The impact of foetal restrictions on mode of delivery in women with inherited bleeding disorders.

OBJECTIVES: Management of pregnancy in women with congenital bleeding disorders (CBD) is challenging and requires understanding of risks conferred to both the mother and the foetus. Some elements of labour management are considered to increase the risk of neonatal bleeding and are not recommended for neonates at risk of a significant bleeding disorder. The impact of these restrictions on obstetric outcomes in women with CBD is unknown. METHODS: We retrospectively reviewed obstetric outcomes in a large cohort of women with CBD attending a specialised obstetric/haematology antenatal clinic over a 6-year period. RESULTS: Ninety-four pregnancies in 76 women with a wide variety of CBDs were assessed. Foetal precautions were recommended in the majority of cases (88%). Twenty (21.2%) were delivered by elective Caesarean section (CS), predominantly for obstetric indications. Of the 63 women who laboured with foetal precautions in place, 6 (10%) had a CS that was performed because of these precautions. There was no neonatal bleeding but primary postpartum haemorrhage (PPH) occurred in 12.2% of women. CONCLUSIONS: These data show that foetal precautions in labour recommended for women with CBDs will influence mode of delivery in approximately 10% of cases. This is important information for counselling these women about labour and delivery.

Nitrogen-related intermediate band in P-rich GaNxPyAs1-x-y alloys.

The electronic band structure of phosphorus-rich GaNxPyAs1-x-y alloys (x ~ 0.025 and y ≥ 0.6) is studied experimentally using optical absorption, photomodulated transmission, contactless electroreflectance, and photoluminescence. It is shown that incorporation of a few percent of N atoms has a drastic effect on the electronic structure of the alloys. The change of the electronic band structure is very well described by the band anticrossing (BAC) model in which localized nitrogen states interact with the extended states of the conduction band of GaAsP host. The BAC interaction results in the formation of a narrow intermediate band (E- band in BAC model) with the minimum at the Γ point of the Brillouin zone resulting in a change of the nature of the fundamental band gap from indirect to direct. The splitting of the conduction band by the BAC interaction is further confirmed by a direct observation of the optical transitions to the E+ band using contactless electroreflectance spectroscopy.

Antiphase domain tailoring for combination of modal and 4¯ -quasi-phase matching in gallium phosphide microdisks.

We propose a novel phase-matching scheme in GaP whispering-gallery-mode microdisks grown on Si substrate combining modal and 4¯ -quasi-phase-matching for second-harmonic-generation. The technique consists in unlocking parity-forbidden processes by tailoring the antiphase domain distribution in the GaP layer. Our proposal can be used to overcome the limitations of form birefringence phase-matching and 4¯ -quasi-phase-matching using high order whispering-gallery-modes. The high frequency conversion efficiency of this new scheme demonstrates the competitiveness of nonlinear photonic devices monolithically integrated on silicon.

How long does a photoreceptor cell take to die? Implications for the causative cell death mechanisms.

The duration of cell death may allow deducing the underlying degenerative mechanism. To find out how long a photoreceptor takes to die, we used the rd1 mouse model for retinal neurodegeneration, which is characterized by phosphodiesterase-6 (PDE6) dysfunction and photoreceptor death triggered by high cGMP levels. Based on cellular data on the progression of cGMP accumulation, cell death, and survival, we created a mathematical model to simulate the temporal development of the degeneration and the clearance of dead cells. Both cellular data and modelling suggested that at the level of the individual cell, the degenerative process was rather slow, taking around 80 h to complete. Organotypic retinal explant cultures derived from wild-type animals and exposed to the selective PDE6 inhibitor zaprinast, confirmed the surprisingly long duration of an individual photoreceptor cell's death. We briefly discuss the possibility to link different cell death stages and their temporal progression to specific enzymatic activities known to be causally connected to cell death. This in turn opens up new perspectives for the treatment of inherited retinal degeneration, both in terms of therapeutic targets and temporal windows-of-opportunity.

Retinitis pigmentosa: rapid neurodegeneration is governed by slow cell death mechanisms.

For most neurodegenerative diseases the precise duration of an individual cell's death is unknown, which is an obstacle when counteractive measures are being considered. To address this, we used the rd1 mouse model for retinal neurodegeneration, characterized by phosphodiesterase-6 (PDE6) dysfunction and photoreceptor death triggered by high cyclic guanosine-mono-phosphate (cGMP) levels. Using cellular data on cGMP accumulation, cell death, and survival, we created mathematical models to simulate the temporal development of the degeneration. We validated model predictions using organotypic retinal explant cultures derived from wild-type animals and exposed to the selective PDE6 inhibitor zaprinast. Together, photoreceptor data and modeling for the first time delineated three major cell death phases in a complex neuronal tissue: (1) initiation, taking up to 36 h, (2) execution, lasting another 40 h, and finally (3) clearance, lasting about 7 h. Surprisingly, photoreceptor neurodegeneration was noticeably slower than necrosis or apoptosis, suggesting a different mechanism of death for these neurons.

Analysis of coherent surface wave dispersion and attenuation for non-destructive testing of concrete.

Rayleigh waves measurements are used to characterise cover concrete and mortar in the frequency range 60-180 kHz. At these frequencies, the wavelength is comparable to the size of the aggregates, and waves propagate in a multiple scattering regime. Acquired signals are then difficult to interpret due to an important incoherent part. The method proposed here is the study of the coherent waves, obtained by averaging signals over several configurations of disorder. Coherent waves give information on an equivalent homogeneous medium. To acquire a large amount of measurements with accuracy, an optimised piezoelectric source is used with a laser interferometer for reception. Adapted signal processing technique are presented to evaluate the coherent phase and group velocities and also the coherent attenuation parameter. The sensitivity of these three parameters with the properties of concrete is discussed, as well as the necessity to use coherent waves to obtain accurate results.

Dilemmas caused by endogenous pararetroviruses regarding the taxonomy and diagnosis of yam (Dioscorea spp.) badnaviruses: analyses to support safe germplasm movement.

The discovery of endogenous pararetroviral sequences (EPRVs) has had a deep impact on the approaches needed for diagnosis, taxonomy, safe movement of germplasm and management of diseases caused by pararetroviruses. In this article, we illustrate this through the example of yam (Dioscorea spp.) badnaviruses. To enable progress, it is first necessary to clarify the taxonomical status of yam badnavirus sequences. Phylogeny and pairwise sequence comparison of 121 yam partial reverse transcriptase sequences provided strong support for the identification of 12 yam badnavirus species, of which ten have not been previously named. Virus prevalence data were obtained, and they support the presence of EPRVs in D. rotundata, but not in D. praehensilis, D. abyssinica, D. alata or D. trifida. Five yam badnavirus species characterised by a wide host range seem to be of African origin. Seven other yam badnavirus species with a limited host range are probably of Asian-Pacific origin. Recombination under natural circumstances appears to be rare. Average values of nucleotide intra-species genetic distances are comparable to data obtained for other RNA and DNA virus families. The dispersion scenarios proposed here, combined with the fact that host-switching events appear common for some yam badnaviruses, suggest that the risks linked to introduction via international plant material exchanges are high.

Application of the scatter diagram technique to the scanning electron microscope: preliminary results from diamond.

Using primary beam energies E0 ranging from 0.2 to 15 keV and an in-lens detector, a series of images of the same region of an artificial microstructured diamond sample have been acquired in scanning electron microscopy. Next, the images were analysed by using a scatter diagram technique to underline the topographic contrast change and contrast reversal. The results obtained from 0.5 to 15 keV are discussed with the help of an expression derived from the constant loss model for the secondary electron yield delta of diamond, but including the respective roles of the angle of incidence, i, and of the angle of detection, alpha. More surprising is the quality of images obtained at a beam energy as low as 0.2 keV, and more difficult to explain is the significant contrast change between 0.2 keV and 0.5 keV. For the first time, scatter diagrams are used as a diagnostic tool in scanning electron microscopy, and after some improvements it is hoped that the experimental approach followed here may lead to quantitative estimates of the local tilts of a specimen surface.

Picosecond-resolution study of nonlinear scattering in carbon black suspensions in water and ethanol.

The physical origin of the nonlinear scattering of light induced by focusing of intense laser pulses onto carbon black suspensions (CBS's) is discussed through the interpretation of limitation, time-resolved pump-probe transmission, and angularly and time-resolved scattering experiments performed with picosecond resolution. Comparison of the experimental results performed on two different solutions of CBS's in water and in ethanol leads us to the conclusion that the scattering phenomenon begins most probably with growing microplasmas and that the influence of the solvent is significant only at longer times.

Optical architecture for programmable filtering of microwave signals.

We present a new optoelectronic architecture, based on parallel canceled delay lines, that performs programmable filtering of microwave signals. The new architecture can process optically carried microwave signals over frequency bandwidths as large as 20 GHz, with a time-frequency product up to 10(3). The operating principle of this structure is detailed, followed by the preliminary experimental demonstration at 1.2 GHz of a 40-dB rejection filter.