2,786 research outputs found

    Slingshot non-sequential double ionization as a gate to anti-correlated two electron escape

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    At intensities below-the-recollision threshold, we show that re-collision-induced excitation with one electron escaping fast after re-collision and the other electron escaping with a time delay via a Coulomb slingshot motion is one of the most important mechanisms of non-sequential double ionization, for strongly-driven He at 400 nm. Slingshot-NSDI is a general mechanism present for a wide range of low intensities and pulse durations. Anti-correlated two-electron escape is its striking hallmark. This mechanism offers an alternative explanation of anti-correlated two-electron escape obtained in previous studies.Comment: 6 pages, 3 figure

    Momentum scalar triple product as a measure of chirality in electron ionization dynamics of strongly-driven atoms

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    We formulate a transparent measure that quantifies chirality in single electron ionization triggered in atoms, which are achiral systems. We do so in the context of Ar driven by a new type of optical fields that consists of two non-collinear laser beams giving rise to chirality that varies in space across the focus of the beams. Our computations account for realistic experimental conditions. To define this measure of chirality, we first find the sign of the electron final momentum scalar triple product pkâ‹…(piĂ—pj)\mathrm{{\bf{p}}_{k}\cdot ({\bf{p}}_{i}\times {\bf p}_{j})} and multiply it with the probability for an electron to ionize with certain values for both pk\mathrm{p_{k}} and pipj\mathrm{p_{i}p_{j}}. Then, we integrate this product over all values of pk\mathrm{p_{k}} and pipj\mathrm{p_{i}p_{j}}. We show this to be a robust measure of chirality in electron ionization triggered by globally chiral electric fields

    Retrorectal endometrioid cyst: a case report

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    <p>Abstract</p> <p>Introduction</p> <p>Developmental cysts are the most common retrorectal cystic lesions in adults, whereas reports of endometrioid cysts in this anatomic location are extremely rare.</p> <p>Case presentation</p> <p>A 21-year-old nulliparous Greek woman presented with chronic noncyclic pelvic pain, and a retrorectal cyst was diagnosed. The lesion was resected through a laparotomy and, on histologic examination, was found to be an endometrioid cyst. The treatment was completed with a six-month course of a gonadotropin-releasing hormone analogue. One year after surgery, the woman remained free of symptoms, and pelvic imaging showed no recurrence of the lesion. Reviewing the literature, we found only three previous reports of an endometrioid cyst in this anatomic location.</p> <p>Conclusion</p> <p>In women of reproductive age, endometriosis must be included in the differential diagnosis of retrorectal cysts.</p

    Mapping the direction of electron ionization to phase delay between VUV and IR laser pulses

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    We theoretically demonstrate a one-to-one mapping between the direction of electron ionization and the phase delay between a linearly polarized vacuum ultraviolet (VUV) and a circular infrared (IR) laser pulse. To achieve this, we use an ultrashort VUV pulse that defines the moment in time and space when an above-threshold electron is released in the IR pulse. The electron can then be accelerated to high velocities escaping in a direction completely determined by the phase delay between the two pulses. The dipole matrix element to transition from an initial bound state of the N2 molecule, considered in this work, to the continuum is obtained using quantum-mechanical techniques that involve computing accurate continuum molecular states. Following release of the electron in the IR pulse, we evolve classical trajectories, neglecting the Coulomb potential and accounting for quantum interference, to compute the distribution of the direction and magnitude of the final electron momentum. The concept we theoretically develop can be implemented to produce nanoscale ring currents that generate large magnetic fields

    Multi-target mode of action of a Clerodane-type diterpenoid from Polyalthia longifolia targeting African trypanosomes.

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    Natural products have made remarkable contributions to drug discovery and therapy. In this work we exploited various biochemical approaches to investigate the mode of action of 16-α-hydroxycleroda-3,13 (14)-Z-dien-15,16-olide (HDK-20), which we recently isolated from Polyalthia longifolia, on Trypanosoma brucei bloodstream trypomastigotes. HDK20 at concentrations ≥ EC50 (0.4μg/ml) was trypanocidal, with its efect irreversible after only a brief exposure time (&lt;1h). Fluorescence microscopic assessment of DNA confguration revealed severe cell cycle defects after 8h of incubation with the compound, the equivalent of a single generation time. This was accompanied by DNA fragmentation as shown by Terminal deoxynucleotidyl transferase dUTP Nick-End Labelling (TUNEL) assays. HDK-20 also induced a fast and profound depolarisation of the parasites’ mitochondrial membrane potential and depleted intracellular ATP levels of T. brucei. Overall, HDK20 showed a multi-target mechanism of action, which provides a biochemical explanation for the promising antitrypanosomatid activity in our previous report

    Extensions of operator algebras I

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    We transcribe a portion of the theory of extensions of C*-algebras to general operator algebras. We also include several new general facts about approximately unital ideals in operator algebras and the C*-algebras which they generate

    Evaluation of food photographs assessing the dietary intake of children up to 10 years old

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    OBJECTIVE: Young children lack basic skills related to recognizing the types of foods they consume and dietary surveys often rely on parents' response. The present study aimed to evaluate how well parents of children aged from 3 months to 10 years perceive images of portions of foods commonly consumed by young children. DESIGN: Pre-weighed, actual food portions (n 2314) were shown to the study participants who were asked to indicate the picture that corresponded to the food in view. Mean differences between picture numbers selected and shown were estimated and compared using unpaired t tests or Tukey-Cramer pairwise comparisons. SETTING: Real-time testing of parents' perception of food images presenting portion sizes consumed by children up to 10 years old. SUBJECTS: A convenience sample of 138 parents/caregivers of young children (69 % females). RESULTS: Individuals selected the correct or adjacent image in about 97 % of the assessments. Images presenting amorphous solids (i.e. pies and pastries with a filling), liquid or semi-liquid dishes (i.e. soups, porridges, fruit and vegetable purées) were more prone to bias. There was no indication that personal characteristics (gender, age, educational background, age, number of offspring) were associated with differences in the way parents/caregivers perceived the food pictures. CONCLUSIONS: Food pictures may not be appropriate to quantify the intake of liquid, semi-liquid or amorphous solid foods in surveys addressing young children and studies evaluating their performance as food portion anchors should ensure the inclusion of several and various amorphous foods in the assessment
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