Crossover Technique Research Articles

Laser angioplasty of peripheral arteries after unsuccessful recanalization of the superficial femoral artery.

AIM: To demonstrate the range of applying laser angioplasty after unsuccessful recanalization of the superficial femoral artery (SFA) with conventional interventional techniques. MATERIALS AND METHODS: In a prospective trial in 94 cases with occlusion of the SFA and formerly unsuccessful conventional percutaneous transluminal angioplasty, laser angioplasty for recanalization was applied. The average occlusion length of the SFA was 17.5 cm (range 4-36 cm). The recanalization attempt was made using the crossover technique in 78 patients, in eight patients with the antegrade technique and in another eight patients using the transpopliteal technique. The primary recanalization attempt was performed with Terumo wires (curved and straight) as well as different catheters (Multipurpose/Vertebralis/Cobra). After the unsuccessful recanalization attempt the laser catheter was applied. RESULTS: The application of laser angioplasty demonstrated a successful recanalization of the SFA in 76/94 patients (80.9%). In 18 patients (19.1%) the recanalization was not possible even with percutaneous transluminal laser angioplasty (PTLA). The reason for the unsuccessful PTLA was in 10 cases due to obstructing calcified material, which was resistant to PTLA application. In four cases obstructing calcifications caused the laser catheter to be positioned in subintimal tissue, resulting in perforation of the SFA. In another four patients there was an aberrant anatomy of the SFA which resulted in a direct vessel injury after advancing the laser catheter. After a follow-up period of 12 months primary, primary-assisted and secondary patency rates were 50.0%, 65.8% and 73.7%, respectively. DISCUSSION: In primarily unsuccessful recanalization of the SFA, PTLA allows in 80% of cases a successful recanalization of the SFA. The technical success rate and the patency rate support the application of PTLA.

Variations on the "baby-sitter" procedure for reconstruction of facial paralysis.

Four cases of fresh facial paralysis were treated using the "baby-sitter" procedure, with fairly satisfactory results obtained. This procedure involves a combination of cross-face nerve grafting and a nerve cross-over technique such as using a hypoglossal-facial nerve or accessory-facial nerve anastomosis. Two stages are required. Nerve cross-over and cross-face nerve grafting using the sural nerve are performed in the first stage. After 1 year nerve anastomosis between the stump of the cross-face nerve graft and that of a buccal branch in the paralyzed cheek is performed during the second stage. The recovery of facial animation through this method is good, with patients able to create a near-natural smile. Electromyography demonstrates double innervation in the paralyzed cheek area.

An improved genetic algorithm for generation expansion planning

This paper presents a development of an improved genetic algorithm (IGA) and its application to a least-cost generation expansion planning (GEP) problem. Least-cost GEP problem is concerned with a highly constrained nonlinear dynamic optimization problem that can only be fully solved by complete enumeration, a process which is computationally impossible in a real-world GEP problem. In this paper, an improved genetic algorithm incorporating a stochastic crossover technique and an artificial initial population scheme is developed to provide a faster search mechanism. The main advantage of the IGA approach is that the "curse of dimensionality" and a local optimal trap inherent in mathematical programming methods can be simultaneously overcome. The IGA approach is applied to two test systems, one with 15 existing power plants, 5 types of candidate plants and a 14-year planning period, and the other, a practical long-term system with a 24-year planning period.

Withdrawal effects of antianginal therapy:: Comparison of isosorbide dinitrate and nifedipine

We compared the effects of abrupt cessation of nifedipine and isosorbide dinitrate therapy in patients with stable angina pectoris. Eighteen males were studied. Each patient received isosorbide dinitrate and nifedipine continuously for 5 weeks by randomised cross-over technique. Exercise treadmill tests were performed before each treatment period, at the beginning of treatment, 4 weeks after initiation of treatment and on the first and eighth days of drug withdrawal. At the end of treatment the antianginal effect of both agents attenuated (versus acute administration). Abrupt cessation of isosorbide dinitrate caused only a tendency towards decrease in exercise tolerance versus pre-treatment level. Alternatively, abrupt cessation of nifedipine resulted in substantial deterioration in exercise tolerance, which was statistically significant 21 and 24 h after the last dose administration. The number of anginal attacks increased >25% in two patients after cessation of isosorbide dinitrate and in eight patients after cessation of nifedipine. In no patient rest angina episodes appeared after stopping of isosorbide dinitrate, however, after stopping of nifedipine rest angina episodes appeared in three patients. We conclude that withdrawal phenomenon of nifedipine is much more pronounced than that of isosorbide dinitrate and may emerge on the first day of drug cessation. Such a phenomenon may be evident even in patients in whom nifedipine effect have attenuated due to the development of tolerance.

Multicriteria inventory classification using a genetic algorithm

One of the application areas of genetic algorithms is parameter optimization. This paper addresses the problem of optimizing a set of parameters that represent the weights of criteria, where the sum of all weights is 1. A chromosome represents the values of the weights, possibly along with some cut-off points. A new crossover operation, called continuous uniform crossover, is proposed, such that it produces valid chromosomes given that the parent chromosomes are valid. The new crossover technique is applied to the problem of multicriteria inventory classification. The results are compared with the classical inventory classification technique using the Analytical Hierarchy Process.

Self-crossover-a new genetic operator and its application to feature selection

Crossover is an important genetic operation that helps in random recombination of structured information to locate new points in the search space, in order to achieve a good solution to an optimization problem. The conventional crossover operation when applied on a pair of binary strings will usually not retain the total number of is in the offsprings to be the same as that of their parents, but there are many optimization problems which require such a constraint. In this article, we propose a new crossover technique called ‘self-crossover’, which satisfies this constraint as well as retaining the stochastic and evolutionary characteristics of genetic algorithms. This new operator serves the combined role of crossover and mutation. We have proved that self crossover can generate any permutation of a given string. As an illustration, the effectiveness of this new technique has been demonstrated for the feature selection problem of pattern recognition. Performance of self-crossover for feature selection is also compared with that of ordinary crossover

Genetic Algorithms for Large-Scale Clustering Problems

We consider the clustering problem in the case where the distances between elements are metric and both the number of attributes and the number of clusters are large. In this environment the genetic algorithm approach gives high quality clusterings, but at the expense of long running time. Three new and efficient crossover techniques are introduced here. The hybridization of the genetic algorithm and k-means algorithm is discussed.

Advanced engineered-conditioning genetic approach to power economic dispatch

Computational efficiency and reliability are the major concerns in the application of genetic algorithms (GAS) to practical problems. Effort has been made in two directions to improve the performance of GAs: the investigation of advanced genetic operators and the development of genetic algorithm hybrids. In this paper, an advanced engineered-conditioning genetic algorithm hybrid (AEC-GA) is proposed, which is a combination strategy involving local search algorithms and genetic algorithms. Moreover, several advanced techniques which enhance program efficiency and accuracy, such as elite policy, adaptive mutation prediction, nonlinear fitness mapping and different crossover techniques, are explored. Using power economic dispatch problems as a basis for comparisons, the outcome of the study clearly demonstrates the advantages of the AEC-GA.

Channel assignment in cellular radio using genetic algorithms

The channel assignment problem has become increasingly important in mobile telephone communication. Since the usable range of the frequency spectrum is limited, the optimal assignment problem of channels has become increasingly important. Recently Genetic Algorithms (GAs) have been proposed as new computational tools for solving optimization problems. GAs are more attractive than other optimization techniques, such as neural networks or simulated annealing, since GAs are generally good at finding an acceptably good global optimal solution to a problem very quickly. In this paper, a new channel assignment algorithm using GAs is proposed. The channel assignment problem is formulated as an energy minimization problem that is implemented by GAs. Appropriate GAs operators such as reproduction, crossover and mutation are developed and tested. In this algorithm, the cell frequency is not fixed before the assignment procedures as in the previously reported channel assignment algorithm using neural networks. The average generation numbers and the convergence rates of GAs are shown as a simulation result. When the number of cells in one cluster are increased, the generation numbers are increased and the convergence rates are decreased. On the other hand, with the increased minimal frequency interval, the generation numbers are decreased and the convergence rates are increased. The comparison of the various crossover and mutation techniques in a simulation shows that the combination of two points crossover and selective mutation technique provides better results. All three constraints are also considered for the channel assignments: the co-channel constraint, the adjacent channel constraint and the co-site channel constraint. The goal of this paper is the assignment of the channel frequencies which satisfied these constraints with the lower bound number of channels.

Investigation of hematite-serpentine and ilmenite-limonite concretes for reactor radiation shielding

This work is concerned with the study of the attenuation properties of hematite-serpentine and ilmenite-limonite concretes for fast neutrons and γ-rays. Investigations were carried out using a collimated reactor beam of neutrons and γ-rays. The neutrons and γ-spectra have been measured by a scintillation spectrometer with stilbene crystal. Discrimination against undesired pulses of γ-rays or neutrons was achieved by a zero crossover technique. The obtained data are displayed in the form of spectra and attenuation curves. The obtained results were also used to derive the total cross sections for fast neutrons and the linear attenuation coefficients for γ-rays. Two semiempirical formulae have been derived to calculate the integral flux for fast neutrons and γ-rays behind different thicknesses of any of the two types of concretes under investigations using the corresponding integral flux obtained for the other type. A good agreement between the calculated and the measured values was obtained.

XCORR: a cross-over technique to adjust track data : Shu-Kun Hsu, Computers & Geosciences, 21(2), 1995, pp 259–271

XCORR: a cross-over technique to adjust track data : Shu-Kun Hsu, Computers & Geosciences, 21(2), 1995, pp 259–271

XCORR: A cross-over technique to adjust track data

Cross-over errors (XOEs) from track data may give rise to pseudostructures in a contoured map. Such pitfalls can be reduced by adjusting all the measured values. FORTRAN programs are presented to determine automatically cross-over points (XOPs) and XOEs, to adjust XOEs to zero and to correct the data proportionally between every two XOPs.

A Comparative Study of Three Low-molecular Weight Heparins (LMWH) and Unfractionated Heparin (UH) in Healthy Volunteers

The levels of anti-IIa and anti-Xa activity, as reported in laboratory and clinical studies on low molecular weight heparin (LMWH) preparations, show a high degree of variability. This variation has been proposed as correlated to the variation in incidence of postoperative deep vein thrombosis (DVT) (8-30%) in different LMWH studies on comparable populations undergoing elective hip surgery. The aim of this study was to compare the ex vivo potency of Clexane (enoxaparin), Fragmin (dalteparin) and Logiparin (tinzaparin), applying the concept of bioequivalence, although unknown which activity/activities are best correlated to efficacy. Unfractionated heparin (UH) was included in the study as a reference drug. The drugs were studied with a cross-over technique in 12 healthy subjects and given subcutaneously in the doses recommended for orthopedic surgery. Blood samples were drawn each hour up to 10 h and at 12 h after administration. Anti-Xa and anti-IIa activities were measured using chromogenic substrate methods. The anti-Xa peak activity (Cmax) and the area under the curve (AUC) were highest for Clexane and Fragmin and lower for Logiparin and UH. Clexane and Fragmin were considered bioequivalent in anti-Xa activity. Regarding anti-IIa activity, no bioequivalence was found between the products. Fragmin was clearly different, with Cmax and AUC approximately twice as high as the other drugs. Whether the demonstrated differences in anti-Xa and anti-II activities are of any clinical significance remains unclear and can only be established by comparative clinical studies.

A comparison between classical cross-over techniques and a stochastic-deterministic approach

An alternative approach to classical cross-over adjustment was developed for small ocean basins such as the Baltic, the Mediterranean and the North Sea. This alternative approach is compared to a classical cross-over method in order to show advantages and disadvantages for each method in the three test areas. The comparison is done using simulated altimeter data which include white noise as a first step towards actual observations. The alternative approach depends on the availability of several selected tide gauges for which space coordinates (such as GPS data) are available. Several test configurations are considered for which associated criteria are established.

Modified crossover and guidewire loop technique for double-balloon angioplasty of the aortic bifurcation.

A modified form of crossover railroad technique is described for iliac and aortic bifurcation obstructions in which the iliac occlusion is crossed from the opposite side by a guidewire which is brought out through the ipsilateral puncture site. After forming a loop in the abdominal aorta, dilatation with two balloons is performed. This procedure was successfully performed in 2 patients having iliac artery occlusions and aortic bifurcation obstruction.

Valgus Knee Bracing for Medical Gonarthrosis

A double crossover study was designed and carried out on 39 patients to test the efficacy of valgus bracing using a GII brace in patients with medial gonarthrosis. Two brace designs were studied—one with a medial and one with a lateral hinge. The double crossover technique involved evaluating each p

Observations in the Canary Basin and the Azores frontal region using Geosat data

This paper discusses observations of the sea level in the Azores frontal region and the Canary Basin as seen by the Geosat altimeter frorn 5° to 45°W and 25° to 45°N. Two years of Geosat exact repeat data were processed by colocating the data on a 0.06° grid then removing the mean by the along track difference method and removing the orbit error by a crossover analysis technique. The data set was then interpolated by the successive correction method onto 15‐day, 0.5° maps to produce 47 residual height fields which were analyzed using complex empirical orthogonal functions (EOF) and spectral analysis. The results show that there is a region of high variability in the northwest corner reflecting the Gulf Stream extension and a region of medium variability at approximately 35°N reflecting the Azores Current. The variability changes only slightly throughout the year, with the winter season being the highest. The data set also shows first mode baroclinic Rossby waves between 30° and 35°N. There is evidence that these Rossby waves have different wavenumbers to the east and west of the Mid‐Atlantic Ridge. It is postulated that these waves have different generation mechanisms, the Mid‐Atlantic Ridge topography in the west and some other generation mechanism in the Canary Basin. Rossby waves are not apparent at 40°N.

Absolute calibration of accelerator beam energies by the crossover technique

An absolute method for the determination of the energy of a charged particle beam is described. The method is based on 0423 0450 V 2 scattering kinematics and exploits the variation with angle of the energy of particles scattered by elastic and inelastic processes 0423 0450 V 3 from different target nuclei. A determination of the angle at which particles scattered by two different reactions have the same 0423 0450 V 3 energy allows a precise calculation of the energy of the incident ion beam if the relativistic corrections are taken into account. A 0423 0450 V 3 simple system capable of supplying an absolute and accurate information on the beam energy in a short time has been designed and 0423 0450 V 3 tested. The system allows beam energy determinations over a wide energy range, from a few MeV up to several tens MeV and is not limited to some energy values in particular, in contrast with the use of resonance or threshold reactions. The system can in particular be employed for the calibration of accelerator beam energies in the energy interval typical of medium-energy commercial 0423 0450 V 3 cyclotrons, an increasing number of which are in operation in industry and in many fields of applied research. The paper briefly illustrates the theory underlying the “crossover” technique, describes the experimental apparatus and procedure and reports on experimental results for 12–36 MeV protons. The correction factors to be considered to fully exploit the accuracy of the technique 0423 0450 V 3 are discussed. The application of the method to the energy calibration of beams of deuterons and helium ions is described. A secondary and faster calibration procedure is also reported. This is derived from the main technique and can be routinely used once a number of energies have been determined and a sufficient data base of energy values has been built up. It is demonstrated that this secondary method is almost as accurate as the main technique.

A comparative clinical and pharmacokinetic study of a new slow-release versus conventional preparations of valproic acid in children with intractable epilepsy

Thirteen children with intractable epilepsy were treated by means of three-times-daily administration of a conventional preparation of valproic acid (C-VPA) and twice-daily administration of a new slow-release preparation of VPA (SR-VPA) with the cross-over technique. The frequency of seizures, side effect and steady-state pharmacokinetics of VPA were evaluated. With the change from C-VPA tid to SR-VPA bid, four patients exhibited a significant reduction in seizure frequency. The steady-state minimum concentration (Cmin) was higher, the maximum concentration (Cmax) lower and there were less diurnal fluctuations with SR-VPA, than with the respective values obtained in the C-VPA group, all the differences being statistically significant. Furthermore, a significant difference was unexpectedly found in the area under the curve (AUC) from 0 to 24 hours, the mean AUC in the period of SR-VPA being 9% higher than that with C-VPA. Five of the nine patients under 6 years of age showed more than 10% increase, and all four patients over 6 years of age less than 10% increase or a decrease in AUC. It was concluded that with SR-VPA bid, the pharmacokinetic features were more stable, the age-related AUC value was larger and the clinical effect was better than in comparison to C-VPA tid in children with intractable epilepsy.

Effects of Ipratropium Bromide Nebulizer Solution with and without Preservatives in the Treatment of Acute and Stable Asthma

In a recent study, it was suggested that the preservatives in ipratropium bromide nebulizer solution may cause a paradoxic bronchoconstrictor response in 20 percent or more of patients with stable asthma. The frequency of this response in patients with acute asthma is unknown. The aim of this study was to examine the acute effects of the usual dose of nebulized ipratropium bromide (0.25 mg) in patients with either stable or acute asthma using formulations with and without added preservatives. Twenty-five patients with stable asthma and 25 patients with acute asthma were studied. Each subject was given preservative-containing ipratropium bromide, preservative-free ipratropium bromide, pH 7 preservative-free ipratropium bromide, and saline solution in random order using a double-blind crossover technique with at least 4 h between drug administrations. Very frequent measurements of FEV1 were made for 30 min after each drug administration and then 5 mg of albuterol was nebulized and the FEV1 was measured again after another 30 min. Changes in FEV1 were expressed as a percentage of the predicted FEV1. Paradoxic bronchoconstriction to ipratropium was detected in only one patient with acute asthma (12 percent fall in FEV1) but in none of the patients with stable asthma. A 6 percent fall in FEV1 change occurred with the saline solution in this subject suggesting that the response may have been a nonspecific one due to increased bronchial responsiveness. The mean response (+/- 1 SD) to albuterol plus either preservative-containing ipratropium, preservative-free ipratropium, or pH7 preservative-free ipratropium was significantly greater (p less than 0.05) than the response to albuterol alone both in the patients with acute asthma (25 +/- 12 percent, 27 +/- 15 percent, 26 +/- 15 percent, and 20 +/- 15 percent, respectively) and stable asthma (26 +/- 7 percent, 25 +/- 8 percent, 24 +/- 6 percent, and 22 +/- 9 percent) supporting the use of ipratropium bromide as an additional bronchodilator in patients with asthma who do not show a satisfactory response to nebulized beta-adrenergic agonist.