Brief intervals of shear prior to a temperature quench accelerate crystallization, resulting in much smaller spherulites. Crystallization kinetics of five commercial linear isotactic polypropylenes ...were investigated, using a rheometer to impose shear and monitor crystallization after quenching. Shear and quench temperatures, shear rate, and duration were all systematically varied. The crystallization rate increases with increasing applied work, up to a value independent of undercooling beyond which the rate remains constant. This saturation is consistent with a maximum number of nuclei, possibly set by the concentration of heterogeneous impurities. The crystallization rate likewise increases with increasing shear rate, saturating at about 1 s–1 for all grades studied. Only chains in the high molecular weight tail, above about 104 kg/mol, are stretched at this shear rate. Faster crystallization after shear was observed for grades with lower isotacticity. Flow-induced crystallization persists even when shear is applied well above the equilibrium melting temperature (187 °C), finally weakening above the Hoffman–Weeks temperature (210 °C), perhaps because flow-induced precursors are no longer metastable.
Brief intervals of strong flow stretch chains in a semicrystalline polymer melt to form flow-induced precursors, which accelerate crystallization kinetics and transform the morphology. Using ...commercial isotactic polypropylene, the persistence and lifetime of flow-induced precursors were investigated, focusing on the effects of specific work and annealing time and temperature. Precursors were formed by shearing polypropylene in a rotational rheometer and then quenching to a desired temperature. The crystallization time and crystallization temperature of the sheared samples were investigated using novel rheology and DSC experiments. For sufficiently large shear rates, the appearance of flow-induced precursors is controlled by the applied work. A qualitative change in many properties related to precursors takes place at a critical work value W c, about 7 MPa for our iPP material. To erase the persistent “memory” of flow-induced nuclei, samples must be annealed for a very long time below 210 °C (>3000 min) or a shorter time above 210 °C (e.g., 300 min at 250 °C). Annealing above the Hoffman–Weeks temperature (208 °C) evidently erases flow-induced precursors much faster, although at 210 °C still requiring times a factor of 50 longer than the reptation times of the longest chains.
Colony stimulation factor-1 receptor (CSF-1R), which is also known as FMS kinase, plays an important role in initiating inflammatory, cancer, and bone disorders when it is overstimulated by its ...ligand, CSF-1. Innate immunity, as well as macrophage differentiation and survival, are regulated by the stimulation of the CSF-1R. Another ligand, interlukin-34 (IL-34), was recently reported to activate the CSF-1R receptor in a different manner. The relationship between CSF-1R and microglia has been reviewed. Both CSF-1 antibodies and small molecule CSF-1R kinase inhibitors have now been tested in animal models and in humans. In this Perspective, we discuss the role of CSF-1 and IL-34 in producing cancer, bone disorders, and inflammation. We also review the newly discovered and improved small molecule kinase inhibitors and monoclonal antibodies that have shown potent activity toward CSF-1R, reported from 2012 until 2017.
Deformation applied to a semicrystalline polymer melt prior to quenching can dramatically increase the concentration of nuclei and even transform the final crystalline morphology, phenomena ...collectively known as flow-induced crystallization (FIC). Using polarized optical microscopy and atomic force microscopy, we image the changes in morphology of an isotactic polypropylene (iPP) sample previously sheared in a rotational rheometer. Sufficiently large deformations promote the formation of “rice grain” shaped crystalline domains. These anisotropic structures are randomly oriented and are about 1.5–3.0 μm long (depending on applied work), with an aspect ratio of about 2:1. Well below the critical specific work threshold W c, the crystalline morphology of our iPP sample is predominately composed of spherulites, with a fraction of rice grains that increases as the applied work increases. Above W c, rice grains predominate, with no visible spherulites. The size of spherulites appears to be independent of applied work. In contrast, the size of rice grains decreases with increasing applied work, up to a saturation specific work W sat, remaining constant thereafter. Similarly, the isothermal crystallization time decreases with increasing applied work up to W sat and is constant thereafter. The effects of flow-induced precursors persist after repeated melting and recrystallizations, observable by elevated freezing temperatures in DSC experiments. Here, we probe directly the robustness of these precursors in optical microscopy, in which we repeatedly melt, anneal, and recrystallize a thin slice of an FIC sample. We observe rice grain domains appearing over and over, with the first domains to crystallize tending to reappear near the same locations.
The neutron inelastic scattering of carbon-12, populating the Hoyle state, is a reaction of interest for the triple-alpha process. The inverse process (neutron upscattering) can enhance the Hoyle ...state's decay rate to the bound states of
C, effectively increasing the overall triple-alpha reaction rate. The cross section of this reaction is impossible to measure experimentally but has been determined here at astrophysically-relevant energies using detailed balance. Using a highly-collimated monoenergetic beam, here we measure neutrons incident on the Texas Active Target Time Projection Chamber (TexAT TPC) filled with CO
gas, we measure the 3α-particles (arising from the decay of the Hoyle state following inelastic scattering) and a cross section is extracted. Here we show the neutron-upscattering enhancement is observed to be much smaller than previously expected. The importance of the neutron-upscattering enhancement may therefore not be significant aside from in very particular astrophysical sites (e.g. neutron star mergers).
Introduction/Purpose. Tracheoesophageal fistula (TEF) represents one of the most common congenital developmental malformations of the upper digestive tract. The optimal surgical management has ...several controversies, particularly in rapidly developing countries. Morbidity and mortality are highly variable between centers and are dependent on various factors. However, complex medical care has considerably improved, especially in developing countries. This study describes the experience of our center in patients with TEF with emphasis on the clinical characteristics, postoperative immediate and long-term respiratory and gastrointestinal complications, and the mortality rate of such cases which would allow us to compare our results with other regional pediatric tertiary centers. Methods. This is a retrospective review of the medical electronic charts of patients with TEF that were followed at Sidra Medicine in the state of Qatar. The review included the patients who were operated upon in the period of 2011-2021 but continued to follow at our institution in the period of 2018-2021. Demographic data, associated anomalies, preoperative, operative, and postoperative courses, and growth parameters were collected. Results. A total of 35 patients with TEF (24 males and 11 females) were collected. 49% were full term. We identified seven patients (20%) with isolated TEF, TEF with VACTERL association in 29% of our patients, other chromosomal anomalies in 17%, or associated with other anomalies (not related to VACTERL) in 34% of the patients. The majority of the patients (94%) were of type C-TEF (TEF with esophageal atresia–EA/TEF). All patients were operated except for one patient who died at 2 days of life due to cardiac complications. Median age at which surgery was performed was 2 days (range 1-270 days). Median follow-up was 32 months (range 7-115 months). Immediate postoperative complications were encountered in eleven patients (33%) and included anastomosis leak in 12%, air leak in 6%, sepsis in 6%, chylothorax in 3%, vocal cord palsy and fistula recurrence (combined) in 3%, and failure of TEF closure in 3% of the patients. Long-term respiratory complications were encountered in 43% of our patients. Long-term gastrointestinal complications included gastroesophageal reflux (GERD) in 63%, dysphagia in 31%, and anastomotic stricture in 34% of the patients. Growth was affected in around a quarter of the patients at 6 months after surgery and 22% at 12-month assessment postoperatively. While only five patients died at our institution, only one was directly related to failure of TEF closure and postoperative complications. Conclusion. This descriptive study reports the clinical outcome of TEF from a rapidly developing country. The distribution of the patients’ characteristics and postoperative complications was almost comparable to those from developed countries. This study would aid in addressing the prognostic factors and establishment of evidence-based management pathways of newborns with TEF to improve the clinical outcome in our center and other pediatric tertiary centers in developing countries.
In this paper, an analytical method is developed to study the dynamic behavior of functionally imperfect Euler-Bernoulli and Timoshenko graded beams with differing boundary conditions, namely, ...hinged-hinged, clamped-clamped, clamped-hinged, and clamped-free. A transfer matrix method is used to obtain the natural frequency equations. The modified rule of mixture is used to describe the material properties of the functionally graded beams having porosities. The porosities are assumed to be evenly distributed over the beam cross-section. In this study, the effects of boundary conditions, material volume fraction index, slenderness ratio, beam theory, and porosity on natural frequency are determined. The present results are validated with results available in the literature.
The purpose of this study was to determine the effect of operative experience on perioperative outcomes for laparoscopic Roux-en-Y gastric bypass (LGB).
Between July 1997 and September 2001, 750 ...patients underwent LGB for the treatment of morbid obesity at our center. We evaluated the perioperative outcomes of the first 150 consecutive patients to determine if a learning curve effect could be demonstrated. The patients were divided into three groups (1, 2, and 3) of 50 consecutive patients, and outcomes for each group were compared.
The patients in group 3 had a larger body mass index (BMI), were more likely to have had prior abdominal surgery, and were more likely to have secondary operations at the time of LGB. Operating time decreased from a mean of 311 min in group 11 to 237 min in group 3, and technical complications were reduced by 50% after an experience of 100 cases.
Operative time and technically related complications decreased with operative experience even though heavier patients and higher-risk patients were more predominant in the latter part of our experience. LGB is a technically challenging operation with a long learning curve. To minimize morbidity related to the learning curve, strategies for developing training programs must address these challenges.
Introduction
Spinal muscular atrophy (SMA) is an inherited progressive neuromuscular disorder characterized by generalized hypotonia, respiratory failure and early death. The introduction of gene ...replacement therapy (GRT) modified the natural history of the disease. However, more data is needed to understand the long‐term effect of GRT on measurable respiratory outcomes. We report the respiratory outcomes in our cohort of patients with SMA post‐GRT in 2‐year period.
Methods
A retrospective chart‐review of genetically confirmed children with SMA who received GRT between 2019 and 2021 in Qatar. The evaluated respiratory outcomes were chronic respiratory support, respiratory hospitalizations, escalation of respiratory support and polysomnography results before and after GRT. Nonrespiratory outcomes; nutritional status, swallowing, and motor functions; were also assessed.
Results
A total of 11 patients (9 patients with SMA‐1 and 2 patients with SMA‐2) received GRT at a median age of 12 months and 22 months in patients with SMA‐1 and SMA‐2, respectively. All patients were successfully weaned off Noninvasive ventilation (NIV) except one patient who remained on mechanical ventilation through tracheostomy tube. The annualized hospitalization rate dropped by half after GRT. The average length of stay (LOS) in intensive care unit (ICU) decreased by 17.32 days/patient/year after GRT. Duration of required escalation of respiratory support during acute hospitalizations has dropped by 18.56 days/patient/year post‐GRT.
Conclusion
We report favorable respiratory outcomes of GRT in our cohort. GRT resulted in discontinuation of chronic respiratory support in majority of ventilated patients. GRT also resulted in decreased respiratory hospitalization rate, hospital‐LOS, ICU‐LOS, and need for escalation of ventilatory support.
While most children with epilepsy find their seizures manageable through medication, some continue to experience seizures despite trying multiple drugs. Failure of medical treatment often becomes ...apparent early on, and for these cases, it is advisable to seek further treatment options at a specialized epilepsy center. Such centers offer additional treatments like epilepsy surgery, vagus nerve stimulation, and ketogenic diets. There is no universal definition for what constitutes "medically intractable" epilepsy. A proposal by a task force from the International League Against Epilepsy suggests that drug-resistant epilepsy could be defined as the inability to control seizures even after two adequate treatment attempts with well-chosen and tolerated medications, either alone or in combination. In this review, the authors discussed the management of intractable epilepsy in children.
