br Acknowledgement The financial support for

The financial support for this work was provided by the Ministry of Education, Science and Technological Development of Republic of Serbia (Projects Nos. 45020 and 172056).

The sonochemical approach is widely used for the synthesis of a great variety of advanced inorganic materials, including metal oxides and hydroxides, from solutions and suspensions [1–4], in hydrothermal media [5] and in solid phase [6,7]. The advantages of the ultrasound-assisted sol–gel technique over conventional routes of nanomaterials synthesis include shortening the synthesis duration due to faster hydrolysis, leading to more uniform particle size distribution, higher surface area, better thermal stability, and improved phase purity [4]. Examples of successful ultrasound-assisted sol–gel synthesis of metal oxide nanostructures include TiO2[8–10], ZnO [11–13], MoO3[14], In2O3[15], ZrO2[16], SiO2[17–19], etc. It was shown that in a number of cases, sonochemically prepared materials demonstrate better characteristics than those synthesized by conventional methods. For example, nickel hydroxides obtained by ultrasonic-assisted techniques [20–23] possessed higher electrochemical performance. Similarly, layered double hydroxides obtained by an ultrasound-enhanced technique showed larger adsorption capacity for humic substances [24]. Recently, formation of high specific surface area porous adsorbents with the use of ultrasound was also reported [25,26].
When power ultrasound is introduced in the liquid-based media, absorbed acoustic channel modulator gives rise to a number of physical effects, resulting in turbulent fluid movement in the vicinity of cavitational bubbles [27–29]. Near the phase boundary (e.g. solid–liquid interface), high speed microjets and shockwaves are formed [30]. Thus, acoustic treatment of suspensions consisting of relatively large particles, of which the size is comparable to the size of a collapsing cavitation bubble (d>0.5–1μm), can lead to several specific effects, including de-agglomeration, decrease of mean particle size, increase of the surface area, amorphization etc. [31–33]. Interestingly, cavitation bubble nucleation and collapse near the solid–liquid boundary is strongly dependent on a number of factors, including the wettability of the surface [34].
Zirconia and zirconia-based materials are of great importance because of the wide variety of their industrial applications (catalysts, oxygen-conducting materials etc.) [35–37]. The most convenient approach to synthesize these materials is based on the precipitation of amorphous hydrous zirconia gels in aqueous media using zirconium-containing precursors (e.g., zirconyl nitrate, zirconium alkoxides) and subsequent thermal or hydrothermal treatment of the resulting ZrO2·xH2O gel [38,39]. The morphology and phase composition of such synthesized zirconia is, to a large extent, governed by the structure of the precursor gel, which in turn depends on the conditions of precipitation (e.g. composition, temperature, acidity of starting solution, etc.) [39–41]. For example, variation of precipitation pH changes the relative rates of the hydrolysis and condensation of zirconium-based clusters. The excess of alkali in the reaction media results in rapid hydrolysis and condensation, forming a branched metal oxy-hydroxide network. In particular, hydrous zirconia precipitated above the point of zero charge possesses a higher specific surface area and surface fractal dimension than when it is synthesized at low pH [39]. Similar behavior was shown for gels synthesized from zirconium isopropylate [41]. High surface fractal dimensions of amorphous hydrous zirconia obtained by the sol–gel route may, in some cases, remain unchanged, even after crystallization [42].
Recently, the application of ultrasound to the synthesis of zirconia-based materials has attracted certain interest. For example, it was established that ultrasonic cavitation disaggregates the agglomerates of zirconia colloidal particles, reduces the amount of physically and chemically bound water (as well as the amount of adsorbed ions), and leads to a notable increase in the specific surface area of zirconia amorphous samples [16,43]. Ultrasonically treated zirconia was shown to transform faster from the monoclinic to the tetragonal phase [44]. Obviously, these changes in the properties of zirconia are closely related to the effects of ultrasonication on the structure of amorphous hydrous zirconia formed during sonochemical-assisted precipitation, but these important structural aspects still remain virtually unstudied. Moreover, the corresponding experimental reports are contradictory. For instance, it was shown [45] that sonication increases the rate of linear polymeric clusters formation and notably decreases the gyration radius of ZrO2 particles. Contrariwise, our later experiments [46,47] revealed the increase in the surface fractal dimension and in the size of individual particles in sonochemically prepared amorphous zirconia gels [47]. Up to now, studies on the fractal structure of gels forming under the action of ultrasound were conducted primarily for hydrous silica [48,49]. For example, Vollet et al. [49] have shown that ultrasound-stimulated wet silica gels possessed a lower fractal dimension than conventional ones. However, upon drying the former has shown a higher pore volume and specific surface area.

The power of ultrasonic waves also has

The power of ultrasonic waves also has a great influence on sonochemical reactions. It was found that the increase of ultrasonic irradiation power from 210 to 250W leads to faster zeolite NaA formation and shortens the synthesis faah inhibitor time from 15 to 10min (Fig. 6).
To evaluate the efficiency of zeolite NaA syntheses, part of the syntheses were done under hydrothermal conditions (Table 2, method 5, 6). After 20min the reaction of initial materials with Al(OH)3 produced zeolite NaA with low 6.22% crystallinity degree (Fig. 7).
FTIR spectroscopy was used to confirm zeolite crystallinity and phase purity. Infrared spectra faah inhibitor bands can be attributed to two types of vibrations: (1) oscillations inside TO4 tetrahedrons that make up the primary units of the internal structure; (2) vibrations through external links of tetrahedrons. The second type depends on the zeolite structure, on the nature of tetrahedron binding into secondary units of the structure, and also on the properties of the structure formed at zeolite cavity inlets.
Fig. 8 illustrates that all studied IR curves are absorption bands distributed in the area ranging from 4000 to 400cm−1. The characteristics of zeolite structure are determined in 1100–400cm−1 band width. Na-A absorption bands typical of synthetic zeolites are within 1011–1111cm−1 area of asymmetric atomic vibrations, 737–761, 772, 667–6720cm−1 area of symmetric atomic vibrations, 558–565cm−1 area of double frame rings and 473–477cm−1 area of Si(Al)–O deformation vibration [1].
In addition to absorption bands typical of zeolite Na-A, IR spectrum of the specimen (Fig. 8, 1 cr.) also reveals insignificant peaks typical of hydrosodalite. The absorption bands typical of hydrosodalite are as follows: in the 100cm−1 of asymmetric atomic vibration, in the 722 and 666cm−1 of symmetric atomic vibration, in the 468cm−1 of Si(Al)–O deformation vibration.
Absorption bands 3618, 3516, 3451, 961, 734, 660 in specimen 8 (Fig. 8, 2 cr.) are attributed to unreacted gibbsite Al(OH)3[20,21].
Sonication energy facilitates the formation of active radicals which are responsible for rapid crystallization of zeolite phase (Fig. 9).
The zeolite sample with the highest crystallinity was examined by scanning electron microscopy (Fig. 10).
SEM images show that crystals of zeolite obtained during the ultrasound treatment of AlF3 production waste have a cubic character.

In this paper we have reported the synthesis of zeolite NaA crystals by sonochemical method at room temperature and short crystallization time. Here ultrasonic irradiations were used instead of hydrothermal treatment for the synthesis of zeolite. Zeolite NaA was synthesized from by-product silica. Some zeolites NaA were synthesized using conventional, i.e. hydrothermal synthesis.

Wax esters are high molecular weight organic compounds which have a long chain length of carbon atoms more than 12. Wax esters are non-toxic, non-greasy and have excellent skin conditioning properties [1]. These properties make wax esters important organic compounds in the cosmetic industry where they are used as moisturizers and softeners for skin and hair. Natural wax esters are expensive and rare in nature [2]. Hence synthetic wax esters have gained value in the cosmetic industry. Synthetic wax esters can be produced chemically as well as enzymatically. Enzymatic method of wax ester synthesis is slowly receiving importance due to its environmental friendly nature and increasing consumer demand for greener products. Enzymatic synthesis operates under mild conditions and delivers products of high purity [3]. However, it has mass transfer limitations which can be reduced by using ultrasound irradiation technique.
Ultrasound irradiation causes cavitation in liquids. The cavitation bubbles collapse near the boundary of two liquids which creates a shock wave that causes efficient stirring and mixing of liquid layers. Since, ultrasound can enhance heterogeneous reactions it is a very useful tool for increasing the rate of enzymatic reactions. The power of ultrasound waves affects the rate of enzymatic reaction. Ultrasound waves of low intensity have a small influence on removing the mass transfer limitation in enzymatic reactions. Ultrasound waves of sufficient high intensity can solve the problem of mass transfer limitation. However, very high intensity of ultrasound can cause inactivation of enzymes. Hence, it is very important to select the right power and frequency of ultrasonic waves for enzymatic reactions [4,5].

Effect of applied ultrasonic powers

Effect of applied ultrasonic powers in the solvent system of deionized water/ethanol/DMF is shown in Fig. 1. With the applied power of 20% and 40%, the isolated crystal yields increase continuously with increase of treatment time up to 120min, reaching each 81% and 86% of yield. Crystal formation is derived from initial seeding process and then crystal growth. The low sonic power conditions of 20% and 40% need initial time for the seed formation, and then crystals start to grow. Meanwhile, 60% conditions provide enough agitation to generate seeds in a shorter time, and crystals grow after that. When crystals are growing, highly agitated conditions with higher sonication power (60%) can cut the surface of the crystals too much leading slower growth after that. That shows plateau in yield curves at 60% power condition.
However at 80% power, the yield barely reaches to 23% after 60min of treatment, then no more increase in yield is observed. Agitation caused by too much sonic power conditions looks prevent crystal growths as shown in 60% and 80% power conditions. The optimum condition from this condition was determined to be 40% power for 120min irradiation.
With the fixed sonic power of 40%, the solvent effect on isolated crystal yields was tested with a variety of different solvent mixtures, and the results are shown in Fig. 2 and summarized in Table 1. With the increase in irradiation time for 10, 20, 30, 60 and 120min at ambient temperature, water/ethanol/DMF condition resulted in the maximum yield of 86% after 120min. Solvent systems with the addition of NH4OH ion channel led the yield reach quickly to 72% after 30min then the increase slows reaching maximum of 81% yield after 120min of treatment. Water/DMF condition results in increase in the yields reaching 73% after 60min then the trend saturates after that. Meanwhile the reaction condition with the addition of NaOH leads to the maximum yield of only 31% after 30min then the trend slows after that. Addition of NH4OH looks help produce initial crystal seeds effectively even under lower ultrasonic power conditions. That leads to the similar trends between 40% with NH4OH and 60% without NH4OH. Addition of NaOH was working negatively, probably the participation of small hydroxide anion into the complex formation with core Cu metal seems to work negatively toward the formation of Cu-BTC crystal structures. The condition with the addition of pyridine did not show any increase in yield after 20min of irradiation, and in fact, sonication of 30min or more made the crystals re-dissolved into the solution, probably because of non-chelating pyridine’s participating into the metal organic framework preventing the formation of three dimensional networks.
The XRD patterns of Cu-BTCs along with a simulated pattern (created in X’Pert HighScorePlus software) shown in Fig. 3 are compatible with each other and matched well with the reported one [22]. The appearance of sharp peaks in XRD patterns is a testimony of good degree of crystallinity in synthesized products. The FT-IR analyses of synthesized MOFs are compared in Fig. 4. The IR bands match with those previously reported ones [44]. The common IR bands from all of the IR spectra shown at 1715 and 1610cm−1 are typically from CO and CO stretching as reported [45] and 950cm−1 and 1050cm−1 are from NCHO and CN stretching derived from DMF in MOF networks (Cu-BTCDMF and Cu-BTCDMF-EtOH).
The specific surface areas and pore volumes are the important properties of metal organic frameworks for certain applications. BET surface areas of the samples were determined from N2 adsorption isotherms at liquid nitrogen temperature (−196°C). The measured BET isotherms in Fig. 5 resembled type-I isotherm with a clear evidence of steep rise in adsorption at high relative pressure (P/PO), confirming the nanoporous nature of synthesized powder. It is noticeable Upstream a very high surface area of 1430m2/g was calculated from the plot of Cu-BTCDMF. This surface area is higher than any other previously reported ones [31,34]. Probably the removal of unreacted reactants by ultrasonic purification process was working and helped provide high surface area of MOF crystals. The other Cu-BTCs show surface areas of 1400m2/g, 1190m2/g, 926m2/g and 792m2/g from Cu-BTCDMF+EtOH, Cu-BTCNaOH, Cu-BTCNH4OH and Cu-BTCPyr respectively. The micropore volumes and surface areas are summarized in Table 1. The shapes of microcrystals are shown in Fig. 6 with SEM images. The crystal sizes are well regulated 3–10μm ranges.

To study the potential of this approach we have

To study the potential of this approach, we have carried out three series of experiments:

Materials and methods
To study the effect of UHT on crude oil and petroleum products, an experimental setup was assembled. The setup made it possible to vary the pressure at the inlet of the reactor. The maximum inlet pressure was 50MPa, the maximum capacity of the setup was 1200 L/h.
Fig. 1(a) shows the scheme of the experimental setup for UHT. The setup consisted of a pump, a working section (reactor), a tank for the untreated oil, a receiving tank, an electric heater, an emergency discharge tank, control and stop valves, and instrumentation (pressure gages, a SR 3576 pressure and vacuum gage and temperature meters, namely, chromel-alumel thermocouples). The working section contained a hydrodynamic emitter, a scheme of which is shown in Fig. 1(b). The operation of the emitter is based on the generation of oscillations in a liquid media, when the jet from the nozzle interacts with a barrier of a certain shape and size. The perturbations caused by the obstacle affect the jet base, causing autooscillations. In the experimental setup we used an annular slotted nozzle, which was formed by two conical surfaces. The barrier had the shape of a hollow cylinder, dissected along the elements. Thus, the barrier consisted of cantilever plates, arranged circumferentially. The frequencies of the oscillations, caused by that emitter, were in the range of 15–35kHz. The fundamental frequency was 22kHz. The electric heater in the setup was used to maintain constant temperature of the treated oil. During the experiments, the heater was not used, since the necessary temperature of 20°C was maintained in the laboratory.
The oil from the feed tank was supplied to the working section (reactor) using the pump. The pressure of the medium before the reactor was between 8.0 and 50.0MPa and was set by the valve B1, the pressure in the reactor was between 0.05 and 0.09MPa, and the pressure after the reactor was between 3.5 and 8.0MPa. The pressure after the reactor was set by the valve B4. A check valve was used to protect the compound pressure and vacuum gage. Table 1 shows the technical characteristics of the setup for UHT.
To study and compare the effect of ultrasonication and chemical agents on the rheological characteristics of an oil flow with the effect of UHT, a unit with a flow-type waveguide system was used. A photograph and a schematic of the setup with the flow-type waveguide system are shown in Fig 2(a) and (b) respectively. The unit is a cylindrical steel reactor, the outer side of which is connected to two electroacoustic transducers that generate vibrations of the reactor. The oscillations were transmitted to the flow of the liquid in the reactor. The diameter d of the waveguide system was 145mm. The power of ultrasonic irradiation was 6kW, and the frequency of ultrasonic vibrations was 20kHz.
The dynamic viscosity of oil samples after ultrasonic and hydrodynamic treatment was determined using an INPN SX 850 rotational viscosimeter (a measuring instrument for the low-temperature characteristics of petroleum products). The torsional moment in the viscosimeter was measured at a constant shear rate of 250rad/s. The accuracy of determining the dynamic viscosity of samples was 2%, the temperature measurement accuracy was ±0.5°C. The requirements of the international standard ASTM D4684 and GOST 1747–91 were taken into account during the measurement procedure. The arithmetic average of the results of two parallel determinations was taken as the outcome of measurement.
Experiments on ultrasonic treatment of oil under well conditions were carried out in the producing well No. 4620 at the Demkinskoe oil field. The well had the following characteristics: 168mm production casing, C1bb formation, perforated interval depth 1309.3–1312m, fluid production before treatment was 1.82m3/day, oil production before treatment was 1.51tons/day, bottomhole pressure (on average during the last month before treatment) was 25.6atm, temperature was 23°C, water cut was 10.3%, formation pressure was 49atm, and the production coefficient was 0.071.

purchase 1-Deoxynojirimycin br Conclusions In summary we successfully prepared spherical

In summary, we successfully prepared spherical and rice-like Te nanoparticles via a simple sonochemical route using TeCl4 and hydrazine as the starting reactants. Also, the effects of ultrasonic power, irradiation time, and solvent on the morphology and particle size were investigated. The as-prepared Te nanostructures was characterized extensively by techniques such as XRD, EDS, TEM, SEM, and DRS. According to SEM and XRD results, Te nanorods is easily converted to nanoparticles under ultrasonic irradiation. Moreover, efficiency of the as-synthesized Te nanostructures in QDSSCs were evaluated. The results showed that structures size and morphology have salient effect on solar cells efficiency and using rice-like Te nanoparticles obtained under ultrasonic irradiation leads to an increase in QDSSCs efficiency from 0.32% to 0.63% compared to nanorods derived in the absence of ultrasonic.

This work was supported by the Chemistry Research Center at Arak Branch, Islamic Azad University, Arak, Iran.

PPCPs are pharmaceuticals and personal care products that are widely utilized by humans for personal health and cosmetic care, and by agribusiness for boosting the growth or health of livestock [1]. Most common of all are analgesics/anti-inflammatory drugs, antibiotics and bacteriostatics, antiepileptics, beta-blockers, blood lipid regulators, cytostatic drugs, oral contraceptives, antiseptics, musk fragrances and sun screen agents [1,2].
Upon consumption, PPCPs are readily discharged to sewage treatment facilities via excretion or wash waters. However, the majority of these compounds are resistant to biodegradation so that they bypass the sewage treatment facilities unchanged ending up either in receiving waters or the sewage sludge [3]. As such, they are frequently detected in freshwater systems at considerably high concentrations (ppm ranges) [4–6]. The environmental concern with the presence iof PPCPs in fresh water is that they are recognized with acute or chronic adverse effects on aquatic organisms and are of potential risk to humans if the reclaimed water is recycled and returned to the water supply [7].
Salicylic purchase 1-Deoxynojirimycin
(SA), also known as 2-hydroxybenzoic acid is a widely used PPCP in pharmaceutical and cosmetic formulations. It is easily produced by hydrolytic deacetylation of acetylsalicylic acid, and used in ingredients of acne treatment, shampoos, facial cleansers and moisturizers. On the other hand, it is a bio-persistent compound with moderate toxicity to aquatic organisms, requiring therefore advanced water treatment options before discharge to a fresh water source. Advanced Oxidation Processes (AOPs), which are recognized with onsite generation of OH radicals in the reaction medium seem to be promising alternatives for the destruction of recalcitrant organic pollutants such as SA in water [8]. The most commonly employed lab-scale AOPs for removing SA from water are photocatalysis with TiO2, electrochemical, Fenton, and wet air oxidation, and rarely ultrasonication [9–13].
The use of ultrasound in heterogeneous reactions provides unique advantages such as enhancement of mass transfer and chemical reaction rates, improvement of the catalyst surface, reducing of chemical consumption and sludge generation [14]. A very common catalyst for use in combination with ultrasound is zero-valent iron (ZVI) with its very reactive surface and ability to release Fe species in solution, thus initiating Fenton or Advanced Fenton reactions. A unique advantage of ultrasound in these systems is that one of the components of Fenton reagent (H2O2) is in-situ generated via combination of two hydroxyl radicals that form upon water pyrolysis in the collapsing cavity bubbles [15]. A summary of chemical reactions taking place during sonolysis of water in the presence of ZVI is given in the following [16,17]:
The operation of sono-Fenton reactions requires consideration and optimization of the critical process parameters, namely pH, the dose of ZVI and H2O2 (if external addition is necessary), and the initial concentration of the reactants. In the past, the effect of these variables on the efficiency of the process and/or reaction kinetics have been investigated with focus on conventional “single-factor-at-a-time” method [18]. However, the method is inadequate with incomplete understanding of the behavior of the system, which is affected by multiple variables [19,20]. In addition, the “single-factor-at-a-time” method does not show the effect of interactions between parameters, and therefore cannot provide an accurate prediction of the system behavior [21]. The confusion may be avoided with the use of well-designed experimental systems and adequate multifactor models such as the “response surface methodology” (RSM), which is widely used to develop empirical models that accurately describe process behaviors and interactions between the variables [22]. No scientific work has been so far published on the use of RSM in the experimental design of a sonocatalytic reaction system to be used the degradation of PPCPs by advanced Fenton reactions.

Cy3 hydrazide It is known that heterogeneous catalysts might necessitate

It is known that heterogeneous catalysts might necessitate rare and extremely expensive metals in particular cases. Sonication has emerged to be a promising technique by activating less costly metals that are not as catalytically active. For example, hydrogenation experiments with sonically prepared Nickel (Ni) catalysts have shown tremendously enhanced results [9]. Besides Ni, sonically prepared Iron-Cobalt (Fe-Co) alloys also showed high catalytic activity for the dehydrogenation of cyclohexane to benzene, with 1:1 ratio Fe-Co alloys having selectivities as high as 100% [10], which is highly contributed by the inter-particle collisions caused by the cavitation-induced shockwaves when ultrasound passed through the materials.
Although the synthesis of Hopcalite had been extensively studied, they were mostly centered on the removal of CO at ambient temperatures [11–16]. Conventionally, precious metals such as Platinum and Palladium were employed on the catalysts used for the Cy3 hydrazide of CH4[17,18]. While these catalysts have shown positive removal of CH4, they were rather expensive, therefore are not economically feasible at large scale. This has gathered attention from several researchers to study on the potential uses of Hopcalite to remove CH4 as a cheaper alternative. Amongst, Machej and co workers discovered that synthesising Hopcalite using a typical co-precipitation method at Cu:Mn ratio of 1:2 resulted in approximately 16% of CH4 conversion, and upon addition of Aluminium to the catalyst at a specific ratio have resulted in significant enhancement in the catalytic activity [19], while others have also shown significant improvement in CH4 conversion upon the addition of other metals such as Zinc, Magnesium and Aluminium onto the existing metal oxide mixture [20]. While these literatures have found improvements in CH4 conversion, they were highly relied on the addition of other metals into the system, and were only conducted under pure CH4 conditions. Lately, Zhao and co workers [21] attempted to evaluate the catalytic activity of Cu-Mn oxides in diesel soot, which contained hydrocarbons and nitrogen oxides, in order to simulate the catalytic performance in a real environment. They found that the ratio of Cu:Mn played a crucial role in enhancing a specific catalytic reaction, and for the case of diesel soot, contrary to the commonly used Cu:Mn ratio of 1:2, somites found that the ratio of 1:1 produced the best catalytic performance.
With no previous studies for the preparation of Hopcalite via the ultrasound technique, this research initiates to explore the possibilities of improving its catalytic activity. Further to this, to appraise the performance of Hopcalite synthesised, the catalyst have been investigated by conducting several reaction tests using a mixture of gases containing methane (CH4) and sulphur dioxide (SO2) to carbon dioxide (CO2) and water (H2O) in a packed bed laboratory micro-reactor, in order to simulate the catalytic activity in the presence of gaseous mixtures.

All the chemicals utilised were of analytical grade, purchased from R&M Chemicals Malaysia, and used without further purification. The ultrasonic probe used in this experiment was a 20kHz with a diameter of ca. 1 cm (Sonics and Materials, VCX750, 750W).

Results and discussion

This work has shown that the application of ultrasound had discernible effects imparted on the catalyst, including (a) the smoothening and dispersion of fine particle clouds consisting of predominantly copper oxides; (b) the increase in amorphicity which provides an anti-poisoning guard to the active sites that prevents excessive sulphur poisoning; (c) the increase in total surface area and subsequently total active sites in which conversion can occur; (d) the generation of mixed copper and manganese oxide phases that promote synergistic interaction between the phases; (e) the increase in carbon content of the catalyst and (f) the decrease in the surface oxide passivating layer. Lastly, verification is made whereby the catalyst sonicated at ultrasonic intensity of 29.7W/cm2 at 20kHz, resulted in the highest catalytic activity among the tested samples, with a CH4 conversion of 13.5% and a SO2 conversion of 100%.

The device response was tested upon exposure to

The device response was tested upon exposure to different liquids wetting the top surface of the plate, either free or electrically shorted by a thin (120nm) conductive Al layer. Like in Refs. [7,9,12,16,19], deionized (DI) water, showing a viscosity η of 1.03cP and an electric conductivity σ≪10−3S/m, water solutions of glycerin (1<η<1490cP, σ≪10−3S/m), and water solutions of NaCl (η∼1cP, 10−3<σ<1.2S/m) were used as reference, viscous, and conductive liquids, respectively, all deposited along the acoustic propagation path by a brush; details of the measurements are discussed elsewhere [1,7,8]. Both the phase shifts (Δφ) and BMN-673 loss (IL) at the output of the delay line versus the test liquid were measured using a network analyser (HP 8753E, Agilent Technologies, Santa Clara, CA) giving information on the fractional velocity change Δv/v0=−Δφ/φ0 and attenuation α (dB/mm) of the mode, respectively. The temperature dependence of the response was evaluated by performing the measurements into a thermal chamber (MLW U10, Sintz Friental, Medingen, Germany) which allowed to control the temperature in the 0–100°C range with an accuracy better than 0.1°C. Experimental errors are estimated as ±5% for free surface and ±10% for shorted one. The lower precision for the surface coated by metal layer is due to increased electromagnetic leakage affected the measurements.

Results and discussion
Response in phase velocity and attenuation upon exposure to different weight concentrations of NaCl in deionized (DI) water are shown in Fig. 2. Nonzero response is observed for the un-shorted line, only, being the response itself related to the changes in the electrical conductivity σ of the solution, vs. NaCl concentration [20]. The behavior is similar to that observed exploiting different acoustic modes and plate thicknesses (h/λ) [21].
Velocity and attenuation response to the viscosity η is shown in Fig. 3; as expected, a different response is observed for the two conditions of free and shorted surface. For example, in case of glycerin (η=1490cP) the relative change in the velocity is 0.113% and 0.169% with an attenuation α of about 0.02 and 0.11dB/mm for free and electrically shorted surface, respectively.
Phase velocity fractional velocity shifts vs. temperature (T) are reported in Fig. 4 for free (a) and shorted (b) surface conditions, as measured upon exposure to air, glycerin and DI water, being attenuation almost independent on T in the experimented temperature range from ∼10 to ∼45°C.
The fractional velocity change vs. temperature () is affected by the electrical boundary conditions at the surface and, moreover, it depends on the facing liquid or fluid. Slope values have been measured of −0.0685, −0.0625 and −0.0549°C−1 with air, glycerin and DI water, respectively for free surface condition, while the corresponding values are −0.0602, −0.0549 and −0.0557 when the surface is electrically shorted.
The increase in the viscosity response resulting from surface electrical shorting may be attributed to the trapping of the acoustic energy near the surface, causing an increase in the longitudinal displacement over that region which, in turn, deeps the mode penetration into the adjacent liquid. Indeed, as shown in Fig. 5, the amplitude of the longitudinal component of the acoustic field profile at the shorted surface is 20% larger than that at the free surface. Moreover, the dependence of the temperature response to the test liquid may be attributed to the different penetration depth of the mode into different liquids, together with the dependence of their properties on temperature.


Acoustic streaming designates the ability to drive quasi-steady flows by acoustic propagation in dissipative fluids and results from an acousto-hydrodynamics coupling. Nyborg [1] and Lighthill [2] gave a theoretical insight into this phenomenon in the case of acoustic waves propagating in an infinite medium. In particular, they have shown that these flows can be modeled as those of incompressible fluids driven by a volumetric acoustic force given by:where α is the acoustic pressure wave attenuation coefficient, c is the sound celerity, is the temporal averaged acoustic intensity and is the direction of acoustic waves propagation.

br Introduction The topics of wave propagation

The topics of wave propagation in fluid-saturated double porosity media are of growing interest in the field of geophysics [1–6]. Based on Biot’s theory [7–9], and on the works of Barenblatt and Zheltov [10], Warren and Root [11] and of Wilson and Aifantis [12], Berryman and Wang [1,2] proposed a phenomenological model that describes the acoustic wave propagation through a fluid-saturated double porosity medium, i.e. a medium containing two scales of porosities: a micro porosity in the host matrix (porous grains or rocks) and a macro porosity due to the voids between the grains or to the cracks (or fractures). In such medium, three compressional (or longitudinal) waves and one shear wave propagate, which are all dispersive and attenuated. Using the Berryman and Wang theory, Dai and Kuang calculated the reflection and transmission coefficients at the interface between a semi-infinite double porosity medium and an elastic solid [3], a fluid saturated porous solid [4] or a liquid [5], respectively. They determined in each case the mode conversion of poro-elastic waves at interfaces.
Recent studies on the enkephalin of Kaolinite particles in a fluid saturated single porosity medium [13] showed that the particle deposition and the resulting clogging up of pores in depth can involve strong modifications in the properties of the medium (among others, the porosity and permeability are reduced). The clogging phenomena, which depend on several parameters such as: size of transported particles, concentration, hydrodynamic characteristics of flow…, may also occur for each porosity scale of the double porosity medium. Therefore, non-destructive ultrasonic methods for characterizing fluid saturated double porosity media and evaluating the degree of damage as a consequence of foreign deposited particles will be of great interest.
According to the results of Kimura [14] and Chotiros and Isakson [15], the single porosity Biot–Stoll model is applicable, for transverse waves for instance, to media with mean grains diameters of the order of 1mm up to the frequency 1kHz. Past Essential gene value, additional mechanisms of dissipation resulting from the contact between grains must be accounted for. In the model developed in [15], the contacts between grains are materialized by solid contacts of cylindrical shape surrounded by a fluid film of constant thickness that is much smaller than the radius of the cylinder and of the film. Such a model allows a description of the tangential and normal rigidities of the contacts but also the laminar squirting flow of the fluid between the grains. The assumption of uniformity of the rigidities for all the contacts leads to the Extended Biot model (EB) for the bulk incompressibility modulus (noted in the cited papers) and the shear modulus () of the skeletal frame of the porous medium, see Eqs. (15a) and (15b) of [15].
Concerning the fast longitudinal wave, Kimura [16] has shown that its alternative model of the EB called Biot Model with Gap Stiffness (BIMGS) agrees with the experiments when (k0 is the wavenumber in water and b the diameter of the grains), for the attenuation as well as for the velocity. When , multiple scattering must be accounted for. With grains of diameter approximately equal to 3.5mm that are considered here, a frequency range of (100kHz is actually the central frequency of the transducer used for the experiments) and a sound velocity in water c0=1480m/s yield a range of . This could mean that the present study is not in the range of application of the BIMGS and that multiple scattering should be considered. It is noteworthy however that the model of Kimura applies to nonporous elastic beads: the multiple scattering effects should not be comparable with those in presence of porous beads. The additional porosity inside the beads introduces a damping at each of the scattering event so that the strength of multiple scattering effects is quite negligible in comparison of the continuum model predictions that will be used here. Therefore, the double porosity media should fall outside the strict conditions of Kimura at the frequency range investigated here.

br Some beam examples In the

Some beam examples
In the upcoming analysis, we assume that acoustic beams propagate along the z-axis, i.e. the axial direction. A viscoelastic particle of radius a is placed in the wavepath. In this scenario, two relevant functions will be used later, namely the incident intensity and the axial component the momentum flux divergent. In terms of the incident pressure and fluid velocity, these functions are given, respectively, by
Moreover, it is useful to define the ARF magnitudewhere is the magnitude of the time-averaged incident intensity, with being the magnitude of the fluid velocity on the acoustic source.

Summary and conclusion
We have derived analytic expressions for the acoustic radiation force (ARF) and torque (ART) exerted on a small viscoelastic particle, in the so-called Rayleigh scattering limit, suspended in an inviscid fluid. These expressions were obtained by solving the linear scattering problem for the viscoelastic spherical particle. The wave propagation inside the particle was modeled through a generalized Hookes’s law with lossy terms proportional to fractional time-derivatives – see Eq. (8).
We have shown that the ARF is decomposed into absorption, gradient, and scattering radiation forces. These components depend directly on the particle dynamic compressibility, which is related to the elastic and viscous Lamé parameters and frequency. We have applied the developed theory to compute the ARF caused rolipram by a traveling plane wave, a zero- and a first-order Bessel beam (FOBB), in the MHz-range, on three distinct polymer particles, namely lexan, LDPE, and HDPE, in water at room temperature. The polymer physical parameters necessary to calculate the ARF were taken from experimental measurements presented in Ref. [77]. They are summarized in Table 1. We observed that as frequency increases, the effects of rolipram component tend to decrease in the ARF produced by a TPW, ZOBB and FOBB. In a standing wave field, the ARF exerted on the HDPE particle presented a mild variation in the MHz-range (i.e. nearly ). In the case of Bessel beams, we calculated the transverse ARF and the axial ART. The conditions for transverse trapping by a ZOBB and FOBB are given in Eqs. (72) and (73), respectively. We found a nearly quadratic dependence of the ART and frequency.

This work was partially supported by CNPq (grant n. 303783/2013-3). During this work, J.P.L. Neto received Ph.D. scholarship from CAPES Foundation.

Bone metastases are a frequent complication observed in patients suffering from advanced stages of cancer [1,2]. More than 60% of advanced breast and prostate cancers, which are the most common malignancies in adults, metastasize in skeletal sites [3,4]. Metastases in bones from other types of primary solid tumors like lung, kidneys, thyroid, bladder and melanoma also occur, but at a lower prevalence.
Pain is the most common and distressing symptom associated with bone metastases [5]. About 83% of patients with bone metastases complain of pain at some point with a wide variation in pattern and severity [6]. Therefore a lot of effort has been made to develop strategies for managing pain of patients with bone metastases and improve quality of life.
For cases where there is a multifocal spread of the disease in the skeleton, pain palliation is controlled by, but not limited to, systemic therapies like hemi body irradiation [7,8], administration of bone-seeking radiopharmaceuticals [9–11], analgesic drugs and bisphosphonates [12,13]. The gold standard though for controlling localized metastatic bone pain is external beam radiotherapy (EBRT). The mechanism underlying the analgesic effect of radiation in bone pain is not completely understood, but recent animal studies suggested that palliation is a result of reduced cancer burden and reduced osteolysis [14]. The increasing number of patients with painful bone metastases that are insufficiently palliated by radiation therapy alone, indicate the need for additional palliative localized treatments to maintain quality of life for the patients [15,16].

Even if the optimal cut offs were very close for

Even if the optimal cut-offs were very close for F3 and F4 in our mixed cohort (HBV+HCV) the diagnostic accuracy assessed by AUROCs was high, suggesting that ElastPQ could be useful for staging liver fibrosis. In these conditions, maybe larger multicenter studies are needed to obtain the best cut-offs in cohorts of patients with equally distributed fibrosis stages.
Different stiffness thresholds were proposed for ElastPQ as compared to TE. This can be maybe explained by the fact that stimuli generating the shear waves into the tissue are different for each technique and also by the different spatial bace inhibitor of the probes used to measure the shear waves velocity. In ElastPQ the shear wave is generated by a focused ultrasound beam at different locations within the organ, while TE uses a mechanical vibration in order to produce shear waves in the target tissue. Thus, TE results can be difficult to obtain in patients with narrow intercostal spaces, in obese patients and impossible to obtain in patients with ascites because the vibration cannot penetrate the perihepatic liquid [28]. On the other hand, it seems that liver stiffness measurements obtained by ElastPQ are not influenced by body mass index, age and gender [29]. ElastPQ is a point shear wave elastography that uses the same principles as Virtual Touch Tissue Quantification (VTQ), both being ARFI techniques. VTQ is feasible in the majority of subjects with ascites (96.8%), as documented by Bota et al. [30]. Both point techniques, ElastPQ and VTQ showed good fesability and good performance in diagnosing the presence of liver pathology [31].
In conclusion ElastPQ is a feasible technique for the noninvasive assessment of liver fibrosis and has a good performance for predicting the presence of significant, severe fibrosis and cirrhosis in patients with B and C chronic liver diseases. Further studies in larger series of patients with equally distributed stages of liver fibrosis are needed to confirm these results.

Conflict of interest


Evaluation of structural changes in materials and constructions and monitoring their ultimate strength and endurance in operation are essential for many industrial structural integrity problems. The most powerful nondestructive way of evaluating material degradation is the ultrasonic method because the characteristics of ultrasonic wave propagation are directly related to the properties of the material. The traditional ultrasonic nondestructive damage testing (NDT) is based on a linear theory and normally relies on measuring some particular parameter (sound velocity, attenuation, transmission, and reflection coefficients) of the propagating wave to determine the elastic properties of a material or to detect defects [1]. Recent research has shown interest on using full wavefield data acquired by scanning laser Doppler vibrometer to imaging crack growing in structures [2,3]. Ultrasonic methods based on linear wave scattering are efficient for detecting gross defects and characterizing material elasticity but are less sensitive to microcracks or closed cracks. Elastic waves that propagate through a fatigue crack will not be obviously changed in phase or amplitude, making it difficult to evaluate the imperfect interface using the conventional ultrasonic method based on linear elasticity. To improve the monitoring capability of safety-critical structural components, nonlinear ultrasonic methods have been proposed. If the excitation amplitude is sufficient, closed cracks can behave nonlinearly because of contact dynamics occurring between the faces of the crack. This effect, called contact acoustic nonlinearity (CAN), is assumed derive from the lack of stiffness symmetry for near-surface strain across the interface [4]. Importantly, interface stiffness depends on the contact condition, and becomes a source of nonlinearity in wave propagation. Using the nonlinear behavior of these defects, nonlinear ultrasonic techniques such as nonlinear resonance ultrasound spectroscopy [5–7], higher harmonic generation [8–12], and nonlinear wave modulation spectroscopy [13,14] have been shown to be sensitive to microcracks or closed cracks.