A mathematical model of plant nutrient uptake

The classical model of plant root nutrient uptake due to Nye. Tinker and Barber is developed and extended. We provide an explicit closed formula for the uptake by a single cylindrical root for all cases of practical interest by solving the absorption-diffusion equation for the soil nutrient concentration asymptotically in the limit of large time. We then use this single root model as a building block to construct a model which allows for root size distribution in a more realistic plant root system, and we include the effects of root branching and growth. The results are compared with previous theoretical and experimental studies

Early Notes of Fines

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Magnetic control assembly qualification model

Fabrication and testing of the magnetic control assembly (MCA) are summarized. The MCA was designed as an add-on unit for certain existing components of the Nimbus and ERTS attitude control system. The MCA system consists of three orthogonal electromagnets; a magnetometer probe capable of sensing external fields in the X, Y, and Z axes; and the control electronics. An operational description of the system is given along with all major drawings and photographs. Manufacturing and inspection procedures are outlined and a chronological list of events is included with the fabrication summary

Continuing Progress on a Lattice QCD Software Infrastructure

We report on the progress of the software effort in the QCD Application Area of SciDAC. In particular, we discuss how the software developed under SciDAC enabled the aggressive exploitation of leadership computers, and we report on progress in the area of QCD software for multi-core architectures.Comment: 5 Pages, to appear in the Proceedings of SciDAC 2008 conference, (Seattle, July 13-17, 2008), Conference Poster Presentation Proceeding

The Equilibrium Distribution of Gas Molecules Adsorbed on an Active Surface

We evaluate the exact equilibrium distribution of gas molecules adsorbed on an active surface with an infinite number of attachment sites. Our result is a Poisson distribution having mean $X = {\mu P P_s \over P_e}$, with $\mu$ the mean gas density, $P_s$ the sticking probability, $P_e$ the evaporation probability in a time interval $\tau$, and $P$ Smoluchowski's exit probability in time interval $\tau$ for the surface in question. We then solve for the case of a finite number of attachment sites using the mean field approximation, recovering in this case the Langmuir isotherm.Comment: 14 pages done in late

Paper Session I-C - Rubicon System for Space Shuttle Vehicle Health Management

The Rubicon (Reasoning Based on Intelligent Computing and Networking) project attempts to do this by providing a vehicle for practical introduction of advanced diagnostic software into an operational environment. Rubicon takes the form of a workstation-based software system giving the engineer access to an array of vehicle health management software and data analysis tools. Rubicon includes graphical user interfaces and controls for advisory system operation and a set of utilities for real time data analysis and display. The engineer can conveniently access a powerful set of fault analysis tools at a single location. Rubicon is being developed by NASA / TV-GDS and Rockwell / Launch Support Services at KSC. It is a step toward operational vehicle health management. Rubicon demonstrates several important points. It shows that multiple advisory systems can run cooperatively on a single workstation. Also, common functions supplied by Rubicon can preclude the need for their redevelopment for future advisory systems. Finally it is possible to automate data analysis tasks that are now performed manually. When completed it will serve as a new data resource for the firing room engineer

Fluorine-plus-proton reactions

The properties of certain energy levels in O16, F19, and Ne20 have been studied by observations on the alpha particles and inelastic protons from the bombardment of fluorine by protons. A high-resolution magnetic analysis of the alpha-particle groups to the 2+ and 1- levels in O16 from the F19(p, α)O16* reaction failed to reveal any doublet structure in these known levels. The angular distributions of the alpha-particle groups to these levels did not indicate degeneracy with a 2- level, nor did a search for new excited levels in O16 up to 8.7-Mev excitation reveal a 2- level. These results are not in agreement with the alpha-particle model of the O16 nucleus which predicts a 2- state close in energy to the 2+ state. Angular distributions of the alpha particles were measured at proton bombarding energies of 873, 935, 1290, 1355, and 1381 kev. The distributions at 1355 kev indicated that the corresponding Ne20 resonance level at 14.16 Mev has spin 2 and odd parity. The spin and parity assignments previously found for the other levels were confirmed. A study of the inelastic proton groups from the F19(p, p′)F19* reaction gave 108.8±0.8 and 196.0±1.4 kev for the excitation energies of the two lowest excited levels of F19. The cross sections at the 1431-kev resonance for these groups in the center-of-mass system were 0.187±0.015 barn for the first group and 0.007 ±0.002 barn for the second group. At 1381 kev the cross section was 0.0427±0.0040 barn for protons to the second excited level. Angular distributions of the proton groups were measured and, in conjunction with other studies made in this laboratory, resulted in spin and parity assignments of ½- and 3/2+ for the first and second excited states of F19, respectively

The Gamma-Radiation from Boron Bombarded by Protons

Employing a Wilson cloud chamber we have determined the distribution in energy of pairs and recoil electrons ejected from lead and carbon laminae by the gamma-radiation from boron bombarded by protons. Both the pair and electron distributions indicate three prominent gamma-ray components at 4.3±0.3 Mev, 11.8±0.5 Mev, and 16.6±0.6 Mev with relative intensities of 1: 1: 1/7, respectively. The radiation is believed to result from proton capture by B11 to form an excited state of C12 which radiates in a single transition to the ground state or in a double transition through the well-known intermediate state at 4.3 Mev. Resonance in the yield has been found only in the region 150→200 kv and the total yield of quanta per incident proton above resonance on a thick boron target is estimated to be ≥5×10^-10

Short Range Alpha-Particles from Fluorine Bombarded with Protons

The ranges of the alpha-particles proceeding from the 334-, 867-, 927-, 1220-, and 1363-kev resonances in the bombardment of fluorine with protons were measured. The Q's of those particles obtained at 334, 867, 927, and 1363 kev were found to be identical, and have the value 1.81 ± 0.04 Mev. The Q of the low energy alpha-particles obtained at the 1220-kev resonance was found to be 1.93±0.07 Mev. The two values thus yield an energy separation of 0.12±0.08 Mev for the two corresponding states of O16. In addition it was shown that at least one of the two resonances which are in the neighborhood of 900 kev must yield short range alpha-particles whose angular distribution is not spherically symmetric

Effective elements of cognitive behaviour therapy for psychosis: results of a novel type of subgroup analysis based on principal stratification

Background. Meta-analyses show that cognitive behaviour therapy for psychosis (CBT-P) improves distressing positive symptoms. However, it is a complex intervention involving a range of techniques. No previous study has assessed the delivery of the different elements of treatment and their effect on outcome. Our aim was to assess the differential effect of type of treatment delivered on the effectiveness of CBT-P, using novel statistical methodology. Method. The Psychological Prevention of Relapse in Psychosis (PRP) trial was a multi-centre randomized controlled trial (RCT) that compared CBT-P with treatment as usual (TAU). Therapy was manualized, and detailed evaluations of therapy delivery and client engagement were made. Follow-up assessments were made at 12 and 24 months. In a planned analysis, we applied principal stratification (involving structural equation modelling with finite mixtures) to estimate intention-to-treat (ITT) effects for subgroups of participants, defined by qualitative and quantitative differences in receipt of therapy, while maintaining the constraints of randomization. Results. Consistent delivery of full therapy, including specific cognitive and behavioural techniques, was associated with clinically and statistically significant increases in months in remission, and decreases in psychotic and affective symptoms. Delivery of partial therapy involving engagement and assessment was not effective. Conclusions. Our analyses suggest that CBT-P is of significant benefit on multiple outcomes to patients able to engage in the full range of therapy procedures. The novel statistical methods illustrated in this report have general application to the evaluation of heterogeneity in the effects of treatment