To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
A deep ice core drilled to 2503 m depth at Dome Fuji, Antarctica, contains 25 visible tephra layers during the past 340 ka. The thickness of tephra layers is in the range 1-24 mm. The thickness and duration at deposition, determined by a simple ice-flow model, suggests that a violent volcanic eruption caused ash to fall onto the Antarctic ice sheet for ~5 years and to form a ~100 mm thick tephra layer at 117 ka BE Two tephra layers at depths of 573 and 2202 m probably originated from volcanoes in the South Sandwich Islands, Southern Ocean, given the size of tephra shards, >20μm in diameter, and their major chemical composition. Only eight of the 25 tephra layers can also be recognized in the Vostok (Antarctica) ice core, but all correspond to the Vostok tephras if we consider cloudy bands to be volcanic.
Mapping observations of nearby large-extended clusters of galaxies (Coma, Perseus, Virgo, etc.) are being performed with ASCA. Such clusters allow us to map physical parameters of hot gas in the clusters, such as temperature, metal abundance, and X-ray surface brightness. To determine such parameters at each part of a cluster, one should take careful care of X-ray contamination from outside of a pointed field, which is mainly due to “stray-light” X-rays (Honda et al. 1997). For this reason, the only way to obtain the distribution of hot gas parameter is to process the whole cluster data in a self-consistent way. For this purpose, we are developing the new analysis system called TERRA.
The Coma cluster has been recognized as an archetype of rich and relaxed clusters, until recent ROSAT observations reveal that the intracluster medium (ICM) has a complex distribution (Briel et al. 1992; White et al. 1993). The X-ray surface brightness distribution shows a secondary peak around the galaxy NGC 4839, at 40' SW from the cluster center.
STJs are promising X-ray detectors as high energy resolution spectrometers due to the small excitation energy to break the Cooper pairs to product detectable electrons. The expected energy resolution is about 5 eV for a 6 keV incident X-rays (see review by Kraus et al. and Esposito et al.). We have developed a large area (178 × 178μm2) Nb/Al/AlOX/Al/Nb STJs (Kurakado et al. 1993) and series-connected STJs with a position resolution of 35μm for α particles (Kurakado 1997) at Nippon Steel Corporation. As a focal plane detector in future X-ray missions, we are developing STJs whose targert characteristics are; an energy resolution of 20 eV at 6keV, an effective area of 1 cm2, and position resolution of 100μm.
Lead-free, piezoelectric (Na,K)NbO3-BaZrO3-(Bi,Li)TiO3 films were epitaxially grown onto (100) SrTiO3 substrate via pulsed laser deposition. The effects of post-annealing temperature on the crystal phases, mosaic spread, and chemical composition of the deposited (Na,K)NbO3 and (Na,K)NbO3-BaZrO3-(Bi,Li)TiO3 films were analyzed. Results indicate the epitaxial growth of (Na,K)NbO3-BaZrO3-(Bi,Li)TiO3 films deposited at an oxygen pressure (PO2) of ≥40 Pa and substrate temperature (Ts) of 800°C. The alkaline-deficiency could be suppressed in the (Na,K)NbO3-BaZrO3-(Bi,Li)TiO3 films deposited at PO2 ≥ 70 Pa. AFM profile of the (Na,K)NbO3 post-annealed at 1000°C indicates the epitaxial growth of film with atomically flat step-terrace structure, while that of the (Na,K)NbO3-BaZrO3-(Bi,Li)TiO3 film post-annealed at 1200°C shows relatively smooth surface with step-terrace structure and several cubic crystals. It was also found that the preferential evaporation of alkaline components could be suppressed by annealing under covered substrate condition.
Studies of the feeding behaviour of aquatic species in their natural environment are difficult, since direct observations are rarely possible. In this study, a newly developed animal-borne underwater sound recorder (AUSOMS-mini) was applied to captive Amazonian (Trichechus inunguis) and Antillean (Trichechus manatus manatus) manatees in order to directly record their feeding sounds. Different species of aquatic plants were offered to the manatees separately. Feeding sounds were automatically extracted using a custom program developed with MATLAB. Compared to ground truth data, the program correctly detected 65–79% of the feeding events, with a 7.3% or lower false alarm rate, which suggests that this methodology is a useful recorder of manatee feeding events. All manatees foraged during both the daytime and night-time. However, manatees tended to be less active and masticated slower during the night than during the day. The manatee mastication cycle duration depended on plant species and individual. This animal-borne acoustic monitoring system could greatly increase our knowledge of manatee feeding ecology by providing the exact time, duration and number of feeding events, and potentially the plant species being fed on.
The feasibility of using a photoconductor with a Ga2O3/CuGaSe2 heterojunction for visible light sensors was investigated. CIGS chalcopyrite semiconductors have both a high absorption coefficient and high quantum efficiency. However, their dark current is too high for image sensors. In this study, we applied gallium oxide (Ga2O3) as a hole-blocking layer for CIGS thin film to reduce the dark current. Experimental results showed that the dark current was drastically reduced, and an avalanche multiplication phenomenon was observed at an applied voltage of over 6 V. However, this structure had sensitivity only in the ultraviolet light region because its depletion region was almost completely spread in the Ga2O3 layer since the carrier density of the Ga2O3 layer was much lower than that of the CIGS layer. These results indicate that the Ga2O3/CuGaSe2 heterojunction has potential for use in visible light sensors but that we also need to increase the carrier density of the Ga2O3 layer to shift the depletion region to the CIGS film.
Organised haematomas of the maxillary sinus are rare, non-neoplastic, haemorrhagic lesions which can extend into the nasal cavity and/or the other paranasal sinuses. This study aimed to investigate the pathology of maxillary sinus organised haematoma, and also proposes a new aetiological hypothesis based on the observed pathology.
Biopsies, computed tomography, magnetic resonance imaging and post-surgical histopathological examination of resected specimens were carried out.
Distinct pathological differences were observed between the basal and peripheral portions of organised haematomas. We propose that an organised haematoma originates from the exudation of blood components between vascular endothelial cells. As a result, the basal portion consists of aggregated, dilated vessels around the natural ostium of the maxillary sinus. In addition, pseudovessels, without endothelial cells, arise from endocapillary vessels within the haematoma. Exudation of additional blood components from the pseudovessels advances the growth of the organised haematoma.
(Na,K)NbO3 is a promising candidate for lead-free piezoelectric materials. (Na1-xKx)NbO3 films (x = 0.3–0.7) were epitaxially grown on a (100)SrTiO3 substrate via pulsed laser deposition. The effects of substrate temperature and oxygen pressure during deposition on the crystallinity of the films were examined: both parameters affected the mosaic spread of the crystallites and the formation of an impurity phase. In this study, the optimum conditions for the preparation of highly crystalline films were a substrate temperature of 800 °C and oxygen pressure of ∼60 Pa. The lattice constants parallel and perpendicular to the substrate surface responded differently to changes in x: the constant parallel to the surface increased with increasing x, while the constant perpendicular to the surface was maximized at x = 0.5. The difference in the dependence of the lattice constants could be explained by the elastic distortion of the lattice.
An aqueous magnetic suspension was prepared by dispersing amphiphilic co-polymer (ACP) coated monodispersed magnetite nanoparticles (MNPs) synthesized through thermal decomposition of iron(III) acetylacetonate in a mixture of oleic acid and oleylamine. ACP composed of poly (maleic anhydride-alt-1-octadecene) and polyethylene glycol methyl ether was applied to disperse MNPs in water and buffer solution. The average diameter of MNPs increased from 6.6 to 12.5 nm with increasing reaction temperature from 200 to 250°C. Infrared spectra and elemental analysis revealed that the surface modified MNPs contain carboxyl groups originated from oleic acid and ACP. The conjugation of MNPs and bovine serum albumin (BSA) antibody was examined. As a result, the as-synthesized MNPs adsorbed BSA antibody effectively than the surface modified MNPs: the BSA antibody adsorption decreased with increasing cross-linker concentration.
We report on the development of a high throughput x-ray diffractometer that concurrently measures spatially resolved x-ray diffraction (XRD) spectra of epitaxial thin films integrated on a substrate. A convergent x-ray is focused into a stripe on a substrate and the diffracted beam is detected with a two-dimensional x-ray detector, so that the snapshot image represents a mapping of XRD intensity with the axes of the diffraction angle and the position in the sample. High throughput characterization of crystalline structure is carried out for a BaxSr1-xTiO3 composition-spread film on a SrTiO3 substrate. Not only the continuous spread of the composition (x), but also the continuous spread of the growth temperature (T) are given to the film by employing a special heating method. The boundary between the strained lattice and relaxed lattice is visualized by the concurrent XRD as functions of x and T in a high throughput fashion.
The minimum energy atomic configurations of stacked GaAs/InAs/GaAs quantum dot structures are calculated by using the conjugate gradient energy minimization with the Stillinger-Weber potentials. The islands are assumed to be either of pyramidal shape or of trapezoidal shape. The numerical results for the five-layer stacked structures show that the normal strains exhibit stepwise up-and-down profiles through the vertical centerlines of the islands and intermediate layers. Next, the molecular dynamics method with the Tersoff potential is applied to single Ge/Si and Si/Ge/Si structures with pyramidal islands in order to investigate the effect of temperature. It is found that there is a considerable difference between the normal strain in the direction perpendicular to the island base obtained by the conjugate gradient minimization with the Stillinger-Weber potential and that obtained by the molecular dynamics method at 800 K.
The basic nature of kinetic processes is examined theoretically. When an isothermal development of order is studied theoretically, sometimes an ordered phase different from the final equilibrium one transiently predominates, while the free energy (Fsys) decreases monotonically although very slowly. There is another category of kinetic changes for which the convenient interpretation is that the Fsys surface itself changes in time. In this second category, a state can initially be a local minimum of Fsys and thus can be called a ‘metastable’ state, but after a certain time, as the Fsys surface itself changes, a kinetic path appears along which Fsys decreases and the system can change along it. To include both categories, the concept of the PSEUDOSTABLE phase is proposed. It is shown that even in the nucleation process, Fsys for the entire system decreases monotonically, although the local free energy may fluctuate.
Magnetic behavior in Co-based Heusler alloys Co2MnZ (Z=Si, Ge, Sn) is investigated as a function of quenching temperature. The mean magnetic moment decreases with increase in quenching temperature in Co2MnSi and Co2MnGe while it remains almost constant in Co2MnSn. Relation between the magnetic behavior and the atomic disorder is discussed.
The results of the lattice constant and the electrical resistance measurements are also reported.
Atomic disorder is investigated for B2- and Heusler-phase CoFe1-xAlx alloys quenched from various temperatures by X-ray diffraction measurements. In the B2-phase region, with increase in quenching temperature, atomic disorder on the Co-site (Co-type disorder) proceeds for x=0.30 but not for x=0.70. In the Heusler-phase region (x=0.45, 0.50 and 0.55), atomic disorder between the Fe- and Al-sites (Fe-Al-type disorder) mainly proceeds. A relation between the magnetic behavior obtained in our previous work and the atomic disorder is examined. As a result, it is found that the Co-type disorder leads to a reduction of the magnetic moment in the B2-phase alloys and that the Fe-Al-type disorder does not significantly affect the magnetic behavior in the Heusler-phase alloys.