Quantifying Cognitive Decrements Caused by Cranial Radiotherapy

With the exception of survival, cognitive impairment stemming from the clinical management of cancer is a major factor dictating therapeutic outcome. For many patients afflicted with CNS and non-CNS malignancies, radiotherapy and chemotherapy offer the best options for disease control. These treatments however come at a cost, and nearly all cancer survivors (~11 million in the US alone as of 2006) incur some risk for developing cognitive dysfunction, with the most severe cases found in patients subjected to cranial radiotherapy (~200,000/yr) for the control of primary and metastatic brain tumors1. Particularly problematic are pediatric cases, whose long-term survival plagued with marked cognitive decrements results in significant socioeconomic burdens2. To date, there are still no satisfactory solutions to this significant clinical problem

Time-domain finite-wave analysis of the engine exhaust system by means of the stationary-frame method of characteristics. Part II: Computed results and experimental corroboration thereof

Time-domain-finite-wave analysis of the engine exhaust system is usually done using the method of characteristics. This makes use of either the moving frame method, or the stationary frame method. The stationary frame method is more convenient than its counterpart inasmuch as it avoids the tedium of graphical computations. In this paper (part I), the stationary-frame computational scheme along with the boundary conditions has been implemented. The analysis of a uniform tube, cavity- pipe junction including the engine and the radiation ends, and also the simple area discontinuities has been presented. The analysis has been done accounting for wall friction and heat-transfer for a one-dimensional: unsteady flow. In the process, a few inconsistencies in the formulations reported in the literature have been pointed out and corrected. In the accompanying paper (part II) results obtained from the simulation are shown to be in good agreement with the experimental observations

Stem Cell Transplantation Strategies for the Restoration of Cognitive Dysfunction Caused by Cranial Radiotherapy

Radiotherapy often provides the only clinical recourse for those afflicted with primary or metastatic brain tumors. While beneficial, cranial irradiation can induce a progressive and debilitating decline in cognition that may, in part, be caused by the depletion of neural stem cells. Given the increased survival of patients diagnosed with brain cancer, quality of life in terms of cognitive health has become an increasing concern, especially in the absence of any satisfactory long-term treatments

Functional equivalence of stem cell and stem cell-derived extracellular vesicle transplantation to repair the irradiated brain.

Cranial radiotherapy, although beneficial for the treatment of brain tumors, inevitably leads to normal tissue damage that can induce unintended neurocognitive complications that are progressive and debilitating. Ionizing radiation exposure has also been shown to compromise the structural integrity of mature neurons throughout the brain, an effect believed to be at least in part responsible for the deterioration of cognitive health. Past work has shown that cranially transplanted human neural stem cells (hNSCs) or their extracellular vesicles (EVs) afforded long-term beneficial effects on many of these cognitive decrements. To provide additional insight into the potential neuroprotective mechanisms of cell-based regenerative strategies, we have analyzed hippocampal neurons for changes in structural integrity and synaptic remodeling after unilateral and bilateral transplantation of hNSCs or EVs derived from those same cells. Interestingly, hNSCs and EVs similarly afforded protection to host neurons, ameliorating the impact of irradiation on dendritic complexity and spine density for neurons present in both the ipsilateral and contralateral hippocampi 1 month following irradiation and transplantation. These morphometric improvements were accompanied by increased levels of glial cell-derived growth factor and significant attenuation of radiation-induced increases in postsynaptic density protein 95 and activated microglia were found ipsi- and contra-lateral to the transplantation sites of the irradiated hippocampus treated with hNSCs or hNSC-derived EVs. These findings document potent far-reaching neuroprotective effects mediated by grafted stem cells or EVs adjacent and distal to the site of transplantation and support their potential as therapeutic agents to counteract the adverse effects of cranial irradiation

Noise suppression of a dipole source by tensioned membrane with side-branch cavities

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Modeling and Simulation of Multi-Lane Traffic Flow

A most important aspect in the field of traffic modeling is the simulation of bottleneck situations. For their realistic description a macroscopic multi-lane model for uni-directional freeways including acceleration, deceleration, velocity fluctuations, overtaking and lane-changing maneuvers is systematically deduced from a gas-kinetic (Boltzmann-like) approach. The resulting equations contain corrections with respect to previous models. For efficient computer simulations, a reduced model delineating the coarse-grained temporal behavior is derived and applied to bottleneck situations.Comment: For related work see http://www.theo2.physik.uni-stuttgart.de/helbing.htm

On sound transmission loss across a Helmholtz resonator in a low Mach number flow duct

A simplified physical model, which described the generation of sound by a Helmholtz resonator upon flow excitation at its neck, was developed in the present investigation to study the drop in sound power transmission loss across such a resonator mounted on the wall of a duct conveying a low Mach number mean flow. Experiments were derived to validate the model. Mitigation methods derived according to the model were also tested experimentally. Results showed that the simplified model gave predictions which agreed with experimental observations. The proposed mitigation methods were also proved to be effective for building services application. It was also found that the sound intensity generated by the flow excited resonator scaled with approximately the ninth power of the flowvelocity inside the duct.Department of Building Services EngineeringAuthor name used in this publication: S. K. Tan

3D acoustic modelling of dissipative silencers with nonhomogeneous properties and mean flow

A finite element approach is proposed for the acoustic analysis of automotive silencers including a perforated duct with uniform axial mean flow and an outer chamber with heterogeneous absorbent material. This material can be characterized by means of its equivalent acoustic properties, considered coordinate-dependent via the introduction of a heterogeneous bulk density, and the corresponding material airflow resistivity variations. An approach has been implemented to solve the pressure wave equation for a nonmoving heterogeneous medium, associated with the problem of sound propagation in the outer chamber. On the other hand, the governing equation in the central duct has been solved in terms of the acoustic velocity potential considering the presence of a moving medium. The coupling between both regions and the corresponding acoustic fields has been carried out by means of a perforated duct and its acoustic impedance, adapted here to include absorbent material heterogeneities and mean flow effects simultaneously. It has been found that bulk density heterogeneities have a considerable influence on the silencer transmission loss.This work was supported by Ministerio de Economia y Competitividad (Projects DPI2010-15412 and TRA2013-45596-C2-1-R), Conselleria d'Educacio, Cultura i Esport (Project Prometeo/2012/023), and Programa de Apoyo a la Investigacion y Desarrollo (PAID-05-12 and Project SP20120452) of Universitat Politecnica de Valencia.Sánchez Orgaz, EM.; Denia, FD.; Martínez-Casas, J.; Baeza, L. (2014). 3D acoustic modelling of dissipative silencers with nonhomogeneous properties and mean flow. Advances in Mechanical Engineering. 2014(1):1-10. https://doi.org/10.1155/2014/537935S11020141Selamet, A., Xu, M. B., Lee, I. J., & Huff, N. T. (2005). Dissipative expansion chambers with two concentric layers of fibrous material. International Journal of Vehicle Noise and Vibration, 1(3/4), 341. doi:10.1504/ijvnv.2005.007531Selamet, A., Xu, M. B., Lee, I. J., & Huff, N. T. (2006). Effect of voids on the acoustics of perforated dissipative silencers. International Journal of Vehicle Noise and Vibration, 2(4), 357. doi:10.1504/ijvnv.2006.012785Antebas, A. G., Denia, F. D., Pedrosa, A. M., & Fuenmayor, F. J. (2013). A finite element approach for the acoustic modeling of perforated dissipative mufflers with non-homogeneous properties. Mathematical and Computer Modelling, 57(7-8), 1970-1978. doi:10.1016/j.mcm.2012.01.021Peat, K. S., & Rathi, K. L. (1995). A finite element analysis of the convected acoustic wave motion in dissipative silencers. Journal of Sound and Vibration, 184(3), 529-545. doi:10.1006/jsvi.1995.0331Allam, S., & Åbom, M. (2006). Sound propagation in an array of narrow porous channels with application to diesel particulate filters. Journal of Sound and Vibration, 291(3-5), 882-901. doi:10.1016/j.jsv.2005.07.022Allard, J. F., & Atalla, N. (2009). Propagation of Sound in Porous Media. doi:10.1002/9780470747339Montenegro, G., Della Torre, A., Onorati, A., & Fairbrother, R. (2013). A Nonlinear Quasi-3D Approach for the Modeling of Mufflers with Perforated Elements and Sound-Absorbing Material. Advances in Acoustics and Vibration, 2013, 1-10. doi:10.1155/2013/546120Sullivan, J. W., & Crocker, M. J. (1978). Analysis of concentric‐tube resonators having unpartitioned cavities. The Journal of the Acoustical Society of America, 64(1), 207-215. doi:10.1121/1.381963Kirby, R., & Cummings, A. (1998). THE IMPEDANCE OF PERFORATED PLATES SUBJECTED TO GRAZING GAS FLOW AND BACKED BY POROUS MEDIA. Journal of Sound and Vibration, 217(4), 619-636. doi:10.1006/jsvi.1998.1811Lee, I., Selamet, A., & Huff, N. T. (2006). Acoustic impedance of perforations in contact with fibrous material. The Journal of the Acoustical Society of America, 119(5), 2785-2797. doi:10.1121/1.2188354Pierce, A. D. (1990). Wave equation for sound in fluids with unsteady inhomogeneous flow. The Journal of the Acoustical Society of America, 87(6), 2292-2299. doi:10.1121/1.399073Delany, M. E., & Bazley, E. N. (1970). Acoustical properties of fibrous absorbent materials. Applied Acoustics, 3(2), 105-116. doi:10.1016/0003-682x(70)90031-9Lee, I., & Selamet, A. (2012). Measurement of acoustic impedance of perforations in contact with absorbing material in the presence of mean flow. Noise Control Engineering Journal, 60(3), 258-266. doi:10.3397/1.3701003Kirby, R., & Denia, F. D. (2007). Analytic mode matching for a circular dissipative silencer containing mean flow and a perforated pipe. The Journal of the Acoustical Society of America, 122(6), 3471-3482. doi:10.1121/1.2793614Selamet, A., Xu, M. B., Lee, I.-J., & Huff, N. T. (2004). Analytical approach for sound attenuation in perforated dissipative silencers. The Journal of the Acoustical Society of America, 115(5), 2091-2099. doi:10.1121/1.1694994Denia, F. D., Selamet, A., Fuenmayor, F. J., & Kirby, R. (2007). Acoustic attenuation performance of perforated dissipative mufflers with empty inlet/outlet extensions. Journal of Sound and Vibration, 302(4-5), 1000-1017. doi:10.1016/j.jsv.2007.01.005Denia, F. D., Antebas, A. G., Selamet, A., & Pedrosa, A. M. (2011). Acoustic characteristics of circular dissipative reversing chamber mufflers. Noise Control Engineering Journal, 59(3), 234. doi:10.3397/1.3560904Kirby, R., & Cummings, A. (1999). Prediction of the bulk acoustic properties of fibrous materials at low frequencies1A shorter version of this paper was presented at the EuroNoise Conference, Lyon, France, 21-23 March 19951. Applied Acoustics, 56(2), 101-125. doi:10.1016/s0003-682x(98)00015-2Selamet, A., Lee, I. ., & Huff, N. . (2003). Acoustic attenuation of hybrid silencers. Journal of Sound and Vibration, 262(3), 509-527. doi:10.1016/s0022-460x(03)00109-3Payri, F., Broatch, A., Salavert, J. M., & Moreno, D. (2010). Acoustic response of fibrous absorbent materials to impulsive transient excitations. Journal of Sound and Vibration, 329(7), 880-892. doi:10.1016/j.jsv.2009.10.015Lee, S.-H., & Ih, J.-G. (2003). Empirical model of the acoustic impedance of a circular orifice in grazing mean flow. The Journal of the Acoustical Society of America, 114(1), 98-113. doi:10.1121/1.158128

A perspective on multinational enterprise’s national identity dilemma

This conceptual paper identifies gaps and contributes to the literature on ‘identity’ dilemmas faced by multinational enterprises operating in a globalised world. Various characteristics and business strategies of multinational enterprises are delineated and analysed through the lens of social identity theory and international business concepts such as market and institutional logic. Our analysis, based on multiple cases, and derived from a variety of industries and countries, associates the identity dilemma to informed business strategy. Our findings suggest that while multinational enterprises face identity dilemmas that they sometimes use to their advantage, it also poses several challenges. Through our conceptualisation, we derive five distinct propositions to shape future research directions