Relaxor-PbTiO3 single crystals and polycrystals: processing, growth and characterisation

Acoustic transducers operate using polycrystalline lead zirconate titanate (PZT) since the 1950s’. Recently, relaxor-lead titanate (relaxor-PT) single crystals have been developed and exhibit up to 650% higher piezoelectric charge coefficient and up to 50% higher electromechanical coupling factor, compared with PZT. Transducers built with relaxor-PT crystals show increased bandwidth, lower power consumption and increased sensitivity. Despite the significant advantages over PZT, a growth method for relaxor-PT single crystals that is both economical and able to produce homogeneous, highly dense crystals is yet to be found. Furthermore, one of the most important relaxor-PT solid solution is Mn modified Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3- PbTiO3 due to its thermal stability and low electrical and mechanical losses compared with other relaxor-PT solid solutions. However, the behaviour of Mn in this compound is not fully understood and control of properties, such as the mechanical quality factor, is difficult. The aim of this study was to compare Bridgman and Solid State techniques for growth of single crystalline Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3. Subsequent to this, several Mn modified compositions were designed and investigated to determine the mechanisms by which mechanical and electrical losses are lowered upon Mn incorporation. Bridgman experiments have shown that a 20 mm ø x 60 mm length and highly dense single crystal can be obtained, with (011) the natural growth direction. Seeded Bridgman was also investigated as a method of controlling the orientation of the grown crystal, but was proven challenging due to nucleation of several crystallites. Solid State experiments, which involve attaching a single crystal seed to a polycrystalline matrix and promoting boundary migration of the seed into the matrix, showed that crystal growth is encouraged when a Pb-based interlayer exists in between the seed and matrix. An epitaxially deposited, uniform thin film as interlayer was found particularly beneficial. More research is needed to determine conditions for growth of a single crystal of useful size by Solid State. Analysis of several relaxorPT compositions modified with the same amount of Mn revealed that alterations of the relaxor-PT formulation affects behaviour of the multi-valent Mn which in turn in- fluences electromechanical properties. These findings are of use to the industrial and scientific communities. Crystal growth results indicate Bridgman as suitable method if growth of crystals is desired in a short time frame, whilst Solid State results provide the basis of a new approach for growing relaxor-PT crystals. The study of Mn modified compositions provides new insights into the role of Mn substitution for manipulating the electrical and mechanical properties of complex, relaxor-PT solid solutions

Verification of JADE Agents Using ATL Model Checking

It is widely accepted that the key to successfully developing a system is to produce a thorough system specification and design. This task requires an appropriate formal method and a suitable tool to determine whether or not an implementation conforms to the specifications. In this paper we present an advanced technique to analyse, design and debug JADE software agents, using Alternating-time Temporal Logic (ATL) which is interpreted over concurrent game structures, considered as natural models for compositions of open systems. In development of the proposed solution, we will use our original ATL model checker. In contrast to previous approaches, our tool permits an interactive or programmatic design of the ATL models as state-transition graphs, and is based on client/server architecture: ATL Designer, the client tool, allows an interactive construction of the concurrent game structures as a directed multi-graphs and the ATL Checker, the core of our tool, represents the server part and is published as Web service

Fractal evaluation aspects in characterizing the roughness of a driving wheel from a locomotive

For comprehending tribological phenomena such as wear, friction, contact deformation and tightness of contact joints is the essential characterisation of the multiple scale topography of roughness surfaces. Wheel roughness obtained through direct measurement and then a description of wheel roughness has been obtained using the fractal function. The statistical parameters and fractal sizes for drive wheels which ran 2000 km and another ones new wheels have been analysed.By registering the results and programmable automaton of the roughness, the principal statistical characteristics were determined to be stands out the Abbott-Firestone curve and respectively, the fractal character. The appearance of roughness on the surface of the wheel causes the production of vertical vibrations that act on the complex wheel-rail system.In the analysis of the wheel irregularity, the fractal geometry was applied, so that to obtain the fractal parameters Dw, respectively Ltw(opothesylength), the method of the structure function was used [1,2].Therefore, the experimental measurement and obtained results processed presentedPostprint (published version

Microbiota signatures in type-2 diabetic patients with chronic kidney disease - A Pilot Study

The human microbiota is paramount for normal host physiology. Altered host-microbiome interactions are part of the pathogenesis of numerous common ailments. Currently, much emphasis is placed on the involvement of the microbiome in the pathogenesis of type-2 diabetes mellitus (T2DM), impaired glucose tolerance, and other metabolic disorders (i.e. obesity). Several studies found highly significant correlations of specific intestinal bacteria with T2DM. A better understanding of the role of the microbiome in diabetes and its complications might provide new insights in the development of new therapeutic principles. Our pilot study investigates the microbiota patterns in Romanian type-2 diabetic patients with diabetic kidney disease. Fecal samples were collected from type 2-diabetic patients and healthy controls and further used for bacterial DNA isolation. Using 16 rDNA qRT-PCR, we analyzed phyla abundance (Bacteroidetes, Firmicutes) as well as the relative abundance of specific bacterial groups (Lactobacillus sp., Enterobacteriaceae, Ruminococus sp., Prevotella sp., Faecalibacterium sp., Clostridium coccoides, Clostridium leptum). Our study also investigates the diabetic fungal microbiome for the first time. Furthermore, we report significant correlations between the treatment regimen and microbiota composition in diabetic nephropathy

Metformin and Its Benefits in Improving Gut Microbiota Disturbances in Diabetes Patients

The human gastrointestinal tract presents a vastly population of microorganisms, called the microbiota. The presence of these microorganisms offers many benefits to the host, through a range of physiological functions. However, there is a potential for these mechanisms to be disrupted condition, known as dysbiosis. Recent results are showing important associations between diabetes and the gut microbiota and how the intestinal flora can influence the prognosis of this illness. Microbial intestinal imbalance has been linked to alterations in insulin sensitivity and in glucose metabolism and may play an important role in the development of diabetes. Metformin is one of the most important and widely used first-line medications for the management of type 2 diabetes (T2D). It is a complex drug with multiple sites of action and multiple molecular mechanisms. In recent years, attention has been directed to other modes of action, other than the classic ones, with increasing evidence of a major key role of the intestine. By analysing the effects of metformin on the homeostasis of the microbiota of diabetes patients, our present topic becomes one of the major importance in understanding how metformin therapy can improve gut microbiota dysbiosis and thus provide a better outcome for this illness

THE IMPORTANCE OF THE FINANCIAL AUDIT IN PREVENTING ACCOUNTING ERRORS AND FRAUD

In the audit of financial statements, the main objective of the auditor is to express an opinion on the accuracy of the reported information, in all significant aspects, in relation to the applicable accounting framework. Although international auditing standards state that auditors are not required to detect financial fraud in audited companies, they must ensure during their engagement that the risk of fraud will not affect the audit opinion. To detect the risk of fraud and reports of accounting manipulation, auditors can use several signal indicators. Practice and literature support that the use of indices to detect accounting manipulation can be achieved through various linear scoring functions including the Beneish Model (1999). In Romania, the problem of assessing the risk of audit fraud has not been adequately addressed, until now. The purpose of this scientific approach is to prevent, analyze and evaluate the risk of fraud, based on the estimated score function and the defined classification interval

Vortex shedding noise of a cylinder with hairy flaps

This study describes the modification of acoustic noise emitted from cylinders in a stationary subsonic flow for a cylinder equipped with flexible hairy flaps at the aft part as a passive way to manipulate the flow and acoustics. The study was motivated by the results from previous water tunnel measurements, which demonstrated that hairy flaps can modify the shedding cycle behind the cylinder and can reduce the wake deficit. In the present study, wind tunnel experiments were conducted on such a modified cylinder and the results were compared to the reference case of a plain cylinder. The acoustic spectrum was measured using two microphones while simultaneously recording the flap motion. To further examine the flow structures in the downstream vicinity of the cylinder, constant temperature anemometry measurements as well as flow visualizations were also performed. The results show that, above a certain Reynolds number, the hairy flaps lead to a jump in the vortex shedding frequency. This phenomenon is similarly observed in the water flow experiments as a jump in the non-dimensional Strouhal number that is related to the change of the shedding cycle. This jump appears to be coupled to a resonant excitation of the flaps. The specific Reynolds number at which the jump occurs is higher in the present case, which is attributed to the lower added mass in air as compared with the one in water. The flow visualizations confirmed that such action of the flaps lead to a more slender elongated shape of the time-averaged separation bubble. In addition, the hairy flaps induce a noticeable reduction of the tonal noise as well as broadband noise as long as the flaps do not touch each other

What Can WMAP Tell Us About The Very Early Universe? New Physics as an Explanation of Suppressed Large Scale Power and Running Spectral Index

The Wilkinson Microwave Anisotropy Probe microwave background data may be giving us clues about new physics at the transition from a ``stringy'' epoch of the universe to the standard Friedmann Robertson Walker description. Deviations on large angular scales of the data, as compared to theoretical expectations, as well as running of the spectral index of density perturbations, can be explained by new physics whose scale is set by the height of an inflationary potential. As examples of possible signatures for this new physics, we study the cosmic microwave background spectrum for two string inspired models: 1) modifications to the Friedmann equations and 2) velocity dependent potentials. The suppression of low ``l'' modes in the microwave background data arises due to the new physics. In addition, the spectral index is red (n<1) on small scales and blue (n>1) on large scales, in agreement with data.Comment: 18 pages, 2 figures, submitted for publication in Physical Review D, references added in this versio

Metabolic profiling detects early effects of environmental and lifestyle exposure to cadmium in a human population

Background: The ‘exposome’ represents the accumulation of all environmental exposures across a lifetime. Topdown strategies are required to assess something this comprehensive, and could transform our understanding of how environmental factors affect human health. Metabolic profiling (metabonomics/metabolomics) defines an individual’s metabolic phenotype, which is influenced by genotype, diet, lifestyle, health and xenobiotic exposure, and could also reveal intermediate biomarkers for disease risk that reflect adaptive response to exposure. We investigated changes in metabolism in volunteers living near a point source of environmental pollution: a closed zinc smelter with associated elevated levels of environmental cadmium. Methods: High-resolution 1H NMR spectroscopy (metabonomics) was used to acquire urinary metabolic profiles from 178 human volunteers. The spectral data were subjected to multivariate and univariate analysis to identify metabolites that were correlated with lifestyle or biological factors. Urinary levels of 8-oxo-deoxyguanosine were also measured, using mass spectrometry, as a marker of systemic oxidative stress. Results: Six urinary metabolites, either associated with mitochondrial metabolism (citrate, 3-hydroxyisovalerate, 4- deoxy-erythronic acid) or one-carbon metabolism (dimethylglycine, creatinine, creatine), were associated with cadmium exposure. In particular, citrate levels retained a significant correlation to urinary cadmium and smoking status after controlling for age and sex. Oxidative stress (as determined by urinary 8-oxo-deoxyguanosine levels) was elevated in individuals with high cadmium exposure, supporting the hypothesis that heavy metal accumulation was causing mitochondrial dysfunction. Conclusions: This study shows evidence that an NMR-based metabolic profiling study in an uncontrolled human population is capable of identifying intermediate biomarkers of response to toxicants at true environmental concentrations, paving the way for exposome research. Keywords: metabonomics, cadmium, environmental health, exposome, metabolomics, molecular epidemiolog