Allelopathic and autotoxic effects ofAnastatica hierochuntica L.

Laboratory experiments were undertaken to investigate the autotoxic effects ofAnastatica hierochuntica and possible effects on five other desert plants:Rumex cyprius, Trigonella stellata, Diplotaxis harra, Cleome droserifolia, andFarsetia aegyptia. Seed germination, seedling growth, and cell division of all species tested were inhibited by the shoot aqueous extract ofA. hierochuntica. A gradual increase in the percentage of prophase and decrease in the other mitotic stages as well as the mitotic index were observed with increasing extract concentration. At an extract concentration of 8% the mitotic index was reduced from the control by 55% inC. droserifolia, 54% inT. stellata, 45% inF. aegyptia, 43% inA. hierochuntica, and 35% inR. cyprius. The inhibitory substances are apparently released onto soil by repeated washing of the standing plants by rain and dew interception.     

Determination of the distribution of consolidants and interpretation of mercury porosimetry data in a sandstone porous network using LSCM

Knowing the 3D distribution of a consolidant within the porous network of a rock is essential for understanding the porosity quantitative data obtained by mercury porosimetry and for observing the effect of consolidants on pore interconnection. In this work, we show for the first time that the distribution of consolidant in the porous network can be determined using laser scanner confocal microscopy (LSCM). Results indicate that consolidants are concentrated in pore throats of less than 40 microm in diameter, affecting both the porous interconnection and the circulation of fluids. LSCM allowed demonstration of the fact that the increase in microporosity detected by mercury porosimetry is due to the development of fissures within the consolidants. No consolidant that produces this kind of fissure can be used in the consolidation of building stones, since it would increase microporosity and, in consequence, vulnerability to weathering agents.     

Staphylococcus aureus nasal carriage in a Moroccan dialysis center and isolates characterization

Staphylococcus aureus, which has its ecological niche in the anterior nares, has been shown to cause a variety of infectious diseases mainly for patients in hemodialysis units. We performed this study to evaluate the prevalence of nasal S. aureus carriage among hemodialysis outpatients, to determine the antimicrobial susceptibility of isolates, to characterize the virulence genes, and to identify associated risk factors. Nares swab specimens were obtained from 70 outpatients on hemodialysis between March and June 2010. Samples were plated immediately onto S. aureus specific media and pattern of antibacterial sensitivity was determined using disk diffusion method. Polymerase chain reaction was used to detect nuc, mecA, and genes encoding staphylococcal toxins. Medical record of patients was explored to determine S.aureus carriage risk factors. Nasal screening identified 42.9% S. aureus carriers with only one (3.3%) methicillin‐resistant S. aureus isolate. Among the methicillin‐susceptible S. aureus isolates, high rate of penicillin resistance (81.8%) has been detected. The identified risk factors were male gender and age ≤ 30 years. Research of virulence factors showed a high genetic diversity among the 30 S. aureus isolates. Twenty‐one (70%) of them had at least one virulence gene, of which 3.3% were Panton‐Valentine leukocidin (lukS/F‐PV) genes. S. aureus carriage must be screened for at regular intervals in hemodialysis patients. Setting up a bacterial surveillance system is one of the strategies to understand the epidemiology of methicillin‐resistant S. aureus, to guide local antibiotic policy and prevent spread of antibiotic‐resistant S. aureus.     

The thermal effect on vibration of zigzag single walled carbon nanotubes using nonlocal Timoshenko beam theory

Based on nonlocal theory of thermal elasticity mechanics, a nonlocal elastic Timoshenko beam model is developed for free vibration analysis of zigzag single-walled carbon nanotube (SWCNT) considering thermal effect. The nonlocal constitutive equations of Eringen are used in the formulations. The equivalent Young’s modulus and shear modulus for zigzag SWCNT are derived using an energy-equivalent model. Results indicate significant dependence of natural frequencies on the temperature change as well as the chirality of zigzag carbon nanotube. These findings are important in mechanical design considerations of devices that use carbon nanotubes.     

Securing physical layer using new chaotic parametric maps

Multimedia Tools and Applications - In this work, to overcome the flaws of standard chaotic maps we generated two new cascaded structures, 3D Cubic-Sine and 2D Cubic-Cat chaotic parametric maps,...     

Microbubbles for optofluidics: controlled defects in bubble crystals

We use liquid–gas microfluidics as a low-cost, tunable microstructuring tool, for which applications can be envisioned in optics. In order to obtain relevant geometries for photonics, beyond simple self-assembled crystals, we propose an original approach that excludes bubbles from chosen zones thanks to tiny pillars. To assess the strength of the exclusion mechanism, we predict the behaviour of a single flattened bubble in front of a thin cylindrical pillar located in a rectangular microchannel. The model compares the hydrodynamic force F _fluid that pushes the bubble and the force F _s, due to surface tension, resulting from the surface augmentation when the bubble rises over the pillar. The resulting predictions have been confirmed by experimental results which showed that the bubble passes over the pillar if F _s < F _fluid and goes around it in other cases. Consistently with this model, dynamic bubble crystals with controlled lacuna defects of one, two, or a line of bubbles have been successfully produced. Defects can be switched on or off by changing the flow. Using a photosensitive polymer as a carrier liquid, static bubble crystals have also been produced.     

On the reactivity of the electrogenerated cobalt(I) species towards aryl halides in the presence of allylethers

The electrochemical behavior of CoBr₂ has been investigated in the presence of allylic ethers in an acetonitrile + pyridine (v/v = 9/1) mixture. Cyclic voltametry experiments show a complexation reaction between the electrogenerated cobalt(I) species and allylethers leading thus to a more stable Co^I via the formation of a (η²-allyl-OR)Co^IBr complex. However, this stabilization is too weak to be observed on the time-scale of cyclic voltametry in the absence of pyridine. The thermodynamic constant for the complexation has been determined. It is also shown that only one molecule of allylether is involved in the stabilisation of Co^I. Interestingly, no intra-molecular oxidative addition of allylether to Co^I was observed on the time-scale of a preparative electrolysis unless the reaction was carried out in an undivided cell in the presence of a sacrificial iron rod releasing iron(II) ions. Conversely, an oxidative addition has been evidenced between the electrogenerated Co^I and aryl halides, ArX. The apparent rate constants for this reaction have been determined for various ArX. Importantly, the rate constants depend on the allylether concentration suggesting that the oxidative addition occurs competitively rather than consecutively with respect to complexation. More importantly, preparative-scale electrolyses of aryl halides and allylphenylether in the presence of CoBr₂ as catalyst lead to the coupling product allylaryl, whereas replacement of allylphenylether with allylethylether produces only ArAr along with ArH.     

Prolonged retention of doubly labeled phosphatidylcholine in human plasma and erythrocytes after oral administration

The plasma kinetics of a preparation of dilinoleoyl phosphatidylcholine (DLPC) specifically labeled with³H in the choline moiety and with¹⁴C in the 2-fatty acid (FA) were evaluated in six healthy volunteers after oral administration. Retention of both isotopes in plasma exceeded expectations, with a half-life in the elimination phase of 172.2 h for³H and 69.7 h for¹⁴C. Up to 60 d after administration, there were still significant levels of radioactivity present in plasma. The relative stability of the [¹⁴C]FA label was demonstrated by the retention for more than 12 h of an isotope ratio close to that of the compound administered. The¹⁴C label of DLPC remained in position-2, as assessed by cleavage of plasma phospholipids with phospholipase A₂. The [³H]choline label showed an early incorporation into high density lipoproteins and subsequently into low density lipoproteins (LDL); conversely, the¹⁴C radioactivity was rapidly incorporated into triacylglycerols that were mainly associated with very low density lipoproteins. Radioactivity measurements revealed that both isotopes remained the longest time in LDL. In red blood cell (RBC) lipids, [³H]choline radioactivity accumulated over time, with a plateau after 48 h, whereas FA radioactivity accumulated more rapidly and was followed by a progressive decay. Analysis of the isotope ratio in these cells suggested an early incorporation of lyso products followed by rapid transfer of FA from plasma. The RBC maintained considerable radioactivity for a prolonged time, thus acting as a possible reservoir for the DLPC administered. Our study showed that dilinoleoyl PC remained in plasma longer than predicted based on earlier studies, and that after absorption the FA label was found in position 2.     

Multiple positive solutions for singular BVPs on the positive half-line

In this work, we are concerned with the existence of multiple positive solutions to a second-order nonlinear singular boundary value problem set on the positive half-line. We mainly use the Krasnozels’ki and Leggett–Williams fixed point theorems in cones to prove existence of one positive solution, two positive solutions and three positive solutions. The results complement, extend and correct some recent ones.