Withdrawal Capacity Research Articles

Screw withdrawal capacity of full-culm P. edulis bamboo

Abstract The withdrawal capacity – as determined by a modified ASTM D1761 test – of screws embedded in Phyllostachys edulis bamboo culm walls is presented, demonstrating capacities and behaviour suitable for structural load bearing applications. This study considers twelve screw type-size combinations and considers whether these are predrilled or the screws are inserted without predrilling, resulting in 20 screw type-size-predrill combinations. For the better-performing screws, average withdrawal parameters exceeding fax = 40 N/mm2 were achieved; twice that determined for three-ply plywood having comparable thickness. Comparison with a comparable dataset of screw withdrawal tests from Guadua angustifolia Kunth bamboo indicates that the value of fax is likely species-dependent. In order to mitigate splitting upon screw insertion into bamboo, screw diameters generally less than 6 mm were required unless the screws are inserted into predrilled holes. There was no advantage observed to using self-drilling screws.

Spatiotemporal Dimensions of Water Stress Accounting: Incorporating Groundwater-Surface Water Interactions and Ecological Thresholds.

Coarse temporal (i.e., annual) and spatial (i.e., watershed) scales camouflage water stress associated with withdrawals from surface water and groundwater sources. To address this "curse of scale", we developed a framework to characterize water stress at different time scales and at fine spatial scales that have not been explored before. Our framework incorporates surface water-groundwater interactions by accounting for spatially cumulative consumptive and nonconsumptive use impacts and associated changes in flow due to depletion and return flow along stream networks. We apply the framework using a rich data set of water withdrawals from more than 6800 principal facilities (i.e., withdrawal capacity >380 000 L/day) across the U.S. Great Lakes Basin. Results underscore the importance of spatiotemporal scale and return flows when characterizing water stress. Although the majority of catchments in this water-rich region do not experience large stress, a number of small headwater catchments with sensitive streams are vulnerable to flow depletion caused by surface water and shallow groundwater withdrawals, especially in a high-withdrawal, low-flow month (e.g., August). The return flow from deep groundwater withdrawals compensates for the streamflow depletion to the extent that excess flow is likely in many catchments. The improved ability to pinpoint the imbalance between natural water supply and withdrawals based on stream-specific ecological water stress thresholds facilitates protecting fragile aquatic ecosystems in vulnerable catchments.

Alkyl Pyridinium Iodocuprate(I) Clusters: Structural Types and Charge Transfer Behavior

The reaction of copper(I) iodide (CuI) and N-alkyl pyridinium (RPy+, R = H, Me, Et, n-propyl = Pr, n-butyl = Bu, n-pentyl = Pn, and n-hexyl = Hx) or N-butyl-3-substituted pyridinium (N-Bu-3-PyX+, X = I, Br, Cl, CN, and OMe) iodide salts yielded pyridinium iodocuprate(I) salts. Crystal structures of iodocuprate ions coupled with RPy+ include {Cu3I63–}n (R = H), {Cu2I3–}n (R = Me), {Cu3I4–}n (R = Et), {Cu6I82–}n (R = Pr), and {Cu5I72–}n (R = Bu, Pn, Hx). The [N-Bu-3-PyX]+ ions were typically paired with the 1-D chain {Cu5I72–}n. Diffuse reflectance spectroscopy performed on the [N-Bu-3-PyX]+ iodocuprate salts revealed that increasing the electron withdrawing capacity of the [N-Bu-3-PyX]+ system reduced the absorption edge of the iodocuprate salt. Variable temperature emission spectra of several [N-Bu-3-PyX]+ compounds revealed two emission peaks, one consistent with a cluster-centered halide to metal charge transfer and the other consistent with an intermolecular mixed halide/metal charge transfer to the organic cation. The emission intensity and emission wavelength of the mixed halide/metal to cation charge transfer depends on the organic cation substitution.

Fundamentals and recent strength results of connections in modern hardwood timber structures

ABSTRACTHardwood is becoming more in focus and more important in timber structures. The natural higher strength increases the potential of timber structures and power to compete with steel or concrete. However, for designing connections, the performance parameters stiffness and load-carrying capacity based on, e.g. embedment strength or withdrawal capacity need to be known but these are less standardized compared to softwood. Since not all types of connections are relevant to be used as high-performing connections in hardwood, structural systems, parameters of connections are summarized and discussed with a focus on relevance for their use in hardwood. For the connection types with glued-in rods and steel dowels, the assembling procedure, the load-carrying capacity and failure behaviour is investigated in relation to the necessary design parameters as a first part of the relevant connections. First, the results of their design and influencing parameters are presented, summarized and compared regarding current design equations.

Modelling of glued laminated timber joints with glued-in rod considering bond-slip location function

It was frequently reported that the bond-slip relationships at different locations along the bonded length are different, which can be illustrated as bond-slip location effect. In order to reveal the influence of this effect on the bond behaviour between glue laminated timber (glulam) and glued-in rod, a 3D finite element model considering bond-slip location function is developed for the glulam joints with glued-in rod in this paper. Moreover, an experimental program conducted on the glulam joints with glued-in rod is also presented. The numerical and experimental results are compared and discussed in terms of withdrawal capacity, typical failure modes, load-slip behaviour, strain development of glued-in rod and the interface shear stress distribution. It is indicated that the non-linear spring elements can be used to simulate the bond behaviour between the glulam and the glued-in rod effectively. The numerical results obtained considering the bond-slip location function are generally in better agreement with the experimental results compared to that obtained neglecting the bond-slip location function. Finally, the withdrawal stiffness of the glued-in rod glulam joints is evaluated by a theoretical approach based on the Volkersen theory. The withdrawal stiffness calculated by the proposed model shows good agreement with the experimental results, which confirms that the calculation model is effective for predicting the withdrawal stiffness of the glulam joints with glued-in rod.

Substituent Dependent Optical Properties of p-phenyl Substituted ethenyl-E-thiophenes.

Various electron donor and acceptor substituted (NO2, CN, Cl, H, OCH3, NH2) p-phenyl ethenyl-E- thiophenes (1-6) were synthesized and substituent dependent optical properties (dipole moment, transition dipole moment, oscillator strength, optical band gap, hyperpolarizability) were studied using Solvatochromism and Density functional theory. It is shown that thiophene acts as a weak electron donor in presence of an electron withdrawing p-phenyl substituent (NO2, CN, Cl), whereas thiophene acts as a weak electron acceptor in presence of an electron donating p-phenyl substituent (OCH3, NH2). In comparison to ethenyl thiophene 4, the HOMO-LUMO energy band gap is decreased upon increasing the electron donating or electron withdrawing capacity of p-phenyl substituent. From the excited state dipole moment calculation, it is shown that the excited state is highly dipolar for nitro and amino compounds 1 and 6, whereas compounds 2-5 show a non-polar excited state. As compared to the ethenyl thiophene 4, the first hyperpolarizability (β) increases upon substitution either with a strong electron withdrawing or strong electron donating p-phenyl substituent. A large β value is found for p-nitro phenyl ethenyl-E-thiophene and p-amino phenyl ethenyl-E- thiophene. Overall, these studies provide useful information in understanding the optical properties of phenyl and heterocyclic based ethenyl systems.

Lateral and Withdrawal Capacity of Fasteners on Hybrid Cross-Laminated Timber Panels

AbstractCross-laminated timber (CLT) is an orthogonally laminated timber panel product made using dimensional lumber. It is gaining traction in the construction industry, as is evident by the incre...

Technical Note: Lateral Connections and Withdrawal Capacity of Western Juniper

The goal of this project is to increase the amount of available information about western juniper wood to encourage its use in structural applications. This project evaluated the performance of connections involving western juniper wood and other common wood-based building materials. The tests for this project included edge lateral nail connection tests (ASTM 2007a), dowel bearing strength tests (ASTM 2007c), and withdrawal tests (ASTM 2007b). The performance of juniper and juniper-oriented strand board (OSB) connections were characterized. The results were also evaluated against predictive design equations found in the National Design Specification (NDS). The data obtained in this study suggest that NDS equations conservatively predict the load-carrying capacity of a juniper-OSB connection but consistently predict the failure mode.

Empirically derived connection design properties for Guadua bamboo

Three connection design properties (dowel embedment strength, slip modulus and screw withdrawal capacity) were determined for one species of bamboo (Guadua angustifolia Kunth) using experimental methods adopted from timber engineering. 151 embedment strength and slip modulus tests were undertaken using smooth dowels with diameters ranging from 3 to 16 mm, whilst 240 screw withdrawal tests were undertaken using 3.5–5 mm diameter self-tapping screws. Using regression analysis, predictive equations for the three connection design properties were derived, based on fastener diameter, density and bamboo wall thickness. Coefficients of determination (R2) ranged from 0.45 to 0.82. The predictive equations for embedment strength and screw withdrawal were adapted to output characteristic values and then compared to similar equations derived for timber contained in Eurocode 5, the latter would seem inappropriate for bamboo.

Withdrawal of pairs of threaded rods with small edge distances and spacings

An experimental investigation on withdrawal of pairs of screwed-in threaded rods embedded in glued-laminated timber elements is presented in this paper. Specimens with varying angles between the rod axis and the grain direction (α = 15°, 30°, 60°, 90°) and 2 different configurations with respect to edge distances and spacings were tested. The diameter and the embedment length of the rods were 20 and 450 mm, respectively. The threaded rods were embedded in a row perpendicular to the plain of the grain. The edge distances and spacings were smaller than the minimum requirements according to Eurocode 5. The withdrawal capacity of pairs of rods was compared to the withdrawal capacity of single rods and the effective number, n ef , was found to be in the range 1.72–1.94, despite the small edge distances and spacings. Based on the experimental results obtained, a simple approximating expression was derived for n ef . An analytical model based on Volkersen theory with an idealized bi-linear constitutive relationship was used to estimate the withdrawal capacity and stiffness. The analytical estimations were in good agreement with the experimental results. Finally, the withdrawal stiffness was estimated by use of finite element simulations. The numerical estimations for the withdrawal stiffness were also in good agreement with the experimental results.

Effects of Nano-Wollastonite on Screw Withdrawal Capacity of Oriented Strand Lumber

The effect of changes of urea-formaldehyde resin content and nanowollastonite content on the withdrawal capacities of sheet metal screws and medium density fiberboard screws from the edge, face, and end surfaces of oriented strand lumber were investigated. The panels were produced with two urea-formaldehyde resin contents (8% and 10%), and two nano-wollastonite contents (10% and 20%). Specimens were prepared and tested according to ASTM standard D 1761-88. Sheet metal screws had a higher withdrawal capacity than medium density fiberboard screws. Withdrawal capacity in the face and edge directions were significantly higher than in the end direction. Changes in urea-formaldehyde resin content had no effect on screw withdrawal capacity in any of the three directions, implying that compaction in the composite panels had higher impact on screw withdrawal strength in comparison to the increase in resincontent from 8% to 10%. However, addition of NW resulted in a decrease in withdrawal capacity values at both resin levels in all directions.

Experimental analysis of Maritime pine and Iroko single shear dowel-type connections

In this study, screwed connections were experimentally evaluated, checking the plausibility of Eurocode 5 for two selected wood species, Iroko (Milícia excelsa) and Maritime pine (Pinus pinaster). Single shear screwed connections, considering self-tapping screws, were tested and the experimental campaign aimed at evaluating various mechanisms of resistance suggested by Eurocode 5 for this typology of connection, including axial withdrawal capacity of the screw, pull through parameter for screws, and local embedment of wood. The experimental results evidenced that the analyzed connection system had similar results with either wood species. The results were consistent with the calculation through Eurocode 5.

Threatening the heart and mind of gender stereotypes: Can imagined contact influence the physiology of stereotype threat?

Research shows that when a gender stereotype is made salient and the target of the stereotype is asked to perform in the stereotyped domain, targets of the stereotype often perform at a lower level compared to situations when the stereotype was not made salient. The noticeable absence of female faculty and students in math and science departments at coed universities throughout the United States may increase the belief in gender stereotypes and discourage women from pursuing careers in these fields. Contact with counterstereotypical exemplars, such as female science experts, decreases belief in gender stereotypes and increases women's motivation to pursue careers in science. Thus, the present study examined whether imagining an interpersonal interaction with a counterstereotypical exemplar removes the physiological and performance effects of stereotype threat. Subjects were asked to imagine either a nature scene or meeting a female math professor, and were also assigned to either a control or stereotype threat condition. Imagination was used because studies have shown it to be an effective method of simulating interpersonal contact. Subjects were 139 young women (mean age 19 years) recruited from a pool of undergraduates. Results showed that the stereotype threat manipulation elicited greater vagal withdrawal and poorer working memory capacity during the n-back, and that vagal withdrawal was attenuated when the stereotype threat manipulation was preceded by a brief imagined interaction with a counterstereotypical exemplar. This study provides novel evidence that exposure to counterstereotypical exemplars can diminish cardiovascular reactions to salient information about threatening gender stereotypes.

Withdrawal capacity of threaded rods embedded in timber elements

In the present paper, the withdrawal capacity of threaded rods embedded in timber elements is investigated using both theoretical and experimental methods. A theoretical approach based on Volkersen theory, assuming a bi-linear constitutive law is developed. Moreover, an experimental investigation of withdrawal of threaded rods from glulam elements is presented. Results for specimens covering a wide range of varying embedment lengths and rod-to-grain angles are provided. The agreement between theoretical estimations and experimental results is good. A nearly linear relation between embedment length and withdrawal capacity, predicted by the theoretical approach, is validated by the experimental results.

Withdrawal Capacity in the Face of Expected and Unexpected Health and Aged-Care Expenses During Retirement

We examine the consequences of taking account of costs associated with age-related health treatment and agedcare services during the retirement phase. Simulating asset return data using historical bootstrap simulation, we derive an optimal withdrawal income during retirement using dynamic optimization techniques. The greatest risk to income sustainability occurs when unexpected health costs combine with above-average longevity for conservative investors. High costs of health treatment without a commensurate adjustment in asset allocation toward assets with a less conservative risk-return profile risk premature wealth depletion. The risk of ruin can be mitigated through a dynamic life-cycle strategy during the retirement phase.

Effect of Heat Treatment of Wild Cherry Wood on Abrasion Resistance and Withdrawal Capacity of Screws

Effect of Heat Treatment of Wild Cherry Wood on Abrasion Resistance and Withdrawal Capacity of Screws

Graphene-based materials for the catalytic wet peroxide oxidation of highly concentrated 4-nitrophenol solutions

Reduced graphene oxide (rGO) samples were prepared from graphene oxide (GO) using different reducing agents (i.e., glucose, hydrazine and vitamin C, resulting in rGOG, rGOH and rGOV, respectively). These samples were tested in the catalytic wet peroxide oxidation (CWPO) of highly concentrated 4-nitrophenol (4-NP) solutions (5gL−1) at mild operating conditions (i.e., atmospheric pressure, T=323K, pH=3, [catalyst]=2.5gL−1 and [H2O2]0=17.8gL−1). The highest catalytic activity was found for the rGOV sample, reaching a 4-NP removal of 1294mgg−1 and a TOC removal of 241mgg−1 after 24h runs (corresponding to 4-NP and TOC removals of 65% and 23%, respectively).The TOC removal per unit of H2O2 decomposed decreases with the increase of the surface oxygen content of the samples, as well as with the increase of their amounts of structural defects. This was ascribed, respectively, to the electron withdrawal capacity of oxygen-containing functionalities and to reduced adsorption of 4-NP in the samples with higher amounts of defects, which diminish the efficiency of the reaction between hydroxyl radicals resulting from the decomposition of H2O2 and the organic compounds.In a series of three consecutive CWPO runs, rGOH was the most stable material (4-NP removal slightly decreasing from 980mgg−1, in the first and second runs, to 841mgg−1 in the third run, corresponding to 4-NP removals of 49% and 42%, respectively). The development of oxygen functionalities at the surface of the rGO samples during the CWPO runs was found to be the major cause of catalyst deactivation.4-Nitrocatechol was the main aromatic intermediate detected in the CWPO of 4-NP. Hydroquinone, benzoquinone, catechol and several low molecular weight carboxylic acids (e.g., malonic, malic, maleic and acetic acids) were also identified as reaction intermediates.To the best of our knowledge, graphene-based materials are reported for the first time as active and stable catalysts in the CWPO process, even when applied to highly polluted waters at mild conditions.

Abstract SY05-02: Targeting kinases with reversible covalent fragments

Abstract The clinical utility of targeting kinases with covalent drugs has been firmly established, culminating in the recent FDA approval of afatinib and ibrutinib, which irreversibly inhibit the tyrosine kinases, EGFR and BTK. More broadly, chemical probes that form a covalent bond with a nonconserved, noncatalytic cysteine often show enhanced potency, selectivity, and utility in biological studies. Despite these advantages, protein-reactive compounds are usually avoided in high-throughput screening campaigns. Motivated by a desire to explore the chemistry of reactive electrophiles and thiols under physiological conditions, we initiated a study of Michael acceptors bearing substituents with increasing electron withdrawing capacity. We hypothesized that the intrinsically labile nature of the cysteine/cyanoacrylamide bond could be exploited to yield cysteine-targeted, reversible covalent inhibitors. These concepts led to the design of ultra-selective cyanoacrylamide-based RSK inhibitors with picomolar affinity and slow dissociation kinetics, the structural basis of which was revealed by x-ray crystallography. The intrinsically reversible, yet thermodynamically favorable nature of the cysteine/cyanoacrylamide bond suggested that this ‘sweet spot’ in electrophile space could form the basis of a fragment-based approach to ligand discovery. Screening a collection of cyanoacrylamide fragments against three kinases (RSK2, NEK2, and PLK1) containing a structurally equivalent cysteine delivered unique inhibitors for all three kinases with potencies in the submicromolar range. Optimization guided by x-ray crystallography rapidly led to the first dual inhibitor of MSK and RSK, with subnanomolar affinity and >500-fold selectivity over NEK2 and PLK1. In close collaboration with Brian Shoichet and Nir London, we have employed covalent docking methods to screen large virtual libraries of electrophilic fragments. We designed a pilot virtual library of 13,000 cyanoacrylamide fragments that can be synthesized in one simple step from commercially available aldehydes. A virtual screen of this library rapidly led to novel inhibitors of NEK2, PLK-, and MSK/RSK-family kinases. Finally, I will discuss our efforts to discover and design new electrophilic chemotypes that form reversible covalent bonds with cysteine residues. Citation Format: Jack Taunton. Targeting kinases with reversible covalent fragments. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr SY05-02. doi:10.1158/1538-7445.AM2014-SY05-02

On the chemical behavior of C60 hosting H2O and other isoelectronic neutral molecules.

The density functional theory (DFT) was used to investigate the chemical behavior of C60 hosting neutral guest molecules (NGM). The deformed atoms in molecules (DAM) allowed identifying the regions of electron density depletion and accumulation. The studied NGM are CH4, NH3, H2O, and HF. Based on dipole moment and polarizabilities analyses it is predicted that the NGM@C60 should be more soluble in polar solvents than C60. The deformations on the surface electron density of the fullerenes explain this finding, which might be relevant for further applications of these systems. It was found that the intrinsic reactivity of studied NGM@C60 is only moderately higher than that of C60. This trend is supported by the global reactivity indexes and the frontier orbitals analyses. The free radical scavenging activity of the studied systems, via single electron transfer, was found to be strongly dependent on the chemical nature of the reacting free radical. The presence of the studied NGM inside the C60 influences only to some extent the reactivity of C60 toward free radicals. The distortion of the electron density on the C60 cage, caused by the NGM, is directly related to the electron withdrawing capacity of the later.

Withdrawal Strength and Bending Yield Strength of Stainless Steel Nails

AbstractIt has been well established that stainless steel nails have superior corrosion performance compared to carbon steel or galvanized nails in treated wood; however, their mechanical fastening behavior is unknown. In this paper, the performance of stainless steel nails is examined with respect to two important properties used in wood connection design: withdrawal strength and nail bending yield strength. Different nail diameters, wood specific gravities, and nail manufacturers were examined. The current withdrawal design equations, developed from carbon steel nail data, overpredict the expected withdrawal strength when used for stainless steel nails, reducing the safety factor. As a result, a new equation was developed to predict the nail stainless steel withdrawal capacity. The data further indicate that nail bending yield strength values for stainless steel were similar to carbon steel data.