On the IMF in a Triggered Star Formation Context

The origin of the stellar initial mass function (IMF) is a fundamental issue in the theory of star formation. It is generally fit with a composite power law. Some clues on the progenitors can be found in dense starless cores that have a core mass function (CMF) with a similar shape. In the low-mass end, these mass functions increase with mass, albeit the sample may be somewhat incomplete; in the high-mass end, the mass functions decrease with mass. There is an offset in the turn-over mass between the two mass distributions. The stellar mass for the IMF peak is lower than the corresponding core mass for the CMF peak in the Pipe Nebula by about a factor of three. Smaller offsets are found between the IMF and the CMFs in other nebulae. We suggest that the offset is likely induced during a starburst episode of global star formation which is triggered by the formation of a few O/B stars in the multi-phase media, which naturally emerged through the onset of thermal instability in the cloud-core formation process. We consider the scenario that the ignition of a few massive stars photoionizes the warm medium between the cores, increases the external pressure, reduces their Bonnor?Ebert mass, and triggers the collapse of some previously stable cores. We quantitatively reproduce the IMF in the low-mass end with the assumption of additional rotational fragmentation.Comment: 3 figure

Study of Xenopus orthologs of novel genes expressed in the mouse AVE

info:eu-repo/semantics/publishedVersio

BCG: Do we have an alternative?

Vaccination is generally used as a form of immunoprophylaxis, so that administration of the vaccine even a long. time before exposure to the wild-type infectious organism should afford protection. Since effector T and B cells are short-lived, a prime requisite for a vaccine is to generate immunological memory.1 In the case organisms such as mycobacteria which are obligate intracellular pathogens and which elicit granulomatous tissue reactions, artificial immunisation with live bacteria is required to induce protection.2,3 The only existing vaccine against tuberculosis is the BCG (Bacille Calmette - Guerin), an attenuated strain of M.bovis and it is mandatory or officially recommended in 182 countries or territories. Under the Expanded Programme on Immuisation (EPT) started by the Government of India in 1978, BCG is recommended to be given to all infants 3-9 months after birth.

Action of metronidazole in combination with isoniazid & rifampicin on persisting organisms in experimental murine tuberculosis

To study the activity of metronidazole on persisting tubercle bacilli, BALB/c mice were infected with Mycobacterium tuberculosis and, after 14 days, treated with isoniazid (H) or rifampicin (R) or isoniazid + rifampicin (HR) for 2 months. An untreated group and a group treated with metronidazole (M) alone served as controls. At the end of 2 months, M was added to the H, R, and HR regimen in half the mice, and the treatment was continued for 1 more month in all mice. At the end of treatment, no viable organisms were detected in the lung or spleen of mice treated with HR or HRM regimens. In contrast, compared to the mice treated with R alone, the log10 colony forming units (cfu) of mice treated with RM were lower by 1.84 and 0.52 in the lung and spleen, respectively. Similarly, compared to the H group, the log10 cfu were lower by 0.67 in the spleen of mice treated with HM, and no additional effect due to M was seen in the lung. Three months after stopping treatment, viable organisms were isolated from both the organs of all the groups. However, the log10 cfu in the lung and spleen for the groups with metronidazole were below the log10 cfu for the respective single or 2 drug groups, except the log10 cfu in the lung for the RM group. These findings suggest that metronidazole, given with bactericidal drugs such as rifampicin and isoniazid may be of value in eliminating persisting tubercle bacilli, but further studies are warranted

Minimal inhibitory concentrations of sulbactam/ampicillin against drug sensitive and drug resistant isolates of Mycobacterium tuberculosis

A total of 92 isolates of Mycobacteriurn tuberculosis consisting of equal numbers of sensitive and resistant strains was tested for their susceptibility to sulbactam and ampicillin (in the ratio of 1:2) on Lowenstein-Jensen (LJ) and 7H11 agar media. The geometric mean MIC was 63.97 μg/ml for the drug sensitive strains and 65.92 μg/ml for the resistant strains, and the overall mean was 65.01 μg/ml. The high MIC on LJ medium could be attributed to the higher protein content which resulted in greater binding of sulbactam/ampicillin. On the other hand, the geometric mean MIC on 7H11 medium was 26.73 μg/ml for sensitive strains and 23.82 μg/ml for resistant strains; the overall mean being 25.23 μg/ml. Although these MlCs of sulbactamampicillin are higher than those reported earlier, they can be easily achieved in serum. Further studies on experimental tuberculosis and in humans will be needed to prove the efficacy of sulbactam/ampicillin in the treatment of patients with multidrug resistant tuberculosis

Evaluation of the BACTEC radiometric method in the early diagnosis of tuberculosis

A comparison of the BACTEC radiometric method with the conventional culture and drug susceptibility testing methods on isolates from clinical specimens in pulmonary and extrapulmonary tuberculosis, childhood TB and TB in HIV-infected individuals was undertaken. In the case of pulmonary TB, the rate of isolation of positive cultures was significantly faster with the BACTEC method, with 87 per cent of the positives being obtained by 7 days, and 96 per cent by 14 days. However, while there was no difference in the total number of positive cultures by the two methods in smear positive pulmonary tuberculosis, in smear negative pulmonary TB, the BACTEC method yielded more number of positive cultures. In extrapulmonary TB, HIV-TB and childhood TB, although the BACTEC method did not yield additional positives, the detection of positives was considerably faster than by the conventional methods, in which the degree of growth was also scanty. The agreement in drug susceptibility tests was 94 per cent for streptomycin and isoniazid, 99 per cent for rifampicin and 91 per cent for ethambutol. Further, most of the drug susceptibility test results became available within 8 days by the BACTEC method. By facilitating early diagnosis, the BACTEC method may prove to be cost effective in a population with a high prevalence of tuberculosis, particularly in the extrapulmonary and paucibacillary forms of the disease

Bactericidal action of pulsed exposure to rifampicin, ethambutol, isoniazid & pyrazinamide on Mycobacterium tuberculosis in vitro

The bactericidal action of pulsed exposure to rifampicin (R), ethambutol (Emb), isoniazid (I) and pyrazinamide (Z) togcthcr on alternate days (REmbIZ) and as REmb and IZ separately on alternate days (REmb/IZ) on M.tuberculosis H37Rv, two isolates of M.tuberculosis sensitive to these drugs, as well as four isolates resistant to one or more drugs, was studied using an in vitro method. The experimental duration was 6 days. REmbIZ and REmb/IZ appeared to have equally good bactericidal action on M.tuberculosis strains in the in vitro system. The results suggest that splitting REmbIZ into REmb and IZ on alternate days in short course chemotherapy regimens for tuberculosis may not affect the bactericidal action of the regimens

Head-on collision of ultrarelativistic charges

We consider the head-on collision of two opposite-charged point particles moving at the speed of light. Starting from the field of a single charge we derive in a first step the field generated by uniformly accelerated charge in the limit of infinite acceleration. From this we then calculate explicitly the burst of radiation emitted from the head-on collision of two charges and discuss its distributional structure. The motivation for our investigation comes from the corresponding gravitational situation where the head-on collision of two ultrarelativistic particles (black holes) has recently aroused renewed interest.Comment: 4 figures, uses the AMSmat

Signal processing in local neuronal circuits based on activity-dependent noise and competition

We study the characteristics of weak signal detection by a recurrent neuronal network with plastic synaptic coupling. It is shown that in the presence of an asynchronous component in synaptic transmission, the network acquires selectivity with respect to the frequency of weak periodic stimuli. For non-periodic frequency-modulated stimuli, the response is quantified by the mutual information between input (signal) and output (network's activity), and is optimized by synaptic depression. Introducing correlations in signal structure resulted in the decrease of input-output mutual information. Our results suggest that in neural systems with plastic connectivity, information is not merely carried passively by the signal; rather, the information content of the signal itself might determine the mode of its processing by a local neuronal circuit.Comment: 15 pages, 4 pages, in press for "Chaos

Protective response in guineapigs exposed to Mycobacterium avium intracellulare/ M. scrofulaceum, BCG & south Indian isolates of M. tuberculosis

The protective immunity resulting from exposure to nontuberculous mycobacteria (NTM), BCG and virulent mycobacteria in different sequences was studied in the guineapig model employing strains prevalent in the south Indian BCG trial area and time kinetics to observe the immuno-modulation. The findings suggest that during the early course of challenge infection in guineapigs there was no interference with the immunity due to BCG, by prior exposure to NTM. In the animals sensitised with M. avium intracellulare before immunisation, the challenge infection was localised and confined to the site of inoculation, and only a few organisms reached the spleen.. However, at the later stages of the infection, as seen by the spleen viable counts at 12 wk, it appeared that the barrier at the localised site of infection may not be intact in the animals with prior exposure to NTM, and a few organisms disseminate to the spleen