Induced and Effective Gravity Theories in D=2

As a preparation for the study of {\it arbitrary} extensions of $d=2$ gravity we present a detailed investigation of $SO(N)$ supergravity. By gauging a chiral, nilpotent subgroup of the $OSp(N|2)$ Wess-Zumino-Witten model we obtain an all order expression for the effective action. Reality of the coupling constant imposes the usual restrictions on $c$ for $N=0$ and 1. No such restrictions appear for $N\geq 2$. For $N=2$, 3 and 4, no renormalizations of the coupling constant beyond one loop occur. These results are related to non-renormalization theorems for theories with extended supersymmetries. Arbitrary (super)extensions of $d=2$ gravity are then analyzed. The induced theory is represented by a WZW model for which a chiral, solvable group is gauged. From this, we obtain the effective action. All order expressions for both the coupling constant renormalization and the wavefunction renormalization are given. From this we classify all extensions of $d=2$ gravity for which the coupling constant gets at most a one loop renormalization. As an application of the general strategy, $N=4$ theories based on D(2,1,\a) and $SU(1,1|2)$, all $WA$ gravities and the $N=2$ $W_n$ models are treated in some detail.Comment: 58 pages, latex, LBL-33738, UCB-PTH-93/06, KUL-TF-93/0

Pulling up the tarnished anchor: The end of silver as a global unit of account

We use the demise of silver-based standards in the 19th century to explore price dynamics when a commodity-based money ceases to function as a global unit of account. We develop a general equilibrium model of the global economy with gold and silver money. Calibration of the model shows that silver ceased functioning as a global price anchor in the mid-1890s - the price of silver is positively correlated with agricultural commodities through the mid-1890s, but not thereafter. In contrast to Fisher (1911) and Friedman (1990), both of whom predict greater price stability under bimetallism, our model suggests that a global bimetallic system, in which the gold price of silver uctuates, has higher price volatility than a global monometallic system. We confirm this result using agricultural commodity price data for 1870-1913

Advancing the use of molecular methods for routine freshwater macroinvertebrate biomonitoring : the need for calibration experiments

Over the last decade, steady advancements have been made in the use of DNA-based methods for detection of species in a wide range of ecosystems. This progress has culminated in molecular monitoring methods being employed for the detection of several species for enforceable management purposes of endangered, invasive, and illegally harvested species worldwide. However, the routine application of DNA-based methods to monitor whole communities (typically a metabarcoding approach) in order to assess the status of ecosystems continues to be limited. In aquatic ecosystems, the limited use is particularly true for macroinvertebrate communities. As part of the DNAqua-Net consortium, a structured discussion was initiated with the aim to identify potential molecular methods for freshwater macroinvertebrate community assessment and identify important knowledge gaps for their routine application. We focus on three complementary DNA sources that can be metabarcoded: 1) DNA from homogenised samples (bulk DNA), 2) DNA extracted from sample preservative (fixative DNA), and 3) environmental DNA (eDNA) from water or sediment. We provide a brief overview of metabarcoding macroinvertebrate communities from each DNA source and identify challenges for their application to routine monitoring. To advance the utilisation of DNA-based monitoring for macroinvertebrates, we propose an experimental design template for a series of methodological calibration tests. The template compares sources of DNA with the goal of identifying the effects of molecular processing steps on precision and accuracy. Furthermore, the same samples will be morphologically analysed, which will enable the benchmarking of molecular to traditional processing approaches. In doing so we hope to highlight pathways for the development of DNA-based methods for the monitoring of freshwater macroinvertebrates