156 research outputs found
Rapid Surface Oxidation as a Source of Surface Degradation Factor for Bi2Se3
Bi2Se3 is a topological insulator with metallic surface states residing in a
large bulk bandgap. It is believed that Bi2Se3 gets additional n-type doping
after exposure to atmosphere, thereby reducing the relative contribution of
surface states in total conductivity. In this letter, transport measurements on
Bi2Se3 nanoribbons provide additional evidence of such environmental doping
process. Systematic surface composition analyses by X-ray photoelectron
spectroscopy reveal fast formation and continuous growth of native oxide on
Bi2Se3 under ambient conditions. In addition to n-type doping at the surface,
such surface oxidation is likely the material origin of the degradation of
topological surface states. Appropriate surface passivation or encapsulation
may be required to probe topological surface states of Bi2Se3 by transport
measurements
Assembling Neurospheres: Dynamics of Neural Progenitor/Stem Cell Aggregation Probed Using an Optical Trap
Optical trapping (tweezing) has been used in conjunction with fluid flow technology to dissect the mechanics and spatio-temporal dynamics of how neural progenitor/stem cells (NSCs) adhere and aggregate. Hitherto unavailable information has been obtained on the most probable minimum time (∼5 s) and most probable minimum distance of approach (4–6 µm) required for irreversible adhesion of proximate cells to occur. Our experiments also allow us to study and quantify the spatial characteristics of filopodial- and membrane-mediated adhesion, and to probe the functional dynamics of NSCs to quantify a lower limit of the adhesive force by which NSCs aggregate (∼18 pN). Our findings, which we also validate by computational modeling, have important implications for the neurosphere assay: once aggregated, neurospheres cannot disassemble merely by being subjected to shaking or by thermal effects. Our findings provide quantitative affirmation to the notion that the neurosphere assay may not be a valid measure of clonality and “stemness”. Post-adhesion dynamics were also studied and oscillatory motion in filopodia-mediated adhesion was observed. Furthermore, we have also explored the effect of the removal of calcium ions: both filopodia-mediated as well as membrane-membrane adhesion were inhibited. On the other hand, F-actin disrupted the dynamics of such adhesion events such that filopodia-mediated adhesion was inhibited but not membrane-membrane adhesion
Institutional tuberculosis transmission : controlled trial of upper room ultraviolet air disinfection : a basis for new dosing guidelines
RATIONALE : Transmission is driving the global tuberculosis epidemic,
especially in congregate settings. Worldwide, natural ventilation is
the most common means of air disinfection, but it is inherently
unreliable and of limited use in cold climates. Upper room germicidal
ultraviolet (UV) air disinfection with air mixing has been shown to be
highly effective, but improved evidence-based dosing guidelines are
needed.
OBJECTIVES : To test the efficacy of upper room germicidal
air disinfection with air mixing to reduce tuberculosis
transmission under real hospital conditions, and to define the
application parameters responsible as a basis for proposed new
dosing guidelines.
METHODS : Over an exposure period of 7 months, 90 guinea pigs
breathed only untreated exhaust ward air, and another 90 guinea pigs
breathed only air from the same six-bed tuberculosis ward on alternate days when upper room germicidal air disinfection was
turned on throughout the ward.
MEASUREMENTS AND MAIN RESULTS : The tuberculin skin test
conversion rates (.6 mm) of the two chambers were compared. The
hazard ratio for guinea pigs in the control chamber converting their
skin test to positive was 4.9 (95% confidence interval, 2.8–8.6), with
an efficacy of approximately 80%.
CONCLUSIONS : Upper room germicidal UV air disinfection with air
mixing was highly effective in reducing tuberculosis transmission
under hospital conditions. These data support using either a total
fixture output (rather than electrical or UV lamp wattage) of
15–20 mW/m3 total room volume, or an average whole-room UV
irradiance (fluence rate) of 5–7 mW/cm2, calculated by a lighting
computer-assisted design program modified for UV use.http://www.atsjournals.org/journal/ajrccm2016-08-31hb201
Malaria Infections Do Not Compromise Vaccine-Induced Immunity against Tuberculosis in Mice
BACKGROUND: Given the considerable geographic overlap in the endemic regions for malaria and tuberculosis, it is probable that co-infections with Mycobacterium tuberculosis and Plasmodium species are prevalent. Thus, it is quite likely that both malaria and TB vaccines may be used in the same populations in endemic areas. While novel vaccines are currently being developed and tested individually against each of these pathogens, the efficacy of these vaccines has not been evaluated in co-infection models. To further assess the effectiveness of these new immunization strategies, we investigated whether co-infection with malaria would impact the anti-tuberculosis protection induced by four different types of TB vaccines in a mouse model of pulmonary tuberculosis. PRINCIPAL FINDINGS: Here we show that the anti-tuberculosis protective immunity induced by four different tuberculosis vaccines was not impacted by a concurrent infection with Plasmodium yoelii NL, a nonlethal form of murine malaria. After an aerogenic challenge with virulent M. tuberculosis, the lung bacterial burdens of vaccinated animals were not statistically different in malaria infected and malaria naïve mice. Multi-parameter flow cytometric analysis showed that the frequency and the median fluorescence intensities (MFI) for specific multifunctional T (MFT) cells expressing IFN-γ, TNF-α, and/or IL-2 were suppressed by the presence of malaria parasites at 2 weeks following the malaria infection but was not affected after parasite clearance at 7 and 10 weeks post-challenge with P. yoelii NL. CONCLUSIONS: Our data indicate that the effectiveness of novel TB vaccines in protecting against tuberculosis was unaffected by a primary malaria co-infection in a mouse model of pulmonary tuberculosis. While the activities of specific MFT cell subsets were reduced at elevated levels of malaria parasitemia, the T cell suppression was short-lived. Our findings have important relevance in developing strategies for the deployment of new TB vaccines in malaria endemic areas
Investigating Macrophages Plasticity Following Tumour–Immune Interactions During Oncolytic Therapies
Impact of glucocorticoids on the incidence of lupus-related major organ damage: a systematic literature review and meta-regression analysis of longitudinal observational studies
OBJECTIVE:
In systemic lupus erythematosus (SLE), disease activity and glucocorticoid (GC) exposure are known to contribute to irreversible organ damage. We aimed to examine the association between GC exposure and organ damage occurrence.
METHODS:
We conducted a literature search (PubMed (Medline), Embase and Cochrane January 1966–October 2021). We identified original longitudinal observational studies reporting GC exposure as the proportion of users and/or GC use with dose information as well as the occurrence of new major organ damage as defined in the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index. Meta-regression analyses were performed. Reviews, case-reports and studies with <5 years of follow-up, <50 patients, different outcomes and special populations were excluded.
RESULTS:
We selected 49 articles including 16 224 patients, 14 755 (90.9%) female with a mean age and disease duration of 35.1 years and of 37.1 months. The mean follow-up time was 104.9 months. For individual damage items, the average daily GC dose was associated with the occurrence of overall cardiovascular events and with osteoporosis with fractures. A higher average cumulative dose adjusted (or not)/number of follow-up years and a higher proportion of patients on GC were associated with the occurrence of osteonecrosis.
CONCLUSIONS:
We confirm associations of GC use with three specific damage items. In treating patients with SLE, our aim should be to maximise the efficacy of GC and to minimise their harms
Malaria pigment crystals as magnetic micro-rotors: Key for high-sensitivity diagnosis
The need to develop new methods for the high-sensitivity
diagnosis of malaria has initiated a global activity in medical
and interdisciplinary sciences. Most of the diverse variety of
emerging techniques are based on research-grade instruments,
sophisticated reagent-based assays or rely on expertise. Here,
we suggest an alternative optical methodology with an easy-to-
use and cost-effective instrumentation based on unique
properties of malaria pigment reported previously and determined
quantitatively in the present study. Malaria pigment, also
called hemozoin, is an insoluble microcrystalline form of heme.
These crystallites show remarkable magnetic and optical
anisotropy distinctly from any other components of blood. As a
consequence, they can simultaneously act as magnetically driven
micro-rotors and spinning polarizers in suspensions. These
properties can gain importance not only in malaria diagnosis and
therapies, where hemozoin is considered as drug target or immune
modulator, but also in the magnetic manipulation of cells and
tissues on the microscopic scale
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