692 research outputs found
Self-organization, scaling and collapse in a coupled automaton model of foragers and vegetation resources with seed dispersal
We introduce a model of traveling agents ({\it e.g.} frugivorous animals) who
feed on randomly located vegetation patches and disperse their seeds, thus
modifying the spatial distribution of resources in the long term. It is assumed
that the survival probability of a seed increases with the distance to the
parent patch and decreases with the size of the colonized patch. In turn, the
foraging agents use a deterministic strategy with memory, that makes them visit
the largest possible patches accessible within minimal travelling distances.
The combination of these interactions produce complex spatio-temporal patterns.
If the patches have a small initial size, the vegetation total mass (biomass)
increases with time and reaches a maximum corresponding to a self-organized
critical state with power-law distributed patch sizes and L\'evy-like movement
patterns for the foragers. However, this state collapses as the biomass sharply
decreases to reach a noisy stationary regime characterized by corrections to
scaling. In systems with low plant competition, the efficiency of the foraging
rules leads to the formation of heterogeneous vegetation patterns with
frequency spectra, and contributes, rather counter-intuitively,
to lower the biomass levels.Comment: 11 pages, 5 figure
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Seshat: The Global History Databank
The vast amount of knowledge about past human societies has not been systematically organized and, therefore, remains inaccessible for empirically testing theories about cultural evolution and historical dynamics. For example, what evolutionary mechanisms were involved in the transition from the small-scale, uncentralized societies, in which humans lived 10,000 years ago, to the large-scale societies with an extensive division of labor, great differentials in wealth and power, and elaborate governance structures of today? Why do modern states sometimes fail to meet the basic needs of their populations? Why do economies decline, or fail to grow? In this article, we describe the structure and uses of a massive databank of historical and archaeological information, Seshat: The Global History Databank. The data that we are currently entering in Seshat will allow us and others to test theories explaining how modern societies evolved from ancestral ones, and why modern societies vary so much in their capacity to satisfy their members’ basic human needsPeer reviewedFinal Published versio
Spontaneous symmetry breaking in amnestically induced persistence
We investigate a recently proposed non-Markovian random walk model
characterized by loss of memories of the recent past and amnestically induced
persistence. We report numerical and analytical results showing the complete
phase diagram, consisting of 4 phases, for this system: (i) classical
nonpersistence, (ii) classical persistence (iii) log-periodic nonpersistence
and (iv) log-periodic persistence driven by negative feedback. The first two
phases possess continuous scale invariance symmetry, however log-periodicity
breaks this symmetry. Instead, log-periodic motion satisfies discrete scale
invariance symmetry, with complex rather than real fractal dimensions. We find
for log-periodic persistence evidence not only of statistical but also of
geometric self-similarity.Comment: 4 pages, 2 color fig
A next-generation inverse-geometry spallation-driven ultracold neutron source
The physics model of a next-generation spallation-driven high-current
ultracold neutron (UCN) source capable of delivering an extracted UCN rate of
around an-order-of-magnitude higher than the strongest proposed sources, and
around three-orders-of-magnitude higher than existing sources, is presented.
This UCN-current-optimized source would dramatically improve cutting-edge UCN
measurements that are currently statistically limited. A novel "Inverse
Geometry" design is used with 40 L of superfluid He (He-II), which acts as
a converter of cold neutrons (CNs) to UCNs, cooled with state-of-the-art
sub-cooled cryogenic technology to 1.6 K. Our design is optimized for a
100 W maximum heat load constraint on the He-II and its vessel. In our
geometry, the spallation target is wrapped symmetrically around the UCN
converter to permit raster scanning the proton beam over a relatively large
volume of tungsten spallation target to reduce the demand on the cooling
requirements, which makes it reasonable to assume that water edge-cooling only
is sufficient. Our design is refined in several steps to reach
s under our other restriction of 1 MW maximum
available proton beam power. We then study effects of the He-II scattering
kernel as well as reductions in due to pressurization to reach
s. Finally, we provide a design for the UCN
extraction system that takes into account the required He-II heat transport
properties and implementation of a He-II containment foil that allows UCN
transmission. We estimate a total useful UCN current from our source of
s from a 18 cm diameter guide 5 m from the source.
Under a conservative "no return" approximation, this rate can produce an
extracted density of cm in 1000~L external experimental
volumes with a Ni (335 neV) cut-off potential.Comment: Submitted to Journal of Applied Physic
Amnestically induced persistence in random walks
We study how the Hurst exponent depends on the fraction of the
total time remembered by non-Markovian random walkers that recall only the
distant past. We find that otherwise nonpersistent random walkers switch to
persistent behavior when inflicted with significant memory loss. Such memory
losses induce the probability density function of the walker's position to
undergo a transition from Gaussian to non-Gaussian. We interpret these findings
of persistence in terms of a breakdown of self-regulation mechanisms and
discuss their possible relevance to some of the burdensome behavioral and
psychological symptoms of Alzheimer's disease and other dementias.Comment: 4 pages, 3 figs, subm. to Phys. Rev. Let
Posttramatic pneumomediastinum
Catedra de anatomie topografică și chirurgie operatorie, Laboratorul de chirurgie hepato-bilio-pancreatică, Catedra de chirurgie nr. 1 „N. Anestiadi”, Universitatea de Stat de Medicină şi Farmacie „Nicolae Testemiţanu”, Chişinău, Republica Moldova, Conferința Ştiinţifică Internaţională ”Probleme actuale ale morfologiei” dedicată celor 70 de ani de la fondarea Universității de Stat de Medicină și Farmacie „Nicolae Testemiţanu”, Chişinău, 15-16 octombrie 2015Abstract
Background: Minor blunt neck injury trauma is a relatively common condition which can be potentially life-threatening in only rare circumstances. Pneumomediastinum may develop in up to 10% patients who have sustained blunt cervical
or thoracic trauma and may be a significant cause of morbidity and mortality in affected individuals because of the associated damage to the oesophagus, larynx or trachea. Management of this condition varies from conservative approach with
close observation and antibiotherapy to surgical intervention, depending on the extent and severity of aerodigestive injuries.
Conclusions: A blunt neck trauma accompanied by subcutaneous emphysema and pneumomediastinum secondary
to an accident, its radiologic appearance, clinical presentation, and the options for initial management in the emergency
department need a special attention
Anatomo-clinical aspects in hirudotherapy
Catedra de anatomie topografică și chirurgie operatorie, Universitatea de Stat de Medicină şi Farmacie „Nicolae Testemiţanu”, Chişinău, Republica Moldova, Conferința Ştiinţifică Internaţională ”Probleme actuale ale morfologiei” dedicată celor 70 de ani de la fondarea Universității de Stat de Medicină și Farmacie „Nicolae Testemiţanu”, Chişinău, 15-16 octombrie 2015Abstract
Background: According to the literature, the history of hirudotherapy includes several millenniums. With the
development of science, researches in medicine have resulted in rapid and quite good treatment of acute diseases. In this
way, in a short period of time a strong pharmaceutical industry, which proposes large amounts of synthetic drugs,has been
developed. As a result, the share of natural remedies has considerably decreased, and the specialists of this field were essentially distressed. Today we observe that modern medicine rediscovers hirudotherapy. The leeches possess a mechanism
that locks the system of hemostasis of the donor, represented by biologically active substances, secreted by the salivary
glands. Due to these substances, hirudotherapy has many therapeutic effects. As mentioned before, hirudotherapy acts on
the human body through general, local and bioenergetical effects.
Conclusions: First of all, zonality of curative effect is determined by regional adjusting of blood and lymphatic circulation. Therefore, the local action is the most important manifestation of hirudotherapy. The general action is based on
the application of leeches in certain reflexogenic areas, arranged to the skin, and in regions of anastomoses between the
deep and superficial venous system. In this context, the role of clinical anatomy is essential in determination of the points
and areas where leeches are applied
How linear features alter predator movement and the functional response
In areas of oil and gas exploration, seismic lines have been reported to alter the movement patterns of wolves (Canis lupus). We developed a mechanistic first passage time model, based on an anisotropic elliptic partial differential equation, and used this to explore how wolf movement responses to seismic lines influence the encounter rate of the wolves with their prey. The model was parametrized using 5 min GPS location data. These data showed that wolves travelled faster on seismic lines and had a higher probability of staying on a seismic line once they were on it. We simulated wolf movement on a range of seismic line densities and drew implications for the rate of predator–prey interactions as described by the functional response. The functional response exhibited a more than linear increase with respect to prey density (type III) as well as interactions with seismic line density. Encounter rates were significantly higher in landscapes with high seismic line density and were most pronounced at low prey densities. This suggests that prey at low population densities are at higher risk in environments with a high seismic line density unless they learn to avoid them
Роль иглоукалывания в современной медицине
Universitatea de Stat de Medicină şi Farmacie „NicolaeTestemiţanu”, Chişinău, Republica Moldova, ICŞ DOSMC. Secţia Reabilitare clinică, Conferinţa Știinţifică Internaţională ”Probleme actuale ale morfologiei” dedicată сentenarului profesorului B.Z. Perlin, Chişinău, 20-22 septembrie 2012Acupuncture is an ancient method of treatment. Its field of activity is human bioenergetics. The implementation of this
method of treatment has been quite difficult to practice in official medicine. Concerning the cost, this treatment is cheaper
and with very little negative effects.
Акупунктура один из методов терапии, которая имеет многовековую историю. Основы этой науки опирается на
биоэнергетику человека. К сожалению, внедрение в практическую медицину этого метода лечения осуществляется
очень трудно. Но, если смотреть на иглоукалывание с материальной точки зрения, то этот метод лечения намного
дешевле и вызывает меньше побочных реакций
Masting by Eighteen New Zealand Plant Species: The Role of Temperature as a Synchronizing Cue
Masting, the intermittent production of large flower or seed crops by a population of perennial plants, can enhance the reproductive success of participating plants and drive fluctuations in seed-consumer populations and other ecosystem components over large geographic areas. The spatial and taxonomic extent over which masting is synchronized can determine its success in enhancing individual plant fitness as well as its ecosystem-level effects, and it can indicate the types of proximal cues that enable reproductive synchrony. Here, we demonstrate high intra- and intergeneric synchrony in mast seeding by 17 species of New Zealand plants from four families across \u3e150000 km2. The synchronous species vary ecologically (pollination and dispersal modes) and are geographically widely separated, so intergeneric synchrony seems unlikely to be adaptive per se. Synchronous fruiting by these species was associated with anomalously high temperatures the summer before seedfall, a cue linked with the La Niña phase of El Niño–Southern Oscillation. The lone asynchronous species appears to respond to summer temperatures, but with a 2-yr rather than 1-yr time lag. The importance of temperature anomalies as cues for synchronized masting suggests that the timing and intensity of masting may be sensitive to global climate change, with widespread effects on taxonomically disparate plant and animal communities
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