Thermodynamics of inclusion formation in Fe-Cr-Ti-N alloys

The thermodynamics of titanium in Fe-Cr alloys and of inclusion formation in Fe-Cr-N-Ti alloys was investigated. A metal-nitride-gas equilibration technique was used to measure the activity of titanium. The equilibrium titanium content of the metal that is in equilibrium with pure solid titanium nitride and nitrogen gas at 1 atm was determined. The activity coefficients of titanium it(f_Ti) relative to 1 wt pct standard state in Fe were calculated for Fe-Cr alloys from the experimental results. The first-order interaction coefficient between titanium and chromium, e _Ti ^Cr , was determined to be 0.024 at 1873 K. The solubility of nitrogen in Fe-Cr alloys was measured and was found to increase with chromium content, which is in agreement with previous work. Thermodynamic calculations were made in order to predict under what conditions titanium nitride will form in 409 stainless steel and was compared with inclusions found in plant samples. The inclusion stability diagrams for 304 stainless steel and Fe-18 pct Cr and Fe-9 pct Cr alloys were computed.     

Power generation expansion planning with adaptive simulated annealing genetic algorithm

In this paper, an adaptive simulated annealing genetic algorithm is proposed to solve generation expansion planning of Turkey's power system. Least‐cost planning is a challenging optimization problem due to its large‐scale, long‐term, nonlinear, and discrete nature of power generation unit size. Genetic algorithms have been successfully applied during the past decade, but they show some limitations in large‐scale problems. In this study, simulated annealing is used instead of mutation operator to improve the genetic algorithm. The improved algorithm is applied to the power generation system with seven types of generating units and a 20‐year planning horizon. The planning horizon is divided into four equal periods. The new algorithm provides approximately 6.6 billion US$ (3.2%) cheaper solution than GA and also shows faster convergence. Copyright © 2006 John Wiley & Sons, Ltd.     

Better visualization of retinoblastoma metastases with Tc-99m sestamibi versus Tl-201

Tc-99m sestamibi has been shown to accumulate in several primary malignant tumors, but data regarding its use in the detection of distant metastases are limited. Despite its physical limitations, Tl-201 now has a definite place in the routine evaluation of certain primary and metastatic tumors. This report describes the value of Tc-99m sestamibi and its superiority to Tl-201 in the visualization of distant metastases in a 2-year-old girl with bilateral retinoblastoma. Three sites of soft tissue and bone metastasis were demonstrated by Tc-99m sestamibi imaging. Of these metastases, the one in the parieto-occipital region showed evident Tl-201 uptake, while the other two in the right arm and chest wall showed only slightly increased uptake, which could hardly be spotted without the confirmation of a later Tc-99m sestamibi scan. The scintigraphic findings were confirmed with histopathologic examination. Tc-99m sestamibi scan is effective and superior to Tl-201 in the detection of distant soft tissue and bone metastases from retinoblastoma.     

The rate of formation of SiO by the reaction of CO or H2 with silica and silicate slags

The rate of formation of SiO(g) by the reaction of CO and H₂ with silica or silicate slags containing SiO₂, CaO, and A1₂O₃ has been measured. The rate with hydrogen for both pure silica and silica in slags is controlled by gas phase mass transport. The rate changed with flow conditions, sample size, and gas properties as predicted by the appropriate mass transfer equations. In particular, the rate is faster in H₂-He than in H₂-Ar gas mixtures with the same hydrogen pressure, which proves conclusively the rate is controlled by gas phase mass transport. The rate of formation of SiO by the reaction of silica with CO did not change with flow conditions or particle size and the rate was the same in CO-He and CO-Ar with the same pressure of CO. In addition, the calculated rate with CO for mass transfer is considerably faster than was observed. These observations strongly indicate the rate is controlled by chemical kinetics on the surface. Similar results were obtained for the rate of reaction of CO with silica in slags and the rate was found to be proportional to the activity of SiO₂ and CO pressure. The present results are discussed in relationship to silicon transfer in slag-metal reactions.     

Estimating Motion From MRI Data

Magnetic resonance imaging (MRI) is an ideal imaging modality to measure blood flow and tissue motion. It provides excellent contrast between soft tissues, and images can be acquired at positions and orientations freely defined by the user. From a temporal sequence of MR images, boundaries and edges of tissues can be tracked by image processing techniques. Additionally, MRI permits the source of the image signal to be manipulated. For example, temporary magnetic tags displaying a pattern of variable brightness may be placed in the object using MR saturation techniques, giving the user a known pattern to detect for motion tracking. The MRI signal is a modulated complex quantity, being derived from a rotating magnetic field in the form of an induced current. Well-defined patterns can also be introduced into the phase of the magnetization, and could be thought of as generalized tags. If the phase of each pixel is preserved during image reconstruction, relative phase shifts can be used to directly encode displacement, velocity and acceleration. New methods for modeling motion fields from MRI have now found application in cardiovascular and other soft tissue imaging. In this review, we shall describe the methods used for encoding, imaging, and modeling motion fields with MRI.     

Two germ-line mutations affecting the same nucleotide at codon 257 of p53 gene, a rare site for mutations

Codon 257 of the p53 gene is an extremely rare target for somatic mutations (accounting for only two of 1600 published mutations). We report here two constitutional mutations both affecting the second nucleotide of codon 257. A thymine to adenine transversion resulting in an amino acid change from leucine to glutamine was found in one proband who developed multiple independent malignant tumors (osteosarcoma, phyllodes tumor, soft-tissue sarcoma). Her mother died of early-onset breast cancer. In the other case, a deletion resulting in a frameshift in the C-terminal coding region of p53 was found in a woman who was diagnosed with breast cancer at age 34. This woman belongs to a family with features of Li-Fraumeni syndrome. In both cases, the p53 mutations identified in the proband was found in other members of the family. Codon 257, even if rarely mutated in somatic cells, may thus be an important target for germ-line mutations.     

The Effect of <Emphasis Type="Italic">Ar</Emphasis> Ambient Pressure and Annealing Duration on the Microstructure,Superconducting Properties and Activation Energies of MgB<Subscript>2</Subscript> Superconductors

MgB₂ samples are produced by ex situ reaction method under vacuum, and various (0, 10, 20 Bar) Ar pressure for 0.5 and 1 h. The effect of ambient pressure and annealing duration on the microstructure and electrical properties of bulk samples are investigated. XRD, SEM, and magnetoresistance measurements are made. The a and c lattice parameters and the grain size values are the highest for the samples produced under vacuum and their values decrease with increasing Ar pressure. Moreover, these values increase when the annealing duration increases from 0.5 to 1 h. The increasing pressure reduces the bond lengths between the atoms thus the grain sizes decrease. Smaller grain size promotes the connection between grains which results in an increase of the critical current density (J _c ). SEM micrographs reveal that the produced samples have granular structure which is a characteristic feature of MgB₂. The decrease of grain sizes and thus enhancement in grain connectivity with increasing pressure is also confirmed by SEM images. Magneto resistivity measurements show that T _c values of the samples produced under vacuum are the highest. T _c values decrease with increasing ambient pressure and applied magnetic field. The activation energies (U ₀) of the samples are calculated using Arrhenius plots due to thermally activated flux flow theory. Existence and increase of Ar pressure causes increase of activation energies. The samples produced with 0.5-h annealing have higher activation energies than the ones produced with 1-h annealing.     

A branch and bound algorithm for scheduling unit size jobs on parallel batching machines to minimize makespan

In this paper, we present a branch and bound algorithm for the parallel batch scheduling of jobs having different processing times, release dates and unit sizes. There are identical machines with a fixed capacity and the number of jobs in a batch cannot exceed the machine capacity. All batched jobs are processed together and the processing time of a batch is given by the greatest processing time of jobs in that batch. We compare our method to a mixed integer program as well as a method from the literature that is capable of optimally solving instances with a single machine. Computational experiments show that our method is much more efficient than the other two methods in terms of solution time for finding the optimal solution.     

Synthesis of Triblock Copolymers via Photopolymerization of Styrene and Methyl Methacrylate Using Macrophotoinitiators Possessing Poly(ethylene glycol) Units

Macrophotoinitiators based on poly(ethylene glycol)s bearing benzyl tereftalmono amid moieties were synthesized by the reaction of poly(ethylene glycol) (PEG) terminated with terephtaloyl chloride and benzyl amine. The initiators possessing PEG with different molecular weights were used in the photoinduced radical polymerization of styrene (S) and methyl methacrylate (MMA) to yield poly(styrene-b-ethylene glycol-b-styrene) and poly(methyl methacrylate-ethylene glycol-b-methyl methacrylate) triblock copolymers. Characterization of macrophotoinitiators were performed by elemental anlysis, IR and ¹H-NMR spectrum. The elemental analysis results agreed with the theoretical values. The IR and ¹H-NMR spectra showed that the poly(ethylene glycol) units were reacting with the tereftloyl chloride and benzylamine. Characterization of the block copolymers was carried out by spectral measurements, GPC and fractional precipitation methods. The polydispersities of the block copolymers were observed between 1.2–2.32 for poly(methyl methacrylate-ethylene glycol-b-methyl methacrylate) and 1.25–1.90 for poly(styrene-b-ethylene glycol-b-styrene) from GPC measurements.