Untersuchung der Adsorption und Koadsorption organischer Moleküle an Platineinkristallelektroden : Ansätze zur Modifizierung von Platineinkristallelektroden

Ziel dieser Arbeit war es, die Kenntnisse über die Reaktivität modifizierter einkristalliner Platinoberflächen zu vertiefen und mögliche Strategien zur gezielten Modifizierung solcher geordneten, periodisch gestuften Substrate zu eruieren. Im ersten Teil dieser Arbeit wurde die Adsorption und Koadsorption ausgewählter Modellmoleküle an Platinelektrodenoberflächen mit Differentieller Elektrochemischer Massenspektrometrie (DEMS) ergänzt durch elektrochemische Rastertunnelmikroskopie (EC-STM) untersucht. Als Substrate wurden verschiedene gestufte Platineinkristalle der [1, -1, 0]-Zone mit monoatomaren (111)-orientierten Stufen und unterschiedlich breiten (111)-orientierten Terrassen ausgewählt. Anhand der ausgewählten Substrate Pt(332) und Pt(665) konnte gezeigt werden, dass die geringere Stufendichte an der Pt(665)-Oberfläche zu einer unvollständigeren kathodischen Desorption des adsorbierten Ethens führt. Ethen desorbiert kathodisch primär von den Stufen. Auf diesen teilblockierten Oberflächen ist hiernach eine deutliche Wasserstoffadsorption an den (111)-Stufen möglich. Diese modifizierten Oberflächen mit freien, monoatomaren Stufen und blockierten Terrassen wurde im Hinblick auf die Koadsorption anderer Moleküle untersucht. Sowohl für kleine Spezies wie 13CO und Ethen, als auch für Aromaten von zunehmender Größe wie Benzen, Styren und Mesitylen war eine Koadsorption an den durch Ethen teilblockierten, modifizierten Oberflächen des Pt(332)/Ethen und Pt(665)/Ethen möglich. EC-STM-Experimente zur Koadsorption von Benzen und Ethen am Pt(111) zeigen, dass eine Domänenbildung auftritt. Eine sterisch wirkende "Adsorptionsschablone" kann durch eine Koadsorption von Ethen und Benzen am Pt(111) mit anschließender gezielter Desorption des Benzens aufgrund dieser Domänenbildung nicht erzeugt werden. Weiterhin wurde die Adsorption und chemische Stabilität verschiedener Kronenether mit einem 18-Krone-6-Grundkörper (Derivate des 18-Krone-6) wurde auf Pt(111)- und auf polykristallinen Pt-Elektroden untersucht, da diese Spezies als mögliche Wirtmoleküle für eine Kationeneinlagerung interessant sind. Diese Modelladsorbentien mit zunehmender Komplexität (von einfachen 18-Krone-6 bis zum komplexeren 4'-Aminodibenzo-18-krone-6) konnten irreversibel und im Wesentlichen chemisch intakt auf den Elektrodenoberflächen adsorbiert werden. Trotz der hohen Reaktivität der Pt-Substrate erfolgt eine Zersetzung der Adsorbate erst anodisch von 0,6 V bzw. kathodisch ab etwa 0,1 V vs. RHE. In Kooperation mit G.A. Attard (Univ. Cardiff) fanden Untersuchungen zur Adsorption von Cinchonin auf verschiedenen Pt-Substraten statt. Die Oberflächenkonzentrationen und die Bindungswechselwirkungen konnten aufgeklärt werden. Es wurde gezeigt, dass durch eine 13CO-Koadsorption das präadsorbierte Cinchonin nicht vollständig desorbiert werden kann und folglich die exocyclische Vinylgruppe des Chinuclidinringes trotz des sterischen Anspruchs zur Anbindung an der Substratoberfläche beiträgt. Die Reaktivität einer mit Cinchonin modifizierten Pt-Elektrode wurde beispielhaft untersucht

Prognostic factors in seminomas with special respect to HCG: Results of a prospective multicenter study

Objective: In a prospective multicenter trial, it was our intention to elucidate clinical prognostic factors of seminomas with special reference to the importance of human chorionic gonadotropin (HCG) elevations in histologically pure seminomas. Methods: Together with 96 participating urological departments in Germany, Austria, and Switzerland, we recruited 803 seminoma patients between 1986 and 1991. Out of 726 evaluable cases, 378 had elevated, while 348 had normal HCG values in the cubital vein. Histology was reviewed by two reference pathologists. HCG levels were determined in local laboratories and in a study laboratory. Standard therapy was defined as radiotherapy in stages I (30 Gy) and IIA/B (36 Gy) to the paraaortal and the ispilateral (stage I) and bilateral (stage IIA/B) iliac lymph nodes; higher stages received polychemotherapy and surgery in case of residual tumor masses. Statistics included chi-square tests, linear Cox regression, and log-rank test. Results: The HCG elevation is associated with a larger tumor mass (primary tumor and/or metastases). HCG-positive and HCG-negative seminomas had no different prognostic outcome after standard therapy. The overall relapse rate of 6% and the survival rate of 98% after 36 months (median) indicate an excellent prognosis. The calculation of the relative risk of developing a relapse discovered only stage of the disease and elevation of the lactate dehydrogenase concentration and its prolonged marker decay as independent prognostic factors for seminomas. A more detailed analysis of the prognostic significance of the stage revealed that the high relapse rate in stage IIB seminomas after radiotherapy (24%) is responsible for this result. Conclusions: We conclude that HCG-positive seminomas do not represent a special entity. Provided standard therapy is applied, HCG has no influence on the prognosis. Patients with stage IIB disease should be treated with chemotherapy because of the demonstrated higher relapse rate outside the retroperitoneum. Copyright (C) 1999 S. Karger AG. Basel

Gamma-ray lines and neutrons from solar flares

The energy spectrum of accelerated protons and nuclei at the site of a limb flare was derived by a technique, using observations of the time dependent flux of high energy neutrons at the Earth. This energy spectrum is very similar to the energy spectra of 7 disk flares for which the accelerated particle spectra was previously derived using observations of 4 to 7 MeV to 2.223 MeV fluence ratios. The implied spectra for all of these flares are too steep to produce any significant amount of radiation from pi meson decay. It is suggested that the observed 10 MeV gamma rays from the flare are bremsstrahlung of relativistic electrons

Results of a randomized trial of treatment modalities in patients with low or early-intermediate risk prostate cancer (PREFERE trial)

Purpose The optimal treatment for patients with low to early-intermediate risk prostate cancer (PCa) remains to be defned. The randomized PREFERE trial (DRKS00004405) aimed to assess noninferiority of active surveillance (AS), externalbeam radiotherapy (EBRT), or brachytherapy by permanent seed implantation (PSI) vs. radical prostatectomy (RP) for these patients. Methods PREFERE was planned to enroll 7600 patients. The primary endpoint was disease specifc survival. Patients with PCa stage≤cT2a, cN0/X, M0, PSA ≤10 ng/ml and Gleason-Score≤3+4 at reference pathology were eligible. Patients were allowed to exclude one or two of the four modalities, which yielded eleven combinations for randomization. Sixty-nine German study centers were engaged in PREFERE. Results Of 2251 patients prescreened between 2012 and 2016, 459 agreed to participate in PREFERE. Due to this poor accrual, the trial was stopped. In 345 patients reference pathology confrmed inclusion criteria. Sixty-nine men were assigned to RP, 53 to EBRT, 93 to PSI, and 130 to AS. Forty patients changed treatment shortly after randomization, 21 to AS. Fortyeight AS patients with follow-up received radical treatment. Median follow-up was 19 months. Five patients died, none due to PCa; 8 had biochemical progression after radical therapy. Treatment-related acute grade 3 toxicity was reported in 3 RP patients and 2 PSI patients. Conclusions In this prematurely closed trial, we observed an unexpected high rate of termination of AS and an increased toxicity related to PSI. Patients hesitated to be randomized in a multi-arm trial. The optimal treatment of low and earlyintermediate risk PCa remains unclear

Termination rates and histological reclassification of active surveillance patients with low- and early intermediate-risk prostate cancer : results of the PREFERE trial

Purpose Active surveillance (AS) strategies for patients with low- and early intermediate-risk prostate cancer are still not consistently defined. Within a controlled randomized trial, active surveillance was compared to other treatment options for patients with prostate cancer. Aim of this analysis was to report on termination rates of patients treated with AS including different grade groups. Methods A randomized trial comparing radical prostatectomy, active surveillance, external beam radiotherapy and brachytherapy was performed from 2013 to 2016 and included 345 patients with low- and early intermediate-risk prostate cancer (ISUP grade groups 1 and 2). The trial was prematurely stopped due to slow accrual. A total of 130 patients were treated with active surveillance. Among them, 42 patients were diagnosed with intermediate-risk PCA. Reference pathology and AS quality control were performed throughout. Results After a median follow-up time of 18.8 months, 73 out of the 130 patients (56%) terminated active surveillance. Of these, 56 (77%) patients were histologically reclassified at the time of rebiopsy, including 35% and 60% of the grade group 1 and 2 patients, respectively. No patients who underwent radical prostatectomy at the time of reclassification had radical prostatectomy specimens ≥ grade group 3. Conclusion In this prospectively analyzed subcohort of patients with AS and conventional staging within a randomized trial, the 2-year histological reclassification rates were higher than those previously reported. Active surveillance may not be based on conventional staging alone, and patients with grade group 2 cancers may be recommended for active surveillance in carefully controlled trials only

The transition towards a sustainable energy system in Europe: What role can North Africa's solar resources play?

Securing energy supply and speeding up the transition towards a reliable, sustainable, low-carbon energy system are among the major current and future challenges facing Europe. Importing dispatchable solar electricity from North Africa is considered as a potential and attractive option. Nevertheless, as things currently stand, the European Commission focuses mainly on the exploitation of the existing wind power potential in the North Sea, largely ignoring the solar power potential in the Sahara region of North Africa. After discussing the major challenges and issues facing Europe to achieve the assigned ambitious objectives, the paper emphasises the importance of North Africa's solar resources in helping Europe to successfully address the challenge of decarbonising its electricity system, in particular with regards to the security of supply and sustainability. Within these two major challenges, the paper explores the issues of access, barriers and opportunities. The paper highlights why the EU’s energy and climate goals will not be achievable without adequate grid expansion and grid-scale energy storage facilities, as well as other innovative measures to manage demand and ensure a secure energy supply. In this respect, the paper shows how the import of dispatchable electricity from North Africa via specific HVDC links could play a key role in helping the EU achieve its energy targets in a cost effective way without recourse to significant investments in transmission infrastructure and storage facilities. The paper then attempts to identify and analyze the main barriers that continue to inhibit the export of solar electricity from North Africa to Europe. Finally, to make the project more attractive and achievable in the near future, the paper proposes a systematic approach for setting up energy import scenarios. A promising import scenario is presented where energy import via Italy is shown to be a more viable and effective solution than via Spain.Peer reviewe

Reasonable potential for GHG savings by anaerobic biomethane in Germany and UK derived from economic and ecological analyses

This study introduces a new approach to estimate biomethane market potential by analysing biogas markets and their relative environmental and economic advantages. This potential is then combined with greenhouse gas emission values for different feedstock shares (farm-fed and waste-fed systems) and different application share to determine the possible contribution of biomethane to national greenhouse gas emission saving goals. Markets that are considered are Germany and the UK being the biggest emitters of CO2eq in the European Union. The current use was compared with the scenarios (i) market projection, derived from literature study and (ii) reasonable potential, derived from environmental and economic calculations. The current market status is presented to show the past market development until the present date and associated greenhouse gas savings. Additionally the potential of biomethane to contribute to greenhouse gas emission savings is extensively described. Results indicate that the share of application in Germany is more environmental beneficial than the one in the UK achieving higher greenhouse gas savings at comparable feed-in level. In contrast, the UK has a higher share of waste-fed systems to produce biomethane. The use of biomethane in CHP plants achieves the highest GHG emission savings and if organic waste is used as feedstock the possible savings are even higher. With an increase of biomethane used in CHP plants and a decrease of biomethane used for direct heating the savings in the UK could increase up to 52%. Current savings of 2446 kt CO2eq (Germany) and 606 kt CO2eq (UK) can be extended to 4483 kt CO2eq (Germany) and 1443 kt CO2eq (UK) respectively. Scenario results were determined based on the environmental and economic advantageousness development of the existing biogas market. In this way positive future market development as well as improved shares of feedstock and application can contribute to further greenhouse gas emission savings of Germany and the UK

Modifikasi Kulit Kacang Tanah Menggunakan Surfaktan Seiltrimetilamonium Bromida (CTAB) Untuk Adsorpsi Pewarna Congo Red

Kulit kacang tanah merupakan bagian tumbuhan yang sering kali menjadi limbah dikarenakan sedikit sekali pemanfaatannya. Banyak masyarakat yang menjadikan kuit kacang tanah hanya sebagai bahan bakar untuk pengolahan tahu. Selain mudah didapat kulit kacang tanah memiliki senyawa organik didalamnya yang mampu digunakan sebagai biosorben. Kemampuan kulit kacang tanah sebagai adsorben sangatlah minim oleh karena itu perlunya modifikasi dengan impregnasi dengan surfaktan Seiltrimetilamonium Bromida (CTAB) sebagai biosorben zat warna anionik. Salah satu pewarna anionik yang banyak digunakan dalam industri tekstil adalah metil jingga. Kulit kacang tanah dilakukan modifikasi dengan penambahan 20% w/w surfaktan CTAB untuk meningkatkan kestabilan pada permukaannya sehingga kemampuan adsorbsinya meningkat. Kulit kacang tanah termodifikasi yang disebut (KKM) ini kemudian digunakan untuk adsorpsi zat warna anionik, . Penentuan kondisi optimum adsorpsi menghasilkan adsorpsi optimum pada waktu 15-20 menit dengan masa adsorben 0,05 g dalam 20 mL lautan 100 ppm menghasilkan persen penghilangan 98,58% dan pada pH asam dengan variabel waktu 5-10 menit pertama, menunjukkan persen penghilangan yang lebuh cepat yakni lebih dari 95%. Adapun karakterisasi untuk mendukung penelitian ini adalah Fourier Transformed Infrared (FTIR) untuk mengetahui gugus fungsi pada sample dan Scanning Electron Microscope Energy Dispersive X-ray (SEM-EDX) untuk mengetahui morfologinya. ================================================================================================ Peanut shells are part of plants that often become waste due to very little use. Many people use peanut butter only as fuel for tofu processing. Besides being easy to obtain, peanut shells have organic compounds in them that can be used as biosorbents. The ability of peanut shells as an adsorbent is minimal, therefore it is necessary to modify it by impregnation with the surfactant Ceiltrimethylammonium Bromide (CTAB) as an anionic dye biosorbent. One of the most widely used anionic dyes in the textile industry is methyl orange. Peanut shells were modified with the addition of 20% w/w CTAB surfactant to increase the stability on the surface so that the adsorption ability increased. The modified peanut shell called (KKM) was then used for the adsorption of the anionic dye, . Determination of optimum adsorption conditions resulted in optimum adsorption at 15-20 minutes with an adsorbent mass of 0.05 g in 20 mL of 100 ppm ocean resulting in 98.58% removal percent and at acidic pH with a variable time of 5-10 minutes. First, it shows a faster removal rate of more than 95%. The characterizations to support this research are Fourier Transformed Infrared (FTIR) to determine the functional groups in the sample and Scanning Electron Microscope Energy Dispersive X-ray (SEM-EDX) to determine the morphology