246 research outputs found
The cosmological dependence of weak interactions
A model for the cosmological time dependence of weak interactions is discused and some experimental tests suggested
Wave and Particle Limit for Multiple Barrier Tunneling
The particle approach to one-dimensional potential scattering is applied to
non relativistic tunnelling between two, three and four identical barriers. We
demonstrate as expected that the infinite sum of particle contributions yield
the plane wave results. In particular, the existence of resonance/transparency
for twin tunnelling in the wave limit is immediately obvious. The known
resonances for three and four barriers are also derived. The transition from
the wave limit to the particle limit is exhibit numerically.Comment: 15 pages, 3 figure
Barrier Paradox in the Klein Zone
We study the solutions for a one-dimensional electrostatic potential in the
Dirac equation when the incoming wave packet exhibits the Klein paradox (pair
production). With a barrier potential we demonstrate the existence of multiple
reflections (and transmissions). The antiparticle solutions which are
necessarily localized within the barrier region create new pairs with each
reflection at the potential walls. Consequently we encounter a new paradox for
the barrier because successive outgoing wave amplitudes grow geometrically.Comment: 10 page
The role of miRNA-133b and its target gene SIRT1 in FAP-derived desmoid tumor.
Signaling pathways have a key role in driving the uncontrolled development of familial adenomatous polyposis (FAP)- associated and sporadic desmoid tumors (DTs). The relationship between the Wnt/b-catenin signaling pathway and DTs has been extensively studied, but no reliable biomarkers able to detect their histological subtype have been identified for the accurate diagnosis. In this study we studied the differences in miRNA expression between sporadic (20 patients) and FAP-associated DTs (7 patients) using microarray confirmed by quantitative PCR (qPCR). The analysis showed 19 dysregulated miRNAs. Among them miR-133b levels were significantly lower in FAP-associated DT than in sporadic DT. Therefore, two mRNAs, associated to miR-133b and β-catenin expression, the SIRT1 and ELAVL1were analyzed. The qPCR analysis showed that SIRT1 mRNA levels were significantly up-regulated in FAP-associated DT than in sporadic DT, whereas no differences in ELAVL1 expression was observed between these two DT types. In addition, a negative correlation was observed between miR-133b and SIRT1 in FAP-associated DTs, but not in sporadic DTs. The miR-133b-SIRT1-β-catenin axis may represent a novel mechanism underlying progression of FAP-associated D
Remarks upon the mass oscillation formulas
The standard formula for mass oscillations is often based upon the
approximation and the hypotheses that neutrinos have been
produced with a definite momentum or, alternatively, with definite energy
. This represents an inconsistent scenario and gives an unjustified
reduction by a factor of two in the mass oscillation formulas. Such an
ambiguity has been a matter of speculations and mistakes in discussing flavour
oscillations. We present a series of results and show how the problem of the
factor two in the oscillation length is not a consequence of gedanken
experiments, i.e. oscillations in time. The common velocity scenario yields the
maximum simplicity.Comment: 9 pages, AMS-Te
Contemplations on Dirac's equation in quaternionic coordinates
A formulation of Dirac's equation using complex-quaternionic coordinates
appears to yield an enormous gain in formal elegance, as there is no longer any
need to invoke Dirac matrices. This formulation, however, entails several
peculiarities, which we investigate and attempt to interpret
Timelapse
We discuss the existence in an arbitrary frame of a finite time for the
transformation of an initial quantum state into another e.g. in a decay.
This leads to the introduction of a timelapse in analogy with
the lifetime of a particle. An argument based upon the Heisenberg uncertainty
principle suggests the value of . Consequences for the
exponential decay formula and the modifications that introduces
into the Breit-Wigner mass formula are described.Comment: 5 pages [2 figs], ReV-Te
Survival law in a potential model
The radial equation of a simple potential model has long been known to yield
an exponential decay law in lowest order (Breit-Wigner) approximation. We
demonstrate that if the calculation is extended to fourth order the decay law
exhibits the quantum Zeno effect. This model has further been studied
numerically to characterize the extra exponential time parameter which
compliments the lifetime. We also investigate the inverse Zeno effect.Comment: 16 pages, 2 tables, 3 figures, AMS-Te
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