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Na Educacao Basica, os conteudos de Quimica sao considerados pouco atrativos pelos estudantes, que nem compreendem efetivamente os fenomenos quimicos e nem sao capazes de associa-los ao cotidiano. Nesse aspecto, o presente trabalho tem como objetivo a elaboracao de um experimento, investigativo e contextualizado, como recurso didatico para a aprendizagem de conceitos quimicos envolvendo densidade, catalisadores, numero de oxidacao, funcoes orgânicas e reacoes quimicas na abordagem da tematica de fraudes no leite. A pesquisa foi realizada no Laboratorio de Quimica da Seara da Ciencia da Universidade Federal do Ceara (Fortaleza-CE), envolvendo alunos do Ensino Medio. Observamos que todos os alunos conseguiram identificar as adulteracoes nas amostras de leite recebidas, alcancando resultados muito satisfatorios. Os experimentos, alem de motivar, auxiliaram na compreensao dos conceitos quimicos, relacionando-os com a realidade dos alunos no seu entorno, a partir da visualizacao macroscopica do conhecimento quimico.

We analyze the effects of dissipation in a charged oscillator in the presence of the Aharonov-Bohm effect by using time-dependent mass (m(t)) Hamiltonians. We consider two different models for the dissipative Hamiltonian and analyze the uncertainties (Δr and Δp) and the quantum mechanical expectation value of energy (⟨E⟩) in terms of time (t), damping parameters and flux parameter (v). For the Caldirola-Kanai model, we observe that the flux parameter v decreases the energy dissipation in a quantum dot for a certain range of t.

Investigamos o emaranhamento para o estado fundamental de duas partículas sem spin, carregadas e harmonicamente acopladas em uma armadilha de Penning. Encontramos uma expressão analítica para a entropia linear, L, e analisamos o grau de emaranhamento em função da variação da constante de acoplamento e dos parâmetros da armadilha de Penning. Os resultados mostram uma competição entre o acoplamento das partículas e os parâmetros da armadilha. Relacionamos os resultados com a incerteza na posição das partículas. We investigate the entanglement-related features of the ground state of two spinless charged particles harmonically coupled in a Penning trap. We find an analytical expression for the linear entropy, L, and analyze the entanglement properties of the ground state as the trap parameters and coupling constant changes. The results show a competition between the coupling constant and trap parameters and can also be related to the uncertainty in the position of the particles.

The Shannon entropy and the Fischer information are calculated for an harmonic oscillator in the presence of an applied electric field ( e ) in a space with metrics given by g x x − 1 ∕ 2 = 1 + γ x . For that metric the harmonic oscillator can be mapped into a Morse potential in an Euclidean space. For e = 0 , the ground state energy decreases when γ increases. However, for certain values of e the energy decrease can be canceled out. The dependence of the uncertainties, the entropy, and the information on the parameters γ and e are shown.

This work aims to present the recent changes and the current trends of Brazilian Private International Law in the area of international contracts with especial focus on the enforcement of Convention on the International Sale of Goods (CISG) in Brazilian legal order. Historically, the recognition of party autonomy in Private International Law has not been uniformily recognized. While since 1996, with the enforcement of the new Arbitration Law, party autonomy has been increasingly accepted in terms of international arbitration, jurisprudence on the choice of law and the choice of court clauses does not show the same progress. In fact, despite of important documents which have already been signed by the government, Brazilian Private International Law of Contracts still dates from 1942. Such contrast with internal material law represents a challenge for the full recognition of Party Autonmy in Brazilian Private International Law.

O Ensino de Quimica no contexto atual exige que educadores busquem cada vez mais novas ferramentas de ensino. A forma tradicional defronta-se com a resistencia e apatia dos alunos. A fim de modificar essa tendencia, muitas metodologias interessantes vem sendo propostas. Dentre elas, uma que vem ganhando bastante destaque, e o teatro cientifico, que une arte e ciencia no palco. Nesta perspectiva, o presente trabalho tem como objetivo relatar experiencias envolvendo teatro cientifico no Ensino de Quimica, atraves de 6 montagens cenicas, decorrentes de tres anos de pesquisas e divulgacao cientifica teatral em parceria com a Seara da Ciencia da Universidade Federal do Ceara (UFC) e outras Instituicoes de Ensino Superior do pais. As pecas produzidas foram: “ A Liga da Ciencia”, “O Alquimista”, “Somos o que Comemos?”, “Lampiao e Maria Bonita em Busca da Quimica do Amor”, “Os Vingadores Quimicos” e “Doutorado em Quimica do Amor”. Para analisar as contribuicoes pedagogicas advindas dessa experiencia utilizou-se questionarios, debates e comentarios com a plateia. Os resultados apontam que atraves deste meio de divulgacao cientifica foi possivel estimular o aprendizado da Quimica e a motivacao dos alunos.

The main goal of this paper is to obtain the exact quantum solutions for charge space in a superconductor with time-dependent parameters using the London approach. We introduce a new quantization scheme for the charge inside a superconductor based on the Lewis and Riesenfeld invariant operator method. From the wave-functions obtained, we calculated the time-dependent uncertainties and the mean energy of the system. Information measures were also obtained, such as Shannon entropy and complexity. The later is always time-independent and also does not depend on conductivity. The other quantities are written in terms of a time-dependent function, ρ ( t ) , c-number quantity satisfying a nonlinear differential equation.

We use the dynamical invariant method and two unitary transformations to obtain the exact Schrodinger wave functions, ψ n m k ( r , t ) , for a spinless charged particle in a time-dependent Penning trap. For the special case n = m = k = 0 , we obtain the analytical expressions for the uncertainties in terms of two c-number functions satisfying a Milne-Pinney-like equation. We analyze the static and the time-dependent cases. For the former, where B ( t ) = B 0 k and V ( t ) = V 0 , we observe that the Heisenberg and Robertson-Schrodinger uncertainty relations are fulfilled and the behavior of the uncertainties Δ x , y and Δ p x , p y when B 0 changes indicates the occurrence of a squeezing phenomenon. For the later, where B ( t ) = ( B 0 2 + B ' c o s 2 ( ν t ) ) 1 / 2 k and V ( t ) = V 0 + V ' C o s 2 ( ν t ) , we observe that Δ x , y oscillate in time exhibiting a squeezing phenomenon. Relations among the uncertainties, Shannon entropies and Fisher lengths were stablished. We observe for both cases that the Shannon entropy in position, S r , and in momentum, S p , satisfy the relation S r + S p ≥ 3 ( 1 + l n π ) , while the Fisher lengths δ r and δ p exhibit a lower bound than the uncertainties Δ r , p .

The spectroscopic characteristics of highly Nd3+-doped lead phosphate glasses (xNd:Pb3(PO4)2) have been investigated. The X-ray spectra show that the matrices are glassy up to 25 wt% of Nd3+ doping. From the Judd–Ofelt analysis we observe that while the Ω(2) parameter remains constant indicating that the 4fN and 4fN−15 d1 configurations are not affected by the Nd3+ doping, the behavior of both Ω(4) and Ω(6) changes for 15 wt% of Nd3+ doping. The reduction of the Ω(6) parameter is related to the increase of the covalence bonding between the ligands and the Nd3+ ions. At this particular concentration, the radiative lifetime has a four-fold enhancement. Such behaviors are likely to be related to a modification in the glass structure for high Nd3+ concentrations.

We calculate the Fisher information and the Shannon entropy for three position-dependent mass oscillators. These systems can be seen as deformed harmonic oscillators in the sense that when the deformation parameter ( λ ) goes to zero, they are identical to the constant mass harmonic oscillator. For two out of the three oscillators we observe that as λ increases the position Fisher information ( F x ) increases while the momentum Fisher information ( F p ) decreases. On the other hand, the Shannon entropy always increases for the three systems with increasing λ . Discussion about squeezing effect in either position or momentum due to the λ variation and a relation between the product of Fisher information and the Shannon entropy are also presented.

We calculate the time-dependent Shannon ( S x and S p ) entropy and Fisher ( F x and F p ) information of three log-periodic oscillators. We obtain a general expression for S x , p and F x , p in the state n = 0 in terms of ρ , a c-number quantity satisfying a nonlinear differential equation. For two out of three oscillators S x , p and F x , p depend on time, but S x + S p and F x F p do not. The other oscillator behaves as the time-independent harmonic oscillator where S x , p and F x , p are all constants. Relations among the Fisher information and the Stam and Cramer–Rao inequalities are also discussed.

In this work, we report on the analysis of both vibrational and magnetic properties of heavy rare-earth molybdates Gd 2 (Mo 0.9 W 0.1 O 4 ) 3 and Gd 1.8 Er 0.2 (MoO 4 ) 3 . The crystal structures, as determined by X-ray powder diffraction and the Rietveld refinement analysis, established that at room temperature both of these materials belong to orthorhombic Pba 2 space group. Magnetization measurements showed that no saturation is present up to 8 T at T =10 K, and the magnetic susceptibility curves show paramagnetic behavior down to T =10 K. The effective magnetic moments and possible short-range magnetic interactions between Gd 3+ ions are treated and discussed. Raman spectra of both of these molybdates are similar to that of the pure compound Gd 2 (MoO 4 ) 3 , indicating that changes in the Raman spectra due to the introduction of either Er or W doping are negligible at the subject dopant concentrations.

We use polarized Raman spectroscopy to obtain the room temperature phonon modes of LiBaB 9 O 15 single crystal, that crystallizes in a trigonal structure belonging to the space group R 3 ¯ c ( D 3 d 6 ) with two molecules per primitive cell ( Z B =2). The structure of the LiBaB 9 O 15 crystal consists of a three-dimensional borate framework, formed by two BO 3 triangles and one BO 4 tetrahedra. Since BO 3 and BO 4 units share the oxygen atoms, we can not obtain a correlation scheme where their internal modes are distributed in terms of the irreducible representations of the D 3 d factor group. The only modes that can unambiguously be assigned are the ν 3 (BO 4 ) with A 1 g symmetry at 983 cm − 1 and the ν 1 (BO 3 ) with E g symmetry at 932 cm −1 . We observed 7 A 1 g +6 E g out of 11 A 1 g +25 E g vibrations predicted by the Group Theory.

We obtain the exact wave function of a monolayer phosphorene under a low- intensity time-dependent magnetic field using the dynamical invariant method. We calculate the quantum-mechanical energy expectation value and the transition probability for a constant and an oscillatory magnetic field. For the former we observe that the Landau level energy varies linearly with the quantum numbers n and m and the magnetic field intensity B_0. No transition takes place. For the latter, we observe that the energy oscillates in time, increasing linearly with the Landau level n and m and nonlinearly with the magnetic field. The (k,l) to (n,m) transitions take place only for l=m. We investigate the (0,0) to (n,0) and (1,l) and (2,l) probability transitions., Comment: 19 pages, 3 figures

In the present study, neodymium-doped lithium silicate glasses have been prepared by the conventional melt-quenching technique. The dielectric properties, electric modulus, and electrical conductivity of SiO 2 –Li 2 O (SiLi–0Nd) and SiO 2 –Li 2 O:Nd 2 O 3 (SiLi-1.35Nd) have been studied from 1 Hz to 1 MHz in the 333–423 K temperature range. At a given temperature and frequency, we observe that the conductivity decreases when neodymium ions are added to the glass matrix. The activation energy of two distinct regions was evaluated from the ln( σ dc ) = f (1/ T ) plot and was found to be E 1 ( T E 2 ( T > 363 K) = 1.26(1.09) eV for SiLi–0Nd (SiLi–1.35Nd). The dielectric constant ( e Re ) decreases while the dielectric loss (tan ( δ )) increases under Nd 2 O 3 doping. We also observe that for both glasses, e Re and tan ( δ ) tend to increase with increasing temperature and decrease with increasing frequency.

In this work we study the effects of the solvent interaction on the nonlinear dynamical structure of a DNA segment, by using a time-independent perturbation approach. Considering a well-known set of values for the spring constant ( k ) and the Morse (solvent) potential parameters D n and a n ( f s and λ s ), we investigate the denaturation temperature profiles of some DNA’s thermodynamical functions, such as the stretching of the hydrogen bonds, the specific heat and the entropy. Besides a sharp thermal profile behavior of these functions, we observe also that the DNA’s melting temperature decreases as the solvent potential increases.

We use the dynamical invariant method and a unitary transformation to obtain the exact Schrodinger wave function, ψ n ( x , t ) , and calculate for n = 0 the time-dependent joint entropy (Leipnik’s entropy) for two classes of quantum damped harmonic oscillators. We observe that the joint entropy does not vary in time for the Caldirola–Kanai oscillator, while it decreases and tends to a constant value ( ln ( e 2 ) ) for asymptotic times for the Lane–Emden ones. This is due to the fact that for the latter, the damping factor decreases as time increases. The results show that the time dependence of the joint entropy is quite complex and does not obey a general trend of monotonously increase with time.

Objective: To evaluate the influence of Everolimus (RAD001) on chemically induced urothelial lesions in mice and its influence on in vitro human bladder cancer cell lines. Methods: ICR male mice were given N-butyl-N-(4-hydroxybutyl) nitrosamine in drinking water for a period of 12 weeks. Subsequently, RAD001 was administered via oral gavage, for 6 weeks. At the end of the experiment, all the animals were sacrificed and tumor development was determined by means of histopathologic evaluation; mammalian target of rapamycin (mTOR) expressivity was evaluated by immunohistochemistry. Three human bladder cancer cell lines (T24, HT1376, and 5637) were treated using a range of RAD001 concentrations. MTT assay, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), and flow cytometry were used to assess cell proliferation, apoptosis index, and cell cycle analysis, respectively. Immunoblotting analysis of 3 cell line extracts using mTOR and Akt antibodies was performed in order to study the expression of Akt and mTOR proteins and their phosphorylated forms. Results: The incidence of urothelial lesions in animals treated with RAD001 was similar to those animals not treated. RAD001 did not block T24 and HT1376 cell proliferation or induce apoptosis. A reduction in cell proliferation rate and therefore G 0 /G 1 phase arrest, as well as a statistically significant induction of apoptosis (P 0.001), was only observed in the 5637 cell line. Conclusion: RAD001 seems not to have a significant effect on chemically induced murine bladder tumors. The effect of RAD001 on tumor proliferation and apoptosis was achieved only in superficial derived bladder cancer cell line, no effect was observed in invasive cell lines. © 2011 Elsevier Inc. All rights reserved.

In this work we investigate the effect of replacing Na2O by TiO2 on the structural and spectroscopic characteristics of the Nd2O3-doped 60B2O3–(20−x)Na2O–10PbO–10Al2O3:xTiO2:yNd2O3 borate glass matrix. Measurements of X-ray patterns, glass temperatures (Tg), vibrational (Raman and infrared (IR)) and optical (absorption and emission) spectra were carried out. The trend of Tg, the Judd–Ofelt parameters and Nephelauxetic ratio as the TiO2 and Nd2O3 concentration increases was interpreted quantitatively and qualitatively in terms of the network bonds and coordination numbers. Measurements of Tg across the Nd-doped glass series for different levels of Ti suggests changes in the rigidity of the matrix due to change of coordination of boron oxide resulting from the BO4–BO3 back conversion effect. The changes observed in the Raman and IR spectra are related to the BO3 → BO4 conversion effect. The variation of the Judd–Ofelt parameters Ω ( 2 ) and Ω ( 6 ) indicates that the average rare earth-ligand radius decreases establishing an electronic density distribution when Nd3+ concentration increases. This effect is interpreted in terms of Judd–Ofelt parameters and by the bonding parameter b 1 / 2 due to Nephelauxetic effect.

In this work, we report the multifunctional character of neodymium-doped LaF3 core/shell nanoparticles. Because of the spectral overlap of the neodymium emission bands with the transparency windows of human tissues, these nanoparticles emerge as relevant subtissue optical probes. For neodymium contents optimizing the luminescence brightness of Nd3+:LaF3 nanoparticles, subtissue penetration depths of several millimeters have been demonstrated. At the same time, it has been found that the infrared emission bands of Nd3+:LaF3 nanoparticles show a remarkable thermal sensitivity, so that they can be advantageously used as luminescent nanothermometers for subtissue thermal sensing. This possibility has been demonstrated in this work: Nd3+:LaF3 nanoparticles have been used to provide optical control over subtissue temperature in a single-beam plasmonic-mediated heating experiment. In this experiment, gold nanorods are used as nanoheaters while thermal reading is performed by the Nd3+:LaF3 nanoparticles. The poss...

We analyzed the noncommutativity effects on the Fisher information (F_(r,p)) and Shannon entropies (S_(r,p)) of a harmonic oscillator immersed in a time-varying electric field in two and three dimensions. We find the exact solutions of the respective time-dependent Schr\"odinger equation and use them to calculate the Fisher information and the Shannon entropy for the simplest case corresponding the lowest-lying state of each system. While there is no problem in defining the Shannon entropy for noncommutating spaces, the definition of the Fisher information had to be modified to satisfy the Cramer-Rao inequalities. We observe for both systems, how the Fisher information and Shannon entropy in position and momentum change due to the noncommutativity of the space. We verified that the Bialynicki-Birula-Mycielski (BBM) entropic uncertainty relation still holds in the systems considered., Comment: 23 pages, 2 figures

Single crystals of potassium tantalate niobate, KTa 1− x Nb x O 3 (KTN x , x = 0.45, 0.50, and 0.55), were synthesized by the top-seeded solution growth method. The Raman scattering technique is used to investigate the sequence of phase transitions undergone by KTN x crystals. We discuss what features in the phonon spectrum are associated to each phase transition.

The room temperature phonon modes of both the alkali metal doped and pure CBN (CaxBa1−xNb2O6) crystals were determined using the Raman scattering technique. Owing to the intrinsic disorder of the tetragonal lattice we observe few and broad bands. The wavenumber of the internal modes observed shifts upwards when the volume of the unit cell increases. This blue shift is likely to be related to the closer packing of the NbO6 octahedrons. The Curie temperatures of the ferroelectric to paraelectric phase transition for the CBN-like crystals were obtained from DSC measurements. The Raman spectra of CBN32 in the temperature range from 300 to 568 K were also recorded in order to investigate the phase transformation.

Optical and vibrational studies have been carried out on 60B{sub 2}O{sub 3}.(20-x)Na{sub 2}O.10PbO.10Al{sub 2}O{sub 3}:xTiO{sub 2} (x=0, 1, 2, 3, 4, and 5 mol%) glasses, in order to understand the role of TiO{sub 2} in the 60B{sub 2}O{sub 3}.20Na{sub 2}O.10PbO.10Al{sub 2}O{sub 3} glass matrix. The X-ray patterns reveal homogeneous glasses over the entire compositional range. The absorption spectra show that the energy of the optical band gap ({Delta}E{sub opt}) and Urbach's energy (E{sub U}) decreases as TiO{sub 2} content increases. The changes observed in the Raman and IR spectra are related to the BO{sub 4}{yields}BO{sub 3} back conversion effect and the appearance of 'loose' BO{sub 4}{sup -} groups. The data indicate that titanium ions act as a network modifier. - Graphical abstract: Behavior of the relative integrated intensity of the IR bands, Ar=A{sub 4}/A{sub 3}, as TiO{sub 2} content increases. A decrease of 45% of Ar indicates that the number of BO{sub 4} groups is decreasing due to the BO{sub 4}{yields}BO{sub 3} back conversion. Highlights: > The XRD data show the amorphous character of all measured glasses. > The optical absorption results evidenced possible change of the glass structure. > The Raman data have revealed some vibrational modifications. > Themore » overall results indicate that titanium acts as a network modifier.« less

The room temperature phonon modes of the isostructural (Nd,Yb):Y{sub x}Gd{sub 1-x}(VO{sub 4}) laser crystals were determined using the Raman scattering technique, and the observed wavenumbers follow the overall mode distribution expected for REVO{sub 4} (RE=rare earth) compounds with the tetragonal zircon structure, D{sub 4h}{sup 19}. They were assigned according to the group theory in terms of the internal modes of the VO{sub 4} tetrahedron and the external modes of the Y{sub x}Gd{sub 1-x}(VO{sub 4}) lattice. No appreciable changes in the phonon wavenumbers were observed for Yb:GdVO{sub 4} (Yb=0.008, 0.015, 0.020, 0.025, and 0.035), indicating that the force fields in the GdVO{sub 4} lattice are not strongly altered by Yb doping at the Gd site. However, most of the phonon wavenumbers in the systems (Nd,Yb):Y{sub x}Gd{sub 1-x}(VO{sub 4}) shifts upwards (one-phonon-like behavior) when Y replaces for Gd. -- Graphical abstract: Plot of the observed wavenumbers of Nd:Y{sub x}Gd{sub 1-x}(VO{sub 4}) versus Y content (x). The linear trend indicates that most of the observed wavenumbers exhibit a one-phonon-like behavior. Display Omitted Research highlights: > Force fields in the GdVO{sub 4} lattice are not strongly altered by Yb doping at the Gd site when the doping content of Yb is below 3.5 at%.more » > Most of the phonon wavenumbers in the systems (Nd,Yb):Y{sub x}Gd{sub 1-x}(VO{sub 4}) shifts upwards with x increasing. > The upward shifting is related to the decrease of the RE-O distance due to the lattice contraction. > Most of the observed wavenumbers exhibits a one-phonon-like behavior.« less

Raman spectroscopy, polarized microscopy and thermal measurements were used to investigate the sequence of phase transition in the lead oxide salts Pb8O5(XO4)2 (where X = As and V). For Pb8O5(AsO4)2, a second-order phase transition is observed at 500 K. For Pb8O5(VO4)2, a second-order and a first-order structural phase transitions are observed at 425 and 525 K, respectively. The ferroelastic character of Pb8O5(VO4)2 is also discussed. Copyright © 2011 John Wiley & Sons, Ltd.

The third-order optical susceptibility and dispersion of the linear refractive index of Er3+-doped lead phosphate glass were measured in the wavelength range between 400 and 1940 nm by using the spectrally resolved femtosecond Maker fringes technique. The nonlinear refractive index obtained from the third-order susceptibility was found to be five times higher than that of silica, indicating that Er3+-doped lead phosphate glass is a potential candidate to be used as the base component for the fabrication of photonic devices. For comparison purposes, the Z-scan technique was also employed to obtain the values of the nonlinear refractive index of Er3+-doped lead phosphate glass at several wavelengths, and the values obtained using the two techniques agree to within 15%.

Polarized Raman Spectroscopy was used to investigate the room-temperature phonon characteristics of a series of rare-earth arsenate (REAsO4, RE = Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb, and Lu) single crystals. The Raman data were interpreted in a systematic manner based on the known tetragonal zircon structure of these compounds, and assignments and correlations were made for the observed bands. We found that the wavenumber of the internal modes of the AsO4 tetrahedron increased with increasing atomic number, and for three out of four lattice wavenumbers observed, this tendency was not nearly so marked as in the case of the internal mode wavenumber.

In this work we investigate the room-temperature Raman spectra of several rare-earth [RE(HCOO)3; RE = La, Pr, Nd, Gd, Tb and Y] formates. Polarized measurements were carried out for La(HCOO)3 yielding the observation of most of the Raman-active phonons predicted by group theory analysis. The respective assignment is given based on the formate vibrations and correlations with previous results in other RE(HCOO)3 systems. The wavenumber ‘softening’ observed when RE goes from Y to La is accounted for the lattice expansion. Copyright © 2009 John Wiley & Sons, Ltd.

Raman scattering and infrared transmittance techniques were used to investigate the room-temperature phonon spectra of the polycrystalline Ba3In2UO9, Sr3In2UO9, Ba3In2WO9 and Sr3In2WO9 double perovskites. Although X-ray diffraction has shown that both Ba3In2UO9 and Ba3In2WO9 crystallize in a disordered cubic (Pm3m − Oh1) structure with one formula unit per unit cell (Z = 1), Raman measurements revealed that both Ba3In2UO9 and Ba3In2WO9 compounds should exhibit a 1:1 ordered domains with Fm3m symmetry, embedded in the Pm3m matrix. Observation of a ν1-like vibration of the InO6 octahedron reflects the occurrence of a two-phonon-like behavior due to the intrinsic occupational disorder at octahedral symmetry sites. Assignment of most of the Raman and infrared phonons is also given. Copyright © 2009 John Wiley & Sons, Ltd.

The phonon modes of the rare-earth calcium oxyborates [RECa 4 O(BO 3 ) 3 , RE = La and Gd] were determined at room-temperature using Raman scattering technique. The observed frequencies were assigned on the basis of the borate (BO 3 ) vibrations and correlations with previous data reported for other similar compounds. The influence of the RE ion substitution on the phonon distribution is discussed. Two main features were observed when La 3+ replaces for Gd 3+ : the frequency of most of the phonons shifts downwards and the frequency difference between the components of the ν 1 (BO 3 ) doublet decreases. All these features result from the monoclinic lattice expansion.

This paper reports on the spectroscopic study of YbVO{sub 4} in the range 10-300 K. All the Raman phonons were properly assigned. Temperature-dependent Raman spectra showed no anomalous changes, which indicate that neither structural phase transition nor strong electron-phonon coupling occur, at least within this temperature range. This result is sharp contrast to those of YbPO{sub 4} where strong mixing of the upper crystal-field states {Gamma}{sub 6} and {Gamma}{sub 7} with an E{sub g}{sup 3} phonon at room-temperature occurs. A possible explanation for the absence of electron-phonon coupling in YbVO{sub 4} is the occurrence of the {Gamma}{sub 6} state at energy higher than the E{sub g}{sup 3} phonon, unlike the coincidence of {Gamma}{sub 6} and E{sub g}{sup 3} energies in YbPO{sub 4}.

Investigations on the excited state absorption signal of 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphyrin, modified by either changing the central ion or adding peripheral groups, were performed using 5 ns laser pulses at 532 nm, in association with linear absorbance and fluorescence decay time measurements. The reverse saturable absorption (RSA) increases remarkably when Zn2+ replaces H+ at the central position of the porphyrin ring. However, it decreases when RuCl2(CO)(PPh3)2 and RuCl2(CO)(dppb) groups are attached at outlying positions through the pyridine rings, for both the free base and zinc porphyrins. A theoretical model based on Jablonski diagram was used to verify the main reason for the decrease on the RSA signal caused by ruthenium groups.

The room-temperature vibrational spectra of the monazite-type rare-earth orthophosphates (RPO4, R = La, Ce, Pr, Nd, Sm, Eu and Gd) have been investigated using polarized Raman and infrared spectroscopies. As in the case of the previously reported Raman results, we also observe 22 peaks, while only 18 Ag/Bg vibrations are predicted by group theoretical analysis. Through a careful review of the combined Raman–IR modes, in conjunction with the measured generalized phonon density of states of LaPO4 by neutron spectroscopy and a comparison with the corresponding data for the xenotime RPO4 members, we have obtained a self-consistent assignment of the Raman and IR modes. We also discuss on the possible origins of the previously unidentified “extra” peaks.

The necessity of producing materials with better performances than those observed in ferroelectric perovskites has induced the investigation of new oxides, especially those belonging to the Aurivillius family which exhibit better performance than PZT in non-volatile ferroelectric memories (FeRAM). In this contribution a Raman analysis of Bi2-xTexSrNb2-xHfxO9 (x = 0.10) is carried out to investigate the vibrational spectra and the ferro-paraelectric phase transition of these compounds.

The Aurivillius type oxide Bi1.9Te0.1SrNb1.9Hf0.1O9 has been studied by Perturbed Angular Correlations spectroscopy using 181Ta probes. The spin precession curves were measured from room temperature up to 873 K. Two sites are occupied by probes and the temperature dependence of both indicates a continuous phase transition at about 625 K. One site is ordered while the other is disordered. This situation is analyzed in terms of simple models already applied to perovskites. The transition temperature of the solid solution Bi2−xTexSrNb2−xHfxO9 (with 0 ≤ x ≤ 0.5 ) shows a strong dependence on composition.

We explore the use of a computer-controlled micro-machined deformable mirror to tailor the spectral phase of an ultrashort laser pulse to control the second-harmonic generation in KDP crystals. The SHG dependence of chirp and phase mask could be observed and adjusted by a simple theory.

The mechanochemical activation method allows one to obtain the Aurivillius phases Bi 4 SrTi 4 O 15 and Bi 4 Sr 2 Ti 5 O 18 with a significant decrease in the temperature of synthesis and reaction time, as compared to the solid-state method, by supplying mechanical energy to the initial reagents. The method leads to homogeneous, activated precursors, whose particle size is reduced to around 250 nm. Further thermal annealing makes crystallinity and particle size to increase. The products are characterized by Raman spectroscopy, X-ray diffraction, thermal analysis and scanning electron microscopy.

The exact wavefunctions for a particle trapped by oscillating fields are obtained in terms of Mathieu functions with the help of linear invariants and the dynamical invariant method. In addition, we construct Gaussian wave packet solutions and calculate the quantum fluctuations in the coordinate and momentum as well as the quantum correlations between coordinate and momentum.

We obtain the Schrödinger wave functions of a generalized pendulum under time-dependent gravitation by making use of the Lewis and Riesenfeld invariant method. As an example, we consider a generalized pendulum with constant gravitation and exponentially increasing mass. We also present a canonical approach to the generalized time-dependent pendulum.