Showing papers by "Chalmers University of Technology published in 1998"
TL;DR: In this paper, two-layer polymer diodes were fabricated by a lamination technique followed by controlled annealing, which achieved a short-circuit photovoltaic quantum efficiency of up to 29% at optimum wavelength and an overall power conversion efficiency of 19% under a simulated solar spectrum.
Abstract: Photoexcited electron transfer between donor and acceptor molecular semiconductors provides a method of efficient charge generation following photoabsorption, which can be exploited in photovoltaic diodes1,2,3 But efficient charge separation and transport to collection electrodes is problematic, because the absorbed photons must be close to the donor–acceptor heterojunction, while at the same time good connectivity of the donor and acceptor materials to their respective electrodes is required Mixtures of acceptor and donor semiconducting polymers3,4 (or macromolecules5) can provide phase-separated structures which go some way to meeting this requirement, providing high photoconductive efficiencies Here we describe two-layer polymer diodes, fabricated by a lamination technique followed by controlled annealing The resulting structures provide good connectivity to the collection electrodes, and we achieve a short-circuit photovoltaic quantum efficiency of up to 29% at optimum wavelength, and an overall power conversion efficiency of 19% under a simulated solar spectrum Given the convenience of polymer processing, these results indicate a promising avenue towards practical applications for such devices
1,303 citations
TL;DR: In this article, the fine-scale precipitation that occurs during age hardening of Al alloy 6061 has been studied using differential scanning calorimetry (DSC), APFIM and transmission electron microscopy (TEM).
1,115 citations
TL;DR: This work measures the kinetics of adsorption of small (12.5-nm radius) unilamellar vesicles onto SiO2, oxidized gold, and a self-assembled monolayer of methyl-terminated thiols, using a quartz crystal microbalance (QCM).
973 citations
TL;DR: A new type of electrometer is described that uses a single-electron transistor (SET) and that allows large operating speeds and extremely high charge sensitivity, and in some ways is the electrostatic "dual" of the well-known radio-frequency superconducting quantum interference device.
Abstract: A new type of electrometer is described that uses a single-electron transistor (SET) and that allows large operating speeds and extremely high charge sensitivity. The SET readout was accomplished by measuring the damping of a 1.7-gigahertz resonant circuit in which the device is embedded, and in some ways is the electrostatic “dual” of the well-known radio-frequency superconducting quantum interference device. The device is more than two orders of magnitude faster than previous single-electron devices, with a constant gain from dc to greater than 100 megahertz. For a still-unoptimized device, a charge sensitivity of 1.2 × 10 −5 e / hertz was obtained at a frequency of 1.1 megahertz, which is about an order of magnitude better than a typical, 1/ f -noise-limited SET, and corresponds to an energy sensitivity (in joules per hertz) of about 41 ℏ.
769 citations
TL;DR: In this article, a new quartz crystal microbalance instrument, allowing simultaneous frequency (f) and dissipation factor (D) measurements, has been used to study protein adsorption kinetics by measuring time-resolved data of both the D-factor, measuring energy dissipation due to the added overlayer, and the f-shift, measuring the effective mass load on the sensor.
Abstract: A new quartz crystal microbalance instrument, allowing simultaneous frequency (f) and dissipation factor (D) measurements, has been used to study protein adsorption kinetics by measuring time-resolved data of both the D-factor, measuring the energy dissipation due to the added overlayer, and the f-shift, measuring the effective mass load on the sensor. Four model proteins (myoglobin, hemoglobin, human serum albumin (HSA), ferritin) and one antibody−antigen reaction (antibody against HSA) were studied on a hydrophobic, methyl-terminated (−CH3) gold surface. In all five cases system-specific, positive D-shifts and negative f-shifts were observed, revealing different adsorption phases. The D-factor measurements provide new information about protein adsorption and improve the interpretation of the frequency shift in terms of mass uptake. Possible mechanisms for the adlayer-induced dissipation are discussed.
632 citations
TL;DR: It is shown that the targeted control element adopts an intrastrand fold-back DNA tetraplex, which requires potassium ions for stability in vitro, and proposed a transcription initiation mechanism that explains how anti-gene therapy silence c-myc at the molecular level.
Abstract: The c-myc oncogene is one of the most commonly malfunctioning genes in human cancers, and is an attractive target for anti-gene therapy. Although synthetic oligonucleotides designed to silence c-myc expression via one of its major control elements function well in vitro, their mode of action has been indefinite. Here we show that the targeted control element adopts an intrastrand fold-back DNA tetraplex, which requires potassium ions for stability in vitro. We believe formation of the tetraplex is important for c-myc activation in vivo, and propose a transcription initiation mechanism that explains how anti-gene therapy silence c-myc at the molecular level.
541 citations
TL;DR: In this paper, an incompressible SIMPLEC code is used with a non-staggered grid arrangement for the convective terms and the time discretization is implicit and a second-order Crank-Nicolson scheme is employed.
Abstract: Calculations of unsteady 2D flow around a square cylinder at incidence (α=0°−45°) are presented. The Reynolds numbers are low (Re=45–200) so that the flow is presumably laminar. A von Karman vortex sheet is predicted behind the cylinders with a periodicity which agrees well with experiments. An incompressible SIMPLEC code is used with a non-staggered grid arrangement. A third-order QUICK scheme is used for the convective terms. The time discretization is implicit and a second-order Crank–Nicolson scheme is employed. At the outlet of the computational domain a convective Sommerfeld boundary condition is compared with a traditional Neumann condition. The convective boundary condition is shown to be more effective in reducing the CPU time, reducing the upstream influence of the outlet and thus reducing the necessary downstream extent of the domain. A study of the effects of spatial resolution and blockage is also provided. The onset of vortex shedding is investigated by using the Stuart–Landau equation at various angles of incidence and for a solid blockage of 5%. A number of quantities such as Strouhal number and drag, lift and moment coefficients are calculated. © 1998 John Wiley & Sons, Ltd.
540 citations
TL;DR: The results suggest that the adsorbed proteins in the second layer were in a native-like state, demonstrating that the QCM technique provides unique information about the mechanisms of protein adsorption to solid surfaces.
Abstract: We have studied the adsorption of two structurally similar forms of hemoglobin (met-Hb and HbCO) to a hydrophobic self-assembled methyl-terminated thiol monolayer on a gold surface, by using a Quartz Crystal Microbalance (QCM) technique. This technique allows time-resolved simultaneous measurements of changes in frequency (f) (c.f. mass) and energy dissipation (D) (c.f. rigidity/viscoelastic properties) of the QCM during the adsorption process, which makes it possible to investigate the viscoelastic properties of the different protein layers during the adsorption process. Below the isoelectric points of both met-Hb and HbCO, the ΔD vs. Δf graphs displayed two phases with significantly different slopes, which indicates two states of the adsorbed proteins with different visco-elastic properties. The slope of the first phase was smaller than that of the second phase, which indicates that the first phase was associated with binding of a more rigidly attached, presumably denatured protein layer, whereas the second phase was associated with formation of a second layer of more loosely bound proteins. This second layer desorbed, e.g., upon reduction of Fe3+ of adsorbed met-Hb and subsequent binding of carbon monoxide (CO) forming HbCO. Thus, the results suggest that the adsorbed proteins in the second layer were in a native-like state. This information could only be obtained from simultaneous, time-resolved measurements of changes in both D and f, demonstrating that the QCM technique provides unique information about the mechanisms of protein adsorption to solid surfaces.
443 citations
TL;DR: The interaction of the fluorescent dye thiazole orange (TO) with nucleic acids is characterized and it is found that TO binds with highest affinity to double-stranded DNA and is about 5-10 times weaker to single- Stranded polypurines, and further 10-1000 times weakerto single-Stranded polypyrimidines.
Abstract: The interaction of the fluorescent dye thiazole orange (TO) with nucleic acids is characterized. It is found that TO binds with highest affinity to double-stranded (ds) DNA [log (K) approximately 5.5 at 100 mM salt], about 5-10 times weaker to single-stranded polypurines, and further 10-1000 times weaker to single-stranded polypyrimidines. TO binds as a monomer to dsDNAs and poly(dA), both as a monomer and as a dimer to poly(dG) and mainly as a dimer to poly(dC) and poly(dT). The fluorescence quantum yield of TO free in solution is about 2 x 10(-4), and it increases to about 0.1 when bound to dsDNA or to poly(dA), and to about 0.4 when bound to poly(dG). Estimated quantum yields of TO bound to poly(dC) and poly(dT) are about 0.06 and 0.01, respectively. The quantum yield of bound TO depends on temperature and decreases about threefold between 5 and 50 degrees C.
432 citations
29 Sep 1998
TL;DR: The system design exploits functional programming language features, such as monads and type classes, to provide multiple interpretations of circuit descriptions that implement standard circuit analyses such as simulation, formal verification and the generation of code for the production of real circuits.
Abstract: Lava is a tool to assist circuit designers in specifying, designing, verifying and implementing hardware. It is a collection of Haskell modules. The system design exploits functional programming language features, such as monads and type classes, to provide multiple interpretations of circuit descriptions. These interpretations implement standard circuit analyses such as simulation, formal verification and the generation of code for the production of real circuits.Lava also uses polymorphism and higher order functions to provide more abstract and general descriptions than are possible in traditional hardware description languages. Two Fast Fourier Transform circuit examples illustrate this.
409 citations
TL;DR: In this paper, the through-thickness variation at the weld and heat affected zone, of the axial and hoop stresses and their sensitivity to variation in weld parameters are studied.
TL;DR: The effect of film formation conditions on structure, mechanical properties and barrier properties of amylose and amylopectin films was studied in this article, where the films were prepared by solution-gel-casting of polyethylene glycerol (PEG) and polypropylene glycolic acid (PGA) from potato.
TL;DR: In this article, the authors take an empirical point of departure from recent findings regarding the positive relationship between technology diversification on the one hand and corporate growth and business diversification, and the findings are thus taken as an explanandum for a proposed approach to formulate a theory of the technology-based firm.
29 Sep 1998
TL;DR: Cayenne as mentioned in this paper is a Haskell-like language with dependent types, i.e., the result type of a function may depend on the argument value, and types of record components (which can be types or values) may be dependent on other components.
Abstract: Cayenne is a Haskell-like language. The main difference between Haskell and Cayenne is that Cayenne has dependent types, i.e., the result type of a function may depend on the argument value, and types of record components (which can be types or values) may depend on other components. Cayenne also combines the syntactic categories for value expressions and type expressions; thus reducing the number of language concepts.Having dependent types and combined type and value expressions makes the language very powerful. It is powerful enough that a special module concept is unnecessary; ordinary records suffice. It is also powerful enough to encode predicate logic at the type level, allowing types to be used as specifications of programs. However, this power comes at a cost: type checking of Cayenne is undecidable. While this may appear to be a steep price to pay, it seems to work well in practice.
TL;DR: If the production process is new to the company it is hypothesised that overall equipment effectiveness will be lower than if the company is already familiar with production process, and performance losses are the dominating ones.
Abstract: Assessment of disturbance data from production equipment provides valuable information for improving productivity. To implement total productive maintenance (TPM) it is necessary to assess the magnitude of different types of production losses, in order to direct activities and allocate resources in an optimal way. In many enterprises, the focus is directed towards major time losses due to break‐downs rather than minor losses in speed and time. A method for implementing data collection is to start gradually by a simple model and develop this to a combined model with computerised systems and manual recording. This gives both an exact assessment of the magnitude of the disturbance and a deeper understanding of the reason for losses. According to about 20 cases, the overall equipment effectiveness was only around 55 per cent. Further, it is quite clear that performance losses are the dominating ones. If the production process is new to the company it is hypothesised that overall equipment effectiveness will be lower than if the company is already familiar with production process.
TL;DR: In this article, it was shown that self-excitation of periodic cluster oscillations in conjunction with sequential processes of cluster charging and decharging appears for a sufficiently large bias voltage.
Abstract: Room-temperature Coulomb blockade of charge transport through composite nanostructures containing organic interlinks has recently been observed. A pronounced charging effect in combination with the softness of the molecular links implies that charge transfer gives rise to a significant deformation of these structures. For a simple model system, we show that self-excitation of periodic cluster oscillations in conjunction with sequential processes of cluster charging and decharging appears for a sufficiently large bias voltage. This new ``electron shuttle'' mechanism of discrete charge transfer gives rise to a current through the nanostructure which is proportional to the cluster vibration frequency.
TL;DR: In this paper, high-temperature reactions between straw ash and kaolin, Al 2 Si 2 O 5 (OH) 4, or dolomite, CaMg(CO 3 ) 2, respectively, were investigated.
Abstract: Straw of various types of rape, wheat and barley have been studied with respect to the formation of crystalline compounds and high-temperature reactions in ash, as well as sintering and melting behaviour. During the low-temperature ashing process simple, crystalline compounds such as carbonates, sulphates and chlorides were formed. A significant part of the ash from wheat and barley straw was amorphous whereas rape ash was found to be mainly crystalline. The large content of potassium compounds present in wheat and barley straw ash contributes to their low melting points. The ash components primarily formed are reactive. Solid state reactions at temperatures above 800°C lead to the formation of secondary products such as oxides and silicates. Minerals such as kaolin and dolomite have been suggested as fuel additives to give the ash a higher melting point. High-temperature reactions between straw ash and kaolin, Al 2 Si 2 O 5 (OH) 4 , or dolomite, CaMg(CO 3 ) 2 , respectively, were therefore investigated. Kaolin was found to be the more effective additive. The reaction between kaolin and potassium salts in straw ash gave KAlSiO 4 and KAlSi 2 O 6 . A laboratory study of reactions involving K 2 SO 4 or KCl and kaolin showed that several products are possible, one of which is KAlSiO 4 . The potassium capture by kaolin partly explains the higher melting point of the ash-additive mixture. Dolomite added to wheat and barley ash reacted with silica to form silicates. No reaction between dolomite and potassium compounds could be detected. The observed enhancement of the melting point caused by dolomite is probably an effect of dilution or adsorption.
TL;DR: In this article, the maximum packing fraction of force free fibers is estimated based on a statistical analysis of the distribution of fiber-fiber contact points, and the forced packing beyond this limit is governed by the bending of fiber segments between contact points.
Abstract: Theories of fiber packing, of use in manufacturing composite materials, are developed. The maximum packing fraction of force free fibers is estimated based on a statistical analysis of the distribution of fiber-fiber contact points. The new expressions are more general than previous ones by allowing for a distribution in fiber length and orientation. The forced packing beyond this limit is governed by the bending of fiber segments between contact points. A micromechanical theory is developed for this, again based on the contact point statistics, and equations relating the force response per unit area of a fiber bed to the fiber volume fraction are derived for three basic types of assembly: a general 3D wad, a planar mat of dispersed fibers, and a bundle of almost parallel fibers. Other types of reinforcement structure, such as woven fabrics, and the effect of lubrication are also treated briefly.
TL;DR: The structure suggests that the electrostatic interactions 'guide' the partners into a position that is optimal for electron transfer, and which may be stabilised by short-range interactions.
TL;DR: The potential of using a quartz crystal microbalance based technique for the characterization of living cells during the process of adhesion to a surface and the evolution of the dissipation factor in combination with resonant frequency is explored.
Abstract: We explore the potential of using a quartz crystal microbalance based technique for the characterization of living cells during the process of adhesion to a surface. The combined information from s...
TL;DR: In this article, a linear dichroism (LD) spectroscopy was used to study the DNA binding geometries for a series of enantiomerically purr substitution-inert ruthenium(II) complexes.
Abstract: The DNA binding geometries for a series of enantiomerically purr substitution-inert ruthenium(II) complexes, containing 1,10-phenanthroline (phen) and 2,2'-bipyridine (bpy) as ligands, have been studied with linear dichroism (LD) spectroscopy, Based on flow LD and emission anisotropy (EA) spectra of the complexes in the presence of calf thymus DNA, their absorption spectra in the visible region have been resolved into three component spectra that are polarized nearly perpendicular to each other. Spectral similarities between the D-3 symmetric [Ru(phen)(3)](2+) and C-2 symmetric [Ru(phen)(2)dppz](2+) (dppz dipyrido[3,2-a :2',3'-c]phenazine), in which dppz is known to be intercalated between the DNA basepairs, indicates a symmetry breaking in the former chromophore, bringing up the long debated question whether one of the three phen ligands of [Ru-(phen)(3)](2+) may be intercalated. Indeed, the complete analysis of the flow LD spectra for [Ru(L)(2)Y](2+) complexes (L bpy or phen) reveals similar angular binding geometries whether Y = dppz or phen. When Y = phen, for both the Delta- and Lambda-enantiomers this ligand is thus found oriented nearly perpendicular to the DNA helix axis as if intercalated and, similar to the orientation of dppz in dppz complexes, with a small but distinct clockwise rotation around the pseudo-dyad axis when viewed toward the minor groove ("positive roll"). A markedly less ordered binding observed when passing from [Ru(bpy)(2)phen](2+) to [Ru(bpy)(3)](2+) supports a stacking interaction of the phen ligand with the nucleobases. However, in contrast to the lengthening of DNA observed with [Ru(phen)(2)dppz](2+) and classical intercalators, the absence of lengthening with [Ru-(phen)(3)](2+) indicates that although a phen may have stacking interaction with the nucleobases, it does not enter a fully opened intercalation pocket. Two alternative binding modes are discussed: semi-intercalation (only edge of the intercalation pocket opened) and quasi-intercalation (indenture of a basepair allowing stacking of adjacent bases with the intruding phen ligand). Fair agreement is found between the proposed binding geometry of [Ru(phen)(3)](2+) and previously reported 2D-NMR NOE data.
TL;DR: In this paper, the effect of random fluctuations in the zero-dispersion wavelength is considered for fiber four-wave mixing and theoretical expressions for average parametric gain, phase-conjugation conversion efficiency, and gain bandwidth are obtained and found to be in good agreement with experiments.
Abstract: The effect of random fluctuations in the zero-dispersion wavelength is considered for fiber four-wave mixing. Theoretical expressions for average parametric gain, phase-conjugation conversion efficiency, and gain bandwidth are obtained and found to be in good agreement with experiments. Possible limitations on the noise figure in phase-sensitive amplifiers based on fiber four-wave mixing are also discussed.
TL;DR: In this paper, a study of waste water systems in Bergsjon, a Goteborg suburb, and Hamburgsund, a coastal village was carried out, and the results showed that the existing waste water treatment consists of mechanical, biological and chemical treatment.
Abstract: Life Cycle Assessment was applied to municipal planning in a study of waste water systems in Bergsjon, a Goteborg suburb, and Hamburgsund, a coastal village. Existing waste water treatment consists of mechanical, biological and chemical treatment. The heat in the waste water from Bergsjon is recovered for the district heating system. One alternative studied encompassed pretreatment, anaerobic digestion or drying of the solid fraction and treatment of the liquid fraction in sand filter beds. In another alternative, urine, faeces and grey water would separately be conducted out of the buildings. The urine would be used as fertilizer, whereas faeces would be digested or dried, before used in agriculture. The grey water would be treated in filter beds. Changes in the waste water system would affect surrounding technical systems (drinking water production, district heating and fertilizer production). This was approached through system enlargement. For Hamburgsund, both alternatives showed lower environmental impact than the existing system, and the urine separation system the lowest. Bergsjon results were more difficult to interpret. Energy consumption was lowest for the existing system, whereas air emissions were lower for the alternatives. Water emissions increased for some parameters and decreased for others. Phosphorous recovery was high for all three alternatives, whereas there was virtually no nitrogen recovery until urine separation was introduced.
TL;DR: In this paper, the authors focus on processes in large circulating fluidized bed combustors, and especially on mixing between fuel and air, which is important for combustion but also for sulphur capture through the formation of reducing zones.
03 May 1998
TL;DR: Two stochastic assessment methods for voltage sags are discussed and applied to a 98-bus model of the 400 kV National Grid of England and Wales and it is shown that the method of critical distances is an acceptable alternative were software or system data are not available for a more accurate analysis.
Abstract: In this paper we discuss two stochastic assessment methods for voltage sags and apply them to a 98-bus model of the 400 kV National Grid of England and Wales. The method of fault positions is most suitable for implementation in a software tool. It has been used to get exposed areas and sag frequencies for each bus. The results are resented in different ways, including a so-called voltage sag map showing the variation of the sag frequency through the network. The method of critical distances is more suitable for hand calculations, as both the amount of data and the complexity of the calculations are very limited. It has been used to obtain sag frequencies for a number of buses. A comparison with the results obtained by using the method of fault positions, shows that the method of critical distances is an acceptable alternative were software or system data are not available for a more accurate analysis.
17 May 1998
TL;DR: In this article, a control principle for a voltage source converter connected to the grid through an LCL-filter is presented, and the dynamic performance is compared with the performance obtained with an L-filter and a dead-beat vector control system.
Abstract: In this paper, a control principle for a voltage source converter connected to the grid through an LCL-filter is presented. The dynamic performance is compared with the performance obtained with an L-filter and a dead-beat vector control system. Measured frequency responses and an active filtering operation verify the control principle. By using an LCL-filter, high attenuation of harmonics caused by the PWM and high dynamic performance can be obtained simultaneously. Different methods for active filtering are compared. It is advantageous to use a Fourier-method since it allows for compensation for time delays occurring in the control system in the frequency domain. By using the LCL-filter along with compensation for time delays in the frequency domain, active filtering can be performed at moderate switching frequencies. This is a major advantage in systems, such as a rectifier with an active filtering option.
TL;DR: In this paper, the ground state and the first singlet excite state of adenine and 2-aminopurine were calculated with three different quantum chemical methods: AM1, CIS/6-31G, and CASSCF/6 -31G.
Abstract: The geometry of the ground state and the first singlet excite state of adenine and 2-aminopurine was calculated with three different quantum chemical methods: AM1, CIS/6-31G, and CASSCF/6-31G. Three possible deactivation mechanisms or reactions of excited molecule were considered: the pseudo Jahn−Teller distortion, excited-state tautomerism, and formation of so-called twisted intramolecular charge transfer (TICT) states. Different mechanisms for the nonradiative decay are operative for the two isomers. The geometrically relaxed excited state of adenine has n → π* character, while it has π → π* character for 2-aminopurine. The state crossing that occurs during the excited-state relaxation of adenine opens up an effective nonradiative deactivation channel not present for 2-aminopurine. Tautomerism in the excited state might explain the difference in luminescence quantum yield upon DNA binding for 2-aminopurine. The excited state of the 7H tautomer of adenine undergoes a large geometry change during the re...
TL;DR: In this article, the authors evaluate the applicability of life cycle assessments (LCAs) on recycling and incineration with energy recovery of paper packaging materials, and discuss lessons learned that can be applied to other materials.
Abstract: Recently published life-cycle assessments (LCAs) on recycling and incineration with energy recovery of paper packaging materials are used as examples in order to discuss the usefulness of LCAs. The type of information that can typically be produced by an LCA is described. The reproducibility of LCAs is evaluated and reasons for possible discrepancies between LCAs are discussed. An attempt is also made to make conclusions on advantages to the environment of recycling versus incineration of paper packaging materials, and discuss lessons learned that can be applied to other materials. In all seven studies, including 12 cases and 27 scenarios, total energy use is consistently lower when paper packaging materials are recycled rather than incinerated. Other, differing results can be explained by the assumptions made concerning the energy source used instead of the energy from incineration when paper is recycled instead of incinerated (called `the alternative energy source'). If fossil fuels are the alternative energy source, incinerated paper replaces fossil fuels, and emissions of CO2 can be decreased. If, on the other hand solid waste (which in other cases would have been landfilled), or biofuels are the alternative energy source, fossil fuels will not be replaced. In these cases, increased recycling will in general lead to decreased emissions of greenhouse gases. It is suggested that the alternative energy source for the near future is usually solid waste. In the longer term this depends on political decisions on waste management in general. Studies which address the issue of transportation consistently conclude that as long as it is reasonably efficient, transportation will not have any effect on the conclusions. It is noted that not all relevant environmental impacts are considered in the studies reviewed. This is one reason why none of the discussed LCAs can alone be used to determine the environmental preference of the alternatives studied. Another reason is that the question is too narrow. The ranking order by environmental impact of the alternatives may depend on other policy decisions. Some of the LCAs can however be used to identify key issues, i.e. critical aspects which need further study or should be considered when choosing between recycling and incineration. Equally important, some of the LCAs can be used to identify aspects which are of limited importance for the decision. It is suggested that this is typical for current LCAs and presumably also for future ones.
TL;DR: Norfloxacin, a quinolone antibacterial reagent, has been studied with respect to its binding to calf thymus DNA using fluorescence and linear dichroism techniques and unwinding of supercoiled DNA.
Abstract: Norfloxacin, a quinolone antibacterial reagent, has been studied with respect to its binding to calf thymus DNA using fluorescence and linear dichroism techniques and unwinding of supercoiled DNA. The fluorescence of norfloxacin is strongly quenched in the presence of DNA and using this decrease in a fluorescence titration the equilibrium constant of the complex formation was established to be 2.8 x 10(3) M-1. The electric transition moments of the norfloxacin chromophore have been analyzed using fluorescence anisotropy, magnetic circular dichroism, and linear dichroism in stretched poly(vinyl alcohol) film and INDO/S calculations. These data are then used to interpret flow linear dichroism results for the norfloxacin-DNA complex. The transition moments for the long-wavelength transitions are found to be oriented at about 65.0-85.0 degrees with respect to the DNA helix axis. A near perpendicular orientation of the norfloxacin chromophore plane makes it possible to exclude classical groove or surface binding modes. The possibility of a classical intercalation binding mode also can be ruled out from unwinding experiments. However, it is shown that the molecular plane of norfloxacin is near perpendicular relative to the DNA helix axis with a possibility of a bending of the DNA helix at the binding site.