Extrapolated Smoothing Descent Algorithm for Constrained Nonconvex and Nonsmooth Composite Problems*

In this paper, the authors propose a novel smoothing descent type algorithm with extrapolation for solving a class of constrained nonsmooth and nonconvex problems,where the nonconvex term is possibly nonsmooth. Their algorithm adopts the proximal gradient algorithm with extrapolation and a safe-guarding policy to minimize the smoothed objective function for better practical and theoretical performance. Moreover, the algorithm uses a easily checking rule to update the smoothing parameter to ensure that any accumulation point of the generated sequence is an (affine-scaled) Clarke stationary point of the original nonsmooth and nonconvex problem. Their experimental results indicate the effectiveness of the proposed algorithm.     

Surface characterization of cellulose fibres by XPS and inverse gas chromatography

Inverse gas chromatography (IGC) was used to determine the dispersive component of the free energy as well as the acid-base properties of cellulose fibre surfaces, before and after modification by corona treatment. It was found that the corona treatment increases both the dispersive contribution to surface energy and its acidic character, whereas only a slight increase in its basicity was observed. It was also found that some chemical degradation of the surface occurs at high corona currents. The extent of modification of the surface properties, as revealed by IGC, was correlated to the surface chemical composition deduced from XPS analysis as well as with the electrical conductance and the pH of the water suspensions of the cellulose fibres.     

Optimizing constrained subtrees of trees

Given a treeG = (V, E) and a weight function defined on subsets of its nodes, we consider two associated problems. The first, called the rooted subtree problem, is to find a maximum weight subtree, with a specified root, from a given set of subtrees.The second problem, called the subtree packing problem, is to find a maximum weight packing of node disjoint subtrees chosen from a given set of subtrees, where the value of each subtree may depend on its root.We show that the complexity status of both problems is related, and that the subtree packing problem is polynomial if and only if each rooted subtree problem is polynomial. In addition we show that the convex hulls of the feasible solutions to both problems are related: the convex hull of solutions to the packing problem is given by pasting together the convex hulls of the rooted subtree problems.We examine in detail the case where the set of feasible subtrees rooted at nodei consists of all subtrees with at mostk nodes. For this case we derive valid inequalities, and specify the convex hull whenk 4.Research supported in part by Nato Collaborative Research Grant CRG 900281, Science Program SC1-CT91-620 of the EEC, and contract No 26 of the programme Pôle d'attraction interuniversitaire of the Belgian government.     

Real-time onboard wind and windshear determination,part 2: Detection

This paper is concerned with windshear detection in connection with real-time wind identification (Ref. 1). It presents a comparative evaluation of two techniques, one based on the shear/downdraft factor and one based on the wind difference index. The comparison is done with reference to a particular microburst, that which caused the 1985 crash of Flight Delta 191 at Dallas-Fort Worth International Airport.The shear/downdraft factor has the merit of combining the effects of the shear and the downdraft into a single entity. However, its effectiveness is hampered by the fact that, in a real situation, the windshear is accompanied by free-stream turbulence, which tends to blur the resulting signal. In turn, this results in undesirable nuisance warnings if the magnitude of the shear factor due to free-stream turbulence is temporarily larger than that due to true windshear. Therefore, proper filtering is necessary prior to using the shear/downdraft factor in detection and guidance. One effective way for achieving this goal is to average the shear/downdraft factor over a specified time interval . The effect of on the average shear/downdraft factor is studied.     

Real-time onboard wind and windshear determination,part 1: Identification

Standard wind identification techniques employed in the analysis of aircraft accidents are post-facto techniques; they are processed after the event has taken place and are based on the complete time histories of the DFDR/ATCR data along the entire trajectory. By contrast, real-time wind identification techniques are processed while the event is taking place; they are based solely on the knowledge of the preceding time histories of the DFDR/ATCR data.In this paper, a real-time wind identification technique is developed. First, a 3D-kinematic approach is employed in connection with the DFDR/ATCR data covering the time interval preceding the present time instant. The aircraft position, inertial velocity, and accelerometer bias are determined by matching the flight trajectory computed from the DFDR data with the flight trajectory available from the ATCR data. This leads to a least-square problem, which is solved analytically every seconds, with / small.With the inertial velocity and accelerometer bias known, an extrapolation process takes place so as to predict the inertial velocity profile over the subsequent -subinterval. At the end of this subinterval, the extrapolated inertial velocity and the newly identified inertial velocity are statistically reconciled and smoothed. Then, the process of identification, extrapolation, reconciliation, and smoothing is repeated. Subsequently, the wind is computed as the difference between the inertial velocity and the airspeed, which is available from the DFDR data. With the wind identified, windshear detection can take place (Ref. 1).As an example, the real-time wind identification technique is applied to Flight Delta 191, which crashed at Dallas-Fort Worth International Airport on August 2, 1985. The numerical results show that the wind obtained via real-time identification is qualitatively and quantitatively close to the wind obtained via standard identification. This being the case, it is felt that real-time wind identification can be useful in windhsear detection and guidance, above all if the shear/downdraft factor signal is replaced by the wind difference signal (Ref. 1).This paper and its companion (Ref. 1) are based on Refs. 2–4.This research was supported by the Aviation Research and Education Foundation and by Texas Advanced Technology Program, Grant No. TATP-003604020.     

Fluorescence lifetimes of diphenylhexatriene-containing probes reflect local probe concentrations: Application to the measurement of membrane fusion

An important process in the life of a cell is fusion between cellular membranes. This is the process by which two cellular compartments surrounded by different membranes join to become a single compartment surrounded by a single membrane, without significant loss of compartment contents. To demonstrate fusion, the cell biophysicist must demonstrate all three critical aspects of the process: (1) mixing of membrane components, (2) mixing of compartment contents; and (3) retention of compartment contents. Most commonly, accomplishing this involves the use of fluorescence probes. The general theme to the methods described involves some form of concentration-dependent quenching. An unique method developed in our laboratory utilizes the concentration dependence of the fluorescence lifetime of a phosphatidylcholine containing carboxyethyl diphenylhexatriene at position 2 and palmitic acid at position 1 of glycerol (DPHpPC). The fluorescence lifetime of this molecule and that of its parent fluorophore diphenylhexatriene (DPH) shorten dramatically as their two-dimensional concentrations in a membrane increase. This lifetime quenching can be described by dimer formation that reduces the symmetry of the DPH excited state. This phenomenon allows one to use the fluorescence lifetime to gain insight into the local concentration of probe in microscopic regions of a membrane. One application of this is in distinguishing lipid transfer between the outer leaflets of two contacting membrane bilayers from fusion between these membranes that leads to mixing of lipids in both the inner and outer leaflets of the membrane bilayers. This allows a single measurement to demonstrate fusion between membrane pairs.Abbreviations PEG poly(ethylene glycol) - Na₂EDTA ethyiene-diamine-tetraacedic acid, disodium salt - LUV large, unilamellar vesicles made by rapid extrusion technique - DPH 1,6-diphenyl-trans-1,3,5-hexatriene - DPHpPC 1-palmitoyl-2-[[[2-[4- (phenyl-trans-1,3,5-hexatrienyl)phenyl]ethyl]oxy]carbonyl]-3-sn-phosphatidylcholine - DPPC 1,2-dipalmitoyl-3-sn-phosphatidylcholine - PA palmitic acid - NBD-PE N-(7-nitro-2,1,3-benzoxadiazol-4-yl)-PE - Rh-PE N-(lissamine Rhodamine B sulfoyl)-PE - R₁₈ octadecyl Rhodamine B chloride - ANTS 1-aminonaphthalene-3,6,8-trisulfonic acid - DPX N,N-p-xylylene-bis(pyradinium bromide)     

Time-resolved fluorescence relaxation of 3-methyllumiflavin in polar solution

We have studied the fluorescent properties of a well-defined model flavin compound (3-methyllumiflavin) in a relatively polar solvent like propylene glycol or ethanol. Inhomogeneous spectral broadening effects were directly time-resolved by detection at the extreme blue and red edges of the fluorescence band of 3-methyllumiflavin using excitation in the main absorption band. At the high-energy side of the emission band a rapid decay component (tens of picoseconds) was resolved indicative for the disappearance of the initially prepared, nonequilibrium state with a characteristic dipolar relaxation time. At the low-energy side the rise of a solvent relaxed fluorescent species could be time-resolved. The wavelength-dependent effects on the dipolar relaxation were abolished when excitation was at the low-energy side of the absorption band. The experimental decays of the flavin solvate at different energies of fluorescence and excitation are presented as they represent an easy diagnosis for energy dependent solvation dynamics. Wavelength dependent rotation of 3-methyllumiflavin, examined by fluorescence anisotropy decay, turned out to be absent for 3-methyllumiflavin in propylene glycol between 263 and 293 K, probably because of the small change in dipole moment upon flavin excitation.     

Direct analysis of thin-layer chromatographic spots of narcotics by means of diffuse reflectance Fourier transform infrared spectroscopy

The technique of diffuse reflectance Fourier transform infrared spectrometry (DRIFT) as an in situ detection method was used for the qualitative and quantitative analysis of drugs (heroin, cocaine and codeine) separated by thin layer chromatography.It was found that at a given interferometer throughput and detector sensitivity the quality of the spectrum depends strongly in the type of the chromatographic thin layer used. A detection limit of approx. 2 g was attained on a microcrystalline cellulose thin layer with a dynamically aligned Bio-Rad Digilab FTS 60A/896 type interferometer and room temperature DTGS detector. A reliable qualitative analysis can be made with as little as 10 to 15 g drug per spot.     

Evaluation of micellar liquid chromatography and capillary zone electrophoresis for dope control in sport

Micellar liquid chromatography (MLC) and capillary zone electrophoresis (CZE) have been evaluated for the analysis of twelve banned drugs in sport including diuretics and -blockers. In MLC, a sodium dodecylsulphate aqueous solution has been used as mobile phase using an octadecylsilica column. In CZE, a pH 8 buffer solution and a silica capillary have been employed. Parameters of retention and efficiency have been compared. Limits of detection with UV detection at 254 nm and relative standard deviations for atenolol, furosemide, nadolol, spironolactone and triamterene were established and compared in both techniques. Examples of direct urine injection into the separation systems are presented. Drugs overlapping in MLC are well resolved in CZE, while the opposite is true for a limited number of drugs. Some interferences from urine may arise in CZE. The selectivity of analysis would be greatly enhanced by using both techniques, which require only filtration as pre-treatment.     

Enantiomeric resolution of anti-HIV agents on a cellulose derivative chiral stationary phase

Summary Anti-HIV enantiomeric 1H, 3H-thiazolo[3, 4-a] benzimidazoles have been stereospecifically analyzed by elution on a column of cellulose tris-(4-methyl-phenylbenzoate)ester adsorbed on macroporous silica (Chiralcel^R OJ).The enantiomeric resolution of the compounds examined is linked to a complex and competitive contribution of different factors.