Center-of-Mass Properties of the Exciton in Quantum Wells

We present high-quality numerical calculations of the exciton center-of-mass dispersion for GaAs/AlGaAs quantum wells of widths in the range 2-20 nm. The k.p-coupling of the heavy- and light-hole bands is fully taken into account. An optimized center-of-mass transformation enhances numerical convergence. We derive an easy-to-use semi-analytical expression for the exciton groundstate mass from an ansatz for the exciton wavefunction at finite momentum. It is checked against the numerical results and found to give very good results. We also show multiband calculations of the exciton groundstate dispersion using a finite-differences scheme in real space, which can be applied to rather general heterostructures.Comment: 19 pages, 12 figures included, to be published in Phys. Rev.

Acetyl Cholinesterase Inhibitors and Cell-Derived Peripheral Inflammatory Cytokines in Early Stages of Alzheimer's Disease

Clinical and preclinical studies firmly support the involvement of the inflammation in the pathogenesis of Alzheimer's disease (AD). Despite acetylcholinesterase inhibitors (AChEI) being widely used in AD patients, there is no conclusive evidence about their impact on the inflammatory response.Funding was received from a program co-financed by the European Social Fund and the Greek State (GSRT LS5-3808)info:eu-repo/semantics/publishedVersio

The potential of depressive symptoms to identify cognitive impairment in ageing

Depressive symptoms are common in mild cognitive impairment (MCI), dementia caused by Alzheimer’s disease (AD dementia) and in cognitively unimpaired older adults. However, it is unclear whether they could contribute to the identification of cognitive impairment in ageing. To assess the potential utility of depressive symptoms to distinguish between healthy cognitive ageing and MCI and AD dementia. The diagnostic workup of the cognitive function of 1737 older cognitively unimpaired individuals, 334 people with MCI and 142 individuals with AD dementia relied on a comprehensive neuropsychiatric assessment, including the Mini Mental State Examination (MMSE). Depressive symptoms were tapped with the 15-item Geriatric Depression Scale (GDS). Proportional odds logistic regression (POLR) models and the machine learning technique Adaptive Boosting algorithm (AdaBoost) were employed. Stratified repeated random subsampling (stratified bootstrap resampling) was used to recursive partitioning to training- and validation set (70/30 ratio). The average accuracy of the POLR models for the GDS total score in distinguishing between cognitive impairment and healthy cognitive ageing exceeded 78% and was inferior to that of MMSE. Of note, the sensitivity of GDS total score was very low. By employing the AdaBoost algorithm and considering GDS items separately, the average accuracy was higher than 0.72 and comparable to that of the MMSE, while sensitivity- and specificity values were more balanced. The findings of the study provide initial evidence that depressive symptoms may contribute to distinguishing between cognitive impairment and cognitively healthy ageing

Ultrafast terahertz probes of transient conducting and insulating phases in an electron–hole gas

Many-body systems in nature exhibit complexity and self-organization arising from seemingly simple laws. The long-range Coulomb interaction between electrical charges generates a plethora of bound states in matter, ranging from the hydrogen atom to complex biochemical structures. Semiconductors form an ideal laboratory for studying many-body interactions of quasi-particles among themselves and with lattice vibrations and light. Oppositely charged electron and hole quasi-particles can coexist in an ionized but correlated plasma, or form bound hydrogen-like pairs called excitons which strongly affect physical properties. The pathways between such states however remain elusive in near-visible optical experiments that detect a subset of excitons with vanishing center-of-mass momenta. In contrast, transitions between internal exciton levels which occur in the far-infrared at terahertz (10 s) frequencies are in dependent of this restriction suggesting their use as a novel pro be of pair dynamics. Here, we employ an ultrafast terahertz probe to directly investigate the dynamical interplay of optically-generated excitons and unbound electron-hole pairs in GaAs quantum wells. Our observations witness an unexpected quasi-instantaneous excitonic enhancement, reveal formation of insulating excitons on a hundred picosecond timescale and manifest conditions under which excitonic populations prevail

A review of neuroimaging findings of apathy in Alzheimer's disease

Background: Apathy is one of the most frequent behavioral and psychological signs and symptoms of dementia (BPSD) encountered in Alzheimer's disease (AD). There is a growing interest in the early diagnosis of apathetic elderly patients in the community since apathy has been associated with reduced daily functioning, caregiver distress, and poor outcome. The generalization of neuroimaging techniques might be able to offer help in this domain. Methods: Within this context we conducted an extensive electronic search from the databases included in the National Library of Medicine as well as PsychInfo and Google Scholar for neuroimaging findings of apathy in AD. Results: Neuroimaging findings lend support to the notion that frontal-subcortical networks are involved in the occurrence of apathy in AD. Conclusions: Longitudinal studies comparing patients and normal individuals might allow us to infer on the association between apathy and neurodegenerative diseases and what can brain imaging markers tell us about the characterization of this association, thus revealing disease patterns, helping to distinguish clinically distinct cognitive syndromes, and allowing predictions. Copyright © International Psychogeriatric Association 2013

A systematic review of non-pharmacological treatments for apathy in dementia

Objective: Apathy is one of the most frequent neuropsychiatric symptoms encountered in dementia. Early diagnosis and timely treatment of apathy in dementia are crucial because apathy has been associated with poor disease outcome, reduced daily functioning, and caregiver distress. Design: Extensive electronic search from the databases included in the National Library of Medicine as well as PsychInfo and Google Scholar for studies which have investigated the effect of non-pharmacological treatments of apathy in dementia. Quality of the studies was appraised. Results: A total of 1303 records were identified and 120 full-texts assessed. Forty-three unique studies were reviewed. A variety of interventions were found to be effective in reducing apathy in demented patients, particularly when provided in a multidisciplinary manner. However, quantification of the effect was limited by the marked methodological heterogeneity of the studies and the small number of studies where apathy was the primary outcome measure. Conclusions: Treatment of apathy in dementia is a complex and underexplored field. Certain studies suggest promise for a variety of non-pharmacological interventions. Standardized and systematic efforts primarily focusing on apathy may establish a benefit from individualized treatments for specific disease groups. Copyright © 2017 John Wiley & Sons, Ltd

A Severe and Irreversible Case of Tardive Rigid-Akinetic Parkinsonian Syndrome: The Role of the DaTscan

In elderly patients, exposure to antipsychotic medication and subsequent withdrawal may lead to the development of persistent extrapyramidal symptoms, possibly including a syndrome suggested to be tardive parkinsonism. We describe a case in which withdrawal of antipsychotics was unexpectedly associated with progressive deterioration, rather than improvement, of extrapyramidal parkinsonian symptoms. Abnormal imaging of presynaptic dopamine transporters (DaTs) using single-photon emission computed tomography (SPECT) with ioflupane I 123 (DaTscan) substantially contributed to the differential diagnosis, suggesting it was likely that the patient had an underlying neurodegenerative disorder that preceded the onset of medication-induced parkinsonian symptoms. Our report illustrates how novel findings from DaTscan may assist with diagnosing the cause of persistent parkinsonian symptoms after antipsychotic withdrawal and provide insight into the controversial concept of tardive parkinsonism

Old age mental health services in Southern Balkans: Features, geospatial distribution, current needs, and future perspectives

Background. Healthcare services are increasingly confronted with challenges related to old age mental disorders. The survey aimed to provide an overview of existing psychogeriatric services in Albania, Bulgaria, Greece, and North Macedonia. Methods. After identification of psychogeriatric units across the four countries, their head physicians were asked to provide data on their clinical, teaching, and research activity, as well as staff composition. Moreover, the attitudes of head physicians to current needs and future service development were explored. Results. A total of 15 psychogeriatric units were identified (3 in Bulgaria, 8 in Greece, and 4 in North Macedonia). Results show wide variation regarding the location, team size and composition, service availability, numbers of patients attending, and inpatient treatment length. Most head physicians underscored the urgent need for breakthroughs in the graduate and postgraduate education in psychogeriatrics of medical and nonmedical professionals, as well as in the interconnection of their units with community primary healthcare services and long-term care facilities for seniors via telemedicine. They would welcome the development of national standards for psychogeriatric units, potentially embodying clear pointers for action. A number of head physicians advocated the development of nationwide old age mental health registries. Conclusions. Regional disparities in resources and services for seniors’ mental health services were unveiled. These data may enrich the dialogue on optimizing psychogeriatric services through planning future cross-border collaborations mainly based on telemedicine services, especially in the era of the novel coronavirus pandemic, and training/education in psychogeriatrics of mental health professionals. © The Author(s), 2020