3,022 research outputs found
Generalized Einstein or Green-Kubo relations for active biomolecular transport
For driven Markovian dynamics on a network of (biomolecular) states, the
generalized mobilities, i.e., the response of any current to changes in an
external parameter, are expressed by an integral over an appropriate
current-current correlation function and thus related to the generalized
diffusion constants. As only input, a local detailed balance condition is
required typically even valid for biomolecular systems operating deep in the
non-equilibrium regime.Comment: 4 page
Botanical Knowledge and its Differentiation by Age, Gender and Ethnicity in Southwestern Niger
Indigenous knowledge is unevenly distributed. Individual knowledge level may be affected by many factors such as gender, age, ethnicity, profession, religious and cultural beliefs, abundance and usefulness of the species. This study documents indigenous knowledge of herbaceous and woody plant species of farmers and herders in southwestern Niger. Specifically, we examine the effects of age, gender, and ethnicity on knowledge of local vegetation. Results from the study showed that on average a higher proportion of woody species was identified by the respondents compared to herbaceous species. Both gender and ethnicity had a significant effect on the identification of herbaceous species but no effect on identification of woody species. Respondents in lower age group (10 to 30 years) identified lower number of species compared to other age classes. There seems to be a curvilinear relationship between age of respondents and number of plant species identified. Results from this study reaffirm the uneven distribution of indigenous knowledge within a given area due to social factors. The main challenge is how to incorporate these social differences in knowledge of native plant species into sustainable management and conservation of community natural resources
Effective adhesion strength of specifically bound vesicles
A theoretical approach has been undertaken in order to model the
thermodynamic equilibrium of a vesicle adhering to a flat substrate. The
vesicle is treated in a canonical description with a fixed number of sites. A
finite number of these sites are occupied by mobile ligands that are capable of
interacting with a discrete number of receptors immobilized on the substrate.
Explicit consideration of the bending energy of the vesicle shape has shown
that the problem of the vesicle shape can be decoupled from the determination
of the optimum allocation of ligands over the vesicle. The allocation of bound
and free ligands in the vesicle could be determined as a function of the size
of the contact zone, the ligand-receptor binding strength and the concentration
of the system constituents. Several approximate solutions for different regions
of system parameters are determined and in particular, the distinction between
receptor-dominated equilibria and ligand-dominated equilibria is found to be
important. The crossover between these two types of solutions is found to occur
at a critical size of the contact zone. The presented approach enables the
calculation of the effective adhesion strength of the vesicle and thus permits
meaningful comparisons with relevant experiments as well as connecting the
presented model with the proven success of the continuum approach for modeling
the shapes of adhering vesicles. The behavior of the effective adhesion
strength is analyzed in detail and several approximate expressions for it are
given.Comment: 19 pages, 6 figures. To appear in Phys. Rev.
Overview of Drug Transporters in Human Placenta
The transport of drugs across the placenta is a point of great importance in pharmacotherapy during pregnancy. However, the knowledge of drug transport in pregnancy is mostly based on experimental clinical data, and the underlying biological mechanisms are not fully understood. In this review, we summarize the current knowledge of drug transporters in the human placenta. We only refer to human data since the placenta demonstrates great diversity among species. In addition, we describe the experimental models that have been used in human placental transport studies and discuss their availability. A better understanding of placental drug transporters will be beneficial for the health of pregnant women who need drug treatment and their fetuses
Complete Genome Sequence of Bacteroides ovatus V975
The complete genome sequence of Bacteroides ovatus V975 was determined. The genome consists of a single circular chromosome of 6,475,296 bp containing five rRNA operons, 68 tRNA genes, and 4,959 coding genes
Coexistence of dilute and densely packed domains of ligand-receptor bonds in membrane adhesion
We analyze the stability of micro-domains of ligand-receptor bonds that
mediate the adhesion of biological model membranes. After evaluating the
effects of membrane fluctuations on the binding affinity of a single bond, we
characterize the organization of bonds within the domains by theoretical means.
In a large range of parameters, we find the commonly suggested dense packing to
be separated by a free energy barrier from a regime in which bonds are sparsely
distributed. If bonds are mobile, a coexistence of the two regimes should
emerge, which agrees with recent experimental observations.Comment: 6 pages, 6 figures, accepted by EP
Implications of macrophyte abundance on algal growth management: The case of three natural swimming pools with distinct macrophyte abundance
Natural swimming pools are small constructed lakes for recreational proposes. They are
composed by a swimming area merging with an area planted with emergent and submerged
macrophytes, which function as biological filters. Fish are absent, however a wide diversity of
phytoplankton, zooplankton and macroinvertebrate species colonize these pools. Therefore,
pools can be regarded as the ideal systems to extrapolate the implications of macrophyte
abundance management on algal growth control. The present study was taken in three pools (A,
B and C) located in Minho Region (Northern Portugal) In early summer the macrophyte area had
a 30% of cover in Pool A, in B 40% and in C 60%. Phytoplankton, zooplankton and filamentous
algae abundance as well as conductivity, pH, dissolved oxygen, hardness, nitrates, nitrites,
ammonia, phosphates were recorded in February, April and June. The lowest densities of
phytoplankton were observed in pool C. Besides, filamentous algae were abundant in the pool A,
whereas in B and C they were recorded only in summer. In Pool A, zooplankton assemblage was
always dominated specialists on small particle feeding, which food preference are detritus and
bacteria. Conversely, in the Pool C herbivorous zooplankton was predominant. The low algal
densities observed in the Pool C are explained by the presence of a well established macrophyte
assemblage. These plants contribute to the reduction of algal densities by (1) creating of areas of
shade; (2) removing nutrients from water column and (3) provide refuges for herbivorous
zooplankton. Therefore, the present study stresses the pertinence of take in account the key role
of aquatic macrophytes when management practices for algal growth control are developed
Effective Confinement as Origin of the Equivalence of Kinetic Temperature and Fluctuation-Dissipation Ratio in a Dense Shear Driven Suspension
We study response and velocity autocorrelation functions for a tagged
particle in a shear driven suspension governed by underdamped stochastic
dynamics. We follow the idea of an effective confinement in dense suspensions
and exploit a time-scale separation between particle reorganization and
vibrational motion. This allows us to approximately derive the
fluctuation-dissipation theorem in a "hybrid" form involving the kinetic
temperature as an effective temperature and an additive correction term. We
show numerically that even in a moderately dense suspension the latter is
negligible. We discuss similarities and differences with a simple toy model, a
single trapped particle in shear flow
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