63 research outputs found
A Multisegment Dynamic Model of Ski Jumping
This paper presents a planar, four-segment, dynamic model for the flight
mechanics of a ski jumper. The model consists of skis, legs, torso and head,
and anns. Inputs include net joint torques that are used to vary the relative
body configurations of the jumper during fiight. The model also relies on
aerodynamic data from previous wind tunnel tests that incorporate the effects
of varying body configuration and orientation on lift, drag, and pitching
moment. A symbolic manipulation program, "Macsyma," is used to derive
the equations of motion automatically. Experimental body segment orientation
data during the fiight phase arc presented for three ski jumpers which
show how jumpers of varying ability differ in flight and demonstrate tlie need
for a more complex analytical model than that previously presented in the
literature. Simulations are presented that qualitatively match the measured
trajectory for a good jumper. The model can be used as a basis for the study
of optimal jumper behavior in fiight which maximizes jump distance
Novel genetic loci associated with hippocampal volume
The hippocampal formation is a brain structure integrally involved in episodic memory, spatial navigation, cognition and stress responsiveness. Structural abnormalities in hippocampal volume and shape are found in several common neuropsychiatric disorders. To identify the genetic underpinnings of hippocampal structure here we perform a genome-wide association study (GWAS) of 33,536 individuals and discover six independent loci significantly associated with hippocampal volume, four of them novel. Of the novel loci, three lie within genes (ASTN2, DPP4 and MAST4) and one is found 200 kb upstream of SHH. A hippocampal subfield analysis shows that a locus within the MSRB3 gene shows evidence of a localized effect along the dentate gyrus, subiculum, CA1 and fissure. Further, we show that genetic variants associated with decreased hippocampal volume are also associated with increased risk for Alzheimer's disease (rg =-0.155). Our findings suggest novel biological pathways through which human genetic variation influences hippocampal volume and risk for neuropsychiatric illness
A Comparison of Techniques Used in Performing the Men’s Compulsory Gymnastic Vault at the 1988 Olympics
3-D Analysis of Yurchenko Vaults Performed by Female Gymnasts During the 1988 Seoul Olympic Games
Blocking and Postflight Techniques of Male Gymnasts Performing the Compulsory Vault at the 1988 Olympics
The effects of source credibility and message variation on mail survey response behaviour
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