Use Of Radioactive Tracers Research Articles

Use of Radioactive Tracers and Nucleonic Gauges to Solve Problems Related to Sediment Transport in Inga I and II Dams’ Channels and the Origin of Stagnant Water in Some Dam’s Plots Faced by the INGA Site

Use of Radioactive Tracers and Nucleonic Gauges to Solve Problems Related to Sediment Transport in Inga I and II Dams’ Channels and the Origin of Stagnant Water in Some Dam’s Plots Faced by the INGA Site

The Use of Radioactive Tracers to Detect and Correct Feed Flowrate Imbalances in Parallel Flotation Banks

This work presents the application of radioactive tracers to detect and correct feed flowrate imbalances in parallel rougher flotation banks. Several surveys were conducted at Minera Los Pelambres concentrator, in banks consisting of 250 m3 mechanical flotation cells. The feed pulp distribution was estimated from the mean residence times, which were obtained from residence time distribution measurements. The tracer was injected in the feed distributor and the inlet and outlet tracer signals of cells 1 and 2 were measured by on-stream sensors. The baseline condition for the pulp distribution was defined by the valve settings in the feed distributor, which led to an unbalanced condition for two parallel rougher banks, with 34% of the pulp being fed to bank A and 66% to bank B. New valve configurations were evaluated, with a fraction of the feed being directed to the rougher bank C, which was not initially fed from the same distributor. The feed distribution was finally balanced with 49% of the pulp being fed to bank A versus 51% to bank B. Thus, the radioactive traces proved to be a powerful tool to industrially detect and improve feed distributions in parallel flotation circuits.

A deep learning pipeline to simulate fluorodeoxyglucose (FDG) uptake in head and neck cancers using non-contrast CT images without the administration of radioactive tracer

ObjectivesPositron emission tomography (PET) imaging is a costly tracer-based imaging modality used to visualise abnormal metabolic activity for the management of malignancies. The objective of this study is to demonstrate that non-contrast CTs alone can be used to differentiate regions with different Fluorodeoxyglucose (FDG) uptake and simulate PET images to guide clinical management.MethodsPaired FDG-PET and CT images (n = 298 patients) with diagnosed head and neck squamous cell carcinoma (HNSCC) were obtained from The cancer imaging archive. Random forest (RF) classification of CT-derived radiomic features was used to differentiate metabolically active (tumour) and inactive tissues (ex. thyroid tissue). Subsequently, a deep learning generative adversarial network (GAN) was trained for this CT to PET transformation task without tracer injection. The simulated PET images were evaluated for technical accuracy (PERCIST v.1 criteria) and their ability to predict clinical outcome [(1) locoregional recurrence, (2) distant metastasis and (3) patient survival].ResultsFrom 298 patients, 683 hot spots of elevated FDG uptake (elevated SUV, 6.03 ± 1.71) were identified. RF models of intensity-based CT-derived radiomic features were able to differentiate regions of negligible, low and elevated FDG uptake within and surrounding the tumour. Using the GAN-simulated PET image alone, we were able to predict clinical outcome to the same accuracy as that achieved using FDG-PET images.ConclusionThis pipeline demonstrates a deep learning methodology to simulate PET images from CT images in HNSCC without the use of radioactive tracer. The same pipeline can be applied to other pathologies that require PET imaging.

High-Level Radioactive Wastes from 18 F and 11 C Isotopes Production

Abstract The production and use of radioactive tracers for positron emission tomography (PET) diagnostics in Poland generates various kinds of solid radioactive waste, the disposal of which require...

Advancing Production Flow Profiling With Subatomic Fingerprints and Big Data Analytics

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 196172, “Unleashing the Power of Smart Particles for Completion Diagnostics: Advancing the Production-Flow-Profiling Technology With Subatomic Fingerprints and Big-Data Analytics,” by Talgat Shokanov, SPE, and Pavel Khudorozhkov, QuantumPro, and Adilkhan K. Shokanov, Abai University, prepared for the 2019 SPE Annual Technical Conference and Exhibition, Calgary, 30 September-2 October. The paper has not been peer reviewed. This paper describes a smart-tracer-portfolio testing and design solution for multistage hydraulic fracturing which will, write the authors, enable operators to reduce operating cost significantly and optimize production in shale wells. The technology combines recently developed smart tracers with advanced subatomic measurements in an automated process with stringent quality control that assures precise tracer addition onsite and provides accurate and actionable completion diagnostics results at a fraction of the cost of production-logging testing, distributed temperature testing, or distributed acoustic sensing. Introduction Multistage hydraulic fracturing operations costs - including high-pressure pumping, proppant, and fluid - ranged from $2.9 million to $5.6 million per well in a typical US shale well in 2018, representing close to 60% of the total drilling and completion cost for each well. Yet industry studies reported that up to 50% of the clusters and stages and up to 40% of the fracture net-works do not produce in the current geometric factory-mode-completion approach, leading to estimates that up to 40% of the drilled and completed shale wells in North America alone could be uneconomical. Additionally, interactions between fractures in adjacent horizontal wells, and the costly negative effects of these interactions, have become the focus of much discussion and debate within the technical community. The impetus for this attention has been the effect of these interactions on productivity and the mechanical integrity of the parent wells. These issues drive the need for oil and gas operators to have more-accurate, affordable, and timely data on the performance of individual fracturing stages, measured intrawell communication, and temporary and long-term frac/frac connections to enable improved decision-making and optimization of multistage hydraulic fracturing operations as well as overall field development. The complete paper describes smart tracer technology, including a patented portfolio and fracturing-/completion-optimization work flow; laboratory testing and performance analysis; and integration with completion diagnostics. Smart Tracer Technology To control the effectiveness of multistage hydraulic fracturing stimulation treatments, it is essential to use special tracing methods based on the addition of the labeled substance to the proppant, water, or gas, and monitor the release of tracers with flowback water and produced oil and gas from the current well or nearby observation wells. Currently, conventional water- and oil-soluble chemical substances with fluorescent properties and ionic, organic materials, or radioactive isotopes, are used as the tracers. Tracers with fluorescent properties and ionic and organic materials are high-cost, limited to chemical-measurement techniques at a molecular level, and often have reported false-positive results for long-term communication. Environmental regulations in many countries prohibit the use of radioactive tracers (i.e., radioactive isotopes) because they pollute the environment and could contaminate subsurface layers.

Ligand-binding assays with OBPs and CSPs.

Assessing the ligand-binding properties of OBPs and CSPs is essential for understanding their physiological function. It also provides basic information when these proteins are used as biosensing elements for instrumental measurement of odors. Although different approaches have been applied in the past to evaluate the affinity of receptors and soluble binding proteins to their ligands, using a fluorescent reporter represents the method of choice for OBPs and CSPs. It offers the advantages of working at the equilibrium, being simple, fast and inexpensive, without requiring the use of radioactive tracers. However, as an indirect method, the fluorescence competitive binding approach presents drawbacks and sometimes requires an elaborate analysis to explain unexpected results. Here, after a brief survey of the different approaches to evaluate affinity constants, we focus on the fluorescence binding assay as applied to OBPs and CSPs, discussing situations that may require closer inspection of the results.

Probe-dependence of competitive fluorescent ligand binding assays to odorant-binding proteins.

Ligand binding experiments between small chemicals and proteins and the evaluation of dissociation constants of their complexes in competitive binding assays often rely on displacement of reporter probes by the tested ligand. The most widely adopted protocol uses a fluorescent ligand which changes its emission spectrum when bound to a protein. A decrease of fluorescence, caused by the addition of a second ligand to the complex is generally interpreted as displacement of the fluorescent probe by the ligand, and therefore as a measure of the affinity of the ligand for the protein. Working with an odorant-binding protein (OBP), we found drastic differences in the calculated affinities when using 1-aminoanthracene or N-phenyl-1-naphthylamine as the fluorescent reporter. This fact was quite unexpected, as OBPs are small compact proteins with a single binding pocket without allosteric sites. Such observation raises doubts on the reliability of the fluorescent binding assay, perhaps the most widely used approach to evaluate affinities of small organic compounds to OBPs and other binding proteins. We recommend that the results of fluorescent binding experiments with OBPs should be confirmed by using two different probes or alternative methods. The reliability of current protocols for ligand binding assays is rather limited, while we still wait for a label-free approach that could be simple, fast and free from the use of radioactive tracers.

Measurement of the enriched stable isotope 58Fe in iron related disorders- comparison of INAA and MC-ICP-MS

As a safer alternative for the use of radioactive tracers, the enriched stable 58Fe isotope has been introduced in studies of iron metabolism. In this study this isotope is measured with instrumental neutron activation analysis (INAA) in blood samples of patients with iron related disorders and controls after oral ingestion of a 58Fe containing pharmaceutical. Results were compared with those derived from MC-ICP-MS, applied on the same samples, and analytical and practical aspects of the two techniques were compared.Both techniques showed an increased absorption and incorporation in red blood cells of the 58Fe isotope in iron deficient patients in contrast to the controls. In all individuals results of INAA measurements were in good agreement with those of MC-ICP-MS (|zeta| < 2). Uncertainties in INAA are substantially higher than those achievable by MC-ICP-MS but the INAA technique offers a high specificity and selectivity for iron close to 100%. In contrast to INAA, sample preparation before measurement is very critical in MC-ICP-MS and interferences with 58Ni and 54Cr may hamper the measurement of 58Fe and 54Fe respectively. Since it takes at least five days after irradiation to reduce the activity of interfering radionuclides (mainly 24Na), INAA is a more time consuming procedure; the need of a nuclear reactor facility makes it also less accessible than MC-ICP-MS. Costs are comparable.Both INAA and MC-ICP-MS are able to adequately measure changes in iron isotope composition in blood when an enriched stable iron isotope is applied in clinical research. Although MC-ICP-MS is more sensitive, is faster and has easier access, in INAA preparative steps before measurement are simpler and there are hardly demands on the kind and size of the samples. This may be relevant working with biomaterials in a clinical setting.

Measurements of Iron Compound Content in the Brain Using a Flexible Core Fluxgate Magnetometer at Room Temperature

It has been observed that patients with neurodegenerative diseases, e.g., Alzheimer’s and Parkinson’s diseases, accumulate metals and, specifically, iron compounds with a magnetic moment, in specific, anatomic regions of the central nervous systems. In this context, several techniques have been exploited in order to measure increased brain iron levels that, typically, accompany neurodegenerative diseases; these techniques include positron emission tomography (PET), magnetic resonance imaging (MRI) and measurement systems based on magnetic sensors (i.e., HTS or LTS SQUID magnetometers). In particular, the measurement approach based on MRI, unlike PET, does not require the use of radioactive tracers and affords superior spatial resolution. However, MRIs can be expensive and not suitable in patients with implanted devices. SQUID-based measurement techniques usually require a very controlled environment, with good compensation for ambient magnetic noise, and are expensive. In this paper, we investigate the possibility of using a flexible core residence time’s difference-fluxgate magnetometer as an alternative low-cost, room temperature solution for carrying out measurements of iron compound contents as observed in neurodegenerative diseases. Our experimental results appear promising enough that one can conclude that it is worth further pursuing this approach, namely, using a very simple sensor to detect ferromagnetic compounds that have accumulated in a localized area in the brain. Our results allow us to state, with good confidence, that monitoring the iron content in (at risk) patients might make it possible to detect the looming onset of some neurodegenerative disorders and could, in fact, be used as a diagnostic tool; all this can be accomplished with an inexpensive, room temperature magnetic field sensor that uses a neuromorphic readout in the time domain.

Forty-First Lauriston S. Taylor Lecture: Environmental Radiation and Life-A Broad View.

Since Earth's creation some 4.5 billion years ago, primordial radioactivity has been part of the planet, and radiations from space have continuously impinged on its surface. Primordial radioactivity has helped shape Earth's surface through the heat from radioactive decay energy, and omnipresent natural radiation has likely influenced the origin, and certainly the evolution, of all life forms in our biosphere today. This paper offers a brief discussion of our natural radiation environment and its impacts, from the beginning of life to the present, and provides a broad overview of present day radioecology, which includes the use of radioactive tracers to study ecosystem functions, the fate and transport of radionuclides in the biosphere, and radiation effects on plants and animals. Large releases of radioactivity, although tragic and regrettable, have been studied to increase our knowledge of Earth's basic processes and of radionuclide transport and accumulation in the environment. On a much smaller scale, purposeful use of natural and anthropogenic radioactive tracers has contributed further knowledge. This information has solidified basic concepts and provided data for constructing dynamic models to calculate concentrations of radionuclides in, and radiation doses to, plants and animals. Sealed radiation sources have been used to study effects of chronic exposure on natural biotic communities. Existing transport models and knowledge of radiation effects provide tools to evaluate human health risks and environmental impacts of radioactive releases. Applications have included guidance for environmental protection, radiation litigation, environmental cleanup decisions and informed responses to releases of radioactivity. This paper concludes with a brief discussion of the more urgent knowledge gaps and potential new research approaches.

The use of radioactive tracers to measure mixing regime in semi-autogenous grinding mills

The radioactive tracer technique was used to evaluate the liquid and solid (fine and coarse) transport in two industrial semi-autogenous grinding (SAG) mills. The residence time distribution (RTD), along with the mean residence times, was obtained. The residence times for the liquid and fine solid were equivalent, approximately 2min, which implies non-significant segregation in this size class. The residence time for coarse solids was approximately 4min. The RTD was modelled by N perfectly mixed tanks in series, in which the number of equivalent mixers was approximately 2 for liquid and fine solids and approximately 3 for the coarse solids. The coarse particles required additional time to pass the grate discharge restriction, which also favoured the mixing.

Value and Efficacy of Sentinel Lymph Node Diagnostics in Patients With Penile Carcinoma With Nonpalpable Inguinal Lymph Nodes: Five-Year Follow-up.

Sentinel lymph node biopsy (SLNB) has been described as a minimally invasive method for lymph node staging in patients with a penile carcinoma and nonpalpable inguinal nodes in national and international guidelines of involved professional societies. However, this method is rarely used. The aim of this study was to validate reliability and morbidity of this method and to discuss radiation exposure of persons involved. Twenty-eight patients with histologically negative sentinel lymph nodes in 47 groins with nonpalpable inguinal lymph nodes were included in this study (17 T1(a/b)-, 8 T2- and 3 T3-stages). We recorded prospectively all cases of lymph node recurrence and complications in patients with initially nonpalpable inguinal lymph nodes and histologically negative sentinel lymph nodes. False-negative findings and morbidity were calculated as qualitative criteria. Inguinal regions with palpable lymph nodes and/or evidence of metastases were not considered in accordance with the guidelines. During a median follow-up of 68 (4-131) months, we observed one case of bilateral lymph node recurrence and one case of prolonged inguinal lymphorrhea, which could be managed conservatively. Per inguinal region, false-negative rate was 4.25%, and morbidity rate was 2.12%; seen per patient, the rates were both 3.57%. Sentinel lymph node biopsy under use of radioactive tracers is a reliable method of lymph node staging in patients with penile carcinoma and nonpalpable inguinal lymph nodes. The methodical complexity is justified by high reliability and low radiation exposure for both patient and medical staff and low morbidity rates.

The Role of Sentinel Lymph Node Biopsy in the Management of Breast Cancer

The sentinel lymph node (SLN) is defined as the first node(s) receiving lymphatic drainage from a primary tumour. A promising alternative to axillary lymph node dissection (ALND) is sentinel lymph node biopsy. SLN biopsy has been introduced as a technique to identify axillary lymph node most likely to contain tumour cells metastasizing from a primary carcinoma of breast. Several methods of identifying the SLN exists, including the use of radioactive tracer, lymphazurin dye or combination of the two via intraparenchymal and/or intradermal, peritumoral or periaerolar injection sites. Intraoperative evaluation of SLNs are done by performing FS(Frozen Section) on all the lymph nodes after serially sectioning them at 3-4mm intervals; at least 2 levels are cut of all the sentinel lymph nodes. In addition, touch preparation cytology(TP) smear may also be made for evaluation. The limitations of SLNB is that a proportion of patients who have metastasis limited to the SLN can be predicted when there is a combination of tumour size &lt;1.0cm, the absence of lymphovascular invasion and micrometastatic disease (&lt;0.2cm) in SLN. However for patients with large breast cancer, the role of SLNB is controversial. Early studies of SLNB in large breast cancer patients demonstrated a high (8-18%) false negative rate, with the accuracy worsening with the increasing size. Excision of SLNs have an extremely low morbidity and a high degree of staging accuracy. A tumour-free SLN virtually excludes lymphatic involvement of the entire regional lymphatic basin. More than 50 observational studies of SLNB validated by a back up ALND demonstrate that SLNB is feasible, accurate and suitable for virtually all patients with operable clinically node negative disease. Sentinel lymph node biopsy not only provide prognostic information, but also aims to guide adjuvant therapy without the untoward side effects of complete axillary dissection.J Bangladesh Coll Phys Surg 2014; 32: 211-217

Variability in laboratory parameters used for management of Cushing's syndrome.

The progress in assay methodology, from the use of radioactive tracers to chemiluminescent signals, from competitive to chromatographic techniques and from serum or urine to saliva has considerably impacted on hormonal measurements. The clinician now may choose among multiple tests but the inherent variability in cortisol and ACTH secretion, coupled to lack of harmonization among assay procedures and normal ranges mandates careful interpretation of any result. The present review will examine factors which affect interpretation of cortisol and ACTH measurements and their impact on tests used for management of Cushing’s syndrome.

New reversed phase-high performance liquid chromatographic method for selective separation of yttrium from all rare earth elements employing nitrilotriacetate complexes in anion exchange mode

Separation of Y from other rare earth elements (REE) is difficult because of similarity of its ionic radius to ionic radii of Tb, Dy and Ho. In the new RP-HPLC system with C18 column, tetra-n-butyl ammonium hydroxide (TBAOH) as an ion interaction reagent (IIR), nitrilotriacetic acid (NTA) as a complexing agent at pH=2.8–3.5, and post column derivatization with Arsenazo III, yttrium is eluted in the region of light REE, between Nd and Sm and is base line separated from Nd and Sm and even from promethium. Simple model employing literature data on complex formation of REE with NTA and based on anion exchange mechanism was developed to foresee the order of elution of individual REE. The model correctly predicted that lanthanides up to Tb will be eluted in the order of increasing Atomic Number (At.No.) but all heavier REE will show smaller retention factors than Tb. Concurrent UV/VIS detection at 658nm and the use of radioactive tracers together with γ-ray spectrometric measurements made possible to establish an unique elution order of elution of REE: La, Ce, Pr, Nd, Pm, Y, Sm, Er, Ho, Tm, Yb, Eu, Lu, Dy+Gd, Tb, Sc. The real place of Y however, in this elution series differs from that predicted by the model (Y between Sm and Eu). The method described in this work enables selective separation of Y from La, Ce, Pr, Nd, Pm, Sm and all heavier REE treated as a group.

Laudatio for professor Dr. Hab. Rajmund S. Dybczyński Hevesy Medal Awardee 2013

Rajmund Stanislaw Dybczynski was born in Warsaw, Poland in 1933. He received his MSc in chemistry from Warsaw University in 1955. He spent 2 years in the Institute of General Chemistry, Warsaw, where he got interested in the theory and practice of ion exchange and worked on physico-chemical methods for characterization of ion exchange resins. In 1957 he joined the Institute of Nuclear Research in Warsaw where he received his PhD in 1963 and DSc in 1971. In 1987, the President of Poland conferred the title of ‘‘Professor in Chemistry’’ upon him. Prof. Dybczynski was the Head of Laboratory for Radiometric Methods of Analysis since 1965, and became the Head of Department of Analytical Chemistry at the Institute of Nuclear Chemistry and Technology (INCT) in Warsaw in 1995 and continued until 2008. He was in charge of the Analytical Quality Control Services section at the IAEA Seibersdorf Laboratory during 1975–1980. His early work was focused on the use of radioactive tracers for studying the thermodynamics of ion exchange reactions, effect of resin cross-linking and of temperature on chromatographic separations and development of schemes for group and individual separation of radionuclides including inter alia rare earth elements (REE). Prof. Dybczynski’s interest in REE chemistry stood the test of time and even in recent years he published several papers on REE separation and determination by NAA, ICP-MS, ion chromatography (IC) and RP-HPLC. Professor Dybczynski has made significant contributions in radiochemical neutron activation analysis by developing a number of new separation methods based on ion exchange and extraction chromatography. He applied his instrumental and radiochemical NAA methods to study environmental pollution through the analysis of air filters, human hair and coal fly ash, to determine impurities in some noble metals, to identify single human hairs for forensic purposes, and to investigate possible correlation between coronary heart disease and levels of certain trace elements such as Cu and Zn, among other projects. INAA, RNAA and non-nuclear methods of inorganic trace analysis were used with success to establish genetic relationship between Baszkowka meteorite that fell in Poland in 1994 and another chondrite Mount Tazerzait which fell in Niger, Africa 3 years earlier. Professor Dybczynski has been interested in QA/QC for a long time and was involved in preparation and certification of CRMs for inorganic trace analysis at IAEA. He developed the approach to evaluate data obtained through interlaboratory comparison and to assign certified and information values. His procedure is sometimes referred to as Dybczynski’s method in the literature and has been adapted by IAEA and some laboratories in Poland, Canada and former Czechoslovakia. Professor Dybczynski initiated the developmental work on highly accurate (definitive) methods for the determination of selected elements by radiochemical NAA. He also developed guidelines to obtain data with high accuracy. He demonstrated that the definitive methods can meet the requirements of a ratio primary reference measurement procedure (RPRMP). He developed definitive methods for As, Cd, Co, Cu, Fe, Mo, Ni, Se, and U and applied them to validate other methods and to help in the certification of 10 candidate CRMs, prepared and issued by INCT. Professor Dybczynski is the author and co-author of over 200 papers published in internationally reputed journals, 5 monographs, A. Chatt (&) Department of Chemistry, Trace Analysis Research Centre, Dalhousie University, 6274 Coburg Road, Room 212, P.O. Box 15000, Halifax, NS B3H 4R2, Canada e-mail: chatt@dal.ca

English

English

John Cymerman Craig

John C Craig, an Emeritus Professor of Chemistry and Pharmaceutical Chemistry at the University of California, San Francisco, died suddenly on 26 September of complications related to cardiac disease. John was 92 years old and still maintained an office at the School of Pharmacy at UCSF. His final research was a series of six papers with colleagues at the London School of Tropical Medicine to find out ‘just how the antimalarials kill the parasites inside the human red blood cells.' John's career began at the University of London where he received Bachelor of Science degrees in both Physics and Chemistry (with first class Honors) followed by a PhD in Organic Chemistry from Imperial College, London. From 1942 to 45 John was a Gas Identification Officer and instructed both military and civilians in Chemical Defense, for which he was awarded the Defense Medal. John taught at London University's Charing Cross Hospital in Organic Chemistry, was Senior Lecturer in Organic Chemistry at the University of Sydney (St Paul's College) from 1948 to 1961, and also received the D.Sc. degree from Sydney University in 1962, for his research in Organic and Medicinal Chemistry. In 1958 he became Visiting Scientist at The National Institutes of Health and Walter Reed Army Medical Center for research in anti-radiation drugs. John began his 30-year career at UCSF in 1960, teaching both at the undergraduate and graduate level. He was Professor of Chemistry from 1963 to 1971, Department of Pharmaceutical Chemistry Chairman from 1963 to 71, and Associate Dean of Research from 1971 to 1992. He was selected by the UCSF Academic Senate as the Annual UCSF Faculty Research Lecturer in 1974, and received the first Academic Senate UCSF Service Award in 1993. His research produced over 250 publications in Organic and Medicinal Chemistry and focused on chemical structure and biological activity, including work on the synthesis of vitamin A, chemotherapy of tuberculosis and malaria, and development of stable isotope tracer technology for diagnostic tests for genetic diseases in infants and newborns (to replace the use of radioactive tracers). John was awarded the Research Award in Natural Products from the American Pharmaceutical Association Foundation in 1967, and the Research Achievement Award in Pharmaceutical Analysis from the American Pharmaceutical Scientists in 1988. He was elected to Fellowship in the Academy of Pharmaceutical Scientist in 1967 and to membership in the American College of Neuropsychopharmacology in 1975. For the past 21 years John was a member of the UCSF board of the Faculty Emeriti Association and served as Vice chairman, Chairman and Historian of the state-wide Council of UC Emeriti. John was active in amateur radio from the age of 14 years. In San Francisco he was a member of the SF Radio Club and the Cathay Radio Club. He participated in the UCSF Emergency Network. Since finding a rare early English cookery book (the earliest cookery books were full of medicinal cures) on a barrow in London as a student, John was busy collecting antiquarian English cookery books. In 1988 the Bancroft Library, University California Berkeley presented 100 volumes of John's collection in an exhibit titled ‘Four Hundred Years of English Diet and Cookery: 1541–1939'. He was a member of the Bancroft Council, Bancroft Library, 1989–1997, and edited ‘The Cookery Manuscript of Lillie Hitchcock Coit, 1870–1890, San Francisco' which the Bancroft published in 1998. He is survived by his wife Elaine of San Francisco, his daughter, Elizabeth (Eric) and grandchildren Benjamin and Katherine of Park City, Utah; his son, Anthony (Ruth) of Dorset, UK, and grandsons Thomas (Kelly) of Perth, Australia, and Matthew (Ruth) of Devon, UK, and four great grandchildren.

Introduction to the special issue ‘Tracer Applications in Sediment Research’

Introduction to the special issue ‘Tracer Applications in Sediment Research’

A light in the shadow: the use of Lucifer Yellow technique to demonstrate nectar reabsorption

BackgroundNectar reabsorption is a widely known phenomenon, related to the strategy of resource-recovery and also to maintain the nectar homeostasis at the nectary. The method currently performed to demonstrate nectar being reabsorbed involves the use of radioactive tracers applied to the nectary. Although this method works perfectly, it is complex and requires specific supplies and equipment. Therefore, here we propose an efficient method to obtain a visual demonstration of nectar reabsorption, adapting the use of Lucifer Yellow CH (LYCH), a fluorescent membrane-impermeable dye that can enter the vacuole by endocytosis.ResultsWe applied a LYCH solution to the floral nectary (FN) of Cucurbita pepo L., which is a species known for its ability of nectar reabsorption, and to the extrafloral nectary (EFN) of Passiflora edulis Sims which does not reabsorb the secreted nectar. In all tests performed, we observed that LYCH stained the nectary tissues differentially according to the reabsorption ability of the nectary. The treated FN of C. pepo presented a concentrated fluorescence at the epidermis that decreased at the deeper nectary parenchyma, until reaching the vascular bundles, indicating nectar reabsorption in the flowers of the species. In contrast, treated EFN of P. edulis presented fluorescence only at the cuticle surface, indicating that nectar is not reabsorbed by that particular tissue.ConclusionLYCH is an efficient marker to demonstrate nectar reabsorption.