Evidence for Nonradiative Energy Transfer in Graphene-Oxide-Based Hybrid Structures

Cataloged from PDF version of article.Solution processed graphene variants including graphene oxide (GO) and reduced graphene oxide (RGO) are promising materials for potential optoelectronic applications. To date, efficiency of the excitation energy transfer into GO and RGO thin layers has not been investigated in terms of donor-acceptor separation distance. In the present work, we study nonradiative energy transfer (NRET) from CdSe/CdS quantum dots into single and/or double layer GO or RGO using time-resolved fluorescence spectroscopy. We observe shorter lifetimes as the separation distance between the QDs and GO or RGO decreases. In accordance with these lifetimes, the rates reveal the presence of two different mechanisms dominating the NRET. Here we show that excitonic NRET is predominant at longer intervals while both excitonic and nonexcitonic NRET exist at shorter distances. In addition, we find the NRET rate behavior to be strongly dependent on the reduction degree of the GO-based layers. We obtain high NRET efficiency levels of similar to 97 and similar to 89% for the closest separation of the QD-RGO pair and the QD-GO pair, respectively. These results indicate that strong NRET from QDs into thin layer GO and RGO makes these solution-processable thin films promising candidates for light harvesting and detection systems

Synthesis of Phosporus Included Multiwalled Carbon Nanotubes by Pyrolysis of Sucrose

Cataloged from PDF version of article.Multiwalled carbon nanotubes (MWCNT) were synthesized by a pyrolysis route which involves a dehydration step using phosphoric acid. The resultants were found to be mostly containing amorphous carbon with scattered MWCNTs using scanning electron and transmission electron microscopy techniques. These MWCNTs were smaller in size and limited in quantity compared to the ones synthesized using other common precursors. Energy dispersive X-ray and electron energy loss spectroscopy analysis indicated the presence of phosphorus both at the MWCNT sidewalls and in the catalyst particles encapsulated inside the MWCNTs. In addition, a comparative investigation for sulfur and phosphorus inclusion to the sidewalls of MWCNTs was carried out using density functional theory calculations. The results of the computational study showed that both phosphorus and sulfur atoms prefer to bind among themselves rather than adsorbing directly on carbon nanotubes (CNT). Furthermore, cluster calculations revealed that phosphorus atoms more likely form carbonaceous clusters which result in a decrease in the number of free carbon atoms that can be used for CNT formation. Therefore, we concluded that MWCNT growth might be hindered (promoted) in a phosphorus (sulfur) rich environment which results in needle like phosphorus containing MWCNTs

Patterned carbon nanotubes as a new three-dimensional scaffold for mesenchymal stem cells

We investigated the cellular adhesive features of mesenchymal stem cells (MSC) on non-coated and collagen coated patterned and vertically aligned carbon nanotube (CNT) structures mimicking the natural extra cellular matrix (ECM). Patterning was achieved using the elasto-capillary induced by water treatment on the CNT arrays. After confirmation with specific markers both at transcript and protein levels, MSCs from different passages were seeded on either collagen coated or non-coated patterned CNTs. Adhesion and growth of MSCs on the patterned CNT arrays were examined using scanning electron microscopy image analysis and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-tetrazolium bromide (MTT) assays. The highest MSC count was observed on the non-coated patterned CNTs at passage zero, while decreasing numbers of MSCs were found at the later passages. Similarly, MTT assay results also revealed a decrease in the viability of the MSCs for the later passages. Overall, the cell count and viability experiments indicated that MSCs were able to better attach to non-coated patterned CNTs compared to those coated with collagen. Therefore, the patterned CNT surfaces can be potentially used as a scaffold mimicking the ECM environment for MSC growth which presents an alternative approach to MSC-based transplantation therapy applications. © 2013 Elsevier B.V

Physical applications of second-order linear differential equations that admit polynomial solutions

Conditions are given for the second-order linear differential equation P3 y" + P2 y'- P1 y = 0 to have polynomial solutions, where Pn is a polynomial of degree n. Several application of these results to Schroedinger's equation are discussed. Conditions under which the confluent, biconfluent, and the general Heun equation yield polynomial solutions are explicitly given. Some new classes of exactly solvable differential equation are also discussed. The results of this work are expressed in such way as to allow direct use, without preliminary analysis.Comment: 13 pages, no figure

Impaired respiratory burst contributes to infections in PKCδ-deficient patients

Patients with autosomal recessive protein kinase C δ (PKCδ) deficiency suffer from childhood-onset autoimmunity, including systemic lupus erythematosus. They also suffer from recurrent infections that overlap with those seen in patients with chronic granulomatous disease (CGD), a disease caused by defects of the phagocyte NADPH oxidase and a lack of reactive oxygen species (ROS) production. We studied an international cohort of 17 PKCδ-deficient patients and found that their EBV-B cells and monocyte-derived phagocytes produced only small amounts of ROS and did not phosphorylate p40phox normally after PMA or opsonized Staphylococcus aureus stimulation. Moreover, the patients' circulating phagocytes displayed abnormally low levels of ROS production and markedly reduced neutrophil extracellular trap formation, altogether suggesting a role for PKCδ in activation of the NADPH oxidase complex. Our findings thus show that patients with PKCδ deficiency have impaired NADPH oxidase activity in various myeloid subsets, which may contribute to their CGD-like infectious phenotype

Diurnal and nocturnal drooling in Parkinson’s disease

Drooling as symptom of Parkinson’s disease (PD) has thus far been poorly defined. This uncertainty is reflected by high variations in published prevalence rates. The aim of this study was to investigate the prevalence of saliva loss versus accumulation of saliva as a possible preliminary stage, and diurnal drooling versus nocturnal drooling. In addition, we evaluated the association between drooling severity and the severity of facial and oral motor disorders. We collected age, disease duration, UPDRS III and Hoehn & Yahr stage from 104 consecutive outpatients with PD. Diurnal and nocturnal drooling was evaluated with a validated questionnaire (ROMP-saliva). A speech pathologist, blinded for drooling severity, rated facial expression, involuntary mouth opening and difficulty with nose breathing and also interviewed patients about sleeping position and nose-breathing during the night. Thirty patients (29%) had no complaints with saliva control (‘non-droolers’), 45 patients (43%) experienced accumulation of saliva or only nocturnal drooling (‘pre-droolers’), and 29 (28%) had diurnal drooling (24 of which also drooled during the night; ‘droolers’). The droolers had longer disease duration (10 vs. 7 years, p = 0.01) and drooling was independently associated with involuntary mouth opening (OR = 2.0; 95% CI 1.02–3.99) and swallowing complaints (OR = 1.2; 95% CI 1.03–1.31). Diurnal drooling—defined as dribbling of saliva while awake—is present in about 28% of PD patients. This is less than usually reported. Diurnal drooling typically appeared later in the disease course. The association with oral motor behavior should encourage the development of behavioral treatment approaches

Biallelic loss-of-function mutation in NIK causes a primary immunodeficiency with multifaceted aberrant lymphoid immunity

Primary immunodeficiency disorders enable identification of genes with crucial roles in the human immune system. Here we study patients suffering from recurrent bacterial, viral and Cryptosporidium infections, and identify a biallelic mutation in the MAP3K14 gene encoding NIK (NF- B-inducing kinase). Loss of kinase activity of mutant NIK, predicted by in silico analysis and confirmed by functional assays, leads to defective activation of both canonical and non-canonical NF- B signalling. Patients with mutated NIK exhibit B-cell lymphopenia, decreased frequencies of class-switched memory B cells and hypogammaglobulinemia due to impaired B-cell survival, and impaired ICOSL expression. Although overall T-cell numbers are normal, both follicular helper and memory T cells are perturbed. Natural killer (NK) cells are decreased and exhibit defective activation, leading to impaired formation of NK-cell immunological synapses. Collectively, our data illustrate the non-redundant role for NIK in human immune responses, demonstrating that loss-of-function mutations in NIK can cause multiple aberrations of lymphoid immunity

Combined immunodeficiency and Epstein-Barr virus-induced B cell malignancy in humans with inherited CD70 deficiency

In this study, we describe four patients from two unrelated families of different ethnicities with a primary immunodeficiency, predominantly manifesting as susceptibility to Epstein-Barr virus (EBV)–related diseases. Three patients presented with EBV-associated Hodgkin’s lymphoma and hypogammaglobulinemia; one also had severe varicella infection. The fourth had viral encephalitis during infancy. Homozygous frameshift or in-frame deletions in CD70 in these patients abolished either CD70 surface expression or binding to its cognate receptor CD27. Blood lymphocyte numbers were normal, but the proportions of memory B cells and EBV-specific effector memory CD8+ T cells were reduced. Furthermore, although T cell proliferation was normal, in vitro–generated EBV-specific cytotoxic T cell activity was reduced because of CD70 deficiency. This reflected impaired activation by, rather than effects during killing of, EBV-transformed B cells. Notably, expression of 2B4 and NKG2D, receptors implicated in controlling EBV infection, on memory CD8+ T cells from CD70-deficient individuals was reduced, consistent with their impaired killing of EBV-infected cells. Thus, autosomal recessive CD70 deficiency is a novel cause of combined immunodeficiency and EBV-associated diseases, reminiscent of inherited CD27 deficiency. Overall, human CD70–CD27 interactions therefore play a nonredundant role in T and B cell–mediated immunity, especially for protection against EBV and humoral immunity

Supportive and symptomatic management of amyotrophic lateral sclerosis

The main aims in the care of individuals with amyotrophic lateral sclerosis (ALS) are to minimize morbidity and maximize quality of life. Although no cure exists for ALS, supportive and symptomatic care provided by a specialist multidisciplinary team can improve survival. The basis for supportive management is shifting from expert consensus guidelines towards an evidence-based approach, which encourages the use of effective treatments and could reduce the risk of harm caused by ineffective or unsafe interventions. For example, respiratory support using noninvasive ventilation has been demonstrated to improve survival and quality of life, whereas evidence supporting other respiratory interventions is insufficient. Increasing evidence implicates a causal role for metabolic dysfunction in ALS, suggesting that optimizing nutrition could improve quality of life and survival. The high incidence of cognitive dysfunction and its impact on prognosis is increasingly recognized, although evidence for effective treatments is lacking. A variety of strategies are used to manage the other physical and psychological symptoms, the majority of which have yet to be thoroughly evaluated. The need for specialist palliative care throughout the disease is increasingly recognized. This Review describes the current approaches to symptomatic and supportive care in ALS and outlines the current guidance and evidence for these strategies