Optimization of signal accumulation time during photometric measuring

2000 ◽  
Author(s):  
B. P. Klym ◽  
Ye. P. Pochapskyi
Keyword(s):  
Accumulation Time ◽  
Signal Accumulation Time

scholarly journals Comparison of fluorescence excitation modes for cdse semi-conductor quantum dots used in medical research

2018 ◽  
pp. 39-45
Author(s):  
Y. A. Kuzishchin ◽  
I. L. Martynov ◽  
E. V. Osipov ◽  
P. S. Samokhvalov ◽  
A. A. Chistyakov ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Fluorescence Spectroscopy ◽  
Medical Research ◽  
Simultaneous Detection ◽  
Mathematical Expression ◽  
Signal To Noise ◽  
Fluorescence Excitation ◽  
Accumulation Time ◽  
Fluorescent Tags ◽  
Signal Accumulation Time

Fluorescence spectroscopy is a powerful tool used in applied biological and medical research. Colloid semi-conductor quantum dots are promising fluorescent tags for simultaneous detection of different biopathogens. The techniques employing these tags can be improved by selecting the optimal modes for signal excitation and detection. The aim of the present work was to derive a mathematical expression to describe the signal-to-noise ratios in the pulsed and modulated excitation modes. Below, we compare these two modes of fluorescence excitation in ultralow quantities of quantum dots. We demonstrate that modulated excitation should be preferred for CdSe/ZnS quantum dots given that signal accumulation time is over 100 mc and the photosensor is exposed to background light of > 1 μW.

Determination of trace amounts of lead by adsorptive cathodic stripping voltammetry with L-3-(3,4-Dihydroxyphenyl)alanine

2009 ◽  
Vol 74 (4) ◽  
pp. 599-610 ◽  
Author(s):  
Mohammad Bagher Gholivand ◽  
Alireza Pourhossein ◽  
Mohsen Shahlaei
Keyword(s):  
Lead Concentration ◽  
Stripping Voltammetry ◽  
Optimum Conditions ◽  
Lead In Blood ◽  
Accumulation Time ◽  
Cathodic Stripping Voltammetry ◽  
Voltammetric Measurement ◽  
Adsorbed Complex ◽  
Reduction Current

A sensitive and selective procedure is presented for the voltammetric determination of lead. The procedure involves an adsorptive accumulation of lead L-3-(3,4-dihydroxyphenyl)alanine (LDOPA) on a hanging mercury drop electrode, followed by a stripping voltammetric measurement of reduction current of an adsorbed complex at –0.15 V (vs Ag|AgCl). Optimum conditions for lead analysis include pH 8.5, 80 μM LDOPA and accumulation potential –0.15 V (vs Ag|AgCl). The peak currents are proportional to the lead concentration 1–300 nmol l–1 with a detection limit of 0.6 nmol l–1 and accumulation time 60 s. The method was used for the determination of lead in blood, dry tea and also in waters.

scholarly journals Image-Guided Neutron Capture Therapy Using the Gd-DO3A-BTA Complex as a New Combinatorial Treatment Approach

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Ki-Hye Jung ◽  
Ji-Ae Park ◽  
Jung Young Kim ◽  
Mi Hyun Kim ◽  
Seyoung Oh ◽  
...  
Keyword(s):  
Tumor Size ◽  
Neutron Capture ◽  
Inhibitory Effect ◽  
Accurate Information ◽  
Therapeutic Effects ◽  
Neutron Capture Therapy ◽  
Accumulation Time ◽  
Related Proteins ◽  
Treat Breast Cancer

Gadolinium-neutron capture therapy (Gd-NCT) is based on the nuclear capture reaction that occurs when 157Gd is irradiated with low energy thermal neutrons to primarily produce gamma photons. Herein, we investigated the effect of neutron capture therapy (NCT) using a small molecular gadolinium complex, Gd-DO3A-benzothiazole (Gd-DO3A-BTA), which could be a good candidate for use as an NCT drug due to its ability to enter the intracellular nuclei of tumor cells. Furthermore, MRI images of Gd-DO3A-BTA showed a clear signal enhancement in the tumor, and the images also played a key role in planning NCT by providing accurate information on the in vivo uptake time and duration of Gd-DO3A-BTA. We injected Gd-DO3A-BTA into MDA-MB-231 breast tumor-bearing mice and irradiated the tumors with cyclotron neutrons at the maximum accumulation time (postinjection 6 h); then, we observed the size of the growing tumor for 60 days. Gd-DO3A-BTA showed good therapeutic effects of chemo-Gd-NCT for the in vivo tumor models. Simultaneously, the Gd-DO3A-BTA groups ([Gd-DO3A-BTA(+), NCT(+)]) showed a significant reduction in tumor size (p<0.05), and the inhibitory effect on tumor growth was exhibited in the following order: [Gd-DO3A-BTA(+), NCT(+)] > [Gd-DO3A-BTA(+), NCT(−)] > [Gd-DO3A-BTA(−), NCT(+)] > [Gd-DO3A-BTA(−), NCT(−)]. On day 60, the [Gd-DO3A-BTA(+), NCT(+)] and [Gd-DO3A-BTA(−), NCT(−)] groups exhibited an approximately 4.5-fold difference in tumor size. Immunohistochemistry studies demonstrated that new combinational therapy with chemo-Gd-NCT could treat breast cancer by both the inhibition of tumor cell proliferation and induction of apoptosis-related proteins, with in vivo tumor monitoring by MRI.

scholarly journals First Electrochemical Method of Nitrothal-Isopropyl Determination in Water Samples

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Dariusz Guziejewski ◽  
Agnieszka Nosal-Wiercińska ◽  
Sławomira Skrzypek ◽  
Witold Ciesielski ◽  
Sylwia Smarzewska
Keyword(s):  
Environmental Samples ◽  
Electrochemical Method ◽  
Concentration Level ◽  
Stripping Voltammetry ◽  
Adsorptive Stripping Voltammetry ◽  
Hanging Mercury Drop Electrode ◽  
Optimal Conditions ◽  
Step Potential ◽  
Accumulation Time

The aim of the research was the use of square wave adsorptive stripping voltammetry (SWAdSV) in conjunction with a hanging mercury drop electrode (HMDE) for the determination of nitrothal-isopropyl. It was found that optimal SW technique parameters were frequency, 200 Hz; amplitude, 50 mV; and step potential, 5 mV. Accumulation time and potential were studied to select the optimal conditions in adsorptive stripping voltammetry: 45 s at 0.0 V, respectively. The calibration curve (SWSV) was linear in the nitrothal-isopropyl concentration range from 2.0 × 10−7 to 2.0 × 10−6 mol L−1 with detection limit of 3.46 × 10−8 mol L−1. The repeatability of the method was determined at a nitrothal-isopropyl concentration level equal to 6.0 × 10−7 mol L−1 and expressed as RSD = 5.5% (n=6). The proposed method was successfully validated by studying the recovery of nitrothal-isopropyl in spiked environmental samples.

scholarly journals Optical spectroanalyzer with extended dynamic range for pharmacokinetic investigations of photosensitizers in biotissue

2019 ◽  
Vol 8 (1) ◽  
pp. 46-51 ◽  
Author(s):  
G. A. Meerovich ◽  
E. V. Akhlyustina ◽  
T. A. Savelieva ◽  
K. G. Linkov ◽  
V. B. Loschenov
Keyword(s):  
Dynamic Range ◽  
Spectrum Analyzer ◽  
Pharmacokinetic Studies ◽  
Fluorescent Properties ◽  
Accumulation Time ◽  
Fluorescent Method ◽  
Calibration Samples ◽  
Hardware Circuit ◽  
Improved Accuracy ◽  
Extended Dynamic

Currently, the most promising method for the study of pharmacokinetics of drugs with fluorescent properties is the spectral-fluorescent method. In this article, we propose an algorithm for expanding the dynamic range of the spectrum analyzer by automatically monitoring the maximum spectral density in the recorded fluorescence spectrum and automatically controlled changes in the accumulation time depending on this value, followed by compensation of the output signal with regard to this change, as well as hardware circuit solutions that allow this algorithm.Testing of LESA-01-"Biospeс" spectrum analyzer, upgraded using the proposed approach, was carried out on photosensitizer dispersions based on tetra-3-phenylthiophthalocyanine hydroxyaluminium of various concentrations (from 0.01 mg/l to 50 mg/l), approximately corresponding to the concentrations realized in the process of studying pharmacokinetics in calibration samples and tissues of experimental animals.The proposed solutions that implement the algorithm for recording fluorescence spectra with automatic change of accumulation time depending on the signal level, ensured a significant expansion of the dynamic range of the spectrum analyzer (up to 3.5 orders of magnitude) and improved accuracy in pharmacokinetic studies.

Localization of amino acid neurotransmitters following in vitro ischemia and anoxia in the rat retina

2001 ◽  
Vol 18 (3) ◽  
pp. 413-427 ◽  
Author(s):  
GENEVIEVE A. NAPPER ◽  
MICHAEL J. PIANTA ◽  
MICHAEL KALLONIATIS
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Cellular Localization ◽  
Time Course ◽  
Enzymatic Reactions ◽  
Glutamate Metabolism ◽  
Accumulation Time ◽  
Glucose Levels ◽  
Acid Loading

Glutamate and γ-aminobutyric acid (GABA) are two of the dominant neurotransmitters in the retina and brain. The production/degradation of glutamate and GABA involves an intricate interrelationship between neurons and glia, as well as aerobic and anaerobic metabolic pathways. The aim of this work was to develop an in vitro model of retinal ischemia/anoxia and determine the changes in cellular localization of glutamate and GABA and the time course for such changes. After anoxic/ischemic insult, glutamate and GABA rapidly accumulate within glia with GABA showing a quicker time course and larger magnitude change. The accumulation time constant for both glutamate and GABA under anoxic conditions was dependent upon glucose concentration: high glucose levels resulted in delayed glial amino acid loading. The differences in time constants between GABA and glutamate glial loading most likely reflect the multitude of glutamate degradation pathways compared to the single aerobically dependent GABA pathway. Oxygen availability and reduced glucose (hypoglycemia) lead to an almost immediate increase (within 1 min) of glutamate and GABA labelling within glia. In addition, altered labelling patterns were found under anoxic/ischemic conditions for amino acids involved in glutamate transamination reactions: aspartate, leucine, alanine, and ornithine. These changes are consistent with alterations of equilibria of enzymatic reactions involved in glutamate metabolism, and thus support a role for all four amino acids in glutamate metabolism within a variety of retinal neurons.

scholarly journals Comparison of different radar-raingauge rainfall merging techniques

2015 ◽  
Vol 17 (3) ◽  
pp. 422-445 ◽  
Author(s):  
Nergui Nanding ◽  
Miguel Angel Rico-Ramirez ◽  
Dawei Han
Keyword(s):  
Spatial Distribution ◽  
Performance Indicators ◽  
Visual Inspection ◽  
Radar Data ◽  
Network Density ◽  
Kriging Method ◽  
Network Configuration ◽  
Accumulation Time ◽  
Precipitation Estimation ◽  
Merging Techniques

The improvement of precipitation estimation with the use of radar-raingauge rainfall merging techniques is influenced by several factors, such as topography, storm types, raingauge network density for adjustment, data quality and the rainfall accumulation time. However, the influence of the raingauge network configuration on the performance of radar-raingauge merging methods is often ignored. The aim of this study is to compare and evaluate the performance of different radar-raingauge merging methods on various densities of raingauge network and raingauge network configurations. The analysis of the effect of the raingauge network density shows that the performance of Kriging merging methods increases with the increase of raingauge network density. The results also showed that the influence of raingauge network configuration on the spatial distribution of precipitation of the merged products is relatively smaller for the Kriging with radar-based error correction (KRE) and Kriging with external drift (KED) methods than for the ordinary Kriging method. This indicates that the inclusion of radar data in the KRE and KED methods helps to maintain the spatial distribution of precipitation on an hourly timescale. According to the statistical performance indicators and visual inspection of the merged rainfall fields, the KED outperforms the other radar-raingauge merging techniques, regardless of raingauge network density and configuration.

Reconstructing surface mass balance from the Greenland ice sheet stratigraphy.

2020 ◽  
Author(s):  
Alexios Theofilopoulos ◽  
Andreas Born
Keyword(s):  
Mass Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Mass Balance ◽  
Accumulation Time ◽  
Independent Dataset ◽  
Surface Mass ◽  
Final Layer ◽  
Climate Simulations ◽  
Wide Range

&lt;p&gt;Our knowledge of the past surface mass balance on Greenland depends on scarce paleoclimate reconstructions and uncertain climate simulations. However, reconstructions of the internal layering of the ice sheet can provide an independent dataset of accumulation. The thickness of isochronal layers is directly affected by accumulation, but modified over time by the flow of ice. Existing methods can disentangle these two effects only near the ice divide where assumptions of stationarity may be justified. To solve this problem and to obtain a spatially comprehensive reconstruction of accumulation, we use an ice sheet model with an isochronal grid. Thinning rates are calculated prognostically by the model and can be used to define an inverse problem that can be solved iteratively. The only input data is the final layer thickness of the target, e.g., reconstructed radio echo layers from the Greenland ice sheet. To test this method and its limitations, we reconstruct the accumulation histories from the stratigraphies of simulations for which the idealized accumulation time series and spatial distributions are known. These simulations represent a two-dimensional cross section of the Greenland ice sheet. The results are robust to a wide range of realistic variations in accumulation for all but the layers closest to the bedrock where the deformation by the flow is most severe.&lt;/p&gt;

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