Phase transformation in the C form of myristic-acid crystals and DFT calculations.

In this study, the vibrational frequencies of myristic acid (CH3(CH2)12COOH) were obtained using density functional theory calculations, and the results were compared with experimental Raman and infrared data. Additionally, Raman spectra of crystalline myristic acid were recorded in the 300-20 K range. Raman spectroscopy gives important insights into the effect of low temperatures on its monoclinic phase. X-ray diffraction was performed from 298 to 133 K to provide additional information about the cryogenic behavior of the crystals. These undergo a phase transformation, which was confirmed by differential scanning calorimetry through an enthalpy anomaly observed at low temperatures. Raman spectra and X-ray diffraction refinement of the cell parameters in combination with differential scanning calorimetry at low temperatures revealed slight modifications, confirming a conformational change in the myristic acid molecules involving rearrangement of dimers within the unit cell.

Polarized Raman and Infrared Spectroscopy and ab Initio Calculation of Palmitic and Stearic Acids in the Bm and C Forms.

A complete experimental study on the vibrational properties of palmitic and stearic acids crystallized in the Bm and C forms, both belonging to the monoclinic system with the P21/a (C2h5) space group, through polarized Raman and infrared spectroscopy, is reported in this paper. Density functional theory calculations were also performed to assign the normal modes and to help in the interpretation of the experimental data. The different polarizations were compared and their influence on the spectral profiles, in both the lattice and the internal mode regions, was discussed. In general, the Raman and infrared spectra exhibit accentuated differences among the polymorphic forms, which are associated with the different molecular modifications, defined as gauche and all-trans conformations. Insights about interaction among different groups are also furnished.

Conformational change in the C form of palmitic acid investigated by Raman spectroscopy and X-ray diffraction.

Fatty acids are substances found in most living beings in nature. Here we report the effect of the low temperature in the vibrational and structural properties of the C form of palmitic acid, a fatty acid with 16 carbon atoms. The Raman spectra were obtained in the temperature interval from 300 to 18K in the spectral range between 30 and 3100 cm(-1). The assignment of the duly observed bands was done based on the density functional theory. On cooling, the main changes observed in the lattice mode region of the Raman spectra were interpreted as a conformational modification undergone by the palmitic acid molecules in the unit cell. The X-ray diffraction measurements were obtained from 290 to 80K showing a slight modification in the lattice parameters at about 210K. Differential scanning calorimetry (DSC) measurements were recorded between 150 and 300K and no enthalpic anomaly in the DSC thermogram was observed. These techniques provided strong evidence of the conformational change in the molecules of palmitic acid at low temperatures.

Low-temperature phase transformation studies in the stearic acid: C form.

This paper reports the temperature-dependent measurements in the C form of stearic acid. Raman scattering, X-ray diffraction, and differential scanning calorimetry measurements were performed at low temperatures. The polarized Raman spectra were measured for temperatures ranging from 8 to 300 K over the spectral range of 30-3000 cm(-1). The spectral changes observed in both the lattice vibrational modes and the internal vibrational modes regions of the Raman spectrum, allowed to identify a phase transition undergone by the stearic acid crystal occurring between 210 and 170 K and a change in the structure continues to be observed down to 8 K. The anharmonicity of some vibrational modes and the possible space groups presented by the crystal at low temperatures were also discussed. Low-temperature X-ray diffraction measurements were performed from 290 to 80 K and the results showed slight changes in the lattice parameters at ∼200 K. Furthermore, the evidence of the phase transformation was provided by the differential scanning calorimetry measurements, which identified an enthalpic anomaly at about 160 K.

KDP:Mn piezoelectric coefficients obtained by X-ray diffraction.

Crystals of pure potassium dihydrogen phosphate KH(2)PO(4) (KDP) and Mn-doped KDP (KDP:Mn) were grown from a water solution by the slow evaporation method and their piezoelectric properties were studied by X-ray diffraction methods. The results have shown an increase in the piezoelectric coefficients with the doping.

Devastating complications after brachytherapy in the treatment of prostate adenocarcinoma.

OBJECTIVE: To report a retrospective chart review of patients who developed recto-urethral fistula (RUF) or several bladder neck contracture (BNC) recurrences after brachytherapy for treating localized prostate cancer. PATIENTS AND METHODS: In the past 3 years 18 patients with devastating complications after prostate brachytherapy were referred to our centre (RUF in 11, BNC in seven; mean age 63 years, range 60-81). All patients with RUF initially underwent diverting colostomy (six cystoprostatectomy with closure of the fistula, omental interposition and urinary diversion; one prostatectomy, bladder neck closure, fistula closure with omentum flap and continent vesicostomy). Three patients had the fistula closed with gracilis muscle flap using the York-Mason approach (one had a bladder neck closure and suprapubic tube; one elected to have no treatment). All patients with BNC had received three or more procedures to resect or incise their contracture. Four had diversion with a catheterizable segment, two used an indwelling Foley catheter and one uses intermittent catheterization. RESULTS: All six patients who had cystoprostatectomy with urinary diversion have had no recurrence of their RUF. All three treated with the York-Mason procedure healed well. One developed recurrent prostate adenocarcinoma and two a secondary neoplasia in the prostate or rectum (leiomyosarcoma and neuroendocrine, respectively). The enterocystoplasty patient developed sepsis after colostomy reversal and subsequently died. In those patients with BNC, the four who underwent urinary diversion fared well; two tolerate the indwelling catheter poorly, and the seventh uses intermittent catheterization with occasional difficulty. CONCLUSIONS: Brachytherapy with or without external irradiation can be associated with severe complications. RUF managed with aggressive anterior pelvic exenteration and urinary diversion can be associated with excellent results. The York-Mason procedure in patients with an adequate urinary continence mechanism and bladder dynamics may provide good functional results. The presence of a secondary malignancy in patients deserves further investigation. Many recurrences of a BNC tend be refractory to transurethral resection/incision; indwelling catheters are then poorly tolerated and patients may require a major reconstructive procedure.

Side-effect profile of sildenafil citrate (Viagra) in clinical practice.

OBJECTIVES: Sildenafil citrate (Viagra) has been shown to be an effective treatment for erectile dysfunction. Initial studies reported a high tolerability and low incidence of certain characteristic adverse reactions. We sought to evaluate the incidence of side effects of sildenafil citrate, independent of industry support and constraints, utilizing a heterogeneous cohort of patients from a university-based practice. METHODS: A prospective, open-label, flexible-dose study of 256 patients treated with sildenafil citrate for erectile dysfunction was performed at a single institution. The patients were questioned explicitly about the occurrence of headache, flushing, dyspepsia, nasal congestion, visual changes, and other side effects. RESULTS: The adverse reactions most commonly observed were flushing (30.8%), headache (25. 4%), nasal congestion (18.7%), and heartburn (10.5%). All events were short lived and mild in nature. In the present study, 31.6% of patients experienced one or more adverse events. However, no one withdrew from the study because of the severity of these events. There was a significant association between higher doses and the occurrence of side effects. CONCLUSIONS: The incidence of adverse events attributable to sildenafil citrate may be higher than initially reported, but an explanation may be the methodology of data collection and the industry-independent nature of this study. The side-effect profile is dose related and mild. Sildenafil citrate remains a safe and well-tolerated treatment for erectile dysfunction.