3,104 research outputs found
Rescaled density expansions and demixing in hard-sphere binary mixtures
The demixing transition of a binary fluid mixture of additive hard spheres is
analyzed for different size asymmetries by starting from the exact low-density
expansion of the pressure. Already within the second virial approximation the
fluid separates into two phases of different composition with a lower consolute
critical point. By successively incorporating the third, fourth, and fifth
virial coefficients, the critical consolute point moves to higher values of the
pressure and to lower values of the partial number fraction of the large
spheres. When the exact low-density expansion of the pressure is rescaled to
higher densities as in the Percus-Yevick theory, by adding more exact virial
coefficients a different qualitative movement of the critical consolute point
in the phase diagram is found. It is argued that the Percus-Yevick factor
appearing in many empirical equations of state for the mixture has a deep
influence on the location of the critical consolute point, so that the
resulting phase diagram for a prescribed equation has to be taken with caution.Comment: 5 pages, 1 figure; to be published in The Journal of Chemical Physic
Flexible temperature probe for biological systems
Probe is sufficiently flexible so that it can be worn comfortably for long periods of time, but relatively rigid to permit easy insertion. Body and electrical leads of small thermistor are imbedded in flexible fluorosilicone matrix contained in vinyl plastic tubing
Catching and rearing postlarval cleaner shrimp for the aquarium trade: results from a WorldFish Center project in Solomon Islands
Between 1999 and 2003, the WorldFish Center in Solomon Islands conducted research into the feasibility of a new fishery based on the capture and culture of postlarval coral reef fish for the live fish trade. The work was carried out in two phases: a research phase from late 1999 to the end of 2002; and a “finetuning” phase in 2003. Most of the species were of value to the marine aquarium trade, with very few live reef food fish recorded. The most valuable ornamentals were the banded cleaner shrimp, Stenopus species. Cleaner shrimp were harvested using crest nets, the method being modified with the addition of a solid, water-retaining cod-end designed to increase survival at capture. Grow-out techniques were improved by rearing the shrimp separately in jars to prevent aggression. The jars were painted black to protect the shrimp from sunlight. An economic model using experimental catch data and farm gate prices indicates that the fishery based on shrimp, supplemented with small numbers of lobster and fish is economically viable. The next step will be setting up a demonstration farm in a village in the Western Province of Solomon Islands.Aquarium culture, Juveniles, Catch culture, Shrimp fisheries, Catch/effort, Solomon I., Stenopus
Qualitative study in Loop Quantum Cosmology
This work contains a detailed qualitative analysis, in General Relativity and
in Loop Quantum Cosmology, of the dynamics in the associated phase space of a
scalar field minimally coupled with gravity, whose potential mimics the
dynamics of a perfect fluid with a linear Equation of State (EoS). Dealing with
the orbits (solutions) of the system, we will see that there are analytic ones,
which lead to the same dynamics as the perfect fluid, and our goal is to check
their stability, depending on the value of the EoS parameter, i.e., to show
whether the other orbits converge or diverge to these analytic solutions at
early and late times.Comment: 12 pages, 7 figures. Version accepted for publication in CQ
Estudio comparado de la genitalia de dos poblaciones españolas de Cataglyphis (Hym., Formicidae), grupo albicans de color negro
El estudio de la genitalia masculina de dos poblaciones de Cataglyphis grupo albicans de color negro, de Tarifa (Cádiz) y Bellaterra (Barcelona), inicialmente consideradas por diferencias de coloración como C. albicans y C. ibericus, respectivamente, pone de manifiesto diferencias importantes entre ellas, coincidentes con el estudio enzimático (De Haro y otros, 1995). Este estudio enzimático motivó la consideración provisional de las poblaciones orientales ibéricas como pertenecientes a C. albicans, dados 10s problemas que planteaba su identidad con la población marroquí C . albicans ruber. La población de Tarifa se consideró un taxón nuevo, no quedando aclarada la situación taxómica de C. ibericus. Estudios geográficamente mis extensos aclararán si estas poblaciones ibéricas forman parte de una clina morfológica y qué taxón o taxones constituyen.The study of male genitalia of two populations of Cataglyphis group albicans, black colour, from Tarifa (Cádiz) and Bellaterra (Barcelona), previously considered by differences in colour as C. albicans and C . ibericus, respectively, show important differences, in coincidence with enzymatic study (De Haro et al., 1995). In these enzymatic studies, the eastern iberian populations were provisionally considered as C. albicans, due to the problems showed by their identity with the morocco population C . albicans ruber. The Tarifa population was considered a new taxon, with no explanation about the taxonomic situation of C . ibericus. Further studies with greater geographical extension will clear up the existence of a possible morphological cline in the iberian populations and which taxon or taxons they constitute
Gravity in the 3+1-Split Formalism II: Self-Duality and the Emergence of the Gravitational Chern-Simons in the Boundary
We study self-duality in the context of the 3+1-split formalism of gravity
with non-zero cosmological constant. Lorentzian self-dual configurations are
conformally flat spacetimes and have boundary data determined by classical
solutions of the three-dimensional gravitational Chern-Simons. For Euclidean
self-dual configurations, the relationship between their boundary initial
positions and initial velocity is also determined by the three-dimensional
gravitational Chern-Simons. Our results imply that bulk self-dual
configurations are holographically described by the gravitational Chern-Simons
theory which can either viewed as a boundary generating functional or as a
boundary effective action.Comment: 25 pages; v2: minor improvements, references adde
Hydra tropomyosin TROP1 is expressed in head-specific epithelial cells and is a major component of the cytoskeletal structure that anchors nematocytes
A cDNA clone encoding a 253 amino acid tropomyosin was
isolated from
Hydra in a differential screen for headspecific
genes. The Hydra tropomyosin gene, designated
trop1, is a single copy gene, lacks introns and is strongly
expressed in tentacle-specific epithelial cells. Analysis of
protein synthesis in head and gastric tissue indicated a high
rate of tropomyosin synthesis in head tissue. Immunolocalization
of tropomyosin in tentacle tissue revealed a
cushion-like tropomyosin-containing structure within
battery cells at the base of nematocytes. The structure
appears to form part of the cytoskeletal anchor for nematocytes.
Tropomyosin cushions were also observed in
epithelial cells along the body column, which contain
mounted stenotele nematocytes
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