Stein C.,Free University of Berlin |
Stein C.,Helmholtz Virtual Institute
Annual Review of Medicine | Year: 2016
Opioids are the oldest and most potent drugs for the treatment of severe pain. Their clinical application is undisputed in acute (e.g., postoperative) and cancer pain, but their long-term use in chronic pain has met increasing scrutiny. This article reviews mechanisms underlying opioid analgesia and other opioid actions. It discusses the structure, function, and plasticity of opioid receptors; the central and peripheral sites of analgesic actions and side effects; endogenous and exogenous opioid receptor ligands; and conventional and novel opioid compounds. Challenging clinical situations, such as the tension between chronic pain and addiction, are also illustrated. © 2016 by Annual Reviews.
Bohringer F.,RWTH Aachen |
Jankowski V.,RWTH Aachen |
Gajjala P.R.,RWTH Aachen |
Zidek W.,Charite - Medical University of Berlin |
And 2 more authors.
ASAIO Journal | Year: 2015
Protein-bound uremic retention solutes accumulate in patients suffering from chronic kidney disease, and the removal of these solutes by hemodialysis is hampered. Therefore, we developed a dialysis technique where the protein-bound uremic retention solutes are removed more efficiently under high ionic strength. Protein-bound uremic solutes such as phenylacetic acid, indoxyl sulfate, and p-cresyl sulfate were combined with plasma in the presence of increased ionic strength. The protein integrity of proteins and enzymatic activities were analyzed. In vitro dialysis of albumin solution was performed to investigate the clearance of the bound uremic retention solutes. In vitro hemodiafiltrations of human blood were performed to investigate the influence of increased ionic strength on blood cell survival. The protein-bound fraction of phenylacetic acid, indoxyl sulfate, and p-cresyl sulfate was significantly decreased from 59.4% ± 3.4%, 95.7% ± 0.6%, 96.9% ± 1.5% to 36.4% ± 3.7%, 87.8% ± 0.6%, and 90.8% ± 1.3%, respectively. The percentage of phenylacetic acid, indoxyl sulfate, and p-cresyl sulfate released from protein was 23.0% ± 5.7%, 7.9% ± 1.1%, and 6.1% ± 0.2%, respectively. The clearance during in vitro dialysis was increased by 13.1% ± 3.6%, 68.8% ± 15.1%, and 53.6% ± 10.2%, respectively. There was no difference in NaCl concentrations at the outlet of the dialyzer using isotonic and hypertonic solutions. In conclusion, this study forms the basis for establishing a novel therapeutic approach to remove protein-bound retention solutes. © 2014 by the American Society for Artificial Internal Organs.
Home > Press > Thin-film solar cells: How defects appear and disappear in CIGSe cells: Concentration of copper plays a crucial role Abstract: Copper-indium-gallium-selenide (CIGSe) solar cells have the highest efficiency of polycrystalline thin-film solar cells. The four elements comprising CIGSe are vapour-deposited onto a substrate together to form a very thin layer of tiny chalcopyrite crystals. It is an exceedingly complex process controlled by many variables. This is why CIGSe modules in standard industrial formats have not yet attained the record efficiency already demonstrated at laboratory scale. One possible cause: defects that reduce the efficiency level can form during the course of fabrication. A collaboration of German, Israeli, and British teams has now conducted detailed studies of how different fabrication techniques influence the microstructure. They were able for the first time to observe the defects as these formed during deposition and under what conditions they self-healed by using in-situ X-ray diffraction and fluorescence analysis capabilities at the BESSY II X-ray source. Additional copper helps defects heal Vapour deposition of thin CIGSe films is a complex process. Indium, gallium, and selenium are first deposited on the substrate. The deposition of the copper and selenium atoms takes place in a second step. These atoms migrate into the In-Ga-Se layer. Tiny CIGSe crystals of chalcopyrite form there. The concentration of copper only reaches the correct value over the course of this second step. The prior copper-poor phase is characterised by numerous defects within the crystal. The defects increasingly disappear with the addition of copper and selenium. If more copper and selenium atoms are added after reaching the "right" ratio, then these two elements no longer fit into the existing crystal matrix and deposit themselves as copper and selenium grains in and on the polycrystalline CIGSe layer. This is actually problematic, since the grains must be removed afterwards. Nevertheless, they apparently have an important function in reducing the defects to near zero, as the current work shows. Analysing growing structures of elements in real time Dr. Roland Mainz and his colleagues at HZB were able to observe the changes to the film structure during deposition using X-ray diffraction at the EDDI beamline of BESSY II - in real time. At the same time, they were able to use X-ray fluorescence to analyse the elemental composition of the thin-film layer as it grew. Simultaneous observation with two methods enabled them to obtain a new insight: "The annihilation of the defects takes place very rapidly - just prior to the excess copper-selenium grains being deposited on the surface of the CIGSe film and the film entering the copper-rich phase. So far, we had only understood the copper-rich phase as being important for the growth of the grains. Now we know that it also plays an important role in the elimination of the defects", explains Mainz. Improving vapour deposition processes for high-quality CIGSe films Helena Stange, co-author of the study, simulated the influence of the various types of defects on the diffraction signal. The in-situ observations fit extremely well with the simulations and with the results derived from different imaging processes used to study the samples in various stages of deposition by teams at the Max Planck Institute for Solid State Research in Stuttgart, the SuperSTEM Lab in Daresbury, England, and at the Racah Institute, Jerusalem. An additional important result is that the temperature during deposition represents a relatively uncritical parameter for defect elimination. As soon as the layer reaches the copper-rich state, it makes little difference whether the process takes place at 400 degrees Celsius or 530 degrees Celsius. This insight is also of assistance in improving the procedure for depositing onto large surface areas. Instead of trying to maintain as homogenous a temperature as possible over the entire surface, other parameters could be optimised. The collaboration is part of the Helmholtz Virtual Institute of "Microstructure control for thin-film solar cells" that has been funded from 2012 to 2018. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Wei Q.,Free University of Berlin |
Wei Q.,Helmholtz Virtual Institute |
Achazi K.,Free University of Berlin |
Liebe H.,Free University of Berlin |
And 5 more authors.
Angewandte Chemie - International Edition | Year: 2014
A rapid and universal approach for multifunctional material coatings was developed based on a mussel-inspired dendritic polymer. This new kind of polymer mimics not only the functional groups of mussel foot proteins (mfps) but also their molecular weight and molecular structure. The large number of catechol and amine groups set the basis for heteromultivalent anchoring and crosslinking. The molecular weight reaches 10 kDa, which is similar to the most adhesive mussel foot protein mfp-5. Also, the dendritic structure exposes its functional groups on the surface like the folded proteins. As a result, a very stable coating can be prepared on virtually any type of material surface within 10 min by a simple dip-coating method, which is as fast as the formation of mussel byssal threads in nature. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA.
A team from Helmholtz-Zentrum Berlin has been able to measure how new bonds influence molecules for the first time: they have reconstructed the energy landscape of acetone molecules using measurement data from the Swiss Light Source (SLS) of the Paul Scherrer Institut, and, thereby, empirically established the formation of hydrogen bonds between acetone and chloroform molecules. The results have been published in Nature Scientific Reports and assist in understanding fundamental phenomena of chemistry. Molecules are composed of atoms that maintain specific intervals and angles between one another. However, the shape of a molecule can change, for example, through proximity to other molecules, external forces and excitations, and also when a molecule makes a chemical connection with another molecule, for instance in a chemical reaction. A very useful concept in describing the changes that are possible in molecules is the use of what are called “potential surfaces” or energy landscapes. However, these are not actual surfaces in real space. They are more viewed as parameters defining the molecule, which can then be portrayed as a surface. An example would be the stretching of a carbon-oxygen bond, or the angle between various molecular groups. You can imagine such surfaces as being like hilly landscapes. If light excites part of the molecule into oscillation, the state of the molecule moves upward, energetically speaking, perhaps even up over a pass or a peak. It either returns finally to its previous energy minimum, or lands in a different energy dip that corresponds to altered angles or bond lengths. Some of these changes allow us to draw conclusions about hydrogen bonding with neighboring molecules. Response after excitation of the double bond C=O analyzed The team headed by Annette Pietzsch and Alexander Föhlisch has now for the first time succeeded in precisely measuring these extremely subtle surfaces surrounding a small molecule named acetone (C H O). They used the resonant inelastic X-ray scattering (RIXS) method at the Swiss Light Source of the Paul Scherrer Institut (PSI) in Switzerland for this work. “We chose to selectively excite the double bond between the carbon and oxygen atom of acetone into oscillation and analyzed the responses in detail,” explains Annette Pietzsch. Thanks to the extremely high resolution of the measurement data, they were successful in mapping the potential surface along this C=O double bond. In the second part of the experiment, they investigated a mixture of acetone and chloroform. A liquid mixture like this is denoted as azeotropic, meaning that the two ingredients can no longer be separated from one another through distillation. The scientists were now able for the first time to empirically observe how the acetone molecules linked tightly to the chloroform molecules via hydrogen bonding. They were able to identify in the measurement data the fingerprint of the hydrogen bonds that form between the C=O group of the acetone molecules and hydrogen groups of the chloroform molecules. “In conclusion, we demonstrated how sub-natural line width vibrational resolved RIXS gives direct experimental access to the ground state potential energy surface around selected atomic sites and moieties, not accessible with other techniques. Our approach to the local ground state potential energy surface (...) resembles finding a needle in a haystack,” writes the team in its contribution published in the periodical Nature Scientific Reports. The performance of this approach will benefit strongly from upcoming high-brilliance synchrotrons and free-electron lasers in combination with upcoming high resolution RIXS instruments. Therefore, they foresee wide applicability of this technique to all thermal, collective and impurity driven chemistry and materials issues in the near future. Annette Pietzsch works at the BESSY II synchrotron source in Berlin, setting up METRIXS—an instrument for resonant inelastic X-ray scattering that will be able to achieve considerably higher resolution in the future. In addition, the meV-RIXS experiment will make high-resolution X-ray scattering in low-energy regions feasible. Alexander Föhlisch heads the HZB Institute for Methods and Instrumentation for Research with Synchrotron Radiation and is spokesperson of Helmholtz Virtual Institute for Dynamic Pathways in Multidimensional Landscapes (Helmholtz Virtual Institute 419).