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- Decoupled catalytic hydrogen evolution from a molecular metal oxide redox mediator in water splitting. [Journal Article, Research Support, Non-U.S. Gov't]
- Science 2014 Sep 12; 345(6202):1326-30.
The electrolysis of water using renewable energy inputs is being actively pursued as a route to sustainable hydrogen production. Here we introduce a recyclable redox mediator (silicotungstic acid) that enables the coupling of low-pressure production of oxygen via water oxidation to a separate, catalytic hydrogen production step outside the electrolyzer that requires no post-electrolysis energy input. This approach sidesteps the production of high-pressure gases inside the electrolytic cell (a major cause of membrane degradation) and essentially eliminates the hazardous issue of product gas crossover at the low current densities that characterize renewables-driven water-splitting devices. We demonstrated that a platinum-catalyzed system can produce pure hydrogen over 30 times faster than state-of-the-art proton exchange membrane electrolyzers at equivalent platinum loading.
- Strong, lightweight, and recoverable three-dimensional ceramic nanolattices. [Journal Article, Research Support, U.S. Gov't, Non-P.H.S.]
- Science 2014 Sep 12; 345(6202):1322-6.
Ceramics have some of the highest strength- and stiffness-to-weight ratios of any material but are suboptimal for use as structural materials because of their brittleness and sensitivity to flaws. We demonstrate the creation of structural metamaterials composed of nanoscale ceramics that are simultaneously ultralight, strong, and energy-absorbing and can recover their original shape after compressions in excess of 50% strain. Hollow-tube alumina nanolattices were fabricated using two-photon lithography, atomic layer deposition, and oxygen plasma etching. Structures were made with wall thicknesses of 5 to 60 nanometers and densities of 6.3 to 258 kilograms per cubic meter. Compression experiments revealed that optimizing the wall thickness-to-radius ratio of the tubes can suppress brittle fracture in the constituent solid in favor of elastic shell buckling, resulting in ductile-like deformation and recoverability.
- Chaotic dynamics of stellar spin in binaries and the production of misaligned hot Jupiters. [Journal Article, Research Support, U.S. Gov't, Non-P.H.S.]
- Science 2014 Sep 12; 345(6202):1317-21.
Many exoplanetary systems containing hot Jupiters are observed to have highly misaligned orbital axes relative to the stellar spin axes. Kozai-Lidov oscillations of orbital eccentricity and inclination induced by a binary companion, in conjunction with tidal dissipation, constitute a major channel for the production of hot Jupiters. We demonstrate that gravitational interaction between the planet and its oblate host star can lead to chaotic evolution of the stellar spin axis during Kozai cycles. As parameters such as the planet mass and stellar rotation period are varied, periodic islands can appear in an ocean of chaos, in a manner reminiscent of other dynamical systems. In the presence of tidal dissipation, the complex spin evolution can leave an imprint on the final spin-orbit misalignment angles.
- Extensive remodeling of a cyanobacterial photosynthetic apparatus in far-red light. [Journal Article, Research Support, U.S. Gov't, Non-P.H.S.]
- Science 2014 Sep 12; 345(6202):1312-7.
Cyanobacteria are unique among bacteria in performing oxygenic photosynthesis, often together with nitrogen fixation and, thus, are major primary producers in many ecosystems. The cyanobacterium, Leptolyngbya sp. strain JSC-1, exhibits an extensive photoacclimative response to growth in far-red light that includes the synthesis of chlorophylls d and f. During far-red acclimation, transcript levels increase more than twofold for ~900 genes and decrease by more than half for ~2000 genes. Core subunits of photosystem I, photosystem II, and phycobilisomes are replaced by proteins encoded in a 21-gene cluster that includes a knotless red/far-red phytochrome and two response regulators. This acclimative response enhances light harvesting for wavelengths complementary to the growth light (λ = 700 to 750 nanometers) and enhances oxygen evolution in far-red light.
- Creating a global observatory for health R&D. [Journal Article]
- Science 2014 Sep 12; 345(6202):1302-4.
A global map of health R&D activity would improve the coordination of research and help to match limited resources with public health priorities, such as combating antimicrobial resistance. The challenges of R&D mapping are large because there are few standards for research classification and governance and limited capacity to report on R&D data, especially in low-income countries. Nevertheless, based on developments in semantic classification, and with better reporting of funded research though the Internet, it is now becoming feasible to create a global observatory for health R&D.
- Antibiotic effectiveness: balancing conservation against innovation. [Journal Article]
- Science 2014 Sep 12; 345(6202):1299-301.
Antibiotic effectiveness is a natural societal resource that is diminished by antibiotic use. As with other such assets, keeping it available requires both conservation and innovation. Conservation encompasses making the best use of current antibiotic effectiveness by reducing demand through vaccination, infection control, diagnostics, public education, incentives for clinicians to prescribe fewer antibiotics, and restrictions on access to newer, last-resort antibiotics. Innovation includes improving the efficacy of current drugs and replenishing effectiveness by developing new drugs. In this paper, I assess the relative benefits and costs of these two approaches to maintaining our ability to treat infections.
- Monitoring parasite diversity for malaria elimination in sub-Saharan Africa. [Journal Article, Research Support, Non-U.S. Gov't]
- Science 2014 Sep 12; 345(6202):1297-8.
The African continent continues to bear the greatest burden of malaria and the greatest diversity of parasites, mosquito vectors, and human victims. The evolutionary plasticity of malaria parasites and their vectors is a major obstacle to eliminating the disease. Of current concern is the recently reported emergence of resistance to the front-line drug, artemisinin, in South-East Asia in Plasmodium falciparum, which calls for preemptive surveillance of the African parasite population for genetic markers of emerging drug resistance. Here we describe the Plasmodium Diversity Network Africa (PDNA), which has been established across 11 countries in sub-Saharan Africa to ensure that African scientists are enabled to work together and to play a key role in the global effort for tracking and responding to this public health threat.
- Virus sharing, genetic sequencing, and global health security. [Journal Article]
- Science 2014 Sep 12; 345(6202):1295-6.
This Perspective focuses on the future of the Pandemic Influenza Preparedness (PIP) Framework, which was initially established to promote the fair sharing of public health-related pandemic influenza samples between countries. We examine the changes that need to be made to address the growing likelihood that genetic sequence data might be shared instead of physical virus samples, as well as the need to expand the PIP framework's scope and to improve its fairness.
- Emerging, evolving, and established infectious diseases and interventions. [Journal Article, Research Support, N.I.H., Extramural]
- Science 2014 Sep 12; 345(6202):1292-4.
Planning, implementing, and evaluating interventions against infectious diseases depend on the nature of the infectious disease; the availability of intervention measures; and logistical, economic, and political constraints. Infectious diseases and vaccine- or drug-based interventions can be loosely categorized by the degree to which the infectious disease and the intervention are well established. Pertussis, polio, and measles are three examples of long-known infectious diseases for which global vaccination has dramatically reduced the public health burden. Pertussis vaccination was introduced in the 1940s, polio vaccination in the 1950s, and measles vaccination in the 1960s, nearly eliminating these diseases in many places.
- Strengthening the evidence base for health programming in humanitarian crises. [Journal Article]
- Science 2014 Sep 12; 345(6202):1290-2.
Given the growing scale and complexity of responses to humanitarian crises, it is important to develop a stronger evidence base for health interventions in such contexts. Humanitarian crises present unique challenges to rigorous and effective research, but there are substantial opportunities for scientific advance. Studies need to focus where the translation of evidence from noncrisis scenarios is not viable and on ethical ways of determining what happens in the absence of an intervention. Robust methodologies suited to crisis settings have to be developed and used to assess interventions with potential for delivery at scale. Strengthening research capacity in the low- to middle-income countries that are vulnerable to crises is also crucial.