Neutral heavy lepton production at next high energy e+e−e^+e^- linear colliders

The discovery potential for detecting new heavy Majorana and Dirac neutrinos at some recently proposed high energy $e^+e^-$ colliders is discussed. These new particles are suggested by grand unified theories and superstring-inspired models. For these models the production of a single heavy neutrino is shown to be more relevant than pair production when comparing cross sections and neutrino mass ranges. The process $e^+e^- \longrightarrow {\nu} e^{\pm} W^{\mp}$ is calculated including on-shell and off-shell heavy neutrino effects. We present a detailed study of cross sections and distributions that shows a clear separation between the signal and standard model contributions, even after including hadronization effects.Comment: 4 pages including 15 figures, 1 table. RevTex. Accepted in Physical Review

Thin-layer agar for detection of resistance to rifampicin, ofloxacin and kanamycin in Mycobacterium tuberculosis isolates

BACKGROUND: In low-income countries there is a great need for economical methods for testing the susceptibility of Mycobacterium tuberculosis to antibiotics. OBJECTIVE: To evaluate the thin-layer agar (TLA) for rapid detection of resistance to rifampicin (RMP), ofloxacin (OFX) and kanamycin (KM) in M. tuberculosis clinical isolates and to determine the sensitivity, specificity and time to positivity compared to the gold standard method. METHODS: One hundred and forty-seven clinical isolates of M. tuberculosis were studied. For the TLA method, a quadrant Petri plate containing 7H11 agar with RMP, OFX and KM was used. Results were compared to the Bactec MGIT960 for RMP and the proportion method for OFX and KM. RESULTS: The sensitivity and specificity for RMP and OFX were 100% and for KM they were 100% and 98.7%, respectively. The use of a TLA quadrant plate enables the rapid detection of resistance to the three anti-tuberculosis drugs RMP, OFX and KM in a median of 10 days. CONCLUSION: TLA was an accurate method for the detection of resistance in the three drugs studied. This faster method is simple to perform, providing an alternative method when more sophisticated techniques are not available in low-resource settings