Hysteresis in the Mott Transition between Plasma and Insulating Gas

We show that hysteresis can occur in the transition between a neutral plasma and the insulating gas consisting of neutral pairs bound by Coulomb attraction. Since the transition depends sensitively on the screening length in the plasma, regions of bistability occur in density--temperature phase space. We present numerical results which indicate where these regions occur for systems such as spin-polarized hydrogen, positronium gas, and excitons in a semiconductor.Comment: 9 pages (Latex/RevTex), 6 postscript figures which are in compressed and uuencoded file, prepared using the utility "uufiles" and separately submitted. They should be automatically included with the text when it is downloaded. Figures also available in hard copy from the authors ([email protected]; [email protected]); paper submitted to Phys. Rev.

Environmental drivers for cheaters of arbuscular mycorrhizal symbiosis in tropical rainforests

Hundreds of nonphotosynthetic mycoheterotrophic plant species cheat the arbuscular mycorrhizal symbiosis. Their patchy local occurrence suggests constraints by biotic and abiotic factors, among which the role of soil chemistry and nutrient status has not been investigated.Here, we examine the edaphic drivers predicting the local‐scale distribution of mycoheterotrophic plants in two lowland rainforests in South America. We compared soil chemistry and nutrient status in plots where mycoheterotrophic plants were present with those without these plants.Soil pH, soil nitrate, and the interaction between soil potassium and nitrate concentrations were the best predictors for the occurrence of mycoheterotrophic plants in these tropical rainforests. Mycoheterotrophic plant occurrences decreased with a rise in each of these predictors. This indicates that these plants are associated with low‐fertility patches. Such low‐fertility conditions coincide with conditions that potentially favour a weak mutualism between plants and arbuscular mycorrhizal fungi according to the trade balance model.Our study points out which soil properties favour the cheating of arbuscular mycorrhizal networks in tropical forests. The patchy occurrence of mycoheterotrophic plants suggests that local soil heterogeneity causes the stability of arbuscular mycorrhizal networks to vary at a very small scale.Environmental Biolog

Protein-olive oil-in-water nanoemulsions as encapsulation materials for curcumin acting as anticancer agent towards MDA-MB-231 cells

The sustainable cellular delivery of the pleiotropic drug curcumin encounters drawbacks related to its fast autoxidation at the physiological pH, cytotoxicity of delivery vehicles and poor cellular uptake. A biomaterial compatible with curcumin and with the appropriate structure to allow the correct curcumin encapsulation considering its poor solubility in water, while maintaining its stability for a safe release was developed. In this work, the biomaterial developed started by the preparation of an oil-in-water nanoemulsion using with a cytocompatible copolymer (Pluronic F 127) coated with a positively charged protein (gelatin), designed as G-Cur-NE, to mitigate the cytotoxicity issue of curcumin. These G-Cur-NE showed excellent capacity to stabilize curcumin, to increase its bio-accessibility, while allowing to arrest its autoxidation during its successful application as an anticancer agent proved by the disintegration of MDA-MB-231 breast cancer cells as a proof of concept

Spontaneous light-mediated magnetism in cold atoms

Cold atom setups are now commonly employed in simulations of condensed matter phenomena. We present a novel approach to induce strong magnetic interactions between atoms on a self-organized lattice using diffraction of light. Diffractive propagation of structured light fields leads to an exchange between phase and amplitude modulated planes which can be used to couple atomic degrees of freedom via optical pumping nonlinearities. In the experiment a cold cloud of Rb atoms placed near a retro-reflecting mirror is driven by a detuned pump laser. We demonstrate spontaneous magnetic ordering in the Zeeman sublevels of the atomic ground state: anti-ferromagnetic structures on a square lattice and ferrimagnetic structures on a hexagonal lattice in zero and a weak longitudinal magnetic field, respectively. The ordered state is destroyed by a transverse magnetic field via coherent dynamics. A connection to the transverse (quantum) Ising model is drawn

Plant stature heritability in wheat: estimate through the regression coefficient

O estudo desenvolvido neste trabalho foi estabelecido para determinar a relação entre o desempenho do caráter estatura de planta, entre linhas F3 ou F4 ou RC1 F2, derivadas de F2 ou F3 ou RC1 F1, de diversos cruzamentos de trigo hexaplóide. Resultados superiores à unidade, para a herdabilidade, foram estimados através dó método de desvio padrão, calculando-se a regressão pela codificação dos dados originais, em termos de unidades de desvio padrão. Uma comparação entre o método convencional e o de unidades de desvio padrão foi realizada para as estimativas de herdabilidade. Em programas de melhoramento fitogenético, muitas questões poderão ser respondidas através da estimativa da herdabilidade de um determinado caráter.  The study reported herein was designed to determine the relationship between the plant stature trait performance of F3 or F4 or RC1 F2 derived lines from F2 or F3 or RC1 F1 in several hexaploid wheat crosses, respectively. The heritability results greater than one were computed through the standard unit method by calculating the regression on data coded in terms of standard deviation units. A comparison was made between heritability estimated by these two methods, conventional and standard units. Heritability estimates provides useful guidelines of answering many questions which arise in a plant breeding program

Bacteriën en schimmels op melkveebedrijf in beeld

Environmental Biolog

Microbiota in dung and milk differ between organic and conventional dairy farms

Organic farming is increasingly promoted as a means to reduce the environmental impact of artificial fertilizers, pesticides, herbicides, and antibiotics in conventional dairy systems. These factors potentially affect the microbial communities of the production stages (soil, silage, dung, and milk) of the entire farm cycle. However, understanding whether the microbiota representative of different production stages reflects different agricultural practices - such as conventional versus organic farming - is unknown. Furthermore, the translocation of the microbial community across production stages is scarcely studied. We sequenced the microbial communities of soil, silage, dung, and milk samples from organic and conventional dairy farms in the Netherlands. We found that community structure of soil fungi and bacteria significantly differed among soil types, but not between organic versus conventional farming systems. The microbial communities of silage also did not differ among conventional and organic systems. Nevertheless, the dung microbiota of cows and the fungal communities in the milk were significantly structured by agricultural practice. We conclude that, while the production stages of dairy farms seem to be disconnected in terms of microbial transfer, certain practices specific for each agricultural system, such as the content of diet and the use of antibiotics, are potential drivers of shifts in the cow's microbiota, including the milk produced. This may reflect differences in farm animal health and quality of dairy products depending on farming practices.Environmental Biolog

Cations extraction of sandy-clay soils from Cavado valley, Portugal, using sodium salts solutions

Cases of contamination by metals in the water wells of the Cavado Valley in north-west Portugal can be attributed to the heavy leaching of clay soils due to an excess of nitrogen resulting from the intensive use of fertilisers in agricultural areas. This work focuses on the natural weathering characteristics of soils, particularly the clay material, through the study of samples collected near the River Cavado. Samples taken from various sites, after physico-chemical characterisation, were subjected to clay dissolution tests, using sodium salts of different ionic forces, to detect the relationship between certain physico-chemical parameters of water, such as pH, nitrate, chloride and sulphate content, in the dissolution of clay and the subsequent extraction of such cations as Al, Fe and K. In acidic sandy clay soils, the mineralogical composition of which was characterised by a predominance of quartz, micas, kaolinite and K-feldspars, decreases of the clay material/water pH ratio increases dissolution of the micaceous and K-feldspars phases. The presence of nitrates in the aqueous solution apparently advanced the extraction of all three cations Al, Fe and K. The specific surface area of the clay material showed a significant correlation with the main kinetic parameters of cation extraction.Têm ocorrido casos de contaminações de águas de poços, por metais, no vale do Rio Cávado, região noroeste de Portugal. A princípio, poderiam ser explicáveis pela elevada lixiviação dos solos arenoargilosos da região, quando da prática de adubações intensivas de nitrogênio em áreas agrícolas. Assim, estudaram-se as características do intemperismo natural dos solos, particularmente da fração argila, característica da margem norte do rio Cávado. Coletaram-se amostras de vários locais, que foram submetidas, após caracterização físico-química, a ensaios de dissolução a partir de soluções de sais de sódio com diferentes forças iônicas. O objetivo foi observar as relações de determinados parâmetros físico-químicos da água, tais como: pH, nitratos, cloretos e sulfatos na dissolução das argilas e a conseqüente extração de espécies químicas tais como Al, K e Fe. Para solos areno-argilosos, ácidos, cuja composição mineralógica se caracteriza por um predomínio de quartzo, micas, caulinita e feldspato-K, o abaixamento do pH da suspensão solo/água promove a solubilização das fases micáceas e feldspáticas. A presença do nitrato nas soluções aquosas promoveu aparentemente a extração de todos os três cátions: Al, K e Fe. O efeito da área superfícial específica das partículas dos solos condicionou fortemente vários dos parâmetros cinéticos estudados relativos à extração dos cátions.(undefined

Age-related shift in LTD is dependent on neuronal adenosine A(2A) receptors interplay with mGluR5 and NMDA receptors

Synaptic dysfunction plays a central role in Alzheimer's disease (AD), since it drives the cognitive decline. An association between a polymorphism of the adenosine A2A receptor (A2AR) encoding gene-ADORA2A, and hippocampal volume in AD patients was recently described. In this study, we explore the synaptic function of A2AR in age-related conditions. We report, for the first time, a significant overexpression of A2AR in hippocampal neurons of aged humans, which is aggravated in AD patients. A similar profile of A2AR overexpression in rats was sufficient to drive age-like memory impairments in young animals and to uncover a hippocampal LTD-to-LTP shift. This was accompanied by increased NMDA receptor gating, dependent on mGluR5 and linked to enhanced Ca(2+) influx. We confirmed the same plasticity shift in memory-impaired aged rats and APP/PS1 mice modeling AD, which was rescued upon A2AR blockade. This A2AR/mGluR5/NMDAR interaction might prove a suitable alternative for regulating aberrant mGluR5/NMDAR signaling in AD without disrupting their constitutive activity