1,419 research outputs found
Unveiling the outer dust disc of TW Hya with deep ALMA observations
Stars and planetary system
Eureka and beyond: mining's impact on African urbanisation
This collection brings separate literatures on mining and urbanisation together at a time when both artisanal and large-scale mining are expanding in many African economies. While much has been written about contestation over land and mineral rights, the impact of mining on settlement, notably its catalytic and fluctuating effects on migration and urban growth, has been largely ignored. African nation-states’ urbanisation trends have shown considerable variation over the past half century. The current surge in ‘new’ mining countries and the slow-down in ‘old’ mining countries are generating some remarkable settlement patterns and welfare outcomes. Presently, the African continent is a laboratory of national mining experiences. This special issue on African mining and urbanisation encompasses a wide cross-section of country case studies: beginning with the historical experiences of mining in Southern Africa (South Africa, Zambia, Zimbabwe), followed by more recent mineralizing trends in comparatively new mineral-producing countries (Tanzania) and an established West African gold producer (Ghana), before turning to the influence of conflict minerals (Angola, the Democratic Republic of Congo and Sierra Leone)
Measurement of the partial widths of the Z into up- and down-type quarks
Using the entire OPAL LEP1 on-peak Z hadronic decay sample, Z -> qbarq gamma
decays were selected by tagging hadronic final states with isolated photon
candidates in the electromagnetic calorimeter. Combining the measured rates of
Z -> qbarq gamma decays with the total rate of hadronic Z decays permits the
simultaneous determination of the widths of the Z into up- and down-type
quarks. The values obtained, with total errors, were Gamma u = 300 ^{+19}_{-18}
MeV and Gamma d = 381 ^{+12}_{-12} MeV. The results are in good agreement with
the Standard Model expectation.Comment: 22 pages, 5 figures, Submitted to Phys. Letts.
Nucleation and growth of biomimetic apatite layers on 3D plotted biodegradable polymeric scaffolds : effect of static and dynamic coating conditions
Apatite layers were grown on the surface of newly developed starch/polycaprolactone (SPCL)-based scaffolds by a 3D plotting technology.
To produce the biomimetic coatings, a sodium silicate gel was used as nucleating agent, followed by immersion in a simulated
body fluid (SBF) solution. After growing a stable apatite layer for 7 days, the scaffolds were placed in SBF under static, agitated (80 strokes
min!1) and circulating flow perfusion (Q = 4 ml min!1; tR = 15 s) for up to 14 days. The materials were characterized by scanning
electron microscopy/energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and thin-film X-ray diffraction.
Cross-sections were obtained and the coating thickness was measured. The elemental composition of solution and coatings was monitored
by inductively coupled plasma spectroscopy. After only 6 h of immersion in SBF it was possible to observe the formation of small
nuclei of an amorphous calcium phosphate (ACP) layer. After subsequent SBF immersion from 7 to 14 days under static, agitated and
circulating flow perfusion conditions, these layers grew into bone-like nanocrystalline carbonated apatites covering each scaffold fiber
without compromising its initial morphology. No differences in the apatite composition/chemical structure were detectable between
the coating conditions. In case of flow perfusion, the coating thickness was significantly higher. This condition, besides mimicking better
the biological milieu, allowed for the coating of complex architectures at higher rates, which can greatly reduce the coating step.The authors acknowledge the Portuguese Foundation for Science and Technology (PhD grant to A.L.O., SFRH/BD/10956/2002 and post-doctoral Grant to R.A.S., SFRH/BPD/17151/2004, under the POCTI Program). This work was partially supported by FCT through POCTI and/or FEDER programmes and also partially supported by the EU Project HIPPOCRATES (NMP3-CT-2003-505758) and EXPERTISSUES (NMP-CT-2004-500283)
Aspergillus species identification in the clinical setting
Multiple recent studies have demonstrated the limited utility of
morphological methods used singly for species identification of clinically
relevant aspergilli. It is being increasingly recognised that comparative
sequence based methods used in conjunction with traditional phenotype based
methods can offer better resolution of species within this genus. Recognising
the growing role of molecular methods in species recognition, the recently
convened international working group meeting entitled
“Aspergillus Systematics in the Genomic Era” has proposed
several recommendations that will be useful in such endeavors. Specific
recommendations of this working group include the use of the ITS regions for
inter section level identification and the β-tubulin locus for
identification of individual species within the various Aspergillus
sections
- …