Although shoulder dub off on gun drills has significant infl

Although shoulder dub-off on gun drills has significant influence on chip transportation behavior, most commercial gun drills adhere to a fixed design of 20° that has limited scientific basis. To determine the effects of shoulder dub-off on chip evacuation, 5 different angles ranging from 0° to 30° as shown in Fig. 12 was studied with the developed CFD model. As the value of dub-off angle increases, the chip would travel deeper towards the bottom of the hole (Fig. 13). Hence, this would heighten the risks of the chip being stuck at the bottom. This happens due to the severity of the sudden expansion of the flow at greater dub-off angles, resulted in greater pressure losses and larger regions of flow Andarine when the dub-off angle is greater than 10°, vacuum pressures begin to appear, and with such a pressure difference between front and rear surfaces of the chip, the tendency is for the chip evacuation gets blocked on bottom of the hole increased (Fig. 14). From the velocity streamline view (Fig. 15) and pressure contour view (Fig. 16), the flow can be guided properly at the cutting edge with 0° dub-off angle. Whereas, at 30° dub-off angle, the flow is deflected away from the cutting edge and leading to the generation of vortices in the vicinity of cutting edge. This finding suggests that shoulder dub-off between 0° and 10° can facilitate chip evacuation much more effectively than the conventional 20°.
Conclusions In this study, an experimentally calibrated computational fluids dynamic model to quantify the linear and rotational flow motion of gun drill chips under high pressure coolant has been developed. With such capabilities, transportation behavior of the chip from the cutting zone can be simulated and thus enable a realistic evaluation of chip evacuation efficiency of a gundrilling process, which is largely governed by the design of gun drills. Based on this study on the effects of dub-off angles, the following conclusions are drawn:
Acknowledgments
Main Text The posttranslational modification of proteins with one or several ubiquitin molecules can alter the fate, activity, localization, and protein-protein interactions of the modified protein. Polyubiquitin chains of eight different linkage types can be generated and the type of linkage between the ubiquitins can determine the outcome of ubiquitylation. Thousands of cellular proteins are modified by ubiquitin and as a consequence, ubiquitylation regulates a wide range of cellular processes in eukaryotes. Deubiquitinases (DUBs) are proteases that reverse this modification by hydrolysing the isopeptide bond between ubiquitin and the target protein, and thereby function as important regulators of ubiquitylation. How DUBs specifically recognize and hydrolyze different polyubiquitin modifications is poorly understood. In this issue, Flierman et al. (2016) describe novel ubiquitin probes that will be valuable tools to study how DUBs recognize ubiquitin chains of different linkage types. There are ∼100 DUBs encoded in the human genome that can be classified into five different families: ubiquitin C-terminal hydrolase (UCH), ubiquitin-specific proteases (USPs), ovarian tumor (OTU), Josephins, and JAB1/MPDN+/MOV34 (JAMM). With the exception of JAMM family DUBs, which are metallo-proteases, the remaining DUBs are thiol proteases. Ubiquitin probes or ubiquitin suicide probes, as they are otherwise referred to, are tools commonly used to study DUBs. These monoubiquitin probes contain a thiol-reactive chemical group or warhead at the C-terminal end of ubiquitin that reacts with the active site cysteine of DUBs (Figure 1B). Such probes have contributed greatly to our understanding of DUBs. For instance, several OTU family DUBs were discovered using these probes (Borodovsky et al., 2002). These probes have also been utilised to obtain crystal structures of DUBs in complex with ubiquitin at the distal or S1 site (Eletr and Wilkinson, 2014). However, these probes provide limited information on how DUBs process polyubiquitin chains.