Time-dependent photoionization of azulene: Competition between ionization and relaxation in highly excited states

Pump-probe photoionization has been used to map the relaxation processes taking place from highly vibrationally excited levels of the S2 state of azulene, populated directly or via internal conversion from the S4 state. Photoelectron spectra obtained by 1+2’ two-color time-resolved photoelectron imaging are invariant (apart from in intensity) to the pump-probe time delay and to pump wavelength. This reveals a photoionization process which is driven by an unstable electronic state (e.g. doubly excited state) lying below the ionization potential. This state is postulated to be populated by a probe transition from S2 and to rapidly relax via an Auger like process onto highly vibrationally excited Rydberg states. This accounts for the time invariance of the photoelectron spectrum. The intensity of the photoelectron spectrum is proportional to the population in S2. An exponential energy gap law is used to describe the internal conversion rate from S2 to S0. The vibronic coupling strength is found to be larger than 60±5 μeV

Process study of the formation of biodegradable polymer microspheres for tissue engineering

A series of polymer microspheres was prepared via solvent evaporation by dispersing dichloromethane solutions of polylactic-co-glycolic acid (PLGA) in water. The dimensions of the final dry particles were measured by laser diffraction and correlated to the main fluid-dynamic parameters of the dispersion process, namely viscosity ratio, volume fraction of dispersed phase, intensity of stirring, and Weber number (We). Data analysis indicated that the system under study can be quantitatively well described by empirical models present in the literature and concerning the dispersion of liquid-liquid immiscible systems. The PLGA microspheres obtained in this way may be employed for fabrication of biodegradable scaffolds for tissue engineering

Towards Precision Photometry with Extremely Large Telescopes: the Double Subgiant Branch of NGC 1851

The Extremely Large Telescopes currently under construction have a collecting area that is an order of magnitude larger than the present largest optical telescopes. For seeing-limited observations the performance will scale as the collecting area but, with the successful use of adaptive optics, for many applications it will scale as $D^4$ (where $D$ is the diameter of the primary mirror). Central to the success of the ELTs, therefore, is the successful use of multi-conjugate adaptive optics (MCAO) that applies a high degree correction over a field of view larger than the few arcseconds that limits classical adaptive optics systems. In this letter, we report on the analysis of crowded field images taken on the central region of the Galactic globular cluster NGC 1851 in $K_s$ band using GeMS at the Gemini South telescope, the only science-grade MCAO system in operation. We use this cluster as a benchmark to verify the ability to achieve precise near-infrared photometry by presenting the deepest $K_s$ photometry in crowded fields ever obtained from the ground. We construct a colour-magnitude diagram in combination with the F606W band from HST/ACS. As well as detecting the "knee" in the lower main sequence at $K_s\simeq20.5$, we also detect the double subgiant branch of NGC 1851, that demonstrates the high photometric accuracy of GeMS in crowded fields.Comment: Accepted for publication in ApJL (3 Sep 2015). A version of the paper with high-res images is available at http://www.astro.uvic.ca/~alan/ms_arxiv_hr.pd

Astrometry with MCAO: HST-GeMS proper motions in the globular cluster NGC 6681

Aims: for the first time the astrometric capabilities of the Multi-Conjugate Adaptive Optics (MCAO) facility GeMS with the GSAOI camera on Gemini-South are tested to quantify the accuracy in determining stellar proper motions in the Galactic globular cluster NGC 6681. Methods: proper motions from HST/ACS for a sample of its stars are already available, and this allows us to construct a distortion-free reference at the epoch of GeMS observations that is used to measure and correct the temporally changing distortions for each GeMS exposure. In this way, we are able to compare the corrected GeMS images with a first-epoch of HST/ACS images to recover the relative proper motion of the Sagittarius dwarf spheroidal galaxy with respect to NGC 6681. Results: we find this to be (\mu_{\alpha}cos\delta, \mu_{\delta}) = (4.09,-3.41) mas/yr, which matches previous HST/ACS measurements with a very good accuracy of 0.03 mas/yr and with a comparable precision (r.m.s of 0.43 mas/yr). Conclusions: this study successfully demonstrates that high-quality proper motions can be measured for quite large fields of view (85 arcsec X 85 arcsec) with MCAO-assisted, ground-based cameras and provides a first, successful test of the performances of GeMS on multi-epoch data.Comment: 5 pages, 4 figures. Accepted for publication by A&A Letter

Long-term thermal stability of high-efficiency polymer solar cells based on photocrosslinkable donor-acceptor conjugated polymers

Highly efficient polymer solar cells based on novel photocrosslinkable donor–acceptor conjugated polymers are fabricated and their long-term thermal stability is reported. After 72 h of thermal annealing at 150 °C, a stable power conversion efficiency as high as 4.7% is maintained. The control of active layer morphology and device performance through annealing is correlated with the synthetic design of the photocrosslinkable polymer

The Low Energy Tagger for the KLOE-2 experiment

The KLOE experiment at the upgraded DAFNE e+e- collider in Frascati (KLOE-2) is going to start a new data taking at the beginning of 2010 with its detector upgraded with a tagging system for the identification of gamma-gamma interactions. The tagging stations for low-energy e+e- will consist in two calorimeters The calorimeter used to detect low-energy e+e- will be placed between the beam-pipe outer support structure and the inner wall of the KLOE drift chamber. This calorimeter will be made of LYSO crystals readout by Silicon Photomultipliers, to achieve an energy resolution better than 8% at 200 MeV.Comment: 4 pages, 5 figures, in the proceedings of "Frontier detectors for frontier physics", isola d'Elba, Italy, May 200

Teleological Essentialism

Placeholder essentialism is the view that there is a causal essence that holds category members together, though we may not know what the essence is. Sometimes the placeholder can be filled in by scientific essences, such as when we acquire scientific knowledge that the atomic weight of gold is 79. We challenge the view that placeholders are elaborated by scientific essences. On our view, if placeholders are elaborated, they are elaborated Aristotelian essences, a telos. Utilizing the same kinds of experiments used by traditional essentialists—involving superficial change (study 1), transformation of insides (study 2), acquired traits (study 3) and inferences about offspring (study 4)—we find support for the view that essences are elaborated by a telos. And we find evidence (study 5) that teleological essences may generate category judgments

Sinonasal mucosal melanoma: Molecular profile and therapeutic implications from a series of 32 cases

BACKGROUND: Primary sinonasal mucosal melanomas are aggressive tumors with a poor clinical control by current treatments, raising the urgent need of novel strategies. METHODS: By fluorescence in situ hybridization (FISH), direct sequencing, and immunohistochemistry, we investigate the spectrum of molecular abnormalities in a cohort of 32 cases of primary sinonasal mucosal melanomas. RESULTS: We found that all primary sinonasal mucosal melanomas lack BRAF V600E mutation; in addition, they are characterized by somatic mutations of NRAS (22%) and KIT (12.5%), together with amplification of RREB1 (100%) and loss of MYB (76%). The large majority of cases showed KIT protein expression (96.9%). Among tumor suppressor genes, primary sinonasal mucosal melanomas showed loss of PTEN (48.1%) and p16/INK4a (55.2%). All tested cases showed expression of pAkt and pErk, suggesting a combined activation of PI3K/Akt and RAS-mitogen-activated protein kinase (MAPK) pathways. CONCLUSIONS: This molecular fingerprint strongly argues against the clinical efficacy of BRAF-inhibitors, but could candidate primary sinonasal mucosal melanomas to therapeutic strategies targeting RAS and KIT mutations or inhibiting PI3K-Akt-mTOR pathway

Comprehensive molecular portrait using next generation sequencing of resected intestinal-type gastric cancer patients dichotomized according to prognosis

In this study, we evaluated whether the presence of genetic alterations detected by next generation sequencing may define outcome in a prognostically-selected and histology-restricted population of resected gastric cancer (RGC). Intestinal type RGC samples from 34 patients, including 21 best and 13 worst prognostic performers, were studied. Mutations in 50 cancer-associated genes were evaluated. A significant difference between good and poor prognosis was found according to clinico-pathologic factors. The most commonly mutated genes in the whole population were PIK3CA (29.4%), KRAS (26.5%), TP53 (26.5%) MET (8.8%), SMAD4 (8.8%) and STK11 (8.8%). Multiple gene mutations were found in 14/21 (67%) patients with good prognosis, and 3/13 (23%) in the poor prognosis group. A single gene alteration was found in 5/21 (24%) good and 6/13 (46%) poor prognosis patients. No mutation was found in 2/21 (9.5%) and 4/13 (31%) of these groups, respectively. In the overall series, ß-catenin expression was the highest (82.4%), followed by E-Cadherin (76.5%) and FHIT (52.9%). The good prognosis group was characterized by a high mutation rate and microsatellite instability. Our proof-of-principle study demonstrates the feasibility of a molecular profiling approach with the aim to identify potentially druggable pathways and drive the development of customized therapies for RGC