1,754,956 research outputs found
Comparison of Mycobacterium tuberculosis drug susceptibility using solid and liquid culture in Nigeria.
Get PDFBACKGROUND: This study compares Mycobacterium tuberculosis culture isolation and drug sensitivity testing (DST) using solid (LJ) and liquid (BACTEC-MGIT-960) media in Nigeria. METHODS: This was a cross sectional survey of adults attending reference centres in Abuja, Ibadan and Nnewi with a new diagnosis of pulmonary tuberculosis (TB) or having failed the first-line TB treatment. Patients were requested to provide three sputum specimens for smear-microscopy and culture on LJ and BACTEC-MGIT-960. Positive cultures underwent DST for streptomycin, isoniazid, rifampicin and ethambutol. RESULTS: 527 specimens were cultured. 428 (81%) were positive with BACTEC-MGIT-960, 59 (11%) negative, 36 (7%) contaminated and 4 (1%) had non-tuberculosis mycobacteria (NTM). 411 (78%) LJ cultures were positive, 89 (17%) negative, 22 (4%) contaminated and 5 (1%) had NTM. The mean (SD) detection time was 11 (6) and 30 (11) days for BACTEC-MGIT-960 and LJ. DST patterns were compared in the 389 concordant positive BACTEC-MGIT-960 and LJ cultures. Rifampicin and isoniazid DST patterns were similar. Streptomycin resistance was detected more frequently with LJ than BACTEC-MGIT-960 and ethambutol resistance was detected more frequently with BACTEC-MGIT-960 than LJ, but differences were not statistically significant. MDR-TB was detected in 27 cases by LJ and 25 by BACTEC-MGIT-960 and using both methods detected 29 cases. CONCLUSIONS: There was a substantial degree of agreement between the two methods. However using the two in tandem increased the number of culture-positive patients and those with MDR-TB. The choice of culture method should depend on local availability, cost and test performance characteristics
ηππ model of X<SUP>0</SUP> and a possible η-π resonance
No full textAn ηππ model of the X0 meson at 960 MeV is proposed through factorable π-π and η-π s-wave forces. The over-all dynamics is described by a three-body Schrödinger equation under a nonrelativistic approximation which is justified by the relatively low Q value (∼120 MeV) of the particle with respect to decay into an ηππ system. The π-π interaction, which is used as input information, is taken to be of two types: (i) a smooth attractive force which falls short of the requirements of a π-π bound state (called ABC-type), and (ii) a force characterized by a long-range barrier surrounding an inner well, which is capable of producing a π-π resonance at several hundred MeV (called σ-type interaction). Using three-body techniques proposed earlier by one of us (A.N.M.), the nature and strength of the η-π interaction is deduced from a knowledge of the energy of the ηππ system at the experimental position of the X0-mass. It is found that a σ-type π-π interaction, designed to produce a π-π resonance at 400-600 MeV, requires the existence of a bound η-π system. On the other hand, an ABC-type π-π interaction demands an η-π resonance in the BeV region (via a σ-type η-π interaction). The physical implications of these results are discussed
Effect of π-π interaction on high-energy π-p scattering
No full textThe object of this paper is to examine the possibility of explaining the second maximum in (π-p) scattering in the framework of the Tamm-Dancoff approximation for (π-p) interaction, by postulating a resonant π-π interaction in the isotopic spin state I=0 of the π-π system. For this purpose the Tamm-Dancoff method in pseudosclar theory, as formulated by Dyson and others, is first extended so as to include the effects of a π-π interaction. This is achieved by introducing a Green's function whose form is determined on the assumption of a zero-range π-π interaction in the state I=0 of the π-π system. The solution of the "modified" integral equation is greatly simplified by assuming the π-p interaction to be weak compared with the π-π interaction (the reasons for which are given). The total inelastic cross section is then derived by using the unitary property of the S matrix.It is found that the Tamm-Dancoff approximation is unable to explain the (π-p) maximum on the basis of the proposed model. This is contrary to the result derived by other authors, who used the impulse approximation for the interaction of the incident meson with the meson cloud surrounding the nucleon
The T<SUB>3</SUB>(π, π) state of acridine
No full textThe 0---0 band maximum of the transition T3(π, π∗)←T1 (π, π∗) of acridine occurs at ≈10200±20 cm-1 in inert (n-hexane, benzene, CCl4), at 10220±20 cm-1 in polar (acetonitrile) and at 10170±50 cm-1 in hydrogen-bonding (methanol, 2-propanol and alkaline water) solvents. Based on the solvent-independent energy of T1 (π, π∗), the T3(π, π∗) state of acridine is estimated at 26050±50 cm-1 in all the solvents
Missed opportunities for tuberculosis diagnosis.
Get PDFBACKGROUND: In high tuberculosis (TB) burden, resource-poor countries, sputum smear microscopy remains the mainstay of diagnosis. The low sensitivity of this test means that patients with smear-negative but culture-positive TB pass undetected through the health care system. Such clinical episodes are missed opportunities for diagnosis and interruption of transmission, which might be averted through the application of more sensitive diagnostic tests. OBJECTIVES: To estimate the proportion of incident TB cases that might have been detected earlier than the actual date of diagnosis if a test more sensitive than smear microscopy had been used at an earlier presentation episode. METHOD: Retrospective cohort study in urban Peru, investigating health care facility interactions for symptoms suggestive of TB prior to TB diagnosis through patient interviews and a review of clinical records. RESULTS: Of 212 participants enrolled, 58% had one or more clinical interactions prior to their diagnostic episode. Of those with a prior episode, the median number of episodes was three. The median delay to diagnosis from first presentation was 26 days. CONCLUSION: There are clear missed opportunities for earlier TB diagnosis, delaying treatment initiation and continued spread of Mycobacterium tuberculosis to the community. The implementation of sensitive diagnostic tests appropriate to resource-poor settings should be given high priority
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Civilian Conservation
No full textMSS B 540 Civilian Conservation Corps Newsletters, 1935-1941Newsletters of Company 960, 193
The different photoisomerization efficiency of Azobenzene in the lowest nπ* and ππ* singlets: the role of a phantom state
No full textAzobenzene EZ photoisomerization, following excitation to the bright S(ππ*) state, is investigated by means of ab initio CASSCF optimizations and perturbative CASPT2 corrections. Specifically, by elucidating the S(ππ*) deactivation paths, we explain the mechanism responsible for azobenzene photoisomerization, the lower isomerization quantum yields observed for the S(ππ*) excitation than for the S1(nπ*) excitation in the isolated molecule, and the recovery of the Kasha rule observed in sterically hindered azobenzenes. We find that a doubly excited state is a photoreaction intermediate that plays a very important role in the decay of the bright S(ππ*). We show that this doubly excited state, which is immediately populated by molecules excited to S(ππ*), drives the photoisomerization along the torsion path and also induces a fast internal conversion to the S1(nπ*) at a variety of geometries, thus shaping (all the most important features of) the S(ππ*) decay pathway and photoreactivity. We reach this conclusion by determining the critical structures, the Minimum Energy Paths originating on the bright S(ππ*) state and on other relevant excited states including S1(nπ*) and by characterizing the conical intersections seams that are important in deciding the photochemical outcome. The model is consistent with the most recent time-resolved spectroscopic and photochemical data
- …
