Restorative Dentistry: Dental composite depth of cure with halogen and blue light emitting diode technology

Objectives To test the hypothesis that a blue light emitting diode (LED) light curing unit (LCU) can produce an equal dental composite depth of cure to a halogen LCU adjusted to give an irradiance of 300 mWcm–2 and to characterise the LCU's light outputs. Materials and methods Depth of cure for three popular composites was determined using a penetrometer. The Student's t test was used to analyse the depth of cure results. A power meter and a spectrometer measured the light output. Results The spectral distribution of the LCUs differed strongly. The irradiance for the LED and halogen LCUs were 290 mWcm–2 and 455 mWcm–2, when calculated from the scientific power meter measurements. The LED LCU cured all three dental composites to a significantly greater (P < 0.05) depth than the halogen LCU. Conclusions An LED LCU with an irradiance 64% of a halogen LCU achieved a significantly greater depth of cure. The LCU's spectral distribution of emitted light should be considered in addition to irradiance as a performance indicator. LED LCUs may have a potential for use in dental practice because their performance does not significantly reduce with time as do conventional halogen LCUs

Interiority, exteriority and the realm of intentionality

The realm of intentionality is definitive of phenomenology as a reflective methodology. Yet it is precisely the focus on the intentional given that has been condemned recently. Speculative realism (e.g. Meillassoux, 2008/2006) argues that phenomenology is unsatisfactory since the reduction to the intentional realm excludes the 'external', i.e. reality independent of consciousness. This criticism allows me to clarify the nature of intentionality. Material phenomenology finds, in contrast, that the intentional realm excludes the 'inner' ('auto-affective life' - Henry, 1973/1963). This criticism allows me to discuss the way in which ipseity enters as an element of experience. Intentionality, viewed psychologically, is rightly the distinct arena of phenomenological psychology. However, there is no doubting the difficulty of maintaining a research focus precisely on the realm of intentionality; there are aporias of the reduction. I discuss some of the difficulties

A scoping review of clinical practices and adherence to UK national guidance related to the placement and position confirmation of adult nasogastric feeding tubes.

The administration of nutrition or medication into the lungs or pleura via a misplaced nasogastric feeding tube is considered a never event. Despite guidance from the National Patient Safety Agency and NHS Improvement this never event is regularly reported. Confirmation of correct placement and correct use of nasogastric tubes requires appropriate actions and decisions by a multidisciplinary team. A scoping review identified 43 records that discussed and supported nasogastric tube misplacement as a Never Event. Searches were completed using Web of Science, CINAHL, Google Scholar, British Nursing Index (BNI), as well as selected journals. A further manual search revealed 22 publicly available NHS Trust policies related to nasogastric feeding tube procedures. Items generated between 2011 and 2020 were considered eligible. A thematic analysis was completed to assess adherence to guidance and the practices in place across the NHS. Three key themes were identified as part of the review: referral and authorisation of radiography, examination description, and visualisation of the nasogastric tube tip. Large variations in practice were identified. While there is recognition of national guidance, records showed inconsistency and lacked the required detail to ensure patient safety. Despite classification as a never event, it is apparent that there is still room for improvement and further guidance in ensuring patient safety with respect to nasogastric tube insertion. Practice requires further standardisation whilst also ensuring optimisation and safety. Guidance should address in depth imaging authorisation, language and exact standards of acceptability for imaging the full length of the nasogastric tube. [Abstract copyright: Crown Copyright © 2022. Published by Elsevier Ltd. All rights reserved.

Application of a helicopter mathematical model to the Langley differential maneuvering simulator for use in a helicopter/fighter evasive maneuver study

A real time simulation study was conducted using a differential maneuvering simulator to determine and evaluate helicopter evasive maneuvers when attacked by fighter aircraft. A general helicopter mathematical model was modified to represent an H-53 helicopter. The helicopter model was compared to H-53 flight test data to determine any differences between the simulated and actual vehicles. The simulated helicopter was also subjectively validated by participating pilots. Two fighter mathematical models validated in previous studies were utilized for the attacking aircraft. The results of this simulation study have been verified in a flight test program conducted by the U. S. Air Force and were found to closely match the flight results

Stabilization and precise calibration of a continuous-wave difference frequency spectrometer by use of a simple transfer cavity

A novel, simple, and inexpensive calibration scheme for a continuous-wave difference frequency spectrometer is presented, based on the stabilization of an open transfer cavity by locking onto the output of a polarization stabilized HeNe laser. High frequency, acoustic fluctuations of the transfer cavity length are compensated with a piezoelectric transducer mounted mirror, while long term drift in cavity length is controlled by thermal feedback. A single mode Ar+ laser, used with a single mode ring dye laser in the difference frequency generation of 2–4 µm light, is then locked onto a suitable fringe of this stable cavity, achieving a very small long term drift and furthermore reducing the free running Ar+ linewidth to about 1 MHz. The dye laser scan provides tunability in the difference frequency mixing process, and is calibrated by marker fringes with the same stable cavity. Due to the absolute stability of the marker cavity, precise frequency determination of near infrared molecular transitions is achieved via interpolation between these marker fringes. It is shown theoretically that the residual error of this scheme due to the dispersion of air in the transfer cavity is quite small, and experimentally that a frequency precision on the order of 1 MHz per hour is routinely obtained with respect to molecular transitions. Review of Scientific Instruments is copyrighted by The American Institute of Physics

Space station automation of common module power management and distribution, volume 2

The new Space Station Module Power Management and Distribution System (SSM/PMAD) testbed automation system is described. The subjects discussed include testbed 120 volt dc star bus configuration and operation, SSM/PMAD automation system architecture, fault recovery and management expert system (FRAMES) rules english representation, the SSM/PMAD user interface, and the SSM/PMAD future direction. Several appendices are presented and include the following: SSM/PMAD interface user manual version 1.0, SSM/PMAD lowest level processor (LLP) reference, SSM/PMAD technical reference version 1.0, SSM/PMAD LLP visual control logic representation's (VCLR's), SSM/PMAD LLP/FRAMES interface control document (ICD) , and SSM/PMAD LLP switchgear interface controller (SIC) ICD

Coherent State Approach to Quantum Clocks

The ``problem of time'' has been a pressing issue in quantum gravity for some time. To help understand this problem, Rovelli proposed a model of a two harmonic oscillators system where one of the oscillators can be thought of as a ``clock'' for the other oscillator thus giving a natural time reference frame for the system. Recently, the author has constructed an explicit form for the coherent states on the reduced phase space of this system in terms of Klauder's projection operator approach. In this paper, by using coherent state representations and other tools from coherent state quantization, I investigate the construction of gauge invariant operators on this reduced phase space, and the ability to use a quantum oscillator as a ``clock.''Comment: 13 pages, Late

On the Cooling of the Neutron Star in Cassiopeia A

We demonstrate that the high-quality cooling data observed for the young neutron star in the supernova remnant Cassiopeia A over the past 10 years--as well as all other reliably known temperature data of neutron stars--can be comfortably explained within the "nuclear medium cooling" scenario. The cooling rates of this scenario account for medium-modified one-pion exchange in dense matter and polarization effects in the pair-breaking formations of superfluid neutrons and protons. Crucial for the successful description of the observed data is a substantial reduction of the thermal conductivity, resulting from a suppression of both the electron and nucleon contributions to it by medium effects. We also find that possibly in as little as about ten years of continued observation, the data may tell whether or not fast cooling processes are active in this neutron star.Comment: 4 pages, 3 figure