Anchorage Conditions Research Articles

Reactivity Assays of Surface Hydroxyl Chain Ends of Poly(ethylene terephthalate) (PET) Film and Membranes Using Original3H- and Fluorine-Labeled Derivatization Reagents

The hydroxyl chain ends (PET-OH) displayed on the surface of poly(ethylene terephthalate) film and track-etched membranes of two different porosities were assayed by derivatization with reagents containing 3H and fluorine tags. After activation by tosylation, the resulting sulfonate esters (PET-OTs) were substituted with l-N-(trifluoroethyl)[4,5-3H]lysinamide. On the other hand, direct coupling of PET-OH with heptafluorobutyl (p-isocyanatobenzoyl)[2-3H]glycinate was performed; subsequent treatement with l-[4,5-3H]lysine partially gave the ester substitution. All the samples were analyzed by liquid scintillation counting (LSC) and X-ray photoelectron spectroscopy (XPS). The ratios of derivatization recorded by LSC measurements, for membranes currently used as substrates in cell cultivation, were within 15−30 pmol/cm2 of fixed amino acid labels. From XPS, we determined that 0.5−1% of the polymer units were derivatized in about 50 Å depth. This study establishes practical conditions for the covalent anchorage of biologically active molecules on PET samples.

Surface Functionalization of Poly(ethylene terephthalate) Film and Membrane by Controlled Wet Chemistry: Chemical Characterization of Carboxylated Surfaces

Surface functionalization of poly(ethylene terephthalate) (PET) film or track-etched membrane was performed using the methods of organic synthesis conducted at the solid-liquid interface. Basic hydrolysis in aqueous acetonitrile followed by permanganate oxidation in diluted sulfuric acid created new carboxylic chain-ends. These reactive functions were assayed as follows: (i) activation with water soluble carbodiimide; (ii) coupling to 3 H-labeled amino acids; and (iii) liquid scintillation counting of the sample-associated radioactivity. Some samples were also analyzed by X-ray photoelectron spectroscopy. Depending on the experimental conditions (temperature and duration of treatment), about 1-2% of the surface repeated units could be functionalized without deterioration of the polymer bulk. This study establishes the best conditions for the covalent anchorage of bioactive substances on the PET surface.

Bar Yield Penetration in Monotonically Loaded Anchorages

The implications that bar softening has on the design of anchorages in earthquake‐resistant concrete structures are considered. A relatively simple one‐dimensional finite‐element formulation is developed to model the response of anchorages under monotonic displacement control to failure. Resistance mechanisms for the cases with and without bar yield are compared and a rationale is presented to determine the terminal depth of yield penetration. Critical anchorage conditions are examined to establish anticipated demand levels in earthquake‐resisting structures. A parametric study of the sensitivity of anchorage performance to confinement conditions, postyield characteristics of reinforcement, bar size, and available development length was made using the analytical formulation. Trends in performance of yielding anchorages with the variables considered provide information useful for extending design standards.

Space closure with T loops (Burstone)--a clinical study

The theoretically favourable aspects of orthodontic space closure with segmented arch technique and the T-loop type A are clinically reproducible. In our study of eleven patients we found for the isolated canine retraction, as well as for the en masse retraction, controlled types of movement for the active units and maximum anchorage situations for the passive units produced by the torquing force. Because of these good anchorage conditions space closure could be done without headgear. The level of the anchorage segments was negligibly influenced but in the anterior segments a marked tilting was found in several cases. Besides other factors the intrusive force of the T-loops type A must be considered. As a rule the positioning of the T-loop between central and lateral incisor is to be recommended.

Modeling of membrane action in a two-layer reinforced soil system

A numerical model is formulated to assess tensile membrane action in a two-layer soil system reinforced by a geotextile. The analysis is based on a two-dimenasional plane strain model of the static equilibrium of an elastic membrane placed at the interface between a granular base and a compressible subgrade. The theory of stochastic stress diffusion in particulate media is used to describe the transmission of load through the gravel base, and a Winkler model is assumed for the subgrade. The model incorporates a Mohr-Coulomb criterion for the frictional interaction at the gravel-fabric interface, and it allows for incomplete anchorage. The numerical solution is provided by an iterative finite difference scheme. The influence of the anchorage conditions on the load-deflection response of the system is illustrated, and it is shown that the performance of high tensile modulus fabrics are affected to a higher degree by an incomplete anchorage than lower modulus fabrics.

The prediction of the fracture of sugar beet roots loaded horizontally

The fracture of single roots during removal from the soil was predicted using a force and deflection analysis in which roots were considered as conical cantilevers. Horizontal loads applied to a root were considered to be resisted by soil reaction forces which were predicted by a narrow tine force model, modified to account for root shape and anchorage conditions. To provide data to validate the model, field measurements were made of horizontal root restraining forces, displacements and associated root fracture for a range of root and soil conditions. A measure of agreement between predicted and measured values of root fracture length was obtained but the model overestimated fracture lengths probably because soil reaction forces were overestimated.

Comparison of recent New Zealand and United States seismic design provisions for reinforced concrete beam-column joints and test results from four units designed according to the New Zealand code

A comparison is made of the seismic design provisions for reinforced concrete beam-column joints required by the new New Zealand concrete design code NZS 3101 and recently proposed United States procedures. Large differences are shown to exist between these new provisions of the two countries. Results are reported of cyclic load tests which were conducted according to the requirements of the new NZS 3101. The test results showed that location of plastic hinges in beams away from the column faces may be of considerable advantage in the design of joints, when member sizes are small and joint shears are high, due to less congestion of reinforcement and better anchorage conditions.

Observations sur l'écologie de Lingula reevei Davidson (Brachiopoda:Inarticulata)

In Kaneohe Bay (Oahu, Hawaii), Lingula reevei Davidson inhabits infralittoral sandy bottoms. Its distribution appears to be related mainly to the nature of substratum, the presence of predators and diggers, and the food supply. The meiofauna is studied and compared between the stations in which L. reevei occurs. The stomach and intestinal contents are analysed, for the first time in Lingula: the nutrients arise mainly from the superficial fauna and flora. L. reevei filters continuously; the arrange- ment of the anterior mantle ciliation forming the three characteristic siphons is described more precisely. No preferential orientation to prevailing currents could be established; however, this cannot be excluded. The depth of the burial and anchorage conditions depend on the nature of the substratum. L. reevei, if removed from the substratum, is unable to re-establish itself or to change its burrow. But this species is capable of upward burrowing through a sediment layer, even if the animal has to autotomize the pedicle (a new one then regenerates). A growth rate curve for estimating the age length in relation to the shell length is proposed and compared to that of L. anatina. L. reevei does not survive more than a few days exposure to adverse environmental conditions: in extremely diluted salinities (<15‰), after several days, Lingula emerging from the sediment dies, and after body putrefaction the valves dislocate and fall onto the substratum. In high salinities (>40‰) or after substratum emersion, the animal dies within the burrow. Tolerance to desiccation does not ever reach 3 days.

A Structural Model of Forces in Buttressed Tropical Rain Forest Trees

Buttressing in tropical rain forest trees has been the subject of numerous monographs seeking to associate the phenomenon with various environmental or ecological factors. Since Senn (1923) and Navez (1930) showed a strong correlation between anchorage conditions and the appearance of on the upwind sides of trees, have been generally accepted as structural members helping to support the tree. The mechanism by which the support is provided has not been previously explored. This paper seeks to determine, by the application of engineering analysis, how the buttress contributes to the structural integrity of the tree. Also, a comparison is made between the advantages inherent in the buttressed configuration and the traditional root anchorage system. CONSIDERABLE CONFUSION has been evident in the past on the reasons for the occurrence of tabular roots or buttresses in tropical rain forest trees. The 1920's and 1930's saw many discussions of the buttressing phenomenon (Francis 1929, Petch 1930, Navez 1930). Several explanations were offered that attempted to associate these peculiar root formations with various ecological and structural variables. At no time, however, was there an attempt made to analyze quantitatively the structural characteristics of the large hardwood root systems in which buttressing is most highly developed. That a struc