A systematic correlation between two-dimensional flow topology and the abstract statistics of turbulence

Velocity differences in the direct enstrophy cascade of two-dimensional turbulence are correlated with the underlying flow topology. The statistics of the transverse and longitudinal velocity differences are found to be governed by different structures. The wings of the transverse distribution are dominated by strong vortex centers, whereas, the tails of the longitudinal differences are dominated by saddles. Viewed in the framework of earlier theoretical work this result suggests that the transfer of enstrophy to smaller scales is accomplished in regions of the flow dominated by saddles.Comment: 4 pages, 4 figure

Costs of Locomotion in Polar Bears: When do the Costs Outweigh the Benefits of Chasing Down Terrestrial Prey?

Trade-offs between locomotory costs and foraging gains are key elements in determining constraints on predator–prey interactions. One intriguing example involves polar bears pursuing snow geese on land. As climate change forces polar bears to spend more time ashore, they may need to expend more energy to obtain land-based food. Given that polar bears are inefficient at terrestrial locomotion, any extra energy expended to pursue prey could negatively impact survival. However, polar bears have been regularly observed engaging in long pursuits of geese and other land animals, and the energetic worth of such behaviour has been repeatedly questioned. We use data-driven energetic models to examine how energy expenditures vary across polar bear mass and speed. For the first time, we show that polar bears in the 125–235 kg size range can profitably pursue geese, especially at slower speeds. We caution, however, that heat build-up may be the ultimate limiting factor in terrestrial chases, especially for larger bears, and this limit would be reached more quickly with warmer environmental temperatures

The Ursinus Weekly, January 12, 1948

Bruins rally in closing minutes to upset Haverford, 52-47 • Work on \u2748 Ruby nearly completed; Request snapshots • Guest speaker claims U.S. change of policy needed to set peace • Bulletin columnist will address gridders at banquet tomorrow • Spanish Club hears Dr. R. Juarez discourse on present-day Cuba • Frats schedule annual rushing period; Joint council also plans Valentine hop • Sophs plan dance to open new term • Contest for May Pageant scripts announced at meeting of senate • Y holds annual retreat; Idler quits cabinet post • West Chester prof gives illustrated talk to FTA • Winter examination schedule • Dr. Miller, Dean Pancoast attend political science convention • Phys-Ed. group names officers • Alumni-society notes • In retrospect • Debate Club organizes for contest with Gettysburg • Red Cross drive nets $41 • Speedy PMC five trips Grizzlies, 60-48; Jayvees rack up 62-60 win in prelim • Court officials\u27 exam given • Bearettes face Albright in opening court game • Pharmacy quintet rallies to shade Grizzlies, 48-46 • Grapplers open Wednesday • Long lads get short end of basketball tusslehttps://digitalcommons.ursinus.edu/weekly/3125/thumbnail.jp

Emerging roles of ATG7 in human health and disease

The cardinal stages of macroautophagy are driven by core autophagy-related (ATG) proteins, whose ablation largely abolishes intracellular turnover. Disrupting ATG genes is paradigmatic of studying autophagy deficiency, yet emerging data suggest that ATG proteins have extensive biological importance beyond autophagic elimination. An important example is ATG7, an essential autophagy effector enzyme that in concert with other ATG proteins, also regulates immunity, cell death and protein secretion, and independently regulates the cell cycle and apoptosis. Recently, a direct association between ATG7 dysfunction and disease was established in patients with biallelic ATG7 variants and childhood-onset neuropathology. Moreover, a prodigious body of evidence supports a role for ATG7 in protecting against complex disease states in model organisms, although how dysfunctional ATG7 contributes to manifestation of these diseases, including cancer, neurodegeneration and infection, in humans remains unclear. Here, we systematically review the biological functions of ATG7, discussing the impact of its impairment on signalling pathways and human pathology. Future studies illuminating the molecular relationship between ATG7 dysfunction and disease will expedite therapies for disorders involving ATG7 deficiency and/or impaired autophagy.Peer reviewe

Quasilinear theory of the 2D Euler equation

We develop a quasilinear theory of the 2D Euler equation and derive an integro-differential equation for the evolution of the coarse-grained vorticity. This equation respects all the invariance properties of the Euler equation and conserves angular momentum in a circular domain and linear impulse in a channel. We show under which hypothesis we can derive a H-theorem for the Fermi-Dirac entropy and make the connection with statistical theories of 2D turbulence.Comment: 4 page

Stent frame movement following endovascular aneurysm sealing in the abdominal aorta

Purpose: We investigated the incidence and extent of stent migration after endovascular sealing of abdominal aortic aneurysms (EVAS), its relationship with adherence to the instructions for use of the Nellix endograft and its association with aneurysm growth. Methods: In this retrospective single centre study, the clinical data and follow-up CT images of patients undergoing infra-renal EVAS with a minimum follow-up of 1 year were reviewed. The first postoperative CT scan at one month and the subsequent scans were used to measure the distances between the proximal end of the stent and reference visceral vessels using a previously validated technique. Device migration was based on the Society of Vascular Surgery definition of >10mm downward movement of either Nellix stent in the proximal landing zone; furthermore, we defined proximal displacement a downward movement of ≥4mm. Patients were categorised according to adherence to the old (2013) or new (2016) Nellix IFU. Aneurysm diameter was measured for each scan and a change of ≥5mm was deemed indicative of aneurysm growth. Results: Seventy-five patients were eligible for inclusion in our study. Over a 4-year period, migration ≥4mm occurred in 42 (56%) patients and migration of ≥10mm in 16 (21%), with similar incidence in right and left stents. Migration ≥4mm was significantly more frequent among patients whose anatomy did not conform to any IFU (p=0.025). Presence of aneurysm growth ≥5mm was observed in 14 patients (19%) and was significantly associated with proximal displacement ≥4mm (p=0.03). Conclusion: Infra-renal EVAS may be complicated by proximal displacement and migration, particularly when performed outside IFU. The definition of migration used for EVAR is inappropriate for EVAS; a new consensus on definition and measurement technique is necessary

Migration of the Nellix Endoprosthesis

Background This study reports the incidence and sequelae of migration of the Nellix (Endologix Inc, Irvine, Calif) endoprosthesis after endovascular aneurysm sealing. Methods A review was performed of the follow-up imaging of all endovascular aneurysm sealing patients in a university hospital endovascular program who had a minimum follow-up of 1 year. The first postoperative and latest follow-up computed tomography scans were used to measure the distances between the proximal and distal borders of the stent grafts relative to reference vessels using a previously validated technique. Device migration was based on previously established criteria and defined as any stent graft movement of ≥4 mm related to a predefined reference vessel. Device movement in a caudal direction was given a positive value, and movement in a cranial direction was denoted by a negative value. Results Eighteen patients (35 stent grafts) were eligible for inclusion in this retrospective review. The mean preoperative abdominal aortic aneurysm diameter was 57 mm (standard deviation [SD], 5; range, 50-67 mm) and aortic neck length was 30 mm (SD, 16; range, 6-62 mm). Proximal migration, according to study definitions, was identified in six stent grafts (17%), all in a caudal direction. At 1 year the mean proximal migration distance was +6.6 mm (SD, 1.6; range, +4.7-+9.2 mm). Migration occurred in a single stent graft in four patients and bilaterally in one. No distal migration occurred. Conclusions Proximal migration of the Nellix endoprosthesis does occur and was without any sequelae in our series. Further investigations into the long-term positional stability of the Nellix device, together with a more thorough understanding of the etiology and consequences of migration, are required. Author conflict of interest: F.T. and R.F.K. have received professional fees and educational grants from Endologix. The editors and reviewers of this article have no relevant financial relationships to disclose per the JVS policy that requires reviewers to decline review of any manuscript for which they may have a conflict of interest