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Uma das mais recentes soluções empregadas na construção de prédios de elevada altura,que permite redução econômica e menor utilização de material é o sistema tubularDiagrid. Esse sistema é composto por diagonais e se comporta de maneira similar auma treliça espacial, oferecendo às fachadas dos prédios uma arquitetura inovadorae notável. O emprego deste novo sistema estrutural pode ocasionar em determinadasconstruções a dispensa da utilização de colunas no interior dos prédios, possibilitandouma maior área livre de circulação, a maior incidência da iluminação natural e umaredução de materiais na construção dos edifícios. As ligações desse tipo de estruturadevem ter atenção especial, a fim de também possibilitar tais reduções. Este trabalhotem como objetivo analisar estrutural e economicamente as ligações Diagrid, por meioda análise do comportamento das ligações empregando o método dos elementos finitospor meio do programa ANSYS, realizando uma comparação entre o aço carbono e oaço inoxidável, proporcionando um melhor entendimento sobre este sistema estrutural.Para as análises estruturais considerou-se a influência das cargas verticais e horizontaisno sistema e a resistência dos materiais empregados. Estudou-se o aço inoxidável dotipo austenítico, duplex e lean duplex, e a influência na angulação da inclinação damalha Diagrid. Observou-se nos estudos desenvolvidos que o ângulo de inclinação queapresentou melhor resistência foi o de 70° e que a comparação de custos, apenas demateriais, entre o aço carbono e o aço inoxidável ainda indica uma diferença considerávelpara a aplicação do aço inoxidável nas estruturas.

Introduction The posterolateral lumbar fusion (PLF) New Zealand White (NZW) (Oryctolagus cuniculus) rabbit model is a long‐standing surgical technique for the preclinical evaluation of materials for spinal fusion. A detailed understanding of lumbar spine anatomy and perioperative care requirements of rabbits is imperative for correct execution of the model both scientifically and ethically. This study describes the preoperative procedures and surgical techniques used in single level PLF in a NZW rabbit model as it pertains to the animal husbandry, lumbar spine anatomy, anesthesia, surgical approach, and perioperative care of rabbits in a research setting. Materials and Methods We describe the surgical technique and perioperative patient care for single level PLF in a NZW rabbit model. Medical records from a single research facility were retrospectively reviewed for adult NZW rabbits that underwent single level PLF (L4‐L5) between January 2016 and December 2019. The number of lumbar vertebrae per rabbit, fusion rates at 12 weeks using iliac crest autograft and complications are reported. Skeletal maturity was confirmed by preoperative fluoroscopic and radiographic documented closure of hindlimb physes. Results The PLF rabbit surgical model and perioperative patient care is described. PLF was performed in 868 adult female entire NZW rabbits. The majority of rabbits had seven lumbar vertebrae (620/868; 71.4%), followed by six (221/868; 25.5%), and eight (27/868; 3.1%). Fusion rates at 12 weeks for PLF using iliac crest autograft as assessed by manual palpation and radiographic assessment was 76.9% and 70.0%, respectively. Postoperative complications included occasional partial autograft site wound dehiscence due to self‐trauma. Conclusions For PLF rabbit models, a detailed understanding of the surgical technique, rabbit lumbar anatomy including number of lumbar vertebrae, and dietary and husbandry requirements of rabbits, is essential for execution of the model and animal welfare.

BACKGROUND CONTEXT Synthetic bone graft substitutes are commonly used in spinal fusion surgery. Preclinical data in a model of spinal fusion to support their efficacy is an important component in clinical adoption to understand how these materials provide a biological and mechanical role in spinal fusion. PURPOSE To evaluate the in vivo response of a nanosynthetic silicated calcium phosphate putty (OstP) combined with autograft compared to autograft alone or a collagen-biphasic calcium phosphate putty (MasP) combined with autograft in a rabbit spinal fusion model. STUDY DESIGN Efficacy of a nanosynthetic silicated calcium phosphate putty as an extender to autograft was studied in an experimental animal model of posterolateral spinal fusion at 6, 9, 12 and 26 weeks, compared to a predicate device. METHODS Skeletally mature female New Zealand White rabbits (70) underwent single level bilateral posterolateral intertransverse process lumbar fusion, using either autograft alone (AG), a nanosynthetic silicated calcium phosphate putty (OstP) combined with autograft (1:1), or a collagen-biphasic calcium phosphate putty (MasP) combined with autograft (1:1). Iliac crest autograft was harvested for each group, and a total of 2 cc of graft material was implanted in the posterolateral gutters per side. Fusion success was assessed at all time points by manual palpation, radiographic assessment, micro-CT and at 12 weeks only using non-destructive range of motion testing. Tissue response, bone formation and graft resorption were assessed by decalcified paraffin histology and by histomorphometry of PMMA embedded sections. RESULTS Assessment of fusion by manual palpation at the 12 week endpoint showed 7 out of 8 (87.5%) bilateral fusions in the OstP extender group, 4 out of 8 (50%) fusions in the MasP extender group, and 6 out of 8 (75%) fusions in the autograft alone group. Similar trends were observed with fusion scores of radiographic and micro-CT data. Histology showed a normal healing response in all groups, and increased bone formation in the OstP extender group at all timepoints compared to the MasP extender group. New bone formed directly on the OstP granule surface within the fusion mass while this was not a feature of the Collagen-Biphasic CaP material. After 26 weeks the OstP extender group exhibited 100% fusions (5 out of 5) by all measures, whereas the MasP extender group resulted in bilateral fusions in 3 out of 5 (60%), assessed by manual palpation, and fusion of only 20 and 0% by radiograph and micro-CT scoring, respectively. Histology at 26 weeks showed consistent bridging of bone between the transverse processes in the Ost P extender group, but this was not observed in the MasP extender group. CONCLUSIONS The nanosynthetic bone graft substituted studied here, used as an extender to autograft, showed a progression to fusion between 6 and 12 weeks that was similar to that observed with autograft alone, and showed excellent fusion outcomes, bone formation and graft resorption at 26 weeks. CLINICAL SIGNIFICANCE This preclinical study showed that the novel nanosynthetic silicated CaP putty, when combined with autograft, achieved equivalent fusion outcomes to autograft. The development of synthetic bone grafts that demonstrate efficacy in such models can eliminate the need for excessive autograft harvest and results from this preclinical study supports their effective use in spinal fusion surgery.

BACKGROUND CONTEXT Synthetic bone grafts are a promising alternative for the treatment of degenerative spine conditions and are available without the added drawbacks associated autografts including limited availability and donor-site morbidity. Of these synthetic materials, calcium phosphate (CaP) with a characteristic needle-shaped submicron surface topography (BCP PURPOSE This study was to evaluate the efficacy of a novel synthetic bone graft using a clinically-relevant “Boden” rabbit posterolateral spine fusion model. The synthetic bone graft comprised of CaP granules with a needle-shaped submicron surface structure (BCP STUDY DESIGN/SETTING The novel synthetic bone graft was first mixed in a 1:1 volume ratio with autologous bone (ABG). Subsequently, grafts were implanted in the rabbit posterolateral spine environment for 3 days, 6, 9 and 12 weeks. An autologous bone graft group was used as a positive control in this study. Outcomes for the test article were additionally compared to historical data for the same material (BCP OUTCOME MEASURES Spinal fusion was determined by manual palpation (MP), X-ray and µCT imaging (based on the Lenke scale), mechanical testing (range of motion testing at 12 weeks only) and histology (decalcified and undecalcified). METHODS Forty skeletally mature New Zealand white rabbits were divided into two groups and underwent single-level bilateral posterolateral intertransverse process spine arthrodesis at L4-5. Animals were euthanized after 3 days, 6, 9 and 12 weeks. RESULTS Based on all endpoints, the test group and positive control group showed an equivalent and gradual progression in bone formation and implant resorption over time, leading to mature fusion masses at 12 weeks. No adverse reactions were observed in any of the groups. Bilateral fusion rates by MP were consistent with the literature (0-40% at 6 weeks; 60-70% at 12 weeks) and similar trends were seen by histological and radiographic assessment (both X-ray and µCT). Flexion-extension and lateral bending results at 12 weeks demonstrated fusion of the treated level consistent with the MP results. The results observed for the test group were consistent with those seen historically for the same material implanted without the fibrillar collagen carrier. CONCLUSIONS These results show that BCP with needle-shaped submicron-scale surface topography (BCP FDA DEVICE/DRUG STATUS Col-BCP

BACKGROUND CONTEXT Delivery and handling of graft material during surgery can be challenging often due to the particulate nature of materials, irrigation and risk of migration. Resorbable mesh pouches (RMP) offer a simple and effective way to handle and implant particulate grafts, maintain host bone contact and avoid migration. The current RMP was composed of a PLGA mesh. Two studies were performed using a well reported single level posterolateral rabbit spinal fusion model. Study 1 evaluated the RMP prefilled with demineralized bone matrix (DBM) and used as an extender with autograft while Study 2 evaluated the RMP filled with corticocancellous iliac crest autograft. An Autograft alone group was used as a positive control group in each study. PURPOSE To confirm that a porous resorbable mesh pouch, used to facilitate placement and containment of graft material does not impede bone formation. STUDY DESIGN/SETTING Preclinical in vivo study. PATIENT SAMPLE Not applicable. OUTCOME MEASURES Not applicable. METHODS Eighty skeletally mature female New Zealand White rabbits were enrolled following ethical approval in two studies. The transverse processes were exposed and decorticated with a pneumatic high-speed burr. The implant groups were 2cc of autograft, 2cc of autograft inside the RMP, or RMP pre-filled with 2cc DBM placed on top of 1cc of autograft bilaterally in the posterolateral gutters. Fusion assessment at 3 days (n=2 per group), 4 and 8 weeks (n=5 per group) and 12 weeks (n=8 per group) included manual palpation, X-rays, Faxitron radiographs, micro CT, histology and histomorphometry for bone formation as well as polymer resorption and reaction using polarized light. Statistical analyses were performed using a non-parametric Kruskal Wallis test for manual palpation, radiographs and micro CT grading while an ANOVA was used for histomorphometry and non-destructive range of motion testing. RESULTS All animals recovered uneventfully following surgery. No adverse reactions were noted macroscopically. The positive control groups performed consistently with the model and literature. Manual palpation at 12 weeks for RMP groups was 6/8 in both studies. Radiograph and micro computed tomographic grading and pmMA histomorphometry did not detect any differences between the groups at any time point. Paraffin histology revealed no adverse reactions associated with the RMP. The RMP pre-filled with DBM and combined with autograft or filled with autograft alone remodeled in the same manner as the positive control. The RMP progressively resorbed with time and was nearly completely resorbed by 8 weeks with no adverse cellular or tissue reactions. CONCLUSIONS The RMP facilitated graft placement and handling and did not impede the biology of healing and remodeling of autograft in the single-level rabbit spine model. FDA DEVICE/DRUG STATUS Resorbable Mesh Bag (Ballast) (Approved for this indication)

BACKGROUND CONTEXT Implant design, material, surfaces, graft and surgical techniques play important roles in the success of interbody fusions and the ability to radiographically assess. PEEK's positive attributes of mechanical properties and radiolucency are maintained using a molecularly bonded submicron deposition of titanium to improve bone on-growth. Novel macroscale topography features on the endplate surfaces and inside the aperture were hypothesized to allow early bone integration and mechanical stability. PURPOSE To evaluate the effect of macroscale topography on a PEEK/Titanium composite cage in a large animal model of interbody fusion. STUDY DESIGN/SETTING Preclinical large animal model. PATIENT SAMPLE Not applicable. OUTCOME MEASURES Not applicable METHODS Lateral L45 interbody fusions were performed in 4-5-year-old ewes using a PEEK/titanium composite cage (Control group) compared to the same cage with macro 3D features on the endplate and inside the aperture (Test group). Iliac crest autograft was placed in the aperture and bilateral pedicle screws and rods for posterior stabilisation. Fusion assessment at 6 and 12 weeks (n=10 per group) included manual palpation, X-rays, mCT, tensile testing and pmMA histology. RESULTS The Test group's manual palpation was 9/10 and 10/10 at 6 and 12 weeks while the control was 4/10 and 7/10 at 6 and 12 weeks. Radiographs and mCT confirmed new bone formation in the aperture of the Control group cages with time while some areas of aperture radiolucency were present. Radiographs and mCT of the Test group cages revealed new bone formation and integration within the topography features on the endplates and inside the aperture which progressed with time. Histology confirmed the radiographic findings in the control group and integration with the host endplates and remodeled bone within the apertures in the Test group. Tensile testing demonstrated nearly a 3-fold statistically significant increase in mechanical properties at both time points for the Test group vs the control group. CONCLUSIONS The macroscale features in the Test group provided multiple opportunities for bone integration between the host endplates and graft within the aperture. Early bony integration translated to a statistically significant increase in mechanical strength compared to the control cage which did not include the same geometric features. Promising data in this clinically relevant animal model warrants further study in humans. FDA DEVICE/DRUG STATUS Shoreline RT (Approved for this indication).

The Jumpstart Our Business Startups (JOBS) Act of 2012 aims at increasing funding access for young firms by easing securities regulation. Motivated by this, we ask if there is a role for the regulation of the market of funds for firms that lack collateral and have a large uncertainty about their ability to generate profits. To answer that we characterize optimal financial contracts in a competitive environment with risk, adverse selection and limited liability. We find that competition among financial intermediaries always forces them to fund projects with negative expected returns both from a private and from a social perspective. Intermediaries use steep payoff schedules to screen entrepreneurs, but limited liability implies this can only be done by giving more to all entrepreneurs.

“El elevado desempleo y la baja creacion de empleo formal siguen siendo importantes cuellos de botella en la economia colombiana, impidiendo que un robusto crecimiento incida en una mayor reduccion de la pobreza y en mayor bienestar. Entender la fuente de estos problemas y enfrentarlos es clave para garantizar la sostenibilidad del crecimiento y la de los sistemas de seguridad social, cuyo funcionamiento depende del mercado de trabajo. Sin embargo, se sabe todavia muy poco acerca de las causas del pobre desempeno laboral en Colombia. Este volumen viene a cubrir ese vacio, presentando informacion novedosa acerca de las tendencias y dinamicas laborales en Colombia, y analizando los efectos que el ciclo economico, el cambio tecnologico y el marco regulatorio generan sobre la situacion laboral. Sin duda, una obra esencial para los que quieran entender la realidad economica colombiana”. Carmen Pages, 2012, Jefe Unidad de Mercados Laborales y Seguridad Social del Banco Interamericano de Desarrollo.

Using the 2003 and 2008 Quality of Life Surveys (QLS) conducted by the National Department of Statistics (DANE), this paper identifies the factors that affect housing tenure decisions in Colombia. Households with higher incomes are more likely to purchase than to rent, and the choice of formal housing is positively associated with wealth. Households eligible for social housing subsidies are more likely to purchase than to rent, and those working in the informal sector are more likely to purchase informal dwellings. Subsidies and access to mortgage credit have a large positive impact on demand. Finally, savings have a positive effect on demand in 2008, but not in 2003. The positive effect on demand of both subsidies and credit is explained by demand for low-income housing.

Informality is at the center of the economic debate in Colombia, fueled by the high level prevalent in the country and its substantial increase during the 1990s. We study the effect of labor market rigidities, namely the increase in non-wage costs and the minimum wage on the size of the informal sector, the transition into and out of informality, and wages. Our results indicate that rises in non-wage costs and the minimum wage, increase the probability of transition into informality as well as the size of the informal sector. The analysis of these effects along the income distribution points towards strong exclusion motives for low skilled informal workers, mainly driven by labor demand adjustments in response to increasing hiring costs; and argues somehow in favor of exit motives for workers at the top of the wage distribution. Furthermore, there is strong indexation of salaries to the minimum wage, except for low skilled informal workers. In addition, firms adjust salaries in response to increasing non-wage costs for all workers within the labor force.