20,515 research outputs found
Intrusive origin of the Sudbury Igneous Complex: Structural and sedimentological evidence
In recent years, many geoscientists have come to believe that the Sudbury event was exogenic rather than endogenic. Critical to a recent exogenic hypothesis is the impact melt origin of the Sudbury Igneous Complex (SIC). Such origin implies that the SIC was emplaced before deposition of the Whitewater Group, in contrast to origins in which the SIC postdates the lithification of the Onaping Formation. Structural and sedimentological evidence is summarized herein that supports an intrusion of the SIC after lithification of all Whitewater Group strata, and conflicts with the hypothesis advanced by other researchers
A New Generating Function for Calculating the Igusa Local Zeta Function
A new method is devised for calculating the Igusa local zeta function
of a polynomial over a -adic field. This involves a new
kind of generating function that is the projective limit of a family of
generating functions, and contains more data than . This resides in
an algebra whose structure is naturally compatible with operations on the
underlying polynomials, facilitating calculation of local zeta functions. This
new technique is used to expand significantly the set of quadratic polynomials
whose local zeta functions have been calculated explicitly. Local zeta
functions for arbitrary quadratic polynomials over -adic fields with odd
are presented, as well as for polynomials over unramified -adic fields of
the form where is a quadratic form and is a linear form where
and have disjoint variables. For a quadratic form over an arbitrary
-adic field with odd , this new technique makes clear precisely which of
the three candidate poles are actual poles.Comment: 54 page
The forests of Kalimpong : an ecological account
Although the vegetation of Sikkim is as well
known as that of any part of India, comparatively
little attention has been paid to the area now
known as the Kaiimpong Sub -Division of the Darjeeling
District.The territory, though originally part of the
Sikkim state, was annexed by the Bhutanese in 1706
and until 1865 it remained in their hands. Under
the Senchula Treaty of 1865 it became part of British
India and was added to the Darjeeling District.
Although both Sikkim and Bhutah were explored by Dr.
Griffith and Sir Joseph Hooker early in the nineteenth
century, little attention was paid to this
area.The most complete accont of the vegetation of
Kalimpong which has hitherto been written was published
by the late Mr. J.S.Gamble in the Indian Forester
in 1875, in an article entitled "Darjeeling
Forests ", and yet in this article Mr. Gamble describes
the area east of the Tista, which is the Kalimpong
Sub -Division, as "practically unexplored ".
Before leaving the District finally in 1882 Mr. Gamble
had visited a considerable part of this area and
noted the prevalence of certain plants in various - localities. These he recorded in his "List of the - Trees, Shrubs and Climbers of the Darjeeling District.Uf subsequent publications relating to Darjeeling
or Sikkim the most important have dealt
with the Alpine Flora of tue higher levels in - Sikkim proper or with plants of a particular family
only. Nothing more than notes of cursory tours
in this area have appeared. The District is included
in the Flora of British India but not in Prain's
Bengal Plants, and for many years Gamble's List has
been the only convenient Forest Flora of the District.
This List was revised by myself and my wife in 1925
and is now being published under the title "The 'frees
of Northern Bengal:'Altogether Three Forest Working Plans for the
Kalimpong Forest Division have been published. The
Third Working Plan was published by myself in 1924
and is the only plan which contains a detailed description
of the forests. The data given in the present
work were collected mainly from 1922 -1924 during
the preparation of the Third Forest Working - Plan and part of the material has already been published
in a different form in the Plan itself. It
has now been supplemented by further observations
made in 1926 and it is believed that the account of
the forest climax communities is fairly complete although
much work still remains to be done before our
knowledge of the herbaceous communities reaches the
same standard. The study of the cryptogamic plants
has only just been begun
Improved V II log() Values, Hyperfine Structure Constants, and Abundance Determinations in the Photospheres of the Sun and Metal-poor Star HD 84937
New experimental absolute atomic transition probabilities are reported for
203 lines of V II. Branching fractions are measured from spectra recorded using
a Fourier transform spectrometer and an echelle spectrometer. The branching
fractions are normalized with radiative lifetime measurements to determine the
new transition probabilities. Generally good agreement is found between this
work and previously reported V II transition probabilities. Use of two
spectrometers, independent radiometric calibration methods, and independent
data analysis routines enables a reduction in systematic uncertainties, in
particular those due to optical depth errors. In addition, new hyperfine
structure constants are measured for selected levels by least squares fitting
line profiles in the FTS spectra. The new V II data are applied to high
resolution visible and UV spectra of the Sun and metal-poor star HD 84937 to
determine new, more accurate V abundances. Lines covering a range of wavelength
and excitation potential are used to search for non-LTE effects. Very good
agreement is found between our new solar photospheric V abundance, log
{\epsilon}(V) = 3.95 from 15 V II lines, and the solar-system meteoritic value.
In HD 84937, we derive [V/H] = -2.08 from 68 lines, leading to a value of
[V/Fe] = 0.24.Comment: 32 pages, 7 tables (3 machine-readable), 8 figures; accepted for
publication in ApJ
Theoretical study of resonant x-ray emission spectroscopy of Mn films on Ag
We report a theoretical study on resonant x-ray emission spectra (RXES) in
the whole energy region of the Mn white lines for three prototypical
Mn/Ag(001) systems: (i) a Mn impurity in Ag, (ii) an adsorbed Mn monolayer on
Ag, and (iii) a thick Mn film. The calculated RXES spectra depend strongly on
the excitation energy. At excitation, the spectra of all three systems
are dominated by the elastic peak. For excitation energies around , and
between and , however, most of the spectral weight comes from
inelastic x-ray scattering. The line shape of these inelastic ``satellite''
structures changes considerably between the three considered Mn/Ag systems, a
fact that may be attributed to changes in the bonding nature of the Mn-
orbitals. The system-dependence of the RXES spectrum is thus found to be much
stronger than that of the corresponding absorption spectrum. Our results
suggest that RXES in the Mn region may be used as a sensitive probe
of the local environment of Mn atoms.Comment: 9 pages, 11 figure
Recommended from our members
Improved Log(gf) Values for Lines of Ti I and Abundance Determinations in the Photospheres of the Sun and Metal-Poor Star HD 84937 (Accurate Transition Probabilities for Ti I)
New atomic transition probability measurements for 948 lines of Ti I are reported. Branching fractions from Fourier transform spectra and from spectra recorded using a 3 m echelle spectrometer are combined with published radiative lifetimes from laser-induced fluorescence measurements to determine these transition probabilities. Generally good agreement is found in comparisons to the NIST Atomic Spectra Database. The new Ti I data are applied to re-determine the Ti abundance in the photospheres of the Sun and metal-poor star HD 84937 using many lines covering a range of wavelength and excitation potential to explore possible non-local thermal equilibrium effects. The variation of relative Ti/Fe abundance with metallicity in metal-poor stars observed in earlier studies is supported in this study.NSF AST-1211055, AST-0908978, AST-1211585NSF REU grant AST-1004881ESO Science Archive Facility 073.D-0024, 266.D-5655NASA NAS 5-26555Astronom
Walking dynamics are symmetric (enough)
Many biological phenomena such as locomotion, circadian cycles, and breathing
are rhythmic in nature and can be modeled as rhythmic dynamical systems.
Dynamical systems modeling often involves neglecting certain characteristics of
a physical system as a modeling convenience. For example, human locomotion is
frequently treated as symmetric about the sagittal plane. In this work, we test
this assumption by examining human walking dynamics around the steady-state
(limit-cycle). Here we adapt statistical cross validation in order to examine
whether there are statistically significant asymmetries, and even if so, test
the consequences of assuming bilateral symmetry anyway. Indeed, we identify
significant asymmetries in the dynamics of human walking, but nevertheless show
that ignoring these asymmetries results in a more consistent and predictive
model. In general, neglecting evident characteristics of a system can be more
than a modeling convenience---it can produce a better model.Comment: Draft submitted to Journal of the Royal Society Interfac
- …