6,898 research outputs found
Shocked Molecular Gas in the Supernova Remnant HB 21
We report the discovery of the shocked molecular gas in the supernova remnant
HB 21. We derive the physical parameters of the shocked gas from CO J=1-0 and
J=2-1 line observations. We discuss the correlation of the shocked molecular
gas with the previously detected, shocked atomic gas and the associated
infrared emission.Comment: 24 pages, 10 figures, To appear in the ApJ, scheduled for the April
10, 2001 issue (v551
Another positivity proof and gravitational energy localizations
Two locally positive expressions for the gravitational Hamiltonian, one using
4-spinors the other special orthonormal frames, are reviewed. A new quadratic
3-spinor-curvature identity is used to obtain another positive expression for
the Hamiltonian and thereby a localization of gravitational energy and positive
energy proof. These new results provide a link between the other two methods.
Localization and prospects for quasi-localization are discussed.Comment: 14 pages REVTe
Terahertz underdamped vibrational motion governs protein-ligand binding in solution
Low-frequency collective vibrational modes in proteins have been proposed as being responsible for efficiently directing biochemical reactions and biological energy transport. However, evidence of the existence of delocalized vibrational modes is scarce and proof of their involvement in biological function absent. Here we apply extremely sensitive femtosecond optical Kerr-effect spectroscopy to study the depolarized Raman spectra of lysozyme and its complex with the inhibitor triacetylchitotriose in solution. Underdamped delocalized vibrational modes in the terahertz frequency domain are identified and shown to blue-shift and strengthen upon inhibitor binding. This demonstrates that the ligand-binding coordinate in proteins is underdamped and not simply solvent-controlled as previously assumed. The presence of such underdamped delocalized modes in proteins may have significant implications for the understanding of the efficiency of ligand binding and protein–molecule interactions, and has wider implications for biochemical reactivity and biological function
Current quark mass effects on chiral phase transition of QCD in the improved ladder approximation
Current quark mass effects on the chiral phase transition of QCD is studied
in the improved ladder approximation. An infrared behavior of the gluon
propagator is modified in terms of an effective running coupling. The analysis
is based on a composite operator formalism and a variational approach. We use
the Schwinger-Dyson equation to give a ``normalization condition'' for the
Cornwall-Jackiw-Tomboulis effective potential and to isolate the ultraviolet
divergence which appears in an expression for the quark-antiquark condensate.
We study the current quark mass effects on the order parameter at zero
temperature and density. We then calculate the effective potential at finite
temperature and density and investigate the current quark mass effects on the
chiral phase transition. We find a smooth crossover for , and a
first-order phase transition for , T=0. Critical exponents are also
studied and our model gives the classical mean-field values. We also study the
temperature dependence of masses of scalar and pseudoscalar bosons. A critical
end point in the - plane is found at MeV,
MeV.Comment: 19 pages, 13 figure
Controlling crystallization and its absence: Proteins, colloids and patchy models
The ability to control the crystallization behaviour (including its absence)
of particles, be they biomolecules such as globular proteins, inorganic
colloids, nanoparticles, or metal atoms in an alloy, is of both fundamental and
technological importance. Much can be learnt from the exquisite control that
biological systems exert over the behaviour of proteins, where protein
crystallization and aggregation are generally suppressed, but where in
particular instances complex crystalline assemblies can be formed that have a
functional purpose. We also explore the insights that can be obtained from
computational modelling, focussing on the subtle interplay between the
interparticle interactions, the preferred local order and the resulting
crystallization kinetics. In particular, we highlight the role played by
``frustration'', where there is an incompatibility between the preferred local
order and the global crystalline order, using examples from atomic glass
formers and model anisotropic particles.Comment: 11 pages, 7 figure
Pim1 promotes human prostate cancer cell tumorigenicity and c-MYC transcriptional activity
<p>Abstract</p> <p>Background</p> <p>The serine/threonine kinase PIM1 has been implicated as an oncogene in various human cancers including lymphomas, gastric, colorectal and prostate carcinomas. In mouse models, Pim1 is known to cooperate with c-Myc to promote tumorigenicity. However, there has been limited analysis of the tumorigenic potential of Pim1 overexpression in benign and malignant human prostate cancer cells <it>in vivo</it>.</p> <p>Methods</p> <p>We overexpressed Pim1 in three human prostate cell lines representing different disease stages including benign (RWPE1), androgen-dependent cancer (LNCaP) and androgen-independent cancer (DU145). We then analyzed <it>in vitro </it>and <it>in vivo </it>tumorigenicity as well as the effect of Pim1 overexpression on c-MYC transcriptional activity by reporter assays and gene expression profiling using an inducible MYC-ER system. To validate that Pim1 induces tumorigenicity and target gene expression by modulating c-MYC transcriptional activity, we inhibited c-MYC using a small molecule inhibitor (10058-F4) or RNA interference.</p> <p>Results</p> <p>Overexpression of Pim1 alone was not sufficient to convert the benign RWPE1 cell to malignancy although it enhanced their proliferation rates when grown as xenografts <it>in vivo</it>. However, Pim1 expression enhanced the <it>in vitro </it>and <it>in vivo </it>tumorigenic potentials of the human prostate cancer cell lines LNCaP and DU145. Reporter assays revealed increased c-MYC transcriptional activity in Pim1-expressing cells and mRNA expression profiling demonstrated that a large fraction of c-MYC target genes were also regulated by Pim1 expression. The c-MYC inhibitor 10058-F4 suppressed the tumorigenicity of Pim1-expressing prostate cancer cells. Interestingly, 10058-F4 treatment also led to a reduction of Pim1 protein but not mRNA. Knocking-down c-MYC using short hairpin RNA reversed the effects of Pim1 on Pim1/MYC target genes.</p> <p>Conclusion</p> <p>Our results suggest an <it>in vivo </it>role of Pim1 in promoting prostate tumorigenesis although it displayed distinct oncogenic activities depending on the disease stage of the cell line. Pim1 promotes tumorigenicity at least in part by enhancing c-MYC transcriptional activity. We also made the novel discovery that treatment of cells with the c-MYC inhibitor 10058-F4 leads to a reduction in Pim1 protein levels.</p
The predictive and prognostic potential of plasma telomerase reverse transcriptase (TERT) RNA in rectal cancer patients
Background: Preoperative chemoradiotherapy (CRT) followed by surgery is the standard care for locally advanced rectal cancer,
but tumour response to CRT and disease outcome are variable. The current study aimed to investigate the effectiveness of plasma
telomerase reverse transcriptase (TERT) levels in predicting tumour response and clinical outcome.
Methods: 176 rectal cancer patients were included. Plasma samples were collected at baseline (before CRT\ubcT0), 2 weeks after
CRT was initiated (T1), post-CRT and before surgery (T2), and 4\u20138 months after surgery (T3) time points. Plasma TERT mRNA levels
and total cell-free RNA were determined using real-time PCR.
Results: Plasma levels of TERT were significantly lower at T2 (Po0.0001) in responders than in non-responders. Post-CRT TERT
levels and the differences between pre- and post-CRT TERT levels independently predicted tumour response, and the prediction
model had an area under curve of 0.80 (95% confidence interval (CI) 0.73\u20130.87). Multiple analysis demonstrated that patients with
detectable TERT levels at T2 and T3 time points had a risk of disease progression 2.13 (95% CI 1.10\u20134.11)-fold and 4.55 (95% CI
1.48\u201313.95)-fold higher, respectively, than those with undetectable plasma TERT levels.
Conclusions: Plasma TERT levels are independent markers of tumour response and are prognostic of disease progression in rectal
cancer patients who undergo neoadjuvant therapy
Limits to Poisson's ratio in isotropic materials - general result for arbitrary deformation
The lower bound usually cited for Poisson's ratio {\nu} is -1, derived from
the relationship between {\nu} and the bulk and shear moduli. From
consideration of the longitudinal and biaxial moduli, we recently determined
that the lower bound on {\nu} for isotropic materials is actually 1/5, a value
also consistent with experimental measurements on real materials. Herein we
generalize this result, first by analyzing expressions for {\nu} in terms of
six common elastic constants, and then by considering arbitrary strains. The
results corroborate the prior finding that 1/5 <= {\nu} for linear elasticity
to be applicable.Comment: 15 pages, 3 figures, 1 tabl
2021 occultations and transits of Linus orbiting (22) Kalliope: I. Polygonal and `cliptracing' algorithm
The satellite Linus orbiting the main-belt asteroid (22) Kalliope exhibited
occultation and transit events in late 2021. A photometric campaign was
organized and observations were taken by the TRAPPIST-South, SPECULOOS-Artemis,
OWL-Net, and BOAO telescopes, with the goal to constrain models of this system.
Our dynamical model is complex, with multipoles (up to the order ),
internal tides, and external tides. The model was constrained by astrometry
(spanning 2001--2021), occultations, adaptive-optics imaging, calibrated
photometry, as well as relative photometry. Our photometric model was
substantially improved. A new precise () light curve
algorithm was implemented, based on polygon intersections, which are computed
exactly -- by including partial eclipses and partial visibility of polygons.
Moreover, we implemented a `cliptracing' algorithm, based again on polygon
intersections, in which partial contributions to individual pixels are computed
exactly. Both synthetic light curves and synthetic images are then very smooth.
Based on our combined solution, we confirmed the size of Linus, . However, this solution exhibits some tension between the light
curves and the PISCO speckle-interferometry dataset. In most solutions, Linus
is darker than Kalliope, with the albedos vs. . This
is confirmed on deconvolved images. A~detailed revision of astrometric data
allowed us to revise also the value of Kalliope. Most
importantly, a~homogeneous body is excluded. For a differentiated body, two
solutions exist: low-oblateness (), with a~spherical iron
core, and alternatively, high-oblateness () with an
elongated iron core. These correspond to the low- and high-energy collisions,
respectively, studied by means of SPH simulations in our previous work.Comment: Astronomy and Astrophysics, accepte
Topical use of MMC in the upper aerodigestive tract: a review on the side effects
Not much is known about the side effects of mitomycin C (MMC), an anti-fibrogenetic agent, in the upper aerodigestive tract. However, its use in ophthalmology is widely known and without quantitatively important side effects. A literature review was performed for side effects of MMC in the upper aerodigestive tract. Forty-six articles, describing the use of MMC to prevent scarring, were retracted from PubMed. Thirty-two are human studies. MMC is used in different concentrations (0.1–10 mg/ml) with different application times (2–5 min) and frequencies (up to 4 times). Five hundred and thirty-eight patients were included in those publications, of whom 19 developed side effects (3.53%). No side effects developed in studies, where post-application irrigation with saline was reported. The longest mean follow-up period is 75.5 months. Direct relations between the reported side effects and MMC seem absent in most studies. Serious complications seem to occur when MMC is used in high concentrations. Unfortunately, sometimes crucial information is lacking. One patient was described who supposedly developed laryngeal carcinoma after repeated treatment of hyperkeratosis and anterior commissure webbing. Animal studies show that excessive fibrin production can lead to acute airway obstruction. In conclusion, topical application of MMC on a wound with consecutive irrigation with saline can be performed safely to prevent scar formation in circular structures of the upper aerodigestive tract. Long-term yearly control of the application site seems advisable
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