南极半岛海洋气候区的土壤Ⅲ.冻-融作用与水分状况

自由水活动在南极海洋性气候区土壤形成与演化过程中发挥极为重要的作用。本文对土壤自由水的来源、冻-融作用、永冻层和活动层动态以及自由水参与下的物质迁移过程等几个方面进行了论述,讨论了上述不同过程的影响因素以及土壤发生学意义,指出以土壤水形态转化和自由水活动为基础的土壤过程具有显著的微域性特点,是决定本区土壤发生类型与分布模式的重要因素之一。     

"Tubules-Within-a-Tubule" Hierarchical Order of Mesoporous Molecular Sieves in MCM-41

The recently discovered mesoporous aluminosilicate MCM-41 consists of hexagonal arrays of nanometer-sized cylindrical pores. It is shown that this material can be synthesized by cooperative condensation of silicate and cylindrical cationic micelles. Careful control of the surfactant-water content and the rate of condensation of silica at high alkalinity resulted in hollow tubules 0.3 to 3 micrometers in diameter. The wall of the tubules consisted of coaxial cylindrical pores, nanometers in size, that are characteristic of those of MCM-41. The formation of this higher order structure may take place through a liquid crystal phase transformation mechanism involving an anisotropic membrane-to-tubule phase change. The hierarchical organization of this "tubules-within-a-tubule" particle texture is similar to that of the frustules of marine diatoms.     

Teleportation of nonclassical wave packets of light

We report on the experimental quantum teleportation of strongly nonclassical wave packets of light. To perform this full quantum operation while preserving and retrieving the fragile nonclassicality of the input state, we have developed a broadband, zero-dispersion teleportation apparatus that works in conjunction with time-resolved state preparation equipment. Our approach brings within experimental reach a whole new set of hybrid protocols involving discrete- and continuous-variable techniques in quantum information processing for optical sciences.     

Utilization of nitrogen and energy by Holstein steers fed formaldehyde- and formic acid-treated alfalfa or orchardgrass silage at two intakes

Our objective was to measure the utilization of energy (E) and N by Holstein steers when fed alfalfa and orchardgrass silages offered at 65 and 90 g DM/kg live weight (LW).75 daily. Twelve steers adapted to the Beltsville respiration chambers were assigned to three Latin squares with 42-d periods. Steers in one square had permanent catheters in the portal and two mesenteric veins. Energy and N balance were measured during a 7-d collection of feces and urine that included a 3-d measurement of respiratory exchange. Energy and N variables were not different between catheterized and uncatheterized steers. Apparent digestibilities of DM, OM, CP, neutral detergent solubles and permanganate lignin were higher (P less than .01) and digestibilities of NDF and ADF, hemicellulose and cellulose were lower (P less than .01) for steers consuming alfalfa compared to orchardgrass silage. When fed alfalfa, steers' daily gross energy intake, DE, urine energy, ME, heat production and tissue energy retention were greater (P less than .01) and fecal energy losses were less (P less than .01) than when they were fed orchardgrass. Partial efficiency of ME use for tissue energy (TE) was greater (P less than .01) for steers when fed alfalfa (46.1%) than when fed orchardgrass (35.6%). Apparent ME (kcal/LW.75) required for maintenance of TE was similar for steers when fed alfalfa (133.9) and orchardgrass (131.2) silages. Nitrogen retention (g/d) was 48% greater (P less than .01) for steers when fed alfalfa (30.6) than when fed orchardgrass (20.7). This study demonstrates that steers used ME from alfalfa more efficiently for TE deposition than ME from orchardgrass.