Static NLO susceptibilities: testing approximation schemes against exact results

The reliability of the approximations commonly adopted in the calculation of static optical (hyper)polarizabilities is tested against exact results obtained for an interesting toy-model. The model accounts for the principal features of typical nonlinear organic materials with mobile electrons strongly coupled to molecular vibrations. The approximations introduced in sum over states and finite field schemes are analyzed in detail. Both the Born-Oppenheimer and the clamped nucleus approximations turn out to be safe for molecules, whereas for donor-acceptor charge transfer complexes deviations from adiabaticity are expected. In the regime of low vibrational frequency, static susceptibilities are strongly dominated by the successive derivatives of the potential energy and large vibrational contributions to hyperpolarizabilities are found. In this regime anharmonic corrections to hyperpolarizabilities are very large, and the harmonic approximation, exact for the linear polarizability, turns out totally inadequate for nonlinear responses. With increasing phonon frequency the role of vibrations smoothly decreases, until, in the antiadiabatic (infinite vibrational frequency) regime, vibrations do not contribute anymore to static susceptibilities, and the purely electronic responses are regained.Comment: 9 pages, including 3 figure

Extracting causal rules from spatio-temporal data

The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-319-23374-1_2This paper is concerned with the problem of detecting causality in spatiotemporal data. In contrast to most previous work on causality, we adopt a logical rather than a probabilistic approach. By defining the logical form of the desired causal rules, the algorithm developed in this paper searches for instances of rules of that form that explain as fully as possible the observations found in a data set. Experiments with synthetic data, where the underlying causal rules are known, show that in many cases the algorithm is able to retrieve close approximations to the rules that generated the data. However, experiments with real data concerning the movement of fish in a large Australian river system reveal significant practical limitations, primarily as a consequence of the coarse granularity of such movement data. In response, instead of focusing on strict causation (where an environmental event initiates a movement event), further experiments focused on perpetuation (where environmental conditions are the drivers of ongoing processes of movement). After retasking to search for a different logical form of rules compatible with perpetuation, our algorithm was able to identify perpetuation rules that explain a significant proportion of the fish movements. For example, approximately one fifth of the detected long-range movements of fish over a period of six years were accounted for by 26 rules taking account of variations in water-level alone.EPSRCAustralian Research Council (ARC) under the Discovery Projects Schem

Mean-Field Effects on the Phosphorescence of Dinuclear Re(I) Complex Polymorphs

A computational study rationalizes the different phosphorescence colors of two highly emitting crystal polymorphs of a dinuclear Re(I) complex, [Re2(μ-Cl)2(CO)6(μ-4,5-(Me3Si)2pyridazine)]. The electrostatic interactions between the charge distributions on neighboring molecules inside the crystal are responsible for the different stabilization of the emitting triplet state because of the different molecular packing. These self-consistent effects play a major role in the phosphorescence of crystals made of polar and polarizable molecular units, offering a powerful handle to tune the luminescence wavelength in the solid state through supramolecular engineering

SURGERY IN PATIENTS WITH TESTICULAR MALIGNANT GERM CELL TUMORS: COMPLIANCE TO SURGICAL GUIDELINES AND RESULTS IN THE ITALIAN COOPERATIVE STUDY

Purpose: Surgery represents a main and often the only treatment in patients with testicular Malignant Germ Cell Tumors (MGCT). We analyzed the compliance to surgical guidelines and the results in a series of patients with testicular MGCT -/+ retroperitoneal node involvement, without distant metastases. Method: 42 patients, observed in 15 Centers were enrolled in the Italian Cooperative Study on MGCT (January2004–December2010). 14/42 were younger than 2 y. of age, 28/42 between 13–18 y. Treatment was delivered according to COG-Staging-System: St.I patients (complete excision with inguinal orchifunicolectomy+decrease of markers, +hemiscrotectomy if scrotal involvement) did not receive further treatment; St.II patients (scrotal involvement after hemiscrotectomy and/or retroperitoneal node (RPN) enlargement:2 cm) had RPN Dissection if residuals were suspected after PEBx3or4. Results: St.I: 26 patients. 3/26 had a scrotal approach due to suspected testicular torsion: 1/3 underwent hemiscrotectomy, 2 did not receive further therapy after decrease of alphaFP, due to patient’s or physician’s decision respectively. 3/26 were successfully treated for RPN relapse, occurred at 3,6,9 months after adequate surgery (2 adolescents, 1 infant). St.II: in 4 patients CTwas delivered due to slight enlargement of RPN (+persistent alphaFP in 1). St.III: 12 patients received CT and RPND (bilateral in 1). Histology was negative in 11/12. All patients are alive without disease, 39 in 1stCR, 3 in 2ndCR (f.u 9–86 m.:med.48). 1 St.1 patient suffered from postoperative scrotal hematoma. Among patients younger than 2 y, 10/14 had a pure YST, 12/14 had St.I disease; among those between 13–18 y, 27/28 had a mixed histology, 14/28 were St.II or St.III. In 3 adolescents a testicular prosthesis was positioned during primary operation. Conclusion: Outcome was excellent. Regional relapses, observed only in St.I patients, were cured. Surgical guidelines were followed in 40/42 cases. Scrotal approach did not worsen the outcome of patients who did not receive further treatment

Chemotherapy-related damage to ovarian reserve in childhood cancer survivors : interpreting the evidence

Chemotherapy during childhood damages ovarian reserve and can affect future fertility. However, recent large epidemiological studies showed that the detrimental impact on fertility is less severe if women seek for pregnancy at a younger age. To explain this observation, we hypothesize that the detrimental effects of previous chemotherapy on the ovarian reserve may be attenuated in young adults for two main reasons. Firstly, recent evidence showed that the amount of ovarian reserve is not a critical factor for effective natural conceptions. Provided that the residual ovarian reserve allows regular ovulatory cycles, the chances of pregnancy are similar in women with intact or reduced ovarian reserve. Secondly, ovarian reserve depletion appears to be a phenomenon that is inversely related to the residual ovarian reserve rather than to age. From a mathematical perspective, this kind of regulation intrinsically attenuates the effects of an early loss of a significant amount of primordial follicles. In conclusion, the detrimental effects of chemotherapy on natural fertility may be less severe if women with a history of chemotherapy during childhood seek for pregnancy early. This information should be part of the counseling

Assessing an ontology for the representation of clinical protocols in decision support systems

In order to assess the expressiveness of the CompGuide ontology for Clinical Practice Guidelines, a study was conducted with fourteen students of the Integrated Masters in Biomedical Engineering from the University of Minho in Portugal to whom it was proposed the representation of multiple guidelines according to the ontology. They were then asked to evaluate the ontology through a questionnaire and written reports. Although the results seem promising, there is the need for significant improvements mainly in: the representation of medication prescriptions, the tasks used to retrieve information from the patient, the diversity of actions offered by the ontology, the expressiveness of conditions regarding the state of a patient, and temporal constraints.FCT - Fundação para a Ciência e a Tecnologiainfo:eu-repo/semantics/publishedVersio

Supramolecular interactions in clusters of polar and polarizable molecules

We present a model for molecular materials made up of polar and polarizable molecular units. A simple two state model is adopted for each molecular site and only classical intermolecular interactions are accounted for, neglecting any intermolecular overlap. The complex and interesting physics driven by interactions among polar and polarizable molecules becomes fairly transparent in the adopted model. Collective effects are recognized in the large variation of the molecular polarity with supramolecular interactions, and cooperative behavior shows up with the appearance, in attractive lattices, of discontinuous charge crossovers. The mean-field approximation proves fairly accurate in the description of the gs properties of MM, including static linear and non-linear optical susceptibilities, apart from the region in the close proximity of the discontinuous charge crossover. Sizeable deviations from the excitonic description are recognized both in the excitation spectrum and in linear and non-linear optical responses. New and interesting phenomena are recognized near the discontinuous charge crossover for non-centrosymmetric clusters, where the primary photoexcitation event corresponds to a multielectron transfer.Comment: 14 pages, including 11 figure

Extremely fast triplet formation by charge recombination in a Nile Red/fullerene flexible dyad

A donor/acceptor dyad was obtained by linking Nile Red and fullerene to a calix[4]arene scaffold. The dyad was spectroscopically characterized, both with steady-state and ultrafast transient absorption experiments, as well as with electrochemical and spectroelectrochemical techniques. We demonstrate extremely fast and efficient formation of a long-lived excited triplet localized on the fullerene moiety in this system, occurring in about 80 ps in toluene and 220 ps in chloroform. The mechanism of this process is investigated and discussed. The spectroscopic and electrochemical characterization suggests the occurrence of electron transfer from Nile Red to fullerene, leading to the formation of a charge-separated state. This state lives very briefly and, because of the small interaction between the electron donor and acceptor, promotes a singlet/triplet state mixing, inducing charge recombination and efficient triplet formation