Laboratory modeling and analysis of aircraft-lightning interactions

Modeling studies of the interaction of a delta wing aircraft with direct lightning strikes were carried out using an approximate scale model of an F-106B. The model, which is three feet in length, is subjected to direct injection of fast current pulses supplied by wires, which simulate the lightning channel and are attached at various locations on the model. Measurements are made of the resulting transient electromagnetic fields using time derivative sensors. The sensor outputs are sampled and digitized by computer. The noise level is reduced by averaging the sensor output from ten input pulses at each sample time. Computer analysis of the measured fields includes Fourier transformation and the computation of transfer functions for the model. Prony analysis is also used to determine the natural frequencies of the model. Comparisons of model natural frequencies extracted by Prony analysis with those for in flight direct strike data usually show lower damping in the in flight case. This is indicative of either a lightning channel with a higher impedance than the wires on the model, only one attachment point, or short streamers instead of a long channel

Exchange Rates and the Trade Balance in Argentina and Peru: Is There a J-curve?

In this paper, I test whether quarterly data either supports or disproves the existence of such a J-curve in two Latin American countries -- Argentina and Peru. The time periods studied will be: for Peru, 1979 quarter 1 to 1991 quarter 2 and for Argentina, 1977 quarter 1 to 1990 quarter 4. Before completing the empirical part of this paper, I expected to find, if any, only a short deterioration in the trade balance following a depretiation of the real exchange rate in these two countries. With prices as well as other economic indicators changing daily, the reaction times of economic actors who deal with Latin America, whether from the inside or the outside, have grown ever shorter. Many contracts are short-term or are indexed so the real terms of the contract will not change as the nominal indicators do. Short reaction times should mean that the import/export market will adjust quickly to any change in the real exchange rate or other indicators. Contracts will be renegotiated quickly because of their short-term nature. This quick adjustment is not only important for the first possible cause of a J-curve, namely stickiness caused by contracts outstanding, but could also lead to a prediction about the second factor involved, that of trade elasticities. Quick renegotiations of contracts as well as a general attitude among actors that are expectant of quick changes would seem to favor a high elasticity of demand. For example if a foreign importer suddenly sees the price of imports from Peru go down, she may be more anxious to take advantage of this fall in price than if the imports were from a more stable economy. Since in the Peruvian economy, things are likely to change quickly, the foreign importer will want to take advantage of the low prices before they are eradicated by, for example, a sudden rise in inflation in Peru. Because of this expectedly short duration of a J-curve, should one exist, I define a significant J-curve as anything longer than two quarters. In other words, if the trade balance does not start to improve before the second lagged quarter after the depretiation (after the quarter of the depretiation and the first lagged quarter), a J-curve exists. Any deterioration shorter than two quarters can be interpreted only as the result of the impossibility of instantaneous reactions on the part of the actors. While this may be a brief J-curve by any standards, I think this definition is appropriate for a study of Latin American countries

Exchange Rates and the Trade Balance in Argentina and Peru: Is There a J-curve?

In this paper, I test whether quarterly data either supports or disproves the existence of such a J-curve in two Latin American countries -- Argentina and Peru. The time periods studied will be: for Peru, 1979 quarter 1 to 1991 quarter 2 and for Argentina, 1977 quarter 1 to 1990 quarter 4. Before completing the empirical part of this paper, I expected to find, if any, only a short deterioration in the trade balance following a depretiation of the real exchange rate in these two countries. With prices as well as other economic indicators changing daily, the reaction times of economic actors who deal with Latin America, whether from the inside or the outside, have grown ever shorter. Many contracts are short-term or are indexed so the real terms of the contract will not change as the nominal indicators do. Short reaction times should mean that the import/export market will adjust quickly to any change in the real exchange rate or other indicators. Contracts will be renegotiated quickly because of their short-term nature. This quick adjustment is not only important for the first possible cause of a J-curve, namely stickiness caused by contracts outstanding, but could also lead to a prediction about the second factor involved, that of trade elasticities. Quick renegotiations of contracts as well as a general attitude among actors that are expectant of quick changes would seem to favor a high elasticity of demand. For example if a foreign importer suddenly sees the price of imports from Peru go down, she may be more anxious to take advantage of this fall in price than if the imports were from a more stable economy. Since in the Peruvian economy, things are likely to change quickly, the foreign importer will want to take advantage of the low prices before they are eradicated by, for example, a sudden rise in inflation in Peru. Because of this expectedly short duration of a J-curve, should one exist, I define a significant J-curve as anything longer than two quarters. In other words, if the trade balance does not start to improve before the second lagged quarter after the depretiation (after the quarter of the depretiation and the first lagged quarter), a J-curve exists. Any deterioration shorter than two quarters can be interpreted only as the result of the impossibility of instantaneous reactions on the part of the actors. While this may be a brief J-curve by any standards, I think this definition is appropriate for a study of Latin American countries

Schr\"odinger operators with complex potential but real spectrum

Several aspects of complex-valued potentials generating a real and positive spectrum are discussed. In particular, we construct complex-valued potentials whose corresponding Schr\"odinger eigenvalue problem can be solved analytically.Comment: 10, pages, LaTeX 2.09, 6 Postscript figures, uses amsfont, figures available at http://faupt100.physik.uni-erlangen.de/junker/papers95-99.ht

Inter-species variation in the oligomeric states of the higher plant Calvin cycle enzymes glyceraldehyde-3-phosphate dehydrogenase and phosphoribulokinase

In darkened leaves the Calvin cycle enzymes glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and phosphoribulokinase (PRK) form a regulatory multi-enzyme complex with the small chloroplast protein CP12. GAPDH also forms a high molecular weight regulatory mono-enzyme complex. Given that there are different reports as to the number and subunit composition of these complexes and that enzyme regulatory mechanisms are known to vary between species, it was reasoned that protein-protein interactions may also vary between species. Here, this variation is investigated. This study shows that two different tetramers of GAPDH (an A2B2 heterotetramer and an A4 homotetramer) have the capacity to form part of the PRK/GAPDH/CP12 complex. The role of the PRK/GAPDH/CP12 complex is not simply to regulate the 'non-regulatory' A4 GAPDH tetramer. This study also demonstrates that the abundance and nature of PRK/GAPDH/CP12 interactions are not equal in all species and that whilst NAD enhances complex formation in some species, this is not sufficient for complex formation in others. Furthermore, it is shown that the GAPDH mono-enzyme complex is more abundant as a 2(A2B2) complex, rather than the larger 4(A2B2) complex. This smaller complex is sensitive to cellular metabolites indicating that it is an important regulatory isoform of GAPDH. This comparative study has highlighted considerable heterogeneity in PRK and GAPDH protein interactions between closely related species and the possible underlying physiological basis for this is discussed. © 2011 The Author(s)

Physical Activity, Obesity Status, and Blood Pressure in Preschool Children.

OBJECTIVE:To examine the combined effects of physical activity and weight status on blood pressure (BP) in preschool-aged children. STUDY DESIGN: The sample included 733 preschool-aged children (49% female). Physical activity was objectively assessed on 7 consecutive days by accelerometry. Children were categorized as sufficiently active if they met the recommendation of at least 60 minutes daily of moderate-to-vigorous physical activity (MVPA). Body mass index was used to categorize children as nonoverweight or overweight/obese, according to the International Obesity Task Force benchmarks. BP was measured using an automated BP monitor and categorized as elevated or normal using BP percentile-based cut-points for age, sex, and height. RESULTS: The prevalence of elevated systolic BP (SBP) and diastolic BP was 7.7% and 3.0%, respectively. The prevalence of overweight/obese was 32%, and about 15% of children did not accomplish the recommended 60 minutes of daily MVPA. After controlling for age and sex, overweight/obese children who did not meet the daily MVPA recommendation were 3 times more likely (OR 3.8; CI 1.6-8.6) to have elevated SBP than nonoverweight children who met the daily MVPA recommendation. CONCLUSIONS: Overweight or obese preschool-aged children with insufficient levels of MVPA are at significantly greater risk for elevated SBP than their nonoverweight and sufficiently active counterparts

Interpretation of F-106B in-flight lightning signatures

Various characteristics of the electromagnetic data obtained on a NASA F-106B aircraft during direct lightning strikes are presented. Time scales of interest range from 10 ns to 400 microsecond. The following topics are discussed: (1) Lightning current, I, measured directly versus I obtained from computer integration of measured I-dot; (2) A method of compensation for the low frequency cutoff of the current transformer used to measure I; (3) Properties of fast pulses observed in the lightning time-derivative waveforms; (4) The characteristic D-dot signature of the F-106B aircraft; (5) An RC-discharge interpretation for some lightning waveforms; (6) A method for inferring the locations of lightning channel attachment points on the aircraft by using B-dot data; (7) Simple, approximate relationships between D-dot and I-dot and between B and I; and (8) Estimates of energy, charge, voltage, and resistance for a particular lightning event

Initial validation of a virtual blood draw exposure paradigm for fear of blood and needles

Fear of blood, injections, and needles commonly prevents or delays individuals' receipt of health care, such as vaccines or blood draws. Innovative methods are needed to overcome these fears and reduce anxiety related to activities of this nature. The present study describes initial testing of an arm illusion paradigm that may prove useful during early phases of graded exposure for people with blood and needle fear. Seventy-four undergraduate students aged 18-29 years were tested. In line with study aims, results indicated that the virtual blood draw paradigm promoted strong perceptions of arm ownership and elicited significant changes in physiological indices (blood pressure, heart rate, electrodermal activity, respiratory rate) in response to key procedure elements (e.g., needle insertion). Further, bivariate correlations indicated that individual differences in self-reported blood and needle fear collected prior to the illusion paradigm were significantly associated with presyncopal symptoms reported following the procedure. In regression analyses, self-reported measures of blood and needle fear explained unique variance in presyncopal symptoms even after controlling for general state anxiety. These findings provide initial support for the virtual blood draw paradigm as a promising tool to help provide graded exposure to medical procedures involving needles and blood draw