Long Distance Fracture Surface Roughness on a Dendritic Aluminum Alloy

1999 ◽  
Vol 578 ◽  
Author(s):  
J. Aldaco ◽  
F.J. Garza ◽  
M. Hinojosa
Keyword(s):  
Aluminum Alloy ◽  
Fracture Surface ◽  
Correlation Length ◽  
Wide Spectrum ◽  
Charpy Impact ◽  
Long Distance ◽  
Length Scales ◽  
Microstructural Parameters ◽  
Roughness Exponent ◽  
Wide Range

AbstractThe long distance roughness of the fracture surface of a dendritic aluminum alloy is studied over a wide range of length scales. Self-affinity analysis was performed over samples broken in Charpy impact tests. Simultaneous use of Atomic Force Microscopy, SEM and stylus profilometry allowed us to cover a wide spectrum of length scales, spanning over seven decades, from a few nanometers up to one centimeter. The roughness exponent and correlation length were obtained using the variable bandwidth method. For the roughness exponent, a value of 0.8 was obtained, corresponding to the reported universal exponent. Correlation length was found to correspond well to the characteristic length of the largest heterogeneities in the complex microstructure. Our results provide information that can help to improve our understanding of the role of microstructural parameters on crack propagation mechanisms.

Self-affine Fracture Surface Parameters and Their Relationship with Microstructure in a Cast Aluminum Alloy

2002 ◽  
Vol 17 (6) ◽  
pp. 1276-1282 ◽  
Author(s):  
M. Hinojosa ◽  
J. Aldaco
Keyword(s):  
Aluminum Alloy ◽  
Fracture Surface ◽  
The Self ◽  
Cast Aluminum Alloy ◽  
Cast Aluminum ◽  
Force Microscopy ◽  
Fracture Surfaces ◽  
Atomic Force ◽  
Roughness Exponent

The possible role of microstructural features in determining the self-affinity of the fracture surface of a cast aluminum alloy is explored in this work. Fracture surfaces generated both in tension and impact tests were topometrically analyzed by atomic force microscopy, scanning electron microscopy, and stylus profilometry. The roughness exponent exhibited the “universal” value ζ ≈ 0.78, and the correlation length ζ was of the order of the grain size. The brittle intermetallic compounds known to be important in crack initiation did not show any correlation with the self-affine parameters of the resulting fracture surfaces in this particular case.

Self-Affine Analysis of Fractures Surfaces of an Aluminum Alloy Using Fractographic Techniques

2007 ◽  
Vol 560 ◽  
pp. 91-96
Author(s):  
M. Hinojosa ◽  
Edgar I. Morales ◽  
N. Mohamed
Keyword(s):  
Grain Size ◽  
Aluminum Alloy ◽  
Crack Propagation ◽  
Correlation Length ◽  
Hurst Exponent ◽  
Charpy Impact ◽  
The Self ◽  
A Value ◽  
Out Of Plane ◽  
Microstructural Condition

We report the self-affine analysis on fracture surfaces of an A319-type aluminum alloy with different modification and refinement treatments, broken both in Charpy impact and cyclic impulse tests. The in-plane and out-of-plane Hurst exponent as well as the correlation length are obtained using quantitative fractographic techniques. It is found that the Hurst exponent, ζ, has a value of about 0.8 and is not influenced neither by the crack propagation modes nor by the microstructural condition. The self-affine correlation length is found to be related to the grain size resulting from the refining and modifying treatments applied to the alloy.

Long Distance Roughness of Fracture Surfaces in Heterogeneous Materials

1998 ◽  
Vol 539 ◽  
Author(s):  
M. Hinojosa ◽  
E. Bouchaud ◽  
B. Nghiem
Keyword(s):  
Atomic Force Microscopy ◽  
Grain Size ◽  
Correlation Length ◽  
Heterogeneous Materials ◽  
Long Distance ◽  
Force Microscopy ◽  
Fracture Surfaces ◽  
Atomic Force ◽  
Wide Range ◽  
Two Samples

AbstractThe long distance roughness of fatigue fracture surfaces of a nickel-based superalloy is reported for two samples of different grain size. Statistical analysis over a wide range of length scales, from a few nanometers to a few millimeters, using scanning electron microscopy and atomic force microscopy allows to obtain accurately the self-affine correlation length. Long distance fracture profiles of 14,000 points were obtained and digitized from overlapping electron micrographs at a resolution of 0.22 micrometers/point. We have also analyzed the long distance roughness of the mirror zone on a soda-lime glass using atomic force microscopy. In the case of the nickel superalloy, correlation lengths are found to correspond well to the grain size. This result gives information about the mechanism of crack propagation in heterogeneous materials and shows that the correlation length of fracture surfaces is of the order of the largest microstructural heterogeneity.

Cucurbitacins as Anticancer Agents: A Patent Review

2019 ◽  
Vol 14 (2) ◽  
pp. 133-143 ◽  
Author(s):  
Hidayat Hussain ◽  
Ivan R. Green ◽  
Muhammad Saleem ◽  
Khanzadi F. Khattak ◽  
Muhammad Irshad ◽  
...  
Keyword(s):  
Anticancer Agents ◽  
Wide Spectrum ◽  
Biological Effects ◽  
Therapeutic Effects ◽  
Cytotoxic Effects ◽  
Natural Sources ◽  
Oh Groups ◽  
Drug Candidates ◽  
The Past ◽  
Wide Range

Background: Cucurbitacins belong to a group of tetracyclic triterpenoids that display a wide range of biological effects. In the past, numerous cucurbitacins have been isolated from natural sources and many active compounds have been synthesized using the privileged scaffold in order to enhance its cytotoxic effects. Objective: his review covers patents on the therapeutic effects of natural cucurbitacins and their synthetic analogs published during the past decade. By far, the majority of patents published are related to cancer and Structure-Activity Relationships (SAR) of these compounds are included to lend gravitas to this important class of natural products. Methods: The date about the published patents was downloaded via online open access patent databases. Results: Cucurbitacins display significant cytotoxic properties, in particular cucurbitacins B and D which possess very potent effects towards a number of cancer cells. Numerous cucurbitacins isolated from natural sources have been derivatized through chemical modification at the C(2)-OH and C(25)- OH groups. Most importantly, an acyl ester of the C(25)-OH and, iso-propyl, n-propyl and ethyl ether groups of the C(2)-OH demonstrated the most increased cytotoxic activity. Conclusion: The significant cytotoxic effects of natural and semi-synthetic cucurbitacins make them attractive as new drug candidates. Moreover, cucurbitacins have the capability to form conjugates with other anticancer drugs which will synergistically enhance their anticancer effects. The authors believe that in order to get lead compounds, there should be a greater focus on the synthesis of homodimers, heterodimers, and halo derivatives of cucurbitacins. In the opinion of the authors the analysis of the published patents on the cucurbitacins indicates that these compounds can be developed into a regimen to treat a wide spectrum of cancers.

scholarly journals Greater trochanteric pain syndrome: Evaluation and management of a wide spectrum of pathology

2021 ◽  
Vol 9 ◽  
pp. 205031212110225
Author(s):  
Mark A Pianka ◽  
Joseph Serino ◽  
Steven F DeFroda ◽  
Blake M Bodendorfer
Keyword(s):  
Wide Spectrum ◽  
Pain Syndrome ◽  
Operative Management ◽  
Hip Pain ◽  
Greater Trochanteric Pain Syndrome ◽  
Trochanteric Bursitis ◽  
Treatment Indications ◽  
Careful Clinical Examination ◽  
Wide Range ◽  
Tendon Pathology

Greater trochanteric pain syndrome is a common cause of lateral hip pain, encompassing a spectrum of disorders, including trochanteric bursitis, abductor tendon pathology, and external coxa saltans. Greater trochanteric pain syndrome is primarily a clinical diagnosis, and careful clinical examination is essential for accurate diagnosis and treatment. A thorough history and physical exam may be used to help differentiate greater trochanteric pain syndrome from other common causes of hip pain, including osteoarthritis, femoroacetabular impingement, and lumbar stenosis. Although not required for diagnosis, plain radiographs and magnetic resonance imaging may be useful to exclude alternative pathologies or guide treatment of greater trochanteric pain syndrome. The majority of patients with greater trochanteric pain syndrome respond well to conservative management, including physical therapy, non-steroidal anti-inflammatory drugs, and corticosteroid injections. Operative management is typically indicated in patients with chronic symptoms refractory to conservative therapy. A wide range of surgical options, both open and endoscopic, are available and should be guided by the specific etiology of pain. The purpose of this review is to highlight pertinent clinical and radiographic features used in the diagnosis and management of greater trochanteric pain syndrome. In addition, treatment indications, techniques, and outcomes are described.

scholarly journals MXenes for future nanophotonic device applications

Nanophotonics ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 1831-1853
Author(s):  
Jaeho Jeon ◽  
Yajie Yang ◽  
Haeju Choi ◽  
Jin-Hong Park ◽  
Byoung Hun Lee ◽  
...  
Keyword(s):  
Solar Cells ◽  
Transition Metal ◽  
Wide Spectrum ◽  
Building Blocks ◽  
Optoelectronic Device ◽  
High Yield ◽  
Saturable Absorption ◽  
Nanophotonic Device ◽  
Wide Range ◽  
Device Applications

AbstractTwo-dimensional (2D) layers of transition metal carbides, nitrides, or carbonitrides, collectively referred to as MXenes, are considered as the new family of 2D materials for the development of functional building blocks for optoelectronic and photonic device applications. Their advantages are based on their unique and tunable electronic and optical properties, which depend on the modulation of transition metal elements or surface functional groups. In this paper, we have presented a comprehensive review of MXenes to suggest an insightful perspective on future nanophotonic and optoelectronic device applications based on advanced synthesis processes and theoretically predicted or experimentally verified material properties. Recently developed optoelectronic and photonic devices, such as photodetectors, solar cells, fiber lasers, and light-emitting diodes are summarized in this review. Wide-spectrum photodetection with high photoresponsivity, high-yield solar cells, and effective saturable absorption were achieved by exploiting different MXenes. Further, the great potential of MXenes as an electrode material is predicted with a controllable work function in a wide range (1.6–8 eV) and high conductivity (~104 S/cm), and their potential as active channel material by generating a tunable energy bandgap is likewise shown. MXene can provide new functional building blocks for future generation nanophotonic device applications.

scholarly journals Subject-specific multiscale modeling of aortic valve biomechanics

2021 ◽  
Author(s):  
G. Rossini ◽  
A. Caimi ◽  
A. Redaelli ◽  
E. Votta
Keyword(s):  
Aortic Valve ◽  
Boundary Conditions ◽  
Narrow Range ◽  
Radial Strain ◽  
Length Scale ◽  
Length Scales ◽  
Anatomical Features ◽  
Wide Range ◽  
Subject Specific ◽  
Cell Strains

AbstractA Finite Element workflow for the multiscale analysis of the aortic valve biomechanics was developed and applied to three physiological anatomies with the aim of describing the aortic valve interstitial cells biomechanical milieu in physiological conditions, capturing the effect of subject-specific and leaflet-specific anatomical features from the organ down to the cell scale. A mixed approach was used to transfer organ-scale information down to the cell-scale. Displacement data from the organ model were used to impose kinematic boundary conditions to the tissue model, while stress data from the latter were used to impose loading boundary conditions to the cell level. Peak of radial leaflet strains was correlated with leaflet extent variability at the organ scale, while circumferential leaflet strains varied over a narrow range of values regardless of leaflet extent. The dependency of leaflet biomechanics on the leaflet-specific anatomy observed at the organ length-scale is reflected, and to some extent emphasized, into the results obtained at the lower length-scales. At the tissue length-scale, the peak diastolic circumferential and radial stresses computed in the fibrosa correlated with the leaflet surface area. At the cell length-scale, the difference between the strains in two main directions, and between the respective relationships with the specific leaflet anatomy, was even more evident; cell strains in the radial direction varied over a relatively wide range ($$0.36-0.87$$ 0.36 - 0.87 ) with a strong correlation with the organ length-scale radial strain ($$R^{2}= 0.95$$ R 2 = 0.95 ); conversely, circumferential cell strains spanned a very narrow range ($$0.75-0.88$$ 0.75 - 0.88 ) showing no correlation with the circumferential strain at the organ level ($$R^{2}= 0.02$$ R 2 = 0.02 ). Within the proposed simulation framework, being able to account for the actual anatomical features of the aortic valve leaflets allowed to gain insight into their effect on the structural mechanics of the leaflets at all length-scales, down to the cell scale.

Dependence of Microstructures and Mechanical Properties on the Growth Rate and Composition in Directionally Solidified Mg-Gd Alloys

2022 ◽  
Vol 327 ◽  
pp. 82-97
Author(s):  
He Qin ◽  
Guang Yu Yang ◽  
Shi Feng Luo ◽  
Tong Bai ◽  
Wan Qi Jie
Keyword(s):  
Mechanical Properties ◽  
Growth Rate ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Dendritic Structure ◽  
Directionally Solidified ◽  
Dendrite Morphology ◽  
Microstructural Parameters ◽  
Wide Range ◽  
Microstructures And Mechanical Properties

Microstructures and mechanical properties of directionally solidified Mg-xGd (5.21, 7.96 and 9.58 wt.%) alloys were investigated at a wide range of growth rates (V = 10-200 μm/s) under the constant temperature gradient (G = 30 K/mm). The results showed that when the growth rate was 10 μm/s, different interface morphologies were observed in three tested alloys: cellular morphology for Mg-5.21Gd alloy, a mixed morphology of cellular structure and dendritic structure for Mg-7.96Gd alloy and dendrite morphology for Mg-9.58Gd alloy, respectively. Upon further increasing the growth rate, only dendrite morphology was exhibited in all experimental alloys. The microstructural parameters (λ1, λ2) decreased with increasing the growth rate for all the experimental alloy, and the measured λ1 and λ2 values were in good agreement with Trivedi model and Kattamis-Flemings model, respectively. Vickers hardness and the ultimate tensile strength increased with the increase of the growth rate and Gd content, while the elongation decreased gradually. Furthermore, the relationships between the hardness, ultimate tensile strength, the growth rate and the microstructural parameters were discussed and compared with the previous experimental results.

A Review on Meropenem

2021 ◽  
pp. 5034-5038
Author(s):  
Mohsina Abed ◽  
Sara Yousuf
Keyword(s):  
Intravenous Administration ◽  
Wide Spectrum ◽  
Gastrointestinal Haemorrhage ◽  
The Body ◽  
Antibacterial Drug ◽  
Bacterial Strains ◽  
Enhanced Absorption ◽  
Bacterial Cell Death ◽  
Wide Range ◽  
Synthetic Derivative

Meropenem is a new Carbapenem antibacterial agent with wide spectrum of activity for intravenous administration. It is synthetic derivative of Thienamycin. Three analogues of Meropenem are evaluated and active against 18 bacterial strains. Meropenem causes rapid bacterial cell death by covalently binding to penicillin binding proteins (PBS). Structural modification at C-2 position, produced double promoiety prodrug of Meropenem and increases bioavailability of oral administration. Other forms of drug such as liposome and nanoparticles are also available with enhanced absorption. 14C labelled Meropenem prepared from 14C Dimethylamine hydrochloride is used for the analysis of M. tuberculosis transpeptidase. ICI213,689 is the only metabolite of Meropenem and it is inactive. Meropenem penetrates well into the body fluids and tissues including cerebrospinal fluid. Its bioavailability is 100% on intravenous administration. Hence it is used in the treatment of meningitis, febrile neutropenia, anthrax and various other skin and skin structure infections. Dosage reduction is required in patient with reduced renal function but not in hepatic impairment. Seizures, gastrointestinal haemorrhage are observed in patients. Vabmoere is the combination of Meropenem and Vaborbactam which is active against the Carbapenem resistant Enterobacteriacea. Meropenem is an effective broad-spectrum antibacterial drug for the treatment of wide range of infection including polymicrobial infection in both children and adult.

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