Reemergence of Epidemic Vibrio cholerae O139, Bangladesh

During March and April 2002, a resurgence of Vibrio cholerae O139 occurred in Dhaka and adjoining areas of Bangladesh with an estimated 30,000 cases of cholera. Patients infected with O139 strains were much older than those infected with O1 strains (p<0.001). The reemerged O139 strains belong to a single ribotype corresponding to one of two ribotypes that caused the initial O139 outbreak in 1993. Unlike the strains of 1993, the recent strains are susceptible to trimethoprim, sulphamethoxazole, and streptomycin but resistant to nalidixic acid. The new O139 strains carry a copy of the Calcutta type CTXCalc prophage in addition to the CTXET prophage carried by the previous strains. Thus, the O139 strains continue to evolve, and the adult population continues to be more susceptible to O139 cholera, which suggests a lack of adequate immunity against this serogroup. These findings emphasize the need for continuous monitoring of the new epidemic strains

Impact of Mastering Engineering on Student Learning and Perceptions in a Strength of Materials Course

The impact of Mastering Engineering on student learning of key concepts in strength of materials has been assessed in this study by comparing homework and examination grades received by students who used Mastering to those from prior years when it was not used. Student perceptions of the effectiveness of Mastering for helping promote learning were obtained through weekly surveys that students completed about their use of the tutorials and videos. In addition, student ratings of teaching effectiveness and the accomplishment of course learning outcomes were evaluated to see if there were any impacts on student perceptions of the course. From all of these evaluations, an assessment is made concerning the educational benefits of using Mastering Engineering in a strength of materials course

Impact of Upgrading Equipment for Strength of Materials Labs on Student Perceptions, Motivation, and Learning

Impact of Upgrading Equipment for Strength of Materials Labs on Student Perceptions, Motivation, and LearningAbstractAn important component of teaching introductory Strength of Materials (Mechanics ofMaterials) concepts to undergraduate engineering and technology students is the inclusion oflaboratory experiments, which give the students the opportunity to conduct tests and collect dataon the materials to obtain relevant properties. These laboratory experiments also allow studentsto observe firsthand the behavior of materials under different loading conditions, thereby givingthem a greater physical feel for these different behaviors. The equipment used to perform small-scale, desktop experiments can range from simple set-ups constructed using every day materialsavailable at a local hardware store to more sophisticated and expensive apparatus manufacturedby companies specializing in educational lab equipment. One question of interest to facultywhen faced with the decision of selecting the apparatus to be used for these small-scaleexperiments is whether student perceptions, motivation, and learning in the course are affectedby the sophistication and quality of the equipment used to conduct the experiments.The purpose of this study is to collect and evaluate data to determine if using more sophisticated,higher quality experimental equipment results in improved student outlooks and learningcompared to using simple set-ups constructed from every day materials purchased at a hardwarestore. Data collected includes student feedback obtained from short, written surveys about theeffectiveness of the laboratories performed with higher quality desktop equipment. Theusefulness of the higher end set-ups for improving student understanding of key concepts isevaluated by analyzing student performance on related examination questions for a cohort whoused more expensive apparatus versus a cohort from the previous year who used simpleexperimental set-ups. In addition, the impact of the laboratory equipment quality andsophistication on student perceptions and motivation for the overall course is studied by lookingat course rating information obtained from these two cohorts. Perceptions of the lab instructorson the advantages and disadvantages of using the more expensive versus less expensiveexperimental set-ups are also presented. The results of this study provides insights on whetherupgrading equipment for Strength of Materials labs helps improve the educational experience ofstudents for the overall course and whether those benefits appear to justify the costs of makingsuch upgrades

High spectro-temporal purity single-photons from silicon micro-racetrack resonators using a dual-pulse configuration

Single-photons with high spectro-temporal purity are an essential resource for quantum photonic technologies. The highest reported purity up until now from a conventional silicon photonic device is 92% without any spectral filtering. We have experimentally generated and observed single-photons with 98.0+-0.3 % spectro-temporal purity using a conventional micro racetrack resonator and an engineered dual pump pulse

Quantifying Hidden Nonlinear Noise in Integrated Photonics

We present experimental and simulated results to quantify the impact of nonlinear noise in integrated photonic devices relying on spontaneous four-wave mixing. Our results highlight the need for design rule adaptations to mitigate the otherwise intrinsic reduction in quantum state purity. The best strategy in devices with multiple parallel photon sources is to strictly limit photon generation outside of the sources. Otherwise, our results suggest that purity can decrease below 40%

Integrate and scale:A source of spectrally separable photon pairs

Integrated photonics is a powerful contender in the race for a fault-tolerant quantum computer, claiming to be a platform capable of scaling to the necessary number of qubits. This necessitates the use of high-quality quantum states, which we create here using an all-around high-performing photon source on an integrated photonics platform. We use a photonic molecule architecture and broadband directional couplers to protect against fabrication tolerances and ensure reliable operation. As a result, we simultaneously measure a spectral purity of $99.1 \pm 0.1$ %, a pair generation rate of $4.4 \pm 0.1$ MHz mW$^{-2}$, and an intrinsic source heralding efficiency of $94.0 \pm 2.9$ %. We also see a maximum coincidence-to-accidental ratio of $1644 \pm 263$. We claim over an order of magnitude improvement in the trivariate trade-off between source heralding efficiency, purity and brightness. Future implementations of the source could achieve in excess of $99$ % purity and heralding efficiency using state-of-the-art propagation losses

Reactivity of [Re\u3csub\u3e2\u3c/sub\u3e(CO)\u3csub\u3e8\u3c/sub\u3e(MeCN)\u3csub\u3e2\u3c/sub\u3e] with Thiazoles: Hydrido Bridged Dirhenium Compounds Bearing Thiazoles in Different Coordination Modes

Reactions of the labile compound [Re2(CO)8(MeCN)2] with thiazole and 4-methylthiazole in refluxing benzene afforded the new compounds [Re2(CO)7{μ-2,3-η2-C3H(R)NS}{η1-NC3H2(4-R)S}(μ-H)] (1, R = H; 2, R = CH3), [Re2(CO)6{μ-2,3-η2-C3H(R)NS}{η1-NC3H2(4-R)S}2(μ-H)] (3, R = H; 4, R = CH3) and fac-[Re(CO)3(Cl){η1-NC3H2(4-R)S}2] (5, R = H; 6, R = CH3). Compounds 1 and 2 contain two rhenium atoms, one bridging thiazolide ligand, coordinated through the C(2) and N atoms and a η1-thiazole ligand coordinated through the nitrogen atom to the same Re as the thiazolide nitrogen. Compounds 3 and 4 contain a Re2(CO)6 group with one bridging thiazolide ligand coordinated through the C(2) and N atoms and two N-coordinated η1-thiazole ligands, each coordinated to one Re atom. A hydride ligand, formed by oxidative-addition of C(2)–H bond of the ligand, bridges Re–Re bond opposite the thiazolide ligand in compounds 1–4. Compound 5 contains a single rhenium atom with three carbonyl ligands, two N-coordinated η1-thiazole ligands and a terminal Cl ligand. Treatment of both 1 and 2 with 5 equiv. of thiazole and 4-methylthiazole in the presence of Me3NO in refluxing benzene afforded 3 and 4, respectively. Further activation of the coordinated η1-thiazole ligands in 1–4 is, however, unsuccessful and results only nonspecific decomposition. The single-crystal XRD structures of 1–5 are reported

Quantum-Referenced Spontaneous Emission Tomography

We present a method of tomography that measures the joint spectral phase (JSP) of spontaneously emitted photon pairs originating from a largely uncharacterized ``target" source. We use quantum interference between our target source and a reference source to extract the JSP with four spectrally resolved measurements, in a process that we call quantum-referenced spontaneous emission tomography (Q-SpET). We have demonstrated this method on a photonic integrated circuit for a target micro-ring resonator photon-pair source. Our results show that spontaneously emitted photon pairs from a micro-ring resonator are distinctively different from that of stimulated emission, and thus cannot in general be fully characterized using classical stimulated emission tomography without detailed knowledge of the source