On the numerical and mesh-dependent parameters in a computationally enhanced phase-field fracture model coupled with a novel mesh refinement strategy

The phase-field method has been proven as a robust and computationally efficient approach to model the propagation of fractures in brittle solids. However, the performance of this technique in the context of finite element method can be questioned due to restrictions in the mesh structure and the element size to capture the fracture as a diffusive damaged region. This study is dedicated to developing a methodology for finding an appropriate length-scale parameter to model the fracturing process in a way that matches the physical character of failure in materials. The fracture process zone is chosen as the key feature in this study to propose relationships for estimating the length-scale parameter based on the tensile strength and cracking properties, and the robustness of the method is verified using experimental data. To employ the phase-field method in modelling large-scale domains and complex geometries, a novel mesh refinement strategy is developed to increase the computational efficiency based on predicting a corrected tensile strength limit depending on the element size to capture the crack-tip effectively. The proposed mesh refinement strategy reduces the computational effort significantly. Reliability and robustness of the developed relationships are successfully examined by simulating benchmark cases and comparisons with physically measured data

Models for Light-Cone Meson Distribution Amplitudes

Leading-twist distribution amplitudes (DAs) of light mesons like pi,rho etc. describe the leading nonperturbative hadronic contributions to exclusive QCD reactions at large energy transfer, for instance electromagnetic form factors. They also enter B decay amplitudes described in QCD factorisation, in particular nonleptonic two-body decays. Being nonperturbative quantities, DAs cannot be calculated from first principles, but have to be described by models. Most models for DAs rely on a fixed order conformal expansion, which is strictly valid for large factorisation scales, but not always sufficient in phenomenological applications. We derive models for DAs that are valid to all orders in the conformal expansion and characterised by a small number of parameters which are related to experimental observables.Comment: 19 pages, 10 figure

A multiloop improvement of non-singlet QCD evolution equations

An approach is elaborated for calculation of "all loop" contributions to the non-singlet evolution kernels from the diagrams with renormalon chain insertions. Closed expressions are obtained for sums of contributions to kernels $P(z)$ for the DGLAP equation and $V(x,y)$ for the "nonforward" ER-BL equation from these diagrams that dominate for a large value of $b_0$, the first $\beta$-function coefficient. Calculations are performed in the covariant $\xi$-gauge in a MS-like scheme. It is established that a special choice of the gauge parameter $\xi=-3$ generalizes the standard "naive nonabelianization" approximation. The solutions are obtained to the ER-BL evolution equation (taken at the "all loop" improved kernel), which are in form similar to one-loop solutions. A consequence for QCD descriptions of hard processes and the benefits and incompleteness of the approach are briefly discussed.Comment: 13 pages, revtex, 2 figures are enclosed as eps-file, the text style and figures are corrected following version, accepted for publication to Phys. Rev.

Superconformal constraints for QCD conformal anomalies

Anomalous superconformal Ward identities and commutator algebra in N = 1 super-Yang-Mills theory give rise to constraints between the QCD special conformal anomalies of conformal composite operators. We evaluate the superconformal anomalies that appear in the product of renormalized conformal operators and the trace anomaly in the supersymmetric spinor current and check the constraints at one-loop order. In this way we prove the universality of QCD conformal anomalies, which define the non-diagonal part of the anomalous dimension matrix responsible for scaling violations of exclusive QCD amplitudes at the next-to-leading order.Comment: 30 pages, 2 figures, LaTe

Investigating the Impact of Collagen-Chitosan Derived from Scomberomorus Guttatus and Shrimp Skin on Second-Degree Burn in Rats Model

Background: The present study focused on burning as one of the main causes of mortality with detrimental economic and social effects in the world. The purpose of this study was to investigate the impact of collagen-chitosan gel extracted from Scomberomorus guttatus and shrimp skin in the treatment of second degree burn healing among rats. Materials & method: To fulfill the purpose of the study, chitosan and collagen were extracted respectively from shrimp and Scomberomorus guttatus skin waste by the acid-based method and were evaluated by using Pico Tag, SDS-PAGE. The burn wound healing efficiency of marine collagen-chitosan gel was examined in vivo using rats. Three different ratios of collagen and chitosan blend (Col-CH, 1:3, 1:1 and 3:1) were prepared to obtain the most effective Col-CH gel for burn wound healing and were compared to the animals treated with silver sulfadiazine ointment. Healing burn wound was studied by measuring wound surface area with Image J and histopathologic examination was carried out based on the mean of epithelialization, fibroblastic cells, acute and chronic inflammatory cells, angiogenesis, structure collagen and the amount of collagen on days 15 and 25 post-burn. Results: The results of SDS-PAGE indicated that the extracted collagen was type I and it was composed of two α (α1 and α2) chains. Amino acid analysis showed a much higher glaycin content in extracted collagen which amounted to one-third of the total amino. The wound surface measurement showed a significant reduction in wound size in the group treated with Col-CH (3:1) compared to silver-sulfadiazine treated group on 15th and 25th days. Histopathological findings represented a high score in epithelialization, collagen, collagen structure, fibroblast cell and a decrease in inflammatory cells infiltration in Col-CH (3:1) treated group on 25th day. The most obvious finding of the present study is that chitosan-collagen gel (3:1) represented a better efficacy compared to sulfadiazine in burn wound healing on day 25 post-burn. © 2021 The Japanese Society for Regenerative Medicin

Complete next-to-leading order perturbative QCD prediction for the pion electromagnetic form factor

We present the results of a complete leading-twist next-to-leading order (NLO) QCD analysis of the spacelike pion electromagnetic form factor at large momentum transfer Q. We have studied their dependence on the form of the pion distribution amplitude. For a given distribution amplitude, we have examined the sensitivity of the predictions to the choice of the renormalization and factorization scales. Theoretical uncertainty of the LO results related to the renormalization scale ambiguity has been significantly reduced by including the NLO corrections. Adopting the criteria according to which a NLO prediction is considered reliable if, both, the ratio of the NLO to LO contributions and the strong coupling constant are reasonably small, we find that reliable perturbative predictions for the pion electromagnetic form factor with all distribution amplitudes considered can already be made at a momentum transfer Q<10 GeV, with corrections to the LO results being typically of the order of ~ 20%. To check our predictions and to discriminate between the distribution amplitudes, it is necessary to obtain experimental data extending to higher values of Q.Comment: 39 pages, RevTex, 17 figures included; revised version (an error in the analytical expression for T_H corrected, numerical results correspondigly modified; presentation of the results modified to some extent and some points discussed in more detail after referees reports

Formation of nanostructured surface layer, the white layer, through solid particles impingement during slurry erosion in a martensitic medium-carbon steel

The extremely altered topmost surface layer, known as the white layer, formed in a medium-carbon low-alloy steel as result of impacts by angular 10–12 mm granite particles during the slurry erosion process is comprehensively investigated. For this purpose, the characteristics, morphology, and formation mechanism of this white layer are described based on the microstructural observations using optical, scanning and transmission electron microscopies as well as nanoindentation hardness measurements and modelling of surface deformation. The white layer exhibits a nanocrystalline structure consisting of ultrafine grains with an average size of 200 nm. It has a nanohardness level of around 10.1 GPa, considerably higher than that of untempered martensitic bulk material (5.7 GPa) achieved by an induction hardening treatment. The results showed that during the high-speed slurry erosion process, solid particle impacts brought forth conditions of high strain, high strain rate, and multi-directional strain paths. This promoted formation of a cell-type structure at first and later, after increasing the number of impacts, development of subgrains following by subgrain rotation and eventually formation of a nanocrystalline structure with ultra-high hardness. The model confirmed that high strain conditions - much higher than required for the onset of plastic deformation - can be achieved on the surface resulting in severe microstructural and property changes during the slurry erosion test.publishedVersionPeer reviewe

The Evolution of the Pion Distribution Amplitude in Next-to-Leading Order

The evolution of the pion distribution amplitude in next-to-leading order is studied for a fixed and a running coupling constant. In both cases, the evolution provides a logarithmic modification in the endpoint region. Assuming a simple parameterization of the distribution amplitude at a scale of $Q_0\sim 0.5\ \rm GeV$, it is shown numerically that these effects are large enough at $Q\sim 2\ \rm GeV$ that they have to be taken into account in the next-to-leading-order analysis for exclusive processes. Alternatively, by introducing a new distribution amplitude that evolves more smoothly, this logarithmic modification can be included in the hard-scattering part of the considered process.Comment: 17 pages LaTeX + 3 uuencoded and compressed postscript figure

Dental sealant knowledge, opinion, values and practice of Spanish dentists

[Background] Multiple guidelines and systematic reviews recommend sealant use to reduce caries risk. Yet, multiple reports also indicate that sealants are significantly underutilized. This study examined the knowledge, opinions, values, and practice (KOVP) of dentists concerning sealant use in the southwest region of Andalusia, Spain. This is a prelude to the generation of a regional plan for improving children’s oral health in Andalusia.[Methods] The survey’s target population was dentists working in western Andalusia, equally distributed in the provinces of Seville, Cadiz, and Huelva (N=2,047). A convenience sample of meeting participants and meeting participant email lists (N=400) were solicited from the annual course on Community and Pediatric Dentistry. This course is required for all public health sector dentists, and is open to all private sector dentists. Information on the dentist’s KOVP of sealants was collected using four-part questionnaire with 31, 5-point Likert-scaled questions.[Results] The survey population demographics included 190 men (48%) and 206 women (52%) with an average clinical experience of 10.6 (± 8.4) years and 9.3 (± 7.5) years, respectively. A significant sex difference was observed in the distribution of place of work (urban/suburb) (p=0.001), but no sex differences between working sector (public/private). The mean ± SD values for each of the four KOVP sections for pit and fissure sealants were: knowledge = 3.57 ± 0.47; opinion = 2.48 ± 0.47; value = 2.74 ± 0.52; and practice = 3.48 ± 0.50. No sex differences were found in KOVP (all p >0.4). Independent of sex: knowledge statistically differed by years of experience and place of work; opinion statistically differed by years of experience and sector; and practice statistically differed by years of experience and sector. Less experienced dentists tended to have slightly higher scores (~0.25 on a Likert 1–5 scale). Statistically significant correlations were found between knowledge and practice (r=0.44, p=0.00) and between opinion and value (r=0.35, p=0.00).[Conclusions] The results suggest that, similar to other countries, Andalusian dentists know that sealants are effective, have neutral to positive attitudes toward sealants; though, based on epidemiological studies, underuse sealants. Therefore, methods other than classical behavior change (eg: financial or legal mechanisms) will be required to change practice patterns aimed at improving children's oral health.We acknowledge the following sources for invaluable financial support NIMHD 1 R34 DE022272 (NIH2385) and NIDCR 1 U24 MD006964

Immunohistochemical expression of estrogen and progesterone receptors in endometrial hyperplasia and endometrioid carcinoma

Background: Endometrial carcinoma (EC) is the most common gynecologic malignancy however, mechanisms underlying its pathogenesis remain obscure. Endometrial carcinoma has been classified into two major categories: type I (related to estrogen or endometrioid adenocarcinoma) and type II (unrelated to estrogen). Estrogen is the main trigger for the abnormal proliferation in the endometrial epithelium but progesterone can inhibit this process. The aim of this study was to analyze the expression of estrogen and progesterone receptors in all types of endometrial hyperplasia in comparison to endometrioid adenocarcinoma of endometrium. Methods: Forty-seven specimens including 23 cases of histopathologically confirmed hyperplastic endometrium (12 simple hyperplasia, 5 complex hyperplasia without atypia, and 6 complex hyperplasia with atypia) and 24 cases of endometrial carcinoma were studied. Immunohistochemical staining of estrogen and progesterone receptors was performed in paraffin-embedded blocks and expression of estrogen and progesterone receptors were scored according to the proportion of positive staining cells. Results: Overexpression of progesterone receptors was seen in 18 (75%) out of 24 cases of endometrial carcinoma and 23 (100%) of all types of endometrial hyperplasia. The aforesaid differences were statistically significant (P=0.023). 70.8% of cases with endometrial carcinoma were 3+ for immunohistochemical staining of progesterone receptors as were 85.7% of the cases with endometrial hyperplasia the difference being also statistically significant (P=0.02). Conclusion: Considering the increased proportion of progesterone receptor expression in all types of hyperplastic endometrium in comparison to endometrial carcinoma, hormonal therapy by progestinal agents is recommended as a treatment of choice