Comparative effects of mono and dipotassium phosphates on cell leakiness in corn leaves

The quantity of nutrients which can be sprayed onto the foliage of plants is limited by the onset of burn damage, but the mechanism(s) of burn induction are not defined. Droplets of KH₂PO₄ applied to intact leaf cuticles induced burn damage at concentrations ≥ 0.50 M whereas K₂HPO₄ was damaging at 0.05 M. Different cuticular penetration rates did not account for these differences. We report here on the comparative effects of these two salts on membrane integrity, as expressed by leakage of U.V. absorbing constituents from leaf cells. Infiltration of a hypotonic solution (0.05 to 0.10 M) of either salt into corn leaf segments did not induce selective acceleration of leakage of U.V. absorbing constituents from leaf cells during a 90 min. incubation. However, incubation in 0.10 M K₂HPO₄ lead to a 87% increase in the efflux of cell constituents when followed by a 10 min. osmotic stress treatment in 1M sucrose and subsequent transfer to water.

The induction of damage by K₂HPO₄ applied to intact plants was inhibited by high humidity low stress conditions. The results suggest that K₂HPO₄ has a selective toxic effect on plant cells which is potentiated by environmental water stress.     

The simplest double slit: interference and entanglement in double photoionization of H2

The wave nature of particles is rarely observed, in part because of their very short de Broglie wavelengths in most situations. However, even with wavelengths close to the size of their surroundings, the particles couple to their environment (for example, by gravity, Coulomb interaction, or thermal radiation). These couplings shift the wave phases, often in an uncontrolled way, and the resulting decoherence, or loss of phase integrity, is thought to be a main cause of the transition from quantum to classical behavior. How much interaction is needed to induce this transition? Here we show that a photoelectron and two protons form a minimum particle/slit system and that a single additional electron constitutes a minimum environment. Interference fringes observed in the angular distribution of a single electron are lost through its Coulomb interaction with a second electron, though the correlated momenta of the entangled electron pair continue to exhibit quantum interference.     

Rotifer community structure in fish‐farming systems associated with a Neotropical semiarid reservoir in north‐eastern Brazil

The study was conducted to assess the community structure of planktonic rotifers and their relation to the environmental impact of Nile tilapia, Oreochromis niloticus (Linaeus, 1758), aquaculture activities (ponds and net‐tanks), associated with a Neotropical semiarid reservoir in Brazil. Our hypothesis was that the ecological attributes of the rotifer community were different when considering the influence of fish aquaculture activities. We identified 28 species, with 10 species from the Brachionidae family. The average density and diversity index of rotifers were higher in reservoir stations, with mean values in the ponds approximately 50% lower than those of the reservoir. The microphagous species dominated during all the time, while the raptorial species were accidental in all studied environments. The ponds were represented by four significant indicator species: Brachionus caudatus, B. leydigi, Dicranophoroides caudatus and Testudinella patina and the reservoir by three: B. falcatus, B. havanaensis and Conochilus dossuarius. In general, nine species were significantly associated with some categories of environmental conditions, such as high or low turbidity and low values of conductivity and TDS. Four of the five best bioindicator species belonged to the microphagous genus Brachionus. B. havanaensis indicated five environmental conditions (IndVal > 93.1%), and it appeared to be a key species in this Neotropical semiarid reservoir influenced by aquaculture activities. The dominance of microphagous rotifers suggests a functional redundancy of species in the studied environments. We found that these systems and their management affected the planktonic rotifer community in this region of Brazil by increasing the species richness.     

Overweight in urban, low-income, African American and Hispanic children attending Los Angeles elementary schools: research stimulating action

OBJECTIVE: This study was undertaken to establish the prevalence and severity of nutritional problems among low-income children of elementary school age in the Los Angeles Unified School District (LAUSD) in order to collect baseline data to inform policy-makers. DESIGN AND METHODS: A cross-sectional survey of children in 14 elementary schools was conducted from January to June, 1998. Nine hundred and nineteen children were measured and interviewed. The planning, design and data analysis were carried out in collaboration with key LAUSD policy-makers. RESULTS: More than 35% of the sample was classified as being at risk for overweight or overweight according to body mass index. CONCLUSION: There is a high prevalence of children who are at risk for overweight or who are overweight in Los Angeles. This finding has triggered the development of multiple school-based intervention programmes.     

Effects of crop density and tillage system on grain yield and N uptake from soil and atmosphere of sole and intercropped pea and oat

Pea (Pisum sativum L.) and oat (Avena sativa L.) were grown as sole and mixed crops in various densities under two different tillage systems on a loess soil near Göttingen/Germany in a 2-year field experiment (2002/2003). In the conventional tillage system a mouldboard plough (CT) was used and in the minimum tillage system a rotary harrow (MT) was employed. The effect of crop density and tillage system on the grain dry matter and grain N yields, N₂ fixation and soil N uptake were determined to address the following questions: (i) which mixture compositions exhibit the highest grain yields compared to the sole crops, (ii) which mixture compositions also fix a high level of N₂ and leave low levels of residual inorganic soil N after harvest, and (iii) whether the intercrop advantage is influenced by the tillage system. For (i) the result in 2002 showed that the highest grain yields of both sole cropped pea and oat and intercropped pea and oat were achieved at the highest densities. In 2003, when the inorganic soil N content was higher and weather conditions were warmer and drier, grain yields were significantly higher than in 2002, but sole as well as intercropped pea and oat gave their highest grain yields at lower densities. For both years and tillage systems, the highest intercrop advantages were achieved in mixtures with densities above the optimal sole crop densities. The result for (ii) was that a distinctly higher proportion of nitrogen was derived from the atmosphere (Ndfa) by intercropped pea than by sole cropped pea. However, the uptake of soil N by intercropped pea and oat was not reduced in comparison with that of sole cropped oat as the decrease in the uptake of N from the soil by oat at lower oat densities in the mixture was compensated for by the soil N uptake of pea. Additionally, the N_min-N content of the soil following the mixtures and sole cropped oat did not differ, especially in the deeper soil layers because oat in mixture was forced to take up more soil N from deeper layers. Therefore, the risk of soil N losses through leaching after mixtures was lower compared to sole cropped pea. The tillage system (iii) had no significant influence on grain yield and soil N uptake, but N₂ fixation and the competitive ability of intercropped pea were higher under CT than with MT. An additional result was that intercropping led to a significantly increased grain N content of both pea and oat compared to the sole crops. The increase in grain N content from sole to intercrop was from 3.30 to 3.42% for pea and from 1.73 to 1.96% for oat as a mean for both years and tillage systems. The present study confirms that growing pea and oat as intercrops highlights potential economic and environmental benefits which still need to be understood in more detail in order to exploit intercropping to a greater extent.     

The (Me5C5)Si+ cation: a stable derivative of HSi+

The reaction of decamethylsilicocene, (Me5C5)2Si, with the proton-transfer reagent Me5C5H2+B(C6F5)4- produces the salt (Me5C5)Si+ B(C6F5)4(2), which can be isolated as a colorless solid that is stable in the absence of air and moisture. The crystal structure reveals the presence of a cationic pi complex with an eta5-pentamethylcyclopentadienyl ligand bound to a bare silicon center. The 29Si nuclear magnetic resonance at very high field (delta = - 400.2 parts per million) is typical of a pi complex of divalent silicon. The (eta5-Me5C5)Si+ cation in 2 can be regarded as the "resting state" of a silyliumylidene-type (eta1-Me5C5)Si+ cation. The availability of 2 opens new synthetic avenues in organosilicon chemistry. For example, 2 reacted with lithium bis(trimethylsilyl)amide to give the disilene E-[(eta1-Me5C5)[N(SiMe3)2]Si]2(3).     

鹅细小病毒VP1与VP3非重叠序列的克隆与原核表达

根据鹅细小病毒GPVH1株基因组核苷酸序列设计了一对引物，对其结构蛋白VP1与VP3非重叠核苷酸序列进行PCR扩增，并克隆到表达性载体pGEX-6p-1，经酶切鉴定筛选出阳性克隆，并转化到大肠杆菌BL21(ED3)plysS进行原核表达，并用SDS—PAGE鉴定，结果表明融合蛋白在表达性细菌BL21中重获得了高效表达。     

Serum creatine kinase activity in dogs and cats with metabolic diseases

Elevated Creatine kinase-activitiy (CK) indicates disturbances of the muscle cell integrity. In addition to primary muscle disease, like trauma, inflammation or dystrophy, diseases of other organs can lead to secondary muscle involvement, which will be indicated by increased serum activities of the CK. The mechanisms of muscle cell disturbance are still unknown. An elevated protein catabolism in the muscle cell is suspected. In the present study we investigated, if dogs and cats with metabolic diseases have increased CK-activity in the serum. From 34 dogs and cats in a group with different metabolic diseases without metabolic acidosis 19% of the dogs and 50% of the cats had increased CK-activity in the serum. From 33 dogs and cats with different metabolic diseases connected with metabolic acidosis 86% of the dogs and 95% of the cats had simultaneously increased CK-activity in the serum. In comparison to healthy dogs and cats animals with metabolic diseases have significant and in cases of metabolic di-seases with metabolic acidosis cats have high significant elevation (dogs significant) of CK-activity in the serum. There was no significant correlation between the groups of patients. In conclusion we think that our results show that metabolic diseases often induce secondary myopathy, measured by CK-activity in the serum, but metabolic acidosis has no direct influence on elevated CK activity in dogs and cats.     

AN IN-VITRO SCREENING METHOD TO STUDY THE ACTIVITY POTENTIAL OF BIOFERTILIZERS BASED ON TRICHODERMA AND BACILLUS SP.

Little scientific information on efficiency of different commercial biofertilizers restricts setup of further reproducible pot or field experiments and hence, provides lack of evidence of biofertilizer application in plant growth promotion and disease suppression. In the present experiment, efficiency of four commercial Trichoderma and one Bacillus biofertilizer was screened by a bio-indicator plant, cucumber (Cucumis sativus L.) under controlled laboratory conditions. Inoculation of cucumber seeds with different commercial biofertilizers significantly increased the germination rates (ca. 20–25%) and stimulated other growth parameters. In seedling establishment test, biofertilizers inoculated cucumber seedlings showed significant higher root dry weight (ca. 32 to 96%), leaf area (ca. 60 to 140%), root length (ca. 30%) and shoot dry weight (ca. 88%) in two weeks culture period compare to that of the control. Additionally, in-vitro antagonistic activity against take-all pathogen (Gaeumannomyces graminis var. tritici, Ggt) in wheat and phosphate solubilizing activity was demonstrated for Trichoderma biofertilizer. However, in-vitro solubilization of Mn was not detected. The results suggested that the potential activity of different commercial biofertilizers could be easily screened within several days with the described rapid bio-test by increasing seed germination, and improving growth and growth related parameters of cucumber grown in nutrient solution under controlled culture system.