Phase-stable, downconverting, microwave photonic link with analysis of balanced heterodyne detection intermodulation.

A coherent downconverting microwave photonic link using balanced heterodyne detection of single-sideband modulated optical signals is analyzed and demonstrated. The intermodulation analysis shows that the second-order photodetector nonlinearity can be the limiting factor in the third-order intermodulation spur performance. The link is designed to phase coherently downconvert 17 GHz of bandwidth in an extended K-band (23-45 GHz) to 1-18 GHz to match the capabilities of modern receivers. The application of the link is for a low-loss >20 µs analog buffer. Spur performance of 112.4 dB/Hz(2/3) is demonstrated when background noise is limited by shot noise.

Rolling and pitching oscillating foil propulsion in ground effect.

In this paper, we investigate the effect of operating near a solid boundary on the forces produced by harmonically oscillating thrust-generating foils. A rolling and pitching foil was towed in a freshwater tank in a series of experiments with varying kinematics. Hydrodynamic forces and torques were measured in the freestream and at varying distances from a solid boundary, and changes in mean lift and thrust were found when the foil approached the boundary. The magnitude of this ground effect exhibited a strong nonlinear dependence on the distance between the foil and the boundary. Significant effects were found within three chord lengths of the boundary, and ground effect can be induced at greater distances from the boundary by biasing the tip of the foil toward the boundary. Lift coefficients changed by as much as [Formula: see text] at the closest approach to the ground, with changes [Formula: see text] [Formula: see text] for all cases across Strouhal numbers ranging from [Formula: see text] to [Formula: see text], and nominal maximum angle of attack ranging from [Formula: see text] to [Formula: see text]. The ubiquity of the ground effect in high thrust kinematics suggests that the ground effect can provide a passive obstacle avoidance capability for foil propelled vehicles. By comparison with previous experimental work, we find that the ground effect experienced by a high-aspect ratio rolling and pitching foil is a fully three-dimensional phenomenon, as it is not accurately predicted when two-dimensional flow and/or two-dimensional kinematics are enforced. While two-dimensional foil kinematics are more easily modeled for numerical studies, three-dimensional foil kinematics may be more practical for real world implementation in underwater vehicles.

Differences in the Treatment of Distal Radius Fractures by Hand Fellowship Trained Surgeons: A Study of ABOS Candidate Data.

PURPOSE: The management of distal radius fractures differs based on the nature of the fracture and the experience of the surgeon. We hypothesized that patients requiring surgical intervention would undergo different procedures when in the care of a surgeon with subspecialty training in hand surgery as compared with surgeons with no subspecialty training in hand surgery. METHODS: We queried the ABOS database for case log information submitted for part II of the ABOS examination. Queries for all codes involved with distal radius fracture management were combined with associated codes for the management of median nerve neuropathy, triangular fibrocartilage complex tears, ulnar shaft, and styloid fractures. Hand fellowship trained orthopedic surgeons were compared with those completing other fellowships and non-fellowship trained orthopedic surgeons during their board collection period. RESULTS: During the study period, 2,317 orthopedic surgeons reported treatment of 15,433 distal radius fractures. Of these surgeons, 411 had hand fellowship training. On a per surgeon basis, fellowship trained hand surgeons operatively treated more multifragment intra-articular distal radius fractures than their non-hand fellowship trained counterparts (5.3 vs 1.2). Additional procedures associated with the management of distal radius fractures were also associated with the fellowship training of the treating surgeon. CONCLUSIONS: Among orthopedic surgeons taking part II of the ABOS certifying examination, differences exist in the type, management, and reporting of distal radius fractures among surgeons with different areas of fellowship training. CLINICAL RELEVANCE: This study describes the association of hand surgery fellowship training on the choice of intervention for distal radius fractures and associated conditions.

Can Radiocarpal-Spanning Fixation Be Made More Functional by Placing the Wrist in Extension? A Biomechanical Study Under Physiologic Loads.

We investigate whether applying an internal radiocarpal-spanning plate with the wrist in slight extension affects the biomechanical stability of the construct. An unstable distal radius fracture was simulated in 10 cadaveric specimens and immobilized with a radiocarpal-spanning plate holding the wrist in a neutral position. This construct was then physiologically loaded through the wrist flexor and extensor tendons. The resulting motion at the fracture was captured with a displacement sensor. The plate was then extended using an in situ bending technique, placing the wrist in extension, and the experiment was repeated. No statistically significant difference in the biomechanical stability afforded by the radiocarpal-spanning plate was detected with the wrist in extension compared to that in the traditional neutral position. The radiocarpal-spanning plate fixation was more stable when loaded through the extensor tendons. We conclude that immobilizing a distal radius fracture with an internal radiocarpal-spanning plate that holds the wrist in extension does not compromise biomechanical stability.

Anatomic relationships in distal radius bridge plating: a cadaveric study.

BACKGROUND: Two separate approaches have been described for radiocarpal spanning internal fixation for high-energy distal radius fractures with metaphyseal extension. To our knowledge, relevant anatomic relationships and structures at risk for iatrogenic injury have not been identified in the literature. METHODS: Twelve fresh frozen cadaver arms were randomized to fixation with a dorsal radiocarpal spanning plate using one of two techniques: (1) index finger metacarpal fixation (index group) or (2) middle finger metacarpal fixation (middle group). Cadaveric dissection and relevant anatomic relationships were assessed in relation to the plate. RESULTS: Superficial branches of the radial sensory nerve were in contact with the index group plate in all specimens, while no contact occurred in the middle group specimens. No extensor digitorum comminus (EDC) middle extensor tendons contacted the plate in the index group; an average of 10 cm of plate contact was seen in the middle group. The extensor pollicis longus (EPL) tendon contacted the plate in both the index and middle groups for an average distance of 12.4 and 25.5 mm, respectively. One complication [EPL and extensor indicis proprius (EIP) entrapment] was observed in the middle finger metacarpal group. CONCLUSION: Mounting the dorsal bridge plate to the index finger metacarpal places the superficial branches of the radial sensory nerve at risk during dissection, while mounting the plate to the middle finger metacarpal leads to a greater degree of tendon-plate contact.

Chronic Scapholunate Ligament Injuries: Treatment with Supplemental Fixation.

Treatment of chronic scapholunate ligament injuries can be challenging. Traditional reconstructive techniques, including varied capsulodeses and tenodeses often yield inconsistent results with loss of reduction and radiographic deterioration. As a result, supplemental hardware fixation has become more popular and may allow more robust stabilization of the scapholunate reconstruction. However, these procedures have complications and few data regarding outcomes are currently available. This article evaluates the role of supplemental fixation in the management of chronic scapholunate instability.

Risk factors for failure of a single surgical debridement in adults with acute septic arthritis.

BACKGROUND: Acute septic arthritis in a native joint may require more than one surgical debridement to eradicate the infection. Our objectives were to determine the prevalence of failure of a single surgical debridement for acute septic arthritis, to identify risk factors for failure of a single debridement, and to develop a prognostic probability algorithm to predict failure of a single surgical debridement for acute septic arthritis in adults. METHODS: We collected initial laboratory and medical comorbidity data of 128 adults (132 native joints) with acute septic arthritis who underwent at least one surgical debridement at our institution between 2000 and 2011. Univariate and logistic regression analyses were used to identify potential risk factors for failure of a single surgical debridement. Stepwise variable selection was used to develop a prediction model and identify probabilities of failure of a single surgical debridement. RESULTS: Of the 128 patients (132 affected joints) who underwent surgical debridement for acute septic arthritis, forty-nine (38%) of the patients (fifty joints) experienced failure of a single debridement and required at least two debridements (range, two to four debridements). Staphylococcus aureus was the most common bacterial isolate (in sixty, or 45%, of the 132 joints). Logistic regression analysis identified five independent clinical predictors for failure of a single surgical debridement: a history of inflammatory arthropathy (odds ratio [OR], 7.3; 95% confidence interval [CI], 2.4 to 22.6; p < 0.001), the involvement of a large joint (knee, shoulder, or hip) (OR, 7.0; 95% CI, 1.2 to 37.5; p = 0.02), a synovial-fluid nucleated cell count of >85.0 x 10(9) cells/L (OR, 4.7; 95% CI, 1.8 to 17.7; p = 0.002), S. aureus as the bacterial isolate (OR, 4.6; 95% CI, 1.8 to 11.9; p = 0.002), and a history of diabetes (OR, 2.6; 95% CI, 1.1 to 6.2; p = 0.04). CONCLUSIONS: Most (62%) of the septic joints were managed effectively with a single surgical debridement. Adults with a history of inflammatory arthropathy, involvement of a large joint, a synovial-fluid nucleated cell count of >85.0 x 10(9) cells/L, an infection with S. aureus, or a history of diabetes had a higher risk of failure of a single surgical debridement for acute septic arthritis and requiring additional surgical debridement(s).

Synthetic aperture ladar imaging demonstrations and information at very low return levels.

We present synthetic aperture ladar (SAL) imaging demonstrations where the return-signal level from the target is near the single-photon level per resolved pixel. Scenes consisting of both specular-point targets and diffuse-reflection, fully speckled targets are studied. Artificial retro-reflector-based phase references and/or phase-gradient-autofocus (PGA) algorithms were utilized for compensation of phase errors during the aperture motion. It was found that SAL images could reliably be formed with both methods even when the final max pixel intensity was at the few photon level, which means the SNR before azimuth compression is below unity. Mutual information-based comparison of SAL images show that average mutual information is reduced when the PGA is utilized for image-based phase compensation. The photon information efficiency of SAL and coherent imaging is discussed.

Primary Arthrodesis of the Tibiotalar Joint in Severely Comminuted High-Energy Pilon Fractures.

BACKGROUND: The treatment of highly comminuted tibial pilon fractures is controversial. The aim of this study was to determine the effectiveness and outcomes of primary arthrodesis following highly comminuted tibial plafond fractures. METHODS: A database search was performed to identify all patients who underwent blade plate arthrodesis at our institution over a sixteen-year period. Inclusion criteria included patients with an Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association type-C2 or type-C3 pilon fracture that was deemed to be non-reconstructable by the treating surgeon. Outcomes were measured using the Short-Form 36-Item Health Survey, time to independent walking, time to consolidation of the arthrodesis, and wound-healing complications. RESULTS: A total of twenty patients were included in this study, and seventeen patients (85%) were available for follow-up at a minimum of two years after their surgery. Wound infections or wound dehiscence did not occur in this series. All patients were walking without crutches or a walker at their latest follow-up. One patient developed an aseptic nonunion and healed successfully after revision surgery. CONCLUSIONS: Blade plate ankle fusion using a posterior approach is a reliable method for the treatment of a small subset of patients with severely comminuted, non-reconstructable pilon fractures. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Shot noise statistics and information theory of sensitivity limits in frequency-modulated continuous-wave ladar.

A theoretical analysis and experimental verification of the sensitivity limits of frequency-modulated continuous-wave (FMCW) ladar in the limit of a strong local oscillator is presented. The single-photon sensitivity of coherent heterodyne detection in this shot-noise dominated limit is verified to extend to linearly chirped waveforms. An information theoretic analysis is presented to estimate the information efficiency of received photons for the task of locating the range to single and multiple targets. It is found that the optimum receive signal level is proportional to the logarithm of the number of resolvable range locations and the maximum theoretical photon information efficiency for FMCW ranging with coherent fields is log(e)≈1.44 bits per received photon.

Maximum-likelihood estimation for frequency-modulated continuous-wave laser ranging using photon-counting detectors.

We analyze the minimum achievable mean-square error in frequency-modulated continuous-wave range estimation of a single stationary target when photon-counting detectors are employed. Starting from the probability density function for the photon-arrival times in photodetectors with subunity quantum efficiency, dark counts, and dead time, we derive the Cramér-Rao bound and highlight three important asymptotic regimes. We then derive the maximum-likelihood (ML) estimator for arbitrary frequency modulation. Simulation of the ML estimator shows that its performance approaches the standard quantum limit only when the mean received photons are between two thresholds. We provide analytic approximations to these thresholds for linear frequency modulation. We also compare the ML estimator's performance to conventional Fourier transform (FT) frequency estimation, showing that they are equivalent if the reference arm is much stronger than the target return, but that when the reference field is weak the FT estimator is suboptimal by approximately a factor of √2 in root-mean-square error. Finally, we report on a proof-of-concept experiment in which the ML estimator achieves this theoretically predicted improvement over the FT estimator.

Functional outcomes, morbidity, mortality, and fracture healing in 26 consecutive geriatric odontoid fracture patients treated with posterior fusion.

STUDY DESIGN: Retrospective review. OBJECTIVE: To evaluate functional outcomes, fracture healing, complications, and mortality associated with posterior fusion surgery (PSF) for the management of geriatric type II odontoid fractures. SUMMARY OF BACKGROUND DATA: Outcomes of C1-2 fusion for geriatric odontoid fractures are not well defined. METHODS: Twenty-six consecutive elderly patients with type II odontoid fractures were treated by the same spinal surgeon at a Level-1 trauma center during an 8-year period. All patients had ≥50% odontoid displacement and were treated with PSF including C1-2 (PSF group; average age, 79 y). Chart reviews were performed evaluating patient comorbidities, treatment complications, and mortality rates. At ultimate follow-up, patients had open mouth, flexion, and extension radiographs to assess fracture stability and healing. In addition, functional outcomes were assessed using Neck Disability Index (NDI), analog pain, and satisfaction questionnaire scores and compared with a group of 40 aged-matched control patients (control group; average age, 79.8 y). RESULTS: The mortality rate was 19.2%, and major complications occurred in 27% of patients. At an average 13-month follow-up (range, 3-48 mo), the fracture-healing rate was only 33%. However, no patient had mobile odontoid nonunion or instability of the C1-2 articulation. NDI scores averaged 18.1 points indicating only mild residual disability. Pain scores were low averaging only 1.8 points. NDI and pain scores did not differ significantly from aged-matched controls (P = 0.16). Treatment satisfaction scores were high. Odontoid nonunion was not associated with significantly higher levels of disability or neck pain and did not affect scores for patient satisfaction. CONCLUSIONS: PSF for geriatric odontoid fractures is associated with moderately high levels of morbidity and mortality. Posttreatment neck pain and disability is low and does not differ significantly from aged-matched cohorts. Odontoid fracture healing after surgical stabilization does not correlate with improved functional outcomes.

Characterization of an actively linearized ultrabroadband chirped laser with a fiber-laser optical frequency comb.

The optical frequency sweep of an actively linearized, ultrabroadband, chirped laser source is characterized through optical heterodyne detection against a fiber-laser frequency comb. Frequency sweeps were measured over approximately 5 THz bandwidths from 1530 nm to 1570 nm. The dominant deviation from linearity resulted from the nonzero dispersion of the fiber delay used as a reference for the sweep linearization. Removing the low-order dispersion effects, the residual sweep nonlinearity was less than 60 kHz rms, corresponding to a constant chirp with less than 15 ppb deviation across the 5 THz sweep.

Predictors of survival from out-of-hospital cardiac arrest: a systematic review and meta-analysis.

BACKGROUND: Prior studies have identified key predictors of out-of-hospital cardiac arrest (OHCA), but differences exist in the magnitude of these findings. In this meta-analysis, we evaluated the strength of associations between OHCA and key factors (event witnessed by a bystander or emergency medical services [EMS], provision of bystander cardiopulmonary resuscitation [CPR], initial cardiac rhythm, or the return of spontaneous circulation). We also examined trends in OHCA survival over time. METHODS AND RESULTS: An electronic search of PubMed, EMBASE, Web of Science, CINAHL, Cochrane DSR, DARE, ACP Journal Club, and CCTR was conducted (January 1, 1950 to August 21, 2008) for studies reporting OHCA of presumed cardiac etiology in adults. Data were extracted from 79 studies involving 142 740 patients. The pooled survival rate to hospital admission was 23.8% (95% CI, 21.1 to 26.6) and to hospital discharge was 7.6% (95% CI, 6.7 to 8.4). Stratified by baseline rates, survival to hospital discharge was more likely among those: witnessed by a bystander (6.4% to 13.5%), witnessed by EMS (4.9% to 18.2%), who received bystander CPR (3.9% to 16.1%), were found in ventricular fibrillation/ventricular tachycardia (14.8% to 23.0%), or achieved return of spontaneous circulation (15.5% to 33.6%). Although 53% (95% CI, 45.0% to 59.9%) of events were witnessed by a bystander, only 32% (95% CI, 26.7% to 37.8%) received bystander CPR. The number needed to treat to save 1 life ranged from 16 to 23 for EMS-witnessed arrests, 17 to 71 for bystander-witnessed, and 24 to 36 for those receiving bystander CPR, depending on baseline survival rates. The aggregate survival rate of OHCA (7.6%) has not significantly changed in almost 3 decades. CONCLUSIONS: Overall survival from OHCA has been stable for almost 30 years, as have the strong associations between key predictors and survival. Because most OHCA events are witnessed, efforts to improve survival should focus on prompt delivery of interventions of known effectiveness by those who witness the event.

Demonstrations of analog-to-digital conversion using a frequency domain stretched processor.

The first proof-of-concept demonstrations are presented for a broadband photonic-assisted analog-to-digital converter (ADC) based on spatial spectral holography (SSH). The SSH-ADC acts as a frequency-domain stretch processor converting high bandwidth input signals to low bandwidth output signals, allowing the system to take advantage of high performance, low bandwidth electronic ADCs. Demonstrations with 50 MHz effective bandwidth are shown to highlight basic performance with approximately 5 effective bits of vertical resolution. Signal capture with 1600 MHz effective bandwidth is also shown. Because some SSH materials span over 100 GHz and have large time apertures (approximately 10 micros), this technique holds promise as a candidate for the next generation of ADCs.

Analysis of mercury in wastewater by microwave digestion followed by inductively coupled plasma mass spectrometry: comparison with u.s. environmental protection agency methods approved in 40 CFR 136.3.

As a cost-saving measure, the use of an existing microwave digestion system and inductively coupled plasma mass spectrometry instrument was investigated for the analysis of mercury in domestic wastewater, industry effluent, stormwater, and other aqueous matrices analyzed under the City of Portland's (Oregon) various National Pollutant Discharge Elimination System (NPDES) permits. A formal alternate test procedure application (ATP) study was undertaken to add total mercury to the analyte list for the CEM microwave digestion method (CEM Corporation, 1992) and for U.S. Environmental Protection Agency (Washington, D.C.) (U.S. EPA) method 200.8, both approved for NPDES work in 40 CFR 136.3 (U.S. EPA, 2001a). The ATP was submitted in March 2005, and final approval was received in November 2006. During the study period and while waiting for approval, all NPDES mercury samples were sent to a contract laboratory for analysis by U.S. EPA method 1631E (U.S. EPA, 2002). Splits were analyzed in-house by the ATP protocol. For treatment plant wastewater and industrial effluents, the 1631E results averaged approximately one-half of those obtained by the ATP method, with a 1% difference slightly above 1000% (order of magnitude) and several in the 200% to 300% range. Preliminary results were confirmed by further studies that compared the ATP method with the room temperature and the heated, closed-vessel digestion option of U.S. EPA methods 245.7 and 1631E (U.S. EPA, 2001b, 2002). This research suggests that the room temperature bromine chloride (BrCl) digestion is ill-suited for the determination of total mercury in wastewater and industrial effluents. Because of the probability of committing type II errors--that is, assuming mercury is present in low concentrations when, in fact, it is not--results for these matrices found using the room temperature BrCl digestion should be interpreted with caution. It is suggested that such results might best be considered "bromine chloride extractable" and, as such, should not be used in studies that require accurate estimates of total mercury.

Reagent preparation and storage for amplification of microarray hybridization targets with a fully automated system.

The advent of automated systems for gene expression profiling has accentuated the need for the development of convenient and cost-effective methods for reagent preparation. We have developed a method for the preparation and storage of pre-aliquoted cocktail plates that contain all reagents required for amplification of nucleic acid by reverse transcription and in vitro transcription reactions. Plates can be stored at -80 degrees C for at least 1 month and kept in a hotel at 4 degrees C for at least 24 h prior to use. Microarray data quality generated from these pre-aliquoted reagent plates is not statistically different between cRNA amplified with stored cocktails and cRNA amplified with freshly prepared cocktails. Deployment of pre-aliquoted, stored cocktail plates in a fully automated system not only increases the throughput of amplifying cRNA targets from thousands of RNA samples, but could also considerably reduce reagent costs and potentially improve process robustness.