The geography of linear baroclinic instability in Earth’s oceans

Satellite observations reveal a mesoscale oceanic circulation dominated by turbulence that is correlated, in most cases, with local baroclinicity. Linear baroclinic instability theory has proved useful in understanding the time and space scales of atmospheric eddies. The question addressed here is, to what degree can the observed oceanic eddy activity be understood through a local, linear stability analysis? This question is addressed as follows. A local quasigeostrophic linear stability calculation is performed on a grid of wavenumbers, ranging in magnitude about the local deformation wavenumber, for each vertical profile in a dataset of neutral density for the world\u27s oceans. The initial results show that nearly the entire ocean is unstable, but in many places, particularly in low latitudes, the instability is dominated by surface intensified modes, resulting in very small-scale, quickly growing waves. At higher latitudes, the primary instabilities are due to thermocline depth shears and have a broader vertical structure. For each unstable wave, at each location, the mean-to-eddy energy conversion rate is also calculated and used to select the growing waves that are both fast and have significant energetic conversion potential. This procedure removes most of the surface-instabilities, which cannot lead to significant energy conversion, and reveals the slower but more powerful thermocline-level instabilities where they exist. The time and space scales of these growing waves are compared to estimates of the Eady growth rate and deformation scale, respectively. It is found that while the timescale is well-approximated by the Eady-estimate, the spatial scales are uniformly smaller than the deformation scale, typically by a factor of 4. The zonally averaged spatial scales are then compared to observed eddy scales. The spatial scales of maximum growth are everywhere significantly smaller than the observed eddy scales. In the Antarctic Circumpolar Current, for example, the scale of maximum growth is about 5 km, much smaller than the observed eddy scales, estimates of which range from 30–100 km. A possible, and unsurprising conclusion is that the observed eddy scales are the result of an inverse cascade, and cannot be understood by linear theory alone

Subsonic stability and control derivatives for an unpowered, remotely piloted 3/8-scale F-15 airplane model obtained from flight test

In response to the interest in airplane configuration characteristics at high angles of attack, an unpowered remotely piloted 3/8-scale F-15 airplane model was flight tested. The subsonic stability and control characteristics of this airplane model over an angle of attack range of -20 to 53 deg are documented. The remotely piloted technique for obtaining flight test data was found to provide adequate stability and control derivatives. The remotely piloted technique provided an opportunity to test the aircraft mathematical model in an angle of attack regime not previously examined in flight test. The variation of most of the derivative estimates with angle of attack was found to be consistent, particularly when the data were supplemented by uncertainty levels

Nuclear magnetic resonance spectroscopy: Abnormal splitting of ethyl groups due to molecular asymmetry

Nuclear magnetic resonance (n.m.r.) spectroscopy provides an excellent means for qualitative identification of ethyl groups by use of the familiar three-four pattern of spin-spin splitting (1). It has been observed previously (2) that the methylene protons of systems of the type R-CH2-CR1R2R3 (where R1 can be the same as R or different) may be magnetically nonequivalent and display AB rather than A2-type spectra (3). We now wish to report several examples of this type of behavior with ethyl groups, particularly ethoxy groups, knowledge of which could be important to anyone using n.m.r. for organic qualitative analysis

Applicability of the control configured design approach to advanced earth orbital transportation systems

The applicability of the control configured design approach (CCV) to advanced earth orbital transportation systems was studied. The baseline system investigated was fully reusable vertical take-off/horizontal landing single-stage-to-orbit vehicle and had mission requirements similar to the space shuttle orbiter. Technical analyses were made to determine aerodynamic, flight control and subsystem design characteristics. Figures of merit were assessed on vehicle dry weight and orbital payload. The results indicated that the major parameters for CCV designs are hypersonic trim, aft center of gravity, and control surface heating. Optimized CCV designs can be controllable and provide substantial payload gains over conventional non-CCV design vertical take-off vehicles

Another Look at the Urbankte Site (41CV26) in Coryell County, Texas

Perttula (2016) had analyzed ceramic sherds and other material culture remains curated at the Texas Archeological Research Laboratory at The University of Texas at Austin (TARL) from four sites in the Brazos River basin in the Central Texas prairie that had been identified as Prairie Caddo sites by Shafer; one of the sites was the Urbankte site (41CV26). The Urbankte site is on the Leon River in Coryell County, at Belton Reservoir; the Leon River is a southward-flowing tributary to the Brazos River. The term “Prairie Caddo” used by Shafer refers to Caddo groups affiliated with Caddo communities in East Texas, most likely affiliated with the George C. Davis site in the Neches River valley, that occupied portions of the Central Texas prairies in Late Prehistoric times, from ca. A.D. 1000-1300. Each of the four assemblages in the Brazos River basin have sherds that stylistically compare closely to decorated Caddo vessels from East Texas Caddo sites, and the distinctive character of these decorated sherds suggested that the four sites were occupied between ca. A.D. 1000-1200 or to post-ca. A.D. 1200-1300 times in the case of the Urbankte site. Where these ceramic assemblages seemed to differ from East Texas Caddo ceramics, however, was in their manufacture: the grog and bone temper inclusions added to the paste of the ceramic vessel sherds from these sites had numerous, large, and coarse-grained temper inclusions, while East Texas Caddo ceramics tend to have more fine-grained temper inclusions, even in the manufacture of utility ware jars. The Urbankte site ceramics (n=118 sherds) I examined at TARL were heavily bone-tempered (88 percent) and had a considerable proportion of brushed sherds (46 percent of the decorated sherds). Both characteristics were consistent with a post A.D. 1200-1300 Prairie Caddo occupation, as was the fact that eight of the nine arrow points in the TARL collections from the Urbankte site are Perdiz arrow points. The common occurrence of both Perdiz points and brushed ceramic sherds suggested then that this Prairie Caddo occupation at the Urbankte site took place sometime after ca. A.D. 1200-1300. As Dr. Shafer mentions below, the artifacts from the Urbankte site that he had discussed in the Prairie Caddo module were from a different part of the site than the TARL collection I had documented, and were from a different and earlier cultural component. We will return to those artifacts shortly

Reconciliation of object interaction models

This paper presents Reconciliation+, a tool-supported method which identifies overlaps between models of different object interactions expressed as UML sequence and/or collaboration diagrams, checks whether the overlapping elements of these models satisfy specific consistency rules, and guides developers in handling these inconsistencies. The method also keeps track of the decisions made and the actions taken in the process of managing inconsistencies

Ekeland’s variational principle in weak and strong systems of arithmetic

We analyze Ekeland’s variational principle in the context of reverse mathematics. We find that that the full variational principle is equivalent to Π11- CA0, a strong theory of second-order arithmetic, while natural restrictions (e.g. to compact spaces or to continuous functions) yield statements equivalent to weak König’s lemma (WKL0) and to arithmetical comprehension (ACA0). We also find that the localized version of Ekeland’s variational principle is equivalent to Π11- CA0, even when restricted to continuous functions. This is a rare example of a statement about continuous functions having great logical strength