Seasonal patterns of production in the sandy-beach amphipod Haustorius canadensis

The Haustorius canadensis population at Long Sands beach in southern Maine was studied over a period of 45 months. The length-weight relationship was examined over 24 months; it showed no difference due to either sex or month. Caloric content of the population displayed a seasonal cycle around a mean of 18·381 KJ gm⁻¹ dry weight, peaking in mid to late summer. The increment summation, instantaneous growth, removal summation and size-frequency methods of calculating production were used and the results compared. The increment summation and instantaneous growth methods provided the best estimates of production, averaging 98·1 gm m⁻¹ y⁻¹ and 100·2 gm m⁻¹ y⁻¹, respectively. The annual production to mean biomass ratio averaged 1·48. The population exhibited strong peaks of production; the four summer months accounting for 4·65 times the production during the remainder of the year. Most of the production was due to one-year-old individuals.     

Dual extraction ofR-mode andQ-mode factor solutions

It is mathematically possible to extract both R-mode and Q-mode factors simultaneously (RQ-mode factor analysis)by invoking the Eckhart-Young theorem. The resulting factors will be expressed in measures determined by the form of the scalings that have been applied to the original data matrix. Unless the measures for both solutions are meaningful for the problem at hand, the factor results may be misleading or uninterpretable. Correspondence analysis uses a symmetrical scaling of both rows and columns to achieve measures of proportional similarity between objects and variables. In the literature, the resulting similarity is a χ ² distance appropriate for analysis of enumerated data, the original application of correspondence analysis. Justification for the use of this measure with interval or ratio data is unconvincing, but a minor modification of the scaling procedure yields the profile similarity, which is an appropriate measure. Symmetrical scaling of rows and columns is unnecessary for RQ-mode factor analysis. If the data are scaled so the minor product W'Wis the correlation matrix, the major product WW'is expressed in the Euclidean distances between objects. Therefore, RQ-mode factor analysis can be performed so that the Rmode is a principal components solution and the Qmode is a principal coordinates solution. For applications where the magnitudes of differences are important, this approach will yield more interpretable results than will correspondence analysis.     

A systematic hailpad calibration procedure for operational hail suppression in Greece

Summary Hailpads are used to provide quantitative hailfall measurements in several hail experiments and hail suppression operations around the world. The dented hailpads record the time-integrated size distribution and concentration of hailfall. In the five-year Greek National Hail Suppression Program (GNHSP) hailpad data have been used to estimate the global (impact) energy of hailswaths for the evaluation of the GNHSP.In this paper a systematic hailpad calibration procedure is developed applicable to operational programs. To meet this objective a calibration experiment has been conducted consisting of several tests to: consider differences between pad types; to examine the effects of ultra violet-light on hailpads for varying periods of time; to investigate the effect of painting and inking of the hailpad surfaces; to consider the effect of analyst's variability, loose hailpad stands, and bouneing; and to develop calibration eqqations. The concluded results seem to justify the design and performance of the hailpad calibration procedure.With 9 Figures     

Drought assessment for the potential of precipitation enhancement in northern Greece

The paper is part of a series earlier studies in which the precipitation enhancement potential in central and northern Greece is assessed. A drought analysis is performed in this study. In particular, the Palmer Drought Severity Index (PDSI) is used for the quantitative estimation of droughts on a monthly basis. Emphasis is placed on drought identification and estimation as well as the severity and areal extent of the phenomenon. The results indicate that there are several drought periods which are common to all stations in central and northern Greece, characterized by significant severity and time duration. There are also a large number of drought periods during the summer months as well as during the winter months.With 7 Figures     

Geochemistry of Precambrian mafic dikes,central Bighorn Mountains,Wyoming, U.S.A.

Precambrian quartz dolerites and metadolerites of the central Bighorn Mountains form dikes that intrude a Precambrian metamorphic and igneous terrane typical of the Laramide uplifts of the middle Rocky Mountains. They have a restricted range of major- and trace-element compositions and are typical of basalts in the middle stages of tholeiitic fractionation. Fractionation in the direction of iron enrichment occurred by removal of plagioclase. Average element concentrations of the two groups are nearly identical to one another, are comparable to those in Archean metabasalts from numerous shield areas, and are intermediate between those of modern oceanic tholeiites and continental tholeiites. These average concentrations suggest a depth of magma generation and thickness of crust intermediate between those for the oceanic and continental environments.     

Screened Auger Sampling: The Technique and Two Case Studies

The screened auger is a laser-slotted, hollow-stem auger through which a representative sample of ground water is pumped from an aquifer and tested for water-quality parameters by appropriate field-screening methods. Screened auger sampling can be applied to ground water quality remedial investigations, providing:(1) a mechanism for determining a monitoring well's optimal screen placement in a contaminant plume; and (2) data to define the three-dimensional configuration of the contaminant plume.
Screened auger sampling has provided an efficient method for investigating hexavalent chromium and volatile organic compound contamination in two sandy aquifers in Cadillac, Michigan. The aquifers approach 200 feet in thickness and more than 1 square mile in area. A series of screened auger borings and monitoring wells was installed, and ground water was collected at 10-foot intervals as the boreholes were advanced to define the horizontal and vertical distribution of the contaminant plumes. The ability of the screened auger to obtain representative ground water samples was supported by the statistical comparison of field screening results and subsequent laboratory analysis of ground water from installed monitoring wells.     

Source parameters of mining-induced seismic events: An evaluation of homogeneous and inhomogeneous faulting models for assessing damage potential

Source parameter estimates based on the homogeneous and inhomogeneous source models have been examined for an anomalous sequence of seven mine-induced events located between 640 and 825 m depth at Strathcona mine, Ontario, and having magnitudes ranging betweenm _N 0.8 and 2.7. The derived Brune static stress drops were found to be similar to those observed for natural earthquakes (30 bars), whereas dynamic stress drops were found to range up to 250–300 bars. Source radii derived from Madariaga's model better fit documented evidence of underground damage. These values of source radii were similar to those observed for the inhomogeneous model. The displacement at the source, based on the observed attenuation relationship, was about 60 mm for three magnitude 2.7 events. This is in agreement with slip values calculated using peak velocities and assuming the asperity as a Brune source within itself (72 mm). By using Madariaga's model for the asperity, the slip was over 3 times larger than observed. Peak velocity and acceleration scaling relations with magnitude were investigated by incorporating available South African data, appropriately reduced to Canadian geophysical conditions. The dynamic stress drop scaled as the square root of the seismic moment, similar to reported results in the literature for crustal earthquakes. This behavior suggests that the size of the asperities responsible for the peak ground motion, with respect to the overall source size, follow distributions that may be similar over a wide range of magnitudes. Measurements of source rupture complexity (ranging from 2 to 4) were found to agree with estimates of overall source to asperity radii, suggesting, together with the observed low rupture velocities (0.3 to 0.6 ), that the sources were somewhat complex. Validation of source model appropriateness was achieved by direct comparison of the predicted ground motion level to observed underground damage in Creighton mine, located within the same regional stress and geological regime as Strathcona mine. Close to the source (<100 m), corresponding to relatively higher damage levels, a good agreement was found between the predicted peak particle velocities for the inhomogeneous model and velocities derived based on established geomechanical relationships. The similarity between asperity radii and the regions of the highest observed damage provided additional support for the use of the inhomogeneous source model in the assessment of damage potential.     

Migrant worker centers: contending with downgrading in the low-wage labor market

Mass migration to major USA cities is reworking patterns of ethnic jobholding and labor market segmentation. Employers in a variety of industries have turned to recent migrants, many of whom are not authorized to work in the USA, as a stable labor supply for low-wage jobs. As a result, many migrant workers enter urban economies through precarious jobs in low-wage industries and the informal economy where they often endure routine violations of labor and employment laws. This paper examines the activities of a “migrant worker center” in improving wages and working conditions in migrant labor markets. Through a case study of a worker center located in a port-of-entry immigrant neighborhood on Chicago’s Southwest Side, we examine the geographies of the low-wage labor market and the problems that have arisen for workers who hold jobs that effectively exist beyond the reach of government regulation. We argue that migrant worker centers will likely emerge as a key resource for workers who are drawn to global cities by the promise of economic opportunity yet confront harsh conditions in the local labor markets in which they are employed.