1,331 research outputs found
In vivo colonization profile study of Bordetella bronchiseptica in the nasal cavity
Bordetella bronchiseptica chronically infects a wide range of mammals, and resides primarily in the nasal cavity of the infected host. Multiple virulence factors of Bordetella species have been studied in the context of lower respiratory tract infections, but relatively less is known about the bacterial life cycle in the nasal cavity. Evidences were discovered for Bvg intermediate (Bvgi) phase expression in vivo and that the major adhesin filamentous hemagglutinin plays a major role in the colonization of B. bronchiseptica in the unciliated olfactory epithelia of the nasal cavity
Observed Tightening of Tropical Ascent in Recent Decades and Linkage to Regional Precipitation Changes
Climate models predict that the tropical ascending region should tighten under global warming, but observational quantification of the tightening rate is limited. Here we show that the observed spatial extent of the relatively moist, rainy and cloudy regions in the tropics associated with largeâscale ascent has been decreasing at a rate of â1%/decade (â5%/K) from 1979 to 2016, resulting from combined effects of interdecadal variability and anthropogenic forcings, with the former contributing more than the latter. The tightening of tropical ascent is associated with an increase in the occurrence frequency of extremely strong ascent, leading to an increase in the average precipitation rate in the top 1% of monthly rainfall in the tropics. At the margins of the convective zones such as the Southeast Amazonia region, the contraction of largeâscale ascent is related to a longâterm drying trend about â3.2%/decade in the past 38 years
Antenna reconfiguration using metasurfaces
The paper describes the designs of a frequency-reconfigurable, polarization reconfigurable and pattern reconfigurable antennas using metasurfaces (MS). The frequency-reconfigurable and polarization reconfigurable antennas are composed of a simple circular patch antenna or slot antenna as the source antenna and a circular MS with the same diameter, with both source antenna and MS implemented using planar technology. The pattern reconfigurable antenna is composed of a circular patch antenna as the source antenna and a semicircular MS with the same diameter. In all these reconfigurable antennas, the MS is placed directly atop of the source antenna, making the antenna very compact and low profile with a thickness of only 0.05λ0. By rotating the MS around the center with respect to the source antenna, the frequency, polarization or pattern of the reconfigurable antenna can be reconfigured.published_or_final_versionThe 2014 Progress In Electromagnetics Research Symposium (PIERS 2014), Guangzhou, China, 25-28 August 2014. In PIERS Proceedings, 2014, p. 2400-240
Vertical Moist Thermodynamic Structure and SpatialâTemporal Evolution of the MJO in AIRS Observations
The atmospheric moisture and temperature profiles from the Atmospheric Infrared Sounder (AIRS)/Advanced Microwave Sounding Unit on the NASA Aqua mission, in combination with the precipitation from the Tropical Rainfall Measuring Mission (TRMM), are employed to study the vertical moist thermodynamic structure and spatialâtemporal evolution of the MaddenâJulian oscillation (MJO). The AIRS data indicate that, in the Indian Ocean and western Pacific, the temperature anomaly exhibits a trimodal vertical structure: a warm (cold) anomaly in the free troposphere (800â250 hPa) and a cold (warm) anomaly near the tropopause (above 250 hPa) and in the lower troposphere (below 800 hPa) associated with enhanced (suppressed) convection. The AIRS moisture anomaly also shows markedly different vertical structures as a function of longitude and the strength of convection anomaly. Most significantly, the AIRS data demonstrate that, over the Indian Ocean and western Pacific, the enhanced (suppressed) convection is generally preceded in both time and space by a low-level warm and moist (cold and dry) anomaly and followed by a low-level cold and dry (warm and moist) anomaly.
The MJO vertical moist thermodynamic structure from the AIRS data is in general agreement, particularly in the free troposphere, with previous studies based on global reanalysis and limited radiosonde data. However, major differences in the lower-troposphere moisture and temperature structure between the AIRS observations and the NCEP reanalysis are found over the Indian and Pacific Oceans, where there are very few conventional data to constrain the reanalysis. Specifically, the anomalous lower-troposphere temperature structure is much less well defined in NCEP than in AIRS for the western Pacific, and even has the opposite sign anomalies compared to AIRS relative to the wet/dry phase of the MJO in the Indian Ocean. Moreover, there are well-defined eastward-tilting variations of moisture with height in AIRS over the central and eastern Pacific that are less well defined, and in some cases absent, in NCEP. In addition, the correlation between MJO-related midtropospheric water vapor anomalies and TRMM precipitation anomalies is considerably more robust in AIRS than in NCEP, especially over the Indian Ocean. Overall, the AIRS results are quite consistent with those predicted by the frictional KelvinâRossby wave/conditional instability of the second kind (CISK) theory for the MJO
Union bounds for BER evaluation and code optimization of space-time codes in 2-by-2 MIMO systems
In this paper, an exact closed-form formula for the Pair-wise Error Probability (PEP) is derived for two transmit and two receive antennas MIMO systems using the probability density function (PDF) of the modified Euclidean distance. An exact Union Bound formed by this formula, together with the Asymptotic Union Bound, are studied for optimization and biterror rate (BER) evaluation of Space-Time (S-T) codes. Numerical calculations and Monte Carlo computer simulation have been used to study these two Union Bounds on a 2-by-2 MIMO system using a rotation-based diagonal S-T code (D code) in a block fading channel. Results show that the exact Union Bound is a very tight Bound for BER evaluation while the Asymptotic Union Bound is very accurate for code optimization. © 2006 IEEE.published_or_final_versionIEEE 63rd Vehicular Technology Conference (VTC 2006-Spring), Melbourne, Australia, 7-10 May 2006. In Proceedings of the 63rd IEEE VTC Spring 2006, v. 3, p. 1506-151
Metastatic Serous Carcinoma of the Testis: A Case Report and Review of the Literature
Serous tumours of the testis and paratestis are rare, with fewer than 50 cases reported in the literature. The majority of the reported cases have been borderline serous tumours, and these tend not to recur or metastasize. Conversely, serous carcinomas can metastasize but this is often a late event. The presence of invasion in an otherwise borderline tumour has also been associated with the development of metastatic disease several years later, thus highlighting the importance of extensive sampling of all cases of borderline serous tumours. We report a case of a young man diagnosed with serous carcinoma of the testis, occurring 18 years after first diagnosis of a testicular germ cell tumour in the contralateral testis. This pattern has not previously been reported
The AI Revolution in Education: Will AI Replace or Assist Teachers in Higher Education?
This paper explores the potential of artificial intelligence (AI) in higher
education, specifically its capacity to replace or assist human teachers. By
reviewing relevant literature and analysing survey data from students and
teachers, the study provides a comprehensive perspective on the future role of
educators in the face of advancing AI technologies. Findings suggest that
although some believe AI may eventually replace teachers, the majority of
participants argue that human teachers possess unique qualities, such as
critical thinking, creativity, and emotions, which make them irreplaceable. The
study also emphasizes the importance of social-emotional competencies developed
through human interactions, which AI technologies cannot currently replicate.
The research proposes that teachers can effectively integrate AI to enhance
teaching and learning without viewing it as a replacement. To do so, teachers
need to understand how AI can work well with teachers and students while
avoiding potential pitfalls, develop AI literacy, and address practical issues
such as data protection, ethics, and privacy. The study reveals that students
value and respect human teachers, even as AI becomes more prevalent in
education. The study also introduces a roadmap for students, teachers, and
universities. This roadmap serves as a valuable guide for refining teaching
skills, fostering personal connections, and designing curriculums that
effectively balance the strengths of human educators with AI technologies. The
future of education lies in the synergy between human teachers and AI. By
understanding and refining their unique qualities, teachers, students, and
universities can effectively navigate the integration of AI, ensuring a
well-rounded and impactful learning experience
Properties of an invariant set of weights of perceptrons
In this paper, the dynamics of weights of perceptrons are investigated based on the perceptron training algorithm. In particular, the condition that the system map is not injective is derived. Based on the derived condition, an invariant set that results to a bijective invariant map is characterized. Also, it is shown that some weights outside the invariant set will be moved to the invariant set. Hence, the invariant set is attracting. Computer numerical simulation results on various perceptrons with exhibiting various behaviors, such as fixed point behaviors, limit cycle behaviors and chaotic behaviors, are illustrated
- âŠ