312 research outputs found
Industrial Clustering and the Returns to Inventive Activity Canadian Biotechnology Firms, 1991-2000
We examine how industrial clustering affects biotechnology firmsâ innovativeness, contrasting similar firms not located in clusters or located in clusters that are or are not focused on the firmâs technological specialization. Using detailed firm level data, we find clustered firms are eight times more innovative than geographically remote firms, with largest effects for firms located in clusters strong in their own specialization. For firms located in a cluster strong in their specialization we also find that R&D productivity is enhanced by a firmâs own R&D alliances and also by the R&D alliances of other colocated firms.Biotechnology, industrial clustering, knowledge spillovers, R&D productivity, strategic alliances
Surveillance of resistance in bacteria causing communityâacquired respiratory tract infections
Bacterial resistance to antibiotics in communityâacquired respiratory tract infections is a serious problem and is increasing in prevalence worldâwide at an alarming rate. Streptococcus pneumoniae, one of the main organisms implicated in respiratory tract infections, has developed multiple resistance mechanisms to combat the effects of most commonly used classes of antibiotics, particularly the ÎČâlactams (penicillin, aminopenicillins and cephalosporins) and macrolides. Furthermore, multidrugâresistant strains of S.âpneumoniae have spread to all regions of the world, often via resistant genetic clones. A similar spread of resistance has been reported for other major respiratory tract pathogens, including Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pyogenes. To develop and support resistance control strategies it is imperative to obtain accurate data on the prevalence, geographic distribution and antibiotic susceptibility of respiratory tract pathogens and how this relates to antibiotic prescribing patterns. In recent years, significant progress has been made in developing longitudinal national and international surveillance programs to monitor antibiotic resistance, such that the prevalence of resistance and underlying trends over time are now well documented for most parts of Europe, and many parts of Asia and the Americas. However, resistance surveillance data from parts of the developing world (regions of Central America, Africa, Asia and Central/Eastern Europe) remain poor. The quantity and quality of surveillance data is very heterogeneous; thus there is a clear need to standardize or validate the data collection, analysis and interpretative criteria used across studies. If disseminated effectively these data can be used to guide empiric antibiotic therapy, and to supportâand monitor the impact ofâinterventions on antibiotic resistance
Mechanisms and outcome of severe mitral regulation after inoue balloon valvuloplasty
AbstractObjectives. The purpose of this study was to assess the incidence, mechanism and outcome of severe mitral regurgitation after treatment of mitral stenosis with percutaneous mitral valvuloplasty using the Inoue balloon.Background. Severe mitral regurgitation occurs in up to 15% of percutaneous balloon valvuloplasty procedures for acquired mitral stenosis. The incidence and mechanism of production of mitral regurgitation with the recently introduced single-ballon lnone technique have not been characterized.Methods. We examined the incidence, mechanism, predictors and outcome of severe mitral regurgitation after Inoue balloon valvuloplasty in 280 patients in the North American multicenter registry. Twenty-one patients who developed either clinically significant or angiographically severe regurgitation were identified, and their echocardiograms were reviewed to determine the mechanism of regurgitation. These patients were then compared with the remaining patients without severe regurgitation to identify predictors of this outcome.Results. The incidence of severe regurgitation in this study was 7.5%, and the mean grade of angiographic regurgitation in these patients increased from 0.9 ± 1.0 to 2.8 ± 0.7 (p < 0.05). The most common cause of regurgitation (43%) was rupture of clhordae tendineae to the anterior or posterior mitral leaflet. Tearing of a leaflet (usually the posterior one) occurred in 30% of patients; and no recognizable structural abnormality, with wide splitting of the commissures and a central regurgitant jet, was present in five patients (26%). All patients with definite posterior leaflet tears had heavily calcified leaflet. Patients who developed severe regurgitation had fewer balloon inflations and a higher grade of preexisting mitral regurgitation but were otherwish similar to the remaining patients without severe regurgitation. During 6-month follow-up, 71% of the patients with severe regurgitation were treated surgically; the grade of regurgitation decreased in four patients (19%), and five (24%) not required mitral valve replacement during 18 ± 5 month of follow-up.Conclusions. Severe mitral regurgitation is a relatively infrequent complication of Inoue balloon valvutoplasty and results from disruption of the valve integrity, chordal rapture and leaflet tearing. Careful balloon positioning may help avoid chordal rapture, and heavily calcified posterior lesflets may be at greater risk of tearing. Most patients who develop severe regurgitation will require nonemergency mitral valve replacement
Antecedent use of fluoroquinolones is associated with resistance to moxifloxacin in Clostridium difficile
ObjectiveMoxifloxacin is characterized by high activity against Gram-positive cocci and some Gram-positive and -negative anaerobes, including Clostridium difficile. This study investigates the role of prior quinolone use in relation to patterns of susceptibility of C. difficile to moxifloxacin.MethodsSixty-three clinical isolates of C. difficile were investigated for toxigenicity, susceptibility to moxifloxacin, and mutations in the DNA gyrase gene. The medical histories for 50 of these patients were available and used to identify previous fluoroquinolone use.ResultsThirty-three (52.4%) strains showed resistance to moxifloxacin (MICs â„ 16 mg/L). All moxifloxacin-resistant strains harbored a mutation at amino acid codon Ser-83 of gyrA. Forty-five isolates (71.4%) were toxigenic; all moxifloxacin-resistant strains were in this group. Resistance to moxifloxacin was associated with prior use of fluoroquinolones (P-value 0.009, chi-square).ConclusionsAlthough the use of moxifloxacin to treat C. difficile-associated diarrhea is not likely to be common, these data show a relationship between antecedent fluoroquinolone use and resistance to moxifloxacin in C. difficile isolates, and raise questions regarding selection pressure for resistance placed on colonizing bacteria exposed to fluoroquinolones. Mutations in gyrA are involved in moxifloxacin resistance
Critical Hysteresis from Random Anisotropy
Critical hysteresis in ferromagnets is investigated through a -component
spin model with random anisotropies, more prevalent experimentally than the
random fields used in most theoretical studies. Metastability, and the
tensorial nature of anisotropy, dictate its physics. Generically, random field
Ising criticality occurs, but other universality classes exist. In particular,
proximity to criticality may explain the discrepancy between
experiment and earlier theories. The uniaxial anisotropy constant, which can be
controlled in magnetostrictive materials by an applied stress, emerges as a
natural tuning parameter.Comment: four pages, revtex4; minor corrections in the text and typos
corrected (published version
The microbiome in chronic inflammatory airway disease : a threatened species
The human body is exposed to a multitude of microbes and infectious organisms throughout life. Many of these organisms colonise the
skin, gastrointestinal tract (GIT) and airway. We now recognise that this colonisation includes the lower airway, previously thought to be
sterile. These colonising organisms play an important role in disease prevention, including an array of chronic inflammatory conditions that
are unrelated to infectious diseases. However, new evidence of immune dysregulation suggests that early colonisation, especially of the GIT
and airway, by pathogenic micro-organisms, has deleterious effects that may contribute to the potential to induce chronic inflammation in
young children, which may only express itself in adult life.The South African Allergic Rhinitis Working Group is an
independent organisation. An annual meeting is supported by an unrestricted
educational grant from Aspen Pharmahttp://www.samj.org.zaam2016Paediatrics and Child Healt
Supersymmetry Without Prejudice at the LHC
The discovery and exploration of Supersymmetry in a model-independent fashion
will be a daunting task due to the large number of soft-breaking parameters in
the MSSM. In this paper, we explore the capability of the ATLAS detector at the
LHC ( TeV, 1 fb) to find SUSY within the 19-dimensional
pMSSM subspace of the MSSM using their standard transverse missing energy and
long-lived particle searches that were essentially designed for mSUGRA. To this
end, we employ a set of k previously generated model points in the
19-dimensional parameter space that satisfy all of the existing experimental
and theoretical constraints. Employing ATLAS-generated SM backgrounds and
following their approach in each of 11 missing energy analyses as closely as
possible, we explore all of these k model points for a possible SUSY
signal. To test our analysis procedure, we first verify that we faithfully
reproduce the published ATLAS results for the signal distributions for their
benchmark mSUGRA model points. We then show that, requiring all sparticle
masses to lie below 1(3) TeV, almost all(two-thirds) of the pMSSM model points
are discovered with a significance in at least one of these 11 analyses
assuming a 50\% systematic error on the SM background. If this systematic error
can be reduced to only 20\% then this parameter space coverage is increased.
These results are indicative that the ATLAS SUSY search strategy is robust
under a broad class of Supersymmetric models. We then explore in detail the
properties of the kinematically accessible model points which remain
unobservable by these search analyses in order to ascertain problematic cases
which may arise in general SUSY searches.Comment: 69 pages, 40 figures, Discussion adde
Supersymmetry Without Prejudice
We begin an exploration of the physics associated with the general
CP-conserving MSSM with Minimal Flavor Violation, the pMSSM. The 19 soft SUSY
breaking parameters in this scenario are chosen so as to satisfy all existing
experimental and theoretical constraints assuming that the WIMP is a
conventional thermal relic, ie, the lightest neutralino. We scan this parameter
space twice using both flat and log priors for the soft SUSY breaking mass
parameters and compare the results which yield similar conclusions. Detailed
constraints from both LEP and the Tevatron searches play a particularly
important role in obtaining our final model samples. We find that the pMSSM
leads to a much broader set of predictions for the properties of the SUSY
partners as well as for a number of experimental observables than those found
in any of the conventional SUSY breaking scenarios such as mSUGRA. This set of
models can easily lead to atypical expectations for SUSY signals at the LHC.Comment: 61 pages, 24 figs. Refs., figs, and text added, typos fixed; This
version has reduced/bitmapped figs. For a version with better figs please go
to http://www.slac.stanford.edu/~rizz
Search for Rare and Forbidden Dilepton Decays of the D+, Ds, and D0 Charmed Mesons
We report the results of a search for flavor-changing neutral current,
lepton-flavor violating, and lepton-number violating decays of D+, Ds, and D0
mesons (and their antiparticles) into modes containing muons and electrons.
Using data from Fermilab charm hadroproduction experiment E791, we examine the
pi,l,l and K,l,l decay modes of D+ and Ds and the l+l- decay modes of D0. No
evidence for any of these decays is found. Therefore, we present
branching-fraction upper limits at 90% confidence level for the 24 decay modes
examined. Eight of these modes have no previously reported limits, and fourteen
are reported with significant improvements over previously published results.Comment: 12 pages, 3 figures, LaTeX, elsart.cls, epsf.sty, amsmath.sty
Submitted to Physics Letters
Observation of a 1750 MeV/c^2 Enhancement in the Diffractive Photoproduction of K^+K^-
Using the FOCUS spectrometer with photon beam energies between 20 and 160
\gev, we confirm the existence of a diffractively photoproduced enhancement in
at 1750 \mevcc with nearly 100 times the statistics of previous
experiments. Assuming this enhancement to be a single resonance with a
Breit-Wigner mass shape, we determine its mass to be
\mevcc and its width to be \mevcc. We find no
corresponding enhancement at 1750 \mevcc in , and again neglecting any
possible interference effects we place limits on the ratio . Our results are consistent with previous
photoproduction experiments, but, because of the much greater statistics,
challenge the common interpretation of this enhancement as the
seen in annihilation experiments.Comment: 10 pages, 5 figure
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