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Heat-assisted magnetic recording (HAMR) is being developed as the next-generation magnetic recording technology. High anisotropy granular media such as FePt-C have been demonstrated as HAMR media for ∼2 Tbpsi (terabits per in2) recording density. In order for this technology to reach its full potential of 4–5 Tbpsi, more progress and innovations are needed for the key requirements for HAMR media, including microstructure, design, magnetic distribution, and thermal design. Beyond granular media, heated-dot magnetic recording (HDMR) is planned to extend areal density toward 10 Tbpsi. HDMR combines similar advanced recording layer materials with advanced patterning techniques to fabricate <10-nm rectangular dot media.
Recent redshift surveys of the Nilson-, Zwicky-, and ESO-Uppsala galaxy catalogues revealed that the bright galaxies in these catalogues follow a spatial distribution where large empty regions are surrounded by sheet-like structures of galaxies and clusters (e.g. Giovanelli & Haynes 1991). From an observer's point of view, one may simply ask if the voids in the above-mentioned galaxy maps are real or if they reflect special observational selection effects, e.g. in surface brightness, integral magnitude or diameter. These catalogues contain many bright galaxies (MB ∼ M∗B), but only very few faint objects (MB ≥ M∗B + 3m). Older work on the distribution of intrinsically faint galaxies, like irregular dwarfs, claimed that the dwarfs follow the distribution which is outlined by the giant galaxies.
In situ observations of comet Halley provided the first photographs of a cometary nucleus and yielded information about its environment, including the emitted gas and dust. The relation between these measurements and properties of and processes on the nucleus is established by theoretical modelling, while laboratory experiments may provide some of the physical parameters needed. In addition, laboratory tests can stimulate new ideas for processes that may be relevant to cometary physics. Processes to be studied in detail by large-scale laboratory experiments may include: (1) heat transport phenomena during sublimation of porous ice-dust mixtures, (2) material modification and chemical fractionation caused by the sublimation processes, (3) buildup and destruction of dust mantles, (4) detailed studies of gas release from mixtures of volatile ices, and (S) the investigation of ice and dust particle release mechanisms. The KOSI-team (Kometensimulation) carried out sublimation experiments with ice-mineral mixtures in a large Space Simulator. During initial experiments, cylindrical samples of 30-cm diameter and 15-cm thickness were irradiated with up to 2700–W/m2 light energy. The samples consisted of water-ice or water- and CO2-ice mineral mixtures. The experiments showed the importance of advection for heat transport into the interior. It was found that the sublimation of CO2 advances into the sample at a higher speed than that of water vapor release. Therefore, emission of volatile gases responded to insolation changes with a time lag of several hours. The ratio of the emitted gas species, as well as the dust-to-gas mass ratio, differs significantly from the values within the sample. A partly permeable refractory mantle of minerals and carbonaceous material developed with time. Dust and ice particle emission has been observed to occur from irradiated dirty ices as well as from dust mantles.
We provide an overview of current techniques and typical applications of numerical bifurcation analysis in fluid dynamical problems. Many of these problems are characterized by high-dimensional dynamical systems which undergo transitions as parameters are changed. The computation of the critical conditions associated with these transitions, popularly referred to as ‘tipping points’, is important for understanding the transition mechanisms. We describe the two basic classes of methods of numerical bifurcation analysis, which differ in the explicit or implicit use of the Jacobian matrix of the dynamical system. The numerical challenges involved in both methods arementioned and possible solutions to current bottlenecks are given. To demonstrate that numerical bifurcation techniques are not restricted to relatively low-dimensional dynamical systems, we provide several examples of the application of the modern techniques to a diverse set of fluid mechanical problems.
Wegener's granulomatosis is a rare but well recognised autoimmune necrotising vasculitis. Presentation of disease in the head and neck is common and mostly consists of nasal crusting, blockage and bloody discharge. Neurological presentation is very uncommon.
We report a patient who presented to the medical emergency services with signs and symptoms of meningitis, but who was eventually diagnosed with Wegener's granulomatosis. A literature search on this topic was carried out using Medline and Embase (1996 to 2011), searching for ‘Wegener's granulomatosis’ and ‘meningitis’.
After thorough neurological and medical investigation, a combination of brain computed tomography, lumbar puncture, nasal biopsy and laboratory results refuted the diagnosis of meningitis and confirmed the diagnosis of Wegener's granulomatosis.
To the best of our knowledge, this is the first English-language case report of a patient with Wegener's granulomatosis presenting with symptoms of meningitis unconfirmed on computed tomography and lumbar puncture.
Initial clinical trials using Trichuris suis eggs (TSO) in autoimmune diseases such as inflammatory bowel disease, revealed a striking suppressive effect on the autoimmune response. Here, we analysed the effect of TSO therapy on the course of multiple sclerosis (MS), as a Th1/Th17-associated autoimmune disease. Different immunological parameters in four patients with secondary progressive MS were surveyed during a 6-month therapy with TSO, focusing on the modulation of T-cell Th1–Th2 balance as well as on the innate immune response. We are able to show a slight downregulation of the Th1-associated cytokine pattern, especially relevant in interleukin (IL)-2 (P < 0.05 after 2 months of therapy), with a temporary increase of Th2-associated cytokines such as IL-4. Furthermore, mild eosinophily and changes in CD4+ and CD8+T cells and natural killer (NK) CD56 bright cell numbers were observed. The findings observed in this group of patients suggest that TSO therapy has a moderate immunomodulatory impact in MS.
Biaxially aligned Indium Tin Oxide (ITO) thin films to be used as electrically conductive buffer layers were prepared by an Ion-Beam Assisted Deposition (IBAD) process on various substrates. Two Kaufman ion sources with 2.5 cm diameter were employed for the assisting and the sputtering beam, respectively. All deposited films revealed (001) oriented film growth with a strong in-plane alignment. The degree of the in-plane orientation was studied depending on the ion-beam parameters and the incident angle. Investigations (TEM and X-ray) of the texture evolution of these IBAD films during film growth were carried out. An in-plane texture of 12.6°FWHM for a 1 μm thick film has been achieved so far. The quality of the buffer has been demonstrated by the subsequent deposition of high-current carrying YBCO-films deposited by thermal coevaporation using a 3–5 nm thick Y2O3 interlayer. A jc of 0.76 MA/cm2 (77K, 0T) has been obtained for a 1 cm × 1 cm sample with ITO of 20° FWHM.
Ion implantation experiments were carried out on a single grain Al-Pd-Mn icosahedral quasicrystal. The influence of Re or Au dopant on the thermopower and the electrical resistivity has been measured. Comparison with ternary and quaternary alloys produced by usual metallurgical techniques is made. The results indicate that the efficiency of this quasicrystalline alloy as a thermoelectric material can be improved by adjusting composition and structural quality, as well as by the addition of a small amount of Re, whereas Au implantation is inefficient in that respect.
Ga-Mn decagonal quasicrystals (DQC), as well as a Ga-Mn approximant and a normal crystal in GaAs are investigated by electron energy-loss spectroscopy (EELS) and energy dispersive X- ray spectroscopy (EDS) combined with Z-contrast imaging. Plasmon peak positions (Ep), full- width-half-maxima (FWHM) and Mn L3/L2ratios of these three phases are derived from their low-loss spectra and core-loss spectra respectively. Mn, Ga and As distributions in ion implanted GaAs layers are characterized by EDS at line-scan mode. These results show that the Ga-Mn DQC has higher Ep and FWHMs than those of its normal crystal counterpart, as well as all other reported QCs. The much larger L3/L2 intensity ratio of the Ga-Mn DQC over that of the Al-Mn icosahedral quasicrystals (IQC) may suggest Mn atoms in the Ga-Mn DQC have much larger local magnetic moments.
Growth experiments have been carried out to characterize the occurrence and development of porosity in Bridgman and flux grown Al-Pd-Mn icosahedral quasicrystals. The porosity level has been observed to fluctuate between values of 0.0 and 3.75 percent along the length of Bridgman single crystals implying that the development of porosity is affected by the local growth conditions. Experiments were conducted to evaluate the influence of the rate of solidification on the occurrence of porosity. Alloys were solidified with different growth rates, 1mm/hr and >10 mm/hr, using the Bridgman configuration and at different cooling rates, ranging from 0.29°C/hr to 10°C/hr, using the flux growth method. Porosity levels were analyzed via optical image analysis. These experiments indicate that porosity percentages are greatly influenced by cooling rates and crystal size.
Five fold i-AlPdMn surface prepared under UHV by ion bombardment and annealing was so far considered to be bulk terminated. This result was substantially based on a quantitative LEED analyses . Analysis of the specular rod in a X ray diffraction experiment at grazing incidence supported this result . We present a new study of this surface by high resolution X ray diffraction at normal incidence. In this Bragg configuration the diffraction peak 18 – 29 for instance is at a photon energy of 2.873keV, the 72 – 116 reflection at 5.725keV. This results in an analyzed thickness of the sample surface of a few micrometers.
The surface was cleaned by ion bombardment. During annealing (T≅880K), we clearly observed the progressive disappearance of the initial Bragg peak characteristic of the as cast bulk sample. Conversely a new Bragg peak grows at an energy position shifted by 1eV compared to the position of the original Bragg peak. This is a clear signature for an irreversible structural transformation which takes place on at least the micron thickness. On the transformed surface, both, a LEED pattern and a RHEED pattern, characteristic for a five fold surface were easily obtained.
This high resolution experiment (the relative Bragg peak shift is 3ׁ10−4) was reproduced on samples from different initial compositions. This shows that five fold i-AlPdMn surface changes after preparation by ion bombardment and annealing at 900K on a micrometer thickness. This is not consistent with the conclusion that the surface is simply terminated by a cut of the original bulk. We conclude that a reorganization process of the quasicrystalline structure during annealing proceeds in the surface vicinity (probed depth is close to a few microns).
Highly faceted microholes (voids) in icosahedral Al-Mn-Pd quasicrystals form during annealing at temperatures between 750 and 830°C via classical Ostwald ripening. The specimens were single-phase icosahedral with a composition of Al71Mn9Pd20. If such a specimen containing voids is cooled to room temperature with a constant cooling rate of typically 0.6 to 5 K/min, the facets of the voids are frequently found to be decorated by a different material. The decorations have typically a morphology similar to fractals. Specimens rapidly quenched after isothermal heat treatments around 830°C never showed similar decorations. By X-ray microanalysis in a scanning electron microscope it has been found that this decoration material is considerably poorer in Al-content that the icosahedral phase, namely: Al60Mn10Pd30. Accordingly, these decorations are precipitations at the surfaces of voids inside a single-phase icosahedral matrix. This implies that these decorations are formed at the void surfaces bya diffusion induced local equilibrium. The local equilibrium can be understood on the basis of the equilbrium results in a single icosahedral phase.
Localized moments are observed on a small fraction of the Mn atoms in Al-Pd-Mn and Al-Mn quasicrystals while a large proportion of magnetic moments is found in liquids in equilibrium with these quasicrystalline phases. As magnetic sites cannot be identified in quasicrystals because of the very small number of Mn atoms involved, we have studied the case of approximant phases in both Al-Mn and Al-Pd-Mn systems. Most of the approximants are non- magnetic but magnetic moments are present on a fraction of the Mn sites in the μ-Al4Mn phase and in the Mn-rich TAlPdMn phase. From both experimental and theoretical investigations, the magnetic sites are identified in these phases. The moment formation can be explained by analysing the local environment of the Mn atoms and indirect Mn-Mn interactions mediated by conduction electrons on relatively large distances. A clear picture of the origin of magnetism in quasicrysals, approximants and liquids in the Al-Mn and Al-Pd-Mn systems can therefore be obtained.
Laser vaporization of an icosahedral Al-Pd-Mn sample with detection by time-of-flight mass spectrometry is used to probe metal clusters made from the alloy. After sample vaporization, clusters form by gas aggregation and may contain several to hundreds of atoms. Multi-photon ionization/fragmentation of these clusters yields mass spectra showing many cluster sizes with enhanced intensity. Clusters are identified at masses near those of pseudo- Mackay and Bergman clusters; however, these clusters do not appear special relative to neighboring clusters. Results of this study and its relationship to the proposed cluster structures in quasicrystalline materials are discussed.
The relationship between approximant structures and quasicrystals is discussed on the example of quantitatively known decagonal quasicrystal and approximant structures in the thoroughly studied system Al-Co-Ni. The binary Al-Co as well as the ternary Al-Co-Ni approximants consist of the same basic pentagonal bipyramidal structure elements as the decagonal phase. The binary Al-Ni approximants, on the other hand, are vacancy ordered superstructures of the AlNi §-phase, which itself is related to the periodic average structure of decagonal Al-Co-Ni. Thus, the decagonal phase may be considered as a compromise between the competing driving forces to form pentagonal structural units on the one side and vacancy ordered superstructures of the AlNi §-phase on the other side. The broad stability range of decagonal Al-Co-Ni can be interpreted in terms of entropy gain by Co/Ni substitutional disorder and phasonic disorder of a part of the Al atoms.
The paper reviews results from in situ straining experiments on Al-Pd-Mn single quasicrystals in a high-voltage electron microscope. Slip planes were determined from the orientation and width of slip traces. Dislocations are generated by a specific cross slip mechanism. On some slip traces, dislocations move at two distinctly different velocities. A stress exponent was determined on a single dislocation by observing its displacement under decreasing load. The in situexperiments reveal the behaviour of individual dislocations in a temperature range where the deformation of bulk specimens is strongly affected by recovery.
Steam reforming of methanol (CH3OH + H2O -> 3H2 + CO2) has been performed on a number of Al-Cu-based stable quasicrystals and related alloys. Alloys leached in NaOH aqueous solution exhibit the highest activity for steam-reforming of methanol. Among the alloys, AlCuFe quasicrystal, after leaching treatment, reveals excellent activity. The production rate of H2 reaches 235 l/kgmin at 573K for steam reforming of methanol. The activity is due to Cu nanoparticles at the surfaces of quasicrystalline grains which are generated by leaching treatment. The quasicrystals have two advantages: one is their brittle nature, which allows them to be crushed efficiently; the other is the involvement of Fe, which suppresses the sintering of Cu particles.