On the rigidity of triangulated hyperbolic paraboloids

The paper investigates the rigidity of two classes of three-dimensional pin-jointed assemblies which describe triangulated surfaces of hyperbolic paraboloidal shape: type 1 with straight boundaries, and type 2 with parabolic boundaries. The two arrangements have identical horizontal plans. The investigation begins with a brief historic review of techniques for detecting lack of rigidity. The behaviour of both type-1 and type-2 assemblies depends on the number n of bars on each edge of the structure and, although both geometric arrangements satisfy Maxwell rule (3 j ═ b , where j is the number of joints and b is the number of bars) for any value of n , all type-1 assemblies with n even and greater than 2 and type-2 assemblies with n > 1 are in fact not rigid. This result is first proved for some specific cases by the zero-load test; and then for arbitrary values of n . The equilibrium equations of each joint are written down in terms of a stress function, and are then assembled in an equilibrium matrix whose rank is found by general matrix manipulations. The number of inextensional mechanisms and static redundancies is also obtained. The rigidity of assemblies consisting of four interconnected type-1 hyperbolic paraboloidal sheets is also discussed, and it is concluded that they are equally prone to the same kind of misbehaviour.

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Three-dimensional kinematics of the lunate, hamate, capitate and triquetrum with type 1 or 2 lunate morphology

Journal of Hand Surgery (European Volume) ◽

10.1177/1753193417744420 ◽

2017 ◽

Vol 43 (4) ◽

pp. 380-386 ◽

Cited By ~ 4

Author(s):

Shingo Abe ◽

Hisao Moritomo ◽

Kunihiro Oka ◽

Kazuomi Sugamoto ◽

Kenji Kasubuchi ◽

...

Keyword(s):

Standard Deviation ◽

Wrist Joint ◽

Three Dimensional ◽

Wrist Flexion ◽

Ulnar Deviation ◽

Dart Throwing ◽

Carpal Kinematics ◽

Throwing Motion

The purpose of this study was to investigate the differences in three-dimensional carpal kinematics between type 1 and 2 lunates. We studied 15 instances of wrist flexion to extension (nine type 1, six type 2), 13 of radial to ulnar deviation (seven type 1, six type 2), and 12 of dart-throwing motion (six each of type 1 and 2) in 25 normal participants based on imaging with computerized tomography. Mean proximal translation of the distal articular midpoint of the triquetrum relative to type 2 lunates during wrist radioulnar deviation was 2.9 mm (standard deviation (SD) 0.7), which was significantly greater than for type 1 lunates, 1.6 mm (SD 0.6). The hamate contacted the lunate in ulnar deviation and ulnar flexion of wrists with type 2 lunates but not with type 1. We conclude that the four-corner kinematics of the wrist joint are different between type 1 and 2 lunates.

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Three-dimensional structure of a mouse-adapted type 2/type 1 poliovirus chimera.

The EMBO Journal ◽

10.1002/j.1460-2075.1991.tb07772.x ◽

1991 ◽

Vol 10 (9) ◽

pp. 2331-2341 ◽

Cited By ~ 54

Author(s):

T.O. Yeates ◽

D.H. Jacobson ◽

A. Martin ◽

C. Wychowski ◽

M. Girard ◽

...

Keyword(s):

Three Dimensional ◽

Dimensional Structure ◽

Three Dimensional Structure

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Targeting Alcohol Septal Ablation in Patients with Obstructive Hypertrophic Cardiomyopathy Candidates for Surgical Myectomy: Added Value of Three-Dimensional Intracoronary Myocardial Contrast Echocardiography

Journal of Clinical Medicine ◽

10.3390/jcm10102166 ◽

2021 ◽

Vol 10 (10) ◽

pp. 2166

Author(s):

Giovanni La La Canna ◽

Iside Scarfò ◽

Irina Arendar ◽

Antonio Colombo ◽

Lucia Torracca ◽

...

Keyword(s):

High Risk ◽

Three Dimensional ◽

Added Value ◽

Alcohol Septal Ablation ◽

High Risk Type ◽

Life Threatening ◽

Surgical Myectomy

Background: Myocardial contrast two-dimensional echocardiography (MC-2DE) is widely used to address alcohol septal ablation (ASA) in obstructive hypertrophic cardiomyopathy (HCM). Owing to its limited cut-planes, MC-2DE may inaccurately identify the contrast misplacement associated with an unsuccessful or complicated ASA outcome. Objective: The aim of this study was to assess the added value of myocardial contrast three-dimensional echocardiography (MC-3DE) compared with MC-2DE to identify the appropriate matching between the target septal zone (TSZ) and coronary artery branch for safe and long-term effective ASA in HCM patients. Methods: A consecutive series of 52 symptomatic obstructive HCM patients referred for isolated surgical myectomy (SM) was analyzed with MC-2DE and MC-3DE following injection of echocontrast into one or more septal branches. MC-2DE and MC-3DE patterns were categorized according to complete (Type 1) or incomplete (Type 2) TSZ covering, high-risk (Type 3) exceeding TSZ, or life-threatening outside TSZ distribution (Type 4). Results: MC-2DE per patient analysis showed a Type 1 pattern in 32 patients and Types 2–4 in the remaining 20 patients; subsequent MC-3DE analysis provided a re-phenotyping of MC-2DE findings in 22 of the 52 patients (42%), showing a high-risk Type 2 pattern in 17 of the 32 patients with Type 1, and a new life-threatening Type 4 in three patients with Type 2, respectively. All patients with MC-3DE Type 1 pattern underwent safe and effective ASA with a long-term uneventful follow-up, while the remaining patients underwent SM. Conclusions: Refining high risk or life-threatening contrast misplacement, MC-3DE is more accurate than conventional MC-2DE to target safe and long-term effective septal reduction with ASA in obstructive HCM patients referred for isolated SM.

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Pecking preferences in hatchlings of the Australian brush-turkey, Alectura lathami (Megapodiidae): the role of food type and colour

Australian Journal of Zoology ◽

10.1071/zo01046 ◽

2002 ◽

Vol 50 (1) ◽

pp. 93 ◽

Cited By ~ 8

Author(s):

Ann Göth ◽

Heather Proctor

Keyword(s):

Three Dimensional ◽

Food Type ◽

Live Prey ◽

Choice Tests ◽

Alectura Lathami ◽

Mealworm Larvae ◽

Strong Contrast

Chicks of megapodes, including the Australian brush-turkey, Alectura lathami, live independently, without parents to show them where and what to eat. This paper represents the first investigation of how megapode chicks find and identify food. The specific questions addressed are: whether naive brush-turkey hatchlings are able to differentiate between food and objects that do not give a nutritional reward; whether they possess a preference for certain types of food; and which factors are most likely to trigger feeding in hatchlings. The three questions were approached by pairwise choice tests of two types. In Type 1, chicks were offered mealworm larvae, fruit cubes, seeds and non-nutritious objects (pebbles); in Type 2, chicks were offered beads of four different colours (red, green, blue and yellow). The median peck rate at pebbles was always significantly lower than that at mealworms, fruit or seeds. Mealworms received significantly more pecks than seeds or pebbles. Chicks showed no clear preference for any colour. All chicks also directed some pecks at ‘other items’ that appeared to display a strong contrast against the background of the box they were kept in, either in colour (e.g. dark knotholes in light brown wood) or in shape (three-dimensional, such as claws and faeces). Hatchlings seem to direct their initial pecks at objects that have certain characteristics in common, such as contrast, movement (for live prey) and reflective surfaces (for fruit or seeds). Preference for these rather general characteristics may be adaptive considering that chicks can hatch in various habitats and different months of the year, making the types of food available at hatching unpredictable.

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A Preliminary Model of the Wrist Midcarpal Joint

Journal of Wrist Surgery ◽

10.1055/s-0041-1728804 ◽

2021 ◽

Author(s):

Martin Pendola ◽

Catherine Petchprapa ◽

Ronit Wollstein

Keyword(s):

Ex Vivo ◽

Three Dimensional ◽

Ct Scans ◽

Ex Vivo Model ◽

Carpometacarpal Joints ◽

Force Transfer ◽

Midcarpal Joint

Abstract Background A challenge to deciphering the effect of structure on function in the wrist involves difficulty in obtaining in-vivo information. To provide a platform to study wrist mechanics using in vivo acquired forces, we developed a model of the midcarpal joint based on computed tomography (CT) scans of normal wrists. Finite element analysis (FEA) can enable application of in vivo collected information to an ex vivo model. Objectives The objectives of this study are to (1) create a three-dimensional model of the midcarpal joint of the wrist based on CT scans and (2) generate separate models for the midcarpal joint based on two distinct wrist types and perform a pilot loading of the model. Methods CT scans from a normal patient database were converted to three-dimensional standard template library (STL) files using OsiriX software. Five type 1 and five type 2 wrists were used for modeling. A simulated load was applied to the carpometacarpal joints in a distal-to-proximal direction, and FEA was used to predict force transfer in the wrist. Results There were 33% type 1 and 67% type 2 wrists. The midcarpal joint dimensional measurements estimated from the model had intermediate agreement between wrist type as measured on CT scan and as predicted by the model: 56% Cohen's kappa (95% confidence interval) = 0.221 (0.05–0.5). Surface stress on the carpometacarpal joints is different in type 1 and type 2 wrists. On loading the neutral wrist, the capitolunate angle was 90 degrees in type 1 wrists and 107 degrees in type 2 wrists (p < 0.0001). Conclusions The model predicted differences in movement and force transfer through the midcarpal joint dependent on structural type. This knowledge can improve our understanding of the development of disparate patterns of degeneration in the wrist.

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Assessment of facial landmarks for bone asymmetry in geometric morphometric studies: A review

South European Journal of Orthodontics and Dentofacial Research ◽

10.5937/sejodr7-29735 ◽

2021 ◽

Vol 7 (2(S)) ◽

pp. 6-16

Author(s):

Ivana Rupic ◽

Ivana Čuković-Bagić ◽

Vladimir Ivković ◽

Tomislav Lauc

Keyword(s):

Systematic Review ◽

Three Dimensional ◽

Facial Asymmetry ◽

Research Subjects ◽

Geometric Morphometric ◽

Three Dimensional Images ◽

Definition Of

Background Anthropometrical points or landmarks are key for facial shape analysis using geometric morphometrics. In the early 1990s Fred Bookstein created a classification system with landmarks type 1., type 2., type 3. based on anatomical landmark homology. However, thirty years later, a uniform referece index of landmarks that can be used for assessing facial asymmetry still does not exist. The criteria for selecting landmark points are not fully defined, which makes classification of homology and and landmarks prone to arbitrary interpretations. A systematic review of literature indicates that authors of studies do not provide explanation for choosing exact points. Most of them also do not provide a clear definition of landmarks and landmarks classification according to homology. Objective The objective of this systematic review was to assess, in an evidence based manner, which landmarks inside the Bookstein groups of on facial hard tissues can be reccomended for facial asymmetry assessment using geometric mophometrics. Search methods An electronic search of 9 databases up to March 2020 by two reviewers was conducted to identify relevant articles. Selection criteria Prospective randomized, non-randomized controlled trials and cross sectional studies reporting on facial asymmetry using three-dimensional images and geometric morphometric methods. The reasons for assessing facial asymmetry were not considered. Data collection and analysis The 23 selected studies were categorized according to the number and specification of the research subjects, types of three-dimensional images, number of landmarks, and the craniofacial region of interest. All landmarks were extracted with the following data: name, abbreviation, and the author’s definition of the location. Results The craniofacial region is divided into neurobasic cranial part, ethmomaxillar part and the mandible. Assessment of neurobasic cranial asymmetry was conducted in 6 studies and 45 different landmarks were recorded, of which 11 were medial and 34 bilateral. Bregma and Lambda occur most frequently and according to homology both belong to type 1 landmarks. Assessment of ethmomaxillary asymmetry was conducted in 21 studies and 68 different landmarks were recorded, of which 16 were medial and 52 bilateral. Nasion and Jugale occur most frequently and according to homology Nasion belongs to type 1 landmarks and Jugale to type 2 landmarks. Conclusion The selection and definition of craniofacial hard tissue landmarks is one of the most important tasks in the design of morphometric studies, and thus for the purpose of assessing facial asymmetry. The review provides an extensive cross-section of possible landmarks with the definition of the location as well as the possible location variation. The list of these landmarks should be observed through the classification of landmarks according to their homology, as well as possible variations of the classification.

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Convective dynamo action in a spherical shell: symmetries and modulation

Journal of Fluid Mechanics ◽

10.1017/jfm.2016.407 ◽

2016 ◽

Vol 799 ◽

Cited By ~ 7

Author(s):

Raphaël Raynaud ◽

Steven M. Tobias

Keyword(s):

Solar Activity ◽

Magnetic Fields ◽

Spherical Shell ◽

Differential Rotation ◽

Three Dimensional ◽

Important Process ◽

Dynamo Action ◽

Grand Minima

We consider dynamo action driven by three-dimensional rotating anelastic convection in a spherical shell. Motivated by the behaviour of the solar dynamo, we examine the interaction of hydromagnetic modes with different symmetries and demonstrate how complicated interactions between convection, differential rotation and magnetic fields may lead to modulation of the basic cycle. For some parameters, type 1 modulation occurs by the transfer of energy between modes of different symmetries with little change in the overall amplitude; for other parameters, the modulation is of type 2, where the amplitude is significantly affected (leading to grand minima in activity) without significant changes in symmetry. Most importantly, we identify the presence of ‘supermodulation’ in the solutions, where the activity switches chaotically between type 1 and type 2 modulation; this is believed to be an important process in solar activity.

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