Background and purpose
Distal involvement of autonomic nerve fibers is critical in familial amyloid polyneuropathy (FAP) due to transthyretin (TTR) mutation. This study compares different methods for ...assessing autonomic foot innervation in TTR‐FAP patients.
Methods
Three groups of seven TTR‐FAP patients were included, according to disease severity: clinically asymptomatic, moderate or advanced neuropathy. The autonomic investigation included the eutectic mixture of local anesthetics test and laser Doppler flowmetry for vasomotor aspects and the Sudoscan® (measuring electrochemical skin conductance) and Neuropad® test for sudomotor aspects. Somatic innervation was assessed by performing nerve conduction studies, quantitative sensory testing including vibration, cold and warm detection threshold (WDT) measurements and laser evoked potentials.
Results
The results of all neurophysiological tests varied according to TTR‐FAP severity (P ≤ 0.01, Kruskal–Wallis test), except for the eutectic mixture of local anesthetics test and laser Doppler flowmetry variables. In addition, the sudomotor tests (Sudoscan or Neuropad) or WDT measurement provided early markers of neuropathy in two of the seven asymptomatic carriers. Finally, all neurophysiological results correlated with the Neuropathy Impairment Score (r values between −0.88 and −0.66, P < 0.005, Spearman test), except the cold detection threshold.
Conclusions
The Neuropad test could be used to detect TTR‐FAP onset, but confirmation requires electrochemical skin conductance and WDT measurement. The Sudoscan technique, but not the Neuropad test (at least assessed at a fixed time point), could be valuable to follow the progression of the neuropathy. Follow‐up investigation should also include large‐fiber investigation (e.g. nerve conduction studies and vibration detection threshold). Conversely, reliable tests for assessing vasomotor disturbances in limb extremities of TTR‐FAP patients are still awaited.
The influence of varying fractions of primary gamma prime precipitates on the hot deformation and annealing behavior of an experimental Nickel-based superalloy containing 24 wt pct. Co was ...investigated. Billets heat treated at 1110 °C or 1135 °C were subjected to hot compression tests at temperatures ranging from 1020 °C to 1060 °C and strain rates ranging from 0.001 to 0.1/s. The microstructures were characterized using electron back scatter diffraction in the as-deformed condition as well as following a super-solvus anneal heat treatment at 1140 °C for 1 hour. This investigation sought to quantify and understand what effect the volume fraction of primary gamma prime precipitates has on the dynamic recrystallization behavior and resulting length fraction ∑3 twin boundaries in the low stacking fault superalloy following annealing. Although deformation at the lower temperatures and higher strain rates led to dynamic recrystallization for both starting microstructures, comparatively lower recrystallized fractions were observed in the 1135 °C billet microstructures deformed at strain rates of 0.1/s and 0.05/s. Subsequent annealing of the 1135 °C billet microstructures led to a higher proportion of annealing twins when compared to the annealed 1110 °C billet microstructures.
Cathodoluminescence (CL) spectroscopy is a suitable technique for studying the luminescent properties of optoelectronic materials because CL has no limitation on the excitable bandgap energy and ...eliminates ambiguous signals due to simple light scattering and resonant Raman scattering potentially involved in the photoluminescence spectra. However, direct CL measurements of atomically thin two-dimensional materials have been difficult due to the small excitation volume that interacts with high-energy electron beams. Herein, distinct CL signals from a monolayer hexagonal BN (hBN), namely mBN, epitaxial film grown on a graphite substrate are shown by using a CL system capable of large-area and surface-sensitive excitation. Spatially resolved CL spectra at 13 K exhibited a predominant 5.5-eV emission band, which has been ascribed to originate from multilayered aggregates of hBN, markedly at thicker areas formed on the step edges of the substrate. Conversely, a faint peak at 6.04 ± 0.01 eV was routinely observed from atomically flat areas, which is assigned as being due to the recombination of phonon-assisted direct excitons of mBN. The CL results support the transition from indirect bandgap in bulk hBN to direct bandgap in mBN. The results also encourage one to elucidate emission properties of other low-dimensional materials by using the present CL configuration.
Background/Objectives: Childhood obesity is prevalent, and dietary habits are a key determinant. Some children skip breakfast for weight control, but studies have shown mixed results. Therefore, we ...assessed the association between breakfast skipping and body mass index (BMI) among young Chinese children in Hong Kong. Design/Subjects and Methods: A cohort of 113 457 primary 4 participants of the Department of Health Student Health Service in 1998-2000 was followed up for 2 years, with 68 606 (60.5%) participants available for analysis in primary 6. The sociodemographic characteristics for traced and untraced participants were similar. At baseline and follow-up, students reported breakfast habit (consumed vs skipped) and other lifestyle characteristics using a standardized questionnaire. BMI was derived using height and weight measured by trained nurses. Multivariable linear regression was used to examine the cross-sectional relationship between breakfast habit and BMI, as well as the prospective association between baseline breakfast habit and change in BMI. Models adjusted for demographic, socioeconomic and lifestyle characteristics. Results: A total of 1805 (5.3%) boys and 1793 (5.2%) girls skipped breakfast at baseline. In cross-sectional analyses, breakfast skippers had a higher mean BMI than did eaters among both primary 4 (beta=0.77, 95% confidence interval (95% CI): 0.67-0.87) (P<0.001) and primary 6 children (beta=0.86, 95% CI: 0.78-0.95) (P<0.001). Compared with eaters, baseline breakfast skippers experienced a greater increase in BMI in the subsequent 2 years (beta=0.11, 95% CI: 0.07–0.16) (P<0.001), and this association was stronger among lunch skippers than eaters (P for interaction=0.04). Conclusion: Our study provided prospective evidence that skipping breakfast predicts a greater increase in BMI among Hong Kong children. As breakfast is a modifiable dietary habit, our results may have important implications for weight control. However, the underlying mechanism of this effect warrants further investigation.
Clinical hypertension is associated with raised serum IgG antibodies. However, whether antibodies are causative agents in hypertension remains unknown. We investigated whether hypertension in mice is ...associated with B-cell activation and IgG production and moreover whether B-cell/IgG deficiency affords protection against hypertension and vascular remodeling. Angiotensin II (Ang II) infusion (0.7 mg/kg per day; 28 days) was associated with (1) a 25% increase in the proportion of splenic B cells expressing the activation marker CD86, (2) an 80% increase in splenic plasma cell numbers, (3) a 500% increase in circulating IgG, and (4) marked IgG accumulation in the aortic adventitia. In B-cell-activating factor receptor-deficient (BAFF-R(-/-)) mice, which lack mature B cells, there was no evidence of Ang II-induced increases in serum IgG. Furthermore, the hypertensive response to Ang II was attenuated in BAFF-R(-/-) (Δ30±4 mm Hg) relative to wild-type (Δ41±5 mm Hg) mice, and this response was rescued by B-cell transfer. BAFF-R(-/-) mice displayed reduced IgG accumulation in the aorta, which was associated with 80% fewer aortic macrophages and a 70% reduction in transforming growth factor-β expression. BAFF-R(-/-) mice were also protected from Ang II-induced collagen deposition and aortic stiffening (assessed by pulse wave velocity analysis). Finally, like BAFF-R deficiency, pharmacological depletion of B cells with an anti-CD20 antibody attenuated Ang II-induced hypertension by ≈35%. Hence, these studies demonstrate that B cells/IgGs are crucial for the development of Ang II-induced hypertension and vessel remodeling in mice. Thus, B-cell-targeted therapies-currently used for autoimmune diseases-may hold promise as future treatments for hypertension.
Lattice-matched graphene on hexagonal boron nitride is expected to lead to the formation of a band gap but requires the formation of highly strained material and has not hitherto been realized. We ...demonstrate that aligned, lattice-matched graphene can be grown by molecular beam epitaxy using substrate temperatures in the range 1600–1710 °C and coexists with a topologically modified moiré pattern with regions of strained graphene which have giant moiré periods up to ∼80 nm. Raman spectra reveal narrow red-shifted peaks due to isotropic strain, while the giant moiré patterns result in complex splitting of Raman peaks due to strain variations across the moiré unit cell. The lattice-matched graphene has a lower conductance than both the Frenkel–Kontorova-type domain walls and also the topological defects where they terminate. We relate these results to theoretical models of band gap formation in graphene/boron nitride heterostructures.
Solving Recent Challenges for Wrought Ni-Base Superalloys Hardy, M. C.; Detrois, M.; McDevitt, E. T. ...
Metallurgical and materials transactions. A, Physical metallurgy and materials science,
06/2020, Letnik:
51, Številka:
6
Journal Article
Recenzirano
Odprti dostop
This paper reviews the status of technology in design and manufacture of new wrought polycrystalline Ni-base superalloys for critical engineering applications. There is a strong motivation to develop ...new alloys that are capable of operating at higher temperatures to realize improvements in thermal efficiency, which are necessary to achieve environmental targets for reduced emissions of harmful green-house gases. From the aerospace sector, the development of new powder metallurgy and ingot metallurgy alloys is discussed for disk rotor and static applications. New compositions for powder metallurgy contain about 50 to 55 pct of gamma prime (
γ
′) strengthening precipitates to ensure components operate successfully at temperatures up to 788 °C (1450 °F). In contrast, new compositions for ingot metallurgy aim to occupy a design space in temperature capability between Alloy 718 and current powder alloys that are in-service, and show levels of
γ
′ of about 30 to 44 pct. The focus in developing these alloys was design for manufacturability. To complement the aerospace developments, a review of work to understand the suitability of candidate alloys for multiple applications in Advanced-Ultra Supercritical (AUSC) power plants has been undertaken by Detrois, Jablonski, and Hawk from the National Energy Technology Laboratory. In these power plants, steam temperatures are required to reach 700 °C to 760 °C. The common thread is to develop alloys that demonstrate a combination of high-temperature properties, which are reliant on both the alloy composition and microstructure and can be produced readily at the right price. For the AUSC applications, the emphasis is on high-temperature strength, long-term creep life, phase stability, oxidation resistance, and robust welding for fabrications. Whereas for powder disk rotors in aircraft engines, the priority is enhanced resistance to time-dependent crack growth, phase stability, and resistance to environmental damage, while extending the current strength levels, which are shown by existing alloys, to higher temperatures.
We demonstrate direct epitaxial growth of high-quality hexagonal boron nitride (hBN) layers on graphite using high-temperature plasma-assisted molecular beam epitaxy. Atomic force microscopy reveals ...mono- and few-layer island growth, while conducting atomic force microscopy shows that the grown hBN has a resistance which increases exponentially with the number of layers, and has electrical properties comparable to exfoliated hBN. X-ray photoelectron spectroscopy, Raman microscopy and spectroscopic ellipsometry measurements on hBN confirm the formation of sp
-bonded hBN and a band gap of 5.9 ± 0.1 eV with no chemical intermixing with graphite. We also observe hexagonal moiré patterns with a period of 15 nm, consistent with the alignment of the hBN lattice and the graphite substrate.
Summary The diagnosis of small fiber neuropathy (SFN) is a challenge for clinical neurophysiology. Conventional nerve conduction studies are inappropriate for this purpose and therefore various ...neurophysiological tests have been proposed. In this study, we compared the diagnostic value of five of these tests in 87 patients with clinically definite ( n = 33) or possible ( n = 54) SFN related to amyloid neuropathy secondary to transthyretin gene mutation or monoclonal gammopathy ( n = 30), primary Sjögren's syndrome ( n = 20), Fabry's disease ( n = 2), or unknown cause ( n = 35). Neurophysiological tests included quantitative sensory testing with determination of warm and cold detection thresholds (WDT, CDT), recording of laser-evoked potentials (LEP) and sympathetic skin responses (SSRs), and measurement of electrochemical skin conductance (ESC) using Sudoscan® device. All tests were performed at the four extremities (hands and feet). All patients with clinically definite SFN and 70% of the patients with possible SFN had at least one abnormal test. The LEP was the most sensitive test (altered in 79% of the patients with at least one abnormal test), followed by ESC (61%), WDT (55%), SSR (41%), and CDT (32%). The combination of LEP, assessing A-delta sensory fibers, WDT, assessing sensory C fibers, and ESC, assessing autonomic C fibers, appears a relevant approach for the diagnosis of SFN. Compared to SSR and CDT, these three tests, LEP, WDT, and ESC, had a significantly better diagnostic sensitivity and their combination further improved diagnostic accuracy.
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