Solar observer created key sunspot record

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Few people have heard of Hisako Koyama, but the dedicated female solar observer, born in Tokyo in 1916, created one of the most important sunspot records of the past 400 years.
via Science Daily
Zazzle Space Exploration market place

Waves of congratulations for the Nobel Prize

This illustration shows the merger of two black holes and the gravitational waves that ripple outward as the black holes spiral toward each other. (Image credit: LIGO/T. Pyle)

CERN congratulates Rainer Weiss, Barry C. Barish and Kip S. Thorne of the LIGO/Virgo Collaboration on the award of the Nobel Prize in Physics "for decisive contributions to the LIGO detector and the observation of gravitational waves".

On 11 February 2016, the Laser Interferometer Gravitational-Wave Observatory (LIGO) scientific collaboration and the Virgo collaboration announced that they had detected gravitational waves – ripples in the fabric of space-time – for the first time. On that day, the collaborations published a historic paper in which they showed a gravitational signal emitted by the collision of two black holes about 1000 million light-years away, 36 and 29 times more massive than our Sun respectively. The first ever direct detection of gravitational waves confirmed one of the major predictions of Einstein’s theory of general relativity, nearly one hundred years since it was proposed.

The first signal was recorded on 14 September 2015. A second signal was detected three months later, and a third came in January 2017 and was announced by researchers in June this year. The LIGO and Virgo collaborations announced that they had detected a fourth gravitational wave signal, the first observation made using three different detectors, just last week.

On the historical day of the first official announcement to the scientific community and the public, Barry Clark Barish, one of the founding fathers of the LIGO experiment, gave a seminar at CERN in a packed Main Auditorium. The relationship between the gravitational wave community and CERN didn’t stop there: on 1 September, scientists from both communities met at CERN to identify technology synergies for the future, from the theoretical and experimental points of view.

“The gravitational wave discovery opens a completely new window to look at the universe. The 21st century will be the century of gravitational wave astronomy. A new golden age is beginning,” said Luis Alvarez-Gaume, theoretical physicist, when the discovery was announced.

via CERN: Updates for the general public
http://home.cern/about/updates/2017/10/waves-congratulations-nobel-prize

Graphene field effect transistors for chemical sensing

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Graphene produced with chemical vapor deposition (CVD) will form the cornerstone of future graphene-based chemical, biological, and other types of sensors. The 2D nature of the material provides intrinsic advantages for sensing applications, because the entire material volume acts as a sensing surface. Furthermore, graphene provides excellent mechanical strength, thermal and electrical conductivity, compactness, and potentially low cost, which is necessary for competing on the crowded sensor market.

Graphene-based gas/vapor sensors have attracted much attention in recent years due to their variety of structures, unique sensing performance, room-temperature working conditions, and tremendous application prospects. Apart from water vapor, graphene has been used to sense gases such as NH₃, NO₂, H₂, CO, SO₂, H₂S, as well as vapor of volatile organic compounds, resulting in a dramatic rise in scientific publication numbers on this topic. Graphene has also been used to detect traces of opioids in concentrations as low as 10 picograms per milliliter of liquid.

Histogram of scientific publications on the topic of graphene gas/vapor sensors (source: ISI Web of Knowledge).

The most simple and common configuration for graphene-based sensors is the graphene field-effect transistor (GFET), a sheet of graphene with a sensing area between two metal contacts. The carrier mobility can be tuned using the electric field effect with a back gate, yielding tunable sensitivity. Such a device was shown to have even single molecule detection capability (Nat. Mater. 6(9), 652–655 (2007)). The detection and working principle of GFET chemical sensors are also very simple: the electrical resistance of the device changes when something attaches to the graphene. Certain gases have shown up to 15% change in resistance, with others like methanol showing an easily detectable change of ~5% (see figure below).

Figure: Sensitivity of graphene sensors to various gases (Sens. Actuators B 163(1), 107–114 (2012)).

CVD graphene sensors have shown detection limits for ammonia on the ppb level, which is superior to commercially available devices (Appl. Phys. Lett. 100, 203120 (2012)). Ammonia not only contributes significantly to the nutritional needs of organisms, but also is a building-block for the synthesis of many pharmaceuticals, and is used in many commercial products. Although widely used, this gas (NH₃) is both caustic and hazardous, and thus it is harmful to humans and causes environmental pollution. Detection of NH₃ is thus a pressing societal requirement.

GFETs were also used to detect nitrogen dioxide. Although also an industrially relevant gas, NO₂ is toxic to humans and the environment. Several reports have shown nitrogen dioxide sensors based on graphene with detection limits below ppm, high sensitivity, excellent selectivity and response speed (Nano-Micro Letters 8, 95 (2016)). All other graphene-based chemical sensors, such as those for hydrogen gas, carbon dioxide, carbon monoxide, methane, and sulfur dioxide, show detection limits better or on par with commercially available sensors.

A critical parameter in device sensitivity is the sheet resistance or carrier mobility in the graphene. Carrier mobility should be high to ensure small losses to heating. Thus, high-quality CVD graphene is a prime candidate for large-area, commercially viable GFET sensors.

via Graphenea