We report on an infrared spectroscopy study of mobile holes in the accumulation layer of organic field-effect transistors based on rubrene single crystals. Our data indicate that both transport and infrared properties of these transistors at room temperature are governed by light quasiparticles in molecular orbital bands with the effective masses m[small star, filled] comparable to free electron mass. Furthermore, the m[small star, filled] values inferred from our experiments are in agreement with those determined from band structure calculations. These findings reveal no evidence for prominent polaronic effects, which is at variance with the common beliefs of polaron formation in molecular solids.

Agrin is an extracellular matrix protein involved in the formation of the postsynaptic apparatus of the neuromuscular junction. In addition to spinal motor neurons, agrin is expressed by many other neuronal populations throughout the nervous system. Agrin's role outside of the neuromuscular junction, however, is poorly understood. Here we use the polymerase chain reaction to examine expression and alternative splicing of agrin in mouse somatosensory cortex during early postnatal development in vivo and in dissociated cell culture. Peak levels of agrin gene expression in developing cortex coincide with ingrowth of thalamic afferent fibres and formation of thalamocortical and intracortical synapses. Analysis of alternatively spliced agrin messenger RNA variants shows that greater than 95% of all agrin in developing and adult somatosensory cortex originates in neurons, including isoforms that have little or no activity in acetylcholine receptor aggregation assays. The levels of expression of "active" and "inactive" isoforms, however, are regulated during development. A similar pattern of agrin gene expression is also observed during a period when new synapses are being formed between somatosensory neurons growing in dissociated cell culture. Changes in agrin gene expression, observed both in vivo and in vitro, are consistent with a role for agrin in synapse formation in the central nervous system.

The growth decline of huanglongbing (HLB)-affected citrus trees is considered to be associated with nutritional disorder, as typical symptoms of HLB such as stunted tree growth, chlorosis or blotchy mottle of leaves, resembles zinc (Zn), iron (Fe) and manganese (Mn) deficiencies, while lower Zn concentration has been consistently reported in the HLB affected compared to healthy plants. Hydroponic culture studies were conducted to evaluate the effects of enhanced Zn nutrition on the mitigation of HLB-affected grapefruit seedlings. Modified Hoagland nutrient solutions were used with three Zn²⁺ levels: 0, 1.0, and 1.5 times that of standard strength. Both HLB-affected and healthy grapefruit seedlings were subjected to the treatments for 49 days. During the growth period, photosynthesis of plant leaves was measured, and at day 49 of the culture, leaf tissues and cells were examined for structural changes using light and scanning electron microscopy. Enhanced Zn nutrition generally improved the growth of HLB plants with less symptom severity. Photosynthesis, in terms of leaf electron transfer rate and photochemical quantum yield, was enhanced. The wax layer and cuticle increased, and the epidermis cells became better organized, with a higher number of normal stomatal openings, compared to the control. In addition, enhanced Zn nutrition resulted in more developed xylem and phloem transport systems, resulting in reduced starch grains and polyphenol substances in the leaf cells. These results indicate that

enhanced Zn nutrition can improve the structure of photosynthetic, transfusion and protective tissue systems, and thus promote photosynthesis, transport of photosynthates, and other related metabolism of HLB-infected citrus.