Toward a Neutrino Mass Matrix

One may identify the general properties of the neutrino mass matrix by generating many random mass matrices and testing them against the results of the neutrino experiments.Comment: 3 pages, 1 figure, talk at DPF200

Epithelial ErbB2 regulation of thymus homeostasis and age-associated T cell mediated immunity

The molecular mechanisms governing the functional and structural decline of thymus with age, causing thymic immunosenescence, are incompletely identified. Using a bitransgenic mouse model, Dr Giangreco discovered that the over-expression of receptor tyrosine kinase ErbB2 causes reversible thymic atrophy. The over-expression of epithelial ErbB2 upon doxycycline administration in bitransgenic mice led to decreased thymus size and cellularity, loss of cortical-medullary boundary and abnormal T cell differentiation, bearing similarity to age-dependent thymic involution. This thesis set out to investigate this observation in more detail. I demonstrated that the observed atrophy in bitransgenic thymuses was because of thymus-specific ErbB2 expression, by employing foetal thymic organ cultures. In addition, I showed that over-expression of epithelial ErbB2 disrupted the thymic epithelial cells distribution. Also, an increase in Sca1+Cd49f+ epithelial cells with stem cell potential was noted, explaining why the thymic atrophy in bitransgenic mice was reversible. Exploration of the potential mechanistic pathways found that the thymic atrophy phenotype of K14-NICDER mice, in which epithelial Notch is activated upon tamoxifen administration, resembled the bitransgenic mouse thymic atrophy phenotype. However, mechanistic studies failed to establish ErbB2 acting upstream of Notch, and require further investigation. Administration of Lapatinib, an ErbB2 inhibitor improved the thymic organization and function in aged mice. Lapatinib treatment of aged mice also enhanced vaccine responses to Prevenar 13, a Streptococcus pneumoniae glycoconjugate vaccine, and increased the efficacy of vaccination to protect against subsequent pneumonia challenge. However my results showed that ErbB2 inhibition does not reverse thymic atrophy in scurfy mice, which have truncated Foxp3 protein, and an autoimmune phenotype. In conclusion, this study highlights the importance of ErbB2 in maintaining thymus homeostasis and thymus mediated immunity, and proposes a novel ErbB2 inhibition therapy for rejuvenating an aged thymus, to counter the associated immunosenescence and thereby improve vaccine responses

Feasibility and benefits of laminar flow control on supersonic cruise airplanes

An evaluation was made of the applicability and benefits of laminar flow control (LFC) technology to supersonic cruise airplanes. Ancillary objectives were to identify the technical issues critical to supersonic LFC application, and to determine how those issues can be addressed through flight and wind-tunnel testing. Vehicle types studied include a Mach 2.2 supersonic transport configuration, a Mach 4.0 transport, and two Mach 2-class fighter concepts. Laminar flow control methodologies developed for subsonic and transonic wing laminarization were extended and applied. No intractible aerodynamic problems were found in applying LFC to airplanes of the Mach 2 class, even ones of large size. Improvements of 12 to 17 percent in lift-drag ratios were found. Several key technical issues, such as contamination avoidance and excresence criteria were identified. Recommendations are made for their resolution. A need for an inverse supersonic wing design methodology is indicated

Soft Glass Equiangular Spiral Photonic Crystal Fiber for Supercontinuum Generation

An equiangular spiral photonic crystal fiber (ES-PCF) design in soft glass is presented that has high nonlinearity ( gamma > 5250 W-1 middot km-1 at 1064 nm and gamma > 2150 W-1 middot km-1 at 1550 nm) with a low and flat dispersion (D ~ 0.8 ps/kmmiddotnm and dispersion slope ~ -0.7 ps/km middot nm2 at 1060 nm). The design inspired by nature is characterized by a full-vectorial finite element method. The ES-PCF presented improves over the mode confinement of triangular core designs and dispersion control of conventional hexagonal PCF, combining the advantages of both designs; it can be an excellent candidate for generating supercontinuum pumped at 1.06 mum

Metal-Coated Defect-Core Photonic Crystal Fiber for THz Propagation

Modal solutions for metal-coated defect-core photonic crystal fiber (PCF) with a central air-hole have been obtained by using a full-vectorial finite element method to model the guidance of THz waves. It has been shown that the surface plasmon modes can couple with the defect-core PCF mode to form supermodes, with potential for sensing applications

The satisfiability problem for probabilistic ordered branching programs

We show that the satisfiability problem for bounded-error probabilistic ordered branching programs is \NP -complete. If the error is very small, however (more precisely, if the error is bounded by the reciprocal of the width of the branching program), then we have a polynomial-time algorithm for the satisfiability problem