D.F., a patient with severe visual form agnosia, has been the subject of extensive research during the past decade. The fact that she could process visual input accurately for the purposes of guiding ...action despite being unable to perform visual discriminations on the same visual input inspired a novel interpretation of the functions of the two main cortical visual pathways or ‘streams’. Within this theoretical context, the authors proposed that D.F. had suffered severe bilateral damage to her occipitotemporal visual system (the ‘ventral stream’), while retaining the use of her occipitoparietal visual system (the ‘dorsal stream’). The present paper reports a direct test of this idea, which was initially derived from purely behavioural data, before the advent of modern functional neuroimaging. We used functional MRI to examine activation in her ventral and dorsal streams during object recognition and object‐directed grasping tasks. We found that D.F. showed no difference in activation when presented with line drawings of common objects compared with scrambled line drawings in the lateral occipital cortex (LO) of the ventral stream, an area that responded differentially to these stimuli in healthy individuals. Moreover, high‐resolution anatomical MRI showed that her lesion corresponded bilaterally with the location of LO in healthy participants. The lack of activation with line drawings in D.F. mirrors her poor performance in identifying the objects depicted in the drawings. With coloured and greyscale pictures, stimuli that she can identify more often, D.F. did show some ventral‐stream activation. These activations were, however, more widely distributed than those seen in control participants and did not include LO. In contrast to the absent or abnormal activation observed during these perceptual tasks, D.F. showed robust activation in the expected dorsal stream regions during object grasping, despite considerable atrophy in some regions of the parietal lobes. In particular, an area in the anterior intraparietal sulcus was activated more for grasping an object than for just reaching to that object, for both D.F. and controls. In conclusion, we have been able to confirm directly that D.F.’s visual form agnosia is associated with extensive damage to the ventral stream, and that her spared visuomotor skills are associated with visual processing in the dorsal stream.
Electron-Ion Collider: The next QCD frontier Accardi, A; Albacete, J L; Anselmino, M ...
The European physical journal. A, Hadrons and nuclei,
09/2016, Letnik:
52, Številka:
9
Journal Article
Recenzirano
Odprti dostop
This White Paper presents the science case of an Electron-Ion Collider (EIC), focused on the structure and interactions of gluon-dominated matter, with the intent to articulate it to the broader ...nuclear science community. It was commissioned by the managements of Brookhaven National Laboratory (BNL) and Thomas Jefferson National Accelerator Facility (JLab) with the objective of presenting a summary of scientific opportunities and goals of the EIC as a follow-up to the 2007 NSAC Long Range plan. This document is a culmination of a community-wide effort in nuclear science following a series of workshops on EIC physics over the past decades and, in particular, the focused ten-week program on “Gluons and quark sea at high energies” at the Institute for Nuclear Theory in Fall 2010. It contains a brief description of a few golden physics measurements along with accelerator and detector concepts required to achieve them. It has been benefited profoundly from inputs by the users’ communities of BNL and JLab. This White Paper offers the promise to propel the QCD science program in the US, established with the CEBAF accelerator at JLab and the RHIC collider at BNL, to the next QCD frontier.
Combined liver–kidney transplantation has become a common practice for the treatment of patients with concurrent end‐stage renal disease and end‐stage liver disease. Liver transplantation in the ...setting of multiorgan transplantation is thought to have a protective effect against humoral rejection even when a positive crossmatch is obtained prior to surgery. In most centers, a pre liver–kidney transplant crossmatch is rarely performed because of the known immunoprotective effect of the liver allograft. In this report, a case of acute humoral rejection in the kidney allograft after a combined liver–kidney transplant is described. Although humoral rejection was treated using plasmapheresis, intravenous immunoglobulin and rituximab, the kidney required 3 months to recover function and finally progressed to chronic allograft nephropathy. A heightened index of suspicion for acute humoral rejection of the renal allograft is necessary when performing combined liver–kidney transplants to highly sensitized patients due to previous organ transplants.
A patient who developed isolated acute antibody‐mediated rejection of the kidney after a liver‐kidney transplant required three months to recover after treatment with IVIG, rituximab, and plasmapheresis.
We performed Monte Carlo calculations in a simple model that relates the radiative capture and electrodisintegration reactions and showed that by using a windowless gas jet target and modern ...energy-recovery linear accelerators (ERLs, CBETA at Cornell, MESA at Mainz, ARIEL e-linac at TRIUMF) to reach high luminosity, a high precision measurement of the electrodisintegration of the 16 O nucleus would provide a method to determine the rate of the α on 12 C radiative capture with a superb statistical precision compared to existing data. The calculations were done for the beam energies of 30, 50 and 114 MeV and show a significant reduction in terms of statistical uncertainties for the energy range Ec.m. < 2 MeV. The 114 MeV setting has the smallest statistical uncertainty, but at the same time the calculations for this beam energy setting were performed the furthest away from the real photon limit. The feasibility of this simple model still needs to be studied experimentally. This could be done with an experiment focused at Ec.m. > 2 MeV region, where the cross section is much larger.
Recently, a new class of soluble inorganic pyrophosphatase (type-C PPase) has been described that is not homologous in amino acid sequence or kinetic properties to the well-studied PPases (types A ...and B) found in many organisms from bacteria to humans and thought to be essential to the cell. Structural studies of the type-C PPases from
Streptococcus gordonii and
Bacillus subtilis reveal a homodimeric structure, with each polypeptide folding into two domains joined by a flexible hinge. The active site, formed at the interface between the N and C-terminal domains, binds two manganese ions approximately 3.6 Å apart in a conformation resembling binuclear metal centres found in other hydrolytic enzymes. An activated water molecule bridging the two metal ions is likely poised for nucleophilic attack of the substrate. Importantly, the
S. gordonii and
B. subtilis enzymes have crystallised in strikingly different conformations. In both subunits of the
S. gordonii crystal structure (1.5 Å resolution) the C-terminal domain is positioned such that the active site is occluded, with a sulphate ion bound in the active site. In contrast, in the
B. subtilis structure (3.0 Å resolution) the C-terminal domain is rotated by about 90 °, leaving the active site wide open and accessible for substrate binding.
Radiative capture reactions play a crucial role in stellar nucleosynthesis but have proved challenging to determine experimentally. In particular, the large uncertainty (≈100%) in the measured rate ...of the 12C(α,γ)16O reaction is the largest source of uncertainty in any stellar evolution model. With development of high-current energy-recovery linear accelerators (ERLs) and high-density gas targets, measurement of the 16O(e,e'α)12C reaction close to threshold using detailed balance allows a new approach to determine the 12C(α,γ)16O reaction rate with significantly increased precision (<20%). We present the formalism to relate photo- and electrodisintegration reactions and consider the design of an optimal experiment to deliver increased precision. Furthermore, once the new ERLs come online, an experiment to validate the approach we propose should be carried out. This approach has broad applicability to radiative capture reactions in astrophysics.
When normal subjects grasp with their right hand a rectangular object placed at different orientations in the horizontal plane, they change from a ‘thumb left’ (clockwise) to a ‘thumb right’ ...(anti-clockwise) grasp when the orientation exceeds about 110°, with respect to the mid-sagittal plane. This suggests planning of the final grip orientation at, or before the start of the prehension movement. The current study assessed performance of two visual agnosic patients (SB and DF) on a grasping task requiring the planning of final grip posture. Five healthy subjects were also tested. Subjects were required to grasp a triangular-section block, which was presented at one of seven different orientations (80–140°). The healthy subjects showed a consistent relation between object orientation and hand orientation just before contact. In addition, they consistently used a clockwise grasp when object orientation was less than 100°, and an anti-clockwise grasp when it was more than 110°, with a sharply defined switch-point being identifiable for each subject. For both visual agnosic patients, hand orientation was also reliably related to object orientation. However, the selection of grasp posture was markedly abnormal: they did not consistently switch between clockwise and anti-clockwise grasps within the normal orientation range, and the switch, when it did occur, was not at all sharply defined. These results suggest that the planning of hand orientation during a grasp depends on a perceptually based judgement of the awkwardness of alternative movements. This would presumably involve ventral stream processing, which is disrupted in the visual agnosic patients.
This White Paper presents the science case of an Electron-Ion Collider (EIC), focused on the structure and interactions of gluon-dominated matter, with the intent to articulate it to the broader ...nuclear science community. It was commissioned by the managements of Brookhaven National Laboratory (BNL) and Thomas Jefferson National Accelerator Facility (JLab) with the objective of presenting a summary of scientific opportunities and goals of the EIC as a follow-up to the 2007 NSAC Long Range plan. This document is a culmination of a community-wide effort in nuclear science following a series of workshops on EIC physics over the past decades and, in particular, the focused ten-week program on “Gluons and quark sea at high energies” at the Institute for Nuclear Theory in Fall 2010. It contains a brief description of a few golden physics measurements along with accelerator and detector concepts required to achieve them. It has been benefited profoundly from inputs by the users’ communities of BNL and JLab. This White Paper offers the promise to propel the QCD science program in the US, established with the CEBAF accelerator at JLab and the RHIC collider at BNL, to the next QCD frontier.
Objective: A non‐silent polymorphism in the mitochondrial coding region of the ND1 gene, a subunit of reduced nicotinamide adenine dinucleotide (NADH) dehydrogenase is associated with resting ...metabolic rate (RMR) in 245 non‐diabetic Pima Indians. The purpose of this investigation was to determine the effect of the ND1 gene polymorphism on mitochondrial function in 14 male Pima Indians.
Methods and Procedures: Seven subjects with an A at site 3547 of the ND1 gene (Ile at amino acid 81), and seven with a G at this site (Val) were studied. Mitochondria were isolated from 0.8 to 1.5 g of skeletal muscle obtained by needle biopsy of the lateral quadriceps muscle. In intact mitochondria, maximal (state‐3) and resting (state‐4) respiration rates were measured polarographically at 37 °C with a variety of single substrates or substrate combinations. Disrupted mitochondria were analyzed for maximal capacities through the entire electron transport chain (ETC) (NADH oxidase (NADHOX)), as well as through a segment of Complex I that is independent of the ND1 component (NADH‐ferricyanide (NADH‐FeCN) reductase).
Results: Mitochondria were well coupled and exhibited higher respiratory control ratios (RCRs) than rodent muscle. There were no differences between the two groups for any of the measured parameters.
Discussion: These results indicate that the cause of the observed association between RMR and the ND1 polymorphism is not related to in vitro mitochondrial function.
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