Total photoionization cross section of planar helium: scaling laws and collision orbits

The total photoionization cross section of planar helium has been calculated up to the single ionization threshold I22 of triple P states. The cross section shows chaotic fluctuations as the energy E approaches the double ionization threshold E=0. By analyzing the fluctuating part of the cross section, we show that its amplitude decreases as ∣E∣ mu for E-> 0- as predicted in Byunet al(2007 Phys. Rev. Lett., 98, 113001). The Fourier transform of the fluctuating part reveals peaks at the classical actions of closed triple collision orbits. Furthermore, the relative height of the peaks is consistent with the semiclassical predictions. Our findings underline that the fluctuating part of the photoionization cross section can be described by classical triple collision orbits in the semiclassical limit. These orbits all lie in the collinear eZe subspace, demonstrating that the fluctuations are dominated by the dynamics of this low dimensional phase space

Scaling laws for the photo-ionisation cross section of two-electron atoms

The cross sections for single-electron photo-ionisation in two-electron atoms show fluctuations which decrease in amplitude when approaching the double-ionisation threshold. Based on semiclassical closed orbit theory, we show that the algebraic decay of the fluctuations can be characterised in terms of a threshold law $\sigma \propto |E|^{\mu}$ as $E \to 0_-$ with exponent $\mu$ obtained as a combination of stability exponents of the triple-collision singularity. It differs from Wannier's exponent dominating double ionisation processes. The details of the fluctuations are linked to a set of infinitely unstable classical orbits starting and ending in the non-regularisable triple collision. The findings are compared with quantum calculations for a model system, namely collinear helium.Comment: 4 pages, 1 figur

GALEX Ultraviolet Photometry of Globular Clusters in M31

We present ultraviolet photometry for globular clusters (GCs) in M31 from 15 square deg of imaging using the Galaxy Evolution Explorer (GALEX). We detect 200 and 94 GCs with certainty in the near-ultraviolet (NUV; 1750 - 2750 Angstroms) and far-ultraviolet (FUV; 1350 - 1750 Angstroms) bandpasses, respectively. Our rate of detection is about 50% in the NUV and 23% in the FUV, to an approximate limiting V magnitude of 19. Out of six clusters with [Fe/H]>-1 seen in the NUV, none is detected in the FUV bandpass. Furthermore, we find no candidate metal-rich clusters with significant FUV flux, because of the contribution of blue horizontal-branch (HB) stars, such as NGC 6388 and NGC 6441, which are metal-rich Galactic GCs with hot HB stars. We show that our GALEX photometry follows the general color trends established in previous UV studies of GCs in M31 and the Galaxy. Comparing our data with Galactic GCs in the UV and with population synthesis models, we suggest that the age range of M31 and Galactic halo GCs are similar.Comment: This paper will be published as part of the Galaxy Evolution Explorer (GALEX) Astrophysical Journal Letters Special Issue. Links to the full set of papers will be available at http://www.galex.caltech.edu/PUBLICATIONS/ after November 22, 200

Primary Cardiac Lymphoma Presenting With Atrioventricular Block

Primary cardiac lymphomas (PCL) are extremely rare. Clinical manifestations may be variable and are attributed to location. Here, we report on a case of PCL presenting with atrioventricular (AV) block. A 55 year-old male had experienced chest discomfort with unexplained dyspnea and night sweating. His initial electrocardiogram (ECG) revealed a first degree AV block. Along with worsening chest discomfort and dyspnea, his ECG changed to show second degree AV block (Mobitz type I). Computed tomography (CT) scan showed a cardiac mass (about 7 cm) and biopsy was performed. Pathologic finding confirmed diffuse large B-cell lymphoma. The patient was treated with multi-drug combination chemotherapy (R-CHOP: Rituximab, cyclophoshamide, anthracycline, vincristine, and prednisone). After treatment, ECG changed to show normal sinus rhythm with complete remission on follow-up CT scan

Toll-like Receptors 2 and 4 and Their Mutations in Patients with Otitis Media and Middle Ear Effusion

ObjectivesToll-like receptors (TLRs) detect microbial infections and they can directly induce innate host defense responses. TLR 2 has been shown to be primarily involved in the recognition of peptidoglycans and lipoteichoic acid of gram positive bacteria. TLR 4 recognizes lipopolysaccharides and lipoteichoic acids from both gram-negative and gram-positive bacteria. Both mutations lead a reduced capacity to elicit inflammation and they increase the risk for gram-positive and negative infections. This study was performed to investigate the expressions of TLR 2 and 4 and their mutations in patients suffering with otitis media and middle ear effusion.MethodsMiddle ear fluid samples were collected from 40 otitis media effusion (OME) patients who had ventilating tubesinserted. Bacteria in the effusion fluid were detected by standard bacterial culture. The secreted IgG, IgA and IgM were measured by Enzyme-linked immunosorbent assay. TLR 2 and 4 were assessed by performing RT-PCR. The genomic DNA from each patient was isolated from the middle ear fluid samples that were collected from 60 OME patients, and the presence of mutations was determined by performing restriction digestion and DNA sequencing analysis.ResultsAmong the 40 middle ear fluid samples, bacteria were detected in 13 middle ear fluid samples. The amounts of IgM, IgA, and IgG were 151.20±60.94 ng/mL, 21.59±7.96 ng/mL and 11.55±16.98 ng/mL, respectively. TLR 2 and 4 were expressed in the middle ear fluid and the expression of TLR 2 was higher than that of TLR 4. However, there was no correlation between the expressions of TLR 2 and 4, and the concentration of immunoglobulin or the presence of bacteria (P>0.05). There ware no mutations of TLR 2 (Arg753Gln, Arg677Trp) and TLR 4 (Asp299Gly, Thr399Ile).ConclusionTLR 2 and 4 were expressed in all the middle ear fluid samples of OME, but the mutations of TLR 2 and 4 were not detected. TLR 2 and 4 may play a vital role in the immunological responses of patients with OME