Shear strength of reinforced mortar beams containing polyvinyl alcohol fibre (PVA)

The current study aims to assess the shear behaviour of reinforced mortar beams including Polyvinyl Alcohol Fibre (PVA) ranges from 0 to 2.25%, fly ash (55%) and silica fume (15%). Fourteen beams were experimentally tested under two concentrated loads. In addition, a finite element model was developed to predict the crack pattern, load–deflection, energy absorption, and shear strength results of the test beams. The studied variables were different percentages of PVA fibres, shear span to depth ratio (a/d), and transverse reinforcement (stirrups) ratio. The fly ash and silica fume were kept constant in all the studied mixes to achieve a compressive strength above 55 MPa at the time of testing (90 days) and to improve PVA-mortar properties. It was found that the inclusion of PVA improves the shear behavior of the tested beams in terms of crack pattern and ductility. It was observed also that reducing a/d led to enhancing the shear capacity without changing the mode of failure. In addition, PVA played the same role as the stirrups and their effect on the ultimate shear capacity was increased with reducing the volume of stirrups. Moreover, the PVA fibres were more effective in lower shear span to depth ratio (a/d = 1.5) giving an enhancement of shear resistance of 221%. The non-linear finite element model showed excellent agreement with the experimental results and the ratio of the predicted to experimental ultimate strength ranged between 0.91 and 1.09. The authors recommend a combination of fly ash, silica fume and at least 1.5% PVA in the presence of minimum stirrups reinforcement (5U6/m) or adding 2.25% PVA without stirrups to achieve adequate shear behaviour and to improve the ductility of PVA-mortar beams

Steel reinforced self-compacting concrete (SCC) cantilever beams: bond behaviour in poor condition zones

Previous investigations carried out on reinforced self-compacted concrete (SCC) beams have reported contradictory results on reinforcement bond behaviour occurring in the zones defined for good bond conditions according to Eurocode2. Cantilevered SCC beams’ critical upper tension reinforcement bond behaviour has previously had limited reporting. In this study, the bond behaviour in normally vibrated concrete (NVC) and self-compacted concrete (SCC) in poor condition s zones are compared and the differences are highlighted. The effect of four parameters , including (i) concrete type (SCC and NVC), (ii) characteristic strength of SCC, (iii) lap splice length, and (iv) depth of concrete cover for the reinforcement is investigated. It was found that for the studied beams, increasing splice length improved the energy absorption and changed the failure mode to a more ductile manner even at the poor bond conditions zones. The maximum measured steel strains in SCC beams in the lap splice zones, were higher than those for NVC specimens. The mean bond stress values, for SCC beams with 25% and 50% lap splice lengths, were higher than those of NVC beams, with the same lap splice lengths, by 16% and 13%, respectively. The results of the current study showed that the empirical equations from the literature overestimated the bond strength of the splice lap length for cantilever upper steel in SCC beams with long splices which agrees with the state of the art as these equations were developed originally for short anchorage lengths

Effects of L-carnitine and cryodevices on the vitrification and developmental competence of invitro fertilized buffalo oocytes

In the current, study the effect of the addition of L-carnitine (LC) in in vitro maturation (IVM) medium for buffalo oocytes and different cryo-devices on developmental competence. They were matured in IVM medium supplemented with 0.0, 0.3, 0.6 and 1.2 mg/mL of LC and vitrified by using either straw (ST), open pulled-straw (OPS), solid surface vitrification (SSV). The effects of LC during invitro fertilization and invitro culture on the developmental potential were examined. ST showed a higher recovery rate when using 0.6 mg/ml; viability rate (VR) when using 0.3mg/ml and lower zona pellucida (ZP) and cytoplasmic abnormalities when using 1.2 mg/ml LC (P<0.05). OPS showed a higher recovery and viability rates when using 0.3 mg (P<0.05). SSD showed a higher recovery and VR when using 0.6 mg/ml LC (P<0.05). Maturation and fertilization rates were increased when using 0.3 mg LC and OPS (P<0.05). Cleavage was increased in 0.3 (OPS) and 0.6 mg LC (SSD). The blastocyst rate was increased in 0.3 (OPS) and 0.6 mg/ml (SSD) (P< 0.05). In conclusion, 0.3 mg/ml LC and OPS gives a higher recovery and viability rates but 0.6 mg/ml LC and of both SSD and ST gives a higher recovery and viability rates

Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey

Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10 years; 78.2% included were male with a median age of 37 years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020

Cathepsin L is Required for Completion of Oocyte Meiotic Maturation in Mammals

Infertility is a major concern affecting a huge population worldwide. Aneuploidy is one of the leading causes of the infertility, usually originated from errors that happens in meiosis I as chromosomal misalignment and abnormal chromosomal segregation. Recent research showed that cathepsins family play an important role in affecting the oocytes developmental competence in many species. Cathepsin B inhibition improved bovine developmental competence of the oocytes, especially in the low-quality oocytes. Here, we are the first to introduce the significance of another member of this family, cathepsin L (CTSL) in the process of oocyte maturation using mouse oocyte model.  In this study we evaluated the expression of CTSL during oocyte meiotic maturation and the effect of CTSL inhibition using specific inhibitor “SCP110” on the subsequent maturation process. We found, CTSL is expressed in all stages of Meiosis I. In addition, inhibition of CTSL resulted in delaying the maturation time by elongation the time required for extrusion of the polar body (PBE). Moreover, CTSL inhibition reduced the maturation rate compared to the control group as we found a significant decrease in PBE percent. Trying to understand the reason of the lower maturation rates, we stained the chromosomes and spindles at metaphase I stage, we found a significant increase in chromosomal misalignment at metaphase plate. Finally, we evaluated matured oocytes quality after CTSL inhibition, importantly, aneuploidy incidence was increased significantly after CTSL inhibition. In summary, CTSL is required for normal meiosis completion in oocytes and production of healthy euploid egg

The probable radioprotective role of Acacia nilotica L. against biochemical and cytogenetic disorders induced in gamma irradiated male rats

Gum Arabic (Acacia nilotica L.) is a respected plant that has many nutrients and curative practices. It hinders, improves, or manages many disorders. The radio-protective activity of Acacia nilotica was investigated against γ-rays-induced testicle damage in rats. Twenty-four rats were correspondingly distributed into 4 groups; control, Acacia nilotica (15mg/kg, daily for 30 days), γ-irradiated (5Gy γ-rays, single dose) and Acacia nilotica plus γ-rays treated groups. The plasma testosterone and total antioxidant status (TAS) were estimated. Lipid peroxidation; malondialdehyde (MDA), reduced glutathione (GSH), malondialdehyde (MDA), superoxide dismutase (SOD), also glutathione peroxidase (GPx), catalase (CAT), tumor necrosis factor-α (TNF-α) with interleukin-1β (IL-1β), were determined in the testicle tissues. A testis weight, sperm count and motility, peripheral-blood and bone-marrow micronuclei (PMN and BMN), and frequency of chromosomal aberrations (CAs) were scored. A significant decline in the levels of plasma testosterone with TAS observed in the γ-irradiated rats. The results also showed significantly increased levels of testicle MDA, inflammatory markers, PMN, BMN and CAs frequencies and decrease in testes weight, sperm count and motility and levels of testicle antioxidants markers in gamma irradiated group. All these biochemical and fertility indices results were significantly enhanced in the Acacia nilotica plus γ-rays treated groups. However, the possible alleviate activity of Acacia nilotica on γ-rays-induced testicle injury in rats has not previously conversed, and this is the topic of this study

Effect of premature loading on punching resistance of reinforced concrete flat slabs

Premature loading of reinforced concrete flat slabs in multi storey buildings during construction may occur after shuttering removal and loading slabs earlier than usual to meet project time targets. Some case studies showed failure of flat slabs, which were prematurely loaded during the construction process before it reaches its full characteristic strength (at 28 days), which was used in structural design. This research aims to address this problem through experimental testing and design application according to current building codes. Eight specimens with dimensions of 1100 * 1100 mm and a total thickness of 120 mm were experimentally tested to study the effect of concrete age and actual compressive strength at loading on the punching shear capacity of reinforced concrete slabs. All specimens were supported by a square column with dimensions of 150 × 150 mm and loaded at the four corners with a span of 1050 mm. Accelerating admixture was used in three studied specimens to achieve higher concrete compressive strength at early ages compared to their companions of normal concrete without these admixtures. It was found that increasing concrete compressive strength of slab from 25 N/mm2 to 35 Nlmm2 (40% increase) for normal concrete, without early admixture, improved punching shear capacity by 26%, while increasing it to 45 N/mm2 (80% increase) improved punching shear capacity by 49% when the specimens were loaded 7 days after casting. In addition, using an accelerating admixture increased early concrete compressive strength, which improved punching shear capacity of reinforced concrete slab over that without accelerating admixture by 31% and 29% after 7 days and 14 days, respectively. According to inclusion of reinforcement ratio, BS8110 - 97 and EC2 design codes showed the most accurate prediction of punching shear capacity at 28 days, while ACI and ECP seemed conservative as their equations do not take steel ratio into consideration. At early ages, BS8110 - 97 and EC2 design equations did not provide accurate prediction of punching shear capacity while ACI and ECP provided reliable equations. It is highly recommended to use the actual compressive strength of concrete at early age (7 days for example) for calculating punching shear resistance of flat slabs in multi storey buildings prior to shuttering removal to prevent any premature loading

Structural behaviour of polystyrene foam lightweight concrete beams strengthened with FRP laminates

Lightweight concrete (LWC) is one of the most important building materials nowadays. Many research studies were focused on LWC produced using lightweight aggregates. However, limited work was cited for LWC produced using polystyrene beads. In this study, LWC beams strengthened with carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymer (GFRP) were experimentally tested to investigate the improvement in their flexural and shear behaviours. LWC in this investigation was achieved by partial replacement of normal aggregate by polystyrene beads and resulted in approximately 30 % less weight compared to Normal weight concrete. Fourteen Reinforced Concrete (RC) LWC beams of 100 mm by 300 mm cross-section having an overall length of 3250 mm were tested under four-point bending. These beams were designed, detailed, and tested to obtain flexural and shear mode of failure. These beams were divided into two groups based on the intended failure mode. In each group, six beams were strengthened using CFRP and GFRP laminates while the remaining one beam was used as control. The tested parameters were the type of FRP, the width of the laminates used in shear strengthening, and the number of layers used in flexural strengthening. It was found that strengthening of LWC beams using CFRP and GFRP layers resulted in increasing the loading capacity and decreasing deflection as compared to control. The strengthening with CFRP and GFRP is also suitable in reducing the crack width and crack propagation which is more significant in LWC beams. The experimental results were also compared with the expressions in codes for forecasting the strength of LWC beams and it was that these expressions are compatible with the experimental results

Effect of partial replacement of coarse aggregate by polystyrene balls on the shear behaviour of deep beams with web openings

Thirteen specimens were experimentally tested under single midspan concentrated loads to study the shear behavior of lightweight concrete (LWC) and normal weight concrete (NWC) deep beams with web openings. In this research, the term LWC refers to the concrete obtained by partially replacing aggregate by polystyrene foam balls not the concrete containing lightweight aggregate. This resulted in a weight reduction of LWC beams in this research by approximately 30 % compared to NWC compartments. The studied variables were the dimensions and location of openings, transverse reinforcement ratio, and shear span to depth ratio (a/d). It was found that the overall shear behavior and failure mode for LWC deep beams are comparable to those of the NWC specimens. This is very promising and encouraging to build lighter deep beams of similar structural behaviour as that of NWC deep beams. Dimensions of the openings have a significant effect on the behaviour of failure and shear strength of LWC and NWC deep beams. It was found that increasing the depth of the opening from 20 % to 40 % of the beam depth led to a reduction in the ultimate load by up to 46.4 %. Finite element modelling of the test beams was carried out to verify numerical results versus experimental work and both were very well correlated. In addition, a parametric study was conducted to assess the effect of internal stiffening around openings in deep beams. The maximum enhancement in the shear capacity was approximately 30 % for beams, internally strengthened by additional reinforcement on the perimeter of openings compared to the beams without any reinforcement around the openings. Strut-and-Tie model (STM) was carried out as a rational approach to predict the shear behaviour of studied beams. It was found that STM underestimates the shear of the studied beams compared to experimental results for different tested beams but the agreement between both of them was acceptable. It is recommended that the depth of opening should not exceed 20 % of the depth of the deep beam and if the depth of opening is more than that or lies in the shear span it is highly recommended to strengthen the opening internally by additional reinforcement around its perimeter