1,475 research outputs found
VLBI and total flux density investigations of the structure of active galactic nuclei
Get PDFThis doctoral thesis studies the structure of active galactic nuclei (AGN) using very long baseline interferometry (VLBI) at high radio frequencies (22 - 86 GHz). The VLBI observations are complemented using information from total flux density (TFD) observations at the corresponding frequencies and the TFD variations are compared to the structure changes seen in the VLBI images.
The basis of this work is the data from the three epoch VLBI monitoring project, which produced 45 images and parameters of 15 extragalactic sources at 22 GHz.
The maximum intrinsic brightness temperature for synchrotron sources is assumed to be limited by the inverse Compton catastrophe to ≅ 1012 K. We have presented two new methods to estimate this limit using total flux density observations, synchrotron-Self-Compton X-ray fluxes and shock parameters from VLBI observations. Using several data sets, we find that both methods yield a value of ≤ 1011 K, which is consistent with the equipartition limit of 1010 - 1011 K.
We have developed a new method for estimating the geometry of the Universe using the linear sizes of shocks in AGN jets. The angular sizes of the shocks from VLBI observations are normalized using intrinsic diameter estimates from TFD observations. Using a very small set of test data, we verify that the accuracy of the derived values compare favourably with traditional methods using much larger samples.
A clear connection between radio and gamma-ray flares and VLBI component ejections was found. Furthermore, it was shown that the origin of the gamma-ray flares is in the shocks and that they can not be produced close to the core of the AGN.
A helical structure was found in the jet of CTA 102, a High Polarised Quasar (HPQ). The apparent proper motions in the jet varied from 4.2 to 13.8 times the speed of the light. This work combined the work of several years of observation, covering wavelengths from 1.3 to 12 mm and angular resolutions from 50 to 500 microarcseconds.
The first 2mm VLBI experiment between Pico Veleta and Metsähovi was performed and correlation fringes were detected on a baseline of 1.55 billion wavelengths. The success of this experiment shows that VLBI observations are possible at very high frequencies leading to very high resolution and enabling to produce images of the fine structure of the cores of the AGN.reviewe
The epidemiology of infections in blood donors and assessment of the risk of transfusion transmitted infections
Get PDFSurveillance of infections in
blood donors
and
blood
recipients
can
be
useful for both transfusion medicine and
public
health. This thesis
describes
how an enhanced surveillance system
for transfusion-transmissible infections
has been established in England and
Wales.
Data from the surveillance system
(1995 to 1999)
have been
used
to
monitor test performance and to
describe the
epidemiology
of
HBV,
HCV
and
HIV in blood donors. The prevalence and
incidence
of
HBV,
HCV
and
HIV
infections in blood donors have been
monitored
and were generally
stable,
and
low compared to other countries and
to
other
groups
in the
UK.
HCV
prevalence decreased throughout the 1990s.
The
exposure
histories
reported
by infected donors indicate that
donor
selection
largely
succeeds
in
excluding
high-risk groups, but also identify some
failures in
communication
of,
or
compliance with, exclusion criteria.
Diagnosed, reported, post-transfusion
infections
were
rare and
after
investigation only 20% (21) were shown
to
have been transmitted
by
transfusion. The majority (52%) of reported transfusion-transmitted infections,
and resulting deaths (3 of 4) were
due to
bacteria.
The
number
of undiagnosed
infections is not known but was
estimated
for
HIV,
HBV
and
HCV
by
calculations of the probability of
infectious
donations
entering
the
blood
supply
due to true or false negatively to tests
performed
on
donations
prior
to
release.
Various methods and assumptions
have
been
used
to investigate the
robustness of these estimates and to
develop
an appropriate
method
for
ongoing use in England and Wales.
An enhanced surveillance system
for transfusion-transmissible
infections, that works in collaboration with
national surveillance
of
infectious
diseases and of non-infectious complications
of
transfusion,
has
been
shown
-
despite some limitations
-
to provide
data
and analyses
that
have
aided
transfusion medicine and public
health in
England
and
Wales.
This
surveillance
continues to develop and improve and
further
related
work
is
planned
Relationship quality and family formation in Europe
Get PDFThe increase in cohabitation and nonmarital childbearing across Europe has raised questions about who still marries either before or after having a child. Although prior studies have addressed the sequence of marriage and childbearing, few have examined the role of relationship quality in these transitions. Here we employ a cross-national perspective to study the association between relationship quality and marriage and/or first birth within cohabitation. Using the Generations and Gender Survey and UK Household Longitudinal Study, we study seven European countries (Austria, France, Hungary, Netherlands, Norway, Sweden, and UK). We employ competing risk hazard models to follow respondents as they 1) transition from cohabitation into marriage or conception (or separation); 2) transition to marriage (or separation) after having a birth within cohabitation. Results show that cohabitors with higher relationship quality are more marriage prone than those in lower quality relationships in Austria, France, Hungary, and the UK, but not in the Netherlands, Norway and Sweden. Instead, higher relationship quality is associated with higher conception risks in cohabitation in Sweden. After childbearing, we find a positive association between relationship quality and marriage among cohabiting parents in the Netherlands, Norway, Sweden, and the United Kingdom. These results suggest that marriage is still important for couples with higher quality relationships; however, in countries where cohabitation is widespread, the timing of marriage may have shifted to after childbearing
Estrogen receptors in skeletal muscle : expression and activation
No full textThere are two estrogen receptors (ERs), ERalpha and ERbeta, which are ligand activated transcription factors. Estrogen, which exerts its effect via ERs, is not only a female reproductive hormone, but acts almost ubiquitously in the human body and is involved in physiological and pathological states in both males and females. Estrogen has effects in bone maintenance and the cardiovascular and central nervous systems as well as the reproductive system. Estrogen reduces blood lipid levels and blood pressure as well as increases insulin sensitivity and endothelial function. The effects of estrogen on skeletal muscle tissue have not been studied extensively, although a few reports indicate a role in muscle strength development and involvement in carbohydrate and lipid metabolism. Just like estrogen physical activity reduces blood lipid levels and blood pressure as well as insulin sensitivity and endothelial function. Interestingly, physical activity transpritionally activates similar genes as estrogen does, for example vascular endothelial growth factor (VEGF). Thus, considering that physical activity and estrogen have actions in common, the question whether estrogen signalling is induced by physical activity and thus could be involved in down-stream exercise-induced gene expression arises.The overall aim of this thesis was to study the expression of ERs and their activation in skeletal muscle tissue. The specific aims were to investigate if ERalpha and ERbeta are present in human skeletal muscle. Thereafter, the ER expression was studied in subjects with low endogenous estrogen levels such as men, children and postmenopausal women. Furthermore, the localisation and possible co-expression of the both receptors were investigated. The expression levels of ERs were compared in highly endurance-trained men and moderately active men together with the target gene VEGF. Finally, the activation of ERs by estrogen as well as by muscle contractions was investigated. It was hypothesised that ERs in skeletal muscle are functional and activated by estrogen and by muscle contractions and are involved in the adaptation of skeletal muscle to physical training.For the first time ERalpha and ERbeta were shown to be expressed in human skeletal muscle representing both sexes and various ages. Approximately 65 % of all nuclei expressed ERalpha and 70 % expressed ERbeta. The ERalpha and ERbeta were located not only to the nuclei of muscle fibres themselves but also to capillaries. Of all ERalpha- or ERbeta-positive nuclei about 25 % were located to capillaries. The two receptors were to a major extent co-expressed in the same nuclei. Endurance-trained men had a higher steady-state mRNA level of both ERalpha and ERbeta compared to normally active men, together with higher expression of VEGF. Muscle contractions of myotubes from rat also increased ERbeta mRNA levels without any effect on ERalpha mRNA. An increase in ERbeta mRNA was also seen with estrogen stimulation of the myotubes. Muscle contractions had a similar functional effect as estrogen in myotubes causing activation of estrogen response elements (ERE). In contrast to estrogen, the effects of muscle contractions were most likely independent of ERs.That ERs are present in the skeletal muscle fibres suggests that this tissue is a target for estrogen action, which was confirmed in myotubes by ERE activation when stimulated with estrogen. In the muscle tissue, estrogen might also have direct effects on the capillaries, since ERs are located to capillaries too. The finding that contraction of myotubes activates ERE-sequences and increases ERbeta mRNA levels as well as the higher mRNA levels of ERs in endurance trained men suggest an involvement of ERs and ER target genes in the adaptation of skeletal muscle to physical exercise.List of scientific papersI. Wiik A, Glenmark B, Ekman M, Esbjörnsson-Liljedahl M, Johansson O, Bodin K, Enmark E, Jansson E (2003). "Oestrogen receptor beta is expressed in adult human skeletal muscle both at the mRNA and protein level." Acta Physiol Scand 179(4): 381-7 https://pubmed.ncbi.nlm.nih.gov/14656376II. Wiik A, Ekman M, Morgan G, Johansson O, Jansson E, Esbjörnsson M (2005). "Oestrogen receptor beta is present in both muscle fibres and endothelial cells within human skeletal muscle tissue." Histochem Cell Biol 124(2): 161-5. Epub 2005 Sep 29 https://pubmed.ncbi.nlm.nih.gov/16133122III. Wiik A, Ekman M, Johansson O, Jansson E, Esbjörnsson M (2008). "Expression of both oestrogen receptor alpha and beta protein in human skeletal muscle." (Submitted)IV. Wiik A, Gustafsson T, Esbjörnsson M, Johansson O, Ekman M, Sundberg CJ, Jansson E (2005). "Expression of oestrogen receptor alpha and beta is higher in skeletal muscle of highly endurance-trained than of moderately active men." Acta Physiol Scand 184(2): 105-12 https://pubmed.ncbi.nlm.nih.gov/15916670V. Wiik A, Hellsten Y, Berthelson P, Lundholm L, Fischer H, Jansson E (2008). "Activation of estrogen response elements is mediated both via estrogen and muscle contractions in rat skeletal muscle myotubes." (Submitted)</p
Oxygen transport in Co-substituted Sr<sub>4</sub>Fe<sub>6</sub>O<sub>1</sub><sub>3</sub>
No full textHuman papillomavirus infection and preterm delivery
Get PDFBackground:
Persistent human papillomavirus (HPV) infection causes cervical intraepithelial neoplasia (CIN). Excisional treatment of CIN has been linked to increased risk of preterm delivery (PTD). The specific mechanism behind is however unclear. Also untreated CIN has been associated with an increased risk of PTD. It is unknown whether this is attributable to the HPV infection itself or other causes.
Aims:
To examine whether HPV infection, untreated CIN and/or previous treatment for CIN is associated with PTD and other adverse obstetric outcomes. To study possible causal pathways for an association, including cone length of treatment, changes in cervical microbiota and infectious complications.
Material and methods:
Paper I; a Swedish register-based study (1999-2016), studying obstetric outcomes in women with normal cervical cytology (NCC) (n=338,109), abnormal cytology (n=11,727) or positive HPV test (n=2,550) - in conjunction with pregnancy, previously treated women (n=23,185), and women with CIN2+ diagnosed after pregnancy (n=33,760).
Paper II; a register-based study from western Sweden (2008-2016), comparing obstetric outcomes in women with NCC (n=42,398), women with CIN during pregnancy (n=1,380) and previously treated women (n=3,250) including a subgroup with cone length measured at treatment (n=2,408).
Paper III; a prospective observational study in Sweden/Norway (n=950) comparing obstetric outcomes in women with or without HPV infection detected in urine at mid-pregnancy and at delivery.
Paper IV; a prospective observational study in Norway with culture and PCR of cervical microbiota in women with CIN (n=89) before and six and 12 months after LEEP and also compared to women with NCC (n=100).
Results:
Paper I; HPV infection (HPVtest) compared to NCC was associated with PTD (aOR 1.2, 95% CI 1.0-1.4), and preterm prelabor rupture of membranes (pPROM) (aOR 1.5, 1.2-2.0), but treated women had higher risk compared to women with HPV infection; PTD (aOR 1.7, 1.4-2.0), pPROM (aOR 1.6, 1.2-2.0). Treatment but also HPV infection were associated with increased risk of neonatal mortality and PROM at term and treatment also with chorioamnionitis and neonatal sepsis.
Paper II; Treatment was associated with an increased risk of PTD (aOR 1.6, 1.2-2.1), pPROM (aOR 2.7, 1.7-4.5), and PROM at term compared to women with CIN, and risks increased with cone length. Small treatments (≤10 mm) were also associated with increased risk for PTD and pPROM.
Paper III; Women positive for high-risk-HPV genotypes at mid-pregnancy had a higher frequency of PTD compared to those negative for high-risk-HPV, but comparisons were non-significant.
Paper IV; Treatment resulted in a reduction of non-Lactobacillus bacterial species. More types of bacterial species were detected in women planned for LEEP than in women with NCC.
Conclusion: Women with HPV infection have increased risk of PTD, pPROM and neonatal mortality. Excisional treatment for CIN, also minor excisions, increases the risks for PTD and pPROM further compared to having untreated CIN/HPV infection. The risks increase with cone length. Previous treatment is also associated with increased risk of PROM at term and maternal and neonatal infectious complications. Treatment appears not to result in a more diverse or dysbiotic cervical microbiota while CIN is associated with increased bacterial diversity
Nrf2 deficiency influences susceptibility to steroid resistance via HDAC2 reduction
Get PDFAbnormal lung inflammation and oxidant burden are associated with a significant reduction in histone deacetylase 2 (HDAC2) abundance and steroid resistance. We hypothesized that Nrf2 regulates steroid sensitivity via HDAC2 in response to inflammation in mouse lung. Furthermore, HDAC2 deficiency leads to steroid resistance in attenuating lung inflammatory response, which may be due to oxidant/antioxidant imbalance. Loss of antioxidant transcription factor Nrf2 resulted in decreased HDAC2 level in lung, and increased inflammatory lung response which was not reversed by steroid. Thus, steroid resistance or inability of steroids to control lung inflammatory response is dependent on Nrf2-HDAC2 axis. These findings have implications in steroid resistance, particularly during the conditions of oxidative stress when the lungs are more susceptible to inflammatory response, which is seen in patients with chronic obstructive pulmonary disease, asthma, rheumatoid arthritis, and inflammatory bowel disease
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