Additive manufacturing in fighting against novel coronavirus COVID-19.

Nowadays, COVID-19 also known as novel coronavirus has become a global pandemic by causing severe respiratory tract infections in humans without any definite treatment or vaccine. Therefore, disease control measures include slowing down or averting the transfer of this viral infection from person to person. Continuous efforts are carried out to avoid the transmission of this disease to frontline healthcare personnel using single-use personal protective equipment (PPE). However, a critical shortage in this equipment around the world is becoming an alarming concern. Therefore, it is vital to present a possible alternative to overcome the acute shortage of protective gear such as face masks against this infectious disease which can have universal accessibility and is easily available. Additive manufacturing (AM), also known as 3D printing, is a possible solution to overcome the shortage of protective gear and can play a vital role in supporting their conventional production supplies during this global pandemic situation. In this context, this paper provides a brief background study of COVID-19, its conventional preventive measure, and a detailed overview regarding the latest AM efforts including designers' providers and makers in the 3D printing community. Moreover, numerous inquiries and questions such as technical factors, testing recommendations and characterization methods and biological concerns such as biocompatibility and sterilization for the AM manufactured medical devices are addressed in this paper. In the end, two examples of AM medical devices, i.e., face mask and Ambu bag ventilator, are presented and studied through numerical simulations.

A 3D elastic micropolar model of vertebral trabecular bone from lattice homogenization of the bone microstructure.

A 3D anisotropic micropolar continuum model of vertebral trabecular bone is presently developed accounting for the influence of microstructure-related scale effects on the macroscopic effective properties. Vertebral trabecular bone is modeled as a cellular material with an idealized periodic structure made of open 3D cells. The micromechanical approach relies on the discrete homogenization technique considering lattice microrotations as additional degrees of freedom at the microscale. The effective elastic properties of 3D lattices made of articulated beams taking into account axial, transverse shearing, flexural, and torsional deformations of the cell struts are derived as closed form expressions of the geometrical and mechanical microparameters. The scaling laws of the effective moduli versus density are determined in situations of low and high effective densities to assess the impact of the transverse shear deformation. The classical and micropolar effective moduli and the internal flexural and torsional lengths are identified versus the same microparameters. A finite element model of the local architecture of the trabeculae gives values of the effective moduli that are in satisfactory agreement with the homogenized moduli.

A micropolar anisotropic constitutive model of cancellous bone from discrete homogenization.

Cosserat models of cancellous bone are constructed, relying on micromechanical approaches in order to investigate microstructure-related scale effects on the macroscopic properties of bone. The derivation of the effective mechanical properties of cancellous bone considered as a cellular solid modeled as two-dimensional lattices of articulated beams is presently investigated. The cell walls of the bone microstructure are modeled as Timoshenko thick beams. The asymptotic homogenization technique is involved to get closed form expressions of the equivalent properties versus the geometrical and mechanical microparameters, accounting for the effects of bending, axial, and transverse shear deformations. Considering lattice microrotations as additional degrees of freedom at both the microscopic and macroscopic scales, an anisotropic micropolar equivalent continuum model is constructed, the effective mechanical properties of which are identified. The effective elastic moduli of various periodic cell structures are computed in situations of low and high effective densities to assess the impact of the transverse shear deformation. The stress distribution in a cracked bone sample is computed based on the effective micropolar model, highlighting the regularizing effect of the Cosserat continuum in comparison to a classical elasticity continuum model.

Survival effects of cyclooxygenase-2 and 12-lipooxygenase in Egyptian women with operable breast cancer.

BACKGROUND: Breast cancer (BC) is the commonest among women in Egypt as well as in many other countries. Cyclo-oxygenase-2 (COX-2) and 12-lipo-oxygenase (12-LOX) are over-expressed in 30-40% of patients and carry a poor prognosis. The objectives of this study were to correlate COX-2 and 12-LOX expression with various clinico-pathologic patients' characteristics and their impact on overall survival (OS) and disease free survival (DFS) in Egyptian women with operable BC. MATERIALS AND METHODS: This prospective study included 57 consecutive BC cases presenting to the Egyptian National Cancer Institute. Sections from BC and nearby normal tissues were examined for expression of COX-2 and 12-LOX using reverse transcriptase polymerase chain reaction. RESULTS: The patients' median age was 45 years. Fifty-three percent were premenopausal. Stage II and III disease represented 25 and 75% respectively. Adjuvant chemotherapy, radiotherapy and tamoxifen were used in 90, 75 and 60% respectively. Sixty percent had hormone-receptor positive tumors and 28% over-expressed HER2/neu. Forty-nine and sixty-five percent showed over-expression of COX-2 and 12-LOX respectively. Patients with higher TNM stage or who developed visceral metastases had significantly higher COX-2 expression. For the whole group of patients, the median DFS was 37 months, while the median OS was not reached. OS or DFS did not differ significantly between patients with normal and over-expression of COX-2. DFS but not OS was significantly higher in 12-LOX over-expression compared to normal expression. CONCLUSION: COX-2 over-expression was associated with poor prognostic criteria in BC, but did not affect DFS or OS. 12-LOX over-expression was associated with better DFS, but not OS.