210 research outputs found
A Validated Reversed-Phase HPLC Method for the Determination of Atorvastatin Calcium in Tablets
A Reversed-Phase Liquid Chromatographic (RP-LC) assay method was developed for the quantitative determination of atorvastatin calcium in the presence of its degradation products. The assay involved an isocratic elution of atorvastatin calcium in a LiChroCARTR 250*4 mm HPLC Cartridge LiChrospherR 100 RP-18 (5 ÎĽm) column using a mobile phase consisting of 0.1% acetic acid solution: acetonitrile (45:55, v/v), pH = 3.8. The flow rate was 0.8 mL/min and the analytes monitored at 246 nm. The assay method was found to be linear from 8.13 to 23.77 ÎĽg/mL. All the validation parameters were within the acceptance range. The developed method was successfully applied to estimate the amount of atorvastatin calcium in tablets.Fil: Simionato, Laura Daniela. Universidad de Buenos Aires. Facultad de Farmacia y BioquĂmica. Departamento de TecnologĂa FarmacĂ©utica; ArgentinaFil: Ferello, L.. Universidad de Buenos Aires. Facultad de Farmacia y BioquĂmica. Departamento de TecnologĂa FarmacĂ©utica; ArgentinaFil: Stamer. S.. Universidad de Buenos Aires. Facultad de Farmacia y BioquĂmica. Departamento de TecnologĂa FarmacĂ©utica; ArgentinaFil: Repetto, M. F.. Universidad de Buenos Aires. Facultad de Farmacia y BioquĂmica. Departamento de TecnologĂa FarmacĂ©utica; ArgentinaFil: Zubata, P. D.. Universidad de Buenos Aires. Facultad de Farmacia y BioquĂmica. Departamento de TecnologĂa FarmacĂ©utica; ArgentinaFil: Segall, Adriana Ines. Universidad de Buenos Aires. Facultad de Farmacia y BioquĂmica. Departamento de TecnologĂa FarmacĂ©utica; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Houssay; Argentin
The Landau Pole at Finite Temperature
We study the Landau pole in the lambda phi^4 field theory at non-zero and
large temperatures. We show that the position of the thermal Landau pole
Lambda_L(T) is shifted to higher energies with respect to the zero temperature
Landau pole Lambda_L(0). We find for high temperatures T > Lambda_L(0),
Lambda_L(T) simeq pi^2 T / log (T / Lambda_L(0)). Therefore, the range of
applicability in energy of the lambda phi^4 field theory increases with the
temperature.Comment: LaTex, 6 pages, 2 .ps figures. Improved version. To appear in Phys.
Rev. D, Rapid Communication
Dissolution Stability study of Cefadroxil extemporaneous suspensions
Dissolution studies have become matter of great significance because, in most cases, drug dissolution is the rate-limiting step in the absorption process. As occurs with solid oral dosage forms, heterogeneous disperse systems (suspensions) could also have some problems with their in vitro dissolution. The dissolution behavior of four different brands of cefadroxil extemporaneous suspensions available in the Argentinian market was evaluated. The deliverable volume, pH, visual appearance, uniformity of dosage units, and assay were also studied. Powders for oral suspension were stored under different aging conditions. Samples at room temperature and refrigerated conditions were taken at several time points to carry out the dissolution stability study during the expiration period of the reconstituted form. Marked differences were recorded with respect to in vitro dissolution behavior between the different products under evaluation.Fil: González Vidal, Noelia Luján. Universidad Nacional del Sur. Departamento de BiologĂa, BioquĂmica y Farmacia. Cátedra de Control de Calidad de Medicamentos; Argentina. Universidad Nacional del Sur. Departamento de BiologĂa, BioquĂmica y Farmacia. Cátedra de Control de Calidad de Medicamentos; ArgentinaFil: Zubata, P. D.. Universidad de Buenos Aires. Facultad de Farmacia y BioquĂmica. Departamento de TecnologĂa FarmacĂ©utica; ArgentinaFil: Simionato, Laura Daniela. Universidad Nacional del Sur. Departamento de BiologĂa, BioquĂmica y Farmacia. Cátedra de Control de Calidad de Medicamentos; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y BioquĂmica. Departamento de TecnologĂa FarmacĂ©utica; ArgentinaFil: Pizzorno, Maria Teresa. Universidad de Buenos Aires. Facultad de Farmacia y BioquĂmica. Departamento de TecnologĂa FarmacĂ©utica; Argentina. Universidad Nacional del Sur. Departamento de BiologĂa, BioquĂmica y Farmacia. Cátedra de Control de Calidad de Medicamentos; Argentin
Fluctuations of the Magnetization in Thin Films due to Conduction Electrons
A detailed analysis of damping and noise due to a {\it sd}-interaction in a
thin ferromagnetic film sandwiched between two large normal metal layers is
carried out. The magnetization is shown to obey in general a non-local equation
of motion which differs from the the Gilbert equation and is extended to the
non-adiabatic regime. To lowest order in the exchange interaction and in the
limit where the Gilbert equation applies, we show that the damping term is
enhanced due to interfacial effects but it also shows oscillations as a
function of the film thickness. The noise calculation is however carried out to
all orders in the exchange coupling constant. The ellipticity of the precession
of the magnetization is taken into account. The damping is shown to have a
Gilbert form only in the adiabatic limit while the relaxation time becomes
strongly dependent on the geometry of the thin film. It is also shown that the
induced noise characteristic of sd-exchange is inherently colored in character
and depends on the symmetry of the Hamiltonian of the magnetization in the
film. We show that the sd-noise can be represented in terms of an external
stochastic field which is white only in the adiabatic regime. The temperature
is also renormalized by the spin accumulation in the system. For large
intra-atomic exchange interactions, the Gilbert-Brown equation is no longer
valid
<i>atonal-</i> and <i>achaete-scute</i>-related genes in the annelid <i>Platynereis dumerilii</i>: insights into the evolution of neural basic-Helix-Loop-Helix genes
Background: Functional studies in model organisms, such as vertebrates and Drosophila, have shown that basic Helix-loop-Helix ( bHLH) proteins have important roles in different steps of neurogenesis, from the acquisition of neural fate to the differentiation into specific neural cell types. However, these studies highlighted many differences in the expression and function of orthologous bHLH proteins during neural development between vertebrates and Drosophila. To understand how the functions of neural bHLH genes have evolved among bilaterians, we have performed a detailed study of bHLH genes during nervous system development in the polychaete annelid, Platynereis dumerilii, an organism which is evolutionary distant from both Drosophila and vertebrates. Results: We have studied Platynereis orthologs of the most important vertebrate neural bHLH genes, i.e. achaete-scute, neurogenin, atonal, olig, and NeuroD genes, the latter two being genes absent of the Drosophila genome. We observed that all these genes have specific expression patterns during nervous system formation in Platynereis. Our data suggest that in Platynereis, like in vertebrates but unlike Drosophila, ( i) neurogenin is the main proneural gene for the formation of the trunk central nervous system, (ii) achaetescute and olig genes are involved in neural subtype specification in the central nervous system, in particular in the specification of the serotonergic phenotype. In addition, we found that the Platynereis NeuroD gene has a broad and early neuroectodermal expression, which is completely different from the neuronal expression of vertebrate NeuroD genes. Conclusion: Our analysis suggests that the Platynereis bHLH genes have both proneural and neuronal specification functions, in a way more akin to the vertebrate situation than to that of Drosophila. We conclude that these features are ancestral to bilaterians and have been conserved in the vertebrates and annelids lineages, but have diverged in the evolutionary lineage leading to Drosophila
A comparative in vitro assay of drug release performance of pyridostigmine bromide tablets
Myasthenia gravis is an autoimmune disease that destroys key components of the neuromuscular system. The most common therapy uses reversible inhibitors of cholinesterase activity, such as pyridostigmine bromide (PB). The nature of this illness implies that we must be sure that all available PB immediate-release tablets produce the same therapeutic response. The aim of this study was to analyze PB immediate-release formulations provided by pharmacies in MERCOSUR countries A, B, and C. The formulations, which were produced in different manufacturing plants of the same multinational company, were analyzed following USP 29 specifications. The products fulfilled the assay, uniformity of dosage units, and dissolution test in S2 stage. Dissolution profiles were carried out following EMEA and FDA regulations, and the similarity factor (f2) was applied to A and C but not B, as this one did not fulfill the dissolution requirements. Pyridostigmine bromide tablets from countries A and C are considered to be similar and could be interchangeable. Formulation B exhibited such different dissolution behavior that its interchangeability is discouraged, as well as its introduction in countries A and C from the manufacturing country B.Fil: Pizzorno, Maria Teresa. Universidad de Buenos Aires. Facultad de Farmacia y BioquĂmica; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Houssay; ArgentinaFil: Zubata, Patricia D.. Universidad de Buenos Aires. Facultad de Farmacia y BioquĂmica; ArgentinaFil: Simionato, Laura Daniela. Universidad de Buenos Aires. Facultad de Farmacia y BioquĂmica; ArgentinaFil: Ercolano, Irma. Universidad de Buenos Aires. Facultad de Farmacia y BioquĂmica; ArgentinaFil: Pizzorno, Maria Teresa. Universidad de Buenos Aires. Facultad de Farmacia y BioquĂmica; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Houssay; Argentin
Regional Seismic Characterization of Shallow Subsoil of Northern Apulia (Southern Italy)
A first-order seismic characterization of Northern Apulia (Southern Italy) has been provided by considering geological information and outcomes of a low-cost geophysical survey. In particular, 403 single-station ambient vibration measurements (HVSR techniques) distributed within the main settlements of the area have been considered to extract representative patterns deduced by Principal Component Analysis. The joint interpretation of these pieces of information allows the identification of three main domains (Gargano Promontory, Bradanic Through and Southern Apennines Fold and Thrust Belt), each characterized by specific seismic resonance phenomena. In particular, the Bradanic Through is homogeneously characterized by low frequency (< 1 Hz) resonance effects associated with relatively deep (> 100 m) seismic impedance, which is contrasting corresponding to the buried Apulian carbonate platform and/or sandy horizons located within the Plio-Pleistocene deposits. In the remaining ones, relatively high frequency (> 1 Hz) resonance phenomena are ubiquitous due to the presence of shallower impedance contrasts (< 100 m), which do not always correspond to the top of the geological bedrock. These general indications may be useful for a preliminary regional characterization of seismic response in the study area, which can be helpful for an effective planning of more detailed studies targeted to engineering purposes
Large scale magnetogenesis from a non-equilibrium phase transition in the radiation dominated era
We study the generation of large scale primordial magnetic fields by a
cosmological phase transition during the radiation dominated era. The setting
is a theory of N charged scalar fields coupled to an abelian gauge field, that
undergoes a phase transition at a critical temperature much larger than the
electroweak scale. The dynamics after the transition features two distinct
stages: a spinodal regime dominated by linear long-wavelength instabilities,
and a scaling stage in which the non-linearities and backreaction of the scalar
fields are dominant. This second stage describes the growth of horizon sized
domains. We implement a recently introduced formulation to obtain the spectrum
of magnetic fields that includes the dissipative effects of the plasma. We find
that large scale magnetogenesis is very efficient during the scaling regime.
The ratio between the energy density on scales larger than L and that in the
background radiation r(L,T) = rho_B(L,T)/rho_{cmb}(T) is r(L,T) \sim 10^{-34}
at the Electroweak scale and r(L,T) \sim 10^{-14} at the QCD scale for L \sim 1
Mpc. The resulting spectrum is insensitive to the magnetic diffusion length. We
conjecture that a similar mechanism could be operative after the QCD chiral
phase transition.Comment: LaTex, 25 pages, no figures, to appear in Phys. Rev.
Magnetic field generation from non-equilibrium phase transitions
We study the generation of magnetic fields during the stage of particle
production resulting from spinodal instabilities during phase transitions out
of equilibrium. The main premise is that long-wavelength instabilities that
drive the phase transition lead to strong non-equilibrium charge and current
fluctuations which generate electromagnetic fields. We present a formulation
based on the non-equilibrium Schwinger-Dyson equations that leads to an exact
expression for the spectrum of electromagnetic fields valid for general
theories and cosmological backgrounds and whose main ingredient is the
transverse photon polarization out of equilibrium. This formulation includes
the dissipative effects of the conductivity in the medium. As a prelude to
cosmology we study magnetogenesis in Minkowski space-time in a theory of N
charged scalar fields to lowest order in the gauge coupling and to leading
order in the large N within two scenarios of cosmological relevance. The
long-wavelength power spectrum for electric and magnetic fields at the end of
the phase transition is obtained explicitly.
It follows that equipartition between electric and magnetic fields does not
hold out of equilibrium. In the case of a transition from a high temperature
phase, the conductivity of the medium severely hinders the generation of
magnetic fields, however the magnetic fields generated are correlated on scales
of the order of the domain size, which is much larger than the magnetic
diffusion length. Implications of the results to cosmological phase transitions
driven by spinodal unstabilities are discussed.Comment: Preprint no. LPTHE 02-55, 30 pages, latex, 2 eps figures. Added one
reference. To appear in Phys. Rev.
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