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Previous experiments have demonstrated a sufficient and necessary involvement of mossy fibers in projecting conditioned stimulus information to the cerebellum during classical eyelid conditioning in rabbits. Presented here are electrophysiological, anatomical, and lesion data that suggest that cells within the lateral pontine nuclear region may be essentially involved in projecting information concerning the occurrence of acoustic conditioned stimuli to the cerebellum during classical conditioning.A number of theories concerning cerebellar function have postulated a role for the cerebellum in motor learning (1-5). A common theme is that cerebellar plasticity is thought to be due to the conjunctive activation of mossy and climbing fibers on a common element, the Purkinje cell, whose axons project ventrally to cerebellar and brainstem nuclei. In our laboratory, a number of lesion, recording, and stimulation studies have demonstrated that the cerebellum is critically involved in the acquisition and retention of classically conditioned skeletal muscle responses (6)(7)(8)(9)(10)(11)(12)(13)(14). From these data we have proposed that neuronal plasticity involved in acquisition and retention of conditioned responses (CRs) is localized to regions of the cerebellum where the conditioned stimulus (CS) and the unconditioned stimulus (US) converge, and that the CS is projected to the cerebellum along mossy fibers while the US is projected to the cerebellum along climbing fibers (15).We have demonstrated the essential involvement of climbing fibers in projecting the US to the cerebellum during classical conditioning. First, lesions placed in rostromedial portions of the dorsal accessory olive (DAO) prevent acquisition in naive rabbits and cause behavioral extinction with continued training in rabbits given lesions after acquisition training (16, 17). Second, stimulation of the DAO-cimbing fiber system, which produces a variety of behaviors (e.g., eyeblink, head turn, limb flexion) can serve as an effective US for classical conditioning (18)(19)(20) MATERIALS AND METHODS Acute Electrophysiological Recording. Twelve male albino rabbits were anesthetized with halothane, the skull above the right pontine nuclei was removed, and the entire extent of the right pontine nuclei and an area 2 mm caudal to the nuclei was mapped for auditory evoked field potentials. Mapping consisted of systematically lowering an insulated, stainless steel recording electrode (50-gm exposed tip) in 1 mm increments to obtain recordings from the entire right pontine nuclei, ventral portions of the right ventral nucleus of the lateral lemniscus (NVLL), and rostral areas of the right superior olive (SO) and trapezoid nucleus (NTB). Three clicks (65 decibels sound pressure level) were presented at each recording site via a speaker located 10 cm from the right ear, and auditory-evoked field potentials were bandpass filtered at 100-1000 Hz, digitized, and stored for further analysis. At the end of the recording session, electrolytic marking lesions wer...

The nictitating membrane/eyelid responses of 18 rabbits were classically conditioned using cerebellar mossy-fiber stimulation as a conditioned stimulus (CS) and air puff as an unconditioned stimulus (US). The dorsolateral, lateral, and medial pontine nuclei and the middle cerebellar peduncle were effective stimulation-CS sites for training. In one group of rabbits, robust conditioned eyelid responses were produced with paired trials and subsequently extinguished with CS-alone and explicitly unpaired presentation of the CS and US. In a second group of rabbits, no conditioned responses were evident for 4 days of unpaired CS and US presentations. Conditioned responses did develop, however, after paired training was begun. Lesions of the interpositus nucleus of the cerebellum completely abolished the conditioned responses of a third group of rabbits overtrained with the mossy-fiber CS and air-puff US. These results support previous studies which have demonstrated that the cerebellum is critically involved in acquisition and retention of simple learned responses. In addition, the present results support previous theories of cerebellar function which have proposed that mossy fibers supply critical "learning" input to the cerebellum for acquisition and retention of motor skills.

The development of a suitable catalyst for the oxygen reduction reaction (ORR), the cathode reaction of proton exchange membrane fuel cells (PEMFC), is necessary to push this technology toward widespread adoption. There have been substantial efforts to utilize bimetallic Pt−M alloys that adopt the ordered face-centered tetragonal (L1 0 ) phase in order to reduce the usage of precious metal, enhance the ORR performance, and improve catalyst stability. In this work, monodisperse Pt−Co nanocrystals (NCs) with well-defined size (4−5 nm) and cobalt composition (25−75 at%) were synthesized via colloidal synthesis. The transformation from the chemically disordered A1 (face-centered cubic, fcc) to the L1 0 phase was achieved via thermal annealing using both a conventional oven and a rapid thermal annealing process. The structure of the Pt−Co catalysts was characterized by a variety of techniques, including transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy in high-angle annular dark-field scanning transmission electron microscopy (STEM-EDS), small-angle X-ray scattering (SAXS), X-ray diffraction (XRD), and inductively coupled plasma−optical emission spectrometry (ICP-OES). The effects of annealing temperature on the composition-dependent degree of ordering and subsequent effect on ORR activity is described. This work provides insights regarding the optimal spatial distribution of elements at the atomic level to achieve enhanced ORR activity and stability.

The primary protocol presented for the treatment of ear keloids produces durable results, with an acceptably low recurrence rate. Stratification of keloids based on an assessment of aggressiveness may allow for a more informed choice in their optimal treatment.

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The use of nanocrystal (NC) building blocks to create metamaterials is a powerful approach to access emergent materials. Given the immense library of materials choices, progress in this area for anisotropic NCs is limited by the lack of co-assembly design principles. Here, we use a rational design approach to guide the co-assembly of two such anisotropic systems. We modulate the removal of geometrical incompatibilities between NCs by tuning the ligand shell, taking advantage of the lock-and-key motifs between emergent shapes of the ligand coating to subvert phase separation. Using a combination of theory, simulation, and experiments, we use our strategy to achieve co-assembly of a binary system of cubes and triangular plates and a secondary system involving two two-dimensional (2D) nanoplates. This theory-guided approach to NC assembly has the potential to direct materials choices for targeted binary co-assembly.

Optimizing the use of expensive precious metals is critical to developing sustainable and low-cost processes for heterogeneous catalysis or electrochemistry. Here, we report a synthesis method that yields core-shell Cu-Ru, Cu-Rh, and Cu-Ir nanoparticles with the platinum-group metals segregated on the surface. The synthesis of Cu-Ru, Cu-Rh, and Cu-Ir particles allows maximization of the surface area of these metals and improves catalytic performance. Furthermore, the Cu core can be selectively etched to obtain nanoshells of the platinum-group metal components, leading to a further increase in the active surface area. Characterization of the samples was performed with X-ray absorption spectroscopy, X-ray powder diffraction, and ex situ and in situ transmission electron microscopy. CO oxidation was used as a reference reaction: the three core-shell particles and derivatives exhibited promising catalyst performance and stability after redox cycling. These results suggest that this synthesis approach may optimize the use of platinum-group metals in catalytic applications.