1,528 research outputs found
Sporadic Aurora near Geomagnetic Equator: In the Philippines, on 27 October 1856
While low latitude auroral displays are normally considered to be a
manifestation of magnetic storms of considerable size, Silverman (2003, JGR,
108, A4) reported numerous "sporadic auroras" which appear locally at
relatively low magnetic latitudes during times of just moderate magnetic
activity. Here, a case study is presented of an aurora near the geomagnetic
equator based on a report from the Philippine Islands on 27 October 1856. An
analysis of this report shows it to be consistent with the known cases of
sporadic aurorae except for its considerably low magnetic latitude. The record
also suggests that extremely low-latitude aurora is not always accompanied with
large magnetic storms. The description of its brief appearance leads to a
possible physical explanation based on an ephemeral magnetospheric disturbance
provoking this sporadic aurora.Comment: 15 pages, 3 figures, accepted for publication in Annales Geophysicae
on 18 August 201
Neutron activation analysis and assessment of trace elements in fingernail from residents of Tokyo, Japan
We report herewith the study of fingernail clippings obtained from the residents of Tokyo, Japan. A total of 18 participants with no health problems and occupational exposure to metals were recruited to provide fingernails samples for this study. Through the use of instrumental neutron activation analysis (INAA), 18 elements (Ag, Al, As, Ca, Cl, Co, Cu, Fe, Hg, K, Mg, Mn, Na, S, Sb, Se, V, and Zn) were determined. The results showed that the toxic elements in the fingernails are in the lower range when compared to literature values. There were no chronic exposures to toxic elements such as As and Hg found. The level of Hg found is lower than that reported 20 years ago, possibly due to the strict regulation control in Japan on the release of Hg to the environment. The elements Se and Zn are found to be rather uniformly distributed among participants and are in agreement with results from other countries. There were no significant differences in elemental concentrations due to genders and smoking habits. The overall data from this study showed similar concentrations to those of healthy participants from other countries. Thus, the current data could represent the background level of elemental concentrations in fingernails of residents in Tokyo, which could serve as reference values for future study
Field dependent effective masses in YbAl
We show for the intermediate valence compound YbAl that the high field
(40 60T) effective masses measured by the de Haas-van
Alphen experiment for field along the direction are smaller by
approximately a factor of two than the low field masses. The field
40T for this reduction is much smaller than the Kondo field ( 670K) but is comparable to the field
where 40K is the temperature for the onset
of Fermi liquid coherence. This suggests that the field scale does not
arise from 4 polarization but is connected with the removal of the anomalies
that are known to occur in the Fermi liquid state of this compound.Comment: 7 pages plus 3 figures Submitted to PRL 9/12/0
Absolute instabilities of travelling wave solutions in a Keller-Segel model
We investigate the spectral stability of travelling wave solutions in a
Keller-Segel model of bacterial chemotaxis with a logarithmic chemosensitivity
function and a constant, sublinear, and linear consumption rate. Linearising
around the travelling wave solutions, we locate the essential and absolute
spectrum of the associated linear operators and find that all travelling wave
solutions have essential spectrum in the right half plane. However, we show
that in the case of constant or sublinear consumption there exists a range of
parameters such that the absolute spectrum is contained in the open left half
plane and the essential spectrum can thus be weighted into the open left half
plane. For the constant and sublinear consumption rate models we also determine
critical parameter values for which the absolute spectrum crosses into the
right half plane, indicating the onset of an absolute instability of the
travelling wave solution. We observe that this crossing always occurs off of
the real axis
Infrared study of valence transition compound YbInCu4 using cleaved surfaces
Optical reflectivity R(w) of YbInCu4 single crystals has been measured across
its first-order valence transition at T_v ~ 42 K, using both polished and
cleaved surfaces. R(w) measured on cleaved surfaces Rc(w) was found much lower
than that on polished surface Rp(w) over the entire infrared region. Upon
cooling through T_v, Rc(w) showed a rapid change over a temperature range of
less than 2 K, and showed only minor changes with further cooling. In contrast,
Rp(w) showed much more gradual and continuous changes across T_v, similarly to
previously reported data on polished surfaces. The present result on cleaved
surfaces demonstrates that the microscopic electronic structures of YbInCu4
observed with infrared spectroscopy indeed undergo a sudden change upon the
valence transition. The gradual temperature-evolution of Rp(w) is most likely
due to the compositional and/or Yb-In site disorders caused by polishing.Comment: 4 pages, 4 figures, Fig.1(a) correcte
Metallic partial melting processes on the acapulcoite-lodranite parent body.
第3回極域科学シンポジウム/第35回南極隕石シンポジウム 11月29日(木) 国立国語研究所 2階講
2-(4-Bromophenoxy)propanohydrazide
The title compound, C9H11BrN2O2, is an important intermediate for the synthesis of heterocyclic compounds such as azoles, 2,5-disubstituted-1,3,4-oxadiazoles and 5-substituted 2-mercapto-1,3,4-oxadiazoles. The bromophenoxy group subtends a dihedral angle of 82.81 (7)° with the plane passing through the propanohydrazide moiety. The crystal structure is stabilized by intermolecular N—H⋯O hydrogen bonds that form columns extending along the b axis
4-(4-Propoxybenzoyloxy)benzoic acid
The title compound, C17H16O5, is an important intermediate for the synthesis of side-chain ligands for polymeric liquid crystals. The propoxy and benzoic acid groups subtend dihedral angles of 4.36 (6) and 55.35 (6)°, respectively, with the central benzoyloxy unit. The crystal structure is stabilized by an intermolecular O—H⋯O hydrogen bond
Pseudogap Formation and Heavy Carrier Dynamics in Intermediate Valence YbAl3
Infrared optical conductivity [] of the intermediate valence
compound YbAl has been measured at temperatures 8 K 690 K to
study its microscopic electronic structures. Despite the highly metallic
characters of YbAl, exhibits a clear pseudogap (strong
depletion of spectral weight) of about 60 meV below 40 K. It also shows a
strong mid-infrared peak centered at 0.25 eV. Energy-dependent effective
mass and scattering rate of the carriers obtained from the data indicate the
formation of a heavy-mass Fermi liquid state. These characteristic results are
discussed in terms of the hybridization states between the Yb 4 and the
conduction electrons. It is argued, in particular, that the pseudogap and the
mid-infrared peak result from the indirect and the direct gaps, respectively,
within the hybridization state. band.Comment: 4 pages, 4 figures, submitted to J. Phys. Soc. Jp
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