Active acoustic metamaterial based on Helmholtz resonators to absorb broadband low frequency noise

Metamaterials are a new class of materials that have properties that cannot be found in nature. Though these artificially engineered structures have not been prominently used in many applications, they have been theoretically studied to have a variety of applications in many sectors. Acoustic metamaterials have the capability of manipulating sound waves in order to achieve the required unique properties.The aim of the project is to design an active acoustic metamaterial consisting of an array of Helmholtz resonators to assist in reduction of noise levels in aerospace applications using the method of 3D printing.This project presents an active Helmholtz resonator based design that can attenuate a broadband range of targeted frequencies in the low-frequency regime. To this end, a passive metamaterial consisting of an array of Helmholtz resonator unit cells, with a single varying design variable, is designed and tested to establish the effectiveness and region of performance. The selected design variable for change is identified through the frequency response for each parameter of the Helmholtz resonance equation, to achieve a broadband frequency range of the metamaterial. An active model of this design is then fabricated and tested. Two actuation mechanisms are presented for this design. The resulting acoustic systems are capable of providing an attenuation of up to 20 dB, for an open system, and up to 35 dB, for a closed system, at frequencies between 150 Hz and 500 Hz. Unlike most other studies conducted, this active acoustic design is capable of attenuating isolated frequencies as well as multiple frequencies simultaneously. The added control that is achieved through the incorporation of the electric linear motor based actuation allows for the advantage of accurate frequency targeting along with the base attenuation levels of the passive resonant acoustic metamaterial.Aerospace Engineerin

Absence/rarity of commonly reported LRRK2 mutations in Indian Parkinson's disease patients

Recent discovery of pathogenic mutations in the leucine-rich repeat kinase 2 (LRRK2) gene in Parkinson's disease (PD) patients in different ethnic groups have raised a hope of diagnostic screening and genetic counseling. We investigated the six most commonly reported mutations in LRRK2 gene among Indian PD patients, using PCR-RFLP method. Mutations G2019S, R1441C, R1441G, and R1441H were screened in 1012 individuals (PD, 800; controls, 212) while mutations I2012T and I2020T were screened in 748 PD patients. We did not observe any of these six mutations in this study sample except in a single female young onset PD patient who showed a heterozygous G2019S mutation. The absence of mutations was reconfirmed by sequencing of probands from several autosomal dominant PD families. Our observations suggest that these mutations may be a rare cause of PD among Indians and therefore of little help for diagnostic screening and genetic counseling for Indian PD patients

Association of N-acetyl transferase 2 gene polymorphism and slow acetylator phenotype with young onset and late onset Parkinson's disease among Indians

Objectives: To investigate the association of (i) seven SNPs and SNP haplotypes in the phase II conjugating enzyme N-acetyl transferase 2 gene; and (ii) slow acetylator phenotype, with the development of young onset (YO) and late onset (LO) Parkinson's disease (PD) among Indians. Methods: A total of 267 cases (132 YOPD, age at onset≤ 40 years; 135 LOPD, age at onset >40 years) and 324 age and sex matched controls (132 for YOPD and 192 for LOPD) were genotyped for NAT2 SNPs. Allelic, genotypic and haplotypic association was tested by Χ 2 using a case-control approach. Χ2 test of association of acetylation phenotype (by genotype) with PD was also carried out. Results: Of the seven SNPs genotyped, SNP191 was monomorphic and therefore, not included for analysis. With SNPs 590 and 857 a significant allelic [OR (95% CI) 4.147 (2.28-7.54) for A allele and 2.565 (1.34-4.92) for A allele, respectively] and genotypic [OR (95% CI) 0.27 (0.14-0.52) for GG and 0.35 (0.174-0.712) for GG, respectively] association with YOPD was observed. There was a significant allelic and genotypic association of SNP 282 with LOPD [Χ2=8.92, P=0.003 and Χ 2=10.2, P=0.006, respectively]. There was also a significant association of protective and predisposing haplotypes TCGG and TCAG [OR (95% CI) 0.446 (0.31-0.63) and 3.742 (2.0-6.99), respectively] with YOPD and predisposing haplotype TCGA [OR (95% CI) 3.214 (1.43-7.22)] with LOPD. Slow acetylator phenotype was significantly associated with YOPD [OR (95% CI) 2.32 (1.2-4.48)]. Conclusion: Specific SNPs and SNP haplotypes in NAT2 and slow acetylator phenotype are significantly associated with YOPD and to a lesser extent with LOPD among Indians

Parkin mutations in familial and sporadic Parkinson's disease among Indians

We observed a mutation frequency of 8.5% in Parkin gene among Indian PD patients based on sequencing and gene dosage analysis of its exons. We identified nine point mutations of which seven are novel and hitherto unreported. These mutations accounted for 14.3% familial PD, 6.9% young onset and 5.9% late onset sporadic PD. Of the 20 PD patients with mutations only two had homozygous mutations and one was a compound heterozygote. Homozygous exonic deletions were absent but heterozygous exon rearrangements were observed in 9.2% of patients (19% familial PD and 4.5% young onset sporadic PD)

Genetic susceptibility to Parkinson's disease among South and North Indians: I. role of polymorphisms in dopamine receptor and transporter genes and association of DRD4 120-bp duplication marker

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