Search

In this study, two core-shell nanohybrids of different morphologies, namely SiO2-coated silver (Ag) with surface-exposed silver seeds (Ag@SiO2@Agseed) and SiO2-coated Ag with surface-exposed Ag nanoparticles (Ag@SiO2@AgNPs), were fabricated using the Stober method. Potential applications in bioimaging and photothermal therapy (PTT) of the two fabricated nanohybrids were also explored. Upon exposure to visible light (400 nm), Ag@SiO2@Agseed with surface-exposed Ag seeds exhibited greater photothermal conversion efficiency than Ag@SiO2@AgNPs. In vitro MTT assays in the dark and subsequent bioimaging using HeLa cells proved the potential biocompatibility of the fabricated core-shell nanohybrids. PTT applications of the two fabricated core-shell nanohybrids were studied by incubating HeLa cells with the nanohybrids, exposure to 400 nm laser, and subsequent staining with annexin V and propidium iodide (PI), and the two core-shell nanohybrids gave distinctively different PI staining results. Interestingly, Ag@SiO2@Agseed caused higher cell death upon light exposure compared to Ag@SiO2@AgNPs as the former generated more heat within the cells. These results demonstrated potential bioimaging and PPT applications of the fabricated core-shell nanohybrids and offer a novel candidate for phototherapy-based biomedical applications.

The concurrent attachment and detachment movements of geckos on virtually any type of surface via their foot pads have inspired us to develop a thermal device with numerous arrangements of a multi-layer thin film together with electrodes that can help modify the temperature of the surface via application of a voltage. A sequential fabrication process was employed on a large-scale integration to generate well-defined contact hole arrays of photoresist for use as templates on the electrode-based device. The photoresist templates were then subjected to sputter deposition of the metallic glass Zr55Cu30Al10Ni5. Consequently, a metallic glass nanotube (MGNT) array having a nominal wall thickness of 100 nm was obtained after removal of the photoresist template. When a water droplet was placed on the MGNT array, close nanochambers of metallic glass were formed. By applying voltage, the surface was heated to increase the pressure inside the nanochambers; this generated an expanding force that raised the droplet; thus, the static water contact angle (SWCA) was increased. In contrast, a sucking force was generated during surface cooling, which decreased the SWCA. Our fabrication strategy exploits the MGNT array surface as nanosuckers, which can mimic the climbing aptitude of geckos as they attach to (>10 N m−2) and detach from (0.26 N m−2) surfaces at 0.5 and 3 V of applied voltage, respectively. Thus, the climbing aptitude of geckos can be mimicked by employing the processing strategy presented herein for the development of artificial foot pads.

In this study, inorganic/organic composites containing poly (N-isopropylacrylamide) coated core-shell SiO2 microspheres were prepared via surface-initiated atom transfer radical polymerization (ATRP). The thermal responsive polymer, N-isopropylacrylamide was treated with methanol, water and CuBr/CuBr2/1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA) at room temperature to form PNIPAM@SiO2 microspheres. The as-prepared PNIPAM@SiO2 microspheres were characterized by FT-IR, TGA, XPS, SEM, TEM analyses. Hemoglobin (Hb) was immobilized onto the surfaces of PNIPAM@SiO2 microspheres via hydrophobic and π-π stacking interactions. The as-prepared Hb/PNIPAM@SiO2 electrode exhibits well-defined redox peak at a formal potential of −0.38 V, validating the direct electrochemistry of Hb. The Hb immobilized composite film retained its bioelectroactivity without any significant loss of catalytic activity. The modified electrode detects H2O2 over a wide linear concentration range (0.1 μM to 333 μM) with a detection limit of 0.07 μM. This modified electrode also successfully detects H2O2 from food and disinfectant samples with appreciable recovery values, validating its practicality. We believe that PNIPAM@SiO2 composite has great potential to be used in the detection of H2O2 and development of other enzyme based biosensors.

We grafted azido-terminated poly(N-isopropylacrylamide) (PNIPAAm) brushes onto thin gold films on silicon as a bottom electrode. A probe of single-stranded DNA (ssDNA) presenting a 4-pentynoic acid succinimidyl ester unit was grafted onto the azido-terminated PNIPAAm brushes through a click reaction, resulting in block copolymer brushes. The PNIPAAm-b-ssDNA copolymer brushes formed homogeneous complexes stabilized via bio-multiple hydrogen bonds (BMHBs), which enhanced proton transfer and thereby decreased the resistivity of the structures. The homogeneous complex state of the PNIPAAm-b-ssDNA copolymer brushes transformed into a phase-separated state after hybridization with 0.5 pg nL−1 of its target DNA, which resulted from competition between the BMHBs and complementary HBs; this phase transformation of the PNIPAAm and probe segments inhibited proton transfer and significantly increased the resistivity. Furthermore, hybridization with mismatched DNA sequences generated sufficient “proton leakage” to decrease the resistivity at temperatures below the lower critical solution temperature (LCST), especially for adenine and guanine units. Sequences with thymine and cytosine mismatches could be distinguished from the target at temperatures above the LCST due to disruption of the BMHBs at increased temperatures (80 °C). The ability to detect label-free DNA and recognize sequence mismatches suggests the potential use of these novel materials in bioelectronics.

Zinc oxide (ZnO) possessing the flower-like structure with the surface covered by Poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) polymer was synthesized successfully through the one-pot chemical synthesis technique. As-synthesized ZnO@PEDOT:PSS modified glassy carbon electrode (GCE) was engaged for effective electrochemical oxidation of chlorogenic acid (CGA). The uniform encapsulation of PEDOT:PSS polymer was confirmed by adopting HR-TEM and FE-SEM method. The physicochemical properties of the as-synthesized composite were studied by using various analytical techniques and the results seem more satisfactorily. Specifically, ZnO@PEDOT:PSS-GCE towards CGA oxidation shows wide-linear range, high sensitivity, limits of detection, and limits of quantification values are 0.03–476.2 μM, 29.38 μA μM−1 cm-2, 0.02 μM, and 0.3 μM, respectively. Furthermore, the potential of ZnO@PEDOT:PSS-GCE for the effectiveness determination of CGA is accessed by using coffee powder and soft drink as real-time samples.

In this study, two core-shell nanohybrids of different morphologies, namely SiO

A microwave-assisted, chemoselective synthesis of oxazolo[5,4-b]quinoline-fused spirooxindoles have been achieved via three-component tandem Knoevenagel/Michael addition reaction of 5-amino-3-methylisoxazole, β-diketones and isatin in good to excellent yields under catalyst- and solvent-free conditions. The main advantages of this protocol are easiness of work-up, mild reaction and eco-friendly reaction conditions.

We grafted thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) brushes from monodisperse SiO2 microspheres through surface-initiated atom transfer radical polymerization (SI ATRP) to generate core-shell structured SiO2@PNIPAM microspheres (SPMs). Regular-sized SPMs dispersed in aqueous solution and packed as photonic crystals (PCs) in dry state. Because of the microscale of the SPMs, the packing behavior of the PCs in water can be observed by optical microscopy. By increasing the temperature above the lower critical solution temperature (LCST) of PNIPAM, the reversible swelling and shrinking of the PNIPAM shell resulted in dispersion and precipitation (three-dimensional aggregation) of the SPM in aqueous solution. The SPMs were microdispersed in a water layer to accommodate the aggregation along two dimensions. In the microdispersion, the SPMs are packed as PCs with microscale spacing between SPMs below the LCST. When the temperature is increased above the LCST, the microdispersed PCs exhibited a close-packed arrangement along two dimensions with decreased spacing between SPMs. The change in spacing with increasing temperature above the LCST resulted in a color change from red to blue, which could be observed by the naked eye at an incident angle. Thus, the SPM array could be applied as a visual temperature sensor.

The title compound, C12H10ClNO3, the indoline ring system is essentially planar, with a maximum deviation of 0.009 Å for the N atom. The indoline ring and acetate group are essentially coplanar, with a maximum deviation of 0.086 Å for the O atom. The mean plane through the methoxycarbonylmethyl group forms a dihedral angle of 3.68 (5)° with the plane of the indoline ring system. The molecular structure is stabilized by an intramolecular C—H...O hydrogen-bond interaction. In the crystal, π–π stacking interactions [centroid–centroid distance = 3.7677 (8) Å] occur between benzene rings, forming a chain running along the c-axis direction.

Parallel marking algorithms use multiple threads to walk through the object heap graph and mark each reachable object as live. Parallel marker threads mark an object "live" by atomically setting a bit in a mark-bitmap or a bit in the object header. Most of these parallel algorithms strive to improve the marking throughput by using work-stealing algorithms for load-balancing and to ensure that all participating threads are kept busy. A purely "processor-centric" load-balancing approach in conjunction with a need to atomically set the mark bit, results in significant contention during parallel marking. This limits the scalability and throughput of parallel marking algorithms.We describe a new non-blocking and lock-free, work-sharing algorithm, the primary goal being to reduce contention during atomic updates of the mark-bitmap by parallel task-threads. Our work-sharing mechanism uses the address of a word in the mark-bitmap as the key to stripe work among parallel task-threads, with only a subset of the task-threads working on each stripe. This filters out most of the contention during parallel marking with 20% improvements in performance.In case of concurrent and on-the-fly collector algorithms, mutator threads also generate marking-work for the marking task-threads. In these schemes, mutator threads are also provided with thread-local marking stacks where they collect references to potentially "gray" objects, i.e., objects that haven't been "marked-through" by the collector. We note that since this work is generated by mutators when they reference these objects, there is a high likelihood that these objects continue to be present in the processor cache. We describe and evaluate a scheme to distribute mutator generated marking work among the collector's task-threads that is cognizant of the processor and cache topology. We prototype both our algorithms within the C4 [28] collector that ships as part of an industrial strength JVM for the Linux-X86 platform.

Present approaches to software security are to a large extent reactive: when vulnerabilities are discovered, developers scramble to fix the underlying error. The advantage is on the side of the attackers because they only have to find a single vulnerability to exploit all vulnerable systems, while defenders have to prevent the exploitation of all vulnerabilities. We argue that the compiler is at the heart of the solution for this problem: when the compiler is translating high-level source code to low-level machine code, it is able to automatically diversify the machine code, thus creating multiple functionally equivalent, but internally different variants of a program.We present two orthogonal compiler-based techniques.With multi-variant execution, a monitoring layer executes several diversified variants in lockstep while examining their behavior for differences that indicate attacks. With massive-scale software diversity, every user gets its own diversified variant, so that the attacker has no knowledge about the internal structure of that variant and therefore cannot construct an attack. Both techniques make it harder for an attacker to run a successful attack. We discuss variation techniques that the compiler can utilize to diversify software, and evaluate their effectiveness for our two execution models.

A large array of privacy sensitive applications like banking servers, medical records processors, and legal software are Java applications. Preserving user privacy is a necessary feature in such applications. For example, in a medical records system, only the authorized doctors and medical staff should be allowed access to patient information. Decentralized Information Flow Control (DIFC) [10] provides an effective means for preserving user privacy. In a traditional setup where the Java Virtual Machine (JVM) runs on top of an Operating System (OS), sensitive information flows both through the JVM and the OS, and effective enforcement of information flow policies requires tracking data across both these entities [12]. Implementing information flow control in such systems requires modification, and subsequent auditing, of both the JVM and OS source code.

In the title compound, C22H20ClN3O4, the central pyrrolidine ring adopts an envelope conformation on the N atom. The indolinone systems are individually roughly planar, with maximum deviations from their mean planes of 0.130 Å for the spiro C atom of the indolinone unit and 0.172 Å for the carbonyl C atom of the 5-chloro-1-methyl-indolinone unit. They make dihedral angles of 77.7 (8) and 86.1 (8)° with the mean plane through the central pyrrolidine ring. In the crystal, mol-ecules are linked by N-H⋯O hydrogen bonds supported by C-H⋯O contacts into chains along the ab diagonal. The structure also features C-H⋯O hydrogen bonds, forming R 2 (2)(8) and R 2 (2)(16) rings and generating a three-dimensional array.