Elucidation of smear wear layer structure and ageing mechanisms of filled tyre tread compounds

This paper explores the microstructure of smear wear particles generated during the abrasion of tyre tread compounds made from different polymers. The compounds tested were synthetic polyisoprene rubber (IR) and styrene-butadiene rubber (SBR) reinforced with either carbon black or silica. This study used a range of different experimental techniques including Gel Permeation Chromatography (GPC), Dynamic Mechanical Analysis (DMA Rheology), Thermal Gravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM) on both fresh and aged smear wear particles to understand their structure and ageing mechanisms. This research reveals that there is significant difference between the molecular weights of the initial uncured rubber and smear wear particles. Significant differences are also observed in the filler volume fraction and the nature of polymer filler interaction between the cured rubber and smear wear particles generated from abrasion. The results also reveal a second relaxation process in smear wear particles, which is attributed to decrosslinked polymer content. After comparing the ageing effect of 1 day and 1 month to smear wear particle properties it was also discovered that the ageing mechanisms are dominated by the recovery of the filler network in the short term and by oxidation-driven crosslinking in the polymer over the longer time frame. The microstructure of the smear wear particles proposed from these results is confirmed by a detailed investigation using SEM techniques

Deglaciation patterns in the Upper Zemmgrund, Austria: An exploration of clean-ice disintegration scenarios

The European Alps are rapidly losing glacier mass due to climatic warming and are anticipated to be largely ice-free by the year 2100. Long-term glacier monitoring in the Alps provides a record of anthropogenically-driven climate change since the Little Ice Age maximum in ~1850. Understanding these long-term glacier changes provides a basis for mitigating hazards (e.g., mass movements) associated with a transition to a paraglacial environment and for predicting future scenarios. Here, we present a post-Little Ice Age-maximum record of glacial landscape changes in the Upper Zemmgrund, Austria, utilising a multi-method framework integrating multi-decadal geomorphological mapping, historical imagery and remote sensing of glacier change. This study contributes a high-resolution, quantifiable record of the transition from a glacial to paraglacial landscape. We find that individual glacier response to climatic change varies within the Upper Zemmgrund, attributed to glacier characteristics such as hypsometry and size. Nonetheless, all glaciers show signs of growing instability such as an increase in crevasses and the collapse of circular tension structures, which have dammed meltwater at the terminus of one glacier, posing a substantial hazard to downstream communities. Future glacier disintegration is anticipated to accelerate in the Upper Zemmgrund, which may result in an ice-free landscape within the next ~40–60 years

Bolla Bollana boulder beds:A Neoproterozoic trough mouth fan in South Australia?

The Bolla Bollana Formation is an exceptionally thick (ca 1500 m), rift-related sedimentary succession cropping out in the northern Flinders Ranges, South Australia, which was deposited during the Sturtian (mid Cryogenian) glaciation. Lithofacies analysis reveals three distinct facies associations which chart changing depositional styles on an ice-sourced subaqueous fan system. The diamictite facies association is dominant, and comprises both massive and stratified varieties with a range of clast compositions and textures, arranged into thick beds (1 to 20 m), representing stacked, ice-proximal glaciogenic debris-flow deposits. A channel belt facies association, most commonly consisting of normally graded conglomerates and sandstones, displays scour and fill structure of ca 10 m width and 1 to 3 m depth: these strata are interpreted as channelized turbidites. Rare mud-filled channels in this facies association bear glacially striated lonestones. Finally, a sheet heterolithics facies association contains a range of conglomerates through sandstones to silty shales arranged into clear, normally graded cycles from the lamina to bed scale. These record a variety of non-channelized turbidites, probably occupying distal and/or inter-channel locations on the subaqueous fan. Coarsening and thickening-up cycles, capped by dolomicrites or mudstones, are indicative of lobe build out and abandonment, potentially as a result of ice lobe advance and stagnation. Dropstones, recognized by downwarped and punctured laminae beneath pebbles to boulders in shale, or in delicate climbing ripple cross-laminated siltstones, are clearly indicative of ice rafting. The co-occurrence of ice-rafted debris and striated lonestones strongly supports a glaciogenic sediment source for the diamictites. Comparison to Pleistocene analogues enables an interpretation as a trough mouth fan, most probably deposited leeward of a palaeo-ice stream. Beyond emphasizing the highly dynamic nature of Sturtian ice sheets, these interpretations testify to the oldest trough mouth fan recorded to date.Daniel P. Le Heron, Marie E. Busfield, and Alan S. Collin

Piezoresistive Elastomer Composites Used for Pressure Sensing

Pressure sensors with capability to detect small physical movements and mechanical deformations have been widely used in wearable and medical applications. However, devices that are commercially available currently require complex designs and fabrication and present only a limited force-range sensitivity. To simplify the design, a thermoplastic polyurethane (TPU)/ carbon nanotubes (CNTs) composite film has been developed using a melt extrusion technique followed by compression moulding. Pressure sensors were made from these films, whose piezoresistive response have been analysed as a function of the concentrations of CNTs, around the percolation threshold. The changes in the voltage of the device with applied pressure was continuously measured using a voltage divider system coupled with an electromechanical test machine that dynamically loaded the sensors under compression. The voltage divider system was tuned to obtain the best sensitivity and signal/noise (S/N) ratio for each device tested. The results showed that sensors containing a target of 2.5 wt.% CNTs had market leading sensitivity and repeatability during long-term stability testing and showed high durability during underwater testing indicating that such devices can be used as a promising robust pressure sensitive sensor in wearable devices

The RMS Survey: 13CO observations of candidate massive YSOs in the southern hemisphere

Abridged: The Red MSX Source (RMS) survey is an ongoing multi-wavelength observational programme designed to return a large, well-selected sample of massive young stellar objects (MYSOs). Here we present 13CO observations made towards 854 MYSOs candidates located in the 3rd and 4th quadrants. We detected 13CO emission towards a total of 751 of the 854 RMS sources observed (~88%). In total 2185 emission components are detected above 3$\sigma$ level. Multiple emission profiles are observed towards the majority of these sources - 455 sources (~60%) - with an average of ~4 molecular clouds along the line of sight. These multiple emission features make it difficult to assign a kinematic velocity to many of our sample. We have used archival CS (J=2-1) and maser velocities to resolved the component multiplicity towards 82 sources and have derived a criterion which is used to identify the most likely component for a further 202 multiple component sources. Combined with the single component detections we have obtained unambiguous kinematic velocities towards 580 sources (~80% of the detections). The 171 sources for which we have not been able to determine the kinematic velocity will require additional line data. Using the rotation curve of Brand and Blitz (1993) and their radial velocities we calculate kinematic distances for all components detected.Comment: Summitted to A&A, the resolution of figure 1 has been reduced, samples of Table 3 and Figure 11 are now included but the full version will only be available in the online version of the journa

Infrared study of the Southern Galactic star forming region associated with IRAS 14416-5937

Aims: We have carried out an infrared study of the southern Galactic massive star forming region associated with IRAS 14416-5937. Methods: This star forming region has been mapped simultaneously in two far infrared bands at ~ 150 & 210 micron using the TIFR 1-m balloon borne telescope with ~ 1' angular resolution. We have used 2MASS JHK$_s$ as well as Spitzer-GLIMPSE data of this region to study the stellar populations of the embedded young cluster. This region comprises of two sources, designated as A & B and separated by ~ 2 pc. The spectrum of a region located close to the source A obtained using the Long Wavelength Spectrometer (LWS) on-board the Infrared Space Observatory (ISO), is presented. Emission from warm dust and from Unidentified Infrared Bands (UIBs) is estimated using the mid-infrared data of the MSX survey. Results: The spatial distributions of (1) the temperature of cool dust and (2) optical depth at 200 micron have been obtained taking advantage of the similar beams in both the TIFR bands. A number of atomic fine structure lines have been detected in the ISO-LWS spectrum, which have been used to estimate the electron density and the effective temperature of the ionising radiation in this region. From the near and mid infrared images, we identify a dust lane due north-west of source A. The dust lane is populated by Class I type sources. Class II type sources are found further along the dust lane as well as below it. Self consistent radiative transfer models of the two sources (A and B) are in good agreement with the observed spectral energy distributions. Conclusions: The spatial distribution of young stellar objects in and around the dust lane suggests that active star formation is taking place along the dust lane and is possibly triggered by the expanding HII regions of A and B.Comment: Accepted by the Astronomy and Astrophysics (21 pages, 7 tables and 13 figures