Separation Of Walls Research Articles

Development of schizogenous intercellular spaces in plants.

Gas exchange is essential for multicellular organisms. In contrast to the circulatory systems of animals, land plants have tissues with intercellular spaces (ICSs), called aerenchyma, that are critical for efficient gas exchange. Plants form ICSs by two different mechanisms: schizogeny, where localized cell separation creates spaces; and lysogeny, where cells die to create ICSs. In schizogenous ICS formation, specific molecular mechanisms regulate the sites of cell separation and coordinate extensive reorganization of cell walls. Emerging evidence suggests the involvement of extracellular signaling, mediated by peptide ligands and leucine-rich repeat receptor-like kinases, in the regulation of cell wall remodeling during cell separation. Recent work on the liverwort Marchantia polymorpha has demonstrated a critical role for a plasma membrane-associated plant U-box E3 ubiquitin ligase in ICS formation. In this review, I discuss the mechanism of schizogenous ICS formation, focusing on the potential role of extracellular signaling in the regulation of cell separation.

Novel insights on the structure and composition of pseudostomata of Sphagnum.

The occurrence of stomata on sporophytes of mosses and hornworts is congruent with a single origin in land plants. Although true stomata are absent in early-divergent mosses, Sphagnum has specialized epidermal cells, pseudostomata, that partially separate but do not open to the inside. This research examined two competing hypotheses that explain the origin of pseudostomata: (1) they are modified stomata, or (2) they evolved from epidermal cells independently from stomata.• Capsule anatomy and ultrastructure of pseudostomata were studied using light and electron microscopy, including immunolocalization of pectins.• Cell walls in pseudostomata are thin, two-layered, and rich in pectins, similar to young moss stomata, including the presence of cuticle on exterior walls. Outer and ventral walls have a thick cuticle that suggests that initial separation of ventral walls involves cuticle deposition as in true stomata. Further mechanical separation between ventral walls does not form a pore and occurs as the capsule dries.• As in moss stomata, pseudostomata wall architecture and behavior facilitate capsule dehydration, shape change, and dehiscence, supporting a common function. The divergent structure and fate of pseudostomata may be explained by the retention of Sphagnum sporophytes within protective leaves until nearly mature. Ultrastructural and immunocytological data suggest that pseudostomata are related to stomata but do not conclusively support either hypothesis. Solving the relationship of early land plants is critical to understanding stomatal evolution. Pseudostomata are structurally and anatomically unique, but their relationship to true stomata remains to be determined.

Cardiology patient page. Spontaneous coronary artery dissection (SCAD).

The coronary arteries carry oxygen- and nutrient-rich blood to the heart, which allows it to pump and supply blood to the body. The coronary arteries can become blocked by various processes related to cholesterol (atherosclerotic) or other causes (nonatherosclerotic), which can cause heart attacks when the blockages are severe enough to impede blood flow to the heart. Although the atherosclerotic form is most common, nonatherosclerotic blockages (especially dissections/tears) are increasingly recognized as important causes of heart attacks, particularly in women. This article focuses on spontaneous coronary artery dissection (SCAD). SCAD is defined as a tear in the coronary arterial wall that is not related to trauma or medical instrumentation. This spontaneous tear can result from a disruption of the innermost lining of the arterial wall, causing blood to rush in from the lumen (center channel of the artery) into the arterial wall. Alternatively, separation of the arterial walls can occur as a result of bleeding caused by spontaneous rupture of small vessels that feed the arterial wall. The buildup of blood inside the arterial wall compresses the lumen, blocking blood flow to the heart. SCAD is considered to be rare in the general population, although it has been underdiagnosed, and its true prevalence is unknown. Overall, it is an infrequent cause of and accounts for only up to 4% of heart attacks.1 However, SCAD proportionally causes a higher number of heart attacks in young women; ≈25% of women ≤50 years old had heart attacks caused by SCAD in 1 series.2 SCAD affects predominantly women in ≈90% …

Porosity imaged by a vector projection algorithm correlates with fractal dimension measured on 3D models obtained by microCT.

Porosity is an important factor to consider in a large variety of materials. Porosity can be visualized in bone or 3D synthetic biomaterials by microcomputed tomography (microCT). Blocks of porous poly(2-hydroxyethyl methacrylate) were prepared with polystyrene beads of different diameter (500, 850, 1160 and 1560 μm) and analysed by microCT. On each 2D binarized microCT section, pixels of the pores which belong to the same image column received the same pseudo-colour according to a look up table. The same colour was applied on the same column of a frontal plane image which was constructed line by line from all images of the microCT stack. The fractal dimension Df of the frontal plane image was measured as well as the descriptors of the 3D models (porosity, 3D fractal dimension D3D, thickness, density and separation of material walls. Porosity, thickness Df and D3D increased with the size of the porogen beads. A linear correlation was observed between Df and D3D. This method provides quantitative and qualitative analysis of porosity on a single frontal plane image of a porous object.

Performance and Retrofitting of Unreinforced Masonry Buildings against Natural Disasters – A Review Study

Un-Reinforced Masonry (URM) buildings are popular all over the world including Sri Lanka because of their durability, low cost, construction easiness and architectural character, need of less skilled labour, eco-friendliness and use of locally available materials such as ashlar or rubble, adobe and brick. However, these buildings have a higher probability of failing under natural disasters such as earthquakes, tsunamis and storm surges, floods, cyclones and landslides. In Sri Lanka, winds, landslides and floods have frequently occurred. In addition, a massive tsunami adversely affected the people in 2004 and its effects to islands on the Indian Ocean have been continued since December, 2004. Minor earthquakes have come off recently with experiences of wall cracks and no deaths. It is also believed that, there is a defused plate boundary in the making some 500 km south of the southern tip of Sri Lanka which might be the cause of these tremors or minor quakes. Further, an earthquake occurred in Colombo area in 1615, has caused around 2000 of human deaths. Therefore investigation of performance of URM buildings against these natural disasters and possible retrofitting methods are increasingly important. In this review study, an attempt is made to identify the performance of URM buildings against natural disasters and identify retrofitting methods that can be applied to existing building, to enhance the strength proper ties of structural components. Common failure mechanisms for URM structures consist of separation of walls at corners, diagonal cracking or vertical cracking in walls, separation of roofing from walls, out-of-plane wall failure, in-plane wall failure, shear cracks and de-lamination. These damages on a wall diminish the service life of building. In addition, different kinds of retrofitting methods: ferrocement, poly propylene mesh and bamboo reinforcement, for URM structures to be seismic resistant are presented. Mechanisms of failure of URM walls and effects of retrofitting techniques to reduce the damage are also discussed. ENGINEER, Vol. 47, No. 03, pp. 71-82, 2014

MASONRY-INFILLED RC FRAMES SUBJECTED TO COMBINED IN-PLANE AND OUT-OF-PLANE LOADING

The structural responses of infilled frames subjected to combined in-plane and out-of-plane loadings are usually analyzed by separately applying in-plane and out-of-plane loads. The interaction effect of in-plane and out-of-plane loads on the structural behavior of the frames is ignored; thus errors in predicting the actual force-transfer mechanisms and modes of failure of the structures can be incurred. To solve the problem, this paper presents a discrete finite element modeling technique, which employs a damage-based cohesive crack representation of fracture behavior of masonry infills, followed by a study on the force-transfer mechanisms and failure modes of the anchored and unanchored infilled reinforced concrete (RC) frames subjected to interactive in-plane and out-of-plane loads. The analysis indicates that under out-of-plane loading the diagonal compressive thrust of masonry-infill walls, which is induced by in-plane lateral loading and acts on the walls, may reduce the in-plane load capacity of the RC frame by up to 50% and cause buckling of infill walls. On the other hand, the anchorage can effectively prevent the separation of infill walls from the bounding frame and provide stabilizing forces to the walls against buckling.

Vacuum alignment and phase structure of holographic bi-layers

We study the D3/probe D5 system with two domain wall hypermultiplets. The conformal symmetry can be broken by a magnetic field, B (or running coupling), which promotes condensation of the fermions on each individual domain wall. Separation of the domain walls promotes condensation of the fermions between one wall and the other. We study the competition between these two effects showing a first order phase transition when the separation is ∼0.56λ1/4B−1/2. We identify extremal brane configurations which exhibit both condensations simultaneously but they are not the preferred ground state.

Virtual Cystoscopy Using 3D Ultrasound

The urinary bladder has many inherent characteristics that make it an ideal structure for evaluating with three-dimensional (3D) volume ultrasound (US). The purpose of this study was to evaluate the application of 3D sonography in assessing bladder pathologies. One hundred patients were evaluated in this study. The cases were taken from the pool referred for the evaluation of the renal system (kidney, ureter, and bladder), abbreviated as US KUB at our hospital. The examination was performed with the bladder filled up to 250–350 ml, or whenever adequate distension was noted with wide separation of the bladder walls. Routine (two-dimensional) 2D scanning was followed with the acquisition of 3D volume using abdominal and endocavitary probes. Application of surface rendering algorithm on obtained 3D data sets yielded near cystoscopy-like images of the urinary bladder. The anatomy of the trigonal region of the bladder and the ureteric orifices was obtained in detail. Various bladder pathologies, notably bladder mass, diverticuli and ectopic ureteric openings, were noted. 3D virtual cystoscopy is a promising technique for evaluating bladder pathologies. Its multiplanar capabilities and surface rendering capabilities are helpful for further characterizing the lesions seen on 2D US. It can serve as a good road map prior to cystoscopy.

Domain Wall Splitting in Extra Dimension

We study the splitting of domain walls in 5-dimensional flat Minkowski spacetime. To construct a domain wall structure we utilize a potential of the form and for simplicity we assume the scalar field to be real. We also assume the coefficient a to be temperature-dependent. We find exact analytical expressions for the energy density of the domain wall and from this expression we find close analytical form for the separation of the divided domain walls. We find that near critical temperature the domain walls split. At the critical temperature, the domain walls rejoin. In the region above this critical temperature, the kink solution is nontopological. We find that the phenomena of splitting of domain walls occurs in this region as well. This effect is especially manifest near the inflection point of the potential.

Role of non‐collinear magnetization: From ferromagnetic nanowires to quantum rings

AbstractWe consider interaction effects related to a non‐uniform magnetization in ferromagnetic nanowires and their possible generalization to nanorings. First we show that the electric current in a ferromagnetic nanowire with more than one domain wall induces an exchange coupling between the walls mediated by the spin‐dependent interference of scattered carriers. This interaction reveals a complex behavior as a function of mutual orientations and separation of the domain walls, thus affecting the domain wall dynamics. Then we consider how the theory should be modified in the case of a magnetized quantum ring. In this case the situation is more complicated because the vortex and onion magnetization states in the ring are not truly ferromagnetic.

Fracture of Open-Cell Nickel Foams Under Quasi-Static Tensile Loading

Open-cell nickel foams with average pore size of 600 μm have been subjected to room temperature tensile tests to explore their tensile properties. Using a state of the art extensometer of noncontact type, foam properties as ultimate tensile strength, yield strength, and the Young’s modulus (E) have been measured accurately. The reason behind the usage of this kind of extensometer is to avoid completely any minor deformation that might be caused by the attachment of conventional extensometer to the sample’s surface prior to testing. The function of this extensometer is based on the usage of a laser (CCD) camera that detects and records the dimensional changes as soon as the load is applied. A series of cyclic loading-unloading tests was performed to determine the foam’s Young’s modulus. The fracture behavior of foam cells was observed to be ductile. Complete separation of struts or cell walls took place successively by necking.

Tensile properties of open-cell nickel foams

Open-cell nickel foams with average pore size of 600 μm have been subjected to room temperature tensile tests to explore their tensile properties. Using a state of the art extensometer of non-contact type, foam properties as ultimate tensile strength (UTS), yield strength (YS) and the Young’s modulus ( E) have been measured accurately. An extensometer of non-contact type was applied for the first time to help the foam’s mechanical properties to be determined accurately. The reason behind the usage of this kind of extensometer is to avoid completely any minor deformation that might be caused by the attachment of conventional extensometer to the sample’s surface prior to testing. The function of this extensometer is based on the usage of a laser (CCD) camera that detects and records the dimensional changes as soon as the load is applied. The fracture behavior of foam cells was observed to be ductile. Complete separation of struts or cell walls took place successively by necking.

Gas diffusion in ‘Golden’ papaya fruit at different maturity stages

In this work the gas diffusion of ‘Golden’ papaya fruit ( Carica papaya L.) was evaluated as a function of different maturity stages, by using a photoacoustic spectrometer. The maturity stages were characterized by the anatomical changes, membrane integrity, pulp firmness, and skin color. Microstructural analysis was performed by means of light and scanning electron microscopy. A significant decrease in the diffusion rate with ripening was observed. Under the experimental conditions it was found that fruit in maturity stage 0 (less mature) had turgid, regular shape parenchyma cells, and relatively little intercellular spaces. However, fruit in maturation stage 5 (more mature) showed separation of cell walls and pectic substance accumulation into the intercellular spaces. The skin color showed a reduction in hue angle values and an increase in chromaticity parameters a* and b*, characterizing the loss of green color during ripening. A loss of firmness of the pulp was also observed during fruit ripening.

Fracture of open cell copper foams under tension

Open cell copper foams having an average pore size of 600 μm have been subjected to room temperature tensile tests to explore their tensile properties. Using a state of the art extensometer of non-contact type, foam properties as ultimate tensile strength (UTS), yield strength (YS) and the Young's modulus ( E) have been measured accurately. A state-of-the art extensometer of non-contact type was applied for the first time to help the foam's mechanical properties to be determined accurately. The reason behind the usage of this kind of extensometer is to avoid even any small deformation that might be caused by the attachment of conventional extensometer to the sample prior to testing. The function of the extensometer is based on the usage of a laser (CCD) camera that detects and records the dimensional changes as soon as the load is applied. The fracture behavior of foam cells was observed to be ductile. The ductility is attributed to the purity of copper that deforms on 12 slip deformation planes. Complete separation of struts or cell walls took place successively by necking.

Self-organized porous and tubular oxide layers on TiAl alloys

The present paper describes the electrochemical fabrication of nanostructured oxide films on a TiAl intermetallic compound. The alloy is investigated under conditions where the individual alloying elements show the growth of ordered oxide structures, i.e. anodization is carried out in fluoride containing and fluoride free H 2SO 4 electrolytes. In 1 M H 2SO 4 the alloy shows randomly ordered nanoporous oxide structures while in HF-containing electrolytes highly ordered films can be formed. The key factor that affects the morphology is the anodizing potential. At low potentials (∼10 V) self-organized nanopores are formed whereas at higher potentials (∼40 V) separation of the pore walls and therefore formation of nanotubes can be observed. The results clearly indicate that on TiAl a wide range of nanoscale morphologies can be achieved ranging from random porous to organized pores to organized tubes.

Anatomy of HH 111 from CO Observations: A Bow‐Shock‐driven Molecular Outflow

We present single-dish and interferometric millimeter line observations of the HH 111 outflow and its driving source. The physical conditions of the core have been determined from the emission of the millimeter line of CO and its isotopomers and CS with the IRAM 30 m telescope, and the CO J = 7 → 6 line with the Caltech Submillimeter Observatory. The emission reveals a small condensation of cold (T = 20-25 K) and dense gas [n(H2) = 3 × 105 cm-3]. The outflow has been mapped with the IRAM Plateau de Bure interferometer (PdBI). The cold gas is distributed in a hollow cylinder surrounding the optical jet. The formation of this cavity and its kinematics are well accounted for in the frame of outflow gas entrainment by jet bow shocks. Evidence of gas acceleration is found along the cavity walls, correlated with the presence of optical bow shocks. The separation of the inner walls reaches 8''-10'', which matches the transverse size of the wings in the bow shock. CSO observations of the J = 7 → 6 line show evidence of a high-velocity and hot gas component (T = 300-1000 K) with a low filling factor. This emission probably arises from shocked gas in the jet. Observations of the 3P2-3P1 [C I] line are consistent with C-type nondissociative shocks. Mapping of the high-velocity molecular bullets B1-B3, located beyond the optical jet, reveals small structures of 3'' × 7'' flattened perpendicular to the flow direction. They are made of cold (T ~ 30 K), moderate density gas [n(H2) = (0.5-1.0) × 104 cm-3], expanding into the low-density surrounding medium. Their properties are consistent with their being shocked gas knots resulting from past time-variable ejections in the jet.

Soft Micro-Balloon Paddy for Brain Retraction in the Protection of Neuronal Tissue

Brain protection is extremely important during arachnoidal dissection and brain separation with a metallic retractor to create a surgical corridor. We have designed a new type of paddy containing air-filled micro-balloons and cotton for use between the metallic retractor and the brain surface for maximal protection of the neuronal tissues from the pressure of the retractor. In neurosurgical operations, cotton paddies are commonly and generally used during the retraction of brain tissue. We hypothesized that air-filled micro-balloon paddies covered with cotton could be helpful in the gentle separation of brain tissue with metallic retractors for minimizing cerebral damage, and for separating sulcal and cisternal walls during brain operations. These paddies are 2 cm in width and 4 cm in length. Multiple air-filled silicon micro-balloons are located in a sheet with 1-2 mm separation from each other. These silicon micro-balloonoid sheets are covered with a cotton sheath. The thickness of this type of paddy is 2-3 mm from the anterior surface to the posterior surface. We used paddies in 86 brain operations where brain retraction was necessary to create a surgical corridor. There was no complication or unwanted events related with the use of these paddies. air-filled silicon micro-balloon paddies are useful materials for the gentle separation of brain tissue with a metallic retractor in order to minimize cerebral damage, and for the separation of sulcal and cisternal walls during the surgical intervention.

The Environment of Vein Formation and Ore Deposition in the Purisima-Colon Vein System, Pachuca Real del Monte District, Hidalgo, Mexico

The Environment of Vein Formation and Ore Deposition in the Purisima-Colon Vein System, Pachuca Real del Monte District, Hidalgo, Mexico

A comparison of cup‐to‐disc ratio measurement in normal subjects using optical coherence tomography image analysis of the optic nerve head and stereo fundus biomicroscopy

To determine the relationships between morphometric optic nerve head (ONH) characteristics defined using optical coherence tomography (OCT) and clinical judgments of cup-to-disc (CD) ratios. CD ratios were estimated in 20 subjects by two experienced clinicians using stereo fundus biomicroscopy. Sagittal OCT images were obtained in positions defined by clinicians corresponding to the location of their horizontal and vertical CD ratio estimates. To estimate CD ratios using the OCT images, disc width was defined as the separation of the terminations of the retinal pigment epithelium on each side of the image. OCT cup widths were determined using two criteria: the first measured the separation of cup walls halfway down each side and the second estimated the separation 1/3 down each side. Cups that were less than 150 microm deep were defined as flat for the OCT images. Data were analysed using mean and standard deviation of the differences between clinical estimates and imaging techniques as well as using intraclass correlations (ICC). Between techniques, the range of ICCs for the 1/2 depth criterion was 0.74-0.90 and for the 1/3 criterion was 0.59-0.81. The limits of agreement for the 1/2 criterion were also better than the 1/3 criterion. Accurate measures of CD ratio may be derived from OCT ONH images. Estimates of clinical CD ratios in normal subjects appear to be made using depth judgments closer to 1/2 of the way down the cup than 1/3.

Anatomical and ultrastructural study of the secretory cavity development of Citrus sinensis and Citrus limon: evaluation of schizolysigenous ontogeny

The ontogeny and ultrastructure of secretory oil glands in the fruits of Citrus sinensis and Citrus limon were studied with light and electron microscopy (TEM). Oil glands were initiated by cell division in globular/oval clusters of young meristematic cells under or including also the epidermis. Successively, the central oil cells increased greatly in size by growth and coalescence of one or more vacuoles. Starting from these cells the oil cavity formation and enlargment occurred by schizogenous and lysigenous precesses which overlap one another. The separation of the cell walls, in both Citrus species, was accompanied by strong structural disorganization of the cytoplasm, loss of nuclei, plasmolysis, and followed by autolysis processes. Prior these changes a great quantity of oil droplets filled the cells. In Citrus sinensis this material was formed in the plastids; on the contrary, in Citrus limon oil droplets appeared only in the cytoplasm, and no connection with the plastids was observed. The processes of schizogeny and lysigeny occurred in a centrifugal direction. The peripheral oil chamber cells were so pushed outward and flattened with the progressive expansion of the gland cavity. Also these cells became vacuolated, showed schizogenous processes together with cytoplasm and nuclei breakdown. These cell modifications were preceded by an abundant essential oil synthesis. Electron dense material appeared in the cavity near the boundary cells. Among the cell layers surrounding the cavity, the outer peripheral cells showed very thick walls. These cells, probably, had a protective function, while the inner cells continued, at least in part, to produce and secrete oil compounds. In the two Citrus species the pattern of oil gland development was practically the same, except the different plastid behaviour.