Radar sounding of the Medusae Fossae Formation Mars: equatorial ice or dry, low-density deposits?

The equatorial Medusae Fossae Formation (MFF) is enigmatic and perhaps among the youngest geologic deposits on Mars. They are thought to be composed of volcanic ash, eolian sediments, or an ice-rich material analogous to polar layered deposits. The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument aboard the Mars Express Spacecraft has detected nadir echoes offset in time-delay from the surface return in orbits over MFF material. These echoes are interpreted to be from the subsurface interface between the MFF material and the underlying terrain. The delay time between the MFF surface and subsurface echoes is consistent with massive deposits emplaced on generally planar lowlands materials with a real dielectric constant of approximately 2.9 +/- 0.4. The real dielectric constant and the estimated dielectric losses are consistent with a substantial component of water ice. However, an anomalously low-density, ice-poor material cannot be ruled out. If ice-rich, the MFF must have a higher percentage of dust and sand than polar layered deposits. The volume of water in an ice-rich MFF deposit would be comparable to that of the south polar layered deposits.     

Mobile TDR for geo-referenced measurement of soil water content and electrical conductivity

The development of site-specific crop management is constrained by the availability of sensors for monitoring important soil and crop related conditions. A mobile time-domain reflectometry (TDR) unit for geo-referenced soil measurements has been developed and used for detailed mapping of soil water content and electrical conductivity within two research fields. Measurements made during the early or late season, when soil moisture levels are close to field capacity, are related to the amount of plant available water and soil texture. Combined measurements of water content and electrical conductivity are closely related to the clay and silt fractions of a variable field. The application to early season field mapping of water content, electrical conductivity and clay content is presented. The water and clay content maps are to be used for automated delineation of field management units. Based on a spatial analysis of the soil water measurements, recommendations are made with respect to sampling strategies. Depending on the variability of a given area, between 15 and 30 ha can be mapped with respect to soil moisture and electrical conductivity with sufficient detail within 8 h.     

The effect of cassava mosaic disease on the genetic diversity of cassava in Uganda

Summary Cassava (Manihot esculenta) is a tropical crop that is grown in Africa, Latin America and Southeast Asia. Cassava was introduced from Latin America into West and East Africa at two independent events. In Uganda a serious threat to cassava's survival is the cassava mosaic disease (CMD). Uganda has had two notable CMD epidemics since the introduction of cassava in the 1850s causing severe losses. SSR markers were used to study the effect of CMD on the genetic diversity in five agroecologies in Uganda with high and low incidence of CMD. Surprisingly, high gene diversity was detected. Most of the diversity was found within populations, while the diversity was very small among agroecological zones and the high and low CMD incidence areas. The high genetic diversity suggests a mechanism by which diversity is maintained by the active involvement of the Ugandan farmer in continuously testing and adopting new genotypes that will serve their diverse needs. However, in spite of the high genetic diversity we found a loss of rare alleles in areas with high CMD incidence. To study the effect of the introgression history on the gene pool the genetic differentiation between East and West Africa was also studied. Genetic similarities were found between the varieties in Uganda and Tanzania in East Africa and Ghana in West Africa. Thus, there is no evidence for a differentiation of the cassava gene pool into a western and an eastern genetic lineage. However, a possible difference in the genetic constitution of the introduced cassava into East and West Africa may have been diminished by germplasm movement.     

Transformation of lily by Agrobacterium

Summary Lily cv. Harmony was inoculated with several Agrobacterium strains to study its susceptibility to Agrobacterium infection and transformation. Tumorous tissue formation on inoculated stem internodes of sterile-grown plantlets, as well as expression of a -glucuronidase marker gene interrupted by an intron in cells of inoculated stem nodes, indicate that the monocotyledon Lilium is a host for Agrobacterium.     

Canine‐chilled Sperm: Study of a Semen Extender Made with Low‐density Lipoproteins from Hen Egg Yolk Supplemented with Glutamine

The objective of this study was to evaluate the effects of a combination of 6% low‐density lipoproteins (LDL) and 20 mm glutamine in comparison with other extenders used for the refrigeration of canine semen: Tris egg yolk (EY) 20% and 6% LDL. The percentages of mobile spermatozoa after 4 days storage in a domestic refrigerator at +4°C were 53.1%, 44.2% and 52.2% for the 6% LDL + 20 mm glutamine, 20% EY and 6% LDL extenders respectively for 100% of the dogs. After 7 days of storage, these percentages fell to 37.8%, 26.4% and 33.6% in the same extenders for 50% of the dogs. In vitro fertility tests were performed with all of the extenders following the mobility results. These tests were conducted on the day of sampling (D0), and 48 and 96 h after sampling. The results of the hypo‐osmotic swelling test were 82.6%, 81.2% and 85.7% on D0, 75.2%, 74.1% and 78.5% on D2, and 70.8%, 71% and 76.1% on D4 for the 6% LDL + 20 mm glutamine, 20% EY and 6% LDL extenders, respectively. For the FITC/pisum sativum agglutinin (PSA) test, the results were 81.5%, 70.2% and 84.8% on D0, 78.9%, 62.3% and 84.2% on D2, and 72.7%, 59.6% and 73.7% on D4 for the 6% LDL + 20 mm glutamine, 20% EY and 6% LDL extenders, respectively. The acridine orange test was positive; in nearly 100% of cases, none of the spermatozoa had been denatured on D0, D2 and D4. The 6% LDL + 20 mm glutamine and the 6% LDL extenders are capable of preserving spermatozoa that have been stored in a domestic refrigerator at +4°C for at least 4 days. This means that the spermatozoa retain good cytoplasmic membrane integrity, had not capacitated and contained intact DNA in comparison with spermatozoa preserved in the egg yolk extender. The duration of storage is a very important consideration when faced with the problem of sending semen over ever‐greater distances.     

Direct observation of molecular preorganization for chirality transfer on a catalyst surface

The chemisorption of specific optically active compounds on metal surfaces can create catalytically active chirality transfer sites. However, the mechanism through which these sites bias the stereoselectivity of reactions (typically hydrogenations) is generally assumed to be so complex that continued progress in the area is uncertain. We show that the investigation of heterogeneous asymmetric induction with single-site resolution sufficient to distinguish stereochemical conformations at the submolecular level is finally accessible. A combination of scanning tunneling microscopy and density functional theory calculations reveals the stereodirecting forces governing preorganization into precise chiral modifier-substrate bimolecular surface complexes. The study shows that the chiral modifier induces prochiral switching on the surface and that different prochiral ratios prevail at different submolecular binding sites on the modifier at the reaction temperature.     

Distance communication transfer of HIV prevention interventions to service providers

Most acquired immunodeficiency syndrome (AIDS) service providers are in countries with little access to scientific developments relevant to their programs. It is critical to transfer advances from the scientific arena to service providers on a global scale. Human immunodeficiency virus (HIV) prevention organizations in 78 countries were randomized to receive either a control condition or a technology transfer condition with an interactive distance learning computer training curriculum and individualized distance consultation. Of 42 nongovernmental organizations in the technology transfer condition, 29 adopted the science-based program in their communities or trained other agencies to also use it. Advanced communication technologies can create a cost-effective infrastructure to disseminate new intervention models to service providers worldwide.