Slotted Tube Research Articles

967-21 Long Term Results of Balloon Expandable Slotted-Tube Nitinol Stents in Canine Coronary Arteries

This study evaluated delivery performance, quantitative angiographic parameters, intravascular ultrasound appearance. long term patency and vascular histology of radio-opaque, slotted-tube nickel titanium (nitinoll stents permanently implanted in canine coronary arteries. Dogs were treated with aspirin for 1 month. Follow-up angiography and histology were performed at 0.5, 1, 3, and 6 months (number of vessels = 2, 4, 6, and 26, respectively). Thirty-eight of 39 (97%) stents were successfully implanted in the mid LAD and LCX of 20 dogs. One stent, which was undersized, was successfully removed by thermal recovery. Tandem stents were placed in 2 dogs without difficulty. Intravascular ultrasound of 6 stents showed symmetrical expansion with good wall contact. Acute angiographic parameters: nominal stent size (mm) ANOVA p 3.0 3.5 4.0 number 4 22 12 – inflation pressure (atm) 5.5 ± 05 6.1 ± 1.4 5.9 ± 1.6 0.47 minimal diameter (mm) 2.93 ± 0.07 3.24 ± 0.14 3.48 ± 0.16 0.0003 balloon to artery ratio 1.23 ± 0.03 1.25 ± 0.10 1.25 ± 0.08 0.65 stent to artery ratio 1.09 ± 0.03 1.14 ± 0.09 1.13 ± 0.07 0.30 percent recoil 11.0 ± 1.8 8.4 ± 1.8 9.9 ± 1.8 0.05 At follow-up, all vessels and 9 of 9 stented sidebranches were patent. The mean percent stenosis at 3 to 6 months was –1.6 ± 5.2 and the late loss was 0.2 ± 0.3 mm. All struts were covered with neointima at 2 weeks. At 6 months the maximal neointimal thickness was 260 ± 50 μ m and was located adjacent to the struts. No thrombi and only occasional areas of granulation tissue with rare inflammatory cells were seen. A slotted tube nitinol stent has delivery performance characteristics and recoil similar to stainless steel slotted-tube stents. Nitinol stents endothelialize rapidly and intimal proliferation is insufficient to create a stenosis in this animal model. These data suggest that a slotted-tube, balloon expandable nitinol stent is sufficiently reliable and biocompatible to warrant clinical trials.

Resorbable dowels for osteosynthesis of noncongruent bone fragments

Dowels, in contrast to screws, offer the great advantage in osteosynthesis that no pressure peaks occur by functional loading rectangular to the screw axis; consequently, there is no bone resorption and no loosening of the fixation because of the even contact of dowel and bony surface. However, dowels must be made of resorbable materials because they cannot be removed. We developed double-spreading dowels with a slotted tube whose outside is cylindric and the inside conical at both ends. Two conical screws in the core of the dowel moved toward each other cause symmetric expansion of the outer surface. Dowel material consisted of polylactic acid with an inherent viscosity >7 dl/g (Resomer 214, Bohringer Ingelheim). A model simulating retromolar sagittal split osteotomy was chosen for experimental research because, in this case, noncongruent bone segments have to be osteosynthesized to regenerate in the sense of distance osteogenesis. Two segments of synthetic material were synthesized like proximal and distal segments after retromolar sagittal split osteotomy fixed by two or three dowels without coherent contact. The synthesized segments underwent a continuous jiggling stress test comparable with the physiologic stress of a jaw for about 4 weeks. Dowel fixation proved to be nearly as stable as position-screw fixation. Resorbable dowel fixation yields experimentally the required stability for the time needed for bony regeneration.

A three dimensional analysis of slotted tube resonator for MRI

A three dimensional model of a slotted tube resonator (STR) used as a probe in the magnetic resonance imaging (MRI), which is loaded by a dielectric body and surrounded by a conducting shield, is analyzed by using the variational method and the dyadic Green's function of a circular waveguide having a dielectric core. Three surface current modes are properly assumed to expand the currents on the STR. The characteristics such as the input impedance, the resonance frequency, the Q value, and the magnetic field distribution are obtained to show the effects of the dielectric body and the conducting shield. Some theoretical results are compared with the measured data to confirm the validity of the present analysis.

Applications of a slotted tube atom trap and flame atomic absorption spectrometry: Determination of tin in copper-based alloys after hydride generation

A sensitive system is reported for the determination of tin in copper-based alloys by flame atomic absorption spectrophotometry. Use of a slotted quartz atom trap coupled with hydride generation improved the sensitivity by a factor of 200, compared with that obtained using conventional flame AAS. The determination of tin in a series of reference samples demonstrates the usefulness of the system for the analysis of metallurgical samples.

Applications of a slotted tube atom trap and flame atomic absorption spectrophotometry: Determination of antimony in copper based alloys

A sensitive system is described for the determination of antimony in copper-based alloys by flame atomic absorption spectrophotometry. The use of a slotted tube quartz atom trap improves precision and reduces the characteristic concentration by factors of 3 and 1.6 compared with the use of conventional flame AAS. Interferences are minimised by coating the internal surfaces of the STAT with copper.

RF coil optimization: Evaluation of B1 field homogeneity using field histograms and finite element calculations

Two-dimensional (2D) finite element analysis has been used to solve the full set of Maxwell's equations for the 2D magnetic field of radiofrequency (RF) coils. The field histogram method has been applied to evaluate and optimize the magnetic field homogeneity of some commonly used RF coils: the saddle coil, the slotted tube resonator, the multiple elements coil and the birdcage resonator, as well as the radial plate coil. Each coil model represents a cross-section of an infinitely long cylinder. The optimum configuration of each of these five RF coils is suggested. It was found that field homogeneity is more strongly dependent on the coil's window angle than on any other parameter. Additionally, eddy currents in the coil's conductive elements distort the current and magnetic field distribution. The frequency dependence of this eddy current distortion is analyzed and discussed.

The use of a long split rectal tube to aid in pull-through procedures for imperforate anus

Problems with loss of correct orientation of the pull-through rectal pouch during posterior sagittal anorectoplasty (PSARP) for high imperforate anus can occur during laparotomy after perineal closure is complete. A simple modification of the de Vries-Peña technique is described that facilitates preservation of orientation and precise anatomical neomuscle construction. A slotted rubber tube preserves correct anatomical orientation of the neorectal pouch and allows accurate construction of the muscle complex around the tube.

Analytical Scheme for the Direct Graphite-Atomizer/Flame Atomic Absorption Spectrometric Determination of Fifteen Trace Elements in Toenails for Biological Monitoring

Abstract An analytical scheme for the determination of up to fifteen trace elements in nails and hair has been proposed. Samples were solubilized by means of aqueous tetraalkylammonium hydroxide (alkyl = methyl or ethyl). Cadmium, Cr, Cu, Fe, Mn, Pb and Zn were determined by pulse-nebulization flame AAS, employing the Slotted Tube Atom Trap (STAT) for Cd and Pb. Suitable chemical modifiers have been applied in electrothermal AAS (ETAAS) determinations of Cd and Pb (ammonium hydrogen phosphate), As, Sb, Se and Sn (palladium), while no modifier was needed in determinations of Al, Co, Cr, Mn, Mo and Ni. Calibration was performed by means of matrix-matched standards and the technique was verified by standard additions, comparison with neutron activation and analysis of hair reference material. The usefulness of this technique for occupational exposure monitoring is briefly discussed.

Application of the slotted quartz tube in flow-injection flame atomic-absorption spectrometry

The slotted quartz has been applied to flow-injection flame atomic-absorption spectrometry (FI-FAAS) showing several important advantages. The tube life was improved by a factor of 5–6 compared to conventional continuous aspiration. Flow impact systems were found not to be necessary in the applications so that larger enhancement factors may be achieved without sacrifice in precision. For 1.0 mg/l. copper, 1.0 mg/l. lead, 0.1 mg/l. cadmium and 1.0 mg/l. gold sensitivity enhancement factors of 3.1, 5.5, 5.3 and 4.0 were obtained with precisions of 1.3%, 1.1%, 1.6% and 1.7% RSD ( n = 11) respectively. Application of the slotted quartz tube FI-FAAS method to the determination of heavy metals in urine has shown improved tolerance to interfering matrices. Recoveries obtained by spiking undiluted urine samples with 0.1 mg/l. copper and lead, and 0.01 mg/l. cadmium were in the range 100–102%.

The determination of tin in zirconium alloys using slotted atom trap (STAT) flame atomic absorption spectrophotometry

An improved system is reported for the determination of tin in Zircaloys by flame atomic absorption spectrophotometry. Use of a slotted quartz tube atom trap improved sensitivity and precision by a factor of 2–3 compared to that obtained by conventional flame AAS. Determination of tin in reference Zircaloys proves the good precision and accuracy of the proposed analytical procedure.

Conformal mapping analyses of microstrips with circular and elliptical cross-sections

A conformal transformation is derived in terms of a Schwarz-Christoffel transformation involving elliptic integrals of the first and third kind. This mapping function is used to give exact solutions for TEM excitations of microstrips and coupled microstrips with circular and elliptical cross-sections. Using these maps, the uniformity of the TEM mode magnetic field inside an elliptical slotted tube transmission line is investigated. >

Separation of seven arsenic compounds by high-performance liquid chromatography with on-line detection by hydrogen–argon flame atomic absorption spectrometry and inductively coupled plasma mass spectrometry

Seven molecular forms of arsenic were separated by anion- and cation-exchange high-performance liquid chromatography (HPLC) with on-line detection by flame atomic absorption spectrometry (FAAS). The interfacing was established by a vented poly(tetrafluoroethylene) capillary tubing connecting the HPLC column to the nebulizer of the atomic absorption spectrometer. Arsenite, arsenate, monomethylarsonate (MMA) and dimethylarsinate (DMA) were separated from each other and from the co-injected cationic arsenic compounds, arsenobetaine (AsB), arsenocholine (AsC) and the tetramethylarsonium ion (TMAs) on an organic polymeric anion-exchange column with 0.1 mol dm–3 carbonate at pH 10.3 as the mobile phase. The three cationic species were separated from each other and from the co-injected anionic species on a silica based cation-exchange column with pyridine at a pH of 2.65 as the mobile phase. The signal-to-noise ratio of the on-line AAS detector was optimized. This involved the use of the hydrogen–argon–entrained air flame, a slotted tube atom trap in the flame for signal enhancement, electronic noise damping and a high-intensity light source. The detection limits in µg cm–3, using 100 mm3 injections of mixtures of arsenic standards into the HPLC system were: arsenite, AsIII 1.1; arsenate, Asv 1.4; MMA 1.4; DMA 0.7; AsB 0.3; AsC 0.5; and the TMAs 0.4. The HPLC–AAS system was used for the analysis of arsenic species in aqueous extracts of soil samples from a polluted land site. Only arsenate was found in the soil extracts. For comparison, inductively coupled plasma mass spectrometry was also used as an on-line detection technique with the same HPLC systems.

Assessment of Copper Status in Preterm Infants: Limited Value of Assays of Erythrocyte Copper Concentration and Superoxide Dismutase Activity.

Preterm infants are particularly at risk of copper deficiency but there is no method for assessing copper status in preterm infants that has been unequivocally accepted. We explored the potential value of assays of erythrocyte copper concentration and erythrocyte superoxide dismutase (SOD) activity. Erythrocyte copper was measured by continuous nebulization flame atomic absorption spectrophotometry using a slotted tube atom trap. Erythrocyte SOD activity was measured by an automated method based on the inhibition of pyrogallol autoxidation. The methods gave reproducible results and the sample volumes were small. Due to the high frequency of blood transfusions, only 38% of the infants investigated had any results for erythrocyte copper or SOD that were considered to be unaffected by transfusion. Compared with adults, there appeared to be a difference in the distribution of copper in the erythrocytes of the small group of infants whose erythrocyte biochemistry was unaffected by blood transfusion. We conclude that neither erythrocyte copper nor erythrocyte SOD is likely to be of much value in assessing copper status in preterm infants.

Analytical quality control by solid sampling GFAAS in the production of animal tissue reference materials: lead and cadmium in bovine liver reference materials

The function of solid sampling graphite furnace atomic absorption spectrometry (SS-GFAAS) in the laboratory-internal preparation, production and standardization of bovine liver reference material is described. Analytical quality assurance was achieved by using a wet digestion decomposition procedure and GFAAS (WD-GFAAS) as well as three different methods of SS-GFAAS. It will be shown, that SS-GFAAS is an adequate and efficacious method of analytical quality control in the production of reference materials. Details are given about the preliminary steps of sample selection and preparation, applying SS-GFAAS both as a screening method and for the detection of contamination during the production of the reference materials. The element contents of the four bovine liver materials measured after decomposition with nitric acid in the open system by GFAAS and also by Flame-AAS, using the ‘slotted tube atom trap’, are compared statistically with the results obtained by SS-GFAAS. In solid sampling analyses three different systems were applied: a solid sampling ZAA-spectrometer with platform-boat, a D2AA-spectrometer with solid sampling graphite tube and platform-drawer and an autoprobe-D2AA-spectrometer with solid sampling autoprobe and graphite tube.

A simple design for a double‐tunable probe head for imaging and spectroscopy at high fields

A double-tunable probe head based on the slotted tube resonator is described. Its performance at 2.35 T is comparable to that of single-tunable designs. The main advantages are a large tuning range, a probe volume that is not reduced by the second circuit, and a simple design.

Vehicle‐Mounted Hydraulic Sampler for Urban Soils

AbstractSampling soils in landscapes and research plots in urban settings is normally done by hand because motorized samplers lack the mobility and small size. To facilitate sampling urban soils, a vehicle‐mounted hydraulic sampler was constructed by making minor modifications to commercially available equipment. The unit consists of a hydraulic sampler with self‐contained engine and hydraulic pump mounted on the back of a turf utility vehicle. Soil cores are taken with a 32 mm diam. ✕ 0.46 m long slotted tube. Samples can be taken to 1.2 m depth.

On-line pre-concentration for the measurement of cadmium in urine by flame atomic absorption spectrometry

The sensitivity for the measurement of cadmium in urine by flame atomic absorption spectrometry was increased 27.7-fold by the use of an on-line alumina microcolumn and a slotted quartz tube. Cadmium in 2.5 ml of sample was trapped on to basic alumina and rapidly eluted with 8%V/V HNO3. The effects of sample pH and column size on performance were investigated. Results obtained with a series of urine specimens compared well with those obtained by electrothermal atomisation atomic absorption spectrometry.

The center-tapped slotted tube autotransformer resonator: a coil for use with a high-resolution small animal imaging system.

A radiofrequency (rf) coil design based on a slotted tube resonator which allows high-resolution imaging of the rodent brain with excellent anatomic definition on a standard G.E. CSI II 2.0-T MR imaging unit with no modification of existing apparatus is described. The coil is easily constructed and permits very rapid tuning to different loading conditions, allowing a high sample throughput.

Resonator coils for magnetic resonance imaging at 6 MHz.

The Alderman and Grant design of the slotted tube resonator has been modified with a different lumped capacitor distribution to obviate the need for a balanced electrical feed at low frequencies (6 MHz). A saddle coil resonator and a strip line resonator have been tuned with similar lumped capacitor distributions to obtain electrically balanced resonance.

In vivo proton spin-lattice relaxation times of normal and dystrophic muscles.

In vivo spin-lattice relaxation times (T1) of water and lipid protons were measured in normal and dystrophic chicken pectoralis muscles at different ages. Values were obtained with a surface coil used as both a receiver and a transmitter. A 2 theta-T1-theta-Acquisition sequence was used for these measurements. Accuracy was verified with an inversion-recovery method using a slotted tube resonator as the transmitter and a surface coil as the receiver. It was observed that the T1 values of water protons in normal muscles decrease with age, the T1 values of water protons do not change with age in dystrophic muscles, and the T1 values of lipid protons increase with age in normal and dystrophic muscles. These results indicate a failure of the normal maturation of dystrophic muscles.