A short proof of MacLane's planarity theorem

This note gives a short and elementary proof of MacLane's theorem on the embedding of graphs in a 2-sphere

Design reuse experience of space and hazardous operations robots

A comparison of design drivers for space and hazardous nuclear waste operating robots details similarities and differences in operations, performance and environmental parameters for these critical environments. The similarities are exploited to provide low risk system components based on reuse principles and design knowledge. Risk reduction techniques are used for bridging areas of significant differences. As an example, risk reduction of a new sensor design for nuclear environment operations is employed to provide upgradeable replacement units in a reusable architecture for significantly higher levels of radiation

Particulate and aerosol detector

A device is described for counting aerosols and sorting them according to either size, mass or energy. The component parts are an accelerator, a capacitor sensor and a readout. The accelerator is a means for accelerating the aerosols toward the face of the capacitor sensor with such force that they partially penetrate the capacitor sensor, momentarily discharging it. The readout device is a means for counting the number of discharges of the capacitor sensor and measuring the amplitudes of these different discharges. The aerosols are accelerated by the accelerator in the direction of the metal layer with such force that they penetrate the metal and damage the oxide layers, thereby allowing the electrical charge on the capacitor to discharge through the damaged region. Each incident aerosol initiates a discharge path through the capacitor in such a fashion as to vaporize the conducting path. Once the discharge action is complete, the low resistance path no longer exists between the two capacitor plates and the capacitor is again able to accept a charge. The active area of the capacitor is reduced in size by the damaged area each time a discharge occurs

Regulation of Collagenase Gene Expression by IL-1 Beta Requires Transcriptional and Post-Transcriptional Mechanisms

Interleukin-1 beta is believed to contribute to the pathophysiology of rheumatoid arthritis by activating collagenase gene expression. We have used a cell culture model of rabbit synovial fibroblasts to examine the molecular mechanisms of IL-1 beta-mediated collagenase gene expression. Stimulation of rabbit synovial fibroblasts with 10 ng/ml recombinant human IL-1 beta resulted in a 20-fold increase in collagenase mRNA by 12 h. Transient transfection studies using collagenase promoter-CAT constructs demonstrated that proximal sequences responded poorly to IL-1 beta, possibly due to insufficient activation of AP-1 by this cytokine. More distal sequences were required for IL-1 beta responsiveness, with a 4700 bp construct showing approximately 5-fold induction above control. To examine post-transcriptional mechanisms, transcript from a human collagenase cDNA was constitutively produced by the simian virus 40 early promoter. IL-1 beta stabilized the constitutively expressed human transcript. Furthermore, mutation of the ATTTA motifs in the 3\u27 untranslated region of the human gene also stabilized the transcript. Finally, the rabbit collagenase 3\u27 untranslated region destabilized a constitutively transcribed chloramphenicol acetyltransferase transcript. These data indicate that in addition to activating transcription, IL-1 beta increases collagenase transcript stability by reversing the destabilizing effects of sequences in the 3\u27 untranslated region

Viking navigation

A comprehensive description of the navigation of the Viking spacecraft throughout their flight from Earth launch to Mars landing is given. The flight path design, actual inflight control, and postflight reconstruction are discussed in detail. The preflight analyses upon which the operational strategies and performance predictions were based are discussed. The inflight results are then discussed and compared with the preflight predictions and, finally, the results of any postflight analyses are presented

Meniscus-assisted solution printing of large-grained perovskite films for high-efficiency solar cells

Control over morphology and crystallinity of metal halide perovskite films is of key importance to enable high-performance optoelectronics. However, this remains particularly challenging for solution-printed devices due to the complex crystallization kinetics of semiconductor materials within dynamic flow of inks. Here we report a simple yet effective meniscus-assisted solution printing (MASP) strategy to yield large-grained dense perovskite film with good crystallization and preferred orientation. Intriguingly, the outward convective flow triggered by fast solvent evaporation at the edge of the meniscus ink imparts the transport of perovskite solutes, thus facilitating the growth of micrometre-scale perovskite grains. The growth kinetics of perovskite crystals is scrutinized by in situ optical microscopy tracking to understand the crystallization mechanism. The perovskite films produced by MASP exhibit excellent optoelectronic properties with efficiencies approaching 20% in planar perovskite solar cells. This robust MASP strategy may in principle be easily extended to craft other solution-printed perovskite-based optoelectronics

Observation of Electroweak Production of a Same-Sign W Boson Pair in Association with Two Jets in pp Collisions root s=13 TeV with the ATLAS Detector

This Letter presents the observation and measurement of electroweak production of a same-sign W boson pair in association with two jets using 36.1     fb − 1 of proton-proton collision data recorded at a center-of-mass energy of √ s = 13     TeV by the ATLAS detector at the Large Hadron Collider. The analysis is performed in the detector fiducial phase-space region, defined by the presence of two same-sign leptons, electron or muon, and at least two jets with a large invariant mass and rapidity difference. A total of 122 candidate events are observed for a background expectation of 69 ± 7 events, corresponding to an observed signal significance of 6.5 standard deviations. The measured fiducial signal cross section is σ fid = 2.89 + 0.51 − 0.48 ( stat ) + 0.29 − 0.28 ( syst )     fb