Fuller\u27s First Fifty - No. 03

A monthly historical newsletter published for the Fuller community during the fiftieth anniversary year. The School of World Mission: a new school for a new movement -- Donald A. McGavran: beginning again at 67 -- George Eldon Ladd: an appreciatio

Effects of μCT radiation on tissue engineered bone-like constructs

High-resolution, non-destructive imaging with micro-computed tomography (μCT) enables in situ monitoring of tissue engineered bone constructs. However, it remains controversial, if the locally imposed X-ray dose affects bone development and thus could influence the results. Here, we developed a model system for μCT monitoring of tissue engineered bone-like constructs. We examined the in vitro effects of high-resolution μCT imaging on the cellular level by using pre-osteoblastic MC3T3-E1 cells embedded into three-dimensional collagen type I matrices. We found no significantly reduced cell survival 2h after irradiation with a dose of 1.9Gy. However, 24h post-irradiation, cell survival was significantly decreased by 15% compared to non-irradiated samples. The highest dose of 7.6Gy decreased survival of the pre-osteoblastic MC3T3-E1 cells by around 40% at 2days post-irradiation. No significant increase of alkaline phosphatase (ALP) activity at 2days post-irradiation was found with a dose of 1.9Gy. However, ALP activity was significantly decreased after 7days. Using our model system, the results indicate that μCT imaging with doses as low as 1.9Gy, which is required to obtain a reasonable image quality, can induce irreparable damages on the cellular leve

Contribution of changes in opal productivity and nutrient distribution in the coastal upwelling systems to Late Pliocene/Early Pleistocene climate cooling

The global Late Pliocene/Early Pleistocene cooling (~3.0–2.0 million years ago – Ma) concurred with extremely high diatom and biogenic opal production in most of the major coastal upwelling regions. This phenomenon was particularly pronounced in the Benguela upwelling system (BUS), off Namibia, where it is known as the Matuyama Diatom Maximum (MDM). Our study focuses on a new diatom silicon isotope (δ30Si) record covering the MDM in the BUS. Unexpectedly, the variations in δ30Si signal follow biogenic opal content, whereby the highest δ30Si values correspond to the highest biogenic opal content. We interpret the higher δ30Si values during the MDM as a result of a stronger degree of silicate utilisation in the surface waters caused by high productivity of mat-forming diatom species. This was most likely promoted by weak upwelling intensity dominating the BUS during the Late Pliocene/Early Pleistocene cooling combined with a large silicate supply derived from a strong Southern Ocean nutrient leakage responding to the expansion of Antarctic ice cover and the resulting stratification of the polar ocean 3.0–2.7 Ma ago. A similar scenario is hypothesized for other major coastal upwelling systems (e.g. off California) during this time interval, suggesting that the efficiency of the biological carbon pump was probably sufficiently enhanced in these regions during the MDM to have significantly increased the transport of atmospheric CO2 to the deep ocean. In addition, the coeval extension of the area of surface water stratification in both the Southern Ocean and the North Pacific, which decreased CO2 release to the atmosphere, led to further enhanced atmospheric CO2 drawn-down and thus contributed significantly to Late Pliocene/Early Pleistocene cooling

The Proper Motion of the Central Compact Object RX J0822-4300 in the Supernova Remnant Puppis A, Revisited

We present an improved proper motion measurement of the central compact object RX J0822-4300, located in the supernova remnant Puppis A. By employing a new data set taken in February 2019 by the High Resolution Camera aboard the Chandra X-ray Observatory, we approximately double the available temporal baseline for our analysis to slightly more than 19 years (7000 days). We correct for the astrometric inaccuracy of Chandra using calibrator stars with known optical positions that are detected in all observations. Thereby, we obtain absolute positions of RX J0822-4300 accurate to around $0.1^{\prime\prime}$ and from these a new best estimate for its total proper motion of $\mu_{\rm tot}= (80.4 \pm 7.7)\,\rm{mas\,yr}^{-1}$. For a remnant distance of 2 kpc, this corresponds to a projected kick velocity of $(763 \pm 73)\, \rm{km\,s}^{-1}$ at a position angle of $\phi_0 = (247.8 \pm 4.4)^{\circ}$. The proper motion measurement of RX J0822-4300 is used for discussing the kinematic age of Puppis A.Comment: 15 pages, 7 figures, Accepted for publication in Ap

Theology, News and Notes - Vol. 43, No. 02

Theology News & Notes was a theological journal published by Fuller Theological Seminary from 1954 through 2014.https://digitalcommons.fuller.edu/tnn/1125/thumbnail.jp

Sweeping of three-dimensional objects

Evaluating the volume swept out by a three-dimensional (3D) object as it moves along an arbitrary path is of interest to many areas of CAD and CAM, such as mechanism design and robot path planning. This paper shows how envelope theory from differential geometry can be used to find the volumes swept out by the individual surfaces of a solid body, and how computer algebra methods may be of use to perform the computations involved. Finally, a new algorithm is presented which shows how the results of sweeping the individual surfaces of a solid body can be combined to form a new 3D model of the swept volume. This algorithm has strong resemblance to hidden line algorithms, but works in one dimension higher

Variability and Proper Motion of X-ray Knots in the Jet of Centaurus A

Accepted to ApJ, 14 pages, 8 figures, 2 tablesWe report results from Chandra observations analyzed for evidence of variability and proper motion in the X-ray jet of Centaurus A. Using data spanning 15 yr, collective proper motion of 11.3 ± 3.3 mas yr -1 , or 0.68 ± 0.20c, is detected for the fainter X-ray knots and other substructure present within the jet. The three brightest knots (AX1A, AX1C, and BX2) are found to be stationary to an upper limit of . Brightness variations up to 27% are detected for several X-ray knots in the jet. For the fading knots, BX2 and AX1C, the changes in spectral slope expected to accompany synchrotron cooling are not found, ruling it out and placing upper limits of ≃80 μG for each of their magnetic field strengths. Adiabatic expansion can account for the observed decreases in brightness. Constraints on models for the origin of the knots are established. Jet plasma overrunning an obstacle is favored as the generator of stationary knots, while moving knots are likely produced either by internal differences in jet speed or the late stages of jet interaction with nebular or cloud material.Peer reviewe