76 resultados para Plastic injection
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OBJECTIVE: The purpose of this study was to compare a standard peripheral end-hole angiocatheter with those modified with side holes or side slits using experimental optical techniques to qualitatively compare the contrast material exit jets and using numeric techniques to provide flow visualization and quantitative comparisons. MATERIALS AND METHODS: A Schlieren imaging system was used to visualize the angiocatheter exit jet fluid dynamics at two different flow rates. Catheters were modified by drilling through-and-through side holes or by cutting slits into the catheters. A commercial computational fluid dynamics package was used to calculate numeric results for various vessel diameters and catheter orientations. RESULTS: Experimental images showed that modifying standard peripheral IV angiocatheters with side holes or side slits qualitatively changed the overall flow field and caused the exiting jet to become less well defined. Numeric calculations showed that the addition of side holes or slits resulted in a 9-30% reduction of the velocity of contrast material exiting the end hole of the angiocatheter. With the catheter tip directed obliquely to the wall, the maximum wall shear stress was always highest for the unmodified catheter and was always lowest for the four-side-slit catheter. CONCLUSION: Modified angiocatheters may have the potential to reduce extravasation events in patients by reducing vessel wall shear stress.
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PURPOSE: To evaluate a widely used nontunneled triple-lumen central venous catheter in order to determine whether the largest of the three lumina (16 gauge) can tolerate high flow rates, such as those required for computed tomographic angiography. MATERIALS AND METHODS: Forty-two catheters were tested in vitro, including 10 new and 32 used catheters (median indwelling time, 5 days). Injection pressures were continuously monitored at the site of the 16-gauge central venous catheter hub. Catheters were injected with 300 and 370 mg of iodine per milliliter of iopamidol by using a mechanical injector at increasing flow rates until the catheter failed. The infusion rate, hub pressure, and location were documented for each failure event. The catheter pressures generated during hand injection by five operators were also analyzed. Mean flow rates and pressures at failure were compared by means of two-tailed Student t test, with differences considered significant at P < .05. RESULTS: Injections of iopamidol with 370 mg of iodine per milliliter generate more pressure than injections of iopamidol with 300 mg of iodine per milliliter at the same injection rate. All catheters failed in the tubing external to the patient. The lowest flow rate at which catheter failure occurred was 9 mL/sec. The lowest hub pressure at failure was 262 pounds per square inch gauge (psig) for new and 213 psig for used catheters. Hand injection of iopamidol with 300 mg of iodine per milliliter generated peak hub pressures ranging from 35 to 72 psig, corresponding to flow rates ranging from 2.5 to 5.0 mL/sec. CONCLUSION: Indwelling use has an effect on catheter material property, but even for used catheters there is a substantial safety margin for power injection with the particular triple-lumen central venous catheter tested in this study, as the manufacturer's recommendation for maximum pressure is 15 psig.
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PURPOSE: To compare tunnelled scleral intravitreal injection with straight scleral intravitreal injection concerning short-term intraocular pressure (IOP) changes, occurrence and amount of vitreous reflux, and patient discomfort. METHODS: Sixty patients were randomly allocated to two groups (tunnelled intravitreal injection and straight intravitreal injection). IOP was measured before and directly (<1 minute) after the injection of 0.05 mL of an antivascular endothelial growth factor agent and then every 5 minutes until IOP was <30 mmHg. Occurrence and amount of vitreous reflux were recorded. Patient discomfort during injection was assessed with a Wong-Baker faces pain rating scale. RESULTS: IOP (mmHg +/- SD) increased significantly directly after injection to 35.97 +/- 8.13 (tunnelled intravitreal injection) and 30.19 +/- 12.14 (straight intravitreal injection). These pressure spikes differed significantly between both groups (P = 0.01, mean difference: -7.11). Five minutes after injection, there was no significant difference in IOP increase between the groups. All IOP measurements were <30 mmHg after 15 minutes. Occurrence and amount of vitreous reflux were significantly higher with straight intravitreal injection. There was no significant difference in Wong-Baker faces pain rating scale score between both groups. CONCLUSION: Tunnelled intravitreal injection seems to be the technique of choice for low-volume intravitreal injection (0.05 mL). There is neither a difference in patient discomfort nor a difference in IOP increase 5 minutes after injection between both groups. Significantly less vitreous reflux with tunnelled intravitreal injection should lead to less postinjectional drug loss.
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The Plasma and Supra-Thermal Ion Composition (PLASTIC) instrument is one of four experiment packages on board of the two identical STEREO spacecraft A and B, which were successfully launched from Cape Canaveral on 26 October 2006. During the two years of the nominal STEREO mission, PLASTIC is providing us with the plasma characteristics of protons, alpha particles, and heavy ions. PLASTIC will also provide key diagnostic measurements in the form of the mass and charge state composition of heavy ions. Three measurements (E/qk, time of flight, ESSD) from the pulse height raw data are used to characterize the solar wind ions from the solar wind sector, and part of the suprathermal particles from the wide-angle partition with respect to mass, atomic number and charge state. In this paper, we present a new method for flight data analysis based on simulations of the PLASTIC response to solar wind ions. We present the response of the entrance system / energy analyzer in an analytical form. Based on stopping power theory, we use an analytical expression for the energy loss of the ions when they pass through a thin carbon foil. This allows us to model analytically the response of the time of flight mass spectrometer to solar wind ions. Thus we present a new version of the analytical response of the solid state detectors to solar wind ions. Various important parameters needed for our models were derived, based on calibration data and on the first flight measurements obtained from STEREO-A. We used information from each measured event that is registered in full resolution in the Pulse Height Analysis words and we derived a new algorithm for the analysis of both existing and future data sets of a similar nature which was tested and works well. This algorithm allows us to obtain, for each measured event, the mass, atomic number and charge state in the correct physical units. Finally, an important criterion was developed for filtering our Fe raw flight data set from the pulse height data without discriminating charge states.
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REASONS FOR PERFORMING STUDY: Proximal diffusion of local anaesthetic solution after perineural anaesthesia may lead to the desensitisation of structures other than those intended. However, there is no evidence-based study demonstrating the potential distribution and diffusion of local anaesthetic solution after perineural analgesia in the distal limb. OBJECTIVE: To document the potential diffusion of local anaesthetic solution using a radiopaque contrast model and to evaluate the influence of walking compared with confinement in a stable after injection. METHODS: Radiopaque contrast medium was injected subcutaneously over one palmar nerve at the base of the proximal sesamoid bones in 6 nonlame mature horses. Horses were assigned randomly to stand still or walk after injection. Radiographs were obtained 0, 5, 10, 15, 20 and 30 min after injection and were analysed to determine the distribution and diffusion of the contrast medium. RESULTS: In 89% of injections an elongated pattern of the contrast medium was observed suggesting distribution along the neurovascular bundle. After 49% of injections a fine radiopaque line extended proximally from the contrast 'patch', and in 25% of injections a line extended distally. There was significant proximal and distal diffusion with time when sequential radiographs of each limb were compared. The greatest diffusion occurred in the first 10 min. Walking did not significantly influence the extent of either proximal or distal diffusion. CONCLUSIONS AND POTENTIAL RELEVANCE: Significant proximal diffusion occurs in the first 10 min after perineural injection in the distal aspect of the limb and should be considered when interpreting nerve blocks. Distribution of local anaesthetic solution outside the fascia surrounding the neurovascular bundle or in lymphatic vessels may explain delayed or decreased effects.
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BACKGROUND Intracoronary administration of autologous bone marrow-derived mononuclear cells (BM-MNC) may improve remodeling of the left ventricle (LV) after acute myocardial infarction. The optimal time point of administration of BM-MNC is still uncertain and has rarely been addressed prospectively in randomized clinical trials. METHODS AND RESULTS In a multicenter study, we randomized 200 patients with large, successfully reperfused ST-segment elevation myocardial infarction in a 1:1:1 pattern into an open-labeled control and 2 BM-MNC treatment groups. In the BM-MNC groups, cells were administered either early (i.e., 5 to 7 days) or late (i.e., 3 to 4 weeks) after acute myocardial infarction. Cardiac magnetic resonance imaging was performed at baseline and after 4 months. The primary end point was the change from baseline to 4 months in global LV ejection fraction between the 2 treatment groups and the control group. The absolute change in LV ejection fraction from baseline to 4 months was -0.4±8.8% (mean±SD; P=0.74 versus baseline) in the control group, 1.8±8.4% (P=0.12 versus baseline) in the early group, and 0.8±7.6% (P=0.45 versus baseline) in the late group. The treatment effect of BM-MNC as estimated by ANCOVA was 1.25 (95% confidence interval, -1.83 to 4.32; P=0.42) for the early therapy group and 0.55 (95% confidence interval, -2.61 to 3.71; P=0.73) for the late therapy group. CONCLUSIONS Among patients with ST-segment elevation myocardial infarction and LV dysfunction after successful reperfusion, intracoronary infusion of BM-MNC at either 5 to 7 days or 3 to 4 weeks after acute myocardial infarction did not improve LV function at 4-month follow-up.
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BACKGROUND Often ignored, hands are one of the most telltale signs of aging. This prospective study was initiated to evaluate the effect of subcutaneous hyaluronic acid (HA) injections in aging hands, with special attention to complications and long-term outcomes. METHODS Between January 2010 and December 2010, a total of 38 patients with skin phototypes II-IV and between 58 and 76 years old were treated with HA injection for aging hands. The quantity of injection never exceeded 1.0-1.5 ml HA per hand. A clinical follow-up was performed at 2 weeks, 4 weeks, 3 months, and 6 months after injection. Complications were reviewed for the whole series. At the first follow-up, 2 weeks after the procedure, ultrasound was carried out to determine if additional filling material was required. At each follow-up, patients were asked to fill out a satisfaction questionnaire. RESULTS Nine patients developed slight ecchymosis that disappeared after 1 week. No other complications were seen in the series. Pain during the injection and discomfort after the procedure were minimal. At the 2-week follow-up, after ultrasound control, nine patients received a complementary injection. At each follow-up, overall patient satisfaction was high and was validated by clearance of rhytids, veins, bony prominences, and dermal and subcutaneous atrophy. CONCLUSION Skin revitalization with injectable HA can improve the clinical appearance of the back of the hands. However, this therapy requires knowledge of the possible complications and their remediation as well as knowledge and respect of injected doses. Moreover, despite excellent results at each follow-up, the results of our series are not as good after 6 months, and a longer follow-up would be needed to determine if this procedure provides long-lasting benefit. LEVEL OF EVIDENCE III This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .
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Numerical simulation experiments give insight into the evolving energy partitioning during high-strain torsion experiments of calcite. Our numerical experiments are designed to derive a generic macroscopic grain size sensitive flow law capable of describing the full evolution from the transient regime to steady state. The transient regime is crucial for understanding the importance of micro structural processes that may lead to strain localization phenomena in deforming materials. This is particularly important in geological and geodynamic applications where the phenomenon of strain localization happens outside the time frame that can be observed under controlled laboratory conditions. Ourmethod is based on an extension of the paleowattmeter approach to the transient regime. We add an empirical hardening law using the Ramberg-Osgood approximation and assess the experiments by an evolution test function of stored over dissipated energy (lambda factor). Parameter studies of, strain hardening, dislocation creep parameter, strain rates, temperature, and lambda factor as well asmesh sensitivity are presented to explore the sensitivity of the newly derived transient/steady state flow law. Our analysis can be seen as one of the first steps in a hybrid computational-laboratory-field modeling workflow. The analysis could be improved through independent verifications by thermographic analysis in physical laboratory experiments to independently assess lambda factor evolution under laboratory conditions.
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The occurrence of gaseous pollutants in soils has stimulated many experimental activities, including forced ventilation in the field as well as laboratory transport experiments with gases. The dispersion coefficient in advective-dispersive gas phase transport is often dominated by molecular diffusion, which leads to a large overall dispersivity gamma. Under such conditions it is important to distinguish between flux and resident modes of solute injection and detection. The influence of the inlet type oil the macroscopic injection mode was tested in two series of column experiments with gases at different mean flow velocities nu. First we compared infinite resident and flux injections, and second, semi-infinite resident and flux injections. It is shown that the macroscopically apparent injection condition depends on the geometry of the inlet section. A reduction of the cross-sectional area of the inlet relative to that of the column is very effective in excluding the diffusive solute input, thus allowing us to use the solutions for a flux Injection also at rather low mean flow velocities nu. If the whole cross section of a column is exposed to a large reservoir like that of ambient air, a semi-infinite resident injection is established, which can be distinguished from a flux injection even at relatively high velocities nu, depending on the mechanical dispersivity of the porous medium.
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Ultraviolet-ozone treatment is used as a standard surface cleaning procedure for removal of molecular organic contamination from analytical and sensing devices. Here, it is applied for injection-molded polymer microcantilevers before characterization and sensing experiments. This article examines the effects of the surface cleaning process using commercial equipment, in particular on the performance and mechanical properties of the cantilevers. It can be shown that the first chemical aging process essentially consist of the cross linking of the polymer chains together with a physical aging of the material. For longer exposure, the expected thermo-oxidative formation of carbonyl groups sets in and an exposure dependent chemical degradation can be detected. A process time of 20 min was found suitable as a trade-off between cleaning and stability
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Understanding and controlling the structural anisotropies of injection-molded polymers is vital for designing products such as cantilever-based sensors. Such micro-cantilevers are considered as cost-effective alternatives to single-crystalline silicon-based sensors. In order to achieve similar sensing characteristics,structure and morphology have to be controlled by means of processing parameters including mold temperature and injection speed. Synchrotron radiation-based scanning small- (SAXS) and wide-angle x-ray scattering techniques were used to quantify crystallinity and anisotropy in polymer micro-cantilevers with micrometer resolution in real space. SAXS measurements confirmed the lamellar nature of the injection-molded semi-crystalline micro-cantilevers. The homogenous cantilever material exhibits a lamellar periodicity increasing with mold temperature but not with injection speed. We demonstrate that micro-cantilevers made of semi-crystalline polymers such as polyvinylidenefluoride, polyoxymethylene, and polypropylene show the expected strong degree of anisotropy along the injection direction.