52,520 research outputs found
Acoustic radiation due to scattering of T-S wave by the mean-flow distortion induced by steady local suction
No full textSubstantial sound waves can be generated by boundary-layer instability modes when the latter are scattered by a rapid mean-flow distortion. This is a rather generic mechanism and operates when an oncoming T-S wave is scattered by a steady local suction slot. This paper focuses on this problem by extending a recently developed Local Scattering Theory (Wu & Dong, J. Fluid Mech. submitted), where a so-called transmission coefficient, defined as the ratio of the T-S wave amplitude downstream of the scatter to that upstream, is introduced to characterize the effect of a local scatter on boundary-layer instability and transition. As in the earlier work, the mathematical formulation is based on triple-deck formulism, but in order to accommodate the acoustic far field, which was not considered in the paper mentioned, the unsteady terms in the upper deck, which play a leading-order role in radiation, are retained, and the influence of the radiated sound on the near-wall perturbation is included. The upper deck equation for the pressure is the Helmholtz equation rather than the Laplace equation. This leads to a modified pressure-displacement relation, which is coupled with the linearized boundary-layer equations in the lower deck. Discretization of the whole system formulates a generalized eigenvalue problem, which is solved numerically. It is found that suction suppresses oncoming T-S waves, and this effect increases with the suction velocity and the slot width. The directivity is ndependent of the flow parameters only when the Mach number is low. The intensity of the radiated sound in general increases with the frequency, the suction velocity and the width of the suction slot. Interestingly, for O(1) suction velocities, the radiated sound is very weak, indicating that the gain of stabilizing effect does not cause aeroacoustic penalty
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The role of CD4 T cells in the rhesus central nervous system during homeostasis and viral-induced neuroinflammation
No full textDespite the advent and implementation of Anti-retroviral therapy (ART) in 1987, people living with HIV (PLWH) continue to experience a high incidence of age-associated comorbidities, particularly HIV associated neurocognitive disorders (HAND) which affect 40-70% of PLWH. Research over the past four decades has predominantly focused on the role of myeloid cells in the development of HAND due, in part, to the initial discovery of HIV-infected myeloid cells in the post-mortem brain tissue of AIDS patients. My dissertation examines the understudied role of T lymphocytes in HAND, in light of three significant advancements in the fields of HIV and neuroimmunology. Firstly, ART treatment has not only stabilized disease progression but has also led to the reconstitution and stabilization of CD4 T cells, highlighting a newfound potential role for CD4 T cells in the neurological disease process. Secondly, we now recognize that T cells are an important immune population within the central nervous system (CNS) both during homeostasis and disease. Thirdly, data from neurodegenerative diseases such as Alzheimer’s, Parkinson’s, and Multiple Sclerosis highlight a critical role for T cells in contributing to neuroinflammation and disease progression.
Together, these advancements collectively provide a strong rationale for developing a more comprehensive understanding of the role of T cells in HAND. Given the early establishment of transmitted/founder (T/F) HIV in the CNS, the surveillance of the CNS by CCR5 (R5) + T helper 1 cells, which serve as primary HIV targets, and the influence of T-cell derived cytokines on microglial activation, we hypothesized that T cells are pivotal in acute CNS viral seeding and neuroinflammation. We tested this hypothesis in rhesus macaques (Macaca mulatta) - among the most robust models for studying the CNS and HIV pathogenesis. We employed models of both acute and chronic simian HIV (SHIV) infection using distinct strains: the R5/CD4 tropic T/F SHIV C.CH505, the virulent R5-T cell-tropic SIVmac251, and the macrophage-tropic SIVCL757, used in studies of neuro-HIV. Together, our studies with these distinct viruses offer the following insights into the role of CD4 T cells in the brain during HIV infection.
In Chapter II, we presented RNA sequencing and viral load data across four synapse-dense regions of the brain susceptible to HIV infection (Prefrontal Cortex (PFC), Superior Temporal Sulcus, Caudate Nucleus, Hippocampus). First, our data demonstrated that these synapse-dense cognitive regions are rich in immune gene signatures at homeostasis. Following infection with T/F SHIV.C.CH505, our analysis showed activation of biological pathways consistent with T cell recruitment and microglial activation. Despite relatively low plasma and cerebrospinal fluid (CSF) viral loads, we observed viral (v)RNA and vDNA within these regions - an observation aligning with infiltration of SIV infected Th1 CD4 T cells into the PFC.
In Chapter III, we delved deeply into the phenotype of CD4 T cells within the CNS, including the brain and its associated border tissues. Our rationale for this comprehensive analysis was to delineate target cells in these regions to better understand susceptibility to viral establishment. We conducted single-cell analysis of CD45+ immune cells in brain parenchyma, comparing them to counterparts in the spleen of both uninfected macaques and those acutely infected with SIVmac251. The data demonstrated colocalization of viral transcripts within CD4 clusters and furthermore showed induction of antiviral responses during acute SIV infection. This supports the observations made in Chapter II that target cells for HIV populate the CNS, including the dura, choroid plexus stroma, and the skull bone marrow. Correspondingly, during the acute phase of SIVmac251 infection, we observed significant levels of viral RNA and DNA in these regions. In animals chronically infected with SIVmac251 (40 weeks) and treated with suboptimal ART, our data demonstrated that despite CSF viral suppression, there is incomplete reconstitution of CD4 T cells in the brain and surrounding CNS tissues underscoring their active engagement during acute and chronic phases of SIVmac251 infection.
In Chapter IV, we comprehensively assessed phenotypic and functional features of CCR7+ cells identified in Chapter III. Leveraging single-transcriptomic analysis, ATAC-seq, spatial transcriptomics and flow cytometry we show that CCR7+ CD4 T cells in the brain have T lymphocyte central memory-like features. Moreover, the skull bone marrow emerged as a potential niche for CCR7+ CD4 T cells. In a cohort of macaques chronically infected (112 weeks) with SIVCL757 and treated with suboptimal ART, we noted a decrease in CCR7+ CD4 T cells within the brain in parallel with evidence for microglial activation and induction of neurodegenerative pathways. These findings suggested that changes in CD4 T cell subsets within the CNS may drive neuroinflammation during chronic HIV infection.
In summary, the findings across my three chapters lead to three major conclusions. First, the presence of both CCR5 and CCR7 CD4 T cells in the parenchymal and border regions of the CNS, renders this organ susceptible to initial HIV infection and establishment of latent reservoirs. Second, our studies of acute infection with two viruses - SHIVC.CH505 and SIVmac251- suggests that CD4 T cells within the brain parenchyma are actively engaged during acute HIV infection serving as both viral targets and mediators of neuroinflammation. Third, our models of chronic infection under suboptimal ART with two viruses - SIVmac251 and SIVCL757 - demonstrate that inadequate CD4 T cell reconstitution together with reduction of CCR7+ CD4 T cells may underlie neuroimmune dysregulation in HIV-infected patients on ART
Measuring industry-science links through inventor-author relations: A profiling method
No full textIn this pilot study we examine the performance of text-based profiling in recovering a set of validated inventor-author links. In a first step we match patents and publications solely based on their similarity in content. Next, we compare inventor and author names on the highest ranked matches for the occurrence of name matches. Finally, we compare these candidate matches with the names listed in a validated set of inventor-author names. Our text-based profile methodology performs significantly better than a random matching of patents and publications, suggesting that text-based profiling is a valuable complementary tool to the name searches used in previous studies.innovation; industry-science links; text-based profiling;
The maternal immune system during pregnancy and its influence on fetal development
No full textThe maternal immune system plays a critical role in the establishment, maintenance, and completion of a healthy pregnancy. However, the specific mechanisms utilized to achieve these goals are not well understood. Various cells and molecules of the immune system are key players in the development and function of the placenta and the fetus. Effector cells of the immune system act to promote and yet limit placental development. The T helper 1 (Th1)/T helper 2 (Th2) immune shift during pregnancy is well established. A fine balance between proinflammatory and anti-inflammatory influences is required. We herein review the evidence regarding maternal tolerance of fetal tissues and the underlying cell-mediated immune and humoral (hormones and cytokines) mechanisms. We also note the many unanswered questions in our understanding of these mechanisms. In addition, we summarize the clinical manifestations of an altered maternal immune system during pregnancy related to susceptibility to common viral, bacterial, and parasitic infections, as well as to autoimmune diseases.Peer reviewe
S-heterocyclic carbene with a disilane backbone
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Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
No full textIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
Letter from Carl Hayden to Fred S. Breen
No full textLetter from Carl T. Hayden to Fred S. Breen concerning the expenditure of $100,000 to purchase Bright Angel Trail
Measurement of the and production cross sections in multilepton final states using 3.2 fb of collisions at = 13 TeV with the ATLAS detector
No full textSee paper for full list of authors - 22 pages plus author list + cover page (40 pages total), 8 figures, 5 tables. Submitted to Eur. Phys. J. C. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2015-22/International audienceA measurement of the and production cross sections in final states with either two same-charge muons, or three or four leptons (electrons or muons) is presented. The analysis uses a data sample of proton-proton collisions at TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015, corresponding to a total integrated luminosity of 3.2 fb. The inclusive cross sections are extracted using likelihood fits to signal and control regions, resulting in pb and pb, in agreement with the Standard Model predictions
Dr. Glendon Swarthout
No full textHosted by Roger M. Busfield, MSU Assistant Professor of Speech and Theater, Meet the Author is designed to introduce a general audience to a contemporary author and their work through in-depth interviews. This episode features a conversation between Dr. Glendon Swarthout, prolific author and English professor at MSU, and assistant professors Sam S. Baskett and Theodore B. Strandness
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