The light aroma type liquor is widely welcomed by consumers due to its pleasant fruity and floral aroma, particularly in northern China. To answer the puzzling question of which key aroma compounds are responsible for the typical aroma, three typical liquors were studied in this paper. A total of 66 aroma compounds were identified in three liquors by means of gas chromatography-olfactometry (GC-O) coupled with mass spectrometry (MS), and 27 odorants were further screened out as the important odorants according to quantitative study and odor activity values (OAVs). For OAV calculation, odor thresholds of the odorants were determined in a hydroalcoholic solution at 46% ethanol by volume. The typical light type aroma dominated by fruity and floral notes was successfully simulated by dissolving these important odorants in the 46% vol hydroalcoholic solution in their natural concentrations. Omission experiments further confirmed β-damascenone and ethyl acetate as the key odorants and revealed the significance of the entire group of esters, particularly ethyl lactate, geosmin, acetic acid, and 2-methylpropanoic acid, for the overall aroma of the light aroma type Chinese liquor.

The computations underlying cognitive functions are performed by a diversity of interactions between interneurons and pyramidal neurons that are subject to modulatory influences. Here we have used paired whole-cell recording to study the influence of dopamine on local inhibitory circuits involving fast-spiking (FS) and non-FS cells, respectively. We found that dopamine depressed inhibitory transmission between FS interneurons and pyramidal neurons but enhanced inhibition between non-FS interneurons and pyramidal cells. FS inhibitory transmission exhibited properties associated with presynaptic action at D(1) receptors that were not evident in non-FS inhibitory connections. In addition, FS and non-FS interneurons differed morphologically, forming contacts on the perisomatic and peridendritic domains, respectively, of their pyramidal cell targets. These findings provide evidence for both a dual mode of inhibition in prefrontal circuitry and circuit-dependent modulation by dopamine.

Graphitic carbons with ordered mesostructure and high surface areas (of great interest in applications such as energy storage) have been synthesized by a direct triblock‐copolymer‐templating method. Pluronic F127 is used as a structure‐directing agent, with a low‐molecular‐weight phenolic resol as a carbon source, ferric oxide as a catalyst, and silica as an additive. Inorganic oxides can be completely eliminated from the carbon. Small‐angle XRD and N2 sorption analysis show that the resultant carbon materials possess an ordered 2D hexagonal mesostructure, uniform bimodal mesopores (about 1.5 and 6 nm), high surface area (∼1300 m2/g), and large pore volumes (∼1.50 cm3/g) after low‐temperature pyrolysis (900 °C). All surface areas come from mesopores. Wide‐angle XRD patterns demonstrate that the presence of the ferric oxide catalyst and the silica additive lead to a marked enhancement of graphitic ordering in the framework. Raman spectra provide evidence of the increased content of graphitic sp2 carbon structures. Transmission electron microscopy images confirm that numerous domains in the ordered mesostructures are composed of characteristic graphitic carbon nanostructures. The evolution of the graphitic structure is dependent on the temperature and the concentrations of the silica additive, and ferric oxide catalyst. Electrochemical measurements performed on this graphitic mesoporous carbon when used as an electrode material for an electrochemical double layer capacitor shows rectangular‐shaped cyclic voltammetry curves over a wide range of scan rates, even up to 200 mV/s, with a large capacitance of 155 F/g in KOH electrolyte. This method can be widely applied to the synthesis of graphitized carbon nanostructures.

The prefrontal cortex plays a fundamental role in the working memory functions of the cerebral cortex and is also the site of dysfunction in several neurological and psychiatric disorders, including schizophrenia. Prefrontal neurons are distinguished by their capacity for sustained activity during the time a stimulus is held in memory, and this mnemonic response is considered a substrate for a variety of cognitive functions. The neuronal basis for sustained activity in prefrontal neurons is unknown but is thought to involve recurrent excitation among pyramidal neurons. Recent studies in awake behaving monkeys have demonstrated that the persistent activity in prefrontal neurons is modulated by dopamine. To examine the mechanisms by which dopamine might modulate transmission in local excitatory circuits, we have performed dual whole-cell recordings in connected pyramidal cell pairs with and without dopamine application. We find that dopamine reduces the efficacy of unitary excitatory neurotransmission in layer V pyramidal cells by decreasing its reliability. These effects, which are reproduced by a selective D1 agonist and blocked by a D1 antagonist, are independent of voltage changes and are not attenuated by blockade of sodium and potassium channels in the postsynaptic neurons. We conclude that attenuation of local horizontal excitatory synaptic transmission in layer V pyramidal neurons by dopamine is through D1 actions at a presynaptic site. T he prefrontal cortex (PFC) plays a primary role in working memory, the mental operation critical for ''online'' processing of information (1, 2). Prefrontal neurons exhibit persistent neuronal firing throughout the delay interval intervening between a stimulus and a memory-guided response. Understanding the cellular and circuit basis of sustained neural activity maintained in the absence of a stimulus is considered an important quest in cognitive neuroscience (2). Previous studies in this laboratory have revealed a role for dopamine (DA) acting at D1 receptors in the modulation of a prefrontal neuron's excitatory response to its preferred stimulus (3). The sustained response of prefrontal neurons in the absence of a stimulus has generated considerable interest (4 -11), but the precise pharmacological and circuit mechanisms underlying this activation remain unclear. As DA terminals and glutamatergic terminals form so-called synaptic triads with dendritic spines of pyramidal neurons (12, 13), we have proposed that DA directly modulates glutamate transmission at such triads, and thereby is a modulator of recurrent excitatory interactions between and among local pyramidal neurons that could promote persistent neural activity. To directly test this hypothesis, we have examined the synaptic effects of DA on recurrent excitatory transmission between pairs of pyramidal neurons by means of dual whole-cell patch clamp recording combined with DA application. In particular, we have examined DA's effects on unitary excitatory postsynaptic potentials (EPSPs), especially DA's modulation...

Oriented self-assembly between inorganic nanocrystals and surfactants is emerging as a route for obtaining new mesocrystalline semiconductors. However, the actual synthesis of mesoporous semiconductor mesocrystals with abundant surface sites is extremely difficult, and the corresponding new physical and chemical properties arising from such an intrinsic porous mesocrystalline nature, which is of fundamental importance for designing high-efficiency nanostructured devices, have been rarely explored and poorly understood. Herein, we report a simple evaporation-driven oriented assembly method to grow unprecedented olive-shaped mesoporous TiO2 mesocrystals (FDU-19) self-organized by ultrathin flake-like anatase nanocrystals (∼8 nm in thickness). The mesoporous mesocrystals FDU-19 exhibit an ultrahigh surface area (∼189 m2/g), large internal pore volume (0.56 cm3/g), and abundant defects (oxygen vacancies or unsaturated Ti3+ sites), inducing remarkable crystallite-interface reactivity. It is found that the mesocrystals FDU-19 can be easily fused in situ into mesoporous anatase single crystals (SC-FDU-19) by annealing in air. More significantly, by annealing in a vacuum (∼4.0 × 10–5 Pa), the mesocrystals experience an abrupt three-dimensional to two-dimensional structural transformation to form ultrathin anatase single-crystal nanosheets (NS-FDU-19, ∼8 nm in thickness) dominated by nearly 90% exposed reactive (001) facets. The balance between attraction and electrostatic repulsion is proposed to determine the resulting geometry and dimensionality. Dye-sensitized solar cells based on FDU-19 and SC-FDU-19 samples show ultrahigh photoconversion efficiencies of up to 11.6% and 11.3%, respectively, which are largely attributed to their intrinsic single-crystal nature as well as high porosity. This work gives new understanding of physical and chemical properties of mesoporous semiconductor mesocrystals and opens up a new pathway for designing various single-crystal semiconductors with desired mesostructures for applications in catalysis, sensors, drug delivery, optical devices, etc.

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EphA family receptor tyrosine kinases and their ephrin-A ligands are involved in patterning axonal connections during brain development, but until now a role for these molecules in the mature brain had not been elucidated. Here, we show that both the EphA5 receptor and its ephrin-A ligands (2 and 5) are expressed in the adult mouse hippocampus, and the EphA5 protein is present in a phosphorylated form. Because there are no pharmacological agents available for EphA receptors, we designed recombinant immunoadhesins that specifically bind to the receptor binding site of the ephrin-A ligand (antagonist) or the ligand binding site of the EphA receptor (agonist) and thus target EphA function. We demonstrate that intrahippocampal infusion of an EphA antagonist immunoadhesin leads to impaired performance in two behavioral paradigms, T-maze spontaneous alternation and context-dependent fear conditioning, sensitive to hippocampal function, whereas activation of EphA by infusion of an agonist immunoadhesin results in enhanced performance on these tasks. Because the two behavioral tasks have different motivational, perceptual, and motor requirements, we infer the changes were not caused by these performance factors but rather to cognitive alterations. We also find bidirectional changes in gene expression and in electrophysiological measures of synaptic efficacy that correlate with the behavioral results. Thus, EphA receptors and their ligands are implicated as mediators of plasticity in the adult mammalian brain.

The goal of this study was to describe the development of gamma‐aminobutyric acid (GABA)‐containing neurons in visual and auditory cortex of ferrets. The laminar and tangential distribution of neurons containing excitatory, inhibitory, and neuromodulatory substances constrain the potential circuits which can form during development. Ferrets are born at an early stage of brain development, allowing examination of inhibitory circuit formation in cerebral cortex prior to thalamocortical ingrowth and cortical plate differentiation. Immunocytochemically labelled nonpyramidal GABA neurons were present from postnatal day 1 throughout development, in all cortical layers, and generally followed the inside‐out pattern of neuronal migration into the cortical plate. Prior to postnatal day 14, pyramidal neurons with transient GABA immunoreactivity were also observed. The density of Nissl‐stained and GABA‐immunoreactive neurons was high early in development, declined markedly by postnatal day 20, then remained relatively constant until adulthood. However, examination of the proportion of GABA neurons revealed an unexpected late peak at postnatal day 60, then a decrease in adulthood. Visual and auditory cortex were similar in most respects, but the peak at postnatal day 60 and the final proportion of GABA neurons was higher in auditory cortex. The late peak suggests that inhibitory circuitry is stabilized relatively late in sensory cortical development, and thus that GABA neurons could provide an important substrate for experience‐dependent plasticity at late stages of development. J. Comp. Neurol. 409:261–273, 1999. © 1999 Wiley‐Liss, Inc.