Type Viscometer Research Articles

Low-cost rolling ball viscometer for the evaluation of Newtonian and shear-thinning fluids

Abstract This article describes the design and testing of a low-cost automatic rolling-ball viscometer. The device has been manufactured from three-dimensional printed parts and conventional and affordable mechanical and electronic components. It is controlled by an Arduino MEGA with a custom code that includes manual and automatic measuring modes. Both the type of viscometer and the models used are, in principle, valid for Newtonian and power-law fluids. However, measurement and calculation procedures have been developed that also makes it possible to determine the viscosity of Herschel–Bulkley fluids that might exhibit a yield stress behaviour within the range studied. By these procedures, viscosity values have been obtained for model fluids – Newtonian, power-law, and Herschel–Bulkley fluids – and compared to those obtained with a commercial rotational rheometer. The proposed setup and measuring method have thus proven to provide very reasonably accurate viscosity values for a low-cost device.

Physicochemical and Thermal Behaviors of Room-Temperature Phosphonium Ionic Liquids Based on Fluorosulfonyl(trifluoromethylsulfonyl)Amide Anion As Potential Electrolytes

Room-temperature ionic liquids (RTILs), i.e. organic molten salts with melting points below 100 ◦C, have been intensively developed for electrolytic media in various electrochemical systems due to the fact that RTILs have unique physicochemical properties such as favorable solubility of organic and inorganic compounds, relatively high ionic conductivity, no measurable vapor pressure, high thermal stability, low flammability, etc. Another advantage of RTILs is a purposive selection of the ion species and their designability. Although typical anion species employed for RTILs include sulfonylamide-based anions, e.g. bis(trifluoromethylsulfonyl)amide (N(SO2CF3)2 -, TFSA) and bis(fluorosulfonyl)amide (N(SO2F)2 -, FSA) anions, asymmetric fluorosulfonyl(trifluoromethylsulfonyl)amide (N(SO2F)(SO2CF3)-, FTA) anion have attracted attention in recent years. In our preliminary approach, FTA anion based RTILs in combination with quaternary phosphonium cationswe previously reported,1,2 examining their transport property behavior. In this work, we report design and synthesis of several FTA-based phosphonium RTILs (Fig. 1) as potential electrolytes available for electrochemical systems, summarizing their physicochemical and thermal characteristics including the thermal decomposition as well as the transport property behaviors.The preparation and purification of the phosphonium RTILs were carried out according to the procedures described in our previously published papers.1-3 The phosphonium RTILs were prepared by aqueous ion exchange reactions of the precursor phosphonium bromides with lithium FTA. The resulting crude RTILs was extracted by dichloromethane, and then purified by washing with pure water several times until no residual bromide anion was detected with the use of AgNO3. The RTILs was dried under high vacuum for at least 1 day at 80 ◦C prior to use. The physicochemical and electrochemical properties such as conductivity (ac impedance method, using a two-Pt electrode cell), viscosity (cone-plate type viscometer), density, melting point (DSC), thermal decomposition temperature (TGA) were measured under dry argon atmosphere.Several phosphonium RTILs melting at ambient temperatures were successfully prepared by combination with the FTA anion. Table 1 lists the physicochemical properties and thermal decomposition temperatures (10% weight loss) of the FTA-based phosphonium RTILs. All FTA-based phosphonium RTILs showed typical temperature-dependent behaviors for density, viscosity and electrical conductivity. It should be noted that P222(1O1)-FTA exhibited the lowest viscosity and the highest conductivity in the FTA-based phosphonium RTILs, which is attributed to the introducing effect of ether oxygen atom into the cation on the flexibility of the alkyl chain. On the other hand, the thermal decomposition temperatures of the FTA-based phosphonium RTILs tended to be relatively low (less than 300 ◦C) compared to those of TFSA-based RTILs. The detailed thermal decomposition behavior observed in the thermogravimetric traces will be discussed in comparison with both corresponding TFSA- and FSA-based RTILs.References1) K. Tsunashima, et al, Electrochem. Commun., 9, 2353 (2007).2) K. Tsunashima, et al, Electrochemistry, 75, 734 (2007).3) K. Tsunashima, et al, Electrochem. Commun., 13, 178 (2011). Figure 1

A comparative study of blood viscometers of 3 different types.

The greater the viscosity of the blood, the more difficult its flow becomes, leading to an increased incidence of diseases caused by blood circulation disorders. These diseases are commonly associated with the cardiovascular and cerebrovascular systems. High blood viscosity is a primary cause of circulatory system diseases. Studies have shown that accurately measuring blood viscosity and applying this data in clinical trials can help prevent circulatory system diseases. Viscosity data can vary depending on the measurement methods used, even when these methods are based on hydrodynamic principles. Despite using approved blood viscometers, the results often differ depending on the type of viscometer used, potentially causing confusion within the medical field. Informing the medical community about these differences and the level of error associated with each measurement method can help reduce this confusion. To our knowledge, the degree of difference in viscosity measurement results due to different measurement methods and the reasons for these differences have not yet been thoroughly explored. In this study, we selected three blood viscosity measurement methods registered with the Ministry of Food and Drug Safety of Korea to analyze the same canine blood. The viscosity measurements were carried out using each device and compared. The parallel plate and scanning capillary methods yielded similar viscosity values, while the cone plate method showed lower viscosity values. The viscosity of blood, as measured by the three viscometers, differed, indicating that more experimental data must be accumulated to evaluate the cause of these differences. In this paper, we identified several causes of inconsistency and suggested measures to avoid this confusion. However, confirming that the test results show systematic differences is expected to assist clinicians who diagnose and prescribe treatments based on blood viscosity results. The findings of this comparative study are anticipated to serve as a starting point for establishing guidelines or standards for blood viscosity measurement methods.

Correct Use of Oscillating-Cup Viscometers for High-Temperature Absolute Measurements of Newtonian Melts

Oscillating-body viscometers have been used in the past to measure, in an absolute way, the viscosity of molten materials at high temperatures, from salts, metals, alloys, and semiconductors. However, the simultaneous use of basic or incomplete mathematical models, to mimic the experiment, and less careful engineering solutions for the design and operation of the instruments, led in the past to high discrepancies between the data obtained in several laboratories. This was caused by the incorrect use of the method’s theory, less accurate solutions of the complex solutions, that involve solid state and fluid mechanics, and unreal instrument design. From these types of viscometers, oscillating-cup instruments have had the most success in measuring viscosity at high temperatures, and they will be the object of this paper. It was written as a resource for workers interested in transport properties of materials when considering its use for the absolute measurement of fluids viscosity in their work, or in judging the results of others' work when comparing data with their own. The paper starts with the most accurate theory of the method’s description, followed by a discussion of its validity, application to instrument design, and consequent operation. Several constraints were identified and recommendations were made to minimize the effects of failing to satisfy them. Finally, a discussion about the uncertainty budget calculations for a real experiment is made. If all these points are followed in the design and operation of the instrument, results in global uncertainties Ur(η) between 0.02 and 0.04 are possible to obtain, up to high temperatures. If these constraints are not satisfied, erroneous measurements can be made, making comparisons and quality assessment difficult.

The RoxyScan is a novel measurement of red blood cell deformability under oxidative and shear stress

Exposure to both oxidative and shear stress, a condition that the red blood cell (RBC) continuously experiences in the circulation in vivo can be mimicked in a Couette type viscometer and monitored by ektacytometry. RBCs maintain their deformation and orientation under shear stress and oxidative stress until a threshold is reached at which these conditions appear to overwhelm the elaborate and complex pathways that maintain a proper redox environment in the cell. Oxidative stress under shear alters the ability of the cell to deform, changes cell morphology, its orientation in the shear stress field, and appears to alter intracellular and membrane characteristics. The application of the RoxyScan technology allows the comparison of oxidant effects and the role of antioxidant systems. This provides the opportunity to study the ability of RBC to deal with oxidative stress in various conditions, including RBC disorders such as sickle cell disease (SCD).

3S consideration (Synthesis, Surfactant, and Sonication) for stability and thermophysical properties enhancement of alumina-water nanofluid

Nanofluid (NF), a homogeneous dispersal of nanoparticle (NP)s in a carrying fluid, is used in many thermal applications due to its exceptional thermal characteristics. The goal of the current study is to use two-step technique for development of stable aqua alumina NF. The NF's stability is increased by using cetyltrimethylammonium bromide, a cationic surfactant. Magnetic stirring with heating is used to improve nanoparticles dispersion in the base fluid (BF). Following the development of the NF, the synthesised sample is examined utilising several stability evaluation procedures at various time intervals, including 1 day, 8 days, 15 days, and 30 days. Utilising modern equipments such as KD2Pro analyzer and double gap rotating cylinder type viscometer, thermophysical properties as thermal conductivity (knf) and viscosity (μnf) of NF were evaluated. According to experimental findings, enhancement in the volume fraction of NPs was accompanied by an increase in the nanofluid’s thermophysical properties. At the highest volume concentration, the highest augmentation in knf and μnf was found as 8.52% and 76.21%, respectively.

Study on the real-time variation laws and mechanism of oil sample viscosity during ultrasonic irradiation

It is rather significant to reveal the real-time variation of oil sample viscosity during ultrasonic irradiation to research the mechanism of viscosity change. In this paper, we first simulate the acoustic field distribution law in the reaction chamber by using the finite element method and orthogonal experiment method, then measure the viscosity of the oil sample with temperature by vibration type viscometer and get the corresponding function equation by fitting. On this basis, we measure the viscosity of the oil sample with ultrasonic irradiation time and electric power change in real-time and in situ, and finally analyze the mechanism of oil sample viscosity variation by using a temperature recorder and cavitation noise method. The results show that the greatest influence on the acoustic pressure in the reaction chamber is the change of the transducer probe in the height Z direction, followed by the width X direction and the depth Y direction. The viscosity of the oil sample shows an exponential decay with the increase in temperature. With the increase of ultrasonic irradiation time and electric power, the viscosity of the oil sample is gradually reduced. By comparing the effect of heating and ultrasonic irradiation on viscosity, it is found that ultrasonic irradiation not only changes the viscosity through thermal effect but also the cavitation noise analysis and the phenomena observed in the experiment confirm that the cavitation effect and mechanical effect exist all the time.

The design of viscometer with smartphone controlling

New design of a viscometer based on the s tokes viscosity measurement method is proposed. The principle of operation of this viscosimetr is based on the use of ball periodic alternated movement in a horizontally positioned cuvette that filled with the test liquid. The movement appears under the in fluence of a magnetic field that created by two electromagnets. Registration of the ball movement inside the cuvette is carried out using an optoelectronic pair. A distinctive feature of the proposed design is control by using a program that installed on t he user's smartphone, which also carries out the primary data processing. Data transmission is carried out over the radio channel using a Bluetooth module. Disposable cuvettes are used for measurements. This approach makes it possible to significantly redu ce both the device production costs and operating costs by eliminating most of the operations for the device preparing for working (the vast majority of existing types of viscometers require thorough flushing of all units in contact with the test medium). In addition, the proposed approach excludes the occurrence of measurement errors associated with insufficiently thorough preparation of the device for operation.

Fluidity of Cement Pastes with Admixtures and Super Plasticizer

The Marsh cone is a simple device for measuring viscosity by observing the time it takes for a known volume of liquid to flow from a cone through a short tube. It is standardized for use by mud engineers to check the quality of drilling mud. Other cones with different geometries and orifice arrangements are called flow cones, but have the same operating principle. The Marsh Cone (SS with Stand) is a simple device used for routine quick measurements of fluid viscosity. It’s a type of viscometer. It is an excellent indicator of changes in drilling fluid properties. The Marsh Funnel conical in shape - 152 mm in diameter at the top and 305 mm long with a capacity of 1,500 cm3. A 12- mesh screen covers half of the top and is designed to remove any foreign matter and drilled cuttings from the fluid. The fluid runs through a fixed orifice at the end of the funnel, which is 50mm long by 4.7 mm diameter in size

COMPARATIVE ANALYSIS OF APPROVED ROTARY VISCOMETERS

Background The oil complex is the leading branch of the Russian industry, which includes the extraction, processing, transportation and marketing of petroleum products. This industry is considered a key indicator of the development of not only the Russian, but also the global energy market. To date, 336 companies in 34 regions of the country are engaged in oil production in Russia. Since the places of oil production are remote from the centers of its processing and consumption, the transportation of raw materials and finished products becomes important. One of the most important technological parameters of oil and petroleum products, which is often analyzed by petrochemical laboratories, is viscosity. The choice of pumping technology, energy consumption for oil transportation depends on it. The viscosity can be found in the quality certificate of diesel fuel, lighting and aviation kerosene, lubricating oils and other petroleum products. The viscosity of the substances is determined with special equipment such as viscometers. Laboratories are faced with the task of choosing a suitable device among the various types of viscometers. Aims and Objectives The purpose of this work is to conduct a comparative analysis of rotary viscometers of various modifications in terms of technical and metrological characteristics. Results The analysis was carried out on the basis of the data obtained from the descriptions of the type of measuring device No. 41702-16 «Viscometers OFITE, modification 1100», No. 35936-07 «Viscometers OFITE, modifications 800, 900» and No. 72700-18 «Rotational viscometers HAAKE». The object of the research is OFITE viscometers of modifications 1100, 900, 800; viscometers HAAKE modifications Viscotester 1 plus, Viscotester 2 plus, Viscotester C versions L and R, Viscotester D versions L and R, Viscotester E versions L and R. Viscometers HAAKE modifications Viscotester 1 plus and Viscotester 2 plus have a high level of software protection against unintentional and intentional changes, viscometers rotational HAAKE modifications Viscotester C versions L and R, Viscotester D versions L and R, Viscotester C, D, E L and R versions are low. The widest operating temperature range belongs to the HAAKE viscometer of the Viscotester E modifications, the L and R versions, the narrowest - to the OFITE viscometer of the 1100 modification. Among the considered devices, OFITE viscometers of modifications 800 and 900 provide the widest range of measurements. However, it is impossible to single out a specific device among all those considered, since the choice of one or another viscometer depends on the goals, the measurement conditions and the sample under study.

Sensorless Self-Excited Vibrational Viscometer with Two Hopf Bifurcations Based on a Piezoelectric Device.

In this study, we propose a high-sensitivity sensorless viscometer based on a piezoelectric device. Viscosity is an essential parameter frequently used in many fields. The vibration type viscometer based on self-excited oscillation generally requires displacement sensor although they can measure high viscosity without deterioration of sensitivity. The proposed viscometer utilizes the sensorless self-excited oscillation without any detection of the displacement of the cantilever, which uses the interaction between the mechanical dynamics of the cantilever and the electrical dynamics of the piezoelectric device attached to the cantilever. Since the proposed viscometer has fourth-order dynamics and two coupled oscillator systems, the systems can produce different self-excited oscillations through different Hopf bifurcations. We theoretically showed that the response frequency jumps at the two Hopf bifurcation points and this distance between them depends on the viscosity. Using this distance makes measurement highly sensitive and easier because the jump in the response frequency can be easily detected. We experimentally demonstrate the efficiency of the proposed sensorless viscometer by a macro-scale measurement system. The results show the sensitivity of the proposed method is higher than that of the previous method based on self-excited oscillation with a displacement sensor.

Determination of thermophysical characteristics and viscous properties of minced raw materials from pond carp

The thermophysical characteristics and structural-mechanical properties of a functional minced fish product have been examined, the knowledge of which is necessary for thermal calculations of the developed or improved freezing units. To find the thermophysical properties, the authors used a probe method based on the thermal inertial properties of a thermocouple, which is rarely used by modern researchers, although its advantages are obvious: in particular, it allows one to determine the desired characteristics during the working process. When studying the viscous rheology of minced semi-finished products, choosing between different types of viscometers, the authors have given a detailed analysis of the principle of their operation, as a result of which it is noted that rotary viscometers are most preferable for minced fish, since they require a smaller amount of test material to achieve the required variability of shear rates in him. Low-temperature processing of raw materials from aquatic organisms, due to its high importance for aquaculture, is constantly in the field of vision of specialists connected with refrigeration technologies for storing and processing food objects. The main trends in the development of freezing technology are aimed at increasing the intensity of processes for removing heat from the objects of freezing, but it is important to ensure the safety of their consumer properties, which directly affect the choice of the applied method of carrying out the technological process. Nowadays, there are a sufficient number of freezing methods, and the choice of the method and technical means of refrigerating various food materials requires a systematic approach, the formation of which is impossible without knowledge of the thermophysical and rheological characteristics of the processing object. The use of the results obtained by the authors, together with other necessary studies, will make it possible to identify rational operating parameters for obtaining frozen minced fish pellets with specified consumer properties. These granulated products will reduce the time for the production of minced fish culinary products at catering enterprises due to the exclusion of the stage of separate defrosting of minced semi-finished product from the technological chain.

Estimation of molecular size of triglyceride in a variety of solvents by using the intrinsic viscosity technique: an important index for transesterification of triglyceride in homogenous system

The effect of solvent type on the molecular size and intermolecular interaction of triglyceride was investigated by the intrinsic viscosity technique. Both the indices may be important for discussing and scrutinizing the behavior of homogeneous transesterification of triglyceride with alcohol since it was found that the co-solvent type influences both the transesterification rate and hydrodynamic size of triglyceride in a homogeneous system. Kinematic viscosity of palm oil dissolved in six different solvents was measured at 298 K by using glass capillary type viscometer to determine the intrinsic viscosity and Huggins constant. By plotting the intrinsic viscosity and Huggins constant against the seven physical properties of the solvents, the polarity of the solvent has been identified as the key factor for molecular size of triglyceride in solution. On the contrary, none of the seven physical properties showed good correlation with the Higgins constant. This may be attributed to more complex nature of the Huggins constant in comparison with the intrinsic viscosity.

A portable instrument with disposable cells for in-situ measurements of viscosity in liquids

Viscosity is a very important property of liquids and its measure is mandatory for quality analysis in different industrial fields, such as food, paints, petroleum based products and cosmetics. Different types of viscometers exist that can measure fluids’ viscosity with high accuracy exploiting different physical principles, however these instruments are generally laboratory based and not suitable for quick in-situ measurements by untrained personnel.In this paper a portable instrument for in-situ measurement of liquids’ viscosity is presented. The instrument is based on the falling ball principle and features a battery operated electronic board, an LCD display and a disposable cell for measurements on samples for which cleaning would be difficult and time consuming. The instrument has been successfully tested by measuring the viscosity of tap water in the temperature range 15° - 45 °C and the viscosity of metalworking fluids in order to estimate oil concentration.

Simulation of particle migration during viscosity measurement of solid-bearing slag using a spindle rotational type viscometer

A Discrete Phase Model (DPM) is adopted to investigate the particle behavior during viscosity measurement of solid-bearing slags. The particle-particle interaction is interpreted by the Discrete Element Method (DEM). The results show that the particle migration is a function of shear time, leading to continuous changes in variable viscosity before a critical shear time. The critical shear time and therefore the viscosity measurement depend on the operational conditions through the particle migration behavior that is influenced by the shear time, rotational speed, gap width and particle content, shape and size. The study of particle size indicates a size segregation of the initially homogeneous system. Based on our results a number of guidelines are formulated to assist in developing more reproducible viscosity measurement methodologies.

Calculation of plastic viscosity of concrete mixture using the modified empirical formula

Nowadays various types of viscometers are being designed to measure the rheological properties of cement paste and fresh concrete. Most of them are very expensive and require specific knowledge about their usage. Then in practice usually the empirical formulas are used to calculate the main rheological properties – yield stress (Pa) and plastic viscosity (Pa·s). Therefore, in the literature, there are some formulas which can’t be used to calculate analytically plastic viscosity of concrete mixture, e.g. it cannot estimate the influence of different chemical admixture on plastic viscosity of concrete. The paper focuses on the modification of the empirical formula to calculate the plastic viscosity of fresh concrete mixture. In this paper the way of viscosity formula modification was described. For an empirical formula modification, the coefficients which describe the influence of different chemical admixture on plastic viscosity of concrete mixture were used. Coefficients Kcalc. were calculated as a ratio between different viscosity values of cement pastes obtained without and with certain chemical admixtures. Viscosity of cement paste was obtained by using rotational viscometer Rheotest RN4. Coefficients describe the change in cement pastes viscosity when adding different type (superplasticizer, viscosity modifying agent, air-entraining agent and air voids removing agent) and amount of chemical admixture.

A portable instrument with disposable cells for in-situ measurements of viscosity in liquids

Viscosity is a very important property of liquids and its measure is mandatory for quality analysis in different industrial fields, such as food, paints, petroleum based products and cosmetics. Different types of viscometers exist that can measure fluids’ viscosity with high accuracy exploiting different physical principles, however these instruments are generally laboratory based and not suitable for quick in-situ measurements by untrained personnel.In this paper a portable instrument for in-situ measurement of liquids’ viscosity is presented. The instrument is based on the falling ball principle and features a battery operated electronic board, an LCD display and a disposable cell for measurements on samples for which cleaning would be difficult and time consuming. The instrument has been successfully tested by measuring the viscosity of tap water in the temperature range 15° - 45 °C and the viscosity of metalworking fluids in order to estimate oil concentration.

The Criteria of Thickened Liquid for Dysphagia Management in Japan.

In Japan, the viscosity of thickened liquids is different among hospitals and nursing homes. In order to standardize viscosity of thickened liquids, the dysphagia diet committee of the Japanese Society of Dysphagia Rehabilitation developed the Japanese Dysphagia Diet 2013 (JDD2013). To decide on a definition of thickened liquids, the committee reviewed categories from other countries. Especially, the criteria of the USA and Australia were used as references. The definition had three levels: mildly thick, moderately thick, and extremely thick. Then a sensory evaluation by health care workers was carried out to decide the viscosity range of each level, and a draft document was made. After collecting public comments, follow-up experiments using thickened water with thickeners using xanthan gum were performed, and the JDD2013 (Thickened Liquid) was determined. The JDD2013 (Thickened Liquid) evaluated the drinking properties, visual properties, and viscosity values of each level. The shear rate of 50s-1 was adopted to measure the viscosity with a cone and plate type viscometer to duplicate the measurement criteria used by the USA. We also set the values of the JDD2013 with the Line Spread Test to promote the use of guidelines in clinical practice. We believe the JDD2013 standards help hospitals and other settings that care for people with dysphagia to use the same thickness level and the same labels. In the future, the JDD2013 levels will be compared with new international guidelines to help with international understanding of the JDD2013 levels.

The Italian primary kinematic viscosity standard: The viscosity scale

The base for all viscosity measurements is the internationally accepted viscosity of double-distilled water at 20°C. Using this water and liquids of ever greater viscosity, INRiM derives by a step-up procedure the constants for its master “glass capillary” Ubbelohde viscometers, and these are used in their turn to determine the viscosity of undetermined liquids and reference materials in the kinematic viscosities range from about 0.4mm2/s to above 700,000mm2/s with temperatures from 10°C to 150°C. From the results obtained on recalibration of the INRiM viscometers and the comparisons made with other independent laboratories, it is concluded that the present scale is realized with an uncertainty of about 0.2% at low viscosities rising to about 0.8% at high viscosities. This enable INRiM to provide traceability to Italian viscosity measurements as well as calibrating various types of viscometers for the highest measurement accuracy i.e. glass capillary, cups, rotational. This paper addresses the relevant procedure on the realisation of the Italian kinematic viscosity scale (viscosity standard) which was conducted over a number of years. The different sources of error in the viscometer calibration, mainly due to the contribution by the kinetic energy of the fluid stream, surface tension variations and, finally, buoyancy are considered. Special emphasis is also given on the uncertainty evaluation and in the international activities which provide evidence of the present measurement capabilities of the Italian laboratory and ensures smaller measurement uncertainties in the future.

Effect of carbon nanotube concentration on cooling behaviors of oil-based nanofluids during the immersion quenching

Oil-based nanofluids including 0.75%—1.75% (mass fraction) carbon nanotubes (CNTs) without any surfactants have been synthesized by a two-step process. The probes machined from 45# steel with 22mm diameter and 50mm length are quenched in the as-synthesized CNT nanofluids for testing the cooling behaviors of the nanofluids. The laser diffraction particle size analyzer, scanning electronic microscope (SEM), X-ray diffractometer and transmission electron microscope (TEM) are used to characterize the quality and distribution of CNTs in the nanofluids. The wettability and viscosity of 30# oil and oil-based CNT nanofluids are measured by a goniometer at 15 ◦C and a rotational type viscometer at 40 ◦C, respectively. The results show that the cooling efficiency of the oil-based CNT nanofluids is better than that of 30# oil. Moreover, the cooling rate of the naonofluids increases with the further increase of the CNT concentration. When the mass fraction of CNTs increases to 1.75%, the cooling rate of the naonofluids reaches a maximum at 760 ◦C and it is increased by 77.8% as compared to that of base oil. The improved cooling rate of oil by CNTs is mainly due to the uniform distribution and excellent thermal conductivity of CNTs.