Plastic Ring Research Articles

Failure mechanism of Mesozoic soft rock roadway in Shajihai coal mine and its surrounding rock control

In view of the buckling failure caused by large deformation of Mesozoic soft rock roadway in Shajihai mining area, such as serious roof fall, rib spalling, floor heave, etc., based on the detail site investigation, theoretical analysis, mineral composition test, microstructure test, water-physical property test and field experiments were carried out. And we revealed the compound failure mechanism of Mesozoic soft rock roadway in Shajihai mining area, namely the molecule expansion-shear slip of weak structural plane-construction disturbance. On this basis, the coupling support technology whose core is constant resistance with large deformation bolt was proposed. The feature of this supporting technology is that a new type of structural composite material was used, which makes the supporting system not only has the ideal deformation characteristics, but also has high supporting resistance. Thus the fully release of plastic energy within surrounding rock and reasonable control of the thickness of the plastic ring were realized. Then the differential deformation between the surrounding rock and support was eliminated by the secondary coupling support of bolt–mesh–cable, and the bolt with high strength was applied in the base angle to control floor. Eventually the collaborative bearing system of surrounding rock–support was formed. Through field tests the validity and rationality of support was also verified.

Role of the precuneus in the detection of incongruency between tactile and visual texture information: A functional MRI study

Visual clues as to the physical substance of manufactured objects can be misleading. For example, a plastic ring can appear to be made of gold. However, we can avoid misidentifying an object׳s substance by comparing visual and tactile information. As compared to the spatial properties of an object (e.g., orientation), however, little information regarding physical object properties (material properties) is shared between vision and touch. How can such different kinds of information be compared in the brain? One possibility is that the visuo-tactile comparison of material information is mediated by associations that are previously learned between the two modalities. Previous studies suggest that a cortical network involving the medial temporal lobe and precuneus plays a critical role in the retrieval of information from long-term memory. Here, we used functional magnetic resonance imaging (fMRI) to test whether these brain regions are involved in the visuo-tactile comparison of material properties. The stimuli consisted of surfaces in which an oriented plastic bar was placed on a background texture. Twenty-two healthy participants determined whether the orientations of visually- and tactually-presented bar stimuli were congruent in the orientation conditions, and whether visually- and tactually-presented background textures were congruent in the texture conditions. The texture conditions revealed greater activation of the fusiform gyrus, medial temporal lobe and lateral prefrontal cortex compared with the orientation conditions. In the texture conditions, the precuneus showed greater response to incongruent stimuli than to congruent stimuli. This incongruency effect was greater for the texture conditions than for the orientation conditions. These results suggest that the precuneus is involved in detecting incongruency between tactile and visual texture information in concert with the medial temporal lobe, which is tightly linked with long-term memory.

Right Hemicolectomy: Intestinal Motility and Exocrine Pancreatic Secretion Changes in Rats. Influence Exerted by the Reinsertion of the Ileo-Cecal Segment as a Self-Service Emptying Pouch in the Left Colon

Introduction: Our objective was to analyze, in rats, intestinal total transit time (TTT) and exocrine pancreatic secretion (EPS) changes induced by right hemicolectomy (RHC) in comparison with a sham group, which is section and reanastomosis of ileon and colon (SRIC). In addition, examine the modifications resulting of associating RHC with the reinsertion of the ileo-cecal segment (ICS) as a self-emptying pouch (SEP). Methods: Twenty-eight adult male Wistar rats (300-500 g), drinking tap water and eating Purina adlibitum, kept in individual cages, were distributed in the following groups: 1) RHC (n=6), 2) SRIC (n=6), 3) C (n=6; non-operated animals), and 4) RHC+SEP (n=10) (Figure 1). In all rats a Thomas cannula was inserted in gastric rumen. Motility was studied with the Hinton method, implanting radio opaque plastic rings through the Thomas cannula. TTT was evaluated measuring feces every 12 hours. Enzyme pancreatic secretion was determined with the Boehringer Monotest Chymotrypsin in feces.Figure 1Results: RHC elicits terminal ileon dilatation, small peptic types of ulcers predominantly close to the anastomosis. In rats with associated SEP, the features of colonization and of mucosal inflammation were markedly diminished. Fecal output was significantly higher in RHC rats with respect to the sham group (SRIC; Table 1). A notorious significant finding was the increase of chymotrypsin secretion in feces (Table 2 and 3, Figure 2).Figure 2TableConclusion: The results give support to our posture that in the conception of a “neural plexus freeway” (NPF; enteric autonomic nervous system) RHC interrupts the ascending flow of inhibitory cholinergic arc reflexes at its upper level (peri-vaterian region) thus triggering an enhancing of both the duodenopancreas and intraglandular cholinergic tone with the consequent shortening of TTT and of excitatory effects, a “pancreon” ecbolic hypersecretion. The improvement of colonization by the reinserted IRSP induces to suggest the probable involvement of a variety of cecal motilin.

Absorber design for the improvement of the efficiency of post-combustion CO2 capture

The objective of this paper is to design the absorber unit in order to separate the CO2 of the flue gases resulted from coal combustion. The design model was made for various types of packages using plastic, ceramic or metal rings. It was also considered that the capture process efficiency was 85%, and the monoethanolamine concentration in the solution varied between 10 and 30%. We analyzed the oldest and the newest types of package rings (Raschig rings, ceramic Berl saddle rings), as well as various types of metal and plastic Pall rings. In the model developed in this paper, the physical properties of package materials were taken into account (density, surface area, void fraction, etc). By applying the proposed model, we obtained results concerning the influence of the L/G ratio on the CO2 capture efficiency, the rich and the lean loading solvent, the solvent flow pumped through the absorber unit, the type and the size of package (height, diameter, etc). The objective of the paper is to compare the experimental results obtained in the CFBC (Circulating Fluidized Bed) pilot installation with those obtained in the mathematical model.

Preparation and characterization of a new polymer/pharmaceutical-based composite. Part I: Meloxicam

Composites of low-density polyethylene (LDPE), poly(ethylene-co-vinyl acetate) (EVA), poly(ethylene-co-octadecene), and an LDPE/EVA blend were prepared with different amounts of meloxicam (1, 3 and 5 wt %) by the melt blending process. Meloxicam was homogenously dispersed in polymer matrices. The polymer–meloxicam composites showed thermal behavior and thermal characteristics similar to those of the original polymers. Meloxicam release from the composites was examined in vitro for 50 days. The composites were incubated in phosphate-buffered solution and meloxicam concentration was determined by high-performance liquid chromatography. The prolonged release of the drug indicates that meloxicam-loaded plastic rings offer potential for control of reproduction and chronic inflammatory conditions.

Correction of diffusion-weighted magnetic resonance imaging for brachytherapy of locally advanced cervical cancer

Background. Geometrical distortion is a major obstacle for the use of echo planar diffusion-weighted magnetic resonance imaging (DW-MRI) in planning of radiotherapy. This study compares geometrical distortion correction methods of DW-MRI at time of brachytherapy (BT) in locally advanced cervical cancer patients.Material and methods. In total 21 examinations comprising DW-MRI, dual gradient echo (GRE) for B0 field map calculation and T2-weighted (T2W) fat-saturated MRI of eight patients with locally advanced cervical cancer were acquired during BT with a plastic tandem and ring applicator in situ. The ability of B0 field map correction (B0M) and deformable image registration (DIR) to correct DW-MRI geometric image distortion was compared to the non-corrected DW-MRI including evaluation of apparent diffusion coefficient (ADC) for the gross tumor volume (GTV).Results. Geometrical distortion correction decreased tandem displacement from 3.3 ± 0.9 mm (non-corrected) to 2.9 ± 1.0 mm (B0M) and 1.9 ± 0.6 mm (DIR), increased mean normalized cross-correlation from 0.69 ± 0.1 (non- corrected) to 0.70 ± 0.10 (B0M) and 0.77 ± 0.1 (DIR), and increased the Jaccard similarity coefficient from 0.72 ± 0.1 (non-corrected) to 0.73 ± 0.06 (B0M) and 0.77 ± 0.1 (DIR). For all parameters only DIR corrections were significant (p < 0.05). ADC of the GTV did not change significantly with either correction method.Conclusion. DIR significantly improved geometrical accuracy of DW-MRI, with remaining residual uncertainties of less than 2 mm, while no significant improvement was seen using B0 field map correction

Intrastromal corneal ring segments for treating keratoconus

Background Keratoconus is a degenerative condition of the cornea that profoundly affects vision and vision-specific quality of life. The axial cornea thins and protrudes, resulting in irregularity and, eventually, scarring of the cornea. There are multiple options available for treating keratoconus. Intrastromal corneal ring segments are small, crescent-shaped plastic rings that are placed in the deep, peripheral corneal stroma in order to flatten the cornea. They are made of polymethylmethacrylate (PMMA). The procedure does not involve corneal tissue nor does it invade the central optical zone. Intrastromal corneal ring segments are approved for use when contact lenses or spectacles are no longer adequate. Objectives To evaluate the effectiveness and safety of intrastromal corneal ring segments as a treatment for keratoconus. Search methods We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2018, Issue 1); Ovid MEDLINE; Embase.com; PubMed; Latin American and Caribbean Health Sciences Literature Database (LILACS); ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We did not implement any date or language restrictions in the electronic search for trials. We last searched the electronic databases on 25 January 2018. Selection criteria Two review authors independently assessed records from the electronic searches to identify randomized controlled trials (RCTs). Disagreements were resolved by discussion. Data collection and analysis We planned for two authors to independently review full-text reports, using standard methodological procedures expected by Cochrane. Main results We found no RCTs comparing intrastromal corneal ring segments with spectacles or contact lenses. Authors' conclusions In the absence of eligible RCTs to review, no conclusions can be drawn.

Abatement of styrene waste gas emission by biofilter and biotrickling filter: comparison of packing materials and inoculation procedures.

The removal of styrene was studied using two biofilters packed with peat and coconut fibre (BF1-P and BF2-C, respectively) and one biotrickling filter (BTF) packed with plastic rings. Two inoculation procedures were applied: an enriched culture with strain Pseudomonas putida CECT 324 for BFs and activated sludge from a municipal wastewater treatment plant for the BTF. Inlet loads (ILs) between 10 and 45gm(-3)h(-1) and empty bed residence times (EBRTs) from 30 to 120s were applied. At inlet concentrations ranging between 200 and 400mgNm(-3), removal efficiencies between 70% and 95% were obtained in the three bioreactors. Maximum elimination capacities (ECs) of 81 and 39gm(-3)h(-1) were obtained for the BF1-P and BF2-C, respectively (IL of 173gm(-3)h(-1) and EBRT of 60s in BF1-P; IL of 89gm(-3)h(-1) and EBRT of 90s in BF2-C). A maximum EC of 52gm(-3)h(-1) was obtained for the BTF (IL of 116gm(-3)h(-1), EBRT of 45s). Problems regarding high pressure drop appeared in the peat BF, whereas drying episodes occurred in the coconut fibre BF. DGGE revealed that the pure culture used for BF inoculation was not detected by day 105. Although two different inoculation procedures were applied, similar styrene removal at the end of the experiments was observed. The use as inoculum of activated sludge from municipal wastewater treatment plant appears a more feasible option.

Impact and rebound of an elastic–plastic ring on a rigid target

This paper studies the impact and rebound behaviour of a thin-walled elastic–plastic circular ring after it impinges onto a rigid wall with initial velocity V0 by finite element method. Through the dimensional analysis and a systematic simulation with different ring geometries and material properties, three non-dimensional parameters are identified, which dominate the impact duration and rebound velocity of the ring; and they are: (1) the ratio of wall thickness to average radius, η=h/R; (2) the yield strain of the material, Y/E; and (3) the non-dimensional initial velocity of the ring, ν≡V0/VY, where VY≡Y/(Eρ)1/2 denotes the yield velocity of the material [3].When the initial velocity is low, the impact between the ring and rigid plate remains elastic, the compression duration could be analytically obtained, and it agrees well with the numerical results, while the restitution duration is about 3/4 of the compression duration. The corresponding coefficient of restitution (COR) is found to be independent from the material property, whereas it increases from 0.75 to 0.78 when the thickness ratio changes from 1/20 to 1/40. With the increasing of initial velocity, a four-hinge crushing mode and a subsequent five-hinge mode are identified, which are different from the crushing mode of a ring under static compression. The variations of compression and restitution durations, rebound velocity and COR are discussed in detail, while some of them are compared with those of the impact of a solid ball onto a rigid wall. The effects of the ring geometry and material properties on these variables are also presented. The rebound velocity is found to reach the maximal at about a half of material׳s yield velocity when the initial velocity of the ring is about twice of the yield velocity, resulting in COR being 0.25 for all the materials and geometries adopted in this paper.

Ion permeability of artificial membranes evaluated by diffusion potential and electrical resistance measurements (719.1)

A novel model of artificial membranes that provides efficient assistance in teaching the origins of diffusion potentials is proposed. These membranes are made of polycarbonate filters fixed to 12 mm plastic rings and then saturated with a mixture of creosol and n‐decane. Electrical resistance and potential difference across these membranes can be easily measured using low‐cost volt‐ohmmeter and home‐made Ag/AgCl electrodes. The advantage of the model is the lack of ionic selectivity of the membrane, which can be modified by introduction of different ionophores to the organic liquid mixture. Membrane treated with the mixture containing valinomycin generates voltages from ‐53 mV to ‐25 mV in the presence of a 10‐fold KCl gradient (in‐to‐out) and from ‐79 mV to ‐53 mV in the presence of a bi‐ionic KCl/NaCl gradient (in‐to‐out). This latter bi‐ionic gradient potential reverses to a value from +9 mV to +20 mV when monensin is present in the organic liquid mixture. Thus, the model can be build stepwise, i.e. all factors leading to the development of diffusion potentials can be introduced sequentially, helping to understand the quantitative relationships of ionic gradients and differential membrane permeability in the generation of cell electrical signals.Grant Funding Source: Supported by FER (ULB)

The Suburban Mystery

The Suburban Mystery Leyna Krow (bio) We found the first action figure almost as soon as we started clearing the bramble and overgrown bushes from the backyard. It was a He-Man doll, sun-bleached and buried to its waist in the damp soil, one plastic arm raised to the sky as if waving for help. I bent down and plucked it from the dirt while Cameron held back the leaves of the diseased rhododendron we’d been trimming. It felt like a team effort, this rescue. We dusted the He-Man off and set it on the fence railing, so it could watch us while we worked. We agreed it was a strange and fortuitous find. It would be our mascot. But after just ten minutes of removing brush, we came across four more toys: a Power Ranger, a pair of G.I. Joes with legs entwined, and a blue-gray robot I didn’t recognize but Cameron said was from a cartoon show. We put them on the fence with the He-Man. When I asked Cameron what he thought about these objects’ origins, he was dismissive. “The people who used to live here had kids,” he said. “Kids lose their toys.” But it wasn’t just toys. As we hacked and pulled each evening after work, clearing the unruly, almost jungle-like yard foot by foot, we found other things too. Golf balls, hand tools, a roller skate, a coffee pot, keys from a keyboard, markers and crayons, a six-pack of soda still in its plastic rings, the skull of an animal—larger than a rodent’s but smaller than a cat’s. We piled these things in the first bare patch of yard we’d cleared. A cascade of odd items filling the space where something else used to be. Cameron and I bought the house on Fourth Street in early October. It was what Cameron’s parents referred to affectionately as “a starter home”— two bedrooms, one bath, a den, a too-small kitchen, a dining room, and almost identical in shape and size to every other house on the block. It was [End Page 70] also what my parents referred to affectionately as “a fixer.” The carpet was worn bare and pulling up at the corners. The kitchen had water damage. The furnace made strange sounds. Everything needed a fresh coat of paint. The front yard was all right, but the back was a mess. The entire yard was overrun with plant life. It was impossible to tell what had been deliberately planted (or why) and what had grown on its own, taking advantage of just the right combination of light, moisture, and inattention. A funny thing about Fourth Street: It was the only numbered street in the neighborhood. The streets to the north were Maple, Harrison, and Sutter. The street to the south was Stoneybrook. We decided we’d start our “fixing” with the backyard. We’d get all the old, overgrown, half-dead stuff cleared out now while the weather was still manageable. Then, come spring, we’d plant what we wanted—a garden of our own. I envisioned space for both vegetables and flowers. Cameron, who often gave lip service to sustainability efforts, was keen on the idea of us growing our own food. We researched what grows best in the Pacific Northwest climate: lettuce, zucchini, sweet peppers, a variety of herbs. We’d never had the room to do anything like this before, living as we had in a series of small city apartments, and we were, initially, excited for the project. But the work of cleaning up the yard was slow going—not only the removal of plant matter but also the seemingly endless parade of objects hiding beneath. Every few feet, a bicycle helmet, a deflated handball, a length of chain as thick as my wrist, and so on. I was fascinated by these things. To me, their randomness made them all the more curious, as if they were a puzzle demanding to be solved. But Cameron didn’t see it that way. For him, they were simply an added burden. When we came across a truck...

“Tie over ring” sutureless compression based gastrointestinal anastomotic method: experimental rat model

IntroductionGiving the ever-rising trend of pediatric minimally invasive surgery besides early neonatal surgical interventions, intestinal anastomosis turns out to be a time consuming stage due to several anatomical as well as technical difficulties. A perfect bowel anastomosis method should be easy, rapid, safe and reliable in creation of bowel continuity with minimal tissue damage. In this light, sutureless anastomotic methods have been introduced, using compression based anastomosis with biofragmentable rings or powerful magnets. Accordingly, this experimental animal model study has evaluated the result of an easy, rapid intestinal sutureless anastomotic technique via simple tying over an intraluminal ring, in comparison with conventional handsewn bowel anastomosis. MethodologyThirty Wistar–Albino male rats were enrolled and small bowel was transected via a midline laparotomy. A grooved plastic ring was inserted into the ileal lumen and both intestinal cutting ends were fixed over the ring with a simple tie in the first group. On the other hand, enteroenterostomy was performed by the conventional method of handsewn anastomosis in the second group. After 14days, rats were sacrificed to evaluate for intraperitoneal adhesion and abscess formation in addition to other evidences of anastomotic leakage. Furthermore, the anastomotic site integrity, tensile strength and healing stage were assessed microscopically. ResultsThe mean operative time and intraoperative bleeding in the tie over ring group were significantly less than those in the handsewn anastomosis group. Anastomotic stricture was more common in the conventional anastomosis group while the anastomotic tensile strength was significantly higher in the tie over ring group. Histopathological healing parameters and final healing score were almost similar in both groups but mean inflammatory cell infiltration in handsewn anastomosis was significantly higher. Conclusion“Tie over ring” is a simple method of anastomosis that is feasible, fast, safe and functionally effective for bowel reconstruction in animal models that could be reconsidered in human bowel anastomosis.

Territoriality of Copsychus malabaricus in Western Part of the Mihintale Sanctuary, Sri Lanka

The White-rumped Shama (Copsychus malabaricus) (WRS) is a small passerine bird whichhas a melodious song and solitary behaviour that holds a territory all year round. Research onterritorial behaviour of WRS is scare in Sri Lanka. Present study was carried out from May toAugust in 2013 at western border of the Mihintale sanctuary to investigate the territorialbehaviour of WRS. The behavioural studies were done by using the focal sampling method.A dummy of WRS and play back calls were used to check the aggressive behaviour andterritory variations of the bird. Territorial mapping was done using standard methoddescribed by Bibby et al (1993). Breeding success was measured by number of eggs in eachnest and number of chicks emerged from relevant nest. The frequently used trees for nestbuilding were measured by frequency of visiting time of each tree species. Individuals ofWRS were marked with coloured plastic rings prior to the study. Three territories wereselected from fragmented and non-fragmented forest patches to continue the study. Duringthe non-breeding period size of territory is approximately 26,255.6 m2 while during thebreeding period their territory size varies to 20,777.51 m2 – 33,296.03 m2. The size of theterritory depends on the degree of habitat disturbances. The results revealed that thesuccessful breeding was observed in non-fragmented forest patch than the fragmented forestpatch. Calling (43%) and moving (43%) behaviours were high in male and femalerespectively during the non-breeding period. During the breeding period lifting tail wasprominent in male while preening was prominent in female. Every 13 seconds male producedcalls both breeding and non-breeding periods. During the site selecting period both have highpercentage (male -50% and female -54%) of moving while during the nest guarding period,male showed high tail lifting and calling behaviours. The perching height varies with the siteselecting behaviour. Average perching height of male and female ranging from 2.348 m(±1.2) to 3.41 m (±1.87) and 1.25 m (±0.75) to 2.63 m (±0.89) respectively. Perching heightis significantly different (p&lt; 0.05) during the breeding and non-breeding periods. Drypetessepiara and Pterospermum canescens were frequently used trees for the nest building. Theyselected 49-150cm height from the ground level for nest construction and the nest length is9.85 cm, 7.7 cm width and thickness is 2.7 cm. Parts of Ficus aerial roots, dried leaves, sticksand grasses used as for nest building materials. Average clutch size was 2±1 and length ofegg was 2.14 cm-2.35 cm and width was 1.18-1.6 cm (ρ=-0.990).

X-ray detection of ingested non-metallic foreign bodies

To determine the utility of X-ray in identifying non-metallic foreign body (FB) and assess inter-radiologist agreement in identifying non-metal FB. Focus groups of nurses, fellows, and attending physicians were conducted to determine commonly ingested objects suitable for inclusion. Twelve potentially ingested objects (clay, plastic bead, crayon, plastic ring, plastic army figure, glass bead, paperclip, drywall anchor, eraser, Lego™, plastic triangle toy, and barrette) were embedded in a gelatin slab placed on top of a water-equivalent phantom to simulate density of a child's abdomen. The items were selected due to wide availability and appropriate size for accidental pediatric ingestion. Plain radiography of the embedded FBs was obtained. Five experienced radiologists blinded to number and types of objects were asked to identify the FBs. The radiologist was first asked to count the number of items that were visible then to identify the shape of each item and describe it to a study investigator who recorded all responses. Overall inter-rater reliability was analyzed using percent agreement and κ coefficient. We calculated P value to assess the probability of error involved in accepting the κ value. Fourteen objects were radiographed including 12 original objects and 2 duplicates. The model's validity was supported by clear identification of a radiolucent paperclip as a positive control, and lack of identification of plastic beads (negative control) despite repeated inclusion. Each radiologist identified 7-9 of the 14 objects (mean 8, 67%). Six unique objects (50%) were identified by all radiologists and four unique objects (33%) were not identified by any radiologist (plastic bead, Lego™, plastic triangle toy, and barrette). Identification of objects that were not present, false-positives, occurred 1-2 times per radiologist (mean 1.4). An additional 17% of unique objects were identified by less than half of the radiologists. Agreement between radiologists was considered almost perfect (kappa 0.86 ± 0.08, P < 0.0001). We demonstrate potential non-identification of commonly ingested non-metal FBs in children. A registry for radiographic visibility of ingested objects should be created to improve clinical decision-making.

Colour ringing programme of the lesser spotted eagle (Aquila pomarina) population in Slovakia and its new results in the period 2009–2012

Abstract In the years 2009-2012 a total of 316 individuals were marked in a colour ringing programme of the population ofA. pomarina in Slovakia. From this a total of 39 inds. were ringed with yellow readable plastic rings with a two-place alphanumeric code (all young in a nest) and 277 inds. (273 young and 4 adult inds.) with light-blue rings. For the entire period of the programme of marking the A. pomarina population in Slovakia in the years 2000-2012 a total of 952 inds. were ringed, 933 of which were young birds in nest and 19 adult individuals. In the period 2009-2012 48 records were obtained from observations of 35 individuals of different age categories (31 individuals from one to 11 years old, three of unknown age and one young individual about one month after fledging the nest). The age categories of immature individuals were determined, and six were found to be one-year-old individuals (12.5%) in the second calendar year of life after their first return from wintering grounds, six were two-year-old eagles (12.5%) and five were three-year-old eagles (10.4%) which spent breeding periods in Europe at a relatively small distance from their place of hatching. Adult individuals were found to be in their current breeding grounds at distances of 8-249 km from their hatching place. In the period 2000-2012 three individuals were recorded 3× and four individuals 2×. The results confirm breeding site fidelity in adults, but also the fidelity of immature individuals to their hatching place, and the return of one-year-old individuals from their wintering grounds to the vicinity of their hatching place immediately in the first year of life (that is, in the second calendar year).

Nanoindentation hardness of intertubular dentin in sound, demineralized and natural caries-affected dentin

The purpose of this study was to investigate the mechanical properties of intertubular dentin in sound, natural caries-affected (NCAD) and artificial caries-affected dentin (ACAD) using nanoindentation. Materials and methodsNon-caries molars and caries molars with International Caries Detection and Assessment System (ICDAS II) score 5 at the occlusal site were used and caries was excavated using a spoon excavator, a round bur at low speed without water and a dye solution as guidance to detect the infected tissue. Specimens with remaining dentin thickness (RDT) >2mm were selected. ACAD teeth were created from sound teeth over 7 days in a demineralizing solution. Specimens were embedded into plastic rings with acrylic resin and then sagittal mesial–distal sectioned from crown to the long axis of the root under cooling water using a low-speed diamond blade. The surface of interest was fine polished sequentially. Hardness measurement was performed within an axial depth of 1000μm with at least of 320 indentations on each sample. Mann–Whitney U Test was used to compare the hardness as the variable among different dentin types (SOUND, NCAD and ACAD) at each dentin depth level. ResultsThere was no significant difference in nanohardness between NCAD and ACAD up to a depth of 130μm (p>0.05). NCAD consistently showed lower hardness. ACAD showed no significant difference in hardness with SOUND dentin beyond 190μm (p<0.05). The lesion front in ACAD was considered to be located around the depth of 180μm. ConclusionNatural and artificial caries-affected dentin tissues were superficially comparable in intertubular nanohardness. There is a certain layer within the natural caries-affected dentin with higher hardness; however the long-term effects of caries beneath the lesion extend deeply through intertubular dentin. Sound dentin at deep areas (close to the pulp chamber) is considered to be soft.

Effect on Vibroengineering of Material Deterioration in a Scale-Down Reinforced Concrete Containment Vessel Specimen

This study is aim to evaluate the natural frequency variation of the scale-down reinforced concrete containment vessel specimen under accelerated corrosion conditions. A plastic ring was sealed around the perimeter of the cylindrical vessel bottom with the 3.5 % NaCl solution to achieve the accelerated corrosion test. Concrete resistivity, open circuit potential, corrosion rate and natural frequencies were tested and discussed in this study. Test results presented that the accelerated corrosion method with a direct 60 voltage applied was a suitable method for estimating and accelerating the concrete vessel specimen. Therefore, the changes in natural frequencies were consistent with the material degradation of the concrete vessel specimen. The natural frequencies decreased with the increasing corrosion rate or decreasing resistivities for the specimen at higher mode, but would be no change for the specimen at the natural frequency of 1st mode.

Ion permeability of artificial membranes evaluated by diffusion potential and electrical resistance measurements

In the present article, a novel model of artificial membranes that provides efficient assistance in teaching the origins of diffusion potentials is proposed. These membranes are made of polycarbonate filters fixed to 12-mm plastic rings and then saturated with a mixture of creosol and n-decane. The electrical resistance and potential difference across these membranes can be easily measured using a low-cost volt-ohm meter and home-made Ag/AgCl electrodes. The advantage of the model is the lack of ionic selectivity of the membrane, which can be modified by the introduction of different ionophores to the organic liquid mixture. A membrane treated with the mixture containing valinomycin generates voltages from -53 to -25 mV in the presence of a 10-fold KCl gradient (in to out) and from -79 to -53 mV in the presence of a bi-ionic KCl/NaCl gradient (in to out). This latter bi-ionic gradient potential reverses to a value from +9 to +20 mV when monensin is present in the organic liquid mixture. Thus, the model can be build stepwise, i.e., all factors leading to the development of diffusion potentials can be introduced sequentially, helping students to understand the quantitative relationships of ionic gradients and differential membrane permeability in the generation of cell electrical signals.

Interpreting hydrodynamic behaviour by the model of stirred tanks in series with exchanged zones: preliminary study in lab-scale trickling filters

In trickling filters for wastewater treatment, hydrodynamic behaviour is affected by the growth of biofilm on the porous medium. Therefore, modelling hydrodynamic behaviour is necessary and efficient to predict the biodegradation of pollutants. In this study, laboratory-scale trickling filters were filled with two different porous media (glass beads and plastic rings) and were fed by a synthetic substrate in batch mode. Total organic carbon (TOC) of the effluent was measured and retention time distribution (RTD) was determined by injecting NaCl. Results showed that medium had no significant effect on TOC removal rate (around 80% and 60% respectively for batch time of seven and two days). However, regarding the hydrodynamic behaviour, the effective volume ratio and hydraulic efficiency in the glass beads bed increased remarkably from 28% and 18% to 80% and 70%, respectively, with the reduction of dispersion coefficient (from 4.55 to 1.53). Moreover, the short batch time accelerated this change. Conversely, no variation of hydrodynamic behaviour in plastic rings bed was evident. Along with the feeding of synthetic substrate, biofilm concentration ranged from 1.5 to 10.1 g/L in the glass beads reactor and it achieved around 2.8 g/L in the plastic rings reactor. Hydrodynamic modelling indicated that the model of stirred tanks in series with exchanged zones fitted the experimental results well. These gave values of mobile and immobile volumes of 51 mL and 17 mL, respectively, in the glass beads filter and 25 mL and 15 mL, respectively, in the plastic rings filter.

Calibration of hydrodynamic behavior and biokinetics for TOC removal modeling in biofilm reactors under different hydraulic conditions

In this study, total organic carbon (TOC) biodegradation was simulated by GPS-X software in biofilm reactors with carriers of plastic rings and glass beads under different hydraulic conditions. Hydrodynamic model by retention time distribution and biokinetic measurement by in-situ batch test served as two significant parts of model calibration. Experimental results showed that TOC removal efficiency was stable in both media due to the enough height of column, although the actual hydraulic volume changed during the variation of hydraulic condition. Simulated TOC removal efficiencies were close to experimental ones with low theil inequality coefficient values (below 0.15). Compared with glass beads, more TOC was removed in the filter with plastic rings due to the larger actual hydraulic volume and lower half saturation coefficient in spite of its lower maximum specific growth rate of biofilm, which highlighted the importance of calibrating hydrodynamic behavior and biokinetics.