Hours Of Darkness Research Articles

Dirt Under Our Fingernails

Dirt Under Our Fingernails Jaclyn Bergamino (bio) and Kori Hensell (bio) On Women Writing in Alaska by Women Writing in Alaska In the spring of 2016, two women in the MFA program at the University of Alaska Fairbanks sat down to discuss the culture of working and writing in Alaska—more specifically, the phenomenal Alaskan women changing the literary landscape. JB: Last summer, my partner Kris and I sat by the fire outside our cabin on Alaska’s Kenai Peninsula. The sun, while it didn’t set, was dipping into the golden hour, which would last throughout that June night. We sat admiring the way that Mount Iliamna, just barely visible, glowed in that light. There was a crash in the brush behind us and for the first time, I was face-to-face with a moose. Not just one—three. A mother and two newborns. At first, I was in awe, excited and captivated by the sight. I was about eye-level with the babies. I could nearly have walked under the cow without ducking. The calves moved to nurse, but the mother saw us and stepped forward. My partner, a lifelong Alaskan stood up, moved between me and the moose. Her ears bowed backwards at us. “Move slowly behind the truck,” Kris said. I stepped as slowly as I could but within seconds I was inside the cabin, crying. I could not deal with how small I am, how fragile. KH: I’ve always felt inconsequential when it came to my place in the natural world, mainly because I was never really in it. I had no idea what I was signing up for when I made the decision to move the 4,087 miles from Tuscaloosa, Alabama to Fairbanks, Alaska. I was one of those kids who read White Fang and from Jack London’s depiction of the arctic, all ideologies about the “wilderness” were [End Page 9] born. For some background, I am not an outside person. I am a person who doesn’t even goes outside to walk to the mailbox. I enjoy the comforts of air conditioning and heat, a good Wi-Fi connection, plumbing, and cable TV. My hands do not know real labor; they are soft. I am soft and afraid of the woods. It is under these conditions that I have lived my almost thirty years. That said, Alaska and all its challenges is making something new of me. I think it remakes everyone who survives a true winter here. By “winter,” I do not simply mean snow and cold. Here, winter means something different to us; it is a psychological obstacle course that must be maneuvered in the heart, and in so doing, we become rougher, kinder creatures. Alaska experiences between 21 and 24 hours of darkness come December, and it changes us. JB: Alaska is home to a rich literary community these days. There is so much to write about, so much work to be done countering the reality TV narrative of Alaska as a harsh man’s frontier. Writers such as Peggy Shumaker, Nicole Stellon O’Donnell, and Bonnie-Sue Hitchcock have begun exploring what it means to be a woman in the largest, least populated state. As relative newcomers to the state, we can look to these women to help us understand the ways that the landscape is shaping us. Just this year alone, Rosemary McGuire, Linda Martin, and Eva Saulitis have examined these themes in fiction, poetry, and nonfiction respectively, giving us insight into the physicality of working, living, and dying in the Great White North. Rosemary McGuire. The Creatures at the Absolute Bottom of the Sea. University of Alaska Press, 2015. Rosemary McGuire’s recent short fiction collection, The Creatures at the Absolute Bottom of the Sea, builds on her experience as a commercial fisherman and her deep knowledge of Alaskan waters. This basis allows her to defy the idealization of the boreal wilderness and to give a clear, deep look at the ways in which Alaskans interact with the environment and each other. In her opening story “The Lost Boys Longline Co,” McGuire brings to light the connections between work, the body, and the...

Lemberg, Lwów, L'viv, 1914–1947: Violence and Ethnicity in a Contested City by Christoph Mick

Reviewed by: Lemberg, Lwów, L'viv, 1914–1947: Violence and Ethnicity in a Contested City by Christoph Mick Samuel J. Kessler Lemberg, Lwów, L'viv, 1914–1947: Violence and Ethnicity in a Contested City. By Christoph Mick. West Lafayette, IN: Purdue University Press, 2015. Pp. 458. Paper $59.95. ISBN 978-1557536716. In Lemberg, Lwów, L'viv, 1914–1947: Violence and Ethnicity in a Contested City, Christoph Mick uses the method of local history to unfold an interesting and complex thesis about the causes of ethnic violence in the former Habsburg crown land of Galicia. To explain what happened, he writes, we cannot merely credit historical differences among groups; we must likewise delve into how shifting regimes of governmental power reinforced, subjugated, or excluded certain populations along ethnic lines, and further, how cultures of memorialization and national remembrance (sometimes supported by existing political systems, sometimes not) valorized and inscribed particular historical episodes to the benefit or detriment of other indigenous groups. Tracing in scrupulous detail the political and social interactions of L'viv's three main ethnic groups (Poles, Ukrainians, and Jews) between 1914 and 1947, Mick argues that "ethnicity and religion were the most important identity markers" in the city (2). Nevertheless, changing administrative regimes and wartime occupations also served to define those ethnic identities in new and often negative ways. At the end of World War I, "religious and social conflicts became nationally charged" (7), with Poles and Ukrainians competing to include L'viv in their newly independent states. Narrating this history through the actions and words of L'viv's city councilors, journalists, academics, and "ordinary" folk—people for whom "L'viv [was] to be both a site and object of contention" (76)—Mick's work is a visceral, often numbingly brutal account of the dreams, hatreds, and fears of L'viv's population during Eastern Europe's darkest hours. The book's structure is informed by the seven "regime changes" that marked the [End Page 661] city's first five decades in the twentieth century: Austro-Hungarian to Russian (1914), Russian to Austro-Hungarian (1915), Austro-Hungarian to Ukrainian (1918), Ukrainian to Polish (1918), Polish to Soviet (1939), Soviet to German (1941), and German to Soviet (1944). Mick's thesis relies on the interplay of ethnicity and economics to explain the relationships of Poles, Ukrainians, and Jews during these political transitions. His method is that of local, descriptive history (what he calls Erfahrungsgeschichte, a history of how events are given meaning), allowing the sources to carry the narrative. Rarely does Mick engage with a broader European context. Instead, he lets Europe and its wars come to L'viv. In so doing, he has written a meticulous account of the interactions of L'viv's ethnic communities before, during, and after each regime change. The fourth chapter, "Reconstruction and Remembrance, 1920–1939," which covers the years after the successful establishment of L'viv as a Polish city following World War I, is perhaps the most theoretically stimulating. It traces the ultimately short-lived attempt by the Poles of L'viv to create a memory culture for their new state, the Second Polish Republic. These pages should be the starting point for a number of fascinating future dissertations. Much of the book is devoted to chronicling successive administrative changes in L'viv—the seemingly mundane, even petty, details that mark political transitions. I remain somewhat skeptical that shifting governments did much more than exacerbate existing tensions, which, by starting the volume in 1914, Mick has little time to mention. Rather, one of the profound insights to be found here is how ethnic strife—and more specifically, the near-continuous eruption of anti-Jewish violence—predated not only the Soviet and German occupations, but the Russian one in 1914 as well. Though Mick seeks repeatedly to stress underlying economic motivations (75, 293), the sources make clear that wealth and class were often merely rhetorical devices serving to disguise other motivations for violence. This seems particularly true for the recurring anti-Jewish pogroms, which (before the arrival of the Soviets and the Germans) tended to erupt during periods of political transition, rather than as the result of...

The effect of photoperiod regimes on daily RNA:DNA ratio rhythms in Chinese soft-shelled turtles (Pelodiscus sinensis)

The ratio of RNA to DNA is widely used to reflect instantaneous animal growth; however, little is known about its daily variation. Photoperiod can modify expression of internal clocks, providing animals with the flexibility to adapt to variable environments. This study focused on the influence of photoperiod regimes on the daily variation of RNA:DNA ratio in Pelodiscus sinensis. We randomly divided 260 turtles into four groups: constant dark (0L), 8 h light with 16 h dark (8L), 12 h light with 12 h dark (12L), and 16 h light with 8 h dark (16L). Turtles were housed under specific photoperiods for 15 days (fed for first 10 days then starved for 5 days), thereafter we sampled the tissues every 2 h for 24 h. We dissected forelimb muscles and measured the concentration of isolated RNA and DNA. There were rhythmic variations in the RNA:DNA ratio, even in turtles under continuous darkness, indicating that P. sinensis has circadian RNA:DNA ratio rhythms, and the rhythms were likely controlled by internal clocks. Additionally, the acrophase was advanced by two hours in constant darkness in contrast to the other three photoperiods, indicating that the photoperiod considerably modified the rhythm set by the internal clocks. Notably, the RNA:DNA ratio differed between photoperiod regimes, with 0L > 16L > 8L ≈ 12L, indicating the photoperiod may be a seasonal indicator for turtles to synchronize their physiological processes with environmental variations.

A fundamental study revisited: Quantitative evidence for territory quality in oystercatchers (Haematopus ostralegus) usingGPSdata loggers

A fundamental study by Ens et al. (1992, Journal of Animal Ecology, 61, 703) developed the concept of two different nest‐territory qualities in Eurasian oystercatchers (Haematopus ostralegus, L.), resulting in different reproductive successes. “Resident” oystercatchers use breeding territories close to the high‐tide line and occupy adjacent foraging territories on mudflats. “Leapfrog” oystercatchers breed further away from their foraging territories. In accordance with this concept, we hypothesized that both foraging trip duration and trip distance from the high‐tide line to the foraging territory would be linearly related to distance between the nest site and the high tide line. We also expected tidal stage and time of day to affect this relationship. The former study used visual observations of marked oystercatchers, which could not be permanently tracked. This concept model can now be tested using miniaturized GPS devices able to record data at high temporal and spatial resolutions. Twenty‐nine oystercatchers from two study sites were equipped with GPS devices during the incubation periods (however, not during chick rearing) over 3 years, providing data for 548 foraging trips. Trip distances from the high‐tide line were related to distance between the nest and high‐tide line. Tidal stage and time of day were included in a mixing model. Foraging trip distance, but not duration (which was likely more impacted by intake rate), increased with increasing distance between the nest and high‐tide line. There was a site‐specific effect of tidal stage on both trip parameters. Foraging trip duration, but not distance, was significantly longer during the hours of darkness. Our findings support and additionally quantify the previously developed concept. Furthermore, rather than separating breeding territory quality into two discrete classes, this classification should be extended by the linear relationship between nest‐site and foraging location. Finally, oystercatcher′s foraging territories overlapped strongly in areas of high food abundance.

EFEITO DO FOTOPERÍODO NO CRESCIMENTO, CONSUMO ALIMENTAR E QUALIDADE DA CARCAÇA DE TILÁPIAS INVERTIDAS

A incidência luminosa pode induzir diversos efeitos sobre o crescimento, alimentação, desenvolvimento e reprodução de peixes. O fotoperíodo é sinal principal para maior influência sobre o ritmo circadiano dos peixes e pode afetar o ganho de peso, a ingestão de alimento e a utilização de energia. O objetivo deste trabalho foi avaliar os efeitos de diferentes regimes de fotoperíodo no crescimento, consumo alimentar e qualidade da carcaça de tilápias invertidas, em um sistema fechado. Foram utilizados 150 alevinos de tilápias invertidas, provenientes da estação de piscicultura. Os peixes foram acondicionados e distribuídos em 15 aquários com a capacidade de 65 litros cada um, em delineamento inteiramente ao acaso, com três tratamentos e cinco repetições. Os tratamentos diferenciarão nas simulações dos fotoperíodos emerais (horas de luz) que durarão T1= 24 horas de escuro, T2= 12 horas de escuro e 12 horas de Luz, T3= 24 horas de luz. Cada peixe foi considerado uma unidade experimental. Não houve diferença significativa para desempenho, mas houve diferença para Índice gonadossomático (IGS). Conclui-se que o fotoperíodo (12L:12E) promove melhor índice gonadossomático em tilápia. Para melhor qualidade de carcaça e desempenho produtivo sugere o fotoperíodo (24L:0E).

Increased Incidence of Breast Cancer Due to Long Exposure of Light

The disturbed circadian rhythm due to long exposure to varied photo periods or to artificial light during night time (LAN) results in hormonal imbalance. The epidemiological survey indicates a clear difference in the incidence of breast cancer (BC) in countries closer to the poles and to the equator. Long-term exposure to LAN during sleep cycle is found to be the root cause of many health problems. Light dependent conversion of melatonin from serotonin plays a major role in cancer development. In rat model it is shown that levels of melatonin are always inversely proportional to oestradiol in the blood. Melatonin decreases the formation of oestrogens (mitogenic hormone) from androgens via aromatise inhibition. In a pilot study we have shown that in menopausal blind (risk age for BC) women the prevalence of BC is very low (1:169; Risk Rate (RR); Cumulative Risk (CR)35-64 age), compared to sighted women (1:78; CR, 35 - 64 age). Data was collected from a total of 2060 blind subjects (18.8% being <40 years of age and 81.2% above 40 years). Partially blind subjects have 11% greater risk of developing BC than those who are totally blind (RR=1.106; 95% CI=.352 to 3.472). Other established risk factors for BC are ineffective in blind. The blind women model (proposed in this study) suggests that dark hours are essential in our daily routine. By management of proper circadian rhythms better management of various endocrine diseases including hormone dependent cancers can be achieved.

Effects of crowding on larval diapause and adult body size in Monochamus alternatus alternatus (Coleoptera: Cerambycidae)

AbstractTo determine the effect of larval crowding on induction of diapause in Monochamus alternatus alternatus Hope (Coleoptera: Cerambycidae), newly hatched larvae were inoculated singly (density 1) or in pairs (density 2) on Pinus thunbergii Parlatore (Pinaceae) bolts and reared at 25 °C and 16 light:8 dark hour photoperiod. Adults emerged at density 1 and 2 between 75 and 139 days after the inoculation. About 150 days after larval inoculation, dissection of pine bolts indicated the incidence of larval diapause was greater at density 1 (0.536) than at density 2 (0.222), indicating inversely density-dependent induction of diapause. For both larval densities, the probability of entering diapause increased as bark surface area per larva (a proxy for per capita amount of food available) increased, showing that diapause induction can be explained by the amount of food available per larva. Adults that emerged at density 1 were heavier than those at density 2. When diapause and nondiapause insects occurred in the same pine bolts, six heavy adults had experienced diapause whereas three heavy adults had not, indicating that bark surface area affected the induction of diapause indirectly through larval interaction. The relationship between two different manners of density-dependent diapause induction and food supply is discussed.

Free-swimming speeds and behavior in adult Pacific Lamprey, Entosphenus tridentatus

Lampreys are extremely efficient anguilliform swimmers, well–designed for long–distance travel, although they are frequently characterized as poor swimmers when compared to salmonids. We examine free–swimming adult Pacific Lamprey, Entosphenus tridentatus, in a raceway environment to approximate swim speeds and behaviors that may occur in the natural environment. Lampreys (mean Body Length 59.2 ± 3.0 cm, range 50–66 cm BL) traveled upstream at a mean groundspeed of 0.34 ± 0.188 BL/s (n=126, range 0.01–0.79 BL/s). Swimming activity was strongly nocturnal. Observed speeds in the lower range may have been the result of swimming in midwater against faster currents, indirect paths or rest periods. Lampreys generally took advantage of lower near–bottom current velocities by swimming within 6 cm of the bottom, where currents were substantially lower. Equivalent swim speeds, without currents, would be 0.49 ± 0.190 BL/s (range 0.17–0.96 BL/s). These speeds are in the high range of daily travel rates encountered in tagging studies of both Pacific Lamprey and Atlantic Sea Lamprey, Petromyzon marinus, but compare well when migration is limited to hours of darkness or tracking was continuous. Such rates suggest that, travelling only at night, lampreys would cover 1,000 km upriver in under four months. It is crucial that managers and designers incorporate the swimming capability, near–bottom association, utilization of boundary flow conditions, and nocturnal behavior of lampreys into their activities if we are to effectively manage in-stream facilities and conserve these key anadromous species.

Helping people through their darkest hours.

On my last placement I met two wonderful people who were in the most frightening situation parents can find themselves in.

Evening choruses in the Perth Canyon and their potential link with Myctophidae fishes.

An evening chorus centered at near 2.2 kHz was detected across the years 2000 to 2014 from seabed receivers in 430-490 m depth overlooking the Perth Canyon, Western Australia. The chorus reached a maximum level typically 2.1 h post-sunset and normally ran for 2.1 h (between 3 dB down points). It was present at lower levels across most of the hours of darkness. Maximum chorus spectrum levels were 74-76 dB re 1 μPa2/Hz in the 2 kHz 1/3 octave band, averaging 6-12 dB and up to 30 dB greater than pre-sunset levels. The chorus displayed highest levels over April to August each year with up to 10 dB differences between seasons. The spatial extent of the chorus was not determined but exceeded the sampling range of 13-15 km offshore from the 300 m depth contour and 33 km along the 300 m depth contour. The chorus comprised short damped pulses. The most likely chorus source is considered to be fishes of the family Myctophidae foraging in the water column. The large chorus spatial extent and its apparent correlation with regions of high productivity suggest it may act as an acoustic beacon to marine fauna indicating regions of high biomass.

Entrainment of circadian rhythms to irregular light/dark cycles: a subterranean perspective.

Synchronization of biological rhythms to the 24-hour day/night has long been studied with model organisms, under artificial light/dark cycles in the laboratory. The commonly used rectangular light/dark cycles, comprising hours of continuous light and darkness, may not be representative of the natural light exposure for most species, including humans. Subterranean rodents live in dark underground tunnels and offer a unique opportunity to investigate extreme mechanisms of photic entrainment in the wild. Here, we show automated field recordings of the daily light exposure patterns in a South American subterranean rodent, the tuco-tuco (Ctenomys aff. knighti ). In the laboratory, we exposed tuco-tucos to a simplified version of this natural light exposure pattern, to determine the minimum light timing information that is necessary for synchronization. As predicted from our previous studies using mathematical modeling, the activity rhythm of tuco-tucos synchronized to this mostly simplified light/dark regimen consisting of a single light pulse per day, occurring at randomly scattered times within a day length interval. Our integrated semi-natural, lab and computer simulation findings indicate that photic entrainment of circadian oscillators is robust, even in face of artificially reduced exposure and increased phase instability of the synchronizing stimuli.

The Jerusalem Staircase and Two Squares

The article tells about the significance of the Jerusalem staircase and the adjoining upper and lower squares in the system of public spaces in Irkutsk. The author proposes reconstruction with the use of not only stone, but also wooden cover for the lower square and the pavement along Podgornaya Street, as well as the active use of local lighting during hours of darkness.

3. Daily dynamics of states of vigilance in mice

Previous studies demonstrated that (a) mice preferentially sleep during light hours and they are preferentially awake during dark hours; (b) mice have fragmented sleep. Despite multiple investigations involving sleep-wake transitions in mice, the exact patterns of sleep-wake alternations are not known. Here we studied sleep-wake pattern distribution in 5 young adult C57BL/6 mice over 5 days using continuous LFP and EMG recordings with a resolution of 5 s. The states were automatically detected based on LFP delta power, theta power and EMG power. We found that daily distribution of states of vigilance in mice was: 12 h of wake, 10.2 h of slow-wave sleep and 1.8 h of REM and it was characterized by several hundred of transitions between different states of vigilance. The majority of detected states lasted less than 40 s. The fragmentation of states of vigilance was higher in the light part of the day and lower in first several hours of the dark part of the day when wake episodes were longer and REM sleep was almost absent. The most stable state of vigilance (longest stable segments) in mice was slow-wave sleep. The main EEG events that contribute to the delta power are slow waves. The existing methods of automatic slow wave detection were not sufficiently robust for their effective automatic recognition in non-anaesthetized mice. We developed a new method for slow wave detection based on neural network pattern recognition and classification, which allowed to retrieve various features of the slow waves in large amounts of data. As expected, we found many slow waves during slow-wave sleep. Surprisingly, isolated slow waves were also present during wake and occasionally during REM sleep. Both delta power and number of slow waves per second were the highest at the beginning of the light cycle, then gradually decreased to the end of the light cycle and reached their minimum in first 3–4 h of the dark cycle. Even though the slow-wave sleep episodes were shorter and occurred less often during dark part of the day, they had higher density in comparison to slow-wave sleep during the light part of the day. We conclude that the results of studies of normal sleep-wake cycle in C57BL/6 mice cannot be directly translated to human research or clinic. Supported by CIHR and NSERC.

Behavioral responses of brown shrimp (Crangon crangon) to reduced seawater pH following simulated leakages from sub-sea geological storage of CO2

ABSTRACTLarge-scale storage of CO2 within sub-sea geological formations is a viable option for reducing the volume of this greenhouse gas released directly to the atmosphere from anthropogenic activities. Risks to benthic marine life following possible leakage of gas through the seabed from this carbon capture and storage (CCS) initiative are not yet well established. This study examined behavior (activity patterns) in brown shrimp (Crangon crangon), exposed to a range of reduced seawater pH conditions (7.6, 7, or 6.5) simulating leakage scenarios of varying scales. Brown shrimp have an endogenous rhythmicity associated with their activity, which dictates they are most active during hours of darkness, presumably as protection against vision-dependent predators. This endogenous rhythm in activity continues to be expressed when shrimp are held under constant low-light conditions in the lab and provides an ecologically relevant endpoint to measure when examining the influence of reduced pH on the behavior of these animals. No marked differences in activity pattern were observed between control shrimp maintained at pH 8.1 and those at pH 7.6. However, changes in activity were evident at pH 7 and pH 6.5, where significant shifts in timing and intensity of activity occurred. There was an unexpected increase in activity within periods of expected light, probably signaling efforts by shrimp to migrate away from reduced seawater pH conditions. The loss of this important member of the benthic community due to migration may have important consequences for many of the resilient species that remain.

Lack of sex-specific movement patterns in an alien species at its invasion front - consequences for invasion speed.

SummaryEfficient targeting of actions to reduce the spread of invasive alien species relies on understanding the spatial, temporal, and individual variation of movement, in particular related to dispersal. Such patterns may differ between individuals at the invasion front compared to individuals in established and dense populations due to differences in environmental and ecological conditions such as abundance of conspecifics or sex‐specific dispersal affecting the encounter rate of potential mates. We assessed seasonal and diurnal variation in movement pattern (step length and turning angle) of adult male and female raccoon dog at their invasion front in northern Sweden using data from Global Positioning System (GPS)‐marked adult individuals and assessed whether male and female raccoon dog differed in their movement behavior. There were few consistent sex differences in movement. The rate of dispersal was rather similar over the months, suggesting that both male and female raccoon dog disperse during most of the year, but with higher speed during spring and summer. There were diurnal movement patterns in both sexes with more directional and faster movement during the dark hours. However, the short summer nights may limit such movement patterns, and long‐distance displacement was best explained by fine‐scale movement patterns from 18:00 to 05:00, rather than by movement patterns only from twilight and night. Simulation of dispersing raccoon dogs suggested a higher frequency of male–female encounters that were further away from the source population for the empirical data compared to a scenario with sex differences in movement pattern. The lack of sex differences in movement pattern at the invasion front results in an increased likelihood for reproductive events far from the source population. Animals outside the source population should be considered potential reproducing individuals, and a high effort to capture such individuals is needed throughout the year to prevent further spread.

Reliability and Cost Analysis of Multistage Boost Converters Connected to PV Panels

In photovoltaic (PV) generation systems, dc–dc boost converters are responsible for maximum power point tracking and voltage regulation. The intent of this paper is to determine the number of the stages in an interleaved boost converter interfacing PV panels for achieving a reliable and costly optimized structure. A comparative study has been done on different modes of operation. including redundant operation or parallel operation in a two-stage interleaved converter. The comparison indicates that working in simultaneous mode would be more reliable. Contemplating this fact, reliability equation of a three-stage interleaved converter is calculated for simultaneous mode of operation. Considering dark hours of the day, a k -means clustering technique has been utilized in the reliability calculations based on the output data of a PV generation system installed at the campus. Besides, mean time to failure criterion is considered in the reliability analysis. Simulation and experimental results are analyzed, considering the costs. The results determine the optimum structure for interfacing the PV panels to the grid.

How competition and predation shape patterns of waterhole use by herbivores in arid ecosystems

Access to surface water is crucial for herbivores in arid ecosystems. Here, we build a game-theoretical model, based on an evolutionary algorithm, to study the influence of ecological factors on the temporal patterns of presence at waterholes in the herbivore community. In this model, we incorporate the specific features of arid environments, namely, the important hydric losses endured by individuals exposed during the warmest hours of the day, and competition for access to water, both within and between species. We also consider the presence of ambushing predators around waterholes, particularly during dark hours. In response to this predation regime, our model predicts a strong aggregative tendency in herbivores. The number of groups, however, is variable, as well as the time these groups choose to attend the waterhole, even if the total number of individuals is fixed. The reason is a multiplicity of possible evolutionarily stable strategies, corresponding to different responses to the trade-off between the advantages of grouping, in terms of risk dilution, and its costs, in terms of increased competition. This variety of possible behavioural responses affects, in turn, the moments when the waterhole is occupied, and the moments when the different species meet each other. In general, herbivores also respond to predation threat by avoiding coming to waterholes after dusk. However, the cumulative effects of a relatively high level of predation during the day and a high level of interspecific competition for access to water may induce an important presence of herbivores at the waterhole at night. Our predictions are discussed in the light of existing empirical studies.

Desempenho e comportamento de suínos em fase de terminação submetidos a diferentes programas de luz

RESUMO Objetivou-se com esse trabalho avaliar o uso de programas de luz sobre o desempenho, concentração plasmática de melatonina e comportamento de suínos em fase de terminação. O experimento foi conduzido no setor de suinocultura da UFLA, utilizando-se 32 suínos em fase de terminação, por 48 dias. Os animais foram alojados em grupos de dois em cada baia (unidade experimental), distribuídos em delineamento em blocos casualizados, de acordo com o peso inicial com quatro tratamentos e quatro blocos. Foram utilizados quatro programas de luz (tratamentos), sendo T1: luz natural (LN); T2: 15 horas de luz e nove de escuro por dia (15L: 9E); T3: 19 horas de luz por dia (19L: 5E); T4: 23 horas de luz por dia (23L: 1E). As variáveis analisadas foram o desempenho (consumo de ração médio diário, ganho de peso médio diário e conversão alimentar), concentração plasmática de melatonina e o comportamento (bebendo, fuçando, ócio e comendo). A alteração no fotoperíodo não alterou o desempenho ou a concentração plasmática de melatonina nos suínos. As variáveis comportamentais “fuçando”, “comendo”, “bebendo”, não diferiram em nenhum dos períodos estudados, porém o comportamento ócio foi mais ocorrente nos suínos que receberam 15 horas de luz. O aumento no fotoperíodo não permitiu expressivas alterações de desempenho ou de comportamento dos animais.

Effect of light quality and light-dark cycle on sporulation patterns of the mite pathogenic fungus Neozygites floridana (Neozygitales: Entomophthoromycota), a natural enemy of Tetranychus urticae

A controlled climatic chamber microcosm experiment was conducted to examine how light affects the hourly sporulation pattern of the beneficial mite pathogenic fungus Neozygites floridana during a 24h cyclus over a period of eight consecutive days. This was done by inoculating two-spotted spider mites (Tetranychus urticae) with N. floridana and placing them on strawberry plants for death and sporulation. Spore (primary conidia) discharge was observed by using a spore trap. Two light regimes were tested: Plant growth light of 150μmolm−2s−1 for 12h supplied by high pressure sodium lamps (HPS), followed by either; (i) 4h of 50μmolm−2s−1 light with similar HPS lamps followed by 8h darkness (full HPS light+reduced HPS light+darkness) or (ii) 4h of 50μmolm−2s−1 red light followed by 8h darkness (full HPS light+red light+darkness). A clear difference in hourly primary conidia discharge pattern between the two different light treatments was seen and a significant interaction effect between light treatment and hour in day during the 24h cycle was observed. The primary conidia discharge peak for treatment (ii) that included red light was mainly reached within the red light hours (19:00–23:00) and the dark hours (23:00–07:00). The primary conidia discharge peak for treatment (i) with HPS light only was mainly reached within the dark hours (23:00–07:00).

Indoor Optical Wireless Power Transfer to Small Cells at Nighttime

The application of wireless backhaul communication and power transfer to outdoor small cells (SCs) could significantly decrease their installation cost. In this paper, the concept of indoor optical wireless power transfer to SCs is investigated in the absence of ambient light, i.e., during darkness hours. An experimental study is conducted by the use of up to four red laser diodes (LDs), a crystalline silicon solar panel and cell placed at $5.2$ m. A value of $69$ % is measured for the fill factor of the solar panel. Also, a total power efficiency of $3.2$ % is measured for an optical wireless (OW) link with an average efficiency of two LDs of $26.8$ %, a solar cell efficiency of $13.3$ % and only $10.6$ % of geometrical losses. A comparison of this link with a state-of-the-art inductive power transfer system shows an improvement of the total power efficiency by $2.7$ times. Another OW link is implemented with a divergence of full width at $36.8$ % of the peak intensity of $3$ and $5.75$ mrad along the small and large axes of the beam, respectively. The experimental levels of harvested power are in the order of mW, whereas approximately $1$ W is required for the operation of a SC. Therefore, a $42$ laser-based transmitter is designed both analytically and by the use of the simulation tool Zemax. The respective results show the feasibility of delivering $7.2$ W of optical power to a solar cell of up to $30$ m distance with geometrical losses of only $2$ %, but a beam enclosure is also required due to eye safety restrictions.