Patients of Obese Representation Require Longer Operative Times: An Evaluation of Acetabular and Pelvic Ring Operative Duration.

Recent literature has determined that operative times for the obese population are greater for both elective and nonelective orthopedic procedures. If time allotted for a given surgical procedure is used as a measure of procedural difficulty, then consideration can be given for using an additional coding modifier (i.e., Modifier 22) for the increased skill and effort associated with longer procedures. A retrospective chart review was conducted on all patients who underwent surgical treatment for an acute fracture about the pelvis at an urban level-1 trauma center from October 1, 2010 through October 31, 2018. After allowing for both inclusion and exclusion criteria, 102 patients with acetabular fractures and 55 patients with pelvic ring injuries were included in this investigation. The obese population within the acetabular fracture cohort demonstrated significantly longer mean times for the duration of surgery, total time in spent in the operating room, and duration under anesthesia (P values of 0.038, 0.05 and 0.035, respectively). Similar results were observed with the pelvic ring injury cohort, with significantly longer procedural times (P = 0.019), total time in the operating room (P = 0.034), and total duration under anesthesia (P = 0.0395). A trend towards a greater risk of infection was found in obese patients (7%) when compared with nonobese patients (1.6%) within the acetabular fracture subset (P = 0.093). Operative duration for acetabular fractures and pelvic ring injuries is significantly longer in the obese population. Furthermore, this indicates that a Modifier 22 may be justified for the surgical treatment of these injuries in the obese and morbidly obese patient populations.

Optically Resonant Bulk Heterojunction PbS Quantum Dot Solar Cell.

We design an optically resonant bulk heterojunction solar cell to study optoelectronic properties of nanostructured p-n junctions. The nanostructures yield strong light-matter interaction as well as distinct charge-carrier extraction behavior, which together improve the overall power conversion efficiency. We demonstrate high-resolution substrate conformal soft-imprint lithography technology in combination with state-of-the art ZnO nanoparticles to create a nanohole template in an electron transport layer. The nanoholes are infiltrated with PbS quantum dots (QDs) to form a nanopatterned depleted heterojunction. Optical simulations show that the absorption per unit volume in the cylindrical QD absorber layer is enhanced by 19.5% compared to a planar reference. This is achieved for a square array of QD nanopillars of 330 nm height and 320 nm diameter, with a pitch of 500 nm on top of a residual QD layer of 70 nm, surrounded by ZnO. Electronic simulations show that the patterning results in a current gain of 3.2 mA/cm2 and a slight gain in voltage, yielding an efficiency gain of 0.4%. Our simulations further show that the fill factor is highly sensitive to the patterned structure. This is explained by the electric field strength varying strongly across the patterned absorber. We outline a path toward further optimized optically resonant nanopattern geometries with enhanced carrier collection properties. We demonstrate a 0.74 mA/cm2 current gain for a patterned cell compared to a planar cell in experiments, owing to a much improved infrared response, as predicted by our simulations.

Passivating Quantum Dot Carrier Transport Layer with Metal Salts.

Quantum dots (QDs) have a wide range of applications in the field of optoelectronics. They have been playing multiple roles within the configuration of a device, by serving as the building blocks for both the active layer and the carrier transport layer. While the performance of various optoelectronic devices has been steadily improving via developments in passivating the QD active layer, the possible improvement via passivation of the QD-based carrier transport layer has been largely overlooked. Here, with lead sulfide QD photovoltaics as the platform of study, we demonstrate that the device performance can be significantly improved by passivating the QD hole transport layer (HTL) with zinc salt post-treatments. The power conversion efficiency is improved from 8.7% of the reference device to 10.2% and 9.5% for devices with zinc acetate (ZnAc)- and zinc iodide (ZnI2)-treated HTLs, respectively. Transient absorption spectroscopy confirms that both treatments effectively reduce band-tail states and increase carrier lifetime of the HTLs. Further elemental analysis shows that ZnAc provides a higher amount of Zn2+ for passivation while maintaining the function of HTL by allowing essential p-doping oxidation. In contrast, the additional I- passivation from ZnI2 inhibits p-doping oxidation and limits the function of HTL. This work demonstrates the potential of improving device performance by passivating the QD-based HTLs, and the method developed is likely applicable to other optoelectronic devices.

Enhanced Power Conversion Efficiency via Hybrid Ligand Exchange Treatment of p-Type PbS Quantum Dots.

PbS quantum dot solar cells (QDSCs) have emerged as a promising low-cost, solution-processable solar energy harvesting device and demonstrated good air stability and potential for large-scale commercial implementation. PbS QDSCs achieved a record certified efficiency of 12% in 2018 by utilizing an n+-n-p device structure. However, the p-type layer has generally suffered from low carrier mobility due to the organic ligand 1,2-ethanedithiol (EDT) that is used to modify the quantum dot (QD) surface. The low carrier mobility of EDT naturally limits the device thickness as the carrier diffusion length is limited by the low mobility. Herein, we improve the properties of the p-type layer through a two-step hybrid organic ligand treatment. By treating the p-type layer with two types of ligands, 3-mercaptopropionic acid (MPA) and EDT, the PbS QD surface was passivated by a combination of the two ligands, resulting in an overall improvement in open-circuit voltage, fill factor, and current density, leading to an improvement in the cell efficiency from 7.0 to 10.4% for the champion device. This achievement was a result of the improved QD passivation and a reduction in the interdot distance, improving charge transport through the p-type PbS quantum dot film.

Thermal properties and behavior of microencapsulated sugarcane wax phase change material.

In this study, a micro-encapsulated phase change material (PCM) was composed of sugarcane wax-Al2O3composite as the core material and gelatin-gum Arabic as the polymer shell materials prepared by complex coacervation. The thermal behavior of solar panels integrated with this encapsulated PCM (EPCM) was investigated. The heat storage-dissipation performance and thermal stability of the sugarcane wax-based composite PCM layer with the heat capacity of 2.86 J/g·°C was influenced by its thickness. Increasing the composite PCM layer thickness from 4 mm to 7 mm could lower the module's front-facing glass temperature by 4% resulting in enhanced the photovoltaic power generation by 12% at the peak, because of the temperature storage ability of the composite PCM. Moreover, the thermal conductivity of the microencapsulated sugarcane wax was calculated using a steady-state one-dimensional energy balance equation. The thermal conductivities estimated across the composite PCM layer depth were found to be temperature dependent. A nonlinear regression of the power law thermal conductivity model gave a good agreement with the observed EPCM-surface temperatures.

A New Passivation Route Leading to Over 8% Efficient PbSe Quantum-Dot Solar Cells via Direct Ion Exchange with Perovskite Nanocrystals.

Colloidal quantum dots (QDs) are promising candidate materials for photovoltaics (PV) owing to the tunable bandgap and low-cost solution processability. Lead selenide (PbSe) QDs are particularly attractive to PV applications due to the efficient multiple-exciton generation and carrier transportation. However, surface defects arising from the oxidation of the PbSe QDs have been the major limitation for their development in PV. Here, a new passivation method for chlorinated PbSe QDs via ion exchange with cesium lead halide (Br, I) perovskite nanocrystals is reported. The surface chloride ions on the as-synthesized QDs can be partially exchanged with bromide or iodide ions from the perovskite nanocrystals, hence forming a hybrid halide passivation. Consistent with the improved photoluminescence quantum yield, the champion PV device fabricated with these PbSe QDs achieves a PCE of 8.2%, compared to 7.3% of that fabricated with the untreated QDs. This new method also leads to devices with excellent air-stability, retaining at least 93% of their initial PCEs after being stored in ambient conditions for 57 d. This is considered as the first reported PbSe QD solar cell with a PCE of over 8% to date.

Short communication: Evaluation of the PREP10 energy-, protein-, and amino acid-allowable milk equations in comparison with the National Research Council model.

The objective of this work was to evaluate the precision and accuracy of the milk yield predictions made by the PREP10 model in comparison to those from the National Research Council (NRC) Nutrient Requirements of Dairy Cattle. The PREP10 model is a ration-balancing system that allows protein use efficiency to vary with production level. The model also has advanced AA supply and requirement calculations that enable estimation of AA-allowable milk (MilkAA) based on 10 essential AA. A literature data set of 374 treatment means was collected and used to quantitatively evaluate the estimates of protein-allowable milk (MilkMP) and energy-allowable milk yields from the NRC and PREP10 models. The PREP10 MilkAA prediction was also evaluated, as were both models' estimates of milk based on the most-limiting nutrient or the mean of the estimated milk yields. For most milk estimates compared, the PREP10 model had reduced root mean squared prediction error (RMSPE), improved concordance correlation coefficient, and reduced mean and slope bias in comparison to the NRC model. In particular, utilizing the variable protein use efficiency for milk production notably improved the estimate of MilkMP when compared with NRC. The PREP10 MilkMP estimate had an RMSPE of 18.2% (NRC = 25.7%), concordance correlation coefficient of 0.82% (NRC = 0.64), slope bias of -0.14 kg/kg of predicted milk (NRC = -0.34 kg/kg), and mean bias of -0.63 kg (NRC = -2.85 kg). The PREP10 estimate of MilkAA had slightly elevated RMSPE and mean and slope bias when compared with MilkMP. The PREP10 estimate of MilkAA was not advantageous when compared with MilkMP, likely because AA use efficiency for milk was constant whereas MP use was variable. Future work evaluating variable AA use efficiencies for milk production is likely to improve accuracy and precision of models of allowable milk.