2,385 research outputs found
Copepods from warm-core ring 82-H
See Supplementary information.txt for information regarding how access and use the files in WHOI-89-24-data.zipNet tows were collected with a Multiple
Opening/Closing Net Environmental Sampling
System (MOCNESS) carrying twenty 1-m2 nets in
October 1982 in and near warm-core ring 82-H in
the North Atlantic (RV/Knorr cruise 98). This
report includes the species list and abundance
tables of the copepods found in five of the tows.
There are four types of abundance tables: raw data,
standardized to #/1000 m3
, integrated #/m2 to 1000
m depth, and cumulative percents over the depth
of the tows.Funding was provided by the National Science Foundation
through grant Number OCE 80-12748, OCE 85-08350, OCE 87-09962,
OCE 80-19055, and OCE 80-17271
Reply to \u27Do oceanic zooplankton aggregate at, or near, the deep chlorophyll maximum?\u27
We appreciate the time and attention given our paper by Longhurst and Herman and the opportunity to reply to their critique. Unfortunately, we believe their difficulties with the presentation of our data are more subjective than substantive. In fact, we believe a careful reading of our text will show that our conclusions are suitably conservative...
Correction of systematic errors in scanning tunnelling spectra on semiconductor surfaces: the energy gap of Si(111)-7x7 at 0.3 K
The investigation of the electronic properties of semiconductor surfaces
using scanning tunnelling spectroscopy (STS) is often hindered by
non-equilibrium transport of the injected charge carriers. We propose a
correction method for the resulting systematic errors in STS data, which is
demonstrated for the well known Si(111)-(7x7) surface. The surface has an odd
number of electrons per surface unit cell and is metallic above 20 K. We
observe an energy gap in the ground state of this surface by STS at 0.3 K.
After correction, the measured width of the gap is (70 +- 15) meV which is
compatible with previous less precise estimates. No sharp peak of the density
of states at the Fermi level is observed, in contrast to proposed models for
the Si(111)-(7x7) surface.Comment: 10 pages, 4 figure
Habitat usage by the cryptic copepods Pseudocalanus moultoni and P. newmani on Georges Bank (Northwest Atlantic)
Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here for personal use, not for redistribution. The definitive version was published in Continental Shelf Research 111 (2015): 83-94, doi:10.1016/j.csr.2015.11.001.The cryptic copepod species, Pseudocalanus moultoni and P. newmani, co-occur on Georges
Bank and in the Gulf of Maine (Northwest Atlantic); even recent studies have reported results
and conclusions based on examination of the combined species. Species-specific PCR (SS-PCR)
based on mitochondrial cytochrome oxidase I (COI) sequence divergence was used in this study
to discriminate the species. Species-specific descriptions of habitat usage and predicted patterns
of transport and retention on Georges Bank were made by mapping distributions and calculating
abundances of each species from January to June, 1999 for four vertical strata (0-15 m, 15-40 m,
40-100 m, and 0-100 m) and five regions (Northern Flank, Bank Crest, Northeast Peak, Southern
Flank, and Slope Water) identified on the basis of bathymetry and circulation. Patterns of
distribution and abundance for the two species during January to June, 1999 were largely
consistent with those described based on vertically integrating mapping and analysis for the same
period in 1997 by McGillicuddy and Bucklin (2002). The region-specific and depth-stratified
analyses allowed further discrimination in habitat usage by the species and confirmed the
distinctive patterns for the two species. The observed differences between the species in
abundances among the five regions and three depth strata over Georges Bank impact their
transport trajectories. The concentration of P. moultoni in deep layers likely explains the higher
rates of retention and lower rates of advective loss of this species from the Bank, compared to P.
newmani, which may be more subject to wind-driven transport in the surface layer. Accurate
identification and discrimination of even closely-related and cryptic species is needed to ensure
full understanding and realistic predictions of changes in diversity of zooplankton and the
functioning of pelagic ecosystems.Funding was provided by the National Science Foundation as part of the
U.S. GLOBEC Program (Award Nos. OCE-9529100 and OCE-9632840 to Ann Bucklin; Award
No. OCE-0815047 to Dennis McGillicuddy)
Circular Polarization of Circumstellar Water Masers around S Per
We present the first circular polarization measurements of circumstellar H2O
masers. Previously the magnetic field in circumstellar envelopes has been
estimated using polarization observations of SiO and OH masers. SiO masers are
probes of the high temperature and density regime close to the central star. OH
masers are found at much lower densities and temperatures, generally much
further out in the circumstellar envelope. The detection of the circular
polarization of the (6_16 - 5_23) rotational transition of the H2O maser could
be attributed to Zeeman splitting due to the magnetic field in the intermediate
temperature and density regime. The fields inferred here agree well with
predicted values for a combination of the r^{-2} dependence of a solar-type
magnetic field, and the coupling of the field to the high density masing
regions. We also discuss the unexpected narrowing of the circular polarization
spectrum.Comment: 4 pages, 4 figures; accepted for publication in Astronomy and
Astrophysics Letter
Phase behaviour of the quantum Lennard-Jones solid
The Lennard-Jones potential is perhaps one of the most widely-used models for
the interaction of uncharged particles, such as noble gas solids. The phase
diagram of the classical LJ solid is known to exhibit transitions between hcp
and fcc phases. However, the phase behaviour of the quantum Lennard-Jones solid
remains unknown. Thermodynamic integration based on path integral molecular
dynamics and lattice dynamics calculations are used to study the phase
stability of the hcp and fcc Lennard-Jones solids. The hcp phase is shown to be
stabilized by quantum effects in PIMD while fcc is shown to be favoured by
lattice dynamics, which suggests a possible re-entrant low pressure hcp phase
for highly quantum systems. Implications for the phase stability of noble gas
solids are discussed. For parameters equating to Helium, the expansion due to
zero-point vibrations is associated with quantum melting: neither crystal
structure is stable at zero pressure
Two inequivalent sublattices and orbital ordering in MnV2O4 studied by 51V NMR
We report detailed 51V NMR spectra in a single crystal of MnV2O4. The
vanadium spectrum reveals two peaks in the orbitally ordered state, which arise
from different internal hyperfine fields at two different V sublattices. These
internal fields evolve smoothly with externally applied field, and show no
change in structure that would suggest a change of the orbital ordering. The
result is consistent with the orbital ordering model recently proposed by
Sarkar et al. [Phys. Rev. Lett. 102, 216405 (2009)] in which the same orbital
that is a mixture of t_2g orbitals rotates by about 45 alternately
within and between orbital chains in the I4_1/a tetragonal space group.Comment: 4 pages, 4 figures, title changed, published in PRB as a rapid com
Biological control of the vernal population increase of \u3cem\u3eCalanus finmarchicus\u3c/em\u3e on Georges Bank
An adjoint data assimilation approach was used to quantify the physical and biological controls on Calanus finmarchicus N3–C6 stages on Georges Bank and its nearby environs. The mean seasonal cycle of vertically averaged distributions, from 5 years of the GLOBEC Georges Bank Broad-Scale Surveys between January and June, was assimilated into a physical–biological model based on the climatological circulation. Large seasonal and spatial variability is present in the inferred supply sources, mortality rates, computed molting fluxes, and physical transports. Estimated mortalities fall within the range of observed rates, and exhibit stage structure that is consistent with earlier findings. Inferred off-bank initial conditions indicate that the deep basins in the Gulf of Maine are source regions of early stage nauplii and late-stage copepodids in January. However, the population increase on Georges Bank from January to April is controlled mostly by local biological processes. Magnitudes of the physical transport terms are nearly as large as the mortality and molting fluxes, but their bank-wide averages are small in comparison to the biological terms. The hypothesis of local biological control is tested in a sensitivity experiment in which upstream sources are set to zero. In that solution, the lack of upstream sources is compensated by a decrease in mortality that is much smaller than the uncertainty in observational estimates
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