Surgery on 3-manifolds with \mathbb{S} 1-actions

We study the topological structure of all 3-manifolds obtained by surgery along principal fibers of a closed orientable -manifold. As a consequence, we give alternative proofs of some classical results due to W. Heil and L. Moser. Moreover, we completely specify the Seifert invariants for the considered manifolds. Finally we classify the manifolds obtained by surgery along certain Seifert links and determine geometric presentations of their fundamental groups.Work performed under the auspices of C.N.R. (National Research Council) of Italy and partially supported by Ministero della Ricerca Scientifica e Tecnologica within the projects Geometria Reale e Complessa and Topologia.     

High-temperature oxygen sensors for glass-forming melts

Electrochemical sensors are reported for the on-line measurement of oxygen partial pressures of oxidic glass-forming melts on a laboratory and technical scale. Based on the principle of solid electrolyte cells without transference, they are principally simple units. The extreme chemical and temperature conditions of their applications, however, demanded extensive fundamental investigations and resulted in specific forms of reference and measuring electrodes, a thermo-dynamic procedure of verifying the correct functioning of such cells, and a method of measuring thermoelectric voltages of non-isothermal glass melts.     

Asymptotic expansions in the integral and local limit theorems in banach spaces with applications to ω-statistics

LetB be a real separable Banach space and letX,X ₁,X ₂,...∈B denote a sequence of independent identically distributed random variables taking values inB. DenoteS _n =n ^?1/2(X ₁+...X _n ). Let π:B→R be a polynomial. We consider (truncated) Edgeworth expansions and other asymptotic expansions for the distribution function of the r.v. π(S _n ) with uniform and nonuniform bounds for the remainder terms. Expansions for the density of π(S _n ) and its higher order derivatives are derived as well. As an application of the general results we get expansions in the integral and local limit theorems for ω-statistics $$\omega _n^p (q)\mathop { = n^{{p \mathord{\left/ {\vphantom {p 2}} \right. \kern-\nulldelimiterspace} 2}} }\limits^\Delta \smallint _{(0,1)} \{ F_n (x) - x\} ^p q(x)dx$$ and investigate smoothness properties of their distribution functions. Herep≥2 is an even number,q: [0, 1]→[0, ∞] is a measurable weight function, andF _n denotes the empirical distribution function. Roughly speaking, we show that in order to get an asymptotic expansion with remainder termO(n ^?α), α<p/2, for the distribution function of the ω-statistic, it is sufficient thatq is nontrivial, i.e., mes{t∈(0, 1):q(t)≠0}>0. Expansions of arbitrary length are available provided the weight functionq is absolutely continuous and positive on an nonempty subinterval of (0, 1). Similar results hold for the density of the distribution function and its derivatives providedq satisfies certain very mild smoothness condition and is bounded away from zero. The last condition is essential since the distribution function of the ω-statistic has no density whenq is vanishing on an nonempty subinterval of (0, 1).     

HPLC fractionation and structural dynamics of humic acids

Different soil extracted humic acids as well as a commercial humic acid sodium salt were fractionated by HPLC. An almost complete recovery could be achieved for the dissolved material. All humic samples show a typical chromatogram of at least five fractions. The separation of humic substances is influenced by an altered hydrophobicity due to changes in the tertiary structure. Three fractions were further investigated by Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy and by HPLC/HPLC separation. DRIFT spectroscopy provided data on the primary structure, whereas HPLC/HPLC results gave insight into the secondary and tertiary structure and their changes. Received: 18 June 1996 / Revised: 9 October 1996 / Accepted: 12 October 1996     

Versuche zur Herstellung eines «Bis(triasterans)» und Synthese des heterocyclischen (Tricyclo[4.4.1.01,6]undeca-3,8-dien-11,11-dimethyl)sulfits

Tentative Synthesis of ‘Bis(triasterane)’ and Synthesis of the Heterocyclic (Tricyclo[4.4.1.0^1,6]undeca-3,8-diene-11,11-dimethyl)sulfite The synthesis of the bis(triasterane) ( 1 ) has been tried; the reaction of ‘isotetraline’ (1,4,5,8-Tetrahydronaphthalene; 2 ) with diazomalonate yielded the tricyclic systems 5 and 6 , and not 4 . Hydrolysis of 5 gave the monocarboxylic acid 7 , and not the dicarboxylic acid 9 . The latter could be obtained from the dibromoderivative 8 , but 9 couldn't be converted to the acyl chloride 10 . The reduction of 9 with LiAlH₄ yielded the crystalline diol 11 , which was cyclized with SOCl₂ to the heterocycle 12 . The spectral data of the new compounds 5, 6, 7, 11 and 12 are reported and discussed.     

Photoelectron spectroscopy of isolated multiply negatively charged oligonucleotides

Ultraviolet photoelectron spectroscopy in an ion beam was used to investigate the electronic properties of isolated DNA oligonucleotides [dA(5)-4H](4-) and [dT(5)-4H](4-), carrying four excess negative charges. We find the fourth adiabatic electron affinity to be slightly negative for [dA(5)-4H](4-), while it is positive for [dT(5)-4H](4-). This implies a significant influence of the base composition on energetics, which is in turn relevant for analytic applications and also for charge transport properties.     

4-Aryldihydropyridines,a New Class of Highly Active Calcium Antagonists

The aryldihydropyridines first prepared by Hantzsch almost 100 years ago have recently been found to be highly effective calcium antagonists with suitable pharmacological profiles. An illustrative example is dimethyl-l,4-dihydro-2,6-dimethyl-4-(o-nitrophenyl)pyridine-3,5-dicarboxylate (Nifedipine) which is already employed therapeutically. This substance lowers the frequency of attack of angina pectoris and reduces blood pressure. The discovery of the therapeutic activity of this class of substances initiated renewed investigation of the Hantzsch condensation and the synthesis of numerous 4-aryldihydropyridines and related compounds. Qualitative and quantitative structure/activity relationships of these substances can be deduced from their biological data.     

Hydrogen bonds of RNA are stronger than those of DNA, but NMR monitors only presence of methyl substituent in uracil/thymine

Recently, Vakonakis and LiWang (J. Am. Chem. Soc. 2004, 126, 5688) reported experimental evidence for stronger hydrogen bonds in RNA A:U than in DNA A:T base pairs, which was based on differences in NMR shielding for adenine C2. We have analyzed the proposed correlation between NMR shielding and hydrogen-bond strength using density functional theory. Although we agree with the conclusion that A:U is more strongly bound, we find no correlation between the hydrogen-bond strength and the NMR shielding of C2. Our study shows that NMR merely probes the presence/absence of the methyl group in thymine/uracil, without any relation to the strength of the hydrogen bonds involved. In other words, one cannot infer the Watson-Crick hydrogen-bond strength from the NMR shielding constant of adenine C2.     

SYNTHESIS OF POSITIVELY CHARGED PHTHALOCYANINES and THEIR ACTIVITY IN THE PHOTODYNAMIC THERAPY OF CANCER CELLS

Positively charged zinc containing or metal free phthalocyanines 6a-c and 7a-c were prepared via a three step procedure starting from 4-nitrophthalonitrile. The phthalocyanines contain alkyl chains of different length in order to influence the hydrophilic vs lipophilic character of the compounds. The partition between a hydrophilic (water) and lipophilic (octanol-1) phase was determined, and the photoredox activities were investigated. Initial results on the photodynamic activity of these compounds were compared with those of Dougherty's Photofrin II on different malignant and non-malignant cell lines (XP 29MAmal, CX1, HeLa, S180 and NO17). Positively charged phthalocyanines in vitro showed a higher photodynamic activity than Photofrin II.     

Theoretical and experimental study of the adsorption on radioactive gases on continuous flow columns

A bimolecular reaction model was used to describe the adsorption process in continuous flow columns filled with solid adsorbents. The analytical solution of the model for low gas concentrations and a cascade-type numerical method for higher gas concentrations were developed. An air flow apparatus using activated carbon as adsorbent and methyl-iodide labelled with¹²⁵I as adsorbate was constructed for measuring breakthrough- and accumulation curves.