Modeling Antiretrovial Treatment to Mitigate HIV in the Brain: Impact of the Blood-Brain Barrier

Current research in Human Immunodeficiency Virus (HIV) focuses on eradicating virus reservoirs that prevent or dampen the effectiveness of antiretroviral treatment (ART). One such reservoir, the brain, reduces treatment efficacy via the blood-brain barrier (BBB), causing an obstacle to drug penetration into the brain. In this study, we develop a mathematical model to examine the impact of the BBB on ART effectiveness for mitigating brain HIV. A thorough analysis of the model allowed us to fully characterize the global threshold dynamics with the viral clearance and persistence in the brain for the basic reproduction number less than unity and greater than unity, respectively. Our model showed that the BBB has a significant role in inhibiting the effect of ART within the brain despite the effective viral load suppression in the plasma. The level of impact, however, depends on factors such as the CNS Penetration Effectiveness (CPE) score, the slope of the drug dose-response curves, the ART initiation timing, and the number of drugs in the ART protocol. These results suggest that reducing the plasma viral load to undetectable levels due to some drug regimen may not necessarily indicate undetectable levels of HIV in the brain. Thus, the effect of the BBB on viral suppression in the brain must be considered for developing proper treatment protocols against HIV infection.

A Reaction-Diffusion Model with Spatially Inhomogeneous Delays

Motivated by population growth in a heterogeneous environment, this manuscript builds a reaction-diffusion model with spatially dependent parameters. In particular, a term for spatially uneven maturation durations is included in the model, which puts the current investigation among the very few studies on reaction-diffusion systems with spatially dependent delays. Rigorous analysis is performed, including the well-posedness of the model, the basic reproduction ratio formulation and long-term behavior of solutions. Under mild assumptions on model parameters, extinction of the species is predicted when the basic reproduction ratio is less than one. When the birth rate is an increasing function and the basic reproduction ratio is greater than one, uniqueness and global attractivity of a positive equilibrium can be established with the help of a novel functional phase space. Permanence of the species is shown when the birth function is in a unimodal form and the basic reproduction ratio is greater than one. The synthesized approach proposed here is applicable to broader contexts of studies on the impact of spatial heterogeneity on population dynamics, in particular, when the delayed feedbacks are involved and the response time is spatially varying.

[How to construct clinical laboratory of the hospital in post epidemic time]

A novel coronavirus pneumonia outbreak in the world. The epidemic of the new coronavirus pneumonia has been preliminarily controlled successfully in China. At this time, how to construct the clinical laboratory in the hospital? This artical puts some forward thoughts, such as improve the construction of biological safety protection ability, detection ability, test platform construction, scientific research ability construction, personnel training and clinical communication ability, etc. These above advices could provide reference for the development direction of the clinical laboratory in post epidemic era.

Effects of periodic intake of drugs of abuse (morphine) on HIV dynamics: Mathematical model and analysis

Drugs of abuse, such as opiates, have been widely associated with diminishing host-immune responses, including suppression of HIV-specific antibody responses. In particular, periodic intake of the drugs of abuse can result in time-varying periodic antibody level within HIV-infected individuals, consequently altering the HIV dynamics. In this study, we develop a mathematical model to analyze the effects of periodic intake of morphine, a widely used opiate. We consider two routes of morphine intake, namely, intravenous morphine (IVM) and slow-release oral morphine (SROM), and integrate several morphine pharmacodynamic parameters into HIV dynamics model. Using our non-autonomous model system we formulate the infection threshold, R_i, for global stability of infection-free equilibrium, which provides a condition for avoiding viral infection in a host. We demonstrate that the infection threshold highly depends on the morphine pharmacodynamic parameters. Such information can be useful in the design of antibody-based vaccines. In addition, we also thoroughly evaluate how alteration of the antibody level due to periodic intake of morphine can affect the viral load and the CD4 count in HIV infected drug abusers.

Importance of Au nanostructures in CO2 electrochemical reduction reaction

Electrochemical conversion of CO₂ into fuels is a promising means to solve greenhouse effect and recycle chemical energy. However, the CO₂ reduction reaction (CO₂RR) is limited by the high overpotential, slow kinetics and the accompanied side reaction of hydrogen evolution reaction. Au nanocatalysts exhibit high activity and selectivity toward the reduction of CO₂ into CO. Here, we explore the Faradaic efficiency (FE) of CO₂RR catalyzed by 50 nm gold colloid and trisoctahedron. It is found that the maximum FE for CO formation on Au trisoctahedron reaches 88.80% at -0.6 V, which is 1.5 times as high as that on Au colloids (59.04% at -0.7 V). The particle-size effect of Au trisoctahedron has also been investigated, showing that the FE for CO decreases almost linearly to 62.13% when the particle diameter increases to 100 nm. The X-ray diffraction characterizations together with the computational hydrogen electrode (CHE) analyses reveal that the (2 2 1) facets on Au trisoctahedron are more feasible than the (1 1 1) facets on Au colloids in stabilizing the critical intermediate COOH*, which are responsible for the higher FE and lower overpotential observed on Au trisoctahedron.

[Effectiveness evaluation of health belief model-based health education intervention for patients with hypertension in community settings]

Objective: To evaluate the effectiveness of health belief model-based health education intervention in improving blood pressure control of patients with hypertension in community settings. Methods: From September 2016 to September 2017, 400 newly diagnosed patients with hypertension were recruited from 6 community healthcare centers with comparable population size and health services in the Shunyi District of Beijing. All community healthcare centers were randomly assigned to the intervention group (206 patients) and the control group (194 patients). Patients in the intervention group received 3 lectures (20-30 min for each) of health belief model-based health education. Patients in the control group received usual care. The basic characteristics, health beliefs, and health literacy were collected, and blood pressure was measured before and after the intervention, respectively. The difference-in-difference model was used to analyze the change of blood pressure and the influencing factors between two groups before and after the intervention. Results: A total of 134 patients in the intervention group and 129 patients in the control group completed the study. After adjusting for the age, gender, family income, medical insurance, chronic diseases and family history, the score of perceived barriers was increased by 1.65 (P=0.016), and perceived seriousness was decreased by 0.73 (P=0.018). The systolic blood pressure of patients was decreased by 7.37 mmHg (1 mmHg=0.133 kPa, P=0.001) and diastolic blood pressure was decreased by 4.07 mmHg (P=0.014), respectively. The β (95%CI) values were -7.37 (-11.88,-2.86) and -4.07 (-7.30, -0.84). The perceived susceptibility and self-efficacy had a significant influence on the blood pressure of patients (P<0.05). Conclusion: Health belief model-based health education intervention could significantly improve the blood pressure control of patients with hypertension in the community settings.

Mathematical analysis of an HBV model with antibody and spatial heterogeneity

In this paper, we modify the HBV model proposed in [1] to include the spatial variations of free antibody, virus-antibody complexes, and free virus. By using comparison arguments and theory of uniform persistence, we can show that the persistene/extinction of HBV can be determined by the reproduction number(s).

Axial ligands tailoring the ORR activity of cobalt porphyrin

In an effort to provide visualization and understanding to the electronic "push effect" of axial ligands on the catalytic activity of cobalt macrocyclic molecules, we design a simple model system involving an [5,10,15,20-tetrakis(4-methoxyphenyl)porphyrin]cobalt(II) (TMMPCo) monolayer axially-coordinated on thiol ligand modified Au electrode and explore the activity of the axial-ligand coordinated TMPPCo toward oxygen reduction reaction (ORR) in acidic medium. Three different ligands, with a decreasing order of coordinating ability as: 4-mercaptopyridine (MPy) > 4-aminothiolphenol (APT) > 4-mercaptobenzonitrile (MBN) are used and a maximum difference in ORR onset potential of 80 mV is observed between the MPy (highest onset potential) and MBN systems (lowest onset potential). The ORR activity of TMPPCo increases with the increase in binding strength of the axial ligand. A detailed mechanism study reveals that ORR on the three ligand coordinated TMPPCo systems shares the same 2-electron mechanism with H₂O₂ as the terminal product. Theoretical calculation into the structure of the ligand coordinated cobalt porphyrins uncovers the variation in atomic charge of the Co(II) center and altered frontier molecular orbital distribution among the three ligand systems. Both properties have great influence on the back-bonding formation between the Co(II) center and O₂ molecules, which has been suggested to be critical toward the O₂ adsorption and subsequent activation process.

Mathematical modeling and analysis of harmful algal blooms in flowing habitats

In this paper, we survey recent developments of mathematical modeling and analysis of the dynamics of harmful algae in riverine reservoirs. To make the models more realistic, a hydraulic storage zone is incorporated into a flow reactor model and new mathematical challenges arise from the loss of compactness of the solution maps. The key point in the study of the evolution dynamics is to prove the existence of global attractors for the model systems and the principal eigenvalues for the associated linearized systems without compactness.

Vagal baro- and chemoreceptors in middle internal carotid artery and carotid body in rat

The glossopharyngeal nerve, via the carotid sinus nerve (CSN), presents baroreceptors from the internal carotid artery (ICA) and chemoreceptors from the carotid body. Although neurons in the nodose ganglion were labelled after injecting tracer into the carotid body, the vagal pathway to these baro- and chemoreceptors has not been identified. Neither has the glossopharyngeal intracranial afferent/sensory pathway that connects to the brainstem been defined. We investigated both of these issues in male Sprague-Dawley rats (n = 40) by injecting neural tracer wheat germ agglutinin-horseradish peroxidase into: (i) the peripheral glossopharyngeal or vagal nerve trunk with or without the intracranial glossopharyngeal rootlet being rhizotomized; or (ii) the nucleus of the solitary tract right after dorsal and ventral intracranial glossopharyngeal rootlets were dissected. By examining whole-mount tissues and brainstem sections, we verified that only the most rostral rootlet connects to the glossopharyngeal nerve and usually four caudal rootlets connect to the vagus nerve. Furthermore, vagal branches may: (i) join the CSN originating from the pharyngeal nerve base, caudal nodose ganglion, and rostral or caudal superior laryngeal nerve; or (ii) connect directly to nerve endings in the middle segment of the ICA or to chemoreceptors in the carotid body. The aortic depressor nerve always presents and bifurcates from either the rostral or the caudal part of the superior laryngeal nerve. The vagus nerve seemingly provides redundant carotid baro- and chemoreceptors to work with the glossopharyngeal nerve. These innervations confer more extensive roles on the vagus nerve in regulating body energy that is supplied by the cardiovascular, pulmonary and digestive systems.

High-Performance Ru@C4N Electrocatalyst for Hydrogen Evolution Reaction in Both Acidic and Alkaline Solutions

We report a high-performance Ru@C₄N electrocatalyst for the hydrogen evolution reaction (HER) in both acidic and alkaline solutions. This catalyst is synthesized by annealing a complex of a covalent organic framework compound coordinated with ruthenium synthesized by a "one-pot" solvothermal method. This Ru@C₄N catalyst shows excellent electrocatalytic activity toward the hydrogen evolution reaction (HER) in both acidic and alkaline solutions with very low overpotentials at 10 mA/cm² (6 mV in 0.5 M H₂SO₄ solution; 7 mV in 1.0 M KOH solution), which outperforms the commercial catalyst Pt/C. The Ru@C₄N electrocatalyst also exhibits high HER turnover frequencies of 0.93 H₂ per s in 0.5 M H₂SO₄ and 0.65 H₂ per s in 1.0 M KOH solutions at 25 mV as well as superior performance stability.

Mathematical analysis of a chemostat system modeling the competition for light and inorganic carbon with internal storage

This paper investigates a mathematical model of competition between two species for inorganic carbon and light in a well-mixed water column. The population growth of the species depends on the consumption of two substitutable forms of inorganic carbon, "CO2" (dissolved CO2 and carbonic acid) and "CARB" (bicarbonate and carbonate ions), which are stored internally. Besides, uptake rates also includes self-shading by the phytoplankton population, that is, an increase in population density will reduce light available for photosynthesis, and thereby reducing further carbon assimilation and population growth. We also incorporate the fact that carbon is lost by respiration, and the respiration rate is assumed to be proportional to the size of the transient carbon pool. Then we study the extinction and persistence of a single-species system. Finally, we show that coexistence of the two-species system is possible, depending on parameter values, and both persistence of one population.

Axons of Passage and Inputs to Superior Cervical Ganglion in Rat

Wheat germ agglutinin-horseradish peroxidase was injected into the entire (0.8 μL) or partial (rostral or caudal, 0.1-0.3 μL) superior cervical ganglion (SCG) of the rat (male Sprague-Dawley, N = 35) to examine the distribution of neurons in the middle (MCG) and inferior (ICG) cervical ganglion that send axons bypass the SCG. Whole-mounts of the SCG, cervical sympathetic trunk (CST), MCG, ICG, and sections of the brainstem and spinal cord were prepared. With entire SCG tracer injection, neurons were labeled evenly in the MCG (left: 258, right: 121), ICG (left: 848, right: 681), and CST (up to 770). Some neurons grouped in a single bulge just rostral to the MCG, which we termed as the "premiddle cervical ganglion" (pMCG). The left pMCG (120) is larger and has more neurons than the right pMCG (82). Centrally, neurons were labeled in lamina IX of cervical segments (C1: 18%, C2: 46%, C3: 33%, C4: 3%), intermediate zone of thoracic segments (T1: 31%, T2: 35%, T3: 27%, T4: 7%), and intermediate reticular nuclei (96%) and perifacial zone (4%) of brainstem. The rostral and caudal SCG injection selectively labeled neurons mainly in brainstem, C1-C2 and in T1-T2, respectively. Before projecting to their peripheral targets, many neurons in pMCG, MCG and ICG run rostrally within the CST rather than segmentally through the closest rami, from the level of SCG or above. Neurons in pMCG and MCG may have similar or complementary function and those in brainstem may be involved in the vestibulo-autonomic interaction. Anat Rec, 301:1906-1916, 2018. © 2018 Wiley Periodicals, Inc.

Exploring the Confinement Effect of Carbon Nanotubes on the Electrochemical Properties of Prussian Blue Nanoparticles

A novel and efficient photochemical method has been proposed for the encapsulation of Prussian blue nanoparticles (PBNPs) inside the channels of carbon nanotubes (PB-in-CNTs) in an acidic ferrocyanide solution under UV/vis illumination, and the confinement effect of CNTs on the electrochemical properties of PBNPs is systematically explored. PB-in-CNTs show a faster electron-transfer process, an enhanced electrocatalytic activity toward the reduction of H₂O₂, and an increased anti-base ability compared to PBNPs loaded outside of CNTs (PB-out-CNTs). In addition, PB-in-CNTs show an increased electrochemical reversibility and an unexpected diameter-independent catalytic activity with the decrease of CNT diameters. The improved electrochemical properties of PB-in-CNTs are attributed to the modified electronic properties and dimensions of PBNPs induced by the confinement effect of CNTs. This work provides further insights into the confinement effect on the properties of nanomaterials and will inspire extensive relevant investigations in the development of novel composites or excellent catalysts.

Synergistically mediated enhancement of cathodic and anodic electrochemiluminescence of graphene quantum dots through chemical and electrochemical reactions of coreactants

A dual potential electrochemiluminescence (ECL) enhancement of graphene quantum dots is achieved through chemical and electrochemical reactions of two different coreactants.

We for the first time propose a new concept where a greater enhancement in dual potential electrochemiluminescence (ECL) of a single graphene quantum dot (GQD) emitter can be achieved through the coupling between chemical and electrochemical reactions of two different coreactants of K₂S₂O₈ and Na₂SO₃.

Vagal nerve endings in visceral pleura and triangular ligaments of the rat lung

The inner thoracic cavity is lined by the parietal pleura, and the lung lobes are covered by the visceral pleura. The parietal and visceral plurae form the pleural cavity that has negative pressure within to enable normal respiration. The lung tissues are bilaterally innervated by vagal and spinal nerves, including sensory and motor components. This complicated innervation pattern has made it difficult to discern the vagal vs. spinal processes in the pulmonary visceral pleura. With and without vagotomy, we identified vagal nerve fibres and endings distributed extensively in the visceral pleura ('P'-type nerve endings) and triangular ligaments ('L'-type nerve endings) by injecting wheat germ agglutinin-horseradish peroxidase as a tracer into the nucleus of solitary tract or nodose ganglion of male Sprague-Dawley rats. We found the hilar and non-hilar vagal pulmonary pleural innervation pathways. In the hilar pathway, vagal sub-branches enter the hilum and follow the pleural sheet to give off the terminal arborizations. In the non-hilar pathway, vagal sub-branches run caudally along the oesophagus and either directly enter the ventral-middle-mediastinal left lobe or follow the triangular ligaments to enter the left and inferior lobe. Both vagi innervate: (i) the superior, middle and accessory lobes on the ventral surfaces that face the heart; (ii) the dorsal-rostral superior lobe; (iii) the dorsal-caudal left lobe; and (iv) the left triangular ligament. Innervated only by the left vagus is: (i) the ventral-rostral and dorsal-rostral left lobe via the hilar pathway; (ii) the ventral-middle-mediastinal left lobe and the dorsal accessory lobe that face the left lobe via the non-hilar pathway; and (iii) the ventral-rostral inferior lobe that faces the heart. Innervated only by the right vagus, via the non-hilar pathway, is: (i) the inferior (ventral and dorsal) and left (ventral only) lobe in the area near the triangular ligament; (ii) the dorsal-middle-mediastinal left lobe; and (iii) the right triangular ligament. Other regions innervated with unknown vagal pathways include: (i) the middle lobe that faces the superior and inferior lobe; (ii) the rostral-mediastinal inferior lobe that faces the middle lobe; and (iii) the ventral accessory lobe that faces the diaphragm. Our study demonstrated that most areas that face the dorsal thoracic cavity have no vagal innervation, whereas the interlobar and heart-facing areas are bilaterally or unilaterally innervated with a left-rostral vs. right-caudal lateralized innervation pattern. This innervation pattern may account for the fact that the respiratory regulation in rats has a lateralized right-side dominant pattern.

Hollow core-shell structured Ni-Sn@C nanoparticles: a novel electrocatalyst for the hydrogen evolution reaction

Pt-free electrocatalysts with high activity and low cost are highly pursued for hydrogen production by electrochemically splitting water. Ni-based alloy catalysts are potential candidates for the hydrogen evolution reaction (HER) and have been studied extensively. Here, we synthesized novel hollow core-shell structure Ni-Sn@C nanoparticles (NPs) by sol-gel, chemical vapor deposition, and etching processes. The prepared electrocatalysts with porous hollow carbon layers have a high conductivity and large active area, which exhibit good electrocatalytic activity toward HER. The Tafel slope of ∼35 millivolts per decade measured in acidic solution for Ni-Sn@C NPs is the smallest one to date for the Ni-Sn alloy catalysts, and exceeds those of the most non-noble metal catalysts, indicating a possible Volmer-Heyrovsky reaction mechanism. The synthetic method can be extended to prepare other hollow core-shell structure electrocatalysts for low-temperature fuel cells.

The room temperature electrochemical synthesis of N-doped graphene and its electrocatalytic activity for oxygen reduction

N doping in graphene can be achieved using a facile and mild approach using electrochemical energy at room temperature with ammonia as the N source, which occurs at the carbon active sites generated in situ during the removal of oxygen containing species at cathodic potentials.

Ice crystals growth driving assembly of porous nitrogen-doped graphene for catalyzing oxygen reduction probed by in situ fluorescence electrochemistry

In recent years, doped carbonaceous materials as alternative catalysts for oxygen reduction reaction (ORR) have received considerable attention due to the low cost and high CO tolerance capability. Different theoretical studies have suggested that oxygen is reduced in a rapid sequence intermediated by diverse oxygen-containing reactive intermediates (ORI). However, due to the short lifetimes of the possible ORI, direct experimental evidence is very difficult to be obtained. Here, we report the synthesis of an ultralight and porous nitrogen-doped graphene (NG) by annealing graphite oxide (GO)-melamine scaffold shaped in ice template. The resultant NG exhibits excellent electrocatalytic activity toward 4e-reduction of oxygen with the onset potential as low as -0.05 V vs. Ag/AgCl in alkaline media. Using this material as model study, sensitive in situ fluorescence spectroelectrochemistry is applied to demonstrate the presence the reactive ORI. The global ORR pathway is unraveled as stepwise electron transfer involving hydroxyl radical as the important intermediate via both inner- and outer-sphere process. This result would likely provide a new insight into the further understanding of ORR mechanism on those intrinsic carbonaceous materials.

Bioinspired copper catalyst effective for both reduction and evolution of oxygen

In many green electrochemical energy devices, the conversion between oxygen and water suffers from high potential loss due to the difficulty in decreasing activation energy. Overcoming this issue requires full understanding of global reactions and development of strategies in efficient catalyst design. Here we report an active copper nanocomposite, inspired by natural coordination environments of catalytic sites in an enzyme, which catalyzes oxygen reduction/evolution at potentials closely approaching standard potential. Such performances are related to the imperfect coordination configuration of the copper(II) active site whose electron density is tuned by neighbouring copper(0) and nitrogen ligands incorporated in graphene. The electron transfer number of oxygen reduction is estimated by monitoring the redox of hydrogen peroxide, which is determined by the overpotential and electrolyte pH. An in situ fluorescence spectroelectrochemistry reveals that hydroxyl radical is the common intermediate for the electrochemical conversion between oxygen and water.

Donnan potential caused by polyelectrolyte monolayers

The Donnan potential is successfully isolated from ion pair potential on a ferrocene-labeled polyelectrolyte (DNA) monolayer. The isolated Donnan potential shifts negatively upon the increase in NaClO4 concentration with a slope of -58.8 mV/decade. With the salt concentration grown up to 1 M, the stretched DNA chains in low salt concentration are found to experience a gradual conformation relaxing process. At salt concentrations higher than 2 M, Donnan breakdown occurs where only the ion pair effect modulates the apparent potential. The apparent formal potential also shows strong dependence on solution pH, which reveals that the charge density in the polyelectrolyte monolayer plays an important role in the establishment of Donnan equilibrium.

Graphene-Ruthenium(II) complex composites for sensitive ECL immunosensors

Non-covalent modification method has been proven as an effective strategy for enhancing the chemical properties of graphene while the structure and electronic properties of graphene can be retained. This work describes a novel strategy to fabricate a solid-state electrochemiluminescent (ECL) immunosensor based on ruthenium(II) complex/3,4,9,10-perylenetetracarboxylic acid (PTCA)/graphene nanocomposites (Ru-PTCA/G) for sensitive detection of α-fetoprotein (AFP). It is found that immobilization of PTCA and reduction of GO can be simultaneously achieved in one-pot synthesis method under alkaline condition and moderate temperature, forming PTCA/G nanocomposites. Further covalent attachment of ruthenium(II) complex to the PTCA assembled on graphene sheets produces the functional Ru-PTCA/G nanocomposites which show good electrochemical activity and ca. 21 times higher luminescence quantum efficiency than the adsorbed derivative ruthenium(II) complex. The Ru-PTCA/G nanocomposites based solid-state ECL sensor exhibits high stability toward the determination of tripropylamine (TPA) coreactant. In addition, a new ECL immunosensor based on steric hindrance effect is fabricated by cross-linking α-fetoprotein antibody (anti-AFP) with chitosan covered on Ru-PTCA/G composites modified electrode for detection of cancer biomarker AFP. This ECL immunosensor shows an extremely sensitive response to AFP in a linear range of 5 pg·mL(-1) -10 ng·mL(-1) with a detection limit of 0.2 pg·mL(-1) . The present approach is effective for various molecules immobilization and may become a promising technique for biomolecular detection.

Conformational change and biocatalysis-triggered spectral shift of single Au nanoparticles

The conformational change of guanine-rich DNA and the biocatalytic process of DNAzyme are observed directly on single gold nanoparticles through NPPR spectra.

Catalyst-free synthesis of nitrogen-doped graphene via thermal annealing graphite oxide with melamine and its excellent electrocatalysis

The electronic and chemical properties of graphene can be modulated by chemical doping foreign atoms and functional moieties. The general approach to the synthesis of nitrogen-doped graphene (NG), such as chemical vapor deposition (CVD) performed in gas phases, requires transitional metal catalysts which could contaminate the resultant products and thus affect their properties. In this paper, we propose a facile, catalyst-free thermal annealing approach for large-scale synthesis of NG using low-cost industrial material melamine as the nitrogen source. This approach can completely avoid the contamination of transition metal catalysts, and thus the intrinsic catalytic performance of pure NGs can be investigated. Detailed X-ray photoelectron spectrum analysis of the resultant products shows that the atomic percentage of nitrogen in doped graphene samples can be adjusted up to 10.1%. Such a high doping level has not been reported previously. High-resolution N1s spectra reveal that the as-made NG mainly contains pyridine-like nitrogen atoms. Electrochemical characterizations clearly demonstrate excellent electrocatalytic activity of NG toward the oxygen reduction reaction (ORR) in alkaline electrolytes, which is independent of nitrogen doping level. The present catalyst-free approach opens up the possibility for the synthesis of NG in gram-scale for electronic devices and cathodic materials for fuel cells and biosensors.

A green approach to the synthesis of graphene nanosheets

Graphene can be viewed as an individual atomic plane extracted from graphite, as unrolled single-walled carbon nanotube or as an extended flat fullerene molecule. In this paper, a facile approach to the synthesis of high quality graphene nanosheets in large scale through electrochemical reduction of exfoliated graphite oxide precursor at cathodic potentials (completely reduced potential: -1.5 V) is reported. This method is green and fast, and will not result in contamination of the reduced material. The electrochemically reduced graphene nanosheets have been carefully characterized by spectroscopic and electrochemical techniques in comparison to the chemically reduced graphene-based product. Particularly, FTIR spectra indicate that a variety of the oxygen-containing functional groups have been thoroughly removed from the graphite oxide plane via electrochemical reduction. The chemically converted materials are not expected to exhibit graphene's electronic properties because of residual defects. Indeed, the high quality graphene accelerates the electron transfer rate in dopamine electrochemistry (DeltaE(p) is as small as 44 mV which is much smaller than that on a glassy carbon electrode). This approach opens up the possibility for assembling graphene biocomposites for electrocatalysis and the construction of biosensors.

Vagal innervation of intestines: afferent pathways mapped with new en bloc horseradish peroxidase adaptation

Neural tracers have not typically been employed to determine the pathways followed by axons between their perikarya and target tissues. We have adapted the tetramethylbenzidine method for horseradish peroxidase (HRP) to stain fibers en bloc in organs and thus to delineate axonal trajectories. We have also applied this protocol to characterize the pathways that vagal afferents follow to the intestines. The protocol confirms that the proximal segment of the duodenum receives afferents carried in the vagal hepatic branch and demonstrates that vagal afferents innervating the remainder of the small and large intestines course through multiple fascicles derived from the celiac branches of the abdominal vagus. These fascicles divide, intermingle, and reorganize along the abdominal aorta and superior mesenteric artery (SMA), but not along the inferior mesenteric artery, and then project to the intestines with secondary arteries that branch from the SMA. The inferior pancreaticoduodenal, jejunal, middle colic, right colic, and ileocecocolic arteries all carry vagal afferents to segments of the intestines. As the arteries derived from the SMA divide repeatedly into successively finer branches and course to the intestines, the vagal afferent fascicles (typically a pair) running with each arterial branch also divide. These divisions generate sets/pairs of finer fascicles coursing with even the highest order arterial radicles. The vagal fascicles enter the intestinal wall with the vessels and appear to innervate the organ near the point of entry. The results verify the practicality and sensitivity of the en bloc HRP technique and suggest that the protocol could delineate other peripheral pathways.