| 1. |
- Chien, Yin-Hsiu, et al.
(författare)
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Mudd's disease (MAT I/III deficiency) : a survey of data for MAT1A homozygotes and compound heterozygotes
- 2015
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Ingår i: Orphanet Journal of Rare Diseases. - : Springer Science and Business Media LLC. - 1750-1172. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Background: This paper summarizes the results of a group effort to bring together the worldwide available data on patients who are either homozygotes or compound heterozygotes for mutations in MAT1A. MAT1A encodes the subunit that forms two methionine adenosyltransferase isoenzymes, tetrameric MAT I and dimeric MAT III, that catalyze the conversion of methionine and ATP to S-adenosylmethionine (AdoMet). Subnormal MAT I/III activity leads to hypermethioninemia. Individuals, with hypermethioninemia due to one of the MAT1A mutations that in heterozygotes cause relatively mild and clinically benign hypermethioninemia are currently often being flagged in screening programs measuring methionine elevation to identify newborns with defective cystathionine beta-synthase activity. Homozygotes or compound heterozygotes for MAT1A mutations are less frequent. Some but not all, such individuals have manifested demyelination or other CNS abnormalities. Purpose of the study: The goals of the present effort have been to determine the frequency of such abnormalities, to find how best to predict whether they will occur, and to evaluate the outcomes of the variety of treatment regimens that have been used. Data have been gathered for 64 patients, of whom 32 have some evidence of CNS abnormalities (based mainly on MRI findings), and 32 do not have such evidence. Results and Discussion: The results show that mean plasma methionine concentrations provide the best indication of the group into which a given patient will fall: those with means of 800 mu M or higher usually have evidence of CNS abnormalities, whereas those with lower means usually do not. Data are reported for individual patients for MAT1A genotypes, plasma methionine, total homocysteine (tHcy), and AdoMet concentrations, liver function studies, results of 15 pregnancies, and the outcomes of dietary methionine restriction and/or AdoMet supplementation. Possible pathophysiological mechanisms that might contribute to CNS damage are discussed, and tentative suggestions are put forth as to optimal management.
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| 2. |
- Gnodtke, C, et al.
(författare)
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Phonon-assisted tunneling through quantum dot stacks
- 2006
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 73:11, s. 1-115338
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Tidskriftsartikel (refereegranskat)abstract
- The impact of electron-phonon interaction on the coherent transport through a quantum dot stack is investigated using the nonequilibrium Green's function technique. While the main resonance is due to the alignment of the single dot levels, satellite peaks occur due to resonances with phonon replica of the bare levels. This effect is analyzed in detail and we show that the inclusion of nondiagonal self-energies leads to a significant reduction of the induced current, which is interpreted as an interference effect.
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| 3. |
- Kapaklis, Vassilios, et al.
(författare)
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Thermal fluctuations in artificial spin ice
- 2014
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Ingår i: Nature Nanotechnology. - 1748-3387 .- 1748-3395. ; 9:7, s. 514-519
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Tidskriftsartikel (refereegranskat)abstract
- Artificial spin ice systems have been proposed as a playground for the study of monopole-like magnetic excitations(1,2), similar to those observed in pyrochlore spin ice materials(3). Currents of magnetic monopole excitations have been observed's, demonstrating the possibility for the realization of magnetic-charge-based circuitry. Artificial spin ice systems that support thermal fluctuations can serve as an ideal setting for observing dynamical effects such as monopole propagation and as a potential medium for magnetricity investigations(1,2). Here, we report on the transition from a frozen to a dynamic state in artificial spin ice with a square lattice. Magnetic imaging is used to determine the magnetic state of the islands in thermal equilibrium. The temperature-induced onset of magnetic fluctuations and excitation populations are shown to depend on the lattice spacing and related interaction strength between islands. The excitations are described by Boltzmann distributions with their factors in the frozen state relating to the blocking temperatures of the array. Our results provide insight into the design of thermal artificial spin ice arrays where the magnetic charge density and response to external fields can be studied in thermal equilibrium.
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| 4. |
- Kiesslich, G, et al.
(författare)
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Counting statistics and decoherence in coupled quantum dots
- 2006
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 73:3, s. 1-033312
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Tidskriftsartikel (refereegranskat)abstract
- We theoretically consider charge transport through two quantum dots coupled in series. The corresponding full counting statistics for noninteracting electrons is investigated in the limits of sequential and coherent tunneling by means of a master equation approach and a density matrix formalism, respectively. We clearly demonstrate the effect of quantum coherence on the zero-frequency cumulants of the transport process, focusing on noise and skewness. Moreover, we establish the continuous transition from the coherent to the incoherent tunneling limit in all cumulants of the transport process and compare this with decoherence described by a dephasing voltage probe model.
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| 5. |
- Litnovsky, Andrey, et al.
(författare)
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Carbon transport, deposition and fuel accumulation in castellated structures exposed in TEXTOR
- 2007
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Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 367, s. 1481-1486
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Tidskriftsartikel (refereegranskat)abstract
- In order to maintain the thermo-mechanical durability of ITER it is proposed to castellate the interior surface of the first wall and divertor by splitting them into small-size cells [W. Daener et a]., Fusion Eng. Des. 61&62 (2002) 61]. A concern is the accumulation of fuel in the gaps of the castellation. In TEXTOR, molybdenum limiters were exposed in the scrape-off layer (SOL) plasma to assess fuel accumulation. The first limiter was exposed under deposition-dominated conditions. Carbon deposits were formed both on top surfaces and in the gaps. About 0.12% of the impinging D-fluence was found in the gaps. Another castellated limiter was exposed under erosion-dominated conditions. Deposited layers were found only on the plasma shadowed areas of the gaps. A significant amount of molybdenum from the limiter was found intermixed in the deposit. The gaps contained similar to 0.03% of the impinging D-fluence. Modeling was performed to simulate carbon transport into the gaps.
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| 6. |
- Pircher, Achmed, et al.
(författare)
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Lipocalin-type Prostaglandin D Synthase Concentration Gradients in the Cerebrospinal Fluid in Normal-tension Glaucoma Patients with Optic Nerve Sheath Compartmentation
- 2021
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Ingår i: Eye and Brain. - : Taylor & Francis. - 1179-2744. ; 13, s. 89-97
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To report on the lipocalin-type prostaglandin D synthase (L-PGDS) concentrations in the cerebrospinal fluid (CSF) of the perioptic and lumbar subarachnoid space (SAS) in patients with radiologically proven optic nerve (ON) sheath compartmentation presenting as normal-tension glaucoma (NTG).Methods: Retrospective biochemical analysis of CSF in thirteen patients with ON sheath compartmentation presenting as NTG (four females, mean age 70 +/- 8 years). CSF was sampled from the SAS of the ON during ON sheath fenestration for ON sheath compartmentation and from the lumbar SAS at the time of lumbar puncture. Nephelometry was used for the quantification of L-PGDS and albumin concentration. Albumin was measured in order to assess the amount of contamination with serum in the CSF samples taken from the ON SAS. Main outcome measures were L-PGDS concentrations in the CSF of the perioptic and lumbar SAS.Results: Mean L-PGDS concentration was 24 +/- 8 mg/L in the lumbar SAS compared to 33 +/- 27 mg/L without correction of serum contamination and 45 +/- 39 mg/L after correction of serum contamination in the perioptic SAS. The difference between the lumbar and the perioptic SAS was statistically significant (P=0.0047 without correction of serum contamination, P=0.0002 with correction of serum contamination; Mann-Witney U-test).Conclusion: This study demonstrates a concentration gradient of L-PGDS levels within the CSF with a statistically significant higher concentration in the compartmentalized perioptic SAS compared to that in the lumbar SAS. Biochemical changes in the perioptic SAS might be involved in the pathophysiology in NTG patients with ON sheath compartmentation.
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| 7. |
- Wetzler, R, et al.
(författare)
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Inhomogeneous charging and screening effects in semiconductor quantum dot arrays
- 2004
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 6, s. 1-81
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Tidskriftsartikel (refereegranskat)abstract
- The electronic properties of quantum dot (QD) arrays are strongly influenced by the Coulomb interaction of electrons within the dot as well as with those in neighbouring dots. In this paper, we investigate this behaviour taking into account screening by a free electron gas in the vicinity of the QDs. We find pronounced effects for standard capacitance - voltage ( CV) measurements of QD structures embedded in a pn-diode. In particular, we show that the three-dimensional nature of the problem is crucial for devices with low dot-density, whereas the self-consistency between electron depletion in the bulk layer and dot occupation is important for high dot-densities. The Coulomb interaction between the dots induces a broadening of the peaks in the CV characteristic which is comparable with the effect of disordered QD arrays, where we considered realistic size and position fluctuations obtained by a kinetic Monte Carlo simulation.
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