Gating of high-mobility InAs metamorphic heterostructures

We investigate the performance of gate-defined devices fabricated on high mobility InAs metamorphic heterostructures. We find that heterostructures capped with In$_{0.75}$Ga$_{0.25}$As often show signs of parallel conduction due to proximity of their surface Fermi level to the conduction band minimum. Here, we introduce a technique that can be used to estimate the density of this surface charge that involves cool-downs from room temperature under gate bias. We have been able to remove the parallel conduction under high positive bias, but achieving full depletion has proven difficult. We find that by using In$_{0.75}$Al$_{0.25}$As as the barrier without an In$_{0.75}$Ga$_{0.25}$As capping, a drastic reduction in parallel conduction can be achieved. Our studies show that this does not change the transport properties of the quantum well significantly. We achieved full depletion in InAlAs capped heterostructures with non-hysteretic gating response suitable for fabrication of gate-defined mesoscopic devices

Histochemical study of the oesophagus in the chukar partridge (Alectoris chukar) embryo

Study of the histogenesis of different organs is a useful laboratory method which helps us achieve accurate basic information about organ development during the embryonic period. It also reveals histological differences of each organ in different species. This research was carried out to study the histogenesis of the oesophagus of chukar partridge. For this purpose, the embryonated eggs were placed in the incubator and the embryos were collected between the 5th to 24th days of incubation period. The specimens were fixed in Bouin’s solution, and routine histotechnique processes were performed. The slides were finally stained with haematoxylin-eosin, Periodic Acid Schiff, Alcian Blue and Masson Trichrome, and the developmental changes of the oesophagus during the embryonic period were studied by light microscope. The four layers of oesophagus, including, the mucosa, submucosa, tunica muscularis and advantitia/serosa, both in cervical and thoracic oesophagus, were studied. During days 5 to 24 of incubation, developmental events in the oesophagus such as changes in the oesophageal epithelium, formation of muscularis mucosae and tunica muscularis, development of the mucous glands and the type of their secretion, were observed. Finally the results were compared with those of other studied avian species and the similarities and differences were discussed

Population dynamics of the Spanish mackerel (Scomberomorus commerson) in coastal waters of Oman Sea

Length composition data of narrow-barred Spanish mackerel, Scomberomorus commerson (Lacepede 1800), landed between April 2002 to March 2004, were monthly used to estimate the growth, mortality and exploitation parameters of the stock. Maximum fork length and weight were 170 cm and 38 kg, respectively. Nonlinear least square fitting provided a complete set of von Bertalanffy growth estimates: L¥=178 cm (FL); K=0.28 and to= -0.36 years. The estimated value of total mortality based on length converted catch curve using these growth parameters is Z=0.95 year-I. Natural mortality based on growth parameters and mean environmental temperature (T=26.5°C) is M=0.36 year-1. Furthermore, the annual instantaneous fishing mortality rate of 0.59 year-1 was by far in excess of the precautionary target (Fopt=0.18 year-1) and limit (Flimit=0.24 year-1) biological reference points, indicating that the resource is heavily over-exploited and the management of this species should be implanted rapidly if they are to remain sustainable

A model-based approach for estimation of changes in lumbar segmental kinematics associated with alterations in trunk neuromuscular strategy

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordThe geometrical information from imaging, if combined with optimization-based methods of neuromuscular assessment, may provide a unique platform for personalized assessment of trunk neuromuscular behavior. Such a method, however, is feasible only if differences in lumbar spine kinematics due to differences in trunk neuromuscular behavior can be captured by the current imaging techniques. A finite element model of the spine within an optimization procedure was used to estimate segmental kinematics of lumbar spine associated with five different hypothetical trunk neuromuscular strategies (TNSs). Each TNS optimized one aspect of lower back biomechanics and was assumed to either represent the TNS of asymptomatic persons or a neuromuscular abnormality. For each TNS, the segmental kinematics of lumbar spine was estimated for a single static trunk flexed posture involving, respectively, 40° and 10° of thoracic and pelvic rotations. Minimum changes in the angular and translational deformations of a motion segment with alterations in TNS ranged from 0° to 0.5° and 0 mm to 0.04 mm, respectively. Maximum changes in the angular and translational deformations of a motion segment with alterations in neuromuscular strategy ranged from 2.4° to 7.5° and 0.11 mm to 0.39 mm, respectively. The differences in kinematics of lumbar segments between each combination of two TNSs in 97% of cases for angular deformation and 55% of cases for translational deformation were within the reported accuracy of current imaging techniques. Combined imaging and computational modeling appears to have potentials for predicting alterations in neuromuscular strategies.This work was supported, in part, by an award (5R03HD086512-02) from the National Center for Medical Rehabilitation Research (NIH-NICHD) and the Office of the Assistant Secretary of Defense for Health Affairs, through the Peer Reviewed Orthopaedic Research Program (award #W81XWH-14-2-0144)

Minimal surfaces in porous materials: x-ray image-based measurement of the contact angle and curvature in gas diffusion layers to design optimal performance of fuel cells

We inject water at a low flow rate through gas diffusion layers containing different percentages of polytetrafluoroethylene (PTFE) coating: 5, 20, 40, and 60%. We use high-resolution three-dimensional X-ray imaging to identify the arrangement of fibers, water, and air in the pore space. We also quantify the contact angle and meniscus curvature once the water has spanned the layer, flow has ceased, and water has reached a position of equilibrium. The average contact angle and water pressure at breakthrough increase with the amount of coating, although we see a wide range of contact angles with values both above and below 90°, indicating a mixed-wet state. We identify that the menisci form minimal surfaces (interfaces of zero curvature) consistent with pinned gas-water-solid contacts. Scanning electron microscopy images of the fibers show that the coated fibers have a rough surface. Between 93 and 100% of the contacts identified were found on the rough, hydrophobic, coated fibers or at the boundary between uncoated (hydrophilic) and coated (hydrophobic) regions; we hypothesize that these contacts are pinned. The one exception is the 60% PTFE layer, which shows distinctly hydrophobic properties and a negative capillary pressure (the water pressure is higher than that of air). The presence of minimal surfaces suggests that the water and gas pressures are equal, allowing water to flow readily without pressure build-up. From topological principles, the negative Gaussian curvature of the menisci implies that the fluid phases are well connected. The implication of these results is explored for the design of porous materials where the simultaneous flow of two phases occurs over a wide saturation range

Carboxylated photoswitchable diarylethenes for biolabeling and super-resolution RESOLFT microscopy.

Reversibly photoswitchable 1,2-bis(2-ethyl-6-phenyl-1-benzothiophene-1,1-dioxide-3-yl)perfluorocyclopentenes (EBT) having fluorescent "closed" forms were decorated with four or eight carboxylic groups and attached to antibodies. Low aggregation, efficient photoswitching in aqueous buffers, specific staining of cellular structures, and good photophysical properties were demonstrated. Alternating light pulses of UV and blue light induce numerous reversible photochemical transformations between two stables states with distinct structures. Using relatively low light intensities, EBTs were applied in biology-related super-resolution microscopy based on the reversible saturable (switchable) optical linear fluorescence transitions (RESOLFT) and demonstrated optical resolution of 75 nm

O ensino das ciências experimentais no liceu, em Portugal, na I República (1910-1926)

O ensino das ciências experimentais (ECE) em Portugal ficou, como pretendemos demonstrar, fortemente marcado pela instauração da República, que comemorou no ano transacto o seu centenário. A República de 1910 pretendeu reformar toda a mentalidade portuguesa, através do pilar base – a educação – pela qual seria capaz de sacudir a nossa maneira de ser, lançando desta forma o país para um progresso de nível europeu. O estudo a que nos propomos, uma investigação documental no domínio da História da Ciência1, visa aprofundar os conhecimentos existentes sobre esta época e perceber o impacto da reforma do ECE, principalmente nos Liceus, caracterizando as principais figuras, políticas e docentes responsáveis pela sua conceptualização e aplicação. Através desta investigação procuraremos lançar as primeiras bases para descobrir as origens deste pensamento, querendo ainda comparar os fundamentos psicopedagógicos, epistemológicos e sociológicos da época com as principais ideias actualmente presentes no ensino da Ciência. Com este trabalho pretendemos, num primeiro momento, apresentar e divulgar o desenho da investigação e os seus objectivos, na procura de estabelecer parcerias e receber contributos da comunidade académica interessada por esta problemática

Mycobacterium iranicum sp. nov., a rapidly growing scotochromogenic species isolated from clinical specimens on three different continents

The isolation and characterization of a novel, rapidly growing, scotochromogenic mycobacterial species is reported. Eight independent strains were isolated from clinical specimens from six different countries of the world, two in Iran, two in Italy and one in each of following countries: Greece, the Netherlands, Sweden and the USA. Interestingly, two of the strains were isolated from cerebrospinal fluid. The strains were characterized by rapid growth and presented orange-pigmented scotochromogenic colonies. DNA-based analysis revealed unique sequences in the four regions investigated: the 16S rRNA gene, the rRNA gene internal transcribed spacer 1 and the genes encoding the 65 kDa heat-shock protein and the beta-subunit of RNA polymerase. The phylogenetic analysis placed the strains among the rapidly growing mycobacteria, being most closely related to Mycobacterium gilvum . The genotypic and phenotypic data both strongly supported the inclusion of the strains investigated here as members of a novel species within the genus Mycobacterium; the name Mycobacterium iranicum sp. nov. is proposed to indicate the isolation in Iran of the first recognized strains. The type strain is M05T ( = DSM 45541T = CCUG 62053T = JCM 17461T)

On the limits to mobility in InAs quantum wells with nearly lattice-matched barriers

The growth and the density dependence of the low temperature mobility of a series of two-dimensional electron systems confined to un-intentionally doped, low extended defect density InAs quantum wells with Al$_{1-x}$Ga$_{x}$Sb barriers are reported. The electron mobility limiting scattering mechanisms were determined by utilizing dual-gated devices to study the dependence of mobility on carrier density and electric field independently. Analysis of the possible scattering mechanisms indicate the mobility was limited primarily by rough interfaces in narrow quantum wells and a combination of alloy disorder and interface roughness in wide wells at high carrier density within the first occupied electronic sub-band. At low carrier density the functional dependence of the mobility on carrier density provided evidence of coulombic scattering from charged defects. A gate-tuned electron mobility exceeding 750,000 cm$^{2}$/Vs was achieved at a sample temperature of 2 K.Comment: 23 pages, 7 figures, 1 tabl