Photochemistry of the PAH pyrene in water ice: the case for ion-mediated solid-state astrochemistry

Context. Icy dust grains play an important role in the formation of complex inter- and circumstellar molecules. Observational studies show that polycyclic aromatic hydrocarbons (PAHs) are abundantly present in the ISM in the gas phase. It is likely that these non-volatile species freeze out onto dust grains as well and participate in the astrochemical solid-state network, but experimental PAH ice studies are largely lacking. Methods. Near UV/VIS spectroscopy is used to track the in situ VUV driven photochemistry of pyrene containing ices at temperatures ranging from 10 to 125 K. Results. The main photoproducts of VUV photolyzed pyrene ices are spectroscopically identified and their band positions are listed for two host ices, \water and CO. Pyrene ionisation is found to be most efficient in \water ices at low temperatures. The reaction products, triplet pyrene and the 1-hydro-1-pyrenyl radical are most efficiently formed in higher temperature water ices and in low temperature CO ice. Formation routes and band strength information of the identified species are discussed. Additionally, the oscillator strengths of Py, Py^+ and PyH are derived and a quantitative kinetic analysis is performed by fitting a chemical reaction network to the experimental data. Conclusions. Pyrene is efficiently ionised in water ice at temperatures below 50 K. Hydrogenation reactions dominate the chemistry in low temperature CO ice with trace amounts of water. The results are put in an astrophysical context by determining the importance of PAH ionisation in a molecular cloud. The photoprocessing of a sample PAH in ice described in this manuscript indicates that PAH photoprocessing in the solid state should also be taken into account in astrochemical models.Comment: 11 pages, 8 figures, accepted for publication in A&

FORMULATION AND EVALUATION OF DASATINIB LOADED SOLID LIPID NANOPARTICLES

Objective: The aim of present work was to formulate and evaluate Dasatinib (DST) loaded solid lipid nanoparticles (SLNs) as a potential anticancer drug delivery system by enhancing its solubility.Methods: SLNs consist of a solid lipid matrix where the drug was incorporated. Surfactants of GRAS grade were used to avoid aggregation and to stabilize the SLNs. DST-SLNs formulations of varying concentrations were prepared by high speed homogenization technique and evaluated for drug excipients compatibility study, poly-dispersity index, particle size analysis, surface morphology, zeta potential and drug release features.Results: It was observed that DST-SLNs with optimum quantities of poloxomer: lecithin ratio showed 88.06% drug release in 6h with good entrapment efficiency of 76.9±0.84 %. Particle size, Poly dispersity index, zeta potential and drug entrapment efficiency for the optimized formulation was found to be optimum. Stability studies revealed that the entrapment efficiency of the SLN dispersion stored in 4 °C was stable.Conclusion: Thus, it can be concluded that formulations of DST loaded SLNs are suitable carriers for improving the solubility and dissolution related problems.Â

Laboratory Determination of the Infrared Band Strengths of Pyrene Frozen in Water Ice: Implications for the Composition of Interstellar Ices

Broad infrared emission features (e.g., at 3.3, 6.2, 7.7, 8.6, and 11.3 microns) from the gas phase interstellar medium have long been attributed to polycyclic aromatic hydrocarbons (PAHs). A significant portion (10%-20%) of the Milky Way's carbon reservoir is locked in PAH molecules, which makes their characterization integral to our understanding of astrochemistry. In molecular clouds and the dense envelopes and disks of young stellar objects (YSOs), PAHs are expected to be frozen in the icy mantles of dust grains where they should reveal themselves through infrared absorption. To facilitate the search for frozen interstellar PAHs, laboratory experiments were conducted to determine the positions and strengths of the bands of pyrene mixed with H2O and D2O ices. The D2O mixtures are used to measure pyrene bands that are masked by the strong bands of H2O, leading to the first laboratory determination of the band strength for the CH stretching mode of pyrene in water ice near 3.25 microns. Our infrared band strengths were normalized to experimentally determined ultraviolet band strengths, and we find that they are generally ~50% larger than those reported by Bouwman et al. based on theoretical strengths. These improved band strengths were used to reexamine YSO spectra published by Boogert et al. to estimate the contribution of frozen PAHs to absorption in the 5-8 micron spectral region, taking into account the strength of the 3.25 micron CH stretching mode. It is found that frozen neutral PAHs contain 5%-9% of the cosmic carbon budget, and account for 2%-9% of the unidentified absorption in the 5-8 micron region.Comment: Accepted for publication in ApJ on 14 Feb 201

Buccal films: A review of therapy possibilities, treatment plans and appropriate evaluation techniques

Due to apparent greater patient acceptance compared to buccal tablets and enormous therapeutic opportunities compared to traditional oral drug delivery methods, particularly for those who suffer from dysphagia, the potential of the mucoadhesive film technology is difficult to ignore. Despite this, there are currently no authorised mucoadhesive buccal films, and the translation of published literature into the commercial market is essentially non-existent. In order to help this patient-centred dosage form become more widely used, this review aims to give an overview of mucoadhesive buccal film technology and highlight crucial areas on which to concentrate scientific efforts. While discussing the patient-related aspects influencing the utilisation of various dosage forms, a number of indications and development potential were noted. A technical description of the processes used to create these films, including solvent casting, hot melt extrusion, inkjet printing, and three-dimensional printing, was also offered. The utilisation of more than thirty mucoadhesive polymers in film formulations was found, and information about their mucoadhesive properties as well as their inclusion with other essential formulation ingredients was supplied

Reduced production of bacterial membrane vesicles predicts mortality in ST45/USA600 methicillin-resistant Staphylococcus aureus bacteremia

Immune biomarkers can stratify mortality risk in staphylococcal bacteremia. Microbial biomarkers may provide more consistent signals during early infection. We demonstrate that in ST45/USA600 bacteremia, bacterial membrane vesicle production in vitro predicts clinical mortality (773 vs. 116 RFU, survivors vs. decedents, p \u3c 0.0001). Using a threshold of 301 relative fluorescence units (RFU), the sensitivity and specificity of the membrane vesicles to predict mortality are 78% and 90%, respectively. This platform is facile, scalable and can be integrated into clinical microbiology lab workflows

Lack of PAH emission toward low-mass embedded young stellar objects

PAHs have been detected toward molecular clouds and some young stars with disks, but have not yet been associated with embedded young stars. We present a sensitive mid-IR spectroscopic survey of PAH features toward a sample of low-mass embedded YSOs. The aim is to put constraints on the PAH abundance in the embedded phase of star formation using radiative transfer modeling. VLT-ISAAC L-band spectra for 39 sources and Spitzer IRS spectra for 53 sources are presented. Line intensities are compared to recent surveys of Herbig Ae/Be and T Tauri stars. The radiative transfer codes RADMC and RADICAL are used to model the PAH emission from embedded YSOs consisting of a PMS star with a circumstellar disk embedded in an envelope. The dependence of the PAH feature on PAH abundance, stellar radiation field, inclination and the extinction by the surrounding envelope is studied. The 3.3 micron PAH feature is undetected for the majority of the sample (97%), with typical upper limits of 5E-16 W/m^2. Compact 11.2 micron PAH emission is seen directly towards 1 out of the 53 Spitzer Short-High spectra, for a source that is borderline embedded. For all 12 sources with both VLT and Spitzer spectra, no PAH features are detected in either. In total, PAH features are detected toward at most 1 out of 63 (candidate) embedded protostars (<~ 2%), even lower than observed for class II T Tauri stars with disks (11-14%). Assuming typical class I stellar and envelope parameters, the absence of PAHs emission is most likely explained by the absence of emitting carriers through a PAH abundance at least an order of magnitude lower than in molecular clouds but similar to that found in disks. Thus, most PAHs likely enter the protoplanetary disks frozen out in icy layers on dust grains and/or in coagulated form.Comment: 13 pages, 9 figures, accepted for publication in A&

Experimental river delta size set by multiple floods and backwater hydrodynamics

River deltas worldwide are currently under threat of drowning and destruction by sea-level rise, subsidence, and oceanic storms, highlighting the need to quantify their growth processes. Deltas are built through construction of sediment lobes, and emerging theories suggest that the size of delta lobes scales with backwater hydrodynamics, but these ideas are difficult to test on natural deltas that evolve slowly. We show results of the first laboratory delta built through successive deposition of lobes that maintain a constant size. We show that the characteristic size of delta lobes emerges because of a preferential avulsion node—the location where the river course periodically and abruptly shifts—that remains fixed spatially relative to the prograding shoreline. The preferential avulsion node in our experiments is a consequence of multiple river floods and Froude-subcritical flows that produce persistent nonuniform flows and a peak in net channel deposition within the backwater zone of the coastal river. In contrast, experimental deltas without multiple floods produce flows with uniform velocities and delta lobes that lack a characteristic size. Results have broad applications to sustainable management of deltas and for decoding their stratigraphic record on Earth and Mars

Novel SSR Markers from BAC-End Sequences, DArT Arrays and a Comprehensive Genetic Map with 1,291 Marker Loci for Chickpea (Cicer arietinum L.)

Chickpea (Cicer arietinum L.) is the third most important cool season food legume, cultivated in arid and semi-arid regions of the world. The goal of this study was to develop novel molecular markers such as microsatellite or simple sequence repeat (SSR) markers from bacterial artificial chromosome (BAC)-end sequences (BESs) and diversity arrays technology (DArT) markers, and to construct a high-density genetic map based on recombinant inbred line (RIL) population ICC 4958 (C. arietinum)×PI 489777 (C. reticulatum). A BAC-library comprising 55,680 clones was constructed and 46,270 BESs were generated. Mining of these BESs provided 6,845 SSRs, and primer pairs were designed for 1,344 SSRs. In parallel, DArT arrays with ca. 15,000 clones were developed, and 5,397 clones were found polymorphic among 94 genotypes tested. Screening of newly developed BES-SSR markers and DArT arrays on the parental genotypes of the RIL mapping population showed polymorphism with 253 BES-SSR markers and 675 DArT markers. Segregation data obtained for these polymorphic markers and 494 markers data compiled from published reports or collaborators were used for constructing the genetic map. As a result, a comprehensive genetic map comprising 1,291 markers on eight linkage groups (LGs) spanning a total of 845.56 cM distance was developed (http://cmap.icrisat.ac.in/cmap/sm/cp/thudi/). The number of markers per linkage group ranged from 68 (LG 8) to 218 (LG 3) with an average inter-marker distance of 0.65 cM. While the developed resource of molecular markers will be useful for genetic diversity, genetic mapping and molecular breeding applications, the comprehensive genetic map with integrated BES-SSR markers will facilitate its anchoring to the physical map (under construction) to accelerate map-based cloning of genes in chickpea and comparative genome evolution studies in legumes

From Interstellar Ice Grains to Evolved Planetary Systems: The Role of Laboratory Studies

Interstellar matter and star formatio