Search

Statement of problem Narrow diameter implants were developed to allow placement in narrow alveolar ridges. Clinicians may have concerns about the durability and function of such implants. Purpose The purpose of this finite element study was to compare the stress values occurring on the implant and at the implant bone interface after the application of the static and dynamic forces on narrow diameter, titanium and titanium-zirconia implants in the maxillary and mandibular second premolar region. Material and methods Titanium (Ti) and titanium-zirconium (Ti-Zr) narrow diameter implants (3.3 mm in diameter, 10 mm in length) were simulated in the maxillary and mandibular second premolar region, and metal-ceramic crown restorations were designed. Forces of 100 N were applied to crowns in a vertical and oblique (45-degree angle to the long axis) direction. Maximum and minimum principal stresses in the cortical and trabecular bone and the von Mises stresses and fatigue strength of the implants were evaluated with 3-dimensional finite element analysis. Results In vertical and oblique static loading, Ti and Ti-Zr implants showed similar stress distribution within the same jaw models. However, the von Mises stresses in Ti-Zr implants were slightly higher than for Ti implants in all models. In oblique static and dynamic loading, all stresses were found higher than vertical loading, and fatigue failure results were found to be more critical than vertical forces. Conclusions Based on a numerical simulation, Ti and Ti-Zr alloys can be used successfully as narrow diameter implants in the second premolar area.

The leather industry generates approximately ten million tons of solid bio-wastes that can be used to synthesize various multifunctional materials with exciting properties. One such approach involves developing advanced hybrid materials, which is considered one of the key areas but the underdeveloped materials science discipline. This work explored methods to use collagen derived from leather industry bio-wastes to form hybrid films via two different ways: to produce luminescent carbon dots (Cdots) and develop hybrid films. The polymeric collagen was mixed with Cdots and reduced graphene oxide (rGO) to create flexible composite films that exhibit improved thermal, mechanical, electrical, and luminescent properties. The Cdot films displayed enhanced luminescence. The Kubelka-Munk transformation of the diffuse reflectance reveals a massive increase in absorbance in the visible light region with the addition of rGO. Besides, the developed films displayed electrical conductivity and weak ferromagnetic characteristics and showed enhanced biocompatibility. These findings highlight new avenues for converting industrial bio-wastes into useful multifunctional materials in scalable and inexpensive ways, thereby diminishing environmental pollution and enhancing environmental sustainability.

Pd supported on biguanide(metformine)-functionalized fullerene (C 60 -Met/Pd 2+ ) hybrid materials was fabricated for the first time. The catalyst prepared was characterized by X-ray diffraction spectroscopy (XRD), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). The catalyst showed excellent activity Suzuki–Miyaura coupling reaction of different aryl iodides and bromides with phenylboronic acid at room temperature in the EtOH:H 2 O (1:1) mixture as solvent. The yields of the products were in the range from 85% to 98%. The catalyst can be readily recovered and reused at least 6 consecutive cycles without significant loss in its catalytic activity. This is the new example for the development of fullerene (C 60 -Met-Pd) complexes which can be used as efficient recyclable catalysts without palladium leaching.

A conducting polymer of 3,5-diphenyl-2,6-dithiophene-2-yl-dithieno[3,2-b;2’,3’-d]thiophene (Thy2Ph2DTT) was synthesized by potentiodynamic method in dichloromethane (DCM)/acetonitrile (AN) (1/1)-NaClO4/LiClO4 (0.1:0.1 M) solvent-electrolyte mixture. The resulting polymer was characterized via cyclic voltammetry (CV), Fourier transform infrared (FTIR) and UV-Vis spectroscopy. Its dual type electrochromic device (ECD) with PEDOT was constructed. Spectroelectrochemical and electrochromic properties of the polymer film and the device were investigated in detail. A potential range of 0.0–2.0 V was found to be suitable for operating the P(Thy2Ph2DTT)/PEDOT device between red and blue colors. The device displayed good open circuit memory and stability. Properties of Thy2Ph2DTT and P(Thy2Ph2DTT) were compared with 3,5-diphenyldithieno[3,2-b;2’,3’-d]thiophene (Ph2DTT) and its polymer P(Ph2DTT), reported previously, which revealed that introduction of thiophenes to the peripherals of Ph2DTT improved the properties of the corresponding polymer.

Selective syntheses of 3,4-vinylenedithiathiophenes (VDTTs) and dithieno[2,3-b;2′,3′-d]thiophenes (DTTs), having Ph, 4-CH3OC6H4, 4-BrC6H4, 4-NO2C6H4 and 4-(CH3)2NC6H4 groups, were achieved through the reaction of 1,8-diketone with phosphorus decasulfide (P4S10). The reaction could be shifted between VDTT and DTT by adding base (sodium bicarbonate) or acid (para-toluenesulfonic acid), respectively, to the reaction mixture. While the VDTTs were obtained in moderate yields, an important achievement has been made with the syntheses of the DTTs, obtaining them in higher yields compared with the previous report. Polymers of the VDTTs, which are the analogues of ethylenedioxythiophene, EDOT, were prepared using FeCl3. Unfortunately, all attempts for their electropolymerization failed. Spin density calculations revealed that none of the VDTTs had a significant positive spin density at the ‘α’ carbon atoms of the thiophene ring. Considering their solubility and functional groups, which could be further derivatized, they are useful building blocks for the preparation of new organic materials.

A novel one-pot photochemical strategy for the preparation of silver–epoxy nanocomposite using a highly conjugated thiophene derivative and silver salt was described. Electron transfer reaction between photoexcited 3,5-bis(4-methoxyphenyl)dithieno[3,2-b;2,3-d]thiophene), (P-DDT) and silver salt could be achieved under visible light irradiation. The polymerization process has been demonstrated to be highly efficient in the concomitant cationic ring-opening polymerization of epoxy ring and silver ion reduction. The produced nanocomposite contains spherical shaped nanoparticles homogenously dispersed in the epoxy network with narrow size distribution in between 25 and 50 nm.

Electropolymerization of 3,5-bis(4-methoxyphenyl)dithieno[3,2- b ;2′,3′- d ]thiophene BMPhDTT, having strong electron-donating methoxy groups, was performed, utilizing potentiodynamic method. The homopolymer was characterized by cyclic voltammetry (CV), Fourier transform infrared (FTIR) and UV–vis spectroscopy. Spectroelectrochemical and electrochromic properties of the homopolymer film were investigated and a PBMPhDTT/PEDOT device was constructed to understand its characteristics in detail. It was revealed that the potential range of 0.0–2.0 V is suitable for operating the device between yellow and blue colors. It indicated a good open circuit memory and stability.

The hemodynamic factors contributing to the clinical symptomatology in patients with mitral stenosis (MS) have been under investigation. The objective of this study was to evaluate the use of the Valsalva maneuver in patients with MS and whether there is an association between the degree of the hemodynamic changes in transmitral gradient (TG) in response to Valsalva maneuver and functional status, systolic pulmonary artery pressure, and left atrial function in patients with MS in sinus rhythm.The study prospectively evaluated 42 patients (37 female, mean age 40 +/- 10 years) with a diagnosis of pure MS in sinus rhythm. Patients were divided into 3 groups according to their New York Heart Association (NYHA) functional class. In all, 12 patients were in NYHA functional class I, 17 patients in class II, and 13 patients in class III. TG, including the mitral peak, mean, and late filling gradients, were calculated by the modified Bernoulli equation at rest and during the strain phase of Valsalva maneuver. The percentage changes in all TG in response to Valsalva were calculated. Traditional echocardiographic parameters for atrial function were also measured.We found that, in patients who were more symptomatic according to NYHA classification, a reduction in TG in response to Valsalva maneuver was blunted and associated with higher systolic pulmonary artery pressure compared with those who were asymptomatic or had mild symptoms. Patients in NYHA class III decreased mitral mean pressure gradient by only 13.5%, significantly less (P.001) than those in classes I (53.9%) and II (41.7%). However, despite the fact that left atrial ejection fraction was low in all patients, it was not associated with functional status in patients with MS.This study, for the first time, suggests that echocardiographically determined changes in TG in response to the Valsalva maneuver may provide an objective, noninvasive means of evaluating patients with MS.

A 63-year-old man was admitted to our emergency department with the complaint of syncope. An electrocardiogram showed complete atrioventricular block with a low ventricular rate. He was hospitalized and a temporary transfemoral pacemaker was inserted under direct fluoroscopy urgently. Immediate postprocedural electrocardiogram in the paced mode showed right bundle branch block morphology that led to suggestion of abnormal lead location. A transthoracic echocardiogram revealed that the pacemaker lead was directly inserted from the right atrium into the left ventricle through the junction of the interatrial and interventricular septums. Because severe multivessel coronary artery disease was diagnosed angiographically in his subsequent hospital course, coronary artery bypass grafting and surgical extraction of the misplaced lead was performed at the same time. Clinical implications, diagnosis, and therapeutic options of left ventricular pacemaker lead malposition are discussed.