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This paper presents the development of a numerical model able to track in time the behavior of nonlinear focused ultrasound when interacting with tiny gas bubbles in a liquid. Our goal here is to analyze the frequency components of the waves by developing a model that can easily be adapted to the geometrical restrictions and complexities that come out in several application frameworks (sonochemistry, medicine, and engineering). We thus model the behavior of nonlinear focused ultrasound propagating in a liquid with gas bubbles by means of the finite-element method in an axisymmetric three-dimensional domain and the generalized-α method in the time domain. The model solves a differential system derived for the nonlinear interaction of acoustic waves and gas bubble oscillations. The high nonlinearity and dispersion of the bubbly medium hugely affect the behavior of the finite-amplitude waves. These characteristics are used here to generate frequency components of the signals that do not exist at the source through nonlinear mixing (parametric antenna). The ability of the model to work with complex geometries, which is the main advantage of the method, is illustrated through the simulation of nonlinear focused ultrasound in a medium excited from two spherical sources in opposite directions.

ESCRT-III filaments are composite cytoskeletal polymers that can constrict and cut cell membranes from the inside of the membrane neck. Membrane-bound ESCRT-III filaments undergo a series of dramatic composition and geometry changes in the presence of an ATP-consuming Vps4 enzyme, which causes stepwise changes in the membrane morphology. We set out to understand the physical mechanisms involved in translating the changes in ESCRT-III polymer composition into membrane deformation. We have built a coarse-grained model in which ESCRT-III polymers of different geometries and mechanical properties are allowed to copolymerise and bind to a deformable membrane. By modelling ATP-driven stepwise depolymerisation of specific polymers, we identify mechanical regimes in which changes in filament composition trigger the associated membrane transition from a flat to a buckled state, and then to a tubule state that eventually undergoes scission to release a small cargo-loaded vesicle. We then characterise how the location and kinetics of polymer loss affects the extent of membrane deformation and the efficiency of membrane neck scission. Our results identify the near-minimal mechanical conditions for the operation of shape-shifting composite polymers that sever membrane necks.

In this paper we study the generation and behavior of subharmonics in a bubbly liquid confined in an acoustic resonator, through numerical simulations carried out at finite-amplitude acoustic pressure. Several configurations in terms of resonator length and driving frequency are considered here. Our results show that these frequency components, created from a higher-frequency signal at the source (ultrasound), are due to the nonlinearity of the medium at high acoustic-pressure amplitude and to the configuration of the resonator (geometry and boundaries). We also show that they have an amplitude-threshold dependence, which is in concordance with the literature. The response of these subharmonics to different sequences of pressure amplitudes also reveals the hysteretic nature of the bubbly liquid.

A nonlinear Rayleigh–Plesset equation for describing the behavior of a gas bubble in an acoustic field written in terms of bubble-volume variation is solved through a linear iterative procedure. The model is validated, and its accuracy and fast convergence are shown through the analysis of several examples of different physical meanings. The simplicity and usefulness of the presented method here in relation to the direct resolution of the whole nonlinear system, which is also discussed, make the method very attractive to solving a problem. This iterative method allows us to solve only linear systems instead of the nonlinear differential problem. Moreover, the implementation of the iterative algorithm includes a tolerance-dependent stopping criterion that is also tested.

The aim of this paper is to optimize the generation of frequencies obtained nonlinearly from the propagation of ultrasound in a bubbly liquid. A study is presented for which the number and size of the gas bubbles in the liquid are varied to determine the optimal medium, which is the one that allows the highest amplitude for these frequency components. We use a previously developed numerical software that tracks the nonlinear behavior of both ultrasound and bubble vibrations in time to carry out several simulations. We focus our attention on two one-dimensional configurations, a resonator of length set at a quarter of the wavelength with a free-wall condition and a cavity of length set at sixteen wavelengths with open-field condition. In each case, we analyze the generation of the 2nd, 3rd, and 4th harmonics of the source frequency. Our results show that, in both cases, the use of higher source amplitudes and lower source frequencies is more useful to increase the harmonic amplitudes. Moreover, smaller bubbles are more adequate when the void fraction is kept constant for this purpose in the first configuration, whereas the modification of void fraction has no influence in the second configuration, for which given a void fraction value, bubble sizes whose ratio are f0/f≈5, f0/f≈7, and f0/f≈9 maximize the 2nd, 3rd, and 4th harmonics, respectively. These conclusions could be of interest for some applications.

The derivation of a nonlinear ordinary differential equation for modeling the nonlinear oscillations of a gas bubble placed in an ultrasonic field is performed in terms of bubble-volume variations up to the fourth-order approximation. The equation, written within the Rayleigh-Plesset framework, is solved through numerical approximations. Results from simulations are compared to data obtained from the classic second-order approximation equation derived in the 1960–70’s, usually used in this framework, and from the third-order approximation equation derived in the 1990’s. This comparison shows that the fourth-order approximation allows us to observe the nonlinear behavior of the bubble at high finite amplitude, which differs from the other approximations when the nonlinearity of the phenomenon is higher, i.e., when the driving acoustic frequency is close to the bubble resonance.

The aim of this work is to study the nonlinear frequency mixing that comes out in the focus region in a bubbly liquid when a spherical transducer emits a dual-frequency ultrasonic wave of finite amplitude in a three-dimensional open domain with axial symmetry. The nonlinear interaction between the acoustic field and the bubble vibrations is modeled through a coupled differential system formed by the wave equation and a Rayleigh-Plesset equation. Simulations are performed by means of an ad-hoc numerical model developed on the basis of multi-dimensional finite-volume and finite-difference techniques. Results show the nonlinear response of the system by showing the space distribution of the fundamental and harmonics for a single-frequency excitation (for which a convergence study is also carried out) and the space distribution of the difference and sum-frequency components for a two-frequency excitation. In the former case a law is proposed for the evolution of each one of the second and third harmonics vs. amplitude. In the latter configuration a law is proposed for the evolution of each one of the difference and sum frequencies vs. amplitude. This work suggests that the combination of two frequencies emitted from a spherical transducer can allow the enhancement of the generation of the difference and sum-frequencies in a restricted volume of the bubbly liquid. This could be used to control the amplitude and space extent of these frequency components by modifying the shape of the spherical transducer, the primary frequencies, and the pressure amplitude. Our results can be useful for industrial and medical processes based on nonlinear frequency mixing. Keywords: Focused ultrasonic field, Numerical model, Nonlinear distortion, Nonlinear frequency mixing

Few data sources in developed countries contain for a representative sample of households information on water expenses alongside a rich set of reliable information on individual and household characteristics. In this Data in Brief we describe the Belgian EU-SILC data, which we used for ‘Measuring water affordability in developing economies. The added value of a needs-based approach’ (Vanhille et al., 2018) [1]. EU-SILC can be obtained from the Belgian National Statistical Institute and is the most important representative household survey on income and living conditions in the European Union, and contains, among others, an advanced measurement of household income. It is not well-known, though, that national datasets often contain more information, making them suitable for studies that are somewhat outside the ‘core scope’ of EU-SILC. One example is studying the consumption of water by households, as can be done for Belgium. In this article we briefly introduce the Belgian EU-SILC and present the data on water expenses for households living in Flanders. In 2015, 50 per cent less than 23 EUR on water, while 90 per cent spent less than 45 EUR on water. Keywords: Survey data, Water expenses, European Union, Income, EU-SILC

Penelitian ini bertujuan untuk melihat sejauh mana pengaruh pemberian jamur perusak kayu (white-rot fungus) terhadap perombakan ligno-selulosa yang terdapat pada limbah kehutanan untuk digunakan sebagai substrat pada fermentasi metan secara padat. Limbah kehutanan yang digunakan adalah serbuk gergaji kayu karet (Hevea brasiliensis) dan pinus (Pinus merkusii) serta daun kayu putih (Melaleuca leucodendron) sisa penyulingan. Jamur yang digunakan adalah Schizophyllum commune Fr. dengan lama waktu inokulasi sampai 5 minggu dan kemudian baru difermentasi. Karet merupakan substrat yang miskin untuk dapat menghasilkan metan. Produksi gas tidak meningkat secara nyata. Pinus sangat sukar dirombak, sedangkan pada limbah daun kayu putih terdapat inhibitor yang menjadi penghalang sewaktu proses berlangsung, namun inhibitor ini agak menjadi lunak untuk difermentasi setelah diberi pra-perlakuan terlebih dahulu dengan jamur perusak kayu. Pada masing-masing substrat terdapat hubungan spesiflk antara berat kering yang hilang selama berlangsungnya aktifltas jamur dengan perubahan produksi metan. Perubahan efisiensi metan berkisar antara 10%-25%. Praktisnva penerapan untuk "biogas generasi" masih diperlukan penelitian lebih lanjut untuk memperoleh produksi secara maksimal. Namun demikian untuk limbah ligno-selulosa lainnya seperti jerami pra-perlakuan ini sangat baik untuk dikembangkan.

Tulisan ini menyajikan percobaan dua teknologi fermentasi biogas dari eceng gondok (Eichhornia crassipes). Fermentasi cair dengan dua phase menghasilkan 1 volume biogas per volume reaktor per hari dengan volume beban 4 kg bobot kering per meter kubik reaktor per hari dan pemakaian waktu 12,5 hari. Sedangkan fermentasi padat menghasilkan lebih banyak biogas, yaitu 3-4 volume biogas pe volume reaktor per hari dengan volume beban 15 kg bobot kering per meter kubik reaktor per hari dan pemakaian waktu 22 hari. Kedua teknologi ini memberikan produksi biogas yang lebih tinggi daripada sistem konvensional seperti batch, Gobar dan semi-kontinu. Terutama fermentasi padat memberi harapan walaupun memerlukan praperlakuan eceng gondok secara intensif. Selain itu suhu merupakan factor penting. Pada suhu 350C (mesophilik); produksi gas lebih tinggi dibandingkan pada suhu ruang (22-280c). Fermentasi pada suhu mesophilik memungkinkan juga penambahan volume beban menjadi lebih tinggi.

Techniques based on ultrasound in nondestructive testing and medical imaging analyze the response of the source frequencies (linear theory) or the second-order frequencies such as higher harmonics, difference and sum frequencies (nonlinear theory). The low attenuation and high directivity of the difference-frequency component generated nonlinearly by parametric arrays are useful. Higher harmonics created directly from a single-frequency source and the sum-frequency component generated nonlinearly by parametric arrays are attractive because of their high spatial resolution and accuracy. The nonlinear response of bubbly liquids can be strong even at relatively low acoustic pressure amplitudes. Thus, these nonlinear frequencies can be generated easily in these media. Since the experimental study of such nonlinear waves in stable bubbly liquids is a very difficult task, in this work we use a numerical model developed previously to describe the nonlinear propagation of ultrasound interacting with nonlinearly oscillating bubbles in a liquid. This numerical model solves a differential system coupling a Rayleigh−Plesset equation and the wave equation. This paper performs an analysis of the generation of the sum-frequency component by nonlinear mixing of two signals of lower frequencies. It shows that the amplitude of this component can be maximized by taking into account the nonlinear resonance of the system. This effect is due to the softening of the medium when pressure amplitudes rise.

This paper studies the nonlinear resonance of a cavity filled with a nonlinear biphasic medium made of a liquid and gas bubbles at a frequency generated by nonlinear frequency mixing. The analysis is performed through numerical simulations by mixing two source signals of frequencies well below the bubble resonance. The finite-volume and finite-difference based model developed in the time domain simulates the nonlinear interaction of ultrasound and bubble dynamics via the resolution of a differential system formed by the wave and Rayleigh–Plesset equations. Some numerical results, consistent with the literature, validate our procedure. Other results reveal the existence of a frequency shift of the cavity resonance at the difference-frequency component, which rises with pressure amplitude and evidences the global changes undergone by the bubbly medium under finite amplitudes. Finally, this work shows the enhancement of the amplitude of the difference-frequency component generated by parametric excitation using the nonlinear resonance shift, which is more pronounced when the second primary frequency is constant, the first one is varied to match the nonlinear resonance, and both have the same amplitude.

In this work, we define the acoustic characteristics of a biphasic fluid consisting of static helium gas bubbles in liquid Fluorinert FC-43 and study the propagation of ultrasound of finite amplitudes in this medium. Very low sound speed and high sound attenuation are found, in addition to a particularly high acoustic nonlinear parameter. This result suggests the possibility of using this medium as a nonlinear enhancer in various applications. In particular, parametric generation of low ultrasonic frequencies is studied in a resonator cavity as a function of driving pressure showing high conversion efficiency. This work suggests that this medium could be used for applications such as parametric arrays, nondestructive testing, diagnostic medicine, sonochemistry, underwater acoustics, and ultrasonic imaging and to boost the shock formation in fluids.

OBJECTIVE:To investigate association between genetic polymorphisms of GST, CYP and renal outcome or occurrence of adverse drug reactions (ADRs) in lupus nephritis (LN) treated with cyclophosphamide (CYC). CYC, as a pro-drug, requires bioactivation through multiple hepatic cytochrome P450s and glutathione S transferases (GST). METHODS:We carried out a multicentric retrospective study including 70 patients with proliferative LN treated with CYC. Patients were genotyped for polymorphisms of the CYP2B6, CYP2C19, GSTP1, GSTM1 and GSTT1 genes. Complete remission (CR) was defined as proteinuria ≤0.33g/day and serum creatinine ≤124 µmol/l. Partial remission (PR) was defined as proteinuria ≤1.5g/day with a 50% decrease of the baseline proteinuria value and serum creatinine no greater than 25% above baseline. RESULTS:Most patients were women (84%) and 77% were Caucasian. The mean age at LN diagnosis was 41 ± 10 years. The frequency of patients carrying the GST null genotype GSTT1-, GSTM1-, and the Ile→105Val GSTP1 genotype were respectively 38%, 60% and 44%. In multivariate analysis, the Ile→105Val GSTP1 genotype was an independent factor of poor renal outcome (achievement of CR or PR) (OR = 5.01 95% CI [1.02-24.51]) and the sole factor that influenced occurrence of ADRs was the GSTM1 null genotype (OR = 3.34 95% CI [1.064-10.58]). No association between polymorphisms of cytochrome P450s gene and efficacy or ADRs was observed. CONCLUSION:This study suggests that GST polymorphisms highly impact renal outcome and occurrence of ADRs related to CYC in LN patients.

This work deals with a theoretical analysis about the possibility of using linear and nonlinear acoustic properties to modify ultrasound by adding gas bubbles of determined sizes in a liquid. We use a two-dimensional numerical model to evaluate the effect that one and several monodisperse bubble populations confined in restricted areas of a liquid have on ultrasound by calculating their nonlinear interaction. The filtering of an input ultrasonic pulse performed by a net of bubbly-liquid cells is analyzed. The generation of a low-frequency component from a single cell impinged by a two-frequency harmonic wave is also studied. These effects rely on the particular dispersive character of attenuation and nonlinearity of such bubbly fluids, which can be extremely high near bubble resonance. They allow us to observe how gas bubbles can change acoustic signals. Variations of the bubbly medium parameters induce alterations of the effects undergone by ultrasound. Results suggest that acoustic signals can be manipulated by bubbles. This capacity to achieve the modification and control of sound with oscillating gas bubbles introduces the concept of bubbly-liquid-based acoustic metamaterials (BLAMMs).

Background Acquired thrombotic thrombocytopenic purpura is still associated with a 10–20% death rate. It has still not been possible to clearly identify early prognostic factors of death. This study involved thrombotic thrombocytopenic purpura patients with acquired severe (

BackgroundAssessing the relative value of cocaine and how it changes with chronic drug use represents a long-standing goal in addiction research. Surprisingly, recent experiments in rats--by far the most frequently used animal model in this field--suggest that the value of cocaine is lower than previously thought.Methodology/principal findingsHere we report a series of choice experiments that better define the relative position of cocaine on the value ladder of rats (i.e., preference rank-ordering of different rewards). Rats were allowed to choose either taking cocaine or drinking water sweetened with saccharin--a nondrug alternative that is not biologically essential. By systematically varying the cost and concentration of sweet water, we found that cocaine is low on the value ladder of the large majority of rats, near the lowest concentrations of sweet water. In addition, a retrospective analysis of all experiments over the past 5 years revealed that no matter how heavy was past cocaine use most rats readily give up cocaine use in favor of the nondrug alternative. Only a minority, fewer than 15% at the heaviest level of past cocaine use, continued to take cocaine, even when hungry and offered a natural sugar that could relieve their need of calories.Conclusions/significanceThis pattern of results (cocaine abstinence in most rats; cocaine preference in few rats) maps well onto the epidemiology of human cocaine addiction and suggests that only a minority of rats would be vulnerable to cocaine addiction while the large majority would be resilient despite extensive drug use. Resilience to drug addiction has long been suspected in humans but could not be firmly established, mostly because it is difficult to control retrospectively for differences in drug self-exposure and/or availability in human drug users. This conclusion has important implications for preclinical research on the neurobiology of cocaine addiction and for future medication development.

Severe ADAMTS13 deficiency occurs in 13% to 75% of thrombotic microangiopathies (TMA). In this context, the early identification of a severe, antibody-mediated, ADAMTS13 deficiency may allow to start targeted therapies such as B-lymphocytes-depleting monoclonal antibodies. To date, assays exploring ADAMTS13 activity require skill and are limited to only some specialized reference laboratories, given the very low incidence of the disease. To identify clinical features which may allow to predict rapidly an acquired ADAMTS13 deficiency, we performed a cross-sectional analysis of our national registry from 2000 to 2007. The clinical presentation of 160 patients with TMA and acquired ADAMTS13 deficiency was compared with that of 54 patients with detectable ADAMTS13 activity. ADAMTS13 deficiency was associated with more relapses during treatment and with a good renal prognosis. Patients with acquired ADAMTS13 deficiency had platelet count < 30 x 10(9)/L (adjusted odds ratio [OR] 9.1, 95% confidence interval [CI] 3.4-24.2, P

Abstract The aim of this work is to study the nonlinear frequency mixing that comes out in the focus region in a bubbly liquid when a spherical transducer emits a dual-frequency ultrasonic wave of finite amplitude in a three-dimensional open domain with axial symmetry. The nonlinear interaction between the acoustic field and the bubble vibrations is modeled through a coupled differential system formed by the wave equation and a Rayleigh-Plesset equation. Simulations are performed by means of an ad-hoc numerical model developed on the basis of multi-dimensional finite-volume and finite-difference techniques. Results show the nonlinear response of the system by showing the space distribution of the fundamental and harmonics for a single-frequency excitation (for which a convergence study is also carried out) and the space distribution of the difference and sum-frequency components for a two-frequency excitation. In the former case a law is proposed for the evolution of each one of the second and third harmonics vs. amplitude. In the latter configuration a law is proposed for the evolution of each one of the difference and sum frequencies vs. amplitude. This work suggests that the combination of two frequencies emitted from a spherical transducer can allow the enhancement of the generation of the difference and sum-frequencies in a restricted volume of the bubbly liquid. This could be used to control the amplitude and space extent of these frequency components by modifying the shape of the spherical transducer, the primary frequencies, and the pressure amplitude. Our results can be useful for industrial and medical processes based on nonlinear frequency mixing. [ABSTRACT FROM AUTHOR]