Suppression of broadband noise radiated by a low-speed fan in a duct

Attenuation of ducted fan noise remains a technical challenge in the low frequency range as traditional duct lining becomes ineffective. This study proposes a reactive method to suppress the sound radiation from an axial-flow fan. The method is particularly effective in the low frequency region and covers a broad band. Its effect is derived from two mechanisms. One is the reduction in the confining effects of duct walls when the duct radius is increased; the other is the acoustic interference between the direct radiation from the fan and reflections by the duct junctions. This interference is always destructive for axial dipoles when the frequency approaches zero. This performance differs from normal passive control methods, which become totally ineffective toward zero frequency. An approximate plane-wave theory explains the essential physics of the method, and its quantitative prediction is found to agree well with a full numerical simulation using a spectral method of Chebyshev collocation. The latter is validated by experiment using an axial-flow fan in a duct of finite length. Broadband noise reduction is achieved while the flow speed is kept unchanged. Practical difficulties of implementation for a fan with high pressure increase are discussed. © 2010 Acoustical Society of America.published_or_final_versio

Offline Signature Verification by Combining Graph Edit Distance and Triplet Networks

Biometric authentication by means of handwritten signatures is a challenging pattern recognition task, which aims to infer a writer model from only a handful of genuine signatures. In order to make it more difficult for a forger to attack the verification system, a promising strategy is to combine different writer models. In this work, we propose to complement a recent structural approach to offline signature verification based on graph edit distance with a statistical approach based on metric learning with deep neural networks. On the MCYT and GPDS benchmark datasets, we demonstrate that combining the structural and statistical models leads to significant improvements in performance, profiting from their complementary properties

High folic acid consumption leads to pseudo-MTHFR deficiency, altered lipid metabolism, and liver injury in mice.

Increased consumption of folic acid is prevalent, leading to concerns about negative consequences. The effects of folic acid on the liver, the primary organ for folate metabolism, are largely unknown. Methylenetetrahydrofolate reductase (MTHFR) provides methyl donors for S-adenosylmethionine (SAM) synthesis and methylation reactions

Influence of Fatty Acid Methyl Esters on Fuel properties of Biodiesel Produced from the Seeds Oil of Curcubita pepo

Oil extracted from the seeds of Curcubita pepo was transesterified using potassium hydroxide in methanol. Fatty acid methyl esters (FAME) profile of the produced diesel was analyzed using Gas chromatograph coupled with mass spectrophotometer (GC-MS). The results indicate the presence of methyl (12E)-octadecenotate as the dominant ester with approximate percentage by composition of 82.90%. Other esters detected were methyl tetradecanoate (0.4%), methyl eicosonoate (2.48%), methyl docosanoate (0.97%) methyl teracosanoate (0.47%). Some critical fuel parameters like oxidation stability, cetane number, iodine value and viscosity were correlated with the methyl ester composition and structural configuration. It was found that the cetane number and oxidation stability of the produced biodiesel is a function of the degree of unsaturation and long chain saturated factor. The profile of methyl esters in the biodiesel produced indicates its likelihood to be a viable fuel source for internal combustion engines

Uric Acid and Chronic Kidney Disease: Still More to Do

Gout and hyperuricemia are present in 25% and 60% of patients with chronic kidney disease (CKD), respectively. Despite the common association, the role of uric acid in the progression of kidney disease and in metabolic complications remains contested. Some authorities argue that the treatment of asymptomatic hyperuricemia in CKD is not indicated, and some have even suggested hyperuricemia may be beneficial. Here, we review the various arguments both for and against treatment. The weight of the evidence suggests asymptomatic hyperuricemia is likely injurious, but it may primarily relate to subgroups, those who have systemic crystal deposits, those with frequent urinary crystalluria or kidney stones, and those with high intracellular uric acid levels. We recommend carefully designed clinical trials to test if lowering uric acid in hyperuricemic subjects with cardiometabolic complications is protective

Bridging the gap: Evidence-based practice guidelines for sports nutritionists

Evidence-based practice is a systematic approach to decision-making developed in the 1990s to help healthcare professionals identify and use the best available evidence to guide clinical practice and patient outcomes amid a plethora of information in often challenging, time-constrained circumstances. Today’s sports nutrition practitioners face similar challenges, as they must assess and judge the quality of evidence and its appropriateness to their athlete, in the often chaotic, time-pressed environment of professional sport. To this end, we present an adapted version of the evidence-based framework to support practitioners in navigating their way through the deluge of available information and guide their recommendations to athletes whilst also reflecting on their practice experience and skills as evidence-based practitioners, thus, helping to bridge the gap between science and practice in sport and exercise nutrition

Graded resonator arrays for spatial frequency separation and amplification of water waves

A structure capable of substantially amplifying water waves over a broad range of frequencies at selected locations is proposed. The structure consists of a small number of C-shaped cylinders in a line array, with the cylinder properties graded along the array. Using linear potential-flow theory, it is shown that the energy carried by a plane incident wave is amplified within specified cylinders for wavelengths comparable to the array length and for a range of incident directions. Transfer-matrix analysis is used to attribute the large amplifications to excitation of local Rayleigh–Bloch waves and gradual slowing down of their group velocity along the array

Alterations in the mechanical properties of the human chondrocyte pericellular matrix with osteoarthritis

Introduction: In articular cartilage, chondrocytes are surrounded by a pericellular matrix (PCM), which together with the chondrocyte have been termed the chondron [1]. This region is characterized by the presence of type VI collagen and increased proteoglycan concentration relative to the extracellular matrix. While the specific function of the PCM is not fully understood, it has been hypothesized to play important roles in regulating the biomechanical, biophysical, and biochemical signals that the chondrocyte perceives during normal joint activity [1,5,7]. A more thorough understanding of the mechanical properties of the PCM would provide important insights into the potential biomechanical function of the chondron as a discrete entity in articular cartilage. Furthermore, previous studies have reported changes in the distribution and amount of collagen VI in osteoarthritic (OA) cartilage, suggesting that the biomechanical function of the PCM may be altered with disease. The goal of this study was to test the hypothesis that the biomechanical properties of the PCM vary with depth from the cartilage surface and are altered with OA. Using a newly developed microaspiration technique, chondrons were extracted from normal and osteoarthritic cartilage. The Young's modulus of the PCM was determined using the micropipette aspiration technique in combination with a recently developed theoretical model that represents the chondron as an elastic, compressible layer overlying an elastic half-space ( Methods: Chondrons were mechanically isolated from full thickness articular cartilage of human femoral heads at the time of joint replacement surgery (N=73 chondrons from 13 donors, ages: 19-75 yr). Chondrons were extracted from two different zones (surface and middle/deep) by applying suction pressure to the cartilage surface with a glass pipette. Chondrons were classified as osteoarthritic ('OA') or nonosteoarthritic ('non-OA') based on a semi-quantitative histology grading scale from 0 (normal) to 20 (OA) of the cartilage from which they were extracted. The ave rage grades for non-OA and OA cartilage were 4.5±3.1 and 15.8 ±2.1, respectively. The elastic properties of chondrons were measured using a new axisymetric layered elastic half-space model for the micropipette aspiration technique Results: The mean Young's modulus of the PCM of chondrons from non-OA cartilage was Enon-OA=66.5±23.3 kPa. With OA, the Young's modulus of the PCM was significantly reduced to EOA=41.3±21.1 kPa (p<0.05). No zonal variation was found in the Young's modulus of PCM of chondrons from OA or non-OA cartilage In contrast to previous studies on enzymatically isolated chondrons [6] which reported a mean Young's modulus of ~1.5 kPa for the PCM [7], our findings suggest that the Young's modulus of the mechanically isolated PCM is nearly 50 times larger than that of the enzymatically isolated chondrons. This difference is most likely attributable to the effects of enzymatic isolation on the properties of the PCM. These findings are consistent with previous studies examining the deformation behavior of enzymatically and mechanically isolated chondrons embedded in an agarose matrix [8], and suggest that the Young's modulus of the mechanically isolated chondrons is greater than the Young's modulus of enzymatically isolated chondrons and in excess of the Young's modulus of the agarose (25kPa). A unique aspect of this study was the development of a new chondron isolation technique, which is based on extraction of chondrons directly from the cartilage by applying suction pressure using a small diameter pipette. This technique requires minimal tissue preparation, and can be used to extract chondrons from precise sites (i.e., zones) of the cartilage. Compared with the homogenization technique [1], our method is fast and easy and yields a large number of chondrons with a smaller amount of debris. Increasing evidence suggests that the chondron is a distinct functional compartment in articular cartilage and serves to regulate the mechanical environment of the chondrocytes [5,8]. The mechanical properties of the PCM determined in this study can be applied in several models of articular cartilage to further examine the mechanical microenvironment of chondrocytes. In addition, the development of an easy chondron extraction technique will further facilitate the investigation of this unique structure in articular cartilage. Acknowledgments: The authors would like to thank Clint Walker from Duke University for his excellent assistance

Nitrogen-inputs regulate microbial functional and genetic resistance and resilience to drying–rewetting cycles, with implications for crop yields

Background and aims The increasing input of anthropogenically-derived nitrogen (N) to ecosystems raises a crucial question: how do N inputs modify the soil microbial stability, and thus affect crop productivity? Methods Soils from an 8-year rice-wheat rotation experiment with increasing N-input rates were subjected to drying–rewetting (DW) cycles for investigating the resistance and resilience of soil functions, in terms of abundances of genes (potential functions) and activities of enzymes (quantifiable functions), to this stress, and particularly the contribution of resistance and resilience on crop production was evaluated. Results Although the DW cycles had a stronger effect compared to N fertilization level, the N input was also important in explaining the variation in the resistance and resilience of functional genes and the activities of enzymes involved in C, N and P cycling. Crop yields benefited from both of high resistance and high resilience of soil microbial functions, though the resistance and resilience of soil enzyme activities exhibited a stronger contribution to crop yields compared to the functional genes and the overall contribution strength was conditioned by N input levels. Conclusions In addition to the well-known direct contribution of N fertilization on crop yields, N input plays an indirect role on crop production via conditioning the resistance and resilience of soil functions in response to repeated DW cycles