16 research outputs found
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A new crystalline form of αβ-D-lactose prepared by oven drying a concentrated aqueous solution of D-lactose
A new crystalline form of αβ-D-lactose (C12H22O11, Z' = 2) has been prepared by rapid drying of an approximately 40 % w/v syrup of D-lactose. Initially identified from its novel powder X-ray diffraction pattern, the monoclinic crystal structure was solved from a microcrystal recovered from the generally polycrystalline, mixed-phase residue obtained at the end of the drying step. This is the second crystalline form of αβ-D-lactose to be identified and it has a high degree of structural 3D similarity to the previously identified triclinic form
Genetic Screening of Anderson-Fabry Disease in Probands Referred From Multispecialty Clinics.
BACKGROUND:
Anderson-Fabry disease (AFD) is a rare X-linked lysosomal storage disease, caused by defects of the alpha-galactosidase A (GLA) gene. AFD can affect the heart, brain, kidney, eye, skin, peripheral nerves, and gastrointestinal tract. Cardiology (hypertrophic cardiomyopathy), neurology (cryptogenic stroke), and nephrology (end-stage renal failure) screening studies suggest the prevalence of GLA variants is 0.62%, with diagnosis confirmation in 0.12%.
OBJECTIVES:
This study sought to expand screening from these settings to include ophthalmology, dermatology, gastroenterology, internal medicine, pediatrics, and medical genetics to increase diagnostic yield and comprehensively evaluate organ involvement in AFD patients.
METHODS:
In a 10-year prospective multidisciplinary, multicenter study, we expanded clinical, genetic, and biochemical screening to consecutive patients enrolled from all aforementioned clinical settings. We tested the GLA gene and α-galactosidase A activity in plasma and leukocytes. Inclusion criteria comprised phenotypical traits and absence of male-to-male transmission. Screening was extended to relatives of probands harboring GLA mutations.
RESULTS:
Of 2,034 probands fulfilling inclusion criteria, 37 (1.8%) were carriers of GLA mutations. Cascade family screening identified 60 affected relatives; clinical data were available for 4 affected obligate carriers. Activity of α-galactosidase A in plasma and leukocytes was diagnostic in male subjects, but not in female subjects. Of the 101 family members harboring mutations, 86 were affected, 10 were young healthy carriers, and 5 refused clinical evaluation. In the 86 patients, involved organs or organ systems included the heart (69%), peripheral nerves (46%), kidney (45%), eye (37%), brain (34%), skin (32%), gastrointestinal tract (31%), and auditory system (19%). Globotriaosylceramide accumulated in organ-specific and non-organ-specific cells in atypical and classic variants, respectively.
CONCLUSIONS:
Screening probands with clinically suspected AFD significantly increased diagnostic yield. The heart was the organ most commonly involved, independent of the clinical setting in which the patient was first evaluated
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Jahn-Teller driven electronic instability in thermoelectric tetrahedrite
Tetrahedrite, Cu12Sb4S13, is an abundant mineral with excellent thermoelectric properties owing to its low thermal conductivity. The electronic and structural origin of the intriguing physical properties of tetrahedrite, including its metal-to-semiconductor transition, remains largely unknown. This work presents the first determination of the low-temperature structure of tetrahedrite that accounts for its unique properties. Contrary to prior conjectures, our results show that the trigonal-planar copper cations remain in planar coordination below the metal-to-semiconductor transition. The atomic displacement parameters of the trigonal-planar copper cations, which have been linked to low thermal conductivity, increase by 200% above the metal-to-semiconductor transition. The phase transition is consequence of the orbital degeneracy of the highest occupied 3d cluster orbitals of the copper clusters found inside the sodalite cages in the cubic phase. This study reveals that a Jahn-Teller electronic instability leads to the formation of “molecular-like” Cu57+ clusters and suppresses copper rattling vibrations due to the strengthening of direct copper-copper interactions. Our first-principles calculations demonstrate that the structural phase transition opens a small band gap in the electronic density of states and eliminates the unstable phonon modes. The present results provide insights on the interplay between phonon transport, electronic properties and crystal structure in mixed-valence compounds
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Plant profit maximisation improves predictions of European forest responses to drought
- Knowledge of how water stress impacts the carbon and water cycles is a key uncertainty in terrestrial biosphere models.
- We tested a new profit maximisation model, where photosynthetic uptake of CO2 is optimally traded against plant hydraulic function, as an alternative to the empirical functions commonly used in models to regulate gas exchange during periods of water stress. We conducted a multi-site evaluation of this model at the ecosystem scale, before and during major droughts in Europe. Additionally, we asked whether the maximum hydraulic conductance in the soil-plant
continuum
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Motion planning of autonomous vehicles in a non-autonomous vehicle environment without speed lanes
Planning is one of the key problems for autonomous vehicles operating in road scenarios. Present planning algorithms operate with the assumption that traffic is organised in predefined speed lanes, which makes it impossible to allow autonomous vehicles in countries with unorganised traffic. Unorganised traffic is though capable of higher traffic bandwidths when constituting vehicles vary in their speed capabilities and sizes. Diverse vehicles in an unorganised exhibit unique driving behaviours which are analysed in this paper by a simulation study. The aim of the work reported here is to create a planning algorithm for mixed traffic consisting of both autonomous and non-autonomous vehicles without any inter-vehicle communication. The awareness (e.g. vision) of every vehicle is restricted to nearby vehicles only and a straight infinite road is assumed for decision making regarding navigation in the presence of multiple vehicles. Exhibited behaviours include obstacle avoidance, overtaking, giving way for vehicles to overtake from behind, vehicle following, adjusting the lateral lane position and so on. A conflict of plans is a major issue which will almost certainly arise in the absence of inter-vehicle communication. Hence each vehicle needs to continuously track other vehicles and rectify plans whenever a collision seems likely. Further it is observed here that driver aggression plays a vital role in overall traffic dynamics, hence this has also been factored in accordingly. This work is hence a step forward towards achieving autonomous vehicles in unorganised traffic, while similar effort would be required for planning problems such as intersections, mergers, diversions and other modules like localisation
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The onset of copper-ion mobility and the electronic transitions in kesterite, Cu2ZnGeSe4
Kesterite-related phases have attracted considerable interest as earth-abundant photovoltaic and thermoelectric materials. For the kesterite Cu2ZnGeSe4, we have established a direct link between anomalies in the temperature dependence of transport properties and an order -disorder
transition. Powder neutron diffraction as a function of temperature reveals an order-disorder transition at 473 K, involving disordering of copper and zinc cations over three
crystallographic positions. Vacancies are simultaneously created on the copper-ion sublattice, indicative of the concomitant onset of copper-ion mobility. Differential scanning calorimetry data show a weak thermal signature in this temperature region, typical of a second-order phase transition, which is consistent with the absence of anomalies in the temperature dependence of the unit cell volume. The partial melting of the copper-ion sublattice
induces a transition in the electrical-transport properties. The changes in electrical resistivity and Seebeck coefficient suggest this involves a transition from a conventional, activated semiconductor, to a degenerate semiconductor. The entry of an increasing fraction
of the copper-ion sub-lattice into a liquid-like state is reflected in a reduction in thermalconductivity above 473 K. The order-disorder phase transition identified here has
consequences for the performance of photovoltaic and thermoelectric devices based on kesterites
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Talnakhite: a potential n-type thermoelectric sulphide with low thermal conductivity
The mineral talnakhite, Cu18Fe16S32, is an n-type semiconductor with low thermal conductivity (average value of 1.5 W m-1·K-1), making it an attractive candidate for thermoelectric applications. The effect of partial cation substitutions and of deviations from the ideal Cu:Fe ratio on the thermoelectric properties of this material, has been investigated through synthesis of Cu17.58M0.02Fe17.6S32 (M = Ag, In, Zn) and Cu17.6+xFe17.6-xS32 (-0.03 ≤ x ≤ 0.03) by high-temperature methods. The results demonstrate that talnakhite exhibits a narrow range of compositional stability for substitution at the cation sites. X-ray photoelectron spectroscopy (XPS) measurements indicate that all compositions contain Fe3+ and Fe2+ cations, together with Cu+. The electrical and thermal transport properties show two anomalies, at approximately 460 and 510 K, which can be related to structural phase transitions. The maximum value of the thermoelectric figure of merit occurs at the temperature of the first structural phase transition, making talnakhite a potential n‐type candidate for near room‐temperature thermoelectric applications. While substitution with silver, zinc or indium does not lead to any significant improvement in thermoelectric performance, changes in the Cu:Fe ratio result in significant reductions in the total thermal conductivity. This is likely to be associated with increased point defect scattering due to the presence of additional vacancies at the cation sites over which iron and copper are partially ordered. For copper-poor phases, the combination of a slightly improved power factor with a reduced thermal conductivity results in an increase in the figure-of-merit by approximately 20% when compared to the stoichiometric phase