Ultrasonication-assisted synthesis of alcohol-based deep eutectic solvents for extraction of active compounds from ginger

An ultrasonication-assisted synthesis of alcohol-based deep eutectic solvents (DESs) is described. Several DESs were synthesized simultaneously under the same conditions. The prepared DESs were used for the extraction of gingerols from ginger powder via ultrasonication-assisted extraction. Notably, some of the prepared DESs exhibited superior extraction performance than those in traditional organic solvents. The viscosity of the DESs, which was suggested to be typically lower than 100 mPa*s had a critical effect on extraction performance. However, the higher gingerol contents in the extracts did not translate to higher active antioxidant abilities. The extraction temperature was found to be a key determinant of the antioxidant capability of the extracted gingerols while the use of higher temperatures (>50 °C) induced degradation and loss of phenolic compounds during extraction. Response surface methodology was applied for determining the optimal extraction conditions to achieve maximum antioxidant capacity with suitable gingerol content. All compounds used for the preparation of the DESs in this study have been widely employed in cosmetic and pharmaceutical fields. Therefore, the extracts in these DES solutions can be considered for direct application development without further product isolation.     

Direct measurement of the local density of states of a disordered one-dimensional conductor

One-dimensional electron systems (1DESs) containing two and one occupied subbands are found below the different types of [11;2] steps of the InAs(110) surface. Using low-temperature scanning tunneling spectroscopy, we determined the subband energies, the disorder potential, and the local density of states of these 1DESs. The rather complete knowledge of the 1DES allowed us to compare the measured LDOS with a single-particle calculation. Surprisingly, we did not find significant deviations from the calculation albeit the electron-electron interaction in the 1DESs is stronger than the electron-disorder interaction.     

Preparation of curved two-dimensional electron systems in InGaAs/GaAs-microtubes

We present a preparation method to realise transport measurements on evenly curved two-dimensional electron systems (2DESs). By combining the method of self-rolling strained double layers with a special lithographic procedure we are able to roll-in and contact AlGaAs/GaAs/AlGaAs quantum well structures into tubes or curved lamellas. Applying a magnetic field to such structures results in a strong modulation with changing sign of the magnetic field components perpendicular to the curved 2DES plane. Our preparation method allows transport measurements along or perpendicular to this modulation. We present and discuss our first magneto-transport measurements on such rolled 2DESs.     

Temperature dependence of the compressibility of two-dimensional electron systems with long-range potential fluctuations in the quantum Hall effect regime

The temperature dependence of the compressibility of two-dimensional electron systems (2DESs) in GaAs/AlGaAs heterostructures in the quantum Hall effect regime have been studied both experimentally and theoretically. The compressibility was determined using the capacitance spectroscopy technique and the measurements of a low-frequency electric field penetrating through the 2DES. The measured temperature dependences of the 2DES compressibility are quantitatively described using a model taking into account inhomogeneity of the electron density at a finite temperature. Changes in the chemical potential of the 2DES in the vicinity of even filling factors determined from the capacitive and transport measurements are mutually consistent and agree with the results of finite-temperature calculations.     

Cascaded dynamic eigenstates of polarization analysis for piezoelectric polarization control

We propose the cascaded dynamic eigenstates (DESs) of polarization to analyze multicomponent polarization control (PC) devices, and achieve the analytical expression of output state of polarization (SOP) as a function of voltage for piezoelectric polarization control (PPC). By measuring the DES at the output port of the device, the prestage DESs will rotate around subsequent ones. Experimental results in PPC confirm the validity of our analysis. The average error of our theoretical output SOP is 1.23 degrees, and the SOP response time is ~10 micros, which is promising to realize a quasi-open-loop high-speed PC.     

Capacitance spectroscopy investigation of the spin polarization of two-dimensional electronic systems

It is shown that capacitance spectroscopy can be used to investigate the spin polarization of two-dimensional electronic systems (2DESs). We employed this method to investigate the spin polarization of 2DESs in a GaAs/AlGaAs heterojunction for filling factors of the magneticquantization levels 0.28<ν<0.9. It is proved that in the presence of states of the fractional quantum Hall effect with ν _f =1/3 and 2/3 the ground state of a 2DES with ν>2/3 is incompletely spin-polarized. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 1, 102–107 (10 January 1997)     

Dimethyl sulfoxide/deep eutectic solvents mixtures as media in the reaction of 1‐fluoro‐2,4‐dinitrobenzene with piperidine: A solvent effect study

Aromatic nucleophilic substitution reaction of 1‐fluoro‐2,4‐dinitrobenzene with piperidine was kinetically investigated in ethylene glycol‐choline chloride and glycerol‐choline chloride as 2 deep eutectic solvents (DESs) mixed with dimethyl sulfoxide, in whole mole fractions, at room temperature. The investigation of the reaction in different concentrations of the piperidine shows that the reaction follows the base‐catalyzed mechanism. The measured rate coefficients of the reaction demonstrated a sharp decreasing in all mixtures with the increasing mole fraction of DESs. Linear free energy relationship investigations confirm that hydrogen bond donor ability in addition to polarity‐polarizability of the media has a major effect on the reaction rate. The decrease in the rate coefficient is attributed to not only hydrogen‐bonding donor interactions of the media with piperidine as both reactant and catalyst but also the preferential solvation of reactants by DES compared with the intermediate of the reaction.     

Heavy fermion fluid in high magnetic fields: an infrared study of CeRu4Sb12

We report a comprehensive infrared magnetospectroscopy study of a CeRu4Sb12 compound revealing quasiparticles with a heavy effective mass m*, with a detailed analysis of optical constants in fields up to 17 T. We find that the applied magnetic field strongly affects the low-energy excitations in the system. In particular, the magnitude of m* approximately = 70 m(b) (m(b) is the quasiparticle band mass) at 10 K is suppressed by as much as 25% at 17 T. This effect is in quantitative agreement with the mean-field solution of the periodic Anderson model augmented with a Zeeman term.     

Optimization and kinetic study of ultrasound assisted deep eutectic solvent based extraction: A greener route for extraction of curcuminoids from Curcuma longa

The use of deep eutectic solvents (DESs) as a new extraction medium is a step towards the development of green and sustainable technology. In the present study, nine DESs based on choline chloride acids, alcohols, and sugar were screened to study the extraction of curcuminoids from Curcuma longa L. Choline chloride and lactic acid DES at 1:1 M ratio gave the maximum extent of extraction. Further, DES based extraction was intensified using ultrasound. The impact of various process parameters such as % (v/v) water in DES, % (w/v) solid loading, particle size, ultrasound power intensity, and pulse mode operation of ultrasound was studied. The maximum curcuminoids yield of 77.13 mg/g was achieved using ultrasound assisted DES (UA-DES) based extraction in 20% water content DES at 5% solid loading and 0.355 mm particle size with 70.8 $W/{\mathit{cm}}^2$ power intensity and 60% (6 sec ON and 4 sec OFF) duty cycle at 30 ± 2 °C in 20 min of irradiation time. Kinetics of UA-DES extraction was explained using Peleg’s model and concluded that it is compatible with the experimental data. Additionally, anti-solvent (water) precipitation technique was applied, which resulted in 41.97% recovery of curcuminoids with 82.22% purity from UA-DES extract in 8 h of incubation at 0 °C. The comparison was made between conventional Soxhlet, batch, DES and UA-DES based processes on the basis of yield, time, solvent requirement, temperature, energy consumption, and process cost. The developed UA-DES based extraction can be an efficient, cost effective, and green alternative to conventional solvent extraction for curcuminoids.     

Light quasiparticles dominate electronic transport in molecular crystal field-effect transistors

We report on an infrared spectroscopy study of mobile holes in the accumulation layer of organic field-effect transistors based on rubrene single crystals. Our data indicate that both transport and infrared properties of these transistors at room temperature are governed by light quasiparticles in molecular orbital bands with the effective masses m* comparable to free electron mass. Furthermore, the m* values inferred from our experiments are in agreement with those determined from band structure calculations. These findings reveal no evidence for prominent polaronic effects, which is at variance with the common beliefs of polaron formation in molecular solids.     

Effective nucleon masses in symmetric and asymmetric nuclear matter

The momentum and isospin dependence of the in-medium nucleon mass are studied. Two definitions of the effective mass, i.e., the Dirac mass m*D and the nonrelativistic mass m*NR which parametrizes the energy spectrum, are compared. Both masses are determined from relativistic Dirac-Brueckner-Hartree-Fock calculations. The nonrelativistic mass shows a distinct peak around the Fermi momentum. The proton-neutron mass splitting in isospin asymmetric matter is m*D,nm*NR,p, which is consistent with nonrelativistic approaches.     

Some Effects on A Single Particle Energies

With the phenomenological Λ-nucleus potentials of Woods-Saxon shape,the effects of the mass-number dependence of the shrinkage,the effective mass mΛ^* and the charge-symmetry breaking (CSB) on the single particle energies are discussed.It is found that the single particle energies are not sensitive to the effective mass mΛ^*.But the radius parameter depended on the mass number (ro(Ac)=r1 r2Ac^-2/3) can substantially improve the results.We also found that CSB effect is significant for heavy hypernuclei with a large neutron excess.     

Resonant Magnetic Fields of a Magnetopolaron in a Parabolic Quantum Dot

It is shown that for a resonant magnetic field, the two cyclotron masses (m₊^* and m_-^*) in a parabolic quantum dot are split into two cyclotron masses, respectively. The cyclotron mass (m₊^*) decreases with decreasing the size of the quantum dot, the stronger the magnetic field strength, the larger the cyclotron mass. The lower branch of the cyclotron mass (m_-^*) increases linearly with increasing the magnetic field strength. The upper branch of the cyclotron mass (m_-^*) is larger than the bare band mass and enhances as the magnetic field strength increases.     

Dependence of spin susceptibility of a two-dimensional electron system on the valley degree of freedom

We report measurements of the spin susceptibility, chi proportional, variant g(v)g*m*, in an AlAs two-dimensional electron system where, via the application of in-plane stress, we transfer electrons from one ellipsoidal conduction-band valley to another (g(v) is the valley degeneracy, and m* and g* are the electron effective mass and g factor). At a given density, when the two valleys are equally populated (g(v)=2), the measured g*m* is smaller than when only one valley is occupied (g(v)=1). This observation counters the common assumption that a two-valley two-dimensional system is effectively more dilute than a single-valley system because of its smaller Fermi energy.     

Probing spin physics in the quantum Hall regime by heat capacity and magnetotransport measurements

We review recent heat capacity and magnetotransport experiments on GaAs/AlGaAs heterostructures containing multilayer two-dimensional electron systems (2DESs) in the quantum Hall regime. Emphasis in this article is on the study of the heat capacity near Landau level filling factor ν=1. We also present a detailed survey of the development of the quantum Hall effect in tilted-magnetic fields for ν≲2. Among the novel phenomena we address is the strong coupling between the nuclear spins and the electrons associated with the spin phase transitions of the 2DES at ν=4/3 and near ν=1. To cite this article: S. Melinte et al., C. R. Physique 3 (2002) 667–676.     

Effective mass of quasiparticles in a Wigner liquid

The exchange interaction and effective mass of fermionic excitation in a low-density (r ^S ? 1) system of two-dimensional electrons are estimated from simple considerations. For the ratio of effective (renormalized due to interaction) to band mass, the dependence ${{m^* } \mathord{\left/ {\vphantom {{m^* } m}} \right. \kern-0em} m} = ({A \mathord{\left/ {\vphantom {A {\sqrt {r_S } }}} \right. \kern-0em} {\sqrt {r_S } }})\exp (\alpha \sqrt {r_S } )$ is obtained, where A and α are constants on the order of unity. The effective g factor is independent of r ^S and is larger than its bare value in the two-valley case (silicon). Comparison with experimental data shows a qualitative agreement with silicon.     

Investigation of the mass dependence of self-diffusion coefficients by molecular dynamics calculations: comparison with the Enskog theory

The dependence of the Enskog self-diffusion coefficients D_i,E on mass ratios m_i* = m_i/m₁ in hard sphere mixtures is described by exponential expressions of the form D_i,E = D⁰ _i,E(m*₂)eX_i,E in the case of binary mixtures and D_i,E = D⁰ _iE (m*₂)eX_i,E(m*₃)eXt_i,E in the case of ternary mixtures. D⁰ _i,E are the self-diffusion coefficients in reference mixtures with m*₂ = m*₃ = 1. ex_i,E (i = 1,2) and ext_i,E (i = 1,2,3) are the so called Enskog exponents of binary and ternary mixtures, respectively. Their dependence on particle mass and diameter, mole fraction, density and temperature is discussed and compared with corresponding results of molecular dynamics calculations.     

Ultrasonic-assisted extraction of polyphenolic compounds from Paederia scandens (Lour.) Merr. Using deep eutectic solvent: optimization,identification, and comparison with traditional methods

Ultrasonic-assisted extraction (UAE) coupled with deep eutectic solvent (DES) is a novel, efficient and green extraction method for phytochemicals. In this study, the effects of 16 DESs coupled with UAE on the extraction rate of polyphenols from Paederia scandens (Lour.) Merr. (P. scandens), an edible and medicinal herb, were investigated. DES synthesised with choline chloride and ethylene glycol at a 1:2 M ratio resulted in the highest extractability. Moreover, the effects of extraction parameters were investigated by using a two-level factorial experiment followed by response surface methodology The optimal parameters (water content in DES of 49.2%, the actual ultrasonic power of 72.4 W, and ultrasonic time of 9.7 min) resulted in the optimal total flavonoid content (TFC) (27.04 mg CE/g DW), ferric-reducing antioxidant power (FRAP) value (373.27 μmol Fe(Ⅱ)E/g DW) and 2,2′-azino-bis(3-ethylbenzthiazoline)-6-sulfonic acid radical (ABTS⁺) value (48.64 μmol TE/g DW), closely matching the experimental results. Furthermore, a comparison study demonstrated that DES-UAE afforded the higher TFC and FRAP value than traditional extraction methods. 36 individual polyphenolic compounds were identified and quantified by ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS) in P. scandens extracts, and of which 30 were found in the extracts obtained by DES-UAE. Additionally, DES-UAE afforded the highest sum of individual polyphenolic compound content. These results revealed that DES-UAE enhanced the extraction efficiency for polyphenols and provided a scientific basis for further processing and utilization of P. scandens.     

Nonlocal magnetic field-tuned quantum criticality in cubic CeIn(3-x)Sn(x) (x = 0.25)

We show that antiferromagnetism in lightly (approximately 8%) Sn-doped CeIn3 terminates at a critical field mu0H(c) = 42 +/- 2 T. Electrical transport and thermodynamic measurements reveal the effective mass m* not to diverge, suggesting that cubic CeIn3 is representative of a critical spin-density wave (SDW) scenario, unlike the local quantum critical points reported in anisotropic systems such as CeCu(6-x)Au(x) and YbRh2Si(2-x)Ge(x). The existence of a maximum in m* at a lower field mu0H(x) = 30 +/- 1 T may be interpreted as a field-induced crossover from local moment to SDW behavior as the Néel temperature falls below the Fermi temperature.     

Search for leptoquark pairs decaying into nunu+jets in pp collisions at square root[s] = 1.8 TeV

We present the results of a search for leptoquark (LQ) pairs in (85.2+/-3.7) pb(-1) of pp* collider data collected by the D0 experiment at the Fermilab Tevatron. We observe no evidence for leptoquark production and set a limit on sigma(pp*-->LQLQ-->nunu+jets) as a function of the mass of the leptoquark (m(LQ)). Assuming the decay LQ-->nuq, we exclude scalar leptoquarks for m(LQ) < 98 GeV/c(2), and vector leptoquarks for m(LQ) < 200 GeV/c(2) and coupling which produces the minimum cross section, at a 95% confidence level.