Propagator of a Charged Particle with a Spin in Uniform Magnetic and Perpendicular Electric Fields

We construct an explicit solution of the Cauchy initial value problem for the time-dependent Schroedinger equation for a charged particle with a spin moving in a uniform magnetic field and a perpendicular electric field varying with time. The corresponding Green function (propagator) is given in terms of elementary functions and certain integrals of the fields with a characteristic function, which should be found as an analytic or numerical solution of the equation of motion for the classical oscillator with a time-dependent frequency. We discuss a particular solution of a related nonlinear Schroedinger equation and some special and limiting cases are outlined.Comment: 17 pages, no figure

High-order above-threshold ionization: The uniform approximation and the effect of the binding potential .

A versatile semiclassical approximation for intense laser-atom processes is presented. This uniform approximation is no more complicated than the frequently used multidimensional saddle-point approximation and far superior, since it applies for all energies, both close to as well as away from the classical cutoffs. In the latter case, it reduces to the standard saddle-point approximation. The uniform approximation agrees accurately with numerical evaluations for potentials, for which these are feasible, and constitutes a practicable method of calculation, in general. The method is applied to the calculation of high-order above-threshold ionization spectra with various binding potentials: Coulomb, Yukawa, and shell potentials which may model C60 molecules or clusters. The shell potentials generate rescattering spectra that are more structured and may feature an apparently higher cutoff

MALIGNANT GERM CELL TUMOURS in CHILDHOOD: the Italian Experience

Malignant Germ Cell Tumours (MGCT) account approximately 3% of all malignancies in the paediatric age group. Although many of them are curable, their natural history, staging, systems and optimal treatment still need to be better defined. Tha data of an Italian co-operative study are reported her

Correlation between the out-of-Plane Components of Magnetizability and Central Magnetic Shielding in Unsaturated Cyclic Molecules

A simple classical model of magnetic-field induced pi-electron flow is discussed, showing that the contribution to the sigma(parallel to) out-of-plane component of the virtual magnetic shielding provided by pi-ring currents, at points P along the C axis of cyclic planar unsaturated hydrocarbons C H with D-nh symmetry, in the presence of a magnetic field B-ext at right angles to the a plane, is, with good approximation, connected with the pi-electron contribution to the out-of-plane component of the magnetizability, xi(parallel to). The relationship is sigma(parallel to) (h) = (mu(0)/2 pi) (s(2) + h(2))(-3/2) xi(parallel to), where s is the distance of a C nucleus from the center of the carbon ring, and h is the distance of P from a. The ring current susceptibility, that is, the strength of the pi currents, expressed in nA/T (nano ampere per tesla) within the SI system of units, is given by partial derivative I/partial derivative B-ext = xi(parallel to)(pi s(2)), which can be used as a reliable virtual measure of magnetotropicity and relative pi-electron mobility in isoelectronic systems. Criteria for the practicality of the proposed ring current model are discussed

Paratesticular rhabdomyosarcoma: a comparison of two Italian studies. A report from the Italian Cooperative Group for Pediatric Soft Tissue Sarcoma

Objective. To evaluate the treatment strategies adopted for children with paratesticular rhabdomyosarcoma (PT-RMS) in two consecutive protocols coordinated by the Italian Cooperative Group on Childhood Soft Tissue Sarcoma. Methods. We considered the clinical data and results of 34 patients with localized PT-RMS treated in Centers affiliated with the Associazione Italiana di Ematologia e Oncolo-gia Pediatrica (AIEOP, Italian Association of Hematology and Pediatric Oncology) and included in the RMS79 (January 1979-December 1986) and RMS88 (January 1988-Decem-ber 1995) protocols. A multidisciplinary approach that included surgery, chemotherapy and radiotherapy was adopted according to disease extension, histology subtype and result of initial surgery. However treatment intensity was reduced in the RMS88 study, by excluding both lymph node biopsy at diagnosis for staging purpose and alkylating agents from chemotherapy. Results. Ten year overall survival was 100% and 95% in the RMS79 and RMS88 protocol respectively, with a non statistically significant difference. Conclusions. A short treatment with vincristine and actinomycin is effective in patients with localized PT-RMS completely resected al diagnosis. Systematic exploration of retroperitoneal lymph nodes could be limited to patients with enlarged lymph nodes at CT scan

Second Malignant tumors after elctive end of therapy for a first cancer in childhood: a multicenter study in Italy.

To evaluate the incidence of second malignant tumors in a cohort of subjects previously treated for childhood cancer, we analyzed data from the Off-Therapy Registry (OTR) of the Italian Association of Pediatric Hematology/Oncology, which collects information on children treated for Hodgkin's disease, non-Hodgkin's lymphoma, Wilms' tumor, acute lymphoblastic leukemia (ALL) and acute non-lymphatic leukemia and who had been removed from treatment in the absence of clinical signs of disease, i.e. the off-therapy stage. Second malignant tumors (SMT), diagnosed before December 31, 1988, were identified through a special enquiry to the 36 institutions cooperating in the registry. Observed cases were compared to expected numbers estimated from age- and sex-specific incidence rates derived from the Cancer Registry of the Province of Varese. In a total of 3,310 study subjects, 27 SMTs have been registered. The Cumulative Risk (CR) of SMT was 2.9% 15 years after the end of treatment and the Standard Incidence Ratio (SIR) was 10.8. The ALL sub-cohort had the highest risk of SMT (SIR 13.6) and 9 cases of CNS tumor occurred in this group (SIR 58.9). All 9 had received prophylactic cranial radiotherapy (CRT) and 5 had been treated on one protocol, characterized by low-dose intrathecal methotrexate (IT MTX) given monthly for 2 years after CRT. The Off-Therapy Registry has unique criteria for inclusion; direct comparisons with similar studies are therefore somewhat problematic. However, our data suggest that the risk of SMT in childhood ALL cancer survivors may be greater than previously reported, and that CNS tumors are the most common SMT in this group. The administration schedule of IT MTX may be an important risk facto