Temperature-induced phase transitions in the rock-salt type SiC: a first-principles study.

The phase transitions in the rock-salt type SiC (B1-SiC) under decompression are studied in the framework of first-principles molecular dynamics simulations up to room temperature. The transformation pathways were determined based on an analysis of the symmetry and phonon spectra of high-symmetry transient structures identified in the simulations. The plausible pathways of the transformation of B1-SiC into the 3C-, 2H-, 4H-, 12R-SiC polytypes were suggested. The transformation paths were found to depend on both the availability of soft phonon modes in an unreconstructed phase and the initial conditions of the simulation. It is shown that an increase in cell volume at decompression leads to the condensation of a certain phonon mode. As a result, an intermediate state forms due to the atomic displacements and to subsequent strains related to this mode. All the decompressed structures were compressed back under pressure of 120-250 GPa depending on the type of the decompressed phase and simulation temperature that was in the range of 300-1200 K. The suggested scheme of structural identification can be used to determine the transition paths for the structural transformations of other similar structures under pressure.

Ground-state properties of rare-earth metals: an evaluation of density-functional theory.

The rare-earth metals have important technological applications due to their magnetic properties, but are scarce and expensive. Development of high-performance magnetic materials with less rare-earth content is desired, but theoretical modeling is hampered by complexities of the rare earths electronic structure. The existence of correlated (atomic-like) 4f electrons in the vicinity of the valence band makes any first-principles theory challenging. Here, we apply and evaluate the efficacy of density-functional theory for the series of lanthanides (rare earths), investigating the influence of the electron exchange and correlation functional, spin-orbit interaction, and orbital polarization. As a reference, the results are compared with those of the so-called 'standard model' of the lanthanides in which electrons are constrained to occupy 4f core states with no hybridization with the valence electrons. Some comparisons are also made with models designed for strong electron correlations. Our results suggest that spin-orbit coupling and orbital polarization are important, particularly for the magnitude of the magnetic moments, and that calculated equilibrium volumes, bulk moduli, and magnetic moments show correct trends overall. However, the precision of the calculated properties is not at the level of that found for simpler metals in the Periodic Table of Elements, and the electronic structures do not accurately reproduce x-ray photoemission spectra.

First-principles study of elastic and stability properties of ZrC-ZrN and ZrC-TiC alloys.

Ab initio calculations of the elastic constants for several cubic ordered structures of zirconium carbonitride (ZrC(x)N(1-x)) and zirconium-titanium carbide (Zr(x)Ti(1-x)C) alloys were carried out. The calculations of total and formation energies, bulk modulus and elastic constants as functions of composition were performed with an ab initio pseudo-potential method. The predicted equilibrium lattice parameters are slightly higher than those found experimentally (on average by 0.2-0.4%). The predicted formation energies indicate that the ZrC(x)N(1-x) alloys are stable even at 0 K in the whole concentration range, while the homogeneous Zr(x)Ti(1-x)C alloys can be stabilized only at high temperatures. Spinodal decomposition of the latter alloys into cubic domains takes place over a wide range of compositions and temperatures. For the carbonitrides, the shear modulus G, the Young's modulus E and the Poisson ratio σ reach an extremum for carbon-rich alloys, and this is attributed to a maximum value of the shear modulus C(44) that corresponds to a valence-electron concentration in the range of 8.2-8.3. This extremal behavior finds its origin in the response of the band structure of ZrC(x)N(1-x) alloys for 0≤x≤1, caused by the monoclinic strain that determines this shear modulus. In contrast, the other shear modulus [Formula: see text] does not exhibit any extremum over the whole composition range. These results are in contrast with those for Zr-Ti carbides for which the elastic properties gradually increase from ZrC to TiC.

Testosterone replacement therapy in male late onset hypogonadism: available pharmacological strategies.

During the last few years, the general aging of the population and the growing knowledge about male hormonal changes in older age have lead the scientific community to focus on the clinical aspects of secondary hypogonadism in aging males. This syndrome is well defined by the term late-onset hypogonadism (LOH). Although the pathophysiology and the diagnostic aspects have been studied and defined and various preparations are available, the debate on androgen supplementation therapy is still ongoing. As the spectrum of effects of endogenous testosterone is essentially based on its metabolism to dihydrotestosterone and estradiol, testosterone is the treatment of choice for male hypogonadism. The aim of the therapy is to establish a physiological concentration of serum testosterone in order to correct the androgen deficiency, relieve its symptoms and prevent long-term sequelae. All of the available products, despite their varying pharmacodynamic and pharmacokinetic profiles, are able to reach this goal. Here we examine the indications for therapy, the characteristics of the different routes of administration and how to monitor therapy in order to make the treatment safe and effective.

Frequency and determinants of erectile dysfunction in Italy.

OBJECTIVE: To analyze the prevalence and risk factors for erectile dysfunction (ED) in Italy in a cross-sectional study. METHODS: Eligible for the study were men aged 18 years or more, randomly identified by 143 general practitioners among their registered patients during the period January 1996 to February 1997. ED was defined as the impossibility to achieve and maintain an erection sufficient for satisfactory sexual performance. RESULTS: Of the 2, 010 men interviewed, 257 (12.8%) reported ED. The prevalence increased with age, from 2% in men aged 18-39 to 48% in those >70 years (tested for trend, p = 0.0001). A history of cardiopathy, diabetes, hypertension, neuropathy, thrombotic/hemorrhagic stroke, peripheral vascular disorders, pelvic/medullary injury and pelvic surgery/radiation all increased the risk of ED. The association of hypertension and diabetes tends to increase the risk of ED. In comparison with nondiabetic and nonhypertensive men, the odds ratio (OR) was 1.4 (95% confidence interval (CI), 0.7-3.2) for hypertensive men without diabetes, 4.6 (95% CI, 1.6-13.7) for diabetic men without hypertension and 8.1 (95% CI, 1.2-55.0) for men with diabetes and hypertension. In comparison with never smokers, the OR of ED was 1.7 (95% CI, 1.2-2.4) for current smokers and 1.6 (95% CI, 1.1-2.3) for ex-smokers and increased with duration of the habit. CONCLUSIONS: The study offers a quantitative estimate of the prevalence of ED and of its main risk factors in Italian men.

[Tridimensional ultrasonography in andrology]. / L'ecografia tridimensionale in andrologia.

Three-dimensional ultrasound has already been employed to improve detection and characterization of the masses in various organs. The system can also be expected to improve qualitative evaluation of vessel pathology. Three-dimensional ultrasound could offer an additional contribution even in Andrology, in at least three fields: in the best evaluation of the anatomical structures; in most accurate measurement of the volumes of the organs; in the study of the Peyronie's disease, for the availability of the coronal plain.

[Unexplained male infertility and testicular microlithiasis]. / Infertilità maschile inspiegata e microlitiasi testicolare.

In this study we analyse the frequency of testicular microlithiasis in a group of otherwise infertile healthy men, visited at the Andrology Service of Prato Hospital. Here the ultrasound machine is located in the ambulatory and it is possible to use it during the first visit of the patient, as we have done in 250 consecutive infertile men. This examination, easy and not invasive, has been performed to evaluate the pampiniform plexus to find possible varicocele, epydidimis for obstructive signs and testes for the presence or absence of parenchymal calcifications or masses. We found 106 positive sonographic records (42.4%) for scrotal diseases. Between them, two cases of testicular microlithiasis (0.8% of 250 consecutive ultrasound examinations and 1.7% in the last twelve months). Our data, although with a lower incidence than literature, show the importance of ultrasound examination in absence of specific diagnostic questions too, in the study of male infertility. Clinical management of testicular microlithiasis is difficult, due to loss of treatment and to cancer risk. A long term follow up is request, with periodical (6-12 months) sonographic controls. A classification (here we propose) can be useful for a more precise monitoring.

Determination of an effective dose of eltenac and its comparison with that of flunixin meglumine in horses after experimentally induced carpitis.

OBJECTIVES: To titrate a clinically effective eltenac dosage (0.1, 0.5, and 1.0 mg/kg of body weight), compared with vehicle only, and to compare efficacy of the most effective eltenac dosage with that of 1.1 mg of flunixin meglumine/kg. ANIMALS: 40 healthy horses, ranked after model induction on the basis of lameness severity, were randomly assigned to 5 treatment groups, with 4 replicates of 10 horses each. PROCEDURE: On day -5, after surgical preparation of the left carpal region, 0.7 ml of Freund's complete adjuvant was injected into the intercarpal space. Horses were observed daily, from the day of carpitis induction to day 0, when stride length was used as the method of ranking horses for randomization to treatment assignment. Treatments were administered i.v. once daily for 3 consecutive days, starting on day 0. Prior to carpitis induction on day -5, and at time 0 (pretreatment), 2, 4, 12, 24, 36, 48, 60, 72, and 96 hours after treatment initiation, resting respiratory rate and pulse, rectal temperature, carpal circumference, carpal flexion angle, stride length, carpal hyperthermia, and signs of carpal pain were recorded. RESULTS: Compared with the vehicle and 0.1 mg of eltenac/kg, 0.5 and 1.0 mg/kg caused statistically significant improvements (ie, reduction of carpal circumference, increase in carpal flexion angle, and increase in stride length of the affected limb), but values did not differ significantly between the 2 dosages. Thus, a dose-response plateau for eltenac was reached at 0.5 mg/kg. Comparison with flunixin meglumine at a dosage of 1.1 mg/kg did not indicate significant differences between the 2 treatment groups at the pivotal time of 96 hours for carpal circumference, carpal flexion angle, stride length, carpal hyperthermia, and signs of carpal pain. Adverse reactions were not observed. CLINICAL RELEVANCE: Under conditions of this study, a dosage plateau for eltenac was determined (0.5 mg/kg) that was statistically equivalent to eltenac (1.0 mg/kg) and flunixin meglumine (1.1 mg/kg) in a 3-day i.v. dosing regimen.

Sedative and analgesic effects of detomidine and romifidine in horses.

In a double blind study, eight horses were treated intravenously at seven-day intervals with detomidine at doses of 10, 20 and 40 micrograms/kg, or with romifidine at doses of 40, 80 and 120 micrograms/kg, or with a placebo solution. Their sedative and analgesic effects were evaluated by objective measurements and by a clinician at 15-minute intervals for three hours and the horses' instability in stocks, locomotor ataxia and heart rate were recorded simultaneously. The administration of both drugs at all doses resulted in sedation. The sedation achieved with romifidine was significantly shallower and shorter-lived than with detomidine at the recommended doses (P < 0.05). The results obtained with the highest dose of romifidine were in some cases significantly inferior and shorter-lived than those obtained with the medium dose (P < 0.05). Detomidine at the 10 micrograms/kg dose was similar in its effects to the two highest doses of romifidine. At all doses detomidine had analgesic properties against the effects of electrical pain stimulation at the withers, the coronary bands on the front and hind legs, and in the perianal region, which were dose-dependent in depth and duration, whereas romifidine was devoid of any analgesic effect. Instability and ataxia were more pronounced with detomidine than with romifidine but the effects were only slight to moderate and not regarded as a hindrance to procedures for which sedation is needed. Bradycardia was evident with both drugs at all doses; its severity and duration was related to the sedative properties of the drugs and was dose related. No other side effects were observed.

[Echographic aspects of gynecomastia]. / Aspetti ecografici della ginecomastia.

Gynecomastia is a size increase of man's breast, due to non neoplastic ductal and glandular stroma proliferation. Prevalent ductal proliferation defines the "florid" type, while prevalent stroma increase defines the "quiescent" type. Pseudo-gynecomastia is a non glandular volume increase. Sonography is able to recognize the different parts of normal male breast and to diagnose gynecomastia. Moreover by sonography we can distinguish three echo-patterns linked to the anatomopathologic pattern which can lead therapy.

Use of a novel non-steroidal anti-inflammatory drug, nimesulide, in the treatment of abacterial prostatovesiculitis.

Nimesulide, a novel non-steroidal anti-inflammatory drug, was used in cases of abacterial prostato-vesiculitis. Thirty patients with a mean age of 33.7 years (range 18-58) were studied. Nimesulide was administered orally 100 mg b.i.d. for three cycles of 10 d each. Dysuric symptoms, semen analysis, and transrectal ultrasound were examined during the study. The concentration-time curves of nimesulide (NIM) and its metabolite, hydroxynimesulide (OH-NIM) in seminal fluid were also evaluated after single oral administration (100 mg) using an HPLC technique. Following administration of the drug, the Cmax was reached in seminal fluid at the second hour for NIM (with a mean value +/- SD of 0.58 +/- 0.13 micrograms ml-1) and at the fourth hour for OH-NIM (2.98 +/- 0.38 micrograms ml-1). Maximal seminal fluid concentrations compared to blood plasma levels were observed at the fourth hour for both substances (31.73 +/- 2.34% for NIM; 31.87 +/- 8.66% for OH-NIM. Dysuric symptoms were relieved in 20 (66%) patients. A clear amelioration of inflammatory signs were observed at transrectal ultrasound evaluation in 16 (54%) patients. No statistically significant changes of sperm count and motility in the whole sample were observed, while a significant reduction in the number of abnormal forms occurred. From these results, nimesulide appears to be an effective anti-inflammatory drug with a good diffusion into the genital apparatus and low side-effects.

Treatment of abacterial prostato-vesiculitis with nimesulide.

The efficacy and tolerability of nimesulide were assessed in the treatment of patients with prostato-vesiculitis. In a noncomparative investigation, 30 patients received oral nimesulide 100mg twice daily for three 10-day cycles. Micturition-related symptoms were resolved in 20 patients and clear amelioration of inflammatory signs was observed with transrectal ultrasound in 16 patients. Abnormal sperm forms decreased from 57 to 49% (p < 0.001). In a comparative investigation, 40 patients received nimesulide 200mg twice daily or ketoprofen 100mg twice daily via the rectal route. Patients and physicians expressed an overall opinion on efficacy in favour of nimesulide. In a pharmacokinetic study of healthy volunteers who received oral nimesulide 100mg as a single dose, the mean maximum nimesulide concentration (0.58 +/- 0.13 mg/L) in seminal fluid was achieved after 2 hours while the maximum seminal fluid: blood plasma ratio 0.32 +/- 0.02 was observed after 4 hours. These data suggest that nimesulide is an effective NSAID in the treatment of abacterial prostato-vesiculitis and also demonstrate that this drug has a favourable disposition within the genital tract.

[Recent diagnostic and therapeutic aspects in male sexual impotence]. / Recenti aspetti diagnostici e terapeutici dell'impotenza sessuale maschile.

Male sexual impotence is the symptom of an alteration of central and peripheral mechanism neuropsychoendocrine, vascular and neurological. Nowadays it affects 8-10% of sexually active population. In some diseases, like diabetes and uremia, it can reach very high percentages of incidence. At our Andrology Center 35% of referrals are represented by sexual complaints. In the last years the diagnostic accuracy has increased, narrowing the percentage of unknown causes. Vasculopathy represents the most relevant pathological condition associated with impotence: it can affect both arterial and venous vessels. The new medical technologies and procedures permit an increase of the life span but often affecting the quality of life. Therefore, the iatrogenic causes of impotence, both pharmacological and surgical, are growing. A modern diagnostic approach starts with an accurate clinical history and physical examination, followed by an NPT (nocturnal penile tumescence) test and/or ICI (intracavernosal injection) with a standard dose of PGE1 and Doppler flowmetry of penile arteries. An endocrine evaluation (LH, testosterone and prolactin) is also performed. Further investigation of a vascular dysfunction is represented by more invasive procedures, like arteriography, cavernosography and cavernosometry. A suspect of neurological disease is confirmed by sacral evoked potentials. According to the findings of these examinations, a correct therapeutical approach can be applied in 100% of cases. An endocrine treatment is adequate only when a clear reduction of T plasma level or hyperprolactinemia are present. The treatment of other central disorders causing psychoneuroendocrine impotence is promising, but still under investigation. The intracavernosal injection of vasoactive drugs, apart from having revolutionized the diagnostic approach to the impotent patient, represents a clear standpoint in medical management of impotence, particularly in vascular and neurological diseases. The great advancement in the technology of penile prostheses has allowed the development of valuable and reliable tools to be used in selected cases.

[Endocrine therapy of sexual impotence in men]. / La terapia endocrina dell'impotenza sessuale maschile.

Male sexual activity is in all mammalian species, included man, androgen-dependent. The role of testosterone (T) starts already during intrauterine life. It continues thereafter, inducing the development of sexual secondary characteristics and libido. Therefore T has represented the "classical" treatment of male sexual dysfunctions. In the therapeutic routinary use T is employed ad ester, like cipionate, enanthate and other i.m., undecanoate per os. When a pituitary defect is present and the testicular receptors are functioning a treatment with HCG can be employed.

[The Rigiscan system in the diagnosis of male sexual impotence]. / Il Rigiscan system nella diagnostica dell'impotenza sessuale maschile.

The article reviews historical basis of Nocturnal Penile Tumescence (NPT) test and the evolution of techniques to perform it. From complex and time-consuming instruments, modern technology has brought us to the use of the Rigiscan system. This is a transportable (home or office usable), computerized method to detect change of penile rigidity and circumference during sleep-related spontaneous-or daytime induced-erections. While the instrument was mainly developed to perform NPT tests, it is nowadays used to record penile rigidity in realtime after the intracavernous injection of vasoactive drugs. In our experience, normal parameters to refer for a NPT evaluation are: number of erectile episodes: 4-5 per night; mean duration od episodes: > 30 minutes; increase of penile circumference: > 3 cm (base loop) and > 2 cm (tip loop); maximal rigidity: > 70% (both base and tip). Reference parameters for realtime monitoring after intracavernous injection of PGEI are: latency of response: < 12 minutes; duration (with a stable plateau): > 30 minutes; constant plateau: > 70%; increase of penile circumference: > 3 cm (base) and > 2 cm (tip). The use of these reference parameters, together with the data coming from other procedures (e.g. penile arterial flow with the Doppler), allows a better diagnostic accuracy in the approach to sexual impotence.

Effects of progesterone administration on follicle-stimulating hormone and prolactin release in estrogen treated eugonadal adult men.

In order to investigate the modulatory effect of steroids on FSH secretion in vivo, we studied 16 human males, aged 51-81 years, affected by prostatic carcinoma. They were given estradiol or E2 plus progesterone (P), added at different times during E2 treatment. Daily blood samples were collected in order to determine LH, FSH, and PRL levels; moreover, blood samples were collected at 2 h intervals for 12 h on the day of P administration. We observed the expected biphasic effect on LH secretion, whereas daily basal FSH levels, during E2 treatment, decreased gradually and progressively from the first day until the end of the study. FSH levels exhibited, after P administration, wide fluctuations, with peak levels observed from 2 to 6 h after P in 4 of 6 patients studied (at 72 h during E2 treatment). A clear trend toward FSH increase was also observed in 3 out of 5 patients in whom P was administrated 96 h after starting E2 administration. In this case, FSH increases were delayed, becoming evident between 8th and 10th h after P injection. Finally, during E2 administration basal PRL levels showed a progressive increase, which was significant in all three groups. In conclusion, these data confirm the biphasic effects of estrogen administration on LH secretion in eugonadal adult human males; while estrogens alone showed an inhibitory effect on FSH secretion, the addition of P induced also a positive action, resulting in a clear FSH peak in some patients tested. The time course of E2 and P administration seems to be critical for the hormone response pattern.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrasound monitoring of testis and prostate maturation in hypogonadotropic hypogonadic males during gonadotropin-releasing hormone treatment.

The effects of the administration of gonadotropin-releasing hormone (GnRH) on the increase of testis and prostate volume was monitored by ultrasound in six patients affected by idiopathic hypogonadotropic hypogonadism. A significant increase of testis volume was observed after 90 and 180 days (6.65 versus 3.32 mL, 99.1% net increase and 8.47 mL, 176.8% increase, respectively) of pulsatile GnRH treatment. A similar increase of prostate volume was observed at day 90 (12.67 versus 7.78 mL, 70.3% net increase) and day 180 (14.70 mL, 97.7% increase). The ultrasound monitoring of the modifications of testis and prostate volume may represent a biological assay of the effects of GnRH treatment and offer additional data on the response of target organs to the hormonal treatment.