Rhythmic limb movements are controlled by pattern-generating neurons within the ventral spinal cord, but little is known about how these locomotor circuits are assembled during development. At early stages of embryogenesis, motor neurons are spontaneously active, releasing acetylcholine that triggers the depolarization of adjacent cells in the spinal cord. To investigate whether acetylcholine-driven activity is required for assembly of the central pattern-generating (CPG) circuit, we studied mice lacking the choline acetyltransferase (ChAT) enzyme. Our studies show that a rhythmically active spinal circuit forms in ChAT mutants, but the duration of each cycle period is elongated, and right-left and flexor-extensor coordination are abnormal. In contrast, blocking acetylcholine receptors after the locomotor network is wired does not affect right-left or flexor-extensor coordination. These findings suggest that the cholinergic neurotransmitter pathway is involved in configuring the CPG during a transient period of development.
RNAi can block retroviral infection in vertebrates. The tissue electroporation method described here should allow RNAi to be used widely to study gene function and control of infection in vertebrate animals.
A series of tris(N,N-dialkylcarbamato)antimony(III) complexes, Sb(O(2)CNR(2))(3) (R = Me, Et, Pr(i)()), have been synthesized and are the first members of this class of compound to have been crystallographically characterized. Sb(O(2)CNMe(2))(3) (1) exists as a weakly bound dimer, whereas its diethyl and diisopropyl analogues (2, 3) are monomeric. In addition, tetrakis(N,N-diethylcarbamato)tin(IV) (4) has been prepared for comparison and shown by single-crystal X-ray analysis to exhibit the relatively rare SnO(8) coordination. Crystallographic data: for 1, a = 8.7520(5) A, b = 14.2970(8) A, c = 11.8150(7) A, beta = 108.029(2) degrees, monoclinic, P2(1)/c, Z = 4; for 2, a = b = 14.4690(2) A, c = 16.6740(2) A, trigonal, Rthremacr;, Z = 6; for 3, a = 11.9881(2) A, b = 11.6521(3) A, c = 19.8780(6) A, beta = 90.401(1) degrees, monoclinic, P2(1)/n, Z = 4; for 4, a = 13.9654(2) A, b = 12.0817(2) A, c = 16.6752(2) A, beta = 108.1960(7) degrees, monoclinic, C2/c, Z = 4. Sb(O(2)CNMe(2))(3) has been used as a single-source precursor in the low-pressure chemical vapor deposition of the senarmonite form of Sb(2)O(3).
Semiconducting metal oxides are the key components in one of the most widely exploited forms of generic sensor devices and represent a fast growing sector of the market. [1±4] Tin oxide in particular has been widely studied in this respect, and numerous studies have shown that sensor selectivity can be brought about by the introduction of a second, dopant metal. [5±10] We have recently demonstrated the fabrication of Pt-doped tin oxide by a dual-source CVD approach. [11,12] Other metal oxides that have been shown to act as sensors include ZnO, [13] In 2 O 3 , [13] TiO 2 , [2,14,15] Ba(Ti,Sn)O 3 , [2,14] Ba 6 (Fe,Nb) 10 O 30 , [2,14] TiNb 2 O 7 , [2,14] as well as a range of other mixed oxides. [1] Two key issues are central to the development of enhanced metal oxide sensors: the morphology of the sensor film, [16±22] and its response integrity under conditions of changing humidity. [23,24] With regard to morphology, the sensing mechanism begins at the surface of the material and subsequent electron transport through the film is grain boundary-limited in granular films. [23,25] Clearly, the production of a sensor thin film by CVD, with experimental control over parameters such as precursor choice, deposition temperature, flow rates, etc., can have a significant impact on the grain size, surface area, intergranular coupling, and, hence, the ultimate properties of the sensor. Indeed, CVD has been noted as a potential solution to many of the current problems (selectivity, temperature/humidity dependence, power consumption) associated with existing ceramic and thick film sensors. [3] Secondly, sensor drift under conditions of variable humidity is one of the key drawbacks of current tin oxide sensors. In this context, a report concerning non-stoichiometric Cd 2 Sb 2 O 7 , detailing its selectivity (e.g., chiral discrimination of R-and S-limonene) and lack of moisture sensitivity, suggests it could form the basis for a new generation of enhanced oxide sensors. [26] Other reports on antimony-based sensors include the use of FeSbO 4 as a sensor for liquid petroleum gas, [27] though, in general, the potential of antimony oxide-based sensors seems to have been largely ignored. We have thus embarked on a programme of study aimed at evaluating the potential of antimony oxide thin films as base materials for sensor devices. The first stage in this process is the delineation of CVD routes to the various antimony oxide phases, which to date have been largely overlooked. To our knowledge, the only report on the CVD of any antimony oxide is the formation of Sb 2 O 5 by aerosol-assisted (AA) CVD from SbCl 5 and H 2 O. [28,29] Though the physical properties of the films were extensively examined, the composition and morphology were largely ignored. In this initial report, we present our findings on the use of two commercially available antimony(III) alkoxides, (RO) 3 Sb (R = Et, n Bu), as CVD precursors for antimony oxides.Our CVD apparatus has been described elsewhere. [30] Pyrex glass slides were used as substrates for the depo...
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