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A stochastic search of the potential energy surface for the formic acid dimers results in 21 welldefined minima. A number of structures are reported here for the first time, others have already been experimentally detected or computationally predicted. Four types of different hydrogen bonds (HBs) are at play stabilizing the clusters: primary C＝O⋯H--O and H--O⋯H--O and secondary C＝O⋯H--C and H--O⋯H--C HBs corresponding to well-characterized bonding paths are identified. A novel C＝O⋯C stabilizing interaction is also reported. The double proton transfer reaction is calculated to occur in a synchronous fashion, with an energy barrier smaller than the energy needed to break up the dimers. [ABSTRACT FROM AUTHOR]

Fifty-eight cadherin-related protocadherin (Pcdh) genes are tandemly arrayed in three clusters ([alpha], [beta], and [gamma]) on mouse chromosome 18. The large number of clustered Pcdh family members, their presence at synapses, and the known binding specificities of other cadherin superfamily members all suggest that these Pcdhs play roles in specifying synaptic connectivity. Consistent with this idea, mice lacking all 22 genes of the Pcdh-[gamma] cluster have decreased numbers of spinal cord synapses and are nearly immobile. Interpretation of this phenotype was complicated, however, by the fact that Pcdh-[gamma] loss also led to apoptosis of many spinal interneurons. Here, we used two methods to circumvent apoptosis and neurodegeneration in Pcdh-[gamma] mutant mice. First, we analyzed mutants lacking both Pcdh-[gamma], proteins and the proapoptotic protein Bax. Second, we generated a hypomorphic allele of Pcdh-[gamma] in which apoptosis was minimal. In both cases, spinal interneurons were preserved but the mice bore dramatically decreased numbers of spinal cord synapses and exhibited profound neurological defects. Moreover, synaptic function was compromised in neurons cultured from the hypomorphs. These results provide evidence for a direct role of [gamma]-Pcdhs in synaptic development and establish genetic tools for elucidating their contribution to synaptic specificity. synaptogenesis | Bax | interneuron

Presynaptic acetylcholine (ACh) synthesis and release is thought to be sustained by a hemicholinium-3-sensitive choline transporter (CHT). We disrupted the murine CHT gene and examined CHT-/and +/- animals for evidence of impaired cholinergic neurotransmission. Although morphologically normal at birth, CHT-/- mice become immobile, breathe irregularly, appear cyanotic, and die within an hour. Hemicholinium-3-sensitive choline uptake and subsequent ACh synthesis are specifically lost in CHT-/- mouse brains. Moreover, we observe a time-dependent loss of spontaneous and evoked responses at CHT-/- neuromuscular junctions. Consistent with deficits in synaptic ACh availability, we also observe developmental alterations in neuromuscular junction morphology reminiscent of changes in mutants lacking ACh synthesis. Adult CHT+/- mice overcome reductions in CHT protein levels and sustain choline uptake activity at wild-type levels through posttranslational mechanisms. Our results demonstrate that CHT is an essential and regulated presynaptic component of cholinergic signaling and indicate that CHT warrants consideration as a candidate gene for disorders characterized by cholinergic hypofunction.

The thermal capacity of totally enclosed fan-cooled converter-fed induction motors varies at the different operating frequencies. Main effects are due to the variation of the cooling airflow, the variation of iron losses, and eventually, the presence of harmonics. This paper presents the results of a complete evaluation of these effects and of the thermal torque at the different operating speeds. Index Terms--AC induction motors, frequency-controlled drives, thermal evaluation.

In this paper a description and operating principles of a consequent-pole permanent-magnet machine are presented. In addition, a sizing analysis, finite-element analysis, and experimental results for a prototype machine are addressed. Due to its particular configuration, this machine allows for a wide range of control of the air-gap flux with minimum field ampere-turn requirements and without brushes or slip rings. Two components of the field flux are produced. One, which is almost constant, is produced by the permanent magnet located on the rotor surface. The other, which is variable, is produced by a field winding positioned circumferentially in the center of the stator. These two flux components converge in the air gap. The excitation level of the machine is manipulated by controlling the dc field current. Three-dimensional finite-element analysis and experimental results demonstrate that it is possible to vary the flux over a wide range to keep the terminal voltage constant as the speed increases. A 3-kW 1000-3000-r/min eight-pole and 32-Vac generator using this configuration is tested to verify the flux control capability of this structure. Index Terms--Electric machine design, flux weakening, permanent-magnet (PM) machine.

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Copyright of Abanico Veterinario is the property of Sistema Superior Editorial and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)