Comments on long-distance free fall

Autorotation of botanical samaras, with a consequent reduction in their rate of descent, increases dispersal range in the presence of horizontal winds. Samaras in initial free fall from rest pass through a brief transitional phase prior to reaching their minimum rate of descent and stable autorotation. By contrast, intense wind gusts and elastic recoil of tree branches can produce impulsive samara detachment and accelerate them rapidly through the air. Here, we investigate the autorotation of maple samaras when launched with a high initial impulse. Norway maple seeds catapulted either vertically or horizontally at approximately 9 m s −1 exhibited remarkably high and rapid decelerations (10–15 g ) and reached a near-zero translational speed in less than 150 ms. The initial rotational frequency of catapulted seeds was up to four times greater than that ultimately reached during steady-state autorotation. These helicopter seeds thus transiently produce very high lift forces (at Reynolds numbers near approximately 10 4 ) that act to enhance aerial transport. These findings are relevant to the modelling of long-distance seed dispersal in unsteady flows, as well as to the design of deceleration mechanisms based on lift generation, rather than drag-based devices such as parachutes.

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Errata in long-distance free fall

The Physics Teacher ◽

10.1119/1.880263 ◽

1999 ◽

Vol 37 (5) ◽

pp. 261-261 ◽

Cited By ~ 2

Author(s):

Joseph Gallant

Keyword(s):

Free Fall ◽

Long Distance

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Comments on long-distance free fall

The Physics Teacher ◽

10.1119/1.880264 ◽

1999 ◽

Vol 37 (5) ◽

pp. 261-261 ◽

Cited By ~ 2

Author(s):

A. P. French

Keyword(s):

Free Fall ◽

Long Distance

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The Fine Structure of Phloem Cells

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100119867 ◽

1985 ◽

Vol 43 ◽

pp. 632-635

Author(s):

James Cronshaw

Keyword(s):

Structural Studies ◽

High Concentration ◽

Long Distance ◽

Phloem Tissue ◽

Sieve Elements ◽

Long Distance Transport ◽

P Protein ◽

Companion Cells ◽

Electron Microscopical ◽

Distance Transport

Long distance transport in plants takes place in phloem tissue which has characteristic cells, the sieve elements. At maturity these cells have sieve areas in their end walls with specialized perforations. They are associated with companion cells, parenchyma cells, and in some species, with transfer cells. The protoplast of the functioning sieve element contains a high concentration of sugar, and consequently a high hydrostatic pressure, which makes it extremely difficult to fix mature sieve elements for electron microscopical observation without the formation of surge artifacts. Despite many structural studies which have attempted to prevent surge artifacts, several features of mature sieve elements, such as the distribution of P-protein and the nature of the contents of the sieve area pores, remain controversial.

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Popliteal entrapment syndrome and age

VASA ◽

10.1024/0301-1526/a000201 ◽

2012 ◽

Vol 41 (4) ◽

pp. 262-268 ◽

Cited By ~ 3

Author(s):

Schweizer ◽

Hügli ◽

Koella ◽

Jeanneret

Keyword(s):

Risk Factors ◽

Leg Pain ◽

Walking Distance ◽

Therapeutic Approaches ◽

Long Distance ◽

Entrapment Syndrome ◽

Long Distance Running ◽

Popliteal Entrapment ◽

Popliteal Entrapment Syndrome ◽

Atherosclerotic Risk Factors

On the occasion of diagnosing a popliteal entrapment syndrome in a 59-year old man with no cardiovascular risk factors, who developed acute ischemic leg pain during long distance running, we give an overview on this entity with emphasis on patientsage. The different types of the popliteal artery compression syndrome are summarized. The diagnostic and therapeutic approaches are discussed. The most important clinical sign of a popliteal entrapment syndrome is the lack of atherosclerotic risk factors in patients with limited walking distance. Not only in young athletes but also in patients more than 50 years old the popliteal entrapment syndrome has to be taken into account.

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Attachment Styles, Physical Proximity, and Relational Satisfaction

Aviation Psychology and Applied Human Factors ◽

10.1027/2192-0923/a000062 ◽

2014 ◽

Vol 4 (2) ◽

pp. 106-112

Author(s):

Anita Shrivastava ◽

Andrea Burianova

Keyword(s):

Attachment Styles ◽

Romantic Relationship ◽

Distinct Type ◽

Relational Satisfaction ◽

Long Distance ◽

Avoidant Attachment ◽

Geographic Separation ◽

Relationship Of ◽

Attachment Dimensions

This study aimed to explore the relationships between attachment styles, proximity, and relational satisfaction. This was achieved by assessing a distinct type of long distance romantic relationship of flying crews, compared with proximal (non-flying crew) romantic relationships. The responses of 139 expatriate professionals revealed significant associations between proximity and anxious and avoidant attachment dimensions. The role of the avoidant dimension in comparison with that of the anxious dimension was found to be a significant predictor of relational satisfaction. This study contributes significantly toward addressing the role of proximity and attachment in relational satisfaction in a new context of geographic separation.

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