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Die optimale Dosierung von Antibiotika ist seit ihrer Einführung unklar geblieben. In den letzten 20 Jahren wurden 3 Pharmakokinetik(PK)-Pharmakodynamik(PD)-Indizes etabliert, die von Messungen der Konzentration des Antibiotikums im Plasma und der mittleren Hemmkonzentration (MHK) des die Infektion verursachenden Keims ausgehen. Für β‑Laktame gibt es Hinweise, dass deren Wirksamkeit von der Zeit abhängt, in der die Plasmakonzentration höher ist als die MHK. Bei Aminoglykosiden soll die Wirkung vom Verhältnis aus der maximal im Plasma erreichbaren Konzentration zur MHK abhängig sein. Für Vancomycin zeigen Studien, dass der Quotient aus der Fläche unter der Plasmaspiegelkurve (AUC) und der MHK mit der Wirksamkeit verbunden sein könnte. Für die Behandlung Schwerstkranker können diese PK-/PD-Parameter nur zur Orientierung dienen. Es fehlen nach wie vor Ergebnisse aus überzeugenden klinischen Studien an ausreichend großen Kollektiven von Schwerstkranken, die eine Vorhersage der Wirksamkeit erlauben. In der Praxis ist es deshalb schwer, ohne Orientierung an den Plasmaspiegeln eine rationale Therapie durchzuführen. Moderne Verfahren zur Analytik von allen derzeit verfügbaren Antibiotika im Plasma und die perfekte Logistik der Probenversendung erlauben es, auch kleineren Kliniken ohne hochspezialisiertes Massenspektroskopielabor ein therapeutisches Drugmonitoring (TDM) von Antibiotika durchzuführen. Vorschläge, wie Kliniken ein effizientes und den Betrieb einer Intensivstation nicht störendes TDM einführen können, werden gegeben. Auch zentrale TDM-Modelle, wie es etwa im Paul-Ehrlich-Antibiotika-Konzentrationsmessung(PEAK)-Projekt, das zu einer Vergleichbarkeit der Plasmakonzentrationen zwischen verschiedenen Zentren führen soll, entwickelt wird, werden vorgestellt. Optimized dosage regimens of antibiotics have remained obscure since their introduction. During the last two decades pharmacokinetic(PK)-pharmacodynamic(PD) relationships, originally established in animal experiments, have been increasingly used in patients. The action of betalactams is believed to be governed by the time the plasma concentration is above the minimum inhibitory concentration (MIC). Aminoglycosides act as planned when the peak concentration is a multiple of the MIC and vancomycin seems to work best when the area under the plasma vs. time curve (AUC) to MIC has a certain ratio. Clinicians should be aware that these relationships can only be an indication in which direction dosing should go. Larger studies with sufficiently high numbers of patients and particularly severely sick patients are needed to prove the concepts. In times where all antibiotics can be measured with new technologies, the introduction of therapeutic drug monitoring (TDM) is suggested for ICUs (Intensive Care Unit). The idea of a central lab for TDM of antibiotics such as PEAK (Paul Ehrlich Antibiotika Konzentrationsmessung) is supported.

Radioresistance is a major obstacle in successful clinical cancer radiotherapy, and the underlying mechanisms are not clear. Here we show that IKKα-mediated miR-196a biogenesis via interaction with Drosha regulates the sensitivity of nasopharyngeal carcinoma (NPC) cells to radiotherapy. Phosphorylation of IKKα at T23 site (p-IKKαT23) promotes the binding of IKKα to Drosha that accelerates the processing of miR-196a primary transcripts, leading to increased expressions of both precursor and mature miR-196a. Dephosphorylation of p-IKKαT23 downregulates miR-196a expression and promotes the resistance of NPC cells to radiation treatment. The miR-196a mimic suppresses while its inhibitor promotes the resistance of NPC to radiation treatment. Importantly, the expression of p-IKKαT23 is positively related to the expression of miR-196a in human NPC tissues, and expression of p-IKKαT23 and miR-196a is inversely correlated with NPC clinical radioresistance. Thus, our studies establish a novel mechanistic link between the inactivation of IKKαT23–Drosha–miR-196a pathway and NPC radioresistance, and de-inactivation of IKKαT23–Drosha–miR-196a pathway would be an efficient way to restore the sensitivity of radioresistant NPC to radiotherapy.

La variabilit? de climat, les inondations et leurs impacts en Europe centrale ont retenu une attention croissante en Allemagne pendant les derni?res ann?es. Ainsi les crues historiques font l?objet de plus en plus d?attention dans la recherche scientifique et dans la protection contre les crues. Le projet ??Xfloods?? de l?Universit? de Freiburg (Allemagne) est int?gr? ? l?initiative du Minist?re F?d?ral de Culture et de Recherche (BMBF) pour un ??Gestion du Risque des Crues Extr?mes?? (RIMAX). Les recherches sont particuli?rement focalis?es sur des crues historiques dans le sud-ouest de l?Allemagne. Le projet int?gre les informations des donn?es historiques pour identifier et mesurer des crues extr?mes comme base de la gestion du risque d?inondation. Les donn?es seront extraites des sources historiques de 1500-1900 et compl?t?es par des mesures instrumentales disponibles depuis le milieu du 18?me?si?cle. Le projet peut contribuer ? ?tablir une meilleure estimation des risques et ? faire un traitement plus s?r des futures crues. Le site des recherche se trouve dans la r?gion du sud-ouest de l?Allemagne et inclue la vall?e sup?rieure du Rhin et ses affluents orientaux comme le Neckar. Cette r?gion a ?t? affect?e par des crues extr?mes dans le pass? comme celles des ann?es 1824, 1845 et 1882. Sur l?exemple de l??v?nement d?inondation d?octobre?1824 dans le bassin du Neckar, la reconstruction d?taill?e des crues historiques sera pr?sent?e.

A discussion of nitrosative deamination of cytosine 1 is presented that argues for the formation of 6 by diazotization of 1 to cytosinediazonium ion 2 and its electrostatic complex 3, dediazoniation to 4 ↔ 5, and amide-bond cleavage to 6. The reaction channels available to 6 include hydrolytic deglycation to 3-isocyanatoacrylonitrile 7, water addition to carbamic acid 9 with the possibility for re-closure to uracil 13, water addition to carbamic acid 9, and decarboxylation to 3-aminoacrylonitrile 10. With a view to the instability of the carbamic acid 9, the carbamate models ethyl (Z)-2-cyanovinylcarbamate 14 and (Z)-2-cyano-1-tert-butylvinylcarbamate 20 were studied. Acid-catalyzed hydrolysis of 14 leads to 2-amino-carbonylphenylcarbamate 15, and its cyclization yields the benzo-fused uracil quinazoline-2,4-dione 16. In contrast to the aromatic system 14, acid-catalyzed cyclization cannot compete with oligomerization in the case of 20, and 5-tert-butyluracil 22 is accessible only with base-catalysis. It is shown that 23, the parent of 10, also easily polymerizes. The experimental results provide a rationale as to why 9, 10, and 12 would have escaped detection in in vitro studies:  they would have oligomerized. In contrast to the in vitro experiments, the oligomerizations of 9, 10, or 12 clearly are not relevant in vivo because of low monomer concentrations. With the exclusion of recyclization and of oligomerization in vivo, attention thus needs to focus on (Z)-3-aminoacrylonitrile 10 as the most likely deamination product of cytosine aside from uracil.

Diffusivities of n-octane in particles of industrial fluid catalytic cracking (FCC) catalysts and in zeolite USY, which is the main zeolitic component of the particles, are reported. Diffusion measurements have been performed by using pulsed field gradient (PFG) NMR for a broad range of molecular displacements and temperatures. The recorded diffusivities are used to evaluate the relevance of various transport modes in the particles of FCC catalysts, such as diffusion in the micropores of the zeolite crystals located in the particles, diffusion through the surface layer of these crystals, and diffusion in the meso- and macropores of the particles, for the rate of molecular exchange between catalyst particles and the surrounding atmosphere. This rate is shown to be primarily related to the diffusion in the meso- and macropores of the particles under the condition of fast molecular exchange between these pores and the zeolite crystals located in the particles. The diffusivity associated with this type of diffusion (i.e., the intraparticle diffusivity) is found to correlate well with the catalytic performance of FCC catalysts having the same fractions of the same zeolite USY but different systems of meso- and macropores.

The protonation of acrylonitrile (1) and of Z- and E-3-aminoacrylonitrile (5 and 9) was studied with the Gaussian-2 method. Ammoniumacrylonitrile ion formation is not important. Nitrilium ion formation is preferred in all cases, and the proton affinities are about 80 kJ/mol higher for aminoacrylonitrile. Remarkably, it is found that C2-protonation of 3-aminoacrylonitriles to form iminium ions can compete with nitrilium ion formation. β-Aminoacrylonitriles thus show propinquity to both acrylonitriles and enamines, and mechanistic and toxicological implications are discussed.

5-Cyanoimino-4-oxomethylene-4,5-dihydroimidazoles (1) (R at N1) have been discussed as possible intermediates in nitrosative guanine deamination, which are formed by dediazoniation and deprotonation of guaninediazonium ion. The parent system 1 (R = H) and its N1 derivatives 2 (R = Me) and 3 (R = MOM) are considered here. Protonation of 1−3, respectively, may occur either at the cyano-N to form cations 4 (R = H), 6 (R = Me), and 8 (R = MOM) or at the imino-N to form cations 5 (R = H), 7 (R = Me), and 9 (R = MOM), respectively. This protonation is the first step in the acid-catalyzed water addition to form 5-cyanoimino-imidazole-4-carboxylic acid, which then leads to oxanosine. There also exists the option of a substitution reaction by water at the R group of 6−9, and this dealkylation forms N-[4-(oxomethylene)-imidazol-5-yl]carbodiimide (10) and N-[4-(oxomethylene)-imidazol-5-yl]cyanamide (11). In the case of DNA, the R group is a deoxyribose sugar, and attack by water leads to deglycation. To explore this reaction option, the SN1 and SN2 reactions of 6−9 with water were studied at the MP2/6-31G*//RHF/6-31G* and CCSD/6-31G*//RHF/6-31G* levels, with the inclusion of implicit solvation at the IPCM(MP2/6-31G*)//RHF/6-31G* level, and the electron density distributions of tautomers 1, 10, and 11 were analyzed. The low barriers determined for the MOM transfer show that the deglycation could occur at room temperature but that the process cannot compete with water addition.

The alkylation of naphthalene with methanol and 2-propanol over the zeolite catalyst LaNaY-73 has been conducted in supercritical carbon dioxide as the reaction medium at 250 °C. Catalytic experiments under flow conditions have been performed at high dilution of the reactants (mole fractions < 0.05) and in the pressure range from 1 to 400 bar. Catalyst deactivation is strongly reduced at supercritical conditions as compared to the one in the gas phase. A pressure increase at supercritical conditions results in a higher catalyst activity. The yield ratio of the major reaction products, i.e., mono- and dialkylnaphthalenes, mainly depends on the alcohol/naphthalene ratio in the feed and is independent of the reaction pressure and the degree of catalyst deactivation. The distribution of isomers within the mono- and dialkylated products changes with time on stream, according to a shift from thermodynamically to kinetically controlled product formation, the extent being dependent on the reaction pressure and the state of the fluid. The results are discussed in terms of the pressure-dependent properties of the supercritical reaction phase. It is proposed that the properties of the supercritical reaction medium mainly affect the processes taking place on the outer surface of the zeolite crystallites rather than those occurring inside the zeolite pores. For a systematic comparison between the experiments in the gas phase and those in the supercritical phase, the influence of the modified residence time, the carrier gas flow rate, the catalyst mass, and the concentration of the reactants in the feed were studied in naphthalene alkylation with methanol at ambient pressure. Adsorption of naphthalene on the zeolite was conducted in the gas phase at 1 bar and at supercritical conditions at 200 bar.

Dediazoniation of adeninediazonium ion, 1, forms the heteroaromatic cation, 2. Ab initio studies at the CCSD(fc)/6-31G**//MP2(full)/6-31G** level now reveal that the cyclic cation 2 is kinetically and thermodynamically unstable with respect to the pyrimidine ring-opened cation, 3. The results suggest that 4-cyano-5-isocyano-imidazole, 4, and 4,5-dicyanoimidazole, 5, might be formed to some extent in nitrosative deaminations of adenine.

The quadrupolarity of carbodiimide, HN&dbd;C&dbd;NH, has been studied in comparison to carbon dioxide. Both heterocumulenes exhibit {− + −} quadrupolarity in all directions. Concepts are formulated to develop an understanding of the origins of quadrupole moments and to trace theoretical level effects to the underlying changes of the electron density. The quadrupole moment tensors have been computed using RHF, MP2 and QCISD theory as well as the B3LYP density functional method. A variety of basis sets have been employed, the two best basis sets are of the types [5s, 4p, 2d, 1f] (23s, 8p, 2d, 1f) and [5s, 4p, 3d, 1f] (12s, 6p, 3d, 1f). The results suggest that the MP2 and B3LYP methods in conjunction with well-polarized triple-ζ basis sets provide a cost-effective and quite accurate method for the estimation of correlation effects on quadrupole moments. The quadrupole moment tensor component Qxx of carbodiimide falls between −16 and −18 DÅ. The components Qyy and Qzz, are similar and they range from −16.5 to −17.5 DÅ and from −17 to −18 DÅ. The correlated methods consistently predict an increase of Qxx, whereas they predict a more modest reduction of Qyy and Qzz. It is for these opposing correlation effects that the average values of the diagonal elements, <Qii>, are essentially independent of the method and exhibit only a minor basis set dependence. The traceless quadrupole moment of carbon dioxide, Θ = Q|| − Q⊥, is −4.3 DÅ. In stark contrast, all of the Θii values of carbodiimide are close to zero and only the off-diagonal quadrupole moment element Θxy is quite large with Θxy = −6.2 DÅ.

An alternative means of epoxidation is reported that uses environmentally benign supercritical carbon dioxide as both a solvent and reactant in combination with aqueous H2O2, which is made possible through the in situ formation of peroxycarbonic acid. Experiments were conducted at 40 °C and 120 bar in which cyclohexene was epoxidized to 1,2-cyclohexene oxide and 1,2-cyclohexanediol in this aqueous−organic biphasic system. Through the addition of NaHCO3 and the hydrophilic cosolvent dimethylformamide, the conversion increased from 0.4 mol % (without additives) to 12.6 mol % (with 0.1 mol % NaHCO3 and 13 mol % dimethylformamide). The results suggest that the reaction occurs within the aqueous phase, which led to investigations using the water-soluble olefin 3-cyclohexen-1-carboxylate sodium salt as a means of verifying the reaction location. Epoxidation of 3-cyclohexen-1-carboxylate sodium salt went to completion in less than 20 h at 40 °C and 120 bar with an epoxide yield of 89 mol % and diol yield of 11 mol %.

Environmentally benign near-critical water offers substantial advantages over traditional organic solvents. In this work we use the hydrolyses of several substituted benzoate esters and a series of substituted anisoles as probes to elucidate the activity of the two ionic species in near-critical water. Each of these hydrolyses can run via both acid- and base-catalyzed pathways, as well as an SN2 pathway. An analysis of Hammett plots suggests that the benzoate esters hydrolyze autocatalytically, following an acid-catalyzed mechanism, whereas the anisoles are hydrolyzed via the SN2 mechanistic pathway. This work suggests that near-critical water offers significant potential, both as a benign solvent and as a reaction medium that does not require neutralization with acid or base after the desired reaction is complete.

Im Beitrag wird über ein Forschungsvorhaben berichtet, bei dem das Verbundverhalten von einbetonierten Drahtseilen untersucht wurde. Bisherige Forschungen beschäftigten sich mit dem Verbundverhalten von Spannstahllitzen bzw. anderen allgemein üblichen Bewehrungsarten, wie z. B. Betonstahl. Die hohe Festigkeit und die geometrische Flexibilität der Stahlseile machen diese für den Einsatz als Bewehrungselement interessant. Es stehen hierbei eine Vielzahl von verschiedenen Seiltypen zur Verfügung. Diese galt es, näher zu untersuchen, um Unterschiede im Tragverhalten aufzuzeigen. Die Untersuchungen wurden an Ausziehkörpern durchgeführt. Es wurden hierzu sechs‐ und achtlitzige verzinkte Rundlitzenseile mit Stahleinlage nach DIN 3051 mit variierenden Seildurchmessern unter Verwendung verschiedener Betonfestigkeiten in die Versuchsreihe einbezogen. Für die Auswertung werden Verbundspannungs‐Verschiebungs‐Beziehungen herangezogen. Hieraus abgeleitete erste Erkenntnisse für verschiedene Einflußfaktoren werden entsprechend dargestellt.

Hydrostatic pressure is used to modulate the intermolecular interactions in the conjugated oligophenyl, para-hexaphenyl. These interactions affect the structural properties and also cause changes in the molecular geometry that directly alter the electronic properties. We use Raman spectroscopy to investigate the nature of the structural changes. Our Raman studies in the temperature range of 12 K to 300 K, under pressures up to 70 kbar, indicate that the potential energy of two neighboring phenyl rings as a function of the torsional angle is “W”-shaped. The libration of the phenyl rings between the two minima of the “W”-shaped potential can be modulated by either promoting the molecule to a higher energy state (activation energy of 0.045 eV) by raising the temperature or by decreasing the intermolecular separation, which makes the potential more “U”-shaped. Both these situations make the molecule seem more planar. We infer the shape of the potential from the relative intensity of the inter-ring C&sbd;C stretch Raman mode at 1280 cm^-1 to the C&sbd;H bending mode at 1220 cm^-1 (I1280/I1220). These results are interpreted within the framework of ab initio electronic and vibrational spectra calculations of a biphenyl molecule. We have also conducted X-ray studies to check the sample purity.

The quadrupolarity of carbon dioxide has been studied with higher level ab initio methods. Carbon dioxide exhibits {− + −} quadrupolarity in all directions and an explanation is provided of the origin of the sign of the diagonal elements Qii. The quadrupole moment tensor has been computed using restricted Hartree–Fock theory, second-order Møller–Plesset perturbation theory and quadratic configuration interaction theory. A variety of basis sets have been employed up to basis sets of the type [5s, 4p, 2d, 1f] (23s, 8p, 2d, 1f). The quadrupole moment tensor component Q∥of carbon dioxide falls in the range between −18.5 and −20.5DebyeÅ. The quadrupole moment tensor components Q⊥of carbon dioxide are smaller, ranging from −14.5 to −15DebyeÅ, and they are less sensitive to the choice of the theoretical model. The correlated methods consistently predict an increase of Q∥while they predict a more modest reduction of Q⊥. It is for the opposing electron correlation effects on Q∥and Q⊥that the average values of the diagonal elements, 〈Qii〉, are essentially independent of the method and exhibit only a small variation depending on the basis set. On the other hand, the anisotropy of the quadrupolarity, the quadrupole moment Θ, is affected most by the opposing electron correlation effects on Q∥and Q⊥. The accurate reproduction of the measured quadrupolarity Θ=−4.3DebyeÅ requires a theoretical model that employs both a good method and a good basis set. The results suggest that the use of second-order Møller–Plesset perturbation theory in conjunction with well-polarized triple-ζbasis sets provides a cost-effective and quite accurate method for the estimation of correlation effects on quadrupole moments.

The atomic polarizabilities of carbon dioxide and carbodiimide, HN&dbd;C&dbd;NH, have been studied with ab initio theoretical methods. Structures were optimized and properties were determined using RHF, MP2, and QCISD theories and a variety of basis sets up to quadruple-ζ quality. The static electric dipole polarizability tensor components were determined using the finite field method. The isotropic polarizability 〈α〉 and the anisotropic polarizabilities Δα and κ were calculated for both heterocumulenes from the respective tensor components. The experimental tensor components and polarizabilities 〈α〉, Δα, and κ are known for carbon dioxide, and these values are used to assess the accuracy of the theoretical methods. This knowledge about the achievable accuracy is then employed in the prediction of the polarizability values of carbodiimide. The only measurable polarizability values for carbodiimide are 〈α〉 and κ. The best level of theory employed in this study is QCISD(fc)/6-311++G(3df,2pd) and this level gives 〈α〉 and κ values of 16.722 and 0.289 au³ for carbon dioxide. These values deviate somewhat from the experimental values of 17.762 and 0.267 au³ and we rationalize these differences based on the calculated polarizability tensor components. The calculated 〈α〉 and κ values of carbodiimide are 28.963 and 0.310 au³. Taking into account the deviations from experiment for the carbon dioxide values, we predict 〈α〉 and κ values of 30.764 and 0.286 au³ for carbodiimide. The discussion emphasizes the important role of the inclusion of three sets of d-polarization functions. The third, diffuse set of d-functions is essential to polarize the electron density described by the diffuse functions and also by the outer valence p-functions.

The structure of “guaninediazonium ion” in its aggregate with cytosine has been explored with ab initio and density functional methods. The hydrogen-bonded aggregate between cytosine and guaninediazonium ion, 1, is a stable minimum, 3. While the isolated enol tautomer of guaninediazonium ion, 2, is significantly more stable than 1, the tautomeric aggregate 4 that results from double-proton-transfer in 3 is almost isoenergetic with 3. Most interesting and entirely unexpected is the finding that neither 3 nor 4 is predicted to be the thermodynamically predominant structure. Instead, single-proton-transfer to cytosine results in the most stable cytosinium−guaninediazo complex, 5.

ABSTRACTDrying of recycled polypropylene powder was studied experimentally in a laboratory pulsed fluid bed dryer (PFB) with relocated air stream. It was proved that fluidization of fine particles having a large specific surface area and a broad size distribution is technically feasible when using the composite supporting grid. Drying and hydrodynamic characteristics for a pulsed fluid bed of fine particles are found to be similar to the ones for coarse particles. Equations for minimum pulsed fluidization velocity, pressure drop, and surface and volumetric heat transfer coefficients are given.

The hetero-Diels−Alder reaction between anthracene and excess 4-phenyl-1,2,4-triazoline-3,5-dione has been investigated in supercritical CO2 at 40 °C and pressures between 75 and 216 bar. Bimolecular reaction rate constants have been measured via fluorescence spectroscopy by following the decrease in anthracene concentration with reaction time. The reaction rate is elevated in the vicinity of the critical pressure. This difference is consistent with local composition enhancement and can be modeled with the Peng−Robinson equation of state.

Attempts were made to superinfect epithelial explant cell cultures prepared from nasopharyngeal carcinomas with Epstein-Barr virus. Virus-specific markers were observed in such cultures 3 days after superinfection. In addition, expression of Epstein-Barr virus early antigens was observed in epithelial cell explant cultures treated with iododeoxyuridine. The results suggest that epithelial cells of at least certain nasopharyngeal carcinomas possess the receptor for the Epstein-Barr virus and that the latent virus genome can be induced from epithelial cells prepared from such tumors.

The extraction of four solvents from three sorbents, using supercritical carbon dioxide was studied. Toluene and isooctane were extracted from Anasorb 747®, a synthetic carbon; 1-butanol from silica gel; and 2-nitropropane from Anasorb 727®, a porous organic polymer. Preliminary experiments indicated that dynamic extraction was required; these experiments also fixed the duration of extraction of the analytes. All extractions were performed at 1.0 mL min−1. The temperature and density of the supercritical extraction fluid were then varied, according to a fractional factorial statistical design. The amounts remaining on the sorbent were determined via solvent desorption of the analytes and gas chromatography of the eluents. The fraction extracted data were modeled as a function of temperature and density according to a thermodynamic approach that permitted computation of constant-density enthalpies of desorption. This study indicates a significant temperature- and density-dependence for quantitative extraction of isooctane and toluene from Anasorb 747®and 1-butanol from silica gel, with no measurable temperature-or density-dependence for extraction of 2-nitropropane from Anasorb 727®. The extracted analytes were also collected via cryotrapping; only higher level masses of 1-butanol were quantitatively recovered. The dependence of the extraction efficiency on the thimble volumes passed over the matrix is discussed.

The spatial and temporal significance of land reclamation from the sea in relation to the development of the three SE Asian small coastal territories of Singapore, Hong Kong and Macau are examined and compared. In all three territories the rate of reclamation has been an index of the rate of economic development. Four phases of land reclamation are identified: (1) pre-1900: involved relatively unplanned and uncostly projects in shallow water and swamplands around the main focus of settlement; (2) 1900–1945: involved military projects outside the main settlement core; (3) 1945–1980: this phase of large-scale projects unconstrained by natural conditions because of advances in technology and high rate of reclamation was driven by rapid industrial and population growth; (4) 1980 to date: a period marked by large infrastructure projects designed to maintain and extend the status of the territories as world economic and commercial centres. Currently 10%, 5% and 33% of the total land surfaces of Singapore, Hong Kong and Macau respectively comprise land reclaimed from the sea and these proportions will continue to rise.

Summary The dependence of the rate constant of Rb+ efflux on extracellular cation concentration was measured. At low ionic strengths Rb+ efflux increased strongly. Permeability coefficients were calculated from the rate constants measured, using the Goldman flux equation, with and without making allowance for surface potentials. Only when allowance was made for surface potentials and the associated differences beween ion concentrations in the bulk solutions and at the membrane surface, the permeability coefficient remained constant. Best agreement between experimental data and theoretically calculated values was obtained when an interior surface potential of − 110 mV was assumed.

Zusammenfassung: Der vorliegende Beitrag behandelt neue methodische Ans�tze zu einer dendroklimatologischen Interpretation von Baumringchronologien aus ann�hernd optimalen Wuchsgebieten. �ber Einzeljahranalysen wurde zun�chst der Einflu� von Wetteranomalien auf signifikante Zuwachs�nderungen (Signaturen) eines Eichenbestandes bei W�rzburg untersucht. Anschlie�end wird das Ergebnis den Resultaten multipler Regressionsanalysen zwischen der Baumringsequenz und der Klimadatenzeitreihe W�rzburg gegen�bergestellt, wobei letztere aus 45 meteorologischen Einzelparametern bestand. Der Signaturtest hat gezeigt, da� faktisch alle Eichensignaturen mit charakteristischen Typen von Witterungsanomalien erkl�rt werden k�nnen, die im Beobachtungszeitraum (1936–1986) wiederholt aufgetreten sind. Die Regressionsanalysen machen dagegen eher �kologische Tendenzen zum Einflu� der Wetterabl�ufe auf das Eichenwachstum deutlich. Dabei werden vor allem auch jahreszeitlich terminierte Klimaeinfl�sse erkennbar. Die Synthese beider Verfahren erm�glicht die Aufstellung eines �kologisch sinnvollen Modells zur klimatischen Pr�gung der ausgewerteten Eichenchronologie. Insgesamt l��t sich nachweisen, da� s�ddeutsche Jahrringchronologien in der kollinen Stufe durchaus zur Verifizierung von Klimazeitreihen herangezogen werden k�nnen. Langfristig soll damit eine Verifizierung s�ddeutscher Klimazeitreihen aus Wein- und Getreideertragsdaten anhand von Jahrringchronologien aus entsprechenden Gebieten erreicht werden.

A new formula is derived for the determination of the potential energy of the central unit cell of a finite crystal; this formula is called the crystal potential formula. The crystal potential formula is based on a two-center Cartesian multipole expansion. The key feature of the crystal potential formula is that it achieves a separation of the lattice geometry and multipole moments. This feature allows one to compute in a highly effective way the crystal energies as a function of the molecules contained in the unit cell. Numerical implementation is discussed, and a numerical example is given. The example mimics an organic crystal composed of dipolar molecules. It is found that the crystal environment may create local minima and that the effects of the environment might be well-approximated by consideration of the proximate unit cells only. Both of these effects have important implications for the crystal engineering of molecular organic materials.

The hsp26 gene of Drosophila melanogaster is expressed in six tissues during development and in a tissue-general response to heat shock. To be able to compare tissue-specific and heat-induced mechanisms of hsp26 expression, we have begun an analysis of the sequences involved in the spermatocyte-specific expression of the hsp26 gene by using germ line transformation. hsp26 mRNA synthesized in the spermatocytes has the same start site as sites previously demonstrated for nurse cell-specific and heat-induced mRNAs. Three regions of the hsp26 gene (nucleotides -351 to -135, -135 to -85, and +11 to +632) were able to stimulate spermatocyte-specific expression when fused with promoter sequences (nucleotides -85 to +11) that alone were insufficient to stimulate expression. These stimulatory regions appear to contain elements that provide redundant functions. While each region was able to stimulate expression independently, the deletion of any one region from a construct was without consequence as long as another compensatory region(s) was still present. There must reside, at a minimum, two independent spermatocyte-specifying elements within the sequences that encompass the three stimulatory regions and the promoter. At least one element is contained within sequences from -351 to -48. This region, in either orientation, can stimulate spermatocyte-specific expression from a heterologous promoter. A second element must reside in sequences from -52 to +632, since these sequences are also sufficient to direct spermatocyte-specific expression.