pCONUS 2 and pCONUS 2-HPC for the treatment of wide-necked intracranial aneurysms: Periprocedural, 6-month, and early 2-year follow-up outcomes.

BACKGROUND/PURPOSE: pCONUS 2 and pCONUS 2-HPC are novel neck-bridging devices designed to support endovascular coil occlusion of wide-necked intracranial bifurcation aneurysms. This study summarises periprocedural outcomes, 6-month, and early 2-year follow-up results following its introduction in an interventional neuroradiology centre. MATERIALS/METHODS: This prospective, single-arm study assessed 20 aneurysms treated over a 40 month time period from time of procedure to 2 years post-procedure. Data collected included patient demographics, aneurysm features, and intraprocedural, 6-month, and 2-year post-procedural complications and angiographic features. RESULTS: The mean age of the cohort was 59+-SD 7.7 years. 16 unruptured aneurysms were treated (pCONUS 2 13/16, pCONUS 2-HPC 3/16) and 4 ruptured aneurysms were treated with pCONUS 2-HPC. Unruptured cases received dual antiplatelet therapy pre- and post-procedure while ruptured cases received single antiplatelet therapy. 9/20 aneurysms were located at the MCA bifurcation and 7/20 at the basilar tip. The remaining 4 aneurysms were at various bifurcations in the anterior circulation. 11/20 were small (<10mm) and 9/20 were large (10-25mm). There was one periprocedural complication: a retroperitoneal bleed. There were no post-procedural intracranial complications or at 6-months follow-up. At 6 months, satisfactory occlusion was achieved in 94% of cases (15/16). There was one delayed death at 2-year follow-up from an unrelated cause. CONCLUSION: pCONUS 2 and pCONUS 2-HPC have excellent short and medium-term safety profiles and clinical outcomes with no procedure-related mortality or morbidity and good occlusion rates at 6-month follow-up. The use of pCONUS 2-HPC with single antiplatelet therapy is feasible and did not cause any complications.

Reliability of the International Spinal Cord Injury Musculoskeletal Basic Data Set.

STUDY DESIGN: Psychometric study. OBJECTIVES: To determine the intra- and inter-rater reliability and content validity of the International Spinal Cord Injury (SCI) Musculoskeletal Basic Data Set (ISCIMSBDS). SETTING: Four centers with one in each of the countries in Australia, England, India and the United States of America. METHODS: A total of 117 participants with a C2 to S1 neurological level and American Spinal Injury Association Impairment Scale A to D injury were recruited. The median (interquartile range) time since injury was 9 years (2-29). Fifty-seven participants were assessed by the same assessor, and 60 participants were assessed by two different assessors on two different occasions to determine the intra- and inter-rater reliability, respectively. Kappa statistics or crude agreement was used to measure reliability. Content validity was assessed through focus group interviews of people with SCI and health-care professionals. RESULTS: The intra-rater reliability ranged from κ=0.62 to 1.00 and crude agreement from 75% to 100% for each of the variables on the ISCIMSBDS. The inter-rater reliability ranged from κ=-0.25 to 1.00, with a diverse crude agreement ranging from 0% to 100%. The inter-rater reliability was unsatisfactory for the following variables: 'Date of fracture', 'Fragility fractures', 'Scoliosis, method of assessment', 'Other musculoskeletal problems' and 'Do any of the above musculoskeletal challenges interfere with your activities of daily living (transfers, walking, dressing, showers, etc.)?'. Results from validity discussions implied no major suggestions for changes. CONCLUSION: Overall, the ISCIMSBDS is reliable and valid, although 5 of the 12 variables may benefit from further refinement.

Dopamine receptor D2 deficiency reduces mouse pup ultrasonic vocalizations and maternal responsiveness.

Dopamine signalling facilitates motivated behaviours, and the D2 dopamine receptor (D2R) is important in mother-infant interactions. D2R antagonists disrupt maternal behaviour and, in isolated rat pups, reduce ultrasonic vocalizations (USVs) that promote maternal interaction. Here, we examined the effects of genetic D2R signalling deficiency on pup-dam interaction with Drd2 knockout (D2R KO) mice. Using heterozygous (HET) cross littermates, the effect of pup genotype on isolation-induced USVs was quantified. Independent of parental genotype, D2R-deficient pups emitted fewer USVs than wild type (WT) littermates in a gene dose-dependent manner. Using reciprocal D2R KO-WT crosses, we examined how parental genotype affects pup USVs. Heterozygous pups from D2R KO dams produced fewer USVs than HET pups from WT dams. Also, exposure to USV-emitting pups increased plasma prolactin levels in WT dams but not in D2R KO dams, and KO dams showed delayed pup retrieval and nest building. These findings indicate the importance of the interaction between pup and dam genotypes on behaviour and further support the role of D2R signalling in maternal care.

A circle swimmer at low Reynolds number.

Swimming in circles occurs in a variety of situations at low Reynolds number. Here we propose a simple model for a swimmer that undergoes circular motion, generalising the model of a linear swimmer proposed by Najafi and Golestanian (Phys. Rev. E 69, 062901 (2004)). Our model consists of three solid spheres arranged in a triangular configuration, joined by two links of time-dependent length. For small strokes, we discuss the motion of the swimmer as a function of the separation angle between its links. We find that swimmers describe either clockwise or anticlockwise circular motion depending on the tilting angle in a non-trivial manner. The symmetry of the swimmer leads to a quadrupolar decay of the far flow field. We discuss the potential extensions and experimental realisation of our model.

Diminished pheromone-induced sexual behavior in neurokinin-1 receptor deficient (TACR1(-/-)) mice.

Studies in mice with targeted deletions of tachykinin genes suggest that tachykinins and their receptors influence emotional behaviors such as aggression, depression and anxiety. Here, we investigated whether TAC1- and TAC4-encoded peptides (substance P and hemokinin-1, respectively) and the neurokinin-1 receptor (NK-1R) are involved in the modulation of sexual behaviors. Male mice deficient for the NK-1R (TACR1 (-/-)) exhibited decreased exploration of female urine in contrast to C57BL/6 control mice and mice deficient for NK-1R ligands such as TAC1 (-/-), TAC4 (-/-) and the newly generated TAC1 (-/-) /TAC4 (-/-) mice. In comparison to C57BL/6 mice, mounting frequency and duration were decreased in male TACR1 (-/-) mice, while mounting latency was increased. Decreased preference for sexual pheromones was also seen in female TACR1 (-/-) mice. Furthermore, administration of the NK-1R-antagonist L-703,606 decreased investigation of female urine by male C57BL/6 mice, suggesting an involvement of NK-1R in urine sniffing behavior. Our results provide evidence for the NK-1R in facilitating sexual approach behavior, as male TACR1 (-/-) mice exhibited blunted approach behavior toward females following the initial interaction compared with C57BL/6 mice. NK-1R signaling may therefore play an important role in pheromone-induced sexual behavior.

Anisotropy in the annihilation dynamics of umbilic defects in nematic liquid crystals.

Umbilic defects of strength s=±1 were induced in a nematic liquid crystal with negative dielectric anisotropy, confined to Hele-Shaw cells with homeotropic boundary conditions, and their annihilation dynamics followed experimentally. The speeds of individual defects of annihilating defect pairs with strengths of equal magnitude and opposite sign were determined as a function of several externally applied parameters, such as cell gap, electric field amplitude, frequency, and temperature. It was shown that annihilating defects do not approach each other at equal speeds, but that a speed anisotropy is observed, with the positive defect moving faster than the negative one. The defects move more slowly as the strength of the applied electric field or the cell gap is increased. The speed anisotropy is found to be essentially constant for varying external conditions which do not change the material properties of the liquid crystal material, i.e., confinement, electric field amplitude, or frequency. Only for applied conditions that change material properties, such as temperature changing viscosity, does the speed anisotropy vary. The annihilation dynamics was also simulated numerically giving good qualitative agreement with the experiments. Using insight gained from the simulations we interpret the defects' speed in terms of their overlap and the speed asymmetry as arising from backflow effects and anisotropy in the elastic constants.

Partial-post Laplace barriers for virtual confinement, stable displacement, and >5 cm s(-1) electrowetting transport.

Laplace barriers composed of full-posts or ridges have been previously reported as a mechanism for virtual fluid confinement, but with unstable displacement (capillary fingering or fluid trapping, respectively). A new platform of 'partial-posts' eliminates the disadvantages of full-posts or ridges, while providing ~60-80% open channel area for rapid electrowetting fluid transport (>5 cm s(-1)). The fluid mechanics of partial-post Laplace barriers are far more complex than previous Laplace barriers as it involves two mechanisms: fluid can first begin to propagate either between, or under, the partial-posts. Careful design of channel and partial-post geometries is required, else one mechanism will dominate over the other. The physics and performance of partial-post Laplace barriers are verified using theoretical equations, experimental results, and dynamic numerical modeling.

Anisotropic imbibition on surfaces patterned with polygonal posts.

We present and interpret lattice Boltzmann simulations of thick films spreading on surfaces patterned with polygonal posts. We show that the mechanism of pinning and depinning differs with the direction of advance, and demonstrate that this leads to anisotropic spreading within a certain range of material contact angles.

Modeling receding contact lines on superhydrophobic surfaces.

We use mesoscale simulations to study the depinning of a receding contact line on a superhydrophobic surface patterned by a regular array of posts. For the simulations to be feasible, we introduce a novel geometry where a column of liquid dewets a capillary bounded by a superhydrophobic plane that faces a smooth hydrophilic wall of variable contact angle. We present results for the dependence of the depinning angle on the shape and spacing of the posts and discuss the form of the meniscus at depinning. We find, in agreement with ref 17 , that the local post concentration is a primary factor in controlling the depinning angle and show that the numerical results agree well with recent experiments. We also present two examples of metastable pinned configurations where the posts are partially wet.

Drop dynamics on hydrophobic and superhydrophobic surfaces.

We investigate the dynamics of micron-scale drops pushed across a hydrophobic or superhydrophobic surface. The velocity profile across the drop varies from quadratic to linear with increasing height, indicating a crossover from a sliding to a rolling motion. We identify a mesoscopic slip capillary number which depends only on the motion of the contact line and the shape of the drop, and show that the angular velocity of the rolling increases with increasing viscosity. For drops on superhydrophobic surfaces we argue that a tank treading advance from post to post replaces the diffusive relaxation that allows the contact line to move on smooth surfaces. Hence drops move on superhydrophobic surfaces more quickly than on smooth geometries.

Superhydrophobicity on hairy surfaces.

We investigate the wetting properties of surfaces patterned with fine elastic hairs, with an emphasis on identifying superhydrophobic states on hydrophilic hairs. We formulate a 2D model of a large drop in contact with a row of equispaced elastic hairs and, by minimizing the free energy of the model, identify the stable and metastable states. In particular, we concentrate on partially suspended states, where the hairs bend to support the drop--singlet states, where all hairs bend in the same direction, and doublet states, where neighboring hairs bend in opposite directions--and find the limits of stability of these configurations in terms of the material contact angle, hair flexibility, and system geometry. The drop can remain suspended in a singlet state at hydrophilic contact angles, but doublets exist only when the hairs are hydrophobic. The system is more likely to evolve into a singlet state if the hairs are inclined at the root. We discuss how, under limited circumstances, the results can be modified to describe an array of hairs in three dimensions. We find that now both singlets and doublets can exhibit superhydrophobic behavior on hydrophilic hairs. We discuss the limitations of our approach and the directions for future work.

Anisotropy of water droplets on single rectangular posts.

We report results of extensive experimental and numerical studies of the anisotropy of water drops deposited on single rectangular posts of mesoscopic size sculpted on different materials. Drops of different volume deposited on the top face of the posts assume an elongated shape along the post direction. Systematic investigations show that while the angle measured along the direction parallel to the post does not change, the one measured across them increases monotonically with the drop volume. The difference in these two angles is found to be proportional to the contact line eccentricity even for very elongated drops, regardless of the post size and material. Results obtained with the lattice Boltzmann method are consistent with these observations and indicate useful trends on the evolution of the drop shape with the system main parameters. We argue that drops deposited on single posts having a very sharp profile represent an ideal model system to investigate anisotropic wetting.

Knot-controlled ejection of a polymer from a virus capsid.

We present a numerical study of the effect of knotting on the ejection of flexible and semiflexible polymers from a spherical, viruslike capsid. The polymer ejection rate is primarily controlled by the knot, which moves to the hole in the capsid and then acts as a ratchet. Polymers with more complex knots eject more slowly and, for large knots, the knot type, and not the flexibility of the polymer, determines the rate of ejection. We discuss the relation of our results to the ejection of DNA from viral capsids and conjecture that this process has the biological advantage of unknotting the DNA before it enters a cell.

Hydrodynamics of linked sphere model swimmers.

We describe in detail the hydrodynamics of a simple model of linked sphere swimmers. We calculate the asymptotic form of both the time averaged flow field generated by a single swimmer and the interactions between swimmers in a dilute suspension, showing how each depends on the parameters describing the swimmer and its swimming stroke. We emphasize the importance of time reversal symmetry in determining the far field flow around a swimmer and show that the interactions between swimmers are highly dependent on the relative phase of their swimming strokes.

Imbibition through an array of triangular posts.

We present and interpret simulation results showing how a fluid moves on a hydrophilic substrate patterned by a square array of triangular posts. We demonstrate that the shape of the posts leads to anisotropic spreading, and discuss how this is influenced by the different ways in which the posts can pin the advancing front.

Capillary filling in microchannels patterned by posts.

We investigate the capillary filling of three-dimensional microchannels with surfaces patterned by posts of square cross section. We show that pinning on the edges of the posts suppresses and can halt capillary filling. We stress the importance of the channel walls in controlling whether filling can occur. In particular for channels higher than the distance between adjacent posts, filling occurs for contact angles less than a threshold angle of approximately 55 degrees , independent of the height of the channel.

Contact line dynamics in binary lattice Boltzmann simulations.

We show that, when a single relaxation time lattice Boltzmann algorithm is used to solve the hydrodynamic equations of a binary fluid for which the two components have different viscosities, strong spurious velocities in the steady state lead to incorrect results for the equilibrium contact angle. We identify the origins of these spurious currents and demonstrate how the results can be greatly improved by using a lattice Boltzmann method based on a multiple-relaxation-time algorithm. By considering capillary filling we describe the dependence of the advancing contact angle on the interface velocity.

Scattering of low-Reynolds-number swimmers.

We describe the consequences of time-reversal invariance of the Stokes equations for the hydrodynamic scattering of two low-Reynolds-number swimmers. For swimmers that are related to each other by a time-reversal transformation, this leads to the striking result that the angle between the two swimmers is preserved by the scattering. The result is illustrated for the particular case of a linked-sphere model swimmer. For more general pairs of swimmers, not related to each other by time reversal, we find that hydrodynamic scattering can alter the angle between their trajectories by several tens of degrees. For two identical contractile swimmers, this can lead to the formation of a bound state.

Lattice Boltzmann study of convective drop motion driven by nonlinear chemical kinetics.

We model a reaction-diffusion-convection system which comprises a liquid drop containing solutes that undergo an Oregonator reaction producing chemical waves. The reactants are taken to have surfactant properties so that the variation in their concentrations induces Marangoni flows at the drop interface which lead to a displacement of the drop. We discuss the mechanism by which the chemical-mechanical coupling leads to drop motion and the way in which the net displacement of the drop depends on the strength of the surfactant action. The equations of motion are solved using a lattice Boltzmann approach.

Designing synthetic, pumping cilia that switch the flow direction in microchannels.

Using computational modeling, we simulate the 3D movement of actuated cilia in a fluid-filled microchannel. The cilia are modeled as deformable, elastic filaments, and the simulations capture the complex fluid-structure interactions among these filaments, the channel walls, and the surrounding solution. The cilia are tilted with respect to the surface and are actuated by a sinusoidal force that is applied at the free ends. We find that these cilia give rise to a unidirectional flow in the system and by simply altering the frequency of the applied force we can controllably switch the direction of the net flow. The findings indicate that beating, synthetic cilia could be harnessed to regulate the fluid streams in microfluidic devices.