139 research outputs found
Entanglement in a Time-Dependent Coupled XY Spin Chain in an External Magnetic Field
We consider an infinite one dimensional anisotropic XY spin chain with a
nearest neighbor time-dependent Heisenberg coupling J(t) between the spins in
presence of a time-dependent magnetic field h(t). We discuss a general solution
for the system and present an exact solution for particular choice of J and h
of practical interest. We investigate the dynamics of entanglement for
different degrees of anisotropy of the system and at both zero and finite
temperatures. We find that the time evolution of entanglement in the system
show non-ergodic and critical behavior at zero and finite temperatures and
different degrees of anisotropy. The asymptotic behavior of entanglement at the
infinite time limit at zero temperature and constant J and h depends only the
parameter lambda=J/h rather than the individual values of J and h for all
degrees of anisotropy but changes for nonzero temperature. Furthermore, the
asymptotic behavior is very sensitive to the initial values of J and h and for
particular choices we may create finite asymptotic entanglement regardless of
the final values of J and h. The persistence of quantum effects in the system
as it evolves and as the temperature is raised is studied by monitoring the
entanglement. We find that the quantum effects dominates within certain regions
of the kT-lambda space that vary significantly depending on the degree of the
anisotropy of the system. Particularly, the quantum effects in the Ising model
case persists in the vicinity of both its critical phase transition point and
zero temperature as it evolves in time. Moreover, the interplay between the
different system parameters to tune and control the entanglement evolution is
explored.Comment: 33 pages, 17 figures; v3: Grammar errors and typos corrected, Figure
17(b) update
Entanglement dynamics of one-dimensional driven spin systems in time-varying magnetic fields
We study the dynamics of entanglement for a one-dimensional spin chain with a
nearest neighbor time dependent Heisenberg coupling J(t) between the spins in
presence of a time dependent external magnetic field h(t) at zero and finite
temperatures. We consider different forms of time dependence for the coupling
and magnetic field; exponential, hyperbolic and periodic. We examined the
system size effect on the entanglement asymptotic value. It was found that for
a small system size the entanglement starts to fluctuate within a short period
of time after applying the time dependent coupling. The period of time
increases as the system size increases and disappears completely as the size
goes to infinity. We also found that when J(t) is periodic the entanglement
shows a periodic behavior with the same period, which disappears upon applying
periodic magnetic field with the same frequency. Solving the particular case
where J(t) and h(t) are proportional exactly, we showed that the asymptotic
value of entanglement depends only on the initial conditions regardless of the
form of J(t) and h(t) applied at t > 0.Comment: 22 pages and 8 figure
An Evaluation of the Effectiveness of a Simulated Classroom-based Intervention on Concussion Rehabilitation Among Individuals with Persistent Post-Concussion Symptoms
Although recent clinical and scientific effort has focused on the development of guidelines for post-concussion return to play/work/learn, there is still relatively little literature that addresses specific treatment methods by which this can be accomplished. Accordingly, this study investigated the effect of a 7-week simulated classroom-based intervention on the self-reporting of symptom scores among 71 individuals with persistent concussion symptoms (26 men and 45 women). All participants were provided with novel strategies for reading, writing, study skills, social communication and technology use. Self-assessment of symptoms were obtained weekly, both before and after each session of the treatment program, in an effort to monitor the cognitive demands of each session, and to identify the extent to which the program produced an improvement over the course of seven weeks. Results suggested that concussion symptoms were exacerbated in the short term by treatment, F(1, 343) = 255.69, p \u3c .05, consistently across the 7 weeks of the program. An overall downward trend was, however, observed for symptom scores, over the seven weeks of the treatment program, and a statistically significant difference was noted between the first and last week of the program, F(6, 343) = 2.29, p \u3c .05. Post-hoc analysis of means (using Tukey’s HSD) suggests that there was a significant improvement (alpha = 0.05) of self-reported symptoms when comparing weeks 1 and 6, and between weeks 1 and 7. These results suggest that, transient exacerbation of symptoms aside; the targeted simulated classroom interventions produced a statistically significant benefit in the management of persistent concussion symptoms within this particular return-to-learn protocol
Measurement quench in many-body systems
Measurement is one of the key concepts which discriminates classical and
quantum physics. Unlike classical systems, a measurement on a quantum system
typically alters it drastically as a result of wave function collapse. Here we
suggest that this feature can be exploited for inducing quench dynamics in a
many-body system while leaving its Hamiltonian unchanged. Importantly, by doing
away with dedicated macroscopic devices for inducing a quench -- using instead
the indispensable measurement apparatus only -- the protocol is expected to be
easier to implement and more resilient against decoherence. By way of various
case studies, we show that our scheme also has decisive advantages beyond
reducing decoherence -- for spectroscopy purposes and probing nonequilibrium
scaling of critical and quantum impurity many-body systems.Comment: 6 pages, 5 figure
Object-Based Coastal Morphological Change Analysis Based on LiDAR and Hurricane Events
Storms are considered one of the rapid climatic events that have a dramatic impact on coastal morphology, hence they require further investigation and quantifying of coastal changes and responses. Light detection and ranging (LiDAR) is the most advanced technology to be widely used by researchers for coastal geomorphological studies. The purpose of this study is to apply an object-based approach using repeated LiDAR surveys to understand the short-term morphological changes that occurred on Santa Rosa Island, Florida after category 3 hurricanes Ivan (2004) and Dennis (2005), making it the first study to apply this method, as opposed to previous studies’ commonly used field-based approaches. The first analysis was conducted using a coastal morphology analysis (CMA) tool. In the second analysis, the extracted mean elevation change values were linked to three factors—mean vegetation, mean slope, and mean elevation—to demonstrate their contribution to the change using ordinary least square (OLS) analysis. The third analysis was carried out using the classification and regression tree (CART) analysis. Of the study area, 18.64% encountered erosional processes and 11.35% with depositional processes during Hurricane Ivan, whereas during Hurricane Dennis, 5.91% faced erosional processes and 8.18% was affected by depositional processes. Both hurricanes resulted in a net sediment loss; 283,167 m3 during Hurricane Ivan and 52,440 m3 during Hurricane Dennis. Generally, objects tended to be irregular, asymmetrical, and shaped with smooth boundaries. Along the coast, most objects tended to have an elongated shape, but inland the shapes were more irregular. The overall OLS model during Hurricane Ivan yielded statistically significant results for the three factors, with a confidence level of 0.00 and an adjusted r-square of 0.40; and during Hurricane Dennis, the mean vegetation and mean elevation results yielded significant statistical results (p-value 0.00), while slope did not show significance and had an adjusted r-square of 0.47. CART analysis of both hurricanes ranked the mean elevation as the most important factor in predicting the mean elevation change, followed by the mean slope and finally the mean vegetation variable
Exploring Pre-Service Special and General Education Teachers’ Beliefs and Attitudes in Mathematics and Learning and Teaching Mathematics
The purpose of this quantitative study was to examine and compare the beliefs and attitudes of pre-service special and general education teacher candidates regarding mathematics and the learning and teaching of mathematics and explore factors including student learning, teaching math, math rated affect (math anxiety and confidence), effectance motivation, usefulness of math, and the effect of previous teachers’ perceptions. The interrelationship among these factors was explored and compared to participants’ academic level and majors (i.e., special education and general) to determine whether these factors influenced the approaches pre-service teachers thought they would use when teaching math. The participants were 362 special and general pre-service teachers (elementary education and secondary math education) at all four academic levels (freshman, sophomore, junior, and senior). Statistical analysis methods employed to obtain the results included multivariate analysis of variance, chi square, and multiple linear regression. Findings revealed statistically significantly differences in beliefs and attitudes toward mathematics among pre-service teachers across their academic majors. In comparison to the other two participant groups, special education pre-service teachers had more anxiety and less confidence in their math abilities and had the lowest mean scores in usefulness of math, effectance motivation, teacher perception, and student learning of all three participant groups. Findings also indicated the relationships between major and planning to teach math and major and desire to teach math were both statistically significant. In this study, special education pre-service teachers were less likely to plan or want to teach math when compared to elementary and secondary math pre-service teachers. Furthermore, findings suggested math rated affect and teacher perception could predict pre-service teachers’ beliefs in student learning. Findings suggested pre-service teachers who had less math anxiety and were more confident in their math ability were more likely to believe in a constructivist approach in student learning. Finally, a significant relationship was found between pre-service teachers’ beliefs in teaching math and effectance motivation, which implied pre-service teachers who had more interest and motivation toward math were more likely to believe teaching math involved constructivist practices. Implications and suggestions for future research were provided based on the results of the current study
H2S donor GYY4137 ameliorates paclitaxel-induced neuropathic pain in mice
Paclitaxel-induced neuropathic pain (PINP) is a dose-limiting side effect that largely affects the patient’s quality of life and may limit the use of the drug as a chemotherapeutic agent for treating metastatic breast cancer and other solid tumors. Recently, a putative role for the gaseous mediator hydrogen sulfide (H2S) in nociception modulation has been suggested. The aim of the present study was to investigate the potential efficacy of the slow release H2S donor GYY4137 to alleviate and prevent PINP. Female BALB/c mice that were intraperitoneally (i.p.) injected with paclitaxel (2 mg/kg) for 5 consecutive days developed thermal hyperalgesia, cold and mechanical allodynia and had reduced of H2S, generation in the spinal cord and paw skin. Treatment of mice with established thermal hyperalgesia with GYY4137 or the analgesic positive control drug gabapentin produced antihyperalgesic activities. The antihyperalgesic activity of GYY4137 was antagonized by the ATP sensitive potassium channels (KATP channels) blocker glibenclamide. Co-treatment with GYY4137 and paclitaxel prevented the paclitaxel-induced decrease in H2S, generation as well as the paclitaxel-induced thermal hyperalgesia, cold allodynia and mechanical allodynia. GYY4137 enhanced paclitaxel\u27s anti-proliferative effects against the breast cancer cell line MCF-7. The present results suggest that GYY4137 alleviates paclitaxel-induced thermal hyperalgesia, via KATP channels. GYY4137 prevents PINP possibly by blocking the paclitaxel-induced reduction in the generation of H2S, in the tissues, while enhancing the anti-cancer activity of paclitaxel, and therefore warrants further research as a candidate for prevention of PINP in clinical settings
Characterizing the effect of retractions on scientific careers
Retracting academic papers is a fundamental tool of quality control when the
validity of papers or the integrity of authors is questioned post-publication.
While retractions do not eliminate papers from the record, they have
far-reaching consequences for retracted authors and their careers, serving as a
visible and permanent signal of potential transgressions. Previous studies have
highlighted the adverse effects of retractions on citation counts and
coauthors' citations; however, the broader impacts beyond these have not been
fully explored. We address this gap leveraging Retraction Watch, the most
extensive data set on retractions and link it to Microsoft Academic Graph, a
comprehensive data set of scientific publications and their citation networks,
and Altmetric that monitors online attention to scientific output. Our
investigation focuses on: 1) the likelihood of authors exiting scientific
publishing following a retraction, and 2) the evolution of collaboration
networks among authors who continue publishing after a retraction. Our
empirical analysis reveals that retracted authors, particularly those with less
experience, tend to leave scientific publishing in the aftermath of retraction,
particularly if their retractions attract widespread attention. We also uncover
that retracted authors who remain active in publishing maintain and establish
more collaborations compared to their similar non-retracted counterparts.
Nevertheless, retracted authors with less than a decade of publishing
experience retain less senior, less productive and less impactful coauthors,
and gain less senior coauthors post-retraction. Taken together, notwithstanding
the indispensable role of retractions in upholding the integrity of the
academic community, our findings shed light on the disproportionate impact that
retractions impose on early-career authors.Comment: 49 pages, 13 figures, 19 table
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