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In order to correctly define the pathology of multiple-leaf stonemasonry walls and determine the appropriate interventions for its conservation and preservation, comprehensive studies on its building materials should be carried out since the overall behaviour of masonry structures is highly dependent on the characterization of its construction materials. Consequently, an interdisciplinary procedure for construction material characterization used in multiple-leaf stone-masonry walls in Egypt has been implemented to enrich documentation, conservation and restoration issues of this type of wall. The research methodology integrates experimental data obtained through on-site sampling, conducted tests and analyses, historical information, and field survey observations. The fundamental physical and mechanical properties of the masonry elements were examined by incorporating stone blocks, mortars and core-infill materials. The mineralogical composition and interlocking textures of the collected samples were investigated utilizing a large range of complementary investigation and analysis techniques, including polarizing microscopy, X-ray diffraction (XRD), thermal analysis (TG/DTA), and environmental scanning electron microscope (ESEM) attached to an EDX unit. Through the results thus obtained, a complete characterization of the mineralogical composition; physical–mechanical, chemical, and thermal properties; and the interlocking textures of the construction materials of both the outer and inner-core layers was performed. The outer leaves of the majority of the multiple-leaf stone-masonry walls in medieval architectural heritage were mainly built of well-dressed limestone blocks with nearly uniform dimensions, while the inner-core layer was usually built of stone-rubble infill with bending lime-based mortar. The uniaxial compressive strengths of core infill (corresponding to the inner core layer) and lime-based mortar of the embedded joints are shown to be 85 and 92.5% lower than the limestone units of the outer layer, respectively. Moreover, experimental observations indicate that the inner core layer exhibits the highest porosity values; consequently, deteriorated, loose and cohesionless core infill could greatly affect the durability and thermal resistivity of this kind of wall. The results provide scientific support for investigating the overall structural behaviour of this type of walls and for decision-making in future conservation and restoration strategies.

For the first time, A. baumannii KdpE is shown to be crucial to pneumonia onset, and targeting this system can be a viable approach to treating these fatal infections.

BackgroundResistant Pseudomonas aeruginosa is a serious concern for antimicrobial therapy, as the common isolates exhibit variable grades of resistance, involving beta-lactamase enzymes, beside native defense mechanisms.ObjectivesThe present study was designed to determine the occurrence of Metallo-β- Lactamases (MBL) and Amp C harboring P. aeruginosa isolates from Suez Canal university hospital in Ismailia, Egypt.MethodsA total of 147 P. aeruginosa isolates, recovered from 311 patients during a 10-month period, were collected between May 2013 and February 2014; the isolates were collected from urine, wound and sputum. Minimum inhibitory concentration (MIC) determined by agar dilution methods was ≥2 μg/mL for meropenem and imipenem. Identification of P. aeruginosa was confirmed using API 20NE. Metallo-β- Lactamases and Amp C were detected based on different phenotypic methods.ResultsOverall, 26.5% of P. aeruginosa isolates (39/147) were carbapenem resistant isolates. Furthermore, 64.1% (25/39) were MBL producers, these isolates were screened by the combined disc and disc diffusion methods to determine the ability of MBL production. Both MBL and Amp C harbored P. aeruginosa isolates were 28% (7/25). Sixty-four percent of P. aeruginosa isolates were multidrug resistant (MDR) (16/25). The sensitivity toward polymyxin, imipenem, norfloxacin, piperacillin-tazobactam and gentamicin was 99%, 91%, 88%, 82% and 78%, respectively. The resistance rate towards cefotaxime, ceftazidime, cefepime, aztreonam and meropenem was 98.6%, 86%, 71.4%, 34% and 30%, respectively.ConclusionsMultidrug resistance was significantly associated with MBL production in P. aeruginosa. Early detection of MBL-producing P. aeruginosa and hospital antibiotic policy prescription helps proper antimicrobial therapy and avoidance of dissemination of these multidrug resistance isolates.

This paper presents various aspects of the kinematic nonlinear interaction of coupled RC/soil system under static and dynamic loads. Conducted are parametric studies for two types of underground structures subjected to high shear deformation transferred through the nonlinear surrounding soil. In this analysis influences of several factors, such as material nonlinearity of RC and soil, stiffness of structure and reinforcement ratio, are investigated. Failure modes, residual deformations and induced force to the RC from soil are examined for rationalized guidelines serving future improvement of the underground structural design.

Stairs play an important role as an escape way and are considered a source of safety in the building during an earthquake. Neglecting the stairs in the 3D analysis model is the main cause of the stairs' failure during the earthquake. Although the previous researchers had focused on the behavior of stairs when changing single variables such as height, location, and layout under seismic loads, no detailed investigation that gathers these variables together was considered. This research studies the effects of changing the number of storeys for a building subjected to an earthquake when considering and neglecting stairs in the 3D analysis with and without shear walls. The effect of the volume and location of the shear wall has been considered through conducting computational analysis using ETABS software to help the structural engineer choose the proper system of stairs and shear walls. Neglecting the staircase in the 3D analysis affects the structure's performance, which leads to ignoring many stresses transferred to the stairs, causing several damages to the stairs during an earthquake. For the existing building without a shear wall, considering the staircases in the analysis improves the performance of the structure under seismic loads. Doi: 10.28991/CEJ-SP2021-07-08 Full Text: PDF

This paper presents reversed cyclic models of coupled RC/soil system. The full path-dependent constitutive models of RC, soil and their interfacial zones which are installed in the FEM program WCOMR-SJ are explained. Consequently, RC/soil hysteresis damping and energy absorption are coherently taken into account with corresponding states of damage and plasticity regarding concrete and reinforcement. This computational tool was systematically verified through coupled RC/soil system subjected to static reversed cyclic loads. The nonlinear interaction of RC/soil system and induced damage of underground RC are investigated.

Multi-leaf stone masonry walls are a typical construction technique in architectural heritage in Egypt. The assessment, modeling, and strengthening of historic masonry walls of multi-leaf systems essentially require suitable knowledge of their construction technology, typology, geometrical characteristics, and the properties of their components. Within the current research project, a comprehensive structural survey of multiple-leaf walls of medieval historic buildings in Cairo was performed. The observation and statistical analyses allowed characterization of the transversal section of the surveyed walls, as well as examination and identification of the construction materials and techniques. The slenderness ratios of this type of wall, its blocks’ dimensions, the utilized connectivity between the inner and outer leaves, and leaves ratio were also investigated. Three construction hypotheses of multiple-leaf stone masonry walls are presented considering weak, thick, and monolithic core infill layers. The study’s objectives were to enlarge the knowledge of typology, morphology, and construction materials used in three-leaf masonry walls and provide a proper characterization as a prerequisite for determining the most suitable materials and techniques for further strengthening interventions.