Urban Clinics in Lusaka

Five large urban clinics in Lusaka (urban and peri-urban population 150,000 in 1966.There are five large urban clinics in Lusaka (urban and peri-urban population 150,000 in 1966)1. These clinics are open from 8 a.in. to 4 p.in. on weekdays and from 8 a.in. to 10 a.in. on Sundays. They are extremely overworked as js the outpatient department of Lusaka Central Hospital to which clinic [)atients are referred. For six weeks during December 1965 and January 1966 a survey was conducted to see exactly what work the clinics and outpatient department were doing, with a view to planning future work. The survey was necessary because the official clinic returns are based on the patient's complaint and not on the diagnosis.Office of Global AIDS/US Department of State

Recurrent Variational Approach to the Two-Leg Hubbard Ladder

We applied the Recurrent Variational Approach to the two-leg Hubbard ladder. At half-filling, our variational Ansatz was a generalization of the resonating valence bond state. At finite doping, hole pairs were allowed to move in the resonating valence bond background. The results obtained by the Recurrent Variational Approach were compared with results from Density Matrix Renormalization Group.Comment: 10 pages, 14 Postscript figure

MEMS Gradiometers for Attitude Determination on CubeSats

This paper presents the design, fabrication and testing of a new high sensitivity gravity sensor for attitude determination in CubeSats. The project is a collaboration between the Institute for Gravitational Research at the University of Glasgow and ÅAC-Clyde. The gravitational gradiometer takes advantages of the technology of microelectromechanical systems (MEMS) and determines the attitude of the satellite by a differential gravity measurement, the principle at the base of gravitational gradiometry. The capacitive readout allows to measure the rotation of the MEMS gradiometer and consequently evaluate the angle changes of the CubeSat. The developed geometry consists of two symmetrical masses connected to a fixed support by four thin flexure hinges. The all-Silicon sensor resonates at a frequency of 6 Hz, and has a total mass of less than 2 g. It is expected that the sensor geometry and the readout demonstrated would be suitable to achieve the performances required from CubeSat systems and detect a rotation of the small satellite of 1 degree, in order to offer performance comparable to other state-of-the-art sensors currently available on the market

Effects of a recombinant gene expression on ColE1-like plasmid segregation in Escherichia coli

<p>Abstract</p> <p>Background</p> <p>Segregation of expression plasmids leads to loss of recombinant DNA from transformed bacterial cells due to the irregular distribution of plasmids between the daughter cells during cell division. Under non-selective conditions this segregational instability results in a heterogeneous population of cells, where the non-productive plasmid-free cells overgrow the plasmid-bearing cells thus decreasing the yield of recombinant protein. Amongst the factors affecting segregational plasmid instability are: the plasmid design, plasmid copy-number, host cell genotype, fermentation conditions etc. This study aims to investigate the influence of transcription and translation on the segregation of recombinant plasmids designed for constitutive gene expression in <it>Escherichia coli </it>LE392 at glucose-limited continuous cultivation. To this end a series of pBR322-based plasmids carrying a synthetic human interferon-gamma (hIFNγ) gene placed under the control of different regulatory elements (promoter and ribosome-binding sites) were used as a model.</p> <p>Results</p> <p>Bacterial growth and product formation kinetics of transformed <it>E. coli </it>LE392 cells cultivated continuously were described by a structured kinetic model proposed by Lee et al. (1985). The obtained results demonstrated that both transcription and translation efficiency strongly affected plasmid segregation. The segregation of plasmid having a deleted promoter did not exceed 5% after 190 h of cultivation. The observed high plasmid stability was not related with an increase in the plasmid copy-number. A reverse correlation between the yield of recombinant protein (as modulated by using different ribosome binding sites) and segregational plasmid stability (determined by the above model) was also observed.</p> <p>Conclusions</p> <p>Switching-off transcription of the hIFNγ gene has a stabilising effect on ColE1-like plasmids against segregation, which is not associated with an increase in the plasmid copy-number. The increased constitutive gene expression has a negative effect on segregational plasmid stability. A kinetic model proposed by Lee et al. (1985) was appropriate for description of <it>E. coli </it>cell growth and recombinant product formation in chemostat cultivations.</p

Niederländisch-Deutsche Kulturbeziehungen 1600-1830

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Activation and deactivation behavior of heteropoly acids as catalyst precursors

Activation and deactivation behavior of heteropoly acids as catalyst precursors O.Timpe, H. Noack, und G. Mestl§ Fitz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin Heteropoly acids (HPA) are important catalysts for selective partial oxidations due to their acid and redox active properties. Thee Keggin-type phosphorus molybdo acid H4[PMo12O40] is the basis for an industrially used catalyst in the methacrylic acid synthesis which contains vanadium too. The protons of the free HPA are partially exchanged by Cs+ ions. The insufficient stability of this class of substances does not allow their optimum use as catalysts. A continuous degradation of their catalytic properties and thus of the possible yields is observed under stationary reaction conditions. Due to their characteristic instability, it is unlikely that intact HPA´s are the active catalysts, although frequently stated in the literature. This correlates with the fact that the HPA has to be activated in the industrial application prior to the actual catalysis. The structural and chemical properties of the precursor-HPA are well characterized, correlate however only indirectly with the catalytic data. The oxides of the constituting transition metals are the final state of the HPA-decomposition, whose stoichiometry or degree of oxidation is determined by the surrounding atmosphere. The reaction pathway to these final decomposition products can be understood as a condensation process followed by complete structural reorganization. The loss of water occurs in two steps. The irreversible loss of structural water at elevated temperatures follows after the reversible loss of crystal water at temperatures below 400K. Oxygen defects are introduced into the Keggin anions with the loss of structural water. These defects are presumably the reason for the low reaction barriers of the subsequent structural reorganization of the defective Keggin anions. It could be shown by comparing thermogravimetric measurements of different molybdenum HPA, containing P as well as Si as the hetero atom, in different atmospheres that the reduction of the HPA occurs only after the loss of structural water. This reduction is the consequence of the loss of structural water because these HPA systems do not have a stability plateau after this step of water removal. Under oxidative conditions, the formation of MoO3 is observed after this step of loss of water. The comparison of HPA´s reveals a continuous mass loss of the P-containing samples after the loss of structural water under isothermal conditions in hydrogen atmosphere, which is qualitatively identified as the loss of P in form of reduced P-compounds, e.g. PH3. Directly after this mass loss, the TG curves show a step which is attributed to the reduction of the transition metal ions. The incorporation of V into the Keggin leads to an enhanced destabilizing effect in case of Si-HPA as compared to P-HPA. Investigations of the catalytic activity (TPRS) can be correlated with the TG data. After the loss of structural water, all investigated HPA are active for the partial oxidation reactions. This catalytic activity decreases with time on stream. Under catalytic conditions, the active fragments are not stable which were formed from the Keggin anions after loss of structural water. Total oxidation increases with the reactor temperature. In case of the Si-HPA, the total oxidation is the major reaction path already after the loss of structural water. It can be concluded from a comparison of the catalytic activities and selectivities of the different HPA that P stabilizes the fragments of the decomposed Keggins, which are characterized by a high degree of partial oxidation, in contrary to Si containing catalysts. Olefins react already at room temperature with the crystal water of the acidic HPA under water addition to alcohols. In this way the loss of water of the HPA samples is considerably increased and occurs already at room temperature. In contrast, HPA are not reduced by hydrogen at room temperature. The loss of structural water is shifted to lower temperatures in a similar way in presence of olefins. HPA preparations in which all protons of the HPA were exchanged by Cs+ ions exhibited an considerably enhanced stability toward reduction. These salts cannot desorb structural water. The decomposition and condensation of the Keggin anion fragments therefore is suppressed. Hence, these Cs salts are catalytically inactive for the partial oxidation. In contrast, more unstable tetraalkyl ammionum salts are catalytically active already at much lower temperatures which correlate with the redox potentials of the cations. It can be concluded that structural intact Keggin anions are catalytically inactive and have to be considered as the precursors of the actual active compounds