12,281 research outputs found
Direct evidence of the dependence of surface state density on the size of SnO2 nanoparticles observed by scanning tunneling spectroscopy
No full textIn this work, we report a scanning tunnelling spectroscopy (STS) study of 30 and 10 nm tin dioxide nanoparticles.
The STS spectra give a surface band gap of 2.5 eV for both samples and show that the density of surface states in the
band gap is around 6 times higher for the 30 nm particles than for the 10 nm particles. This provides direct experimental
evidence for our theoretical model, which predicts a decrease in the surface state density as the particle size decreases,
and partly accounts for the improved sensitivity of gas sensing devices fabricated with nanoparticles
Persistence of helicobacter pylori in heterotrophic drinking-water biofilms
No full textAlthough the route of transmission of Helicobacter pylori remains unknown, drinking water has been considered a possible transmission vector. It has been shown previously that, in water, biofilms are a protective niche for several pathogens, protecting them from stressful conditions, such as low carbon concentration, shear stress, and less-than-optimal temperatures. In this work, the influence of these three parameters on the persistence and cultivability of H. pylori in drinking-water biofilms was studied. Autochthonous biofilm consortia were formed in a two-stage chemostat system and then inoculated with the pathogen. Total numbers of H. pylori cells were determined by microscopy using a specific H. pylori 16S rRNA peptide nucleic acid probe, whereas cultivable cells were assessed by standard plating onto selective H. pylori medium. Cultivable H. pylori could not be detected at any time point, but the ability of H. pylori cells to incorporate, undergo morphological transformations, persist, and even agglomerate in biofilms for at least 31 days without a noticeable decrease in the total cell number (on average, the concentration was between 1.54 × 106 and 2.25 × 106 cells cm?2) or in the intracellular rRNA content may indicate that the loss of cultivability was due to entry into a viable but noncultivable state. Unlike previous results obtained for pure-culture H. pylori biofilms, shear stress did not negatively influence the numbers of H. pylori cells attached, suggesting that the autochthonous aquatic bacteria have an important role in retaining this pathogen in the sessile state, possibly by providing suitable microaerophilic environments or linking biomolecules to which the pathogen adheres. Therefore, biofilms appear to provide not only a safe haven for H. pylori but also a concentration mechanism so that subsequent sloughing releases a concentrated bolus of cells that might be infectious and that could escape routine grab sample microbiological analyses and be a cause of concern for public health
Evidence of band bending flattening of 10 nm polycrystalline SnO2
No full textWe developed a model for n-type metal-oxide semiconductors, which allows one to calculate the density of charged surface states on
nanostructured grains, once the Schottky barrier height is known.We characterised structurally and electrically two sets of polycrystalline
SnO2 films with average grain radius of 30 and 10 nm. The purpose of this experiment was to observe the flattening of the bandbending
and the corresponding decrease in the density of charged surface states which are, in turn, responsible for the pinning of the Fermi level.
Finally, we highlighted how this phenomenon affects the characteristics of the films as gas sensors
A new species of Aleurolobus Quaintance et Baker (Homoptera, Aleyrodidae) from Southern Europe.
No full textAleurolobus teucrii n. sp. is described from southern Italy and the Maltese Islands (Central Mediterranean). The species seems to be monophagous on Teucrium fruticans L. A key to the European species of this genus (A. niloticus Priesner et Hosny, A. olivinus (Silvestri), A. wunni (Ryberg) and A. teucrii n. sp.) is provided.peer-reviewe
Mosquito Larvicidal Constituents from Lantana Viburnoides SP Viburnoides Var Kisi (A. rich) Verdc (Verbenaceae).
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Lantana viburnoides sp viburnoides var kisi is used in Tanzania ethnobotanically to repel mosquitoes as well as in traditional medicine for stomach ache relief. Bioassay-guided fractionation and subtraction bioassays of the dichloromethane extract of the root barks were carried out in order to identify the bioactive components for controlling Anopheles gambiae s.s. mosquito larvae. Twenty late III or early IV instar larvae of An. gambiae s.s. were exposed to various concentrations of the plant extracts, fractions, blends and pure compounds, and were assayed in the laboratory by using the protocol of WHO 1996. Mean mortalities were compared using Dunnett's test (p < 0.05) and lethal concentration calculated by Lackfit Inversel of the SAS programme. The crude extract (LC50 = 7.70 ppm in 72 h) and fractions exhibited different level of mosquito larvicidal activity with subtraction of some fractions resulting in activity enhancement. The active fractions contained furanonaphthaquinones regio-isomers (LC50 = 5.48-5.70 ppm in 72 h) and the lantadene triterpenoid camaric acid (LC50 = 6.19 ppm in 72 h) as active principles while the lupane triterpenoid betulinic acid (LC50 < 10 ppm in 72 h) was obtained from the least active fraction. Crude extracts and some fractions had higher or comparable larvicidal activity to the pure compounds. These results demonstrate that L. viburnoides sp viburnoides var kisi extracts may serve as larvicides for managing various mosquito habitats even in their semi-purified form. The isolated compounds can be used as distinct markers in the active extracts or plant materials belonging to the genus Lantana
Thermotoga lettingae sp. nov., a novel thermophilic, methanol-degrading bacterium isolated from a thermophilic anaerobic reactor
No full textA novel, anaerobic, non-spore-forming, mobile, Gram-negative, thermophilic bacterium, strain TMO(T), was isolated from a thermophilic sulfate-reducing bioreactor operated at 65 degrees C with methanol as the sole substrate. The G C content of the DNA of strain TMO(T) was 39.2 molÐThe optimum pH, NaCl concentration, and temperature for growth were 7.0, 1.0°and 65 degrees C, respectively. Strain TMO(T) was able to degrade methanol to CO(2) and H(2) in syntrophic culture with Methanothermobacter thermautotrophicus DeltaH or Thermodesulfovibrio yellowstonii. Thiosulfate, elemental sulfur, Fe(III) and anthraquinone-2,6-disulfonate were able to serve as electron acceptors during methanol degradation. In the presence of thiosulfate or elemental sulfur, methanol was converted to CO(2) and partly to alanine. In pure culture, strain TMO(T) was also able to ferment methanol to acetate, CO(2) and H(2). However, this degradation occurred slower than in syntrophic cultures or in the presence of electron acceptors. Yeast extract was required for growth. Besides growing on methanol, strain TMO(T) grew by fermentation on a variety of carbohydrates including monomeric and oligomeric sugars, starch and xylan. Acetate, alanine, CO(2), H(2), and traces of ethanol, lactate and alpha-aminobutyrate were produced during glucose fermentation. Comparison of 16S rDNA genes revealed that strain TMO(T) is related to Thermotoga subterranea (98€and Thermotoga elfii (98Ž The type strain is TMO(T) (=DSM 14385(T)=ATCC BAA-301(T)). On the basis of the fact that these organisms differ physiologically from strain TMO(T), it is proposed that strain TMO(T) be classified as a new species, within the genus Thermotoga, as Thermotoga lettingae
Data Science Education: The Signal Processing Perspective [SP Education]
No full textIn the last decade, the signal processing (SP) community has witnessed a paradigm shift from model-based to data-driven methods. Machine learning (ML) - more specifically, deep learning - methodologies are nowadays widely used in all SP fields, e.g., audio, speech, image, video, multimedia, and multimodal/multisensor processing, to name a few. Many data-driven methods also incorporate domain knowledge to improve problem modeling, especially when computational burden, training data scarceness, and memory size are important constraints.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Signal Processing System
Photo-induced unpinning of Fermi level in WO3
No full textAtomic force and high resolution scanning tunneling analyses were carried out on
nanostructured WO3 films. It turned out that the band gap measured by scanning tunneling
spectroscopy at surface is lower than the band gap reported in the literature. This effect is
attributed to the high density of surface states in this material, which allows tunneling into
these states. Such a high density of surface states pins the Fermi level resulting in modest
surface activity at room temperature. Photo activation of WO3 results in unpinning of the
Fermi level and thereby in higher chemical activity at surface
Screening of biodiesel production from waste tuna oil (Thunnus sp.), seaweed Kappaphycus alvarezii and Gracilaria sp.
No full textBiodiesel has several advantages over solar. Compared to solar, biodiesel has more eco-friendly characteristic
and produces lower greenhouse gas emissions. Biodiesel that is made from animal fats can be produced from fish oil,
while other alternative sources from vegetable oils are seaweed Kappaphycus alvarezii and Gracilaria sp. Waste tuna oil
(Thunnus sp.) in Indonesia is commonly a side product of tuna canning industries known as tuna precook oil; on the other
hand, seaweed Gracilaria sp. and Kappaphycus alvarezii are commonly found in Indonesia’s seas. Seaweed waste that
was used in the present study was 100 kg and in wet condition, and the waste oil was 10 liter. The seaweed was extracted
with soxhletation method that used n-hexane as the solvent. To produce biodiesel, trans esterification was performed on
the seaweed oil that was obtained from the soxhletation process and waste tuna oil. Biodiesel manufactured from
seaweed K. alvarezii obtained the best score in flash point, freezing point, and viscosity test. However, according to level
of manufacturing efficiency, biodiesel from waste tuna oil is more efficient and relatively easier compared to biodiesel
from waste K. alvarezii and Gracilaria sp
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