ABSTRACT
Alumina nanopowders belonging to the γ and δ transition phases have been characterized by infrared and Raman spectroscopies. A quantitative interpretation of their vibrational spectra has been provided and related to their crystal structure, with particular emphasis on structural disorder and features not predicted by group-theoretical considerations. Both phases show very similar infrared dielectric functions, but with clear instances of mode-splitting in the δ phase, which are related to ordering in the tetrahedral Al positions. Raman spectroscopy was unable to resolve any modes in the sample identified as γ phase, but the full lattice vibrational region could be measured for the δ sample under UV and red excitation lines. Raman spectra are more complex than those obtained by infrared spectroscopy and cannot be completely explained by factor group analysis, in the absence of dedicated theoretical studies. Finally, the luminescent properties of these materials have been qualitatively explored and linked to disorder and substitutional impurities. In general, the results contained in this work prove that vibrational spectroscopies are powerful tools for quantitative analyses of these disordered nanomaterials and suggest the need for more theoretical work to understand their vibrational properties.
ABSTRACT
We consider a seasonally forced SIR epidemic model where periodicity occurs in the contact rate. This periodical forcing represents successions of school terms and holidays. The epidemic dynamics are described by a switched system. Numerical studies in such a model have shown the existence of periodic solutions. First, we analytically prove the existence of an invariant domain D containing all periodic (harmonic and subharmonic) orbits. Then, using different scales in time and variables, we rewrite the SIR model as a slow-fast dynamical system and we establish the existence of a macroscopic attractor domain K, included in D, for the switched dynamics. The existence of a unique harmonic solution is also proved for any value of the magnitude of the seasonal forcing term which can be interpreted as an annual infection. Subharmonic solutions can be seen as epidemic outbreaks. Our theoretical results allow us to exhibit quantitative characteristics about epidemics, such as the maximal period between major outbreaks and maximal prevalence.
Subject(s)
Communicable Diseases/epidemiology , Epidemics , Models, Biological , Periodicity , Humans , Numerical Analysis, Computer-Assisted , SeasonsABSTRACT
Oocyte donation, initially proposed in agonadal women, saw indications expand to ovarian deficiencies and failures of in vitro fertilization (IVF), resulting in a significant increasing demand. The recruitment of oocyte donors is a critical issue for all countries that have allowed this practice. The French legislation, with the laws of bioethics, is clearly the most restrictive of European countries, imposing an absolute free gift from mother. The different solutions in the neighboring countries are analysed and in particular the interpretations made in respect of gratuity and compensation. Motivating donors (spontaneous, relational, or by reciprocity), but also motivating the medical teams can organize a program of oocyte donation in France. The authors present their results of three years experience, demonstrating that this system is possible in the current legislative framework.
Subject(s)
Oocyte Donation/ethics , Oocyte Donation/legislation & jurisprudence , Confidentiality/ethics , Embryo Disposition/ethics , Female , Fertilization in Vitro/ethics , Fertilization in Vitro/legislation & jurisprudence , France , Humans , Pregnancy , Reproductive Techniques, Assisted/ethics , Tissue and Organ ProcurementABSTRACT
In 2005-2006, 905 punctures of oocytes were realised in the Assisted Reproductive Technology Centre of Rennes' Hospital in France, the source of 173 pregnancies after fresh embryos transfers and 185 pregnancies after frozen embryos transfers. The single-embryo transfer (SET) was proposed in all patients aged less than 38 years with at least two embryos type I or II on the first two cycles. Sixty-three percent of patients (n=293 cycles) chose the SET with 21.5% pregnancies through fresh embryo transfer. The SET with frozen embryos has been completed on 708 cycles with 16.8% of pregnancies per transfer. The cumulative rate of pregnancies by puncture is 39% and the overall risk of multiple pregnancies has dropped to 12%. The SET associated with an effective embryo cryopreservation therefore allows to reduce the risk of multiple births while maintaining a satisfactory pregnancy cumulative rate.
Subject(s)
Embryo Transfer/methods , Adult , Cryopreservation , Female , France , Hospitals , Humans , Pregnancy , Pregnancy Rate , Pregnancy, Multiple/statistics & numerical dataABSTRACT
This paper describes the opportunities given by the synchrotron radiation techniques regarding the structural characterisation of biological entities. After a short recall on the characteristics of the synchrotron radiation, are described the experimental devices based on fluorescence X, wide angle X-ray scattering and X-ray absorption spectroscopy, which may applied for biological samples, especially in the field of stone analysis. Recent progresses in medical research using synchrotron radiation will be also discussed.
Subject(s)
Kidney Calculi/chemistry , Synchrotrons , Crystallography, X-Ray/instrumentation , Equipment Design , Humans , Spectrophotometry, Atomic/instrumentation , Synchrotrons/instrumentationABSTRACT
The short-range order in liquid binary Al-rich alloys (Al-Fe, Al-Ti) was studied by x-ray diffraction. The measurements were performed using a novel containerless technique which combines aerodynamic levitation with inductive heating. The average structure factors, S(Q), have been determined for various temperatures and compositions in the stable liquid state. From S(Q), the pair correlation functions, g(r), have been calculated. The first interatomic distance is nearly temperature-independent, whereas the first-shell coordination number decreases with increasing temperature for all the alloys investigated. For the Al-Fe alloys, room-temperature scanning electron microscropy (SEM) studies show the formation of a microstructure, namely the existence of Al(13)Fe(4) inclusions in the Al matrix.
ABSTRACT
Two new genera and species of Paramphistomidae (Trematoda, Digenea) are described from freshwater fish of Rondônia State, Brazil. Pronamphistoma cichlasomae gen. et sp. nov. from Cichlasoma severum (Heckel) is characterized as having a small, robust body with an anterior collar-like expansion, diverticula within the wall of the oral sucker and vitellaria in lateral fanshaped configurations. Micramphistoma ministoma gen. et sp. nov. from Hypopomus sp lacks oral diverticula, has anteriorly situated parallel tests and a very small postero-ventral acebtabulum. Neither of the new forms closely resembles any known genus
