Photosynthetic maximum quantum yield increases are an essential component of the Southern Ocean phytoplankton response to iron

It is well established that an increase in iron supply causes an increase in total oceanic primary production in many regions, but the physiological mechanism driving the observed increases has not been clearly identified. The Southern Ocean iron enrichment experiment, an iron fertilization experiment in the waters closest to Antarctica, resulted in a 9-fold increase in chlorophyll (Chl) concentration and a 5-fold increase in integrated primary production. Upon iron addition, the maximum quantum yield of photosynthesis (phi(m)) rapidly doubled, from 0.011 to 0.025 mol C.mol quanta(-1). Paradoxically, this increase in light-limited productivity was not accompanied by a significant increase in light-saturated productivity (P-max(b)). P-max(b) maximum Chl normalized productivity, was 1.34 mg C.mg Chl(-1).h(-1) outside and 1.49 mg C.mg Chl(-1)-h(-1) inside the iron-enriched patch. The importance of phi(m) as compared with P-max(b) in controlling the biological response to iron addition has vast implications for understanding the ecological response to iron. We show that an iron-driven increase in phi(m) is the proximate physiological mechanism affected by iron addition and can account for most of the increases in primary production. The relative importance of phi(m) over P-max(b) in this iron-fertilized bloom highlights the limitations of often-used primary productivity algorithms that are driven by estimates of P-max(b) but largely ignore variability in phi(m) and light-limited productivity. To use primary productivity models that include variability in iron supply in prediction or forecasting, the variability of light-limited productivity must be resolved

An Area‐Specific, International Community‐Led Approach to Understanding and Addressing Equality, Diversity, and Inclusion Issues within Supramolecular Chemistry

Diversity, equality, and inclusion (DEI/EDI) are pressing issues in chemistry and the natural sciences. In this Essay we share how an area‐specific approach is “calling in” the community so that it can act to address EDI issues, and support those who are marginalised. Women In Supramolecular Chemistry (WISC) is an international network that aims to support equality, diversity, and inclusion within supramolecular chemistry. WISC has taken a field‐specific approach using qualitative research methods with scientists to identify the support that is needed and the problems the supramolecular community needs to address. Herein, we present survey data from the community which highlight the barriers that are faced by those who take career breaks for any reason, a common example is maternity leave, and the importance of mentoring to aid progression post‐PhD. In conclusion, we set out an interdisciplinary and creative approach to addressing EDI issues within supramolecular chemistry

Semiclassical charged black holes with a quantized massive scalar field

Semiclassical perturbations to the Reissner-Nordstrom metric caused by the presence of a quantized massive scalar field with arbitrary curvature coupling are found to first order in \epsilon = \hbar/M^2. The DeWitt-Schwinger approximation is used to determine the vacuum stress-energy tensor of the massive scalar field. When the semiclassical perturbation are taken into account, we find extreme black holes will have a charge-to-mass ratio that exceeds unity, as measured at infinity. The effects of the perturbations on the black hole temperature (surface gravity) are studied in detail, with particular emphasis on near extreme ``bare'' states that might become precisely zero temperature ``dressed'' semiclassical black hole states. We find that for minimally or conformally coupled scalar fields there are no zero temperature solutions among the perturbed black holes.Comment: 19 pages; 1 figure; ReVTe

Hawking Radiation of Dirac Particles in an Arbitrarily Accelerating Kinnersley Black Hole

Quantum thermal effect of Dirac particles in an arbitrarily accelerating Kinnersley black hole is investigated by using the method of generalized tortoise coordinate transformation. Both the location and the temperature of the event horizon depend on the advanced time and the angles. The Hawking thermal radiation spectrum of Dirac particles contains a new term which represents the interaction between particles with spin and black holes with acceleration. This spin-acceleration coupling effect is absent from the thermal radiation spectrum of scalar particles.Comment: Revtex, 12pt, 16 pages, no figure, to appear in Gen. Rel. Grav. 34 (2002) N0.

Do semiclassical zero temperature black holes exist?

The semiclassical Einstein equations are solved to first order in $\epsilon = \hbar/M^2$ for the case of a Reissner-Nordstr\"{o}m black hole perturbed by the vacuum stress-energy of quantized free fields. Massless and massive fields of spin 0, 1/2, and 1 are considered. We show that in all physically realistic cases, macroscopic zero temperature black hole solutions do not exist. Any static zero temperature semiclassical black hole solutions must then be microscopic and isolated in the space of solutions; they do not join smoothly onto the classical extreme Reissner-Nordst\"{o}m solution as $\epsilon \to 0$.Comment: 5 pages, no figures, minor changes and corrections, to appear in Physical Review Letter

A powerful intervention: general practitioners' use of sickness certification in depression

<b>Background</b> Depression is frequently cited as the reason for sickness absence, and it is estimated that sickness certificates are issued in one third of consultations for depression. Previous research has considered GP views of sickness certification but not specifically in relation to depression. This study aimed to explore GPs views of sickness certification in relation to depression.<p></p> <b>Methods</b> A purposive sample of GP practices across Scotland was selected to reflect variations in levels of incapacity claimants and antidepressant prescribing. Qualitative interviews were carried out between 2008 and 2009.<p></p> <b>Results</b> A total of 30 GPs were interviewed. A number of common themes emerged including the perceived importance of GP advocacy on behalf of their patients, the tensions between stakeholders involved in the sickness certification system, the need to respond flexibly to patients who present with depression and the therapeutic nature of time away from work as well as the benefits of work. GPs reported that most patients with depression returned to work after a short period of absence and that it was often difficult to predict which patients would struggle to return to work.<p></p> <b>Conclusions</b> GPs reported that dealing with sickness certification and depression presents distinct challenges. Sickness certificates are often viewed as powerful interventions, the effectiveness of time away from work for those with depression should be subject to robust enquiry

Thermal divergences on the event horizons of two-dimensional black holes

The expectation value of the stress-energy tensor \langleT_{\mu\nu}\rangle of a free conformally invariant scalar field is computed in a general static two-dimensional black hole spacetime when the field is in either a zero temperature vacuum state or a thermal state at a nonzero temperature. It is found that for every static two-dimensional black hole the stress-energy diverges strongly on the event horizon unless the field is in a state at the natural black hole temperature which is defined by the surface gravity of the event horizon. This implies that both extreme and nonextreme two-dimensional black holes can only be in equilibrium with radiation at the natural black hole temperature.Comment: 13 pages, REVTe

Brief evidence-based interventions for universal child health services: a restricted evidence assessment of the literature

Background Universal child health services (UCHS) provide an important pragmatic platform for the delivery of universal and targeted interventions to support families and optimize child health outcomes. We aimed to identify brief, evidence-based interventions for common health and developmental problems that could be potentially implemented in UCHS. Methods A restricted evidence assessment (REA) of electronic databases and grey literature was undertaken covering January 2006 to August 2019. Studies were eligible if (i) outcomes related to one or more of four areas: child social and emotional wellbeing (SEWB), infant sleep, home learning environment or parent mental health, (ii) a comparison group was used, (iii) universal or targeted intervention were delivered in non-tertiary settings, (iv) interventions did not last more than 4 sessions, and (v) children were aged between 2 weeks postpartum and 5 years at baseline. Results Seventeen studies met the eligibility criteria. Of these, three interventions could possibly be implemented at scale within UCHS platforms: (1) a universal child behavioural intervention which did not affect its primary outcome of infant sleep but improved parental mental health, (2) a universal screening programme which improved maternal mental health, and (3) a targeted child behavioural intervention which improved parent-reported infant sleep problems and parental mental health. Key lessons learnt include: (1) Interventions should impart the maximal amount of information within an initial session with future sessions reinforcing key messages, (2) Interventions should see the family as a holistic unit by considering the needs of parents with an emphasis on identification, triage and referral, and (3) Brief interventions may be more acceptable for stigmatized topics, but still entail considerable barriers that deter the most vulnerable. Conclusions Delivery and evaluation of brief evidence-based interventions from a UCHS could lead to improved maternal and child health outcomes through a more responsive and equitable service. We recommend three interventions that meet our criteria of “best bet” interventions

Black plane solutions in four dimensional spacetimes

The static, plane symmetric solutions and cylindrically symmetric solutions of Einstein-Maxwell equations with a negative cosmological constant are investigated. These black configurations are asymptotically anti-de Sitter not only in the transverse directions, but also in the membrane or string directions. Their causal structure is similar to that of Reissner-Nordstr\"{o}m black holes, but their Hawking temperature goes with $M^{1/3}$, where $M$ is the ADM mass density. We also discuss the static plane solutions in Einstein-Maxwell-dilaton gravity with a Liouville-type dilaton potential. The presence of the dilaton field changes drastically the structure of solutions. They are asymptotically ``anti-de Sitter'' or ``de Sitter'' depending on the parameters in the theory.Comment: 8 pages, RevTex, to appear in Phys. Rev.

Noise Kernel and Stress Energy Bi-Tensor of Quantum Fields in Hot Flat Space and Gaussian Approximation in the Optical Schwarzschild Metric

Continuing our investigation of the regularization of the noise kernel in curved spacetimes [N. G. Phillips and B. L. Hu, Phys. Rev. D {\bf 63}, 104001 (2001)] we adopt the modified point separation scheme for the class of optical spacetimes using the Gaussian approximation for the Green functions a la Bekenstein-Parker-Page. In the first example we derive the regularized noise kernel for a thermal field in flat space. It is useful for black hole nucleation considerations. In the second example of an optical Schwarzschild spacetime we obtain a finite expression for the noise kernel at the horizon and recover the hot flat space result at infinity. Knowledge of the noise kernel is essential for studying issues related to black hole horizon fluctuations and Hawking radiation backreaction. We show that the Gaussian approximated Green function which works surprisingly well for the stress tensor at the Schwarzschild horizon produces significant error in the noise kernel there. We identify the failure as occurring at the fourth covariant derivative order.Comment: 21 pages, RevTeX