The changes in chemical composition during development of the bovine nuchal ligament

Whole bovine nuchal ligaments, or portions thereof (in the case of commercially valuable animals), were obtained from 45 animals (28 fetal and 17 postnatal) ranging in age from 110 days of gestation to 10 yr. Insoluble elastin was quantitatively prepared from the fresh ligaments by extraction with hot alkali and by a combination of multiple extractions with alkaline buffer and then repeated autoclaving. When adult samples were examined, the yields of insoluble residue by these two methods were very similar, but with young fetal samples the second method gave significantly higher values, because of incomplete purification of the elastin residue. The changes in the concentration of collagen, alkali-insoluble elastin, and DNA have been examined. DNA concentration, and, thus, cell population density, fell progressively during the fetal period of development, to reach a steady value soon after birth. Collagen appeared in appreciable quantities before elastin, but its concentration was rapidly halved at about the time of birth. Insoluble elastin concentration was low until the end of the 7th fetal month, at which time it began to rise rapidly. The rate of increase in elastin concentration remained high throughout the next 10–12 wk, by which time the adult value had been reached. Quantitative studies, on the basis of the whole ligament, showed that the total cell content rises to a maximum at birth, but falls soon after to a level about half that at birth. Total collagen production and elastin deposition continue at a steady, maximal rate over the interval from 235 days of gestation to the end of the 1st postnatal month. It is concluded that the immediate postnatal period would be the most favorable phase in which to attempt the isolation of the soluble precursor elastin

An experimental documentation of trailing-edge flows at high Reynolds number

Experiments documenting attached trailing-edge and near-wake flows at high Reynolds numbers are described. A long, airfoil-like model was tested at subsonic and low transonic Mach numbers, and both symmetrical and asymmetrical flows with pressure gradients upstream of the trailing edge were investigated. Model surface pressures and detailed mean and turbulence flow qualities were measured in the vicinity of the trailing edge and in the near-wake. The data obtained are of sufficient quality and detail to be useful as test cases in assessing turbulence models and calculation methods

Results of investigations on an 0.015-scale 140A/B configuration of the Rockwell International space shuttle orbiter (model 49-O) in the NASA/Ames Research Center 3.5-foot hypersonic wind tunnel (OA36)

The results of wind tunnel tests of the 140A/B configuration components are reported for the fuselage, canopy, elevons, bodyflaps, pods, engine nozzles, rudder, vertical tail, and wing. The test facility, and data reduction procedures are described. Test results for each component are graphed, and tabulated source data are included

Mutant CEBPA: Priming Stem Cells for Myeloid Leukemogenesis

In a recent study published in Cancer Cell, Bereshchenko and colleagues (2009) report a knockin mouse model that represents the most frequently occurring biallelic combination of CEBPA mutations found in human acute myeloid leukemia

PU.1 and Junb: Suppressing the formation of acute myeloid leukemia stem cells

Improved understanding of the molecular pathways that suppress the genesis and maintenance of cancer stem cells will facilitate development of rationally targeted therapies. PU.1 is a transcription factor that is required for normal myelomonocytic differentiation in hematopoiesis, and reduced PU.1 activity has been associated with myeloid leukemogenesis in man and in mouse models. A recent study by Steidl et al. demonstrates that Junb and Jun, two AP-1 transcription factors, are critical downstream effectors of the tumor suppressor activity of PU.1, and that reduced expression of Junb, in particular, may be a common feature of acute myeloid leukemogenesis

Case reports as a resource for teaching and learning

Editorial: Case reports allow students to engage with real clinical scenarios, and to contemplate the decision-making and actions of the treating team. However, in addition to the focus on health issues, case reports can be used to stimulate students in considering the wider social, cultural, political, and economic issues that may contribute to and impact on the health status of an individual. This can then be used as a lens to consider issues more broadly

Aerial applications dispersal systems control requirements study

Performance deficiencies in aerial liquid and dry dispersal systems are identified. Five control system concepts are explored: (1) end of field on/off control; (2) manual control of particle size and application rate from the aircraft; (3) manual control of deposit rate on the field; (4) automatic alarm and shut-off control; and (5) fully automatic control. Operational aspects of the concepts and specifications for improved control configurations are discussed in detail. A research plan to provide the technology needed to develop the proposed improvements is presented along with a flight program to verify the benefits achieved

Cryogenic microstripline-on-Kapton microwave interconnects

Simple broadband microwave interconnects are needed for increasing the size of focal plane heterodyne radiometer arrays. We have measured loss and cross-talk for arrays of microstrip transmission lines in flex circuit technology at 297 and 77 K, finding good performance to at least 20 GHz. The dielectric constant of Kapton substrates changes very little from 297 to 77 K, and the electrical loss drops. The small cross-sectional area of metal in a printed circuit structure yields overall thermal conductivities similar to stainless steel coaxial cable. Operationally, the main performance tradeoffs are between crosstalk and thermal conductivity. We tested a patterned ground plane to reduce heat flux.Comment: 3 pages, 3 figures, submitted to The Review of Scientific Instrument