REACTIVITY OF CHLOROPHYLL a/b-PROTEINS AND MICELLAR TRITON X-100 COMPLEXES OF CHLOROPHYLLS a OR b WITH BOROHYDRIDE

The reaction of several plant chlorophyll-protein complexes with NaBH4 has been studied by absorption spectroscopy. In all the complexes studied, chlorophyll b is more reactive than Chi a, due to preferential reaction of its formyl substituent at C-7. The complexes also show large variations in reactivity towards NaBH4 and the order of reactivity is: LHCI > PSII complex > LHCII > PSI > P700 (investigated as a component of PSI). Differential pools of the same type of chlorophyll have been observed in several complexes. Parallel work was undertaken on the reactivity of micellar complexes of chlorophyll a and of chlorophyll b with NaBH4 to study the effect of aggregation state on this reactivity. In these complexes, both chlorophyll a and b show large variations in reactivity in the order monomer > oligomer > polymer with chlorophyll b generally being more reactive than chlorophyll a. It is concluded that aggregation decreases the reactivity of chlorophylls towards NaBH4 in vitro, and may similarly decrease reactivity in naturally-occurring chlorophyll-protein complexes

Termination of the leprosy isolation policy in the US and Japan : Science, policy changes, and the garbage can model

BACKGROUND: In both the US and Japan, the patient isolation policy for leprosy /Hansen's disease (HD) was preserved along with the isolation facilities, long after it had been proven to be scientifically unnecessary. This delayed policy termination caused a deprivation of civil liberties of the involuntarily confined patients, the fostering of social stigmas attached to the disease, and an inefficient use of health resources. This article seeks to elucidate the political process which hindered timely policy changes congruent with scientific advances. METHODS: Examination of historical materials, supplemented by personal interviews. The role that science played in the process of policy making was scrutinized with particular reference to the Garbage Can model. RESULTS: From the vantage of history, science remained instrumental in all period in the sense that it was not the primary objective for which policy change was discussed or intended, nor was it the principal driving force for policy change. When the argument arose, scientific arguments were employed to justify the patient isolation policy. However, in the early post-WWII period, issues were foregrounded and agendas were set as the inadvertent result of administrative reforms. Subsequently, scientific developments were more or less ignored due to concern about adverse policy outcomes. Finally, in the 1980s and 1990s, scientific arguments were used instrumentally to argue against isolation and for the termination of residential care. CONCLUSION: Contrary to public expectations, health policy is not always rational and scientifically justified. In the process of policy making, the role of science can be limited and instrumental. Policy change may require the opening of policy windows, as a result of convergence of the problem, policy, and political streams, by effective exercise of leadership. Scientists and policymakers should be attentive enough to the political context of policies

Evaluation of some approximate Riemann solvers for transient open channel flows

Summarization: This paper constructs, presents and compares four approximate Riemann solvers for use with solving one-dimensional unsteady free surface flows. These solvers are usually the building blocks towards the construction of higher order accurate shock-capturing schemes. Details of the governing equations are presented. One dimensional dam-break flood wave propagations are analysed to demonstrate the applicability and the validity of the Riemann solvers. A treatment of source terms such as friction, slope and non-prismaticity of the channel is also presented. Computed results obtained with these solvers are compared with exact or published numerical solutions to define their characteristics and give an insight into the limitations of the methods, their relative strengths and weaknesses.Presented on: Journal of Hydraulic Researc

Implicit high-resolution methods for modelling one-dimensional open channel flow

Summarization: Three implicit high-resolution total variation diminishing (TVD) schemes are presented for solving the Saint-Venant equations. The applicability, performance and validity of these methods are investigated. Recently created benchmark solutions are reproduced for a wide range of cases, which include friction, nonuniform bed slopes, transitions between subcritical and supercritical flow, nonprismatic cross sections and hydraulic jumps. The tests produce satisfactory results without resorting to excessively fine grids. All the methods also produce satisfactory results for an idealized dambreak problem.Presented on: Journal of Hydraulic Researc