Cadmium soil sorption at low concentrations. IV. Effect of waste leachates on distribution coefficients     

Thomas H. Christensen 《Water, air, and soil pollution》1985,25(3):265-274

Field and laboratory studies were conducted to assess the survival of B.t. var. kurstaki in waters. B.t. var. kurstaki was recovered from rivers and public water distribution systems following aerial application of a commercial B.t. formulation (Thuricide 16B). Laboratory studies indicate that B.t. var. kurstaki can survive for relatively long periods of time in fresh water and the marine environment at 20 °C. The amount of residual Cl normally applied to a standard water purification system does not appear to be sufficient to destroy B.t. var. kurstaki. A total Cl residual of at least 1.5 mg L^?1 and 60 min contact time was needed to inactivate 99% of the B. t. var. kurstaki population in tap water at pH 7.2 and 20 °C.  相似文献   

Monitoring chemical changes of dry-cured Parma ham during processing by surface autofluorescence spectroscopy     

Møller JK  Parolari G  Gabba L  Christensen J  Skibsted LH 《Journal of agricultural and food chemistry》2003,51(5):1224-1230

Parma hams at various processing stages were investigated by surface autofluorescence spectroscopy. Fluorescence "landscapes" of raw meat and salted (3 months), matured (11 and 12 months), and aged (15 and 18 months) Parma hams were obtained, and a three-dimensional data array (sample x emission x excitation) was used to develop a PARAFAC model including five components, which all exhibited characteristics of pure fluorophores regarding both excitation and emission spectra. The relative amount of each component related strongly to the processing stage, and sample age showed good correlation to fluorescence data (R = 0.98), with a relative error of prediction of approximately 1 month. Fluorescence measurements from samples of either semimembranosus or biceps femoris were used to predict chemical or sensory reference data, yielding good correlation for biceps femoris data, thereby enabling moisture content, sensory and instrumental color, and proteolysis value to be fairly well predicted. Overall, surface autofluorescence of Parma hams proved to hold relevant information, relating to major chemical/physical changes during processing. It is concluded that fluorescence spectroscopy has potential as an innovative method of quality control in dry-cured ham.  相似文献   

Clonal and genetic variation in three collembolan species revealed by isozymes and randomly amplified polymorphic DNA     

Vibeke Simonsen  Grothe Christensen Pia 《Pedobiologia》2001,45(2):161

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Volatilisation of aromatic hydrocarbons from soil: Part II,Fluxes from coal tar contaminated soils residing below the soil surface     

Bo Lindhardt  Thomas H. Christensen 《Water, air, and soil pollution》1996,92(3-4):375-389

The non-steady-state fluxes of aromatic hydrocarbons from coal tar contaminated soil, placed below a 5 cm deep layer of uncontaminated soil, were measured in the laboratory over a period of 53 days. The contaminated soil originated from a former gasworks site and contained concentrations of 11 selected aromatic hydrocarbons between 50 to 840 µg/cm³. Where the microbial activity was inhibited, the fluxes stabilized on a semi-steady-state level for the monocyclic aromatic hydrocarbons, naphthalene and 1-methylnaphthalene after a period of 10–20 days. Fluxes of acenaphthene and fluorene were only measurable in an experiment that utilized a cover soil with a low organic content. The fluxes were predicted by a numerical model assuming that the compounds acted independently of each other and that local equilibrium between the air, water, and sorbed phases existed. The model overestimated the fluxes for all the detected aromatic hydrocarbons by a factor of 1.3 to 12. When the cover soil was adapted to degrade naphthalene, the fluxes of naphthalene and 1-methylnaphthalene approached the detection limit after 5 to 8 days. Thereafter the fluxes of these two compounds were less than predicted by the model employing half-life values of 0.5 and 1 day for naphthalene and 1-methylnaphthalene respectively.  相似文献   

Edward Monroe Freeman,Pioneer Plant Pathologist     

Stakman EC  Christensen JJ 《Science (New York, N.Y.)》1954,120(3112):285-286

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Surficial deposits at Gusev Crater along Spirit Rover traverses     

Grant JA  Arvidson R  Bell JF  Cabrol NA  Carr MH  Christensen P  Crumpler L  Des Marais DJ  Ehlmann BL  Farmer J  Golombek M  Grant FD  Greeley R  Herkenhoff K  Li R  McSween HY  Ming DW  Moersch J  Rice JW  Ruff S  Richter L  Squyres S  Sullivan R  Weitz C 《Science (New York, N.Y.)》2004,305(5685):807-810

The Mars Exploration Rover Spirit has traversed a fairly flat, rock-strewn terrain whose surface is shaped primarily by impact events, although some of the landscape has been altered by eolian processes. Impacts ejected basaltic rocks that probably were part of locally formed lava flows from at least 10 meters depth. Some rocks have been textured and/or partially buried by windblown sediments less than 2 millimeters in diameter that concentrate within shallow, partially filled, circular impact depressions referred to as hollows. The terrain traversed during the 90-sol (martian solar day) nominal mission shows no evidence for an ancient lake in Gusev crater.  相似文献   

THE ROCKEFELLER FOUNDATION     

Christensen BE  Hansen E  Cheldelin VH  Stark JB 《Science (New York, N.Y.)》1939,89(2310):319-321

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Fire and the nitrogen cycle in california chaparral     

Christensen NL 《Science (New York, N.Y.)》1973,181(4094):66-68

Analysis of soils from burned and unburned chaparral indicates that high nitrate concentrations following fire are due to the addition of ammonium and organic nitrogen in the ash. Inhibition of mineralization in unburned chaparral results in low nitrate concentrations. Fluctuations in the amount of soil nitrate in unburned chaparral are the direct result of foliar leaching.  相似文献   

Ion binding by synthetic macrocyclic compounds     

Christensen JJ  Hill JO  Izatt RM 《Science (New York, N.Y.)》1971,174(4008):459-467

The existence of synthetic macrocyclic molecules with hydrophilic cavities containing multiple binding atoms and with hydrophobic exteriors gives rise to extraordinary possibilities with respect to the design and synthesis of molecules with specific cation and anion binding properties. The preparation of many new macrocyclic compounds has recently been reported, but few practical applications for them have been suggested. From the information available, it is becoming clear that it should be possible to synthesize macrocycles that will have specified, or selected, ion binding properties. Cavity size can be varied to accommodate only those cations or anions within a specified narrow band of sizes. Numbers and types of coordinating atoms can be chosen to give essentially electrostatic or covalent bonding or a combination of the two in a metalmacrocycle complex. The metal ligand bond appears to be predominantly ionic in the case of the cyclic polyethers but the covalent character increases on substitution of sulfur or nitrogen for oxygen donor atoms. The essential hydrophobic exteriors of the macrocycles can be modified by the addition of side chains and groups to facilitate the solution of anions and cations in organic solvents. The structures of many macrocycles can be made to approximate naturally occurring molecules, that is, cyclic polyethers similar to macrocyclic antibiotics of the valinomycin and nonactin types and cyclic polyamines similar to porphyrins. Macrocycles are also useful as model compounds for the study of metal interactions with biological systems. The synthetic macrocycles thus represent an intriguing new area of coordination chemistry, the systematic study of which should lead to many interesting and useful chemical applications in the field of metal complexation in solution.  相似文献   

To Calculate Days between Two Dates     

Christensen E  Mayall RN 《Science (New York, N.Y.)》1955,122(3169):561

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