Metacarpal Neck Fractures: A Review of Surgical Indications and Techniques

Context: Hand injuries are a common emergency department presentation. Metacarpal fractures account for 40% of all hand fractures and can be seen in the setting of low or high energy trauma. The most common injury pattern is a metacarpal neck fracture. In this study, the authors aim to review the surgical indications for metacarpal neck fractures, the fixation options available along with the risk and benefits of each. Evidence Acquisition: Literature review of the different treatment modalities for metacarpal neck fractures. Review focuses on surgical indications and the risks and benefits of different operative techniques. Results: The indications for surgery are based on the amount of dorsal angulation of the distal fragment. The ulnar digits can tolerate greater angulation as the radial digits more easily lose grip strength. The most widely utilized fixation techniques are pinning with k-wires, dorsal plating, or intramedullary fixation. There is currently no consensus on an optimal fixation technique as surgical management has been found to have a complication rate up to 36%. Plate and screw fixation demonstrated especially high complication rates. Conclusions: Metacarpal neck fractures are a common injury in young and active patients that results in substantial missed time from work. While the surgical indications are well-described, there is no consensus on the optimal treatment modality because of high complication rates. Dorsal plating has higher complication rates than closed reduction and percutaneous pinning, but is necessary in comminuted fractures. The lack of an ideal fixation construct suggests that further study of the commonly utilized techniques as well as novel techniques is necessary

Comparison Of Structure And Properties Of Femtosecond And Nanosecond Laser-Structured Silicon

We compare the optical properties,chemical composition, and crystallinity of siliconmicrostructures formed in the presence of SF6 by femtosecond laserirradiation and by nanosecond laser irradiation. In spite of very different morphology and crystallinity, the optical properties and chemical composition of the two types of microstructures are very similar. The structures formed with femtosecond (fs) pulses are covered with a disordered nanocrystalline surface layer less than 1 μm thick, while those formed with nanosecond (ns) pulses have very little disorder. Both ns-laser-formed and fs-laser-formed structures absorb near-infrared (1.1–2.5 μm) radiation strongly and have roughly 0.5% sulfur impurities

Comparison of Structure and Properties of Femtosecond and Nanosecond Laser-Structured Silicon

We compare the optical properties, chemical composition, and crystallinity of silicon microstructures formed in the presence of SF6 by femtosecond laser irradiation and by nanosecond laser irradiation. In spite of very different morphology and crystallinity, the optical properties and chemical composition of the two types of microstructures are very similar. The structures formed with femtosecond (fs) pulses are covered with a disordered nanocrystalline surface layer less than 1 um thick, while those formed with nanosecond (ns) pulses have very little disorder. Both ns-laser-formed and fs-laser-formed structures absorb near-infrared (1.1 – 2.5 um) radiation strongly and have roughly 0.5% sulfur impurities.Engineering and Applied Science

Fabrication and subband gap optical properties of silicon supersaturated with chalcogens by ion implantation and pulsed laser melting

Topographically flat, single crystal silicon supersaturated with the chalcogens S, Se, and Te was prepared by ion implantation followed by pulsed laser melting and rapid solidification. The influences of the number of laser shots on the atomic and carrier concentration-depth profiles were measured with secondary ion mass spectrometry and spreading resistance profiling, respectively. We found good agreement between the atomic concentration-depth profiles obtained from experiments and a one-dimensional model for plane-front melting, solidification, liquid-phase diffusion, with kinetic solute trapping, and surface evaporation. Broadband subband gap absorption is exhibited by all dopants over a wavelength range from 1 to 2.5 microns. The absorption did not change appreciably with increasing number of laser shots, despite a measurable loss of chalcogen and of electronic carriers after each shot.One of the authors M.T. acknowledges the financial support of the Fulbright Program. This research was supported in part by the U.S. Army ARDEC under Contract No. W15QKN-07- P-0092

Analysis of a consumer survey on plug-in hybrid electric vehicles

Plug-in Hybrid Electric Vehicles (PHEVs) show potential to reduce greenhouse gas (GHG) emissions, increase fuel efficiency, and offer driving ranges that are not limited by battery capacity. However, these benefits will not be realized if consumers do not adopt this new technology. Several agent-based models have been developed to model potential market penetration of PHEVs, but gaps in the available data limit the usefulness of these models. To address this, we administered a survey to 1000 stated US residents, using Amazon Mechanical Turk, to better understand factors influencing the potential for PHEV market penetration. Our analysis of the survey results reveals quantitative patterns and correlations that extend the existing literature. For example, respondents who felt most strongly about reducing US transportation energy consumption and cutting greenhouse gas emissions had, respectively, 71 and 44 times greater odds of saying they would consider purchasing a compact PHEV than those who felt least strongly about these issues. However, even the most inclined to consider a compact PHEV were not generally willing to pay more than a few thousand US dollars extra for the sticker price. Consistent with prior research, we found that financial and battery-related concerns remain major obstacles to widespread PHEV market penetration. We discuss how our results help to inform agent-based models of PHEV market penetration, governmental policies, and manufacturer pricing and marketing strategies to promote consumer adoption of PHEVs. © 2014 The Authors

Supersaturating silicon with transition metals by ion implantation and pulsed laser melting

We investigate the possibility of creating an intermediate band semiconductor by supersaturating Si with a range of transition metals (Au, Co, Cr, Cu, Fe, Pd, Pt, W, and Zn) using ion implantation followed by pulsed laser melting (PLM). Structural characterization shows evidence of either surface segregation or cellular breakdown in all transition metals investigated, preventing the formation of high supersaturations. However, concentration-depth profiling reveals that regions of Si supersaturated with Au and Zn are formed below the regions of cellular breakdown. Fits to the concentration-depth profile are used to estimate the diffusive speeds, v D, of Au and Zn, and put lower bounds on v D of the other metals ranging from 10² to 10⁴ m/s. Knowledge of v D is used to tailor the irradiation conditions and synthesize single-crystal Si supersaturated with 10¹⁹ Au/cm³ without cellular breakdown. Values of v D are compared to those for other elements in Si. Two independent thermophysical properties, the solute diffusivity at the melting temperature, D s(T m), and the equilibrium partition coefficient, k e, are shown to simultaneously affect v D. We demonstrate a correlation between v D and the ratio D s(T m)/k e ⁰·⁶⁷, which is exhibited for Group III, IV, and V solutes but not for the transition metals investigated. Nevertheless, comparison with experimental results suggests that D s(T m)/k e ⁰·⁶⁷ might serve as a metric for evaluating the potential to supersaturate Si with transition metals by PLM.Research at Harvard was supported by The U.S. Army Research Office under contracts W911NF-12-1-0196 and W911NF-09-1-0118. M.T.W. and T.B.’s work was supported by the U.S. Army Research Laboratory and the U.S. Army Research Office under Grant No. W911NF-10-1-0442, and the National Science Foundation (NSF) Faculty Early Career Development Program ECCS-1150878 (to T.B.). M.J.S., J.T.S., M.T.W., T.B., and S.G. acknowledge a generous gift from the Chesonis Family Foundation and support in part by the National Science Foundation (NSF) and the Department of Energy (DOE) under NSF CA No. EEC- 1041895. S.C. and J.S.W.’s work was supported by The Australian Research Council. J.M. was supported by a National Research Council Research Associateship

Morphological stability during solidification of silicon incorporating metallic impurities

We study the stability of a planar solidification front during pulsed laser melting-induced rapid solidification of silicon containing high concentrations of ion-implated metallic impurities. We calculate the critical impurity concentration for destabilizing plane-front solidification, and introduce the "amplification coefficient", which is an empirical parameter describing the degree of amplification that must accord between the time the planar liquid-solid interface first becomes unstable, and the time of formation of morphological features of interface breakdown that are later observed in the microstructure. By connecting our calculations to experimental observations from the literature we determine this parameter for Au, Co, Cr, Fe, Ga, In, and Zn in (100) Si and Ti in (111) Si, and find that it increases with impurity diffusive speed vd approximately as vd^.56. We present an approximate but simple method of estimating the maximum impurity concentration that may be incorporated in a surface layer of a given thickness without the appearance of cellular breakdown.Engineering and Applied Science

Supersaturating silicon with transition metals by ion implantation and pulsed laser melting

We investigate the possibility of creating an intermediate band semiconductor by supersaturating Si with a range of transition metals (Au, Co, Cr, Cu, Fe, Pd, Pt, W, and Zn) using ion implantation followed by pulsed laser melting (PLM). Structural characterization shows evidence of either surface segregation or cellular breakdown in all transition metals investigated, preventing the formation of high supersaturations. However, concentration-depth profiling reveals that regions of Si supersaturated with Au and Zn are formed below the regions of cellular breakdown. Fits to the concentration-depth profile are used to estimate the diffusive speeds, v [subscript D], of Au and Zn, and put lower bounds on v [subscript D] of the other metals ranging from 10[superscript 2] to 10[superscript 4] m/s. Knowledge of v [subscript D] is used to tailor the irradiation conditions and synthesize single-crystal Si supersaturated with 10[superscript 19] Au/cm[superscript 3] without cellular breakdown. Values of v [subscript D] are compared to those for other elements in Si. Two independent thermophysical properties, the solute diffusivity at the melting temperature, D [subscript s](T [subscript m]), and the equilibrium partition coefficient, k [subscript e], are shown to simultaneously affect v [subscript D]. We demonstrate a correlation between v [subscript D] and the ratio D [subscript s](T [subscript m])/k [subscript e] [superscript 0.67], which is exhibited for Group III, IV, and V solutes but not for the transition metals investigated. Nevertheless, comparison with experimental results suggests that D [subscript s](T [subscript m])/k [subscript e] [superscript 0.67] might serve as a metric for evaluating the potential to supersaturate Si with transition metals by PLM.National Science Foundation (U.S.) (Faculty Early Career Development Program ECCS-1150878)Chesonis Family FoundationUnited States. Army Research Laboratory (United States. Army Research Office Grant W911NF-10-1-0442)National Science Foundation (U.S.) (United States. Dept. of Energy NSF CA EEC-1041895