CO2 snow depth and subsurface water-ice abundance in the northern hemisphere of Mars

Observations of seasonal variations of neutron flux from the high-energy neutron detector (HEND) on Mars Odyssey combined with direct measurements of the thickness of condensed carbon dioxide by the Mars Orbiter Laser Altimeter (MOLA) on Mars Global Surveyor show a latitudinal dependence of northern winter deposition of carbon dioxide. The observations are also consistent with a shallow substrate consisting of a layer with water ice overlain by a layer of drier soil. The lower ice-rich layer contains between 50 and 75 weight % water, indicating that the shallow subsurface at northern polar latitudes on Mars is even more water rich than that in the south.     

The scanning ion-conductance microscope

A scanning ion-conductance microscope (SICM) has been developed that can image the topography of nonconducting surfaces that are covered with electrolytes. The probe of the SICM is an electrolyte-filled micropipette. The flow of ions through the opening of the pipette is blocked at short distances between the probe and the surface, thus, limiting the ion conductance. A feedback mechanism can be used to maintain a given conductance and in turn determine the distance to the surface. The SICM can also sample and image the local ion currents above the surfaces. To illustrate its potential for imaging ion currents through channels in membranes, a topographic image of a membrane filter with 0.80-micrometer pores and an image of the ion currents flowing through such pores are presented.     

High-pressure and high-temperature experiments on core-mantle segregation in the accreting Earth

The abundances of siderophile elements in the Earth's silicate mantle are too high for the mantle to have been in equilibrium with iron in the core if equilibrium occurred at low pressures and temperatures. It has been proposed that this problem may be solved if equilibrium occurred at high pressures and temperatures. Experimental determination of the distribution of siderophile elements between liquid metal and liquid silicate at 100 kilobar and 2000 degrees C demonstrates that it is unlikely that siderophile element abundances were established by simple metal-silicate equilibrium, which indicates that the segregation of the core from the mantle was a complex process.     

Swedish agriculture at a turning point

This paper gives an overview of the present state of Swedish agriculture and discusses some problems and experiences of general interest. After an introductory section on the characteristics of Swedish agriculture, a number of problems are described, such as social problems, market imbalances, environmental damage, changes in landscape amenities, and animal health. Possible causes of these problems are discussed. Recent attempts to solve the problems as well as the current Swedish debate on more radical changes in agricultural policy are also discussed. The main components of a suggested program are subsidies to farmers based on their acreage of grazed land or grassland and elimination of the present price supports and market regulations.     

Visualization of turbulent flame fronts with planar laser-induced fluorescence

This report concerns the quantitative time-resolved visualization of reaction zones in laminar, transitional, and turbulent nonpremixed flames. Two-dimensional OH molecular concentrations were measured with planar laser-induced fluorescence excited by a sheet of light (formed from a single tunable ultraviolet laser pulse) and detected with a two-dimensional, image-intensified photodiode array camera. From the resulting data details of instantaneous flame front structures (including positions, shapes, and widths) were obtained.     

Parameters of the plasma affecting the radiation of pulsar 1

Analysis of the relation between time delay and frequency for pulses from Pulsar 1 shows that the dispersive region of the ray path must exceed 300 astronomical units and have an average electron number density less than 8000 per cubic centimeter and average magnetic field strength less than 2 x 10(-3) gauss. These requirements almost guarantee that the observed dispersion takes place in the interstellar medium.     

Nitrogen Fertilizer Influences Fruit Quality,Soil Nutrients and Cover Crops,Leaf Color and Nitrogen Content,Biennial Bearing and Cold Hardiness of ‘Golden Delicious’

Four rates of ammonium nitrate (NH₄NO₃) (0, 151, 454, and 908 g actual N/tree) were applied each spring for 6 years to ‘Golden Delicious’ (Malus domestica) apple trees. High rates of nitrogen (N) increased N concentration of Orchardgrass (Dactylis glomerata) blades and increased cover-grass growth whereas various legume species were prevalent at the low rates. Leaf N in spur or mid-terminal leaves increased yearly, and was related to leaf color by visual comparison and reflectance. Fruit from the higher N rates had greener peel and lower firmness, soluble solids content and titratable acidity. In vitro freeze tests indicated trees fertilized with lower rates of N were more cold hardy during the fall, winter and spring than those receiving the higher rates. In a similar long-term study on ‘Delicious,’ cold hardiness was related not only to seasonal temperature cycles and shoot dry matter, but to total sugars and sorbitol content in wood or sap.     

Influence of different calcium materials and spray timing on mineral composition,yield, fruit quality,and control of fruit disorders of ‘anjou’ pears

During a six‐year period (1980, 1985–1989), 20 different calcium (Ca) materials were sprayed at an early (3X; June to July), late (3X; July to August), and an early plus late (5X; June to August) timing on 25‐year‐old ‘Anjou’ pear (Pyrus communis L.) trees. Calcium chloride (CaCl₂) sprays increased fruit Ca in the cortex by an average of 10.5% greater than in unsprayed controls and cork spot was reduced by an average of six‐fold. Yield from trees sprayed with Ca materials averaged greater than 13% more crop load than the unsprayed control trees. Leaf and fruit injury from CaCl₂ sprays in 1980 were near borderline acceptability, but injury was reduced slightly by halving the spray concentration rate to 681 g CaCl₂ per 379 liters of water in 1985 to 1989. Due to temperatures above 26°C, leaf and fruit injury from Ca sprays, particularly calcium nitrate [Ca(NO₃)₂], were more severe for the late or early plus late sprays than for the early sprays. Fruit size was slightly larger on trees sprayed only three times (early or late sprays) versus trees sprayed five times during the season (early plus late sprays). Best control of cork spot occurred with early plus late sprays. Best control of alfalfa greening and black end occurred with late or early plus late sprays. The importance of fruit Ca for controlling cork spot is illustrated when triiodobenzoic acid (TIBA) was sprayed on trees which resulted in reduced fruit Ca and increased incidence of fruit disorders, alfalfa greening, black end, and cork spot. Sprays containing nitrates or sulfates were frequently associated with a higher incidence of fruit disorders. Although fruit quality was not significantly influenced by Ca treatments or spray time, it was related to Ca in fruit peel or cortex due to annual variations in Ca concentrations.     

Calcium sprays,time of harvest,and duration in cold storage affects fruit quality of d'Anjou pears in a critical year

Calcium chloride (CaCl₂) sprays increased calcium (Ca) concentrations in d'Anjou fruit (Pyrus communis L.), reduced the incidence of cork spot and improved shelf‐life by increasing fruit firmness in a critical year that had lower fruit Ca concentrations due to record high spring and late season temperatures. The third and final harvest in late September resulted in larger fruit size, lower fruit Ca concentrations, higher incidence of cork spot, more extractable juice and yellow fruit skin color, higher soluble solids and sucrose concentrations, but lower acidity than earlier harvested fruits. Fruit held longer in cold storage (145 days) had higher concentrations of fruit Ca, lower concentrations of carbon dioxide (CO₂) and ethylene (C₂H₄), less fruit firmness, soluble solids and acidity, lower concentrations of sucrose, glucose and fructose, and less green color of fruit skin than short term storage (45 days). Shelf‐life of CaCl₂‐sprayed fruit was improved because of higher concentrations of fruit Ca that resulted in a lower incidence of cork spot and brown core, fruit firmness was higher, levels of CO₂ and C₂H₄ were lower, and soluble solids, acidity, and extractable juices were affected less for ripened fruit.