Fundamental and applied research on core engine/combustion noise of aircraft engines

Some results of a study of the importance of geometrical features of the combustor to combustion roughness and resulting noise are presented. Comparison is made among a perforated can flame holder, a plane slotted flame holder and a plane slotted flame holder which introduces two counter swirling streams. The latter is found to permit the most stable, quiet combustion. Crosscorrelations between the time derivative of chamber pressure fluctuations and far field noise are found to be stronger than between the far field noise and the direct chamber pressure signal. Temperature fluctuations in the combustor nozzle are also found to have a reasonably strong crosscorrelation with far field sound

Recurrent ~24 h Periods in RXTE ASM Data

Analysis of data from the Rossi X-ray Timing Explorer satellite's All Sky Monitor instrument for several X-ray binary sources has identified a recurrent \~24 h period. This period is sometimes highly significant, giving rise to the possibility of it being identified as an orbital or super-orbital period. Further analysis has revealed the same period in a number of other X-ray sources. As a result this period has been discounted as spurious, described variously as arising from daily variations in background levels and beating between the sampling period and long-term secular trends in the light curves. We present here an analysis of the spurious periods and show that the dominant mechanism is in fact spectral leakage of low-frequency power present in the light curves.Comment: 9 Pages, 10 figures, 1 table, submitted to PASA 20th December 2004. Added 1 page of text and 3 figures to clarify results and discussion. Resubmitted 16th May 2005. Accepted 25th June 200

Inorganic nitrogen availability alters Eucalyptus grandis receptivity to the ectomycorrhizal fungus Pisolithus albus but not symbiotic nitrogen transfer.

Forest trees are able to thrive in nutrient-poor soils in part because they obtain growth-limiting nutrients, especially nitrogen (N), through mutualistic symbiosis with ectomycorrhizal (ECM) fungi. Addition of inorganic N into these soils is known to disrupt this mutualism and reduce the diversity of ECM fungi. Despite its ecological impact, the mechanisms governing the observed effects of elevated inorganic N on mycorrhizal communities remain unknown. We address this by using a compartmentalized in vitro system to independently alter nutrients to each symbiont. Using stable isotopes, we traced the nutrient flux under different nutrient regimes between Eucalyptus grandis and its ectomycorrhizal symbiont, Pisolithus albus. We demonstrate that giving E. grandis independent access to N causes a significant reduction in root colonization by P. albus. Transcriptional analysis suggests that the observed reduction in colonization may be caused, in part, by altered transcription of microbe perception genes and defence genes. We show that delivery of N to host leaves is not increased by host nutrient deficiency but by fungal nutrient availability instead. Overall, this advances our understanding of the effects of N fertilization on ECM fungi and the factors governing nutrient transfer in the E. grandis-P. microcarpus interaction

Combustion contribution to noise in jet engines

The relative importance of combustion as a source of noise in a flow regime representative of a subsonic jet engine exhaust was investigated. The combustion noise source characteristics were obtained from pressure and temperature fluctuation measurements in the combustor and exhaust nozzle. The similarity between the fluctuations in this source region and the far field noise were compared. In the jet exhaust velocity range between 450 and 660 ft/sec investigated in detail, the frequencies of dominant pressure and temperature fluctuations in the combustor were also the frequencies of the dominant far field noise. The overall noise levels were 14 to 20 dB higher than from a corresponding clean jet in the same velocity range. Thus it seemed clear that the unsteadiness associated with the combustion process was responsible for the dominant noise in the far field. A simple analysis to predict the far field noise due to the internal pressure fluctuations causing exit plane velocity fluctuations produced trends closely resembling the measured results, but under predicted the far field noise over the spectral range examined. The possible reason for the higher far field noise is direct transmission of acoustic waves through the nozzle, which was not accounted for in the prediction scheme

Increased Incidence of Lymphosarcoma in Long-Term Murine Survivors of Lethal Radiation: A Classification of Subtypes

poster abstractResidual bone marrow damage (RBMD) persists for years following exposure to radiation and is thought to be due to decreased self-renewal of hematopoietic stem cells (HSC). We previously examined RBMD in murine survivors of lethal radiation modeling a terrorist event [800cGy total-body irradiation (TBI)]. We reported severely deficient HSC potential up to 20mo post-TBI compared to non-TBI age-matched controls, evidenced by minimal engraftment skewed to myeloid cells. CBC and BM cellularity were decreased in TBI mice, most dramatically in old age (>16mo). The percentage of some hematopoietic progenitors was consistently increased in TBI mice (~1.4x higher than non-TBI) possibly due to an increased cell cycling rate compared to non-TBI cells. Of interest, we now report the occurrence of a thymic mass developing in 13-24% of TBI mice 2-19 months post-TBI, compared to <1% of non-TBI. We characterized the Lymphosarcoma into the following groups based on the St. Jude pathology subclassification: Diffuse Lymphosarcoma involving multiple organs, Thymic lymphoma (usually associated with thymic and around the heart), Lymphosarcoma (potentially starting in the spleen and peri-pancreatic lymph nodes (Ab=abdomen)), and follicular lymphoma seen as a diffuse proliferation of lymphocytes in the white pulp area in the spleen. Thymic lymphomas were the most common, followed by Lymphosarcoma (Ab), follicular lymphoma (restricted to white pulp area in the spleen) and diffuse Lymphosarcoma. Immunostain markers revealed the thymic lymphomas were from T-cell lineage and the abdominal Lymphosarcoma were mainly from B-cell lineage. A few mice had disease involving the bone marrow. Taken together, these data suggest that the increased cycling among primitive hematopoietic cells in survivors of lethal radiation may contribute to stem cell exhaustion and subsequent RBMD, as well as predispose survivors to hematopoietic neoplasias

Leveraging genomics to understand the broader role of fungal small secreted proteins in niche colonization and nutrition

The last few years have seen significant advances in the breadth of fungi for which we have genomic resources and our understanding of the biological mechanisms evolved to enable fungi to interact with their environment and other organisms. One field of research that has seen a paradigm shift in our understanding concerns the role of fungal small secreted proteins (SSPs) classified as effectors. Classically thought to be a class of proteins utilized by pathogenic microbes to manipulate host physiology in support of colonization, comparative genomic studies have demonstrated that mutualistic fungi and fungi not associated with a living host (i.e., saprotrophic fungi) also encode inducible effector and candidate effector gene sequences. In this review, we discuss the latest advances in understanding how fungi utilize these secreted proteins to colonize a particular niche and affect nutrition and nutrient cycles. Recent studies show that candidate effector SSPs in fungi may have just as significant a role in modulating hyphosphere microbiomes and in orchestrating fungal growth as they do in supporting colonization of a living host. We conclude with suggestions on how comparative genomics may direct future studies seeking to characterize and differentiate effector from other more generalized functions of these enigmatic secreted proteins across all fungal lifestyles

Tenting on the Old Campground: A Social History of the U.S. Regular and State Volunteer Troops in the 5th Corps, Army of the Potomac, 1862-1865

In the annals of the American Civil War, the regular U.S. Army has not been the focus of historical works until very recently, which is surprising in light of the noble and honorable service it rendered during the 19th century, without thanks or praise from the society it protected and served. After being scattered across the American frontiers for decades, the U.S. Army’s infantry, by far the largest branch, was consolidated into one solid division within the 5th corps in 1862. Instead of being separated from each other and having to rely on themselves for support, they now fought as never before, with approximately 10,000 men of the regulars fighting as one, providing a dramatic contrast to the 90,000 volunteers enrolled in the Army of the Potomac. Professional soldiers fighting and dying together, a solid core and reserve for the rest of the army to form around and take inspiration from, an inspiration that would give us an apocryphal quote from a 5th corps volunteer: “For two years the regulars showed us how to fight like soldiers, in the Wheatfield at Gettysburg they showed us how to die like soldiers.

Survival efficacy of the PEGylated G-CSFs Maxy-G34 and neulasta in a mouse model of lethal H-ARS, and residual bone marrow damage in treated survivors

In an effort to expand the worldwide pool of available medical countermeasures (MCM) against radiation, the PEGylated G-CSF (PEG-G-CSF) molecules Neulasta and Maxy-G34, a novel PEG-G-CSF designed for increased half-life and enhanced activity compared to Neulasta, were examined in a murine model of the Hematopoietic Syndrome of the Acute Radiation Syndrome (H-ARS), along with the lead MCM for licensure and stockpiling, G-CSF. Both PEG-G-CSFs were shown to retain significant survival efficacy when administered as a single dose 24 h post-exposure, compared to the 16 daily doses of G-CSF required for survival efficacy. Furthermore, 0.1 mg kg of either PEG-G-CSF affected survival of lethally-irradiated mice that was similar to a 10-fold higher dose. The one dose/low dose administration schedules are attractive attributes of radiation MCM given the logistical challenges of medical care in a mass casualty event. Maxy-G34-treated mice that survived H-ARS were examined for residual bone marrow damage (RBMD) up to 9 mo post-exposure. Despite differences in Sca-1 expression and cell cycle position in some hematopoietic progenitor phenotypes, Maxy-G34-treated mice exhibited the same degree of hematopoietic stem cell (HSC) insufficiency as vehicle-treated H-ARS survivors in competitive transplantation assays of 150 purified Sca-1+cKit+lin-CD150+cells. These data suggest that Maxy-G34, at the dose, schedule, and time frame examined, did not mitigate RBMD but significantly increased survival from H-ARS at one-tenth the dose previously tested, providing strong support for advanced development of Maxy-G34, as well as Neulasta, as MCM against radiation