Diel vertical migration and seasonal timing of the larvae of three sympatric cancrid crabs,Cancer spp., in Southeastern Alaska

Diel vertical migration (DVM) and seasonal timing of three sympatricCancer spp. larvae were investigated in southeastern Alaska. Diel sampling was conducted at a station in Icy Strait at 0400, 0700, 1000, 1300 h in the first day, and 1300, 1600, 1900, and 2200 h in the second day from June to September 2001. Larvae were collected with Bongo nets (333 and 505 μm mesh) towed vertically from 20 m depth to the surface. During flood tides surface temperature increased slightly and salinity decreased; the reverse occurred during ebb tides. Zooplankton biomasses were higher in the early morning and evening than during the midday. A total of 4,482 larvae were examined for the study.Cancer oregonensis larvae were most abundant (4,238), followed byC. magister (205) andC. productus (39). Larval density peaked in June while no larvae were found in September.C. magister larvae had a crepuscular migration; larval abundance peaked in early morning and evening.C. oregonensis larvae comprised 94.6% of allCancer spp. larvae collected and had a strong DVM in June. Earlier zoeal stages ofC. oregonensis were relatively more abundant during midday, while later stages were more abundant at night. In July, later larval stages ofC. oregonensis were distributed at the surface all day with a peak at 2200 h. Larvae ofC. productus first occurred in July and peaked in August.C. productus had DVM but many were at the surface diurnally.C. magister andC. oregonensis larvae co-occurred seasonally as they do in the lower latitudes, e.g., Washington and British Columbia; however,C. productus appeared approximately 2 mo later thanC. magister andC. oregonensis in southeastern Alaska.     

Long-lived coronal structures and recurrent geomagnetic patterns in 1974

Daily measurements of the intensity distribution of the Sun's white-light corona over the height range $\text{1.1–2.7. R}{}_{\mathrm{?}}$ show that the global structure became quite stable (constant over periods of several months) in late 1973 and throughout 1974, as flares, ascending prominences and other transient activity became less frequent with the decline of the solar activity cycle. A highly persistent pattern of geomagnetic activity prevailed for much of this time. Bright coronal structures in the ecliptic plane were associated with geomagnetically quiet conditions, and faint coronal regions (“holes”) with geomagnetic disturbance, after a delay of about three days. These results confirm the “cone-of-avoidance” model for M-regions and reinforce the postulate that high-speed streams in the solar wind originate from coronal holes. Identification of coronal holes from ground-based K-coronal observations corresponds well with those made from spacecraft EUV and X-ray experiments on OSO-7 and Skylab.     

The economic and food security implications of climate change in mali

The study focuses on economic and food security implications of projected climate change on Malian agriculture sector. Climate change projections made by two global circulation models are considered. The analysis focuses on the effects on crops, forages, and livestock and the resultant effects on sectoral economics and risk of hunger in Mali. Results show that under climate change, crop yield changes are in the range of minus 17% to plus 6% at national level. Simultaneously, forage yields fall by 5 to 36% and livestock animal weights are reduced by 14 to 16%. The resultant economic losses range between 70 to $142 million, with producers gaining, but consumers losing. The percentage of population found to be at risk of hunger rises from a current estimate of 34% to an after climate change level of 64% to 72%. A number of policy and land management strategies can be employed to mitigate the effects of climate change. In particular, we investigate the development of heat resistant cultivars, the adoption of existing improved cultivars, migration of cropping pattern, and expansion of cropland finding that they effectively reduce climate change impacts lowering the risk of hunger to as low as 28%.     

Brightness variations of the white light corona during the years 1964–67

Observations of the white light corona were made on over 900 days during the years 1964–67 at heights between 1.125 and 2.0 R with the K-coronameter at Mount Haleakala and Mauna Loa, Hawaii. The brightness distribution of the minimum corona was elliptical with average equatorial intensities three times the polar. Coronal features of the new cycle at 1.125 R occurred predominantly in the sunspot zones at 25–30° latitude and in a high latitude zone which migrated toward the North pole before solar maximum. The brightness of the inner corona doubled over this period and a close association is found between the average corona and 10.7-cm solar radio flux. Electron densities in the equatorial regions were nearly twice those of Van de Hulst's model corona, in agreement with the results of recent eclipse observations.At Hawaii Institute of Geophysics.     

Frictional effects on trapped shelf waves

This paper revisits models of coastal trapped waves and examines them with the inclusion of friction. In addition we use a numerical method which at least theoretically will have enhanced accuracy. The model has continuous stratification and variable depth. It is linear, quasigeostrophic and hydrostatic, and utilizes perturbation from this fundamental state. The model is applied with both idealized and realistic topography and stratification.Responsible Editior: Phil Dyke     

Global distribution of filaments during solar cycle No. 20

By tracing the positions of filaments on the solar disk for a series of consecutive Carrington rotations, one can make a compact representation of the changes in general topology of photospheric magnetic fields during the course of a solar cycle. Examples are shown for the time period 1964–1974, which may provide some insight into the long-term relationship of the mid-latitude diagonal filaments and the high latitude polar crown.     

The bulk mineralogy,elemental composition,and water content of the Winchcombe CM chondrite fall

On the microscale, the Winchcombe CM carbonaceous chondrite contains a number of lithological units with a variety of degrees of aqueous alteration. However, an understanding of the average hydration state is useful when comparing to other meteorites and remote observations of airless bodies. We report correlated bulk analyses on multiple subsamples of the Winchcombe meteorite, determining an average phyllosilicate fraction petrologic type of 1.2 and an average water content of 11.9 wt%. We show the elemental composition and distribution of iron and iron oxidation state are consistent with measurements from other CM chondrites; however, Winchcombe shows a low Hg concentration of 58.1 ± 0.5 ng g⁻¹. We demonstrate that infrared reflectance spectra of Winchcombe are consistent with its bulk modal mineralogy, and comparable to other CM chondrites with similar average petrologic types. Finally, we also evaluate whether spectral parameters can estimate H/Si ratios and water abundances, finding generally spectral parameters underestimate water abundance compared to measured values.     

A Self-tuning Robust Control System for nonlinear real-time hybrid simulation

In a real-time hybrid simulation, a transfer system is used to enforce the interface interaction between computational and physical substructures. A model-based, multilayer nonlinear control system is developed to accommodate extensive performance variations and uncertainties in a physical substructure. The aim of this work is to extend the application of real-time hybrid simulation to investigating failure, nonlinearity, and nonstationary behavior. This Self-tuning Robust Control System (SRCSys) consists of two layers: robustness and adaptation. The robustness layer synthesizes a nonlinear control law such that the closed-loop dynamics perform as intended under a broad range of parametric and nonparametric uncertainties. Sliding mode control is employed as the control scheme in this layer. Then, the adaptation layer reduces uncertainties at run time through slow and controlled learning of the control plant. The tracking performance of the SRCSys is evaluated in two experiments that have highly uncertain physical specimens.