Ultrafast laser inscription of mid-IR directional couplers for stellar interferometry

We report the ultrafast laser fabrication and mid-IR characterization (3.39 microns) of four-port evanescent field directional couplers. The couplers were fabricated in a commercial gallium lanthanum sulphide glass substrate using sub-picosecond laser pulses of 1030 nm light. Straight waveguides inscribed using optimal fabrication parameters were found to exhibit propagation losses of 0.8 dB/cm. A series of couplers were inscribed with different interaction lengths, and we demonstrate power splitting ratios of between 8% and 99% for mid-IR light with a wavelength of 3.39 microns. These results clearly demonstrate that ultrafast laser inscription can be used to fabricate high quality evanescent field couplers for future applications in astronomical interferometry.Comment: 4 pages, 4 figure

Modulation-assisted tunneling in laser-fabricated photonic Wannier-Stark ladders

We observe Wannier-Stark localization in curved photonic lattices, realized using arrays of evanescently coupled optical waveguides. By correctly tuning the strength of inter-site coupling in the lattice, we observe that Wannier-Stark states become increasingly localized, and eventually fully localized to one site, as the curvature of the lattice is increased. We then demonstrate that tunneling can be successfully restored in the lattice by applying a sinusoidal modulation to the lattice position, an effect that is a direct analogue of photon-assisted tunneling. This precise tuning of the tunneling matrix elements, through laser-fabricated on-site modulations, opens a novel route for the creation of gauge fields in photonic lattices.Comment: 5 pages. Comments are welcom

Pyrroloquinoline quinone increases the expression and activity of Sirt1 and -3 genes in HepG2 cells.

Sirtuin (Sirt) 1 and Sirt 3 are nicotinamide adenine dinucleotide ((+))-dependent protein deacetylases that are important to a number of mitochondrial-related functions; thus, identification of sirtuin activators is important. Herein, we hypothesize that pyrroloquinoline quinone (PQQ) can act as a Sirt1/Sirt3 activator. In HepG2 cell cultures, PQQ increased the expression of Sirt1 and Sirt3 gene, protein, and activity levels (P < .05). We also observed a significant increase in nicotinamide phosphoribosyltransferase gene expression (as early as 18 hours) and increased NAD(+) activity at 24 hours. In addition, targets of Sirt1 and Sirt3 (peroxisome proliferator-activated receptor γ coactivator 1α, nuclear respiratory factor 1 and 2, and mitochondrial transcription factor A) were increased at 48 hours. This is the first report that demonstrates PQQ as an activator of Sirt1 and Sirt3 expression and activity, making it an attractive therapeutic agent for the treatment of metabolic diseases and for healthy aging. Based on our study and the available data in vivo, PQQ has the potential to serve as a therapeutic nutraceutical, when enhancing mitochondrial function

Observation of a localized flat-band state in a photonic Lieb lattice

We show experimentally how a non-diffracting state can be excited in a photonic Lieb lattice. This lattice supports three energy bands, including a perfectly flat middle band, which corresponds to an infinite effective mass with zero dispersion. We show that a suitable optical input state can be prepared so as to only excite the flat band. We analyse, both experimentally and theoretically, the evolution of such photonic flat-band states, and show their remarkable robustness, even in the presence of disorder.Comment: Accepted for publication in Physical Review Letter

Optimisation of ultrafast laser assisted etching in fused silica

Observations of runout distances combined with velocity measurements suggest that “major” dry-mixed avalanches show a scale invariance to the total drop height HSC. This is in accordance to the proposed upper-limit envelope of the maximum velocity by McClung and Schaerer (2006). The observations are also supported by a simple scaling analysis using a simple mass block model on cycloidal and parabolic tracks (Gauer, 2018b), concluding Umax~ gHSC/2 . In this supplementary paper, a simple mass block model is presented that includes basic observations of major dry-mixed avalanches, such as mass entrainment and deposition, and that reflects this scale invariance. Almost all model parameters can principally be observed in the field. Model results are compared with a series of avalanche observations of runout and velocity and match well, considering that the model is a first order approximation

The Data Conservancy: Building a Sustainable System for Interdisciplinary Scientific Data Curation and Preservation

Presentation at the PV 2009 conference in Madrid, SpainThe Data Conservancy (DC) is one of two awards through the US National Science Foundation’s DataNet program. The goal of the DataNet program is to create “a set of exemplar national and global data research infrastructure organizations (dubbed DataNet Partners) that provide unique opportunities to communities of researchers to advance sci- ence and/or engineering research and learning.” The DC embraces a shared vision: data curation is not an end, but rather a means to col- lect, organize, validate, and preserve data to address the grand research challenges that face society. The overarching goal of The Data Conservancy is to support new forms of inquiry and learning to meet these challenges through the creation, implementation, and sustained management of an integrated and comprehensive data curation strategy. DC will address this overarching goal with a comprehensive project comprising four inter- dependent threads: 1) infrastructure research and development, 2) computer science and information science research, 3) broader impacts, and 4) sustainability. The DC is led by the Sheridan Libraries at Johns Hopkins University. Working with the Sloan Digital Sky Survey data and the US National Virtual Observatory, the Sheridan Libraries have developed an initial architectural design, data models and metadata pro- files, and organizational models to support data curation. The DC will build upon these initial lessons learned from the partnership between the library and astronomy commu- nity and extend them into the life sciences, earth sciences, and social sciences. Use cases will provide the initial framework for technical requirements. A robust information sci- ence and computer science research agenda will highlight the scientific requirements and inform the development of a data framework for observations and a theoretical frame- work for data curation. These activities will guide the development of new curriculum at library and information science schools thereby building capacity for a new generation of data scientists. One of the central tenets of DC’s sustainability plan relates to the leadership role of the library. The Sheridan Libraries at Johns Hopkins University have established a leader- ship position in prototyping data curation systems and services, especially as they relate to astronomy. One of the key outcomes of DC will be a new model for libraries in the digital age. There are several fundamental implications for libraries in the realm of data curation as they relate to collections, services, and infrastructure. The North American Association of Research Libraries has already engaged the DC in its effort to consider these implications strategically as a means to transform the library’s role and contribu- tions toward building and sustaining data curation infrastructure.National Science Foundation, Office of Cyberinfrastructure DataNet Award #0830976; Institute of Museum and Library Services national leadership grant award LG0606018206; Microsoft Researc