Local quantum critical point in the pseudogap Anderson model: finite-T dynamics and omega/T scaling

The pseudogap Anderson impurity model is a paradigm for locally critical quantum phase transitions. Within the framework of the local moment approach we study its finite-T dynamics, as embodied in the single-particle spectrum, in the vicinity of the symmetric quantum critical point (QCP) separating generalized Fermi-liquid (Kondo screened) and local moment phases. The scaling spectra in both phases, and at the QCP itself, are obtained analytically. A key result is that pure omega/T-scaling obtains at the QCP, where the Kondo resonance has just collapsed. The connection between the scaling spectra in either phase and that at the QCP is explored in detail.Comment: 12 pages, 7 figure

The Radio Jets and Accretion Disk in NGC 4261

The structure of AGN accretion disks on sub-parsec scales can be probed through free-free absorption of synchrotron emission from the base of symmetric radio jets. We present new VLBA observations of the nearby FR-I radio galaxy NGC 4261 at 22 and 43 GHz, and combine these with previous VLBA observations at 1.6 and 8.4 GHz to map absorption caused by an inner accretion disk. Assuming the disk is geometrically and optically thin and composed of a uniform 10^4 K plasma, the average electron density in the inner 0.1 pc is 10^3 - 10^8 cm^-3. Equating thermal gas pressure and magnetic field strength gives a disk magnetic field of 10^-4 - 10^-2 Gauss at 0.1 pc. The jet opening angle is between 0.3 and 20 degrees during the first 0.2 pc of the jet, and must be less than 5 degrees during the first 0.8 pc. We include an appendix containing expressions for a simple, optically thin, gas pressure dominated accretion disk model which may be applicable to other galaxies in addition to NGC 4261.Comment: 15 pages plus 6 postscript figures, accepted by Ap

Transforming a 4th year Modern Optics Course Using a Deliberate Practice Framework

We present a study of active learning pedagogies in an upper division physics course. This work was guided by the principle of deliberate practice for the development of expertise, and this principle was used in the design of the materials and the orchestration of the classroom activities of the students. We present our process for efficiently converting a traditional lecture course based on instructor notes into activities for such a course with active learning methods. Ninety percent of the same material was covered and scores on common exam problems showed a 15 % improvement with an effect size greater than 1 after the transformation. We observe that the improvement and the associated effect size is sustained after handing off the materials to a second instructor. Because the improvement on exam questions was independent of specific problem topics and because the material tested was so mathematically advanced and broad (including linear algebra, Fourier Transforms, partial differential equations, vector calculus), we expect the transformation process could be applied to most upper division physics courses having a similar mathematical base.Comment: 31 page

The on-farm impact of alternative grazing management options to improve sustainability in western Chinese grasslands

Chinese grasslands are suffering considerable pressures from human and livestock populations. It has been estimated that 90% of Chinese grasslands are suffering from light to heavy levels of degradation. Allied to this is the low household income of herders and farmers dependant upon livestock products for their livelihood. Although a range of reasons have been proposed for the high levels of grassland degradation, principal among these are the high stocking rates adopted by farmers. This not only results in high utilisation rates of the pasture biomass, leading to bare areas and soil erosion, but individual animal productivity rates also decline. This paper presents the results of a modelling study of a grassland system in Gansu Province and Inner Mongolia Autonomous Region in northern China. This shows that reducing stocking rates leads to not only an increase in livestock productivity, but whole-farm returns are also increased. From a sustainability perspective, the greater pasture biomass remaining on the grassland also reduces the incidence of soil erosion in the areas.sustainable grazing, bioeconomic model, China, Farm Management, Livestock Production/Industries, Resource /Energy Economics and Policy,

An Economic Evaluation of Research into the Improved Management of the Annual Grass Weed Vulpia in Temperate Pastures in South-Eastern Australia

NSW Agriculture has a history of research investment in managing weed problems in the temperate pasture areas. One focus of that research has been on the development of improved management practices for the major annual grass weed vulpia. Recent surveys have found that weeds comprised up to 80% of pasture biomass in some temperate areas and that typical vulpia contents are between 30 and 40% of pasture biomass. Temperate pasture degradation is recognised as being a major contributor to the wider environmental problems of soil erosion, salinity and acidity. This evaluation related to a project (1996-2002) that focussed on the vulpia problem in the New South Wales temperate pasture areas. The benefits of that research were measured as the difference in the economic returns from the project (the with-research scenario) and those that would have resulted if the project had not been initiated (the without-research scenario). The results indicated high levels of economic benefits from the vulpia project. The annual net project benefit had a mean value of $58 million. The benefit-cost analysis generated a mean NPV of$196.9 million and a mean BCR of 22.2. These results demonstrate that research by NSW Agriculture into the improved management of vulpia has the potential to generate substantial long-term economic benefits. Other socio-economic aspects of the results showed that wool producers outside the New South Wales temperate areas lost economic surplus (from a mean -$21.7 million to -$47.8 million) because they were unable to adopt the cost-reducing technology and faced a reduced wool price. All wool consumers gained from vulpia research because of expanded wool production and lower wool prices. Improved vulpia management is also considered to produce important environmental benefits by encouraging a greater use of deep-rooted perennial grasses and the beneficial effects of these on mitigating soil problems and reducing water table discharges.benefit cost analysis, research evaluation, annual grass weeds, vulpia, Research and Development/Tech Change/Emerging Technologies, Q160,

DETERMINANTS OF PRICE ELASTICITIES FOR STORE BRANDS AND NATIONAL BRANDS OF CHEESE

A two-stage modeling process is developed to estimate factors that determine price sensitivities for store and national brands of cheese. Results show that several factors affect price sensitivities. AIDS and LA/AIDS models are used in the analyses and meta-regression results show no difference in own-price elasticities for these two models.Demand and Price Analysis,

A SOCIOECONOMIC APPROACH TO ASSESSING PRICE COMPETITION BETWEEN PRIVATE LABELS AND NATIONAL BRANDS: THE CASE OF SHREDDED CHEESE

An LA/AIDS model is developed to estimate demand elasticities for packages of 8-oz shredded cheese for higher- and lower-income consumers. Data used in this study are scanner data for six supermarket stores in two distinct socioeconomic areas. Results show that: (1) lower-income shoppers are more price-sensitive than higher-income shoppers for both private labels and national brands; (2) compared with private labels, consumers are very sensitive to national brands price changes even in higher-income areas; (3) cross-price elasticities between private labels and national brands are all positive, i.e., private labels and national brands are substitutes in both lower- and higher-income stores; and (4) the number of promoted items does not have a statistically significant impact on sales; instead, the percentage of price discount affects sales for both private labels and national brands.Demand and Price Analysis,

Monitoring and Stabilisation of the Giants Seat Landslip, U.K.

The landslip is located in the Giant’s Seat Woods area of Kearsley, Bolton in Greater Manchester, England. The ground conditions at the site comprise made ground material over mudstones of the Manchester Marls. An area of land crossed by Red Rock Lane had, since the late 1700s, experienced land slip resulting in the ground generally moving south towards the adjacent river. By the late 1990’s the movement of the slip had resulted in fractures and fissures under the road and damage to several other services. A project was developed to stabilise the land along approximately 130m of Red Rock Lane. Options to provide a solution included service diversion, improved drainage, toe weighting, dig out and replace, soil nailing, piled wall and a rock anchored pile wall. The ground conditions and compact nature of the site suggested that a drilled minipile and anchored wall would offer the optimum performance. Inclinometer results confirmed clearly that the slip surface lay predominantly within the mudstones, moving at up to 40mm a month, at depths ranging between 3 and 10m below road level. Continued monitoring of the inclinometers and piezometers through construction of the wall provided interesting and useful results regarding the slip behaviour and was finally able to confirm the restoration of the groundwater table and the curtailment of the slip movement