Strong Unification

We investigate the possibility that unification occurs at strong coupling. We show that, despite the fact the couplings pass through a strong coupling regime, accurate predictions for their low energy values are possible because the couplings of the theory flow to infrared fixed points. We determine the low-energy QCD coupling in a favoured class of strong coupling models and find it is reduced from the weak coupling predictions, lying close to the experimentally measured value. We extend the analysis to the determination of quark and lepton masses and show that (even without Grand Unification) the infra-red fixed point structure may lead to good predictions for the top mass, the bottom to tau mass ratio and $\tan \beta$. Finally we discuss the implications for the unification scale finding it to be increased from the MSSM value and closer to the heterotic string prediction.Comment: 12 pages, LateX, no figure

Biodegradation and antimicrobial properties of zinc oxide–polymer composite materials for urinary stent applications

Research advancements in the field of urinary stents have mainly been in the selection of materials and coatings to address commonly faced problems of encrustation and bacterial adhesion. In this study, polylactic acid (PLA) and polypropylene (PP) were evaluated with zinc oxide (ZnO) coating to assess its ability to reduce or eliminate the problems of encrustation and bacteria adhesion. PLA and PP films were prepared via twin screw extrusion. ZnO microparticles were prepared using sol-gel hydrothermal synthesis. The as-prepared ZnO microparticles were combined in the form of a functional coating and deposited on both polymer substrates using a doctor blade technique. The ZnO-coated PP and PLA samples as well as their uncoated counterparts were characterized from the physicochemical standpoints, antibacterial and biodegradation properties. The results demonstrated that both the polymers preserved their mechanical and thermal properties after coating with ZnO, which showed a better adhesion on PLA than on PP. Moreover, the ZnO coating successfully enhanced the antibacterial properties with respect to bare PP/PLA substrates. All the samples were investigated after immersion in simulated body fluid and artificial urine. The ZnO layer was completely degraded following 21 days immersion in artificial urine irrespective of the substrate, with encrustations more evident in PP and ZnO-coated PP films than PLA and ZnO-coated PLA films. Overall, the addition of ZnO coating on PLA displayed better adhesion, antibacterial activity and delayed the deposition of encrustations in comparison to PP substrates

Infra-red fixed points in supersymmetry

Model independent constraints on supersymmetric models emerge when certain couplings are drawn towards their infra-red (quasi) fixed points in the course of their renormalization group evolution. The general principles are first reviewed and the conclusions for some recent studies of theories with R-parity and baryon and lepton number violations are summarized.Comment: 5 pages Latex with 2 figures embedded as eps files Talk given at WHEPP6, Chennai, India, January 3-15, 2000, to appear in special issue of Praman

Infrared alignment of SUSY flavor structures

The various experimental bounds on flavor-changing interactions severely restrict the low-energy flavor structures of soft supersymmetry breaking parameters. In this work, we show that with a particular assumption of Yukawa couplings, the fermion mass and sfermion soft mass matrices are simultaneously diagonalized by common mixing matrices and we then obtain an alignment solution for the flavor problems. The required condition is generated by renormalization group evolutions and achieved at low-energy scale independently of high-energy structures of couplings. In this case, the diagonal entries of the soft scalar mass matrices are determined by gaugino and Higgs soft masses. We also discuss possible realizations of this scenario and the characteristic sparticle spectrum in the models.Comment: 18 pages, 1 figur

Infrared Fixed Point Structure in Minimal Supersymmetric Standard Model with Baryon and Lepton Number Violation

We study in detail the renomalization group evolution of Yukawa couplings and soft supersymmetry breaking trilinear couplings in the minimal supersymmetric standard model with baryon and lepton number violation. We obtain the exact solutions of these equations in a closed form, and then depict the infrared fixed point structure of the third generation Yukawa couplings and the highest generation baryon and lepton number violating couplings. Approximate analytical solutions for these Yukawa couplings and baryon and lepton number violating couplings, and the soft supersymmetry breaking couplings are obtained in terms of their initial values at the unification scale. We then numerically study the infrared fixed surfaces of the model, and illustrate the approach to the fixed points.Comment: 16 pages REVTeX, figures embedded as epsfigs, replaced with version to appear in Physical Review D, minor typographical errors eliminated and references reordered, figures correcte

Lifetime Bipolar Disorder comorbidity and related clinical characteristics in patients with primary Obsessive Compulsive Disorder: a report from the International College of Obsessive-Compulsive Spectrum Disorders (ICOCS)

IntroductionBipolar disorder (BD) and obsessive compulsive disorder (OCD) are prevalent, comorbid, and disabling conditions, often characterized by early onset and chronic course. When comorbid, OCD and BD can determine a more pernicious course of illness, posing therapeutic challenges for clinicians. Available reports on prevalence and clinical characteristics of comorbidity between BD and OCD showed mixed results, likely depending on the primary diagnosis of analyzed samples.MethodsWe assessed prevalence and clinical characteristics of BD comorbidity in a large international sample of patients with primary OCD (n = 401), through the International College of Obsessive-Compulsive Spectrum Disorders (ICOCS) snapshot database, by comparing OCD subjects with vs without BD comorbidity.ResultsAmong primary OCD patients, 6.2% showed comorbidity with BD. OCD patients with vs without BD comorbidity more frequently had a previous hospitalization (p < 0.001) and current augmentation therapies (p < 0.001). They also showed greater severity of OCD (p < 0.001), as measured by the Yale-Brown Obsessive Compulsive Scale (Y-BOCS).ConclusionThese findings from a large international sample indicate that approximately 1 out of 16 patients with primary OCD may additionally have BD comorbidity along with other specific clinical characteristics, including more frequent previous hospitalizations, more complex therapeutic regimens, and a greater severity of OCD. Prospective international studies are needed to confirm our findings.Peer reviewe

Fermion Mass Hierarchies and Small Mixing Angles from Extra Dimensions

In this paper we study renormalization-group evolutions of Yukawa matrices enhanced by Kaluza-Klein excited modes and analyze their infrared fixed-point structure. We derive necessary conditions to obtain hierarchies between generations on the fixed point. These conditions restrict how the fields in the models can extend to higher dimension. Several specific mechanisms to realize the conditions are presented. We also take account of generation mixing effects and find a scenario where the mixing angles become small at low energy even with large initial values at high-energy scale. A toy model is shown to lead realistic quark mass matrices.Comment: 23 pages, 7 figures, LaTeX, a supplementary explanation and references adde

Nonminimal Supersymmetric Standard Model with Baryon and Lepton Number Violation

We carry out a comprehensive analysis of the nonminimal supersymmetric standard model (NMSSM) with baryon and lepton number violation. We catalogue the baryon and lepton number violating dimension four and five operators of the model. We then study the renormalization group evolution and infrared stable fixed points of the Yukawa couplings and the soft supersymmetry breaking trilinear couplings of this model with baryon and lepton number (and R-parity) violation involving the heaviest generations. We show analytically that in the Yukawa sector of the NMSSM there is only one infrared stable fixed point. This corresponds to a non-trivial fixed point for the top-, bottom-quark Yukawa couplings and the $B$ violating coupling $\lambda_{233}''$, and a trivial one for all other couplings. All other possible fixed points are either unphysical or unstable in the infrared region. We also carry out an analysis of the renormalization group equations for the soft supersymmetry breaking trilinear couplings, and determine the corresponding fixed points for these couplings. We then study the quasi-fixed point behaviour, both of the third generation Yukawa couplings and the baryon number violating coupling, and those of the soft supersymmetry breaking trilinear couplings. From the analysis of the fixed point behaviour, we obtain upper and lower bounds on the baryon number violating coupling $\lambda_{233}''$, as well as on the soft supersymmetry breaking trilinear couplings. Our analysis shows that the infrared fixed point behavior of NMSSM with baryon and lepton number violation is similar to that of MSSM.Comment: 35 pages, Revtex, 6 eps fig

Large Neutrino Mixing from Renormalization Group Evolution

The renormalization group evolution equation for two neutrino mixing is known to exhibit nontrivial fixed point structure corresponding to maximal mixing at the weak scale. The presence of the fixed point provides a natural explanation of the observed maximal mixing of $\nu_{\mu}-\nu_{\tau}$ if the $\nu_{\mu}$ and $\nu_{\tau}$ are assumed to be quasi-degenerate at the seesaw scale without constraining on the mixing angles at that scale. In particular, it allows them to be similar to the quark mixings as in generic grand unified theories. We discuss implementation of this program in the case of MSSM and find that the predicted mixing remains stable and close to its maximal value, for all energies below the $O$(TeV) SUSY scale. We also discuss how a particular realization of this idea can be tested in neutrinoless double beta decay experiments.Comment: Latex file, 21 pages and 4 ps figures include

Mass predictions based on a supersymmetric SU(5) fixed point

I examine the possibility that the third generation fermion masses are determined by an exact fixed point of the minimal supersymmetric SU(5) model. When one-loop supersymmetric thresholds are included, this unified fixed point successfully predicts the top quark mass, 175 +(-) 2 GeV, as well as the weak mixing angle. The bottom quark mass prediction is sensitive to the supersymmetric thresholds; it approaches the measured value for mu <0 and very large unified gaugino mass. The experimental measurement of the tau lepton mass determines tan(beta), and the strong gauge coupling and fine structure constant fix the unification scale and the unified gauge coupling.Comment: 40 pages, 9 figures, 9 tables, Revtex