The Light Growth Response of Phycomyces

With the help of an automated tracking system we have studied the characteristics of the transient light growth response of Phycomyces. The response shows a sharply defined latency. The Q10 of the reciprocal latency is 2.4. Response patterns at different peaks of the action spectrum are the same. The gradual variation of response magnitude over a wide range of adapted intensifies parallels that of phototropism. The responses to saturating stimuli exhibit a strong oscillation with a constant period of 1.6 min and variable damping. The growth responses to sinusoidally varying light intensities show a system bandwidth of 2.5 x 10-3 Hz. The linear dependence of phase shift on frequency is largely attributable to the latency observed with pulse stimuli. In the high intensity range a previously suspected increase of the steady-state growth rate with intensity has been confirmed. The light growth responses of mutants selected for diminished phototropism have been investigated. Many of these mutants have sizable but grossly distorted growth responses

A Versatile Pseudo-Random Noise Generator

A detailed design is presented for a digital pseudo-random noise generator. The instrument is built with standard integrated circuits. It produces both binary noise (pseudo-random binary sequences) and white Gaussian noise of variable bandwidth. By setting front panel switches to match tabulated octal codes, one may select a vast number of independent noise programs

Platforming Gamification as a Means of Engagement in Employee Recruitment and Onboarding

Gamification, generally understood as the application of game elements and design concepts in non-game contexts, is a field of academic study and multibillion-dollar business tool whose popularity is growing as a means of employee engagement, education and training, and talent selection. While there are companies that attempt to gamify separate processes within the employee life cycle, no company exists that gamifies the stages surrounding talent selection: attraction and recruitment of applicants and onboarding of final candidates. To this end, this thesis proposes a software and consulting company, GameON Business Solutions, that will work with small and medium enterprises to expand and diversify the talent pool and prepare new employees for working at the company

Direct Freeform Fabrication of Spatially Heterogeneous Living Cell-Impregnated Implants

The objectives of this work are the development of the processes, materials, and tooling to directly “3-D print” living, pre-seeded, patient-specific implants of spatially heterogeneous compositions. The research presented herein attempts to overcome some of the challenges to scaffolding, such as the difficulty of producing spatially heterogeneous implants that require varied seeding densities and/or cell-type distributions. In the proposed approach, living implants are fabricated by the layer-wise deposition of pre-cell-seeded alginate hydrogel. Although alginate hydrogels have been previously used to mold living implants, the properties of the alginate formulations used for molding were not suitable for 3-D printing. In addition to changing the formulation to make the alginate hydrogels “printable,” we developed a robotic hydrogel deposition system and supporting CAD software to deposit the gel in arbitrary geometries. We demonstrated this technology’s capabilities by printing alginate gel implants of multiple materials with various spatial heterogeneities, including, implants with completely embedded material clusters. The process was determined to be both viable (94±5% n=15) and sterile (less than one bacterium per 0.9 µL after 8 days of incubation). Additionally, we demonstrated the printing of a meniscus cartilage-shaped gel generated directly from a CT Scan. The proposed approach may hold advantages over other tissue printing efforts [5,9]. This technology has the potential to overcome challenges to scaffolding and could enable the efficient fabrication of spatially heterogeneous, patient-specific, living implants.Mechanical Engineerin

Fully Recyclable Multi-Material Printing

Recycling is often a costly and inefficient process, particularly for objects composed of multiple integrated materials. Here, we demonstrate a freeform fabrication system that prints with fully reusable physical voxels and minimal recycling effort. This new paradigm of digital (discrete) matter enables any number of materials to be printed together in any configuration. The individual voxels may then be reclaimed at will by dissolving the bonds holding the structure together. Coupled with a compatible voxel sorting process, we demonstrate multiple generations of freeform fabricated objects using the same physical material. This opens the door to a flexible desktop fabrication process in which 3D multi-material objects are fully recyclable and re-usable with minimal infrastructure.Mechanical Engineerin

STL 2.0: A Proposal for a Universal Multi-Material Additive Manufacturing File Format

The de-facto standard STL file format has served the rapid prototyping community for over two decades, but falls short with the advent of new technological developments such as the ability to handle multiple and graded materials, specify volumetric digital inkjet patterns and surface colors. We study a variety of requirements for additive fabrication technologies and propose a new compact XML-based file format. The new Additive Manufacturing File (AMF) format allows the resolution-independent specification of geometry and material properties. Regions may be defined geometrically either using a triangle mesh, using functional representations, or through a voxel bitmap. Each region is associated with a material, which may be defined as a base (single) material or hierarchically by a combination of other materials, either functionally (enabling smooth gradients) or voxel-wise (for arbitrary microstructure). Files can be self-contained or refer to external or online material libraries. With a simple conversion, the AMF file format is both forward and backwards compatible with the current standard STL format, and the flexibility of the XML structure enables additional features to be adopted as needed by CAD programs and future additive manufacturing processes. Code and examples are publicly available.Mechanical Engineerin

Microbial community structure and soil pH correspond to methane production in Arctic Alaska soils

While there is no doubt that biogenic methane production in the Arctic is an important aspect of global methane emissions, the relative roles of microbial community characteristics and soil environmental conditions in controlling Arctic methane emissions remains uncertain. Here, relevant methane‐cycling microbial groups were investigated at two remote Arctic sites with respect to soil potential methane production (PMP). Percent abundances of methanogens and iron‐reducing bacteria correlated with increased PMP, while methanotrophs correlated with decreased PMP. Interestingly, α‐diversity of the methanogens was positively correlated with PMP, while β‐diversity was unrelated to PMP. The β‐diversity of the entire microbial community, however, was related to PMP. Shannon diversity was a better correlate of PMP than Simpson diversity across analyses, while rarefied species richness was a weak correlate of PMP. These results demonstrate the following: first, soil pH and microbial community structure both probably control methane production in Arctic soils. Second, there may be high functional redundancy in the methanogens with regard to methane production. Third, iron‐reducing bacteria co‐occur with methanogens in Arctic soils, and iron‐reduction‐mediated effects on methanogenesis may be controlled by α‐ and β‐diversity. And finally, species evenness and rare species abundances may be driving relationships between microbial groups, influencing Arctic methane production

Structure of 2-Methyl-5,6,7-triphenyl-6,7-dihydropyrazolo[2,3-\u3cem\u3ea\u3c/em\u3e]pyrimidine

C25H21N3, Mr = 363.46, monoclinic, P21/n, a = 9.245 (2), b = 23.502 (5), c = 9.340 (2) Å, β= 103.50(3)°, V=1973.3(2) Å3, Z=4, Dx= 1.220 (2) g cm-3, λ (Mo Kα )= 0.71069 Å, μ = 0.068 cm-1, F(000) = 768, T= 292 K, R = 0.091 for 1442 unique observed reflections. The dihydropyrimidine ring adopts a distorted sofa conformation. The aryl substituents on the saturated C atoms have an axial orientation

Metabolic trade-offs and the maintenance of the fittest and the flattest.

This is the post print version of the article, deposited in accordance with SHERPA RoMEO guidelines. The final definitive version is available from: http://www.nature.com/nature/journal/v472/n7343/full/nature09905.htmlHow is diversity maintained? Environmental heterogeneity is considered to be important, yet diversity in seemingly homogeneous environments is nonetheless observed. This, it is assumed, must either be owing to weak selection, mutational input or a fitness advantage to genotypes when rare. Here we demonstrate the possibility of a new general mechanism of stable diversity maintenance, one that stems from metabolic and physiological trade-offs. The model requires that such trade-offs translate into a fitness landscape in which the most fit has unfit near-mutational neighbours, and a lower fitness peak also exists that is more mutationally robust. The 'survival of the fittest' applies at low mutation rates, giving way to 'survival of the flattest' at high mutation rates. However, as a consequence of quasispecies-level negative frequency-dependent selection and differences in mutational robustness we observe a transition zone in which both fittest and flattest coexist. Although diversity maintenance is possible for simple organisms in simple environments, the more trade-offs there are, the wider the maintenance zone becomes. The principle may be applied to lineages within a species or species within a community, potentially explaining why competitive exclusion need not be observed in homogeneous environments. This principle predicts the enigmatic richness of metabolic strategies in clonal bacteria and questions the safety of lethal mutagenesis as an antimicrobial treatment

A simple beam combination for stellar interferometry

In stellar interferometry, image quality improves significantly with the inclusion of more telescopes and the use of phase closure. We demonstrate, using first coherent and then partially coherent white light, a compact and efficient pair-wise combination of twelve or more beams. The input beams are lined up and spread through a cylindrical lens into a comb of parallel ellipses, which interferes with a perpendicular copy of itself to form a matrix of interferograms between all pairs. The diagonal elements show interference of each beam with itself, for in-tensity calibration. The measured white-light visibilities were high and stable