Initial Tubes Research Articles

Vibration Characteristics of a Functionally Graded Viscoelastic Fluid-Conveying Pipe with Initial Geometric Defects under Thermal–Magnetic Coupling Fields

In this study, the Kevin–Voigt viscoelastic constitutive relationship is used to investigate the vibration characteristics and stability of a functionally graded viscoelastic(FGV) fluid-conveying pipe with initial geometric defects under thermal–magnetic coupling fields. First, the nonlinear dimensionless differential equations of motion are derived by applying Timoshenko beam theory. Second, by solving the equilibrium position of the system, the nonlinear term in the differential equations of motion is approximated as the sum of the longitudinal displacement at the current time and longitudinal displacement relative to the position, and the equations are linearized. Third, these equations are discretized using the Galerkin method and are numerically solved under simply supported conditions. Finally, the effects of dimensionless temperature field parameters, dimensionless magnetic field parameters, thermal–magnetic coupling, initial geometric defect types, and the power-law exponent on the complex frequency of the pipe are examined. Results show that increasing the magnetic field intensity enhances the critical velocity of first-order mode instability, whereas a heightened temperature variation reduces the critical velocity of first-order diverge instability. Under thermal–magnetic fields, when the magnetic field intensity and temperature difference are simultaneously increased, their effects on the complex frequency can partially offset each other. Increasing the initial geometric defect amplitude increases the imaginary parts of the complex frequencies; however, for different types of initial geometric defect tubes, it exhibits the most distinct influence only on a certain order.

Multi‐Scale Kelvin‐Helmholtz Instability Dynamics Observed by PMC Turbo on 12 July 2018: 2. DNS Modeling of KHI Dynamics and PMC Responses

AbstractKjellstrand et al. (2022), https://10.1029/2021JD036232 describes the evolution and dynamics of a strong, large‐scale Kelvin‐Helmholtz instability (KHI) event observed in polar mesospheric clouds (PMCs) on 12 July 2018 by high‐resolution imagers aboard the PMC Turbulence (PMC Turbo) stratospheric long‐duration balloon experiment. The imaging provides evidence of KH billow interactions and instabilities that are strongly influenced by gravity waves at larger scales. Specific features include initially separated regions of KHI, secondary convective and KH instabilities of individual billows, and “tubes” and “knots” that arise where billow cores are mis‐aligned or discontinuous along their axes. This study describes a direct numerical simulation of KH billow interactions in a periodic domain seeded with random initial noise that enables excitation of multiple KH billows exhibiting variable phase structures that capture multiple features of the observed KHI dynamics. Variable KH billow phases along their axes yield initial vortex tubes having diagonal alignments that link adjacent, but mis‐aligned, billow cores. Weak initial vortex tubes and billow cores having nearly orthogonal alignments amplify, interact strongly, and drive intense vortex knots at these sites. These vortex tube and knot (T&K) dynamics excite “twist waves” that unravel the initial vortex tubes, and drive increasingly strong vortex interactions and a cascade of energy and enstrophy to successively smaller scales in the turbulence inertial range. The implications of T&K dynamics are much more rapid and intense breakdown and decay of the KH billows, and significantly enhanced energy dissipation rates, where these interactions occur.

Cascades and reconnection in interacting vortex filaments

At high Reynolds number, the interaction between two vortex tubes leads to intense velocity gradients, which are at the heart of fluid turbulence. This vorticity amplification comes about through two different instability mechanisms of the initial vortex tubes, assumed anti-parallel and with a mirror plane of symmetry. At moderate Reynolds number, the tubes destabilize via a Crow instability, with the nonlinear development leading to strong flattening of the cores into thin sheets. These sheets then break down into filaments which can repeat the process. At higher Reynolds number, the instability proceeds via the elliptical instability, producing vortex tubes that are perpendicular to the original tube directions. In this work, we demonstrate that these same transition between Crow and Elliptical instability occurs at moderate Reynolds number when we vary the initial angle $\beta$ between two straight vortex tubes. We demonstrate that when the angle between the two tubes is close to $\pi/2$, the interaction between tubes leads to the formation of thin vortex sheets. The subsequent breakdown of these sheets involves a twisting of the paired sheets, followed by the appearance of a localized cloud of small scale vortex structures. At smaller values of the angle $\beta$ between the two tubes, the breakdown mechanism changes to an elliptic cascade-like mechanism. Whereas the interaction of two vortices depends on the initial condition, the rapid formation of fine-scales vortex structures appears to be a robust feature, possibly universal at very high Reynolds numbers.

Scratch-resistant and well-adhered nanotube arrays produced via anodizing process on β-titanium alloy

Well-adhered nanotube arrays were produced through the anodizing technique on a Ti-25Nb-25Ta alloy and tribo-mechanically evaluated by nanoindentation and nanoscratch tests. Disregarding substrate effects, the hardness of the nanotube arrays layer was 0.7 ± 0.1 GPa and elastic modulus was < 12 GPa, respectively. With the load increase and nanotubes compaction, hardness reached 1.8 GPa and elastic modulus stabilized in ∼40 GPa, which features a mechanically biocompatible gradient zone for implant applications. Under scratching, plastic deformations predominated in the nanotube arrays coating, which mechanism was load-dependent: in the first stage (up to 50 mN) and the initial tubes collapsing, the coating presented low cohesive strength; under higher loads and the progressive nanotubes compaction, the cohesive strength increased, as suggested by the pattern of cracks produced. The scratch resistance for the coating failure was higher than 500 mN, consisting of an excellent bonding adhesion for a nanotube layer produced by anodization.

The new crustacean amphipod genus Kapalana from Australian waters (Senticaudata, Ischyroceridae, Ischyrocerinae, Cerapodini)

Kapalana g. nov. is proposed and described for seven new species of Australian cerapodin amphipods: K. amelga sp. nov.; K. durraween sp. nov.; K. kimbla sp. nov.; K. maia sp. nov.; K. michaelmas sp. nov.; K. stebbingi sp. nov. and K. wadei sp. nov. In all of these species the females show a form of parental care in that the juveniles build their initial tubes in a ring around the tube of the adult female. Cerapus flindersi Stebbing, 1888 is tentatively assigned to the new genus Kapalana.

Design of the laser dieless drawing process of tubes from magnesium alloy using FEM model

This paper is dedicated to a computer aided design of the laser dieless drawing process used for production of magnesium alloy tubes. Using laser as a heat source allows quick control of the heating and helps to regulate the temperature during sample deformation. One of important problems related to the development of this technology is a prediction of diameters of final product. The problem is caused by the character of the process in which elongation of tubes not predetermined by the tool but takes place due to pulling and free forming of the material. To design of technology a code based on finite element method (FEM) dedicated to the laser dieless drawing process and related method of design was developed.A numerical experiment was carried out by performing calculations with varied tension and heating parameters. The calculation results (in form of technological diagrams) allow determination of the process parameters needed for reaching specific final dimensions of the tube and for explanation of limitations of this process related to low ductility of the tubes. Examples of a fracture observed in experiments were related to a neck formation during elongation of the tubes. Two reasons for the neck formation were observed in modeling. The first was related to overheating of a tube and high gradient of temperatures along a centerline of the tube. The second corresponds to a high value of deformation and material hardening.To validation of the FEM model, measured values of temperature, load, tube diameter and fracture monitoring were used. Further, the model allowed to identify a window of permissible process parameters. It was shown that using out-of-the-window parameters leads to non-homogeneous distribution of the tube diameter or fracture.Based on the model results a set of selected design parameters from the processing window were used for a practical production of tubes from AZ31 alloy with a preset external diameter. Analyses of microstructure of initial tubes and tubes after the laser dieless drawing show that the process allows to obtain tubes with homogeneous distribution of grains and to improve initial inhomogeneity of the microstructure.

Apically extruded debris associated with different instrumentation systems and irrigation needles

Aim Of this study is to compare apically extruded debris associated with canal shaping using 2Shape, ProTaper Universal and Reciproc systems using two different irrigation needle tips, open-ended and side-vented. Patients and methods Sixty freshly extracted human mandibular premolars were randomly divided into six groups (n = 10) as follows; group 1 and 2, 2Shape system was used in root canal preparation, in groups 3 and 4, ProTaper Universal preparation system was used, but In groups 5 and 6, Reciproc preparation was performed. In groups 1, 3 and 5 irrigation was done with open-ended needle while in groups 2, 4 and 6 side-vented needle was used. One Eppendorf tube for each tooth was weighed with an electronic weighing machine before instrumentation procedures. During instrumentation, irrigation was performed after every instrument with 1 ml distilled water. On completion of the preparation, teeth were removed from the Eppendorf tubes. All of the tubes were incubated at 37°C for 15 days, to evaporate the irrigant. After the incubation period, the tubes were weighed again. The difference between initial and final tubes weights was calculated, and statistical evaluation was performed using two-way analysis of variance at 5% level of significance. Results A statistically significant difference was observed between all groups (P≤0.05). The highest mean extruded debris value was recorded with group 3 while the lowest value was recorded with group 6. Open-ended needles were associated with significantly more extruded debris than side-vented needles regardless of the instrumentation system used (P≤0.05). Conclusion All the tested rotary instruments resulted in extrusion of debris beyond the apical foramen to an extent but Reciproc system is associated with less amount of apically extruded debris in comparison with 2Shape, ProTaper Universal systems. Side-vented needles extruded significantly less debris than open-ended needles.

The efficacy of tracheostomy tube changes by speech-language pathologists: A retrospective review

Background/Aims: The number of tracheostomised patients in the acute care setting are increasing, resulting in an equal need of providers who can safely change tracheostomy tubes without complications. The objective of this retrospective study was to ascertain if trained speech-language pathologists were able to safely and efficiently perform tracheostomy tube changes in the acute care setting with minimal adverse events. Methods: Our retrospective case series spans from June 2010 to March 2015 and was completed at an academic hospital with a level 1 trauma designation. A total of 107 consecutive referrals undergoing a tracheostomy tube change, with a speech-language pathologist, were identified. Success was defined as the placement of the tracheostomy tube into the tracheal lumen with confirmation of placement. Only complications occurring at the time of the tracheostomy tube change were considered and were defined as an airway loss event: oxygen desaturation &lt;85%; uncontrollable bleeding &gt;5mL; and the inability to perform the attempted tracheostomy tube change for any other reason. Results: All of the tracheostomy tubes changes were performed at the bedside at a mean of 13 days post tracheotomy (range 3–28). A total of 106 (99%) of 107 tracheostomy tubes changes were successfully completed without complications; 83 (79%) of the tracheostomy tubes changes performed were the initial tracheostomy tubes change completed post tracheotomy. The remaining 23 (21%) were a combination of either the second or third change. One, (less than 1%), of the procedures was attempted and discontinued before the removal of the tracheostomy tubes, and referred back to the surgical services and was successfully managed with no untoward effects to the patient. Conclusions: This is the first study to audit the outcome of speech-language pathologists' ability to successfully change a tracheostomy tube. The findings suggest that specially trained speech-language pathologists, acting as part of a multi-disciplinary care team, have the potential to safely change tracheostomy tubes in an acute care setting with the availability of immediate physician and respiratory therapy support. Additional clinical benefits of the speech-language pathologist changing tracheostomy tubes may include earlier facilitation of communication, decannulation and initiation of nutrition/hydration.

Thermalization of anisotropic quark–gluon plasma produced by decays of color flux tubes

Kinetic equations are used to study thermalization of the anisotropic quark-gluon plasma produced by decays of color flux tubes possibly created at the very early stages of relativistic heavy-ion collisions. The decay rates of the initial color tubes are given by the Schwinger formula, while the collision terms are taken in the relaxation-time approximation. By connecting the relaxation time with viscosity we analyze production and thermalization processes in the plasma characterized by different values of the ratio of the shear viscosity to entropy density.

Additional material feeding method by plunger shape design for hydroforming of triangular tubes

In this study, a hydroforming process is used for the manufacture of a bicycle frame tube, one side end of which is expanded to an acute-angled triangular shape from the initial tube, which has a regular triangular cross section. The end section of the expanding side is designed to be smoothly connected with the initial tube cross section to maintain sealing by the plunger. The tube hydroforming process is controlled using an axial feeding plunger and a pressure intensifier. Various load conditions can be applied to the initial tubes through these units. However, the experimental results showed that forming into the desired shape without bursting at the expanding area or shear cracking at other areas was not possible. These problems seem to occur because the circumferential propagation of plastic deformation is constrained by the triangular cross-sectional profile of the initial tube. To resolve this problem, less axial feeding should be supplied to the compressing zone compared with the expanding zone even in a single tube. In this work, besides conventional axial feeding, an additional axial feeding method by an end cam–shaped plunger is suggested to supply different axial feeding for each circumferential location of the tube. Finite element simulation and experimental studies are performed to verify the effectiveness of the concept.

Global flow of glasma in high energy nuclear collisions

We discuss the energy flow of the classical gluon fields created in collisions of heavy nuclei at collider energies. We show how the Yang–Mills analog of Faradayʼs Law and Gaussʼ Law predicts the initial gluon flux tubes to expand or bend. The resulting transverse and longitudinal structure of the Poynting vector field has a rich phenomenology. Besides the well-known radial and elliptic flow in transverse direction, classical quantum chromodynamics predicts a rapidity-odd transverse flow that tilts the fireball for non-central collisions, and it implies a characteristic flow pattern for collisions of non-symmetric systems A+B. The rapidity-odd transverse flow translates into a directed particle flow v1 which has been observed at RHIC and LHC. The global flow fields in heavy ion collisions could be a powerful check for the validity of classical Yang–Mills dynamics in high energy collisions.

478 LOWER URINARY TRACT RECONSTRUCTION WITH CONCOMITANT CECOSTOMY BUTTON FOR ANTEGRADE ENEMA

You have accessJournal of UrologyPediatrics: Neuropathic Bladder/Reconstruction1 Apr 2013478 LOWER URINARY TRACT RECONSTRUCTION WITH CONCOMITANT CECOSTOMY BUTTON FOR ANTEGRADE ENEMA Chandra Singh, Daryl McLeod, Cheryl Baxter, Seth Alpert, and Venkata Jayanthi Chandra SinghChandra Singh Columbus, OH More articles by this author , Daryl McLeodDaryl McLeod Columbus, OH More articles by this author , Cheryl BaxterCheryl Baxter Columbus, OH More articles by this author , Seth AlpertSeth Alpert Columbus, OH More articles by this author , and Venkata JayanthiVenkata Jayanthi Columbus, OH More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2013.02.1870AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Procedures to enable antegrade enema improve the quality of life in children with intractable constipation related to neurogenic bowel and bladder dysfunction. Appendicocecostomy (AC) and Cecostomy button (CB) allow easy access for colonic wash-outs and help to achieve socially acceptable fecal continence. In children undergoing lower urinary tract reconstruction (LUTR), we have been offering concomitant CB to achieve total continence as an alternate to AC. This study aims to evaluate the outcome of LUTR with concomitant CB. METHODS We retrospectively reviewed the records of patients who underwent CB for intractable bowel dysfunction at the time of LUTR. Initial temporary cecostomy tubes were placed in the right iliac fossa during LUTR. After six weeks, this was exchanged for a Chait trapdoor CB. Subsequently, patients were scheduled for six month or annual exchange of the Chait tube by interventional radiology. Antegrade enema irrigation regimens varied and included water with or without additives. The outcome, follow up and complications were evaluated. RESULTS Between 2001 and 2011, a total of 110 patients underwent CB of whom 27 were performed at the time of LUTR, which included bladder outlet procedures, augmentations and abdominal catheterizable channels. There were 11 males and 16 females. The mean age at the time of surgery was 9.6 years (range 3.8–24.9). The mean follow was 29 months (range 1–115 months). Patients had an average of 4.2 (range 1–15) elective fluoroscopy guided tube changes during the study period. At studies end, 22 (81.5%) of patients continued to use their CB, reporting good functional results. Accidental removal of the CB occurred three times, and was managed by fluoroscopic replacement. Other self limiting complications included mucous discharge and pain around the tube. None of the patients required a visit to the operating room for complications related to CB. CONCLUSIONS Cecostomy button is a simple procedure for antegrade colonic enema administration. It can be combined with LUTR as an alternative to AC. By avoiding AC, the appendix can be spared for consideration during the LUTR, with minimal morbidity or complications noted in our study population. © 2013 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 189Issue 4SApril 2013Page: e196 Advertisement Copyright & Permissions© 2013 by American Urological Association Education and Research, Inc.MetricsAuthor Information Chandra Singh Columbus, OH More articles by this author Daryl McLeod Columbus, OH More articles by this author Cheryl Baxter Columbus, OH More articles by this author Seth Alpert Columbus, OH More articles by this author Venkata Jayanthi Columbus, OH More articles by this author Expand All Advertisement Advertisement PDF DownloadLoading ...

Interpreting Red Blood Cells in Lumbar Puncture: Distinguishing True Subarachnoid Hemorrhage From Traumatic Tap

The study purpose was to determine the optimal use of lumbar puncture (LP) red blood cell (RBC) counts to identify subarachnoid hemorrhage (SAH) when some blood remains in the final tube. A case series was performed at a tertiary emergency department (ED). Records of 4,496 consecutive adult patients billed for LPs between 2001 and 2009 were reviewed. Inclusion criteria were headache (HA), final tube RBCs ≥ 5, and neurovascular imaging within 2 weeks of the visit. Demographics, relevant history and physical examination components, LP results, and neuroimaging findings were recorded for 280 patients. True-positive (TP) and true-negative (TN) SAH were strictly defined. Primary outcomes were the areas under the receiver operating characteristic curves (AUC) for final tube RBC count, differential RBC count between the final and initial tubes, and absolute differential RBC count between the final and initial tubes divided by the mean RBC count of the two tubes (also called the percent change in RBC count). There were 26 TP and 196 TN results; 58 patients were neither. The TP group consisted of 19 patients with visible or possible SAH on imaging (17 on noncontrast head computed tomography [CT; 12 definite and five possible] and two on magnetic resonance imaging), six with xanthochromia and a vascular lesion (aneurysm or arteriovenous malformation [AVM] > 2 mm), and one with xanthochromia and polymerase chain reaction (PCR)-positive meningitis. As a test for SAH, final tube RBC AUC was 0.85 (95% confidence interval [CI] = 0.80 to 0.91). Interval likelihood ratios (LRs) for final tube RBC count were LR 0 (95% CI = 0 to 0.3) for RBCs < 100, LR 1.6 (95% CI = 1.1 to 2.3) for 100 < RBCs < 10,000, and LR 6.3 (95% CI = 4.8 to 23.4) for RBCs > 10,000. Differential RBC count was not associated with SAH, with AUC 0.45 (95% CI = 0.31 to 0.60). However, the percent change in RBC count between the final and initial tubes had an AUC 0.84 (95% CI = 0.78 to 0.90), and the optimal test threshold for SAH was 0.63, with positive LR 3.6 (95% CI = 2.7 to 4.7) and negative LR 0.10 (95% CI = 0.03 to 0.4) for percent change <63% and >63%, respectively. This test added additional independent information to the final tube RBC count based on improved logistic regression model fit and discriminatory ability as measured by the LR test and c statistic, respectively. Final LP tube RBC count and the percent change in RBC count, but not the simple differential count between the final and initial tubes, were associated with SAH. In this sample, there were no patients with SAH who had RBCs < 100 in the final tube, and RBCs > 10,000 increased the odds of SAH by a factor of 6.

A Fast Hidden Surface Removal Approach for Complex SAR Scene Based on Adaptive Ray-tube Splitting Method

Traditional hidden surface removal algorithm based on hardware Z-Buffer technique cannot give attention to precision or efficiency at the same time when dealing with the non-uniform triangulated SAR (Synthetic Aperture Radar) scene model. A novel high-precision hidden surface removal approach using fast ray-tube splitting algorithm is proposed, where the SAR scene hidden surface removal problem is decomposed into two simple procedures, i.e. a Delaunay triangulator is used to generate the initial ray tubes from the projected point clouds of all incident visible vertices, then an adaptive ray-tube splitting method is adopted to carry out the complex scene shading situations and resultant visible model reconstruction. Simulation results of typical aircraft and T-72 tank show that, the new approach is feasible and effective.

Understanding anisotropy generated by fluctuations in heavy-ion collisions

Event-by-event fluctuations are central to the current understanding of ultrarelativistic heavy-ion collisions. In particular, fluctuations in the geometry of the early-time collision system are responsible for new phenomena such as triangular flow, which have solved important puzzles in existing data. We propose a simple model where initial fluctuations stem from independent flux tubes randomly distributed in the transverse plane. We calculate analytically the moments of the initial anisotropies (dipole asymmetry, eccentricity, triangularity), which are the sources of anisotropic flow, and their mutual correlations. Our analytic results are in good agreement with calculations from commonly-used Monte-Carlo codes, providing a simple understanding of the fluctuations contained in these models. Any deviation from these results in future experimental data would thus indicate the presence of non-trivial correlations between the initial flux tubes and/or extra sources of fluctuations that are not present in current models.

Dependence of the Magnetic Energy of Solar Active Regions on the Twist Intensity of the Initial Flux Tubes

Abstract We present a series of numerical experiments that model the evolution of magnetic flux tubes with a different amount of initial twist. As a result of calculations, tightly twisted tubes reveal a rapid two-step emergence to the atmosphere with a slight slowdown at the surface, while weakly twisted tubes show a slow two-step emergence waiting longer the secondary instability to be triggered. This picture of the two-step emergence is highly consistent with recent observations. These tubes show multiple magnetic domes above the surface, indicating that the secondary emergence is caused by an interchange mode of magnetic buoyancy instability. In the case of the weakest twist, the tube exhibits an elongated photospheric structure, and never rises into the corona. The formation of the photospheric structure is due to an inward magnetic tension force of the azimuthal field component of the rising flux tube (i.e., tube's twist). When the twist is weak, the azimuthal field cannot hold the tube's coherency, and the tube extends laterally at the subadiabatic surface. In addition, we newly found that the total magnetic energy measured above the surface depends on the initial twist. Strong twist tubes follow the initial relation between the twist and the magnetic energy, while weak twist tubes deviate from this relation, because these tubes store their magnetic energy in the photospheric structure.

Mechanics of viscous vortex reconnection

This work is motivated by our long-standing claim that reconnection of coherent structures is the dominant mechanism of jet noise generation and plays a key role in both energy cascade and fine-scale mixing in fluid turbulence [F. Hussain, Phys. Fluids 26, 2816 (1983); J. Fluid Mech. 173, 303 (1986)]. To shed further light on the mechanism involved and quantify its features, the reconnection of two antiparallel vortex tubes is studied by direct numerical simulation of the incompressible Navier–Stokes equations over a wide range (250–9000) of the vortex Reynolds number, Re (=circulation/viscosity) at much higher resolutions than have been attempted. Unlike magnetic or superfluid reconnections, viscous reconnection is never complete, leaving behind a part of the initial tubes as threads, which then undergo successive reconnections (our cascade and mixing scenarios) as the newly formed bridges recoil from each other by self-advection. We find that the time tR for orthogonal transfer of circulation scales as tR≈Re−3/4. The shortest distance d between the tube centroids scales as d≈a[Re(t0−t)]3/4 before reconnection (collision) and as d≈b[Re(t−t0)]2 after reconnection (repulsion), where t0 is the instant of smallest separation between vortex centroids. We find that b is a constant, thus suggesting self-similarity, but a is dependent on Re. Bridge repulsion is faster than collision and is more autonomous as local induction predominates, and, given the associated acceleration of vorticity, is potentially a source of intense sound generation. At the higher Re studied, the tails of the colliding threads are compressed into a planar jet with multiple vortex pairs. For Re&amp;gt;6000, there is an avalanche of smaller scales during the reconnection, the rate of small scale generation and the spectral content (in vorticity, transfer function and dissipation spectra) being quite consistent with the structures visualized by the λ2 criterion. The maximum rate of vortex circulation transfer, enstrophy production, and dissipation scale as Re1, Re7/4, and Re−1/2, respectively. A more detailed study of subsequent reconnection of threads requires much higher-resolution simulations that are currently not feasible.

Molecular dynamics of zigzag single walled carbon nanotube immersion in water

The results of enthalpy of immersion in water for finite single-walled carbon nanotubes are reported. Using molecular dynamics simulation, we discuss the relation between the value of this enthalpy and tube diameters showing that the obtained plot can be divided into three regions. The structure of water inside tubes in all three regions is discussed and it is shown that the existence of the strong maximum of enthalpy observed for tube diameter ca. 1.17 nm is due to freezing of water under confinement. The calculations of hydrogen bond statistics and water density profiles inside tubes are additionally reported to confirm the obtained results. Next, we show the results of calculation for the same tubes but containing surface carbonyl oxygen groups at pore entrances. A remarkable rise in the value of enthalpy of immersion in comparison to the initial tubes is observed. We also discuss the influence of charge distribution between oxygen and carbon atom forming surface carbonyls on the structure of confined water. It is concluded for the first time that the presence of surface oxygen atoms at the pore entrances remarkably influences the structure and stability of ice created inside nanotubes, and surface carbonyls appear to be chaotropic (i.e. structure breaking) for confined water. This effect is explained by the pore blocking leading to a decrease (compared to initial structure) in the number of confined water molecules after introduction of surface oxygen groups at pore entrances.

Optimization of process parameters and part geometry for high diameter tube hydroforming

The aim of this research is to study the feasibility of vases with tube hydroforming, identifying the limits of this technology. The goal of the simulation study was the identification of the maximum pressure needed to realize vases with big diameter and length. Initially the attention was focused on the realization of a square vase geometry. The initial tubes have a high diameter of 120 mm. Many simulations were conducted to optimize process parameters for this square geometry, namely actuators stroke and water pressure, but it wasn’t possible to completely achieve the die shape at the protrusion edges due to the big diameter expansion and to the rib geometries (thickness, height and fillet radii). Different vase geometries characterized by lower diameter expansion and same dimension of the ribs, were tested. The formability results were improved but there are still problems when the material is filling the ribs (material breakage). In order to realize a safe square part, it was necessary to optimize the rib geometrical dimensions. Other simulations were conducted for a round vase geometry, to check the maximum diameter expansion. Some general design rules were finally summarized.

Percutaneous Fluoroscopically Guided Jejunostomy Placement

To describe our experience with fluoroscopically guided direct jejunostomy placement in patients with enterocutaneous fistula, or neoplastic or postsurgical changes of the stomach or duodenum that preclude traditional gastrostomy placement. Nineteen patients underwent percutaneous direct jejunostomy tube placement with fluoroscopic guidance from August 2004 through March 2006. There were 15 men and four women whose ages ranged from 28 to 82 years (mean, 54 years). Seven patients had surgical changes to the stomach that precluded traditional gastrostomy access, one patient had a duodenal tumor, two had unresectable gastric tumors, and nine had small bowel pathology that required distal access. Jejunal access was initially successful in 18 of 19 (95%) procedures. Follow-up ranged from 10 days to 509 days. Two catheters were removed as they were no longer needed. Seven patients' initial tubes were still functioning at the end of their follow-up. One tube was removed secondary to pain and irritation at the insertion site. Three tubes were occluded. One patients' tube was inadvertently pulled out. In two patients, feeding was not tolerated secondary to fistula distal to the jejunostomy. Two patients died with their initial tubes. Primary patency was 285 days (95% CI 162-407). One death occurred 10 days postprocedure for a 30-day mortality of 1 of 19 (5%). Percutaneous direct jejunostomy placement is a relatively safe and effective means of gaining enteral access in patients who have enterocutaneous fistula or who have either postsurgical or neoplastic changes of the stomach that preclude traditional gastrostomy placement.