1,668 research outputs found
Overcoming system-size limitations in spin glasses
In order to overcome the limitations of small system sizes in spin-glass
simulations, we investigate the one-dimensional Ising spin chain with power-law
interactions. The model has the advantage over traditional higher-dimensional
Hamiltonians in that a large range of system sizes can be studied. In addition,
the universality class of the model can be changed by tuning the power law
exponent, thus allowing us to scan from the mean-field to long-range and
short-range universality classes. We illustrate the advantages of this model by
studying the nature of the spin glass state where our results hint towards a
replica symmetry breaking scenario. We also compute ground-state energy
distributions and show that mean-field and non-mean-field models are
intrinsically different.Comment: 5 pages, 2x2 figures, proceedings of the 2004 SPDSA Conference in
Hayama, Japan, July 12 - 15, 200
Social Work handbook
2002 handbook for the Board of Studies in Social Wor
Behavioral and Electrophysiological Measures of Speech-in-Noise Perception in Normal Hearing and Hearing Impaired Adults
University of Minnesota Ph.D. dissertation. July 2017. Major: Speech-Language-Hearing Sciences. Advisors: Dr. Yang Zhang, Dr. Peggy B. Nelson. 1 computer file (PDF): vii, 161 pages.Understanding speech in background noise is difficult for many individuals. Mechanisms responsible for variability in speech-in-noise performance across individuals are not well understood. Electrophysiological measures allow for an examination of the timing and strength of neural responses to speech along the auditory pathway and can be used to explore mechanisms underlying reduced speech perception in noise. This dissertation used behavioral and electrophysiological measures to examine the effects of background noise on the neural coding of speech and to identify potential neural correlates of speech perception in individuals with and without hearing impairment. N1-P2, mismatch negativity (MMN), and P3 auditory event-related potentials (AERPs) and associated event-related cortical oscillations in various frequency bands of interest were collected in response to syllable-level stimuli in noise. Behavioral measures consisted of phoneme discrimination and sentence recognition in noise. Results indicated that in addition to impacting averaged AERP responses, background noise disrupted cortical oscillatory rhythms in response to speech in frequency bands of interest across participants. Results also showed that the effects of background noise and hearing impairment on the neural coding of speech are different at different levels of cortical processing. This work revealed that AERPs and associated cortical oscillations represent potential neural correlates of speech perception in noise in individuals with and without hearing impairment. These findings have potential theoretical and practical implications regarding the use of electrophysiological measures for the assessment and rehabilitation of communication difficulties in background noise
The action of pancreatic desoxyribonuclease. I. Isolation of mono- and dinucleotides
The nature of the products of the action of pancreatic desoxyribonuclease (DNase) upon highly polymerized desoxyribonucleic acid (DNA) has been the subject of numerous investigations. Titrimetric studies (1-5) have
revealed that, during the digestion, approximately one secondary phosphate group becomes titratable per 4 phosphorus atoms, which may be interpreted to mean that the products are, on the average, of the magnitude of tetranucleotides. More recently, ionophoretic (9), diffusion (5), and dialysis (10, 11) studies of the digest have suggested that it contains a complex mixture of polynucleotides of a range of magnitudes
A Single Circumbinary Disk in the HD 98800 Quadruple System
We present sub-arcsecond thermal infrared imaging of HD 98800, a young
quadruple system composed of a pair of low-mass spectroscopic binaries
separated by 0.8'' (38 AU), each with a K-dwarf primary. Images at wavelengths
ranging from 5 to 24.5 microns show unequivocally that the optically fainter
binary, HD 98800B, is the sole source of a comparatively large infrared excess
upon which a silicate emission feature is superposed. The excess is detected
only at wavelengths of 7.9 microns and longer, peaks at 25 microns, and has a
best-fit black-body temperature of 150 K, indicating that most of the dust lies
at distances greater than the orbital separation of the spectroscopic binary.
We estimate the radial extent of the dust with a disk model that approximates
radiation from the spectroscopic binary as a single source of equivalent
luminosity. Given the data, the most-likely values of disk properties in the
ranges considered are R_in = 5.0 +/- 2.5 AU, DeltaR = 13+/-8 AU, lambda_0 =
2(+4/-1.5) microns, gamma = 0+/-2.5, and sigma_total = 16+/-3 AU^2, where R_in
is the inner radius, DeltaR is the radial extent of the disk, lambda_0 is the
effective grain size, gamma is the radial power-law exponent of the optical
depth, tau, and sigma_total is the total cross-section of the grains. The range
of implied disk masses is 0.001--0.1 times that of the moon. These results show
that, for a wide range of possible disk properties, a circumbinary disk is far
more likely than a narrow ring.Comment: 11 page Latex manuscript with 3 postscript figures. Accepted for
publication in Astrophysical Journal Letters. Postscript version of complete
paper also available at
http://www.hep.upenn.edu/PORG/web/papers/koerner00a.p
Correlation of Early Outcomes and Intradiscal Interleukin-6 Expression in Lumbar Fusion Patients.
OBJECTIVE: To determine if there is correlation between intradiscal levels of interleukin-6 (IL-6) and early outcome measures in patients undergoing lumbar fusion for painful disc degeneration.
METHODS: Intervertebral disc tissue was separated into annulus fibrosus/nucleus pulposus and cultured separately in vitro in serum-free medium (Opti-MEM). Conditioned media was collected after 48 hours. The concentration of IL-6 was quantified using enzyme-linked immunosorbent assay. Pearson correlation coefficients quantified relationships between IL-6 levels and pre- and postoperative visual analogue scale (VAS) back pain and Oswestry Disability Index (ODI), as well as change in VAS/ODI.
RESULTS: Sixteen discs were harvested from 9 patients undergoing anterior lumbar interbody fusion (mean age, 47.4 years; range, 21-70 years). Mean preoperative and 6-month postoperative VAS were 8.1 and 3.7, respectively. Mean preoperative and postoperative ODI were 56.2 and 25.6, respectively. There were significant positive correlations between IL-6 expression and postoperative VAS (ρ = 0.38, p = 0.048) and ODI (ρ = 0.44, p = 0.02). No significant correlations were found between intradiscal IL-6 expression and preoperative VAS (ρ = -0.12, p = 0.54). Trends were seen associating IL-6 expression and change in VAS/ODI (ρ = -0.35 p = 0.067; ρ = -0.34, p = 0.08, respectively). A trend associated IL-6 and preoperative ODI (ρ = 0.36, p = 0.063).
CONCLUSION: The direct association between IL-6 expression and VAS/ODI suggests patients with elevated intradiscal cytokine expression may have worse early outcomes than those with lower expression of IL-6 after surgery for symptomatic disc degeneration
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