Ranking coherence in Topic Models using Statistically Validated Networks

Probabilistic topic models have become one of the most widespread machine learning techniques in textual analysis. Topic discovering is an unsupervised process that does not guarantee the interpretability of its output. Hence, the automatic evaluation of topic coherence has attracted the interest of many researchers over the last decade, and it is an open research area. The present article offers a new quality evaluation method based on Statistically Validated Networks (SVNs). The proposed probabilistic approach consists of representing each topic as a weighted network of its most probable words. The presence of a link between each pair of words is assessed by statistically validating their co-occurrence in sentences against the null hypothesis of random co-occurrence. The proposed method allows one to distinguish between high-quality and low-quality topics, by making use of a battery of statistical tests. The statistically significant pairwise associations of words represented by the links in the SVN might reasonably be expected to be strictly related to the semantic coherence and interpretability of a topic. Therefore, the more connected the network, the more coherent the topic in question. We demonstrate the effectiveness of the method through an analysis of a real text corpus, which shows that the proposed measure is more correlated with human judgement than the state-of-the-art coherence measures

Energetic and economic analysis of a solar assisted heat pump for pasteurization process

In the present paper, the energetic and economic analysis of a solar-assisted heat pump for an industrial pasteurization process is investigated. The considered system consists of thermal energy storage, a water-to-water heat pump and a solar field made up of both photovoltaic-thermal collectors and evacuated tube collectors. A mathematical model of each component of the system is built and validated, while the overall model of the system is built with a bottom-up approach. The energetic and economic analysis is performed on a yearly basis varying the storage size and the solar field size and considering a boiler-only scenario as the reference system. The results show that, from the energetic point of view, the best system could provide up to 90% of the energy required by the process and, consequently, significantly reduce auxiliary boiler consumption. On the other side, from an economic point of view, the best solution provides a minimum payback time approximately equal to 8 years with 14.4% internal rate of return

Fluoride Concentration of Some Brands of Fermented Milks Available in the Market

Objectives: To evaluate the fluoride ion concentration in some fermented milks present in the market. Methods: Three brands of 6 fermented milks (Parmalat®-uva, Chamyto®, Paulista®, Batavito®, Yakult®, Vigor Club®) were analyzed. Fluoride concentration was evaluated after facilitated microdiffusion by HDMS. Results: Parmalat® products ranged from 0.022 μgF/g to 0.031 μgF/g, Chamyto® from 0.228 μgF/g to 0.272 μgF/g, Paulista® from 0.182 μgF/g to 0.220 μgF/g, Batavito® from 0.028 μgF/g to 0.030 μgF/g, Yakult® from 0.115 μgF/g to 0.206 μgF/g and Vigor Club® from 0.808 μgF/g to 1.171 μgF/g. Conclusions: The presence of fluoride could be observed in all of the fermented milks analyzed which can contribute with the total fluoride daily intake

Aerodynamic Properties and Drug Solubility of Dry Powders Prepared by Spray Drying: Clarithromycin Versus its Hydrochloride Salt

Aerodynamic Properties and Drug Solubility of Dry Powders Prepared by Spray Drying: Clarithromycin Versus its Hydrochloride Salt. Russo P, Manniello M.D., Simonetti A., Petrone A.M., Porta A., Del Gaudio P., Aquino R.P. Department of Pharmacy (DIFARMA), University of Salerno, Fisciano (SA) – Italy; ([email protected]). Introduction and Objectives. The antibiotic therapy for a direct administration to the lung in cystic fibrosis patients has to provide suitable drug availability, possibly in the lower respiratory tract characterized by the presence of thick secretions. Apart from deposition, systemic or local pharmacological activity of an inhalation product depends on drug dissolution into the biological fluids lining the lung. Therefore, one of the crucial step in the therapeutic management of the respiratory disease is the drug solubilization in this site of action. Clarithromycin (CLA; fig.1) is a broad spectrum and a well know macrolide antibiotic usually prescribed particularly for the treatment of respiratory infections, interestingly showing an additional anti-inflammatory effect (Pukhalsky et al., 2004); CLA is characterized by a very poor water solubility (0.33 mg/L). One of the common strategy, for increasing drug solubility in aqueous medium is represented by the production of dry powders in amorphous form using the spray drying technique (Yonemochi et al., 1999). Moreover, CLA has a dimethylamino group, which can be salified for solubility/dissolution improvement (fig.1). Hence, the aim of the present study was to obtain respirable powders of clarithromycin, while improving drug aqueous solubility. Powders were produced with CLA or CLA hydrochloride and characterized in terms of drug content, aerodynamic properties and drug solubility. Finally, in order to assess the effect of the spray-drying process on the antibiotic activity of the engineered particles, microbiological tests were performed. Materials and Methods. Several batches of micronized particles were prepared by spray drying different feed solutions; critical process parameters were solvent composition (isopropyl alcohol/water ratio), drug concentration and pH of the liquid feeds (table 1). Saturated solubility measurements were carried out keeping an excess amount of CLA raw material (RM), CLA spray-dried suspension and hydrochloride spray-dried in phosphate buffer (0.05 M, pH 6.75) at 37°C for 72h. After filtration, the solubility was measured by HPLC method and expressed in mg/ml. The results were reported as mean of three measurements and standard deviation. Particle size distribution of Raw Material and engineered particles was determined using a light-scattering laser granulometer, while particle morphology was assessed by scanning electron microscopy (SEM). The in vitro deposition of the micronized powders was evaluate by means of a Single-Stage Glass Impinger (SSGI; apparatus A; European Pharmacopoeia 8.0), using a proper device for the aerosolization. The antibacterial assay was carried out in MHB by microdilution method using 96-well microtiter plates. Briefly, 200 µl of 1X107 CFU/ml of P. aeruginosa ATCC 27853 were incubated at 37°C with different concentration of drug (4, 6 and 8 µg/ml). Results and Discussion. Morphology and aerodynamic properties of spray-dried particles were strongly dependent on organic solvent concentration as well as on pH of the liquid feeds processed, both influencing drug solubility. Adding clarithromycin to hydroalcoholic mixtures, alkaline feeds (pH~10.5; #1, #2, tab.1) in form of suspensions were obtained.   The resulting spray-dried powders showed good process yield, but unsatisfactory aerodynamic properties, due to a high particle size (tab. 1) and the presence of residual drug crystals mixed to spherical particles (fig.2; #2). With the aim to obtain clear feeds in form of solutions, we tested clarithromycin in its hydrochloride salt form, obtained lowering pH values of feed solutions (pH 6.5). Micronized salified powders showed higher process yield and very interesting FPF values, thanks to smaller and wrinkled particles (fig.2 #4, #6; tab.1). Moreover, water solubility of spray-dried powders was strongly influenced by clarithromycin form. Powders obtained from alkaline feed suspensions showed lower solubility in a phosphate buffer 0.05 M, pH 6.75 (fig.3, # 1). A substantial increase in drug solubility was obtained, at the same conditions, with powders dried from feed solution containing clarithromycin hydrochloride (fig.3 #9-#5). To verify the ability of the produced formulations to was performed. Three different drug concentrations were tested in a multi-well plate. Clarithromycin raw material (RM, line C, figure 4) and #1 (line D, figure 4) showed a lower activity against P. aeruginosa growth compared to #4, #5, #6, containing the hydrochloride form. This different behavior against P. aeruginosa may be due to the lower CLA solubility; at higher concentration, clarithromycin precipitates in RM and #1 wells, becoming unavailable for antibiotic purpose. Conclusions. Clarithromycin inhalable powders containing the drug in its hydrochloride form showed good aerodynamic properties and higher water solubility. Thanks to a fine-tuning of the process parameters and liquid feed composition, no excipients were necessary to obtain respirable powders. The spray drying process of CLA hydrochloride not only preserved antimicrobial activity, but also, increasing drug solubility, improved drug efficacy against P. aeruginosa. References. Pukhalsky, A. L., Shmarina, G. V., Kapranov, N. I., Kokarovtseva, S. N., Pukhalskaya, D., & Kashirskaja, N. J. (2004). Anti-inflammatory and immunomodulating effects of clarithromycin in patients with cystic fibrosis lung disease. Mediators Inflamm, 13(2), 111-117. doi: 10.1080/09629350410001688495 Yonemochi, E., Kitahara, S., Maeda, S., Yamamura, S., Oguchi, T., & Yamamoto, K. (1999). Physicochemical properties of amorphous clarithromycin obtained by grinding and spray drying. Eur J Pharm Sci, 7(4), 331-338

Seasonal thaws under mid-to-low pressure atmospheres on Early Mars

Despite decades of scientific research on the subject, the climate of the first 1.5 Gyr of Mars history has not been fully understood yet. Especially challenging is the need to reconcile the presence of liquid water for extended periods of time on the martian surface with the comparatively low insolation received by the planet, a problem which is known as the Faint Young Sun (FYS) Paradox. In this paper we use ESTM, a latitudinal energy balance model with enhanced prescriptions for meridional heat diffusion, and the radiative transfer code EOS to investigate how seasonal variations of temperature can give rise to local conditions which are conductive to liquid water runoffs. We include the effects of the martian dichotomy, a northern ocean with either 150 or 550 m of Global Equivalent Layer (GEL) and simplified CO$_2$ or H$_2$O clouds. We find that 1.3-to-2.0 bar CO$_2$-dominated atmospheres can produce seasonal thaws due to inefficient heat redistribution, provided that the eccentricity and the obliquity of the planet are sufficiently different from zero. We also studied the impact of different values for the argument of perihelion. When local favorable conditions exist, they nearly always persist for $>15\%$ of the martian year. These results are obtained without the need for additional greenhouse gases (e.g. H$_2$, CH$_4$) or transient heat-injecting phenomena (e.g. asteroid impacts, volcanic eruptions). Moderate amounts (0.1 to 1\%) of CH$_4$ significantly widens the parameter space region in which seasonal thaws are possible.Comment: Second and final version, 27 pages, 10 figures, accepted for publication in Ap

Protective effect of procyanidin-rich grape seed extract against Gram-negative virulence factors

Biofilm formation and lipopolysaccharide (LPS) are implicated in the pathogenesis of gastrointestinal (GI) diseases caused by Gram-negative bacteria. Grape seeds, wine industry by-products, have antioxidant and antimicrobial activity. In the present study, the protective effect of procyanidin-rich grape seed extract (prGSE), from unfermented pomace of Vitis vinifera L. cv Bellone, on bacterial LPS-induced oxidative stress and epithelial barrier integrity damage has been studied in a model of Caco-2 cells. The prGSE was characterized at the molecular level using HPLC and NMR. The in vitro activity of prGSE against formation of biofilm of Salmonella enterica subsp. enterica serovar Typhimurium and Escherichia coli was investigated. In vivo, prGSE activity using infected Galleria mellonella larvae has been evaluated. The results show that the prGSE, if administered with LPS, can significantly reduce the LPS-induced permeability alteration. Moreover, the ability of the extract to prevent Reactive Oxygen Species (ROS) production induced by the LPS treatment of Caco-2 cells was demonstrated. prGSE inhibited the biofilm formation of E. coli and S. Typhimurium. In terms of in vivo activity, an increase in survival of infected G. mellonella larvae after treatment with prGSE was demonstrated. In conclusion, grape seed extracts could be used to reduce GI damage caused by bacterial endotoxin and biofilms of Gram-negative bacteria