Abundances and search for vertical stratification in the atmospheres of four HgMn stars

Using high resolution, high-S/N archival UVES spectra, we have performed a detailed spectroscopic analysis of 4 chemically peculiar HgMn stars (HD 71066, HD 175640, HD 178065 and HD 221507). Using spectrum synthesis, mean photospheric chemical abundances are derived for 22 ions of 16 elements. We find good agreement between our derived abundances and those published previously by other authors. For the 5 elements that present a sufficient number of suitable lines, we have attempted to detect vertical chemical stratification by analyzing the dependence of derived abundance as a function of optical depth. For most elements and most stars we find no evidence of chemical stratification with typical 3\sigma upper limits of \Delta\log N_elem/N_tot~0.1-0.2 dex per unit optical depth. However, for Mn in the atmosphere of HD 178065 we find convincing evidence of stratification. Modeling of the line profiles using a two-step model for the abundance of Mn yields a local abundance varying approximately linearly by ~0.7 dex through the optical depth range log \tau_5000=-3.6 to -2.8.Comment: 11 figures, 9 tables, table 6-9 (online material), accepted by MNRA

Pharmacokinetics of PEGylated Gold Nanoparticles: In Vitro—In Vivo Correlation

Data suitable for assembling a physiologically-based pharmacokinetic (PBPK) model for nanoparticles (NPs) remain relatively scarce. Therefore, there is a trend in extrapolating the results of in vitro and in silico studies to in vivo nanoparticle hazard and risk assessment. To evaluate the reliability of such approach, a pharmacokinetic study was performed using the same polyethylene glycol-coated gold nanoparticles (PEG-AuNPs) in vitro and in vivo. As in vitro models, human cell lines TH1, A549, Hep G2, and 16HBE were employed. The in vivo PEG-AuNP biodistribution was assessed in rats. The internalization and exclusion of PEG-AuNPs in vitro were modeled as first-order rate processes with the partition coefficient describing the equilibrium distribution. The pharmacokinetic parameters were obtained by fitting the model to the in vitro data and subsequently used for PBPK simulation in vivo. Notable differences were observed in the internalized amount of Au in individual cell lines compared to the corresponding tissues in vivo, with the highest found for renal TH1 cells and kidneys. The main reason for these discrepancies is the absence of natural barriers in the in vitro conditions. Therefore, caution should be exercised when extrapolating in vitro data to predict the in vivo NP burden and response to exposure

A Fiber-Optic Fluorescence Microscope Using a Consumer-Grade Digital Camera for In Vivo Cellular Imaging

BACKGROUND: Early detection is an essential component of cancer management. Unfortunately, visual examination can often be unreliable, and many settings lack the financial capital and infrastructure to operate PET, CT, and MRI systems. Moreover, the infrastructure and expense associated with surgical biopsy and microscopy are a challenge to establishing cancer screening/early detection programs in low-resource settings. Improvements in performance and declining costs have led to the availability of optoelectronic components, which can be used to develop low-cost diagnostic imaging devices for use at the point-of-care. Here, we demonstrate a fiber-optic fluorescence microscope using a consumer-grade camera for in vivo cellular imaging. METHODS: The fiber-optic fluorescence microscope includes an LED light, an objective lens, a fiber-optic bundle, and a consumer-grade digital camera. The system was used to image an oral cancer cell line labeled with 0.01% proflavine. A human tissue specimen was imaged following surgical resection, enabling dysplastic and cancerous regions to be evaluated. The oral mucosa of a healthy human subject was imaged in vivo, following topical application of 0.01% proflavine. FINDINGS: The fiber-optic microscope resolved individual nuclei in all specimens and tissues imaged. This capability allowed qualitative and quantitative differences between normal and precancerous or cancerous tissues to be identified. The optical efficiency of the system permitted imaging of the human oral mucosa in real time. CONCLUSION: Our results indicate this device as a useful tool to assist in the identification of early neoplastic changes in epithelial tissues. This portable, inexpensive unit may be particularly appropriate for use at the point-of-care in low-resource settings

Microfluidic In Vitro Platform for (Nano)Safety and (Nano)Drug Efficiency Screening

Microfluidic technology is a valuable tool for realizing more in vitro models capturing cellular and organ level responses for rapid and animal‐free risk assessment of new chemicals and drugs. Microfluidic cell‐based devices allow high‐throughput screening and flexible automation while lowering costs and reagent consumption due to their miniaturization. There is a growing need for faster and animal‐free approaches for drug development and safety assessment of chemicals (Registration, Evaluation, Authorisation and Restriction of Chemical Substances, REACH). The work presented describes a microfluidic platform for in vivo‐like in vitro cell cultivation. It is equipped with a wafer‐based silicon chip including integrated electrodes and a microcavity. A proof‐of‐concept using different relevant cell models shows its suitability for label‐free assessment of cytotoxic effects. A miniaturized microscope within each module monitors cell morphology and proliferation. Electrodes integrated in the microfluidic channels allow the noninvasive monitoring of barrier integrity followed by a label‐free assessment of cytotoxic effects. Each microfluidic cell cultivation module can be operated individually or be interconnected in a flexible way. The interconnection of the different modules aims at simulation of the whole‐body exposure and response and can contribute to the replacement of animal testing in risk assessment studies in compliance with the 3Rs to replace, reduce, and refine animal experiments

Šesták–Berggren equation: now questioned but formerly celebrated—what is right

Některé současné publikace zpochybňují originalitu Šestákovy-Berggrenovy (Š-B) rovnice, přestože je tato rovnice citována již v 785 případech. SB rovnice je důkladně analyzována a porovnána s jednotlivými geometrickými modely a jinými přístupy. Š-B rovnice je dále studována z hlediska obecné logistické rovnice, díky čemuž je zřejmá odlišná filozofická strategie mezi tradiční geometrickou JMAYK teorií a neslučitelnou kinetikou vyjádřenou dvou parametrickou SB rovnicí. Historie logistického modelování zahrnuje také využití ogivní sigmoidy. Široká aplikovatelnost této rovnice je doložena více než osmdesáti zdroji.Some recent papers doubt the originality of Sˇesta´k–Berggren equation even though it received until today as many as 785 citation responses. The SB equation is thus thoroughly analyzed and weighed against individual geometrical models and rivalry proposals. Moreover, the SB equation is examined in terms of general logistic equation showing divergent philosophical strategy between the traditional geometrical JMAYK versus the incommensurable kinetics through two parametric SB. The history of logistic modeling is revealed including ogive sigmoidal functions. The widespread application is noticed covering as many as eighty references