Hydrodynamic interaction in quasi-two-dimensional suspensions

Confinement between two parallel surfaces is found, theoretically and experimentally, to drastically affect the hydrodynamic interaction between colloid particles, changing the sign of the coupling, its decay with distance and its concentration dependence. In particular, we show that three-body effects do not modify the coupling at large distances as would be expected from hydrodynamic screening.Comment: 8 pages, 2 figure

Acylation of glucosaminyl phosphatidylinositol revisited. Palmitoyl-CoA dependent palmitoylation of the inositol residue of a synthetic dioctanoyl glucosaminyl phosphatidylinositol by hamster membranes permits efficient mannosylation of the glucosamine residue

Two critical steps in the assembly of yeast and mammalian glycosylphosphatidylinositol (GPI) anchor precursors are palmitoylation of the inositol residue and mannosylation of the glucosamine residue of the glucosaminyl phosphatidylinositol (GlcNα-PI) intermediate. Palmitoylation has been reported to be acyl-CoA dependent in yeast membranes (Costello, L. C., and Orlean, P. (1992) J. Biol. Chem. 267, 8599-8603) but strictly acyl- CoA independent in rodent membranes (Stevens, V. L., and Zhang, H. (1994) J. Biol. Chem. 269, 31397-31403), and thus poorly conserved. In addition, it was suggested that acylation must precede mannosylation in both yeast (Costello, L. C., and Orlean, P. (1992) J. Biol. Chem. 276, 8599-8603) and rodent (Urakaze, M., Kamitani, T., DeGasperi, R., Sugiyama, E., Chang, H.-M., Warren, C. D., and Yeh, E. T. H. (1992) J. Biol. Chem. 267, 6459-6462) cells because GlcNα-acyl-PI accumulates in vivo when mannosylation is blocked. However, GlcNα-acyl-PI accumulation would also be expected if mannosylation and acylation were independent of each other. These issues were addressed by the use of a synthetic dioctanoyl GlcNα-PI analogue (GlcNα-PI(C8)) as an in vitro substrate for GPI-synthesizing enzymes in Chinese hamster ovary cell membranes. GlcNα-PI(C8) was acylated in an manner requiring acyl-CoA. Thus, the process involving acyl-CoA reported for yeast has been conserved in mammals. Furthermore, both GlcNα-PI(C8) and GlcNα-acyl-PI(C8) could be mannosylated in vitro, but mannosylation of the latter was significantly more efficient. This provides direct support for the earlier suggestion that acylation precedes mannosylation in rodents cells. A similar result was also observed with the Saccharomyces cerevisiae mannosyltransferase. In contrast, it has been reported that mannosylation of endogenous GlcNα-PI by Trypansoma brucei membranes occurs without prior acylation. The same result was obtained with GlcNα-PI(C8), confirming that the mannosyltransferase of trypanosomes is divergent from those in yeasts and rodents

Security analysis for agroterrorism: applying the threat, vulnerability, consequence framework to developing countries

"We examine access to, use of, and participation in decisions on improved water supply in the Volta basin of Ghana, one of the first countries to introduce a community-based approach to rural water supply on a large scale. While 71 percent of the households interviewed have access to improved water, 43 percent of these continue to use unsafe sources as their main domestic water source. Our results indicate that quality perceptions and opportunity costs play an important role in households' choice of water source. The effect of prices and income levels on this choice differs according to the pricing system used. Given that supply characteristics such as the location and pricing system affect household decisions to use the improved source, households may try to influence these characteristics in their favor during the community decision-making process for the improved source. However, less than 40 percent of the households interviewed participated in decisions on location or technology. We argue that the decision whether to participate depends on three main factors: (i) the household's bargaining power, (ii) the potential benefits from influencing outcomes, and (iii) the cost of participation, (mainly opportunity cost of time). Our results indicate that bargaining power matters In some developing countries the potential exists for agroterrorism to cause widespread disruption through loss of sustenance, income and production. Defense of agriculture may also be problematic because of the lack stability and basic biosecurity infrastructure for the detection and prevention of diseases or invasive species. Currently new methodological approaches for terrorism risk assessments are being actively explored for resource prioritization. One such methodology for risk based allocation of resources is Threat, Vulnerability, and Consequence (TVC) Analysis. A qualitative application of the TVC framework is used to analyze the risk of agroterrorism in developing countries relative to industrialized countries. The analysis suggests that evidence exists to demonstrate general terrorist threats, vulnerability of agriculture and, depending on the country, potentially serious consequences arising from argoterrorism. Where specific threats emerge, action may be needed by the international community to strengthen biosecurity systems in developing countries through: increasing global cooperation, capacity building in monitoring, remediation and risk analysis technologies, and the dissemination of novel technologies for control of pests and diseases." Authors' AbstractCapacity strengthening, Water-supply Management, Agroterrorism, Biosecurity, Risk analysis, resource allocation, Terrorism, Governance,

Has the character of gastric cancer changed? A descriptive study of a IO-year period

Over the 10-year period January 1976 - December 1985, 446 patients with histologically verified adenocarcinoma of the stomach were treated at Tygerberg Hospital. Coloured patients made up 63,4% of the study population and a significant increase in the annual proportion of this group was observed. Coloured men comprised 47,6% of the total group. The mean age of white and coloured patients differed significantly (68,9 v. 56,5; P < 0,001). The symptom complex was essentially similar in the two racial groups and in general the character of the symptoms had no bearing on the prevalence of resection. Although antral tumours were most common in whites and in coloureds, there was a significant increase in tumours located in the fundus in whites. The resection rate remained unchanged over the 10-year period. Only 4 cases of early gastric cancer were detected during this period without any signs of an increased yield of early lesions over time. This audit revealed no beneficial changes over time, which is in stark contrast with reports from Japan regarding the proportion of curable lesions

Near real-time GPS applications for tsunami early warning systems

GPS (Global Positioning System) technology is widely used for positioning applications. Many of them have high requirements with respect to precision, reliability or fast product delivery, but usually not all at the same time as it is the case for early warning applications. The tasks for the GPS-based components within the GITEWS project (German Indonesian Tsunami Early Warning System, Rudloff et al., 2009) are to support the determination of sea levels (measured onshore and offshore) and to detect co-seismic land mass displacements with the lowest possible latency (design goal: first reliable results after 5 min). The completed system was designed to fulfil these tasks in near real-time, rather than for scientific research requirements. The obtained data products (movements of GPS antennas) are supporting the warning process in different ways. The measurements from GPS instruments on buoys allow the earliest possible detection or confirmation of tsunami waves on the ocean. Onshore GPS measurements are made collocated with tide gauges or seismological stations and give information about co-seismic land mass movements as recorded, e.g., during the great Sumatra-Andaman earthquake of 2004 (Subarya et al., 2006). This information is important to separate tsunami-caused sea height movements from apparent sea height changes at tide gauge locations (sensor station movement) and also as additional information about earthquakes' mechanisms, as this is an essential information to predict a tsunami (Sobolev et al., 2007). <br><br> This article gives an end-to-end overview of the GITEWS GPS-component system, from the GPS sensors (GPS receiver with GPS antenna and auxiliary systems, either onshore or offshore) to the early warning centre displays. We describe how the GPS sensors have been installed, how they are operated and the methods used to collect, transfer and process the GPS data in near real-time. This includes the sensor system design, the communication system layout with real-time data streaming, the data processing strategy and the final products of the GPS-based early warning system components

CYP-13A12 of the nematode Caenorhabditis elegans is a PUFA-epoxygenase involved in behavioural response to reoxygenation

A specific behavioural response of Caenorhabditis elegans, the rapid increase of locomotion in response to anoxia/reoxygenation called the O2-ON response, has been used to model key aspects of ischaemia/reperfusion injury. A genetic suppressor screen demonstrated a direct causal role of CYP (cytochrome P450)-13A12 in this response and suggested that CYP-eicosanoids, which in mammals influence the contractility of cardiomyocytes and vascular smooth muscle cells, might function in C. elegans as specific regulators of the body muscle cell activity. In the present study we show that co-expression of CYP-13A12 with the NADPH-CYP-reductase EMB-8 in insect cells resulted in the reconstitution of an active microsomal mono-oxygenase system that metabolized EPA (eicosapentaenoic acid) and also AA (arachidonic acid) to specific sets of regioisomeric epoxy and hydroxy derivatives. The main products included 17,18-EEQ (17,18-epoxyeicosatetraenoic acid) from EPA and 14,15-EET (14,15-epoxyeicosatrienoic acid) from AA. Locomotion assays showed that the defective O2-ON response of C20-PUFA (polyunsaturated fatty acid)-deficient, Δ-12 and Δ-6 fatty acid desaturase mutants (fat-2 and fat-3 respectively) can be restored by feeding the nematodes AA or EPA, but not ETYA (eicosatetraynoic acid), a non-metabolizable AA analogue. Short-term incubation with 17,18-EEQ was sufficient to rescue the impaired locomotion of the fat-3 strain. The endogenous level of free 17,18-EEQ declined during anoxia and was rapidly restored in response to reoxygenation. On the basis of these results, we suggest that CYP-dependent eicosanoids such as 17,18-EEQ function as signalling molecules in the regulation of the O2-ON response in C. elegans. Remarkably, the exogenously administered 17,18-EEQ increased the locomotion activity under normoxic conditions and was effective not only with C20-PUFA-deficient mutants, but to a lesser extent also with wild-type worms

Polaron Formation in the Three-Band Peierls-Hubbard Model for Cuprate Superconductors

Exact diagonalization calculations show a continuous transition from delocalized to small polaron behavior as a function of intersite electron-lattice coupling. A transition, found previously at Hartree-Fock level [Yonemitsu et al., Phys. Rev. Lett. {\bf 69}, 965 (1992)], between a magnetic and a non magnetic state does not subsist when fluctuations are included. Local phonon modes become softer close to the polaron and by comparison with optical measurements of doped cuprates we conclude that they are close to the transition region between polaronic and non-polaronic behavior. The barrier to adiabatically move a hole vanishes in that region suggesting large mobilities.Comment: 7 pages + 3 poscript figures, Revtex 3.0, MSC-199

The Electron-Phonon Interaction in the Presence of Strong Correlations

We investigate the effect of strong electron-electron repulsion on the electron-phonon interaction from a Fermi-liquid point of view: the strong interaction is responsible for vertex corrections, which are strongly dependent on the $v_Fq/\omega$ ratio. These corrections generically lead to a strong suppression of the effective coupling between quasiparticles mediated by a single phonon exchange in the $v_Fq/\omega \gg 1$ limit. However, such effect is not present when $v_Fq/\omega \ll 1$. Analyzing the Landau stability criterion, we show that a sizable electron-phonon interaction can push the system towards a phase-separation instability. A detailed analysis is then carried out using a slave-boson approach for the infinite-U three-band Hubbard model. In the presence of a coupling between the local hole density and a dispersionless optical phonon, we explicitly confirm the strong dependence of the hole-phonon coupling on the transferred momentum versus frequency ratio. We also find that the exchange of phonons leads to an unstable phase with negative compressibility already at small values of the bare hole-phonon coupling. Close to the unstable region, we detect Cooper instabilities both in s- and d-wave channels supporting a possible connection between phase separation and superconductivity in strongly correlated systems.Comment: LateX 3.14, 04.11.1994 Preprint no.101

Overview of the Nordic Seas CARINA data and salinity measurements

Water column data of carbon and carbon relevant hydrographic and hydrochemical parameters from 188 previously non-publicly available cruises in the Arctic, Atlantic, and Southern Ocean have been retrieved and merged into a new database: CARINA (CARbon IN the Atlantic). The data have been subject to rigorous quality control (QC) in order to ensure highest possible quality and consistency. The data for most of the parameters included were examined in order to quantify systematic biases in the reported values, i.e. secondary quality control. Significant biases have been corrected for in the data products, i.e. the three merged files with measured, calculated and interpolated values for each of the three CARINA regions; the Arctic Mediterranean Seas (AMS), the Atlantic (ATL) and the Southern Ocean (SO). With the adjustments the CARINA database is consistent both internally as well as with GLODAP (Key et al., 2004) and is suitable for accurate assessments of, for example, oceanic carbon inventories and uptake rates and for model validation. The Arctic Mediterranean Seas include the Arctic Ocean and the Nordic Seas, and the quality control was carried out separately in these two areas. This contribution provides an overview of the CARINA data from the Nordic Seas and summarises the findings of the QC of the salinity data. One cruise had salinity data that were of questionable quality, and these have been removed from the data product. An evaluation of the consistency of the quality controlled salinity data suggests that they are consistent to at least ±0.005