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Tomato fruits ripened 95, 65, 46 and 42d after flower opening when plants were grown under controlled environmental conditions at 14, 18, 22 and 26°C, respectively. A similar response to temperature was observed when the temperature of individual trusses was modified while the plants were grown at 20°C. These data were used to develop a thermal time model for fruit maturation. However, when buds/fruits were heated at different stages in their development, the thermal time model proved to be a poor predictor of the time of ripening. Fruits were more sensitive to elevated temperature in their later stages of maturation. Temperature also affected the rates of fruit growth in volume; these could be adequately described using a Gompertz function. Low temperatures reduced absolute volume growth rates and delayed the time at which the absolute growth rate became maximal. However, the response of fruit growth to temperature differed when only the temperature of the fruits was modified. There was a tendency towards small parthenocarpic fruits at both high (26°C) and low (14°C) temperature regimes which, combined with low flower numbers and poor fruit set at 26°C, resulted in low fruit yields. Temperature also affected the shoot dry matter content and partitioning.

The effects of temperature, photoperiod and light integral on the time to first flowering of pansy (Viola×wittrockianaGams) were investigated. Plants were grown at six temperatures (means between 14.8 and 26.1 °C), combined with four photoperiods (8, 11, 14 and 17 h). The rate of progress to flowering increased linearly with temperature (up to an optimum of 21.7 °C) and with increase in photoperiod (r2=0.91, 19 d.f.), the latter indicating that pansies are quantitative long day plants (LDPs). In a second experiment, plants were sown on five dates between July and December 1992 and grown in glasshouse compartments under natural day lengths at six temperatures (means between 9.4 and 26.3 °C). The optimum temperature for time to flowering decreased linearly (from 21.3 °C) with declining light integral from 3.4 MJ m−2d−1(total solar radiation). Data from both experiments were used to construct a photo-thermal model of flowering in pansy. This assumed that the rate of progress to flowering increased as an additive linear function of light integral, temperature and photoperiod. Independent data from plants sown on three dates, and grown at five temperatures (means between 9.8 and 23.6 °C) were used to validate this model which gave a good fit to the data (r2=0.88, 15 d.f.). Possible confounding of the effects of photoperiod and light integral are discussed.

Studies of protein function would be facilitated by a general method to inactivate selected proteins in living cells noninvasively with high spatial and temporal precision. Chromophore-assisted light inactivation (CALI) 1 uses photochemically generated, reactive oxygen species to inactivate proteins acutely, but its use has been limited by the need to microinject dye-labeled nonfunction-blocking antibodies. We now demonstrate CALI of connexin43 (Cx43) and α 1C L-type calcium channels, each tagged with one or two small tetracysteine (TC) motifs 2 that specifically bind the membrane-permeant, red biarsenical dye, ReAsH 3 , 4 . ReAsH-based CALI is genetically targeted, requires no antibodies or microinjection, and inactivates each protein by ∼90% in <30 s of widefield illumination. Similar light doses applied to Cx43 or α 1C tagged with green fluorescent protein (GFP) had negligible to slight effects with or without ReAsH exposure, showing the expected molecular specificity. ReAsH-mediated CALI acts largely via singlet oxygen because quenchers or enhancers of singlet oxygen respectively inhibit or enhance CALI.

Pansies (Viola×wittrockianaGams.) cv. Universal Violet were sown on five dates between Jul. and Dec. 1992 and placed in six temperature-controlled glasshouse compartments set to provide mean temperatures between 6.5 and 30 °C. Shoot dry weight and leaf number were recorded. A model was constructed, to analyse the effects of light and temperature on dry matter accumulation, which assumed that relative growth rate (RGR) declined linearly with thermal time accumulated from sowing, reflecting ontogenetic drift. Furthermore, it assumed that RGR was a semi-ellipsoid function of temperature, rising to an optimum of 25.3 °C and declining thereafter, and a positive linear function of light integral. When fitted to data collected in this study the model accounted for 94% of the variance in RGR. Independent validation using data from four further crops grown in glasshouse compartments at four different set point temperatures showed that the model could also be used to predict plant dry weight accurately (r2=0.98). The rate of mainstem leaf production was also linearly related to both light integral and temperature.

Flowering in petunias is hastened by long days, but little is known about when the plants are most sensitive to photoperiod, or how light integral or temperature affect such phases of sensitivity. The effects of these factors on time to flowering was investigated using reciprocal transfer experiments between long (16 h d(-1)) and short days (8 h d(-1)). The effect of light integral on the phases of photoperiod sensitivity was examined using two sowing dates and a shading treatment (53% transmission). The effects of temperature were investigated by conducting reciprocal transfer experiments in glasshouse compartments at five temperature regimes (means of 13(.)7, 19(.)2, 22(.)3, 25(.)0 and 28.7 degrees C). The length of the photoperiod-insensitive juvenile phase of development, when flowering cannot be induced by any environmental stimulus, was sensitive to light integral; low light integrals prolonged this phase, from 23 d at 2(.)6 MJ m(-2) d(-1) to 36 d at 1(.)6 MJ m(-2) d(-1) (total solar radiation). The length of this development phase was shortest (12(.)5 d) at 21 degrees C; it was longer under cooler (21 d at 13(.)5 degrees C) and warmer temperatures (17(.)6 d at 28(.)3 degrees C). After this phase, time to flowering was influenced greatly by photoperiod, with long days hastening flowering by between 28 and 137 d, compared with short days. Plants also showed some sensitivity to both temperature and light integral during this phase, but the duration of the final phase of flower development, during which plants were photoperiod-insensitive, was dependent primarily on the temperature at which the plants were grown; at 14(.)5 degrees C, 33(.)9 d were required to complete this phase compared with 11(.)4 d at 25(.)5 degrees C. The experimental approach gave valuable information on the phases of sensitivity to photothermal environment during the flowering process, and could provide the basis of a more physiologically-based quantitative model of flowering than has hitherto been attempted. The information is also useful in the scheduling of lighting and temperature treatments to give optimal flowering times of high quality plants.

Flowering in petunias is hastened by long days, but little is known about when the plants are most sensitive to photoperiod, or how light integral or temperature affect such phases of sensitivity. The effects of these factors on time to flowering was investigated using reciprocal transfer experiments between long (16 h d-1) and short days (8 h d-1). The effect of light integral on the phases of photoperiod sensitivity was examined using two sowing dates and a shading treatment (53% transmission). The effects of temperature were investigated by conducting reciprocal transfer experiments in glasshouse compartments at five temperature regimes (means of 13.7, 19.2, 22.3, 25.0 and 28.7 °C). The length of the photoperiod-insensitive juvenile phase of development, when flowering cannot be induced by any environmental stimulus, was sensitive to light integral; low light integrals prolonged this phase, from 23 d at 2.6 MJ m-2d-1to 36 d at 1.6 MJ m-2d-1(total solar radiation). The length of this development phase was shortest (12.5 d) at 21 °C; it was longer under cooler (21 d at 13.5 °C) and warmer temperatures (17.6 d at 28.3 °C). After this phase, time to flowering was influenced greatly by photoperiod, with long days hastening flowering by between 28 and 137 d, compared with short days. Plants also showed some sensitivity to both temperature and light integral during this phase, but the duration of the final phase of flower development, during which plants were photoperiod-insensitive, was dependent primarily on the temperature at which the plants were grown; at 14.5 °C, 33.9 d were required to complete this phase compared with 11.4 d at 25.5 °C. The experimental approach gave valuable information on the phases of sensitivity to photothermal environment during the flowering process, and could provide the basis of a more physiologically-based quantitative model of flowering than has hitherto been attempted. The information is also useful in the scheduling of lighting and temperature treatments to give optimal flowering times of high quality plants.

Acceleration in discovery of rare genetic variants possibly linked with disease may mean an increased risk of false-positive reports of causality; this Perspective proposes guidelines to distinguish disease-causing sequence variants from the many potentially functional variants in a human genome, and to assess confidence in their pathogenicity, and highlights priority areas for development. Gene variation and human disease The wide-scale availability of high-throughput DNA sequencing technologies means that data on genetic variation in human diseases are accumulating rapidly. In this Perspective, Daniel MacArthur and colleagues sound a note of caution, pointing out that up to a quarter of reported disease-linked mutations have been found to either be common polymorphisms or have lacked sufficient evidence for pathogenicity. The authors discuss the key challenges associated with assessing sequence variants in human disease and propose guidelines for the robust differentiation between disease-causing genetic variants and other variants present in the human genome. They highlight several areas where research and resource development are urgently needed if genomic research findings are to be successfully translated into the clinical diagnostic setting. The discovery of rare genetic variants is accelerating, and clear guidelines for distinguishing disease-causing sequence variants from the many potentially functional variants present in any human genome are urgently needed. Without rigorous standards we risk an acceleration of false-positive reports of causality, which would impede the translation of genomic research findings into the clinical diagnostic setting and hinder biological understanding of disease. Here we discuss the key challenges of assessing sequence variants in human disease, integrating both gene-level and variant-level support for causality. We propose guidelines for summarizing confidence in variant pathogenicity and highlight several areas that require further resource development.

'Difficult' oil could be a gas More than half of the world's oil inventory consists of biodegraded heavy oil and tar sand deposits. Recovery of oil from these sources is complicated and expensive. Recent findings suggest that anaerobic bacteria may cause this hydrocarbon degradation, but the actual degradation pathway occurring in oil reservoirs remains obscure. Using a combination of laboratory oil degradation experiments and analysis of oilfield samples, it is now shown that the dominant process of subsurface biodegradation is methanogenesis, involving anaerobic degradation of oil hydrocarbons to produce methane. This suggests an alternative way of exploiting these 'difficult' oilfields: by accelerating the natural hydrocarbon degradation process, it may be possible to recover energy as methane, rather than conventionally as oil. Laboratory experiments in microcosms monitoring the hydrocarbon composition of degraded oils are used with carbon isotopic compositions of gas and oil samples taken at wellheads and a Rayleigh isotope fractionation box model to elucidate the mechanisms of hydrocarbon degradation in reservoirs. The data imply a common methanogenic biodegradation mechanism in subsurface degraded oil reservoirs resulting in consistent patterns of hydrocarbon alteration. Biodegradation of crude oil in subsurface petroleum reservoirs has adversely affected the majority of the world’s oil, making recovery and refining of that oil more costly 1 . The prevalent occurrence of biodegradation in shallow subsurface petroleum reservoirs 2 , 3 has been attributed to aerobic bacterial hydrocarbon degradation stimulated by surface recharge of oxygen-bearing meteoric waters 2 . This hypothesis is empirically supported by the likelihood of encountering biodegraded oils at higher levels of degradation in reservoirs near the surface 4 , 5 . More recent findings, however, suggest that anaerobic degradation processes dominate subsurface sedimentary environments 6 , despite slow reaction kinetics and uncertainty as to the actual degradation pathways occurring in oil reservoirs. Here we use laboratory experiments in microcosms monitoring the hydrocarbon composition of degraded oils and generated gases, together with the carbon isotopic compositions of gas and oil samples taken at wellheads and a Rayleigh isotope fractionation box model, to elucidate the probable mechanisms of hydrocarbon degradation in reservoirs. We find that crude-oil hydrocarbon degradation under methanogenic conditions in the laboratory mimics the characteristic sequential removal of compound classes seen in reservoir-degraded petroleum. The initial preferential removal of n -alkanes generates close to stoichiometric amounts of methane, principally by hydrogenotrophic methanogenesis. Our data imply a common methanogenic biodegradation mechanism in subsurface degraded oil reservoirs, resulting in consistent patterns of hydrocarbon alteration, and the common association of dry gas with severely degraded oils observed worldwide. Energy recovery from oilfields in the form of methane, based on accelerating natural methanogenic biodegradation, may offer a route to economic production of difficult-to-recover energy from oilfields.

In transition-edge sensors (TESs), the addition of normal metal stripes on top of the superconducting bilayer, perpendicular to the current direction, is known to globally alter the sensitivity of the resistance R to changes in temperature T and current I. Here, we describe measurements of the dependence of the TES current on magnetic field B, bath temperature and voltage bias in devices with various numbers of stripes. We show that the normal metal features have a profound effect on the appearance of localized regions of very large (T/R) dR/dT. We associate this with changes in the current distribution and corresponding changes in the oscillatory pattern of I (B). 140 μm TESs with no stripes are found to have a relatively smooth resistive transition and sufficiently low noise that the measured energy resolution is 1.6 eV for X-rays of 1.5 keV. The predicted energy resolution at 6 keV is better than 2 eV, once the heat capacity is optimized for these higher energies..

The X-ray Integral Field Unit(X-IFU) of the Athena observatory, scheduled for launch in the mid2030's, will provide X-ray spectroscopy data with unprecedented spectral and spatial resolution. This will be achieved with a 2kilo-pixel array of transition-edge sensor (TES) microcalorimeters. The complete detection chain is under development by a large international collaboration. In order to perform an end-to-end demonstration of the X-IFU readout chain, a 50 mK test bench is being developed at IRAP in collaboration with CNES. The test bench uses a two-stage ADR cryostat from Entropy GmbH, a 1024-pixelarray, and will initially be operated using a warm electronics chain from NIST and NASA Goddard Space Flight Center. We describe the complete system being installed in the cryostat and the current results obtained with these electronics. We also review the status of the integration of the digital readout electronics (DRE)prototype into the demonstration chain and the plan for integrating and testing the complete X-IFU readout chain.