We have used computer simulations to reveal how colloidal crystals may be assembled by engineering the shape and charge of polymeric additives, which act as structure-directing agents (SDAs). Using these agents, only a single desired polymorph may be obtained from a crystallizing mixture of colloids and polymers, which would otherwise result in a defective crystal in the absence of these agents. Building on previous work, which demonstrated this principle in the limiting case of high-density, close-packed crystals, we have now achieved this control over low-density, open crystals, which have broad utility especially in optical applications. These results reveal the general utility of the SDA paradigm in assembling tailored colloidal crystals, which represents a new design method that does not rely on any modification of the colloids themselves.
In 1928 Alexander Fleming made his groundbreaking discovery of penicillin. Antibiotics have since been our most powerful weapons against bacterial infections: The average life expectancy significantly increased and previously risky surgeries became standard medical interventions that revolutionized medicine. Nowadays resistance development casts its shadow on the once shiny drugs that saved millions of lives. Today more than 90% of pathogenicStaphylococcus aureus are resistant against penicillin. The full depth of the problem has long been obscured by the seemingly unlimited number of antibiotics. However, in the last years the number of new antibiotics has drastically decreased while the development and spread of resistances has dramatically increased.
We have fabricated an instrument designed to couple both the imaging process in scanning electron microscopy and the precise positioning of scanning probe microscopy. This microscope is comprised of a metallic field emitter that generates an electron beam with a minimal impingement diameter of approximately one nanometer. In particular, the sensitivity of the field emission current to local topographic variations on the specimen surface enables the microscope to achieve atomic vertical resolution.
We report on an accurate computational method to calculate hydration free energies - a key property in predicting the pharmacokinetics of novel pharmaceutical molecules.
Lipids serve important functions as membrane constituents and also as energy storing molecules. Beside these functions certain lipid species have been recognized as signaling molecules that regulate a multitude of cellular responses, including cell growth and death, and also key aspects of important diseases. Bioactive lipids were described that are controlling inflammatory processes in one or the other way [1]. Paradigmatically, this review will highlight the present knowledge about bioactive lipids that modulate inflammatory reactions and, consequently, represent potential targets for therapeutic intervention.
The study of nanometer sized semiconductor crystallites, also known as quantum dots (QDs), has seen rapid advancements in recent years in scientific disciplines ranging from chemistry, physics, biology, materials science, and engineering. QD materials of CdSe, ZnSe, InP, as well as many others, can be prepared in the size range of 1-10 nm producing uniform, nearly monodisperse materials that are typically coated with organic molecules [1-3]. The strength of charge carrier confinement, which dictates the size-dependent properties, in these QDs depends on the nature of the material and can be correlated to the Bohr radius for the system of interest. For instance, the Bohr radius for CdSe is {approx} 5 nm, while in the more covalent structure of InP, the Bohr radius approaches {approx} 10 nm. The study of CdSe QDs has been particularly extensive during the last decade because they exhibit unique and tunable optical properties and are readily synthesized with high-crystallinity and narrow size dispersions. Although the core electronic properties of CdSe are explained in terms of the quantum confinement model, experimental efforts to elucidate the surface structure of these materials have been limited. Typically, colloidal CdSe QDs are coated with an organic surfactant, which typically consists ofmore » an organo-phosphine, -thiol, or -amine, that has the function of energetically relaxing defect states via coordination to partially coordinated surface atoms. The organic surfactant also acts to enhance carrier confinement and prevent agglomeration of the particles. Chemically, it has been shown that the bonding of the surfactant to the CdSe QD occurs through Cd atoms resulting cleavage of the Se atoms and formation of a Cd-rich (i.e. non-stoichiometric) particle [5].« less
This article describes a straightforward ion chromatographic method that uses isocratic elution and pulsed amperometric detection (PAD) to sensitively determine water-soluble polyols and sugar alcohols as well as mono-, diand oligosaccharides in essential and non-essential foodstuffs. While carbohydrate determination of most foodstuffs requires only minimal sample pretreatment such as dilution and filtration, samples with interfering matrices such as protein-containing dairy products have to be dialyzed prior to injection.
In the expanding field of nutritional metabolomics the use of optimized and robust strategies are essential to find meaningful and significant results. Data from nutritional studies can be extremely large, multidimensional and complex. Moreover the data may hide just a subtle biological variation due to the nutritional treatment, and the effect may be highly variable across individuals. Usually the treatment effects are much smaller than the biological variations between individuals. A properly chosen experimental design and a well-adapted data analysis strategy are therefore essential to ensure that the intended information in the data can be assessed and that the biological question of interest can be answered.
Published and anecdotal evidence suggests that bioassay results may be compromised by pharmacologically active compounds leaching from plastic ware into buffers and solvents. False positives, false negatives, lost productivity and unnecessary expense can be minimized if researchers follow some simple guidelines.
In the 1950s, the Indian botanist Singh observed that crop production was considerably increased by a specific sound frequency. After playing traditional Indian raga in the presence of Asian aquatic plants, he examined the plants under a microscope and observed protoplasmic streaming that was the same as if the plants were illuminated by the sun. This observation suggested that music stimulated the movement of protoplasm in plant cells [8].
