CoCoA: A General Framework for Communication-Efficient Distributed Optimization

The scale of modern datasets necessitates the development of efficient distributed optimization methods for machine learning. We present a general-purpose framework for distributed computing environments, CoCoA, that has an efficient communication scheme and is applicable to a wide variety of problems in machine learning and signal processing. We extend the framework to cover general non-strongly-convex regularizers, including L1-regularized problems like lasso, sparse logistic regression, and elastic net regularization, and show how earlier work can be derived as a special case. We provide convergence guarantees for the class of convex regularized loss minimization objectives, leveraging a novel approach in handling non-strongly-convex regularizers and non-smooth loss functions. The resulting framework has markedly improved performance over state-of-the-art methods, as we illustrate with an extensive set of experiments on real distributed datasets

Functional and anatomic response of the retina and the choroid to intravitreal bevacizumab for macular edema.

Purpose: This study evaluated the rate of change of best corrected visual acuity (BCVA), central retinal sensitivity, and retinal and choroidal thickness in patients with macular edema after intravitreal bevacizumab. Methods: This was a prospective, nonrandomized, interventional study. Thirty-four consecutive eyes (34 patients) with macular edema were included in the study. Choroidal neovascularization was present in 21 cases, stage 1 retinal angiomatous proliferation in 6 cases, branch retinal vein occlusion in 4 cases, and diabetic edema in 3 cases. Evaluation of BCVA (Early Treatment Diabetic Retinopathy Study [ETDRS] logarithm of the minimum angle of resolution [LogMAR]), central retinochoroidal thickness (RCT) at standardized A-scan, combined optical coherence tomography/microperimetric assessment of central retinal thickness (RT), central scotoma, and fixation behavior was performed during 12 months after treatment. Choroidal thickness was considered as the difference between RCT and RT. All patients received two initial intravitreal bevacizumab injections (1.25 mg/0.05 mL) at a 1-month interval. Results: BCVA and RT during follow-up were significantly better than at baseline. BCVA was improved of 0.32 +/- 0.3 LogMAR (P < 0.001) at month 1,0.18 +/- 0.4 LogMAR (P = 0.05) at month 6, and 0.14 +/- 0.2 (P = 0.09) at month 12. RT was reduced by 172.9 +/- 192.8 mu m (P < 0.001) at month 1,157.7 +/- 134.2 mu m (P = 0.003) at month 6, and 164.3 +/- 122.3 (P = 0.002) at month 12. Mean retinal sensitivity significantly increased during the first month; it decreased afterward, but an improvement if compared with baseline was present at each visit during follow-up. In 23.5% of cases, a choroidal thinning was present during follow-up, and in this group visual acuity at baseline and final visual improvement were significantly greater if compared with patients showing a choroidal thickening. Conclusion: Intravitreal bevacizumab for macular edema determines significant functional and anatomic improvement at the 12-month follow-up. Visual acuity at baseline and following treatment could be influenced by the choroidal involvement

One-pot thiol–amine bioconjugation to maleimides: simultaneous stabilisation and dual functionalisation

Maleimide chemistry is widely used in the site-selective modification of proteins. However, hydrolysis of the resultant thiosuccinimides is required to provide robust stability to the bioconjugates. Herein, we present an alternative approach that affords simultaneous stabilisation and dual functionalisation in a one pot fashion. By consecutive conjugation of a thiol and an amine to dibromomaleimides, we show that aminothiomaleimides can be generated extremely efficiently. Furthermore, the amine serves to deactivate the electrophilicity of the maleimide, precluding further reactivity and hence generating stable conjugates. We have applied this conjugation strategy to peptides and proteins to generate stabilised trifunctional conjugates. We propose that this stabilisation-dual modification strategy could have widespread use in the generation of diverse conjugates

A rigorous bound on quark distributions in the nucleon

I deduce an inequality between the helicity and the transversity distribution of a quark in a nucleon, at small energy scales. Then I establish, thanks to the positivity constraint, a rigorous bound on longitudinally polarized valence quark densities, which finds nontrivial applications to d-quarks. This, in turn, implies a bound for the distributions of the longitudinally polarized sea, which is probably not SU(3)-symmetric. Some model predictions and parametrizations of quark distributions are examined in the light of these results.Comment: Talk given at the QCD03 Conference, Montpellier, 2-9 July 200

Unified model of baryonic matter and dark components

We investigate an interacting two-fluid cosmological model and introduce a scalar field representation by means of a linear combination of the individual energy densities. Applying the integrability condition to the scalar field equation we show that this "exotic quintessence" is driven by an exponential potential and the two-fluid mixture can be considered as a model of three components. These components are associated with baryonic matter, dark matter and dark energy respectively. We use the Simon, Verde & Jimenez (2005) determination of the redshift dependence of the Hubble parameter to constrain the current density parameters of this model. With the best fit density parameters we obtain the transition redshift between non accelerated and accelerated regimes z_{acc}=0.66 and the time elapsed since the initial singularity t_0= 19.8 Gyr. We study the perturbation evolution of this model and find that the energy density perturbation decreases with the cosmological time.Comment: 8 pages, 6 figures A new section adde

Testing the meson cloud in the nucleon in Drell-Yan processes

We discuss the present status of the \bar u-\bar d asymmetry in the nucleon and analize the quantities which are best suited to verify the asymmetry. We find that the Drell-Yan asymmetry is the quantity insensitive to the valence quark distributions and very sensitive to the flavour asymmetry of the sea. We compare the prediction of the meson cloud model with different experimental data including the Fermilab E772 data and recent data of the NA51 Collaboration at CERN and make predictions for the planned Drell-Yan experiments.Comment: written in ReVTeX, 26 pages + 10 PS-figure

New Bifunctional Chelators Incorporating Dibromomaleimide Groups for Radiolabeling of Antibodies with Positron Emission Tomography Imaging Radioisotopes

Positron Emission Tomography (PET) imaging with antibody-based contrast agents frequently uses the radioisotopes [{64}^Cu]Cu^{2+} and [{89}^Zr]Zr^{4+}. The macrobicyclic chelator commonly known as sarcophagine (sar) is ideal for labeling receptor-targeted biomolecules with [{64}^Cu]Cu^{2+}. The siderophore chelator, desferrioxamine-B (dfo), has been widely used to incorporate [{89}^Zr]Zr^{4+}, respectively, in near quantitative radiochemical yield (>99%). Serum stability studies, in vivo PET imaging, and biodistribution analyses using these radiolabeled immunoconjugates demonstrate that both [{64}^Cu]Cu-sar–dtm–trastuzumab and [{89}^Zr]Zr-dfo–dtm–trastuzumab possess high stability in biological milieu. Dibromomaleimide technology can be easily applied to enable stable, site-specific attachment of radiolabeled chelators, such as sar and dfo, to native interstrand disulfide regions of antibodies, enabling tracking of antibodies with PET imaging

Detailed Balance and Intermediate Statistics

We present a theory of particles, obeying intermediate statistics ("anyons"), interpolating between Bosons and Fermions, based on the principle of Detailed Balance. It is demonstrated that the scattering probabilities of identical particles can be expressed in terms of the basic numbers, which arise naturally and logically in this theory. A transcendental equation determining the distribution function of anyons is obtained in terms of the statistics parameter, whose limiting values 0 and 1 correspond to Bosons and Fermions respectively. The distribution function is determined as a power series involving the Boltzmann factor and the statistics parameter and we also express the distribution function as an infinite continued fraction. The last form enables one to develop approximate forms for the distribution function, with the first approximant agreeing with our earlier investigation.Comment: 13 pages, RevTex, submitted for publication; added references; added sentence

Longitudinal Polarization of Lambda and anti-Lambda Hyperons in Lepton-Nucleon Deep-Inelastic Scattering

We consider models for the spin transfers to $\Lambda$ and $\bar{\Lambda}$ hyperons produced in lepton-nucleon deep-inelastic scattering. We make predictions for longitudinal $\Lambda$ and $\bar{\Lambda}$ spin transfers for the COMPASS experiment and for HERA, and for the spin transfer to $\Lambda$ hyperons produced at JLAB. We demonstrate that accurate measurements of the spin transfers to $\Lambda$ and $\bar{\Lambda}$ hyperons with COMPASS kinematics have the potential to probe the intrinsic strangeness in the nucleon. We show that a measurement of $\bar{\Lambda}$ polarisation could provide a clean probe of the spin transfer from $\bar{s}$ quarks and provides a new possibility to measure the antistrange quark distribution function. COMPASS data in a domain of x that has not been studied previously will provide valuable extra information to fix models for the nucleon spin structure. The spin transfer to $\bar{\Lambda}$ hyperons, which could be measured by the COMPASS experiment, would provide a new tool to distinguish between the SU(6) and Burkardt-Jaffe (BJ) models for baryon spin structure. In the case of the HERA electron-proton collider experiments with longitudinally-polarised electrons, the separation between the target and current fragmentation mechanisms is more clear. It provides a complementary probe of the strange quark distribution and helps distinguish between the SU(6) and BJ models for the $\Lambda$ and $\bar{\Lambda}$ spin structure. Finally, we show that the spin transfer to $\Lambda$ hyperons measured in a JLAB experiment would be dominated by the spin transfer of the intrinsic polarised-strangeness in the remnant nucleon, providing an independent way to check our model predictions.Comment: minor changes after accepted to EPJ

The AIMSS Project – III. The Stellar Populations of Compact Stellar Systems

In recent years, a growing zoo of compact stellar systems (CSSs) have been found whose physical properties (mass, size, velocity dispersion) place them between classical globular clusters (GCs) and true galaxies, leading to debates about their nature. Here we present results using a so far underutilized discriminant, their stellar population properties. Based on new spectroscopy from 8–10m telescopes, we derive ages, metallicities, and [α/Fe] of 29 CSSs. These range from GCs with sizes of merely a few parsec to compact ellipticals (cEs) larger than M32. Together with a literature compilation, this provides a panoramic view of the stellar population characteristics of early-type systems. We find that the CSSs are predominantly more metal rich than typical galaxies at the same stellar mass. At high mass, the cEs depart from the mass–metallicity relation of massive early-type galaxies, which forms a continuous sequence with dwarf galaxies. At lower mass, the metallicity distribution of ultracompact dwarfs (UCDs) changes at a few times 107 M⊙, which roughly coincides with the mass where luminosity function arguments previously suggested the GC population ends. The highest metallicities in CSSs are paralleled only by those of dwarf galaxy nuclei and the central parts of massive early types. These findings can be interpreted as CSSs previously being more massive and undergoing tidal interactions to obtain their current mass and compact size. Such an interpretation is supported by CSSs with direct evidence for tidal stripping, and by an examination of the CSS internal escape velocities