Anomalous flows in a sunspot penumbra

High-resolution spectropolarimetric observations of active region NOAA 11271 were obtained with the spectro-polarimeter on board Hinode to analyze the properties of an anomalous flow in the photosphere in a sunspot penumbra. We detect a blue-shifted feature that appeared on the limb-side penumbra of a sunspot and that was present intermittently during the next two hours. It exhibited a maximum blue-shift of 1.6 km/s, an area of 5.2 arcsec^2, and an uninterrupted lifetime of 1 hr. The blue-shifted feature, when present, lies parallel to red-shifts. Both blue and red shifts flank a highly inclined/horizontal magnetic structure that is radially oriented in the penumbra. The low-cadence SP maps reveal changes in size, radial position in the penumbra and line-of-sight velocity of the blue-shifted feature, from one scan to the other. There was an increase of nearly 500 G in the field strength and a marginal reduction in the field inclination of about 10 deg with the onset of the blue-shifts. In the chromosphere, intense, arc-shaped brightenings were observed close to the location of the blue-shifts, that extend from the edge of the umbral core to the penumbra-quiet Sun boundary. The strongest and largest brightenings were observed about 30 min after the strongest blue-shifts were detected at the photosphere. The close spatial proximity of the two phenomenon strongly suggests a causal relationship. The blue-shifted feature represents plasma motion that could be related to a magnetic structure that rises in the solar atmosphere and subsequently reconnects with the ambient chromospheric magnetic field of the sunspot or an inverse Evershed flow, which would be unique in the photosphere. This transient phenomena is presumably related to the dynamic stability of the sunspot because the corresponding umbral core separated two days later at the location of the blue-shifts and fragmented subsequently.Comment: Accepted for publication in A&A: 8 pages, 8 figure

Core Loaded Thin-walled Sleeved Column System

In conventional columns, the load carrying capacity is governed by the yield strength of the material and its buckling strength. The yield strength of the compression member is governed by the mechanical property of the material and its area of cross section while its elastic buckling strength depends on the least flexural stiffness (EI) ofthe cross section and its effective unsupported length. The elastic flexural buckling strength of a compression member is given by the well known Euler equation. In practice the strength of conventional compression members is less than bot.h the yield strength and Euler buckling strength due to the effects of imperfections, residual stresses etc.(Bjorhovde(1988)). In this paper behaviour of a novel patented concept, referred to as core loaded thin-walled sleeved column system, is discussed

Clinicopathological profile of colorectal polyps: retrospective analysis from tertiary care center in Southern India

Background: Colorectal Cancer is the fourth most commonly diagnosed and chronological changes in colorectal polyps and cancer is important in efficacy of screening strategies. In this study, we aimed to compare clinicopathological features of colorectal polyps and also aimed to characterise the distribution and the pathological features of polyps during an 18-year period divided in to two groups.Methods: This is retrospective analysis of cases that underwent colonoscopy and found to have colorectal polyps were re-viewed retrospectively for 18 year period are retrieved. 18 year period was divided in to 2001 to 2010 and 2011 to 2018.Results: Among 4230 patients underwent colonoscopy between January 2001 and September 2018, 1356 were excluded; of the remaining 2874, 986 were found to have 1,272 polyps. 306 patients had 412 polyps in 2001 to 2010 group and 680 patients had 860 polyps in 2011 to 2018 group. Adenomas on the left sided colon were significantly higher in the first time period (40.2% vs 30%, p <0.0003). Polyps on the right sided colon were significantly higher in the second time period (37.3% vs 36.9%, p <0.0005). The most common histology in the both periods is tubular adenoma. Histology of adenomas with high grade dysplasia were significantly more in first period (12.4% vs 7.6%, p <0.005).Conclusions: Our data shows shift in polyps from left side to right side colon in recent years. There was no significant change in shift in advanced adenomas from left side to right side of colon

Direct Fabrication of Planar Grating by Ultrafast Laser Beam

Femtosecond laser pulse has been used for the machining of the gratings primarily due to its superior advantages over conventional continuous wave (CW) and long pulse lasers for micromachining. In this paper, we develop a novel technique for the fabrication of planar gratings by colliding two beams to generate interference fringes. This technique is simple, fast and low cost. We have successfully fabricated planar gratings on a copper substrate.Singapore-MIT Alliance (SMA

Towards an Immersive Driving Simulator to Study Factors Related to Cybersickness

What makes a good cybersickness testbed great? In this work, we discuss the characteristics of a high fidelity, realistic immersive virtual reality driving simulator developed to study cybersickness, a malady that is caused as a consequence of Virtual Reality usage. The simulator’s feasibility was evaluated by conducting a preliminary study. Results suggest that our platform is reliable and robust, making for an excellent testbed/ platform to study factors associated with cybersickness in Immersive Virtual Environments

Femtosecond Pulsed Laser Direct Writing System for Photomask Fabrication

Photomasks are the backbone of microfabrication industries. Currently they are fabricated by lithographic process, which is very expensive and time consuming since it is a several step process. These issues can be addressed by fabricating photomask by direct femtosecond laser writing, which is a single step process and comparatively cheaper and faster than lithography. In this paper we discuss about our investigations on the effect of two types of laser writing techniques, namely, front and rear side laser writing with regard to the feature size and the edge quality of the feature. It is proved conclusively that for the patterning of mask, front side laser writing is a better technique than rear side laser writing with regard to smaller feature size and better edge quality. Moreover the energy required for front side laser writing is considerably lower than that for rear side laser writing.Singapore-MIT Alliance (SMA

Supersonic Downflows in a Sunspot Light Bridge

We report the discovery of supersonic downflows in a sunspot light bridge using measurements taken with the spectropolarimeter on board the Hinode satellite. The downflows occur in small patches close to regions where the vector magnetic field changes orientation rapidly, and are associated with anomalous circular polarization profiles. An inversion of the observed Stokes spectra reveals velocities of up to 10 km/s, making them the strongest photospheric flows ever measured in light bridges. Some (but not all) of the downflowing patches are cospatial and cotemporal with brightness enhancements in chromospheric Ca II H filtergrams. We suggest that these flows are due to magnetic reconnection in the upper photosphere/lower chromosphere, although other mechanisms cannot be ruled out.Comment: 4 pages, 5 figures, Published in ApJ Letter