Microwave absorption studies of MgB2 superconductor

Microwave absorption studies have been carried out on MgB₂ superconductor using a standard X-band EPR spectrometer. The modulated low-field microwave absorption signals recorded for polycrystalline (grain size ∼ 10 μm) samples suggested the absence of weak-link character. The field dependent direct microwave absorption has been found to obey a ✓H dependence with two different slopes, which indicated a transition from strongly pinned lattice to flux flow regime.     

Laryngeal Gestures During Stop Production Using High-Speed Digital Images

On acoustic and fiberscopic studies of stop consonants, voice onset time and glottal width have been shown to be greatest in heavily aspirated stops, next greater for slightly aspirated stops, and least for unaspirated stops. Integrated activity of the thyroarytenoid and posterior cricoarytenoid muscles has been reported to be involved in differentiating aspirate characteristics of the stops. However, the fine movement of mucosal edges of vocal folds during the production of stops has not been well documented. In recent years, a new method for high-speed digital recording of laryngeal dynamics has made this possible. In the current study, the movements of vocal fold edges were documented during the period of stop production using a fiberscopic system of high-speed digital images. By observing the glottal width and the visual vibratory movements of vocal folds before voice onset, the heavily aspirated stop was characterized as being more prominent and dynamic than the slightly aspirated and unaspirated stops.     

Behavior of the ferroelectric polarization as a function of temperature in sol-gel derived strontium bismuth tantalate thin films

Strontium bismuth tantalate (SBT) thin films of nominal composition Sr_0.8Bi_2.2Ta₂O₉ have been prepared on (111)Pt/TiO₂/SiO₂/(100)Si substrates by Chemical Solution Deposition (CSD) methods, using two different thermal treatments of crystallization. The evolution of the ferroelectric polarization as a function of temperature has been studied using hysteresis loops, thermo stimulated current (TSC) measurements and the evolution of the pyroelectric coefficient (γ_M) with temperature. The results of remnant polarization (P _r) obtained from hysteresis loops and γ_M as a function of temperature showed different trends, indicating the presence of polarizing bias field in the prepared thin films due to induced asymmetry of the electrical and mechanical conditions produced at the top and bottom film electrode interfaces. The competition between internal bias fields due to differences in contact potentials of bottom and top electrodes and flexoelectric bias fields induced by stress gradient, can be in the origin of the γ_M fluctuation with temperature. A critical temperature (T ^*) is found that can be explained as the crossover between the dominant effects. It can be related to a possible ferroelectric-ferroelectric phase transition previously reported. The results also indicate that the P _r is not stable for temperatures over ≈425 K.     

Antitumor Potential of Annona muricata Linn. An Edible and Medicinal Plant in Mexico: In Vitro,In Vivo,and Toxicological Studies

Annona muricata (Am) is a plant used in traditional Mexican medicine to treat cancer. In this study, ethanol extracts of Am collected in Acapulco and Tecpan from Guerrero state were evaluated orally on Balb/c mice inoculated with 4T1 cells, for cytotoxic activity (CA) on 4T1 cells, in brine shrimp lethality assay (BSLA), and for acute oral toxicity in mice. In addition, ethanol extracts were subjected to high-performance liquid chromatography (HPLC) with diode array detection. Results showed that the extracts collected in December in Acapulco (AcDe) and Tecpan (TeDe) exhibited the most significant antitumor and cytotoxic activity. In the BSLA, the most important effect was observed in the extracts from Acapulco and Tecpan collected in June (AcJu) and August (TeAg), respectively. The samples from Acapulco (AcJu, and AcAg) and Tecpan (TeJu and TeAg) showed the highest toxicity. The analysis of the extracts, AcDe and TeDe, by HPLC revealed that flavonoids, rutin, narcissin, and nicotinflorin were the major components. These findings suggest that extracts from Am collected in Acapulco and Tecpan in the month of December may be an important source to obtain flavonoid glycosides with anticancer potential specifically against breast cancer. This also supports the use of Am to treat cancer in Mexican traditional medicine.     

Tests of significance using selected sample quantiles

Large sample tests of significance for the location parameter, the scale parameter, and quantiles for a location-scale family of distributions based on a few optimally chosen sample quantiles are considered.     

Effects of Testosterone Replacement on a Male Professional Singer

Testosterone has been known to play an important role in the development of the postpubertal male voice for many centuries. In fact, the prevention of pubertal development of the voice by castrating young male singers was a well-known practice, especially in Italy beginning in the sixteenth century. The “castrati” were well known for their clear, high-pitched voices. Because of the resulting small larynx and vocal folds, castrati apparently produced a distinctive resonance as well as the high pitch, which cannot be matched even by the counter tenors of today. Busy voice labs occasionally see males with sex hormone deficiencies secondary to chromosomal or gonadal problems. This is a presentation of an unusual patient who was a trained tenor singer and was found to have hypogonadism on a premarital health examination. Administration of replacement testosterone resulted in significant vocal register and voice quality changes.     

Dynamical symmetries for superintegrable quantum systems

We study the dynamical symmetries of a class of two-dimensional superintegrable systems on a 2-sphere, obtained by a procedure based on the Marsden-Weinstein reduction, by considering its shape-invariant intertwining operators. These are obtained by generalizing the techniques of factorization of one-dimensional systems. We firstly obtain a pair of noncommuting Lie algebras su(2) that originate the algebra so(4). By considering three spherical coordinate systems, we get the algebra u(3) that can be enlarged by “reflexions” to so(6). The bounded eigenstates of the Hamiltonian hierarchies are associated to the irreducible unitary representations of these dynamical algebras. The text was submitted by the authors in English.     

Trace element analysis of whole blood and urine samples of diabetic patients

A number of samples of whole blood, and urine from diabetic and non-diabetic persons have been analyzed for their trace elemental contents using the proton-induced X-ray emission. The elemental contents of the diabetic and non-diabetic samples are compared.     

Synthesis, characterization, DNA-binding, photocleavage, cytotoxicity and docking studies of Co(III) mixed ligand complexes

A new ligand, (2-ethoxy-6-(1H imadazo[4,5-f][1,10]phenanthroline-2-yl)phenol) (HEPIP) and its three Co(III) complexes [Co(phen)₂(HEPIP)](ClO₄)₃ (1), [Co(bpy)₂(HEPIP)](ClO₄)₃ (2) and [Co(dmb)₂(HEPIP)](ClO₄)₃ (3) have been synthesized and characterized. All three Co(III) complexes exhibited antitumor activity against four human tumor cell lines. The interaction of these complexes with calf thymus DNA was studied by absorption and emission spectroscopy, viscosity measurements and DNA cleavage assays. The DNA-binding constants of complexes 1, 2 and 3 were determined as 6.13 × 10⁵, 4.46 × 10⁵ and 3.72 × 10⁵ M^?1, respectively. The complexes appear to interact with DNA through intercalation. Studies on the mechanism of photocleavage indicated that both superoxide anion radical and singlet oxygen may play an important role.     

Unusual Hydrogen-bonding Networks Consisting of π-Extended 4,4′-Bipyridines and Chloranilic Acid

Hydrogen-bonding networks of π-extended 4,4′-bipyridines, 2,5-di(4-pyridyl)thiophene (1), 2,5-di(4-pyridyl)furan (2) and 1,4-di(4-pyridyl)benzene (3) with 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid, CA) have been investigated. The dipyridyl compounds afforded complexes 4 [(dication of 1)·(monoanion of CA)²], 5 [(dication of 2)·(dianion of CA)·(MeOH)] and 6 [(3)·(dication of 3)·(dianion of CA)·(H²O)⁶] with CA. X-ray structure analyses revealed the formation of unusual molecular tape and sheet structures involving N–H ?O, O–H ?O, C–H ?O and N–H ?N hydrogen bonds, where the aromatic spacer groups play an important role in constructing the unique crystal structures.