Finite element analysis of footings and embankment dam cores

Imperial Users onl

Association of insertion/deletion mutations in angiotensin converting enzyme (ACE) gene and effectiveness of Glibenclamide therapy in Iranian type 2 diabetic patients

Abstract Introduction: Type 2 diabetes mellitus (T2DM) is an expanding global health problem, closely linked to the epidemic of obesity. The incidence of diabetes is increasing because of aging, changing ethnic mix of the population and worsening obesity. Glibenclamide is used for the treatment of patients with type II diabetes mellitus. Some patients respond well to this therapy while others need to use higher doses along with other medications. Since polymorphisms in ACE gene has been associated with type 2 diabetes mellitus, in the present study we investigated the association of insertion/deletion mutations of this gene with the effectiveness of Glibenclamide in treating Iranian type 2 diabetic patients.   Methods and Results: In this experimental study, blood samples from type II diabetic patients were collected (n=99) and their genomic DNA was isolated. Specific primers for the detection of insertion/deletion mutation were used and polymerase chain reactions (PCR) were conducted using specific thermal cycles. The amplified DNA samples were detected by electrophoresis of these samples on a 0.7% agarose gel. Statistical analysis of the obtained data was performed using t-test and chi-square test. A total of 99 patients were enrolled to the study. The frequency distribution of DD, ID, and II polymorphisms were 72%, 20%, and 8%, respectively. There were no differences among genotypic groups (P = 0.146). In terms of cholesterol, there was a significant difference between DD and DI (P = 0.012). There was a significant difference between the two DD and II genotypes in terms of creatinine (P = 0.034)   Conclusions: Although the results of our study indicated no association of ACE I/D polymorphisms and Effectiveness of Glibenclamide therapy, DD genotype may play a role on effectiveness of Glibenclamide Therapy

Experimental and theoretical investigations of thermal transport in graphene

Graphene has been actively investigated because its unique structural, electronic, and thermal properties are desirable for a number of technological applications ranging from electronic to energy devices. The thermal transport properties of graphene can influence the device performances. Because of the high surface to volume ratio and confinement of phonons and electrons, the thermal transport properties of graphene can differ considerably from those in graphite. Developing a better understanding of thermal transport in graphene is necessary for rational design of graphene-based functional devices and materials. It is known that the thermal conductivity of single-layer graphene is considerably suppressed when it is in contact with an amorphous material compared to when it is suspended. However, the effects of substrate interaction in phonon transport in both single and multi-layer graphene still remains elusive. This work presents sensitive in-plane thermal transport measurements of few-layer and multi-layer graphene samples on amorphous silicon dioxide with the use of suspended micro-thermometer devices. It is shown that full recovery to the thermal conductivity of graphite has yet to occur even after the thickness of the supported multi-layer graphene sample is increased to 34 layers, which is considerably thicker than previously thought. This surprising finding is explained by the long intrinsic scattering mean free paths of phonons in graphite along both the basal-plane and cross-plane directions, as well as partially diffuse scattering of phonons by the graphene-amorphous support interface, which is treated by an interface scattering model developed for highly anisotropic materials. In addition, an experimental method is introduced to investigate electronic thermal transport in graphene and other layered materials through the measurement of longitudinal and transverse thermal and electrical conductivities and Seebeck coefficient under applied electric and magnetic fields. Moreover, this work includes an investigation of quantitative scanning thermal microscopy measurements of electrically biased graphene supported on a flexible polyimide substrate. Based on a triple scan technique and another zero heat flux measurement method, the temperature rise in flexible devices is found to be higher by more than one order of magnitude, and shows much more significant lateral heat spreading than graphene devices fabricated on silicon.Mechanical Engineerin

Integrated Circuits for Programming Flash Memories in Portable Applications

Smart devices such as smart grids, smart home devices, etc. are infrastructure systems that connect the world around us more than before. These devices can communicate with each other and help us manage our environment. This concept is called the Internet of Things (IoT). Not many smart nodes exist that are both low-power and programmable. Floating-gate (FG) transistors could be used to create adaptive sensor nodes by providing programmable bias currents. FG transistors are mostly used in digital applications like Flash memories. However, FG transistors can be used in analog applications, too. Unfortunately, due to the expensive infrastructure required for programming these transistors, they have not been economical to be used in portable applications. In this work, we present low-power approaches to programming FG transistors which make them a good candidate to be employed in future wireless sensor nodes and portable systems. First, we focus on the design of low-power circuits which can be used in programming the FG transistors such as high-voltage charge pumps, low-drop-out regulators, and voltage reference cells. Then, to achieve the goal of reducing the power consumption in programmable sensor nodes and reducing the programming infrastructure, we present a method to program FG transistors using negative voltages. We also present charge-pump structures to generate the necessary negative voltages for programming in this new configuration

Numerical and Experimental Investigations on Corrosion and Self-Protection Processes in Reinforced Concrete

The chloride induced corrosion of steel in concrete is one of the biggest durability issues affecting structures worldwide. Concrete structures that are installed in marine environment and those exposed frequently to de-icing salts in the winter season, such as bridges and parking structures, are particularly susceptible to corrosion induced damage. In worst cases, the structure is unable to fulfil its entire service life and needs extensive repairs or is decommissioned quite early. Such situations can have a strong impact on society which is dependent on infrastructures for mobility and transportation of essential materials. Moreover, the economic losses are predicted in billions in the coming future and can impact the global economy. In an attempt to increase the service life of concrete structures with respect to chloride durability, Layered Double Hydroxides (LDH) are introduced as chloride ion entrapping additive in concrete. LDH encapsulates chloride ions from the environment which can extend the service life of concrete structures. It can also be tailored to deliver corrosion inhibiting ions which can mitigate the chloride induced damage in concrete. A new concrete mix with LDH was developed in this work for building long lasting infrastructure exposed to chloride ingress in submerged marine zones. Predictive modelling approaches are used to study the corrosion processes and chloride durability of concrete. Multi-ion transport model is used to predict the efficiency of LDH in concrete concerning chloride ingress. Computational results are presented which compare chloride ingress in concrete with and without LDH. Formation factor has been used in this study to determine the microstructure related properties of concrete with and without LDH. Additionally, experimental investigations are presented which report on the stability and chloride binding capacity of LDH in synthetic alkaline solutions, concrete pore solutions, mortars and also in concrete. The compatibility of LDH with cement is also presented. The work highlights that LDH is able to improve the chloride durability of concrete. Furthermore, In-situ investigations are carried out to understand the stability of LDH inside concrete