Resonance multiplicities in a hadron transport approach

In this article we focus on the multiplicities of resonances, ratios of resonant over non-resonant states and rescattering processes in heavy ion collisions. Therefore we utilize a hadron transport model (UrQMD v1.3). We find that rescattering of decay particles is of great importance when studying resonances in a hadronic medium.     

Enantioselective Preparation of 2‐Aminomethyl Carboxylic Acid Derivatives: Solving the β2‐Amino Acid Problem with the Chiral Auxiliary 4‐Isopropyl‐5,5‐diphenyloxazolidin‐2‐one (DIOZ). Preliminary Communication

Multigram amounts of suitably protected β²‐amino acids with 17 of the 20 proteinogenic side chains are prepared by diastereoselective reactions of Li, B, or Ti enolates of the corresponding 3‐acyl‐4‐isopropyl‐5,5‐diphenyloxazolidin‐2‐ones (acyl‐DIOZ; 1 ) with appropriate electrophiles (amidomethylation, hydroxyalkylation, (benzyloxycarbonyl)methylation) in yields of 55–90% and with diastereoselectivities of 80 to >97% (Scheme). The primary products 2 – 8 thus obtained are converted to protected β²‐amino acids by standard procedures (Table 1). Many of the DIOZ derivatives are highly crystalline compounds (31 X‐ray crystal structures in Table 2). The chiral auxiliary DIOZ, readily prepared in either enantiomeric form, is recovered with high yield.     

Transport studies in boron-ion implanted type II<Emphasis Type="Italic">a</Emphasis> diamond

We have investigated low-temperature electrical transport mechanisms in the surface layer of a type IIa diamond which has been heavily implanted with boron-ions at low temperatures and then annealed at high temperatures. The boron atoms occupy substitutional sites giving rise to a heavily doped wide-bandgap semiconductor. The dc-conductivity results suggest that for the maximum boron doping that has been achieved, the diamond sample is close to the insulator-metal transition. A model to account for the observed increase in activated boron centres with ion dose is presented. On the insulating side of the transition, the data are interpreted in terms of variable-range hopping laws.     

Optical sensor systems for bioprocess monitoring

Bioreactors are closed systems in which microorganisms can be cultivated under defined, controllable conditions that can be optimized with regard to viability, reproducibility, and product-oriented productivity. To drive the biochemical reaction network of the biological system through the desired reaction optimally, the complex interactions of the overall system must be understood and controlled. Optical sensors which encompass all analytical methods based on interactions of light with matter are efficient tools to obtain this information. Optical sensors generally offer the advantages of noninvasive, nondestructive, continuous, and simultaneous multianalyte monitoring. However, at this time, no general optical detection system has been developed. Since modern bioprocesses are extremely complex and differ from process to process (e.g., fungal antibiotic production versus mammalian cell cultivation), appropriate analytical systems must be set up from different basic modules, designed to meet the special demands of each particular process. In this minireview, some new applications in bioprocess monitoring of the following optical sensing principles will be discussed: UV spectroscopy, IR spectroscopy, Raman spectroscopy, fluorescence spectroscopy, pulsed terahertz spectroscopy (PTS), optical biosensors, in situ microscope, surface plasmon resonance (SPR), and reflectometric interference spectroscopy (RIF).     

Thermodynamik und Struktur von Ni1−xTe*

Zusammenfassung DurchEMK-Messungen und Röntgenbeugungsaufnahmen wurden die thermodynamischen und strukturellen Eigenschaften von Ni₁–xTe untersucht. Die Phase Ni₁–xTe reicht von NiTe (x=0) mit dem Strukturtype des NiAs bis zu Ni_0,5Te mit dem Strukturtyp des CdJ₂. Das Phasenfeld zwischen den beiden Verbindungen ist homogen und zeigt umx=0,25 einen Übergang zweiter Ordnung. Bei dieser Zusammensetzung ändert sich der Anstieg der Kurve Ni-Aktivität gegen Zusammensetzung. Auch der Gitterparameterc ₀ ändert sich drastisch, und Beugungslinien der geordneten CdJ₂-Struktur beginnen aufzutreten. Die Intensität der Beugungslinien ändert sich von der NiAs-Struktur bis zur CdJ₂-Struktur gleichmäßig. Istx<0,2, so stimmen die Intensitäten mit denen überein, die man für die NiAs-Struktur berechnet, fürx>0,4 mit denen der CdJ₂-Struktur. Aus den Aktivitätsmessungen wurde die Fehlstellenwechselwirkungsenergie berechnet. In dem Strukturtyp NiAs ist die Wechselwirkungsenergie zwischen zwei Leerstellen gleich Null. Die Leerstellen stoßen einander also weder ab noch ziehen sie einander an, sie sind also statistisch verteilt. Im Bereich der CdJ₂-Struktur ist die Wechselwirkungsenergie zwischen zwei Leerstellen positiv, und zwarE ₁₁=26,5 kcal/Mol. Die Leerstellen stoßen einander ab, und dac ₀/2 kleiner ist alsa ₀, trachten die Leerstellen, benachbarte Schichten zu vermeiden, und bilden so die CdJ₂-Struktur.

---

Thermodynamics and Structure of Ni_1–xTe

The thermodynamic properties and structural properties of Ni_1–xTe have been studied using galvanic cell and X-ray diffraction techniques. The Ni_1–xTe phase extends from NiTe (x=0) which has a NiAs type structure to Ni_0.5Te (x=0.5) which has the CdI₂ structure. The phase field between the two compounds is continuous and a second order type transition is taking place aroundx=0.25. At that composition the Ni-activity vs. composition curve changes slope. Thec _o lattice parameter also changes drastically and diffraction lines due to the ordered CdI₂ structure start to appear. The intensity of diffraction lines varies smoothly from the NiAs structure to the CdI₂ structure. The intensities agree with that calculated for NiAs whenx<0.2, it agrees with the CdI₂ intensity whenx>0.4. From the activity measurement, the defect interaction energy was calculated. In the NiAs type structure, the vacancyvacancy interaction energy is zero, the vacancies do not repel or attract each other and thus are random. In the CdI₂ structure region the vacancy-vacancy interaction energy is positiveE ₁₁=26.5 kcal/mole. The vacancies repel each other and asc ₀/2 is smaller thana ₀ the vacancies tend to avoid adjacent layers and thus form the CdI₂ structure.

---

---

Mit 9 Abbildungen

---

Herrn Prof. Dr.H. Nowotny gewidmet.

---

Diese Arbeit wurde zum Teil durch die National Aeronautics and Space Administration mit dem Grant NSG (T) 43 1101-020 unterstützt.     

Multiplexed hybridizations of positively charge-tagged peptide nucleic acids detected by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Peptide nucleic acid (PNA) is a novel class of DNA analogues in which the entire sugar-phosphate backbone is replaced by a pseudopeptide counterpart. Owing to its neutral character and the consequent lack of electrostatic repulsion, PNA exhibits very stable heteroduplex formation with complementary nucleic acid that is essentially ionic strength independent and enables hybridization under minimum salt conditions. This feature as well as its superior ion stability and easy ionization compared to DNA renders PNA very attractive for hybridization-based matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) applications. We have developed an approach to DNA characterization that takes advantage of multiplexed PNA hybridizations analyzed by MALDI-TOFMS. Our motivation was the further development of oligonucleotide fingerprinting, an efficient technique for cDNA and genomic DNA library characterization. Through positive 'charge-tagging' of PNA the efficiency of detection in MALDI-TOFMS was considerably enhanced permitting an unparalleled degree of multiplexing. Results from the simultaneous hybridization of 21 charge-tagged PNA hexamer oligonucleotides showed that genomic DNA and cDNA clones are successfully characterized on the basis of their hybridization profiles. The degree of multiplexing achieved may render a significant increase in throughput and hence efficiency of oligonucleotide fingerprinting possible.     

Preparation and redox properties of N,N,N-1,3,5-trialkylated flavin derivatives and their activity as redox catalysts

Eight different flavin derivatives have been synthesized and the electronic effects of substituents in various positions on the flavin redox chemistry were investigated. The redox potentials of the flavins, determined by cyclic voltammetry, correlated with their efficiency as catalysts in the H2O2 oxidation of methyl p-tolyl sulfide. Introduction of electron-withdrawing groups increased the stability of the reduced catalyst precursor.     

A (bpy)2Ru-coordinated dehydro[12]annulene with exotopically fused diimine binding sites

Synthesis and electronic properties of a dinuclear (bpy)(2)Ru(II) polypyridyl complex are described in which the bridging ligand consists of two dipyridophenazines fused to a formally antiaromatic dehydro[12]annulene and where the electronic and electrochemical properties of the complex are markedly influenced by the cyclic all-carbon core.