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The fluctuations in the charge transport system of an EN Tandem Van de Graaff accelerator have been investigated by means of a frequency spectrum analyser. Frequency spectra of the terminal ripple, the short-circuit current and the voltage at the belt charge screen have been measured. Also the correlation function is examined between the last two signals. The mechanisms which can cause the measured fluctuations are discussed. The influence of fluctuations in the belt velocity and of vibrations is apparent.
Infection with HIV is characterized by very diverse disease-progression patterns across patients, associated with a wide variation in viral set-points. Progression is a multifactorial process, but an important role has been attributed to the HIV-specific T-cell response. To explore the conditions under which different setpoints may be explained by differences in initial CD4 and CD8 T-cell responses and virus inoculum, we have formulated a model assuming that HIV-specific CD4 cells are both targets for infection and mediators of a monoclonal or polyclonal immune response. Clones differ in functional avidity for HIV epitopes. Importantly, in contrast to previous models, in this model we obtained coexistence of multiple clones at steady-state viral set-point, as seen in HIV infection. We found that, for certain parameter conditions, multi...
Niet alleen Zakes Mda verbindt in zijn recente Zuid-Afrikaanse roman Het Rode Hart de geschiedenis van zijn personages met die van Saartjie Baartman. Saartjie Baartman duikt met grote regelmaat op in hedendaagse Zuid-Afrikaanse artefacten. Al in 1976 publiceerde de Zuid-Afrikaanse dichter Stephen Gray een dichtbundel getiteld Hottentot Venus.
The axiom system ACP of [BEK84a] was extended to cliscrete time in [BAB95]. Here we proceed to define the silent step in this theory in branching bisimulation semantics [GLW91, BAW90] rather than weak bisimulation semantics [MIL89, BEK85]. We present versions based on relative timing and on absolute timing. Both approaches are integrated using parametric timing. The time free ACP theory is embedded in the discrete time theory.
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