Ureteroscopy and laser lithotripsy: technologic advancements.

Ureteroscopic lithotripsy has evolved since the first reported cases employing rigid rod-lens endoscopes and stiff ultrasonic lithotrites. Fiber optics facilitated rigid endoscope miniaturization and the development of a steerable, deflectable flexible ureteroscopes. Over 30 years of technical innovations culminating in digital imagers and powerful, precise laser lithotrites, complimented by progressive endoscopic techniques have produced efficient endoscopic therapies with minimal morbidity and commonly performed in an outpatient setting.

A study of van der Waals complexes of 1,2-dichloroethane in paraffin oil by FTIR spectroscopy and ab initio calculations.

Weak molecular interactions of 1,2-dichloroethane dissolved in paraffin oil were investigated by FTIR spectroscopy. Occurrence of isosbestic points in the spectra along with the factor analysis showed that DCE⋯DCE dimers are formed in solutions at DCE concentrations between 7 and 15 vol.%. It was found that both trans and gauche conformers are involved in the complexation, forming a tg-dimer. From the spectra collected at 200-222 K, the complexation enthalpy was determined: -4.2±0.4 kcal mol(-1). The equilibrium geometry of tg-dimer and the vibrational frequencies were determined from the density functional calculations performed at B3LYP/6-311++G(d,p) and 6-31G(d,p) levels. The C-C bonds of the two molecules involved in tg-dimers were found to be oriented nearly perpendicular to each other. The complexation energy calculated using 6-31G(d,p) and 6-311++G(d,p) basis sets was found to be -1.59 and -1.52 kcal mol(-1), respectively.

Conformational mobility of small molecules in glass-forming solutions studied by FTIR spectroscopy.

Small molecules with two or more stable conformations when embedded in a glass-forming liquid (matrix) serve the role of "conformational probes", i.e., their conformational transitions are used to follow local mobility in the matrix. In the present study, conformational probes were embedded in low-molecular-weight glass-forming liquids, and the molecular mobility was studied in a broad temperature range including the glass transition temperature (T(g)). Paraffin oil, dibutylphthalate, bis(2-ethylhexyl)phthalate and isopropylbenzene were used as glass-forming liquids while 1,2-dichloroethane, 1,2-diphenylethane, chlorocyclohexane and bromocyclohexane were used as conformational probes. For some of the matrix/probe systems, the conformational mobility was found to freeze-in at T(g), while for the others it froze-in at certain temperatures T(f)

The vibrational spectra of 1,3-dithiane-1-oxide and 1,3-dithia-1-oxocyclohept-5-ene.

The IR spectra of 1,3-dithiane-1-oxide (I) and 1,3-dithia-1-oxocyclohept-5-ene (II) were recorded in solution, solid and liquid phase over 4000-400 cm(-1) spectral range. It was found that both (I) and (II) in liquid phase and solutions exist in two conformations: (I) chair-e (Ce) and chair-a (Ca) with equatorial and axial positions of the S=O bond, respectively, and (II) chair-e (Ce) and boat-e (Be). The intensity variations with temperature (300-180 K) of the bands 632 (Ca) and 644 cm(-1) (Ce) of (I) in acetone-d6 and the bands 482 (Be) and 448 cm(-1) (Ce) of (II) in melt were employed in Van't Hoff plot and gave the values DeltaH degrees (Ca-Ce) = 380 +/- 40 cal mol(-1) (I) and DeltaH degrees (Be-Ce) = 400 +/- 100 cal mol(-1) (II). Ab initio calculations were carried out with the Gaussian 98 program using the basis set 6-31G(d) for (I) and 6-311++G(d,p) for (II). The energy difference between Ca and Ce conformations for (I) and Be and Ce for (II) are in a good agreement with experimental results. Vibrational frequencies for both conformations (I) and (II) were calculated. After appropriate scaling a reasonably good agreement between the experimental and calculated wave numbers was obtained.

Vibrational spectra and structure of isopropylbenzene.

Infrared spectra (4,000-400 cm(-1)) and Raman spectra (1,700-40 cm(-1)) of the liquid and two crystalline solids of isopropylbenzene (cumene) and isopropylbenzene-d(12) have been recorded. The spectra indicate that in the liquid and crystalline solids isopropylbenzene exists in planar conformation only (CH bond is in the plane of the benzene ring). An assignment of the observed band wave numbers both isopropylbenzene and isopropylbenzene-d(12) is discussed by comparison with normal mode wave numbers and IR intensities calculated from ab initio 6-31G (d) force fields.

Application of probability circles analysis to the construction of calibration curves for infra red spectroscopy.

A new method, based on the presentation of initial data in the form of probability circles (PC), has been developed for constructing a calibration curve, which shows a monotonic dependence with respect to the given concentration. The centre of the reference probability circle is defined by its mean value and the radius of the circle is calculated as the value of the standard deviation of the sampling considered. The comparative probability circle is defined by the same corresponding parameters but rotated, relative to the initial reference circle, by an angle, which is related to the Pearson's correlation coefficient (PCC). The two parameters of the PCC and the statistical proximity factor (PCF), which defines the positions of the centres of the circles relative to each other, can be chosen as statistical parameters for the construction of the desired calibration curve. Experiments realized with the mixture of two liquids (chloroform serves as the basic matrix) and acetone (serves as an additive) confirm the efficiency of this new analytical method and demonstrate a possible increase sensitivity for the detection of lower concentration limit by approximately one order of magnitude. This new approach, which is free from model assumptions, and having very clear geometrical meaning, can be applied for different types of spectra and has many potential applications in the construction of calibration curves for different additives embedded within different matrices.

A cryosolution infrared and ab initio study of the van der Waals complexes of cyclopentene with hydrogen chloride and boron trifluoride.

The formation of weak molecular complexes of cyclopentene with HCl and BF3, dissolved in liquid argon is investigated using infrared spectroscopy. Evidence is found for the formation of 1:1 complexes in which the Lewis acid under study binds to the CC double bond. At higher concentrations of HCl, weak absorption bands due to 1:2 species are also observed. From spectra recorded at different temperatures between 92 and 127 K, the complexation enthalpies for CP.HCl and CP.BF3 are determined to be -9.5(3) and -16.1(9) kJ mol-1, while for CP.(HCl)2 a value of -17.0(6) kJ mol-1 is obtained. For the 1:1 and 1:2 complexes, structural and spectral information is obtained from ab initio calculations at the MP2/6-31+G(d) level. Using free energy perturbation Monte Carlo simulations to calculate the solvation enthalpies and statistical thermodynamics to account for zero-point vibrational and thermal contributions, the complexation energies for CP.HCl and CP.(HCl)2 are estimated from the experimental complexation enthalpies to be -17.4(14) and -34.0(20) kJ mol-1, while the value for CP.BF3 was derived to be -23.4(22) kJ mol-1. The experimental complexation energies are compared with the theoretical values derived from the MP2/6-31+G(d) potential energy surfaces and with single point energies calculated at the MP2/6-311++G(3df,2pd) level.

The vibrational spectra and conformations of ethylbenzene.

Infrared spectra (4000-250 cm-1) of the liquid, amorphous, crystalline solids and solutions in liquid krypton and Raman spectra (2500-20 cm-1) of the liquid as well as the amorphous and crystalline solids of ethylbenzene and its deuterated analogue-ethylbenzene-d(10) have been recorded. The spectra indicate that in the liquid and amorphous solids a small amount of a second conformer is present, whereas only one conformer remains in the crystalline phases. Assignments of the observed band wave numbers are discussed by comparison with normal mode wave numbers and IR and RS intensities calculated from ab initio 6-31G force fields and optimised geometries for both conformers for two species. All of the normal modes of conformers have been assigned.

[Dependence of the intensity of 2,4,6-trinitrotoluene-induced mutagenesis on the physiological state of tester strains of Salmonella typhimurium]. / Zavisimost' velichiny indutsirovannogo 2,4,6-trinitrotoluolom mutageneza ot fiziologicheskogo sostoianiia testernykh shtammov Salmonella typhimurium.

The dependence of the mutagenic potential of 2,4,6-trinitrotoluene (TNT) on the growth phase of the Salmonella typhimurium tester strains TA100 and TA98 is shown. The mutagenic potential proved to be maximal for log-phase cultures, being higher with strain TA100 than TA98. The amount of TNT absorbed by bacteria in the first minutes of contact varied, depending on culture age, and was the largest at the beginning of the exponential growth phase. A direct relation between the number of microbial cells and the amount of TNT absorbed from the medium was shown. The analysis of infrared (IR) spectra of cells after a 3-min contact with TNT, demonstrated that, at physiological temperatures, 2.4% of the original amount of TNT was present in cells of the tester strain in an unaltered form, while, at a lowered temperature, this value was 10.3%. Thus, the retardation of physiological processes in the cell changes the intensity of mutagen absorption and transformation. It is emphasized that an accurate assessment of mutagenicity should take into account the physiological state of tester bacteria.