Dynamic Response of Historical Masonry Minaret under Seismic Excitation

In order to study the dynamic response of historical masonry structures, a scaled down brick masonry model constructed in civil engineering department at Baghdad University to simulate a part of a real case study, which is Alkifil historic minaret. Most of the previous researches about masonry structures try to understand the behavior of the masonry under seismic loading by experimental and numerical methods. In this paper, the masonry units (bricks) simulated in scale (S= 1/6) with the exact shape of the prototype bricks. Cementitious tile adhesive was selected to be the mortar for the modeling. The height of the model designed to be 1.5 m with a 0.5 m diameter. Detailed construction steps were presented in this paper. Experts built the model with high accuracy. A shaking table and other dynamic testing facilities were used at the University of Baghdad. The model was tested using the time-compressed El Centro 1940 NS earthquake at different amplitudes. The first ground motion of (PGA= 0.05g) which considered as weak ground motion was used to check the adequacy of the conventional behavior of the masonry model and the limit of the elastic behavior of the model during weak earthquakes. Moderate ground motion (PGA=0.15g) was performed to investigate the response of the model with minor to moderate damages. The severe ground motions were not appropriate to use in such circumstances because of the possibility to overturn the model. The experimental results showed very adequacy of the model to withstand the weak and moderate earth motion with no observed cracks

Nanoscale intermittent contact-scanning electrochemical microscopy

A major theme in scanning electrochemical microscopy (SECM) is a methodology for nanoscale imaging with distance control and positional feedback of the tip. We report the expansion of intermittent contact (IC)-SECM to the nanoscale, using disk-type Pt nanoelectrodes prepared using the laser-puller sealing method. The Pt was exposed using a focused ion beam milling procedure to cut the end of the electrode to a well-defined glass sheath radius, which could also be used to reshape the tips to reduce the size of the glass sheath. This produced nanoelectrodes that were slightly recessed, which was optimal for IC-SECM on the nanoscale, as it served to protect the active part of the tip. A combination of finite element method simulations, steady-state voltammetry and scanning electron microscopy for the measurement of critical dimensions, was used to estimate Pt recession depth. With this knowledge, the tip-substrate alignment could be further estimated by tip approach curve measurements. IC-SECM has been implemented by using a piezo-bender actuator for the detection of damping of the oscillation amplitude of the tip, when IC occurs, which was used as a tip-position feedback mechanism. The piezo-bender actuator improves significantly on the performance of our previous setup for IC-SECM, as the force acting on the sample due to the tip is greatly reduced, allowing studies with more delicate tips. The capability of IC-SECM is illustrated with studies of a model electrode (metal/glass) substrate

Laser-zone growth in a Ribbon-To-Ribbon (RTR) process, silicon sheet growth development for the large area silicon sheet task of the low cost silicon solar array project

The objective of this research is to fully investigate the Ribbon-To-Ribbon (R-T-R) approach to silicon ribbon growth. Initial work has concentrated on modification and characterization of an existing R-T-R apparatus. In addition, equipment for auxiliary heating of the melt is being evaluated and acquired. Modification of the remote viewing system and mechanical staging are nearly complete. Characterization of the laser and other components is in progress and several auxiliary heating techniques are being investigated

Embedded disposable functionalized electrochemical biosensor with a 3D-printed flow cell for detection of hepatic oval cells (HOCs)

Hepatic oval cells (HOCs) are considered the progeny of the intrahepatic stem cells that are found in a small population in the liver after hepatocyte proliferation is inhibited. Due to their small number, isolation and capture of these cells constitute a challenging task for immunosensor technology. This work describes the development of a 3D-printed continuous flow system and exploits disposable screen-printed electrodes for the rapid detection of HOCs that over-express the OV6 marker on their membrane. Multiwall carbon nanotube (MWCNT) electrodes have a chitosan film that serves as a scaffold for the immobilization of oval cell marker antibodies (anti-OV6-Ab), which enhance the sensitivity of the biomarker and makes the designed sensor specific for oval cells. The developed sensor can be easily embedded into the 3D-printed flow cell to allow cells to be exposed continuously to the functionalized surface. The continuous flow is intended to increase capture of most of the target cells in the specimen. Contact angle measurements were performed to characterize the nature and quality of the modified sensor surface, and electrochemical measurements (cyclic voltammetry (CV) and square wave voltammetry (SWV)) were performed to confirm the efficiency and selectivity of the fabricated sensor to detect HOCs. The proposed method is valuable for capturing rare cells and could provide an effective tool for cancer diagnosis and detection

Nature of the low magnetization decay on stacks of second generation superconducting tapes under crossed and rotating magnetic field experiments

The extremely low decay factor on the trapped magnetic field by stacks of second-generation high-temperature superconducting tapes reported in Appl. Phys. Lett. 104, 232602 (2014), is in apparent contradiction with the classical results for the demagnetization of superconducting bulks and thin films, where the samples undergo a severe and progressive decay under crossed magnetic field conditions. Nevertheless, in this paper, we demonstrate how the theoretical approaches and experimental measurements on superconducting bulks, thin films, and stacks of superconducting tapes can be reconciled, not only under the crossed field configuration but also under rotating magnetic field conditions, by showing that the stacks of commercial tapes behave as a system of electrically unconnected layers preventing the deformation of profiles of current along its external contour. This study extends up to the consideration of using novel superconducting/ferromagnetic metastructures, where soft ferromagnetic films are interlayered, reporting a further reduction on the magnetization decay of about 50% in the crossed field configuration. Remarkably, after applying the same number of cycles either of rotating or crossed magnetic field to these metastructures, the difference between the magnetization decay is found to be negligible, what demonstrates their highly superior performance when compared to conventional stacks of superconducting tapes

Laser-zone Growth in a Ribbon-to-ribbon (RTR) Process Silicon Sheet Growth Development for the Large Area Silicon Sheet Task of the Low Cost Solar Array Project

A technique for growing limited-length ribbons continually was demonstrated. This Rigid Edge technique can be used to recrystallize about 95% of the polyribbon feedstock. A major advantage of this method is that only a single, constant length silicon ribbon is handled throughout the entire process sequence; this may be accomplished using cassettes similar to those presently in use for processing Czochralski waters. Thus a transition from Cz to ribbon technology can be smoothly affected. The maximum size being considered, 3 inches x 24 inches, is half a square foot, and will generate 6 watts for 12% efficiency at 1 sun. Silicon dioxide has been demonstrated as an effective, practical diffusion barrier for use during the polyribbon formation

Distribution and status of Posidonia oceanica meadows on the North-Western coast of Algeria

Posidonia oceanica is an endemic species of the Mediterranean Sea that in pristine coastal waters forms extensive meadows, which are, actually, exposed to natural and anthropogenic pressures, causing their regression throughout the basin. The aim of our study is to summarise and evaluate current knowledge about the characterisation of Posidonia oceanica along the Western Algerian coast, in order to provide new evidence about the distribution and health status this species. To realize our objectives, we combined extracted data from published articles, theses, results of project reports, in situ observations and laboratory analysis. The results show the presence of the meadows in fifteen coastal zones of Western Algeria, mainly located in shallow surface waters from 0.5 to 18 metres depth.The mean leaf length across all sites ranged from 153 to 667 mm. The mean number of leaves/shoot ranged between 4.7 ± 0.9 and 6.0 ± 0.5 leaves/shoot. Leaf length showed a highly significant difference between the cold and hot season. The data analysis shows that the leaf biometric values and the shoot densities of the P. oceanica are greater than those of Mediterranean samples although these measures tend to decrease deeply. The analyses carried out on structural features of P. oceanica show that the Western Algerian meadows are, globally, in good health status according to standardised scale. The available data on P. oceanica summarised in this article represent an important starting point to build effective plans for understanding levels of environmental threats and for supporting conservation strategies for these important ecosystems. Conversely, the limited information available on this seagrass along the Western Algerian costs only allows the description of some structural features, and permits us to draw overall conclusions on its general health status

Fiduciary duty or loyalty? Evidence from co-opted boards and corporate misconduct

We examine the effect of co-opted boards on corporate misconduct and document a significant positive relationship. Utilising a large sample of public U.S. companies from the period 2001 to 2015, we find that a one standard deviation increase in the proportion of co-opted directors on a board leads to a 4.3% rise in corporate misconduct. This outcome is robust to a series of sensitivity tests and continues to hold after accounting for potential endogeneity concerns. Further analyses indicate that co-opted directors propose fewer board agenda items, exhibit lower attendance at board meetings, and receive compensation packages in excess of industry norms, which exacerbate stakeholder-agency conflicts. Cross-sectional analysis demonstrates that the documented relationship is most pronounced among firms with weak external monitoring, greater CEO-board social ties, boards whose members have high career concerns, and where CEO power is low. Additional tests reveal that co-opted directors engage in more environmental- and workplace-related violations than other types of stakeholder violations. Overall, our investigation generates original evidence that the presence of co-opted directors aggravates the incidence of corporate wrongdoing. Our study contributes to the continuing debate on the role of boards of directors and has policy implications for those responsible for devising and monitoring effective systems of corporate governance