A matrix-valued point interactions model

We study a matrix-valued Schr\"odinger operator with random point interactions. We prove the absence of absolutely continuous spectrum for this operator by proving that away from a discrete set its Lyapunov exponents do not vanish. For this we use a criterion by Gol'dsheid and Margulis and we prove the Zariski denseness, in the symplectic group, of the group generated by the transfer matrices. Then we prove estimates on the transfer matrices which lead to the H\"older continuity of the Lyapunov exponents. After proving the existence of the integrated density of states of the operator, we also prove its H\"older continuity by proving a Thouless formula which links the integrated density of states to the sum of the positive Lyapunov exponents

A memetic algorithm with adaptive hill climbing strategy for dynamic optimization problems

Copyright @ Springer-Verlag 2008Dynamic optimization problems challenge traditional evolutionary algorithms seriously since they, once converged, cannot adapt quickly to environmental changes. This paper investigates the application of memetic algorithms, a class of hybrid evolutionary algorithms, for dynamic optimization problems. An adaptive hill climbing method is proposed as the local search technique in the framework of memetic algorithms, which combines the features of greedy crossover-based hill climbing and steepest mutation-based hill climbing. In order to address the convergence problem, two diversity maintaining methods, called adaptive dual mapping and triggered random immigrants, respectively, are also introduced into the proposed memetic algorithm for dynamic optimization problems. Based on a series of dynamic problems generated from several stationary benchmark problems, experiments are carried out to investigate the performance of the proposed memetic algorithm in comparison with some peer evolutionary algorithms. The experimental results show the efficiency of the proposed memetic algorithm in dynamic environments.This work was supported by the National Nature Science Foundation of China (NSFC) under Grant Nos. 70431003 and 70671020, the National Innovation Research Community Science Foundation of China under Grant No. 60521003, and the National Support Plan of China under Grant No. 2006BAH02A09 and the Engineering and Physical Sciences Research Council (EPSRC) of UK under Grant EP/E060722/01

A multi-transition HCN and HCO+ study of 12 nearby active galaxies: AGN versus SB environments

Recent studies have indicated that the HCN-to-CO(J=1-0) and HCO+-to-HCN(J=1-0) ratios are significantly different between galaxies with AGN (active galactic nucleus) and SB (starburst) signatures. In order to study the molecular gas properties in active galaxies and search for differences between AGN and SB environments, we observed the HCN(J=1-0), (J=2-1), (J=3-2), HCO+(J=1-0) and HCO+(J=3-2), emission with the IRAM 30m in the centre of 12 nearby active galaxies which either exhibit nuclear SB and/or AGN signatures. Consistent with previous results, we find a significant difference of the HCN(J=2-1)-to-HCN(J=1-0), HCN(J=3-2)-to-HCN(J=1-0), HCO+(J=3-2)-to-HCO+(J=3-2), and HCO+-to-HCN intensity ratios between the sources dominated by an AGN and those with an additional or pure central SB: the HCN, HCO+ and HCO+-to-HCN intensity ratios tend to be higher in the galaxies of our sample with a central SB as opposed to the pure AGN cases which show rather low intensity ratios. Based on an LVG analysis of these data, i.e., assuming purely collisional excitation, the (average) molecular gas densities in the SB dominated sources of our sample seem to be systematically higher than in the AGN sources. The LVG analysis seems to further support systematically higher HCN and/or lower HCO+ abundances as well as similar or higher gas temperatures in AGN compared to the SB sources of our sample. Also, we find that the HCN-to-CO ratios decrease with increasing rotational number J for the AGN while they stay mostly constant for the SB sources.Comment: accepted for publication in ApJ; 20 pages, 7 figures; in emulateApJ forma

Behavioral Effects of Tyrosine During Sustained Wakefulness

The fatigue and cognitive performance deficits associated with sleep loss and stress, like that experienced during sustained flight operations and nighttime flying, have motivated the search for effective nonpharmacological countermeasures. The behavioral effects of the potential countermeasure tyrosine, an amino-acid precursor to dopamine and norepinephrine, were examined during an episode of continuous nighttime work involving one night\u27s sleep loss. Volunteers performed nine iterations of a battery of cognitive and subjective tasks for approximately 13 h, beginning at 1930 and ending at 0820 the following morning. Subjects remained awake throughout the day on which the experiment began and were awake for approximately 24 h by the end of testing. Six hours after the start of the experiment, one-half of the subjects received 150 mg/kg tyrosine in a split dose while the other half received a cornstarch placebo in a double-blind procedure. The tracking-task performance of tyrosine subjects declined less during the night than that of placebo subjects. Tyrosine administration was also associated with nonsignificant trends toward reducing (a) lapses on a high-event-rate vigilance task, (b) subjective sleepiness, and (c) the intensities of several fatigue-related symptoms

Linking the chiral and deconfinement phase transitions

We show that the electric glueball becomes critical at the end-point of the deconfinement phase transition in finite temperature QCD. Based on this observation and existing lattice data, we argue that the chiral phase transition at a zero quark mass and the deconfinement phase transition at an infinite quark mass are continuously connected by the glueball-sigma mixing.Comment: 4 pages, terminology corrected. To appear in Phys. Rev.

Automated quantification of uveitic keratic precipitates by use of anterior segment optical coherence tomography

BACKGROUND: Evaluation of ocular inflammation via common imaging modalities like optical coherence tomography (OCT) has emphasised cell visualisation, but automated detection of uveitic keratic precipitates (KPs) remains unexplored. METHODS: Anterior segment (AS)-OCT dense volumes of the corneas of patients with uveitic KPs were collected at three timepoints: with active (T0), clinically improving (T1), and resolved (T2) inflammation. At each visit, visual acuity and clinical grading of the anterior chamber cells were assessed. A bespoke algorithm was used to create an en face rendering of the KPs and to calculate their volume and a ratio of the volume of precipitates over the analysed area. The variation of AS-OCT-derived measurements over time was assessed, and compared with clinical grading. RESULTS: Twenty eyes from 20 patients (13 females, mean age 39 years) were studied. At T0, the mean volume of the corneal KPs was 0.1727 mm3 , and it significantly reduced to 0.1111 mm3 (p = 0.03) only at T2. The ratio between the volume of the KPs and the corneal area decreased from T0 (0.007) to T1 (0.006; p = 0.2) and T2 (0.004; p = 0.009). There was a statistically significant correlation between the AC cell count and the AS-OCT volume measurements of the KPs at the three time points. CONCLUSIONS: AS-OCT can image uveitic KPs and through a bespoke algorithm we were able to create an en face rendering allowing us to extrapolate their volume. We found that objective quantification of KPs correlated with inflammatory cell counts in the anterior chamber

Angles from BB Decays with Charm

Proceedings of the CKM 2005 Workshop (WG5), UC San Diego, 15-18 March 2005.Comment: 62 pages, 55 figures. Proceedings of the CKM 2005 Workshop (WG5), UC San Diego, 15-18 March 200

Responsive Nucleic Acid-Based Organosilica Nanoparticles

The development of smart nanoparticles (NPs) that encode responsive features in the structural framework promises to extend the applications of NP-based drugs, vaccines, and diagnostic tools. New nanocarriers would ideally consist of a minimal number of biocompatible components and exhibit multiresponsive behavior to specific biomolecules, but progress is limited by the difficulty of synthesizing suitable building blocks. Through a nature-inspired approach that combines the programmability of nucleic acid interactions and sol-gel chemistry, we report the incorporation of synthetic nucleic acids and analogs, as constitutive components, into organosilica NPs. We prepared different nanomaterials containing single-stranded nucleic acids that are covalently embedded in the silica network. Through the incorporation of functional nucleic acids into the organosilica framework, the particles respond to various biological, physical, and chemical inputs, resulting in detectable physicochemical changes. The one-step bottom-up approach used to prepare organosilica NPs provides multifunctional systems that combine the tunability of oligonucleotides with the stiffness, low cost, and biocompatibility of silica for different applications ranging from drug delivery to sensing