1,640 research outputs found
Clean subglacial access: prospects for future deep hot-water drilling
No full textAccessing and sampling subglacial environments deep beneath the Antarctic Ice Sheet presents several challenges to existing drilling technologies. With over half of the ice sheet believed to be resting on a wet bed, drilling down to this environment must conform to international agreements on environmental stewardship and protection, making clean hot-water drilling the most viable option. Such a drill, and its water recovery system, must be capable of accessing significantly greater ice depths than previous hot-water drills, and remain fully operational after connecting with the basal hydrological system. The Subglacial Lake Ellsworth (SLE) project developed a comprehensive plan for deep (greater than 3000?m) subglacial lake research, involving the design and development of a clean deep-ice hot-water drill. However, during fieldwork in December 2012 drilling was halted after a succession of equipment issues culminated in a failure to link with a subsurface cavity and abandonment of the access holes. The lessons learned from this experience are presented here. Combining knowledge gained from these lessons with experience from other hot-water drilling programmes, and recent field testing, we describe the most viable technical options and operational procedures for future clean entry into SLE and other deep subglacial access targets.<br/
Prececal amino acid digestibility of soybean cake in fast- and slow-growing broiler chickens
No full textThe objective of the present study was to determine whether there are differences in prececal amino acid digestibility between commonly used slow- and fast-growing broiler strains when the regression approach is applied. ISA J-275 and Ross 308 were selected as common representatives of slow- and fast-growing broiler strains, respectively. The experimental diets with soybean cake at levels of 0, 100, and 200 g/kg were offered for ad libitum consumption between 22 and 29 d post-hatch. Titanium dioxide was used as an indigestible marker. Each treatment was tested with six pens comprising 10 birds each. Digesta samples were collected on a pen basis from the distal two-thirds of the intestine section between Meckel's diverticulum and 2 cm anterior to the ileocecal-colonic junction. The prececal amino acid digestibility of soybean cake was calculated by linear regression simultaneously for both strains. There was no significant interaction between broiler strain and inclusion level of soybean cake with respect to the prececal CP and amino acid digestibility of complete diets; there was a significant strain effect for 5 out of the 16 measured amino acids. The prececal CP and amino acid digestibility of soybean cake did not differ significantly between strains and was numerically almost identical. The results of the present study provide evidence of the transferability between broiler strains of prececal amino acid digestibility data, determined using the regression approach, thus improving the accuracy of diet formulation without drawbacks
Vacuum Bloch-Siegert Shift in Cyclotron Resonance
No full textM. Bamba, X. Li and J. Kono, "Vacuum Bloch-Siegert Shift in Cyclotron Resonance," 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), Nagoya, 2018, pp. 1-3.In a two-dimensional electron gas (2DEG) inside a terahertz (THz) cavity in a perpendicular magnetic field, we observed a clear resonance-frequency shift originating from the counter-rotating coupling between the electrons' cyclotron resonance and THz cavity modes. This shift can be understood as a vacuum Bloch-Siegert shift, arising from the ultrastrong counter-rotating coupling between the cyclotron-orbiting 2DEG and the vacuum fluctuations of the THz cavity modes. While such a shift has been difficult to observe clearly and is usually neglected under the rotating-wave approximation, here an unambiguous observation was made possible by the broken time-reversal symmetry of the 2DEG in a magnetic field and the use of an ultrahigh-mobility 2DEG, a high-quality-factor cavity, and circularly polarized THz radiation
The Jost function and Siegert pseudostates from
No full textThe single-channel Jost function is calculated with the computational R-matrix on a Lagrange-Jacobi mesh, in order to study its behaviour at complex wavenumbers. Three potentials derived from supersymmetric transformations, two of which never previously studied, are used to test the accuracy of the method. Each of these potentials, with s-wave or p-wave bound, resonance or virtual states, has a simple analytical expression for the Jost function, which is compared with the calculated Jost function. Siegert states and Siegert pseudostates are determined by finding the zeros of the calculated Jost function. Poles of the exact Jost function are not present in the calculated Jost function due to the truncation of the potential in the R-matrix method. Instead, Siegert pseudostates arise in the vicinity of the missing poles
A revised inventory of Antarctic subglacial lakes
No full textThe locations and details of 145 Antarctic subglacial lakes are presented. The inventory is based on a former catalogue of lake-type features, which has been subsequently reanalysed, and on the results from three additional datasets. The first is from Italian radio-echo sounding (RES) of the Dome C region of East Antarctica, from which 14 new lakes are identified. These data also show that, in a number of occasions, multiple lake-type reflectors thought previously to be individual lakes are in fact reflections from the same relatively large lake. This reduces the former total of lake-type reflectors by six, but also adds a significant level of information to these particular lakes. The second dataset is from a Russian survey of the Dome A and Dome F regions of East Antarctica, which provides evidence of 18 new lakes and extends the coverage of the inventory considerably. The third dataset comprises three airborne RES surveys undertaken by the US in East Antarctica over the last five years, from which forty three new lakes have been identified. Reference to information on Lake Vostok, from Italian and US surveys taken in the last few years, is now included
Interferometric Bloch-Siegert B1+ mapping at 7T
No full textTo achieve a sufficient dynamic range for single channel B1+ mapping required for calibration of multi-channel transmit arrays two distinct solutions have been suggestion recently: (1) Bloch-Siegert effect based B1+ mapping and (2) B1+ mapping using linear combinations of transmit channels. In this work, both approaches are combined and interferometric Bloch-Siegert B1+ mapping is introduced. This approach is cross-validated against two recently introduced interferometric B1+ mapping methods based on actual flip angle imaging (AFI) and a multi flip-angle pre-pulse method as well as against single-channel AFI based B1+ mapping
Theory-based approach to goal setting
No full textWe begin this chapter with an overview of what theory is and what it can be used for. We suggest that theory is central to the development of a cumulative evidence base, especially in an area as complex as rehabilitation. However, it is possible to identify numerous theories relevant to rehabilitation in general and goal setting in particular. As a consequence, researchers and practitioners are faced with the problem of selecting a theory or theories suitable for their particular problem or question. Theory integration may offer a solution to this problem and we discuss recent work on theory integration in relation to goal setting within rehabilitation. We then go on to illustrate the process of theory selection and development by describing, in detail, a programme of work to develop a theory-based goal-setting professional practice framework. This practice framework focuses on stroke rehabilitation in a community setting but the development process is easily transferred across health conditions and settings
Paleofluvial Mega-Canyon Beneath the Central Greenland Ice Sheet
No full textSubglacial topography plays an important role in modulating the distribution and flow of basal water. Where topography predates ice sheet inception, it can also reveal insights into former tectonic and geomorphological processes. Although such associations are known in Antarctica, little consideration has been given to them in Greenland, partly because much of the ice sheet bed is thought to be relatively flat and smooth. Here, we present evidence from ice-penetrating radar data for a 750-km-long subglacial canyon in northern Greenland that is likely to have influenced basal water flow from the ice sheet interior to the margin. We suggest that the mega-canyon predates ice sheet inception and will have influenced basal hydrology in Greenland over past glacial cycles
Microbiology: lessons from a first attempt at Lake Ellsworth
No full textDuring the attempt to directly access, measure and sample Subglacial Lake Ellsworth in 2012–2013, we conducted microbiological analyses of the drilling equipment, scientific instrumentation, field camp and natural surroundings. From these studies, a number of lessons can be learned about the cleanliness of deep Antarctic subglacial lake access leading to, in particular, knowledge of the limitations of some of the most basic relevant microbiological principles. Here, we focus on five of the core challenges faced and describe how cleanliness and sterilization were implemented in the field. In the light of our field experiences, we consider how effective these actions were, and what can be learnt for future subglacial exploration missions. The five areas covered are: (i) field camp environment and activities, (ii) the engineering processes surrounding the hot water drilling, (iii) sample handling, including recovery, stability and preservation, (iv) clean access methodologies and removal of sample material, and (v) the biodiversity and distribution of bacteria around the Antarctic. Comparisons are made between the microbiology of the Lake Ellsworth field site and other Antarctic systems, including the lakes on Signy Island, and on the Antarctic Peninsula at Lake Hodgson. Ongoing research to better define and characterize the behaviour of natural and introduced microbial populations in response to deep-ice drilling is also discussed. We recommend that future access programmes: (i) assess each specific local environment in enhanced detail due to the potential for local contamination, (ii) consider the sterility of the access in more detail, specifically focusing on single cell colonization and the introduction of new species through contamination of pre-existing microbial communities, (iii) consider experimental bias in methodological approaches, (iv) undertake in situ biodiversity detection to mitigate risk of non-sample return and post-sample contamination, and (v) address the critical question of how important these microbes are in the functioning of Antarctic ecosystems.<br/
A multi-step biocatalytic approach for the continuous generation and use of HCN towards chiral O-acetylcyanohydrins
No full textContinuous processing technologies have been shown to be a powerful concept in order to tune reaction
conditions in a very precise manner, enhance the sustainability and facilitate the scale-up of the chemical
processes involving hazardous reagents. This becomes even more important during those multi-step
approaches, where the use of modular components for the downstream processing together with
automated in-line analytics allow the control and coordination of all the stages of the processes.
In spite of these advantages, surprisingly few applications to multi-step biocatalytic strategies in flow1
have been reported so far in contrast to discrete single-step biotransformations.2
The advantages of the continuous flow technology will be described with regard to a novel orthogonal
biocatalytic approach, involving two sequential biotransformations, towards the preparation of chiral Oacetylcyanohydrins. Lipase B from Candida antarctica (CalB) and hydroxynitrile lyase from Arabidopsis
thaliana (AtHNL) were employed in a robust continuous telescoped process, involving an in situ HCN
generation followed by addition to aldehydes and an in-line stabilization of products (scheme 1).
Using the formation of (R)-mandelonitrile as an example, the process was optimized with both
immobilized isolated enzyme (celite-AtHNL) and whole-recombinant E. coli BL21-DE3 cells expressing
AtHNL as biocatalysts.3
Key process parameters and the further applications will be reported.
1
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S.; Liese, A. Beilstein J. Org. Chem. 2011, 7, 1449–1467. c) Itabaiana, I.; Leal, I. C. R.; Miranda, L. S. M.; Souza, R. O. M. a. J. Flow Chem.
2013, 3, 122–126.
2
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Sanekli, M.; Graber, M.; Maugard, T. J. Mol. Catal. B: Enzym. 2014, 109, 143 – 153. d) Baxendale, I. R.; Ernst, M.; Krahnert, W.-R.; Ley, S. V.
Synlett 2002, 1641 – 1644. e) Baxendale, I. R.; Griffiths-Jones, C. M.; Ley, S. V.; Tranmer, G. K. Synlett 2006, 427 – 430. f) Andrade, L. H.;
Kroutil, W.; Jamison, T. F. Org. Lett. 2014, 16, 6092 – 6095. g) Tomaszewski, B.; Lloyd, R. C.; Warr, A. J.; Buehler, K.; Schmid, A.
ChemCatChem 2014, 6, 2567 – 2576. h) Andrade, L. H.; Kroutil, W.; Jamison, T. F. Org. Lett. 2014, 16, 6092–6095.
3 B. Musio, A. Brahma, U. Ismayilova, N. Nikbin, S. B. Kamptmann, P. Siegert, G. E. Jeromin, S. V. Ley, M. Pohl Synlett, in pres
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