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We report the utility of whole-genome sequencing (WGS) conducted in a clinically relevant time frame (ie, sufficient for guiding management decision), in managing a Streptococcus pyogenes outbreak, and present a comparison of its performance with emm typing.
A 2,000-bed tertiary-care psychiatric hospital.
Active surveillance was conducted to identify new cases of S. pyogenes. WGS guided targeted epidemiological investigations, and infection control measures were implemented. Single-nucleotide polymorphism (SNP)–based genome phylogeny, emm typing, and multilocus sequence typing (MLST) were performed. We compared the ability of WGS and emm typing to correctly identify person-to-person transmission and to guide the management of the outbreak.
The study included 204 patients and 152 staff. We identified 35 patients and 2 staff members with S. pyogenes. WGS revealed polyclonal S. pyogenes infections with 3 genetically distinct phylogenetic clusters (C1–C3). Cluster C1 isolates were all emm type 4, sequence type 915 and had pairwise SNP differences of 0–5, which suggested recent person-to-person transmissions. Epidemiological investigation revealed that cluster C1 was mediated by dermal colonization and transmission of S. pyogenes in a male residential ward. Clusters C2 and C3 were genomically diverse, with pairwise SNP differences of 21–45 and 26–58, and emm 11 and mostly emm120, respectively. Clusters C2 and C3, which may have been considered person-to-person transmissions by emm typing, were shown by WGS to be unlikely by integrating pairwise SNP differences with epidemiology.
WGS had higher resolution than emm typing in identifying clusters with recent and ongoing person-to-person transmissions, which allowed implementation of targeted intervention to control the outbreak.
Mental health law in Colombia has evolved over the past 50 years, in concert with worldwide recognition and prioritisation of mental healthcare. Laws and policies have become increasingly sophisticated to accommodate the ongoing transformations throughout Colombia's healthcare system and improvements in mental health screening, treatment and supportive care. Mental health law and policy development have been informed by epidemiological data on patterns of mental disorders in Colombia. Colombia is distinguished by the fact that its mental health laws and policies have been formulated during a 60-year period of continuous armed conflict. The mental health of Colombian citizens has been affected by population-wide exposure to violence and, accordingly, the mental health laws that have been enacted reflect this feature of the Colombian experience.
The copolymerization between TEOS (tetraethoxysilane) and silane derivatives was promoted by the application of high power ultrasound to the precursor liquid mixtures in the same way as in the classical sol-gel method. The specific organic precursor was selected from the silanol-terminated polymer family with different molecular functionality and the inorganic precursor was from the silicon alkoxide family. Ultrasound, through the acoustic cavitation process, influences the formation of a very fine distribution of silica particles and avoids cyclidation of the polymer, thus favoring copolymerization with the inorganic particles and leading to the formation of a highly porous and rubber-like solid aerogel. Creep compliance curves, corresponding to the time-dependent depth response to a step load, are imprint site dependent, with pore, soft and stiff sites discerned. In all cases, an instantaneous elastic deformation is apparent. For longer test times, depending on the imprint sites, elastic deformation and newtonian flow produce the rise and fall of the creep curve. Linear parts of the curve on a log-log scale indicate potential growth with small exponents for the creep compliance level. Isochrones stress-strain diagrams show a superlinear trend and an increase with time, which reveals the nonlinear viscoelasticity of these hybrid aerogels. The elasto-plastic response to creep can be tuned by the molecular functionality of the different silane derivatives studied.
We compare the dynamic responses of reflection high energy electron diffraction (RHEED) and optical reflectance-difference (RD) signals caused by abrupt changes in incident fluences of Ga and As during MBE growth of GaAs on (001) GaAs. Our results reveal that RHEED and RD originate mainly, although not completely, from structural order and chemical bonding, respectively, and thus provide complementary information for real-time studies of MBE growth. We also measure the wavelength dependence of the RD spectrum and show that it can be described approximately from 2 to 4 eV by a single Lorentzian absorption line centered at 2.4 eV.
We report the first investigation of the effect of dry etching parameters on the sidewall carrier recombination rate of GaAs/AIGaAs and lnPilnGaAsP microstructures. Surface recombination was measured as a function of ion voltage and etching time. The increase in recombination rate due to etching can be reversed by subsequent chemical removal of the immediate sidewall layer. By monitoring the recovery in recombination rate as a function of the amount of sidewall layer removed, the effective damage depth is inferred.
The epitaxical and thermally stable NiAI/(AI, Ga)As system is shown to meet all of the basic materials criteria for buried metal/compound semiconductor heterostructures. We describe the growth of these heterostructures by molecular beam epitaxy. Even the thinnest buried NiAI films grown thus far (1.5 nm) are electrically continuous and metallic. Electron tunneling and lateral transport measurements provide strong evidence for size quantization in NiAl films thinner than 3.5 nm. The merging of compound semiconductor tunneling barriers with epitaxical metallic quantum wells and the ability to selectively contact buried metallic quantum wells is expected to yield novel three-terminal devices.
We have investigated the carrier concentration effect on AlGaAs/GaAs superlattice mixing enhanced by Si doping. The Al0.01Ga0.99As/GaAs superlattice sample with various Si-doping concentrations was grown by molecular beam epitaxy (MBE). Secondary ion mass spectrometry (SIMS) and carrier concentration profiling were used to characterize the Al diffusion and the free-carrier concentration profiles. The Al diffusion coefficients at 800 C show a high power dependence on the free carrier concentration which is not consistent with a Ga vacancy diffusion mechanism. A possible explanation can be provided by a mechanism based on a Si pair diffusion model.
Understanding metal/semiconductor contacts is important for the fabrication of device structures. To date most studies have been aimed at understanding the metallurgical or the electrical properties. Directly measuring the impurity concentrations immediately beneath a contact rather than inferring it from electrical measurements has up until now been difficult. This paper describes a backside SIMS technique which not only demonstrates the ability of measuring doping concentrations close to a metal/semiconductor contact but also is capable of measuring the consumption of semiconductor material during a metal/semiconductor reaction. The sample preparation technique can be used to enable backside profiling using other profiling techniques such as Auger and x-ray photoelectron spectroscopy depth profiling, Rutherford backscattering, and backside electrical evaluation. The Ge/Pd/GaAs solid phase ohmic contact is used to demonstrate the technique.
The basic issues involved in the growth by molecular beam epitaxy (MBE) of
vertical-cavity surface-emitting lasers (VCSELs) are discussed. Successful
VCSEL optical information processing applications demonstrated to date are
discussed, including two-dimensional arrays, holographic memory retrieval,
optical addressing, wavelength division multiplexing, and tunable VCSEL
A variety of optical methods are now available for studying surface processes and for monitoring layer thicknesses and compositions during semiconductor crystal growth by molecular beam epitaxy (MBE), organometallic chemical vapor deposition (OMCVD), and related techniques. New capabilities for surface analysis are being provided by developing techniques such as reflectance-difference spectroscopy (RDS), which use intrinsic symmetries to suppress ordinarily dominant bulk contributions. Bulk and microstructural properties such as compositions and layer thicknesses can be determined by techniques such as spectroellipsometry (SE), which return information integrated over the penetration depth of light. Recent advances include the application of reflectance to monitor dynamic surface processes, RDS to characterize (001) GaAs surfaces in OMCVD environments, and SE to control growth of AlxGa1-x, As materials and structures.
We have studied excitation transfer from the host quantum well to strain-confined quantum dots. We find that there is a long-lived intermediate state acting as a reservoir, holding the excitation before it is thermally activated over a barrier to reach the quantum dot. The barrier height increases monotonically with dot size.
The first results of the females reproductive cycle of Maja brachydactyla (Braquiura: Majidae) off the coast of Asturias (north-west Spain) are presented. Mean size of mature females was 133·4 mm (N=1022) in 1997 and 125·0 mm (N=942) in 1998. Only one cohort is exploited each fishing season. This cohort passed through the terminal moult the year before and recruited in to the fishery beginning in June. The breeding cycle off the coast of Asturias begins in December and ends in November the following year. Results from this study indicate that females produce 3–4 broods per year in these waters, which is the highest reported number for M. brachydactyla. The results are discussed in terms of their importance for management of the fishery.
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