253 research outputs found
States on pseudo effect algebras and integrals
We show that every state on an interval pseudo effect algebra satisfying
some kind of the Riesz Decomposition Properties (RDP) is an integral through a
regular Borel probability measure defined on the Borel -algebra of a
Choquet simplex . In particular, if satisfies the strongest type of
(RDP), the representing Borel probability measure can be uniquely chosen to
have its support in the set of the extreme points of $K.
Tilt order parameters, polarity and inversion phenomena in smectic liquid crystals
The order parameters for the phenomenological description of the smectic-{\it
A} to smectic-{\it C} phase transition are formulated on the basis of molecular
symmetry and structure. It is shown that, unless the long molecular axis is an
axis of two-fold or higher rotational symmetry, the ordering of the molecules
in the smectic-{\it C} phase gives rise to more than one tilt order parameter
and to one or more polar order parameters. The latter describe the indigenous
polarity of the smectic-{\it C} phase, which is not related to molecular
chirality but underlies the appearance of spontaneous polarisation in chiral
smectics. A phenomenological theory of the phase transition is formulated by
means of a Landau expansion in two tilt order parameters (primary and
secondary) and an indigenous polarity order parameter. The coupling among these
order parameters determines the possibility of sign inversions in the
temperature dependence of the spontaneous polarisation and of the helical pitch
observed experimentally for some chiral smectic-{\it } materials. The
molecular interpretation of the inversion phenomena is examined in the light of
the new formulation.Comment: 12 pages, 5 figures, RevTe
The Lattice and Simplex Structure of States on Pseudo Effect Algebras
We study states, measures, and signed measures on pseudo effect algebras with
some kind of the Riesz Decomposition Property, (RDP). We show that the set of
all Jordan signed measures is always an Abelian Dedekind complete -group.
Therefore, the state space of the pseudo effect algebra with (RDP) is either
empty or a nonempty Choquet simplex or even a Bauer simplex. This will allow
represent states on pseudo effect algebras by standard integrals
Study of variable stars in the MOA data base: long-period red variables in the Large Magellanic Cloud
One hundred and forty six long-period red variable stars in the Large
Magellanic Cloud (LMC) from the three year MOA project database were analysed.
A careful periodic analysis was performed on these stars and a catalogue of
their magnitudes, colours, periods and amplitudes is presented. We convert our
blue and red magnitudes to band values using 19 oxygen-rich stars. A group
of red short-period stars separated from the Mira sequence has been found on a
(log P, K) diagram. They are located at the short period side of the Mira
sequence consistent with the work of Wood and Sebo (1996). There are two
interpretations for such stars; a difference in pulsation mode or a difference
in chemical composition. We investigated the properties of these stars together
with their colour, amplitude and periodicity. We conclude that they have small
amplitudes and less regular variability. They are likely to be higher mode
pulsators. A large scatter has been also found on the long period side of the
(log P, K) diagram. This is possibly a systematic spread given that the blue
band of our photometric system covers both standard B and V bands and affects
carbon-rich stars.Comment: 19 pages, 19 figures, accepted for publication in MNRA
Functional diversity of chemokines and chemokine receptors in response to viral infection of the central nervous system.
Encounters with neurotropic viruses result in varied outcomes ranging from encephalitis, paralytic poliomyelitis or other serious consequences to relatively benign infection. One of the principal factors that control the outcome of infection is the localized tissue response and subsequent immune response directed against the invading toxic agent. It is the role of the immune system to contain and control the spread of virus infection in the central nervous system (CNS), and paradoxically, this response may also be pathologic. Chemokines are potent proinflammatory molecules whose expression within virally infected tissues is often associated with protection and/or pathology which correlates with migration and accumulation of immune cells. Indeed, studies with a neurotropic murine coronavirus, mouse hepatitis virus (MHV), have provided important insight into the functional roles of chemokines and chemokine receptors in participating in various aspects of host defense as well as disease development within the CNS. This chapter will highlight recent discoveries that have provided insight into the diverse biologic roles of chemokines and their receptors in coordinating immune responses following viral infection of the CNS
A stochastic model for heart rate fluctuations
Normal human heart rate shows complex fluctuations in time, which is natural,
since heart rate is controlled by a large number of different feedback control
loops. These unpredictable fluctuations have been shown to display fractal
dynamics, long-term correlations, and 1/f noise. These characterizations are
statistical and they have been widely studied and used, but much less is known
about the detailed time evolution (dynamics) of the heart rate control
mechanism. Here we show that a simple one-dimensional Langevin-type stochastic
difference equation can accurately model the heart rate fluctuations in a time
scale from minutes to hours. The model consists of a deterministic nonlinear
part and a stochastic part typical to Gaussian noise, and both parts can be
directly determined from the measured heart rate data. Studies of 27 healthy
subjects reveal that in most cases the deterministic part has a form typically
seen in bistable systems: there are two stable fixed points and one unstable
one.Comment: 8 pages in PDF, Revtex style. Added more dat
Muscle RING-finger 2 and 3 maintain striated-muscle structure and function
Background: The Muscle-specific RING-finger (MuRF) protein family of E3 ubiquitin ligases is important for maintenance of muscular structure and function. MuRF proteins mediate adaptation of striated muscles to stress. MuRF2 and MuRF3 bind to microtubules and are implicated in sarcomere formation with noticeable functional redundancy. However, if this redundancy is important for muscle function in vivo is unknown. Our objective was to investigate cooperative function of MuRF2 and MuRF3 in the skeletal muscle and the heart in vivo. Methods: MuRF2 and MuRF3 double knockout mice (DKO) were generated and phenotypically characterized. Skeletal muscle and the heart were investigated by morphological measurements, histological analyses, electron microscopy, immunoblotting, and real-time PCR. Isolated muscles were subjected to in vitro force measurements. Cardiac function was determined by echocardiography and working heart preparations. Function of cardiomyocytes was measured in vitro. Cell culture experiments and mass-spectrometry were used for mechanistic analyses. Results: DKO mice showed a protein aggregate myopathy in skeletal muscle. Maximal force development was reduced in DKO soleus and extensor digitorum longus. Additionally, a fibre type shift towards slow/type I fibres occurred in DKO soleus and extensor digitorum longus. MuRF2 and MuRF3-deficient hearts showed decreased systolic and diastolic function. Further analyses revealed an increased expression of the myosin heavy chain isoform beta/slow and disturbed calcium handling as potential causes for the phenotype in DKO hearts. Conclusions: The redundant function of MuRF2 and MuRF3 is important for maintenance of skeletal muscle and cardiac structure and function in vivo
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