An Investigation of the Polymerization of Orthodontic Adhesives by the Transillumination of Tooth Tissue

1989 ◽  
Vol 16 (3) ◽  
pp. 183-188 ◽  
Author(s):  
L. Cheng ◽  
J. W. Ferguson ◽  
P. Jones ◽  
H. J. Wilson
Keyword(s):  
Healthy Volunteers ◽  
Light Source ◽  
Degree Of Polymerization ◽  
Surface Microhardness ◽  
Orthodontic Adhesives ◽  
Direct Exposure ◽  
Tooth Tissue ◽  
Control Samples

Prepared samples of light-activated composite were cured by transillumination of tooth tissue in healthy volunteers. Positioning of the samples and the direction of illumination was designed to simulate curing during direct bonding. The effectiveness of curing was investigated by determination of surface microhardness. The degree of polymerization of the specimens cured by transillumination was found to be reduced compared to the control samples cured by direct exposure to the light source.

scholarly journals Viscoelastometry for detecting oral anticoagulants

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Philipp Groene ◽  
Daniela Wagner ◽  
Tobias Kammerer ◽  
Lars Kellert ◽  
Andreas Giebl ◽  
...  
Keyword(s):  
Healthy Volunteers ◽  
Prospective Observational Study ◽  
Oral Anticoagulants ◽  
Plasma Concentrations ◽  
Factor Xa ◽  
Clotting Time ◽  
Emergency Situations ◽  
Tissue Plasminogen ◽  
The Impact

Abstract Background Determination of anticoagulant therapy is of pronounced interest in emergency situations. However, routine tests do not provide sufficient insight. This study was performed to investigate the impact of anticoagulants on the results of viscoelastometric assays using the ClotPro device. Methods This prospective, observational study was conducted in patients receiving dabigatran, factor Xa (FXa)-inhibitors, phenprocoumon, low molecular weight heparin (LMWH) or unfractionated heparin (UFH) (local ethics committee approval number: 17–525-4). Healthy volunteers served as controls. Viscoelastometric assays were performed, including the extrinsic test (EX-test), intrinsic test (IN-test) Russel’s viper venom test (RVV-test), ecarin test (ECA-test), and the tissue plasminogen activator test (TPA-test). Results 70 patients and 10 healthy volunteers were recruited. Clotting time in the EX-test (CTEX-test) was significantly prolonged versus controls by dabigatran, FXa inhibitors and phenprocoumon. CTIN-test was prolonged by dabigatran, FXa inhibitors and UFH. Dabigatran, FXa inhibitors and UFH significantly prolonged CTRVV-test in comparison with controls (median 200, 207 and 289 vs 63 s, respectively; all p < 0.0005). Only dabigatran elicited a significant increase in CTECA-test compared to controls (median 307 vs 73 s; p < 0.0001). CTECA-test correlated strongly with dabigatran plasma concentration (measured by anti-IIa activity; r = 0.9970; p < 0.0001) and provided 100% sensitivity and 100% specificity for detecting dabigatran. Plasma concentrations (anti-XA activity) of FXa inhibitors correlated with CTRVV-test (r = 0.7998; p < 0.0001), and CTRVV-test provided 83% sensitivity and 64% specificity for detecting FXa inhibitors. Conclusions In emergency situations, ClotPro viscoelastometric assessment of whole-blood samples may help towards determining the presence and type of anticoagulant class that a patient is taking. Trial registration German clinical trials database ID: DRKS00015302.

scholarly journals Determination of light source modules on blood glucose biomimetics using the reflectance method

2021 ◽  
Author(s):  
Bayu Prastowo ◽  
Renan Prasta Jenie ◽  
Ichsan Hardyanto ◽  
Muhammad Dahrul ◽  
Johan Iskandar ◽  
...  
Keyword(s):  
Blood Glucose ◽  
Light Source

Light source with light emitting diodes. Determination of limited frequencies and of the crest factor of illuminance meters and luminance meters

1989 ◽  
Vol 20 (5) ◽  
pp. 205-217
Author(s):  
J Deforges ◽  
P Garcia ◽  
J Bastie ◽  
F Marandet ◽  
J Bernard ◽  
...  
Keyword(s):  
Light Source ◽  
Light Emitting Diodes ◽  
Crest Factor ◽  
Light Emitting

scholarly journals Determination of Transformers’ Insulating Paper State Based on Classification Techniques

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 427 ◽  
Author(s):  
Sherif S. M. Ghoneim
Keyword(s):  
Prediction Model ◽  
Power Flow ◽  
Degree Of Polymerization ◽  
Classification Techniques ◽  
Aging Rate ◽  
Insulating Oil ◽  
Insulating Paper ◽  
Key Indicator ◽  
Carbon Dioxide Co2

The continuity of transformer operation is very necessary for utilities to maintain a continuity of power flow in networks and achieve a desired revenue. Most failures in a transformer are due to the degradation of the insulating system, which consists of insulating oil and paper. The degree of polymerization (DP) is a key detector of insulating paper state. Most research in the literature has computed the DP as a function of furan compounds, especially 2-furfuraldehyde (2-FAL). In this research, a prediction model was constructed based on some of most periodical tests that were conducted on transformer insulating oil, which were used as predictors of the insulating paper state. The tests evaluated carbon monoxide (CO), carbon dioxide (CO2), breakdown voltage (VBD), interfacial tension (IF), acidity (ACY), moisture (M), oil color (OC), and 2-furfuraldehyde (2-FAL). The DP, which was used as the key indicator for the paper state, was categorized into five classes labeled 1, 2, 3, 4, and 5 to express the insulating paper normal aging rate, accelerating aging rate, excessive aging danger zone, high risk of failure, and the end of expected life, respectively. The classification techniques were applied to the collected data samples to construct a prediction model for the insulating paper state, and the results revealed that the fine tree was the best classifier of the data samples, with a 96.2% prediction accuracy.

The effect of cytochalasin D on preprophase band organization in root tip cells of Allium

1992 ◽  
Vol 103 (4) ◽  
pp. 989-998 ◽  
Author(s):  
E.P. Eleftheriou ◽  
B.A. Palevitz
Keyword(s):  
Preprophase Band ◽  
Cytochalasin D ◽  
Root Tip ◽  
Average Width ◽  
Exact Position ◽  
The Relationship ◽  
Tip Cells ◽  
Root Tip Cells ◽  
Control Samples

The relationship between microfilaments (Mfs) and microtubules (Mts) in the organization of the preprophase band (PPB) was investigated in Allium root tip cells subjected to treatment with cytochalasin D (CD). Mts and Mfs were visualized by indirect immunofluorescence and various parameters such as PPB width were analyzed quantitatively. In control samples, the PPB first appears as a wide Mt band that progressively narrows to an average width of 4 micrometre in mid-prophase. Randomly oriented Mfs are present throughout the cytoplasm of most interphase control cells. Preprophase and prophase cells, however, contain cortical Mfs arranged parallel to the PPB. The Mfs initially occupy much of the cortex but in most cells they progressively become restricted to an area wider than the PPB. In the presence of CD, the PPB fails to narrow and remains at least two-fold wider than in control cells. PPB width expressed as a percentage of nuclear or cell length also increases compared to controls. Widening is concentration dependent, and the effect of 10 micromolar CD is near maximal only 15 min after application of the drug. This rapid response suggests that a rebroadening of already condensed PPBs takes place. After as little as 15 min in CD, Mfs are replaced by many small specks and rods. Dual localizations of both Mts and Mfs show that prophase cells contain broad PPBs without Mfs. The rapid disorganization of Mfs, by CD, therefore coincides with the rebroadening of PPBs. CD-treated cells in metaphase, anaphase and telophase contain larger actin aggregates at the poles, as previously reported. The results indicate that Mfs play an important role in the narrowing of the PPB, which in turn is essential for determination of the exact position of the plane of division. They also indicate that movement of intact Mts is important in PPB organization.

Applicability of Exposure Reciprocity Law for Fast Polymerization of Restorative Composites Containing Various Photoinitiating Systems

2021 ◽  
Author(s):  
A Tichy ◽  
P Bradna
Keyword(s):  
High Power ◽  
Irradiation Time ◽  
Spectral Characteristics ◽  
Degree Of Polymerization ◽  
High Irradiance ◽  
Bottom Surface ◽  
Surface Microhardness ◽  
Radiant Exposure ◽  
Reciprocity Law ◽  
Restorative Composites

SUMMARY Objectives: The exposure reciprocity law (ERL) has been used to calculate the optimal irradiation time of dental composites. This study examined the applicability of ERL for fast polymerization of restorative composites containing various photoinitiating systems using a high-power multi-peak light-emitting diode (LED) lamp. Methods: Three commercial composites differing in photoinitiating systems were tested: Filtek Ultimate Universal Restorative (FU) with a camphorquinone-amine (CQ-A) photoinitiating system, Tetric EvoCeram (TEC) with CQ-A and (2,4,6-trimethylbenzoyl)phosphine oxide (TPO), and Estelite Σ Quick (ESQ) with CQ and a radical amplified photopolymerization (RAP) initiator. Specimens 2-mm thick were polymerized using a high-power multipeak LED lamp (Valo) at 3 pairs of radiant exposures (referred to as low, moderate, and high) ranging from 15.8–26.7 J/cm2. They were achieved by different combinations of irradiation time (5–20 seconds) and irradiance (1300–2980 mW/cm2) as determined with a calibrated spectrometer. Knoop microhardness was measured 1, 24, and 168 hours after polymerization on specimen top (irradiated) and bottom surfaces to characterize the degree of polymerization. The results were statistically analyzed using a three-way analysis of variance and Tukey’s post hoc tests, α = 0.05. Results: Microhardness increased with radiant exposure and except for ESQ, top-surface microhardness was significantly higher than that on bottom surfaces. Combinations of high irradiance and short irradiation time significantly increased the top-surface microhardness of TEC at low and moderate radiant exposures, and the bottom-surface microhardness of FU at a low radiant exposure. In contrast, the microhardness of ESQ on both surfaces at high radiant exposure increased significantly when low irradiance and long irradiation time were used. With all tested composites, bottom-surface microhardness obtained at low radiant exposure was below 80% of the maximum top-surface microhardness, indicating insufficient polymerization. Conclusion: Combinations of irradiance and irradiation time had a significant effect on microhardness, which was affected by photoinitiators and the optical properties of composites as well as spectral characteristics of the polymerization lamp. Therefore, ERL cannot be universally applied for the calculation of optimal composite irradiation time. Despite high irradiance, fast polymerization led to insufficient bottom-surface microhardness, suggesting the necessity to also characterize the degree of polymerization on the bottom surfaces of composite increments when assessing the validity of ERL.

Οπτικοί βιοαισθητήρες για την ανίχνευση βιομορίων χωρίς τη χρήση ιχνηθετών

2015 ◽  
Author(s):  
Αιμιλία Ψαρούλη
Keyword(s):  
Light Source ◽  
Silicon Substrate ◽  
Serum Samples ◽  
Fully Integrated ◽  
Monolithically Integrated ◽  
Immunochemical Determination ◽  
Wide Range ◽  
Myocardial Infraction ◽  
Biological Recognition

Recent developments in the fields of bioanalytical chemistry and microelectronics have resulted in a growing trend of transferring the classical analytical methods from the laboratory bench to the field through the development of portable devices or microsystems based on biosensors. Biosensors are self-contained integrated devices capable to provide analytical information using biological recognition molecules in direct spatial contact with a transducer. Biosensors using antibodies or antigens as biological recognition elements are termed as immunosensors and they are based on the same principle as the classical solid-phase immunoassays.The aim of this thesis was to develop and evaluate an optical immunosensor based on Mach-Zehnder Interferometry and integrated on silicon substrate for the immunochemical determination of clinical analytes. The optical sensor developed is fabricated entirely by mainstream silicon technology by the Optical Biosensors group of the Institute of Nanoscience and Nanotechnology of NCSR “Demokritos” and combines arrays of ten sensors in a single silicon chip. Each sensor consists of an integrated on silicon light source that emits a broad spectrum in visible-near ultraviolet range and it is coupled to an integrated silicon nitride waveguide which has been patterned into Mach-Zehnder interferometer. The signal is recorded either through a photodetector monolithically integrated onto the same silicon chip (fully integrated configuration) or through an external spectrometer (semi-integrated configuration). In the fully integrated configuration, the signal recorded is the total photocurrent across the whole spectral range, while in semi-integrated configuration the whole transmission spectrum is continuously recorded and is mathematically transformed (Fourier Transform) to phase shift. As in the classical Mach-Zehnder interferometers, the waveguide in the proposed sensor is split into two arms, the sensing one which is appropriately modified with recognition biomolecule and the reference arm that is covered by a protective layer. The specific binding of the analyte with the immobilized onto the surface recognition biomolecule causes an effective refractive index change at the surface of the sensing arm thus affecting the phase of the waveguided light with respect to the reference arm. Thus, when the two arms converge again, an interference spectrum is generated that is altered during bioreaction providing the ability of monitoring in real-time and without using labels. The main difference of the sensor developed with respect to classical Mach-Zehnder interferometers is that the light source is monolithically integrated on the same silicon substrate with the waveguides and the waveguided light is not monochromatic, but broad spectrum.At first in this study, the method for chemical activation of biofunctionalization of chips was optimized. It was found that the highest signals were obtained when chips where activated by (3-aminopropyl)triethoxysilane and deposition of biomolecules solutions using a microarray spotter. Then, a comparison of the two sensor configurations, i.e. the fully and the semi-integrated configuration was performed using a model binding assay namely the streptavidin-biotin reaction. Semi-integrated configuration provided higher detection sensitivities mainly due to lower between-sensor signal variation in the same chip and between different chips. Thus, this configuration was selected for further evaluation with respect to the determination of analytes of clinical interest and especially of immunochemical determination of C-reactive protein in human serum samples. CRP is a marker of inflammation widely used in everyday clinical practice for diagnosis and therapy monitoring of inflammatory situations. Nevertheless, CRP has been also proposed as a prognostic marker of myocardial infraction and three risk levels have been established; low risk for serum CRP concentrations < 1 μg/mL; medium risk for concentrations in the range 1-3 μg/mL; and high risk for concentrations >3 μg/mL. In the frame of the present thesis, enzyme immunoassays for the determination of CRP in microtitration plates both competitive and non-competitive were developed in order to select the most appropriate reagents and define the immunoassay conditions. Then both assay format were transferred and evaluated on the sensor. It was found that the non-competitive format offered higher responses and ability for regeneration of immobilized onto the sensor antibody against CRP and was therefore selected for the final sensor evaluation. The assay developed following the competitive format was sensitive and accurate as was demonstrated through recovery and dilution linearity experiments, and provided for analysis of samples with a wide range of CRP concentrations since it was immune to the presence of serum. In addition, the CRP values determined with the immunosensor developed in serum samples from unknown donors were in good agreement with those determined for the same samples by commercially available kits and instruments showing the reliability of the determinations performed with the immunosensor developed and its potential for analysis of clinical samples.

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