Experimental investigation of the transient bleed valve noise

This study presents the first step of an experimental study of the transient bleed valve noise. It was carried out on a simplified TBV geometry composed of a cylindrical inlet pipe leading to a diaphragm or a perforated disk for the purpose of generating pressure drops. Numerous diaphragms and grids have been tested in order to identify parameters that influence the acoustic radiation of the TBV and for NPR (Nozzle pressure ratio) from 1.2 to 3.6 to cover both subsonic and supersonic regimes. A large number of acoustic behaviors have been identified. For diaphragms far field acoustic spectra are dominated by mixing noise for all NPR and by shock-associated noise (screech and broadband shock associated noise (BBSAN)) when the critical value of the NPR delimiting the subsonic and supersonic behavior (NPRc = 1.89)is exceeded. For grids the mixing noise is still present but is composed of two humps. The parametric study allowed to associate the first hump to the noise of an equivalent jet having the smallest diameter encircling the grid perforations while the second is associated to the noise of the outer isolated jets. A first prediction model has thus been proposed based on this double source. Furthermore, the grids other a significant noise reduction in the audible range with respect to a diaphragm of the same cross-section by shifting the radiation towards the high frequencies. The noise associated with supersonic phenomena (screech and BBSAN) are also strongly reduced and even suppressed in most of the tested cases

Experimental investigation of the acoustic role of the output duct in the discharge of a high pressure flow through diaphragms and perforated plates

This work presents the second step of an experimental study of the noise radiated by a complete flow discharge/control system allowing to expand or evacuate a flow under pressure by passing though diaphragms or perforated plates. The first step of the study, focused on the study of the noise radiated by the passage of the flow through the perforated plates/diaphragms, allowed to identify the presence of three distinct radiation sources: a broadband noise associated with the mixing of the flow at the exit of the perforations and which is strongly linked to the geometry, a shock noise (screech and broadband shock associated noise) associated with the presence of shock cells in the ow for supersonic regimes and a tonal noise associated with a feedback loop and appearing for low subsonic operating points. By adding a duct downstream to the discharge zone to be closer to real geometries found in industry, the broadband noise is strongly modified by the appearance of strong acoustic resonances in the outlet duct. These resonances are moreover strongly affected by the operating point which drives the flow intensity in the duct. A simple analytical model is proposed in order to quickly predict the different acoustic modificationscations induced by the outlet duct in case of simple geometries. Finally, the shock noise, as observed without duct, is totally suppressed but is replaced by "base-pressure oscillation" responsible for strong low frequency tones for diaphragms and perforated plates with large cross-sections

Experimental study of the noise radiated by an air flow discharge through diaphragms and perforated plates

An experimental analysis of the noise radiated by a high pressure flow discharge through diaphragms and perforated plates is carried out for a large range of subsonic and supersonic operating conditions (nozzle pressure ratio (NPR) from 1 to 3.6). A parametric study of the geometrical parameters is also achieved to characterize their influence onto the acoustic radiation and ways to reduce it. This reaches from single diaphragms to multi-perforated plates with variable hole diameters and arrangements that are placed at the exit of a duct. Different acoustic behaviors are observed: in all cases the far-field acoustic radiation is dominated by a broadband contribution associated with the turbulent mixing in shear layers. In the diaphragm cases, this broadband noise has similar characteristics as the mixing noise of classical unheated jets while in the multi-perforated plates cases, it is composed of two distinct humps associated with different parts of the jets development. For supersonic regimes, in addition to this broadband radiation, shock associated noise (screech and broadband shock associated noise) appears for all diaphragm cases and for the perforated plate with the closest holes. Finally for the smallest NPR, a high frequency tonal noise has been observed in most of the multi-perforated cases and for the smallest diaphragm. Different regimes of this radiation have also been observed with a possible amplitude modulation of the dominant tone. This radiation may be attributed to vortex shedding due to the sharp section reduction that would trigger a flow resonance between the small ducts of the holes and their sharp edges

Experimental investigation of the noise radiated by a ducted air flow discharge though diaphragms and perforated plates

An experimental investigation of the noise radiated by a ducted high pressure flow discharge through diaphragms and perforated plates is carried out for a large range of subsonic and supersonic operating conditions (Nozzle Pressure Ratio (NPR) from 1.2 to 3.6). A parametric study of the geometrical parameters is also conducted to characterize their influence on the acoustic radiation. This covers configurations from single diaphragms to multi-perforated plates with variable hole diameters and arrangements that are placed inside a cylindrical duct. Compared with the free discharge analysed in a first part of the study (perforated plates placed directly at the output of the duct), the discharge into a duct, which is closer to the practical applications, generates strong acoustic modifications. As expected, the broadband noise is disturbed by strong modulations due to acoustic resonances in the output duct (longitudinal resonances and transversal duct modes). However, as in the free configuration, a strong effect of the plate geometries on the mixing noise is observed, allowing to adapt or reduce this source. In particular, the increase of the ratio between the perforation spacing and the perforation diameter allows reducing the maximum amplitude of the mixing noise. Compared to the free-field discharge, the Sound Pressure Level (SPL) in the ducted configuration is on average proportional to the 6-th power of the velocity instead of the 8-th power. Moreover, there are two dominant frequency humps in the sound spectra. The low frequency one is characterized by a constant Helmholtz number, suggesting that the sound is shaped by the duct geometry, whereas the high frequency one is characterized by a constant Strouhal number suggesting that the sound is directly generated by the flow. Finally, for supersonic operating points, the screech radiation appearing with diaphragms in the free configuration is suppressed when the output duct is added but new high amplitude and low frequency tones appear for the largest diaphragms and perforated plates. These lines are due to a coupling between normal shock oscillations and longitudinal resonances

DNA damage and repair kinetics after microbeam radiation therapy emulation in living cells using monoenergetic synchrotron X-ray microbeams

The molecular response of mammalian cells to a monoenergetic synchrotron X-ray microbeam which emulated microbeam radiation configurations has been investigated. Very few γH2AX foci were found outside the irradiated zone within 1 h of irradiation, even within a single nucleus. Furthermore, 12 h after radiation there was a large decrease in foci number but many cells still contained γH2AX foci, of which many were outside the directly irradiated regions

Health promotion and screening for people with an intellectual disability

People with intellectual disability have significantly worse health than those without, and have a higher level of complex health needs. The life expectancy for men and women is 13 and 20 years shorter, respectively, than the general population. The increasing role of general practice in delivering and coordinating care across health and social care settings requires expert generalist skills to implement an integrated approach to care. This article explores how general practice can improve the health of people with intellectual disability, by making reasonable adjustments within health promotion, disease prevention, screening and detection

Multivalent binding of PWWP2A to H2A.Z regulates mitosis and neural crest differentiation

Replacement of canonical histones with specialized histone variants promotes altering of chromatin structure and function. The essential histone variant H2A.Z affects various DNA-based processes via poorly understood mechanisms. Here, we determine the comprehensive interactome of H2A.Z and identify PWWP2A as a novel H2A.Z-nucleosome binder. PWWP2A is a functionally uncharacterized, vertebrate-specific protein that binds very tightly to chromatin through a concerted multivalent binding mode. Two internal protein regions mediate H2A.Z-specificity and nucleosome interaction, whereas the PWWP domain exhibits direct DNA binding. Genome-wide mapping reveals that PWWP2A binds selectively to H2A.Z-containing nucleosomes with strong preference for promoters of highly transcribed genes. In human cells, its depletion affects gene expression and impairs proliferation via a mitotic delay. While PWWP2A does not influence H2A.Z occupancy, the C-terminal tail of H2A.Z is one important mediator to recruit PWWP2A to chromatin. Knockdown of PWWP2A in Xenopus results in severe cranial facial defects, arising from neural crest cell differentiation and migration problems. Thus, PWWP2A is a novel H2A.Z-specific multivalent chromatin binder providing a surprising link between H2A.Z, chromosome segregation, and organ development

PWWP2A binds distinct chromatin moieties and interacts with an MTA1-specific core NuRD complex.

Chromatin structure and function is regulated by reader proteins recognizing histone modifications and/or histone variants. We recently identified that PWWP2A tightly binds to H2A.Z-containing nucleosomes and is involved in mitotic progression and cranial-facial development. Here, using in vitro assays, we show that distinct domains of PWWP2A mediate binding to free linker DNA as well as H3K36me3 nucleosomes. In vivo, PWWP2A strongly recognizes H2A.Z-containing regulatory regions and weakly binds H3K36me3-containing gene bodies. Further, PWWP2A binds to an MTA1-specific subcomplex of the NuRD complex (M1HR), which consists solely of MTA1, HDAC1, and RBBP4/7, and excludes CHD, GATAD2 and MBD proteins. Depletion of PWWP2A leads to an increase of acetylation levels on H3K27 as well as H2A.Z, presumably by impaired chromatin recruitment of M1HR. Thus, this study identifies PWWP2A as a complex chromatin-binding protein that serves to direct the deacetylase complex M1HR to H2A.Z-containing chromatin, thereby promoting changes in histone acetylation levels