Confinement interaction in nonlinear generalizations of the Wick-Cutkosky model

We consider nonlinear-mediating-field generalizations of the Wick-Cutkosky model. Using an iterative approach and eliminating the mediating field by means of the covariant Green function we arrive at a Lagrangian density containing many-point time-nonlocal interaction terms. In low-order approximations of $\phi^3{+}\phi^4$ theory we obtain the usual two-current interaction as well as a three-current interaction of a confining type. The same result is obtained without approximation for a version of the dipole model. The transition to the Hamiltonian formalism and subsequent canonical quantization is performed with time non-locality taken into account approximately. A relativistic three-particle wave equation is derived variationally by using a three-particle Fock space trial state. The non-relativistic limit of this equation is obtained and its properties are analyzed and discussed.Comment: 15 pages, 1 figure, LaTe

Non-destructive Method of Leaf Area Estimation for Oleander (Nerium oleander L.) Cultivated in the Iraqi Kurdistan Region

This study was conducted in the Iraqi Kurdistan region in January 2014 to determine the individual leaf area of oleander (Nerium oleander L.) by easy, accurate, inexpensive, and nondestructive method. Simple, multiple and exponential regression analyses were used by length (L) and width (W) and their combinations as independent variables and with leaf area as dependent variable to determine more accurate models (high coefficient of determination and less MSE). The results showed that the best fitting models that show more accurate estimation of oleander leaf area, compared to other models, were the simple linear regression that depends on length multiple width for Koya and Erbil cities and the total leaves of the two cities plants. On the other hand, the best fitting multiple linear equations were those which depend on square length and square width for Koya city and the total leaves of the two cities plants, whereas for Erbil city the best model was that depends on leaves with square length and width. Multiple linear regressions were the more accurate among the models, followed by simple linear regression, whereas the exponential model had the lowest accuracy. All coefficients of regressions values were found to be significant at the P < 0.0001 level

Mitigating Cotton Revenue Risk Through Irrigation, Insurance, and Hedging

This study focuses on managing cotton production and marketing risks using combinations of irrigation levels, put options (as price insurance), and crop insurance. Stochastic cotton yields and prices are used to simulate a whole-farm financial statement for a 1,000 acre furrow irrigated cotton farm in the Texas Lower Rio Grande Valley under 16 combinations of risk management strategies. Analyses for risk-averse decision makers indicate that multiple irrigations are preferred. The benefits to purchasing put options increase with yields, as they are more beneficial when higher yields are expected from applying more irrigation applications. Crop insurance is strongly preferred at lower irrigation levels.cotton, crop insurance, irrigation, options, puts, risk, simulation, stochastic efficiency with respect to a function, Farm Management, Risk and Uncertainty, D81, Q12, Q15,

The onset of the permo-carboniferous glaciation: Reconciling global stratigraphic evidence with biogenic apatite δ18O records in the late Visean

The δ18O values of phosphatic microfossils recovered from NW Ireland are used to determine the timing and magnitude of cooling associated with the onset of the Carboniferous glaciation. Microfossil fish δ18Oapatite demonstrates a +2.4‰ (V-SMOW) shift, which, once corrected for δ18Oseawater changes owing to evolving ice volumes, equates to an approximate 4.5°C reduction in equatorial sea surface temperature between the earliest Asbian and the mid-Brigantian (late Visean). Both conodont and microfossil fish δ18Oapatite indicate stabilization of an ‘icehouse’ climate during the Brigantian and into the Serpukhovian. Substantial late Visean cooling identified herein is in good agreement with global glacioeustatic records

Variational Derivation of Relativistic Fermion-Antifermion Wave Equations in QED

We present a variational method for deriving relativistic two-fermion wave equations in a Hamiltonian formulation of QED. A reformulation of QED is performed, in which covariant Green functions are used to solve for the electromagnetic field in terms of the fermion fields. The resulting modified Hamiltonian contains the photon propagator directly. The reformulation permits one to use a simple Fock-space variational trial state to derive relativistic fermion-antifermion wave equations from the corresponding quantum field theory. We verify that the energy eigenvalues obtained from the wave equation agree with known results for positronium.Comment: 25 pages, accepted in Journal of Mathematical Physics (2004

Bound-State Variational Wave Equation For Fermion Systems In QED

We present a formulation of the Hamiltonian variational method for QED which enables the derivation of relativistic few-fermion wave equation that can account, at least in principle, for interactions to any order of the coupling constant. We derive a relativistic two-fermion wave equation using this approach. The interaction kernel of the equation is shown to be the generalized invariant M-matrix including all orders of Feynman diagrams. The result is obtained rigorously from the underlying QFT for arbitrary mass ratio of the two fermions. Our approach is based on three key points: a reformulation of QED, the variational method, and adiabatic hypothesis. As an application we calculate the one-loop contribution of radiative corrections to the two-fermion binding energy for singlet states with arbitrary principal quantum number $n$, and $l =J=0$. Our calculations are carried out in the explicitly covariant Feynman gauge.Comment: 26 page

Farming inWisconsin at the End of the Century: Results of the 1999 Wisconsin Farm Poll

Farming in Wisconsin has undergone considerable change in the last few decades. U.S. Census statistics suggest that the state lost almost 13 percent of its farms and over 10 percent of its farmland between 1987-1997. The decline in farm numbers was particularly severe for mid-sized commercial livestock farms. During this period, the number of hog farms dropped by almost 60 percent, dairy farms fell by 40 percent, and farms with any harvested cropland declined by more than 20 percent (Buttel, 1999). Meanwhile, when dairy and hog farm number declines are removed from the equation, census results show that there was actually significant growth in part-time and hobby farm numbers during the 1990s in Wisconsin. While the periodic Census of Agriculture provides some key insights into the long-term trends in the Wisconsin farm sector, the Census asks relatively few questions about a number of important topics. Specifically, there is little information gathered about the use of different agricultural technologies or management practices. In addition, despite the fact that most Wisconsin farms are run as family businesses, there is virtually no information collected about members of the farm household (other than the lead operator) or the household’s involvement in off-farm as well as farming activities. Finally, the Census asks no questions about the opinions or views of Wisconsin farmers concerning important public policy questions

Assessing the fidelity of marine vertebrate microfossil δ18O signatures and their potential for palaeo-ecological and -climatic reconstructions

Conodont biogenic apatite has become a preferred analytical target for oxygen isotope studies investigating ocean temperature and palaeoclimate changes in the Palaeozoic. Despite the growing application in geochemically-based palaeoenvironmental reconstructions, the paucity or absence of conodont fossils in certain facies necessitates greater flexibility in selection of robust oxygen-bearing compounds for analysis. Vertebrate microfossils (teeth, dermal denticles, spines) offer a potential substitute for conodonts from the middle Palaeozoic. Vertebrate bioapatite is particularly advantageous given a fossil record extending to the present with representatives across freshwater to fully marine environments, thus widening the scope of oxygen isotope studies on bioapatite. However, significant tissue heterogeneity within vertebrates and differential susceptibility of these tissues to diagenetic alteration have been raised as potential problems affecting the reliability of the oxygen isotope ratios as palaeoclimatic proxies. Well-preserved vertebrate microfossils and co-occurring conodont fossils from the Upper Devonian and Lower Carboniferous of the Lennard Shelf, Canning Basin, Western Australia, were analysed using bulk (gas isotope ratio mass spectrometry, GIRMS) and in-situ (secondary ion mass spectrometry, SIMS) methodologies, with the latter technique allowing investigation of specific tissues within vertebrate elements. The d18Oconodont results may be interpreted in terms of palaeolatitudinally and environmentally sensible palaeo-salinity and -temperature and provide a baseline standard for comparison against vertebrate microfossil d18O values. Despite an absence of obvious diagenetic modification, GIRMS of vertebrate denticles yielded d18O values depleted in 18O by 2–4‰ relative to co-occurring conodonts. SIMS analysis of dentine tissues exhibited significant heterogeneity, while hypermineralised tissues in both scales and teeth produced d18O values comparable with those of associated conodonts. The susceptibility of permeable phosphatic fossil tissues to microbial activity, fluid interaction and introduction of mineral precipitates post-formation is demonstrated in the dentine of vertebrate microfossils, which showed significant heterogeneity and consistent depletion in 18O relative to conodonts. The hypermineralised tissues present in both teeth and scales appear resistant to many diagenetic processes and indicate potential for palaeoclimatic reconstructions and palaeoecological investigations

Assessment in Practice: A Companion Guide to the ASK Standards

Colleges today are asked to provide greater proof that they are providing quality educational experiences to their students. There has been a growing need for student affairs to provide documentation that their areas also impact learning and student experience. However, many student affairs professionals are overwhelmed by the idea of assessment and are looking for examples of best practices in this area. Several years ago the American College Personnel Association\u27s Commission Director for Assessment and Evaluation developed the Assessment Skills and Knowledge Standards for practitioners. This document provides exampes of these standards in practice

New Second Preimage Attacks on Dithered Hash Functions with Low Memory Complexity

Dithered hash functions were proposed by Rivest as a method to mitigate second preimage attacks on Merkle-Damgard hash functions. Despite that, second preimage attacks against dithered hash functions were proposed by Andreeva et al. One issue with these second preimage attacks is their huge memory requirement in the precomputation and the online phases. In this paper, we present new second preimage attacks on the dithered Merkle-Damgard construction. These attacks consume significantly less memory in the online phase (with a negligible increase in the online time complexity) than previous attacks. For example, in the case of MD5 with the Keranen sequence, we reduce the memory complexity from about 2^51 blocks to about 2^26.7 blocks (about 545 MB). We also present an essentially memoryless variant of Andreeva et al. attack. In case of MD5-Keranen or SHA1-Keranen, the offline and online memory complexity is 2^15.2 message blocks (about 188–235 KB), at the expense of increasing the offline time complexity