5,055 research outputs found
Asphericity and clumpiness in the winds of Luminous Blue Variables
We present the first systematic spectropolarimetric study of Luminous Blue
Variables (LBVs) in the Galaxy and the Magellanic Clouds, in order to
investigate the geometries of their winds. We find that at least half of our
sample show changes in polarization across the strong H emission line,
indicating that the light from the stars is intrinsically polarized and
therefore that asphericity already exists at the base of the wind. Multi-epoch
spectropolarimetry on four targets reveals variability in their intrinsic
polarization. Three of these, AG Car, HR Car and P Cyg, show a position angle
(PA) of polarization which appears random with time. Such behaviour can be
explained by the presence of strong wind-inhomogeneities, or `clumps' within
the wind. Only one star, R 127, shows variability at a constant PA, and hence
evidence for axi-symmetry as well as clumpiness. However, if viewed at low
inclination, and at limited temporal sampling, such a wind would produce a
seemingly random polarization of the type observed in the other three stars.
Time-resolved spectropolarimetric monitoring of LBVs is therefore required to
determine if LBV winds are axi-symmetric in general.
The high fraction of LBVs ( 50%) showing intrinsic polarization is to be
compared with the lower 20-25 % for similar studies of their
evolutionary neighbours, O supergiants and Wolf-Rayet stars. We anticipate that
this higher incidence is due to the lower effective gravities of the LBVs,
coupled with their variable temperatures within the bi-stability jump regime.
This is also consistent with the higher incidence of wind asphericity that we
find in LBVs with strong H emission and recent (last 10 years)
strong variability.Comment: 20 pages, 12 figures, accepted by A&
Climate-smart agriculture appreciation event for the members of the Philippine Network of Environmental Journalists
The appreciation event was organized to provide the members of the media with the basic concepts about the effects of climate change to agriculture, and of the contribution of agriculture to climate change; to facilitate collection stories on field-based experiences through interactions with farmers who have adopted practices that helped them adapt to climate risks; and to showcase climate smart agriculture approaches in demo farms, school garden, and farmers field. Through this activity, they can also help IIRR extend its reach and scale-out learnings from various CSA initiatives. Once available, these media products will be collated
Trogocytosis by Entamoeba histolytica Mediates Acquisition and Display of Human Cell Membrane Proteins and Evasion of Lysis by Human Serum.
We previously showed that Entamoeba histolytica kills human cells through a mechanism that we termed trogocytosis ("trogo-" means "nibble"), due to its resemblance to trogocytosis in other organisms. In microbial eukaryotes like E. histolytica, trogocytosis is used to kill host cells. In multicellular eukaryotes, trogocytosis is used for cell killing and cell-cell communication in a variety of contexts. Thus, nibbling is an emerging theme in cell-cell interactions both within and between species. When trogocytosis occurs between mammalian immune cells, cell membrane proteins from the nibbled cell are acquired and displayed by the recipient cell. In this study, we tested the hypothesis that through trogocytosis, amoebae acquire and display human cell membrane proteins. We demonstrate that E. histolytica acquires and displays human cell membrane proteins through trogocytosis and that this leads to protection from lysis by human serum. Protection from human serum occurs only after amoebae have undergone trogocytosis of live cells but not phagocytosis of dead cells. Likewise, mutant amoebae defective in phagocytosis, but unaltered in their capacity to perform trogocytosis, are protected from human serum. Our studies are the first to reveal that amoebae can display human cell membrane proteins and suggest that the acquisition and display of membrane proteins is a general feature of trogocytosis. These studies have major implications for interactions between E. histolytica and the immune system and also reveal a novel strategy for immune evasion by a pathogen. Since other microbial eukaryotes use trogocytosis for cell killing, our findings may apply to the pathogenesis of other infections.IMPORTANCE Entamoeba histolytica causes amoebiasis, a potentially fatal diarrheal disease. Abscesses in organs such as the liver can occur when amoebae are able to breach the intestinal wall and travel through the bloodstream to other areas of the body. Therefore, understanding how E. histolytica evades immune detection is of great interest. Here, we demonstrate for the first time that E. histolytica acquires and displays human cell membrane proteins by taking "bites" of human cell material in a process named trogocytosis ("trogo-" means "nibble"), and that this allows amoebae to survive in human serum. Display of acquired proteins through trogocytosis has been previously characterized only in mammalian immune cells. Our study suggests that this is a more general feature of trogocytosis not restricted to immune cells and broadens our knowledge of eukaryotic biology. These findings also reveal a novel strategy for immune evasion by a pathogen and may apply to the pathogenesis of other infections
Beliefs and Attitudes of Medical Students from Public and Private Universities in Malaysia towards Individuals with HIV/AIDS
We describe the findings from a survey assessing the beliefs regarding testing, confidentiality, disclosure, and environment of care and attitudes towards care of people with HIV/AIDS (PLHWA), in 1020, 4th and 5th year medical students, from public and private medical universities in Malaysia. A self-administered validated questionnaire based on the UNAIDS Model Questionnaire with a 5-point Likert scale (5, strongly disagree; 4, disagree; 3, neutral; 2, agree; 1, strongly agree) was used as a survey tool. The survey included demographic data and data on undergraduate training received on HIV/AIDS. Statistical significance in the demographic data and training received by respondents was evaluated using the chi-square test while the independent Student's t-test was used for comparison of means between public and private universities. A P value of <0.05 was considered statistically significant with 95% confidence interval. Our study revealed less than 20% of medical students received adequate training to care for PLHWA. They had prevalent negative beliefs regarding testing, confidentiality, disclosure and environment of care towards PLHWA although in giving care to PLHWA, their attitudes were largely positive and nondiscriminatory.Article Link:
http://www.hindawi.com/journals/tswj/2013/462826
Changes in the flagellar bundling time account for variations in swimming behavior of flagellated bacteria in viscous media
Although the motility of the flagellated bacteria, Escherichia coli, has been
widely studied, the effect of viscosity on swimming speed remains
controversial. The swimming mode of wild-type E.coli is often idealized as a
"run-and- tumble" sequence in which periods of swimming at a constant speed are
randomly interrupted by a sudden change of direction at a very low speed. Using
a tracking microscope, we follow cells for extended periods of time in
Newtonian liquids of varying viscosity, and find that the swimming behavior of
a single cell can exhibit a variety of behaviors including run-and-tumble and
"slow-random-walk" in which the cells move at relatively low speed. Although
the characteristic swimming speed varies between individuals and in different
polymer solutions, we find that the skewness of the speed distribution is
solely a function of viscosity and can be used, in concert with the measured
average swimming speed, to determine the effective running speed of each cell.
We hypothesize that differences in the swimming behavior observed in solutions
of different viscosity are due to changes in the flagellar bundling time, which
increases as the viscosity rises, due to the lower rotation rate of the
flagellar motor. A numerical simulation and the use of Resistive Force theory
provide support for this hypothesis
Realization and Characterization of a Four-Channel Integrated Optical Young Interferometer
In this paper, we report the realization and characterization of a four-channel integrated optical Young interferometer (YI), which enables simultaneous and independent monitoring of three binding processes. The simultaneous and independent measurement of three different glucose concentrations shows the multi-purpose feature of such device. The phase resolution for different pairs of channels was /spl sim/1/spl times/10/sup -4/ fringes, which corresponds to a refractive index resolution of /spl sim/8.5/spl times/10/sup -8/ . The observed errors, which are caused due to mismatching of spatial frequencies of individual interference patterns with those determined from the CCD camera, have been reduced by using different reduction schemes. In addition, we have investigated a novel method for discrimination of the refractive index change from the thickness of a bound layer during an immunoreaction, as well as measuring the temperature change the takes place during such a process
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