Hand-Injectable Acrylic Bone Cement Applicator for Skull Base Bone Replacement

One of the only existing procedures to remove brain tumors at the skull base is endoscopic endonasal neurosurgery. The most difficult part of this surgery is closing the hole created in the skull, which currently is solved by stuffing fat and biocompatible foam in the hole and sealing it with glue. A better way of sealing this hole would be to use poly methyl methacrylate (PMMA) so that the hole is replaced with a material which more closely resembles bone. In order to better understand the delivery and application of PMMA bone cement into a patient?s skull through the nasal passages by a surgeon, we modeled three-dimensional viscous fluid flow within a surgical device prototype. The model is comprised of a 5-mm diameter tube with a 1-mm diameter wire running through its center. This wire is secured in place with vertical and horizontal supports. We analyzed the effects of the supports and wire on velocity and pressure drop of PMMA material moving through the tube to see if there was any resistance created in the tube that would be unmanageable by an unaided surgeon. To model the fluid flow, we created a three dimensional geometric schematic of the device in COMSOL. We acquired material properties from related literature and ran multiple simulations with several mesh sizes with COMSOL using the 3-D incompressible Navier-Stokes steady state application mode. The overall goal of this project was to determine if a surgeon could push PMMA through the tube without assistance from machines. Using this model we could then determine the manual pressure needed to administer the PMMA into a patient?s skull at an appropriate velocity. Our results indicated that the amount of applied pressure required would be 1.7 lbf, which is much less than the minimal value (~17 lbf) found in the literature regarding thumb strength. From simulations we obtained multiple velocity profiles and plots of pressure drop. Pressure decreases at a constant rate until the tube bends, the wire is introduced, or fluid passes by an obstruction at each point drop in pressure increases. The total amount of pressure drop in the tube was found to be 380 kPa. As we increased inlet velocity, the required applied pressure increased significantly, but not to a magnitude that would be unbearable to a human thumb. The model also gives valuable insight on the effects of obstructions on continuous, viscous fluid flow in a narrow tube

(Re)considering new agents: a review of labour market intermediaries within labour geography

The world of work continues to change. Labour markets in most countries are increasingly shaped by policies of neoliberal deregulation while strategies of flexibility dominate public policy and corporate strategy across an array of sectors. At the forefront of these changes are the myriad labour market intermediaries that are used by workers and employees to enhance their ability to navigate ever more complex and volatile labour markets. For some, mediated employment, recruitment and work practices mean greater career progression and profit making ability, but for many others, it means increased precarity, vulnerability and insecurity. This paper critically reviews existing literature within geography on three types of private labour market intermediary, namely temporary staffing agencies and contract brokers; executive search firms and headhunters; and informal intermediaries such as gangmasters. The final section addresses the future for research in labour geography and, in particular, suggests new ways in which to broaden our understanding of labour market intermediaries and their impact on worker agency

How to classify the oldest old according to their health status: A study on 1160 subjects belonging to 552 90+ Italian sib-ships characterized by familial longevity recruited within the GEHA EU Project

The health status of the oldest old, the fastest increasing population segment worldwide, progressively becomes more heterogeneous, and this peculiarity represents a major obstacle to their classification. We compared the effectiveness of four previously proposed criteria (Franceschi et al., 2000; Evert et al., 2003; Gondo et al., 2006; Andersen-Ranberg et al., 2001) in 1160 phenotypically fully characterized Italian siblings of 90 years of age and older (90+, mean age: 93 years; age range: 90-106 years) belonging to 552 sib-ships, recruited in Northern, Central and Southern Italy within the EU-funded project GEHA, followed for a six-year-survival. Main findings were: (i) "healthy" subjects varied within a large range, i.e. 5.2% (Gondo), 8.7% (Evert), 17.7% (Franceschi), and 28.5% (Andersen-Ranberg); (ii) Central Italy subjects showed better health than those from Northern and Southern Italy; (iii) mortality risk was correlated with health status independently of geographical areas; and (iv) 90+ males, although fewer in number, were healthier than females, but with no survival advantage. In conclusion, we identified a modified version of Andersen-Ranberg criteria, based on the concomitant assessment of two basic domains (cognitive, SMMSE; physical, ADL), called "Simple Model of Functional Status" (SMFS), as the most effective proxy to distinguish healthy from not-healthy subjects. This model showed that health status was correlated within sib-ships, suggesting a familial/genetic component. © 2013 Elsevier Ireland Ltd