8,355 research outputs found
The role of the immune system in brain metastasis
Metastatic brain tumors are the most common brain tumors in adults. With numerous successful advancements in systemic treatment of most common cancer types, brain metastasis is becoming increasingly important in the overall prognosis of cancer patients. Brain metastasis of peripheral tumor is the result of complex interplay of primary tumor, immune system and central nervous system microenvironment. Once formed, brain metastases hide behind the blood brain barrier and become inaccessible to chemotherapies that are otherwise successful in targeting systemic cancer. The approval of immune checkpoint inhibitors for several common cancers such as advanced melanoma and lung cancers brings with it the opportunity and obligation to further understand the mechanisms of immunosuppression by tumors that spread to the brain as well as the interaction between the brain environment and tumor microenvironment. In this review paper we define the central role of the immune system in the development of brain metastases. We performed a comprehensive review of the literature to outline the molecular mechanisms of immunosuppression used by tumors and how the immune system interacts with the central nervous system to facilitate brain metastasis. In particular we discuss the tumor-type-specific mechanisms of metastasis of cancers that preferentially metastasize to the brain as well as the therapies that effectively modulate the immune response, such as immune checkpoint inhibitors and vaccines
Magnetic Sensors Based on Long Josephson Tunnel Junctions - An Alternative to SQUIDs
The properties of Josephson devices are strongly affected by geometrical
effects. A loop-shaped superconducting electrode tightly couples a long
Josephson tunnel junction with the surrounding electromagnetic field. Due to
the fluxoid conservation, any change of the magnetic flux linked to the loop
results in a variation of the shielding current circulating around the loop,
which, in turn, affects the critical current of the Josephson junction. This
method allows the realization of a novel family of robust superconducting
devices (not based on the quantum interference) which can function as a
general-purpose magnetic sensors. The best performance is accomplished without
compromising the noise performance by employing an in-line-type junction few
times longer than its Josephson penetration length. The linear (rather than
periodic) response to magnetic flux changes over a wide range is just one of
its several advantages compared to the most sensitive magnetic detectors
currently available, namely the Superconducting Quantum Interference Devices
(SQUID). We will also comment on the drawbacks of the proposed system and
speculate on its noise properties.Comment: 13 pages, 4 figure
High frequency acoustic modes in liquid gallium at the melting point
The microscopic dynamics in liquid gallium (l-Ga) at melting (T=315 K) has
been studied by inelastic x-ray scattering. We demonstrate the existence of
collective acoustic-like modes up to wave-vectors above one half of the first
maximum of the static structure factor, at variance with earlier results from
inelastic neutron scattering data [F.J. Bermejo et al. Phys. Rev. E 49, 3133
(1994)]. Despite the structural (an extremely rich polymorphism and rather
complex phase diagram) and electronic (mixed valence) peculiarity of l-Ga, its
collective dynamics is strikingly similar to the one of Van der Walls and
alkali metals liquids. This result speaks in favor of the universality of the
short time dynamics in monatomic liquids rather than of system-specific
dynamics.Comment: LaTex format, 11 pages, 4 EncapsulatedPostScript figure
Defect formation in superconducting rings: external fields and finite-size effects
Consistent with the predictions of Kibble and Zurek, scaling behaviour has
been seen in the production of fluxoids during temperature quenches of
superconducting rings. However, deviations from the canonical behaviour arise
because of finite-size effects and stray external fields.
Technical developments, including laser heating and the use of long Josephson
tunnel junctions, have improved the quality of data that can be obtained. With
new experiments in mind we perform large-scale 3D simulations of quenches of
small, thin rings of various geometries with fully dynamical electromagnetic
fields, at nonzero externally applied magnetic flux. We find that the outcomes
are, in practice, indistinguishable from those of much simpler Gaussian
analytical approximations in which the rings are treated as one-dimensional
systems and the magnetic field fluctuation-free.Comment: 10 pages, 3 figures, presentation at QFS2012, to appear in JLT
Chemical abundances of the metal-poor horizontal-branch stars CS 22186-005 and CS 30344-033
We report on a chemical-abundance analysis of two very metal-poor
horizontal-branch stars in the Milky Way halo: CS 22186-005 ([Fe/H]=-2.70) and
CS 30344-033 ([Fe/H]=-2.90). The analysis is based on high-resolution spectra
obtained at ESO, with the spectrographs HARPS at the 3.6 m telescope, and UVES
at the VLT. We adopted one-dimensional, plane-parallel model atmospheres
assuming local thermodynamic equilibrium. We derived elemental abundances for
13 elements for CS 22186-005 and 14 elements for CS 30344-033. This study is
the first abundance analysis of CS 30344-033. CS 22186-005 has been analyzed
previously, but we report here the first measurement of nickel (Ni; Z = 28) for
this star, based on twenty-two NiI lines ([Ni/Fe]=-0.210.02); the
measurement is significantly below the mean found for most metal-poor stars.
Differences of up to 0.5 dex in [Ni/Fe] ratios were determined by different
authors for the same type of stars in the literature, which means that it is
not yet possible to conclude that there is a real intrinsic scatter in the
[Ni/Fe] ratios. For the other elements for which we obtained estimates, the
abundance patterns in these two stars match the Galactic trends defined by
giant and turnoff stars well. This confirms the value of horizontal-branch
stars as tracers of the chemical properties of stellar populations in the
Galaxy. Our radial velocities measurements for CS 22186-005 differ from
previously published measurements by more than the expected statistical errors.
More measurements of the radial velocity of this star are encouraged to confirm
or refute its radial velocity variability
Constraining Cosmological Models by the Cluster Mass Function
We present a comparison between two observational and three theoretical mass
functions for eight cosmological models suggested by the data from the recently
completed BOOMERANG-98 and MAXIMA-1 cosmic microwave background (CMB)
anisotropy experiments as well as peculiar velocities (PVs) and type Ia
supernovae (SN) observations. The cosmological models have been proposed as the
best fit models by several groups. We show that no model is in agreement with
the abundances of X-ray clusters at .On the
other hand, we find that the BOOM+MAX+{\sl COBE}:I, Refined Concordance and
MDM are in a good agreement with the abundances of optical clusters.
The P11 and especially Concordance models predict a slightly lower abundances
than observed at . The BOOM+MAX+{\sl COBE}:II
and PV+CMB+SN models predict a slightly higher abundances than observed at
. The nonflat MAXIMA-1 is in a fatal conflict
with the observational cluster abundances and can be safely ruled out.Comment: 17 pages, 2 figures, reference added, figures changes, substantial
revision mad
Evidence of anomalous dispersion of the generalized sound velocity in glasses
The dynamic structure factor, S(Q,w), of vitreous silica, has been measured
by inelastic X-ray scattering in the exchanged wavevector (Q) region Q=4-16.5
nm-1 and up to energies hw=115 meV in the Stokes side. The unprecedented
statistical accuracy in such an extended energy range allows to accurately
determine the longitudinal current spectra, and the energies of the vibrational
excitations. The simultaneous observation of two excitations in the acoustic
region, and the persistence of propagating sound waves up to Q values
comparable with the (pseudo-)Brillouin zone edge, allow to observe a positive
dispersion in the generalized sound velocity that, around Q=5 nm-1, varies from
6500 to 9000 m/s: this phenomenon was never experimentally observed in a glass.Comment: 5 pages, 3 figures. To appear in Phys. Rev.
Temperature dependence of iron local magnetic moment in phase-separated superconducting chalcogenide
We have studied local magnetic moment and electronic phase separation in
superconducting KFeSe by x-ray emission and absorption
spectroscopy. Detailed temperature dependent measurements at the Fe K-edge have
revealed coexisting electronic phases and their correlation with the transport
properties. By cooling down, the local magnetic moment of Fe shows a sharp drop
across the superconducting transition temperature (T) and the coexisting
phases exchange spectral weights with the low spin state gaining intensity at
the expense of the higher spin state. After annealing the sample across the
iron-vacancy order temperature, the system does not recover the initial state
and the spectral weight anomaly at T as well as superconductivity
disappear. The results clearly underline that the coexistence of the low spin
and high spin phases and the transitions between them provide unusual magnetic
fluctuations and have a fundamental role in the superconducting mechanism of
electronically inhomogeneous KFeSe system.Comment: 6 pages, 5 figure
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