Fractionalization and Fermi surface volume in heavy fermion compounds: the case of YbRh2_2 Si2_2

We establish an effective theory for heavy fermion compounds close to a zero temperature Anti-Ferromagnetic (AF) transition. Coming from the heavy Fermi liquid phase across to the AF phase, the heavy electron fractionalizes into a light electron, a bosonic spinon and a {\it new} excitation: a spinless fermionic field. Assuming this field acquires dynamics and dispersion when one integrates out the high energy degrees of freedom, we give a scenario for the volume of its Fermi surface through the phase diagram. We apply our theory to the special case of YbRh$_2$(Si$_{1-x}$ Ge$_x$)$_2$ where we recover, within experimental resolution, several low temperature exponents for transport and thermodynamics.Comment: 4 pages, 5 figure

Lost in Translation: Piloting a Novel Framework to Assess the Challenges in Translating Scientific Uncertainty From Empirical Findings to WHO Policy Statements.

BACKGROUND:Calls for evidence-informed public health policy, with implicit promises of greater program effectiveness, have intensified recently. The methods to produce such policies are not self-evident, requiring a conciliation of values and norms between policy-makers and evidence producers. In particular, the translation of uncertainty from empirical research findings, particularly issues of statistical variability and generalizability, is a persistent challenge because of the incremental nature of research and the iterative cycle of advancing knowledge and implementation. This paper aims to assess how the concept of uncertainty is considered and acknowledged in World Health Organization (WHO) policy recommendations and guidelines. METHODS:We selected four WHO policy statements published between 2008-2013 regarding maternal and child nutrient supplementation, infant feeding, heat action plans, and malaria control to represent topics with a spectrum of available evidence bases. Each of these four statements was analyzed using a novel framework to assess the treatment of statistical variability and generalizability. RESULTS:WHO currently provides substantial guidance on addressing statistical variability through GRADE (Grading of Recommendations Assessment, Development, and Evaluation) ratings for precision and consistency in their guideline documents. Accordingly, our analysis showed that policy-informing questions were addressed by systematic reviews and representations of statistical variability (eg, with numeric confidence intervals). In contrast, the presentation of contextual or "background" evidence regarding etiology or disease burden showed little consideration for this variability. Moreover, generalizability or "indirectness" was uniformly neglected, with little explicit consideration of study settings or subgroups. CONCLUSION:In this paper, we found that non-uniform treatment of statistical variability and generalizability factors that may contribute to uncertainty regarding recommendations were neglected, including the state of evidence informing background questions (prevalence, mechanisms, or burden or distributions of health problems) and little assessment of generalizability, alternate interventions, and additional outcomes not captured by systematic review. These other factors often form a basis for providing policy recommendations, particularly in the absence of a strong evidence base for intervention effects. Consequently, they should also be subject to stringent and systematic evaluation criteria. We suggest that more effort is needed to systematically acknowledge (1) when evidence is missing, conflicting, or equivocal, (2) what normative considerations were also employed, and (3) how additional evidence may be accrued

Mixed Statistics on 01-Fillings of Moon Polyominoes

We establish a stronger symmetry between the numbers of northeast and southeast chains in the context of 01-fillings of moon polyominoes. Let \M be a moon polyomino with $n$ rows and $m$ columns. Consider all the 01-fillings of \M in which every row has at most one 1. We introduce four mixed statistics with respect to a bipartition of rows or columns of \M. More precisely, let $S \subseteq \{1,2,..., n\}$ and $\mathcal{R}(S)$ be the union of rows whose indices are in $S$. For any filling $M$, the top-mixed (resp. bottom-mixed) statistic $\alpha(S; M)$ (resp. $\beta(S; M)$) is the sum of the number of northeast chains whose top (resp. bottom) cell is in $\mathcal{R}(S)$, together with the number of southeast chains whose top (resp. bottom) cell is in the complement of $\mathcal{R}(S)$. Similarly, we define the left-mixed and right-mixed statistics $\gamma(T; M)$ and $\delta(T; M)$, where $T$ is a subset of the column index set $\{1,2,..., m\}$. Let $\lambda(A; M)$ be any of these four statistics $\alpha(S; M)$, $\beta(S; M)$, $\gamma(T; M)$ and $\delta(T; M)$, we show that the joint distribution of the pair $(\lambda(A; M), \lambda(\bar A; M))$ is symmetric and independent of the subsets $S, T$. In particular, the pair of statistics $(\lambda(A;M), \lambda(\bar A; M))$ is equidistributed with (\se(M),\ne(M)), where \se(M) and $\ne(M)$ are the numbers of southeast chains and northeast chains of $M$, respectively.Comment: 20 pages, 6 figure

Sacrificial charge and the spectral resolution performance of the Chandra Advanced CCD Imaging Spectrometer

Soon after launch, the Advanced CCD Imaging Spectrometer (ACIS), one of the focal plane instruments on the Chandra X-ray Observatory, suffered radiation damage from exposure to soft protons during passages through the Earth's radiation belts. The ACIS team is continuing to study the properties of the damage with an emphasis on developing techniques to mitigate charge transfer inefficiency (CTI) and spectral resolution degradation. A post-facto CTI corrector has been developed which can effectively recover much of the lost resolution. Any further improvements in performance will require knowledge of the location and amount of sacrificial charge - charge deposited along the readout path of an event which fills electron traps and changes CTI. We report on efforts by the ACIS Instrument team to characterize which charge traps cause performance degradation and the properties of the sacrificial charge seen on-orbit. We also report on attempts to correct X-ray pulseheights for the presence of sacrificial charge.Comment: 9 pages, 7 figures to be published in Proc. SPIE 485

Effects of Urbanization and Habitat on the Diet and Reproduction of Red-shouldered Hawks in Central California

Urbanization alters biological community interactions and trophic structures compared to natural habitats; these changes may be reflected in the diets of apex predators such as raptors. The red-shouldered hawk (Buteo lineatus) is a dietary generalist that is expanding from natural and rural habitats into urbanized areas. In this study, direct observation was used to quantify the diet and reproductive success of red-shouldered hawks in Santa Clara County, California during the 2019 breeding season. GIS methods were used to quantify the nesting habitat and level of urbanization at each nest. Hawk diet consisted of mammals (50.4% by frequency and 77.7% by biomass) and reptiles (20.9% by frequency and 11.1% by biomass), along with limited birds, frogs, and crayfish. The number of chicks fledged did not differ among urban, suburban, and rural nests, but the mean number of chicks fledged from successful nests was greater for rural nests than for suburban or urban nests. Nests were subject to high levels of external activity, with 93% from anthropogenic sources, but hawks responded to only 3.5% of nearby activity. Road length, developed landcover, and tree canopy cover significantly correlated with total prey biomass, mammal biomass and frequency, and reptile frequency. Red-shouldered hawks were able to find adequate prey to breed successfully over a range of urbanized habitats within Santa Clara Valley and are highly tolerant of human activity in this locality