Tunable biohybrid hydrogels from coacervation of hyaluronic acid and PEO‐based block copolymers

Accurately tuning the macroscopic properties of biopolymer‐based hydrogels remains challenging due to the ill‐defined molecular architecture of the natural building blocks. Here, we report a biohybrid coacervate hydrogel, combining the biocompatibility and biodegradability of naturally occurring hyaluronic acid (HA) with the tunability of a synthetic polyethylene oxide (PEO) ‐based ABA‐triblock copolymer. Coacervation of the cationic ammonium or guanidinium‐functionalized copolymer A‐blocks with the anionic HA leads to hydrogel formation. Both mechanical properties and water content of the self‐healing hydrogels can be controlled independently by altering the copolymer structure. By controlling the strength of the interaction between the polymer network and small‐molecule cargo, both release rate and maximum release are controlled. Finally, we show that coacervation of HA and the triblock copolymer leads to increased biostability upon exposure to hyaluronidase. We envision that noncovalent crosslinking of HA hydrogels through coacervation is an attractive strategy for the facile synthesis of tunable hydrogels for biomedical applications

Survei Tingkat Kepentingan Dan Penerapan Sumber Dan Siklus Material Dari Greenship Rating Tools Pada Proyek Konstruksi

Indonesia merupakan salah satu negara yang telah menerapkan konsep green building yang ditandai dengan diterbitkannya Greenship rating tools oleh Green Building Council Indonesia. Greenship rating tools menilai suatu bangunan berdasarkan 6 aspek, yang salah satunya adalah sumber dan siklus material yang berkaitan erat dengan proyek konstruksi. Penelitian ini membahas bagaimana tanggapan pelaku konstruksi terhadap tingkat kepentingan dan penerapan dari poin sumber dan siklus material. Penyebaran kuesioner dilakukan pada pelaku konstruksi dengan jumlah kuesioner kembali sebanyak 53 responden (38 kontraktor, 6 konsultan, dan 9 developer). Metode pengolahan data dilakukan dengan menggunakan analisa mean, uji Anova dan Importance-Performance Analysis dari data yang berasal dari kuesioner. Hasil penelitian menunjukan responden beranggapan bahwa poin sumber dan siklus material adalah penting, namun masih jarang penerapannya. Beberapa variabel yang menunjukkan hasil di bawah 2,50 ialah “Material Hasil Daur Ulang”, “Material Sumber Daya Terbarukan”, dan “Material Prafabrikasi”. Selain itu, ditemukan juga adanya perbedaan tingkat kepentingan dan penerapan antara beberapa variabel sumber dan siklus material

Estimating Kinetic Parameters for the Spontaneous Polymerization of Glycidol at Elevated Temperatures

The ring-opening polymerization of glycidol at elevated temperatures is investigated. To improve the synthesis of dendritic polyether polyols, experiments are carried out without initiator to identify the influence of thermal side reactions. This results in a step-growth polymerization caused by the spontaneous combination of monomers. Kinetic parameters of the side reactions are estimated by fitting simulated number- and weight-average molecular weights to the experimental values measured at different reaction times during the polymerization. The reactions are conducted at three different temperatures of 90, 105, and 120 8C. It is shown that thermal side reactions lead to high dispersities of the final product and are highly sensitive to the reactor operating temperature

Attosecond double-slit experiment

A new scheme for a double-slit experiment in the time domain is presented. Phase-stabilized few-cycle laser pulses open one to two windows (``slits'') of attosecond duration for photoionization. Fringes in the angle-resolved energy spectrum of varying visibility depending on the degree of which-way information are observed. A situation in which one and the same electron encounters a single and a double slit at the same time is discussed. The investigation of the fringes makes possible interferometry on the attosecond time scale. The number of visible fringes, for example, indicates that the slits are extended over about 500as.Comment: 4 figure

Is It Rational to Assume that Infants Imitate Rationally? A Theoretical Analysis and Critique

It has been suggested that preverbal infants evaluate the efficiency of others' actions (by applying a principle of rational action) and that they imitate others' actions rationally. The present contribution presents a conceptual analysis of the claim that preverbal infants imitate rationally. It shows that this ability rests on at least three assumptions: that infants are able to perceive others' action capabilities, that infants reason about and conceptually represent their own bodies, and that infants are able to think counterfactually. It is argued that none of these three abilities is in place during infancy. Furthermore, it is shown that the idea of a principle of rational action suffers from two fallacies. As a consequence, is it suggested that it is not rational to assume that infants imitate rationally. Copyright (C) 2012 S. Karger AG, Base

Adiabatic Theory of Electron Detachment from Negative Ions in Two-Color Laser Field

Negative ion detachment in bichromatic laser field is considered within the adiabatic theory. The latter represents a recent modification of the famous Keldysh model for multiphoton ionization which makes it quantitatively reliable. We calculate angular differential detachment rates, partial rates for particular ATD (Above Threshold Detachment) channels and total detachment rates for the Hydrogen ion in a bichromatic field with 1:3 frequency ratio and various phase differences. Reliability of the present, extremely simple approach is testified by comparison with much more elaborate earlier calculations.Comment: 22 pages, 6 Postscript figure

Laser Induced Non-Sequential Double Ionization Investigated at and Below the Threshold for Electron Impact Ionization

We use correlated electron–ion momentum measurements to investigate laserinduced non-sequential double ionization of Ar and Ne. Light intensities are chosen in a regime at and below the threshold where, within the rescattering model, electron impact ionization of the singly charged ion core is expected to become energetically forbidden. Yet we find Ar2+ ion momentum distributions and an electron–electron momentum correlation indicative of direct impactionization. Within the quasistatic model this may be understood by assuming that the electric field of the light wave reduces the ionization potential of the singly charged ion core at the instant of scattering. The width of the projection of the ion momentum distribution onto an axis perpendicular to the light beam polarization vector is found to scalewiththe square root of the peak electric field strength in the light pulse. A scaling like this is not expected from the phase space available after electron impact ionization. It may indicate that the electric field at the instant of scattering is usually different fromzero and determines the transverse momentum distribution. A comparison of our experimental results with several theoretical results is give

Attosecond control of electrons emitted from a nanoscale metal tip

Attosecond science is based on steering of electrons with the electric field of well-controlled femtosecond laser pulses. It has led to, for example, the generation of XUV light pulses with a duration in the sub-100-attosecond regime, to the measurement of intra-molecular dynamics by diffraction of an electron taken from the molecule under scrutiny, and to novel ultrafast electron holography. All these effects have been observed with atoms or molecules in the gas phase. Although predicted to occur, a strong light-phase sensitivity of electrons liberated by few-cycle laser pulses from solids has hitherto been elusive. Here we show a carrier-envelope (C-E) phase-dependent current modulation of up to 100% recorded in spectra of electrons laser-emitted from a nanometric tungsten tip. Controlled by the C-E phase, electrons originate from either one or two sub-500as long instances within the 6-fs laser pulse, leading to the presence or absence of spectral interference. We also show that coherent elastic re-scattering of liberated electrons takes place at the metal surface. Due to field enhancement at the tip, a simple laser oscillator suffices to reach the required peak electric field strengths, allowing attosecond science experiments to be performed at the 100-Megahertz repetition rate level and rendering complex amplified laser systems dispensable. Practically, this work represents a simple, exquisitely sensitive C-E phase sensor device, which can be shrunk in volume down to ~ 1cm3. The results indicate that the above-mentioned novel attosecond science techniques developed with and for atoms and molecules can also be employed with solids. In particular, we foresee sub-femtosecond (sub-) nanometre probing of (collective) electron dynamics, such as plasmon polaritons, in solid-state systems ranging in size from mesoscopic solids via clusters to single protruding atoms.Comment: Final manuscript version submitted to Natur

Cerebral blood flow predicts differential neurotransmitter activity

Application of metabolic magnetic resonance imaging measures such as cerebral blood flow in translational medicine is limited by the unknown link of observed alterations to specific neurophysiological processes. In particular, the sensitivity of cerebral blood flow to activity changes in specific neurotransmitter systems remains unclear. We address this question by probing cerebral blood flow in healthy volunteers using seven established drugs with known dopaminergic, serotonergic, glutamatergic and GABAergic mechanisms of action. We use a novel framework aimed at disentangling the observed effects to contribution from underlying neurotransmitter systems. We find for all evaluated compounds a reliable spatial link of respective cerebral blood flow changes with underlying neurotransmitter receptor densities corresponding to their primary mechanisms of action. The strength of these associations with receptor density is mediated by respective drug affinities. These findings suggest that cerebral blood flow is a sensitive brain-wide in-vivo assay of metabolic demands across a variety of neurotransmitter systems in humans