The probiotic potential of lactobacilli isolated from Nile tilapia (Oreochromis niloticus)’s intestine

The potential probiotic acid lactic bacteria isolated from Nile tilapia (Oreochromis niloticus)fs intestine was tested for fish farming. In our collection, 10 Lactobacillus strains were targeted to confront a series of antibiotics in order to draw their resistance profile, and to test their degree of inhibitory to four pathogenic bacteria, Staphylococcus aureus, Escherichia coli, Streptococcus sp. and Pseudomonas sp. The power of acidification and tolerance was tested. Overall, our results show that strains BLT31 and BLT21 are fully susceptible and resistance to the tested antibiotics. Strains BLT3, BLT20, BLT21 and BLT23 have a good antagonistic effect against pathogenic bacteria that cause the highest damage in aquaculture. For acid lactic production, strains BLT3, BLT26, BLT27, BLT28, and BLT31 are considered fast since Ģ pH . 4U in less than three hours. As for the resistance to pH and bile salts, two strains BLT3 and BLT31 showed significant power which gives them acceptable probiotic potential.Key words: Probiotics, antibiotics, aquaculture, the Nile Tilapia, inhibitory activities, lactobacilli

Quantification of Outdoor Thermal Comfort Levels under Sea Breeze in the Historical City Fabric: The Case of Algiers Casbah

Thermal comfort in cities is an influential factor for citizens’ wellbeing and life quality. Urban microclimate studies have gained popularity following increasing urbanization trends and global climate change in recent years. Urban fabric and morphology in traditional cities represent a unique pattern both spatially and climatically. However, few studies have investigated traditional cities’ urban thermal comfort conditions. Therefore, this study aimed to assess the thermal comfort in different subspaces of Algiers Casbah’s historic urban fabric, which falls in the hot Mediterranean climate (Csa). This research evaluated the human thermal sensation by applying the physiological equivalent temperature (PET) index. The methodology used was a mixed approach, including field measurements, calculations, and a survey questionnaire. The results indicate the presence of a high-stress level during the measurement periods, and notable differences between the subspaces in January (ΔPETMax.Jan = 3.7 °C) and August (ΔPETMax.Aug = 2.2 °C). The highest discomfort was recorded in spaces with collapsed buildings, especially during the hot hours of the day. The findings also highlight a strong impact of the sky view factor on the mean radiant temperature (Tmrt) and the physiological equivalent temperature (PET). The study discusses recommendations and ways to improve the design of outdoor spaces and relieve heat stress in the streets of traditional cities. Finally, this work helps urban managers and heritage conservators in urban rehabilitation policies concerning outdoor microclimate improvement

Formation of beads-on-a-string structures during break-up of viscoelastic filaments

Break-up of viscoelastic filaments is pervasive in both nature and technology. If a filament is formed by placing a drop of saliva between a thumb and forefinger and is stretched, the filament’s morphology close to break-up corresponds to beads of several sizes interconnected by slender threads. Although there is general agreement that formation of such beads-on-a-string (BOAS) structures occurs only for viscoelastic fluids, the underlying physics remains unclear and controversial. The physics leading to the formation of BOAS structures is probed by numerical simulation. Computations reveal that viscoelasticity alone does not give rise to a small, satellite bead between two much larger main beads but that inertia is required for its formation. Viscoelasticity, however, enhances the growth of the bead and delays pinch-off, which leads to a relatively long-lived beaded structure. We also show for the first time theoretically that yet smaller, sub-satellite beads can also form as seen in experiments.National Science Foundation (U.S.). ERC-SOPS (EEC-0540855)Nanoscale Interdisciplinary Research Thrust on 'Directed Self-assembly of Suspended Polymer Fibers' (NSF-DMS0506941

Infestation of dogs by <em>Rhipicephalus sanguineus</em> in two regions of the Far Northeast of Algeria

From March to August 2009, 120 dogs were examined in two bioclimatic regions of the Far Northeast of Algeria (10 dogs per month per region) to estimate the rate and intensity of infestation by the Rhipicephalus sanguineus tick. All the dogs examined were infested by these mites and 895 adult ticks were collected. R. sanguineus was the only species found in Souk-Ahras region, whereas it represented 77% of the collected ticks in El-Kala region. Two other species were identified in that area: Ixodes ricinus and Haemaphysalis punctata with 13 and 10% rates, respectively. The parasite burden was significantly higher (p < 0.01) in the semiarid region of Souk- Ahras with 9.4 ticks per dog, than in the humid region of El- Kala with 4.2 ticks per dog. The ticks have been continuously present throughout the study period. These results should be taken into account in projects to control tick infestation of dogs, with a focus on Rhipicephalus sanguineus, which is responsible for the transmission of both human and animal vector-borne diseases

FRACTURE ENERGY OF CONCRETE AT VERY EARLY AGES BY INVERSE ANALYSIS

In this paper, the fracture characteristics of concrete at very early ages are investigated. Experimentally , three point bending tests are performed on notched beams at very early-ages (before 24 h) and the Load-CMOD curves are obtained. In order to find the trend of the evolution of the fracture energy, an inverse analysis procedure is developed. A damage model based on an energetic regular-ization is combined with a non linear inverse analysis algorithm. As the stress-strain curve (and the stress-crack opening one) given by the damage model is non linear, the Levenberg-Marquardt algorithm is chosen. Results obtained from numerical simulations show that fracture energy of concrete increases with age

Numerical modelling of autogenous healing and recovery of mechanical properties in ultra-high performance concrete

Cracks, caused by shrinkage or external loading, reduce the durability of concrete structures as aggressive substances can easily enter in the capillary network of the cementitious matrix. Natural \u91autogenous\u92 healing ability of concrete by further hydration or precipitation has been studied experimentally for many years. Autogenous healing of concrete by further hydration of residual unhydrated cement particles is triggered by the ingress of water and/or moisture into the crack and leads to a partial recovery of mechanical properties (Young\u92s modulus, tensile strength,...). However, theoretical studies and computer simulations still need to be developed in order to explain macroscopic behaviour of healed specimens and conditions of occurrence of the self-healing phenomenon. In this study, a hydro-chemo-mechanical model was developed to simulate autogenous healing by further hydration. Firstly, a simulation of a three-point-bending test was performed to represent the initial damaged state before the self-healing process. The volume fraction of the residual cement clinkers at this moment has been calculated with a hydration model. Then, the self-healing phenomenon of concrete beams immersed into water was modelled based on micro-mechanical observations. The diffusion process has been simulated using the Fick\u92s law in order to describe the ingress of water into concrete. The hydration model, based on the Arrhenius law, is then used to simulate the chemical reactions between residual clinkers and water. The mechanical properties of the new formed hydrates are therefore evaluated in order to describe the partial recovery of mechanical properties of healed concrete