With the technology development on the compressive strength of concrete over the years, the use of high strength concrete has proved most popular in terms of economy, superior strength, stiffness and durability due to many advantages it could offer. However, strength and ductility are inversely proportional. High strength concrete is a brittle material causing failure to be quite sudden and 'explosive' under loads. It is also known that true axial compression of structural concrete columns (axially compressed) rarely occurs in practice. The stress concentrations caused by the eccentric loading further reduce the strength and Ductility of high strength concrete. This paper presents results of testing eccentrically loaded Columns externally wrapped with different types of materials. The experimental results show That external reinforcement can enhance the properties of high strength concrete columns.      

High strength concrete (HSC) provides high strength but lower ductility compared to normal strength concrete. This low ductility limits the benefit of using HSC in building safe structures. This means that a designer should be aware of limiting the amount of tensile reinforcement to prevent the brittle failure of concrete. Therefore the full potential of the use of steel reinforcement cannot be achieved. This paper presents a method to prevent the brittle failure of concrete beams. Five beams made of HSC were cast and tested. The cross section of the beams was 200x300 mm, with a length of 4 m and a clear span of 3.6 m subjected to four-point loading, with emphasis placed on the midspan deflection. The first beam served as a reference beam. The remaining beams had different tensile reinforcement and the confinement shapes were changed to gauge their effectiveness in improving the strength and ductility of the beams. The compressive strength of the concrete was 85 MPa and the tensile strength of the steel was 500 MPa and for the stirrups was 250 MPa. Results of testing the five beams proved that placing helixes with the right diameter and pitch in the compression zone of reinforced concrete beams improve their strength and ductility.

The use of unbounded tendons is common in prestressed concrete structures and evaluation of the stress increase in unbonded tendons at ultimate flexural strength of such structure has posed a great challenge over the years. Based on the bending experiment for two-span continuous post-tension beams with unbounded tendons and externally applied CFRP sheets, the monitoring of the stress increment of unbounded tendons is made in the loading process. For these aims, in this paper there are presented results of two continuous un-bonded post-tensioned I-beams were cast with high strength concrete (HSC) and monitored by electrical strain gauges. The beams are made of which are compared with the theory proposed by different codes. The results indicate that the ACI 318-2011 provides better estimates than AASHTO-2010 model whereas this model provides better estimates than BS 8110-97. Comparison of experimental ultimate tendon stress increase of strengthened and non-strengthened beams casted with HSC indicates that increase in tendon stress at an ultimate state in strengthened unbounded post-tensioned beam is lower than non-strengthened unbounded post-tension beam casted with HSC.

The remarkable ability of stem cells to renew themselves and to give rise to specialized cell types has raised huge hope for their clinical application. However, our limited understanding of the mechanisms that regulate stem cells poses a substantial hurdle for their clinical use: Since we know relatively little about how stem cells function, it is not surprising that we also struggle in growing them in a cell culture dish; most likely an important requirement for stem cell-based therapies.I believe that one cause of this problem is the inadequacy of tools that we have available to study stem cells at the single cell level. That is to say, even after careful prospective isolation based on immunophenotype, individual stem cells of a well-defined population behave highly heterogeneous in culture: some cells divide rapidly and others more slowly; some self-renew while others begin to differentiate; some can give rise to more lineages than others, etc. Because of this inherent variability, population-based studies of stem cells are essentially ‘black boxes’ and often unable to accurately address key biological questions, such as defining the discrete development steps from a single stem cell to a complex population of specialized cells (lineage development), or elucidating the mechanisms that regulate symmetric versus asymmetric divisions of stem cells.In this talk I will highlight recent efforts in my lab to address this important problem by developing and applying microfluidic technology to sequentially capture single HSC after multiple divisions to assess their fate, and in particular the symmetry of division, by multigene single cell qRT-PCR.