Fast Sodium Ion Research Articles

Ultrafine CoSe nano-crystallites confined in leaf-like N-doped carbon for long-cyclic and fast sodium ion storage

Considerable efforts have been devoted to developing sodium-ion batteries for large-scale energy storage due to the high abundance and low cost of sodium resources. However, the inferior cyclability and reaction kinetics of electrodes toward sodium ions still impedes their further development. In this study, we designed a two-dimensional (2D) composite where ultrafine CoSe nano-crystallites were confined in N-doped carbon (CoSe/NC-L) to attain excellent cycling performance and fast sodium ion storage. The CoSe/NC-L was successfully prepared through a high-temperature reaction of leaf-like Co-based ZIF (ZIF-L) and Se powder. It is demonstrated that the particle size of Se powder plays an important role in the formation of ultrafine CoSe nano-crystallites and encapsulated configuration. The combined merits of ultrafine CoSe and encapsulation into 2D NC matrix effectively enhance reaction kinetics, accommodate volume change expansion of CoSe and inhibit the formation of unstable SEI. Therefore, the CoSe/NC-L composite displayed high initial specific capacity of 530 mAh g−1 and Coulombic efficiency of 67.2% at 0.2 A g−1. Notably, superior capacity retention of 82.2% with stable Coulombic efficiency of 97.0% is achieved at 0.5 A g−1 after 150 cycles in NaClO4 electrolyte system. This work casts a new light on the smart design of metal selenide electrode materials for sodium ions batteries.

(Invited) Ion Transport in Low-Dimensional Ionic Conductors

We discuss ionic transport in fast lithium and sodium ion conductors, which receive renewed attention as solid-state electrolytes for all-solid-state batteries. Because transport of ions across interfaces can differ strongly from that in the bulk, the DC conductivity relevant for battery operation cannot be measured directly by impedance spectroscopy. We discuss models that accurately describe the impedance spectra of prototypical solid-state electrolyte materials including the effect of grain boundaries and ion-ion correlations.

Precise carbon structure control by salt template for high performance sodium-ion storage

Carbon materials are considered to be one of the most promising anode materials for sodium-ion batteries (SIBs), but the well-ordered graphitic structure limits the intercalation of sodium ions. Besides, the sluggish intercalation kinetics of sodium ions impedes the rate performance. Thus, the precise structure control of carbon materials is important to improve the battery performance. Herein, a 3D porous hard-soft composite carbon (3DHSC) was prepared using the NaCl as the template and phenolic resin and pitch as carbon precursors. The NaCl template restrains the growth of the graphite crystallite during the carbonization process, resulting in small graphitic domains with expanded interlayer spacing which is favorable for the sodium storage. Moreover, the NaCl templates help to create abundant mesopores and macropores for fast sodium ion diffusion. The porous structure and the graphite crystalline structure can be precisely controlled by simply adjusting the mass ratio of NaCl, and thus, the suitable structure can be prepared to reach high capacity and rate performance while keeping a relatively high Coulombic efficiency. Typically, a high reversible capacity (215 mA h g−1 at 0.05 A g−1), an excellent rate capability (97 mA h g−1 at 5 A g−1), and a high initial Coulombic efficiency (60%) are achieved.

Fast Sodium-Ion Conductivity in Supertetrahedral Phosphidosilicates.

Fast sodium-ion conductors are key components of Na-based all-solid-state batteries which hold promise for large-scale storage of electrical power. We report the synthesis, crystal-structure determination, and Na+ -ion conductivities of six new Na-ion conductors, the phosphidosilicates Na19 Si13 P25 , Na23 Si19 P33 , Na23 Si28 P45 , Na23 Si37 P57 , LT-NaSi2 P3 and HT-NaSi2 P3 , based entirely on earth-abundant elements. They have SiP4 tetrahedra assembled interpenetrating networks of T3 to T5 supertetrahedral clusters and can be hierarchically assigned to sphalerite- or diamond-type structures. 23 Na solid-state NMR spectra and geometrical pathway analysis show Na+ -ion mobility between the supertetrahedral cluster networks. Electrochemical impedance spectroscopy shows Na+ -ion conductivities up to σ (Na+ )=4×10-4 S cm-1 . The conductivities increase with the size of the supertetrahedral clusters through dilution of Na+ -ions as the charge density of the anionic networks decreases.

Self-assembled Mn-doped MoS2 hollow nanotubes with significantly enhanced sodium storage for high-performance sodium-ion batteries

Mn-Doped MoS2 hollow nanotubes as an anode exhibit an enhanced fast sodium ion transport capability and superb electrochemical properties in sodium-ion batteries.

An open holey structure enhanced rate capability in a NaTi2(PO4)3/C nanocomposite and provided ultralong-life sodium-ion storage.

Sodium-ion battery (SIB) technology is competitive in the fields of transportation and grid storage, which require electrode materials showing rapid energy conversion (high rate capability) and long cycle life. In this work, a NaTi2(PO4)3/C (NTP/C) nanocomposite with an open holey-structured framework was successfully prepared for the first time using a solvothermal reaction followed by pyrolysis. The nanocomposite realized fast sodium-ion transport and thus preferable battery performances. Within the wide rate range of 0.5-50C, only a very small decrease in capacity from 124 to 120 mA h g-1 was observed. A high discharge capacity of 103 mA h g-1 (88.3% retention of the 1st cycle) was delivered even after 10 000 cycles at an ultrahigh rate of 50C without any obvious morphological change and without structural pulverization. Forming open channels for ion transport proved to contribute to such performance enhancement and therefore has the potential to become a universal model for the development of sustainable electrode materials in SIBs and other battery systems.

Reversible and fast Na-ion storage in MoO2/MoSe2 heterostructures for high energy-high power Na-ion capacitors

Sodium ion capacitors (SICs) combine the advantages of electric double layer capacitors and sodium ion batteries. Molybdenum diselenide (MoSe2) holds promise for sodium ion storage because of fast sodium ion transport. However, the formation of irreversible Na2Se species consequentially leads to capacity decay and limited life-span. This work introduced MoO2 nanoclusters immobilized on two-dimensional (2D) MoSe2-graphene interfaces to promote the reversible conversion of MoSe2. The adsorption of Na2Se species on MoO2 during the discharge process was confirmed by direct observation of the separator and Na chip, in-situ bottle-cell process, and ex-situ XRD/TEM techniques. The combined merits of each component displayed a high rate capacity with a dominant pseudocapacitive contribution of 85% at 1mVs−1 and excellent cycling stability without degradation at 5Ag−1 for 800 cycles in sodium half cells. A hybrid sodium ion capacitor device delivered a maximum energy density and power output of 71Whkg−1 and 14316Wkg−1, respectively, and an excellent cycling life-span with 8% capacitance loss after 7000 cycles at 6Ag−1, outperforming other reported hybrid SIC devices. The superior energy-power behavior bridges the performance gap between batteries and capacitors, holding promise for next-generation high-energy and high-power devices.

5Wh Class Planar Sodium Nickel Chloride (Na-NiCl2) Battery Operated at below 200oc for Grid Scale Energy Storage

Sodium nickel chloride (Na/NiCl2) battery is one of the most promising candidates as a large scale electrochemical energy storage device. The battery comprises molten Na and NiCl2 as negative and positive electrodes, respectively, in its charged state, separating them by a β”-Al2O3 solid electrolyte (BASE). In order to facilitate fast sodium ion transport in the cathode compartment, molten NaAlCl4, as a secondary electrolyte (or catholyte), is infiltrated into the cathode materials powder. The battery typically operates at 250~300oC so as to maximize the ionic flux in the NaAlCl4 and through the solid electrolyte, and to minimize the dissolution of NiCl2into the melt. However, this efficient battery is yet to be widely used in grid scale energy storage applications since it is still expensive and hard to dramatically reduce the cell price mainly due to its use of expensive sealing technologies. The presentation introduces Korea-US collaborative efforts to develop a lower temperature operating sodium beta-alumina battery (LT-NBB) with a Na/NiCl2 chemistry. Since the novel battery runs at below 200oC, it can be fabricated at an ultra low manufacturing cost by introducing a new planar cell design with a greatly reduced number of cell components, and by eliminating expensive conventional sealing technologies. Enhanced degradation resistance of cathode materials is another important advantage of this technology. In this presentation, challenges and progress in building 5Wh class prototype LT-NBB cells using BASE with 70 mm in diameter will be discussed. Figure 1

Porous organic polymer/RGO composite as high performance cathode for half and full sodium ion batteries

Abstract Redox-active organic polymers are promising cathode electrodes owing to the advantages of open and flexible frame-works, renewability and environmental friendliness. Sodium salt of poly (2, 5-dihydroxy-p-benzoquinonyl sulfide)/RGO (Na2PDHBQS/RGO) composite has been fabricated via a convenient route and applied as a high performance and stable cathode for sodium ion batteries. The Na2PDHBQS/RGO was investigated in ether-based electrolyte, which demonstrated better electrochemical performances (228, 214, 203, 193, 172 and 147 mAh g−1 at 0.1, 0.2, 0.4, 0.8, 2 and 4C, respectively) than that in traditional ester-based ones. The high specific capacity, excellent cycle stability and reversibility of Na2PDHBQS/RGO may be attributed to the special porous structure, enhanced electronic conductivity by the introduction of RGO and fast sodium ion and electron diffusion rate in ether-based electrolyte. In addition, the Na2PDHBQS/RGO cathode has been assembled with disodium terephthalate (Na2TP) anode to compose a full cell for the first time, which presents an initial reversible capacity of 210 mAh g−1 at 0.1C.

Development of a Lower Temperature Operating Sodium Beta-Alumina Battery (LT-NBB): Strategies and Technical Challenges

The sodium nickel chloride (Na/NiCl2) battery is one of the most promising candidates for a large scale electrochemical energy storage device. The battery comprises NiCl2 and molten Na as positive and negative electrodes in its charged state, and uses a Na+ ion conducting β"-Al2O3 solid electrolyte (BASE) to separate the cathode and anode. In order to facilitate fast sodium ion transport in the cathode compartment, molten NaAlCl4, as a secondary electrolyte (or catholyte), is infiltrated into the powdered cathode material. The battery typically operates at 250~300°C to maximize the ionic flux in the NaAlCl4 and through the solid electrolyte, and to minimize the dissolution of NiCl2into the melt. However, this efficient battery has yet to be widely used in grid scale energy storage applications, since it is still expensive; it is difficult to dramatically reduce the cell price in its present form mainly due to its use of expensive sealing technologies. The presentation introduces U.S.-Korea collaborative efforts to develop a sodium beta-alumina battery with a Na/NiCl2 chemistry that operates at a lower temperature. Since the novel battery runs below 200°C, it can be fabricated at an ultralow manufacturing cost by (1) introducing a new planar cell design with a greatly reduced number of cell components, and (2) eliminating expensive sealing technologies. Enhanced degradation resistance of cathode materials is another important advantage of this technology. This presentation will start by stating problems found in traditional sodium beta-alumina batteries, and our strategies to resolve the issues will be described. Technical challenges and progress in materializing prototype LT-NBB cells and related core technologies will be briefly discussed, which include cell design, a highly toughened BASE, an enhanced wetting agent, and an inexpensive sealing method.

Novel Cobalt Sulfide/Reduced Graphene Oxides Composite As Advanced Anode for Sodium-Ion Batteries

As an alternative energy storage technology to the predominantly employed lithium-ion batteries (LIBs), sodium-ion batteries (SIBs) have revitalized increasing scientific attention for large-scale applications, mainly because of the low cost, large resource availability, and similar chemistry of sodium with lithium. However, the main bottleneck to the commercialization of SIBs is the limited choice of anode materials. It is well known that Na ions are about 55% larger in radius compared with Li ions, which significantly hinders the utilization of well-developed electrode materials in LIBs owing to the insufficient interlayer spacing. Therefore, it is difficult to find suitable materials that can accommodate Na ions and allow reversible ion insertion/deinsertion. Up to now, various alternative materials, including carbon, layered metal oxides, alloy-based materials and metal chalcogenides, have been explored as potential anodes for SIBs. Although some encouraging progress have been made, developing appropriate electrode materials with high capacity and good reversibility is less successful and still require further research. We demonstrate a simple solvothermal method to in situ decorate 2D CoS nanoplates on rGO nanosheets. The resulting CoS@rGO hybrid architecture offers unique characteristics, which is needed for advanced anode. Benefiting from the novel structure and improved electric conductivity, CoS@rGO hybrid composite exhibits high capacity (540 mAh g-1 at 1 A g-1), superior rate capability (636 mAh g-1 at 0.1 A g-1 and 306 mA h g-1 at 10 A g-1), and ultra-long cycle life (420 mAh g-1 at 1 A g-1 after 1000 cycles) as anode for SIBs. These results endow CoS@rGO composite as advanced anode for SIBs. Remarkably, a full cell, which is based on CoS@rGO hybrid anode and electrospun Na3V2PO4@carbon (NVP@C) cathode, has been assembled and manifests high capacity and outstanding cycle stability, indicating its huge potential as promising anode for SIBs industry. CoS@rGO hybrid composites has been prepared by a one-pot solvothermal strategy using Co(CH3COO)2 (Co(Ac)2), thiourea (Tu), and GO as precursors in ethanol medium at 180 °C for 12 h. As shown in the schematic illustration in Figure 1a, in situ directly growth of CoS@rGO composites is induced by the heterogeneous nucleation of CoS on graphene. During the reaction process, GO provides large amounts of defects/functional groups as nucleation sites for in situ growth of CoS nanplates. The presence of carboxyl and hydroxyl groups on the GO sheets can make the thiourea grafted on the GO through surface functional groups, as the amino groups in thiourea are activated by the C=S bonds. Moreover, Co2+ could incorporate on the GO sheet by electrostatic force. As a consequence, the absorbed Co2+ reacts with the gradual release of S2- ions deriving from the decomposition of Tu to form CoS nuclei that are tightly anchored onto graphene sheet with well dispersion. Meanwhile, GO sheets are reduced to rGO sheets with ethanol medium as a mild reductant. Thus, the continuous solvothermal reaction resulted in oriented alignment of CoS nanoplates grown on rGO sheets. This unique structure is expected to provide high accessibility to the electrolyte and fast sodium-ion transport pathways. In summary, the novel CoS@rGO hybrid composites with precisely controlled unique configurations have been successfully developed by an efficient in situ solvothermal technique. The well-defined CoS nanoplates with a thickness of around 10 nm are uniformly grown on rGO frames with strong adhesion, which provides structually stable host for Na-ion intercalation and deintercalation. Suprisingly, as anode for SIBs, an impressive high specific capacity (540 mAh g-1 at 1 A g-1), excellent rate capability (636 mAh g-1 at 0.1 A g-1 and 306 mA h g-1 at 10 A g-1), and extraordinarily cycle stability (420 mAh g-1 at 1 A g-1 after 1000 cycles) has been demonstrated by CoS@rGO for sodium storage. The 2D conductive framwork of rGO, ultrathin feature of CoS nanoplates, as well as the unique nanoarchitecture with enhanced electrolyte penetration, are responsible for the outstanding electrochemical performances of the CoS@rGO composite. Such intriguing electrochemical properties of CoS@rGO make it a promising anode materials for advanced SIBs. Acknowledgements The authors are thankful for the support by funding from the National Research Foundation, Clean Energy Research Project (Grant Number: NRF2009EWT-CERP001-036) and TUM CREATE center for Electromobility.

Synthesis, Characterization and Pharmacological Evaluation of Thiosalicylamide Derivative as a Class of Calcium Channel Blocker

Objective: Hypertension is one of the major causes of the cardiovascular diseases and in the later stages, it also damages the brain, kidneys, eyes and coronary arteries. It is also life threatening as it causes heart strokes and attacks. The calcium channels regulates blood pressure by muscle contraction triggered by neurotransmitter release to electrical excitation. Method: Calcium channel blocker drugs reduce intracellular calcium transfer to limit ATP release to reduce muscle cell contractility. They act, especially on the nodal tissues in the heart and arterial smooth muscle cells in which only slow calcium channel blockers opens without triggering of fast sodium ion channels. Pharmacophore approach is employed to generate novel thiosalicylamide derivatives having calcium channel blocking activity for treatment of hypertension. Result: These novel thiosalicylamide derived lead molecules are synthesized and tested for their in-vivo pharmacological activity by using isolated guinea-pig ileum muscles.

Aqueous and Nonaqueous Sodium-Air Cells with Nanoporous Gold Cathode

ABSTRACT Two types of sodium-air cells, i.e., nonaqueous and mixed aqueous-nonaqueous (abbreviated as ‘aqueous’) cells, have been compared to elucidate factors limiting performances of nonaqueous air cells and how the aqueous electrolyte is effective to reliving these limitation. The two cells have the same configuration consisting of a nanoporous gold (NPG) air electrode and a ceramic separator of fast sodium ion conductor, NASICON. Only the selection of catholyte, either alkyl carbonate-based nonaqueous solution of NaClO4 or aqueous solution of NaOH, is different. All performances are demonstrated to be better for the aqueous one. Lower overpotential of aqueous cell leads to better round-trip efficiency. A large resistance relevant to oxygen reduction reaction in the nonaqueous cell is relieved by changing the catholyte to the aqueous electrolyte, affording higher rate capability and power density. The aqueous electrolyte is also effective to remove the limitation of the discharge capacity defined by the volumetric amount of air electrode, as has been claimed in previous studies on aqueous Na-air cells. Furthermore, the aqueous cell is demonstrated to be robust and less sensitive and to atmosphere. The NPG electrode works reversibly in the half-cell reaction of the aqueous cell, while an electrodeposition of metallic Na on the anode during charging requires an improvement.

Important Role of Functional Groups for Sodium Ion Intercalation in Expanded Graphite

Expanded graphite oxide (GO) has recently received a great deal of attention as a sodium ion battery anode due to its superior characteristics for sodium ion storage. Here, we report that the sodium ion intercalation behavior of expanded GO strongly depends on the amounts and ratios of different functional groups. The epoxide-rich GO shows significantly higher specific capacities than those of the hydroxyl-rich counterpart utilizing strong sodium–epoxide attractions and appropriately enlarged interlayer spacing during sodiation. The epoxide-rich GO also enables fast sodium ion transport on account of the diminishment of interlayer hydrogen bonds that could reduce the free volume. Our calculations suggest that the theoretical capacity of epoxide-only GO with a stoichiometry of Na2.5C6O3 can reach 930 mAh g–1, which is far higher than recent experimental results as well as even those of conventional graphite materials in lithium ion batteries.

High-capacity antimony sulphide nanoparticle-decorated graphene composite as anode for sodium-ion batteries

Sodium-ion batteries are an alternative to lithium-ion batteries for large-scale applications. However, low capacity and poor rate capability of existing anodes are the main bottlenecks to future developments. Here we report a uniform coating of antimony sulphide (stibnite) on graphene, fabricated by a solution-based synthesis technique, as the anode material for sodium-ion batteries. It gives a high capacity of 730 mAh g(-1) at 50 mA g(-1), an excellent rate capability up to 6C and a good cycle performance. The promising performance is attributed to fast sodium ion diffusion from the small nanoparticles, and good electrical transport from the intimate contact between the active material and graphene, which also provides a template for anchoring the nanoparticles. We also demonstrate a battery with the stibnite-graphene composite that is free from sodium metal, having energy density up to 80 Wh kg(-1). The energy density could exceed that of some lithium-ion batteries with further optimization.

Electrospun Sb/C Fibers for a Stable and Fast Sodium-Ion Battery Anode

Sodium-ion batteries (SIBs) are considered a top alternative to lithium-ion batteries (LIBs) for large-scale renewable energy storage units due to their low cost and the abundance of sodium-bearing precursors in the earth's mineral deposits. However, the development of anode materials for SIBs to date has been mainly limited to carbonaceous materials with minimal research devoted to high capacity alloy-based materials. In this study, an antimony (Sb)/carbon (C) electrode with ~30 nm Sb nanoparticles (NPs) uniformly encapsulated in interconnecting one-dimensional (1D) 400 nm carbon fibers (denoted as SbNP@C) was fabricated using a simple and scalable electrospinning method. This binder-free, current collector-free SbNP@C electrode demonstrated high capacity and stable long-term cycling performance at various current densities. The SbNP@C electrode showed an initial total capacity of 422 mAh/gelectrode and retained 350 mAh/gelectrode after 300 deep charge-discharge cycles under 100 mA/gSb. Moreover, because of the efficient 1D sodium-ion transport pathway and the highly conductive network of SbNP@C, the electrode preserved high overall capacities even when cycled at high currents, extending its usability to high power applications.

Heterovalent substitutions in Na2M2TeO6 family: Crystal structure, fast sodium ion conduction and phase transition of Na2LiFeTeO6

A new solid electrolyte Na2LiFeTeO6 has been prepared by solid-state reactions in air at 700°C and characterized by powder X-ray diffraction, redox titration and impedance measurements on ceramic samples. It is a new superstructure type of the well-known hexagonal layered P2 type with complete ordering of Li, Fe and Te in octahedral brucite-like layers: orthorhombic, P212121, a=5.2109(1), b=8.9791(2), c=11.2389(2)Å, Z=4. At room temperature, sodium ions in the interlayer gap are concentrated in two of the six non-equivalent trigonal prisms; at elevated temperatures, they exhibit high ionic conductivity, e.g., 4S/m at 300°C. Orthorhombic distortion decreases on heating, presumably due to sodium movement, and vanishes at ca. 400°C giving rise to the hexagonal Na2Co2TeO6-type structure. Analogous Na2LiRTeO6 (R=Al or Ga), Na2LiFeWO6, Na2Mn2TeO6, Na2M2WO6 (M=Ni or Cu), Na2NiMSbO6 (M=Al or Fe) and Na2NiAlTO6 (T=Nb or Ta) could not be prepared.

Electrochemical detection of volatile organic compounds using a Na 3Zr 2Si 2PO 12/Bi 2Cu 0.1V 0.9O 5.35 heterojunction device

A fast sodium ion conductor, NASICON (Na 3Zr 2Si 2PO 12), has been widely used for gas sensor applications. In this study, we demonstrate that a device combining NASICON with an oxygen-ion conductor of BiCuVOx (Bi 2Cu 0.1V 0.9O 5.35) can electrochemically detect volatile organic compounds (VOCs), such as ethanol, formaldehyde, and toluene. The sensing electrode made of BiCuVOx was attached onto a sintered NASICON disk at high temperature to produce an interfacial layer that had a different morphology and composition from those of NASICON and BiCuVOx, as observed by scanning electron microscopy-energy dispersive X-ray spectroscopy analysis. The device in which NASICON was fitted with the BiCuVOx-based electrode was found to efficiently detect VOCs in ppm concentrations. The sensor signal (electromotive force) exceeded 100 mV in response to 10 ppm HCOH at 400 °C, demonstrating the high sensitivity of the device. It also exhibited a relatively quick response, reproducible and stable sensor signals, and high selectivity to VOCs. The sensor responses followed behavior typical for mixed-potential-type gas sensors based on oxygen-ion conductors. It was thus suggested that the electrochemical oxidation of VOCs with oxide ions took place at the interfacial oxygen ion-conductive layer that was formed by the reaction of NASICON with BiCuVOx.

Antidepressants: From MAOIs to SSRIs and more

Byline: Chaitra. Ramachandraih, Narayana. Subramanyam, Kral. Bar, Glen. Baker, Vikram. Yeragani The era of antidepressants started with isoniazid, an antitubercular agent, which was accidentally found to have euphoric effects in patients with tuberculosis who were receiving this drug. The mood elevating property of the drug, considered to be a side effect, became the primary effect in depression and heralded the synthesis of generations of newer antidepressants. It also shifted the focus of psychiatrists from psychodynamic processes to a biological basis of the illness. [sup][1] Isoniazid belongs to a group of hydrazine compounds, which were synthesized by Fischer in the 1870's. Isonicotinyl hydrazine (isoniazid) was synthesized by Meyer and Malley at Prague from these hydrazine compounds. Forty years later it was re-synthesized by another group of scientists. By chance, it was found to be an effective antitubercular agent. In 1952, Zeller discovered that iproniazid, another hydrazine derivative, inhibited monoamine oxidase (MAO) enzyme, so named by a group of scientists led by Blaschko and Richter in 1937. The enzyme caused the oxidation of adrenaline, a monoamine and was inhibited by ephedrine. However, Mary Hare had observed similar results in 1928 with an enzyme, tyramine oxidase, which later was found to be MAO. The MAO enzyme acts on a number of endogenous and exogenous amines (serotonin, catecholamines, tyramine, beta-phenylethylamine, benzylamine). In the year 1952, Selikoff and Robidzek observed that iproniazid had greater psychostimulatory effects than isoniazid in patients with and without tuberculosis. Subsequent studies by Smith, Kamman, and del Pino found similar stimulatory effects. The effects were described as mood elevating. The patients showed increased vigor and appetite, weight gain, improved sleep, and sociability. In some cases, it caused psychomotor agitation, hypersexuality and psychoses, behavior described as "dancing in the hall". Lurie, a private psychiatrist, coined the term "antidepressant" for the psychostimulatory effects of isoniazid in depressed patients. Until then various terms such as "thymeretics" and "psychic energizers" were used to describe these effects. Kline, Loomer, and Saunders found a correlation between the effects of the antitubercular agents and their inhibitory action on MAO and used iproniazid for the first time on a group of patients with depression. They recorded significant improvement in 70% of the patients. Later studies showed that its MAO-inhibiting property increased serotonin levels in the brain similar to the effects seen with 5-hydroxytrytophan, a precursor of serotonin, which crosses the blood-brain barrier. This was also substantiated by the reversal of reserpine-induced depression by iproniazid, as reserpine depletes biogenic amines. These studies showed promising results in depression through clinical and biochemical observations, Iproniazid was launched as an antitubercular agent because of disagreements among psychiatrists and also due to its hepato and nephrotoxicity. The drug and some other hydrazine derivatives were later taken off of the market. [sup][2],[3] The above findings paved the way to the develolpment of the first class of exclusive MAO inhibitors such as isocarboxazid, tranylcypramine, phenelzine, mebanazine, nialamide, pheniprazine, and etryptamine (an indole derivative). In the meantime, the enzyme MAO was reported by Johnston, in 1968, to exist in two isomeric forms. MAO-A was found in the small intestine and MAO-B was extracted from rat brain. MAO-A deaminated adrenaline, noradrenaline, and serotonin, whereas MAO-B acted on benzylamine and [sz]-phenylethylamine. Dopamine and tyramine were the substrates for both of the isomeric forms. The classical MAO inhibitors such as tranylcypramine and phenelzine inhibited both the isoenzymes. Tranylcypramine, a derivative of cyclopropylamine, was first used in 1959 as an antidepressant, and soon MAO inhibitors became frequently prescribed antidepressants. …

Channel formation and intermediate range order in sodium silicate melts and glasses.

We use inelastic neutron scattering and molecular dynamics simulation to investigate the interplay between the structure and the fast sodium ion diffusion in various sodium silicates. With increasing temperature and decreasing density the structure factors exhibit an emerging prepeak around 0.9 A(-1). We show that this prepeak has its origin in the formation of sodium rich channels in the static structure. The channels serve as preferential ion conducting pathways in the relative immobile Si-O matrix. On cooling below the glass transition this intermediate range order is frozen in.