The surface composition of low alloy steel after N_2^+ implantation was studied with X-ray photo-electron spectroscopy (XPS). The effect of the implantation on the mechanical hardness was evaluated by ultra-micro hard...The surface composition of low alloy steel after N_2^+ implantation was studied with X-ray photo-electron spectroscopy (XPS). The effect of the implantation on the mechanical hardness was evaluated by ultra-micro hardness indentation. Chemical characterisation of the surface indi- cated that a thin layer rich in N, C and Si was formed. It is shown that Fe played little role in the chemical composition and the structure of the modified surface. The mechanical hardness of N_2^+ implanted surface was 35-50 GPa compared with a value of 10 GPa for the untreated sample. It is thought that the high hardness observed on the surface and in the sub-surface was as a result of chemical modification to form a film of Si doped carbon nitride. There is strong evidence from the XPS and the nanoindentation studies that the bonding structure of the C-N in the near surface is essentially sp^3 types expected in crystalline C_3N_4. The value of nitrogen ion implantation as process for improving the wear resistance of low alloy steels is emphasized.展开更多
In this work we repo rt on structural and spect roscopic properties of Yb^3+doped and Pr^3+/Yb^3+co-doped TeO2-Bi2 O3-ZnO-Li2 O-Nb2 O5(TBZLN)tellurite glasses.Bending and stretching modes of TeO2 and Te-OH bond(strong...In this work we repo rt on structural and spect roscopic properties of Yb^3+doped and Pr^3+/Yb^3+co-doped TeO2-Bi2 O3-ZnO-Li2 O-Nb2 O5(TBZLN)tellurite glasses.Bending and stretching modes of TeO2 and Te-OH bond(strong and weak)were analysed from the deconvolution of observed Raman and FT-IR spectra.Based on the absorption measurements,the energy bands of Yb^3+and Pr^3+ions are assigned.The spectroscopic properties for the radiative transitions of Yb^3+and Pr^3+ions were reported using McCumber and Judd-Ofelt theories.Visible emission bands originating from 3 P1 and 3 P0 to lower lying levels of Pr^3+were registered under 447 nm excitation.The emission band around 1334 nm assigned to the Pr3:1 G4→3 H5 was observed when excited at 980 nm.The stimulated emission cross-section(σemi(λ))and effective linewidth(Δλeff)for the 3 P1→3 H6,3 P1→3 H5,3 P0→3 H6,3 P0→3 F2,3 P1→3 F3,3 P1→3 F4,3 P0→3 F4 and 1 G4→3 H5 transitions of Pr^3+are reported.Upconversion luminescence in Pr^3+/Yb^3+codoped glass upon 980 nm excitation was measured.Possible resonant transfer processes between Yb^3+and Pr^3+ions are presented and discussed.The chromaticity co-ordinates were also evaluated from the visible emission spectra showing that Pr^3+/Yb^3+co-doped glass may be suitable for the development of yellow-orange(λexc=447 nm)and near white light(λexc=980 nm)emitting devices in photonics.展开更多
The recent review for the Restriction of Hazardous Substances Directive(RoHS)by the expert committee,appointed by the European Union,stated that the replacement of PZT“…may be scientifically and technologically prac...The recent review for the Restriction of Hazardous Substances Directive(RoHS)by the expert committee,appointed by the European Union,stated that the replacement of PZT“…may be scientifically and technologically practical to a certain degree…”,although replacement“…is scientifically and technically still impractical in the majority of applications.”Thus,two decades of sustained research and development may be approaching fruition,at first limited to a minority of applications.Therefore,it is of paramount importance to assess the viability of lead-free piezoceramics over a broad range of application-relevant properties.These are identified and discussed in turn:1.Cost,2.Reproducibility,3.Mechanical and Thermal Properties,4.Electrical Conductivity,and 5.Lifetime.It is suggested that the worldwide efforts into the development of lead-free piezoceramics now require a broader perspective to bring the work to the next stage of development by supporting implementation into real devices.Guidelines about pertinent research requirements into a wide range of secondary properties,measurement techniques,and salient literature are provided.展开更多
Background:Newly diagnosed breast cancer patients experience symptoms that may affect their quality of life,treatment outcomes,and survival.Preventing and managing breast cancer-related symptoms soon after diagnosis i...Background:Newly diagnosed breast cancer patients experience symptoms that may affect their quality of life,treatment outcomes,and survival.Preventing and managing breast cancer-related symptoms soon after diagnosis is essential.The purpose of this study was to investigate the associations between health-related fitness(HRF)and patient-reported symptoms in newly diagnosed breast cancer patients.Methods:This study utilized baseline data from the Alberta Moving Beyond Breast Cancer Cohort Study that were collected within 90 days of diagnosis.HRF measures included peak cardiopulmonary fitness(peak volume of oxygen consumption(VO_(2peak))),maximal muscular strength and endurance,flexibility,and body composition.Symptom measures included depression,sleep quality,and fatigue.Adjusted multivariable logistic regression was performed for analyses.Results:Of 1458 participants,51.5%reported poor sleep quality,26.5%reported significant fatigue,and 10.4%reported moderate depression.In multivariable-adjusted models,lower relative VO_(2peak)was independently associated with a greater likelihood of all symptom measures,including moderate depression(p<0.001),poor sleep quality(p=0.009),significant fatigue(p=0.008),any symptom(p<0.001),and multiple symptoms(p<0.001).VO_(2peak)demonstrated threshold associations with all symptom measures such that all 3 lower quartiles exhibited similar elevated risk compared to the highest quartile.The strength of the threshold associations varied by the symptom measure with odds ratios ranging from-1.5 for poor sleep quality to-3.0 for moderate depression and multiple symptoms.Moreover,lower relative upper body muscular endurance was also independently associated with fatigue in a dose-response manner(p=0.001),and higher body weight was independently associated with poor sleep quality in an inverted U pattern(p=0.021).Conclusion:Relative VO_(2peak)appears to be a critical HRF component associated with multiple patient-reported symptoms in newly diagnosed breast cancer patients.Other HRF parameter展开更多
Knowledge of the soil water characteristic curve is fundamental for understanding unsaturated soils.The objective of this work was to find scanning hysteresis loops of two fine textured soils at water potentials below...Knowledge of the soil water characteristic curve is fundamental for understanding unsaturated soils.The objective of this work was to find scanning hysteresis loops of two fine textured soils at water potentials below wilting point.This was done by equilibration over NaCl solutions with water potentials of-6.6 to-18.8 MPa at 25℃.When cycled repeatedly through a series of potentials in the range noted previously both soils exhibited a hysteresis effect.The experimental differences in water content between the drying and wetting soils at the same water potential were much too large to be accounted for by failure to allow sufficient time to attain equilibrium as predicted by the exponential decay model.The wetting versus drying differences were relatively small,however,at only 4 mg g-1 or less in absolute terms and about 3% of the mean of wetting and drying,in relative terms.Hysteresis should be a consideration when modeling biological and physical soil processes at water contents below the wilting point,where small differences in water content result in large potential energy changes.展开更多
The recently proposed Equivalent Dipole Model for describing the electromechanical properties of ionic solids in terms of 3 ions and 2 bonds has been applied to PZT ceramics and lead-free single crystal piezoelectric ...The recently proposed Equivalent Dipole Model for describing the electromechanical properties of ionic solids in terms of 3 ions and 2 bonds has been applied to PZT ceramics and lead-free single crystal piezoelectric materials,providing analysis in terms of an effective ionic charge and the asymmetry of the interatomic force constants.For PZT it is shown that,as a function of composition across the morphotropic phase boundary,the dominant bond compliance peaks at 52%ZrO_(2).The stiffer of the two bonds shows little composition dependence with no anomaly at the phase boundary.The effective charge has a maximum value at 50%ZrO_(2),decreasing across the phase boundary region,but becoming constant in the rhombohedral phase.The single crystals confirm that both the asymmetry in the force constants and the magnitude of effective charge are equally important in determining the values of the piezoelectric charge coefficient and the electromechanical coupling coefficient.Both are apparently temperature dependent,increasing markedly on approaching the Curie temperature.展开更多
Background Cognitive decline in Alzheimer’s disease(AD)is associated with hyperphosphorylated tau(pTau)propagation between neurons along synaptically connected networks,in part via extracellular vesicles(EVs).EV biog...Background Cognitive decline in Alzheimer’s disease(AD)is associated with hyperphosphorylated tau(pTau)propagation between neurons along synaptically connected networks,in part via extracellular vesicles(EVs).EV biogenesis is triggered by ceramide enrichment at the plasma membrane from neutral sphingomyelinase2(nSMase2)-mediated cleavage of sphingomyelin.We report,for the first time,that human tau expression elevates brain ceramides and nSMase2 activity.Methods To determine the therapeutic benefit of inhibiting this elevation,we evaluated PDDC,the first potent,selective,orally bioavailable,and brain-penetrable nSMase2 inhibitor in the transgenic PS19 AD mouse model.Additionally,we directly evaluated the effect of PDDC on tau propagation in a mouse model where an adeno-associated virus(AAV)encoding P301L/S320F double mutant human tau was stereotaxically-injected unilaterally into the hippocampus.The contralateral transfer of the double mutant human tau to the dentate gyrus was monitored.We examined ceramide levels,histopathological changes,and pTau content within EVs isolated from the mouse plasma.Results Similar to human AD,the PS19 mice exhibited increased brain ceramide levels and nSMase2 activity;both were completely normalized by PDDC treatment.The PS19 mice also exhibited elevated tau immunostaining,thinning of hippocampal neuronal cell layers,increased mossy fiber synaptophysin immunostaining,and glial activation,all of which were pathologic features of human AD.PDDC treatment reduced these changes.The plasma of PDDC-treated PS19 mice had reduced levels of neuronal-and microglial-derived EVs,the former carrying lower pTau levels,compared to untreated mice.In the tau propagation model,PDDC normalized the tau-induced increase in brain ceramides and significantly reduced the amount of tau propagation to the contralateral side.Conclusions PDDC is a first-in-class therapeutic candidate that normalizes elevated brain ceramides and nSMase2 activity,leading to the slowing of tau spread in AD mice.展开更多
文摘The surface composition of low alloy steel after N_2^+ implantation was studied with X-ray photo-electron spectroscopy (XPS). The effect of the implantation on the mechanical hardness was evaluated by ultra-micro hardness indentation. Chemical characterisation of the surface indi- cated that a thin layer rich in N, C and Si was formed. It is shown that Fe played little role in the chemical composition and the structure of the modified surface. The mechanical hardness of N_2^+ implanted surface was 35-50 GPa compared with a value of 10 GPa for the untreated sample. It is thought that the high hardness observed on the surface and in the sub-surface was as a result of chemical modification to form a film of Si doped carbon nitride. There is strong evidence from the XPS and the nanoindentation studies that the bonding structure of the C-N in the near surface is essentially sp^3 types expected in crystalline C_3N_4. The value of nitrogen ion implantation as process for improving the wear resistance of low alloy steels is emphasized.
基金Project supported by Programa Nacional de Pos-Doutorado(PNPD/CAPES-086/2013)-Brazil。
文摘In this work we repo rt on structural and spect roscopic properties of Yb^3+doped and Pr^3+/Yb^3+co-doped TeO2-Bi2 O3-ZnO-Li2 O-Nb2 O5(TBZLN)tellurite glasses.Bending and stretching modes of TeO2 and Te-OH bond(strong and weak)were analysed from the deconvolution of observed Raman and FT-IR spectra.Based on the absorption measurements,the energy bands of Yb^3+and Pr^3+ions are assigned.The spectroscopic properties for the radiative transitions of Yb^3+and Pr^3+ions were reported using McCumber and Judd-Ofelt theories.Visible emission bands originating from 3 P1 and 3 P0 to lower lying levels of Pr^3+were registered under 447 nm excitation.The emission band around 1334 nm assigned to the Pr3:1 G4→3 H5 was observed when excited at 980 nm.The stimulated emission cross-section(σemi(λ))and effective linewidth(Δλeff)for the 3 P1→3 H6,3 P1→3 H5,3 P0→3 H6,3 P0→3 F2,3 P1→3 F3,3 P1→3 F4,3 P0→3 F4 and 1 G4→3 H5 transitions of Pr^3+are reported.Upconversion luminescence in Pr^3+/Yb^3+codoped glass upon 980 nm excitation was measured.Possible resonant transfer processes between Yb^3+and Pr^3+ions are presented and discussed.The chromaticity co-ordinates were also evaluated from the visible emission spectra showing that Pr^3+/Yb^3+co-doped glass may be suitable for the development of yellow-orange(λexc=447 nm)and near white light(λexc=980 nm)emitting devices in photonics.
文摘The recent review for the Restriction of Hazardous Substances Directive(RoHS)by the expert committee,appointed by the European Union,stated that the replacement of PZT“…may be scientifically and technologically practical to a certain degree…”,although replacement“…is scientifically and technically still impractical in the majority of applications.”Thus,two decades of sustained research and development may be approaching fruition,at first limited to a minority of applications.Therefore,it is of paramount importance to assess the viability of lead-free piezoceramics over a broad range of application-relevant properties.These are identified and discussed in turn:1.Cost,2.Reproducibility,3.Mechanical and Thermal Properties,4.Electrical Conductivity,and 5.Lifetime.It is suggested that the worldwide efforts into the development of lead-free piezoceramics now require a broader perspective to bring the work to the next stage of development by supporting implementation into real devices.Guidelines about pertinent research requirements into a wide range of secondary properties,measurement techniques,and salient literature are provided.
基金funded by a Team Grant(#107534)to KSC,CMF,SNCR,MLM,JKV,GJB,and JRMa Project Grant(#155952)to CMF,KSC,SNCR,MLM,JKV,and JRM+1 种基金a Foundation Grant(#159927)to KSC,CMF,SNCR,MLM,and JKV from the Canadian Institutes of Health Research.KSC and JKV are supported by the Canada Research Chairs ProgramCMF was supported by an Alberta Innovates Health Senior Scholar Award and by the Alberta Cancer Foundation Weekend to End Women’s Cancers Breast Cancer Chair.
文摘Background:Newly diagnosed breast cancer patients experience symptoms that may affect their quality of life,treatment outcomes,and survival.Preventing and managing breast cancer-related symptoms soon after diagnosis is essential.The purpose of this study was to investigate the associations between health-related fitness(HRF)and patient-reported symptoms in newly diagnosed breast cancer patients.Methods:This study utilized baseline data from the Alberta Moving Beyond Breast Cancer Cohort Study that were collected within 90 days of diagnosis.HRF measures included peak cardiopulmonary fitness(peak volume of oxygen consumption(VO_(2peak))),maximal muscular strength and endurance,flexibility,and body composition.Symptom measures included depression,sleep quality,and fatigue.Adjusted multivariable logistic regression was performed for analyses.Results:Of 1458 participants,51.5%reported poor sleep quality,26.5%reported significant fatigue,and 10.4%reported moderate depression.In multivariable-adjusted models,lower relative VO_(2peak)was independently associated with a greater likelihood of all symptom measures,including moderate depression(p<0.001),poor sleep quality(p=0.009),significant fatigue(p=0.008),any symptom(p<0.001),and multiple symptoms(p<0.001).VO_(2peak)demonstrated threshold associations with all symptom measures such that all 3 lower quartiles exhibited similar elevated risk compared to the highest quartile.The strength of the threshold associations varied by the symptom measure with odds ratios ranging from-1.5 for poor sleep quality to-3.0 for moderate depression and multiple symptoms.Moreover,lower relative upper body muscular endurance was also independently associated with fatigue in a dose-response manner(p=0.001),and higher body weight was independently associated with poor sleep quality in an inverted U pattern(p=0.021).Conclusion:Relative VO_(2peak)appears to be a critical HRF component associated with multiple patient-reported symptoms in newly diagnosed breast cancer patients.Other HRF parameter
文摘Knowledge of the soil water characteristic curve is fundamental for understanding unsaturated soils.The objective of this work was to find scanning hysteresis loops of two fine textured soils at water potentials below wilting point.This was done by equilibration over NaCl solutions with water potentials of-6.6 to-18.8 MPa at 25℃.When cycled repeatedly through a series of potentials in the range noted previously both soils exhibited a hysteresis effect.The experimental differences in water content between the drying and wetting soils at the same water potential were much too large to be accounted for by failure to allow sufficient time to attain equilibrium as predicted by the exponential decay model.The wetting versus drying differences were relatively small,however,at only 4 mg g-1 or less in absolute terms and about 3% of the mean of wetting and drying,in relative terms.Hysteresis should be a consideration when modeling biological and physical soil processes at water contents below the wilting point,where small differences in water content result in large potential energy changes.
文摘The recently proposed Equivalent Dipole Model for describing the electromechanical properties of ionic solids in terms of 3 ions and 2 bonds has been applied to PZT ceramics and lead-free single crystal piezoelectric materials,providing analysis in terms of an effective ionic charge and the asymmetry of the interatomic force constants.For PZT it is shown that,as a function of composition across the morphotropic phase boundary,the dominant bond compliance peaks at 52%ZrO_(2).The stiffer of the two bonds shows little composition dependence with no anomaly at the phase boundary.The effective charge has a maximum value at 50%ZrO_(2),decreasing across the phase boundary region,but becoming constant in the rhombohedral phase.The single crystals confirm that both the asymmetry in the force constants and the magnitude of effective charge are equally important in determining the values of the piezoelectric charge coefficient and the electromechanical coupling coefficient.Both are apparently temperature dependent,increasing markedly on approaching the Curie temperature.
基金supported by the National Institute of Health Grants R01 AG059799(to BSS),R01AG057420 and R01MH131219(to NJH),P30 MH075673(to NJH and BSS)a grant from the Tau Consortium and Alzheimer’s Association(T-PEP-18-579974C,to BSS)a grant from the Richman Family Precision Medicine Center of Excellence in Alzheimer’s disease(to BSS and DK).KC and TRJ were Funded by NIH R25GM109441(Hopkins PREP).
文摘Background Cognitive decline in Alzheimer’s disease(AD)is associated with hyperphosphorylated tau(pTau)propagation between neurons along synaptically connected networks,in part via extracellular vesicles(EVs).EV biogenesis is triggered by ceramide enrichment at the plasma membrane from neutral sphingomyelinase2(nSMase2)-mediated cleavage of sphingomyelin.We report,for the first time,that human tau expression elevates brain ceramides and nSMase2 activity.Methods To determine the therapeutic benefit of inhibiting this elevation,we evaluated PDDC,the first potent,selective,orally bioavailable,and brain-penetrable nSMase2 inhibitor in the transgenic PS19 AD mouse model.Additionally,we directly evaluated the effect of PDDC on tau propagation in a mouse model where an adeno-associated virus(AAV)encoding P301L/S320F double mutant human tau was stereotaxically-injected unilaterally into the hippocampus.The contralateral transfer of the double mutant human tau to the dentate gyrus was monitored.We examined ceramide levels,histopathological changes,and pTau content within EVs isolated from the mouse plasma.Results Similar to human AD,the PS19 mice exhibited increased brain ceramide levels and nSMase2 activity;both were completely normalized by PDDC treatment.The PS19 mice also exhibited elevated tau immunostaining,thinning of hippocampal neuronal cell layers,increased mossy fiber synaptophysin immunostaining,and glial activation,all of which were pathologic features of human AD.PDDC treatment reduced these changes.The plasma of PDDC-treated PS19 mice had reduced levels of neuronal-and microglial-derived EVs,the former carrying lower pTau levels,compared to untreated mice.In the tau propagation model,PDDC normalized the tau-induced increase in brain ceramides and significantly reduced the amount of tau propagation to the contralateral side.Conclusions PDDC is a first-in-class therapeutic candidate that normalizes elevated brain ceramides and nSMase2 activity,leading to the slowing of tau spread in AD mice.
