We present suitable materials with good optical and mechanical properties, simple processing, efficient and optimized for two-photon polymerization (TPP) with femtosecond fiber lasers. We selected readily available acrylic monomer Bisphenol A ethoxylate diacrylate (BPA-EDA) with three different photo-initiators (PIs), isopropyl thioxanthone (ITX), 7-diethylamino-3-thenoylcoumarin (DETC), and 4,4′ bis(diethylamino) benzophenone (BDEB), since their absorption spectra match well with the laser wavelength at 780 nm. These PIs grant efficient radical generation, reactivity and high solubility in acrylic monomers. Finally, good optical and mechanical properties are demonstrated by the fabrication of different micro-structures.

Biofouling is the major problem of reverse osmosis (RO) membranes used for desalting seawater (SW). The use of chlorine is a conventional and common practice to control/prevent biofouling. Unlike polyamide RO membranes, cellulose triacetate (CTA) RO membranes display a high chlorine tolerance. Due to this characteristic, CTA membranes are used in most of the RO plants located in the Middle East region where the elevated seawater temperature and water quality promote the risk of membrane biofouling. However, there is no detailed study on the investigation/characterization of CTA-RO membrane fouling. In this investigation, the fouling profile of a full–scale SWRO desalination plant operating with not only continuous chlorination of raw seawater but also intermittent chlorination of CTA-RO membranes was studied. Detailed water quality and membrane fouling analyses were conducted. Profiles of microbiological, inorganic, and organic constituents of analysed fouling layers were extensively discussed. Our results clearly identified biofilm development on these membranes. The incapability of chlorination on preventing biofilm formation on SWRO membranes could be assigned to its failure in effectively reaching throughout the different regions of the permeators. This failure could have occurred due to three main factors: plugging of membrane fibers, chlorine consumption by organics accumulated on the front side fibers, or chlorine adaptation of certain bacterial populations.

It is of great importance to fabricate integrated supercapacitors with extended operation voltages as high energy density storage devices. In this work, we develop a novel direct electrode deposition on separator (DEDS) process to fabricate graphene based integrated tandem supercapacitors for the first time. The DEDS process generates compact graphene-polyaniline electrodes directly on the separators to form integrated supercapacitors. The integrated graphene-polyaniline tandem supercapacitors demonstrate ultrahigh volumetric energy density of 52.5 Wh L^(−1) at power density of 6037 W L^(−1) and excellent gravimetric energy density of 26.1 Wh kg^(−1) at power density of 3002 W kg^(−1) with outstanding electrochemical stability for over 10000 cycles. This study show great promises for the future development of integrated energy storage devices.

IspG is the penultimate enzyme in non-mevalonate biosynthesis of the universal terpene building blocks isopentenyl diphosphate and dimethylallyl diphosphate. Its mechanism of action has been the subject of numerous studies but remained unresolved due to difficulties in identifying distinct reaction intermediates. Using a moderate reducing agent as well as an epoxide substrate analogue, we were now able to trap and crystallographically characterize various stages in the IspG catalyzed conversion of 2-C-methyl-D-erythritol-2,4-cyclo-diphosphate (MEcPP) to (E)-1-hydroxy-2-methylbut-2-enyl-4-diphosphate (HMBPP). In addition, the enzyme’s structure was determined in complex with several inhibitors. These results, combined with recent electron paramagnetic resonance data, allowed us to deduce a detailed and complete IspG catalytic mechanism which describes all stages from initial ring opening to formation of HMBPP via discrete radical and carbanion intermediates. The data presented in this article provide a guide for the design of selective drugs against many pro- and eukaryotic pathogens to which the non-mevalonate pathway is essential for survival and virulence.

The membrane morphology significantly influences membrane performance. For osmotically driven membrane processes, the morphology strongly affects the internal concentration polarization. Different membrane morphologies were generated by simulation and their influence on membrane performance was studied, using a 3D model. The simulation results were experimentally validated for two classical phase-inversion membrane morphologies: sponge- and finger-like structures. Membrane porosity and scanning electron microscopy image information were used as model input. The permeance results from the simulation fit well the experimentally measured permeances. Water permeances were predicted for different kinds of finger-like cavity membranes with different finger-like cavity lengths and various finger-like cavity sets, as well as for membranes with cylindrical cavities. The results provide realistic information on how to increase water permeance, and also illustrate that membrane’s complete morphology is important for the accurate water permeance evaluation. Evaluations only based on porosity might be misleading, and the new 3D simulation approach gives a more realistic representation.

Two new gold(I) complexes that contain tri-ter-butylphosphine and dialkyl dithiocarbamate ligands were synthesized and characterized by FTIR, NMR spectroscopy, Cyclic voltammetry, elemental analysis and X-ray diffraction. The in vitro cytotoxicity of both complexes was examined against A549 (lung cancer), MCF7 (breast cancer), and HeLa (cervical cancer) human cancer cell lines. Both complexes exhibit very strong in vitro cytotoxic effects against A549, MCF7 and HeLa cell lines. The screening of the cytotoxic activity based on IC50 data against the A549, MCF7, and HeLa lines shows that the synthesized gold(I) complexes are highly effective, particularly against HeLa cancer cell line. Based on IC50 data, the cytotoxic activity of both complexes is better than well-known commercial anticancer drug cisplatin against all the three cancer lines tested.

This paper studies the joint optimization problem of energy and delay in a multi-hop wireless network. The optimization variables are the transmission rates, which are adjustable according to the packet queueing length in the buffer. The optimization goal is to minimize the energy consumption of energy-critical nodes and the packet transmission delay throughout the network. In this paper, we aim at understanding the well-known decentralized algorithms which are threshold based from a different research angle. By using a simplified network model, we show that we can adopt the semi-open Jackson network model and study this optimization problem in closed form. This simplified network model further allows us to establish some significant optimality properties. We prove that the system performance is monotonic with respect to (w.r.t.) the transmission rate. We also prove that the threshold-type policy is optimal, i.e., when the number of packets in the buffer is larger than a threshold, transmit with the maximal rate (power); otherwise, no transmission. With these optimality properties, we develop a heuristic algorithm to iteratively find the optimal threshold. Finally, we conduct some simulation experiments to demonstrate the main idea of this paper.

We analyze the problem of buffer sizing for backlogged TCP flows in 802.11-based wireless mesh networks. Our objective is to maintain high network utilization while providing low queueing delays. Unlike wired networks where a single link buffer feeds a bottleneck link, the radio spectral resource in a mesh network is shared among a set of contending mesh routers. We account for this by formulating the buffer size problem as sizing a collective buffer distributed over a set of interfering nodes. In this paper we propose mechanisms for sizing and distributing this collective buffer among the mesh nodes constituting the network bottleneck. Our mechanism factors in the network topology and wireless link rates, improving on pre-set buffer allocations that cannot optimally work across the range of configurations achievable with 802.11 radios. We evaluate our mechanisms using simulations as well as experiments on a testbed. Our results show that we can reduce the RTT of a flow by 6× or more, at the cost of less than 10% drop in end-to-end flow throughput.

In this paper we study the interactions of TCP and IEEE 802.11 MAC in Wireless Mesh Networks (WMNs). We use a Markov chain to capture the behavior of TCP sessions, particularly the impact on network throughput due to the effect of queue utilization and packet relaying. A closed form solution is derived to numerically determine the throughput. Based on the developed model, we propose a distributed MAC protocol called Timestamp-ordered MAC (TMAC), aiming to alleviate the unfairness problem in WMNs. TMAC extends CSMA/CA by scheduling data packets based on their age. Prior to transmitting a data packet, a transmitter broadcasts a request control message appended with a timestamp to a selected list of neighbors. It can proceed with the transmission only if it receives a sufficient number of grant control messages from these neighbors. A grant message indicates that the associated data packet has the lowest timestamp of all the packets pending transmission at the local transmit queue. We demonstrate that a loose ordering of timestamps among neighboring nodes is sufficient for enforcing local fairness, subsequently leading to flow rate fairness in a multi-hop WMN. We show that TMAC can be implemented using the control frames in IEEE 802.11, and thus can be easily integrated in existing 802.11-based WMNs. Our simulation results show that TMAC achieves excellent resource allocation fairness while maintaining over 90% of maximum link capacity across a large number of topologies.

FAST TCP is important for promoting data-intensive applications since it can cleverly react to both packet loss and delay for detecting network congestion. This paper provides a continuous time model and extensive stability analysis of FAST TCP congestion-control mechanism in bufferless Optical Burst Switched Networks (OBS). The paper first shows that random burst contentions are essential to stabilize the network, but cause throughput degradation in FAST TCP flows when a burst with all the packets from a single round is dropped. Second, it shows that FAST TCP is vulnerable to burst delay and fails to detect network congestion due to the little variation of round-trip time, thus unstable. Finally it shows that introducing extra delays by implementing burst retransmission stabilizes FAST TCP over OBS. The paper proves that FAST TCP is not stable over barebone OBS. However, it is locally, exponentially, and asymptotically stable over OBS with burst retransmission.