Iron chalcogenide superconductors at high magnetic fields

Iron chalcogenide superconductors have become one of the most investigated superconducting materials in recent years due to high upper critical fields, competing interactions and complex electronic and magnetic phase diagrams. The structural complexity, defects and atomic site occupancies significantly affect the normal and superconducting states in these compounds. In this work we review the vortex behavior, critical current density and high magnetic field pair-breaking mechanism in iron chalcogenide superconductors. We also point to relevant structural features and normal-state properties.     

Improved metabolic control does not reverse left ventricular filling abnormalities in newly diagnosed non-insulin-dependent diabetes patients

In this study left ventricular diastolic function at rest was evaluated in ten newly diagnosed, non-insulin-dependent diabetic patients by Doppler echocardiography, performed at the onset of disease and after 6 and 12 months of adequate glycaemic control. Glycosylated haemoglobin A1C, total cholesterol and triglyceride levels were assessed at the same time. The control group consisted of ten healthy subjects of matching age and body mass index. The following parameters of left ventricular function were evaluated: ejection fraction (EF), peak velocity of the early (E) and late atrial (A) mitral flow, A/E ratio, duration of the early (Ei) and of the atrial (Ai) filling phase, and heart rate. The diabetic patients had significantly higher total cholesterol and triglyceride levels compared with healthy subjects. These remained elevated throughout the follow-up period, in spite of improved glycaemic control. A significantly shorter duration of Ei (0.15 +/- 0.008 vs 0.18 +/- 0.004, P < 0.01) and a higher value of A (0.51 +/- 0.02 vs 0.39 +/- 0.01, P < 0.001) and A/E (1.06 +/- 0.05 vs 0.73 +/- 0.02, P < 0.001) were found in the diabetic patients before treatment. The parameters did not significantly change after 1 year of adequate glycaemic control. These results indicate a left ventricular filling abnormality which is present in newly diagnosed non-insulin-dependent diabetic patients and does not reverse with improved glycaemic control.     

Epidemiology of end‐stage renal disease and hemodialysis treatment in Serbia at the turn of the millennium

The study presents the epidemiological features of patients treated with renal replacement therapy (RRT) in Serbia from 1997 to 2009 and compares the results of hemodialysis treatment in 1999 and 2009. Epidemiological data were obtained from the National Registry of RRT patients and data on hemodialysis treatment from special surveys conducted in 1999 and 2009. Within the period 1997–2009 the incidence of patients on RRT increased from 108 to 179 per million population (pmp), prevalence rose from 435 to 699 pmp, while mortality rate fell from 20.7% to 16.7%. The frequency of patients with glomerulonephritis decreased, while that of patients with diabetes and hypertensive nephropathy increased. In late 2009 there were 5208 patients receiving RRT in Serbia. Within the examined period new hemodialysis and reverse osmosis equipment were purchased, high‐flux dialyzers with synthetic membranes were increasingly used and the number of patients receiving hemodiafiltration increased to 17.6%. Kt/V greater than 1.2 was recorded in 16% of the patients in 1999 but 52% in 2009. Options for correction of anemia and mineral disorders have also improved. The percentage of patients with HbsAg (13.8% vs. 4.8%) as well as anti‐hepatitis C virus antibodies positive patients (23.2% vs. 12.7%) was significantly lower in 2009 than in 1999. Both the incidence and prevalence of RRT patients in Serbia are rising continuously, while the mortality rate is falling. More favorable conditions for dialysis treatment have brought about significant improvement in the results over the last 10 years.     

The study of chlorination kinetics of copper(I)sulfide by calcium chloride in the presence of oxygen

The article investigates the influence of temperature, time, quantity of calcium chloride, and oxygen flow on the chlorination degree of copper(I)sulfide by calcium chloride in the presence of oxygen. Scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis were used to determine morphological changes occurring with the change of temperature and time. The law of additive time and the method of stationary point were used to determine kinetic parameters, i.e., rate constant and activation energy.     

An <Emphasis Type="Italic">H</Emphasis>∞ modified robust disturbance observer design for mechanical-positioning systems

This article presents a modified robust disturbance observer-RIC for a mechanicalpositioning system. The proposed RIC structure ensures a higher level of stability margin and offers transparent selection of the controller’s structure and feedback dynamic. The modified RIC controller design is divided into two main stages, where the first stage provides a design for the internal robust controller and the second a design for the external performance controller. The controller structure ensures a robust stability and performances property and good capability of low-frequency input and output disturbances suppression. The controller synthesis based on a pole-placement technique using optimization of the robust criteria based on even polynomials, and positive conditions. The solution to the problem is based on a multi-criterion optimization algorithm with a fixed order controller structure.     

Space and time optimal parallel sequence alignments

We present the first space and time optimal parallel algorithm for the pairwise sequence alignment problem, a fundamental problem in computational biology. This problem can be solved sequentially in O(mn) time and O(m+n) space, where m and n are the lengths of the sequences to be aligned. The fastest known parallel space-optimal algorithm for pairwise sequence alignment takes optimal O(m+n/p) space, but suboptimal O((m+n)/sup 2//p) time, where p is the number of processors. On the other hand, the most space economical time-optimal parallel algorithm takes O(mn/p) time, but O(m+n/p) space. We close this gap by presenting an algorithm that achieves both time and space optimality, i.e. requires only O((m+n)/p) space and O(mn/p) time. We also present an experimental evaluation of the proposed algorithm on an IBM xSeries cluster. Although presented in the context of full sequence alignments, our algorithm is applicable to other alignment problems in computational biology including local alignments and syntenic alignments. It is also a useful addition to the range of techniques available for parallel dynamic programming.     

Zirconia ceramic fixed partial dentures after cyclic fatigue tests and clinical evaluation: a systematic review

ABSTRACT

Zirconia fixed prosthetic dentures are extensively used for replacing missing teeth. The primary objective of this systematic review was to gather and present the results of all in vitro studies and clinical trials conducted on zirconia fixed prosthetic dentures. This review concentrated exclusively on bilayered zirconia and monolithic fixed prosthetic dentures. As such this paper can act as a guideline for more comparable future experimental work on zirconia ceramics. Future studies must use a more systematic approach such as the uniform use of abutment material, material for simulating periodontal support, data about fracture strength before and after fatigue, number of cycles, information about position and size of the indenter. The new digital techniques with long-term follow-up are desirable in further clinical studies.     

Temperature induced evolution of structure/microstructure parameters and their correlations with electric/magnetic properties of nanocrystalline Nickel ferrite

Nickel ferrite nanoparticles were annealed in order to find dependence of electric/magnetic properties on crystallite size. The following correlations of crystallite size with physical parameters were found: (a) lattice parameter decreases with the increase in size and it reaches value for bulk counterpart approximately for crystallites bigger than 7 nm, (b) ac electrical resistivity at room temperature increases with the increase in crystallite size, (c) for crystallites of ~7 nm or smaller electrical resistivity have maximum value at 50 °C, (d) the real part of permittivity at selected frequency generally decreases with the increase in crystallite size and (e) magnetization increases with the increase in crystallite size. Deviation of stoichiometry, cation polyvalence, and cation redistribution with annealing are the main factors that influence physical properties of Nickel ferrite nanoparticles.     

Deoxidation of Weld Metal When Welding with Self-Shielding Cored Wires

With self-shielding cored wires, high-quality and high-productivity welding can be carried out without an external shielding. In this case, porosity of welds is usually prevented by the major weakening of the oxygen activity in the weld metal by means of a strong deoxidation by titanium and aluminum. The weakening of the oxygen activity in the weld metal prevents the generation of carbon monoxide in the weld pool in the course of welding.

Alloying of the weld metal with titanium and aluminum, however, has an unfavorable influence on the quality of welded joints. An increased titanium content, i.e., above 0.3 wt%, produces a primarily martensitic microstructure with a toughness level below 20 J at 20°C. Also, the deoxidation by aluminum provides a little lower toughness at the expense of a less favorable microstructure. Welds with around 0.75% of Al and 0.1% of Ti show a ferritic/pearlitic microstructure with toughness of around 100 J at 20°C.

With some types of cored wires for surfacing, surfacing without an external shielding can produce high-quality surfacing welds. These are cored wires for surfacing of casting metals containing strong deoxidants (Ti, Al, etc.) and also cored wires for surfacing of wear-resistant materials with a high carbon content, i.e., above 2 wt%. The occurrence of porosity in wear-resistant surfacing welds is prevented by a strong deoxidation of the weld metal by carbon and by an increased partial pressure of carbon monoxide generated above the weld pool due to carbon combustion at elevated arc temperatures.