University of Kiel

About: University of Kiel is a education organization based out in Kiel, Germany. It is known for research contribution in the topics: Population & Transplantation. The organization has 27816 authors who have published 57114 publications receiving 2061802 citations. The organization is also known as: Christian Albrechts University & Christian-Albrechts-Universität zu Kiel.

Topology in chemistry: designing Möbius molecules.

Abstract: In 1747, Johann Sebastian Bach wrote a series of canons and fugues on the occasion of his visit to King Frederick the Great of Prussia in Potsdam. His music of homage, the “Musikalisches Opfer” (Musical Offering, BWV1079), includes a canon that is probably one of the oldest man-made examples of an object with Mobius topology.1 The canon cancricans (crab canon) is written for two violins playing the same score in two different directions. If you cut the score, paste it in such way that it forms a band with the notes of the first violin on top and those of the second violin below, fold it lengthwise between the two notes, give one end a half twist, and join both ends, you end up with a endless Mobius-shaped score (Figure 1). After every turn the two violins change their parts. Karl Amadeus Hartmann, Nicolas Slonimsky,2 and others several centuries later wrote further examples of Mobius music. Note that there are two different ways to form the Mobius score, by twisting the strip either clockwise or anticlockwise. The two Mobius strips are enantiomers (the music, unfortunately, is not) and exhibit the highest symmetry a Mobius object can attain: C2. More than 100 years later, August Ferdinand Mobius and Johann Benedict Listing (Figure 2), both students of Carl Friedrich Gauss in Gottingen, published their seminal work on projective planes and one-sided surfaces. Nowadays, the credit goes almost exclusively to Mobius3 after whom the famous band is named, even though Listing published 4 years earlier.4 Both mathematicians mentioned the “Mobius” band in unpublished papers for the first time in 1858; however, again Listing’s unpublished note (July) predates the one of Mobius (September) by 2 months. It would probably be fair to name the one-sided band a “Listing band”. There are good reasons to assume that Listing was not adequately credited because of social rather than scientific reasons.5 Most of the objects we are dealing with in our everyday lives are two-sided. They have an inside and an outside surface like a sphere, a cube, or a torus. This is also true for most two-dimensional mathematical objects. According to the mathematical definition, a normal vector on the surface of a two-sided object cannot be shifted to any other point on the surface without crossing a border or interpreted in anthropomorphic terms: walking upright on the outside surface you cannot enter the inside and vice versa. The Mobius band is probably the simplest and best-known exception (Figure 3). Any closed band with an odd number of 180° twists is one-sided, and those with an even number of 180° twists are two-sided. Unfortunately, the sidedness is not an intrinsic property, because it requires that the surface is embedded in a † In memory of Professor Edgar Heilbronner. * To whom correspondence should be addressed. Telephone: ++49 431 88

Rare Copy Number Variation Discovery and Cross-Disorder Comparisons Identify Risk Genes for ADHD

Abstract: Attention deficit hyperactivity disorder (ADHD) is a common and persistent condition characterized by developmentally atypical and impairing inattention, hyperactivity, and impulsiveness. We identified de novo and rare copy number variations (CNVs) in 248 unrelated ADHD patients using million-feature genotyping arrays. We found de novo CNVs in 3 of 173 (1.7%) ADHD patients for whom we had DNA from both parents. These CNVs affected brain-expressed genes: DCLK2, SORCS1, SORCS3, and MACROD2. We also detected rare inherited CNVs in 19 of 248 (7.7%) ADHD probands, which were absent in 2357 controls and which either overlapped previously implicated ADHD loci (for example, DRD5 and 15q13 microduplication) or identified new candidate susceptibility genes (ASTN2, CPLX2, ZBBX, and PTPRN2). Among these de novo and rare inherited CNVs, there were also examples of genes (ASTN2, GABRG1, and CNTN5) previously implicated by rare CNVs in other neurodevelopmental conditions including autism spectrum disorder (ASD). To further explore the overlap of risks in ADHD and ASD, we used the same microarrays to test for rare CNVs in an independent, newly collected cohort of 349 unrelated individuals with a primary diagnosis of ASD. Deletions of the neuronal ASTN2 and the ASTN2-intronic TRIM32 genes yielded the strongest association with ADHD and ASD, but numerous other shared candidate genes (such as CHCHD3, MACROD2, and the 16p11.2 region) were also revealed. Our results provide support for a role for rare CNVs in ADHD risk and reinforce evidence for the existence of common underlying susceptibility genes for ADHD, ASD, and other neuropsychiatric disorders.

Ultralow-fatigue shape memory alloy films

Abstract: Functional shape memory alloys need to operate reversibly and repeatedly. Quantitative measures of reversibility include the relative volume change of the participating phases and compatibility matrices for twinning. But no similar argument is known for repeatability. This is especially crucial for many future applications, such as artificial heart valves or elastocaloric cooling, in which more than 10 million transformation cycles will be required. We report on the discovery of an ultralow-fatigue shape memory alloy film system based on TiNiCu that allows at least 10 million transformation cycles. We found that these films contain Ti2Cu precipitates embedded in the base alloy that serve as sentinels to ensure complete and reproducible transformation in the course of each memory cycle.

Warming of the tropical Atlantic Ocean and slowdown of thermohaline circulation during the last deglaciation

Abstract: Evidence for abrupt climate changes on millennial and shorter timescales is widespread in marine and terrestrial climate records1,2,3,4. Rapid reorganization of ocean circulation is considered to exert some control over these changes5, as are shifts in the concentrations of atmospheric greenhouse gases6. The response of the climate system to these two influences is fundamentally different: slowing of thermohaline overturn in the North Atlantic Ocean is expected to decrease northward heat transport by the ocean and to induce warming of the tropical Atlantic7,8, whereas atmospheric greenhouse forcing should cause roughly synchronous global temperature changes9. So these two mechanisms of climate change should be distinguishable by the timing of surface-water temperature variations relative to changes in deep-water circulation. Here we present a high-temporal-resolution record of sea surface temperatures from the western tropical North Atlantic Ocean which spans the past 29,000 years, derived from measurements of temperature-sensitive alkenone unsaturation in sedimentary organic matter. We find significant warming is documented for Heinrich event H1 (16,900–15,400 calendar years bp) and the Younger Dryas event (12,900–11,600 cal. yr bp), which were periods of intense cooling in the northern North Atlantic. Temperature changes in the tropical and high-latitude North Atlantic are out of phase, suggesting that the thermohaline circulation was the important trigger for these rapid climate changes.

Semiconductor losses in voltage source and current source IGBT converters based on analytical derivation

Abstract: A crucial criterion for the dimensioning of three phase PWM converters is the cooling of the power semiconductors and thus determination of power dissipation in the semiconductors at certain operating points and its maximum. Methods for the calculation and simulation of semiconductor losses in the most common voltage source and current source three phase PWM converters are well known. Here a complete analytical calculation of the power semiconductor losses for both converter types is presented, most parts are already known, some parts are developed here, as far as the authors know. Conduction losses as well as switching losses are included in the calculation using a simplified model, based on power semiconductor data sheet information. This approach should benefit the prediction and further investigations of the performance of power semiconductor losses for both kinds of converters. Results of the calculation are shown. Dependencies of the semiconductor power losses on the type of converter, the operating point and the pulse width modulation are pointed out, showing the general behaviour of power losses for both converter types.