Broadband Electrically Small Circularly Polarized Directive Antenna

© 2013 IEEE. A broadband electrically small antenna with directive circularly polarized radiation is presented. It is composed of a compact single-feed crossed dipole driver, which is backed by a near-field resonant parasitic (NFRP) reflector to achieve the directive radiation pattern. The NFRP reflector is designed to generate extra resonances and minimum axial ratio (AR) points in the antenna system. These features are combined with those resulting from the driver to broaden the operational bandwidth. The proposed antenna was fabricated and measured. The antenna prototype, with a low profile (0.066 λo at 1.45 GHz) and an electrically small size (ka = 0.71 at 1.45 GHz), has a measured S11<-10 dB bandwidth of 25.66% (1.362-1.763 GHz) and a 3-dB AR bandwidth of 10.56% (1.390-1.545 GHz). Additionally, the measurements resulted in a broadside gain of 2.31 ± 0.4 dBic and an average radiation efficiency of 80% within the operational bandwidth

Reconfigurable circularly polarized cross-dipole antenna with a near-field resonant parasitic element

© Institution of Engineering and Technology.All Rights Reserved. This paper presents a polarization switchable circularly polarized (CP) antenna that consists of a compact single-feed crossed dipole loaded with a near-field resonant parasitic (NFRP) element. This antenna is placed above a metallic reflector to enhance its gain and broadside radiation pattern. A meander line with an arrowhead-shaped ending was applied to all arms of the crossed dipole and NFRP elements for compactness. By adjusting the end size of the NFRP element, the antenna was capable of switching its polarization from right-hand circular polarization to left-hand circular polarization and vice versa. The reconfigurability is realized by controlling the ON/OFF states of 8 PIN-diodes, which are inserted into the arrowhead endings of the NFRP element. For the RHCP mode, the antenna yields a |S11| 6.0 dBic and a radiation efficiency of > 70% across its operational bandwidth

Applications of circularly polarized crossed dipole antennas

© 2014 IEEE. Circularly polarized crossed dipole antennas are presented in this paper. A compact crossed dipole is realized with the use of a meander line and a barbed end in each dipole arm. A vacant-quarter printed ring is used as a 90° phase delay line to achieve circularly polarized radiation. For multi-band applications, each dipole arm is divided into multi-branches with different lengths to obtain multiple resonances. These radiators can be equipped with different reflectors, such as a finite planar metallic conductor, a cavity-backed metallic conductor, and a finite artificial magnetic conductor to obtain the desired antenna radiation characteristics. These antennas are quite practical for many wireless communication systems, such as satellite communications, global positioning systems, wireless local area networks, and radio-frequency identification devices

Compact Crossed-Dipole Antennas Loaded with Near-Field Resonant Parasitic Elements

© 2016 IEEE. Two compact planar crossed-dipole antennas loaded with near-field resonant parasitic (NFRP) elements are reported. The NFRP and crossed-dipole elements are designed for the desired circularly polarized (CP) radiation. By placing the NFRP element over the driven element at angles of 0° and 45°, respectively, dual-band and broadband CP antennas are realized. All radiating elements of antennas are 35 mm × 35 mm × 0.508 mm (0.187 λ0 × 0.187 λ0 × 0.0027 λ0 at 1.6 GHz) in size. The dual-band CP antenna has a measured S11 <-10-dB bandwidth of 226 MHz (1.473-1.699 GHz) and measured 3-dB axial ratio (AR) bandwidths of 12 MHz (1.530-1.542 GHz) and 35 MHz (1.580-1.615 GHz) with minimum AR CP frequencies of 1.535 GHz (AR = 0.26 dB) and 1.595 GHz (AR = 2.08 dB), respectively. The broadband CP antenna has a measured S11 <-10-dB bandwidth of 218 MHz (1.491-1.709 GHz) and a 3-dB AR bandwidth of 145 MHz (1.490-1.635 GHz). These compact antennas yield bidirectional electromagnetic fields with high radiation efficiency across their operational bandwidths

Neurogenesis Drives Stimulus Decorrelation in a Model of the Olfactory Bulb

The reshaping and decorrelation of similar activity patterns by neuronal networks can enhance their discriminability, storage, and retrieval. How can such networks learn to decorrelate new complex patterns, as they arise in the olfactory system? Using a computational network model for the dominant neural populations of the olfactory bulb we show that fundamental aspects of the adult neurogenesis observed in the olfactory bulb -- the persistent addition of new inhibitory granule cells to the network, their activity-dependent survival, and the reciprocal character of their synapses with the principal mitral cells -- are sufficient to restructure the network and to alter its encoding of odor stimuli adaptively so as to reduce the correlations between the bulbar representations of similar stimuli. The decorrelation is quite robust with respect to various types of perturbations of the reciprocity. The model parsimoniously captures the experimentally observed role of neurogenesis in perceptual learning and the enhanced response of young granule cells to novel stimuli. Moreover, it makes specific predictions for the type of odor enrichment that should be effective in enhancing the ability of animals to discriminate similar odor mixtures

Emergent Phenomena Induced by Spin-Orbit Coupling at Surfaces and Interfaces

Spin-orbit coupling (SOC) describes the relativistic interaction between the spin and momentum degrees of freedom of electrons, and is central to the rich phenomena observed in condensed matter systems. In recent years, new phases of matter have emerged from the interplay between SOC and low dimensionality, such as chiral spin textures and spin-polarized surface and interface states. These low-dimensional SOC-based realizations are typically robust and can be exploited at room temperature. Here we discuss SOC as a means of producing such fundamentally new physical phenomena in thin films and heterostructures. We put into context the technological promise of these material classes for developing spin-based device applications at room temperature

Non-Sexual Transmission of Trichomonas vaginalis in Adolescent Girls Attending School in Ndola, Zambia

OBJECTIVES: To identify risk factors for trichomoniasis among young women in Ndola, Zambia. METHOD: The study was a cross-sectional study among adolescent girls aged 13-16 years in Ndola, Zambia. Study participants were recruited from schools in selected administrative areas that represented the different socio-economic strata in town. Consenting participants were interviewed about their socio-demographic characteristics; sexual behaviour; and hygiene practices. Self-administered vaginal swabs were tested for Trichomonas vaginalis. HSV-2 antibodies were determined on serum to validate the self-reported sexual activity. RESULTS: A total of 460 girls participated in the study. The overall prevalence of trichomoniasis was 27.1%, 33.9% among girls who reported that they had ever had sex and 24.7% among virgins. In multivariate analysis the only statistically significant risk factor for trichomoniasis was inconsistent use of soap. For the virgins, none of the risk factors was significantly associated with trichomoniasis, but the association with use of soap (not always versus always) and type of toilet used (pit latrine/bush versus flush toilet) was of borderline significance. CONCLUSION: We found a high prevalence of trichomoniasis in girls in Ndola who reported that they had never had sex. We postulate that the high prevalence of trichomoniasis in virgins in Ndola is due to non-sexual transmission of trichomoniasis via shared bathing water and inconsistent use of soap

Unemployment and ill health: a connection through inflammation?

<p>Abstract</p> <p>Background</p> <p>Unemployment is a source of acute and long-term psychosocial stress. Acute and chronic psychosocial stress can induce pronounced changes in human immune responses. In this study we tested our hypothesis that stress-induced low-grade tissue inflammation is more prevalent among the unemployed.</p> <p>Methods</p> <p>We determined the inflammatory status of 225 general population subjects below the general retirement age (65 years in Finland). Those who had levels of both interleukin-6 (≥ 0.97 pg/mL) and high-sensitivity C-reactive protein (≥ 1.49 mg/L) above the median were assessed to have an elevated inflammatory status (n = 72).</p> <p>Results</p> <p>An elevated inflammatory status was more common among the unemployed than among other study participants (59% versus 30%, p = 0.011). In the final multivariate model, those who were unemployed had over five-fold greater odds for having an elevated inflammatory status (OR 5.20, 95% CI 1.55-17.43, p = 0.008).</p> <p>Conclusion</p> <p>This preliminary finding suggests that stress-induced low-grade inflammation might be a link between unemployment and ill health.</p

The serine protease domain of MASP-3: enzymatic properties and crystal structure in complex with ecotin.

International audienceMannan-binding lectin (MBL), ficolins and collectin-11 are known to associate with three homologous modular proteases, the MBL-Associated Serine Proteases (MASPs). The crystal structures of the catalytic domains of MASP-1 and MASP-2 have been solved, but the structure of the corresponding domain of MASP-3 remains unknown. A link between mutations in the MASP1/3 gene and the rare autosomal recessive 3MC (Mingarelli, Malpuech, Michels and Carnevale,) syndrome, characterized by various developmental disorders, was discovered recently, revealing an unexpected important role of MASP-3 in early developmental processes. To gain a first insight into the enzymatic and structural properties of MASP-3, a recombinant form of its serine protease (SP) domain was produced and characterized. The amidolytic activity of this domain on fluorescent peptidyl-aminomethylcoumarin substrates was shown to be considerably lower than that of other members of the C1r/C1s/MASP family. The E. coli protease inhibitor ecotin bound to the SP domains of MASP-3 and MASP-2, whereas no significant interaction was detected with MASP-1, C1r and C1s. A tetrameric complex comprising an ecotin dimer and two MASP-3 SP domains was isolated and its crystal structure was solved and refined to 3.2 Å. Analysis of the ecotin/MASP-3 interfaces allows a better understanding of the differential reactivity of the C1r/C1s/MASP protease family members towards ecotin, and comparison of the MASP-3 SP domain structure with those of other trypsin-like proteases yields novel hypotheses accounting for its zymogen-like properties in vitro

Chromatin Remodeling Pathways in Smooth Muscle Cell Differentiation, and Evidence for an Integral Role for p300

Phenotypic alteration of vascular smooth muscle cells (SMC) in response to injury or inflammation is an essential component of vascular disease. Evidence suggests that this process is dependent on epigenetic regulatory processes. P300, a histone acetyltransferase (HAT), activates crucial muscle-specific promoters in terminal (non-SMC) myocyte differentiation, and may be essential to SMC modulation as well.We performed a subanalysis examining transcriptional time-course microarray data obtained using the A404 model of SMC differentiation. Numerous chromatin remodeling genes (up to 62% of such genes on our array platform) showed significant regulation during differentiation. Members of several chromatin-remodeling families demonstrated involvement, including factors instrumental in histone modification, chromatin assembly-disassembly and DNA silencing, suggesting complex, multi-level systemic epigenetic regulation. Further, trichostatin A, a histone deacetylase inhibitor, accelerated expression of SMC differentiation markers in this model. Ontology analysis indicated a high degree of p300 involvement in SMC differentiation, with 60.7% of the known p300 interactome showing significant expression changes. Knockdown of p300 expression accelerated SMC differentiation in A404 cells and human SMCs, while inhibition of p300 HAT activity blunted SMC differentiation. The results suggest a central but complex role for p300 in SMC phenotypic modulation.Our results support the hypothesis that chromatin remodeling is important for SMC phenotypic switching, and detail wide-ranging involvement of several epigenetic modification families. Additionally, the transcriptional coactivator p300 may be partially degraded during SMC differentiation, leaving an activated subpopulation with increased HAT activity and SMC differentiation-gene specificity