Series Study of a Spin-Glass Model in Continuous Dimensionality

A high-temperature series expansion for the Edwards and Anderson spin-glass order-parameter susceptibility is computed for Ising spins on hypercubic lattices with nearest-neighbor interactions. The series is analyzed by Padé approximants with Rudnick-Nelson-type corrections to scaling. The results agree with the first-order ε expansion of Harris, Lubensky, and Chen. The critical exponent γQ increases monotonically with decreasing dimension, d, for d\u3c6, and apparently tends to infinity at d=4; however, the critical temperature does not appear to go to zero at d=4

Critical Behavior of Random Resistor Networks Near the Percolation Threshold

We use low-density series expansions to calculate critical exponents for the behavior of random resistor networks near the percolation threshold as a function of the spatial dimension d. By using scaling relations, we obtain values of the conductivity exponent μ. For d=2 we find μ=1.43±0.02, and for d=3, μ=1.95±0.03, in excellent agreement with the experimental result of Abeles et al. Our results for high dimensionality agree well with the results of ε-expansion calculations

Long Range Order in Random Anisotropy Magnets

High temperature series for the magnetic susceptibility, χ, of random anisotropy axis models in the limit of infinite anisotropy are presented, for two choices of the number of spin components, m. For m=2, we find T c =1.78 J on the simple cubic lattice, and on the face‐centered cubic lattice we find T c =4.29 J. There is no divergence of χ at finite temperature for m=3 on either lattice. For the four‐dimensional hypercubic lattice, we find finite temperature divergences of χ for both m=2 and m=3

High-Temperature Series for Random-Anisotropy Magnets

High-temperature series expansions for thermodynamic functions of random-anisotropy-axis models in the limit of infinite anisotropy are presented, for several choices of the number of spin components, m. In three spatial dimensions there is a divergence of the magnetic susceptibility χM for m=2. We find Tc/J=1.78±0.01 on the simple cubic lattice, and on the face-centered cubic lattice, we find Tc/J=4.29±0.01. There is no divergence of χM at finite temperature for m≥3 on either lattice. We also give results for simple hypercubic lattices

Critical Behavior of Random Resistor Networks

We present numerical data and scaling theories for the critical behavior of random resistor networks near the percolation threshold. We determine the critical exponents of a suitably defined resistance correlation function by a Padé analysis of low-concentration expansions as a function of dimensionality. We verify that d=6 is the critical dimensionality for the onset of mean-field behavior. We use the coherent-potential approximation to construct a mean-field scaling function for the critical region

A CURRENT ASSESSMENT OF VOLE DAMAGE AND NUMBERS AND OF METHODS USED TO CONTROL VOLES IN ONTARIO APPLE ORCHARDS

A province-wide evaluation of the amount, distribution, source and control of damage to Ontario apple trees was initiated. Data we re obtained from 280 responses to a questionnaire distributed to growers across Ontario, and from trap censuses in three widely separated areas. Meadow voles (Microtus pennsylvanicus) damaged or destroyed 8,423 trees in our questionnaire sample and other mammals damaged another 10,307 trees. No relationship was found between application of rodenticide and levels of damage, but rodenticide-treated baits sharply reduced numbers of voles on our trap plots. Orchards with high levels of damage were on average only one-third as large as the average orchard in our total sample. All damage by voles appeared to be caused by meadow voles and no pine voles (M. pinetorum) were found. Numbers of voles varied greatly among our three study areas. Future work will concentrate on factors causing high levels of damage and on the relationship between dispersal of voles and the effects of rodenticide treatment

Relationship Between Seasonal Changes in Forage Quality and Feeding Patterns in Meadow Voles (Microtus pennsylvanicus)

Forage analyses revealed that mowed orchards provide a relatively high quality forage to meadow voles (Microtus pennsylvanicus), especially in the fall. Mowed forage was characterized by significantly higher protein and moisture content and significantly lower acid and neutral detergent fibre and lignin than forage from an abandoned orchard. Energy and fat were not significantly affected by mowing. However, vole numbers declined markedly in mowed regions in comparison to undisturbed areas. Voles preferred to inhabit areas with dense cover even though vegetative dieback had occurred. Voles did not exhibit any distinct preference for either cracked corn (rodenticide carrier agent) or available forage at any time during the study. Voles did not change rates of forage consumption over the 6-month study. We conclude that mowing will not reduce acceptability of cracked corn and that removal of dense ground cover from the orchard would be one of the most effective and economical ways to reduce numbers of voles and minimize tree damage

Control of Damage by Mammals in Ontario Orchards

Each year, mammalian wildlife causes extensive and costly damage to fruit tree growers throughout Ontario. In 1981, in response to the concern among fruit growers over high levels of this damage, the Ontario Apple Marketing Commission and the Ontario Ministry of Agriculture and Food requested that we initiate a long-term study of this problem. However, the desire to improve available control practices was impeded by a general lack of know ledge of the scope of mammalian pest problems in Ontario. For example, the extent and degree of damage in relation to seasonal and regional differences, pest population levels and management practices was unknown. Accordingly, our research program has four basic objectives: first, to assess level of tree injury caused by mammalian pests and to deter-mine the costs of this damage and of methods currently used to control the pest species; second, to identify the species causing damage; third, to identify biological indicators that could be used by growers to predict periods of potential high damage; fourth, to develop and recommend a cost-effective, long-range program to monitor and control pest species

A CURRENT ASSESSMENT OF VOLE DAMAGE AND NUMBERS AND OF METHODS USED TO CONTROL VOLES IN ONTARIO APPLE ORCHARDS

A province-wide evaluation of the amount, distribution, source and control of damage to Ontario apple trees was initiated. Data we re obtained from 280 responses to a questionnaire distributed to growers across Ontario, and from trap censuses in three widely separated areas. Meadow voles (Microtus pennsylvanicus) damaged or destroyed 8,423 trees in our questionnaire sample and other mammals damaged another 10,307 trees. No relationship was found between application of rodenticide and levels of damage, but rodenticide-treated baits sharply reduced numbers of voles on our trap plots. Orchards with high levels of damage were on average only one-third as large as the average orchard in our total sample. All damage by voles appeared to be caused by meadow voles and no pine voles (M. pinetorum) were found. Numbers of voles varied greatly among our three study areas. Future work will concentrate on factors causing high levels of damage and on the relationship between dispersal of voles and the effects of rodenticide treatment

Comparison of the diagnostic accuracy of three current guidelines for the evaluation of asymptomatic pancreatic cystic neoplasms.

Asymptomatic pancreatic cysts are a common clinical problem but only a minority of these cases progress to cancer. Our aim was to compare the accuracy to detect malignancy of the 2015 American Gastroenterological Association (AGA), the 2012 International Consensus/Fukuoka (Fukuoka guidelines [FG]), and the 2010 American College of Radiology (ACR) guidelines.We conducted a retrospective study at 3 referral centers for all patients who underwent resection for an asymptomatic pancreatic cyst between January 2008 and December 2013. We compared the accuracy of 3 guidelines in predicting high-grade dysplasia (HGD) or cancer in resected cysts. We performed logistic regression analyses to examine the association between cyst features and risk of HGD or cancer.A total of 269 patients met inclusion criteria. A total of 228 (84.8%) had a benign diagnosis or low-grade dysplasia on surgical pathology, and 41 patients (15.2%) had either HGD (n = 14) or invasive cancer (n = 27). Of the 41 patients with HGD or cancer on resection, only 3 patients would have met the AGA guideline\u27s indications for resection based on the preoperative cyst characteristics, whereas 30/41 patients would have met the FG criteria for resection and 22/41 patients met the ACR criteria. The sensitivity, specificity, positive predictive value, negative predictive value of HGD, and/or cancer of the AGA guidelines were 7.3%, 88.2%, 10%, and 84.1%, compared to 73.2%, 45.6%, 19.5%, and 90.4% for the FG and 53.7%, 61%, 19.8%, and 88% for the ACR guidelines. In multivariable analysis, cyst size \u3e3 cm, compared to ≤3 cm, (odds ratio [OR] = 2.08, 95% confidence interval [CI] = 1.11, 4.2) and each year increase in age (OR = 1.07, 95% CI = 1.03, 1.11) were positively associated with risk of HGD or cancer on resection.In patients with asymptomatic branch duct-intraductal papillary mucinous neoplasms or mucinous cystic neoplasms who underwent resection, the prevalence rate of HGD or cancer was 15.2%. Using the 2015 AGA criteria for resection would have missed 92.6% of patients with HGD or cancer. The more inclusive FG and ACR had a higher sensitivity for HGD or cancer but lower specificity. Given the current deficiencies of these guidelines, it will be important to determine the acceptable rate of false-positives in order to prevent a single true-positive