Efficient Waveforms Research Articles

Improving the Efficacy of Magnetic Nanoparticle-Mediated Hyperthermia Using Trapezoidal Pulsed Electromagnetic Fields as an In Vitro Anticancer Treatment in Melanoma and Glioblastoma Multiforme Cell Lines.

Magnetic hyperthermia (MHT) is an oncological therapy that uses magnetic nanoparticles (MNPs) to generate localized heat under a low-frequency alternating magnetic field (AMF). Recently, trapezoidal pulsed alternating magnetic fields (TPAMFs) have proven their efficacy in enhancing the efficiency of heating in MHT as compared to the sinusoidal one. Our study aims to compare the TPAMF waveform's killing effect against the sinusoidal waveform in B16F10 and CT2A cell lines to determine more efficient waveforms in causing cell death. For that purpose, we used MNPs and different AMF waveforms: trapezoidal (TP), almost-square (TS), triangular (TR), and sinusoidal signal (SN). MNPs at 1 and 4 mg/mL did not affect cell viability during treatment. The exposition of B16F10 and CT2A cells to only AMF showed nonsignificant mortality. Hence, the synergetic effect of the AMF and MNPs causes the observed cell death. Among the explored cases, the nonharmonic signals demonstrated better efficacy than the SN one as an MHT treatment. This study has revealed that the application of TP, TS, or TR waveforms is more efficient and has considerable capability to increase cancer cell death compared to the traditional sinusoidal treatment. Overall, we can conclude that the application of nonharmonic signals enhances MHT treatment efficiency against tumor cells.

Adaptive optimization technology of segmented reconstruction signal based on genetic algorithm for enhancing radar jamming effect

Given the improved capabilities of radar systems, addressing unfamiliar signals presents a challenge for radar jamming technology. To tackle this issue, this study proposes an adaptive technique for optimizing jamming waveforms to suppress multiple false targets in escort jamming scenarios. The objective is to minimize the detectability of false targets by fine-tuning phase modulation and individual waveform parameters. The optimization model adjusts the energy and delay of jamming waveform segments using intercepted radar signal phase modulation and direct forwarding. Real-time adaptation is achieved through the utilization of a genetic algorithm and radar constant false alarm rate detection based on received emissions. The key findings highlight the advantages of adaptivity in effectively suppressing false targets under diverse conditions. The technique successfully learns efficient waveforms through feedback, even without specific knowledge of the radar system. The optimized waveforms maintain consistent jamming impact across different constant false alarm rate settings, surpassing the limitations associated with fixed assumptions. The introduction of phase modulation enhances the resilience of false targets by creating noise-like characteristics. Remarkably, robust jamming is achieved with only 12 false targets, reducing complexity. The unified waveform design is particularly suitable for single platform jamming, eliminating the need for multiple jammers. Furthermore, the optimized waveforms demonstrate improved coverage of real targets under position errors. As a result, the approach exhibits versatility across various signals, processing methods, and scenarios. This study suggests that increased adaptability and the incorporation of machine learning techniques contribute to the advancement of radar jamming capabilities. By optimizing jamming waveforms, the adaptive approach presented in this study may enhance the effectiveness of countering advanced radar systems.

Assessing the detectability of the secondary spin in extreme mass-ratio inspirals with fully relativistic numerical waveforms

Extreme mass-ratio inspirals (EMRIs) detectable by the Laser Inteferometric Space Antenna (LISA) are unique probes of astrophysics and fundamental physics. Parameter estimation for these sources is challenging, especially because the waveforms are long, complicated, known only numerically, and slow to compute in the most relevant regime, where the dynamics is relativistic. We perform a time-consuming Fisher-matrix error analysis of the EMRI parameters using fully relativistic numerical waveforms to leading order in an adiabatic expansion on a Kerr background, taking into account the motion of the LISA constellation, higher harmonics, and also including the leading correction from the spin of the secondary in the postadiabatic approximation. We pay particular attention to the convergence of the numerical derivatives in the Fisher matrix and to the numerical stability of the covariance matrix, which for some systems requires computing the numerical waveforms with approximately 90-digit precision. Our analysis confirms previous results (obtained with approximated but much more computationally efficient waveforms) for the measurement errors on the binary's parameters. We also show that the inclusion of higher harmonics improves the errors on the luminosity distance and on the orbital angular momentum angles by one order and two orders of magnitude, respectively, which might be useful to identify the environments where EMRIs live. We particularly focus on the measurability of the spin of the secondary, confirming that, for spin-aligned EMRIs on quasicircular orbits, it cannot be measured with sufficient accuracy. However, due to correlations, its inclusion in the waveform model can deteriorate the accuracy on the measurements of other parameters by orders of magnitude, unless a physically motivated prior on the secondary spin is imposed.

Low complexity FBMC for wireless MIMO systems

Filter Bank Multicarrier (FBMC) has become popular as an alternative to OFDM (Orthogonal Frequency Division Multiplexing). However, current FBMC systems found in the literature are not as compatible with MIMO (Multiple Input and Multiple Output) as OFDM is. This is due to the presence of inherent self-interference in current FBMC structures. Current literature uses maximal spectrally efficient waveforms, which have high interference among sub-carriers, thereby requiring complex post-processing in MIMO systems. In this work, we relax the spectral efficiency and show quantitatively that both the interference and out of band ripple energy can be decreased. We analyze this interference and its effects on different modulations at various SNR (Signal to Noise Ratio) values. We observe that the interference effect is more dominant at high SNR and affects higher order modulations more significantly. Reducing the interference enables near-orthogonal FBMC designs for practical SNR values and higher order modulations while still retaining MIMO receiver structures with low design complexity. We also show that error correcting codes can mitigate the effects of this interference. In this paper, first we compare our proposed FBMC system with OFDM and then with Filtered OFDM, one of the leading waveform candidates for 5G. Our simulations reveal that there is less than 1 dB gap between OFDM and FBMC having 84% and 97% spectral efficiencies respectively, using a 4 × 4 MIMO-VBLAST for 64-QAM at 30 dB SNR. Also, a comparison with Filtered OFDM system reveals that the proposed FBMC system is computationally more efficient for 5G systems.

A Multifunction Dense Array System With Reconfigurable Depth of Penetration

Noninvasive neuromodulation techniques such as Transcranial Magnetic Stimulation are enabled by electromagnetic induction with applications in neuroscience research and the treatment of neurological disorders. Current systems are effective but research continues on improving key performance metrics such as precise targeting, focality, and depth of penetration. Additional functions are also being studied; tunable excitation field patterning, reconfigurable depth of penetration, multiple excitation sites, power efficient waveforms and reduced extraneous excitation. Multichannel, multi-coil arrays show promise in achieving many of these parameters in one multifunctional array as opposed to the single-function commercial coils (circular, figure-8 or H coil) being used today. As such, our central focus is to determine whether multifunction dense arrays, despite their many challenges, are a tractable technical approach for future neuromodulation systems. Therefore, the results in this paper are twofold. First, we report the design, fabrication and demonstration of a scalable multichannel (12 channels) or multifunction dense array system to assess the potential to perform these functions in one system. Second, we demonstrate that the depth of penetration of the magnetic field can be reconfigured by varying current magnitude and phase of the smaller coil diameters in the array to achieve the same decay profile performance of a larger diameter coil. Only simulations exist in the literature to date, to the best of our knowledge, we report the first measurements of hexagonal shaped coils in multi-coil arrays have increased depth of penetration over circular shaped coil-based arrays.

Influence of pulse shaping filters on cyclostationary features of 5G waveforms candidates

Abstract Spectrally efficient waveforms have been extensively investigated in the last few years for the upcoming 5G systems. Filter Bank Multicarrier (FBMC) and Generalized Frequency Division Multiplexing (GFDM) are two of the best contenders that offer very low out of band emissions. To make better use of the available spectral resources, we propose coupling the 5G waveforms candidates with Cognitive Radio (CR). To perform spectrum sensing, we rely on cyclostationary detection. Although some papers have addressed second order cyclic features of the aforementioned waveforms, they are special cases of the results presented herein. In fact, in the present work, we first derive the explicit theoretical mth order pth conjugate cyclic cumulants of both FBMC and GFDM. Our analysis reveals that FBMC has distinctive cyclostationary properties. GFDM exhibits rich cyclic features as a result of the block filtering, the Cyclic Prefix (CP) insertion and the use of subsymbol guards. The obtained results are then exploited for signal detection purposes. Detection probability of FBMC is the best among the considered waveforms, followed by GFDM, where both outperform OFDM detection, specially if the used CP is low.

Efficient effective one body time-domain gravitational waveforms

Computationally efficient waveforms are of central importance for gravitational wave data analysis of inspiralling and coalescing compact binaries. We show that the post-adiabatic (PA) approximation to the effective-one-body (EOB) description of the binary dynamics, when pushed to high-order, allows one to accurately and efficiently compute the waveform of coalescing binary neutron stars (BNSs) or black holes (BBHs) up to a few orbits before merger. This is accomplished bypassing the usual need of numerically solving the relative EOB dynamics described by a set of ordinary differential equations (ODEs). Under the assumption that radiation reaction is small, the Hamilton's equations for the momenta can be solved {\it analytically} for given values of the relative separation. Time and orbital phase are then recovered by simple numerical quadratures. For the least-adiabatic BBH case, equal-mass, quasi-extremal spins anti-aligned with the orbital angular momentum, 6PA/8PA orders are able to generate waveforms that accumulate less than $10^{-3}$ rad of phase difference with respect to the complete EOB ones up to $\sim 3$ orbits before merger. Analogous results hold for BNSs. The PA waveform generation is extremely efficient: for a standard BNS system from 10Hz, a nonoptimized Matlab implementation of the TEOBResumS EOB model in the PA approximation is more than 100 times faster ($\sim 0.09$ sec) than the corresponding $C^{++}$ code based on a standard ODE solver. Once optimized further, our approach will allow to: (i) avoid the use of the fast, but often inaccurate, post-Newtonian inspiral waveforms, drastically reducing the impact of systematics due to inspiral waveform modelling; (ii) alleviate the need of constructing EOB waveform surrogates to be used in parameter estimation codes.

On the cyclostationarity of Universal Filtered Multi-Carrier UFMC

In order to meet the explosion of connected devices with their heterogeneous applications, the upcoming 5G systems focus on the design of spectrally efficient waveforms. Universal Filtered Multicarrier (UFMC) is one of the major waveforms contenders that offers low out of band emissions, compatibility with the existing Multiple Input Multiple Output techniques as well as multiple services support. In this paper, we propose to couple UFMC with Cognitive Radio (CR) to make better use of the available spectral resources. To perform spectrum sensing for the CR, we rely on cyclostationary detection. UFMC cyclostationarity characteristics have not been researched before. Hence in the present work, we first derive the explicit theoretical m-th order cyclic cumulants of UFMC, considering a multipath channel, frequency and timing offsets. Our analysis reveals that the per-subband filtering used in this waveform produces distinctive cyclostationary signatures. Then we exploit these signatures for signal detection. The obtained results are compared to those of the well studied Orthogonal Frequency Division Multiplexing (OFDM). Detection probability of UFMC outperforms the one of OFDM specially when the used Cyclic Prefix (CP) is low.

Spectrum Efficient, Localized, Orthogonal Waveforms: Closing the Gap With the Balian-Low Theorem

The Balian-Low theorem (BLT) states the fundamental impossibility to design waveforms for ${\rm{L}}^2(\mathbb R) $ , which 1) form an orthogonal set, 2) are time-frequency localized, and 3) attain a critical waveform density such that they form an orthogonal basis. This article closes the gap between existing waveform designs and the BLT. The main contribution is the design of orthogonal, time-frequency localized, spectrum efficient waveforms for hexagonal lattices. The waveform design is adaptive by a single design parameter, which tradesoff time-frequency localization with the waveform density. As the orthogonalization procedure is based on employing the minimum number of most time-frequency localized waveforms (Hermite functions) it is argued that the results may be optimal in terms of combined spectrum efficiency and time-frequency localization. An example is provided for waveforms for a hexagonal lattice, which are quasi-orthogonal, time-frequency localized, and up to 99% of the critical waveform density. Although the designed waveforms are not strictly orthogonal, their cross-correlation can be made arbitrarily small. The robustness in doubly dispersive channels and the efficiency for multiuser scenarios are discussed and compared to conventional orthogonal frequency division multiplexing (OFDM).

A high power efficient multi-waveform current stimulator used in implantable neural stimulation

This paper presents a current stimulator circuit that its output can be configured to generate the three most efficient current waveforms used in neural stimulation; rising exponential, falling exponential and rectangular. The stimulation amplitude range can be varied from 0 to 1 mA in a manner that each range can be divided into 16 steps by a 4 bit binary weighted digital to analog converter (DAC). The DAC features the maximum DNL and INL of 0.008 and 0.096 LSB respectively. Rising and falling exponential time constants are tunable from 13 to 106 $$\upmu$$μs. The approach for producing both rising and falling exponential currents is to apply a controllable rising and falling ramp voltage to the gate of the NMOS transistors which are biased to work in the subthreshold region while for the rectangular pulse, a constant subthreshold voltage is needed instead. The ramp generator used in exponential mode, employs a proposed low power 5 nA current source followed by a 3-bit current steering DAC. In the output stage, the stimuli current is buffered through the gain boosting technique which needs the maximum headroom voltage of 0.15 V. The DC output impedance is increased up to at least 24 M$$\Omega$$Ω. A simple electrode shortening is used for the charge balancing purpose at the end of the stimulation phases. The presented stimulator is designed and simulated in a 180nm CMOS technology and for the output driver, a HV 180 nm CMOS is used with the supply voltage equal to 3.3 V. The simulated power consumption of the proposed stimulator for one channel is 23.2 $$\upmu W$$μW and the maximum achieved power efficiency is 94.7 $$\%$$%.

Accurate and efficient waveforms for compact binaries on eccentric orbits

Compact binaries that emit gravitational waves in the sensitivity band of ground-based detectors can have non-negligible eccentricities just prior to merger, depending on the formation scenario. We develop a purely analytic, frequency-domain model for gravitational waves emitted by compact binaries on orbits with small eccentricity, which reduces to the quasicircular post-Newtonian approximant TaylorF2 at zero eccentricity and to the postcircular approximation of Yunes et al. [Phys. Rev. D 80, 084001 (2009)] at small eccentricity. Our model uses a spectral approximation to the (post-Newtonian) Kepler problem to model the orbital phase as a function of frequency, accounting for eccentricity effects up to $\mathcal{O}({e}^{8})$ at each post-Newtonian order. Our approach accurately reproduces an alternative time-domain eccentric waveform model for $e\ensuremath{\in}[0,0.4]$ and binaries with total mass $\ensuremath{\lesssim}12{M}_{\ensuremath{\bigodot}}$. As an application, we evaluate the signal amplitude that eccentric binaries produce in different networks of existing and forthcoming gravitational waves detectors. Assuming a population of eccentric systems containing black holes and neutron stars that is uniformly distributed in comoving volume, we estimate that second-generation detectors like Advanced LIGO could detect approximately 0.1--10 events per year out to redshift $z\ensuremath{\sim}0.2$, while an array of Einstein Telescope detectors could detect hundreds of events per year to redshift $z\ensuremath{\sim}2.3$.

Performance of new BOC-AW-modulated signals for GNSS system

Abstract In this paper, we propose efficient signal waveforms (WFs) with optimized spectrum for multipath (MP) mitigation and jamming reduction in global navigation satellite system. These WFs are based on the use of sine-phased binary offset carrier (BOC) with adjustable width (BOC-AW). They are generated by adjusting the width of the three-level WF {-1, 0, 1}. By exploiting the three-level BOC-AW subcarriers in sine-phasing signal model, we developed several forms of BOC-AW by means of superposition and width adjustment. The resulting power spectral densities and autocorrelation functions of the proposed WFs were calculated and introduced. Also calculated were the spectral separation coefficients (SSCs) and the Cramér-Rao lower bounds (CRLBs). The SSCs and CRLBs prove the efficiency of the proposed WFs in terms of interference separation. In addition, the simulation results show that the proposed WFs present better performances in MP mitigation compared to the WFs adopted by the Galileo and global positioning system modernization.

Numerical prediction of the electrical waveform effect on electrocoalescence kinetic

The effect of external electric field characteristics on the binary water droplet coalescence in stagnant oil has been studied using Computational Fluid Dynamics (CFD) simulations. Volume of Fluid (VOF) approach is applied as a multiphase model, in which the hydrodynamic equations consisting of Navier–Stokes and interface tracking equations are solved using finite volume discretization scheme. Dipole-induced-dipole (DID) model is utilized to calculate the electrostatic force on water droplets. Different types of electrical waveforms have been implemented using appropriate potential functions. The studied electrical voltages are sine, triangle, sawtooth, pulsed DC, and bipolar square waveforms. The predicted kinetic for electrocoalescence is in good agreement with the experimental data of the literature. The results demonstrated that a bipolar square wave provided the most efficient waveform, while sine and pulsed DC voltages gave lower efficiencies due to the time variation and off-time intervals, respectively. Triangle and sawtooth waveforms produced the least efficient waveforms. In addition, the effect of frequency has been studied for the aforesaid electrical waveforms in the adopted binary drop system. No significant differences have been proved in the approaching time of the drops from the studied frequencies. The results revealed that the electric fields with higher value of root mean squares (RMS) result in more efficient electrocoalescences. Furthermore, it was manifested that the higher voltage amplitude in every waveform improves this phenomenon.

Design of spectrally efficient ultra-wideband waveforms using Hermite–Rodriguez functions

Spectral efficiency is a major requirement in ultra-wideband (UWB) communication systems because of very low power spectral density (PSD) regulations imposed on the transmitted signals. Besides, large number of orthogonal waveforms is highly desirable in multiuser systems. In this study, the design of a set of spectrally efficient orthogonal waveforms is investigated. The design of UWB waveforms based on orthogonal Hermite–Rodriguez basis functions and linear frequency modulation (LFM) is proposed herein. The design is formulated as a quadratic semi-infinite programming problem with spectral and orthogonality constraints. Numerical examples are presented to illustrate the effectiveness of Hermite–Rodriguez-based waveforms with the proposed optimisation approach. Comparison with a recent result shows that the proposed approach compares favourably with those reported in the literatures in terms of the number of waveforms can be produced and the achievable spectral efficiency of the designed waveforms.

Erratum: Computing waveforms for spinning compact binaries in quasi-eccentric orbits [Phys. Rev. D82, 044028 (2010)

Several scenarios have been proposed in which the orbits of binary black holes enter the band of a gravitational wave detector with significant eccentricity. To avoid missing these signals or biasing parameter estimation it is important that we consider waveform models that account for eccentricity. The ingredients needed to compute post-Newtonian (PN) waveforms produced by spinning black holes inspiralling on quasi-eccentric orbits have been available for almost two decades at 2 PN order, and this work has recently been extended to 2.5 PN order. However, the computational cost of directly implementing these waveforms is high, requiring many steps per orbit to evolve the system of coupled differential equations. Here we employ the standard techniques of a separation of timescales and a generalized Keplerian parameterization of the orbits to produce efficient waveforms describing spinning black hole binaries with arbitrary masses and spins on quasi-eccentric orbits to 1.5 PN order. We separate the fast orbital timescale from the slow spin-orbit precession timescale by solving for the orbital motion in a non-interial frame of reference that follows the orbital precession. We outline a scheme for extending our approach to higher post-Newtonian order.

Computing waveforms for spinning compact binaries in quasi-eccentric orbits

Several scenarios have been proposed in which the orbits of binary black holes enter the band of a gravitational wave detector with significant eccentricity. To avoid missing these signals or biasing parameter estimation it is important that we consider waveform models that account for eccentricity. The ingredients needed to compute post-Newtonian (PN) waveforms produced by spinning black holes inspiralling on quasi-eccentric orbits have been available for almost two decades at 2 PN order, and this work has recently been extended to 2.5 PN order. However, the computational cost of directly implementing these waveforms is high, requiring many steps per orbit to evolve the system of coupled differential equations. Here we employ the standard techniques of a separation of time scales and a generalized Keplerian parameterization of the orbits to produce efficient waveforms describing spinning black hole binaries with arbitrary masses and spins on quasi-eccentric orbits to 1.5 PN order. We separate the fast orbital time scale from the slow spin-orbit precession time scale by solving for the orbital motion in a noninterial frame of reference that follows the orbital precession. We outline a scheme for extending our approach to higher post-Newtonian order.

Design of the Family of Orthogonal and Spectrally Efficient UWB Waveforms

In this paper, a method for the design of nonlinear phase, full-band, ultra-wideband (UWB) pulses that satisfy the Federal Communications Commission's effective isotropic radiation power spectrum mask, or more generally, any other given mask, is introduced. The method uses convex programming in each step of the iterative procedure that updates the phase distribution of the goal function. Thanks to its mathematical structure, this method can be easily modified in order to be applied, in sequential fashion, to several different orthogonal UWB pulse-design problems, addressed later in the paper. The first among them is a problem considered in literature-design of multiple pulses, orthogonal when radiated. When employed for solving this problem, the method proposed here produces a considerably larger number of orthogonal pulses with high energy compared to the methods introduced before. As a novelty, the problem of designing pulses which are orthogonal in reception is considered. Then, a modification of our method is presented that can be used to solve this problem. We also introduce statistical criteria of robustness of pulses' orthogonality in reception, to the variation of the pulses' shape caused by the channel transfer function. After that, a modification of the proposed method is presented that is capable of producing a set of pulses with predefined maximum value of this criteria. Furthermore, it is shown that the method proposed can be used to efficiently design orthogonal pulses using a suboptimal value of the sample rate. All the concepts introduced are illustrated by design examples

Impact of diverse polarisations on clutter statistics

The author addresses the impact of diverse polarisations on clutter statistics in the context of waveform diversity for multi-functional operation from a specific platform as well as for multiple sensing from multiple platforms. A key issue in this context is that of clutter mitigation via the use of diverse waveforms. Classical space–time adaptive processing (STAP) methods for radar target detection can be viewed in the context of a whiten and match filter. To this end, efficient waveforms that lend themselves for such processing are sought. The author specifically considers a statistical analysis of experimental data collected at low grazing angles to validate the fact that vertical transmit–vertical receive (VV) polarised data conform to Rayleigh scatter, whereas horizontal transmit–horizontal receive data do not. Consequently, VV data are suitable for whiten and match processing adopted in conventional radar STAP.

Transthoracic defibrillation with chopping-modulated biphasic waveforms

The superiority of different biphasic pulses for transthoracic defibrillation was proven by several studies. These efficient waveforms were implemented in some commercially available defibrillators. Recently we have devised and evaluated a biphasic waveform with a specially balanced ratio of the first-to-second phase voltages and with 5 kHz frequency 1 : 1 on-off chopping. It used less than half the energy for successful defibrillation in comparison with the 'classic' monophasic damped sinusoidal wave and showed considerably less postshock negative effects. This experience led us to try several laws of chopping modulation. A pulse-width modulation, combining low energy with gradual upslope of the modelled transmembrane potential, proved to have better performance than the standard damped sinusoid wave and the nonchopped biphasic truncated exponential pulse. This waveform was tested in a series of animal experiments in comparison with other modulated pulses, with the non-modulated waveform and the standard damped sinusoid wave. The experiments demonstrated the superiority of the modulated waveform, assessed by combining the parameters of threshold defibrillation energy and of post-shock disturbances reduction.

Relation between shock-related myocardial injury and defibrillation efficacy of monophasic and biphasic shocks in a canine model.

Certain biphasic waveforms with specific time ratios of positive and negative components require less energy for successful defibrillation of the fibrillating ventricles than monophasic waveforms. However, if more efficient waveforms were also to be associated with more injurious effects on myocardial function, they might not provide a true biological advantage. This study investigates the relation between defibrillation efficacy and potential toxicity of monophasic and asymmetric, single capacitor, biphasic waveforms with equal durations of positive and negative components. The myocardial lactate extraction rate (LER) was used to measure the injurious effects on myocardial oxidative metabolism of two synchronized 35-J shocks in sinus rhythm. LER, mean arterial pressure (MAP) and, in a subset of experiments, cardiac output (CO) and coronary blood flow (CBF) were measured at baseline, 30 seconds, 60 seconds, 90 seconds, 150 seconds, 300 seconds, and 600 seconds after the shocks. In 12 dogs, three different waveforms (M 10: monophasic 10 milliseconds; BI 10: biphasic 10 milliseconds; BI 20: biphasic 20 milliseconds) were tested as series of two consecutive shocks (60 seconds apart) resulting in a total of 36 sets of data. At baseline, LER was 25 +/- 11%. After monophasic shocks, LER decreased significantly more than after biphasic shocks (LER at 150 seconds: M 10: -6 +/- 31% versus BI 10: 21 +/- 15% versus BI 20: 21 +/- 16%; M 10 versus BI 10 and M 10 versus BI 20, P < .05) and showed also a slower recovery (LER at 300 seconds: M 10: 1 +/- 24% versus BI 10: 20 +/- 11% versus BI 20: 20 +/- 15%; M 10 versus BI 10 and M 10 versus BI 20, P < .05). The maximal decrease in LER was 41 +/- 27% for M 10 compared with 18 +/- 15% for BI 10 and 15 +/- 11% for BI 20 (both, M 10 versus BI 10 and M 10 versus BI 20, P < .05). There was a similar decrease in CO and MAP, with the lowest MAP after monophasic shocks. The maximal decrease in MAP was significantly greater after M 10 compared with BI 20 (-29 +/- 15 mm Hg versus -13 +/- 11 mm Hg, P < .05). The defibrillation threshold was 18.6 +/- 8 J for M 10 compared with 11.5 +/- 4.0 J for BI 10 (P < .05) and 15.0 +/- 6.1 J for BI 20, respectively (P = NS). Our results suggest that these specific biphasic waveforms are associated with less injurious effects on myocardial oxidative metabolism and hemodynamic performance. Given their higher defibrillation efficacy as well, biphasic waveforms may provide important long-term benefits in patients receiving frequent shocks from implantable cardioverter-defibrillators.