Systematic evaluation of magnetic sensitivities of anisotropic magnetoresistive sensors at liquid helium temperature for superconducting cavities.

Trapped magnetic flux in bulk superconductors reduces the quality factor Q in superconducting radio-frequency (SRF) cavities. However, the mechanisms underlying flux trapping and radio-frequency loss are not well understood. Detailed observation of the magnetic distributions is important for understanding such phenomena. Magnetic field mapping is useful for observing the magnetic field distribution around SRF cavities. Measuring the change in the magnetic field around the cavity elucidates the flux trapping behavior. Anisotropic magnetoresistive (AMR) sensors are inexpensive and small devices that can detect magnetic flux density. The magnetic sensitivities of AMR sensors need to be evaluated at liquid helium temperature for the magnetic field mapping of SRF cavities. In this study, a test stand was constructed to calibrate the magnetic sensitivities of AMR sensors in liquid helium, and 110 AMR sensors were tested using this stand. The magnetic sensitivities were evaluated systematically. A solenoid coil was used to control the uniform external magnetic field and to measure the magnetic sensitivity at low temperatures. All AMR sensors exhibited suitable sensitivities to the magnetic field around the SRF cavity. The variation in these sensitivities in all AMR sensors was ∼1%. The AMR sensors were found to have sufficient sensitivity for mapping the magnetic field around the exterior surface of the SRF cavity.

The semantics of syntactic structures.

Over the past 15 years, both linguists and psycholinguists have shown a growing interest in the idea that syntactic structures can carry meanings that are independent of the meanings of specific words. This article considers how this idea relates to traditional notions of compositionality in generative grammar, and examines two modern theories that, although based on different starting assumptions, both readily allow syntactic structures to bear independent meaning. We review work from psycholinguistics suggesting that observation alone is often insufficient to support the efficient learning of word meanings, and that some of the 'slack' left by observation can be picked up by the semantics of the syntactic structures in which words appear. We argue that this convergence between linguistic theory and psycholinguistic experimentation should be no surprise, because language must be learnable.

First contact in verb acquisition: defining a role for syntax.

The goal of this research was to address 2 questions regarding children's use of syntactic information in acquiring verbs: First, what are children's biases for actions in the absence of syntactic information; and second, how specific is the meaning derived for verbs when syntactic information is present? In 3 experiments we presented nonsense verbs either in syntactic isolation (e.g., "Look! Sebbing!") or embedded within a transitive syntactic frame (e.g., "The frog is sebbing the duck"). These actions were then separated, and the children (mean age = 2 years, 3 months) were asked to select the action which was the referent of the verb. In Experiment 1, Causative actions (in which 1 character forces another to move in some way) were paired with Synchronous actions (in which both characters move simultaneously). In Experiment 2, the same Synchronous actions were now paired with Contact actions (in which 1 character merely touches the other). In Experiment 3, the Contact actions were paired with Causative ones. 2 results emerged: (1) Children have identifiable action biases in the absence of syntactic information and (2) these biases can be shifted by the addition of a transitive syntactic frame. We conclude that the meaning derived from the transitive frame is not specifically Causative or Contact but, more generally, a sense that 1 character is affecting another.

Speech production, syntax comprehension, and cognitive deficits in Parkinson's disease.

Speech samples were obtained that were analyzed for voice onset time (VOT) for 40 nondemented English speaking subjects, 20 with mild and 20 with moderate Parkinson's disease. Syntax comprehension and cognitive tests were administered to these subjects in the same test sessions. VOT disruptions for stop consonants in syllable initial position, similar to those noted for Broca's aphasia, occurred for nine subjects. Longer response times and errors in the comprehension of syntax as measured by the Rhode Island Test of Sentence Comprehension (RITLS) also occurred for these subjects. Anovas indicate that the VOT overlap subjects had significantly higher syntax error rates and longer response times on the RITLS than the VOT nonoverlap subjects--F(1, 70) = 12.38, p less than 0.0008; F(1, 70) = 7.70, p less than 0.007, respectively. The correlation between the number of VOT timing errors and the number of syntax errors was significant. (r = 0.6473, p less than 0.01). VOT overlap subjects also had significantly higher error rates in cognitive tasks involving abstraction and the ability to maintain a mental set. Prefrontal cortex, acting through subcortical basal ganglia pathways, is a component of the neural substrate that regulates human speech production, syntactic ability, and certain aspects of cognition. The deterioration of these subcortical pathways may explain similar phenomena in Broca's aphasia. Results are discussed in relation to "modular" theories.