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  • 1
    Electronic Resource
    Electronic Resource
    Notes on the Complexity of Exact View Graph Algorithms for Piecewise Smooth Algebraic Surfaces (1998)
    Springer
    Discrete & computational geometry 20 (1998), S. 205-229 
    Details
    ISSN: 1432-0444
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. The view graph of a surface N in 3-space is a graph embedded in the space ${\cal V}$ of centers or directions of projection, whose nodes correspond to maximal connected regions of ${\cal V}$ which yield equivalent views of N . The size of the view graph of a piecewise smooth algebraic surface N with transverse self-intersection curves and isolated triple-points and cross-caps is O(n K dim $\cal V$ d 6 dim $\cal V$), where n and d denote the number of ``component surfaces'' of N and their maximal degree, respectively, and where K=6 in general or K=3 for N diffeomorphic to the boundary of a polyhedron. (For surfaces without cross-caps, this bound has been established in [17].) Also, for the special piecewise linear case, where d=1 and K=3 , it is known that the size of the view graph is actually $\Theta$ (n3 dim $\cal V$). It is shown that the exact view graphs of such surfaces can be determined in O(n K(2 dim $\cal V$ +1)). $\cal P$ (d,L) time by a deterministic algorithm and in O(n K dim $\cal V +\epsilon$). $\cal P$ (d,L) expected time by a randomized algorithm. Here $\cal P$ is some polynomial, L is the maximal coefficient size of the defining polynomials of N , and ε is an arbitrarily small positive constant. Note that the randomized algorithm is, in terms of combinatorial complexity (where d and L are assumed to be constants which do not depend on n ), nearly optimal—its combinatorial time complexity exceeds the size of the view graph only by ε in the exponent. 〈lsiheader〉 〈onlinepub〉7 August, 1998 〈editor〉Editors-in-Chief: &lsilt;a href=../edboard.html#chiefs&lsigt;Jacob E. Goodman, Richard Pollack&lsilt;/a&lsigt; 〈pdfname〉20n2p205.pdf 〈pdfexist〉yes 〈htmlexist〉no 〈htmlfexist〉no 〈texexist〉no 〈sectionname〉 〈/lsiheader〉
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00009383
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  • 2
    Electronic Resource
    Electronic Resource
    Evidence for a constitutive, verapamil-sensitive, non-P-glycoprotein multidrug resistance phenotype in malignant glioma that is unaltered by radiochemotherapy in vivo (2000)
    Springer
    Acta neuropathologica 99 (2000), S. 555-562 
    Details
    ISSN: 1432-0533
    Keywords: Key words Glioma ; Multidrug resistance ; Chemotherapy ; Endothelial ; Blood brain barrier
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Human malignant gliomas are commonly resistant to chemotherapy. Here, we examined the role of the multidrug resistance (mdr) mechanism in the chemoresistance of these tumors, using a twofold approach: (i) by assessing a possible mdr phenotype before and after chronic drug exposure of glioma cells in vitro, and (ii) by assessing the modulation of expression of the mdr-associated P-glycoprotein (Pgp) using radiotherapy and serial cycles of chemotherapy in human glioblastoma patients in vivo. T98G, and to a lesser degree, LN-229 human malignant glioma cells exhibit a constitutive mdr phenotype as determined by the modulation of dye transport and by the augmentation of chemosensitivity by the mdr antagonist, verapamil. Thus, coexposure to verapamil enhances the cytotoxicity of vincristine, doxorubicin and VM26 in T98G cells and that of vincristine in LN-229 cells. Chronic exposure of the cells to low concentrations of vincristine and doxorubicin, but not VM26, topotecan or BCNU, moderately enhances the mdr-like phenotype, as assessed by drug expulsion assays. However, chronic exposure to increasing drug concentrations does not significantly alter the sensitivity to the respective drugs. These data are consistent with a constitutive, but not drug-inducible, mdr-like drug resistance in glioma cells in vitro. Immunocytochemical analysis of human malignant gliomas in vivo reveals that Pgp expression is more abundant in endothelial cells within the gliomas, than in the glioma cells proper. Importantly, Pgp expression is unaltered by radiochemotherapy, assessed by comparative immunocytochemistry of glioma specimens obtained serially before and after radiochemotherapy. We conclude that (i) glioma cells exhibit constitutive mdr-like drug resistance that is not significantly altered by chronic drug exposure in vitro; (ii) endothelial cells may play an important role in Pgp-mediated drug resistance of gliomas in vivo; (iii) radiotherapy and repeated chemotherapy cycles do not modulate Pgp expression in human malignant gliomas in vivo; (iv) there is preliminary evidence for a non-Pgp, verapamil-sensitive drug transport activity in glioma cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004010051160
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  • 3
    Electronic Resource
    Electronic Resource
    Arteriovenous haemofiltration: A new and simple method for treatment of over-hydrated patients resistant to diuretics (1977)
    Springer
    Journal of molecular medicine 55 (1977), S. 1121-1122 
    Details
    ISSN: 1432-1440
    Keywords: Niereninsuffizienz ; Diuretika ; Dyspnoe ; Ödeme ; Flüssigkeitsbilanz ; Hämofiltration ; Renal failure ; Diuretics ; Dyspnoea ; Oedema ; Fluid balance ; Haemofiltration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Fluid withdrawal in over-hydrated patients resistant to diuretics was obtained by means of a capillary haemofilter, using the arterio-venous pressure gradient for blood perfusion at a rate of 100 ml/min. The ultrafiltration rate was 200–600 ml/h and could be maintained as long as 48 h without changing the haemofilter. This method, which needs no technical investment, is easy and simple to handle for the physician, bears only a very low risk for the patient, and ensures a negative fluid balance even at a mean blood pressure of only 60 mm Hg.
    Notes: Zusammenfassung Unter Ausnutzung des arteriovenösen Blutdruckgradienten wurden überwässerte Patienten, bei denen eine Ausschwemmung mit Diuretika nicht mehr zu erreichen war, mit einem Kapillarhämofilter entwässert. Mit einer Blutperfusionsrate von 100 ml/min lag die Ultrafiltrationsrate bei 200–600 ml/h und konnte bis zu 48 h ohne Wechsel des Hämofilters aufrechterhalten werden. Der besondere Vorteil der arteriovenösen Hämofiltration liegt in der einfachen Handhabung für den Arzt und dem geringen Risiko für den Patienten im Vergleich zur maschinellen Hämofiltration. Eine technische Investition ist nicht erforderlich. Auch bei Blutdruckwerten um 60 mm Hg ist eine negative Flüssigkeitsbilanz möglich.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01477940
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  • 4
    Electronic Resource
    Electronic Resource
    Anwendung von niedermolekularem Heparin bei Hämodialysepatienten (1985)
    Springer
    Journal of molecular medicine 63 (1985), S. 49-55 
    Details
    ISSN: 1432-1440
    Keywords: Low-molecular-weight heparin ; Hemodialysis ; Coagulation ; Lipoproteinlipase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Low-molecular-weight (LMW) heparin has been compared to standard unfractionated (UF) heparin in a total of 49 patients on hemodialysis and hemofiltration in order to determine the necessary therapeutic dose and its effect on the coagulation system. A LMW heparin dose corresponding to 50% of the normal UF heparin dose was found to produce similar plasma heparin levels (anti-FXa-U/ml) in particular on minimal heparinization. At higher doses, UF heparin produced a more marked increase in plasma-heparin than did LMW heparin. Highly significant differences were found between UF and LMW heparin in their effects on PTT and thrombin time. Partial thromboplastin time (PTT) increased under UF heparin by an average of 120 s whereas LMW heparin only produced an increase of 5–7 s. Thrombin time was increased by 250–280 s under UF heparin and by 5–8 s under LMW heparin. With this LMW heparin dose of 50% of the UF heparin dose, no thrombosis of the extracorporal system occurred and no macroscopic detectable thrombotic material was found in the dialyzers or filters. No significant differences were observed between the effects of UF and LMW heparin on Factor VIII activity and fibrin monomers, so that a difference in coagulation activation between the two heparins can be excluded. Furthermore, there were no changes in thromboplastin time according to Quick, fibrinogen, antithrombin III, plasminogen, and a2-antiplasmin. Thus effective Anti-FXa levels and by similar antithrombotic activity, LMW heparin will probably present less of a bleeding risk because of its reduced effect on PTT and thrombin time. LMW heparin therefore appears to be a good alternative to UF heparin for patients with renal insufficiency requiring dialysis. LMW heparin is indicated in particular in patients at bleeding risk, with diabetic retinopathy, on therapy with oral anticoagulants or platelet aggregation inhibitors, and with thrombocytopenia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01733067
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  • 5
    Electronic Resource
    Electronic Resource
    Recognizing unstable equidimensional maps, and the number of stable projections of algebraic hypersurfaces (1999)
    Springer
    Manuscripta mathematica 99 (1999), S. 73-91 
    Details
    ISSN: 1432-1785
    Keywords: Mathematics Subject Classification (1991):58C27 (primary), 14J70 (secondary)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract: We study the recognition of -classes of multi-germs in families of corank-1 maps from n-space into n-space. From these recognition conditions we deduce certain geometric properties of bifurcation sets of such families of maps. As applications we give a formula for the number of -codimension-1 classes of corank-1 multi-germs from ℂ n to ℂ n and an upper bound for the number of stable projections of algebraic hypersurfaces in ℝ n +1 into hyperplanes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002290050163
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  • 6
    Electronic Resource
    Electronic Resource
    Generic properties of edges and “corners” on smooth greyvalue surfaces (1992)
    Springer
    Biological cybernetics 66 (1992), S. 497-502 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The edge line on a smooth greyvalue surface, defined as locus of maximal slope, is a curve embedded in the negatively curved part of the greyvalue surface. For an open and dense set of greyvalue functions the edge line has transverse double points as its only singular points, meets the parabolic curve tangentially at isolated points, and intersects the zero crossings of the Laplacean of the greyvalue function transversely. Defining a greyvalue corner as a curvature extremum of the edge line one can show that, again for an open and dense set of greyvalue functions, these corners are isolated points in the image corresponding to ordinary curvature extrema of the edge. Detecting such corners in greyvalue images requires differential operators containing partial derivatives of order five, which raises some doubts about the existence of numerically robust algorithms for detecting these features in digital images.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00204114
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  • 7
    Electronic Resource
    Electronic Resource
    Human visual navigation in the presence of 3-D rotations (1985)
    Springer
    Biological cybernetics 52 (1985), S. 377-381 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract We report on the ability of human observers in judging their direction of translation from sparse, moving random dot patterns for varying extents of 3-D rotation. The observers have to discriminate possible axes of translation with angular separations of 2.5 deg or 5 deg. The field of view is either 20x20 deg or 10x10 deg. The simulated observer movement is relative to two types of scenes. The first type consists of dots located on a single plane at a depth Z. The second type of scenes consists of dots located on two transparent planes at different depths Z and Z+dZ. Unlike in the single plane condition, where the judgements about the direction of translation deteriorate quickly as the magnitude of 3-D rotation increases, we find for movements relative to planes at different distances a stable performance over a range of rotational magnitudes. Moreover we find that a reduction of the field of view from 20x20 deg to 10x10 deg does not affect the judgements significantly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00449594
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of the Onsager coefficient and internal relaxation modes on spinodal decomposition in the high molecular isotopic blend polystyrene/deutero-polystyrene studied with small angle neutron scattering (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 5326-5337 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The early state of spinodal decomposition was studied by small angle neutron scattering in the critical mixture of the isotopic blend deutero-polystyrene/polystyrene (d-PS/PS) of equal molecular volume of 1.42×106 cm3/mol in a temperature range 12 K≤||Tc−T||≤82 K. This process can be described by the relaxation between two static structure factors, S(Q) representing the equilibrium values of the system in the mixed state and at the temperature where phase separation occurs. The time evolution of the relaxation process is described by the dynamical structure factor, L(Q,t) which depends on the dynamic properties of the mixture. It will be shown that the static structure factor of a mixed system can also be determined in the unstable two-phase region during the early state of spinodal decomposition. Consistent values for the Flory–Huggins parameter were found in comparison with a lower molecular d-PS/PS sample and, therefore, a lower critical temperature which was even smaller than the phase separation temperatures of the present system.The observed time evolution of the fluctuation modes is nonexponential. Therefore, it was originally supposed that internal modes of the coil come into play. The analysis of the data with an ansatz by Akcasu, which takes internal modes into account showed, however, that the phase separation in the experimental range of wave number and time is dominated by the centre of mass diffusion as in the C–H–C case and the nonexponential behavior was attributed to a time dependent increase of the "range'' of the Onsager coefficient. A range of the Onsager coefficient larger than the radius of gyration of a single coil is predicted in case of entangled polymers. However, no time dependence was predicted so far. The evaluated diffusion constants follow an Arrhenius behavior and are consistent with earlier studies. They show a D0∝N−2 scaling consistent with reptation. A further result is the observation of a second order peak in the structure factor already in the early times of spinodal decomposition. So far, this was only attributed to the late state of spinodal decomposition. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471262
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  • 9
    Electronic Resource
    Electronic Resource
    Ar ion beam and CCl4 reactive ion etching: A comparison of etching damage and of damage passivation by hydrogen (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 4282-4291 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Damage produced in single-crystal silicon by two distinctly different dry etching techniques, Ar ion beam etching and CCl4 reactive ion etching is characterized and compared using spectroscopic ellipsometry, reflected high- energy electron diffraction, and current-voltage (I-V) characteristics of Au contacts to the etched Si. Secondary ion mass spectroscopy is also used to further characterize the CCl4 exposed samples. The effectiveness of low-energy hydrogen ion implants in passivating this dry etching induced damage is explored. The restoration of I-V characteristics caused by H+ implants is correlated with the evolution of the spectroscopic ellipsometry, reflected high- energy electron diffraction, and secondary ion mass spectroscopy data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335513
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  • 10
    Electronic Resource
    Electronic Resource
    Epitaxial CaF2 on GaAs(100) after ambient transfer with arsenic overlayer (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 1655-1656 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By using an amorphous overlayer of arsenic, it is shown that a GaAs(100) wafer, with a layer of GaAs grown on it by molecular-beam epitaxy, can be satisfactorily transferred in the laboratory atmosphere from one ultrahigh vacuum chamber to another. The clean GaAs(100) surface is retrieved in the second chamber by low-temperature (350 °C) evaporation of the arsenic overlayer. An epitaxial layer of CaF2 was grown successfully on a smooth GaAs surface retrieved in this manner. This technique offers an opportunity to investigate GaAs/epifluoride/GaAs structures by transferring samples between the GaAs growth chamber and the fluoride growth chamber without subjecting them to a higher temperature (600 °C) cleaning process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338056
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