Dig through the JUnQ

Here you find all contributions made by external authors to JUnQ. This includes peer-reviewed articles and editorial board reviewed open questions.

Jul 302016
 
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Dr. Gerta Ruecker, a mathematician by training, works as a biostatistician at the Medical Center – University of Freiburg, Germany. Her special area is meta-analysis, and she is associated with Cochrane Germany. She has written a large
number of research papers on statistical methods, and co-authored a number of Cochrane reviews. Additionally, she is engaged in teaching meta-analysis methods and is one of the authors of a book ‘Use R for meta-analysis’.

Find the Interview here: Interview with Dr. Gerta Ruecker

Jul 302016
 
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PD Dr. Nicolai Bissantz is a mathematician at the Ruhr University Bochum, Germany. His research fields are applied and mathematical statistics, in particular with applications in science and engineering. Amongst these fields are applications of statistical inverse problems in astronomy and in image reconstruction. Such problems arise e.g., in the recovery of images from fluorescence microscopy imaging and in medical imaging devices such as PET (positron emission tomography).

Find the Interview here: Interview with PD Dr. Nicolai Bissantz

Jul 302016
 
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Dr. Rainer Wanke is a physicist working in the field of experimental particle physics at the University of Mainz, Germany. He is working on the NA62 experiment at the European Organization for Nuclear Research (CERN) in Geneva, Switzerland, which measures ultra-rare K-meson decays. This involves both, particle detector development and the analysis of data taken with those particle detectors. He furthermore teaches statistics for undergraduate students in Mainz.

Find the Interview here: Interview with Dr. Rainer Wanke

Jul 282016
 
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Theresa Weidner

JUnQ, 6, 2, XXVII–XXVIII, 2016

A Commentary on “Most People are not WEIRD” by Joseph Henrich et al., Nature (2010)

Prof. Joseph Henrich is an anthropologist at the Department of Human Evolutionary Biology at Harvard University, Cambridge, USA. His focus is on evolutionary approaches to psychology, decision-making and culture. Together with his colleagues Stephen J. Heine and Ara Norenzayan at the University of British Columbia, Vancouver, CA, he was the first to point out that, in economics, psychology and cognitive science, conclusions are generally drawn from study participants with the same background: Western, Educated, Industrialized, Rich and Democratic (WEIRD). In addition, primarily students form the majority of test subjects. Still, researchers – often unintentionally – claim that their findings apply to everybody.

Read the full article here: The Use of the Term “People” in Research

Jul 282016
 
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Kai Litzius

JUnQ, 6, 2, XXV–XXVI, 2016

Open access sharing contributes nowadays a major part to the publication process in many different scientific disciplines. One could think it is an invention of modern time, however, the idea to make data and literature widely available is quite old: Libraries.

Read the full article here: A Quick Word on Open Access Sharing

Jul 282016
 
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Dear Reader,

Even though I was a member of this editorial board for almost five years, I never wrote the editorial of an issue. Since I finished my university education and will soon start my industrial career, forcing me to leave JUnQ, it is my pleasure to write it for the current issue.

The feature topic this time deals with a problem, which has been in the press a lot lately: Misuse of Statistics.

Read the whole Editorial Note by Andreas Neidlinger.

Jul 252016
 
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JC

Dear Readers,

We are delighted to bring to you the 12th issue of JUnQ. This time round, the central theme deals with Statistics in Science and what it entails and how can it be misused. We held insightful interviews with few of the best experts in Statistics and we present their views about the current era where mis-interpretations of data abound. It is heartening to see that the publication of negative or null results still is important for many in science. We have an article on Pretreatment of Steel and Zinc surfaces that highlights such details. Also in the days ahead, open access will be the norm and we present an excellent commentary on it.

We hope you feel excited about our newest issue of JUnQ!

— Soham Roy on behalf of the editorial board

Download JUnQ Volume 6 Issue 2

Jul 242016
 
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If you ever wander about the barren lands of southern Africa, like the scarcely vegetated Namib desert in Namibia, you will most certainly stumble across a fascinating malformation of the soil called fairy circles. They are circle shaped bare patches of dry ground with a diameter of several meters enclosed by taller grass at the edge, compared to the steppe landscape of the surroundings.

Fairy circles in the Namib Naukluft Park, Namibia. (© Heike D?nzer)

Fairy circles in the Namib Naukluft Park, Namibia. (© Heike Daenzer)

Their origin has long been a cause of intense discussions. The earliest interpretation of their appearance may come from the Himba people, who share the legend that the circles are the footprints left behind by their ancestor Mukuru. Other stories tell of aliens, dragons or fairies.[1] On the other hand though, science suggests toxic gases or residues from already dead plants, radioactive elements or insects to be the origin of the features.[2] Lots of investigation have been made in the last decades to prove each theory but no one could come to a substantial and indisputable conclusion. Since no toxic or radioactive substances were found in the soil of the fairy circles, they must arise from something else.[2]

Supported by satellite images, Dr W. Tschinkel, from the Florida State University, was able to offer proof that the circles are not permanent. They grow and develop and after a lifespan of 41 years on average, they “die”.[3]

Cramer et al. used an empirical model considering various biological, chemical and weather factors to predict the appearance of fairy circles. They conclude that circle formation must be the result of plant organization and competition for nutrients since the plants at the periphery of the circles are more lush than the plants farther away.[4]

A very vivid explanation comes from N. Juergens who examined the termite population of fairy circles. The sand termite Psammotermes allocerus, their nest and tunnels were the only similarity found in 100 % of the investigated circles and even in young circles. Apparently they feed on plant roots and keep large areas free of water accumulating vegetation which causes also a higher water content in the ground centered beneath the circle.[5]

Only a few years ago, fairy circles were found in Pilbara, Australia similar to those in Africa. Getzin et al. doubt the dependence of the pattern formation from termites or ants since many circles didn’t host any of these insects. They blame pattern-creating plants in water-limited environments, such as in a desert, to be responsible.[6]

– Tatjana Daenzer

Read more:
[1] http://www.nytimes.com/2013/03/29/science/fairy-circles-in-africa-may-be-work-of-termites.html?_r=1
[2] van Rooyen, J. Arid Environ., 2004, 57, 467–485
[3] Tschinkel, PLOS ONE, 2012, 7, 1–17
[4] Cramer, PLOS ONE, 2013, 8, 1–12
[5] Juergens, Science, 2013, 339, 1618–1622
[6] Getzin, PNAS, 2016, 113, 3551–3556

Jul 032016
 
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We all know what the color ‘black’ is. If I ask anyone, I will get different responses. From the familiar blackboard in the classroom to the ubiquitous asphalt of the roads. Some might recall, with fondness, it as the color of the little dress on their high-school prom date. Others might be more correct, and remind me that “true” black is the absence of any reflected light. And point me towards the nearest black hole (at the center of the milky way or on the Sagittarius arm of it, depending on what one believes [1]).

Is it Black or is it Grey ?

Is it Black or is it Gray ?

Even then, when I show the above graphic, all (including me) will be unequivocal in declaring the colors to be shades of black. Although those are hues of gray. Such befuddlement ails us all. As Dr. Stephen Westland, professor of color science and technology at Leeds University, is right in saying, “Unless you are looking at a black hole, nobody has actually seen something which has no light.” [2]

Given our feeble attempts at defining and rendering ‘Black’, it becomes quite a challenge to explain Vantablack – the blackest material known [3, 4], where Vanta is an acronym for Vertically Aligned Nano Tube Arrays. Although, NASA might argue that their super-black deserves that title [5]. It is easy to visualize Vantablack as a forest of carbon nano tubes. The tubes are stacked in a vertical orientation, with the length of the individual tubes being much much larger than their diameter.

Vantablack (downloaded from https://upload.wikimedia.org)

Vantablack (downloaded from https://upload.wikimedia.org)

Yet, that still doesn’t explain why it is the ‘blackest’ of blacks and could rewrite and replace all previous conceptions of black [6]. When light hits the Vantablack surface, it gets trapped in between the carbon nano tubes. The photons undergo a lot of collisions with the walls of these tubes. They lose their energies as heat to the walls and the tiniest amount is reflected back as light, all of 0.035 % [2, 7].

Such properties make it very exciting as future prospects. From manufacturing telescope coatings, where even the tiniest speck of scattered light can seriously affect its contrast and resolving power. To the defense and stealth sectors, who find the material extremely fascinating [7].

Yet, it is still baffling to answer how does it feel to see the blackest material known. We understand a surface by its depth or its topological features. These features change reflectance. But for Vantablack, even when it is crumpled up, it defies perception. “You expect to see the hills and all you can see … it’s like black, like a hole, like there’s nothing there. It just looks so strange”, as Surrey Nanosystems CTO Ben Jensen puts it [2].

Vantablack is the darkest material we have that is as close to perceiving what a black hole would look like. This might be a bit disconcerting for us in the future, expecting to see textures but being greeted with an abyss. “And if you gaze long into an abyss, the abyss also gazes into you.”

-Soham Roy

References:
[1] http://www.universetoday.com/75723/where-is-the-nearest-black-hole/
[2] http://www.independent.co.uk/news/science/blackest-is-the-new-black-scientists-have-developed-a-material-so-dark-that-you-cant-see-it-9602504.html
[3] https://www.surreynanosystems.com/vantablack
[4] E. Theocharous et al., Optics Express 2014, 22, 7290-7307.
[5] http://www.nasa-usa.de/topics/technology/features/super-black-material.html
[6] https://www.theguardian.com/fashion/shortcuts/2014/jul/14/vantablack-nanofabric-new-black
[7] http://www.extremetech.com/extreme/186229-its-like-staring-into-a-black-hole-worlds-darkest-material-will-be-used-to-make-very-stealthy-aircraft-better-telescopes

Jun 122016
 
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Modern aviation is one of the most important and possibly, also the safest when it comes to transportation and travel. As a result of the increasing need for fast and reliable transfer of resources, airplanes have become increasingly complex and nowadays only a relatively small number of people know how they are operated.

Figure 1: Landing of a modern aircraft.(downloaded from https://upload.wikimedia.org)

Figure 1: Landing of a modern aircraft.(downloaded from https://upload.wikimedia.org)

In this Question of the Week, we want to focus on one particular detail of aviation: The landing. A typical airplane approaches the airstrip with a speed of around 270 km/h and has to decelerate within a very short time to guarantee a safe landing. So how do you brake an airplane?

To answer this question, we first have to think about how braking works in the case of any wheel-based vehicle. In a nutshell, the braking process always exerts a torque upon the wheels which then use friction with the ground to lose kinetic energy. Friction, however, is massively dependent on the weight that rests on the wheels. In case of landing an airplane, the aerodynamic lift basically nullifies the weight of the plane and therefore makes braking while using the wheels extremely inefficient. As a result, the plane needs other ways to slow down until the aerodynamic lift and speed is sufficiently reduced. In modern aviation, this is done by two different braking systems: The Spoilers and the Reversers, that both are usually operated by a computer, which tries to reach a constant deceleration of convenient magnitude (about 0.17 – 0.3 g).

spoilers

Figure 2 : Spoilers on an aircraft. (downloaded from https://upload.wikimedia.org)

As soon as the wheels get in contact with the ground, the Spoilers (Figure 2) are fully activated. These are flaps located on the back-end of the wings and can significantly reduce the aerodynamic lift as well as increase the drag. These flaps are extremely important for the braking process because without them the friction of the wheels is not sufficient for efficient braking. Basically, wheel brakes and Spoilers together can already be sufficient for slowing down an airplane.

reversers

Figure 3 : Reversers on an aircraft. (downloaded from https://upload.wikimedia.org)

However, to reduce the amount of stress the wheel brakes have to withstand, there is an additional system: The Reversers (Figure 3). These are mechanisms located at the engines that can be activated to redirect the engine’s exhaust forward, rather than backwards (commonly referred to as thrust reversal). All three systems together can be used by a computer to reach an extremely smooth braking process without putting too much stress on the single components.

As a result, the landing process by itself is extremely complex and depends on many factors. Most of them can be controlled by a computer, however, in case of any unforeseen circumstances, the pilots have to be prepared to take over and land the airplane manually. This (and many other factors) makes the training of pilots one of the most demanding educational processes of our time.

– Kai Litzius

Further reading:
1. walter.bislins.ch/blog/index.asp?page=Wie+bremst+ein+Verkehrsflugzeug+nach+der+Landung%3F
2. http://www.smartcockpit.com/aircraft-ressources/A320_Flight_Deck_and_Systems_Briefing_For_Pilots.html
3. http://www.airspacemag.com/flight-today/how-things-work-stopping-the-a380-27549065/