scholarly journals The developing kidney actively negotiates geometric packing conflicts to avoid defects

2021 ◽  
Author(s):  
Louis S Prahl ◽  
John M Viola ◽  
Jiageng Liu ◽  
Alex James Hughes
Keyword(s):  
Packing Density ◽  
Geometric Constraints ◽  
Material Modeling ◽  
Limited Area ◽  
Surface Imaging ◽  
Vertical Orientation ◽  
Geometric Packing ◽  
Developing Kidney ◽  
Physical Limitations ◽  
Necessary And Sufficient

The physiological functions of several organs rely on branched tubular networks, but little is known about conflicts in development between building enough tubules for adequate function and geometric constraints imposed by organ size. We show that the mouse embryonic kidney epithelium negotiates a physical packing conflict between tubule tip duplication and limited area at the organ surface. Imaging, computational, and soft material modeling of tubule 'families' identifies six geometric packing phases, including two defective ones. Experiments in kidney explants show that a retrograde tension on tubule families is necessary and sufficient for them to avoid defects by switching to a vertical orientation that increases packing density. These results reveal developmental contingencies in response to physical limitations, and create a framework for classifying kidney defects.

scholarly journals Mitochondrial volume fraction and translation duration impact mitochondrial mRNA localization and protein synthesis

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Tatsuhisa Tsuboi ◽  
Matheus P Viana ◽  
Fan Xu ◽  
Jingwen Yu ◽  
Raghav Chanchani ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Energy Demand ◽  
Volume Fraction ◽  
Protein Composition ◽  
Mrna Localization ◽  
Geometric Constraints ◽  
Specific Gene ◽  
Translation Elongation ◽  
Mitochondrial Volume ◽  
Necessary And Sufficient

Mitochondria are dynamic organelles that must precisely control their protein composition according to cellular energy demand. Although nuclear-encoded mRNAs can be localized to the mitochondrial surface, the importance of this localization is unclear. As yeast switch to respiratory metabolism, there is an increase in the fraction of the cytoplasm that is mitochondrial. Our data point to this change in mitochondrial volume fraction increasing the localization of certain nuclear-encoded mRNAs to the surface of the mitochondria. We show that mitochondrial mRNA localization is necessary and sufficient to increase protein production to levels required during respiratory growth. Furthermore, we find that ribosome stalling impacts mRNA sensitivity to mitochondrial volume fraction and counterintuitively leads to enhanced protein synthesis by increasing mRNA localization to mitochondria. This points to a mechanism by which cells are able to use translation elongation and the geometric constraints of the cell to fine-tune organelle-specific gene expression through mRNA localization.

Structured Motion Planning in the Local Configuration Space

Robotica ◽  
1991 ◽  
Vol 9 (1) ◽  
pp. 81-92 ◽  
Author(s):  
A. M. S. Zalzala ◽  
A. S. Morris
Keyword(s):  
Configuration Space ◽  
Robot Manipulator ◽  
Time History ◽  
Geometric Constraints ◽  
Polynomial Splines ◽  
Time Motion ◽  
Local Configuration ◽  
Travelling Time ◽  
Physical Limitations ◽  
Manipulator Design

SUMMARYThe minimum-time motion of robot manipulators is solved by defining a suitable time history for the arm end-effector to traverse. As the planning is performed in the configuration space, the uniqueness of the proposed algorithm emerges from the combination of both cubic and quadratic polynomial splines. Furthermore, the highly efficient time optimisation procedure could be applied to local segments of each joint trajectory, leading to a significant reduction of the travelling time. In addition, the ability to perform a search in the work space is granted, exploiting all possible options for an optimum motion. The method proposed considers all realistic physical limitations inherent in the manipulator design, in addition to any geometric constraints imposed on the path. Simulation programs have been written, and results are reported for the Unimation PUMA 560 robot manipulator.

scholarly journals A FEMDEM NUMERICAL MODEL STUDY OF RUBBLE-MOUND STRUCTURES ARMOURED WITH CONCRETE ARMOUR UNITS

2012 ◽  
Vol 1 (33) ◽  
pp. 37
Author(s):  
John-Paul Latham ◽  
Eleni Anastasaki ◽  
Jiansheng Xiang
Keyword(s):  
Numerical Model ◽  
Packing Density ◽  
Single Layer ◽  
Geometric Constraints ◽  
Mechanical Equilibrium ◽  
Wave Loading ◽  
Model Study ◽  
Rubble Mound ◽  
Run Up ◽  
Numerical Model Study

A new method for the numerical creation of random single-layer systems of concrete armour units is illustrated. The armour layer pack is created by a FEMDEM solver that ensures mechanical equilibrium between all concrete units and rocks of the underlayer. The local and average packing density together with geometric constraints indicative of randomness and interlocking are assessed using analysis tools and shown to be in accordance with unit designer requirements. This solids modelling research is an essential pre-requisite to future simulation of the armour layer response to wave loading and more realistic modelling of wave run-up and overtopping on rubble-mound structures.

scholarly journals Handling and Curing Characteristics of Cut-Strip Tobacco. Part 1: Effect of Strip-Size, Packing Density and Mode of Orientation

2002 ◽  
Vol 20 (1) ◽  
pp. 7-13
Author(s):  
WH Johnson ◽  
JH Young ◽  
GH Ellington ◽  
WW Weeks ◽  
JC Tutor
Keyword(s):  
Packing Density ◽  
Energy Use ◽  
Energy Savings ◽  
Reducing Sugars ◽  
Leaf Chemistry ◽  
Vertical Orientation ◽  
Leaf Quality ◽  
Horizontal Orientation ◽  
Total Alkaloids ◽  
Packing Densities

AbstractPrevious work has demonstrated potential handling and curing efficiencies in the use of cut-strip tobacco. The present work considers further the effect of cut-strip size, packing density and mode of orientation on cured leaf chemistry (starch, reducing sugars, and total alkaloids) and leaf quality. Results showed that cured leaf chemistry of 15.2 × 22.9 cm cut-strip more closely matched properties of whole leaf than pieces 15.2 × 15.2 cm or smaller. Starch contents were significantly higher for the smaller cut-strip sizes, perhaps due to edge drying effects, while alkaloids were significantly lower. Within the range of 194 to 292 kg/m, packing density had little effect on leaf chemistry, with the exception that reducing sugars were slightly lower for the higher packing densities. This could be due to a longer time for the drying front to move through the more tightly packed tobacco, and hence more respiratory loss of sugars. Government grades and average market prices of cured strips were essentially unaffected over the range of strip sizes or packing densities tested. Based on airflow resistance measurements and observed drying characteristics, vertical orientation of strips was far superior to horizontal orientation, both with vertical airflow through the tobacco. The higher packing density reduced specific energy use (kWh/kg green tobacco) by as much as 22%, indicating potential energy savings for cut-strip over whole leaf curing.

The extinction time of a general birth and death process with catastrophes

1986 ◽  
Vol 23 (04) ◽  
pp. 851-858 ◽  
Author(s):  
P. J. Brockwell
Keyword(s):  
Laplace Transform ◽  
Size Distribution ◽  
Sufficient Conditions ◽  
Necessary And Sufficient Conditions ◽  
Death Process ◽  
Extinction Time ◽  
Birth And Death Process ◽  
Different Types ◽  
The Laplace Transform ◽  
Necessary And Sufficient

The Laplace transform of the extinction time is determined for a general birth and death process with arbitrary catastrophe rate and catastrophe size distribution. It is assumed only that the birth rates satisfyλ0= 0,λj> 0 for eachj> 0, and. Necessary and sufficient conditions for certain extinction of the population are derived. The results are applied to the linear birth and death process (λj=jλ, µj=jμ) with catastrophes of several different types.

High Resolution Low Loss Microscopy of Crystalline Surfaces

1980 ◽  
Vol 38 ◽  
pp. 162-163
Author(s):  
William Krakow ◽  
Alec N. Broers
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Surface Topography ◽  
Secondary Electron ◽  
Objective Lens ◽  
Surface Imaging ◽  
Low Loss ◽  
Fine Grained ◽  
Scanning Electron ◽  
Crystalline Surfaces

Low-loss scanning electron microscopy can be used to investigate the surface topography of solid specimens and provides enhanced image contrast over secondary electron images. A high resolution-condenser objective lens has allowed the low-loss technique to resolve separations of Au nucleii of 50Å and smaller dimensions of 25Å in samples coated with a fine grained carbon-Au-palladium layer. An estimate of the surface topography of fine grained vapor deposited materials (20 - 100Å) and the surface topography of underlying single crystal Si in the 1000 - 2000Å range has also been investigated. Surface imaging has also been performed on single crystals using diffracted electrons scattered through 10−2 rad in a conventional TEM. However, severe tilting of the specimen is required which degrades the resolution 15 to 100 fold due to image forshortening.

Thoughts on Grammar Intervention in AAC

2008 ◽  
Vol 17 (2) ◽  
pp. 43-49 ◽  
Author(s):  
Marc Fey
Keyword(s):  
Language Impairment ◽  
Specific Language Impairment ◽  
Augmentative And Alternative Communication ◽  
Communication Systems ◽  
Target Language ◽  
Alternative Communication ◽  
Physical Limitations ◽  
Communication Needs ◽  
Communication Interventions ◽  
Planning Intervention

Abstract In this article, I propose that, for several reasons, grammar should be an early focus of communication interventions for young children using augmentative and alternative communication (AAC) systems. The basic goals for such programs should be to facilitate the child's comprehension of the language of the community, or the target language, thus leading the way to literacy, and to foster the child's use of symbol combinations that mirror the grammatical patterns of speaking children acquiring the target language, even if they cannot be fully grammatically complete. I introduce five principles that underlie most successful approaches to grammar interventions with children with specific language impairment. My initial attempts to apply these principles to interventions with children with complex communication needs indicate that they may be of considerable value to clinicians planning intervention programs. On the other hand, the challenges posed by the intellectual and physical limitations of many AAC users and their communication systems make it necessary to modify at least Principle 5 if the basic goals of intervention are to be met.

New AAC Access Strategy for Gesture Tracking: A Technical Note

2012 ◽  
Vol 21 (1) ◽  
pp. 11-16 ◽  
Author(s):  
Susan Fager ◽  
Tom Jakobs ◽  
David Beukelman ◽  
Tricia Ternus ◽  
Haylee Schley
Keyword(s):  
Augmentative And Alternative Communication ◽  
Technical Note ◽  
Head Tracking ◽  
Alternative Communication ◽  
Access Methods ◽  
Cord Injury ◽  
Physical Limitations ◽  
Gesture Tracking ◽  
Communication Needs ◽  
Tracking Device

Abstract This article summarizes the design and evaluation of a new augmentative and alternative communication (AAC) interface strategy for people with complex communication needs and severe physical limitations. This strategy combines typing, gesture recognition, and word prediction to input text into AAC software using touchscreen or head movement tracking access methods. Eight individuals with movement limitations due to spinal cord injury, amyotrophic lateral sclerosis, polio, and Guillain Barre syndrome participated in the evaluation of the prototype technology using a head-tracking device. Fourteen typical individuals participated in the evaluation of the prototype using a touchscreen.

Responding to Clinicians' Challenges in Working With Geriatric Patients

2011 ◽  
Vol 16 (1) ◽  
pp. 22-29
Author(s):  
Lisa Y. Milliken ◽  
Dawn Ralph ◽  
Sally Jones-McNamara
Keyword(s):  
Health Care ◽  
Geriatric Patients ◽  
Clinical Scenario ◽  
Medical Diagnoses ◽  
Communication Deficits ◽  
Resident Care ◽  
Physical Limitations

Clinicians work with older residents who have not only multiple physical limitations, but cognitive loss, communication deficits, dysphagia, and multiple medical diagnoses. They must work within procedural, regulatory, and reimbursement systems that challenge them to provide optimal resident care. In this article, the authors will discuss some specific challenges brought forth by clinicians in response to a clinical scenario and will provide information and feedback from several health-care consultants.

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