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Measuring and Quantifying Ultraviolet Radiation Exposures
Published in Francis N. Marzulli, Howard I. Maibach, Dermatotoxicology Methods: The Laboratory Worker’s Vade Mecum, 2019
Prior to any discussion of light sources and measurements, it is important to consider those physical quantities and units useful in photobiology. These quantities are termed radiometric (and spectroradiometric), and they should not be confused with the photometric system of measurements (lumens and candelas) used by lighting engineers (CIE, 1987). Radiometry is the science of measurement of optical radiation. Photometry is the science of measuring visible radiation, that is, light. Radiometric quantities such as radiant power—used to describe the output power (not electrical input power) of a source in watts (W)—must be used to describe and quantify ultraviolet radiation (UVR). Photometric quantities such as luminous power— used to describe the luminous output of a lamp in lumens (lm)—are based upon the relative visibility of different spectral sources as seen by a human “standard observer.” In illuminating engineering, light levels are spectrally weighted by the standard photometric visibility curve, which peaks at 550 nm for the human eye (CIE, 1987).
Spectroscopy and Fluorimetry
Published in Joseph Chamberlain, The Analysis of Drugs in Biological Fluids, 2018
The pH of samples used for measurement can dramatically affect the absorption spectrum, and this property should also be utilized in the development of a spectro-photometric method. The classic examples of this phenomenon are phenol and aniline. Phenol in its un-ionized form absorbs at 270 nm with a molar absorptivity of 1450. In alkaline solution, however, the phenate ion absorbs at 287 nm with an ɛ value of 2600. This increased absorbance is due to the presence of additional unshared electrons available for conjugation with the phenyl ring. Aniline, on the other hand, already has a pair of unshared electrons available for conjugation in the nonprotonated form; the absorption maximum of aniline in neutral or alkaline solution is at 280 nm with an ɛ value of 1430. The addition of acid results in protonation of the unpaired electrons, conjugation is decreased, and the absorption maximum shifts to 254 nm with an ɛ value of 160.
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Published in Anton Sebastian, A Dictionary of the History of Medicine, 2018
Microchemistry Technique for measuring concentration of chemicals in small samples of biological fluids was introduced around 1910. The photometer, an instrument which utilized a photocell linked to a sensitive microammeter, for analysis of the chemical constituents in small samples of blood and urine, was invented by G.E. Davis and C. Sheard of America in 1927. A photoelectric hemoglobinometer was developed by Sheard and A.H. Sanford in 1928.
Characterization of high-molecular weight by-products in the production of a trivalent bispecific 2+1 heterodimeric antibody
Published in mAbs, 2023
Dario A. T. Cramer, Vojtech Franc, Anna-Katharina Heidenreich, Michaela Hook, Mahdi Adibzadeh, Dietmar Reusch, Albert J. R. Heck, Markus Haberger
Although fully purified 2 + 1 CrossMAb product is already highly pure (Figure 1), it is always crucial to have a good understanding of low abundant by-products. With the approach presented here, we provide a range of strategies to answer questions about the chemical binding nature or structures and modifications of HMW by-products. In addition, we use well-described methods.13,29,34,35 Our multi-method approach helped explain differences in potency and characterize by-products formed during production. We were able to show by SDS-PAGE that there are multiple and non-covalent by-products in the HMW1 fraction. These results were complemented by mass photometry. By simply adding acid and comparing photometric data to the SDS-PAGE, we saw the partial non-covalent nature of the tetravalent variant. Mass photometry is a handy and rapid tool to give insight into therapeutics and by-products under different conditions and is already finding its place in the analysis of therapeutics.29 It allows the manipulation of the environment by introducing other buffers and reducing agents and ligands all within minutes per measurement. Another advantage is that this approach is not limited to only complex mAb formats. This also includes effects such as polymerization and aggregation, of which a recent example is the investigation of the multiple forms of haptoglobin.22 The main disadvantage of mass photometry is the lower resolution when analyte mass differences are below ~20 kDa.
Ocular surface predisposing factors for digital display-induced dry eye
Published in Clinical and Experimental Optometry, 2023
Cristian Talens-Estarelles, José Vicente García-Marqués, Alejandro Cerviño, Santiago García-Lázaro
All measurements were taken in the same laboratory. The approximate duration of each session was 45 minutes. All the sessions were carried out at the same time of the day (first thing in the morning, at 9 am) and under the same, constant environmental conditions (temperature and humidity). In addition, participants were asked not to use other digital displays 30 minutes before the session and not to drink any beverage containing caffeine 24 hours before the measurements to prevent any disruption of the ocular surface or blinking alterations prior to the visit.21 The laboratory was set up 15 minutes prior to each participants’ visit. To minimise the effects of outdoor conditions on the way to the laboratory, a 15-minute acclimatisation period was left between the entry of the participants into the room and the measurements. The whole experiment was carried out under constant background illumination. The room was free from ambient lighting. Room illuminance was maintained at approximately 220 ± 7.14 lux on the plane of the eyes of the participants. Chroma Metre CL-200 lux metre (Konica Minolta, Ramsey, NJ) was used to measure photometric values. Room temperature and humidity were constantly monitored and remained stable at 22.7 ± 1.6 °C and 42.8 ± 4.7%, respectively.
Effect of hematocrit, galactose and ascorbic acid on the blood glucose readings of three point-of-care glucometers
Published in Scandinavian Journal of Clinical and Laboratory Investigation, 2022
Fawaz Albloui, James John, Osama Alghamdi, Faisal Alseraye, Abdullah Alqahtani, Waleed Tamimi, Abdullah Albloshi, Fahad M. Aldakheel, Ayesha Mateen, Rabbani Syed
POCGs are widely used in hospitals, emergency rooms, outpatient clinics, ICUs and ambulatory medical care (e.g. ambulances). One of the main advantages of using POCGs is that the results are immediate for urgent medical decisions about diagnostic and therapeutic procedures. Patients usually measure their blood glucose levels with small handheld meters with strips containing specific enzymes to initiate the reaction, followed by photometric or electrochemical detection that quantitatively measures glucose in whole blood [8]. Because of the use of different glucose detection methods, enzymes and variations in the quality of the meters and test strips, the accuracy of measured glucose values may vary between different instruments. Causative factors that interfere with some POCG results include certain medical conditions, diet or medications, such as hypertriglyceridemia, hyperuricemia, hypoxia, acetaminophen or medications containing excessive galactose, maltose, xylose and ascorbic acid (vitamin C) [9]. In addition, high concentrations of ascorbic acid and galactose in blood are potential causes of misdiagnosis of hypoglycemia and hyperglycemia and can lead to death [10,11].