Stable Concentrations Research Articles

Graded Atmospheres of Volatile Pyrethroid Overlaid on Host Cues Can Be Established and Quantified Within a Novel Flight Chamber for Mosquito Behavior Studies.

Spatial repellents are emerging as a promising approach to reduce vector-disease burden; however, the evolution of genetically resistant mosquitoes decreases repellent efficacy. The development of flight chambers to investigate spatial repellent application techniques is vital for sustainable mosquito control. We present an air-dilution chamber as a novel bioassay to study mosquito flight behavior responses to chemical gradients of the volatile, pyrethroid transfluthrin (TF). Air dilution was used to simulate a larger environment of stable concentration gradients verified with carbon dioxide (CO2) which was homogenously delivered and measured across the chamber to achieve a 5× inlet/outlet [CO2] ratio with 0.17 m/s outlet velocity. Female Aedes (Ae.) aegypti (Diptera: Culicidae, Linnaeus, 1762) were exposed to volatilized TF paired with heat, CO2, and Biogents-Sweetscent host-cues. Tandem solvent extraction-gas chromatography-mass spectrometry (SE-GC-MS) was used to quantify air samples taken during TF emanations with a limit of detection (LOD) and quantification (LOQ) of 2 ± 1 and 5 ± 2 parts-per-trillion (ppt) TF, respectively. Homogenous air diluted emanation of the spatial repellent TF was at least twice that of the 5× CO2 gradient with the same air flow in the chamber. The airborne TF concentrations the mosquitoes were exposed to range from 1 to 170 ppt. Video recordings of mosquito behavior during host-cues exposure revealed increased inlet activity, while exposure to TF protected host resulted in decreased inlet activity over time with inlet-outlet mosquito positional variation. This novel flight chamber design can simulate 'long'-range exposure with simultaneous quantitation of airborne spatial repellent to understand dose-dependent effects on mosquito behavior.

Effect of oral administration of gabapentin on the minimum alveolar concentration of isoflurane in cats.

To determine if oral gabapentin decreases the minimum alveolar concentration (MAC) of isoflurane in cats. Prospective, randomized, blinded, crossover, and experimental study. A total of six healthy adult cats (three male, three female) aged 18-42 months, weighing 3.31 ± 0.26 kg. Cats were randomly given oral gabapentin (100 mg cat-1) or placebo 2 h before starting MAC determination, with the crossover treatment given at least 7 days apart. Anesthesia was induced and maintained with isoflurane in oxygen. Isoflurane MAC was determined in duplicate using an iterative bracketing technique and tail clamp method. Hemodynamic and other vital variables were recorded at each stable isoflurane concentration and were compared between gabapentin and placebo treatments at lowest end-tidal isoflurane concentration when cats did not respond to tail clamping. A paired t-test was used to compare normally distributed data, and a Wilcoxon signed-rank test was applied for non-normally distributed data. Significance was set at p < 0.05. Data are mean ± standard deviation. Isoflurane MAC in the gabapentin treatment was 1.02 ± 0.11%, which was significantly lower than that in the placebo treatment (1.49 ± 0.12%; p < 0.001), decreasing by 31.58 ± 6.94%. No significant differences were found in cardiovascular and other vital variables between treatments. Oral administration of gabapentin 2 h before starting MAC determination had a significant isoflurane MAC-sparing effect in cats with no observed hemodynamic benefit.

Closed-loop control of air supply to whole-room indirect calorimeters to improve accuracy and standardize measurements during 24-hour dynamic metabolic studies.

The aimof this study was to test proportional-integral-derivative (PID) control of air inflow rate in a whole-room indirect calorimeter to improve accuracy in measuring oxygen (O2 ) consumption ( ) and carbon dioxide (CO2 ) production ( ). A precision gas blender infused nitrogen (N2 ) and CO2 into the calorimeter over 24 hours based on static and dynamic infusion profiles mimicking and patterns during resting and non-resting conditions. Constant (60 L/min) versus time-variant flow set by a PID controller based on the CO2 concentration was compared based on errors between measured versus expected values for respiratory exchange ratio, and metabolic rate. Compared with constant inflow, the PID controller allowed both a faster rise time and long-term maintenance of a stable CO2 concentration inside the calorimeter, resulting in more accurate estimates (mean hourly error, PID: -0.9%, 60 L/min=-2.3%, p < 0.05) during static infusions. During dynamic infusions mimicking exercise sessions, the PID controller achieved smaller errors for (mean: -0.6% vs. -2.7%, p=0.02) and respiratory exchange ratio (mean: 0.5% vs. -3.1%, p=0.02) compared with constant inflow conditions, with similar (p=0.97) and metabolic rate (p=0.76) errors. PID control in a whole-room indirect calorimeter system leads to more accurate measurements of substrate oxidation during dynamic metabolic studies.

Homoepitaxial Si-doped Gallium Oxide films by MOCVD with tunable electron concentrations and electrical properties

Doping technology with stable carrier concentration regulation is a guarantee for optimizing β-Ga2O3-based high-power electronic devices and optoelectronic devices. In this study, β-Ga2O3 homoepitaxial epitaxial films with stable and tunable electron concentrations were grown on Fe-doped (010)-oriented β-Ga2O3 substrates by using metal-organic chemical vapor deposition (MOCVD). XRD shows that the basic bulk properties of β-Ga2O3 film, i. e. the structure and crystal orientation, are stable with low Si-doping, however, its electrical properties vary remarkably depending on concentrations of Si ions incorporated by Si source flow rate during the film growth process. Hall measurement is utilized to confirm high-quality β-Ga2O3 films with tunable electron concentration of 1017–1019 cm−3. As a consequence, the electron concentration-dependent behavior of β-Ga2O3 Schottky barrier diodes (SBDs) was studied. The β-Ga2O3 SBDs exhibited better forward current output electrical performance with reduction in built-in potential difference (Vbi) from 2.4 V to 0.3 V and on-resistance (Ron) from 257 Ω cm to 26 Ω cm. Our results suggest that stable and tunable electron concentration provides high-quality material assurance for constructing power electronic devices of Ga2O3.

Size and light absorption of miniature-inverted-soot-generator particles during operation with various fuel mixtures

The Argonaut miniature inverted soot generator (MISG) serves as a convenient and stable source of soot black-carbon aerosol particles. The MISG performance has been previously characterized for ethylene and propane, in a simple two-flow setup of fuel and air. These fuels produce soot size distributions with geometric median diameters (GMDs) of 150–200 nm. These sizes are substantially larger than the soot particles emitted from typical internal-combustion and aviation gas turbine engines. Here, we sought to produce substantially smaller soot particles, representative of aviation gas turbine engine emissions, by using five different fuels (acetylene, methane, ethylene, propane, and dimethyl ether) and by enriching the combustion air with oxygen. We developed a rapid screening protocol for each fuel, to allow the full range of stable flame conditions to be explored. We monitored the size distribution, mass concentration, and mass absorption cross section (MAC) of denuded MISG soot in real time. We considered only operating conditions where stable soot mass concentrations above 3 μg/m3 were emitted, corresponding to a non-flickering and open-tipped flame. For virtually all operating conditions, the measured MAC was consistent with literature values for mature soot. The only exception was a propane-acetylene mixture, for which the measured MAC was much lower than literature values. The observed GMDs fell into two groups, and we did not identify any trends leading to the mixtures falling into either group. The two groups were at approximately 100 nm and 160 nm. Therefore, while this study identified conditions that reduced the soot particles to 100 nm, it did not identify conditions where even smaller soot particles could be produced. This study has demonstrated that the soot properties produced by the MISG are highly repeatable and relatively insensitive to fuel composition.

The effect of corticosteroids on the morphobiochemical composition of blood and reproductive function in cows

The effect of the glucocorticoidcontaining drug on the morphobiochemical composition of blood and reproductive function in cattle was studied. It was found that against the background of treatment in the postpartum period with corticosteroids, the concentration of eosinophils in the blood decreases by 87.5% (P &lt;0.05), with a stable concentration of platelets. In animals without hormone therapy, an increase in the level of total protein was observed by 18.8% (P&lt;0.01) with a decrease in the albuminglobulin coefficient by 26.4% (P&lt;0.01), which was not observed when using corticosteroids. In the experimental group, the magnesium concentration decreased by 18.1% (P&lt;0.05), with a stable level of phosphorus and calcium. The activity of transaminases against the background of the use of glucocorticoids had no significant changes, whereas in control animals an increase in the activity of AsAT was observed by 29.5% (P &lt; 0.05). The level of total immunoglobulins in animals of the control group decreased by 77.4% (P≤0.001), whereas against the background of Cortexone use, the indicator was 3.9 times higher (P≤0.001). The small-sized CEC in the first group of cows decreased by 58.8%, which is 4.4 times lower (P&lt;0.05) compared to the control group, where, on the contrary, the indicator increased 3.4 times (P&lt;0.05). Similarly, in control cows, a decrease in the size of the CEC was observed, whereas against the background of the use of corticosteroids, on the contrary, their enlargement was observed by 83.8% (P≤0.001). The fertilization of animals after the first insemination against the background of the use of corticosteroids was 43.3% higher, with a lower (0.57) multiplicity of inseminations during fertilization and a shorter (19.2 days; P&lt;0.05) period of infertility. Thus, the use of glucocorticoids in the postpartum period had a positive effect on metabolic processes and contributed to the optimization of reproductive function in cows.

Poly(ethylene oxide) Concentration Gradient-Based Microfluidic Isolation of Circulating Tumor Cells

Circulating tumor cells (CTCs) have emerged as promising circulating biomarkers for non-invasive cancer diagnosis and management. Isolation and detection of CTCs in clinical samples are challenging due to the extreme rarity and high heterogeneity of CTCs. Here, we describe a poly(ethylene oxide) (PEO) concentration gradient-based microfluidic method for rapid, label-free, highly efficient isolation of CTCs directly from whole blood samples. Stable concentration gradients of PEO were formed within the microchannel by co-injecting the side fluid (blood sample spiked with 0.025% PEO) and center fluid (0.075% PEO solution). The competition between the elastic lift force and the inertial lift force enabled size-based separation of large CTCs and small blood cells based on their distinct migration patterns. The microfluidic device could process 1 mL of blood sample in 30 min, with a separation efficiency of >90% and an enrichment ratio of >700 for tumor cells. The isolated CTCs from blood samples were enumerated by immunofluorescence staining, allowing for discrimination of breast cancer patients from healthy donors with an accuracy of 84.2%. The concentration gradient-based microfluidic separation provides a powerful tool for label-free isolation of CTCs for a wide range of clinical applications.

Delivery of nitric oxide with a pH-responsive nanocarrier for the treatment of renal fibrosis

Fibrosis is an excessive accumulation of extracellular matrix (ECM) that may cause severe organ dysfunction. Nitric oxide (NO), a multifunctional gaseous signaling molecule, may inhibit fibrosis, and delivery of NO may serve as a potential antifibrotic strategy. However, major limitations in the application of NO to treat fibrotic diseases include its nonspecificity, short half-life and low availability in fibrotic tissue. Herein, we aimed to develop a stimuli-responsive drug carrier to deliver NO to halt kidney fibrosis. We manufactured a nanoparticle (NP) composed of pH-sensitive poly[2-(diisopropylamino)ethyl methacrylate (PDPA) polymers to encapsulate a NO donor, a dinitrosyl iron complex (DNIC; [Fe2(μ-SEt)2(NO)4]). The NPs were stable at physiological pH7.4 but disintegrated at pH4.0-6.0. The NPs showed significant cytotoxicity to cultured human myofibroblasts and were able to inhibit the activation of myofibroblasts, as indicated by a lower expression level of α-smooth muscle actin and the synthesis of a major ECM component, collagen I, in cultured human myofibroblasts. When given to mice treated with unilateral ureteral ligation/obstruction (UUO) to induce kidney fibrosis, these NPs remained in blood at a stable concentration for as long as 24h and might enter the fibrotic kidneys to suppress myofibroblast activation and collagen I production, leading to a 70% reduction in the fibrotic area. In summary, our strategy to assemble a NO donor, the iron nitrosyl complex DNIC, into pH-responsive NPs proves effective in treating renal fibrosis and warrants further investigation for its therapeutic potential.

In Vitro Properties and Pharmacokinetics of Temporarily PEGylated Onc72 Prodrugs.

The favorable properties of antimicrobial peptides (AMPs) to rapidly kill pathogens are often limited by unfavorable pharmacokinetics due to fast degradation and renal clearance rates. Here, a prodrug strategy linking proline-rich AMP Onc72 to polyethylene glycol (PEGs) with average molecular weights of 5 and 20kDa via a peptide linker containing a protease cleavage site is tested for the first time in vivo. Onc72 is released from these 5k- and 20k-prodrugs in mouse serum with half-life times (t1/2 ) of 8 and 14h, respectively. Importantly, PEGylation protects Onc72 from proteolytic degradation providing a prolonged release of Onc72, balancing the degradation of free Onc72, and leading to relatively stable Onc72 concentrations and high antibacterial activities. The prodrugs are not hemolytic on human erythrocytes and show only slight cytotoxic effects on human cell lines indicating promising safety margins. When administered subcutaneously to female CD-1 mice, the prodrugs elimination t1/2 are 66min and ≈5.5h, respectively, compared to 43min of free Onc72. The maximal Onc72 plasma levels are obtained ≈1 and ≈8h postadministration, respectively. In conclusion, the prodrugs provide extended elimination t1/2 and a constant release of Onc72 in mice, potentially limiting adverse effects and increasing efficacy.

Safety of discontinuation of anticoagulants after venous thromboembolism: whether D-dimer level should be taken into account?

Due to the continued risk of recurrence after a first episode of proximal deep vein thrombosis (DVT) of the lower extremities and/ or pulmonary embolism (PE) occurring without major transient risk factors, long-term use of anticoagulants is indicated in many cases. One attractive way to individualize the duration of treatment in these cases appears to be the assessment of blood D-dimer concentration. However, according to the prospective studies PROLONG, PROLONG II and REVERSE II, even persistent normalization of blood D-dimer concentration does not guarantee the absence of relapse. The available evidence also does not allow a differentiated approach to the assessment of the role of D-dimer for cases where proximal DVT and/or PE occurs in patients without identifiable risk factors or with minor risk factors. An attempt to clarify some of these uncertainties was made in the prospective APIDULCIS study, which included 732 patients who first had proximal DVT and/or PE, with symptoms occurring in the absence of obvious provoking factors (75.6% of cases) or associated with minor (weak) and transient risk factors (24.4%). The prerequisites included a normal blood D-dimer concentration. Patients were discontinued anticoagulants and blood D-dimer concentration measurements were repeated after 15, 30, and 60 days. If it remained low, the anticoagulant was not resumed (39.1% of cases), and when it first increased, apixaban was administered in a dose of 2.5 mg twice daily. The APIDULCIS study confirmed that anticoagulants cannot be discontinued after 1 year of use after the first unprovoked episode of proximal DVT and/or PE, even with persistent normal blood D-dimer concentration; it was shown that recurrence rate after the first episode of proximal DVT and/or PE, provoked by a minor transient risk factor, is high enough even after at least 1 year of anticoagulant treatment and at stable normal blood D-dimer concentration after their cancellation; comfirmed the effectiveness and safety of a reduced dose of apixaban (2.5 mg 2 times a day) during prolonged treatment of the first episode of proximal DVT and/or PE.

One-year stable pilot-scale operation demonstrates high flexibility of mainstream anammox application

Mainstream nitrogen removal via anammox is widely recognized as a promising wastewater treatment process. However, its application is challenging at large scale due to unstable suppression of nitrite-oxidizing bacteria (NOB). In this study, a pilot-scale mainstream anammox process was implemented in an Integrated Fixed-film Activated Sludge (IFAS) configuration. Stable operation with robust NOB suppression was maintained for over one year. This was achieved through integration of three key control strategies: i) low dissolved oxygen (DO = 0.4 ± 0.2 mg O2/L), ii) regular free nitrous acid (FNA)-based sludge treatment, and iii) residual ammonium concentration control (NH4+ with a setpoint of ∼8 mg N/L). Activity tests and FISH demonstrated that NOB barely survived in sludge flocs and were inhibited in biofilms. Despite receiving organic-deficient wastewater from a pilot-scale High-Rate Activated Sludge (HRAS) system as the feed, the system maintained a stable effluent total nitrogen concentration mostly below 10 mg N/L, which was attributed to the successful retention of anammox bacteria. This study successfully demonstrated large-scale long-term mainstream anammox application and generated new practical knowledge for NOB control and anammox retention.

Pharmacokinetic Study of Triptolide Nanocarrier in Transdermal Drug Delivery System-Combination of Experiment and Mathematical Modeling.

Compared with traditional oral and injection administration, the transdermal administration of traditional Chinese medicine has distinctive characteristics and advantages, which can avoid the "first pass effect" of the liver and the destruction of the gastrointestinal tract, maintain a stable blood concentration, and prolong drug action time. However, the basic theory and technology research in transdermal drug delivery are relatively limited at present, especially regarding research on new carriers of transdermal drug delivery and pharmacokinetic studies of the skin, which has become a bottleneck of transdermal drug delivery development. Triptolide is one of the main active components of Tripterygium wilfordii, which displays activities against mouse models of polycystic kidney disease and pancreatic cancer but its physical properties and severe toxicity limit its therapeutic potential. Due to the previously mentioned advantages of transdermal administration, in this study, we performed a detail analysis of the pharmacokinetics of a new transdermal triptolide delivery system. Triptolide nanoemulsion gels were prepared and served as new delivery systems, and the ex vivo characteristics were described. The metabolic characteristics of the different triptolide transdermal drug delivery formulations were investigated via skin-blood synchronous microdialysis combined with LC/MS. A multiscale modeling framework, molecular dynamics and finite element modeling were adopted to simulate the transport process of triptolide in the skin and to explore the pharmacokinetics and mathematical patterns. This study shows that the three-layer model can be used for transdermal drug delivery system drug diffusion research. Therefore, it is profitable for transdermal drug delivery system design and the optimization of the dosage form. Based on the drug concentration of the in vivo microdialysis measurement technology, the diffusion coefficient of drugs in the skin can be more accurately measured, and the numerical results can be verified. Therefore, the microdialysis technique combined with mathematical modeling provides a very good platform for the further study of transdermal delivery systems. This research will provide a new technology and method for the study of the pharmacokinetics of traditional Chinese medicine transdermal drug delivery. It has important theoretical and practical significance in clarifying the metabolic transformation of percutaneous drug absorption and screening for appropriate drugs and dosage forms of transdermal drug delivery.

Non-Invasive In Vivo Estimation of HbA1c Using Monte Carlo Photon Propagation Simulation: Application of Tissue-Segmented 3D MRI Stacks of the Fingertip and Wrist for Wearable Systems

The early diagnosis of diabetes mellitus in normal people or maintaining stable blood sugar concentrations in diabetic patients requires frequent monitoring of the blood sugar levels. However, regular monitoring of the sugar levels is problematic owing to the pain and inconvenience associated with pricking the fingertip or using minimally invasive patches. In this study, we devise a noninvasive method to estimate the percentage of the in vivo glycated hemoglobin (HbA1c) values from Monte Carlo photon propagation simulations, based on models of the wrist using 3D magnetic resonance (MR) image data. The MR image slices are first segmented for several different tissue types, and the proposed Monte Carlo photon propagation system with complex composite tissue support is then used to derive several models for the fingertip and wrist sections with different wavelengths of light sources and photodetector arrangements. The Pearson r values for the estimated percent HbA1c values are 0.94 and 0.96 for the fingertip transmission- and reflection-type measurements, respectively. This is found to be the best among the related studies. Furthermore, a single-detector multiple-source arrangement resulted in a Pearson r value of 0.97 for the wrist. The Bland-Altman bias values were found to be -0.003 ± 0.36, 0.01 ± 0.25, and 0.01 ± 0.21, for the two fingertip and wrist models, respectively, which conform to the standards of the current state-of-the-art invasive point-of-care devices. The implementation of these algorithms will be a suitable alternative to the invasive state-of-the-art methods.

Low-temperature oxidation studies on canola and coconut-derived biodiesel in a motored engine

This work reports results on the low-temperature oxidation of canola and coconut-derived biodiesel in a motored engine. A lean premixed fuel–air mixture of equivalence ratio 0.25 at an intake temperature of 125 °C was subject to reaction with pure compression. The extent of the reaction was controlled by changing the compression ratio in the range of 5.5–9.0. In-cylinder pressure measurements were used for heat release analysis, and detailed speciation analysis of the reaction products was done using a gas chromatography-mass spectrometry system. The canola-derived biodiesel shows minor low-temperature heat release, while coconut biodiesel exhibits a relatively higher heat release. It was found that the low-temperature oxidation chemistry for these biodiesels is similar to saturated single-component methyl esters. However, the heat release was somewhat suppressed due to unsaturated compounds in the two biodiesel fuels. The heat release suppression correlates well with the extent of unsaturation. The oxidation end products under the test conditions were similar for both fuels. The relatively higher reactivity of the coconut over the canola biodiesel was also seen in the speciation results, and its stable intermediate concentrations were much higher than the canola. The experimental results were compared to computations using an existing kinetic model. The onset of heat release was predicted with reasonable accuracy. However, the peak and accumulated heat release were significantly overpredicted.

THEORETICAL-AND-EXPERIMENTAL STUDY OF ACARICIDE CONCENTRATIONS CHANGING IN THE WORKING EMULSION

The animal and the of sheep production quality (especially wool) largely depends on sheep preventive treatment of against parasitic diseases effectiveness. The reliable disease prevention's determining factor is acaricidal substances' stable concentration in working emulsion during sheep treatment observance. At manual of the bath refueling, with 200-300 sheep bathing is carried out, if the first batches at a normal concentration of acaricides in the working emulsion are processed, then subsequent batches in solutions below the recommended values are processed, which is the cause of infectious diseases appearance. So acaricides low concentration in emulsion can lead to ticks' resistant population emergence that develop the using drug's resistance. The methods of theoretical-and-experimental studies analyzing of the of actual data's field experiments on acaricide concentration reducing in the working emulsion during sheep processing were used. As a result, empirical dependences describe regularities of acaricide concentration reducing in the working emulsion's were obtained. At manual bath refueling, regularity exponent has decreasing, that contradicts the quality requirements of animals' antisoroptotic treatment. At bath refueling with a dispenser intensive method, acaricide stable concentration in the working emulsion during the entire period of bathing sheep is observed. The acaricide solution's refueling mass per sheep is 421,7 ± 77,22 ml, depending on the sex and age of sheep groups.

Dissolvable polymeric microneedles loaded with aspirin for antiplatelet aggregation

To reduce mucosal damage in the gastrointestinal tract caused by aspirin, we developed a dissolvable polymeric microneedle (MN) patch loaded with aspirin. Biodegradable polymers provide mechanical strength to the MNs. The MN tips punctured the cuticle of the skin and dissolved when in contact with the subcutaneous tissue. The aspirin in the MN patch is delivered continuously through an array of micropores created by the punctures, providing a stable plasma concentration of aspirin. The factors affecting the stability of aspirin during MNs fabrication were comprehensively analyzed, and the hydrolysis rate of aspirin in the MNs was less than 2%. Compared to oral administration, MN administration not only had a smoother plasma concentration curve but also resulted in a lower effective dose of antiplatelet aggregation. Aspirin-loaded MNs were mildly irritating to the skin, causing only slight erythema on the skin and recovery within 24 h. In summary, aspirin-loaded MNs provide a new method to reduce gastrointestinal adverse effects in patients requiring aspirin regularly.

Treatment of acute diabetic metabolic crises in adults (Update2023) : Hyperglycemic hyperosmolar state and ketoacidotic metabolic disorder

Diabetic ketoacidosis (DKA) and the hyperglycemic hyperosmolar state (HHS) represent potentially life-threatening situations in adults. Therefore, rapid comprehensive diagnostic and therapeutic measures with close monitoring of vital and laboratory parameters are required. The treatment of DKA and HHS is essentially the same and replacement of the mostly substantial fluid deficit with several liters of aphysiological crystalloid solution is the first and most important step. Serum potassium concentrations need to be carefully monitored to guide its substitution. Regular insulin or rapid acting insulin analogues can be initially administered as an i.v. bolus followed by continuous infusion. Insulin should be switched to subcutaneous injections only after correction of the acidosis and stable glucose concentrations within an acceptable range.

Chemical looping oxidative propane dehydrogenation controlled by oxygen bulk diffusion over FeVO4 oxygen carrier pellets

The oxygen distribution and evolution within the oxygen carrier exert significant influence on chemical looping processes. This paper describes the influence of oxygen bulk diffusion within FeVO4 oxygen carrier pellets on the chemical looping oxidative propane dehydrogenation (CL-ODH). During CL-ODH, the oxygen concentration at the pellet surface initially decreased and then maintained stable before the final decrease. At the stage with the stable surface oxygen concentration, the reaction showed a stable C3H6 formation rate and high C3H6 selectivity. Therefore, based on Fick’s second law, the oxygen distribution and evolution in the oxygen carrier at this stage were further analyzed. It was found that main reactions of selective oxidation and over-oxidation were controlled by the oxygen bulk diffusion. C3H8 conversion rate kept decreasing during this stage due to the decrease of the oxygen flux caused by the decline of oxygen gradient within the oxygen carrier, while C3H6 selectivity increased due to the decrease of over-oxidation. In addition, reaction rates could increase with the propane partial pressure due to the increase of the oxygen gradient within the oxygen carrier until the bulk transfer reached its limit at higher propane partial pressure. This study provides fundamental insights for the diffusion-controlled chemical looping reactions.

Levodopa u terapiji Parkinsonove bolesti

January 2023 marks the 100th anniversary of the birth of Arvid Carlsson, a Swedish scientist, one of the three winners of the Nobel Prize in Medicine in 2000 "for proving that Dopamine is a brain neurotransmitter whose deficiency leads to the symptoms of Parkinson's disease". Levodopa therapy is one of the main achievements of neurology in the twentieth century, and Parkinson' s disease was the first disease in which a specific neurochemical deficiency was confirmed in defined regions of the brain, which forms the basis for rational, chemically supported therapy. The paper briefly reviews the most important achievements in the discovery of Dopamine and levodopa, as well as their functions in the development of Parkinson's disease. Dopamine synthesis, understanding of levodopa synthesis method, possibility of measuring Dopamine concentration in putamen and caudate and its loss in Parkinson' s disease, along with histochemical visualization of nigrostriatal pathway and animal lesion model, enabled understanding of the role of nigrostriatal Dopamine system in the development of Parkinson's disease symptoms. Part of the work is devoted to the metabolism of Dopamine in healthy dopaminergic neurons, and then to its functioning in dopaminergic neurons of Parkinson's disease patients. It is known that in Parkinson's disease, Dopamine deficiency occurs due to selective degeneration of nigrostriatal dopaminergic neurons. Their suffering is triggered by a cascade of events that included the action of potential toxins, the influence of susceptibility genes on the body's response to them, oxidative stress caused by mitochondrial dysfunction, dysfunction of the ubiquitous proteasomal system that leads to the accumulation of incorrectly "packaged" proteins, the exhaustion of the endoplasmic reticulum system and the activation of mycoglia that follows inflammatory process. These changes can lead to programmed cell death of dopaminergic neurons with consequent Dopamine deficiency and the development of PD. Special attention is paid to the consequences of neuron loss on the functioning of the remaining dopaminergic neurons and Dopamine receptors, with reference to the therapeutic motor complications that may arise on that occasion. The basic assumptions about the occurrence of therapeutic complications are still related to the pharmacokinetics of levodopa and the model of its delivery to the brain, which results in non-physiological, pulsatile stimulation of Dopamine receptors. Today's possibilities in achieving a more stable concentration of levodopa with existing strategies are presented, with an answer to the question of whether continuous stimulation can be achieved under the conditions of standard, regular patients' levodopa therapy. In the short final part, the position of levodopa in the guidelines and recommendations for treatment is commented. It is expected that L-dopa will remain the "gold standard" for the treatment of PD at least until the development of more potent and safer Dopamine agonists or the development of neuroprotective or neurorestorative therapies.

Spatial and temporal distribution of polyhalogenated carbazoles in sediments from the Yangtze River estuary and adjacent East China Sea

Polyhalogenated carbazoles (PHCZs) have been increasingly detected in marine sediment, raising concerns in recent years. In this study, sediment samples (42 surface and one core) were collected from the Yangtze River estuary and the adjacent East China Sea, and eleven PHCZs and unsubstituted carbazole were measured. The total concentration of PHCZs in surface sediments ranged from 0.19 to 2.49 ng/g dry weight (d.w.) (median 1.03 ng/g d. w.). The congener compositions of PHCZs in the surface sediment were dominated by 3,6-dichlorocarbazole (36-CCZ, 53.2%), followed by 3-chlorocarbazole (14.9%) and 3,6-dibromocarbazole (36-BCZ, 11.8%). Carbazole in the surface sediment ranged from not detected to 9.89 ng/g (median 1.25 ng/g), with a detection frequency of 81.0%. The spatial distribution of 36-CCZ in surface sediments exhibited a clear decline from the coast to offshore, while 36-BCZ showed the opposite trend. The depth profile of 36-CCZ was maintained at a relatively low and stable concentration (about 0.36 ng/g) in core segments from 1903 to 1951, followed by a steady increase to 1.5 ng/g in 2006. This increase coincides with the industrial and agricultural development in China that began in the 1950s. In contrast, the other detected PHCZs and carbazole maintained stable, low concentrations over time. These spatial and temporal patterns suggest that 36-CCZ in this area is predominantly from anthropogenic sources, while 36-BCZ has a natural origin. Toxic equivalent estimations indicated that dioxin-like effects for the observed PHCZs were low. These results provide useful information for understanding the origin of PHCZs and carbazole in this area.