Searches for New Particles

\begin{abstract} Searches for Standard Model and Supersymmetric Higgs, supersymmetric particles and leptoquark at HERA, LEP and TEVATRON colliders are reviewed. No evidence for a positive signal is seen, but significant and constraining limits are placed. In particular the Standard Model Higgs boson must be heavier than 77.5 GeV and the lightest neutralino heavier than 14.0 GeV for all $\tan\beta$ and all sneutrino masses. A lower limit on the mass of a first generation scalar leptoquark of 225 GeV at 95\% C.L. has also been obtained. \end{abstract

A discrete time relativistic Toda lattice

Four integrable symplectic maps approximating two Hamiltonian flows from the relativistic Toda hierarchy are introduced. They are demostrated to belong to the same hierarchy and to examplify the general scheme for symplectic maps on groups equiped with quadratic Poisson brackets. The initial value problem for the difference equations is solved in terms of a factorization problem in a group. Interpolating Hamiltonian flows are found for all the maps.Comment: 32 pages, LaTe

Visual evoked potentials in succinate semialdehyde dehydrogenase (SSADH) deficiency

In mammals, increased GABA in the central nervous system has been associated with abnormalities of visual evoked potentials (VEPs), predominantly manifested as increased latency of the major positive component P100. Accordingly, we hypothesized that patients with a defect in GABA metabolism, succinate semialdehyde dehydrogenase (SSADH) deficiency (in whom supraphysiological levels of GABA accumulate), would manifest VEP anomalies. We evaluated VEPs on two patients with confirmed SSADH deficiency. Whereas the P100 latencies and amplitudes for binocular VEP analyses were within normal ranges for both patients, the P100 latencies were markedly delayed for left eye (OS) (and right eye (OD), patient 1) and monocular OS (patient 2): 134-147 ms; normal <118 ms. We hypothesize that elevated GABA in ocular tissue of SSADH patients leads to a use-dependent downregulation of the major GABAergic receptor in eye, GABA(C), and that the VEP recordings' abnormalities, as evidenced by P100 latency and/or amplitude measurements, may be reflective of abnormalities within visual systems. This is a preliminary finding that may suggest the utility of performing VEP analysis in a larger sample of SSADH-deficient patients, and encourage a neurophysiological assessment of GABA(C) receptor function in Aldh5a1(-/-) mice to reveal new pathophysiological mechanisms of this rare disorder of GABA degradation

On the dimensions of secant varieties of Segre-Veronese varieties

This paper explores the dimensions of higher secant varieties to Segre-Veronese varieties. The main goal of this paper is to introduce two different inductive techniques. These techniques enable one to reduce the computation of the dimension of the secant variety in a high dimensional case to the computation of the dimensions of secant varieties in low dimensional cases. As an application of these inductive approaches, we will prove non-defectivity of secant varieties of certain two-factor Segre-Veronese varieties. We also use these methods to give a complete classification of defective s-th Segre-Veronese varieties for small s. In the final section, we propose a conjecture about defective two-factor Segre-Veronese varieties.Comment: Revised version. To appear in Annali di Matematica Pura e Applicat

Distribution of Salmonella enterica isolates from human cases in Italy, 1980 to 2011

n/

Molecular characterization of multidrug-resistant strains of Salmonella enterica serotype Typhimurium and Monophasic variant isolated from human infections in Italy

Salmonella enterica serovar Typhimurium (STM) represents the prevalent cause of foodborne gastroenteritis in Italy with the majority of isolates exhibiting multidrug resistance. A resistant pattern that includes ampicillin (A), streptomycin (S), sulfonamide (Su), and tetracycline (T) (ASSuT) but lacks resistance to chloramphenicol (C) has recently emerged in Italy among strains of STM and of its monophasic variant, S. enterica subspecies enterica serovar S. 4,[5],12:i:-. With the aim to evaluate their clonal relationships, 553 strains of STM and S. 4,[5],12:i:- with the ASSuT and ACSSuT resistance patterns isolated in Italy from human infections between 2003 and 2006 were characterized by pulsed-field gel electrophoresis (PFGE) according to the PulseNet-Europe protocol and nomenclature. Among both the STM and S. 4,[5],12:i:- ASSuT strains, the predominant PFGE profile was STYMXB.0079 (53.2-73.0% of strains, respectively), while the STM ACSSuT strains belonged to the STYMXB.0061 (37.2% of strains) and STYMXB.0067 (29.9% of strains). Bionumerics cluster analysis of the nonunique PFGE profiles showed that more than 90% of ASSuT and ACSSuT-resistant strains were included in two distinct clusters with a genetic homology of 73% each other, suggesting that the ASSuT-resistant strains belong to a same clonal lineage different from that of the ACSSuT strains. Phage typing showed that 23% of the ASSuT STM strains were not typeable and 22.3% were U302. The same phage types were observed among the ASSuT strains of S. 4,[5],12:i:-. A different figure was observed for the ACSSuT strains: the STM isolates mostly belonged to DT104 (70.2%), while none of the S. 4,[5],12:i:- strains belonged to this phage type. This study indicates that the tetra-resistant ASSuT strains of STM and S. 4,[5],12:i:-, increasingly isolated in Italy, belong to a same clonal lineage and that the S. 4,[5],12:i:- strains circulating in our country mainly derive from this STM clonal lineage