The mechanically activated synthesis of hafnium diboride HfB2 from partially hydrated hafnium tetrachloride "HfCl4" is first described. Monocrystalline rods with submicron to micron lengths and a ...diameter of about 100 nm are synthesized by annealing, at 1373 K, of powder mixtures of "HfCl4" and boron ground with steel tools. The monocrystalline rods grow parallel to the c-axis of the HfB2 structure from iron-rich grains of the activated powder and are defect-free. Facetted nanometer-sized single crystals are obtained instead when magnesium is added to the starting mixtures. The fractureless transformation of single-crystal anatase particles with different initial sizes into orthorhombic TiO2-II by milling is then described. Milling yields either monocrystalline anatase particles coated with a layer of nanograins of TiO2-II (grain size about 10 nm) or fully transformed anatase particles according to the initial diameters of about 150 nm and about 25 nm respectively. The relevance of a milling parameter, namely the average power injected per unit volume of powder trapped during a collision, is finally emphasized.
Nanocrystalline Fe-based spinels with composition Fe
2.5Ti
0.5O
4 can be synthesized using two different routes: soft chemistry and high-energy ball milling. This paper is focussed on the fact that ...each type of synthesis process can lead to powders with a crystallite size of about 15
nm but with significant differences in the grain size distribution and the agglomeration state. Whereas in the case of mechanosynthesis, the ball-milled powders consist of aggregates, those obtained by soft chemistry are very well dispersed. Moreover the chosen investigated nanopowders present a blocked/superparamagnetic transition depending on the grain size. The grain size morphologies obtained by the two techniques of synthesis can then be fully characterized by complementary experiments: in addition to high-resolution image processing, specific measurements adapted to the study of magnetic relaxation can be used for weighting differently their small and large size tails: namely, magnetization measurements and Mössbauer spectrometry.
The binding of the spermatozoon to the zona pellucida is a species-specific phenomenon. We have previously shown that the binding of hamster sperm to the homologous zona pellucida involves a sperm ...26-kDa glycoprotein, the P26h, originating in the epididymis. In order to establish to what extent this sperm protein is involved in the species-specific recognition of the egg's extracellular coat, we have compared the inhibitory properties of anti-P26h antibodies in a sperm-zona pellucida assay using hamster and mouse gametes. Anti-P26h IgGs inhibit, in a dose-dependent manner, gamete interactions in both species, although in a less efficient manner in the mouse than in the hamster. While anti-26kDa Fab fragments are as efficient as the intact IgG to inhibit hamster sperm-zona pellucida binding, they have no effect on mouse gamete interaction. ELISA, Western blot, and immunohistochemical experiments have been performed in order to characterize the mouse antigen(s) recognized by the anti-P26h antiserum. ELISA and Western blots showed that this antiserum recognized two proteins on mouse spermatozoa that are less reactive than the hamster P26h. These antigens are localized in the acrosomal region of epididymal spermatozoa of both species. These results indicate that the hamster P26H involved in zona pellucida interaction has certain unique epitopes, while others are common to the sperm of both species.
Mechanical alloying has been used to prepare powder mixtures of alumina and yttria as a means to create composites with a dominant matrix phase together with small particles of a dispersed second ...phase. The yttria–alumina system, containing five possible phases, has the potential for creating eight combinations of matrix and dispersed phases. Here compositions designed to give YAlO
3 (YA) dispersed in Y
3Al
5O
12 (Y
3A
5 i.e. YAG) or Y
4Al
2O
9 (Y
2A) were studied. After milling with steel tools for times up to 8 h, the powders were subjected to thermal cycles up to 1500°C during which the phase evolution was monitored using X-ray diffractometry (including high-temperature XRD) and differential thermal analysis. During milling the original crystal structures were quickly broken down, in some cases partially replaced by an intermediate structure after milling. Upon subsequent heating the milled mixtures crystallized to give the expected phases, YA in Y
3A
5 and YA in Y
2A respectively, but the reaction route was seen to be different depending on the amount of amorphization of the yttria. Contamination by iron was seen to affect the phase distribution and the lattice parameters.
Among smart activable nanomaterials used for nanomedicine applications, carbon-based nanocomposites are well known to ensure phototherapy while their use for controlled drug delivery is still rarely ...investigated. In this work, original hybrid mesoporous silica (MS)–coated carbon nanotubes (CNTs) nanoplatforms have been designed to provide phototherapy combined with drug release mediated by NIR laser excitation. The responsive CNT@MS are chemically modified with original isobutyramide (IBAM) grafts acting as non-covalent binders, which ensure a very high drug loading capacity (≥to 80 wt%) of the antitumor drug doxorubicin (DOX) as well as the final adsorption of a human serum albumin (HSA) shell as biocompatible interface and drug gate-keeping. The drug is demonstrated to unbind from the nanocomposite only upon photothermal excitation and to release in the solution. Such smart platforms are further shown to deliver drug upon several pulsatile NIR excitations with controlled temperature profiles. Regarding antitumor action, we demonstrate here that the NIR light induced photothermic effect from the nanocomposites is the main effect accounting for cancer cell toxicity and that DOX delivery mediated by the NIR light brings an additional toxicity allowing a synergistic effect to efficiently kill tumor cells. Finally, when our nanocomposites are embedded within a hydrogel mimicking extracellular matrix, the resulting smart responsive scaffolds efficiently release DOX upon NIR light to the cells localized above the composite hydrogel. These results demonstrate that such nanocomposites are highly promising as new components of implantable antitumor scaffolds that are able to respond to external stimuli in time and location for a better disease management.
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•Hybrid carbon nanotubes@mesoporous silica are designed.•Isobutyramide grafts ensure a very high drug loading capacity (≥to 80 wt%).•They provide NIR-mediated phototherapy combined with pulsatile drug release.•Upon NIR light applied, they induce cancer cell toxicity.•Such nanocomposites are embedded within a hydrogel mimicking extracellular matrix.
Nanocrystalline Fe-based spinels with composition Fe2.5Ti0.5O4were synthesized using two different routes: soft chemistry and high-energy ball milling. In the first case, two steps were involved: ...precipitation in an aqueous solution followed by thermal annealing under a reducing mixture of N2/H2/H2O gases. In the second case, the spinel phase was directly formed in the mill at room temperature and under argon atmosphere from Fe, Fe2O3, and TiO2in stoichiometric proportions. The as-prepared powders are characterized by X-ray diffraction, scanning and transmission electron microscopy, surface area measurement, and Mössbauer spectrometry. In both cases, the crystallite's size is about 15 nm, but whereas in the case of mechanosynthesis, the ball-milled powders consist of aggregates, those obtained by soft chemistry are very well dispersed. In contrast to the soft chemistry route, both lattice defects and cation site inversion are induced by high energy ball milling, as evidenced by X-ray diffraction and thermogravimetric analysis. Finally, the particle coercivity is studied and discussed according to particle size and the degree of oxidation of Fe cations inferred from thermogravimetry.
Abstract Upconverting nanoparticles (UCNPs) were successfully dendronized for fluorescence medical imaging applications. The structural and morphological characterizations of resulting core/shell ...NaYF4 :Yb,Tm@dendrons nanoparticles were performed by means of X-ray diffraction, infrared spectroscopy and transmission electron microscopy. In vitro cytotoxicity assays have evidenced their low toxicity. In vivo fluorescence imaging study was performed in mice upon IR excitation, showing promising imaging capacities at low concentrations (0.5 mg/mL) and low power (50 mW/cm2 ).
Impact of nitrogen deposition at the species level Payne, Richard J.; Dise, Nancy B.; Stevens, Carly J. ...
Proceedings of the National Academy of Sciences - PNAS,
01/2013, Volume:
110, Issue:
3
Journal Article
Peer reviewed
Open access
In Europe and, increasingly, the rest of the world, the key policy tool for the control of air pollution is the critical load, a level of pollution below which there are no known significant harmful ...effects on the environment. Critical loads are used to map sensitive regions and habitats, permit individual polluting activities, and frame international negotiations on transboundary air pollution. Despite their fundamental importance in environmental science and policy, there has been no systematic attempt to verify a critical load with field survey data. Here, we use a large dataset of European grasslands along a gradient of nitrogen (N) deposition to show statistically significant declines in the abundance of species from the lowest level of N deposition at which it is possible to identify a change. Approximately 60% of species change points occur at or below the range of the currently established critical load. If this result is found more widely, the underlying principle of no harm in pollution policy may need to be modified to one of informed decisions on how much harm is acceptable. Our results highlight the importance of protecting currently unpolluted areas from new pollution sources, because we cannot rule out ecological impacts from even relatively small increases in reactive N deposition.
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