Energy and momentum of cylindrical gravitational waves. II

Recently Nathan Rosen and the present author obtained the energy and momentum densities of cylindrical gravitational waves in Einstein's prescription and found them to be finite and reasonable. In the present paper we calculate the same in prescriptions of Tolman as well as Landau and Lifshitz and discuss the results.Comment: 8 pages, LaTex, To appear in Pramana- J. Physic

Energy and Momentum of a Class of Rotating Gravitational Waves

We calculate energy and momentum for a class of cylindrical rotating gravitational waves using Einstein and Papapetrou's prescriptions. It is shown that the results obtained are reduced to the special case of the cylindrical gravitational waves already available in the literature.Comment: 11 pages, no figure, Late

Contributions of temporal encodings of voicing, voicelessness, fundamental frequency, and amplitude variation to audiovisual and auditory speech perception

Auditory and audio-visual speech perception was investigated using auditory signals of invariant spectral envelope that temporally encoded the presence of voiced and voiceless excitation, variations in amplitude envelope and F-0. In experiment 1, the contribution of the timing of voicing was compared in consonant identification to the additional effects of variations in F-0 and the amplitude of voiced speech. In audio-visual conditions only, amplitude variation slightly increased accuracy globally and for manner features. F-0 variation slightly increased overall accuracy and manner perception in auditory and audio-visual conditions. Experiment 2 examined consonant information derived from the presence and amplitude variation of voiceless speech in addition to that from voicing, F-0, and voiced speech amplitude. Binary indication of voiceless excitation improved accuracy overall and for voicing and manner. The amplitude variation of voiceless speech produced only a small increment in place of articulation scores. A final experiment examined audio-visual sentence perception using encodings of voiceless excitation and amplitude variation added to a signal representing voicing and F-0. There was a contribution of amplitude variation to sentence perception, but not of voiceless excitation. The timing of voiced and voiceless excitation appears to be the major temporal cues to consonant identity. (C) 1999 Acoustical Society of America. [S0001-4966(99)01410-1]

Effects of acoustic periodicity and intelligibility on the neural oscillations in response to speech

Although several studies have investigated neural oscillations in response to acoustically degraded speech, it is still a matter of debate which neural frequencies reflect speech intelligibility. Part of the problem is that effects of acoustics and intelligibility have so far not been considered independently. In the current electroencephalography (EEG) study the amount of acoustic periodicity (i.e. the amount of time the stimulus sentences were voiced) was manipulated, while using the listeners’ spoken responses to control for differences in intelligibility. Firstly, the total EEG power changes in response to completely aperiodic (noise-vocoded) speech and speech with a natural mix of periodicity and aperiodicity were almost identical, while an increase in theta power (5–6.3 Hz) and a trend for less beta power (11–18 Hz) were observed in response to completely periodic speech. These two effects are taken to indicate an information processing conflict caused by the unnatural acoustic properties of the stimuli, and that the subjects may have internally rehearsed the sentences as a result of this. Secondly, we separately investigated effects of intelligibility by sorting the trials in the periodic condition according to the listeners’ spoken responses. The comparison of intelligible and largely unintelligible trials revealed that the total EEG power in the delta band (1.7–2.7 Hz) was markedly increased during the second half of the intelligible trials, which suggests that delta oscillations are an indicator of successful speech understanding

The Revenues-Expenditures Nexus: Evidence from Local Government Data

This paper examines the intertemporal linkages between local government expenditures and revenues. In the terminology that has become standard in the literature on vector autoregression analysis, the issue is whether revenues Granger-cause expenditures, or expenditures Granger-cause revenues. The main results that emerge from an analysis of fiscal data from 171 municipal governments over the period 1972-1980 are that: 1) one or two years are sufficient to summarize the relevant dynamic interrelationships; 2) there are important intertemporal linkages between expenditures, taxes and grants; and 3) past revenues help predict current expenditures, but past expenditures do not alter the future path of revenues. This last finding is contrary to results that have emerged from previous analyses of federal fiscal data, and hence suggests the need for additional research on the differences in the processes generating local and federal decisions.

Pathway of human AS3MT arsenic methylation

A synthetic gene encoding human As(III) S-adenosylmethionine (SAM) methyltransferase (hAS3MT) was expressed, and the purified enzyme was characterized. The synthetic enzyme is considerably more active than a cDNA-expressed enzyme using endogenous reductants thioredoxin (Trx), thioredoxin reductase (TR), NADPH, and reduced glutathione (GSH). Each of the seven cysteines (the four conserved residues, Cys32, Cys61, Cys156, and Cys206, and nonconserved, Cys72, Cys85, and Cys250) was individually changed to serine. The nonconserved cysteine derivates were still active. None of the individual C32S, C61S, C156S, and C206S derivates were able to methylate As(III). However, the C32S and C61S enzymes retained the ability to methylate MAs(III). These observations suggest that Cys156 and Cys206 play a different role in catalysis than that of Cys32 and Cys61. A homology model built on the structure of a thermophilic orthologue indicates that Cys156 and Cys206 form the As(III) binding site, whereas Cys32 and Cys61 form a disulfide bond. Two observations shed light on the pathway of methylation. First, binding assays using the fluorescence of a single-tryptophan derivative indicate that As(GS)3 binds to the enzyme much faster than inorganic As(III). Second, the major product of the first round of methylation is MAs(III), not MAs(V), and remains enzyme-bound until it is methylated a second time. We propose a new pathway for hAS3MT catalysis that reconciles the hypothesis of Challenger ((1947) Sci. Prog., 35, 396-416) with the pathway proposed by Hayakawa et al. ((2005) Arch. Toxicol., 79, 183-191). The products are the more toxic and more carcinogenic trivalent methylarsenicals, but arsenic undergoes oxidation and reduction as enzyme-bound intermediates

No evidence for a benefit from masker harmonicity in the perception of speech in noise

When assessing the intelligibility of speech embedded in background noise, maskers with a harmonic spectral structure have been found to be much less detrimental to performance than noise-based interferers. While spectral "glimpsing"in between the resolved masker harmonics and reduced envelope modulations of harmonic maskers have been shown to contribute, this effect has primarily been attributed to the proposed ability of the auditory system to cancel harmonic maskers from the signal mixture. Here, speech intelligibility in the presence of harmonic and inharmonic maskers with similar spectral glimpsing opportunities and envelope modulation spectra was assessed to test the theory of harmonic cancellation. Speech reception thresholds obtained from normal-hearing listeners revealed no effect of masker harmonicity, neither for maskers with static nor dynamic pitch contours. The results show that harmonicity, or time-domain periodicity, as such, does not aid the segregation of speech and masker. Contrary to what might be assumed, this also implies that the saliency of the masker pitch did not affect auditory grouping. Instead, the current data suggest that the reduced masking effectiveness of harmonic sounds is due to the regular spacing of their spectral components

Nonet Symmetry and Two-Body Decays of Charmed Mesons

The decay of charmed mesons into pseudoscalar (P) and vector (V) mesons is studied in the context of nonet symmetry. We have found that it is badly broken in the PP channels and in the P sector of the PV channels as expected from the non-ideal mixing of the \eta and the \eta'. In the VV channels, it is also found that nonet symmetry does not describe the data well. We have found that this discrepancy cannot be attributed entirely to SU(3) breaking at the usual level of 20--30%. At least one, or both, of nonet and SU(3) symmetry must be very badly broken. The possibility of resolving the problem in the future is also discussed.Comment: 9 pages, UTAPHY-HEP-

Getting Jobs, Keeping Jobs, and Earning a Living Wage: Can Welfare Reform Work?

Most discussions of welfare and work have focused on how demographic characteristics, schooling, training, and work experience limit welfare mothers’ employment and wages, but they have largely ignored factors such as inappropriate workplace behaviors, expectations of discrimination and harassment, depression, alcoholism, and domestic violence, all of which may affect welfare mothers and make employment difficult. In this paper we review the prevalence of these individual-level barriers and argue that they, in combination with an economy which does not pay low-skill workers well, are likely to impede employment and self-sufficiency for a large proportion of welfare mothers. At the end of the review, we summarize the current state of knowledge about barriers to the employment of welfare recipients and suggest several ways in which welfare-to-work programs might address these barriers.