Predicted field-induced hexatic structure in an ionomer membrane

Coarse-grained molecular-dynamics simulations were used to study the morphological changes induced in a Nafion$^{\tiny \textregistered}$-like ionomer by the imposition of a strong electric field. We observe the formation of novel structures aligned along the direction of the applied field. The polar head groups of the ionomer side chains aggregate into clusters, which then form rod-like formations which assemble into a hexatic array aligned with the direction of the field. Occasionally these lines of sulfonates and protons form a helical structure. Upon removal of the electric field, the hexatic array of rod-like structures persists, and has a lower calculated free energy than the original isotropic morphology.Comment: 4 pages, 7 figure

Convolution of chemoattractant secretion rate, source density, and receptor desensitization direct diverse migration patterns in leukocytes

Chemoattractants regulate diverse immunological, developmental, and pathological processes, but how cell migration patterns are shaped by attractant production in tissues remains incompletely understood. Using computational modeling and chemokine-releasing microspheres (CRMs), cell-sized attractant-releasing beads, we analyzed leukocyte migration in physiologic gradients of CCL21or CCL19 produced by beads embedded in 3D collagen gels. Individual T-cells that migrated into contact with CRMs exhibited characteristic highly directional migration to attractant sources independent of their starting position in the gradient (and thus independent of initial gradient strength experienced) but the fraction of responding cells was highly sensitive to position in the gradient. These responses were consistent with modeling calculations assuming a threshold absolute difference in receptor occupancy across individual cells of [similar]10 receptors required to stimulate chemotaxis. In sustained gradients eliciting low receptor desensitization, attracted T-cells or dendritic cells swarmed around isolated CRMs for hours. With increasing CRM density, overlapping gradients and high attractant concentrations caused a transition from local swarming to transient “hopping” of cells bead to bead. Thus, diverse migration responses observed in vivo may be determined by chemoattractant source density and secretion rate, which govern receptor occupancy patterns in nearby cells.National Institutes of Health (U.S.) (NIH EB007280)Howard Hughes Medical Institute (Investigator

Perbandingan Pola Biodistribusi 99mtc-ctmp dan 99mtc-mdp pada Hewan Uji sebagai Radiofarmaka Penyidik Tulang

1,4,8,11-tetraaza cyclotetradecyl-1,4,8,11-tetramethylene phosponic acid (CTMP) sebagai senyawa baru untuk penyidik tulangtelah berhasil disintesis di PTNBR-BATAN Bandung yang kemudian ditandai denganradioisotop 99mTc. Uji biodistribusi dari senyawa ini dilakukan pada mencit untuk mengetahui uptake-nya di tulang dan organ-organ yang lain. Pada penelitian ini dilakukan juga uji biodistribusiradiofarmaka 99mTc-MDP sebagai pembanding untuk mengevaluasi kehandalan radiofarmaka99mTc-CTMP. Hasil uji biodistribusi memperlihatkan up take radiofarmaka 99mTc-CTMP padatulang sebesar 3,57; 2,90; 4,14 dan 4,39 (%ID/g) masing-masing pada 1, 3, 5 dan 24 jam, hasilini masih lebih rendah dibandingkan up take radiofarmaka 99mTc-MDP pada tulang sebesar10,73; 10,12; 10,48; dan 5,95 (%ID/g) pada 1, 3, 5 dan 24 jam. Meskipun up take radiofarmaka99mTc-CTMP lebih rendah dibandingkan dengan 99mTc-MDP, radiofarmaka 99mTc-CTMPmemiliki stabilitas in vivo yang lebih baik dari radiofarmaka 99mTc-MDP sehingga memberikangambar pencitraan tulang yang lebih jelas dibandingkan dengan radiofarmaka 99mTc-MDP

The published research paper: is it an important indicator of successful operational research at programme level?

Is a published research paper an important indicator of successful operational research at programme level in low-income countries? In academia, publishing in peer-reviewed scientific journals is highly encouraged and strongly pursued for academic recognition and career progression. In contrast, for those who engage in operational research at programme level, there is often no necessity or reward for publishing the results of research studies; it may even be criticized as being an unnecessary detraction from programme-related work. We present arguments to support publishing operational research from low-income countries; we highlight some of the main reasons for failure of publication at programme level and suggest ways forward

Shape of the spatial mode function of photons generated in noncollinear spontaneous parametric downconversion

We show experimentally how noncollinear geometries in spontaneous parametric downconversion induce ellipticity of the shape of the spatial mode function. The degree of ellipticity depends on the pump beam width, especially for highly focused beams. We also discuss the ellipticity induced by the spectrum of the pump beam