An observation on Carnapʼs Continuum and stochastic independencies

We characterize those identities and independencies which hold for all probability functions on a unary language satisfying the Principle of Atom Exchangeability. We then show that if this is strengthen to the requirement that Johnson's Sufficientness Principle holds, thus giving Carnap's Continuum of inductive methods for languages with at least two predicates, then new and somewhat inexplicable identities and independencies emerge, the latter even in the case of Carnap's Continuum for the language with just a single predicate

A review of size and geometrical factors influencing resonant frequencies in metamaterials

Although metamaterials and so-called left-handed media have originated from theoretical considerations, it is only by their practical fabrication and the measurement of their properties that they have gained credibility and can fulfil the potential of their predicted properties. In this review we consider some of the more generally applicable fabrication methods and changes in geometry as they have progressed, exhibiting resonant frequencies ranging from radio waves to the visible optical region

Generalized seniority from random Hamiltonians

We investigate the generic pairing properties of shell-model many-body Hamiltonians drawn from ensembles of random two-body matrix elements. Many features of pairing that are commonly attributed to the interaction are in fact seen in a large part of the ensemble space. Not only do the spectra show evidence of pairing with favored J=0 ground states and an energy gap, but the relationship between ground state wave functions of neighboring nuclei show signatures of pairing as well. Matrix elements of pair creation/annihilation operators between ground states tend to be strongly enhanced. Furthermore, the same or similar pair operators connect several ground states along an isotopic chain. This algebraic structure is reminiscent of the generalized seniority model. Thus pairing may be encoded to a certain extent in the Fock space connectivity of the interacting shell model even without specific features of the interaction required.Comment: 10 pages, 7 figure

Sound produced by the rapidly inflating Santiaguito lava dome, Guatemala

Vertical inflation of the Caliente lava dome at Santiaguito (Guatemala) occurs coincidentally with the onset of explosive eruptions and produces infrasound that is generally peaked between 0.5 and 2 Hz with amplitude of up to 5 Pa (at ∼1 km from vent). Inflation of up to ∼1 m progresses rapidly (within ∼2 s) and can encompass the entire surface of the ∼200-m-diameter dome. We use particle image velocimetry to quantify the time history of dome uplift and demonstrate that deflection of a volcano's solid surface can generate infrasound waves with amplitudes of a few Pa. The volumetric displacement history is used to model linear volumetric acoustic sources, both compact and of finite extent. Synthetic waveforms match recorded infrasound in terms of timing and frequency content. Amplitude fit is very good for a station located 3.3 km from the vent and less good for stations shielded by near vent topography

Influence of previous crops and nematicide treatments on root lesion nematode populations and crop yields

Nous avons étudié au champ l'influence du précédent cultural, de la séquence culturelle et de traitements à l'aldicarbe sur les populations de nematodes des nodosités et sur les rendements de diverses cultures à l'île-du Prince-Édouard. La culture précédente a eu le plus grand impact sur le nombre de nematodes. Les séquences des cultures ont parfois eu une influence sur les populations de nematodes des nodosités (principalement Pratylenchus penetrans) et sur les rendements. Dans les champs commerciaux d'orge (Hordeum vulgare), les nematodes des nodosités étaient plus nombreux lorsque l'orge suivait une culture combinée de trèfle rouge (Trifolium pratense) et de fléole (Phleum pratense) et les nematodes du rabougrissement (Tylenchorynchus spp., principalement T. dubiuset Merlinius spp.) étaient plus nombreux quand l'orge était semée pendant deux années consécutives. La masse de la matière sèche combinée du feuillage et du grain était plus importante lorsque l'orge était semée auprès des pommes de terre (Solanum tuberosum) et cette masse était plus faible avec deux cultures successives d’orge ou avec un mélange de trèfle rouge et de fléole. En conditions expérimentales au champ, les populations de nématodes des nodosités étaient plus élevées dans les racines d’orge lorsque celle-ci était cultivée après des pommes de terre et les rendements en grain étaient plus faibles lorsque l’orge était cultivée pendant deux années consécutives. Les changements dans les populations de nématodes chez la pomme de terre n’étaient pas associés aux séquences débutant avec le blé (Triticum aestivum) ou l’orge que dans les séquences débutant avec les pommes de terre ou le soya (Glycine max). L’aldicarbe a réduit le nombre de nématodes des nodosités en plus d’accroître les rendements en pommes de terre et en soya.A field study assessing the influence of the previous crop, the crop sequence, and aldicarb treatments on root lesion nematode populations and crop yields was carried out in Prince-Edward-Island, Canada. The most recent crop had the greatest impact on nematode numbers. The crop sequences had an influence in some cases on root lesion nematode populations (primarily Pratylenchus penetrans) and on crop yields. In commercial barley (Hordeum vulgare) fields, root lesion nematodes in roots were greatest when barley followed a red clover (Trifolium pratense) timothy (Phleum pratense) ley, and stunt nematodes (Tylenchorhynchus spp., primarily T. dubius, and Merlinius spp.) were more common when barley followed barley. The combined dry weight of foliage and grain was larger when barley was planted after potato (Solanumtuberosum) and smaller when barley followed barley or a red clover-timothy mixture. Under experimental field conditions, root lesion nematode populations were largest in barley roots when barley followed potato and grain yields were smallest when barley followed barley. Changes in nematode populations in potato were not associated with crop sequences. Potato tuber yields were higher in the sequences that began with wheat (Triticum aestivum) or barley than in the sequences that began with potato or soybean (Glycine max). Aldicarb reduced the numbers of root lesion nematodes in roots with concomitant yield increases in potato and soybean

Local Charge Excesses in Metallic Alloys: a Local Field Coherent Potential Approximation Theory

Electronic structure calculations performed on very large supercells have shown that the local charge excesses in metallic alloys are related through simple linear relations to the local electrostatic field resulting from distribution of charges in the whole crystal. By including local external fields in the single site Coherent Potential Approximation theory, we develop a novel theoretical scheme in which the local charge excesses for random alloys can be obtained as the responses to local external fields. Our model maintains all the computational advantages of a single site theory but allows for full charge relaxation at the impurity sites. Through applications to CuPd and CuZn alloys, we find that, as a general rule, non linear charge rearrangements occur at the impurity site as a consequence of the complex phenomena related with the electronic screening of the external potential. This nothwithstanding, we observe that linear relations hold between charge excesses and external potentials, in quantitative agreement with the mentioned supercell calculations, and well beyond the limits of linearity for any other site property.Comment: 11 pages, 1 table, 7 figure

The Predictive Validity of the Early Warning System Tool

The Early Warning System (EWS) is a tool developed by the National High School Center to collect data on indicators including attendance, GPA, course failures and credits earned. These indicators have been found to be highly predictive of a student’s likelihood of dropping out of high school in large, urban areas. The EWS tool was studied in two suburban schools. With the exception of attendance data, findings suggest that the indicators and suggested threshold for risk determination are predictive in suburban contexts

Volcanic eruptions, lightning, and a waterfall: Differentiating the menagerie of infrasound in the Ecuadorian jungle

In northeastern Ecuador, near Reventador Volcano, the airwaves are filled with infrasound. Here we identify the locations and characterize three distinct sources of local infrasound, including two types of infrasonic sources, which are not commonly discussed in the literature. The first of these novel sources is an intense and continuous radiator with a fixed location corresponding to San Rafael Waterfall. The signal from the river exhibits a tremor-like envelope that is well correlated across the 3-element infrasound network. Beyond the river, we also observe and map spatially variable sources corresponding to thunder. These transient signals have impulsive onsets, but are not well correlated across the network and are attributable to spatially-distributed source regions. Finally, we identify plentiful infrasound corresponding to Reventador's volcanic vent that is associated with unrest. This study demonstrates the utility of dispersed infrasound networks for distinguishing variable sources and improving interpretation of mechanisms of infrasound radiators

Degassing explosions at Karymsky Volcano, Kamchatka

During the summer of 1997, Karymsky Volcano produced summit explosions about six times each hour. Typical explosive episodes lasted between 30 seconds and three minutes, produced gas and ash columns several hundred meters high, and ejected some incandescent material. To better understand the physical source mechanisms responsible, we recorded hundreds of explosions with a three component broad-band seismometer and microphone located 1650 meters from the active vent. Nearly every explosion is recorded as an emergent yet identical seismic wavelet which is followed 4.15 s later by an impulsive acoustic arrival. We interpret the signals as a near-surface gas volume burst which fractures the vent 'plug,' lowers the lithostatic pressure within the magma column, and often induces further degassing. When degassing continues, it is generally manifested as either a series of regular one second 'chugging' explosions, steady higher frequency 'jetting', or a hybrid combination. We believe that the seismic signature for 'chugs,' short duration harmonic tremor with integer overtones, is the result of repeated gas volume bursts at the vent. In contrast, seismograms for jetting are non-harmonic and contain higher frequencies. We believe that the competing degassing behaviors are influenced by the gas flux as well as the plug/conduit characteristics. We propose that a plug exists due to a viscosity gradient caused by volatile depletion in the upper conduit.During the summer of 1997, Karymsky Volcano produced summit explosions about six times each hour. Typical explosive episodes lasted between 30 seconds and three minutes, produced gas and ash columns several hundred meters high, and ejected some incandescent material. To better understand the physical source mechanisms responsible, we recorded hundreds of explosions with a three component broad-band seismometer and microphone located 1650 meters from the active vent. Nearly every explosion is recorded as an emergent yet identical seismic wavelet which is followed 4.15 s later by an impulsive acoustic arrival. We interpret the signals as a near-surface gas volume burst which fractures the vent 'plug', lowers the lithostatic pressure within the magma column, and often induces further degassing. When degassing continues, it is generally manifested as either a series of regular one second 'chugging' explosions, steady higher frequency 'jetting', or a hybrid combination. We believe that the seismic signature for 'chugs,' short duration harmonic tremor with integer overtones, is the result of repeated gas volume bursts at the vent. In contrast, seismograms for jetting are non-harmonic and contain higher frequencies. We believe that the competing degassing behaviors are influenced by the gas flux as well as the plug/conduit characteristics. We propose that a plug exists due to a viscosity gradient caused by volatile depletion in the upper conduit