Stability of quantum motion in regular systems: a uniform semiclassical approach.

We study the stability of quantum motion of classically regular systems in the presence of small perturbations. On the basis of a uniform semiclassical theory we derive the fidelity decay which displays a quite complex behavior, from Gaussian to power law decay t(-alpha), with 1

Uniform semiclassical approach to fidelity decay in the deep Lyapunov regime.

We use the uniform semiclassical approximation in order to derive the fidelity decay in the regime of large perturbations. Numerical computations are presented which agree with our theoretical predictions. Moreover, our theory allows us to explain previous findings, such as the deviation from the Lyapunov decay rate in cases where the classical finite-time instability is nonuniform in phase space.

LDL physical properties, lipoprotein and Lp(a) levels in acromegalic patients. Effects of octreotide therapy. Italian Multicenter Octreotide Study Group.

High vascular morbidity and mortality is associated with acromegaly. The aim of the present study was to assess the effects of octreotide therapy on several known cardiovascular risk factors and to correlate them with octreotide-induced hormonal changes. Lipid levels, LDL particle size distribution as evaluated by single vertical spin density gradient ultracentrifugation, apolipoproteins AI and B, lipoprotein (a) [Lp(a)] concentrations and apo(a) phenotypes were evaluated in 20 non-diabetic acromegalic patients (6 M, 14 F), with normal thyroid, adrenal and gonadal function, aged 29-66 years. Normal subjects (20), matched for age, sex and BMI served as control for lipid variables. Acromegalic patients were characterized by lower HDL cholesterol (and apoA-I) and by higher Lp(a) concentrations in comparison to controls. Treatment with octreotide (100 microg t.i.d. for 3 months) led to: an increase in HDL cholesterol (median: + 22%), a decrease in LDL cholesterol (-14%) and a decrease of the Lp(a) levels (all phenotypes) (-28%). The expected decreases of IGF-I levels (median: -48%) and 7-h AUC of GH (-50%), insulin (-40%) and glucagon (-20%) were observed. Only Lp(a) modifications showed a correlation with GH modifications. The study of LDL physical properties showed that acromegalic patients had smaller and/or more dense LDL particles, in comparison with normal controls (relative flotation rate, Rf: 0.40 +/- 0.03 versus 0.42 +/- 0.02 P < 0q05), an alteration that might contribute to the high vascular risk of acromegalic patients. However, the LDL subfraction distribution remained unmodified during octreotide therapy (Rf 0.39 +/- 0.03). In conclusion, this study shows that in acromegalic patients octreotide treatment is indeed associated with an amelioration of some lipoprotein parameters, i.e. LDL, HDL, and Lp(a) concentrations. However, this treatment has no effect on the small and/or dense LDL particles present in these patients.

Effect of modulation of protein kinase C activity on cisplatin cytotoxicity in cisplatin-resistant and cisplatin-sensitive human osteosarcoma cells.

The effect of modulation of protein kinase C (PKC) activity by 12-O-tetradecanoylphorbol-13-acetate (TPA) on cisplatin cytotoxicity was examined in a human osteosarcoma U2-OS cell line and in a U2-OS variant (U2-OS/Pt) selected after continuous exposure to increasing concentrations of cisplatin. U2-OS/Pt cells showed a 7.5-fold resistance to the drug. A 24 h exposure of cells to TPA caused a potentiation of cisplatin cytotoxicity in sensitive and in resistant cells; under these conditions, PKC activity was shown to be down-regulated. In contrast, a short-term exposure of cells to TPA did not affect cisplatin cytotoxicity in U2-OS or in U2-OS/Pt cells. These results support the involvement of PKC in cellular response to cisplatin. However, this enzyme is probably not directly implicated in the mechanisms of acquired resistance in this cell system.

Effects of treatment with octreotide in acromegalic patients--a multicenter Italian study. Italian Multicenter Octreotide Study Group.

Treatment of acromegaly is effective in reversing the reduced life-span of patients only when serum growth hormone (GH) concentrations are lowered to less than 2.5 micrograms/l. Usual treatments achieve this goal in no more than 50-60% of patients. The effects of octreotide were studied in a prospective, open label study with 68 acromegalic patients enrolled in 10 Italian centers. Octreotide was administered sc at a dose of 100 micrograms t.i.d. for 1 year. After 3 months of therapy, octreotide was effective in decreasing serum GH levels below 2.5 micrograms/l in 16 out of 64 acromegalic patients (25%). Fifteen of them had pretreatment GH levels below 25 micrograms/l. Insulin-like growth factor I (IGF-I) levels normalized in about 40% of patients. No further GH reduction was observed after 1 year of treatment. The presence of abnormal GH responses to thyrotropin-releasing hormone (TRH) and gonadotropin-releasing hormone was reduced from 54 to 24% and from 16 to 12%, respectively. Tumor shrinkage was observed in 50% of 26 non-irradiated patients after 12 months of treatment. Both basal and TRH-stimulated serum prolactin levels significantly decreased in the 11 hyperprolactinemic patients. Although serum thyrotropin, free triiodothyronine and free thyroxine concentrations were not modified, a significant reduction of thyrotropin response to TRH was observed in the 9th month of therapy. In non-diabetic patients, an increase of mean blood glucose levels without modifications of fasting morning concentrations was found. About one-quarter of the patients with overt diabetes mellitus had an impairment of their metabolic control. Main clinical symptoms of acromegaly improved in 70-80% of patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Triangle map: A model of quantum chaos

We study an area preserving parabolic map which emerges from the Poincare map of a billiard particle inside an elongated triangle. We provide numerical evidence that the motion is ergodic and mixing. Moreover, when considered on the cylinder, the motion appears to follow a Gaussian diffusive process.

Fractal survival probability fluctuations

We study fluctuations of survival probability in an open quantum system classically described by a map with a mixed phase space. Our results provide the first numerical support to theoretical predictions that such fluctuations have a fractal structure, quantitatively related to the algebraic decay of the classical survival probability.

Quantum Poincare recurrences for a hydrogen atom in a microwave field

We study the time dependence of the ionization probability of Rydberg atoms driven by a microwave field, both in classical and in quantum mechanics. The quantum survival probability follows the classical one up to the Heisenberg time and then decays algebraically as P(t) approximately 1/t. This decay law derives from the exponentially long times required to escape from some region of the phase space, due to tunneling and localization effects. We also provide parameter values which should allow one to observe such decay in laboratory experiments.

Quantum resonances of the kicked rotor and the SU(q) group

The quantum kicked rotor map is embedded into a continuous unitary transformation generated by a time-independent quasi Hamiltonian. In some vicinity of a quantum resonance of order q, we relate the problem to the regular motion along a circle in a (q(2)-1) component inhomogeneous "magnetic" field of a quantum particle with q intrinsic degrees of freedom described by the SU(q) group. This motion is in parallel with the classical phase oscillations near a nonlinear resonance.

Phonemic identification defect in aphasia.

Eight-four right-handed patients with unilateral hemispheric damage (50 aphasics, 12 non-aphasic left brain-damaged and 22 right brain-damaged patients) and 53 control patients without cerebral lesions were given a test of phoneme identification which examined the S's ability to identify the acoustic boundary between the two phonemes, /d/ and /t/, expressed in terms of voice-onset time (VOT). Phonemic identification defect (PID), defined with reference to the performance of the control group, was found to be virtually limited aphasics; in over 70 per cent of them, the identification of the boundary zone between voiced and voiceless consonants along the VOT continuum was either impossible or abnormal, While neither the fluency - nonfluency dimension of speech nor the level of comprehension seemed to be crucially associated with PID, some evidence pointed to disordered phonemic output as to one dimension of aphasia that is specifically related to it.

[Effect of GH/IGF-I deficiency on bone and collagen turnover in children and adults with GH deficiency]. / Effetti della carenza di GH/IGF-I sul turnover osseo e collagene in bambini ed adulti con deficit di GH.

Serum bone Gla protein (BGP), marker of osteoblastic function, carboxyterminal cross-linked telopeptide of type I collagen (ICTP), index of bone resorption, and aminoterminal propeptide of type III procollagen, marker of collagen synthesis, were evaluated in children with GH deficiency (GHD), in adults with childhood-onset GHD and in adults with acquired GHD in adultlife. In children with GHD, serum BGP (12.7 +/- 0.5 ng/ml), ICTP (8.5 +/- 0.9 ng/ml) and PIIINP (3.4 +/- 0.4 ng/ml) were significantly lower (p < 0.0001, p < 0.0001 and p < 0.001, respectively) than those observed in a sex and age matched control group (BGP:18.9 +/- 0.9 ng/ml, ICTP: 14.4 +/- 0.6 ng/ml, PIIINP: 6.7 +/- 0.7 ng/ml). In adults with childhood onsed GHD, BGP levels (3.7 +/- 0.4 ng/ml) were significantly lower (p < 0.0001) than those recorded in a sex and age matched control group (5.4 +/- 0.1 ng/ml), while ICTP (4.7 +/- 0.7 ng/ml) and PIIINP (3.7 +/- 0.5 ng/ml) levels were similar to those found in controls (ICTP: 4.1 +/- 0.3 ng/ml; PIIINP: 3.3 +/- 0.2 ng/ml). In adults with acquired GHD, serum BGP (5.3 +/- 0.4 ng/ml), ICTP (3.8 +/- 0.4 ng/ml) and PIIINP (3.6 +/- 0.3 ng/ml) levels were not significantly different from those recorded in controls (BGP: 5.4 +/- 0.1 ng/ml, ICTP: 4.1 +/- 0.3 ng/ml, PIIINP: 3.3 +/- 0.2 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Stability of quantum motion: beyond Fermi-golden-rule and Lyapunov decay.

We study, analytically and numerically, the stability of quantum motion for a classically chaotic system. We show the existence of different regimes of fidelity decay. In particular, when the underlying classical dynamics is weakly chaotic, deviations from Fermi-golden-rule and Lyapounov regimes are observed and discussed.

Quantum phase transition in the Frenkel-Kontorova chain: from pinned instanton glass to sliding phonon gas.

We study analytically and numerically the one-dimensional quantum Frenkel-Kontorova chain in the regime where the classical model is located in the pinned phase characterized by the gaped phonon excitations and devil's staircase. By extensive quantum Monte Carlo simulations, we show that for the effective Planck constant Planck smaller than the critical value Planck(c) the quantum chain is in the pinned instanton glass phase. In this phase, the elementary excitations have two branches: phonons, separated from zero energy by a finite gap, and instantons that have an exponentially small excitation energy. At Planck = Planck(c) the quantum phase transition takes place and for Planck > Planck(c) the pinned instanton glass is transformed into the sliding phonon gas with gapless phonon excitations. This transition is accompanied by the divergence of the spatial correlation length and appearance of sliding modes at Planck > Planck(c).

Fractal spin glass properties of low energy configurations in the Frenkel-Kontorova chain.

We study, numerically and analytically, the classical one-dimensional Frenkel-Kontorova chain in the regime of pinned phase characterized by phonon gap. Our results show the existence of exponentially many static equilibrium configurations that are exponentially close to the energy of the ground state. The energies of these configurations form a fractal quasidegenerate band structure that is described on the basis of elementary excitations. Contrary to the ground state, the configurations inside these bands are disordered.

Regular and anomalous quantum diffusion in the Fibonacci kicked rotator.

We study the dynamics of a quantum rotator, impulsively kicked according to the almost-periodic Fibonacci sequence. A special numerical technique allows us to carry on this investigation for as many as 10(12) kicks. It is shown that above a critical kick strength, the excitation of the system is well described by regular diffusion, while below this border it becomes anomalous and subdiffusive. A law for the dependence of the exponent of anomalous subdiffusion on the kick strength is established numerically. The analogy between these results and quantum diffusion in models of quasicrystals and in the kicked Harper system is discussed.

Synthesis and LC characterization of clenbuterol molecularly imprinted polymers.

Highly selective non-covalent clenbuterol (CL) imprinted polymers were prepared using methacrylic acid as monomer and ethylene glycol dimethacrylate as cross-linking agent. HPLC experiments with columns packed with this material showed that CL are selectively recognised with respect to all other adrenergic substances studied using a phosphate buffer/acetonitrile eluent. The separation was strongly dependent on pH and the organic/aqueous phase ratio. An important contribution to the recognition mechanism from hydrophobic interactions was found at higher water content. These results demonstrate that a novel family of absorbents with high selectivity for CL was obtained which can be exploited in solid phase extractions or as recognition elements for selective sensors.

[Complication of erroneous application of an IUD. Rapid hysterographic resolution of diagnostic problems]. / Incidente da errata applicazione di dispositivo intrauterino (IUD). Rapida risposta isterografica ai questii diagnostici.

PIP: This article reports on an observation case of traumatic hemoperitoneum caused by uterine perforation due to an incorrectly applied coil IUD. After careful examination of the various diagnostic criteria employed in recovering coils in which the thread cannot be retrieved, hysterography is recommended. This technique, previously suggested by Pesetto, is judged to be the only simple way to resolve even complex cases in the space of a few minutes. (author's modified)^ieng

[Clinical problem caused by intrauterine devices with missing tails]. / Il problema clinico degli IUD in caso di "scomparsa dei fili".

PIP: The cases of disappearance of IUD strings are numerous; complications can offur only if the disappearance is caused by dislocation of the device inside the uterine cavity, in which case uterine perforation is possible. Hysterography is advisable in difficult cases, surgical removal of the IUD in most other cases. This article reports 12 cases of disappearance of IUD strings; in 3 cases the strings were discovered in the endocervix, in 7 cases dilatation of the cervix was necessary, and in 2 cases laparotomy was performed. Diagnosis for the proper retrieval of IUD strings should be made according to every specific case. It must also be remembered that a correct technique of IUD insertion can often avoid later complications, and should at all times be performed by specialist only.^ieng