Effect of side holes in cervical fusion cages: a finite element analysis study

The objective of this study was to investigate the effect of side holes on the predicted von Mises stress levels in cervical spinal fusion cages subjected to compressive loading. Models with between zero and ten side holes were developed. Finite element analysis (FEA) was used to simulate compression of the cage, made from the polymer PEEK (polyetheretherketone), between two adjacent vertebrae. The analyses were validated by experimental tests. In all of the models, the von Mises stress was highest at the cage-vertebrae interface with peak stresses of between 14 and 18 MPa. Increasing the Young's modulus of the vertebrae from 12 to 30 GPa increased the peak stress on average by 29 per cent. The stresses in the models were lower than the compressive strength of PEEK (118 MPa), and are well within the PEEK fatigue strength reported (60 MPa at 10 million cycles). This study suggests that the number of side holes had a negligible effect on the stress distribution within the cage; the stress magnitudes were fairly constant across all of the models and did not change substantially with the number of holes. Hence, a cervical cage with side holes is unlikely to fail in compression.     

Influence of surface roughness on flotation kinetics of quartz

Surface roughness of quartz particles was determined by measuring the specific surface area of particles. The wettability characteristics of particles were determined by measuring the flotation rate using a laboratory flotation cell. Experimental results show that the rod mill product has higher roughness than the ball mill product. For the particles with larger surface roughness, the flotation kinetics constant is also higher. Finally, empirical relationships between surface roughness (r) and the flotation kinetics constant (k) of quartz particles as k=A+Br+Cr ^0.5lnr+D/lnr+E/r and k=A+Br are presented, in which A, B, C, D and E are constants related to experimental conditions and mineralogical properties of mineral.     

Convenient synthesis of sulfonamides from amines and p‐toluene sulfonyl chloride mediated by crosslinked poly(4‐vinylpyridine)

A general, mild, and convenient method has been developed for the synthesis of various N‐substituted and N, N‐disubstituted sulfonamides, as a class of sulfa drugs, from the corresponding amines and p‐toluene sulfonyl chloride in the presence of readily available crosslinked poly(4‐vinylpyridine) as a catalyst, base or polymeric substrates. The use of polymeric catalyst simplifies routine sulfonylation of amines because it eliminates the traditional purification. The polymer can be removed quantitatively and it can be regenerated and reused for several cycles without losing its activity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

New,Non‐quinone Fluorogeldanamycin Derivatives Strongly Inhibit Hsp90

Streptomyces hygroscopicus is a natural producer of geldanamycin. Mutasynthetic supplementation of an AHBA‐blocked mutant with all possible monofluoro 3‐aminobenzoic acids provided new fluorogeldanamycins. These showed strong antiproliferative activity and inhibitory effects on human heat shock protein Hsp90. Binding to Hsp90 in the low nanomolar range was determined from molecular modelling, AFM analysis and by calorimetric studies.     

Experimental investigation of tornado-like vortex dynamics with swirl ratio: The mean and turbulent flow fields

An experimental simulation of tornado-like vortices is conducted in a small tornado vortex simulator in order to study the effect of swirl ratio on flow characteristics. Particle Image Velocimetry (PIV) method is employed to quantitatively determine the tornado-vortex velocity field for swirl ratios ranging from 0.08 to 1. The radial and tangential components of velocity as well as the core radius of the tornado increase with increase in swirl ratio. The location of the maximum radial and tangential velocities is adjacent to the ground where the tornado vortex interacts with the surface. The values of normal and shear turbulent stresses indicate the existence of a laminar core for small swirl. As expected the shear stresses increase with swirl ratio as the vortex becomes turbulent. The highest turbulent production corresponds to the critical case of vortex touchdown.     

Constitutive Relationships for Steel Fibre Reinforced Concrete at Elevated Temperatures

Steel fibre reinforced concrete (SFRC) is an advanced cementitious composite where fibres can act as a profitable replacement for diffused reinforcement, like welded steel mesh, especially for thin cross sections. In this case fire becomes a very important condition in the design. Previous experimental research has shown the benefits in fire resistance of steel fibres, when structural elements are bent. The proper understanding of the effects of elevated temperatures on the properties of SFRC is necessary. In this study, constitutive relationships are developed for high-strength FRSC subjected to fire, with the purpose of given that capable modelling and to specify the fire-performance criteria for concrete structures. They are developed for unconfined FRSC specimens that include compressive and tensile strengths, modulus of elasticity, modulus of rupture, strain at peak stress, and compressive stress–strain relationships at elevated temperatures. The proposed relationships at elevated temperature are compared with experimental results. These results are used to establish compressive stress–strain relationships. Further experimental results for tension and the other main parameters at elevated temperature are needed in order to establish well-founded models and to improve the proposed constitutive relationships, which are general, rational, and fit well with the experimental results.     

High Strength Polypropylene Fibre Reinforcement Concrete at High Temperature

Concrete is an inherently brittle material with a relatively low tensile strength compared to compressive strength. Reinforcement with randomly distributed short fibres presents an effective approach to the stabilization of the crack and improving the ductility and tensile strength of concrete. A variety of fibre types, including steel, synthetics, and natural fibres, have been applied to concrete. Polypropylene (PP) fibre reinforcement is considered to be an effective method for improving the shrinkage cracking characteristics, toughness, and impact resistance of concrete materials. Also, the use of PP fibre has been recommended by all of the researchers to reduce and eliminate the risk of the explosive spalling in high strength concrete at elevated temperatures. In this study, constitutive relationships are developed for normal and high-strength PP fibre reinforcement concrete (PPFRC) subjected to high temperatures to provide efficient modelling and specify the fire-performance criteria for concrete structures. They are developed for unconfined PPFRC specimens that include compressive and tensile strengths, elastic modulus, modulus of rupture, strain at peak stress as well as compressive stress–strain relationships at elevated temperatures. The proposed relationships at elevated temperature are compared with experimental results. These results are used to establish more accurate and general compressive stress–strain relationships prediction. Further experimental results for tension and the other main parameters at elevated temperature are needed in order to establish well-founded models and to improve the proposed constitutive relationships, which are general, rational, and fit well with the experimental results.     

Situational constraint effects on performance, affective reactions, and turnover: A field replication and extension.

Administered a demographic questionnaire, ability and personality tests, and measures of job performance, satisfaction, turnover, and situational constraints to 731 20–65 yr old store managers, 555 22–62 yr old supervisors, and 164 25–60 yr old district managers from the same company. Results replicate previous laboratory findings and show that higher situational constraints were associated with lower employee performance. The performance ratings given to managers facing the most severe situational constraints were significantly poorer than those received by managers dealing with lower levels of constraints. The presence of situational constraints is associated with employees expressing greater dissatisfaction and frustration. The group facing the highest level of situational constraints had the highest level of turnover. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exploring the recovery of fatigue damage in bituminous mixtures: the role of rest periods

Recovery capability of bituminous materials plays a significant role in the development of new technologies for extending the service life of asphalt pavements. This capability originates from various phenomena such as thixotropy, cooling, relaxation of hardening, or healing. However, their real effect on mechanical response is not clear. This article aims to investigate how rest periods (RPs) available between traffic loads can contribute to the damage recovery of bituminous materials. For this purpose, different types and durations of RPs were applied during the laboratory evaluation of fatigue resistance of these materials using the University of Granada Fatigue Asphalt Cracking Test method. The results indicate that the addition of RPs to the loading regime could lead to an extension in the fatigue life of bituminous materials. Additionally, an increase in the RP duration showed a positive impact on the resistance of the materials against cyclic loading. Nonetheless, these benefits are not only related to the recovery of lost properties during RPs, but also a growth in the amount of plastic deformations as a result of the applying RPs could delay the appearance of damages (i.e. cracking). Consequently, the bituminous material can tolerate a higher number of load cycles during fatigue test.     

Metal‐Based Nanomaterials in Biomedical Applications: Antimicrobial Activity and Cytotoxicity Aspects

Microbial colonization on material surfaces is ubiquitous. Biofilms derived from surface‐colonized microbes pose serious problems to the society from both an economical perspective and a health concern. Incorporation of antimicrobial nanocompounds within or on the surface of materials, or by coatings, to prevent microbial adhesion or kill the microorganisms after their attachment to biofilms, represents an important strategy in an increasingly challenging field. Over the last decade, many studies have been devoted to preparing meta‐based nanomaterials that possess antibacterial, antiviral, and antifungal activities to combat pathogen‐related diseases. Herein, an overview on the state‐of‐the‐art antimicrobial nanosized metal‐based compounds is provided, including metal and metal oxide nanoparticles as well as transition metal nanosheets. The antimicrobial mechanism of these nanostructures and their biomedical applications such as catheters, implants, medical delivery systems, tissue engineering, and dentistry are discussed. Their properties as well as potential caveats such as cytotoxicity, diminishing efficacy, and induction of antimicrobial resistance of materials incorporating these nanostructures are reviewed to provide a backdrop for future research.