Photophysics of PbS Quantum Dot Films Capped with Arsenic Sulfide Ligands

PbS quantum dots (QDs) of different sizes capped with short (NH₄)₃AsS₃ inorganic ligands are produced via ligand exchange processes from oleate‐capped PbS QDs. The solid‐state photophysical properties of the control organic‐capped and the inorganic‐ligand‐capped QDs are investigated to determine their potential for optoelectronic applications. Ultrafast transient transmission shows that in the oleate‐capped QDs, carrier recombination at sub‐nanosecond scales occurs via Auger recombination, traps, and surface states. At longer times, intense signals associated with radiative recombination are obtained. After ligand exchange, the QDs become decorated with (NH₄)₃AsS₃ complexes and relaxation is dominated by efficient carrier transfer to the ligand states on timescales as fast as ≈2 ps, which competes with carrier thermalization to the QD band edge states. Recombination channels present in the oleate‐capped QDs, such as radiative and Auger recombination, appear quenched in the inorganic‐capped QDs. Evidence of efficient carrier trapping at shallow ligand states, which appears more intense under excitation above the (NH₄)₃AsS₃ gap, is provided. A detailed band diagram of the various relaxation and recombination processes is proposed that comprehensively describes the photophysics of the QD systems studied.     

Serum‐free spheroid suspension culture maintains mesenchymal stem cell proliferation and differentiation potential

There have been many clinical trials recently using ex vivo‐expanded human mesenchymal stem cells (MSCs) to treat several disease states such as graft‐versus‐host disease, acute myocardial infarction, Crohn's disease, and multiple sclerosis. The use of MSCs for therapy is expected to become more prevalent as clinical progress is demonstrated. However, the conventional 2‐dimensional (2D) culture of MSCs is laborious and limited in scale potential. The large dosage requirement for many of the MSC‐based indications further exacerbates this manufacturing challenge. In contrast, expanding MSCs as spheroids does not require a cell attachment surface and is amenable to large‐scale suspension cell culture techniques, such as stirred‐tank bioreactors. In the present study, we developed and optimized serum‐free media for culturing MSC spheroids. We used Design of Experiment (DoE)‐based strategies to systematically evaluate media mixtures and a panel of different components for effects on cell proliferation. The optimization yielded two prototype serum‐free media that enabled MSCs to form aggregates and proliferate in both static and dynamic cultures. MSCs from spheroid cultures exhibited the expected immunophenotype (CD73, CD90, and CD105) and demonstrated similar or enhanced differentiation potential toward all three lineages (osteogenic, chondrogenic, adipogenic) as compared with serum‐containing adherent MSC cultures. Our results suggest that serum‐free media for MSC spheroids may pave the way for scale‐up production of MSCs in clinically relevant manufacturing platforms such as stirred tank bioreactors. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:974–983, 2014     

Psychosocial distress and functioning of Greek youth with cystic fibrosis: a cross-sectional study

Background

To assess psychosocial functioning and distress of children and adolescents with cystic fibrosis compared to healthy controls.

Methods

Thirty-six patients with cystic fibrosis aged 8–18 years (24 boys, mean age?±?SD: 11.5?±?2.6 years) and 31 sex- and age-matched healthy control subjects (18 boys, mean age?±?SD: 12?±?2.5 years) were enrolled in the study. In order to assess the self-esteem, social adjustment, and family functioning of these young people, the Culture-free Self-esteem Inventory, the Social Adjustment Scale–Self-Report, and the Family Assessment Device were administered. Emotional/ behavioral problems were assessed through the Youth Self Report and the Child Behavior Checklist given to both the subjects and their parents.

Results

No significant differences were found for self-esteem between the two study groups. Regarding social adjustment, children with cystic fibrosis reported significantly worse friendship and overall adjustment (P?<?0.05). Moreover, no difference was found in the levels of family functioning between the two groups. No significant differences between the groups were found in emotional/ behavioral problems from the self-reports. On the contrary, parents of children with cystic fibrosis reported significantly higher levels of withdrawal/ depression, thought problems, and delinquent behavior (P?≤?0.01) as compared to controls.

Conclusions

Children and adolescents with cystic fibrosis appear to be a psychosocially vulnerable group. A biopsychosocial approach should emphasize the assessment and treatment of the psychosocial distress of these patients alongside multiple somatic treatments.

     

The EICAT+ framework enables classification of positive impacts of alien taxa on native biodiversity

Species introduced through human-related activities beyond their native range, termed alien species, have various impacts worldwide. The IUCN Environmental Impact Classification for Alien Taxa (EICAT) is a global standard to assess negative impacts of alien species on native biodiversity. Alien species can also positively affect biodiversity (for instance, through food and habitat provisioning or dispersal facilitation) but there is currently no standardized and evidence-based system to classify positive impacts. We fill this gap by proposing EICAT+, which uses 5 semiquantitative scenarios to categorize the magnitude of positive impacts, and describes underlying mechanisms. EICAT+ can be applied to all alien taxa at different spatial and organizational scales. The application of EICAT+ expands our understanding of the consequences of biological invasions and can inform conservation decisions.

Various schemes assess negative impacts of alien species on native biodiversity, but alien species can also positively affect biodiversity. This Consensus View proposes EICAT+, a scheme which uses five semi-quantitative scenarios to categorise positive impacts, describes underlying mechanisms, and can be applied to all alien taxa and across various invasion contexts.     

Smooth ROC curves and surfaces for markers subject to a limit of detection using monotone natural cubic splines

The use of ROC curves in evaluating a continuous or ordinal biomarker for the discrimination of two populations is commonplace. However, in many settings, marker measurements above or below a certain value cannot be obtained. In this paper, we study the construction of a smooth ROC curve (or surface in the case of three populations) when there is a lower or upper limit of detection. We propose the use of spline models that incorporate monotonicity constraints for the cumulative hazard function of the marker distribution. The proposed technique is computationally stable and simulation results showed a satisfactory performance. Other observed covariates can be also accommodated by this spline‐based approach.     

The Influence of Naringin or Hesperidin Dietary Supplementation on Broiler Meat Quality and Oxidative Stability

An experiment was conducted to examine the effects of supplementing broiler feed with hesperidin or naringin, on growth performance, carcass characteristics, breast meat quality and the oxidative stability of breast and thigh meat. Two hundred and forty 1-day-old Ross 308 broiler chickens were randomly assigned to 6 groups. One of the groups served as a control (C) and was given commercial basal diets, whereas the other five groups were given the same diets further supplemented with naringin at 0.75 g/kg (N1), naringin at 1.5 g/kg (N2), hesperidin at 0.75 g/kg (E1), hesperidin at 1.5 g/kg (E2) and a-tocopheryl acetate at 0.2 g/kg (E). At 42 days of age, 10 chickens per treatment group were slaughtered for meat quality and oxidative stability assessment. No significant differences were observed among groups in final body weight, carcass weight and internal organs weights (P>0.05) apart from liver that decreased linearly with increased levels of naringin (P-linear<0.05). Regarding the breast meat quality parameters, only redness (a*) value was higher in E1 and N1 group compared to VE group (P<0.05), while all the others i.e. shear values (N/mm²), pH₂₄, cooking loss (%) and L* and b* color parameters were not significantly different among groups (P>0.05). Measurement of lipid oxidation values showed that after hesperidin and naringin dietary supplementation, malondialdehyde values decreased in tissue samples in a dose depended manner (P-linear<0.05). In conclusion, hesperidin and naringin, positively influence meat antioxidative properties without negative implications on growth performance and meat quality characteristics in poultry, thus appearing as important additives for both the consumer and the industry.     

Stress-mediated progression of solid tumors: effect of mechanical stress on tissue oxygenation,cancer cell proliferation,and drug delivery

Oxygen supply plays a central role in cancer cell proliferation. While vascular density increases at the early stages of carcinogenesis, mechanical solid stresses developed during growth compress tumor blood vessels and, thus, drastically reduce not only the supply of oxygen, but also the delivery of drugs at inner tumor regions. Among other effects, hypoxia and reduced drug delivery compromise the efficacy of radiation and chemo/nanotherapy, respectively. In the present study, we developed a mathematical model of tumor growth to investigate the interconnections among tumor oxygenation that supports cancer cell proliferation, the heterogeneous accumulation of mechanical stresses owing to tumor growth, the non-uniform compression of intratumoral blood vessels due to the mechanical stresses, and the insufficient delivery of oxygen and therapeutic agents because of vessel compression. We found that the high vascular density and increased cancer cell proliferation often observed in the periphery compared to the interior of a tumor can be attributed to heterogeneous solid stress accumulation. Highly vascularized peripheral regions are also associated with greater oxygenation compared with the compressed, less vascularized inner regions. We also modeled the delivery of drugs of two distinct sizes, namely chemotherapy and nanomedicine. Model predictions suggest that drug delivery is affected negatively by vessel compression independently of the size of the therapeutic agent. Finally, we demonstrated the applicability of our model to actual geometries, employing a breast tumor model derived from MR images.     

Curriculum for education and training of Medical Physicists in Nuclear Medicine: Recommendations from the EANM Physics Committee,the EANM Dosimetry Committee and EFOMP

PurposeTo provide a guideline curriculum covering theoretical and practical aspects of education and training for Medical Physicists in Nuclear Medicine within Europe.Material and methodsNational training programmes of Medical Physics, Radiation Physics and Nuclear Medicine physics from a range of European countries and from North America were reviewed and elements of best practice identified. An independent panel of experts was used to achieve consensus regarding the content of the curriculum.ResultsGuidelines have been developed for the specialist theoretical knowledge and practical experience required to practice as a Medical Physicist in Nuclear Medicine in Europe. It is assumed that the precondition for the beginning of the training is a good initial degree in Medical Physics at master level (or equivalent). The Learning Outcomes are categorised using the Knowledge, Skill and Competence approach along the lines recommended by the European Qualifications Framework. The minimum level expected in each topic in the theoretical knowledge and practical experience sections is intended to bring trainees up to the requirements expected of a Medical Physicist entering the field of Nuclear Medicine.ConclusionsThis new joint EANM/EFOMP European guideline curriculum is a further step to harmonise specialist training of Medical Physicists in Nuclear Medicine within Europe. It provides a common framework for national Medical Physics societies to develop or benchmark their own curricula. The responsibility for the implementation and accreditation of these standards and guidelines resides within national training and regulatory bodies.     

Rapid clinical‐scale propagation of mesenchymal stem cells using cultures initiated with immunoselected bone marrow CD105+ cells

Current clinical protocols used for isolation and purification of mesenchymal stem cells (MSC) are based on long-term cultures starting with bone marrow (BM) mononuclear cells. Using a commercially available immunoselection kit for enrichment of MSC, we investigated whether culture of enriched BM-CD105⁺ cells could provide an adequate number of pure MSC in a short time for clinical use in the context of graft versus host disease and graft failure/rejection. We isolated a mean of 5.4 × 10⁵ ± 0.9 × 10⁵ CD105⁺ cells from 10 small volume (10–25 ml) BM samples achieving an enrichment >100-fold in MSC. Seeding 2 × 10³ immunoselected cells/cm² we were able to produce 2.5 × 10⁸ ± 0.7 × 10⁸ MSC from cultures with autologous serum enriched medium within 3 weeks. Neither haematopoietic nor endothelial cells were detectable even in the primary culture cell product. Expanded cells fulfilled both phenotypic and functional current criteria for MSC; they were CD29⁺, CD90⁺, CD73⁺, CD105⁺, CD45⁻; they suppressed allogeneic T-cell reaction in mixed lymphocyte cultures and retained in vitro differentiation potential. Moreover, comparative genomic hybridization analysis revealed chromosomal stability of the cultured MSC. Our data indicate that adequate numbers of pure MSC suitable for clinical applications can be generated within a short time using enriched BM-CD105⁺ cells.