12 research outputs found
Copulation and Oviposition in the Green-blotched Giant Anole, Anolis smallwoodi (Squamata: Dactyloidae), from southeastern Cuba
Crown-giant anole ecomorphs have evolved independently across the Greater Antilles (Cuba, Hispaniola, Jamaica, and Puerto Rico), but only a few of these species have well documented life histories. Herein we report previously undocumented observations of copulation, oviposition, and hatchlings for the Green-blotched Giant Anole (Anolis smallwoodi) of southeastern Cuba. We observed eight mating events (three with A. s. smallwoodi and five with A. s. palardis) along the coastline between Santiago de Cuba and Guantánamo Province during June 2010 and September 2011. One female A. s. palardis mated with two males in the same territory. Females dig a hole with their snouts, oviposit single eggs, and cover them with substrate. We monitored eight eggs incubated in slightly moist vermiculite. The minimum incubation times were 54-69 days (varying with temperature). Juveniles usually are colored like adults, bright green with white spots on the body, pale postlabial bands, and suprascapular stripes
Magnetic field dependence of the coherence length and penetration depth of MgB2 single crystals
International audienceWe report on specific heat and Hall probe magnetization measurements in magnesium diboride single crystals. A magnetic field dependence of the coherence length has been deduced from the former assuming that the electronic excitations are localized in field dependent vortex cores in which case is related to the Sommerfeld coefficient = Cp /T T→0 throughout, H /a0 2 a0 being the vortex spacing . The reversible part of the magnetization has been analyzed with a phenomenological Ginzburg-Landau model introducing field dependent parameters i.e., penetration depth and which account for the decreasing contribution of the -band with increasing field. This approach perfectly reproduces the experimental data by combining the field dependence of deduced from Cp 1/ 2 B with an almost linear increase of from 450 Å at low field to 700 Å close to Hc2. These field dependences can then be used to consistently describe the field dependence of the critical current density, small angle neutron scattering form factor, and muon spin relaxation rate
Superconductivity in MgB_2 doped with Ti and C
Measurements of the superconducting upper critical field, H_{c2}, and
critical current density, J_c, have been carried out for MgB_2 doped with Ti
and/or C in order to explore the problems encountered if these dopants are used
to enhance the superconducting performance. Carbon replaces boron in the MgB_2
lattice and apparently shortens the electronic mean free path thereby raising
H_c2. Titanium forms precipitates of either TiB or TiB_2 that enhance the flux
pinning and raise J_c. Most of these precipitates are intra-granular in the
MgB_2 phase. If approximately 0.5% Ti and approximately 2% C are co-deposited
with B to form doped boron fibers and these fibers are in turn reacted in Mg
vapor to form MgB_2, the resulting superconductor has H_{c2}(T=0) ~ 25 T and
J_c ~ 10,000 A/cm**2 at 5 K and 2.2 T.Comment: 11 pages, 10 figure
Systematic effects of carbon doping on the superconducting properties of Mg(BC)
The upper critical field, , of Mg(BC) has been
measured in order to probe the maximum magnetic field range for
superconductivity that can be attained by C doping. Carbon doped boron
filaments are prepared by CVD techniques, and then these fibers are then
exposed to Mg vapor to form the superconducting compound. The transition
temperatures are depressed about C and rises at about C. This means that 3.5% C will depress from to and
raise from to . Higher fields are probably
attainable in the region of 5% C to 7% C. These rises in are
accompanied by a rise in resistivity at from about
to about . Given that the samples are polycrystalline wire
segments, the experimentally determined curves represent the upper
manifold associated with
Is Delta_{pi}-gap-only superconductivity possible in Mg_{1-x}Al_{x}B_{2} and Mg(B_{1-y}C_{y})_{2} alloys?
Using density-functional-based method, we study the k-resolved sigma- and
pi-band holes in Mg_{1-x}Al_{x}B_{2} and Mg(B_{1-y}C_{y})_{2} alloys. We find
that the calculated profiles of the loss of sigma- and pi-band holes in these
two systems as a function of impurity concentration are in qualitative
agreement with experiments, as expected. We also describe its implications
vis-a-vis superconductivity in Mg_{1-x}Al_{x}B_{2} and Mg(B_{1-y}C_{y})_{2}.Comment: 4 pages, 3 figure
The use of quotation marks in contemporary media texts (on the example of the word »vykadit«)
V članku autorky popisují užití uvozovek v novinářských textech na příkladu vulgarismu vykadit. Autorky projednávají o různých potenciálních významech uvozovek, důvodech jejich použití a nadměrném používání.The paper deals with use of quotation marks in journalistic texts on the example of vulgarism vykadit. It discusses various potential meanings of quotation marks, reasons of their use and over-use.
Influence of Al doping on the gap values in MgB2 single crystals
International audienceWe report on the evolution of the small and large gap values in Mg1 xAlxB2 single crystals (for x = 0, 0.1 and 0.2) by specific heat and point contact spectroscopy. The values deduced from the temperature dependence of the electronic contribution to the specific heat are very close to those obtained by point contact spectroscopy. The evolution of those gaps with Al concentration suggests that both band filling and interband scattering effects are present and may lead to a merging of the two gaps for Tc 10-15 K
Built to bite : feeding kinematics, bite forces, and head shape of a specialized durophagous lizard, Dracaena Guianensis (Teiidae)
Most lizards feed on a variety of food items that may differ dramatically in their physical and behavioral characteristics. Several lizard families are known to feed upon hard-shelled prey (durophagy). Yet, specializations toward true molluscivory have been documented for only a few species. As snails are hard and brittle food items, it has been suggested that a specialized cranial morphology, high bite forces, and an adapted feeding strategy are important for such lizards. Here we compare head and skull morphology, bite forces, and feeding kinematics of a snail-crushing teiid lizard (Dracaena guianensis) with those in a closely related omnivorous species (Tupinambis merianae). Our data show that juvenile D. guianensis differ from T. merianae in having bigger heads and greater bite forces. Adults, however, do not differ in bite force. A comparison of feeding kinematics in adult Dracaena and Tupinambis revealed that Dracaena typically use more transport cycles, yet are more agile in manipulating snails. During transport, the tongue plays an important role in manipulating and expelling shell fragments before swallowing. Although Dracaena is slow, these animals are very effective in crushing and processing hard-shelled prey. J. Exp. Zool. 317A:371381, 2012. (c) 2012 Wiley Periodicals, Inc
Built to Bite: Feeding Kinematics, Bite Forces, and Head Shape of a Specialized Durophagous Lizard, Dracaena Guianensis (Teiidae)
Most lizards feed on a variety of food items that may differ dramatically in their physical and behavioral characteristics. Several lizard families are known to feed upon hard-shelled prey (durophagy). Yet, specializations toward true molluscivory have been documented for only a few species. As snails are hard and brittle food items, it has been suggested that a specialized cranial morphology, high bite forces, and an adapted feeding strategy are important for such lizards. Here we compare head and skull morphology, bite forces, and feeding kinematics of a snail-crushing teiid lizard (Dracaena guianensis) with those in a closely related omnivorous species (Tupinambis merianae). Our data show that juvenile D. guianensis differ from T. merianae in having bigger heads and greater bite forces. Adults, however, do not differ in bite force. A comparison of feeding kinematics in adult Dracaena and Tupinambis revealed that Dracaena typically use more transport cycles, yet are more agile in manipulating snails. During transport, the tongue plays an important role in manipulating and expelling shell fragments before swallowing. Although Dracaena is slow, these animals are very effective in crushing and processing hard-shelled prey. J. Exp. Zool. 317A:371381, 2012. (c) 2012 Wiley Periodicals, Inc