Interactive software for mapping concentrated displacements in masonry arches

Arches are an important part of the masonry architectural heritage and also serve as infrastructure for bridges and culverts. The behavior testing and structural health monitoring of masonry arches require effective measurement methods. There have been a lot of testing methods applied regarding this subject, among which the vision-based non-destructive methods are very appealing. However, as the demands of measuring accuracy and range increase, the labor and economic costs expand to uneconomical levels. A novel, cheap, and fast measurement strategy which focuses directly on the mechanical failure of masonry arches has been developed. This strategy termed Behavior Mapping (BM) is based on homography and does not require a high-precision camera or extensive experimental setup. A scale dry-stack arch was subjected to repeated collapses through springing displacements during the proof-of-concept development of BM. This generated a huge amount of data and required the development of a MATLAB® based graphical user interface (GUI). The objective of this article is to introduce the GUI and the accompanying data for the purpose of providing educational insight into the behavior of masonry arches. These educational experimental cases integrated in the GUI provide the possibility to better understand the failure mechanism of dry-stone arch under foot displacement, as well to easily identify the occurrence of mechanical joints and determine the value of deformations. This GUI can also be adapted for different arch configurations, as well for further real-time monitoring

A novel fast and low-cost masonry monitoring strategy and application on arches

This work proposes a novel non-destructive, vision-based measurement strategy to identify and quantify mechanical deformations between rigid blocks. First the possible motions between two rigid blocks were identified and measured, under the application of a perpendicular, parallel and symmetrical 4x4 point grid around the masonry joint line. Repeated calculations of lengths, dot products, and right triangles improved the precision of measurements through redundancy. Then, this method was verified via photographic images with defined deformation and 2D holography, showing good adaptability and precision. Finally, this strategy was performed to a video recording of an arch under tilting test until failure. With the dimensions of the points grid being the only known parameter, the mechanical joint, the type of rigid block motion, the failure point and the rotation angle were successfully determined

Revitalizing the Study of Self-Directed Adult Learning

Self-directed learning has been an important research area in adult education for the past three decades, and holds much potential for future scholarship. Three areas for possible future inquiry are examined

Surface Tethered Epidermal Growth Factor Protects Proliferating and Differentiating Multipotential Stromal Cells from FasL-Induced Apoptosis

Multipotential stromal cells or mesenchymal stem cells (MSCs) have been proposed as aids in regenerating bone and adipose tissues, as these cells form osteoblasts and adipocytes. A major obstacle to this use of MSC is the initial loss of cells postimplantation. This cell death in part is due to ubiquitous nonspecific inflammatory cytokines such as FasL generated in the implant site. Our group previously found that soluble epidermal growth factor (sEGF) promotes MSC expansion. Furthermore, tethering EGF (tEGF) onto a two-dimensional surface altered MSC responses, by restricting epidermal growth factor receptor (EGFR) to the cell surface, causing sustained activation of EGFR, and promoting survival from FasL-induced death. sEGF by causing internalization of EGFR does not support MSC survival. However, for tEGF to be useful in bone regeneration, it needs to allow for MSC differentiation into osteoblasts while also protecting emerging osteoblasts from apoptosis. tEGF did not block induced differentiation of MSCs into osteoblasts, or adipocytes, a common default MSC-differentiation pathway. MSC-derived preosteoblasts showed increased Fas levels and became more susceptible to FasL-induced death, which tEGF prevented. Differentiating adipocytes underwent a reduction in Fas expression and became resistant to FasL-induced death, with tEGF having no further survival effect. tEGF protected undifferentiated MSC from combined insults of FasL, serum deprivation, and physiologic hypoxia. Additionally, tEGF was dominant in the face of sEGF to protect MSC from FasL-induced death. Our results suggest that MSCs and differentiating osteoblasts need protective signals to survive in the inflammatory wound milieu and that tEGF can serve this function.National Institute of General Medical Sciences (U.S.) (GM069668)National Institute of Dental and Craniofacial Research (U.S.) (DE019523

Irrecoverable collapse time for a fixed-hinge dry-stack arch under constant horizontal acceleration

The collapse of dry-stack masonry arches results from the transformation of a static system to a mechanical state through the development of mechanical joints. The traditional failure condition is this mechanization through the formation of four-hinges in a kinematically admissible configuration. The first-order analysis of an arche’s seismic capacity is obtained through limit analysis (LA) approaches. One approach is the equilibrium assessment of the kinematic theorem through the use of a kinematic collapse load calculator (KCLC). Utilizing a custom KCLC developed and validated from an experimental arch, with the added control of the single degree-of-freedom rotations, an analytic solution is developed between the applied acceleration and the minimum time duration required for collapse. The collapse multiplier and arch centroid data is recorded for all the admissible conditions that exist in the spatial deformation propagation. From this information, the work required to collapse the arch under kinematic equilibrium is established and utilized to decompose the static and kinematic energy contributions. The time-displacement domain is then defined from the resulting kinematic energy of the overloaded arch and used to evaluate the time where the kinematic energy exceeds the remaining work required for the loss of the kinematically admissible condition. This results in a simple analytical function linking excess static acceleration with a time limit of recovery

Simplified measurement technique for rigid-body deformations of two masonry blocks

Under the traditional rigid-no tension assumptions of dry-stack masonry and the assumption of no out of plane motion, the displacements of the arch can be explicitly defined by the combined set of eight defined motions. The ability to identify and measure these displacements thus provide the opportunity to describe the motion of the system. This work establishes a simplified measurement technique for these common rigid-body displacements between two blocks of a masonry arch in contact

Non-Linear Dynamic Joint Selection Strategy for Hinge Controlled Masonry Arches

Masonry arches are vulnerable to seismic actions. Over the last few years, extensive research has developed strengthening strategies and methods to resist these seismic actions. However, from such studies, it is evident that the application of reinforcement to a masonry arch is done such that its failure limit is transformed from stability to a strength. This direct transformation overlooks the intermittent stages that exist, and thus provides an incomplete picture to the potential behaviors of the system. These intermittent stages can be established through subjecting the arch to hinge control and have shown the potential to increase capacity and control failure, but the computational costs for assessing the nonlinear dynamic behavior of all potential mechanisms is high. This work presents a hinge-joint selection strategy from magnitude variations of short span non-linear dynamic loading through the two-dimensional Discrete Element Method (DEM) based software UDEC. Each voussoir of the arch was represented by a distinct block within the DEM. Mortar joints were modelled as zero thickness interfaces which can open and close. Twenty-five unique configurations of an arch with controlled hinges were developed and each was subjected to short duration seismic velocity profile with varying magnitudes. From this analysis an optimal hinge set with is identified

Renal health after long-term exposure to tenofovir disoproxil fumarate (TDF) in HIV/HBV positive adults in Ghana

Objectives: The study assessed markers of renal health in HIV/HBV co-infected patients receiving TDF- containing antiretroviral therapy in Ghana. Methods: Urinary protein-to-creatinine ratio (uPCR) and albumin-to-protein ratio (uAPR) were measured cross-sectionally after a median of four years of TDF. At this time, alongside extensive laboratory testing, patients underwent evaluation of liver stiffness and blood pressure. The estimated glomerular filtration rate (eGFR) was measured longitudinally before and during TDF therapy. Results: Among 101 participants (66% women, median age 44 years, median CD4 count 572 cells/mm 3 ) 21% and 17% had detectable HIV-1 RNA and HBV DNA, respectively. Overall 35% showed hypertension, 6% diabetes, 7% liver stiffness indicative of cirrhosis, and 18% urinary excretion of Schistosoma antigen. Tubular proteinuria occurred in 16% of patients and was independently predicted by female gender and hypertension. The eGFR declined by median 1.8 ml/min/year during TDF exposure (IQR −4.4, −0.0); more pronounced declines ( ≥5 ml/min/year) occurred in 22% of patients and were associated with receiv-ing ritonavir-boosted lopinavir rather than efavirenz. HBV DNA, HBeAg, transaminases, and liver stiffness were not predictive of renal function abnormalities. Conclusions: The findings mandate improved diagnosis and management of hypertension and suggest targeted laboratory monitoring of patients receiving TDF alongside a booster in sub-Saharan Africa

Long Term Radio Monitoring of SN 1993J

We present our observations of the radio emission from supernova (SN) 1993J, in M 81 (NGC 3031), made with the VLA, from 90 to 0.7 cm, as well as numerous measurements from other telescopes. The combined data set constitutes probably the most detailed set of measurements ever established for any SN outside of the Local Group in any wavelength range. Only SN 1987A in the LMC has been the subject of such an intensive observational program. The radio emission evolves regularly in both time and frequency, and the usual interpretation in terms of shock interaction with a circumstellar medium (CSM) formed by a pre-SN stellar wind describes the observations rather well considering the complexity of the phenomenon. However: 1) The 85 - 110 GHz measurements at early times are not well fitted by the parameterization, unlike the cm wavelength measurements. 2) At mid-cm wavelengths there is some deviation from the fitted radio light curves. 3) At a time ~3100 days after shock breakout, the decline rate of the radio emission steepens without change in the spectral index. This decline is best described as an exponential decay starting at day 3100 with an e-folding time of ~1100 days. 4) The best overall fit to all of the data is a model including both non-thermal synchrotron self-absorption (SSA) and a thermal free-free absorbing (FFA) components at early times, evolving to a constant spectral index, optically thin decline rate, until the break in that decline rate. Moreover, neither a purely SSA nor a purely FFA absorbing models can provide a fit that simultaneously reproduces the light curves, the spectral index evolution, and the brightness temperature evolution. 5) The radio and X-ray light curves exhibit similar behavior and suggest a sudden drop in the SN progenitor mass-loss rate at ~8000 years prior to shock breakout.Comment: 45 pages, 13 figures, accepted for Ap