Security Estimates for Quadratic Field Based Cryptosystems

We describe implementations for solving the discrete logarithm problem in the class group of an imaginary quadratic field and in the infrastructure of a real quadratic field. The algorithms used incorporate improvements over previously-used algorithms, and extensive numerical results are presented demonstrating their efficiency. This data is used as the basis for extrapolations, used to provide recommendations for parameter sizes providing approximately the same level of security as block ciphers with $80,$ $112,$ $128,$ $192,$ and $256$-bit symmetric keys

Architecture’s Direct Impact

How valuable is architecture? The effects of the 2008 recession, namely sustained unemployment in the profession still lingering around 13.9%, have forced soul-searching within the discipline. Recent headlines in the New York Times: “Want a Job? Go to College, and Don’t Major in Architecture” lay bare the value proposition of the profession—the public doesn’t see one

David Dexter Perkins (1919-2007)

Obituary of David Dexter Perkin

Stable p-branes in Chern-Simons AdS supergravities

We construct static codimension-two branes in any odd dimension D, with negative cosmological constant, and show that they are exact solutions of Chern-Simons (super)gravity theory for (super)AdS coupled to external sources. The stability of these solutions is analyzed by counting the number of preserved supersymmetries. It is shown that static massive (D-3)-branes are unstable unless some suitable gauge fields are added and the brane is extremal. In particular, in three dimensions, a 0-brane is recognized as the negative mass counterpart of the BTZ black hole. For these 0-branes, we write explicitly electromagnetically charged BPS states with various number of preserved supersymmetries within the OSp(p|2) x OSp(q|2) supergroups. In five dimensions, we prove that stable 2-branes with electromagnetic charge always exist for the generic supergroup SU(2,2|N), where N is different than 4. For the special case N=4, in which the CS supergravity requires the addition of a nontrivial gauge field configuration in order to preserve maximal number of degrees of freedom, we show for two different static 2-branes that they are BPS states (one of which is the ground state), and from the corresponding algebra of charges we show that the energy is bounded from below. In higher dimensions, our results admit a straightforward generalization, although there are presumably more solutions corresponding to different intersections of the elementary objects.Comment: 43 pages, revtex4.cls; v2: slight amendments and references added to match published versio

Low-Valent Titanium Porphyrin Complexes. Synthesis and Structural Characterization of the First Titanium(II) Porphyrin Complex, (ɳ2-Diphenylacetylene)Oitanium Octaethylporphyrin

The anaerobic reduction of the dlchlorotltanlum( IV) porphyrins (OEP)TICI2 and (TTP)TICI2 (OEP = octaethylporphyrlnato, TTP = meso -tetra-p -tolylporphyrlnato) with LIAIH4 in the presence of diphenylacetylene In toluene produces the 11 -alkyne T~II) aclducts (OEP)TI(172-Phc==cPh) (1) and (TTP)Ti(172-PhC==cPh) (2). The structure of 1 has been determined by single-crystal X-ray diffraction analysis. Complex 1 crystallizes in the centrosymrnetrlc space group C2/c with a= 49.369 (7) A, b = 13.734 (9) A, c = 36.042 (5) A, {3 = 136.62 (1)0 , V = 16784 (9) A3, Z = 16, R = 0.061, and Rw = 0.063. The asymmetric unit of 1 contains two molecules. Alkyne C-C distances and Ti-alkyne distances are 1.30 ( 1) (C27-C28), 2.016 (5) (TI 1-C27), 2.015 (5) (Ti 1-C~8), 1.30 (1) (C81-C62), 2.007 (7) (T12-C61 ), and 2.028 (7) A (Ti2-C62)

The Aquarius Co-Moving Group is Not a Disrupted Classical Globular Cluster

We present a detailed analysis of high-resolution, high S/N spectra for 5 Aquarius stream stars observed with the MIKE spectrograph on the Magellan Clay telescope. Our sample represents one third of the 15 known members in the stream. We find the stream is not mono-metallic: the metallicity ranges from [Fe/H] = -0.63 to -1.58. No anti-correlation in Na-O abundances is present, and we find a strong positive Mg-Al relationship, similar to that observed in the thick disk. We find no evidence that the stream is a result of a disrupted classical globular cluster, contrary to a previously published claim. High [(Na, Ni, alpha)/Fe] and low [Ba/Y] abundance ratios in the stream suggests it is not a tidal tail from a disrupted dwarf galaxy, either. The stream is chemically indistinguishable from Milky Way field stars with the exception of one candidate, C222531-145437. From its position, velocity, and detailed chemical abundances, C222531-145437 is likely a star that was tidally disrupted from omega-Centauri. We propose the Aquarius stream is Galactic in origin, and could be the result from a disk-satellite perturbation in the Milky Way thick disk on the order of a few Gyr ago: derived orbits, UVW velocities, and angular momenta of the Aquarius members offer qualitative support for our hypothesis. Assuming C222531-145437 is a tidally disrupted member of omega-Centauri, this system is the most likely disk perturber. In the absence of compelling chemical and/or dynamical evidence that the Aquarius stream is the tidal tail of a disrupted satellite, we advocate the "Aquarius group" as a more appropriate description. Like the Canis Major over-density, as well as the Hercules and Monoceros groups, the Aquarius group joins the list of kinematically-identified substructures that are not actually accreted material: they are simply part of the rich complexity of the Milky Way structure.Comment: Accepted to MNRAS. Updated to journal versio

Cardiac Troponin Assessment Following Atrial Fibrillation Ablation: Implications for Chest Pain Evaluation

Background: The range of elevation of troponin I (tI) that is within expected limits from left atrial radiofrequency ablation for atrial fibrillation (AF) is not well described, though such information may be of clinical value. Objectives: Identify the expected range of tI values post-atrial fibrillation (AF) ablation. Methods: 31 patients undergoing AF ablation had a single tI level drawn the day following the procedure. Clinical variables were also collected, such as ablation type and radiofrequency (RF) time. Results: Paroxysmal AF was present in 23 patients, and 8 had chronic AF. The average RF time was 2627.8 ± 737.5 seconds. The mean RF power was 61.7 ± 4.3W (range 55-70W). The mean RF temperature limit was 53.6 ± 2.0°C (range 50-55°C). There was no clinical or electrocardiographic evidence of coronary ischemia in this population. The mean tI the following day was 3.21 ± 1.5 (range 1.48-8.41). There was no correlation between RF time, ablation type, ablation catheter size, and ablation temperature or ablation power and tI levels. Conclusions: Troponin I elevation post-ablation was ubiquitous. Knowledge of expected post-ablation tI levels may be helpful in the evaluation of post-procedure chest pain

Cone Deactivation Kinetics and GRK1/GRK7 Expression in Enhanced S Cone Syndrome Caused by Mutations in NR2E3

PURPOSE: To determine the relationship between cone deactivation kinetics in patients with the enhanced S cone syndrome (ESCS) caused by mutations in NR2E3 and the immunoreactivity to G-protein-coupled receptor kinase 1 (GRK1) and GRK7. METHODS: Electroretinogram (ERG) photoresponses were used to investigate activation kinetics of cones with a model of cone phototransduction. Deactivation kinetics of cones after bright flashes was quantified with a paired-flash ERG paradigm. Immunocytochemistry was performed with antibodies against cone opsins and kinases GRK1 and GRK7 in postmortem normal and ESCS retinal tissue. RESULTS: Activation kinetics of long/middle-wavelength-sensitive (L/M) cone-mediated responses in patients with ESCS were similar to those of normal L/M cones. Activation kinetics of ESCS short-wavelength-sensitive (S) cones, when compared with normal L/M cone responses evoked by the same stimulus, were slower by an amount consistent with the expected differences in spectral sensitivities. After bright flashes chosen to evoke identical activation kinetics, ESCS S cones deactivated much more slowly than ESCS or normal L/M cones. Normal human retina revealed strongly labeled cone outer segments with anti-GRK1 and anti-GRK7. In an ESCS retina, outer segments positive for L/M opsin were strongly labeled with anti-GRK1, whereas outer segments positive for S opsin showed no detectable GRK1 reactivity. GRK7 labeling was absent in all photoreceptors of the ESCS retina. CONCLUSIONS: The cone-dominant human retina resulting from NR2E3 mutations affords greater understanding of the physiological roles of GRK1 and GRK7 in human cone photoreceptors. Normal deactivation kinetics in human L/M cones can occur without GRK7 when GRK1 is present in ESCS, but does not occur when GRK7 is present but GRK1 is deficient in Oguchi disease. Lack of both GRK1 and GRK7 in S cones of patients with ESCS results in a more pronounced abnormality in deactivation kinetics and suggests the existence of partial compensation by either GRK when the other is deficient