N=5,6,8) Type Perovskite Compounds

The present study on the preparation , characterization and microwave dielectric properties of AnBn-1O3n (N=5,6,8) type perovskite compounds. The explored ceramics show dielectric constant between 11 and 54,quality factor in the range 2400 to 88900 GHz and Tf in the range -73 to +231ppm/0C.Most of the investigated cation deficient hexagonal perovskites show intermediate dielectric constant with high quality factors. This study gives a general introduction about material, scientific and technological aspects of DRs.Three important ,€r ,Q and Tf, used for the DR characterization are described. The relationship of the above parameters with the fundamental material characteristics is discussed. Different modes are excited when a DR is excited with suitable microwave spectrum of frequencies .A description of analytical determination of frequencies and construction of mode charts used for sample design and mode identification are also discussed. In this study several ceramics are developed for DR purposes, very little attention has been paid to grow the single crystals. It might be due to the fact that the difficulties and time involved in the growth of single crystals, big enough to function as microwave resonators make them expensive .However single crystals of these materials may have very high Q values. It is also possible that a better understanding of the dielectric properties in relation to the structure can be arrived using single crystals. Hence one of the future directions of dielectric resonator research should be to grow good quality single crystals of the above materials.

Comparison of Electromagnetic Band Gap and Split-Ring Resonator Microstrip Lines as Stop Band Structures

In this paper, microstrip lines magnetically coupled to splitring resonators (SRRs) are conquved to electromagnetic bundgup (EBG) nr,rrostrip lines in terns q/ their stop-heard penjbrnmrnce and dimensions. In bath types o/ trunsmis•siou lines, signal propagation is inhibited in it certain jequency bwuL For EBG microstrip lines, the central frequency of such a forbidden band is determined by the period of the structure, whereas in SRR-hased microstrip lines the position of the frequency gap depends on the quasi-static resonant frequency of the rings. The main relevant conrributiun of this paper is to provide a tuning procedure to control the gap width in SRR microstrip lines, and to show that by using SRRs, device dimensions ale much smaller than those required by EBGs in order to obtain similar stop-banal performance. This has been demonstrated by fill-wave electromagnetic simulations and experimentally verified from the characterization ql two fabricated microstrip lines: one with rectangular SRRs etched on the upper substrate side, and the other with a periodic perturbation cf'strip width. For similar rejection and 1-(;H,. gap width centered at 4.5 Gllz, it has been found that the SRR microstrip line is•,fve times shorter. In addition, no ripple is appreciable in the allowed band for the .SRR-hared structure, whereas due to dispersion, certain mismatch is expected in the EBG prototype. Due to the high-frequency selectivity, controllable gap width, and small dimensions, it is believed that SRR coupled to planar transmission lines can have an actual impact on the design of stop-band filters compatible with planar technology, and can be an alternative to present solutions based on distributed approaches or EBG

Dielectric properties of certain biological materials at microwave frequencies.

In the medical field, microwaves play a larger role for treatment than diagnosis. For the detection of diseases by microwave methods, it is essential to know the dielectric properties of biological materials. For the present study, a cavity perturbation technique was employed to determine the dielectric properties of these materials. Rectangular cavity resonators were used to measure the complex permittivity of human bile, bile stones, gastric juice and saliva. The measurements were carried out in the S and J bands. It is observed that normal and infected bile have different dielectric constant and loss tangent. Dielectric constant of infected bile and gastric juice varies from patient to patient. Detection and extraction of bile stone with possible method of treatment is also discussed.

Chipless RFID Tag Using Multiple Microstrip Open Stub Resonators

A novel compact RFID tag employing open stubs in a microstrip transmission line is proposed. The prototype of the tag is fabricated on a substrate of dielectric constant 4.4 and loss tangent 0.0018. The tag consists of microstrip open stub resonators and cross polarized transmitting and receiving disc monopole antennas. A prototype of 8 bit data encoded tag is demonstrated in this communication. Method for enhancing the performance of the RFID tag is also proposed. Magnitude or group delay response can be used to decode the tag informations

Frequency Coded Chipless RFID Tag using Spurline Resonators

A novel compact chipless RFID tag using spurline resonators is discussed in this paper. The detection of the tag's ID is using the spectral signature of a spurline resonator circuit. The tag has a data capacity of 8-bits in the range 2.38 to 4.04 GHz. The tag consists of a spurline multiresonating circuit and two cross polarized antennas. The prototype of the tag is fabricated on a substrate CMET/ LK4.3 of dielectric constant 4.3 and loss tangent 0.0018. The measured results show that group delay response can also be used to decode the tag’s identity

Bound Variable, Split Antecedent and Ellipsis Interpretations in L2 Portuguese: Implications for L2 Acquisition Theories.

Recently, in light of minimalist assumptions, some partial UG accessibility accounts to adult second language acquisition have made a distinction between the post-critical period ability to acquire new features based on their LF-interpretability (i.e. interpretable vs. uninterpretable features) (HAWKINS, 2005; HAWKINS; HATTORI, 2006; TSIMPLI; MASTROPAVLOU, 2007; TSIMPLI; DIMITRAKOPOULOU, 2007). The Interpretability Hypothesis (TSIMPLI; MASTROPAVLOU, 2007; TSIMPLI; DIMITRAKOPOULOU, 2007) claims that only uninterpretable features suffer a post-critical period failure and, therefore, cannot be acquired. Conversely, Full Access approaches claim that L2 learners have full access to UG’s entire inventory of features, and that L1/L2 differences obtain outside the narrow syntax. The phenomenon studied herein, adult acquisition of the Overt Pronoun Constraint (OPC) (MONTALBETTI, 1984) and inflected infinitives in nonnative Portuguese, challenges the Interpretability hypothesis insofar as it makes the wrong predictions for what is observed. The present data demonstrate that advanced learners of L2 Portuguese acquire the OPC and the syntax and semantics of inflected infinitives with native-like accuracy. Since inflected infinitives require the acquisition of new uninterpretable φ-features, the present data provide evidence in contra Tsimpli and colleagues’ Interpretability Hypothesis.

Performance and hormonal profile in broiler chickens fed with different energy levels during post restriction period

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influence of semen storage and cryoprotectant on post-thaw viability and fertility of stallion spermatozoa

The aim of the current study was to verify that stallion, spermatoza could be cooled for 24 hours and then frozen. In experiment I, one ejaculate from each of 13 stallions was used. Semen was collected and split into two parts; one part immediately frozen using standard cryo-preservation techniques and the other diluted, stored in an Equitainer for 24 hours, and then frozen. In experiment II, one ejaculate from each of 12 stallions was collected, diluted with Botu-Semen, and split into two parts: one cooled in an Equitainer and the other in Max-Semen Express without prior centrifugation. After 24 hours of cooling, the samples were centrifuged to remove seminal plasma and concentrate the sperm, and resuspended in Botu-Crio (R) extender containing on e of three cryoprotectant treatments (1% glycerol + 4% dimethylformamide, 1% glycerol + 4% dimethylacetamide and 1% glycerol + 4% methylformamide), maintained at 5 degrees C for 20 minutes, then frozen in nitrogen vapour. No difference was observed between the two cooling systems. The association of 1% glycerol and 4% methylformamide provided the best post-thaw progressive motility. For experiment III, two stallions were used for a fertility trial. Forty three inseminations were performed using 22 mares. No differences were seen in semen parameters and pregnancy rates when comparing the two freezing protocols (conventional and cooled/frozen). Pregnancy rates for conventional and cooled/frozen semen were, respectively, 72.7% and 82.3% (stallion A), and 40.0% and 50.0% (stallion B). We concluded that cooling equine-semen for 24 hours before freezing while maintaining sperm viability and fertility is possible.

Role of oxygen vacancies in the magnetic and dielectric properties of the high-dielectric-constant system CaCu3Ti4O12: An electron-spin resonance study

We report experiments of electron spin resonance (ESR) of Cu2+ in polycrystalline samples of CaCu3Ti4O12 post-annealed in different atmospheres. After being synthesized by solid state reaction, pellets of CaCu3Ti4O12 were annealed for 24 h at 1000 degrees C under air, Ar or O-2. Our temperature dependent ESR data revealed for all samples nearly temperature independent g value (2.15(1)) and linewidth for T > T-N approximate to 25 K. However, the values of ESR linewidth are strongly affected by the oxygen content in the sample. For instance, argon post-annealed samples show a much larger linewidth than the O-2 or air post-annealed samples. We attribute this broadening to an increase of the dipolar homogeneous broadening of the Cu2+ ESR lines due to the presence of oxygen vacancies which induce an S=1/2 spin inside the TiO6 octahedra. Correlation between a systematic dependence of the ESR linewidth on the oxygen content and the high dielectric constant of these materials is addressed. Also, ESR, magnetic susceptibility, and specific heat data for a single crystal of CaCu3Ti4O12 and for polycrystals of CdCu3Ti4O12 are reported.

Microstructure, crystalline phase, and dielectric property analyses of TiO2 composition with ZrO2 addition

For microwave applications, including mobile and satellite communications, ceramic resonators should have a high dielectric constant, low dielectric losses, and high frequency stability. In this sense, TiO2-ZrO 2 ceramics have been investigated as a function of sintering behavior, phase composition, and microstructure. The ceramics were densified reaching a value of about 86% of theoretical density at 1400°C sintering temperature. The ceramics are prepared by mixing raw materials with the following TiO2-ZrO2 weight % ratio: 100 to 0, 90 to 10, and 80 to 20, respectively. The measured dielectric constants are between 79 and 88 values, while the quality factor due to dielectric losses are between 2820 and 5170. These results point out the influence of Ti/Zr ratio on controlling the dielectric properties. © (2010) Trans Tech Publications.

Modeling Habitat Split: Landscape and Life History Traits Determine Amphibian Extinction Thresholds

Habitat split is a major force behind the worldwide decline of amphibian populations, causing community change in richness and species composition. In fragmented landscapes, natural remnants, the terrestrial habitat of the adults, are frequently separated from streams, the aquatic habitat of the larvae. An important question is how this landscape configuration affects population levels and if it can drive species to extinction locally. Here, we put forward the first theoretical model on habitat split which is particularly concerned on how split distance - the distance between the two required habitats - affects population size and persistence in isolated fragments. Our diffusive model shows that habitat split alone is able to generate extinction thresholds. Fragments occurring between the aquatic habitat and a given critical split distance are expected to hold viable populations, while fragments located farther away are expected to be unoccupied. Species with higher reproductive success and higher diffusion rate of post-metamorphic youngs are expected to have farther critical split distances. Furthermore, the model indicates that negative effects of habitat split are poorly compensated by positive effects of fragment size. The habitat split model improves our understanding about spatially structured populations and has relevant implications for landscape design for conservation. It puts on a firm theoretical basis the relation between habitat split and the decline of amphibian populations. © 2013 Fonseca et al.