Low Fluid Research Articles

Intracranial Hypotension and Bilateral Isolated Cortical Vein Thrombosis: A Case Report and Literature Review

Background: Intracranial hypotension (IH) is a clinical manifestation of low cerebrospinal fluid pressure with reports of isolated cortical venous thrombosis (ICVT) rarely described. Case Presentation: A 23-year-old man presented with postural headache followed by blurry vision and horizontal binocular diplopia with extreme gaze. Patient workup showed diffuse thickening and enhancement of the dura suggestive of intracranial hypotension and biparietal superficial cortical vein thrombosis was noted on imaging. The patient was started on folate and therapeutic anticoagulation and his condition improved. Conclusion: Patients with IH are at risk for CVT due to the dilation of the venous sinuses of the brain. Changes in the characteristics of the headache of the patient or the onset of new neurological symptoms should warrant further investigation. Prophylactic systemic anticoagulation might cautiously be indicated in high-risk patients with IH to prevent ICVT.

Numerical Study of Natural Convection Flow in a Square Porous Enclosure Filled with Casson Viscoelastic Fluid

The present simulation, a numerical investigation of natural convection of Casson viscoelastic fluid in a porous square enclosure has been reported. Darcy-Boussinesq approximation mathematical model has been considered. The enclosure has been uniformly heated from the left wall and uniformly cooled from right side wall. The developed partial differential equations of the present computational domain are employed by using stream function approach along with finite difference scheme. The house-computational numerical algorithm has been validated against with the previous work and the computational results have been registered a good correlation. All the important results as shown by streamlines, isotherms, and local Nusselt numbers, the impact of Casson fluid parameter (β), Rayleigh number (Ra) is examined. It has been observed that with the increase in Casson fluid parameter (β), the buoyancy induced fluid circulation and convection effect decreases inside the enclosure. For each Rayleigh number, there correspond a critical Casson fluid parameter (β), for which the heat transfer inside the enclosure takes place solely by conduction mode. It has been also observed that at high Casson viscoelastic fluid the effect of increase in Rayleigh number on average Nusselt number is lesser compared to the effect of increasing Rayleigh number at low Casson viscoelastic fluid.

Carnivorous Nepenthes Pitchers with Less Acidic Fluid House Nitrogen-Fixing Bacteria.

Carnivorous pitcher plants are uniquely adapted to nitrogen limitation, using pitfall traps to acquire nutrients from insect prey. Pitcher plants in the genus Sarracenia may also use nitrogen fixed by bacteria inhabiting the aquatic microcosms of their pitchers. Here, we investigated whether species of a convergently evolved pitcher plant genus, Nepenthes, might also use bacterial nitrogen fixation as an alternative strategy for nitrogen capture. First, we constructed predicted metagenomes of pitcher organisms from three species of Singaporean Nepenthes using 16S rRNA sequence data and correlated predicted nifH abundances with metadata. Second, we used gene-specific primers to amplify and quantify the presence or absence of nifH directly from 102 environmental samples and identified potential diazotrophs with significant differential abundance in samples that also had positive nifH PCR tests. Third, we analyzed nifH in eight shotgun metagenomes from four additional Bornean Nepenthes species. Finally, we conducted an acetylene reduction assay using greenhouse-grown Nepenthes pitcher fluids to confirm nitrogen fixation is indeed possible within the pitcher habitat. Results show active acetylene reduction can occur in Nepenthes pitcher fluid. Variation in nifH from wild samples correlates with Nepenthes host species identity and pitcher fluid acidity. Nitrogen-fixing bacteria are associated with more neutral fluid pH, while endogenous Nepenthes digestive enzymes are most active at low fluid pH. We hypothesize Nepenthes species experience a trade-off in nitrogen acquisition; when fluids are acidic, nitrogen is primarily acquired via plant enzymatic degradation of insects, but when fluids are neutral, Nepenthes plants take up more nitrogen via bacterial nitrogen fixation. IMPORTANCE Plants use different strategies to obtain the nutrients that they need to grow. Some plants access their nitrogen directly from the soil, while others rely on microbes to access the nitrogen for them. Carnivorous pitcher plants generally trap and digest insect prey, using plant-derived enzymes to break down insect proteins and generate a large portion of the nitrogen that they subsequently absorb. In this study, we present results suggesting that bacteria living in the fluids formed by Nepenthes pitcher plants can fix nitrogen directly from the atmosphere, providing an alternative pathway for plants to access nitrogen. These nitrogen-fixing bacteria are only likely to be present when pitcher plant fluids are not strongly acidic. Interestingly, the plant's enzymes are known to be more active under strongly acidic conditions. We propose a potential trade-off where pitcher plants sometimes access nitrogen using their own enzymes to digest prey and at other times take advantage of bacterial nitrogen fixation.

Direct Numerical Simulation of Low and Unitary Prandtl Number Fluids in Reactor Downcomer Geometry

Mixed convection of low and unitary Prandtl fluids in a vertical passage is fundamental to passive heat removal in liquid metal and gas-cooled advanced reactor designs. Capturing the influence of buoyancy in flow and heat transfer in engineering analysis is hence a cornerstone to the safety of the next-generation reactor. However, accurate prediction of the mixed convection phenomenon has eluded current turbulence and heat transfer modeling approaches, yet further development and validation of modeling methods is limited by a scarcity of high-fidelity data pertaining to reactor heat transfer. In this work, a series of direct numerical simulations was conducted to investigate the influence of buoyancy on descending flow of liquid sodium, lead, and unitary Prandtl fluid in a differentially heated channel that represents the reactor downcomer region. From time-averaged statistics, flow-opposing/aiding buoyant plumes near the heated/cooled wall distort the mean velocity distribution, which gives rise to promotion/suppression of turbulence intensity and modification of turbulent shear stress and heat flux distribution. Frequency analysis of time series also suggests the existence of large-scale convective and thermal structures rising from the heated wall. As a general trend, fluids of lower Prandtl number were found to be more susceptible to the buoyancy effect due to stronger differential buoyancy across the channel. On the other hand, the effectiveness of convective heat transfer of the three studied fluids showed a distinct trend against the influence of buoyancy. Physical reasoning on observation of the Nusselt number trend is also discussed.

Blending in unbaffled and baffled mechanically agitated vessels – Effect of Reynolds number and liquid height

The standard vessel for mixing in the process industry is a baffled tank. This design is very common especially for low viscosity fluids. Nonetheless, unbaffled vessels are found in industry and the laboratory. The reasons given for using unbaffled vessels are primarily concerns around cleaning the vessel between batches and the possibility of stagnation zones in high viscosity fluids particularly when properties change over the processing time. In this paper we will examine the effect of baffles on the blend time using one vessel: with and without baffles. The blend time was measured using the iodine color change method using a range of viscosities and Reynolds Numbers. The depth of the vortex was also measured. The same axial flow-down pumping impeller is used. In this work we observed that the flow patterns are dramatically different between unbaffled and baffled tanks. At high Reynolds Numbers with the baffled configuration, we see the familiar turbulent diffusion throughout the vessel. Without the baffles the fluid segregates into two zones: a swirling inner zone near the shaft and a more turbulent outer zone. The overall blend time is longer in the baffled tank at the same rotational speed compared to the baffled tank. This difference decreases with increasing Reynolds Number. We identified two blend times in using unbaffled tanks, a short blend time for the outer zone and a much longer time for the inner vortex centered zone which defines the overall blend time for the vessel. At low Reynolds Numbers the baffled blending is in the transitional flow regime between turbulent and laminar with a combination of eddies and striations. The last region of the tank to become completely mixed is located behind the baffles. Unbaffled blend times are shorter and as the Reynolds Number decreases the difference increases. The vortex is also reduced with decreasing Reynolds number. We consider this work just a beginning step in a long study and hope this work will be picked up by other researchers as happened so many times with Professor Nienow’s work.

The Effect of Lower Urinary Tract Symptoms on Quality of Life and Complementary Therapies for Patients with Multiple Sclerosis

Multiple sclerosis patients face many physiological, psychological, and social problems depending on the type and course of the disease. One of the physiological problems is lower urinary tract symptoms (LUTS). Problems such as urinary incontinence, frequent urination, sudden urination, inability to urinate, inability to empty the bladder completely affect the daily life of the patients. These patients may avoid social interaction because of frequent urination and incontinence. Patients with multiple sclerosis refrain from shopping, meeting with friends, and other social activities due to urinary problems. In addition, they also restrict their fluid intake because they urinate frequently. Urinary tract infections associated with low fluid intake and inability to urinate are more common in multiple sclerosis patients than in the normal population. These problems restrict the patient’s life and negatively affect their quality of life. These complaints can be minimized by bladder training, pelvic floor muscle exercises, nerve stimulation, or use of urinary catheter in order to eliminate these problems and improve the quality of life of the patients. While bladder training prolongs the urination intervals of patients, pelvic floor muscle exercises reduce urinary incontinence by strengthening the muscles. Neuromodulation reduces these problems by suppressing nerve impulses. Catheters are important for patients who cannot urinate or have urinary incontinence. Urinary incontinence, retention, and urinary infection can be reduced by using catheters.

Effect of viscosity (or lack thereof) on the flooding point in a gassed stirred tank

Flooding is a condition where gas rises vertically upwards from the sparger and through the stirrer region. The flooding point, the impeller speed at which flooding is overcome, is usually considered the minimum operating condition for gas-liquid mixing processes in stirred tanks. Most previous studies on flooding have been performed using low viscosity fluids in the turbulent regime. The present study shows that the flooding point does not change significantly when the viscosity increases (and therefore the Reynolds number decreases) by three orders of magnitude.

Predictive Modeling and Analyses of National Emergency Department Data for Improving Patient Outcomes of Nephrolithiasis.

Nephrolithiasis, or kidney stones, imposes a significant burden of disease in the United States and comes with considerable costs, pain, and morbidity.The exact cause of stone formation is undefined, but the formation is a process. Risk factors include environmental, diabetes, obesity, metabolic syndromes, low fluid intake, dehydration, diet, inflammatory bowel disorders, irritable bowel syndrome (IBS), and genetics.Laboratory testing and appropriate diagnostic imaging studies are two key components of assessment and prevention. This is a retrospective, quantitative study utilizing the Healthcare Cost and Utilization Project's (HCUP) National Emergency Department Sample (NEDS)'s existing databases from 2012 to 2014 to classify outcomes for nephrolithiasis patients.International Classification of Diseases, Ninth Revision (ICD-9-CM)billing codes related to nephrolithiasis, relevant medical imaging exams, and procedural and surgical billing codes for interventions and procedures were selected. Descriptive statistical analyses as well as multiple regression modelswere used to analyze frequencies and percentages of variables and the relationship of the data, identify co-linearity amongvariables, and predict outcomes. Results: The study sample includes a total of 509,192 emergency department (ED) visits for nephrolithiasis from 2012 to 2014 and reveals that IBS patients are two times more likely to require intervention. Stepwise regression models yield P-values of 0.004 for gender, 0.017 and 0.018 for minor diagnostic procedures, 0.006 and 0.001 for minor therapeutic procedures, and 0.000 and 0.001 for major therapeutic procedures when predicting total cost of care, and have a statistically significant impact on patient outcomes of nephrolithiasis. This research offers an investigation of the prevalence of nephrolithiasis based on age, gender, and co-morbidity, specifically IBS, and is the first to report on patient outcomes. This analysis also provides clinicians with recommendations to utilize for a comprehensive assessment of nephrolithiasis patients in the ED.

Injectable Hyaluronan-Based Thermoresponsive Hydrogels for Dermatological Applications.

Most marketed HA-based dermal fillers use chemical cross-linking to improve mechanical properties and extend their lifetime in vivo; however, stiffer products with higher elasticity require an increased extrusion force for injection in clinical practice. To balance longevity and injectability, we propose a thermosensitive dermal filler, injectable as a low viscosity fluid that undergoes gelation in situ upon injection. To this end, HA was conjugated via a linker to poly(N-isopropylacrylamide) (pNIPAM), a thermosensitive polymer using "green chemistry", with water as the solvent. HA-L-pNIPAM hydrogels showed a comparatively low viscosity (G' was 105.1 and 233 for Candidate1 and Belotero Volume®, respectively) at room temperature and spontaneously formed a stiffer gel with submicron structure at body temperature. Hydrogel formulations exhibited superior resistance against enzymatic and oxidative degradation and could be administered using a comparatively lower injection force (49 N and >100 N for Candidate 1 and Belotero Volume®, respectively) with a 32G needle. Formulations were biocompatible (viability of L929 mouse fibroblasts was >100% and ~85% for HA-L-pNIPAM hydrogel aqueous extract and their degradation product, respectively), and offered an extended residence time (up to 72 h) at the injection site. This property could potentially be exploited to develop sustained release drug delivery systems for the management of dermatologic and systemic disorders.

Solidification acceleration of phase change material in a horizontal latent heat thermal energy storage system by using spiral fins

One important solution for societies to overcome the energy crisis is to manage the production and storage of energy. In this regard, the latent heat energy storage systems have recently gained a remarkable attention. Hence, this work is devoted to enhance performance of a latent heat tube-shell storage system by using novel spiral fins with different geometrical characteristics. Different number of vanes have been employed on the fins with constant twisting pitch. The different cases studied include the cases with single-fin, double-fin, triple-fin and quadruple-fin. These fins have been employed to augment heat transfer from a low temperature fluid to the PCM inside the shell container during the solidification process. To model the phase change, the enthalpy-porosity technique has been adopted. Various parameters have been used to assess the functionality of the system including the Nusselt number, total solidification time, temperature, solid fraction evolution, solid fraction contours, temperature contours and etc. The results demonstrated that the triple-fin and double-fin cases took the advantage in heat transfer augmentation and discharging process while the case with single-fin showed the worst performance. The results indicated that fin number is not the only influencing factor and fin length also has a dominant role.

Pore-scale evaluation on a volumetric solar receiver with different optical property control strategies

Pore-scale flow and heat transfer model is built for a volumetric solar receiver subjected to highly concentrated irradiation, in order to provide insight into the detailed thermal and hydrodynamic performance. Direct three-dimensional simulations on the coupled radiation-convection-conduction are performed based on the Weaire-Phelan structure which is used to represent the open-cell ceramic foam absorber. The energy conversion characteristics with two ceramic materials (SiC and Al2O3) are firstly predicted and compared. And then several cases focused on the control approaches for the optical property (absorption/reflection/emission) of the solar absorber are introduced and investigated, including gradient surface absorptivity, spectral selectivity, and combination design of semi-transparent and opaque configuration. The results show that a moderate volumetric effect can be achieved at very low inlet fluid velocity for both ceramic materials, however presenting low conversion efficiency. Increasing the inlet velocity could enlarge the thermal non-equilibrium between solid and fluid phases and lower the outlet temperature. SiC absorber shows improved performance compared to Al2O3 absorber, and the efficiency changes obviously with the inlet velocity, while a variation of 24% is found. The optical property of the absorber front region significantly affects the overall performance. Decreasing absorptivity design and spectral selective design both show positive impact, especially for the Al2O3 absorber with an increment by 33% in efficiency relative to the basic one. Among the different strategies, spectral selective improvement shows the best effectiveness. Besides, adding porous fused silica as the front absorber layer can effectively move the high-temperature area inward at a cost of small decrement in efficiency, herein, honeycomb structure shows preponderance compared to the foam silica.

Effect of Crude Oil Quality on Properties of Hydrocracked Vacuum Residue and Its Blends with Cutter Stocks to Produce Fuel Oil

The production of heavy fuel oil from hydrocracked vacuum residue requires dilution of the residue with cutter stocks to reduce viscosity. The hydrocracked residue obtained from different vacuum residue blends originating from diverse crude oils may have divergent properties and interact with the variant cutter stocks in a dissimilar way leading to changeable values of density, sediment content, and viscosity of the obtained fuel oil. H-Oil hydrocracked vacuum residues (VTBs) obtained from different crude blends (Urals, Siberian Light (LSCO), and Basrah Heavy) were diluted with the high aromatic fluid catalytic cracking (FCC) light cycle, heavy cycle, and slurry oil, and the low aromatic fluid catalytic cracking feed hydrotreater diesel cutter stocks and their densities, sediment content, and viscosity of the mixtures were investigated. Intercriteria analysis evaluation of the data generated in this study was performed. It was found that the densities of the blends H-Oil VTB/cutter stocks deviate from the regular solution behavior because of the presence of attractive and repulsive forces between the molecules of the H-Oil VTB and the cutter stocks. Urals and Basrah Heavy crude oils were found to enhance the attractive forces, while the LSCO increases the repulsive forces between the molecules of H-Oil VTBs and those of the FCC gas oils. The viscosity of the H-Oil VTB obtained during hydrocracking of straight run vacuum residue blend was established to linearly depend on the viscosity of the H-Oil vacuum residue feed blend. The applied equations to predict viscosity of blends containing straight run and hydrocracked vacuum residues and cutter stocks proved their good prediction ability with an average relative absolute deviation (%AAD) of 8.8%. While the viscosity was found possible to predict, the sediment content of the blends H-Oil VTBs/cutter stocks was recalcitrant to forecast.

Experimental study on interlayer interference effect of CBM commingled production in a multi-pressure system under output control mode

This research adopted the self-developed test device to conduct tests to understand the interlayer interference in a multi-pressure system under output control mode. It analyzed the reservoir response and gas production characteristics in coalbed methane (CBM)'s commingled production and discussed the interlayer interference mechanism. The results revealed that the CBM's commingled production at the initial stage would generate interlayer interference under the output control mode, causing the cross-fluids of interlayer fluids. The interlayer interference would form a gas-production state. That is, the gas production of reservoirs with high fluid energy would inhibit that of the reservoirs with low fluid energy. When the gas production of reservoirs with high fluid energy is attenuated, that of reservoirs with low fluid energy would start recovering to maintain stable production. The reservoir pressure gradients positively influence interlayer interference. The more significant the difference between the reservoir's fluid energies aggravates, the more severe this interlayer interference. The output control values negatively affect the interlayer interference, as their increase would weaken the severity of interlayer interference. Therefore, the output control design should appropriately increase the output value or rationally select the reservoirs with a slighter difference in fluid energies. The gas model can be divided into three: conventional type, inhibitory type, and reverse-flow type, and their production stage can be divided into five different phases: gas rise, gas inhibition, reverse flow, gas recovery, and gas attenuation.

One-step spraying preparation of omniphobic membrane with anti-wetting behavior for membrane distillation

Membrane distillation (MD) with the application of omniphobic membranes shows much promise for desalinating saline wastewater containing low surface tension contaminants. However, the complicated membrane production steps and the wetting of the membranes have hindered its industrial application. This study reported a simple and highly efficient air spraying strategy to fabricate an omniphobic membrane by spraying a coating solution comprising fluorinated multi-walled carbon nanotubes (F-MWCNTs) onto a commercial polytetrafluoroethylene (PTFE) membrane. The contact angles for water and hexadecane on the surface reached 173.0° and 161.2°, and the water flux remained stable for 12 h when tested in DCMD with low surface tension fluids (SDS and STAC). The omniphobic membrane showed higher wetting resistance in direct membrane distillation (DCMD) experiments than the PTFE membrane when feeding low surface tension feed solutions. During spraying, F-MWCNTs randomly accumulated, and solvent evaporation resulted in micron-level mounds and surface roughness. The presence of air gaps on the membrane surface prevented the surfactant molecules from directly contacting the membrane surface and enabled the membrane to operate generally in the liquid with surfactant for a long time. The membrane was not only resistant to wetting of liquids containing low surface tension but was also easy to prepare and was expected to be used for large-scale desalination of low surface tension wastewater.

Semi-analytical simulation of seismic waves generated by a point source in 1-D layered half-space of double-porosity media

SUMMARYIn this study, we present a semi-analytical method to simulate the propagation of seismic waves in horizontally stratified double-porosity media. We solve the governing equations in the frequency–wavenumber domain and then compute the time–space domain solutions by Hankel and fast Fourier transforms. We conduct numerical simulations to study the properties of the seismic waves in the double-porosity media. The results show the existence of three P waves, one fast P wave and two slow P waves. The two slow P waves are highly attenuated and can be observed by assuming a low fluid viscosity. By comparing the fast P wave in a single-porosity medium and that in a double-porosity medium, we find that the double-porosity model predicts much higher attenuation of the fast P wave due to the local fluid flow between the background medium and the inclusions. We also study the parameters affecting the attenuation, such as the radius of the spherical inclusions, the viscosity of the pore fluid, the permeability of the background medium and the porosity of the inclusions. Finally, we present a cross-well survey model to investigate the seismic responses in the double-porosity media and compare them with the responses in the single-porosity media. We find that both the amplitude and velocity of the fast P wave decrease with the increase of the volume ratio of the inclusions.

New Insight into Enhancing Organic-Rich Shale Gas Recovery: Shut-in Performance Increased through Oxidative Fluids

Oxidizing stimulation of organic-rich shale reservoirs, as a supplement of hydraulic fracturing, was proposed to enhance shale gas recovery. Previous publications revealed that the interaction between organic-rich shale and oxidative fluids causes the components’ dissolution, which induces lots of pores and microfractures, resulting in rock microfracturing without confined pressure and associated increments of the matrix permeability, and improving unpropped fracture conductivity. However, the enhancement of shale gas recovery with oxidative fluids still lacks an implementation clue targeted for specific engineering problems. In recent years, water–rock interaction inducing microfractures indicates a positive effect of retained fracturing fluid on the stimulation after the fracturing operation, which sheds light in the enhancement of shale gas production by shut-in. The objectives of this study are to provide a new perspective whereby the shut-in performance to enhance shale gas recovery could be increased by the injection of oxidative fluids into the formation during the fracturing operation. Firstly, the mechanisms of shut-in performance increased by oxidative dissolution, which illustrate the increment of the density of fracture networks, the improvement of fracture network conductivity, and the promotion of gas desorption and diffusivity, are demonstrated. Then, the feasibility of using oxidative fluids to increase shut-in performance, which follows the geological and engineering characteristics of organic-rich shale reservoirs, is evaluated. Finally, according to the analysis of production performance for two typical types of shale gas wells, in which one is a low gas production and a high fracturing fluid recovery (LGP-HFR) and the other is a high gas production and a low fracturing fluid recovery (HGP-LFR), a shut-in strategy with oxidative fluids to enhance shale gas recovery is developed. This indicates that the injection of oxidative fluids during the fracturing operation may become a promising and cost-effective approach to enhance shale gas recovery.

Development of a Novel Surfactant-Based Viscoelastic Fluid System as an Alternative Nonpolymeric Fracturing Fluid and Comparative Analysis with Traditional Guar Gum Gel Fluid.

Surfactant-based viscoelastic (SBVE) fluids have recently gained interest from many oil industry researchers due to their polymer-like viscoelastic behaviour and ability to mitigate problems of polymeric fluids by replacing them during various operations. This study investigates an alternative SBVE fluid system for hydraulic fracturing with comparable rheological characteristics to conventional polymeric guar gum fluid. In this study, low and high surfactant concentration SBVE fluid and nanofluid systems were synthesized, optimized, and compared. Cetyltrimethylammonium bromide and counterion inorganic sodium nitrate salt, with and without 1 wt% ZnO nano-dispersion additives, were used; these are entangled wormlike micellar solutions of cationic surfactant. The fluids were divided into the categories of type 1, type 2, type 3, and type 4, and were optimized by comparing the rheological characteristics of different concentration fluids in each category at 25 °C. The authors have reported recently that ZnO NPs can improve the rheological characteristics of fluids with a low surfactant concentration of 0.1 M cetyltrimethylammonium bromide by proposing fluids and nanofluids of type 1 and type 2. In addition, conventional polymeric guar gum gel fluid is prepared in this study and analyzed for its rheological characteristics. The rheology of all SBVE fluids and the guar gum fluid was analyzed using a rotational rheometer at varying shear rate conditions from 0.1 to 500 s-1 under 25 °C, 35 °C, 45 °C, 55 °C, 65 °C, and 75 °C temperature conditions. The comparative analysis section compares the rheology of the optimal SBVE fluids and nanofluids in each category to the rheology of polymeric guar gum fluid for the entire range of shear rates and temperature conditions. The type 3 optimum fluid with high surfactant concentration of 0.2 M cetyltrimethylammonium bromide and 1.2 M sodium nitrate was the best of all the optimum fluids and nanofluids. This fluid shows comparative rheology to guar gum fluid even at elevated shear rate and temperature conditions. The comparison of average viscosity values under a different group of shear rate conditions suggests that the overall optimum SBVE fluid prepared in this study is a potential nonpolymeric viscoelastic fluid candidate for hydraulic fracturing operation that could replace polymeric guar gum fluids.

A Novel Equivalent Time Sampling-Based Method for Pulse Transit Time Estimation with Applications into the Cardiovascular Disease Diagnosis.

The increasing incidence of cardiovascular diseases (CVDs) is reflected in additional costs for healthcare systems all over the world. To date, pulse transit time (PTT) is considered a key index of cardiovascular health status and for diagnosis of CVDs. In this context, the present study focuses on a novel image analysis-based method for PTT estimation through the application of equivalent time sampling. The method, which post-processes color Doppler videos, was tested on two different setups: a Doppler flow phantom set in pulsatile mode and an in-house arterial simulator. In the former, the Doppler shift was due to the echogenic properties of the blood mimicking fluid only, since the phantom vessels are non-compliant. In the latter, the Doppler signal relied on the wall movement of compliant vessels in which a fluid with low echogenic properties was pumped. Therefore, the two setups allowed the measurement of the flow average velocity (FAV) and the pulse wave velocity (PWV), respectively. Data were collected through an ultrasound diagnostic system equipped with a phased array probe. Experimental outcomes confirm that the proposed method can represent an alternative tool for the local measurement of both FAV in non-compliant vessels and PWV in compliant vessels filled with low echogenic fluids.

LA-ICPMS trace elements and C-O isotopes constrain the origin of the Danaopo Cd-Ge-bearing Zn-Pb deposit, western Hunan, China

The Danaopo Zn-Pb deposit, hosted in algal limestone, is the second largest Zn-Pb deposit (150 Mt ores at an average grade of 3.06% Zn + Pb) in the western Hunan-eastern Guizhou metallogenic belt (WHEGMB). Here we investigate the trace elements of sphalerite and C-O isotopes and rare earth elements (REEs) of calcite in the Danaopo deposit, aiming to present insights into the mineralization potentiality of critical metals and origin of Zn-Pb deposits in the WHEGMB. In-situ trace element reveals the inhomogeneous distribution of critical metals within sphalerite, including Cd (1520 to 11570 ppm), Ge (0.73 to 236 ppm), Ga (0.04 to 26.90 ppm), and Tl (0.01 to 3.62 ppm). Cd and Ge exceed the Chinese comprehensive utilization standard. The LA-ICPMS elemental map and inter-element correlations suggest that Cd and Ge enter sphalerite lattice via the substitution of Zn2+ ↔ Cd2+ and 4Zn2+ ↔ Ge4+ + 2Fe2+ + □ (vacancy), respectively. The δ13CPDB (-3.93 to −0.12‰) values of the ore-stage calcite indicate that the carbon in hydrothermal fluids primarily originates from the dissolution of Cambrian algal limestone. Calculated δ18Ofluid (+5.23 to + 9.95‰) values on calcites lies between the oxygen isotopic compositions of the algal limestone (+18.76 to + 23.87‰) and the basinal hot brine (+4 to + 10‰), implying that the oxygen was sourced from a binary mixing of ore-host rocks and basin brine. Besides, the REE distribution pattern of Cal-Ⅰ falls within the field of ore-host rocks. In contrast, Cal-Ⅱ is plotted between the Cambrian ore-host and Proterozoic Banxi Group to Cambrian Niutitang Formation footwall. These findings suggest that REE of Cal-Ⅰ was mainly sourced from country carbonate rocks, while Cal-Ⅱ has mixed REE origins from ore-host rocks and footwall sedimentary and metamorphic basement rocks. Overall, based on detailed deposit geology, sphalerite trace elements, and calcite C-O and REE evidences, this study concludes that the Danaopo is a classic Mississippi Valley-type (MVT) Zn-Pb deposit with a low-temperature and low fO2 reductive ore-forming fluid.

Accurate measurement of thermal conductivity of micro-quantity liquids by dielectric transient current method

The thermal conductivity of liquids is of a great significant parameter for engineering applications that require the use of liquids to enhance heat transfer. Although a number of experimental methods for measuring thermal conductivity of liquids have been reported, many of these methods have limitations in principle or accuracy for small amounts of liquids, particularly for some nanofluids with low thermal conductivity or high electrical conductivity. This paper presents a novel method for measuring thermal conductivity of micro-quantity liquid based on the modified thermal pulse method. The main principle of the measurement is based on fitting the changing characteristics of the thermal response current of a thin dielectric film thermally coupled to the tested liquid. The paper analyses the factors affecting the measurement range and accuracy of the technique through numerical simulations and experiments. The feasibilities and uncertainties of the proposed technique are discussed in relation to six typical samples including pure water, insulating oil and conductive nanofluids. The experimental results show that the method for testing the thermal conductivity of liquids has the advantages of low measuring time down to 10 ms, low fluid usage down to 60 nL, wide measurement range from 0.01 to 10 W/(m·K), good sample compatibility and high accuracy. It should be noted that the method is highly dependent on the thermal conductivity and thickness of the dielectric film, which limits the measurement range of the method.