Impact Strength of Various Types of Acrylic Resin: An In Vitro Study

AIM

The aim of this study is to evaluate and compare the impact strength of conventional acrylic resin, high-impact acrylic resin, high-impact acrylic resin reinforced with silver nanoparticles, and high-impact acrylic resin reinforced with a zirconium oxide powder.

MATERIALS AND METHODS

A total of 60 samples were prepared of dimensions 60 mm length × 7 mm width × 4 mm thickness to test impact strength. Machined stainless steel dies of the same dimension were used to form molds for the fabrication of these samples. Of 60 samples, 15 samples were prepared each from conventional acrylic resin (Group A1), high-impact acrylic resin (Group A2), acrylic resin reinforced with silver nanoparticles (Group A3), and acrylic resin reinforced with zirconium oxide powder (Group A4). Izod-Charpy pendulum impact testing machine was used.

RESULTS

The impact strength of group A1 was in the range of 2.83-3.30 kJ/m² (M = 3.12 kJ/m², SD = 0.16), group A2 was in range of 5.10-5.78 kJ/m² (M = 5.51 kJ/m², SD = 0.18), group A3 was in range 3.18-3.56 kJ/m² (M = 3.37 kJ/m², SD = 0.11), and group A4 was in range 7.18-7.78 kJ/m² (M = 7.5 kJ/m², SD = 0.18). Statistical analysis using one-way ANOVA and t-test revealed significant differences (p < 0.001).

CONCLUSION

High-impact acrylic resin reinforced with zirconium oxide powder has the highest impact strength.

CLINICAL SIGNIFICANCE

This research sheds light on the usefulness of novel filler materials in clinical prosthodontics.

An Overview of Autonomous Vehicles Sensors and Their Vulnerability to Weather Conditions

Autonomous vehicles (AVs) rely on various types of sensor technologies to perceive the environment and to make logical decisions based on the gathered information similar to humans. Under ideal operating conditions, the perception systems (sensors onboard AVs) provide enough information to enable autonomous transportation and mobility. In practice, there are still several challenges that can impede the AV sensors' operability and, in turn, degrade their performance under more realistic conditions that actually occur in the physical world. This paper specifically addresses the effects of different weather conditions (precipitation, fog, lightning, etc.) on the perception systems of AVs. In this work, the most common types of AV sensors and communication modules are included, namely: RADAR, LiDAR, ultrasonic, camera, and global navigation satellite system (GNSS). A comprehensive overview of their physical fundamentals, electromagnetic spectrum, and principle of operation is used to quantify the effects of various weather conditions on the performance of the selected AV sensors. This quantification will lead to several advantages in the simulation world by creating more realistic scenarios and by properly fusing responses from AV sensors in any object identification model used in AVs in the physical world. Moreover, it will assist in selecting the appropriate fading or attenuation models to be used in any X-in-the-loop (XIL, e.g., hardware-in-the-loop, software-in-the-loop, etc.) type of experiments to test and validate the manner AVs perceive the surrounding environment under certain conditions.

Pharmacomechanical Catheter-Directed Thrombolysis for Deep-Vein Thrombosis

BACKGROUND

The post-thrombotic syndrome frequently develops in patients with proximal deep-vein thrombosis despite treatment with anticoagulant therapy. Pharmacomechanical catheter-directed thrombolysis (hereafter "pharmacomechanical thrombolysis") rapidly removes thrombus and is hypothesized to reduce the risk of the post-thrombotic syndrome.

METHODS

We randomly assigned 692 patients with acute proximal deep-vein thrombosis to receive either anticoagulation alone (control group) or anticoagulation plus pharmacomechanical thrombolysis (catheter-mediated or device-mediated intrathrombus delivery of recombinant tissue plasminogen activator and thrombus aspiration or maceration, with or without stenting). The primary outcome was development of the post-thrombotic syndrome between 6 and 24 months of follow-up.

RESULTS

Between 6 and 24 months, there was no significant between-group difference in the percentage of patients with the post-thrombotic syndrome (47% in the pharmacomechanical-thrombolysis group and 48% in the control group; risk ratio, 0.96; 95% confidence interval [CI], 0.82 to 1.11; P=0.56). Pharmacomechanical thrombolysis led to more major bleeding events within 10 days (1.7% vs. 0.3% of patients, P=0.049), but no significant difference in recurrent venous thromboembolism was seen over the 24-month follow-up period (12% in the pharmacomechanical-thrombolysis group and 8% in the control group, P=0.09). Moderate-to-severe post-thrombotic syndrome occurred in 18% of patients in the pharmacomechanical-thrombolysis group versus 24% of those in the control group (risk ratio, 0.73; 95% CI, 0.54 to 0.98; P=0.04). Severity scores for the post-thrombotic syndrome were lower in the pharmacomechanical-thrombolysis group than in the control group at 6, 12, 18, and 24 months of follow-up (P<0.01 for the comparison of the Villalta scores at each time point), but the improvement in quality of life from baseline to 24 months did not differ significantly between the treatment groups.

CONCLUSIONS

Among patients with acute proximal deep-vein thrombosis, the addition of pharmacomechanical catheter-directed thrombolysis to anticoagulation did not result in a lower risk of the post-thrombotic syndrome but did result in a higher risk of major bleeding. (Funded by the National Heart, Lung, and Blood Institute and others; ATTRACT ClinicalTrials.gov number, NCT00790335 .).

C-reactive protein as predictor of antidepressant response in late onset depression

Introduction

Late-onset depression has been associated with history of vascular disease and atherosclerosis. As immune dysregulation is critically involved in vascular disease. We hypothesized that responsiveness of late onset depression can be associated with level of inflammatory markers in these subjects.

Objective

Role of inflammatory mediator in antidepressant responses in late onset depression.

Aim

To study C-reactive protein as predictor of antidepressant response in late onset depression.

Methods

Depressed patient (as per ICD 10 DCR) age > 60 years recruited from department of psychiatry and complete clinical assessment done and base line depression severity measure on Hamilton Depression Rating Scale (HDRS). C reactive protein level was assessed at base line. Patient prescribed antidepressant medication and at 8 week follow up re assed for depression severity in HDRS. Data analyzed with spss.21 and spearman correlation was used.

Result

Mean age of responder (n = 6) 63.5 ± 4.9 year and HDRS at base line 16 ± 1.9. Mean age of partial responder or non-responder (n = 19) 65.1 ± 6.1 year and HDRS at base line 18.5 ± 3.9. Continuous decrease in depression severity during study period and antidepressant response rate was 24%. Base line CRP level had negative correlation with antidepressant responsiveness (r = –0.6, P < 0.05).

Discussion

Late onset depression was less responsive to antidepressant medication and poor antidepressant response rate was associated with higher level of CRP in late onset depression.

Document not received.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Traumatic complications from placement of thoracic catheters and tubes

The volume of critically ill patients requiring stabilization in emergency departments (EDs) throughout the USA has increased from 42 million per year in 1960 to over 92 million in 1990, as reported by Goldstein [Crit Care Clinics 21(1):81-89, 2005] and Rivers et al. [Curr Opin Crit Care 8(6):600-606, 2002]. With the increase in this patient population, the number of procedures, both invasive and noninvasive, performed in the ED to improve clinical outcomes has also increased. Therefore, emergency medicine physicians must add to their repertoire the ability to recognize potentially fatal traumatic complications. This review will provide readers with imaging findings of traumatic complications from placement of thoracic catheters and tubes and briefly discuss pitfalls of performing these procedures. In particular, complications arising from placement of hemodialysis catheters, central venous catheters, Swan-Ganz catheters, chest tubes, nasogastric and feeding tubes, and endotracheal tubes will be reviewed.

Stability of foot-and-mouth disease virus, its genome and proteins at 37 degrees C

Infectivity titers of foot-and-mouth disease virus (FMDV) types Asia 1 and 0 were reduced by 4 and 2 log units, respectively, after incubation at 37 degrees C for 12 hrs. The stability of the FMDV RNA genome at 37 degrees C was studied using 32P-labelled virus. The RNA of FMDV type 0 was found to be more stable than that of type Asia 1. Oligo(dT)-cellulose chromatography showed that 21% and 31% of the labelled RNA were bound to the column in the case of types Asia 1 and 0, respectively. Possible correlation between the poly(A) tail length, accessibility of the genome to nucleases and thermostability of the infective virus is discussed. A positive correlation between the thermostability of the genome and general distribution of a particular virus type seems to exist. A stable genome associated with poor virus immunogenicity may be responsible for the prevalence of FMDV type 0 in the nature. The isoelectric focussing of structural proteins isolated from the virus samples incubated at 37 degrees C revealed charge differences in the major immunogen between the two FMDV types. A rapid proteolytic degradation of the viral immunogen and stability of the genome may be responsible for frequent outbreaks of FMD, at least, in the endemic countries.

Caffeine-derived N-nitroso compounds. IV: Kinetics of mononitrosocaffeidine demethylation by rat liver microsomes

The study describes the kinetics of demethylation of mononitrosocaffeidine (MNC), a new asymmetric N-nitrosamine derived from caffeine. The demethylation of its precursor compound caffeidine was also studied. The results presented here suggest (a) that liver microsomes from fasted rats preferentially demethylate the N-methylnitrosamine group in MNC indicating the demethylation by cytochrome P450IIE1, (b) demethylation of MNC shows two apparent Km values, one of 117-166 microM responsible for the demethylation at the N-methylnitrosamino group of MNC, and the other Km of 1.84-2.26 mM for the remaining N-demethylations, (c) in contrast, caffeidine is a low affinity substrate for microsomal demethylation as indicated by a high Km of 14.3-16.3 mM, and (d) the demethylation at amino-N amino-N, and N-1 in both these compounds are mainly catalysed by P450 enzymes induced by Aroclor 1245 in rats.

Caffeine-derived N-nitroso compounds. III: Mutagenicity in S. typhimurium and in vitro induction of DNA single-strand breaks in rat hepatocytes by mononitrosocaffeidine and dinitrosocaffeidine

Mutagenesis in S. typhimurium and in vitro induction of DNA single-strand breaks in primary rat hepatocytes (DNA-SSB) have been investigated for two new N-nitroso compounds, mononitrosocaffeidine (MNC) and dinitrosocaffeidine (DNC). Mononitrosamidocaffeidine (MNAC) and tert.-(butyloxy)carbonyl-mononitrosamidocaffeidine (t-BOC-MNAC), both nitrosated derivatives of caffeidine with nitrosation at methylcarboxamide-N only, were also similarly studied. MNC, an asymmetric nitrosamine, failed to show mutagenicity in any of the tester strains used, and also did not induce DNA-SSB in rat hepatocytes. DNC, having both N-nitrosamide and N-nitrosamine groups in the molecule, showed direct mutagenicity in TA100, TA1535 and TA102. The mutagenic potential of the compound was found to increase on S9 activation. However, it was non-mutagenic in TA98 and TA1537. DNC also exhibited a high potential for inducing alkali-labile DNA-SSB in rat hepatocytes (70-78% C-T value) and was cytotoxic at concentrations over 0.1 mumole/ml. Both MNC and DNC were found to produce formaldehyde on S9 activation. MNAC was not mutagenic directly but showed weak mutagenicity on metabolic activation, whereas t-BOC-MNAC was mutagenic both with and without S9 activation in TA100, TA1535 and TA102. t-BOC-MNAC was more cytotoxic to hepatocytes than MNAC, though both caused DNA-SSB to the same extent (62% C-T value). On the basis of the presented data it is inferred that while DNC is a direct-acting mutagen in TA100, TA1535 and TA102 due to the presence of a reactive N-methylnitrosamido group, its mutagenic potential is greatly enhanced in the presence of S9 possibly due to the synergistic influence of an activated N-methylnitrosamino group in the molecule. Additionally, the study shows a qualitative consistency between Salmonella mutagenicity, genotoxicity in hepatocytes and the reactivity of the methyl group at the nitrosamido-N in nitrosated caffeidine compounds.

Effects of genetically different strains of mice on the microsomal activation of 2-aminofluorene

Five strains of mice were examined for microsomal cytochrome P450 (Cyt P450) activity and ability of the microsomal preparation to activate 2-aminofluorene (2-AF) to its mutagenic form. Each strain was assayed under normal and induced conditions. Group A strains known to be easily induced to carcinogenesis by chemicals (C57BL/6J and BALB/cJ) showed higher levels of Cyt P450 and increased mutagenesis activity of the metabolized 2-AF than Group B strains which are known to be high spontaneous tumor producers (CE/J, A/HeJ, C3H/HeJ). Induction of the hepatic microsomes with Aroclor 1254 increased the difference between the two groups.

Immunosuppressive effects of 8,9-epoxyhexahydrocannabinol (EHHC)

8,9-Epoxyhexahydrocannabinol (EHHC)-treated mice showed an inhibition of both humoral and cell-mediated immunity. The hemolytic plaque forming assay was employed to determine both the IgM and IgG antibody response. The effect of EHHC on IgM antibody production was measured in BDG1 male mice given X 10(8) sheep erythrocytes i.p. followed 24 and 48 hours later by i.p. injections of EHHC. EHHC produced a dose-dependent inhibition of plaque forming cells (PFC)/10(6) spleen cells and PFC/spleen on days 3, 4 and 5 after antigen administration. On day 4 the ED50 for PFC/10(6) spleen cells and PFC/spleen was 28 and 18 mg/kg, respectively. Peak response to IgG antibody production was observed on day 9. EHHC (100 mg/kg) administered i.p. 48 hours after antigen produced a 58 and 46% suppression of PFC/10(6) leucocyte on days 7 and 9, respectively. CDF1 male mice received 100 microng of Cornybacterium parvum in the left footpad. Two days after sensitization, EHHC was administered in doses of 0.75 to 50 mg/kg i.p. A challenge dose of 100 microng of Cornybacterium parvum was injected into the right footpad on day 6 and footpad swelling was measured 24 hours later by mercury displacement. EHHC at a dose of 0.78 mg/kg produced a 95% inhibition of the delayed-type hypersensitivity response. These studies showed that EHHC inhibits both the humoral and cellular arm of the immune response.