Meet Irreducible Ideals and Representations of Limit Algebras

In this paper we give a criterion for an ideal of a TAF algebra to be meet irreducible. We show that an ideal $J$ of $A$ is meet irreducile if and only if the C$^*$-envelope of the quotient $A/J$ is primitive. In that case, A/J admits a nest representation which extends to a *-representation of the C$^*$-envelope for $A/J.$ We also characterize the meet irreducible ideals as the kernels of nest representations; this settles the question of whether the n-primitive and meet irreducible ideals coincide.Comment: 8 pages; accepted in JF

Dilating covariant representations of the non-commutative disc algebras

Let $\phi$ be an isometric automorphism of the non-commutative disc algebra \fA_n for $n \geq 2$. We show that every contractive covariant representation of (\fA_n, \phi) dilates to a unitary covariant representation of (\O_n, \phi). Hence the C*-envelope of the semicrossed product \fA_n \times_{\phi} \bZ^+ is \O_n \times_{\phi} \bZ.Comment: 18 page

Signatures of magnetic-field effects in nonsequential double ionization manifesting as backscattering for molecules versus forward scattering for atoms

For two-electron diatomic molecules, we investigate magnetic field effects in nonsequential double ionization where recollisions prevail. We do so by formulating a three-dimensional semiclassical model that fully accounts for the Coulomb singularities and for magnetic field effects during time propagation. Using this model, we identify a prominent signature of nondipole effects. Namely, we demonstrate that the recolliding electron backscatters along the direction of light propagation. Hence, this electron escapes opposite to the direction of change in momentum due to the magnetic field. This is in striking contrast to strongly driven atoms where the recolliding electron forward scatters along the direction of light propagation. We attribute these distinct signatures to the different gate that the magnetic field creates jointly with a soft recollision in molecules compared to a hard recollision in atoms. These two different gates give rise, shortly before recollision, to different momenta and positions of the recolliding electron along the direction of light propagation. As a result, we show that the Coulomb forces from the nuclei act to backscatter the recolliding electron in molecules and forward scatter it in atoms along the direction of light propagation

Retrorectal endometrioid cyst: a case report

<p>Abstract</p> <p>Introduction</p> <p>Developmental cysts are the most common retrorectal cystic lesions in adults, whereas reports of endometrioid cysts in this anatomic location are extremely rare.</p> <p>Case presentation</p> <p>A 21-year-old nulliparous Greek woman presented with chronic noncyclic pelvic pain, and a retrorectal cyst was diagnosed. The lesion was resected through a laparotomy and, on histologic examination, was found to be an endometrioid cyst. The treatment was completed with a six-month course of a gonadotropin-releasing hormone analogue. One year after surgery, the woman remained free of symptoms, and pelvic imaging showed no recurrence of the lesion. Reviewing the literature, we found only three previous reports of an endometrioid cyst in this anatomic location.</p> <p>Conclusion</p> <p>In women of reproductive age, endometriosis must be included in the differential diagnosis of retrorectal cysts.</p

How to estimate the association between change in a risk factor and a health outcome?

Estimating the effect of a change in a particular risk factor and a chronic disease requires information on the risk factor from two time points; the enrolment and the first follow-up. When using observational data to study the effect of such an exposure (change in risk factor) extra complications arise, namely (i) when is time zero? and (ii) which information on confounders should we account for in this type of analysis? From enrolment or the 1st follow-up? Or from both?. The combination of these questions has proven to be very challenging. Researchers have applied different methodologies with mixed success, because the different choices made when answering these questions induce systematic bias. Here we review these methodologies and highlight the sources of bias in each type of analysis. We discuss the advantages and the limitations of each method ending by making our recommendations on the analysis plan