Trapping and sorting active particles: motility-induced condensation & smectic defects

We present an experimental realization of the collective trapping phase transition [Kaiser et al., PRL 108, 268307 (2012)], using motile polar granular rods in the presence of a V-shaped obstacle. We offer a theory of this transition based on the interplay of motility-induced condensation and liquid-crystalline ordering and show that trapping occurs when persistent influx overcomes the collective expulsion of smectic defect structures. In agreement with the theory, our experiments find that a trap fills to the brim when the trap angle $\theta$ is below a threshold $\theta_c$, while all particles escape for $\theta > \theta_c$. Our simulations support a further prediction, that $\theta_c$ goes down with increasing rotational noise. We exploit the sensitivity of trapping to the persistence of directed motion to sort particles based on the statistical properties of their activityComment: 6 pages, 5 figures, for supplementary mpg files, see "https://www.dropbox.com/sh/3cmswfoysdn0sb6/AACpEp-G3768B6Y62nDFj_Hea?dl=0". This paper supersedes our earlier version arXiv:1603.08535 and contains substantial new results including revised theoretical treatmen

Vorticity moments in four numerical simulations of the 3D Navier–Stokes equations

The issue of intermittency in numerical solutions of the 3D Navier–Stokes equations on a periodic box [0,L]3 is addressed through four sets of numerical simulations that calculate a new set of variables defined by Dm(t)=(ϖ−10Ωm)αm for 1≤m≤∞ where αm=2m/(4m−3) and [Ωm(t)]2m=L−3∫V|ω|2mdV with ϖ0=νL−2. All four simulations unexpectedly show that the Dm are ordered for m=1,…,9 such that Dm+1<Dm. Moreover, the Dm squeeze together such that Dm+1/Dm↗1 as m increases. The values of D1 lie far above the values of the rest of the Dm, giving rise to a suggestion that a depletion of nonlinearity is occurring which could be the cause of Navier–Stokes regularity. The first simulation is of very anisotropic decaying turbulence; the second and third are of decaying isotropic turbulence from random initial conditions and forced isotropic turbulence at fixed Grashof number respectively; the fourth is of very-high-Reynolds-number forced, stationary, isotropic turbulence at up to resolutions of 40963

Two-dimensional, homogeneous, isotropic fluid turbulence with polymer additives

We present the most extensive direct numerical simulations, attempted so far, of statistically steady, homogeneous, isotropic turbulence in two-dimensional fluid films with air-drag-induced friction and with polymer additives. Our study reveals that the polymers (a) reduce the total fluid energy, enstrophy, and palinstrophy, (b) modify the fluid energy spectrum both in inverse- and forward-cascade regimes, (c) reduce small-scale intermittency, (d) suppress regions of large vorticity and strain rate, and (e) stretch in strain-dominated regions. We compare our results with earlier experimental studies; and we propose new experiments.Comment: 8 pages, 8 figure

Functional results of AO 13C fractures managed with bicolumnar plating in a tertiary care centre of North India

Background: Distal humerus fractures are associated with many problems like fracture comminution and complex fracture anatomy. Achieving a good functional range of motion at the elbow with stability are the primary objectives in managing a comminuted distal humerus fracture.Methods: 25 consecutive patients were operated with bicolumnar plating for fracture distal humerus AO type 13C. The patients were kept in follow up for at least six months. Mayo elbow performance (MEP) score and flexion extension arc was calculated to study the outcome.Results: All patients achieved fracture union with mean MEP score of 73.2 and mean flexion extension arc of 93º. This was within the functional range of elbow. Stiffness was observed to be most common complication.Conclusions: Our study concluded that internal fixation with bicolumnar plating offers good functional results in comminuted intra-articular fractures even in osteoporotic bone with negligible complications

Active nonreciprocal attraction between motile particles in an elastic medium

We present a theory for the interaction between motile particles in an elastic medium on a substrate, relying on two arguments: a moving particle creates a strikingly fore-aft asymmetric distortion in the elastic medium; this strain field reorients other particles. We show that this leads to sensing, attraction and pursuit, with a non-reciprocal character, between a pair of motile particles. We confirm the predicted distortion fields and non-mutual trail-following in our experiments and simulations on polar granular rods made motile by vibration, moving through a dense monolayer of beads in its crystalline phase. Our theory should be of relevance to the interaction of motile cells in the extracellular matrix or in a supported layer of gel or tissue.Comment: Revised, experimental results added, SI expanded to include fits, some figures and bibliography modified, See Supplementary movies here https://www.dropbox.com/sh/od5lg00cxijk7b9/AAB3j6el7jFdaZ0q1xOo0Eqza?dl=

Three years follow up of open medial sub-talar dislocation of ankle: a case report

Open medial sub-talar dislocation is a rare lesion in traumatology. Even after early treatment, these injuries progress to sub-talar arthrosis. Here we describe a case of 24 years male with open type 3B medial sub-talar dislocation with calcaneum sustentaculum tali fracture following road traffic accident. He underwent emergency wound debridement and internal fixation with K-wires and VAC application. He was on regular monthly follow-up for 6 months and then 6 monthly follow-ups till date. K-wires were removed 8 weeks after surgery and gradual range of movement was started. Partial weight bearing was started at 12 weeks. He was pain free and returned to work after 8 months. At 3 years follow up patient is able to walk without pain, normal painless ROM at ankle. To the best of our knowledge, long term follow-up of patient with these lesions is not reported. Here we present a case with 3 years follow-up showing good results in patient with open sub-talar dislocation after early management with internal fixation with K-wires and VAC dressing

Outcome analysis of solitary osteochondromas of femur managed surgically: a series of 32 patients

Background: Osteochondroma is the commonest benign bone tumor in humans. This tumor may either be solitary or present as multiple lesions. Solitary osteochondromas are much more common. Femur is the single most common long bone involved followed by tibia and humerus. Osteochondromas may be either asymptomatic or may present as pain, pressure symptoms or functional impairment. Most of the symptomatic lesions need surgical excision.Methods: This was a prospective study which included 32 patients with solitary osteochondromas of femur, who were managed with surgical excision. Only the symptomatic cases were operated. Minimum follow-up period was 18 months after surgery.Results: This study involved 23 males (71.87%) and nine females (28.12%). 30 osteochondromas (93.75%) were located in the distal femoral metaphysis while as only two cases (6.25%) of proximal metaphyseal involvement were seen. The commonest indication for surgery was pain. Other indications included cosmetic causes, restricted joint movement, fracture of osteochondroma and paresthesia or numbness. The complications included post-operative hematoma formation which was seen in 2 patients (6.25%), infection which was seen in one patient (3.12%), post-operative hypoaesthesia in 2 patients (6.25%) and recurrence of the tumor occurred in one patient (3.12%).Conclusions: Surgical excision of the solitary symptomatic femoral osteochondromas is a rewarding and safe procedure with minimal complications.