Press releases

 

Nov 8 2016
11:58

CLOUD data are fed into a global aerosol model to calculate climate effects / Publication in "Science"

Successful calculation of human and natural influence on cloud formation

FRANKFURT. When new particles develop in the atmosphere, this influences cloud formation and with that the climate too. Since a few years, these complex processes have been reproduced in a large air chamber within the CLOUD experiment at CERN. Researchers have now used the results for the first time to calculate the production of aerosol particles in all the Earth’s regions and at different heights. The study published in the journal “Science”, in which researchers from Goethe University Frankfurt were involved, deciphers the role of the various chemical systems which are responsible for particle formation. They also determined the influence of ions which develop through cosmic radiation.

Soot particles, dust lifted up by the wind or sea spray account for only some of the particles in the atmosphere. Others develop from certain trace vapours, for example when individual sulphuric acid and water molecules cluster as tiny droplets. This formation of new particles is known as nucleation. Clouds are formed by water condensing on the larger aerosol particles or what are known as cloud condensation nuclei. The more cloud droplets develop, the more sunlight is reflected back into space. Climate models show that the additional particles caused by human activity produce a cooling effect which partially offsets the greenhouse effect. It is, however, less than previously assumed.

Aerosol particles from sulphuric acid and ammonia emissions

The model calculations presented in “Science” prove that about half the cloud condensation nuclei in the atmosphere originate from nucleation. In the atmosphere today, particle formation is dominated almost everywhere by mechanisms where at least three chemical components must come together: apart from the two basic substances, i.e. sulphuric acid and water, these are either ammonia or specific organic compounds such as oxidation products from terpenes. Close to ground level, organic substances from natural sources are important, whilst ammonia plays a key role higher up in the troposphere. Ammonia and sulphur emissions have increased considerably over the past decades as a result of human activities.

11-year solar cycle has scarcely any influence

CLOUD has also investigated how the 11-year solar cycle influences the formation of aerosol particles in our present-day atmosphere. The model calculations show that the effects as a result of changes in ionisation through the sun are too small to make a significant contribution to cloud formation. Although the ions are originally involved in the development of almost one third of all newly formed particles, the concentration of the large cloud condensation nuclei in the course of the 11-year cycle changes by only 0.1 percent – not enough to have any sizeable influence on the climate.

Cooling effects 27 percent less than expected

The CLOUD team has also presented first global model calculations for aerosol formation caused without the involvement of sulphuric acid and solely through extremely low volatile substances of biological origin (Gordon et al., PNAS). According to the findings, this process contributed significantly to particle formation above all in the pre-industrial atmosphere, since at that time far less sulphur components were released into the atmosphere. The number of particles in the pre-industrial atmosphere is now estimated to be far greater through the additional process than was shown in earlier calculations. The model calculations, which are based on data from the CLOUD experiment, reveal that the cooling effects of clouds are 27 percent less than in climate simulations without this effect as a result of additional particles caused by human activity: Instead of a radiative effect of -0.82 W/m2 the outcome is only -0.60 W/m2.

E.M. Dunne, et al., 2016: Global particle formation from CERN CLOUD measurements, Science First Release, DOI: 10.1126/science.aaf2649

This article appeared online via First Release in Science on Thursday, 27th of October 2016. http://science.sciencemag.org/cgi/doi/10.1126/science.aaf2649

H. Gordon, et al., 2016: Reduced anthropogenic aerosol radiative forcing caused by biogenic new particle formation, PNAS, 113 (43) 12053-12058; published ahead of print on the 10th of October 2016, DOI:10.1073/pnas.1602360113
http://www.pnas.org/content/113/43/12053.abstract

A photograph can be downloaded from: http://www.muk.uni-frankfurt.de/63775996

Further information: Prof. Dr. Joachim Curtius, Institute of Atmospheric and Environmental Sciences, Riedberg Campus, Tel.: ++49(0)798-40258, curtius@iau.uni-frankfurt.de

 

Nov 1 2016
11:46

Maria Roser Valenti is new fellow of the American Physical Society

Distinction for Frankfurt physicist

FRANKFURT. Professor Maria Roser Valenti has been elected as a fellow of the American Physical Society (APS) in the "Division of Computational Physics". She was awarded this high distinction for her contribution to the microscopic understanding of electronically strongly correlated materials, which include high-temperature superconductors. To access these highly complex materials she uses a combination of various theoretical approaches.

Professor Enrico Schleiff, Vice-President of Goethe University Frankfurt: "We congratulate the American Physical Society on this decision as Ms. Valenti is a recognized expert in the field of Theoretical Condensed Matter Physics. She unites all the characteristics of an excellent researcher: she is a constantly driving force for creative ideas, is engaged in international projects at the highest scientific level, devotes herself to her discipline both within and outside the University and is a role model for young academics. She will breathe her own new vigour into the APS, just as she did at Goethe University during her time as vice-president."

Maria Roser Valenti studied Physics at the University of Barcelona and gained her doctorate in 1989. From 1990 to 1991 she was a post-doctoral researcher at the University of Florida in Gainesville. She then became a research associate at TU Dortmund University where in 1997 she began her habilitation with a grant from the German Research Foundation (DFG - Deutsche Forschungsgemeinschaft). In 1999 she moved to Saarland University and completed her habilitation one year later. In 2002 she was awarded one of the prestigious Heisenberg scholarships of the German Research Foundation, which prepares early career researchers for a long-term professorship. In 2003 she became professor at the Institute of Theoretical Physics of Goethe University Frankfurt. From 2009 to 2012, the mother of three children was vice-president of Goethe University. Her research work focuses on the quantum mechanics of materials. She develops theoretical methods to describe unconventional superconductivity, frustrated magnetism, exotic spin liquids or systems with phases with non-trivial topology, among others.

With over 50.000 members worldwide, the APS is the second largest association for physicists. (The largest is the German Physical Society (DPG - Deutsche Physikalische Gesellschaft)). The APS was founded in 1899 with the goal of advancing the knowledge of physics and fostering the next generation of researchers. It is regarded as a great honour to be elected as a fellow. Only those researchers are taken into consideration who have made a significant contribution to basic research or contributed substantially to the development of scientific or technical applications.

 

Oct 21 2016
15:33

Boron compounds extend range of possible chemical synthesis applications

Non-metal catalyst splits hydrogen molecule

Hydrogen (H2) is an extremely simple molecule and yet a valuable raw material which as a result of the development of sophisticated catalysts is becoming more and more important. In industry and commerce, applications range from food and fertilizer manufacture to crude oil cracking to utilization as an energy source in fuel cells. A challenge lies in splitting the strong H-H bond under mild conditions. Chemists at Goethe University have now developed a new catalyst for the activation of hydrogen by introducing boron atoms into a common organic molecule. The process, which was described in the Angewandte Chemie journal, requires only an electron source in addition and should therefore be usable on a broad scale in future.

The high energy content of the hydrogen molecule meets with a particularly stable bonding situation. It was Paul Sabatier who in 1897 detected for the first time that metals are suitable catalysts for splitting the molecule and harnessing elementary hydrogen for chemical reactions. In 1912 he was awarded the Nobel Prize for Chemistry for this important discovery. The hydrogenation catalysts mostly used today contain toxic or expensive heavy metals, such as nickel, palladium or platinum. Only ten years ago non-metal systems based on boron and phosphorous compounds were discovered which allow comparable reactions.

“My doctoral researcher, Esther von Grotthuss, has achieved yet another major simplification of the non-metal strategy which requires only the boron component”, says Professor Matthias Wagner from the Institute of Inorganic and Analytical Chemistry of Goethe University Frankfurt. “What we additionally need is just an electron source. In the laboratory we chose lithium or potassium for this. When put into practice in the field, it should be possible to substitute this with electrical current.”

In order to explain the intricacies of hydrogen activation above and beyond experimental findings, quantum chemical calculations were carried out in cooperation with Professor Max Holthausen (Goethe University Frankfurt). Detailed knowledge of the reaction process is very important for the system’s further expansion. The objective lies not only in replacing transition metals in the long term but also in opening up the possibility for reactions which are not possible with conventional catalysts.

The chemists in Frankfurt consider that especially substitution reactions are highly promising which permit easy access to compounds of hydrogen with other elements. Expensive and potentially hazardous processes are still mostly used for such syntheses. For example, the simplified production of silicon-hydrogen compounds would be extremely attractive for the semiconductor industry.

Image for download: www.uni-frankfurt.de/63671511

Information: Prof. Matthias Wagner, Institute of Anorganic and Analytical Chemistry, Phone +49 (0)69 798-29156, Matthias.Wagner@chemie.uni-frankfurt.de

 

Oct 21 2016
10:42

Theoretical phyiscists model the sound of gravitational waves

Did LIGO detect black holes or gravastars?

The idea of black holes has been around for a long time. From the original "dark stars" suggested by John Michell and Pierre Laplace 200 years ago, to ubiquitous sci-fi movies and TV series like Star Trek, the black hole (whose name was coined by John Wheeler in the 1960's) has become a familiar concept, albeit not so well understood.

And that also goes for physicists and astrophysicists working with them. Some of the strange mathematical properties of black holes, coming from Karl Schwarzschild's first solution of the Einstein field equations of general relativity in 1915, still puzzle the scientists. The existence of an event horizon and a central singularity, leading to conundrums like the information paradox, have inspired some researchers to propose alternative theories.

One of the alternative models is the gravastar (a gravitational vacuum condensate star) proposed by Pawel Mazur and Emil Mottola in 2001. A gravastar would be made of a core of exotic matter similar to dark energy, that prevents the collapse of a matter shell surrounding it, made of the normal matter that once made up a star. When the star started to collapse at the end of its life, a phase transition would happen that could create this exotic matter before the event horizon could be formed. This speculative object would be almost as compact as a black hole, but the tiny difference between them would be enough to prevent the formation of the event horizon and the conceptual questioning that comes with it.

How, then, could we tell a gravastar from a black hole? It would be almost impossible to "see" a gravastar, because of the same effect that makes a black hole "black": any light would be so deflected by the gravitational field that it would never reach us. However, where photons would fail, gravitational waves can succeed! It has long since been known that when black holes are perturbed, they "vibrate" emitting gravitational waves. Indeed, they behave as "bells", that is with a signal that progressively fades away, or "ringsdown". The tone and fading of these waves depends on the only two properties of the black hole: its mass and spin. Gravastars also emit gravitational waves when they are perturbed, but, interestingly, the tones and fading of these waves are different from those of black holes. This is a fact that was alreadyknown soon after gravastars were proposed.

After the first direct detection of gravitational waves that was announced last February by the LIGO Scientific Collaboration and made news all over the world, Luciano Rezzolla (Goethe University Frankfurt, Germany) and Cecilia Chirenti (Federal University of ABC in Santo André, Brazil) set out to test whether the observed signal could have been a gravastar or not.

When considering the strongest of the signals detected so far, i.e. GW150914, the LIGO team has shown convincingly that the signal was consistent with the a collision of two black holes that formed a bigger black hole. The last part of the signal, which is indeed the ringdown, is the fingerprint that could identify the result of the collision. "The frequencies in the ringdown are the signature of the source of gravitational waves, like different bells ring with different sound", explains Professor Chirenti.

After modelling the expected sound from a gravastar that would have the same characteristics of the final black hole, the two researchers have concluded that it would be very hard to explain the frequencies observed in the ringdown of GW150914 with a gravastar. To use the same language introduced before, although the gravitational-wave signals from gravastars are very similar to those of black holes, the tones and fadings are different. Just like two keys in a piano emit different notes, the "notes" measured with GW150914 simply do not match those that can be produced by gravastars. Hence, the signal measured cannot have been produced by two gravastars merging into another and larger gravastars. This result was recently resented in a paper published on Physical Review D.

"As a theoretical physicist I'm always open to new ideas no matter how exotic; at the same time, progress in physics takes place when theories are confronted with experiments. In this case, the idea of gravastars simply does not seem to match the observations", says Professor Rezzolla.

Publikation:
Cecilia Chirenti, Luciano Rezzolla: "Did GW150914 produce a rotating gravastar?", in Physical Review D 94, 084016 (2016). https://doi.org/10.1103/PhysRevD.94.084016.

Image for download: www.uni-frankfurt.de/63684192

Image caption: Gravitational wave signal from GW150914 as measured in the two detectors at Livingston and Hanford (top panel); artistic rendering of a gravastar (lower panel).

 

Sep 28 2016
14:43

Renowned scientists from Germany and abroad discuss the location of religious topics in modern science

Religious education: Where the debate is taking place

FRANKFURT.Professional mobility and immigration have changed society permanently, and homogenous religious landscapes in Germany belong to the past. The impact of this development on religious upbringing and education will be discussed at a conference held by the Faculty of Protestant Theology at Frankfurt's Goethe University on the 12th and 13th October 2016. All interested are welcome to attend.

In Germany, the teaching of religious studies in state schools is anchored in the constitution, and training for the required teachers takes place at universities. Until the 1960s, this was also reflected in teacher training publications, just as all other areas of education have their place in general educational science today. However, discussions about the role of religious education in modern societies have been moved out of educational and into theological faculties since Germany's student movement of 1968.

Changes in society due to increasing mobility and migratory movements also indicate a changing view of religious upbringing, education, and socialisation. The growing percentage of Muslims in the population and the request for Islamic religious studies also sheds new light on Christian religious education. However, in which field of science should the debate about this take place? Has religion been neglected in educational research until now? Or should educational research have more weight in the field of theology?

The conference "Religion and Educational Research. National Traditions and Transnational Perspectives", initiated by Prof. David Käbisch, scholar in the field of Protestant religious education, will question the significance of religion-related research in educational science, especially when compared internationally. Renowned scientists from different countries have been invited to participate, including Prof. Deirdre Raftery (Dublin, Ireland), Prof. Daniel Lindmark (Umeå, Sweden), Dr. Ezequiel Gomez Caride (Buenos Aires, Argentina), and Prof. Mette Buchardt (Aalborg, Denmark).

Against the backdrop of topical discussions about state schools as a location for Islamic religious education and the current dynamic of political conflicts in France, Turkey, the Levant, and North Africa, the conference will hear from speakers whose research projects have a special focus on Islam. Frankfurt education researcher Prof. Harry Harun Behr will speak about “Islamic Education-Research in Germany”, and Islamic studies researcher Prof. Armina Omerika will discuss "Transnationalizing the History of Islam and Islamic Education" in the case of Bosnia-Herzegovina. The main topic of the conference is one that will become more important in the future, especially in the Rhine-Main region due to its dynamic population. At the same time, it will promote the international networking of religion-related research at Frankfurt University.