Nanoimprinting ultrasmall and high-aspect-ratio structures by using rubber-toughened UV cured epoxy resist.

A simple and robust scheme is proposed for the fabrication of nanoscale (20 nm line width) and high-aspect-ratio (9:1) structures by using modulus-tunable UV curable epoxy resists. Additionally, the ability to control the Young's modulus of the imprinted material from hard to rigiflex using these epoxy resists is demonstrated. The physical properties of the new epoxy resists were controlled by adjusting the ratio of bisphenol F-type epoxy resin and acrylonitrile-butadiene rubber-based epoxy resin in the formulation of the resist. The mechanical properties of the resist were tuned to obtain various aspect ratios as well as mold flexibility for conformal contact over non-planar surfaces and large areas. In order to reduce the line width of the imprinted patterns, a process to conformally coat the mold structure by atomic layer deposition of alumina was also developed. Narrow lines with high-aspect-ratio features and with very low defect density were achieved via the new approach and the high mechanical strength of the new resist formulation.

Facile route of flexible wire grid polarizer fabrication by angled-evaporations of aluminum on two sidewalls of an imprinted nanograting.

In this study, we report a new method to fabricate a wire grid polarizer (WGP) that greatly relaxes the requirement on patterning and etching, and can be easily applied to produce flexible WGPs. The technique is to pattern a high aspect ratio and narrow linewidth grating by nanoimprint lithography followed by two angled aluminum depositions in opposite directions to produce the narrow spacing between the aluminum lines required for a visible band WGP. Anisotropic reactive ion etching is used to remove the aluminum deposited at the top of the grating but leave the aluminum layer on the grating sidewalls, thereby forming a metal wire grid with much smaller spacings than a lithographically defined grating. As a result, the fabricated WGP showed good performance in a wide range of visible wavelength.

A Comparison of Anesthetic Quality Between Interscalene Block and Superior Trunk Block for Arthroscopic Shoulder Surgery: A Randomized Controlled Trial.

BACKGROUND: Interscalene block is the most commonly used nerve block for shoulder surgery, and superior trunk block has been investigated as a phrenic-sparing alternative. This randomized controlled trial compared ultrasound-guided interscalene block and superior trunk block as anesthesia for arthroscopic shoulder surgery. OBJECTIVES: Our aims were to determine the superiority of anesthesia quality and compare the risk of hemidiaphragmatic paralysis between these 2 blocks. STUDY DESIGN: A randomized, controlled trial. SETTING: Department of Anesthesiology and Pain Medicine, Korea University Anam Hospital. METHODS: Forty-eight patients undergoing elective arthroscopic shoulder surgery under an ultrasound guided brachial plexus block were randomized to receive either an interscalene block (ISB group, n = 24) or a superior trunk block (STB group, n = 24) for surgery. Ten milliliters of 2% lidocaine and 10 mL of 0.75% ropivacaine were used as local anesthesia in both brachial plexus block groups (total 20 mL). In the ISB group, the local anesthesia was injected between the C5-C6 root and at the upper part of C5 with equally divided doses. In the STB group, the local anesthesia was injected into the anterior and posterior parts of the superior trunk with equally divided doses. Sensory blockade of each trocar's insulting site (supraclavicular, axillary, and suprascapular nerve areas) and motor blockade of the axillary nerve (shoulder abduction) and the suprascapular nerve (shoulder external rotation) were assessed by a blinded observer at 5-minute intervals for 30 minutes after the block. Anesthesia quality was assessed using 3 grades (excellent/insufficient/failure). The blinded investigator also assessed the grade of hemidiaphragmatic paralysis (normal/partial/complete) by comparing pre- and postoperative chest radiographs. Primary outcome variables were anesthesia grade and rate of hemidiaphragmatic paralysis. Secondary outcome variables were performance time and anesthesia onset time. RESULTS: The anesthetic grade was significantly different between the 2 groups (22/2/0 in the ISB group vs. 16/3/5 in the STB group, P = 0.046). Both groups displayed equivalent incidence of hemidiaphragmatic paralysis (12/6/6 in the ISB group vs. 7/14/3 in the STB group, P = 0.063). No intergroup differences were found in terms of performance time and anesthesia onset time. LIMITATIONS: Our sensory and motor function test was not applied to the subscapular nerve, which serves internal rotation of the humeral head so may be difficult to evaluate in patients with rotator cuff tears. We assessed the diaphragmatic movement by chest radiographs instead of by ultrasound. CONCLUSIONS: The superior trunk block provided lower quality of surgical anesthesia than the interscalene block and did not effectively decrease the risk of hemidiaphragmatic paralysis during arthroscopic shoulder surgery for rotator cuff syndrome.

Aharonov-Bohm effect in graphene-based Fabry-Pérot quantum Hall interferometers.

Interferometers probe the wave-nature and exchange statistics of indistinguishable particles-for example, electrons in the chiral one-dimensional edge channels of the quantum Hall effect (QHE). Quantum point contacts can split and recombine these channels, enabling interference of charged particles. Such quantum Hall interferometers (QHIs) can unveil the exchange statistics of anyonic quasi-particles in the fractional quantum Hall effect (FQHE). Here, we present a fabrication technique for QHIs in van der Waals (vdW) materials and realize a tunable, graphene-based Fabry-Pérot (FP) QHI. The graphite-encapsulated architecture allows observation of FQHE at a magnetic field of 3T and precise partitioning of integer and fractional edge modes. We measure pure Aharonov-Bohm interference in the integer QHE, a major technical challenge in small FP interferometers, and find that edge modes exhibit high-visibility interference due to large velocities. Our results establish vdW heterostructures as a versatile alternative to GaAs-based interferometers for future experiments targeting anyonic quasi-particles.

Postoperative hypoalbuminemia is an independent predictor of 1-year mortality after surgery for geriatric intertrochanteric femoral fracture: A retrospective cohort study.

ABSTRACT: Preoperative hypoalbuminemia from malnutrition is associated with increased morbidity and mortality after geriatric hip fracture surgery. However, little is known regarding the correlation between postoperative hypoalbuminemia and mortality. This study aimed to evaluate whether postoperative hypoalbuminemia could predict 1-year mortality after intertrochanteric femoral fracture surgery in elderly patients.The medical records of 263 geriatric patients (age ≥65 years) who underwent intertrochanteric femoral fracture surgery between January 2013 and January 2016 in a single hospital were reviewed retrospectively. The patients were allocated to 2 groups based on lowest serum albumin levels within 2 postoperative days (≥3.0 g/dL [group 1, n = 46] and <3.0 g/dL [group 2, n = 217]. Data between the non-survival and survival groups were compared. Multivariable logistic regression analysis was conducted to identify the independent predictor for 1-year mortality.The 1-year mortality rate was 16.3% after intertrochanteric femoral fracture surgery. Multivariable logistic regression analysis revealed that postoperative hypoalbuminemia was significantly associated with 1-year mortality (adjusted odds ratio, 8.03; 95% confidence interval, 1.37-47.09; P = .021). The non-survival group showed a significantly increased incidence of postoperative hypoalbuminemia (95.4% vs 80.0%, P = .015) and intensive care unit admission (11.6% vs 2.7%, P = .020), older age (82.5 ±â€Š5.8 years vs 80.0 ±â€Š7.2 years, P = .032), lower body mass index (20.1 ±â€Š3.2 kg/m2 vs 22.4 ±â€Š3.8 kg/m2, P < .001), and increased amount of transfusion of perioperative red blood cells (1.79 ±â€Š1.47 units vs 1.43 ±â€Š2.08 units, P = .032), compared to the survival group.This study demonstrated that postoperative hypoalbuminemia is a potent predictor of 1-year mortality in geriatric patients undergoing intertrochanteric femoral fracture surgery. Therefore, exogenous albumin administration can be considered to improve postoperative outcomes and reduce the risk of mortality after surgery for geriatric hip fracture.

Experimental Study on the Effects of Alumina Abrasive Particle Behavior in MR Polishing for MEMS Applications.

Recently, the magnetorheological (MR) polishing process has been examined asa new ultra-precision polishing technology for micro parts in MEMS applications. In theMR polishing process, the magnetic force plays a dominant role. This method uses MRfluids which contains micro abrasives as a polishing media. The objective of the presentresearch is to shed light onto the material removal mechanism under various slurryconditions for polishing and to investigate surface characteristics, including shape analysisand surface roughness measurement, of spots obtained from the MR polishing process usingalumina abrasives. A series of basic experiments were first performed to determine theoptimum polishing conditions for BK7 glass using prepared slurries by changing the processparameters, such as wheel rotating speed and electric current. Using the obtained results,groove polishing was then performed and the results are investigated. Outstanding surfaceroughness of Ra=3.8nm was obtained on the BK7 glass specimen. The present resultshighlight the possibility of applying this polishing method to ultra-precision micro partsproduction, especially in MEMS applications.

High-strength magnetically switchable plasmonic nanorods assembled from a binary nanocrystal mixture.

Next-generation 'smart' nanoparticle systems should be precisely engineered in size, shape and composition to introduce multiple functionalities, unattainable from a single material. Bottom-up chemical methods are prized for the synthesis of crystalline nanoparticles, that is, nanocrystals, with size- and shape-dependent physical properties, but they are less successful in achieving multifunctionality. Top-down lithographic methods can produce multifunctional nanoparticles with precise size and shape control, yet this becomes increasingly difficult at sizes of ∼10 nm. Here, we report the fabrication of multifunctional, smart nanoparticle systems by combining top-down fabrication and bottom-up self-assembly methods. Particularly, we template nanorods from a mixture of superparamagnetic Zn0.2Fe2.8O4 and plasmonic Au nanocrystals. The superparamagnetism of Zn0.2Fe2.8O4 prevents these nanorods from spontaneous magnetic-dipole-induced aggregation, while their magnetic anisotropy makes them responsive to an external field. Ligand exchange drives Au nanocrystal fusion and forms a porous network, imparting the nanorods with high mechanical strength and polarization-dependent infrared surface plasmon resonances. The combined superparamagnetic and plasmonic functions enable switching of the infrared transmission of a hybrid nanorod suspension using an external magnetic field.