Laser Doppler anemometry measurements of steady flow through two bi-leaflet prosthetic heart valves

Introduction

In vitro hydrodynamic characterization of prosthetic heart valves provides important information regarding their operation, especially if performed by noninvasive techniques of anemometry. Once velocity profiles for each valve are provided, it is possible to compare them in terms of hydrodynamic performance. In this first experimental study using laser doppler anemometry with mechanical valves, the simulations were performed at a steady flow workbench.

Objective

To compare unidimensional velocity profiles at the central plane of two bi-leaflet aortic prosthesis from St. Jude (AGN 21 - 751 and 21 AJ - 501 models) exposed to a steady flow regime, on four distinct sections, three downstream and one upstream.

Methods

To provide similar conditions for the flow through each prosthesis by a steady flow workbench (water, flow rate of 17L/min. ) and, for the same sections and sweeps, to obtain the velocity profiles of each heart valve by unidimensional measurements.

Results

It was found that higher velocities correspond to the prosthesis with smaller inner diameter and instabilities of flow are larger as the section of interest is closer to the valve. Regions of recirculation, stagnation of flow, low pressure, and flow peak velocities were also found.

Conclusions

Considering the hydrodynamic aspect and for every section measured, it could be concluded that the prosthesis model AGN 21 - 751 (RegentTM) is superior to the 21 AJ - 501 model (Master Series). Based on the results, future studies can choose to focus on specific regions of the these valves.     

Relationship between the width of the zone of keratinized tissue and thickness of gingival tissue in the anterior maxilla

The aim of this study was to evaluate whether there is a positive correlation between the width of the zone of gingival keratinized tissue and its thickness. Maxillary right canines, lateral incisors, and central incisors of 60 patients (30 men, 30 women) between the ages of 20 and 35 years were examined. Using an endodontic spacer with a rubber cursor and a digital caliper of 0.01-mm resolution, the values of the width of the zone of gingival keratinized tissue and gingival thickness were obtained. It was observed that the lateral incisor has the largest mean zone of gingival keratinized tissue (5.54 ± 1.09 mm), followed by the central incisor (4.62 ± 1.02 mm) and canine (4.32 ± 1.33 mm). The mean gingival thickness was greater in the central incisor (1.17 ± 0.20 mm), followed by the lateral incisor (1.04 ± 0.24 mm) and canine (0.87 ± 0.27 mm). No statistically significant difference was verified for the mean width of the zone of gingival keratinized tissue and gingival thickness between men and women. A positive correlation between gingival thickness and width of the zone of gingival keratinized tissue was observed in the maxillary canine (Pearson r = 0.398, P < .05), lateral incisor (Pearson r = 0.369, P < .05), and central incisor (Pearson r = 0.492, P < .05). In patients 20 to 35 years of age, there was a positive correlation between gingival thickness and width of the zone of gingival keratinized tissue for the maxillary right canine, lateral incisor, and central incisor.     

Evaluation of root external temperature during the application of ultrasound in removal of intraradicular posts

This study evaluated the temperature rise on external root surfaces by simulating the removal of metallic posts by applying ultrasound, with or without refrigeration and at different times. The crowns of 30 healthy maxillary central incisors were removed and the roots were treated endodontically. The prosthetic spaces were prepared and impressions were taken with self-curing acrylic resin. After casting with a copper-aluminum alloy, the posts were blasted with aluminum oxide and cemented with resin cement. The specimens were randomly assigned to three groups according to the time of ultrasonic vibration (30, 60, or 120 seconds) and were subdivided into two groups, those cooled with and without water refrigeration. A thermocouple connected to a digital thermometer was positioned on the root external surface and the maximum temperature was recorded. Data were submitted to ANOVA and Tukey's test. Analysis of the results revealed statistical difference among groups (p < 0.01). Ultrasound (with and without water spray) increased root temperature significantly, reaching values of more than 50 degrees C. The exception was the group that used 30 seconds of ultrasound with refrigeration; root temperature reached 35.4 degrees C, making it the only tested condition that remained below the critical value (50 degrees C).     

Cytomegalovirus shedding in the oral cavity of allogeneic haematopoietic stem cell transplant patients

OBJECTIVE: This study was designed to investigate the effect of allogeneic haematopoietic stem cell transplantation (HSCT) on cytomegalovirus (CMV) shedding in the saliva by nested polymerase chain reaction (nested PCR) and its impact on patient survival. PATIENTS AND METHODS: One hundred and twenty-four HSCT patients and 124 healthy volunteers were included in the study. Oral swabs were taken before, after 100 days and 1 year of HSCT at the buccal mucosa. Nested PCR was used to detect CMV in the saliva. Time of death after HSCT was displayed, by means of the Kaplan-Meier method, for the following parameters: age and gender of the patient, donor gender, primary disease, stem cell source, platelet number, chronic graft vs host disease (cGVHD) of salivary glands and oral mucosa, and oral CMV shedding. Cox proportional hazards model was used for multivariate survival analysis. RESULTS: While none of the individuals in the control group showed positive swabs for CMV, the frequency of positive CMV oral swabs in patients at day + 100 after HSCT (45.2%) was statistically higher than before (7.2%) and 1 year after HSCT (17.5%). The presence of CMV was not associated with cGVHD and did not have any impact on post-transplant survival. CONCLUSIONS: The present study shows that oral CMV shedding occurs after HSCT, especially at day +100 post-transplant. Identification of CMV in the saliva might be important for the early diagnosis of CMV infection in allo-HSTC.     

Cysteine-Induced Hybridization of 2D Molybdenum Disulfide Films for Efficient and Stable Hydrogen Evolution Reaction

The noble, metal-free materials capable of efficiently catalyzing water splitting reactions currently hold a great deal of promise. In this study, we reported the structure and electrochemical performance of new MoS₂-based material synthesized with L-cysteine. For this, a facile one-pot hydrothermal process was developed and an array of densely packed nanoplatelet-shaped hybrid species directly on a conductive substrate were obtained. The crucial role of L-cysteine was determined by numerous methods on the structure and composition of the synthesized material and its activity and stability for hydrogen evolution reaction (HER) from the acidic water. A low Tafel slope of 32.6 mV dec⁻¹, close to a Pt cathode, was registered for the first time. The unique HER performance at the surface of this hybrid material in comparison with recently reported MoS₂-based electrocatalysts was attributed to the formation of more defective 1T, 2H-MoS₂/MoO_x, C nanostructures with the dominant 1T-MoS₂ phase and thermally degraded cysteine residues entrapped. Numerous stacks of metallic (1T-MoS₂ and MoO₂) and semiconducting (2H-MoS₂ and MoO₃) fragments relayed the formation of highly active layered nanosheets possessing a low hydrogen adsorption free energy and much greater durability, whereas intercalated cysteine fragments had a low Tafel slope of the HER reaction. X-ray photoelectron spectroscopy, scanning electron microscopy, thermography with mass spectrometry, high-resolution transmission electron microscopy, Raman spectroscopy techniques, and linear sweep voltammetry were applied to verify our findings.     

No evidence of de novo amyloidosis in recipients of domino liver transplantation: 12 to 40 (mean 24) month follow-up.

Domino liver transplantation (DLT) has been performed for selected recipients at several centers, but de novo amyloidosis in recipients of livers from patients with familial amyloid polyneuropathy (FAP) remains a serious concern. AIM: To evaluate the occurrence of de novo amyloidosis in recipients of DLT. PATIENTS AND METHODS: Seven recipients of FAP livers were followed for clinical and electroneuromyographic signs of FAP and also for de novo amyloid deposition in the gut. RESULTS: No signs and symptoms of de novo FAP nor any evidence of amyloid deposits in the gut were observed in recipients of DLT after a mean follow-up of 24 [12-40] months. CONCLUSIONS: Signs and symptoms of FAP do not occur early in recipients of DLT. These livers could therefore be offered to patients suitable for conventional LT, particularly older subjects in whom the event of de novo amyloidosis would seem improbable.