Dose response of hydrazine – Deproteinated tooth enamel under blue light stimulation

The beta dose response and Optically Stimulated Luminescence (OSL) signal stability characteristics of human tooth enamel deproteinated by hydrazine reagent under blue photon stimulation are reported. Removal of the protein organic component of tooth enamel resulted in a higher OSL sensitivity and slower fading of OSL signals. The effect of chemical sample preparation on the enamel sample sensitivity is discussed and further steps to make this deproteinization treatment suitable for in vitro dose reconstruction studies are suggested.     

Pure uterine lipoma

Lipomatous tumors of the uterus are unusual, benign neoplasms seen in postmenopausal women. Although many of the mixed-type cases such as lipoleiomyoma and fibrolipoma have been reported, pure uterine lipomas are extremely rare. In the literature, a few cases with pure uterine lipoma have been reported. We first present the advanced magnetic resonance findings of pure uterine lipoma, followed by those of ultrasonography (US) and computed tomography (CT). We markedly detected lipid peaks on the magnetic resonance spectroscopy (MRS) and the apparent diffusion coefficient value to be 0.00 due to chemical-shift effects with diffusion-weighted imaging (DWI). Although pelvic lipomatous tumors can be diagnosed with US and CT, in some cases, further workup may be required to localize the lesion. MRI may yield more valuable data for differential diagnosis. MRS and DWI findings provide additional clues on the nature of the lesion.     

A2B2 type miktoarm star copolymers via alkyne homocoupling reaction

The terminal alkyne homocoupling reaction (oxidative alkyne coupling) is presented here as a new route for the preparation of A₂B₂ type 4‐miktoarm star copolymer. The block copolymer with terminal alkyne at the junction point prepared by NMP‐ATRP and ROP‐NMP sequential routes is coupled via diyne formation to give (PS)₂‐(PMMA)₂ and (PCL)₂‐(PS)₂ 4‐miktoarm star polymers, respectively, by using a combination of (PPh₃)₂PdCl₂/PPh₃/CuI in a solvent mixture of Et₃N/CH₃CN at room temperature for 72 h. The molecular weight, intrinsic viscosity ([η]), radius of gyration (R_g), and hydrodynamic radius (R_h) of A₂B₂ 4‐miktoarm star copolymers were calculated using triple‐detection GPC as results of three detectors response. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6703–6711, 2008     

Star polymers with POSS via azide–alkyne click reaction

Azidopropyl‐heptaisobutyl‐substituted polyhedral oligomeric silsesquioxane (POSS‐N₃) was reacted with 1,1,1‐tris[4‐(2‐propynyloxy)phenyl]‐ethane ( 1 ) and poly(ethylene glycol) (PEG)‐b‐poly(methyl methacrylate) (PMMA) copolymer with alkyne at its center (PEG‐PMMA‐alkyne) affording the first time synthesis of 3‐arm star POSS and PEG‐PMMA‐POSS 3‐miktoarm star terpolymer, respectively, in the presence of CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as catalyst and N,N‐dimethylformamide/tetrahydrofuran as solvent at room temperature. The precursors and the target star polymers were characterized comprehensively by ¹H NMR, GPC, and DSC. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5947–5953, 2009     

Dynamic phase transitions in the kinetic spin-1 Blume-Capel model on the Bethe lattice

The stationary states of the kinetic spin-1 Blume-Capel (BC) model on the Bethe lattice are analyzed in detail in terms of recursion relations. The model is described using a Glauber-type stochastic dynamics in the presence of a time-dependent oscillating external magnetic field (h) and crystal field (D) interactions. The dynamic order parameter, the hysteresis loop area and the dynamic correlation are calculated. It is found that the magnetization oscillates around nonzero values at low temperatures (T) for the ferromagnetic (F) phase while it only oscillates around zero values at high temperatures for the paramagnetic (P) phase. There are regions of the phase space where the two solutions coexist. The dynamic phase diagrams are obtained on the (kT/J,h/J) and (kT/J,D/J) planes for the coordination number q=4. In addition to second-order and first-order phase transitions, dynamical tricritical points and triple points are also observed.     

Crystal structure and magnetic properties of dinuclear iron(III) complex with ONNO-donor ligand

A new dinuclear Fe(III) complex, [Fe(5-MeOL1)(OH)_0.86(CH₃O)_0.14]₂?2(CH₃OH), [H₂-5-MeOL1 = N,N′-bis(5-methoxy-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine], 1 has been synthesized and characterized by single crystal structure analysis. The structure of 1 consists of two Fe(III) centers with one tetradentate schiff base ligand (N₂O₂) which are bridged by dihydroxo/dimethoxo groups to yield a Fe₂O₂ core. Complex 1 exhibits weak antiferromagnetic exchange interaction between Fe(III) ions with J = ?0.21 cm^–1.     

Installation of multiple aryl ether crosslinks onto non-native substrate peptides by the vancomycin OxyB

The biosynthesis of glycopeptide antibiotics (GPAs) has been an active area of research for decades. But, insights into the activity of the cytochrome P450 enzymes required for installing the aromatic crosslinks, which form their cup-shaped topologies and render GPAs bioactive, have only recently emerged. Presently, little is known about the substrate scope and promiscuity of the P450 enzymes. Herein, we report that OxyB_van, the P450 enzyme that installs the first crosslink in vancomycin biosynthesis, is capable of catalyzing the formation of its conventional C-O-D bis-aryl ether bond in non-natural substrates and, furthermore, the formation of a second, novel linkage when D-Trp is incorporated at position 6. HR-MS/MS and isotope labeling studies indicate the second crosslink is formed between rings A and B, resulting in a novel GPA-type scaffold. OxyB is also capable of installing two crosslinks in kistamicin- and complestatin-like substrate peptides. These findings highlight the utility of OxyB_van in creating crosslinked GPA derivatives and provide clues regarding the unusual biosynthesis of kistamicin.     

Measurement of Creep Deformation across Welds in 316H Stainless Steel Using Digital Image Correlation

Spatially resolved measurement of creep deformation across weldments at high temperature cannot be achieved using standard extensometry approaches. In this investigation, a Digital Image Correlation (DIC) based system has been developed for long-term high-temperature creep strain measurement in order to characterise the material deformation behaviour of separate regions of a multi-pass weld. The optical system was sufficiently stable to allow a sequence of photographs to be taken suitable for DIC analysis of creep specimens tested at a temperature of 545 °C for over 2000 h. The images were analysed to produce local creep deformation curves from two cross-weld samples cut from contrasting regions of a multi-pass V-groove weld joining thick-section AISI Type 316H austenitic stainless steel. It is shown that for this weld, the root pass is the weakest region of the structure in creep, most likely due to the large number of thermal cycles it has experienced during the fabrication process. The DIC based measurement method offers improved spatial resolution over conventional methods and greatly reduces the amount of material required for creep characterisation of weldments.     

The statistical mechanics of spin-1 Ising model with AFM/AFM interactions on a bilayer Bethe lattice

The spin-1 Ising model is studied for the case of antiferromagnetic (AFM)/AFM interactions on the bilayer Bethe lattice by using the pairwise approach for several values of the coordination numbers q=3, 4 and 6 when the layers are linked with the external magnetic fields. The ground state (GS) phase diagrams, thermal variations of the order-parameters and the response functions are studied in detail to obtain the phase diagrams of the model. It was found that the system gives only one Néel temperature, T_N, for q=3. Two T_N's and first-order phase transition temperature, T_t, thus tricritical point, are found and the existence of two T_N's leads to the reentrant behavior when q=4 and 6 for some given system parameters.     

Improvement of the Contour Method for Measurement of Near-Surface Residual Stresses from Laser Peening

A study was conducted to develop a methodology to obtain near-surface residual stresses for laser-peened aluminium alloy samples using the contour method. After cutting trials to determine the optimal cut parameters, surface contours were obtained and a new data analysis method based on spline smoothing was applied. A new criterion for determining the optimal smoothing parameters is introduced. Near-surface residual stresses obtained from the contour method were compared with X-ray diffraction and incremental hole drilling results. It is concluded that with optimal cutting parameters and data analysis, reliable near-surface residual stresses can be obtained by the contour method.