Epiteliopatía en limpiaparabrisas en pacientes con blefaroespasmo o espasmo hemifacial / Lid wiper epitheliopathy in patients with blepharospasm and/or hemifacial spasm

Objetivo Evaluar la presencia de epiteliopatía en limpiaparabrisas en pacientes con blefaroespasmo o espasmo hemifacial antes del tratamiento habitual con toxina botulínica y 4 semanas después. Métodos Estudio prospectivo compuesto por 31 ojos de 20 pacientes con diagnóstico neurológico de espasmo hemifacial (9 ojos de 9 pacientes) y blefaroespasmo esencial (22 ojos de 11 pacientes). Se evaluaron antes y 4 semanas después de la infiltración con toxina botulínica diversos parámetros de superficie ocular con el cuestionario OSDI, test de Schirmer, tiempo de rotura lagrimal y tinciones de fluoresceína y verde de lisamina valoradas con el test de Oxford y el grado de afectación del limpiaparabrisas palpebral. Resultados El 100% de los pacientes presentaron afectación del limpiaparabrisas palpebral antes (30% grado leve y 70% moderado) y después del tratamiento con toxina (100% grado leve). El 75% de los pacientes presentaron un OSDI normal-leve antes del tratamiento; después del tratamiento fue del 80%. El tiempo de rotura lagrimal fue de 7,2±0,2 s antes y de 7,5±0,7 s después del tratamiento. El test de Schirmer fue de 11,4±5,5 y 12,5±5,5mm antes y después del tratamiento. El test de Oxford resultó patológico inicialmente en el 69,3% de los pacientes; tras 4 semanas solo fue patológico en el 54%. Conclusión La epiteliopatía en limpiaparabrisas está presente en el 100% de los pacientes con blefaroespasmo o espasmo hemifacial. El principal mecanismo fisiopatológico que la desencadena en estos pacientes es el aumento en el coeficiente de fricción, ya que el volumen y la estabilidad lagrimal son normales (AU)

Objective To evaluate the presence of wiper epitheliopathy in patients with blepharospasm and/or hemifacial spasm before and 4 weeks after routine treatment with botulinum toxin. Methods Prospective study comprising 31 eyes of 20 patients with neurological diagnosis of hemifacial spasm (9 eyes of 9 patients) and essential blepharospasm (22 eyes of 11 patients). Various ocular surface parameters were assessed before and 4 weeks after infiltration with botulinum toxin using the OSDI questionnaire, Schirmer's test, tear break-up time, fluorescein and lissamine green staining assessed with the Oxford test and the degree of involvement of the palpebral wiper. Results 100% of the patients had palpebral wiper involvement before (30% mild and 70% moderate) and after toxin treatment (100% mild). 75% of patients had mild-normal OSDI before treatment, after treatment it was 80%. The tear break-up time was 7.2±0.2 sg before and 7.5±0.7 sg after treatment. Schirmer's test was 11.4±5.5 and 12.5±5.5mm before and after treatment. The Oxford test was initially pathological in 69.3% of patients, after 4 weeks it was pathological in only 54%. Conclusion Wiper epitheliopathy is present in 100% of patients with blepharospasm and/or hemifacial spasm. The main pathophysiological mechanism that triggers it in these patients is the increase in the coefficient of friction, as tear volume and stability are norma (AU)

Lid wiper epitheliopathy in patients with blepharospasm and/or hemifacial spasm.

OBJECTIVE: To evaluate the presence of wiper epitheliopathy in patients with blepharospasm and/or hemifacial spasm before and 4 weeks after routine treatment with botulinum toxin. METHODS: Prospective study comprising 31 eyes of 20 patients with neurological diagnosis of hemifacial spasm (9 eyes of 9 patients) and essential blepharospasm (22 eyes of 11 patients). Various ocular surface parameters were assessed before and 4 weeks after infiltration with botulinum toxin using the OSDI questionnaire, Schirmer's test, tear break-up time (BUT), fluorescein and lissamine green staining assessed with the Oxford test and the degree of involvement of the palpebral wiper. RESULTS: 100% of the patients had palpebral wiper involvement before (30% mild and 70% moderate) and after toxin treatment (100% mild). 75% of patients had mild-normal OSDI before treatment, after treatment it was 80%. The BUT was 7.2 ±â€¯0.2 sg before and 7.5 ±â€¯0.7 sg after treatment. Schirmer's test was 11.4 ±â€¯5.5 and 12.5 ±â€¯5.5 mm before and after treatment. The Oxford test was initially pathological in 69.3% of patients, after 4 weeks it was pathological in only 54%. CONCLUSION: Wiper epitheliopathy is present in 100% of patients with blepharospasm and/or hemifacial spasm. The main pathophysiological mechanism that triggers it in these patients is the increase in the coefficient of friction, as tear volume and stability are normal.

Amblyopia due a dentigerous cyst. Case report and literature review.

PURPOSE: The goal of this article is to present an infrequent clinical case and to review the available literatura, with an emphasis on ophthalmological symptoms. METHODS: We present the case of a 4-year-old girl with a large dentigerous cyst on the maxillary bone, who had long-standing unilateral epiphora associated with progressive ocular dystopia, facial asymmetry and ipsilateral amblyopia. A multidisciplinary approach was taken by the maxillofacial surgery, ophthalmology and optometry teams. This included systemic antibiotic administration, surgical cyst drainage and amblyopia treatment. The literature review was carried out in the MEDLINE database through the free electronic access to PubMed in March 2020. RESULTS: At the 6-month follow-up, the patient was asymptomatic. The most common symptoms of dentigerous cysts are epiphora 36.8%, ocular dystopia 31.2%, diplopia 21.1%, proptosis, nasolacrimal duct obstruction and blurred vision at 10.5%. Amblyopia has not been reported. CONCLUSIONS: Dentigerous cysts are benign odontogenic cysts, which can be found in the jaw and less frequently on the maxillary bone. They are usually asymptomatic, and the occurrence of ophthalmic complications is very infrequent. Multidisciplinary management is essential to avoiding long-term morbidity of maxillary dentigerous cysts and should include an ophthalmologist.

New methods to remove volatile organic compounds from post-consumer plastic waste.

While the annual European demand for polyolefins is 25 million tonnes, only 3 million tonnes of recycled polyolefins find their place in the market, despite collecting 15 million tonnes of post-consumer polyolefins every year. Brand owners of care products are showing their interest in using post-consumer recycled plastics for their packaging. However, there is a general concern in using these materials, as recycled polymers can contain unwanted substances that may expose the consumer to health risks or make the packaging unattractive. Accordingly, the presence of these contaminants narrows the market opportunity of recycled plastics to applications with low-quality requirements and in which the product is not in direct contact with the consumer. Though mechanical recycling is the most widespread solution presents limitations in terms of decontamination, as only superficial substances are removed. Thereby, the volatile organic compounds (VOCs) migrated to the polymer matrix remain inside. Consequently, there is a need to find a solution to purify recycled plastics and increase their market share. This study focuses on removing VOCs from post-consumer recycled HDPE through two innovative methods applied for the first time in this field, steam stripping and polyethylene glycol (PEG) extraction. The methodology implemented to analyze the volatile organic compounds in HDPE was HS-SPME-GC/MS. Both methods showed a decrease above 70% in the VOCs content compared to extrusion-degassing. Moreover, these were compared to hot air stripping, a new technology developed at an industrial scale for the removal of VOCs. As a result, steam stripping improved efficiency in reducing the overall VOCs compared to hot air stripping. The PEG extraction method lowered the volatile polar compounds further than using hot air stripping. Additionally, none of these technologies modified the HDPE melting flow index.

Non-intentionally added substances (NIAS) in recycled plastics.

The demand for high quality recycled polymers in the European plastic industry is on the increase, likely due to the EU's Plastic Strategy intended to implement the circular economy model in this sector. The problem is that there is not enough recycled plastic in the market. In terms of volume, post-consumer plastic waste could be key to meet the current and future demand. Nevertheless, a high level of contamination originated during the product's life cycle restricts its use. The first step to change this must be identifying the undesired substances in post-consumer plastics and performing an effective risk assessment. The acquired knowledge will be fundamental for the development of innovative decontamination technologies. In this study, 134 substances including volatile and semi-volatile compounds have been identified in recycled LDPE and HDPE from domestic waste. Headspace and solvent extraction followed by GC/MS were used. The possible origin of each substance was studied. The main groups were additives, polymer and additives breakdown products, and contamination from external sources. The results suggest that recycled LDPE contains a broader number of additives and their degradation products. Some of them may cause safety concerns if reused in higher added value applications. Regarding recycled HDPE, the contaminants from the use phase are predominant creating problems such as intense odors. To reduce the number of undesired substances, it is proposed to narrow the variety of additives used in plastic manufacturing and to opt for separate waste collection systems to prevent cross-contamination with organic waste.

Synergy between pyroelectric and photovoltaic effects for optoelectronic nanoparticle manipulation.

The combined action of the pyroelectric (PY) and photovoltaic (PV) effects, exhibited by z-cut LiNbO3:Fe substrates, has been investigated for particle trapping and patterning applications. The novel hybrid procedure provides new possibilities and versatility to optoelectronic manipulation on LiNbO3 substrates. It has allowed obtaining periodic and arbitrary 2D patterns whose particle density distribution is correlated with the light intensity profile but can be tuned through ΔT according to the relative strength of the PV and PY effects. A relevant result is that the PY and PV contributions compete for a ΔT range of 1-20 °C, very accessible for experiments. Moreover, the synergy of the PY and PV has provided two additional remarkable applications: i) A method to measure the PV field, key magnitude for photovoltaic optoelectronic tweezers. Using this method, the minimum field needed to obtain a particle pattern has been determined, resulting relatively high, E~60 kV/cm, and so, requiring highly doped crystals when only using the PV effect. ii) An strategy combining the PY and PV to get particle patterning in samples inactive for PV trapping when the PV field value is under that threshold.

Mapeo de los cambios de grosor en el glaucoma de las capas retinianas maculares segmentadas usando el programa de polo posterior de la tomografía de coherencia óptica de dominio espectral / Mapping the thickness changes on retinal layers segmented by spectral-domain optical coherence tomography using the posterior pole program in glaucoma

Objetivos: Evaluar los cambios de las capas retinianas maculares (CRM) usando el programa de OCT de polo posterior (PP) en el glaucoma primario de ángulo abierto (GPAA). Material y métodos: Ciento veintiocho pacientes con GPAA y 103 controles sanos con mapas de PP (rejilla macular 8×8) obtenidos mediante SD-OCT fueron incluidos. Solo un ojo por paciente fue considerado. Entonces 9 CRM se segmentaron automáticamente mediante un software prototipo obteniendo: capas de fibras nerviosas maculares, capa de células ganglionares (GCL), plexiforme interna, nuclear interna (INL), plexiforme+nuclear externa, capa de fotorreceptores, epitelio pigmentario de la retina (RPE) y retina externa completa. Se obtuvieron los valores de grosor de las 64 celdas de la rejilla para cada una de las CRM y se calcularon los grosores promedio de los hemisferios superior e inferior. Se realizó una comparación de los grosores promedio de dichos hemisferios y de los grosores celda a celda entre los 2 grupos. Las diferencias en comparaciones celda a celda fueron representadas mediante mapas de calor para cada CRM. Resultados: Al comparar los grosores de los hemisferios se encontraron adelgazamientos en capas de fibras nerviosas maculares, capa de células ganglionares y plexiforme interna y engrosamientos en INL, fotorreceptores y RPE en GPAA. Los mapas de calor mostraron patrones de adelgazamiento simétricos entre ambos hemisferios (superior e inferior) en capas de la retina interna (excepto INL) y patrones de engrosamiento asimétricos en las CRM externas en GPAA. Conclusiones: Existen patrones de cambio en el grosor en todas las CRM en el GPAA estudiadas mediante el programa PP. Los adelgazamientos de las capas internas (excepto INL) y los engrosamientos de las externas en el GPAA presentan diferentes patrones de simetría respecto al meridiano horizontal

Objectives: To evaluate changes in retinal layers of the macula (mRLs) using OCT posterior pole program (PPP) in primary open-angle glaucoma (POAG). Material and methods: The study included 128 patients with POAG and 103 healthy controls who had PPP maps (macular grid 8×8) drawn by SD-OCT. Only one eye per patient was studied. The 9 mRLs were automatically segmented by prototype software, obtaining: a macular retinal nerve fibre layer (mRNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform+nuclear layer, photoreceptor layer, retinal pigment epithelium (RPE), outer retina and RPE+outer retina. Thickness values were obtained on 64 cells of the grid for each mRL, and mean thickness of superior and inferior hemispheres were calculated. Comparisons of mean thickness of these hemispheres and thickness of each cell between groups were determined. Differences in the cell by cell comparisons were represented quantitatively by heat maps for each mRL. Results: Photoreceptors and RPE were found in POAG group when comparing thickness of hemispheres, thinning of mRNFL, GCL, IPL, and thickening of INL. Heat maps showed symmetrical thinning patters between superior and inferior hemispheres in inner retinal layers (except for INL) and asymmetrical thickening patters in outer retinal layers in GPAA group. Conclusions: There are thickness changes in all mRLs in POAG, when studied by PPP. Thinning of inner layers (except for INL), and thickening of outer layers in POAG show different symmetry patterns in relation to horizontal meridian

Mapping the thickness changes on retinal layers segmented by spectral-domain optical coherence tomography using the posterior pole program in glaucoma. / Mapeo de los cambios de grosor en el glaucoma de las capas retinianas maculares segmentadas usando el programa de polo posterior de la tomografía de coherencia óptica de dominio espectral.

OBJECTIVES: To evaluate changes in retinal layers of the macula (mRLs) using OCT posterior pole program (PPP) in primary open-angle glaucoma (POAG). MATERIAL AND METHODS: The study included 128 patients with POAG and 103 healthy controls who had PPP maps (macular grid 8×8) drawn by SD-OCT. Only one eye per patient was studied. The 9 mRLs were automatically segmented by prototype software, obtaining: a macular retinal nerve fibre layer (mRNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform+nuclear layer, photoreceptor layer, retinal pigment epithelium (RPE), outer retina and RPE+outer retina. Thickness values were obtained on 64 cells of the grid for each mRL, and mean thickness of superior and inferior hemispheres were calculated. Comparisons of mean thickness of these hemispheres and thickness of each cell between groups were determined. Differences in the cell by cell comparisons were represented quantitatively by heat maps for each mRL. RESULTS: Photoreceptors and RPE were found in POAG group when comparing thickness of hemispheres, thinning of mRNFL, GCL, IPL, and thickening of INL. Heat maps showed symmetrical thinning patters between superior and inferior hemispheres in inner retinal layers (except for INL) and asymmetrical thickening patters in outer retinal layers in GPAA group. CONCLUSIONS: There are thickness changes in all mRLs in POAG, when studied by PPP. Thinning of inner layers (except for INL), and thickening of outer layers in POAG show different symmetry patterns in relation to horizontal meridian.

Diffractive optical devices produced by light-assisted trapping of nanoparticles.

One- and two-dimensional diffractive optical devices have been fabricated by light-assisted trapping and patterning of nanoparticles. The method is based on the dielectrophoretic forces appearing in the vicinity of a photovoltaic crystal, such as Fe:LiNbO3, during or after illumination. By illumination with the appropriate light distribution, the nanoparticles are organized along patterns designed at will. One- and two-dimensional diffractive components have been achieved on X- and Z-cut Fe:LiNbO3 crystals, with their polar axes parallel and perpendicular to the crystal surface, respectively. Diffraction gratings with periods down to around a few micrometers have been produced using metal (Al, Ag) nanoparticles with radii in the range of 70-100 nm. Moreover, several 2D devices, such as Fresnel zone plates, have been also produced showing the potential of the method. The diffractive particle patterns remain stable when light is removed. A method to transfer the diffractive patterns to other nonphotovoltaic substrates, such as silica glass, has been also reported.

Particle trapping and structuring on the surface of LiNbO3:Fe optical waveguides using photovoltaic fields.

We report on the successful trapping and patterning of micro- and nanometric particles on the surface of LiNbO3 optical waveguides via photovoltaic tweezers. A waveguide configuration is used for the first time combined with this recently proposed technique. The electric field pattern is generated by light propagating in the waveguide, allowing us to separate the light channel with the region in which particles are deposited. Results on micro- and nanoparticle trapping, by two different deposition methods on two types of planar waveguides (by soft proton exchanged and by swift heavy ion irradiation), and using single-beam and two-beam interferometric configuration, are presented and discussed.

NiTi superelastic orthodontic archwires with polyamide coating.

Twenty orthodontic archwires with 55.2% Ni and 44.8% Ti (% weight) were subjected to a dipping treatment to coat the NiTi surface by a polyamide polymer. It has been selected a Polyamide 11 due to its remarkable long lasting performance. The transformation temperatures as well as the transformation stresses of the NiTi alloy were determined in order to know whether the coating process can alter its properties. The adhesive wear tests have been demonstrated that the wear rates as well as the dynamic friction coefficients µ of polymer coated wires are much lower than metallic wires. The corrosion studies have shown that the use of this polymer, as coating, seals the NiTi surface to prevent corrosion and the release of nickel ions. The average decrease of Ni ions release due to this coating is around 85%.

Analysis of photorefractive optical damage in lithium niobate: application to planar waveguides.

Photorefractive optical damage of single beams in LiNbO(3) crystals is analyzed within a framework of two photoactive centres (Fe(2+)/Fe(3+) and Nb(Li) (4+)/Nb(Li) (5+)). It compares model simulations and significant experimental measurements in LiNbO(3) waveguides. A good agreement is found in the performed comparisons: photovoltaic currents, refractive index changes and, especially relevant, in degraded beam-profiles. The progress of the degraded wavefront has been simulated by implementing a finite-difference beam-propagating method which includes the model equations. These results, together with previous ones on grating recording, provide a comprehensive, satisfactory explanation of most important questions on photorefractive optical damage.

Cancer mortality trends in Spain: 1980-2007.

INTRODUCTION: Since the 1990s, there has been a downturn in mortality for specific types of tumour in Spain and other European countries. This article reports on the current situation of cancer mortality in Spain, as well as mortality trends over the period 1980-2007, and provides an overview of cancer mortality trends in Europe in recent years. METHODS: Data were sourced from the National Statistics Institute (Instituto Nacional de Estadística - INE) and the World Health Organization mortality database. Mortality trends were studied using change-point Poisson regression models. RESULTS: All-cancer mortality decreased in both sexes from 1980 to 2007, owing to the fact that the tumours responsible for the highest number of deaths registered declining trends from the mid-1990s onwards. In men, mortality due to stomach and prostate cancer fell by >3% per annum in the last 10 years of the study period. In women, the largest contributions to the fall in cancer mortality were due to breast and colorectal cancers. In contrast, female mortality due to smoking-related cancers rose significantly. Within the European context, Spain's estimated 2005 mortality rates were intermediate for men and low for women. CONCLUSION: Cancer control is progressing in the right direction in Spain. Further interventions directed to reduce tobacco-related cancer mortality remain a priority, particularly for women.

Correlation between photorefractive index changes and optical damage thresholds in z-cut proton-exchanged-LiNbO(3) waveguides.

An interferometric Mach-Zehnder technique very recently developed has been applied to measure photorefractive index changes in different types of z-cut proton-exchanged planar waveguides in LiNbO(3). These measurements are complemented by determining the intensitythreshold for the onset of optical damage with a standard single-beam setup. In the intensity region just below the threshold-intensity obtained in the single-beam experiment the refractive index change is found to saturate at values around1x10(-4). Furthermore, we measure the dark conductivities of proton-exchanged waveguides by monitoring the decay of the light-induced index changes. Via the time constant of the decay we obtain dark conductivities of the order of about 5x10(-16) Omega (-1) cm (-1), that are negligible compared with the photoconductivity within the light intensity range used. The results of the measurements compare well with the predictions of a recent work, that uses a two-center model to explain the optical damage.

Understanding light intensity thresholds for catastrophic optical damage in LiNbO3.

The appearance of light intensity thresholds for catastrophic optical damage in LiNbO3 is satisfactorily explained by using a photorefractive model based on the Fe(2+)?Fe(3+) and NbLi(4+)?NbLi(5+) defect pairs. Model simulations of the photorefractive amplification gain as a function of the light intensity present sharp threshold behavior. A similar behavior is shown by the saturating refractive index change. In agreement with experiments, predicted thresholds appear shifted towards higher intensities (up to a 10(4) factor) when the Nb(Li) concentration is decreased or the temperature is increased. The model also explains very recent data on the threshold enhancement with the Fe(2+)/Fe(3+) ratio in optical waveguides.

Nonlinear optical waveguides generated in lithium niobate by swift-ion irradiation at ultralow fluences.

A novel method to produce optical waveguides is demonstrated for lithium niobate (LiNbO(3)). It is based on electronic excitation damage by swift ions, i.e., with energies at approximately 1 MeV/amu or above. The new technique uses high-energy medium-mass ions, such as Cl, with electronic stopping powers above the threshold value for amorphization (5-6 keV/nm), reaching the maximum value a few micrometers inside the crystal. At the ultralow fluence regime (10(12)-10(13) cm(-2)) an effective nanostructured medium is obtained that behaves as an optical waveguide where light propagates transversally to the amorphous nanotracks created by every single impact. The method implies a reduction of 4 orders of magnitude with respect to He implantation. The optical waveguides present reasonable losses (~10 dB/cm) and significant second-harmonic generation (SHG) and electro-optic (EO) responses (>50% bulk) for the lowest fluences.

Optical damage control via the Fe2+/Fe3+ ratio in proton-exchanged LiNbO3 waveguides.

Intensity thresholds for the onset of optical damage in alpha-phase proton-exchanged waveguides on undoped LiNbO(3) have been increased from the substrate value to a factor 500 greater. This has been achieved by increasing the exchange time, which in turn increases the [Fe(2+)]/[Fe(3+)] ratio in the guide. Intensity thresholds have been measured with a single-beam configuration, while [Fe(2+)]/[Fe(3+)] ratios have been determined from decay measurements during optical erasure of photorefractive gratings. In heavily Fe-doped guides, thresholds are too small to be measured, but the dependence of the Fe(2+) absorption on the exchange time appears similar to undoped samples.

In utero alcohol exposure increases mammary tumorigenesis in rats.

Findings in humans and animal models suggest that in utero hormonal and dietary exposures increase later breast cancer risk. Since alcohol intake by adult women consistently increases their breast cancer risk, we wondered whether maternal alcohol consumption during pregnancy increases female offspring's mammary tumorigenesis. In our study, pregnant female rats were pair-fed isocaloric diets containing either 0 (control), 16 or 25 g alcohol kg(-1) feed between days 7 and 19 of gestation. These alcohol exposures generate blood alcohol levels that correspond to low and moderate alcohol consumption and are lower than those that induce foetal alcohol syndrome. Serum oestradiol levels were elevated in pregnant rats exposed to alcohol (P<0.003). When adult, female offspring of alcohol-exposed dams developed significantly more 7,12-dimethylbenz[a]anthracene -induced mammary tumours, compared to the controls (tumour multiplicity; mean+/-s.e.m., controls: 2.0+/-0.3, 16 g alcohol: 2.7+/-0.4 and 25 g alcohol: 3.7+/-0.4; P<0.006). In addition, the mammary epithelial tree of the alcohol-exposed offspring was denser (P<0.004) and contained more structures that are susceptible for the initiation of breast cancer (P<0.001). Immunohistochemical assessment indicated that the mammary glands of 22-week-old in utero alcohol-exposed rats contained elevated levels of oestrogen receptor-alpha (P<0.04) that is consistent with the changes in mammary gland morphology. In summary, maternal alcohol intake during pregnancy increases female offspring's mammary tumorigenesis, perhaps by programming the foetal mammary gland to exhibit persistent alterations in morphology and gene expression. It remains to be determined whether an increase in pregnancy oestradiol levels mediated alcohol's effects on offspring's mammary tumorigenesis.

Specific surface area of snow samples determined by CH4 adsorption at 77 K and estimated by optical microscopy and scanning electron microscopy.

Snow is a divided medium that can adsorb atmospheric trace gases. Evaluating the impact of the snow cover on atmospheric chemistry therefore requires the knowledge of the specific surface area (SSA) of snow. This paper compares the results of three methods used to measure or estimate the SSA of four snow samples: CH4 adsorption at 77 K, optical microscopy (OM), and scanning electron microscopy (SEM, used only on two samples). Within error bars, CH4 adsorption and OM yield similar results on three of the four snow samples. Values for the 4th sample are within a factor of 2. For both samples where CH4 adsorption, OM, and SEM are used, all three methods yield similar results, but CH4 adsorption always has a better accuracy and a much better precision. Thus, despite its ease of use, estimates from OM images are often not accurate enough to monitor the evolution of snow SSA. The main sources of error in the OM method are the difficulty to determine snow crystal thicknesses and to take into account the topography of the snow crystal surface. The combination of CH4 adsorption and OM or SEM can provide useful information on the evolution of both the SSA and the shape of snow crystals. This will be useful to evaluate the respective contributions of adsorption/desorption and sublimation/condensation processes to the impact of the snow cover on atmospheric chemistry.

Maternal and prepubertal diet, mammary development and breast cancer risk.

At present, we do not know what causes sporadic breast cancer. Environmental factors,particularly diet, appear to explain at least 70% of newly diagnosed breast cancers, but it is not clear what these factors are. We propose that the lack of progress in this area is due to a lack of considering the effect of timing of environmental and dietary exposures on the breast. The evidence provided above suggests that an in utero exposure to an estrogenic environment-including that caused by diet [high (n-6) PUFA or genistein]-increases breast cancer risk. This increase may be mediated by an increased presence of TEB in the mammary epithelial tree and increased ER-alpha levels, reduced ER-beta levels or both. Prepubertal estrogenic exposure, in contrast, reduces later risk of developing breast cancer. The protective effect of estrogens may be mediated by early epithelial differentiation, reduced presence of ER-alpha and increased levels of ER-beta in the mammary gland. The challenge we are now facing is to determine whether the data obtained mainly through the use of animal models is relevant to women and if so, how we might be able to modulate pregnancy and childhood estrogenic exposure by appropriate dietary modifications to reduce breast cancer risk in women.