Cross phase modulation in a five--level atomic medium: Semiclassical theory

The interaction of a five-level atomic system involving electromagnetically induced transparency with four light fields is investigated. Two different light-atom configurations are considered, and their efficiency in generating large nonlinear cross-phase shifts compared. The dispersive properties of those schemes are analyzed in detail, and the conditions leading to group velocity matching for two of the light fields identified. An analytical treatment based on amplitude equations is used in order to obtain approximate solutions for the susceptibilities, ehich are shown to fit well with the numerical simulations of the full Bloch equations in a large parameter region.Comment: New version: section on pulse propagation added, reference list expanded; 17 pages, 15 figure

Chlorpyrifos- and chlorpyrifos oxon-induced neurite retraction in pre-differentiated N2a cells is associated with transient hyperphosphorylation of neurofilament heavy chain and ERK 1/2

Chlorpyrifos (CPF) and CPF-oxon (CPO) are known to inhibit neurite outgrowth but little is known about their ability to induce neurite retraction in differentiating neuronal cells. The aims of this study were to determine the ability of these compounds to destabilize neurites and to identify the key molecular events involved. N2a cells were induced to differentiate for 20 h before exposure to CPF or CPO for 2-8 h. Fixed cell monolayers labeled with carboxyfluorescein succinimidyl ester or immunofluorescently stained with antibodies to tubulin (B512) or phosphorylated neurofilament heavy chain (Ta51) showed time- and concentration-dependent reductions in numbers and length of axon-like processes compared to the control, respectively, retraction of neurites being observed within 2 h of exposure by live cell imaging. Neurofilament disruption was also observed in treated cells stained by indirect immunofluorescence with anti- phosphorylated neurofilament heavy chain (NFH) monoclonal antibody SMI34, while the microtubule network was unaffected. Western blotting analysis revealed transiently increased levels of reactivity of Ta51 after 2 h exposure and reduced levels of reactivity of the same antibody following 8 h treatment with both compounds, whereas reactivity with antibodies to anti-total NFH or anti-tubulin was not affected. The alteration in NFH phosphorylation at 2 h exposure was associated with increased activation of extracellular signal-regulated protein kinase ERK 1/2. However, increased levels of phosphatase activity were observed following 8 h exposure. These findings suggest for the first time that organophosphorothionate pesticide-induced neurite retraction in N2a cells is associated with transient increases in NFH phosphorylation and ERK1/2 activation

Surviving precarious work: Differing forms, tactics and strategies

Purpose: This article explores differentiation in the responses of precarious workers to the instability and uncertainty imposed on their work by employing organizations. Our focus is on the ways in which different workers respond to precarious working conditions, with a particular interest on marginalised groups who have been especially overlooked by studies of workforce precarity. Design/methodology/approach: Employs an approach akin to grounded theory in an exploratory research design and utilizes indepth, semi-structured interviews of 56 precarious workers. Findings: Finds that different precarious workers, with divergent characteristics and resources, facing differing working conditions, and diverse structural constraints vary in the ways in which their strategies of surviving precarious work are manifested. Uncovers three differing forms of precarious workers who each employ a different range of tactics and strategies in work. Originality: Generates insights into differentiation of precarious workers in their responses to the ambiguous, challenging and, in many ways, subjugating conditions of their working conditions

Progress towards the vindication of panspermia

Theories of panspermia are rapidly coming into vogue, with the possibility of the transfer of viable bacterial cells from one planetary abode to another being generally accepted as inevitable. The panspermia models of Hoyle and Wickramasinghe require the transfer of viable bacterial cells from interstellar dust to comets and back into interplanetary and interstellar space. In such a cycle a viable fraction of as little as 10−18 at the inception of a newly formed comet/planet system suffices for cometary panspermia to dominate over competing processes for the origin and transfer of life. The well-attested survival attributes of microbes under extreme conditions, which have recently been discovered, gives credence to the panspermia hypothesis. The prediction of the theory that comets bring microbes onto the Earth at the present time is testable if aseptic collections of stratospheric air above the tropopause can be obtained. We describe a recent collection of this kind and report microbiological analysis that shows the existence of viable cells at 41 km, falling to Earth at the rate of a few tonnes per day over the entire globe. Some of these cells have been cultured in the laboratory and found to include microorganisms that are not too different from related species on the Earth. This is in fact what the Hoyle-Wickramasinghe theory predicts. The weight of evidence goes against the more conservative explanation that organisms are being lofted to the high atmosphere from the ground

In it for the long haul: the complexities of managing overweight in family practice: qualitative thematic analysis from the Health eLiteracy for Prevention in General Practice (HeLP-GP) trial

Background: Australia has one of the highest rates of overweight and obesity in the developed world, and this increasing prevalence and associated chronic disease morbidity reinforces the importance of understanding the attitudes, views, and experiences of patients and health providers towards weight management interventions and programs. The purpose of this study was to investigate patients, family practitioners and family practice nurses’ perceptions and views regarding the receipt or delivery of weight management within the context of the HeLP-GP intervention. Methods: A nested qualitative study design including semi-structured interviews with family practitioners (n = 8), family practice nurses (n = 4), and patients (n = 25) attending family practices in New South Wales (n = 2) and South Australia (n = 2). The patient interviews sought specific feedback about each aspect of the intervention and the provider interviews sought to elicit their understanding and opinions of the strategies underpinning the intervention as well as general perceptions about providing weight management to their patients. Interviews were recorded and transcribed verbatim, and coding and management conducted using NVivo 12 Pro. We analysed the interview data using thematic analysis. Results: Our study identified three key themes: long-term trusting and supportive relationships (being ‘in it for the long haul’); initiating conversations and understanding motivations; and ensuring access to multi-modal weight management options that acknowledge differing levels of health literacy. The three themes infer that weight management in family practice with patients who are overweight or obese is challenged by the complexity of the task and the perceived motivation of patients. It needs to be facilitated by positive open communication and programs tailored to patient needs, preferences, and health literacy to be successful. Conclusions: Providing positive weight management in family practice requires ongoing commitment and an open and trusting therapeutic relationship between providers and patients. Behaviour change can be achieved through timely and considered interactions that target individual preferences, are tailored to health literacy, and are consistent and positive in their messaging. Ongoing support of family practices is required through funding and policy changes and additional avenues for referral and adjunctive interventions are required to provide comprehensive weight management within this setting