628 research outputs found

    Lucky Cars and the Quicksort Algorithm

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    Quicksort is a classical divide-and-conquer sorting algorithm. It is a comparison sort that makes an average of 2(n+1)Hn4n2(n+1)H_n - 4n comparisons on an array of size nn ordered uniformly at random, where Hn=i=1n1iH_n = \sum_{i=1}^n\frac{1}{i} is the nnth harmonic number. Therefore, it makes n![2(n+1)Hn4n]n!\left[2(n+1)H_n - 4n\right] comparisons to sort all possible orderings of the array. In this article, we prove that this count also enumerates the parking preference lists of nn cars parking on a one-way street with nn parking spots resulting in exactly n1n-1 lucky cars (i.e., cars that park in their preferred spot). For n2n\geq 2, both counts satisfy the second order recurrence relation fn=2nfn1n(n1)fn2+2(n1)! f_n=2nf_{n-1}-n(n-1)f_{n-2}+2(n-1)! with f0=f1=0f_0=f_1=0.Comment: 8 pages, and 2 figures, to appear in The American Mathematical Monthl

    Simulation of mallet percussion instruments by a coupled modal vibroacoustic finite element model

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    A three-dimensional coupled vibroacoustic finite element model for physics-based simulations of sound generation by mallet percussion instruments in the time domain is discussed in the present paper. The mechanical model takes the orthotropic material properties of the wooden sound bars and the nonlinear nature of the interaction force between the mallet head and the sound bar into account while the acoustical model considers radiation into an unbounded domain. A direct coupling of the sound bars, acoustical cavity resonators, and the excitation by a mallet is considered with exploiting the modal basis to reduce the number of degrees of freedom of the system. Both the mechanical and the acoustical models are validated by comparing them to measurements performed on an Orff xylophone. A case study shows the capabilities of the coupled model, including the analysis of the energy balance, the effect of tuning the resonator, and the excitation of the torsional modes of the sound bar

    Value migration: digitalization of shipping as a mechanism of industry dethronement

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    In this conceptual paper, we review latest developments related to unmanned vessels and sketch potential scenarios that implicate with the existing maritime industry structure. On the one hand, we isolate a range of challenges that make the imminent realization of unmanned vessels seem like a rather utopian pursuit. On the other hand, we explain the reasons that may catalyse their emergence. Inspired by these opposing tensions, we highlight that the digital transformation of the shipping industry has the potential to enhance value within the industry’s ecosystem. However, we also contend that unmanned vessels -if realized- pose a very particular threat to the identity of the shipping industry as we know it. In particular, we build upon the concept of value migration and we highlight the drastic existential changes that may likely stem from a shift to non-seafarer-centric shipping. We conclude with questions that matter for industry dethronement purposes i.e., the possibility that existing industry structures may be substantially reconfigured following a removal of the seafarer as the nucleus of value creation in shipping

    Discovery and Differential Processing of HLA Class II-Restricted Minor Histocompatibility Antigen LB-PIP4K2A-1S and Its Allelic Variant by Asparagine Endopeptidase

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    Minor histocompatibility antigens are the main targets of donor-derived T-cells after allogeneic stem cell transplantation. Identification of these antigens and understanding their biology are a key requisite for more insight into how graft vs. leukemia effect and graft vs. host disease could be separated. We here identified four new HLA class II-restricted minor histocompatibility antigens using whole genome association scanning. For one of the new antigens, i.e., LB-PIP4K2A-1S, we measured strong T-cell recognition of the donor variant PIP4K2A-1N when pulsed as exogenous peptide, while the endogenously expressed variant in donor EBV-B cells was not recognized. We showed that lack of T-cell recognition was caused by intracellular cleavage by a protease named asparagine endopeptidase (AEP). Furthermore, microarray gene expression analysis showed that PIP4K2A and AEP are both ubiquitously expressed in a wide variety of healthy tissues, but that expression levels of AEP were lower in primary acute myeloid leukemia (AML). In line with that, we confirmed low activity of AEP in AML cells and demonstrated that HLA-DRB1*03:01 positive primary AML expressing LB-PIP4K2A-1S or its donor variant PIP4K2A-1N were both recognized by specific T-cells. In conclusion, LB-PIP4K2A-1S not only represents a novel minor histocompatibility antigen but also provides evidence that donor T-cells after allogeneic stem cell transplantation can target the autologous allelic variant as leukemia-associated antigen. Furthermore, it demonstrates that endopeptidases can play a role in cell type-specific intracellular processing and presentation of HLA class II-restricted antigens, which may be explored in future immunotherapy of AML.Immunobiology of allogeneic stem cell transplantation and immunotherapy of hematological disease

    Discovery and Differential Processing of HLA Class II-Restricted Minor Histocompatibility Antigen LB-PIP4K2A-1S and Its Allelic Variant by Asparagine Endopeptidase

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    Minor histocompatibility antigens are the main targets of donor-derived T-cells after allogeneic stem cell transplantation. Identification of these antigens and understanding their biology are a key requisite for more insight into how graft vs. leukemia effect and graft vs. host disease could be separated. We here identified four new HLA class II-restricted minor histocompatibility antigens using whole genome association scanning. For one of the new antigens, i.e., LB-PIP4K2A-1S, we measured strong T-cell recognition of the donor variant PIP4K2A-1N when pulsed as exogenous peptide, while the endogenously expressed variant in donor EBV-B cells was not recognized. We showed that lack of T-cell recognition was caused by intracellular cleavage by a protease named asparagine endopeptidase (AEP). Furthermore, microarray gene expression analysis showed that PIP4K2A and AEP are both ubiquitously expressed in a wide variety of healthy tissues, but that expression levels of AEP were lower in primary acute myeloid leukemia (AML). In line with that, we confirmed low activity of AEP in AML cells and demonstrated that HLA-DRB1*03:01 positive primary AML expressing LB-PIP4K2A-1S or its donor variant PIP4K2A-1N were both recognized by specific T-cells. In conclusion, LB-PIP4K2A-1S not only represents a novel minor histocompatibility antigen but also provides evidence that donor T-cells after allogeneic stem cell transplantation can target the autologous allelic variant as leukemia-associated antigen. Furthermore, it demonstrates that endopeptidases can play a role in cell type-specific intracellular processing and presentation of HLA class II-restricted antigens, which may be explored in future immunotherapy of AML

    Fetal magnetoencephalography (fMEG).

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    The human brain is one of the most complex organs which develops and adapts continuously over lifetime. Until now, neurophysiological research is mainly related to brain development from birth to adulthood, and neurophysiological research concerning prenatal human brain development only started in the last decades. Magnetoencephalography (MEG) is especially suited for fetal investigation, because it is completely noninvasive and not affected by the biological tissue separating the fetus from the outside. The first successful fetal MEG (fMEG) recording was reported in 1985 (Blum et al. Br J Obstet Gynaecol 92(12):1224-1229, 1985). Since the human brain in utero is highly vulnerable to internal and external influences, prenatal brain research is highly important to understand its development during that time period. Therefore, measurement techniques were improved, and basic research concerning brain development in utero was conducted. So far, mainly auditory and visual stimulation was used to assess fetal brain development by means of changes in signal processing speed or the development of basic forms of learning. The goal of basic fMEG research is to understand healthy fetal brain development and enable an early detection of possible deviations from it. In the future this may allow the development of early, even prenatal treatments and reduce the risk of adverse outcomes. This chapter gives an overview over structural and functional brain development and introduces the fMEG, a measurement technique to noninvasively assess functional fetal brain development in utero. Moreover, current fMEG studies are introduced, and the potential of the method of fMEG is illustrated and discussed

    Fano Resonances in the Linear and Nonlinear Plasmonic Response

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    Fano resonances manifest novel phenomena both in linear and nonlinear response of plasmonic nanomaterials. They can extend the lifetime of plasmonic excitations, enabling the operation of nanolasers, or they can increase the fluorescence of quantum emitters. They also provide control over nonlinear optical processes such as second harmonic generation and surface enhanced Raman scattering. Fano resonances can both enhance and suppress nonlinear response. Interference of two or more absorption/conversion paths is responsible for the appearance of these effects. In this Chapter, we demonstrate explicitly—on a single equation—how path interference takes part in linear and nonlinear Fano resonances
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