Designing Thiadiazoloquinoxaline-Based Conjugated Polymers for Efficient Organic Photovoltaics: A DFT/TDDFT Study.

Clean and renewable energy development is becoming frontier research for future energy resources, as renewable energy offers sustainable and environmentally friendly alternatives to non-renewable sources such as fossil fuels. Among various renewable energy sources, tremendous progress has been made in converting solar energy to electric energy by developing efficient organic photovoltaics. Organic photovoltaic materials comprising conjugated polymers (CP) with narrow optical energy gaps are promising candidates for developing sustainable sources due to their potentially lower manufacturing costs. Organic semiconductor materials with a high electron affinity are required for many optoelectronic applications. We have designed a series of organic semiconductors comprised of cyclopentadithiophene as a donor and thiadiazoloquinoxaline (TQ) as an acceptor, varying the π-conjugation and TQ-derivatives. We have employed density functional theory (DFT) and time-dependent DFT (TDDFT) to evaluate the designed CP's optoelectronic properties, such as optical energy gap, dipole moment, and absorption spectra. Our DFT/TDDFT result shows that the energy gap of CPs is lowered and redshifted in the absorption spectra if there is no insertion of conjugation units such as thiophene and selenophene between donor and acceptor. In addition, selenophene shows relatively better redshift behavior compared to thiophene. Our work also provides rational insight into designing donor/acceptor-based CPs for organic solar cells.

Dissociation Time, Quantum Yield, and Dynamic Reaction Pathways in the Thermolysis of trans-3,4-Dimethyl-1,2-dioxetane.

The thermolysis of trans-3,4-dimethyl-1,2-dioxetane is studied by trajectory surface hopping. The significant difference between long and short dissociation times is rationalized by frustrated dissociations and the time spent in triplet states. If the C-C bond breaks through an excited state channel, then the trajectory passes over a ridge of the potential energy surface of that state. The calculated triplet quantum yields match the experimental results. The dissociation half-times and quantum yields follow the same ascending order as per the product states, justifying the conjecture that the longer dissociation time leads to a higher quantum yield, proposed in the context of the methylation effect. The populations of the molecular Coulomb Hamiltonian and diagonal states reach equilibrium, but the triplet populations with different Sz components fluctuate indefinitely. Certain initial velocities, leading the trajectories to given product states, can be identified as the most characteristic features for sorting trajectories according to their product states.

Comparison of Fine-Needle Aspiration Cytopathology with Histopathological Examination of the Thyroid Gland in Patients Undergoing Elective Thyroid Surgery: Do We Still Need Fine-Needle Aspiration Cytopathology?

BACKGROUND: The thyroid gland is responsible for various functions, but it is susceptible to pathologies. The gold standard for preliminarily diagnosing thyroid abnormalities is fine-needle aspiration cytology (FNAC), although it has some limitations; thus, postoperative histopathological examination confirms the diagnosis. The aim of the present study was to compare preoperative FNAC results with postoperative histopathological examination. METHODS: This study is a retrospective study based on FNAC and postoperative histopathology examination, which were compared and analyzed. RESULTS: This study included 344 patients between 18 and 86 years old (mean age: 53.06 ± 13.89), comprising 274 females and 70 males (mean ages 52.72 ± 13.86 and 54.39 ± 14.05, respectively) with a 3.9:1 female-to-male ratio. Statistical significance between the FNAC and histopathology results was observed (p = 0.0000), and 86 (25.00%) patients were found to have been diagnosed incorrectly based on FNAC. The sensitivity of FNAC was 92.31%, and its specificity was 82.08%, with positive and negative predictive values of 68.57% and 96.08%, respectively. CONCLUSIONS: Due to many factors, FNAC may lead to over- or under-diagnosis, increasing the chances of complications associated with the selected treatment. However, we do not have any other more accurate tools; therefore, FNAC should still remain as the gold standard of preliminary examination.

Impact of Internal Carotid Stenosis Treatment on Cerebral Blood Flow Volume: A Comparative Study between Preoperative and Postoperative Values.

BACKGROUND Among patients with ICA stenosis, there are some cases with elevated, undisrupted, and diminished cerebral blood flow (CBF). The aim of this study was to assess the influence of ICA stenosis treatment on postoperative CBF changes in relation to preoperative CBF values. MATERIAL AND METHODS We qualified 58 patients ≥65 years old (28 males, 30 females, mean age 71.02±6.34 years) for surgical intervention due to symptomatic ≥70% ICA stenosis. In all patients, a flow volume in all extracranial arteries (internal carotid [ICA], external carotid [ECA], and vertebral arteries [VA]) was measured preoperatively and 2-3 days following the surgery. The CBF values were compared with the ones established for a healthy population of the same age. RESULTS Preoperatively, there were 3 subgroups of patients, comparing to healthy population: with elevated CBF - "significant compensation," with undisrupted CBF - "mild compensation," and with diminished CBF - "no compensation." Postoperatively, a significant CBF increase was observed in patients with preoperative "no" and "mild compensation" - 277.18±154.26 ml/min (P=0.0000001) and 221.56±98.8 ml/min (P=0.0000001). In a "significant compensation" group, there was no flow increase observed (CBF change of 2.57±58.5 ml/min, P=0.954) - a redistribution of flow was observed. CONCLUSIONS In patients with lower preoperative CBF values, surgical treatment caused a significant increase in global cerebral inflow, which was more prominent in patients with the lowest preoperative CBF. In patients with high preoperative CBF, surgical treatment resulted in a flow redistribution, but did not cause a CBF increase. Volumetric flow assessment in DUS can predict hemodynamic benefit from surgery in terms of CBF increase.

Degradation of NTO induced by superoxide and hydroperoxyl radicals: a comprehensive DFT study.

Reactive oxygen species, produced in the aquatic environment under sunlight irradiation, actively take part in degradation of environmental pollutants. NTO (5-nitro-1,2,4-triazol-3-one), being a primary ingredient in a suite of insensitive munitions formulations, may be released into training range soils after incomplete detonations and dissolved in surface water and groundwater due to good water solubility. A detailed investigation of a possible mechanism for NTO decomposition in water induced by superoxide and hydroperoxyl radicals as one of the pathways for NTO environmental degradation was performed with a computational study at the PCM(Pauling)/M06-2X/6-311++G(d,p) level. Superoxide causes rapid deprotonation of NTO. Decomposition of NTO induced by hydroperoxyl radicals was found to be a multistep process leading to mineralization of the nitrocompound. The reaction process may begin with hydroperoxyl radical attachment to carbon atom of the CN double bond of NTO, then proceeds through rupture of C-N bonds and addition of water molecules leading to the formation of nitrous acid, ammonia, nitrogen gas, hydrazine, and carbon(IV) oxide. The obtained results indicate that the anionic form of NTO shows a higher reactivity towards hydroperoxyl radicals than its neutral form. Excitation of NTO by sunlight enables complete mineralization of NTO induced by superoxide. The calculated activation energies and exergonicity of the studied processes support the contribution of hydroperoxyl radicals and superoxide to the degradation of NTO in the environment into low-weight inorganic compounds.

The System of Self-Consistent Models: The Case of Henry's Law Constants.

Data on Henry's law constants make it possible to systematize geochemical conditions affecting atmosphere status and consequently triggering climate changes. The constants of Henry's law are desired for assessing the processes related to atmospheric contaminations caused by pollutants. The most important are those that are capable of long-term movements over long distances. This ability is closely related to the values of Henry's law constants. Chemical changes in gaseous mixtures affect the fate of atmospheric pollutants and ecology, climate, and human health. Since the number of organic compounds present in the atmosphere is extremely large, it is desirable to develop models suitable for predictions for the large pool of organic molecules that may be present in the atmosphere. Here, we report the development of such a model for Henry's law constants predictions of 29,439 compounds using the CORAL software (2023). The statistical quality of the model is characterized by the value of the coefficient of determination for the training and validation sets of about 0.81 (on average).

Role of Hydroxyl Radical in Degradation of NTO: DFT Study.

Hydroxyl radicals are important reactive oxygen species produced in the aquatic environment under sunlight irradiation. Many organic pollutants may be decomposed as they encounter hydroxyl radicals, due to their high oxidative ability. NTO (5-nitro-1,2,4-triazol-3-one), an energetic material used in military applications, may be released to the environment and dissolved in surface water and groundwater due to its good water solubility. A detailed investigation of the possible mechanism for NTO decomposition in water induced by hydroxyl radical as one of the pathways for NTO environmental degradation was performed by computational study at the PCM/M06-2X/6-311++G(d,p) level. Decomposition of NTO was found to be a multistep process that may begin with an addition of hydroxyl radical to the carbon atom of C═N double bond and consequent release of a nitrite radical. The formed intermediate undergoes a series of chemical transformations that include the attachments of hydroxyl radical to carbon atoms, the transfer of hydrogen to hydroxyl radical, isomerization, and bond cleavage, leading to low-weight inorganic compounds, such as ammonia, nitrogen gas, nitrous acid, nitric acid, and carbon(IV) oxide. The anionic form of NTO is more reactive toward interaction with the hydroxyl radical as compared with its neutral form. Calculated activation energies and high exergonicity of the studied process support the significant contribution of the hydroxyl radical to NTO mineralization in environment.

Ultrahigh Capacitive Energy Density in Stratified 2D Nanofiller-Based Polymer Dielectric Films.

Dielectric capacitors are critical components in electronics and energy storage devices. The polymer-based dielectric capacitors have the advantages of device flexibility, fast charge-discharge rates, low loss, and graceful failure. Elevating the use of polymeric dielectric capacitors for advanced energy applications such as electric vehicles (EVs), however, requires significant enhancement of their energy densities. Here, we report a polymer thin film heterostructure-based capacitor of poly(vinylidene fluoride)/poly(methyl methacrylate) with stratified 2D nanofillers (Mica or h-BN nanosheets) (PVDF/PMMA-2D fillers/PVDF), that shows enhanced permittivity, high dielectric strength, and an ultrahigh energy density of ≈75 J/cm3 with efficiency over 79%. Density functional theory calculations verify the observed permittivity enhancement. This approach of using oriented 2D nanofillers-based polymer heterostructure composites is expected to be versatile for designing high energy density thin film polymeric dielectric capacitors for myriads of applications.

Fused Double Donor Design with a Cross-Conjugated Dibenzosilin for Dye-Sensitized Solar Cells.

Dye-sensitized solar cells (DSCs) can provide a clean energy solution to growing energy demands. In order to have devices of high performance, sensitizers that are able to absorb in the near-infrared region (NIR) are needed. Stronger electron donors are needed for intramolecular charge-transfer sensitizers to access longer wavelength photons. Thus, two novel organic dyes with a cross-conjugated dibenzosilin double donor design are studied herein. The double donor delocalizes multiple filled orbitals across both amine donors due to the fused design that planarizes the donor as observed computationally, which improves intramolecular charge-transfer strength. The dyes are studied via density functional theory (DFT), optical spectroscopy, electrochemistry, and in DSC devices. The studies indicate that the dye design can reduce recombination losses, allowing for improved DSC device performances relative to a single arylamine donor. The reduction in recombination losses is attributed to the six alkyl chains that are incorporated into the donor, which offer good surface protection.

Does the Treatment of Pelvic Venous Insufficiency Really Not Influence Lower Limb Venous Disease?

Pelvic venous insufficiency is a common problem in multiparous women. Besides burdensome symptoms, it correlates with the development of venous disease in the lower limbs. Therefore, the sequential treatment of abdominal/pelvic before leg veins could improve treatment effectiveness. The medical records of 243 patients with venous disease who were subjected to sequential treatment were analyzed retrospectively. The symptoms and patient satisfaction were assessed using dedicated questionnaires, both before and after treatment. Clinical effectiveness was verified using a Doppler scan, both before and after treatment. Among 243 analyzed cases, 195 underwent whole treatment; however, 48 women after embolization did not require further intervention. The total-symptom-score change (11.6 vs. 13.0, respectively) and the satisfaction score (1.6 vs. 1.5, respectively) did not differ between groups. After embolization, some patients, besides symptoms improvement, experienced reflux reduction and, hence, might avoid further intervention. A better explanation for this beneficial effect of the sequential/descending approach requires further studies.

May the Number of Pregnancies Predict the Progression and the Outcome of Venous Disease Treatment?

Pregnancy is a well-known risk factor for venous insufficiency. However, even nulliparous women experience venous problems. Therefore, we aimed to assess the possible associations between the number of pregnancies, veins condition and treatment outcome in women with venous disease. The retrospective assessment concerned data of 297 women with diagnosed venous insufficiency. Based on their pregnancy history, the patients' records were divided into: nulliparous women (15.5%), those after 1-2 term pregnancies (57.9%) and those after ≥3 pregnancies (26.6%). The analysis concerned data from the diagnostics of the abdominal/pelvic and leg veins and the treatment results expressed as a symptoms/satisfaction score. Most of the nulliparous women developed venous disease due to mild anatomic abnormalities of the abdominal/pelvic veins. They responded to treatment (mostly unilateral embolization) very well. In the second group, the majority of the combined venous abnormalities responded to treatment with significant improvement, even after embolization alone, although nearly two-thirds still required further leg treatment. The third group was comprised of more advanced cases; nearly 40% of them with recurrence. In order to improve their condition, three-fourths of the cases required sequential treatment in both the pelvic and leg veins compartments. In conclusion, the number of pregnancies is a potent modifying factor in the pathogenesis of venous disease, especially in multiparous women. Together with abnormal venous anatomy, it may determine the treatment outcome.

Investigating the Effects of Donors and Alkyne Spacer on the Properties of Donor-Acceptor-Donor Xanthene-Based Dyes.

NIR dyes have become popular for many applications, including biosensing and imaging. For this reason, the molecular switch mechanism of the xanthene dyes makes them useful for in vivo detection and imaging of bioanalytes. Our group has been designing NIR xanthene-based dyes by the donor-acceptor-donor approach; however, the equilibrium between their opened and closed forms varies depending on the donors and spacer. We synthesized donor-acceptor-donor NIR xanthene-based dyes with an alkyne spacer via the Sonogashira coupling reaction to investigate the effects of the alkyne spacer and the donors on the maximum absorption wavelength and the molecular switching (ring opening) process of the dyes. We evaluated the strength and nature of the donors and the presence and absence of the alkyne spacer on the properties of the dyes. It was shown that the alkyne spacer extended the conjugation of the dyes, leading to absorption wavelengths of longer values compared with the dyes without the alkyne group. In addition, strong charge transfer donors shifted the absorption wavelength towards the NIR region, while donors with strong π-donation resulted in xanthene dyes with a smaller equilibrium constant. DFT/TDDFT calculations corroborated the experimental data in most of the cases. Dye 2 containing the N,N-dimethylaniline group gave contrary results and is being further investigated.

Synthesis and Characterization of Novel Thienothiadiazole-Based D-π-A-π-D Fluorophores as Potential NIR Imaging Agents.

As fluorescence bioimaging has increased in popularity, there have been numerous reports on designing organic fluorophores with desirable properties amenable to perform this task, specifically fluorophores with emission in the near-infrared II (NIR-II) region. One such strategy is to utilize the donor-π-acceptor-π-donor approach (D-π-A-π-D), as this allows for control of the photophysical properties of the resulting fluorophores through modulation of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels. Herein, we illustrate the properties of thienothiadiazole (TTD) as an effective acceptor moiety in the design of NIR emissive fluorophores. TTD is a well-known electron-deficient species, but its use as an acceptor in D-π-A-π-D systems has not been extensively studied. We employed TTD as an acceptor unit in a series of two fluorophores and characterized the photophysical properties through experimental and computational studies. Both fluorophores exhibited emission maxima in the NIR-I that extends into the NIR-II. We also utilized electron paramagnetic resonance (EPR) spectroscopy to rationalize differences in the measured quantum yield values and demonstrated, to our knowledge, the first experimental evidence of radical species on a TTD-based small-molecule fluorophore. Encapsulation of the fluorophores using a surfactant formed polymeric nanoparticles, which were studied by photophysical and morphological techniques. The results of this work illustrate the potential of TTD as an acceptor in the design of NIR-II emissive fluorophores for fluorescence bioimaging applications.

Development of Self-Consistency Models of Anticancer Activity of Nanoparticles under Different Experimental Conditions Using Quasi-SMILES Approach.

Algorithms of the simulation of the anticancer activity of nanoparticles under different experimental conditions toward cell lines A549 (lung cancer), THP-1 (leukemia), MCF-7 (breast cancer), Caco2 (cervical cancer), and hepG2 (hepatoma) have been developed using the quasi-SMILES approach. This approach is suggested as an efficient tool for the quantitative structure-property-activity relationships (QSPRs/QSARs) analysis of the above nanoparticles. The studied model is built up using the so-called vector of ideality of correlation. The components of this vector include the index of ideality of correlation (IIC) and the correlation intensity index (CII). The epistemological component of this study is the development of methods of registration, storage, and effective use of experimental situations that are comfortable for the researcher-experimentalist in order to be able to control the physicochemical and biochemical consequences of using nanomaterials. The proposed approach differs from the traditional models based on QSPR/QSAR in the following respects: (i) not molecules but experimental situations available in a database are considered; in other words, an answer is offered to the question of how to change the plot of the experiment in order to achieve the desired values of the endpoint being studied; and (ii) the user has the ability to select a list of controlled conditions available in the database that can affect the endpoint and evaluate how significant the influence of the selected controlled experimental conditions is.

Serpentinization-Associated Mineral Catalysis of the Protometabolic Formose System.

The formose reaction is a plausible prebiotic chemistry, famed for its production of sugars. In this work, we demonstrate that the Cannizzaro process is the dominant process in the formose reaction under many different conditions, thus necessitating a catalyst for the formose reaction under various environmental circumstances. The investigated formose reactions produce primarily organic acids associated with metabolism, a protometabolic system, and yield very little sugar left over. This is due to many of the acids forming from the degradation and Cannizaro reactions of many of the sugars produced during the formose reaction. We also show the heterogeneous Lewis-acid-based catalysis of the formose reaction by mineral systems associated with serpentinization. The minerals that showed catalytic activity include olivine, serpentinite, and calcium, and magnesium minerals including dolomite, calcite, and our Ca/Mg-chemical gardens. In addition, computational studies were performed for the first step of the formose reaction to investigate the reaction of formaldehyde, to either form methanol and formic acid under a Cannizzaro reaction or to react to form glycolaldehyde. Here, we postulate that serpentinization is therefore the startup process necessary to kick off a simple proto metabolic system-the formose protometabolic system.

The validation of predictive potential via the system of self-consistent models: the simulation of blood-brain barrier permeation of organic compounds.

CONTEXT: To apply the quantitative relationships "structure-endpoint" approach, the reliability of prediction is necessary but sometimes challenging to achieve. In this work, an attempt is made to accomplish the reliability of forecasts by creating a set of random partitions of data into training and validation sets, followed by constructing random models. A system of random models for a helpful approach should be self-consistent, giving a similar or at least comparable statistical quality of the predictions for models obtained using different splits of available data into training and validation sets. METHOD: The carried out computer experiments aimed at obtaining blood-brain barrier permeation models showed that, in principle, can be used such an approach (the Monte Carlo optimization of the correlation weights for different molecular features) for the above purpose taking advantage of specific algorithms to optimize the modelling steps with applying of new statistical criteria such as the index of ideality of correlation (IIC) and the correlation intensity index (CII). The results so obtained are good and better than what was reported previously. The suggested approach to validation of models is non-identic to traditionally applied manners of the checking up models. The concept of validation can be used for arbitrary models (not only for models of the blood-brain barrier).

CORAL: Model of Ecological Impact of Heavy Metals on Soils via the Study of Modification of Concentration of Biomolecules in Earthworms (Eisenia fetida).

The traditional application for quantitative structure-property/activity relationships (QSPRs/QSARs) in the fields of thermodynamics, toxicology or drug design is predicting the impact of molecular features using data on the measurable characteristics of substances. However, it is often necessary to evaluate the influence of various exposure conditions and environmental factors, besides the molecular structure. Different enzyme-driven processes lead to the accumulation of metal ions by the worms. Heavy metals are sequestered in these organisms without being released back into the soil. In this study, we propose a novel approach for modeling the absorption of heavy metals, such as mercury and cobalt by worms. The models are based on optimal descriptors calculated for the so-called quasi-SMILES, which incorporate strings of codes reflecting experimental conditions. We modeled the impact on the levels of proteins, hydrocarbons, and lipids in an earthworm's body caused by different combinations of concentrations of heavy metals and exposure time observed over two months of exposure with a measurement interval of 15 days.

Elucidating Atomistic Insight into the Dynamical Responses of the SARS-CoV-2 Main Protease for the Binding of Remdesivir Analogues: Leveraging Molecular Mechanics To Decode the Inhibition Mechanism.

To combat mischievous coronavirus disease followed by continuous upgrading of therapeutic strategy against the antibody-resistant variants, the molecular mechanistic understanding of protein-drug interactions is a prerequisite in the context of target-specific rational drug development. Herein, we attempt to decipher the structural basis for the inhibition of SARS-CoV-2 main protease (Mpro) through the elemental analysis of potential energy landscape and the associated thermodynamic and kinetic properties of the enzyme-inhibitor complexes using automated molecular docking calculations in conjunction with classical force field-based molecular dynamics (MD) simulations. The crux of the scalable all-atom MD simulations consummated in explicit solvent media is to capture the structural plasticity of the viral enzyme due to the binding of remdesivir analogues and ascertain the subtle interplay of noncovalent interactions in stabilizing specific conformational states of the receptor that controls the biomolecular processes related to the ligand binding and dissociation kinetics. To unravel the critical role of modulation of the ligand scaffold, we place further emphasis on the estimation of binding free energy as well as the energy decomposition analysis by employing the generalized Born and Poisson-Boltzmann models. The estimated binding affinities are found to vary between -25.5 and -61.2 kcal/mol. Furthermore, the augmentation of inhibitory efficacy of the remdesivir analogue crucially stems from the van der Waals interactions with the active site residues of the protease. The polar solvation energy contributes unfavorably to the binding free energy and annihilates the contribution of electrostatic interactions as derived from the molecular mechanical energies.

Role of Molecular Singlet Oxygen in Photochemical Degradation of NTO: DFT Study.

NTO (5-nitro-1,2,4-triazol-3-one), an energetic material used in military applications, may be released to the environment and dissolved in surface water and groundwater due to its good water solubility. Singlet oxygen is an important reactive oxygen species produced in the aquatic environment under sunlight irradiation. A detailed investigation of the possible mechanism for NTO decomposition in water induced by singlet oxygen as one of the pathways for NTO environmental degradation was performed by a computational study at PCM(Pauling)/M06-2X/6-311++G(d,p) level. Decomposition of NTO was found to be a multistep process that may begin with singlet oxygen attachment to the carbon atom of the C═N double bond. The formed intermediate undergoes cycle opening, and nitrogen gas, nitrous acid, and carbon (IV) oxide elimination. Isocyanic acid, arisen transiently, hydrolyzes into ammonia and carbon (IV) oxide. The obtained results show a significant increase in reactivity of the anionic form of NTO as compared to its neutral form. The calculated activation energies and high exothermicity of the studied processes support the contribution of singlet oxygen to NTO degradation into low-weight inorganic compounds in the environment.

Volumetric Flow Assessment in Extracranial Arteries in Patients with 70-99% Internal Carotid Artery Stenosis.

Background: Cerebral blood flow (CBF) can be related to the risk of occurrence of neurological symptoms. Well-developed collateral circulation is a good prognostic factor in patients with cerebrovascular disease. Understanding the mechanisms of collateral circulation may be important in the diagnosis, treatment, and monitoring in this group of patients. The aim of this study covered the assessment of CBF in patients with 70−99% Internal carotid artery (ICA) stenosis, focusing on the circulation pathways and flow volume in extracranial arteries. Materials and methods: 53 patients with 70−99% ICA stenosis (mean age 73.4 ± 7 years old; 17 female, mean age 73.9 ± 7.5 years old; 36 male, mean age 73.2 ± 6.8 years old) were included in the study. In all patients a Doppler ultrasound (DUS) examination, measuring blood flow volume in the internal carotid artery (ICA), external carotid artery (ECA), and vertebral artery (VA), was performed. The cerebral blood flow (CBF) was compared to the previously reported CBF values in the healthy population > 65 years old. Results: Among the study groups three subgroups with flow differences were identified: patients with elevated CBF (significant volumetric flow compensation­26/53, 49%), patients with CBF similar to (mild compensation­17/53, 32%), and patients with CBF lower than (no compensation­10/53, 19%) the healthy, equally aged population. The percentage of patients with significant volumetric flow compensation was the highest in age groups 65−69 years old (62.5%) and >80 years old (60%). In the oldest age group (>80 years old) no patients without flow compensation (0%) were observed. The level of compensation depends on the number of the arteries with compensatory increased flow. In patients with significant volumetric flow compensation, the compensatory increased flow was observed, on average, in 3.31 arteries, in the mild compensation group­in 2.18 arteries, and in the no compensation group only in 1 artery. ICA plays the most important role in the volumetric flow compensation­the increase in the flow volume, in comparison to the reference values, was between 116.7 mL/min and 251.9 mL/min (in the ECA 57.6 mL/min−110.4 mL/min; in the VA 73.9 mL/min−104.9 mL/min). The relative flow increase was highest in the VA: 215−246%, then in the ECA: 163−206%, and finally in the ICA: 148.6−192%. The increased flow was most commonly observed in the VA­57 arteries, in second place in the ECA­42 arteries, and ICA­31 arteries. In patients with unilateral ICA stenosis, the volumetric flow increase was stated more frequently in the ipsilateral ECAs then in the contralateral ones (23 vs. 14). In the VA the opposite tendency was observed (29 contralateral vs. 23 ipsilateral). The ability of volumetric flow compensation decreased significantly with increasing age. Conclusions: Understanding the mechanisms of collateral circulation and their assessment in Doppler ultrasonography may provide a novel and easily accessible tool of identifying and monitoring patients with cerebrovascular disease.