Highlights • Unlike neurons in dlPFC, neurons in V1 do not lose spines with age in rhesus monkeys. • Aging decreases the proportion of thin spines in macaque dlPFC but not in V1. • Smaller dlPFC mean ...spine head diameter correlates with fewer trials to criterion on DR and DNMS tasks.
This investigation addresses a need for higher quality surfaces and wear resistance of coatings used on load bearing medical implants. Multilayered cathodic arc deposited coatings are candidates for ...such applications and were the subject of this study. Nb–Ti–N coatings were deposited by cathodic arc using TiNb compound cathodes. The microstructure and properties of the coatings were characterized using XRD, TEM/STEM, EDS, nanoindentation, scratch tests and pin-on-disc testing. Throughout the coating, macroparticles consisting of a Nb rich core and a nitrided titanium porous shell were evidenced by STEM and EDS. It was shown that inhomogeneities related with the soft and malleable metallic Nb inclusions alter the tribological behavior of the coatings. The underlying mechanism of wear in hip-simulator test liquid against UHMWPE was investigated. During pin-on-disc tests, the top layers of the coatings were removed and the embedded niobium droplets became visible. The wear of UHMWPE during pin-on-disks tests was increased on Nb–Ti–N counter surfaces compared to the wear of UHMWPE on TiN itself. It is inferred that the wear of the coatings is initiated by the growth discontinuities and pores around the Nb droplets. The debris released from the coating acts as third body wear particles, grinds the remaining coating and causes the wear of UHMWPE pins.
•Nb–Ti–N coatings deposited from TiNb compound cathodes have a multilayered structure.•Metallic Nb rich inclusions embedded throughout the macroparticles were evidenced.•The Nb inclusions favor debris from Nb–Ti–N coatings in wear tests against UHMWPE.•The debris generated from Nb–Ti–N coatings acts as third-body wear particles.
Abstract In the past few decades it has become clear that estrogen signaling plays a much larger role in modulating the cognitive centers of the brain than previously thought possible. We have ...developed a nonhuman primate (NHP) model to investigate the relationships between estradiol (E) and cognitive aging. Our studies of cyclical E treatment in ovariectomized (OVX) young and aged rhesus monkeys have revealed compelling cognitive and synaptic effects of E in the context of aging. Delayed response (DR), a task that is particularly dependent on integrity of dorsolateral prefrontal cortex (dlPFC) area 46 revealed the following: (1) that young OVX rhesus monkeys perform equally well whether treated with E or vehicle (V), and (2) that aged OVX animals given E perform as well as young adults with or without E, whereas OVX V-treated aged animals display significant DR impairment. We have analyzed the structure of layer III pyramidal cells in area 46 in these same monkeys. We found both age and treatment effects on these neurons that are consistent with behavioral data. Briefly, reconstructions of pyramidal neurons in area 46 from these monkeys showed that cyclical E increased the density of small, thin spines in both young and aged monkeys. However, this effect of E was against a background of age-related loss of small, thin spines, leaving aged V-treated monkeys with a particularly low density of these highly plastic spines, and vulnerable to cognitive decline. Our current interpretation is that E not only plays a critically important role in maintaining spine number, but also enables synaptic plasticity through a cyclical increase in small highly plastic spines that may be stabilized in the context of learning. Interestingly, recent studies demonstrate that chronic E is less effective at inducing spinogenesis than cyclical E. We have begun to link certain molecular attributes of excitatory synapses in area 46 to E effects and cognitive performance in these monkeys. Given the importance of synaptic estrogen receptor α (ER-α) in rat hippocampus, we focused our initial studies on synaptic ER-α in area 46. Three key findings have emerged from these studies: (1) synaptic ER-α is present in axospinous synapses in area 46; (2) it is stable across treatment and age groups (which is not the case in rat hippocampus); and (3) the abundance and distribution of synaptic ER-α is a key correlate of individual variation in cognitive performance in certain age and treatment groups. These findings have important implications for the design of hormone treatment strategies for both surgically and naturally menopausal women. This article is part of a Special Issue entitled: Neuroactive Steroids: Focus on Human Brain.
New preshower detector for the DIRAC experiment Pentia, M.; Aogaki, S.; Dumitriu, D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2015, Letnik:
795
Journal Article
Recenzirano
Odprti dostop
The Preshower (PSh) detector 1 is a component of the DIRAC setup 2. It is designed to identify and reject the huge e−e+ pairs background in the ππ and Kπ pairs measurement produced in a hadronic atom ...ionization process. In the high energy region used for kaon detection, the small Nitrogen Cherenkov detector has low electron rejection efficiency. To increase the overall efficiency, a new two-layer scintillator Preshower detector has been developed and built. The new Preshower–Cherenkov combination ensures an electron rejection efficiency better than 99% in the momentum range 1–7GeV/c.
After having announced the statistically significant observation (5.6σ) of the new exotic πK atom, the DIRAC experiment at the CERN proton synchrotron presents the measurement of the corresponding ...atom lifetime, based on the full πK data sample: τ=(5.5−2.8+5.0)×10−15 s. By means of a precise relation (≈1%) between atom lifetime and scattering length, the following value for the S-wave isospin-odd πK scattering length a0−=13(a1/2−a3/2) has been derived: |a0−|=(0.072−0.020+0.031)Mπ−1.
The observation of hydrogenlike πK atoms, consisting of π^{-}K^{+} or π^{+}K^{-} mesons, is presented. The atoms are produced by 24 GeV/c protons from the CERN PS accelerator, interacting with ...platinum or nickel foil targets. The breakup (ionization) of πK atoms in the same targets yields characteristic πK pairs, called "atomic pairs," with small relative momenta Q in the pair center-of-mass system. The upgraded DIRAC experiment observed 349±62 such atomic πK pairs, corresponding to a signal of 5.6 standard deviations. This is the first statistically significant observation of the strange dimesonic πK atom.
The adapted DIRAC experiment at the CERN PS accelerator observed for the first time long-lived hydrogenlike π^{+}π^{-} atoms, produced by protons hitting a beryllium target. A part of these atoms ...crossed the gap of 96 mm between the target and a 2.1 μm thick platinum foil, in which most of them dissociated. Analyzing the observed number of atomic pairs, n_{A}^{L}=436_{-61}^{+157}|_{tot}, the lifetime of the 2p state is found to be τ_{2p}=(0.45_{-0.30}^{+1.08}|_{tot})×10^{-11} s, not contradicting the corresponding QED 2p state lifetime τ_{2p}^{QED}=1.17×10^{-11} s. This lifetime value is three orders of magnitude larger than our previously measured value of the π^{+}π^{-} atom ground state lifetime τ=(3.15_{-0.26}^{+0.28}|_{tot})×10^{-15} s. Further studies of long-lived π^{+}π^{-} atoms will allow us to measure energy differences between p and s atomic states and so to discriminate between the isoscalar and isotensor ππ scattering lengths with the aim to check QCD predictions.
An atomic clock based on x-ray fluorescence yields has been used to estimate the mean characteristic time for fusion followed by fission in reactions 238U + 64Ni at 6.6 MeV/A. Inner shell vacancies ...are created during the collisions in the electronic structure of the possibly formed Z=120 compound nuclei. The filling of these vacancies accompanied by a x-ray emission with energies characteristic of Z=120 can take place only if the atomic transitions occur before nuclear fission. Therefore, the x-ray yield characteristic of the united atom with 120 protons is strongly related to the fission time and to the vacancy lifetimes. K x rays from the element with Z=120 have been unambiguously identified from a coupled analysis of the involved nuclear reaction mechanisms and of the measured photon spectra. A minimum mean fission time τ(f)=2.5×10(-18) s has been deduced for Z=120 from the measured x-ray multiplicity.
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