Tree Level Unitarity Bounds for the Minimal B-L Model

We have derived the unitarity bounds in the high energy limit for the minimal B-L extension of the Standard Model by analysing the full class of Higgs and would-be Goldstone boson two-to-two scatterings at tree level. Moreover, we have investigated how these limits could vary at some lower critical value of the energy.Comment: 20 pages, 4 figures, 2 tables; 1d figure modified, typos corrected, bibliography augmented; published in PRD after minor adjustmen

The Z' boson of the minimal B-L model at future Linear Colliders in e+e- --> mu+mu-

We study the capabilities of future electron-positron Linear Colliders, with centre-of-mass energy at the TeV scale, in accessing the parameter space of a $Z'$ boson within the minimal $B-L$ model. We carry out a detailed comparison between the discovery regions mapped over a two-dimensional configuration space ($Z'$ mass and coupling) at the Large Hadron Collider and possible future Linear Colliders for the case of di-muon production. As known in the literature for other $Z'$ models, we confirm that leptonic machines, as compared to the CERN hadronic accelerator, display an additional potential in discovering a $Z'$ boson as well as in allowing one to study its properties at a level of precision well beyond that of any of the existing colliders.Comment: 5 pages, proceeding of LC09 (Perugia), published by the Italian Physical Society in the Nuovo Cimento C (Colloquia

Scaling function in AdS/CFT from the O(6) sigma model

Asymptotic behavior of the anomalous dimensions of Wilson operators with high spin and twist is governed in planar N=4 SYM theory by the scaling function which coincides at strong coupling with the energy density of a two-dimensional bosonic O(6) sigma model. We calculate this function by combining the two-loop correction to the energy density for the O(n) model with two-loop correction to the mass gap determined by the all-loop Bethe ansatz in N=4 SYM theory. The result is in agreement with the prediction coming from the thermodynamical limit of the quantum string Bethe ansatz equations, but disagrees with the two-loop stringy corrections to the folded spinning string solution.Comment: 25 pages, 2 figure

Inclusive hadron and photon production at LHC in dipole momentum space

Using a momentum space model for the dipole scattering amplitude we present an analysis of the saturation effects at LHC energies, describing the data on proton-proton and proton-lead collisions. The model is based on the asymptotic solutions of the Balitsky-Kovchegov equation, being ideal in the saturation domain where the target wave function has a high occupation number. We also make predictions for the nuclear modification ratios on charged hadron and prompt photon production in the forward region, where the high parton density effects are important.Comment: New section added and typos corrected. To be published in PR

Prognostic factors of survival in patients treated with nab-paclitaxel plus gemcitabine regimen for advanced or metastatic pancreatic cancer: A single institutional experience.

The objectives of this study were to evaluate the effectiveness of nab-paclitaxel plus gemcitabine (NAB-P/GEM) regimen in an unselected population of patients with advanced inoperable or metastatic pancreatic cancer (PC), and to identify the prognostic factors influencing overall survival (OS). EXPERIMENTAL DESIGN: Patients with age < 85 years, ECOG-performance status (PS) < 3, and adequate renal, hepatic and hematologic function were eligible. NAB-P (125 mg/m2) and GEM (1000 mg/m2) day 1,8,15 every 4 weeks were employed for 3-6 cycles or until highest response. RESULTS: Overall, 147 cycles (median 4, range 1-11 cycles) were administered on thirty-seven consecutive patients (median 66 years old, range 40-82) treated. The median overall progression-free survival and OS were 6.2 and 9.2 months, respectively. The G 3-4 dose-limiting toxicity were neutropenia (20.7%), severe anemia (17.2%), and cardiovascular toxicity (10.3%). PS, number of cycles, baseline CA 19-9 and LDH serum levels, were found to be significantly related to OS. The multivariate analysis showed that both number of cycles (HR = 9.14, 95% CI 1.84-45.50, p = 0.001) and PS (HR = 13.18, 95% CI 2.73-63.71, p = 0.001) were independently associated with OS. CONCLUSION: NAB-P/GEM regimen should be used in all patients with advanced or metastatic PC, with the exception of those with serious contraindications to chemotherapy, such as severe renal or hepatic impairment or major cardiovascular diseases

Phenomenology of the minimal B-L extension of the Standard Model

We present the Large Hadron Collider (LHC) discovery potential in the $Z'$ and heavy neutrino sectors of a $U(1)_{B-L}$ enlarged Standard Model also encompassing three heavy Majorana neutrinos. This model exhibits novel signatures at the LHC, the most interesting arising from a $Z'$ decay chain involving heavy neutrinos, eventually decaying into leptons and jets. In particular, this signature allows one to measure the $Z'$ and heavy neutrino masses involved. In addition, over a large region of parameter space, the heavy neutrinos are rather long-lived particles producing distinctive displaced vertices that can be seen in the detectors. Lastly, the simultaneous measurement of both the heavy neutrino mass and decay length enables an estimate of the absolute mass of the parent light neutrino. For completeness, we will also compare the LHC and a future Linear Collider (LC) discovery potentials.Comment: 4 pages, no figures. LaTeX. Talk given at "The 2009 Europhysics Conference on High Energy Physics", Krakow, Poland, July 16-22, 200

ANNOTATION AND EXPRESSION OF FDM-LIKE GENES IN SEXUAL AND APOMICTIC H. PERFORATUM ACCESSIONS

Apomixis is an asexual reproductive strategy that permits to the inheritance of the maternal genome over generations without genetic recombination events. From a biological point of view, this modality of asexual reproduction by seed could be the consequence of heterocronic expression of genes involved in fundamental aspects of sexual reproduction, such as meiosis and spore selection, leading to the formation of functional un-reduced gametes which retain the ability to form an embryo eventually bypassing double fertilization. Although this process is well documented in many flowering plants, and despite its revolutionary potentials in plant breeding strategies, the genetic control of apomixes is still not properly understood. Recently, a number of independent studies on sexual model species provided experimental evidences linking single components of apomixis to the deregulation of genes involved in the RNA-directed DNA methylation pathway (RdDM). RNA-directed DNA methylation refers to a specific process in which small interfering RNAs produced by the RNA interference pathway guide de novo methylation of cytosines at the homologous DNA region, thereby regulating the expression of specific genes. Remarkably, gene expression studies in the apomictic model species Hypericum perforatum corroborate the hypothesis that miss expression of genes involved in this pathway is functionally associated with early events of apomixes in this species. The aim of the present research is a better understanding of the role of a class of genes involved in the RdDM known as Factor of DNA Methylation (FDM), in the frame of ovule cell fate change, megagametogenesis and, ultimately, aposporous apomixis. To this end, computational investigations were performed in order to annotate the H. perforatum FDM genes. The expression of these genes in H. perforatum pistils and ovules was studied by qPCR and ISH assays on sexual and apomictic accessions. Furthermore, Arabidopsis thaliana knock out lines were characterized in order to elucidate the role of specific genes in relation to gametophyte and/or seed formation. All data will be presented and critically discussed as they prove a better understanding of molecular bases of apomixes in H. perforatum

TRANSCRIPTOMIC ANALYSIS OF OVULE-SPECIFIC CELL LINEAGES TO IDENTIFY GENES RELATED TO APOSPOROUS APOMIXIS IN HYPERICUM PERFORATUM L.

The medicinal plant St. John\u2019s wort (Hypericum perforatum L.) is an attractive model system for the study of aposporous apomixis. The key biological features of apomixis in this species are the by-passing of meiosis, the differentiation of aposporous initials into embryo sacs containing unreduced egg cells, their autonomous development in functional embryos without fertilization, and the formation of viable endosperm either via fertilization-independent means or following fertilization with a sperm nucleus. The aim of this research is to define gene expression changes occurring in the nucellar cell types of the ovules primarily involved in the differentiation of the megaspore mother cells and aposporous initials. To this end, a laser-capture microdissection approach was adopted in combination with the RNA-seq technology in order to restrict the frame of our investigations to a specific portion of the ovule, i.e. the nucellus, at developmental stages preceding the differentiation of aposporous initials. Overall, our gene expression analysis identified 270 and 81 unigenes that were found significantly up- and down-regulated between ovules collected from sexual and apomictic accessions. Ontological annotation of differentially expressed genes indicated that genes up-regulated in apomictic ovules were significantly enriched in ontological terms related to the RNA-directed DNA polymerase activity and the RNA binding. Among these genes, several actors of the RdDM pathway were found, suggesting that the phenotypic expression of early events of aposporous apomixis is associated to changes in de novo DNA methylation mediated by small RNAs. Furthermore, as deregulation of single components of the sexual developmental pathway is believed to be a trigger of the apomictic reproductive program, genes involved in sporogenesis, gametogenesis and response to hormonal stimuli were annotated and investigated in great detail. The expression analysis of candidate genes was performed not only by Real-Time qPCR but also by ISH assays in order to verify the temporal and spatial expression patterns of selected transcripts in the ovule. Finally, the activity of specific genes in relation to embryo sac and/or embryo formation was investigated by using A. thaliana knock-out lines. Overall, our data suggest that phenotypic expression of aposporous apomixis is concomitant with the modulation of key genes involved in the sexual reproductive pathway, hormones and other actors likely playing a crucial role in the RNA-directed DNA methylation pathway