1,123 research outputs found
Las Vegas Academy Jazz Band III: A Celebration of Black History Month
Program listing performers and works performed
Analysis of a Waveguide-Fed Metasurface Antenna
The metasurface concept has emerged as an advantageous reconfigurable antenna
architecture for beam forming and wavefront shaping, with applications that
include satellite and terrestrial communications, radar, imaging, and wireless
power transfer. The metasurface antenna consists of an array of metamaterial
elements distributed over an electrically large structure, each subwavelength
in dimension and with subwavelength separation between elements. In the antenna
configuration we consider here, the metasurface is excited by the fields from
an attached waveguide. Each metamaterial element can be modeled as a
polarizable dipole that couples the waveguide mode to radiation modes. Distinct
from the phased array and electronically scanned antenna (ESA) architectures, a
dynamic metasurface antenna does not require active phase shifters and
amplifiers, but rather achieves reconfigurability by shifting the resonance
frequency of each individual metamaterial element. Here we derive the basic
properties of a one-dimensional waveguide-fed metasurface antenna in the
approximation that the metamaterial elements do not perturb the waveguide mode
and are non-interacting. We derive analytical approximations for the array
factors of the 1D antenna, including the effective polarizabilities needed for
amplitude-only, phase-only, and binary constraints. Using full-wave numerical
simulations, we confirm the analysis, modeling waveguides with slots or
complementary metamaterial elements patterned into one of the surfaces.Comment: Original manuscript as submitted to Physical Review Applied (2017).
14 pages, 14 figure
Questioning the Sustainability of English-Medium Instruction Policy in Science Classrooms: Teachers’ and Students’ Experiences at a Hong Kong Secondary School
Teaching science through English as a medium of instruction (EMI) is a growing phenomenon around the world. In Hong Kong, this was realised on a large scale in 2010, with the implementation of a “fine-tuning” compulsory language policy. This allowed Chinese-medium schools to adopt EMI fully. Yet, despite such rapid and widespread adoption, an adequate understanding of key stakeholders’ experiences in relation to their perceptions of what constitutes effective EMI science education remains scarce. Thus, we question the sustainability of EMI programs that are driven by top-down policy. In this case study, we explore the perspectives and experiences of six EMI science teachers and thirteen of their students as their secondary school transitions from partial to full EMI. From in-depth interviews (complemented by classroom observations), findings reveal that the transition to full EMI has presented challenges that appear to hinder students’ development of scientific knowledge and the language of science in English. This directly counters the primary goal of the fine-tuning policy. Nevertheless, findings also illuminate a number of coping strategies teachers and students use to deal with their changing curricula. Overall, we offer insights into this under-researched context of transitioning EMI programs and provide recommendations for future research and practice
KIFCI, A Novel Putative Prognostic Biomarker for Ovarian Adenocarcinomas: Delineating Protein Interaction Networks and Signaling Circuitries
Background: Amplified centrosomes in cancers are recently garnering a lot of attention as an emerging hub of diagnostic, prognostic and therapeutic targets. Ovarian adenocarcinomas commonly harbor supernumerary centrosomes that drive chromosomal instability. A centrosome clustering molecule, KIFC1, is indispensable for the viability of extra centrosome-bearing cancer cells, and may underlie progression of ovarian cancers. Methods: Centrosome amplification in low- and high- grade serous ovarian adenocarcinomas was quantitated employing confocal imaging. KIFC1 expression was analyzed in ovarian tumors using publically-available databases. Associated grade, stage and clinical information from these databases were plotted for KIFC1 gene expression values. Furthermore, interactions and functional annotation of KIFC1 and its highly correlated genes were studied using DAVID and STRING 9.1. Results: Clinical specimens of ovarian cancers display robust centrosome amplification and deploy centrosome clustering to execute an error-prone mitosis to enable karyotypic heterogeneity that fosters tumor progression and aggressiveness. Our in silico analyses showed KIFC1 overexpression in human ovarian tumors (n = 1090) and its upregulation associated with tumor aggressiveness utilizing publically-available gene expression databases. KIFC1 expression correlated with advanced tumor grade and stage. Dichotomization of KIFC1 levels revealed a significantly lower overall survival time for patients in high KIFC1 group. Intriguingly, in a matched-cohort of primary (n = 7) and metastatic (n = 7) ovarian samples, no significant differences in KIFC1 expression were detectable, suggesting that high KIFC1 expression may serve as a marker of metastases onset. Nonetheless, KIFC1 levels in both primary and matched metastatic sites were significantly higher compared to normal tissue . Ingenuity based network prediction algorithms combined with pre-established protein interaction networks uncovered several novel cell-cycle related partner genes on the basis of interconnectivity, illuminating the centrosome clustering independent agenda of KIFC1 in ovarian tumor progression. Conclusions: Ovarian cancers display amplified centrosomes, a feature of aggressive tumors. To cope up with the abnormal centrosomal load, ovarian cancer cells upregulate genes like KIFC1 that are known to induce centrosome clustering. Our data underscore KIFC1 as a putative biomarker that predicts worse prognosis, poor overall survival and may serve as a potential marker of onset of metastatic dissemination in ovarian cancer patients
Phenotypic and Genotypic Antibiotic Resistant diarrheagenic Escherichia coli pathotypes isolated from Children with Diarrhea in Nairobi City, Kenya
BACKGROUND፡ The marked genome plasticity of diarrheagenic Escherichia coli promotes emergence of pathotypes displaying unique phenotypic and genotypic resistance. This study examined phenotypic and genotypic antibiotic resistant diarrheagenic Escherichia coli pathotypes among children in Nairobi City, Kenya.METHODS: In a cross-sectional study, diarrheagenic Escherichia coli pathotypes were isolated from stool samples and their phenotypic and genotypic resistance against eight antimicrobial agents assayed.RESULTS: Diarrheagenic Escherichia coli was detected in 136(36.4%) children. Most of diarrheagenic Escherichia coli that were resistant to ampicillin, ceftriaxone, streptomycin, gentamycin, ciprofloxacin, chloramphenicol, erythromycin and tetracycline, harbored citm, bla CMY, aadA1, aac(3)-IV, qnr, catA, ere(A) and tet(A) corresponding resistant genes.CONCLUSION: Antimicrobial-resistant genes are highly prevalent among phenotypic resistant ETEC pathotypes indicating a possibility of horizontal gene transfer in spreading antibiotic resistant genes among E. coli pathotypes
Supernova 1998S at 14 years Postmortem: Continuing Circumstellar Interaction and Dust Formation
We report late-time spectroscopic observations of the Type IIn SN 1998S,
taken 14 years after explosion using the Large Binocular Telescope. The optical
spectrum exhibits broad emission features of [O I], [O II], [O III], H-alpha,
H-beta, and [Fe II]. The last decade of evolution has exhibited a strengthening
of the oxygen transitions, evidence that the late-time emission is powered by
increasingly metal-rich SN ejecta crossing the reverse shock. The H-alpha
luminosity requires that SN 1998S is still interacting with dense circumstellar
material (CSM), probably produced by the strong wind of a red supergiant
progenitor at least ~1000 years before explosion. The emission lines exhibit
asymmetric blueshifted profiles, which implies that the receding hemisphere of
the SN is obscured by dust. The [O III] line, in particular, exhibits a
complete suppression of its red wing. This could be the result of the expected
wavelength dependence for dust extinction or a smaller radial distribution for
[O III]. In the latter case, the red wing of [O III] could be absorbed by core
dust, while both the blue and red wings are absorbed by dust within the cool
dense shell between the forward and reverse shocks; this interpretation could
explain why late-time [O III] emission from SNe is often weaker than models
predict. The [O I] line exhibits double-peaked structure on top of the broader
underlying profile, possibly due to emission from individual clumps of ejecta
or ring-like structures of metal-rich debris. The centroids of the peaks are
blueshifted and lack a red counterpart. However, an archival spectrum obtained
on day 1093 exhibits a third, redshifted peak, which we suspect has become
extinguished by dust that formed over the last decade. This implies that the
"missing" red components of multi-peaked oxygen profiles observed in other SNe
might be obscured by varying degrees of dust extinction.Comment: Accepted to MNRAS on May 16 201
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