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The objectives of root canal treatment are elimination of microorganisms, removal of pulpal remnants, removal of debris, and shaping of the root canal system so that it may be obturated. The most important step in endodontic therapy is canal preparation which can be achieved by accurate working length determination. Working length determines the extent of placing the instruments into the canal, it affects the degree of pain and discomfort which the patient will experience post treatment and it plays an important role in the success of the treatment if placed within correct limits. The cementodentinal junction, where the pulp tissue changes into the apical tissue, is the ideal physiologic apical limit of WL because at this point healing is supposed to be optimal, and the wound to the periapical tissues is minimal.The apical constriction is however, histological and is impossible to locate clinically or radiographically. There are several methods of determining working length which include radiographical methods, digital tactile sense, apical periodontal sensitivity, paper point method and electronic apex locators. The requirements of an ideal method for determining working length include rapid location of the apical constriction in all pulpal conditions, easy measurement, rapid periodic monitoring and confirmation, patient and clinician comfort, minimal radiation to the patient; ease of use in special patients; and cost effectiveness. To achieve the highest degree of accuracy in working length determination, a combination of several methods should be used. This article reviews the different methods to determine WL and their clinical implications. KEY WORDS Working Length, Apex Locator, Radiographic Method.

Decentralized wastewater treatment has become inevitable as conventional wastewater treatment plants involve huge construction and maintenance costs. One of the most popularly used decentralized wastewater treatments is constructed wetlands. Constructed wetlands are a cost-effective and sustainable treatment method for domestic and industrial wastewater. Over the years, there has been a lot of improvement in the design and process approaches of constructed wetlands. This review paper aims to find the impacts of design processes like artificial aeration, design and flow pattern, effluent recirculation, substrate media, vegetation, and C/N ratio on the treatment performance of constructed wetlands. Based on the review, it is found that intermittent aeration along with recirculation, hybrid constructed wetlands and baffled constructed wetlands are an effective way to remove ammonia and organics from wastewater. Phosphorous removal in constructed wetlands is highly dependent on substrates rather than wetland plants. Further, the paper discusses the future scopes and challenges in terms of improving the efficiency of constructed wetlands, reuse of industrial waste as substrate, solar energy based aeration, etc., to make constructed wetlands a sustainable wastewater treatment technology.

Normal modes and their dispersion are obtained for planar zig-zag form of poly(β-hydroxybutyrate) using Urey–Bradley force field. A comparison is made with the spectra of its helical form. Apart from detailed assignment of modes, various characteristic features of dispersion curves have been explained as arising due to internal symmetry in energy momentum space. The density-of-states have been used to calculate heat capacity in the temperature range 10–450 K using Debye's formalism.

computing principles focus on large-scale resource sharing in distributed systems in a flexible, secure and coordinated fashion. The most widespread contemplation is performance, because computational grid servers must offer cost-effective and high-availability services in the elongated period, thus they have to be scaled to meet the expected load. Performance measurements can be the base for performance modeling and prediction. With the help of performance models, the performance metrics (like buffer estimation, waiting time) can be determined at the development process. This paper describes the possible queue models those can be applied in the estimation of queue length to estimate the final value of the memory size. Both simulation and experimental studies using synthesized workloads and analysis of real-world Gateway Servers demonstrate the effectiveness of the proposed system.

Microbial poly(e-L-lysine)(M-e-PL) is a naturally occurring biomaterial, which is water soluble, biodegradable, edible and non-toxic towards humans and environment. Normal mode analysis including phonon dispersion has been performed to understand completely the vibrational spectra of this polymer. Various characteristic features of the dispersion curves have been reported. The heat capacity is calculated as a function of temperature via density-of-states in the range 1-450 K.

Vibration Spectra of Polyglycine Chain

Poly(β-benzyl- l -aspartate) (PBLA) shows unusual conformational variety and under varying conditions of preparation it is capable of adopting four different conformations, namely left-handed α helix (αl), right-handed α helix (αr), ω helix and β pleated sheet. We present here a complete phonon dispersion and heat capacity study on the β form of PBLA. A comparison of the characteristic features and the conformational dependence of modes for α, β and ω forms of PBLA are made. It is observed that the dispersion of modes in the β form is in general larger than in the α form. Crossing over and repulsion of various dispersion branches are discussed.

The normal modes and their dispersions for form 1 of syndiotactic poly(1-butene) have been obtained using Wilson’s GF matrix method as modified by Higgs. Optically active frequencies corresponding to the zone center and zone boundary are identified and discussed. The Urey Bradley potential field is obtained by least square fitting of the observed Fourier transform infrared absorption bands. Specific heat has been obtained from dispersion curves via density of states. A comparative study of isotactic and syndiotactic forms of poly(1-butene) is presented.

Normal modes and their dispersion are reported for the α-helical form of poly( l -aspartic acid) which is an important polypeptide used in the sustained release of drugs. Characteristic features of dispersion curves such as bunching and repulsion are discussed. Heat capacity is derived from the dispersion curves via density-of-states and compared with the available experimental data on sodium salt of the polymer.

In continuation to our work on the oligomapping of the dispersion curves of poly(L-valine) in β form, the present work is a study of normal modes and their dispersion in the α form. The Urey Bradley force field used in Wilson's GF matrix method has been transferred from the β form and refitted to explain the FTIR spectra. The characteristic features of the dispersion curves involve repulsion with character exchange and tendency of certain pair of modes involving the motion of C α atom to come closer near the helix angle. Predictive value of heat capacity is obtained from the density-of-states. It is observed that the mixed modes make the maximum contribution.

A study of the normal modes of vibration and their dispersion in polyinosinic acid [poly (I)] along the helix axis based on Urey-Bradley force field is reported. It leads to a better interpretation of Raman and FTIR spectra. A comparison of dispersion curves of poly (I) with poly (G) has been made. Characteristic features of dispersion curves, such as regions of high density-of-states, repulsion and character mixing are discussed. Predictive value of heat capacity as a function of temperature is reported.

The small-angle X-ray scattering (SAXS) curves for ultralongn-alkanes obtained by Ungar and Keller at different times after reaching the crystallization temperature have been Fourier analysed. The correlation curves so obtained at different temperatures and different annealing times reflect sensitively all those morphological features which are broadly characteristic of the scattering curves. In addition the correlation curves clearly show a transition from a non-integer-fraction length to extended chain structure. Crystalline and amorphous lengths, degree of order and half-widths which characterize kinetics of morphological changes are also reported.

The vibration-rotation spectrum of HDO in the 2400-3300 per cm region has been studied at 0.01 per cm resolution with a Fourier transform spectrometer. Values of the ground state levels and levels in the (100) and (020) states have been determined from the data. The ground state levels are fitted to a Watson-type Hamiltonian from which 17 rotational constants are obtained. Measurements of the strengths of over 1100 lines have been made using a nonlinear least-squares fitting technique, and 548 of these lines are analyzed to determine the band strengths, the coefficients of the F factors, and the Coriolis interaction parameters. The strengths of the A- and B-type (100) bands and the A- and B-type (020) bands are 53.2 + or - 0.9, 0.43 + or - 0.07, 6.00 + or - 0.54, and 2.75 + or - 0.12 per sq cm per atm at 296 K, respectively.

Collagen is one of the most important proteins containing mostly proline hydroxyproline and glycine. In collagen, approximately 33 percent of the amino acid residues are glycine and they occur at every third position, whereas remaining percentage is constituted by mainly proline or hydroxyproline and some part by alanine etc. having no definite positional placement in the chain. Thus, a study of conformation of proline and glycine containing dipeptides and tripeptides is important for understanding the conformation of collagen as a sequence of its constituent amino acids. In the present communication, we have studied spectral features of L-proline, L-prolyl-glycine (PG), L-prolyl-alanine (PA), L-glycylglycine (GG), Collagen and L-prolyl-glycyl-glycine (PGG). We have carried out detailed normal mode analysis of only PGG, because interpretation of spectra of other proline and glycine containing peptides can be treated as derivatives of this molecule. Urey-Bradley force field, which involves non-bonded interactions in the gem and cis configurations is used for calculation of normal modes. The "best-fit" set of constants are generated for PGG.

In continuation to our work on order-order and order-disorder transition in triple stranded DNA when it is bounded to netropsin, we report in this communication the stabilizing/destabilizing effect of disulphide linkage on the phase dynamics of the triplex using the amended Zimm-Bragg theory. It is observed that in contrast to the sequential triplex--duplex --single strand melting of the uncrosslinked triplex, crosslinking causes the triplex state to melt directly to the single stranded state, with no apparent intermediary of a duplex state. Since there is no overall difference in the enthalpy of crosslinked and uncrosslinked triplexes, the transition is entropy driven.

Normal coordinate analysis has been made for gammexane using the Wilson's G-F matrix method with Urey-Bradley force field. Molecular orbital calculations using CNDO/2 method have also been carried out for the five isomers of hexachlorocyclohexane to give the valence charge densities on the atoms of the molecules. A toxicity parameter that takes into account a shape factor and the valence charge density on the atoms has been defined. On the toxicity scale so defined the gamma-isomer alone has a significant value.

A complete normal coordinate analysis of Met5- and Leu5-enkephalins using Wilson's GF matrix method and Urey Bradley force field has been carried out to understand the dynamical behaviour of enkephalins. In addition, the charge distributions on different atoms of the two enkephalins and morphine using CNDO/2 method are also reported. The similarity in the charge distribution on the part of these two molecules is indicative of the possible interactions at the same receptor site as that of morphine and its derivatives. Apart from the topographical features and charge distribution, binding onto receptor site is not a static but a dynamic process and low frequency modes must play an important role in the recognition process. The significance of the out-of-plane amide VII band and other skeletal modes as characteristic of conformational states of Met5- and Leu5-enkephalins are discussed.

Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi-221 005 Manuscript received 31 August 1993 Ad ducts and substituted products of tin tetrachloride and monoorganotin trichloride with unsymmetrical trifluroro- ,β-diketones, CF3COCH2COR (LH) (R =Me, Et, i-Pr and Ph) have been prepared and characterised. Ir spectra of adducts, SnCl4.LH are consistent with the enolic form of the chelating diketone leading to an octahedral structure. X-ray crystal and molecular structure of complex, SnCI2(CF3COCHCOPh)2confirms cis-trans-cis stereochemistry. 1H nmr spectra suggest these to be fluxional in solution. For organotin complexes, only tentative structures could be proposed from the limited spectral data.

The Zimm and Bragg theory of the helix--coil transition has been modified to explain order--order transitions in polynucleotides, in particular B--Z--psi(-)--coil transitions in poly(dG-dC) and poly(dG-me5dC). Lambda anomalies in specific heat measurements around the transition point have also been explained by a further modification of the same theory. Theoretical results are found to be in good agreement with the experimental data. The nucleation parameter is consistent with the stabilization/destabilization of the ordered states (Z helix) under various environmental conditions, e.g. methylation of cytosine residue at C5 position or change in the cationic concentration of the solvent.

Department of Chemistry, Faculty of Science,Banaras Hindu University, Varanasi-221 005 Manuscript received 27 February 1989, revised 24 January 1990,accepted 28 February 1990 Complexation of Dimethyltin(IV) Ion with 2-Mercaptopyridine-N-oxide and 8 -Hydroxyquinoline-N-oxide

A series of tributyl- (or triphenyl-) stannylamidoximes, R(H2N)CNO · SnR′3 (where R = Me, Et, Pr or Ph and R′ = Bu or Ph) were prepared by the reaction of tributyl- or triphenyl-tin isopropoxide with amidoximes. Trimethylstannyl derivatives of amidoximes were prepared from the reaction of trimethyltin chloride with amidoximes in the presence of an equimolar amount of sodium or potassium alkoxide. Tributylstannyl amidoximes were prepared from a mixture of bis(tributyltin) oxide and amidoxime in a 12 molar ratio.

The preparation and properties of mono-, bis- and tris-(trimethylsilyl)amidoximes are described.

New monomeric dialkyl- or diphenyl-silylbisamidoximes and dialkyl(ethoxy)silylamidoximes have been characterised. Their infrared spectra have been interpreted and diamagnetic susceptibility of some of them has been determined.

A study of the complexation reactions of dialkyltin dichloride with catechol has been carried out by potentiometric method and the correctness of the observed formation of 1:1 complex has been confirmed by preparative studies both in aqueous and non-aqueous media.

A number of distillable complexes have been obtained from reaction between dibutyltin diethoxide and acetylacetone, methyl acetoacetate or ethyl acetoacetate. The products are monomeric, which indicates possible octahedral configuration. The triethyltin acetylacetonate has also been shown to be monomeric in benzene, and may contain a five-coordinated tin atom. Trimethyltin methoxide also is only slightly associated in benzene or either.

Dibutyltin diethoxide was found to interchange its ethoxy groups readily with thiols forming Bu2Sn(SR)2. These thiolates can also be synthesized by refluxing the crude Bu2SnO with thiols in the presence of benzene. Molecular weight determinations showed them monomeric. Some of these higher homologues can be prepared by displacement reactions with higher thiols. The reaction of dipropanethiodibutylstannane with ethanol is very slow even in the presence of catalyst.

Chemical Laboratories, University of Rajasthan, Jaipur-302 004 A few new monothio-β-diketones, [RCSCH2COR', where R =Ph, Me ; R' =.C6H4(\(p\)), C6H4Br(\(p\)), C6H4Me(\(p\)), C6H4OCH4(\(p\))]have been synthesized and their metal complexes with CO(II), Ni(II), Co(III) and Fe(III) were prepared. These were characterized by elemental analysis, ir, magnetic measurements, electronic spectra. Molecular weight determination in refining chloroform showed them to be monomeric.

Chemical Laboratories, University of Rajasthan, Jaipur-302 004 A few new monothio-��-diketones, [RCSCH2COR', where R = Ph, Me ; R' =.C6H4(\(p\)), C6H4Br(\(p\)), C6H4Me(\(p\)), C6H4OCH4(\(p\))] have been synthesized and their metal complexes with CO(II), Ni(II), Co(III) and Fe(III) were prepared. These were characterized by elemental analysis, ir, magnetic measurements, electronic spectra. Molecular weight determination in refining chloroform showed them to be monomeric.

Department of Chemistry, Faculty of science, Banaras Hindu University, Varanasi-221 005 The complexes of Ni(II), Cu(II), Co(ll), Cd(II) and Fe(lll) with dietbylamioo methyl ester of 2-amlno-1-cyclopeateoe-1-dltbiocarboxyllc acid,\( \begin{matrix} RHNCCH_2 CH_ CH_2 C- \\ \mid & \mid \end{matrix}\) C(S)S o' [LH when R=H and R'=CH2 N(C2H5 )2] and Ni(II) with methyl ester of N-methyl acid [L'H when R=R'=CH3] have been synthesized and characterized.

Chemical Laboratories, University of Rajasthan, Jaipur-302004 Manuscript received 24 January 1974; revised 19 August 1974; accepted 20 August 1974 Titanium alkoxides react with N-ethylaminoethanols in stoichiometric ratios to give com­pounds with general formula, (OR)4-n Ti(OCH2CH2NR'R")n [R = Et and Pri; R' = H, R" = Et; R' = R" = Et; n 1-4]. Physical properties like molecular weight, infrared spectra and thermal stability are recorded. Reactions of tetrakisderivatives with phenylisocyanate and acetyl chloride are studied.

Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi-221 005 Manuscript received 26 July 1982, accepted 3 August 1983 Thermodynamic Parameters of Dialkyltin(IV)N- Arylhydroxamic Acid Chelates

Chemistry Department, Rajasthan University, Jaipur-302004 Manuscript received 9 November 1976, accepted 2 April 1977 1, 3, 5, 2-Oxadiazaboroles of the types, R(HN)C =NOB - OR', └―――┘ R(HN)C =NOB - ON= C(R)NH—BON=C(NH)R, R(HN)C =NOB. Ph and └―――┘ └―――┘ └―――┘ [R(HN)C=NOB]2—O, (where R=Me, Et, Pr or Ph and R' =Et or Pri) └―――┘ have been synthesized from the reactions of alkylborates, phenylboronic acid or boric acid with amidoximes and characterized

Department of Chemistry, Faculty of Science. Banaras Hindu University, Varanasi-221 005 Manuscript received 3 June 1980, revised 25 November 1980, accepted 23 February 1981 2-Methoxyethanol complexes of tin(IV) and titanium(IV) have been synthesized and their probable structures on the basis of the ligand conformations have been discussed with the help of spectral data.

Chemistry Department, University of Rajasthan, Jaipur-302 004 Manuscript received 23 October 1979, accepted20 December 1979 Mono-organotin (IV) Derivatives of Hydroxamic Adds &nbsp

Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi-221 005 Manuscript received 29 July 1981, revised 30 November 1981, accepted 7 January 1982 Metal Complexes of Sulfur-Nitrogen Chelating Agents : Organotin(IV) Derivatives of Diethylaminomethyl Ester of 2-Amino-1- cyclopentene-1-carbodlthioic Acid.

A detailed study has been made of the reaction between stannic chloride and acetylacetoie. In the re-fluxing benzene, the reaction in varying molar ratios yields a light brown crystalline solid, corresponding to SnCI2(AcAc)2 (I) which has been shown to be a simple monomeric, non-conducting compound. In cold, a product, corresponding in analysis to SnCl4.HAcAc, is obtained, to which the plausible formula [HAcAo)2 SnCl2]SnCl6 has been assigned. This has been confirmed by its observed conductance in nitrobenzene as well as by the isolation of an identical product by adding stannic chloride to [(HAcAc)2SnCl2]Cl2, obtained by passing hydrogen chloride in a solution of (I).

Chemical Laboratories, University of Rajasthan, Jaipur Received 6 September 1971 Potentiometric titrations of dialkyltin dichloride with chromotropic acid (sodium salt) in varying molar ratios have been carried out. The formation of only dialkyltin monochloromo­tropate chelates have been indicated in the lower pH range.