Regional economic integration and foreign direct investment: The case of NAFTA

Abstract and Key Results

An Efficient Transmission Scheme for Minimizing User Waiting Time in Video-On-Demand Systems

To take the advantage of skewed popularity of videos, efficient video-on-demand (VOD) systems are more likely to deliver the most popular videos through periodic broadcasting and the least popular videos through on-demand multicasting. While videos delivered through multicasting usually share a pool of server channels, broadcasting of each video demands one or more channels dedicated to it. Given a total number of available channels, distributing them for individual broadcasting and the multicasting pool to achieve the optimal average user waiting time is a nonlinear optimization problem. This letter addresses this problem by proposing a hybrid transmission scheme, which uses dynamic programming approach to ensure optimally for any given number of channels and request arrival rate     

Strain rate effect on crystallinity variations in the double yield region of polyethylene

The double yield phenomenon was studied using numerous specimens uniaxially deformed up to different elongations of linear low‐density polyethylene samples. Extruded samples prepared under different conditions were deformed at 1, 10, and 50 mm/min. The crystallinity under stressed state was calculated using the wide‐angle X‐ray scattering technique. The crystallinity degrees of the samples without deformation were less than 55%. This parameter, as a function of the elongation, presented a multistep behavior. An increment before the first yield point and a decrement after this point; then, at higher elongation values around the second yield point, another decrement and an abrupt increment. The behavior was more notorious at intermediate and lower strain rates. The results around the second yield point were interpreted in terms of melting of the less perfect crystallites followed by a recrystallization process. These experimental findings show that the partial melting–recrystallization process is one of the main mechanisms of the double yield phenomenon. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The prognostic factors for early mortality and for total or partial gammagraphic resolution in venous thromboembolic disease

Our objective was to investigate possible factors implicated in either early death from or scintigraphic resolution of pulmonary embolism. To that end we conducted a retrospective study of 116 patients with either a high likelihood of pulmonary thromboembolism (PTE) diagnosed by scintiscan or with a fair probability of PTE by scintiscan accompanied by a positive phlebograph. The images were taken upon admission, at 7 days, 10 days and 6 months. The factors analyzed were age, sex, trauma, immobility, surgery, obesity, hemiplegia, venous insufficiency, cardiopulmonary disease, neoplasia, chest X-ray and ECG alterations, D(A-a)O2 and size of perfusion defects upon admission and 7 to 10 days later. We performed single-variable analyses and multiple logical regression analyses using perfusion defect at 6 months as the dependent variable. The early mortality rate (13%) was higher in patients with neoplasms, a larger alveolar-arterial index and greater perfusion defects upon admission. Scintiscans became normal in 28%. Multivariate analysis to predict total or partial resolution at 6 months showed that size of perfusion defects at 7 to 10 days was the best predictive factor. A cutoff point was calculated by analyzing the ROC for this factor. Thus, when the defect at 7 to 10 days was equal to or greater than 1 segment, the probability of residual defects remaining after 6 months was twice as great (sensitivity 83%, specificity 57%). In conclusion, early death was more likely in PTE patients with neoplasms, larger defects upon admission and greater alveolar-arterial difference. Scintigrams showed resolution 6 months after admission in 28%. The size of perfusion defects 7 to 10 days after admission was the factor that best predicted total of partial resolution at 6 months.     

Novel velocity and call duration support for QoS provision in mobile wireless networks

This article presents a novel mobility-based resource reservation and call admission control scheme that is applicable to any real wireless multimedia network. The scheme exploits three key mobility parameters - the position, direction, and speed of a mobile unit - together with the duration of a particular call to accurately estimate the cell visiting probability in order to identify a shadow cluster of cells the unit is most likely to visit. Each cell in the cluster reserves resources for an estimated time interval, which is adapted depending on the aggregated probability of all active units visiting a particular cell. Simulation results confirm the superiority of the new scheme over the existing predictive mobility support scheme in terms of three QoS parameters: call blocking rate, call dropping rate, and channel utilization.     

A Facile Access to New Polymethylmethacrylate-Anchored Ferrocene Substituted Nickel(II) Unsymmetrical Schiff Base Complexes: Synthesis and Characterization

This paper discloses two new side-chain metallopolymers containing an unsymmetrical organometallic Schiff base complex of Ni(II) linked to a polymethylmethacrylate (PMMA) matrix. The neutral ferrocene substituted Schiff base complex 1, Ni{CpFe(η⁵-C₅H₄)-C(O)CH=C(CH₃)N–o-C₆H₄N=CH-(2-O,5-OH-C₆H₃)} where (Cp = η⁵-C₅H₅), was synthesized via template reaction by condensation of the tridentate half-unit metalloligand Fc-C(O)CH=C(CH₃)-N(H)-o-C₆H₄NH₂ (Fc = ferrocenyl = CpFe(η⁵-C₅H₄)) with 2,5-dihydroxybenzaldehyde in the presence of nickel(II) acetate tetrahydrate. The binuclear Schiff base complex of Ni(II) containing an aromatic free hydroxyl group was reacted under basic conditions with PMMA to afford, upon trans-esterification reaction, metallopolymers 2 (complex 1 monomeric unit/PMMA = 1/5) and 3 (complex 1 monomeric unit/PMMA = 1/3). Elemental analysis, FT-IR, ¹H and ¹³C NMR spectroscopies, and cyclic voltammetry were utilized to characterize the newly synthetized compounds. Surface morphology of the metallopolymer film of 2 was studied using atomic force microscopy.     

Mycosynthesis of zinc oxide nanoparticles using Pleurotus floridanus and optimization of process parameters

Zinc nanoparticles are ideal candidates for biomedical applications due to their exceptional properties and biocompatible nature. The conventional methods are unsuitable for biomedical applications owing to the use of toxic chemicals during synthesis. In this context, the synthesis of biocompatible nanoparticles using plants and microorganisms are gaining more attention. In the present study, the mycosysnthesis of zinc oxide nanoparticles were carried out using P. floridanus culture filtrate employing four different methods. The spectral analysis of the samples revealed that the method described by Malek et al. is an efficient method for the synthesis of zinc nanoparticles using mushroom culture extract. The zinc nanoparticles exhibited absorption maxima at 360 nm. The optimum pH and substrate concentration were identified to be 10 and 300 mM respectively. TEM analysis of the synthesized nanoparticles revealed that they have a spherical shape and the SAED analysis confirmed the crystalline nature of the nanoparticles with an average size of 7 nm. The stoichiometric mass percentages of zinc and oxygen were determined using EDAX and found to be 80.34% and 19.66%, respectively which corresponds to the mass percentage for pure zinc oxide nanoparticles. The XRD analysis confirmed that the synthesized nanoparticles had a hexagonal wurtzite structure.     

Thermal properties of 2:1 bismuth borate: Temperature-dependent characterizations of lone electron pairs

Applications of bismuth borate ceramics require understanding of the microscopic features, leading to macroscopic behaviors such as thermal expansion. We report the structural and spectroscopic features of Bi₄B₂O₉ between 4 K and 900 K using a combination of temperature-dependent neutron and X-ray powder diffractions and Raman spectroscopy. Lattice thermal expansion was modeled using the Debye-Einstein-Anharmonicity (DEA) fit. The model also follows four independent thermal expansion tensors of the monoclinic system. Phonon density of states obtained from the density functional theory (DFT) calculations helps to understand the low Debye temperature calculated from the metric expansion as well as from the isotropic atomic displacement parameters. Both Wang-Liebau eccentricity (WLE) parameter and Liebau density vector (LDV) are calculated from the structural data and from the DFT calculation, respectively. Whereas, the dimensionless absolute value of WLE measures the degree of deformation of the electronic deformation density of the 6s² lone electron pairs (LEPs) of the Bi³⁺ cations, LDV additionally shows the changes of the orientation of the LEP-lobes as function of temperature. Analyses of the temperature-dependent frequencies of some selected Raman modes support the choice of the elastic model of the Debye approach.