64 research outputs found
Visualization of Active Faulting using 3-D GPR Data Recorded Across the Alpine Fault, New Zealand
Three-dimensional (3-D) GPR data were acquired
across braided river sediments cut by the Alpine Fault at Calf
Paddock, New Zealand. We used 100 MHz antennas to obtain
images of the subsurface to a depth of 15 m. Cross-sections and
depth-converted time slices selected from the migrated data volume
show both the structural contrast generated by recent offsets
of the fault and the variable orientation of the dipping structures
within the braided river deposits. A trace-correlation technique is
used to generate dip and dip-direction attribute maps that allow us
to visualize the 3-D orientation of the dipping structures. The
attribute maps reveal at least 3 different reflection patterns and the
presence of minor faulting away from the main fault. A correlation-
based migration technique applied to a 2-D GPR profile resulted
in the successful identification of the main fault and subsidiary
faults at distances up to 50 m from the main fault
Subsequent cultivation of chondrocytes and mesenchymal stem cells on the devitalised tissue
The regeneration of cartilage lesions still represents a major challenge.
Cartilage has a tissue-specific architecture, complicating recreation by
synthetic biomaterials. A novel approach for reconstruction is the use of
devitalised cartilage. Treatment with high hydrostatic pressure (HHP) achieves
devitalisation while biomechanical properties are remained. Therefore, in the
present study, cartilage was devitalised using HHP treatment and the potential
for revitalisation with chondrocytes and mesenchymal stem cells (MSCs) was
investigated. The devitalisation of cartilage was performed by application of
480âMPa over 10âminutes. Effective cellular inactivation was demonstrated by
the trypan blue exclusion test and DNA quantification. Histology and electron
microscopy examinations showed undamaged cartilage structure after HHP
treatment. For revitalisation chondrocytes and MSCs were cultured on
devitalised cartilage without supplementation of chondrogenic growth factors.
Both chondrocytes and MSCs significantly increased expression of cartilage-
specific genes. ECM stainings showed neocartilage-like structure with positive
AZAN staining as well as collagen type II and aggrecan deposition after three
weeks of cultivation. Our results showed that HHP treatment caused
devitalisation of cartilage tissue. ECM proteins were not influenced, thus,
providing a scaffold for chondrogenic differentiation of MSCs and
chondrocytes. Therefore, using HHP-treated tissue might be a promising
approach for cartilage repair
Crustal constraint through complete model space screening for diverse geophysical datasets facilitated by emulation
Deep crustal constraint is often carried out using deterministic inverse methods, sometimes using seismic refraction, gravity and electromagnetic datasets in a complementary or âjointâ scheme. With increasingly powerful parallel computer systems it is now possible to apply joint inversion schemes to derive an optimum model from diverse input data. These methods are highly effective where the uncertainty in the system is small. However, given the complex nature of these schemes it is often difficult to discern the uniqueness of the output model given the noise in the data, and the application of necessary regularization and weighting in the inversion process means that the extent of user prejudice pertaining to the final result may be unclear. We can rigorously address the subject of uncertainty using standard statistical tools but these methods also become less feasible if the prior model space is large or the forward simulations are computationally expensive. We present a simple Monte Carlo scheme to screen model space in a fully joint fashion, in which we replace the forward simulation with a fast and uncertainty-calibrated mathematical function, or emulator. This emulator is used as a proxy to run the very large number of models necessary to fully explore the plausible model space. We develop the method using a simple synthetic dataset then demonstrate its use on a joint data set comprising first-arrival seismic refraction, MT and scalar gravity data over a diapiric salt body. This study demonstrates both the value of a forward Monte Carlo approach (as distinct from a search-based or conventional inverse approach) in incorporating all kinds of uncertainty in the modelling process, exploring the entire model space, and shows the potential value of applying emulator technology throughout geophysics. Though the target here is relatively shallow, the methodology can be readily extended to address the whole crust
Cube law, condition factor and weight-length relationships: history, meta-analysis and recommendations
This study presents a historical review, a meta-analysis, and recommendations for users about weightâlength relationships, condition factors and relative weight equations. The historical review traces the developments of the respective concepts. The meta-analysis explores 3929 weightâlength relationships of the type W = aLb for 1773 species of fishes. It shows that 82% of the variance in a plot of log a over b can be explained by allometric versus isometric growth patterns and by different body shapes of the respective species. Across species median b = 3.03 is significantly larger than 3.0, thus indicating a tendency towards slightly positive-allometric growth (increase in relative body thickness or plumpness) in most fishes. The expected range of 2.5 < b < 3.5 is confirmed. Mean estimates of b outside this range are often based on only one or two weightâlength relationships per species. However, true cases of strong allometric growth do exist and three examples are given. Within species, a plot of log a vs b can be used to detect outliers in weightâlength relationships. An equation to calculate mean condition factors from weightâlength relationships is given as Kmean = 100aLbâ3. Relative weight Wrm = 100W/(amLbm) can be used for comparing the condition of individuals across populations, where am is the geometric mean of a and bm is the mean of b across all available weightâlength relationships for a given species. Twelve recommendations for proper use and presentation of weightâlength relationships, condition factors and relative weight are given
Verification of velocity-resistivity relationships derived from structural joint inversion with borehole data
We present results of three-dimensional joint inversion of seismic, magnetotelluric, and gravity data over a marine salt dome. Such structures are difficult to image with a single method, and our results demonstrate how combining different techniques can yield improved results. More importantly, we examine the reliability of velocity-conductivity relationships derived from structure-coupled joint inversion approaches. Comparison with a seismic reflection section shows that our models match the upper limit of the salt. Furthermore, velocity and resistivity logs from a borehole drilled into the salt dome's flank match, within error, those recovered by the inversion. The good match suggests that the difference in length scale does not have a significant effect in this case. This provides a strong incentive to incorporate borehole data into the joint inversion in the future and substantiates approaches that use the relationships derived from joint inversion models for lithological classification
- âŠ