Lack Of Confinement Research Articles

Moment tensor inversion of single-hole mining cast blasts

We carried out a controlled field experiment to characterize the single-hole shots typically used in multishot mining blasts. Eight single-hole mining shots were detonated on an overburden bench, and near-source (49–54 m) ground accelerations were recorded. The sources were characterized by their cylindrical geometry, proximity (6 m) to an 11-m vertical free face and the Earth’s free surface, and lack of confinement at the horizontal free surface and the vertical free face. Charge sizes ranged from 59 to 296 kg. The ground motion data, supplemented with standard refraction data, were used to constrain the local velocity model. The resultant Green’s functions and the observational data were used to invert for the second-order, time-dependent source moment tensors with a frequency domain method. Despite the large isotropic component (~80 per cent), the source moment tensors show a significant degree of asymmetry among the diagonal components. The first peak of the vertical component M33 is 39 per cent (±15 per cent) larger than the first peaks of the two horizontal components, which have similar amplitudes. This observation cannot be explained by the cylindrical geometry of the source or the presence of the vertical free face in the source region. The complex source time history, an associated spectral peak and the increase of the degree of asymmetry with time among diagonal moment tensor components are indicative of secondary source effects. Together with the source asymmetry, they could be explained by the effects of a vertical spall source that includes both the vertical cast of the burden and, more importantly, the vertical spallation of the strata around the source. The horizontal cast of the burden was not resolved in the inverted source moment tensors, possibly due to their long period and low seismic efficiency. Although the off-diagonal moment tensor components are much smaller than the diagonal components, they contribute significantly to the seismic wave generation. Further studies are required to interpret their generating mechanisms.

Interpreting Settlement Profiles of Earth Dams

This paper presents a general framework for interpreting the settlement profiles measured along the cross section of an earth dam during the construction stages. Dams showing asymmetric profiles are schematically viewed as one-dimensional nonhomogeneous fill, with variable stiffness or unit weight. The results of one-dimensional analyses are used as a reference to discuss the effects of geometrical factors, like load transfer and lack of confinement, in two-dimensional plane-strain problems. In this way, it is possible to outline the factors affecting the shape of the settlement profile in both homogeneous and zoned earth dams. To show its practical usefulness, this conceptual procedure is used to interpret the behavior of two case histories: the zoned dams of Kastraki and Beliche. These two interpretations also provide some indications about back-analysis procedures deemed more appropriate to analyze in detail the dam behavior.

StrangeS-wave excitation of the Nambu-Jona-Lasinio soliton

The recently developed method to investigate mesonic fluctuations off the chiral soliton in the Nambu-Jona-Lasinio model is applied to kaons in the $S$-wave channel. It is shown that for commonly accepted choices of parameters the presence of the soliton and the lack of confinement in this model provide an unphysical (valence) quark threshold which is lower than the kaon mass. Choosing parameters such that this threshold is avoided, a bound state is obtained in the $S$-wave channel. After semiclassical quantization this state acquires the quantum numbers of an odd parity $\ensuremath{\Lambda}$ and is predicted at about 420 MeV above the nucleon mass.

Coupled fermion gap and vertex equations for chiral-symmetry breakdown in QCD.

The fermion gap equation for QCD is usually posed as a simple variant of the Baker-Johnson-Willey equation, with {ital ad} {ital hoc} cutoffs for infrared singularities in the running charge imposed as needed, and no confinement effects taken into account. While we too omit confinement effects, we replace the {ital ad} {ital hoc} cutoffs with a physically consistent picture of QCD, with a dynamically generated gluon mass {ital m} serving as an infrared regulator, and study not only the fermion gap equation but also nonlinear vertex equations which determine the running charge. Fermion loops are included in the vertex equations, which allows us to study the dependence of {alpha}{sub {ital s}}({ital q}{sup 2}) on the fermion constituent mass {ital M}. As one might expect from the one-loop running charge, {alpha}{sub {ital s}}(0) is an increasing function of {ital M}. When we use a standard form of the fermion gap equation and leave out all confinement effects, the relations between {alpha}{sub {ital s}}(0) and {ital M} which follow from the gap equation and the vertex equation are inconsistent with each other, for any value of the gluon mass {ital m}. Although our model is crude, this suggests that confinement plays anmore » important role in chiral-symmetry breakdown in QCD. Furthermore, lack of confinement above the deconfining temperature may explain why the chiral-symmetry-restoration temperature is so close to the deconfining temperature.« less

Lack of confinement in SU(2) lattice gauge theory with an unbounded action.

Numerical simulations of SU(2) lattice gauge theory are performed using an action which has the same continuum limit as the Wilson action, but which is infinite for negative values of the plaquette variable, and therefore unbounded from above. The weak-coupling behavior matches that of the Wilson action theory, but they differ markedly at strong coupling. The interquark potential at all couplings is well fit by a logarithmically modified Coulomb potential, in concert with asymptotic freedom. Wilson loops are finite in the strong-coupling limit, suggesting that the theory reaches a finite renormalized infrared fixed point, possibly without ever entering a linear confining phase. A likely reason for the difference in the theories is that single-plaquette vortices and monopoles are absent in the alternative formulation, although such structures may still occur at larger scales.

Human reticular formation: Cholinergic neurons of the pedunculopontine and laterodorsal tegmental nuclei and some cytochemical comparisons to forebrain cholinergic neurons

Choline acetyltransferase immunohistochemistry showed that the human rostral brainstem contained cholinergic neurons in the oculomotor, trochlear, and parabigeminal nuclei as well as within the reticular formation. The cholinergic neurons of the reticular formation were the most numerous and formed two intersecting constellations. One of these, designated Ch5, reached its peak density within the compact pedunculopontine nucleus but also extended into the regions through which the superior cerebellar peduncle and central tegmental tract course. The second constellation, designated Ch6, was centered around the laterodorsal tegmental nucleus and spread into the central gray and medial longitudinal fasciculus. There was considerable transmitter-related heterogeneity within the regions containing Ch5 and Ch6. In particular, Ch6 neurons were intermingled with catecholaminergic neurons belonging to the locus coeruleus complex. The lack of confinement within specifiable cytoarchitectonic boundaries and the transmitter heterogeneity justified the transmitter-specific Ch5 and Ch6 nomenclature for these two groups of cholinergic neurons. The cholinergic neurons in the nucleus basalis (Ch4) and those of the Ch5-Ch6 complex were both characterized by perikaryal heteromorphism and isodendritic arborizations. In addition to choline acetyltransferase, the cell bodies in both complexes also had high levels of acetylcholinesterase activity and nonphosphorylated neurofilament protein. However, there were also marked differences in cytochemical signature. For example, the Ch5-Ch6 neurons had high levels of NADPHd activity, whereas Ch4 neurons did not. On the other hand, the Ch4 neurons had high levels of NGF receptor protein, whereas those of Ch5-Ch6 did not. On the basis of animal experiments, it can be assumed that the Ch5 and Ch6 neurons provide the major cholinergic innervation of the human thalamus and that they participate in the neural circuitry of the reticular activating, limbic, and perhaps also extrapyramidal systems.