Sodium liquid ion exchanger microelectrode used to measure large extracellular sodium transients

A new liquid membrane microelectrode has been developed that is easily fabricated and can measure fast sodium transients in the presence of potassium interference. It responds to a sudden change in sodium activity within 1 second. The electrode has been used to provide the first direct evidence of large sodium transients in the extracellular space of the brain of the catfish.     

电感耦合等离子体质谱法测定高温合金中痕量镉和碲

研究了由于高温合金中Mo的存在而对痕量元素Cd和Te产生的难熔多原子离子质谱干扰,考察了电感耦合等离子体质谱的高频功率、雾化气流速及离子透镜参数等因素对减小或消除95MoO+、94MoO2+干扰的影响。通过反复试验,确立了基于95MoO+峰在111Cd处所产生的等效浓度值与Mo含量间存在着二元线性关系的数学校正公式;94MoO2+峰对126Te的干扰则通过各同位素间的丰度比例关系进行校正。试验表明,采用所建立的数学校正法可以很好地校正高温合金中Mo产生的95MoO+、94MoO2+干扰。Cd和Te的测定下限分别为0.08μg/g和1.0μg/g。方法应用于Mo的质量分数为2%的高温合金标准物质中1~10μg/g痕量Cd和0.5~100μg/g痕量Te的测定,测定值与标准值吻合较好,RSD小于20%。     

Glyphosate is an inhibitor of plant cytochrome P450: functional expression of Thlaspi arvensae cytochrome P45071B1/reductase fusion protein in Escherichia coli

Radiofrequency (RF) energy has many advantages in thermal tumor ablation protocols. With the recent development of open MRI systems, interventional MRI procedures, including thermal ablation, have become the focus of great research interest. However, the significant interference between RF generators and MR imagers has prevented simultaneous imaging and RF ablation and, until now, has limited the role of RF-based thermal therapy in interventional MRI. Here, a simple switching circuit designed with consideration of patient safety provides compatibility between open MRI systems and RF thermal lesion generators. The experimental results show that the switching circuit allows imaging during RF ablation and opens new opportunity for MR-guided thermal therapy.     

电感耦合等离子体原子发射光谱法测定铌铁中硅

在常温下用HNO₃和HF溶解样品,采用标准加入法消除样品基体的干扰,通过电感耦合等离子体发射光谱仪的专利分析软件选择适当的背景点扣除背景,解决了传统的标准加入法只能用于数量少的样品分析和不能消除背景干扰的缺点。通过编辑分析程序自动绘制工作曲线和计算结果,采用钇内标加入法提高了方法的稳定性,实现了采用电感耦合等离子体原子发射光谱法(ICP-AES)铌铁中硅的测定。考察并选择了电感耦合等离子体光谱仪的RF功率、雾化气流量、辅助气流量等最佳分析参数。对一铌铁试样中硅进行10次测定,测定结果的相对标准偏差为2.4%,标样的测定值与认定值相符。     

Effect of cryopreservation on survival of composite tissue grafts

Recent studies have suggested that the attenuation of the local electrogram amplitude recorded from the ablation electrode during radiofrequency (RF) application predicts lesion growth. This study examined the time course of local electrogram amplitude during ongoing RF delivery in patients with common atrial flutter (AFl). In 71 patients with AFl. RF energy was applied to the anatomical isthmus. Termination of AFl was noted during 68 of 625 applications of RF energy. The changes in local atrial electrogram amplitude observed at all successful sites were analyzed. With increasing duration of the RF delivery, the electrogram amplitude decreased exponentially to reach a steady state within a mean duration of 17+/-3 sec, which was significantly longer than that of the steady-state temperature. The average decrease in the amplitude was 67+/-13%. In 16 patients in whom an increase in the power of RF energy had resulted in AFl termination, there was a dose-response relationship between the power and the amplitude decrease. The decrease in local electrogram amplitude appears to be a reliable marker for the efficacy of tissue heating and may be useful as an endpoint for individual applications. Local electrogram monitoring may offer an optimal energy strategy in AFl ablation.     

Radiofrequency delivery through a cooled catheter tip allows the creation of larger endomyocardial lesions in the ovine heart

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

Radiofrequency catheter ablation of septal accessory pathways within the triangle of Koch: importance of energy titration testing other than the local electrogram characteristics for identifying the successful target site

Radiofrequency (RF) catheter ablation of accessory atrioventricular (AV) connections in the proximity of His bundle or AV node is at high risk of developing complete heart block. A safe and effective protocol has not been well established. Nineteen consecutive patients with 19 septal accessory pathways within the triangle of Koch underwent a protocol with power-titrated RF energy testing to identify the target site for successful catheter ablation. At every potential target site preselected by local electrogram characteristics, RF energy was started at 5 W for 10 seconds, with an increment of 5 W (duration remained at 10 s) until maximally 30 W or the observation of transient interruption of accessory pathway conduction. By this stepwise RF energy testing, we successfully localized and ablated 18 (94.7%) of the 19 septal accessory pathways, 10 close to His bundle (zone I) and 8 away from it (zone II). The test-effective RF power was 20 W or less in 9 of all 11 septal accessory pathways in zone I, and 5 of the 8 in zone II (P = 0.68). Meanwhile, the final RF power for successful ablation was 30 W or less in 9 of the 10 zone I and 6 of the 8 zone II septal accessory pathways (P = 0.83). One patient with an accessory pathway in zone I was complicated with complete AV block after final ablation at 30 W. None of the local electrogram characteristics except continuous electrical activity during retrograde mapping was helpful in the prediction of ablation outcome. Careful RF energy titration testing could effectively help identify the target site for successful RF catheter ablation of septal accessory pathways within the triangle of Koch. The dependence on local electrogram manifestations could be frustrated by a low probability of success.     

Effect of surface modification of high-density polyethylene by direct current and radio frequency glow discharge on wetting and adhesion characteristics

The present investigation aims to optimize the process parameters of Direct Current (DC) and Radio Frequency (RF) glow discharge treatment through air in terms of discharge power and time of exposure for the surface modification of high-density polyethylene (HDPE) sheet, for attaining best adhesive joint of the polymer to mild steel. In order to estimate the extent of surface modification, the surface energies of the polymer surfaces exposed to glow discharge have been determined by measuring contact angles using two standard test liquids of known surface energies. It is observed that at a given power level of DC glow discharge, surface energy and its polar component increase with increasing exposure time, attaining a maximum and then decreasing. In the case of RF glow discharge, surface energy and its polar component increase with increasing exposure time and then saturate. Surface modification by DC glow discharge increases the surface energy of HDPE relatively more at a lower power compared to that observed for RF glow discharge. The dispersion component of surface energy remains almost unaffected. The surfaces have also been studied by electron spectroscopy for chemical analysis (ESCA) and energy-dispersive spectra (EDS). A significant oxygen peak is observed for surface-modified polymer as detected by ESCA and EDS. Lap shear tensile test of an adhesive (Araldite AY 105) joint of HDPE with mild steel has been carried out in optimizing the parameters of DC and RF glow discharge for maximum joint strength. When HDPE is exposed to DC glow discharge, improvement of adhesive joint strength of HDPE to mild steel is found to be by a factor more than 7. On the other hand, when HDPE is exposed to RF glow discharge, results in improvement of adhesive joint strength of HDPE to mild steel by a factor nearer to 7 are found. Thus, DC glow discharge is more capable for increasing wetting and adhesion characteristics of the polymer.     

Analysis of Electrochemical Current Noise From Metastable Pitting of SS304L in NaCl Solutions

Electrochemical noise emanating from a corrosion situation gives indication about the nature and form of corrosion. An attempt has been made to analyse electrochemical current noise signal generated under potentiostatic condition (for metastable pitting) for SS304L–NaCl system. To begin with polarisation plots of SS304L were obtained in various test solutions to precisely know pitting potential of SS304L. It is found that E_pit and i_pass increase on increasing chloride content. The electrochemical current noise was measured at potentials 20–30 mV below the pitting potentials. The current time record shows two types of current transients; (i) slow rise and rapid decay and (ii) rapid rise and slow decay. Power spectral density analysis of current noise shows that the power (A²/Hz) of the signal measured at metastable pitting range increases with increasing chloride. Sampling frequency has to be properly selected otherwise some of the spikes are not recorded and as a result, size and shape of few current transients is altered.     

Serum- and bradykinin-induced calcium transients in familial Alzheimer's fibroblasts

The calcium-sensitive photoprotein, aequorin, was used to examine serum- and bradykinin-induced transient increases in free cytosolic calcium ions in skin fibroblasts from 10 individuals with early onset familial AD (FAD), including four who were biopsied before their clinical symptoms would allow a diagnosis of AD, 2 individuals with late onset FAD, 8 at-risk but nonsymptomatic individuals, and 13 controls. The data show that (a) among controls, the peaks of the calcium transients increase in height as a function of donor age; (b) transients induced by 10% serum, 10 nM bradykinin (BK) or 100 nM BK were generally lower in FAD fibroblasts, including those from donors in the early stages of the disease, than in age-matched control cells; (c) such transients are reduced in cells from a proportion of the nonsymptomatic, at-risk individuals. Thus, serum- and BK-induced calcium transients are reduced in fibroblasts from both early and more advanced stage FAD donors and perhaps even from donors who are presymptomatic carriers of the defective gene. The data also suggest that changes in calcium transients in FAD fibroblasts neither mimic nor exaggerate the effects of normal aging.     

Deformation mechanisms in superplastic AA5083 materials

The plastic deformation of seven 5083 commercial aluminum materials, produced from five different alloy heats, are evaluated under conditions of interest for superplastic and quick-plastic forming. Two mechanisms are shown to govern plastic deformation in AA5083 over the strain rates, strains, and temperatures of interest for these forming technologies: grain-boundary-sliding (GBS) creep and solutedrag (SD) creep. Quantitative analysis of stress transients following rate changes clearly differentiates between GBS and SD creep and offers conclusive proof that SD creep dominates deformation at fast strain rates and low temperature. Furthermore, stress transients following strain-rate changes under SD creep are observed to decay exponentially with strain. A new graphical construction is proposed for the analysis and prediction of creep transients. This construction predicts the relative size of creep transients under SD creep from the relative size of changes in an applied strain rate or stress. This construction reveals the relative size of creep transients under SD creep to be independent of temperature; temperature dependence resides in the “steady-state” creep behavior to which transients are related.     

Monitoring of radio frequency tissue ablation in an interventional magnetic resonance environment. Preliminary ex vivo and in vivo results

RATIONALE AND OBJECTIVES: The authors evaluate the feasibility of monitoring radio frequency (RF) ablation in an interventional, open-configuration, 0.5-tesla magnetic resonance (MR) environment. METHODS: Ex vivo and in vivo RF coagulation necrosis were induced in porcine paraspinal muscle tissue using a 300 kHz monopolar RF generator applying 5 to 20 W over 3 to 9 minutes. Images were acquired simultaneous to RF application, after RF application, and in an intermittent mode (60 seconds of RF followed by 15 seconds of MR imaging). Temperature changes were monitored based on amplitude (ex vivo) and phase alterations (in vivo) of a T1-weighted graded refocused echo (GRE) sequence enabling an update every 2.5 seconds. A standardized color-coded subtraction technique enhanced signal changes. Additionally, T2- and T1-weighted spin echo (SE) images were acquired with and without intravenous contrast. Macroscopic coagulation size was compared with lesion size seen on MR images. RESULTS: Although lesion diameters were related directly to applied RF power, the application mode had no significant impact on coagulation size (P > 0.05). As could be expected, MR imaging during RF ablation resulted in major image distortion. Radio frequency effects were seen on images acquired in the continuous and intermittent modes. Coagulation size seen on GRE images correlated well with macroscopy both ex vivo (r = 0.89) and in vivo (r = 0.92). Poorer correlation was found with postinterventional SE sequences (r = 0.78-0.84). CONCLUSIONS: Magnetic resonance monitoring of RF effects is feasible both ex vivo as well as in vivo using temperature-sensitive sequences in an open-configuration MR environment.     

Observations of melt rate as a function of arc power,CO pressure,and electrode gap during vacuum consumable arc remelting of Inconel 718

Statistically designed experiments were conducted at two different production melt shops to evaluate the influence of arc power, CO pressure, and electrode gap on melt rate. Approximately 11,000 kg of Inconel 718 alloy 0.4 m diameter electrodes were vacuum consumable arc remelted into 0.5 m diameter ingots. Analysis of the experimental results revealed that melting efficiency (melting rate/kW) was maximized when CO pressure and electrode gap were held at low levels. Under these conditions, the heat distribution (created by the vacuum arc) on the electrode tip and the molten pool exhibited macro uniformity. Increased CO pressure and/or electrode gap depressed the melt rate, and at 13.3 Pa (100 microns) and a 0.050 m electrode gap, this depression exceeds 46 pct. Increasing these parameters also changed the arc behavior to that of a constricted arc with a highly localized heat input. It is hypothesized that the change from the usual diffuse arc to this constricted arc results in intense Lorentz pumping in a localized region of the molten pool atop the ingot causing fluid flow transients. These transients could, in turn, create solidification defects.     

A direct estimation of the context effect on the efficiency of termination

An in vitro assay in which terminating Escherichia coli ribosomes with different stop signals in the A-site compete for a limited amount of a release factor (RF1 or RF2) has been used to estimate the relative termination efficiencies at stop codons with different adjacent downstream nucleotides. The assay allows direct measurements of relative kcat/Km parameters for the productive association of release factors to ribosomes. The kcat/Km parameter is larger for UAA(U) than for UAA(C) programmed ribosomes and the difference in kcat/Km is much larger for RF2 (about 80%) than for RF1 (about 30%). These differences in the kcat/Km parameter are not affected by the addition of release factor RF3. The only discernible effect of RF3 is a considerable acceleration of RF1/2 recycling.The estimated kcat/Km parameters correlate well with the affinities of release factors for ribosomes programmed with different stop signals. These affinities were estimated from the extent of inhibition of ribosomal recycling by high concentrations of release factors in the absence of release factor RF3. The affinity for RF2 depends on the immediate downstream context of the stop codon in the translated mRNA and is about three times higher for UAA(U) than for UAA(C). The corresponding difference in affinities for RF1 is twofold. For all stop signals studied, the estimated affinity of RF2 for terminating ribosomes is much lower than that of RF1. It is also striking that the affinity of ribosomes for a chromosomally expressed RF2 is at least three times higher than for RF2 isolated from an overproducing E. coli strain.     

Thermal Transients During Processing of 3003 Al-H18 Multilayer Build by Very High-Power Ultrasonic Additive Manufacturing

Previous investigations suggested a gradient in bond microstructure along the height of a “build” made by very high power ultrasonic additive manufacturing—a rapid prototyping process that is based on ultrasonic seam welding. The bonding of foils is associated with the occurrence of dynamic recrystallization at the interfaces between them. To understand heating patterns across the build that may be responsible for such microstructure evolution, temperatures from different interface regions were recorded simultaneously during the fabrication of a 3003 Al-H18 multilayer build under a given processing condition. Thermal transients were observed over multiple interfaces of the build during welding of each layer. The temperatures were the highest for the layer processed and were found to diminish beneath with each subsequent layer. Such maximum temperatures also depended on the height at which the new layer was bonded. The occurrence of transients across the build is rationalized based on heat being conducted away from the processed layer.     

Successful irrigated-tip catheter ablation of atrial flutter resistant to conventional radiofrequency ablation

BACKGROUND: Catheter ablation of typical right atrial flutter is now widely performed. The best end point has been demonstrated to be bidirectional isthmus block. We investigated the use of irrigated-tip catheters in a small subset of patients who failed isthmus ablation with conventional radiofrequency (RF) ablation. METHODS AND RESULTS: Of 170 patients referred for ablation of common atrial flutter, conventional ablation of the cavotricuspid isthmus with >21 applications failed to create a bidirectional block in 13 (7.6%). An irrigated-tip catheter ablation was performed on identified gaps in the ablation line according to a protocol found to be safe in animals: a moderate flow rate of 17 mL/min and temperature-controlled (target, 50 degrees C) RF delivery with a power limit of 50 W. Bidirectional isthmus block was achieved in 12 patients by use of a mean delivered power of 40+/-6 W with a single application in 6 patients and 2 to 6 applications in the other 6. No side effects occurred during or after the procedure. CONCLUSIONS: Irrigated-tip catheter ablation is safe and effective for achieving cavotricuspid isthmus block when conventional RF energy has failed.     

Estimating costs of programme services and products using information provided in standard financial statements

OBJECTIVE: To determine whether spectral analysis of unprocessed radiofrequency (RF) signal offers advantages over standard videodensitometric analysis in identifying the morphology of coronary atherosclerotic plaques. METHODS: 97 regions of interest (ROI) were imaged at 30 MHz from postmortem, pressure perfused (80 mm Hg) coronary arteries in saline baths. RF data were digitised at 250 MHz. Two different sizes of ROI were identified from scan converted images, and relative amplitudes of different frequency components were analysed from raw data. Normalised spectra was used to calculate spectral slope (dB/MHz), y-axis intercept (dB), mean power (dB), and maximum power (dB) over a given bandwidth (17-42 MHz). RF images were constructed and compared with comparative histology derived from microscopy and radiological techniques in three dimensions. RESULTS: Mean power was similar from dense fibrotic tissue and heavy calcium, but spectral slope was steeper in heavy calcium (-0.45 (0.1)) than in dense fibrotic tissue (-0.31 (0.1)), and maximum power was higher for heavy calcium (-7.7 (2.0)) than for dense fibrotic tissue (-10.2 (3.9)). Maximum power was significantly higher in heavy calcium (-7.7 (2.0) dB) and dense fibrotic tissue (-10.2 (3.9) dB) than in microcalcification (-13.9 (3.8) dB). Y-axis intercept was higher in microcalcification (-5.8 (1.1) dB) than in moderately fibrotic tissue (-11.9 (2.0) dB). Moderate and dense fibrotic tissue were discriminated with mean power: moderate -20.2 (1.1) dB, dense -14.7 (3.7) dB; and y-axis intercept: moderate -11.9 (2.0) dB, dense -5.5 (5.4) dB. Different densities of fibrosis, loose, moderate, and dense, were discriminated with both y-axis intercept, spectral slope, and mean power. Lipid could be differentiated from other types of plaque tissue on the basis of spectral slope, lipid -0.17 (0.08). Also y-axis intercept from lipid (-17.6 (3.9)) differed significantly from moderately fibrotic tissue, dense fibrotic tissue, microcalcification, and heavy calcium. No significant differences in any of the measured parameters were seen between the results obtained from small and large ROIs. CONCLUSION: Frequency based spectral analysis of unprocessed ultrasound signal may lead to accurate identification of atherosclerotic plaque morphology.     

Calcium transients in single myocytes and membranous ultrastructures during the development of cardiac hypertrophy and heart failure in rats

1. We examined changes in intracellular calcium transients of separated single myocytes from the right ventricle (RV) of the rat heart during the change from adaptation to maladaptation in response to a pressure overload. 2. Right ventricular hypertrophy (RVH) secondary to pulmonary hypertension was induced by a subcutaneous injection of monocrotaline. Developed tensions of the RV-free wall were decreased as RVH progressed. Single myocytes were separated from the RV during different stages of RVH. Fura-2/AM-loaded cells were field stimulated, and changes in calcium transients were measured by Olympus OSP-3 system. We also examined membranous ultrastructures (sarcoplasmic reticulum, mitochondria, surface caveolae) involved in calcium metabolism in the hearts using scanning electron microscopy. 3. We observed characteristic changes in calcium transients during the change from adaptation to maladaptation, and also found that one parameter (amplitude) of calcium transients appeared to be correlated with the changes in the number of sarcoplasmic reticulum. 4. These results provided some insights into the mechanism of calcium handling of hypertrophied heart in response to a pressure overload from adaptation to maladaptation especially when stimulatory frequency was high, and suggested that heart rate control is a very important factor for the treatment of patients with congestive heart failure.     

plane-strain work hardening and transient behavior of interstitial-free steel

Stress transients resulting from abrupt changes in strain path have been shown to be important to subsequent formability. In order to investigate whether these transients result from strain aging or related interstitial effects, two-stage experiments were performed on Armco interstitial-free steel After a prestrain in plane-strain tension, the material was strained in uniaxial tension in the direction of zero initial extension. The stress-strain curve in plane strain was found to deviate markedly from that predicted by usual plasticity theory (Hill’s theory withM = 2.0). Comparison of monotonie curves from uniaxial and plane-strain tension using a newly-developed, self-consistent calculation suggested that IF steel follows Hill’s new theory with constantM ≈ 2.9. After the change from plane strain to uniaxial tension, positive stress transients (flow stress exceeds the monotonie flow stress) were measured. This form of transient agrees with ones measured for other steels. It therefore appears that the origin of the transient phenomenon is independent of interstitial content, and that static strain aging is not the mechanism by which these stress transients occur. Formerly A. E. Browning, Graduate Research Associate, Department of Metallurgical Engineering, The Ohio State University     

Doxorubicin cardiotoxicity: diastolic cardiac myocyte dysfunction as a result of impaired calcium handling in isolated cardiac myocytes

We examined intracellular calcium transients of isolated single cardiac myocytes from rats with doxorubicin (DOX)-induced cardiomyopathy with simultaneous measurement of cell motion. DOX was administered i.p. to Sprague-Dawley rats at 2.5 mg/kg once a week for 10 weeks. Field-stimulated calcium transients and simultaneous cell motion in single myocytes were measured in the presence or absence of isoproterenol using fura-2/AM. Histopathologic examination revealed slight changes. The time courses of both calcium transients and cell motion were significantly prolonged by DOX. There was a slight but not significant reduction in parameters of contractility in both calcium transients and cell motion. The beta-adrenoceptor responsiveness of both calcium transients and cell motion was not significantly impaired compared with the controls. Our data indicated that, despite the slight histologic changes in the heart in DOX-induced cardiomyopathy, impaired sequestration of intracellular free calcium ions in individual myocytes may be one factor leading to diastolic dysfunction. Monitoring of diastolic function is important to detect early cardiotoxicity caused by DOX.