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

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

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 $\mathrm{{\bf{p}}_{k}\cdot ({\bf{p}}_{i}\times {\bf p}_{j})}$ and multiply it with the probability for an electron to ionize with certain values for both $\mathrm{p_{k}}$ and $\mathrm{p_{i}p_{j}}$. Then, we integrate this product over all values of $\mathrm{p_{k}}$ and $\mathrm{p_{i}p_{j}}$. We show this to be a robust measure of chirality in electron ionization triggered by globally chiral electric fields

Essays in financial stability and intermediation

This thesis empirically examines the contribution of financial institutions to systemic risk by looking at their interactions with market-based finance. The financial crisis of 2007-09 catalysed the transformation of the financial system with the introduction of the post-crisis regulations, which were aimed at mitigating systemic risk by addressing vulnerabilities that manifested in the crisis. This resulted in the increased resilience of the banking sector, which was at the centre of the financial crisis, as well as the proliferation of market-based finance as an alternative source of funding for corporations. Yet, as the recent market turmoil due to Covid 19 has showcased, this has created new vulnerabilities which necessitate the continuous assessment of the evolving financial system. The thesis is based on three essays. The first essay examines the effects of the mandatory collateralisation of over-the-counter derivatives contracts on counterparty, liquidity and systemic risks of the largest dealer banks and central counterparties (CCPs). Using a stress test network model calibrated to the banks’ balance sheet data, we document riskshifting effects in the form of risk transformation from counterparty to liquidity risk and a reduction of systemic risk at the expense of increased propensity for contagion from the CCP to its members. In addition, we find that the expansion of central clearing reduces systemic risk, in accordance with regulatory predictions. The second essay examines the effects of exchange-traded funds (ETFs) on the underlying securities’ liquidity, returns and volatility via information links which are formed when investors use information from one asset to price the other. Using a proprietary dataset of Irish ETF holdings from the Central Bank of Ireland, we find that ETFs form close information links with the underlying equities but weak ones with the underlying corporate debt securities because of the higher accessibility of the former, leading to stronger co-movements of liquidity, returns and volatility with the equities compared to the corporate debt securities. The results indicate that ETFs can affect the underlying markets in different ways depending on their accessibility, contributing to the ongoing debate on the role of ETFs in propagating shocks and systemic risk. Finally, the third essay examines the resilience of banks to liquidity shocks originating from money market funds (MMFs) using a stress test network model calibrated to the full US MMF holdings data, following the introduction of post-crisis regulations in both sectors. My findings suggest that while the banks can withstand a withdrawal of shortterm funding from MMFs due to their high liquidity reserves, the MMFs can incur severe fire sales losses in the face of large redemption shocks and in the absence of a regulatory authority acting as buyer of last resort of commercial paper, despite the regulations introduced to increase their resilience

Retrorectal endometrioid cyst: a case report

<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

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.

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

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

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