scholarly journals Intensive study on structure transformation of muscovite single crystal under high-dose γ -ray irradiation and mechanism speculation

2019 ◽  
Vol 6 (7) ◽  
pp. 190594 ◽  
Author(s):  
Honglong Wang ◽  
Yaping Sun ◽  
Jian Chu ◽  
Xu Wang ◽  
Ming Zhang
Keyword(s):  
Single Crystal ◽  
Chemical Structure ◽  
Defect Formation ◽  
High Dose ◽  
Low Doses ◽  
Lattice Plane ◽  
Structure Transformation ◽  
Intensive Study ◽  
Dose Irradiation ◽  
High Doses

Intensive study on structure transformation of muscovite single crystal under high-dose γ -ray irradiation is essential for its use in irradiation detection and also beneficial for mechanism cognition on defect formation within a matrix of clay used in the disposal of high-level radioactive waste (HLRW). In this work, muscovite single crystal was irradiated with Co-60 γ ray in air at a dose rate of 54 Gy min −1 with doses of 0–1000 kGy. Then, structure transformation and mechanism were explored by Raman spectrum, Fourier-transform infrared spectrum, X-ray diffraction, thermogravimetric analysis, CA, scanning electron microscope and atomic force microscopy. The main results show that variations in the chemical/crystalline structure are dose-dependent. Low-dose irradiation sufficiently destroyed the structure, removing Si–OH, thus declining hydrophilicity. With dose increase up to 100 kGy, CA increased from 20° to 40°. Except for hydrophilicity variation, shrink occurred in the (004) lattice plane which later recovered; the variation range at 500 kGy irradiation was 0.5% close to 0.02 Å. The main mechanisms involved were framework break and H 2 O radiolysis. Framework break results in Si–OH removal and H 2 O radiolysis results in extra OH introduction. The extra introduced OH probably results in Si–OH bond regeneration, lattice plane shrink and recovered surface hydrophilicity. The importance of framework break and H 2 O radiolysis on structure transformation is dose-dependence. At low doses, framework break seems more important while at high doses H 2 O radiolysis is important. Generally, variations in the chemical structure and surface property are nonlinear and less at high doses. This indicates using the chemical structure or surface property variation to describe irradiation is correct at low doses but not at high doses. This finding is meaningful for realizing whether muscovite is suitable for detecting high-dose irradiation or not, and mechanism exploration is efficient for identifying the procedure for defect formation within the matrix of clay used in disposal HLRW in practice.

scholarly journals Low-DoseAronia melanocarpaConcentrate Attenuates Paraquat-Induced Neurotoxicity

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
A. J. Case ◽  
D. Agraz ◽  
I. M. Ahmad ◽  
M. C. Zimmerman
Keyword(s):  
Reactive Oxygen Species ◽  
Hydrogen Peroxide ◽  
Cell Death ◽  
Neuronal Cell Death ◽  
Neuronal Cell ◽  
Reactive Oxygen ◽  
High Dose ◽  
Low Doses ◽  
Oxygen Species ◽  
High Doses

Herbicides containing paraquat may contribute to the pathogenesis of neurodegenerative disorders such as Parkinson’s disease. Paraquat induces reactive oxygen species-mediated apoptosis in neurons, which is a primary mechanism behind its toxicity. We sought to test the effectiveness of a commercially available polyphenol-richAronia melanocarpa(aronia berry) concentrate in the amelioration of paraquat-induced neurotoxicity. Considering the abundance of antioxidants in aronia berries, we hypothesized that aronia berry concentrate attenuates the paraquat-induced increase in reactive oxygen species and protects against paraquat-mediated neuronal cell death. Using a neuronal cell culture model, we observed that low doses of aronia berry concentrate protected against paraquat-mediated neurotoxicity. Additionally, low doses of the concentrate attenuated the paraquat-induced increase in superoxide, hydrogen peroxide, and oxidized glutathione levels. Interestingly, high doses of aronia berry concentrate increased neuronal superoxide levels independent of paraquat, while at the same time decreasing hydrogen peroxide. Moreover, high-dose aronia berry concentrate potentiated paraquat-induced superoxide production and neuronal cell death. In summary, aronia berry concentrate at low doses restores the homeostatic redox environment of neurons treated with paraquat, while high doses exacerbate the imbalance leading to further cell death. Our findings support that moderate levels of aronia berry concentrate may prevent reactive oxygen species-mediated neurotoxicity.

scholarly journals Extrapolation of the DNA Fragment-Size Distribution after High-Dose Irradiation to Predict Effects at Low Doses

2001 ◽  
Vol 156 (5) ◽  
pp. 594-597 ◽  
Author(s):  
A. L. Ponomarev ◽  
F. A. Cucinotta ◽  
R. K. Sachs ◽  
D. J. Brenner ◽  
L. E. Peterson
Keyword(s):  
Size Distribution ◽  
Fragment Size ◽  
High Dose ◽  
Low Doses ◽  
Fragment Size Distribution ◽  
Dose Irradiation ◽  
Dna Fragment

scholarly journals Hormetic effect of amyloid-beta peptide in hippocampal synaptic plasticity and memory

2021 ◽  
Vol 11 (40) ◽  
pp. 156-156
Author(s):  
Daniela Puzzo ◽  
Agostino Palmeri
Keyword(s):  
Synaptic Plasticity ◽  
Amyloid Beta ◽  
Hippocampal Slices ◽  
Reference Memory ◽  
High Dose ◽  
Low Doses ◽  
Hormetic Effect ◽  
Physiologic Function ◽  
High Doses

Background: The term hormesis refers to a biphasic dose-response phenomenon characterized by low-dose stimulation and high-dose inhibition represented by a J-shaped or U-shaped curve, depending on the parameter measured (Calabrese and Baldwin, Hum Exp Toxicol, 2002). Indeed, several, if not all, physiological molecules (i.e. glutamate, glucocorticoids, nitric oxide) are likely to present a hormetic effect, exhibiting opposite effects at high or low concentrations. In the last few years, we have focused on amyloid-beta (A), a peptide widely known because it is produced in high amounts during Alzheimer’s disease (AD). A is considered a toxic fragment causing synaptic dysfunction and memory impairment (Selkoe, Science, 2002). However, the peptide is normally produced in the healthy brain and growing evidences indicate that it might have a physiologic function. Aim: Based on previous results showing that picomolar concentrations of A42 enhance synaptic plasticity and memory (Puzzo et al, J Neurosci, 2008) and that endogenous A is necessary for synaptic plasticity and memory (Puzzo et al, Ann Neurol, 2011), the aim of our study was to demonstrate the hormetic role of A in synaptic plasticity and memory. Methods: We used 3-month old wild type mice to analyze how synaptic plasticity, measured on hippocampal slices in vitro, and spatial reference memory were modified by treatment with different doses of A (from 2 pM to 20 μM). Results: We demonstrated that A has a hormetic effect (Puzzo et al, Neurobiol Aging, 2012) with low-doses (200 pM) stimulating synaptic plasticity and memory and high-doses (≥ 200 nM) inhibiting these processes. Conclusions: Our results suggest that, paradoxically, very low doses of A might serve to enhance memory at appropriate concentrations and conditions. These findings raise several issues when designing effective and safe approaches to AD therapy.

ANDROGENIZATION OF THE NEONATAL FEMALE RAT WITH VERY LOW DOSES OF ANDROGEN

1973 ◽  
Vol 57 (1) ◽  
pp. 33-45 ◽  
Author(s):  
P. J. SHERIDAN ◽  
M. X. ZARROW ◽  
V. H. DENENBERG
Keyword(s):  
Low Dose ◽  
Physiological Effect ◽  
Neonatal Rat ◽  
Female Rats ◽  
High Dose ◽  
Female Rat ◽  
Low Doses ◽  
Minimal Effective Dose ◽  
High Doses ◽  
Long Acting

SUMMARY The administration of a high dose of androgen on a single day to a neonatal female rat has been shown repeatedly to induce persistent vaginal cornification (PVC). However, this type of treatment does not parallel the continuous androgen secretion present in the male, and the high doses that have been used could represent a pharmacological and not a physiological effect. Experiments were carried out to determine the minimal effective dose of testosterone propionate (TP) needed to cause PVC when the androgen is administered to the neonatal rat for the first 10 days of life or as a long-acting ester. Injection of 1, 3 or 9 μg TP on days 1–10 of life in female rats induced PVC in adulthood. All three doses were found to be more effective than a testicular transplant on day 1. In female rats injected with low doses of TP twice daily for the first 10 days of life, PVC was shown between 90 and 100 days of life in 21 out of 22 animals given 0·5 μg TP/injection, and in eight out of 22 animals given 0·05 μg TP/injection. In an experiment where female rats were given a single injection of 0·1, 1·0 or 10·0 μg TP, or 0·1 or 1·0 μg testosterone cyclopentylpropionate (TC, a long-acting androgen) on the first day after birth, PVC occurred at 90–100 days of age in 15 of the 18 animals which were injected with 10 μg TP, in none of the 17 animals which were injected with 1 μg TP, and in 10 of 11 animals which were injected with 1 μg TC. The effects of all treatments on vaginal opening, first oestrus, ovarian weight, body weight and sexual behaviour are reported. The use and implications of low dose regimens are discussed in relation to the construction of an experimental model for the study of sexual differentiation.

Crystallisation and Diffusion in Oriented Sapphire Amorphised by Zinc Ion Implantation

1990 ◽  
Vol 201 ◽  
Author(s):  
L. A. Bunn ◽  
D. K. Sood
Keyword(s):  
Epitaxial Growth ◽  
Zinc Ion ◽  
High Dose ◽  
Low Doses ◽  
Surface Layers ◽  
Rapid Diffusion ◽  
High Doses ◽  
Amorphous Surface ◽  
And Diffusion ◽  
Post Implantation

AbstractHigh dose zinc implantation (1×1016 to 6×1016 ions/cm2) into c-axis sapphire at 770K produces amorphous surface layers. Post-implantation annealing at temperatures at and above 800°C show that the modes of recrystallisation are strongly dependant on ion dose. At low doses formation of crystallites of α and γ phase Al2O3 is seen, with no evidence of any planar epitaxial growth at the original crystalline-amorphous interface. The zinc is seen to diffuse isotropically within the crystallised layer and becomes partially substitutional within the crystallites. At high doses, however, the formation of crystallites is inhibited, with the layer remaining amorphous. A more rapid diffusion of zinc is seen in the amorphous Al2O3, with some of the zinc being lost at the surface.

The effect of ion induced damage on the hardness, wear, and friction of zirconia

1990 ◽  
Vol 5 (2) ◽  
pp. 385-391 ◽  
Author(s):  
E. L. Fleischer ◽  
W. Hertl ◽  
T. L. Alford ◽  
P. Børgesen ◽  
J. W. Mayer
Keyword(s):  
Single Crystal ◽  
Friction And Wear ◽  
Inert Gas ◽  
High Dose ◽  
Low Doses ◽  
A Value ◽  
Wear And Friction ◽  
Knoop Microhardness ◽  
Pin On Disk ◽  
Ion Species

Microhardness measurements were carried out on ion implanted single crystal Y2O3 stabilized cubic ZrO2. Inert gas ions (Ne, Ar, Xe) and N, Si, Ti, and W were implanted up to fluences of 3 × 1017 ions/cm2. Implantation energies were selected to give equivalent ranges. Comparison of the Knoop microhardness values of ZrO2 implanted with various species over a range of fluences showed that the principal variable causing hardness changes is damage energy and not the ion fluence nor the ion species. For all implants studied, the hardness versus damage energy gives a unified plot. At low doses the hardness rises with increasing deposited damage energy to a value 15% higher than that of unimplanted zirconia. With additional damage the hardness drops to a value 15% lower than that of the unimplanted zirconia. Friction and wear measurements in a pin-on-disk assembly showed very different behavior for high dose versus unimplanted ZrO2. The unimplanted samples showed debris with an associated rise in friction. The implanted system showed much less debris and a constant value of friction even after 10 000 cycles.

Recrystallization of ion-implanted α-SiC

1987 ◽  
Vol 2 (1) ◽  
pp. 107-116 ◽  
Author(s):  
H. G. Bohn ◽  
J. M. Williams ◽  
C. J. McHargue ◽  
G. M. Begun
Keyword(s):  
Raman Scattering ◽  
Single Crystal ◽  
Temperature Interval ◽  
High Dose ◽  
Low Doses ◽  
Surface Layers ◽  
Annealing Behavior ◽  
Narrow Temperature Interval ◽  
Amorphous Surface ◽  
Ion Implanted

The annealing behavior of ion-implanted α-SiC single crystal was determined for samples implanted with 62 keV 14N to doses of 5.5X1014/cm2 and 8.0X1016/cm2 and with 260 keV 52Cr to doses of 1.5X1014/cm2 and 1.0X1016/cm2. The high-dose samples formed amorphous surface layers to depths of 0.17 μm (N) and 0.28 μm (Cr), while for the low doses only highly damaged but not randomized regions were formed. The samples were isochronically annealed up to 1600°C, holding each temperature for 10 min. The remaining damage was analyzed by Rutherford backscattering of 2 MeV He+, Raman scattering, and electron channeling. About 15% of the width of the amorphous layers regrew cpitaxially from the underlying undamaged material up to 1500°C, above which the damage annealed rapidly in a narrow temperature interval. The damage in the crystalline samples annealed linearly with temperature and was unmeasurable above 1000°C.

Hormesis and risk assessment

2005 ◽  
Vol 24 (5) ◽  
pp. 255-257 ◽  
Author(s):  
Karl K Rozman
Keyword(s):  
Mathematical Method ◽  
Risk Assessment ◽  
Point Estimate ◽  
High Dose ◽  
Low Doses ◽  
Beneficial Effects ◽  
Dose Effects ◽  
High Doses ◽  
Living Organisms

It is postulated in this paper that at low doses all chemicals have hormetic/hormoligotic (beneficial) effects in living organisms. It has been known since Paracelsus that at high doses all chemicals are toxic. The combination of low and high dose effects can be empirically described by a β-curve or an inverted β-curve. A mathematical method is suggested to determine the maximum of the β-curve or the minimum of the inverted β-curve, yielding a point estimate for risk assessment.

scholarly journals Anti-Inflammatory Properties of Low and High Doxycycline Doses: AnIn VitroStudy

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Roberta Di Caprio ◽  
Serena Lembo ◽  
Luisa Di Costanzo ◽  
Anna Balato ◽  
Giuseppe Monfrecola
Keyword(s):  
Gene Expression ◽  
Skin Diseases ◽  
High Dose ◽  
Low Doses ◽  
Dose Administration ◽  
Doxycycline Treatment ◽  
Anti Inflammatory ◽  
High Doses ◽  
Bacterial Resistances

Doxycycline is used to treat infective diseases because of its broadspectrum efficacy. High dose administration (100 or 200 mg/day) is often responsible for development of bacterial resistances and endogenous flora alterations, whereas low doses (20–40 mg/day) do not alter bacteria susceptibility to antibiotics and exert anti-inflammatory activities. In this study, we wanted to assess the efficacy of both low and high doxycycline doses in modulating IL-8, TNF-α, and IL-6 gene expression in HaCaT cells stimulated with LPS. Three experimental settings were used, differing in the timing of doxycycline treatment in respect to the insult induced by LPS: pretreatment, concomitant, and posttreatment. Low doses were more effective than high doses in modulating gene expression of LPS-induced proinflammatory cytokines (IL-8, TNF-α, and IL-6), when added before (pretreatment) or after (posttreatment) LPS stimulation. This effect was not appreciated when LPS and doxycycline were simultaneously added to cell cultures: in this case high doses were more effective. In conclusion, ourin vitrostudy suggests that low doxycycline doses could be safely used in chronic or acute skin diseases in which the inflammatory process, either constantly in progress or periodically recurring, has to be prevented or controlled.

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