Coulomb-Volkov approach of ionization by extreme ultraviolet laser pulses in the subfemtosecond regime

In conditions where the interaction betweeen an atom and a short high-frequency extreme ultraviolet laser pulse is a perturbation, we show that a simple theoretical approach, based on Coulomb-Volkov-type states, can make reliable predictions for ionization. To avoid any additional approximation, we consider here a standard case : the ionization of hydrogen atoms initially in their ground state. For any field parameter, we show that the method provides accurate energy spectra of ejected electrons, including many above threshold ionization peaks, as long as the two following conditions are simultaneously fulfilled : (i) the photon energy is greater than or equal to the ionization potential ; (ii) the ionization process is not saturated. Thus, ionization of atoms or molecules by the high order harmonic laser pulses which are generated at present may be addressed through this Coulomb-Volkov treatment.Comment: 19 pages including 5 figures and figure caption

Mécanismes immunopathologiques associés aux granulomes et kystes odontogènes: revue générale

The authors make a general survey of the immunopathological mechanisms involved in odontogenic cysts and granulomas. The dental pulp and the sound periapical tissues contain neither inflammatory nor immunoglobin-producing cells.Dental decay associated with bacterial agression of the dental pulp and periapical tissues might induce a non-specific inflammation which subsequently becomes more specific. Immunoglobulins are present in fluid aspirates from odontogenic cysts and granulomas.Several investigations have pointed out non-specific inflammatory mediators (including the C3 complement components), T lymphocytes (helpers and suppressors), B lymphocytes, Protein S-100 + cells (Langerhans cells).The presence of immunoglobulins, immunocompetent cells and C3 complement components confirms that all constituents of both humoral and cell-mediated immunological reactions might play an essential role in the pathogenesis of osteolysis.Les auteurs font une mise au point concernant les mécanismes immunopathologiques associés aux granulomes et kystes odontogènes.L’apparition de la carie dentaire suivie de l’agression des tissus pulpaires et périapicaux par les bactéries et leurs toxines pourrait induire une réponse inflammatoire non spécifique d’abord, puis spécifique ensuite.Les kystes odontogènes inflammatoires et ceux liés au développement, mais secondairemlent infectés, sont également le siège de réactions inflammatoires chroniques.On sait que les IgG, les IgA et les IgM sont présents dans le produit d’aspiration du kyste. Les IgE ont également été mises en évidence mais dans une moindre proportion.Plusieurs investigations rapportées dans la littérature ont mis en évidence dans les lésions kystiques et les granulomes dentaires:— les différents médiateurs non spécifiques de l’inflammation (y compris les produits dérivés de la fraction C3 du complémnt)— les lymphocytes T («helper» et «suppressor»)— les lymphocytes B— les cellules «protéine S-100 positives».La présence de toutes les classes d’immunoglobulines, de cellules immuno-compétentes et des produits dérivés de la fraction C3 du complément dans les kystes et granulomes dentaires pourrait expliquer la pathogénie des lésions d’ostéolyse qui les accompagnent

Synthesis and reactivity of bis(alkoxysilylamido)yttrium eta(2)-pyridyl and eta(2)-alpha-picolyl compounds

The synthesis and reactivity of bis(alkoxysilylamido)yttrium pyridyl and alpha-picolyl complexes [Me2Si(NCMe3)(OCMe3)](2) YR (R=eta(2)-(C,N)-2-NC5H4(1); R=eta(2)(C,N)-CH2-2-NC5H4 (2); R=eta(2)-(C,N)-C(H)Me-2-NC5H4 (3); R=eta(2)-(C,N)-C(H)Me-2-NC5H3-6-Me (4)) is reported 1-4 have been prepared by C-H activation of pyridine and the corresponding methyl (ethyl) and dimethyl-substituted pyridines from [Me2Si(NCMe3)(OCMe3)](2)YCH(SiMe3)(2) and by salt metathesis with the appropriate lithium salts from [Me2Si(NCMe3)(OCMe3)](2) YCl . THF. The molecular structure of 2 shows that the picolyl group is bonded to yttrium in an eta(3)-aza-allylic fashion. With dihydrogen, stepwise hydrogenation of the pyridyl fragment of 1 has been observed, finally yielding the 2,3-dihydropyridyl complex [Me2Si(NCMe3)(OCMe3)](2)YNC5H8(7). Compound 1 inserts ethene to form the alpha-methylpicolyl derivative 4. Polymerization of ethene was not observed. The pyridyl compound 1 reacts with PhC drop CH to yield the corresponding acetylide pyridine complex [Me2Si(NCMe3)(OCMe3)](2) YC drop CPh . Py (8). The complexed pyridine can be substituted by THF to give [Me2Si(NCMe3)(OCMe3)](2) YC drop CPh . THF (9), which easily loses THF and forms the base-free acetylide [Me2Si(NCMe3)(OCMe3)](2) YC drop CPh (10). Compounds 1 and 2 readily insert nitriles yielding imido-pyridine complexes. The imido-pyridine complexes that contain alpha-hydrogen readily undergo a 1,3-H shift affording the corresponding enamido-pyridine compounds. With CO, the pyridyl compound 1 gives a dipyridylketone complex {[Me2Si(NCMe3)(OCMe3)](2) Y}{mu,eta(2),eta(2)-(N,N',O)-OC(2-NC5H4)(2)} (15)

Ultrashort pulse laser cutting of glass by controlled fracture propagation

International audienceLaser induced controlled fracture propagation has great potential in cutting brittle materials such as glass or sapphire. In this paper we demonstrate that the use of ultrashort pulse laser sources may be advantageous since it allows to overcome several restrictions of the convenient method

Immunization coverage and risk factors for failure to immunize within the Expanded Programme on Immunization in Kenya after introduction of new Haemophilus influenzae type b and hepatitis b virus antigens

Background: Kenya introduced a pentavalent vaccine including the DTP, Haemophilus influenzae type b and hepatitis b virus antigens in Nov 2001 and strengthened immunization services. We estimated immunization coverage before and after introduction, timeliness of vaccination and risk factors for failure to immunize in Kilifi district, Kenya. Methods: In Nov 2002 we performed WHO cluster-sample surveys of > 200 children scheduled for vaccination before or after introduction of pentavalent vaccine. In Mar 2004 we conducted a simple random sample (SRS) survey of 204 children aged 9 - 23 months. Coverage was estimated by inverse Kaplan-Meier survival analysis of vaccine- card and mothers' recall data and corroborated by reviewing administrative records from national and provincial vaccine stores. The contribution to timely immunization of distance from clinic, seasonal rainfall, mother's age, and family size was estimated by a proportional hazards model. Results: Immunization coverage for three DTP and pentavalent doses was 100% before and 91% after pentavalent vaccine introduction, respectively. By SRS survey, coverage was 88% for three pentavalent doses. The median age at first, second and third vaccine dose was 8, 13 and 18 weeks. Vials dispatched to Kilifi District during 2001 - 2003 would provide three immunizations for 92% of the birth cohort. Immunization rate ratios were reduced with every kilometre of distance from home to vaccine clinic (HR 0.95, CI 0.91 - 1.00), rainy seasons ( HR 0.73, 95% CI 0.61 - 0.89) and family size, increasing progressively up to 4 children ( HR 0.55, 95% CI 0.41 - 0.73). Conclusion: Vaccine coverage was high before and after introduction of pentavalent vaccine, but most doses were given late. Coverage is limited by seasonal factors and family siz

Gene expression differences in relation to age and social environment in queen and worker bumble bees

Eusocial insects provide special insights into the genetic pathways influencing aging because of their long-lived queens and flexible aging schedules. Using qRT-PCR in the primitively eusocial bumble bee Bombus terrestris (Linnaeus), we investigated expression levels of four candidate genes associated with taxonomically widespread age-related pathways (coenzyme Q biosynthesis protein 7, COQ7; DNA methyltransferase 3, Dnmt3; foraging, for; and vitellogenin, vg). In Experiment 1, we tested how expression changes with queen relative age and productivity. We found a significant age-related increase in COQ7 expression in queen ovary. In brain, all four genes showed higher expression with increasing female (queen plus worker) production, with this relationship strengthening as queen age increased, suggesting a link with the positive association of fecundity and longevity found in eusocial insect queens. In Experiment 2, we tested effects of relative age and social environment (worker removal) in foundress queens and effects of age and reproductive status in workers. In this experiment, workerless queens showed significantly higher for expression in brain, as predicted if downregulation of for is associated with the cessation of foraging by foundress queens following worker emergence. Workers showed a significant age-related increase in Dnmt3 expression in fat body, suggesting a novel association between aging and methylation in B. terrestris. Ovary activation was associated with significantly higher vg expression in fat body and, in younger workers, in brain, consistent with vitellogenin's ancestral role in regulating egg production. Overall, our findings reveal a mixture of novel and conserved features in age-related genetic pathways under primitive eusociality