Douglas Experience in Flight Flutter Testing

Douglas Aircraft Company experience in flight flutter testing is reviewed briefly, with comments on state-of-the-art excitation and instrumentation techniques used up to the present time. The limitations of previous techniques are discussed with emphasis on the problem of: (1) establishing a flutter margin of safety for predicted marginal flutter modes; (2) resolving instances of flutter not predicted by theoretical calculations in advance; and (3) delaying the airplane demonstration by time consumed in acquisition and reduction of flutter data. Current Douglas philosophy in flight flutter testing is presented and a description given of steady-state vane excitation system development, automatic data handling system, and the potential application of automatic computing methods for increasing flutter data yield

Comparison of the Elemental Geochemistry of the Arkansas Novaculite and the Boone Chert in their Type Regions, Arkansas

The name Arkansas Novaculite was proposed by A.H. Purdue, 1909 to replace the name Arkansas Stone assigned by L. S. Griswold, 1892, but deemed too generic, to an interval of Early Devonian-Early Mississippian, very fine-grained, even textured, siliceous sedimentary rock famous for use as whetstones. The interval is exposed along the margins of the Benton Uplift, south flank of the Ouachita Mountains, west-central Arkansas, where it reaches a maximum thickness of 243.8 m (800 ft). The Arkansas Novaculite comprises informal lower and upper members characterized by massive beds of nearly pure novaculite, separated by a shale-bearing middle member that spans the Devonian-Mississippian boundary. The formation represents deep water deposition below carbonate compensation depths, in contrast to contemporaneous chert-bearing intervals, such as the Early Mississippian Boone Formation in the southern Ozarks, with chert formed in shallower marine conditions, or as a replacement of associated limestone beds. Source of the prodigious quantities of silica forming the Arkansas Novaculite has been controversial. Geochemical analyses, using both EDX and trace element analysis, were performed using mass spectrometry and have identified a significant contribution by both aluminum and potassium, which would seem to eliminate a biogenic origin and favor a volcanic source, perhaps related to an island arc system that formed during the Ouachita Orogeny as Laurasia collided with Gondwana. Trace element analysis also suggests that the Arkansas Novaculite and the chert in the Boone Formation may have both been formed from the same volcanic source

Letters between W. H. Philbrick and W. J. Kerr

Letters concerning recommendation for position in music department at Utah Agricultural College

Effect of changes in regional forest abundance on the decline and recovery of a forest bird community

Bird populations were monitored for 32 years in a 23-ha tract of hemlock-hardwood forest. Between 1953 and 1976 the total abundance of long-distance migrants declined significantly and four species disappeared, but after 1976 both the total abundance and the number of species increased. Multiple regression analysis shows that the abundance of long-distance migrants was negatively related to abundance of bird species characteristic of suburban habitats and positively related to the amount of forest within 2 km of the study area. The decline in long-distance migrants before 1976 occurred when suburban species were increasing and nearby forest was destroyed. The increase after 1976 is best explained by reforestation in the surrounding area because suburban birds were still increasing. A diversity of forest species, including many long-distance migrants, became established in the reforested areas. This pattern suggests that immigration from nearby forests is important in maintaining the abundance of long-distance migrants

Does A Diagnostic Algorithm Reduce the Overuse of Chest CT Angiography in Suspected Pulmonary Embolism? : A Pre- and Post-Intervention Retrospective Study in a Critical Access Hospital

Background: Pulmonary embolism (PE) is a common and potentially fatal disease. Although CTA is a gold standard for diagnosis, it carries risks for patients. We sought to minimize the overutilization of chest CTA by implementing a diagnostic algorithm in the hospital to evaluate the likelihood of PE and determine the need for imaging with CTA. Methods: A retrospective medical chart review was performed for all patients suspicious of PE at Redington-Fairview General Hospital 3 months before and after diagnostic algorithm implementation. Patients who underwent either D-dimer testing or chest CTA were included. Patients were excluded if d-dimer testing was performed for suspected deep vein thrombosis (DVT) alone or chest CTA was performed for other reasons. Patients were divided into 3 categories of probability according to their Wells scores. The algorithms from the American College of Physicians (ACP) were used to determine the next step of management. Results: A total of 414 patients were included in our study, 236 (57%) patients in 2017 and 178 (43%) patients in 2018. The mean age was 51 years (SD=19.17). A total of 168 CTAs were performed and found that 11 patients (15%) had PEs. There was a significant increase in the ordering of D-dimer levels after the diagnostic algorithm had been implemented (80.9% vs 89.3%, p=0.019), particularly in the low probability group. The use of D-dimer increased among patients in the low probability group who met PERC criteria (80.3% vs 97.17%, p=0.001). We observed an 11% reduction in the CTAs ordered in the post-intervention group compared to the pre-intervention group (45.3% vs 34.3%, p=0.023). Conclusion: Our study found that the implementation of a diagnostic algorithm for PE led to a significant reduction in the use of CTA