Discovery of period doubling in BL Herculis stars of the OGLE survey. Observations and theoretical models

We report the discovery of a period doubling behaviour in a 2.4d BL Herculis-type variable of the Galactic bulge. Another bulge BL Her-type star (P=2.25d) is a strong period doubling candidate. Both objects have been identified with the OGLE-III photometry. Possibility of period doubling in this type of pulsators has been predicted almost twenty years ago by Buchler & Moskalik. Our finding is the first observational confirmation of their theoretical results. Discovery of the first BL Herculis star showing the period doubling effect motivates a new theoretical investigation with the state-of-the-art convective pulsation codes. We present the results of initial model survey, specifically aimed at studying the observed period-doubled BL Her variable. All of our non-linear models have P=2.4d. The computations confirm that the period doubling effect is caused by the 3:2 resonance between the fundamental mode and the first overtone, as indicated by earlier radiative models of Buchler & Moskalik. Comparison of the computed and the observed light curves allows to constrain the parameters of the star, in particular its metallicity, which appears to be high, Z is approximately 0.01. The recent evolutionary tracks put also constraint on the mass of the star, which is close to M=0.50 solar masses.Comment: 18 pages, 18 figures, accepted for publication in MNRA

Mittelfristige Ergebnisse nach mediokarpaler Teilarthrodese mit kortikospongiösem Beckenkammspan bei SLAC/SNAC-wrist Grad II/III

Purpose: The four-corner-fusion is an option for grade II/III SNAC-/SLAC-wrists. The case-control study evaluates the results of a four-corner-fusion with a screw-fixed iliac crest cortical chip. Methods: Ten patients with SNAC/SLAC-wrist >= grade II were treated. The evaluation occurred after 24 months using a standard study protocol. Results: The mean postoperative active range of motion were 46% (extension/flexion) and 52% (radial/ulnar deviation) of the contralateral wrist respectively. The postoperative mean grip strength was 43% of the contralateral side, and 84% compared to the preoperative values. The mean Cooney-Bussey Score was 63 and the mean DASH score was 25 (p<=0.05). Four of the patients (40%) had to undergo a partial removal of the osteosynthetic material because of radiodorsal impingement. Conclusions: The four-corner fusion using an iliac crest cortical chip represents an alternative operating procedure for treatment, even though the period of immobilisation cannot be reduced.Hintergrund: Die mediokarpale Teilarthrodese stellt eine anerkannte Behandlungsmethode bei karpalen Kollaps nach Skaphoidpseudarthrose (SNAC-wrist) oder nach Ruptur des skapholunären Bandes (SLAC-wrist) dar. Anhand der vorliegenden Fall-Kontrollstudie wurden die Ergebnisse nach mediokarpaler Teilarthrodese unter Verwendung eines kortikospongiösen Beckenkammspanes evaluiert. Material und Methoden: Zehn Patienten wurden 24 Monate nach mediokarpaler Teilarthrodese bei mit SLAC/SNAC-wrist Grad II/III mit einem kortikospongiösen Beckenkammspan nachuntersucht. Ergebnisse: Das mittlere postoperative Bewegungsausmaß des Handgelenkes betrug für Extension/Flexion 46% und für Radial-/Ulnaradduktion 52% im Vergleich zur unbehandelten Gegenseite. Die postoperative Griffstärke betrug im Mittel 43% der Gegenseite und 84% der präoperativen Werte. Der mittlere Cooney-Bussey-Score lag bei 63, der mittlere DASH-Score bei 25 (p<=0.05). Bei vier Patienten (40%) erfolgte eine partielle Entfernung des Osteosynthesematerials aufgrund eines radiodorsalen Impingements. Schlussfolgerung: Die mediokarpale Teilarthrodese mit einem kortikospongiösen Beckenkammspan stellt eine mögliche Behandlungsalternative dar, obwohl die Dauer der Immobilisation nicht reduziert werden kann

Mediokarpale Teilarthrodese mit einem kortikospongiösem Beckenkammspan zur Behandlung des karpalen Kollapses im Stadium II/III nach Scaphoidpseudarthrose (SNAC-wrist) bzw. scapholunärer Dissoziation (SLAC-wrist)

Paul Lucas' Big Wheel - BW61 - photographed 8 July 2000