Gravity complexes as a focus of seafloor fluid seepage: the Rio Grande Cone, SE Brazil.

Seafloor methane emissions can affect Earth's climate and ocean chemistry. Vast quantities of methane formed by microbial decomposition of organic matter are locked within gas hydrate and free gas on continental slopes, particularly in large areas with high sediment accumulations such as deep-sea fans. The release of methane in slope environments has frequently been associated with dissociation of gas hydrates near the edge of the gas hydrate stability zone on the upper slope, with discharges in greater water depths less understood. Here we show, using data from the Rio Grande Cone (western South Atlantic), that the intrinsic, gravity-induced downslope collapse of thick slope sediment accumulations creates structures that serve as pathways for gas migration, unlocking methane and causing seafloor emissions via giant gas flares in the water column. The observed emissions in the study region (up to 310 Mg year-1) are three times greater than estimates for the entire US North Atlantic margin and reveal the importance of collapsing sediment accumulations for ocean carbon cycling. Similar outgassing systems on the Amazon and Niger fans suggest that gravity tectonics on passive margins is a common yet overlooked mechanism driving massive seafloor methane emissions in sediment-laden continental slopes.

Development of Superconducting On-chip Fourier Transform Spectrometers.

Superconducting On-chip Fourier Transform Spectrometers (SOFTS) are broadband, ultra-compact and electronic interferometers. SOFTS will enable kilo-pixel spectro-imaging focal planes, enhancing sub-millimeter astrophysics and cosmology. Particular applications include cluster astrophysics, cosmic microwave background (CMB) science, and line intensity mapping. This article details the development, design and bench-marking of radio frequency (RF) on-chip architecture of SOFTS for Ka and W-bands.

Durable memories and efficient neural coding through mnemonic training using the method of loci.

Mnemonic techniques, such as the method of loci, can powerfully boost memory. We compared memory athletes ranked among the world's top 50 in memory sports to mnemonics-naïve controls. In a second study, participants completed a 6-week memory training, working memory training, or no intervention. Behaviorally, memory training enhanced durable, longer-lasting memories. Functional magnetic resonance imaging during encoding and recognition revealed task-based activation decreases in lateral prefrontal, as well as in parahippocampal and retrosplenial cortices in both memory athletes and participants after memory training, partly associated with better performance after 4 months. This was complemented by hippocampal-neocortical coupling during consolidation, which was stronger the more durable memories participants formed. Our findings advance knowledge on how mnemonic training boosts durable memory formation through decreased task-based activation and increased consolidation thereafter. This is in line with conceptual accounts of neural efficiency and highlights a complex interplay of neural processes critical for extraordinary memory.

The renin secretion profile under the influence of sleep deprivation and the neuropeptides CRH and GHRH.

It is already known that during normal sleep plasma renin activity (PRA) shows oscillations with decreases during rapid-eye-movement (REM) sleep and increases during non-REM (NREM) sleep. We also know that renin correlates positively with slow-wave sleep (SWS). Sleep deprivation is known to enhance significantly SWS and slow wave activity (SWA, known as δ power). Based on these findings we addressed the question whether and to which extent sleep deprivation may affect the synchronization found between PRA and REM sleep during normal sleep and whether this synchronization is affected by other sleep regulating factors. To investigate these questions we compared sleep EEG and sleep-related free renin levels in 48 normal women and men 19-69 years old between nights before and after 40 h of sleep deprivation. During the recovery night, four bolus injections of either GHRH, CRH or placebo were injected via long catheter around sleep onset. When compared to baseline after each of the treatments SWS, SWA and renin levels increased. The characteristical oscillation profiles of renin during normal sleep were also preserved after sleep deprivation. Similar to normal sleep our data support also a distinct link between nocturnal renin secretion and SWS after sleep deprivation and that independent of the applied treatments.

Salivary cortisol response to psychosocial stress in the late evening depends on CRHR1 genotype.

The activation of the hypothalamus-pituitary-adrenal (HPA) axis is induced by stress. Imbalances in this system increase the risk of developing stress related disorders including mental illness. Variants in the single nucleotide polymorphism (SNP) rs110402 of the corticotropin-releasing hormone receptor type I (CRHR1) gene have been shown in interaction with childhood maltreatment to increase the vulnerability to develop depressive symptoms in adulthood. In this study, the direct contribution of polymorphism of the CRHR1 gene (rs110402) to the salivary cortisol response to stress independently from childhood adversity was investigated. Healthy young men between the ages of 18 and 30, free from childhood maltreatment and early trauma, were genotyped (n = 121). To increase the power of the genetic analysis, only homozygous carriers of the common C (n = 31) and of the rare T (n = 21) allele were selected for this study and exposed to a Trier Social Stress Test (TSST) in the late evening (22.30 to 22.40). Salivary samples for the assessment of cortisol and its inactive metabolite cortisone were taken early in the evening (20.00), just before (22.30) and immediately after (22.40) as well as 15 minutes after stress exposure (22.55). Participants with the TT genotype showed higher cortisol levels 15 minutes post stress compared to participants with the CC genotype. No genotype differences were found for cortisone. Interestingly, TT participants reported lower subjective perceived stress levels before the TSST, but not after stress exposure. These results confirm that variants of rs110402 in the CRHR1 gene contribute to an increased stress response. Contrary to previous findings, however, this effect could be observed in subjects reporting no exposure to childhood maltreatment or early trauma.

2D:4D and spatial abilities: From rats to humans.

Variance in spatial abilities are thought to be determined by in utero levels of testosterone and oestrogen, measurable in adults by the length ratio of the 2nd and 4th digit (2D:4D). We confirmed the relationship between 2D:4D and spatial performance using rats in two different tasks (paired-associate task and watermaze) and replicated this in humans. We further clarified anatomical and functional brain correlates of the association between 2D:4D and spatial performance in humans.

Sleep after intranasal progesterone vs. zolpidem and placebo in postmenopausal women - A randomized, double-blind cross over study.

CONTEXT: The loss of progesterone during menopause is linked to sleep complaints of the affected women. Previously we demonstrated sleep promoting effects of oral progesterone replacement in postmenopausal women. The oral administration of progesterone, however, is compromised by individual differences in bioavailability and metabolism of the steroid. OBJECTIVE: We compared the sleep-endocrine effects after intranasal progesterone (MPP22), zolpidem and placebo in healthy postmenopausal women. DESIGN: This was a randomized double-blind cross-over study. SETTING: German monocentric study PARTICIPANTS: Participants were 12 healthy postmenopausal women. INTERVENTIONS: Subjects received in randomized order four treatments, 2 doses of intranasal progesterone (4.5 mg and 9 mg of MPP22), 10 mg of zolpidem and placebo. OUTCOME MEASURES: Main outcome were conventional and quantitative sleep-EEG variables. Secondary outcomes were the subjective sleep variables and the sleep related concentrations of cortisol, growth hormone (GH), melatonin and progesterone. RESULTS: Sleep promoting effects were found after the higher dosage of MPP22 and after zolpidem. Zolpidem prompted benzodiazepine-like effects on quantitative sleep EEG as expected, whereas no such changes were found after the two dosages of MP22. Nocturnal progesterone levels increased after 9.0 mg MPP22. No other changes of hormone secretion were found. CONCLUSIONS: Our study shows sleep promoting effects after intranasal progesterone. The spectral signature of intranasal progesterone did not resemble the sleep-EEG alterations induced by GABA active compounds. Progesterone levels were elevated after 9.0 mg MPP22. No other endocrine effects were observed.

Background corrected measurements of optical quantities in the far-infrared spectral range.

By definition, optical quantities transmittance and reflectance can basically be determined as the ratio of two flux measurements. One measurement is performed with, and the other without, the sample under test in the optical path. However, at longer wavelengths the temperature radiation of the sample itself as well as of the applied spectrometer and detector increasingly contribute to the detected radiation budget. This leads to growing systematic errors in the determination of the transmittance and reflectance of samples with Fourier transform infrared spectrometers at longer wavelengths. We present an effective method to overcome this problem by measuring a sequence of four measurements at two different flux levels. Results obtained with this method are compared to the basic ratio method over a spectral range from 200 cm-1 to 30 cm-1 (0.9 THz to 6 THz).

Intercomparison of far-infrared transmittance measurements.

We present the results of the first systematic "round-robin" comparison of far-infrared transmittance spectra measurements, which was performed by five laboratories and piloted by Physikalisch-Technische (PTB). The transmittance spectra of four different samples were measured by the participating laboratories in the 600 cm-1 to 10 cm-1 range (16.67 µm to 1000 µm) in a blind comparison. Different types of instruments, Fourier transform infrared (FT-IR) spectrometers of Michelson type and a laser radiation-based system were used for the transmittance measurements. FT-IR spectrometers are the most popular and commonly used instruments for the spectral characterization of materials in the infrared spectral range, and are well established for quantitative measurements in the mid- and near-infrared spectral ranges. However, obtaining quantitative transmittance measurements in the far-infrared spectral range by means of these instruments is challenging, because it involves weaker radiation sources, stronger diffraction effects, significant radiation originating from the sample itself and temperature gradients inside the spectrometer that may not be given proper consideration. Therefore, this comparison was initiated to test the actual capability of and identify problems with FT-IR transmittance measurements in this spectral region. We discuss the results and the possible reasons for the observed discrepancies.

Corticotropin-releasing hormone induces depression-like changes of sleep electroencephalogram in healthy women.

We reported previously that repetitive intravenous injections of corticotropin-releasing hormone (CRH) around sleep onset prompt depression-like changes in certain sleep and endocrine activity parameters (e.g. decrease of slow-wave sleep during the second half of the night, blunted growth hormone peak, elevated cortisol concentration during the first half of the night). Furthermore a sexual dimorphism of the sleep-endocrine effects of the hormones growth hormone-releasing hormone and ghrelin was observed. In the present placebo-controlled study we investigated the effect of pulsatile administration of 4×50µg CRH on sleep electroencephalogram (EEG) and nocturnal cortisol and GH concentration in young healthy women. After CRH compared to placebo, intermittent wakefulness increased during the total night and the sleep efficiency index decreased. During the first third of the night, REM sleep and stage 2 sleep increased and sleep stage 3 decreased. Cortisol concentration was elevated throughout the night and during the first and second third of the night. GH secretion remained unchanged. Our data suggest that after CRH some sleep and endocrine activity parameters show also depression-like changes in healthy women. These changes are more distinct in women than in men.

Ghrelin modulates encoding-related brain function without enhancing memory formation in humans.

Ghrelin regulates energy homeostasis in various species and enhances memory in rodent models. In humans, the role of ghrelin in cognitive processes has yet to be characterized. Here we show in a double-blind randomized crossover design that acute administration of ghrelin alters encoding-related brain activity, however does not enhance memory formation in humans. Twenty-one healthy young male participants had to memorize food- and non-food-related words presented on a background of a virtual navigational route while undergoing fMRI recordings. After acute ghrelin administration, we observed decreased post-encoding resting state fMRI connectivity between the caudate nucleus and the insula, amygdala, and orbitofrontal cortex. In addition, brain activity related to subsequent memory performance was modulated by ghrelin. On the next day, however, no differences were found in free word recall or cued location-word association recall between conditions; and ghrelin's effects on brain activity or functional connectivity were unrelated to memory performance. Further, ghrelin had no effect on a cognitive test battery comprising tests for working memory, fluid reasoning, creativity, mental speed, and attention. In conclusion, in contrast to studies with animal models, we did not find any evidence for the potential of ghrelin acting as a short-term cognitive enhancer in humans.

High-Field High-Repetition-Rate Sources for the Coherent THz Control of Matter.

Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented quasi-continuous-wave repetition rates up to the MHz regime. We demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude. The peak fields and the repetition rates are highly scalable and once fully operational this type of sources will routinely provide 1 MV/cm electric fields and 0.3 T magnetic fields at repetition rates of few 100 kHz. We benchmark the unique properties by performing a resonant coherent THz control experiment with few 10 fs resolution.

Neuroscience-driven discovery and development of sleep therapeutics.

Until recently, neuroscience has given sleep research and discovery of better treatments of sleep disturbances little attention, despite the fact that disturbed sleep has overwhelming impact on human health. Sleep is a complex phenomenon in which specific psychological, electrophysiological, neurochemical, endocrinological, immunological and genetic factors are involved. The brain as both the generator and main object of sleep is obviously of particular interest, which makes a neuroscience-driven view the most promising approach to evaluate clinical implications and applications of sleep research. Polysomnography as the gold standard of sleep research, complemented by brain imaging, neuroendocrine testing, genomics and other laboratory measures can help to create composite biomarkers that allow maximizing the effects of individualized therapies while minimizing adverse effects. Here we review the current state of the neuroscience of sleep, sleep disorders and sleep therapeutics and will give some leads to promote the discovery and development of sleep medicines that are better than those we have today.

Sleep timing is more important than sleep length or quality for medical school performance.

Overwhelming evidence supports the importance of sleep for memory consolidation. Medical students are often deprived of sufficient sleep due to large amounts of clinical duties and university load, we therefore investigated how study and sleep habits influence university performance. We performed a questionnaire-based study with 31 medical students of the University of Munich (second and third clinical semesters; surgery and internal medicine). The students kept a diary (in 30-min bins) on their daily schedules (times when they studied by themselves, attended classes, slept, worked on their thesis, or worked to earn money). The project design involved three 2-wk periods (A: during the semester; B: directly before the exam period--pre-exam; C: during the subsequent semester break). Besides the diaries, students completed once questionnaires about their sleep quality (Pittsburgh Sleep Quality Index [PSQI]), their chronotype (Munich Chronotype Questionnaire [MCTQ]), and their academic history (previous grades, including the previously achieved preclinical board exam [PBE]). Analysis revealed significant correlations between the actual sleep behavior during the semester (MS(diary); mid-sleep point averaged from the sleep diaries) during the pre-exam period and the achieved grade (p = 0.002) as well as between the grades of the currently taken exam and the PBE (p = 0.002). A regression analysis with MS(diary) pre-exam and PBE as predictors in a model explained 42.7% of the variance of the exam grade (effect size 0.745). Interestingly, MS(diary)--especially during the pre-exam period-was the strongest predictor for the currently achieved grade, along with the preclinical board exam as a covariate, whereas the chronotype did not significantly influence the exam grade.

Pathology of sleep, hormones and depression.

In patients with depression, characteristic changes of sleep electroencephalogram and nocturnal hormone secretion occur including rapid eye movement (REM) sleep disinhibition, reduced non-REM sleep and impaired sleep continuity. Neuropeptides are common regulators of the sleep electroencephalogram (EEG) and nocturnal hormone secretion and changes in their activity appear to contribute to the aberrances of sleep in affective disorders. A reciprocal interaction of the sleep-promoting growth hormone-releasing hormone (GHRH) and corticotrophin-releasing hormone (CRH), which promotes wakefulness and REM sleep, plays a key role in sleep regulation, at least in male subjects. Also galanin and ghrelin promote sleep in men. Neuropeptide Y is involved in the timing of sleep onset. The effects of peptides of sleep are influenced by the time of administration, age, gender and depression. In healthy subjects and in remitted depressed patients motoric memory learning is consolidated during sleep. This effect is absent in depressed patients who are at least 30 years old, and is probably related to elevated glucocorticoid levels.

The interaction between sleep quality and academic performance.

Sleep quality has significant effects on cognitive performance and is influenced by multiple factors such as stress. Contrary to the ideal, medical students and residents suffer from sleep deprivation and stress at times when they should achieve the greatest amount of learning. In order to examine the relationship between sleep quality and academic performance, 144 medical students undertaking the pre-clinical board exam answered a survey regarding their subjective sleep quality (Pittsburgh sleep quality index, PSQI), grades and subjective stress for three different time points: semester, pre- and post-exam. Academic performance correlated with stress and sleep quality pre-exam (r = 0.276, p < 0.001 and r = 0.158, p < 0.03, note that low performance meant low sleep quality and high stress), however not with the stress or sleep quality during the semester and post-exam. 59% of all participants exhibited clinically relevant sleep disturbances (PSQI > 5) during exam preparation compared to 29% during the semester and 8% post-exam. This study shows that in medical students it is not the generally poor sleepers, who perform worse in the medical board exams. Instead students who will perform worse on their exams seem to be more stressed and suffer from poor sleep quality. However, poor sleep quality may negatively impact test performance as well, creating a vicious circle. Furthermore, the rate of sleep disturbances in medical students should be cause for intervention.

Renin-angiotensin-aldosterone system: the forgotten stress hormone system: relationship to depression and sleep.

INTRODUCTION: Neuroendocrine changes in depression have long been recognized, with a focus mainly on hypercortisolism. The other hormone of the hypothalamus-pituitary adrenocortical system, aldosterone, has been widely neglected. METHODS: Here we summarize the involvement of the renin-angiotensin-aldosterone system (RAAS) and the regulation of aldosterone in health with a particular focus on sleep-related changes and its role in stress-related conditions, like major depression. RESULTS: We highlight its role in functional systems which could be relevant in the therapy for refractory depression, like inflammatory mechanisms, the monoaminergic and the glutamatergic systems. Furthermore, anatomic areas which specifically mediate the action of aldosterone have been identifi ed. In particular the nucleus of the solitary tract (NTS) seems to have an important role and appears to be a target for antidepressive manipulations, like vagus nerve stimulation. Clinical data demonstrating the efficacy of aldosterone-reducing strategies for specific depressive syndromes are reviewed. DISCUSSION: In particular aspects of differentiation between melancholic vs. atypical depression spectrum disorders are discussed.

Anomalous piezoresistance effect in ultrastrained silicon nanowires.

In this paper we demonstrate that under ultrahigh strain conditions p-type single crystal silicon nanowires possess an anomalous piezoresistance effect. The measurements were performed on vapor-liquid-solid (VLS) grown Si nanowires, monolithically integrated in a microelectro-mechanical loading module. The special setup enables the application of pure uniaxial tensile strain along the <111> growth direction of individual, 100 nm thick Si nanowires while simultaneously measuring the resistance of the nanowires. For low strain levels (nanowire elongation less than 0.8%), our measurements revealed the expected positive piezoresistance effect, whereas for ultrahigh strain levels a transition to anomalous negative piezoresistance was observed. For the maximum tensile strain of 3.5%, the resistance of the Si nanowires decreased by a factor of 10. Even at these high strain amplitudes, no fatigue failures are observed for several hundred loading cycles. The ability to fabricate single-crystal nanowires that are widely free of structural defects will it make possible to apply high strain without fracturing to other materials as well, therefore in any application where crystallinity and strain are important, the idea of making nanowires should be of a high value.