Hospital-Acquired Venous Thromboembolism or Bleeding Following Total Joint Arthroplasty: A Systematic Review and meta-analysis for the Association of the Gene Polymorphism.

This review seeks to understand the current existing literature on genetic polymorphisms to VTE following orthopedic surgery. Using PRISMA guidelines, 234 studies were retrieved from PubMed and Cochrane. The eligibility assessment yielded 16 studies including a systematic review. A STREGA and STROBE quality assessment found these studies to have high methodological quality. A significant association was found between the PAI-1 4G/4G genotype and resistance to anticoagulation therapy (OR = 2.692; 95% CI = 1.302 - 4.702). Moreover, the MTHFR C677T and A1298C polymorphisms significantly increased the incidence of VTE in patients that are compound heterozygotes (OR = 2.89; 95% CI = 1.40 – 5.96; p = .006). A significant association was also found for the Factor XI C25264C polymorphism (OR = 2.42; 95% CI 1.16 – 5.03). Finally, SNP rs710446 of the KNG1 gene (OR = 1.27; p = .00016), and SNP rs2069588 in the 3’ UTR of the BDK4B2 (OR = 1.29; p = .00056) were also significantly associated with VTE following orthopedic surgery

2.5D and conformal negative stiffness honeycombs under static and dynamic loading

Negative stiffness honeycombs have been shown to provide nearly ideal impact mitigation with elastically recoverable configuration and mechanical behavior. This capability allows for reliable mitigation of multiple impacts, which conventional honeycombs cannot accommodate because of plastic deformation and collapse. A more in-depth characterization of the mechanical behavior of these negative stiffness honeycombs is presented. The starting point is a 2.5D configuration in which the negative stiffness honeycomb configuration is varied in-plane and extruded out-of-plane. Impact mitigation is investigated by subjecting the 2.5D honeycombs to various drop heights on a purpose-built, drop-test rig. Several embodiments of the 2.5D honeycomb are designed and tested, including nylon versus aluminum, constrained versus unconstrained, and altered configurations with different numbers of rows and columns of negative stiffness elements. While the 2.5D configuration performs well in response to in-plane loading, it is not designed to accommodate out-of-plane loading. A conformal negative stiffness honeycomb design is introduced that conforms to curved surfaces and accommodates out-of-plane loading that is not orthogonal to the load concentrator on top of the honeycomb. Quasi-static mechanical and dynamic mechanical impulse testing of the conformal honeycomb are conducted to characterize the mechanical performance of the conformal design. The final chapter includes a multi-element study that demonstrates how multiple elements perform in an assembly in a more realistic setting. A FEA framework is built to automate the simulation of the 2.5D and conformal negative stiffness honeycomb designs. The framework is built within the commercial Abaqus® FEA package using its Python scripting interface. Automating the design, meshing, loading, and boundary conditions allows for rapid design iteration. Simulations using the FEA framework are compared to experimental quasi-static, impact, and impulse tests. The conformal design was developed to be manufactured additively. The additive manufacturing process introduces sources of potentially significant geometric and material property variability that affect the performance of the honeycombs. The FEA framework is used to conduct a predictability and reliability study that incorporates several sources of variability into the analysis and returns estimates of the expected force threshold and its distribution.Mechanical Engineerin

A high-speed optical star network using TDMA and all-optical demultiplexing techniques

The authors demonstrate the use of time-division multiplexing (TDM) to realize a high capacity optical star network. The fundamental element of the demonstration network is a 10 ps, wavelength tunable, low jitter, pulse source. Electrical data is encoded onto three optical pulse trains, and the resultant low duty cycle optical data channels are multiplexed together using 25 ps fiber delay lines. This gives an overall network capacity of 40 Gb/s. A nonlinear optical loop mirror (NOLM) is used to carry out the demultiplexing at the station receiver. The channel to be switched out can be selected by adjusting the phase of the electrical signal used to generate the control pulses for the NOLM. By using external injection into a gain-switched distributed feedback (DFB) laser we are able to obtain very low jitter control pulses of 4-ps duration (RMS jitter <1 ps) after compression of the highly chirped gain switched pulses in a normal dispersive fiber. This enables us to achieve excellent eye openings for the three demultiplexed channels. The difficulty in obtaining complete switching of the signal pulses is presented. This is shown to be due to the deformation of the control pulse in the NOLM (caused by the soliton effect compression). The use of optical time-division multiplexing (OTDM) with all-optical switching devices is shown to be an excellent method to allow us to exploit as efficiently as possible the available fiber bandwidth, and to achieve very high bit-rate optical networks

Tunable transform-limited pulse generation using self-injection locking of an FP laser

Wavelength-tunable, near transform-limited pulses have been generated using a Fabry-Perot laser diode coupled to a fiber loop containing a fiber Fabry-Perot resonator (FFPR) and a polarization controller. The ratio of transmitted to reflected light from the loop can be adjusted using the polarization controller. Single-mode operation of the gain-switched laser is achieved by self-injection locking, which is induced by light reflected from the fiber loop. The resulting output pulse has a time-bandwidth product of 0.4 and is tunable over about 15 nm by varying the tuning voltage of the FFPR

Optimized performance map of an EAM for pulse generation and demultiplexing via FROG characterization

We demonstrate the complete characterization of a sinusoidally driven electro-absorption modulator (EAM) over a range of RF drive voltages and reverse bias conditions. An accurate performance map for the EAM, to be employed as a pulse generator and demultiplexer in an optical time division multiplexed (OTDM) system, can be realized by employing the Frequency Resolved Optical Gating technique. The generated pulses were characterized for chirp, extinction ratio (ER) and pulse width (<4 ps). The optimization of the EAM’s drive conditions is important to ensure that the generated pulses have the required spectral and temporal characteristics to be used in high-speed systems. The ER and pulse width also influence the demultiplexing performance of an EAM in an OTDM system. This is confirmed by utilizing the EAM as a demultiplexer in an 80 Gb/s OTDM system and measuring the BER as a function of the received optical power for various values of the ER and pulse width. It is of paramount importance to accurately characterize the performance of each individual EAM as the modulators characteristics are device dependant, thus optimum performance can be achieved with slight variations to the device’s drive conditions. By employing FROG, an optimum performance map of each specific device can be deduced. Simulations carried out verified the experimental results achieved

A Pressure-Induced Incommensurate Phase in Ammonium Hydrogen Oxalate Hemihydrate

We report evidence for the existence of a new incommensurate phase in a crystal of ammonium hydrogen oxalate hemihydrate. This phase is remarkable in two aspects: it exists only above a critical pressure Pc, and the incommensurate wave vector, which is parallel to the vector c* of the reciprocal lattice, has the largest variation ever reported, varying continuously from 0.147c* at 4.3 kbar to ~ 0.25c* at the maximum pressure (8 kbar) used to date

Time resolved chirp measurements of gain switched semiconductor laser using a polarization based optical differentiator

We present a novel implementation of the “phase reconstruction using optical ultra fast differentiation” (PROUD) technique and apply it to characterize the time resolved chirp of a gain switched semiconductor laser. The optical temporal differentiator is a fiber based polarization interferometer. The method provides a fast and simple recovery of the instantaneous frequency from two temporal intensity measurements, obtained by changing the spectral response of the interferometer. Pulses with different shapes and durations of hundreds of picoseconds are fully characterized in amplitude and phase. The technique is validated by comparing the measured pulse spectra with the reconstructed spectra obtained from the intensity and the recovered phase