2,363 research outputs found
CCDC 1953060: Experimental Crystal Structure Determination
No full textRelated Article: Michael J. Celestine, Mark A.W. Lawrence, Olivier Schott, Vincent Picard, Garry S. Hanan, Emily M. Marquez, Chekeyl G. Harold, Cole T. Kuester, Blaise A. Frenzel, Christopher G. Hamaker, Sean E. Hightower, Colin D. McMillen, Alvin A. Holder|2021|Inorg.Chim.Acta|517|120195|doi:10.1016/j.ica.2020.12019
"The 'fightin'est' Canadian general:" Brigadier Christopher Vokes and his approach to military command, June 1942 -- August 1943
No full textThis thesis evaluates the manner in which Brigadier Christopher Yokes dealt with the technical and human aspects of command while commanding the 2nd Canadian Infantry Brigade from 25 June 1942 until the end of the Sicilian campaign in August 1943. It seeks to promote a greater understanding of brigade-level command and to rehabilitate Vokes's reputation as a commander, which has largely been based on certain negative personality traits. The author argues that Yokes was a successful commander because he maintained a good balance between technical skills such as planning and directing operations and his ability to understand, motivate, and lead soldiers, and because his actions were guided by a sound philosophy of command based on personal leadership and teamwork. These elements allowed Christopher Yokes to train and lead a highly effective and cohesive fighting force that defeated some of Germany's best troops in the physically demanding environment of the Sicilian battlefield
"The 'fightin'est' Canadian general:" Brigadier Christopher Vokes and his approach to military command, June 1942 -- August 1943
No full textThis thesis evaluates the manner in which Brigadier Christopher Yokes dealt with the technical and human aspects of command while commanding the 2nd Canadian Infantry Brigade from 25 June 1942 until the end of the Sicilian campaign in August 1943. It seeks to promote a greater understanding of brigade-level command and to rehabilitate Vokes's reputation as a commander, which has largely been based on certain negative personality traits. The author argues that Yokes was a successful commander because he maintained a good balance between technical skills such as planning and directing operations and his ability to understand, motivate, and lead soldiers, and because his actions were guided by a sound philosophy of command based on personal leadership and teamwork. These elements allowed Christopher Yokes to train and lead a highly effective and cohesive fighting force that defeated some of Germany's best troops in the physically demanding environment of the Sicilian battlefield
Founders: Christopher Taylor
No full text\ua9 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. ‘Founders’ is an intermittent series of short, critical appreciations of scholars, researchers and others whose work and ideas, mainly in Britain, have made particularly sweeping, influential and foundational contributions to the development of historically- and archaeologically-informed landscape studies. This latest addition to the series concerns Christopher Taylor, whose death on 28th May 2021 was noted in the Landscapes editorial in issue 21.2
Pannexin-1 and P2X7-Receptor Are Required for Apoptotic Osteocytes in Fatigued Bone to Trigger RANKL Production in Neighboring Bystander Osteocytes
No full textOsteocyte apoptosis is required to induce intracortical bone remodeling after microdamage in animal models, but how apoptotic osteocytes signal neighboring “bystander” cells to initiate the remodeling process is unknown. Apoptosis has been shown to open pannexin-1 (Panx1) channels to release adenosine diphosphate (ATP) as a “find me” signal for phagocytic cells. To address whether apoptotic osteocytes use this signaling mechanism, we adapted the rat ulnar fatigue-loading model to reproducibly introduce microdamage into mouse cortical bone and measured subsequent changes in osteocyte apoptosis, receptor activator of NF-kB ligand (RANKL) expression and osteoclastic bone resorption in wild-type (WT; C57Bl/6) mice and in mice genetically deficient in Panx1 (Panx1KO). Mouse ulnar loading produced linear microcracks comparable in number and location to the rat model. WT mice showed increased osteocyte apoptosis and RANKL expression at microdamage sites at 3 days after loading and increased intracortical remodeling and endocortical tunneling at day 14. With fatigue, Panx1KO mice exhibited levels of microdamage and osteocyte apoptosis identical to WT mice. However, they did not upregulate RANKL in bystander osteocytes or initiate resorption. Panx1 interacts with P2X7R in ATP release; thus, we examined P2X7R-deficient mice and WT mice treated with P2X7R antagonist Brilliant Blue G (BBG) to test the possible role of ATP as a find-me signal. P2X7RKO mice failed to upregulate RANKL in osteocytes or induce resorption despite normally elevated osteocyte apoptosis after fatigue loading. Similarly, treatment of fatigued C57Bl/6 mice with BBG mimicked behavior of both Panx1 KO and P2X7RKO mice; BBG had no effect on osteocyte apoptosis in fatigued bone but completely prevented increases in bystander osteocyte RANKL expression and attenuated activation of resorption by more than 50%. These results indicate that activation of Panx1 and P2X7R are required for apoptotic osteocytes in fatigued bone to trigger RANKL production in neighboring bystander osteocytes and implicate ATP as an essential signal mediating this process.Peer reviewe
The effects of estrogen deficiency on cortical bone microporosity and mineralization
No full textRecent studies have demonstrated matrix-mineral alterations in bone tissue surrounding osteocytes in estrogen-deficient animals.While cortical bone porosity has been shown to be a contributor to the mechanical properties of bone tissue, little analysis has been done to investigate the effects of estrogen deficiency on bone's microporosities, including the vascular and osteocyte lacunar porosities. In this study we examined alterations in cortical bone microporosity, mineralization, and cancellous bone architecture due to estrogen deficiency in the ovariectomized rat model of postmenopausal osteoporosis. Twenty-week-old female Sprague–Dawley rats were subjected to either ovariectomy or sham surgery. Six weeks post-surgery tibiae were analyzed using high-resolution micro-CT, backscattered electron imaging, nanoindentation, and dynamic histomorphometry. Estrogen deficiency caused an increase in cortical bone vascular porosity, with enlarged vascular pores and little change in tissue mineral density in the proximal tibial metaphysis. Measurements of cancellous architecture corresponded to previous studies reporting a decrease in bone volume fraction, an increase in trabecular separation, and a decrease in trabecular number in the proximal tibia due to estrogen deficiency. Nanoindentation results showed no differences in matrix stiffness in osteocyte-rich areas of the proximal tibia of estrogen-deficient rats, and bone labeling and backscattered electron imaging showed no significant changes in mineralization around the vascular pores. The findings demonstrate local surface alterations of vascular pores due to estrogen deficiency. An increase in cortical vascular porosity may diminish bone strength as well as alter bone mechanotransduction via interstitial fluid flow, both of which could contribute to bone fragility during postmenopausal osteoporosis.Peer reviewe
Heritability and Linkage Analysis of Appendicitis Utilizing Age at Onset
No full textAppendicitis usually afflicts the young, but there is a large tail in the distribution of onset age. The genetics of this disease are still not well understood. A heritability analysis and genome wide linkage analysis of a large twin dataset was undertaken. Treating age of onset of appendicitis as a censored survival trait revealed a heritability of 0.21, and found evidence of linkage to Chromosome 1p37.3. Author(s): Christopher Oldmeadow 1 * | Kerrie Mengersen 2 | Nicholas Martin 3 | David L. Duffy
A New “Quasi-Dynamic” Method for Determining the Hamaker Constant of Solids Using an Atomic Force Microscope
No full textIn order to minimize the effects
of surface roughness and deformation,
a new method for estimating
the Hamaker constant, A, of solids using the approach-to-contact
regime of an atomic force microscope (AFM) is presented. First, a
previous “jump-into-contact” quasi-static method for
determining A from AFM measurements is analyzed and
then extended to include various AFM tip-surface force models of interest.
Then, to test the efficacy of the “jump-into-contact”
method, a dynamic model of the AFM tip motion is developed. For finite
AFM cantilever-surface approach speeds, a true “jump”
point, or limit of stability, is found not to appear, and the quasi-static
model fails to represent the dynamic tip behavior at close tip-surface
separations. Hence, a new “quasi-dynamic” method for
estimating A is proposed that uses the dynamically
well-defined deflection at which the tip and surface first come into
contact, dc, instead of the dynamically
ill-defined “jump” point. With the new method, an apparent
Hamaker constant, Aapp, is calculated
from dc and a corresponding quasi-static-based
equation. Since Aapp depends on the cantilever’s
approach speed, vc, and the AFM’s
sampling resolution, δ, a double extrapolation procedure is
used to determine Aapp in the quasi-static
(vc → 0) and continuous sampling
(δ → 0) limits, thereby recovering the “true”
value of A. The accuracy of the new method is validated
using simulated AFM data. To enable the experimental implementation
of this method, a new dimensionless parameter τ is introduced
to guide cantilever selection and the AFM operating conditions. The
value of τ quantifies how close a given cantilever is to its
quasi-static limit for a chosen cantilever-surface approach speed.
For sufficiently small values of τ (i.e., a cantilever that
effectively behaves “quasi-statically”), simulated data
indicate that Aapp will be within ∼3%
or less of the inputted value of the Hamaker constant. This implies
that Hamaker constants can be reliably estimated using a single measurement
taken with an appropriately chosen cantilever and a slow, yet practical,
approach speed (with no extrapolation required). This result is confirmed
by the very good agreement found between the experimental AFM results
obtained using this new method and previously reported predictions
of A for amorphous silica, polystyrene, and α-Al2O3 substrates obtained using the Lifshitz method
Evaluation of transmission infrared spectroscopy and digital and optical refractometers to identify low immunoglobulin G concentrations in alpaca serum.
No full textThis study aimed to evaluate the digital Brix and optical serum total protein (STP) refractometers for measuring concentrations of serum immunoglobulin G (IgG) in alpacas and compare them to IgG concentrations measured by the reference method of radial immunodiffusion (RID) assay. The appropriate cutoff point for Brix and STP refractometers and the transmission infrared (TIR) spectroscopy method was determined for low IgG concentrations (< 10 g/L). Serum samples were collected from alpacas (N = 169) and tested by both refractometers. The correlation between Brix % and STP was high [correlation coefficient (r) = 0.99]. However, the correlation coefficients between Brix % and STP with serum RID-IgG concentrations were only 0.56 and 0.55, respectively. Twenty-one (12.4%) of 169 alpaca serum samples had IgG concentrations of < 10 g/L. Using receiver operator characteristic curve (ROC) analysis, the optimal cutoff points for the TIR assay, digital Brix, and optical STP refractometers for assessing low IgG (RID < 10 g/L) were 13 g/L, 8.8%, and 50 g/L, respectively. The TIR assay showed higher sensitivity (Se = 95.2%) and specificity (Sp = 96.8%) than either the digital Brix (Se = 90.5% and Sp = 65.5%) or optical STP (Se = 81% and Sp = 73.7%) refractometers for assessing alpacas with low IgG. In conclusion, the Brix and STP refractometers lack accuracy in measuring alpaca IgG concentrations, but may be useful for screening animals for low serum IgG. However, the TIR assay with a cutoff point of 13 g/L was more appropriate for identifying low IgG than either refractometer. Another study that focuses on neonatal crias is recommended in order to evaluate the usefulness of these assays for field diagnosing of failure of transfer of passive immunity (FTPI).journal article2017 Julimporte
By
No full textii for Karen, my friend, my con dant, my wife. iii iv Acknowledgements The author would like to thank his advisor, Dr. Ronald C. Arkin, for directly supporting this research and for support encompassing the entire period of his enrollment. Special thanks are given to the other committee members: Dr. Christopher G. Atkeson, Dr. Richard J. Leblanc, Dr. Wayne J. Book, and Dr. John T. Stasko for the helpful advice given during the progression of this research and for the time spen
- …
