Size-dependent oscillator strength and quantum efficiency of CdSe quantum dots controlled via the local density of states

We study experimentally time-resolved emission of colloidal CdSe quantum dots in an environment with a controlled local density of states (LDOS). The decay rate is measured versus frequency and as a function of distance to a mirror. We observe a linear relation between the decay rate and the LDOS, allowing us to determine the size-dependent quantum efficiency and oscillator strength. We find that the quantum efficiency decreases with increasing emission energy mostly due to an increase in nonradiative decay. We manage to obtain the oscillator strength of the important class of CdSe quantum dots. The oscillator strength varies weakly with frequency in agreement with behavior of quantum dots in the strong confinement limit. Surprisingly, previously calculated tight-binding results differ by a factor of 5 with the measured absolute values. Results from pseudopotential calculations agree well with the measured radiative rates. Our results are relevant for applications of CdSe quantum dots in spontaneous emission control and cavity quantum electrodynamic

Human Milk Oligosaccharide 2′-Fucosyllactose Modulates Local Viral Immune Defense by Supporting the Regulatory Functions of Intestinal Epithelial and Immune Cells

Human milk contains bioactive components that provide protection against viral infections in early life. In particular, intestinal epithelial cells (IEC) have key regulatory roles in the prevention of enteric viral infections. Here we established an in vitro model to study the modulation of host responses against enteric viruses mimicked by poly I:C (pIC). The effects of 2′-fucosyllactose (2′FL), abundantly present in human milk, were studied on IEC and/or innate immune cells, and the subsequent functional response of the adaptive immune cells. IEC were pre-incubated with 2′FL and stimulated with naked or Lyovec™-complexed pIC (LV-pIC). Additionally, monocyte-derived dendritic cells (moDC) alone or in co-culture with IEC were stimulated with LV-pIC. Then, conditioned-moDC were co-cultured with naïve CD4+ T helper (Th)-cells. IEC stimulation with naked or LV-pIC promoted pro-inflammatory IL-8, CCL20, GROα and CXCL10 cytokine secretion. However, only exposure to LV-pIC additionally induced IFNβ, IFNλ1 and CCL5 secretion. Pre-incubation with 2′FL further increased pIC induced CCL20 secretion and LV-pIC induced CXCL10 secretion. LV-pIC-exposed IEC/moDC and moDC cultures showed increased secretion of IL-8, GROα, IFNλ1 and CXCL10, and in the presence of 2′FL galectin-4 and -9 were increased. The LV-pIC-exposed moDC showed a more pronounced secretion of CCL20, CXCL10 and CCL5. The moDC from IEC/moDC cultures did not drive T-cell development in moDC/T-cell cultures, while moDC directly exposed to LV-pIC secreted Th1 driving IL-12p70 and promoted IFNγ secretion by Th-cells. Hereby, a novel intestinal model was established to study mucosal host-defense upon a viral trigger. IEC may support intestinal homeostasis, regulating local viral defense which may be modulated by 2′FL. These results provide insights regarding the protective capacity of human milk components in early life

Laser propulsion of microelectronic components: releasing mechanism investigation

Laser propulsion has gained increasing attention in the recent years. Ultra-high average power laser systems have emerged and found applications in launching satellites to the space. The impulse generated by ablation can also be used to move small parts. This article describes laser-induced releasing of microelectronic components from its carrier material. The releasing mechanisms can be divided in: ablative and thermal releasing, depending from polymers, which are used as the component's carrier material and whether low or high laser fluence is used. The directional variation and speed variations under different operating conditions were studied and presented. Application of this technique as a fast microelectronics components assembly method is demonstrated

A capillary micro-reactor as a tool to study pressurized reactions; The influence of pressure on the stereoselectivity of the diels-alder reaction of 2- and 3-furylmethanol with maleimides

The influence of a pressure of 60 MPa on theconversion and the stereoselectivity of the Diels-Alderreaction of 2- and 3-furylmethanol with methyl-, benzyl-, andphenylmaleimide was studied in a capillary micro-reactor. Inthe case of 2-furylmethanol, a 1.7-fold higher conversion wasobtained at 60 MPa with respect to 0.1 MPa experiments.Pressure positively affects the formation of the exo isomer,whereas in the case of 3-furylmethanol pressure does notaffect the reaction

Enzymes in consumer products. An inventory of non-food products, regulatory frameworks, hazards and considerations for risk assessment

Enzymes are increasingly being added to consumer products such as cleaning products and personal care products. This is done to dissolve dirt or stains, for example. The Netherlands Food and Consumer Product Safety Authority (NVWA) wants to know whether the use of enzymes is safe, especially in new types of products. RIVM has therefore made an overview of the products containing them and which regulatory frameworks apply to them. It was also examined whether it is possible to assess whether the use is safe. The overview makes it clear that there is insufficient information available about the amount of enzymes in certain products and about the amount that is safe for specific enzymes. It is also not clear to what extent consumers are exposed to enzymes. As a result, there is not enough information to assess whether the use of products containing enzymes is safe. This research helps to make recommendations for future evaluation of enzymes in consumer products. The inventory identified 184 cleaning products, 46 personal care products, 12 veterinary hygiene products and 2 pet care products containing enzymes. The products are subject to various regulatory frameworks, such as for personal care products or for cleaning products. The type of enzymes used and the amount were usually not stated on the packaging. In addition, a survey among manufacturers showed that most would not share their product enzyme concentrations. They do expect to use more enzymes in the future. The main health effect that enzymes can cause is respiratory sensitisation. This effect can arise, for example, if consumers are exposed to enzymes through air when using sprays. RIVM conducted this study on behalf of the Netherlands Food and Consumer Product Safety Authority (NVWA). It is a follow-up to the earlier study into microbial cleaning products

Enzymen in consumentenproducten. Een inventarisatie van non-food producten, wetgeving, gevaarseigenschappen en overwegingen voor risicobeoordeling

Enzymes are increasingly being added to consumer products such as cleaning products and personal care products. This is done to dissolve dirt or stains, for example. The Netherlands Food and Consumer Product Safety Authority (NVWA) wants to know whether the use of enzymes is safe, especially in new types of products. RIVM has therefore made an overview of the products containing them and which regulatory frameworks apply to them. It was also examined whether it is possible to assess whether the use is safe. The overview makes it clear that there is insufficient information available about the amount of enzymes in certain products and about the amount that is safe for specific enzymes. It is also not clear to what extent consumers are exposed to enzymes. As a result, there is not enough information to assess whether the use of products containing enzymes is safe. This research helps to make recommendations for future evaluation of enzymes in consumer products. The inventory identified 184 cleaning products, 46 personal care products, 12 veterinary hygiene products and 2 pet care products containing enzymes. The products are subject to various regulatory frameworks, such as for personal care products or for cleaning products. The type of enzymes used and the amount were usually not stated on the packaging. In addition, a survey among manufacturers showed that most would not share their product enzyme concentrations. They do expect to use more enzymes in the future. The main health effect that enzymes can cause is respiratory sensitisation. This effect can arise, for example, if consumers are exposed to enzymes through air when using sprays. RIVM conducted this study on behalf of the Netherlands Food and Consumer Product Safety Authority (NVWA). It is a follow-up to the earlier study into microbial cleaning products.Enzymen worden steeds vaker toegevoegd aan producten voor consumenten, zoals schoonmaakmiddelen en persoonlijke verzorgingsproducten. Dit wordt gedaan om bijvoorbeeld vuil of vlekken op te lossen. De Nederlandse Voedsel- en Warenautoriteit (NVWA(Nederlandse Voedsel- en Warenautoriteit)) wil weten of het gebruik van enzymen veilig is, vooral in nieuwe soorten producten. Het RIVM heeft daarom een overzicht gemaakt van de producten waar ze in zitten en welke wetten daarvoor gelden. Ook is gekeken of het mogelijk is om te bepalen of het gebruik veilig is. Het overzicht maakt duidelijk dat er onvoldoende informatie beschikbaar is over de hoeveelheid enzymen in bepaalde producten en welke hoeveelheid voor specifieke enzymen veilig is. Ook is niet duidelijk in welke mate consumenten aan enzymen blootstaan. Daardoor is er ook niet genoeg informatie om te kunnen beoordelen of het gebruik van producten met enzymen veilig is. Dit onderzoek helpt om aanbevelingen te doen voor een toekomstige evaluatie van enzymen in producten voor consumenten. In ons marktonderzoek zijn er 184 schoonmaakproducten met enzymen gevonden, 46 producten voor persoonlijke verzorging, 12 veterinaire hygieneproducten en 2 huisdierverzorgingsproducten. De producten vallen onder verschillende wetten, zoals voor persoonlijke verzorgingsproducten of voor schoonmaakmiddelen. Het gebruikte type enzymen en de hoeveelheid stonden meestal niet op de verpakking vermeld. Ook bleek uit een enquete onder producenten dat de meeste hun enzymenconcentraties niet konden delen. Wel verwachten ze in de toekomst meer enzymen te gaan gebruiken. Het belangrijkste effect op de gezondheid dat enzymen kunnen veroorzaken is sensibilisatie van de luchtwegen. Dit effect kan bijvoorbeeld ontstaan als consumenten bij het gebruik van sprays via de lucht aan enzymen worden blootgesteld. Het RIVM heeft dit onderzoek gedaan in opdracht van de NVWA. Het is een vervolg op de eerdere studie naar microbiele reinigingsmiddelen