Computing Multidimensional Persistence

The theory of multidimensional persistence captures the topology of a multifiltration -- a multiparameter family of increasing spaces. Multifiltrations arise naturally in the topological analysis of scientific data. In this paper, we give a polynomial time algorithm for computing multidimensional persistence. We recast this computation as a problem within computational algebraic geometry and utilize algorithms from this area to solve it. While the resulting problem is Expspace-complete and the standard algorithms take doubly-exponential time, we exploit the structure inherent withing multifiltrations to yield practical algorithms. We implement all algorithms in the paper and provide statistical experiments to demonstrate their feasibility.Comment: This paper has been withdrawn by the authors. Journal of Computational Geometry, 1(1) 2010, pages 72-100. http://jocg.org/index.php/jocg/article/view/1

Synthesis and Characterization of 5-Substituted 1H-Tetrazoles in the Presence of Nano-TiCl4.SiO2

Nano-TiCl4.SiO2 was found to be an extremely efficient catalyst for the preparation of 5-substituted 1H-tetrazole derivatives. Nano-TiCl4.SiO2 is a solid Lewis-acid was synthesized by the reaction of nano-SiO2 and TiCl4. The structure characterization of this acid was achieved with X-ray diffraction, thermogravimetric analysis and electron microscopy. The synthesis of the catalyst is simple and environmentally benign with a good yield. Furthermore, the catalyst is conveniently recoverable and was reused for at least three times. The antimicrobial activities of the synthetic compounds were also determined by both micro dilution methods as recommended by the Clinical Laboratory Standard Institute, but unfortunately did not exhibit antibacterial activities at the highest concentration (256 μL mL–1). Further studies are still needed to investigate the potential biological activities of these compounds against other diseases.KEYWORDS Nano-TiCl4.SiO2, heterogeneous catalyst, 5-substituted 1H-tetrazoles, antibacterial.PDF and Supp files attache

Introducing the Mendeley Software

Academic research is one of the main concerns of students, professors and academic staff. The variety of different journals and the large amount of publications in a single research field has lead to some degrees of confusion regarding the management of articles for citation. Therefore, reference manager software are becoming increasingly popular. These software are capable of creating a library of articles and documents, categorizing them, as well as providing easy citation methods for authors and researchers. One of these software is the Mendeley. Mendeley can manage and organize research for its users. One of its various advantages over other similar software is that it is free of charge. In this article, we will review the various characteristics of this reference manager. Then we will compare it with other similar software and show that it has a better applicability

Gait-based carried object detection using persistent homology

There are surveillance scenarios where it is important to emit an alarm when a person carrying an object is detected. In order to detect when a person is carrying an object, we build models of naturally-walking and object-carrying persons using topological features. First, a stack of human silhouettes, extracted by background subtraction and thresholding, are glued through their gravity centers, forming a 3D digital image I. Second, different filters (i.e. orderings of the cells) are applied on ∂ K(I) (cubical complex obtained from I) which capture relations among the parts of the human body when walking. Finally, a topological signature is extracted from the persistence diagrams according to each filter. We build some clusters of persons walking naturally, without carrying object and some clusters of persons carrying bags. We obtain vector prototypes for each cluster. Simple distances to the means are calculated for detecting the presence of carrying object. The measure cosine is used to give a similarity value between topological signatures. The accuracies obtained are 95.7% and 95.9% for naturally-walking and object-carrying respectively

Mesenchymal Stem Cells as a Potent Cell Source for Bone Regeneration

While small bone defects heal spontaneously, large bone defects need surgical intervention for bone transplantation. Autologous bone grafts are the best and safest strategy for bone repair. An alternative method is to use allogenic bone graft. Both methods have limitations, particularly when bone defects are of a critical size. In these cases, bone constructs created by tissue engineering technologies are of utmost importance. Cells are one main component in the manufacture of bone construct. A few cell types, including embryonic stem cells (ESCs), adult osteoblast, and adult stem cells, can be used for this purpose. Mesenchymal stem cells (MSCs), as adult stem cells, possess characteristics that make them good candidate for bone repair. This paper discusses different aspects of MSCs that render them an appropriate cell type for clinical use to promote bone regeneration

Finite element model for predicting the shear behavior of FRP-strengthened RC members

The shear behavior of FRP strengthened reinforced concrete (FRP strengthened RC) membrane elements can be predicted by developing logical models that satisfy the principles of mechanics of materials namely stress equilibrium, strain compatibility, and constitutive relationships of concrete, steel and, FRP reinforcements. The Softened Membrane Model (SMM), which was developed for predicting the shear behavior of reinforced concrete (RC) membrane elements, is extended to FRP strengthened RC members subjected to shear. This new analytical model, referred to as the Softened Membrane Model for FRP strengthened RC members (SMM-FRP), considers new constitutive laws for each material component of the member. Similar to the case of the SMM model for RC, this new SMM-FRP model can predict the entire stress-strain curve, including pre- and post-cracking, and the ascending and descending branches. The SMM-FRP is implemented into an OpenSees-based finite element program for a membrane 2-D element that will allow structural engineers to predict the monotonic responses of FRP strengthened RC members subjected to shear. The developed program is validated in this paper by the prediction of the monotonic responses of 10 FRP strengthened RC panels subjected to pure shear stresses. The good agreement between the experimental and analytical results confirms the validity of the analytical model in predicting the shear behavior of RC members strengthened with FRP sheets

Clear and Compress: Computing Persistent Homology in Chunks

We present a parallelizable algorithm for computing the persistent homology of a filtered chain complex. Our approach differs from the commonly used reduction algorithm by first computing persistence pairs within local chunks, then simplifying the unpaired columns, and finally applying standard reduction on the simplified matrix. The approach generalizes a technique by G\"unther et al., which uses discrete Morse Theory to compute persistence; we derive the same worst-case complexity bound in a more general context. The algorithm employs several practical optimization techniques which are of independent interest. Our sequential implementation of the algorithm is competitive with state-of-the-art methods, and we improve the performance through parallelized computation.Comment: This result was presented at TopoInVis 2013 (http://www.sci.utah.edu/topoinvis13.html

Energy and economic performance of rooftop PV panels in the hot and dry climate of Iran

Photovoltaic (PV) Panels, one of the more promising renewable energy technologies, are growing rapidly nowadays, especially in developed countries. However, these systems have not achieved public acceptance in some countries due to low energy efficiency and poor economic performance, especially in countries which are subsidized in energy tariffs. In this paper, the energy and economic performance of fourteen rooftop PV systems with the power of 5 kW in the hot and dry climate of Iran are assessed by monitoring the total annual energy production and simulation. The monitored data is used to analyze systems’ economic performance via Pay-Back Period (PBP), Net Present Value (NPV), Return of Investment (ROI) and Levelized Cost of Energy (LCOE). Results show that single array configuration systems have the maximum energy production while dividing the system decreases the production. Economic analysis shows that the average PBP is 11.6 years under actual price of electricity (0.21$), however it is 46.9–50.5 years under subsidized average tariffs. ROI values range from 2.6 to 3.2 with the average of 2.9 for actual prices. Under subsidized prices, the cash generated by investment cannot even offset the costs that the investment requires during its lifetime with NCF and NPV being both negative. Overall, the systems are not economically beneficial under subsidized average tariffs in Iran, which discourages private and public sectors to investment on these systems. Environmentally, each PV system can averagely reduce 500 kg CO2 emission in the first year of installation and fourteen of them can approximately reduce 1,613,900 kg of CO2 emission during life time of PV panels