2,204 research outputs found
Development and flight tests of a Kalman filter for navigation during terminal area and landing operations
A Kalman filter for aircraft terminal area and landing navigation was implemented and flight tested in the NASA Ames STOLAND avionics computer onboard a Twin Otter aircraft. This system combines navaid measurements from TACAN, MODILS, air data, radar altimeter sensors along with measurements from strap-down accelerometer and attitude angle sensors. The flight test results demonstrate that the Kalman filter provides improved estimates of the aircraft position and velocity as compared with estimates from the more standard complementary filter. The onboard computer implementation requirements to achieve this improved performance are discussed
Human monoclonal islet specific autoantibodies share features of islet cell and 64 kDa antibodies
The first human monoclonal islet cell antibodies of the IgG class (MICA 1-6) obtained from an individual with Type 1 (insulin-dependent) diabetes mellitus were cytoplasmic islet cell antibodies selected by the indirect immunofluorescence test on pancreas sections. Surprisingly, they all recognized the 64 kDa autoantigen glutamate decarboxylase. In this study we investigated which typical features of cytoplasmic islet cell antibodies are represented by these monoclonals. We show by double immunofluorescence testing that MICA 1-6 stain pancreatic beta cells which is in agreement with the beta-cell specific expression of glutamate decarboxylase. In contrast an islet-reactive IgM monoclonal antibody obtained from a pre-diabetic individual stained all islet cells but lacked the tissue specificity of MICA 1-6 and must therefore be considered as a polyreactive IgM-antibody. We further demonstrate that MICA 1-6 revealed typical features of epitope sensitivity to biochemical treatment of the target tissue which has been demonstrated for islet cell antibodies, and which has been used to argue for a lipid rather than a protein nature of target antigens. Our results provide direct evidence that the epitopes recognized by the MICA are destroyed by methanol/chloroform treatment but reveal a high stability to Pronase digestion compared to proinsulin epitopes. Conformational protein epitopes in glutamate decarboxylase therefore show a sensitivity to biochemical treatment of sections such as ganglioside epitopes. MICA 1-6 share typical features of islet cell and 64 kDa antibodies and reveal that glutamate decarboxylase-reactive islet cell antibodies represent a subgroup of islet cell antibodies present in islet cell antibody-positive sera
Three-body Interactions Improve the Prediction of Rate and Mechanism in Protein Folding Models
Here we study the effects of many-body interactions on rate and mechanism in
protein folding, using the results of molecular dynamics simulations on
numerous coarse-grained C-alpha-model single-domain proteins. After adding
three-body interactions explicitly as a perturbation to a Go-like Hamiltonian
with native pair-wise interactions only, we have found 1) a significantly
increased correlation with experimental phi-values and folding rates, 2) a
stronger correlation of folding rate with contact order, matching the
experimental range in rates when the fraction of three-body energy in the
native state is ~ 20%, and 3) a considerably larger amount of 3-body energy
present in Chymotripsin inhibitor than other proteins studied.Comment: 9 pages, 2 tables and 5 figure
Bragg spectroscopy of a cigar shaped Bose condensate in optical lattices
We study properties of excited states of an array of weakly coupled
quasi-two-dimensional Bose condensates by using the hydrodynamic theory. We
calculate multibranch Bogoliubov-Bloch spectrums and its corresponding
eigenfunctions. The spectrum of the axial excited states and its eigenfunctions
strongly depends on the coupling among various discrete radial modes within a
given symmetry. This mode coupling is due to the presence of radial trapping
potential. The multibranch nature of the Bogoliubov-Bloch spectrum and its
dependence on the mode-coupling can be realized by analyzing dynamic structure
factor and momentum transferred to the system in Bragg spectroscopy
experiments. We also study dynamic structure factor and momentum transferred to
the condensate due to the Bragg spectroscopy experiment.Comment: 7 pages, 5 figures, to appear in Journal of Physics B: Atomic,
Molecular & Optical Physic
Ozone Monitoring Instrument (OMI) UV aerosol index data analysis over the Arctic region for future data assimilation and climate forcing applications
Due to a lack of high-latitude ground-based and
satellite-based data from traditional passive- and active-based
measurements, the impact of aerosol particles on the Arctic region is one of
the least understood factors contributing to recent Arctic sea ice changes.
In this study, we investigated the feasibility of using the ultraviolet (UV)
aerosol index (AI) parameter from the Ozone Monitoring Instrument (OMI), a
semi-quantitative aerosol parameter, for quantifying spatiotemporal changes
in UV-absorbing aerosols over the Arctic region. We found that OMI AI data
are affected by an additional row anomaly that is unflagged by the OMI quality
control flag and are systematically biased as functions of observing
conditions, such as azimuth angle, and certain surface types over the Arctic
region, resulting in an anomalous “ring” of climatologically high AI
centered at about 70∘ N, surrounding an area of low AI over the pole.
Two methods were developed in this study for quality-assuring the Arctic AI
data. Using quality-controlled OMI AI data from 2005 through 2020, we found
decreases in UV-absorbing aerosols in the spring months (April and May) over
much of the Arctic region and increases in UV-absorbing aerosols in the
summer months (June, July, and August) over northern Russia and northern
Canada. Additionally, we found significant increases in the frequency and
size of UV-absorbing aerosol events across the Arctic and high-Arctic (north
of 80∘ N) regions for the latter half of the study period
(2014–2020), driven primarily by a significant increase in boreal
biomass-burning plume coverage.</p
Interplay Between Time-Temperature-Transformation and the Liquid-Liquid Phase Transition in Water
We study the TIP5P water model proposed by Mahoney and Jorgensen, which is
closer to real water than previously-proposed classical pairwise additive
potentials. We simulate the model in a wide range of deeply supercooled states
and find (i) the existence of a non-monotonic ``nose-shaped'' temperature of
maximum density line and a non-reentrant spinodal, (ii) the presence of a low
temperature phase transition, (iii) the free evolution of bulk water to ice,
and (iv) the time-temperature-transformation curves at different densities.Comment: RevTeX4, 4 pages, 4 eps figure
Students as co-creators of teaching approaches, course design and curricula: implications for academic developers
Within higher education, students’ voices are frequently overlooked in the design of teaching approaches, courses and curricula. In this paper we outline the theoretical background to arguments for including students as partners in pedagogical planning processes. We present examples where students have worked collaboratively in design processes along with the beneficial outcomes of these examples. Finally we focus on some of the implications and opportunities for academic developers of proposing collaborative approaches to pedagogical planning
Low-Lying Excited States and Low-Temperature Properties of an Alternating Spin-1 / Spin-1/2 Chain : A DMRG study
We report spin wave and DMRG studies of the ground and low-lying excited
states of uniform and dimerized alternating spin chains. The DMRG procedure is
also employed to obtain low-temperature thermodynamic properties of the system.
The ground state of a 2N spin system with spin-1 and spin-1/2 alternating from
site to site and interacting via an antiferromagnetic exchange is found to be
ferrimagnetic with total spin from both DMRG and spin wave analysis.
Both the studies also show that there is a gapless excitation to a state with
spin and a gapped excitation to a state with spin .
Surprisingly, the correlation length in the ground state is found to be very
small from both the studies for this gapless system. For this very reason, we
show that the ground state can be described by a variational ``ansatz'' of the
product type. DMRG analysis shows that the chain is susceptible to a
conditional spin-Peierls' instability. The DMRG studies of magnetization,
magnetic susceptibility () and specific heat show strong magnetic-field
dependence. The product shows a minimum as a function of
temperature() at low-magnetic fields and the minimum vanishes at
high-magnetic fields. This low-field behaviour is in agreement with earlier
experimental observations. The specific heat shows a maximum as a function of
temperature and the height of the maximum increases sharply at high magnetic
fields. It is hoped that these studies will motivate experimental studies at
high-magnetic fields.Comment: 22 pages in latex; 16 eps figures available upon reques
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