Effects of extension ladder fly configuration on climbing safety.

Fall injuries often occur on extension ladders. The extendable fly section of an extension ladder is typically closer to the user than the base section, though this design is minimally justified. This study investigates the effects of reversing the fly on foot placement, frictional requirements, adverse stepping events (repositioning the foot or kicking the rung), and user preferences. Participant foot placement was farther posterior (rung contacted nearer to toes) in the traditional ladder compared to the reversed fly condition during descent, with farther anterior foot placements during ascent. The reversed configuration had similar friction requirements during early/mid stance and significantly lower frictional requirements during late stance. Increased friction requirements during late stance were associated with farther anterior foot placement and further plantar flexed foot orientation. The reversed fly had 5 adverse stepping events versus 22 that occurred in the traditional configuration. Users typically preferred the reversed fly. These results suggest that a reversed extension ladder configuration offers potential benefits in reducing fall-related injuries that should motivate future research and development work.

During roof-to ladder transitions, walk-through extensions modify required friction direction.

Severe and fatal falls involving ladders commonly occur during transitions across the ladder and another support surface. Slipping is a common initiating event in ladder falls. This study characterized the friction requirements and body kinematics of descending roof-to-ladder transitions with and without a walk-through extension. Healthy adults who regularly climb ladders (n = 17) completed descending roof-to-ladder transitions, while foot-rung kinetics and body kinematics were recorded. The peak required coefficient of friction (RCOF) with respect to the plane of the shoe sole was calculated. The RCOF and body angle were calculated using their resultant values and projections in the frontal and sagittal planes. Foot angle was calculated in the sagittal plane. Repeated-measures ANOVA determined that compared to a walk-through ladder, a traditional ladder was associated with a higher RCOF in the medial-lateral (ML) direction (F1,16 = 190.07, p < 0.001) and a lower RCOF in the anterior-posterior (AP) direction (F1,16 = 11.02, p = 0.004), but had no significant relationship with the resultant RCOF (F1,16 = 0.098, p = 0.76). Spearman's rho tests performed across all testing configurations identified significant associations between foot angle and overall RCOF (rs = -0.724, p < 0.001), foot angle and AP RCOF (rs = -0.871, p < 0.001), and frontal plane body angle and ML RCOF (rs = 0.782, p < 0.001). Clustering in the data suggests that ladder attachments reduced frontal plane kinematics, which altered the direction of RCOF by reducing the medial-lateral component. These results have implications for designing rungs with good friction in multiple directions and the potential for body position monitoring in ladder tasks.

Layer-Dependent Magnetism and Spin Fluctuations in Atomically Thin van der Waals Magnet CrPS4.

van der Waals (vdW) magnets, an emerging family of two-dimensional (2D) materials, have received tremendous attention due to their rich fundamental physics and significant potential for cutting-edge technological applications. In contrast to the conventional bulk counterparts, vdW magnets exhibit significant tunability of local material properties, such as stacking engineered interlayer coupling and layer-number dependent magnetic and electronic interactions, which promise to deliver previously unavailable merits to develop multifunctional microelectronic devices. As a further ingredient of this emerging topic, here we report nanoscale quantum sensing and imaging of the atomically thin vdW magnet chromium thiophosphate CrPS4, revealing its characteristic layer-dependent 2D static magnetism and dynamic spin fluctuations. We also show a large tunneling magnetoresistance in CrPS4-based spin filter vdW heterostructures. The excellent material stability and robust strategy against environmental degradation in combination with tailored magnetic properties highlight the potential of CrPS4 in developing state-of-the-art 2D spintronic devices for next-generation information technologies.