The Galaxy Evolution Explorer: A Space Ultraviolet Survey Mission

We give an overview of the Galaxy Evolution Explorer (GALEX), a NASA Explorer Mission launched on April 28, 2003. GALEX is performing the first space UV sky-survey, including imaging and grism surveys in two bands (1350-1750 Angstroms and 1750-2750 Angstroms). The surveys include an all-sky imaging survey (m[AB] ~ 20.5), a medium imaging survey of 1000 square degrees (m[AB] ~ 23), a deep imaging survey of 100 square degrees (m[AB] ~ 25), and a nearby galaxy survey. Spectroscopic grism surveys (R=100-200) are underway with various depths and sky coverage. Many targets overlap existing or planned surveys. We will use the measured UV properties of local galaxies, along with corollary observations, to calibrate the UV-global star formation rate relationship in local galaxies. We will apply this calibration to distant galaxies discovered in the deep imaging and spectroscopic surveys to map the history of star formation in the universe over the redshift range 0 < z < 1.5, and probe the physical drivers of star formation in galaxies. The GALEX mission includes a Guest Investigator program supporting the wide variety of programs made possible by the first UV sky survey.Comment: This paper will be published as part of the Galaxy Evolution Explorer (GALEX) Astrophysical Journal Letters Special Issue. Links to the full set of papers will be available at http:/www.galex.caltech.edu/PUBLICATIONS/ after November 22, 200

PNIPAM-Coated Brushy Beads and How They Collapse

Stimuli-responsive polymers are a group of powerful switchable materials with a broad range of applications. Induced by a stimulus, the properties of such polymers can change dramatically. One popular polymer is poly(N- isopropylacryamide) (PNIPAM). PNIPAM is interesting for a number of applications, including in technologies as sensors, actuators, microfluidics, and mineral retrieval, but also in biology, and in medicine. One powerful place to use them is in colloids. By themselves, colloids are a center point of interest, owing to the fact that their properties depend on their surfaces rather than on their bulk. Adding to this fact a stimuli-responsiveness will open up new possibilities for applications. What is missing to make full use of PNIPAM is a thorough understanding of its properties and how they respond to stimuli. Understanding PNIPAM requires understanding its response to stimuli. To this end, I investigated two of PNIPAM’s main stimuli: temperature and solvent. With temperature, PNIPAM mostly displays a simple collapse while above a certain temperature, the lower critical solution temperature (LCST). In some cases, however, PNIPAM has been reported to show a rather complex, not fully understood, two-stage collapse. With solvent, PNIPAM exhibits the co-non-solvency effect. PNIPAM swells well in either water or in alcohols, yet it collapses in intermediate mixtures. The exact cause of the co-non- solvency effect is still debated, however. The study of the effects of these two stimuli on PNIPAM-based colloids is not straightforward: many techniques are technologically quite involved, average over a multitude of colloids, or are invasive and change the response of the sampled colloids to stimuli. Hence, a better understanding of these two stimuli would be greatly benefited by the ability to study them in a simple, non-invasive manner. In this thesis, I present a new method to observe responses of PNIPAM-based colloids to stimuli. The method is optical, and is based on interference and microscopy. Specifically, I studied colloidal glass beads that were coated with an end-grafted PNIPAM brush (51 ± 3 nm thick) near a glass surface. The Brownian motion of such beads is dominated by the brush layer’s viscoelastic properties, which change as a response to stimuli. As a result, monitoring the Brownian motion through interference allows observing viscoelastic changes of the PNIPAM brush in a simple and non-invasive manner. Consequently, this method allowed me to study how various stimuli affected the PNIPAM brush coating. Taking temperature as a stimulus, I observed a two-stage collapse of the PNIPAM brush-coated beads. Upon increasing the temperature, I first ob- served a change at 36°C. This change was attributed to the LCST volume collapse of PNIPAM, which induced an increase of polymer brush density and subsequent increase of viscosity of the brush layer. Then, increasing temperature above 46°C induced a second transition. I attributed this second transition to the complete collapse of the brush layer. Upon this complete collapse, the brush layer became stiffer throughout, which made the Brownian motion more elastic. These results indicate that PNIPAM undergoes a type II-phase transition. The better understanding will play a role towards proper application of PNIPAM brush coatings. Furthermore, I investigated the co-non-solvency effect using the same method. For this effect, there exist a few hypotheses regarding the underlying cause. One leading hypothesis is based on the preferential binding of alcohol to PNIPAM, rather than water to PNIPAM. Through monitoring the viscoelastic changes in my experiments, I provide support for the theory of preferential binding. These viscoelastic responses to stimuli provide us with a better insight into responsive thin coatings. Being non-invasive, simple, flexible, repeatable, yet measuring single coated colloids in-situ, the optical method that I developed and described proved to be a useful tool. This method can be integrated into the standard set of techniques to investigate changes in stimuli-responsive colloids. --- For the non-scientists --- Stimuli-responsive polymers are a group of powerful switchable materials with a broad range of applications. One popular responsive polymer is PNIPAM, or poly(N-isopropylacryamide) in full. It is interesting for a range of applications as a technology in sensors, actuators, microfluidics or for mineral retrieval but also as an in-body medicine carrier. What makes PNIPAM so interesting is that it responds to stimuli: changes of its environment. For example, changing the temperature can dramatically change the properties of PNIPAM. However, exactly why and how PNIPAM responds is not completely known. Therefore, before we can fully use its potential, we first need to understand PNIPAM better. There are several forms and shapes of polymers and of PNIPAM. I looked at PNIPAM brushes. Such brushes are basically like the brush of a broom, but very short; only about a hundred nanometer thick – a thousand times thinner than printer paper. Such brushes can be coatings. What is nice in the case of a PNIPAM brush coating, is that the coated surface becomes stimuli-responsive. I investigated such PNIPAM brush-coatings on small glass beads. To look at the response of these PNIPAM brush-coated beads, I exposed them to different temperatures. Through a special microscope set-up that I developed, I was able to study the response of the PNIPAM brush coating. The response of PNIPAM to temperature showed an interesting result. Most of the time, PNIPAM responds at a single temperature. In my experiments, I found that there are two distinct transitions, at two distinct temperatures. I could explain these results by looking at the thin layer of the PNIPAM brush and how it changed its thickness and stiffness. In a further study, I also looked at the influence of another stimulus: solvent, and these experiments support for one of the possible theories. All in all, we now understand thin responsive coatings a little bit better, which was made possible because of the new experimental optical method that I developed

Shedding Light on the Nature of Photoinduced States Formed in a Hydrogen-Generating Supramolecular RuPt Photocatalyst by Ultrafast Spectroscopy

Photoinduced electronic and structural changes of a hydrogen-generating supramolecular RuPt photocatalyst are studied by a combination of time-resolved photoluminescence, optical transient absorption, and X-ray absorption spectroscopy. This work uses the element specificity of X-ray techniques to focus on the interplay between the photophysical and -chemical processes and the associated time scales at the catalytic Pt moiety. We observe very fast (10 μs time scale. However, the photosensitizing Ru moiety is fully restored on a much shorter ∼300 ns time scale. This reaction scheme implies that we may withdraw two electrons from a catalyst that is activated by a single photon

Genotype and tumor locus determine expression profile of pseudohypoxic pheochromocytomas and paragangliomas

Contains fulltext : 118484.pdf (publisher's version ) (Open Access)Pheochromocytomas (PHEOs) and paragangliomas (PGLs) related to mutations in the mitochondrial succinate dehydrogenase (SDH) subunits A, B, C, and D, SDH complex assembly factor 2, and the von Hippel-Lindau (VHL) genes share a pseudohypoxic expression profile. However, genotype-specific differences in expression have been emerging. Development of effective new therapies for distinctive manifestations, e.g., a high rate of malignancy in SDHB- or predisposition to multifocal PGLs in SDHD patients, mandates improved stratification. To identify mutation/location-related characteristics among pseudohypoxic PHEOs/PGLs, we used comprehensive microarray profiling (SDHB: n = 18, SDHD-abdominal/thoracic (AT): n = 6, SDHD-head/neck (HN): n = 8, VHL: n = 13). To avoid location-specific bias, typical adrenal medulla genes were derived from matched normal medullas and cortices (n = 8) for data normalization. Unsupervised analysis identified two dominant clusters, separating SDHB and SDHD-AT PHEOs/PGLs (cluster A) from VHL PHEOs and SDHD-HN PGLs (cluster B). Supervised analysis yielded 6937 highly predictive genes (misclassification error rate of 0.175). Enrichment analysis revealed that energy metabolism and inflammation/fibrosis-related genes were most pronouncedly changed in clusters A and B, respectively. A minimum subset of 40 classifiers was validated by quantitative real-time polymerase chain reaction (quantitative real-time polymerase chain reaction vs. microarray: r = 0.87). Expression of several individual classifiers was identified as characteristic for VHL and SDHD-HN PHEOs and PGLs. In the present study, we show for the first time that SDHD-HN PGLs share more features with VHL PHEOs than with SDHD-AT PGLs. The presented data suggest novel subclassification of pseudohypoxic PHEOs/PGLs and implies cluster-specific pathogenic mechanisms and treatment strategies

Shedding Light on the Nature of Photoinduced States Formed in a Hydrogen-Generating Supramolecular RuPt Photocatalyst by Ultrafast Spectroscopy

Photoinduced electronic and structural changes of a hydrogen-generating supramolecular RuPt photocatalyst are studied by a combination of time-resolved photoluminescence, optical transient absorption, and X-ray absorption spectroscopy. This work uses the element specificity of X-ray techniques to focus on the interplay between the photophysical and -chemical processes and the associated time scales at the catalytic Pt moiety. We observe very fast (<30 ps) photoreduction of the Pt catalytic site, followed by an ∼600 ps step into a strongly oxidized Pt center. The latter process is likely induced by oxidative addition of reactive iodine species. The oxidized Pt species is long-lived and fully recovers to the original ground state complex on a >10 μs time scale. However, the photosensitizing Ru moiety is fully restored on a much shorter ∼300 ns time scale. This reaction scheme implies that we may withdraw two electrons from a catalyst that is activated by a single photon

Conjunctival melanoma treatment outcomes in 288 patients: a multicentre international data-sharing study

Background To relate conjunctival melanoma characteristics to local control. Methods Retrospective, registry-based interventional study with data gathered from 10 ophthalmic oncology centres from 9 countries on 4 continents. Conjunctival melanoma patients diagnosed between January 2001 and December 2013 were enrolled in the study. Primary treatments included local excision, excision with cryotherapy and exenteration. Adjuvant treatments included topical chemotherapy, brachytherapy, proton and external beam radiotherapy (EBRT). Cumulative 5-year and 10-year Kaplan-Meier local recurrence rates were related to clinical and pathological T-categories of the eighth edition of the American Joint Committee on Cancer (AJCC) staging system. Results 288 patients had a mean initial age of 59.7 +/- 16.8 years. Clinical T-categories (cT) were cT1 (n=218,75.7%), cT2 (n=34, 11.8%), cT3 (n=15, 5.2%), cTx (n=21,7.3%) with no cT4. Primary treatment included local excision (n=161/288, 55.9%) followed by excision biopsy with cryotherapy (n=108/288, 37.5%) and exenteration (n=5/288, 1.7%). Adjuvant therapies included topical mitomycin (n=107/288, 37.1%), plaque-brachytherapy (n=55/288, 19.1%), proton-beam (n=36/288, 13.5%), topical interferon (n=20/288, 6.9%) and EBRT (n=15/288, 5.2%). Secondary exenteration was performed (n=11/283, 3.9%). Local recurrence was noted in 19.1% (median=3.6 years). Cumulative local recurrence was 5.4% (3.2-8.9%), 19.3% (14.4-25.5%) and 36.9% (26.5-49.9%) at 1, 5 and 10 years, respectively. cT3 and cT2 tumors were twice as likely to recur than cT1 tumours, but only cT3 had statistically significantly greater risk of local recurrence than T1 (p=0.013). Factors such as tumour ulceration, plica or caruncle involvement and tumour thickness were not significantly associated with an increased risk of local recurrence. Conclusion This multicentre international study showed that eighth edition of AJCC tumour staging was related to the risk of local recurrence of conjunctival melanoma after treatment. The 10-year cumulative local recurrence remains high despite current management.OV