Tube Extension Research Articles

Effects of different loads on structure stress of “L”-type large-diameter pipeline under burying and trench conditions based on fluid–structure–heat coupling

The research object of this paper is “L”-type heat pipe network, which was studied using the flow–heat–solid coupling method. The ANSYS Workbench platform was used to simulate heat transfer and the flow of the medium in the pipe network. The pressure and temperature of the flow field and the temperature; and equivalent stress of the solid structure under different conditions were calculated, and the force characteristics of pipe network and elbow caused by coupled and non-coupled loads under burying and trench conditions were compared. Results show that the temperature and velocity fields of the liquid domains under burying and trench laying conditions were the same, and the structure temperature distributions of the pipe network under the two laying conditions were also the same. The pressure and temperature loads were not separate from each other, thereby affecting the stress of the pipe network simultaneously, and the stress under the coupled loads was lower than the sum of the pressure and temperature loads individually. The stress distribution of the outer and inner surfaces under burying laying condition was opposite that under trench laying condition because of the soil that hinders the extension of the heating tube.

P.066 Intrajejunal levodopa infusion (ILI) for Parkinson’s Disease (PD): a Canadian experience

Background: ILI has been in use in Canada since 2011 to treat advanced PD. We review the benefits and complications of ILI for PD in a tertiary movement disorders center in Canada. Methods: Detailed chart review of patients treated with ILI at including motor UPDRS scores, ILI pump and PEG-J tube complications. Patients and caregivers were interviewed at regular clinic follow up about their experience with ILI. Results: 13 patients received ILI [10M, 3F; mean age 65.6 yrs, range (51.8-79.5); PD duration 14.2 yrs, range (9.1-22.0); mean follow-up 1.8 yrs, range (0.2-4.8)]. Patients reported improvement in motor function, decreased dyskinesias and ‘OFF times’ [mean motor UPDRS: pre-ILI 37.1, 1-6months post-ILI 27.5]. Common complications included dislodgement, knotting or blockage of the jejunal tube extension requiring endoscopic re- insertion (29 incidents in 6 patients over 5 yrs). Four patients discontinued Duodopa treatment, for reasons of declining cognition, inability to care for the pump, and/or minimal benefit. Conclusions: ILI is useful for the treatment of advanced PD, in patients that can care for the pump apparatus.

Epithelial tension in the second heart field promotes mouse heart tube elongation

Extension of the vertebrate heart tube is driven by progressive addition of second heart field (SHF) progenitor cells to the poles of the heart. Defects in this process cause a spectrum of congenital anomalies. SHF cells form an epithelial layer in splanchnic mesoderm in the dorsal wall of the pericardial cavity. Here we report oriented cell elongation, polarized actomyosin distribution and nuclear YAP/TAZ in a proliferative centre in the posterior dorsal pericardial wall during heart tube extension. These parameters are indicative of mechanical stress, further supported by analysis of cell shape changes in wound assays. Time course and mutant analysis identifies SHF deployment as a source of epithelial tension. Moreover, cell division and oriented growth in the dorsal pericardial wall align with the axis of cell elongation, suggesting that epithelial tension in turn contributes to heart tube extension. Our results implicate tissue-level forces in the regulation of heart tube extension.

Tube inflation of viscoelastic fluids at a constant growth rate

ABSTRACTThe simultaneous radial inflation and axisymmetric extension of an incompressible viscoelastic tube is modeled analytically as an idealization of the blow-molding process. The working fluid is assumed to obey a single integral constitutive model with a power-law damping function, accommodating behavior ranging from extreme strain hardening (akin to the Lodge–Maxwell model) to strain thinning leading to plastic flow. The tube is sufficiently long so that end effects can be neglected. The axial and radial extension rates at the outer tube radius are assumed to be constant in time. Exact analytical expressions are derived for the tube thickness H, the pressure difference ΔP across the tube wall, and the axial force F required for sustaining the tube inflation with constant stretch history. Their evolution is studied over a variety of deformation intensities, operating conditions, and flow geometries. A valuable insight in the effects of rheology on the blow-molding process is gained.

Macroscopic analysis of filtering bleb functionality after XEN Gel Stent implantation with Anterior Segment Optical Coherence Tomography

PurposeThe new approach of Micro invasive Glaucoma Surgery, XEN Gel Stent is made of soft collagen and it is introduced by a corneal incision, trough the anterior chamber angle and it stands under the conjunctiva space.To study the bleb macroscopic morphology with Anterior Segment Optical Coherence Tomography and correlate it with the clinical evaluation.MethodsProspective case‐control study with 10 eyes of 8 patients with the range follow‐up to 6 months after XEN Gel Stent implantation. Two groups were characterized according to the clinical evaluation (Intraocular Pressure, topical treatment or additional procedures, as YAG‐LASER and Needling). Group 1 describes those patients with IOP under 21 mmHg without topical treatment even if it was necessary an additional YAG‐LASER or needling (n = 8). Group 2 was formed with IOP above 21 mmHg or under 21 mmHg with topical treatment (n = 2). The parameters analyzed were the bleb structure (diffuse or cystic), extension (height, width and length), chamber angle aperture and tube extension (anterior chamber and scleral).ResultsThe group 1 appears to be with indifferently diffuse or cystic higher extensions of filtering blebs than those in group 2. The structural analysis with OCT was concordant with the macroscopic morphology in slit lamp evaluation. The tube extension in anterior chamber and under conjunctiva and its chamber angle entrance was relatively variable over all patients.ConclusionsThe clinical assessment of the filtering bleb has proved a significant concordance with the filtering bleb macroscopic morphology in the AS‐OCT. Additional longitudinal studies about this topic will be necessary to improve the knowledge and the surgeon's management capabilities.

Structure-Function Analysis of the ϕX174 DNA-Piloting Protein Using Length-Altering Mutations.

Although the ϕX174 H protein is monomeric during procapsid morphogenesis, 10 proteins oligomerize to form a DNA translocating conduit (H-tube) for penetration. However, the timing and location of H-tube formation are unknown. The H-tube's highly repetitive primary and quaternary structures made it amenable to a genetic analysis using in-frame insertions and deletions. Length-altered proteins were characterized for the ability to perform the protein's three known functions: participation in particle assembly, genome translocation, and stimulation of viral protein synthesis. Insertion mutants were viable. Theoretically, these proteins would produce an assembled tube exceeding the capsid's internal diameter, suggesting that virions do not contain a fully assembled tube. Lengthened proteins were also used to test the biological significance of the crystal structure. Particles containing H proteins of two different lengths were significantly less infectious than both parents, indicating an inability to pilot DNA. Shortened H proteins were not fully functional. Although they could still stimulate viral protein synthesis, they either were not incorporated into virions or, if incorporated, failed to pilot the genome. Mutant proteins that failed to incorporate contained deletions within an 85-amino-acid segment, suggesting the existence of an incorporation domain. The revertants of shortened H protein mutants fell into two classes. The first class duplicated sequences neighboring the deletion, restoring wild-type length but not wild-type sequence. The second class suppressed an incorporation defect, allowing the use of the shortened protein. The H-tube crystal structure represents the first high-resolution structure of a virally encoded DNA-translocating conduit. It has similarities with other viral proteins through which DNA must travel, such as the α-helical barrel domains of P22 portal proteins and T7 proteins that form tail tube extensions during infection. Thus, the H protein serves as a paradigm for the assembly and function of long α-helical supramolecular structures and nanotubes. Highly repetitive in primary and quaternary structure, they are amenable to structure-function analyses using in-frame insertions and deletions as presented herein.

On nonlinear thermo-electro-elasticity.

Electro-active polymers (EAPs) for large actuations are nowadays well-known and promising candidates for producing sensors, actuators and generators. In general, polymeric materials are sensitive to differential temperature histories. During experimental characterizations of EAPs under electro-mechanically coupled loads, it is difficult to maintain constant temperature not only because of an external differential temperature history but also because of the changes in internal temperature caused by the application of high electric loads. In this contribution, a thermo-electro-mechanically coupled constitutive framework is proposed based on the total energy approach. Departing from relevant laws of thermodynamics, thermodynamically consistent constitutive equations are formulated. To demonstrate the performance of the proposed thermo-electro-mechanically coupled framework, a frequently used non-homogeneous boundary-value problem, i.e. the extension and inflation of a cylindrical tube, is solved analytically. The results illustrate the influence of various thermo-electro-mechanical couplings.

Validation and Evaluation of the Effects of Semi-Occluded Face Mask Straw Phonation Therapy Methods on Aerodynamic Parameters in Comparison to Traditional Methods

Traditional semi-occluded vocal tract therapies have the benefit of improving vocal economy but, do not allow for connected speech during rehabilitation. In this study, we introduce a semi-occluded face mask (SOFM) as an improvement upon current methods. This novel technique allows for normal speech production, and will make the transition to everyday speech more natural. We hypothesize that use of an SOFM will lead to the same gains in vocal economy seen in traditional methods. Repeated measures excised canine larynx bench experiment with each larynx subject to controls and a randomized series of experimental conditions. Aerodynamic data were collected for 30 excised canine larynges. The larynges were subjected to conditions including a control, two tube extensions (15 and 30 cm), and two tube diameters (6.5 and 17 mm) both with and without the SOFM. Results were compared between groups and between conditions within each group. No significant differences were found between the phonation threshold pressure and phonation threshold flow measurements obtained with or without the SOFM throughout all extension and constriction levels. Significant differences in phonation threshold pressure and phonation threshold flow were observed when varying the tube diameter while the same comparison for varying the tube length at least trended toward significance. This study suggests that a SOFM can be used to elicit the same gains in vocal economy as what has been seen with traditional semi-occluded vocal tract methods. Future studies should test this novel technique in human subjects to validate its use in a clinical setting.

NADPH oxidases as electrochemical generators to produce ion fluxes and turgor in fungi, plants and humans.

The NOXs are a family of flavocytochromes whose basic structure has been largely conserved from algae to man. This is a very simple system. NADPH is generally available, in plants it is a direct product of photosynthesis, and oxygen is a largely ubiquitous electron acceptor, and the electron-transporting core of an FAD and two haems is the minimal required to pass electrons across the plasma membrane. These NOXs have been shown to be essential for diverse functions throughout the biological world and, lacking a clear mechanism of action, their effects have generally been attributed to free radical reactions. Investigation into the function of neutrophil leucocytes has demonstrated that electron transport through the prototype NOX2 is accompanied by the generation of a charge across the membrane that provides the driving force propelling protons and other ions across the plasma membrane. The contention is that the primary function of the NOXs is to supply the driving force to transport ions, the nature of which will depend upon the composition and characteristics of the local ion channels, to undertake a host of diverse functions. These include the generation of turgor in fungi and plants for the growth of filaments and invasion by appressoria in the former, and extension of pollen tubes and root hairs, and stomatal closure, in the latter. In neutrophils, they elevate the pH in the phagocytic vacuole coupled to other ion fluxes. In endothelial cells of blood vessels, they could alter luminal volume to regulate blood pressure and tissue perfusion.

Combined Cytological and Transcriptomic Analysis Reveals a Nitric Oxide Signaling Pathway Involved in Cold-Inhibited Camellia sinensis Pollen Tube Growth.

Nitric oxide (NO) as a signaling molecule plays crucial roles in many abiotic stresses in plant development processes, including pollen tube growth. Here, the signaling networks dominated by NO during cold stress that inhibited Camellia sinensis pollen tube growth are investigated in vitro. Cytological analysis show that cold-induced NO is involved in the inhibition of pollen tube growth along with disruption of the cytoplasmic Ca2+ gradient, increase in ROS content, acidification of cytoplasmic pH and abnormalities in organelle ultrastructure and cell wall component distribution in the pollen tube tip. Furthermore, differentially expressed genes (DEGs)-related to signaling pathway, such as NO synthesis, cGMP, Ca2+, ROS, pH, actin, cell wall, and MAPK cascade signal pathways, are identified and quantified using transcriptomic analyses and qRT-PCR, which indicate a potential molecular mechanism for the above cytological results. Taken together, these findings suggest that a complex signaling network dominated by NO, including Ca2+, ROS, pH, RACs signaling and the crosstalk among them, is stimulated in the C. sinensis pollen tube in response to cold stress, which further causes secondary and tertiary alterations, such as ultrastructural abnormalities in organelles and cell wall construction, ultimately resulting in perturbed pollen tube extension.

多孔質体を用いた高圧水素漏洩時における自発点火の防止

High-pressure hydrogen can ignite spontaneously without any ignition sources if it leaks from the storage container or a transport pipe. The released hydrogen generates a shock wave that heats the surrounding air around the release area. As a result, the heated air is mixed with the released hydrogen, leading to self-ignition. It is well known that porous material attenuates a shock wave. In the present work, the shock wave is passed through a porous tube and attenuated so that the self-ignition is prevented. The self-ignition is detected using a photomultiplier tube and attenuation of the shock wave is confirmed by measuring the shock speed. The experimental results show that the attenuation of the shock wave is enhanced with extension of the porous tube. The porous tube set near the release position of hydrogen weakens the shock wave effectively. However, a longer porous tube that is placed near the release position of hydrogen promotes mixing between the released hydrogen and the shock-heated air, resulting in self-ignition by a weaker shock wave.

Transition from multi-center fracture to fragmentation statistics under intensive loading

Statistics of transition from damage to fragmentation is studied based on the analysis of multi-scale mechanisms of nucleation and growth of cracks in hollow cylindrical (tubular) specimens made of Al2O3 ceramics. Specimens are loaded by underwater electrical wire explosion. Around 98% of the initial mass of the specimen was recovered as a fragments. The fragments were classified into two types: quasi-two-dimensional (2D) samples, the characteristic size of which d* was greater than (or equal to) the wall thickness of the tube d; and three-dimensional (3D) samples of size d* < d. The analysis of the fragment geometry allows us to determine the mechanisms responsible for the formation of 2D and 3D fragments. The 2D fragments are formed by the large cracks (Mott mechanism) as a result of tube extension in the radial direction. The 3D objects are formed due to instability of fast crack propagation, which leads to microbranching, as was shown in Sharon (1996). The 3D fragments size distribution is governed by the power law, which corresponds to the microbranch distribution. The study of the influence of the initial sample porosity indicates that the distribution of the porosity is described by the power function with an exponent slightly differing from that of the fragments distribution. We suppose that both the initial porosity and crack instability influence the formation of small fragments. The preliminary analysis of the initial porosity of the material shows us that the initial porosity has a direct effect on the formation of 3D fragments. According to the scenario, the initial defects (pores) provide the conditions for multi-site fracture of ceramics under high rate loading.

Mechanisms of resistance in Brassica carinata, B. napus and B. juncea to Pseudocercosporella capsellae

Studies were undertaken to compare susceptible and resistant host responses to Pseudocercosporella capsellae in cotyledons of Brassica carinata, B. juncea and B. napus in order to define the mechanisms of resistance in these three species. On both resistant and susceptible hosts, hyphal penetration was always through stomatal openings and without infection pegs or appressoria. On resistant B. carinata ATC94129P, up to 72% of spores disintegrated and, generally, germination (&lt;22%) and germ tube lengths (&lt;25 μm) were comparatively low. Resistant B. napus Hyola 42 had the lowest germination (8%) and susceptible B. carinata UWA#012 had the highest (51%). On resistant B. carinata ATC94129P, germ tube extension was impeded across 24–60 h post‐inoculation (hpi) and percentage stomatal penetration lower (4%) at 60 hpi compared with susceptible B. carinata UWA#012 (26%). Stomatal densities (stomata/14 757 μm2) on resistant B. juncea Dune (2·12) and B. napus Hyola 42 (1·62) were lower than for susceptible B. juncea Vardan (2·40) and B. napus Trilogy (2·03). Resistant B. carinata ATC94129P had greater stomatal density (1·89) than susceptible B. carinata UWA#012 (1·58). Overall, B. juncea had greater stomatal density (2·26) compared with B. napus (1·83) and B. carinata (1·74). In resistant B. carinata ATC94129P, P. capsellae induced 28% stomata to close, while in susceptible B. carinata UWA#012 no such closure was induced. Epicuticular wax crystalloids were present only on resistant B. carinata ATC94129P and probably also contribute towards resistance.

Carbidopa levodopa enteral suspension

Introduction: The search for consistent, effective treatments in Parkinson’s disease (PD) is ongoing. The importance of continuous dopaminergic stimulation (CDS) is understood to underlie best medical therapy for PD by providing closer replication of physiological patterns of dopamine release in healthy brains.Areas covered: An overview of interventions to improve motor fluctuations in PD is presented. Significant improvements in off-time are achieved by providing continuous therapy using targeted deep brain stimulation (DBS), subcutaneous apomorphine infusion and carbidopa/levodopa enteral suspension (Duopa). Duopa is a newly approved treatment in the US for advanced PD that delivers levodopa pumped to the intestinal tract through a percutaneous gastrostomy with jejunum tube extension (PEG-J tube). Trials with carbidopa/levodopa enteral suspension show improvement in motor fluctuations, reduction in plasma levodopa variation and improvement in overall “on” time compared with oral immediate release formulation of carbidopa/levodopa.Expert opinion: The degree of improvement in number of off hours per day on carbidopa/levodopa enteral suspension infusion rivals that seen with DBS and apomorphine infusion and makes this new treatment a valuable option in advanced fluctuating PD patients, especially those who are neither candidates for DBS or who do not have access to apomorphine infusion therapy or who have failed either or both therapies.

Linear poynting’s effect at torsion and extension of curvilinearly anisotropic tubes

On the basis of the theoretical analysis of deformations of tubes composed of orthorhombic crystals, it is shown that the torsion of chiral curvilinearly anisotropic tubes is accompanied by their extension (direct Poynting’s effect), and the extension is accompanied by torsion (reverse Poynting’s effect). Contrary to classical nonlinear Poynting’s effect for nonlinear isotropic elastic materials, the effect found for anisotropic tubes has a linear character and disappears at zero chirality.

CCM-3/STRIPAK promotes seamless tube extension through endocytic recycling.

The mechanisms governing apical membrane assembly during biological tube development are poorly understood. Here, we show that extension of the C. elegans excretory canal requires cerebral cavernous malformation 3 (CCM-3), independent of the CCM1 orthologue KRI-1. Loss of ccm-3 causes canal truncations and aggregations of canaliculular vesicles, which form ectopic lumen (cysts). We show that CCM-3 localizes to the apical membrane, and in cooperation with GCK-1 and STRIPAK, promotes CDC-42 signalling, Golgi stability and endocytic recycling. We propose that endocytic recycling is mediated through the CDC-42-binding kinase MRCK-1, which interacts physically with CCM-3-STRIPAK. We further show canal membrane integrity to be dependent on the exocyst complex and the actin cytoskeleton. This work reveals novel in vivo roles of CCM-3·STRIPAK in regulating tube extension and membrane integrity through small GTPase signalling and vesicle dynamics, which may help explain the severity of CCM3 mutations in patients.

The BED finger domain protein MIG-39 halts migration of distal tip cells in Caenorhabditis elegans

Organs are often formed by the extension and branching of epithelial tubes. An appropriate termination of epithelial tube extension is important for generating organs of the proper size and morphology. However, the mechanism by which epithelial tubes terminate their extension is mostly unknown. Here we show that the BED-finger domain protein MIG-39 acts to stop epithelial tube extension in Caenorhabditis elegans. The gonadal leader cells, called distal tip cells (DTCs), migrate in a U-shaped pattern during larval development and stop migrating at the young adult stage, generating a gonad with anterior and posterior U-shaped arms. In mig-39 mutants, however, DTCs overshot their normal stopping position. MIG-39 promoted the deceleration of DTCs, leading to the proper timing and positioning of the cessation of DTC migration. Among three Rac GTPase genes, mutations in ced-10 and rac-2 enhanced the overshoot of anterior DTCs, while they suppressed that of posterior DTCs of mig-39 mutants. On the other hand, the mutation in mig-2 suppressed both the anterior and posterior DTC defects of mig-39. Genetic analyses suggested that MIG-39 acts in parallel with Rac GTPases in stopping DTC migration. We propose a model in which the anterior and posterior DTCs respond in an opposite manner to the levels of Rac activities in the cessation of DTC migration.

Heart fields and cardiac morphogenesis.

In this review, we focus on two important steps in the formation of the embryonic heart: (i) the progressive addition of late differentiating progenitor cells from the second heart field that drives heart tube extension during looping morphogenesis, and (ii) the emergence of patterned proliferation within the embryonic myocardium that generates distinct cardiac chambers. During the transition between these steps, the major site of proliferation switches from progenitor cells outside the early heart to proliferation within the embryonic myocardium. The second heart field and ballooning morphogenesis concepts have major repercussions on our understanding of human heart development and disease. In particular, they provide a framework to dissect the origin of congenital heart defects and the regulation of myocardial proliferation and differentiation of relevance for cardiac repair.

Arabidopsis thaliana calmodulin-like protein CML24 regulates pollen tube growth by modulating the actin cytoskeleton and controlling the cytosolic Ca(2+) concentration.

Cytosolic free calcium ([Ca(2+)]cyt), which is essential during pollen germination and pollen tube growth, can be sensed by calmodulin-like proteins (CMLs). The Arabidopsis thaliana genome encodes over 50 CMLs, the physiological role(s) of most of which are unknown. Here we show that the gene AtCML24 acts as a regulator of pollen germination and pollen tube extension, since the pollen produced by loss-of-function mutants germinated less rapidly than that of wild-type (WT) plants, the rate of pollen tube extension was slower, and the final length of the pollen tube was shorter. The [Ca(2+)]cyt within germinated pollen and extending pollen tubes produced by the cml24 mutant were higher than their equivalents in WT plants, and pollen tube extension was less sensitive to changes in external [K(+)] and [Ca(2+)]. The pollen and pollen tubes produced by cml24 mutants were characterized by a disorganized actin cytoskeleton and lowered sensitivity to the action of latrunculin B. The observations support an interaction between CML24 and [Ca(2+)]cyt and an involvement of CML24 in actin organization, thereby affecting pollen germination and pollen tube elongation.

Decreased Pollen Viability and Thicken Pollen Intine in Antisense Silenced Brassica campestris Mutant of BcMF19

Brassica campestris male fertility 19 (BcMF19; GenBank accession number GQ902048.1), a gene that is specially expressed in tapetum cells and microspores during anther development in B. campestris ssp. chinensis, which is learned from the previous in situ hybridization study. In the present study, we constructed antisense-silenced plants of BcMF19 using B. campestris ssp. chinensis to validate this prediction. The morphology of the pistils, long anthers, and short anthers was significantly affected in 35sbcmf19 compared with the control samples. 4′-6-Diamidino-2-phenylindole staining revealed that two generative nuclei and one large vegetative nucleus were not affected in the mutant compared with control. Statistical analysis of Alexander's staining results showed that 96% of the control pollen grains had vitality, whereas only 86% of the mutant pollen grains did. Under scanning electron microscopy, the mutant demonstrated numerous abnormal pollen grains and resembled dried persimmon. The frequency of normal pollen grains was approximately 18%. Under transmission electron microscopy, the pollen intine during the binucleate and mature pollen stages in 35sbcmf19 exhibited abnormal thickening, especially at the germinal furrows, compared with control. In vitro pollen germination test showed that the tips of the mutant pollen tubes transformed into globular alveoli and stopped growing compared with control. On the other hand, in vivo pollen germination test suggested that BcMF19 affected the pollen tube extension in the pistil. These findings indicate that BcMF19 is essential to the pollen development and pollen tube extension of B. campestris ssp. chinensis.