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One of the most important contributors to the environmental impacts from use of highways is the energy exerted by vehicles, particularly routes that carry higher volumes of traffic. Part of this energy is consumed by response of the vehicle’s tires and suspension to pavement surface roughness and macrotexture. Another part of the energy consumed is by energy dissipation due to the structural response of the pavement itself under the moving load. This document is the theoretical and validation manual tor tBeam, standalone software for the analysis of energy dissipation in pavements under moving vehicles. tBeam was developed as part of the improvement of modeling capabilities for environmental life cycle assessment of pavements being conducted the University of California Pavement Research Center for the California Department of Transportation. The energy consumed due to structural response are controlled by the structural properties of the pavement which are dependent on the time of day, the season, and the condition (damage) of the pavement. The energy dissipation also depends on the speed and weight of each moving wheel load. As a result, estimating the lifetime energy dissipated in a pavement structure requires multiple analyses considering the thousands of permutations of these variables for a given segment of the highway network. Therefore, models for pavement-vehicle energy dissipation must balance two opposing needs: obtaining a reasonably accurate estimate of the dissipated energy, and high numerical efficiency. For numerical efficiency, the tBeam software employs a one-dimensional finite-element based solution of a wheel traveling at a constant velocity on a viscoelastic beam-foundation system, and a further reduction of numerical effort is obtained by formulating the model relative to a moving coordinate system attached to the wheel. The one-dimensional solution is, by nature, an approximation to the three-dimensional world. This approximation can be improved by incorporating a “correction factor,” which is based on comparisons with pavement simulations accounting for the double curvature observed in loaded pavements. In this report prediction disparity for a single structure is studied. The results show a clear trend where the correction factor decreases with rising temperature, and increases with higher velocity. The present study was insufficient to establish a law for the correction factor even for the single case studied. The correction factor ranged from about 1.25 at low temperature and high velocity to about 0.6 for high temperature and low velocity. The first part of this report presents the underlying theory for tBeam and implementation details. The second part presents closed form solutions for specialized pavement-foundation systems. The third component of the report presents some of the validation simulations undertaken to demonstrate the performance of tBeam, including comparisons with closed form solutions provided in this report, and recommendations for further development of tBeam.

Cancer is one of the most complex and challenging human diseases, with rising incidences and cancer-related deaths despite improved diagnosis and personalized treatment options. Targeted alpha therapy (TαT) offers an exciting strategy emerging for cancer treatment which has proven effective even in patients with advanced metastatic disease that has become resistant to other treatments. Yet, in many cases, more sophisticated strategies are needed to stall disease progression and overcome resistance to TαT. The combination of two or more therapies which have historically been used as stand-alone treatments is an approach that has been pursued in recent years. This review aims to provide an overview on TαT and the four main pillars of therapeutic strategies in cancer management, namely external beam radiation therapy (EBRT), immunotherapy with checkpoint inhibitors (ICI), cytostatic chemotherapy (CCT), and brachytherapy (BT), and to discuss their potential use in combination with TαT. A brief description of each therapy is followed by a review of known biological aspects and state-of-the-art treatment practices. The emphasis, however, is given to the motivation for combination with TαT as well as the pre-clinical and clinical studies conducted to date. [ABSTRACT FROM AUTHOR]

We demonstrate that regioselective aryl transfer to the nucleophile occurs rapidly under mild conditions via reductive elimination and show that regioselectivity is primarily governed by steric factors imparted by ortho substituents on the recipient ring. Computational modeling and x‐ray crystallography confirm that the recipient aryl ring is positioned in the equatorial coordination site and oriented orthogonally to the axial X−Bi−Ph bond (X=nucleophile) in a trigonal bipyramidal structure. The orientation of the ortho‐substituted aryl ring allows the appropriate orbital to overlap between its ipso carbon and nucleophile, which enhances the rate of aryl transfer to the nucleophile and dictates the regioselective reductive elimination from Bi(V) compounds. This level of stereoelectronic control results in significantly enhanced reaction rate and selectivity and creates an opportunity to rationally design ligand systems for selective aryl transfer reactions. [ABSTRACT FROM AUTHOR]

This paper describes a theoretical analysis of a type of thermal expansion bridge bearing which could be used as a lightweight low-cost elastomeric seismic isolator for application to housing, schools, and other public buildings in earthquake-prone areas of the developing world. The analysis covers the effect of the frictional resistance of the supports on the vertical stiffness of this type of isolator. The most important aspect of these bearings is that they do not have end plates, which reduces their weight, but also means that they are not bonded to the upper and lower support surfaces and are held in place only by friction. This at first sight might seem to be a deficiency of this design, but it has the advantage that it eliminates the presence of tensile stresses in the bearings. It is these tensile stresses and the bonding requirements that arise from them that lead to the high costs of conventional isolation bearings. A theoretical analysis of the response of these bearings to vertical load shows that slip between the unbonded surfaces and rigid supports above and below can have a significant influence on the vertical stiffness and the internal pressure distribution. DOI: 10.1061/(ASCE)EM.1943-7889.0000019 CE Database subject headings: Load bearing capacity; Bridges; Friction; Seismic effects; Stiffness; Earthquakes.

Existing models for isolation bearings neglect certain aspects of their response behavior. For instance, rubber bearings have been observed to decrease in stiffness with increasing axial load, and soften in the vertical direction at large lateral deformations. The yield strength of lead rubber bearings has also been observed to vary with axial load, such that a lightly loaded bearing may not achieve its theoretical strength. Models that include these axial-load effects in lead--rubber bearings are developed by extending an existing linear two-spring model to include nonlinear behavior. The nonlinearity includes an empirical equation for the experimentally observed variation of yield strength. For numerical implementation, the bearing forces are found by solving the nonlinear equilibrium and kinematic equations using Newton's method, and the instantaneous bearing stiffness matrix is formed from the differentials of these equations. The response behavior of the models is confirmed by comparison with experimental data. DOI: 10.1061/(ASCE)0733-9399(2005)131:12(1270) CE Database subject headings: Axial forces; Axial loads; Rubber; Lead; Base isolation; Numerical models; Nonlinear analysis; Plasticity.

The compression buckling of mutilayer elastomeric beatings which are widely used as vibration mounts, bridge bearings, and seismic isolators for buildings is well understood and is governed by theoretical analysis and confirmed by extensive experimental work. What is not well known is that the theoretical analysis that predicts the compression buckling behavior also predicts that a bearing could be subject to buckling in tension with a tension buckling load that is of the same order as the compressive buckling load and a buckled shape that is the same as that in compression. The tensile buckling load will not be achievable in practice in most bearings since it will generally be much larger than the load that will induce cavitation in the elastomer, but the analysis can be very valuable in explaining the behavior of seismic isolators when loaded in tension while laterally displaced. This can occur when extreme seismic loading on an isolated building induces global overturning. Isolators at the periphery of the building can be in a state of combined tension and shear. The analysis shows that the elastomer can sustain the tension load without cavitation since rotation of the central portion converts tension to rotated shear. CE Database subject headings: Buckling; Elastomer; Isolation; Bearing capacity.

The reinforcing elements of multilayer elastomeric isolation bearings, which are normally steel plates, are replaced by a fiber reinforcement. The fiber-reinforced isolator is significantly lighter and could lead to a much less labor-intensive manufacturing process. In contrast to the steel reinforcement, which is assumed to be rigid, the fiber reinforcement is flexible in extension. This paper presents theoretical approaches for analyzing the compressive stiffness and bending stiffness of fiber-reinforced rectangular isolators. The influence of fiber flexibility on the stiffness of isolators is studied. In addition to theoretical stiffness solutions which are expressed in series form, simplified stiffness formulas based on the solutions of an infinitely long strip pad are also presented. DOI: 10.1061/(ASCE)0733-9399(2002)128:4(462) CE Database keywords: Stiffness; Fiber reinforced materials; Seismic isolation.

The paper provides an experimental study on the feasibility of base isolation for seismic protection of nonstructural secondary system such as sensitive instrumentation, computer equipment, communication network, HVAC facilities, and power transmission systems housed in nonisolated primary structures. Damages to these secondary systems may result in significant social chaos and costly economic loss. A one-sixth-scaled three-story building model with a single-degree-of-freedom secondary system placed on its third floor is employed in this study. The secondary system is base-isolated by a laminated rubber bearing (LRB) base isolation system from the supporting floor. The ground motion input is simulated by a shaking table which generates three different types of signal including sweeping harmonic sinusoidal, the SOOE component of the 1940 El Centro earthquake, and the simulated white noise. The experimental results demonstrate significant reduction in both displacement and acceleration responses of the secondary system by using the base isolation. Effects of parameters of the base isolation such as damping ratio and mass on its performance are also investigated. This study provides a valuable guideline for future work in this area and also verifies some previous analytical work by the authors (Hou et al., 2001). Secondary systems in a structure can be divided into two categories: structural and nonstructural. A thorough review of these types of systems and their response behavior under seismic loading has been presented by (Chen and Soong, 1988). In this paper, only nonstructural secondary systems are the subject of the study. These systems include sensitive instrumentation, computer equipment, communication network, HVAC facilities, and power transmission system that reside within a primary structure system. The huge investment made, the mission, and the critical role played by secondary systems in modern day warrant an effective protection strategy against earthquake-induced vibrations. Studies on employing base isolation techniques to protect primary structures have shown the ability of such techniques to limit dynamic response of structures in seismic disturbance (Kelley, 1986; and Ahmadi, 1988); this paper proposes the adoption of a base isolation mechanism for seismic protection of secondary systems and presents the experimental results achieved with this strategy in a scaled-down system designed without primary structural isolation. This study provides a valuable guideline for future work in this area and also verifies some previous analytical work by the authors (Ghantous, 1991; and Samaha, 1992). [DOI: 10.1115/1.1445795]

Background: As 225Ac-labeled radiopharmaceuticals continue to show promise as targeted alpha therapeutics, there is a growing need to standardize quality control (QC) testing procedures. The determination of radiochemical purity (RCP) is an essential QC test. A significant obstacle to RCP testing is the disruption of the secular equilibrium between actinium-225 and its daughter radionuclides during labeling and QC testing. In order to accelerate translation of actinium-225 targeted alpha therapy, we aimed to determine the earliest time point at which the RCP of an 225Ac-labeled radiopharmaceutical can be accurately quantified. Results: Six ligands were conjugated to macrocyclic metal chelators and labeled with actinium-225 under conditions designed to generate diverse incorporation yields. RCP was determined by radio thin layer chromatography (radioTLC) followed by exposure of the TLC plate on a phosphor screen either 0.5, 2, 3.5, 5, 6.5, or 26 h after the plate was developed. The dataset was used to create models for predicting the true RCP for any pre-equilibrium measurement taken at an early time point. The 585 TLC measurements span RCP values of 1.8–99.5%. The statistical model created from these data predicted an independent data set with high accuracy. Predictions made at 0.5 h are more uncertain than predictions made at later time points. This is primarily due to the decay of bismuth-213. A measurement of RCP > 90% at 2 h predicts a true RCP > 97% and guarantees that RCP will exceed 90% after secular equilibrium is reached. These findings were independently validated using NaI(Tl) scintillation counting and high resolution gamma spectroscopy on a smaller set of samples with 10% ≤ RCP ≤ 100%. Conclusions: RCP of 225Ac-labeled radiopharmaceuticals can be quantified with acceptable accuracy at least 2 h after radioTLC using various methods of quantifying particle emissions. This time point best balances the need to accurately quantify RCP with the need to safely release the batch as quickly as possible. [ABSTRACT FROM AUTHOR]

In this paper, the problem of viscous heating of passive and controllable fluid dampers is analyzed at the limit of long-stroke motions, where most of the fluid travels through the damper orifice(s) or valve(s). This study is of interest in the case of strong earthquake motions where dampers are subjected to long-stroke motions. It is shown that under long-stroke motions the temperature rise of the entire fluid within the damper is nearly uniform. The one-dimensional energy equation presented in the companion paper is further contracted to a macroscopic energy balance equation over the entire fluid within the damper. Closed-form expressions for the temperature rise in viscous, nonlinear, viscoelastic, and controllable fluid dampers are developed under harmonic and triangular wave motions; and it is shown that under long-stroke motions the temperature rise is proportional to the pressure drop and independent of the piston velocity.

Experiments conducted to determine the mechanical characteristics of low shape factor bearings demonstrated that low shape factor elastomeric bearings that were bolted to their endplates - as opposed to bearings with doweled-type endplate connections - showed an increase in horizontal stiffness at large shear strains. This strain-induced crystallization at large shear strains offers a good reserve of shear resistance for bearings subjected to large deformation, thereby providing a high safety factor against failure under earthquake loads that exceed the design level. Modeling this property would be invaluable for structural engineers designing isolators for use in highly seismic areas. This paper presents an analytical method that adequately models the strain-induced crystallization of the elastomer at large shear strains. This model extends the linear elastic relationship developed in earlier studies to predict the buckling load of an elastomeric bearing in the case of material nonlinearity. Here, the nonlinear elastic response of the rubber is taken into account by replacing the shear modulus, G, by a shear modulus-shear strain relationship and calculating the shear strain from a root mean square average of the shear strains of the elastomeric bearing that is due to compression, bending, and shearing.

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The effects of temperature on the energy dissipation of viscoelastic dampers for seismic mitigation of structures are investigated. To simulate the damper behavior, an evolutionary model is proposed to describe the dependence of the mechanical properties of the damper on the deformation frequency and the temperature increase due to dissipation. Thermorheologically simple materials are considered and the influence of the deformation frequency on the storage and loss moduli is modeled using fractional derivative operators. The effect of material temperature on the force-deformation relation is modeled using the concept of evolutionary transfer function, and the proposed model is implemented using a step-by-step technique in the frequency domain. The predictions of the proposed model in the case of sinusoidal and seismic deformations show good agreement with experimental results. Finally, the response spectra of single-degree-of-freedom structures with added vis-coelastic dampers and subjected to seismic excitation are computed using the proposed evolutionary model; the results obtained show that the thermal effect due to energy dissipation is not always negligible.

The modal strain energy (MSE) method is a technique for approximate analysis of structures whose models in the frequency domain show frequency-dependent stiffness and damping matrices such as structures containing viscoelastic dampers. In this paper, the concept of modal coupling in the frequency domain is addressed and expressions for diagonalizable frequency-dependent stiffness and damping matrices are given. The MSE method is described and the accuracy of this technique is investigated by computing the exact and approximate mean square responses of structures subjected to random excitation. Closed-form expressions of the mean square error are obtained for single-degree-of-freedom systems with linear hysteretic and Maxwell-type damping and the accuracy of the MSE method in the estimation of response of multi-degree-of-freedom structures with nonclassical, hysteretic, and Maxwell-type damping is investigated using a simple base-isolated model. Finally, the use of the MSE method for preliminary sizing of viscoelastic dampers is illustrated using a moment-resistant steel frame.

In this paper the causality of linear viscoelastic models with complex coefficients is examined. Such constitutive models have been found effective in describing the response of practical dampers and other dissipation devices used for seismic protection of structures. Complex-parameter viscoelastic models must be subjected only to complex-valued excitations that are analytic functions, i.e., their imaginary and real parts are related with the Hilbert transform. First, it is shown that the resulting force from complex parameter constitutive models is also an analytic signal. Subsequently, the analyticity of the impedances of constitutive models with complex-coefficients is investigated and it is found that under certain conditions they satisfy the Kramers-Kronig relations. These relations ensure that the differential operator used in the model is causal; however, the entire model (differential operator and analytic input) is noncausal, since the Hilbert transform needed to construct the analytic input requires information from the future. Finally, a general real-valued representation of these models is developed. Real-valued representations are needed when the analysis of the response is performed in the time domain using step-by-step integration techniques. Time-domain techniques are necessary when the proposed constitutive models describe devices which are incorporated in structures that exhibit nonlinear response. The equivalence between complex-valued and real-valued representations is shown through a practical example, and the noncausality of these models is analyzed.

The problem of a block of nearly incompressible elastic material, bonded on its top and bottom parallel faces to rigid end plates, against which any slip is prevented, and subjected to direct compression, is examined. Approximate solutions are obtained using the minimum potential energy and Hellinger-Reissner variational principles. Bulk compressibility is naturally included in these solutions. The necessity of avoiding a severe overestimation of the effective compressive stiffness of thin blocks is demonstrated. For such blocks, the results confirm solutions, extensively used in engineering design, which are based on the assumption of a pressure distribution within the block.

Experimental observations have shown that the dissipation per cycle in many materials does not depend on the deformation frequency over a wide frequency range. A linear model used frequently to represent this type of mechanical behavior is the concept of linear hysteretic damping. Also referred to as structural damping and complex stiffness in the literature, this noncausal model is characterized by storage and loss moduli independent of frequency. In the present paper, a consistent time-domain representation for linear hysteretic damping is presented using the Hilbert transform. This time-domain representation is a mathematically correct way to replace the complex-stiffness parameters or frequency-dependent damping coefficients commonly used in differential equations that model the dynamics of structures with linear hysteretic damping. A technique is proposed for the computation of the response of structures containing linear hysteretic elements in the time domain; the convergence of the iterative technique is analyzed; and simple numerical examples are developed to illustrate the application of the method.