The electric cone penetration test (CPT) has been in use for over 40 years and is growing in popularity in North America. This paper provides some recent updates on the interpretation of some key ...geotechnical parameters in an effort to develop a more unified approach. Extensive use is made of the normalized soil behaviour type (SBTn) chart based on normalized cone resistance (Q
t
) and normalized friction ratio (F
r
). Updates are provided regarding the normalization process and its application to the identification of soil type. The seismic CPT has provided extensive data linking CPT net cone resistance to shear-wave velocity and soil modulus. New correlations are presented in the form of contours of key parameters on the SBTn chart. These new relationships enable a more unified interpretation of CPT results over a wide range of soils. Updates are also provided in terms of in situ state parameter, peak friction angle, and soil sensitivity. The correlations are evaluated using available laboratory and full-scale field test results. Many of the recommendations contained in this paper are focused on low to moderate risk projects where empirical interpretation tends to dominate. For projects where more advanced methods are more appropriate, the recommendations provided in this paper can be used as a screening to evaluate critical regions-zones where selective additional in situ testing and sampling maybe appropriate.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A soil classification system is used to group soils according to shared qualities or characteristics based on simple cost-effective tests. The most common soil classification systems used in ...geotechnical engineering are based on physical (textural) characteristics such as grain size and plasticity. Ideally, geotechnical engineers would also like to classify soils based on behaviour characteristics that have a strong link to fundamental in situ behaviour. However, existing textural-based classification systems have a weak link to in situ behaviour, since they are measured on disturbed and remolded samples. The cone penetration test (CPT) has been gaining in popularity for site investigations due to the cost-effective, rapid, continuous, and reliable measurements. The most common CPT-based classification systems are based on behaviour characteristics and are often referred to as a soil behaviour type (SBT) classification. However, some confusion exists, since most CPT-based SBT classification systems use textural-based descriptions, such as sand and clay. This paper presents an update of popular CPT-based SBT classification systems to use behaviour-based descriptions. The update includes a method to identify the existence of microstructure in soils, and examples are used to illustrate the advantages and limitations of such a system.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Chemical compounds that may be used as sources for dihydrogen are discussed. In particular, the use of ammonia-borane and related compounds as hydrogen donors are examined.
The Role of Cholesterol in Cancer Kuzu, Omer F; Noory, Mohammad A; Robertson, Gavin P
Cancer research (Chicago, Ill.),
04/2016, Letnik:
76, Številka:
8
Journal Article
Row-crop agriculture is a major source of nitrous oxide (N₂O) globally, and results from recent field experiments suggest that significant decreases in N₂O emissions may be possible by decreasing ...nitrogen (N) fertilizer inputs without affecting economic return from grain yield. We tested this hypothesis on five commercially farmed fields in Michigan, USA planted with corn in 2007 and 2008. Six rates of N fertilizer (0-225 kg N ha⁻¹) were broadcast and incorporated before planting, as per local practice. Across all sites and years, increases in N₂O flux were best described by a nonlinear, exponentially increasing response to increasing N rate. N₂O emission factors per unit of N applied ranged from 0.6% to 1.5% and increased with increasing N application across all sites and years, especially at N rates above those required for maximum crop yield. At the two N fertilizer rates above those recommended for maximum economic return (135 kg N ha⁻¹), average N₂O fluxes were 43% (18 g N₂O-N ha⁻¹ day⁻¹) and 115% (26 g N₂O-N ha⁻¹ day⁻¹) higher than were fluxes at the recommended rate, respectively. The maximum return to nitrogen rate of 154 kg N ha⁻¹ yielded an average 8.3 Mg grain ha⁻¹. Our study shows the potential to lower agricultural N₂O fluxes within a range of N fertilization that does not affect economic return from grain yield.
A method to evaluate the susceptibility of soils to undrained strength loss that could result in flow liquefaction as well as a method to estimate the resulting liquefied undrained shear strength of ...predominately sand-like soils using the cone penetration test (CPT) were outlined by Robertson in 2010. Based on published data and recent case histories, this technical note describes a recommended update to these methods to estimate the large-strain liquefied or remolded undrained shear strength for both sand-like and clay-like soils as well as soils that transition from sand-like to clay-like. The proposed update acknowledges that soil behavior can vary from sand-like to clay-like and that CPT interpretation to estimate large-strain undrained shear strength changes due to the changing drainage conditions during the CPT. The updated method builds upon previously published data combined with recent experience and case histories.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Amine and phosphine adducts are classic examples of compounds synthesized by Lewis acid-Lewis base reactions. An examination of research into new applications for these old compounds is presented.
Despite the widespread interest in direct neuronal reprogramming, the mechanisms underpinning fate conversion remain largely unknown. Our study revealed a critical time point after which cells either ...successfully convert into neurons or succumb to cell death. Co-transduction with Bcl-2 greatly improved negotiation of this critical point by faster neuronal differentiation. Surprisingly, mutants with reduced or no affinity for Bax demonstrated that Bcl-2 exerts this effect by an apoptosis-independent mechanism. Consistent with a caspase-independent role, ferroptosis inhibitors potently increased neuronal reprogramming by inhibiting lipid peroxidation occurring during fate conversion. Genome-wide expression analysis confirmed that treatments promoting neuronal reprogramming elicit an anti-oxidative stress response. Importantly, co-expression of Bcl-2 and anti-oxidative treatments leads to an unprecedented improvement in glial-to-neuron conversion after traumatic brain injury in vivo, underscoring the relevance of these pathways in cellular reprograming irrespective of cell type in vitro and in vivo.
Display omitted
•Oxidative stress is a major hurdle in converting different cell types into neurons•Ferroptosis inhibitors and antioxidants improve direct neuronal reprogramming•Bcl-2 reduces ROS and promotes direct neuronal reprogramming also in vivo•Antioxidants potently improve maturation of induced neurons in vitro and in vivo
By imaging cell fate conversion over time, Gascón, Murenu, and colleagues find that high levels of oxidative stress prevent successful direct neuronal reprogramming, instead causing extensive cell death. They identify inhibitors of ferroptosis, antioxidants, and Bcl-2 as key metabolic agents in improving generation of iNs from a range of somatic cells and in vivo after brain injury.
Whole soil profile assessments of soil C stocks are enormously important for evaluating a soil's potential for sequestering C. Carbon stock measurements are often highly variable, which makes the ...detection of statistically significant differences among different land uses and management systems difficult. A common mistake is to interpret a lack of statistical significance as evidence for the absence of differences. This mistake is costly: failure to identify practices and habitats that accumulate C can affect our understanding of soil C cycling and hide possible sequestration potentials. In this study, we investigated inadequate replication as a major cause of a lack of statistical significance. Power analysis is a well-established statistical tool that allows researchers to infer whether the lack of statistical significance is due to the absence of meaningful differences or due to insufficient replication. We used data from two published studies to illustrate the value of power analysis. In particular, we showed that in these studies the chances of detecting even substantial (e.g., 50%) differences among experimental treatments can be as low as 20 to 60% due to the natural variability in soil C concentrations and stocks. Carbon variability in different soil horizons suggests that statistical analyses of soil C stocks should be conducted separately for each sampled horizon and that conclusions about the profile as a whole should be made based on the individual horizon results. Devising an optimal sampling strategy that identifies the appropriate number of replicates needed to detect significant C change by horizon is essential.
PDF
