Leaf Panels Research Articles

Experimental study on airborne sound insulation performance of lightweight double leaf panels

To create a healthy and comfortable indoor environment, higher requirements are put forward for the airborne sound insulation performance of buildings. The control of airborne noise transmission is a key measure to improve the airborne sound insulation performance of buildings. In this study, the airborne sound insulation performance of the lightweight double leaf wall was studied, and the influence of stud type, stud spacing, cavity filling (type and thickness of filling materials), panel layers (type, layer number, thickness and mass) on the airborne sound insulation performance of the lightweight wall was emphatically analyzed. The test results show that the airborne sound insulation performance of the lightweight double leaf wall can be improved by the following five measures: (1) increasing the stud spacing; (2) expanding the size of the independent panel; (3) using stone wool or glass wool as the filling materials; (4) increasing the number of panel layers or panel mass; and (5) reducing the structural connection.

Techniques to improve the low frequency and broadband performance of microperforated panel absorbers

Microperforated panel absorbers can be considered as the combination of the perforated panel and backing airspace. It has been demonstrated that partitioning the airspace improves performance. Additional performance improvements can be obtained by varying the depth of the backing cavity, adding resonators behind the panel, or using double leaf panels. Each of these configurations is first considered for a single cell backing using plane wave simulation. Comparisons are made to impedance tube measurements with acceptable agreement. Following this, the diffuse field sound absorption for each configuration was measured in a small reverberation room. Each test sample consisted of a 0.6 m x 0.4 m panel with a backing cavity partitioned into 24 equal size cells. For the double leaf configuration, the cavity betwen panels was honeycomb partitioned but the backing cavity was unpartitioned.

Seismic In-plane performance of retrofitted masonry walls

Retrofitting of masonry to improve its seismic performance is the focus of research community all around the globe. In the present work, a new masonry retrofitting technique using externally anchored steel strips mesh is presented. An extensive experimental programme was carried out to study the effects of proposed technique on masonry lateral strength, ductility, energy dissipation, response and damping factor under lateral cyclic loading. A total of twenty tests were carried out; 1) twelve were lateral cyclic tests, 2) four monotonic lateral tests and 3) four pure compression tests. The test results were analysed in five separate groups and this paper presents the analysis of group 3, which deals with the effect of steel retrofitting of un-reinforced masonry wall panels on its seismic performance. Six single leaf panels with aspect ratio of 0.67 were constructed using same type of material and workmanship. It was observed that amount of steel reinforcement and meshing pattern of steel strips had significant effect on seismic performance and failure modes. The simplicity, cost effectiveness and efficacy of this proposed technique could help the local designers and engineers to enhance seismic performance of existing masonry structures.

Response of Masonry Walls Strengthened with CFRP and Steel Strips

Strengthening of un-reinforced masonry (URM) to improve its seismic performance is an international research focus. This paper presents the effect of masonry strengthening using steel strips and carbon fiber reinforced polymer (CFRP) strips on seismic performance of URM wall panels. Three single leaf panels with aspect ratio of 0.7 were constructed in the laboratory using the same type of materials and workmanship. Both CFRP and steel strips significantly improved the seismic performance compared to the un-reinforced wall panel. After analysis of test results, we found that lateral strength increase for the steel strengthened wall was less, but other seismic parameters were better than for the CFRP strengthened wall. However, both CFRP and steel strengthening of masonry were quite effective in improving overall lateral strength and ductility.

ICCAP-a linear time sparsification and reordering algorithm for 3-D BEM capacitance extraction

This paper presents an efficient, simple, hierarchical, and sparse three-dimensional capacitance extraction algorithm, i.e., ICCAP. Most previous capacitance extraction algorithms, such as FastCap and HiCap, introduce intermediate variables to facilitate the hierarchical potential calculation, but still preserve the basic panels as basis. In this paper, we discover that those intermediate variables are a fundamentally much better basis than leaf panels. As a result, we are able to explicitly construct the sparse potential coefficient matrix and solve it with linear memory and linear run time in comparison with the most recent hierarchical O(nlogn) approach in PHiCap. Furthermore, the explicit sparse formulation of a potential matrix not only enables the usage of preconditioned Krylov subspace iterative methods, but also the reordering technique. A new reordering technique, i.e., level-oriented reordering (LOR), is proposed to further reduce over 20% of memory consumption and run time compared with no reordering techniques applied. In fact, LOR is even better than the state-of-the-art minimum degree reordering and more efficient. Without complicated orthonormalization matrix computation, ICCAP is very simple, efficient, and accurate. Experimental results demonstrate the superior run time and memory consumption over previous approaches while achieving similar accuracy.

In planta measurements of oxidative bursts elicited by avirulent and virulent bacterial pathogens suggests that H2O2 is insufficient to elicit cell death in tobacco

ABSTRACTA rapid and localized programmed cell death – the hypersensitive response (HR) – is a widely utilized plant resistance mechanism against pathogens. Studies have implicated H2O2 generation as a key elicitory mechanism in the HR. The causal relationship between the kinetics of the in planta oxidative burst, the HR and certain defence gene expression was examined. H2O2 generation following challenge with avirulent strains of Pseudomonas syringae pv. (P. s. pv.) syringae occurred in two phases. The effects of ROS generation were investigated using the H2O2‐responsive transgene AoPR10‐GUS, the dually responsive (H2O2 and salicylic acid) PR1a‐GUS as well as measures of cell death. Co‐application of catalase with P. s. pv. syringae into tobacco leaf panels suppressed AoPR10‐ and PR1a‐GUS expression and cell death. Conversely, varying H2O2 generation with glucose: glucose oxidase influenced both defence gene expression and cell death. AoPR10‐GUS proved to be primarily responsive to apoplastic not intracellular oxidative stress, suggesting that the apoplasm was a distinctive source of oxidative signals. A biphasic oxidative burst was also observed with virulent P. s. pv. tabaci, which, although delayed compared to that observed during HR, persisted at equivalent levels for a longer period. Taking all these data together we suggest that either (1) additional factors to the apoplastic oxidative burst are required to explain the rapid kinetics of defence signalling and cell death associated with the HR or (2) P. s. pv. tabaci successfully suppresses the effects of H2O2 generation by an unknown mechanism.

Changes in Methanol Evolution and Pectin Methylesterification in Resistant and Susceptible Pepper Leaves Inoculated with Xanthomonas campestris pv. vesicatoria

The hypersensitive response in resistant plants exposed to incompatible pathogens involves structural changes in the plant cell wall and plasma membrane. Cell wall changes may include pectin deesterification resulting in release of methanol. The time course of methanol production was characterized from `Early Calwonder 20R' pepper (Capsicum annuum L.) leaves infiltrated with the incompatible pathogen, Xanthomonas campestris pv. vesicatoria (Doidge) Dye race 1 (XCV). In the first time course experiment, leaves were infiltrated with either 108 colony-forming units/mL of XCV or water control. Leaf panels (1 × 5 cm) were excised after dissipation of water soaking, then incubated in vials at 24 °C. Headspace gas was analyzed at 6-hour intervals up to 24 hours. The rate of methanol production from resistant pepper leaves infiltrated with XCV was greatest during the first 12 hours after excision. In another experiment, leaf panels were harvested at 6-hour intervals up to 24 hours after inoculation and incubated for 12 hours at 24 °C to determine the relationship between the interval from inoculation to leaf excision and methanol production. The highest rate of methanol production was obtained when the interval between bacterial infiltration and leaf excision was 18 hours. The relationship between methanol release and changes in the degree of methylesterification (DOM) of cell wall pectin was determined in near isogenic lines of `Early Calwonder' pepper plants resistant (20R) and susceptible (10R) to XCV race 1. Cell walls were prepared from resistant and susceptible pepper leaves infiltrated with XCV or water. XCV-treated resistant leaves had 18% DOM and 9.7 nmol·g-1·h-1 of headspace methanol, and the susceptible leaves had 48% DOM with 0.2 nmol·g-1·h-1 methanol. Susceptible and resistant control leaves infiltrated with water had 55% and 54% DOM, respectively, with no detectable methanol production. Increased methanol production in resistant pepper leaves inoculated with XCV coincided with an increase in cell wall pH. Intercellular washing fluid of resistant pepper leaves had a significantly higher pH (6.9) compared to susceptible leaves (pH 5.1) and control leaves infiltrated with water (pH 5.1). Both 10R and 20R pepper leaves infiltrated with buffer at increasing pH's of 5.1, 6.9 or 8.7 had increased methanol production. Since deesterified pectin is more susceptible to degradation, demethylation may facilitate formation of pectic oligomers with defensive signalling activity.

Elicitins from Phytophthora and basic resistance in tobacco.

Elicitins are a family of small proteins secreted by species of Phytophthora. They are thought to be major determinants of the resistance response of tobacco against these oomycetes, since purified elicitins, alone and at low concentrations, can induce vigorous defense responses in tobacco (i.e., hypersensitive cell death and resistance against subsequent pathogen attack), and in vitro elicitin production by Phytophthora isolates is strongly negatively correlated with their pathogenicity on tobacco plants. A number of elicitins have been purified and their amino acid sequences have been determined and found to be conserved. A three-dimensional structure for elicitin is emerging from nuclear magnetic resonance studies. Two structural classes, alpha and beta, are distinguished by their biological effects when applied to decapitated stems or petioles; the beta class causes more necrosis on leaves and provides better subsequent protection against pathogen attack. However, both these classes of elicitins will similarly cause necrosis when each is, instead, directly infiltrated into tobacco leaf panels. Effects of elicitins on tobacco cells include rapid electrolyte leakage, changes in protein phosphorylation and amounts of active oxygen species, and later production of ethylene and capsidiol. The sites of initial interaction with tobacco cells are unknown, but the interaction appears to induce general defense-related responses.

Modification of the Pseudomonas syringae pv. tabaci -tobacco leaf interaction by bacterial oligosaccharides

Cell-associated oligosaccharides were extracted with trichloroacetic acid treatment from Pseudomonas syringae pv. aptata, purified by column chromatography, analysed by GC-MS and fast atom bombardment-mass spectrometry, and bioassayed on tobacco leaves. The material was shown to be a mixture of neutral oligosaccharides, with a mol. wt of 800–1800, degree of polymerization 5–11, and linear glucose and mannose chains. Local infiltrations of the mixture, in concentrations of 1 mg, 100, 10 and 1 μg ml−1, did not cause tobacco tissue necrosis within 1 week. When the mixture was infiltrated in the interveinal leaf panels, in concentrations of 1 μg, 100, 10 and 1 ng ml−1, 48 h before challenge inoculation, it delayed or prevented normosensitive necrosis by P. syringae pv. tabaci but not hypersensitive necrosis by P. syringae pv. aptata. Five days after inoculation with P. syringae pv. tabaci, inhibition of normosensitive necrosis, as compared with the control tissue, was 80·55, 77·21, 56·36 and 45·46 % for the four concentrations. In the bioassay with P. syringae pv. tabaci the efficacy threshold was assessed at approx. 1 ng ml−1. Pre-treatment with oligosaccharides (1 μg significantly inhibited the growth of P. syringae pv. tabaci between 3 and 5 days after inoculation and, between day 6 and 8, it delayed the death of bacteria when the tissue was not subject to necrosis. An interval of 6 h was necessary between the infiltration of oligosaccharides (1 μg ml−1) and inoculation of P, syringae pv. tabaci for a clear inhibition of normosensitive necrosis. These oligosaccharides acted as signal molecules by modifying, at nanomolar concentrations, the P. syringae pv. tabaci—tobacco leaf interaction, but they were not elicitors of the hypersensitive reaction.

Distinguishing Isolates ofPeronospora tabacinafrom Geographic Regions Utilizing Tobacco Leaf Disks and Fluorescence Microscopy

A laboratory bioassay to distinguish isolates of Peronospora tabacina D.B. Adam was developed utilizing 7-mm acetone-dipped disks cut from tobacco leaf panels from several cultivars of Nicotiana tabacum, sporangiospores of P. tabacina, a germination indicator (Calcofluor), and fluorescence microscopy. Sporangiospore germination percentage of each isolate X cultivar pair was determined. Mean germination of sporangiospores differed between domestic and international collection locations (except between the two Mexican isolates). These results suggest the presence of different pathotypes of P. tabacina

Spatial and temporal accumulation of defense gene transcripts in bean (Phaseolus vulgaris) leaves in relation to bacteria-induced hypersensitive cell death.

Primary leaves of 7- to 9-day-old Red Mexican bean plants were inoculated with virulent or avirulent isolates of Pseudomonas syringae pv. phaseolicola, or saprophytic P. fluorescens either by vacuum infiltration of the whole leaf lamina, or by syringe-inoculation of selected leaf panels. In the incompatible combination, resistance was associated with a hypersensitive response (HR). Syringe-inoculated leaves were sampled in three zones: zone 1, the inoculated leaf area; zone 2, the surrounding 0.5-0.7 cm of leaf tissue; and zone 3, the remainder of the leaf. Northern blots of RNA from zones 1, 2, and 3 were probed with bean cDNAs for phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chitinase (CHT), and lipoxygenase (LOX). Accumulation of PAL, CHS, and CHT transcripts was more rapid and generally of greater magnitude in the incompatible than in the compatible interaction and, in both cases, was observed essentially only in zone 1 tissues. Similarly, antibacterial phytoalexins were only detected in zone 1 from the incompatible interaction. Young primary leaves have a background level of LOX transcripts, which declines as leaves age. This decline was accelerated over the first 12 hr postinoculation (hpi) with avirulent bacteria, whereas a weak transient induction, peaking at 5-6 hpi, was observed in the compatible interaction. A subsequent, strong accumulation of LOX transcripts was seen in both the compatible and incompatible interactions outside the inoculation site starting about 14 hpi. LOX transcripts did not accumulate at the inoculation site itself in the incompatible interaction compared to a relatively strong induction in the compatible interaction. Interestingly, inoculation of leaves with cells of the saprophyte P. fluorescens also induced the accumulation of transcripts for CHS, CHT, and LOX, but generally to a lesser degree than in the incompatible interaction. No HR occurred and no macroscopic cell damage was apparent in leaves inoculated with P. fluorescens. However, at the microscopic level individual, trypan blue-stained, necrotic plant cells were visible. In spite of this and the accumulation of CHS transcripts, no phytoalexin accumulation was found up to 48 hr after inoculation. The spatial and temporal relationship of the hypersensitive reaction to defense gene transcript and phytoalexin accumulation is discussed.

Involvement of the Oxidative Burst in Phytoalexin Accumulation and the Hypersensitive Reaction

The role of the oxidative burst, transient production of activated oxygen species such as H(2)O(2) and superoxide (O(2) (-)) in elicitation of phytoalexins and the hypersensitive reaction (HR) was investigated in white clover (Trifolium repens L.) and tobacco (Nicotiana tabacum L.). H(2)O(2) and O(2) (-) production was measured as chemiluminescence (CL) mediated by luminol, which was added to suspension-cultured white clover just before measurement in an out-of-coincidence mode scintillation counter. Maximum CL occurred between 10 and 20 min after addition of 0.4 x 10(8) colony-forming units/mL of incompatible Pseudomonas corrugata or 158 mum HgCl(2). Autoclaved P. corrugata produced a slightly higher response. Elicitation of cells with 25 mum HgCl(2) did not produce CL. Preincubation of plant cells in superoxide dismutase, which converts O(2) (-) to H(2)O(2), for 2 min before addition of bacteria did not significantly increase maximum CL levels (P >/= 0.05). Preincubation of plant cells with catalase for 2 min before addition of bacteria prevented the increase in CL, confirming that H(2)O(2) is the substrate for the luminol reaction. Addition of live bacteria or HgCl(2) (25 and 158 mum) to white clover increased levels of the phytoalexin medicarpin during a 24-h period, but addition of autoclaved bacteria did not elicit formation of medicarpin. Preincubation of plant cells with catalase, which quenched the bacteria-induced oxidative burst, did not decrease phytoalexin accumulation. Live bacteria infiltrated into Havana 44 tobacco leaf panels induced development of the HR, but autoclaved bacteria did not. Incubation of live bacteria with superoxide dismutase and catalase before infiltration into tobacco leaves did not interfere with development of the HR. Tobacco leaf panels infiltrated with up to 158 mum HgCl(2) did not develop an HR. These results suggest that an oxidative burst consisting of H(2)O(2) and O(2) (-) does occur during these two plant defense responses, but it may not be a necessary element of the signaling system for HR and phytoalexin formation.

The measurement of the transmission loss of single leaf walls and panels by an impulse method

The standard methods of measurement and rating of sound insulation of panels and walls are generally time-consuming and require expensive and often bulky equipment. In addition, the methods establish only that there has been failure to comply with insulation requirements without indicating the mode of failure. An impulse technique is proposed for the measurement of walls and partitions in situ. The method requires the digital capture of a short duration signal generated by a loudspeaker, and the isolation of the direct component from other reflected and scattered components by time-of-flight methods and windowing. The signal, when transferred from the time to frequency domain by means of fast Fourier transforms, can yield the sound insulation of a partition expressed as a transfer function. Experimental problems in the use of this technique, including those resulting from sphericity of the incident wave front and concentric bending excitation of the partition, are identified and methods proposed for their elimination. Most of the results presented are of single leaf panels subjected to sound at normal incidence, although some measurements were undertaken at oblique incidence. The range of surface densities considered was 7–500 kg/m2, the highest value corresponding to a brick and plaster wall of thickness 285 mm. Measurement is compared with theoretical prediction, at one-third octave intervals in a frequency range of 100–5000 Hz, or as a continuous function of frequency with a typical resolution of 12·5 Hz. The dynamic range of the measurement equipment sets an upper limit to the measurable transmission loss. For the equipment eventually employed this was represented by a random incidence value of 50 dB.

Case design, construction and ontogeny of building in Glyphotaelius pellucidus caddisfly larvae

Comparison was made of original and rebuilt cases of mature Glyphotaelius pellucidus (Retzius) (Trichoptera: Limnephilidae) larvae, and the procedure of case building was observed. A long-term case-building observation (1973 hours) was made to discover how cases change after the time in which building of a new case appears to cease. Ontogenetic changes in building procedure were observed in a sample of larvae reared to maturity from eggs. Examination was made of the technique of cutting single leaf discs. Finally, changes to cases prior to pupation were found through examination of pupal cases. The building trials led first to knowledge of the case design and building technique of mature larvae. Definitive cases have two walls of leaf discs covering side walls of small leaf panels. Like other case-building caddis, all larvae made naked will first construct a rough preliminary case of panels, which is replaced by the typical case of discs and panels. This definitive style occurs in all larval instars. Across larval instars, size is the only major difference between cases. By stadium two (of five), the quality of leaf pieces cut by larvae has virtually reached its peak. During the building of a single case by an at first naked larva, it is observed that both leaf piece size and quality improve steadily, with an upward step coinciding with the point at which provisional style changes to the definitive style. For a naked larva, the need for a case evidently has a high priority. The rate of building is most rapid during the initial body covering. Not until after the change to definitive style does the rate decline and are activities such as feeding allowed. These case-building experiments shed light upon development of the building control system in Glyphotaelius throughout larval ontogeny. Case attributes can be broken down into three features–size, quality and procedure. Procedurally, the building mechanism is constant, but apparent adjustments to that part of the control scheme that directs qualitative aspects of building results in size increase and a gradual improvement in the quality of leaf pieces cut.

Plant virus uncoating as a result of virus-cell wall interactions

The fate of tobacco rattle virus (TRV) particles was studied after leaf panel infiltration. It was found that end-on virus attachment to cell walls of hosts ( Nicotiana tobacum L. var. Xanthi-nc) and nonhosts ( Zea mays L.) occurred, and that a virus degradative phase commenced immediately after attachment. Length of TRV particles changed drastically following infiltration. The normal length of the particles became smaller than that of the particle carrying the coat protein gene (108 nm). Five days after infiltration, no particles could be detected on the walls of cells bordering intercellular spaces. Virus attachment and degradation was thus shown to be nonspecific. Autoradiographic studies showed that iodinated viral coat protein or a breakdown product of this protein ( 125I-label in coat protein of complete virus) and not virus particles are transported to the vascular bundle after infiltration. Tobacco mosaic virus (TMV) and TRV were infiltrated into their respective local lesion hosts. There was an initial time interval early after the infiltration during which wounding (pin pricking) the infiltrated leaf panels resulted in local lesion formation. The results are discussed with regard to the phenomenon of viral genome release in the plant virus infection process.

Improvement and Termination of House Building in the Caddis Larva Lepidostoma Hirtum Curtis

AbstractA 5th instar larva of Lepidostoma hirtum is found in the wild in a house of regularly cut leaf panels; however it was shown that, if a larva was removed from this house, it first built a house of sand grains before building onto the front of that, a leaf panel house. The most anterior panels of the house from which the larva had been removed obtained a higher score, as measured by a number of panel features, than the most posterior panels of the reconstructed house. As house reconstruction progressed, however, the panel scores rose until they reached their previous level. When the reconstructed leaf panel portion of the house covered the body of the larva, it cut away the sand grain portion. A larva with anal hooks and hairs removed reconstructed a house that was longer in both sand and leaf portions than that of an intact larva. It differed from an intact larva in not cutting off the sand grain portion of the reconstructed house, and also in the improvement of leaf panel cutting along the length of a reconstructed house. A mechanism controlling the changes in house building is suggested to account for the observed differences between intact and operated animals.

Case building behaviour of the caddis fly larva, Lepidostoma hirtum

On hatching from the egg, a larva of Lepidosroma hirtum Curtis constructed a tubular, sand grain case. As the larva became older it periodically added new material to the anterior of the case and, once in every instar except the 1st, cut off ⅓ to ¼ of the posterior of the case. In the 3rd instar the larva changed from adding sand grains to cutting out and attaching almost rectangular leaf panels. By the 5th instar the case was composed entirely of leaf panels. The case was then square in section and composed of one row of panels for each of the sides. The panels were not truly rectangular but convex on the leading edge and sides and concave at the back, so that the anterior convexity of one panel fitted into the posterior concavity of the panel in front. Panels were arranged with their long axes across the case. The seams between panels in the roof were half a panel length out of phase with those in the sides but in phase with those in the floor. The convex sides of a panel allowed it to overlap the seams between panels on the two adjacent sides. If a 5th instar larva was removed from its case it first built a sand grain case followed by a leaf panel case. The animal cut panels from the leaf with its mandibles and then further shaped them by chewing round the edge. Just prior to pupation, the case was modified by the attachment of further panels to the anterior; these included panels which for the first time in the life of the larva were arranged with their long axes along the case.

Border and orientation effects and their elimination in experimental swards of subterranean clover (Trifolium subterraneum L.)

Two experiments were carried out in swards of subterranean clover, of the variety Bacchus Marsh, to determine the width of the border required firstly at the edge of swards and secondly between harvest areas. Peripheral growth was restricted by (a) root panels, (b) leaf panels, and (c) root and leaf panels; a fourth treatment with no lateral restrictions was also used. The results showed that in a sward growing without restrictions, a border at the edge of only 2 in. was required before homogeneous dry weights were reached. This border effect could be eliminated by using leaf- or leaf- and root-restricting panels, but not by root panels alone. The data for borders between harvest areas were more difficult to interpret, but growing swards without panels while allowing for a 3 in. border, both at the periphery and between defoliated areas, is recommended as the simplest procedure. From a consideration of marginal growth under the different peripheral restriction regimes it was concluded that water and nutrients were non-limiting, but that sward growth was limited by the amount of light energy intercepted.