Frost weathering of chalk

The processes and factors that determine the heave and fracture of frost-susceptible bedrock exposed to temperature cycling above and below 0°C are little known but important to understanding of rock deformation, weathering and ground conditions. To investigate the early stages of heave, settlement and fracture of intact chalk, physical modelling experiments were performed on blocks of Saint Cyr Tuffeau and Totternhoe Clunch. Unidirectional (downward) freezing simulated seasonally frozen bedrock in non-permafrost regions, and bidirectional (upward from permafrost and downward from the surface) simulated an active layer above permafrost. Heave and settlement of the top of the blocks were monitored in relation to rock temperature and unfrozen water content. Heave and settlement showed complex behavior that varied with moisture content, freezing regime and time. Progressive heave of wet chalk during thaw periods (simulated summers) is attributed to microcracking in near-surface permafrost. Macrocracking was favoured near the rock top during unidirectional freezing and near the permafrost table during bidirectional freezing, producing extensive fracture networks. Four processes, operating singly or in combination, account for the heave and settlement behavior: (1) thermal expansion and contraction in dry chalk; (2) volumetric expansion of freezing water, causing bursts of heave; (3) ice segregation, causing sustained heave and rock fracture; and (4) freeze‒thaw cycling, causing initial consolidation and settling of wet chalk during unidirectional freezing. The experimental data and field observations of chalk weathering profiles elucidate the nature and origin of chalk brecciation. Type 1 brecciation (angular or subangular rock fragments separated by unfilled fractures with matched sides) is attributed primarily to ice segregation. Type 2 brecciation (subangular to rounded lumps of rock—lithorelicts—set in a fine-grained matrix of the same, but softer and remoulded material) probably resulted from frost weathering and limited ground movement, particularly beneath the sides and bottoms of wet (now dry) valleys

Transient transcriptional events in human skeletal muscle at the outset of concentric resistance exercise training

We sought to ascertain the time course of transcriptional events that occur in human skeletal muscle at the outset of resistance exercise (RE) training in RE naive individuals and determine whether the magnitude of response was associated with exercise-induced muscle damage. Sixteen RE naive men were recruited; eight underwent two sessions of 5 × 30 maximum isokinetic knee extensions (180°/s) separated by 48 h. Muscle biopsies of the vastus lateralis, obtained from different sites, were taken at baseline and 24 h after each exercise bout. Eight individuals acted as nonexercise controls with biopsies obtained at the same time intervals. Transcriptional changes were assessed by microarray and protein levels of heat shock protein (HSP) 27 and αB-crystallin in muscle cross sections by immunohistochemistry as a proxy measure of muscle damage. In control subjects, no probe sets were significantly altered (false discovery rate < 0.05), and HSP27 and αB-crystallin protein remained unchanged throughout the study. In exercised subjects, significant intersubject variability following the initial RE bout was observed in the muscle transcriptome, with greatest changes occurring in subjects with elevated HSP27 and αB-crystallin protein. Following the second bout, the transcriptome response was more consistent, revealing a cohort of probe sets associated with immune activation, the suppression of oxidative metabolism, and ubiquitination, as differentially regulated. The results reveal that the initial transcriptional response to RE is variable in RE naive volunteers, potentially associated with muscle damage and unlikely to reflect longer term adaptations to RE training. These results highlight the importance of considering multiple time points when determining the transcriptional response to RE and associated physiological adaptation

Women's need for information before attending genetic counselling for familial breast or ovarian cancer: a questionnaire, interview, and observational study

OBJECTIVES: To describe women's information needs prior to genetic counselling for familial breast or ovarian cancer. DESIGN: Prospective study including semistructured telephone interviews before genetic counselling, observations of consultations, completion of postal questionnaires, and face-to face interviews within two months of counselling. SUBJECTS: 46 women attending genetic counselling for familial breast or ovarian cancer. MAIN OUTCOME MEASURES: Subjects' understanding of process and content of genetic counselling before attending and attitudes about their preparation for the counselling session. RESULTS: Although all women interviewed before the clinic expected to discuss their risk of developing cancer and risk management options, there was evidence of a lack of knowledge about the process and content of genetic counselling, 17 (37%) women said they did not know what else would happen. Most women interviewed after counselling viewed it positively, but 26 (65%) felt they had been inadequately prepared and 11 (28%) felt that their lack of preparation meant that they could not be given an accurate estimation of their risk of cancer. CONCLUSIONS: Some women felt that they did not obtain optimum benefit from genetic counselling because they were inadequately prepared for it. We suggest that cancer family history clinics should provide women with written information about the process and content of genetic counselling before their clinic attendance

Marine mineral exploration with controlled source electromagnetics at the TAG Hydrothermal Field, 26°N Mid‐Atlantic Ridge

Seafloor massive sulfide (SMS) deposits are of increasing economic interest in order to satisfy the relentless growth in worldwide metal demand. The Trans‐Atlantic Geotraverse (TAG) hydrothermal field at 26°N on the Mid‐Atlantic Ridge hosts several such deposits. This study presents new controlled source electromagnetic, bathymetric, and magnetic results from the TAG field. Potential SMS targets were selected based on their surface expressions in high‐resolution bathymetric data. High‐resolution reduced‐to‐the‐pole magnetic data show negative anomalies beneath and surrounding the SMS deposits, revealing large areas of hydrothermal alteration. Controlled source electromagnetic data, sensitive to the electrical conductivity of SMS mineralization, further reveal a maximum thickness of up to 80 m and conductivities of up to 5 S/m. SMS samples have conductivities of up to a few thousand Siemens per meter, suggesting that remotely inferred conductivities represent an average of metal sulfide ores combined with silicified and altered host basalt that likely dominates at greater depths

Architecture of North Atlantic contourite drifts modified by transient circulation of the Icelandic mantle plume

Overflow of Northern Component Water, the precursor of North Atlantic Deep Water, appears to have varied during Neogene times. It has been suggested that this variation is moderated by transient behavior of the Icelandic mantle plume, which has influenced North Atlantic bathymetry through time. Thus pathways and intensities of bottom currents that control deposition of contourite drifts could be affected by mantle processes. Here, we present regional seismic reflection profiles that cross sedimentary accumulations (Björn, Gardar, Eirik and Hatton Drifts). Prominent reflections were mapped and calibrated using a combination of boreholes and legacy seismic profiles. Interpreted seismic profiles were used to reconstruct solid sedimentation rates. Björn Drift began to accumulate in late Miocene times. Its average sedimentation rate decreased at ∼2.5 Ma and increased again at ∼0.75 Ma. In contrast, Eirik Drift started to accumulate in early Miocene times. Its average sedimentation rate increased at ∼5.5 Ma and decreased at ∼2.2 Ma. In both cases, there is a good correlation between sedimentation rates, inferred Northern Component Water overflow, and the variation of Icelandic plume temperature independently obtained from the geometry of diachronous V-shaped ridges. Between 5.5 and 2.5 Ma, the plume cooled, which probably caused subsidence of the Greenland-Iceland-Scotland Ridge, allowing drift accumulation to increase. When the plume became hotter at 2.5 Ma, drift accumulation rate fell. We infer that deep-water current strength is modulated by fluctuating dynamic support of the Greenland-Scotland Ridge. Our results highlight the potential link between mantle convective processes and ocean circulationThis work is partly supported by Natural Environment Research Council Grant NE/G007632/1. RPT was supported by the University of Cambridge Girdler Fund and by BP Exploration.This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1002/2015GC00594

On the Reconstruction of Palaeo-Ice Sheets: Recent Advances and Future Challenges

Reconstructing the growth and decay of palaeo-ice sheets is critical to understanding mechanisms of global climate change and associated sea-level fluctuations in the past, present and future. The significance of palaeo-ice sheets is further underlined by the broad range of disciplines concerned with reconstructing their behaviour, many of which have undergone a rapid expansion since the 1980s. In particular, there has been a major increase in the size and qualitative diversity of empirical data used to reconstruct and date ice sheets, and major improvements in our ability to simulate their dynamics in numerical ice sheet models. These developments have made it increasingly necessary to forge interdisciplinary links between sub-disciplines and to link numerical modelling with observations and dating of proxy records. The aim of this paper is to evaluate recent developments in the methods used to reconstruct ice sheets and outline some key challenges that remain, with an emphasis on how future work might integrate terrestrial and marine evidence together with numerical modelling. Our focus is on pan-ice sheet reconstructions of the last deglaciation, but regional case studies are used to illustrate methodological achievements, challenges and opportunities. Whilst various disciplines have made important progress in our understanding of ice-sheet dynamics, it is clear that data-model integration remains under-used, and that uncertainties remain poorly quantified in both empirically-based and numerical ice-sheet reconstructions. The representation of past climate will continue to be the largest source of uncertainty for numerical modelling. As such, palaeo-observations are critical to constrain and validate modelling. State-of-the-art numerical models will continue to improve both in model resolution and in the breadth of inclusion of relevant processes, thereby enabling more accurate and more direct comparison with the increasing range of palaeo-observations. Thus, the capability is developing to use all relevant palaeo-records to more strongly constrain deglacial (and to a lesser extent pre-LGM) ice sheet evolution. In working towards that goal, the accurate representation of uncertainties is required for both constraint data and model outputs. Close cooperation between modelling and data-gathering communities is essential to ensure this capability is realised and continues to progress

Anomalous buried hollows in London: development of a hazard susceptibility map

Engineering works carried out in central London over many decades have revealed a number of buried hollows that exhibit curious characteristics. Some extend deep into the bedrock geology and are in-filled with disturbed superficial deposits and reworked bedrock. Others are contained within the superficial deposits. They can be up to 500 m wide and more than 60 m in depth. As the infill material often has different behavioural characteristics from the surrounding deposits failure to identify them during an initial site investigation can prove costly. This paper considers their common characteristics and describes the method used to develop a buried hollow hazard susceptibility map. This map provides planners with a broader awareness of the potential location of difficult ground conditions associated with them, thereby reducing the potential for unforeseen ground conditions through effective site investigation design. The paper continues with a discussion of some of the likely processes associated with their formation, which are attributed to cryogenic processes, and concludes with potential future research directions

Characterization and Separation Performance of a Novel Polyethersulfone Membrane Blended with Acacia Gum

Novel polyethersulfone (PES) membranes blended with 0.1–3.0 wt. % of Acacia gum (AG) as a pore-former and antifouling agent were fabricated using phase inversion technique. The effect of AG on the pore-size, porosity, surface morphology, surface charge, hydrophilicity, and mechanical properties of PES/AG membranes was studied by scanning electron microscopy (SEM), Raman spectroscopy, contact angle and zeta potential measurements. The antifouling -properties of PES/AG membranes were evaluated using Escherichia coli bacteria and bovine serum albumine (BSA). The use of AG as an additive to PES membranes was found to increase the surface charge, hydrophilicity (by 20%), porosity (by 77%) and permeate flux (by about 130%). Moreover, PES/AG membranes demonstrated higher antifouling and tensile stress (by 31%) when compared to pure PES membranes. It was shown that the prepared PES/AG membranes efficiently removed lead ions from aqueous solutions. Both the sieving mechanism of the membrane and chelation of lead with AG macromolecules incorporated in the membrane matrix contributed to lead removal. The obtained results indicated that AG can be used as a novel pore-former, hydrophilizing and antifouling agent, as well as an enhancer to the mechanical and rejection properties of the PES membranes