North Carolina State University

About: North Carolina State University is a education organization based out in Raleigh, North Carolina, United States. It is known for research contribution in the topics: Population & Thin film. The organization has 44161 authors who have published 101744 publications receiving 3456774 citations. The organization is also known as: NCSU & North Carolina State University at Raleigh.

Gas transport properties of poly(ether-b-amide) segmented block copolymers

Abstract: The permeation properties of H2, N2, and CO2 were determined at 35 °C and pressures up to 15 atm in phase-separated polyether-b-polyamide segmented block copolymers. These polymers contain poly(ethylene oxide) [PEO] or poly(tetramethylene oxide) [PTMEO] as the rubbery polyether phase and nylon-6 [PA6] or nylon-12 [PA12] as the hard polyamide phase. Extremely high values of polar (or quadrupolar)/nonpolar gas selectivities, coupled with high CO2 permeability coefficients, were observed. CO2/H2 selectivities as high as 9.8 and CO2/N2 selectivities as high as 56 were obtained in polymers with CO2 permeability coefficients of approximately 220 × 10−10 cm3(STP) cm/(cm2 s cmHg). As the amount of polyether increases, permeability increases. Gas permeability is higher in polymers with less polar constituents, PTMEO and PA12, than in those containing the more polar PEO and PA6 units. CO2/N2 and CO2/H2 selectivities are higher in polymers with higher concentrations of polar groups. These high selectivity values derive from large solubility selectivities in favor of CO2. Because CO2 is larger than H2 and has, therefore, a lower diffusion coefficient than H2, the weak size-sieving ability of the rubbery polyether phase, which is the locus of most of the gas permeation, also contributes to high CO2/H2 selectivity. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2051–2062, 2000

Furthering the integration of routine activity and social disorganization theories: small units of analysis and the study of street robbery as a diffusion process

Abstract: Attempts to integrate the two predominant spatial theories of crime, social disorganization and routine activity theories, may benefit from examining empirical relationships at units of analysis smaller than the relatively large units characteristic of most ecological research (cities, SMSAs, census tracts, multiple city blocks) Small units of analysis, specifically, face blocks (both sides of a city block between two intersections) are analyzed in a study of street robbery within a medium-size southeastern US city Models of street robbery and street-robbery “potential” suggest a crime diffusion process Several interaction effects between variables of social disorganization and routine activity theory are found, which may form the basis in future research for successful theoretical integration

Crop pests and predators exhibit inconsistent responses to surrounding landscape composition

Abstract: The idea that noncrop habitat enhances pest control and represents a win-win opportunity to conserve biodiversity and bolster yields has emerged as an agroecological paradigm. However, while noncrop habitat in landscapes surrounding farms sometimes benefits pest predators, natural enemy responses remain heterogeneous across studies and effects on pests are inconclusive. The observed heterogeneity in species responses to noncrop habitat may be biological in origin or could result from variation in how habitat and biocontrol are measured. Here, we use a pest-control database encompassing 132 studies and 6,759 sites worldwide to model natural enemy and pest abundances, predation rates, and crop damage as a function of landscape composition. Our results showed that although landscape composition explained significant variation within studies, pest and enemy abundances, predation rates, crop damage, and yields each exhibited different responses across studies, sometimes increasing and sometimes decreasing in landscapes with more noncrop habitat but overall showing no consistent trend. Thus, models that used landscape-composition variables to predict pest-control dynamics demonstrated little potential to explain variation across studies, though prediction did improve when comparing studies with similar crop and landscape features. Overall, our work shows that surrounding noncrop habitat does not consistently improve pest management, meaning habitat conservation may bolster production in some systems and depress yields in others. Future efforts to develop tools that inform farmers when habitat conservation truly represents a win-win would benefit from increased understanding of how landscape effects are modulated by local farm management and the biology of pests and their enemies.

The Development of Pine Plantation Silviculture in the Southern United States

Abstract: In the 1950s there were vast acreages of cutover forestland and degraded agricultural land across the South. Less than 2 million ac of southern pine plantations existed at that time. By the end of the 20th century, there were 32 million ac of southern pine plantations in the US South and this region is the wood basket of the world. The success story that is southern pine forestry was facilitated by the application of research results generated through cooperative work of the US Forest Service, southern forestry schools, state forestry agencies, and forest industry. This article reviews the contributions of applied silvicultural research in tree improvement, nursery management, site preparation, weed control, and fertilization to plantation forestry in the South. These practices significantly increased productivity of southern pine plantations. Plantations established in the 1950s and 1960s, which produced less than 90 ft 3 ac 1y r 1 , have been replaced by plantations established in the 2000s, which may produce in excess of 400 ft 3 ac 1y r 1 . Currently, southern pine plantations are among the most intensively managed forests in the world. Growth of plantations managed using modern, integrated, site-specific silvicultural regimes now can rival that of plantations of fast-growing exotic species in the Southern Hemisphere.

Materials Fabricated by Micro- and Nanoparticle Assembly ― The Challenging Path from Science to Engineering

Abstract: and strategies for the assembly of particle structures classified on the basis of their dimensionality. We survey the potential areas of application of the structures assembled from particles, and discuss why the technological potential of these structures is at present largely unrealized. Many of the challenges in the area of nanocolloidal assembly relate to the development of assembly processes that are scalable, controllable, rapid, and inexpensive. The power and versatility of colloidal-particle assemblies are best illustrated by the vast number of structures and strategies for their fabrication reported in the literature. A convenient way to classify the majority of the colloidal assemblies could be based on their dimensionality and degree of ordering ‐ three, two, one-dimensional, or independent clusters. In order to evaluate the ease and precision of the controlled fabrication of such materials, we also need to analyze in each case the physical principles by which a certain structure is assembled. The assembly can be accomplished by an extensive array of techniques based on numerous physical mechanisms. A survey of a few major groups of methods that have found use in the controlled assembly of particles into materials with well-organized and defined microstructures is presented in Table 1. The goal of these techniques is to collect the particles,