139 research outputs found
Perturbation theory for very long-range potentials
Systems with very long-range interactions (that decay at large distances like
with where is the space dimensionality) are
difficult to study by conventional statistical mechanics perturbation methods.
Examples of these systems are gravitational and charged (non-electroneutral).
In this work we propose two alternative methodologies to avoid these
difficulties and capture some of the properties of the original potential. The
first one consists in expressing the original potential in terms of a finite
sum of hard-core Yukawa potentials. In the second one, the potential is
rewritten as a damped potential, using a damping function with a parameter that
controls the range of the interaction. These new potentials, which mimic the
original one, can now be treated by conventional statistical mechanics methods.Comment: 25 pages, 11 figure
Nowhere safe? Exploring the influence of urbanization across mainland and insular seashores in continental Portugal and the Azorean Archipelago
Differences in the structure and functioning of intensively urbanized vs. less human-affected systems are reported,
but such evidence is available for amuch larger extent in terrestrial than in marine systems.Weexamined the
hypotheses that (i) urbanization was associated to different patterns of variation of intertidal assemblages between
urban and extra-urban environments; (ii) such patterns were consistent acrossmainland and insular systems,
spatial scales from 10s cm to 100s km, and a three months period. Several trends emerged: (i) a more
homogeneous distribution of most algal groups in the urban compared to the extra-urban condition and the opposite
pattern of most invertebrates; (ii) smaller/larger variances of most organisms where these were, respectively,
less/more abundant; (iii) largest variability of most response variables at small scale; (iv) no facilitation of
invasive species by urbanization and larger cover of canopy-forming algae in the insular extra-urban condition.
Present findings confirmthe acknowledged notion that futuremanagement strategieswill require to include representative
assemblages and their relevant scales of variation associated to urbanization gradients on both the
mainland and the islands
Chiari’s Network as a Cause of Fetal and Neonatal Pathology
Chiari’s network is a remnant of the eustachian valve located in the right atrium. Incomplete involution of the fetal sinus venosus valves results in “redundant” Chiari’s network, which may compromise cardiovascular function. This report describes a case with the novel finding of prenatal compromise due to redundant Chiari’s network and an uncommon case with significant postnatal symptoms. In both cases, the symptoms (fetal hydrops and postnatal cyanosis) resolved spontaneously. The variety of cardiovascular pathologies described in the literature is believed to be associated with persistence of a Chiari network. Knowledge about this not always harmless structure is important for perinatologists, pediatricians, and pediatric cardiologists alike. The clinical importance of this rare pathology is that prenatal counseling may anticipate a generally positive outcome and that surgical intervention generally should be avoided
Synchronous bursts on scale-free neuronal networks with attractive and repulsive coupling
This paper investigates the dependence of synchronization transitions of
bursting oscillations on the information transmission delay over scale-free
neuronal networks with attractive and repulsive coupling. It is shown that for
both types of coupling, the delay always plays a subtle role in either
promoting or impairing synchronization. In particular, depending on the
inherent oscillation period of individual neurons, regions of irregular and
regular propagating excitatory fronts appear intermittently as the delay
increases. These delay-induced synchronization transitions are manifested as
well-expressed minima in the measure for spatiotemporal synchrony. For
attractive coupling, the minima appear at every integer multiple of the average
oscillation period, while for the repulsive coupling, they appear at every odd
multiple of the half of the average oscillation period. The obtained results
are robust to the variations of the dynamics of individual neurons, the system
size, and the neuronal firing type. Hence, they can be used to characterize
attractively or repulsively coupled scale-free neuronal networks with delays.Comment: 15 pages, 9 figures; accepted for publication in PLoS ONE [related
work available at http://arxiv.org/abs/0907.4961 and
http://www.matjazperc.com/
Recommended from our members
Adaptación cultural al español del instrumento de evaluación de funcionalidad física en Unidad de Paciente Crítico: “The Chelsea Critical Care Physical Assessment Tool (CPAx)”
Las Unidades de Cuidados Intensivos (UCI), presentan una
sobrevida cada vez mayor de los pacientes que ingresan a ellas,
donde se ven enfrentados a una nueva entidad fisiopatológica
llamada Debilidad Muscular Adquirida en UCI (DAUCI).
Algunos test desarrollados para la evaluación de función motriz,
que permiten objetivar la progresión del paciente, son la escala
de fuerza muscular del Medical Research Council (MRC), el
Functional status score for the intensive care unit (FSS-ICU) y
el “Chelsea Critical Care Physical Assessment Tool (CPAx). La ventaja del CPAx radica en que este test incluye mayor información
asociada al funcionamiento humano como recomienda la OMS,
incorporando tanto el componente ventilatorio (que también se ve
deteriorado por DAUCI) como neuromuscular lo que permite
al profesional kinesiólogo tener una herramienta objetiva más
completa del nivel funcional del paciente.
Para que sea confiable, todo test debe ser validado en el país donde
quiere aplicarse, pero antes de esto debe ser adaptado culturalmente.
El objetivo de este trabajo fue efectuar la adaptación transcultural
(AT) al español del test de funcionalidad física de aplicación
kinésica CPAx. Se utilizó el proceso establecido por Beaton y cols
que incluye la formación de un comité de expertos multidisciplinario
que da una visión integral a la adaptación y una prueba piloto en
que kinesiólogos de UCI sin capacitación previa del test lo lean,
posteriormente lo apliquen y entreguen sus observaciones.
Conclusiones: Realizar la AT permite dimensionar la importancia
que tiene cada una de las etapas de este proceso. El test es el mismo,
equivalente al original, pero contiene nuestras características
culturales y condiciones técnicas, que lo hace ser comprensible y
aplicable en nuestro país. Esta adaptación transcultural también
es útil a nivel latinoamericano; para los países de habla hispana
que quieran validarlo tenerlo adaptado al español, hace el proceso
menos complejo.
Palabras clave: Evaluación funcional, Unidad de cuidados
intensivos, CPAx, adaptación transcultural
Precision restoration: a necessary approach to foster forest recovery in the 21st century
We thank S. Tabik, E. Guirado, and Garnata Drone SL for fruitful debates about the application of remote sensing and artificial intelligence in restoration. E. McKeown looked over the English version of the manuscript. Original drawings were made by J. D. Guerrero. This work was supported by projects RESISTE (P18-RT-1927) from the Consejeria de Economia, Conocimiento, y Universidad from the Junta de Andalucia, and AVA201601.19 (NUTERA-DE I), DETECTOR (A-RNM-256-UGR18), and AVA2019.004 (NUTERA-DE II), cofinanced (80%) by the FEDER Program. F.M.-R. acknowledges the support of the Agreement 4580 between OTRI-UGR and the city council of La Zubia. We thank an anonymous reviewer for helpful comments that improved the manuscript.Forest restoration is currently a primary objective in environmental management policies at a global scale, to the extent that
impressive initiatives and commitments have been launched to plant billions of trees. However, resources are limited and the
success of any restoration effort should be maximized. Thus, restoration programs should seek to guarantee that what is
planted today will become an adult tree in the future, a simple fact that, however, usually receives little attention. Here, we advocate
for the need to focus restoration efforts on an individual plant level to increase establishment success while reducing negative
side effects by using an approach that we term “precision forest restoration” (PFR). The objective of PFR will be to ensure
that planted seedlings or sowed seeds will become adult trees with the appropriate landscape configuration to create functional
and self-regulating forest ecosystems while reducing the negative impacts of traditional massive reforestation actions. PFR can
take advantage of ecological knowledge together with technologies and methodologies from the landscape scale to the individual-
plant scale, and from the more traditional, low-tech approaches to the latest high-tech ones. PFR may be more expensive at
the level of individual plants, but will be more cost-effective in the long term if it allows for the creation of resilient forests able to
providemultiple ecosystemservices. PFR was not feasible a few years ago due to the high cost and low precision of the available
technologies, but it is currently an alternative that might reformulate a wide spectrum of ecosystem restoration activities.Junta de Andalucia P18-RT-1927European Commission AVA201601.19
A-RNM-256-UGR18
AVA2019.004OTRI-UGR 4580city council of La Zubia 458
Primary biliary cirrhosis
Primary biliary cirrhosis (PBC) is an immune-mediated chronic cholestatic liver disease with a slowly progressive course. Without treatment, most patients eventually develop fibrosis and cirrhosis of the liver and may need liver transplantation in the late stage of disease. PBC primarily affects women (female preponderance 9–10:1) with a prevalence of up to 1 in 1,000 women over 40 years of age. Common symptoms of the disease are fatigue and pruritus, but most patients are asymptomatic at first presentation. The diagnosis is based on sustained elevation of serum markers of cholestasis, i.e., alkaline phosphatase and gamma-glutamyl transferase, and the presence of serum antimitochondrial antibodies directed against the E2 subunit of the pyruvate dehydrogenase complex. Histologically, PBC is characterized by florid bile duct lesions with damage to biliary epithelial cells, an often dense portal inflammatory infiltrate and progressive loss of small intrahepatic bile ducts. Although the insight into pathogenetic aspects of PBC has grown enormously during the recent decade and numerous genetic, environmental, and infectious factors have been disclosed which may contribute to the development of PBC, the precise pathogenesis remains enigmatic. Ursodeoxycholic acid (UDCA) is currently the only FDA-approved medical treatment for PBC. When administered at adequate doses of 13–15 mg/kg/day, up to two out of three patients with PBC may have a normal life expectancy without additional therapeutic measures. The mode of action of UDCA is still under discussion, but stimulation of impaired hepatocellular and cholangiocellular secretion, detoxification of bile, and antiapoptotic effects may represent key mechanisms. One out of three patients does not adequately respond to UDCA therapy and may need additional medical therapy and/or liver transplantation. This review summarizes current knowledge on the clinical, diagnostic, pathogenetic, and therapeutic aspects of PBC
Dopamine Receptor Antagonists Enhance Proliferation and Neurogenesis of Midbrain Lmx1a-expressing Progenitors
Degeneration of dopamine neurons in the midbrain causes symptoms of the movement disorder, Parkinson disease. Dopamine neurons are generated from proliferating progenitor cells localized in the embryonic ventral midbrain. However, it remains unclear for how long cells with dopamine progenitor character are retained and if there is any potential for reactivation of such cells after cessation of normal dopamine neurogenesis. We show here that cells expressing Lmx1a and other progenitor markers remain in the midbrain aqueductal zone beyond the major dopamine neurogenic period. These cells express dopamine receptors, are located in regions heavily innervated by midbrain dopamine fibres and their proliferation can be stimulated by antagonizing dopamine receptors, ultimately leading to increased neurogenesis in vivo. Furthermore, treatment with dopamine receptor antagonists enhances neurogenesis in vitro, both from embryonic midbrain progenitors as well as from embryonic stem cells. Altogether our results indicate a potential for reactivation of resident midbrain cells with dopamine progenitor potential beyond the normal period of dopamine neurogenesis
Systematic Review of Potential Health Risks Posed by Pharmaceutical, Occupational and Consumer Exposures to Metallic and Nanoscale Aluminum, Aluminum Oxides, Aluminum Hydroxide and Its Soluble Salts
Aluminum (Al) is a ubiquitous substance encountered both naturally (as the third most abundant element) and intentionally (used in water, foods, pharmaceuticals, and vaccines); it is also present in ambient and occupational airborne particulates. Existing data underscore the importance of Al physical and chemical forms in relation to its uptake, accumulation, and systemic bioavailability. The present review represents a systematic examination of the peer-reviewed literature on the adverse health effects of Al materials published since a previous critical evaluation compiled by Krewski et al. (2007).
Challenges encountered in carrying out the present review reflected the experimental use of different physical and chemical Al forms, different routes of administration, and different target organs in relation to the magnitude, frequency, and duration of exposure. Wide variations in diet can result in Al intakes that are often higher than the World Health Organization provisional tolerable weekly intake (PTWI), which is based on studies with Al citrate. Comparing daily dietary Al exposures on the basis of “total Al”assumes that gastrointestinal bioavailability for all dietary Al forms is equivalent to that for Al citrate, an approach that requires validation. Current occupational exposure limits (OELs) for identical Al substances vary as much as 15-fold.
The toxicity of different Al forms depends in large measure on their physical behavior and relative solubility in water. The toxicity of soluble Al forms depends upon the delivered dose of Al+ 3 to target tissues. Trivalent Al reacts with water to produce bidentate superoxide coordination spheres [Al(O2)(H2O4)+ 2 and Al(H2O)6 + 3] that after complexation with O2•−, generate Al superoxides [Al(O2•)](H2O5)]+ 2. Semireduced AlO2• radicals deplete mitochondrial Fe and promote generation of H2O2, O2 • − and OH•. Thus, it is the Al+ 3-induced formation of oxygen radicals that accounts for the oxidative damage that leads to intrinsic apoptosis. In contrast, the toxicity of the insoluble Al oxides depends primarily on their behavior as particulates.
Aluminum has been held responsible for human morbidity and mortality, but there is no consistent and convincing evidence to associate the Al found in food and drinking water at the doses and chemical forms presently consumed by people living in North America and Western Europe with increased risk for Alzheimer\u27s disease (AD). Neither is there clear evidence to show use of Al-containing underarm antiperspirants or cosmetics increases the risk of AD or breast cancer. Metallic Al, its oxides, and common Al salts have not been shown to be either genotoxic or carcinogenic. Aluminum exposures during neonatal and pediatric parenteral nutrition (PN) can impair bone mineralization and delay neurological development. Adverse effects to vaccines with Al adjuvants have occurred; however, recent controlled trials found that the immunologic response to certain vaccines with Al adjuvants was no greater, and in some cases less than, that after identical vaccination without Al adjuvants.
The scientific literature on the adverse health effects of Al is extensive. Health risk assessments for Al must take into account individual co-factors (e.g., age, renal function, diet, gastric pH). Conclusions from the current review point to the need for refinement of the PTWI, reduction of Al contamination in PN solutions, justification for routine addition of Al to vaccines, and harmonization of OELs for Al substances
- …