Analysis of the stability of InGaN/GaN multiquantum wells against ion beam intermixing

Ion-induced damage and intermixing was evaluated in InGaN/GaN multi-quantum wells (MQWs) using 35 keV N(+) implantation at room temperature. In situ ion channeling measurements show that damage builds up with a similar trend for In and Ga atoms, with a high threshold for amorphization. The extended defects induced during the implantation, basal and prismatic stacking faults, are uniformly distributed across the quantum well structure. Despite the extremely high fluences used (up to 4 × 10(16) cm(-2)), the InGaN MQWs exhibit a high stability against ion beam mixing.

Selective ion-induced intermixing and damage in low-dimensional GaN/AlN quantum structures

Ion-induced intermixing and damage is evaluated in GaN/AlN superlattices of quantum dots (QDs) and quantum wells (QWs) using 100 keV Ar(+) implantation at low temperature (15 K). Despite the similar damage build up at low fluences, a significant increase of the damage accumulation takes place for QDs at high fluences. Elemental depth profiles were fitted with a diffusion model, revealing the higher intermixing efficiency in QD superlattices, significantly higher than for QWs. The scaling of diffusion length with the local fluence and defect concentration is understood on the basis of cascade mixing and migration of defects in the cation sublattice. The selective intermixing/damage of QDs is explained by the promotion of lateral diffusion mechanisms that result in smooth interfaces, as well as by an enhanced diffusivity due to the characteristic strain distribution in QD superlattices.

Phase mapping of aging process in InN nanostructures: oxygen incorporation and the role of the zinc blende phase

Uncapped InN nanostructures undergo a deleterious natural aging process at ambient conditions by oxygen incorporation. The phases involved in this process and their localization is mapped by transmission electron microscopy (TEM)-related techniques. The parent wurtzite InN (InN-w) phase disappears from the surface and gradually forms a highly textured cubic layer that completely wraps up a InN-w nucleus which still remains from the original single-crystalline quantum dots. The good reticular relationships between the different crystals generate low misfit strains and explain the apparent easiness for phase transformations at room temperature and pressure conditions, but also disable the classical methods to identify phases and grains from TEM images. The application of the geometrical phase algorithm in order to form numerical moiré mappings and RGB multilayered image reconstructions allows us to discern among the different phases and grains formed inside these nanostructures. Samples aged for shorter times reveal the presence of metastable InN:O zinc blende (zb) volumes, which act as the intermediate phase between the initial InN-w and the most stable cubic In(2)O(3) end phase. These cubic phases are highly twinned with a proportion of 50:50 between both orientations. We suggest that the existence of the intermediate InN:O-zb phase should be seriously considered to understand the reason for the widely scattered reported fundamental properties of thought to be InN-w, as its bandgap or superconductivity.

Specific twin junctions in doped zirconia

The effect of different dopant cations on the phase transformations of the initially stabilized supersaturated tetragonal ZrO2 phase during various heat treatments has been studied. The obtained fraction of monoclinic grains develop twinned structures, but there is still a lack of information about the character of grain boundaries formed in doped monoclinic solid solutions. The inspection of particular selected-area electron diffraction patterns provides an alternative method with respect to high-resolution electron microscopy or electron back-scattered diffraction for characterizing different twin junctions in various doped zirconia systems. The classification of these special twins is based on the coincidence site lattice concept.

Evasion mechanisms to tumor necrosis factor alpha (TNF-alpha) of small cell lung carcinoma and non-small cell lung carcinoma cell lines: comparison with the erythroleukaemia K-562 cell line

The tumour necrosis factor alpha (TNF-alpha) is produced by mononuclear phagocytes as a defence mechanism against malignant cells. However, these cells can evade destruction by TNF-alpha. The present study evaluates in three lung cancer cell lines (small cell carcinoma NCI-H69, adenocarcinoma A-427, squamous carcinoma SK-MES-1) and one erythroleukaemia (K-562) cell line the following evasion mechanisms: (1) inhibition of TNF-alpha production, in indirect and direct co-cultures with monocytes; (2) the expression of type I and type II receptors for TNF-alpha (TNFRI and TNFRII) by tumour cell lines, using indirect immunofluorescence and flow cytometry; (3) the sensitivity of tumour cell lines to the toxic action of recombinant human TNF-alpha (rhTNF-alpha). With the exception of cell line NCI-H69, the other tumour cell lines liberated soluble factors that inhibited TNF-alpha production in monocytes. This effect occurred even after membrane contact with the A-427 and SK-MES-1 cell lines. Erythroleukaemia K-562 cells expressed both types of receptors for TNF-alpha, whereas the NCI-H69 cells expressed only TNFRI, and the A-427 and SK-MES-1 cells expressed no receptors. Lines NCI-H69, A-427 and K-562 were insensitive to the cytotoxic action of rhTNF-alpha. In conclusion, different lung cancer cell lines may evade destruction by TNF-alpha by various mechanisms that range from blocking TNF-alpha production by monocytes to blocking the cytotoxic action of this molecule. For selecting the most effective immunotherapy, knowledge of the evasion mechanisms would be useful.

Microprocessor exercise physiology systems vs a nonautomated system. A comparison of data output

Several microprocessor exercise physiology systems have been introduced recently. Comparison of the data output between these systems and more traditional nonautomated systems has not been reported extensively. Twelve normal adult men were exercised in random sequence on different days on a Sensormedics MMC Horizon system, the Medical Graphics Corporation System 2000, and a nonautomated system. heart rate, minute ventilation, tidal volume, respiratory frequency, oxygen consumption, and carbon dioxide production were compared at each level of work during a maximal incremental test and during a constant work load test. The overall data output between the three systems was comparable. However, minute ventilation was consistently higher on the Medical Graphics system, oxygen consumption was consistently lower on the Horizon system, and a technical error was discovered in the Medical Graphics system which resulted in a systematic overestimation of carbon dioxide production. Different methods of analyzing the data from the same test (60-s average, 15-s average, breath-by-breath, and 8-breath average) resulted in differences of up to 20 percent in the maximal values. This was greater than the differences between the three systems. Despite the comparability of the data output, important differences did exist which can be potentially significant when data output from one system are compared to predicted normal values obtained under different conditions.

Diagnosis of parenchymal Hodgkin's disease using bronchoalveolar lavage

The usefulness of bronchoalveolar lavage in the diagnosis of parenchymal Hodgkin's disease is illustrated in this case report. Recovery of characteristic Reed-Sternberg cells from the lavage fluid may serve as both a diagnostic and staging procedure and potentially may obviate more invasive steps such as thoracotomy.