The Jet Propulsion Laboratory low-cost solar array project, 1974-1986

The overall objective of the photovoltaic program is to ensure that photovoltaic conversion systems play a significant role in the nation's energy supply by stimulating an industry capable of providing approximately 50 GWe of installed electricity generating capacity by the year 2000. In order to achieve this overall objective, several time-phased program goals have been defined. Near-term goals are to achieve photovoltaic flat-plate module or concentrator array prices of $2 per peak watt (1975 dollars) at an annual production rate of 20 peak megawatts in 1982. At this price level, energy costs should range from 100 to 200 mills/kwh. Mid-term goals are to achieve photovoltaic flat-plate module or concentrator array prices of$0.50 per peak watt (in 1975 dollars), and an annual production rate of 500 peak megawatts in 1986. Studies project that photovoltaic systems will begin to compete for both distributed and larger load-center utility-type applications and thereby open up significant markets for large-scale photovoltaic systems. Far term goals are to achieve the photovoltaic flat-plate module or concentrator array price goal of $0.10 to$0.30 per peak watt in 1990 (in 1975 dollars), and an annual production rate of 10 to 20 peak gigawatts in 2000. At this price range, energy cost should be in the range of 40 to 60 mills. kwh and be cost effective for utility applications. Achievement of these goals can make photovoltaic systems economically competitive with other energy sources for dispersed on-site applications as well as for central power generation

On the linearity of the stratospheric and Euro-Atlantic sector response to ENSO

The dependence of the winter stratospheric and Euro-Atlantic climate response on ENSO amplitude is investigated using the HadGEM3 model. Experiments are performed with imposed east Pacific sea surface temperature perturbations corresponding to Niño-3.4 anomalies of 60.75, 1.5, 2.25, and 3.0 K. In the North Pacific, El Niño (EN) deepens and shifts the Aleutian low eastward, while the equivalent magnitude La Niña (LN) perturbations drive anomalies of opposite sign that are around 4 times weaker. The muted North Pacific response to LN can be traced back to the weaker response of tropical convection and the associated anomalous Rossby wave source. The EN perturbations weaken the Arctic polar vortex, with the winter mean zonal mean zonal wind at 608N and 10 hPa decreasing approximately linearly with Niño-3.4 anomaly by around 23.6 m s21 K21 . For the strongest EN case (13 K), the frequency of sudden stratospheric warmings (SSWs) increases by ;60% compared to the control experiment. Hence the results do not support a saturation of the stratospheric pathway for strong EN as suggested in previous literature. The equivalent amplitude LN perturbations cause a weak strengthening of the polar vortex and no substantial change in SSW frequency, in contrast to some reanalysis-based studies. EN induces a negative North Atlantic Oscillation (NAO) index throughout boreal winter, which increases approximately linearly with the Niño-3.4 anomaly by around 20.6 standard deviations K21 . Only the response to the strongest LN perturbations projects onto a weak positive NAO in November, suggesting that the mechanism for the Euro-Atlantic response to LN may be distinct from EN

Effects of intraocular lens glistenings on visual function: A prospective study and presentation of a new glistenings grading methodology

Objective To investigate the effect of intraocular lens (IOL) glistenings on visual performance and evaluate a new glistenings grading methodology. Methods and Analysis Thirty-four patients (34 eyes) were recruited. Corrected distance visual acuity (CDVA), mesopic gap acuity (MGA), functional contrast sensitivity (FCS) and forward light scatter were measured (Advanced Vision and Optometric Tests, City Occupational, London, UK). The IOL centre was imaged and glistenings density graded by three observers using the Miyata scale and a new system. Inter-rater reliability, association between the two grading scales, and correlations between glistenings grades and visual performance parameters were evaluated. Results The intraclass correlation coefficient between graders for the new grading system was 0.769 (95% Confidence Interval [CI] 0.636 to 0.868). There was a significant association between the Miyata scale and the new grading system for all graders (r s =0.533-0.895, p≤0.001). There was no association between CDVA or MGA and glistenings grade (r s =- 0.098, p=0.583 and r s =0.171, p=0.359, respectively). There was no association between FCS at mesopic light levels and glistenings grade (r s =-0.032, p=0.864), or the straylight parameter and glistenings grade (r s =0.021, p=0.916). No association was found between the integrated straylight parameter and glistenings grade (r s =0.078, p=0.701). Conclusion The new glistenings grading scale was highly reproducible. In this cohort, glistenings in the same hydrophobic acrylic IOL after cataract surgery were not associated with changes in visual function, as assessed by a series of tests not previously used in glistenings research

Processing The Interspecies Quorum-Sensing Signal Autoinducer-2 (AI-2) Characterization Of Phospho-(S)-4,5-Dihydroxy-2,3-Pentanedione Isomerization By LsrG Protein

The molecule (S)-4,5-dihydroxy-2,3-pentanedione (DPD) is produced by many different species of bacteria and is the precursor of the signal molecule autoinducer-2 (AI-2). AI-2 mediates interspecies communication and facilitates regulation of bacterial behaviors such as biofilm formation and virulence. A variety of bacterial species have the ability to sequester and process the AI-2 present in their environment, thereby interfering with the cell-cell communication of other bacteria. This process involves the AI-2-regulated lsr operon, comprised of the Lsr transport system that facilitates uptake of the signal, a kinase that phosphorylates the signal to phospho-DPD (P-DPD), and enzymes (like LsrG) that are responsible for processing the phosphorylated signal. Because P-DPD is the intracellular inducer of the lsr operon, enzymes involved in P-DPD processing impact the levels of Lsr expression. Here we show that LsrG catalyzes isomerization of P-DPD into 3,4,4-trihydroxy-2-pentanone-5-phosphate. We present the crystal structure of LsrG, identify potential catalytic residues, and determine which of these residues affects P-DPD processing in vivo and in vitro. We also show that an lsrG deletion mutant accumulates at least 10 times more P-DPD than wild type cells. Consistent with this result, we find that the lsrG mutant has increased expression of the lsr operon and an altered profile of AI-2 accumulation and removal. Understanding of the biochemical mechanisms employed by bacteria to quench signaling of other species can be of great utility in the development of therapies to control bacterial behavior

Future Arctic ozone recovery: the importance of chemistry and dynamics

Future trends in Arctic springtime total column ozone, and its chemical and dynamical drivers, are assessed using a seven-member ensemble from the Met Office Unified Model with United Kingdom Chemistry and Aerosols (UM-UKCA) simulating the period 1960–2100. The Arctic mean March total column ozone increases throughout the 21st century at a rate of  ∼  11.5 DU decade⁻¹, and is projected to return to the 1980 level in the late 2030s. However, the integrations show that even past 2060 springtime Arctic ozone can episodically drop by  ∼  50–100 DU below the corresponding long-term ensemble mean for that period, reaching values characteristic of the near-present-day average level. Consistent with the global decline in inorganic chlorine (Clᵧ) over the century, the estimated mean halogen-induced chemical ozone loss in the Arctic lower atmosphere in spring decreases by around a factor of 2 between the periods 2001–2020 and 2061–2080. However, in the presence of a cold and strong polar vortex, elevated halogen-induced ozone losses well above the corresponding long-term mean continue to occur in the simulations into the second part of the century. The ensemble shows a significant cooling trend in the Arctic winter mid- and upper stratosphere, but there is less confidence in the projected temperature trends in the lower stratosphere (100–50 hPa). This is partly due to an increase in downwelling over the Arctic polar cap in winter, which increases transport of ozone into the polar region as well as drives adiabatic warming that partly offsets the radiatively driven stratospheric cooling. However, individual winters characterised by significantly suppressed downwelling, reduced transport and anomalously low temperatures continue to occur in the future. We conclude that, despite the projected long-term recovery of Arctic ozone, the large interannual dynamical variability is expected to continue in the future, thereby facilitating episodic reductions in springtime ozone columns. Whilst our results suggest that the relative role of dynamical processes for determining Arctic springtime ozone will increase in the future, halogen chemistry will remain a smaller but non-negligible contributor for many decades to come.We thank NCAS Computational Model Support for help with setting up and porting the model. We acknowledge the ARCHER UK National Supercomputing Service. We acknowledge use of the MONSooN system, a collaborative facility supplied under the Joint Weather and Climate Research Programme, which is a strategic partnership between the UK Met Office and the NERC. Amanda C. Maycock, John A. Pyle and N. Luke Abraham were supported by the National Centre for Atmospheric Science, a NERC-funded research centre. We acknowledge funding from the ERC for the ACCI project (grant number 267760), including a PhD studentship for Ewa M. Bednarz. Amanda C. Maycock acknowledges support from an AXA postdoctoral fellowship and NERC grant NE/M018199/1

Comparative vessel traits of Macaranga gigantea and Vatica dulitensis from Malaysian Borneo

Trade-offs in wood anatomical characteristics reflect different strategies used by trees to deal with water transport in response to variation in environmental conditions. To study vascular strategies for Bornean rainforest trees, we compared water transport-related anatomical characteristics in branch wood between the common tree species Vatica dulitensis (Dipterocarpaceae) from old-growth forest and the common pioneer tree species Macaranga gigantea (Euphorbiaceae) from selectively logged forest. We hypothesised that the vessel traits of the pioneer species would reflect the need to capture and transport resources to support its fast growth rate (resource-acquisitive strategy), while the species of the old-growth forest would display more conservative vessel traits (resource-conservative strategy). We found that M. gigantea had significantly greater vessel area, hydraulically weighted diameter, vessel area to number ratio, and potential hydraulic conductivity than V. dulitensis. These results suggest that vessel traits of the common old-growth species would ensure high hydraulic safety during occasional drought when soil moisture is limited, while the common species of selectively logged forest possesses an efficient water transport system but its vessels would confer lower hydraulic safety during drought conditions. These contrasting vascular strategies highlight the potential for divergent responses of species of Bornean forest trees to future climatic extremes

A remarkable remnant mesic deciduous forest stand: are composition and structure of old-growth retained?

Old-growth forests are declining throughout eastern North America, especially toward the northern limit of the deciduous formation where gently undulating topography and milder climate especially encourage human activity. Remnants exist, but do they retain the defining characteristics of the original vegetation? The objective was tomarshal information required to answer this question, and toward this objective we assessed vegetation in a small 1 ha remnant of maple-beech forest with no history of past logging and compared it to well known and larger old-growth areas in the region. We used Curtis. s (1959) Point Quarter method to provide full quantitative data for trees, saplings, shrub and herbs. Size class distribution of trees and successional status of the stand were assessed. As a general conclusion, we found that tree species richness of our remnant was higher than most recognized large old-growth forests and, while the herbaceous understorey was poorer in species than larger tracts, it exhibited three provincially rare species. Furthermore, the successional status and structural complexity of the remnant were typical of old-growth forests. In overall comparative terms, the remnant was found not be an outlier when ordinated with larger forests. It thus is safe to conclude that this remnant constitutes an ecological benchmark well worth protection, despite its limited size

Are patterns of fine-scale spatial genetic structure consistent between sites within tropical tree species?

JRS was funded by the Swiss National Science Foundation (SNF) (http://www.snf.ch/en/Pages/default.aspx) grant number PDFMP3_132479 / 1 awarded to JG. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

The radiative role of ozone and water vapour in the annual temperature cycle in the tropical tropopause layer

Abstract. The structure and amplitude of the radiative contributions of the annual cycles in ozone and water vapour to the prominent annual cycle in temperatures in the tropical tropopause layer (TTL) are considered. This is done initially through a seasonally evolving fixed dynamical heating (SEFDH) calculation. The annual cycle in ozone is found to drive significant temperature changes predominantly locally (in the vertical) and roughly in phase with the observed TTL annual cycle. In contrast, temperature changes driven by the annual cycle in water vapour are out of phase with the latter. The effects are weaker than those of ozone but still quantitatively significant, particularly near the cold point (100 to 90 hPa) where there are substantial non-local effects from variations in water vapour in lower layers of the TTL. The combined radiative heating effect of the annual cycles in ozone and water vapour maximizes above the cold point and is one factor contributing to the vertical structure of the amplitude of the annual cycle in lower-stratospheric temperatures, which has a relatively localized maximum around 70 hPa. Other important factors are identified here: radiative damping timescales, which are shown to maximize over a deep layer centred on the cold point; the vertical structure of the dynamical heating; and non-radiative processes in the upper troposphere that are inferred to impose a strong constraint on tropical temperature perturbations below 130 hPa. The latitudinal structure of the radiative contributions to the annual cycle in temperatures is found to be substantially modified when the SEFDH assumption is relaxed and the dynamical response, as represented by a zonally symmetric calculation, is taken into account. The effect of the dynamical response is to reduce the strong latitudinal gradients and inter-hemispheric asymmetry seen in the purely radiative SEFDH temperature response, while leaving the 20° N–20° S average response relatively unchanged. The net contribution of the annual ozone and water vapour cycles to the peak-to-peak amplitude in the annual cycle of TTL temperatures is found to be around 35 % of the observed 8 K at 70 hPa, 40 % of 6 K at 90 hPa, and 45 % of 3 K at 100 hPa. The primary sensitivity of the calculated magnitude of the temperature response is identified as the assumed annual mean ozone mixing ratio in the TTL. </jats:p

Space Station Engineering Design Issues

Space Station Freedom topics addressed include: general design issues; issues related to utilization and operations; issues related to systems requirements and design; and management issues relevant to design