Humidity-tolerant porous polymer coating for passive daytime radiative cooling.

Coating building envelopes with a passive daytime radiative cooling (PDRC) material has attracted enormous attention as an alternative cooling technique with minimal energy consumption and carbon footprint. Despite the exceptional performance and scalability of porous polymer coating (PPC), achieving consistent performance over a wide range of drying environments remains a major challenge for its commercialization as a radiative cooling paint. Herein, we demonstrate the humidity vulnerability of PPC during the drying process and propose a simple strategy to greatly mitigate the issue. Specifically, we find that the solar reflectance of the PPC rapidly decreases with increasing humidity from 30% RH, and the PPC completely losses its PDRC ability at 45% RH and even become a solar-heating material at higher humidity. However, by adding a small amount of polymer reinforcement to the PPC, it maintains its PDRC performance up to 60% RH, resulting in a 950% increase in estimated areal coverage compared to PPC in the United States. This study sheds light on a crucial consistency issue that has thus far been rarely addressed, and offers engineering guidance to handle this fundamental threat to the development of dependable PDRC paint for industrial applications.

Multi isotope systematics of precipitation to trace the sources of air pollutants in Seoul, Korea.

Multiple sulfur (δ34Ssulfate, Δ33Ssulfate, & Δ36Ssulfate), nitrogen and oxygen (δ15Nnitrate & δ18Onitrate) and strontium (87Sr/86Sr) isotope compositions of precipitation collected from Seoul, South Korea were analyzed to study the sources, transportation and deposition of air pollutants in East Asia. The δ34Ssulfate values (from 1.9 to 14.6‰ with a median of 4.7‰) and the δ15Nnitrate values (from -2.0 to 13.3‰ with a median of 1.0‰) suggest that fossil fuel use (emission from coal combustion and vehicle exhaust) is a predominant source for sulfur and nitrogen, but other natural sources including biogenic contributions of DMS also add to their total budget. The seasonal variations are observed in δ34Ssulfate and δ15Nnitrate values (both higher in winter season), which is likely to result from the increase of coal use for domestic heating in China. The δ18Onitrate values also varied seasonally depending on the NOx oxidation pathway, being about 20‰ higher in winter than in summer season. The Δ33Ssulfate and Δ36Ssulfate values are not anomalous, showing the absence of MIF signals in precipitation of Seoul. The 87Sr/86Sr ratio of the precipitation samples range from 0.70988 to 0.71487 with a median of 0.71073, indicating the influence of at least three end-member (silicate dust, carbonate dust and anthropogenic emission). Ionic ratios such as (K++NH4+)/(Ca2++Mg2+) and Cl-/Na+ suggest the overwhelming effect of anthropogenic input rather than carbonate dust on the end-member with lower 87Sr/86Sr ratios.

The origin and migration of the dissolved sulfate from precipitation in Seoul, Korea.

This study incorporated stable isotope analyses with chemical analyses to determine the origin and migration of sulfur sources in East Asia, and these findings were compared with our decadal research from 2000 to 2001 and 2002 to 2003. The multiple sulfur isotope composition (32S, 33S and 34S) of the dissolved sulfate in precipitation was first measured from 2011 to 2013 in Seoul, South Korea. The δ34Snss values were -1.1‰ to 7.9‰ (avg. 3.6‰), strongly suggesting that sulfur derived from the combustion of Chinese coal is the predominant source of sulfate in the Seoul region. Low NO3/SO42- ratios in the precipitation samples indicated an insignificant effect of sulfur from vehicle exhaust. The seasonal variation of δ34Snss values appears to be caused by increasing biogenic sulfur activity during the spring and summer seasons. The some Δ33S values (0.13‰-0.16‰) measured in the three samples were sufficiently small; thus, whether these values can be attributed to mass-independent fractionation remains unclear. Measuring the Δ33S anomalies in dissolved sulfate provides valuable insights for identifying the sources of sulfur transferred from the stratosphere to the troposphere and upper troposphere.

High-Temperature Current Collection Enabled by the in Situ Phase Transformation of Cobalt-Nickel Foam for Solid Oxide Fuel Cells.

For the commercial development of solid oxide fuel cells (SOFCs), cathode current collection has been one of the most challenging issues because it is extremely difficult to form continuous electric paths between two rigid components in a high-temperature oxidizing atmosphere. Herein, we present a Co-Ni foam as an innovative cathode current collector that fulfills all strict thermochemical and thermomechanical requirements for use in SOFCs. The Co-Ni foam is originally in the form of a metal alloy, offering excellent mechanical properties and manufacturing tolerance during stack assembly and startup processes. Then, it is converted to the conductive spinel oxide in situ during operation and provides nearly ideal structural and chemical characteristics as a current collector, gas distributor, and load-bearing component. The functionality and durability of the Co-Ni foam are verified by unit cell test and 1 kW-class stack operation, demonstrating performance that is equivalent to that of precious metals as well as an exceptional stability under dynamic conditions with severe temperature and current variations. This work highlights a cost-effective technique to achieve highly reliable electric contacts over the large area using the in situ metal-to-ceramic phase transformation that could be applied to various high-temperature electrochemical devices.

High refractive index metamaterials using corrugated metallic slots.

We report on a method for realizing high refractive index metamaterials using corrugated metallic slot structures at terahertz frequencies. The effective refractive index and peak index frequency can be controlled by varying the width of the air gap in the corrugated slot arrays. The phenomenon occurs because of the secondary resonance effect due to the fundamental inductive-capacitive resonance, which generates a red-shift of the fundamental resonance determined by twice the length of the corrugated metallic slots. In addition, multiple gaps in the corrugated slots act as plasmonic hotspots which have the properties of three-dimensional subwavelength confinement due to extremely strong enhancement of the terahertz waves. The versatile characteristics of the structures may have many potential applications in designing compact optical devices incorporating various functionalities and in developing highly sensitive spectroscopic/imaging systems.

Effect of physiological posterolateral rotatory laxity on early results of posterior cruciate ligament reconstruction with posterolateral corner reconstruction.

BACKGROUND: The purpose of this study was to evaluate the influence of physiological posterolateral rotatory laxity on posterior cruciate ligament (PCL) reconstruction in terms of posterior stability and clinical outcomes. METHODS: We retrospectively reviewed the records of sixty-five patients who had undergone arthroscopic PCL reconstruction with simultaneous reconstruction of the posterolateral corner from March 2004 to April 2009. Patients were categorized into three groups according to the amount of tibial external rotation at 90° of knee flexion on the uninjured side: Group 1 (<40°; n = 26), Group 2 (between 40° and 50°; n = 21), and Group 3 (>50°; n = 18). Knee instability was assessed with posterior and varus stress radiographs as well as with the dial test at 30° and 90° of knee flexion. Functional scores were assessed with use of the Lysholm score and the International Knee Documentation Committee (IKDC) score preoperatively and at the time of final follow-up. RESULTS: At the time of follow-up, there was no significant difference among the three groups with regard to the mean side-to-side difference in posterior translation as measured with Telos stress radiography (Group 1: 3.6 ± 1.3 mm, Group 2: 3.3 ± 1.6 mm, and Group 3: 4.3 ± 1.6 mm; p = 0.098). There was also no significant difference among the groups with respect to knee stability as assessed on the varus stress radiographs or with the dial test at 30° and 90° of flexion. Finally, there was no significant difference among the groups with respect to the Lysholm or IKDC functional scores. CONCLUSIONS: This study suggests that the instability of knees that have PCL and posterolateral corner injuries with physiological posterolateral rotatory laxity can be controlled successfully with PCL reconstruction and simultaneous reconstruction of the posterolateral corner. Physiological posterolateral rotatory laxity should not be considered a risk factor for abnormal knee laxity after PCL reconstruction with simultaneous reconstruction of the posterolateral corner.

Arthroscopic repair of concomitant type II SLAP lesions in large to massive rotator cuff tears: comparison with biceps tenotomy.

BACKGROUND: There are no studies examining superior labrum anterior and posterior (SLAP) repair combined with repair of large to massive rotator cuff tears, and it is unclear whether a combined SLAP repair would lead to better outcomes than biceps tenotomy. HYPOTHESIS: Tenotomy and rotator cuff repair would lead to better outcomes compared with those of combined SLAP and rotator cuff repair. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: Our study population consisted of 36 patients who had undergone either combined SLAP and rotator cuff repair (when the biceps was too healthy to cut; group R = 16 patients) or tenotomy and rotator cuff repair (when any fraying or partial tear existed in the biceps tendon; group T = 20 patients) for concomitant type II SLAP lesions and large to massive rotator cuff tears. The cuff repair was performed in a single row for both groups. Outcomes were assessed by comparing range of motion as well as Simple Shoulder Test (SST), American Shoulder and Elbow Surgeons (ASES), and University of California, Los Angeles (UCLA) scores between the 2 groups. RESULTS: At the 2-year follow-up, both groups demonstrated significant improvements in functional shoulder scores and range of motion. However, group T had better SST scores (group T, 9.3 ± 1.6; group R, 7.8 ± 1.9; P = .012), ASES scores (group T, 88.6 ± 8.9; group R, 80.4 ±8.9; P = .009), UCLA scores (group T, 29.6 ± 3.0; group R, 26.0 ± 4.2; P = .007), and forward flexion (group T, 145.9° ± 13.0°; group R, 132.5° ± 15.3°; P = .008). The mean tear size and the degree of preoperative muscle atrophy and fatty infiltration on magnetic resonance imaging were similar between the groups. CONCLUSION: For patients with concomitant type II SLAP lesions and large to massive rotator cuff tears, the outcomes of simultaneous arthroscopic SLAP and rotator cuff repair were inferior to those of arthroscopic biceps tenotomy and cuff repair in terms of functional shoulder scores and range of motion. Biceps tenotomy and rotator cuff repair may be a more reliable method to address concomitant type II SLAP lesions and large to massive rotator cuff tears in patients, although a randomized controlled trial is needed to confirm the results.

Arthroscopic partial repair of irreparable large to massive rotator cuff tears.

PURPOSE: The aim of this study was to evaluate the outcome of arthroscopic partial repair and margin convergence of irreparable large to massive rotator cuff tears. METHODS: Between January 2003 and July 2008, 27 patients who met the inclusion criteria underwent arthroscopic partial repair and margin convergence of irreparable large to massive rotator cuff tears. An irreparable tear was defined as a tear with a minimum anterior-to-posterior width of 3 cm or larger, where it was not feasible to completely cover the humeral head with the cuff at the time of surgery. RESULTS: The mean preoperative tear size was 42.1 ± 6.2 mm. The mean size of the postoperative residual defect in the repaired tendon along the medial margin of the greater tuberosity was 12.0 ± 5.5 mm. All shoulder scores showed improvement. The Simple Shoulder Test improved from 5.1 ± 1.2 to 8.8 ± 2.1 (P < .001), the Constant score from 43.6 ± 7.9 to 74.1 ± 10.6 (P < .001), and the University of California, Los Angeles score from 10.5 ± 3.0 to 25.9 ± 5.0 (P < .001). Both Constant and University of California, Los Angeles shoulder scores also showed an inverse correlation with defect size. We compared muscle strength between the affected and contralateral sides and found that the strength of the affected side was not restored to the same level as the contralateral side (P < .001). CONCLUSIONS: Arthroscopic partial repair and margin convergence showed satisfactory short-term outcomes in irreparable large to massive rotator cuff tears. Thus it is suggested that, even in a large to massive tear that appears irreparable, attempting to repair it as much as possible to possibly convert it into a functional rotator cuff tear by re-creating a balanced forced couple can be helpful in reducing pain, as well as improving functional outcomes. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Anatomical Reconstruction for Chronic Posterolateral Instability Combined with Posterior Cruciate Ligament Reconstruction: Surgical Technique.

INTRODUCTION: We present surgical techniques for the anatomical reconstruction of the popliteus tendon and the lateral collateral ligament (LCL) with use of a tibialis posterior allograft for posterolateral corner insufficiency combined with anterolateral transtibial single-bundle posterior cruciate ligament (PCL) reconstruction with use of an Achilles tendon-bone allograft with a one-incision technique. STEP 1 CREATE THE PORTALS: Use a parapatellar high anteromedial portal, a far anterolateral portal, and a high posteromedial portal. STEP 2 PREPARE THE TIBIAL TUNNEL AND FEMORAL SOCKET FOR THE PCL RECONSTRUCTION: To reduce the graft/socket divergence, (1) flex the knee >100°, (2) push the proximal part of the tibia backward as much as possible, and (3) introduce the cannulated headed reamer through the far anterolateral portal with a smooth plastic sheath and push up posteriorly to make contact with the lateral femoral condyle. STEP 3 PREPARE PASS AND FIX THE GRAFT FOR THE PCL RECONSTRUCTION: Tie a 9-mm EndoPearl device securely to the tip of the tendon to improve the fixation strength. STEP 4 MAKE THE SKIN INCISION AND DEVELOP THE SURGICAL PLANE FOR THE POSTEROLATERAL CORNER RECONSTRUCTION: Create a 7-mm fibular tunnel in a counterclockwise direction to avoid breaking the lateral cortex of the fibular tunnel or injuring the peroneal nerve. STEP 5 PREPARE PASS AND FIX THE GRAFT FOR THE POSTEROLATERAL CORNER RECONSTRUCTION: Change the patient's position to a lateral or semi-lateral decubitus position to prevent an inappropriate posterolateral corner reconstruction by the posterolateral corner of the knee sagging in the supine position due to gravity. STEP 6 POSTOPERATIVE REHABILITATION: Immobilize the knee in extension, with the proximal part of the tibia supported with cotton pads to prevent posterior drooping, which may lead to graft stretch or failure. RESULTS: We performed a two-year follow-up study comparing the procedures described here (Group A) with the same PCL reconstruction technique combined with a modified biceps rerouting tenodesis to address the posterolateral corner deficiency (Group B). WHAT TO WATCH FOR: IndicationsContraindicationsPitfalls & Challenges.

Bio-solid-State processes for synthesis of Li-Fe-phosphate.

Lithium-Fe-phosphates have become of great interest as storage cathodes for rechargeable Li-batteries because of their high density, environmental friendliness, and safety. The objective of this study was to examine bio-solid-state synthesis of LiFePO4 by microbial processes at room temperature. The microbial reduction of Fe(III)-citrate using an organic carbon, glucose, as an electron donor in the presence of NaHPO4 and lithium that resulted in the formation of Li-substituted iron phosphate. Our studies showed that bacteria enriched from inter-tidal flat sediments, designated as Haejae-1, synthesized Li-substituted iron phosphate. Characterization by X-ray diffraction showed the reduction of Fe(III)-citrate in the presence of NaHPO4 and LiCl2 resulted in the precipitation of Li-substituted vivianite [Li(x)Fe(3-x)(PO4)2 x 8H2O]. SEM-EDX, FTIR, and ESCA analyses showed the chemical composition of the synthesized phases was Li, Fe, P, C, and O. Based on the chemical and physical structure of the mineral, the novel bio-nano-material may be potentially useful to the development of energy storage materials.

Evidence for anthropogenic 210Po in the urban atmosphere of Seoul, Korea.

We have measured the concentrations of 210Po, 210Pb, SO4(2-), Na+, and 34S in precipitation samples from two metropolitan cities, Seoul and Busan, Korea. The delta34S values ranged from 0 to 10% in most Seoul and Busan precipitation samples, indicating major contributions from industrial sources to S levels. A high level of excess 210Po, which is not produced by 210Pb decay in the troposphere, was observed in both regions. The excess 210Po activities in some samples from Busan, a harbor city, were influenced strongly by sea salt (i.e., sea-surface microlayer) which could be traced using [Na+] and delta34S values. In Seoul precipitations, we observed a good correlation between non-sea-salt SO4(2-) and excess 210Po, suggesting that both species are controlled mainly by the same factor. This correlation and the delta34S values indicate that the major source for both species in this region is likely to be anthropogenic, rather than from traditionally suggested sources such as soil resuspension, stratospheric air intrusion, sea sprays, volcanic emissions, and biogenic emissions.