Patchy particles are a popular paradigm for the design and synthesis of nanoparticles and colloids for self-assembly. In "traditional" patchy particles, anisotropic interactions arising from patterned coatings, functionalized molecules, DNA, and other enthalpic means create the possibility for directional binding of particles into higher-ordered structures. Although the anisotropic geometry of nonspherical particles contributes to the interaction patchiness through van der Waals, electrostatic, and other interactions, how particle shape contributes entropically to self-assembly is only now beginning to be understood. The directional nature of entropic forces has recently been elucidated. A recently proposed theoretical framework that defines and quantifies directional entropic forces demonstrates the anisotropic-that is, patchy-nature of these emergent, attractive forces. Here we introduce the notion of entropically patchy particles as the entropic counterpart to enthalpically patchy particles. Using three example "families" of shapes, we show how to modify entropic patchiness by introducing geometric features to the particles via shape operations so as to target specific crystal structures assembled here with Monte Carlo simulations. We quantify the emergent entropic valence via a potential of mean force and torque. We show that these forces are on the order of a few kBT at intermediate densities below the onset of crystallization. We generalize these shape operations to shape anisotropy dimensions, in analogy with the anisotropy dimensions introduced for enthalpically patchy particles. Our findings demonstrate that entropic patchiness and emergent valence provide a way of engineering directional bonding into nanoparticle systems, whether in the presence or absence of additional, non-entropic forces.

The quantitative relationship between intraventricular fluid formation and choroid plexus Na+/K+-activated (transport) adenosine triphosphatase (ATPase) was studied in rabbit and dog by perfusing the ventricular system with a solution containing ouabain (10(-8) to 10(-3) M). The effect of ouabain in the same range of concentrations on ATPase activity was also measured by the release of inorganic orthophosphate from in vitro choroid plexus tissue. Normally, about 20 to 25% of ATPase activity in lateral ventricle plexus is Na+/K+-activated, and this component is almost completely inhibited by ouabain in a concentration of 10(-4) M. At this concentration, the rate of intraventricular cerebrospinal fluid (CSF) formation is decreased some 70 to 80% in dog and rabbit. The results of this study suggest that a portion of the intraventricular fluid formation is insensitive to cardiac glycoside inhibition and that either there are two different mechanisms responsible for choroid plexus fluid formation or there is a significant non-ATPase dependent extrachoroidal source of CSF.

Findings on medical expulsive therapy are mixed, with lower 6-week payments but more frequent repeat emergency department visits. These data inform patients who are candidates for medical expulsive therapy or endoscopic stone removal when making decisions about their care.

Objective: To use a Likert scale method to optimize image quality (IQ) for cone beam CT (CBCT) soft-tissue matching for image-guided radiotherapy of the prostate. Methods: 23 males with local/locally advanced prostate cancer had the CBCT IQ assessed using a 4-point Likert scale (4 5 excellent, no artefacts; 3 5 good, few artefacts; 2 5 poor, just able to match; 1 5 unsatisfactory, not able to match) at three levels of exposure. The lateral separations of the subjects were also measured. The Friedman test and Wilcoxon signed-rank tests were used to determine if the IQ was associated with the exposure level. We used the point-biserial correlation and a x 2 test to investigate the relationship between the separation and IQ.Results: The Friedman test showed that the IQ was related to exposure (p 5 2 3 10 27) and the Wilcoxon signed-rank test demonstrated that the IQ decreased as exposure decreased (all p-values ,0.005). We did not find a correlation between the IQ and the separation (correlation coefficient 0.045), but for separations ,35 cm, it was possible to use the lowest exposure parameters studied. Conclusion:We can reduce exposure factors to 80% of those supplied with the system without hindering the matching process for all patients. For patients with lateral separations ,35 cm, the exposure factors can be reduced further to 64% of the original values. Advances in knowledge: Likert scales are a useful tool for measuring IQ in the optimization of CBCT IQ for soft-tissue matching in radiotherapy image guidance applications.

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