16,660 research outputs found

### Abnormal Myocardial Blood Flow Reserve Observed in Cardiac Amyloidosis

We performed real-time myocardial contrast echocardiography on a patient with cardiac amyloidosis and previous normal coronary angiography presenting with atypical chest pain to assess myocardial blood flow reserve (MBFR). Myocardial contrast echocardiography was performed and flash microbubble destruction and replenishment analysis was used to calculate myocardial blood flow. Dipyridamole was used to achieve hyperemia. MBFR was derived from the ratio of peak myocardial blood flow at hyperemia and rest. The results show a marked reduction in MBFR in our patient. Previous reports of luminal obstruction of intramyocardial rather than epicardial vessels by amyloid deposition may be causing microvascular dysfunction

### Hamiltonian formulation of SL(3) Ur-KdV equation

We give a unified view of the relation between the $SL(2)$ KdV, the mKdV, and
the Ur-KdV equations through the Fr\'{e}chet derivatives and their inverses.
For this we introduce a new procedure of obtaining the Ur-KdV equation, where
we require that it has no non-local operators. We extend this method to the
$SL(3)$ KdV equation, i.e., Boussinesq(Bsq) equation and obtain the hamiltonian
structure of Ur-Bsq equationin a simple form. In particular, we explicitly
construct the hamiltonian operator of the Ur-Bsq system which defines the
poisson structure of the system, through the Fr\'{e}chet derivative and its
inverse.Comment: 12 pages, KHTP-93-03 SNUTP-93-2

### Behavior of tachyon in string cosmology based on gauged WZW model

We investigate a string theoretic cosmological model in the context of the
gauged Wess-Zumino-Witten model. Our model is based on a product of non-compact
coset space and a spectator flat space; $[SL(2,R)/U(1)]_k \times {\bf R}^2$. We
extend the formerly studied semiclassical consideration with infinite Kac-Moody
level $k$ to a finite one. In this case, the tachyon field appears in the
effective action, and we solve the Einstein equation to determine the behavior
of tachyon as a function of time. We find that tachyon field dominates over
dilaton field in early times. In particular, we consider the energy conditions
of the matter fields consisting of the dilaton and the tachyon which affect the
initial singularity. We find that not only the strong energy but also the null
energy condition is violated.Comment: 10 figure

### On commuting $U$-operators in Jordan algebras

Recently J.A.Anquela, T.Cort\'es, and H.Petersson proved that for elements
$x, y$ in a non-degenerate Jordan algebra $J$, the relation $x \circ y = 0$
implies that the $U$-operators of $x$ and $y$ commute: $U_xU_y = U_yU_x$. We
show that the result may be not true without the assumption on non-degeneracity
of $J$. We give also a more simple proof of the mentioned result in the case of
linear Jordan algebras, that is, when $char\, F\neq 2$

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### ManiNetCluster: a novel manifold learning approach to reveal the functional links between gene networks.

BACKGROUND:The coordination of genomic functions is a critical and complex process across biological systems such as phenotypes or states (e.g., time, disease, organism, environmental perturbation). Understanding how the complexity of genomic function relates to these states remains a challenge. To address this, we have developed a novel computational method, ManiNetCluster, which simultaneously aligns and clusters gene networks (e.g., co-expression) to systematically reveal the links of genomic function between different conditions. Specifically, ManiNetCluster employs manifold learning to uncover and match local and non-linear structures among networks, and identifies cross-network functional links. RESULTS:We demonstrated that ManiNetCluster better aligns the orthologous genes from their developmental expression profiles across model organisms than state-of-the-art methods (p-value <2.2Ã—10-16). This indicates the potential non-linear interactions of evolutionarily conserved genes across species in development. Furthermore, we applied ManiNetCluster to time series transcriptome data measured in the green alga Chlamydomonas reinhardtii to discover the genomic functions linking various metabolic processes between the light and dark periods of a diurnally cycling culture. We identified a number of genes putatively regulating processes across each lighting regime. CONCLUSIONS:ManiNetCluster provides a novel computational tool to uncover the genes linking various functions from different networks, providing new insight on how gene functions coordinate across different conditions. ManiNetCluster is publicly available as an R package at https://github.com/daifengwanglab/ManiNetCluster

### Fate of global symmetries in the Universe: QCD axion, quintessential axion and trans-Planckian inflaton decay-constant

Pseudoscalars appearing in particle physics are reviewd systematically. From
the fundamental point of view at an ultra-violat completed theory, they can be
light if they are realized as pseudo-Goldstone bosons of some spontaneously
broken global symmetries. The spontaneous breaking scale is parametrized by the
decay constant $f$. The global symmetry is defined by the lowest order terms
allowed in the effective theory consistent with the gauge symmetry in question.
Since any global symmetry is known to be broken at least by quantum
gravitational effects, all pseudoscalars should be massive. The mass scale is
determined by $f$ and the explicit breaking terms $\Delta V$ in the effective
potential and also anomaly terms $\Delta\Lambda^4_G$ for some non-Abelian gauge
groups $G$. The well-known example by non-Abelian gauge group breaking is the
potential for the "invisible" QCD axion, via the Peccei-Quinn symmetry, which
constitutes a major part of this review. Even if there is no breaking terms
from gauge anomalies, there can be explicit breaking terms $\Delta V$ in the
potential in which case the leading term suppressed by $f$ determines the
pseudoscalar mass scale. If the breaking term is extremely small and the decay
constant is trans-Planckian, the corresponding pseudoscalar can be a candidate
for a `quintessential axion'. In general, $(\Delta V)^{1/4}$ is considered to
be smaller than $f$, and hence the pseudo-Goldstone boson mass scales are
considered to be smaller than the decay constants. In such a case, the
potential of the pseudo-Goldstone boson at the grand unification scale is
sufficiently flat near the top of the potential that it can be a good candidate
for an inflationary model, which is known as `natural inflation'. We review all
these ideas in the bosonic collective motion framework.Comment: 41 pages with 27 figure

### Microstructure of severely deformed metals from X-ray line profile analysis

Two essentially different materials, cubic Ti(49.8)Ni(50.2) shape memory alloy and hexagonal AZ91 Mg alloy, were deformed by equal channel angular pressing (ECAP). The microstructure developed as a result of severe plastic deformation was studied by X-ray line profile analysis. The correlation between the microstructure and the mechanical behavior was also investigated. Below 100 degrees C the tensile strength of the Mg alloy increased as a consequence of the increase of the dislocation density owing to ECAP. Above 200 degrees C the strength decreased and the ductility increased as a result of the breakage of the Al(12)Mg(17) precipitates due to ECAP. The analysis of the dislocation contrast factors of Ti(49.8)Ni(50.2) revealed that {110} dislocations with line vector formed during ECAP

### Evidence for the two pole structure of the Lambda(1405) resonance

The K^- p --> pi^0 pi^0 Sigma^0 reaction is studied within a chiral unitary
model. The distribution of pi^0 Sigma^0 states forming the Lambda(1405) shows,
in agreement with a recent experiment, a peak at 1420 MeV and a relatively
narrow width of Gamma = 38 MeV. The mechanism for the reaction is largely
dominated by the emission of a pi^0 prior to the K^- p interaction leading to
the Lambda(1405). This ensures the coupling of the Lambda(1405) to the K^- p
channel, thus maximizing the contribution of the second state found in chiral
unitary theories, which is narrow and of higher energy than the nominal
Lambda(1405). This is unlike the pi^- p --> K^0 \pi Sigma reaction, which gives
more weight to the pole at lower energy and with a larger width. The data of
these two experiments, together with the present theoretical analysis, provides
a firm evidence of the two pole structure of the Lambda(1405).Comment: 4 pages, 6 figure

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