Frank–Wolfe and friends: a journey into projection-free first-order optimization methods

Invented some 65 years ago in a seminal paper by Marguerite Straus-Frank and Philip Wolfe, the Frank–Wolfe method recently enjoys a remarkable revival, fuelled by the need of fast and reliable first-order optimization methods in Data Science and other relevant application areas. This review tries to explain the success of this approach by illustrating versatility and applicability in a wide range of contexts, combined with an account on recent progress in variants, improving on both the speed and efficiency of this surprisingly simple principle of first-order optimization.

     

Selenated and Sulfurated Analogues of Triacyl Glycerols: Selective Synthesis and Structural Characterization

The synthesis of sulfur- and selenium-containing isosters of triacyl glycerols is herein described. Regioselective fluoride-induced ring-opening reaction of suitable substituted thiiranes with bis(trimethyl)silyl selenide, followed by in situ S- and Se-acylation with fatty acid acyl chlorides, enables the one pot synthesis of mixed chalcogeno esters in good yield. The key step of this methodology is the functionalization of S−Si and Se−Si bonds of silyl chalcogenides, generated in situ under mild conditions. A related procedure for the synthesis of functionalized selenides, bearing two thiol ester and two ester moieties, was also developed through a fine tuning of the reaction conditions. The physico-chemical properties of these novel fatty acid chalcogeno esters have been investigated through DSC, SAXS, WAXS, FTIR and polarized optical microscopy, and compared to those of the common triglycerides in order to highlight the effect of the replacement of oxygen with other chalcogen elements in the polar head of the lipid.     

Telomerase Inhibitors from Cyanobacteria: Isolation and Synthesis of Sulfoquinovosyl Diacylglycerols from Microcystis aeruguinosa PCC 7806

By using the Telospot assay, 27 different extracts of cyanobacteria were evaluated for telomerase inhibition. All extracts showed varying, but significant activity. We selected Microcystis aeruguinosa PCC 7806 to identify the active compound and a bioassay guided fractionation led us to isolate mixtures of sulfoquinovosyl diacylglycerols (SQDGs), which were identified by 2D NMR and MS/MS experiments. Pure SQDG derivatives were then synthesized. The IC₅₀ values of pure synthetic sulfoquinovosyl dipalmitoylglycerol and the monopalmitoylated derivative against telomerase were determined to be 17 and 40 μM , respectively. A structure–activity relationship study allowed the identification of compounds with modified lipophilic acyl groups that display improved activity.     

Three-way principal component analysis of chemical data from Lake Como watershed

A large data set obtained by a one-year monthly determination of ions (F⁻, Cl⁻, Br⁻, NO₃⁻, NO₂⁻, PO₄³⁻, SO₄²⁻, Na⁺, K⁺, Ca²⁺, Mg²⁺, NH₄⁺) and trace metals of environmental concern (Ni, Co, Mn, Fe) from the tributaries of Lake Como (Lombardy, Northern Italy) was treated by three-way Principal Component Analysis. The results showed that the chemical features of the investigated rivers are mainly related to the lithology of the watershed. Some cases of contamination were evidenced and rationalized on the basis of anthropic pollution or on the basis of the geochemical features of the territory. The method here proposed allows an easy and quick interpretation of the chemical data by means of graphical devices. The information extracted by the three-way models would be very useful to regional agencies in developing a strategy to manage water resources in the whole basin of Lake Como.     

Arbitrage in skew Brownian motion models

Empirical skewness of asset returns can be reproduced by stochastic processes other than the Brownian motion with drift. Some authors have proposed the skew Brownian motion for pricing as well as interest rate modelling. Although the asymmetric feature of random return involved in the stock price process is driven by a parsimonious one-dimensional model, we will show how this is intrinsically incompatible with a modern theory of arbitrage in continuous time. Application to investment performance and to the Black-Scholes pricing model clearly emphasize how this process can provide some kind of arbitrage.     

Aeroacoustics research in Europe: The CEAS-ASC report on 2009 highlights

The Council of European Aerospace Societies (CEAS) Aeroacoustics Specialists Committee (ASC) supports and promotes the interests of the scientific and industrial aeroacoustics community on an European scale and European aeronautics activities internationally. In this context, “aeroacoustics” encompasses all aerospace acoustics and related areas. Each year the committee highlights some of the research and development projects in Europe.This paper is a report on highlights of aeroacoustics research in Europe in 2009, compiled from information provided to the ASC of the CEAS.In April 2009, the Level-2 project OPENAIR of the Seventh Framework Programme of the European Commission has been launched with the goal of delivering a step change in noise reduction, beyond the successful achievements of the predecessor SILENCE(R).Some contributions submitted to the editor summarizes findings from programmes launched before 2009, while other contributions report on activities supported by national associations and industries. Furthermore, a concise summary of the workshop on “Resolving Uncertainties in Airframe Noise Testing and CAA Code Validation” held in Bucharest is included in this report. Enquiries concerning all contributions should be addressed to the authors who are given at the end of each subsection.     

Assessment of accuracy and precision in speciation analysis by competitive ligand equilibration-cathodic stripping voltammetry (CLE-CSV) and application to Antarctic samples

The analytical performances of Competitive Ligand Equilibration with Cathodic Stripping Voltammetric detection of the labile fraction (CLE-CSV) were assessed. This speciation method enables the concentration of natural ligand(s) and their conditional stability constants for the complexation of the investigated metal to be determined through thermodynamic considerations.Literature data were discussed and general trends in the precision of the determined parameters identified: ligand concentrations were affected, on average, by a 10% relative percentage standard deviation (RSD%), whereas conditional stability constants showed much lower precision, with an average RSD% of 50%.New experimental data were collected to obtain a complete assessment of accuracy and precision attainable for the determination of strong ligands at the ultra trace level, enabling the whole protocol to be evaluated. Firstly, the side reaction coefficient alpha for the formation of the complex between the added ligand and the investigated metal (α_CuL) was determined. The method was subsequently applied to the analysis of solution containing ligand at trace levels (5-50 nM) with known complexing characteristics. Copper was used as the model metal ion and ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) as the model ligands. Results evidenced that the CLE-CSV protocol is not affected by systematic errors in the determination of both ligand concentration and the conditional stability constants. Good precision is obtained for ligand concentrations, with an average relative standard deviation (RSD%) of 5%; an average RSD% of 23% was calculated for the conditional stability constants. Including the contribution of the uncertainty in the value of α_CuL in the evaluation of the uncertainty in the latter parameter increased the RSD% up to 40%. The CLE-CSV protocol was subsequently applied to the detection of strong ligands in water samples collected in Antarctica: precision was shown to be comparable with literature data.