Gel Medium Research Articles

Effect of repetitive pecking at working length for glide path preparation using G-file.

ObjectivesGlide path preparation is recommended to reduce torsional failure of nickel-titanium (NiTi) rotary instruments and to prevent root canal transportation. This study evaluated whether the repetitive insertions of G-files to the working length maintain the apical size as well as provide sufficient lumen as a glide path for subsequent instrumentation.Materials and MethodsThe G-file system (Micro-Mega) composed of G1 and G2 files for glide path preparation was used with the J-shaped, simulated resin canals. After inserting a G1 file twice, a G2 file was inserted to the working length 1, 4, 7, or 10 times for four each experimental group, respectively (n = 10). Then the canals were cleaned by copious irrigation, and lubricated with a separating gel medium. Canal replicas were made using silicone impression material, and the diameter of the replicas was measured at working length (D0) and 1 mm level (D1) under a scanning electron microscope. Data was analysed by one-way ANOVA and post-hoc tests (p = 0.05).ResultsThe diameter at D0 level did not show any significant difference between the 1, 2, 4, and 10 times of repetitive pecking insertions of G2 files at working length. However, 10 times of pecking motion with G2 file resulted in significantly larger canal diameter at D1 (p < 0.05).ConclusionsUnder the limitations of this study, the repetitive insertion of a G2 file up to 10 times at working length created an adequate lumen for subsequent apical shaping with other rotary files bigger than International Organization for Standardization (ISO) size 20, without apical transportation at D0 level.

A novel method for the separation of mono and ortho polymorphs of paracetamol in gel matrix.

The nucleation control and separation of mono and ortho polymorphs of the important pharmaceutical solid paracetamol were carried out through a crystallization process in gel media for the first time. Crystallization of mono and ortho polymorphic forms of paracetamol was achieved by optimizing the experimental parameters such as the specific gravity, pH, height of the gel column and solute concentration at ambient temperature. The optimized experimental conditions favor the generation of necessary supersaturation responsible for the nucleation of preferred polymorph at different levels in the gel column and also endure the stability of the grown orthorhombic polymorphs at ambient conditions. Accordingly the needle like metastable orthorhombic polymorph nucleates at the top portion of the gel column whereas the prismatic stable monoclinic polymorph nucleates mostly at the bottom level. Morphology of the nucleated polymorphs was analyzed and their crystalline structures were confirmed by PXRD. FTIR analysis revealed the shifting of absorption peaks of few functional groups corresponding to both the polymorphs due to the difference in their structural nature. DSC analysis revealed that the grown ortho polymorph form II transforms to mono form I at 89.47°C while the grown mono form I retains its phase until melting.

Synthesis, Characterization, and Thermal Kinetics of Mixed Gadolinium: Calcium Heptamolybdate System.

Synthesis of mixed gadolinium calcium heptamolybdate (GdCaHM) system in silica gel medium using single gel single tube technique has been successfully achieved. The grown crystal exhibits various morphologies, which includes spherulites, multifaceted, and square platelets. The nature of the grown material was established by X-ray diffraction (XRD) studies. Fourier transform infrared spectroscopy (FTIR) study signifies the presence of heptamolybdate (Mo7O24) and water symmetry structure, whereas energy dispersive X-ray analysis (EDAX) establishes the stoichiometric of the grown crystal as GdCaMo7O24·8H2O. The thermal behaviour was studied using the thermoanalytical techniques, which include thermogravimetry (TG), differential thermal analysis (DTA), and differential scanning calorimetry (DSC). Results obtained on the application of TG based models, namely, Horowitz-Metzger, Coats-Redfern, and Piloyan-Novikova, suggest the contracting cylindrical model as the relevant model for the thermal decomposition of the material. The kinetic parameters, namely, the order of reaction (n), activation energy (E a), frequency factor (Z), and entropy (ΔS∗), were also calculated using these three models.

English

Lead-cobalt mixed levo tartrate crystals for different compositions of lead and cobalt were grown by using single diffusion gel growth method in silica hydro gel medium. Long and dendrite type white crystals as well as spherulitic crystals were obtained. The metallic composition in the crystals was estimated by EDAX. It was found that the metallic composition in the crystals did not vary as per the composition of supernatant solution, i.e., lead content was found more than cobalt content. The powder XRD suggested the orthorhombic nature for all crystals. The grown crystals were characterized by FTIR spectroscopy and thermal studies. The FTIR spectra revealed the presence of water molecules, O-H, C-H, C-O and C=O functional groups. The thermo-grams suggested that the crystals were thermally unstable and decomposed into oxide through carbonate stage.

A complete system for 3D reconstruction of roots for phenotypic analysis.

Here we present a complete system for 3D reconstruction of roots grown in a transparent gel medium or washed and suspended in water. The system is capable of being fully automated as it is self calibrating. The system starts with detection of root tips in root images from an image sequence generated by a turntable motion. Root tips are detected using the statistics of Zernike moments on image patches centred on high curvature points on root boundary and Bayes classification rule. The detected root tips are tracked in the image sequence using a multi-target tracking algorithm. Conics are fitted to the root tip trajectories using a novel ellipse fitting algorithm which weighs the data points by its eccentricity. The conics projected from the circular trajectory have a complex conjugate intersection which are image of the circular points. Circular points constraint the image of the absolute conics which are directly related to the internal parameters of the camera. The pose of the camera is computed from the image of the rotation axis and the horizon. The silhouettes of the roots and camera parameters are used to reconstruction the 3D voxel model of the roots. We show the results of real 3D reconstruction of roots which are detailed and realistic for phenotypic analysis.

Bioinspired synthesis of mesoporous ZrO2nanomaterials with elevated defluoridation performance in agarose gels

Mesoporous ZrO2 nanomaterials were synthesized in an agarose gel medium by a bioinspired approach, and their adsorption capacity for the fluoride anion was also evaluated. The obtained ZrO2 samples after calcination at 600 °C for 2 h are primarily composed of tetragonal nanocrystals about 11.8 nm in size. Moreover, the samples possess bimodal mesopores about 3.5 nm and 5.9 nm in diameter, which are generated by removing the agarose gel fibers embedded in the ZrO2 particles during their growth process. The pore volume and specific surface area of mesoporous ZrO2 nanomaterials are 0.091 cm3 g−1 and 40.14 m2 g−1, respectively, which increase with the increase of gel concentration, while decrease with the increase of initial ZrOCl2 concentration. The ZrO2 samples synthesized in agarose gel show a higher fluoride adsorption capacity than those synthesized in the aqueous solution by the same method. This study may provide a broader insight into the bioinspired synthesis of metal oxides in hydrogel medium under mild conditions.

Comparison of electrochemical- and nuclear magnetic resonance spectroscopy methods for determination of diffusion coefficients in gel environment

Two advanced methods: one based on chronoamperometry in solution of any ionic strength and the second one related to nuclear magnetic resonance spectroscopy (NMR) were used to determine the difusion coefficients of the selected species in complex polymeric gels. For this purpose a series of polyacrylamide gels with different content of monomer and crosslinker were synthesized. Rod shaped samples of polymers were swelled with solutions of either 1,1'-ferrocenedimethanol, or 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt or cis-dichlorobis(2,2′-bipyridine) ruthenium(II) in D2O. These compounds were good probes for examining the transport in the gel medium due to electrochemical reaction and well-defined signals in 1H NMR spectroscopy. The values of diffusion coefficients obtained by both methods were compared and the limitations of the methods were discussed. The measurements were done at three temperatures: 25, 35 and 45°C.

Dynamic scaling analysis of two-dimensional cell colony fronts in a gel medium: A biological system approaching a quenched Kardar-Parisi-Zhang universality

The interfacial two-dimensional spreading dynamics of quasilinear Vero cell colony fronts in methylcellulose (MC)-containing culture medium, under a constant average front displacement velocity regime, was investigated. Under comparable experimental conditions, the average colony front displacement velocity becomes lower than that reported for a standard culture medium. Initially, the presence of MC in the medium hinders both the colony spreading, due to a gradual change in the average size and shape of cells and their distribution in the colony, and the cell motility in the gelled medium. Furthermore, at longer culture times enlarged cells appear at random in the border region of the colony. These cells behave as obstacles (pinning sites) for the displacement of smaller cells towards the colony front. The dynamic scaling analysis of rough fronts yields the set of exponents α=0.63±0.04,β=0.75±0.05, and z=0.84±0.05, which is close to that expected for a quenched Kardar-Parisi-Zhang model.

Electrophoresis of a colloidal particle embedded in electrolyte saturated porous media

We consider a charged colloidal sphere undergoing steady migration under an imposed electric field through an uncharged hydrogel, modeled as a Brinkman medium. The transport of ions is governed by the Nernst–Planck equation coupled with the Brinkman equation for fluid flow and Poisson equation for electric field. The motion deterring effects due to the induced electric field and electroosmosis in a gel medium are governed by the degree of the double layer polarization and electromigration of ions. These effects are correctly accounted in the present model. Based on the effective medium (EM) approach, we have estimated the mobility of the particle through the balance of hydrodynamical and electrical forces for a wide range of electrokinetic parameters such as, charge density of the particle, hydrogel permeability and ionic concentration (Debye layer thickness). A correct measure of the hydrodynamical drag and electrical force experienced by the particle in electrophoresis is made. We have validated our computed results for mobility by comparing with the available experimental and theoretical results. The role of electroosmosis on the hydrodynamics of the particle is analyzed by comparing the drag with the corresponding uncharged case. Our results suggest that the retardation effects are strong for moderate values of the Debye–Huckel parameter and grow as the permeability of the hydrogel is increased.

Effects of plant growth regulators, carbon sources and pH values on callus induction in Aquilaria malaccensis leaf explants and characteristics of the resultant calli

The endangered tropical tree, Aquilaria malaccensis, produces agarwood for use in fragrance and medicines. Efforts are currently underway to produce valuable agarwood compoundsn tissue culture. The purpose of this study was to develop an optimal growth medium, specifically, the best hormone combination for callus suspension culture. Using nursery-grown A. malaccensis, sterilized leaf explants were first incubated on basic Murashige and Skoog (MS) gel medium containing 15g/L sucrose and at pH 5.7. Different auxin types including 1-naphthaleneacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), and indole-3-butyric acid (IBA), were tested at various concentrations (0.55, 1.1 and 1.65 μM) using the basic medium. Leaf explants were incubated for 30 days in the dark. Callus induced by 1.1 μM NAA had the highest biomass dry weight (DW) of 17.3 mg; however the callus was of a compact type. This auxin concentration was then combined with either 6-benzylaminopurine (BAP) or kinetin at 0.55, 1.1, 2.2 or 3.3 μM to induce growth of friable callus. The 1.1μM NAA + 2.2μM BAP combination produced friable callus with the highest biomass (93.3mg DW). When testing the different carbon sources and pHs, sucrose at 15g/L and pH at 5.7 yielded highest biomasses at 87.7mg and 83mg DW, respectively. Microscopic observations revealed the arrangement of the friable cells as loosely packed with relatively large cells, while for the compact callus, the cells were small and densely packed. We concluded that MS medium containing 15 g/L sucrose, 1.1 μM NAA + 2.2 μM BAP hormone combination, and a pH of 5.7 was highly effective for inducing friable callus from leaf explants of A. malaccensis for the purpose of establishing cell suspension culture.

In vitro Development of Cauliflower Synthetic Seeds and Development of Plantlets In vivo

Synthetic seeds of cauliflower cv. Chillout were developed by encapsulating mature somatic embryos in neutral gel media. Somatic embryos were obtained by optimizing callus and cell suspension cultures of cauliflower. Friable, yellowish embryogenic calli were obtained on MS supplemented with 2 mg/l 2,4-D and 0.5 mg/l BAP using hypocotyl as explants, while calli were regenerated in media consisting of 5 mg/l BAP, 2 mg/l Kn and 6 mg/l GA3. Somatic embryo-genesis was induced in cell suspension culture where auxins were removed in successive steps triggering conversion of globular cells into the heart, torpedo stage (71%) and finally into cotyledonary/somatic embryos (28%). The mature somatic embryos were encapsulated by mixing mature cell suspension with sodium alginate and calcium chloride mixture (1 : 4). Developed synthetic seeds germinated into complete plantlets when placed in neutral gel media. Germination efficiency of synthetic seeds decreased to about 50 per cent after 12 weeks of storage at 4ºC followed by a rapid decrease to zero per cent after 16 weeks. It was also observed that cauliflower plantlets from synthetic seeds survived successfully when transferred to soil demonstrating that cauliflower synthetic seeds is a promising step towards their in vivo direct use. Plant Tissue Cult. &amp; Biotech. 24(1): 27-36, 2014 (June) D. O. I. http://dx.doi.org/10.3329/ptcb.v24i1.19193

Growth, characterization and dielectric property studies of gel grown barium succinate single crystals

. Single crystals of barium succinate (BaC4H4O4) were grown in silica gel medium using controlled chemical reaction method. Plate-like single crystals of size up to 3 × 2 × 0·2 mm3 was obtained. Single crystal X-ray diffraction (XRD) studies confirmed that structure of the title compound is tetragonal. Powder X-ray diffraction (PXRD) pattern of the grown crystal and the Fourier transform infrared (FT–IR) spectrum in the range 400–4000 cm–1 are recorded. The vibrational bands corresponding to different functional groups are assigned. Thermal stability of the grown crystals is confirmed by differential scanning calorimetry (DSC). Dielectric constant and dielectric loss have been calculated and discussed as a function of frequency at different temperatures.

Dielectric, ferroelectric and optical behaviour of terbium hydrogen tartrate trihydrate crystals

Gel diffusion technique, using agar–agar as gel medium, has been employed to obtain single crystals of terbium hydrogen tartrate trihydrate. The grown crystals are characterised by X-ray diffraction, scanning electron microscopy, CHN technique, thermogravimetric methods and UV–Vis spectroscopy. Dielectric, ferroelectric and optical studies on this metal–organic compound have been carried out. The dielectric constant has been measured as a function of temperature and frequency in the ranges of 20–250 °C and 20 Hz–3 MHz, respectively. The study of dielectric behaviour as a function of temperature reveals two dielectric anomalies at 95 and 198 °C. The dielectric anomaly at 95 °C is suggested to be due to ferroelectric phase transition brought about in the material. The study of polarisation versus electric field shows a hysteresis loop which thereby confirms the ferroelectric nature of terbium hydrogen tartrate trihydrate crystals. The dielectric anomaly at 198 °C is suggested to be due to loss of water molecules in the compound. The results of thermal study show that the material is thermally stable up to temperature of about 200 °C. Optical studies show that the terbium hydrogen tartrate trihydrate crystal has good transparency in the entire visible and infra red range of the spectrum.

Functionalizing Single Crystals: Incorporation of Nanoparticles Inside Gel‐Grown Calcite Crystals

AbstractSynthetic single crystals are usually homogeneous solids. Biogenic single crystals, however, can incorporate biomacromolecules and become inhomogeneous solids so that their properties are also extrinsically regulated by the incorporated materials. The discrepancy between the properties of synthetic and biogenic single crystals leads to the idea to modify the internal structure of synthetic crystals to achieve nonintrinsic properties by incorporation of foreign material. Intrinsically colorless and diamagnetic calcite single crystals are turned into colored and paramagnetic solids, through incorporation of Au and Fe3O4 nanoparticles without significantly disrupting the crystalline lattice of calcite. The crystals incorporate the nanoparticles and gel fibers when grown in agarose gel media containing the nanoparticles, whereas the solution‐grown crystals do not. As such, our work extends the long‐history gel method for crystallization into a platform to functionalize single‐crystalline materials.

Functionalizing Single Crystals: Incorporation of Nanoparticles Inside Gel‐Grown Calcite Crystals

Synthetic single crystals are usually homogeneous solids. Biogenic single crystals, however, can incorporate biomacromolecules and become inhomogeneous solids so that their properties are also extrinsically regulated by the incorporated materials. The discrepancy between the properties of synthetic and biogenic single crystals leads to the idea to modify the internal structure of synthetic crystals to achieve nonintrinsic properties by incorporation of foreign material. Intrinsically colorless and diamagnetic calcite single crystals are turned into colored and paramagnetic solids, through incorporation of Au and Fe3O4 nanoparticles without significantly disrupting the crystalline lattice of calcite. The crystals incorporate the nanoparticles and gel fibers when grown in agarose gel media containing the nanoparticles, whereas the solution-grown crystals do not. As such, our work extends the long-history gel method for crystallization into a platform to functionalize single-crystalline materials.

Effect of micellar and sol–gel media on the spectral and kinetic properties of tetracycline and its complexes with Mg2+

The spectroscopic and photophysical properties of the broad-spectrum antibiotic tetracycline (TC) and its Mg(2+) complexes were studied in organized media attained by means of three iso-structural quaternary ammonium surfactants able to self-assemble in water at low c.m.c. values, thus giving spherical micelles and sol-gel media upon increasing the concentration. Specific protonated forms of TC and its complexes were introduced in these micro-heterogeneous environments and then investigated through steady-state (both in absorption and emission) and pulsed (up to femtosecond resolution) spectroscopic techniques. Free TC showed minor spectral and kinetic variations while complexes remained unchanged in the presence of spherical micelles, meaning that TC is likely to be placed at the interface between the micelle and the bulk aqueous solution, without altering its bioactivity. Ultrafast transient absorption spectroscopy proved to be a powerful tool to gain deep insight into the distribution of the investigated species between the heterogeneous structure of sol-gel media. In fact, according to the polarity and net charge of free TC and its complexes, these species can be mostly found in the hydrophobic (intertwined worm-like micelles) or in the hydrophilic domains (basically aqueous pools) that the sol-gel is made up of. In the first case, the properties are dramatically altered (highly enhanced fluorescence and lengthened lifetime of the first singlet excited state up to the nanosecond time scale), leading to the improved traceability of the drug.

Growth and characterization of struvite-Na crystals

Sodium magnesium phosphate heptahydrate [NaMgPO4·7H2O], also known as struvite-Na, is the sodium analog to struvite. Among phosphate containing bio-minerals, struvite has attracted considerable attention, because of its common occurrence in a wide variety of environments. Struvite and family crystals were found as urinary calculi in humans and animals. Struvite-Na crystals were grown by a single diffusion gel growth technique in a silica hydro gel medium. Struvite-Na crystals with different morphologies having transparent to translucent diaphaneity were grown with different growth parameters. The phenomenon of Liesegang rings was also observed with some particular growth parameters. The powder XRD study confirmed the structural similarity of the grown struvite-Na crystals with struvite and found that struvite-Na crystallized in the orthorhombic Pmn21 space group with unit cell parameters such as a= 6.893Å, b=6.124Å, c=11.150Å, and α=β=γ=90°. FT-IR spectra of struvite-Na crystals revealed the presence of functional groups. The TGA, DTA and DSC were carried out simultaneously. The kinetic and thermodynamic parameters of dehydration/decomposition process were calculated. The variation of dielectric constant with frequency of applied field was studied in the range from 400Hz to 100kHz.

Poroelastic longitudinal wave equation for soft living tissues

Making use of the poroelastic theory for hydrated polymeric matrices, the ultrasound (US) propagation in a gel medium filled by spherical cells is studied. The model describes the connection between the poroelastic structure of living tissues and the propagation behavior of the acoustic waves. The equation of fast compressional wave, its phase velocity and its attenuation as a function of the elasticity, porosity and concentration of the cells into the gel external matrix are investigated. The outcomes of the theory agree with the measurements done on Alginic acid gel scaffolds inseminated by porcine liver cells at various concentrations. The model is promising in the quantitative non-invasive estimation of parameters that could assess the change in the tissue structure, composition and architecture.

Variation in the Morphology of Bacillus mycoides Due to Applied Force and Substrate Structure

Response to mechanical force is a well characterised phenomenon in eukaryotic organisms, helping to organise multicellular structures. Mechanotactic responses have only rarely been observed in prokaryotic taxa. This work reports on a morphological change due to variations in applied force and surface structure by Bacillus mycoides Flügge. B. mycoides is a ubiquitous soil organism well known among microbiologists for its characteristic spreading colony morphology. An apparent mechanotactic response is elicited by physical deformation of the gel media on which B.mycoides is growing, including applied forces of compression or tension. Variations in the surface such as curvature produced by casting the agar gel in the presence of curved objects also elicited the change. The morphological change in B.mycoides colonies associated with the application of force manifests as a pattern of parallel rhizoid filaments perpendicular to compressing force and parallel to stretching force in the agar medium. The phenomenon is most clearly demonstrated by reversible changes in the orientation of B. mycoides filaments during time-lapse microscopy.

Synthesis and Crystal Structures of Various Phases of the Microporous Three-Dimensional Coordination Polymer [Zr(OH)2(C2O4)]n

A homometallic Zr(IV)-oxalate three-dimensional (3-D) coordination polymer of formula [Zr(OH)2(C2O4)·0.5H2O] is reported. This compound was found to be a microporous solid with reversible sorption abilities. Upon guest release and sorption, the crystalline material undergoes single crystal to single crystal transitions. The crystal structures for three phases have been solved from single crystal diffraction studies. They consist of the guest containing frameworks [Zr(OH)2(C2O4)·0.5H2O], 1, 3, and the guest-free porous phase [Zr(OH)2(C2O4)], 2; all are found with tetragonal space group I4/m. Phase 1 has been obtained by controlled diffusion of the reagents (ZrO(NO3)2 and H2C2O4) in a silica gel medium; the other phases have been formed from 1 by thermal activation (2) and re-adsorption of H2O (3).