Secondary Shrinkage Research Articles

Peculiarities of endoscopic treatment of vesicoureteral reflux in children

Background. Vesicoureteral reflux is a disease of the bladder-ureter joint, caused by a violation of the closing mechanism of the lower part of the urinary tract, as a result of which a certain amount of urine transported through the ureter into the bladder, under the influence of intravesical pressure, constantly or periodically returns (regurgitation) to the upper urinary tract in the direction of the kidney. According to the literature, vesicoureteral reflux affects approximately 1% of all children, according to various sources. Purpose – is to highlight the importance of the pathology of vesicoureteral reflux using data from the literature and own observations. Materials and Methods. 31 patients who were diagnosed with VUR were included in the study. Previously, these children were examined in the conditions of somatic departments of Vinnitsia Regional Pediatric Clinical Hospital. Patients underwent endoscopic correction of VUR using gels (Nubiplant, Vantrix, Deflux, Dexell) according to the STING method. Results. An analysis of the medical records of 31 inpatients who were treated in the surgical department of the Vinnytsia Regional Pediatric Clinical Hospital from 2019 to 2023 was conducted. During the stay in the hospital, the patient underwent a diagnostic examination (taking an anamnesis, general blood and urine tests, determining the level of urea and creatinine; ultrasound of the kidneys, micturition cystoureterography, if necessary – excretory urography, echocardiography). Endoscopic treatment was performed – endovesical injection of a volume-forming gel into the submucosal part of the refluxing ureter (above the ureter, into the bladder wall) – the STING (Subureteric Teflon Injection) variant. Conclusions. VUR is a fairly common pathology among children, which has a multifactorial nature. The variety of manifestations, the high prevalence of this pathology and the severity of complications require early diagnosis and determination of treatment tactics. Regarding the gender distribution of the pathology, it should be noted that girls are sick more often than boys. Unilateral and bilateral VUR occurs with the same frequency, while reflux of the II–III stages occurs most often. The maximum morbidity was observed at the age of 6 to 9 years, and from 0 to 3 years. In 35–60% of cases, reflux causes sclerotic changes in the kidney, secondary shrinkage of the kidney. According to the literature, nephrosclerosis due to chronic pyelonephritis in VUR is formed in 30–60% of cases, which leads to the development of the terminal stage of chronic renal failure in 25–60% of patients, due to a decrease in the functional renal reserve, as an indicator of the compensatory capabilities of the kidneys. Most research suggests that endoscopic and surgical intervention are the best treatment methods for VUR with frequent manifestations of infection.

2D CFD modeling for pyrolysis of a large biomass particle: Effect of L/D ratio, internal convection and shrinkage

A transient 2D kinetic-heat transfer model for the pyrolysis of a large biomass particle, incorporating, primary and secondary reaction kinetics, internal convection and shrinkage in particles was developed and validated with experimental results. The RMS errors between the predicted and experimental temperature and residual mass fraction were estimated to be small - 0.020, 0.017, 0.011, 0.018 and 0.024, 0.022, 0.016, 0.025 at reactor temperatures of 573, 623, 673, 723 K, respectively. The pyrolysis behaviour was explained by the computed spatial distributions of velocity, pressure, temperature and residual mass fraction within the biomass particle. At a high L/D (∼5), two symmetric hot spots were formed near the two axial flat edges after 400 s, which formed a single dumbbell-shaped in the axial central core after 600 s and existed for a long time of 1500 s. It merged into a single spherical hot spot at the centre after a long reaction time. For a low L/D (∼1), however, an elliptical-shaped hot spot formed after 400 s changes to a spherical hot spot at the particle centre after 500 s. Uniformity in temperature inside the particle was attained much earlier at a smaller L/D ratio.

A comprehensive pyrolysis model for lignocellulosic biomass particles with a special emphasis on the anisotropic characteristics

The porous and fibrous structural tissue of lignocellulosic biomass serves as a transport channel for water and nutrients along the growth direction, indicating a highly anisotropic nature of biomass. The anisotropies of the thermal and structural properties of biomass have substantial influences on particle-scale reactions, transport processes, and morphological evolution during thermal conversions. An in-depth investigation of the anisotropic characteristics of these physicochemical phenomena in pyrolysis benefits in the understanding of biomass gasification and combustion processes. In this study, a comprehensive 2D axisymmetric mathematical model is developed to quantitatively analyze the pyrolysis behaviors of a cylindrical wood particle with or without anisotropy. Correlative unsteady energy and mass conservation equations are combined with a multistep kinetic model of biomass devolatilization. To improve the numerical descriptions of volatiles flowing in a porous biomass matrix, the constitutive equations of the Brinkman equation and dusty gas model are adopted. Moreover, a binary differential equation is used to calculate the simultaneous changes in the pore structure and shrinkage of the wood particles. When considering anisotropy, validations of the model against literature data demonstrate that it can reliably predict the intraparticle temperature profiles, weight loss, and particle shrinking degree of lignocellulosic biomass. Using this model, the coupling effects of multi-physical fields and reactions inside pyrolyzing wood particles are explored. It is revealed that the anisotropic characteristics of biomass influence not only the orientations of intraparticle heat and mass transport processes but also their mechanisms, resulting in varying degrees of secondary reactions and particle shrinkage.

Cyclic swell shrink behaviour of lime and lignosulphonate amended expansive soil—An experimental quantification and comparison

The behaviour of expansive soils is majorly influenced by the mineralogy and the environmental conditions contributed by the seasonal moisture changes. Many structures found on the expansive soil depict severe distress due to the volume change behaviour of the soil. The volume changes correspond to moisture fluctuations which occur with the wetting–drying cycles associated with climatic variations. The wetting–drying​ cycles also impact the chemical treatment methods adopted to curtail swelling and shrinkage. The present study evaluates and compares the magnitude of swelling and shrinkage depicted by Lime and Lignosulphonate amended soils under wetting and drying cycles imposed under laboratory conditions. A specially modified oedometer apparatus was adopted to simulate the field drying conditions. The untreated soil exhibits higher swelling strain than the shrinkage strains with cycles of wetting and drying. There is a decrease of nearly 9% in swelling and 5% in shrinkage from the first cycle to steady state cycle. The swelling strain followed a decline to the steady state, however lime and LS amended soil depicted an initial decrease and then an increase in swelling strains before steady state. The treated and untreated soils also attain equilibrium characterized by different bandwidths and also exhibit difference in swelling and shrinkage rates, with untreated soil exhibiting a longer time to complete the swell-shrink cycles. The study further quantifies these variations for treated and untreated soil and the respective rates of primary and secondary swelling and shrinkage. The results are also justified with a physicochemical analysis of the leachate collected during the wetting–drying cycles.

Study of fluid system for pressure reduction and injection of long-term injection wells in sensitive reservoirs

Due to the sensitivity of the reservoir itself and the aggravation of reservoir damage caused by long-term water injection in a sensitive reservoir of a block in northwest China, the phenomenon of high wellhead pressure and water injection difficulty of new injection Wells is presented in different degrees. Based on the analysis of the effect of increasing injection measures in each stage, combined with the analysis of the cause of reservoir scaling and the sensitivity of long-term water injection volume flow, a new composite treatment liquid system was developed. The system integrates the secondary precipitation inhibition technology, anti-expansion and shrinkage composite technology, deep acidification technology and foam composite acidification technology, and achieves the dissolution rate of the main treatment solution of 22.5%, can maintain a low pH for a long time, and meet the long-term scale inhibition rate of 84.89%. In the evaluation of the core flow experiment, the core permeability recovered and increased after the treatment of the working fluid system, and achieved a good effect of plugging removal and injection increase in the field practical application.

Dimensional stability of cement paste and concrete subject to early-age carbonation curing

Early-age carbonation curing of concrete is receiving more interest in terms of performance improvement and emission reduction. However, the volume change of cement-based products subject to carbonation curing may become a concern because of the potential carbonation shrinkage and its related shrinkage cracking. The purpose of this study was to investigate the dimensional stability of cement paste and concrete subject to the early-age carbonation curing. It was found that the carbonation curing introduced first an initial shrinkage due to water evaporation upon gas injection and then generated an expansion due to CO2 uptake and carbonate precipitation. As carbonation proceeded, the deformation was switched to a secondary shrinkage after expansion. The residual deformation due to carbonation curing was shrinkage in cement paste samples and expansion in concrete samples. This was because the relative expansion due to carbonate precipitation in paste was not large enough to compensate for the shrinkage caused by water loss. However, for concrete samples, the introduction of aggregates reduced the pore spaces in concrete, leading to an expansion owing to the limited precipitation. The results of carbon dioxide uptake, XRD, and SEM analysis confirmed that calcium carbonate formation played a critical role in the relative expansion. The study also showed that cement-based products were more resistant to weathering carbonation after the early-age carbonation curing. After 61-day weathering carbonation exposure, both paste and concrete samples exhibited carbonation shrinkage as a result of carbonation of hydration products. However, the magnitude of shrinkage was much smaller in carbonation curing than in weathering carbonation because of the short period of exposure. Both carbonations did not significantly affect the compressive strength of carbonated products. Carbonation curing likely makes concrete products more dimensionally stable in the long-term service.

Evaporation and shrinkage processes of compacted bentonite-sand mixtures

The deterioration of compacted bentonite-sand mixtures (CBSMs) after suffering desiccation increases the hydraulic conductivity of clay barriers, posing risks to the environment. This work compressed bentonite-sand mixtures (BSMs) to various dry densities in order to conduct the free-drying tests, focusing on the evaporation and shrinkage processes. The compaction constrained the permeability of the mixtures and resulted in the delay in evaporation and shrinkage of the CBSMs’ internal parts (compared to their external parts). Subsequently, the secondary shrinkage occurred (i.e., the smaller volumetric shrinkage after the shrinkage limit reached). Compaction constrained the plate-like smectite particles in being propped up and led them to orientate. This structure reinforced the CBSMs’ shrinkage property and contributed to their lower air entry value, shrinkage limit, and final void ratio. During the design and maintenance of compacted clay barriers, secondary shrinkage and the reinforced shrinkage property are proposed to be taken into consideration.

Re-examination of steel frame office buildings in preventing collapse when subject to intense fires

The purpose of the paper is to investigate the extent to which present-day design of steel framed buildings is susceptible to total collapse when subjected to extreme fire events. We select a 50 storey structure in which 2 and 4 adjacent storeys located at different above-ground heights are, in separate scenarios engulfed in raging fires. A total of 8 scenarios are analyzed, employing Newtonian mechanics and realistic energy dissipating properties of H-shaped columns and normal concrete floor slabs possessing secondary (shrinkage and temperature) reinforcement alone. While the present Canadian building code is the basis for our column designs, other standards provide very similar specifications. Although fire proofing is required in virtually all high rise building construction, we are excluding such materials in order to simplify the analyses, but clearly do not advocate its omission – quite the opposite in fact. As well, attributes such as floor beams, partitions and furnishings of every description, all of which would in practice participate in absorbing the kinetic energy of a crush-down upper block are excluded. Despite such a vast array of conservative assumptions, it is shown that partial collapse may occur during crush-down, however, in no case will total collapse be the consequence. These results should provide some comfort to code writers that their requirements should indeed prevent the most catastrophic of failures due to fires.

Features of Structure and Solidification of Extended Double Ingots for Hollow Forgings. Part 1

Results are provided for a study of features of the structure of extended double hot-topped ingots. In the upper half of a test ingot, there is significant development of defects of shrinkage origin (closed secondary shrinkage cavities and zone of axial porosity), and they are significantly developed over the height and insignificantly over the diameter. Defects of shrinkage origin are concentrated within the upper half of an ingot body. It is established that within a double ingot nonmetallic inclusion distribution and cast structure parameters differ from the distribution for an ingot of normal geometry. Comparison of mathematical modeling data with results of studying ingot structure shows that a higher temperature in a narrow axial part of an actual ingot slows down solidification. This leads to an increase in dendrite parameter, a reduction in dendrite structure density, an increase in porosity, the amount of readily melting sulfide and complex oxysulfide nonmetallic inclusions, and also formation of a closed secondary shrinkage cavities. This position of defects of shrinkage and liquation origin facilitates their removal during ingot forging, and provides the possibility of obtaining hollow forgings from them. In test ingot forgings, there is a fourfold reduction in their chemical inhomogeneity and an increase in mechanical property stability over an object’s length. Use of extended double ingots for preparing hollow billets makes it possible to increase output of finished metal in a forging by 8%.

Quo Vadis Breast Tissue Engineering?

Quo Vadis Breast Tissue Engineering?

Energy absorption potential of concrete floors containing secondary (shrinkage and temperature) reinforcements

This paper experimentally investigates the energy absorption potential of two types of concrete floors, namely, normal density concrete and structural low-density concrete, containing secondary (shrinkage and temperature) reinforcements. The test program considered the following secondary reinforcements: 1) traditional welded-wire steel mesh, 2) steel fiber and 3) poly composite fiber. To estimate the extent to which crushing of floor slab materials would help absorb energy, a series of concrete penetration tests employing patch loading was undertaken on scaled down model slabs. Each concrete-secondary reinforcement combination considered slabs of 50 mm in depth with square plan dimensions ranging from 50 to 500 mm, resulting in a total of 30 test specimens. The first part of the paper discusses the test specimens, the test setup, and the test procedure. The second part of the paper presents the experimental results and establishes the energy absorption of different concrete-secondary reinforcement combinations. Sieve analysis results of the crushed specimens were used to derive a “work index” value that relates the pulverized particle size distributions to energy inputs. The work index values of concrete-secondary reinforcement systems can be used to assess the energy dissipation potential associated with such floor slabs in buildings undergoing progressive collapse. The results indicate that floors with secondary reinforcements could play an important role in helping arrest global progressive collapse.

Mouse intracerebral hemorrhage models produce different degrees of initial and delayed damage, axonal sprouting, and recovery.

The mechanisms of delayed damage and recovery after intracerebral hemorrhage (ICH) remain poorly defined. Two rodent models of ICH are commonly used: injection of the enzyme collagenase (cICH) and injection of autologous blood (bICH). In mice, we compared the effects of these two models on initial and delayed tissue damage, motor system connections, and behavioral recovery. There is no difference in lesion size between models. Injection of autologous blood causes greater mass effect and early mortality. However, cICH produces greater edema, inflammation, and cell death. Injection of the enzyme collagenase causes greater loss of cortical connections and secondary shrinkage of the striatum. Intracerebral hemorrhage occurs within the motor system connections of the striatum. Mapping of the projections of the forelimb motor area shows a significant sprouting in motor cortex projections only in cICH. Both models of ICH produce deficits in forelimb motor control. Behavioral recovery occurs by 5 weeks in cICH and 9 weeks in bICH. In summary, cICH and bICH differ in almost every facet of initial and delayed stroke pathophysiology, with cICH producing greater initial and secondary tissue damage and greater motor system axonal sprouting than bICH. Motor recovery occurs in both models, suggesting that motor system axonal sprouting in cICH is not causally associated with recovery.

Effect of the aggregation structure on the thermal shrinkage of polyacrylonitrile fibers during the heat‐treatment process

AbstractSecondary thermal shrinkage or chemical shrinkage involved in the thermal shrinkage of polyacrylonitrile (PAN) fibers was not only associated with the cyclization degree but also the thermal mobility of molecular chains in the aggregation structures during crosslinking. In this study, the cyclization process was monitored with differential scanning calorimetry and IR spectroscopy. The evolution of aggregation structures throughout cyclization and variations in the secondary shrinkage for the PAN fibers were characterized with wide‐angle X‐ray diffraction and thermal mechanical analysis, respectively. The results show that with increasing temperature, the cyclization degree increased; the cyclization occurred first in amorphous regions and then extended to the crystalline regions. Correspondingly, the secondary shrinkage also increased and could be separated into two stages: those of the amorphous and crystalline phases. The shrinkage of the crystalline regions was much bigger than that of the amorphous regions. For fibers with different aggregation structures, the crystallinity affected the cyclization degree in the amorphous and crystalline regions and resulted in the difference in total shrinkage. Furthermore, because the unoriented molecular chains in both the amorphous and crystalline regions shrank more after cyclization, the shrinkage of both regions was primarily decided by the level of orientated molecular chains participating in the cyclization. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Extended Forehead Skin Expansion and Single-Stage Nasal Subunit Plasty for Nasal Reconstruction

Forehead skin is often insufficient to use for nasal reconstruction because of a low hairline. In addition, skin graft used to repair donor-site defects results in obvious mismatched patches, whereas healing by secondary intention of donor-site defects causes conspicuous scars. To make up for the shortage of forehead skin used for nasal reconstruction and primary donor-site defect closure, the authors challenged the conventional idea of late shrinkage of expanded forehead flaps for nasal construction, and suggest a technique combining extended forehead skin expansion with single-stage nasal subunit plasty. This technique was applied to 43 patients for nasal reconstruction over a 9-year period. The technique consists of three stages: extended forehead skin expansion, single-stage nasal contouring and subunit plasty, and pedicle restoration. All cases were followed for at least 12 months. Outcomes were evaluated in terms of aesthetics, function, and donor-site aesthetics. No secondary shrinkage occurred in any of the cases. Eighty-one percent of the patients assessed themselves as satisfactory for aesthetics, 70 percent assessed themselves as satisfactory for function, and 77 percent assessed themselves as satisfactory for donor-site aesthetics. The complications included minor brow elevation (five cases), L-strut distortion (four cases), stuffiness of the nostrils (four cases), flap hyperpigmentation (one case), flap skin paleness (one case), and alar graft extrusion (one case). The combination of extended forehead skin expansion with single-stage nasal subunit plasty overcomes the defect of late shrinkage of an expanded flap for nasal reconstruction and achieved satisfactory results in aesthetics (nose and donor site) and function.

Analysis of soil shrinkage data

A precise mathematical formula for, and accurate curve-fitting of, shrinkage data are prerequisites for the evaluation of an array of structural properties as functions of the water content (moisture ratio) of non-rigid (swelling) soils. Such a formula is used here, together with its first (slope) and second (curvature) derivatives. The structural property that is of particular interest in this paper is the “shrinkage limit”, which occurs at the water content where the curvature of the shrinkage line (dry side) reaches its maximum value. Using a set of experimental data, found in the literature, it is shown here, that beyond the shrinkage limit (on the dry side), a secondary shrinkage process may be initiated, leading to a second (lower) shrinkage limit that would not usually be noticed.

Development of brain infarct volume as assessed by magnetic resonance imaging (MRI): follow-up of diffusion-weighted MRI lesions.

To investigate the development of ischemic brain lesions, as present in the acute stroke phase, by diffusion-weighted magnetic resonance imaging (DWI), and in the subacute and chronic phases until up to four months after stroke, in fluid-attenuated inversion recovery (FLAIR)- and T2-weighted (T2W) magnetic resonance (MR) images. Twelve consecutive patients with their first middle cerebral artery (MCA) infarction were included. Lesion volumes were assessed on T2W images recorded with a turbo spin echo (TSE) and on images recorded with the FLAIR sequence on average on day 8 and after about four months. They were compared with acute lesion volumes in perfusion and DWI images taken within 24 hours of stroke onset. On day 8, lesion volumes in images obtained with FLAIR exceeded the acute infarct volumes in DWI. The chronic lesion volumes were almost identical in T2W and FLAIR images but significantly reduced compared with the acute DWI lesions. The lesion volumes assessed on DWI images correlated highly with the lesions in the images obtained with TSE or FLAIR, as did the lesions in the images obtained with FLAIR and TSE. The secondary lesion shrinkage was accompanied by ventricular enlargement and perilesional sulcal widening, as most clearly visible in the images obtained with FLAIR. Our results show that the acute DWI lesions are highly predictive for the infarct lesion in the chronic stage after stroke despite a dynamic lesion evolution most evident in MR images obtained with FLAIR.

Delayed shrinkage of the brain after ischemic stroke: preliminary observations with voxel-guided morphometry.

The most important effect of cerebral ischemia is brain infarction. In this magnetic resonance imaging (MRI) study, the authors aimed at assessing postischemic brain atrophy. Ten patients suffering from their first acute cerebral ischemia in the territory of the middle cerebral artery were studied retrospectively. Three-dimensional MRI volume scans were recorded in the acute and chronic stage after infarction and analyzed voxel by voxel intraindividually with the newly developed voxel-guided morphometry. Shrinkage of brain tissue was detected in all patients, not only in the perilesional cortical structures but also in contralateral homolog cortex areas and subcortically in the striatum and thalamus. This secondary shrinkage was not related to the size of the infarcts or to the clinical outcome of patients. Our study suggests that delayed brain atrophy after acute ischemic stroke involved areas anatomically connected with the ischemic brain lesion but nevertheless was accompanied by a simultaneous improvement of the neurological deficit.

Effects of Risering Design and Chemical Composition on Formation of Shrinkage Caviry in Gray Cast Iron

The effects of risering design and alloying element on the formation of defects such as external depression, primary and secondary shrinkage cavity in gray cast iron were investigated. Two types of risering design for the cylindrically step-wise specimen, No. 1(progressive solidification) and No. 2(directional solidification) risering designs, were prepared and five different alloy compositions were casted. In the No. 1 risering design, external depression or primary shrinkage cavity due to liquid contraction was observed in all the specimens from ISO 150 to ISO 350. The primary shrinkage cavity was located right under the top surface or connected to the top surface, and was characterized by smooth surface. Its size increased with an increase in ISO number. However, neither secondary shrinkage cavity nor swollen surface was observed in all the castings. In the No.2 risering design, neither primary shrinkage cavity nor secondary shrinkage cavity was observed in all the specimens due to proper risering design. A swollen surface was also not observed in all the castings with the application of pep-set mold.

Recurrent Rectoneovaginal Fistula Caused by an Incidental Squamous Cell Carcinoma of the Neovagina in Mayer–Rokitansky–Küster–Hauser Syndrome

Objective. Mayer–Rokitansky–Küster–Hauser syndrome is a congenital malformation characterized by an absence of the vagina associated with a variable abnormality of the uterus and the urinary tract but functional ovaries. Surgical correction requires the creation of a neovaginal canal by the performance of a neovaginoplasty and an accurate long-term application of an artificial phallus phantom to avoid secondary shrinkage of the canal. Due to the chronic alteration of the posterior neovaginal wall, ulcers and consecutive fistulae may occur. We report the clinical course of a female who required surgical intervention for a rectoneovaginal fistula and developed a recurrence of the fistula due to one of the extremely rare squamous cell carcinomas of the neovaginal epithelium in order to show potential diagnostic and therapeutic features.Method. The systematic report of a case is presented.Result. Almost 13 years following the initial construction of a neovagina the patient developed a single-tract rectoneovaginal fistula. After surgical repair she represented with a recurrence due to a vast squamous cell carcinoma of the former operation site. Tumor en bloc resection was performed and currently (follow-up: 4 months) she has no signs of new tumor progression.Conclusion. Creation of a neovagina is the standard procedure for treating vaginal atresia or aplasia. Because of the long clinical course postoperatively, complications may occur. This report of a case of a malignant transformation in neovaginal epithelium shows the potential risk of malignancy and underlines the necessity of a close follow-up.

Eye socket reconstruction with the prefabricated temporal island flap.

Insufficiency of tissues and progressive contraction usually restrict the application of prosthetic devices in anophthalmic eye sockets. To achieve a successful reconstruction, the plastic surgeon has to form a socket that has proper dimensions and is completely covered by a well vascularized epithelial surface. Eye socket reconstruction with free skin, mucous membrane, or dermis-fat grafts usually remains unsatisfactory in severe cases. We have used a prefabricated temporal island flap to solve this difficult problem since 1983. In this method, a full-thickness skin graft is applied over the temporal fascia to create a prefabricated island flap based on the superficial temporal vessels. This flap is transposed into the eye socket 3 weeks later. Some modifications in flap design have been done to get better fitting of the prosthesis since that time. Thirty-three patients with constricted eye sockets that could not use prosthetic devices were treated with prefabricated temporal island flaps since 1983. The follow-up period was between 1 and 13 years. Eye sockets with adequate size and volume were created in all patients, and the results were successful. This method prevented secondary graft shrinkage, and the prefabricated island flaps preserved their dome shape during the follow-up period. We believe this method is a useful one in the treatment of the contracted socket.