Sexual Activity After Total Hip Arthroplasty: A Motion Capture Study

The Journal of Arthroplasty
Volume 29, Issue 3, Pages 640-647, March 2014
doi:10.1016/j.arth.2013.07.043

Caecilia Charbonnier, PhD [a], Sylvain Chagué, MS [a], Matteo Ponzoni, MS [b], Massimiliano Bernardoni, MS [b], Pierre Hoffmeyer, MD [c], Panayiotis Christofilopoulos, MD [c]

[a] Medical Research Department, Artanim Foundation, Geneva, Switzerland
[b] Medacta International SA, Lugano, Switzerland
[c] Department of Surgery, Orthopedics and Trauma Service, University Hospitals of Geneva, Geneva, Switzerland

Abstract

Relative risk of impingement and joint instability during sexual activities after total hip arthroplasty (THA) has never been objectively investigated. Hip range of motion necessary to perform sexual positions is unknown. A motion capture study with two volunteers was performed. 12 common sexual positions were captured and relevant hip joint kinematics calculated. The recorded data were applied to prosthetic hip 3D models to evaluate impingement and joint instability during motion. To explore the effect of acetabular component positioning, nine acetabular cup positions were tested. Four sexual positions for women requiring intensive flexion (> 95°) caused prosthetic impingements (associated with posterior instability) at 6 cup positions. Bony impingements (associated with anterior instability) occurred during one sexual position for men requiring high degree of external rotation (> 40°) combined with extension and adduction at all cup positions. This study hence indicates that some sexual positions could be potentially at risk after THA, particularly for women.

http://www.sciencedirect.com/science/article/pii/S0883540313005615

http://www.arthroplastyjournal.org/article/S0883-5403%2813%2900561-5/abstract

Coins falling in water

Journal of Fluid Mechanics
Volume 742 / March 2014, pp 243-253
Cambridge University Press
DOI: http://dx.doi.org/10.1017/jfm.2014.6

Luke Heisinger, Paul Newton and Eva Kanso

University of Southern California, Los Angeles, CA 90089, USA

Abstract

When a coin falls in water, its trajectory is one of four types, determined by its dimensionless moment of inertia I∗ and Reynolds number Re: (A) steady; (B) fluttering; (C) chaotic; or (D) tumbling. The dynamics induced by the interaction of the water with the surface of the coin, however, makes the exact landing site difficult to predict a priori. Here, we describe a carefully designed experiment in which a coin is dropped repeatedly in water to determine the probability density functions (p.d.f.s) associated with the landing positions for each of the four trajectory types, all of which are radially symmetric about the centre drop-line. In the case of the steady mode, the p.d.f. is approximately Gaussian distributed with small variances, indicating that the coin is most likely to land at the centre, right below the point from which it is dropped. For the other falling modes, the centre is one of the least likely landing sites. Indeed, the p.d.f.s of the fluttering, chaotic and tumbling modes are characterized by a ‘dip’ around the centre. In the tumbling mode, the p.d.f. is a ring configuration about the centreline whereas in the chaotic mode, the p.d.f. is generally a broadband distribution spread out radially symmetrically about the centreline. For the steady and fluttering modes, the coin never flips, so the coin lands with the same side up as when it was dropped. The probability of heads or tails is close to 0.5 for the chaotic mode and, in the case of the tumbling mode, the probability of heads or tails is based on the height of the drop which determines whether the coin flips an even or odd number of times during descent.

The original version of this article was published with the incorrect order of authors. A notice detailing this has been published and the error rectified in the online and print PDF and HTML copies.

http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9179743

Development of the external genitalia: Perspectives from the spotted hyena (Crocuta crocuta)

Differentiation. 2014 pii: S0301-4681(13)00087-X
doi: 10.1016/j.diff.2013.12.003
Available online 28 February 2014
[Epub ahead of print]

Gerald R. Cunha [a,b], Gail Risbridger [b], Hong Wang [b], Ned J. Place [c], Mel Grumbach [d], Tristan J. Cunha [a], Mary Weldele [e], Al J. Conley [f], Dale Barcellos [g], Sanjana Agarwal [g], Argun Bhargava [g], Christine Drea [h], Geoffrey L. Hammond [i], Penti Siiteri [j], Elizabeth M. Coscia [k], Michael J. McPhaul [l], Laurence S. Baskin [a], Stephen E. Glickman [e]

[a] Department of Urology, University of California San Francisco, 400 Parnassus Avenue, Box A610, San Francisco, CA 94143, United States
[b] Department of Anatomy & Developmental Biology, Monash University, Clayton Campus, Building 76 Level 3, Wellington Road, Clayton, VIC, Australia
[c] Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, United States
[d] Department of Pediatrics, University of California San Francisco, Box 0434, San Francisco, CA 94143, United States
[e] Departments of Psychology and Integrative Biology, University of California, Berkeley, CA 94720, United States
[f] Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA 95616, United States
[g] Monte Vista High School, Cupertino, CA 95014, United States
[h] Departments of Evolutionary Anthropology and Biology, Duke University, Durham, NC 27708, United States
[i] Department of Cellular & Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
[j] Department of Obstetrics and Gynecology, University of California San Francisco, 400 Parnassus Avenue, Box A610, San Francisco, CA 94143, United States
[k] Salesian High School, Richmond, CA 94804, United States
[l] University of Texas Southwestern, Division of Endocrinology and Metabolism, 5323 Harry Hines Blvd., Dallas, TX, 75390-8857 and Quest Diagnostics, Endocrine Division, 33608 Ortega Highway, San Juan Capistrano, CA 92675, United States

Abstract

This review/research paper summarizes data on development of the external genitalia of the spotted hyena, a fascinating mammal noted for extreme masculinization of the female external genitalia. The female spotted hyena is the only extant mammal that mates and gives birth through a pendulous penis-like clitoris. Our studies indicate that early formation of the phallus in both males and females is independent of androgens; indeed the phallus forms before the fetal testes or ovaries are capable of synthesizing androgens. Likewise, pre- and postnatal growth in length of the penis and clitoris is minimally affected by “androgen status”. Nonetheless, several internal morphologies, as well as external surface features of the phallus, are androgen-dependent and thus account for dimorphism between the penis and clitoris. Finally, estrogens play a critical role in penile and clitoral development, specifying the position of the urethral orifice, determining elasticity of the urethral meatus, and facilitating epithelial–epithelial fusion events required for proper formation of the distal urethra/urogenital sinus and prepuce. Accordingly, prenatal inhibition of estrogen synthesis via administration of letrozole (an aromatase inhibitor) leads to malformations of the glans as well as the prepuce (hypospadias). The effects of prenatal androgens, anti-androgens and impaired estrogen synthesis correlated with the tissue expression of androgen and estrogen receptors.

http://www.sciencedirect.com/science/article/pii/S030146811300087X

Shrouded in the Veil of Darkness: Machiavellians but not narcissists and psychopaths profit from darker weather in courtship

Personality and Individual Differences
Available online 7 February 2014
In Press, Corrected Proof
http://dx.doi.org/10.1016/j.paid.2014.01.020

John F. Rauthmann [a], Marlit Kappes [a], Johannes Lanzinger [b]

[a] Humboldt-Universität zu Berlin, Departmernt of Psychology, Rudower Chaussee 18, D-12489 Berlin-Adlershof, Germany
[b] Leopold-Franzens Universität Innsbruck, Department of Psychology, Innrain 52, A-6020 Innsbruck, Austria

Abstract

We proposed in the “Veil of Darkness” hypothesis that dark personalities (narcissists, Machiavellians, psychopaths) profit from conditions of less illumination where they can better manipulate others. As an initial test of this hypothesis in the domain of mating, we predicted that male dark personalities should be more successful in their courtship during dark/cloudy rather than bright/sunny weather. In a large naturalistic field-study, 59 men romantically advanced 1395 women on the street, while they were unobtrusively followed by confederate observers. We thus obtained ratings from men, women, and observers on women’s reactions to men’s advances. Machiavellians, but not narcissists and psychopaths, elicited more positive reactions from women during cloudy weather. This effect was mediated by Machiavellian men’s assuredness. We discuss different mechanisms that may constitute the observed Veil of Darkness effect for Machiavellianism.

Keywords

Dark Triad; Narcissism; Machiavellianism; Psychopathy; Courtship; Mating; Veil of Darkness

Highlights

• Veil of Darkness hypothesis: dark personalities perform well during less illumination.
• Tested in courtship/mating domain for dark/cloudy vs. bright/sunny weather.
• Male Machiavellians (but not narcissists and psychopaths) elicited more positive responses from women during dark weather.

http://www.sciencedirect.com/science/article/pii/S0191886914000403