829 research outputs found
Connecting numbers to discrete quantification: A step in the child’s construction of integer concepts
The present study asks when young children understand that number words quantify over sets of discrete individuals. For this study, 2- to 4-year-old children were asked to extend the number word five or six either to a cup containing discrete objects (e.g., blocks) or to a cup containing a continuous substance (e.g., water). In Experiment 1, only children who knew the exact meanings of the words one, two and three extended higher number words (five or six) to sets of discrete objects. In Experiment 2, children who only knew the exact meaning of one extended higher number words to discrete objects under the right conditions (i.e., when the problem was first presented with the number words one and two). These results show that children have some understanding that number words pertain to discrete quantification from very early on, but that this knowledge becomes more robust as children learn the exact, cardinal meanings of individual number words
Biocidal silver and silver/titania composite films grown by chemical vapour deposition
This paper describes the growth and testing of highly active biocidal films based on photocatalytically active films of TiO2, grownby
thermal CVD, functionally and structurallymodified by deposition of nanostructured silver via a novel flame assisted combination
CVD process. The resulting composite films are shown to be highly durable, highly photocatalytically active and are also shown to
possess strong antibacterial behaviour. The deposition control, arising from the described approach, offers the potential to control
the film nanostructure, which is proposed to be crucial in determining the photo and bioactivity of the combined film structure,
and the transparency of the composite films. Furthermore, we show that the resultant films are active to a range of organisms,
including Gram-negative and Gram-positive bacteria, and viruses. The very high-biocidal activity is above that expected from the
concentrations of silver present, and this is discussed in terms of nanostructure of the titania/silver surface. These properties are
especially significant when combined with the well-known durability of CVD deposited thin films, offering new opportunities for
enhanced application in areas where biocidal surface functionality is sought
Photocatalytic antimicrobial activity of thin surface films of TiO2, CuO and TiO2 /CuO dual layers on Escherichia coli and bacteriophage T4
TiO2 coated surfaces are increasingly studied for their ability to inactivate microorganisms. The activity of glass coated with thin films of TiO2, CuO and hybrid CuO/TiO2 prepared by atmospheric Chemical Vapour Deposition (Ap-CVD) and TiO2 prepared by a sol-gel process was investigated using the inactivation of bacteriophage T4 as a model for
inactivation of viruses. The chemical oxidising activity was also determined by measuring stearic acid oxidation. The results showed that the rate of inactivation of bacteriophage T4 increased with increasing chemical oxidising activity with the maximum rate obtained on
highly active sol-gel preparations. However these were delicate and easily damaged unlike the Ap-CVD coatings. Inactivation rates were highest on CuO and CuO/TiO2 which had the lowest chemical oxidising activities. The inactivation of T4 was higher than that of Escherichia coli on low activity surfaces. The combination of photocatalysis and toxicity of copper acted synergistically to inactivate bacteriophage T4 and retained some selfcleaning activity. The presence of phosphate ions slowed inactivation but NaCl had no effect. The results show that TiO2/CuO coated surfaces are highly antiviral and may have applications in the food and healthcare industries
Constraining study of circular orbits and accretion disk around nonlinear electrodynamics black hole
The very latest observation of supermassive black hole (BH) by the
Event Horizon Telescope (EHT) provides the accretion onto BHs is an interesting
study in the theory of gravity. We study the geodesics structure and accretion
near a nonlinear electrodynamics BH in strong and weak field approximations.
These approximations provide the disc-like structure under the geodesic motion
and accretion around the BH. Near the equatorial plane, we provide some new
reasons to make circular orbits and accretion of test particles around the BH.
Then we investigate perturbations, the critical speed of the fluid and the mass
accretion rate of particles around the central object. The physical validity of
this study shows that the parameter and play an important role in
the circular orbits and the mass accretion rate in strong and weak field
approximations.Comment: 21 pages, 12 figure
Water extract of Cryphaea heteromalla (Hedw.) D. Mohr bryophyte as a natural powerful source of biologically active compounds
Bryophytes comprise of the mosses, liverworts, and hornworts. Cryphaea heteromalla, (Hedw.) D. Mohr, is a non-vascular lower plant belonging to mosses group. To the date, the most chemically characterized species belong to the liverworts, while only 3.2% and 8.8% of the species belonging to the mosses and hornworts, respectively, have been investigated. In this work, we present Folin–Ciocalteu and oxygen radical absorbance capacity (ORAC) data related to crude extracts of C. heteromalla obtained by three different extraction solvents: pure water (WT), methanol:water (80:20 v/v) (MET), and ethanol:water (80:20 v/v) (ETH). The water extract proved to be the best solvent showing the highest content of biophenols and the highest ORAC value. The C. heteromalla-WT extract was investigated by HPLC-TOF/MS (High Performance Liquid Chromatography-Time of Flight/Mass Spectrometry) allowing for the detection of 14 compounds, five of which were phenolic compounds, derivatives of benzoic, caffeic, and coumaric acids. Moreover, the C. heteromalla WT extract showed a protective effect against reactive oxygen species (ROS) generation induced by tert-butyl hydroperoxide (TBH) on the murine NIH-3T3 fibroblast cell line
Inferences on physico-chemical conditions and gas-water interaction by new quantitative approaches: The case of Panarea (Italy)
We have developed two new quantitative approaches to
calculate temperatures in hydrothermal reservoirs by using the
CO2-CH4-CO-H2 gaseous system and to model selective
dissolution of CO2-H2S-N2-CH4-He-Ne mixtures in fresh
and/or air saturated seawater. The anomalous outgassing
starting November 2003 from the submarine exhalative
system offshore Panarea island (Italy), was the occasion to
apply such approaches to the extensive collection of volcanic
gases.
Gas geothermometry suggest the presence of a deep
geothermal system at temperature up to 350°C and about 12
mol% CO2 in the vapor, which feeds the submarine emissions.
Based on the fractional dissolution model, the rising
geothermal vapor interacts with air-saturated seawater at low
depths, dissolving 30-40% CO2 and even more H2S,
modifying the pH of the aqueous solution and stripping the
dissolved atmospheric volatiles (N2, Ne). Interaction of the
liquid phase of the thermal fluids with country rocks, as well
extensive mixing with seawater, have been also recognized
and quantified.
The measured output of hydrothermal fluids from Panarea
exhalative field [1] accounts for the involvement of volatiles
from an active degassing magma, nonetheless the climax of
the investigated phenomenon is probably overcome and the
system is new tending towards a steady-state. Our quantitative
approaches allow us to monitor the geochemical indicators of
the geothermal physico-chemical conditions and their
potential evolution towards phreatic events or massive gas
releases, which certainly are the main hazards to be expected
in the area. The event at Panarea has in fact highlighted how
hydrothermal systems can exhibit dramatic and sudden
changes of their physico-chemical conditions and rate of fluid
release, as a response to variable activity of feeding magmatic
systems
Hydrogel scaffolds based on k-Carrageenan/xyloglucan blends to host spheroids from human adipose stem cells
Hydrogels are water-swollen networks of hydrophilic polymer. They can be fabricated in various shapes and swell in water or aqueous solutions maintaining their original shape or undergo progressive erosion; can exibit large volume phase transitions with the change of one environmental parameter (stimuli-responsivness), shock absorption and low sliding friction properties (1). The morphology and mechanical properties of hydrogels are strongly affected by the network composition, the nature and degree of crosslinking and the degree of swelling. Indeed, when hydrogels are designed as scaffolds for human tissues remodeling, they must have sufficient mechanical integrity to provide support to the cells from the time of implantation to the completion of the process. The large amount of water present in the hydrogels and its microscopic pores interconnectivity allows transportation of nutrients, oxygen and metabolites, that ensures cells viability, and permits cells migration and scaffold colonization. The polymeric network can immobilize biomolecules that may affect cells growth or differentiation, control drug release profiles and enzymatic degradation (2,3). The combination of two hydrogelforming polymers with different chemistries and crosslinking densities can be used to tailor the morphology, mechanical strength and toughness of the scaffold to meet specific requirements (1). This work investigates the physico-chemical, morphological and mechanical properties of hydrogels formed by the blend of two polysaccharides, k-Carrageenan (k-C) and Degalactosylated Xyloglucan (Deg-XG) undergoing salt-induced and temperature-induced solgel transition, respectively. It also studies the compatibility of the two biopolymers with spheroids from adipose-derived stem cells (S-ASCs) in the prospect of developing instructive scaffolds for use in regenerative medicine
Agarose/Îş-carrageenan-based hydrogel film enriched with natural plant extracts for the treatment of cutaneous wounds
Hydrogels for complex and chronic wound dressings must be conformable, absorb and retain wound exudates and maintain hydration. They can incorporate and release bioactive molecules that can accelerate the healing process. Wound dressings have to be in contact with the wound and epidermis, even for long periods, without causing adverse effects. Hydrogel dressing formulations based on biopolymers derived from terrestrial or marine flora can be relatively inexpensive and well tolerated. In the present article hydrogel films composed by agarose (1.0 wt%), Îş-carrageenan at three different concentrations (0.5, 1.0 and 1.5 wt%) and glycerol (3.0 wt%) were prepared without recourse to crosslinking agents, and characterized for their mechanical properties, morphology, swelling and erosion behavior. The films resulted highly elastic and able to absorb and retain large amounts of fluids without losing their integrity. One of the films was loaded with the aqueous extract from Cryphaea heteromalla (Hedw.) D. Mohr for its antioxidant properties. Absence of cytotoxicity and ability to reduce the oxidative stress were demonstrated on NIH-3T3 fibroblast cell cultures. These results encourage further biological evaluations to assess their impact on the healing process
- …