Identification of paramagnetic centers in irradiated Sn-doped silicon dioxide by first-principles

We present a first-principles investigation of Sn paramagnetic centers in Sn-doped vitreous silica based on calculations of the electron paramagnetic resonance (EPR) parameters. The present investigation provides evidence of an extended analogy between the family of Ge paramagnetic centers in Ge-doped silica and the family of Sn paramagnetic centers in Sn-doped silica for SnO2concentrations below phase separation. We infer, also keeping into account the larger spin-orbit coupling of Sn atoms with respect to Ge atoms, that a peculiar and highly distorted three-fold coordinated Sn center (i.e. the Sn forward-oriented configuration) should give rise to an orthorhombic EPR signal of which we suggest a fingerprint in the EPR spectra recorded by Chiodiniet al(2001Phys. Rev.B64073102). Given its structural analogy with theEα'and Ge(2) centers, we here name it as the 'Sn(2) center'. Moreover, we show that the single trapped electron at a SnO4tetrahedron constitutes a paramagnetic center responsible for the orthorhombic EPR signal reported in Chiodiniet al(1998Phys. Rev.B589615), confuting the early assignment to a distorted variant of the Sn-E' center. We hence relabel the latter orthorhombic EPR signal as the 'Sn(1) center' due to its analogy to the Ge(1) center in Ge-doped silica.

v-P2O5 micro-clustering in P-doped silica studied by a first-principles Raman investigation

Synthetic vitreous silica is currently the preferred material for the production of optical fibres because of the several excellent properties of this glass, e.g. high transmission in the visible and IR domains, high mechanical strength, chemical durability, and ease of doping with various materials. For instance, fiber lasers and amplifiers exploit the light amplification properties provided by rare-earth ions employed as dopants in the core of silica-based optical fibers. The structure and composition of the nearest neighbor shell surrounding rare-earth ions in silica-based optical fibers and amplifiers have been intensively debated in the last decade. To reduce aggregation effects between rare-earth ions, co-dopants such as phosphorus and aluminium are added as structural modifiers; phosphorus-doping, in particular, has proved to be very efficient in dissolving rare-earth ions. In this work, we provide further insights concerning the embedding of P atoms into the silica network, which may be relevant for explaining the ease of formation of a phosphorus pentoxide nearest-neighbor shell around a rare-earth dopant. In particular, by means of first-principles calculations, we discuss alternative models for an irradiation (UV, x-, γ-rays) induced paramagnetic center, i.e. the so called room-temperature phosphorus-oxygen-hole center, and its precursors. We report that the most likely precursor of a room-temperature phosphorus-oxygen-hole center comprises of a micro-cluster of a few (at least two) neighboring phosphate tetrahedra, and correspondingly that the occurrence of isolated [(O-)2P(=O)2]- units is unlikely even at low P-doping concentrations. In fact, this work predicts that the symmetric stretching of P=O bonds in isolated [(O-)2P(=O)2]- units appears as a Raman band at a frequency of ~1110 cm-1, and only by including at least another corner-sharing phosphate tetrahedron, it is shown to shift to higher frequencies (up to ~40 cm-1) due to the shortening of P=O bonds, thereby leading to an improved agreement with the observed Raman band located at ~1145 cm-1.

Colour differences in Caucasian and Oriental women's faces illuminated by white light-emitting diode sources

OBJECTIVE

To provide an approach to facial contrast, analysing CIELAB colour differences (ΔEab,10∗) and its components in women's faces from two different ethnic groups, illuminated by modern white light-emitting diodes (LEDs) or traditional illuminants recommended by the International Commission on Illumination (CIE).

METHODS

We performed spectrophotometric measurements of spectral reflectance factors on forehead and cheek of 87 young healthy women (50 Caucasians and 37 Orientals), plus five commercial red lipsticks. We considered a set of 10 white LED illuminants, representative of technologies currently available on the market, plus eight main illuminants currently recommended by the CIE, representative of conventional incandescent, daylight and fluorescent light sources. Under each of these 18 illuminants, we analysed the magnitude and components of ΔEab,10∗ between Caucasian and Oriental women (considering cheek and forehead), as well as for cheek-forehead and cheek-lipsticks in Caucasian and Oriental women. Colour-inconstancy indices for cheek, forehead and lipsticks were computed, assuming D65 and A as reference illuminants.

RESULTS

ΔEab,10∗ between forehead and cheek were quantitatively and qualitatively different in Orientals and Caucasians, but discrepancies with respect to average values for 18 illuminants were small (1.5% and 5.0% for Orientals and Caucasians, respectively). ΔEab,10∗ between Caucasians and Orientals were also quantitatively and qualitatively different both for forehead and cheek, and discrepancies with respect to average values were again small (1.0% and 3.9% for forehead and cheek, respectively). ΔEab,10∗ between lipsticks and cheek were at least two times higher than those between forehead and cheek. Regarding ΔEab,10∗ between lipsticks and cheeks, discrepancies with respect to average values were in the range 1.5-12.3%, although higher values of up to 54.2% were found for a white RGB LED. This white RGB LED provided the highest average colour-inconstancy indices: 17.1 and 11.5 CIELAB units, under reference illuminants D65 and A, respectively.

CONCLUSION

Colour contrasts in women's faces under CIE standard illuminants for outdoor and indoor conditions may be strongly altered using specific white LEDs. More research needs to be performed on the impact of spectral power distribution of light sources with high colour rendering indices on visual colour appearance of cosmetic products.

Strain-driven diffusion process during silicon oxidation investigated by coupling density functional theory and activation relaxation technique

The reaction of oxygen molecules on an oxidized silicon model-substrate is investigated using an efficient potential energy hypersurface exploration that provides a rich picture of the associated energy landscape, energy barriers, and insertion mechanisms. Oxygen molecules are brought in, one by one, onto an oxidized silicon substrate, and accurate pathways for sublayer oxidation are identified through the coupling of density functional theory to the activation relaxation technique nouveau, an open-ended unbiased reaction pathway searching method, allowing full exploration of potential energy surface. We show that strain energy increases with O coverage, driving the kinetics of diffusion at the Si/SiO₂ interface in the interfacial layer and deeper into the bulk: at low coverage, interface reconstruction dominates while at high coverage, oxygen diffusion at the interface or even deeper into the bottom layers is favored. A changing trend in energetics is observed that favors atomic diffusions to occur at high coverage while they appear to be unlikely at low coverage. Upon increasing coverage, strain is accumulated at the interface, allowing the oxygen atom to diffuse as the strain becomes large enough. The observed atomic diffusion at the interface releases the accumulated strain, which is consistent with a layer-by-layer oxidation growth.

Photoactivated processes in optical fibers: generation and conversion mechanisms of twofold coordinated Si and Ge atoms

In this work we present an extensive investigation of nanoscale physical phenomena related to oxygen-deficient centers (ODCs) in silica and Ge-doped silica by means of first-principles calculations, including nudged-elastic band, electron paramagnetic resonance parameters calculations, and many-body perturbation theory (GW and Bethe-Salpeter equation) techniques. We show that by neutralizing positively charged oxygen monovacancies we can obtain model structures of twofold Si and Ge defects of which the calculated absorption spectra and singlet-to-triplet transitions are in excellent agreement with the experimental optical absorption and photo-luminescence data. In particular we provide an exhaustive analysis of the main exciton peaks related to the presence of twofold defects including long-range correlation effects. By calculating the reaction pathways and energy barriers necessary for the interconversion, we advance a double precursory origin of the [Formula: see text] and Ge(2) centers as due to the ionization of neutral oxygen monovacancies (Si-Si and Ge-Si dimers) and as due to the ionization of twofold Si and Ge defects. Furthermore two distinct structural conversion mechanisms are found to occur between the neutral oxygen monovacancy and the twofold Si (and Ge) atom configurations. Such conversion mechanisms allow to explain the radiation induced generation of the ODC(II) centers, their photobleaching, and also their generation during the drawing of optical fibers.

First report of human infection due to Streptococcus devriesei

So far, Streptococcus devriesei, which belongs to the mutans streptococci group, has been incriminated in the formation of caries in Equidae. We report the first human infection due to this species in a 54-year-old man with gangrenous cholecystitis. The patient was treated successfully by cholecystectomy and ceftriaxone.

[Effectiveness of management of children with severe trauma in a pediatric trauma center and in an adult trauma center: A before-after study]

OBJECTIVE

To compare management of injured children in an adult trauma center (TC) with competencies in pediatric trauma care (2005-2007) and in a pediatric-only trauma center (2010-2012).

STUDY DESIGN

A before-after retrospective study.

PATIENTS AND METHODS

Fifty-nine children between 1 and 15 years of age admitted to the adult TC (2005-2007) were compared to 56 children admitted to the pediatric TC (2010-2012). Epidemiological data, severity scores, early outcome, and care duration in trauma resuscitation before whole-body CT were collected and compared between the two periods.

RESULTS

This study found no significant differences between the two periods in terms of care duration before the whole-body CT scan (28 min [18-40] vs 26.5 min [21-36], P=0.89) and early mortality (eight children [13.5%] vs ten children [17.8%], P=0.35).

CONCLUSION

With no differences in early management of injured children demonstrated, this study validates the organization within our pediatric trauma center. The effectiveness of management of children between 1 and 15 years of age with severe trauma seems to be similar in the two contexts.

CYP24A1 Mutations in a Cohort of Hypercalcemic Patients: Evidence for a Recessive Trait

CONTEXT

Loss-of-function mutations of CYP24A1 (which encodes the 25-OH-D3-24-hydroxylase) have recently been reported to cause hypercalcemia.

OBJECTIVES

The aims of this study were: 1) to evaluate the frequency of CYP24A1 mutations in patients with medical history of hypercalcemia; 2) to show the clinical utility of a simultaneous assay of serum 25-hydroxyvitamin D3 (25-OH-D3) and 24,25-dihydroxyvitamin D3 (24,25-[OH]2D3) by liquid chromatography tandem mass spectrometry (LC-MS/MS); and 3) to investigate biochemical parameters in heterozygous gene carriers with CYP24A1 mutations.

PATIENTS AND METHODS

We screened for CYP24A1 mutations in 72 patients with serum calcium levels > 2.6 mmol/L and PTH levels < 20 pg/mL and recruited 24 relatives after genetic counseling for subsequent investigations. Vitamin D metabolite concentrations were assessed in a subset of patients by LC-MS/MS and results expressed as a ratio (R) of 25-OH-D3:24,25-(OH)2D3.

RESULTS

Twenty-five patients with hypercalcemia (35%) harbored CYP24A1 variations. Twenty (28%) had biallelic variations, mostly found in subjects with nephrocalcinosis or renal stones (19/20). Five patients, all neonates, were heterozygous, without renal disease. We describe 15 new variations leading to loss-of-function according to pathogenicity prediction programs, and we functionally characterized 5 of them in vitro. A dramatic increase of R, usually >80, was found in patients harboring biallelic mutations providing evidence in vivo for the loss of CYP24A1 activity. In contrast, R value remains <25 in patients without CYP24A1 mutations. Subjects carrying one mutant allele, hypercalcemic individuals, as well as gene-carrier relatives, had a detectable 24,25-(OH)2D3 level and R < 25, indicating normal 24-hydroxylase activity.

CONCLUSION

CYP24A1 biallelic mutations are frequently found in patients presenting with hypercalcemia, low PTH, and renal disease. We confirm the accuracy and effectiveness of a novel blood test estimating the ratio between relevant vitamin D metabolites as a useful screening tool for CYP24A1 mutations. Haploinsufficiency is not associated with CYP24A1 deficiency.

Synthesis of the 19th ArgoSpine Symposium

After a short introduction of the meeting by the President 2015, Wilco Peul, the opening lecture was delivered by Bart Koes, who dealt with Health Technology Assessment and Guidelines. Then, it was the turn of Carmen Vleggert to show whether there was any Evidence for the Use of Implants in Spinal Stenosis. The final presentation of this session was delivered by Björn Strömqvist who dealt with Surgery for Lumbar Disc Herniation, patients' selection and outcomes. Developing the subject of "Do Not's", Jeremy Fairbank described the UK experience for Low Back Pain. Yves Coppens then took over and further elaborated on "Lucy's legacy". Prof. Coppens recalled that Lucy is a partial skeleton of a pre-human found in Ethiopia among other remains. Prof. Alan Crockard offered what he called "a whimsical view" of his practice of Craniocervical Surgery. Wafa Skalli was asked to speak about Finite Element Analysis of the Spine and Arts et Métiers Paris Tech where there is a long tradition of close collaboration between engineers and clinicians. Rune Hedlund, who will serve as 2016 Symposium President, further elaborated on Scoliosis with a focus on Unsolved Issues in Adolescent Idiopathic Scoliosis Treatment.

Synthesis of the 18th ArgoSpine Symposium

The subject of this 18th Symposium of ArgoSpine Association was the space of the intervertebral discs. Space of the intervertebral discs must be initially defined anatomically and histologically. A geometrical rebuilding in 3D is possible and must allow a modeling of the intervertebral discs. The physiology of the disc, its nutrition, must be known, in particular that of the center of the disc. The disc constitutes the base of the balance of the rachis, balances which can be only dynamic. The degenerative cascade by the loss of the proteoglycans involves the loss of the biomechanical properties of the disc. The consequences of this degenerative cascade are the base of all the vertebral pathology of origin of the intervertebral discs and even of the posterior articular facets. The origin of the pains and the diagnosis, especially at the lumbar level, are studied by the speakers. Traumatology of the intervertebral discs is the object of a particular chapter. Finally, the average therapeutic ones, that is, decompression of the intervertebral discs, fusion of the intervertebral discs, the recovery of mobility of the intervertebral discs, and the capacity of restoration of space of the intervertebral discs, are studied in detail. The infection of the disc is studied in detail.

Ma Huang, du complement alimentaire a l'abus

Dietary supplements containing Ma Huang (chinease ephedra) are available on the web sites and dietary shops in USA. They are widely promoted and used as a mean of weight reduction and energy enhancement. They contain Ma Huang alone or combined with Guarana (caffeine), creatine, St Jonh's wort, carnitine and are proposed with different labels. Numerous reports of adverse reactions and acute intoxication related to these products use were described in the medical literature. In the light of the severity of these cases, some of which resulted in permanent injury and death, the Food and Drug Administration has proposed limits on the dose and duration of use of such supplements. A review of 140 reports submitted to the FDA between June 1997 and March 1999, 47 % involved cardiovascular symptoms, 18 % neurological symptoms. Severe hypertension was the single most frequent adverse effect followed by tachycardia, myocardial infarction, stroke, seizure. Ten events resulted in death and 13 produced permanent impairment. In France, ampleness of the use of dietary supplements containing ephedra alkaloids is unknown. Two French recent severe poisonings (one with "ripped Fuel" for losing weight and the other with "Energy pills" in a body builder) show that there is serious health risks for the chronic users. Dietary supplements are not subject to control under "la Direction Générale de la Santé". Informations for general public, medical community and health-care authorities are necessary to be aware of potential health hazards of these products use.

Oxygen deficient centers in silica: optical properties within many-body perturbation theory

The electronic and optical properties of neutral oxygen vacancies, also called oxygen deficient centers (ODC(I)s), have been investigated in pure and germanium doped silica (both amorphous and α-quartz) through first-principles calculations. By means of density functional theory and many-body perturbation theory (GW approximation and the solution of the Bethe-Salpeter equation), we obtain the atomic and electronic structures as well as the optical absorption spectra of pure and Ge-doped silica in the presence of ODCs (SiODC(I)s and GeODC(I)s); our study allows us to interpret and explain the very nature of the optical features in experimental absorption spectra. The theoretical optical absorption signatures of these defects show excellent agreement with experiments for the SiODC(I)s, i.e. two absorption bands arise around 7.6 eV due to transitions between the defect levels. Our theoretical results also explain the experimental difficulty in measuring the GeODC(I) absorption band in Ge-doped silica, which was in fact tentatively assigned to a broad and very weak absorption signature, located between 7.5 and 8.5 eV. The influence of Ge-doping induced disorder on the nature of the defect-related optical transitions is discussed. We find that even if the atomic and electronic structures of SiODC(I) and GeODC(I) defects are relatively similar, the slight network distortion induced by the presence of the Ge atom, together with the increase in the Ge-Si bond asymmetry, completely changes the nature of the optical absorption edge.

Progressive osseous heteroplasia: a model for the imprinting effects of GNAS inactivating mutations in humans

CONTEXT

Heterozygous GNAS inactivating mutations are known to induce pseudohypoparathyroidism type 1a when maternally inherited and pseudopseudohypoparathyroidism when paternally inherited. Progressive osseous heteroplasia (POH) is a rare disease of ectopic bone formation, and studies in different families have shown that POH is also caused by paternally inherited GNAS mutations.

OBJECTIVE

Our purpose was to characterize parental origin of the mutated allele in de novo cases of POH and to draw phenotype/genotype correlations according to maternal or paternal transmission of a same GNAS mutation.

DESIGN AND SETTING

We conducted a retrospective study on patients addressed to our referral center for the rare diseases of calcium and phosphorus metabolism.

PATIENTS AND METHODS

We matched 10 cases of POH with cases of pseudohypoparathyroidism type 1a carrying the same GNAS mutations.

MAIN OUTCOME MEASURES

The parental origin of the mutated allele was studied using informative intragenic polymorphisms and subcloning of PCR products.

RESULTS

Paternal origin of GNAS mutations was clearly demonstrated in eight POH cases including one patient with mutation in exon 1. Genotype/phenotype analyses suggest that there is no direct correlation between the ossifying process and the position of the inactivating GNAS mutation. It is, however, more severe in patients in whom origin of the mutation is paternal. Severe intrauterine growth retardation was clearly evidenced in paternally inherited mutations.

CONCLUSIONS

Clinical heterogeneity makes genetic counseling a delicate matter, especially in which paternal inheritance is concerned because it can lead to either a mild expression of pseudopseudohypoparathyroidism or a severe expression of POH.

[Epigenetics and pseudohypoparathyroidism]

Parental imprinting and the type of the genetic alteration play a determinant role in the phenotype expression of GNAS locus associated to pseudohypoparathyroidism (PHP). This imprint is tissue-specific, mainly localized in the kidney and the thyroid. Only the maternal allele is expressed at this level. An alteration in the coding sequence of the gene leads to an haplo-insufficiency and a dysmorphic phenotype (Albright's syndrome). If the alteration is on the maternal allele, there is a hormonal resistance to the PTH at the kidney level and to the TSH at the thyroid level. The phenotype is known as a PHP1a. If the alteration is on the paternal allele, there are few clinical signs with no hormonal resistance and the phenotype is known as pseudo-pseudo-hypoparathyroidism (PPHP). Methylation anomalies of GNAS locus, in particular of exon 1A, are responsible for a lack of expression of Gαs at kidney and thyroid levels only. If these anomalies concern the maternal allele (the only one expressed) with a paternal pattern, there is no haplo-insufficiency and no dysmorphic syndrome. The hormonal resistance is yet again limited to PTH and TSH. The phenotype is known as PHP1b. In the familial forms, these methylation anomalies are associated with a deletion of the syntaxine 16 gene in the maternal allele. This gene contains probably the imprinting center of the locus.

KiSS-1 and GPR54 genes are co-expressed in rat gonadotrophs and differentially regulated in vivo by oestradiol and gonadotrophin-releasing hormone

Kisspeptin, the product derived from KiSS-1, and its cognate receptor, GPR54, both exert a role in the neuroendocrine control of reproduction by regulating gonadotrophin-releasing hormone (GnRH) secretion. In the present study, we demonstrate, using dual immunofluorescence with specific antibodies, that the KiSS-1 and GPR54 genes are both expressed in rat gonadotrophs. All luteinising hormone beta-immunoreactive (LH beta-ir) cells were stained by the KiSS-1 antibody but some kisspeptin-ir cells were not LH beta positive; thus, we cannot exclude the possibility that kisspeptins are expressed in other pituitary cells. All GPR54-ir are co-localised with LH beta cells, but only a subset of LH beta cells are stained with the GPR54 antibody. Using the real-time reverse transcription-polymerase chain reaction (RT-PCR), we found that the expression of KiSS-1 and GPR54 is differentially regulated by steroids. In the female, KiSS-1 mRNA levels dramatically decreased following ovariectomy (OVX), and this decrease was prevented by administration of 17beta-oestradiol (E(2)), but not by administration of GnRH antagonist or agonist. Administration of E(2) in OVX rats receiving either GnRH antagonist or agonist clearly shows that E(2) acts directly on the pituitary to positively control KiSS-1 expression. In OVX rats, administration of the selective oestrogen receptor (ER)alpha ligand propylpyrazoletriol, but not the selective ER beta ligand diarylpropionitrile, mimics this effect. By contrast, our study shows that GPR54 expression is positively regulated by GnRH and negatively controlled by chronic exposure to E(2). In summary, our data document for the first time that, in the female rat pituitary, KiSS-1 expression is up-regulated by oestradiol, similarly to that seen in the anteroventral periventricular nucleus of the hypothalamus. Conversely, GPR54 is up-regulated by GnRH, which exclusively targets gonadotrophs.

Liver and muscle metabolic changes induced by dietary energy content and genetic selection in rainbow trout (Oncorhynchus mykiss)

We combined genetic selection and dietary treatment to produce a model to study metabolic pathways involved in genetic and nutritional control of fat deposition in fish muscle. Two experimental lines of rainbow trout, selected for a lean (L) or fat (F) muscle, were fed with diets containing either 10 or 23% lipids from the first feeding, up to 6 mo. At the end of the feeding trial, trout were distinguished by very different muscle fat content (from 4.2 to 10% wet weight), and line x diet interactions were observed for parameters related to fat storage. We analyzed the activity and gene expression of key enzymes involved in lipid metabolism (fatty acid synthase, hydroxyacyl-CoA dehydrogenase, carnitine palmitoyltransferase 1 isoforms, and peroxisome proliferator-activated receptor alpha) and glycolysis (hexokinase 1 and pyruvate kinase) as well as energy production (isocitrate dehydrogenase, citrate synthase, and cytochrome oxidase) in the liver and the white muscle of rainbow trout. The lipid-rich diet repressed the activity of the lipogenic enzymes and stimulated enzymes involved in fatty acid oxidation and glycolysis in liver but had little effect on muscle enzymes assessed in this study. Regarding the selection effect, enzyme activity and expression suggest that compared with the L line, the F line presented reduced hepatic fatty acid oxidation as well as reduced mitochondrial oxidative capacities and enhanced glucose utilization in both liver and muscle. Very few line x diet interactions were found, suggesting that the two factors (i.e., dietary energy content and selection) used in this study to modify muscle lipid content exerted some additive but mostly independent effects on these metabolic actors.

[Mechanisms of action of targeted therapies... and mechanisms of resistance]

EGFR is a tyrosine kinase (TK) receptor overexpressed in lung adenocarcinomas. EGF binding to EGFR leads to K-Ras activation, promoting signaling of division, survival, and cell invasion. Adenocarcinomas addicted to EGFR signaling pathway for proliferation (10%), exhibit mutations of EGFR tyrosine kinase domain. Inhibition of these mutated receptors favors apoptosis signaling, taking account for dramatic tumoral responses. On the other side, 30% of adenocarcinomas have K-Ras mutations making the cells resistant to EGFR TK inhibitors (TKI). Secondary resistances are induced in 50% of initially sensitive tumors by an additional EGFR mutation (T790M), lowering receptor affinity for the inhibitor. The use of high affinity inhibitors ("irreversible") is tested in those patients. In 30% of cases, secondary resistance to TKI is induced by amplification of C-Met gene that encodes for another TK receptor, stimulating cell survival by substitution to EGFR. The use of C-Met inhibitors could overcome this kind of resistance. Angiogenesis is an early event in lung cell cancerization of which main cell signaling uses TK receptors to VEGF. Inhibition of this pathway consists in a major therapeutic advance in solid tumors. Finally, stimulation of anti-tumoral immunological response using anti-tumoral "vaccination", or agonists of innate immunity receptors, has given encouraging therapeutic preliminary results in lung cancer but needs phase 3 validation trials.

Structural analysis and application to brain imaging

Our goal is to organize the ElectroEncephaloGram (EEG) signal so as to describe and image various brain activities. Our work is based on a data structure, a graph, which sums up the brain activity in the spatial, temporal and frequency domains. From the information contained in the time-frequency map of EEG signals, a graph is constructed. In order to analyze the complexity of the signal, our method is based on a multi-scale approach with several levels of information extraction. To compare different EEG signals, we use techniques of graph-matching with our data structure. The developed algorithm is based on the A* algorithm that allows us to compare variations of the recorded EEG in term o f latency, frequency, energy and activated areas. The results of this project show first, that the graph is an appropriate tool to reduce the cortical activity complexity, and second, that graph-matching offers some interesting perspectives in order to describe functional brain activity.

Difficulty for oxygen to incorporate into the silicon network during initial O2 oxidation of Si(100)-(2×1)

First principles calculations and scanning tunneling microscopy studies of the oxidation of Si(100)-(2x1) surfaces by molecular oxygen reveal that the surface silanone (O)(Si=O) species is remarkably stable, constituting the key intermediate for initial oxidation. The propensity for oxygen to remain within the top surface layer as opposed to incorporating within Si-Si backbonds is surprisingly high. This resistance to incorporation into a cubic lattice even at higher coverages could be a factor to facilitate surface amorphization in subsequent steps.

[New biological treatments for lung cancer]

Therapies targeted on cell signal pathways that control cell division and tumor angiogenesis have been developed over the last five years for non small cell lung cancer (NSCLC) with some amazing results, in subgroups of selected patients, predicting more significant success in the upcoming years. Compounds targeted on EGF tyrosine kinase receptor have been tested in large clinical phase 2 and 3 trials including thousands of patients. Their efficacy has been proved, in second and third line trials, after first line cisplatin-based chemotherapy for non-mucinous adenocarcinoma in non-smokers, women and Asian patients. Response rates vary from 10% in non selected Caucasian patients to 40% in non-smoking Asian patients with long survivals. Therapeutic targeting improves success rates, either relying on EGFR gene amplification detection by FISH, or search for EGFR tyrosine kinase domain mutations. Commercial kits are available for routine molecular diagnosis of domain mutations potentially enabling molecular targeting in addition to clinical targeting. Angiogenesis inhibitors, especially monoclonal antibody to VEGF, bevacizumab, have also been developed in the last few years. Bevacizumab associated with classical cytotoxic chemotherapy led, in selected patients (with non squamous cell lung cancer and no past history of cardiovascular disease) to an increase of median survival to more than 12 months with tolerable toxicity. Other drugs that have both anti-EGFR activity and anti-angiogenic properties will be soon developed, since future bioactive anti-cancer drugs will probably be multi-targeted drugs.

Color image retrieval: from low-level representation to high-level concept

This work takes place within the framework of color image retrieval in specialized databases. A CBIR scheme has been proposed allowing to use a description thanks to low-level features in the framework of a high-level concept using a knowledge management. Starting from a representation of the three most frequently used features i.e. color, texture and shape, cooperation techniques are proposed in order to use the expert knowledge in the combination process. Two types of cooperation have been defined; the first is without categorization and the second with categorization. The second approach allows to make a selection of the query category in order to simplify queries in large image databases. Finally, in order to avoid the standard relevance feedback stage, a competition technique has been proposed allowing an unsupervised refinement of the submitted query. The proposed techniques have shown their performances and their robustness and are generalizable to all types of image databases.

[The place of targeted therapies in the management of non-small cell bronchial carcinoma. Biological mechanisms of bronchial carcinogenesis: towards a better understanding and the development of new therapies]

An increasing knowledge of cell signal transduction pathways has led to a better understanding of multi-step bronchial carcinogenesis. This new data has been used to design new drugs targeting specific proteins involved in epithelial cell transformation. New biotherapies are a major part of the evolving strategies to fight lung cancer and actually represent a true revolution for subsets of patients. Future treatments in lung cancer patients will be tailored on the basis of routine molecular analysis of surgical and bronchoscopic biopsy specimens. Tyrosine-kinase EGFR inhibitors and VEGF inhibitors are the first molecules in this new class of therapies for lung cancer. Their mechanism of action and the resistance mechanisms that occur with these new drugs continue to be analysed, and this knowledge will help to improve the targeting of therapeutic regimes. In the same way, a better knowledge of the molecular resistance mechanisms to classical chemotherapy agents (platinum compounds, anti-metabolite agents or tubulin-interacting agents) will lead to a tailored use of these drugs, based again on the molecular characteristics of tumor specimens. The surprisingly long survivals observed among subsets of 'molecular-selected' patients, treated with frontline EGFR tyrosine-kinase inhibitors (TKIs) in still limited prospective clinical trials, could herald significant improvement in the global efficacy of lung cancer therapeutics.

Routine detection of EGFR mutations in patients with NSCLC: A comparative study of three alternative methods in 105 patients

7184

Background: The efficacy of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) has been reported in lung adenocarcinoma patients with tumoral EGFR mutations. Those mutations were found mainly by direct genomic sequencing on snap-frozen surgical specimens. Conversely, TKIs are used in metastatic patients who do not undergo tumor resection. In these patients, there is a need for routine sensitive molecular procedures, to overcome the small size of non-surgical bronchoscopy paraffin-embedded biopsy samples. Methods: Patients were selected on clinical and pathological characteristics: never (n = 43) or former smokers, patients with non-squamous NSCLC (n = 105) or patients with bronchioloalveolar adenocarcinoma (n = 34). Direct genomic sequencing assay was performed as reported elsewhere. Denaturing, high-performance, liquid chromatography (DHPLC) assay was performed with EGFR-specific primers that amplify exons 18, 19, and 21. A multiplex, allele-specific, oligonucleotide PCR (MASO-PCR) assay was carried out with a set of primers that identify the 14 most frequent molecular events described for the EGFR gene, which covers 90% of EGFR gain-of-function mutations described to date. Results: 123 samples were screened from 105 non-squamous NSCLC patients (female/male ratio = 0.84). Non-surgical biopsy specimens were available in 38 patients. EGFR mutations were detected by at least two of three procedures in 18/105 patients (17%). In paraffin-embedded specimens with low tumor content, EGFR heterozygous mutations were found either by MASO-PCR alone (n = 2, confirmed in the matched surgical sample by another procedure), or both by MASO-PCR and DHPLC (n = 16); they were missed by nucleotidic sequencing in 6 samples. 18 patients received TKI. 6 dramatic responses were achieved in patients with EGFR mutation, while no mutation could be found in non-responsive patients. Overall disease control was obtained in 8/18 patients (44%). Conclusions: MASO-PCR and DHPLC appear more sensitive than direct sequencing in non-surgical paraffin-embedded biopsies, which represent the bulk of samples in lung cancer patients. We propose that the cost-effective MASO-PCR be used for routine screening of EGFR mutations in NSCLC patients.

No significant financial relationships to disclose.

Identifying primary stressors impacting macroinvertebrates in the Salinas River (California, USA): relative effects of pesticides and suspended particles

Laboratory dose-response experiments with organophosphate and pyrethroid pesticides, and dose-response experiments with increasing particle loads were used to determine which of these stressors were likely responsible for the toxicity and macroinvertebrate impacts previously observed in the Salinas River. Experiments were conducted with the amphipod Hyalella azteca, the baetid mayfly Procloeon sp., and the midge Chironomus dilutus (Shobanov, formerly Chironomus tentans). The results indicate the primary stressor impacting H. azteca was pesticides, including chlorpyrifos and permethrin. The mayfly Procloeon sp. was sensitive to chlorpyrifos and permethrin within the range of concentrations of these pesticides measured in the river. Chironomus dilutus were sensitive to chlorpyrifos within the ranges of concentrations measured in the river. None of the species tested were affected by turbidity as high as 1000 NTUs. The current study shows that pesticides are more important acute stressors of macroinvertebrates than suspended sediments in the Salinas River.

[Influenza in pediatric intensive cure unit]

OBJECTIVES

The purpose was to identify clinical presentation leading to admission to PICU of children affected by influenza, to describe predisposing factors and outcome and to propose preventive measures.

METHODS

Ten years (1989-1999) retrospective study carried out in the ten beds PICU. Every child in PICU with an influenza positive culture was enrolled.

RESULTS

Twenty four cases collected, aged two weeks-15 years (m =43 months), 19 males. Acute respiratory failure (16/24 =67%) was the first manifestation: pneumonia (13), bronchiolitis (2), status asthmaticus (1). Eleven children had underlying diseases including five immunocompromized. Thirteen patients required mechanical ventilation (mean duration: 22 days), seven developed ARDS (4 immunocompromized) and three died. Central nervous system was the second system affected (8 cases). Four exhibited a chronical cerebral disease and five presented afebrile status epilepticus which required i.v. barbiturates and mechanical ventilation (mean duration: 22 hours). One presented encephalitis, one an apparent life-threatening event, both had a favorable outcome. One child exhibited severe hyperpyrexia and died from multiorgan failure.

CONCLUSION

Severe forms of influenza are rare in children but may lead to life-threatening conditions and death(16.5%). Most occur in children with underlying disease, particularly immunocompromized who may exhibit ARDS.

Pneumocystoses graves en réanimation pédiatrique étude rétrospective 1980–2002

OBJECTIVE

The objective of this study was to ascertain the clinical and epidemiological characteristics of Pneumocystis carinii pneumonia (PCP) cases admitted to the Pediatric Intensive Care Unit (PICU).

PATIENTS AND METHODS

A retrospective study was carried out for the 10 PCP cases admitted to the PICU from 1980 to 2002. The variables studied were: age, sex, PRISM, underlying diseases, immunological status, clinical manifestations, radiology, response to therapy and clinical follow up.

RESULTS

Age of the patients varied between 5 months and 15 years and 4 months and there were 7 females and 3 males. Underlying diseases included: AIDS (3 cases), renal transplant (2 cases), West syndrome (1 case), cancer (4 cases). All presented an acute respiratory failure and 8/10 needed mechanical ventilation (mean duration: 14 days). All were treated by trimethoprim-sulfamethoxazole and 6/10 received steroids. Only one child died.

CONCLUSION

PCP is rare and affects mainly immunocompromised children who exhibit ARDS. Steroids treatment is now considered as an useful therapeutic adjuvant. A preventive treatment should be administered to children at risk.

Integrated assessment of the impacts of agricultural drainwater in the Salinas River (California, USA)

The Salinas River is the largest of the three rivers that drain into the Monterey Bay National Marine Sanctuary in central California. Large areas of this watershed are cultivated year-round in row crops and previous laboratory studies have demonstrated that acute toxicity of agricultural drainwater to Ceriodaphnia dubia is caused by the organophosphate (OP) pesticides chlorpyrifos and diazinon. In the current study, we used a combination of ecotoxicologic tools to investigate incidence of chemical contamination and toxicity in waters and sediments in the river downstream of a previously uncharacterized agricultural drainage creek system. Water column toxicity was investigated using a cladoceran C. dubia while sediment toxicity was investigated using an amphipod Hyalella azteca. Ecological impacts of drainwater were investigated using bioassessments of macroinvertebrate community structure. The results indicated that Salinas River water downstream of the agricultural drain is acutely toxic to Ceriodaphnia, and toxicity to this species was highly correlated with combined toxic units (TUs) of chlorpyrifos and diazinon. Laboratory tests were used to demonstrate that sediments in this system were acutely toxic to H. azteca, which is a resident genus. Macroinvertebrate community structure was moderately impacted downstream of the agricultural drain input. While the lowest macroinvertebrate abundances were measured at the station demonstrating the greatest water column and sediment toxicity and the highest concentrations of pesticides, macroinvertebrate metrics were more significantly correlated with bank vegetation cover than any other variable. Results of this study suggest that pesticide pollution is the likely cause of laboratory-measured toxicity in the Salinas River samples and that this factor may interact with other factors to impact the macroinvertebrate community in the system.

fMRI retinotopic mapping--step by step

fMRI retinotopic mapping provides detailed information about the correspondence between the visual field and its cortical representation in the individual subject. Besides providing for the possibility of unambiguously localizing functional imaging data with respect to the functional architecture of the visual system, it is a powerful tool for the investigation of retinotopic properties of visual areas in the healthy and impaired brain. fMRI retinotopic mapping differs conceptually from a more traditional volume-based, block-type, or event-related analysis, in terms of both the surface-based analysis of the data and the phase-encoded paradigm. Several methodological works related to fMRI retinotopic mapping have been published. However, a detailed description of all the methods involved, discussing the steps from stimulus design to the processing of phase data on the surface, is still missing. We describe here step by step our methodology for the complete processing chain. Besides reusing methods proposed by other researchers in the field, we introduce original ones: improved stimuli for the mapping of polar angle retinotopy, a method of assigning volume-based functional data to the surface, and a way of weighting phase information optimally to account for the SNR obtained locally. To assess the robustness of these methods we present a study performed on three subjects, demonstrating the reproducibility of the delineation of low order visual areas.