Dynamics of wide binary stars: A case study for testing Newtonian dynamics in the low acceleration regime

Extremely wide binary stars represent ideal systems to probe Newtonian dynamics in the low acceleration regimes (<10e-10 m/s/s) typical of the external regions of galaxies. Here we present a study of 60 alleged wide binary stars with projected separation ranging from 0.004 to 1 pc, probing gravitational accelerations well below the limit were dark matter or modified dynamics theories set in. Radial velocities with accuracy ~100 m/s were obtained for each star, in order to constrain their orbital velocity, that, together with proper motion data, can distinguish bound from unbound systems. It was found that about half of the observed pairs do have velocity in the expected range for bound systems, out to the largest separations probed here. In particular, we identified five pairs with projected separation >0.15 pc that are useful for the proposed test. While it would be premature to draw any conclusion about the validity of Newtonian dynamics at these low accelerations, our main result is that very wide binary stars seem to exist in the harsh environment of the solar neighborhood. This could provide a tool to test Newtonian dynamics versus modified dynamics theories in the low acceleration conditions typical of galaxies. In the near future the GAIA satellite will provide data to increase significantly the number of wide pairs that, with the appropriate follow up spectroscopic observations, will allow the implementation of this experiment with unprecedented accuracy.Comment: Accepted for publication on International Journal of Modern Physics

A folding inhibitor of the HIV-1 Protease

Being the HIV-1 Protease (HIV-1-PR) an essential enzyme in the viral life cycle, its inhibition can control AIDS. The folding of single domain proteins, like each of the monomers forming the HIV-1-PR homodimer, is controlled by local elementary structures (LES, folding units stabilized by strongly interacting, highly conserved, as a rule hydrophobic, amino acids). These LES have evolved over myriad of generations to recognize and strongly attract each other, so as to make the protein fold fast and be stable in its native conformation. Consequently, peptides displaying a sequence identical to those segments of the monomers associated with LES are expected to act as competitive inhibitors and thus destabilize the native structure of the enzyme. These inhibitors are unlikely to lead to escape mutants as they bind to the protease monomers through highly conserved amino acids which play an essential role in the folding process. The properties of one of the most promising inhibitors of the folding of the HIV-1-PR monomers found among these peptides is demonstrated with the help of spectrophotometric assays and CD spectroscopy

On the Impact of Temporal Representations on Metaphor Detection

State-of-the-art approaches for metaphor detection compare their literal - or core - meaning and their contextual meaning using metaphor classifiers based on neural networks. However, metaphorical expressions evolve over time due to various reasons, such as cultural and societal impact. Metaphorical expressions are known to co-evolve with language and literal word meanings, and even drive, to some extent, this evolution. This poses the question of whether different, possibly time-specific, representations of literal meanings may impact the metaphor detection task. To the best of our knowledge, this is the first study that examines the metaphor detection task with a detailed exploratory analysis where different temporal and static word embeddings are used to account for different representations of literal meanings. Our experimental analysis is based on three popular benchmarks used for metaphor detection and word embeddings extracted from different corpora and temporally aligned using different state-of-the-art approaches. The results suggest that the usage of different static word embedding methods does impact the metaphor detection task and some temporal word embeddings slightly outperform static methods. However, the results also suggest that temporal word embeddings may provide representations of the core meaning of the metaphor even too close to their contextual meaning, thus confusing the classifier. Overall, the interaction between temporal language evolution and metaphor detection appears tiny in the benchmark datasets used in our experiments. This suggests that future work for the computational analysis of this important linguistic phenomenon should first start by creating a new dataset where this interaction is better represented

Circum-galactic medium in the halo of quasars

The properties of circum-galactic gas in the halo of quasar host galaxies are investigated analyzing Mg II 2800 and C IV 1540 absorption-line systems along the line of sight close to quasars. We used optical spectroscopy of closely aligned pairs of quasars (projected distance $\leq$ 200 kpc, but at very different redshift) obtained at the VLT and Gran Telescopio Canarias to investigate the distribution of the absorbing gas for a sample of quasars at z$\sim$1. Absorption systems of EW $\geq$ 0.3 $\rm{\AA}$ associated with the foreground quasars are revealed up to 200 kpc from the centre of the host galaxy, showing that the structure of the absorbing gas is patchy with a covering fraction quickly decreasing beyond 100 kpc. In this contribution we use optical and near-IR images obtained at VLT to investigate the relations between the properties of the circum-galactic medium of the host galaxies and of the large scale galaxy environments of the foreground quasars.Comment: 6 pages, 3 figures, proceedings of the conference "QUASARS at all cosmic epochs", accepted for publication on Frontiers in Astronomy and Space Scienc

On the Impact of Temporal Representations on Metaphor Detection

State-of-the-art approaches for metaphor detection compare their literal - or core - meaning and their contextual meaning using metaphor classifiers based on neural networks. However, metaphorical expressions evolve over time due to various reasons, such as cultural and societal impact. Metaphorical expressions are known to co-evolve with language and literal word meanings, and even drive, to some extent, this evolution. This poses the question of whether different, possibly time-specific, representations of literal meanings may impact the metaphor detection task. To the best of our knowledge, this is the first study that examines the metaphor detection task with a detailed exploratory analysis where different temporal and static word embeddings are used to account for different representations of literal meanings. Our experimental analysis is based on three popular benchmarks used for metaphor detection and word embeddings extracted from different corpora and temporally aligned using different state-of-the-art approaches. The results suggest that the usage of different static word embedding methods does impact the metaphor detection task and some temporal word embeddings slightly outperform static methods. However, the results also suggest that temporal word embeddings may provide representations of the core meaning of the metaphor even too close to their contextual meaning, thus confusing the classifier. Overall, the interaction between temporal language evolution and metaphor detection appears tiny in the benchmark datasets used in our experiments. This suggests that future work for the computational analysis of this important linguistic phenomenon should first start by creating a new dataset where this interaction is better represented.Comment: 12 pages, 4 figure

Novel Mutants of the Human β1-Adrenergic Receptor Reveal Amino Acids Relevant for Receptor Activation

Activation of G protein-coupled receptors like the beta(1)-adrenergic receptor results in conformational changes that ultimately lead to signal propagation through a G protein to an effector like adenylyl cyclase. In this study we identified amino acids that seem to be critical for activation of the human beta(1)-adrenergic receptor. Activation patterns of mutant receptors were analyzed using two structurally different ligands for beta-adrenergic receptors that both are mixed agonist/antagonists. Broxaterol and terbutaline are agonists at beta(2)- and beta(3)-receptors; however, they act as antagonists at the beta(1)-subtype. We reasoned that this functional selectivity may be reflected by a corresponding sequence pattern in the receptor subtypes. Therefore, we exchanged single amino acids of the beta(1)-adrenergic receptor for residues that were identical in the beta(2)- and beta(3)-subtypes but different in the beta(1)-receptor. Pharmacological characterization of such receptor mutants revealed that binding of a panel of agonists and antagonists including broxaterol and terbutaline was unaltered. However, two of the mutants (I185V and D212N) were activated by broxaterol and terbutaline, which acted as antagonists at the wild-type receptor. Two additional mutants (V120L and K253R) could be activated by terbutaline alone, which is structurally more closely related to endogenous catecholamines like epinephrine than to broxaterol. A model of the human beta(1)-adrenergic receptor showed that the four gain-of-function mutations are outside of the putative ligand-binding domain substantiating the lack of an effect of the mutations on binding characteristics. These results support the notion that Val-120, Ile-185, Asp-212, and Lys-253 are critically involved in conformational changes occurring during receptor activation

Hemp Biomass Pretreatment and Fermentation with non- Saccharomyces Yeasts: Xylose Valorization to Xylitol

Hemp hurds are the main byproduct from hemp fibers supply chain and they could represent valuable feedstock of lignocellulosic biomass for biorefineries. The industrial hemp variety "Carmagnola", is characterized by low amounts of ash and high amount of carbohydrates. Alpha-cellulose (44% w/w), hemicellulose (25%), and lignin (23%) were fractionated using an organosolv pretreatment. The enzymatic hydrolysis of the cellulose fraction yielded up to 60% of glucose, that can easily find application as substrate for industrial fermentations. On the other hand, the black liquor originating from hemicellulose contains mainly xylose and minor amounts of other sugars. In the perspective of finding an application of black liquor, 50 yeasts belonging to 24 ascomycetous species were screened both in aerobiosis and anaerobiosis for the production of ethanol and the sugar alcohols xylitol and arabitol from xylose. Pichia fermentans WC 1507, Wickerhamomyces anomalus WC 1501, and Kluyveromyces bacillosporus WC 1404 were found to consume xylose, yielding xylitol in aerobic conditions. In particular, aerobic flask cultures of P. fermentans WC 1507 containing 120 g/L xylose showed the highest xylitol production values, yielding 63.5 g/L xylitol with a YP/S of 71.5%. Black liquor, exploited as a carbon source, has been successfully utilized by the three selected yeast strains at a concentration of 20 g/L in the culture medium, resulting in comparable or higher yields of biomass and xylitol compared to the medium containing pure xylose. A higher concentration of black liquor in the culture medium (to reach 120 g/l of xylose) has determined an inhibition of the growth of yeasts indicating the need for treatments for the removal of inhibitors. These preliminary results can be considered promising for the microbial valorization of lignocellulosic hemp feedstock toward the production of xylitol

Endometriosis of the ureteral stump: An entity with severe manifestations

A 50-year-old woman on continuous oral estroprogestin therapy and with a history of endometriosis presented with gross hematuria and right reno-ureteral colic pain. Fifteen years before she had undergone total nephrectomy for loss of function of her right kidney due to an ureteral endometriotic nodule resulting in ureteral obstruction. The ureter had not been removed. For the following 15 years-period she had not manifested symptoms or signs of endometriosis. Although imaging investigations allowed to suspect endometriosis of the ureteral stump, urothelial cancer or carcinoma arising in endometriosis nodule could not be excluded. A laparoscopic hysterosalpingo- oophorectomy with the residual ureteral stump removal was performed. Some endometriotic implants on the ureteral stump wall were histologically detected. Proximal ureterectomy should be recommended in patients affected by ureteral endometriosis with a non-functioning kidney since long-term severe complications could derive from the residual stump. A continuous estroprogestin therapy does not totally prevent these complications

4-Hydroxyacetophenone monooxygenase from Pseudomonas fluorescens ACB as an oxidative biocatalyst in the synthesis of optically active sulfoxides

Recombinant 4-hydroxyacetophenone monooxygenase (HAPMO) from Pseudomonas fluorescens ACB has been tested as a catalyst in sulfoxidation reactions on a set of aromatic sulfides. With a few exceptions, excellent enantioselectivities in the synthesis of chiral phenyl and benzyl sulfoxides were achieved. The bacterial Baeyer–Villiger monooxygenase was also shown to accept racemic sulfoxides, a prochiral diketone and an organoboron compound as substrates. This study demonstrates the great biocatalytic potential of this novel oxidative enzyme