23,975 research outputs found
Inversion of Parahermitian matrices
Parahermitian matrices arise in broadband multiple-input multiple-output (MIMO) systems or array processing, and require inversion in some instances. In this paper, we apply a polynomial eigenvalue decomposition obtained by the sequential best rotation algorithm to decompose a parahermitian matrix into a product of two paraunitary, i.e.lossless and easily invertible matrices, and a diagonal polynomial matrix. The inversion of the overall parahermitian matrix therefore reduces to the inversion of auto-correlation sequences in this diagonal matrix. We investigate a number of different approaches to obtain this inversion, and and assessment of the numerical stability and complexity of the inversion process
Robust Hypothesis Tests for Detecting Statistical Evidence of 2D and 3D Interactions in Single-Molecule Measurements
A variety of experimental techniques have improved the 2D and 3D spatial
resolution that can be extracted from \emph{in vivo} single-molecule
measurements. This enables researchers to quantitatively infer the magnitude
and directionality of forces experienced by biomolecules in their native
cellular environments. Situations where such forces are biologically relevant
range from mitosis to directed transport of protein cargo along cytoskeletal
structures. Models commonly applied to quantify single-molecule dynamics assume
that effective forces and velocity in the (or ) directions are
statistically independent, but this assumption is physically unrealistic in
many situations. We present a hypothesis testing approach capable of
determining if there is evidence of statistical dependence between positional
coordinates in experimentally measured trajectories; if the hypothesis of
independence between spatial coordinates is rejected, then a new model
accounting for 2D (3D) interactions should be considered to more faithfully
represent the underlying experimental kinetics. The technique is robust in the
sense that 2D (3D) interactions can be detected via statistical hypothesis
testing even if there is substantial inconsistency between the physical
particle's actual noise sources and the simplified model's assumed noise
structure. For example, 2D (3D) interactions can be reliably detected even if
the researcher assumes normal diffusion, but the experimental data experiences
"anomalous diffusion" and/or is subjected to a measurement noise characterized
by a distribution differing from that assumed by the fitted model. The approach
is demonstrated on control simulations and on experimental data (IFT88 directed
transport in the primary cilium).Comment: 7 pages, 6 figure
Non-classical symmetries and the singular manifold method: A further two examples
This paper discusses two equations with the conditional Painleve property.
The usefulness of the singular manifold method as a tool for determining the
non-classical symmetries that reduce the equations to ordinary differential
equations with the Painleve property is confirmed once moreComment: 9 pages (latex), to appear in Journal of Physics
Laser Interferometer Gravitational-Wave Observatory beam tube component and module leak testing
Laser Interferometer Gravitational-Wave Observatory (LIGO) is a joint project of the California Institute of Technology and the Massachusetts Institute of Technology funded by the National Science Foundation. The project is designed to detect gravitational waves from astrophysical sources such as supernova and black holes. The LIGO project constructed observatories at two sites in the U.S. Each site includes two beam tubes (each 4 km long) joined to form an "L" shape. The beam tube is a 1.25 m diam 304 L stainless steel, ultrahigh vacuum tube that will operate at 1Ă10^â9 Torr or better. The beam tube was manufactured using a custom spiral weld tube mill from material processed to reduce the outgassing rate in order to minimize pumping costs. The integrity of the beam tube was assured by helium mass spectrometer leak testing each component of the beam tube system prior to installation. Each 2 km long, isolatable beam tube module was then leak tested after completion
Allelic variation in HLA-B and HLA-C sequences and the evolution of the HLA-B alleles
Several new HLA-B (B8, B51, Bw62)- and
HLA-C (Cw6, Cw7)-specific genes were isolated either as
genomic cosmid or cDNA clones to study the diversity
of HLA antigens. The allele specificities were identified
by sequence analysis in comparison with published HLAB
and -C sequences, by transfection experiments, and
Southern and northern blot analysis using oligonucleotide
probes. Comparison of the classical HLA-A, -B, and -C
sequences reveals that allele-specific substitutions seem
to be rare events. HLA-B51 codes only for one allelespecific
residue: arginine at position 81 located on the cd
helix, pointing toward the antigen binding site. HLA-B8
contains an acidic substitution in amino acid position 9
on the first central/3 sheet which might affect antigen binding
capacity, perhaps in combination with the rare
replacement at position 67 (F) on the Alpha-l helix. HLA-B8
shows greatest homology to HLA-Bw42, -Bw41, -B7, and
-Bw60 antigens, all of which lack the conserved restriction
sites Pst I at position 180 and Sac I at position 131.
Both sites associated with amino acid replacements seem
to be genetic markers of an evolutionary split of the HLA-B
alleles, which is also observed in the leader sequences.
HLA-Cw7 shows 98% sequence identity to the JY328
gene. In general, the HLA-C alleles display lower levels
of variability in the highly polymorphic regions of the Alpha 1
and Alpha 2 domains, and have more distinct patterns of locusspecific
residues in the transmembrane and cytoplasmic
domains. Thus we propose a more recent origin for the
HLA-C locus
Keeping a Quantum Bit Alive by Optimized -Pulse Sequences
A general strategy to maintain the coherence of a quantum bit is proposed.
The analytical result is derived rigorously including all memory and
back-action effects. It is based on an optimized -pulse sequence for
dynamic decoupling extending the Carr-Purcell-Meiboom-Gill (CPMG) cycle. The
optimized sequence is very efficient, in particular for strong couplings to the
environment.Comment: 4 pages, 2 figures; revised version with additional references for
better context, more stringent discussio
CLONING OF THE 1.4-kb mRNA SPECIES OF HUMAN COMPLEMENT FACTOR H REVEALS A NOVEL MEMBER OF THE SHORT CONSENSUS REPEAT FAMILY RELATED TO THE CARBOXY TERMINAL OF THE CLASSICAL 150-kDa MOLECULE
Three factor H mRNA species of 4.3 kb, 1.8 kb,
and 1.4 kb are constitutively expressed in human
liver. Having previously characterized full-length
cDNA clones derived from the 4.3-kb and 1.8-kb
factor mRNA, we report here the isolation and eucaryotic
expression of full-length cDNA clones coding
for the 1.4-kbm RNA species. The 1266-bp cDNA
codes for a polypeptide of 330 amino acids and
contains two polyadenylation signals and a short
poly(A)+tailT. he protein is composed of a leader
peptide followed by five short consensus repeat domains.
It shows a hybrid structure with the last
three domains being almost identical to the carboxy-
terminal of thcel assical 1 BO-kDa factor H molecule
and the two first domains representing unique
short consensus repeat structures. Eucaryotic
expression in COS7 cells revealed two polypeptides
derived from one cDNA clone that area lso found in
human serum. Differences between the cDcNloAn es
within the last three domains indicate two distinct,
possibly allelic sequences that, in addition, differ
from the authentic 150-kDa factor H sequence.
Southern blot results support the notion that the
4.3-kb factor H and the 1.4-kb factor H-related
mRNA are transcribed from two separate but highly
homologous genes.
Factor H, a glycoprotein of 150,00
Non-Markovian master equation for a damped oscillator with time-varying parameters
We derive an exact non-Markovian master equation that generalizes the
previous work [Hu, Paz and Zhang, Phys. Rev. D {\bf 45}, 2843 (1992)] to damped
harmonic oscillators with time-varying parameters. This is achieved by
exploiting the linearity of the system and operator solution in Heisenberg
picture. Our equation governs the non-Markovian quantum dynamics when the
system is modulated by external devices. As an application, we apply our
equation to parity kick decoupling problems. The time-dependent dissipative
coefficients in the master equation are shown to be modified drastically when
the system is driven by pulses. For coherence protection to be effective,
our numerical results indicate that kicking period should be shorter than
memory time of the bath. The effects of using soft pulses in an ohmic bath are
also discussed
Human complement factor H
We isolated cDNA clones coding for the functionally important tryptic N-terminal38-
kDa fragment of human complement control protein factor H using polyclonal and
monoclonal antibodies to screen a human liver cDNA library cloned in a bacterial
expression vector, PEX-1. By testing the reactivity of antibodies specific for the
recombinant proteins produced by individual clones with proteolytic fragments of
serum H the exact position of these cDNA clones within H was mapped. One clone,
H-19, coding for the 38-kDa fragment of H was sequenced and found to code for 289
amino acids derived from the 38-kDa N-terminal fragment as well as for the first 108
amino acids belonging to the complementary 142-kDa tryptic fragment. The derived
protein sequence could be arranged in 6 highly homologous repeats of about 60 amino
acids each, the homology between the repeats being determined by the characteristic
position of cysteine, proline, glycine, tyrosine and tryptophane residues. The region
coding for the epitope recognized by one of our monoclonal antibodies was localized
by subcloning restriction fragments of H-19 into the expression plasmid and testing
for the expression of this epitope
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