Active Brownian Particles. From Individual to Collective Stochastic Dynamics

We review theoretical models of individual motility as well as collective dynamics and pattern formation of active particles. We focus on simple models of active dynamics with a particular emphasis on nonlinear and stochastic dynamics of such self-propelled entities in the framework of statistical mechanics. Examples of such active units in complex physico-chemical and biological systems are chemically powered nano-rods, localized patterns in reaction-diffusion system, motile cells or macroscopic animals. Based on the description of individual motion of point-like active particles by stochastic differential equations, we discuss different velocity-dependent friction functions, the impact of various types of fluctuations and calculate characteristic observables such as stationary velocity distributions or diffusion coefficients. Finally, we consider not only the free and confined individual active dynamics but also different types of interaction between active particles. The resulting collective dynamical behavior of large assemblies and aggregates of active units is discussed and an overview over some recent results on spatiotemporal pattern formation in such systems is given.Comment: 161 pages, Review, Eur Phys J Special-Topics, accepte

KRAS G12C Inhibition with Sotorasib in Advanced Solid Tumors

Background: No therapies for targeting KRAS mutations in cancer have been approved. The KRAS p.G12C mutation occurs in 13% of non-small-cell lung cancers (NSCLCs) and in 1 to 3% of colorectal cancers and other cancers. Sotorasib is a small molecule that selectively and irreversibly targets KRASG12C. Methods: We conducted a phase 1 trial of sotorasib in patients with advanced solid tumors harboring the KRAS p.G12C mutation. Patients received sotorasib orally once daily. The primary end point was safety. Key secondary end points were pharmacokinetics and objective response, as assessed according to Response Evaluation Criteria in Solid Tumors (RECIST), version 1.1. Results: A total of 129 patients (59 with NSCLC, 42 with colorectal cancer, and 28 with other tumors) were included in dose escalation and expansion cohorts. Patients had received a median of 3 (range, 0 to 11) previous lines of anticancer therapies for metastatic disease. No dose-limiting toxic effects or treatment-related deaths were observed. A total of 73 patients (56.6%) had treatment-related adverse events; 15 patients (11.6%) had grade 3 or 4 events. In the subgroup with NSCLC, 32.2% (19 patients) had a confirmed objective response (complete or partial response) and 88.1% (52 patients) had disease control (objective response or stable disease); the median progression-free survival was 6.3 months (range, 0.0+ to 14.9 [with + indicating that the value includes patient data that were censored at data cutoff]). In the subgroup with colorectal cancer, 7.1% (3 patients) had a confirmed response, and 73.8% (31 patients) had disease control; the median progression-free survival was 4.0 months (range, 0.0+ to 11.1+). Responses were also observed in patients with pancreatic, endometrial, and appendiceal cancers and melanoma. Conclusions: Sotorasib showed encouraging anticancer activity in patients with heavily pretreated advanced solid tumors harboring the KRAS p.G12C mutation. Grade 3 or 4 treatment-related toxic effects occurred in 11.6% of the patients. (Funded by Amgen and others; CodeBreaK100 ClinicalTrials.gov number, NCT03600883.)

Planktonic copepods reacting selectively to hydrodynamic disturbances

In the water column, planktonic copepods encounter small-scale hydrodynamic disturbances generated by fellow zooplankters. Our question is whether or not the copepods can distinguish between hydrodynamic disturbances created by predators, prey, conspecifics and/or mates. We used a Schlieren optical system with a density gradient in the water volume and filmed at 48 frames per second to record the behaviour of copepods during encounters with an artificial hydrodynamic disturbance. We observed the reactions of Cyclops scutifer and Epischura nordenskioldi towards disturbances of different strengths. We also re-examined an earlier report on tandem swimming in C. scutifer while attempting to mate, using novel mathematical tools to analyse possible correlations between the two mates. We conclude that the information within the hydrodynamic disturbances created by swimming zooplankters has enough content for differentiated reactions. We also suggest that the adaptive value of tandem swimming during mating results in offspring capable of executing escape reactions comparable in strength to the disturbances

Locomotion in copepods: pattern of movements and energetics of Cyclops

6 pages, 5 figuresThe cost of swimming in copepods has generally been estimated through the application of fluid dynamics theory to data on velocity and acceleration obtained by means of movies. It has also been estimated through the changes in fat content of copepods after sustained swimming (i.e. vertical migration). However, the range of estimated costs of locomotion is exceedingly large (from 0.1% to 95% of total metabolism). This communication studies the pattern of swimming movements and the work done by Cyclops, using high speed cinematographic techniques. The contribution of swimming to the energy expenditure of the individual is estimated, and consideration of the possible role of rubber-like proteins in the cuticle of copepods is made. © 1988 Kluwer Academic Publisher

Copepod flow modes and modulation: a modelling study of the water currents produced by an unsteadily swimming copepod

Video observation has shown that feeding-current-producing calanoid copepods modulate their feeding currents by displaying a sequence of different swimming behaviours during a time period of up to tens of seconds. In order to understand the feeding-current modulation process, we numerically modelled the steady feeding currents for different modes of observed copepod motion behaviours (i.e. free sinking, partial sinking, hovering, vertical swimming upward and horizontal swimming backward or forward). Based on observational data, we also reproduced numerically a modulated feeding current associated with an unsteadily swimming copepod. We found that: (i) by changing its propulsive force, a copepod can switch between different swimming behaviours, leading to completely different flow-field patterns in self-generated surrounding flow; (ii) by exerting a time-varying propulsive force, a copepod can modulate temporally the basic flow modes to create an unsteady feeding current which manipulates precisely the trajectories of entrained food particles over a long time period; (iii) the modulation process may be energetically more efficient than exerting a constant propulsive force onto water to create a constant feeding current of a wider entrainment range. A probable reason is that the modulated unsteady flow entrains those water parcels containing food particles and leaves behind those without valuable food in them

Filter-feeding in copepods: observation by means of high speed motion

1 pagePeer Reviewe

Suspension feeding by herbivorous calanoid copepods: A cinematographic study

7 pages, 5 figures, 1 tableMany planktonic calanoid copepods are commonly described as “filter-feeders”. Direct observations using high-speed micro-cinematography indicate that these animals are “suspension-feeders”. They capture and handle the food particles not passively according to size and shape but, in most cases, actively using sensory inputs for detection, motivation to capture, and ingestio

Catching the algae: A first account of visual observations on filter-feeding calanoids

Proceedings of a symposium on the structure of zooplankton communities held at Dartmouth College, 20–25 August 1978. American Society of Limnology and Oceanography.-- 8 pages, 2 figuresThe phenomenon of reinventing the wheel occurs regularly when one does research in a manner contrary to the rules of the National Science Foundation. About 80 years ago researchers started a very lively debate on the nutrition and mechanics of the food gathering of zooplankters. [...