Multifunctionality Analysis of Structural Supercapacitors- A Review

Structural supercapacitors (SSCs) are multifunctional energy storage composites (MESCs) that combine the mechanical properties of fiber-reinforced polymers and the electrochemical performance of supercapacitors to reduce the overall mass in lightweight applications with electrical energy consumption. These novel MESCs have huge potentials, and their properties have improved dramatically since their introduction in the early 2000's. However, the current properties of SSCs are not sufficient for complete energy supply of electrically driven devices. To overcome this drawback, the aim of the current study is to identify key areas for enhancement of the multifunctional performance of SSCs. Critical modification paths for the SSC constituents are systematically analyzed. Special focus is given to the improvement of carbon fiber-based electrodes, the selection of structural electrolytes and the implementation of separators for the development of more efficient SSCs. Finally, current SSCs are compared in terms of their multifunctionality including material combinations and modifications.

Determination of a Representative and 3D-Printable Root Canal Geometry for Endodontic Investigations and Pre-Clinical Endodontic Training-An Ex Vivo Study

Models of artificial root canals are used in several fields of endodontic investigations and pre-clinical endodontic training. They allow the physical testing of dental treatments, the operating of instruments used and the interaction between these instruments and the tissues. Currently, a large number of different artificial root canal models exist whose geometry is created either on the basis of selected natural root canal systems or to represent individual geometrical properties. Currently, only a few geometric properties such as the root canal curvature or the endodontic working width are taken into consideration when generating these models. To improve the representational capability of the artificial root canal models, the aim of the current study is therefore to generate an artificial root canal based on the statistical evaluation of selected natural root canals. Here, the approach introduced by Kucher for determining the geometry of a root canal model is used, which is based on the measurement and statistical evaluation of the root canal center line's curvatures and their cross-sectional dimensions. Using the example of unbranched distal root canals of mandibular molars (n = 29), an artificial root canal model representing the mean length, curvature, torsion and cross-sectional dimensions of these teeth could be derived.

Physicochemical Modeling of Electrochemical Impedance in Solid-State Supercapacitors

Solid-state supercapacitors (SSCs) consist of porous carbon electrodes and gel-polymer electrolytes and are used in novel energy storage applications. The current study aims to simulate the impedance of SSCs using a clearly defined equivalent circuit (EC) model with the ultimate goal of improving their performance. To this end, a conventional mathematical and a physicochemical model were adapted. The impedance was measured by electrochemical impedance spectroscopy (EIS). An EC consisting of electrical elements was introduced for each modeling approach. The mathematical model was purely based on a best-fit method and utilized an EC with intuitive elements. In contrast, the physicochemical model was motivated by advanced theories and allowed meaningful associations with properties at the electrode, the electrolyte, and their interface. The physicochemical model showed a higher approximation ability (relative error of 3.7%) due to the interface impedance integration in a more complex circuit design. However, this model required more modeling and optimization effort. Moreover, the fitted parameters differed from the analytically calculated ones due to uncertainties in the SSC's microscale configuration, which need further investigations. Nevertheless, the results show that the proposed physicochemical model is promising in simulating EIS data of SSCs with the additional advantage of utilizing well-reasoned property-based EC elements.

An Automated Measurement Method for the Endodontic Working Width of Lower Molars by Means of Parametric Models Using Cone-beam Computed Tomographcy and Micro-Computed Tomography

INTRODUCTION

A new method for the approximation of the root canal's cross-sectional shape and its working width using cone-beam computed tomographic (CBCT) or micro-computed tomographic (micro-CT) imaging was introduced.

METHODS

Scanned data from 29 extracted human mandibular first and second molar distal root canals without instrumentation were reconstructed and analyzed with a self-developed measurement algorithm. The 3-dimensional volume models were sliced perpendicular to the vertical axis. Using different 2-dimensional parametric models, the contour of each root canal slice was approximated and used to determine the canal's cross-sectional dimensions. The measurements of minor width, major width, and the root canal's conicity were statistically analyzed using analysis of variance.

RESULTS

The measured minor and major widths of the investigated root canals were significantly higher (probability value P < .05) when evaluated by CBCT images than the results obtained from micro-CT data. Both dimensions increased starting from the apical foramen (P < .01). The narrowest measured canal widths were 0.19-0.24 mm for CBCT imaging and 0.09-0.21 mm for micro-CT imaging in the apical part. The maximum values for conicity were between 13% and 17% in the cervical third.

CONCLUSIONS

The 3-dimensional imaging data from CBCT and micro-CT imaging enabled a valuable anatomic assessment of the root canal's cross-sectional working width along the canal up to the physiological foramen in order to determine an adequate apical diameter as well as the correct measured taper in the cervical and medial part.

Mapping of the Micro-Mechanical Properties of Human Root Dentin by Means of Microindentation

The extensive knowledge of root dentin's mechanical properties is necessary for the prediction of microstructural alterations and the teeth's deformations as well as their fracture behavior. Standardized microindentation tests were applied to apical, medial, and cervical root sections of a mandibular human first molar to determine the spatial distribution of the hard tissue's properties (indentation modulus, indentation hardness, Martens hardness, indentation creep). Using an indentation mapping approach, the inhomogeneity of mechanical properties in longitudinal as well as in transversal directions were measured. As a result, the tooth showed strongly inhomogeneous material properties, which depended on the longitudinal and transversal positions. In the transversal cutting planes of the cervical, medial, apical sections, the properties showed a comparable distribution. A statistical evaluation revealed an indentation modulus between 12.2 GPa and 17.8 GPa, indentation hardness between 0.4 GPa and 0.64 GPa and an indentation creep between 8.6% and 10.7%. The established standardized method is a starting point for further investigations concerning the intensive description of the inhomogeneous mechanical properties of human dentin and other types of dentin.

Effects of Endodontic Irrigants on Material and Surface Properties of Biocompatible Thermoplastics

Passive irrigation is an efficient method for a successful endodontic treatment. During sonic activation biocompatible polymer tips are used to activate irrigants. Compared to ultrasonic activation with metallic tips, polymer tips have the advantage of a reduced risk of fracture and minimise dentine damage. Hence, two polymers, polyether ether ketones (PEEK) and polyamide (PA6), were identified for the manufacturing of novel irrigation tips. The chemical resistance against the irrigants ethylenediaminetetraacetic acid (EDTA) 20%, chlorhexidine gluconate (CHX) 2% and sodium hypochlorite (NaOCl) 5.25% was analysed. Using microindentation, the change of hardness, elasticity, surface roughness and appearance of the polymers was determined. PA6 had a high absorption of irrigant compared to PEEK. PEEK was resistant to the investigated irrigants and showed no significant alteration of surface and mechanical properties, whereas PA6 slightly increased its hardness, elastic modulus and surface roughness during long-term exposure at 37 °C. However, PA6 tips seem to be a promising disposable product due to the material’s high deformability and low manufacturing costs. Particularly with regard to structural-dynamic properties and high chemical resistance, PEEK can be considered as a material for reusable irrigation tips.

Carriage of methicillin-resistant staphylococci by healthy companion animals in the US

Antimicrobial-resistant staphylococci have been associated with wounded or ill companion animals, but little is known about the prevalence of resistant staphylococci among healthy animals. In this study, 276 healthy dogs and cats from veterinary clinics were tested for the presence of antimicrobial-resistant Staphylococcus spp. Isolates were tested for antimicrobial susceptibility and the presence of select resistance genes, and typed using Pulsed-Field Gel Electrophoresis (PFGE). Staphylococcus aureus and Staphylococcus pseudintermedius were also characterized using multilocus sequence typing (MLST), spa typing and SCCmec typing. Approximately 5% (14/276) of the animals were positive by enrichment for five species of staphylococci [Staph. aureus (n = 11), Staph. pseudintermedius (n = 4), Staphylococcus sciuri (n = 6), Staphylococcus simulans (n = 1) and Staphylococcus warneri (n = 1)]. Seventy-eight per cent (18/23) of staphylococci were resistant to oxacillin and also multidrug resistant (resistance to ≥ 2 antimicrobials). All Staph. aureus isolates were mecA+ and blaZ+, SCCmec type II, spa type t002, ST5 and clonal using PFGE. Staphylococcus pseudintermedius were SCCmec type IV or V, spa type t06 and ST170; two of the isolates were pvl(+) . These results suggest that healthy companion animals may be a reservoir of multidrug-resistant staphylococci, which may be transferred to owners and others who handle companion animals.

SIGNIFICANCE AND IMPACT OF THE STUDY

In this study, antimicrobial-resistant coagulase-negative and coagulase-positive staphylococci were isolated from various body sites on healthy dogs and cats. Resistance to 14 antimicrobials was observed including resistance to oxacillin; the majority of staphylococci were also multidrug resistant. Results from this study suggest that healthy dogs and cats may act as reservoirs of antimicrobial-resistant bacteria that may be transferred to people by simple interaction with the animals. Such carriage poses an underlying risk of infection, which should be considered during handling of healthy dogs and cats by pet owners and veterinary personnel.

Anatomical distribution and genetic relatedness of antimicrobial-resistant Escherichia coli from healthy companion animals

AIMS

Escherichia coli have been targeted for studying antimicrobial resistance in companion animals because of opportunistic infections and as a surrogate for resistance patterns in zoonotic organisms. The aim of our study is to examine antimicrobial resistance in E. coli isolated from various anatomical sites on healthy dogs and cats and identify genetic relatedness.

METHODS AND RESULTS

From May to August, 2007, healthy companion animals (155 dogs and 121 cats) from three veterinary clinics in the Athens, GA, USA, were sampled. Escherichia coli was isolated from swabs of nasal, oral, rectal, abdomen and hindquarter areas. Antimicrobial susceptibility testing against 16 antimicrobials was performed using broth microdilution with the Sensititre™ system. Clonal types were determined by a standardized pulsed-field gel electrophoresis protocol. Although rectal swabs yielded the most E. coli (165/317; 52%) from dogs and cats, the organism was distributed evenly among the other body sites sampled. Escherichia coli isolates from both dogs and cats exhibited resistance to all antimicrobials tested with the exception of amikacin, cephalothin and kanamycin. Resistance to ampicillin was the most prevalent resistance phenotype detected (dogs, 33/199; 17%; and cats, 27/118; 23%). Among the resistant isolates, 21 resistance patterns were observed, where 18 patterns represented multidrug resistance (MDR; resistance ≥ 2 antimicrobial classes). Also among the resistant isolates, 33 unique clonal types were detected, where each clonal type contained isolates from various sampling sites. Similar resistance phenotypes were exhibited among clonal types, and three clonal types were from both dogs and cats.

CONCLUSIONS

Healthy companion animals can harbour antimicrobial-resistant E. coli on body sites that routinely come in contact with human handlers.

SIGNIFICANCE AND IMPACT OF THE STUDY

  This study is the first report that demonstrates a diverse antimicrobial-resistant E. coli population distributed over various sites of a companion animal's body, thereby suggesting potential transfer of resistant microflora to human hosts during contact.

Mechanisms of antimicrobial resistance and genetic relatedness among enterococci isolated from dogs and cats in the United States

AIMS

In this study, mechanisms of antimicrobial resistance and genetic relatedness among resistant enterococci from dogs and cats in the United States were determined.

METHODS AND RESULTS

Enterococci resistant to chloramphenicol, ciprofloxacin, erythromycin, gentamicin, kanamycin, streptomycin, lincomycin, quinupristin/dalfopristin and tetracycline were screened for the presence of 15 antimicrobial resistance genes. Five tetracycline resistance genes [tet(M), tet(O), tet(L), tet(S) and tet(U)] were detected with tet(M) accounting for approx. 60% (130/216) of tetracycline resistance; erm(B) was also widely distributed among 96% (43/45) of the erythromycin-resistant enterococci. Five aminoglycoside resistance genes were also detected among the kanamycin-resistant isolates with the majority of isolates (25/36; 69%) containing aph(3')-IIIa. The bifunctional aminoglycoside resistance gene, aac(6')-Ie-aph(2'')-Ia, was detected in gentamicin-resistant isolates and ant(6)-Ia in streptomycin-resistant isolates. The most common gene combination among enterococci from dogs (n = 11) was erm(B), aac(6')-Ie-aph(2'')-Ia, aph(3')-IIIa, tet(M), while tet(O), tet(L) were most common among cats (n = 18). Using pulsed-field gel electrophoresis (PFGE), isolates clustered according to enterococcal species, source and antimicrobial gene content and indistinguishable patterns were observed for some isolates from dogs and cats.

CONCLUSION

Enterococci from dogs and cats may be a source of antimicrobial resistance genes.

SIGNIFICANCE AND IMPACT OF THE STUDY

Dogs and cats may act as reservoirs of antimicrobial resistance genes that can be transferred from pets to people. Although host-specific ecovars of enterococcal species have been described, identical PFGE patterns suggest that enterococcal strains may be exchanged between these two animal species.