Swelling and drying kinetics of polytetrahydrofuran and polytetrahydrofuran–poly (methyl methacrylate) gels: A photon transmission study

A bifunctional polytetrahydrofuran (PTHF) macromonomer was synthesized by termination of the living polymerization of tetrahydrofuran (THF) initiated by triflic anhydride and the subsequent termination by sodium methacrylate. The PTHF macromonomer thus prepared was polymerized and copolymerized with methyl methacrylate (MMA) by free‐radical polymerization to yield a network and a segmented network of PTHF, both being homogeneous, respectively. These PTHF and PTHF–PMMA gels were used for swelling experiments in chloroform and chloroform vapor. Drying processes were monitored after removing the gels from the solvent and solvent vapor. Photon transmission from PTHF and PTHF–PMMA gels was monitored during swelling and drying processes using a UV‐visible (UVV) spectrophotometer. Transmitted light intensities, I_tr, from these gels increased when they were immersed in chloroform and/or subjected to its vapor. The increase in I_tr was attributed to the homogeneous lattice structure of PTHF and PTHF–PMMA gels which appeared during swelling. The increase in I_tr was modeled using the Li–Tanaka equation from which time constants, τ₁, and cooperative diffusion coefficients, D_C, were determined. A decrease in I_tr after removing choloform and/or its vapor from the cell was observed and attributed to the decrease in homogeneity of lattice structures during drying of the corresponding gels. Time constants, τ2, for the drying processes were also determined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 632–640, 2003     

Respirometric kinetic parameter calculations of a batch jet loop bioreactor treating leachate and oxygen uptake rate estimation by DTM

A novel circulating jet loop bioreactor adapted for organic matter oxidation has been designed and constructed. In this study, the input was leachate samples collected from Kemerburgaz Odayeri waste landfill site located on the European side of Istanbul. Controlling the jet loop bioreactor to realize high rates of purification depends on maintaining the appropriate loadings and operating conditions. This requires collecting various system data to estimate the dynamics of the system satisfactorily with the aim of keeping certain parameters within the specified range. The differential transform method (DTM) based solution of the state equations reveals the current state of the process so that any deviation in the system parameters can be immediately detected and regulated accordingly. The respirometric method for kinetic parameter calculations for biodegradation has been used for some time. In many studies, the respirometer was designed separately, usually in bench-scale. However, when a separate respirometer is used, the scale effect and parameters that affect the hydrodynamic structure of the system should be taken into consideration. In this study, therefore, the jet loop reactor itself was used as a respirometer. Thus, the kinetic parameters found reflecting the characteristics of microorganisms used for biodegradation would be more realistic. If the main reactor, here the jet loop reactor, would be used as the respirometer, the kinetic parameter changes can easily be monitored in the long run. Using the bioreactor as a respirometer, the most important kinetic parameters, Ks, kd and micromax were found to be 11,000 mg L(-1), 0.019 day(-1), and 0.21 day(-1), respectively. The stoichiometric coefficient, Y, was found to be 0.28 gr gr(-1) for the present system.     

Wear Behavior of Borided AISI D2 Steel under Linear Reciprocating Sliding Conditions

Protection of Metals and Physical Chemistry of Surfaces - AISI D2 steel is the most commonly used cold-work tool steel in its grade. In this study, micro-structural characterization and some...     

Heat Transfer Mechanisms Within the Mixing Region of a HiPCO Reactor

This paper explores the heat transfer mechanisms involved in a high-pressure carbon monoxide (HiPCO) chemical reactor, which is used to produce single-wall carbon nanotubes (SWCNTs). The efficiency of catalyst usage, and of the reaction itself, depends upon the thermal conditions in the mixing region. This is directly linked to the costs associated with producing SWCNTs, as well as the ability to scale the manufacturing of SWCNTs to increase the material availability for nanotechnology development. Simple models are used to study several user-configurable contributions (gas flow rates, gas temperatures, reactor geometry, and reactor orientation) to the energy balance within the reactor mixing region. Results of these models are used to identify means of improving reaction efficiency. All contributions are then combined into a computational fluid dynamics model to confirm the findings of the simpler models. The results identify the design features that lead to a maximally efficient HiPCO reactor.     

Neural models for an asymmetric coplanar stripline with an infinitely wide strip

This paper presents a new approach, based on artificial neural networks (ANNs), to determine the characteristic impedance and the effective permittivity of an asymmetric coplanar stripline (ACPS) with an infinitely wide strip. ANNs are trained with five learning algorithms to obtain better performance and faster convergence with simpler structure. The best results for training and test were obtained from the models trained with the Levenberg–Marquardt and the Bayesian regularization algorithms. The results obtained by using the neural model are in very good agreement with the results available in the literature. The neural models presented in this work provide simplicity and accuracy to determine both the parameters of an ACPS. The method is not time consuming and is easily included in a CAD system.     

Exploring the influence of the built environment on human experience through a neuroscience approach: A systematic review

The built environment provides a habitat for the most sophisticated mammal in our universe, the human being. Developments in science and technology are forcing us to reconsider the priority of human needs in current theories of architecture and the built environment. Newly developed theories and methodologies in neuroscience have allowed us to improve and deepen our knowledge of human experience in the built environment. The potential of the relationship between neuroscience and architecture for knowledge creation generates an increasing interest in theoretical and methodological approaches to explore this intersection. Thus, a common ground on which to conduct interdisciplinary studies investigating developing and emerging concepts at the intersection must be established. However, few reviews in the literature have systematically examined developing and emerging concepts at the intersection of neuroscience and architecture. The present review aims to examine the existing literature systematically to explain the influence of the built environment on human experience by using approaches from neuroscience by examining the conceptualizations in the field. The study is conducted as a systematic qualitative review that analyzes and synthesizes the developing and emerging concepts that have appeared in the ever-evolving literature. The study concludes with an overall discussion about these concepts as a means of deeply understanding the influence of the built environment on human experience, responses to the environment based on approaches from neuroscience, and their potential for providing further directions for future research.     

Development of viral nanoparticles for efficient intracellular delivery

Viral nanoparticles (VNPs) based on plant viruses such as Cowpea mosaic virus (CPMV) can be used for a broad range of biomedical applications because they present a robust scaffold that allows functionalization by chemical conjugation and genetic modification, thereby offering an efficient drug delivery platform that can target specific cells and tissues. VNPs such as CPMV show natural affinity to cells; however, cellular uptake is inefficient. Here we show that chemical modification of the CPMV surface with a highly reactive, specific and UV-traceable hydrazone linker allows bioconjugation of polyarginine (R5) cell penetrating peptides (CPPs), which can overcome these limitations. The resulting CPMV-R5 particles were taken up into a human cervical cancer cell line (HeLa) more efficiently than native particles. Uptake efficiency was dependent on the density of R5 peptides on the surface of the VNP; particles displaying 40 R5 peptides per CPMV (denoted as CPMV-R5H) interact strongly with the plasma membrane and are taken up into the cells via an energy-dependent mechanism whereas particles displaying 10 R5 peptides per CPMV (CPMV-R5L) are only slowly taken up. The fate of CPMV-R5 versus native CPMV particles within cells was evaluated in a co-localization time course study. It was indicated that the intracellular localization of CPMV-R5 and CPMV differs; CPMV remains trapped in Lamp-1 positive endolysosomes over long time frames; in contrast, 30-50% of the CPMV-R5 particles transitioned from the endosome into other cellular vesicles or compartments. Our data provide the groundwork for the development of efficient drug delivery formulations based on CPMV-R5.     

Production of Co–Cr–Ti Composite and Investigation of Mechanical Properties

Intermetallic materials such as Co₂Ti, Cr₂Ti are among advanced technology materials that have outstanding mechanical and physical properties for high temperature applications. Especially creep resistance, low density and high hardness properties stand out in such intermetallics. The microstructure, mechanical properties of %64Co–%32Cr and %4Ti powders were investigated using specimens produced by tube furnace sintering at 800–1200 °C temperature. A composite consisting of ternary additions, a metallic phase, Ti, Cr and Co have been prepared under Ar shroud and then sintered in tube furnace. XRD, scanning electron microscope, were used to characterize the properties of the specimens. Experimental results carried out for composition %64Co–%32Cr–%4Ti at 1200 °C suggest that the best properties as 182.09 HV and 5,584 g/cm³ density were obtained at 1200 °C.     

Evaluation of association between atherogenic index of plasma and intima‐media thickness of the carotid artery for subclinic atherosclerosis in patients on maintenance hemodialysis

Incidence of cardiovascular diseases in the patients having chronic kidney disease (CKD) is between 25% and 60%. This increased rate is proposed to be associated with “accelerated atherosclerosis.” Increased carotid intima‐media thickness (CIMT) is a subclinical atherosclerosis marker. Small‐dense low‐density lipoprotein particles are a strong risk factor for atherosclerosis. It was shown that atherogenic index of plasma (AIP = log(TG/HDL‐c)) is correlated with size of the lipoprotein particles. We investigated the correlation between AIP and CIMT which is a subclinical atherosclerosis marker, in hemodialysis (HD) patients. A total of 62 persons with 31 patients under HD therapy and 31 volunteers were included in the study. In all the participants, CIMT was measured and AIP were calculated. AIP and CIMT values of the participants were compared with blood pressures, lipid profiles and the other risk factors. AIP (0.39 ± 0.32) and CIMT (0.57 ± 0.13) were found significantly higher in the patient group than in the controls (0.04 ± 0.36 and 0.45 ± 0.119, respectively); (P = 0.0001 and 0.0001, respectively). There was a significant correlation between AIP and increased CIMT in the patient group (P = 0.0001, r = 0.430). Among the lipid parameters, the strongest correlation was found between CIMT and AIP. We demonstrated the significant increase of AIP and CIMT in HD patients. A correlation was found between AIP and CIMT. AIP was found to show a correlation with a greater number of risk factors, both classical and CKD specific, than CIMT. These data suggest that AIP might be a method which can be used both in diagnosis of subclinical atherosclerosis and in deceleration processes of its progression.     

The Influences of Nb2O5, MnO2, CuO and B2O3 Addition on the Magnetic Properties of BaFe12O19 Magnets

In the present study, we have investigated the influence of different types of doping elements on magnetic properties of M-type BaFe₁₂O₁₉ samples. It was observed that Nb₂O₅ addition increases the coercive field, the remanence magnetization (M _r), and saturation magnetization (M _s) values by about 27 %, 47 %, and 53 %, respectively. In the same manner, MnO₂ also improves the magnetic parameters significantly. The M _r and M _s values show increments up to 40 % in magnitude. On the other hand, the best magnetic properties were achieved by the addition of CuO to the B₂O₃ doped BaFe₁₂O₁₉. These materials have M _r and M _s values up to ～34 emu/g and ～62 emu/g, respectively.