3D printing of PEEK-based medical devices

open access articlePolyether-ether-ketone (PEEK) is an excellent thermoplastic alternative to metallic biomaterials which is used for loadbearing applications due to its high strength and stiffness, and biocompatibility with no cytotoxic effects. However, a potential clinical concern is that PEEK alone is not bioactive enough, and thus has limited fixation to bone. To overcome this problem, bioactive materials and/or porosity are incorporated into PEEK medical devices. The latest developments in these two strategies are presented. in this paper. Bioactive PEEK/hydroxyapatite (HA) prepared by integration of 3D printing and compression molding is presented in this paper. In addition, nozzle and build plate temperatures for 3D printing of porous PEEK were optimized using genetic algorithm (GA) to achieve the highest mechanical strength for load bearing applications such as spinal fusion cages

Carotid body tumor resection utilizing a covered stent graft to enable resection of the tumor en bloc with the internal carotid artery

Surgical excision is the primary treatment for carotid body tumors (CBT) and infrequently involves carotid vessels reconstruction. A CBT that extends distally to the level of the skull base makes surgical reconstruction very challenging. We report a case of a 30-year-old man who presented with a CBT (Shamblin III) extending to the base of the skull. A covered stent graft was placed in the internal carotid artery. Subsequently, a successful resection of the tumor with the arterial wall en bloc was performed, leaving the stent graft exposed as a bridge between the two ends of ICA

Momentum-dependent relaxation dynamics of the doped repulsive Hubbard model

We study the dynamical behavior of doped electronic systems subject to a global ramp of the repulsive Hubbard interaction. We start with formulating a real-time generalization of the fluctuation-exchange approximation. Implementing this numerically, we investigate the weak-coupling regime of the Hubbard model both in the electron-doped and hole-doped regimes. The results show that both local and nonlocal (momentum-dependent) observables evolve toward a thermal state, although the temperature of the final state depends on the ramp duration and the band filling. We further reveal a momentum-dependent relaxation rate of the distribution function in doped systems and trace back its physical origin to the anisotropic self-energies in the momentum space

Short range Coulomb correlations render massive Dirac fermions massless

Tight binding electrons on a honeycomb lattice are described by an effective Dirac theory at low energies. Lowering symmetry by an alternate ionic potential ($\Delta$) generates a single-particle gap in the spectrum. We employ the dynamical mean field theory (DMFT) technique, to study the effect of on-site electron correlation ($U$) on massive Dirac fermions. For a fixed mass parameter $\Delta$, we find that beyond a critical value $U_{c1}(\Delta)$ massive Dirac fermions become massless. Further increasing $U$ beyond $U_{c2}(\Delta)$, there will be another phase transition to the Mott insulating state. Therefore the competition between the single-particle gap parameter, $\Delta$, and the Hubbard $U$ restores the semi-metallic nature of the parent Hamiltonian. The width of the intermediate semi-metallic regime shrinks by increasing the ionic potential. However, at small values of $\Delta$, there is a wide interval of $U$ values for which the system remains semi-metal.Comment: 4 pages, 5 figure

Soil Moisture Data for the Validation of Permafrost Models Using Direct and Indirect Measurement Approaches at Three Alpine Sites

To date, there has been no comprehensive review of the epidemiology, risk factors, species distribution, and outcomes of candidemia in Iran. This study aimed to perform a systematic review and meta-analysis of all reported candidemia cases in Iran until December 2015. The review process occurred in three steps, namely a literature search, data extraction and statistical analyses. After a comprehensive literature search, we identified 55 cases. The mean age of patients was 46.80±24.30 years (range 1–81 years). The main risk factors for candidemia were surgery and burns (23.6%), followed by malignancies (20%), use of broad-spectrum antibiotics (18.2%), and diabetes (7.3%). Candida parapsilosis (n=17, 30.8%) was the leading agent, followed by Candida albicans (n=15, 27.3%), Candida glabrata (n=10, 18.2%), and Candida tropicalis (n=8, 14.5%). The frequencies of candidemia cases due to C. glabrata, C. parapsilosis, and C. albicans were significantly higher among patients aged>60, 21–40, and 41–60 years, respectively. Comparison of risk factors for candidemia by multiple logistic regression showed that one of the most important risk factors was surgery (OR: 4.245; 95% CI: 1.141–15.789; P=0.031). The outcome was recorded in only 19 cases and 13 of those patients (68.4%) expired. This study confirms that knowledge of the local epidemiology is important when conducting surveillance studies to prevent and control candidemia and will be of interest for antifungal stewardship

Implementation of wampac security and stability improvement of power grids with systems

In this paper, due to the importance of extensive monitoring, protection and control systems as well as the importance of hybrid systems, both the AC and DC sectors have been attempted to make the implementation of the WAMPAC system more transparent to these types of networks. As a general rule, the main purpose of using extensive monitoring, protection and control systems is to consider the stability and security of power systems. Therefore, in this paper, the above principles are considered and, with respect to the sample network, the relevant strategies have been implemented, and the simulation results point to improving security and stability in the power grid