Floating gellan-chitosan polyelectrolyte complex beads: effect of gelucires incorporation on encapsulation efficiency and drug release

The purpose of the present investigation is to study the effect of incorporation of gelucire 39/01 and 50/13 on encapsulation efficiency and release of water soluble drug (metronidazole, log P = 0.0) from floating gellan-chitosan polyelectrolyte complex (PEC) beads. Floating emulsion PEC beds were prepared in one step without using any chemical crosslinker. Briefly, an emulsion of gellan gum (GG) with gelucire 39/01 and 50/13 containing CaCO3 and drug was extruded dropwise into low molecular weight chitosan (LMCH) solution. Beads formed instantaneously were cured for 15 min at elevated temperature (37 °C). Prepared beads showed excellent buoyancy along with significantly improved encapsulation efficiency and sustained release of metronidazole when compared to floating gellan-chitosan PEC beads prepared in the similar manner but without gelucires. Experimental data obtained from the present investigation showed that floating emulsion PEC beads may form a potential stomach site specific drug delivery system for the delivery of highly water soluble drugs with an absorption window in the upper gastrointestinal tract.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Online algorithm for unsupervised sequential selection with contextual information

In this paper, we study Contextual Unsupervised Sequential Selection (USS), a new variant of the stochastic contextual bandits problem where the loss of an arm cannot be inferred from the observed feedback. In our setup, arms are associated with fixed costs and are ordered, forming a cascade. In each round, a context is presented, and the learner selects the arms sequentially till some depth. The total cost incurred by stopping at an arm is the sum of fixed costs of arms selected and the stochastic loss associated with the arm. The learner’s goal is to learn a decision rule that maps contexts to arms with the goal of minimizing the total expected loss. The problem is challenging as we are faced with an unsupervised setting as the total loss cannot be estimated. Clearly, learning is feasible only if the optimal arm can be inferred (explicitly or implicitly) from the problem structure. We observe that learning is still possible when the problem instance satisfies the so-called ‘Contextual Weak Dominance’ (CWD) property. Under CWD, we propose an algorithm for the contextual USS problem and demonstrate that it has sub-linear regret. Experiments on synthetic and real datasets validate our algorithm.https://papers.nips.cc/paper/2020/file/08e5d8066881eab185d0de9db3b36c7f-Paper.pdfPublished versio

Preparation and characterization of gellan-chitosan polyelectrolyte complex beads

The purpose of the present investigation was to prepare gellan-chitosan polyelectrolyte complex beads in one step and to explore the potential of the prepared beads in the oral delivery of metronidazole (log P = 0.0) and metronidazole benzoate (log P = 2.19). Beads were prepared by extruding aqueous solution of gellan gum (with or without drugs) into chitosan solution in acetic acid pH adjusted to 3.5. Prepared beads exhibited poor encapsulation and burst release for metronidazole, while very high encapsulation and extended release was observed for metronidazole benzoate in simulated gastric fluid (SGF, pH 1.2). Incorporation of type A & B gelatin significantly improved the metronidazole encapsulation in the beads but the release pattern remained the same. Overall, gellan-chitosan beads showed poor retardant capacity of drug release for metronidazole whereas good retardant capacity was observed for metronidazole benzoate.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Optical spectroscopy of Gaia detected protostars with DOT: can we probe protostellar photospheres?

Optical spectroscopy offers the most direct view of the stellar properties and the accretion indicators. Standard accretion tracers, such as $H\beta$, $H\alpha$, and, Ca II triplet lines, and most photospheric features, fall in the optical wavelengths. However, these tracers are not readily observable from deeply embedded protostars because of the large line of sight extinction (Av $\sim$ 50-100 mag) toward them. In some cases, however, it is possible to observe protostars at optical wavelengths if the outflow cavity is aligned along the line-of-sight that allows observations of the photosphere, or the envelope is very tenuous and thin such that the extinction is low. In such cases, we can not only detect these protostars at optical wavelengths but also follow up spectroscopically. We have used the HOPS catalog (Furlan et al. 2016) of protostars in Orion to search for optical counterparts for protostars in the Gaia DR3 survey. Out of the 330 protostars in the HOPS sample, an optical counterpart within 2" is detected for 62 of the protostars. For 17 out of 62 optically detected protostars, we obtained optical spectra { (between 5500 to 8900 $\AA$) using the Aries-Devasthal Faint Object Spectrograph \& Camera (ADFOSC) on the 3.6-m Devasthal Optical Telescope (DOT) and Hanle Faint Object Spectrograph Camera (HFOSC) on 2-m Himalayan Chandra Telescope (HCT)}. We detect strong photospheric features, such as the TiO bands in the spectra {(of 4 protostars)}, hinting that photospheres can form early on in the star formation process. We further determined the spectral types of protostars, which show photospheres similar to a late M-type. Mass accretion rates derived for the protostars are similar to those found for T-Tauri stars, in the range of 10$^{-7}$ to 10$^{-8}$ $M_\odot$/yr.Comment: 9 pages, 5 figures accepted in Journal of Astrophysics and Astronomy as part of the "Star formation studies in the context of NIR instruments on 3.6m DOT" special issu