SNTF immunostaining reveals previously undetected axonal pathology in traumatic brain injury

Diffuse axonal injury (DAI) is a common feature of severe traumatic brain injury (TBI) and may also be a predominant pathology in mild TBI or “concussion”. The rapid deformation of white matter at the instant of trauma can lead to mechanical failure and calcium-dependent proteolysis of the axonal cytoskeleton in association with axonal transport interruption. Recently, a proteolytic fragment of alpha-II spectrin, “SNTF”, was detected in serum acutely following mild TBI in patients and was prognostic for poor clinical outcome. However, direct evidence that this fragment is a marker of DAI has yet to be demonstrated in either humans following TBI or in models of mild TBI. Here, we used immunohistochemistry (IHC) to examine for SNTF in brain tissue following both severe and mild TBI. Human severe TBI cases (survival <7d; n = 18) were compared to age-matched controls (n = 16) from the Glasgow TBI archive. We also examined brains from an established model of mild TBI at 6, 48 and 72 h post-injury versus shams. IHC specific for SNTF was compared to that of amyloid precursor protein (APP), the current standard for DAI diagnosis, and other known markers of axonal pathology including non-phosphorylated neurofilament-H (SMI-32), neurofilament-68 (NF-68) and compacted neurofilament-medium (RMO-14) using double and triple immunofluorescent labeling. Supporting its use as a biomarker of DAI, SNTF immunoreactive axons were observed at all time points following both human severe TBI and in the model of mild TBI. Interestingly, SNTF revealed a subpopulation of degenerating axons, undetected by the gold-standard marker of transport interruption, APP. While there was greater axonal co-localization between SNTF and APP after severe TBI in humans, a subset of SNTF positive axons displayed no APP accumulation. Notably, some co-localization was observed between SNTF and the less abundant neurofilament subtype markers. Other SNTF positive axons, however, did not co-localize with any other markers. Similarly, RMO-14 and NF-68 positive axonal pathology existed independent of SNTF and APP. These data demonstrate that multiple pathological axonal phenotypes exist post-TBI and provide insight into a more comprehensive approach to the neuropathological assessment of DAI

Sampling Time Effects for Persistence and Survival in Step Structural Fluctuations

The effects of sampling rate and total measurement time have been determined for single-point measurements of step fluctuations within the context of first-passage properties. Time dependent STM has been used to evaluate step fluctuations on Ag(111) films grown on mica as a function of temperature (300-410 K), on screw dislocations on the facets of Pb crystallites at 320K, and on Al-terminated Si(111) over the temperature range 770K - 970K. Although the fundamental time constant for step fluctuations on Ag and Al/Si varies by orders of magnitude over the temperature ranges of measurement, no dependence of the persistence amplitude on temperature is observed. Instead, the persistence probability is found to scale directly with t/Dt where Dt is the time interval used for sampling. Survival probabilities show a more complex scaling dependence which includes both the sampling interval and the total measurement time tm. Scaling with t/Dt occurs only when Dt/tm is a constant. We show that this observation is equivalent to theoretical predictions that the survival probability will scale as Dt/L^z, where L is the effective length of a step. This implies that the survival probability for large systems, when measured with fixed values of tm or Dt should also show little or no temperature dependence.Comment: 27 pages, 10 figure

Sampling the Number of Neutrons Emitted per Fission

I define in detail the model used to sample the number of prompt neutrons emitted in fission; this description is based on publications defining the model [1] as well as publications comparing the model to experimental measurements [2]. The model described in these publications is exactly what the TART [3] Monte Carlo transport code uses. Based on comparisons between TART [3] and MCNPX [4], it is obvious that at the time this report was published these two computer codes are not using the same model, and the results significantly differ. It is my hope that this report will contribute toward better understanding of this model, and hopefully eventually to agreement between TART and MCNPX results. Partial success has already been achieved in the sense that based upon reading a preliminary version of this report, John Hendrichs [5], one author of MCNPX, acknowledged that the sources of differences as described in this report demonstrate an error in MCNPX (John even offered me the traditional $20 reward for reporting an error in MCNPX; I declined to accept). John is presently updating MCNPX to eliminate these sources of differences; hopefully in the not too distant future this correction will be available in MCNPX, and we will obtain agreement between TART and MCNPX, which is the ultimate objective of this report

POINT 2012: ENDF/B-VII.1 Final Temperature Dependent Cross Section Library

This report is one in the series of 'POINT' reports that over the years have presented temperature dependent cross sections for the then current version of ENDF/B [R1]. In each case I have used my personal computer at home and publicly available data and codes: (1) publicly available nuclear data (the current ENDF/B data, available on-line at the National Nuclear Data Center, Brookhaven National Laboratory, http://www.nndc.bnl.gov/) and, (2) publicly available computer codes (the current PREPRO codes, available on-line at the Nuclear Data Section, IAEA, Vienna, Austria, http://www-nds.iaea.or.at/ndspub/endf/prepro/) and, (3) My own personal computer located in my home. I have used these in combination to produce the temperature dependent cross sections used in applications and described in this report. I should mention that today anyone with a personal computer can produce these results: by its very nature I consider this data to be born in the public domain

POINT 2007: A Temperature Dependent ENDF/.B-VII.0 Data Cross Section Library

This report is one in the series of ''POINT'' reports that over the years have presented temperature dependent cross sections for the then current version of ENDF/B. In each case I have used publicly available nuclear data (the current ENDF/B data, available online at the National Nuclear Data Center, Brookhaven National Laboratory http://www.nndc.bnl.gov/) and publicly available computer codes (the current PREPRO codes, available on-line at the Nuclear Data Section, IAEA, Vienna, Austria http://wwwnds. iaea.or.at/ndspub/endf/prepro/). I have used these in combination to produce the temperature dependent cross sections used in applications and presented in this report. The preceding POINT 2004 report [R1] presented results for the now frozen last version of ENDF/B-VI, Release 8. The current POINT 2007 report is based on data from recently released ENDF/B-VII.0, which is the first release of ENDF/B-VII