1,263 research outputs found
A wideband CPW ring power combiner with low insertion loss and high port isolation
In this paper we present a coplanar waveguide (CPW)-based ring power combiner that exhibits less than 0.8 dB insertion loss, better than 15 dB port match and higher than 22 dB isolation loss over the frequency range from 50 GHz to 100 GHz. Compared with the conventional 2-way Wilkinson combiner, the proposed ring power combiner replaces the resistor between the two input ports with two quasi quarter-wave CPWs, a 180º CPW phase inverter, and two resistors that lead to frequency-insensitive port isolation and wideband port match. The power combiner is realized using an electron beam-based GaAs MMIC process along with simple electron beam airbridge technology. These results agree well with 3D full-wave simulations
Circular Rydberg states of atomic hydrogen in an arbitrary magnetic field
We report a theoretical scheme using a B-spline basis set to improve the poor
computational accuracy of circular Rydberg states of hydrogen atoms in the
intermediate magnetic field. This scheme can produce high accuracy energy
levels and valid for an arbitrary magnetic field. Energy levels of hydrogen are
presented for circular Rydberg states with azimuthal quantum numbers = 10
- 70 as a function of magnetic field strengths ranging from zero to 2.35
10 T. The variation of spatial distributions of electron
probability densities with magnetic field strengths is discussed and
competition between Coulomb and magnetic interactions is illustrated.Comment: 14 pages, 2 figure
1,4-Dioxane-degrading consortia can be enriched from uncontaminated soils: prevalence of Mycobacterium and soluble di-iron monooxygenase genes
Two bacterial consortia were enriched from uncontaminated soil by virtue of their ability to grow on 1,4-dioxane (dioxane) as a sole carbon and energy source. Their specific dioxane degradation rates at 30°C, pH = 7 (i.e. 5.7 to 7.1 g-dioxane per g-protein per day) were comparable to those of two dioxane-metabolizing archetypes: Pseudonocardia dioxanivoransCB1190 and Mycobacterium dioxanotrophicusPH-06. Based on 16S rRNA sequencing, Mycobacterium was the dominant genus. Acetylene inhibition tests suggest that dioxane degradation was mediated by monooxygenases. However, qPCR analyses targeting the tetrahydrofuran/dioxane monooxygenase gene (thmA/dxmA) (which is, to date, the only sequenced dioxane monooxygenase gene) were negative, indicating that other (as yet unknown) catabolic gene(s) were responsible. DNA sequence analyses also showed threefold to sevenfold enrichment of group 5 and group 6 soluble di-iron monooxygenase (SDIMO) genes relative to the original soil samples. Whereas biodegradation of trace levels of dioxane is a common challenge at contaminated sites, both consortia degraded dioxane at low initial concentrations (300 μg l−1) below detectable levels (5 μg l−1) in bioaugmented microcosms prepared with impacted groundwater. Overall, this work shows that dioxane-degrading bacteria (and the associated natural attenuation potential) exist even in some uncontaminated soils, and may be enriched to broaden bioaugmentation options for sites experiencing insufficient dioxane catabolic capacity
Growth, immunity and ammonia excretion of albino and normal Apostichopus japonicus (Selenka) feeding with various experimental diets
An experiment was conducted to evaluate the effects of six experimental diets on growth performance, ammonia excretion and immunity of albino and normal Apostichopus japonicus. A factorial design was used, the factors being type of diets (six levels) and colour of A. japonicus (two levels). A total of 30 randomly selected albino A. japonicus were housed in each (60 × 50 × 30 cm3) of 18 blue plastic aquaria to form six groups in triplicate, and the same set-up
was used for the normal A. japonicus. Each group of animals was fed with one of the six experimental diets. Apparent dry matter digestibility (ADMD) and apparent crude protein digestibility (ACPD) were analysed using acid-insoluble
ash (AIA) content method. At the end of the experiment, all
A. japonicus were harvested and weighed to calculate growth parameters. After weighing, six individuals from each aquarium were randomly sampled for immune indices.
Results indicated that all growth parameters of A. japonicus increased with decreasing nutrient content in their diets (p < .01), whereas an opposite result was observed in
case of the ammonia-nitrogen production by A. japonicus. Normal A. japonicus grew better (p < .01) and produced lower (p < .01) quantity of ammonia nitrogen compared to the albino A. japonicus. Immunity particularly superoxide dismutase and lysozyme activities was higher (p < .05) in normal compared to albino A. japonicus. Considering
all measured variables, D1 (diet containing crude protein, crude lipid, carbohydrate and crude ash 51.8, 8.7, 231.3, 708.2 g/kg, respectively) was the best diet among all
experimental diets. More research is still needed to optimize nutrients in the diet of A. japonicus, as this study does not provide information about critical threshold level of nutrients in diets. Until then, diet D1 can be recommended for A. japonicus aquaculture
Reconstruction of Objects by Direct Demodulation
High resolution reconstruction of complicated objects from incomplete and
noisy data can be achieved by solving modulation equations iteratively under
physical constraints. This direct demodulation method is a powerful technique
for dealing with inverse problem in general case. Spectral and image
restorations and computerized tomography are only particular cases of general
demodulation. It is possible to reconstruct an object in higher dimensional
space from observations by a simple lower dimensional instrument through direct
demodulation. Our simulations show that wide field and high resolution images
of space hard X-rays and soft gamma rays can be obtained by a collimated
non-position-sensitive detector without coded aperture masks.Comment: 11 pages, 6 figure
The causal boundary of wave-type spacetimes
A complete and systematic approach to compute the causal boundary of
wave-type spacetimes is carried out. The case of a 1-dimensional boundary is
specially analyzed and its critical appearance in pp-wave type spacetimes is
emphasized. In particular, the corresponding results obtained in the framework
of the AdS/CFT correspondence for holography on the boundary, are reinterpreted
and very widely generalized. Technically, a recent new definition of causal
boundary is used and stressed. Moreover, a set of mathematical tools is
introduced (analytical functional approach, Sturm-Liouville theory, Fermat-type
arrival time, Busemann-type functions).Comment: 41 pages, 1 table. Included 4 new figures, and some small
modifications. To appear in JHE
Experimental Study and Finite Element Analysis of Critical Stresses of Reinforced Thermoplastic Pipes under Various Loads
In this paper, reinforced thermoplastic pipes (RTP) were studied under various loads. A total of five groups of specimens were designed to study the mechanical properties of RTPs under internal pressure, bending, a combination of internal pressure and bending moment, external pressure, and tension. This study obtained the bursting pressure of RTPs under internal pressure, the minimum bending radius under the bending moment, and the failure pressure under external pressure. At the same time, the mechanical properties of RTPs under various loads were analyzed using the finite element analysis. Analytical results agree well with the experimental ones. The finite element model established in this paper can be used for further research on the mechanical properties of RTPs
Electromagnetically induced transparency in multi-level cascade scheme of cold rubidium atoms
We report an experimental investigation of electromagnetically induced
transparency in a multi-level cascade system of cold atoms. The absorption
spectral profiles of the probe light in the multi-level cascade system were
observed in cold Rb-85 atoms confined in a magneto-optical trap, and the
dependence of the spectral profile on the intensity of the coupling laser was
investigated. The experimental measurements agree with the theoretical
calculations based on the density matrix equations of the rubidium cascade
system.Comment: 9 pages, 5 figure
Transverse momentum dependence of transverse flow in relativistic heavy-ion collisions
The strength of transverse flow is examined as a function of transverse
momentum using a simple, transversely moving thermal model and a more
realistic, relativistic transport model (ART). It is shown that the
dependence reveals useful information about the collective flow that is
complementary to that obtained from the standard in-plane transverse momentum
analysis. Interesting features of using the dependence to study the
equation of state of the superdense hadronic matter formed in relativistic
heavy-ion collisions are demonstrated.Comment: Latex file, 10 pages, 3 figures availabe upon request; Phys. Rev. C
(Aug., 1996) in pres
- …