Showing papers by "University of Hamburg published in 1986"
TL;DR: In this article, the "oriented smoothness" constraint was introduced to restrict variations of the displacement vector field only in directions with small or no variation of gray values, which creates difficulties at gray value transitions which correspond to occluding contours.
Abstract: A mapping between one frame from an image sequence and the preceding or following frame can be represented as a displacement vector field. In most situations, the mere gray value variations do not provide sufficient information in order to estimate such a displacement vector field. Supplementary constraints are necessary, for example the postulate that a displacement vector field varies smoothly as a function of the image position. Taken as a general requirement, this creates difficulties at gray value transitions which correspond to occluding contours. Nagel therefore introduced the ``oriented smoothness'' requirement which restricts variations of the displacement vector field only in directions with small or no variation of gray values. This contribution reports results of an investigation about how such an ``oriented smoothness'' constraint may be formulated and evaluated.
735 citations
TL;DR: They were mostly considered, at that time and even later, a kind of artifact of Bohr's model of the atom whose real existence was questionable and, anyway, not to be verified with the common large atomic ensembles.
Abstract: We have recorded the laser-excited resonance fluorescence of one to three ${\mathrm{Ba}}^{+}$ ions and observed Bohr's "quantum jumps" when an ion decayed to the metastable $^{2}D_{\frac{5}{2}}$ state, suddenly quenching its fluorescence. Most of the jumps mark Raman-Stokes scattering from the $^{2}S_{\frac{1}{2}}$ and $^{2}D_{\frac{3}{2}}$ levels.
487 citations
TL;DR: In this article, a renormalization scheme for the electroweak standard model is presented in which the electric charge and the masses of the gauge bosons, Higgs particle and fermions are used as physical parameters.
Abstract: A renormalization scheme for the electroweak standard model is presented in which the electric charge and the masses of the gauge bosons, Higgs particle and fermions are used as physical parameters. The photon is treated such that quantum electrodynamics is contained as a simple substructure. Field renormalization respecting the gauge symmetry gives finite propagators and vertex functions. The Ward identities between the Green functions of the unphysical sector allow a renormalization that maintains the simple pole structure of the propagators in the t'Hooft-Feynman gauge. We give a complete list of self energies and all renormalization constants also in the unphysical Higgs and ghost sector. Explicit results are given for the renormalized self energies, vertex functions and boxes that enter the evaluation of 1-loop radiative corrections to fermionic processes. We calculate the 1-loop radiative corrections to purely leptonic reactions like $\mu$ decay, $
u \mu \mu e$ scattering and $\mu$ pair production in $e^+ e^−$ annihilation. A test of the standard model is performed by comparing these low energy data with the results of the $p \bar{p}$ collider experiments for the W and Z boson masses.
352 citations
TL;DR: In this article, the authors compared 2nd-order QCD calculations with 3-and 4-jet models in the energy range of 14.0-46.7 GeV and showed that the observed excess of spherical events can partially be explained by the production of multi-parton events expected from higher order QCD contributions.
Abstract: Hadronic jet production bye+e−-annihilation has been studied in the energy range of 14.0–46.7 GeV. The data have been analysed in terms of a cluster algorithm and other topological quantities. The results are compared with 2nd order QCD calculations which incorporate models for the fragmentation of quarks and gluons into hadrons. At the higher energies we observe more spherical and 4-jet like events than predicted by these calculations. We cannot achieve a simultaneous description of the observed 3- and 4-jet production by adjusting the strong coupling constant αs or the fragmentation parameters of the 2nd order QCD models. The observed excess of spherical events can partially be explained by the production of multi-parton events expected from higher order QCD contributions. Consequences of the presented results for the value of αs, determined in previous analyses, are discussed. QCD parton shower models, including soft gluon interference, are able to describe the observed number of spherical events.
292 citations
TL;DR: A new chemolithotrophic nitrite-oxidizing bacterium, for which the name Nitrospira marina is proposed, was isolated from the Gulf of Maine.
Abstract: A new chemolithotrophic nitrite-oxidizing bacterium, for which the name Nitrospira marina is proposed, was isolated from the Gulf of Maine N marina is a Gramnegative curved rod which may form spirals with 1 to 12 turns Cells have a unique periplasmic space and lack intracytoplasmic membranes and carboxysomes N marina is an obligate chemolithotroph, but best growth is obtained in a mixotrophic medium N marina may be one of the most prevalent nitrite-oxidizing bacteria in some oceanic environments Type strain is field with American Type Culture Collection (ATCC 43039)
245 citations
TL;DR: In this article, a physically motivated condition on the energy-level density of well-localized states is proposed and discussed, and it is shown that any model satisfying this condition obeys a strong form of the principle of causal (statistical) independence, which manifests itself in a specific algebraic structure of the local algebras.
Abstract: Within the general framework of local quantum field theory a physically motivated condition on the energy-level density of well-localized states is proposed and discussed. It is shown that any model satisfying this condition obeys a strong form of the principle of causal (statistical) independence, which manifests itself in a specific algebraic structure of the local algebras (“split property”). It is also shown that the proposed condition holds in a free field theory.
240 citations
TL;DR: In this article, a gas-liquid chromatographic analysis of fatty acids and alcohols of lipid extracts is described, and the major and most of the minor compounds can be determined.
237 citations
TL;DR: In this paper, a search for decays of heavy neutrinos was conducted by the CHARM Collaboration in a prompt neutrino beam produced by dumping 400 GeV protons in a Cu target.
226 citations
TL;DR: The model simulates accurately macroscopic phenomena of traffic flow while at the same time reproducing the main mechanisms of microscopic models, making it possible to simulate large traffic networks on personal computers.
223 citations
TL;DR: The anatomical basis for this dissociation is the abundance of FNEs and absence of Merkel terminals and typical Meissner corpuscles in the covering of the glans, and the converse in glabrous skin of the digit.
218 citations
TL;DR: Investigation of Pancreatic specimens of nine patients suffering from multiple endocrine neoplasia type I found that among hormone‐positive tumors, pancreatic polypeptide tumors (PPomas), glucagonomas, and insulinomas were the most frequent, and Immunocytochemical screening revealed that the high incidence of PPomas in these pancreases probably accounts for the elevated serum PP levels found in many MEN I patients.
Abstract: Pancreatic specimens of nine patients suffering from multiple endocrine neoplasia type I (MEN I) were investigated with regard to tumor frequency and growth pattern, islet hyperplasia and endocrine cell neoformation, immunocytochemical hormone profile of the tumors, and correlation to clinical symptoms. The majority of the 201 tumors were microadenomas (diameter less than 0.5 cm), which frequently displayed a trabecular growth pattern. Microadenomatosis was considered the most distinct feature of the MEN I pancreas. Additional larger tumors (diameter greater than 1.0 cm) were found in five patients. Whereas islet hyperplasia appears not to belong to the spectrum of the pancreatic lesions in MEN I, nesidioblastosis was occasionally observed. Immunocytochemical screening revealed that among hormone-positive tumors (approximately 80% of the tumors), pancreatic polypeptide tumors (PPomas), glucagonomas, and insulinomas were the most frequent. The high incidence of PPomas in these pancreases probably accounts for the elevated serum PP levels found in many MEN I patients. Somatostatinomas, gastrinomas, vasoactive intestinal polypeptide tumors (VIPomas), and neurotensinomas were rare. Clinically overt hyperinsulinism, observed in two patients and associated with a large insulinoma, was cured by tumor resection. Eight of nine patients presented a Zollinger-Ellison's syndrome (ZES), but only in two patients were gastrin-producing tumors found. The source of gastrin in MEN I patients with a ZES, in whom no gastrinoma could be detected, remains unclear.
TL;DR: In the Salivary Gland Register, 10,944 cases were collected during 1965 and 1985 and 108 cases of metastatic tumors to the parotid and submandibular glands were found as discussed by the authors.
Abstract: The distinction between primary salivary gland tumors and metastases of other primary tumors in salivary glands is of special importance for therapy and prognosis. In the files of the Salivary Gland Register, 10,944 cases were collected during 1965 and 1985. Among these cases, there were 108 cases of metastatic tumors to the parotid and submandibular gland. The pathohistological analysis of these tumors revealed the following data: 47 cases (43%) of metastatic tumors were localized in the parenchyma of the parotid gland (37 cases) or of the submandibular gland (10 cases). 61 cases (57%) displayed metastases in the lymph nodes of the parotid gland (38 cases) or of the submandibular gland (23 cases). The sublingual gland was free of metastatic tumors. 65 metastatic tumors originated from primary tumors in the neighborhood (head and neck). 32 tumors were carcinomas of the skin, 17 tumors were melanomas, and 13 tumors were nasopharyngeal cancers. Metastases of thyroid cancers were found in 3 cases. The relative frequency of metastases in the lymph nodes of the salivary glands is due to the intense drainage with lymph vessels and the presence of many lymph nodes which are localized especially in the gland parenchyma or around the parotid gland. 21 metastatic tumors originated from primary tumors distant from the head and neck region. There were metastases of lung cancers (7 cases), renal cancers (6 cases), mammary cancers (6 cases), colonic cancer (1 case) and uterus cancer (1 case). Clear cell carcinomas in salivary gland tissue should always be checked for a metastasis of a primary renal cancer.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: In this article, it was shown that a state carrying an electric charge which can be determined with the help of Gauss' law cannot be an eigenstate of the mass operator.
TL;DR: The data support previous suggestions that actin is involved in virus budding and show that budding itself is possibly the result of a vectorial growth of actin filaments.
TL;DR: In this article, the free-running characteristics and the effective emission cross section of the Ti:Al2O3 were analyzed under argon-ion laser pumping and the temperature dependence of the 2E lifetime was measured from 4 to 650 K.
Abstract: Cw laser action of Ti:Al2O3 under argon-ion laser pumping is presented. We analyze the free-running characteristics and the effective emission cross section of the laser. The temperature dependence of the 2E lifetime was measured from 4 to 650 K and is explained in a single-phonon model. The quantum efficiency of Ti:Al2O3 at room temperature is 80%.
TL;DR: In this paper, suspended sediments from the Indus River collected during 1981 through 1983 were analyzed for POC and its constituent fractions including amino acids, amino sugars and sugars, and their contributions to POC varied between 2 and 60% for amino acids and amino sugars.
TL;DR: An optical fiber whose structure is similar to that of the PANDA fiber, but with two open channels in the place of the stress members, is investigated.
Abstract: An optical fiber whose structure is similar to that of the PANDA fiber, but with two open channels in the place of the stress members, is investigated. Variations of the internal or external gas pressure permit tuning of the fiber birefringence (10−4 rad m−1 Pa−1) over a wide range, including sign reversal, and application as a pressure sensor.
TL;DR: In this article, various acidic compounds were tested as potential initiators of the cationic polymerization of L,L-dilactide, and only trifluoromethanesulfonic acid and methyl triflate proved to be useful initiators.
Abstract: Various acidic compounds were tested as potential initiators of the cationic polymerization of L,L-dilactide. Regardless of solvent and temperature only trifluoromethanesulfonic acid and methyl triflate proved to be useful initiators. With methyl triflate as initiator L,L-dilactide polymerizes faster than diglycolide, whereas diglycolide is more reactive when anionic or complexing initiators are used. Initiation with methyl triflate yields poly(L-lactide) with methyl ester endgroups indicating that the chain growth proceeds via cleavage of the alkyl-oxygen bond. At polymerization temperatures > 100°C the resulting poly(L-lactide) is 100% optically active indicating that the chain growth does not proceed via free carbenium ions, but via triflate ester endgroups. All attemps to identify cyclic dioxocarbenium ions as reaction intermediates failed, because propagation is much faster than initiation. However, in nitromethane oligomers with triflate ester endgroups were detected. For comparison the reaction of γ-valerolactone with methyl triflate was studied by means of IR and 1H NMR spectroscopy. Methylation of the exocyclic oxygen yielding a cyclic dioxocarbenium ion was found to be the sole reaction.
TL;DR: One of the basic defects in acute pancreatitis is the uncontrolled release of enzymes from peripheral acinar cells into the interstitial space which, in turn, presumably by the action of lipase, leads to autodigestive fat necrosis.
Abstract: Human acute pancreatitis results from an autodigestive process frequently associated with alcohol abuse, gall stone disease and shock. Peripancreatic fat necrosis was identified as one of the earliest visible lesions, whereas acinar cell necrosis and haemorrhage were regarded as secondary changes. To examine the alterations in acinar cells in more detail, their enzyme content and fine structural features were studied immunocytochemically using antisera against α-amylase, lipase, trypsin, chymotrypsin and pancreatic stone protein, and electronmicroscopically in pancreatic tissues from patients with severe acute pancreatitis. Peripheral acinar cells in the immediate vicinity of fat necrosis were found to be heavily degranulated, while acinar cells at some distance of necrosis fully retained their enzyme content. Other frequent changes of the acinar cells included cuboidal transformation, loss of microvilli, increased occurrence of autophagosomes, and formation of enlarged acinar lumina. As there was no apparent cell membrane leakage or rupture of duct lumina, it is concluded that the acinar cells adjacent to fat necrosis release their granules by undirected basolateral extrusion. The findings thus suggest that one of the basic defects in acute pancreatitis is the uncontrolled release of enzymes from peripheral acinar cells into the interstitial space which, in turn, presumably by the action of lipase, leads to autodigestive fat necrosis.
TL;DR: In this article, a set of methods and numerical tools are discussed for a computer-based approach to perturbative calculations in lattice gauge theory, including automatic generation of gluon vertex programs, derivation of the Faddeev-Popov determinant on lattices with boundary, the use of a partially finite lattice with twisted boundary conditions as an infrared cutoff without zero modes, and finally the numerical extrapolation of lattice Feynman diagrams to the continuum limit.
TL;DR: In this paper, the adsorption of CO on pure and Ni-covered Cu(111) surfaces has been studied by means of LEED, TDS, UPS and work function measurements during adaption and desorption.
TL;DR: Of 1,453 such lesions found in 23,616 white persons over 35 years of age, the most common were palatal and mandibular tori, with a combined prevalence rate of 27.1%, and the prevalence of all oral masses was 61.4/1,000.
TL;DR: It is shown here that initiation of transcription of the mutant gene is reduced 20–100-fold, which indicates that the virus-induced change of chromatin structure in the promoter region of the Mutant gene prevents RNA polymerase from binding to its DNA template.
Abstract: Mov13 mice carry a single Moloney murine leukaemia virus (M–MuLV) proviral copy in the first intron of the α1(I) collagen gene. Virus insertion interferes with the synthesis of stable α1(I) collagen messenger RNA and causes a recessive lethal mutation1,2. The virus insertion has induced changes of the methylation pattern3 as well as the chromatin conformation in the mutated gene. Specifically, a DNase-hypersensitive site which is associated with active transcription of the wild-type collagen gene is not present in the mutant allele4. The block of collagen expression could be caused by virus-induced instability of collagen mRNA or by impaired initiation of transcription. To distinguish between these possibilities, we have compared the activity of the α1(I)collagen gene promoter in cell lines derived from wild-type and Mov 13 embryos by nuclear run-on transcription experiments and S1 mapping of nuclear RNA. We show here that initiation of transcription of the mutant gene is reduced 20–100-fold. This indicates that the virus-induced change of chromatin structure in the promoter region of the mutant gene prevents RNA polymerase from binding to its DNA template. Our results are consistent with the notion that the promoter-associated DNase-hypersensitive site is a prerequisite for rather than a consequence of gene activity.
TL;DR: A macrocyclic aminopolyether (Kryptofix®2.2.c.2.) supported labelling method for the preparation of n.a. [17-18F]- fluoroheptadecanoic acid is described, which allows a direct isolation of the product from the reaction mixture by means of reverse phase HPLC.
Abstract: A macrocyclic aminopolyether (Kryptofix®2.2.2.) supported labelling method for the preparation of n.c.a. [17-18F]- fluoroheptadecanoic acid is described. The equimolar complex of potassium carbonate and the aminopolyether ([2.2.2./K]+2;CO32-) is used to provide 18F-fluoride of high nucleophilicity in a homogeneous solution of acetonitrile. Nucleophilic 18F-for-Br substitution in the methylester of 17-bromoheptadecanoic acid is accomplished with radiochemical yields of 94 + 3%. Subsequent quantitative ester hydrolysis with KOH leads to a simple “one pot” procedure. Minimization of reagent concentrations allows a direct isolation of the product from the reaction mixture by means of reverse phase HPLC. The corrected radiochemical yield of high activity level routine production is 82 + 2% after 90 minutes of synthesis time. The specific activity is > 10,000 Ci/mmol.
TL;DR: Techniques for obtaining stable, relatively pure, haemocyte populations from the Lepidopterans, Manduca sexta and Galleria mellonella and the Dictyopteran, and the Blaberus craniifer have been developed.
TL;DR: Doplicher and Longo as discussed by the authors extended the construction of local generators of symmetries to space-time and supersymmetries, and established a weak form of Noether's theorem in quantum field theory.
TL;DR: Subinhibitory concentrations of trimethoprim-sulfamethoxazole increased the total yield of Shiga-like toxin (SLT), produced by Shigella dysenteria 1 and by enterophathogenic and enterohemorrhagic strains of Escherichia coli.
Abstract: Subinhibitory concentrations of trimethoprim-sulfamethoxazole increased the total yield of Shiga-like toxin (SLT), produced by Shigella dysenteria 1 and by enterophathogenic and enterohemorrhagic strains of Escherichia coli . Stimulation of SLT synthesis by trimethoprim-sulfamethoxazole was demonstrated by an increase in cytotoxic activity for HeLa cells and the diameter of the zone formed around bacterial colonies probed with monoclonal antibodies to SLT. Thus, supplementation of culture media with trimetroprimsulfamethoxazol will facilitate SLT purification and detection of SLT-producing bacteria.
TL;DR: In this paper, the steady-state limit of the stacking-fault energy of pure f.c. metals at intermediate and high temperatures was analyzed by analyzing the steady state limit for 〈 111 〉 single crystals.
TL;DR: In this paper, the microstructure and the mechanical properties of hot-pressed tetragonal ZrO/sub 2/ polycrystals (TZP) reinforced with up to 30 vol% SiC whiskers were studied.
Abstract: The microstructure and the mechanical properties of hot-pressed tetragonal ZrO/sub 2/ polycrystals (TZP) reinforced with up to 30 vol% SiC whiskers were studied. The SiC whisker-TZP composites were stable under the hot-pressing conditions at 1450/sup 0/C. Annealing in an oxidizing atmosphere at approx. =1000/sup 0/C resulted in glass formation and microcracking caused by whisker oxidation and transformation of the ZrO/sub 2/ grains near the whiskers to monoclinic symmetry. The fracture toughness was markedly improved by the dispersed whiskers (approx. =12 MPa.m/sup 1/2/ at 30 vol% SiC) compared to the values measured for the matrix (approx. = MPa.m/sup 1/2/) The flexural strength of the hot-pressed TZP-30 vol% SiC whisker composite at 1000/sup 0/C (approx. =400 MPa) was twice that of the TZP matrix.
TL;DR: The homogeneous Ziegler-Natta-catalysts, consisting of a zirconocene compound and methyl-aluminoxane, lead to extremely high polymerization activities as discussed by the authors.
Abstract: The homogeneous Ziegler-Natta–catalysts, consisting of a zirconocene compound and methyl-aluminoxane, lead to extremely high polymerization activities. With bis(cyclopentadienyl)zirconium dichloride pure atactic polypropylene and polyethylene with activities up to 30.106 g PE/g Zr·h are formed. The higher the degree of oligomerization of the aluminoxane the more active are the catalysts. The density of polyethylene (LLDPE) can be lowered by using 1-butene or 1-hexene as comonomers. Incorporation of dienes gives EPDM-elastomers. Highly isotactic polypropylene can be prepared by using chiral rac-ethylene bis–(tetrahydroindenyl) zirconium dichloride together with methylaluminoxane as cocatalyst. The toluene soluble part here consists of less than 0.2 weight percent. After resolution of this racemate it is also possible to produce optically active polypropylene and polybutene.