Wireless sensor network as a distribute database

Wireless sensor networks (WSN) have played a role in various fields. In-network data processing is one of the most important and challenging techniques as it affects the key features of WSNs, which are energy consumption, nodes life circles and network performance. In the form of in-network processing, an intermediate node or aggregator will fuse or aggregate sensor data, which are collected from a group of sensors before transferring to the base station. The advantage of this approach is to minimize the amount of information transferred due to lack of computational resources. This thesis introduces the development of a hybrid in-network data processing for WSNs to fulfil the WSNs constraints. An architecture for in-network data processing were proposed in clustering level, data compression level and data mining level. The Neighbour-aware Multipath Cluster Aggregation (NMCA) is designed in the clustering level, which combines cluster-based and multipath approaches to process different packet loss rates. The data compression schemes and Optimal Dynamic Huffman (ODH) algorithm compressed data in the cluster head for the compressed level. A semantic data mining for fire detection was designed for extracting information from the raw data by the semantic data-mining model is developed to improve data accuracy and extract the fire event in the simulation. A demo in-door location system with in-network data processing approach is built to test the performance of the energy reduction of our designed strategy. In conclusion, the added benefits that the technical work can provide for in-network data processing is discussed and specific contributions and future work are highlighted

Sequence-Dependent Orientational Coupling and Electrostatic Attraction in Cation-Mediated DNA–DNA Interactions

Condensation of DNA is vital for its biological functions and controlled nucleic acid assemblies. However, the mechanisms of DNA condensation are not fully understood due to the inability of experiments to access cation distributions and the complex interplay of energetic and entropic forces during assembly. By constructing free energy surfaces using exhaustive sampling and detailed analysis of cation distributions, we elucidate the mechanism of DNA condensation in different salt conditions and with different DNA sequences. We found that DNA condensation is facilitated by the correlated dynamics of the localized cations at the grooves of DNA helices. These dynamics are strongly dependent on the salt conditions and DNA sequences. In the presence of magnesium ions, major groove binding facilitates attraction. In contrast, in the presence of polyvalent cations, minor groove binding serves to create charge patterns, leading to condensation. Our findings present a novel advancement in the field and have broad implications for understanding and controlling nucleic acid complexes in vivo and in vitro

Sequence-Dependent Orientational Coupling and Electrostatic Attraction in Cation-Mediated DNA–DNA Interactions

Condensation of DNA is vital for its biological functions and controlled nucleic acid assemblies. However, the mechanisms of DNA condensation are not fully understood due to the inability of experiments to access cation distributions and the complex interplay of energetic and entropic forces during assembly. By constructing free energy surfaces using exhaustive sampling and detailed analysis of cation distributions, we elucidate the mechanism of DNA condensation in different salt conditions and with different DNA sequences. We found that DNA condensation is facilitated by the correlated dynamics of the localized cations at the grooves of DNA helices. These dynamics are strongly dependent on the salt conditions and DNA sequences. In the presence of magnesium ions, major groove binding facilitates attraction. In contrast, in the presence of polyvalent cations, minor groove binding serves to create charge patterns, leading to condensation. Our findings present a novel advancement in the field and have broad implications for understanding and controlling nucleic acid complexes in vivo and in vitro

Sequence-Dependent Orientational Coupling and Electrostatic Attraction in Cation-Mediated DNA–DNA Interactions

Condensation of DNA is vital for its biological functions and controlled nucleic acid assemblies. However, the mechanisms of DNA condensation are not fully understood due to the inability of experiments to access cation distributions and the complex interplay of energetic and entropic forces during assembly. By constructing free energy surfaces using exhaustive sampling and detailed analysis of cation distributions, we elucidate the mechanism of DNA condensation in different salt conditions and with different DNA sequences. We found that DNA condensation is facilitated by the correlated dynamics of the localized cations at the grooves of DNA helices. These dynamics are strongly dependent on the salt conditions and DNA sequences. In the presence of magnesium ions, major groove binding facilitates attraction. In contrast, in the presence of polyvalent cations, minor groove binding serves to create charge patterns, leading to condensation. Our findings present a novel advancement in the field and have broad implications for understanding and controlling nucleic acid complexes in vivo and in vitro

High-Density Silicon Nanowires Prepared via a Two-Step Template Method

High density ordered Si nanowire arrays can be fabricated from a Fe₂O₃ template annealed from polystyrene (PS) microsphere layers via a metal-assisted chemical etching method. The metal mesh films, containing position- and density-defined pores that determine the position and density of the remaining structures after etching, are extremely important for achieving high quality Si nanowires. By adding a structural inversion process, a Au metal mesh with arrays of high density nanopores is devised as a catalyst for metal-assisted chemical etching of silicon. The density of Si nanowires can be increased to two times that of the single-layer PS microspheres and further to three times when a double layer of PS microspheres is introduced. The two-step template method for the preparation of high-density Si nanowires shows great potential in the fields of nanofabrication and nanoelectronics

Colorimetric Sensor Array for Discrimination of Heavy Metal Ions in Aqueous Solution Based on Three Kinds of Thiols as Receptors

In the present work, we report a novel colorimetric sensor array for rapid identification of heavy metal ions. The sensing mechanism is based on the competition between thiols and urease for binding with the metal ions. Due to the different metal ion-binding abilities between the thiols and urea, different percentages of urease are free of metal ions and become catalytically active in the presence of varied metal ions. The metal ion-free urease catalyzes the decomposition of urea releasing ammonia and changing the pH of the analyte solution. Bromothymol blue, the pH indicator, changes its color in response to the metal-caused pH change. Three different thiols (l-glutathione reduced, l-cysteine, and 2-mercaptoethanol) were used in our sensor array, leading to a unique colormetric repsonse pattern for each metal. Linear discriminant analysis (LDA) was employed to analyze the patterns and generate a clustering map for identifying 11 species of metal ions (Ni²⁺, Mn²⁺, Zn²⁺, Ag⁺, Cd²⁺, Fe³⁺, Hg²⁺, Cu²⁺, Sn⁴⁺, Co²⁺, and Pb²⁺) at 10 nM level in real samples. The method realizes the simple, fast (within 30 s), sensitive, and visual discrimination of metal ions, showing the potential applications in environmental monitoring

A New Route To Fabricate Large-Area, Compact Ag Metal Mesh Films with Ordered Pores

Ordered Si nanowire (SiNW) arrays can be fabricated by metal-assisted chemical etching. The metal mesh films (MMFs) are extremely important for achieving a high quality of the SiNWs. We have developed a two-step chemical deposition method to obtain compact porous Ag MMFs. By the separation of the nucleation and growth stages of the metal in the two-step deposition processes, the overgrowth of the metals to form randomly aggregated irregular metal particles can be overcome. Hexagonally arranged polystyrene (PS) latex microspheres have been employed as a template for the deposition of porous Ag MMFs. The spacing of the pores in the Ag MMFs is determined by the diameter of PS microspheres, and the pore size can also be tuned by changing Ar plasma etching time. One of the main advantages of the two-step deposition method lies in that Ag MMFs can be produced with PS microspheres that are not limited to a single layer, which dramatically simplifies the tedious processes of producing a monolayered PS template. The two-step chemical deposition method shows great potential in metal-assisted chemical etching

Zinc Phthalocyanine Covalent Polymers as Recyclable Catalysts for NIR-Photocontrolled RAFT Polymerization in Water

An excellent catalyst plays key roles and is always pursued by researchers for various controlled polymerizations. In this work, flexible triethylene glycol is used for the first time to bridge zinc phthalocyanine to form zinc phthalocyanine covalent polymers (ZnPc-CPs) as highly efficient heterogeneous photocatalysts for the generation of singlet oxygen (1O2) and thereafter to catalyze an aqueous reversible addition–fragmentation chain transfer polymerization under irradiation with near-infrared (NIR) LED light (λmax = 730 nm) at room temperature. The oxygen content is crucial to the polymerization. Trace oxygen in the polymerization produces an active hydrogen peroxide initiator to accelerate the polymerization, while a large amount of oxygen will terminate the polymerization. Additionally, benefiting from the high penetrating power of NIR light, the polymerization can still proceed in the presence of barriers. More importantly, compared to homogeneous photocatalysts, heterogeneous ZnPc-CPs can be reused by simple post-treatment and recycled without a significant decrease in the catalytic efficiency. The significant advantages, including employing NIR LED light irradiation, water as a solvent, a recyclable heterogeneous photocatalyst, and no need of prior deoxygenation, make this polymerization system not only easy to manipulate but also highly economical and environmentally beneficial

Facile Fabrication of Biocompatible and Tunable Multifunctional Nanomaterials via Iron-Mediated Atom Transfer Radical Polymerization with Activators Generated by Electron Transfer

A novel strategy of preparing multifunctional nanoparticles (NPs) with near infra red (NIR) fluorescence and magnetism showing good hydrophilicity and low toxicity was developed via surface-initiated atom transfer radical polymerization with activators generated by electron transfer (AGET ATRP) of poly­(ethylene glycol) monomethyl ether methacrylate (PEGMA) and glycidyl methacrylate (GMA) employing biocompatible iron as the catalyst on the surface of silica coated iron oxide (Fe₃O₄@SiO₂) NPs. The small molecules (CS2), a NIR fluorescent chromophore, can be fixed into the covalently grafted polymer shell of the NPs by chemical reaction through a covalent bond to obtain stable CS2 dotted NPs Fe₃O₄@SiO₂@PPEGMA-<i>co</i>-PGMA@CS2. The fluorescence intensity of the as-prepared NPs could be conveniently regulated by altering the silica shell thickness (varying the feed of silica source TEOS), CS2 feed, or the feed ratio of <i>V</i>_PEGMA/<i>V</i>_GMA, which are easily realized in the preparation process. Thorough investigation of the properties of the final NPs including <i>in vivo</i> dual modal imaging indicate that such NPs are one of the competitive candidates as imaging agents proving a promising potential in the biomedical area

Surface Structure-Dependent Molecular Oxygen Activation of BiOCl Single-Crystalline Nanosheets

We demonstrate that BiOCl single-crystalline nanosheets possess surface structure-dependent molecular oxygen activation properties under UV light. The (001) surface of BiOCl prefers to reduce O₂ to ·O₂^– through one-electron transfer, while the (010) surface favors the formation of O₂^2– via two-electron transfer, which is cogoverned by the surface atom exposure and the situ generated oxygen vacancy characteristics of the (001) and (010) surfaces under UV light irradiation