CROSS-SECTIONAL ESTIMATION OF U.S. DEMAND FOR BEEF PRODUCTS: A CENSORED SYSTEM APPROACH

Demands for beef products are investigated using the U.S. Department of AgricultureÂ’'s 1987-88 Nationwide Food Consumption Survey data. The censored translog demand system is estimated with full-information and simulated maximum-likelihood procedures. These procedures represent different approaches to evaluation of multiple probability integrals in the likelihood function, but produce very similar parameter and elasticity estimates. Findings suggest sociodemographic variables play important roles in the demand for beef, and that demand for different cuts of beef should be treated differently.Demand and Price Analysis,

HOUSEHOLD DEMAND FOR FINFISH: A GENERALIZED DOUBLE-HURDLE MODEL

This study estimates household demand for finfish in the United States using a limited dependent variable model that accounts for both participation and consumption decisions and also accommodates nonnormal heteroskedastic errors. Results suggest that own-price elasticity is near unitary and income elasticity is small. Price of finfish, shopping frequency, Northeast, Black and other non-Whites, and the life-cycle variable “"young, single, no children”" are they key factors that affect significantly both the probability of participation and the level of finfish consumption. Furthermore, a variable may exert opposite effects on the probability and level of consumption.Consumer/Household Economics, Demand and Price Analysis,

ESTIMATION OF A DEMAND SYSTEM WITH LIMITED DEPENDENT VARIABLES

The study employs the full-information maximum-likelihood method to estimate a censored translog demand system. U.S. household consumption of steak, roast, and ground beef are used to demonstrate the application of the estimation procedure. The proposed methodology produces more efficient estimates than the popular two-step procedures found in demand literature.Demand and Price Analysis,

Two paths of cluster evolution: global expansion versus core collapse

All gravitationally bound clusters expand, due to both gas loss from their most massive members and binary heating. All are eventually disrupted tidally, either by passing molecular clouds or the gravitational potential of their host galaxies. However, their interior evolution can follow two very different paths. Only clusters of sufficiently large initial population and size undergo the combined interior contraction and exterior expansion that leads eventually to core collapse. In all other systems, core collapse is frustrated by binary heating. These clusters globally expand for their entire lives, up to the point of tidal disruption. Using a suite of direct N-body calculations, we trace the "collapse line" in r_v-N space that separates these two paths. Here, r_v and N are the cluster's initial virial radius and population, respectively. For realistic starting radii, the dividing N-value is from 10^4 to over 10^5. We also show that there exists a minimum population, N_min, for core collapse. Clusters with N < N_min tidally disrupt before core collapse occurs. At the Sun's Galactocentric radius, R_G = 8.5 kpc, we find N_min >~ 300. The minimum population scales with Galactocentric radius as R_G^{-9/8}. The position of an observed cluster relative to the collapse line can be used to predict its future evolution. Using a small sample of open clusters, we find that most lie below the collapse line, and thus will never undergo core collapse. Most globular clusters, on the other hand, lie well above the line. In such a case, the cluster may or may not go through core collapse, depending on its initial size. We show how an accurate age determination can help settle this issue.Comment: Accepted for publication in MNRAS. 14 Pages, 9 Figures, 2 Table

Logarithmic Conformal Field Theory Solutions of Two Dimensional Magnetohydrodynamics

We consider the application of logarithmic conformal field theory in finding solutions to the turbulent phases of 2-dimensional models of magnetohydrodynamics. These arise upon dimensional reduction of standard (infinite conductivity) 3-dimensional magnetohydrodynamics, after taking various simplifying limits. We show that solutions of the corresponding Hopf equations and higher order integrals of motion can be found within the solutions of ordinary turbulence proposed by Flohr, based on the tensor product of the logarithmic extension ${\tilde c}_{6,1}$ of the non-unitary minimal model $c_{6,1}$. This possibility arises because of the existence of a continuous hidden symmetry present in the latter models, and the fact that there appear several distinct dimension -1 and -2 primary fields.Comment: 15 pages, Latex; references adde

Charge and spin collective modes in a quasi-1D model of Sr2RuO4

Given that Sr2RuO4 is a two-component p-wave superconductor, there exists the possibility of well defined collective modes corresponding to fluctuations of the relative phase and spin-orientation of the two components of the order parameter. We demonstrate that at temperatures much below Tc, these modes have energies small compared to the pairing gap scale if the superconductivity arises primarily from the quasi 1D (dxz and dyz) bands, while it is known that their energies become comparable to the pairing gap scale if there is a substantial involvement of the quasi 2D (dxy) band. Therefore, the orbital origin of the superconductivity can be determined by measuring the energies of these collective modes.Comment: 11 pages (6 pages for main text), 2 figure

Adoption of robotic assisted partial nephrectomies: a population-based analysis of U.S. surgeons from 2004-2013

The advent of minimally invasive and robotic techniques has resulted in the rapid adoption of this novel technology, with the field of urology at the forefront. Since the first Robotic‐Assisted Laparoscopic Radical Prostatectomy (RALP) was performed in 2000 using  the da Vinci Surgical System (Intuitive Surgical, Inc., Sunnyvale, CA, USA), surgeons have rapidly incorporated robotic technology for the use of radical prostatectomies for prostatic carcinoma. Prior to 2005, only a minority of surgeons‐‐fewer than 2.5%‐‐performing radical  prostatectomies utilized robotic assistance.  However, robotic assistance has become the predominant approach for radical prostatectomies, increasing from 22% to 85% between the years 2002 to 2013, representing a nearly five‐fold increase in utilization

The Kapustin-Witten equations and nonabelian Hodge theory

Arising from a topological twist of $\mathcal{N} = 4$ super Yang-Mills theory are the Kapustin-Witten equations, a family of gauge-theoretic equations on a four-manifold parametrized by $t\in\mathbb{P}^1$. The parameter corresponds to a linear combination of two super charges in the twist. When $t=0$ and the four-manifold is a compact K\"ahler surface, the equations become the Simpson equations, which was originally studied by Hitchin on a compact Riemann surface, as demonstrated independently in works of Nakajima and the third-named author. At the same time, there is a notion of $\lambda$-connection in the nonabelian Hodge theory of Donaldson-Corlette-Hitchin-Simpson in which $\lambda$ is also valued in $\mathbb{P}^1$. Varying $\lambda$ interpolates between the moduli space of semistable Higgs sheaves with vanishing Chern classes on a smooth projective variety (at $\lambda=0$) and the moduli space of semisimple local systems on the same variety (at $\lambda=1$) in the twistor space. In this article, we utilise the correspondence furnished by nonabelian Hodge theory to describe a relation between the moduli spaces of solutions to the equations by Kapustin and Witten at $t=0$ and $t \in \mathbb{R} \setminus \{ 0 \}$ on a smooth, compact K\"ahler surface. We then provide supporting evidence for a more general form of this relation on a smooth, closed four-manifold by computing its expected dimension of the moduli space for each of $t=0$ and $t \in \mathbb{R} \setminus \{ 0 \}$.Comment: 17 page