Effect of sound insulation on noise reduction in an agricultural tractor cab.

Tractor cab interior noise is a risk factor that degrades operators' work performance and threatens their health; therefore, the noise must be reduced to ensure farmworkers' safety and efficiency. Cab interior noise can be classified as structure-borne noise and air-borne noise. Structure-borne noise has been extensively studied. However, although air-borne noise greatly contributes to cab interior noise, detailed frequency-domain analyses have not been performed. In this study, the components of cab interior noise were identified in the frequency domain through an order analysis, which helped improve the sound insulation of the cab and reduce the effects of air-borne noise. A test was performed while driving a tractor on a chassis dynamometer in a semi-anechoic chamber for reproducible measurement and evaluation. The A-weighted sound pressure was transformed by a fast Fourier transform algorithm, and its order was tracked by the engine speed signal. In addition, a direct path was identified by acoustic images using a sound camera. The contributions of major noise sources were identified through an order analysis. We proved that air-borne noise significantly contributes to the interior noise of tractor cabs and that improvement of the cab sound insulation is an effective noise-reduction technique.

Maize harvester gearbox design modification for improved fatigue life.

The gearbox has the advantage of being able to change the torque and rotational speed according to the gear ratio and has high power transmission efficiency by transmitting power through the contact of the gear pair. When evaluating the strength and fatigue life of a gearbox using a design load or an equivalent load, there is a possibility that the results will be very different from the actual ones. Therefore, in this study, the load duration distribution (LDD) constructed based on the actual workload was used to evaluate the strength and fatigue life of the gearbox reliably. As a result of evaluating the strength and fatigue life of the gearbox using LDD, it was confirmed that the existing gearbox did not satisfy the target lifespan in the operating environment. Therefore, the reasons for these results were analyzed, and design modification was performed based on the analyzed results. As a result of design modification, shaft deflection decreased by rearrangement of the bearings, from an overhung type to a straddle type, thereby improving the fatigue life of gears and bearings. Finally, the load distribution acting on the gear tooth surface was improved through micro-geometry modification of the gears.

Transnitrosylation from DJ-1 to PTEN attenuates neuronal cell death in parkinson's disease models.

Emerging evidence suggests that oxidative/nitrosative stress, as occurs during aging, contributes to the pathogenesis of Parkinson's disease (PD). In contrast, detoxification of reactive oxygen species and reactive nitrogen species can protect neurons. DJ-1 has been identified as one of several recessively inherited genes whose mutation can cause familial PD, and inactivation of DJ-1 renders neurons more susceptible to oxidative stress and cell death. DJ-1 is also known to regulate the activity of the phosphatase and tensin homolog (PTEN), which plays a critical role in neuronal cell death in response to various insults. However, mechanistic details delineating how DJ-1 regulates PTEN activity remain unknown. Here, we report that PTEN phosphatase activity is inhibited via a transnitrosylation reaction [i.e., transfer of a nitric oxide (NO) group from the cysteine residue of one protein to another]. Specifically, we show that DJ-1 is S-nitrosylated (forming SNO-DJ-1); subsequently, the NO group is transferred from DJ-1 to PTEN by transnitrosylation. Moreover, we detect SNO-PTEN in human brains with sporadic PD. Using x-ray crystallography and site-directed mutagenesis, we find that Cys106 is the site of S-nitrosylation on DJ-1 and that mutation of this site inhibits transnitrosylation to PTEN. Importantly, S-nitrosylation of PTEN decreases its phosphatase activity, thus promoting cell survival. These findings provide mechanistic insight into the neuroprotective role of SNO-DJ-1 by elucidating how DJ-1 detoxifies NO via transnitrosylation to PTEN. Dysfunctional DJ-1, which lacks this transnitrosylation activity due to mutation or prior oxidation (e.g., sulfonation) of the critical cysteine thiol, could thus contribute to neurodegenerative disorders like PD.

Hypoxia enhances S-nitrosylation-mediated NMDA receptor inhibition via a thiol oxygen sensor motif.

Under ambient air conditions, NO inhibits NMDAR activity by reacting with the NR2A subunit C399 along with two additional cysteine pairs if their disulfide bonds are reduced to free thiol groups [NR1(C744,C798); NR2(C87,C320)]. Here we demonstrate that relative hypoxia enhances S-nitrosylation of NMDARs by a unique mechanism involving an "NO-reactive oxygen sensor motif" whose determinants include C744 and C798 of the NR1 subunit. Redox reactions involving these two thiol groups sensitize other NMDAR sites to S-nitrosylation and consequent receptor inhibition, while their own nitrosylation has little effect on NMDAR activity. The crystal structure of the ligand-binding domain of NR1 reveals a flexible disulfide bond (C744-C798), which may account for its susceptibility to reduction and subsequent reaction with NO that is observed with biochemical techniques. These thiols may be nitrosylated preferentially during increasing hypoxia or stroke conditions, thus preventing excessive activity associated with cytotoxicity while avoiding blockade of physiologically active NMDARs.

Crystallization and preliminary X-ray analysis of the Mj0684 gene product, a putative aspartate aminotransferase, from Methanococcus jannaschii.

A putative aspartate aminotransferase from the hyperthermophilic archaeon Methanococcus jannaschii encoded by the Mj0684 gene has been overexpressed in Escherichia coli and crystallized at 296 K using the sitting-drop vapour-diffusion method. The crystals belong to space group P4(1)2(1)2 (or P4(3)2(1)2), with unit-cell parameters a = b = 111.87, c = 60.86 A. They diffract to 2.2 A resolution using Cu Kalpha X-rays. The asymmetric unit contains a single subunit of the recombinant Mj0684 gene product, giving a corresponding V(M) of 2.25 A(3) Da(-1) and a solvent content of 45.3% by Volume. An X-ray diffraction data set has been collected to 2.2 A at 295 K.