The influence of spatial separation on divided listening

If spatial attention acts like a "spotlight," focusing on one location and excluding others, it may be advantageous to have all targets of interest within the same spatial region. This hypothesis was explored using a task where listeners reported keywords from two simultaneous talkers. In Experiment 1, the two talkers were placed symmetrically about the frontal midline with various angular separations. While there was a small performance improvement for moderate separations, the improvement decreased for larger separations. However, the dependency of the relative talker intensities on spatial configuration accounted for these effects. Experiment 2 tested whether spatial separation improved the intelligibility of each source, an effect that could counteract any degradation in performance as sources fell outside the spatial spotlight of attention. In this experiment, intelligibility of individual sources was equalized across configurations by adding masking noise. Under these conditions, the cost of divided listening (the drop in performance when reporting both messages compared to reporting just one) was smaller when the spatial separation was small. These results suggest that spatial separation enhances the intelligibility of individual sources in a competing pair but increases the cost associated with having to process both sources simultaneously, consistent with the attentional spotlight hypothesis.     

Synthesis of enantiopure allylamines by reductive alkylation of amino epoxides with organolithium reagents

[reaction: see text] Transformation of enantiopure (2R,1'S)-2-(1-aminoalkyl)epoxides 1 into the corresponding allylamines 2 is described. The opening of the epoxide ring with different organolithium compounds takes place with total selectivity and in high yields.     

On the Hörmander Classes of Bilinear Pseudodifferential Operators

Bilinear pseudodifferential operators with symbols in the bilinear analog of all the Hörmander classes are considered and the possibility of a symbolic calculus for the transposes of the operators in such classes is investigated. Precise results about which classes are closed under transposition and can be characterized in terms of asymptotic expansions are presented. This work extends the results for more limited classes studied before in the literature and, hence, allows the use of the symbolic calculus (when it exists) as an alternative way to recover the boundedness on products of Lebesgue spaces for the classes that yield operators with bilinear Calderón–Zygmund kernels. Some boundedness properties for other classes with estimates in the form of Leibniz’ rule are presented as well.     

The obrechkoff integral transform: properties and relation to a generalized fractional calculus

This survey is devoted to one of the most general Laplace-type integral transforms, the so-called Obrechkoff integral transform, introduced and studied for the first time by Obrechkoff[25]. It has been modified by Dimovski [5],[6] and used as a basis of a Mikusinski-type operational calculus for the hyper-Bessel differential operators of arbitrary order. Later, in a series of papers Dimovski and Kiryakova [8],[9],[10] have found operational properties, complex and real inversion formulas, Abel-type theorems for the Obrechkoff transform. This theory has been further developed by Kiryakova [16],[17],[18] using the tools of the Meijer's G-functions and of the fractional calculus. Namely, a new definition as a G-transform has been given for the Obrechkoff transform. The hyper-Bessel operators themselves, have given rise to a new generalized fractional calculus and further extensive use of the G-functions. Many other generalized differentiation and integration operators happen to be special cases in this calculus, too. Special cases of the Obrechkoff transform have been "rediscovered" later by many authors. We give examples how their results could be derived from the general ones surveyed here.     

Incompatible elements in bottom sediments of the Itaipú Dam Reservoir by EDXRF

Journal of Radioanalytical and Nuclear Chemistry - Sediments play an important role in the distribution of trace elements in the aquatic system and act as a sink for metals. Incompatible elements...     

Studies towards the synthesis of ertugliflozin from l-Arabinose

A new method for the diastereoselective synthesis of enantiomerically pure ertugliflozin was developed. The crucial step involves an aldol condensation between 1-(4-chloro-3-(4-ethoxybenzyl)phenyl)ethanone and (4R,5R)-5-(((tert-butyldimethylsilyl)oxy)methyl)-2,2-dimethyl-5-((trityloxy)methyl)-1,3-dioxolane-4-carbaldehyde, which was prepared from known 2-C-trityloxymethyl-2,3-O-isopropylidene-l-erythrose (easily accessible in three steps from l-arabinose) by standard reduction/oxidation and protection/deprotection manipulations. Dihydroxylation of the aldol condensation product and further global deprotection led to the formation of the target molecule.     

Photosensitizer-Mesoporous Silica Nanoparticles Combination for Enhanced Photodynamic Therapy†

Mesoporous silica nanoparticles (MSNs) are widely known for their versatile applications. One of the most extended is as drug delivery systems for the treatment of cancer and other diseases. This review compiles the most representative examples in the last years of functionalized MSNs as photosensitizer carriers for photodynamic therapy (PDT) against cancer. Several commercially available photosensitizers (PSs) demonstrated poor solubility in an aqueous medium and insufficient selectivity for cancer tissues. The tumor specificity of PSs is a key factor for enhancing the PDT effect and at the same time reducing side effects. The use of nanoparticles and particularly MSNs, in which PS is covalently anchored or physically embedded, can overcome these limitations. For that, PS-MSNs can be externally decorated with compounds of interest in order to act as an active target for certain cancer cells, demonstrating enhanced phototoxicity in vitro and in vivo. The objective of this review is to collect and compare different nanosystems based on PS-MSNs pointing out their advantages in PDT against diverse types of cancers.     

The genomisotopic approach: a systematic method to isolate products of orphan biosynthetic gene clusters

With the increasing number of genomes sequenced and available in the public domain, a large number of orphan gene clusters, for which the encoded natural product is unknown, have been identified. These orphan gene clusters represent a tremendous source of novel and possibly bioactive compounds. Here, we describe a "genomisotopic approach," which employs a combination of genomic sequence analysis and isotope-guided fractionation to identify unknown compounds synthesized from orphan gene clusters containing nonribosomal peptide synthetases. Analysis of the Pseudomonas fluorescens Pf-5 genome led to the identification of an orphan gene cluster predicted to code for the biosynthesis of a lipopeptide natural product. Application of the genomisotopic approach to isolate the product of this gene cluster resulted in the discovery of orfamide A, founder of a group of bioactive cyclic lipopeptides.     

1H NMR direct observation of enantiomeric exchange in palladium(II) and platinum(II) complexes containing N,N' bidentate aryl-pyridin-2-ylmethyl-amine ligands

The complexes [MCl(2)(kappa2-N approximately N')] (N approximately N' = 2-C(5)H(4)N-CH2-NHAr; Ar = 4-MeC(6)H(4), a; 2,6-Me(2)C(6)H(3), b; 4-MeOC(6)H(4), c; 4-CF(3)C(6)H(4), d; M = Pd, 1a-d; Pt, 2a-d) have been prepared and fully stereochemically characterized both in the solid state and in solution. Their behavior in DMSO-d6 solution is dependent on the substituents of the aryl group and on the metal. Complexes of palladium with substituents at the para position (1a, 1c, 1d) display a dynamic 1H NMR pattern when the solutions are heated. An enantiomeric exchange Slambda/Rdelta is suggested to explain such behavior. On the basis of the calculated negative DeltaS values, an associative mechanism involving the solvent is proposed. Under the same conditions, analogous complexes of platinum (2a, 2c, 2d) proved to be unstable, and release of the N approximately N' ligand was observed. Complexes 1b and 2b show temperature-variable 1H NMR spectra without any evidence accounting for enantiomeric exchange or decoordination. DFT calculations on models of 1a and 1b show that diastereomeric exchange Sdelta/Slambda is a process where the complex with the higher sterical hindrance, 1b, has a lower energy barrier.     

Diastereoselectivity in the self-assembly of As2L2Cl2 macrocycles is directed by the As-pi interaction

The As-pi interaction, in conjunction with reversible As-thiolate bond formation, is used to direct the self-assembly of dinuclear As2L2Cl2 (L = a dithiolate) macrocycles that exist as equilibrium mixtures of both syn and anti diastereomers. The diastereomeric excess of these self-assembly reactions is controlled in a predictable manner by prudent choice of different achiral, isomeric ligands. A general method for the preparation of As2L2Cl2 macrocycles is established, and strategies to control the diastereoselective self-assembly of regioisomeric macrocycles in solution and the crystalline state are described. A mechanism for the interconversion between diastereomers (a slow process on the NMR time scale) is suggested, and variable-temperature NMR spectroscopic data show that the diastereomeric excess (de) decreases with increasing temperature. anti-As2(L2,6)2Cl2 crystallizes in monoclinic space group P2(1)/n with a = 6.3949(13), b = 19.675(4), c = 10.967(2) A, beta = 106.817(3) degrees , and Z = 2. anti-As2(L1,5)2Cl2 crystallizes in monoclinic space group P2(1)/c with a = 6.813(4), b = 19.085(12), c = 10.277(6) A, beta = 107.788(10) degrees , and Z = 4. syn-As2(L1,4)2Cl2.CHCl3 crystallizes in triclinic space group P(-) with a = 19.313(4), b = 19.923(4), c = 24.508(5) A, alpha = 78.110(4) degrees , beta = 78.860(5) degrees , gamma = 89.183(5) degrees , and Z = 12. As2(L1,4)2Cl2.C6H6 crystallizes in monoclinic space group P2(1)/n with a = 10.3332(7), b = 34.375(2), c = 17.8593(12) A, beta = 98.9650(10) degrees , and Z = 8.