Direct DNA hybridization at disposable graphite electrodes modified with carbon nanotubes

The performance of glassy carbon (GCE) and graphite pencil electrodes (PGE) modified with multiwalled carbon nanotubes (CNTs) are compared, based on the direct electrochemical detection of nucleic acids. This is accomplished by monitoring the differential pulse voltammetry changes of the guanine signal. CNT-modified PGE compares favorably to that of the commonly used CNT-modified GCE owing to the intrinsic improved performance of the supporting PGE. The better intrinsic characteristics of the PGE are related to its composite structure and higher level of porosity compared to GCE. The performance characteristics of the direct DNA hybridization on the disposable CNT-modified PGE are studied in terms of optimum analytical conditions such as probe concentration, target concentration, hybridization time, and selectivity. The new DNA biosensor described here has shown some important advantages such being inexpensive, sensitive, selective, and able to generate reproducible results using a simple and direct electrochemical protocol.     

Determination and comparison of wind loads for industrial reinforced concrete chimneys

Like all other tall structures, determination of wind loads is important for industrial reinforced concrete chimneys. All countries use different wind load standards. These different wind load standards are compared with each other in some studies. For example, in one study by Zhou et al., major international codes and standards for tall buildings were compared. In the first part of this study, modelling information about 10 selected industrial reinforced concrete chimneys is given. All structural and material information about the chimneys are given in the first section. In addition, the first mode natural periods of model chimneys are given. In the second part of this study, procedures of standards used for calculating wind loads are introduced. These standards are ACI 307/98, CICIND 2001, DIN 1056, Eurocode 1 and TS 498. In the third part of the study, the calculated wind loads according to these five standards are shown and compared with each other. In the last part of the study, a conclusion and discussion part is taking place. Copyright © 2010 John Wiley & Sons, Ltd.     

Analysis of Annular Ring Microstrip Antenna with Air Gap and Uniaxial Substrate Superstrate Layers

Analysis of superstrate loaded, air gap tuned annular ring microstrip antenna is performed and effects of air gap tuning on the resonant frequency are investigated. Results obtained indicate that due to air gap tuning, resonant frequency can be incrementally or decrementally changed depending on the adjustment of anisotropy ratio of substrate and superstrate layers. Results can be used to obtain tunable, wideband antenna operation.     

‘Effects of novel root repair materials on attachment and morphological behaviour of periodontal ligament fibroblasts: Scanning electron microscopy observation’

The aim of this study was to evaluate the adhesion of periodontal ligament fibroblasts (PDLs) on newly proposed root repair materials [Biodentine, MM‐MTA, polymethylmethacrylate (PMMA) bone cement, and SDR], in comparison with contemporary root repair materials [IRM, Dyract compomer, ProRoot MTA (PMTA), and Vitrebond]. Five discs from each material were fabricated in sterile Teflon molds, and the specimens were aged and prewetted in cell culture media for 96 hours. Three material discs were used for scanning electron microscopy (SEM) for the assessment of the attachment, density, and morphological changes in the PDLs, while two samples were used for energy dispersive x‐ray spectroscopy (SEM‐EDX) to determine the elemental composition of the materials. Human PDLs were plated onto the materials at a density of 10,000/well, and incubated for 3 days. The SEM micrographs were taken at different magnifications (500× and 5000×). In the SEM, the cells were attached and well spread‐out on the surfaces of the Biodentine, PMTA, and Dyract compomer, while varied cell densities and morphological alterations were observed in the Vitrebond, IRM, MM‐MTA, SDR, and PMMA bone cement groups. The SEM‐EDX analysis revealed a maximum calcium percentage in the PMTA specimens, as well a maximum silicon percentage in the Dyract compomer specimens. This in vitro study demonstrated that the Biodentine and Dyract compomer supported PDL cell adhesion and spreading. The PMTA presented a favorable scaffold for better attachment of the PDL cell aggregates. Therefore, the calcium and silicon content of a material may enhance the PDL cell attachment.     

Investigation of layered elastic theory prediction accuracy for asphalt concrete pavement design using micromechanical viscoelastic finite element modeling

In this study, predictions of full-scale micromechanical (MM) finite element (FE) models, developed from X-ray computed tomography images of asphalt concrete samples that were sawn from the accelerated pavement test sections, were used to evaluate the accuracy of layered elastic theory (LET) models that are used in pavement design today. First, MM FE and LET models were both calibrated using the measured strain gauge responses. Predictions of calibrated models were compared to evaluate the reasonableness of LET model outputs at high temperatures. Second, asphalt concrete stiffnesses measured in the laboratory were directly used for LET model development without performing any strain gauge calibration to evaluate the actual predictive capability of LET models in pavement design by using the calibrated MM FE model outputs as the ground truth. Recommendations were also made for future use of the MM FE models to improve the predictive capability of LET models.