84 research outputs found
Mesoscopic Phase Fluctuations: General Phenomenon in Condensed Matter
General conditions for the occurrence of mesoscopic phase fluctuations in
condensed matter are considered. The description of different thermodynamic
phases, which coexist as a mixture of mesoscopically separated regions, is
based on the {\it theory of heterophase fluctuations}. The spaces of states,
typical of the related phases, are characterized by {\it weighted Hilbert
spaces}. Several models illustrate the main features of heterophase condensed
matter.Comment: 23 pages, Latex, no figure
Pseudo-boundaries in discontinuous 2-dimensional maps
It is known that Kolmogorov-Arnold-Moser boundaries appear in sufficiently
smooth 2-dimensional area-preserving maps. When such boundaries are destroyed,
they become pseudo-boundaries. We show that pseudo-boundaries can also be found
in discontinuous maps. The origin of these pseudo-boundaries are groups of
chains of islands which separate parts of the phase space and need to be
crossed in order to move between the different sub-spaces. Trajectories,
however, do not easily cross these chains, but tend to propagate along them.
This type of behavior is demonstrated using a ``generalized'' Fermi map.Comment: 4 pages, 4 figures, Revtex, epsf, submitted to Physical Review E (as
a brief report
Femtomolar detection of the heart failure biomarker NT-proBNP in artificial saliva using an immersible liquid-gated aptasensor with reduced graphene oxide
Measuring NT-proBNP biomarker is recommended for preliminary diagnostics of
the heart failure. Recent studies suggest a possibility of early screening of
biomarkers in saliva for non-invasive identification of cardiac diseases at the
point-of-care. However, NT-proBNP concentrations in saliva can be thousand time
lower than in blood plasma, going down to pg/mL level. To reach this level, we
developed a label-free aptasensor based on a liquid-gated field effect
transistor using a film of reduced graphene oxide monolayer (rGO-FET) with
immobilized NT-proBNP specific aptamer. We found that, depending on ionic
strength of tested solutions, there were different levels of correlation in
responses of electrical parameters of the rGO-FET aptasensor, namely, the Dirac
point shift and transconductance change. The correlation in response to
NT-proBNP was high for 1.6 mM phosphate-buffered saline (PBS) and zero for 16
mM PBS in a wide range of analyte concentrations, varied from 1 fg/mL to 10
ng/mL. The effects of transconductance and Dirac point shift in PBS solutions
of different concentrations are discussed. The biosensor exhibited a high
sensitivity for both transconductance (2 uS/decade) and Dirac point shift (2.3
mV/decade) in diluted PBS with the linear range from 10 fg/mL to 1 pg/mL. The
aptasensor performance has been also demonstrated in undiluted artificial
saliva with the achieved limit of detection down to 41 fg/mL (~4.6 fM)
The field theory of symmetrical layered electrolytic systems and the thermal Casimir effect
We present a general extension of a field-theoretic approach developed in
earlier papers to the calculation of the free energy of symmetrically layered
electrolytic systems which is based on the Sine-Gordon field theory for the
Coulomb gas. The method is to construct the partition function in terms of the
Feynman evolution kernel in the Euclidean time variable associated with the
coordinate normal to the surfaces defining the layered structure. The theory is
applicable to cylindrical systems and its development is motivated by the
possibility that a static van der Waals or thermal Casimir force could provide
an attractive force stabilising a dielectric tube formed from a lipid bilayer,
an example of which are t-tubules occurring in certain muscle cells. In this
context, we apply the theory to the calculation of the thermal Casimir effect
for a dielectric tube of radius and thickness formed from such a
membrane in water. In a grand canonical approach we find that the leading
contribution to the Casimir energy behaves like which gives
rise to an attractive force which tends to contract the tube radius. We find
that for the case of typical lipid membrane t-tubules. We
conclude that except in the case of a very soft membrane this force is
insufficient to stabilise such tubes against the bending stress which tend to
increase the radius. We briefly discuss the role of lipid membrane reservoir
implicit in the approach and whether its nature in biological systems may
possibly lead to a stabilising mechanism for such lipid tubes.Comment: 28 pages, 2 figures, LaTe
Management approaches and aquaculture of sturgeons in the Lower Danube region countries
Summary This paper presents the status and trends in management of sturgeon species and the development of sturgeon aquaculture in the Lower Danube countries: Romania, Bulgaria, Serbia, Ukraine and Moldova. Sturgeon fishery moratoria and aquaculture development represent first steps in the Lower Danube countries to combat extirpation. Supportive stocking was used as a compensation for the impact of sturgeon fishery and dam construction, but these efforts unfortunately lacked adequate cooperation and coordination between and among region countries. Unsolved problems remain, such as the presence of illegal sturgeon fishery, water pollution, habitat destruction and fragmentation. Construction of fish passes and habitat restoration project developments are two key issues that have yet to be tackled in the Lower Danube region
Hypericum sp.: essential oil composition and biological activities
Phytochemical composition of Hypericum
genus has been investigated for many years. In the recent past, studies on the essential oils (EO) of this genus have been progressing and many of them have reported interesting biological activities. Variations in the EO composition of Hypericum species influenced
by seasonal variation, geographic distribution, phenological cycle and type of the organ in which EO are produced and/or accumulated have also been reported. Although many reviews attributed to the characterization
as well as biological activities of H. perforatum
crude extracts have been published, no review has been published on the EO composition and biological activities of Hypericum species until recently (Crockett
in Nat Prod Commun 5(9):1493â1506, 2010;
Bertoli et al. in Global Sci Books 5:29â47, 2011). In this article, we summarize and update information regarding the composition and biological activities of Hypericum species EO. Based on experimental work carried out in our laboratory we also mention possible biotechnology approaches envisaging EO improvement of some species of the genus.Fundação para a CiĂȘncia e a Tecnologia (FCT) - project PTDC/AGR AAM/70418/2006, SFRH/BD/
13283/2003
Les travaux de recherches sur les esturgeons et les poissons spatules se concentrent sur les espÚces à faible risque et négligent les espÚces en danger d'extinction
International audienceSturgeons and paddlefish are among the most commercially valuable groups of fishes and include both low risk and highly endangered species. However, a recent bibliometric study on sturgeon and paddlefish research revealed that disproportionately little attention has been paid to those species that are endangered or face a high probability of extinction. With the exception of European sturgeon Acipenser sturio, all of the 8 species that are highly threatened with extinction or functionally extinct, were each addressed in less than 1% of the publications dealing with sturgeons or paddlefishes. Information on the biology and sensitive life-cycle phases of threatened sturgeon and paddlefish species, as well as knowledge of their interactions with their respective habitats, is especially deficient or lacking, thus rendering the planning and execution of protection measures even more difficult. We argue that a more stringent focus has to be placed upon conservation research and management for vulnerable species and populations that are threatened with a high risk of extinction. This also makes it a necessity to overcome the apparent lack of commitment which has been observed in some regions to developing and/or implementing effective and concerted regional actions which address sturgeon and paddlefish rehabilitation
Assessment of extinction risk and reasons for decline in sturgeon
Sturgeon populations in the Danube River have been affected by a combination of hydropower development, over-harvesting, habitat degradation from agricultural and industrial practices and from urbanization. The effects of these changes have been monitored on six sturgeon species inhabiting the Danube River. Two of them are resident species, while the other four migrate to the river for spawning. Atlantic sturgeon (Acipenser sturio) has completely disappeared from this region. Ship sturgeon (Acipenser nudiventris) is very rare in professional fishing catches. Beluga (Huso huso), Russian sturgeon (Acipenser gueldenstaedtii), stellate sturgeon (Acipenser stellatus) and sterlet (Acipenser ruthenus) are endangered with different levels of extinction risk. Here, we model the time dependence of the beluga and Russian sturgeon catch in the Serbian part of the Danube River. Predicted extinction of Russian sturgeon was estimated to fall around the middle of the century, and for beluga approximately at middle of the millennium. Suggestions for sturgeon conservation measures on a national level and coordination of all relevant institutions in Serbia are also presented
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