New polynomial and multidimensional extensions of classical partition results

In the 1970s Deuber introduced the notion of $(m,p,c)$-sets in $\mathbb{N}$ and showed that these sets are partition regular and contain all linear partition regular configurations in $\mathbb{N}$. In this paper we obtain enhancements and extensions of classical results on $(m,p,c)$-sets in two directions. First, we show, with the help of ultrafilter techniques, that Deuber's results extend to polynomial configurations in abelian groups. In particular, we obtain new partition regular polynomial configurations in $\mathbb{Z}^d$. Second, we give two proofs of a generalization of Deuber's results to general commutative semigroups. We also obtain a polynomial version of the central sets theorem of Furstenberg, extend the theory of $(m,p,c)$-systems of Deuber, Hindman and Lefmann and generalize a classical theorem of Rado regarding partition regularity of linear systems of equations over $\mathbb{N}$ to commutative semigroups.Comment: Some typos, including a terminology confusion involving the words `clique' and `shape', were fixe

A Profile of Immigrants in Arkansas

Discusses key demographic trends, economic factors, and public policy issues associated with immigrants in Arkansas, which has the fourth-fastest-growing immigrant population in the nation

Electrostatic Solar Sail: A Propellantless Propulsion Concept for an Interstellar Probe Mission

The propulsion of an electrostatic solar sail (E Sail) is obtained by extracting momentum from the solar wind through electrostatic repulsion of the positively charged solar wind ions (see Figure 1). The positively charged solar wind protons are deflected by the electric field created around the tethers.This electric field grows in diameter as the spacecraft moves away from the Sun, therefore the E Sail effective area grows. The growth of the E-Sail effective area allows the propulsive force to decrease as 1/r up to distances of 20 AU as it moves away from the Sun, unlike solar sail propulsion whose thrust decreases as 1/r 2 but only to distances of 5AU. This propulsive force is created without using propellant and, therefore, E-sail avoids both the mass and complexity of chemical rockets (that require large amounts of propellant, propellant storage tanks, plumbing, valves, and insulation)

Structure of the Proline Utilization A Proline Dehydrogenase Domain Inactivated by \u3ci\u3eN\u3c/i\u3e-propargylglycine Provides Insight into Conformational Changes Induced by Substrate Binding and Flavin Reduction

Proline utilization A (PutA) from Escherichia coli is a flavoprotein that has mutually exclusive roles as a transcriptional repressor of the put regulon and a membrane-associated enzyme that catalyzes the oxidation of proline to glutamate. Previous studies have shown that the binding of proline in the proline dehydrogenase (PRODH) active site and subsequent reduction of the FAD trigger global conformational changes that enhance PutA-membrane affinity. These events cause PutA to switch from its repressor to enzymatic role, but the mechanism by which this signal is propagated from the active site to the distal membrane-binding domain is largely unknown. Here, it is shown that N-propargylglycine irreversibly inactivates PutA by covalently linking the flavin N(5) atom to the ε-amino of Lys329. Furthermore, inactivation locks PutA into a conformation that may mimic the proline reduced, membrane-associated form. The 2.15 Å resolution structure of the inactivated PRODH domain suggests that the initial events involved in broadcasting the reduced flavin state to the distal membrane binding domain include major reorganization of the flavin ribityl chain, severe (35 degree) butterfly bending of the isoalloxazine ring, and disruption of an electrostatic network involving the flavin N(5), Arg431, and Asp370. The structure also provides information about conformational changes associated with substrate binding. This analysis suggests that the active site is incompletely assembled in the absence of the substrate, and the binding of proline draws together conserved residues in helix 8 and the β1-αl loop to complete the active site

Masked Bobwhite Recovery: The Need for a Multifaceted Approach

Masked bobwhite (Colinus virginianus ridgwayi) is a critically endangered quail historically found in the Sonoran grasslands of southern Arizona, USA and Sonora, Mexico. Native populations of masked bobwhite may already be extinct in the wild, but captive populations exist in the United States at G. M. Sutton Avian Research Center (Oklahoma, USA), Buenos Aires National Wildlife Refuge (Arizona, USA), and various zoos. The 47,000-hectare Buenos Aires National Wildlife Refuge, located in south-central Arizona, was established primarily for reintroduction of this bird. Recovery efforts within the refuge boundary in the 1980s and 1990s were initially successful but suffered debilitating setbacks that ultimately resulted in failure. Substantial releases were suspended in 2005. Improved habitat restoration efforts and promising conditioning and release techniques led to the belief that reintroductions could again be attempted and successful. In 2016–2017 plans were developed to increase captive propagation and reinitiate release efforts. Releases began in 2018. Over-winter survival of birds released in 2018–2019 was encouraging, and reproduction of wild birds was documented in 2019. An existing base of wild birds established from these releases could help masked bobwhite populations recover in the state. Habitat restoration, better methods of rearing, release, and conditioning, and improved production from captive facilities also inspire hope that a full recovery of the species in Arizona is possible

Analysis of boundary layer sounding data from the FIRE Marine Stratocumulus Project

October 1987.FIRE volume 2 on cover.Includes bibliographical references.We present an analysis of the boundary layer thermodynamic data obtained by the CLASS radiosonde system during the marine boundary layer experiment on San Nicolas Island in the summer of 1987. The analysis procedure retains the highest possible vertical resolution in the data. Plots of temperature, dew point temperature, potential temperature, equivalent potential temperature and saturation equivalent potential temperature are presented for each of the sixty-nine soundings taken during FIRE. Conditions were mostly cloudy with fifty-five of the sixty-nine soundings being released with stratocumulus overhead. For the fifty-live cloudy soundings, cloud top Jumps of equivalent potential temperature i, and total water mixing ratio r were also determined. Each of these soundings is then represented by a point in the (~11., ~r) plane. Fifteen of these soundings are on the unstable aide of the evaporative instability line, and there appears to be some tendency for break-up under these conditions

Core handling and processing for the WAIS Divide ice-core project

On 1 December 2011 the West Antarctic Ice Sheet (WAIS) Divide ice-core project reached its final depth of 3405 m. The WAIS Divide ice core is not only the longest US ice core to date, but is also the highest-quality deep ice core, including ice from the brittle ice zone, that the US has ever recovered. The methods used at WAIS Divide to handle and log the drilled ice, the procedures used to safely retrograde the ice back to the US National Ice Core Laboratory (NICL) and the methods used to process and sample the ice at the NICL are described and discussed