This paper provides an overview of alloy and process developments in aluminum and magnesium castings for lightweight automotive applications. Wear-resistant aluminum alloys, creep-resistant and high strength/ductility...This paper provides an overview of alloy and process developments in aluminum and magnesium castings for lightweight automotive applications. Wear-resistant aluminum alloys, creep-resistant and high strength/ductility magnesium alloys have been developed for automotive applications. On the process front, vacuumassisted die casting and high vacuum die casting technologies have been developed for high-integrity body and chassis applications. Thin-wall and hollow casting components are being produced by low-pressure die casting processes for structural applications. Overcasting technology is gaining traction and has enabled mixed material designs for automotive sub-systems such as engine cradles and instrument panel beams. Simulation tools developed to predict the interfacial interactions of the dissimilar components and the structural integrity of the overcast systems are being validated in the casting trials.展开更多
The effect of hot-humid exposure(i.e., 40 C and 98% R.H.) on the quasi-static strength of the adhesive-bonded aluminum alloys was studied. Test results show that the hot-humid exposure leads to the significant decreas...The effect of hot-humid exposure(i.e., 40 C and 98% R.H.) on the quasi-static strength of the adhesive-bonded aluminum alloys was studied. Test results show that the hot-humid exposure leads to the significant decrease in the joint strength and the change of the failure mode from a mixed cohesive and adhesive failure with cohesive failure being dominant to adhesive failure being dominant. Careful analyses of the results reveal that the physical bond is likely responsible for the bond adhesion between L adhesive and aluminum substrates. The reduction in joint strength and the change of the failure mode resulted from the degradation in bond adhesion, which was primarily attributed to the corrosion of aluminum substrate. In addition, the elevated temperature exposure significantly accelerated the corrosion reaction of aluminum, which accelerated the degradation in joint strength.展开更多
Grain refinement is critical for fabricating high-quality Al-Si casting components in the application of automobile and aerospace industries,while the well-known Si-poisoning effect makes it difficult.Nbbased refiners...Grain refinement is critical for fabricating high-quality Al-Si casting components in the application of automobile and aerospace industries,while the well-known Si-poisoning effect makes it difficult.Nbbased refiners offer an effective method to refine Al-Si casting alloys,but their anti Si-poisoning capability is far from being understood.In this work,the grain refining mechanism and the anti Si-poisoning effect in the Al-10 Si/Al-5 Nb-B system were systematically investigated by combining transmission electron microscope,first-principles calculations,and thermodynamic calculations.It is revealed that NbB_(2)provides the main nucleation site in the Al-10 Si ingot inoculated by 0.1 wt.%Nb Al-5 Nb-B refiner.The exposed Nb atoms on the(0001)NbB_(2)and(1-100)NbB_(2)surface can be substituted by Al to form(Al,Nb)B_(2)intermedia layers.In addition,a layer of NbAl_(3)-like compound(NbAl_(3)')can cover the surface of NbB_(2)with the orientation relation of(1-100)[11-20]NbB_(2/)/(110)[110]NbAl_(3)'.Both of the(Al,Nb)B_(2)and NbAl_(3)'intermedia layers contribute to enhancing the nucleation potency of NbB_(2)particles.These discoveries provide fundamental insight to the grain refining mechanism of the Nb-B based refiners for Al-Si casting alloys and are expected to guide the future development of stronger refiners for Al-Si casting alloys.展开更多
Casting aluminum(Al)alloys have been widely used in the automotive industry to improve fuel economy as well as to reduce greenhouse gas(GHG)emissions in the vehicle use phase.However,the casting Al alloys used for loa...Casting aluminum(Al)alloys have been widely used in the automotive industry to improve fuel economy as well as to reduce greenhouse gas(GHG)emissions in the vehicle use phase.However,the casting Al alloys used for load-bearing body and chassis components today are mostly made from primary Al with a low impurity Fe content typically less than 0.2 wt.%,owing to the requirements for high ductility and adequate fatigue strength.Primary Al is made directly from alumina which was refined from aluminum ore(bauxite),using an electrolytic process which consumes a lot of energy and produces GHG emissions that are much higher than those from steel making.The objective of this paper is to present a Unified Casting(UniCast)Al alloy concept as a sustainable materials solution for vehicle lightweighting.The UniCast alloy chemistry is intentionally designed to be more tolerant of Fe impurity.This chemistry can not only satisfy the requirements on castability,but also deliver mechanical properties needed for a variety of thin-walled and thick-walled automotive structural components that are produced by various casting processes.The UniCast alloy concept will contribute to the establishment of a closed-loop recycling system in the future as the shredded scrap obtained from the disposed end-of-life vehicles can be directly recycled back into UniCast alloy ingot with a more efficient sorting process.In addition,by setting the upper limit of Fe content in the UniCast alloy to a higher level,it will become possible to use a high fraction of post-consumer scraps to produce this alloy.To demonstrate the feasibility of this concept,an exemplary UniCast alloy chemistry has been elaborated in this article.Furthermore,challenges and future research opportunities related to the realization of UniCast alloy concept in the automotive industry are discussed.It is hoped that this article will be of great implication to industrial researchers and academicians for making concerted efforts to establish closed-loop recycling of Al castings for the automotive and other transportation industry segments.展开更多
Copper-exchanged chabazite（Cu/CHA） catalysts have been found to be affected by alkali metal and alkaline earth ions. However, the effects of Na＋ ions on Cu/SAPO-34 for ammonia selective catalytic reduction（NH_3-SC...Copper-exchanged chabazite（Cu/CHA） catalysts have been found to be affected by alkali metal and alkaline earth ions. However, the effects of Na＋ ions on Cu/SAPO-34 for ammonia selective catalytic reduction（NH_3-SCR） are still unclear. In order to investigate the mechanism, five samples with various Na contents were synthesized and characterized. It was observed that the introduced Na＋ ion-exchanges with H＋and Cu2＋of Cu/SAPO-34. The exchange of H＋is easier than that of isolated Cu2＋. The exchanged Cu2＋ions aggregate and form ＂CuAl_2O4-like＂ species.The NH_3-SCR activity of Cu/SAPO-34 decreases with increasing Na content, and the loss of isolated Cu2＋and acid sites is responsible for the activity loss.展开更多
The activity and hydrothermal stability of the Rh/Ce_(x)Zr_(1-x)O_(2)(x=0,0.05,0.3,0.5) model three-way catalysts for gasoline vehicle emissions control were investigated in this work.Among the Rh/Ce_(x)Zr_(1-x)O_(2) ...The activity and hydrothermal stability of the Rh/Ce_(x)Zr_(1-x)O_(2)(x=0,0.05,0.3,0.5) model three-way catalysts for gasoline vehicle emissions control were investigated in this work.Among the Rh/Ce_(x)Zr_(1-x)O_(2) samples with different Ce/Zr ratios,the Rh/ZrO_(2) sample exhibits a significantly better activity and hydrothermal stability than the rest of the samples.The impacts of having more Ce components in the Rh/Ce_(x)Zr_(1-x)O_(2) catalysts are associated with the strong Rh-O-Ce interaction that tends to over stabilize the rhodium species.A significant amount of such rhodium atoms can be found in the bulk of the support oxides after a hydrothermal aging at 1050℃ with 10% H_(2)O in air for 12 h.Differently,the sintering of rhodium on the surface of Rh/ZrO_(2) catalysts is the main reason for the catalyst deactivation during the hydrothermal aging.These findings provide an example where high dispersion of supported metal induced by strong metal-support interactions does not necessarily lead to high catalytic activity.展开更多
We report results of a large computational ＇alloy by design＇ study, in which the ＇chemical composition-mechanical strength＇ space is explored for austenitic, ferritic and martensitic creep resistant steels. The ap...We report results of a large computational ＇alloy by design＇ study, in which the ＇chemical composition-mechanical strength＇ space is explored for austenitic, ferritic and martensitic creep resistant steels. The approach used allows simultaneously optimization of alloy composition and processing parameters based on the integration of thermodynamic, thermo-kinetics and a genetic algorithm optimization route. The nature of the optimisation depends on both the intended matrix（ferritic, martensitic or austenitic） and the desired precipitation family. The models are validated by analysing reported strengths of existing steels. All newly designed alloys are predicted to outperform existing high end reference grades.展开更多
The development of maintenance hemodialysis(HD)for end stage kidney disease patients is a success story that continues to save many lives.Nevertheless,intermittent renal replacement therapy is also a source of recurre...The development of maintenance hemodialysis(HD)for end stage kidney disease patients is a success story that continues to save many lives.Nevertheless,intermittent renal replacement therapy is also a source of recurrent stress for patients.Conventional thrice weekly short HD is an imperfect treatment that only partially corrects uremic abnormalities,increases cardiovascular risk,and exacerbates disease burden.Altering cycles of fluid loading associated with cardiac stretching(interdialytic phase)and then fluid unloading(intradialytic phase)likely contribute to cardiac and vascular damage.This unphysiologic treatment profile combined with cyclic disturbances including osmotic and electrolytic shifts may contribute to morbidity in dialysis patients and augment the health burdenof treatment. As such, HD patients are exposed to multiple stressors including cardiocirculatory,inflammatory, biologic, hypoxemic, and nutritional. This cascade of events can be termed thedialysis stress storm and sickness syndrome. Mitigating cardiovascular risk and morbidityassociated with conventional intermittent HD appears to be a priority for improving patientexperience and reducing disease burden. In this in-depth review, we summarize the hidden effectsof intermittent HD therapy, and call for action to improve delivered HD and develop treatmentschedules that are better tolerated and associated with fewer adverse effects.展开更多
Low carbon footprint aluminum structure castings are the mainstream development direction of alu-minum alloys in the future.Enhancing the Fe content tolerance upper limit in casting aluminum alloys is considered an ef...Low carbon footprint aluminum structure castings are the mainstream development direction of alu-minum alloys in the future.Enhancing the Fe content tolerance upper limit in casting aluminum alloys is considered an effective way to promote the application of recycled aluminum production.In this work,it was found that with the Ce and TiCN NPs(nanoparticles)addition simultaneously to A356 alloys,the acicular Fe-rich phases(β-Al 5 FeSi)which damages the properties can be changed into beneficial phases(core-shell heterostructures)for the alloy,and hence the mechanical properties of A356 alloys can be im-proved.The TiCN nanoparticles and rare element Ce play crucial roles in the formation of core-shell het-erostructures.The formation mechanism of core-shell heterostructure was also systematically researched from the perspective of thermodynamics and kinetics.This study provides a simple and feasible strategy to eliminate the harmful effects of Fe impurity and contributes to the industrialization of low carbon footprint aluminum structure castings.展开更多
AIM: The purpose of this analysis was to construct appropriate models to characterise population pharmacokinetics (PK) for PHA-794428 and PK/pharmacodynamics (PD) for the efficacy biomarker Insulin-like Growth factor-...AIM: The purpose of this analysis was to construct appropriate models to characterise population pharmacokinetics (PK) for PHA-794428 and PK/pharmacodynamics (PD) for the efficacy biomarker Insulin-like Growth factor-1 (IGF-1). METHODS: Fifty-six male healthy volunteers were enrolled into a clinical study. Subjects received in a randomised manner 3 subcutaneous injections over 3 periods: i) 3.6 mg recombinant human growth hormone (rhGH), ii) PHA-794428 0, 3, 10, 30, 60, 100, 300 or 500 μg/kg, and iii) PHA-794428 0, 10, or 30 μg/kg. Both PK and IGF-1 data were collected up to 336 h post-dose. The PK and PK/PD models were constructed in 3 stages: i) the PK model was developed, ii) the PK parameters were fixed during IGF-1 model building, iii) PK and IGF-1 data were analysed simultaneously. RESULTS: PHA-794428 exhibited non-linearity with respect to dose. A one-compartment disposition model with parallel linear and non-linear elimination most appropriately described the PHA-794428 serum concentrations versus time data. The absorption of PHA-794428 was characterised as a first-order process involving two absorption rate constants. The nonlinear elimination, characterised in terms of the maximal elimination capacity (Vmax=91.5 μg/h for 70 kg) and Michaelis-Menten constant (Km=73.9 μg/L) describing the concentration at which elimination is at half Vmax. The non-linear elimination pathway is approximately 10 times higher than the linear route (0.129 L/h). PHA-794428 has a limited distribution in the blood (V=4.4 L), due to its large molecular weight. Serum IGF-1 concentrations versus time data were best described by an indirect response model with PEG-hGH stimulating IGF-1 production rate. Drug effect was appropriately characterised by a maximum effect (Emax) model. The maximal IGF-1 production rate could increase up to 8-fold across the dose range studied. The PHA-794428 concentration at half Emax (EC50) is 56.5 ng/mL. A negative feedback loop was incorporated into the PK/IGF-1 model. The maximal inhibition (Imax) of IGF-1 on endogenous GH secretion was set to 100% and IC50, the IGF-1 concentration decreasing GH secretion by 50%, was 382 ng/mL. Placebo effect was negligible. CONCLUSION: Serum data of PHA-794428 and IGF-1 could be adequately described by PK and PK/IGF-1 models, which were successfully used to predict the doses and time course of PK and IGF-1 and study design for the subsequent clinical trials in adult patients with growth hormone deficiency (AGHD). PK/PD modelling and simulation demonstrated that PHA-794428 has a potential to return low IGF-1 levels to within the normal range by weekly dosing.展开更多
The objective is to identify the Infra-Red (IR) spectral analysis of the diterpene glycosides present in the commercial extracts of Stevia rebaudiana was achieved by PerkinElmer Spectrum 400 Fourier Transform (FT) spe...The objective is to identify the Infra-Red (IR) spectral analysis of the diterpene glycosides present in the commercial extracts of Stevia rebaudiana was achieved by PerkinElmer Spectrum 400 Fourier Transform (FT) spectrometer employing a PerkinElmer Universal Attenuated Total Reflection (ATR) accessory. Using this technique the IR spectral pattern of 15 steviol glycosides which belongs to three different classes of ent-kaurane diterpene glycosides namely ent-13-hydroxykaur-16-en-19-oic acid, ent-13-hydroxykaur-15-en-19-oic acid, and 13-methyl-16-oxo-17-norent- kauran-19-oic acid were identified. From the wave numbers found for all 15 steviol glycosides, it was observed that that though there are differences in the number of sugar units, nature of sugar units, and their attachments;there are not any notable differences in the IR values.展开更多
Background: 5-HT4receptors in cortex and hippocampus area are considered as a possible target for modulation of cognitive functions in Alzheimer’s disease (AD). A systems pharmacology approach was adopted to evaluate...Background: 5-HT4receptors in cortex and hippocampus area are considered as a possible target for modulation of cognitive functions in Alzheimer’s disease (AD). A systems pharmacology approach was adopted to evaluate the potential of the 5-HT4 modulation in providing beneficialeffects on cognition in AD. Methods: A serotonergic synaptic cleft model was developed by integrating serotonin firing, release, synaptic half-life, drug/tracer properties (affinity and agonism) as inputs and5-HT4 activity as output. The serotonergic model was calibrated using bothinvivo data on free 5-HT levels in preclinical models and human imaging data. The model was further expanded to other neurontransmitter systems and incorporated into a computer-based cortical network model which implemented the physiology of 12 different membrane CNS targets. A biophysically realistic, multi-compartment model of 80 pyramidal cells and 40 interneurons was further calibrated usingdata reported for working memory tasks in healthyhumans and schizophrenia patients. Model output was the duration of the network firing activity in response to an external stimulus. Alzheimer’s disease (AD) pathology, in particular synapse and neuronal cell loss in addition to cholinergic deficits, was calibrated to align with the natural clinical disease progression. The model was used to provide insights into the effect of 5-HT4 activation on working memory and to prospectively simulate the response of PF- 04995274, a 5-HT4partial agonist, in a scopolamine-reversal trial in healthy human subjects. Results: The model output suggested a beneficial effect of 5-HT4 agonism on working memory. The model also projected no effect or an exacerbation of scopolamine impairment for low in- trinsic activity 5-HT4agonists, which was supported by the subsequent human trial outcome. The clinical prediction of the disease model strongly suggests that 5-HT4 agonists with high intrinsic activity may have a beneficial effect on cognition in AD patients.展开更多
A high throughput screen of the Pfizer compound collection was carried out using a hepatitis C virus (HCV) genotype 1b subgenomic replicon cell line. Those confirmed hits that demonstrated broad spectrum activity with...A high throughput screen of the Pfizer compound collection was carried out using a hepatitis C virus (HCV) genotype 1b subgenomic replicon cell line. Those confirmed hits that demonstrated broad spectrum activity without overt cytotoxicity were further evaluated, leading to the identification of a series of pyrrolopyridines with excellent antiviral activity in a fully infectious HCV cell-based assay and pharmacokinetic properties.展开更多
Hydrogen adsorption isotherms were measured at ambient temperature to pressures exceeding 300 bar for three benchmark adsorbents: two metal-organic frameworks, Cu3(btc)2 (btc = 1,3,5-benzenetricarboxylate) and Zn4O(bt...Hydrogen adsorption isotherms were measured at ambient temperature to pressures exceeding 300 bar for three benchmark adsorbents: two metal-organic frameworks, Cu3(btc)2 (btc = 1,3,5-benzenetricarboxylate) and Zn4O(btb)2 (btb = 1,3,5-benzenetribenzoate), and the activated carbon MSC-30. The Dubinin-Astakhov model was applied to calculated absolute adsorption isotherms as a function of the fugacity to determine the adsorption enthalpy at ambient temperature. Comparisons of the calculated enthalpies and the surface excess concentration (excess adsorption per square meter of surface) show that Zn4O(btb)2 has an adsorption enthalpy comparable to MSC-30, but that the spacing between adsorbed molecules is much larger.展开更多
Multi-gram synthesis and densification is presented for a porous polymer network (PPN-4) examined as a possible vehicular methane storage material. Compaction at 17,000 psi doubled the bulk density of the material and...Multi-gram synthesis and densification is presented for a porous polymer network (PPN-4) examined as a possible vehicular methane storage material. Compaction at 17,000 psi doubled the bulk density of the material and unexpectedly increased microporosity within the material. As a result, the densified material exhibits higher excess gravimetric methane uptake and improved total volumetric methane uptake relative to the powder.展开更多
This paper presents an analysis of the electric power flows in a hot rolling mill plant using a power quality analyzer and developing simulation models with Matlab-Simulink. The model inputs have been taken from proce...This paper presents an analysis of the electric power flows in a hot rolling mill plant using a power quality analyzer and developing simulation models with Matlab-Simulink. The model inputs have been taken from process data by the process computer of the plant. Data from different rolling campaigns have been analysed. A STATCOM （static synchronous compensator） with a control strategy based on voltage oriented control with d-q coordinates is used as solution to improve the reactive compensation as well as to minimize the voltage fluctuations and sags effect. The overall electric model has been simulated with the STATCOM to check the improvement in the voltage stability and the consumption.展开更多
文摘This paper provides an overview of alloy and process developments in aluminum and magnesium castings for lightweight automotive applications. Wear-resistant aluminum alloys, creep-resistant and high strength/ductility magnesium alloys have been developed for automotive applications. On the process front, vacuumassisted die casting and high vacuum die casting technologies have been developed for high-integrity body and chassis applications. Thin-wall and hollow casting components are being produced by low-pressure die casting processes for structural applications. Overcasting technology is gaining traction and has enabled mixed material designs for automotive sub-systems such as engine cradles and instrument panel beams. Simulation tools developed to predict the interfacial interactions of the dissimilar components and the structural integrity of the overcast systems are being validated in the casting trials.
基金funded by General Motors Global Research and Development Center(Grant No.:PS21025708)
文摘The effect of hot-humid exposure(i.e., 40 C and 98% R.H.) on the quasi-static strength of the adhesive-bonded aluminum alloys was studied. Test results show that the hot-humid exposure leads to the significant decrease in the joint strength and the change of the failure mode from a mixed cohesive and adhesive failure with cohesive failure being dominant to adhesive failure being dominant. Careful analyses of the results reveal that the physical bond is likely responsible for the bond adhesion between L adhesive and aluminum substrates. The reduction in joint strength and the change of the failure mode resulted from the degradation in bond adhesion, which was primarily attributed to the corrosion of aluminum substrate. In addition, the elevated temperature exposure significantly accelerated the corrosion reaction of aluminum, which accelerated the degradation in joint strength.
基金supported by the National Natural Science Foundation of China(51871138)Science and Technology Commission of Shanghai Municipality(19010500400)the 111 project(No.D16002)。
文摘Grain refinement is critical for fabricating high-quality Al-Si casting components in the application of automobile and aerospace industries,while the well-known Si-poisoning effect makes it difficult.Nbbased refiners offer an effective method to refine Al-Si casting alloys,but their anti Si-poisoning capability is far from being understood.In this work,the grain refining mechanism and the anti Si-poisoning effect in the Al-10 Si/Al-5 Nb-B system were systematically investigated by combining transmission electron microscope,first-principles calculations,and thermodynamic calculations.It is revealed that NbB_(2)provides the main nucleation site in the Al-10 Si ingot inoculated by 0.1 wt.%Nb Al-5 Nb-B refiner.The exposed Nb atoms on the(0001)NbB_(2)and(1-100)NbB_(2)surface can be substituted by Al to form(Al,Nb)B_(2)intermedia layers.In addition,a layer of NbAl_(3)-like compound(NbAl_(3)')can cover the surface of NbB_(2)with the orientation relation of(1-100)[11-20]NbB_(2/)/(110)[110]NbAl_(3)'.Both of the(Al,Nb)B_(2)and NbAl_(3)'intermedia layers contribute to enhancing the nucleation potency of NbB_(2)particles.These discoveries provide fundamental insight to the grain refining mechanism of the Nb-B based refiners for Al-Si casting alloys and are expected to guide the future development of stronger refiners for Al-Si casting alloys.
基金the National Natural Science Foundation of China(No.51904352)the Scientific Research Foundation of Hunan Provincial Education Department,China(No.22A0004).
文摘Casting aluminum(Al)alloys have been widely used in the automotive industry to improve fuel economy as well as to reduce greenhouse gas(GHG)emissions in the vehicle use phase.However,the casting Al alloys used for load-bearing body and chassis components today are mostly made from primary Al with a low impurity Fe content typically less than 0.2 wt.%,owing to the requirements for high ductility and adequate fatigue strength.Primary Al is made directly from alumina which was refined from aluminum ore(bauxite),using an electrolytic process which consumes a lot of energy and produces GHG emissions that are much higher than those from steel making.The objective of this paper is to present a Unified Casting(UniCast)Al alloy concept as a sustainable materials solution for vehicle lightweighting.The UniCast alloy chemistry is intentionally designed to be more tolerant of Fe impurity.This chemistry can not only satisfy the requirements on castability,but also deliver mechanical properties needed for a variety of thin-walled and thick-walled automotive structural components that are produced by various casting processes.The UniCast alloy concept will contribute to the establishment of a closed-loop recycling system in the future as the shredded scrap obtained from the disposed end-of-life vehicles can be directly recycled back into UniCast alloy ingot with a more efficient sorting process.In addition,by setting the upper limit of Fe content in the UniCast alloy to a higher level,it will become possible to use a high fraction of post-consumer scraps to produce this alloy.To demonstrate the feasibility of this concept,an exemplary UniCast alloy chemistry has been elaborated in this article.Furthermore,challenges and future research opportunities related to the realization of UniCast alloy concept in the automotive industry are discussed.It is hoped that this article will be of great implication to industrial researchers and academicians for making concerted efforts to establish closed-loop recycling of Al castings for the automotive and other transportation industry segments.
基金financially supported by the National Key Research and Development program(No.2017YFC0211302)the National Natural Science Foundation of China(No.21676195)+1 种基金the Science Fund of State Key Laboratory of Engine Reliability(No.skler-201714)finical support from GM Global Research&Development(No.GAC1539)
文摘Copper-exchanged chabazite（Cu/CHA） catalysts have been found to be affected by alkali metal and alkaline earth ions. However, the effects of Na＋ ions on Cu/SAPO-34 for ammonia selective catalytic reduction（NH_3-SCR） are still unclear. In order to investigate the mechanism, five samples with various Na contents were synthesized and characterized. It was observed that the introduced Na＋ ion-exchanges with H＋and Cu2＋of Cu/SAPO-34. The exchange of H＋is easier than that of isolated Cu2＋. The exchanged Cu2＋ions aggregate and form ＂CuAl_2O4-like＂ species.The NH_3-SCR activity of Cu/SAPO-34 decreases with increasing Na content, and the loss of isolated Cu2＋and acid sites is responsible for the activity loss.
基金Project supported by the National Key Research and Development Program(2017YFC0211003)GM Global Research and Development(GAC 2696)。
文摘The activity and hydrothermal stability of the Rh/Ce_(x)Zr_(1-x)O_(2)(x=0,0.05,0.3,0.5) model three-way catalysts for gasoline vehicle emissions control were investigated in this work.Among the Rh/Ce_(x)Zr_(1-x)O_(2) samples with different Ce/Zr ratios,the Rh/ZrO_(2) sample exhibits a significantly better activity and hydrothermal stability than the rest of the samples.The impacts of having more Ce components in the Rh/Ce_(x)Zr_(1-x)O_(2) catalysts are associated with the strong Rh-O-Ce interaction that tends to over stabilize the rhodium species.A significant amount of such rhodium atoms can be found in the bulk of the support oxides after a hydrothermal aging at 1050℃ with 10% H_(2)O in air for 12 h.Differently,the sintering of rhodium on the surface of Rh/ZrO_(2) catalysts is the main reason for the catalyst deactivation during the hydrothermal aging.These findings provide an example where high dispersion of supported metal induced by strong metal-support interactions does not necessarily lead to high catalytic activity.
基金financial support from the Chinese Scholarship Council(CSC)and internal funding of TU Delft
文摘We report results of a large computational ＇alloy by design＇ study, in which the ＇chemical composition-mechanical strength＇ space is explored for austenitic, ferritic and martensitic creep resistant steels. The approach used allows simultaneously optimization of alloy composition and processing parameters based on the integration of thermodynamic, thermo-kinetics and a genetic algorithm optimization route. The nature of the optimisation depends on both the intended matrix（ferritic, martensitic or austenitic） and the desired precipitation family. The models are validated by analysing reported strengths of existing steels. All newly designed alloys are predicted to outperform existing high end reference grades.
文摘The development of maintenance hemodialysis(HD)for end stage kidney disease patients is a success story that continues to save many lives.Nevertheless,intermittent renal replacement therapy is also a source of recurrent stress for patients.Conventional thrice weekly short HD is an imperfect treatment that only partially corrects uremic abnormalities,increases cardiovascular risk,and exacerbates disease burden.Altering cycles of fluid loading associated with cardiac stretching(interdialytic phase)and then fluid unloading(intradialytic phase)likely contribute to cardiac and vascular damage.This unphysiologic treatment profile combined with cyclic disturbances including osmotic and electrolytic shifts may contribute to morbidity in dialysis patients and augment the health burdenof treatment. As such, HD patients are exposed to multiple stressors including cardiocirculatory,inflammatory, biologic, hypoxemic, and nutritional. This cascade of events can be termed thedialysis stress storm and sickness syndrome. Mitigating cardiovascular risk and morbidityassociated with conventional intermittent HD appears to be a priority for improving patientexperience and reducing disease burden. In this in-depth review, we summarize the hidden effectsof intermittent HD therapy, and call for action to improve delivered HD and develop treatmentschedules that are better tolerated and associated with fewer adverse effects.
基金We would like to thank the Analytical&Testing Center of Sichuan University for providing the DFT simulation tools.We also would like to thank Ruifeng Zhang for providing the software Miedema Calculator4.3.
文摘Low carbon footprint aluminum structure castings are the mainstream development direction of alu-minum alloys in the future.Enhancing the Fe content tolerance upper limit in casting aluminum alloys is considered an effective way to promote the application of recycled aluminum production.In this work,it was found that with the Ce and TiCN NPs(nanoparticles)addition simultaneously to A356 alloys,the acicular Fe-rich phases(β-Al 5 FeSi)which damages the properties can be changed into beneficial phases(core-shell heterostructures)for the alloy,and hence the mechanical properties of A356 alloys can be im-proved.The TiCN nanoparticles and rare element Ce play crucial roles in the formation of core-shell het-erostructures.The formation mechanism of core-shell heterostructure was also systematically researched from the perspective of thermodynamics and kinetics.This study provides a simple and feasible strategy to eliminate the harmful effects of Fe impurity and contributes to the industrialization of low carbon footprint aluminum structure castings.
文摘AIM: The purpose of this analysis was to construct appropriate models to characterise population pharmacokinetics (PK) for PHA-794428 and PK/pharmacodynamics (PD) for the efficacy biomarker Insulin-like Growth factor-1 (IGF-1). METHODS: Fifty-six male healthy volunteers were enrolled into a clinical study. Subjects received in a randomised manner 3 subcutaneous injections over 3 periods: i) 3.6 mg recombinant human growth hormone (rhGH), ii) PHA-794428 0, 3, 10, 30, 60, 100, 300 or 500 μg/kg, and iii) PHA-794428 0, 10, or 30 μg/kg. Both PK and IGF-1 data were collected up to 336 h post-dose. The PK and PK/PD models were constructed in 3 stages: i) the PK model was developed, ii) the PK parameters were fixed during IGF-1 model building, iii) PK and IGF-1 data were analysed simultaneously. RESULTS: PHA-794428 exhibited non-linearity with respect to dose. A one-compartment disposition model with parallel linear and non-linear elimination most appropriately described the PHA-794428 serum concentrations versus time data. The absorption of PHA-794428 was characterised as a first-order process involving two absorption rate constants. The nonlinear elimination, characterised in terms of the maximal elimination capacity (Vmax=91.5 μg/h for 70 kg) and Michaelis-Menten constant (Km=73.9 μg/L) describing the concentration at which elimination is at half Vmax. The non-linear elimination pathway is approximately 10 times higher than the linear route (0.129 L/h). PHA-794428 has a limited distribution in the blood (V=4.4 L), due to its large molecular weight. Serum IGF-1 concentrations versus time data were best described by an indirect response model with PEG-hGH stimulating IGF-1 production rate. Drug effect was appropriately characterised by a maximum effect (Emax) model. The maximal IGF-1 production rate could increase up to 8-fold across the dose range studied. The PHA-794428 concentration at half Emax (EC50) is 56.5 ng/mL. A negative feedback loop was incorporated into the PK/IGF-1 model. The maximal inhibition (Imax) of IGF-1 on endogenous GH secretion was set to 100% and IC50, the IGF-1 concentration decreasing GH secretion by 50%, was 382 ng/mL. Placebo effect was negligible. CONCLUSION: Serum data of PHA-794428 and IGF-1 could be adequately described by PK and PK/IGF-1 models, which were successfully used to predict the doses and time course of PK and IGF-1 and study design for the subsequent clinical trials in adult patients with growth hormone deficiency (AGHD). PK/PD modelling and simulation demonstrated that PHA-794428 has a potential to return low IGF-1 levels to within the normal range by weekly dosing.
文摘The objective is to identify the Infra-Red (IR) spectral analysis of the diterpene glycosides present in the commercial extracts of Stevia rebaudiana was achieved by PerkinElmer Spectrum 400 Fourier Transform (FT) spectrometer employing a PerkinElmer Universal Attenuated Total Reflection (ATR) accessory. Using this technique the IR spectral pattern of 15 steviol glycosides which belongs to three different classes of ent-kaurane diterpene glycosides namely ent-13-hydroxykaur-16-en-19-oic acid, ent-13-hydroxykaur-15-en-19-oic acid, and 13-methyl-16-oxo-17-norent- kauran-19-oic acid were identified. From the wave numbers found for all 15 steviol glycosides, it was observed that that though there are differences in the number of sugar units, nature of sugar units, and their attachments;there are not any notable differences in the IR values.
文摘Background: 5-HT4receptors in cortex and hippocampus area are considered as a possible target for modulation of cognitive functions in Alzheimer’s disease (AD). A systems pharmacology approach was adopted to evaluate the potential of the 5-HT4 modulation in providing beneficialeffects on cognition in AD. Methods: A serotonergic synaptic cleft model was developed by integrating serotonin firing, release, synaptic half-life, drug/tracer properties (affinity and agonism) as inputs and5-HT4 activity as output. The serotonergic model was calibrated using bothinvivo data on free 5-HT levels in preclinical models and human imaging data. The model was further expanded to other neurontransmitter systems and incorporated into a computer-based cortical network model which implemented the physiology of 12 different membrane CNS targets. A biophysically realistic, multi-compartment model of 80 pyramidal cells and 40 interneurons was further calibrated usingdata reported for working memory tasks in healthyhumans and schizophrenia patients. Model output was the duration of the network firing activity in response to an external stimulus. Alzheimer’s disease (AD) pathology, in particular synapse and neuronal cell loss in addition to cholinergic deficits, was calibrated to align with the natural clinical disease progression. The model was used to provide insights into the effect of 5-HT4 activation on working memory and to prospectively simulate the response of PF- 04995274, a 5-HT4partial agonist, in a scopolamine-reversal trial in healthy human subjects. Results: The model output suggested a beneficial effect of 5-HT4 agonism on working memory. The model also projected no effect or an exacerbation of scopolamine impairment for low in- trinsic activity 5-HT4agonists, which was supported by the subsequent human trial outcome. The clinical prediction of the disease model strongly suggests that 5-HT4 agonists with high intrinsic activity may have a beneficial effect on cognition in AD patients.
文摘A high throughput screen of the Pfizer compound collection was carried out using a hepatitis C virus (HCV) genotype 1b subgenomic replicon cell line. Those confirmed hits that demonstrated broad spectrum activity without overt cytotoxicity were further evaluated, leading to the identification of a series of pyrrolopyridines with excellent antiviral activity in a fully infectious HCV cell-based assay and pharmacokinetic properties.
文摘Hydrogen adsorption isotherms were measured at ambient temperature to pressures exceeding 300 bar for three benchmark adsorbents: two metal-organic frameworks, Cu3(btc)2 (btc = 1,3,5-benzenetricarboxylate) and Zn4O(btb)2 (btb = 1,3,5-benzenetribenzoate), and the activated carbon MSC-30. The Dubinin-Astakhov model was applied to calculated absolute adsorption isotherms as a function of the fugacity to determine the adsorption enthalpy at ambient temperature. Comparisons of the calculated enthalpies and the surface excess concentration (excess adsorption per square meter of surface) show that Zn4O(btb)2 has an adsorption enthalpy comparable to MSC-30, but that the spacing between adsorbed molecules is much larger.
基金supported by a contract between General Motors Company and Tsinghua University,National Natural Science Foundation of China(61425027,60736027,61021063,61074034,61174105)
文摘Multi-gram synthesis and densification is presented for a porous polymer network (PPN-4) examined as a possible vehicular methane storage material. Compaction at 17,000 psi doubled the bulk density of the material and unexpectedly increased microporosity within the material. As a result, the densified material exhibits higher excess gravimetric methane uptake and improved total volumetric methane uptake relative to the powder.
文摘This paper presents an analysis of the electric power flows in a hot rolling mill plant using a power quality analyzer and developing simulation models with Matlab-Simulink. The model inputs have been taken from process data by the process computer of the plant. Data from different rolling campaigns have been analysed. A STATCOM （static synchronous compensator） with a control strategy based on voltage oriented control with d-q coordinates is used as solution to improve the reactive compensation as well as to minimize the voltage fluctuations and sags effect. The overall electric model has been simulated with the STATCOM to check the improvement in the voltage stability and the consumption.
