Effect Of Time Lapse Research Articles

Effect of Time-Lapse between Intermediate Restoration and Final Restoration on Survival Rate and Changing of Radiographic Periapical Lesion

Abstract Objective This study aimed to assess the impact of intermediate restoration time-lapse on the survival rate and changes in radiographic periapical lesions of endodontically treated teeth. Materials and Methods The included treatment records and periapical films of 62 patients were divided into two groups based on the time-lapse of intermediate restoration: within 4 months group (≤4 m group) and more than 4 months group (>4 m group). Statistical Analysis Survival analysis was conducted using Kaplan–Meier and log-rank test. The predictive clinical factors were assessed using a Cox regression model and hazard ratio, considering both clinical and radiographic outcomes from the latest recall appointment. Changes in periapical index (PAI) scores on radiographs were evaluated using the Chi-square test. Statistical significance was set at p < 0.05. Results The mean survival rate of endodontically treated teeth was 77.4%. The survival rates of the ≤4 m group and >4 m group were 83.3 and 69.2%, respectively, without statistical significance. None of the clinical factors significantly affected the clinical outcome. However, the >4 m group exhibited significantly worse changes in PAI scores between the final restoration appointment and the latest recall. Conclusion Different time-lapses for intermediate restoration did not significantly affect the survival rate. However, an intermediate restoration time-lapse of more than 4 months tended to result in worse changes in PAI scores.

Effect of Interlayer Time-Lapse and Workability Retention on Printed Concrete Performance

Effect of Interlayer Time-Lapse and Workability Retention on Printed Concrete Performance

S631 Overnight Split Dosing With 1L Polyethylene Glycol + Ascorbic Acid Bowel Preparation Delivers High Levels of High-Quality Cleansing for Colonoscopy: A Sub-Analysis of a Large Real-World Study

Introduction: Clinical guidelines recommend evening/morning split dosing for routine colonoscopy procedures. Overnight split dosing with 1 liter polyethylene glycol + ascorbic acid (1L PEG+ASC) has demonstrated strong cleansing performance in clinical trials. Here we report a sub-analysis from the largest real-world study to date of 1L PEG+ASC, evaluating patients who received this split dosing regimen. Methods: An observational, multicenter, retrospective study evaluated the medical records of colonoscopy outpatients between July 2019 and September 2021 at 12 centers in Spain and Portugal. Eligible adults (aged ≥18 years) had a screening, surveillance, or diagnostic colonoscopy after an evening/morning (split dose) or same-day regimen of 1L PEG+ASC. Bowel cleansing was assessed by site endoscopists using the Boston Bowel Preparation Scale (BBPS). Segmental BBPS scores of 3 defined high-quality cleansing. High adherence was defined as consumption of ≥75% of each dose and safety was assessed based on registered adverse events (AEs). BBPS scores were compared between time to colonoscopy groups with the Wilcoxon rank-sum test. Results: A total of 13,169 patients from the 12 centers were enrolled in the study, of which 4,316 received a split-dosing regimen and were included in this analysis. In the split-dose group, 48.0% of patients were male, mean (SD) age was 58.1 ± 13.4 years, and 33.4% were ≥65 years old. An overall BBPS score of 9 was attained in 58.3% of patients (Figure A). High rates of BBPS 3 were observed in all segments (Figure B). There was no effect of time lapse to colonoscopy on segmental cleansing in the transversal and left colon (Figure C). Only 1.6% of colonoscopies were incomplete, 0.39% due to poor preparation. Overall, 3.9% (95% CI: 3.4%–4.6%) of patients experienced an AE. The main AEs were nausea (2.4%), vomiting (1.2%), and abdominal pain (0.4%). Adherence was high at 97.6% of those 1,834 patients who reported volume intake. Conclusion: Results from this analysis show that overnight split dosing with 1L PEG+ASC delivered an excellent overall and segmental bowel cleansing quality in real-world settings.Figure 1.: Bowel cleansing performance of split dose 1L PEG+ASC: (A) Rates of overall colon high-quality cleansing (BBPS score >6); (B) Rates of segmental high-quality cleansing (BBPS score 3); (C) Effect of time to colonoscopy on mean segmental BBPS scores.

An in vitro Study on the Role of Hepatitis B Virus X Protein C-Terminal Truncation in Liver Disease Development.

Hepatitis B virus X protein C-terminal 127 amino acid truncation is often found expressed in hepatocellular carcinoma (HCC) tissue samples. The present in vitro study tried to determine the role of this truncation mutant in the hepatitis B–related liver diseases such as fibrosis, cirrhosis, HCC, and metastasis. HBx gene and its 127 amino acid truncation mutant were cloned in mammalian expression vectors and transfected in human hepatoma cell line. Changes in cell growth/proliferation, cell cycle phase distribution, expression of cell cycle regulatory genes, mitochondrial depolarization, and intracellular reactive oxygen species (ROS) level were analyzed. Green fluorescent protein (GFP)–tagged version of HBx and the truncation mutant were also created and the effects of truncation on HBx intracellular expression pattern and localization were studied. Effect of time lapse on protein expression pattern was also analyzed. The truncation mutant of HBx is more efficient in inducing cell proliferation, and causes more ROS production and less mitochondrial depolarization as compared with wild type (wt) HBx. In addition, gene expression is altered in favor of carcinogenesis in the presence of the truncation mutant. Furthermore, mitochondrial perinuclear aggregation is achieved earlier in the presence of the truncation mutant. Therefore, HBx C-terminal 127 amino acid truncation might be playing important roles in the development of hepatitis B–related liver diseases by inducing cell proliferation, altering gene expression, altering mitochondrial potential, inducing mitochondrial clustering and oxidative stress, and changing HBx expression pattern.

Forced locomotor activity improves walking ability of male turkeys and modifies carcass characteristics

ABSTRACT1. This trial investigated the effect of forced locomotor activity (training) on walking ability, leg posture, and growth performance, as well as carcass composition and meat quality in male fattening turkeys.2. A flock of 744 commercial turkeys was divided into three experimental groups, either without any training period (control), training from weeks 2 to 8 (short-term), or training from weeks 2 to 21 (long-term). All birds were slaughtered at an age of 21 weeks. To study the effect of short vs. long time lapse between shackling and stunning (suspension time), each training group was split into two halves that were hooked on the shackle for either 15 s or 3 min prior to stunning.3. Long-term physical training, compared to short-term or no training, resulted in better walking ability and in a lower percentage of leg malposition, as assessed at the end of fattening. No effect on final body weight was detected.4. In a subsample, the composition of 80 carcasses was determined by dissection. Long-term training favoured the percentage of the drumstick over that of the breast cut in comparison to the group without any training.5. Meat quality parameters were determined for breast muscle. The pH values 20 min post-mortem were reduced by long-term training, and the highest value was observed for a combination of no training with short suspension. After 24 h, pH values did not differ between experimental groups. The breast muscles were characterised as fast-glycolysing. Prolonged suspension time resulted in higher electrical conductivity after 24 h, and in higher a* values (redness).6. In conclusion, the study revealed that a long-term training period improved walking ability and leg posture of heavy male turkeys. Thus, training can contribute to the improvement of animal welfare in turkey husbandry. Meat quality variables of breast muscles were partially influenced by locomotor activity and suspension time.

Change in Functional Beta Cell Capacity With Time Following Autologous Islet Transplantation.

Autologous islet transplantation (AIT) is performed to preserve insulin secretory function in chronic pancreatitis patients undergoing total pancreatectomy (TP). No data exist on the effect of time lapse on beta cell function post TP-AIT. We aimed to investigate the factor of time lapse on beta cell function following TP-AIT. Retrospectively, we identified 31 adult patients with chronic pancreatitis who underwent TP-AIT between 2008 and 2016. Changes in beta cell function were assessed using (1) BETA-2 scores and (2) analysis of posttransplant mixed-meal tolerance testing. Significant decrease in functional beta cell capacity expressed by BETA-2 scores was seen in the first 2 years following TP-AIT, with an annual decrease of 6.3 points in median BETA-2 score (interquartile range, 4.6-11.6; P = 0.002). In the mixed-meal tolerance testing analysis, nonsignificant trends toward higher glucose, lower insulin, and lower C-peptide were seen with time lapse. Additionally, higher hemoglobin A1c values (P = 0.033) and higher insulin requirements (P = 0.04) were seen with longer follow-up after AIT. A steady drop in functional beta cell capacity was observed in the 2 years following TP and AIT. To our knowledge, to date this is the first report of the BETA-2 score applicability in the AIT setting.

Change of Thermal Conductivity and Cooling Performance for Water Based Al2O3-Surfactant Nanofluid with Time Lapse

An experimental research was performed to study the effect of time lapse on the change of water-Al2O3 nanofluid thermal conductivity and its convection heat transfer. The size of Al2O3 nanoparticle size was 20[Formula: see text]nm and 70[Formula: see text]nm, and initial volumetric concentration range was from 0.5% to 3%. A surfactant was added to the nanofluid and the change of thermal conductivity and convection heat transfer was also measured. The surfactant was Sodium Dodecyl Benzene Sulfonate (SDBS) and its mass fractions in the nanofluid were from 0.5% to 3.0%. Thermal conductivity of water and nanofluid was measured by the transient hot wire method. The accuracy of the measurement method was confirmed by the measurement error with 0.92% for distilled water at 20[Formula: see text]C. The thermal conductivity of the nanofluid without SDBS increased up to 11.3% and the enhancement decreased with time lapse. The reduction of thermal conductivity enhancement with the time lapse could be retarded by the addition of SDBS and its effect became higher with the increase of its mass fraction. The convection heat transfer characteristics of the nanofluid was measured in a small cooling system. Compared with pure water, nanofluid convection heat transfer could be enhanced but higher pressure drop also occurred. Compared with the convection heat transfer enhancement for the nanofluid without SDBS, the addition of SDBS decreased the enhancement at the initial stage of the experiment, but it could retard the reduction of convection heat transfer with time lapse.

気分がカテゴリ一致情報、不一致情報処理に及ぼす影響 : 実験直後と遅延後の記憶再生を用いた検討

気分がカテゴリ一致情報、不一致情報処理に及ぼす影響 : 実験直後と遅延後の記憶再生を用いた検討

Eight-Year Retrospective Study of the Critical Time Lapse between Root Canal Completion and Crown Placement: Its Influence on the Survival of Endodontically Treated Teeth

IntroductionThe purpose of this study was to investigate the effects of factors associated with various coronal restorative modalities after root canal treatment (RCT) on the survival of endodontically treated teeth (ETT) and to assess the effect of time lapse between RCT and crown placement after RCT to form a tooth loss hazard model. MethodsComputerized analysis was performed for all patients who received posterior RCT from 2008 to 2016 in the graduate endodontic department. Data collected included dates of RCT, type of post-endodontic restoration, and time of extraction if extracted. Teeth that received crown after RCT were also divided into 2 groups: receiving crown before 4 months and after 4 months after RCT. Data were analyzed by using Kaplan-Meier log-rank test and Cox regression model (α = 0.05) by using SPPS Statistic 21. ResultsType of restoration after RCT significantly affected the survival of ETT (P = .001). ETT that received composite/amalgam buildup restorations were 2.29 times more likely to be extracted compared with ETT that received crown (hazard ratio, 2.29; confidence interval, 1.29–4.06; P = .005). Time of crown placement after RCT was also significantly correlated with survival rate of ETT (P = .001). Teeth that received crown 4 months after RCT were almost 3 times more likely to get extracted compared with teeth that received crown within 4 months of RCT (hazard ratio, 3.38; confidence interval, 1.56–6.33; P = .002). ConclusionsPatients may benefit by maintaining their natural dentition by timely placement of crown after RCT, which otherwise may have been extracted and replaced by implant because of any delay in crown placement.

Dimensional stability of two solder index materials.

Objectives:This study aimed to compare the dimensional accuracy of two indexing materials, an acrylic resin (GC pattern resin) and a castable composite (Bredent). The effect of time lapse until investment was also investigated.Materials and Methods:Two standardized brass dies 15 mm apart were prepared and then 20 identical coping-bar assemblies were designed and fabricated by a rapid prototyping device. Each bar was sectioned at the center, and indices were fabricated from an acrylic resin or castable composite (n = 10 per group). The distances between the reference points were measured with a digital microscope at ×80 magnifications at 15 min, 60 min, and 24 h after indexing. Data were statically analyzed using repeated-measure ANOVA (α = 0.05).Results:The distance between the reference points without the coping being joined was considered as the baseline measurement (control group). The mean distance was 19.30 ± 0.04 mm between the reference points where the copings were not joined. When indexed with acrylic resin, the mean ± standard deviation (SD) dimensions were 19.27 ± 0.087 mm (15 min), 19.25 ± 0.09 mm (60 min), and 18.98 ± 0.1 mm (24 h). The mean ± SD dimensions for composite were 19.29 ± 0.087 mm (15 min), 19.28 ± 0.08 mm (60 min), and 19.26 ± 0.08 mm (24 h). All tested groups showed significant differences compared to the control group except when it was indexed with composite and where the distances were measured after 15 and 60 min (P > 0.05).Conclusions:The most accurate indexed-assemblies belonged to castable composite at 15 and 60 min.

Effect of Time Lapse on the Diagnostic Accuracy of Cone Beam Computed Tomography for Detection of Vertical Root Fractures.

Accurate and early diagnosis of vertical root fractures (VRFs) is imperative to prevent extensive bone loss and unnecessary endodontic and prosthodontic treatments. The aim of this study was to assess the effect of time lapse on the diagnostic accuracy of cone beam computed tomography (CBCT) for VRFs in endodontically treated dog's teeth. Forty-eight incisors and premolars of three adult male dogs underwent root canal therapy. The teeth were assigned to two groups: VRFs were artificially induced in the first group (n=24) while the teeth in the second group remained intact (n=24). The CBCT scans were obtained by NewTom 3G unit immediately after inducing VRFs and after one, two, three, four, eight, 12 and 16 weeks. Three oral and maxillofacial radiologists blinded to the date of radiographs assessed the presence/absence of VRFs on CBCT scans. The sensitivity, specificity and accuracy values were calculated and data were analyzed using SPSS v.16 software and ANOVA. The total accuracy of detection of VRFs immediately after surgery, one, two, three, four, eight, 12 and 16 weeks was 67.3%, 68.7%, 66.6%, 64.6%, 64.5%, 69.4%, 68.7%, 68% respectively. The effect of time lapse on detection of VRFs was not significant (p>0.05). Overall sensitivity, specificity and accuracy of CBCT for detection of VRFs were 74.3%, 62.2%, 67.2% respectively. Cone beam computed tomography is a valuable tool for detection of VRFs. Time lapse (four months) had no effect on detection of VRFs on CBCT scans.

Effect of Time Lapse between Endodontic and Periodontal Therapies on the Healing of Concurrent Endodontic-Periodontal Lesions without Communication: A Prospective Randomized Clinical Trial

IntroductionThe aim of this prospective randomized clinical trial was to evaluate the effect of a time lapse between endodontic treatment and nonsurgical periodontal treatment on periodontal healing of concurrent endodontic-periodontal lesions without communication. MethodsThirty-one patients were randomly divided into 2 groups: group 1: endodontic treatment and scaling and root planning (SRP) were performed simultaneously and group 2: SRP was performed 3 months after endodontic treatment. Both groups were followed for 3 and 6 months after SRP. Primary outcome variables were the probing depth, clinical attachment level, and periapical index score. ResultsBoth the groups showed a significant improvement in all the clinical parameters evaluated after the completion of endodontic and periodontal treatment (P < .05). No statistically significant difference in improvement was observed between the 2 groups at 3 and 6 months after SRP (P > .05). Periodontal healing responses were comparable in the 2 groups, with no apparent detriment resulting from simultaneous treatment. Improvements in periodontal parameters that were achieved in 6 months in group 2 were achieved only in 3 months in group 1 (P > .05). ConclusionsNonsurgical periodontal treatment may be performed simultaneously with endodontic treatment in the management of concurrent endodontic-periodontal lesions without communication, and an observation period after endodontic treatment may not be required.

Effect of the Use of a Neutralizing Step after Antimicrobial Application on Microbial Counts during Challenge Studies for Orange Disinfection

The effects of using a neutralizer after applying antimicrobial treatments and the effect of time lapse between treatment application and subsequent recovery and enumeration of Escherichia coli O157:H7 and Salmonella were investigated in Valencia oranges. Inoculated oranges surfaces were washed with distilled water for 15 s and then sprayed with a solution containing 200 mg/liter sodium hypochlorite (pH 6.5) for 15 s; they were then dipped in l-lactic acid (2.0% at 55°C) for 1 min or in distilled water at 80°C for 1 min. Posttreatment, oranges were divided into two groups. In the first group, oranges were dipped in neutralization treatment: 270 ml of buffered peptone water for 2 min for lactic acid-treated oranges, 270 ml of Dey-Engley broth for 2 min for chlorine-treated oranges, or 3.7 liters of tap water (25°C) for 10 s for hot water-treated oranges. The second group of treated oranges was not subjected to any neutralizer. All oranges then were kept at room temperature (average 26.2°C) and sampled at 0, 7.5, and 15 min for enumeration of surviving Salmonella and E. coli O157:H7. The orange surface (30 cm ) was excised for pathogen enumeration. The presence of free chlorine and changes in pH and temperature on the orange surface were determined in uninoculated, treated oranges. Free chlorine was detected on oranges after treatment; the change in temperature of orange surfaces was greater during treatment with hot water than with lactic acid. Nevertheless, pathogen enumeration did not show any impact of neutralizer use on the residual activity of antimicrobials or any impact of the time elapsed between antimicrobial treatment and recovery of bacterial pathogens from inoculated oranges (P ≥ 0.05). The results of this study indicate that the lack of a neutralizing step before enumeration of pathogens is not likely to affect the accuracy of results during challenge studies to test pathogen reduction strategies on oranges.

Evaluation of two anaerobic systems for isolation of anaerobes

Many systems are available for the isolation of anaerobic bacteria from clinical specimens. The jar system is the oldest and more adapted while the pouches are not popular with many investigators. The anaerobic chambers are expensive to maintain and technically inflexible. This study evaluated the efficacy of the Oxoid anaerobic jar and the GENbag pouches as anaerobic incubation systems. Anaerobic cultures were set up for 145 middle ear exudates and incubation was in the anaerobic jar, GENbag or a combination of both. The effect of specimen transport system and time lapse before culturing on the performance of the anaerobic systems were evaluated Ten genera of anaerobic bacteria were isolated with both systems (P &amp;gt; 0.05). &lt;em&gt;Peptostreptococcus&lt;/em&gt; and &lt;em&gt;Prevotella&lt;/em&gt; were isolated more frequently in Oxoid jar than in GENbag (P &amp;lt; 0.05) but both systems were not discriminatory for &lt;em&gt;Clostridium&lt;/em&gt;, &lt;em&gt;Propionibacterium&lt;/em&gt; and &lt;em&gt;Veillonella&lt;/em&gt;. The use of GENbag as a backup to Oxoid jar increased isolation rate from 56.6% to 90.3% (P &amp;gt; 0.05). Type of transport media or vehicle did not affect the recovery of anaerobes adversely as did delay in processing of specimen. A careful application of a number of variables may improve isolation of anaerobes from clinical specimens

The effect of water storage, elapsed time and contaminants on the bond strength and interfacial polymerization of a nanohybrid composite.

To systematically characterize the effect of time lapse, water storage, and selected contaminants on the bond strength of a nanofilled dental composite. Half-dumbbell-shaped samples were fabricated out of light-polymerizing composite resin. To function as substrates they were aged for 30 days in water. Prior to bonding, the substrates' surfaces were subjected to the following treatments: 1) Removing a 0.2- to 0.4-mm layer using a fluted carbide bur; 2) grit blasting with 50 microm alumina particles; 3) etching with phosphoric acid gel; 4) grit blasting followed by etching; 5) blasting with tribochemical particles followed by silane application; 6) sanding with 400-grit paper, air aging of the adherent half-sample before bonding; 7) surface contamination with saliva; 8) surface contamination with blood. In each group (n = 30), freshly polymerized (except in group 6) adherent half-samples were bonded to the substrate half-samples by a layer of unfilled adhesive resin. Fifteen full dumbbell-shaped specimens were subjected to tensile testing after 1 h and 15 after 7 days water storage. In a positive control group, freshly cured half-samples were bonded shortly after fabrication. The tensile strength was analyzed using Weibull statistics and presented in terms of the material's characteristic strength and shape parameter. Fractographs of the two weakest and strongest samples of each group were produced. The surfaces were searched to locate hackle, wake hackle and the origin of the fracture. Surface roughness and time lapse increased the bond strength of the repaired specimens. All groups in which surface roughness was produced before bonding increased in repair strength. Post-bonding aging improved strength. Fractographs yielded interpretable data whenever larger surfaces of single phase bonding resin were present. 1) Roughening and etching an aged composite's surface prior to applying a coat of unfilled resin and the filled material increases repair bond strength by up to 100%. 2) The repair bond strength of a roughened aged composite is 25% to 30% inferior to the tensile strength of solid specimens. 3) After 7 days' storage in water, no detrimental effect could be seen from saliva or blood contamination if the surfaces were properly rinsed.

High-intensity interval aerobic training reduces hepatic very low-density lipoprotein-triglyceride secretion rate in men

A single bout of strenuous endurance exercise reduces fasting plasma triglyceride (TG) concentrations the next day (12-24 h later) by augmenting the efficiency of very low-density lipoprotein (VLDL)-TG removal from the circulation. Although much of the hypotriglyceridemia associated with training is attributed to the last bout of exercise, the relevant changes in VLDL-TG metabolism have never been investigated. We therefore examined basal VLDL-TG kinetics in a group of sedentary young men (n=7) who underwent 2 mo of supervised high-intensity interval training (3 sessions/wk; running at 60 and 90% of peak oxygen consumption in 4-min intervals for a total of 32 min; gross energy expenditure: 446+/-29 kcal) and a nonexercising control group (n=8). Each subject completed two stable isotope-labeled tracer infusion studies in the postabsorptive state, once before and again after the intervention (approximately 48 h after the last exercise bout in the training group). Peak oxygen consumption increased by approximately 18% after training (P <or= 0.05), whereas body weight and body composition were not altered. Fasting plasma VLDL-TG concentration was reduced after training by approximately 28% (P <or= 0.05), and this was due to reduced hepatic VLDL-TG secretion rate (by approximately 35%, P <or= 0.05) with no changes (<5%, P>0.7) in VLDL-TG plasma clearance rate and the mean residence time of VLDL-TG in the circulation. No significant changes in VLDL-TG concentration and kinetics were observed in the nonexercising control group (all P >or= 0.3). We conclude that a short period of high-intensity interval aerobic training lowers the rate of VLDL-TG secretion by the liver in previously sedentary men. This is different from the mechanism underlying the hypotriglyceridemia of acute exercise; however, it remains to be established whether our finding reflects an effect of the longer time lapse from the last exercise bout, an effect specific to the type of exercise performed, or an effect of aerobic training itself.

The effect of time lapse on the accuracy of two acrylic resins used to assemble an implant framework for soldering

Statement of problem There are insufficient data on the accuracy of resin indexing materials for the assembly of implant prostheses in vivo. Material and methods This in vitro study assessed the fit of an implant framework with the use of 2 common acrylic resins. Purpose A standardized type IV gold alloy cast framework with 3 stainless steel implant replicas secured to 3 premachined gold cylinders placed 200 mm apart using a parallelometer was fabricated on a flat type IV stone model. Wax was placed around the center of each bar section, and a silicone matrix was fabricated to enable the same quantity of material to be used for each assembly. Each bar was sectioned at the center of the matrix, and indices (n=20) were fabricated from Duralay and GC Pattern acrylic resins. The materials were allowed to polymerize for 15 minutes before the assemblies were removed from the model. Frameworks were visually assessed for fit after an additional 15 minutes, after 2 hours, and after 24 hours, using the Sheffield 1-screw test. Observational outcomes are presented indicating visually perceived fit relative to the type of indexing resin. Results Both indexing materials were judged to be visually accurate at the 15-minute time interval only. Conclusion Within the limitations of this in vitro study, both resin-indexed implant assemblies were judged visually accurate for fit 15 minutes after polymerization but not at subsequent test intervals.

Dynamics of Bitumen Fractions by Thin-Layer Chromatography/Flame Ionization Detection

Thin-layer chromatography/flame ionization detection (TLC/FID) allows for the fractionation of bitumen into four fractions, namely, the saturates, the aromatics, the resins A and the resins B (SARAB). The technique is rapid and economical, but it lacks reproducibility. The effect of chromarod aging on reproducibility was investigated along with that of the time between bitumen dissolution and its analysis (time lapse effects). It is found that chromarod aging causes a 2−5% variation in SARAB content, and that time lapse causes a 50−75% variation in the aromatics and resins A content. The effect of time lapse stems from the aging of bitumen in solution. A mechanism for this aging is provided. It is demonstrated to be a physical rather than a chemical transformation of bitumen that reveals itself as a conversion of aromatics into resins. The physical nature of aging is shown by the absence of oxidation and aromatization in solution and by the successful modeling of aging after a reversible process. The conversion of aromatics into resins is explained by the grouping of alkyl-aromatics into micelles. Micelles mimic resins during chromatography and cause an apparent increase in resins concentration.

In vitro bond strengths of three current dentin adhesives to primary and permanent teeth

The in vitro shear bond strengths of three chemically different dentin bonding agents were tested between both permanent and deciduous dentin and their respective anterior composite filling materials. The effect of the post-mortem age of the teeth on bond strength was evaluated by comparison of fresh (extracted within 24 h) and old (extracted within 10 d) teeth. The results indicated that these materials bonded more strongly to the dentin of permanent than to deciduous teeth (8.8±4.9 MN/m 2 vs. 6.2±4.8 MN/m 2). The intermaterial comparison indicated that the bonds to dentin were strongest for Scotchbond 2 (12.3±4.4 MN/m 2) followed by Tenure (6.9±3.3 MN/m 2) and then Gluma (3.3± 1.7 MN/m 2). Both the above findings were shown to be statistically significant. The effect of time lapse after extraction of the teeth was not statistically significant.

Studies of methamidophos-C-14 in Costa Rican vegetables and soils

In order to see the effect of time lapse between the last application of methamidophos and harvesting insecticide was applied on lettuce plants (6,84 μCi in one experiment and 4,03 μCi in the other experiment). Analysis of the crops harvested 3 days after last application showed 9,7 ppm residues on leaves, while crops harvested 1 day after application showed residues of 12,7 ppm (25% more). Treatment of tomato plants (39,65 μCi, 1,01 kg/ha) gave residues in fruits 4,92 ppm after 8 days interval between last application and harvesting. 40 days gap between the last application and harvesting leaved residues of 0,7 ppm in fruits which is much less as recommended by FAO/WHO (1 – 2 ppm). Degradation of this insecticide is dependent on the matrix of the soil, this breakdown is observed in the first ten days and than after it remains constant. C-14 radioactivity extracted from soil and plant analysis was methamidophos (92%)