Saturation in cascaded optical amplifier free-space optical communication systems

The performance of a free-space optical (FSO) communication system in a turbulent atmosphere employing an optical amplifier (OA) cascade to extend reach is investigated. Analysis of both single and cascaded OA FSO communication links is given and the implications of using both adaptive (to channel state) and non-adaptive decision threshold schemes are analysed. The benefits of amplifier saturation, for example in the form of effective scintillation reduction when a non-adaptive decision threshold scheme is utilised at the receiver for different atmospheric turbulence regimes, are presented. Monte Carlo simulation techniques are used to model the probability distributions of the optical signal power, noise and the average bit error rate due to scintillation for the cascade. The performance of an adaptive decision threshold is superior to a non-adaptive decision threshold for both saturated and fixed gain preamplified receivers and the ability of a saturated gain OA to suppress scintillation is only meaningful for system performance when a non-adaptive decision threshold is used at the receiver. An OA cascade can be successfully used to extend reach in FSO communication systems and specific system implementations are presented. The optimal cascade scheme with a non-adaptive receiver would use frequent low gain saturated amplification

Climate policy meets national development contexts: Insights from Kenya and Mozambique

Despite the growth in work linking climate change and national level development agendas, there has been limited attention to their political economy. These processes mediate the winners, losers and potential trade-offs between different goals, and the political and institutional factors which enable or inhibit integration across different policy areas. This paper applies a political economy analysis to case studies on low carbon energy in Kenya and carbon forestry in Mozambique. In examining the intersection of climate and development policy, we demonstrate the critical importance of politics, power and interests when climate-motivated initiatives encounter wider and more complex national policy contexts, which strongly influence the prospects of achieving integrated climate policy and development goals in practice. We advance the following arguments: First, understanding both the informal nature and historical embeddedness of decision making around key issue areas and resource sectors of relevance to climate change policy is vital to engaging actually existing politics; why actors hold the positions they do and how they make decisions in practice. Second, we need to understand and engage with the interests, power relations and policy networks that will shape the prospects of realising climate policy goals; acting as barriers in some cases and as vehicles for change in others. Third, by looking at the ways in which common global drivers have very different impacts upon climate change policy once refracted through national levels institutions and policy processes, it is easier to understand the potential and limits of translating global policy into local practice. And fourth, climate change and development outcomes, and the associated trade-offs, look very different depending on how they are framed, who frames them and in which actor coalitions. Understanding these can inform the levers of change and power to be navigated, and with whom to engage in order to address climate change and development goals

Measuring acute effects of subanesthetic ketamine on cerebrovascular hemodynamics in humans using TD-fNIRS

Quantifying neural activity in natural conditions (i.e. conditions comparable to the standard clinical patient experience) during the administration of psychedelics may further our scientific understanding of the effects and mechanisms of action. This data may facilitate the discovery of novel biomarkers enabling more personalized treatments and improved patient outcomes. In this single-blind, placebo-controlled study with a non-randomized design, we use time-domain functional near-infrared spectroscopy (TD-fNIRS) to measure acute brain dynamics after intramuscular subanesthetic ketamine (0.75 mg/kg) and placebo (saline) administration in healthy participants (n = 15, 8 females, 7 males, age 32.4 ± 7.5 years) in a clinical setting. We found that the ketamine administration caused an altered state of consciousness and changes in systemic physiology (e.g. increase in pulse rate and electrodermal activity). Furthermore, ketamine led to a brain-wide reduction in the fractional amplitude of low frequency fluctuations, and a decrease in the global brain connectivity of the prefrontal region. Lastly, we provide preliminary evidence that a combination of neural and physiological metrics may serve as predictors of subjective mystical experiences and reductions in depressive symptomatology. Overall, our study demonstrated the successful application of fNIRS neuroimaging to study the physiological effects of the psychoactive substance ketamine in humans, and can be regarded as an important step toward larger scale clinical fNIRS studies that can quantify the impact of psychedelics on the brain in standard clinical settings

Acute effects of subanesthetic ketamine on cerebrovascular hemodynamics in humans: A TD-fNIRS neuroimaging study

Quantifying neural activity in natural conditions (i.e. conditions comparable to the standard clinical patient experience) during the administration of psychedelics may further our scientific understanding of the effects and mechanisms of action. This data may facilitate the discovery of novel biomarkers enabling more personalized treatments and improved patient outcomes. In this single-blind, placebo-controlled study with a non-randomized design, we use time-domain functional near-infrared spectroscopy (TD-fNIRS) to measure acute brain dynamics after intramuscular subanesthetic ketamine (0.75 mg/kg) and placebo (saline) administration in healthy participants (n= 15, 8 females, 7 males, age 32.4 ± 7.5 years) in a clinical setting. We found that the ketamine administration caused an altered state of consciousness and changes in systemic physiology (e.g. increase in pulse rate and electrodermal activity). Furthermore, ketamine led to a brain-wide reduction in the fractional amplitude of low frequency fluctuations (fALFF), and a decrease in the global brain connectivity of the prefrontal region. Lastly, we provide preliminary evidence that a combination of neural and physiological metrics may serve as predictors of subjective mystical experiences and reductions in depressive symptomatology. Overall, our studies demonstrated the successful application of fNIRS neuroimaging to study the physiological effects of the psychoactive substance ketamine and can be regarded as an important step toward larger scale clinical fNIRS studies that can quantify the impact of psychedelics on the brain in standard clinical settings

Land cover change and carbon emissions over 100 years in an African biodiversity hotspot

Agricultural expansion has resulted in both land use and land cover change (LULCC) across the tropics. However, the spatial and temporal patterns of such change and their resulting impacts are poorly understood, particularly for the pre-satellite era. Here we quantify the LULCC history across the 33.9 million ha watershed of Tanzania's Eastern Arc Mountains, using geo-referenced and digitised historical land cover maps (dated 1908, 1923, 1949 and 2000). Our time series from this biodiversity hotspot shows that forest and savanna area both declined, by 74% (2.8 million ha) and 10% (2.9 million ha), respectively, between 1908 and 2000. This vegetation was replaced by a five-fold increase in cropland, from 1.2 million ha to 6.7 million ha. This LULCC implies a committed release of 0.9 Pg C (95% CI: 0.4-1.5) across the watershed for the same period, equivalent to 0.3 Mg C ha(-1) yr(-1) . This is at least three-fold higher than previous estimates from global models for the same study area. We then used the LULCC data from before and after protected area creation, as well as from areas where no protection was established, to analyse the effectiveness of legal protection on land cover change despite the underlying spatial variation in protected areas. We found that, between 1949 and 2000, forest expanded within legally protected areas, resulting in carbon uptake of 4.8 (3.8-5.7) Mg C ha(-1) , compared to a committed loss of 11.9 (7.2-16.6) Mg C ha(-1) within areas lacking such protection. Furthermore, for nine protected areas where LULCC data is available prior to and following establishment, we show that protection reduces deforestation rates by 150% relative to unprotected portions of the watershed. Our results highlight that considerable LULCC occurred prior to the satellite era, thus other data sources are required to better understand long-term land cover trends in the tropics. This article is protected by copyright. All rights reserved

Rapid dynamic activation of a marine-based Arctic ice cap

We use satellite observations to document rapid acceleration and ice loss from a formerly slow-flowing, marine-based sector of Austfonna, the largest ice cap in the Eurasian Arctic. During the past two decades, the sector ice discharge has increased 45-fold, the velocity regime has switched from predominantly slow (~ 101 m/yr) to fast (~ 103 m/yr) flow, and rates of ice thinning have exceeded 25 m/yr. At the time of widespread dynamic activation, parts of the terminus may have been near floatation. Subsequently, the imbalance has propagated 50 km inland to within 8 km of the ice cap summit. Our observations demonstrate the ability of slow-flowing ice to mobilize and quickly transmit the dynamic imbalance inland; a process that we show has initiated rapid ice loss to the ocean and redistribution of ice mass to locations more susceptible to melt, yet which remains poorly understood.This work was supported by the UK Natural Environment Research Council.This article was originally published in Geophysical Research Letters (M McMillan, A Shepherd, N Gourmelen, A Dehecq, A Leeson, A Ridout, T Flament, A Hogg, L Gilbert, T Benham, M van den Broeke, JA Dowdeswell, X Fettweis, B Noël, T Strozzi, Geophysical Research Letters 2014, 41, 8902–8909)

Pan-cancer Alterations of the MYC Oncogene and Its Proximal Network across the Cancer Genome Atlas

Although theMYConcogene has been implicated incancer, a systematic assessment of alterations ofMYC, related transcription factors, and co-regulatoryproteins, forming the proximal MYC network (PMN),across human cancers is lacking. Using computa-tional approaches, we define genomic and proteo-mic features associated with MYC and the PMNacross the 33 cancers of The Cancer Genome Atlas.Pan-cancer, 28% of all samples had at least one ofthe MYC paralogs amplified. In contrast, the MYCantagonists MGA and MNT were the most frequentlymutated or deleted members, proposing a roleas tumor suppressors.MYCalterations were mutu-ally exclusive withPIK3CA,PTEN,APC,orBRAFalterations, suggesting that MYC is a distinct onco-genic driver. Expression analysis revealed MYC-associated pathways in tumor subtypes, such asimmune response and growth factor signaling; chro-matin, translation, and DNA replication/repair wereconserved pan-cancer. This analysis reveals insightsinto MYC biology and is a reference for biomarkersand therapeutics for cancers with alterations ofMYC or the PMN

Genomic, Pathway Network, and Immunologic Features Distinguishing Squamous Carcinomas

This integrated, multiplatform PanCancer Atlas study co-mapped and identified distinguishing molecular features of squamous cell carcinomas (SCCs) from five sites associated with smokin