Depth to magnetic sources determination using Source Parameter Imaging (SPI) of aeromagnetic data of parts of Central and North-Eastern Nigeria: a reconnaissance tool for geothermal exploration in the area

Source Parameter Imaging (SPI) of aeromagnetic data covering an area located approximately between latitude 7.5o N and 11.5o N and longitude 7.5o E and 10.5o E, which corresponds to parts of the Benue trough (lower part of the Upper Benue trough, the entire middle Benue trough, and upper part of the Lower Benue trough), lower part of the Gongola and Yola Basins, the Precambrian Basement, the Jurassic Younger Granites and two prominent hot Springs, Wiki hot spring in Bauchi state (in the north-eastern part) and Akiri hot spring in Nasarawa state (in the south-western part) of central and north-eastern Nigeria, was carried out for the purpose of estimating the depth to magnetic basement of the area. The estimated depths to magnetic sources from Source parameter imaging (SPI), range from 0.12 to 12.26 km. The highest depth can be found at the south-western part of the study area. The depth to magnetic basement is shallower mainly in the north and extreme north-eastern parts of the study area with magnetic high flanking areas of magnetic low. The above characteristics of these areas and the location of warm springs at the north-eastern and south-western parts of the study area (Wikki and Akiri hot springs respectively). Which suggests the occurrence of tectonic activities in the area, hence is an indication that, there might probably be good sources for geothermal and thereby recommended for both geothermal exploration and exploitation

The Energy Landscape, Folding Pathways and the Kinetics of a Knotted Protein

The folding pathway and rate coefficients of the folding of a knotted protein are calculated for a potential energy function with minimal energetic frustration. A kinetic transition network is constructed using the discrete path sampling approach, and the resulting potential energy surface is visualized by constructing disconnectivity graphs. Owing to topological constraints, the low-lying portion of the landscape consists of three distinct regions, corresponding to the native knotted state and to configurations where either the N- or C-terminus is not yet folded into the knot. The fastest folding pathways from denatured states exhibit early formation of the N-terminus portion of the knot and a rate-determining step where the C-terminus is incorporated. The low-lying minima with the N-terminus knotted and the C-terminus free therefore constitute an off-pathway intermediate for this model. The insertion of both the N- and C-termini into the knot occur late in the folding process, creating large energy barriers that are the rate limiting steps in the folding process. When compared to other protein folding proteins of a similar length, this system folds over six orders of magnitude more slowly.Comment: 19 page

Longitudinal relationships between caloric expenditure and gray matter in the cardiovascular health study

Background: Physical activity (PA) can be neuroprotective and reduce the risk for Alzheimer’s disease (AD). In assessing physical activity, caloric expenditure is a proxy marker reflecting the sum total of multiple physical activity types conducted by an individual. Objective:To assess caloric expenditure, as a proxy marker of PA, as a predictive measure of gray matter (GM) volumes in the normal and cognitively impaired elderly persons. Methods: All subjects in this study were recruited from the Institutional Review Board approved Cardiovascular Health Study (CHS), a multisite population-based longitudinal study in persons aged 65 and older. We analyzed a sub-sample of CHS participants 876 subjects (mean age 78.3, 57.5% F, 42.5% M) who had i) energy output assessed as kilocalories (kcal) per week using the standardized Minnesota Leisure-Time Activities questionnaire, ii) cognitive assessments for clinical classification of normal cognition, mild cognitive impairment (MCI), and AD, and iii) volumetric MR imaging of the brain. Voxel-based morphometry modeled the relationship between kcal/week and GM volumes while accounting for standard covariates including head size, age, sex, white matter hyperintensity lesions, MCI or AD status, and site. Multiple comparisons were controlled using a False Discovery Rate of 5 percent. Results: Higher energy output, from a variety of physical activity types, was associated with larger GM volumes in frontal, temporal, and parietal lobes, as well as hippocampus, thalamus, and basal ganglia. High levels of caloric expenditure moderated neurodegeneration-associated volume loss in the precuneus, posterior cingulate, and cerebellar vermis. Conclusion:Increasing energy output from a variety of physical activities is related to larger gray matter volumes in the elderly, regardless of cognitive status.Cyrus A. Raji, David A. Merrill, Harris Eyre, Sravya Mallam, Nare Torosyan, Kirk I. Erickson, Oscar L. Lopez , James T. Becker, Owen T. Carmichael, H. Michael Gach, Paul M. Thompson, W.T. Longstreth, Jr. and Lewis H. Kulle

Knotted vs. Unknotted Proteins: Evidence of Knot-Promoting Loops

Knotted proteins, because of their ability to fold reversibly in the same topologically entangled conformation, are the object of an increasing number of experimental and theoretical studies. The aim of the present investigation is to assess, on the basis of presently available structural data, the extent to which knotted proteins are isolated instances in sequence or structure space, and to use comparative schemes to understand whether specific protein segments can be associated to the occurrence of a knot in the native state. A significant sequence homology is found among a sizeable group of knotted and unknotted proteins. In this family, knotted members occupy a primary sub-branch of the phylogenetic tree and differ from unknotted ones only by additional loop segments. These "knot-promoting" loops, whose virtual bridging eliminates the knot, are found in various types of knotted proteins. Valuable insight into how knots form, or are encoded, in proteins could be obtained by targeting these regions in future computational studies or excision experiments

Mechanical Bonds and Topological Effects in Radical Dimer Stabilization

While mechanical bonding stabilizes tetrathiafulvalene (TTF) radical dimers, the question arises: what role does topology play in catenanes containing TTF units? Here, we report how topology, together with mechanical bonding, in isomeric [3]- and doubly interlocked [2]catenanes controls the formation of TTF radical dimers within their structural frameworks, including a ring-in-ring complex (formed between an organoplatinum square and a {2+2} macrocyclic polyether containing two 1,5-dioxynaphthalene (DNP) and two TTF units) that is topologically isomeric with the doubly interlocked [2]catenane. The separate TTF units in the two {1+1} macrocycles (each containing also one DNP unit) of the isomeric [3]catenane exhibit slightly different redox properties compared with those in the {2+2} macrocycle present in the [2]catenane, while comparison with its topological isomer reveals substantially different redox behavior. Although the stabilities of the mixed-valence (TTF2)^(•+) dimers are similar in the two catenanes, the radical cationic (TTF^(•+))_2 dimer in the [2]catenane occurs only fleetingly compared with its prominent existence in the [3]catenane, while both dimers are absent altogether in the ring-in-ring complex. The electrochemical behavior of these three radically configurable isomers demonstrates that a fundamental relationship exists between topology and redox properties

Donning time of marine abandonment immersion suits under simulated evacuation conditions.

Maritime emergencies often occur rapidly in unpredictable circumstances. In a scenario where it becomes necessary to abandon a vessel or offshore platform evacuation, personal flotation and thermal protection greatly increase chances of survival for individuals escaping directly into water. Marine abandonment immersion suits, intended to be quickly donned in the case of an emergency, can provide effective protection against dangers of cold shock and prolonged immersion. The ability to locate and correctly don an immersion suit prior to abandoning is critical. Canadian Standard CAN/CGSB-65.16-2005 dictates that an immersion suit must be unpacked and properly donned without assistance within two minutes. Tests are performed on a fixed, stable deck. No empirical investigation has been conducted on time required to don immersion suits in a dynamic environment. Thirty-two participants, with similar knowledge and training, performed immersion suit donning tasks using two types of suit. Trials were performed on a motion bed that simulated maritime conditions with varying combinations of platform motions and levels of ambient illumination. Participant donning times and donning task errors were recorded for each trial. Across all conditions the mean donning time was 102.7 seconds (SD = 39.6 sec). There was a significant difference between donning time and suit manufacturer (p < .0001). Although overall mean donning time was within the two-minute requirement, in total there was a 26.1% failure rate in the completion of full donning tasks within two minutes. Donning task error rates were recorded as high as 56.3% per donning attempt. Results indicate that training standards need to more adequately reflect realistic environmental conditions and demands. Performance-based standards will more likely ensure that all personnel are better educated and prepared to don an abandonment suit successfully within the required time period, and thus increase chances of survival and rescue. Performance based standards that include reference to donning suits in a dynamic environment will be more likely to lead to the development of suits and training that meet the needs of users in real conditions