Fracturas estallido de columna toracolumbar: Evaluación clinicoradiológica y terapéutica de 90 casos

Presentamos un estudio retrospectivo de 90 fracturas toracolumbares tipo estallido con un seguimiento mínimo de 12 meses. Se realizó tratamiento ortopédico en 43 casos y en 47 se indicó una artrodesis instrumentada. Realizamos una evaluación clínico-radiológica en base al dolor residual y evolución del ángulo de cifosis con el objetivo de valorar el tratamiento ortopédico como opción terapéutica y la necesidad de distinguir fracturas estallido con afectación de 2 ó 3 columnas. No apreciamos diferencias estables significativas en el dolor y la lesión de las tres columnas. El aumento de cifosis angular media en las fracturas estallido estable no operadas es de 4.7º y de 5.2º en las fracturas estallido inestables tratadas ortopédicamente. Observamos una alta incidencia de complicaciones relacionadas con la fijación (21%) cuando la fractura asentaba en la charnela y se instrumentaba a un solo nivel. El tratamiento ortopédico es una opción aceptable en las fracturas estallido en pacientes neurológicamente indemnes.Ninety burst fractures of the thoracolumbar spine were retrospectively assessed with a minum follow-up of 12 months. Conservative treatment was indicated in 43 cases, and reduction and surgical stabilization in 47. The aim was to compare the two treatment modalities according to fracture stability. Clinical and radiological evaluation included chronic pain and kyphotic angle progression. No statistical differences were found between stable and unstable fractures as to chronic pain. The kyphotic angle average progression for stable burst fractures was 4.7º and 5.2º for unstable fractures conservatively treated. There was a high rate of complications related to instrumentation (21%) particularly when the fracture was at the thoracolumbar junction and a single level was fixed. The orthopaedic treatment is an acceptable alternative treatment for stable burst fractures without neurological injury

A model for the sustainable selection of building envelope assemblies

The aim of this article is to define an evaluation model for the environmental impacts of building envelopes to support planners in the early phases of materials selection. The model is intended to estimate environmental impacts for different combinations of building envelope assemblies based on scientifically recognised sustainability indicators. These indicators will increase the amount of information that existing catalogues show to support planners in the selection of building assemblies.To define the model, first the environmental indicators were selected based on the specific aims of the intended sustainability assessment. Then, a simplified LCA methodology was developed to estimate the impacts applicable to three types of dwellings considering different envelope assemblies, building orientations and climate zones. This methodology takes into account the manufacturing, installation, maintenance and use phases of the building. Finally, the model was validated and a matrix in Excel was created as implementation of the model

Modulating the water behavior, microstructure, and viscoelasticity of plasma-derived hydrogels by adding silica nanoparticles with tailored chemical and colloidal properties

The viscoelastic properties of hydrogels depend on the tridimensional polymeric structure and the behavior of the liquid confined in their pores. The objective here is to modulate these characteristics in plasma-derived hydrogels by the addition of glycidoxypropyl-silica nanoparticles. These nanoparticles exhibited a hydrodynamic average size between 105.4 − 151.0 nm and surface coverage with (3-Glycidoxypropyl) trimethoxysilane of 0–96 %. The reinforced hydrogels are porous networks with spherical nanoparticles homogeneously distributed into their walls. The silanol groups of silica increase four-fold humidity retention compared with the native hydrogel. This correlates with bound water &gt; 45 % on these reinforced hydrogels, in contrast with 75 % of free water on the native one (calculated from DSC in frozen hydrogels). The humidity stability can be also achieved in the hydrogel prepared with nanoparticles exhibiting 96 % organic coverage. Furthermore, this organic content promotes the microstructure chemical crosslinking, resulting in 3.9 and 1.6 higher Young's modulus compared with native and silica-reinforced hydrogels, respectively. The presence of glycidoxypropyl-silica nanoparticles in reinforced hydrogels modulated its viscoelasticity behavior, decreasing stress relaxation, which was explained using the generalized Maxwell-Wiechert model. In conclusion, novel organic-inorganic hybrid hydrogels based on plasma-derived ones and glycidoxypropyl-silica nanoparticles were developed. These nanoparticles are versatile and allow the production of hydrogels with improved viscoelastic behavior that also exhibits high water retention and morphological stability.</p

Modulating the water behavior, microstructure, and viscoelasticity of plasma-derived hydrogels by adding silica nanoparticles with tailored chemical and colloidal properties

The viscoelastic properties of hydrogels depend on the tridimensional polymeric structure and the behavior of the liquid confined in their pores. The objective here is to modulate these characteristics in plasma-derived hydrogels by the addition of glycidoxypropyl-silica nanoparticles. These nanoparticles exhibited a hydrodynamic average size between 105.4 − 151.0 nm and surface coverage with (3-Glycidoxypropyl) trimethoxysilane of 0–96 %. The reinforced hydrogels are porous networks with spherical nanoparticles homogeneously distributed into their walls. The silanol groups of silica increase four-fold humidity retention compared with the native hydrogel. This correlates with bound water &gt; 45 % on these reinforced hydrogels, in contrast with 75 % of free water on the native one (calculated from DSC in frozen hydrogels). The humidity stability can be also achieved in the hydrogel prepared with nanoparticles exhibiting 96 % organic coverage. Furthermore, this organic content promotes the microstructure chemical crosslinking, resulting in 3.9 and 1.6 higher Young's modulus compared with native and silica-reinforced hydrogels, respectively. The presence of glycidoxypropyl-silica nanoparticles in reinforced hydrogels modulated its viscoelasticity behavior, decreasing stress relaxation, which was explained using the generalized Maxwell-Wiechert model. In conclusion, novel organic-inorganic hybrid hydrogels based on plasma-derived ones and glycidoxypropyl-silica nanoparticles were developed. These nanoparticles are versatile and allow the production of hydrogels with improved viscoelastic behavior that also exhibits high water retention and morphological stability.</p

Application of the multimodal transfer matrix method in dielectric periodic structures with higher symmetries

The Multimodal Transfer Matrix Method (MMTMM) is a hybrid method to compute the propagation constants of periodic structures that combines in-house/commercial software and later post-processing [1], [2]. Its main advantage over commercial eigensolvers is the possibility to find the attenuation constant not only due to material losses but also to electromagnetic bandgaps and/or radiation. However, thanks to the use of commercial software, any complex structure with different materials and/or arbitrary geometry can be analyzed, as opposed to other quasi-analytical and numerical approaches found in the literature such as circuit models [3] or mode matching [4]. The MMTMM models the unit cell of a periodic structure as a multiport network where each pair of ports accounts for a propagative/evanescent/leaky mode in the structure. This means that the coupling between higher order modes is considered in the simulation, which is more accurate in general, and essential in other cases, such as in the study of higher-symmetric periodic structures. In this work, we propose the use of the MMTMM to obtain the attenuation constant, as well as having a fundamental understanding of two periodic dielectric structures with higher symmetries. A periodic structure possesses a higher symmetry if it is invariant after more than one geometrical operator [5]. Two main spatial higher symmetries can be found in the literature: glide and twist. A glide-symmetric structure is invariant after a mirroring and a translation of half of the period. Differently, a periodic structure possesses twist symmetry after a number N of rotations and translations. The first structure under study is a glide-symmetric dielectric-filled corrugated waveguide. As previously reported in [6], this structure allows for the propagation of backward modes below the hollow waveguide cut-off frequency. This backward mode was analyzed with a convergence study of the MMTMM to investigate the waveguide modes that contribute to its propagation. The second structure under study is a twist-symmetric dielectric waveguide. In [7], it was reported that the employed three-fold configuration of this structure allows for the propagation of circularly-polarized modes that makes it polarization selective in a specific frequency band. This polarization selection band is characterized with the MMTMM to estimate the losses of both left and right-handed modes

Teacher Questioning in Problem Solving in Community College Algebra Classrooms

In this chapter, we focus on the ways two community college instructors worked with students to demonstrate the solution of contextualized algebra problems in their college algebra lessons. We use two classroom episodes to illustrate how they sought to elicit students' mathematical ideas of algebraic topics, attending primarily to teachers' questioning approaches. We found that the instructors mostly asked questions of lower cognitive demand and used a variety of approaches to elicit the mathematical ideas of the problems, such as using examples relevant to the students and dividing the problems into smaller tasks, that together help identify a solution. We conclude by offering considerations for instruction at community colleges and potential areas for professional development

Momentum distribution in heavy deformed nuclei: role of effective mass

The impact of nuclear deformation on the momentum distributions (MD) of occupied proton states in $^{238}$U is studied with a phenomenological Woods-Saxon (WS) shell model and the self-consistent Skyrme-Hartree-Fock (SHF) scheme. Four Skyrme parameterizations (SkT6, SkM*, SLy6, SkI3) with different effective masses are used. The calculations reveal significant deformation effects in the low-momentum domain of $K^{\pi}=1/2^{\pm}$ states, mainly of those lying near the Fermi surface. For other states, the deformation effect on MD is rather small and may be neglected. The most remarkable result is that the very different Skyrme parameterizations and the WS potential give about identical MD. This means that the value of effective mass, being crucial for the description of the spectra, is not important for the spatial shape of the wave functions and thus for the MD. In general, it seems that, for the description of MD at $0\le k \le 300$ MeV/c, one may use any single-particle scheme (phenomenological or self-consistent) fitted properly to the global ground state properties.Comment: 14 pages, 6 figure