Magnitude Of Relaxation Research Articles

S3-S4 Loop Modulates Voltage Sensing Domain Relaxation

Following activation, S4-based voltage sensing domains (VSD) undergo a voltage independent transition, known as relaxation, shifting their voltage dependence to more negative potentials. The molecular determinants for relaxation remain unknown. However, studies on Ci-VSP suggest that relaxation likely involves secondary and tertiary structure rearrangements within the VSD. Since relaxation is seemingly an intrinsic property of VSDs, we sought to identify regions of the domain involved in the triggering of relaxation. For this, we focused our study on the loop connecting the S3 and S4 segments (S3-S4 loop). We argue that, like the S4-S5 linker coupling the VSD to the pore domain, the S4 segment can do electromechanical work on the rest of the VSD using the S3-S4 loop as “coupling element”. Several studies have proposed that the S3-S4 is helically structured. Hence, we hypothesized that the movement of the S4 segments can be readily transmitted to the S3 segment and the rest of the VSD causing relaxation through a “rigid” S3-S4 loop. Conversely, a “flexible” S3-S4 would be able to absorb the movement of the S4 segment, dissipating mechanical energy and diminishing relaxation. To test this idea, we determined amplitude and timing of relaxation by performing cut-open voltage-clamp recordings of potassium currents from ShakerIR S3-S4 loop proline-to-alanine mutants. We reason that, since prolines disrupt helical structure, introduction of a “helix-friendly” alanine will increase the rigidity of the loop. Consistently, our data indicate that the proline-to-alanine mutations increase the magnitude of relaxation. Hence, we proposed that S3-S4 loop's prolines act as “hinges” conferring flexibility to this region. Similar results were obtained with glycine-to-cysteine S3-S4 loop mutants of Ci-VSP, suggesting that the S3-S4 segments may have similar function. In summary, we conclude that the S3-S4 helix seemingly acts as a mechanical stress dissipater in VSDs.

Observation and possible mechanism of irradiation induced creep in ceramics

Stress relaxation of elastically strained silicon carbide samples during high flux neutron irradiation to ∼2 displacements per atom at intermediate (390–540°C) to high (790–1180°C) temperatures is presented. The magnitude of stress relaxation normalized to the initial stress magnitude is independent of the initial stress magnitude, indicating a stress exponent of unity for irradiation creep in SiC. The creep strain increases with the increasing fluence while the strain rate significantly decreases. A linear relationship was found between the creep strain and the transient swelling that occurs due to irradiation defect accumulation. The apparent irradiation creep compliances for silicon carbide are substantially smaller than those associated with pure metals and alloys. Microstructural examination suggests that incoherent grain boundaries likely play a major role in determining the primary transient irradiation creep of these materials at high temperatures with a potential additional contribution from basal slip at very high temperatures.

Phosphodiesterase-9 (PDE9) inhibition with BAY 73-6691 increases corpus cavernosum relaxations mediated by nitric oxide–cyclic GMP pathway in mice

Phosphodiesterase-9 (PDE9) specifically hydrolyzes cyclic GMP, and was detected in human corpus cavernosum. However, no previous studies explored the selective PDE9 inhibition with BAY 73-6691 in corpus cavernosum relaxations. Therefore, this study aimed to characterize the PDE9 mRNA expression in mice corpus cavernosum, and investigate the effects of BAY 73-6691 in endothelium-dependent and -independent relaxations, along with the nitrergic corpus cavernosum relaxations. Male mice received daily gavage of BAY 73-6691 (or dimethylsulfoxide) at 3 mg kg(-1) per day for 21 days. Relaxant responses to acetylcholine (ACh), nitric oxide (NO) (as acidified sodium nitrite; NaNO2 solution), sildenafil and electrical-field stimulation (EFS) were obtained in corpus cavernosum in control and BAY 73-6691-treated mice. BAY 73-6691 was also added in vitro 30 min before construction of concentration-responses and frequency curves. PDE9A and PDE5 mRNA expression was detected in the mice corpus cavernosum in a similar manner. In vitro addition of BAY 73-6691 neither itself relaxed mice corpus cavernosum nor changed the NaNO2, sildenafil and EFS-induced relaxations. However, in mice treated chronically with BAY 73-6691, the potency (pEC50) values for ACh, NaNO2 and sildenafil were significantly greater compared with control group. The maximal responses (Emax) to NaNO2 and sildenafil were also significantly greater in BAY 73-6691-treated mice. BAY 73-6691 treatment also significantly increased the magnitude and duration of the nitrergic corpus cavernosum relaxations (8-32 Hz). In conclusion, murine corpus cavernosum expresses PDE9 mRNA. Prolonged PDE9 inhibition with BAY 73-6691 amplifies the NO-cGMP-mediated cavernosal responses, and may be of therapeutic value for erectile dysfunction.

Serum nitric oxide synthase activity is a novel predictor of impaired vasorelaxation in rats

1. It is well documented that both acetylcholine (ACh)-evoked arterial relaxation and brachial artery flow-mediated vasodilatation are blunted in hypercholesterolaemic patients. However, there are no simple diagnostic methods to detect the pathology of blood vessels of patients. 2. To establish the use of serum nitric oxide synthase (NOS) activity as a diagnostic parameter for impaired vasorelaxation, animals with different levels of vascular healthiness were made by feeding Sprague-Dawley rats a normal diet, a high-cholesterol diet (HCD) or an HCD supplemented with 10 mg/kg per day, p.o., simvastatin, a cholesterol-lowering drug, for 30 days. Serum total cholesterol levels, serum NOS activity and ACh-induced vasorelaxation of the isolated aorta were determined at the end of the experiment. 3. Consumption of HCD for 30 days resulted in an increase in serum total cholesterol, attenuated ACh-induced nitric oxide/endothelium-dependent aortic relaxation and decreased NOS activity. Concomitant administration of simvastatin lowered the elevated blood cholesterol levels with complete reversal of the attenuated ACh-induced aortic relaxation and serum NOS activity. An attempt was made to correlate serum NOS activity and the magnitude of ACh-elicited vascular relaxation among the different groups. A positive correlation (r = 0.8329; P < 0.001; n = 30) was found between serum NOS activity and vascular relaxation. 4. This finding is a good foundation for the development of a simple and low-cost alternative for diagnosing vascular diseases and evaluating the effectiveness of drugs on the vascular system in patients.

Abstract 60: Reduced Macrophage-dependent Inflammation Improves Endothelial Function and Vascular Remodeling, Oxidative Stress and Inflammation in a Model Of Endothelin-1 Induced Vascular Injury

Background: Transgenic mice with endothelium specific preproendothelin-1 overexpression (eET-1) exhibit endothelial dysfunction and vascular remodeling, oxidative stress and inflammation independently of hemodynamic effects. However, it is unclear whether vascular inflammation is causally implicated in adverse vascular effects of endothelin-1 (ET-1). We hypothesized that ET-1-induced vascular injury is decreased in a model of reduced macrophage-dependent inflammation, macrophage colony stimulating factor ( mCsf ) mice heterozygote for the osteopetrosis (Op) mutation. Methods and Results: Wild type (WT), eET-1, mCsf Op/+ and eET-1/ mCsf Op/+ mice were studied. There was no difference in tail-cuff systolic blood pressure between groups. Endothelial function and vascular structure were determined on a pressurized myograph. Endothelium-dependent relaxation in response to acetylcholine was similar in eET-1 and eET-1/ mCsf Op/+ . However, in the presence of L-NAME, the magnitude of NO-independent relaxation was greater in eET-1/ mCsf Op/+ compared to eET-1 (72.4±6.7% vs. 40.8±14.4%, P &lt;0.001). Media-to-lumen ratio was greater in eET-1 than WT (0.13±0.01 vs. 0.08±0.01, P &lt;0.01) and unchanged in eET-1/ mCsf Op/+ (0.10±0.01). Media cross-sectional area (μm 2 ) was greater in eET-1 than WT (13521±2106 vs. 8112±381, P &lt;0.05) and unchanged in eET-1/ mCsf Op/+ (8966±1125). Dihydroethidium staining revealed that reactive oxygen species production in aorta was 4-fold higher in eET-1 than WT ( P &lt;0.01) and unchanged in eET-1/mCsf Op/+ . Aortic monocyte/macrophage infiltration was increased 2.6-fold in eET-1 ( P &lt;0.01) and tended to decrease by 45% in eET-1/mCsf Op/+ compared to WT. Conclusion: Reduction of macrophage-dependent inflammation in mice overexpressing ET-1 in endothelium results in improved vascular relaxation and reduced vascular remodeling, oxidative stress and inflammation, providing evidence for a role of macrophages and innate immunity in ET-1-induced vascular damage.

Internal anal sphincter relaxation associated with bisacodyl‐induced colonic high amplitude propagating contractions in children with constipation: a colo‐anal reflex?

Describe the association of internal anal sphincter (IAS) relaxation with colonic high- amplitude peristaltic contractions (HAPCs). Retrospective review of colon manometry tracings of children with constipation to determine the IAS relaxation characteristics associated with HAPC's (HAPC-IASR) events and compare them to the those seen during the performance of the anorectal manometry (ARMRAIR) events. A total of 70 HAPC- IASRs were observed in 15 patients, 65 after bisacodyl, two during fasting and three after a meal. In 64% of events, the IAS relaxation started when the HAPC reached left colon and in 36% as proximal as the hepatic flexure. High- amplitude peristaltic contraction propagation seems to be important in HAPC-IASR characteristics; those propagating distal to sigmoid colon demonstrated larger and longer IAS relaxation as well as lower residual pressure, but equivalent resting pressure compared with HAPC's ending proximal to sigmoid colon. Although IAS resting pressure was comparable for ARM-RAIRs and HAPC-IASRs, the duration and magnitude of anal relaxation was higher, and the anal residual pressure was lower in HAPC-IASRs. We demonstrated that IAS relaxation in constipated children is associated with HAPCs migrating in the proximal and distal colon; in most cases, starting when peristalsis is migrating through left colon and in an important proportion while migrating proximally. We also demonstrated that HAPC-IASRs are different from ARM-RAIRs suggesting a neurally mediated reflex. Finally, the IAS relaxation characteristics are highly dependent on the degree of propagation of HAPCs, which could have important implications in the understanding of defecation disorders.

Thermal relaxation of residual stress in laser shock peened Ti–6Al–4V alloy

Laser shock peening (LSP) induced residual stresses in Ti–6Al–4V, and their thermal relaxation due to short-term exposure at elevated temperatures are investigated by an integrated modeling/simulation and experimental approach. A rate and temperature-dependent plasticity model in the form of Johnson–Cook (JC) has been employed to represent the nonlinear constitutive behavior under both LSP and thermal loads. By comparing the simulation results with experimental data, model parameters for Ti–6Al–4V are first calibrated and subsequently applied in analyzing the thermal stability of the residual stress in LSP-treated Ti–6Al–4V. The analysis shows that the magnitude of stress relaxation increases with the increase of applied temperature due to material softening. Most of stress relaxation occurs before 10min to 20min exposure in this study, and stress distribution becomes more uniform after thermal exposure. An analytical model based on the Zener–Wert–Avrami formula is then developed based on the simulation results. The activation enthalpy of the relaxation process for laser shock peened Ti–6Al–4V is determined to be in the range of 0.71eV to 1.37eV.

Dielectric properties of polypyrrole/pillared clay nanocomposites

Dielectric constant ɛ′ and loss factor ɛ″ were measured in intercalated polypyrrole/aluminum pillared montmorillonite (PPy/Al-PMMT) clay nanocomposites in the frequency range 100 Hz to 1 MHz. The PPy/Al-PMMT nanocomposites were prepared by in situ polymerization of pyrrole in aqueous dispersion of varying amounts of (Al-PMMT) clay from 0.2 to 10%, using FeCl3 · 6H2O as an oxidant. Formation of the nanocomposite was studied by FTIR and intercalation of PPy in the clay galleries was confirmed by XRD. The nanocomposites exhibited very large values of ɛ′ and ɛ″ at low frequency which decreased with frequency and increased with the clay content in the samples. Electric modulus formalism exhibited a peak in the frequency dependence curves of imaginary part of the electric modulus due to conductivity relaxation process. The peak of conductivity relaxation shifted towards higher frequencies and the magnitude of relaxation decreased with the increase of MMT content in the composites.

Quantitative Analysis of Carbon in Ferrite in Dual-Phase Steels by Mechanical Loss Measurements

To establish the method for determining the amount of carbon in the ferrite phase in ferrite + martensite dual-phase low-alloy steels, mechanical loss measurements have been performed on a series of Fe–C alloys with varying constitution. The observed mechanical loss spectra of two-phase alloys turned out to be simple superposition of those of single phase alloys, of ferrite and of martensite. The concentrations of carbon in solution evaluated from the magnitude of the Snoek relaxation in the two-phase alloys agree well with those expected from the Fe–C phase diagram. It is thus possible to selectively analyse the carbon dissolved in the ferrite phase in the complex structure, at least in simple binary alloys.

K0 Compression and Stress Relaxation of Pumice Sand

AbstractPumice sand particles have a vesicular nature, making them light and crushable. Previous research showed that the in situ relative density of pumice deposits cannot be estimated from conventional cone penetration testing. Because of this, a need exsits for more study of the geotechnical properties of this material. First, to distinguish compression behavior of loose and dense sand, K0 compression tests were performed on pumice specimens at various strain rates, from 0.33% to 1,000%/min, until a final compression of approximately 33% of the original specimen length was achieved. Second, after compression, the maximum displacement was held constant for a period of time during which the relaxation of the axial stress was monitored. After unloading, the particle-size distribution was measured to confirm particle crushing. From these results, the magnitude of stress relaxation of loose sand was found to be slightly larger than that of dense sand. On the other hand, dense sand particles exhibited more c...

Effect of indometacin pretreatment on protamine sulfate-mediated relaxation of the isolated rat uterus: the role of the antioxidative defense system

Previous results in this laboratory indicate that protamine sulfate (PS) evokes dose-dependent relaxation of both spontaneous and calcium ion-induced uterus activity mediated predominantly by potassium channels and, to a small extent, via β-adrenergic receptors or nitric oxide (NO)-dependent pathways. Indometacin is a nonselective inhibitor of cyclooxygenase (COX 1 and COX 2) that has the ability to delay premature labor by reducing uterine contractions through the inhibition of prostanglandin synthesis in the uterus. This study investigates the effects of indometacin (0.1 and 1µg/ml) pretreatment on the PS-induced relaxation of isolated uterine smooth muscle.Indometacin pretreatment per se did not change the activity of the uteri. However, indometacin significantly increased PS-induced relaxation of spontaneous uterine contractions. Indometacin pretreatment significantly decreased the magnitude and slope of PS-induced relaxation of calcium ion-induced uterine contractions. Indometacin pretreatment increased CuZnSOD activity and slightly increased GR activity during spontaneous uterine contractions when compared to PS alone. In calcium ion-induced contractions, indometacin pretreatment increased CuZnSOD, GSH-Px and GR activities. These results suggest that, in addition to its COX inhibitory effects, indometacin influences the effects of PS. Therefore, it is possible that indometacin regulates diverse cell functions via its association with lipid membranes by altering micro-environments within the membranes. The above-mentioned processes appear to be partly mediated by redox processes involving ROS, lipid peroxides and antioxidant enzymes. The extent of the PS-mediated effect was different in spontaneous versus calcium ion-induced active uteri.

Martensite evolution in a NiTi shape memory alloy when thermal cycling under an applied load

The microstructural evolution of a near equiatomic NiTi shape memory alloy has been studied by in situ synchrotron diffraction, whilst being thermally cycled under an applied load. The martensite texture was found to be cyclically dynamic and an elongation of the sample was observed with each thermal cycle. The martensite formed when cooling under load exhibited progressive variant selection, in an attempt to accommodate the applied stress, accompanied by strain relaxation of the material. The characteristic transformation temperatures were found to decrease with cycling, possibly as a result of the generation and accumulation of dislocations. The magnitude of elongation, variant selection, lattice relaxation and damage accumulation were found to increase as a function of applied stress and their rate decrease with cycle number.

Electronic Structure and Spectroscopy of Nucleic Acid Bases: Ionization Energies, Ionization-Induced Structural Changes, and Photoelectron Spectra

We report high-level ab initio calculations and single-photon ionization mass spectrometry study of ionization of adenine (A), thymine (T), cytosine (C), and guanine (G). For thymine and adenine, only the lowest-energy tautomers were considered, whereas for cytosine and guanine we characterized the five lowest-energy tautomeric forms. The first adiabatic and several vertical ionization energies were computed using the equation-of-motion coupled-cluster method for ionization potentials with single and double substitutions. Equilibrium structures of the cationic ground states were characterized by DFT with the ωB97X-D functional. The ionization-induced geometry changes of the bases are consistent with the shapes of the corresponding molecular orbitals. For the lowest-energy tautomers, the magnitude of the structural relaxation decreases in the following series, G > C > A > T, the respective relaxation energies being 0.41, 0.32, 0.25, and 0.20 eV. The computed adiabatic ionization energies (8.13, 8.89, 8.51-8.67, and 7.75-7.87 eV for A, T, C, and G, respectively) agree well with the onsets of the photoionization efficiency (PIE) curves (8.20 ± 0.05, 8.95 ± 0.05, 8.60 ± 0.05, and 7.75 ± 0.05 eV). Vibrational progressions for the S(0)-D(0) vibronic bands computed within double-harmonic approximation with Duschinsky rotations are compared with previously reported experimental photoelectron spectra and differentiated PIE curves.

Calcium binding kinetics of troponin C strongly modulate cooperative activation and tension kinetics in cardiac muscle

Tension development and relaxation in cardiac muscle are regulated at the thin filament via Ca2+ binding to cardiac troponin C (cTnC) and strong cross-bridge binding. However, the influence of cTnC Ca2+-binding properties on these processes in the organized structure of cardiac sarcomeres is not well-understood and likely differs from skeletal muscle. To study this we generated single amino acid variants of cTnC with altered Ca2+ dissociation rates (koff), as measured in whole troponin (cTn) complex by stopped-flow spectroscopy (I61Q cTn>WT cTn>L48Q cTn), and exchanged them into cardiac myofibrils and demembranated trabeculae. In myofibrils at saturating Ca2+, L48Q cTnC did not affect maximum tension (Tmax), thin filament activation (kACT) and tension development (kTR) rates, or the rates of relaxation, but increased duration of slow phase relaxation. In contrast, I61Q cTnC reduced Tmax, kACT and kTR by 40–65% with little change in relaxation. Interestingly, kACT was less than kTR with I61Q cTnC, and this difference increased with addition of inorganic phosphate, suggesting that reduced cTnC Ca2+-affinity can limit thin filament activation kinetics. Trabeculae exchanged with I61Q cTn had reduced Tmax, Ca2+ sensitivity of tension (pCa50), and slope (nH) of tension–pCa, while L48Q cTn increased pCa50 and reduced nH. Increased cross-bridge cycling with 2-deoxy-ATP increased pCa50 with WT or L48Q cTn, but not I61Q cTn. We discuss the implications of these results for understanding the role of cTn Ca2+-binding properties on the magnitude and rate of tension development and relaxation in cardiac muscle.

Disturbance and recovery of trunk stiffness and reflexive muscle responses following prolonged trunk flexion: Influences of flexion angle and duration

Background Experimental studies suggest that flexed working postures reduce passive support of the spine, which could represent a significant risk factor for the development of occupational low back disorders. Neuromuscular compensations to reduced passive stiffness include increases in baseline activity or reflexive activation of trunk muscles. Yet, alterations and recovery of the synergy between active and passive tissues following prolonged flexion in humans are currently unknown. Methods Twelve healthy participants were exposed to all combinations of two trunk flexion durations (2 and 16 min) and three flexion angles (33, 66, and 100% of individual flexion–relaxation angle). Load relaxation was recorded throughout exposures, whereas trunk stiffness and reflexive behaviors of the lumbar extensor muscles were investigated during dynamic responses to sudden perturbations. Findings The magnitude of load relaxation increased with increasing flexion angle. Trunk stiffness decreased and reflex gains increased following flexion exposures; for both outcomes, acute changes were larger following exposure to increasing flexion angle. Reflex gains remained elevated one hour after exposure to maximum flexion. Interpretation Exposure to prolonged trunk flexion changed trunk stiffness and reflex behavior in patterns consistent with epidemiological evidence linking such exposure with the risk of occupational low back disorders. Observed increases in reflex gains, at least among healthy individuals, may be a compensation for decreases in passive trunk stiffness following acute exposure to flexed postures. It remains to be determined whether the neuromuscular system can similarly respond to accumulated disturbances in passive structures following exposure to repeated flexion tasks.

Lower esophageal sphincter relaxation reflex kinetics: effects of peristaltic reflexes and maturation in human premature neonates

We defined the sensory-motor characteristics of the lower esophageal sphincter relaxation (LESR) (stimulus threshold volume, response onset, and relaxation period, relaxation magnitude, nadir) during maturation in human neonates. We hypothesized that LESR kinetics differs during maturation and with peristaltic reflex type. Basal and adaptive esophageal motility testing was performed (N = 20 premature neonates) at 34.7 and 39.1 wk (time 1 and time 2). Effects of midesophageal provocation with graded stimuli (N = 1,267 stimuli, air and liquids) on LESR kinetics during esophagodeglutition response (EDR) and secondary peristalsis (SP) were analyzed by mixed models. Frequency of LESR with basal primary peristalsis were different during maturation (P = 0.03). During adaptive responses with maturation, 1) the frequencies of peristaltic reflexes and LESR were similar; 2) liquid stimuli resulted in a shorter LESR response latency and LESR nadir and greater LESR magnitude (all P < 0.05); 3) media differences were noted with LESR response latency (air vs. liquids, P < 0.02); and 4) infusion flow rate-LESR were different (P < 0.01 for air and liquids). Mechanistically, 1) frequency of LESR was greater during peristaltic reflexes at both times (vs. none, P < 0.0001); 2) LESR response latency, duration, and time to complete LESR were longer with EDR (all P < 0.05, vs. SP at time 2); and 3) graded stimulus volume LESR were different for air and liquids (P < 0.01). In conclusion, sensory-motor characteristics of LESR depend on the mechanosensitive properties of the stimulus (media, volume, flow), type of peristaltic reflex, and postnatal maturation. Maturation modulates an increased recruitment of inhibitory pathways that favor LESR.

Vagally‐mediated gastrointestinal reflexes are modulated by central glucose levels

The vagally‐mediated receptive relaxation reflex is activated upon distension of the esophagus and induces gastric relaxation and delays gastric emptying. Many gastrointestinal (GI) hormones exert dramatic control over vagally‐mediated GI functions via brainstem sites of action. The aim of this study was to determine whether glucose‐induced alterations in GI reflexes are achieved, in part, by brainstem sites of action.A balloon was used to distend the esophagus of adult rats and the resulting gastric relaxation measured via miniature strain gauges affixed to the stomach. Increasing blood glucose levels decreased the magnitude of the receptive relaxation from 0.6±0.1g to 0.4±0.1g and 0.3±0.1g at 3±0.2mM glucose, 6±0.5 and 10±1.8mM blood glucose, respectively (n=3). Similarly, altering brainstem glucose directly (via 4th ventricular application 3, 4.5 or 10mM glucose) decreased the receptive relaxation by 5±3, 15±0 and 20±3%, respectively (n=3). The glucose‐induced decreased receptive relaxation was blocked by brainstem application of the 5‐HT3 antagonist, ondansetron (30nmoles; 15±0.3% reduction to 10mM glucose vs 0±0.1% reduction in the presence of ondansetron, n=3).These results suggest that alterations in brainstem glucose levels, either directly or indirectly, exerts profound effects upon vagally‐mediated GI reflexes possibly via mechanism involving alterations in brainstem 5‐HT3 levelsSupported by DK 55530

Expression of PDE5 and its stimulation by cGMP‐dependent protein kinase (PKG) determine the magnitude of smooth muscle relaxation in different regions of the stomach

The contractile phenotypes of proximal and distal gastric smooth muscle are distinct with proximal smooth muscle exhibiting tonic characteristics and distal smooth muscle phasic characteristics. In smooth muscle, the main cGMP hydrolyzing enzyme phosphodiesterase 5 (PDE5) plays an important role in determining the strength and duration of cGMP signaling, and thus muscle relaxation. The activity of PDE5 is stimulated by phosphorylation via PKG.AimTo determine the expression and regulation of PDE5 activity in proximal versus distal regions of the stomach.MethodsExpression of PDE5 and PKG‐mediated phosphorylation of PDE5 at Ser 92 were measured by western blot. PDE5 activity was measured using [3H]cGMP and cGMP‐mediated relaxation was measured by scanning micrometry.ResultsMuscle cells from proximal stomach contained 2 times more PDE5 than muscle cells from distal stomach. Activation of PKG by the NO‐donor caused an increase in PDE5 phosphorylation and activity, but the responses were higher in muscle cells from proximal stomach. In contrast, muscle relaxation was greater in muscle cells from distal stomach consistent with the lower amounts of PDE5 in muscle cells from this region.Conclusion. Higher expression of PDE5 and greater PKG‐mediated augmentation of PDE5 activity in muscle cells from proximal stomach correlate with the tonic phenotype of muscle in proximal stomach relative to distal stomach.

Experimental and ab initio study of the nuclear quadrupole interaction of 181 Ta-probes in an α-Fe2O3 single crystal

We report perturbed-angular-correlation (PAC) experiments on 181Hf (→181Ta)-implanted corundum α-Fe2O3 single crystal in order to determine the magnitude, symmetry and orientation of the electric-field-gradient (EFG) tensor at Ta donor impurity sites of this semiconductor. These results are analyzed in the framework of ab initio full-potential augmented-plane wave plus local orbital (FP-APW+lo) calculations. This combined analysis enables us to quantify the magnitude of the lattice relaxations induced by the presence of the impurity and to determine the charge state of the impurity donor level introduced by Ta in the band gap of the semiconductor.

Theoretical study of the heteroepitaxial growth of Pd on Cu(111), Pd on Ni(111), Ni on Pd(111), and Cu on Pd(111) using a semiempirical method

Heteroepitaxy has been widely studied by many different theoretical and experimental techniques. Each technique focuses on some features of the growth process, and only by combining the information each provides a full characterization can be given. In this work, the growth of Pd on Ni(111), Pd on Cu(111), Cu on Pd(111), and Ni on Pd(111) is studied with a purely energetic approach which consists of determining a unit cell with a size that depends on the relation between the lateral misfit of the deposited film and the substrate. The energetic is evaluated using a semiempirical coupled with a genetic algorithm global search method to determine with accuracy the relaxation magnitudes of the system. With this approach, features such as interlayer spacings, variation in the film's lattice parameter with coverage, and diffusion influence in the growth process are studied qualitative and quantitatively. The results obtained are directly compared with experimental findings from literature and also presented in this work. The theory-experiment comparison shows that the methodology used is successful in describing qualitatively most features of all four systems. However, for the Pd on Cu(111) case, poor agreement is found, and the analysis of the influence of diffusion and temperature suggests that a somewhat complex alloy formation in the interface is expected for this particular system.