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The low-temperature magnetic properties of the Ce atoms in the intermetallic compounds CeMn2Ge2 and CeMn2Si2 were studied. Previous neutron scattering measurements did not detect an ordered moment at Ce atoms in either compound despite the fact that they are surrounded by the Mn moments ordered ferromagnetically in the CeMn2Ge2 and antiferromagnetically in the CeMn2Si2 .C ontrasting with this result, a recen tm easurement performed with the tim ed ifferential perturbed angular correlation (TDPAC) technique showed th ep resence of a pronounced magnetic hyperfine field (MHF) at Ce sites in the CeMn2Ge2 compound and no MHF in CeMn2Si2 .T he absence of the Ce magnetic moment and MHF in the silicide can be understood in terms of too weak a Ce–Ce magnetic interaction while in the germanide the TDPAC result suggests that some magnetic ordering of Ce atoms may occur. Aiming to understand the effects which result in the quenching of the Ce 4f moment in both cases, we performed first-principle sb and-structure calculations for both systems, using the full potential linear augmented plane wave method. It is show nt hat the magnetism of the Ce sublattice has fundamentally different nature in CeMn2Si2 and CeMn2Ge2 .W hile the Ce atoms are intrinsically nonmagnetic in the silicide, having a zero magnetic moment with both spin and orbital contributions identically zero, they display magnetic properties in the CeMn2Ge2 since their very small total moment is composed of finite spin and orbital components which almost cancel each other accidentally.

Laves-phase compounds with the hexagonal C14-type structure Zr(Cr 1− x Fe x ) 2 ( x =0.3–0.7) were charged to maximum H capacity, which ranged from 3.6 to 2.5 H/f.u. for increasing x . The biggest cell volume expansion was 22%. Magnetic properties were investigated with magnetometry and Mossbauer spectroscopy. The hydrides exhibited spin-glass behavior, similar to their parent compounds, but with larger Fe moments and lower freezing temperatures. Electric hyperfine interactions were measured in the 78–350 K temperature range at the Fe sites and at the Zr site, using 57 Fe MS and 181 Ta TDPAC, respectively. Activation energies for H jump diffusion were determined by these two complementary techniques, yielding 72(4) and 246(30) meV respectively.

A semiconducting delafossite compound CuAlO2 containing either Zn or Ni impurity substituting for a Cu position has been investigated. The electronic structure and the electric field gradients (EFGs) for both donor (Zn) and acceptor (Ni) doped systems have been calculated using a full potential linear augmented plane-wave method with generalized gradient approximation accounting for the exchange and correlation effects. The results clearly indicate that the presence of Zn impurities changes the electric properties of CuAlO2 by producing n-type semiconductivity, in a similar way as we have previously shown for the Cd impurity. In the case when Ni substitutes Cu the results of calculations indicate p-type semiconductivity in the material. Despite the fact that both Zn and Ni exhibit a similar hybridization scheme for the bonding with neighboring oxygens, their d electron clouds have different shapes due to deficit (Ni) and excess (Zn) of the dz2 electrons. This effect is responsible for the large difference between the EFG values calculated at the Ni and Zn nuclei in the compound.

The TDPAC technique was applied to verify a hypothesis about the influence of electron capture after-effects on the integrity of radiometal complexes with organic ligands in aqueous solutions. The neutral aqueous solutions of DTPA-complexes with two parent isotopes, 111 In(EC) 111 Cd and 111m Cd, were used for direct comparison of dynamic interaction parameters. Data for the parent 111 In–DTPA complexes revealed three fractions with essentially different relaxation constants, including an “unperturbed” fraction, which, according to the hypothesis, is due to small fragments of the initial complexes disintegrated as a result of Auger-process and the following Coulomb fragmentation. Only one fraction with a relaxation constant of 3(1)×10 6 s −1 was observed for the 111m Cd–DTPA solution confirming the proposal about the influence of electron capture after-effects. Measurements with the frozen solutions allowed determining the electric field gradient (EFG) at Cd-sites in complexes with DTPA, V zz =6.7(2)×10 21 V/m 2 with an asymmetry parameter η =0.75(5).

We report on first-principles band-structure calculations of the semiconducting CuAlO2 delafossite compound in the pure form and also with Cd impurity occupying either a Cu or Al position. The computational tool was a full-potential linear augmented plane-wave method, with the generalized gradient approximation accounting for the exchange and correlation effects. The changes caused by the presence of Cd are studied by the analysis of the electronic structure and the electric field gradient (EFG) in both Cd-doped and pure CuAlO2 systems. Good agreement between the calculated and measured EFGs at Cd substituting for Cu or Al atoms in CuAlO2 indicates that the calculations were able to correctly describe the ground state of the system containing the impurity. It is shown that a specific hybridization scheme, involving Cu (and Cd) s and dz2 orbitals and neighbouring O pz orbitals, takes place at the Cu sites in CuAlO2 as proposed earlier. The results of the calculations indicate that the Cd-doped system changes its electrical properties when Cd replaces Cu atoms (producing an n-type semiconductor), but not when it substitutes for Al atoms.

Fil: Richard, Diego. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina. Universidad de la Republica; Uruguay

In this paper, the effect in structural and magnetic properties of iron doping with concentration of 20% in hafnium dioxide (HfO2) nanoparticles is investigated. HfO2 is a wide band gap oxide with great potential to be used as high-permittivity gate dielectrics, which can be improved by doping. Nanoparticle samples were prepared by sol-gel chemical method and had their structure, morphology, and magnetic properties, respectively, investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) with electron back scattering diffraction (EBSD), and magnetization measurements. TEM and SEM results show size distribution of particles in the range from 30 nm to 40 nm with small dispersion. Magnetization measurements show the blocking temperature at around 90 K with a strong paramagnetic contribution. XRD results show a major tetragonal phase (94%).

The magnetic properties of PrMn2Ge2 compound have been investigated by perturbed γ−γ angular correlation (PAC) spectroscopy using 111In(111Cd) as probe nuclei as well as by magnetization measurements. This ternary intermetallic compound exhibits different magnetic structures depending on the temperature. The magnetic ordering is mainly associated with the magnetic moment of 3d-Mn sublattice but at low temperatures a magnetic contribution due to ordering of the magnetic moment from 4f-Pr sublattice appears. PAC results with 111Cd probe nuclei at Mn sites show that the temperature dependence of hyperfine field Bhf(T) follows the expected behavior for the host magnetization, which could be fitted by two Brillouin functions, one for antiferromagnetic phase and the other for ferromagnetic phase, associated with the magnetic ordering of Mn ions. Magnetization measurements showed the magnetic behavior due to Mn ions highlighting the antiferromagnetic to ferromagnetic transition around 326 K and an increase in the magnetization around 36 K, which is ascribed to Pr ions ordering.

In this work, perturbed angular correlation (PAC) spectroscopy is used to study differences in the nuclear quadrupole interactions of Cd probes in DNA molecules of mice infected with the Y-strain of Trypanosoma cruzi. The possibility of investigating the local genetic alterations in DNA, which occur along generations of mice infected with T. cruzi, using hyperfine interactions obtained from PAC measurements and density functional theory (DFT) calculations in DNA bases is discussed. A comparison of DFT calculations with PAC measurements could determine the type of Cd coordination in the studied molecules. To the best of our knowledge, this is the first attempt to use DFT calculations and PAC measurements to investigate the local environment of Cd ions bound to DNA bases in mice infected with Chagas disease. The obtained results also allowed the detection of local changes occurring in the DNA molecules of different generations of mice infected with T. cruzi, opening the possibility of using this technique as a complementary tool in the characterization of complicated biological systems.

Electronic band structure calculations for the CeIn3 compound utilizing the full potential linearized augmented plane waves method were performed with the aim to compute the hyperfine fields acting on Ce and In atoms. The latter are found to be in reasonable agreement with the values measured at low temperatures. The 4f orbital contribution dominates the magnetic hyperfine field at Ce ions while the contact field is negligible due to an almost complete cancellation of valence and core contributions. A non-zero magnetic hyperfine field appears at In sites due to the spin-polarization of the 5p sub-shells through the hybridization with the extended 6s, 6p and 5d Ce states which, in turn, are spin-polarized by the Ce 4f states. No net magnetic moment at In is observed since the sum of its 5p sub-shell spins is zero. The 5p shell of In is responsible for the presence of an electric field gradient at In nuclei.

Time Differential Perturbed γ–γ Angular Correlation (TDPAC) technique was used to measure the magnetic hyperfine field at both Ge and Ce sites in CeMn2Ge2 and CeCo2Ge2 intermetallic compounds. The 111In (111Cd) probe nuclei was used to investigate the hyperfine interaction at Ge sites, while the 140La (140Ce) nuclei was used to measure the magnetic hyperfine field at Ce site. The present measurements cover the temperature ranges from 10–460 K for CeMn2Ge2 and 9–295 K for CeCo2Ge2, respectively. The result for 111Cd probe showed two distinct electric quadrupole frequencies above magnetic transition temperatures, in both compounds and a combined interaction in the magnetic region. The temperature dependence of the magnetic hyperfine field at 111Cd at Mn site for the CeMn2Ge2 compound showed a transition from ferromagnetic to antiferromagnetic phase around 320 K and from antiferromagnetic to paramagnetic phase at 420 K. While a small magnetic field was measured on 111Cd at Co site, no magnetic field on 140Ce site was observed in CeCo2Ge2.

The magnetic hyperfine field Bhf for Cd in the Heusler alloy Pd2MnSn at the site of chemically introduced Ag has been investigated by PAC following the β− decay of 111Ag. Sign and temperature dependence of Bhf have been determined. Comparison of the result Bhf(T=0)=+8.0(1) T with earlier data and ab-initio band structure calculations leads to the conclusion that the Ag activity has been incorporated at the Mn site.

The concentration dependence of the electric field gradient (EFG) in PZT ceramics was studied by Time Differential Perturbed Angular Correlations (PAC) using the 181Ta radioactive probe in samples with x=0.3, 0.5 and 0.8 at room temperature. This phase presents two sites, probably related to defects close to probes, caused by oxygen and lead vacancies. We can also state that both the paraelectric and ferroelectric phases of these systems have two sites with different characteristics and that the high-frequency quadrupolar frequency site presents the highest fraction. The concentration dependence revealed by our results is discussed by comparing the latter with previous PAC studies.

Magnetic hyperfine fields (mhf) at 111Cd and 140Ce nuclei, dilutely substituting the In and Ce sites, respectively, have been measured in the intermetallic compound CeIn3 using perturbed angular correlation technique. A pure electric quadrupole interaction with an axially symmetric electric field gradient was observed at 111In(EC) 111Cd probe nuclei at room temperature while a combined magnetic dipole and electric quadrupole interaction is observed below 10K. Below the ordering temperature, only a magnetic interaction is observed at 140La(β−) 140Ce probe. The values of mhf measured experimentally as a function of temperature are discussed in terms of critical behavior.

Magnetic hyperfine field (mhf) acting on 181Ta at the Ti site has been investigated in the alloy Pd2TiSn by Perturbed Angular Correlation (PAC) measurements using the (133–482) keV γ–γ cascade in 181Ta following the β− decay of 181Hf. The magnetic hyperfine field was measured as a function of temperature in the range of 45–1000K. The magnetization measurements were carried out with a vibrating sample magnetometer. The interpretation of the experimental results is based on the assumption that the probe nuclei occupy both the regular Ti sites as well as the Ti atom sites randomly distributed on the Pd sublattice.

The perturbed angular correlation (PAC) technique has been used to study the electric field gradient (EFG) in LaCoO3 perovskite. The results are compared with those for LaCrO3, LaFeO3 measured earlier. The PAC probe, 111In → 111Cd, was introduced in the oxide lattice by means of chemical reaction during sample preparation. In the present work, the temperature dependence of the electric quadrupole interaction parameters, for LaCoO3 was investigated. The resulting systematics of EFG at 111Cd, in La(Cr,Fe,Co)O3 perovskites, reveals a linear dependence with temperature.

In the present work bulk samples of pure as well as Co-doped ZnO with different concentrations were prepared by sol–gel method from highly pure metallic Zn (99.9999%) and Co (99.9999%). The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray microanalysis (EDS) and perturbed gamma–gamma angular correlation (PAC) spectroscopy. Carrier-free 111 In nuclei were introduced during preparation of the samples and used as probe nuclei at Zn sites for PAC measurements. PAC results show that both pure and Zn 1 - x Co x O ( x ≤ 0.15 ) samples have the same electric quadrupole frequency when Co-doped samples are annealed in air, argon or nitrogen atmosphere at 1173 K. SEM and EDS results showed that Co-doped samples are homogeneous without any secondary Co phases. These observations indicate that Co ions are substituted for Zn ions and have a similar electronic structure of Zn ions. A weak local magnetism was observed at temperatures below about 300 K for Co concentration of 10% when sample was annealed in Nitrogen.

The electric field gradient (efg) at the Nb site in the intermetallic compounds Nb3X (X = Al, In, Si, Ge, Sn) was measured by the Perturbed Angular Correlation (PAC) method using the well-known gamma-gamma cascade of 133 -482 keV in 181Ta from the β- decay of 181Hf, substituting approximately 0.1 atom percent of Nb. The PAC results show that Vzz drops by nearly 40% when X changes from Al to In, and by about 25% when X changes from Si to Ge and Sn. This behavior is most probably related to the change in the degree of sp hybridization in these compounds. The Vzz values of the studied compounds do not follow the well known universal correlation for the efg's in non-cubic metals but the observed trend is well reproduced by results of ab-initio electronic structure calculations. In the case of Nb3 Al a linear temperature dependence of the quadrupole frequencies was observed in the temperature range of 6.5 to 1210 K.

Purpose The effects of topiramate (TPM) on sodium-dependent action potentials were studied by using cultured mouse spinal cord neurons. Methods The ability of TPM to limit (block) depolarization-induced spontaneous repetitive firing (SRF) was determined and compared with corresponding effects of phenytoin (PHT) and lamotrigine (LTG) in cultured mouse spinal neurons. Results Topiramate at concentrations of > or =3 microM caused a voltage-sensitive and time-dependent limitation of SRF that was associated with a decrease in the velocity of the upstroke of the action potential. At high concentrations (30-600 microM), TPM rapidly blocked SRF in about one third of the neurons tested and did not affect SRF in about one third. In some neurons, TPM caused an intermittent limitation (sputtering) of SRF (approximately 30% of the neurons) or blocked SRF only after a delay of several seconds (approximately 10%). This complex pattern of effects is distinctly different from that of PHT and LTG, in which the effect was always a rapid limitation or complete blockade of SRF. Another difference between TPM and the other anticonvulsants (AEDs) is that the effects of TPM were more dependent on the length of time the neurons were exposed to the compound and the intensity or duration of neuronal activity. Conclusions The results of this study do not support the concept that Na+ channel blockade is the primary mechanism responsible for the anticonvulsant activity of TPM.

Structural, magnetic and hyperfine interaction measurements have been carried out on the novel compound La 3.5 Ru 4 O 13 prepared under two different atmospheres (air and oxygen flow). This compound is formed in the orthorhombic structure (space group Pmmm, # 47). The coexistence of the triple-layered perovskite-type planes (quasi-2D structure) and the rutile-like slabs (1D structure) leads to interesting magnetic and electronic properties in this compound. The magnetic susceptibility of this system shows a peak at T ~47 K associated with antiferromagnetic interactions. The Curie–Weiss behaviour of the susceptibility provides an effective magnetic moment consistent with Ru ions in low-spin state. Perturbed angular correlation measurements carried out with 111 Cd probe in the temperature range 10–60 K reveal only quadrupole interactions and indicate the occurrence of structural distortions for T

The electric field gradient (EFG) at 111Cd nuclei dilutely substituting the cation site in bixbyite rare-earth oxides Tl2O3, Eu2O3, Lu2O3 and Tm2O3 has been measured using perturbed angular correlation technique. The 111In(EC) 111Cd probe nuclei were introduced into the samples by thermal diffusion. The experimental EFG values are compared with those calculated using the point charge model (PCM). The results are discussed in terms of a correlation between the electric field gradient and cation–oxygen bond length in metal oxides.

The magnetic hyperfine field (mhf) at Dy sites in DyAg and DyCu was investigated with perturbed gamma–gamma angular correlation technique using 140 La– 140 Ce probe nuclei. The temperature dependence of the observed mhf shows a deviation from an expected Brillouin-like behavior with a sharp increase of mhf values for temperatures below approximately half of T N for each compound. This additional magnetic interaction is believed to result from the polarization of Ce spin moments induced by the magnetic field from Dy atoms. The experimental results for the temperature dependence of mhf are fitted by using a model based in the molecular field theory. The results are discussed in terms of the RKKY model for the indirect magnetic coupling between the magnetic Dy ions.

The book is focused on constitutive description of mechanical behaviour of engineering materials: both conventional (polycrystalline homogeneous isotropic or anisotropic metallic materials) and non-conventional (heterogeneous multicomponent anisotropic composite materials). Effective material properties at the macro-level depend on both the material microstructure (originally isotropic or anisotropic) as well as dissipative phenomena occurred on fabrication and consecutive loading phase (hardening) resulting in irreversible microstructure changes (acquired anisotropy). The material symmetry is a background and anisotropy is a core around which the book is formed. In this way a revision of classical rules of enhanced constitutive description of materials is required.

Background Many inhalation anesthetics at clinically relevant concentrations inhibit plasma membrane Ca2+-adenosine triphosphatase (PMCA) ion pumping in brain synaptic membranes and in cultured cells of neural origin. In this study, the authors investigated the effect of inhalation anesthetics on cytosolic calcium homeostasis in cortical neurons maintained at physiologic and room temperatures and on cortical neurons and pheochromocytoma cells with antisense blockade of specific PMCA isoforms. Methods Using Ca2+-specific confocal microfluorimetry, the anesthetic effects on Ca2+ dynamics were examined in mouse embryonic cortical neurons in association with ligand-stimulated Ca2+ influx. Studies were done at 21 degrees C and 37 degrees C. Mouse embryonic cortical neurons with oligodeoxyribonucleotide blockade of PMCA2 expression and transfected rat pheochromocytoma cells with blocked expression of PMCA1 were also examined. Results Baseline and poststimulation peak cytosolic calcium concentrations ([Ca2+]i) were increased, and Ca2+ clearance was delayed in cells exposed at 37 degrees C, but not at 21 degrees C, to concentrations < or = 1 minimum alveolar concentration (MAC)-equivalent of halothane, isoflurane, and sevoflurane. Neurons exposed to xenon solutions < or = 0.4, 0.6, and 0.8 MAC showed dose-related perturbations of cytosolic Ca2+. Calcium dynamics were altered in neural cells with blocked PMCA isoform production, but at much lower halothane concentrations: 0.5 MAC for cortical neurons and 0.1 MAC for pheochromocytoma cells. Conclusions By extruding Ca2+ through the plasma membrane, PMCA maintains resting neuronal [Ca2+]i at low levels and clears physiologic loads of Ca2+ after influx through calcium channels. Inhalation anesthetics perturb this process and thus may interfere with neurotransmitter release, altering interneuronal signaling.

Gabapentin (1-[aminomethyl]-cyclohexaneacetic acid; Neurontin, Park-Davis, Morris Plains, NJ) is a new anticonvulsant approved by the Food and Drug Administration for adults in the treatment of partial seizures, with or without secondary generalization. Gabapentin has been on the market since 1994, and it demonstrates good anticonvulsant efficacy and extremely low toxicity. The mechanisms of action of gabapentin remain unclear, although it binds to a specific receptor in the brain, inhibits voltage-dependent sodium (Na) currents, interacts with a central nervous system L-type Na+-independent amino acid transporter, and modulates several neurotransmitters actions and release. Other actions of gabapentin have been tested in different neurologic and psychiatric disorders. Gabapentins analgesic properties have been known since 1995. In this chapter, we review some of the known and documented mechanisms of action of gabapentin, targeting the drugs possible efficacy in the treatment of acute and chronic pain states of nociceptive and neurogenic origin.

The magnetic hyperfine field (mhf) acting on a probe dilutely substituted at the non-magnetic transition element site has been investigated for the pseudo-quaternary Heusler alloys , , , and with and 0.8 by TDPAC measurements utilizing the 133 - 482 keV gamma - gamma cascade in following the -decay of . Magnetization measurements on samples were carried out by using a vibrating-sample magnetometer. The Curie temperature and the saturation magnetization were obtained for each alloy. The lattice parameters of the alloys were determined by x-ray diffraction measurements. The results for the mhf acting on Ta occupying the non-magnetic transition element site are discussed and compared with the mhf systematics for the cobalt-based Heusler alloys.

Halothane inhibits neural plasma membrane Ca(2+)-ATPase, a pump that ejects Ca2+ from the cell after influx through voltage- or ligand-activated channels. Intracellular microelectrode recordings in mouse embryonic cortical and spinal cord neurons showed that halothane and eosin, a pump inhibitor, prolonged repolarization associated with spontaneous bursts of depolarization. These agents also prolonged the repolarization phases of electrically induced action potentials and of capsaicin-mediated Ca(2+)-dependent depolarization in mouse adult dorsal root ganglion neurons. In keeping with these findings, confocal microfluorimetry showed that halothane delayed clearance of intracellular Ca2+ accumulated by N-methyl-D-aspartate stimulation of single neurons.

A fundamental problem in automating object database storage reclamation is determining how often to perform garbage collection. We show that the choice of collection rate can have a significant impact on application performance and that the "best" rate depends on the dynamic behavior of the application, tempered by the particular performance goals of the user. We describe two semi-automatic, self-adaptive policies for controlling collection rate that we have developed to address the problem. Using trace-driven simulations, we evaluate the performance of the policies on a test database application that demonstrates two distinct reclustering behaviors. Our results show that the policies are effective at achieving user-specified levels of I/O operations and database garbage percentage. We also investigate the sensitivity of the policies over a range of object connectivities. The evaluation demonstrates that semi-automatic, self-adaptive policies are a practical means for flexibly controlling garbage collection rate.

Objective: To study the effect of mesh-glove afferent stimulation on motor control of voluntary wrist movement in stroke patients who have chronic neurological deficits. Design: Case series. Motor control was evaluated by surface EMG of the arm muscles and kinematics of voluntary wrist movements on 3 occasions: before and immediately after the initial session of mesh-glove stimulation, and then after a daily mesh-glove stimulation program conducted over several months. Setting: Tertiary care center. Patients: The inclusion criteria were: a history of stroke lasting longer than 6 months; completion of a rehabilitation program during early recovery; and preserved cognitive and communicative ability. Fourteen referred patients (age 63 ± 9yr; time since stroke 31 ± 22 mo) fulfilled the criteria and completed the daily stimulation program. Intervention: A single initial and then daily mesh-glove electrical afferent stimulation was applied to the hand of the involved upper limb for 20 to 30min. Main Outcome Measures: Surface EMGs from the affected biceps brachii and wrist extensor muscles and amplitudes of wrist movements were analyzed. Results: The single, initial mesh-glove application had no effect on outcome measures. Following a daily mesh-glove stimulation program, however, both the amplitude of wrist extension movement and wrist extensor integrated EMG were significantly increased while coactivation of biceps brachii decreased. These findings were most prominent in subjects with partially preserved voluntary wrist movements. Conclusion: We conclude that daily mesh-glove stimulation can modify altered motor control and improve voluntary wrist extension movement in stroke subjects with chronic neurological deficits.

The novel anticonvulsant, remacemide HCl [(+/-)-2-amino-N-(1-methyl-1,2-diphenylethyl)acetamide monohydrochloride; FPL12924AA], and a desglycinated metabolite [(+/-)-1-methyl-1,2-diphenylethylamine monohydrochloride; FPL 12495AA] reversibly limited sustained high-frequency repetitive firing (SRF) of sodium-dependent action potentials by mouse spinal cord neurons in monolayer dissociated cell culture. Limitation occurred with an IC50 of 7.9 X 10(-6) M for remacemide and 1.2 X 10(-6) M for FPL 12495AA (P < 0.05 vs. remacemide). Stereoisomers of the desglycinate limited SRF with IC50 values of 3.3 X 10(-6) M and 3.5 X 10(-6) M for the S(+) and R(-) compounds, respectively. The concentration of racemic desglycinate and of either stereoisomer that produced limitation in all neurons tested was 10(-4) M. Maximal rate of rise (Vmax) of action potentials decreased progressively until firing ceased during 400-ms depolarizing pulses. Efficacy of remacemide, but not of the desglycinate, increased with time (maximum at 16-36 h). The limitation was voltage dependent. In addition, reduction of Vmax and action potential failure occurred during stimulation with 400-ms pulses and trains of brief (1 ms) depolarizations at different frequencies. These findings suggest an effect on voltage-sensitive sodium current that generates the action potential upstroke. Remacemide and the desglycinate also significantly reduced the amplitude of neuronal responses to pressure application of NMDA in use-dependent manner at concentrations equal to the IC50 values for limitation of action potential firing. Resting potential and input resistance were not changed significantly by either drug. Limitation of high-frequency firing of action potentials by both remacemide HCl and FPL 12495AA may contribute to the anticonvulsant efficacy of these compounds at concentrations overlapping the range required to block glutamatergic hyperexcitability.