Highly Dynamic Voltage Control of a Dual Active Bridge over the Full Voltage Range by Operating Point Dependent Manipulated Variable Limitation

This paper presents a highly dynamic voltage control for the Dual Active Bridge over the full operating range. Maximum dynamics is achieved by using the maximum available manipulated variable in combination with a feedforward control of the capacitor current at a setpoint change. Operation within the system limits is ensured by a variable limitation of the manipulated variable considering the current operating point. The simulation results are validated by measurements on a 35 kW Dual Active Bridge test bench

Loss Estimation of a Dual Active Bridge as part of a Solid State Transformer using Frequency Domain Modelling

This paper proposes an improved method for the loss estimation of a Dual Active Bridge (DAB) using frequency domain modelling. The method uses a detailed, frequency depending transformer model to describe even highly utilized DABs. The model is used to estimate the occurring losses of a DAB as part of an modular Solid State Transformer (SST). The influence of the SST\u27s phase power ripple is considered for the loss estimation. The results of the frequency domain model and the loss calculation are validated using measurement data of an SST-cell prototype

Design and Characterization of a 500 kW 20 kHz Dual Active Bridge using 1.2 kV SiC MOSFETs

High power Silicon Carbide (SiC) semiconduc-tor enable an increase of the power level for the Dual Active Bridge (DAB). This paper presents a concept for a novel high power DAB up to 500 kW. 1200 V SiC MOSFETs are used as power semiconductors, which are operated with a switching frequency of 20 kHz. In order to investigate the feasibility of such high power DABs basic design rules are presented and the influence of parasitic components is deduced. It is shown that these parasitic effects become more and more important with increasing power and therefore cannot be neglected as in the case of lower power DABs. Using a calorimetric measurement setup a detailed loss distribution is presented. Measurements confirm the concept for the parasitic influence and design target of 500 k W

General diseases and medications in 687 patients reporting on adverse effects from dental materials.

OBJECTIVES Examination of patients claiming adverse effects from dental materials can be very challenging. Particularly, systemic aspects must be considered besides dental and orofacial diseases and allergies. Therefore, the aim of this study was to investigate a cohort of 687 patients reporting on adverse effects from dental materials focusing on findings related to known general diseases or conditions or medication-related findings with relevance to their subjective complaints. METHODS Six hundred eighty-seven patients visiting a specialized consultation on claimed adverse effects from dental materials were retrospectively investigated for their subjective complaints, findings related to known general diseases or conditions, medication-related findings, dental and orofacial findings, or allergies with relevance to their subjective complaints. RESULTS The most frequent subjective complaints were burning mouth (44.1%), taste disorders (28.5%), and dry mouth (23.7%). In 58.4% of the patients, dental and orofacial findings relevant to their complaints could be found. Findings related to known general diseases or conditions or medication-related findings were found in 28.7% or 21.0% of the patients, respectively. Regarding medications, findings related to antihypertensives (10.0%) and psychotropic drugs (5.7%) were found most frequently. Relevant diagnosed allergies toward dental materials were found in 11.9%, hyposalivation in 9.6% of the patients. In 15.1% of the patients, no objectifiable causes for the expressed complaints could be found. CONCLUSIONS For patients complaining of adverse effects from dental materials, findings related to known general diseases or conditions and medications should be given particular consideration, while still in some patients, no objectifiable causes for their complaints can be found. CLINICAL RELEVANCE For patients complaining about adverse effects from dental materials, specialized consultations and close collaboration with experts from other medical fields are eligible

Antibacterial efficacy of cold atmospheric plasma against Enterococcus faecalis planktonic cultures and biofilms in vitro

Nosocomial infections have become a serious threat in our times and are getting more difficult to handle due to increasing development of resistances in bacteria. In this light, cold atmospheric plasma (CAP), which is known to effectively inactivate microorganisms, may be a promising alternative for application in the fields of dentistry and dermatology. CAPs are partly ionised gases, which operate at low temperature and are composed of electrons, ions, excited atoms and molecules, reactive oxygen and nitrogen species. In this study, the effect of CAP generated from ambient air was investigated against Enterococcus faecalis, grown on agar plates or as biofilms cultured for up to 72 h. CAP reduced the colony forming units (CFU) on agar plates by > 7 log10 steps. Treatment of 24 h old biofilms of E. faecalis resulted in CFU-reductions by ≥ 3 log10 steps after CAP treatment for 5 min and by ≥ 5 log10 steps after CAP treatment for 10 min. In biofilm experiments, chlorhexidine (CHX) and UVC radiation served as positive controls and were only slightly more effective than CAP. There was no damage of cytoplasmic membranes upon CAP treatment as shown by spectrometric measurements for release of nucleic acids. Thus, membrane damage seems not to be the primary mechanism of action for CAP towards E. faecalis. Overall, CAP showed pronounced antimicrobial efficacy against E. faecalis on agar plates as well as in biofilms similar to positive controls CHX or UVC

Membrane damage as mechanism of photodynamic inactivation using Methylene blue and TMPyP in Escherichia coli and Staphylococcus aureus

The worldwide threat of antibiotic resistance requires alternative strategies to fight bacterial infections. A promising approach to support conventional antibiotic therapy is the antimicrobial photodynamic inactivation (aPDI). The aim of this work was to show further insights into the antimicrobial photodynamic principle using two photosensitizers (PS) of different chemical classes, Methylene Blue (MB) and TMPyP, and the organisms Escherichia coli and Staphylococcus aureus as Gram-negative and Gram-positive representatives. Planktonic cultures of both species were cultured under aerobic conditions for 24 h followed by treatment with MB or TMPyP at various concentrations for an incubation period of 10 min and subsequent irradiation for 10 min. Ability to replicate was evaluated by CFU assay. Accumulation of PS was measured using a spectrophotometer. The cytoplasmic membrane integrity was investigated by flow cytometry using SYBR Green and propidium iodide. In experiments on the replication ability of bacteria after photodynamic treatment with TMPyP or MB, a killing rate of 5 log10 steps of the bacteria was achieved. Concentration-dependent accumulation of both PS was shown by spectrophotometric measurements whereby a higher accumulation of TMPyP and less accumulation of MB was found for S. aureus as compared to E. coli. For the first time, a membrane-damaging effect of TMPyP and MB in both bacterial strains could be shown using flow cytometry analyses. Furthermore, we found that reduction of the replication ability occurs with lower concentrations than needed for membrane damage upon MB suggesting that membrane damage is not the only mechanism of aPDI using MB

Randomized clinical split-mouth study on a novel self-adhesive bulk-fill restorative vs. a conventional bulk-fill composite for restoration of class II cavities – results after three years

Objectives This randomized prospective split-mouth study evaluated the clinical performance of a novel, tooth-colored, self-adhesive bulk-fill restorative (SABF, 3M) for restoration of class II cavities as compared to a conventional bulk-fill composite (Filtek One, 3M; FOBF) over 36 months. The null-hypothesis was that both materials perform equally regarding clinical success and performance according to the FDI clinical criteria and scoring system. Methods 30 patients received one SABF and one FOBF restoration each. For FOBF, Scotchbond Universal (3M) was used as adhesive (self-etch mode), whereas SABF was applied without adhesive. Two blinded examiners evaluated the restorations at baseline, 24 and 36 months using FDI criteria. Data were analyzed non-parametrically (χ2-tests; α=0.05). Results 29 patients were available for the 24- and 36-month examinations. Clinical success rate was 96.6% for both materials at 36-mo (one restoration failure due to secondary caries each). All other restorations revealed clinically acceptable FDI scores at all recalls. FOBF performed significantly better than SABF at all time points regarding surface lustre (p<0.001) and color match and translucency (p<0.001) and regarding marginal staining at 36-months (p=0.008). Marginal staining and marginal adaptation deteriorated significantly over time for both materials (both p<0.001). Conclusions The null-hypothesis could only partially be rejected. Both materials performed similarly regarding clinical success and performance within 36 months of clinical service, but SABF exhibited significantly inferior, but clinically fully acceptable esthetic properties as compared to FOBF. Both restorative materials showed clinically fully acceptable results over 36 months of clinical service and thus may be recommended for clinical use. Clinical significance The novel tooth-colored self-adhesive bulk-fill restorative exhibited clinically fully acceptable results over 36 months of clinical service, similarly to a conventional bulk-fill restorative used with a universal adhesive, but with slight shortcomings in esthetic properties. Therefore, both restorative materials may be recommended for clinical use

The Optimal Effective Concentration Combination (OPECC) as a Novel Method for Evaluating the Effects of Binary Application of Antibacterial Compounds

Combination therapies appear to be beneficial for preventing bacterial resistance to antibacterial approaches. The aim of this study was to define and determine an optimal effective concentration combination (OPECC) for binary application of antibacterial compounds. The antiseptics chlorhexidine (CHX), benzalkonium chloride (BAC), and cetylpyridinium chloride (CPC), as well as the antibiotic ciprofloxacin (CIP), were tested against planktonic Escherichia coli in binary combinations by applying a checkerboard assay, and then evaluated according to the established synergism principles. Extending the checkerboard method, the optical density (OD) of the wells was measured photometrically. On the borderline between effective (OD = 0) and non-effective (OD > 0) eradication of the bacterial cultures, the OPECC was determined. Binary combinations of CPC or CHX with BAC were assessed as either synergistic or indifferent, respectively, while there was no OPECC to calculate. For all other binary combinations, an OPECC was derivable, and these were assessed as either synergistic or indifferent. In conclusion, the evaluation of the binary combination application of antibacterial compounds based on the checkerboard method was refined to such an extent that it was possible to determine at least one concentration pair that could be defined and considered as an OPECC, independently of the evaluation of the system according to the different synergy principles. In general, the method presented herein for determining an OPECC can be applied to any conceivable method or system aimed at the eradication of a pathogen