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Beginning teachers (BTs) are increasingly expected to teach ambitiously from day one. However, they continue to face classroom management challenges. This study presents case studies of two elementary BTs that explore (1) the relationship between BTs' management and instructional practices in mathematics and English language arts and (2) its consequences for the ambitiousness of their teaching. Drawing on cultural historical activity theory, the cases highlight (1) the limits of a hierarchical model that positions classroom management as foundational to BTs' subject-matter instruction, (2) the potential of a polymotivated model of ambitious instruction for supporting BTs' development, and (3) the role of race in mediating this development. Implications for research and for efforts to support ambitious teaching among elementary BTs are explored. [ABSTRACT FROM AUTHOR]

The development of synthetic materials and their use in tissue engineering applications has attracted much attention in recent years as an option for trabecular bone grafting. Bioabsorbable polyesters of the poly(α-hydroxy acids) family, and specifically polylactic acid (PLA), are well known bioabsorbable materials and are currently used for numerous biomedical applications. The incorporation of an inorganic phase, such as a soluble calcium phosphate glass in the P2O5 − CaO − Na2O − TiO2 system, into the polymeric matrix enhances the mechanical integrity of the material. In fact, the flexural elastic modulus increases from 3.2 to 10 GPa with 50 wt/wt % of glass particles. It also improves the biological behavior and modifies the degradation pattern of the polymer. The presence of glass particles accelerates the material degradation and induces the formation of calcium phosphate precipitates in the surface of the composite. Therefore, the combination of a bioabsorbable polymer such as PLA with a soluble calcium phosphate glass leads to a fully degradable composite material with a high bone regenerative potential. The success of a 3D scaffold depends on several parameters that go from the macro- to the nanoscale. The solvent and casting technique, together with particulate leaching, allows the elaboration of 95 %-porosity scaffolds with a well interconnected macro- and microporosity. Factors such as surface chemistry, surface energy, and topography can highly affect the cell-material response. Indeed, the addition of glass particles in the PLA matrix modifies the material surface properties such as wettability AI (Area index or real-surface-area/nominal-area ratio) and roughness, improving the cell response and inducing morphological changes in the cytoskeleton of the osteoblasts. This study offers valuable insight into the parameters affecting cell-scaffold behavior, and discusses the special relevance that a comprehensive characterization and manufacturing control of the composite surface can have for monitoring the biological–synthetic interactions. [ABSTRACT FROM AUTHOR]

Bone marrow adipocytes accumulate with age and in diverse disease states. However, their origins and adaptations in these conditions remain unclear, impairing our understanding of their context-specific endocrine functions and relationship with surrounding tissues. In this study, by analyzing bone and adipose tissues in the lipodystrophic 'fat-free' mouse, we define a novel, secondary adipogenesis pathway that relies on the recruitment of adiponectin-negative stromal progenitors. This pathway is unique to the bone marrow and is activated with age and in states of metabolic stress in the fat-free mouse model, resulting in the expansion of bone marrow adipocytes specialized for lipid storage with compromised lipid mobilization and cytokine expression within regions traditionally devoted to hematopoiesis. This finding further distinguishes bone marrow from peripheral adipocytes and contributes to our understanding of bone marrow adipocyte origins, adaptations, and relationships with surrounding tissues with age and disease. [ABSTRACT FROM AUTHOR]

Global attention on teacher evaluation increasingly compels teachers to enter public debates about their work. Drawing on pragmatic sociology, the authors present analyses of media texts from 2008 to 2017 that identify the justification frameworks teachers mobilized to critique a prominent US evaluation policy and defend teaching as a complex craft. Policymakers, reformers, and researchers, however, re-articulated teachers' critiques, narrowly focusing the debate on teachers' technical effectiveness. The study contributes to scholarship on teacher evaluation and the mediatization of teaching by illuminating teachers' pragmatic capacity to shape public understanding of teaching. • Teachers exercised pragmatic agency to critique enhanced teacher evaluation. • Teachers promoted visions of quality teaching emphasizing craft, care and creativity. • Other stakeholders narrowly focused public debate on teachers' technical effectiveness. • Educators' justification work narrowly defined equity as fairness or effectiveness. [ABSTRACT FROM AUTHOR]

High doses of the nicotinic acetylcholine receptor (nAChR) antagonist mecamylamine can elicit somatic signs resembling those associated with nicotine withdrawal in nicotine-naïve adult rats. Understanding this phenomenon, and its possible modulation by acute nicotine and age, could inform the use of mecamylamine as both an experimental tool and potential pharmacotherapy for tobacco dependence and other disorders. This study evaluated the ability of high-dose mecamylamine to elicit somatic signs in adolescent rats, and the potential for acute nicotine pretreatment to potentiate this effect as previously reported in adults. Single or repeated injections of mecamylamine (1.5 or 3.0 mg/kg, s.c.) elicited somatic signs in nicotine-naive adolescents, but this effect was not influenced by two hour pretreatment with acute nicotine (0.5 mg/kg, s.c.). In an initial evaluation of the effects of age in this model, mecamylamine (2.25 mg/kg, s.c.) elicited somatic signs in nicotine-naive adolescents and adults. This effect was modestly enhanced following acute nicotine injections in adults but not in adolescents, even when a higher nicotine dose (1.0 rather than 0.5 mg/kg, s.c.) was used in adolescents to account for age differences in nicotine pharmacokinetics. These studies are the first to show that mecamylamine elicits somatic signs in nicotine-naïve adolescent rats, an effect that should be considered when designing and interpreting studies examining effects of high doses of mecamylamine in adolescents. Our findings also provide preliminary evidence that these signs may be differentially modulated by acute nicotine pretreatment in adolescents versus adults.

First bite syndrome (FBS) is a sharp unilateral pain in the vicinity of the angle of the mandible after taking the first bite of a meal that presents typically after surgery in the area of the ipsilateral parapharyngeal space. It is not confirmed what the pathophysiology is that causes this pain, but the proposed mechanism is the iatrogenic damage of sympathetic fibers that extend from the superior cervical ganglion (SCG) to innervate the parotid gland. The presentation of this syndrome has been acknowledged in patients who have undergone head and neck tumor resections, but it has not been documented in the same thorough manner among vascular surgery cases in the parapharyngeal space, possibly because of a higher risk of development in other head and neck surgeries, or to under-reporting of cases. To date, only 5 cases of FBS status post carotid endarterectomy have been documented in the literature. Definitive treatment of FBS has not been established. Some studies have shown improvement with amitriptyline, and carbamazepine as well as botulinum toxin injections. We will present the case of a 75 year old male who developed first bite syndrome after a right carotid endarterectomy with efforts of raising awareness of a potential acute complication of carotid endarterectomy.

Glucocorticoids (GCs), stress hormones produced by the adrenal gland, are involved in many pathways in physiology and metabolism including glucose homeostasis and inflammation. Excess GC signaling results in Cushing's syndrome and possibly metabolic syndrome. Diabetes, central adiposity, and hyperlipidemia are components of both syndromes. Here, we discuss the mechanisms of GC action, clinical syndromes of GC excess, modulation of glucose homeostasis by GCs, and future treatments for diabetes based on GC signaling.

Biodegradable polymers reinforced with an inorganic phase such as calcium phosphate glasses may be a promising approach to fulfil the challenging requirements presented by 3D porous scaffolds for tissue engineering. Scaffolds' success depends mainly on their biological behaviour. This work is aimed to the in vitro study of polylactic acid (PLA)/CaP glass 3D porous constructs for bone regeneration. The scaffolds were elaborated using two different techniques, namely solvent-casting and phase-separation. The effect of scaffolds' micro and macrostructure on the biological response of these scaffolds was assayed. Cell proliferation, differentiation and morphology within the scaffolds were studied. Furthermore, polymer/glass scaffolds were seeded under dynamic conditions in a custom-made perfusion bioreactor. Results indicate that the final architecture of the solvent-cast or phase separated scaffolds have a significant effect on cells' behaviour. Solvent-cast scaffolds seem to be the best candidates for bone tissue engineering. Besides, dynamic seeding yielded a higher seeding efficiency in comparison with the static method.

This study involves the mechanical and structural characterisation of completely degradable scaffolds for tissue engineering applications. The scaffolds are a composite of polylactic acid (PLA) and a soluble calcium phosphate glass, and are thus completely degradable. A factorial experimental design was applied to optimise scaffold composition prior to simultaneous microtomography and micromechanical testing. Synchrotron X-ray microtomography combined with in situ micromechanical testing was performed to obtain three-dimensional (3D) images of the scaffolds under compression. The 3D reconstruction was converted into a finite element mesh which was validated by simulating a compression test and comparing it with experimental results. The experimental design reveals that larger glass particle and pore sizes reduce the stiffness of the scaffolds, and that the porosity is largely unaffected by changes in pore sizes or glass weight content. The porosity ranges between 93% and 96.5%, and the stiffness ranges between 50 and 200 kPa. X-ray projections show a homogeneous distribution of the glass particles within the PLA matrix, and illustrate pore-wall breakage under strain. The 3D reconstructions are used qualitatively to visualise the distribution of the phases of the composite material, and to follow pore deformation under compression. Quantitatively, scaffold porosity, pore interconnectivity and surface/volume ratios have been calculated. Finite element analysis revealed the stress and strain distribution in the scaffold under compression, and could be used in the future to characterise the mechanical properties of the scaffolds.

The goal of this study was to characterise the surface properties of completely degradable composite, polylactic acid and calcium phosphate glass, scaffolds. The composite scaffolds are made by solvent casting or phase-separation, using chloroform and dioxane as a solvent respectively. The surface properties were measured on composite films which were made using the same procedure as for the three-dimensional (3D) scaffolds without the pore-creating step. The surface morphology, roughness, wettability and protein adsorption capacity of the films was measured before and after sterilisation with ethylene oxide. The results reveal the influence of solvent type, glass weight content and sterilisation on the wettability, surface energy and protein adsorption capacity of the materials. The addition of glass particles increase the hydrophylicity, roughness and protein adsorption capacity of the surface. This effect, however, depends on the extent of the coating of the glass particles by the polymer film, which is much higher for dioxane films than for chloroform films. This information can be used to interpret and understand the biological behaviour of the 3D scaffolds made of this composite materials.

In diaphyseal femoral fractures, an accurate quantification of the biomechanical differences between implants can help the surgeon make his choice. This study uses the finite element (FE) method to characterize the differences between intramedullary nails and osteosynthesis plates at different stages of femoral fracture healing, and assesses how these differences are affected by the size and consolidation of the fracture. Simulations were performed using a femur model with a 1 and 3 mm diaphyseal fracture at two stages of consolidation. The fracture was stabilized with an osteosynthesis plate or an intramedullary nail made of stainless steel (SS), titanium (Ti) or a composite material. The Ti implants bore lower von Mises stresses ( ó vM ) than the SS implants, and ó vM in the implants decreased with fracture consolidation. Nails tended to bear higher stresses than plates, though these differences were reduced in unstable fractures. This change in trend proves that fixation choice is critical for weak fractures. Both the dilatational stress ó dil and the octahedral shear strain å oct of the fractures varied significantly with the type of fracture and fixation device. In accordance with the literature, our results suggest that plates induce fracture healing through intramembranous ossification without fracture callus formation. Nails, on the other hand, induce endochondral ossification with fibrous tissue formation. The composite implants have mechanical limitations, but increasing their yield stress could overcome these drawbacks.