scholarly journals Active escape dynamics: The effect of persistence on barrier crossing

2019 ◽  
Vol 150 (2) ◽  
pp. 024902 ◽  
Author(s):  
Lorenzo Caprini ◽  
Umberto Marini Bettolo Marconi ◽  
Andrea Puglisi ◽  
Angelo Vulpiani
Keyword(s):  
Barrier Crossing ◽  
Escape Dynamics ◽  
Active Escape

scholarly journals The use of nocturnal flights for barrier crossing in a diurnally migrating songbird

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Christie D. Lavallée ◽  
Saeedeh Bani Assadi ◽  
Alicia M. Korpach ◽  
James D. Ray ◽  
Jason D. Fischer ◽  
...  
Keyword(s):  
Energy Savings ◽  
Open Water ◽  
Gps Tracking ◽  
Future Research ◽  
Barrier Crossing ◽  
Migration Patterns ◽  
Migration Strategies ◽  
Diurnal Migrant ◽  
Time And Energy ◽  
High Degree

Abstract Background The migration patterns of land birds can generally be divided into those species that migrate principally during the day and those that migrate during the night. Some species may show individual plasticity in the use of day or night flight, particularly when crossing large, open-water or desert barriers. However, individual plasticity in circadian patterns of migratory flights in diurnally migrating songbirds has never been investigated. Methods We used high precision GPS tracking of a diurnal, migratory swallow, the purple martin (Progne subis), to determine whether individuals were flexible in their spring migration strategies to include some night flight, particularly at barrier crossing. Results Most (91%) of individuals made large (sometimes > 1000 km), open-water crossings of the Caribbean Sea and the Gulf of Mexico that included the use of night flight. 32% of all water crossings were initiated at night, demonstrating that night flight is not only used to complete large crossings but may confer other advantages for diurnal birds. Birds were not more likely to initiate crossings with supportive winds, however crossings were more likely when they reduced travel distances. Our results are consistent with diurnal birds using night flight to help achieve time- and energy-savings through ‘short cuts’ at barrier crossings, at times and locations when foraging opportunities are not available. Conclusions Overall, our results demonstrate the use of nocturnal flight and a high degree of individual plasticity in migration strategies on a circadian scale in a species generally considered to be a diurnal migrant. Nocturnal flights at barrier crossing may provide time and energy savings where foraging opportunities are low in an otherwise diurnal strategy. Future research should target how diel foraging and refueling strategies support nocturnal flights and barrier crossing in this and other diurnal species.

scholarly journals Escape dynamics of active particles in multistable potentials

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
A. Militaru ◽  
M. Innerbichler ◽  
M. Frimmer ◽  
F. Tebbenjohanns ◽  
L. Novotny ◽  
...  
Keyword(s):  
Transition State Theory ◽  
Silica Nanoparticle ◽  
State Theory ◽  
Biological Processes ◽  
Correlated Noise ◽  
Stochastic Force ◽  
Escape Dynamics ◽  
Active Particles ◽  
Bistable Potential ◽  
Quantitative Understanding

AbstractRare transitions between long-lived metastable states underlie a great variety of physical, chemical and biological processes. Our quantitative understanding of reactive mechanisms has been driven forward by the insights of transition state theory and in particular by Kramers’ dynamical framework. Its predictions, however, do not apply to systems that feature non-conservative forces or correlated noise histories. An important class of such systems are active particles, prominent in both biology and nanotechnology. Here, we study the active escape dynamics of a silica nanoparticle trapped in a bistable potential. We introduce activity by applying an engineered stochastic force that emulates self-propulsion. Our experiments, supported by a theoretical analysis, reveal the existence of an optimal correlation time that maximises the transition rate. We discuss the origins of this active turnover, reminiscent of the much celebrated Kramers turnover. Our work establishes a versatile experimental platform to study single particle dynamics in non-equilibrium settings.

scholarly journals Trojan Horse Transit Contributes to Blood-Brain Barrier Crossing of a Eukaryotic Pathogen

mBio ◽  
2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Felipe H. Santiago-Tirado ◽  
Michael D. Onken ◽  
John A. Cooper ◽  
Robyn S. Klein ◽  
Tamara L. Doering
Keyword(s):  
Experimental Evidence ◽  
Cryptococcus Neoformans ◽  
Blood Brain Barrier ◽  
Fungal Pathogen ◽  
Trojan Horse ◽  
Brain Barrier ◽  
Barrier Crossing ◽  
Blood Brain ◽  
The Brain

ABSTRACT The blood-brain barrier (BBB) protects the central nervous system (CNS) by restricting the passage of molecules and microorganisms. Despite this barrier, however, the fungal pathogen Cryptococcus neoformans invades the brain, causing a meningoencephalitis that is estimated to kill over 600,000 people annually. Cryptococcal infection begins in the lung, and experimental evidence suggests that host phagocytes play a role in subsequent dissemination, although this role remains ill defined. Additionally, the disparate experimental approaches that have been used to probe various potential routes of BBB transit make it impossible to assess their relative contributions, confounding any integrated understanding of cryptococcal brain entry. Here we used an in vitro model BBB to show that a “Trojan horse” mechanism contributes significantly to fungal barrier crossing and that host factors regulate this process independently of free fungal transit. We also, for the first time, directly imaged C. neoformans-containing phagocytes crossing the BBB, showing that they do so via transendothelial pores. Finally, we found that Trojan horse crossing enables CNS entry of fungal mutants that cannot otherwise traverse the BBB, and we demonstrate additional intercellular interactions that may contribute to brain entry. Our work elucidates the mechanism of cryptococcal brain invasion and offers approaches to study other neuropathogens. IMPORTANCE The fungal pathogen Cryptococcus neoformans invades the brain, causing a meningoencephalitis that kills hundreds of thousands of people each year. One route that has been proposed for this brain entry is a Trojan horse mechanism, whereby the fungus crosses the blood-brain barrier (BBB) as a passenger inside host phagocytes. Although indirect experimental evidence supports this intriguing mechanism, it has never been directly visualized. Here we directly image Trojan horse transit and show that it is regulated independently of free fungal entry, contributes to cryptococcal BBB crossing, and allows mutant fungi that cannot enter alone to invade the brain. IMPORTANCE The fungal pathogen Cryptococcus neoformans invades the brain, causing a meningoencephalitis that kills hundreds of thousands of people each year. One route that has been proposed for this brain entry is a Trojan horse mechanism, whereby the fungus crosses the blood-brain barrier (BBB) as a passenger inside host phagocytes. Although indirect experimental evidence supports this intriguing mechanism, it has never been directly visualized. Here we directly image Trojan horse transit and show that it is regulated independently of free fungal entry, contributes to cryptococcal BBB crossing, and allows mutant fungi that cannot enter alone to invade the brain.

Critical phenomena and scaling behavior in theories of activated barrier crossing

1992 ◽  
Vol 68 (17) ◽  
pp. 2608-2611 ◽  
Author(s):  
Surjit Singh ◽  
R. Krishnan ◽  
G. W. Robinson
Keyword(s):  
Critical Phenomena ◽  
Scaling Behavior ◽  
Barrier Crossing

scholarly journals Barrier crossing of semiflexible polymers

2004 ◽  
Vol 66 (5) ◽  
pp. 763-769 ◽  
Author(s):  
P Kraikivski ◽  
R Lipowsky ◽  
J Kierfeld
Keyword(s):  
Semiflexible Polymers ◽  
Barrier Crossing

scholarly journals Entrance and escape dynamics for the typical set

2018 ◽  
Vol 97 (1) ◽  
Author(s):  
Schuyler B. Nicholson ◽  
Jonah S. Greenberg ◽  
Jason R. Green
Keyword(s):  
Escape Dynamics
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