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  • 1
    Electronic Resource
    Electronic Resource
    Silicon Carbide: A Playground for 1D-Modulation Electronics (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 527-529 (Oct. 2006), p. 355-358 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Optoelectronic devices with 1D modulation of the potential through hetero-structure ordoping superlattices have so far been the privilege of III-V semiconductors. Based on the fact thatSiC can be grown monolayer by monolayer, and that Si–Si and C–C double layers have been observedin it, we suggest the possibility of a stress-free polarization superlattice, consisting of theperiodic variation of Si-face and C-face domains along the hexagonal axis of 4H-SiC. Such a structurecould, in principle, be grown by molecular source atomic layer epitaxy. Investigating suchsuperlattices by density functional theory, using a hybrid functional, we show that Si–Si and C–Cdouble layers at the antiphase boundaries confine electrons within ~0.5 nm, and the periodic polarizationfield causes zig-zag shaped band edges which gives rise to tunable absorption, to spatialseparation of free electrons and holes, as well as to optical nonlinearity. These properties couldallow the application of SiC also in optoelectronics and photonics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/13/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.527-529.355.pdf
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  • 2
    Electronic Resource
    Electronic Resource
    The DNA sequence of the human X chromosome (2005)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 434 (2005), S. 325-337 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The human X chromosome has a unique biology that was shaped by its evolution as the sex chromosome shared by males and females. We have determined 99.3% of the euchromatic sequence of the X chromosome. Our analysis illustrates the autosomal origin of the mammalian sex chromosomes, the stepwise ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature03440
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  • 3
    Electronic Resource
    Electronic Resource
    Functional profiling of the Saccharomyces cerevisiae genome (2002)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 418 (2002), S. 387-391 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Determining the effect of gene deletion is a fundamental approach to understanding gene function. Conventional genetic screens exhibit biases, and genes contributing to a phenotype are often missed. We systematically constructed a nearly complete collection of gene-deletion mutants (96% of ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature00935
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  • 4
    Electronic Resource
    Electronic Resource
    Relationship Between Shock Energy and Postdefibrillation Ventricular Arrhythmias in Patients with Implantable Defibrillators (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 10 (1999), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Postdefibrillation Ventricular Arrhythmias. Background: The relationship between postdefibrillation ventricular arrhythmias and shock strength is poorly understood in patients with implantable defibrillators. The purpose of this study was to characterize the relationship between postdefibrillation ventricular arrhythmias and shock strength. Methods and Results: Forty-three patients with an implanted defibrillator underwent six separate inductions of ventricular fibrillation (VF) after a step-down defibrillation energy requirement (7.3 ± 4.6 J) was determined. For each of the first three inductions of VF, the first two shocks were low energy and equal to approximately 75 % of the defibrillation energy requirement (5.4 ± 3.3 J), or to the defibrillation energy requirement plus 10 J (17.5 ± 4.3 J). After the first two shocks, subsequent shocks were programmed to the maximum available energy (29.0 ± 2.5 J). The alternate technique was used for the subsequent three inductions of VF. Post defibrillation ventricular arrhythmias were noted. Post defibrillation ventricular arrhythmias with a cycle length ≤ 300 msec were more frequent after a low-energy shock (19%), than after a high-energy shock (1.5 %; P = 0.005). Postdefibrillation ventricular arrhythmias with a cycle length 〉 300 msec were more frequent after a high-energy shock (32%), than after a low-energy shock (7.1%; P = 0.002). A relationship between the cycle length of the post defibrillation ventricular arrhythmias and the absolute defibrillation energy was observed (P 〈 0.001; r = 0.6), and ventricular arrhythmias with a cycle length 〉 300 msec were uncommon after shocks ≤ 10 J (P = 0.001). The characteristics of ventricular arrhythmias after maximum-energy shocks were similar to those that occurred after high-energy shocks. Conclusions: Post defibrillation ventricular arrhythmias with a cycle length ≤ 300 msec are more common after shocks of strength associated with a low probability of successful defibrillation. Postdefibrillation ventricular arrhythmias with a cycle length of 〉 300 msec are more common after high- and maximum-energy shocks, and are directly related to the absolute defibrillation energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1999.tb00685.x
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  • 5
    Electronic Resource
    Electronic Resource
    Clinical Observations with Long-term Atrial Pacing (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 21 (1998), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Atrial pacing (AP), despite its beneficial hemodynamic and antiarrhythmic effect, is still an underused mode of stimulation. The main purpose of this study was to evaluate the long-term results of AP. Sixty four patients (pts) with sinus node disease (28 male and 36 female: mean age 54,2; range:44–88 years), 3,2% of the total implantation at our clinic were treated with AP between 1982–96. Criteria for atrial pacing were: no AV block in the history, no AV-block during carotid sinus massage, Wenckebach point 〉 130/min, left atrium 〈50mm, left ventricular EF 〉40%. The indication for pacing was predominant sinus bradycardia (SB) in 34 pts and tachycardia-bradycardia syndrome (TBS) in 30 pts. Pts with TBS were on antiarrhythmic treatment, while most pts with SB received no antiarrhythmic drugs. All the pts were checked up at every 3–6 month. Sixty-two pts were followed for 3–154 (mean: 67) months, two pts were lost for follow-up. Repeated lead dislodgment occurred in two pts, which made a pacing mode change necessary. Four pts died during the follow-up period for non-cardiac reasons. At the end of the follow-up period the data of 60 pts were available for evaluation (33 pts with SB, 27 pts with TBS). All the pts with SB were in sinus rhythm, and no patient developed AV block by the end of the follow-up period Seven out of 27 pts with TBS developed chronic atrial fibrillation, 3 out of them suffered a cerebral embolism; the remaining 20 pts were in sinus rhythm, and the number of paroxysmal attacks decreased significantly, which improved their quality of life significantly. Three pts in this group developed a temporary complete AV block, which regressed with decreasing the dosage of antiarrhythmic drugs. Atrial pacing is proved to be a safe and reliable treatment for sick sinus syndrome. Proper patient selection is crucial in preventing the development of AV conduction disturbance. Atrial stimulation had a satisfactory long-term antiarrhythmic effect in pts with sick sinus syndrome (SSS).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1998.tb01097.x
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of Ventricular Shock Strength on Cardiac Hemodynamics (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 9 (1998), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Ventricular Defibrillation and Cardiac Function. Introduction: The effect of implantable defibrillator shocks on cardiac hemodynamics is poorly understood. The purpose of this study was to test the hypothesis that ventricular defibrillator shocks adversely effect cardiac hemodynamics. Methods and Results: The cardiac index was determined by calculating the mitral valve inflow with transesophogeal Doppler during nonthoracotomy defibrillator implantation in 17 patients. The cardiac index was determined before, and immediately, 1 minute, 2 minutes, and 4 minutes after shocks were delivered during defibrillation energy requirement testing with 27- to 34-, 15-, 10-, 5-, 3-, or 1-J shocks. The cardiac Index was also measured at the same time points after 27- to 34-, and 1-J shocks delivered during the baseline rhythm. The cardiac index decreased from 2.30 ± 0.40 L/min per m2 before a 27- to 34-J shock during defibrillation energy requirement testing to 2.14 ± 0.45 L/min per m2 immediately afterwards (P= 0.001). This effect persisted for 〉4 minutes. An adverse hemodynamic effect of similar magnitude occurred after 15 J (P= 0.003) and 10-J shocks (P= 0.01), but dissipated after 4 minutes and within 2 minutes, respectively. There was a significant correlation between shock strength and the percent change in cardiac index (r = 0.3, P= 0.03). The cardiac index decreased 14% after a 27- to 34-J shock during the baseline rhythm (P 〈 0.0001). This effect persisted for 〈4 minutes. A 1- J shock during the baseline rhythm did not effect the cardiac index. Conclusion: Defibrillator shocks 〉9 J delivered during the baseline rhythm or during defibrillation energy requirement testing result in a 10% to 15% reduction in cardiac index, whereas smaller energy shocks do not affect cardiac hemodynamics. The duration and extent of the adverse effect are proportional to the shock strength. Shock strength, and not ventricular fibrillation, appears to be most responsible for This effect. Therefore, the detrimental hemodynamic effects of high-energy shocks may be avoided when low-energy defibrillation is used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1998.tb00118.x
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  • 7
    Electronic Resource
    Electronic Resource
    Changes in Cardiac Repolarization Following Short Periods of Ventricular Pacing (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 9 (1998), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Cardiac Memory. Introduction: “Cardiac memory” (primary T wave change) is thought to occur after 15 minutes to several hours of right ventricular (RV) pacing. The two components of the temporal change in repolarization are memory and accumulation. The purpose of this study was to examine quantitatively the effect of short periods of ventricular pacing on the human cardiac action potential, using monophasic action potential (MAP) recordings. Methods and Results: Thirty-one patients (ages 43 ± 14 years) with structurally normal hearts undergoing a clinically indicated electrophysiologic procedure were enrolled. Catheters were placed in the right atrium (RA) and RV, and a MAP catheter was positioned at the RV septum. APD90 was calculated from digitized MAP recordings. MAP morphology comparisons were performed using the root mean square (RMS) of the difference between complexes. All pacing was at 500-msec cycle length. There were four pacing protocols: (1) RA pacing was performed for approximately 15 minutes to evaluate temporal stability of the MAP recordings (5 pts); (2) to evaluate the memory phenomenon, four successive 1-minute episodes of RV pacing were interspersed with 2 minutes of RA pacing (5 pts); (3) the accumulation phenomenon was evaluated by assessing the effects of 1, 5, 10, and 15 minutes of RV pacing on the MAP during RA pacing (16 pts); and (4) 20 minutes of RV pacing was followed by 10 minutes of RA pacing to correlate visually apparent T wave changes with changes in MAP recordings (5 pts). In the control patients, no changes in APD90 or RMS analysis were noted during 14.9 ± 1.4 minutes of RA pacing. In the second protocol, RMS of the difference between the baseline MAP complexes and the signal average of the first 50 beats following each of four 1-minute RV pacing trains demonstrated progressively greater differences in morphology after successive episodes of RV pacing. In protocol 3, RMS analysis identified a progressively greater difference between the baseline MAP recording and the average of the first 50 beats after 1,5, 10, and 15 minutes of RV pacing. In protocol 4, visually apparent changes in T waves occurred in parallel with the RMS of the difference between the baseline MAP recordings and the average of the first 50 beats after 20 minutes of RV pacing. Similar changes also were demonstrated by APD90 analysis. Conclusion: This study is the first to demonstrate that episodes of abnormal ventricular activation as short as 1 minute in duration may exert lingering effects on the repolarization process once normal ventricular activation resumes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1998.tb00912.x
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  • 8
    Electronic Resource
    Electronic Resource
    Temperature and Impedance Monitoring During Slow Pathway Ablation in Patients with AV Nodal Reentrant Tachycardia (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 7 (1996), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Slow Pathway Ablation. Introduction: Successful radiofrequency ablation of an accessory pathway has been demonstrated to be associated with an electrode-tissue interface temperature of approximately 60°C or an impedance change of −5 to −10 Ω. However, the temperature and impedance changes associated with ablation of AV nodal reentrant tachycardia (AVNRT) using the slow pathway approach have not been reported. Therefore, the purpose of this study was to define the temperature and impedance changes achieved during ablation of AVNRT. Methods and Results: The study included 35 consecutive patients with AVNRT undergoing radiofrequency ablation of the slow pathway with a fixed power output of 32 W, and using a catheter with a thermistor bead embedded in the distal 4-mm electrode. The procedure was successful in each patient. The steady-state electrode-tissue interface temperature during successful applications of energy was 48.5 ± 3.3°C (range 42° to 56°C), and the steady-state temperature during ineffective applications was 46.8°± 5.5°C (P = 0.03). The mean impedance change during all applications of energy was −1.4 ± 2.8 ω, and did not differ significantly during effective and ineffective applications. Coagulum formation resulted during five applications (2.7%) in two patients (5.7%). There were no recurrences during 114 ± 21 days of follow-up. Conclusions: Successful ablation of AVNRT using fixed power output is achieved at an electrode-tissue interface temperature of approximately 48°C and is associated with a drop in impedance of 1 to 2 ω. These findings suggest that slow pathway ablation requires less heating at the electrode-tissue interface than does accessory pathway or AV junction ablation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1996.tb00530.x
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  • 9
    Electronic Resource
    Electronic Resource
    A Prospective Evaluation of Two Defibrillation Safety Margin Techniques in Patients with Low Defibrillation Energy Requirements (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 9 (1998), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Low-Energy Defibrillation. Introduction: In patients undergoing defibrillator implantation, an appropriate defibrillation safety margin has been considered to be either 10 J or an energy equal to the defibrillation energy requirement. However, a previous clinical report suggested that a larger safety margin may be required in patients with a low defibrillation energy requirement. Therefore, the purpose of this prospective study was to compare the defibrillation efficacy of the two safety margin techniques in patients with a low defibrillation energy requirement. Methods and Results: Sixty patients who underwent implantation of a defibrillator and who had a low defibrillation energy requirement (≤ 6 J) underwent six separate inductions of ventricular fibrillation, at least 5 minutes apart. For each of the first three inductions of ventricular fibrillation, the first two shocks were equal to either the defibrillation energy requirement plus 10 J (14.6 ± 1.0 J), or to twice the defibrillation energy requirement (9.9 ± 2.3 J). The alternate technique was used for the subsequent three inductions of ventricular fibrillation. For each induction of ventricular fibrillation, the first shock success rate was 99.5%± 4.3% for shocks using the defibrillation energy requirement plus 10 J, compared to 95.0%± 17.2% for shocks at twice the defibrillation energy requirement (P = 0.02). The charge time (P 〈 0.0001) and the total duration of ventricular fibrillation (P 〈 0.0001) were each approximately 1 second longer with the defibrillation energy requirement plus 10 J technique. Conclusion: This study is the first to compare prospectively the defibrillation efficacy of two defibrillation safety margins. In patients with a defibrillation energy requirement ≤ 6 J, a higher rate of successful defibrillation is achieved with a safety margin of 10 J than with a safety margin equal to the defibrillation energy requirement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1998.tb00865.x
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  • 10
    Electronic Resource
    Electronic Resource
    Long-Term Evaluation of the Ventricular Defibrillation Energy Requirement (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 9 (1998), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Defibrillation Energy Requirements. Introduction: Defibrillation energy requirements in patients with nonthoracotomy defibrillators may increase within several months after implantation. However, the stability of the defibrillation energy requirement beyond 1 year has not been reported. The purpose of this study was to characterize the defibrillation energy requirement during 2 years of clinical follow-up. Methods and Results: Thirty-one consecutive patients with a biphasic nonthoracotomy defibrillation system underwent defibrillation energy requirement testing using a step-down technique (20, 15, 12, 10, 8, 6, 5, 4, 3, 2, and 1 J) during defibrillator implantation, and then 24 hours, 2 months, 1 year, and 2 years after implantation. The mean defibrillation energy requirement during these evaluations was 10.9 ± 5.5 J, 12.3 ± 7.3 J, 11.7 ± 5.6 J, 10.2 ± 4.0 J, and 11.7 ± 7.4 J, respectively (P= 0.4). The defibrillation energy requirement was noted to have increased by 10 J or more after 2 years of follow-up in five patients. In one of these patients, the defibrillation energy requirement was no longer associated with an adequate safety margin, necessitating revision of the defibrillation system. There were no identifiable clinical characteristics that distinguished patients who did and did not develop a 10-J or more increase in the defibrillation energy requirement. Conclusion: The mean defibrillation energy requirement does not change significantly after 2 years of biphasic nonthoracotomy defibrillator system implantation. However, approximately 15% of patients develop a 10-J or greater elevation in the defibrillation energy requirement, and 3% may require a defibrillation system revision. Therefore, a yearly evaluation of the defibrillation energy requirement may he appropriate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1998.tb00132.x
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