Creating a Foundation for Open Knowledge: Technology Assessment of Web-based Learning

Presentation that covers:* Problems of Access and Quality of Academic Content* Basic Strategy and Assumptions including Theory of Action* Hewlett Grantees and Demonstrations* Challenge

California's Community Colleges: Hewlett Foundation Education Technology

A powerpoint presentation addressing problems with using academic content on the web, basic strategy, challenges to open knowledge, funding examples, and possible community college models

Unification modulo a partial theory of exponentiation

Modular exponentiation is a common mathematical operation in modern cryptography. This, along with modular multiplication at the base and exponent levels (to different moduli) plays an important role in a large number of key agreement protocols. In our earlier work, we gave many decidability as well as undecidability results for multiple equational theories, involving various properties of modular exponentiation. Here, we consider a partial subtheory focussing only on exponentiation and multiplication operators. Two main results are proved. The first result is positive, namely, that the unification problem for the above theory (in which no additional property is assumed of the multiplication operators) is decidable. The second result is negative: if we assume that the two multiplication operators belong to two different abelian groups, then the unification problem becomes undecidable.Comment: In Proceedings UNIF 2010, arXiv:1012.455

A Synthetic Gene Drive System for Local, Reversible Modification and Suppression of Insect Populations

Replacement of wild insect populations with genetically modified individuals unable to transmit disease provides a self-perpetuating method of disease prevention but requires a gene drive mechanism to spread these traits to high frequency. Drive mechanisms requiring that transgenes exceed a threshold frequency in order to spread are attractive because they bring about local but not global replacement, and transgenes can be eliminated through dilution of the population with wild-type individuals and 6]. These features are likely to be important in many social and regulatory contexts. Here we describe the first creation of a synthetic threshold-dependent gene drive system, designated maternal-effect lethal underdominance (UD^(MEL)), in which two maternally expressed toxins, located on separate chromosomes, are each linked with a zygotic antidote able to rescue maternal-effect lethality of the other toxin. We demonstrate threshold-dependent replacement in single- and two-locus configurations in Drosophila. Models suggest that transgene spread can often be limited to local environments. They also show that in a population in which single-locus UDMEL has been carried out, repeated release of wild-type males can result in population suppression, a novel method of genetic population manipulation

Characterization of an electron conduit between bacteria and the extracellular environment

A number of species of Gram-negative bacteria can use insoluble minerals of Fe(III) and Mn(IV) as extracellular respiratory electron acceptors. In some species of Shewanella, deca-heme electron transfer proteins lie at the extracellular face of the outer membrane (OM), where they can interact with insoluble substrates. To reduce extracellular substrates, these redox proteins must be charged by the inner membrane/periplasmic electron transfer system. Here, we present a spectro-potentiometric characterization of a trans-OM icosa-heme complex, MtrCAB, and demonstrate its capacity to move electrons across a lipid bilayer after incorporation into proteoliposomes. We also show that a stable MtrAB subcomplex can assemble in the absence of MtrC; an MtrBC subcomplex is not assembled in the absence of MtrA; and MtrA is only associated to the membrane in cells when MtrB is present. We propose a model for the modular organization of the MtrCAB complex in which MtrC is an extracellular element that mediates electron transfer to extracellular substrates and MtrB is a trans-OM spanning ß-barrel protein that serves as a sheath, within which MtrA and MtrC exchange electrons. We have identified the MtrAB module in a range of bacterial phyla, suggesting that it is widely used in electron exchange with the extracellular environment

Determination of the Partial Contributions to the Electrical Conductivity of TiO2 - SiO2 - Al2O3 - MgO - CaO Slags: Role of the Experimental Processing Conditions

The electrical transport properties of molten TiO2–SiO2–Al2O3–MgO–CaO slags were determined as a function of temperature and oxygen partial pressure. To avoid the corrosion of crucible materials by this slag at ultra high temperatures, the pendant droplet technique was used inside a modified floating zone furnace. Electronic and ionic transference numbers were estimated using stepped-potential chronoamperometry experiments to quantify the contribution of the electronic/ionic conductivity to the total electric conductivity. The results show that these slags are mixed conductors, where current is carried by ionic and electronic carriers. The oxygen partial pressure dependence of the electronic transference numbers, te, indicated a semiconducting mechanism in the molten slag. The ratio of the different valences of the transition metal ions had a predominant effect on the te. The TiO2 content also favoured electronic conduction, while the effect of temperature and structure was less noticeable within the temperature and composition range studied

Going beyond personal protection against mosquito bites to eliminate malaria transmission: population suppression of malaria vectors that exploit both human and animal blood

Protecting individuals and households against mosquito bites with long-lasting insecticidal nets (LLINs) or indoor residual spraying (IRS) can suppress entire populations of unusually efficient malaria vector species that predominantly feed indoors on humans. Mosquitoes which usually feed on animals are less reliant on human blood, so they are far less vulnerable to population suppression effects of such human-targeted insecticidal measures. Fortunately, the dozens of mosquito species which primarily feed on animals are also relatively inefficient vectors of malaria, so personal protection against mosquito bites may be sufficient to eliminate transmission. However, a handful of mosquito species are particularly problematic vectors of residual malaria transmission, because they feed readily on both humans and animals. These unusual vectors feed often enough on humans to be potent malaria vectors, but also often enough on animals to evade population control with LLINs, IRS or any other insecticidal personal protection measure targeted only to humans. Anopheles arabiensis and A. coluzzii in Africa, A. darlingi in South America and A. farauti in Oceania, as well as A. culicifacies species E, A. fluviatilis species S, A. lesteri and A. minimus in Asia, all feed readily on either humans or animals and collectively mediate residual malaria transmission across most of the tropics. Eliminating malaria transmission by vectors exhibiting such dual host preferences will require aggressive mosquito population abatement, rather than just personal protection of humans. Population suppression of even these particularly troublesome vectors is achievable with a variety of existing vector control technologies that remain underdeveloped or underexploited

Electrochemical study on the reduction of Si and Ti from molten TiO2 − SiO2 − Al2O3 − MgO − CaO slag

The reduction process during the electrochemical production of titanium via the electrolysis of molten TiO2 − SiO2 − Al2O3 − MgO − CaO slags has been investigated. A laboratory scale, electrolytic cell was designed to study the effect of TiO2 concentration at ultra-high temperatures. Galvanostatic and potentiostatic experiments were performed and results were consistent with thermodynamic predictions using FactSage. We demonstrate the direct production of Si-Ti alloys from the molten oxide mixture. The reduction of Si and Ti ions from the melt on a molybdenum electrode is a complex process that combines electron transfer and chemical phenomena. For the concentrations studied, the extraction of pure metallic Ti directly from ironmaking slag is unlikely without the prior removal of SiO2 or other chemical modifications to the system

Impact of HIV-Associated Conditions on Mortality in People Commencing Anti-Retroviral Therapy in Resource Limited Settings

To identify associations between specific WHO stage 3 and 4 conditions diagnosed after ART initiation and all cause mortality for patients in resource-limited settings (RLS). DESIGN, SETTING: Analysis of routine program data collected prospectively from 25 programs in eight countries between 2002 and 2010