Reabsorption Process Research Articles

Re-absorption and scattering of chlorophyll fluorescence in canopies: A revised approach

The measurement of chlorophyll fluorescence in remote way represents a tool that is becoming increasingly important in relation to the diagnosis of plant health and carbon budget on the planet. However, the detection of this emission is severely affected by distortions, due to processes of light re-absorption both in the leaf and in the canopy. Even though some advances have been made to correct the signal in the far-red, the whole spectral range needs to be addressed, in order to accurately assess plant physiological state. In 2018, we introduced a model to obtain fluorescence spectra at leaf level, from what was observed at canopy level. In this present work, we publish a revision of that physical model, with a more rigorous and exact mathematical treatment. In addition, multiple scattering between the soil and the canopy, and the fraction of land covered by vegetation have also been taken into consideration. We validate this model upon experimental measures, in three types of crops of agronomic interest (Pea, Rye grass and Maize) with different architecture. Our model accurately predicts both the shape of fluorescence spectra at leaf level from that measured at canopy level and the fluorescence ratio. Furthermore, not only do we eliminate artifacts affecting the spectral shape, but we are also able to calculate the quantum yield of fluorescence corrected for re-absorption, from the experimental quantum yield at canopy level. This represents an advance in the study of these systems because it offers the opportunity to make corrections for both the fluorescence ratio and the intensity of the observed fluorescence.

Investigasi Difusi pada Sistem Urinari untuk Gangguan Fungsi Ginjal Model Empat Kompartemen menggunakan Metode Monte Carlo

Kidney is a pair of organ in our urinary system that function to filter blood and urine establishment through filtration, reabsorption and secretion process.Formation of urine is done through one of processes, named tubular reabsorption. This process is a process of diffusion, passively and facilitated. The process happens in tubular reabsorption in kidney can be simulated by using Monte Carlo Cell simulation. Making model of 4 compartments consist of blood vessel, 2 kidneys with one kidney experiencing decreased function of kidney and bladder. Two kidney compartments with one of it experiencing decreased function affect the diffusion process that happens in substance reabsorption process in kidney.The purpose of this research is to study the diffusion process which happens in kidney by selecting several fixed variable and indicators which will be inspected by using Monte Carlo Cell simulation. The use of Monte Carlo Cell simulation enable to try any probabilities that occur in diffusion process of filtration, reabsorption and secretion process in kidney. The result of this research shows that the fewer number of molecules, the slower the molecular displacement and also the fewer number of surface molecules, the slower the molecular displacements.

Effect of reabsorption and photon recycling on photoluminescence spectra and transients in lead-halide perovskite crystals

Explaining the time-dependent evolution of photoluminescence spectra of halide perovskite single crystals after pulsed excitation requires the consideration of a range of physical mechanisms, including electronic transport, recombination and reabsorption. The latter process of reabsorption and re-generation of electron-hole pairs from a photon created by radiative recombination in the single crystal itself is termed photon recycling and has been a highly controversial topic. We use photoluminescence experiments performed under different illumination conditions combined with numerical simulations that consider photon recycling to show which parameters affect temporal decays, spectral shifts and differences in the illumination direction. In addition, we use numerical simulations with and without photon recycling to understand the relative importance of charge-carrier transport and photon recycling. We conclude that under most relevant illumination conditions and times after the pulse, electronic transport is more important than photon recycling for the spectral behavior of the transients. However, inclusion of photon recycling is imperative for the understanding of the absolute density of electrons and holes present in the crystal during a certain time after the pulse.

Oxidative Stress in the Pathophysiology of Kidney Disease: Implications for Noninvasive Monitoring and Identification of Biomarkers.

Kidney disease represents a serious global health problem. One of the main concerns is its late diagnosis, only feasible in a progressed disease state. The lack of a clinical manifestation in the early stages and the fact that the commonly measured parameters of renal function are markedly reduced only during advanced stages of the disease are the main cause. Changes at the molecular level of the kidney tissue occur even before nitrogenous substances, such as creatinine and urea, start to accumulate in the blood. Renal proximal tubules contain a large number of mitochondria and are critical for the energy-demanding process of reabsorption of water and solutes. Mitochondria are the largest producers of oxygen radicals, which, in turn, increase the susceptibility of kidneys to oxidative stress-induced damage. Free radicals and prooxidants produced during acute or chronic kidney injury may further aggravate the course of the disease and play a role in the pathogenesis of subsequent complications. Prevention might be the solution in CKD, but patients are often reluctant to undergo preventive examinations. Noninvasive markers and the possibility to obtain samples at home might help to increase compliance. This review will provide an overview of the possible uses of markers of oxidative status in noninvasive biofluids in patients with renal disease.

Analysis of ultrastructural morphometric changes of pigeon kidneys affected by colibacteriosis

Abstract. The article provides data on the morphometric changes in the kidneys of pigeons with colibacteriosis . Patho-morphological examination of the kidneys revealed focal hyperemia of the kidney cortical area and edema of the loose fibrous tissue. The convoluted renal tubule epitheliocytes were enlarged in size. In this case, the tubules get narrow and become slit-shaped. The convoluted tubules epithelium showed signs of granular dystrophy. In the chronic course of colibacteriosis , granuloma formation and signs of chronic interstitial nephritis were observed, in which the loose connective tissue of the cortical area is replaced by fibrous tissue. Morphometric analysis revealed that in the experimental group there was a decrease in the nephrocyte diameter (p= <0.05) to 98.06±0.46µm and the nephrocyte area to 6319.38±9.62µm. This results in a significant reduction (p= <0.05) of the sub-capsular space to 11.14±0.16µm compared to the control group. The distal and proximal convoluted tubules diameter also decreased to 127.43±20.78μm and 39.50±1.63μm, respectively. Accordingly, the area of the distal and proximal convoluted tubules decreased significantly (p= <0.05) to 10164.10±0.43µm and 2974.43±4.01µm, respectively. The patho-genetic effect of E. coli toxins revealed the renal tubular obstruction and slowing of the reabsorption and urinary excretion processes resulting in a reduction of glomerular filtration capacity of the kidney. Due to the prolonged course of salmonellosis occurring during the latent course, the area of renal filtration was also reduced. Accumulation of nitrogen metabolism products that enter the bloodstream caused impaired water-salt metabolism and acid-base equilibrium.

Nephrotoxicity induced by antimicrobial drugs

The negative effect of toxic chemicals and drugs on the kidneys leads to nephrotoxicity due to a disturbance of the physiological regulation functions such as the hydro-saline and acid-base equilibrium, detoxification of metabolic intermediates, and elimination of drugs and toxic metabolites. The nephrotoxic effect is more predominant in patients with kidney disease and may be manifested by acute or chronic renal failure with disruption of the processes of filtration, secretion, reabsorption and concentration of urine. The symptoms of kidney failure are various and in most cases depend on the nature of the nephrotoxics. The most common symptoms include azotemia, increased serum urea, hematuria, anemia, proteinuria, albuminuria, acidosis, edema, hepatomegaly, ascites to convulsions, and coma. The range of nephrotoxic substances is quite varied and numerous, and includes: drugs, solvents, pesticides, herbicides, alcohols, fuels, mushrooms, plants. A special aspect is represented by the antimicrobial drugs such as: antibiotics (aminoglycosides, glycopeptides, ansamycins, polymyxins, tetracyclines, cephalosporins, penicillins), sulfamides, fluoroquinolones, antifungals, antivirals etc.

Risk Assessment Metabolic Disorders by Prolonged Exposure to Low Doses of Benzene

Benzene is one of the most common environmental pollutants. However, the main attention of researchers is drawn to its carcinogenic and hematotoxic effect. The metabolic effects of this hydrocarbon have been studied to a lesser extent and are mainly related to high effects. The risks associated with the effect on the body of non-toxic doses of this pollutant are practically not studied, which was the purpose of the present study. Experiments lasting 7 weeks were carried out on animals that received drinking water containing benzene at a concentration of 10 µg/l, which is 1 maximum permissible concentration (MPC). It was shown that long-term consumption of water containing benzene in concentration equal to 1 MPC in animals led to changes in biochemical parameters in blood serum, characterized by a decrease in the level of total protein and albumin, a moderate increase in the activity of serum enzymes – alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH). Simultaneously, developed hypercholesterolemia, triacylglycerolemia and dislipoproteinemia. In addition, there was a decrease in the concentration of urea and uric acid. The detected changes are considered as changes in liver functions under the influence of benzene. In addition, there was a decrease in the level of calcium, sodium and potassium in the blood serum, which may reflect the effect of the pollutant on the processes of reabsorption of electrolytes in the renal tubules on the one hand, as well as on the regulation of electrolyte metabolism. In addition, under the influence of low doses of benzene in animals developed insulin resistance (IR), estimated by glucose tolerance test (GTT). The possible role of oxidative stress in the development of the described disorders is discussed.

Dynamics of anion exchange in cesium lead halide (CsPbX3) perovskite nanocrystals

By investigating in situ PL spectra, the anion exchange of perovskite nanocrystals is divided into three stages, i.e. photon reabsorption process, initial anion exchange, and adequate anion exchange.

A Novel Route for a Fluorescent Temperature Sensor Based on the Reabsorption Process in Sm2+‐Doped KCl

Fluorescent temperature sensors have attracted attention in recent years, due to their potential for use in situations where conventional temperature sensors are unsuitable. There are a lack of appropriate sensors at the microscale for industrial, laboratory, and medical applications. Sm2+:KCl crystals possess luminescence properties that enable them to be used as sensors in a new approach for local temperature measurements, by determining the blueshift or the ratio between the intensities from the allowed 4f–5d transitions. A broad emission band centered at 750 nm at 300 K, with high quantum yield (1.00 ± 0.05), is observed when exciting these crystals in the ultraviolet (UV)–vis range. This emission lies within the optical response range of commercial Si‐based photodetectors, which are readily available at relatively low costs. Furthermore, the crystals can be excited using red light‐emitting diodes (LEDs) or a solid‐state laser at 600–650 nm, which are used to produce fluorescent thermometers with a relative sensitivity of 0.24% K−1 (A1/A2 ratio) at 299 K and 1.43 cm−1 K−1 (blueshift).

Quantitative Effects of Pigmentation on the Re‐absorption of Chlorophyll a Fluorescence and Energy Partitioning in Leaves

This study comparatively examined spectroscopic features, photosynthetic parameters and energy partitioning in plants of Fittonia albivenis cv. Agyroneura and Fittonia albivenis cv. Verschaffeltii with different pigmentation. Fittonia albivenis cv. Verschaffeltii, rich in anthocyanins, presented lower values than the green variety (cv. Agyroneura) for several parameters: the ratio chlorophyll a/b, the carotenoid content, the heat dissipation by nonphotochemical quenching (NPQ) and the energy-dependent component of the quantum yield of NPQ. Additionally, the red plant displayed higher resistance to water shortage. The spectral distribution of the chlorophyll a fluorescence, free from distortions due to light reabsorption processes, was obtained for both varieties by application of a physical model previously developed in our group. From this modeling, a higher ratio photosystem II/photosystem I was inferred for the red variety, in agreement with the screening effect of anthocyanins. From a thorough analysis of the fluorescence, the different operating strategies adopted by these plants with dissimilar pigmentation could be elucidated. These strategies were related to the photosystem stoichiometry, the distribution of the absorbed energy and the dissipationofheatunder increasing light intensities.

Genetic variability in sodium-glucose cotransporter 2 influences glycemic control and risk for diabetic retinopathy in type 2 diabetes patients.

Gluconeogenesis and renal glucose excretion in kidneys both play an important role in glucose homeostasis. Sodium-glucose cotransporter (SGLT2), coded by the SLC5A2 gene is responsible for reabsorption up to 99% of the filtered glucose in proximal tubules. SLC5A2 genetic polymorphisms were suggested to influence glucose homeostasis. We investigated if common SLC5A2 rs9934336 polymorphism influences glycemic control and risk for macro or microvascular complications in Slovenian type 2 diabetes (T2D) patients. All 181 clinically well characterized T2D patients were genotyped for SLC5A2 rs9934336 G>A polymorphism. Associations with glycemic control and T2D complications were assessed with nonparametric tests and logistic regression. SLC5A2 rs9934336 was significantly associated with increased fasting blood glucose levels (P<0.001) and HbA1c levels under the dominant genetic model (P=0.030). After adjustment for T2D duration, significantly higher risk for diabetic retinopathy was present in carriers of at least one polymorphic SLC5A2 rs9934336 A allele compared to non-carriers (OR=7.62; 95%CI=1.65-35.28; P=0.009). Our pilot study suggests an important role of SLC5A2 polymorphisms in the physiologic process of glucose reabsorption in kidneys in T2D patients. This is also the first report on the association between SLC5A2 polymorphism and diabetic retinopathy.

Efficient reabsorption of transintestinally excreted cholesterol is a strong determinant for cholesterol disposal in mice

Transintestinal cholesterol excretion (TICE) is a major route for eliminating cholesterol from the body and a potential therapeutic target for hypercholesterolemia. The underlying mechanism, however, is largely unclear, and its contribution to cholesterol disposal from the body is obscured by the counteracting process of intestinal cholesterol reabsorption. To determine the quantity of TICE independent from its reabsorption, we studied two models of decreased intestinal cholesterol absorption. Cholesterol absorption was inhibited either by ezetimibe or, indirectly, by the genetic inactivation of the intestinal apical sodium-dependent bile acid transporter (ASBT; SLC10A2). Both ezetimibe treatment and Asbt inactivation virtually abrogated fractional cholesterol absorption (from 46% to 4% and 6%, respectively). In both models, fecal neutral sterol excretion and net intestinal cholesterol balance were considerably higher than in control mice (5- and 7-fold, respectively), suggesting that, under physiological conditions, TICE is largely reabsorbed. In addition, the net intestinal cholesterol balance was increased to a similar extent but was not further increased when the models were combined, suggesting that the effect on cholesterol reabsorption was already maximal under either condition alone. On the basis of these findings, we hypothesize that the inhibition of cholesterol (re)absorption combined with stimulating TICE will be most effective in increasing cholesterol disposal.

Assessment of coupled Zn concentration and natural stable isotope analyses of urine as a novel probe of Zn status.

Zinc is a common trace metal in the human body, present in about 10% of proteins. Despite numerous roles of Zn in health and disease, there is still a need for a robust biomarker of Zn status. Many parameters have been proposed, with varying levels of success, with plasma Zn often favoured. This study investigates if Zn status can be assessed from the natural stable Zn isotope composition of urine. To this end, 60 urine samples were analysed from ten healthy participants. Remarkably, samples with lower Zn concentrations are systematically enriched in heavy Zn isotopes. Most of the low-Zn urine originated from individuals who omitted dairy, meat or both from their diets. When data for blood serum from age-matched, healthy individuals are compared with the urine results, the former plot at the extension of the urine trend at higher Zn concentrations and lighter isotope compositions. The observed co-variation of Zn isotope compositions with concentrations is indicative of an isotope fractionation system where both properties are controlled by the same processes. It is interpreted as arising from filtration and/or reabsorption processes within the kidney, which are associated with absorbed dietary Zn. The data suggest that the Zn in blood serum that is bound to low molecular weight molecules has an isotope composition distinct from total serum, due to the different affinities of molecular Zn-binding residues to heavy and light Zn isotopes. This technique provides additional information into an individual's Zn status compared to urine or plasma Zn levels alone.

Dual-Waveband Self-Pulsed Laser at 3 $\mu$ m and 2.1 $\mu$ m

We report dual-waveband self-pulsing at 3 and 2.1 μm in a Ho-doped ZBLAN fiber laser, for the first time to our knowledge. In a linear cavity bi-directionally pumped at 1150 nm, stable 3- and 2.1-μm self-pulsing in the kHz region with a ns~μs scale was simultaneously achieved. Their behaviors depending on the pump power were similar to Q-switching and gain-switching, respectively. The preliminary experimental results indicated that the origin of the 3-μm self-pulsing was probably the excited state re-absorption process <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> → <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> and the 2-μm self-pulsing should be induced by the 3-μm self-pulsing by the way of gain-switching. At the maximum pump power of 8.72 W, the largest output power of 917.5 mW (3 μm)/414.7 mW (2.1 μm) and pulse energy of 5.87 μJ (3 μm)/2.62 μJ (2.1 μm) were gained. This demonstration provides an alternative way for 3- and 2.1-μm dual-waveband short pulse generation in a simple scheme, which can find direct medical applications.

White‐Light Generation Upon In‐Situ Amorphization of Single Crystals of [{(Me3P)3AuSn}(PhSn)3S6] and [{(Et3P)3AgSn}(PhSn)3S6

AbstractIn order to gain more information on the white‐light generation by amorphous molecular materials, the influence of metal complex substituents on the photophysical properties of potential white‐light emitters is investigated. Three compounds of the general type [{(R3P)3MSn}{PhSn}3S6)], with R/M = Me/Au (1), Et/Ag (4), and Me/Cu (5), are produced by reactions of the organotin sulfide cluster [(PhSn)4S6] (A) with the corresponding coinage metal complexes [M(PR3)3Cl]. Excess of the gold complex in the reaction leads to rearrangement and formation of [Au(PMe3)4][Au(PMe3)2][(PhSnCl)3S4] (2). The use of PMe3 instead of PEt3 in the reaction with the silver salt causes decomposition and affords [(Me3P)3AgSnCl3] (3). All compounds are structurally characterized, and the necessity of sterically stabilizing PEt3 groups at the silver complex in 4 are rationalized by density functional theory (DFT) calculations. Measurements of the photophysical properties of 1, 4, and 5 show that the introduction of the metallo‐ligands indeed affects the materials properties, and at the same time confirm that the reduction of the molecular symmetry alone is not a sufficient condition for white‐light generation (WLG), which still requires amorphicity of the compound. This is realized for 1 and 4 in situ, while reabsorption processes inhibit WLG in case of the copper compound 5.

Numerical estimation of photon reabsorption process and optical crosstalk in arrays of HgCdTe photodiodes

The effect of photon reabsorption (recycling) on photoelectric parameters of non-equilibrium P+nN+ photodiodes, for example the pixels of the detector array, was analyzed. We solved the system of transport equations additionally extended by two balances equations for photons. It was shown that the density of photons in photodiodes is strongly dependent on the concentration of charge carriers. This phenomenon results in a drastic reduction in the rate of radiative recombination and generation in analyzed photodiodes. Additionally, the phenomenon of optical crosstalk between the nearest pixels in the matrix was examined. The increase in the dark current caused by this phenomenon was estimated. It depends on the size of the pixel, the distance between pixels, and the value of bias voltage. The increase in the current is around 0.5% for a pixel with surface 10 × 10 µm2, and around 1% for one with 5 × 5 µm2, both reverse biased with 0.2 V.

Monitoring energy distribution of nonradiative energy transfer and reabsorption process in an upconversion nanoparticle detection system

Exploiting the energy transfer (ET) direction is important in nanoscale fluorescent detection systems. In a typical detection system based on ET, the quenching efficiency was evaluated by decrease of donor's emission intensity, but there exists reabsorption process apart from nonradiative ET process. Here, we propose a method to analyze the individual contribution of nonradiative ET and reabsorption to quenching efficiency. These two processes influence in a different way on the nanoplatform consisting of NaYF4:20%Yb,2%Er UCNPs and a sulfonyl modified cyanine dye. We find that nonradiative ET process contributes more than reabsorption and possesses a better detection sensitivity (2.27 folds). Our work presents a thorough understanding of detection process, which will be conducive in evaluating the sensitivity of similar detection systems.

Upper-laser-level lifetime measurement of rear earth dopant in active fiber

The upper-laser-level lifetime (fluorescence lifetime) of the rear earth dopant in the active fiber is a key parameter which indicates the performance of the fiber, and takes an important role in designing the laser system. However, the accurate measurement of fluorescence lifetime in active fiber remains challenging, which mainly rely on the direct measurement of laser induced fluorescence lifetime of the active fiber or lifetime measurement of bulk laser glass. The former method suffers the error due to the amplified spontaneous emission and the reabsorption process, while the latter ignores the influence of high temperature and tension produced during the fiber drawing on the emission behavior of the material. Therefore, the accuracy of these measurements can become a problem. In this work, we propose a new approach to measuring the upper-laser-level lifetime of the rear earth dopant in the active fiber based on the power/energy performance of the fiber amplifier. The population inversion, i. e. the energy storage, in the active fiber of a fiber amplifier is a function of upper-laser-level lifetime. Therefore, the upper-laser-level lifetime can be derived by measuring the average power or output pulse energy of the amplifier, given that the energy storage in the active fiber is extracted adequately by a seed laser. Using the rate equations, we model the population inversion and energy storage in the active fiber each as a function of pump power and time, and the resulting relationship between the upper-laser-level lifetime and the average output power. The upper-laser-level lifetimes of several commercial Yb-doped active fibers are experimentally measured by this method through using the fibers as the gain media of the amplifier operated at 1064 nm. The convenience of experimental data processing is also discussed. The measured lifetime and evolution trend of the lifetime with dopant concentration exhibitthat they are in good agreement with those from other reports and the theoretical model, which verifies the feasibility of this method.

Type II Na+-phosphate Cotransporters and Phosphate Balance in Teleost Fish.

Teleost fish are excellent models to study the phylogeny of the slc34 gene family, Slc34-mediated phosphate (Pi) transport and how Slc34 transporters contribute Pi homeostasis. Fish need to accumulate Pi from the diet to sustain growth. Much alike in mammals, intestinal uptake in fish is partly a paracellular and partly a Slc34-mediated transcellular process. Acute regulation of Pi balance is achieved in the kidney via a combination of Slc34-mediated secretion and/or reabsorption. A great plasticity is observed in how various species perform and combine the different processes of secretion and reabsorption. A reason for this diversity is found in one or two whole genome duplication events followed by potential gene loss; consequently, teleosts exhibit distinctly different repertoires of Slc34 transporters. Moreover, due to habitats with vastly different salinity, teleosts face the challenge of either preserving water in a hyperosmotic environment (seawater) or excreting water in hypoosmotic freshwater. An additional challenge in understanding teleost Pi homeostasis are the genome duplication and retention events that diversified peptide hormones such as parathyroid hormone and stanniocalcin. Dietary Pi and non-coding RNAs also regulate the expression of piscine Slc34 transporters. The adaptive responses of teleost Slc34 transporters to e.g. Pi diets and vitamin D are informative in the context of comparative physiology, but also relevant in applied physiology and aquaculture. In fact, Pi is essential for teleost fish growth but it also exerts significant adverse consequences if over-supplied. Thus, investigating Slc34 transporters helps tuning the physiology of commercially valuable teleost fish in a confined environment.

Modeling the structural and dynamical changes of the epithelial calcium channel TRPV5 caused by the A563T variation based on the structure of TRPV6

TRPV5, transient receptor potential cation channel vanilloid subfamily member 5, is an epithelial Ca2+ channel that plays a key role in the active Ca2+ reabsorption process in the kidney. A single nucleotide polymorphism (SNP) rs4252499 in the TRPV5 gene results in an A563T variation in the sixth transmembrane (TM) domain of TRPV5. Our previous study indicated that this variation increases the Ca2+ transport function of TRPV5. To understand the molecular mechanism, a model of TRPV5 was established based on the newly deposited structure of TRPV6 that has 83.1% amino acid identity with TRPV5 in the modeled region. Computational simulations were performed to study the structural and dynamical differences between the TRPV5 variants with A563 and T563. Consistent with the TRPV1-based simulation, the results indicate that the A563T variation increases the contacts between residues 563 and V540, which is one residue away from the key residue D542 in the Ca2+-selective filter. The variation enhanced the stability of the secondary structure of the pore region, decreased the fluctuation of residues around residue 563, and reduced correlated and anti-correlated motion between monomers. Furthermore, the variation increases the pore radius at the selective filter. These findings were confirmed using simulations based on the recently determined structure of rabbit TRPV5. The simulation results provide an explanation for the observation of enhanced Ca2+ influx in TRPV5 caused by the A563T variation. The A563T variation is an interesting example of how a residue distant from the Ca2+-selective filter influences the Ca2+ transport function of the TRPV5 channel.Communicated by Ramaswamy H. Sarma