16,854 research outputs found
Corrugated horn with stable phase center for Ka-band compact antenna test range measurement systems
No full textIn this article, a corrugated horn feed antenna with a stable phase center is designed for the millimeter wave compact antenna test range (CATR). The calculation method of the phase center of a horn is analyzed in this article. The 45°-plane phase center is used as the combined phase center of the horn in order to perform the phase center calculation only once, thus faster, and to optimize the phase performance more conveniently. By adding an absorbing material surrounding the edge of the outer surface of the horn, the irregular currents on the outer surface of the horn are suppressed, thus achieving a more stable phase center. The absorbing material can also reduce the radar cross section of the antenna. The designed corrugated horn works in the 24–40 GHz wide band with the following performances: the deviation of the phase center in the working frequency band is less than ±0.25 mm, the phase variation within a ±30° beam width is less than ±2.5°. Moreover, the measured return loss is lower than −10 dB, the measured gain is 8–12 dBi, and the measured cross-polarization level is less than −30 dB. The beamwidth is about 56°–70° in the whole band, and the beamwidth difference between different planes is less than 5°. The achieved targets listed above makes the proposed corrugated horn suitable for very precise antenna measurements in CATR systems
sj-pdf-1-jdr-10.1177_00220345211044681 – Supplemental material for Trem1 Induces Periodontal Inflammation via Regulating M1 Polarization
No full textSupplemental material, sj-pdf-1-jdr-10.1177_00220345211044681 for Trem1 Induces Periodontal Inflammation via Regulating M1 Polarization by D. Wu, Y. Weng, Y. Feng, B. Liang, H. Wang, L. Li and Z. Wang in Journal of Dental Research</p
An 1.7–2.7 GHz all-weather broadband High-gain antenna with W-shape reflector for maritime communications
No full textAn all-weather broadband high-gain antenna for maritime communication applications is developed in this paper. The proposed antenna, which is devised from the perspective of hydrodynamics, hydrostatics, and electromagnetic performance, is based on combining a wideband high-efficiency electromagnetic radiation structure (WHEMS) and a W reflector to achieve both superior mechanical and electrical performances. The proposed W reflector has a fractional 3-dB gain bandwidth of 150 % for a three-dipole array radiator, which is 53 % and 90 % larger than the gain bandwidth of the classic planar reflectors and the corner reflectors, respectively. To better adapt to the harsh marine environment and its potential IoT demands, the proposed antenna is devised to be light weight, small wind loading, high mechanical strength, small size, low cost, lightning-strike resistant, and consistent coefficient of thermal expansion, without the need of any radome. Two W reflector prototypes are ideated and manufactured from sheets and metal rods, denoted as Antenna I and Antenna II, respectively. Both the antennas realize 10–13 dBi gains in a 45 % bandwidth (1.7–2.7 GHz) with the sidelobe level lower than 12 dB, and a front-to-back ratio larger than 18 dB. The anti-deformation property of the proposed Antenna II is demonstrated to be 3.8 times higher than that of the classic Yagi antenna to be used in an open-ocean environment with a typhoon of force 1
Lyman break galaxies and the star formation rate of the Universe at z ~ 6
Get PDFWe determine the space density of UV-luminous starburst galaxies at z≈ 6 using deep HST ACS SDSS-i′ (F775W) and SDSS-z′ (F850LP) and VLT ISAAC J and Ks band imaging of the Chandra Deep Field South. We find eight galaxies and one star with (i′−z′) > 1.5 to a depth of z′AB= 25.6 (an 8σ detection in each of the 3 available ACS epochs). This corresponds to an unobscured star formation rate of ≈15 h−270 M⊙ yr−1 at z= 5.9, equivalent to L* for the Lyman-break population at z= 3–4 (ΩΛ= 0.7, ΩM= 0.3). We are sensitive to star-forming galaxies at 5.6 ≲z≲ 7.0 with an effective comoving volume of ≈1.8 × 105h−370 Mpc3 after accounting for incompleteness at the higher redshifts due to luminosity bias. This volume should encompass the primeval subgalactic-scale fragments of the progenitors of about a thousand L* galaxies at the current epoch. We determine a volume-averaged global star formation rate of (6.7 ± 2.7) × 10−4h70 M⊙ yr−1 Mpc−3 at z∼ 6 from rest-frame UV selected starbursts at the bright end of the luminosity function: this is a lower limit because of dust obscuration and galaxies below our sensitivity limit. This measurement shows that at z∼ 6 the star formation density at the bright end is a factor of ∼6 times less than that determined by Steidel et al. for a comparable sample of UV-selected galaxies at z= 3–4, and so extends our knowledge of the star formation history of the Universe to earlier times than previous work and into the epoch where reionization may have occurred
Fabrication and characterization of polyimide/Al2O3 composite films via surface modification and ion exchange technique
No full textPurpose: The aim of this study was to fabricate polyimide (PI)/Al2O3 composite films via surface modification and ion exchange techniques, and examine their properties. Design/methodology/approach: The method involves hydrolyzing the PI film double surface layers in an aqueous potassium hydroxide (KOH) solution and incorporating aluminium ions (Al3) into the hydrolyzed layers of the PI film via subsequent ion exchange, followed by a treatment of the Al3-loaded PI films with an aqueous ammonia solution, which leads to the formation of Al(OH)3 in the surface-modified layers. After a final thermal annealing treatment in ambient air, the Al(OH)3 decomposes to Al2O3, and forms composite layers on both surfaces of the re-imidized PI film. Findings: The PI/Al2O3 composite film obtained with a 6 hours of KOH treatment exhibited excellent thermal stability, good mechanical properties and better electric breakdown strength and corona-resistance properties than the pristine PI film. Practical implications: The method for obtaining the composite films in this paper is worth consideration, but additional research will be needed. Furthermore, this method is of general importance for the fabrication of composite PI films with tailored properties. Originality/value: This study showed that surface modification and ion-exchange techniques are powerful methodologies for the fabrication of PI/Al2O3 composite films
A diluent for prolonged motility of ocean pout (Macrozoarces americanus L.) sperm
No full textThe present study describes a new semen diluent (diluent C) which prolongs the sustained motility of ocean pout sperm, a distinguishing feature of the sperm of internally fertilizing teleosts. Sperm motilities were compared in the new diluent (C), based on the ionic composition of ocean pout seminal plasma, vs. four other semen diluents (A, B, D and E) ordinarily used for extending the semen of external fertilizers. While sperm retained motility after extension of ocean pout semen in all of these diluents, motility was significantly reduced following sperm resuspension in diluents B and D. Since sperm motility remained high in diluent C, formulated to closely mimic the composition of ocean pout seminal plasma, it was selected for additional experimentation. Negative effects were observed on sperm motility after dilution (> 1:10) of ocean pout semen with diluent C, but sperm motility could be restored by replacement of the seminal plasma. Of practical importance for storage of ocean pout sperm at 4 degrees C, it was shown that semen dilution 1:3 in diluent C preserved sperm motility beyond 5 days. Although ocean pout sperm tolerate a fairly wide range of K+ levels (0-30 mmol/l), the best motility was observed from 10-20 mmol/l [K+], similar to the ionic levels found in seminal plasma. Finally, since no change in fertility of ocean pout sperm occurred following 1:3 dilution of semen in diluent C, we conclude that diluent C is an effective medium for in vitro artificial egg insemination and prolonged motility of ocean pout sperm. (C) 1999 Elsevier Science B.V. All rights reserved.PT: J; CR: BAYNES SM, 1981, J FISH BIOL, V19, P259 BILLARD R, 1992, J EXP ZOOL, V261, P122 BILLARD R, 1993, AQUAT LIVING RESOUR, V6, P67 CHAMBEYRON F, 1990, AQUACULTURE, V90, P345 CHAUVAUD L, 1995, ENVIRON BIOL FISH, V43, P341 COBB JLS, 1973, J FISH BIOL, V5, P587 ERDAHL AW, 1987, AQUACULTURE, V60, P311 ERDAHL AW, 1987, AQUACULTURE, V60, P323 GALLANT RK, 1993, THERIOGENOLOGY, V40, P479 GATTI JL, 1990, J CELL PHYSIOL, V143, P546 GOODALL JA, 1989, AQUACULTURE, V77, P243 OHTA H, 1996, AQUACULTURE, V142, P107 PAVLOV DA, 1994, AQUACULTURE, V122, P295 STOSS J, 1983, AQUACULTURE, V30, P229 SUQUET M, 1993, J FISH BIOL, V42, P509 WANG Z, 1997, FISH PHYSIOL BIOCHEM, V16, P77 YAO Z, 1995, MOL REPROD DEV, V42, P58 YAO Z, 1995, P 5 INT S REPR PHYS YAO ZX, 1995, AQUACULTURE, V130, P361 YAO ZX, 1995, J FISH BIOL, V47, P171; NR: 20; TC: 6; J9: AQUACULTURE; PG: 11; GA: 182MLSource type: Electronic(1
Molecular and biological characterization of a novel mild strain of citrus tristeza virus in California
No full textStrain differentiating marker profiles of citrus tristeza virus (CTV) isolates from California have shown the presence of multiple genotypes. To better define the genetic diversity involved, full-length genome sequences from four California CTV isolates were determined by small-interfering RNA sequencing. Phylogenetic analysis and nucleotide sequence comparisons differentiated these isolates into the genotypes VT (CA-VT-AT39), T30 (CA-T30-AT4), and a new strain called S1 (CA-S1-L and CA-S1-L65). S1 isolates had three common recombination events within portions of genes from VT, T36 and RB strains and were transmissible by Aphis gossypii. Virus indexing showed that CA-VT-AT39 could be classified as a severe strain, whereas CA-T30-AT4, CA-S1-L and CA-S1-L65 were mild. CA-VT-AT39, CA-S1-L, and CA-S1-L65 reacted with monoclonal antibody MCA13, whereas CA-T30-AT4 did not. RT-PCR and RT-qPCR detection assays for the S1 strain were developed and used to screen MCA13-reactive isolates in a CTV collection from central California collected from 1968 to 2011. Forty-two isolates were found to contain the S1 strain, alone or in combinations with other genotypes. BLAST and phylogenetic analysis of the S1 p25 gene region with other extant CTV sequences from the NCBI database suggested that putative S1-like isolates might occur elsewhere (e.g., China, South Korea, Turkey, Bosnia and Croatia). This information is important for CTV evolution, detection of specific strains, and cross-protectio
Auswirkungen der Einbringung von Buche (Fagus sylvatica L.) auf die Artendiversität und Naturnähe von Nadelholzbeständen in Niedersachsen
No full textThe promotion and extension of continuous cover mixed stands with a simultaneous reduction of conifer-monocultures play a major role in current silvicultural practices in Central Europe. It is assumed that the admixture of the natural dominant beech (Fagus sylvatica) in pure non site-specific conifer stands automatically indicates better conditions in terms of nature conservation and forest management. To test this hypothesis three different conifer-beech-comparisons of pure and mixed stands in Lower Saxony are studied, analyzing plant species diversity and naturalness of understory vegetation as one important indicator for the ecological status of forests. Each comparison includes pure coniferous stands (Picea abies, Pinus sylvestris, Pseudotsuga menziesii), mixed coniferous-beech-stands, and pure beech stands on similar acidic mineral soils where the potential natural vegetation will be an oligotrophic beech forest (L u z u l o - Fa g e t um). The age of stands varies between 50 and 150 years. To specify tree species influence on site conditions and vegetation, the study also includes light climate and soil data of the stands. It is observed that, with regard to all comparisons, the admixture of beech reduces plant species diversity but increases naturalness of the stands. The intensity of beech admixture effects differs. While in Scots pine stands the impact of admixed beech is very noticeable, with the mixed stands being nearly identical with pure beech stands, the species change in Douglas-fir and Norway spruce stands proceeds more slowly. Assuming that the status in nature conservation and forest management is improving with increasing plant species diversity and increasing naturalness, the results of this study show a contrary development on a stand scale, as the potential natural vegetation of the L u z u l o - F a g e t u m is in its self very species poor on vascular plants.Die Förderung und Ausweitung von Mischwäldern bei gleichzeitiger Reduktion reiner Nadelholz-Bestände spielt aktuell eine große Rolle im mitteleuropäischen Waldbau. Gemeinhin wird angenommen, dass die Beimischung der standortsgemäßen Buche (Fagus sylvatica) in standortsfremden Nadelholz Monokulturen die Bedingungen im Sinne des Naturschutzes und der Forstwirtschaft verbessert. Diese Hypothese wird auf der Grundlage von drei unterschiedlichen Nadelholz- Buchen-Versuchsreihen geprüft. Im Mittelpunkt steht dabei die Bodenvegetation als wichtiger und sensitiver Indikator für den ökologischen Zustand von Wäldern. Jede Versuchsreihe umfasst reine Nadelholz-Bestände (Picea abies, Pinus sylvestris, Pseudotsuga menziesii), Nadelholz-Buchen- Mischbestände und reine Buchen-Bestände auf sauren Mineralböden, auf denen von Natur aus nährstoffarme Buchenwälder (L u z u l o - Fa g e t um) vorherrschen würden. Das Alter der Bestände variiert zwischen 50 und 150 Jahren. Schwerpunkte der Analyse sind die Artenvielfalt und Naturnähe der Bodenvegetation. Um den Einfluss der Baumarten auf den Standort und die Vegetation zu bewerten, werden die Licht- und Bodenverhältnisse der Bestände charakterisiert. Es zeigt sich, dass mit der Beimischung der Buche in allen Versuchsreihen die Pflanzenartenvielfalt abnimmt und die Naturnähe zunimmt. Unterschiedlich ist dabei die Intensität der Veränderungen. Zwischen den Kiefern-Buchen-Mischbeständen und den Kiefern-Reinbeständen bestehen sehr deutliche Unterschiede im Aufbau der Bodenvegetation, so dass die Mischbestände den Buchen-Reinbeständen bereits sehr ähnlich sind. In den Douglasien- und Fichten-Versuchsreihen vollzieht sich der Artenwechsel vergleichsweise unauffällig und kontinuierlich. Wenn man davon ausgeht, dass der naturschutzfachliche und waldbauliche Status sich sowohl mit zunehmender Phytodiversität als auch bei zunehmender Naturnähe verbessert, so zeigen diese Ergebnisse auf Bestandesebene eine gegenläufige Entwicklung, da das in der Region der potenziell natürlichen Vegetation entsprechende L u z u l o - Fa g e tum von Natur aus sehr artenarm an Gefäßpflanzen ist
The Benefits of Being Economics Professor A (and not Z)
Get PDFAlphabetic name ordering on multi-authored academic papers, which is the convention in the economics discipline and various other disciplines, is to the advantage of people whose last name initials are placed early in the alphabet. As it turns out, Professor A, who has been a first author more often than Professor Z, will have published more articles and experienced afaster growth rate over the course of her career as a result of reputation and visibility. Moreover, authors know that name ordering matters and indeed take ordering seriously: Several characteristics of an author group composition determine the decision to deviate from the default alphabetic name order to a significant extent.performance measurement, incentives, economists, name ordering
Logarithmic variance profiles and the corresponding f-1 spectra of temperature fluctuations in turbulent Rayleigh-Bénard convection
No full textWe report experimental results for the temperature variance 2(z) and the corresponding frequency spectra P(f) in turbulent Rayleigh-Bénard convection (RBC) in a cylindrical sample of aspect ratioT= D/L = 1:00 (D = 1:12 m is the diameter and L = 1:12 m the height). The measurements were conducted in the Rayleigh-number range 1011 < Ra < 1:35 1014 and Pr ' 0:8. For Ra = 1:35x1014, 2(z) could be described well by a logarithmic dependence on the vertical position z in a range of z 1 < z < z 2 with z 1 ' 70 and z 2 = 0:1L. Here L=(2Nu) is the thickness of a thin thermal sublayer adjacent to the horizontal plate where the heat flux (denoted by the Nusselt number Nu) is carried mostly by thermal diffusion. In the log layer, we found that the temperature spectra had a significant frequency range over which P(f) f with close to 1. As Ra decreased, increased so that the log layer became thinner. At Ra = 2:05 1011, z 2 < z 1 and therefore there was no range for a log layer. Correspondingly, the temperature spectrum near the horizontal plate did not have the f1 scaling form either
- …
