208 research outputs found
Coexistence of multiple sclerosis and brain tumors: a literature review.
Concurrent development of primary brain tumors and multiple sclerosis is quite rare. Only a few dozens of such comorbidity have been reported. Nevertheless, given the fact that such pathologies are characterized by similar clinical picture and neuroimaging findings, issues about diagnosis and differential diagnosis of such conditions often arise, which makes the problem relevant. A literature review was conducted using PubMed, by selecting articles on concurrent multiple sclerosis and brain tumors, particularly glial origin tumors, over the past 20 years (1989 to 2019). The search was performed in English, Russian, and Ukrainian using the following key words and terms: comorbidity, concomitance, multiple sclerosis, brain tumor, glioma, astrocytoma, glioblastoma. The analysis included all articles on etiology, pathogenesis, clinical picture, diagnosis, differential diagnosis, neuroimaging, and pathomorphological assessment. After identifying all the articles that met the inclusion criteria and removing duplicate data, 35 literature sources on concurrent primary brain tumors and multiple sclerosis were selected. The conclusion on whether concurrent primary brain tumors and multiple sclerosis develop randomly or have common pathophysiological mechanisms is still under discussion. Potential causes of pathogenesis of both diseases include viral infection, chronic inflammation, neoplastic transformation, and involvement of neurotropic growth factors. The likelihood that two processes, demyelinating and neoplastic, can develop in parallel will never be underestimated. In such cases, strong clinical suspicion arises due to atypical clinical picture characterized by aggressive and rapidly growing neurological symptoms such as aphasia, spastic hemiparesis, epileptic seizures, or signs of intracranial hypertension. In MRI diagnosis, pathological findings such as single lesion of more than 2 cm; mass effect, edema, signal amplification in the form of ring-shaped shadow are the reasons for a more thorough examination and applying additional diagnostic methods: CT, MR spectroscopy, PET, CSF tests to determine oligoclonal antibodies and other markers content, cerebral biopsy. According to the literature, cases of concurrent primary brain tumors and multiple sclerosis are rare though described. Atypical clinical signs, neuroimaging data, and cerebral biopsy which is currently considered as the only method for making accurate diagnosis are helpful in the diagnostic process
Coexistence of multiple sclerosis and brain tumours: Case report and review
In the present report, a review of the literature on the combination of multiple sclerosis and brain tumours is performed. Additionally, the frequency of such combination, possible etiopathogenetic mechanisms, current diagnostic criteria and treatment approaches are reviewed. Furthermore, the case of a 30-year-old man with multiple sclerosis and anaplastic astrocytoma of the right temporal lobe is described in detail. Specifically, the patient underwent a series of tests, including laboratory analyses of blood and cerebrospinal fluid, brain MRI in various modes, MR spectroscopy and excised tumour’s pathohistological and immunohistochemical examination. Results of the tests are reported here. A staged examination and treatment of the patient allowed the researchers to perform a correct diagnosis and obtain a satisfactory functional outcome
Combinatorial identities for binary necklaces from exact ray-splitting trace formulae
Based on an exact trace formula for a one-dimensional ray-splitting system,
we derive novel combinatorial identities for cyclic binary sequences (P\'olya
necklaces).Comment: 15 page
N-body simulations with generic non-Gaussian initial conditions I: Power Spectrum and halo mass function
We address the issue of setting up generic non-Gaussian initial conditions
for N-body simulations. We consider inflationary-motivated primordial
non-Gaussianity where the perturbations in the Bardeen potential are given by a
dominant Gaussian part plus a non-Gaussian part specified by its bispectrum.
The approach we explore here is suitable for any bispectrum, i.e. it does not
have to be of the so-called separable or factorizable form. The procedure of
generating a non-Gaussian field with a given bispectrum (and a given power
spectrum for the Gaussian component) is not univocal, and care must be taken so
that higher-order corrections do not leave a too large signature on the power
spectrum. This is so far a limiting factor of our approach. We then run N-body
simulations for the most popular inflationary-motivated non-Gaussian shapes.
The halo mass function and the non-linear power spectrum agree with theoretical
analytical approximations proposed in the literature, even if they were so far
developed and tested only for a particular shape (the local one). We plan to
make the simulations outputs available to the community via the non-Gaussian
simulations comparison project web site
http://icc.ub.edu/~liciaverde/NGSCP.html.Comment: 23 pages, 10 figure
Constraining stellar assembly and AGN feedback at the peak epoch of star formation
We study stellar assembly and feedback from active galactic nuclei (AGN)
around the epoch of peak star formation (1<z<2), by comparing hydrodynamic
simulations to rest-frame UV-optical galaxy colours from the Wide Field Camera
3 (WFC3) Early-Release Science (ERS) Programme. Our Adaptive Mesh Refinement
simulations include metal-dependent radiative cooling, star formation, kinetic
outflows due to supernova explosions, and feedback from supermassive black
holes. Our model assumes that when gas accretes onto black holes, a fraction of
the energy is used to form either thermal winds or sub-relativistic
momentum-imparting collimated jets, depending on the accretion rate. We find
that the predicted rest-frame UV-optical colours of galaxies in the model that
includes AGN feedback is in broad agreement with the observed colours of the
WFC3 ERS sample at 1<z<2. The predicted number of massive galaxies also matches
well with observations in this redshift range. However, the massive galaxies
are predicted to show higher levels of residual star formation activity than
the observational estimates, suggesting the need for further suppression of
star formation without significantly altering the stellar mass function. We
discuss possible improvements, involving faster stellar assembly through
enhanced star formation during galaxy mergers while star formation at the peak
epoch is still modulated by the AGN feedback.Comment: 6 pages, 4 figures, accepted for publication in MNRAS Letter
The Century Survey Galactic Halo Project III: A Complete 4300 deg^2 Survey of Blue Horizontal Branch Stars in the Metal-Weak Thick Disk and Inner Halo
We present a complete spectroscopic survey of 2414 2MASS-selected blue
horizontal branch (BHB) candidates selected over 4300 deg^2 of the sky. We
identify 655 BHB stars in this non-kinematically selected sample. We calculate
the luminosity function of field BHB stars and find evidence for very few hot
BHB stars in the field. The BHB stars located at a distance from the Galactic
plane |Z|<4 kpc trace what is clearly a metal-weak thick disk population, with
a mean metallicity of [Fe/H]= -1.7, a rotation velocity gradient of
dv_{rot}/d|Z|= -28+-3.4 km/s in the region |Z|<6 kpc, and a density scale
height of h_Z= 1.26+-0.1 kpc. The BHB stars located at 5<|Z|<9 kpc are a
predominantly inner-halo population, with a mean metallicity of [Fe/H]= -2.0
and a mean Galactic rotation of -4+-31 km/s. We infer the density of halo and
thick disk BHB stars is 104+-37 kpc^-3 near the Sun, and the relative
normalization of halo to thick-disk BHB stars is 4+-1% near the Sun.Comment: 12 pages in emulateapj format, accepted for publication in February
A
The Case for the Dual Halo of the Milky Way
Carollo et al. have recently resolved the stellar population of the Milky Way
halo into at least two distinct components, an inner halo and an outer halo.
This result has been criticized by Schoenrich et al., who claim that the
retrograde signature associated with the outer halo is due to the adoption of
faulty distances. We refute this claim, and demonstrate that the Schoenrich et
al. photometric distances are themselves flawed because they adopted an
incorrect main-sequence absolute magnitude relationship from the work of
Ivezi\'c et al. When compared to the recommended relation from Ivezi\'c et al.,
which is tied to a Milky Way globular cluster distance scale and accounts for
age and metallicity effects, the relation adopted by Schoenrich et al. yields
up to 18% shorter distances for stars near the main-sequence turnoff (TO). Use
of the correct relationship yields agreement between the distances assigned by
Carollo et al. and Ivezi\'{c} et al. for low-metallicity dwarfs to within
6-10%. Schoenrich et al. also point out that intermediate-gravity stars (3.5 <=
log g <= 4.0) with colors redder than the TO region are likely misclassified,
with which we concur. We implement a new procedure to reassign luminosity
classifications for the TO stars that require it. New derivations of the
rotational behavior demonstrate that the retrograde signature and high velocity
dispersion of the outer-halo population remains. We summarize additional lines
of evidence for a dual halo, including a test of the retrograde signature based
on proper motions alone, and conclude that the preponderance of evidence
strongly rejects the single-halo interpretation.Comment: 46 pages, 2 tables, 15 figures, Accepted for publication in the
Astrophysical Journa
Spectra of regular quantum graphs
We consider a class of simple quasi one-dimensional classically
non-integrable systems which capture the essence of the periodic orbit
structure of general hyperbolic nonintegrable dynamical systems. Their behavior
is simple enough to allow a detailed investigation of both classical and
quantum regimes. Despite their classical chaoticity, these systems exhibit a
``nonintegrable analog'' of the Einstein-Brillouin-Keller quantization formula
which provides their spectra explicitly, state by state, by means of convergent
periodic orbit expansions.Comment: 32 pages, 10 figure
Quantum fingerprints of classical Ruelle-Pollicot resonances
N-disk microwave billiards, which are representative of open quantum systems,
are studied experimentally. The transmission spectrum yields the quantum
resonances which are consistent with semiclassical calculations. The spectral
autocorrelation of the quantum spectrum is shown to be determined by the
classical Ruelle-Pollicot resonances, arising from the complex eigenvalues of
the Perron-Frobenius operator. This work establishes a fundamental connection
between quantum and classical correlations in open systems.Comment: 6 pages, 2 eps figures included, submitted to PR
Two Stellar Components in the Halo of the Milky Way
The halo of the Milky Way provides unique elemental abundance and kinematic
information on the first objects to form in the Universe, which can be used to
tightly constrain models of galaxy formation and evolution. Although the halo
was once considered a single component, evidence for its dichotomy has slowly
emerged in recent years from inspection of small samples of halo objects. Here
we show that the halo is indeed clearly divisible into two broadly overlapping
structural components -- an inner and an outer halo -- that exhibit different
spatial density profiles, stellar orbits and stellar metallicities (abundances
of elements heavier than helium). The inner halo has a modest net prograde
rotation, whereas the outer halo exhibits a net retrograde rotation and a peak
metallicity one-third that of the inner halo. These properties indicate that
the individual halo components probably formed in fundamentally different ways,
through successive dissipational (inner) and dissipationless (outer) mergers
and tidal disruption of proto-Galactic clumps.Comment: Two stand-alone files in manuscript, concatenated together. The first
is for the main paper, the second for supplementary information. The version
is consistent with the version published in Natur
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