1,182 research outputs found
The mean velocity of two-state models of molecular motor
The motion of molecular motor is essential to the biophysical functioning of
living cells. In principle, this motion can be regraded as a multiple chemical
states process. In which, the molecular motor can jump between different
chemical states, and in each chemical state, the motor moves forward or
backward in a corresponding potential. So, mathematically, the motion of
molecular motor can be described by several coupled one-dimensional hopping
models or by several coupled Fokker-Planck equations. To know the basic
properties of molecular motor, in this paper, we will give detailed analysis
about the simplest cases: in which there are only two chemical states.
Actually, many of the existing models, such as the flashing ratchet model, can
be regarded as a two-state model. From the explicit expression of the mean
velocity, we find that the mean velocity of molecular motor might be nonzero
even if the potential in each state is periodic, which means that there is no
energy input to the molecular motor in each of the two states. At the same
time, the mean velocity might be zero even if there is energy input to the
molecular motor. Generally, the velocity of molecular motor depends not only on
the potentials (or corresponding forward and backward transition rates) in the
two states, but also on the transition rates between the two chemical states
Determinan Kejadian Komplikasi Persalinan Di Indonesia (Analisis Data Sekunder Survei Demografi Dan Kesehatan Indonesia Tahun 2007)
Analisis data sekunder SDKI 2007 guna mengidentifikasi determinan kejadian komplikasi persalinan di Indonesia. Sampel adalah wanita usia 15-49 tahun yang melahirkan anak 5 tahun terakhir sebelum survei dalam hal ini yang dianalisis adalah kelahiran anak terakhir yaitu sebesar 15.334. Variabel dependen adalah kejadian komplikasi persalinan. Diketahui bahwa proporsi kejadian komplikasi persalinan di Indonesia antara kurun waktu tahun 2002-2007 sebanyak 43,7%. Hasil determinan kejadian komplikasi persalinan adalah paritas 1/≥4 anak, adanya komplikasi kehamilan, adanya riwayat komplikasi persalinan dahulu, adanya masalah dalam mendapatkan pelayanan kesehatan, kunjungan minimal pemeriksaan antenatal, dan penolong persalinan tenaga kesehatan dan tempat persalinan. Dan faktor yang paling dominan berhubungan dengan kejadian komplikasi persalinan adalah riwayat komplikasi persalinan dahulu dengan odds ratio 5,52. Diharapkan adanya kerjasama semua pihak dalam menurunkan angka komplikasi persalinan ini antara pemegang program pusat, daerah dan puskesmas dengan perencanaan program antenatal care terpadu yang merupakan bagian dari pelayanan antenatal guna mendeteksi secara dini kehamilan risiko tinggi dan tanda-tanda komplikasi kehamilan dan mencegah komplikasi persalinan dan nifas
Recommended from our members
Semiquantitative Estimates of Rainfall Variability During the 8.2 kyr Event in California Using Speleothem Calcium Isotope Ratios
A multiproxy record from a fast-growing stalagmite reveals variable hydroclimate on the California coast across the 8.2 kyr event and a precursor event likely caused by initial drainage of proglacial Lake Agassiz. Using speleothem δ Ca, we develop the first semiquantitative estimates of paleorainfall variability for California through calibration with measurements of the modern climate and cave environment. We find that the magnitude of rainfall variability during the 8.2 kyr event approached the multiyear variability observable in the recent past (1950–2019) and the magnitude of variability during the precursor event likely exceeded this range. Additionally, we observe other instances of multidecadal variability comparable in magnitude to the precursor event during the record. Our work suggests that speleothem calcium isotope ratios are a powerful semiquantitative means to reconstruct paleorainfall, although numerous factors must be assessed in each cave system before applying this approach. 4
Pattern formation of reaction-diffusion system having self-determined flow in the amoeboid organism of Physarum plasmodium
The amoeboid organism, the plasmodium of Physarum polycephalum, behaves on
the basis of spatio-temporal pattern formation by local
contraction-oscillators. This biological system can be regarded as a
reaction-diffusion system which has spatial interaction by active flow of
protoplasmic sol in the cell. Paying attention to the physiological evidence
that the flow is determined by contraction pattern in the plasmodium, a
reaction-diffusion system having self-determined flow arises. Such a coupling
of reaction-diffusion-advection is a characteristic of the biological system,
and is expected to relate with control mechanism of amoeboid behaviours. Hence,
we have studied effects of the self-determined flow on pattern formation of
simple reaction-diffusion systems. By weakly nonlinear analysis near a trivial
solution, the envelope dynamics follows the complex Ginzburg-Landau type
equation just after bifurcation occurs at finite wave number. The flow term
affects the nonlinear term of the equation through the critical wave number
squared. Contrary to this, wave number isn't explicitly effective with lack of
flow or constant flow. Thus, spatial size of pattern is especially important
for regulating pattern formation in the plasmodium. On the other hand, the flow
term is negligible in the vicinity of bifurcation at infinitely small wave
number, and therefore the pattern formation by simple reaction-diffusion will
also hold. A physiological role of pattern formation as above is discussed.Comment: REVTeX, one column, 7 pages, no figur
Labyrinthine Turing Pattern Formation in the Cerebral Cortex
I propose that the labyrinthine patterns of the cortices of mammalian brains
may be formed by a Turing instability of interacting axonal guidance species
acting together with the mechanical strain imposed by the interconnecting
axons.Comment: See home page http://lec.ugr.es/~julya
NF kappa B induces overexpression of bovine FcRn: a novel mechanism that further contributes to the enhanced immune response in genetically modified animals carrying extra copies of FcRn
Among the many functions of the neonatal Fc receptor (FcRn) for
IgG, it binds to IgG-opsonized antigen complexes and propagates
their traffic into lysosomes where antigen processing occurs. We
previously reported that transgenic (Tg) mice and rabbits that
carry multiple copies and overexpress FcRn have augmented
humoral immune responses. Nuclear factor-kappa B (NFκB) is a
critical molecule in the signaling cascade in the immune
response. NFκB induces human FcRn expression and our previous in
silico analysis suggested NFκB binding sites in the promoter
region of the bovine (b) FcRn α-chain gene (FCGRT). Here, we
report the identification of three NFκB transcription binding
sites in the promoter region of this gene using luciferase
reporter gene technology, electromobility shift assay and
supershift analysis. Stimulation of primary bovine endothelial
cells with the Toll like receptor-4 ligand lipopolysaccharide
(LPS), which mediates its effect via NFκB, resulted in rapid
upregulation of the bFcRn expression and a control gene, bovine
E-selectin. This rapid bFcRn gene induction was also observed in
the spleen of bFcRn Tg mice treated with intraperitoneally
injected LPS, analyzed by northern blot analysis. Finally, NFκB-
mediated bFcRn upregulation was confirmed at the protein level
in macrophages isolated from the bFcRn Tg mice using flow
cytometry with a newly developed FcRn specific monoclonal
antibody that does not cross-react with the mouse FcRn. We
conclude that NFκB regulates bFcRn expression and thus optimizes
its functions, e.g., in the professional antigen presenting
cells, and contributes to the much augmented humoral immune
response in the bFcRn Tg mice
Gene expression time delays & Turing pattern formation systems
The incorporation of time delays can greatly affect the behaviour of partial differential equations and dynamical systems. In addition, there is evidence that time delays in gene expression due to transcription and translation play an important role in the dynamics of cellular systems. In this paper, we investigate the effects of incorporating gene expression time delays into a one-dimensional putative reaction diffusion pattern formation mechanism on both stationary domains and domains with spatially uniform exponential growth. While oscillatory behaviour is rare, we find that the time taken to initiate and stabilise patterns increases dramatically as the time delay is increased. In addition, we observe that on rapidly growing domains the time delay can induce a failure of the Turing instability which cannot be predicted by a naive linear analysis of the underlying equations about the homogeneous steady state. The dramatic lag in the induction of patterning, or even its complete absence on occasions, highlights the importance of considering explicit gene expression time delays in models for cellular reaction diffusion patterning
Characterization of Turing diffusion-driven instability on evolving domains
In this paper we establish a general theoretical framework for Turing diffusion-driven instability for reaction-diffusion systems on time-dependent evolving domains. The main result is that Turing diffusion-driven instability for reaction-diffusion systems on evolving domains is characterised by Lyapunov exponents of the evolution family associated with the linearised system (obtained by linearising the original system along a spatially independent solution). This framework allows for the inclusion of the analysis of the long-time behavior of the solutions of reaction-diffusion systems. Applications to two special types of evolving domains are considered: (i) time-dependent domains which evolve to a final limiting fixed domain and (ii) time-dependent domains which are eventually time periodic. Reaction-diffusion systems have been widely proposed as plausible mechanisms for pattern formation in morphogenesis
- …