Synthesis and Characterization of Ultrathin Silver Sulfide Nanoplatelets

© 2017 American Chemical Society. We report the synthesis of ultrathin silver sulfide (Ag2S) nanoplatelets (NPLs) synthesized via a one-pot method in ethylene glycol with 3-mercaptopropionic acid serving as both the sulfur precursor and the platelet ligand. The colloidally synthesized nanoplatelets are exceptionally thin, with a thickness of only 3.5 ± 0.2 Å and a 1S exciton Bohr diameter to confinement ratio of ∼12.6. The NPL growth is shown to be quantized by layer thickness using absorption and photoluminescence (PL) spectroscopy. Transmission electron microscopy, atomic force microscopy, and X-ray diffraction analyses of the NPLs show that they correspond to the (202) plane of the β-Ag2S structure. The PL quantum yield of these NPLs is ∼30%, suggesting their potential use in biomedical imaging. Optoelectronic properties were evaluated via sensitized photocurrent spectroscopy with the resulting spectra closely matching the distinctive absorption spectral shape of the Ag2S NPLs

A psychodynamic approach to suicide prevention

This paper sets forth a new theoretical approach to understanding the psychological etiology of suicide. The theory is demonstrated by an in-depth clinical case example, and its implications for the management of the suicidal candidate in his acute interim and long-term care are described. The theory assumes that the primary motivation to suicide comes from a clinically characteristic, unremitting psychological pain. The role of the suicidal prevention center is discussed with specific emphasis on the quality of the engagement between a center staff person and the suicidal patient. A future course for suicide centers is suggested based on the theory .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44296/1/10597_2005_Article_BF01411076.pd

Selective drug delivery approaches to lesioned brain through blood brain barrier disruption

Introduction: The development of therapeutics for central nervous system (CNS) disorders is still considered a challenging area in drug development due to insufficient translocation through the blood-brain barrier (BBB). Under normal conditions, BBB restrict the penetration of more than 98% of blood-borne molecules including drugs to the CNS. However, recent research findings have proven that the nature of the BBB is altered in several neurological conditions. This complexity encourages revisiting drug delivery strategies to the CNS as this can give a wide range of opportunities for CNS drug development. Areas covered: This review focuses on nanotechnology-based drug delivery platforms designed for selective recruitment into the lesioned brain by taking advantages of BBB disruption that is associated with certain neurological conditions. Expert opinion: Current CNS therapeutic strategies do not fully address the pathophysiological adaptation of BBB in their design. The lack of selective delivery to the brain lesions has been the culprit behind the failure of many CNS therapeutics. This highlighted the need for smart designs of advanced drug delivery systems that take advantage of BBB structural changes in CNS diseases. Recently, promising examples have been reported in this area, however, more work is still required beyond the preclinical testing

Sleep disturbances in highly stress reactive mice: Modeling endophenotypes of major depression

<p>Abstract</p> <p>Background</p> <p>Neuronal mechanisms underlying affective disorders such as major depression (MD) are still poorly understood. By selectively breeding mice for high (HR), intermediate (IR), or low (LR) reactivity of the hypothalamic-pituitary-adrenocortical (HPA) axis, we recently established a new genetic animal model of extremes in stress reactivity (SR). Studies characterizing this SR mouse model on the behavioral, endocrine, and neurobiological levels revealed several similarities with key endophenotypes observed in MD patients. HR mice were shown to have changes in rhythmicity and sleep measures such as rapid eye movement sleep (REMS) and non-REM sleep (NREMS) as well as in slow wave activity, indicative of reduced sleep efficacy and increased REMS. In the present study we were interested in how far a detailed spectral analysis of several electroencephalogram (EEG) parameters, including relevant frequency bands, could reveal further alterations of sleep architecture in this animal model. Eight adult males of each of the three breeding lines were equipped with epidural EEG and intramuscular electromyogram (EMG) electrodes. After recovery, EEG and EMG recordings were performed for two days.</p> <p>Results</p> <p>Differences in the amount of REMS and wakefulness and in the number of transitions between vigilance states were found in HR mice, when compared with IR and LR animals. Increased frequencies of transitions from NREMS to REMS and from REMS to wakefulness in HR animals were robust across the light-dark cycle. Detailed statistical analyses of spectral EEG parameters showed that especially during NREMS the power of the theta (6-9 Hz), alpha (10-15 Hz) and eta (16-22.75 Hz) bands was significantly different between the three breeding lines. Well defined distributions of significant power differences could be assigned to different times during the light and the dark phase. Especially during NREMS, group differences were robust and could be continuously monitored across the light-dark cycle.</p> <p>Conclusions</p> <p>The HR mice, i.e. those animals that have a genetic predisposition to hyper-activating their HPA axis in response to stressors, showed disturbed patterns in sleep architecture, similar to what is known from depressed patients. Significant alterations in several frequency bands of the EEG, which also seem to at least partly mimic clinical observations, suggest the SR mouse lines as a promising animal model for basic research of mechanisms underlying sleep impairments in MD.</p

Mourning and melancholia revisited: correspondences between principles of Freudian metapsychology and empirical findings in neuropsychiatry

Freud began his career as a neurologist studying the anatomy and physiology of the nervous system, but it was his later work in psychology that would secure his place in history. This paper draws attention to consistencies between physiological processes identified by modern clinical research and psychological processes described by Freud, with a special emphasis on his famous paper on depression entitled 'Mourning and melancholia'. Inspired by neuroimaging findings in depression and deep brain stimulation for treatment resistant depression, some preliminary physiological correlates are proposed for a number of key psychoanalytic processes. Specifically, activation of the subgenual cingulate is discussed in relation to repression and the default mode network is discussed in relation to the ego. If these correlates are found to be reliable, this may have implications for the manner in which psychoanalysis is viewed by the wider psychological and psychiatric communities