Atom collision-induced resistivity of carbon nanotubes

We report the observation of unusually strong and systematic changes in the electron transport in metallic single-walled carbon nanotubes that are undergoing collisions with inert gas atoms or small molecules. At fixed gas temperature and pressure, changes in the resistance and thermopower of thin films are observed that scale as roughly M(1/3), where M is the mass of the colliding gas species (He, Ar, Ne, Kr, Xe, CH4, and N2). Results of molecular dynamics simulations are also presented that show that the maximum deformation of the tube wall upon collision and the total energy transfer between the colliding atom and the nanotube also exhibit a roughly M(1/3) dependence. It appears that the transient deformation (or dent) in the tube wall may provide a previously unknown scattering mechanism needed to explain the atom collision-induced changes in the electrical transport.     

The causes of piping in a set of abandoned agricultural terraces in southeast Spain

This study aims to identify some of the factors contributing to the piping process in abandoned terraces in seven sites located in the Murcia Region (southeast Spain). The local landscape has the appearance of badland geomorphology, possessing deep valleys which until the 1970s were terraced and cultivated. The terraces have now been abandoned to the piping process. The research focuses on the relationship between the size and position of pipes and the physical and geochemistry properties of the local highly dispersive marl lithology; and the extent to which the reworking of the materials for terrace cultivation has exacerbated piping erosion.Morphologically, the terracing in the stream beds has resulted in a series of gentle benches separated by steeper risers with variable ‘drop’, (riser height). A series of flat infiltration surfaces result, and because the resculpting produces a reduced bulk density infill with enhanced throughflow, infiltrating water is forced along steep hydraulic gradients to a low outfall at the base of the riser.Paralleling studies of land levelling and terrace abandonment in similar materials elsewhere, piping in the study area is shown to be closely related to the physical and chemical characteristics of the materials its sodicity and dispersive character. Considerable differences in structure, texture, mineralogical composition and material's surface crust and subsoil geochemical properties emerged from ‘site signature’ plots, and these results suggest that agricultural processes affect the dispersive character of the crust materials, presumably because agricultural activity increases the buffering effect of organic acids on the dispersed clay. This is supported by the observation that on the one site that was levelled but not used for agriculture, a stable organically-distinct crust like the abandoned agricultural sites has not formed. The changes to the material's aggregate stability and bulk density properties when terracing occurs is examined, but insufficient evidence is available from the data collected to unpick the causes of aggregate stability changes in the study plots. The way in which differences between crust and subsoil enhance infiltration is discussed, and the role of the terrace ‘drop’ in influencing hydraulic gradients and pipe development is illustrated. A possible index to describe the relationship between evacuated material volumes and the controlling parameters discussed above is tested.It is concluded that terracing which is intended as a conservation practice has, in dispersive materials, actually enhanced piping, leading to the abandonment of farming.     

Insights into the virulence‐related genes of Edwardsiella tarda isolated from turbot in Europe: genetic homogeneity and evidence for vibrioferrin production

Edwardsiella tarda has long been known as a pathogen that causes severe economic losses in aquaculture industry. Insights gained on E. tarda pathogenesis may prove useful in the development of new methods for the treatment of infections as well as preventive measures against future outbreaks. In this report, we have established the correlation between the presence of virulence genes, related with three aspects typically involved in bacterial pathogenesis (chondroitinase activity, quorum sensing and siderophore‐mediated ferric uptake systems), in the genome of E. tarda strains isolated from turbot in Europe and their phenotypic traits. A total of 8 genes were tested by PCR for their presence in 73 E. tarda isolates. High homogeneity was observed in the presence/absence pattern of all the strains. Positive results in the amplification of virulence‐related genes were correlated with the detection of chondroitinase activity in agar plates, in vivo AHL production during fish infection and determination of type of siderophore produced by E. tarda. To the best of our knowledge, this is the first study carried out with European strains on potential virulence factors. Furthermore, we demonstrated for the first time that E. tarda produces the siderophore vibrioferrin.     

Effect of paratuberculosis on the diagnosis of bovine tuberculosis in a cattle herd with a mixed infection using interferon-gamma detection assay

Interferon-gamma (IFN-gamma) detection assay is being applied as an ancillary test to tuberculin tests in the diagnosis of bovine tuberculosis to detect the maximum number of infected animals. Among possible factors influencing the performance of tuberculosis-diagnostic tests, paratuberculosis, a widespread disease in Spain and other European countries, has been pointed out as a cause of false positive reactions. Still, its effect on the sensitivity of these tests in cattle has yet to be fully characterized. The impact of paratuberculosis in the apparent sensitivity of IFN-gamma assay was studied in a bullfighting cattle herd with a mixed tuberculosis-paratuberculosis infection, using culture of Mycobacterium bovis and Mycobacterium avium paratuberculosis as the gold standard to determine the infection status of every animal. A total of 218 animals were slaughtered and sampled for bacteriology after blood sampling. IFN-gamma assay showed a lower apparent sensitivity in animals with a mixed infection (50%) compared to all animals suffering tuberculosis (78.3%). This finding indicates that the presence of paratuberculosis in tuberculosis-infected herds could imply a serious impairment in the sensitivity of IFN-gamma detection test.     

A combination of Lactobacillus buchneri and Pediococcus pentosaceus extended the aerobic stability of conventional and brown midrib mutants–corn hybrids ensiled at low dry matter concentrations by causing a major shift in their bacterial and fungal community

We evaluated the effects of applying a combination inoculant to four corn hybrids harvested at high moisture on their nutritive value and microbial populations. The treatment design was the factorial combination of corn hybrids ensiled with (INO) and without (CON) inoculant. The hybrids were TMF2R737 (MCN), F2F817 (MBR), P2089YHR (PCN), and PI144XR (PBR), ensiled at dry matter (DM) concentrations of 30.5%, 26.3%, 31.1%, and 31.5%, respectively; MBR and PBR were brown midrib mutants (BMR). The inoculant contained Lactobacillus buchneri and Pediococcus pentosaceus (4 × 10⁵ and 1 × 10⁵ cfu/g of fresh corn). The experiment had a complete randomized design with treatments replicated six times. Corn was treated or not with inoculant, packed into 7.6 L bucket silos, and stored for 100 d. At d 0, the relative abundance (RA, %) of Enterobacteriaceae was lower in PBR vs. the other hybrids [51.3 vs. x¯ = (average of) 58.4] and in the case of fungi, incertae sedis (i.s.) Tremellales and Mucoraceae were more and less abundant, respectively, in conventional hybrids vs. BMRs (x¯= 25.8 vs. x¯ = 13.9 and x¯ = 3.64 vs. x¯ = 7.52; P < 0.04). After ensiling, INO had higher LAB (9.3 vs. 7.1 log cfu/g of fresh corn) and acetic acid (3.44% vs. 1.32% of DM) and lower yeast (3.1 vs. 4.6) and molds (1.5 vs. 3.0), and also extended the aerobic stability (582 vs. 111 h) but decreased DM recovery (95.6% vs. 97.4%) vs. CON (P < 0.02). Inoculation reduced bacterial phylogenetic diversity (6.75 vs. 14.4) but increased fungal observed taxonomical units (46 vs. 20) vs. CON (P < 0.01). Also, a higher relative abundance (RA) for Lactobacillaceae (99.2% vs. 75.7%) and lower for Enterobacteriaceae (0.28 vs. 9.93) was observed due to inoculation (P < 0.001). For fungi, INO had a lower RA compared to CON for Monascaceae (12.6 vs. 44.7) and increased i.s. Tremellales (8.0 vs. 1.2) and i.s. Saccharomycetales (6.4% vs. 0.3%; P < 0.006). Inoculation changed the diverse bacterial community found in the phyllosphere across hybrids to a taxonomically uneven one dominated by Lactobacillaceae. In the case of fungi, INO application increased the fungal diversity at d 100 mainly by reducing the dominance of Monascaceae vs. CON. In conclusion, the INO treatment overwhelmed the disparate microbial populations found across BMR and conventional hybrids ensiled at low DM concentrations and ensured a significant concentration of acetic acid that modified fungal populations and in turn extended the aerobic stability of all hybrids.     

Evaluation of chlorfenapyr for control of the bed bug,Cimex lectularius L.

BACKGROUND: The presence of bed bug populations resistant to pyrethroids demands the development of new control tactics, including the use of insecticides with new modes of action. Insecticides that disrupt oxidative phosphorylation in insect mitochondria can be an option. Laboratory assays were used to measure the toxicity of chlorfenapyr to susceptible strains and two strains highly resistant to pyrethroids. The effectiveness of two chlorfenapyr‐based formulations was compared, and behavioral responses of bed bugs to dry residues of aerosol sprays were evaluated. RESULTS: Chlorfenapyr was effective against all bed bug strains, killing them at a similar rate, regardless of their susceptibility status to pyrethroids. Dry residues aged for 4 months were as toxic as fresh dry residues. The aerosol formulation had contact activity and caused faster mortality than a water‐based formulation. Bed bugs did not avoid resting on surfaces treated with aerosol. CONCLUSION: Chlorfenapyr is an option for controlling pyrethroid‐resistant bed bugs. While it does not cause quick knockdown, its long residual activity and no avoidance behavior of bed bugs to dry residues appear to make this insecticide suitable for bed bug control. A faster insecticidal effect is obtained with the aerosol formulation, suggesting greater bioavailablity of the toxicant. Copyright © 2010 Society of Chemical Industry     

Antioxidant activity of uruguayan propolis. In vitro and cellular assays

The antioxidant capacity of propolis from the southern region of Uruguay was evaluated using in vitro as well as cellular assays. Free radical scavenging capacity was assessed by ORAC, obtaining values significantly higher than those of other natural products (8000 μmol Trolox equiv/g propolis). ORAC values correlated well with total polyphenol content (determined by Folin-Ciocalteu method) and UV absorption. Total polyphenol content (150 mg gallic acid equiv/g propolis) and flavonoids (45 mg quercetin equiv/g propolis) were similar to values reported for southern Brazilian (group 3) and Argentinean propolis. Flavonoid composition determined by RP-HPLC indicates a strong poplar-tree origin. Samples high in polyphenols efficiently inhibit low-density lipoprotein lipoperoxidation and tyrosine nitration. In addition, Uruguayan propolis was found to induce the expression of endothelial nitric oxide synthase and inhibit endothelial NADPH oxidase, suggesting a potential cardiovascular benefit by increasing nitric oxide bioavailability in the endothelium.     

AhaP,A Quorum Quenching Acylase from Psychrobacter sp. M9-54-1 That Attenuates Pseudomonas aeruginosa and Vibrio coralliilyticus Virulence

Although Psychrobacter strain M9-54-1 had been previously isolated from the microbiota of holothurians and shown to degrade quorum sensing (QS) signal molecules C6 and C10-homoserine lactone (HSL), little was known about the gene responsible for this activity. In this study, we determined the whole genome sequence of this strain and found that the full 16S rRNA sequence shares 99.78–99.66% identity with Psychrobacter pulmonis CECT 5989^T and P. faecalis ISO-46^T. M9-54-1, evaluated using the agar well diffusion assay method, showed high quorum quenching (QQ) activity against a wide range of synthetic N-acylhomoserine lactone (AHLs) at 4, 15, and 28 °C. High-performance liquid chromatography-mass-spectrometry (HPLC-MS) confirmed that QQ activity was due to an AHL-acylase. The gene encoding for QQ activity in strain M9-54-1 was identified from its genome sequence whose gene product was named AhaP. Purified AhaP degraded substituted and unsubstituted AHLs from C4- to C14-HSL. Furthermore, heterologous expression of ahaP in the opportunistic pathogen Pseudomonas aeruginosa PAO1 reduced the expression of the QS-controlled gene lecA, encoding for a cytotoxic galactophilic lectin and swarming motility protein. Strain M9-54-1 also reduced brine shrimp mortality caused by Vibrio coralliilyticus VibC-Oc-193, showing potential as a biocontrol agent in aquaculture.     

The Effect of Natural Mulches on Crop Performance, Weed Suppression and Biochemical Constituents of Catnip and St. John's Wort

Because of expanding markets for high-value niche crops, opportunities have increased for the production of medicinal herbs in the USA. An experiment was conducted in 2001 and 2002 near Gilbert, IA, to study crop performance, weed suppression, and environmental conditions associated with the use of several organic mulches in the production of two herbs, catnip (Nepeta cataria L.) and St. John's wort (Hypericum perforatum L. 'Helos'). Treatments were arranged in a completely randomized design and included a positive (hand-weeded) control, a negative (nonweeded) control, oat straw, a flax straw mat, and a nonwoven wool mat. Catnip plant height was significantly greater in the oat straw than the other treatments at 4 wk through 6 wk in 2001; at 4 to 8 wk in 2002, catnip plant height and width was significantly lower in the negative control compared with the other treatments. Catnip yield was significantly higher in the flax straw mat than all other treatments in 2001. In 2002, St. John's wort yields were not statistically different in any treatments. All weed management treatments had significantly fewer weeds than the non-weeded rows in 2002. Total weed density comparisons in each crop from 2 yr showed fewer weeds present in the flax straw and wool mat treatments compared with positive control plots. There was no significant weed management treatment effect on the concentration of the target compounds, nepetalactone in catnip and pseudohypericin-hypericin in St. John's wort, although there was a trend toward higher concentrations in the flax straw treatment.     

Effects of reducing leaf area and tuber number on the growth rates of tubers on individual potato plants

Summary Potato plants (Solanum tuberosum L. cv. Ostara) were grown in nutrient solution culture in a controlled environment. Growth rates of individual tubers were determined daily by measuring the increase in their volume. Decreasing the source:sink ratio of individual plants by removing half of the leaf area, decreased tuber growth rate per plant by 50%. Increasing the source: sink ratio of individual plants by cooling to 8°C, or by removing individual tubers of known growth rate, increased the growth rate of non-cooled, remaining tubers within 2–4 days. The potential of the tubers to increase their growth rates was not related to the date of tuber removal after tuber initiation. It is concluded that during the phase of linear tuber bulking, tuber growth is neither limited by pathway nor sink, but by the source capacity of the plant.

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Zusammenfassung Kartoffelpflanzen (Solanum tuberosum L. cv. Ostara) wuchsen in N?hrl?sung unter kontrollierten Umweltbedingungen (14 h Tagesl?nge, 22°C/18°C Tag/Nachttemperatur, 60–80% relative Luftfeuchtigkeit, Licht-intensit?t in Pflanzenh?he ≈380 μE m⁻² s⁻¹). Die Wachstumsraten der einzelnen Knollen wurden t?glich aus ihrer Volumenzunahme bestimmt. Die Auswirkungen von Source- und Sink-Manipulationen auf die Wachstumsraten der Knollen wurden w?hrend der Phase linearen Knollenwachstums untersucht. Eine Reduzierung der Source-St?rke einzelner Pflanzen durch Entfernen jedes 2. Fiederblattes oder eines von 2 gleichwertigen hauptstengeln pro Pflanze bewirkte eine sofortige Abnahme des Knollenwachstums pro Pflanze um 50% (Abb. 4). In den meisten F?llen nahm auch die Wachtstumsrate der einzelnen Knollen an den Pflanzen um etwa 50% ab (Abb. 5). Durch Kühlung einzelner Knollen auf +8°C wurden deren Wachstumsraten im Durchschnitt von 4,5 auf 1,6 cm³ d⁻¹ gesenkt, w?hrend gleichzeitig die Wachstumsraten der ungekühlten Knollen von 2,8 auf 5,2 cm³ d⁻¹ anstiegen (Tab. 1). Das Entfernen einzelner Knollen, die bis dahin durch-schnittlich zu 60% am Gesamtknollenwachstum pro Pflanze beteiligt waren, führte innerhalb von 2–4 Tagen zu einem mehr als doppelt so schnellen Wachstum der an den Pflanzen verbliebenen Knollen, so dass das Gesamtknollenwachstum pro Pflanze nicht signifikant ver?ndert wurde (Abb. 1). Hierbei wurden die Wachstumsraten aller an der Pflanze verbliebenen Knollen erh?ht, wobei Wachstumsraten von mehr als 8 cm³ pro Einzelknolle und Tag erreicht wurden (Abb. 3). Die F?higkeit der Knollen, ihre Wachstumsrate dem jeweiligen Assimilatangebot anzupassen, war nicht davon abh?ngig, zu welchem Zeitpunkt nach der Knolleninduktion (10–30 d) einzelne Knollen entfernt wurden (Abb. 2). Aus den Untersuchungen wird gefolgert, dass in der phase des linearen Knollenwachstums eine Limitierung des Knollenwachstums weder durch den transportweg noch durch die Speicherf?higkeit der Knollen bewirkt wird, sondern durch die F?higkeit des oberirdischen Sprosses, Assimilate zur Verfügung zu stellen.

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Résumé Des plantes de pommes de terre (Solanum tuberosum L. cv. Ostara) sont cultivées dans une solution nutritive sous atmosphère contr?lée (longueur de jours 14 h; températures jour/nuit 22°C/18°C; humidité relative de l'air 60 à 80%; intensité du rayonnement photosynthétique à hauteur de la plante ≃380 μF m⁻² s⁻¹). Le grossissement des tubercules est déterminé chaque jour en mesurant l'augmentation de leur volume. Les effets de la source d'assimilation et du puits d'absorption sont analysés pendant la phase linéaire de grossissement des tubercules. Une diminution du rapport source: puits d'absorption est obtenue en supprimant la moitié de la surface foliaire de chaque plante. Le grossissement des tubercules diminue en conséquence de 50% (figure 4). Mis à part quelques exceptions, les taux de croissance des tubercules individuels baissent également de 50% (figure 5). Le refroidissement de certains tubercules d'une même plante à 8°C entra?ne une diminution moyenne de leur grossissement de 4,5 à 1,6 cm³/jour. Dans le même temps, les autres tubercules voient leur croissance augmenter de 2,8 à 5,2 cm³/jour (tableau 1). La suppression de certains tubercules qui avaient contribué pour 60% au grossissement total obtenu par plante, entr?ne une augmentation de croissance de plus de 100% des tubercules restants, ceci en moins de 2 à 4 jours. De ce fait, la croissance totale, par plante n'est pas significativement inférieure (figure 1). Après suppression de certains tubercules, on constate que pour tous les tubercules restants leur grossissement augmente et le taux maximum de croissance atteint 8 cm³/jour (figure 3). Les tubercules ajustent leur grossissement en fonction de l'apport effectif de photosynthèse sans liaison avec la date de suppression de certains tubercules après leur initiation (figure 2). En conclusion, pendant la phase linéaire de grossisement, la croissance des tubercules n'est pas limitée par le puits d'absorption, mais par la capacité de la source d'assimilation de la plante.