Structural characterization of newly-developed Al79Ni5Fe5Y11 and Al79Ni11Fe5Y5 alloys with amorphous matrixes.

The low glass-forming ability of aluminium-based metallic glasses significantly limits their development and preparation. This paper updates the current state of knowledge by presenting the results of structural studies of two newly-developed Al79Ni5Fe5Y11 and Al79Ni11Fe5Y5 alloys with a reduced aluminium content (< 80 at.%). The alloys were produced by conventional casting (ingots) and melt-spinning (ribbons). Structural characterization was carried out for bulk ingots first, and then for the melt-spun ribbons. The ingots possessed a multiphase crystalline structure, as confirmed by X-ray diffraction and scanning electron microscopy observations. The amorphous structure of the melt-spun ribbons was determined by X-ray diffraction and transmission electron microscopy. SEM observations and EDX element maps of the cross-section of melt-spun ribbons indicated a homogeneous elemental composition. Neutron diffraction revealed the presence of nanocrystals in the amorphous matrix of the melt-spun ribbons. DSC data of the melt-spun ribbons showed exothermic events corresponding to the first crystallization at temperatures of 408 °C and 387 °C for Al79Ni5Fe5Y11 and Al79Ni11Fe5Y5, respectively.

A neutron tomography study: probing the spontaneous crystallization of randomly packed granular assemblies.

We study the spontaneous crystallization of an assembly of highly monodisperse steel spheres under shaking, as it evolves from localized icosahedral ordering towards a packing reaching crystalline ordering. Towards this end, real space neutron tomography measurements on the granular assembly are carried out, as it is systematically subjected to a variation of frequency and amplitude. As expected, we see a presence of localized icosahedral ordering in the disordered initial state (packing fraction ≈ 0.62). As the frequency is increased for both the shaking amplitudes (0.2 and 0.6 mm) studied here, there is a rise in packing fraction, accompanied by an evolution to crystallinity. The extent of crystallinity is found to depend on both the amplitude and frequency of shaking. We find that the icosahedral ordering remains localized and its extent does not grow significantly, while the crystalline ordering grows rapidly as an ordering transition point is approached. In the ordered state, crystalline clusters of both face centered cubic (FCC) and hexagonal close packed (HCP) types are identified, the latter of which grows from stacking faults. Our study shows that an earlier domination of FCC gives way to HCP ordering at higher shaking frequencies, suggesting that despite their coexistence, there is a subtle dynamical competition at play. This competition depends on both shaking amplitude and frequency, as our results as well as those of earlier theoretical simulations demonstrate. It is likely that this involves the very small free energy difference between the two structures.

Outcome of Ocular Steroid Hypertensive Response in Children.

PURPOSE: The aim of our study was to analyze the epidemiological profile and outcome of steroid-induced ocular hypertension in children below 12 years of age in a tertiary eye center. METHODS: Hospital records of patients attending the pediatric glaucoma clinic from July 2005 to December 2012 at our center were retrospectively reviewed. Steroid-induced ocular hypertension was defined as intraocular pressures (IOP)>21 mm Hg (or an increase of>6 mm from baseline) with or without associated glaucomatous optic neuropathy after intake of steroids in any form. Demographic data, management details and IOP, anterior segment, and posterior segment findings were recorded. The main outcome measure was the control of IOP after treatment. RESULTS: Of the acquired pediatric glaucoma patients, 24% were steroid-induced ocular hypertensives (36 of 150 patients) (mean age group 9.2 ± 2.4 y). We studied 57 eyes of 36 patients that had an IOP>21 mm Hg after steroid intake. Of the 36 patients, 22 had bilateral steroid hypertensive response. Of all the patients, 15 (41.6%) received steroids because of vernal conjunctivitis, 16 (22 eyes) could be managed by withdrawing steroids only, 13 (25 eyes) were controlled by medical therapy, and 7 (10 eyes) needed surgery. Favorable outcome (defined as<21 mm of Hg with/without topical antiglaucoma medications) was achieved in 80.5% at the last follow-up (mean 17.4 ± 23.47 mo; range 4 mo to 8 y). CONCLUSIONS: Our paper emphasizes on the ocular hypertensive side effects of steroids in children. There are many instances where one can avoid the use of steroids and consider nonsteroidal/anti-inflammatory alternatives. Withdrawal of steroids and antiglaucoma medicines are effective in controlling IOP in majority (80.5%).

Influence of B-site disorder in La0.5Ca0.5Mn(1 - x)B(x)O3 (B = Fe, Ru, Al and Ga) manganites.

We have investigated the influence of B-site doping on the crystal and magnetic structure in La(0.5)Ca(0.5)Mn(1 - x)B(x)O(3) (B = Fe, Ru, Al and Ga) compounds using neutron diffraction, small angle neutron scattering, magnetization and resistivity techniques. The B-site doped samples are isostructural and possess an orthorhombic structure in the Pnma space group at 300 K. A structural transition from orthorhombic to monoclinic is found to precede the magnetic transition to the CE-type antiferromagnetic state in a few of these samples. On doping with Fe, the charge and orbitally ordered CE-type antiferromagnetic state is suppressed, followed by growth of the ferromagnetic insulating phase in 0.02 ≤ x ≤ 0.06 compounds. At higher Fe doping in x > 0.06, the ferromagnetic state is also suppressed and no evidence of long range magnetic ordering is observed. In Ru doped samples (0.01 ≤ x ≤ 0.05), the ferromagnetic metallic state is favored at T(C)≈200 K and T(MI)≈125 K and no significant change in T(C) and T(MI) as a function of Ru doping is found. In contrast, with non-magnetic Al substitution for 0.01 ≤ x ≤ 0.03, the charge ordered CE-type antiferromagnetic state coexists with the ferromagnetic metallic phase. With further increase in Al doping (0.05 ≤ x ≤ 0.07), both CE-type antiferromagnetic and ferromagnetic phases are gradually suppressed. This behavior is accompanied by the evolution of an A-type antiferromagnetic insulating state. Eventually, at higher Al doping (0.10 ≤ x ≤ 0.13), this phase is also suppressed and the signature of a spin glass like transition is evident in M(T). Likewise, substitution with Ga is observed to induce similar effects to those described for Al doped samples. The presence of short ranged ferromagnetic ordering has been further explored using small angle neutron scattering measurements in a few of the selected samples.

Structural and magnetic ordering in La(0.5)Ca(0.5-x)Ba(x)MnO(3) (0 < x ≤ 0.5) manganite.

We report a structural, magnetic and transport study in La(0.5)Ca(0.5-x)Ba(x)MnO(3) (0