High-viscosity Media Research Articles

Ultrafast Intersystem Crossing in Benzanthrone: Effect of Hydrogen Bonding and Viscosity.

Understanding the intricate factors governing intersystem crossing (ISC) in aromatic carbonyl compounds remains a long-standing interest among researchers. This study unveils the crucial roles of vibration in influencing the ISC of a typical aromatic carbonyl chromophore, benzanthrone, and how hydrogen bonding and solvent viscosity affect these vibrations and, thus, the associated ISC kinetics. We demonstrate that for benzanthrone, the ISC is exceedingly facile in an aprotic solvent, while in protic solvents, the ISC is significantly suppressed through the formation of the hydrogen-bonded state. Moreover, in a high-viscosity medium, ISC is further retarded due to restrictions of volume-changing motions, which may assist ISC. Theoretical calculations revealed that the C═O bond vibration and specific out-of-plane vibrations accompanying a volume change could be the probable coordinates for ISC. These findings provide valuable insights for tailoring the excited-state behavior of carbonyl-functionalized materials for diverse applications in photocatalysis, organic electronics, and biomedicine.

Flow field analysis and flow prediction of pressure reducing valves in power-law media

A robust hydraulic system is necessary for industrial gluing equipment in order to transfer and regulate a variety of chemical fluid media. Certain operational conditions call for a certain flow output. In hydraulic systems, pressure reduction valves are frequently employed to regulate flow and pressure output. In order to analyze the flow of high viscosity special media inside the valve body, a colloidal medium that complies with the power-law constitutive law and a novel type of pressure-reducing valve appropriate for high viscosity fluids were chosen as the research objects in this study. First, the valve channel's flow performance and flow field characteristics were researched with a combination of simulation and experiments. Then the impact of pressure differences, opening, and temperature variations on flow rate was investigated. The proposed flow prediction formulas can be used to forecast the flow rate in engineering applications accurately which is verified by the comparison of the numerical and experimental results. Lastly, an analysis was done on the pressure reducing valve's capacity to regulate pressure under various operating circumstances. The research can offer a specific reference for the analysis of flow field characteristics inside valves in high viscosity media and the design of pressure-reducing valve bodies in non-Newtonian media. Furthermore, the research results can help determine whether the pressure reducing valve's operating condition is normal.

Machine learning prediction and optimization of CO2 foam performance for enhanced oil recovery and carbon sequestration: Effect of surfactant type and operating conditions

Foam flooding handles the challenges of gas injection constituting a high viscosity medium that sweeps oil more efficiently meanwhile creating a barrier that prevents leakage of gas phase. Therefore, it is a promising enhanced oil recovery (EOR) method, simultaneously an efficient carbon dioxide (CO2) storage technology. The foam's performance displays susceptibility to various reservoir and operational parameters. Numerous laboratory experiments would need to be carried out to study foams and find the optimum foam formulation for the given core conditions. Data-driven approaches can be an alternative method to the time-consuming experimental and conventional modeling techniques, which often face challenges to incorporate the effect of important related parameters such as temperature and type of surfactant to the performance of foam. In the current study, machine learning (ML) models were constructed to predict the CO2 foam apparent viscosity in carbonate and sandstone formations focusing on experimental data from the literature for CO2 foams stabilized by different surfactants. Various anionic, cationic, and nonionic surfactants were considered and characterized based on the hydrophilic-lipophilic balance (HLB) number. Predictive models were developed using ML algorithms based on the data available for eight key process parameters. Artificial neural networks and extra randomized tree algorithms provided the most precise prediction among the applied algorithms. Various predictions for foam apparent viscosity on hypothetical case studies were made on altered input parameters, enabling CO2 mobility to co-optimize EOR and CO2 sequestration while selecting the optimum surfactant for each case.

High-viscosity driven modulation of biomechanical properties of human mesenchymal stem cells promotes osteogenic lineage

Biomechanical cues could effectively govern cell gene expression to direct the differentiation of specific stem cell lineage. Recently, the medium viscosity has emerged as a significant mechanical stimulator that regulates the cellular mechanical properties and various physiological functions. However, whether the medium viscosity can regulate the mechanical properties of human mesenchymal stem cells (hMSCs) to effectively trigger osteogenic differentiation remains uncertain. The mechanism by which cells sense and respond to changes in medium viscosity, and regulate cell mechanical properties to promote osteogenic lineage, remains elusive. In this study, we demonstrated that hMSCs, cultured in a high-viscosity medium, exhibited larger cell spreading area and higher intracellular tension, correlated with elevated formation of actin stress fibers and focal adhesion maturation. Furthermore, these changes observed in hMSCs were associated with activation of TRPV4 (transient receptor potential vanilloid sub-type 4) channels on the cell membrane. This feedback loop among TRPV4 activation, cell spreading and intracellular tension results in calcium influx, which subsequently promotes the nuclear localization of NFATc1 (nuclear factor of activated T cells 1). Concomitantly, the elevated intracellular tension induced nuclear deformation and promoted the nuclear localization of YAP (YES‐associated protein). The concurrent activation of NFATc1 and YAP significantly enhanced alkaline phosphatase (ALP) for pre-osteogenic activity. Taken together, these findings provide a more comprehensive view of how viscosity-induced alterations in biomechanical properties of MSCs impact the expression of osteogenesis-related genes, and ultimately promote osteogenic lineage.

Deletion of the Sodium Glucose Cotransporter 1 (Sglt-1) impairs mouse sperm movement.

The Sodium Glucose Cotransporter Isoform 1 (Sglt-1) is a symporter that moves Na+ and glucose into the cell. While most studies have focused on the role of Sglt-1 in the small intestine and kidney, little is known about this transporter's expression and function in other tissues. We have previously shown that Sglt-1 is expressed in the mouse sperm flagellum and that its inhibition interferes with sperm metabolism and function. Here, we further investigated the importance of Sglt-1 in sperm, using a Sglt-1 knockout mouse (Sglt-1 KO). RNA, immunocytochemistry, and glucose uptake analysis confirmed the ablation of Sglt-1 in sperm. Sglt-1 KO male mice are fertile and exhibit normal sperm counts and morphology. However, Sglt-1 null sperm displayed a significant reduction in total, progressive and other parameters of sperm motility compared to wild type (WT) sperm. The reduction in motility was exacerbated when sperm were challenged to swim in media with higher viscosity. Parameters of capacitation, namely protein tyrosine phosphorylation and acrosomal reaction, were similar in Sglt-1 KO and WT sperm. However, Sglt-1 KO sperm displayed a significant decrease in hyperactivation. The impaired motility of Sglt-1 null sperm was observed in media containing glucose as the only energy substrate. Interestingly, the addition of pyruvate and lactate to the media partially recovered sperm motility of Sglt-1 KO sperm, both in the low and high viscosity media. Altogether, these results support an important role for Sglt-1 in sperm energetics and function, providing sperm with a higher capacity for glucose uptake.

Characteristics and suppression of beam distortion in a high repetition rate nanosecond stimulated Brillouin scattering phase conjugation mirror

Abstract The stimulated Brillouin scattering phase conjugation mirror (SBS-PCM) based on liquid media is widely used in high-power laser systems due to its robust thermal load capacity, high energy conversion efficiency and improved beam quality. Nevertheless, with an increase in the pump repetition rate, thermally-induced blooming and optical breakdown can emerge, leading to distortions in the Stokes beam. In this study, we delved into the thermal effects in liquid SBS-PCMs employing hydrodynamic analysis, establishing a relationship between beam profile distortion and the thermal convection field. We calculated the temperature and convection velocity distribution based on the pump light parameters and recorded the corresponding beam profiles. The intensities of the beam profiles were modulated in alignment with the convection directions, reaching a velocity peak of 2.85 mm/s at a pump pulse repetition rate of 250 Hz. The residual sum of squares (RSS) was employed to quantify the extent of beam profile distortion relative to a Gaussian distribution. The RSS escalated to 7.8, in contrast to 0.7 of the pump light at a pump pulse repetition rate of 500 Hz. By suppressing thermal convection using a high-viscosity medium, we effectively mitigated beam distortion. The RSS was reduced to 0.7 at a pump pulse repetition rate of 500 Hz, coinciding with a twentyfold increase in viscosity, thereby enhancing the beam quality. By integrating hydrodynamic analysis, we elucidated and mitigated distortion with targeted solutions. Our research offers an interdisciplinary perspective on studying thermal effects and contributes to the application of SBS-PCMs in high-repetition-rate laser systems by unveiling the mechanism of photothermal effects.

Abrasive flow machining of specimens of cast billets from austenomartensitic steel with high-viscosity media

The paper presents the results of research on abrasive flow machining of removable specimens of cast billets made of austenomartensitic steel placed in a simulator of a closed curvilinear channel. The change in the roughness and micro-hardness of the surface of the samples was evaluated. There are two stages of machining. At the first stage of machining, most of the casting skin is removed. At the second stage, the casting skin is removed completely and the base metal layer is removed. It was established that the main mechanism for removing material from the surface of a cast billet is microcutting at the level of elementary real areas of contact of individual grain micro-protrusions. According to the results of the experiments, it is recommended to use abrasive flow machining with highly viscous medium to improve the roughness and increase the micro-hardness of the inner surfaces of the closed channels of cast billets.

Beyond analytic solution: Analysis of FRAP experiments by spatial simulation of the forward problem

Fluorescence redistribution after photobleaching is a commonly used method to understand the dynamic behavior of molecules within cells. Analytic solutions have been developed for specific, well-defined models of dynamic behavior in idealized geometries, but these solutions are inaccurate in complex geometries or when complex binding and diffusion behaviors exist. We demonstrate the use of numerical reaction-diffusion simulations using the Virtual Cell software platform to model fluorescence redistribution after photobleaching experiments. Multiple simulations employing parameter scans and varying bleaching locations and sizes can help to bracket diffusion coefficients and kinetic rate constants in complex image-based geometries. This approach is applied to problems in membrane surface diffusion as well as diffusion and binding in cytosolic volumes in complex cell geometries. In addition, we model diffusion and binding within phase-separated biomolecular condensates (liquid droplets). These are modeled as spherical low-affinity binding domains that also define a high viscosity medium for exchange of the free fluorescently labeled ligand with the external cytosol.

Human sperm cooperate to transit highly viscous regions on the competitive pathway to fertilization

Human sperm compete for fertilization. Here, we find that human sperm, unexpectedly, cooperate under conditions mimicking the viscosity contrasts in the female reproductive tract. Sperm attach at the head region to migrate as a cooperative group upon transit into and through a high viscosity medium (15-100 cP) from low viscosity seminal fluid. Sperm groups benefit from higher swimming velocity, exceeding that of individual sperm by over 50%. We find that sperm associated with a group possess high DNA integrity (7% fragmentation index) – a stark contrast to individual sperm exhibiting low DNA integrity (> 50% fragmentation index) – and feature membrane decapacitation factors that mediate sperm attachment to form the group. Cooperative behaviour becomes less prevalent upon capacitation and groups tend to disband as the surrounding viscosity reduces. When sperm from different male sources are present, related sperm preferentially form groups and achieve greater swimming velocity, while unrelated sperm are slowed by their involvement in a group. These findings reveal cooperation as a selective mode of human sperm motion – sperm with high DNA integrity cooperate to transit the highly viscous regions in the female tract and outcompete rival sperm for fertilization – and provide insight into cooperation-based sperm selection strategies for assisted reproduction.

Apparent viscosity of high-density fluidized bed and synergistic effect of density and apparent viscosity on particle separation

ABSTRACT For gas-solid fluidization separation, mineral particles are separated under the joint action of bed density and apparent viscosity. In present study, the apparent viscosity of high-density binary mixture media was investigated by the falling ball method. Moreover, the significant effects of bed density and apparent viscosity on simulated mineral pellets and their interactions were investigated. The apparent viscosity model of high-density gas-solid fluidized beds was modified, and it was found that the Pearson correlation coefficient is 0.86. The results show that the apparent viscosity of high-density gas-solid fluidized bed decreases with increasing fluidization gas velocity. When the fluidization number is higher than 1.3, the apparent viscosity is basically stable in the range of 3.96–5.21 Pa·s. Under low apparent viscosity, when the pellet diameter is 20 mm and the density difference ∆ρ is greater than 0.27 g/cm3, gravity is the dominant factor affecting the settling behavior of the pellet. Under high apparent viscosity, the effect of viscous resistance on the settling behavior of pellets is dominant when the ∆ρ is less than 0.27 g/cm3. Based on the performed analyses, the low-viscosity medium can be selected for the separation of large mineral particles. Furthermore, for high-viscosity medium, the influence of bubbles on particle sedimentation can be effectively alleviated and it can be selected for the separation of small particles.

A near-infrared fluorescent probe for monitoring abnormal mitochondrial viscosity in cancer and fatty-liver mice model

Viscosity is an important component of cell microenvironment, and abnormal mitochondrial viscosity is associated with many diseases such as tumor and fatty liver. Herein, a near-infrared fluorescence probe (QX-V) based on quinoline-xanthene dye for detecting viscosity is constructed. In high viscosity medium, the free rotation of single bond is inhibited and the fluorescence is released. The probe shows high sensitivity together with good selectivity. Notably, QX-V has a long excitation wavelength (710 nm) and emission wavelength (786 nm). At the same time, the probe is a positively charged molecule that can target mitochondria. QX-V can not only distinguish cancer cells from normal cells, but also make a distinction between normal cells and fatty hepatocytes. In addition, QX-V is used to image viscosity abnormality in tumor-bearing mice. The probe also has a good ability to image viscosity abnormality caused by liver injury in fatty-liver mice.

Influence of structure and magnetic properties of surface modified nanoparticles for hyperthermia application

We report the study of CoFe2O4 with biopolymers (chitosan and dextran), synthesized via a solvothermal method. The formation of the CoFe2O4 spinel phase has been validated using XRD and Rietveld analyses. The pattern of polyhedral and spherical shapes was observed for uncoated and coated samples using TEM. Mössbauer's study revealed the mixed spinel nature of the nanoparticles, in which Fe3+ and Co2+ ions are distributed in both tetrahedral and octahedral sites. The M − H curves obtained at ambient temperature show the typical ferromagnetic behavior for all the magnetic nanoparticles. The surface modification influences the specific loss power (SLP) value of the magnetic nanoparticles. Furthermore, our study revealed that dipole-dipole interactions are responsible for the self-heating behavior. SLP values demonstrated non-monotonic behavior for all the nanoparticle samples, implying that both Néel and Brownian relaxation is the responsible for heat generation in a high viscosity medium.

Extracellular Hydraulic Resistance Enhances Cell Migration.

Cells migrating in vivo encounter microenvironments with varying physical properties. One such physical variable is the fluid viscosity surrounding the cell. Increased viscosity is expected to increase the hydraulic resistance experienced by the cell and decrease cell speed. The authors demonstrate that contrary to this expected result, cells migrate faster in high viscosity media on 2‐dimensional substrates. Both actin dynamics and water dynamics driven by ion channel activity are examined. Results show that cells increase in area in high viscosity and actomyosin dynamics remain similar. Inhibiting ion channel fluxes in high viscosity media results in a large reduction in cell speed, suggesting that water flux contributes to the observed speed increase. Moreover, inhibiting actin‐dependent vesicular trafficking that transports ion channels to the cell boundary changes ion channel spatial positioning and reduces cell speed in high viscosity media. Cells also display altered Ca2+ activity in high viscosity media, and when cytoplasmic Ca2+ is sequestered, cell speed reduction and altered ion channel positioning are observed. Taken together, it is found that the cytoplasmic actin‐phase and water‐phase are coupled to drive cell migration in high viscosity media, in agreement with physical modeling that also predicts the observed cell speedup in high viscosity environments.

P-094 Fundamental understanding of sperm motion in viscoelastic media

Abstract Study question How does viscosity influence the flagellar beating behaviour of free-swimming bull, mouse, and human sperm? Summary answer Sperm flagellar beating behaviour exhibits a transition from an irregular three-dimensional (3D) beating at 5 mPa·s to an organized two-dimensional (2D) waveform at 20 mPa·s. What is known already Sperm migrate in a complex viscoelastic environment through the female reproductive tract. The viscoelastic properties of the oviductal fluid significantly influence the progressive motility of sperm, acting as one of the key guidance mechanisms in vivo. However, the biomechanics of sperm flagellar activity in response to varying viscosity of the oviductal fluid is poorly understood. Understanding sperm flagellar behaviour in physiologically relevant environments is crucial to understanding reproduction and may help to describe unknown causes of infertility. Lack of high-speed high-resolution imaging techniques and automated image-analysis capabilities have been the main barriers to fully describe the flagellar beating behaviour. Study design, size, duration We used a custom-built high-speed high-resolution dark-field microscopy platform to resolve the flagellar dynamics of human, bull, and mouse sperm near surfaces in viscoelastic media ranging in viscosity from 1 to 250 mPa·s. The imaging system includes an automated image analysis algorithm to quantify sperm flagellar waveform and motility characteristics by extracting the flagellar centreline, reconstructing the waveform and calculating tangent-angle profiles. 20 sperm from 3 different bull, mice and humans were analyzed. Participants/materials, setting, methods Bull, mouse, and human sperm were used in this study. In each experiment, a diluted sperm sample in a buffer supplemented with methylcellulose was used and free-swimming sperm were imaged using dark-field microscopy at 200 frames per second. An automated image analysis algorithm was used to extract sperm flagellar centreline and Proper Orthogonal Decomposition (POD) was then used to study sperm flagellar waveform. Statistical analysis was performed using one-way ANOVA. Main results and the role of chance The reconstructed flagellar beating pattern was different for sperm swimming in low and high-viscosity media. Bull sperm exhibited a lower flagellar beating amplitude along the end piece when swimming in a high-viscosity media, a potential energy-efficient strategy to navigate a high viscosity fluid. The first two dominant POD modes (shape modes) describe more than 90% of the beating pattern for all species. Bull sperm exhibited a transition mode with irregular loops in 5 mPa·s buffer, but the flagellar shape cycle created an organised repetitive circular cycle in 1 mPa.s (3D beating) buffer and at viscosities higher than 5 mPa·s (2D beating). Human sperm also indicated a similar behaviour but with the transition happening at higher viscosities. Mouse sperm in high-viscosity media had a lower flagellar beating amplitude across the principal piece and higher beating amplitude across the end piece. The flagellar shape cycle in mouse sperm showed a periodic flagellar beating behaviour at high-viscosities (>20 mPa·s), but a shape cycle with distorted loops at lower viscosities. Our results showed in quantitative detail that increasing viscosity alters sperm flagellar beating pattern, and how sperm migration behaviour in low viscosity media can be distinct from their swimming behaviour in vivo. Limitations, reasons for caution A more comprehensive study of sperm motility parameters such as curvilinear velocity, average path velocity and straight line velocity with a larger sample size is required to fully characterise sperm swimming behaviour as a function of viscosity. Wider implications of the findings The increasing viscosity of the oviductal fluid regulates the sperm flagellar beating behaviour to switch from a 3D swimming behaviour with irregular shape cycles at lower viscosities to a 2D slithering mode with repetitive circular shape cycles at higher viscosities to achieve a more energy-efficient beating pattern for navigation. Trial registration number Not applicable

Molecular rotational conformation controls the rate of singlet fission and triplet decay in pentacene dimers.

Three pentacene dimers have been synthesized to investigate the effect of molecular rotation and rotational conformations on singlet fission (SF). In all three dimers, the pentacene units are linked by a 1,4-diethynylphenylene spacer that provides almost unimpeded rotational freedom between the pentacene- and phenylene-subunits in the parent dimer. Substituents on the phenylene spacer add varying degrees of steric hindrance that restricts both the rotation and the equilibrium distribution of different conformers; the less restricted conformers exhibit faster SF and more rapid subsequent triplet-pair recombination. Furthermore, the rotational conformers have small shifts in their absorption spectra and this feature has been used to selectively excite different conformers and study the resulting SF. Femtosecond transient absorption studies at 100 K reveal that the same dimer can have orders of magnitude faster SF in a strongly coupled conformer compared to a more weakly coupled one. Measurements in polystyrene further show that the SF rate is nearly independent of viscosity whereas the triplet pair lifetime is considerably longer in a high viscosity medium. The results provide insight into design criteria for maintaining high initial SF rate while suppressing triplet recombination in intramolecular singlet fission.

An in vivo assay to study locomotion in Caenorhabditis elegans

Adaptation in the sensory-mechanical loop during locomotion is a powerful mechanism that allows organisms to survive in different conditions and environments. Motile animals need to alter motion patterns in different environments. For example, crocodiles and other animals can walk on solid ground but switch to swimming in water beds. The nematode Caenorhabditis elegans also shows adaptability by employing thrashing behaviour in low viscosity media and crawling in high viscosity media. The mechanism that enables this adaptability is an active area of research. It has been attributed previously to neuro-modulation by dopamine and serotonin. This study introduces an experimental assay to physiologically investigate the neuronal mechanisms of modulation of locomotion by dopamine. The technique is utilized to test gait switching while imaging the mechanosensory dopaminergic neurons PDE. Results revealed their role to be not limited to touch sensation, but to sensing surrounding environment resistance as well. The significance of such characterization is improving our understanding of dopamine gait switching which gets impaired in Parkinson's disease.-A locomotion pattern switching system was devised to allow studying this process in vivo in the nematode C. elegans.-This system allowed the study of dopaminergic neurons PDE response as the worms switched from crawling to swimming.

Two birds with one stone: A novel dual-functional fluorescent probe for simultaneous monitoring and real-time imaging of alkaline pH and viscosity in living cells

Viscosity and pH are two crucial microenvironment parameters, and their abnormal fluctuations at the cellular level can act as key indicators of various diseases diagnosis. Considering that the traditional viscosity/pH meters cannot work in the cellular environment, developing some viscosity/pH-sensitive fluorescent probes is urgently demanded. Herein, a novel dual-functional camphor-based fluorescent probe PN-SP for viscosity and pH detection was constructed based on spiropyran open/closed-ring switching strategy. PN-SP exhibited an intense green emission in response to alkaline pH while a bright red fluorescence was observed in high-viscosity media, which could avoid some problems caused by the use of multiple probes such as cross-talk spectrum and different localizations. The sensing performances of PN-SP were also demonstrated for monitoring viscosity and pH fluctuations in living HeLa cells by means of different emisson channels. Therefore, we believed that this work will provide guidance for designing some dual-functional fluorescent probes.

Review of previous Russian studies in the abrasive flow machining

Abrasive flow machining (abrasive flow machining (AFM)) is increasingly used worldwide. It is used for finishing and removing surface stresses in parts, the finishing machining of which using traditional methods is difficult. By now there are a large number of publications on this topic. A special interest are the articles in which previous works on various aspects of this technology are systematized. Due to a number of reasons, there are no publications from the scientific periodicals of Russia. This article presents a review of the works of Russian researchers in modelling the machining process by abrasive flow. They are aimed at modelling the rheological characteristics of the medium and contact interactions in processing. Particular attention is paid to the machining of an abrasive flow with an aligning device, as well as parts from powder molybdenum. The purpose of this article is to acquaint the wide range of readers with the works of Russian studies in the treatment of the abrasive flow of high viscosity medium.

Longer and faster sperm exhibit better fertilization success in Japanese quail

In birds, sperm storage tubules (SST) located in the utero-vaginal junction are thought to be a site of sperm selection; however, the exact mechanism of sperm selection is poorly understood. Here, we investigated sperm entry into the SST and subsequent fertilization success under a competitive situation created by artificial insemination of a sperm mixture obtained from 2 males. We employed 2 quail strains, a wild-type and a dominant black (DB) type, as this allows easy assessment of paternity by feather coloration. We found paternity of embryos was biased toward DB males when a sperm mix with similar sperm numbers from the 2 males strains was artificially inseminated into females. Our novel sperm staining method with 2 different fluorescent dyes showed that the DB-biased fertilization was because of the better ability of DB sperm to enter the SST. Moreover, we found that DB sperm had a longer flagellum and midpiece. These characteristics probably allow sperm to swim faster in a high viscosity medium, which may be a similar environment to the lumen of the female reproductive tract. Our results indicated that sperm competition occurs to win a place in the SST and that filling the SST with their own spermatozoa is a critical step to achieve better fertilization success for the male Japanese quail.

Influence of Temperature and Pressure on Viscoelastic Fluid Flow in a Plane Channel

The hydrodynamics of a steady-state nonisothermal flow of a viscoelastic polymer medium in a plane channel and heat transfer in it under boundary conditions of the first kind have been investigated. Fluid flow with a low Reynolds number and a high Peclet number was investigated, which made it possible to neglect the gravity and inertial forces, as well as the longitudinal thermal conductivity of the medium. From the rheological viewpoint, the polymer melt represents a viscoelastic fluid; therefore the Phan-Thien–Tanner fluid model was used as a rheological model of the fluid, with viscosity depending on temperature and pressure. A high-viscosity medium was considered; therefore a dissipation term was included into the equation of the energy of its flow. With the use of the indicated rheological model the velocity profile of fluid flow was obtained in an explicit form from the equation of fluid motion. It has been established that the dependence of the fluid viscosity on temperature and pressure exerts a noticeable influence on the distribution of the Nusselt number and of bulk temperature of the fluid along the channel length. It is shown that account for the temperature dependence of fluid viscosity leads to a decrease in the role of energy dissipation of its flow in the process of flow heating and that, conversely, the dependence of the fluid viscosity on pressure considerably enhances the dissipation effect. The problem has been solved numerically by the method of finite differences.