Structure determination of tolbutamide

N-​[(Butylamino)​carbonyl]​-​4-​methylbenzenesulfonamide, is an antidiabetic drug which crystd. in orthorhombic space group Pn21a, with a 20.16(2)​, b 9.05(1)​, c 7.85(1) Å; Z = 4, d.(exptl.) = 1.24 and d.(calcd.) = 1.25 for Z = 4. The structure was solved by the Patterson search method and refined to R = 0.083 for 615 visually measured reflections. At. parameters are given. The structure is stabilized by H bonding between the polar ground and van der Waals interactions between the nonpolar groups. Of the three H bonds, two are weakly as they are bifurcated

The structure of 2-​piperidinotricyclo[5.2.2.02.6]​undecan-​9-​on

The title compd. is monoclinic, space group Cc, with a 24.28(4)​, b 8.76(6)​, c 14.03(2) Å, and β 108.00(9)​°; d.(exptl.) = 1.18 and d.(calcd.) = 1.16 for Z = 4 (2 mols.​/Z)​. The structure was detd. to obtain accurate information about the geometry of the mol. as there was ambiguity in the chem. structure. The structure was refined to R = 6.3​% for 1165 visually measured reflections. At parameters, bond angles and distances are given. The established structure proposed on the basis of chem. and phys. data. The new structure explains some reactions which could not be understood from the previously proposed structure

5(S)​-​cyano-​9-​oxotricyclo[4.2.1.1.4,​7]​dec-​2-​en-​8-​yl methanesulfonate

The title compd. is orthorhombic, space group Pca21, with a 10.159(5)​, b 8.656(3)​, and c 13.950(5) Å; d.(exptl.) = 1.43 and d.(calcd.) = 1.45 for Z = 4. The structure was solved by the Patterson search method and refined to R = 0.054 for 960 reflections. At. parameters, bond lengths, and bond angles are given. No H bonding is obsd. and the structure is held together by van der Waals interactions

Extended rigidity percolation and chemical thresholds in Ge-Te-Pb glasses as revealed by MDSC

Thermal analysis of Ge20Te80−xPbx (2≤x≤8) glasses has been undertaken using modulated differential scanning calorimetry (MDSC). The compositional dependence of thermal parameters is investigated. The crystallization temperatures (Tc) estimated from the total heat flow show detectable changes at compositions x=4, 6.5 and 7.5. Further, the heat capacity change at the glass transition temperature, measured from the reversible heat flow curve (ΔCpR), is found to exhibit a maximum and an inflexion at compositions x=4 and 6.5 and minimum at x=7.5, respectively. Also, the relaxation enthalpy, estimated from the area under the non-reversing heat flow curve (ΔHNR), exhibits similar features at the said compositions. From the observed MDSC results, it has been proposed that the compositions x=4 and x=6.5 denote to the onset and completion of rigidity percolation and x=7.5 corresponds to the chemical threshold of the system

Generation of femtosecond pulses by passive mode-locking of broad-band lasers using bacteriorhodopsin films

Closed-form analysis of passive mode-locking of homogeneously broadened broad-band laser systems using bacteriorhodopsin films as slow saturable absorber is presented. The analysis consists of the self-consistent approach to obtain the closed-form solutions to the mode-locked pulse energy and pulse width.The dependence of mode-locked pulse energy and pulse width on the system parameters such as the thickness of the film, the total number density of active molecules, the initial number density of molecules in B-state and the gain of the laser medium are presented in the graphical form. The analysis shows that passive mode-locking of a typical broad-band laser system like Ti:sapphire using bacteriorhodopsin film of thickness 50 μm can generate pulses of â 58 fs duration with â 90 nJ energy

Absorption characteristics of bacteriorhodopsin molecules

The bacteriorhodopsin molecule absorbs light and undergoes a series of structural transformation following a well-defined photocycle. The complex photocycle is transformed to an equivalent level diagram by considering the lifetime of the intermediate states. Assuming that only B and M states are appreciably populated at any instant of time, the level diagram is further simplified to two-level system. Based on the rate equations for two-level system, an analytic expression for the absorption coefficient of bacteriorhodopsin molecule is derived. It is applied to study the behaviour of absorption coefficient of bacteriorhodopsin film in the visible wavelength region of 514 nm. The dependence of absorption coefficient of bacteriorhodopsin film on the thickness of the film, total number density of active molecules and initial number density of molecules in B-state is presented in the graphical form

X-​ray study of silver amalgam and its stoichiometry

The powder diffraction data and cell consts. of Ag amalgam crystals grown from N​/50 AgNO3 soln. and a globule of Hg are given. The crystals are hexagonal, space group P62 or P6222, with a 8.147(2) and c 8.855(3) Å; d. (exptl.) = 12.11 and d. (calcd.) = 12.07 for Z = 12

Transient and steady state photoconductivity studies on bulk glasses and amorphous films of Ge-Te-Pb - Composition and spectral dependence

Transient photoconductivity studies have been undertaken on bulk Ge 20Te80-x Pbx glasses with varied lead content (2 ⤠x ⤠8); The composition dependence of normalized photoconductivity and photo-decay have been investigated upon white light incidence. The photoconductivity rise and its decay with time indicate that the process may best be understood in terms of the recombination within the localized states, Further, it has been found that the addition of lead results in an initial decrease in the photoconductivity, showing anomalous variations at compositions x = 5, 6.5 and 7.5. Steady state photoconductivity studies on amorphous Ge 20Te80-xPbx thin films (2 ⤠x ⤠8) have also been undertaken. The intensity dependence of steady state photoconductivity indicates the existence of continuous distribution of localized states in the mobility gap of this material, Further, the spectral dependence of photoconductivity has been studied using various interference filters. The composition dependence of steady state photoconductivity due to white light incidence, shows pronounced anomalies at x = 5, 6.5 and 7.5, Based on the present photoconductivity studies and other investigations, it has been proposed that the rigidity percolation occurs in Ge20Te 80-x Pbx glasses, over an extended composition region with the composition x = 5 (xc1) and x = 6.5 (xc2) being the onset and completion of the rigidity percolation. The composition x = 7.5 corresponds to the chemical threshold of the system

Analysis of mode-locked internally frequency doubled broad-band continuous wave lasers

Closed-form analysis of pulse evolution in the transient regime in an actively modelocked internally frequency doubled broad-band continuous wave laser is presented. The analysis enables investigation of the effect of nonlinear crystal inside the laser cavity on mode-locked pulse parameters at the fundamental frequency. It is shown that the presence of internal second harmonic crystal broadens the fundamental mode-locked pulse while accelerating the approach of the system to steady-state. The dependence of pulse parameters on the bandwidth of the tuning element, modulation depth of the active mode-locker and conversion efficiency of the frequency doubler is presented in detailed graphical form. © 1995 Indian Academy of Sciences

Electrical switching studies of lead-doped germanium telluride glasses

Samples of bulk Ge20Te80-xPbx(2 ⤠x ⤠8) glasses have been prepared by melt quenching and their electrical switching behavior has been investigated as a function of lead content and sample thickness. The samples are found to exhibit a threshold type of switching. The switching voltages are found to decrease with increase in lead content and they show an anomaly at the composition x = 5 and a minimum at the composition x = 7.5 respectively. The samples are found to withstand about 28 switching cycles, before latching permanently to the ON state