We report the formation of a nanocomposite comprised of chemically converted graphene and carbon nanotubes. Our solution-based method does not require surfactants, thus preserving the intrinsic electronic and mechanical properties of both components, delivering 240 Ω/0 at 86% transmittance. This low-temperature process is completely compatible with flexible substrates and does not require a sophisticated transfer process. We believe that this technology is inexpensive, is massively scalable, and does not suffer from several shortcomings of indium tin oxide. A proof-of-concept application in a polymer solar cell with power conversion efficiency of 0.85% is demonstrated. Preliminary experiments in chemical doping are presented and show that optimization of this material is not limited to improvements in layer morphology.

A method which enables the investigation of the buried interfaces without altering the properties of the polymer films is used to study vertical phase separation of spin‐coated poly(3‐hexylthiophene) (P3HT):fullerene derivative blends. X‐ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analysis reveals the P3HT enrichment at the free (air) surfaces and abundance of fullerene derivatives at the organic/substrate interfaces. The vertical phase separation is attributed to the surface energy difference of the components and their interactions with the substrates. This inhomogeneous distribution of the donor and acceptor components significantly affects photovoltaic device performance and makes the inverted device structure a promising choice.

SUMMARY Studies of resting state activity in the brain have provoked critical questions about the brain’s functional organization but, its biological basis is not clear. Specifically, the relationships between interregional correlations in resting state measures of activity, neuronal functional connectivity and anatomical connectivity are much debated. To investigate these relationships, we have examined both anatomical and steady state functional connectivity within the hand representation of primary somatosensory cortex (areas 3b and 1) in anesthetized squirrel monkeys. The comparison of three data sets (fMRI, electrophysiological, anatomical) indicate two primary axes of information flow within SI: prominent interdigit interactions within area 3b and predominantly homotopic interactions between area 3b and area 1. These data support a strikingly close relationship between baseline functional connectivity and anatomical connections. This study is also the first to extend findings derived from large-scale cortical networks to the realm of local mm-scale networks.

A transfer printing process that allows precise patterning of chemically converted graphene is reported. The use of a polydimethylsiloxane (PDMS) stamp and surface energy manipulation resulted in successfully transferring spin‐coated materials from one substrate to another. The method is capable of transferring sharp features to precise locations. This represents large‐scale, high‐throughput transfer printing of chemically converted graphene and paves the way for future complementary circuit design.

Recent demonstrations of correlated low-frequency MRI signal variations between subregions of the spinal cord at rest in humans, similar to those found in the brain, suggest that such resting-state functional connectivity constitutes a common feature of the intrinsic organization of the entire central nervous system. We report our detection of functional connectivity within the spinal cords of anesthetized squirrel monkeys at rest and show that the strength of connectivity within these networks is altered by the effects of injuries. By quantifying the low-frequency MRI signal correlations between different horns within spinal cord gray matter, we found distinct functional connectivity relationships between the different sensory and motor horns, a pattern that was similar to activation patterns evoked by nociceptive heat or tactile stimulation of digits. All horns within a single spinal segment were functionally connected, with the strongest connectivity occurring between ipsilateral dorsal and ventral horns. Each horn was strongly connected to the same horn on neighboring segments, but this connectivity reduced drastically along the spinal cord. Unilateral injury to the spinal cord significantly weakened the strength of the intrasegment horn-to-horn connectivity only on the injury side and in slices below the lesion. These findings suggest resting-state functional connectivity may be a useful biomarker of functional integrity in injured and recovering spinal cords.hand | spinal cord injury | resting state fMRI | monkey | cervical spinal cord R esting-state functional connectivity (rsFC) has been widely used to identify and characterize neural circuits in the brain (1-3), and its presentation at various spatial scales and its changes with specific physiological conditions confirm its fundamental role in maintaining normal brain function (4, 5). More importantly, alterations of rsFC networks in various disease conditions have altered our view about the functional significance of spontaneous baseline neural activity (3). Two very recent reports of success in detecting intrinsic functional circuits in human spines using resting-state fMRI once more suggest that rsFC is a fundamental, common feature of the entire nervous system (6, 7).Despite these exciting findings in human subjects, the functional and behavioral relevance of the intrinsic functional networks within the spine gray matter remains largely obscure, and there have been no previous reports attempting to understand their significance. One way to address this question is to manipulate the network and then examine how the network reacts to the manipulation. This type of approach is impossible to execute in humans but can be performed in nonhuman primates in a very well-controlled manner. Thus, this study aimed to better understand the functional and behavioral relevance of newly identified rsFC in the spinal cord by first determining whether similar intrinsic rsFC networks can be detected in the spinal cords of anesthetized monkeys. We also sought to determ...

This study aimed to evaluate the ability of BOLD signals at high MRI field (7 Tesla) to map fine-scale single-digit activations in subdivisions (areas 3b and 1) of the human primary somatosensory cortex (SI) in individual subjects. We acquired BOLD-fMRI data from cortical areas around the central suclus in six healthy human subjects while stimulating individual finger pads with 2 Hz air puffs. Discrete, single-digit responses were identified in an area along the posterior bank of the central sulcus corresponding to area 3b and in an area along the crest of the postcentral gyrus corresponding to area 1. In single subjects, activations of digits 1 to 4 in both areas 3b and 1 were organized in a somatotopic manner. The separation of digit representations was measured for adjacent digits, and was approximately 1.6 times greater in area 3b than in area 1. Within individual subjects, the cortical responses to single-digit stimulations and the magnitude of the BOLD signals were reproducible across imaging runs and were comparable across subjects. Our findings demonstrate that BOLD-fMRI at 7 T is capable of revealing the somatotopic organization of single-digit activations with good within-subject reliability and reproducibility, and activation maps can be acquired within a reasonably short time window, which are essential characteristics for several neurological applications within patient populations.

Optical imaging of intrinsic cortical activity was used to study the somatotopic map and the representation of pressure, flutter, and vibration in area 3b of the squirrel monkey (Saimiri sciureus) cortex under pentothal or isoflurane anesthesia. The representation of the fingerpads in primary somatosensory cortex was investigated by stimulating the glabrous skin of distal fingerpads (D1-D5) with Teflon probes (3-mm diam) attached through an armature to force feedback-controlled torque motors. Under pentothal anesthesia, intrinsic signal maps in area 3b obtained in response to stimulation (trapezoidal indentation) of individual fingerpads showed focal activations. These activations (ranging from 0.5 to 1.0 mm) were discrete and exhibited minimal overlap between adjacent fingerpad representations. Consistent with previously published maps, a somatotopic representation of the fingerpads was observed with an orderly medial to lateral progression from the D5 to D1 fingerpads. Under isoflurane anesthesia, general topography was still maintained, but the representation of fingerpads on adjacent fingers had higher degrees of overlap than with pentothal anesthesia. Multi- and single-unit recordings in the activation zones confirmed the somatotopic maps. To examine preferential inputs from slowly adapting type I (SA) and rapidly adapting type I (RA) and type II (PC) mechanoreceptors, we applied stimuli consisting of sinusoidal indentations that produce sensations of pressure (1 Hz), flutter (30 Hz), and vibration (200 Hz). Under pentothal anesthesia, activation patterns to these different stimuli were focal and coincided on the cortex. Under isoflurane, activation zones from pressure, flutter, and vibratory stimuli differed in size and shape and often contained multiple foci, although overall topography was maintained. Subtraction and vector maps revealed cortical areas (approximate 250-microm diam) that were preferentially activated by the sensations of pressure, flutter, and vibration. Multi- and single-unit recordings aided in the interpretation of the imaging maps. In conclusion, the cortical signals observed with intrinsic signal optical imaging delineated a somatotopic organization of area 3b and revealed different topographical cortical activation patterns for pressure, flutter, and vibratory stimuli. These patterns were dependent on anesthesia type. Possible relationships of these anesthesia effects to somatosensory cortical plasticity are discussed.

A multi-source/component spray coating process to fabricate the photoactive layers in polymer solar cells is demonstrated. Well-defined domains consisting of polymer:fullerene heterojunctions are constructed in ambient conditions using an alternating spray deposition method. This approach preserves the integrity of the layer morphology while forming an interpenetrating donor (D)/acceptor (A) network to facilitate charge transport. The formation of multi-component films without the prerequisite of a common solvent overcomes the limitations in conventional solution processes for polymer solar cells and enables us to process a wide spectrum of materials. Polymer solar cells based on poly(3-hexylthiophene):[6,6]-phenyl C(61) butyric acid methyl ester spray-coated using this alternating deposition method deliver a power conversion efficiency of 2.8%, which is comparable to their blend solution counterparts. More importantly, this approach offers the versatility to independently select the optimal solvents for the donor and acceptor materials that will deliver well-ordered nanodomains. This method also allows the direct stacking of multiple photoactive polymers with controllable absorption in a tandem structure even without an interconnecting junction layer. The introduction of multiple photoactive materials through multisource/component spray coating offers structural flexibility and tenability of the photoresponse for future polymer solar cell applications.