Acoustic behaviors of the microperforated panel absorber array in nonlinear regime under moderate acoustic pressure excitation.

The acoustic performance of a microperforated panel (MPP) absorber array in the nonlinear regime is investigated both numerically and experimentally. The MPP absorber array is constructed by three parallel-arranged MPP absorbers with different cavity depths. A finite element model is used to simulate the acoustic response of the MPP absorber array by adopting the nonlinear impedance model. The results show that the absorption of the MPP absorber array is affected by the incident sound pressure when it is beyond around 100 dB. With appropriate structural and perforation property of MPP, the MPP absorber array in non-linear regime outperforms that in linear regime due to the improvement of equivalent acoustic impedance matching with ambient air over wide frequency range. However, when the sound pressure excitation is too high, the local resonance effect of the resonating component MPP absorber is diminished and the sound absorption is decreased. With the carefully chosen properties of MPP, the performance degradation induced by panel vibration can be avoided. An optimal set of MPP properties to avoid the performance degradation induced by panel vibration is determined. The measured normal absorption coefficients of a prototype MPP absorber array compare well with the numerical prediction in both linear and nonlinear regimes.

Vortex sound radiation in a flow duct with a dipole source and a flexible wall of finite length.

The noise attenuation of fan-ducted noise at low blade-passage frequency remains a challenge. The present study investigates the noise reduction mechanism of a tensioned membrane housing device that directly controls the sound radiation from the doublet which is enclosed in an infinitely long duct with a point vortex. The time dependent sound radiation mechanism and the vibro-acoustics coupling mechanism of the systems are studied by adopting the potential theory and matched asymptotic expansion technique. The silencing performance of such a passive approach depends on the amplitude and phase of the sound field created by the doublet and the acoustic pressure induced by the membrane oscillation in order to achieve sound cancellation. Results show that the response of membrane vibration is strongly associated with the flow field induced by the grazing uniform flow and also the fluid loading generated by the inviscid vortex. The geometrical property of the cavity and the mechanical properties of the flexible membranes play important roles in controlling the performance of the proposed device.

ASPP2 deficiency causes features of 1q41q42 microdeletion syndrome.

Chromosomal abnormalities are implicated in a substantial number of human developmental syndromes, but for many such disorders little is known about the causative genes. The recently described 1q41q42 microdeletion syndrome is characterized by characteristic dysmorphic features, intellectual disability and brain morphological abnormalities, but the precise genetic basis for these abnormalities remains unknown. Here, our detailed analysis of the genetic abnormalities of 1q41q42 microdeletion cases identified TP53BP2, which encodes apoptosis-stimulating protein of p53 2 (ASPP2), as a candidate gene for brain abnormalities. Consistent with this, Trp53bp2-deficient mice show dilation of lateral ventricles resembling the phenotype of 1q41q42 microdeletion patients. Trp53bp2 deficiency causes 100% neonatal lethality in the C57BL/6 background associated with a high incidence of neural tube defects and a range of developmental abnormalities such as congenital heart defects, coloboma, microphthalmia, urogenital and craniofacial abnormalities. Interestingly, abnormalities show a high degree of overlap with 1q41q42 microdeletion-associated abnormalities. These findings identify TP53BP2 as a strong candidate causative gene for central nervous system (CNS) defects in 1q41q42 microdeletion syndrome, and open new avenues for investigation of the mechanisms underlying CNS abnormalities.

Reactive control of subsonic axial fan noise in a duct.

Suppressing the ducted fan noise at low frequencies without varying the flow capacity is still a technical challenge. This study examines a conceived device consisting of two tensioned membranes backed with cavities housing the axial fan for suppression of the sound radiation from the axial fan directly. The noise suppression is achieved by destructive interference between the sound fields from the axial fan of a dipole nature and sound radiation from the membrane via vibroacoustics coupling. A two-dimensional model with the flow effect is presented which allows the performance of the device to be explored analytically. The air flow influences the symmetrical behavior and excites the odd in vacuo mode response of the membrane due to kinematic coupling. Such an asymmetrical effect can be compromised with off-center alignment of the axial fan. Tension plays an important role to sustain the performance to revoke the deformation of the membrane during the axial fan operation. With the design of four appropriately tensioned membranes covered by a cylindrical cavity, the first and second blade passage frequencies of the axial fan can be reduced by at least 20 dB. The satisfactory agreement between experiment and theory demonstrates that its feasibility is practical.

Hybrid noise control in a duct using a light micro-perforated plate.

A plate silencer consists of an expansion chamber with two side-branch cavities covered by light but extremely stiff plates. It works effectively with a wide stopband from low-to-medium frequencies only if the plate is extremely stiff, to ensure a strong reflection of acoustic wave to the upstream in the duct. However, a plate with a slightly weak bending stiffness will result in non-uniform transmission loss (TL) spectra with narrowed stopband. In this study, a hybrid silencer is proposed by introducing micro-perforations into the plate to elicit the sound absorption in order to compensate for the deficiency in the passband caused by the insufficient sound reflection in a certain frequency range due to weaker plate stiffness. A theoretical model, capable of dealing with the strong coupling between the vibrating micro-perforated plate and sound fields inside the cavity and the duct, is developed. Through proper balancing between the sound absorption and reflection, the proposed hybrid silencer provides a more flattened and uniform TL and a widened stopband by more than 20% while relaxing the harsh requirement on the bending stiffness of the plate. Theoretical predictions are validated by experimental data, with phenomenon explained through numerical analyses.

Noise suppression of a dipole source by tensioned membrane with side-branch cavities.

Reducing the ducted-fan noise at the low frequency range remains a big technical challenge. This study presents a passive approach to directly suppress the dipole sound radiation from an axial-flow fan housed by a tensioned membrane with cavity backing. The method aims at achieving control of low frequency noise with an appreciable bandwidth. The use of the membrane not only eliminates the aerodynamic loss of flow, but also provides flexibility in controlling the range of the stopband with high insertion loss by varying its tension and mass. A three-dimensional model is presented which allows the performance of the proposed device to be explored analytically. With the proper design, this device can achieve a noise reduction of 5 dB higher than the empty expansion cavity recently proposed by Huang et al. [J. Acoust. Soc. Am. 128, 152-163 (2010)]. Through the detailed modal analysis, even in vacuo modes of the membrane vibration are found to play an important role in the suppression of sound radiation from the dipole source. Experimental validation is conducted with a loudspeaker as the dipole source and good agreement between the predicted and measured insertion loss is achieved.

Clinical and biochemical profiles of maple syrup urine disease in malaysian children.

INTRODUCTION: Maple Syrup Urine Disease (MSUD) is an autosomal recessive disorder caused by defects in the branched-chain α-ketoacid dehydrogenase complex resulting in accumulation of branched-chain amino acids (BCAAs) and corresponding branched-chain ketoacids (BCKAs) in tissues and plasma, which are neurotoxic. Early diagnosis and subsequent nutritional modification management can reduce the morbidity and mortality. Prior to 1990s, the diagnosis of MSUD and other inborn errors of metabolism (IEM) in Malaysia were merely based on clinical suspicion and qualitative one-dimensional thin layer chromatography technique. We have successfully established specific laboratory diagnostic techniques to diagnose MSUD and other IEM. We described here our experience in performing high-risk screening for IEM in Malaysia from 1999 to 2006. We analysed the clinical and biochemical profiles of 25 patients with MSUD. METHODS: A total of 12,728 plasma and urine samples from patients suspected of having IEM were received from physicians all over Malaysia. Plasma amino acids quantitation using fully automated amino acid analyzer and identification of urinary organic acids using Gas Chromatography Mass Spectrometry (GCMS). Patients' clinical information were obtained from the request forms and case records Results: Twenty-five patients were diagnosed MSUD. Nineteen patients (76%) were affected by classical MSUD, whereas six patients had non-classical MSUD. Delayed diagnosis was common among our case series, and 80% of patients had survived with treatment with mild-to-moderate learning difficulties. CONCLUSION: Our findings suggested that MSUD is not uncommon in Malaysia especially among the Malay and early laboratory diagnosis is crucial.

Infantile Progressive Hepatoencephalomyopathy with Combined OXPHOS Deficiency due to Mutations in the Mitochondrial Translation Elongation Factor Gene GFM1.

Mitochondrial disorders are a heterogeneous group of often multisystemic and early fatal diseases caused by defects in the oxidative phosphorylation (OXPHOS) system. Given the complexity and intricacy of the OXPHOS system, it is not surprising that the underlying molecular defect remains unidentified in many patients with a mitochondrial disorder. Here, we report the clinical features and diagnostic workup leading to the elucidation of the genetic basis for a combined complex I and IV OXPHOS deficiency secondary to a mitochondrial translational defect in an infant who presented with rapidly progressive liver failure, encephalomyopathy, and severe refractory lactic acidemia. Sequencing of the GFM1 gene revealed two inherited novel, heterozygous mutations: a.539delG (p.Gly180AlafsX11) in exon 4 which resulted in a frameshift mutation, and a second c.688G > A (p.Gly230Ser) mutation in exon 5. This missense mutation is likely to be pathogenic since it affects an amino acid residue that is highly conserved across species and is absent from the dbSNP and 1,000 genomes databases. Review of literature and comparison were made with previously reported cases of this recently identified mitochondrial disorder encoded by a nuclear gene. Although limited in number, nuclear gene defects causing mitochondrial translation abnormalities represent a new, rapidly expanding field of mitochondrial medicine and should potentially be considered in the diagnostic investigation of infants with progressive hepatoencephalomyopathy and combined OXPHOS disorders.

The causal relationship between electricity consumption and economic growth in a Gaming and Tourism Center: The case of Macao SAR, the People's Republic of China.

A number of Asian cities decided to establish gaming and resort facilities in order to capitalize on the growing number of gamblers and their family members in Asia. In doing so, they expect to sustain economic growth but, on the other hand, will consume a considerable amount of energy. Nevertheless, the causal relationship between economic growth and electricity consumption in this type of service-oriented territories has never been investigated. Using the historical data obtained from the Government of Macao SAR, we found that electricity consumption and economic growth in terms of gross domestic product are co-integrated for the period of 1999 Quarter 1-2008 Quarter 4. Moreover, vector error correction (VEC) models indicated a lack of short-run relationships but showed that there was a long-run equilibrium relationship between electricity consumption and gross domestic product. The accuracy of VEC models was assessed by using the mean squared error and the mean absolute error. The error analysis shows that VEC models reproduced time series of gross domestic product and electricity consumption in difference form accurately.

Clinical and biochemical features of aromatic L-amino acid decarboxylase deficiency.

OBJECTIVE: To describe the current treatment; clinical, biochemical, and molecular findings; and clinical follow-up of patients with aromatic l-amino acid decarboxylase (AADC) deficiency. METHOD: Clinical and biochemical data of 78 patients with AADC deficiency were tabulated in a database of pediatric neurotransmitter disorders (JAKE). A total of 46 patients have been previously reported; 32 patients are described for the first time. RESULTS: In 96% of AADC-deficient patients, symptoms (hypotonia 95%, oculogyric crises 86%, and developmental retardation 63%) became clinically evident during infancy or childhood. Laboratory diagnosis is based on typical CSF markers (low homovanillic acid, 5-hydroxyindoleacidic acid, and 3-methoxy-4-hydroxyphenolglycole, and elevated 3-O-methyl-l-dopa, l-dopa, and 5-hydroxytryptophan), absent plasma AADC activity, or elevated urinary vanillactic acid. A total of 24 mutations in the DDC gene were detected in 49 patients (8 reported for the first time: p.L38P, p.Y79C, p.A110Q, p.G123R, p.I42fs, c.876G>A, p.R412W, p.I433fs) with IVS6+ 4A>T being the most common one (allele frequency 45%). CONCLUSION: Based on clinical symptoms, CSF neurotransmitters profile is highly indicative for the diagnosis of aromatic l-amino acid decarboxylase deficiency. Treatment options are limited, in many cases not beneficial, and prognosis is uncertain. Only 15 patients with a relatively mild form clearly improved on a combined therapy with pyridoxine (B6)/pyridoxal phosphate, dopamine agonists, and monoamine oxidase B inhibitors.

Sound propagation in and low frequency noise absorption by helium-filled porous material.

Low-frequency noise is difficult to deal with by traditional porous material due to its inherent high acoustic impedance. This study seeks to extend the effective range of sound absorption to lower frequencies by filling a low density gas, such as helium, in the porous material. Compared with conventional air-filled absorption material, the helium-filled porous material has a much reduced characteristic impedance; hence, a good impedance matching with pure air becomes more feasible at low frequencies. The acoustic properties of a series of helium-filled porous materials are investigated with a specially designed test rig. The characteristic of the sound propagation in a helium-filled porous material is established and validated experimentally. Based on the measured acoustic properties, the sound absorption performance of a helium-filled absorber (HA) of finite thickness is studied numerically as well as experimentally. For a random incidence field, the HA is found to perform much better than the air-filled absorber at low frequencies. The main advantage of HA lies in the middle range of oblique incidence angles where wave refraction in the absorber enhances sound absorption. The advantage of HA as duct lining is demonstrated both numerically and experimentally.

Nano-mechanics of bone and bioactive bone cement interfaces in a load-bearing model.

Many bioactive bone cements were developed for total hip replacement and found to bond with bone directly. However, the mechanical properties at the bone/bone cement interface under load bearing are not fully understood. In this study, a bioactive bone cement, which consists of strontium-containing hydroxyapatite (Sr-HA) powder and bisphenol-alpha-glycidyl dimethacrylate (Bis-GMA)-based resin, was evaluated in rabbit hip replacement for 6 months, and the mechanical properties of interfaces of cancellous bone/Sr-HA cement and cortical bone/Sr-HA cement were investigated by nanoindentation. The results showed that Young's modulus (17.6+/-4.2 GPa) and hardness (987.6+/-329.2 MPa) at interface between cancellous bone and Sr-HA cement were significantly higher than those at the cancellous bone (12.7+/-1.7 GPa; 632.7+/-108.4 MPa) and Sr-HA cement (5.2+/-0.5 GPa; 265.5+/-39.2 MPa); whereas Young's modulus (6.3+/-2.8 GPa) and hardness (417.4+/-164.5 MPa) at interface between cortical bone and Sr-HA cement were significantly lower than those at cortical bone (12.9+/-2.2 GPa; 887.9+/-162.0 MPa), but significantly higher than Sr-HA cement (3.6+/-0.3 GPa; 239.1+/-30.4 MPa). The results of the mechanical properties of the interfaces were supported by the histological observation and chemical composition. Osseointegration of Sr-HA cement with cancellous bone was observed. An apatite layer with high content of calcium and phosphorus was found between cancellous bone and Sr-HA cement. However, no such apatite layer was observed at the interface between cortical bone and Sr-HA cement. And the contents of calcium and phosphorus of the interface were lower than those of cortical bone. The mechanical properties indicated that these two interfaces were diffused interfaces, and cancellous bone or cortical bone was grown into Sr-HA cement 6 months after the implantation.

Measurement of in-duct acoustic properties by using a single microphone with fixed position.

Acoustic properties of sound absorption materials and other acoustic structures can be measured in an impedance tube using the well-established two-microphone method to resolve the two traveling wave components of a standing wave pattern. The accuracy of such measurements depends crucially on the calibration of the two microphones placed in close proximity. To eliminate such calibration, the one-microphone method [Chu, J. Acoust. Soc. Am. 80, 555-560 (1986)] uses the same microphone to probe at two positions sequentially using the voltage driving the loudspeaker as a reference signal. A variant of this method is introduced in this study in which the microphone is fixed at one position while a rigid end plate moves between two positions to resolve the standing wave. The sound source is installed as a side branch, and its driving signal is also used as a reference in the two-step measurement. Close agreement is found with the established two-microphone method, and factors which might affect the accuracy of the new technique are discussed. As a demonstration of the robustness of the method, a low-budget electret microphone is used and the result also matches well with those obtained by the two-microphone method with high-quality condenser type microphones.

Drum silencer with shallow cavity filled with helium.

The motivation of this study is twofold: (a) to produce a flow-through silencer with zero pressure loss for pressure-critical applications, and (b) to tackle low frequency noise with limited sideway space using cavities filled with helium. The work represents a further development of our recently conceived device of a drum-like silencer with conventional air cavity [Huang, J. Acoust. Soc. Am. 112, 2014-2025 (2002); Choy and Huang, ibid. 112, 2026-2035 (2002)]. Theoretical predictions are validated by experimental data. The new silencer consists of two highly tensioned membranes lining part of a duct, and each membrane is backed by a cavity filled with helium. For a typical configuration of a duct with height h, membrane length L = 7h, cavity depth h = 0.2h, and tension T = 0.52rho0c0(2)h2, where rho0 and c0 are the ambient density and speed of sound in air, respectively, the transmission loss has a continuous stop band of TL > 6.35 dB for frequency 0.03c0/h to 0.064c0/h, which is much better than traditional duct lining. In addition to the mechanisms at work for drum silencers with air cavity, the low density of helium reduces the masslike reactance of the cavity on the second in vacuo mode of membrane vibration. The reduction greatly enhances the membrane response at this mode, which is found to be critical for achieving a broadband performance in the low-frequency regime.

Morbidity in Alagille syndrome in 6 Malaysian children.

We retrospectively studied the records of 6 Malaysian children who were diagnosed with Alagille Syndrome (AGS) according to this criteria from January 1999 to January 2001, at the Institute of Paediatrics, Kuala Lumpur Hospital. Four patients (66%) had a positive family history. Thirteen individuals (6 patients and 7 relatives) were diagnosed with AGS in these 5 families. Only 6/13 (46%) of them presented with liver involvement. All 6 patients presented with typical facies and cholestasis (100%). Three (50%) presented with portal hypertension (PHT) with synthetic liver dysfunction (1 died), 1/6 (17%) have PHT and normal synthetic liver function. Two have cleared their jaundice but have biochemical evidence of hepatitis and hepatomegaly, four have congenital heart disease 5/6 posterior embryotoxon, 2/6 butterfly vertebrae, 4/6 hyperlipidaemia and 4/6 failure to thrive. One patient has a Jagged-1 gene disruption at the translocation breakpoint locus 20p12.3 2n = 46,XX,t(12.20) (q22, p12.3). 5/6 (83%) are still alive. Two-thirds of our patients developed chronic liver disease by 3 years of age. Two-thirds of the index patients have a family history. Only 46% of individuals in these families have clinical evidence of liver involvement. Mortality depends on cardiac/renal disease, end-stage liver failure and intercurrent infection.

Experimental studies of a drumlike silencer.

The theoretical finding of the broadband performance of a reactive silencer is validated experimentally. The silencer consists of two highly stretched membranes lining part of the duct and backed by two long and shallow cavities. The test rig was built with a small square duct of 5 cm in dimension, and each cavity is 5 cm deep and 25 cm long. Two types of metal foils, stainless steel and copper, were used, and the lowest membrane-to-air mass ratio was 1.3. A transmission loss in excess of 10 dB was achieved over more than one octave band. For one configuration close to the optimal parameters, the predicted ratio of the frequency band limits is 2.47, while the experiment gave 2.35. Three spectral peaks were found in the stopband, as predicted, but the peaks were broader than prediction, indicating the presence of significant sound energy dissipation mechanisms. Comparison with theoretical simulation shows that the cavity damping dominates over membrane friction. Tests using heavier membranes and membrane with different levels of tension also agree with predictions. Issues of practical implementation of the concept as a flow-through silencer are also addressed.

Mutational analysis in a cohort of 224 tuberous sclerosis patients indicates increased severity of TSC2, compared with TSC1, disease in multiple organs.

Tuberous sclerosis (TSC) is a relatively common hamartoma syndrome caused by mutations in either of two genes, TSC1 and TSC2. Here we report comprehensive mutation analysis in 224 index patients with TSC and correlate mutation findings with clinical features. Denaturing high-performance liquid chromatography, long-range polymerase chain reaction (PCR), and quantitative PCR were used for mutation detection. Mutations were identified in 186 (83%) of 224 of cases, comprising 138 small TSC2 mutations, 20 large TSC2 mutations, and 28 small TSC1 mutations. A standardized clinical assessment instrument covering 16 TSC manifestations was used. Sporadic patients with TSC1 mutations had, on average, milder disease in comparison with patients with TSC2 mutations, despite being of similar age. They had a lower frequency of seizures and moderate-to-severe mental retardation, fewer subependymal nodules and cortical tubers, less-severe kidney involvement, no retinal hamartomas, and less-severe facial angiofibroma. Patients in whom no mutation was found also had disease that was milder, on average, than that in patients with TSC2 mutations and was somewhat distinct from patients with TSC1 mutations. Although there was overlap in the spectrum of many clinical features of patients with TSC1 versus TSC2 mutations, some features (grade 2-4 kidney cysts or angiomyolipomas, forehead plaques, retinal hamartomas, and liver angiomyolipomas) were very rare or not seen at all in TSC1 patients. Thus both germline and somatic mutations appear to be less common in TSC1 than in TSC2. The reduced severity of disease in patients without defined mutations suggests that many of these patients are mosaic for a TSC2 mutation and/or have TSC because of mutations in an as-yet-unidentified locus with a relatively mild clinical phenotype.

Superiority of denaturing high performance liquid chromatography over single-stranded conformation and conformation-sensitive gel electrophoresis for mutation detection in TSC2.

We evaluated denaturing high pressure liquid chromatography (DHPLC) as a scanning method for mutation detection in TSC2, and compared it to conformation-sensitive gel electrophoresis (CSGE) and single-stranded conformation polymorphism analysis (SSCP). The first 20 exons of TSC2 were amplified from 84 TSC patients and screened initially by CSGE and then by DHPLC. Optimization of DHPLC analysis of each exon was carried out by design of primers with minimum variation in the melting temperature of the amplicon, and titration of both elution gradient and temperature. CSGE analysis identified 40 shifts (21 unique) in the 84 patients and 20 exons. All of these variants were detected by DHPLC, and an additional 27 changes (14 unique) were identified. Overall 15 of 28 (54%) unique single base substitutions were detected by CSGE; all were detected by DHPLC. 25 definite or probable mutations were found in these 84 patients (30%) in exons 1-20 of TSC2. In a subsequent blinded analysis of 15 samples with 18 distinct TSC2 sequence variants originally detected by SSCP in another centre, all variants were detected by DHPLC except one where the variation occurred within the primer. Ten other (7 unique) sequence variants were detected in these samples which had not been detected by SSCP. Overall, 11 of 16 (69%) unique single base substitutions were detected by SSCP; all were detected by DHPLC. We conclude that DHPLC is superior to both CSGE and SSCP for detection of DNA sequence variation in TSC2, particularly for single base substitution mutations.

Dengue encephalitis: a true entity?

Involvement of the central nervous system in dengue fever and dengue hemorrhagic fever has always been thought to be secondary to vasculitis with resultant fluid extravasation, cerebral edema, hypoperfusion, hyponatremia, liver failure, and/or renal failure. Thus, the condition has been referred to as dengue encephalopathy. Encephalitis or direct involvement of the brain by the virus was thought to be unlikely. This paper reports on six children who were seen over a period of two years presenting on the second or third day of illness with dengue encephalitis. The diagnosis was based upon a clinical picture of encephalitis and confirmed by cerebrospinal fluid (CSF) microscopy and electroencephalography changes. All six cases were confirmed dengue infections. Dengue 3 virus was isolated from the CSF of four cases and in one case, dengue 2 was detected by the polymerase chain reaction in both the CSF and blood. In the sixth case, virologic evidence was negative but dengue immunoglobulin M was detected in the CSF and blood. Since the onset of encephalitis appears early in the course of illness coinciding with the viremic phase, we postulate that the virus crosses the blood-brain barrier and directly invades the brain causing encephalitis. This study provides strong evidence that dengue 2 and 3 viruses have neurovirulent properties and behave similarly to other members of the Flaviviridae.