551 research outputs found
Variational Approach to Hydrogen Atom in Uniform Magnetic Field of Arbitrary Strength
Extending the Feynman-Kleinert variational approach, we calculate the
temperature-dependent effective classical potential governing the quantum
statistics of a hydrogen atom in a uniform magnetic at all temperatures. The
zero-temperature limit yields the binding energy of the electron which is quite
accurate for all magnetic field strengths and exhibits, in particular, the
correct logarithmic growth at large fields.Comment: Author Information under this
http://www.physik.fu-berlin.de/~kleinert/institution.html Latest update of
paper also at this http://www.physik.fu-berlin.de/~kleinert/30
Quantum key distribution without alternative measurements
Entanglement swapping between Einstein-Podolsky-Rosen (EPR) pairs can be used
to generate the same sequence of random bits in two remote places. A quantum
key distribution protocol based on this idea is described. The scheme exhibits
the following features. (a) It does not require that Alice and Bob choose
between alternative measurements, therefore improving the rate of generated
bits by transmitted qubit. (b) It allows Alice and Bob to generate a key of
arbitrary length using a single quantum system (three EPR pairs), instead of a
long sequence of them. (c) Detecting Eve requires the comparison of fewer bits.
(d) Entanglement is an essential ingredient. The scheme assumes reliable
measurements of the Bell operator.Comment: REVTeX, 5 pages, 2 figures. Published version with some comment
The dependence of the EIT wave velocity on the magnetic field strength
"EIT waves" are a wavelike phenomenon propagating in the corona, which were
initially observed in the extreme ultraviolet (EUV) wavelength by the EUV
Imaging Telescope (EIT). Their nature is still elusive, with the debate between
fast-mode wave model and non-wave model. In order to distinguish between these
models, we investigate the relation between the EIT wave velocity and the local
magnetic field in the corona. It is found that the two parameters show
significant negative correlation in most of the EIT wave fronts, {\it i.e.},
EIT wave propagates more slowly in the regions of stronger magnetic field. Such
a result poses a big challenge to the fast-mode wave model, which would predict
a strong positive correlation between the two parameters. However, it is
demonstrated that such a result can be explained by the fieldline stretching
model, \emph{i.e.,} that "EIT waves" are apparently-propagating brightenings,
which are generated by successive stretching of closed magnetic field lines
pushed by the erupting flux rope during coronal mass ejections (CMEs).Comment: 11 pages, 8 figures, accepted for publication in Solar Phy
The Society for Immunotherapy of Cancer consensus statement on immunotherapy for the treatment of squamous cell carcinoma of the head and neck (HNSCC)
Head and neck cancers, including those of the lip and oral cavity, nasal cavity, paranasal sinuses, oropharynx, larynx and nasopharynx represent nearly 700,000 new cases and 380,000 deaths worldwide per annum, and account for over 10,000 annual deaths in the United States alone. Improvement in outcomes are needed for patients with recurrent and or metastatic squamous cell carcinoma of the head and neck (HNSCC). In 2016, the US Food and Drug Administration (FDA) granted the first immunotherapeutic approvals - the anti-PD-1 immune checkpoint inhibitors nivolumab and pembrolizumab - for the treatment of patients with recurrent squamous cell carcinoma of the head and neck (HNSCC) that is refractory to platinum-based regimens. The European Commission followed in 2017 with approval of nivolumab for treatment of the same patient population, and shortly thereafter with approval of pembrolizumab monotherapy for the treatment of recurrent or metastatic HNSCC in adults whose tumors express PD-L1 with a 65 50% tumor proportion score and have progressed on or after platinum-containing chemotherapy. Then in 2019, the FDA granted approval for PD-1 inhibition as first-line treatment for patients with metastatic or unresectable, recurrent HNSCC, approving pembrolizumab in combination with platinum and fluorouracil for all patients with HNSCC and pembrolizumab as a single agent for patients with HNSCC whose tumors express a PD-L1 combined positive score 65 1. These approvals marked the first new therapies for these patients since 2006, as well as the first immunotherapeutic approvals in this disease. In light of the introduction of these novel therapies for the treatment of patients with head and neck cancer, The Society for Immunotherapy of Cancer (SITC) formed an expert committee tasked with generating consensus recommendations for emerging immunotherapies, including appropriate patient selection, therapy sequence, response monitoring, adverse event management, and biomarker testing. These consensus guidelines serve as a foundation to assist clinicians' understanding of the role of immunotherapies in this disease setting, and to standardize utilization across the field for patient benefit. Due to country-specific variances in approvals, availability and regulations regarding the discussed agents, this panel focused solely on FDA-approved drugs for the treatment of patients in the U.S
On the Nature and Genesis of EUV Waves: A Synthesis of Observations from SOHO, STEREO, SDO, and Hinode
A major, albeit serendipitous, discovery of the SOlar and Heliospheric
Observatory mission was the observation by the Extreme Ultraviolet Telescope
(EIT) of large-scale Extreme Ultraviolet (EUV) intensity fronts propagating
over a significant fraction of the Sun's surface. These so-called EIT or EUV
waves are associated with eruptive phenomena and have been studied intensely.
However, their wave nature has been challenged by non-wave (or pseudo-wave)
interpretations and the subject remains under debate. A string of recent solar
missions has provided a wealth of detailed EUV observations of these waves
bringing us closer to resolving their nature. With this review, we gather the
current state-of-art knowledge in the field and synthesize it into a picture of
an EUV wave driven by the lateral expansion of the CME. This picture can
account for both wave and pseudo-wave interpretations of the observations, thus
resolving the controversy over the nature of EUV waves to a large degree but
not completely. We close with a discussion of several remaining open questions
in the field of EUV waves research.Comment: Solar Physics, Special Issue "The Sun in 360",2012, accepted for
publicatio
Self-control and early adolescent antisocial behavior: A longitudinal analysis
Contains fulltext :
73179.pdf (publisher's version ) (Closed access)The article discusses a three-wave longitudinal study that investigates the relationship between self-control and aggressive and delinquent behavior of early adolescent boys and girls. The sample consists of 1,012 Dutch adolescents (mean age = 12.3) in their first year of secondary education. Structural equation modeling analyses reveal that high levels of self-control consistently decrease aggressive and delinquent behavior in the subsequent 6 months follow-up intervals. Results for the total sample do not support the hypothesis that self-control is influenced by previous levels of aggression or delinquency. For boys, the partial evidence found indicates reciprocal effects of self-control and delinquency.21 p
X-ray Spectroscopy and Variability of AGN Detected in the 2 Ms Chandra Deep Field-North Survey
We investigate the nature of the faint X-ray source population through X-ray
spectroscopy and variability analyses of 136 AGN detected in the 2 Ms Chandra
Deep Field-North survey with > 200 background-subtracted 0.5-8.0 keV counts
[F(0.5-8.0 keV)=(1.4-200)e-15 erg cm^{-2} s^{-1}]. Our preliminary spectral
analyses yield median spectral parameters of Gamma=1.61 and intrinsic
N_H=6.2e21 cm^{-2} (z=1 assumed when no redshift available) when the AGN
spectra are fitted with a simple absorbed power-law model. However,
considerable spectral complexity is apparent (e.g., reflection, partial
covering) and must be taken into account to model the data accurately.
Moreover, the choice of spectral model (i.e., free vs. fixed photon index) has
a pronounced effect on the derived N_H distribution and, to a lesser extent,
the X-ray luminosity distribution. Ten of the 136 AGN (~7%) show significant Fe
Kalpha emission-line features with equivalent widths in the range 0.1-1.3 keV.
Two of these emission-line AGN could potentially be Compton thick (i.e., Gamma
< 1.0 and large Fe Kalpha equivalent width). Finally, we find that 81 (~60%) of
the 136 AGN show signs of variability, and that this fraction increases
significantly (~80-90%) when better photon statistics are available.Comment: Submitted to Advances in Space Research for New X-ray Results from
Clusters of Galaxies and Black Holes (Oct 2002; Houston, TX), eds. C. Done,
E.M. Puchnarewicz, M.J. Ward. Requires cospar.sty (6 pgs, 10 figs
Obtenção de uma estirpe mutante ntrC- de Rhizobium sp. NGR234
Research into fetal development and medicin
Large-scale Bright Fronts in the Solar Corona: A Review of "EIT waves"
``EIT waves" are large-scale coronal bright fronts (CBFs) that were first
observed in 195 \AA\ images obtained using the Extreme-ultraviolet Imaging
Telescope (EIT) onboard the \emph{Solar and Heliospheric Observatory (SOHO)}.
Commonly called ``EIT waves", CBFs typically appear as diffuse fronts that
propagate pseudo-radially across the solar disk at velocities of 100--700 km
s with front widths of 50-100 Mm. As their speed is greater than the
quiet coronal sound speed (200 km s) and comparable to the
local Alfv\'{e}n speed (1000 km s), they were initially
interpreted as fast-mode magnetoacoustic waves ().
Their propagation is now known to be modified by regions where the magnetosonic
sound speed varies, such as active regions and coronal holes, but there is also
evidence for stationary CBFs at coronal hole boundaries. The latter has led to
the suggestion that they may be a manifestation of a processes such as Joule
heating or magnetic reconnection, rather than a wave-related phenomena. While
the general morphological and kinematic properties of CBFs and their
association with coronal mass ejections have now been well described, there are
many questions regarding their excitation and propagation. In particular, the
theoretical interpretation of these enigmatic events as magnetohydrodynamic
waves or due to changes in magnetic topology remains the topic of much debate.Comment: 34 pages, 19 figure
Facilitating children's self-concept: A rationale and evaluative study
This study reports on the design and effectiveness of the Exploring Self-Concept program for primary school children using self-concept as the outcome measure. The program aims to provide a procedure that incorporates organisation, elaboration, thinking, and problem-solving strategies and links these to children's multidimensional self-concept. The results of this research support the notion that teachers and guidance counsellors need to establish a nonthreatening framework that allows them to discuss with children a range of relevant issues related to peer pressure, parent relations, self-image, body image, gender bias, media pressure, values and life goals, in a systematic, objective and cooperative manner. Within the paper, notions associated with self-concept maturation, 'crystallisation' of self-concept beliefs, cognitive differentiation and self-concept segmentation are reviewed
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