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The scattering of an arbitrary incoming electromagnetic wave by an unrestricted scattering object is described in terms of a tensor scattering matrix. General reciprocity relations and the cross-section theorem, including an interesting extension, are established using this representation. The results are related to the special case of plane-wave scattering and the scattering matrix is explicitly exhibited in terms of the planewave scattering amplitude for two mutually perpendicular directions of polarization. GENERAL FORMULATION

In situ transgenesis methods such as viruses and electroporation can rapidly create somatic transgenic mice but lack control over copy number, zygosity, and locus specificity. Here we establish mosaic analysis by dual recombinase-mediated cassette exchange (MADR), which permits stable labeling of mutant cells expressing transgenic elements from precisely defined chromosomal loci. We provide a toolkit of MADR elements for combination labeling, inducible and reversible transgene manipulation, VCre recombinase expression, and transgenesis of human cells. Further, we demonstrate the versatility of MADR by creating glioma models with mixed reporter-identified zygosity or with ''personalized'' driver mutations from pediatric glioma. MADR is extensible to thousands of existing mouse lines, providing a flexible platform to democratize the generation of somatic mosaic mice.

A simple bipolar thunderstorm model, in which it is assumed that the atmospheric conductivity increases exponentially from the earth to a conducting layer high in the atmosphere, is proposed for the purpose of estimating the electrical conduction currents in the vicinity of the storm. Calculations based on the model indicate that the separate measurements on electrical structure of thunderstorms, atmospheric conductivity, and upward conduction currents from storms are mutually consistent within the limits of uncertainty of the measurements. The computed current density at the surface of the earth at distances of several tens of kilometers from the storm is very much smaller than the normal fair‐weather current density, but is very sensitive to the value assumed for the height of the upper conducting layer. The latter result suggests that, if the maximum in conductivity observed at about 19 km altitude is a persistent feature of the atmosphere, the disturbance of normal atmospheric conduction produced by storms may be observed at distances of the order of 100 km. This mechanism is suggested as an explanation of disturbed atmospheric electrical conditions observed many tens of kilometers from weather fronts.

SummaryTrophic factor delivery to the brain using stem cell-derived neural progenitors is a powerful way to bypass the blood-brain barrier. Protection of diseased neurons using this technology is a promising therapy for neurodegenerative diseases. Glial cell line-derived neurotrophic factor (GDNF) has provided benefits to Parkinsonian patients and is being used in a clinical trial for amyotrophic lateral sclerosis. However, chronic trophic factor delivery prohibits dose adjustment or cessation if side effects develop. To address this, we engineered a doxycycline-regulated vector, allowing inducible and reversible expression of a therapeutic molecule. Human induced pluripotent stem cell (iPSC)-derived neural progenitors were stably transfected with the vector and transplanted into the adult mouse brain. Doxycycline can penetrate the graft, with addition and withdrawal providing inducible and reversible GDNF expression in vivo, over multiple cycles. Our findings provide proof of concept for combining gene and stem cell therapy for effective modulation of ectopic protein expression in transplanted cells.

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