271 research outputs found
Computable General Equilibrium Models in Economics: A Survey on Theoretical Foundations and Applications
Computable general equilibrium (CGE) models have become an increasingly popular tool in macroeconomic analysis. The model tradition has proved particularly suitable for the study of structural changes in economy and long-run impacts of policy measures. The main fields of application include trade policy, fiscal policy, development strategies and environmental and energy policies.
The aim of this paper is to give an overview of the modeling tradition, its theoretical foundation, characteristic features and main applications. Because the paper serves as a preliminary report to the Government Institute for Economic Research particular attention is paid to the possibilities CGE-modelling offers to research in public economics
Characterization and topical delivery of phenylethyl resorcinol
Objective:
Phenylethyl resorcinol (PR) has been used widely in the personal care industry as a novel skin lightening ingredient. Surprisingly, there is only limited information describing the physicochemical properties of this active. Therefore, the primary objective of this study was to perform a comprehensive characterization of PR. A secondary objective was to investigate the delivery of this molecule to mammalian skin.
Methods:
Phenylethyl resorcinol was characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and nuclear magnetic resonance (NMR). A new high‐performance liquid chromatographic (HPLC) method for analysis of PR was developed and validated. The log P (octanol water partition coefficient), value, solubility and short‐term stability of PR in a series of vehicles were also determined using HPLC. The evaporation of the selected vehicles was examined using dynamic vapour sorption (DVS). The permeation profiles of PR were investigated under finite dose conditions in porcine and human skin.
Results:
The melting point of PR was determined to be 79.13 °C and the measured log P (octanol water partition coefficient) at 21 °C was 3.35 ± 0.03. The linearity of the HPLC analytical method was confirmed with an r2 value of 0.99. Accuracy of the method was evaluated by average recovery rates at three tested concentrations, and the values ranged from 99 to 106%. The limit of detection (LOD) and limit of quantification (LOQ) were 0.19 and 0.57 μg mL−1, respectively. The solubility of PR in PG, DMI, glycerol was within the range of 367 to 877 mg mL−1. The stability of PR in tested solvents was also confirmed by the 72 h stability studies. From the DVS studies, 70–125% of applied formulations were recovered at 24 h. The permeation through porcine skin at 24 h ranged from 4 to 13 μg cm−2, while the corresponding amounts of PR delivered through human skin were 2 to 10 μg cm−2.
Conclusion:
The physicochemical properties of PR confirm it is suitable for dermal delivery. In this study, propylene glycol was the most promising vehicle for PR delivery to human skin. Future work will expand the range of vehicles studied and explore the percutaneous absorption from more complex formulations
A new polymorphic material? Structural degeneracy of ZrMn_2
Based on density functional calculations, we propose that ZrMn_2 is a
polymorphic material. We predict that at low temperatures the cubic C15, and
the hexagonal C14 and C36 structures of the Laves phase compound ZrMn_2 are
nearly equally stable within 0.3 kJmol^{-1} or 30 K. This degeneracy occurs
when the Mn atoms magnetize spontaneously in a ferromagnetic arrangement
forming the states of lowest energy. From the temperature dependent free
energies at T approx 160K we predict a transition from the most stable C15 to
the C14 structure, which is the experimentally observed structure at elevated
temperatures.Comment: 4 pages, 3 figure
Removing Orbital Debris with Lasers
Orbital debris in low Earth orbit (LEO) are now sufficiently dense that the
use of LEO space is threatened by runaway collisional cascading. A problem
predicted more than thirty years ago, the threat from debris larger than about
1 cm demands serious attention. A promising proposed solution uses a high power
pulsed laser system on the Earth to make plasma jets on the objects, slowing
them slightly, and causing them to re-enter and burn up in the atmosphere. In
this paper, we reassess this approach in light of recent advances in low-cost,
light-weight modular design for large mirrors, calculations of laser-induced
orbit changes and in design of repetitive, multi-kilojoule lasers, that build
on inertial fusion research. These advances now suggest that laser orbital
debris removal (LODR) is the most cost-effective way to mitigate the debris
problem. No other solutions have been proposed that address the whole problem
of large and small debris. A LODR system will have multiple uses beyond debris
removal. International cooperation will be essential for building and operating
such a system.Comment: 37 pages, 15 figures, in preparation for submission to Advances in
Space Researc
The possibilities of optical methods in the early diagnosis of gliomas
A novel approach based on the Raman and absorption spectroscopy for detection of gliomas molecular markers in brain tissue and blood will be discussed. Using the mice model of the U87 human glioblastoma, we have shown the possibility of glioma development control by a combination of Raman, infrared (IR), and Terahertz (THz) pulsed spectroscopy
Implementing virtual collaborative inquiry practises in a middle-school context
The aim of the present study was to investigate the challenges that relate to the implementation of virtual inquiry practises in middle school. The case was a school course in which a group of Finnish students (N = 14) and teachers (N = 7) completed group inquiries through virtual collaboration, using a web-based learning environment. The task was to accomplish a cross-disciplinary inquiry into cultural issues. The students worked mainly at home and took much responsibility for their course achievements. The investigators analysed the pedagogical design of the course and the content of the participants' interaction patterns in the web-based environment, using qualitative content analysis and social network analysis. The findings suggest that the students succeeded in producing distinctive cultural products, and both the students and the teachers adopted novel roles during the inquiry. The web-based learning environment was used more as a coordination tool for organizing the collaborative work than as a forum for epistemic inquiry. The tension between the school curriculum and the inquiry practises was manifest in the participants' discussions of the assessment criteria of the course.The aim of the present study was to investigate the challenges that relate to the implementation of virtual inquiry practises in middle school. The case was a school course in which a group of Finnish students (N = 14) and teachers (N = 7) completed group inquiries through virtual collaboration, using a web-based learning environment. The task was to accomplish a cross-disciplinary inquiry into cultural issues. The students worked mainly at home and took much responsibility for their course achievements. The investigators analysed the pedagogical design of the course and the content of the participants' interaction patterns in the web-based environment, using qualitative content analysis and social network analysis. The findings suggest that the students succeeded in producing distinctive cultural products, and both the students and the teachers adopted novel roles during the inquiry. The web-based learning environment was used more as a coordination tool for organizing the collaborative work than as a forum for epistemic inquiry. The tension between the school curriculum and the inquiry practises was manifest in the participants' discussions of the assessment criteria of the course.The aim of the present study was to investigate the challenges that relate to the implementation of virtual inquiry practises in middle school. The case was a school course in which a group of Finnish students (N = 14) and teachers (N = 7) completed group inquiries through virtual collaboration, using a web-based learning environment. The task was to accomplish a cross-disciplinary inquiry into cultural issues. The students worked mainly at home and took much responsibility for their course achievements. The investigators analysed the pedagogical design of the course and the content of the participants' interaction patterns in the web-based environment, using qualitative content analysis and social network analysis. The findings suggest that the students succeeded in producing distinctive cultural products, and both the students and the teachers adopted novel roles during the inquiry. The web-based learning environment was used more as a coordination tool for organizing the collaborative work than as a forum for epistemic inquiry. The tension between the school curriculum and the inquiry practises was manifest in the participants' discussions of the assessment criteria of the course.Peer reviewe
Protecting High Energy Barriers: A New Equation to Regulate Boost Energy in Accelerated Molecular Dynamics Simulations
Molecular dynamics (MD) is one of the most common tools in computational chemistry. Recently, our group has employed accelerated molecular dynamics (aMD) to improve the conformational sampling over conventional molecular dynamics techniques. In the original aMD implementation, sampling is greatly improved by raising energy wells below a predefined energy level. Recently, our group presented an alternative aMD implementation where simulations are accelerated by lowering energy barriers of the potential energy surface. When coupled with thermodynamic integration simulations, this implementation showed very promising results. However, when applied to large systems, such as proteins, the simulation tends to be biased to high energy regions of the potential landscape. The reason for this behavior lies in the boost equation used since the highest energy barriers are dramatically more affected than the lower ones. To address this issue, in this work, we present a new boost equation that prevents oversampling of unfavorable high energy conformational states. The new boost potential provides not only better recovery of statistics throughout the simulation but also enhanced sampling of statistically relevant regions in explicit solvent MD simulations
Protonation States of Remote Residues Affect Binding-Release Dynamics of the Ligand but not the Conformation of apo Ferric Binding Protein
We have studied the apo (Fe3+ free) form of periplasmic ferric binding
protein (FbpA) under different conditions and we have monitored the changes in
the binding and release dynamics of H2PO4- that acts as a synergistic anion in
the presence of Fe3+. Our simulations predict a dissociation constant of
2.20.2 mM which is in remarkable agreement with the experimentally
measured value of 2.30.3 mM under the same ionization strength and pH
conditions. We apply perturbations relevant for changes in environmental
conditions as (i) different values of ionic strength (IS), and (ii) protonation
of a group of residues to mimic a different pH environment. Local perturbations
are also studied by protonation or mutation of a site distal to the binding
region that is known to mechanically manipulate the hinge-like motions of FbpA.
We find that while the average conformation of the protein is intact in all
simulations, the H2PO4- dynamics may be substantially altered by the changing
conditions. In particular, the bound fraction which is 20 for the wild type
system is increased to 50 with a D52A mutation/protonation and further to
over 90 at the protonation conditions mimicking those at pH 5.5. The change
in the dynamics is traced to the altered electrostatic distribution on the
surface of the protein which in turn affects hydrogen bonding patterns at the
active site. The observations are quantified by rigorous free energy
calculations. Our results lend clues as to how the environment versus single
residue perturbations may be utilized for regulation of binding modes in hFbpA
systems in the absence of conformational changes.Comment: 26 pages, 4 figure
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