Empty Tunnels Research Articles

The Application of Mixed Reality in Root Canal Treatment

The priority of modern dentistry is to keep patients’ teeth for as long as possible. Tooth extraction is a procedure performed as a last resort when conservative methods and endodontic surgery procedures have not brought the expected results. As a consequence, the number of patients in dental offices, who require first and repeated endodontic treatment, is increasing. Thus, the development of new technologies in the medical industry, including microscopy, computer tomography (CT), as well as diode and neodymium-YAG-erbium lasers, enables dentists to increase the percentage of successful treatments. Moreover, mixed reality (MR) is a very new technology, in which the 3D view can help plan or simulate various types of tasks before they will be carried out in real life. In dentistry, 3D holography can be applied to display CT data to plan endodontic treatment. The most important element in effective root canal treatment is the precise imaging of the root canal. The CT scans allow dentists to view the anatomy of the patient’s tooth with much higher precision and understanding than using 2D radiography (RTG-radiographic photo) pictures. Recently, the development of new 3D technologies allows dentists to obtain even more data from existing CT scans. In this paper, the CT scan data were applied to generate patient teeth in 3D and simulate the view of the root canal’s anatomy in MR devices, i.e., Microsoft HoloLens 2. Using DICOM RAW data from the CT exam, we generated a 3D model of the jaw with a tooth. In the next step, the crown of the tooth was removed in a similar way to how a dentist would do this using a dental handpiece. Furthermore, all root canals were cleaned of everything inside. This way we achieved empty tunnels, namely root canals. Finally, we added appropriate lighting, similar to the type of lighting that dentists use. The proposed approach enables to display of the root canals in the same way as during the endodontic procedure using a microscope. It allows for the visualization of the root canal and changing its direction, in which dimensional accuracy is crucial. It turns out that mixed reality can be considered a complementary method to the traditional approach, which reduces the amount of time for the root canal treatment procedure by up to 72.25%, depending on the complexity of the case, and increases its effectiveness. Thus, the mixed reality-based system can be considered an effective tool for planning dental treatment.

Seismic Signaling for Detection of Empty Tunnels in the Plateau Zokor, Eospalax baileyi.

There are considerable challenges involved in studying the behavior of subterranean rodents owing to the underground nature of their ecotope. Seismic communication plays a crucial role in the behavior of subterranean rodents, particularly solitary ones. The plateau zokor (Eospalax baileyi), a solitary subterranean rodent species endemic to the Qinghai-Tibet Plateau, will usually occupy empty neighboring tunnels in order to extend their territory. Little is known, however, about the process of territorial occupation or the function of animal communication when occupation is taking place. Based on previous studies of subterranean rodent communication, we hypothesized that plateau zokors use seismic signals to detect neighboring tunnels and then occupy them when it was found their neighbors were absent. To test this, we placed artificial tunnels close to active original zokor tunnels to simulate the availability of an empty neighboring tunnel, and then the seismic signals when a zokor chose to occupy the empty artificial tunnel were recorded. The results showed that the frequency of zokors occupying artificial empty tunnels within 48 h was 7/8, In all of these instances, the zokors generated seismic signals before and after occupation of the empty artificial tunnel. The number of seismic signals generated by the zokors increased significantly (p = 0.024) when they detected and occupied the artificial tunnels, compared to those generated in their original tunnels without the presence of an artificial tunnel alongside. Inside the original tunnels, the inter-pulse time interval of the seismic signals was significantly higher (p < 0.001), the peak frequency of these signals was significantly higher (p < 0.01), and the energy of the signals was significantly lower (p = 0.006), compared with those when an artificial tunnel was positioned next to the original. The results of this study suggest that plateau zokors first generate seismic signals to detect empty neighboring tunnels and that they are empty. In the absence of neighbor plateau zokors, they occupy the empty tunnels to extend their own territory.

The Diversity of Fish in Seagrass Beds and Bare Sand channel In Tablolong Waters, Kupang Regency

Seagrass ecosystems in Tablolong waters have important values related to the availability of fish resources. However, this seagrass meadow experiences a lot of fragmentation in the form of empty sand areas without vegetation (bare sand), both in the form of channels and tidal pools which provide many small living spaces (microhabitats) that are interesting for aquatic ecology studies. The aim of this research was to analyze the diversity and dominance of fish species in the seagrass beds and bare sand channels, as well as to determine the dominant species of seagrasses in the seagrass beds. The study was conducted through direct observation by catching fish specimens using gillnets (# 1.5 inches and #1.25 inches, @ length 20 m x height 1.5 m) and scoop nets three (3) times sampling with time intervals. 7-10 days in the time period of October-November 2021. The results showed that the seagrass beds in the Tablolong Waters are classified as heterospecific from at least 6 (six) seagrass species with an average density of all species reaching 219.2 stands/m2 and an average cover of 40.0% (medium level of cover) where Thalassia hemprichii was the dominant seagrass species in terms of density value (more than 50%of total species) and cover value almost 40% of total species. The fish collection obtained as a whole consisted of 22 fish species from 17 families with 86 individuals where the fish community in the seagrass beds (9 species, 8 families, 17 individuals) was recorded to be lower than the fish community in the empty sand tunnel (13 species, 11 families, 49 individuals), each with a ratio of 41%:59% in species, a ratio of 47%:65% in families and a ratio of 43%:57% in the number of individuals. The status of the fish species that dominates was the occasional visitor fish of 90% (20 species) compared to seasonal visitor fish and whole life resident fish of 5% (1 species). The index value of fish species diversity in seagrass beds was moderate (H’ 2) which was lower than the fish community in empty sand tunnels which was high (H’ 4) and the total number of fish species on Tablolong beach was high (H’ > 4). The fish species dominance index value showed that in both fish in seagrass beds (D 0.28), in empty sandtunnels (D 0.11), and the whole area (D 0.25) in Tablolong waters there were no dominant fish species. So that the structure of the fish community tends to be stable or the diversity of fish species tends to be high.

Tunnel-structured willemite Zn2SiO4: Electronic structure, elastic, and thermal properties

Willemite Zn2SiO4 crystallizes in such a way that Zn and Si are tetrahedrally coordinated with O in an ionic-covalent manner to form ZnO4 and SiO4 tetrahedra as the building units. The tetrahedra are corner-sharing, of which one SiO4 tetrahedron connects eight ZnO4 tetrahedra, and one ZnO4 tetrahedron links four ZnO4 tetrahedra and four SiO4 tetrahedra. The unique crystallographic configuration gives rise to parallel tunnels with a diameter of 5.7 Å along the c-axis direction. The tunnel structure of Zn2SiO4 definitely correlates with its interesting elastic and thermal properties. On the one hand, the elastic modulus, coefficient of thermal expansion (CTE), and thermal conductivity are low. Zn2SiO4 has low Vickers hardness of 6.6 GPa at 10 N and low thermal conductivity of 2.34 W/(m·K) at 1073 K. On the other hand, the elastic modulus and CTE along the c-axis are significantly larger than those along the a- and b-axes, showing obvious elastic and thermal expansion anisotropy. Specifically, the Young’s modulus along the z direction (Ez = 179 GPa) is almost twice those in the x and y directions (Ex = Ey = 93 GPa). The high thermal expansion anisotropy is ascribed to the empty tunnels along the c-axis, which are capable of more accommodating the thermal expansion along the a- and b-axes. The striking properties of Zn2SiO4 in elastic modulus, hardness, CTE, and thermal conductivity make it much useful in various fields of ceramics, such as low thermal expansion, thermal insulation, and machining tools.

Enhancing the spectral tunability of localized surface plasmon resonance and small polaron transfer in Li-doped CsxWO3 nanocrystals for energy-efficient windows

CsxWO3 nanocrystals which exhibit localized surface plasmon resonance (LSPR) and small polaron transfer in wavelength of the near-infrared radiation have attracted great attention to fabricate the spectrally selective coating. Enhancing the LSPR and small polaron transfer of CsxWO3 nanocrystals is effectively achieved by introducing aliovalent dopant into its empty trigonal tunnels of the crystal lattice, but the lack of controllable synthesis process reserves some essential issues unanswered with respect to the effects of the dopant concentration on absorption coefficient, free carrier density and carrier mobility. Herein, Li-doped CsxWO3 nanocrystals were successfully prepared with the highest reported absorption coefficient, which demonstrated stronger absorption performance than the CsxWO3 nanocrystals without Li doping. The introduction of lithium into the crystal structure as a cation dopant can enhance the free carrier density of the nanocrystals, which leads to a higher absorption coefficient. The absorption coefficient variation of LSPR and small polaron transfer of Li-doped CsxWO3 nanocrystals was explained by the free carrier density and carrier mobility. This doping strategy allows CsxWO3 nanocrystals to become spectrally tunable within the wavelength of near-infrared radiation. When the Li/W molar ratio was 0.4, the free carrier density reached 10.22 × 1014 cm−3. The spectrally selective coating prepared by Li-doped CsxWO3 nanocrystals displayed excellent spectral selectivity with TVis, TNIR, Tlum, and Tsol of 68.79 %, 9.17 %, 72.61 % and 47.95 %, respectively. This doping strategy provides a promising potential to improve the spectral tunability of CsxWO3 nanocrystals for the practical application of energy-saving windows.

Preparation, thermal stability and crystal structure of Li3UF7: New insights into LiF-UF4 binary phase diagram

In this manuscript the crystal structure of Li3UF7 from powder X-ray and neutron diffraction studies is reported. The existence of Li3UF7 has been debated for a long time, as it is often missed in a number of phase diagram studies. This study adopted a judicious composition of LiF and UF4, and an optimum cooling rate to prepare Li3UF7. The Li3UF7 phase could be obtained by cooling the molten LiF-UF4 with large excess of LiF at a rate of 5 K/min while slower cooling tends to form LiUF5. The crystal structures of Li3UF7 and LiUF5 in the temperature range of 300–10 K have been obtained from the powder neutron diffraction studies. At 300 K, Li3UF7 has an orthorhombic lattice with unit cell parameters: a = 8.698(2) Å, b = 8.692(2) Å, c = 12.803(1) Å, V = 968.0(4) Å3; Z = 8 (Space group: Ccca), and is isostructural to orthorhombic Li3ThF7. On cooling, the orthorhombic distortion of Li3UF7 increases but does not reveal any structural transition down to 10 K. The crystal structure of Li3UF7 is built from the defective (Li-deficient) layers of edge shared octahedral LiF6 and layers corner connected UF9 polyhedra. Analogous studies on LiUF5 have also been carried out, which has a tetragonal (Space Group: I41/a) lattice with unit cell parameters: a = 14.8882(8) Å, c = 6.5438(7) Å, V = 1450.5(2) Å3; Z = 16. The structure of LiUF5 is built from the three-dimensional sub-lattice formed by U4F30 units and the empty tunnels of the sublattice are occupied by Li4F16 clusters formed by four edge shared LiF6 octahedra. Also, the details of crystal chemistry of the compounds in LiF-UF4 systems and their thermal stabilities are discussed. The complexity in the crystal chemistry in LiF-UF4 system is manifested in multiple close by thermal events in the DTA runs which has also been discussed in the manuscript.

Influence of elevated temperature on the microstructure and mechanical performance of cement composites reinforced with recycled carbon fibers

This study comprises the investigation on the effects of elevated temperatures (up to 900 °C) on the reinforcement mechanism of recycled carbon fiber (rCF) based cement composites. A detail investigation was conducted to study the interaction of rCF with hydration products at different temperatures (25 °C, 200 °C, 400 °C, 600 °C, 800 °C and 900 °C) by using x-ray diffraction (XRD), differential thermogravimetric (DTG) analysis and scanning electron microscopic techniques. Furthermore, mechanical properties, including compressive strength (ƒ'c), splitting tensile strength (ƒ's), and flexural strength (ƒ'F), were experimentally studied as a function of rCF dosage and elevated temperature. Results revealed that the reinforcing effect of rCFs was promising up to 600 °C due to the release of high-pressure steam through channels on the surface of rCFs. At 900 °C, rCFs were fully decomposed and resulted in empty tunnels which subsequently effected the performance of cement composites. A sharp decrease in the compressive and splitting tensile strength was observed at 800 °C while the flexural strength was significantly reduced at 600 °C. In the end, the relation of rCF dosage and elevated temperature with residual mechanical properties of cement composites was discussed through multivariate statistical models.

Synergistic effects of hybrid polypropylene and steel fibers on explosive spalling prevention of ultra-high performance concrete at elevated temperature

This study investigated synergetic effects of hybrid polypropylene (PP) and steel fibers on explosive spalling prevention of ultra-high performance concrete (UHPC) at elevated temperature. Permeability of UHPC was measured and correlated to the extent of spalling quantitatively. Microstructures of UHPC before and after elevated temperature exposure were examined to reveal potential mechanisms responsible for changes in permeability. Results showed that the use of hybrid PP and steel fibers completely prevented explosive spalling even at low fiber dosage of both fibers due to significant increase of permeability. Microstructural analysis revealed that such synergistic effect on increased permeability of hybrid PP and steel fiber-reinforced UHPC was attributed to enhanced connectivity of empty PP fiber tunnels by multiple microcracks generated from the thermal expansion of both fibers.

Temperature dependent structural, vibrational and magnetic properties of K3Gd5(PO4)6.

Herein we report the evolution of the crystal structure of K3Gd5(PO4)6 in the temperature range from 20 K to 1073 K, as observed from variable temperature X-ray diffraction and Raman spectroscopic studies. K3Gd5(PO4)6 has an open tunnel containing a three dimensional structure built by [Gd5(PO4)6]3- ions which in turn are formed of PO4 tetrahedra and GdOn (n = 8 and 9) polyhedra. The empty tunnels in the structure are occupied by K+ ions and maintain charge neutrality in the lattice. Evolution of unit cell parameters with temperature shows a systematic increase with temperature. The average axial thermal expansion coefficients between 20 K and 1073 K are: αa = 10.6 × 10-6 K-1, αb = 5.5 × 10-6 K-1 and αc = 16.4 × 10-6 K-1. The evolution of distortion indices of the various coordination polyhedra with temperature indicates a gradual decrease with increasing temperature, while those of Gd2O9 and K2O8 polyhedra show opposite trends. The overall anisotropy of the lattice thermal expansion is found to be controlled largely by the effect of temperature on GdOn polyhedra and their linkages. Temperature dependent Raman spectroscopic studies indicated that the intensities and wavenumbers of most of the Raman modes decrease continuously with increasing temperature. Anharmonic analyses of Raman modes indicated that the lattice, rigid translation and librational modes have larger contributions towards thermal expansion of K3Gd5(PO4)6 compared to high frequency internal modes. The temperature and field dependent magnetic measurements indicated no long range ordering down to 2 K and the observed effective magnetic moment per Gd3+ ion and the Weiss constant are 7.91 μB and 0.38 K, respectively.

Nonstoichiometric control of tunnel-filling order, thermal expansion, and dielectric relaxation in tetragonal tungsten Bronzes Ba0.5-xTaO3-x.

Ordering of interpolated Ba(2+) chains and alternate Ta-O rows (TaO)(3+) in the pentagonal tunnels of tetragonal tungsten bronzes (TTB) is controlled by the nonstoichiometry in the highly nonstoichiometric Ba0.5-xTaO3-x system. In Ba0.22TaO2.72, the filling of Ba(2+) and (TaO)(3+) groups is partially ordered along the ab-plane of the simple TTB structure, resulting in a √2-type TTB superstructure (Pbmm), while in Ba0.175TaO2.675, the pentagonal tunnel filling is completely ordered along the b-axis of the simple TTB structure, leading to a triple TTB superstructure (P21212). Both superstructures show completely empty square tunnels favoring Ba(2+) conduction and feature unusual accommodation of Ta(5+) cations in the small triangular tunnels. In contrast with stoichiometric Ba6GaTa9O30, which shows linear thermal expansion of the cell parameters and monotonic decrease of permittivity with temperature within 100-800 K, these TTB superstructures and slightly nonstoichiometric simple TTB Ba0.4TaO2.9 display abnormally broad and frequency-dependent extrinsic dielectric relaxations in 10(3)-10(5) Hz above room temperature, a linear deviation of the c-axis thermal expansion around 600 K, and high dielectric permittivity ∼60-95 at 1 MHz at room temperature.

Electrochemical Li/Na Intercalation in TiOSO4, First Member of the Phosphate Tungsten Bronze-Type Family

The oxysulfate TiOSO4 has been prepared by an easy soft chemistry method based on the dissolution of metallic titanium in sulfuric acid at 170°C. First member of the phosphate tungsten-type bronze family, this oxysulfate, whose structure offers empty pentagonal tunnels, is shown to intercalate up to 0.9 Li per formula unit (f.u) and 0.8 Na/f.u. at an average voltage of 2.45 V vs Li+/Li and 2.12 V vs Na+/Na, respectively. The intercalation/deintercalation process is reversible according to a solid solution mechanism. Its comparison with the titanium Nasicon shows that it exhibits a similar redox voltage, but a significantly larger reversible capacity of 120 mAh/g vs Li+/Li and 100 mAh/g vs Na+/Na after 20 cycles. The open structure of this material, its low cost, and its easy synthesis, pave the way to the investigation of other transition metal oxysulfates for the realization of electrodes for rechargeable sodium ion batteries.

A Mode-Based Approach for Channel Modeling in Underground Tunnels under the Impact of Vehicular Traffic Flow

In underground tunnels with vehicular traffic flow, wireless communications experience severe fading problems due to the signal reflections and diffractions on the tunnel walls and the mobile vehicles. Currently, most of the existing tunnel channel models can only characterize the signal propagation in empty tunnels. Existing investigations on the influence of the vehicles are all limited to experimental or numerical results. This paper provides a theoretical analysis of the wireless channel in tunnels with vehicular traffic flow. First, the effects of a single vehicle on the signal propagation in a tunnel are investigated. The analytical expressions of the in-mode loss and the mode coupling coefficients are provided using the uniform theory of diffraction (UTD), Poisson summation formula, and the saddle point method. Then the channel model in a tunnel with either deterministic or random vehicular traffic flow is provided according to the analysis on a single vehicle's effect. The predicted received power given by our theoretical model has a good match with the numerical simulation results. Our channel model shows that the signal propagation in tunnels with vehicular traffic flow is influenced by multiple factors, including the number, the size and position of the vehicles, the size and the curvature of the tunnel, the vehicular traffic load, and the vehicle velocity.

Chemistry Education: Lighting a Fire

Dark tunnels deep below the forest floor. Explosions. Heavy trucks. Great boulders, no longer buried in the hidden sediments of time, rolling helplessly against the merciless metal balls that crush them to the same size. Small brownish beads swiftly carried along endless rubber belts, to be inspected and judged. Computerized probes seeking only those beads that glow under the intense glare of their lights. Two streams now – one narrow, for the beads that glow, the other wide, for those that do not. The beads in the narrow stream journey forward, the rest are dropped back into the empty tunnels whence they came, the few hours of golden sunlight soon forgotten in the endless dark. My imagination was running overtime when, about 20 years ago, an enthusiastic young physicist described the process used by Argyl Diamonds to separate diamonds from waste rock. The driving force behind the development of this machinery was, of course, economics. However, as he talked excitedly about the science behind the process, the educator in me could only think of the story behind all those diamonds. Formed within the warm embrace of clay over millions of years, the diamonds that were detected under those bright lights now only knew the touch of cold grey machinery, as they were formed into cutting edges for other machines, and even scalpels. My mind then turned to the larger diamonds, now crushed to the same size as all the others. Yet had they been discovered earlier, each would have known the loving caress of a craftsman – one who could look with wonder at the inner strength already bestowed by Nature, then design a way to reveal its sparkle and fire. And then there were the smaller diamonds, hidden under a skin of clay, unable to glow and so undetected and cast out as worthless. ‘They’re not worth worrying about’ he shrugged, when asked – an attitude no doubt shaped by the ‘bean-counters’ who employed him. Not worth it? The chemist in me could only visualize that beautiful diamond structure and the long story behind its creation, a story that began in some ancient giant star, and shudder at the loss. Then my thoughts went to the clay itself. Is it really worthless? Is it not clay that sustains our life, holding within it the moisture andminerals our plants need to grow?And is it not clay that for thousands of years has been shaped and moulded to create objects from simple pots to great works of art? Clay even has held the records our ancient history – the thoughts and stories and beliefs of our forbears. This was one of those pivotal moments for me as a Chemistry teacher. To me, the diamond-sorting machinery was a powerful metaphor for the machinery that operates in our society – the machinery by which we sort and judge people, both in our social interactions and in our education system. All too often we readily judge and label others – by their gender, age, race, appearance, abilities and disabilities, personality, degree of formal education, the kind of job they do, how ‘successful’ they are, and their interests, values, and beliefs. And no doubt over our lifetimeswe all have been on the receiving end of this kind of judgement, ormisjudgement. This can have a very powerful influence on the direction our life takes. I think now of Ernest Rutherford, that eminent physicist who pronounced: ‘All Science is either Physics or stampcollecting!’ How many brilliant young minds were turned off Chemistry by an attitude like that? Ironically he only ever won the Nobel Prize for Chemistry, not for Physics. How he must have hated that! I think too of the standout moment that decided the direction I would take in my academic studies. This was the moment my Year 10 history teacher asked me which course of study I would take in Year 11. My favourite subjects were history and maths, but at that time we could only choose between Science, Humanities, or Commerce. So I said I was thinking of doing Science. ‘Girls don’t do Science!’ he roared. My respect for my hitherto outstanding teacher was shattered in one blow. To his great disappointment, all that he achieved was to make me determined to prove him wrong. And so I was the first girl in the school to study Science. Mind you, several boys in my class at school clearly shared his view and gave me a hard time, not that I ever let my anger at their injustice show. Instead I became all themore determined to show them girls could ‘do Science’, and do it better than them!

Estimation of the penetration angle of a man-made tunnel using time of arrival measured by short-pulse cross-borehole radar

The relatively fast propagation of electromagnetic signals through empty man-made tunnels has played a key role in detecting deep underground tunnels using a short-pulse cross-borehole radar system. Our cross-borehole radar system measured the pulse signatures of an obliquely penetrating tunnel using eight different borehole pairs at a test site in Korea. Compared to the arrival times of the first peaks, the arrival times of the first received signals at an appropriate amplitude level provided an increasingly clear indication of the empty tunnel as its penetration angle became more oblique. A quadratic relationship between the arrival time of the first received signal and the oblique angle of the empty tunnel was obtained in pure granite.

Dimensionality and morphology of particle and bubble clusters in turbulent flow

We conduct numerical experiments to investigate the spatial clustering of particles and bubbles in simulations of homogeneous and isotropic turbulence. On varying the Stokes parameter and the densities, striking differences in the clustering of the particles can be observed. To quantify these visual findings we use the Kaplan–Yorke dimension. This local scaling analysis shows a dimension of approximately 1.4 for the light bubble distribution, whereas the distribution of very heavy particles shows a dimension of approximately 2.6. However, clearly different parameter combinations yield the same dimensions. To overcome this degeneracy and to further develop the understanding of clustering, we perform a morphological (geometrical and topological) analysis of the particle distribution. For such an analysis, Minkowski functionals have been successfully employed in cosmology, in order to quantify the global geometry and topology of the large-scale distribution of galaxies. In the context of dispersed multiphase flow, these Minkowski functionals – being morphological order parameters – allow us to discern the filamentary structure of the light particle distribution from the wall-like distribution of heavy particles around empty interconnected tunnels. Movies are available with the online version of the paper.

The Risk of Growth Changes During Transphyseal Drilling in Sheep With Open Physes

A sheep model was used to evaluate the risk of growth disturbances of transphyseal drilling and anterior cruciate ligament (ACL) reconstruction. In group A, comprised of six 4-month-old Merino sheep, the ACL was resected and 5-mm tunnels were drilled and left empty. Unilateral ACL reconstruction using an autologous Achilles tendon graft, extracortical fixation, and tunnel diameters of 5 mm was performed in group B. A single-stranded graft with a diameter of 5 mm was used in group B-1 (N = 6) and a 3-mm double-stranded graft in group B-2 (N = 6). Six months after the procedure, the animals were euthanized. Growth changes were evaluated macroscopically, by magnetic resonance imaging, and by histology. Central growth plate lesions on the tibia did not induce growth abnormalities. On the peripheral femur, posterolateral growth plate injuries with empty tunnels led to a shortening of the lateral femur of 8 mm (7 to 10 mm), a valgus deformity of 12.8 degrees (12 degrees to 14 degrees ), and a flexion deformity of 8.6 degrees (5 degrees to 15 degrees ). Histology revealed a strong bone bridge over the physis and an injury to the perichondral structures. Transphyseal ACL replacements did not cause growth disturbances on either the tibia or the femur, even if a drilling injury of the perichondral structures occurred. Despite consistent physeal damage, ACL reconstructions did not lead to clinically relevant growth disturbances. The results suggest that transphyseal ACL reconstruction procedures might yield similar results in children with substantial growth remaining.

Experimental results of donor site filling for autologous osteochondral mosaicplasty

Purpose: Autologous osteochondral mosaicplasty has become a treatment option for focal chondral and osteochondral defects in recent years. Excessive postoperative bleeding from the donor site was reported as a possible complication of the procedure. The purpose of this study was to investigate different biodegradable materials for donor site filling, which could prevent excessive postoperative bleeding from these sites but would allow reasonable blood clot formation on the articular surfaces of donor tunnels. Type of Study: Basic science evaluation. Methods: In an experimental model, “donor site plugs” made from hydroxylapatite, carbon fiber, polyglyconate-B, compressed collagen, and 2 versions of polycaprolactones were used to fill the bony tunnels created by harvesting. These materials were tested in 100 knees of 50 German Shepherd dogs to determine the quality of the repair tissue formation on the surfaces of the harvesting holes filled by these materials. Arthroscopies of the dogs were performed at several intervals, from 4 weeks to 26 weeks, and macroscopic studies were performed on euthanized animals between 8 weeks and 30 weeks to evaluate donor site filling and coverage. Empty donor tunnels served as controls for the evaluation of the different filling materials. Results: All tested materials effectively decreased postoperative bleeding. Hydroxylapatite, carbon rods, polyglyconate-B, and melted polycaprolactone materials showed a good integration to the surrounding cancellous bone, but these fillings showed only a limited repair tissue formation, even at 30 weeks postoperatively. Second-look arthroscopy and histologic evaluation of necropsies showed the best fibrocartilage coverage after filling by compressed collagen. Technical details of the filling also had certain importance in the quality of the repair tissue formation. Conclusions: According to histologic results, compressed collagen appears to be a good material to fill donor tunnels of osteochondral graft harvest. This material is substituted gradually by bone formation and its articular surface can serve as an appropriate scaffold for fibrocartilage coverage created by the natural intrinsic repair process.

Polychalcogenophosphate Flux Synthesis of 1D‐KInP2Se6 and 1D and 3D‐NaCrP2S6.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Polychalcogenophosphate flux synthesis of 1D-KInP2Se6 and 1D and 3D-NaCrP2S6

Three new chalcogenophosphates, 1D-KInP2Se6 (I), 1D-NaCrP2S6 (II) and 3D-NaCrP2S6 (III), have been synthesized and their structure determined from single crystal diffraction analysis. (I) and (II) crystallize in the monoclinic system (space group P21/n, No. 14) with cell parameters a=7.5112(11), b=6.4861(5), c=22.789(2) Å and β=98.912(16)° (V=1096.9(2) Å3), Z=4 and R/Rw(F2)=0.0234/0.0387 (for 900 observed reflections and 92 refined parameters) for (I) and a=7.0279(5), b=5.8797(2), c=21.2578(14) Å and β=92.110(3)° (V=877.82(9) Å3), Z=4 and R/Rw(F2)=0.0572/0.1151 (for 1455 observed reflections and 92 refined parameters) for (II). Both materials exhibit 1/∞[MP2Q6]− chains built upon [MQ6] octahedra (M=In, Cr; Q=Se, S) sharing edges to define 1/∞[MQ4]5− zigzag fibers which are capped by tetradentate ethane-like [P2Q6] groups. (III) crystallizes in the orthorhombic system (space group Fdd2, No. 43) with cell parameters a=10.9742(7), b=7.9828(6), c=20.8590(19) Å (V=1827.3(4) Å3), Z=8 and R/Rw=0.0184/0.0378 (for 967 observed reflections and 47 refined parameters), and displays a three-dimensional framework arrangement. Its structure is similar to that of TiP2S6 where titanium atoms are substituted for the chromium, the sodium atoms being inserted in the empty tunnels to ensure the charge balance. The exfoliation properties of 1D-NaCrP2S6 in polar solvents are reported.

Stabilization of a W(V) Diphosphate, W2O3·P2O7, with an Empty Tunnel Structure

A new form of WPO5 has been synthesized which is to our knowledge the second pentavalent tungsten phosphate actually known. This phase is isotypic to CsP8W8O40 and consequently can be described as a tungsten diphosphate, W2O3·P2O7, with large empty eight-sided tunnels. Although it fundamentally differs from the first form, which is a monophosphate, WOPO4, the two structures are closely related by the existence of ReO3-type chains and slices, interconnected by P2O7 or PO4 groups, respectively. The stabilization of such an opened structure by adducts such as PbF2 or KBr is discussed.