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The COVID-19 pandemic revealed during the first global wave of this infectious disease that mass diagnostic testing was necessary to more rapidly detect infection in patients and control the pandemic. Therefore, extra research efforts to develop reliable and more accessible techniques for disease diagnosis are of supreme importance. Here, a target-responsive assembly of gold nanoparticle-core hairpin-spherical nucleic acids (AuNP-core H-SNAs) was implemented to modify the conventional polymerase chain reaction (PCR) assay for the "naked-eye" colorimetric detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA. Two hairpin DNA ligands are designed based on the two highly conserved regions within N and E genes of SARS-CoV-2 RNA by positioning two short palindromic arms (stem) on either side of a recognition sequence (loop). In the presence of a sequence-specific probe (activator), hairpin DNAs anchored to the surface of AuNPs unfold and expose the palindromic ends to the DNA-directed assembly of AuNPs. The sequence of the activator probes was chosen to be identical to the TaqMan probe in a real-time reverse transcription PCR (RT-PCR) assay for specifically targeting the N and E genes of SARS-CoV-2 RNA. They may either be degraded by the 5'-exonuclease activity of DNA polymerase during PCR cycles or stay intact depending on the presence or absence of the target template in the sample, respectively. Post-addition of H-SNA solutions to the final PCR products of some preconfirmed clinical samples for COVID-19 generated naked-eye-observable red and blue colors for positive and negative cases, respectively, with similar sensitivity to that of the real-time RT-PCR method.

In this work, a new nano-structured catalyst with phosphorus acid moieties, synthesized by the reaction of carbon quantum dots (CQDs) and phosphorus acid under refluxing EtOH. The structure and morphology of CQDs–N(CH2PO3H2)2 were fully characterized using various techniques such as Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, thermogravimetric (TG) analysis, fluorescence and X-ray diffraction (XRD) measurements. The new CQDs–N(CH2PO3H2)2 catalyst was successfully used for the synthesis of 2-amino-6-(2-methyl-1H-indol-3-yl)-4-phenyl-4H-pyran-3,5-dicarbonitriles by the one-pot reaction of various aromatic aldehydes, 3-(1H-indol-3-yl)-3-oxopropanenitrile derivatives and malononitrile in refluxing EtOH and/or ultrasonic irradiation conditions.

Introduction:Tooth hypersensitivity is among the most common patient complaints caused by the response of exposed dentin to external stimuli. No definite treatment has been suggested so far for dentin hypersensitivity (DH). This study aimed to compare the efficacy of the diode laser alone and in combination with Gluma and chromophore in occluding opened dentine tubules and the treatment of DH.Methods:This in vitro study was conducted on 30 extracted human third molars kept in 0.1% thymol solution. The teeth were mounted in transparent acrylic resin and the buccal enamel was cut to expose the outer third of dentin. The samples were then divided into 6 groups of negative control (no smear layer removal), positive control (smear layer removal with 6% citric acid application), 810 nm diode laser irradiation (energy density 55.55 J/cm2 , 1 W for 20 seconds in a continuous mode), chromophore (1 mg/mL indocyanine green, ICG) plus diode laser irradiation (1 W, 20 seconds), Gluma plus diode laser irradiation, and Gluma + chromophore + diode laser. Dentinal tubules were evaluated under a scanning electron microscope at x2000 magnification. The mean percentage of the obstruction of dentinal tubules was reported as mean and standard deviation. Considering the normal distribution of the data, two-way ANOVA was applied to compare the efficacy of treatments, and an independent-samples t test was used for pairwise comparisons at PResults:The highest mean percentage of the obstruction of dentinal tubules was noted in the diode laser/chromophore/Gluma group (65.68±12.31%) while the lowest value was noted in the diode laser/Gluma group (24.33±5.90%). Pairwise comparisons revealed significant differences between all groups (PP=0.20).Conclusion:It seems that chromophore increases the efficacy of the diode laser for the obstruction of dentinal tubules.

Objectives The advantages of indirect composite restorations such as less crack formation during their computer-aided design/computer-aided manufacturing process, compared with ceramic restorations, have resulted in their growing popularity. However, restoration failure is a major concern with regard to the long-term clinical success of restorations and may occur as the result of propagation of a crack originated from an internal flaw in the restoration. This study aimed to compare the fracture toughness of three indirect composite resins. Materials and Methods In this in vitro experimental study, 10 specimens measuring 3 × 3 × 18 mm were fabricated of Gradia, Crios, and high impact polymer composite indirect composites. A single edge notch with a diameter < 0.3 mm and 0.3 mm length was created in the 9 mm longitudinal dimension of specimens using a no. 11 surgical scalpel. The specimens were then subjected to 4-point flexural strength test in a universal testing machine with a crosshead speed of 0.1 mm/s until failure. Statistical Analysis Data were analyzed using IBM SPSS Statistics via one-way analysis of variance (ANOVA) and Tukey’s HSD (honestly significant difference) test. The statistical power was set at p ˂ 0.05. Results One-way ANOVA showed a significant difference in fracture toughness of the three composite groups (p = 0.000). According to the Tukey HSD analysis, the fracture toughness of HIPC was significantly higher than that of the other two composites. The fracture toughness of Gradia was significantly lower among all. Conclusions Within the limitations of this study, the results showed that high temperature-pressure polymerization can increase resistance to crack propagation and subsequently improve the clinical service of indirect composite restorations. Although we do not know the filler volume percentage of HIPC, it seems that filler volume percentage of the composite is inversely correlated with fracture toughness.

Objectives: Toothpastes and mouthwashes contain ingredients that may be toxic for oral mucosal tissues. This study aimed to assess the cytotoxicity of the ingredients of commonly used toothpastes and mouthwashes. Materials and Methods: This experimental study was performed on 16 toothpastes and four mouthwashes widely available in the Iranian market. First, the concentration of six main ingredients of these products, namely sodium fluoride (NaF), sodium lauryl sulfate, cocamidopropyl betaine, zinc lactate, paraben, and sodium benzoate, was determined. The methyl thiazolyl tetrazolium (MTT) assay was used to assess the cytotoxicity of these materials for human gingival fibroblasts (HGFs). The MTT assay was performed at 1, 15, and 30 minutes following exposure to five concentrations of each material in triplicate (according to the concentrations obtained in the isolation step). Data were analyzed using three-way analysis of variance (ANOVA). Results: The difference in the cytotoxicity of the materials was statistically significant (P90%. The cytotoxicity of NaF varied from 25% to 70%, and the cytotoxicity of all concentrations of zinc lactate and sodium benzoate was

Objectives: Color change of cements over time can be detected through translucent ceramic veneers, compromising the aesthetic appearance of restorations in the long-term. This study aimed to assess the color stability of ceramic laminate veneers cemented with self-adhesive resin cements after accelerated aging. Materials and Methods: In this study, 21 IPS e.max ceramic discs, measuring 8mm in diameter and 0.7 mm in thickness, were fabricated and divided into three groups (n=7) for the application of Choice 2 total-etch light-cure resin cement, RelyX U200 dual-cure self-adhesive resin cement, and SpeedCEM self-cure self-adhesive resin cement. The ceramic discs in each group were cemented on the prepared facial surface of bovine teeth. The color parameters were assessed using a spectrophotometer. Subsequently, the samples were subjected to accelerated aging for 100 hours, and the color parameters were measured again. The data were analyzed using two-way repeated-measures analysis of variance (ANOVA) and Tamhane’s post-hoc test (P3.5). The color change of the other two groups was clinically acceptable (1

Background: Proper selection of cement plays an effective role in the success of ceramic laminate veneers. The cement can affect the final color by changing the optical properties of the ceramic. Objective: Due to the ease of clinical use of the seventh generation of cement (Self-Adhesive Cement), this study aimed to evaluate the effect of this type of cement on the final color of Ceramic Veneers (CV). Methods: In this study, 21 IPS e.max ceramic disks (8mm× 0.7 mm) were used. They were divided into 3 groups of 7, depending on the type of cement. (Choice 2, RelyX U200, Speed Cem). In the first stage, ceramic disks were set on the facial surface of bovine’s teeth by bonding agents and the color properties were analyzed by spectrophotometer. In the next stage, specimens were cemented on the prepared surfaces according to the manufacturer’s instructions and their color was evaluated subsequently. Results: Results were analyzed by repeated measures two-way ANOVA and TAMHANE post hoc methods (P < 0.05). Results showed that cement influences the color of the ceramic laminate. ∆E values were reported to be higher than the critical point after cementation (∆E > 2.69). Conclusion: There was no significant difference between the effects of three cement types on the final color of the ceramic veneers.

In this study, we have designed, synthesized and full characterized a novel biological based acidic nano organocatalyst via condensations reaction of uric acid and phosphorous acid. The obtained compound was named theacrine tetrakis(phosphonic acid) (TTPA) and prepared under refluxing ethanol. This new nano organocatalyst was applied as an efficient and recyclable catalyst for the preparation of novel pyridines with indole moieties via a cooperative vinylogous anomeric based oxidation with good to excellent yields.

In this work, a new nano-structured catalyst with phosphorus acid moieties, synthesized by the reaction of carbon quantum dots (CQDs) and phosphorus acid under refluxing EtOH. The structure and morphology of CQDs-N(CH

Objectives: Toothpastes and mouthwashes contain chemicals that may be harmful to oral tissues. This study assessed the cytotoxicity and antibacterial activity of toothpastes and compare the Iranian and foreign toothpastes and mouthwashes available in the Iranian market in this respect. Materials and Methods: Twenty samples (13 toothpastes and 4 mouthwashes) were selected. The cytotoxicity of 1, 10, and 50 mg/mL of toothpastes and 0.05, 2 and 10 µL of mouthwashes was measured after 1, 15 and 30 min of exposure to human gingival fibroblasts, each in triplicate. The methyl thiazolyl tetrazolium (MTT) assay was used for cytotoxicity testing. The serial dilution method was utilized to determine the minimum inhibitory concentration (MIC) of each sample against Lactobacillus acidophilus (L. acidophilus) and Streptococcus mutans (S. mutans). Two-way ANOVA and Tukey’s test were used for data analysis. Results: A significant difference in cytotoxicity was noted among different products (P=0.00). The difference in cytotoxicity of each sample was not significant at 1, 15 and 30 min (P=0.08). The obtained MIC for all toothpastes and mouthwashes was between 0.0039 mg/mL and 0.0156 mg/mL, except for Sensodyne toothpaste and Oral B mouthwash. Conclusion: Some brands of toothpastes have higher cytotoxicity due to their composition, and their cytotoxicity should not be overlooked. The antibacterial activity of the samples was almost equal when they were in contact with L. acidophilus and S. mutans except for the Irsha mouthwash, Sehat, Darugar and Bath toothpastes. The antibacterial effect of toothpastes and mouthwashes increased with an increase in exposure time.

Graphical abstract, Highlights • The amplification power of PCR is coupled with programmability of SNA assembly for detection of COVID-19. • A linker-based single-component assembly system based on E gene of SARS-CoV-2 RNA provides a post PCR colorimetric response with comparable sensitivity to real time RT-PCR. • The palindromic linker is disintegrated based on 5’-exonuclease activity in the course of PCR amplification. • The positive and negative viral COVID-19 samples are simply distinguished via different colors by naked eyes., Continuous identification of suspected infectious cases is crucial to control the recent pandemic caused by the novel human coronavirus SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2). Real-time polymerase chain reaction (real-time PCR) technology cannot be implemented easily and in large scale in some communities due to lack of resources and infrastructures. Here, we report a simple colorimetric strategy derived from linker-based single-component assembly of gold nanoparticle core-spherical nucleic acids (AuNP-coreSNAs) for visual detection of PCR products of SARS-CoV-2 ribonucleic acid (RNA) template. A palindromic linker is designed based on E gene of SARS-CoV-2 to program the identical colloidal SNAs into large assemblies along with a distinct red-to-purple color change. The linker acts as a probe of SARS-CoV-2 RNA in conventional PCR reaction. In the presence of the correct template, the palindromic linker, which is complementary to a short region within the amplicon, is cleaved by 5’-exonuclease activity of deoxyribonucleic acid (DNA) polymerase. Disintegrating the palindromic linker during the amplification process inhibits the post single-component assembly formation of SNAs. So, positive and negative viral samples produce simply red and purple colors in the post PCR colorimetric test, respectively. Evaluation of the samples obtained from cases with laboratory-confirmed SARS-CoV-2 infection revealed that our assay can rival with Real-time PCR method in sensitivity.

Introduction: Tooth hypersensitivity is among the most common patient complaints caused by the response of exposed dentin to external stimuli. No definite treatment has been suggested so far for dentin hypersensitivity (DH). This study aimed to compare the efficacy of the diode laser alone and in combination with Gluma and chromophore in occluding opened dentine tubules and the treatment of DH. Methods: This in vitro study was conducted on 30 extracted human third molars kept in 0.1% thymol solution. The teeth were mounted in transparent acrylic resin and the buccal enamel was cut to expose the outer third of dentin. The samples were then divided into 6 groups of negative control (no smear layer removal), positive control (smear layer removal with 6% citric acid application), 810 nm diode laser irradiation (energy density 55.55 J/cm2 , 1 W for 20 seconds in a continuous mode), chromophore (1 mg/mL indocyanine green, ICG) plus diode laser irradiation (1 W, 20 seconds), Gluma plus diode laser irradiation, and Gluma + chromophore + diode laser. Dentinal tubules were evaluated under a scanning electron microscope at x2000 magnification. The mean percentage of the obstruction of dentinal tubules was reported as mean and standard deviation. Considering the normal distribution of the data, two-way ANOVA was applied to compare the efficacy of treatments, and an independent-samples t test was used for pairwise comparisons at P

In this paper, a novel porous polymer capable of coordinating to bismuth (PCPs-Bi) was synthesized. The Bi-PCPs was then reacted with phosphorous acid to produce a novel polymer PCPs(Bi)N(CH2PO3H2)(2) which is shown to act as an efficient and recyclable catalyst. The mentioned catalyst was applied for the efficient synthesis of new mono and bis naphthoquinone-based salts of piperidine and/or piperazine via the reaction of hennotannic acid with various aldehydes, piperidine and/or piperazine, respectively. The structure of the resulting mono and bis substituted piperazine or piperidine-based naphthoquinone salts was thoroughly characterized spectroscopically. The electrochemical behavior of the products was also investigated. The presented protocol has the advantages of excellent yields (82-95%), short reaction times (4-30 min) and simple work-up.

Objectives Advances in laboratory composites and their high wear resistance and fracture toughness have resulted in their growing popularity and increasing use for dental restorations. This study sought to assess the fracture toughness of three indirect composites bonded to dental substrate and polyether ether ketone (PEEK) polymer. Materials and Methods This in vitro study was conducted on two groups of dental and polymer substrates. Each substrate was bonded to three indirect composite resins. Sixty blocks (3 × 3 × 12 mm) were made of sound bovine anterior teeth and PEEK polymer. Sixty blocks (3 × 3 × 12 mm) were fabricated of CRIOS (Coltene, Germany), high impact polymer composite (HIPC; Bredent, Germany), and GRADIA (Indirect; GC, Japan) composite resins. Composites were bonded to dentin using Panavia F 2.0 (Kuraray, Japan). For bonding to PEEK, Combo.lign (Bredent) and Visio.Link (Bredent) luting cements were used. In all samples, a single-edge notch was created by a no. 11 surgical blade at the interface. The samples were subjected to 3,500 thermal cycles, and their fracture toughness was measured in a universal testing machine (Zwick/Roell, Germany) by application of four-point flexural load. Statistical Analysis Data were analyzed using one-way analysis of variance, Kruskal–Wallis. Results The fracture toughness of CRIOS–PEEK interface was significantly higher than HIPC–PEEK. The fracture toughness of GRADIA–PEEK was not significantly different from that of HIPC and CRIOS. The fracture toughness of GRADIA–dentin was significantly higher than HIPC–dentin. Conclusion Considering the limitations of this study, GRADIA has the highest bond strength to dentin, while CRIOS shows the highest bond strength to PEEK.

Kinetic spectrophotometric second order data based on the reaction of 1,2-naphthoquinone-4-sulphonate (NQS) coupled with multivariate curve resolution-alternating least squares (MCR-ALS) has been proposed for simultaneous determination of ethylamine, propylamine and butylamine. Using second-order advantage, MCR-ALS methodology can solve problems of quantitation of analyte in the presence of unknown and uncalibrated interferences. Ethylamine, propylamine and butylamine react differentially with NQS at pH 9.5. Therefore, determination of these amines has been carried out due to the difference between their reaction rates. Quantitative determination of each amine in the mixture is performed using a synthetic solution as standard containing only the amine of interest. The MCR-ALS results are evaluated by the residuals and parameters such as lack of fit. The quantitative determination of these amines in different synthetic mixtures and some real samples such as river water, well water, tap water and soil has been performed and the results have been found to have good recoveries.

Background and aims Data are limited about the effect of ceramic primers on the bond of zirconia to restorative resin composite. The aim of this study was to assess the effect of different surface treatments and two ceramic primers on shear bond strength (SBS) of zirconia to restorative resin composite. Materials and methods 100 samples of zirconium ceramic blocks were randomly divided into 5 groups (n = 20) and received the following surface treatments: a)Control groupb)AL2O3 abrasionc)Nd:YAG laserd)Er:YAG lasere)Bur preparation.Next, each group was divided into two subgroups of 20. In ten out of 20 specimens in each group, monobond plus and Tetric ceram composite resin were applied on the surface. ZPrime Plus and Elite composite were applied on the surfaces of the remaining 10 specimens in each group. Samples were then subjected to shear bond strength test in a universal testing machine until fracture. The mean SBS were calculated and statistically analyzed by two-way ANOVA and T-Test. P < 0.05 was considered statistically significant. Results In ZPrime plus subgroups, diamond bur yielded the highest bond strength. Laser groups showed no significant difference with the control group. In monobond plus subgroups, SBS of air abrasion and diamond bur subgroups was highest and Nd:YAG laser showed the lowest SBS. The lowest bond strength belonged to the Nd:YAG laser subgroup of monobond plus group. Conclusions Type of surface preparation significantly affected the bond strength.

In this article a convenient method for the synthesis of novel piperazine based bis(4-hydroxy-2H-chromen-2-one) derivatives using pyrazine-1,4-diium tricyanomethanide {[1,4-DHPyrazine][C(CN)(3)](2)} as a new nanostructured molten salt (NMS) catalyst has been described. These compounds were synthesized via Mannich type reaction between several aromatic aldehyde, piperazine and 4-hydroxycoumarin under solvent-free condition at room temperature. The NMS catalyst was fully characterized via Fourier transform infrared (FT-IR), nuclear magnetic resonance (H-1 NMR and C-13 NMR), mass spectrometry, thermal gravimetric, derivative thermal gravimetric, differential thermal analysis, X-ray diffraction patterns, scanning electron microscopy and transmission electron microscopy analysis. The new compounds synthesized by using this NMS catalyst were also characterized by FT-IR, H-1 NMR and C-13 NMR, high-resolution mass spectrometry techniques. The new NMS catalyst simply recovers and can be reused several times without significant loss of catalytic activity. The major advantages of the described method in comparison to the classical reactions are low catalyst loading, short reaction time, high yields, simple isolation of product and reusability of the NMS catalyst.Pyrazine-1,4-diium tricyanomethanide as a nano molten salt catalyst was designed, synthesized and used for the synthesis of novel biological piperazine based bis(4-hydroxy-2H-chromen-2- one) derivatives as bioactive and drug candidates.[GRAPHICS].

Triphenylammonium tricyanomethanide (Ph3NH)[C(CN)3] was synthesized and used as an efficient and recyclable nanostructured molten-salt (NMS) catalyst for the synthesis of N-benzylidene-2-arylimidazo[1,2-a]pyridin-3-amines by the reaction of various (het)aryl aldehydes with trimethylsilyl cyanide and pyridin-2-amine under solvent-free conditions at 50 °C. The NMS catalyst could be simply recycled and reused several times without significant loss of its catalytic activity.

Gold nanoparticle-core spherical nucleic acids (AuNP core-SNAs), by virtue of the programmable nature of oligonucleotides, have yielded access to the innovative strategies for targeted biodiagnostics. Here, DNA-directed self-assembly of AuNP core-SNAs has been used to design a colorimetric method to sense HIV-1 viral nucleic acid. This strategy utilizes an oligonucleotide with sequence of 5'-untranslated region (5' UTR) of the HIV-1 RNA genome anchored on the surface of AuNPs and a complementary linker strand with a palindromic sequence tail. In the absence of HIV-1 target nucleic acid the complementary linker induces self-assembly of SNAs based on sequence symmetry in the free palindromic tail which can bridge two DNA double helices. While in the presence of the target DNA, due to linker-target duplex formation, the colloidal stability and the red color of the SNAs solution are preserved. Picomole amounts of target DNA can easily be detected with the naked eyes. A 95-mer synthetic DNA strand with the same sequence of HIV-1 viral RNA was utilized for positive control of HIV-1 RNA. The selectivity of the selected linker was satisfactory up to 90% match.

The interaction of iodine as electron acceptor with nortriptyline and imipramine drugs as electron donors has been investigated spectrophotometrically at various temperatures in chloroform and dichloromethane solutions. The observed time dependence of the charge–transfer band and subsequent formation of in solution were related to the slow transformation of the initially formed iodine: drug outer complex to an inner electron donor–acceptor (EDA) complex, followed by fast reaction of the inner complex with iodine to form a triiodide ion. The pseudo-first-order rate constants and activation parameters for the transformation process were evaluated from the absorbance-time data. Stoichiometrices of the complexes were defined by the Job’s method of the continuos variation and obtaind 2: 1 for iodine: drug complexes. The formation constants and molar absorptivities were evaluated from the absorbance-mole ratio data. Thermodynamic parameters of the complexes have been determined from the temperature dependence of the stability constant by Van’t Hoff equation.

In this chapter the attitude of mothers to the use of computer-assisted language learning (CALL) in their children's language learning was investigated. 118 Iranian mothers were selected based on convenient sampling. Their attitude towards CALL was assessed by a 12-item questionnaire. The result of data analysis revealed that generally mothers have roughly positive attitudes towards CALL. Significant differences were reported when mothers with higher education were compared with those mothers who did not have university degrees. However, gender, age, and mother's profession did not have any role in their attitudes towards CALL.

We present the fabrication and testing of graphene-based dipole antennas on cardboard which is a promising low-cost, recyclable, and flexible substrate for future wireless electronics. The article presents the details of the manufacturing, as well as results from the measurements and simulations. The measured sheet resistance of graphene antenna is 1.9 Ω/sq. Overall, a graphene-based planar dipole antenna with the length of 143 mm achieved the measured total efficiency of 40% and the realized gain of –2.18 dBi at 889 MHz. Moreover, a passive ultra-high-frequency radio-frequency tag based on a graphene dipole antenna on cardboard achieved the attainable read range of more than five meters at 950 MHz. acceptedVersion

In this work, an application of mean centering of ratio spectra is proposed to the study of pollutant dyes degradation using Fenton reaction. Two-way kinetic-spectrophotometric data related to dye(s) mixtures degradation are divided into simulated kinetic profiles, mean centered and their ranks were monitored versus simulated dye degradation constant. For accurate dye degradation constant(s), the rank of resulted matrix will be reduced by one. By this search, all kinetic constants related to all included dyes are acquired. To find out which k values are related to the degradation of dye of interest, a preliminary deflation of data from its contribution is done and the procedure is repeated. By this search, the kinetic constant related to dye of interest will be omitted while others will be remained. The applicability of the proposed method was evaluated using model data. Finally, second-order kinetic-spectrophotometric data in the degradation of malachite green in the presence of crystal violet and methylene blue were analyzed by the proposed method as a real system.

Objectives: The aim of this study was to compare the permeability of dentin after using diamond bur and Er:YAG laser. Materials and Methods: Seventy-two recently extracted, intact, and restoration-free human permanent molars were used in this study. The samples were randomly divided into three groups of 24 each and class I cavities were prepared as follows. Group 1: High speed diamond bur with air and water spray. Group 2: Er:YAG laser. Group 3: Er:YAG laser followed by additional sub-ablative laser treatment. Each group consisted of two subgroups with different cavity depths of 2mm and 4mm. The entire cavity floor was in dentin. Two samples from each subgroup were observed under scanning electron microscope (SEM). The external surfaces of other samples were covered with nail varnish (except the prepared cavity) and immersed in 0.5% methylene blue solution for 48 hours. After irrigation of samples with water, they were sectioned in bucco-lingual direction. Then, the samples were evaluated under a stereomicroscope at ×160 magnification. The data were analyzed using two-way ANOVA and Tukey’s HSD test. Results: Two-way ANOVA showed significant difference in permeability between groups 2 and 3 (laser groups with and without further treatment) and group 1 (bur group). The highest permeability was seen in the group 1. There was no significant difference in dentin permeability between groups 2 and 3 and no significant difference was observed between different depths (2mm and 4mm). Conclusion: Cavities prepared by laser have less dentin permeability than cavities prepared by diamond bur.

A simple procedure for the quantitative determination of mixtures of nitrophenols pollutants in environmental and biological samples based on continuous spectrophotometric acid–base titrations and multivariate curve resolution has been proposed. The procedure simultaneously takes into account the spectroscopic and acid–base properties of the nitrophenols, which leads to a higher selectivity. The quantitative determination of analyte in the presence of unknown and uncalibrated interferences is a general benefit of the method. Moreover, only one single synthetic standard containing of the analyte of interest is enough to perform the analysis. Because of the rank-deficiency phenomena, the pure spectra and concentration profiles of the species of interest can only be recovered through matrix augmentation. Even in the presence of the rank deficiencies, in most cases accurate quantitation with relative errors in prediction lower than 5 % was obtained. The percent recoveries obtained (92–108 %) were satisfactory.

Mixtures of acetylsalicylic acid (ASA), paracetamol (PAR), and caffeine (CAF) have been successfully analyzed by constrained multivariate curve resolution-alternating least squares (MCR-ALS). The MCR-ALS methodology adequately exploits the second-order advantage which enables quantitation of analyte in the presence of unknown and uncalibrated interferences. The procedure simultaneously takes into account the spectroscopic and pH-dependent properties of the compounds, which leads to a higher selectivity. Specially, for CAF determination fully protonated or deprotonated forms of CAF are not dominant in the pH range of data acquisition but spectral changes with pH were recorded and used for accurate determination of CAF. Furthermore, quantitative determination of an analyte in a complex mixture is performed using a synthetic solution as standard containing only the analyte of interest. Even in the presence of the rank deficiencies, in most cases accurate quantitation with relative errors in prediction lower than 5 % was obtained. The procedure was successfully applied to the analysis of real samples (pharmaceuticals) using synthetic external standards. Percent relative errors of 4.03, 3.26, and 5.85 were obtained for ASA, PAR, and CAF, respectively, in A.C.A tablets and 4.49 and 2.75 for PAR and CAF, respectively in Novafen capsules.

A new approach that takes advantage of both soft-modeling and pattern recognition methods is proposed to analyze kinetic data monitored spectrometrically to classify structurally similar nitroaniline isomers. The colorimetric condensation reaction of 1,2-naphthoquinone-4-sulfonate (NQS) with amines has been used to classify 2-, 3-, and 4-nitroaniline on the basis of their different kinetic properties. These nitroanilines react differentially with NQS at pH 7 to produce a colored product. Soft-modeling approaches such as multivariate curve resolution–alternating least squares (MCR–ALS) and simple-to-use interactive self-modeling mixture analysis (SIMPLISMA) followed by multiplicative signal correction have been used as preprocessing procedures to obtain patterns diagnostic for the analytes. Rank analysis was initially performed using determination of rank by augmentation to detect any species present during the course of the reaction in the system under investigation. The spectra and kinetic profiles of all absorbing species present in the raw measurements were obtained from SIMPLISMA and MCR–ALS resolution. The kinetic profiles were then used as input of the pattern recognition algorithm. The response patterns were systematically classified using linear discriminant analysis with high classification accuracy. Either all or one of the resolved profiles related to the components involved in the reaction can be used for identification of nitroaniline isomers. Copyright © 2013 John Wiley & Sons, Ltd.

Using the formation constants of 74 charge–transfer complexes in which iodine and iodine monochloride act as acceptors, quantitative structure–property relationships models were developed for predicting these constants for the first time. The procedure was based on reducing a large number of the descriptors based on the variable importance in projection and subsequent selection by stepwise regression and genetic algorithm. The most important variables influencing the charge–transfer interactions were identified and interpreted. Models were obtained by linear methods of multiple linear regression and partial least squares regression and the nonlinear method of radial basis function–partial least squares. The best predictions were obtained with the Gaussian radial basis function with σ = 0.9 and LV = 10. The obtained results confirm the capability of the proposed approach to give predictive models for K CT.

This work presents an exploratory study of the kinetic of the reaction between the drug, amlodipine, and 1,2-naphthoquinone-4-sulfonate (NQS) and gives an interpretation of the kinetic pathway. The kinetic reaction was investigated under pH10.50 and 25 °C by UV–vis spectrophotometric data. Model elucidation was performed by principal component analysis (PCA), multivariate curve resolution-alternating least squares (MCR-ALS) and augmentation of data acquired in different conditions. A data analysis approach based on global hard-modelling was applied to further elucidate the mechanism of the kinetic process, resolve the kinetic and pure spectral profiles of the intermediates and products and evaluate the rate constants. The kinetic process was evaluated with different kinetic two-step consecutive models which their first step was a second-order step. The results of the global hard-modelling of different possible reaction pathways (models) were compared. In spite of the rank deficiency, model parameters in most cases can be obtained by hard-modelling of the single data matrices. However, for some of the kinetic models and experimental conditions, because of the rank deficiency of the concentration matrix, the pure component concentration and spectral profiles cannot be computed since the linear regression step cannot be performed. Here, we applied matrix augmentation to solve this problem.

This letter studies a dual-interrogation-mode (hybrid chip-enabled/chipless) technique to detect an embroidered radio frequency identification (RFID)-enabled sensor. We have created a hybrid RFID strain sensor utilizing both chipped and chipless approaches. A comparison between the read-range extraction technique, which relies upon the detection of the threshold power that is required to activate an RFID IC, and a radar-cross-section (RCS)-based technique that does not require any protocol is presented. An embroidered RFID sensor with an electrical length that is directly linked to the applied strain is realized and interrogated using both techniques. The sensitivities for the chipless radar technique and for the chip-enabled read range extraction technique are 0.66% and 0.43% frequency shift, respectively, for 1% strain variation. Simulations and measurements validate the dual interrogation mode and provide the proof of concept that a chip-enabled RFID sensor tag can be detected accurately utilizing backscattering RCS measurements.

Objectives: The aim of this study was to assess the effect of artificial accelerated aging (AAA) on color change of direct and indirect fiber-reinforced composite (FRC) restorations. Materials and Methods: Direct (Z250) and indirect (Gradia) composite resins were reinforced with glass (GF) and polyethylene fibers (PF) based on the manufacturers’ instructions. Forty samples were fabricated and divided into eight groups (n=5). Four groups served as experimental groups and the remaining four served as controls. Color change (∆E) and color parameters (∆L*, ∆a*, ∆b*) were read at baseline and after AAA based on the CIELAB system. Three-way ANOVA and Tukey’s test were used for statistical analysis. Results: Significant differences were found in ΔE, ΔL*, Δa* and Δb* among the groups after AAA (P

The charge–transfer (CT) complex of donor antipyrine with Π-acceptor 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) has been investigated spectrophotometrically in different halocarbon and acetonitrile solvents. The results indicated immediate formation of an electron donor–acceptor complex (DA), which is followed by two relatively slow consecutive reactions. The pseudo–first-order rate constants for the formation of the ionic intermediate and the final product at various temperatures were evaluated from the absorbance–time data. The activation parameters, viz. activation energy, enthalpy, entropy, and free energy of activation, were computed from temperature dependence of rate constants. The stoichiometry of the complex was found to be 1:1 by Job's method of continuous variation. The formation constants of the resulting DA complexes were determined by the Benesi–Hildebrand equation at four different temperatures. The enthalpies and entropies of the complex formation reactions have been obtained by temperature dependence of the formation constants using Van't Hoff equation. The results indicate that DDQ complexes of antipyrine in all solvents are enthalpy stabilized but entropy destabilized. Both the kinetics of the interaction and the formation constants of the complexes are dependent upon the polarity of the solvents. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 45: 81–91, 2013

A quantitative structure–property relationship (QSPR) study was conducted to develop models to relate the structure of 46 donor compounds to their charge–transfer complex formation constants with chloranil for the first time. Donors were a diverse set of organic compounds having different functional groups. QSPR models were calculated using multiple linear regressions (MLR) and partial least squares regression (PLSR) to predict charge–transfer complex formation constants. Some important descriptors in charge–transfer complex formation were calculated and added to the descriptors taken from DRAGON software. After a reduction step using variable importance in projection, stepwise regression was employed to select the most relevant descriptors and develop the QSPR models. Results of the PLSR and MLR modeling by the selected descriptors were markedly similar. The results showed that descriptors related to nitrogen, carbonyl group, and polarizability strengthen the charge–transfer interactions.