Intracranial microembolic signals during radiofrequency ablation of accessory pathways

Intracranial microembolic signals, probably caused by gaseous emboli, are readily detectable in patients undergoing radiofrequency ablation in the left side of the heart only. Clinical value of the detected signals could not be equivocably assessed, because only 2 of the patients who were examined (both emboli positive) had transient neurologic symptoms.     

An analytical/numerical approach for cracked elastic strips under concentrated loads — transient response

An analytical/numerical approach is presented for the determination of the near-tip stress field arising from the scattering of SH waves by a long crack in a strip-like elastic body. The waves are generated by a concentrated anti-plane shear force acting suddenly on each face of the crack. The problem has two characteristic lengths, i.e. the strip width, and the distance between the point of application of the concentrated forces and the crack tip. It is well-known that the second characteristic length introduces a serious difficulty in the mathematical analysis of the problem. In particular, a non-standard Wiener-Hopf (W-H) equation arises, that contains a forcing term with unbounded behaviour at infinity in the transform plane. In addition, the presence of the strip's finite width results in a complicated W-H kernel introducing, therefore, further difficulties. Nevertheless, a procedure is described here which circumvents the aforementioned difficulties and holds hope for solving more complicated problems (e.g. the plane-stress/strain version of the present problem) having similar features. Our method is based on integral transform analysis, an exact kernel factorization, usage of certain theorems of analytic function theory, and numerical Laplace-transform inversion. Numerical results for the stress-intensity-factor dependence upon the ratio of characteristic lengths are presented.     

A Method for the Delay Analysis of Random Multiple-Access Algorithms Whose Delay Process is Regenerative

Random multiple-access algorithms are used to control the accessing of a common communication channel by a large population of bursty channel users. For such algorithms, the induced transmission delay is a key performance measure. A systematic method for finding the delay characteristics of random multiple-access algorithms, whose delay process is regenerative, is presented. The method uses a powerful result from the theory of regenerative processes, in effect, to reduce the problem of determining the delay moments to the problem of solving denumerable dimensional systems of linear equations. Techniques for finding tight bounds on the solutions of such systems are presented. The "0.487" algorithm is used to exemplify the method.     

Scattering from two parallel cylinders of finite length

Contents The electromagnetic scattering of two conducting cylinders of finite length is examined. The two cylinders are placed with their axes parallel to each other. The integral equation is used for the determination of the current density on the cylindrical surfaces and on the bases of the cylinders. For the numerical computation the method of moments is applied [5]. The incident field has an abritrary direction. For the computation of the RCS a special technique is used, which is based on the symmetry of the configuration [3].

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Streuung an zwei parallelen Zylindern endlicher Länge

Übersicht Es wird die elektromagnetische Streuung an zwei leitenden Zylindern von endlicher Länge untersucht. Die beiden Zylinder liegen mit ihren Achsen parallel zueinander. Die Integralgleichung wird zur Bestimmung der Stromdichte der zylindirschen Oberflächen und der Grundflächen des Zylinders benutzt. Bei dem numerischen Rechenprogramm ist die Momentenmethode angewandt worden [5]. Das einfallende Feld hat eine willkürliche Richtung. Bei der Berechnung von RCS ist eine spezielle Technik angewandt worden, welche auf der Symmetrie des Gebildes basiert [3].

     

Resource-constrained production planning in semicontinuous food industries

The resource-constrained production planning problem in semicontinuous multiproduct food industries is addressed. In particular, the case of yogurt production, a representative food process, in a real-life dairy facility is studied in detail. The problem in question is mainly focused on the packing stage, whereas timing and capacity constraints are imposed with respect to the batch stage to ensure the generation of feasible production plans. A novel mixed discrete/continuous-time mixed-integer linear programming model, based on the definition of families of products, is proposed. Timing and sequencing decisions are taken for product families rather than for products; thus, reducing significantly the model size. Additionally, material balances are realized for every particular product, permitting the detailed optimization of inventory and operating costs. Packing units operate in parallel and share resources. Qualitative as well as quantitative objectives are considered. Several industrial case studies, including also some unexpected events scenarios, have been solved to optimality.     

Comparison of standard forearm prosthetic loop grafts to composite semiloop forearm grafts (“semi‐grafts”) in hemodialysis patients: A prospective study

Introduction: To prospectively assess the performance of composite semiloop antebrachial grafts (“semi‐grafts,” SGs) in hemodialysis patients. Methods: Eighty‐five patients who received 67 loop antebrachial grafts (LG‐group) and 25 antebrachial semigrafts (SG‐group) were enrolled. SGs were defined as those originating from the brachial artery and anastomosed with the proximal mature mid‐antebrachial cephalic vein. Cephalic vein length should be at least 10 cm in length and of ≥5 mm in diameter for inclusion in the SG‐group. LG‐group included all possible outflow vein options of minimum diameter 3 mm. Kaplan‐Meier statistics was used for comparison of groups. Findings: Main indication for a SG was a failing radiocephalic fistula with extensive distal cephalic vein stenosis not amenable to correction or failed after endovascular repair or requiring long interposition grafting. The mean follow‐up period was 20.16 ± 22.6 and 29.6 ± 36.7 months for the LG‐ and SG‐group, respectively (P = 0.14). Forty‐two patients died during the follow‐up. Primary patency (up to first intervention or failure) at 6 and 12 months for LG‐ vs. SG‐group was 93.9% vs. 83.7% and 47% vs. 55.8% (P = 0.08). Secondary patency (up to abandonment) was 58.2% vs. 61.1% and 36% vs. 45.8% at 12 and 24 months (P = 0.18). Mortality at 48 months was 22.4% (LG‐group) and 24% (SG‐group) (P = 0.9). Discussion: There was a trend toward better primary and secondary patency rates for the SGs especially in the long‐term. This is a valuable option in selected patients that access surgeons and nephrologists should be aware of.     

A Pan Photoaffinity Probe for Detecting Active Forms of Matrix Metalloproteinases

A photoaffinity probe based on the scaffold of a potent broad‐spectrum phosphinic peptide inhibitor of matrix metalloproteinases (MMPs) has been developed. A photolabile diazirine group for covalent modification of MMP active forms was incorporated at the P₁′ position, and a tritium radioactive label for the sensitive detection of MMP covalent adducts by radioimaging was attached. The probe was characterized on seven catalytic domains of human MMPs (MMP‐2, ‐3, ‐8, ‐9, ‐12, ‐13 and ‐14) and was found to display nanomolar affinities towards this set of MMPs, covalently modifying them with crosslinking yields varying from 12 to 58 %, thus leading to highly sensitive detection of these MMPs. In a complex proteome complemented with four recombinant MMPs (MMP‐2, ‐9, ‐12 and ‐13), this probe enabled their simultaneous detection with a threshold of few femtomoles and low background labelling. Those properties should make this new pan‐activity‐based MMP probe a valuable tool for the detection of MMP active forms from biological fluids or tissue extracts.     

Sensitivity of trace-element analysis by X-ray emission induced by 0.1–10 MeV electrons

Bremsstrahlung production cross sections have been calculated as a function of target and angle for electrons in the energy range 0.1–10 MeV. Used in conjunction with the corresponding K and L X-ray production cross sections and nonfundamental experimental quantities (detector resolution and ambient background), they allow determination of the theoretical detection limit using K or L X-ray emission induced by direct electron beam excitation.     

Energy-Aware Broadcast Trees in Wireless Networks

In this paper we address the problem of broadcasting in wireless networks, so that the power consumed by any node is as small as possible. This approach is motivated by the fact that nodes in such networks often use batteries and, hence, it is important to conserve energy individually, so that they remain operational for a long time. We formulate the problem as a lexicographic node power optimization one. The problem is in general NP-complete. We provide an optimal algorithm which runs in polynomial time in certain cases. We also provide a heuristic algorithm whose performance relative to the optimal one is fairly satisfactory. We next show that these algorithms can also be used to solve the problem of broadcasting so that the residual energy of any node after the broadcast process is as large as possible. Finally, we discuss the issues of implementing the above algorithms distributively, as well as their multicast extensions.     

Bifurcation predictions for moving cracks by the T-criterion

The directional instability of moving cracks was studied within the context of the maximum dilatational energy density, or T-criterion. To make bifurcation predictions according to the T-criterion theory it suffices to consider only the singular stress field. In this paper the stress field for a non-uniformly propagating crack under mode-I deformation was adopted. Predictions concerning both the critical crack velocity and the bifurcation angle was given. In this way, not only totally brittle fractures described previously by the S-criterion were correctly encountered, but also the results were extended to initially ductile materials where the T-criterion conserves its total efficiency.

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Résumé On a étudié l'instabilité directionnelle de fissures en cours de propagation, en recourant au critère d'énergie de dilatation maximum, ou critère T. Pour prédire les bifurcations de la fissure suivant le critère T, il suffit de considérer le champ de contraintes singulières. On a adopté dans la présente étude le champ de contraintes correspondant à une fissure se propageant de manière non uniforme sous une déformation de mode I. On fournit les prédictions de la vitesse critique de propagation et de l'angle de bifurcation de la fissure. De la sorte, on a non seulement retrouvé de manière correcte les résultats de rupture totalement fragiles décrits précédemment par le critère S, mais on a pu également élargir les résultats à des matériaux initialement ductiles, pour lesquels le critère T s'avère être parfaitement adapté.