4,316 research outputs found
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An Unfortunate Pandemic
Student generated description: A poem describing my experience and feelings during the COVID-19 pandemic
The impact of stripped Nuclei on the Super-Massive Black Hole number density in the local Universe
The recent discovery of super-massive black holes (SMBHs) in the centers of
high-mass ultra compact dwarf galaxies (UCDs) suggests that at least some UCDs
are the stripped nuclear star clusters of lower mass galaxies. Tracing these
former nuclei of stripped galaxies provides a unique way to track the assembly
history of a galaxy or galaxy cluster. In this paper we present a new method to
estimate how many UCDs host an SMBH in their center and thus are stripped
galaxy nuclei. We revisit the dynamical mass measurements that suggest many
UCDs have more mass than expected from stellar population estimates, which
recent observations have shown is due to the presence of an SMBH. We revise the
stellar population mass estimates using a new empirical relation between the
mass-to-light ratio (M/L) and metallicity, and use this to predict which UCDs
are most likely to host an SMBH. This enables us to calculate the fraction of
UCDs that host SMBHs across their entire luminosity range for the first time.
We then apply the SMBH occupation fraction to the observed luminosity function
of UCDs and estimate that in the Fornax and Virgo cluster alone there should be
stripped nuclei with SMBHs. This analysis shows that stripped
nuclei with SMBHs are almost as common in clusters as present-day galaxy
nuclei. We estimate the local SMBH number density in stripped nuclei to
, which represents a significant fraction (10-40\%)
of the SMBH density in the local Universe. These SMBHs hidden in stripped
nuclei will increase expected event rates for tidal disruption events and
SMBH-SMBH and SMBH-BH mergers. The existence of numerous stripped nuclei with
SMBHs are a direct consequence of hierarchical galaxy formation, but until now
their impact on the SMBH density had not been quantified.Comment: 15 pages, 8 Figures, accepted for publication in Ap
Evaluering av nedbrytningsegenskaper for utvalgte offshorekjemikalier
Project manager Aina C. Wennberg and Karina PetersenA review of biodegradation data for specific oil field chemicals and chemical groups were performed in order to evaluate if the current categorisation of these were appropriate based on the biodegradation properties. Data were compiled from databases like ECHA and MITI and from the literature. For compounds with limited or inconclusive test data, biodegradation was also estimated by the BIOWIN models, and the EAWAG-BBD pathway prediction system was used to predict plausible biodegradation pathways. A weight of evidence approach was used to assess the compiled information and a conclusion regarding categorisation of the single chemicals and/or chemical groups were performed whenever possible. For most compounds, no clear conclusion on the biodegradability could be drawn. Only two of the investigated compounds, benzotriazole and N-methyldiethanolamine, were assessed to very likely and likely have a biodegradability of less than 20% in seawater.Norwegian Environment Agenc
Immunohistochemical Expression of Matrix Metalloprotease-2 and Matrix Metalloprotease-9 in the Disks of Patients with Temporomandibular Joint Dysfunction
Purpose
Matrix metalloproteases (MMPs) are tissue-remodeling enzymes that function during the remodeling process, such as in immune-inflammatory diseases. Metalloprotease-2 (MMP-2) and metalloprotease-9 (MMP-9) are gelatinases that degrade several types of extracellular matrix collagen. It is hypothesized that in temporomandibular joint (TMJ) dysfunction, MMP-2 and MMP-9 expression levels may be elevated. Therefore, the objective of this study is to determine the association of MMP-2 and MMP-9 expression with temporomandibular joint dysfunction using an immunohistochemical approach to evaluate the joint disk. Material and Methods
A total of 45 human temporomandibular joint samples were collected, with 36 samples in the test group (patients with anterior disk displacement with reduction (n = 29) and without reduction (n = 7)) and nine samples in the control group. The immunostaining of the TMJ disks was statistically compared between the groups (P \u3c 0.05). Results
There was a statistically significant difference for the area of MMP-2 immunostaining between the control group and the displacement disks with reduction group (ADDwR) (P = 0.048) and between the groups with disk displacement and without reduction (ADDwoR) (P = 0.029). The expression of MMP-2 was significantly elevated in the ADDwoR group. Conclusion
No statistically significant difference was found between the variable area of MMP-9 expression in the disk with and without disk displacement, as determined by immunohistochemical analysis. However, there was an elevation of MMP-2 expression in the disks of patients with displacement and without reduction (more severe alteration)
Accuracy of MRI skeletal age estimation for subjects 12–19. Potential use for subjects of unknown age
In forensic practice, there is a growing need for accurate methods of age estimation, especially in the cases of young individuals of unknown age. Age can be estimated through somatic features that are universally considered associated with chronological age. Unfortunately, these features do not always coincide with the real chronological age: for these reasons that age determination is often very difficult. Our aim is to evaluate accuracy of skeletal age estimation using Tomei's MRI method in subjects between 12 and 19 years old for forensic purposes.
Two investigators analyzed MRI images of the left hand and wrist of 77 male and 74 female caucasian subjects, without chronic diseases or developmental disorders, whose age ranged from 12 to 19 years. Skeletal maturation was determined by two operators, who analyzed all MRI images separately, in blinded fashion to the chronological age. Inter-rater agreement was measured with Pearson (R (2)) coefficient. One of the examiners repeated the evaluation after 6 months, and intraobserver variation was analyzed. Bland-Altman plots were used to determine mean differences between skeletal and chronological age.
Inter-rater agreement Pearson coefficient showed a good linear correlation, respectively, 0.98 and 0.97 in males and females. Bland-Altman analysis demonstrated that the differences between chronological and skeletal age are not significant. Spearman's correlation coefficient showed good correlation between skeletal and chronological age both in females (R (2) = 0.96) and in males (R (2) = 0.94).
Our results show that MRI skeletal age is a reproducible method and has good correlation with chronological age
Interleukin-6 Expression in Disc Derangement of Human Temporomandibular Joint and Association with Osteoarthrosis
The inflammatory process is a coordinated response that protects host after infection or trauma, involving several molecular reactions. Once the inflammation is closely linked to the process of destruction of the temporomandibular joint, this study aims to examine, by immunohistochemistry, the expression of interleukin-6 (IL-6), an important inflammatory marker, in temporomandibular articular discs of patients with anterior disc displacement with (ADDwR) and without reduction (ADDwoR) and its association with osteoarthrosis (OA). Thirty-eight (n = 38) articular discs were divided into two cutoffs: 1) analysis 1: 4 control (acute pathology), 17 ADDwR, 17 ADDwoR; and 2) analysis 2: without OA (n = 21) and with OA (n = 17). The area of immunostaining was compared statistically between groups (p \u3c 0.05). In the disc samples, no significant differences were observed between the groups ADDwR and ADDwoR, and with and without OA, in respect to the expression of IL-6 by immunohistochemical examination. Future studies should be conducted with a larger sample size, which could clarify the association of the inflammatory mediator IL-6 with temporomandibular joint dysfunction
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Analysis of the internal electric fields of pristine ice crystals and aggregate snowflakes, and their effect on scattering
The discrete dipole approximation is used to explore the internal electric fields of plane-wave-illuminated ice particles, and analyse their differential scattering cross sections. The results are displayed for monocrystals and aggregates of size parameters x=2 and x=10. We show that the field is relatively uniform for x=2, but for monocrystals of x=10 there is a complex internal structure. For a hexagonal plate, this structure is a combination of two components: a "distorted" plane wave, with wavefronts aligned perpendicular to the incident wave close to the centre of the plate, and curved forward near the particle boundary; and a standing wave, internally reflected around the perimeter. The former is due to the transverse component of the field i.e., the component perpendicular to the incident wave, and the latter is due to the component parallel to the incident direction. Focussing of the field towards the forward side of the particle is observed. As the particle complexity is increased due to aggregation, the field becomes smoother and less focussing is seen. For complex aggregates, the individual monomers act independently of one another, suggesting simplified methods of calculating scattering from such particles. The influence of the internal fields on far-field scattering is explored. It is demonstrated that scattering in the forward and backward directions is dominated by the transverse component. The parallel component contributes to sidescattering, with its influence on total scattering decreasing with particle complexity. We propose that this is due to the inability of complex particles to maintain a standing wave, diminishing much of the sidescattering observed for monocrystals. Comparisons of the far-field scattering properties of complex aggregates using the discrete dipole and Rayleigh-Gans approximations are also presented for x=2 and x=10, along with results obtained using a soft sphere approximation
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