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PloS One 2016Supereruptions catastrophically eject 100s-1000s of km3 of magma to the surface in a matter of days to a few months. In this study, we use zoning in quartz crystals from...
Supereruptions catastrophically eject 100s-1000s of km3 of magma to the surface in a matter of days to a few months. In this study, we use zoning in quartz crystals from the Bishop Tuff (California) to assess the timescales over which a giant magma body transitions from relatively quiescent, pre-eruptive crystallization to rapid decompression and eruption. Quartz crystals in the Bishop Tuff have distinctive rims (<200 μm thick), which are Ti-rich and bright in cathodoluminescence (CL) images, and which can be used to calculate Ti diffusional relaxation times. We use synchrotron-based x-ray microfluorescence to obtain quantitative Ti maps and profiles along rim-interior contacts in quartz at resolutions of 1-5 μm in each linear dimension. We perform CL imaging on a scanning electron microscope (SEM) using a low-energy (5 kV) incident beam to characterize these contacts in high resolution (<1 μm in linear dimensions). Quartz growth times were determined using a 1D model for Ti diffusion, assuming initial step functions. Minimum quartz growth rates were calculated using these calculated growth times and measured rim thicknesses. Maximum rim growth times span from ~1 min to 35 years, with a median of ~4 days. More than 70% of rim growth times are less than 1 year, showing that quartz rims have mostly grown in the days to months prior to eruption. Minimum growth rates show distinct modes between 10-8 and 10-10 m/s (depending on sample), revealing very fast crystal growth rates (100s of nm to 10s of μm per day). Our data show that quartz rims grew well within a year of eruption, with most of the growth happening in the weeks or days preceding eruption. Growth took place under conditions of high supersaturation, suggesting that rim growth marks the onset of decompression and the transition from pre-eruptive to syn-eruptive conditions.
Topics: Crystallization; Diffusion; Electrons; Geological Phenomena; Luminescent Measurements; Quartz; Time Factors; Titanium
PubMed: 27438605
DOI: 10.1371/journal.pone.0159200 -
Cureus Mar 2024Background This study aimed to compare the radicular dentin thickness in single-rooted maxillary and mandibular anterior and premolar teeth by measuring on four...
Background This study aimed to compare the radicular dentin thickness in single-rooted maxillary and mandibular anterior and premolar teeth by measuring on four different surfaces (buccal, lingual, mesial, and distal) at three different levels (apical, middle, and coronal). Methods A total of 150 single-rooted human anterior and premolar teeth were included in the present study. The teeth were sectioned at the cemento-enamel junction (CEJ; coronal), 4 mm away from the apex (apical), and the midpoint between these two distances (middle). First, the teeth were divided buccolingually into two parts, and the dentin thickness in the mesial/distal region was measured. Subsequently, both parts were divided again to measure the dentin thickness in the buccal/lingual region. All measurements were recorded, and statistical analysis was performed. Results Apical radicular dentin thickness was significantly less than CEJ (p < 0.001). The maxillary central incisor, maxillary, and mandibular canine exhibited the maximum radicular dentin thickness, whereas the mandibular premolars showed the minimum. Radicular dentin thicknesses on the lingual and buccal surfaces were significantly higher than those on other surfaces (p < 0.001). Conclusion The lowest radicular dentin thickness values were observed in the premolars, especially on mesial and distal surfaces. Considering these areas as danger zones and paying attention during dental procedures are essential to avoid possible complications.
PubMed: 38665753
DOI: 10.7759/cureus.56974 -
Journal of Healthcare Engineering 2023To evaluate the mechanical properties of porous polyetherketoneketone (PEKK) meshes with different thicknesses, pore sizes, and porosities through finite element...
OBJECTIVE
To evaluate the mechanical properties of porous polyetherketoneketone (PEKK) meshes with different thicknesses, pore sizes, and porosities through finite element analysis to provide an optimal PEKK design for alveolar bone augmentation in the posterior mandibular region.
METHODS
A three-dimensional evaluation model of severe alveolar bone defects in the mandibular posterior was constructed based on cone beam computerized tomography (CBCT) data. Then, PEKK meshes with different structural designs were obtained. Two key parameters were set with different values: five levels of thickness (0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, and 0.6 mm) and three levels of pore size (1 mm, 2 mm, and 3 mm) with a corresponding porosity of 19.18%-42.67%. A 100 N physiological force was simultaneously loaded by finite element analysis (FEA), and the deformation and stress data were outputted for further analysis.
RESULTS
The deformation and stress of the PEKK meshes are negatively correlated with the changes in thickness and positively correlated with the changes in pore size. The FEA results show that the maximum deformation, equivalent stress, and maximum principal stress of the PEKK meshes are 0.168 mm-0.478 mm, 49.243 MPa-124.890 MPa, and 31.549 MPa-104.200 MPa, respectively. The PEKK mesh group with a thickness of 0.2 mm, pore size of 3 mm, and porosity of 42.67% is in danger of plastic deformation or even fracture during use.
CONCLUSION
According to the FEA results, the PEKK meshes with larger thicknesses and smaller pore sizes and porosities behave better. In consideration of reducing soft tissue stimulation and promoting bone regeneration, an ultrathin porous PEKK mesh with a pore size of no more than 3 mm, porosity of no more than 42.67%, and thickness of 0.2 mm can be used clinically to meet the mechanical performance requirements of the guided bone regeneration (GBR) structure.
Topics: Humans; Finite Element Analysis; Surgical Mesh; Polymers; Benzophenones
PubMed: 36760836
DOI: 10.1155/2023/8487380 -
Heliyon Mar 2021A 2.5D gravity modelling along seven selected profiles that covers the Western Cape Province of South Africa was carried out to deduce the depositional surface and...
Variations in isochore thickness and depositional surface of the Dwyka, Ecca and Beaufort Groups in the Western Cape Province of South Africa as deduced from 2.5D gravity profile models.
A 2.5D gravity modelling along seven selected profiles that covers the Western Cape Province of South Africa was carried out to deduce the depositional surface and isochore (true vertical) thickness of the Dwyka, Ecca and Beaufort Group sediments. The results revealed that the Karoo Basin deepens to a depth of about 4600 m in the south-western region, near the front of the Cape Fold Belt. Also, the model gives indication that the Karoo dolerite intrusions are interconnected at depth and are mostly concentrated at the centre of the basin. The isochore thickness maps show that the Beaufort Group is the thickest group in the Karoo Supergroup, with a maximum thickness of about m, followed by the Ecca and Dwyka Groups with thicknesses of around m and m, respectively. The maximum depositional surface (elevation) for the Dwyka, Ecca and Beaufort sediments are approximately 1696 m, 1247 m and 1491 m, respectively, whereas the maximum depth below sea level are around 3668 m, 3209 m and 480 m, respectively. Furthermore, the isochore thickness maps indicate that the Ecca Group, which is the main target for hydrocarbon exploration in the Karoo, thickens toward the south, away from the centre of the basin and reaches thickness of greater than 3680 m. The correlation of the depositional surfaces with the isochore thickness maps revealed that the sediments in structural high areas were subsided, eroded and deposited in structural low areas. Consequently, the structural low areas are characterised by thick sediments cover and vice versa.
PubMed: 33748506
DOI: 10.1016/j.heliyon.2021.e06478 -
Sports (Basel, Switzerland) Jun 2017The purpose of the present study was to examine the relationships between bat swing speed (BSS), muscle thickness, and muscle thickness asymmetry in collegiate baseball...
The purpose of the present study was to examine the relationships between bat swing speed (BSS), muscle thickness, and muscle thickness asymmetry in collegiate baseball players. Twenty-four collegiate baseball players participated in this study. Maximum BSS in hitting a teed ball was measured using a motion capture system. The muscle thicknesses of the trunk (upper abdominal rectus, central abdominal rectus, lower abdominal rectus, abdominal wall, and multifidus lumborum), upper limb, and lower limb were measured using a B-mode ultrasonography. Lateral asymmetry between each pair of muscles was determined as the ratio of the thickness of the dominant side to that of the non-dominant side. Statistically significant positive correlations were observed between BSS and muscle thicknesses of the abdominal wall and multifidus lumborum on the dominant side ( = 0.426 and 0.431, respectively; < 0.05), whereas only trends against this significance were observed between BSS and muscle thicknesses on the non-dominant side. No statistical correlations were found between BSS and the lateral asymmetry of any muscles. These findings indicate the importance of the trunk muscles for bat swing, and the lack of association between BSS and lateral asymmetry of muscle size.
PubMed: 29910393
DOI: 10.3390/sports5020033 -
Journal of Prosthodontic Research Apr 2023Purpose We aimed to assess removable partial denture occlusal rests composed of polyether-ether-ketone (PEEK) and zirconia, using finite element analysis.Methods...
Purpose We aimed to assess removable partial denture occlusal rests composed of polyether-ether-ketone (PEEK) and zirconia, using finite element analysis.Methods Three-dimensional PEEK and zirconia rest models, including the occlusal rest (1.5 mm thickness at the basal portion, 3.0 mm width) and minor connector (1.5 mm thickness, 6.0 mm height), and rest seat models with mechanical properties of enamel were constructed. The radius of transitional curvature between the rest and minor connector was 0.1-0.5 mm. The rest and rest seat model interfaces were set as frictional contacts (μ = 0.1), and the base of the rest seat model was restrained in all the directions. A 100 N downward load was applied perpendicular to the bottom surface of the minor connector. The maximum value of the first principal stress (Max-S1) was compared to the flexural and fatigue strengths of each material. Occlusal rests with 1.0-2.0 mm thickness, 2.0-3.5 mm width, and 0.5 mm radius of transitional curvature were analyzed.Results Max-S1 was observed at the transitional part and decreased with increasing radius of the transitional curvature, rest width, and thickness. PEEK rests with at least 1.5 mm thicknesses and 3.0 mm widths showed lower Max-S1 than the flexural strength. Max-S1 of all PEEK rests exceeded the PEEK fatigue strength, whereas Max-S1 of the zirconia rests was lower than the zirconia fatigue strength.Conclusions Zirconia occlusal rests with conventional metal rest designs have sufficient fatigue strength. PEEK occlusal rests have insufficient fatigue strength and may not withstand repeated mastication.
Topics: Denture, Partial, Removable; Finite Element Analysis; Rest; Dental Stress Analysis; Polyethylene Glycols; Ketones
PubMed: 35644568
DOI: 10.2186/jpr.JPR_D_22_00011 -
The Indian Journal of Medical Research Mar 2021A etiologically symmetric and asymmetric small for gestational age (SGA) infants are two distinct entities. In view of absence of longitudinal information on growth...
BACKGROUND & OBJECTIVES
A etiologically symmetric and asymmetric small for gestational age (SGA) infants are two distinct entities. In view of absence of longitudinal information on growth pattern of skinfold thicknesses (SFTs) among Indian infants, this study was conducted to assess the auxological dynamics of SFTs (sub-cutaneous fat) of symmetric and asymmetric SGA infants.
METHODS
Triceps, sub-scapular, biceps, mid-axillary and anterior thigh SFTs among full-term, 100 symmetric SGA, 100 asymmetric SGA and 100 appropriate for gestational age (AGA) infants were measured at one, three, six, nine and 12 months. Ponderal Index (PI) was used to categorize infants into symmetric SGA (PI ≥2.2 g/cm) and asymmetric SGA (PI <2.2 g/cm). Intra-group (symmetric vs. asymmetric), inter-group (SGA vs. AGA) and gender differences were quantified.
RESULTS
SFTs among symmetric, asymmetric SGA infants increased to attain peak by six months. Maximum fat deposition in SGA infants was noticed for triceps, minimum for mid-axillary SFT. Mean triceps and sub-scapular skinfolds were measured higher in symmetric SGA than in asymmetric infants. SGA infants had significantly (P≤0.05) thinner SFTs than AGA. Growth velocity for SFTs, among symmetric and asymmetric SGA, was measured maximum between one and three months, threreafter it declined and relatively, steepness of fall was maximum for mid-axillary SFT followed by sub-scapular SFT.
INTERPRETATION & CONCLUSIONS
Thinner SFTs obtained for symmetric and asymmetric SGA as compared to AGA infants reveal their compromised adiposity and nutritional status. Comparatively, higher SFTs in symmetric than in asymmetric SGA infants appear to suggest that the former have a tendency to accumulate more fat, than the latter during infancy.
Topics: Gestational Age; Humans; Infant; Infant, Newborn; Infant, Small for Gestational Age; Obesity; Severe Fever with Thrombocytopenia Syndrome; Skinfold Thickness
PubMed: 35345071
DOI: 10.4103/ijmr.IJMR_298_20 -
Materials (Basel, Switzerland) Mar 2018In 4D printing research, different types of complex structure folding and unfolding have been investigated. However, research on cross-folding of origami structures...
In 4D printing research, different types of complex structure folding and unfolding have been investigated. However, research on cross-folding of origami structures (defined as a folding structure with at least two overlapping folds) has not been reported. This research focuses on the investigation of cross-folding structures using multi-material components along different axes and different horizontal hinge thickness with single homogeneous material. Tensile tests were conducted to determine the impact of multi-material components and horizontal hinge thickness. In the case of multi-material structures, the hybrid material composition has a significant impact on the overall maximum strain and Young's modulus properties. In the case of single material structures, the shape recovery speed is inversely proportional to the horizontal hinge thickness, while the flexural or bending strength is proportional to the horizontal hinge thickness. A hinge with a thickness of 0.5 mm could be folded three times prior to fracture whilst a hinge with a thickness of 0.3 mm could be folded only once prior to fracture. A hinge with a thickness of 0.1 mm could not even be folded without cracking. The introduction of a physical hole in the center of the folding/unfolding line provided stress relief and prevented fracture. A complex flower petal shape was used to successfully demonstrate the implementation of overlapping and non-overlapping folding lines using both single material segments and multi-material segments. Design guidelines for establishing cross-folding structures using multi-material components along different axes and different horizontal hinge thicknesses with single or homogeneous material were established. These guidelines can be used to design and implement complex origami structures with overlapping and non-overlapping folding lines. Combined overlapping folding structures could be implemented and allocating specific hole locations in the overall designs could be further explored. In addition, creating a more precise prediction by investigating sets of in between hinge thicknesses and comparing the folding times before fracture, will be the subject of future work.
PubMed: 29510503
DOI: 10.3390/ma11030376 -
World Journal of Gastrointestinal... Dec 2020Current medical treatments can achieve remission of ulcerative colitis (UC). Surgery is required when potent drug treatment is ineffective or when colon cancer or...
BACKGROUND
Current medical treatments can achieve remission of ulcerative colitis (UC). Surgery is required when potent drug treatment is ineffective or when colon cancer or high-grade dysplasia develops. The standard procedure is restorative proctocolectomy (RPC) with ileal pouch-anal anastomosis, commonly performed as two- or three-stage RPC with diverting ileostomy. Postoperative stoma outlet obstruction (SOO) is frequent, but the causes are not well known.
AIM
To identify the risk factors for SOO after stoma surgery in patients with UC.
METHODS
We retrospectively reviewed the files of 148 consecutive UC patients who underwent surgery with stoma construction. SOO was defined as small bowel obstruction symptoms and intestinal dilatation just below the penetrating part of the stoma on computed tomography. Patients were divided into two groups: Those who developed SOO within 30 d after surgery and those who did not. Patient characteristics, intraoperative parameters, the stoma site, and rectus abdominis muscle thickness were collected. Moreover, we identified the patients who repeatedly developed SOO. Univariate and multivariate analyses were performed to identify risk factors for SOO and recurring SOO.
RESULTS
Eighty-nine patients who underwent two-stage RPC were included between January 2008 and March 2020. Postoperatively, SOO occurred in 25 (16.9%) patients after a median time of 9 d (range 2-26). Compared to patients without SOO, patients with SOO had a significantly higher rate of malignant tumors or dysplasia (36.0% 17.1%, = 0.032), lower total glucocorticoid dose one month before surgery (0 mg 0 mg, = 0.026), higher preoperative total protein level (6.8 g/dL 6.3 g/dL, = 0.048), higher rate of loop ileostomy (88.0% 55.3%, = 0.002), and higher maximum stoma drainage volume (2300 mL 1690 mL, = 0.004). Loop ileostomy (OR = 6.361; 95%CI 1.322-30.611; = 0.021) and maximum stoma drainage volume (OR = 1.000; 95%CI 1.000-1.001; = 0.015) were confirmed as independent risk factors for SOO. Eighteen patients with SOO were treated conservatively without recurrence (sSOO group). Seven (28.0%) patients repeatedly developed SOO (rSOO group) during the observation period. A significant difference was observed in the rectus abdominis muscle thickness between the two groups (sSOO 9.3 mm, rSOO 12.7 mm, = 0.006). Muscle thickness was confirmed as an independent risk factor for recurring SOO (OR = 2.676; 95%CI 1.176-4.300; = 0.008).
CONCLUSION
In this study, high maximum stoma drainage volume and loop ileostomy are independent risk factors for SOO. Additionally, among patients with a thick rectus abdominis muscle, the risk of SOO recurrence is high.
PubMed: 33437402
DOI: 10.4240/wjgs.v12.i12.507 -
Orthopaedic Surgery Jun 2023Bone cement releases a large amount of heat as it polymerizes. Skin burns caused by discarded bone cement are not well understood during arthroplasty. It is important to...
OBJECTIVE
Bone cement releases a large amount of heat as it polymerizes. Skin burns caused by discarded bone cement are not well understood during arthroplasty. It is important to study the correlates and mechanisms of scalding and to accurately evaluate the severity of burns to guide treatment decisions.
METHODS
Standardized burns were created in eight anesthetized rabbits using different thicknesses of bone cement. Bone cement was uniformly stirred to make thicknesses of 1 mm, 4 mm, 8 mm, 12 mm, 16 mm, and 20 mm and a 20 × 40 mm cuboid. Bone cement samples were then placed on the back of a rabbit, and the temperature changes were recorded with an industrial digital thermometer. One hour later, the appearance of scalded skin was observed, and the rabbits were euthanized. The scalded parts were cut to make pathological sections and stained with HE, and the differences in the depth of the scalded skin caused by different thicknesses of bone cement were observed under a light microscope.
RESULTS
Damage caused by 1 mm-, 4 mm-, 8 mm-, 12 mm-, 16 mm-, and 20 mm-thick bone cement samples mainly involved the epidermis, the papillary dermis, the reticular dermis layer, and the full thickness of the skin and the subcutaneous tissue. The maximum temperature of 1 mm, 4 mm, 8 mm, and 12 mm bone cementation had a statistically significant difference (p < 0.001), while there was no significant difference between 12 mm, 16 mm, and 20 mm samples (p = 0.856). The time to severe scalding with bone cement at temperatures above 70°C was significantly different between different thicknesses (p < 0.001).
CONCLUSION
The heat released by different thicknesses of bone cement leads to different maximum temperatures and the duration of severe burns, resulting in different degrees of skin burns. Attention should be paid to discarded bone cement to prevent this potential complication in knee arthroplasty.
Topics: Animals; Rabbits; Bone Cements; Skin; Hot Temperature; Arthroplasty, Replacement, Knee; Burns
PubMed: 37092381
DOI: 10.1111/os.13700