Effect of different denture adhesives on retention of complete dentures: an in vivo study

The increase in prevalence of tooth loss with the effect of population aging produces the growing need for complete dentures. The success and acceptance of complete dentures by the patient depends on sufficient retention and stability. Therefore, denture adhesives are regularly used by denture wearers to improve the function of complete denture. We evaluated the effect of three different denture adhesives (Corega, Protefix, Fittydent) on the retention of maxillary complete denture (MCD) using with digital dynamometer (DD). For this purpose, denture adhesives were applied on MCDs of 30 participants. After chewing procedure, the force was applied at 45° to the palatal surface of denture by DD. Dislodgement force was recorded by means of Newton. There were four measurements on each patient including; group of control: Group C; Group CR: Corega; Group F: Fittydent; Group P: Protefix. The result of the study was statistically evaluated by using analysis of variance (ANOVA) and Tukey HSD test. Statistics of ANOVA showed a significant difference among all the four groups (p = 0.00, <0.05). Tukey HSD test indicated that there was a statistical difference between Group F and the other groups, but there was not a significant difference between the other groups. The highest adhesive strength value was observed in group F, the lowest in group C. Use of denture adhesives improved the retentive strength of complete denture.     

Harmonic analysis and performance improvement of slip energyrecovery induction motor drives

Slip energy recovery induction motor drives are used in high power applications, in which by controlling the slip power a variable speed drive system is provided. However, poor power factor is a disadvantage of the system. Presence of sub-harmonics of the line frequency on the stator side is one of the special features of these drives. A phase-controlled inverter can absorb the reactive power from the supply and inject the low-order current harmonics with relatively high amplitudes to the supply. This paper simulates the harmonic content of waveforms in various points of drive at different speeds, based on the hybrid model (dqabc). Then the sinusoidal pulse-width-modulation (SPWM) control technique is used in order to improve the power factor of the drive and to weaken the injected low-order harmonics to the supply. Based on the frequency spectrum, total harmonic distortion, distortion factor and power factor, two phase control and SPWM techniques are compared and the advantage of the SPWM technique over the phase control technique is shown     

Some numerical studies of interface advection properties of level set method

In this paper, we discuss the results of a series of tests carried out to assess the level set methodology for capturing interfaces between two immiscible fluids. The tests are designed to investigate the accuracy of convection process, the preservation of interface shape, and the mass conservation properties of individual fluids. These test cases involve the advection of interfaces of different shapes exposed to translation, rotation, deformation, and shear flow. Prescribed solenoidal velocity fields are used and no attempt is made to couple the advection of the level set function with the momentum equations. For the solution of level set equation we have employed first-order upwind scheme, MacCormack method, second-order ENO scheme, and fifth-order WENO scheme. Our studies show that the level set method perform well when higher-order schemes are used for the solution of advection equation. However, for certain type of shearing and vortical velocity fields mass conservation is an issue on coarser meshes even with higher order schemes. Finer mesh must be used in such situations to reduce numerical diffusion.     

Risk assessment of combined photogenotoxic effects of sunlight and food additives

The presence of flavored colorants (peach and raspberry), flavors (caramel, citric acid and vanilla) and food preservatives (sodium nitrite, sodium nitrate, sodium benzoate, benzoic acid, potassium sorbate and sodium chloride) in Escherichia coli suspension during exposure to sunlight did not change the extent of cell survival. No effect on viability and mutation induction (kanamycin resistant) was also seen when cells were kept in contact with any of the additives for 80 min in the dark. However, when the relevant additive was present in cell suspension during sunlight exposure the number of induced mutations was increased to varying extents over that seen with sunlight alone. Raspberry and peach increased the number of mutations in a dose dependent manner, while vanilla produced mutations in an additive fashion. Nitrite, nitrate, benzoate, sorbate and benzoic acid increased mutation somewhat additively over that of sunlight. Sodium chloride and citric acid were not effective. The impact of this investigation reflects the significance of combination of sunlight and chemical food additives as potential risk, which requires special attention and necessitates further investigations to evaluate the risk.     

A new metal chelate sorbent for glucose oxidase: Cu(II)- and Co(II)-chelated poly(N-vinylimidazole) gels

Poly(N-vinylimidazole) (PVIm) gels were prepared by irradiating a binary mixture of N-vinylimidazole (VIm)–water in a ⁶⁰Co-γ source having 4.5 kGy/h dose rate. In the glucose oxidase (GOx) adsorption studies, affinity gels with a swelling ratio of 1100% for PVIm and 40 and 55% for Cu(II)- and Co(II)-chelated PVIm gels, respectively, at pH 6.5 in phosphate buffer were used. FTIR spectra were taken for PVIm and Cu(II)- and Co(II)-chelated PVIm, and glucose oxidase adsorption on these gels, to characterize the nature of the interactions in each species. The results show that PVIm–glucose oxidase interaction is mainly electrostatic and metal ion–chelated PVIm gel–glucose oxidase interaction is of coordinate covalent nature. Cu(II) and Co(II) ions were chelated within the gels via amine groups on the imidazole ring of the gel. Different amounts of Cu(II) and Co(II) ions [maximum 3.64 mmol/g dry gel for Cu(II) and 1.72 mmol/g dry gel for Co(II)] were loaded on the gels by changing the initial concentration of Cu(II) and Co(II) ions at pH 7.0. GOx adsorption on these gels from aqueous solutions containing different amounts of GOx at different pH was investigated in batch reactors. GOx adsorption capacity was further increased when Cu(II) and Co(II) ions were attached [up to 0.53 g GOx/g dry Co(II)-chelated PVIm gels]. More than 90% of the adsorbed GOx was desorbed in 5 h in desorption medium containing 1.0M KSCN at pH 7.0 for plain gel and 0.05M EDTA at pH 4.9 for metal-chelated gel. Nonspecific glucose oxidase adsorption on/in the metal ion–chelated PVIm gel was investigated using 0.02M of phosphate buffer solution. The nonspecific GOx adsorption was determined to be about 18% for PVIm and 8% for the metal ion–chelated PVIm gels. The ionic strength effect was investigated both on PVIm and on the metal ion–chelated PVIm gels for the glucose oxidase adsorption. It was found that ionic strength was more effective on the PVIm gel because of the electrostatic interaction between protonated gel and the deprotonated glucose oxidase side chain. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 446–453, 2001     

Pivotal Role of Phytohormones and Their Responsive Genes in Plant Growth and Their Signaling and Transduction Pathway under Salt Stress in Cotton

The presence of phyto-hormones in plants at relatively low concentrations plays an indispensable role in regulating crop growth and yield. Salt stress is one of the major abiotic stresses limiting cotton production. It has been reported that exogenous phyto-hormones are involved in various plant defense systems against salt stress. Recently, different studies revealed the pivotal performance of hormones in regulating cotton growth and yield. However, a comprehensive understanding of these exogenous hormones, which regulate cotton growth and yield under salt stress, is lacking. In this review, we focused on new advances in elucidating the roles of exogenous hormones (gibberellin (GA) and salicylic acid (SA)) and their signaling and transduction pathways and the cross-talk between GA and SA in regulating crop growth and development under salt stress. In this review, we not only focused on the role of phyto-hormones but also identified the roles of GA and SA responsive genes to salt stress. Our aim is to provide a comprehensive review of the performance of GA and SA and their responsive genes under salt stress, assisting in the further elucidation of the mechanism that plant hormones use to regulate growth and yield under salt stress.     

The growth of chondrocytes using Gelfoam® as a biodegradable scaffold

Successful articular cartilage resurfacing must overcome several problems: the implant must easily fit the defect, it must be stable within the defect before full incorporation of repair tissue has occurred, and the reparative tissue must closely approximate the structure of normal hyaline cartilage. To this end, several natural and synthetic components have been used, both in vivo and in vitro, to provide a scaffold. These include isolated chondrocyte allografts, intact cartilage allografts, periossteal grafts, reconstructed collagen sponges, hydrogels and carbon fibres. However, promising results have been reported using three dimensional scaffolds in culture with isolated chondrocytes with subsequent implantation. This preliminary in vitro study utilizes Gelfoam^® (a purified gelatin sponge) as such a scaffold. The biocompatibility of Gelfoam with both chondrocytes and osteoblast cells was first confirmed. The ability of chondrocytes to replicate and differentiate within Gelfoam scaffolds was assessed biochemically by measurement of the DNA content and glycosaminoglycans (GAG) production over 25 days in culture. The distribution of the cartilagenous matrix produced was observed by light microscopy, and the constituents of this matrix were assessed using specific antibodies and immunolocalization.     

Labeling of cysteine 231 in acetylcholinesterase from Torpedo nobiliana by the active-site directed reagent, 1-bromo-2-[14C] pinacolone. Effects of 2,2'-dipyridyl disulfide and other sulfhydryl reagents

Acetylcholinesterase (AcChE, EC 3.1.1.7) was isolated from the electric organ of T. nobiliana and treated with the active-site-directed alkylating agent 1-bromo-2-[14C]pinacolone ([14C]BrPin), or with BrPin, which acts initially as a competitive inhibitor, Ki = 0.18 mM, and then inactivates the enzyme, k2 = 1.8 x 10(-4) s-1. AcChE aliquots were digested with trypsin and fractionated by reversed phase high performance liquid chromatography. Inactivation caused a decrease in one absorption peak and an increase in another, identified as the peptide beginning at Ala-222 and extending to Arg-242. 5-Trimethylammonio-2-pentanone, a competitive inhibitor, isosteric with acetylcholine, retarded the inactivation and decreased the quantity of labeled peptide. On sequencing, the 14C label was found associated with Cys-231. This was confirmed by comparison with synthesized S-pinacolonylcysteine, by study of effects of blocking the sequencing by o-phthalaldehyde, and by inactivation by 2,2'-dipyridyl disulfide (2-PDS), a thiol-specific reagent that acts initially as a competitive inhibitor, Ki = 0.042 mM, and then inactivates the enzyme, k2 = 5.0 x 10(-4) s-1. This is retarded by 5-trimethylammonio-2-pentanone, and prior inactivation by 2-PDS prevents subsequent reaction of [14C]BrPin in the active site. BrPin inactivates AcChEs from Electrophorus electricus and from human erythrocyte, but 2-PDS does not. Neither reagent inactivates butyrylcholinesterases from human and horse serum.     

Experimental studies on the suitability of human mesothelial cells for seeding vascular prostheses: shear stress resistance in vitro

This investigation forms part of a study on the suitability of human omentum mesothelial cells (HOMES) as an alternative to endothelial cells (EC) for seeding vascular grafts. Isolated HOMES were grown in primary culture and characterized by their morphology (light microscopy and scanning electron microscopy (SEM)), as well as by fluorescence-activated cell sorting (FACS) and immunocytochemistry. The latter two methods showed cells which were positive for smooth muscle-type actin and cytokeratin, but negative for factor VIII-related antigen. HOMES were grown to confluence on glass with or without a fibronectin coating. Controlled shear stress was applied for up to 30 min using a plate and cone rheometer at 20 dynes/cm². These dynamic culture conditions led to loss of only occasional cells. The most marked alterations seen on SEM were some cell elongation, marked raising of the nucleus and loss of luminal cytoplasmic microvilli. Time-lapse video microscopy revealed that shear stress also increased the spreading capacity of some cells. Similar experiments with venous endothelial cells gave a shearing off of a confluent monolayer. This investigation shows the marked shear-stress resistance of HOMES, a pre-requisite for their use to seed vascular prostheses.