Refractory high-entropy alloys (RHEAs) are newly developed candidate materials for high-temperature applications. Among the existing RHEAs, NbMoTaW RHEA possesses the best mechanical properties with ...combined high strength, excellent thermal stability and softening resistance at elevated temperatures. However, the NbMoTaW RHEA is quite brittle at room temperature, which would restrict its application as structural material. Here, TixNbMoTaW RHEAs were developed by alloying Ti in the NbMoTaW RHEA. It shows that the room temperature ductility of the RHEAs increases from 1.9% of the NbMoTaW RHEA to 11.5% of the TiNbMoTaW RHEA, and the yield strength increases from 996MPa of the NbMoTaW RHEA to 1455MPa of the TiNbMoTaW RHEA. In addition, the TixNbMoTaW RHEAs keep stable single BCC structure up to their melt points. The present result indicates that Ti addition could effectively enhance both the ductility and strength of the NbMoTaW RHEA. The combined performance of superior mechanical properties and high thermal stability of the TixNbMoTaW RHEAs promises them an important role in engineering applications.
Previous authors have shown that the transverse relaxivity R2* and frequency shifts that characterize gradient echo signal decay in magnetic resonance imaging are closely associated with the ...distribution of iron and myelin in the brain's white matter. In multiple sclerosis, iron accumulation in brain tissue may reflect a multiplicity of pathological processes. Hence, iron may have the unique potential to serve as an in vivo magnetic resonance imaging tracer of disease pathology. To investigate the ability of iron in tracking multiple sclerosis-induced pathology by magnetic resonance imaging, we performed qualitative histopathological analysis of white matter lesions and normal-appearing white matter regions with variable appearance on gradient echo magnetic resonance imaging at 7 Tesla. The samples used for this study derive from two patients with multiple sclerosis and one non-multiple sclerosis donor. Magnetic resonance images were acquired using a whole body 7 Tesla magnetic resonance imaging scanner equipped with a 24-channel receive-only array designed for tissue imaging. A 3D multi-gradient echo sequence was obtained and quantitative R2* and phase maps were reconstructed. Immunohistochemical stainings for myelin and oligodendrocytes, microglia and macrophages, ferritin and ferritin light polypeptide were performed on 3- to 5-µm thick paraffin sections. Iron was detected with Perl's staining and 3,3′-diaminobenzidine-tetrahydrochloride enhanced Turnbull blue staining. In multiple sclerosis tissue, iron presence invariably matched with an increase in R2*. Conversely, R2* increase was not always associated with the presence of iron on histochemical staining. We interpret this finding as the effect of embedding, sectioning and staining procedures. These processes likely affected the histopathological analysis results but not the magnetic resonance imaging that was obtained before tissue manipulations. Several cellular sources of iron were identified. These sources included oligodendrocytes in normal-appearing white matter and activated macrophages/microglia at the edges of white matter lesions. Additionally, in white matter lesions, iron precipitation in aggregates typical of microbleeds was shown by the Perl's staining. Our combined imaging and pathological study shows that multi-gradient echo magnetic resonance imaging is a sensitive technique for the identification of iron in the brain tissue of patients with multiple sclerosis. However, magnetic resonance imaging-identified iron does not necessarily reflect pathology and may also be seen in apparently normal tissue. Iron identification by multi-gradient echo magnetic resonance imaging in diseased tissues can shed light on the pathological processes when coupled with topographical information and patient disease history.
A series of pseudo-quinary Ti20Zr20Hf20Be20(Cu20-xNix) (x=2.5, 5, 7.5, 10, 12.5, 15, 17.5 and 20at.%) high entropy bulk metallic glasses (HE-BMGs) with large glass forming ability (GFA) were ...successfully prepared by copper mold tilt-casing. The critical diameters (Dc) of these HE-BMGs are all above 12mm. In particular, the developed Ti20Zr20Hf20Be20(Cu7.5Ni12.5) and Ti20Zr20Hf20Be20Ni20 high entropy alloys (HEAs) can be produced in the amorphous state with diameters up to 30mm and 15mm, respectively, which are the largest HE-BMG and quinary HE-BMG hitherto. The two HE-BMGs also exhibit high yield strength, together with the plastic strain values of (3.0±1.1) % and (4.0±0.9) %, respectively. With increasing Ni additions in the pseudo-quinary HEAs, the crystallization growth resistance and thermal stability have been improved, which is apparently due to the sluggish diffusion of the atoms in the HEAs.
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•These high entropy bulk metallic glasses (HE-BMGs) have large glass-forming ability.•These HE-BMGs have a critical diameter up to 30mm.•This is the largest size in the HE-BMGs reported so far.•All the developed HE-BMGs exhibit good mechanical properties.•The developed HE-BMGs possess high thermal stability.
By solving the Muskhelishvili–Omnès integral equations, the scalar form factors of the semileptonic heavy meson decays
D
→
π
ℓ
¯
ν
ℓ
,
D
→
K
¯
ℓ
¯
ν
ℓ
,
B
¯
→
π
ℓ
ν
¯
ℓ
and
B
¯
s
→
K
ℓ
ν
¯
ℓ
are ...simultaneously studied. As input, we employ unitarized heavy meson–Goldstone boson chiral coupled-channel amplitudes for the energy regions not far from thresholds, while, at high energies, adequate asymptotic conditions are imposed. The scalar form factors are expressed in terms of Omnès matrices multiplied by vector polynomials, which contain some undetermined dispersive subtraction constants. We make use of heavy quark and chiral symmetries to constrain these constants, which are fitted to lattice QCD results both in the charm and the bottom sectors, and in this latter sector to the light-cone sum rule predictions close to
q
2
=
0
as well. We find a good simultaneous description of the scalar form factors for the four semileptonic decay reactions. From this combined fit, and taking advantage that scalar and vector form factors are equal at
q
2
=
0
, we obtain
|
V
cd
|
=
0.244
±
0.022
,
|
V
cs
|
=
0.945
±
0.041
and
|
V
ub
|
=
(
4.3
±
0.7
)
×
10
-
3
for the involved Cabibbo–Kobayashi–Maskawa (CKM) matrix elements. In addition, we predict the following vector form factors at
q
2
=
0
:
|
f
+
D
→
η
(
0
)
|
=
0.01
±
0.05
,
|
f
+
D
s
→
K
(
0
)
|
=
0.50
±
0.08
,
|
f
+
D
s
→
η
(
0
)
|
=
0.73
±
0.03
and
|
f
+
B
¯
→
η
(
0
)
|
=
0.82
±
0.08
, which might serve as alternatives to determine the CKM elements when experimental measurements of the corresponding differential decay rates become available. Finally, we predict the different form factors above the
q
2
-
regions accessible in the semileptonic decays, up to moderate energies amenable to be described using the unitarized coupled-channel chiral approach.
In metallic glasses, a high Poisson’s ratio often corresponds to a large plasticity and ductility. Yet the physics underpinning such a connection is still poorly understood. Here through finite ...element simulations, we reveal that a high Poisson’s ratio could promote the inhomogeneous stress distribution in metallic glasses. The inhomogeneous stress field could cause earlier nucleation and easier arrest of shear bands, and therefore better plasticity. Experimental results also show a trend of decreasing shear limit with Poisson’s ratio. These findings suggest that the stress inhomogeneity might be a key to understand the effects of Poisson’s ratio and loading condition on the plastic deformation behaviors of metallic glasses.
The performance of clinical synthetic small diameter vascular grafts remains disappointing due to the fast occlusion caused by thrombosis and intimal hyperplasia formation. Poly(vinyl alcohol) (PVA) ...hydrogels have tunable mechanical properties and a low thrombogenic surface, which suggests its potential value as a small diameter vascular graft material. However, PVA does not support cell adhesion and thus requires surface modification to encourage endothelialization. This study presents a modification of PVA with fucoidan. Fucoidan is a sulfated polysaccharide with anticoagulant and antithrombotic properties, which was shown to potentially increase endothelial cell adhesion and proliferation. By mixing fucoidan with PVA and co-crosslinked by sodium trimetaphosphate (STMP), the modification was achieved without sacrificing mechanical properties. Endothelial cell adhesion and monolayer function were significantly enhanced by the fucoidan modification. In vitro and ex-vivo studies showed low platelet adhesion and activation and decreased thrombin generation with fucoidan modified PVA. The modification proved to be compatible with gamma sterilization. In vivo evaluation of fucoidan modified PVA grafts in rabbits exhibited increased patency rate, endothelialization, and reduced intimal hyperplasia formation. The fucoidan modification presented here benefited the development of PVA vascular grafts and can be adapted to other blood contacting surfaces.
► Fe addition effectively enhances the glass-forming ability of Ti–Zr–Be alloys. ► Ti41Zr25Be28Fe6 bulk metallic glass possesses a large ΔTx (107K). ► Ti41Zr25Be28Fe6 glassy alloy possesses high ...specific strength (4.02×105Nm/kg). ► Ti41Zr25Be28Fe6 glassy alloy exhibits good compressive plasticity (11.2%).
The influence of Fe addition on the glass-forming ability (GFA) and mechanical properties in Ti41Zr25Be34−xFex (x=0, 2, 4, 5, 6, 8, 10at.%) alloys was studied. It has been found that the glass forming-ability and mechanical property of the Ti–Zr–Be alloys could be significantly improved by addition of Fe element. Among the present alloys, the Ti41Zr25Be28Fe6 glassy alloy shows the largest supercooled liquid range ΔTx (ΔTx=107K), and a large critical size of 8mm for fabricating BMGs by copper mold casting method. The yield strength, ultimate strength and plastic strain are dramatically enhanced from 1755, 1914MPa and 2.9% for Ti41Zr25Be34 glassy alloy to 1964MPa, 2268MPa and 11.2% for Ti41Zr25Be28Fe6 glassy alloy, respectively. Especially, the specific strength (yield strength/density) is 4.02×105Nm/kg, greatly larger than that of most other BMGs. The experimental results show that Fe addition is an effective way for improving the glass-forming ability and mechanical properties of Ti–Zr–Be glassy alloy.
Despite much effort, synthetic small diameter vascular grafts still face limited success due to vascular wall thickening known as intimal hyperplasia (IH). Compliance mismatch between graft and ...native vessels has been proposed to be one of a key mechanical factors of synthetic vascular grafts that could contribute to the formation of IH. While many methods have been developed to determine compliance both in vivo and in vitro, the effects of compliance mismatch still remain uncertain. This review aims to explain the biomechanical factors that are responsible for the formation and development of IH and their relationship with compliance mismatch. Furthermore, this review will address the current methods used to measure compliance both in vitro and in vivo. Lastly, current limitations in understanding the connection between the compliance of vascular grafts and the role it plays in the development and progression of IH will be discussed.
The isochronal and isothermal DSC annealing techniques have been employed to investigate the crystallization behavior of a newly developed Ti16.7Zr16.7Hf16.7Cu16.7Ni16.7Be16.7 high entropy bulk ...metallic glass. In non-isothermal condition, the activation energies for glass transition, onset and the first crystallization process were determined by Kissinger equation, to be 331.8±8.0, 215.3±4.5 and 245.5±6.3kJ/mol, respectively. The isothermal kinetics was modeled by the Johnson–Mehl–Avrami (JMA) equation. During the crystallization process, the isothermal activation energy calculated by the Arrhenius equation changes little with an average value of 259.9kJ/mol. The Avrami exponent is in the range from 1.81 to 2.04, indicating that the crystallization process is mainly dominated by growth of particles with a decreasing nucleation rate.
•The first report on crystallization kinetics of high entropy bulk metallic glasses.•Ti16.7Zr16.7Hf16.7Cu16.7Ni16.7Be16.7 alloy was chosen as a model material.•Both non-isothermal and isothermal modes.•The nucleation rate decreases during the crystallization process.
This study aimed to evaluate traditional Chinese medicine (TCM) in improving quality of life (QOL), reducing chemotoxicity and modulating immune function in patients undergoing chemotherapy.
Patients ...with ovarian cancer were randomized to receive either TCM or placebo in addition to standard chemotherapy. The primary outcome was global health status (GHS) score, assessed by European Organization for Research and Treatment of Cancer questionnaire, while the secondary outcomes were other QOL items, chemotoxicity according to World Health Organization criteria and alterations in immune function as measured by immune cells count and the numbers of cytokines-secreting cells.
There was no significant difference in the GHS between the two groups. With adjustment for stage, chemotherapy type, disease status, age and baseline value, emotional function, cognitive function and nausea and vomiting were found to be worse or less improved in the TCM group compared with placebo group after six cycles of chemotherapy. The TCM group had less neutropenia after three cycles (0% grade 4 neutropenia versus 28.6%). There were no other significant differences in terms of chemotoxicity. Lymphocyte counts and cytokine activities decreased less in the TCM group.
TCM did not improve QOL but did have some effects in terms of maintaining immune function.
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