The String Calculation of QCD Wilson Loops on Arbitrary Surfaces

Compact string expressions are found for non-intersecting Wilson loops in SU(N) Yang-Mills theory on any surface (orientable or nonorientable) as a weighted sum over covers of the surface. All terms from the coupled chiral sectors of the 1/N expansion of the Wilson loop expectation values are included.Comment: 10 pages, LaTeX, no figure

Actor network analysis to leverage improvements in conservation and development outcomes in Cambodia

Network analysis has emerged as a useful practice for characterizing governance relationships and providing insights to the power relations that affect landscapes. We applied actor network analysis in two rural Cambodian landscapes to examine decision-making structures that affect conservation and development systems. Using questionnaire data, we analyze structural features of networks of cooperation and exchange to identify patterns of action and processes of change. We supplement our analysis with qualitative information gathered on power and social ecological components of landscapes to enrich our understanding of natural resource systems. We find that power in Cambodia is concentrated in a central hierarchy, and external actors aiming to influence decision making would benefit from operating at multiple scales; there is no single leverage point for interventions. Cooperation between conservation and development actors is lacking; we observe that actors tend to cluster within similar groups. Cross-sectoral collaboration may be enhanced by knowledge brokers, but current actors lack resources to fulfil this role and require external support. Our study highlights the importance of nongovernment actors as conveners and facilitators to shape natural resource governance in the context of weak institutions. We advocate more institutionalized use of diagnostics, such as actor network analysis, for enhanced natural resource governance

Directed mutagenesis as a technique to study protein function: application to β-lactamase

The function of a protein follows uniquely from its three-dimensional structure, which is unambiguously determined by the linear sequence of amino acids. Thus to undertake a systematic study of the relationship between protein structure and function, one would ideally like to be able to alter the structural gene in various ways to encode proteins with novel sequences, structures and functions. Various mutagenic strategies and methods have recently been developed that allow one to achieve these objectives

Eye Movement Monitoring Reveals Differential Influences of Emotion on Memory

Research shows that memory for emotional aspects of an event may be enhanced at the cost of impaired memory for surrounding peripheral details. However, this has only been assessed directly via verbal reports which reveal the outcome of a long stream of processing but cannot shed light on how/when emotion may affect the retrieval process. In the present experiment, eye movement monitoring (EMM) was used as an indirect measure of memory as it can reveal aspects of online memory processing. For example, do emotions modulate the nature of memory representations or the speed with which such memories can be accessed? Participants viewed central negative and neutral scenes surrounded by three neutral objects and after a brief delay, memory was assessed indirectly via EMM and then directly via verbal reports. Consistent with the previous literature, emotion enhanced central and impaired peripheral memory as indexed by eye movement scanning and verbal reports. This suggests that eye movement scanning may contribute and/or is related to conscious access of memory. However, the central/peripheral tradeoff effect was not observed in an early measure of eye movement behavior, i.e., participants were faster to orient to a critical region of change in the periphery irrespective of whether it was previously studied in a negative or neutral context. These findings demonstrate emotion's differential influences on different aspects of retrieval. In particular, emotion appears to affect the detail within, and/or the evaluation of, stored memory representations, but it may not affect the initial access to those representations

The Overlooked Potential of Generalized Linear Models in Astronomy-III: Bayesian Negative Binomial Regression and Globular Cluster Populations

In this paper, the third in a series illustrating the power of generalized linear models (GLMs) for the astronomical community, we elucidate the potential of the class of GLMs which handles count data. The size of a galaxy's globular cluster population $N_{\rm GC}$ is a prolonged puzzle in the astronomical literature. It falls in the category of count data analysis, yet it is usually modelled as if it were a continuous response variable. We have developed a Bayesian negative binomial regression model to study the connection between $N_{\rm GC}$ and the following galaxy properties: central black hole mass, dynamical bulge mass, bulge velocity dispersion, and absolute visual magnitude. The methodology introduced herein naturally accounts for heteroscedasticity, intrinsic scatter, errors in measurements in both axes (either discrete or continuous), and allows modelling the population of globular clusters on their natural scale as a non-negative integer variable. Prediction intervals of 99% around the trend for expected $N_{\rm GC}$comfortably envelope the data, notably including the Milky Way, which has hitherto been considered a problematic outlier. Finally, we demonstrate how random intercept models can incorporate information of each particular galaxy morphological type. Bayesian variable selection methodology allows for automatically identifying galaxy types with different productions of GCs, suggesting that on average S0 galaxies have a GC population 35% smaller than other types with similar brightness.Comment: 14 pages, 12 figures. Accepted for publication in MNRA

Short small-polaron lifetime in the mixed-valence perovskite Cs2_2Au2_2I6_6 from high-pressure pump-probe experiments

We study the ultrafast phonon response of mixed-valence perovskite Cs$_2$Au$_2$I$_6$ using pump-probe spectroscopy under high-pressure in a diamond anvil cell. We observed a remarkable softening and broadening of the Au - I stretching phonon mode with both applied pressure and photoexcitation. Using a double-pump scheme we measured a lifetime of the charge transfer excitation into single valence Au$^{2+}$ of less than 4 ps, which is an indication of the local character of the Au$^{2+}$ excitation. Furthermore, the strong similarity between the pressure and fluence dependence of the phonon softening shows that the inter-valence charge transfer plays an important role in the structural transition.Comment: 4 pages, 4 figure

Learning from local perceptions for strategic road development in Cambodia's protected forests

Road development in tropical forest landscapes is contentious. Local preferences are often subordinated to global economic and environmental concerns. Opportunities to seek solutions based on local context are rare. We examined local perspectives on road development within Cambodia's Keo Seima Wildlife Sanctuary to explore opportunities for optimizing conservation and development outcomes. We conducted household surveys to document the perceived benefits and risks of road development. We found that in the sanctuary, road rehabilitation may accelerate transitions to intensified agriculture and diversified, off-farm incomes. All households prefer good roads and poorer households prioritize road development over other village infrastructure. Households perceive the most prominent benefit of roads to be access to hospital. Local government authorities are responsible for controlling land use and conversion within village boundaries and are therefore highly influential in determining the social and environmental outcomes of roads. Strategies to mitigate environmental risks of roads without constraining development benefits must focus on improving local capacity for decision-making and transparency. Local institutions in tropical forest landscapes must have greater control over development benefits if they are to reinvest assets to achieve conservation success