Urban spatial pattern as self-organizing system: An empirical evaluation of firm location decisions in Cleveland–Akron PMSA,Ohio

Economic models of urban spatial patterns have largely ignored complexity as an attribute of urban systems. Complexity theorists on the other hand have not made sufficiently serious and sustained attempts to verify empirically the relevance of complex systems models for urban spatial patterns. This research bridges this gap by simulating the evolution of an urban employment pattern as a self-organizing complex system and seeking its empirical validation. It estimates the model’s parameters by using firm data aggregated to the level of municipalities in Cleveland-Akron Consolidated Metropolitan Statistical Area in Ohio. The interaction among four parameters, forces of attraction and dispersion and their respective rates of dissipation with distance, are modeled as a two-dimensional complex system. The research compares the states of the modeled system with empirical data to present viable methods for verification, calibration and validation of such models.

---

     

Short communication: Effect of pomegranate-residue supplement on Cryptosporidium parvum oocyst shedding in neonatal calves

Cryptosporidium parvum is considered one of the most common enteropathogens, responsible for the high incidence of diarrhea and deleterious implications on immunity and health in neonatal calves. The pomegranate is well known for its health-promoting properties. Two experiments were designed to test the antiparasitical and antidiarrheal effects of concentrated pomegranate extract (CPE) supplement in milk in neonatal Holstein calves. Forty-one calves were randomly divided into control (n = 20) and treatment (n = 21) groups. For the first experiment, the treatment group was supplemented with 3.75% CPE in the daily milk ration, between 3 and 14 d of age, whereas the control group received only milk. Fecal samples were collected between d 5 and 13 to quantify Cryptosporidium oocysts, and the duration and intensity of diarrhea were evaluated. Reduced fecal oocyst count and diarrhea intensity and duration were revealed in the 3.75% CPE calves. No difference was noted in average daily gain between groups. In a second experiment, which was designed to test the effect of a lower CPE concentration (0.6% of daily milk allocation), no effects on fecal oocyst count and average daily gain were observed. However, compared with control, the lower CPE group was characterized by a shorter duration of diarrhea and higher weight gain among males at 14 d of age. These results suggest that the CPE supplement-to-calf milk ratio may potentially alleviate intestinal morbidity caused by Cryptosporidium.     

Porous CaP/silk composite scaffolds to repair femur defects in an osteoporotic model

The most common complication for patients with postmenopausal osteoporosis is bone-related defects and fractures. While routine medication has a high probability of undesirable side effects, new approaches have aimed to develop regeneration procedures that stimulate new bone formation while reversing bone loss. Recently, we have synthesized a new hybrid CaP/silk scaffold with a CaP-phase distribution and pore architecture better suited to facilitate cell differentiation and bone formation. The aim of the present study was to compare the involved remodeling process and therapeutic effect of porous CaP/silk composite scaffolds upon local implantation into osteoporotic defects. Wistar rats were used to induce postmenopausal osteoporotic model by bilateral ovariectomy. The pure silk and hybrid CaP/silk scaffolds were implanted into critical sized defects created in distal femoral epiphysis. After 14 and 28 days, the in vivo osteogenetic efficiency was evaluated by μCT analysis, hematoxylin and eosin staining, Safranin O staining, tartrate-resistant acid phosphatase staining, and immunohistochemical assessment. Animals with or without critical-sized defects were used as drill or blank controls, respectively. The osteoporotic defect model was well established with significantly decreased μCT parameters of BV/TV, Tb.N and increased Tb.Sp, porosity, combined with changes in histological observations. During the healing process, the critical-sized drill control defects failed to regenerate appreciable bone tissue, while more significantly increased bone formation and mineralization with dynamic scaffold degradation and decreased osteoclastic bone resorption could be detected within defects with hybrid CaP/silk scaffolds compared to pure silk scaffolds.     

PALS free volume study of dry and water saturated epoxies

Free volume cavity sizes and fractions of epoxy specimens were determined using positron annihilation lifetime spectroscopy (PALS). PALS data were obtained before and after specimen water equilibration. Specimens were bisphenol A epoxide (B) and/or glycol epoxide (G) cured with a polyamide. Free volume sites increased linearly and cavity sizes decreased linearly with epoxide B:G ratio. Glass transition temperature (T_g) increased with epoxide B:G ratio. Water molecules in wet epoxy B filled approximately six percent of the cavities. Epoxy G cavity size increased 11.4% after water equilibrium and was ascribed to cavity expansion. PALS results differed for commercial corrosion inhibitors in wet and dry mixtures of these epoxides. Zettlemoyer Center for Surface Studies, 7 Asa Dr., Bethlehem, PA 18015. MAHMOUD M. MADANI is with the Zettlemoyer Center for Surface Studies at Lehigh University. He received his B.S. Degree in Physics from Pars College, Tehran, Iran in 1975; his B.S. Honors in 1981, M.S. Degree in 1982, and his Ph.D. Degree in 1986 from Royal Holloway and Bedford New Colleges, University of London. Dr. Madani’s current research studies include the physical chemical characteristics of polymeric coatings and the reliability and characterization of microelectronic packaging materials using PALS, EIS, XPS, SEM, XRD, and MS. He has developed several computer codes for instrumentation interfaces and data analyses. Previously, he was a lecturer in Physics at the University of Bophutatswana, South Africa. Dr. Madani is author and co-author of more than 20 scientific publications. Dr. Madani is a member of the American Physics Society. ROY R. MIRON is a Visiting Research Scientist at the Zettlemoyer Center for Surface Studies at Lehigh University. He received his B.A. and his Ph.D. Degrees from Lehigh University and his M.S. from Middlebury College. Dr. Miron has a broad background in coatings technology. He is the holder of several patents and his publications have appeared inAnalytical Chemistry, Journal Applied Polymer Science, Plastics Paint and Rubber, Plant Engineering, Western Paint Review, and the Hydrocarbon Processing and Petroleum Refiner. He has held memberships in the American Chemical Society and Society of Plastics Engineers. Dr. Miron has presented papers to the Society of Plastics Industry, Society of Plastics Engineers, and the Liberty Bell Corrosion Course. RICHARD D. GRANATA is Lehigh University Senior Research Scientist and Director of the Corrosion Laboratory. He received B.S. and Ph.D. Degrees from The American University in Washington, D.C., studying electrochemistry with Robert Foley. As a Research Scientist at Carnegie-Mellon Institute of Research with Howard Gerhart, he worked on cathodic electrocoating formulations. Moving to Lehigh University, Dr. Granata joined Henry Leidheiser at the Zettlemoyer Center for Surface Studies and continued research in protective polymers and electrochemical corrosion. He has one patent and over 50 technical papers as the author or co-author. His research experience has been acquired in cooperative work on industry and government sponsored programs. He has acquired a broad perspective on corrosion science and technology through this experience with problems involving electrochemical corrosion mechanisms, surface modification by ion implantation, cathodic delamination mechanism, corrosion inhibition, food container life-predictions, corrosion mechanisms in electronics packaging, and protective mechanisms of polymer coatings. Dr. Granata is a member of the Philadelphia Society for Coatings Technology, ECS, National Association of Corrosion Engineers, American Society for Testing and Materials, Steel Structures Paint Council, and American Chemical Society.     

Digestibility by dairy cows of monosaccharide constituents in total mixed rations containing citrus pulp

Ten lactating cows were divided into two groups and individually fed ad libitum one of two experimental total mixed rations (TMR) as follows: 1) a TMR containing 20% corn grain and 10% dry citrus pulp (high corn); and 2) a TMR containing 21% citrus pulp and 9% corn grain (high citrus pulp). Both TMR also contained corn silage (28%), legume haylage (19.5%), extruded full fat soybeans (13.5 to 14%), soybean meal (6.5%), and minerals and vitamins. Voluntary dry matter intake of cows consuming the high corn ration tended to be higher than for cows in the high citrus pulp group (22.2 vs. 20.7 +/- 1.0 kg/cow per day, respectively). Digestibility of NDF was higher for the TMR with high citrus pulp compared with the TMR with higher corn. Across treatments, neutral detergent fiber (NDF) glucose was more digestible than NDF xylose and uronic acids and less digestible than NDF arabinose, galactose, and mannose. Digestibility of total neutral detergent soluble carbohydrates was also higher in the high citrus pulp group (86.8, high citrus pulp vs. 80.3 +/- 1.7%, high corn); with glucose and uronic acids accounting for most of that difference. Consequently, higher total carbohydrate digestibility was obtained in the TMR containing higher citrus pulp compared with the TMR with a higher percentage of corn (77.1 and 72.5 +/- 1.0%, respectively). Slightly lower carbohydrate intake in cows fed higher citrus pulp was compensated by higher digestibility of carbohydrates and protein. Thereby, partial replacement of corn by citrus pulp in TMR of high producing dairy cows improved feed efficiency.     

Fluorescence anisotropy--a parameter for characterizing membrane fluidity

The lipophilic fluorescent probe diphenylhexatriene (DPH) has been shown previously to behave as a marker of plasma membrane in living cell systems, and it is therefore been widely used in membrane fluidity studies via fluorescence anisotropy measurements. The anisotropic coefficient, which is inversely related to the rotational motion of the probe in membrane phospholipids, was significantly higher at 37 degrees C than at 23 degrees C for 9 series of red blood cells ghosts obtained from three healthy subjects. We also have studied the importance of the nature of two different polaroid films which permits the observation of fluorescence polarization.     

Effect of Fe content on positron annihilation in neutron irradiated V---Fe alloys

Neutron irradiated V---xFe alloys (with x from 0 to 5 at.%) have been studied by the conventional positron annihilation technique. A remarkable narrowing of angular correlation of annihilation radiation (ACAR) curves was observed for all alloys investigated. A specific feature of ACAR curves in pure vanadium is the presence of a narrow component attributed usually to the positronium (Ps) formation in voids, with inner surfaces covered by gaseous impurities such as oxygen. Significant changes in the ACAR curve component intensities with increase of iron content has been observed. At Fe concentration of about 1 at.% the narrow component disappears completely and the intensity of the middle one decreases significantly. It was concluded that the increase of Fe concentration in V---Fe alloys suppresses the void surface contamination by oxygen atoms and changes the positron work function from bulk materials into voids. Such behavior of the ACAR curve component intensities can be explained in terms of radiation-induced segregation of iron atoms at point defect sinks.     

Effect of Fe content on positron annihilation in neutron irradiated VFe alloys

Neutron irradiated VxFe alloys (with x from 0 to 5 at.%) have been studied by the conventional positron annihilation technique. A remarkable narrowing of angular correlation of annihilation radiation (ACAR) curves was observed for all alloys investigated. A specific feature of ACAR curves in pure vanadium is the presence of a narrow component attributed usually to the positronium (Ps) formation in voids, with inner surfaces covered by gaseous impurities such as oxygen. Significant changes in the ACAR curve component intensities with increase of iron content has been observed. At Fe concentration of about 1 at.% the narrow component disappears completely and the intensity of the middle one decreases significantly. It was concluded that the increase of Fe concentration in VFe alloys suppresses the void surface contamination by oxygen atoms and changes the positron work function from bulk materials into voids. Such behavior of the ACAR curve component intensities can be explained in terms of radiation-induced segregation of iron atoms at point defect sinks.     

Seeking the truth about ad hoc join costs

In this paper, we re-examine the results of prior work on methods for computing ad hoc joins. We develop a detailed cost model for predicting join algorithm performance, and we use the model to develop cost formulas for the major ad hoc join methods found in the relational database literature. We show that various pieces of “common wisdom” about join algorithm performance fail to hold up when analyzed carefully, and we use our detailed cost model to derive op timal buffer allocation schemes for each of the join methods examined here. We show that optimizing their buffer allocations can lead to large performance improvements, e.g., as much as a 400% improvement in some cases. We also validate our cost model's predictions by measuring an actual implementation of each join algorithm considered. The results of this work should be directly useful to implementors of relational query optimizers and query processing systems. Edited by M. Adiba. Received May 1993 / Accepted April 1996