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Control over the shape of a metal nanostructure grants control over its properties, but the processes that cause solution-phase anisotropic growth of metal nanostructures are not fully understood. ...

The aspect ratio-dependent properties of gold nanorods are used in a variety of applications, but the cause of anisotropic nanorod growth remains unclear. Measurements utilizing single-crystal elec...

Since about 20 years ago, researchers have developed a variety of syntheses to control the morphology of metal nanostructures grown in solution.1 Control over nanostructure morphology has enabled the optimization of their properties for applications including electrocatalysis, solution-coatable transparent conducting films, conductive composites and plasmonic biosensors.1 To explain how anisotropic nanostructures can grow from metals with symmetric cubic crystal structures, researchers have often invoked the capping agent hypothesis, which proposes that the organic additives added to nanostructure syntheses are facet-selective in that they block atomic addition to certain facets but not others. However, direct evidence of such facet-selective blocking by organic additives has been lacking. This talk will discuss efforts to use electrochemical measurements on single crystals to test the capping agent hypothesis. For a copper nanowire synthesis in which ethylenediamine was thought to act as a capping agent for {100} facets, single crystal measurements showed it in fact acted as a facet-selective promoter of Cu nanowire growth by keeping the {111} facets on the ends of a nanowire relatively free of surface oxidation.2 In another synthesis in which hexadecylamine is thought to serve as a capping agent for {100} facets, single crystal measurements showed that in fact hexadecylamine passivates both Cu(111) and Cu(100) equally.3 The presence of chloride ions in the synthesis selectively disrupts the alkylamine monolayer on the {111} facets on the ends of the nanowires, enabling anisotropic growth. Addition of iodide ions to the same copper nanowire synthesis results in the formation of Cu microplates instead of nanowires. Single-crystal electrochemistry confirmed that a 75 micromolar concentration of iodide resulted in passivation of {111} facets on the top and bottom surface of microplates due to the displacement of chloride by iodide. At the same time, iodide activated the {100} facets on the sides of the microplates by disrupting the hexadecylamine monolayer on those facets. Results from density functional theory calculations indicate the stronger binding affinity of iodide causes it to displace both chloride and the hexadecylamine monolayer from copper surfaces. The binding of iodide to copper leads to a lower surface energy for {111} facets than {100} facets, resulting in the preferential atomic addition of Cu to the {100} facets on the sides of microplates. These examples illustrate that organic additives do not always act as facet-selective capping agents, and that halide ions can play a dominant in driving the anisotropic growth of copper nanostructures. 1. Huo, D.; Kim, M.J.; Lyu, Z.; Shi, Y.; Wiley, B.J.; Xia, Y. One-Dimensional Metal Nanostructures: From Colloidal Syntheses to Applications. Chem. Rev., 2019, 119, 8972-9073. 2. Kim, M.J.; Flowers, P.F.; Stewart, I.E.; Ye, S.; Baek, S.; Kim, J.J.; Wiley, B.J. Ethylenediamine Promotes Cu Nanowire Growth by Inhibiting Oxidation of Cu (111). J. Am. Chem. Soc. 2017, 39, 277-284. 3. Kim, M.J.; Alvarez, S.; Chen, Z.; Fichthorn, K.A.; Wiley, B.J. Single-Crystal Electrochemistry Reveals Why Metal Nanowires Grow. J. Am. Chem. Soc., 2018, 140, 14740-14746.

The purpose of this prospective, open-label pilot study was to determine whether treatment with levetiracetam improves neuropsychological functioning in children and adolescents who have evidence of subclinical spike production associated with attention and learning difficulties. Six participants (mean age 9.8 years) were treated with levetiracetam up to 40 mg/kg per day and evaluated using neuropsychological (Wide Range Assessment of Memory and Learning, Second Edition), academic (Wechsler Individual Achievement Test, Second Edition, Abbreviated), and electroencephalographic assessments at baseline and after 10 weeks of treatment. Statistically significant improvements on indexes of the Wide Range Assessment of Memory and Learning, Second Edition were observed in 4 participants after 10 weeks. No statistically significant differences were observed for the Wechsler Individual Achievement Test, Second Edition, Abbreviated. Concomitant spike suppression was observed. Levetiracetam was generally well tolerated. A subset of patients exists with attention and learning problems that have associated aberrant cortical electrical activity without clinical seizures and associated neuropsychological deficits that may improve after treatment with levetiracetam.

A 13-year-old girl presented with refractory seizures since the age of 5 years. Clinical exam and MRI studies were normal. Ictal EEG discharges suggested possible left posterior quadrant distribution but were not well localized with standard methods. A seizure was recorded during 128-channel EEG video long-term monitoring prior to invasive recordings. Applying a source analysis method, seizure onset and propagation patterns were calculated and displayed on an MRI model. The onset was localized to the left inferior posterior occipital cortex, followed by propagation to the right, then left, posterior cerebral hemispheres, and finally to the left superior-medial parietal lobe. These patterns were replicated closely on subsequent invasive recordings. Surgery was based on intracranial findings and she is seizure-free 30 months after resection. Noninvasive dense-array EEG, used in conjunction with realistic source analysis methods, may have the potential to assist in localizing seizure onsets when standard methods fail.

Current use of microbes for metabolic engineering suffers from loss of metabolic output due to natural selection. Rather than combat the evolution of bacterial populations, we chose to embrace what makes biological engineering unique among engineering fields – evolving materials. We harnessed bacteria to compute solutions to the biological problem of metabolic pathway optimization. Our approach is called Programmed Evolution to capture two concepts. First, a population of cells is programmed with DNA code to enable it to compute solutions to a chosen optimization problem. As analog computers, bacteria process known and unknown inputs and direct the output of their biochemical hardware. Second, the system employs the evolution of bacteria toward an optimal metabolic solution by imposing fitness defined by metabolic output. The current study is a proof-of-concept for Programmed Evolution applied to the optimization of a metabolic pathway for the conversion of caffeine to theophylline in E. coli. Introduced genotype variations included strength of the promoter and ribosome binding site, plasmid copy number, and chaperone proteins. We constructed 24 strains using all combinations of the genetic variables. We used a theophylline riboswitch and a tetracycline resistance gene to link theophylline production to fitness. After subjecting the mixed population to selection, we measured a change in the distribution of genotypes in the population and an increased conversion of caffeine to theophylline among the most fit strains, demonstrating Programmed Evolution. Programmed Evolution inverts the standard paradigm in metabolic engineering by harnessing evolution instead of fighting it. Our modular system enables researchers to program bacteria and use evolution to determine the combination of genetic control elements that optimizes catabolic or anabolic output and to maintain it in a population of cells. Programmed Evolution could be used for applications in energy, pharmaceuticals, chemical commodities, biomining, and bioremediation.

Summary: Purpose: To determine whether specific regions of cerebral cortex are activated at the onset and during the propagation of absence seizures. Methods: Twenty-five absence seizures were recorded in five subjects (all women; age 19‐58 years) with primary generalized epilepsy. To improve spatial resolution, all studies were performed with dense-array, 256-channel scalp EEG. Source analysis was conducted with equivalent dipole (BESA) and smoothed linear inverse (LORETA) methods. Analyses were applied to the spike components of each spike‐wave burst in each seizure, with sources visualized with standard brain models. Results :F or each patient, the major findings were apparent on inspection of the scalp EEG maps and waveforms, and the two methods of source analysis gave generally convergent results. The onset of seizures was typically associated with activation of discrete, often unilateral areas of dorsolateral frontal or orbital frontal lobe. Consistently across all seizures, the negative slow wave was maximal over frontal cortex, and the spike that appeared to follow the slow wave was highly localized over frontopolar regions of orbital frontal lobe. In addition, sources in dorsomedial frontal cortex were engaged for each spike‐wave cycle. Although each patient showed unique features, the absence seizures of all patients showed rapid, stereotyped evolution to engage both mesial frontal and orbital frontal cortex sources during the repeating cycles of spike‐wave activity. Conclusions: These data suggest that absence seizures are not truly “generalized,” with immediate global cortical involvement, but rather involve selective cortical networks, including orbital frontal and mesial frontal regions, in the propagation of ictal discharges. Ke yW ords: Absence seizures—EEG—Source analysis—Dipole—Cerebral cortex—Thalamus.

A 13-year-old girl presented with refractory seizures since the age of 5 years. Clinical exam and MRI studies were normal. Ictal EEG discharges suggested possible left posterior quadrant distribution but were not well localized with standard methods. A seizure was recorded during 128-channel EEG video long-term monitoring prior to invasive recordings. Applying a source analysis method, seizure onset and propagation patterns were calculated and displayed on an MRI model. The onset was localized to the left inferior posterior occipital cortex, followed by propagation to the right, then left, posterior cerebral hemispheres, and finally to the left superior-medial parietal lobe. These patterns were replicated closely on subsequent invasive recordings. Surgery was based on intracranial findings and she is seizure-free 30 months after resection. Noninvasive dense-array EEG, used in conjunction with realistic source analysis methods, may have the potential to assist in localizing seizure onsets when standard methods fail.

Neural mechanisms of conscious attention require thalamic control of widespread cortical networks. Absence spells involve a momentary loss of voluntary control of attention, during which the person is inactive and unresponsive. The spike-wave seizure discharges of these spells rapidly engage both cerebral hemispheres in the classic sign of a "generalized" seizure. Animal evidence suggests that spike-wave seizures are caused by a disruption of thalamic circuitry, with extensive spread to cortex through thalamocortical propagation. We applied advanced methods of electrical source analysis to dense array (256-channel) electroencephalographic recordings of spike-wave discharges of absence spells. Neither the onset nor the spread of these seizures is generalized. Rather, the slow waves of the discharges are restricted to frontotemporal networks, and the spikes represent a highly localized and stereotyped progression of electrophysiological activity in ventromedial frontal networks. Given the current knowledge of the neurophysiology of absence seizures, this specificity of the frontal cortical discharges suggests the hypothesis that absence spells are associated with pathology in a circuit comprising ventromedial frontal cortex, rostral thalamic reticular nucleus, and limbic nuclei of the thalamus. Disrupted in absence, this circuit appears to regulate important aspects of the voluntary control of conscious attention.