Continuous Coaxial Nozzle Design for LMD based on Numerical Simulation

AbstractThe LMD technology is becoming one of the most important emerging manufacturing technologies in the modern industry, due to its benefits when building-up geometries, repairing damaged parts or the creation of coatings to improve material properties and behaviour. One of the most relevant parameters in LMD process is the efficiency of the trapped powder into the melt pool, since metallic material powders use to be very expensive.With the aim of improving the ratio between the trapped powder in the deposited area and the total injected powder, the work presents a new methodology for continuous coaxial nozzle design for the LMD process based on a complete CFD model. The numerical model can predict particle flow, speed, powder concentration, etc. and design can be optimized using this input data.The model has been validated and then, it has been used for the design of two different nozzles: one discrete and one continuous coaxial nozzle

The enterococcal surface protein, Esp, is involved in Enterococcus faecalis biofilm formation

The enterococcal surface protein, Esp, is a high-molecular-weight surface protein of unknown function whose frequency is significantly increased among infection-derived Enterococcus faecalis isolates. In this work, a global structural similarity was found between Bap, a biofilm-associated protein of Staphylococcus aureus, and Esp. Analysis of the relationship between the presence of the Esp-encoding gene (esp) and the biofilm formation capacity in E. faecalis demonstrated that the presence of the esp gene is highly associated (P < 0.0001) with the capacity of E. faecalis to form a biofilm on a polystyrene surface, since 93.5% of the E. faecalis esp-positive isolates were capable of forming a biofilm. Moreover, none of the E. faecalis esp-deficient isolates were biofilm producers. Depending on the E. faecalis isolate, insertional mutagenesis of esp caused either a complete loss of the biofilm formation phenotype or no apparent phenotypic defect. Complementation studies revealed that Esp expression in an E. faecalis esp-deficient strain promoted primary attachment and biofilm formation on polystyrene and polyvinyl chloride plastic from urine collection bags. Together, these results demonstrate that (i) biofilm formation capacity is widespread among clinical E. faecalis isolates, (ii) the biofilm formation capacity is restricted to the E. faecalis strains harboring esp, and (iii) Esp promotes primary attachment and biofilm formation of E. faecalis on abiotic surfaces

A feedforward controller for tuning laser cladding melt pool geometry in real time

In this paper, a feedforward proportional-integral (PI) controller is developed to effectively control and tune the laser cladding melt pool geometry in real time. Width setpoint is included in the computer numerically controlled (CNC) programming, making possible its instantaneous change in relation to the position and time, as opposed to conventional controllers that do not have real-time information about these variables. The new concept of variable setpoint at different positions applied to laser cladding represents a great improvement in its use for changeable geometry applications such as blade fabrication. Several experiments are performed to characterize the behaviour of the system, revealing some key factors from monitoring system and image processing crucial for the controller. Laser power is selected as the input control variable, and the clad width is chosen as the output. The width of the melt pool is obtained based on measurements of CMOS camera images and an in-house image processing software algorithm. Closed-loop parameters are identified from the experimental data and Matlab simulations. The architecture of the controller consists on a conventional PI feedback loop and a feedforward module that shows low overshoot and fast response times. Instantaneous connections between laser, CNC, and PC systems allow for knowing the relationship among the exact position and real and setpoint melt pool values. The performance of the controller is verified in the fabrication of cladded parts with variable widths and in real time.The authors wish to acknowledge the support of the partners of the AMCOR project and the European Commission for their support in the FP7 project ‘Additive Manufacturing for Wear and Corrosion Applications’ (EU Project Reference NMP2-SE-2012-314324)

The enterococcal surface protein, Esp, is involved in Enterococcus faecalis biofilm formation

The enterococcal surface protein, Esp, is a high-molecular-weight surface protein of unknown function whose frequency is significantly increased among infection-derived Enterococcus faecalis isolates. In this work, a global structural similarity was found between Bap, a biofilm-associated protein of Staphylococcus aureus, and Esp. Analysis of the relationship between the presence of the Esp-encoding gene (esp) and the biofilm formation capacity in E. faecalis demonstrated that the presence of the esp gene is highly associated (P < 0.0001) with the capacity of E. faecalis to form a biofilm on a polystyrene surface, since 93.5% of the E. faecalis esp-positive isolates were capable of forming a biofilm. Moreover, none of the E. faecalis esp-deficient isolates were biofilm producers. Depending on the E. faecalis isolate, insertional mutagenesis of esp caused either a complete loss of the biofilm formation phenotype or no apparent phenotypic defect. Complementation studies revealed that Esp expression in an E. faecalis esp-deficient strain promoted primary attachment and biofilm formation on polystyrene and polyvinyl chloride plastic from urine collection bags. Together, these results demonstrate that (i) biofilm formation capacity is widespread among clinical E. faecalis isolates, (ii) the biofilm formation capacity is restricted to the E. faecalis strains harboring esp, and (iii) Esp promotes primary attachment and biofilm formation of E. faecalis on abiotic surfaces

Risk factors for reading disability in families with rolandic epilepsy

OBJECTIVE: The high prevalence and impact of neurodevelopmental comorbidities in childhood epilepsy are now well known, as are the increased risks and familial aggregation of reading disability (RD) and speech sound disorder (SSD) in rolandic epilepsy (RE). The risk factors for RD in the general population include male sex, SSD and ADHD but it is not known if these are the same in RE or whether there is a contributory role of seizure and treatment related variables. METHODS: An observational study of 108 RE probands (age range 3.6–22 years) and their 159 siblings (age range 1–29 years; 83 with EEG data) singly ascertained in the US or UK through an affected RE proband. We used a nested case-control design, multiple logistic regression and generalized estimating equations to test the hypothesis of association between RD and seizure variables or antiepileptic drug treatment in RE; we also assessed an association between EEG focal sharp waves and RD in siblings. RESULTS: RD was reported in 42% of probands and 22% of siblings. Among probands, RD was strongly associated with a history of SSD (OR 9.64, 95% CI: 2.45–37.21), ADHD symptoms (OR 10.31, 95% CI: 2.15–49.44), and male sex (OR 3.62, 95% CI: 1.11–11.75), but not with seizure or treatment variables. Among siblings, RD was independently associated only with SSD (OR 4.30, 95%CI: 1.42–13.0) and not with the presence of interictal EEG focal sharp waves. SIGNIFICANCE: The principal risk factors for RD in RE are SSD, ADHD and male sex, the same risk factors as for RD without epilepsy. Seizure or treatment variables do not appear to be important risk factors for RD in RE probands, and there was no evidence to support interictal EEG focal sharp waves as a risk factor for RD in siblings. Future studies should focus on the precise neuropsychological characterisation of RD in RE families, and on the effectiveness of standard oral-language and reading interventions