Light influences human physiology and behavior by regulating circadian rhythms, melatonin secretion, and alertness. Previous research has reported sex differences in melatonin secretion and circadian rhythms, possibly related to women's greater sensitivity to bright light. Other studies have suggested reduced photosensitivity and earlier circadian phases in summer than in winter in midlatitude regions. This study explores the effects of sex, seasonality, and their combination on melatonin suppression and subjective sleepiness in response to moderate light exposure, considering prior light history and menstrual phases in females. We conducted a controlled, within-subject experiment with 48 healthy adults (18-35 years, 50% female) across different seasons. The study design included two 9-hour laboratory sessions, with at least 5-day washout in between. Participants were exposed to dim and moderate light through a screen for 2 hours after their habitual bedtime. Female participants exhibited greater melatonin suppression (+4.69%) but a lower alerting response (−6.00%) to moderate light compared to males. Both sexes demonstrated increased sensitivity to the non-image forming effects of light in winter, with stronger melatonin suppression (+18.05%) and increased alertness (+7.60%) compared to summer. While prior light history did not significantly impact melatonin suppression or alertness, it was associated with an earlier dim light melatonin onset (DLMO). Females during their luteal phase had earlier DLMO than those in their follicular phase. Our findings indicate an interaction between sex, seasonality, and light exposure in modulating melatonin suppression, emphasising the need for personalized light exposure recommendations according to individual biological and environmental contexts.

This study investigated the effects of supplemental LED lighting regime (morning, afternoon, and all-day) on the vegetative growth, reproductive development, yield, and water-soluble vitamin content of sweet pepper (Capsicum annuum L.) grown in winter season under deficit sunlight hours.Supplemental lighting regimes included morning lighting from 05:00 to 10:00 (T 1 ), afternoon lighting from 16:00 to 21:00 (T 2 ), all-day lighting for 16 hours from 06:00 to 22:00 (T 3 ), and a control with no supplemental lighting (T 0 ).Results demonstrated that morning lighting (T 1 ) significantly enhanced plant height, leaf length, number of leaves and leaf area, indicating effective promotion of vigorous vegetative growth during early development.In contrast, all-day lighting (T 3 ) reduced vegetative growth but significantly increased stem diameter, node length to first flower, and fruit set, suggesting facilitation of the transition to reproductive growth.Accordingly, T 3 resulted in significantly higher cumulative yield and fruit weight compared to the control, with a marketable fruit rate of 92.0%.Afternoon lighting (T 2 ) showed positive effects on overall growth and yield, particularly contributing to increased fruit size during the enlargement stage.Analysis of fruit water-soluble vitamins revealed distinct responses to lighting periods: T 1 elevated vitamins B 1 and B 5 contents, while T 3 markedly increased vitamin B 2 concentration.Vitamin C content was highest in T 3 and T 0 , possibly reflecting physiological stress and antioxidant accumulation under differing light environments.These findings suggest that a growth stage specific supplemental lighting strategy such as morning lighting to maintain vegetative vigor during early growth and all-day lighting to enhance reproductive growth and yield can optimize sweet pepper production under winter light deficit conditions in a greenhouse.

The development of remote methods for identifying plant light stress (LS) is an urgent task in agriculture and forestry. Evergreen conifers, which experience winter light stress (WLS) annually, are ideal subjects for studying the mechanisms of light stress and developing identification methods. Proximal hyperspectral imaging (HSI) was used to identify WLS in Platycladus orientalis. Using the random forest (RF), the spectral characteristics of P. orientalis shoots were analysed and the conditions ‘Winter Light Stress’ and ‘Optimal Condition’ were classified with high accuracy. The out-of-bag (OOB) estimate of the error rate was only 0.35%. Classification of the conditions ‘Cold Stress’ and ‘Optimal Condition’—with an OOB estimate of error rate of 3.19%—can also be considered successful. The conditions ‘Winter Light Stress’ and ‘Cold Stress’ were more poorly separated (OOB error rate 15.94%). Verifying the RF classification model for the three states ‘Optimal condition’, ‘Cold stress’ and ‘Winter Light Stress’ simultaneously using data from the crown field survey showed that the ‘Winter Light Stress’ state was well identified. In this case, ‘Optimal condition’ was mistakenly defined as ‘Cold stress’. The following vegetation indices were significant for identifying WLS: CARI, CCI, CCRI, CRI550, CTRI, LSI, PRI, PRIm1, modPRI and TVI. Therefore, spectral phenotyping using HSI is a promising method for identifying WLS in conifers.

This study develops a “Bio-Social-Cognitive Dynamic Interaction Model” to explore seasonal mental health risks in Chinese adolescents. Using data from cross-sectional surveys (N = 6,121), longitudinal tracking (N = 1,000), and RCTs (N = 200), we assess mental health via PHQ-9, GAD-7, and SADQ scales. We analyze multidimensional indicators (melatonin, vitamin D, academic stress) via SEM and ARIMA, considering school stage and gender. Results show winter has the highest depression and anxiety scores (PHQ-9: M = 14.5 ± 4.8), linked to vitamin D deficiency (β=-0.25, p < 0.001) and social stress. Spring academic stress affects emotional stability via melatonin and sleep issues (β = 0.15, p = 0.002), while summer anxiety is tied to social overload and body dissatisfaction (β = 0.10, p = 0.04). Winter light therapy increases vitamin D (Δ = 8.2 ng/mL, p < 0.001) and reduces depression (ΔPHQ-9=-3.1, p = 0.005). We recommend seasonal interventions like winter light therapy, flexible spring exams, and summer social media literacy programs, and emphasize year-round monitoring for effective risk mitigation.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-18486-w.

Eucalyptus cultivation in Brazil benefits from techniques such as mini cutting; however, adverse climatic conditions in the southern region of the country limit seedling production. This study evaluated the effects of LED lighting (blue, red, combined, and natural) and cultivation environments (greenhouse with and without heating, and conventional nursery) on the propagation of Eucalyptus dunnii. The experiment, conducted in Otacílio Costa, SC, followed a two-factor (4 × 4) design with biweekly data collection from March to September 2024. Variables analyzed included sprout productivity, rooting performance, phytosanitary status (powdery mildew incidence), physiological parameters (photosynthetic rate, stomatal conductance, transpiration), and nutritional content. The results showed that LED lighting and cultivation environments did not affect the incidence of powdery mildew. Rooting was enhanced during winter in the heated mini-tunnel system. Sprout productivity was highest in the mini tunnel (~360 sprouts/m2 under red light in winter), while heated environments led to a reduction in sprout production. Physiological variables such as photosynthetic rate and stomatal conductance were improved in the heated mini-tunnel, and transpiration responded to the interaction between light spectrum and environment. The evaluated factors did not cause significant changes in the nutritional profile of the mini stumps. It is concluded that the mini tunnel, particularly when heated during winter, enhances rooting and physiological responses, while red LED light increases sprout productivity. Supplemental LED lighting proved to be a strategic tool for overcoming seasonal limitations in Eucalyptus propagation.

This study investigated the spatial distribution and temporal variations of winter PM2.5 concentrations and light precipitation in North China from 2013 to 2022, and explored the relationship between them. The results show that winter PM2.5 concentrations in North China exhibit a south-high-north-low spatial pattern, with higher concentrations in the east than in the west, and a maximum average PM2.5 concentration exceeding 100 μg/m3. The overall interannual PM2.5 concentration shows a decreasing trend, which is most significant in the northern part of Hebei Province. Winter precipitation in North China demonstrates a similar south-high-north-low spatial pattern, with an upward trend in mean annual precipitation. PM2.5 concentration changes predominantly influence the frequency of light rainfall events. The relationship between PM2.5 concentrations and light rainfall frequency shows a clear spatial pattern: a significant positive correlation is observed west of the Taihang-Yanshan mountain range, and a negative correlation east of the mountain range. This occurs because rainfall frequency initially increases then decreases with increasing PM2.5 concentration. The differing background PM2.5 concentrations on either side of the mountain range result in opposing trends in light rainfall frequency relative to PM2.5 concentration changes.

The latitudinal range of modern shallow-water tropical corals is controlled by temperature, and presently limited to waters warmer than 16-18°Cyear-round. However, even during Cenozoic climates with such temperatures in polar regions, coral reefs are not found beyond >50° latitude. Here, we test the hypothesis that daily available solar radiation limited poleward expansion of coral reefs during warm climates, using a new box model of shallow marine coral calcification. Our results show that calcification rates start to decline beyond 40° latitude and drop severely beyond 50° latitude, due to decreasing winter light intensity and day length, irrespective of aragonite saturation. This suggests that light ultimately prohibits further poleward expansion in warm climates. In addition, fossil coral reef distribution is not a robust proxy for water temperatures and poleward expansion of reefs beyond 50° latitude is not an expected carbon cycle feedback of climate warming.

Ongoing climate change is projected to intensify drought stress globally. Understanding the response mechanisms of Phyllostachys edulis (Carrière) J. Houz. (moso bamboo) to long-term drought is crucial, given its significance as a carbon sequestration resource. In this study, precipitation exclusion was implemented to simulate drought stress and we investigated the effects of long-term drought on the photosynthetic parameters, stomatal conductance, and water use efficiency of moso bamboo. The results showed that throughout all growth seasons, the maximum net photosynthetic rates (Pmax) of bamboo at all ages under long-term drought conditions (after 8 years of precipitation exclusion treatment) were significantly lower than those of the control (p &lt; 0.05). It can be concluded that long-term drought reduced the maximum photosynthetic capacity of the bamboo at all ages. Under long-term drought conditions, there were many seasons where the light saturation point (LSP) of first-degree (1–2 years old) bamboo and third-degree (5–6 years old) bamboo under drought was significantly lower than those of the control, while the LSP value of second-degree (3–4 years old) bamboo under drought was significantly higher than that of the control. This suggests that long-term drought reduced the ability of first-degree and third-degree bamboo to utilize strong light, while improving the ability of second-degree bamboo to utilize strong light in summer, autumn, and winter. Under long-term drought conditions, the light compensation point (LCP) and the apparent quantum efficiency (AQY) of the bamboo decreased. It can be concluded that long-term drought reduced the ability of first-degree bamboo to utilize weak light in all seasons, as well as the ability of second-degree bamboo to utilize weak light in spring and autumn; meanwhile, it improved the ability of second-degree bamboo to utilize weak light in summer and winter, and the ability of third-degree bamboo to utilize weak light in spring, summer, and autumn. In the high light range (PARi &gt; 1000 µmol · m−2 · s−1), there were significant differences in stomatal conductance (gs) among different the different treatments of bamboo, which were influenced by both the growing season and the forest age. Compared to the control, under drought conditions, the stomatal conductance of third-degree bamboo increased in spring and that of the second-degree bamboo increased in autumn. The correlation analysis showed that the relationship between the stomatal conductance and vapor pressure deficit (VPDL) of bamboo under long-term drought conditions showed a significant polynomial relationship in both high and low light ranges. The correlation between the instantaneous water use efficiency (iWUE) and VPDL for the drought and control treatments of bamboo also showed a significant polynomial relationship in high light ranges. It was found that long-term drought changed the photosynthetic parameters of the bamboo, reflecting its ability to tolerate and adapt to drought in different seasons. Age-related differences in photosynthetic parameters should be fully considered in forest age structure adjustments and forest thinning procedures to strengthen the light intensity and maintain the opening of the stoma. These results provide a theoretical basis for the efficient and sustainable cultivation of bamboo under global climate change.

The interaction between light and phytohormones is crucial for plant growth and development. The practice of supplementing light at night during winter to promote pitaya flowering and thereby enhance yield has been shown to be crucial and widely used. However, it remains unclear how supplemental winter light regulates phytohormone levels to promote flowering in pitaya. In this study, through analyzing the transcriptome data of pitaya at four different stages (NL, L0, L1, L2), we observed that differentially expressed genes (DEGs) were mainly enriched in the phytohormone biosynthesis pathway. We further analyzed the data and found that cytokinin (CK) content first increased at the L0 stage and then decreased at the L1 and L2 stages after supplemental light treatment compared to the control (NL). Gibberellin (GA), auxin (IAA), salicylic acid (SA), and jasmonic acid (JA) content increased during the formation of flower buds (L1, L2 stages). In addition, the levels of GA, ethylene (ETH), IAA, and abscisic acid (ABA) increased in flower buds after one week of development (L2f). Our results suggest that winter nighttime supplemental light can interact with endogenous hormone signaling in pitaya, particularly CK, to regulate flower bud formation. These results contribute to a better understanding of the mechanism of phytohormone interactions during the induction of flowering in pitaya under supplemental light in winter.

Farkında olunsun ya da olunmasın, insan düşüncesinin tamamına yakını ahlaki yargı içinde gerçekleşir. Çünkü insan ahlaki bir varlıktır. Seçimlerini kendisi aracılığı ile gerçekleştirdiği iyi-kötü kavram çiftinin, bu yargılamanın merkezi yapısını oluşturduğu söylenebilir. İyi kavramının önemi ve değerini anlamakta zorlanmayan insan bilincinin, kötülük kavramını anlamlandırma çabası devam etmektedir. Bu çalışmada felsefe tarihinde önemli bir konu olan kötülük probleminin sinema tarihindeki işlenişi üzerinde durulmuştur. İsveçli yönetmen Ingmar Bergman’ın yönetmenliğini yaptığı 1962 yapımı “Kış Işığı” isimli sinema filmi, kötülük problemi açısından ele alınmıştır. Nitel analiz yönteminin kullanıldığı bu çalışmada, öncelikle felsefe tarihi içinde kötülük probleminin nasıl tanımlandığı üzerinde durulmuş, sonrasında yönetmen ve film hakkında bilgi verilmiştir. Son olarak kötülük probleminin, filmin temasıyla ilişkisine değinilmiştir. Bergman, Kış Işığı filminde Tanrı’nın suskunluğuna ve umutsuzluğa çare olarak sevgiyi, insanların birbirini sevmesini göstermektedir.

Endolithic microorganisms, ranging from microeukaryotes to bacteria and archaea, live within the cracks and crevices of rocks. Deception Island in Antarctica constitutes an extreme environment in which endoliths face environmental threats such as intense cold, lack of light in winter, high solar radiation in summer, and heat emitted as the result of volcanic eruptions. In addition, the endolithic biome is considered the harshest one on Earth, since it suffers added threats such as dryness or lack of nutrients. Even so, samples from this hostile environment, collected at various points throughout the island, hosted diverse and numerous microorganisms such as bacteria, fungi, diatoms, ciliates, flagellates and unicellular algae. These endoliths were first identified by Scanning Electron Microscopy (SEM). To understand the molecular mechanisms of adaptation of these endoliths to their environment, genomics techniques were used, and prokaryotic and eukaryotic microorganisms were identified by metabarcoding, sequencing the V3-V4 and V4-V5 regions of the 16S and 18S rRNA genes, respectively. Subsequently, the sequences were analyzed by bioinformatic methods that allow their metabolism to be deduced from the taxonomy. The results obtained concluded that some of these microorganisms have activated the biosynthesis routes of pigments such as prodigiosin or flavonoids. These adaptation studies also revealed that microorganisms defend themselves against environmental toxins by activating metabolic pathways for the degradation of compounds such as ethylbenzene, xylene and dioxins and for the biosynthesis of antioxidant molecules such as glutathione. Finally, these Antarctic endolithic microorganisms are of great interest in astrobiology since endolithic settings are environmentally analogous to the primitive Earth or the surfaces of extraterrestrial bodies.

Differences in leaf photoprotection strategies of tree species at different successional stages in subtropical forests under seasonal climate change and their relationship to construction cost strategies

Insufficient solar light in winter inside the greenhouse may lead to a lower quality of vegetable seedlings, and supplemental light is an effective technique to solve this problem. This study evaluated the impacts of supplementary white (W)-light-emitting diodes (LEDs), ultraviolet A LEDs (UV-A), white and blue LEDs (WB), the combinations of white and UV-A LEDs (W-UVA), and white, blue, and UV-A LEDs (WB-UVA) on the leaf morphology, photosynthetic traits, biomass accumulation, root architecture, and hormone content of cucumber (Cucumis sativus L. cv. Tianjiao No. 5) seedlings grown in the greenhouse. The results indicated that supplementary LED lighting led to a decreased plant height, shorter hypocotyl length, bigger leaf area, and thicker leaf compared with those grown with solar light only, regardless of light quality. The shoot fresh weight, root fresh weight, and seedling quality index of cucumber seedlings grown under the combinations of white, blue, and UVA radiations increased by 30.8%, 3.2-fold, and 1.8-fold, respectively, compared with those grown with natural light only. However, no significant differences were exhibited in the biomass accumulation of greenhouse-grown cucumber seedlings between the control and the UVA treatment. The cellulose content and stem firmness of greenhouse-grown cucumber seedlings grown under the combinations of white, blue, and UVA radiations increased by 49.9% and 13.1%, respectively, compared with those grown under white light only. Additionally, the cytokinin content of cucumber seedlings was promoted by over 36.7% by applying supplementary light. In summary, the combinations of white, blue, and UVA radiations led to compact morphological characteristics, superior mechanical properties, and preferable growth performance, which could be applied as an available lighting strategy to obtain the desired morphological and quality properties of vegetable seedlings.

A Thousand Faces Jessie van Eerden (bio) Hard to brush the West Texas wind from my hair. All the silt and mesquite smoke knotted up. One morning he climbs the hill, always with pen and notebook, whistling like a surreptitious bird to let me know where he is. The mist rises from the river warmer than the cold air and, still in camp, I pull on all my thermal layers and start to brush my hair. Same long johns and wool socks, same enormous Chihuahuan Desert silence, his man-size self gone small up on the bluff. I spend considerable time on the knots, then climb the hill to him, following turkey and wild mule tracks across the washes, passing signs of an old firepit and possible shelter, some cans and blue glass—no plastics, so an old site. Despite the leave-no-trace protocols, I always want to see the traces, am heartened by somebody’s edibles wrapper, the old blue glass, a shoe sewn together many times, then discarded at the camp on the Mexican side where they once made wax from candelilla. From the hilltop, we can see across the few miles to the canyon we’ve just paddled through. Downriver, a ranch, an old water tower, the invisible sound of someone running a chainsaw. We drove out here to West Texas from Virginia, canoe strapped to the Subaru roof, to paddle the Rio Grande through Boquillas Canyon, to see the world laid bare. Seeking the most elemental sort of revelation: stone unto wind and water and all stages of winter light. Revelation from the Latin [End Page 89] stem revelare: to unveil, uncover, lay bare. We wanted to see how an ancient river has unveiled faces in the canyon wall, cutting the rock downward over millions of years as the western rim of the Sierra Del Carmen rose. How the slow river has shown the path through limestone and shaley slope to the feral horse and the lion. We have made this trip during the COVID-19 pandemic. We minimize contact at gas stations, keep rubbing alcohol in the car and masks on the dash, aware the Texas infection rates are dismal. We both teach at a university on winter break, and our middle-age togetherness, after failed marriages, is relatively new, just over a year old. I harbor that basic desire, too, then, to know more deeply the person I love, to have him laid bare. May we see each other’s faces in a new light, out of our semester routines. From motels on the drive out, he calls his children nightly at their mother’s. I have no children of my own and that I also carry, a question that might yield, who knows, under desert light. It is late December. We have shifted our noses to the southwest, like the lucky beasts we are. In my hair, the wind through the carrizo cane, the black phoebes crying out, tying knots. ________ Come, morning, and remake us and all the grasses and silver-iced trees and the rye grasses, the butternut trees. A small fable of revelation from my childhood: A girl heads out, in the late-fall cold of hardwood mountains, to make a leaf rubbing. How to choose—the poplar, the black walnut, or sassafras? Dawn pinks up her face; she takes her time choosing. She picks up several to press in a book, the serrated and veined, all crisp with color. She holds each petiole, the midrib like a tiny spine. For the rubbing, she chooses a sugar maple glowing gold-orange-red as if painted. She sets the leaf on a smooth, hard place and overlays her paper and rubs her charcoal flat-side down. The outline says hello. Into being comes the jagged lobe, the gutter of sinus, a lobe again, and another, the bones clean in their bright-dark presence. She loves how the leaf is remade on the page torn from her notebook, a full nothing until the charcoal scrubs and discovers. This is revelation. [End Page 90] In this fable, the girl is growing up in a tucked-away mountain church and thus learns young...

Simulation analysis of appropriate solutions to demands of light and heat in winter from the perspective of keeping health culture

Seasonal changes in peripheral inflammation are well documented in both humans and animal models, but seasonal changes in neuroinflammation, especially the impact of seasonal lighting environment on neuroinflammation remain unclear. To address this question, the present study examined the effects of environmental lighting conditions on neuroinflammation in a diurnal rodent model, Nile grass rats (Arvicanthis niloticus). Male and female grass rats were housed in either bright (brLD) or dim (dimLD)light during the day to simulate a summer or winter light condition, respectively. After 4weeks, microglia markers Iba-1 and CD11b, as well as pro-inflammatory cytokines TNF-α and IL-6, were examined in the anterior cingulate cortex (ACC), basolateral amygdala (BLA), and dorsal hippocampus (dHipp). The results revealed that winter-like dim light during the day leads to indicators of increased neuroinflammation in a brain site- and sex-specific manner. Specifically,relatively few changes in the neuroinflammatory markers were observed in the ACC, whilenumerous changes werefound in the BLA and dHipp. In the BLA, winter-like dimLD resulted in hyper-ramified microglia morphology and increased expression of the pro-inflammatory cytokine IL-6, but only in males. In the dHipp, dimLD led to a higher number and hyper-ramified morphology of microglia as well as increased expression of CD11b and TNF-α, but only in females. Neuroinflammatory state is thus influenced by environmental light, differently in males and females, and could play a role in sex differences in the prevalence and symptoms of psychiatric or neurological disorders that are influenced by season or otherenvironmental light conditions. Diurnal Nile grass rats were housed under bright or dim light during the day for 4weeks, simulating seasonal fluctuations in daytime lighting environment. Dim light housing resulted in hyper-ramified morphology of microglia (scale bar, 15μm) and altered expression of pro-inflammatory cytokines (TNF-α) in a sex- and brain region-specific manner.

Back to the Future

Plants growing in subtropical regions are often affected by high temperature and high light in summer and low temperature and high light in winter. However, few studies have compared the photoprotection mechanism of tree species at different successional stages in these two environments, although such studies would be helpful in understanding the succession of forest communities in subtropical forests. In order to explore the strategies used by dominant species at different successional stages to cope with these two environmental conditions, we selected two dominant species in the mid-successional stage, Schima superba and Castanopsis chinensis, and two dominant species in the late-successional stage, Machilus chinensis and Cryptocarya chinensis. The cell membrane permeability, chlorophyll fluorescence, chlorophyll content, and a few light-protective substances of these dominant species were measured in summer and winter. The results show that in summer, the young leaves of dominant species in the mid-successional stage showed higher anthocyanin content and superoxide dismutase (SOD) activity, while those in the late-successional stage showed higher flavonoid and total phenolic content, total antioxidant activity, non-photochemical quenching (NPQ), and carotenoid/chlorophyll (Car/Chl) ratio. In winter, young leaves of dominant species in the mid-successional stage were superior to those in the late-successional stage only in terms of catalase (CAT) activity and NPQ, while the anthocyanin, flavonoids, and total phenol content, total antioxidant capacity, and Car/Chl ratio were significantly lower compared to the late-successional stage. Our results show that the dominant species in different successional stages adapted to environmental changes in different seasons through the alterations in their photoprotection strategies. In summer, the dominant species in the mid-successional stage mainly achieved photoprotection through light shielding and reactive-oxygen-species scavenging by SOD, while the antioxidant capacity of trees in the late-successional stage mainly came from an increased antioxidative compounds and heat dissipation. In winter, the dominant species in the mid-successional stage maintained their photoprotective ability mainly through the scavenging of reactive oxygen species by CAT and the heat dissipation provided by NPQ, while those in the late-successional stage were mainly protected by a combination of processes, including light shielding, heat dissipation, and antioxidant effects provided by enzymatic and non-enzymatic antioxidant systems. In conclusion, our study partially explains the mechanism of community succession in subtropical forests.

Background: Skin is the outermost covering of the human body that serves as a barrier from extrinsic etiological challenges including physical, chemical and biological insults. Ultraviolet (UV)-B (280–320 nm) is the lead environmental agent responsible for causing skin pathologies, overexposure of ultraviolet radiation, particularly UV-B radiations, due to high energy and shorter wave length which are causes for most of the pathological states of skin. Skin cancers are classified into two main categories, non-melanoma skin cancer (NMSC) and cutaneous melanoma (CM). While melanoma originates through the transformation of melanocytes, NMSC arises from other epidermal cells, mainly keratinocytes, are subdivided into basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). Skin cancers are considered to be one of the most preventable malignancies. By protecting the skin and limiting the amount of unprotected exposure to UVR, skin cancer risk can be decreased. Objective: To describe the demographic and clinical features of skin cancer and evaluate the harmful effects of excess UVR exposure on human skin. Patients and Methods: A cross-sectional stud was conducted at the dermatology department in Baquba teaching hospital in Diyala, Iraq. A total of 100 patients were included, in the study, who attended the outpatient clinic of dermatology department of Baquba teaching hospital, from first of September 2020 to end May 2021. Results: A total of 100 patients diagnosed as skin cancer, were eligible for the study, aged between 30-80 years, The majority of them aged 41-50 years (39%), 50% of them were males and 50% were females, The majority of the patients, were laborer (31%), and 22% of them were housewives, Regarding residence, the majority of the patients (32%) lived in Kalar, and 27% resided in the Baquba, while just 3% from Mendeley, 83%percent of the patients, had white skin while just 17% of them had brown skin, and no one had black skin color, Regarding the affected site of the body, the face was the most common affected site of the body, found in (52%) of the patients. While face and neck were the most common affected site in 35% of the patients, and the least affected site was the face and hand found in 4% of the patients. Of the total patients, 99% were exposed to normal light while just 1% exposed to additional artificial light. Most of the patients (65%) said that they were exposed to the light over, all the season, while 24% of them were exposed to light just in summer, 8% and 3% of them were exposed in spring, summer and spring respectively. No one was exposed to light in autumn or winter, Just 4% of the patients had family history of skin cancer. There were 79% of the patients diagnosed as basal cell carcinoma; 14% had actinic keratosis, 5% had sun burn; and 2% had seborrheic keratosis. Regarding the patients with (BCC), most of the patients aged less than 70 years. Females were 50.6% of the patients with BCC, while males were 49.4%. The mean age of females was (53.6±12.9 years) was the same for males (53.6±11.6 years), females were affected by BCC in &lt; 50 and ≥70 age group more than males, while males were affected more in 50-69 age group. Sixty-five percent of the patients had white skin while just 14% of them had brown skin. Regarding the affected site of the body, the face was the most common affected site of the body, found in (53.2%) of the patients, while face and neck were the most common affected site in 34.2% of the patients, and the least affected site was the face and hand found in 5.1% of the patients. Conclusion:Outdoor workers, especially those without protective measures, and in high altitude areas, are more liable to develop skin cancer especially basal cell carcinoma, so it is important to use sun-protective measures. Keywords: Photodamage, UV Rays ,Skin

Abstract Central to the Southern Ocean's role in setting atmospheric CO2 is the seasonal alternation between upward mixing of nutrients and their subsequent consumption by phytoplankton. Active nutrient cycling within the mixed layer, including the release of ammonium (NH4+) and its removal by phytoplankton and nitrifiers, also affects Southern Ocean CO2 drawdown, yet remains poorly understood. We conducted kinetics experiments across the Southern Ocean south of Africa to investigate the dependence of NH4+ uptake (summer, winter) and oxidation (winter) on NH4+ concentration. NH4+ uptake followed a Michaelis–Menten function in both seasons, with the maximum rate (Vmax) decreasing poleward, apparently controlled mainly by light in winter and temperature in summer. The half‐saturation constant (Km) increased poleward with increasing ambient NH4+ ([NH4+]amb) and was threefold higher in winter (150–405 nM) than in summer (41–115 nM), suggesting that summertime phytoplankton are adapted to low‐NH4+ conditions while winter communities typically receive a higher NH4+ supply. NH4+ oxidation showed a high affinity for NH4+ (Km = 28–137 nM), suggesting a dominant role for ammonia‐oxidizing archaea, and followed a Michaelis–Menten curve only when [NH4+]amb was ≤ 90 nM. Vmax was near‐constant across the region regardless of [NH4+]amb, temperature, or light. From coincident mixed‐layer NH4+ oxidation and iron measurements, we hypothesize that iron availability may (co‐)limit the Vmax of NH4+ oxidation. If verified, this suggestion has implications for models that parameterize nitrification as a linear function of [NH4+]amb. Additionally, iron depletion may limit the role of mixed‐layer nitrification, which is dominant in the winter Southern Ocean, in offsetting phytoplankton CO2 drawdown annually.