Moderate Light Research Articles

On the Prospects of BaF2 as a Fast Scintillator for Time-of-Flight Positron Emission Tomography Systems

Future time-of-flight positron emission tomography (TOF-PET) will be in need of ultrafast scintillation materials, with potential seen in cross-luminescence (CL). BaF2, for example, shows a sub-100-ps decay time with 300 photons produced per MeV. However, it poses challenges, such as medium radiation length, low photofraction, moderate light yield, and vacuum ultraviolet (VUV) emission around 200nm. Recent developments in UV-sensitive solid-state photodetectors (SiPMs) have the potential to establish CL for ultrafast TOF in PET. In this work, we aim to study BaF2, read out by these new VUV SiPMs, as a viable alternative to cerium-doped lutetium–yttrium oxyorthosilicate (LYSO:Ce). In order to investigate the prospects of BaF2 in TOF-PET, we compare the CTR of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 2\times $ </tex-math></inline-formula> 20 mm 3 undoped and yttrium-doped BaF2 crystals, readout by Hamamatsu S13370–3050CN SiPMs with a maximum photon detection efficiency (PDE) of 14% at 200nm and air coupling, to LYSO:Ce:Ca crystals of the same size. With high-frequency readout electronics, we reached 233ps with undoped BaF2 and 213ps with BaF2:Y, while the performance of LYSO:Ce:Ca was 125ps (measured with HPK S14160–3050HS, PDE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 60$ </tex-math></inline-formula> % and glue coupling). Conducting measurements at different depth of interaction positions shows a pronounced impact on the CTR. Furthermore, we investigated the performance for systems of BaF2 with TOFPET2c ASIC measurements and Geant4 simulations for effective sensitivity comparisons to LYSO:Ce:Ca.

EFFECTS OF VARIOUS LIGHT INTENSITIES ON PHYCOCYANIN COMPOSITION OF CYANOBACTERIUM LIMNOSPIRA FUSIFORMIS (VORONICHIN) NOWICKA-KRAWCZYK, MÜHLSTEINOVÁ &amp; HAUER

Phycocyanin denotes a photosynthetic pigment discovered in Rhodophyta and cyanobacteria, which has been used in medical, industrial, and agricultural applications. In general, phycocyanin production by cyanobacteria depends on many environmental conditions, mainly light during the cultivation period. The goal of this research was to see how various light intensities of 47, 52, as well as 60 µmol m-2 s-1, affected the Phycocyanin production of cyanobacterium Limnospira fusiformis cultured in Zarrouk medium with a maximum temperature of 28°C. The outcomes revealed that with mild light intensity (52 µmol m-2 s-1), increased phycocyanin production of 11.94 ng/mg took place. With regard to greater light intensity (60 µmol m-2 s-1), the lesser phycocyanin production of 0.57 ng/mg took place. These results give a good impression that moderate lighting increases phycocyanin production, but high light intensity inhibits it. The statistical analysis results also showed that there are significant differences between the light intensities used in the study at a level of p&lt;0.05. Therefore, this study concluded that phycocyanin was affected by light intensity. Light regime optimization gives a good yield of this pigment. In this study, high phycocyanin production by cyanobacterium Limnospira fusiformis occurred in mild light intensity (52 µmol m-2 s-1).

Prevalence of Schistosoma haematobium and Intestinal Helminth Infections among Nigerian School Children

Schistosomiasis and soil-transmitted helminthiases (STH) are two parasitic diseases mainly affecting school children. The purpose of this study was to estimate the current prevalence and infection intensity, in addition to the associations of these infections with age and sex, in children aged 4-17 years living in Osun State, Nigeria. From each participant (250 children), one urine and one stool sample were taken for the study, for the microscopic detection of eggs or larvae in faeces by means of the Kato-Katz method and eggs in filtrated urine. The overall prevalence of urinary schistosomiasis was 15.20%, with light infection. The intestinal helminthic species identified (and their prevalence) were S. stercoralis (10.80%), S. mansoni (8%), A. lumbricoides (7.20%), hookworm (1.20%), and T. trichiura (0.4%), all of them being classified as light infections. Single infections (67.95%) are more frequent than multiple infections (32.05%). With this study, schistosomiasis and STH are still endemic in Osun State, but with a light to moderate prevalence and light infection intensity. Urinary infection was the most prevalent, with higher prevalence in children over 10 years. The >10 years age group had the highest prevalence for all of the intestinal helminths. There were no statistically significant associations between gender and age and urogenital or intestinal parasites.

Manipulating the Subcellular Localization and Anticancer Effects of Benzophenothiaziniums by Minor Alterations of N-Alkylation

Cationic, water-soluble benzophenothiaziniums have been recognized as effective type I photosensitizers (PSs) against hypoxic tumor cells. However, the study of the structure-property relationship of this type of PS is still worth further exploration to achieve optimized photodynamic effects and minimize the potential side effects. Herein, we synthesized a series of benzophenothiazine derivatives with minor N-alkyl alteration to study the effects on the structure-property relationships. The cellular uptake, subcellular organelle localization, reactive oxygen species (ROS) generation, and photocytotoxicity performances were systematically investigated. NH2NBS and EtNBS specifically localized in lysosomes and exhibited high toxicity under light with a moderate phototoxicity index (PI) due to the undesirable dark toxicity. However, NMe2NBS with two methyl substitutions accumulated more in mitochondria and displayed an excellent PI value with moderate light toxicity and negligible dark toxicity. Without light irradiation, NH2NBS and EtNBS could induce lysosomal membrane permeabilization (LMP), while NMe2NBS showed no obvious damage to lysosomes. After irradiation, NH2NBS and EtNBS were released from lysosomes and relocated into mitochondria. All compounds could induce mitochondria membrane potential (MMP) loss and nicotinamide adenine dinucleotide phosphate (NADPH) consumption under light to cause cell death. NMe2NBS exhibited remarkable in vivo photodynamic therapy (PDT) efficacy in a xenograft mouse tumor (inhibition rate, 89%) with no obvious side effects. This work provides a valuable methodology to investigate the structure-property relationships of benzophenothiazine dyes, which is of great importance in the practical application of PDT against hypoxia tumor cells.

Effects of rainfall intensity and underground pore density on the soil erosion mechanism of sloping maize farmland in a typical karst area of SW China

AbstractThe rainfall intensity, slope, and underground pore density are major factors affecting the soil erosion of maize‐covered karst slopes. We studied the erosion process of maize‐covered karst slopes and the influencing mechanism of soil erosion on these slopes under different rainfall intensities, slopes, and underground pore density via simulated rainfall tests. The results are as follows: (1) No runoff was observed on the slope surface under light rainfall (30 mm hr−1); instead, subsurface flow was predominant. However, runoff from the surface and subsurface flows under moderate rainfall (60 mm hr−1) increased with the rainfall intensity. The average surface runoff under extreme rainfall (90 mm hr−1) was 2.3‐times that under moderate rainfall. In addition, the average subsurface runoff under extreme rainfall was 1.6‐ and 3.5‐times that under moderate rainfall and light rainfall, respectively. The total amounts of surface and subsurface soil losses increased as the rainfall intensity increased. The surface and subsurface soil losses from light to moderate and extreme rainfall events increased by 258% and 151%, respectively. The soil loss from the surface was 5.3‐times greater than that from the subsurface, indicating that the erosion of maize‐covered karst slopes mainly occurs on the surface and that the subsurface loss is relatively small. (2) As the slope angle increased, the runoff, sediment yield, and proportion of erosion on the surface increased, and vice versa. (3) The subsurface runoff and sediment yield increased as the underground pore density increased, while the opposite occurred on the surface. Multiple regression analysis showed that the rainfall intensity is the most critical factor affecting the soil erosion of maize ‐covered slopes in karst areas, followed by the slope, while the influence of the underground pore density is small.

Optimization of novel exoscopic blue light filter during fluorescence-guided resection of Glioblastoma.

Operative guidelines and use optimization for new surgical exoscopes are not well described in the literature. In this study, we evaluated use of the ORBEYE (Olympus) surgical exoscope system during 5-ALA fluorescence-guided resection of GBMs to optimize workflow and exoscope settings. The ORBEYE exoscope system was fitted with a blue light filter for 5-ALA mediated fluorescence-guided surgery (FGS). Intraoperative images were obtained during 5-ALA FGS in 9 patients with primary or recurrent GBM. The exoscope was set up at constant, increasing focal distances from the target tissue, and light source intensity varied. High-resolution 4K images were captured and analyzed. Comparisons of fluorescence to background were then generated for use optimization. Light intensity did not significantly influence tumor fluorescence (P = 0.878). However, focal distance significantly impacted relative fluorescent intensity (P = 0.007). Maximum average fluorescence was seen consistently at a focal length of 220mm and a light intensity of approximately 75% maximum. Decreasing focal distance from 400mm to 220mm significantly increased visualized fluorescence (P = 0.0038). The ORBEYE surgical exoscope system with blue light filter is a powerful imaging tool for 5-ALA FGS in GBM. The ORBEYE blue filter performs optimally at shorter focal distance with moderate light intensity. Similar to microscope systems, decreasing focal distance significantly influences visualized fluorescence.

Thermal photo-physiological responses of massive heat-resistant coral Porites lutea under fish predated versus non-predated conditions

Abstract. Ricot M, Jeetun S, Joggee S, Kaullysing D, Taleb-Hossenkhan N, Bhagooli R. 2023. Thermal photo-physiological responses of massive heat-resistant coral Porites lutea under fish predated versus non-predated conditions. Indo Pac J Ocean Life 7: 38-47. Fish predation on corals leading to polyp and tissue loss has been identified as a significant stressor to corals and is often associated with reduced growth, reproduction, and even mortality. However, how climate change-driven ocean warming may impact such a biological stressor is yet to be thoroughly understood. This study aimed to assess elevated temperature’s effects on the photo-physiology of fish-predated and non-predated parts of the thermally resistant coral Porites lutea (Quoy &amp; Gaimard, 1833). The objectives were to assess the photo-physiological parameters such as effective quantum yield at photosystem II (FPSII), relative maximum electron transport rate (rETRmax), maximum photo-chemical quenching (NPQmax), photosynthetic efficiency (?), photoinhibition (?) and Ik at fish bite-affected (BA) and non-affected (NA) coral parts at temperatures of 28°C and 32°C under low-light (10 µmol quanta m-2s-1) and moderate-light (110 µmol quanta m-2s-1) conditions for a duration of 48hr. FPSII, rETRmax and NPQmax were not negatively affected by fish predation conditions. Under moderate light, the rETRmax increased in the non-predated condition at 28°C but not at 32°C while the NPQmax exhibited a more pronounced increase at 32°C compared to the 28°C treatment. The absence of significant declines in FPSII and rETRmax accompanied by a significant increase in NPQmax at 32°C is indicative of a lack of photo-inhibition and an active quenching of energy in a non-harmful way at PSII. No significant interactions of temperature and predation condition and light and predation condition were found, indicating that short-term exposure of 2 days to an elevated temperature of 32°C and moderate light intensity of 110 µmol quanta m-2s-1 did not result in any exacerbated negative photo-physiological impacts of fish predation in P. lutea. These findings suggest that both fish-predated and non-predated conditions in P. lutea are equally tolerant to the tested elevated temperature level. Thus, ocean warming events may not differentially impact their photosynthetic activities.

Long-Term Vegetation Changes and Socioeconomic Effects of River Engineering in Industrialized Areas (Southern Poland).

The exploitation of mineral resources associated with human mining activities leads to the degradation of both terrestrial and aquatic biocenotic systems. The drastic disturbance of water relations as a result of the relocation of the riverbed of the Biala Przemsza River (southern Poland) for coal and filler sand mining will lead to changes in plant ecosystems. The purpose of this study was to determine and compare the diversity and distribution of vegetation in the Biała Przemsza valley in sections of channel straightening with the old riverbed and areas undisturbed by engineering works against the background of land use in temporal and spatial aspects. The results of the ecological and phytosociological studies showed that the composition of flora and vegetation types varied. Within the transformed riverbed, anthropogenic mixed forests with species characteristic of different ecological systems are developing, whereas the non-regulated section of the river is overgrown by an alder riparian forest with an almost complete species composition for this plant community. The highest Simpson's biodiversity index was found in the anthropogenically disturbed section of the river (0.86), and in the undisturbed section, it was 0.83. Both sections of the river were dominated by species of the family Compositae, Poaceae, Caryophyllaceae, Rosaceae and Apiaceae. The diversity of the flora in the transformed sections of the valley is determined by the presence of mosaics and microhabitats, as well as the nature of the surrounding vegetation, which is reflected in the ecological requirements of the flora concerning light preference (moderate light [56.25%]), and almost 90% of the flora from the area of the regulated section of the valley develops on humus-poor and mineral-humus soils. Although this area has lost its original natural function, it is now valuable for selected economic and social functions, especially in highly urbanized regions.

Modulation by S-nitrosoglutathione (a natural nitric oxide donor) of photosystem in Pisum sativum leaves, as revealed by chlorophyll fluorescence: Light-dependent aggravation of nitric oxide effects

The reported effects of nitric oxide (NO), a signaling molecule, on the photochemical components of leaves are ambiguous. We examined the changes by a natural NO donor, S-nitrosoglutathione (GSNO). The effect of GSNO on Pisum sativum leaves was studied after a 3-hour exposure in dark, moderate (ML), or high light (HL). The NO levels in GSNO-treated samples were at their maximum under HL, compared to those under ML or dark. Most of the elevated NO was decreased by 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), a NO scavenger, confirming the NO increase. Treatment with GSNO caused inhibition of photosynthesis/respiration and restricted electron transport mediated by both photosystem (PS)II and PSI. However, the inhibition by NO-donor of PSII components was stronger than those of PSI. A marked increase in the PSI acceptor side limitation [Y(NA)] and a decrease in PSI donor side limitation [Y(ND)] indicated an upregulation of cyclic electron transport, possibly to balance the damage to PSII by GSNO. We suggest that NO aggravated the HL-induced inhibition of photosynthesis and dark respiration.

Increasing air temperature relative to water temperature makes the mixed layer shallower, reducing phytoplankton biomass in a stratified lake

Abstract The depth of the mixed layer is a major determinant of nutrient and light availability for phytoplankton in stratified waterbodies. Ongoing climate change influences surface waters through meteorological forcing, which modifies the physical structure of fresh waters including the mixed layer, but effects on phytoplankton biomass are poorly known. To determine the responses of phytoplankton biomass to the depth of the mixed layer, light availability and associated meteorological forcing, we followed daily changes in weather and water column properties in a boreal lake over the first half of a summer stratification period. Phytoplankton biomass increased with the deepening of the mixed layer associated with high wind speeds and low air temperature relative to the temperature of the mixed layer (Tair−Tmix &lt; 0), whereas heatwave conditions—shallow mixed layer driven by high Tair−Tmix value and low wind speed—reduced the biomass. Improving light availability from low to moderate light conditions increased the phytoplankton biomass, while the highest light availability was associated with low phytoplankton biomass. Our study demonstrates that the climatic impact‐drivers wind speed and Tair−Tmix are major drivers of mixed layer depth, which controlled phytoplankton biomass during the early summer stratification period. Our study suggests that increasing air temperature relative to water temperature and declining wind speeds have potential to lead to reduced phytoplankton biomass due to a shallower mixed layer during the first half of the stratification period in non‐eutrophic lakes with sufficient light availability.

Effects of moderate exercise versus light exercise on fasting blood glucose in obese patients with type 2 diabetes mellitus

IntroductionDiabetes is an important cause of mortality throughout the world. Type 2 diabetes mellitus (T2DM) is characterized by hyperglycemia and obesity, which are aggravated by a sedentary lifestyle. The consequences of long-term hyperglycemia include neurological or vascular complications and can lead to amputation, retinopathy, kidney failure, or other severe complications and a consequently poor quality of life. This study was conducted to report the effect of moderate exercise versus light exercise on fasting blood glucose in obese patients with T2DM.MethodsFor three months, 60 patients with sedentary lifestyles aged 35 to 60 years were randomly assigned to one of two groups in this two-arm cluster randomized controlled trial. Group 1 received 30 minutes of treadmill walking at 40–60% of maximum heart rate. Group 2 was given 30 minutes of treadmill walking per day, divided into 5 minutes every 2 hours.ResultsAt the base line, no significant difference was found between both groups in BMI, waist to hip ratio, 6-minutes’ walk, fasting blood glucose and SF-36. After three months of treatment, there was no significant difference in BMI, &lt;i&gt;p&lt;/i&gt; = 0.111, waist to hip ratio, p = 0.271, 6 minutes’ walk, &lt;i&gt;p&lt;/i&gt; = 0.614, blood glucose, &lt;i&gt;p&lt;/i&gt; = 0.105, and SF-36, &lt;i&gt;p&lt;/i&gt; = 0.106 between the two groups, despite the fact, that among each group significant differences for all analyzed parameters were observed.ConclusionsRepeated short walking has a similar effect on blood glucose, obesity, and quality of life as continuous long walking. Walking for 5 minutes every 2 hours may be a useful alternative for patients with T2DM.

Accuracy and precision of sea-finding orientation as a function of dune proximity in hatchlings of two species of sea turtles

Context Sea turtle hatchlings generally emerge at night from nests on sand beaches and immediately orient using visual cues, which are believed to entail the difference in brightness between the light seen in the seaward direction and that seen in the duneward direction. Aim The aim of this study was to understand how dune proximity affected hatchling orientations in two sea turtle species that share a nesting beach 15 km long and 25.3 ± 9.4 m (N = 215) from dune to waterline, with low to moderate artificial light nearby. Methods For hatchling loggerhead and green turtles, we measured accuracy and precision of orientation, tested differences in distance from nest to dune, and investigated the effect of dune proximity on hatchling orientation. Key results We found a significant decrease in hatchling orientation accuracy and precision in both species as the distance increased from nests to dune. Loggerhead and green turtles showed similar orientation ability when in the same proximity to the dune. Conclusions We conclude that dune features provide important cues for hatchling orientation on sea turtle nesting beaches. Implications Restoring and maintaining natural beach profiles, especially dune systems, is likely to increase the accuracy and precision of sea finding in hatchling sea turtles.

Dynamics of competition model between two plants based on stoichiometry.

The dynamics of two-plant competitive models have been widely studied, while the effect of chemical heterogeneity on competitive plants is rarely explored. In this study, a model that explicitly incorporates light and total phosphorus in the system is formulated to characterize the impacts of limited carbon and phosphorus on the dynamics of the two-plant competition system. The dissipativity, existence and stability of boundary equilibria and coexistence equilibrium are proved, when the two plants compete for light equally. Our simulations indicate that, with equal competition for light ($ b_{12} = b_{21} $) and a fixed total phosphorus in the system ($ T $), plants can coexist with moderate light intensity ($ K $). A higher $ K $ tends to favor the plant with a lower phosphorus loss rate ($ d_1 $ vs $ d_2 $). When $ K $ is held constant, a moderate level of $ T $ leads to the dominance of the plant with a lower phosphorus loss rate ($ d_1 $ vs $ d_2 $). At high $ T $ levels, both plants can coexist. Moreover, our numerical analysis also shows that, when the competition for light is not equal, the low level of total phosphorus in the system may lead the model to be unstable and have more types of bistability compared with the two-dimensional Lotka-Volterra competition model.

Effects of High Irradiance and Low Water Temperature on Photoinhibition and Repair of Photosystems in Marimo (Aegagropila linnaei) in Lake Akan, Japan.

The green alga Aegagropila linnaei often forms spherical aggregates called "marimo" in Lake Akan in Japan. In winter, marimo are exposed to low water temperatures at 1-4 °C but protected from strong sunlight by ice coverage, which may disappear due to global warming. In this study, photoinhibition in marimo was examined at 2 °C using chlorophyll fluorescence and 830 nm absorption. Filamentous cells of A. linnaei dissected from marimo were exposed to strong light at 2 °C. Photosystem II (PSII) was markedly photoinhibited, while photosystem I was unaffected. When the cells with PSII damaged by the 4 h treatment were subsequently illuminated with moderate repair light at 2 °C, the maximal efficiency of PSII was recovered to the level before photoinhibition. However, after the longer photoinhibitory treatments, PSII efficiency did not recover by the repair light. When the cells were exposed to simulated diurnal light for 12 h per day, which was more ecological, the cells died within a few days. Our results showed new findings of the PSII repair at 2 °C and serious damage at the cellular level from prolonged high-light treatments. Further, we provided a clue to what may happen to marimo in Lake Akan in the near future.

COMPARATIVE STUDY OF PRESERVATION METHODS IN THREE SELECTED HOTELS IN BAYELSA STATE, NIGERIA

The study is geared towards comparing electronic preservation methods in three selected hotels in Bayelsa State. Four research objectives were formulated to guide the study bordering on the types of records created, kept, and maintained by the selected hotels. Their records retention policies, their electronic preservation methods, and challenges encountered in the preservation of their records. Works of literature related to the objectives of the study were reviewed. The study population comprised a total of 18 personnel in the three selected hotels in Bayelsa state (6 staff in Majels Hotels, 6 in Engoye Hotels, and 6 in De-Alamis Hotels); they are both in the senior and junior categories responsible for handling records in the hotels. From the study population of 18, a Total Enumerative Sampling Technique was used; this implies that the entire population of 18 was used for the study. Out of the 18 copies of the questionnaire administered, 18 copies were completed by the respondents and found useable for analysis, giving a very high return rate of 100%. The questionnaire formed the major instrument for collecting the needed data; the questionnaires were distributed and retrieved without losing any. The data collected were analyzed using descriptive statistics of percentages and frequencies. The findings revealed that the preservation methods employed by the 3 hotels under study were: "Installation of water alarms", "Moderate lighting"; "Records areas are cleaned and dusted regularly"; "Periodic fumigation"; and "Monitoring of abuse and mishandling". The study recommended that qualified librarians should be employed to handle records maintenance, security, and preservation of records in Hotels in Bayelsa state.

Effective fucoxanthin production in the flagellate alga Poterioochromonas malhamensis by coupling heterotrophic high-cell-density fermentation with illumination.

The unicellular flagellate algae Poterioochromonas malhamensis is a potential fucoxanthin-rich resource for sustainable and cost-effective fucoxanthin production. Light and nutrients are critical regulators for the accumulation of fucoxanthin in P. malhamensis. In this study, the maximum fucoxanthin yield of 50.5mgL-1 and productivity of 6.31mgL-1 d-1 were achieved by coupling high-cell-density fermentation with illumination. It was found that the combined use of organic and inorganic nitrogen (N) nutrition could improve the fucoxanthin yield as single inorganic or organic N had limitation to enhance cell growth and fucoxanthin accumulation. White light was the optimal light quality for fucoxanthin accumulation. Under white light and a moderate light intensity of 150μmolm-2 s-1, the highest biomass concentration and fucoxanthin content reached 32.9gL-1 and 1.56mgg-1 of dry cell weight (DCW), respectively. This is the first study on effective fucoxanthin production in P. malhamensis by integrating illumination with high-cell-density fermentation, which paved the way for further development of P. malhamensis as a potential source for commercial fucoxanthin production.

Processing bulk wood into a light-permeable passive radiative cooling material for energy-efficient building

Reducing carbon emissions from building materials production and operation would have a huge impact on the global energy and environment. Wood presents great potential as an environment-friendly building material due to its relatively low carbon emission and cost. However, several issues, including the mechanical anisotropic, extremely low optical transparency, and single function, greatly hinder the further application of wood as a building material. Herein, hybrid wood-derived laminates were dedicatedly fabricated through top-down strategy using bulk wood as raw materials. The obtained hybrid laminates demonstrate low anisotropic mechanical factor of 1.14, which was only one-eighth of the corresponding value of natural wood (8.07). Besides, such wood laminates exhibit moderate light permeability (35% of transmittance), which could provide with softening of glare and uniform illumination, thereby reducing the power consumption. Also, the remaining wood cellulose and incorporated inorganic microspheres in our laminates backscatter solar radiation and emit thermal, resulting in continuous cooling with a dT of 12 °C under one solar intensity irradiation. Combined with excellent water stability and self-cleaning property, our laminates are expected to be used as the building blocks for the construction of energy-efficient buildings with low carbon emission.

The lifetime of the oxygen-evolving complex subunit PSBO depends on light intensity and carbon availability in Chlamydomonas.

PSBO is essential for the assembly of the oxygen-evolving complex in plants and green algae. Despite its importance, we lack essential information on its lifetime and how it depends on the environmental conditions. We have generated nitrate-inducible PSBO amiRNA lines in the green alga Chlamydomonas reinhardtii. Transgenic strains grew normally under non-inducing conditions, and their photosynthetic performance was comparable to the control strain. Upon induction of the PSBO amiRNA constructs, cell division halted. In acetate-containing medium, cellular PSBO protein levels decreased by 60% within 24 h in the dark, by 75% in moderate light, and in high light, the protein completely degraded. Consequently, the photosynthetic apparatus became strongly damaged, probably due to 'donor-side-induced photoinhibition', and cellular ultrastructure was also severely affected. However, in the absence of acetate during induction, PSBO was remarkably stable at all light intensities and less substantial changes occurred in photosynthesis. Our results demonstrate that the lifetime of PSBO strongly depends on the light intensity and carbon availability, and thus, on the metabolic status of the cells. We also confirm that PSBO is required for photosystem II stability in C. reinhardtii and demonstrate that its specific loss also entails substantial changes in cell morphology and cell cycle.

Plastid and cytoplasmic origins of 1O2-mediated transcriptomic responses.

The reactive oxygen species singlet oxygen, 1O2, has an extremely short half-life, yet is intimately involved with stress signalling in the cell. We previously showed that the effects of 1O2 on the transcriptome are highly correlated with 80S ribosomal arrest due to oxidation of guanosine residues in mRNA. Here, we show that dysregulation of chlorophyll biosynthesis in the flu mutant or through feeding by δ-aminolevulinic acid can lead to accumulation of photoactive chlorophyll intermediates in the cytoplasm, which generates 1O2 upon exposure to light and causes the oxidation of RNA, eliciting 1O2-responsive genes. In contrast, transcriptomes derived from DCMU treatment, or the Ch1 mutant under moderate light conditions display commonalties with each other but do not induce 1O2 gene signatures. Comparing 1O2 related transcriptomes to an index transcriptome induced by cycloheximide inhibition enables distinction between 1O2 of cytosolic or of plastid origin. These comparisons provide biological insight to cases of mutants or environmental conditions that produce 1O2.

Strong coupling in the entanglement dynamics of two qubits interacting with a graphene nanodisk

We investigate the entanglement dynamics of two qubits interacting with a graphene nanodisk using the macroscopic quantum electrodynamics method. By modifying the free-space decay rate of each qubit, we study the coupling strength between the nanoparticle and the qubits. We find that as the free-space decay rate increases, the decaying Rabi oscillations featured in the qubit population dynamics change to complex non-Markovian dynamical population evolution. This is also reflected on the concurrence, which at weak or moderate light–matter coupling conditions, attains values up to 0.5, while as the coupling conditions become stronger, larger values are also transiently observed. Our findings indicate that graphene nanostructures can provide a platform for the realization of high degree of entanglement in the strong coupling regime at the nanoscale, essential for quantum technology applications.