1,938 research outputs found
figure4_A
No full textThis data is made available to support the paper “Optimal Geocentric/Egocentric Switching Strategies in Navigation”, by Orit Peleg and L. Mahadevan, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138,USA
Data description, corresponding to the manuscript’s figures:
% figure4_A.txt and figure4_B.txt , theta^, penalty A\theta^, detection_error, Optimal estimated , optimal attention span $\tau
figure3_A
No full textThis data is made available to support the paper “Optimal Geocentric/Egocentric Switching Strategies in Navigation”, by Orit Peleg and L. Mahadevan, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138,USA
Data description, corresponding to the manuscript’s figures:
% figure3_A.txt N, , reorientation interval , cost $f
figure3_B
No full textThis data is made available to support the paper “Optimal Geocentric/Egocentric Switching Strategies in Navigation”, by Orit Peleg and L. Mahadevan, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138,USA
Data description, corresponding to the manuscript’s figures:
% figure3_B.txt N, , n^{opt
Dynamic Instability of a Growing Adsorbed Polymorphic Filament
No full textAbstractThe intermittent transition between slow growth and rapid shrinkage in polymeric assemblies is termed “dynamic instability”, a feature observed in a variety of biochemically distinct assemblies including microtubules, actin, and their bacterial analogs. The existence of this labile phase of a polymer has many functional consequences in cytoskeletal dynamics, and its repeated appearance suggests that it is relatively easy to evolve. Here, we consider the minimal ingredients for the existence of dynamic instability by considering a single polymorphic filament that grows by binding to a substrate, undergoes a conformation change, and may unbind as a consequence of the residual strains induced by this change. We identify two parameters that control the phase space of possibilities for the filament: a structural mechanical parameter that characterizes the ratio of the bond strengths along the filament to those with the substrate (or equivalently the ratio of longitudinal to lateral interactions in an assembly), and a kinetic parameter that characterizes the ratio of timescales for growth and conformation change. In the deterministic limit, these parameters serve to demarcate a region of uninterrupted growth from that of collapse. However, in the presence of disorder in either the structural or the kinetic parameter the growth and collapse phases can coexist where the filament can grow slowly, shrink rapidly, and transition between these phases, thus exhibiting dynamic instability. We exhibit the window for the existence of dynamic instability in a phase diagram that allows us to quantify the evolvability of this labile phase
Flow-driven branching in a frangible porous medium
No full text© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Derr, N. J., Fronk, D. C., Weber, C. A., Mahadevan, A., Rycroft, C. H., & Mahadevan, L. Flow-driven branching in a frangible porous medium. Physical Review Letters, 125(15), (2020): 158002, doi:10.1103/PhysRevLett.125.158002.Channel formation and branching is widely seen in physical systems where movement of fluid through a porous structure causes the spatiotemporal evolution of the medium. We provide a simple theoretical framework that embodies this feedback mechanism in a multiphase model for flow through a frangible porous medium with a dynamic permeability. Numerical simulations of the model show the emergence of branched networks whose topology is determined by the geometry of external flow forcing. This allows us to delineate the conditions under which splitting and/or coalescing branched network formation is favored, with potential implications for both understanding and controlling branching in soft frangible media.N. D. was partially supported by the NSF-Simons Center for Mathematical and Statistical Analysis of Biology at Harvard, Grant No. 1764269, and the Harvard Quantitative Biology Initiative. C. H. R. and N. D. were partially supported by the National Science Foundation under Grant No. DMS-1753203. C. H. R. was partially supported by the Applied Mathematics Program of the U.S. DOE Office of Science Advanced Scientific Computing Research under Contract No. DE-AC02-05CH11231. L. M. was partially supported by the National Science Foundation under Grants No. DMR-2011754 and No. DMR-1922321
Proposals for International Support to an Intercountry Cooperative Research Programme on the Water Buffalo
No full textReport of P. Mahadevan, a consultant commissioned by TAC to prepare proposals for an international water buffalo program. Based on an analysis of the world distribution of water buffalo and their economic importance, and an assessment of current national research on buffalo nutrition, reproduction, breeding, health problems and production systems, the author identifies priority areas for research. Consideration of a number of institutional and organizational alternatives leads to the recommendation for an international network of cooperating national institutions for buffalo research. Agenda document presented at the seventeenth meeting of TAC, September 1977
Not Available
No full textNot AvailableIN a recent communication (Mahadevan 1959) attention was drawn to an interesting
association of the pearl fish Fierasfer homei (Richardson) with the wing mussel Pteria
sp., * * found in the Gulf of Mannar off Tuticorin. A re -examination of the pearl
fish showed that the position of the vent is at the base of a line just behind pectoral
origin and the origin of the dorsal is in a line above the middle of pectoral (Plate,
1, Fig. C). Further, other distinguishing characters of this fish described elsewhere
in this account justified the earlier doubts (Mahadevan op. cit.) of the likelihood
of its coming under Carapus (syn : Fierasfer) margaritiferae (Rendahl), a brief
account of which is given by de Beaufort (1951) based on specimens collected from
Pulu Punga, Pulu Missa, coast of Flores and Cape Jaubert N. W. Australia, mostly
in association with the wing mussel or sometimes with a holothurian. Smith (1955),
while reviewing the family Carapidae has mentioned the occurrence of C margaritiferae
in South African waters also where three specimens, 75 -93 mm. in length, were
' taken from inside clams at Durban.' The data on two specimens of 63.5 and 85.0
mm. examined by the present author indicate differences in some of the characteristics
as compared with the South African form described by Smith. In order to facilitate
comparison of the Indian form with others occurring elsewhere a detailed
description of the material in hand is given below.Not Availabl
The Pearl fish Carapus margaritiferae (Rendahl), a new record for the Indian waters
No full textIN a recent communication (Mahadevan 1959) attention was drawn to an interesting
association of the pearl fish Fierasfer homei (Richardson) with the wing mussel Pteria
sp.,** found in the Gulf of Mannar off Tuticorin. A re-examination of the pearl
fish showed that the position of the vent is at the base of a line just behind pectoral
origin and the origin of the dorsal is in a line above the middle of pectoral (Plate,
1, Fig. C). Further, other distinguishing characters of this fish described elsewhere
in this account justified the earlier doubts (Mahadevan op. cit.) of the likelihood
of its coming under Carapus (syn : Fierasfer) margaritiferae (Rendahl), a brief
account of which is given by de Beaufort (1951) based on specimens collected from
Pulu Punga, Pulu Missa, coast of Flores and Cape Jaubert N. W. Australia, mostly
in association with the wing mussel or sometimes with a holothurian. Smith (1955),
while reviewing the family Carapidae has mentioned the occurrence of C margaritiferae
in South African waters also where three specimens, 75-93 mm. in length, were
' taken from inside clams at Durban.' The data on two specimens of 63.5 and 85.0
mm. examined by the present author indicate differences in some of the characteristics
as compared with the South African form described by Smith. In order to facilitate
comparison of the Indian form with others occurring elsewhere a detailed
description of the material in hand is given below
The shallow turn of a worm
No full textSUMMARY
When crawling on a solid surface, the nematode Caenorhabditis elegans (C. elegans) moves forward by propagating sinusoidal dorso-ventral retrograde contraction waves. A uniform propagating wave leads to motion that undulates about a straight line. When C. elegans turns as it forages or navigates its environment, it uses several different strategies of reorientation. These modes include the well-known omega turn, in which the worm makes a sharp angle turn forming an Ω-shape, and the reversal, in which the worm draws itself backwards. In these two modes of reorientation, C. elegans strongly disrupts its propagating sinusoidal wave, either in form or in direction, leading to abrupt directional change. However, a third mode of reorientation, the shallow turn, involves a gentler disruption of the locomotory gait. Analyzing the statistics of locomotion suggests that the shallow turn is by far the most frequent reorienting maneuver in navigation in the absence of food. We show that the worm executes a shallow turn by modulating the amplitude and wavelength of its curvature during forward movement, and provide a minimal description of the process using a three-parameter mathematical model. The results of our study augment the understanding of how these parameters are controlled at the neuromotor circuit level.</jats:p
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