Improved dynamic geomagnetic rigidity cutoff modeling: testing predictive accuracy

. In the polar atmosphere, significant chemical and ionization changes occur during solar proton events (SPE). The access of solar protons to this region is limited by the dynamically changing geomagnetic field. In this study we have used riometer absorption observations to investigate the accuracy of a model to predict Kp-dependent geomagnetic rigidity cutoffs, and hence the changing proton fluxes. The imaging riometer at Halley, Antarctica is ideally situated for such a study, as the rigidity cutoff sweeps back and forth across the instrument's field of view, providing a severe test of the rigidity cutoff model. Using observations from this riometer during five solar proton events, we have confirmed the basic accuracy of this rigidity model. However, we find that the model can be improved by setting a lower Kp limit (i.e., Kp=5 instead of 6) at which the rigidity modeling saturates. We also find that for L>4.5 the apparent L-shell of the beam moves equatorwards. In addition, the Sodankyla Ion and Neutral Chemistry model is used to determine an empirical relationship between integral proton precipitation fluxes and nighttime ionosphere riometer absorption, in order to allow consideration of winter time SPEs. We find that during the nighttime the proton flux energy threshold is lowered to include protons with energies of >5 MeV in comparison with >10 MeV for the daytime empirical relationships. In addition, we provide an indication of the southern and northern geographic regions inside which SPEs play a role in modifying the neutral chemistry of the stratosphere and mesosphere

Case Study of On-Farm Experiments and Farm Management Decision Making

Farm Management,

Analytical Formulation of the Jacobian Matrix for Non-linear Calculation of the Forced Response of Turbine Blade Assemblies with Wedge Friction Dampers

A fundamental issue in turbomachinery design is the dynamical stress assessment of turbine blades. In order to reduce stress peaks in the turbine blades at engine orders corresponding to blade natural frequencies, friction dampers are employed. Blade response calculation requires the solution of a set of non-linear equations originated by the introduction of friction damping. Such a set of non-linear equations is solved using the iterative numerical Newton-Raphson method. However, calculation of the Jacobian matrix of the system using classical numerical finite difference schemes makes frequency domain solver prohibitively expensive for structures with many contact points. Large computation time results from the evaluation of partial derivatives of the non-linear equations with respect to the displacements. In this work a methodology to compute efficiently the Jacobian matrix of a dynamic system having wedge dampers is presented. It is exact and completely analytical. The proposed methods have been successfully applied to a real intermediate pressure turbine (IPT) blade under cyclic symmetry boundary conditions with underplatform wedge dampers. Its implementation showed to be very effective, and allowed to achieve relevant time savings without loss of precision

The Effectiveness of a Far Lateral L5-S1 Microdiscectomy in Pain Reduction

Diagnosis of far lateral disc herniations has become more common in recent years. This study describes the surgical procedure used for L5-S1 far lateral disc herniations, shows the benefits derived from a far lateral approach and retrospectively evaluates the outcome of the surgery. Eight patients were included in the study, five females and three males. The mean age was 62 years (range, 45-77 years). VAS pain scale, OSW index and SF-36 forms were used to evaluate the surgical outcome. Both the VAS pain scale and OSW index were improved postoperatively. The SF-36 scores were significantly lower (p\u3c0.05) for the far lateral patients compared to both the low back pain population and the U.S. aged 55-64 year population

Scripted Dialogue Task for People with Aphasia: Effects of Verb, Object Pronoun, and Sentence Structure Differences

Purpose: Simple syntactic structures are often difficult to produce correctly for people with aphasia (PWA). There has been variability in the literature about how lexical syntax (i.e., ‘parts of speech’) correlates to production of grammatical errors. We aimed to assess verb and object pronoun errors in English-speaking PWA while reducing working memory demands, using a modified replication of Rossi et. al. (2013). Methods: We used a scripted dialogue paradigm to assess how (a) declarative (“the man wants to eat the cookies”) and imperative (“eat the cookies”) sentence structures, (b) verbs, and (c) object pronouns differentially affected accuracy of sentence completion. The paradigm provides a sentence fragment to prime the sentence structure, then asks participants to complete the sentence. Sixteen verbs were tested, each presented in dialogue scripts twice. Verb-object pairs were counterbalanced for number (singular vs. plural). Physical props aided object recall, while proctors acted out verbs. Results: Data collection is ongoing, but 9 participants’ errors have been coded. Participants varied greatly in overall accuracy (M=71%; min=24%; max=100%) with less errors in verb accuracy than pronoun accuracy approaching significance (min=56%; max=87%; t(16)=-1.87, p=.080). Although overall verb errors were low, there was some variability in individual verb accuracy (max accuracy: 92%, min accuracy 77%). There were no significant differences in pronoun number (i.e., singular vs. plural; t(16)=.50, p=.626) nor sentence structure (i.e., declarative versus imperative; t(16)=-.03, p=.977). Significance: Though participants varied in the structures they had difficulty with as well as the types of errors, only differences between verb and pronoun production accuracy were significant. Interestingly, verb and pronoun productions have similar grammatical complexity, but only pronoun production was significantly impaired. This difference could be due to differential working memory requirements. Future directions include lesion-symptom mapping and cross-language comparisons