In this article we present the development of a set of opto-mechanical components (a kinematic mount, a translation stage and an integrating sphere) that can be easily built using a 3D printer based ...on Fused Filament Fabrication (FFF) and parts that can be found in any hardware store. Here we provide a brief description of the 3D models used and some details on the fabrication process. Moreover, with the help of three simple experimental setups, we evaluate the performance of the opto-mechanical components developed by doing a quantitative comparison with its commercial counterparts. Our results indicate that the components fabricated are highly customizable, low-cost, require a short time to be fabricated and surprisingly, offer a performance that compares favorably with respect to low-end commercial alternatives.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A detailed understanding of the properties of electronic excited states and the reaction mechanisms that molecules undergo after light irradiation is a fundamental ingredient for following ...light‐driven natural processes and for designing novel photonic materials. The aim of this review is to present an overview of the ab initio quantum chemical and time‐dependent density functional theory methods that can be used to model spectroscopy and photochemistry in molecular systems. The applicability and limitations of the different methods as well as the main frontiers are discussed. To illustrate the progress achieved by excited‐state chemistry in the recent years as well as the main challenges facing computational chemistry, three main applications that reflect the authors’ experience are addressed: the UV/Vis spectroscopy of organic molecules, the assignment of absorption and emission bands of organometallic complexes, and finally, the obtainment of non‐adiabatic photoinduced pathways mediated by conical intersections. In the latter case, special emphasis is put on the photochemistry of DNA. These applications show that the description of electronically excited states is a rewarding but challenging area of research.
Are we there yet? The progress and challenges in the calculation of electronic excited states is reviewed. The state‐of‐the‐art, advantages and disadvantages of methods based on monoconfigurational, multiconfigurational, and density functional theory calculations is discussed in the light of different applications (see picture).
The correlation between mRNA and protein abundances in the cell has been reported to be notoriously poor. Recent technological advances in the quantitative analysis of mRNA and protein species in ...complex samples allow the detailed analysis of this pathway at the center of biological systems. We give an overview of available methods for the identification and quantification of free and ribosome-bound mRNA, protein abundances and individual protein turnover rates. We review available literature on the correlation of mRNA and protein abundances and discuss biological and technical parameters influencing the correlation of these central biological molecules.
We report the formation of cylindrical micelles, sheet-like micelles, tubular micelles, as well as polymer vesicles by a new series of amphiphilic linear−dendritic block-copolymers (BCs). The BCs, ...noted as PEGm-AZOn , are composed of poly(ethylene glycol) (PEG) chains of different molecular weights as hydrophilic blocks and the first four generations of azobenzene-containing dendrons based on 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) as hydrophobic blocks (m represents the degree of polymerization of PEG, and n is the number of azobenzene units at the periphery of dendron). The polymeric aggregates were formed by adding water to solutions of the BCs in dioxane. The micellar dispersions in water were finally obtained by removing dioxane via dialysis against water. The morphology of the micellar self-assemblies was studied by transmission electron microscopy (TEM), cryo-electron microscopy (cryo-TEM), and atomic force microscopy (AFM). A generation-dependent aggregation behavior was found for the series of BCs PEG45-AZOn . Core−shell structured nanofibers with an inner diameter of 8 nm were observed for the copolymer PEG45-AZO2 (hydrophilic/hydrophobic weight ratio equal to 67/33). Lyotropic liquid crystalline behavior was detected for the aqueous solution of the nanofibers. The coexistence of sheet-like aggregates and tubular micelles was detected for the copolymer PEG45-AZO8 in which the number of cyanoazobenzene units is increased to 8 (hydrophilic/hydrophobic weight ratio equal to 33/67). The tubular micelles could be intermediates in the sheet-like aggregate-to-vesicle transition. Polymer vesicles (polymersomes) with a diameter in the range 300−800 nm were observed for the copolymer PEG45-AZO16 (hydrophilic/hydrophobic weight ratio equal to 20/80). The membrane of the sheet-like aggregates, tubular micelles, and polymersomes was shown to have a bilayer structure, as revealed by cryo-TEM. UV illumination of the aqueous polymersome dispersion induced the formation of wrinkles in the vesicle membrane, thus showing that this type of polymeric aggregate is photoresponsive.
We report on the synthesis and characterization of a series of amphiphilic linear–dendritic block copolymers (LDBCs) as well as their self-assembly in water. The LDBCs are composed of a 2000 g/mol ...poly(ethylene glycol) (PEG) linear segment linked to the fourth generation of a 2,2-di(hydroxymethyl)propionic acid (bis-MPA)-based dendron containing 4-isobutyloxyazobenzene units (AZO) and hydrocarbon chains (C18) randomly connected to the periphery of the dendron. TEM and cryo-TEM images show that all the LDBCs form stable vesicles in water. The influence of AZO/C18 ratio in the photoresponse of the self-assemblies has been assessed as well as the encapsulation of both hydrophilic (Rhodamine B) and hydrophobic (Nile Red) fluorescent probes and the use of light as an external stimulus to trigger the release of the probes. The results show that by diluting the azobenzene content at the periphery of the dendron, the trans-to-cis photoisomerization rate can be substantially accelerated and the light-induced release activity can be tuned being the vesicles with a 50/50 AZO/C18 ratio the ones suffering the most significant changes upon irradiation.
While a plethora of protocols exist for the synthesis of sub-10-nm gold nanoparticles (AuNPs), independent control over the size and surface composition remains restricted. This poses a particular ...challenge for systematic studies of AuNP structure–function relationships and the optimization of crucial design parameters. To this end, we report on a modular two-step approach based on the synthesis of AuNPs in oleylamine (OAm) followed by subsequent functionalization with thiol ligands and mixtures thereof. The synthesis of OAm-capped AuNPs enables fine-tuning of the core size in the range of 2–7 nm by varying the reaction temperature. The subsequent thiol-for-OAm ligand exchange allows a reliable generation of thiol-capped AuNPs with target surface functionality. The compatibility of this approach with a vast library of thiol ligands provides detailed control of the mixed ligand composition and solubility in a wide range of solvents ranging from water to hexane. This decoupled control over the AuNP core and ligand shell provides a powerful toolbox for the methodical screening of optimal design parameters and facile preparation of AuNPs with target properties.
This tutorial review provides insight into helical columnar assemblies based on thermotropic as well as lyotropic liquid crystals on the basis of the structural characteristics that promote ...hierarchical self-organization. The structural features of molecular materials that can present helical organizations imply the action of different driving forces that include pi-interactions, hydrogen bonding or metal-coordination. In addition, columnar liquid crystals offer the possibility of combining these interactions towards the control of the geometry and orientation of the supramolecular organization leading to well-defined helical columnar assemblies.
Natural selection shapes cancer genomes. Previous studies used signatures of positive selection to identify genes driving malignant transformation. However, the contribution of negative selection ...against somatic mutations that affect essential tumor functions or specific domains remains a controversial topic.
Here, we analyze 7546 individual exomes from 26 tumor types from TCGA data to explore the portion of the cancer exome under negative selection. Although we find most of the genes neutrally evolving in a pan-cancer framework, we identify essential cancer genes and immune-exposed protein regions under significant negative selection. Moreover, our simulations suggest that the amount of negative selection is underestimated. We therefore choose an empirical approach to identify genes, functions, and protein regions under negative selection. We find that expression and mutation status of negatively selected genes is indicative of patient survival. Processes that are most strongly conserved are those that play fundamental cellular roles such as protein synthesis, glucose metabolism, and molecular transport. Intriguingly, we observe strong signals of selection in the immunopeptidome and proteins controlling peptide exposition, highlighting the importance of immune surveillance evasion. Additionally, tumor type-specific immune activity correlates with the strength of negative selection on human epitopes.
In summary, our results show that negative selection is a hallmark of cell essentiality and immune response in cancer. The functional domains identified could be exploited therapeutically, ultimately allowing for the development of novel cancer treatments.
The morphology of bulk heterojunction organic photovoltaic cells controls many of the performance characteristics of devices. However, measuring this morphology is challenging because of the small ...length-scales and low contrast between organic materials. Here we use nanoscale photocurrent mapping, ultrafast fluorescence and exciton diffusion to observe the detailed morphology of a high-performance blend of PTB7:PC71BM. We show that optimized blends consist of elongated fullerene-rich and polymer-rich fibre-like domains, which are 10-50 nm wide and 200-400 nm long. These elongated domains provide a concentration gradient for directional charge diffusion that helps in the extraction of charge pairs with 80% efficiency. In contrast, blends with agglomerated fullerene domains show a much lower efficiency of charge extraction of ~45%, which is attributed to poor electron and hole transport. Our results show that the formation of narrow and elongated domains is desirable for efficient bulk heterojunction solar cells.
We have successfully grown ultrasmall cobalt nanostructures (lateral size below 30 nm) by optimization of the growth conditions using focused electron-beam-induced deposition techniques. This ...direct-write nanolithography technique is thus shown to produce unprecedented resolution in the growth of magnetic nanostructures. The challenging magnetic characterization of such small structures is here carried out by means of electron holography techniques. Apart from growing ultranarrow nanowires, very small Hall sensors have been created and their large response has been unveiled.
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