Underwater optical wireless communications : depth dependent variations in attenuation

Depth variations in the attenuation coefficient for light in the ocean were calculated using a one-parameter model based on the chlorophyll-a concentration Cc and experimentally-determined Gaussian chlorophyll-depth profiles. The depth profiles were related to surface chlorophyll levels for the range 0–4  mg/m2, representing clear, open ocean. The depth where Cc became negligible was calculated to be shallower for places of high surface chlorophyll; 111.5 m for surface chlorophyll 0.8<Cc<2.2  mg/m3 compared with 415.5 m for surface Cc<0.04  mg/m3. Below this depth is the absolute minimum attenuation for underwater ocean communication links, calculated to be 0.0092  m−1 at a wavelength of 430 nm. By combining this with satellite surface-chlorophyll data, it is possible to quantify the attenuation between any two locations in the ocean, with applications for low-noise or secure underwater communications and vertical links from the ocean surface

Calcium entry into stereocilia drives adaptation of the mechanoelectrical transducer current of mammalian cochlear hair cells

Mechanotransduction in the auditory and vestibular systems depends on mechanosensitive ion channels in the stereociliary bundles that project from the apical surface of the sensory hair cells. In lower vertebrates, when the mechanoelectrical transducer (MET) channels are opened by movement of the bundle in the excitatory direction, Ca2+ entry through the open MET channels causes adaptation, rapidly reducing their open probability and resetting their operating range. It remains uncertain whether such Ca2+-dependent adaptation is also present in mammalian hair cells. Hair bundles of both outer and inner hair cells from mice were deflected by using sinewave or step mechanical stimuli applied using a piezo-driven fluid jet. We found that when cochlear hair cells were depolarized near the Ca2+ reversal potential or their hair bundles were exposed to the in vivo endolymphatic Ca2+ concentration (40 µM), all manifestations of adaptation, including the rapid decline of the MET current and the reduction of the available resting MET current, were abolished. MET channel adaptation was also reduced or removed when the intracellular Ca2+ buffer 1,2-Bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA) was increased from a concentration of 0.1 to 10 mM. The findings show that MET current adaptation in mouse auditory hair cells is modulated similarly by extracellular Ca2+, intracellular Ca2+ buffering, and membrane potential, by their common effect on intracellular free Ca2+. Hearing and balance depend on the transduction of mechanical stimuli into electrical signals. This process depends on the opening of mechanoelectrical transducer (MET) channels located at the tips of the shorter of pairs of adjacent stereocilia (1), which are specialized microvilli-like structures that form the hair bundles that project from the upper surface of hair cells (2,3). Deflection of hair bundles in the excitatory direction (i.e., toward the taller stereocilia) stretches specialized linkages, the tip-links, present between adjacent stereocilia (3⇓–5), opening the MET channels. In hair cells from lower vertebrates, open MET channels reclose during constant stimuli via an initial fast adaptation mechanism followed by a much slower, myosin-based motor process, both of which are driven by Ca2+ entry through the channel itself (6⇓⇓⇓⇓⇓⇓–13). In mammalian auditory hair cells, MET current adaptation seems to be mainly driven by the fast mechanism (14⇓–16), although the exact process by which it occurs is still largely unknown. The submillisecond speed associated with the adaptation kinetics of the MET channels in rat and mouse cochlear hair cells (17, 18) indicates that Ca2+, to cause adaptation, has to interact directly with a binding site on the channel or via an accessory protein (16). However, a recent investigation on rat auditory hair cells has challenged the view that Ca2+ entry is required for fast adaptation, and instead proposed an as-yet-undefined mechanism involving a Ca2+-independent reduction in the viscoelastic force of elements in series with the MET channels (19). In the present study, we further investigated the role of Ca2+ in MET channel adaptation in mouse cochlear hair cells by deflecting their hair bundles using a piezo-driven fluid jet, which is believed to produce a more uniform deflection of the hair bundles (20⇓⇓–23) compared with the piezo-driven glass rod (19, 24)

Tmc1 point mutation affects Ca2+ sensitivity and block by dihydrostreptomycin of the mechanoelectrical transducer current of mouse outer hair cells

The transduction of sound into electrical signals depends on mechanically sensitive ion channels in the stereociliary bundle. The molecular composition of this mechanoelectrical transducer (MET) channel is not yet known. Transmembrane channel-like protein isoforms 1 (TMC1) and 2 (TMC2) have been proposed to form part of the MET channel, although their exact roles are still unclear. Using Beethoven (Tmc1Bth/Bth) mice, which have an M412K point mutation in TMC1 that adds a positive charge, we found that Ca2+ permeability and conductance of the MET channel of outer hair cells (OHCs) were reduced. Tmc1Bth/Bth OHCs were also less sensitive to block by the permeant MET channel blocker dihydrostreptomycin, whether applied extracellularly or intracellularly. These findings suggest that the amino acid that is mutated in Bth is situated at or near the negatively charged binding site for dihydrostreptomycin within the permeation pore of the channel. We also found that the Ca2+ dependence of the operating range of the MET channel was altered by the M412K mutation. Depolarization did not increase the resting open probability of the MET current of Tmc1Bth/Bth OHCs, whereas raising the intracellular concentration of the Ca2+ chelator BAPTA caused smaller increases in resting open probability in Bth mutant OHCs than in wild-type control cells. We propose that these observations can be explained by the reduced Ca2+ permeability of the mutated MET channel indirectly causing the Ca2+ sensor for adaptation, at or near the intracellular face of the MET channel, to become more sensitive to Ca2+ influx as a compensatory mechanism

The Ground on Which We All Stand: A Conversation About Menstrual Equity Law and Activism

This essay grows out of a panel discussion among five lawyers on the subject of menstrual equity activism. Each of the authors is a scholar, activist or organizer involved in some form of menstrual equity work. The overall project is both enriched and complicated by an intersectional analysis. This essay increases awareness of existing menstrual equity and menstrual justice work; it also identifies avenues for further inquiry, next steps for legal action, and opportunities that lie ahead. After describing prior and current work at the junction of law and menstruation, the contributors evaluate the successes and limitations of recent legal changes. The authors then turn to conceptual issues about the relationship between menstrual equity and gender justice, as well as the difference between equity and equality. The essay concludes with consideration of the future of menstrual equity and menstrual justice work. The authors envision an expanded, inclusive group of individuals working for greater gender justice

Chewing gum and impasse-induced self-reported stress

An insoluble anagram task (Zellner et al., 2006) was used to investigate the proposition that chewing gum reduces self-rated stress (Scholey et al., 2009). Using a between-participants design, forty participants performed an insoluble anagram task followed by a soluble anagram task. These tasks were performed with or without chewing gum. Self-rated measures were taken at baseline, post-stressor, and post-recovery task. The insoluble anagram task was found to amplify stress in terms of increases in self-rated stress and reductions in both self-rated calmness and contentedness. However, chewing gum was found not to mediate the level of stress experienced. Furthermore, chewing gum did not result in superior performance on the soluble anagram task. The present study fails to generalise the findings of Scholey et al. to an impasse induced stress that has social components. The explanation for the discrepancy with Scholey et al. is unclear; however, it is suggested that the impossibility of the insoluble anagram task may negate any secondary stress reducing benefits arising from chewing gum-induced task improvement

2FGL J0846.0+2820: A new neutron star binary with a giant secondary and variable γ\gamma-ray emission

We present optical photometric and spectroscopic observations of the likely stellar counterpart to the unassociated \emph{Fermi}-Large Area Telescope (LAT) $\gamma$-ray source 2FGL J0846.0+2820, selected for study based on positional coincidences of optical variables with unassociated LAT sources. Using optical spectroscopy from the SOAR telescope, we have identified a late-G giant in an eccentric ($e$ = 0.06) 8.133 day orbit with an invisible primary. Modeling the spectroscopy and photometry together lead us to infer a heavy neutron star primary of $\sim 2 M_{\odot}$ and a partially stripped giant secondary of $\sim 0.8 M_{\odot}$. H$\alpha$ emission is observed in some of the spectra, perhaps consistent with the presence of a faint accretion disk. We find the $\gamma$-ray flux of 2FGL J0846.0+2820 dropped substantially in mid-2009, accompanied by an increased variation in the optical brightness, and since then it has not been detected by \emph{Fermi}. The long period and giant secondary are reminiscent of the $\gamma$-ray bright binary 1FGL J1417.7--4407, which hosts a millisecond pulsar apparently in the final stages of the pulsar recycling process. The discovery of 2FGL J0846.0+2820 suggests the identification of a new subclass of millisecond pulsar binaries that are the likely progenitors of typical field millisecond pulsars.Comment: 12 pages, 8 figures, 3 tables. Accepted for publication in Ap

Stress and Burnout in Nurse Leaders

Problem: Nurse leaders commonly experience stress and self-reported burnout. The associated negative consequences are compelling, yet few studies to date consider the nurse leader population. Stress is “a multidimensional phenomenon determined by a person’s perceptions and may be assessed as harm, loss, threat, or challenge” (Udod, Cummings, Care, & Jenkins, 2017a, p. 160). Burnout is a lack of professional fulfillment caused by emotional, physical, and psychological stress (Nurse Burnout, 2019). Drivers are associated and contributing factors which lead to stress and self-reported burnout. Purpose: The purposes of this correlational study are to (a) identify drivers from the literature and adapt an existing model to nurse leader populations, (b) investigate associations between drivers of stress among two nurse leader groups: Nurse Mangers/Nurse Supervisors and Chief Nursing Officers/Nurse Directors, (c) investigate association between drivers and self-reported burnout among all nurse leaders, and (d) compare drivers identified in the literature to drivers from the Minnesota Organization of Leaders in Nursing (MOLN) study. Conceptual Framework: The Job Demands-Resources (JD-R) Model of Burnout guided the literature review. We adapted our own model on stress leading to burnout in nurse leaders entitled Johnson, Nichols, and Sakhitab (JNS) Model of Stress Leading to Burnout in Nurse Leaders. The focus of the JNS model was to identify the drivers of stress leading to burnout in nurse leaders. Literature Search: Eight drivers of stress leading to burnout from the literature were: administrative duties, organizational constraints, role overload, lack of control, preparation, personal characteristics, quality patient care, and social support. Methods Data Analysis: The research method used for this thesis was a secondary analysis of the 2018 MOLN and the Minnesota Hospital Association Nurse Leader Burnout Survey. The Pearson product-moment correlation was used to assess relationships between drivers, stress, and burnout. The total sample included 210 nurse leaders. Results Data Analysis: Results from this secondary analysis found statistically significant drivers of stress in Nurse Managers and Nurse Supervisors (n = 90) were time (r = -.500, p = .000), control (r = -.321, p = .002), and resources (r = -.254, p = .016). The statistically significant drivers of stress in Chief Nursing Officers and Nurse Directors (n = 74) were time (r = -.492, p \u3c .000), resources (r = -.441, p = .000) control (r = -.387, p = .001), team efficiency (r = -.338, p = .003), and autonomy (r = -.250, p =.031). Drivers of self-reported burnout in nurse leaders (n = 210) in order of correlational strength were control, time, autonomy, resources, appreciation, team efficiency, value and quality (-.419 \u3c r \u3c -.181, p ≤ .009). Implications for Practice: Nurse leaders carry a high degree of responsibility and are unable to achieve optimal work/life balance. One solution is to restructure leadership hierarchy to include a co-manager role. A second implication for practice relates to the lack of control driver of stress; nurse leaders desire the freedom, empowerment, and autonomy to make decisions without fear for retribution. Lastly, an implication for practice relates to the drivers of social support and appreciation. It will be prudent for health care administrators to re-focus energies on provision of appreciation and recognition to nurse leaders. Implications for Research: The gap in longitudinal designed studies creates an opportunity for future research. We recommend replicating the MOLN study longitudinally and nationally to support findings from this secondary analysis. Future studies focusing on self-reported burnout need a standardized measurement tool. This will allow for direct comparison of data and stronger analysis of findings. Lastly, drivers of stress leading to burnout in nurse leaders must be universally defined