Biological Response of Biphasic Hydroxyapatite/Tricalcium Phosphate Scaffolds Intended for Low Load-Bearing Orthopaedic Applications:

In this study, a calcium phosphate scaffold of hydroxyapatite (HAp) and dicalcium phosphate dihydrate (DCPD) for application in osteoconductive and osteoinductive scaffolds was synthesized and characterized. The important note is that the prepared composites converted to HAp/tricalcium phosphate (TCP) after heat-treatment. This class of composites is interesting because porous HAp/TCP generally degrade more rapid than HAp due to the increased resorption rate of TCP. According to the obtained results, the values of elastic modulus, compressive strength and density of the samples reduced with increasing the percentage of the DCPD phase. It is worth mentioning that the mechanical properties of the prepared samples were near the natural compact bone. The samples were examined in vitro to confirm the apatite forming ability of the composites. Also, in vivo examination in a rabbit model was employed. After fully observation it was concluded that new bone formed on the pore walls, as osteoids and osteoclasts were evident two months postoperatively. Based on the obtained results, the prepared scaffolds seem to be a promising biomaterial for low weight bearing orthopaedic applications

Effects of the adjustable ring-mode laser on intermetallic formation and mechanical properties of steel to aluminium laser welded lap joints

Research has confirmed a positive effect of laser beam shaping on controlling weld profiles and keyhole stabilisation, with significant reductions of porosity in weldments. However, few attempts with scattered results have studied the impact of laser beam shaping on intermetallic phase formation. This paper implements the adjustable-ring mode (ARM) laser and studies the impact of the core/ring power ratio to explore the impact on intermetallic phase formation and mechanical properties during remote laser welding of IF steel to 1050 aluminium. It was found that in conduction mode, the core/ring power ratio of 0.2 provided a larger surface area for bonding at the weld interface, and this was translated through the maximum lap-shear strength of 97.6 N/mm2 (joint efficiency 71%). Furthermore, this significantly reduced the Fe2Al5 intermetallic compound (IMC) thickness by 62% and total IMC thickness by 40% in contrast to a core-dominant beam (power ratio greater than one). In keyhole mode, cracking and lower lap-shear strengths were observed compared to the conduction mode. Notably, with a core/ring power ratio of 0.5 a significant grain refinement in the steel side of the weld was observed

Technical pitfalls and proposed modifications of instructions for use for endovascular aortic aneurysm repair using the Gore Excluder conformable device in angulated and short landing zones

We describe a case of an abdominal aortic aneurysm (AAA) and angulated proximal neck treated with a Gore Excluder conformable endoprosthesis and show relevant technical pitfalls in the deployment of the graft main body. An 82-year-old man presented with a 71-mm asymptomatic AAA with an angulated infrarenal proximal neck (75°) and was referred to our unit. The patient was treated with a 26-mm Gore Excluder conformable device, which was deployed slightly above the renal arteries after precatheterization of the lowest renal artery. The graft was then repositioned with support of the introducer sheath and a stiff guide wire. The proximal sealing zone was ballooned before the endograft delivery system was retrieved to avoid distal migration. Technical success was achieved. The patient was discharged with no complications. No type Ia endoleak was present on the 6-month computed tomography scan. Endovascular treatment of an AAA with a severe angulated proximal neck can be effective with a conformable stent graft if technical measures are used during deployment of the main body to optimize the seal.</p

Effects of the adjustable ring-mode laser on intermetallic formation and mechanical properties of steel to aluminium laser welded lap joints

Research has confirmed a positive effect of laser beam shaping on controlling weld profiles and keyhole stabilisation, with significant reductions of porosity in weldments. However, few attempts with scattered results have studied the impact of laser beam shaping on intermetallic phase formation. This paper implements the adjustable-ring mode (ARM) laser and studies the impact of the core/ring power ratio to explore the impact on intermetallic phase formation and mechanical properties during remote laser welding of IF steel to 1050 aluminium. It was found that in conduction mode, the core/ring power ratio of 0.2 provided a larger surface area for bonding at the weld interface, and this was translated through the maximum lap-shear strength of 97.6 N/mm2 (joint efficiency 71%). Furthermore, this significantly reduced the Fe2Al5 intermetallic compound (IMC) thickness by 62% and total IMC thickness by 40% in contrast to a core-dominant beam (power ratio greater than one). In keyhole mode, cracking and lower lap-shear strengths were observed compared to the conduction mode. Notably, with a core/ring power ratio of 0.5 a significant grain refinement in the steel side of the weld was observed

Comparison of chemical characteristics of shoot, root and litter in three range species of Salsola rigida, Artemisia sieberi and Stipa barbata

Some chemical characteristics of root, shoot and litter of index species such as Salsola rigida, Artemisia sieberi and Stipa barbata commonly used in rangeland development projects were evaluated and compared. Chemical properties of soil under and between the above mentioned species were also studied. For this purpose, vegetation types of Stipa barbata and Artemisia sieberi - Salsola rigida were selected in Zarand-eSaveh rangelands. Totally, 30 individuals of each species within each type were randomly selected for shoot, root and litter sampling and chemical analyses. Also, values of N, P, K, C and C/N ratio were measured in different parts of the species. Results showed that the highest and lowest C/N ratios were related to Stipa barbata root and Artemisia sieberi shoots, respectively. N and P values of Stipa barbata litter were the lowest while Artemisia sieberi and Salsola rigida shoots had the highest values of P and N, respectively. Litter of Salsola rigida and shoot of Artemisia sieberi had the lowest and highest K, respectively. C/N ratio of A. sieberi soil was lower than rest of the species

Comparison of single- and multistage strategies during fenestrated-branched endovascular aortic repair of thoracoabdominal aortic aneurysms

Objective: The aim of this study was to compare outcomes of single or multistage approach during fenestrated-branched endovascular aortic repair (FB-EVAR) of extensive thoracoabdominal aortic aneurysms (TAAAs). Methods: We reviewed the clinical data of consecutive patients treated by FB-EVAR for extent I to III TAAAs in 24 centers (2006-2021). All patients received a single brand manufactured patient-specific or off-the-shelf fenestrated-branched stent grafts. Staging strategies included proximal thoracic aortic repair, minimally invasive segmental artery coil embolization, temporary aneurysm sac perfusion and combinations of these techniques. Endpoints were analyzed for elective repair in patients who had a single- or multistage approach before and after propensity score adjustment for baseline differences, including the composite 30-day/in-hospital mortality and/or permanent paraplegia, major adverse event, patient survival, and freedom from aortic-related mortality. Results: A total of 1947 patients (65% male; mean age, 71 ± 8 years) underwent FB-EVAR of 155 extent I (10%), 729 extent II (46%), and 713 extent III TAAAs (44%). A single-stage approach was used in 939 patients (48%) and a multistage approach in 1008 patients (52%). A multistage approach was more frequently used in patients undergoing elective compared with non-elective repair (55% vs 35%; P < .001). Staging strategies were proximal thoracic aortic repair in 743 patients (74%), temporary aneurysm sac perfusion in 128 (13%), minimally invasive segmental artery coil embolization in 10 (1%), and combinations in 127 (12%). Among patients undergoing elective repair (n = 1597), the composite endpoint of 30-day/in-hospital mortality and/or permanent paraplegia rate occurred in 14% of single-stage and 6% of multistage approach patients (P < .001). After adjustment with a propensity score, multistage approach was associated with lower rates of 30-day/in-hospital mortality and/or permanent paraplegia (odds ratio, 0.466; 95% confidence interval, 0.271-0.801; P = .006) and higher patient survival at 1 year (86.9±1.3% vs 79.6±1.7%) and 3 years (72.7±2.1% vs 64.2±2.3%; adjusted hazard ratio, 0.714; 95% confidence interval, 0.528-0.966; P = .029), compared with a single stage approach. Conclusions: Staging elective FB-EVAR of extent I to III TAAAs was associated with decreased risk of mortality and/or permanent paraplegia at 30 days or within hospital stay, and with higher patient survival at 1 and 3 years

Influence of single and binary doping of strontium and lithium on in vivo biological properties of bioactive glass scaffolds

Effects of strontium and lithium ion doping on the biological properties of bioactive glass (BAG) porous scaffolds have been checked in vitro and in vivo. BAG scaffolds were prepared by conventional glass melting route and subsequently, scaffolds were produced by evaporation of fugitive pore formers. After thorough physico-chemical and in vitro cell characterization, scaffolds were used for pre-clinical study. Soft and hard tissue formation in a rabbit femoral defect model after 2 and 4 months, were assessed using different tools. Histological observations showed excellent osseous tissue formation in Sr and Li + Sr scaffolds and moderate bone regeneration in Li scaffolds. Fluorochrome labeling studies showed wide regions of new bone formation in Sr and Li + Sr doped samples as compared to Li doped samples. SEM revealed abundant collagenous network and minimal or no interfacial gap between bone and implant in Sr and Li + Sr doped samples compared to Li doped samples. Micro CT of Li + Sr samples showed highest degree of peripheral cancellous tissue formation on periphery and cortical tissues inside implanted samples and vascularity among four compositions. Our findings suggest that addition of Sr and/or Li alters physico-chemical properties of BAG and promotes early stage in vivo osseointegration and bone remodeling that may offer new insight in bone tissue engineering

Finite and infinite element method applied to water wave diffraction problems

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN023687 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

A new infinite element for unbounded water wave problems

A new mapped infinite wave envelope element is developed to model two-dimensional unbounded water wave problems in conjunction with wave finite elements. The infinite elements may be used on the exterior of an ellipse or other shapes. Examples are implemented to test the model for the two special cases of circular and elliptical cylinder diffraction problems. Comparisons are made between the analytical and finite/infinite element solutions. The errors are small, around 2% for a very coarse mesh and decrease to around 0.5% when the wave envelope infinite elements are located reasonably far from the diffracting object, i.e. at a distance equal to the semi-major axis of the ellipse

Optimum light weight concrete mix design against high temperature

The fire phenomenon can cause the loss of structural materials resistance which may end to damage or even structural total collapse. Physical and chemical changes in concrete due to firing also make serious structural defects in concrete structures. Therefore, prevention of reduction of concrete resistance is attended in this research. The primary idea is based on decreasing concrete thermal conductivity to increase chemical and physical resistance. Because of low density and porosity light weight aggregate concrete has low thermal conductivity which can postpone the resistant loss due to high temperature. A set of tests performed to achieve an optimum light weight aggregate concrete mix design in room normal temperature by changing the amount of sensitive mix components and controlling compressive strength and density. In next step some effective additives were implemented to make the optimum mix design against high temperature. For this purpose, 9 different mix designs obtained from the Taguchi method were prepared. For each mix design, 9 test specimens were made. At each, ambient temperature, 400 ͦC and 800 ͦC, three samples of each design are tested. The experiments conducted in this research include testing of compressive strength, ultrasonic pulse, and weight loss and heat effect on the appearance of lightweight concrete. It was seen that the effect of temperature above 400 ͦC is more significant on concrete compressive strength and in temperatures below 400 ͦC density loss is more considerable. The results of tests indicate that reducing the water to cement ratio and using super plasticizer has a desirable effect on the physical and mechanical properties of lightweight concrete at higher temperatures. However, test results showed that the presence of silica fume up to 15 percent of weight of cement can’t improve the strength of lightweight concrete neither in ambient nor in elevated temperature. Optimum mix design lost about 49 percent of compressive strength in 800 ͦC. Also it was observed that loss of density and compressive strength due to elevated temperature are in direct relation