Revealing the superfluid lambda transition in the universal thermodynamics of a unitary Fermi gas

Fermi gases, collections of fermions such as neutrons and electrons, are found throughout nature, from solids to neutron stars. Interacting Fermi gases can form a superfluid or, for charged fermions, a superconductor. We have observed the superfluid phase transition in a strongly interacting Fermi gas by high-precision measurements of the local compressibility, density, and pressure. Our data completely determine the universal thermodynamics of these gases without any fit or external thermometer. The onset of superfluidity is observed in the compressibility, the chemical potential, the entropy, and the heat capacity, which displays a characteristic lambda-like feature at the critical temperature T(c)/T(F) = 0.167(13). The ground-state energy is 3/5ξN E(F) with ξ = 0.376(4). Our measurements provide a benchmark for many-body theories of strongly interacting fermions.     

Optimization of a duplex real-time PCR method for relative quantitation of infectious laryngotracheitis virus

Infectious laryngotracheitis is a highly contagious respiratory disease of chickens controlled by biosecurity and vaccination with live attenuated or recombinant vaccines. Infectious laryngotracheitis virus (ILTV) infections are characterized by a peak of viral replication in the trachea followed by a steady decrease in replication that results in the establishment of latency. Estimation of viral load is an important tool to determine the stage of ILTV infection. Here, a multiplex real-time PCR was optimized for the quantification of ILTV genomes. Quantification of viral genomes was based on the amplification of the ILTV UL44 gene, and sample variability was normalized using the chicken (Gallusgallus domesticus) alpha2-collagen gene as an endogenous control in a duplex reaction.     

A phenomenological model of dry matter partitioning among plant organs for simulation of potato growth

A mathematical model of the process of dry matter partitioning among plant organs during the autotrophic period of potato development is presented. The model consists of a system of differential equations based on the concept of a sink. The sink strength is proportional to the dry matter (DM) biomass, subject to total photosynthesis production. The ageing process is taken into account. The equations contain a set of parameters which are estimated by fitting the numerical solution to the empirical data recorded from growth analysis in field experiments.     

A model for simulation of potato growth on the plant community level

A model for the main processes in potato growth is developed and used for the simulation of crop production under different meteorological conditions. The main control factors considered in the model are irrigation, fertilization and timing of harvest. The model is constructed on the level of the plant community. The time interval for the simulation of general dynamic processes is one day. To describe some important physiological processes during a day, the simulation is performed by subroutines with hourly time steps.     

A link between hurricane-induced tree sprouting, high stem density and short canopy in tropical dry forest

The physiognomy of Caribbean dry forest is shorter, denser and contains a greater proportion of multi-stemmed trees than other neotropical dry forests. Our previous research, conducted after Hurricane Georges in 1998, has shown that dry forest trees sprout near the base following hurricane disturbance, even if the trees have not incurred structural damage. However, for these hurricane-induced sprouts to contribute to the physiognomy of the forest, they must grow and survive. We followed sprout dynamics and stem mortality on 1,407 stems from 1998, after Hurricane Georges, until 2005. The number of surviving sprouts and the proportion of sprouting stems decreased during the 7-year period, but the sprouting rate was still 3-fold higher and the proportion of sprouting stems 5-fold higher than before the hurricane. Mortality of non-sprouting stems (15.4%) was about the same as for sprouting stems (13.9%) after 7 years. The mean length of the dominant sprout surpassed 1.6 m by 2005, with over 13% of the dominant sprouts reaching subcanopy height. Sprout growth and survival varied among species. These results demonstrate that, despite some thinning, hurricane-induced sprouts survive and grow and that the unique physiognomic characteristic of Caribbean dry forests is related to hurricane disturbance.     

Geometrical and physicochemical considerations of the pit membrane in relation to air seeding: the pit membrane as a capillary valve

A theoretical treatment of some of the factors influencing air seeding at the pit membranes of xylem vessels is given. Pit membrane structure, viewed as a three-dimensional mesh of intercrossing fibrils, and vulnerability to water-stress-induced air seeding are examined in the context of the Young-Laplace equation. Simple geometrical considerations of the porous membrane show that the vapor-liquid interface curvature radius is a function of fiber-fiber distance, fiber radius, wetting angle and position of the wetting line. Air seeding (maximum pressure) occurs at the minimum curvature radius, therefore air seeding is not simply determined by the fiber-fiber distance but is a function of the geometry of the pit membrane and of physicochemical quantities like surface tension and wetting angle. As a consequence of considering a wetting angle different from zero, the minimum curvature radius becomes larger than half the fiber-fiber distance. The present model considers that, for a given pressure difference at the pit membrane, all local interface curvatures are the same. In this sense, pit membranes work as variable capillary valves that allow or prevent air seeding by adjusting local curvatures and interface positions relative to the pore-forming fibers, following the pressure differences across the membranes. The theoretical prediction for the air seeding threshold is consistent with recent experimental data for angiosperm trees.     

Biochemical side effects of the herbicide FINALE<Superscript>®</Superscript> on <Emphasis Type="Italic">bar</Emphasis> gene-containing transgenic pineapple plantlets

Pineapple is one of the most important tropical fruits and therefore intensive genetic improvement programs are being carried out in many countries, including Cuba. Our research team has previously introduced the bar gene, along with chitinase and AP24 genes, into the pineapple genome. Herein, we report on the biochemical side effects of the herbicide FINALE^® on these transgenic plantlets during hardening. Levels of aldehydes and chlorophylls, and peroxidase activity were recorded. The transformed clone studied here, not sprayed with FINALE^®, showed the following side effects because of transgenesis only. Levels of malondialdehyde, other aldehydes, chlorophyll b, and total chlorophyll pigments decreased. The most remarkable biochemical differences between transgenic and non-transgenic plantlets after application of FINALE^® follow. Levels of malondialdehyde and other aldehydes in transgenic material were not decreased by FINALE^®, perhaps because these levels were already low as a result of transformation. FINALE^® increased peroxidase activity in transgenic plantlets but such increase was higher in non-transgenic material. The herbicide increased contents of chlorophyll pigments (a, b, total) in transformed plantlets. However, as expected, non-transgenic plantlets decreased levels of chlorophylls (a, b, total) after application of FINALE^®. The genetic transformation of pineapple with the bar gene not only conferred resistance to the herbicide FINALE^®, but also promoted other biochemical changes.     

The completely additive effects of two barley phenology‐related genes (eps2S and sdw1) are explained by specific effects at different periods within the crop growth cycle

We used the ‘Baronesse’/‘Full Pint’ doubled haploid population to analyse the genetic factors controlling flowering date under South American conditions. Both parents have similar heading dates, but the population shows transgressive segregation. Two genes, eps2S on chromosome 2H and sdw1 on chromosome 3H, explained most of the phenotypic variation for anthesis date, with the later allele carried by ‘Baronesse’ and ‘Full Pint’ , respectively. Both effects were completely additive with no interaction. We studied three plant developmental periods: seedling emergence to tillering (Z10–Z20), tillering (Z20–Z30) and end of tillering to anthesis (Z30–Z49) under field conditions at three contrasting planting dates. Z10–Z20 was also measured under semi‐controlled conditions. eps2S controlled Z30–Z49 periods, while sdw1 controlled Z20–Z30. Each of the two genes for the end‐point phenotype—anthesis date—was a determinant of flowering at a different developmental stage. No gene x planting date interactions were detected.