Simulation of nitrogen dynamics and biomass production in winter wheat using the Danish simulation model DAISY

A dynamic simulation model for the soil plant system is described. The model includes a number of main modules, viz., a hydrological model including a submodel for soil water dynamics, a soil temperature model, a soil nitrogen model including a submodel for soil organic matter dynamics, and a crop model including a submodel for nitrogen uptake. The soil part of the model has a one-dimensional vertical structure. The soil profile is divided into layers on the basis of physical and chemical soil characteristics. The simulation model was used to simulate soil nitrogen dynamics and biomass production in winter wheat grown at two locations at various levels of nitrogen fertilization. The simulated results were compared to experimental data including concentration of inorganic nitrogen in soil, crop yield, and nitrogen accumulated in the aboveground part of the crop. Based on this validation it is concluded that the overall performance of the model is satisfactory although some minor adjustments of the model may prove to be necessary.     

Battery State-Of-Charge Based Altitude Controller for Small, Low Cost Multirotor Unmanned Aerial Vehicles

Small unmanned aerial vehicles (UAV) are typically driven by Lithium polymer batteries. The batteries have their own dynamics, which changes during discharge. Classical approaches to altitude control assume a time-invariant system and therefore fail. Adaptive controllers require an identified system model which is often unavailable. Battery dynamics can be characterized and used for a battery model-based controller. This controller is useful in situations when no feedback from actuators (such as RPM or thrust) is available. After measuring the battery dynamics for two distinct types of batteries, a controller is designed and experimentally verified, showing a consistent performance during entire discharge test and a consequent flight verification.     

Chemical inhibitors when timing is critical: a pharmacological concept for the maturation of T cell contacts

Cellular signal transduction proceeds through a complex network of molecular interactions and enzymatic activities. The timing of these molecular events is critical for the propagation of a signal and the generation of a specific cellular response. To define the timing of signalling events, we introduce the combination of high-resolution confocal microscopy with the application of small-molecule inhibitors at various stages of signal transduction in T cells. Inhibitors of Src-family tyrosine kinases and actin dynamics were employed to dissect the role of the lymphocyte-specific tyrosine kinase Lck in the formation and maintenance of T cell receptor/CD3-dependent contacts. Anti-CD3epsilon-coated coverslips served as a highly defined stimulus. The kinetics of the recruitment of the yellow fluorescent protein-tagged signalling protein ZAP-70 were detected by high-resolution confocal microscopy. The analysis revealed that at 5 min after receptor engagement, Lck activity was required for maintenance of contacts. In contrast, after 20 min of receptor engagement, the contacts were Lck-independent. The relevance of the timing of inhibitor application provides a pharmacological concept for the maturation of T cell-substrate contacts.     

Plasma desorption mass spectrometry, an analytical tool in protein engineering: characterization of modified insulins

Californium-252 plasma desorption mass spectrometry (PDMS) hasbeen employed for the characterization of a series of humaninsulin derivatives in order to evaluate the performance ofthis technique as an analytical tool in protein engineering.Several of the characterized modifications result in a 1 a.m.u.mass change. The precision in mass determination obtainableby PDMS analysis is not sufficient for unambiguous verificationof such modifications based on the molecular weight alone. Itis, however, possible to carry out in situ enzymatic digestionof the sample. Subsequent PDMS analysis will in most cases revealif the modification has been introduced as intended.     

Nitrate leaching from loamy soils as affected by crop rotation and nitrogen fertilizer application

Nitrate leaching as affected by cropping system/crop rotation, history of farmyard manure application or fertilizer nitrogen application (0 N, 0.5 N and 1 N) was studied at nine sites on loamy soils during 1986/87, 1987/88 and 1988/89. Soil solution from 80 to 90 cm soil depth was sampled every second week in the period November to May by the use of porous ceramic cups and analysed for NO₃-N and Cl. Climatical conditions were obtained from standard meteorological observations in the region. Drainage from soil profiles was calculated from measured and simulated values of precipitation and actual evapotranspiration, respectively.The results show that type of crop is of the utmost importance for the leaching magnitude of nitrate as 40% of the total variance in nitrate concentrations in the soil solution could be explained by the type of crop.The second factor of importance was the history of farmyard manure (FYM) application, which was able to explain 28% of the total variation in nitrate concentration in the soil solution. Nitrate concentration/leaching from arable land without FYM ever being applied was considerably lower than from arable land which received periodical FYM applications until the early 70's or from arable land which besides periodical FYM applications in the past presently still receives regular applications of FYM. Only about 1% of the total variation in nitrate concentration in the soil solution was explainable by the level of fertilizer nitrogen application.Differences between years explained 14% of the total variation in nitrate concentration in the soil solution due to differences between the years in soil temperatures and water run-off. The run-off during the autumn and winter of 1986/87, 1987/88 and 1988/89 was 95, 275 and 55 mm, respectively. As expected nitrate leaching increased with increasing run off. However, nitrate leaching at the 275 mm run off was considerably lower than expected, which seems explainable by a substantial denitrification. The soil at the sites in question seems thus partly to purify the soil solution for nitrate before it leaves the root zone at the observed high run off conditions.     

Evaluation of nucleation activation energy in metal CVD processes

A new approach to evaluate activation energy for nucleation in metal chemical vapor deposition (CVD) is presented. Deposition is performed by laser induced chemical vapor deposition (LCVD) using a low laser power and a high scan speed, so that only discrete particles in the initial nucleation stage are formed. The nucleation activation energy is then obtained from a relationship between the laser-induced surface temperature distribution and the particle distribution. The activation energy is directly related to the nucleation barrier, and hence the difference in the nucleation activation energies on different substrates may be used to explain the chemical selectivity which is often observed during metal CVD processes. This approach is experimentally applied to aluminum CVD using dimethylethylamine alane (DMEAA) precursor, and its nucleation activation energy is found to be 25kcal/mol on silicon surface.     

Fear Appeals,Message Processing Cues,and Credibility in the Websites of Violent,Ideological, and Nonideological Groups

Ideological groups use the Internet to deliver their messages unhindered by the constraints of traditional media. We examined how ideological groups promote their worldview through their websites. Using the elaboration likelihood model (ELM), this research used trained coders to examine the websites of nonideological groups (n = 37), nonviolent ideological groups (n = 36), and violent ideological groups (n = 32) for credibility, persuasion processing cues, and interactivity factors. Results of this study found that the websites of violent ideological groups use more fear appeals, were less interactive, and were the least credible of the 3 groups. All 3 groups used more central cues than peripheral suggesting they focused on evidence for their arguments rather than emotion.     

Hydrocarbon synthesis over sulfide catalysts. Break-down of the Anderson-Schulz-Flory distribution

The kinetics of hydrocarbon synthesis over sulfide-based catalysts was studied. It appears that the formation of methane follows another reaction path than that of higher hydrocarbons. This might explain the very high selectivities for ethane and propane as compared with conventional Fischer-Tropsch catalysts. Reference is made to testing of the catalysts at industrial conditions.     

Characteristics of the lipase from the mold,Geotrichum candidum: A review

The moldGeotrichum candidum produces an extracellular lipase, readily concentrated by removal of the culture medium in which the microorganism is grown. The lipase is characterized by a unique, but not absolute, specificity for fatty acids containingcis-9 orcis,cis-9, 12 unsaturation, hydrolyzing both regardless of position within the triglyceride molecule. The enzyme also hydrolyzescis-9-16∶1,cis,trans-9,12-18∶2,trans,cis-9,12-18∶2, palmitoyl oleate and cholesteryl oleate. Digested at comparatively slow rates are:trans,trans-9,12-18∶2, double bond positional isomers of 18∶1 (other thancis-9), stearolic acid, oleoylpalmitate, dilinoleoyl phosphatidyl choline, and saturated acids. The enzyme has an optimum pH of 8.2, and the lyophilized powder is extremely stable, retaining activity for at least eight years when stored at-20 C. A purification of 81-fold has been achieved. One of five papers presented in the Symposium “Microbial Lipolytic Enzymes,” AOCS Spring Meeting, New Orleans, April 1973. Scientific contribution 556, Agricultural Experiment Station, University of Connecticut, Storrs, Conn. 06268.     

A microscopic model for catalytic surfaces—I. Catalytic wires and gauzes

A new “fuzzy wire” model of catalytic wires and gauzes is presented which is in good agreement with observed ignition, extinction, and flickering phenomena. The model predicts both simple harmonic oscillations as well as a wide variety of nonperiodic chaotic oscillations. Quantitative comparisons with data for butane oxidation and cyclohexene oxidation are quite good; however, the very long period oscillations observed for H₂ and CO oxidation are not predicted by the simplest forms of the model.