8,977 research outputs found
Relativistic quantum mechanics of a Dirac oscillator
The Dirac oscillator is an exactly soluble model recently introduced in the
context of many particle models in relativistic quantum mechanics. The model
has been also considered as an interaction term for modelling quark confinement
in quantum chromodynamics. These considerations should be enough for
demonstrating that the Dirac oscillator can be an excellent example in
relativistic quantum mechanics. In this paper we offer a solution to the
problem and discuss some of its properties. We also discuss a physical picture
for the Dirac oscillator's non-standard interaction, showing how it arises on
describing the behaviour of a neutral particle carrying an anomalous magnetic
moment and moving inside an uniformly charged sphere.Comment: 19 pages, 1 figur
From circular paths to elliptic orbits: A geometric approach to Kepler's motion
The hodograph, i.e. the path traced by a body in velocity space, was
introduced by Hamilton in 1846 as an alternative for studying certain dynamical
problems. The hodograph of the Kepler problem was then investigated and shown
to be a circle, it was next used to investigate some other properties of the
motion. We here propose a new method for tracing the hodograph and the
corresponding configuration space orbit in Kepler's problem starting from the
initial conditions given and trying to use no more than the methods of
synthetic geometry in a sort of Newtonian approach. All of our geometric
constructions require straight edge and compass only.Comment: 9 pages, 4 figure
Relativistically extended Blanchard recurrence relation for hydrogenic matrix elements
General recurrence relations for arbitrary non-diagonal, radial hydrogenic
matrix elements are derived in Dirac relativistic quantum mechanics. Our
approach is based on a generalization of the second hypervirial method
previously employed in the non-relativistic Schr\"odinger case. A relativistic
version of the Pasternack-Sternheimer relation is thence obtained in the
diagonal (i.e. total angular momentum and parity the same) case, from such
relation an expression for the relativistic virial theorem is deduced. To
contribute to the utility of the relations, explicit expressions for the radial
matrix elements of functions of the form and
---where is a Dirac matrix--- are presented.Comment: 21 pages, to be published in J. Phys. B: At. Mol. Opt. Phys. in Apri
Precision neuromodulation: Promises and challenges of spinal stimulation for multi-modal rehabilitation
Spinal cord injury results in multiple, simultaneous sensorimotor deficits. These include, but are not limited to, full or partial paralysis of muscles below the lesion, muscle spasms, spasticity, and neuropathic pain. Bowel, bladder, and sexual dysfunction are also prevalent. Yet, the majority of emerging spinal stimulation-based therapies focus on a single issue: locomotor rehabilitation. Despite the enormous potential of these translational advances to transform the lives of people living with spinal cord injury, meaningful recovery in other domains deemed critical priorities remains lacking. Here, we highlight the importance of considering the diverse patterns of neural transmission that underlie clinically similar presentations when developing spinal stimulation-based therapies. We also motivate advancement of multi-modal rehabilitation paradigms, which leverage the dense interconnectivity of sensorimotor spinal networks and the unique ability of electrical stimulation to modulate these networks to facilitate and guide simultaneous rehabilitation across domains
Synchronous or collision solid neoplasms and lymphomas: A systematic review of 308 case reports.
The presence of a lymphoma associated with a solid synchronous neoplasm or collision neoplasm has been rarely in the literature, and a detailed characterization of these cases is lacking to date.
To describe the main clinicopathological features of synchronous/collision tumors.
A systematic search in PubMed, Scielo, and Virtual Health Library literature databases for cases or case series of synchronous or collision lymphoma and other solid neoplasms reported up to March 2021 was performed. Three reviewers independently screened the literature, extracted data, and assessed the quality of the included studies. The systematic review was performed following the Preferred Reporting Items for Systematic Meta-Analyses guidelines.
Mean age of patients was 62.9 years (52.9% men). A total of 308 cases were included (62% synchronous and 38% collision). The most frequent location of both synchronous and collision tumors was the gastrointestinal tract with the most common solid neoplasm being adenocarcinoma, and the most frequent lymphoma diffuse large B-cell lymphoma (21.7%) and mucosa-associated lymphoid tissue lymphoma (20.4%). Of the total number of mucosa-associated lymphoid tissue lymphomas and gastric adenocarcinomas, the presence of Helicobacter pylori infection was documented in 47.3% of them. Only 2% of all cases had a previous history of lymphoma. Thus, in most cases (98%), lymphoma was discovery incidentally. In addition, nodal lymphoma was associated with metastasis in 29 (9.4%) cases as collision tumor, most commonly (90%) in locoregional lymph nodes of the solid neoplasm.
The frequent association of some type of B-cell lymphoma and adenocarcinoma in synchronous/collision tumors of the gastrointestinal tract points to common pathogenic mechanisms in both neoplasia, particularly related to chronic inflammation in this location. In most cases, lymphoma identified in locoregional lymph nodes or distant of a carcinoma seems to represent an incidental finding during the carcinoma diagnostic/therapeutic approach. A synergy between carcinoma and lymphoma (involving inflammation and immunosuppression mechanisms) may favor tumor progression and dissemination. A better understating of the interactions lymphoma/carcinoma in the setting of synchronous/collision tumors may help to improve patient management and prognosis
Caveolin-1 is required for TGF-ÎČ-induced transactivation of the EGF receptor pathway in hepatocytes through the activation of the metalloprotease TACE/ADAM17
Transforming growth factor-beta (TGF-ÎČ) plays a dual role in hepatocytes, inducing both pro- and anti-apoptotic responses, whose balance decides cell fate. Survival signals are mediated by the epidermal growth factor receptor (EGFR) pathway, which is activated by TGF-ÎČ in these cells. Caveolin-1 (Cav1) is a structural protein of caveolae linked to TGF-ÎČ receptors trafficking and signaling. Previous results have indicated that in hepatocytes, Cav1 is required for TGF-ÎČ-induced anti-apoptotic signals, but the molecular mechanism is not fully understood yet. In this work, we show that immortalized Cav1â/â hepatocytes were more sensitive to the pro-apoptotic effects induced by TGF-ÎČ, showing a higher activation of caspase-3, higher decrease in cell viability and prolonged increase through time of intracellular reactive oxygen species (ROS). These results were coincident with attenuation of TGF-ÎČ-induced survival signals in Cav1â/â hepatocytes, such as AKT and ERK1/2 phosphorylation and NFÎș-B activation. Transactivation of the EGFR pathway by TGF-ÎČ was impaired in Cav1â/â hepatocytes, which correlated with lack of activation of TACE/ADAM17, the metalloprotease responsible for the shedding of EGFR ligands. Reconstitution of Cav1 in Cav1â/â hepatocytes rescued wild-type phenotype features, both in terms of EGFR transactivation and TACE/ADAM17 activation. TACE/ADAM17 was localized in detergent-resistant membrane (DRM) fractions in Cav1+/+ cells, which was not the case in Cav1â/â cells. Disorganization of lipid rafts after treatment with cholesterol-binding agents caused loss of TACE/ADAM17 activation after TGF-ÎČ treatment. In conclusion, in hepatocytes, Cav1 is required for TGF-ÎČ-mediated activation of the metalloprotease TACE/ADAM17 that is responsible for shedding of EGFR ligands and activation of the EGFR pathway, which counteracts the TGF-ÎČ pro-apoptotic effects. Therefore, Cav1 contributes to the pro-tumorigenic effects of TGF-ÎČ in liver cancer cells
Urban road surface discrimination by tire-road noise analysis and data clustering
The surface condition of roadways has direct consequences on a wide range of processes related to the transportation technology, quality of road facilities, road safety, and traffic noise emissions. Methods developed for detection of road surface condition are crucial for maintenance and rehabilitation plans, also relevant for driving environment detection for autonomous transportation systems and e-mobility solutions. In this paper, the clustering of the tire-road noise emission features is proposed to detect the condition of the wheel tracks regions during naturalistic driving events. This acoustic-based methodology was applied in urban areas under nonstop real-life traffic conditions. Using the proposed method, it was possible to identify at least two groups of surface status on the inspected routes over the wheel-path interaction zone. The detection rate on urban zone reaches 75% for renewed lanes and 72% for distressed lanes
Avocado oil extraction: an industrial experiment
Se analizan los resultados obtenidos en un experimento industrial de obtenciĂłn de aceite de aguacate por un proceso continuo similar al de obtenciĂłn de aceite de oliva, indicando las posibles modificaciones para mejorar el rendimiento.The results of an industrial experiment to obtain avocado oil by continuous process similar to that for obtaining olive oil are analysed. Possible ways of improving the method and thus the yield are pointed out
A pilot randomised controlled trial on the effectiveness of infant massage on the acceptance, commitment and awareness of influence in parents of babies with Down syndrome
Background The emotional state of parents of babies
with Down syndrome affects their babiesâ
development and their parentâchild bonding. The
aim for this study was to conduct a pilot randomised
controlled evaluation of the effect of infant massage
on parents of babies with Down syndrome.
Methods This pilot study compared two groups
(intervention and control), each with 16 parents of
babies with Down syndrome. Indices of acceptance,
engagement and awareness of influence were
measured at two different time points (pre-test and
after 5 weeks) using the âThis Is My Babyâ Interview.
The allocation of families to each group was
randomised. The experimental group performed
infant massage, applied by the parents, for 5 weeks,
every day for at least 10 min. The massage protocol
was based on the methodology created by Vimala
McClure. Parents in the control group received the
intervention after completion of the study.
Results The indices of acceptance, commitment and
awareness of influence improved in the experimental
group and in the control group. The 2 Ă 2
mixed-model analysis of variance indicates a
statistically significant group-by-time interaction for
all indices (P < 0.001), which was significantly higher
in the experimental group than in the control group.
Conclusions The application of infant massage, by
parents to their babies, improves the rates of
acceptance, commitment and awareness of influence
of parents of babies with Down syndrome in the
short termFunding for open access charge: Universidad de
MĂĄlaga / CBU
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