Characterization of long-term oral anticoagulant adherence trajectories among patients with atrial fibrillation: a retrospective observational study

Background

Medication taking is a dynamic behaviour that changes over time. Conventional adherence summary measures (e.g. proportion days covered) used in the OAC adherence studies conducted so far, however, are insensitive to the fluid nature of adherence. For example, identical PDC values can be calculated for patients with initial good adherence followed by poor adherence, and for those with periodic non-adherence throughout the course of therapy.

Purpose

The objective of this study was to characterize atrial fibrillation (AF) patients' long-term unique oral anticoagulant (OAC) adherence trajectories.

Methods

Using linked, population-based administrative data containing physician billings, hospitalization and prescription records of 4.8 million British Columbians (1996–2019), incident adult cases of AF were identified. Only patients who had prescription refill data available for five years were included in the analysis. The primary measure of OAC adherence was the proportion of days covered (PDC) over consecutive 90-day rolling windows. We modelled continuous 90-day PDC values over time. The time variable was number of years since OAC initiation. Group-Based Trajectory Modelling (GBTM) was used to identify patients' unique longitudinal adherence trajectories. To determine the best model, a relative comparison was done between models using Bayesian information criteria (BIC), and the Akaike information criterion (AIC).

Results

The study cohort was 19,749 AF patients [mean age 70.6y (SD 10.64), 56% male, mean CHA2DS2-VASc score 2.77 (SD 1.39]. The model that best fit our data identified four distinct OAC adherence trajectories (Figure). These were “consistent good adherence” (n=14,631 patients, 74.1% of the cohort), “rapid decline and discontinuation” (n=2327, 11.8%), “rapid decline with recovery” (n=1973, 9.99%), and “slow decline and discontinuation” (n=819, 4.2%).

Our results show that there is heterogeneity among non-adherers. PDC dropped significantly in the first year after therapy initiation for those with “rapid decline and discontinuation” trajectory. Patients exhibiting “rapid decline with recovery” also displayed a rapid decline in adherence in the first year but showed improvements around the third year. Those in the “slow decline and discontinuation” trajectory displayed slow decline in adherence over first three years which eventually led to permanent discontinuation of therapy.

Conclusion

In this retrospective study we distinguished between the different kinds of non-adherence in terms of timing and rate. While a majority of our cohort adhered to their medications, we identified three unique trajectories displaying declining adherence over time at varying rates. Our results emphasize the importance of early intervention and have direct implications for improving the design of adherence interventions.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Canadian Institutes of Health Research grant

Comparative adherence between DOAC and VKA in patients with atrial fibrillation: a 23-year retrospective observational study in Canada

Background

A recent systematic review highlighted significant gaps in the evidence on atrial fibrillation (AF) patients' adherence to oral anticoagulants (OAC). Current evidence suffers from short follow-up times, focuses on the first OAC and does not take switching into account. There is also lack of observational data on adherence to warfarin due to its varying dose that complicates the calculations. As such there is lack of evidence on comparative adherence between VKAs and DOACs and whether the convenience of DOACs translates into better adherence in AF patients.

Purpose

Our objective was to measure AF patients' long-term OAC adherence and compare the impact of taking direct oral anticoagulants (DOAC) versus vitamin K antagonists (VKA) on adherence, while accounting for switching.

Methods

Using linked, population-based administrative data containing physician billings, hospitalization and prescription records of 4.8 million British Columbians (1996–2019), incident adult cases of AF were identified. The primary measure of adherence was proportion of days covered (PDC). Consecutive rolling 90-day windows were created for each patient starting from their first OAC prescription fill date until the end of their follow-up. The PDC for each 90-day rolling window was calculated and averaged to yield mean adherence over the follow-up period for each patient. Permanent medication discontinuation resulted in a PDC of 0 for all subsequent rolling windows after their supply ran out. As such, both poor execution and non-persistence were measured simultaneously. The association between drug class and adherence was assessed using generalized mixed effect linear regression models with drug class treated as time-varying covariate to account for switching.

Results

The study cohort was 30,264 AF patients [mean age 72.2 years (SD11.0), 44.6% female, mean CHA2DS2-VASc 2.94 (SD1.4)] with mean follow-up of 7.7 (SD 4.8) years. The mean PDC was 0.71 (SD 0.27) with 51% of the cohort having mean PDC values below the conventional threshold of adherence (PDC<0.8). Adherence dropped over time with the greatest decline in the first two years after therapy initiation. After controlling for all other confounders and accounting for switching, taking VKA compared to DOAC was, on average, associated with a 1-day decrease in number of days of medication-taking per year.

Conclusion

AF patients' OAC adherence was below the conventional threshold of 0.8, and dropped over time, particularly in the first two years. Drug class had no clinically meaningful impact on medication adherence. Our study highlights the need for effective adherence interventions particularly early in OAC therapy. Our findings also emphasizes that prescribers should not assume inherently better adherence for DOACs and should instead choose OAC in conversation with the patient and in accordance with their values and preferences.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Canadian Institutes of Health Research grant

A novel deep interval type-2 fuzzy LSTM (DIT2FLSTM) model applied to COVID-19 pandemic time-series prediction

Currently, the novel COVID-19 coronavirus has been widely spread as a global pandemic. The COVID-19 pandemic has a major influence on human life, healthcare systems, and the economy. There are a large number of methods available for predicting the incidence of the virus. A complex and non-stationary problem such as the COVID-19 pandemic is characterized by high levels of uncertainty in its behavior during the pandemic time. The fuzzy logic, especially Type-2 Fuzzy Logic, is a robust and capable model to cope with high-order uncertainties associated with non-stationary time-dependent features. The main objective of the current study is to present a novel Deep Interval Type-2 Fuzzy LSTM (DIT2FLSTM) model for prediction of the COVID-19 incidence, including new cases, recovery cases, and mortality rate in both short and long time series. The proposed model was evaluated on real datasets produced by the world health organization (WHO) on top highly risked countries, including the USA, Brazil, Russia, India, Peru, Spain, Italy, Iran, Germany, and the U.K. The results confirm the superiority of the DIT2FLSTM model with an average area under the ROC curve (AUC) of 96% and a 95% confidence interval of [92–97] % in the short-term and long-term. The DIT2FLSTM was applied to a well-known standard benchmark, the Mackey-Glass time-series, to show the robustness and proficiency of the proposed model in uncertain and chaotic time series problems. The results were evaluated using a 10-fold cross-validation technique and statistically validated through the t-test method. The proposed DIT2FLSTM model is promising for the prediction of complex problems such as the COVID-19 pandemic and making strategic prevention decisions to save more lives.

The emergence of Q1 genotype of avian infectious bronchitis virus in Iran, 2019: the first report

BACKGROUND

Avian infectious bronchitis (IB) is an infectious viral disease of chickens. The effective protection of chickens against many different infectious bronchitis virus (IBV) variants is not achieved unless the circulating genotypes in the region are identified and the cross-protection of the potential of vaccines in use is assessed.

AIMS

In a monitoring program of IBVs, a new genotype was identified in the north of Iran, 2019. This work was conducted to isolate and characterize this new IBV genotype.

METHODS

Tracheal tissues were collected from chickens showing signs of respiratory involvement. Specimens were homogenized and inoculated to the allantoic fluid of embryonated specific pathogen-free (SPF) eggs. Infectious bronchitis virus was detected using real time-polymerase chain reaction (RT-PCR). The hypervariable region of the IBV S1 gene was amplified for sequencing.

RESULTS

Positive samples were phylogenetically analyzed, and both positive isolates were clustered with Q1 IBV strains.

CONCLUSION

This is the first report of the Q1 outbreak in Iran. More investigations are needed to find the role of Q1 IBV in the respiratory disease complex of chickens.

Efficient Acetylation and Formylation of Alcohols in the Presence of Zr(Hso4)4

Acetylation and formylation of alcohols with acetic and formic acids have been carried out in the presence of catalytic amounts of Zr(HSO4)4 under mild and heterogeneous conditions.

Radiation-induced Non-targeted Effect and Carcinogenesis; Implications in Clinical Radiotherapy

Bystander or non-targeted effect is known to be an interesting phenomenon in radiobiology. The genetic consequences of bystander effect on non-irradiated cells have shown that this phenomenon can be considered as one of the most important factors involved in secondary cancer after exposure to ionizing radiation. Every year, millions of people around the world undergo radiotherapy in order to cure different types of cancers. The most crucial aim of radiotherapy is to improve treatment efficiency by reducing early and late effects of exposure to clinical doses of radiation. Secondary cancer induction resulted from exposure to high doses of radiation during treatment can reduce the effectiveness of this modality for cancer treatment. The perception of carcinogenesis risk of bystander effects and factors involved in this phenomenon might help reduce secondary cancer incidence years after radiotherapy. Different modalities such as radiation LET, dose and dose rate, fractionation, types of tissue, gender of patients, etc. may be involved in carcinogenesis risk of bystander effects. Therefore, selecting an appropriate treatment modality may improve cost-effectiveness of radiation therapy as well as the quality of life in survived patients. In this review, we first focus on the carcinogenesis evidence of non-targeted effects in radiotherapy and then review physical and biological factors that may influence the risk of secondary cancer induced by this phenomenon.

Opium consumption: A potential risk factor for lung cancer and pulmonary tuberculosis

OBJECTIVE

Lung cancer is the most common malignancy, as well as the leading cause of cancer-related mortality worldwide. Several studies have shown the causative effect of cigarettes smoking in lung cancer, however, the effect of opium consumption has not yet been well studied. This study has been designed to evaluate the risk of developing lung cancer and pulmonary tuberculosis in pure opium addicts.

MATERIALS AND METHODS

We designed an analytic case-control study with 490 participants. People were divided into three groups: Group A were pure opium addicts, Group B consisted of nonsmoker patients who visited the chest medicine clinic due to complaints such as asthma, respiratory tract infections, and other signs and symptoms unrelated to smoking. Group C were chosen from nonsmoker individuals who visited the Emergency Department due to nonrespiratory problems.

RESULTS

Statistical analysis showed that the three groups were similar with respect to mean age and gender. In Group A, one patient was diagnosed as having bronchoalveolar carcinoma. No other case of lung cancer was found in all three groups. Furthermore, four patients in Group A (5.3%; 95% confidence interval, 1.3-10.3) were found to have pulmonary tuberculosis, as this was significantly higher as compared with groups B and C (P = 0.009 and P< 0.001, respectively).

CONCLUSION

Although, owing to limited number of cases, a robust conclusion cannot be made, this study can be considered as a base for a well-designed, larger study to further clarify the potential effect of opium abuse in developing lung cancer.

Molecular identification of miR-145 and miR-9 expression level as prognostic biomarkers for early-stage cervical cancer detection

BACKGROUND

MicroRNAs (miRNAs) may act as carcinogen or tumor suppressor genes by targeting various biological molecules. Therefore, it is important to identify significant markers for prognosis, diagnosis treatment strategies of cancers.

OBJECTIVE

To evaluate the clinical importance and prognostic value of miR-9 and miR-145 in cervical cancer.

METHOD

miRNAs expression was detected using quantitative real-time polymerase chain reaction in cervical cancer specimens and adjacent normal tissues.

RESULTS

MiR-9 up-regulated in cervical cancer specimens than adjacent normal tissues (9.743 ± 2.172 vs. 2.131 ± 1.083; P < 0.05). MiR-145 was decreased in cervical cancer specimens compared to corresponding normal tissues (2.189 ± 0. 724 vs. 7.173 ± 1.558 P < 0.05). In addition, increased expression of miR-9 was strongly linked to lymph node metastasis (P = 0.017) and vascular invasion (P = 0.011). On the other hand, the low expression of miR-145 was related to advanced FIGO stage (P = 0.007), lymph node metastasis (P = 0.02) and vascular invasion (0.026). Kaplan-Meier survival and log-rank analysis suggested that patients with high expression of miR-9 had shorter overall survival compared with those with low expression (log-rank test P = 0.028; P < 0.001). In addition, shorter overall survival time was remarkably linked to decreased expression of miR-145 (log-rank test P < 0.001). Multivariate Cox proportional hazards model analysis of miR-9 and miR-145 showed that FIGO stage (P = 0.011) high expression of miR-9 and low expression of miR-145 (P = 0.023; P = 0.031) were independent prognostic factors for overall survival of patients.

CONCLUSIONS

miRNA-145 and 9 may be as potential prognostic marker in patients suffering from cervical cancer.

Optimal model of PDIG based microgrid and design of complementary stabilizer using ICA

The generalized Heffron-Phillips model (GHPM) for a microgrid containing a photovoltaic (PV)-diesel machine (DM)-induction motor (IM)-governor (GV) (PDIG) has been developed at the low voltage level. A GHPM is calculated by linearization method about a loading condition. An effective Maximum Power Point Tracking (MPPT) approach for PV network has been done using sliding mode control (SMC) to maximize output power. Additionally, to improve stability of microgrid for more penetration of renewable energy resources with nonlinear load, a complementary stabilizer has been presented. Imperialist competitive algorithm (ICA) is utilized to design of gains for the complementary stabilizer with the multiobjective function. The stability analysis of the PDIG system has been completed with eigenvalues analysis and nonlinear simulations. Robustness and validity of the proposed controllers on damping of electromechanical modes examine through time domain simulation under input mechanical torque disturbances.

ABILITY OF LANDSAT-8 OLI DERIVED TEXTURE METRICS IN ESTIMATING ABOVEGROUND CARBON STOCKS OF COPPICE OAK FORESTS

The role of forests as a reservoir for carbon has prompted the need for timely and reliable estimation of aboveground carbon stocks. Since measurement of aboveground carbon stocks of forests is a destructive, costly and time-consuming activity, aerial and satellite remote sensing techniques have gained many attentions in this field. Despite the fact that using aerial data for predicting aboveground carbon stocks has been proved as a highly accurate method, there are challenges related to high acquisition costs, small area coverage, and limited availability of these data. These challenges are more critical for non-commercial forests located in low-income countries. Landsat program provides repetitive acquisition of high-resolution multispectral data, which are freely available. The aim of this study was to assess the potential of multispectral Landsat 8 Operational Land Imager (OLI) derived texture metrics in quantifying aboveground carbon stocks of coppice Oak forests in Zagros Mountains, Iran. We used four different window sizes (3×3, 5×5, 7×7, and 9×9), and four different offsets ([0,1], [1,1], [1,0], and [1,-1]) to derive nine texture metrics (angular second moment, contrast, correlation, dissimilar, entropy, homogeneity, inverse difference, mean, and variance) from four bands (blue, green, red, and infrared). Totally, 124 sample plots in two different forests were measured and carbon was calculated using species-specific allometric models. Stepwise regression analysis was applied to estimate biomass from derived metrics. Results showed that, in general, larger size of window for deriving texture metrics resulted models with better fitting parameters. In addition, the correlation of the spectral bands for deriving texture metrics in regression models was ranked as b4&gt;b3&gt;b2&gt;b5. The best offset was [1,-1]. Amongst the different metrics, mean and entropy were entered in most of the regression models. Overall, different models based on derived texture metrics were able to explain about half of the variation in aboveground carbon stocks. These results demonstrated that Landsat 8 derived texture metrics can be applied for mapping aboveground carbon stocks of coppice Oak Forests in large areas.

A physical impact of organic fouling layers on bacterial adhesion during nanofiltration

Organic conditioning films have been shown to alter properties of surfaces, such as hydrophobicity and surface free energy. Furthermore, initial bacterial adhesion has been shown to depend on the conditioning film surface properties as opposed to the properties of the virgin surface. For the particular case of nanofiltration membranes under permeate flux conditions, however, the conditioning film thickens to form a thin fouling layer. This study hence sought to determine if a thin fouling layer deposited on a nanofiltration membrane under permeate flux conditions governed bacterial adhesion in the same manner as a conditioning film on a surface. Thin fouling layers (less than 50 μm thick) of humic acid or alginic acid were formed on Dow Filmtec NF90 membranes and analysed using Atomic Force Microscopy (AFM), confocal microscopy and surface energy techniques. Fluorescent microscopy was then used to quantify adhesion of Pseudomonas fluorescens bacterial cells onto virgin or fouled membranes under filtration conditions. It was found that instead of adhering on or into the organic fouling layer, the bacterial cells penetrated the thin fouling layer and adhered directly to the membrane surface underneath. Contrary to what surface energy measurements of the fouling layer would indicate, bacteria adhered to a greater extent onto clean membranes (24 ± 3% surface coverage) than onto those fouled with humic acid (9.8 ± 4%) or alginic acid (7.5 ± 4%). These results were confirmed by AFM measurements which indicated that a considerable amount of energy (10(-7) J/μm) was dissipated when attempting to penetrate the fouling layers compared to adhering onto clean NF90 membranes (10(-15) J/μm). The added resistance of this fouling layer was thusly seen to reduce the number of bacterial cells which could reach the membrane surface under permeate conditions. This research has highlighted an important difference between fouling layers for the particular case of nanofiltration membranes under permeate flux conditions and surface conditioning films which should be considered when conducting adhesion experiments under filtration conditions. It has also shown AFM to be an integral tool for such experiments.

Introducing the RadBioStat Educational Software: Computer-Assisted Teaching of the Random Nature of Cell Killing

The interaction of radiation with cells and tissues has a random nature. Therefore, understanding the random nature of cell killing that is determined by Poisson distribution statistics is an essential point in education of radiation biology. RadBioStat is a newly developed educational MATLAB-based software designed for computer-assisted learning of the target theory in radiation biology. Although its potential applications is developing rapidly, currently RadBioStat software can be a useful tool in computer-assisted education of radiobiological models such as single target single hit, multiple target single hit and multiple target multiple hit. Scholars' feedback is valuable to the producers of this software and help them continuously improve this product, add new features and increase its desirability and functionality.

Does exposure to GSM 900 MHz mobile phone radiation affect short-term memory of elementary school students?

BACKGROUND

Now-a-days, children are exposed to mobile phone radiation at a very early age. We have previously shown that a large proportion of children in the city of Shiraz, Iran use mobile phones. Furthermore, we have indicated that the visual reaction time (VRT) of university students was significantly affected by a 10 min real/sham exposure to electromagnetic fields emitted by mobile phone. We found that these exposures decreased the reaction time which might lead to a better response to different hazards. We have also revealed that occupational exposures to radar radiations decreased the reaction time in radar workers. The purpose of this study was to investigate whether short-term exposure of elementary school students to radiofrequency (RF) radiation leads to changes in their reaction time and short-term memory.

MATERIALS AND METHODS

A total of 60 elementary school children ages ranging from 8 to 10 years studying at a public elementary school in Shiraz, Iran were enrolled in this study. Standardized computer-based tests of VRT and short-term memory (modified for children) were administered. The students were asked to perform some preliminary tests for orientation with the VRT test. After orientation, to reduce the random variation of measurements, each test was repeated ten times in both real and sham exposure phases. The time interval between the two subsequent sham and real exposure phases was 30 min.

RESULTS

The mean ± standard deviation reaction times after a 10 min talk period and after a 10 min sham exposure (switched off mobile) period were 249.0 ± 82.3 ms and 252.9 ± 68.2 ms (P = 0.629), respectively. On the other hand, the mean short-term memory scores after the talk and sham exposure periods were 1062.60 ± 305.39, and 1003.84 ± 339.68 (P = 0.030), respectively.

CONCLUSION

To the best of our knowledge, this is the first study to show that short-term exposure of elementary school students to RF radiation leads to the better performance of their short-term memory.

Effect of beverages on the hardness and tensile bond strength of temporary acrylic soft liners to acrylic resin denture base

STATEMENT OF PROBLEM

Two potential problems commonly identified with a denture base incorporating a resilient liner are failure of the bond between acrylic resin and soft liner material, and loss of resiliency of the soft liner over time. Since patients may drink different beverages, it is important to evaluate their effects on physical properties of soft lining materials.

PURPOSE

The objective of this in vitro study was to evaluate the effect of different beverages on the hardness of two temporary acrylic-based soft lining materials and their bond strength to the denture base resin.

MATERIALS AND METHOD

For the hardness test; a total of 80 rectangular specimens (40mm×10mm×3mm) were fabricated from a heat-polymerized polymethylmethacrylate. Two commercially auto-polymerized acrylic resin-based resilient liners; Coe-Soft and Visco-gel were prepared according to the manufacturers' instructions and applied on the specimens. For the tensile test, 160 cylindrical specimens (30mm×10mm) were prepared. The liners were added between specimens with a thickness of 3 mm. The specimens of both soft liners were divided into 4 groups (n=10) and immersed in distilled water as the control group, Coca-Cola, 8% and 50% ethanol. All groups were stored in separate containers at 37(o)C for 12 days. All beverages were changed daily. The hardness was determined using a Shore A durometer and tensile bond strength was determined in a ZwickRoell testing machine at a cross-head speed of 5mm/min. The results were analyzed using two-way ANOVA.

RESULTS

There was no significant interaction between the soft liners and the drinks for both hardness (p= 0.748) and bond strength (p= 0.902). There were statistically significant differences between all drinks for both hardness (p< 0.001) and bond strength (p< 0.05).

CONCLUSION

Within the limitations of this study, it seems that drinking Coca-Cola and alcoholic beverages would not be potentially causing any problems for the temporary acrylic soft liners.

The importance of laboratory water quality for studying initial bacterial adhesion during NF filtration processes

Biofouling of nanofiltration (NF) and reverse osmosis (RO) membranes for water treatment has been the subject of increased research effort in recent years. A prerequisite for undertaking fundamental experimental investigation on NF and RO processes is a procedure called compaction. This involves an initial phase of clean water permeation at high pressures until a stable permeate flux is reached. However water quality used during the compaction process may vary from one laboratory to another. The aim of this study was to investigate the impact of laboratory water quality during compaction of NF membranes. A second objective was to investigate if the water quality used during compaction influences initial bacterial adhesion. Experiments were undertaken with NF 270 membranes at 15 bar for permeate volumes of 0.5 L, 2 L, and 5 L using MilliQ, deionized or tap water. Membrane autopsies were performed at each permeation point for membrane surface characterisation by contact angle measurements, profilometry, and scanning electron microscopy. The biological content of compacted membranes was assessed by direct epi-fluorescence observation following nucleic acid staining. The compacted membranes were also employed as substrata for monitoring the initial adhesion of Ps. fluorescens under dynamic flow conditions for 30 min at 5 min intervals. Compared to MilliQ water, membrane compaction using deionized and tap water led to decreases in permeate flux, increase in surface hydrophobicity and led to significant build-up of a homogeneous fouling layer composed of both living and dead organisms (>10(6) cells cm(-2)). Subsequent measurements of bacterial adhesion resulted in cell loadings of 0.2 × 10(5), 1.0 × 10(5) cells cm(-2) and 2.6 × 10(5) cells cm(-2) for deionized, tap water and MilliQ water, respectively. These differences in initial cell adhesion rates demonstrate that choice of laboratory water can significantly impact the results of bacterial adhesion on NF membranes. Standardized protocols are therefore needed for the fundamental studies of bacterial adhesion and biofouling formation on NF and RO membrane. This can be implemented by first employing pure water during all membrane compaction procedures and for the modelled feed solutions used in the experiment.

Reversible Photo-Induced Currents in Epitaxial Pb(Zr0.52Ti0.48)O3 Thin Films

The pyroelectric and photogalvanic effects have been studied extensively in epitaxial Pb(Zr0.52Ti0.48)O3 (PZT) thin films. For the first time, photo-induced currents, which were completely reversible by electrical voltage, were observed in ferroelectric thin films. The photo-induced currents exhibited transient and steady state components. The transient component, in turn, consisted of two components with fast (<1 µs) and slow (∼hours) relaxation times. The mechanisms of the photo-induced currents in PZT films and their possible application in non-destructive readout ferroelectric memory are discussed.

Processing of Novel Electroceramic Components by SFF Techniques

Novel piezoelectric ceramic and ceramic/polymer composite structures were fabricated by solid freeform fabrication (SFF) for sensor and actuator applications. SFF techniques including fused deposition of ceramics (FDC) and Sanders prototyping (SP) were utilized to fabricate a variety of complex structures directly from a computer aided design (CAD) file. Novel composite structures including volume fraction gradients (VFG) and staggered rods, as well as actuator designs such as tubes, spirals and telescopes were made using the flexibility provided by the above processes. VFG composites were made by SP technique with the ceramic content decreasing from the center towards the edges. This resulted in a reduction of side lobe intensity in the acoustic beam pattern. The FDC technique was used to manufacture high authority actuators utilizing novel designs for the amplification of strain under applied electric field. The design, fabrication and electromechanical properties of these composite and actuator structures are discussed in this paper.

Using Layered Manufacturing to Create Textured Microstructures in Si3N4 Ceramics

In recent years, seeding has been shown to be an effective method to create textured microstructures in Si 3N4, Al2O3 and PZT ceramics. The objective of this research is to create anisotropic and textured Si3N4 parts using the Fused Deposition of Ceramics (FDC) process. This technique is currently being developed to fabricate high performance structural Si 3N4 based components. In order to create the textured microstructures, rod-like β-Si3N4 seed particles are introduced into the FDC feedstock filaments. In this study, anisometric β-Si3N4 seeds were introduced into the starting α-Si3N4 powder (Honeywell's AS800 grade) at a 10 vol.% loading. The effects of the seeds (aspect ratio ∼4) on the viscosity and resultant microstructure were evaluated using capillary rheology, scanning electron microscopy, coefficient of thermal expansion (CTE) measurements, and x-ray diffraction. It is observed that the seeds do align during filament extrusion and a significant texture has been detected by x-ray diffraction and CTE measurements in FDC feedstock filaments and sintered FDC parts.

Homogeneity, Anisotropy, and Texture In Si3n4 Ceramics made by Fused Deposition

The Fused Deposition of Ceramics (FDC) process is an extrusion based layered manufacturing technique. In this study, the microstructural and property homogeneity of GS44-Si3N4 parts made by FDC is examined. The feedstock, green, and sintered parts were examined using characterization techniques such as optical and scanning electron microscopy, x-ray radiography, and x-ray diffraction. In addition, mechanical properties (σf, and Klc), shrinkage, and warpage results were used to characterize the FDC parts. It was found that by using proper build parameters and tool paths, dense, homogenous, near-net-shape GS44-Si3N4 parts can be fabricated. While the mechanical properties of these parts are shown to be isotropic, there is some degree of texturing detected with XRD. Si3N4 filament feedstock intentionally textured with 5.5 vol% of β-seed particles has also been made.

Mechanical Properties of Feedstock Material for Fused Deposition of Ceramics

A scientific methodology to characterize the critical mechanical properties of feedstock material for fused deposition of ceramics has been developed. A detailed discussion of the methodology of mechanical characterization and results for lead zirconate titanate (PZT) fused deposition of ceramics (FDC) feedstock is presented. The effect of storage time, temperature and crosshead displacement rates on the mechanical properties of the PZT FDC feedstock was studied. The modulus and the failure stress increase with displacement rate. The modulus and failure stress decrease with temperature indicating the necessity for cooling filaments prior to entrance to liquefier. The modulus also decreases with storage time in 50% RH while failure strain increases with storage time in 50% RH.

Process-Property-Performance Relationship for Fused Deposition of Ceramics (FDC) Feedstock Materials

Fused deposition of ceramics (FDC) is an extrusion based layered manufacturing process. It uses a high solids loaded (>50 vol. % ceramic or metal powder) thermoplastic binder in filament form as the feedstock material. The filament acts as both the piston driving the extrusion process and the feedstock material being deposited in the X-Y direction onto a Z-stage platform. The primary mode of failure of the filament during the FDC process is via buckling. Earlier work has shown that the filament compressive modulus and the feedstock viscosity control the buckling behavior of the filament material in FDC. A study was conducted to investigate the effect of particle/polymer interface on the viscosity and compressive modulus of the PZT filled ECG9 system. The relative viscosity of the untreated and the surface treated particle filled systems increases with solids loading. It is found that both of the surface treated materials (stearic acid and titanate coupling agent) exhibit a lower relative viscosity than the untreated material. A rheological model (Krieger-Dougherty model) was used to investigate the possible reasons for the decrease in relative viscosity due to the surface treatment of particles. The investigaton showed that the coupling agent acted as a dispersant (increasing value of ϕm) and thereby decreased the viscosity. The stearic acid may act as a dispersant (increasing value of ϕm) and as a lubricant (decreasing value of KE). The compressive modulus of all the different systems studied showed an increase with solids loading. A generalized Nielsen model was used to describe the relative modulus vs. solids loading behavior for all the different systems studied. Also, the measured compressive modulus of the filled system was found to be insensitive to the modifications in the particle surface treatment.

Congenital Insensitivity to Pain with Anhidrosis (CIPA): A Case Report

Congenital insensitivity to pain with anhidrosis (CIPA) is a rare disorder characterized by episodes of fever and the inability to sense of pain despite the fact that all other sensory modalities remain intact or minimally impaired. The patient also may exhibit the signs of self-mutilation, mental retardation and little or no perspiration. We present a 10 years old Iranian patient diagnosed with CIPA with the above-mentioned clinical characteristics. The prosthetic treatment and the subsequent six month follow-up are discussed. Follow-up of the patient revealed that, with the use of this prosthesis, the patient's oral function and esthetics were established and the mouth lesions improved. Therefore especial dental management of CIPA patients according to their mental status, age, oral and dental condition is essential for solving the specific problems each case may present and the full mouth teeth extraction should be considered as the last treatment.

A novel RAB27A mutation in a patient with Griscelli syndrome type 2

Griscelli syndrome type 2 is a rare autosomal recessive primary immunodeficiency disease caused by a mutation in the RAB27A gene and characterized by oculocutaneous hypopigmentation and variable cellular immunodeficiency. We report the case of a 6-month-old infant with silvery hair, eyelashes, and eyebrows who was referred to our center because of fever and hepatosplenomegaly. Bone marrow studies indicated hemophagocytosis, whilst microscopic examination of the hair showed irregular agglomerations of pigment in hair shafts. Molecular analysis revealed a novel homozygous mutation in exon 5, namely, a single-base substitution (g.42996 A>G) leading to an amino acid change (S115G) and thus confirming the diagnosis of Griscelli syndrome type 2. Griscelli syndrome could be more common than thought, especially in regions with high rates of consanguinity. As the prognosis of disease is usually poor, prompt diagnosis and appropriate treatment are vital to avoid complications.

Electrostrictive properties of nanosize PbTiO(3)

Properties of nanosize PbTiO(3) are discussed from the standpoint of the effects of crystallite size on electrostrictive behavior. Experimental results based on crystallite size-dependent primary and secondary order parameters (spontaneous polarization and strain) show that the critical crystallite size (CCS) for the stabilization of the cubic paraelectric phase at 298 K is around 15 nm. The CCS inversely scales with the cubic-tetragonal transition temperature (T(tr)). Electrostrictive coefficients exhibit an order of magnitude increase at 28 nm, which is attributed to the anharmonicity of the perovskite lattice. First order calculations indicate that the increase in the electrostrictive coefficients offsets the decrease in spontaneous polarization and results in an increase in piezoelectric moduli suggesting that piezoelectric activity could, in principle, be observed in the nanosize regime.

Design optimization of dome actuators

This paper reports the conceptual design, analysis, and modeling of the electromechanical behavior of dome actuators. The geometric parameters of the actuator (dome thickness, width, radius, and depth), poling direction, electric field, and material properties (elastic compliance, piezoelectric constants, and dielectric permittivity) have been taken into account in the modeling work. The results of the analysis indicate that a dome actuator with a tangentially alternating poling direction and electric field (Case C) exhibits much larger displacement and force responses than dome actuators with other poling directions and electric fields. The first mode of natural frequency of the Case C dome actuator also was investigated, and its predicted performance was compared with that of moonie and rainbow actuators. The findings of this research clearly demonstrate the merit of design optimization of electromechanical devices.