Search Results - (Author, Cooperation:J. Marcus)

2018-01-11

Wiley-Blackwell

2045-7758

Biology

2014-07-26

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

*Biological Evolution ; Humans ; Indians, North American/*genetics ; *Skeleton

2018-11-30

American Society of Hematology (ASH)

0006-4971

1528-0020

Biology

Medicine

Immunobiology and Immunotherapy

1540-8167

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

VF After Synchronized Internal Atrial Defibrillation. This case describes ventricular proarrhythmia as a result of a synchronized internal atrial defibrillation shock in a 29-year-old man with Ebstein's anomaly referred for radiofrequency ablation of a right posterior accessory pathway. During the electrophysiologic study, atrial fibrillation was induced and 3/3 msec shocks of various strengths were delivered between two decapolar defibrillation catheters in the coronary sinus and right atrial appendage. A 2.0-J biphasic shock synchronized to an R wave after a short-long-short ventricular cycle length pattern with a preshock coupling interval of 245 msec induced ventricular fibrillation, which was externally defibrillated with 200 J. This observation has implications for the development of implantable atrial defibrillators.

Electronic Resource

1540-8167

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Electronic Resource

1745-6584

Blackwell Publishing Journal Backfiles 1879-2005

Energy, Environment Protection, Nuclear Power Engineering

Geosciences

A hydrochemical study is outlined which demonstrates the mixing of two different ground-water types in the Lincolnshire Limestone aquifer. The two water types consist of a modern recharge water and an ancient possibly connate water. The hydrochemistry of the “interface zone” between the two waters is discussed in detail. In the younger water a relationship between sulphate reduction and bicarbonate is illustrated approaching the “interface zone” and is considered to be related indirectly to the mixing. Carbon isotope content is shown to be radically different in the various ground waters and supports the mixing hypothesis.

Electronic Resource

1745-6584

Blackwell Publishing Journal Backfiles 1879-2005

Energy, Environment Protection, Nuclear Power Engineering

Geosciences

Due to chemical reactions between steel casing and stored water in capped artesian wells, the pH, Eh, TDS, major and trace ion concentrations and saturation indices can be significantly, but relatedly altered from their aquifer values. To obtain true aquifer water samples, either all the stored water must be flushed from the well or a sampling tube must be used to ensure that the water is taken from within the aquifer. Flushing time can be calculated from well dimensions and best be monitored in the field by measuring temperature and electrical conductivity.This study has been made of confined wells in a fissured limestone, but the reactions which occur are likely to be common to aquifers of different hydrogeology.

Electronic Resource

1442-1984

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Abstract The flux of individuals within populations is dependent upon six controlling processes: the intrinsic rate of increase of the plant, intraspecific competition for resources, interspecific competition, natural enemies, mutualisms and refuge effects such as the immigration of seeds from other populations. Although population interactions are generally believed to play a major role in determining the flux of individuals within populations, little attempt has been made to quantify the strength of these interactions and their role in the dynamics of populations. In this paper we examine the role of competition, herbivory and mutualistic interactions in determining the dynamics of a range of annual plant species. Firstly, it is shown that the dynamics of three weed species (Bromus sterilis, Galium aparine, Papaver rhoeas) in an experimental community in an arable cropping system of winter wheat are determined primarily by the rapid population growth of B. sterilis. Interactions between the species play a minor part in the dynamics of the system. Secondly, it is shown that current levels of grazing by overwintering populations of brent geese have a minor impact on the abundance of Salicornia europaea, but that increased grazing has the potential to reduce abundance and increase the instability of S. europaea populations. This is a consequence of the aggregative response of the geese, which results in an increasing proportion of the seeds of S. europaea being eaten as plant density increases. Thirdly, it is shown that there is a complex interaction between root pathogenic and arbuscular mycorrhizal fungi in natural field populations of Vulpia ciliata and that the benefit of mycorrhizal fungi to the plant is in providing protection against pathogens.

Electronic Resource

0020-8027

Economics

0020-8027

Economics

1540-8159

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

We report a 51-year-old man with severe ischemia cardiomyopathy and heart failure in whom incessant bigeminal ventricular ectopy failed to generate a detectable arterial pressure. This created a mechanical bradycardia despite an adequate electrical heart rate. Dual chamber pacing increased the effective heart rate and allowed discontinuation of an intraaortic balloon pump from which the patient could not otherwise be weaned.

Electronic Resource

1540-8159

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Although changes in autonomic tone affect ventricular defibrillation, little is known about the effect of increased parasympathetic or sympathetic tone on the atrial defbrillation threshold. Methods: To evaluate the effect of reflexly increased parasympathetic and increase α- and β-adrenergic tone on the atrial defibrillation threshold (ADFT), atrial fibrillation was induced in 14 patients. ADFTs, right atrial refractory period (RARP), and monophasic action potential duration (MAPD) were determined before and after autonomic intervention. ADFTs were determined with a step-up protocol using 3/3-ms biphasic shocks delivered through decapolar catheters in the right atrial appendage and coronary sinus. Two groups were studied. Group I (N = 8) had ADFTs determined at baseline, after receiving phenylephrine (PE), and with PE plus atropine (A). Group 2 (N = 6) had ADFTs determined at baseline and after receiving isoproterenol (ISO). Results: Group I: PE significantly increased sinus cycle length (SR-CL) compared to baseline (742 ± 123 to 922 ± 233 ms) without significantly changing RARP, MAPD, or ADFT (2.3 ± 1.3 J vs 2.3 ± 0.8 J). With PE + A, SR-CL significantly decreased (529 ± 100 ms vs 742 ± 123 ms) and MAPD shortened (231 ± 41 ms vs 279 ± 49 ms) without altering RARP or ADFT (1.94 ± 0.9 J vs 2.25 ± 1.25 J). Group 2: ISO decreased SR-CL (486 ± 77 ms vs 755 ± 184 ms) and MAPD (169 ± 37 ms vs 226 + 58 ms) but not RARP or ADFT (2.25 ± 1.21 J vs 2.33 ± 1.75 J). Conclusions: Increasing parasympathetic, α-, or β-adrenergic tone does not affect the ADFT despite causing significant electrophysiological changes in the atria.

Electronic Resource

1540-8159

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

During testing of a CPI model 1715 ICD, an apparent sensing abnormality was noted following shock delivery for VF. Close inspection of the recording prior to the defib-rillation attempt revealed that the surface leads spontaneously lost 848 ms of data while the event marker was unaffected. Computer simulations revealed that an inadequate buffer size for the ampHfied (surface ECC) data was the likely source of data loss. It is important to recognize tbat a discordance between surface leads and event marker may represent an abnormality in tlie data acquisition system and simulate an ICD or lead malfunction.

Electronic Resource

1540-8167

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Bundle Branch Reentry and Interfascicular Reentry. A case of bundle branch reentry tachycardia with an unusual induction pattern is presented. Unlike typical cases of this arrhythmia in which tachycardia is usually inducible with routine programmed ventricular stimulation and/or short-long sequences, tachycardia in this case was inducible only with atrial stimulation. It also arose spontaneously during atrial flutter and during isoproterenol administration. After ablation of the right bundle, possible interfascicular reentry tachycardia with a similar induction pattern was observed. This tachycardia was successfully ablated in the region of the posterior fascicle of the left bundle branch.

Electronic Resource

1540-8167

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Implantable Atrial Defibrillators. Due to the limited efficacy of antiarrhythmic drugs for atrial fibrillation, several nonpharmacologic therapeutic options have evolved. One of these is an implantable atrial defibrillator. Recent studies have shown that internal atrial defibrillation is feasible with relatively low energies. To date, the optimal electrode configuration involves large surface area catheters in the right atrium and coronary sinus. In humans, atrial defibrillation can generally be achieved with 〈 2 J using this electrode configuration and a biphasic shock waveform. For shocks 〈 5 J, there is no significant pathological damage to the atria or coronary sinus. Further investigation is needed to guarantee that atrial defibrillation shocks do not provoke ventricular arrhythmias. Preliminary data suggest that atrial defibrillation shocks synchronized to R waves that are not closely coupled are safe. In addition, the shocks are well tolerated if the shock energy is 〈 1.5 J. With additional studies to confirm the safety of implantable atrial defibrillators, further reduce shock energy, and improve patient tolerance, an implantable atrial defibrillator can become an acceptable therapy for patients with symptomatic, paroxysmal atrial fibrillation.

Electronic Resource

1540-8167

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

RF Lesions From Cooled Electrode. Introduction: The delivery of radiofrequency (RF) energy through conventional catheter electrodes is often associated with coagulation necrosis at the tissue-electrode interface, with resultant impedance rise and limited lesion size. This study was performed to examine the effects of catheter tip cooling during RF delivery, to test the hypothesis that such cooling would decrease the likelihood of impedance rise and allow the creation of larger endomyocardial lesions. Methods and Results: The experiments were performed in eight open chest, anesthetized sheep. RF lesions were created within both ventricular chambers of each animal through a catheter tip that could he cooled with a saline perfusate. Assignment of cooled versus non-cooled RF delivery to either ventricle was alternated from one animal to the next. In each set of experiments, lesion volumes relative to the mode of RF delivery were compared. The mean power delivered via the cooled electrode (22.04 ± 4.51 W) was significantly higher than that delivered via the noncooled electrode (6.10 ± 2.47 W; P 〈 0.001). The mean duration of RF delivery was 42.7 ± 11.2 sec for noncooled lesions versus 49.2 ± 6.8 sec for cooled lesions (P 〈 0.01). Mean lesion volume was 436.07 ± 177.00 mm3 for noncooled RF delivery versus 1247.78 ± 520.51 mm3 for cooled RF delivery (P 〈 0.001). This significantly larger lesion size with cooled RF delivery was associated with no instance of impedance rise in 27 attempts versus 11 impedance rises in 28 attempts with noncooled RF (P 〈 0.001). Conclusions: Delivery of RF energy through a cooled catheter tip allows the creation of larger endomyocardial lesions by limiting the occurrence of impedance rise despite the delivery of greater energy. These observations suggest that, under certain conditions, resistive tissue heating at a distance from the site of current delivery may play an important role in RF ablation therapy.

Electronic Resource

1540-8159

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Limited information is available regardIng potential adverse Interactions between transvenous nonthoracotomy cardioverter defibrillators and pacemakers. We describe our experience with 37 patients who have undergone successful Implantation of both a transvenous defibrillator and pacemaker. The patients’mean age was 64 ± 12,9 years. Thirty-three were male and four were female. The mean LVEF wos 30.8%±11.8%, The indications for pacemaker implantation included sick sinus syndrome in 13 patients, complete heart block in 15 patients, sinus brady-cardia secondary to medications In 8 patients, and neurocardlogenlc syncope In 1 patient. The Indications for Insertion of a defibrillator Included medically refractory VT in 27 patients and sudden cardiac death in 10 patients. Twenty-three patients received an Endotak lead and 14 patients received o Transvene lead. Eighteen patients had a pacemaker prior to an ICD, 14 patients had an ICD prior to a pacemaker, and 4 patients had both devices placed simultaneously. Interaction was evaluated at Implant of the second device and 1–3 days after both devices were placed. Detection of VF/VT was analyzed during asynchronous pacing (DOO/VOO) with maximum pacing output. In addition, in six patients, DFT was determined before and after pacemaker implantation. In 14 patients (38%), device interactions that could not always be optimally corrected were observed. In five patients, the pacemaker was reset to the “noise reversion” mode after high energy ICD discharge, Oversensing of atrial pacemaker stimuli resulted in inappropriate ICD firings in four patients. This wos observed only with a specific device ond could not be prevented by atriol leod repositioning in two of them, but required reprogramming of the pacemaker to the VVImode. An increase in DFT was observed in five patients who had a pacemaker implanted after on ICD. Compared with previously published studies, a greater frequency of tronsvenous ICD and pacemaker Interactions were observed. Considering that almost 50% of the patients already have o pacemaker ot the time of ICD Implant, the ovalloblllty of deflbrlllotors with dual chamber pocing capability will not eliminate the potential for this problem.

Electronic Resource

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] Animals that forage socially often stand to gain from coordination of their behaviour. Yet it is not known how group members reach a consensus on the timing of foraging bouts. Here we demonstrate a simple process by which this may occur. We develop a state-dependent, dynamic game model of ...

Electronic Resource

0020-8027

Economics

0020-8027

Economics