Effect of the cap layer growth temperature on the Sb distribution in InAs/InSb/InAs sub-monolayer heterostructures for mid-infrared devices.

Sub-monolayer (SML) deposition of InSb within InAs matrix by migration enhanced epitaxy tends to form type II SML nanostructures offering efficient light emission within the mid-infrared (MIR) range between 3 and 5 µm. In this work, we report on the Sb distribution in InSb/InAs SML nanostructures with InAs cap layers grown at temperatures lower than that associated with the under-grown InSb active layer. Analysis by transmission electron microscopy (TEM) in 002 dark field conditions shows that the reduction in the growth temperature of the InAs cap layer increases the amount of Sb deposited in the layers, in good agreement with the x-ray diffraction results. TEM micrographs also show that the layers are formed by random InSbAs agglomerates, where the lower cap temperature leads to a more continuous InSb layer. Quantitative atomic column resolved high angle annular dark field-scanning (S)TEM analyses also reveal atomic columns with larger composition of Sb for the structure with the lowest InAs cap layer temperature. The dependence of the Sb distribution on InAs cap growth temperature allows tuning the corresponding emission wavelength in the MIR range, as shown by the photoluminescence emission spectra.

Investigation on Sb distribution for InSb/InAs sub-monolayer heterostructure using TEM techniques.

InSb/InAs sub-monolayer (SML) nanostructures such as SML quantum dots offer sharper emission spectra, a better modal gain and a larger modulation bandwidth compared to its Stranski-Krastanov counterpart. In this work, the Sb distribution of SML InSb layers grown by migration enhanced epitaxy has been analyzed by transmission electron microscopy (TEM) techniques. The analysis of the material by diffraction contrast in 002 dark field conditions and by atomic column resolved high angle annular dark field-scanning TEM reveal the presence of a low Sb content InSbAs continuous layer with scarce Sb-rich InSbAs agglomerates. The intensity profiles obtained by both techniques point to Sb segregation during growth. This segregation has been quantified using the Muraki segregation model obtaining a high segregation coefficient R of 0.81 towards the growth direction. The formation of a continuous InSbAs wetting layer as a result of a SML deposition of Sb on the InAs surface is discussed.

Ultrasonographic evaluation of the ankle after unilateral traumatic lower limb amputations.

BACKGROUND: Unilateral lower limb amputation can alter the tissue morphology leading to increase future risk of degenerative secondary disorders. METHODS: Thirty-four consecutive male patients with unilateral lower limb amputations of different levels and 34 well matched male controls were included. To explore whether the ankles of traumatic lower limb amputees were undergoing morphological changes, three different tissue types i.e. talar cartilage, plantar fascia and Achilles tendon thicknesses in the intact limb of the lower limb amputee and healthy controls were measured by using ultrasound. RESULTS: Plantar fascia was found to be thicker (p=0.013) and talar cartilage was thinner (p<0.001) on the intact sides of the patients than those of the controls. Achilles tendon thickness was found to be similar. In patients group, plantar fascia thickness was positively correlated with age (r=0.601, p<0.001), BMI (r=0.454, p=0.007) and durations of amputation (r=0.443, p=0.009) and prosthetic use (r=0.429, p=0.011). Achilles tendon thickness was positively correlated with durations of amputation (r=0.338, p=0.05) and prosthetic use (r=0.468, p=0.005). In controls group, talar cartilage thickness was negatively correlated with age (r=-0.640, p<0.001) and BMI (r=-0.401, p=0.019). CONCLUSIONS: The talar cartilage seemed to be thinner and the plantar fascia to be thicker on the intact sides of the unilateral limb amputees.

Humoral Dysregulation Associated with Increased Systemic Inflammation among Injection Heroin Users.

BACKGROUND: Injection drug use is a growing major public health concern. Injection drug users (IDUs) have a higher incidence of co-morbidities including HIV, Hepatitis, and other infections. An effective humoral response is critical for optimal homeostasis and protection from infection; however, the impact of injection heroin use on humoral immunity is poorly understood. We hypothesized that IDUs have altered B cell and antibody profiles. METHODS AND FINDINGS: A comprehensive systems biology-based cross-sectional assessment of 130 peripheral blood B cell flow cytometry- and plasma- based features was performed on HIV-/Hepatitis C-, active heroin IDUs who participated in a syringe exchange program (n = 19) and healthy control subjects (n = 19). The IDU group had substantial polydrug use, with 89% reporting cocaine injection within the preceding month. IDUs exhibited a significant, 2-fold increase in total B cells compared to healthy subjects, which was associated with increased activated B cell subsets. Although plasma total IgG titers were similar between groups, IDUs had significantly higher IgG3 and IgG4, suggestive of chronic B cell activation. Total IgM was also increased in IDUs, as well as HIV Envelope-specific IgM, suggestive of increased HIV exposure. IDUs exhibited numerous features suggestive of systemic inflammation, including significantly increased plasma sCD40L, TNF-α, TGF-α, IL-8, and ceramide metabolites. Machine learning multivariate analysis distilled a set of 10 features that classified samples based on group with absolute accuracy. CONCLUSIONS: These results demonstrate broad alterations in the steady-state humoral profile of IDUs that are associated with increased systemic inflammation. Such dysregulation may impact the ability of IDUs to generate optimal responses to vaccination and infection, or lead to increased risk for inflammation-related co-morbidities, and should be considered when developing immune-based interventions for this growing population.