Dynamic X-Ray Diffraction Technique for Measuring the Crystal Lattice Response in Semicrystalline Polymers against Mechanical Excitations

Dynamic mechanical and crystallographic features which are associated with mechanical excitations on the bulk specimen of the semicrystalline polymers are generalized on the basis of factors such as mechanical dispersions of orientation of crystallites and deformation of the crystal superstructure. The latter factor may further be divided into inter-lamellae and intra-lamella responses within the superstructure such as spherulite. The present paper describes the theory and techniques set up to observe the intralamella response in the semicrystalline polymers against mechanical excitations by means of a dynamic x-ray diffraction technique. This observation is required to measure the inphase and out-of-phase components of the angular vibration of the diffraction maximum raised by the forced sinusoidal strain of the test specimen. For this purpose, it was shown that a twin detector technique could successfnlly be applicable where the diffraction peak shift was amplified by simultaneous measurements of the shoulder intensities of the diffraction perk at the higher and the lower diffraction angles to the peak maximum

Dynamic X-ray Diffraction Technique for Measuring Rheo-optical Properties of Crystalline Polymeric Materials

A dynamic X-ray diffraction technique, which can follow the responses of polymer crystals (crystallization, orientation, and lattice deformation) to a mechanical excitation of sinusoidal strain induced to a bulk specimen, was described. The descriptions for such responses are qualitatively made by using a narrow sector technique, which can measure the X-ray diffraction intensity distribution at a particular phase angle of the sinusoidal strain as a function of static and dynamic strains, temperature, and angular frequency. A typical result is demonstrated in terms of the investigation of orientationcrystallization phenomena of natural rubber vulcanizates. More quantitative descriptions can be made by using a half-circle sector technique, which can measure the in-phase and out-of phase components of the dynamic X-ray diffraction intensity distribution. From these, one can obtain the dynamic strain-induced crystallization and orientation coefficients and the dynamic response of lattice deformation of a specific crystal plane both as functions of temperature and frequency. After a brief survey of the principle of the half-circle sector technique, frequency dependence of the dynamic strain-induced crystallization coefficients of the (002) and (200) crystal planes of natural rubber vulcanizates is demonstrated in terms of the two frequency dispersion regions around 10⁻² and 10¹ Hz at a room temperature. The former and latter dispersions must be correlated with the crystallization processes of the so-called α- and γ-filaments, respectively. In addition, frequency and temperature dispersions of the dynamic strain-induced orientation coefficient and the dynamic response of lattice deformation of the (110) crystal plane of polyethylene are demonstrated in relation to the so-called a₁ and a₂ dispersions of dynamic mechanical modulus function of this material

Understanding the formation of maxillary sinus in Japanese human foetuses using cone beam CT

The formation of the maxillary sinus (MS) is tied to the maturation of the craniofacial bones during development. The MS and surrounding bone matrices in Japanese foetal specimens were inspected using cone beam computed tomography relative to the nasal cavity (NC) and the surrounding bones, including the palatine bone, maxillary process, inferior nasal concha and lacrimal bone. The human foetuses analysed were 223.2 ± 25.9 mm in crown-rump length (CRL) and ranged in estimated age from 20 to 30 weeks of gestation. The amount of bone in the maxilla surrounding the MS increased gradually between 20 and 30 weeks of gestation. Various calcified structures that formed the bone matrix were found in the cortical bone of the maxilla, and these calcified structures specifically surrounded the deciduous tooth germs. By 30 weeks of gestation, the uncinate process of the ethmoid bone formed a border with the maxilla. The distance from the midline to the maximum lateral surface border of the MS combined with the width from the midline to the maximum lateral surface border of the inferior nasal concha showed a high positive correlation with CRL in Japanese foetuses. There appears to be a complex correlation between the MS and NC formation during development in the Japanese foetus. Examination of the surrounding bone indicated that MS formation influences maturation of the maxilla and the uncinate process of the ethmoid bone during craniofacial bone development

Crystal structure analysis of human serum albumin complexed with sodium 4-phenylbutyrate

Sodium 4-phenylbutyrate (PB) is an orphan drug for the treatment of urea cycle disorders. It also inhibits the development of endoplasmic reticulum stress, the action of histone deacetylases and as a regulator of the hepatocanalicular transporter. PB is generally considered to have the potential for use in the treatment of the diseases such as cancer, neurodegenerative diseases and metabolic diseases. In a previous study, we reported that PB is primarily bound to human serum albumin (HSA) in plasma and its binding site is drug site 2. However, details of the binding mode of PB to HSA remain unknown. To address this issue, we examined the crystal structure of HSA with PB bound to it. The structure of the HSA–PB complex indicates that the binding mode of PB to HSA is quite similar to that for octanoate or drugs that bind to drug site 2, as opposed to that for other medium-chain length of fatty acids. These findings provide useful basic information related to drug–HSA interactions. Moreover, the information presented herein is valuable in terms of providing safe and efficient treatment and diagnosis in clinical settings. Keywords: Human serum albumin, X-ray crystallography, Sodium 4-phenylbutyrate, Drug interaction, Drug site

The use and performance of artificial intelligence applications in dental and maxillofacial radiology: A systematic review

OBJECTIVES: To investigate the current clinical applications and diagnostic performance of artificial intelligence (AI) in dental and maxillofacial radiology (DMFR). METHODS: Studies using applications related to DMFR to develop or implement AI models were sought by searching five electronic databases and four selected core journals in the field of DMFR. The customized assessment criteria based on QUADAS-2 were adapted for quality analysis of the studies included. RESULTS: The initial electronic search yielded 1862 titles, and 50 studies were eventually included. Most studies focused on AI applications for an automated localization of cephalometric landmarks, diagnosis of osteoporosis, classification/segmentation of maxillofacial cysts and/or tumors, and identification of periodontitis/periapical disease. The performance of AI models varies among different algorithms. CONCLUSION: The AI models proposed in the studies included exhibited wide clinical applications in DMFR. Nevertheless, it is still necessary to further verify the reliability and applicability of the AI models prior to transferring these models into clinical practice.status: publishe

Experimental evidence for epitaxial silicene on diboride thin films

As the Si counterpart of graphene, silicene may be defined as an at least partially sp^2-hybridized, atom-thick honeycomb layer of Si that possesses π-electronic bands. Here we show that two-dimensional, epitaxial silicene forms through surface segregation on zirconium diboride thin films grown on Si wafers. A particular buckling of silicene induced by the epitaxial relationship with the diboride surface leads to a direct π-electronic band gap at the Γ point. These results demonstrate that the buckling and thus the electronic properties of silicene are modified by epitaxial strain

Frequency and type of incidentally detected radiodensities in the maxillary sinus: a retrospective analysis using cone beam computed tomography (CBCT)

OBJECTIVES: To evaluate the frequency, location, and characteristics of radiodensities in the maxillary sinus using cone beam computed tomography (CBCT). MATERIALS AND METHODS: All CBCT scans with a large field of view with both maxillary sinuses entirely visible were initially screened. Patients were included, if there was no suspicion of sinus pathology and no history of surgical intervention/trauma in the sinus region. The location and shape of the radiodensities were evaluated in axial, coronal, and sagittal CBCT views. The findings were correlated with age, gender, condition of the sinus mucosa, and status of the dentition. RESULTS: A total of 169 patients (338 maxillary sinuses) were included. Radiodensities were found in 35 sinuses (10.4%) of 28 patients (16.6%) with a mean age of 32.0 years. Most of the 35 affected sinuses had one radiodensity (19/54.2%). The radiodensities were typically located at the sinus floor (22/62.9%). Of the sinuses presenting with radiodensities, 17 (48.6%) were exhibiting reactive changes of the Schneiderian membrane. The presence of periodontal pathology was found to be associated with the presence of radiodensities. Age and sinus pathology were influencing factors on the shape of radiodensities, and the status of the dentition was an influencing factor on the number of lesions. CONCLUSIONS: One-sixth of the patients analyzed had incidentally diagnosed radiodensities in their maxillary sinuses. As almost 50% of the sinuses with radiodensities exhibited a form of chronic rhinosinusitis, the diagnosed ectopic calcifications may have formed as a result of mucosal changes of inflammatory origin. The presence of periodontal pathology was associated with a higher incidence of radiodensities. Nevertheless, this finding has to be interpreted with some caution due to the limited sample size available. CLINICAL RELEVANCE: Incidentally detected radiodensities in the maxillary sinus are not an infrequent finding in CBCT scans of asymptomatic patients, and are located typically on the sinus floor. Future studies are needed to assess the clinical significance of these findings especially with regard to planned surgical interventions in the posterior maxilla.status: publishe