ALMA unveils wider environment of distant red protocluster core

ABSTRACT We report observations with the Atacama Large Millimetre Array (ALMA) of six submillimetre galaxies (SMGs) within 3 arcmin of the Distant Red Core (DRC) at z = 4.0, a site of intense cluster-scale star formation, first reported by Oteo et al. We find new members of DRC in three SMG fields; in two fields, the SMGs are shown to lie along the line of sight towards DRC; one SMG is spurious. Although at first sight this rate of association is consistent with earlier predictions, associations with the bright SMGs are rarer than expected, which suggests caution when interpreting continuum overdensities. We consider the implications of all 14 confirmed DRC components passing simultaneously through an active phase of star formation. In the simplest explanation, we see only the tip of the iceberg in terms of star formation and gas available for future star formation, consistent with our remarkable finding that the majority of newly confirmed DRC galaxies are not the brightest continuum emitters in their immediate vicinity. Thus, while ALMA continuum follow-up of SMGs identifies the brightest continuum emitters in each field, it does not necessarily reveal all the gas-rich galaxies. To hunt effectively for protocluster members requires wide and deep spectral-line imaging to uncover any relatively continuum-faint galaxies that are rich in atomic or molecular gas. Searching with short-baseline arrays or single-dish facilities, the true scale of the underlying gas reservoirs may be revealed.

Polyaniline–Si Nanoparticle Nanocapsules as a Dual Photovoltaic Sensitizer

ABSTRACTWe examine the optical and structural properties of polyaniline–silicon nanoparticle capsules — a novel organic/inorganic material. The Si particles absorb UV/blue efficiently and green moderately, while polyaniline (PANI) in its green emeraldine state absorbs UV and red/IR efficiently, effectively providing absorption over a wide range of the solar spectrum. The capsules are produced by miniemulsion of aniline monomers in the presence of Si nanoparticles. Thin films of the capsules were formed on a variety of substrates. We use high resolution transmission electron microscopy (HTEM) and scanning electron microscopy (SEM) to record the structural properties. We also monitor the optical properties of the Si core and the PANI shell using fluorescence microscopy under UV and visible irradiation. Upon on-off cycles of UV irradiation and visible light, the red core switches reversibly between bright and dark states while PANI switches reversibly between emeraldine green and pernigraniline violet states. The results are analyzed in terms of excitonic excitation, charge separation, and transport between the core and the shell, which is useful for photovoltaic applications.

Photosynthetic Response of Carrots to Varying Irradiances, CO2 Concentrations, Moisture, and Nutrition

Genotypes and environmental parameters interactively act on plants and modify their yield responses through modifying photosynthetic processes. In order to optimize yield, it is critical to understand the photosynthetic behavior of the crop as altered by genotypes and environment. Leaf gas exchange parameters of carrot (Daucus carota L.) cultivars Cascade, Carson, Oranza, and Red Core Chantenay (RCC) were examined in response to various irradiances, fertility levels, moisture regimes, and to elevated CO2 concentrations. Leaf net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) were measured. Cultivars responded similarly to increasing PAR and CO2 concentrations and did not differ in photosynthetic parameters. Increasing PAR from 100 to 1000 μmol·m-2·s-1 increased PN, which did not reach saturation. The gs and E increased to a peak between 600 and 800 μmol·m-2·s-1, then rapidly declined, resulting in a sharp increase in water use efficiency (WUE). Increasing CO2 concentrations from 50 to 1050 μmol·mol-1 increased PN until saturation at 650 μmol·mol-1. The gs and E increased to a peak at 350 μmol·mol-1 and then declined. WUE increased linearly with increasing CO2. Carrots exposed to drought over a period of 5 days decreased PN and E. The PN decrease was cultivar specific. Nutrient concentrations of 0 to 400 ppm gave a similar pattern of decrease for PN, E, and gs. Treatment of 50 ppm had the highest PN, E, and gs. The WUE generally increased with increasing nutrient concentration.

(430) Leaf Gas Exchange of Carrots in Response to Increasing Leaf Temperatures

Increasing temperature as a result of global climate change is expected to exert a great influence on agricultural crops, possibly through effects on photosynthesis. Response to temperature of leaf gas exchange parameters of carrot (Daucus carota L. var. sativus) cultivars Cascade, Carson, Oranza, and Red Core Chantenay (RCC) were examined in a controlled growth room experiment. Leaf net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) were measured at temperatures ranging from 15 to 35 °C at 370 μmol·mol-1 (CO2) and 450±20 μmol·m-2·s-1 PAR. The cultivars responded similarly to increasing temperature and did not differ in most photosynthetic parameters except gs. The PN increased between 20 and 30 °C, thereafter increasing only slightly to 35 °C. On average, increasing temperature from 20 to 30 °C increased PN by 69%. Carboxylation efficiencies (Ca/Ci ratio) ranged from 1.12–2.33 mmol·mol-1 while maximum PN were 3.25, 3.90, 5.49, 4.19 μmol·m-2·s-1 for Carson, RCC, Cascade, and Oranza, respectively. The E did not reach maximum at 35 °C while gs peaked at 30 °C and then decreased by 93% at 35 °C. The water use efficiency (WUE) decreased with an increase in temperature due to increases in both PN and E. The results indicate that increasing temperatures above the seasonal average (<20 °C) increases both PN and E up to 30–35 °C. An increase in photosynthesis due to an increase in temperature is expected to hasten growth. Carrots may be able to withstand a moderate increase in temperature.

Plant Population Modulate Occurrence of Green Shoulders (GS) and Internal Greening (IG) in Carrots (Daucus carota var. sativus)

Green shoulder (GS) and Internal Greening (IG) are the physiological disorders in carrots due to chlorophyll accumulates either at the crown or internal tissues or both. GS and IG affect root quality and makes carrot roots unfit for consumption and cause a great lose to the processing industry. One of the hypothesis in our study was that plant population modulate GS and IG due to its variation in light interception. The objectives of this study were to identify the effect of plant population on the occurrence of GS and IG and establish a relationship between them. Dicer (Red core chantenay) and Slicer (Caro choice) varieties were seeded at various seeding rates. The experiment used a Randomized Block design. Each treatment was replicated four times. GS and IG were measured using a Chlorophyll meter and the output was read as Chlorophyll Index (CI). Leaf area index (LAI) was determined using a LAI-2000 Plant canopy analyzer. Carrot roots were also collected per meter for each plot. Plant population showed a significant negative correlation with GS. Correlation also existed between GS and LAI. However, plant population and LAI had poor correlation with IG in both the Dicer as well as in the Slicer varieties. It is possible that the IG may perhaps be induced prior to canopy development. Also, a poor correlation existed between IG and GS in both the Slicers and Dicers implying that one does not control other event.