Morris Water Maze Test for Learning and Memory Deficits in Alzheimer's Disease Model Mice

The Morris Water Maze (MWM) was first established by neuroscientist Richard G. Morris in 1981 in order to test hippocampal-dependent learning, including acquisition of spatial memoryand long-term spatial memory 1. The MWM is a relatively simple procedure typically consisting of six day trials, the main advantage being the differentiation between the spatial (hidden-platform) and non-spatial (visible platform) conditions 2-4. In addition, the MWM testing environment reduces odor trail interference 5. This has led the task to be used extensively in the study of the neurobiology and neuropharmacology of spatial learning and memory. The MWM plays an important role in the validation of rodent models for neurocognitive disorders such as Alzheimer’s Disease 6, 7. In this protocol we discussed the typical procedure of MWM for testing learning and memory and data analysis commonly used in Alzheimer’s disease transgenic model mice

Hyper Velocity Stars and the Restricted Parabolic 3-body Problem

Motivated by detections of hypervelocity stars that may originate from the Galactic Center, we revist the problem of a binary disruption by a passage near a much more massive point mass. The six order of magnitude mass ratio between the Galactic Center black hole and the binary stars allows us to formulate the problem in the restricted parabolic three-body approximation. In this framework, results can be simply rescaled in terms of binary masses, its initial separation and binary-to-black hole mass ratio. Consequently, an advantage over the full three-body calculation is that a much smaller set of simulations is needed to explore the relevant parameter space. Contrary to previous claims, we show that, upon binary disruption, the lighter star does not remain preferentially bound to the black hole. In fact, it is ejected exactly in 50% of the cases. Nonetheless, lighter objects have higher ejection velocities, since the energy distribution is independent of mass. Focusing on the planar case, we provide the probability distributions for disruption of circular binaries and for the ejection energy. We show that even binaries that penetrate deeply into the tidal sphere of the black hole are not doomed to disruption, but survive in 20% of the cases. Nor do these deep encounters produce the highest ejection energies, which are instead obtained for binaries arriving to 0.1-0.5 of the tidal radius in a prograde orbit. Interestingly, such deep-reaching binaries separate widely after penetrating the tidal radius, but always approach each other again on their way out from the black hole.[shortened]Comment: 10 pages, 10 Figures, Apj submitte

A qualitative document analysis of policies influencing preeclampsia management by midwives in Ghana

Background: Preeclampsia is a global issue that causes significant morbidity and mortality in low- and middle-income countries (LMICs). The care women with preeclampsia receive in LMICs is below the standard experienced by women in westernised countries due to multiple interacting factors. A review of policy factors influencing the management of preeclampsia in Ghana is needed. Aim: This study focuses on the midwife\u27s role and scope of practice concerning preeclampsia management. The study aimed to explore the congruence between Ghanaian preeclampsia guidelines and international best practice recommendations for midwifery practice. The study also aimed to describe how recommendations are incorporated into Ghanaian guidelines. Method/design: This study was a qualitative document analysis of national and tertiary hospital policies related to midwives’ scope of practice in Ghana. Altheide\u27s five-step process (sampling, data collection, data coding and organisation, data analysis and report) was used to systematically source and analyse the content of written documents. Results: The findings illustrated several recommendation shortcomings in Ghanaian documents at the national and tertiary hospital levels. The content of Ghanaian preeclampsia management guidelines was not comprehensive, contained conflicting information, and was not backed by research evidence. The standards of practice for midwives were consistent at both the national and tertiary hospital levels. Midwives had limited roles in detection, management, stabilisation, and referral of women with preeclampsia. Conclusion: Uniform guidelines incorporating international recommendations are urgently needed to improve multi-professional collaboration, solidify midwives’ roles, and optimise maternal and fetal outcomes

Pre-eclampsia training needs of midwives in a Ghanaian tertiary hospital: A cross-sectional study

Aim: This study aimed to assess the specific clinical and non-clinical training needs of midwives and determine their preferred approach to enhancing performance. Background: Pre-eclampsia remains one of the leading causes of maternal deaths in low and middle-income countries. Pre-eclampsia-related deaths may be due to reduced midwifery knowledge and inadequate management. Therefore, a training needs assessment is vital in identifying gaps in practice, especially, in poorly resourced settings for maximal use of training resources. Design: A hospital-based cross-sectional study. Setting: The largest tertiary hospital in Ghana. Methods: An online version of the validated WHO Hennessy-Hicks Training Needs Analysis questionnaire was used to assess midwives’ training needs on the management of pre-eclampsia. The tool has good psychometric properties and was used to assess 1) midwives’ confidence in performing tasks, 2) the importance of the task to their role and 3) their preferred performance improvement approach. Data analysis adhered to the guidelines specified in the Hennessy-Hicks Training Needs Analysis Questionnaire and the priority training requirements of the midwives were assessed through descriptive statistics and a series of independent t-tests. Results: Among the 250 midwives who responded, most possessed 1–5 years of experience (74.7 %). All 28 tasks were viewed by midwives as essential responsibilities in pre-eclampsia management. Midwives had the greatest need for training in research/audit and clinical skills domains respectively (p \u3c 0.001, 95 % confidence interval: 1.08–1.47, Cohen\u27s-D = 1.27; and p \u3c 0.001, 95 % confidence interval: 0.69–1.06, Cohen\u27s-D = 0.87). The foremost primary training necessity, as recognised by midwives, was undertaking health promotion activities, including antenatal health education (MD= 0.43, 95 % confidence interval: 0.29–0.57). Training courses were identified as the preferred approach to address training needs and improve overall proficiency. Conclusion: Midwives in Ghana require comprehensive training covering research and clinical-based competencies to improve pre-eclampsia management. Considering the pivotal role of Ghanaian midwives in safeguarding maternal well-being, there is a compelling need to enhance the calibre of midwifery services. These findings can guide stakeholders in countries with comparable healthcare contexts in creating effective, resource-efficient training programs that avoid counterproductivity, ultimately supporting national initiatives to enhance pre-eclampsia management and the quality of care

Midwives’ experiences of providing pre-eclampsia care in a low- and middle-income country – A qualitative study

Problem: Like other low- and middle-income countries, Ghana has high maternal mortality stemming from pre-eclampsia. Ghanaian midwives are frontline service providers of emergency care in obstetric complications and have the greatest potential to maximise pre-eclampsia outcomes. Little is known about the potential barriers and challenges to midwives\u27 capacity to provide quality care in pre-eclampsia in Ghana. Therefore, we aimed to explore and gain insights into midwives’ experiences of pre-eclampsia care including their knowledge, skills, and psychological aspects such as midwives\u27 resilience. Background: There is a rising global incidence of pre-eclampsia. Quality midwifery care in inter-professional collaborative practice is crucial to reducing pre-eclampsia-related morbidity and mortality. Methods: A qualitative descriptive exploratory study. In-depth semi-structured interviews (n = 35) were performed in 2021 and analysed by thematic analysis. Findings: There were three main themes. 1) Competence and Confidence in care; midwives provided timely and appropriate care based on sound knowledge and skills; they explained how pre-eclampsia care was organised within a multidisciplinary context and described collaborative working amongst midwives for mutual learning and support. 2) Emotional concerns and empathy; midwives’ described fulfillment in achieving positive pre-eclampsia outcomes. In contrast, maternal loss was distressing and traumatic. 3) Call for improved care resources for pre-eclampsia; midwives recommended expansion of continuing professional development opportunities, appropriate infrastructure, resources, tailored public education, and a review of pre-service education to support their participation in pre-eclampsia care. Conclusion: To improve the quality of care in pre-eclampsia, midwives should be capacitated, systems should promptly address barriers, and prioritise midwives’ emotional well-being

The spatial and velocity distributions of hypervelocity stars

Hypervelocity stars (HVSs) found in the Galactic halo are probably the dynamical products of interactions between (binary) stars and the massive black hole(s) (MBH) in the Galactic center (GC). It has been shown that the detected HVSs are spatially consistent with being located on two thin disks (Lu et al.), one of which has the same orientation as the clockwise-rotating stellar disk in the GC. Here we perform a large number of three-body experiments of the interactions between the MBH and binary stars bound to it, and find that the probability of ejecting HVSs is substantially enhanced by multiple encounters between the MBH and binary stars at distances substantially larger than the initial tidal breakup radii. Assuming that the HVS progenitors are originated from the two disks, the inclination distribution of the HVSs relative to the disk planes can be reproduced by either the mechanism of tidal breakup of binary stars or the mechanism of ejecting HVSs by a hypothetical binary black hole (BBH) in the GC. However, an isotropical origination of HVS progenitors is inconsistent with the observed inclination distribution. Assuming that the HVSs were ejected out by the tidal breakup mechanism, its velocity distribution can be reproduced if their progenitors diffuse onto low angular momentum orbits slowly and most of the progenitors were broken up at relatively large distances due to multiple encounters. Assuming that the HVSs were ejected out by a BBH within the allowed parameter space in the GC, our simulations produce relatively flatter velocity spectra compared to the observed ones; however, the BBH mechanism cannot be statistically ruled out, yet. Future surveys of HVSs and better statistics of their spatial and velocity distributions should enable to distinguish the ejection mechanisms of HVSs and shed new light on the dynamical environment of the MBH.(abridged)Comment: 19 pages, 16 figure

Elastic positron-cadmium scattering at low energies

The elastic and annihilation cross sections for positron-cadmium scattering are reported up to the positronium-formation threshold (at 2.2 eV). The low-energy phase shifts for the elastic scattering of positrons from cadmium were derived from the bound and pseudostate energies of a very large basis configuration-interaction calculation of the e+-Cd system. The s-wave binding energy is estimated to be 126±42 meV, with a scattering length of Ascat=(14.2±2.1)a0, while the threshold annihilation parameter, Zeff, was 93.9±26.5. The p-wave phase shift exhibits a weak shape resonance that results in a peak Zeff of 91±17 at a collision energy of about 490±50 meV

The properties of dynamically ejected runaway and hyper-runaway stars

Runaway stars are stars observed to have large peculiar velocities. Two mechanisms are thought to contribute to the ejection of runaway stars, both involve binarity (or higher multiplicity). In the binary supernova scenario a runaway star receives its velocity when its binary massive companion explodes as a supernova (SN). In the alternative dynamical ejection scenario, runaway stars are formed through gravitational interactions between stars and binaries in dense, compact clusters or cluster cores. Here we study the ejection scenario. We make use of extensive N-body simulations of massive clusters, as well as analytic arguments, in order to to characterize the expected ejection velocity distribution of runaways stars. We find the ejection velocity distribution of the fastest runaways (>~80 km s^-1) depends on the binary distribution in the cluster, consistent with our analytic toy model, whereas the distribution of lower velocity runaways appears independent of the binaries properties. For a realistic log constant distribution of binary separations, we find the velocity distribution to follow a simple power law; Gamma(v) goes like v^(-8/3) for the high velocity runaways and v^(-3/2) for the low velocity ones. We calculate the total expected ejection rates of runaway stars from our simulated massive clusters and explore their mass function and their binarity. The mass function of runaway stars is biased towards high masses, and depends strongly on their velocity. The binarity of runaways is a decreasing function of their ejection velocity, with no binaries expected to be ejected with v>150 km s^-1. We also find that hyper-runaways with velocities of hundreds of km s^-1 can be dynamically ejected from stellar clusters, but only at very low rates, which cannot account for a significant fraction of the observed population of hyper-velocity stars in the Galactic halo.Comment: Now matching published ApJ versio

Metal-poor hypervelocity star candidates from the Sloan Digital Sky Survey

Hypervelocity stars are believed to be ejected out from the Galactic center through dynamical interactions of (binary) stars with the central massive black hole(s). In this letter, we report 13 metal-poor F-type hypervelocity star candidates selected from 370,000 stars of the data release 7 of the Sloan Digital Sky Survey. With a detailed analysis of the kinematics of these stars, we find that seven of them were likely ejected from the Galactic center (GC) or the Galactic disk, four neither originated from the GC nor the Galactic disk, and the other two were possibly ejected from either the Galactic disk or other regions. Those candidates which unlikely originated from the GC or the Galactic disk, may be explained by other mechanisms, like the tidal disruption of the Milky Way's dwarf galaxies in the Galactic potential, or the gravitational interactions with a massive black hole at the center of M31 or M32

Hypervelocity Collisions of Binary Stars at the Galactic Centre

Recent surveys have identified seven hypervelocity stars (HVSs) in the halo of the Milky Way. Most of these stars may have originated from the breakup of binary star systems by the nuclear black hole SgrA*. In some instances, the breakup of the binary may lead to a collision between its member stars. We examine the dynamical properties of these collisions by simulating thousands of different binary orbits around SgrA* with a direct N-body integration code. For some orbital parameters, the two stars collide with an impact velocity lower than their escape velocity and may therefore coalesce. It is possible for a coalescing binary to have sufficient velocity to escape the galaxy. Furthermore, some of the massive S-stars near Sgr A* might be the merger remnants of binary systems, however this production method can not account for most of the S-stars.Comment: 5 pages, 2 figures, accepted for publication in MNRA