Biocatalytically Triggered Co‐Assembly of Two‐Component Core/Shell Nanofibers

For the development of applications and novel uses for peptide nanostructures, robust routes for their surface functionalization, that ideally do not interfere with their self‐assembly properties, are required. Many existing methods rely on covalent functionalization, where building blocks are appended with functional groups, either pre‐ or post‐assembly. A facile supramolecular approach is demonstrated for the formation of functionalized nanofibers by combining the advantages of biocatalytic self‐assembly and surfactant/gelator co‐assembly. This is achieved by enzymatically triggered reconfiguration of free flowing micellar aggregates of pre‐gelators and functional surfactants to form nanofibers that incorporate and display the surfactants’ functionality at the surface. Furthermore, by varying enzyme concentration, the gel stiffness and supramolecular organization of building blocks can be varied.     

Self-sustaining smoldering combustion for NAPL remediation: laboratory evaluation of process sensitivity to key parameters

Smoldering combustion has been introduced recently as a potential remediation strategy for soil contaminated by nonaqueous phase liquids (NAPLs). Published proof-of-concept experiments demonstrated that the process can be self-sustaining (i.e., requires energy input only to start the process) and achieve essentially complete remediation of the contaminated soil. Those initial experiments indicated that the process may be applicable across a broad range of NAPLs and soils. This work presents the results of a series of bench-scale experiments that examine in detail the sensitivity of the process to a range of key parameters, including contaminant concentration, water saturation, soil type, and air flow rates for two contaminants, coal tar and crude oil. Smoldering combustion was observed to be self-sustaining in the range 28,400 to 142,000 mg/kg for coal tar and in the range 31,200 to 104,000 mg/kg for crude oil, for the base case air flux. The process remained self-sustaining and achieved effective remediation across a range of initial water concentrations (0 to 177,000 mg/kg water) despite extended ignition times and decreased temperatures and velocities of the reaction front. The process also exhibited self-sustaining and effective remediation behavior across a range of fine to coarse sand grain sizes up to a threshold maximum value between 6 mm and 10 mm. Propagation velocity is observed to be highly dependent on air flux, and smoldering was observed to be self-sustaining down to an air Darcy flux of at least 0.5 cm/s for both contaminants. The extent of remediation in these cases was determined to be at least 99.5% and 99.9% for crude oil and coal tar, respectively. Moreover, no physical evidence of contamination was detected in the treatment zone for any case where a self-sustaining reaction was achieved. Lateral heat losses to the external environment were observed to significantly affect the smoldering process at the bench scale, suggesting that the field-scale lower bounds on concentration and air flux and upper bound on grain size were not achieved; larger scale experiments and field trials where lateral heat losses are much less significant are necessary to define these process limits for the purposes of field application. This work provides valuable design data for pilot field trials of both in situ and ex situ smoldering remediation applications.     

Thermomagnetically written domains in TbFeCo thin films

Characteristic features of thermomagnetically written domains in amorphous Tb_x(Fe₉₀Co₁₀)_100-x thin films having different magnetic properties are reported. In particular, the writing process in materials with low Tb content (x⩽21), which is dominated by the demagnetizing field, is compared to the bias-field-dominated process in Tb-rich samples (22⩽x⩽25). Domain-wall movement over lateral dimensions of the bit size is found for Tb-poor materials, while for x⩽22 the domain boundaries are primarily determined by the area heated up to the Curie temperature. The importance of mechanical stress in domain formation and irreversible changes of the storage medium due to overheating in the writing process are reported     

Incorporation of gradient into random search optimization

To improve the rate of convergence of random search optimization procedures, the incorporation of a gradient-oriented one-dimensional search is investigated. With this modification to the random search procedure based on uniform sampling and region contraction [1], convergence to within 0.01% of the global optimum was obtained substantially faster for typical chemical engineering problems. It was also found that the reliability of obtaining the global optimum was improved.     

Continuously variable gigahertz phase-shifter IC covering more thanone frequency decade

A monolithic integrated silicon bipolar circuit which allows phase shifting of arbitrarily shaped clock signals by 0 to -2π within a frequency range from about 60 MHz to 1.8 GHz is described. The phase can be adjusted by a single potentiometer or by an externally applied voltage. The wide frequency and phase-shifting ranges were achieved by a mainly digital circuit principle. The temperature coefficient of the phase can be adjusted within a specific range. The circuit was realized by use of a very conservative 2-μm standard technology     

Identifying 5-methylcytosine and related modifications in DNA genomes

Intense interest in the biological roles of DNA methylation, particularly in eukaryotes, has produced at least eight different methods for identifying 5-methylcytosine and related modifications in DNA genomes. However, the utility of each method depends not only on its simplicity but on its specificity, resolution, sensitivity and potential artifacts. Since these parameters affect the interpretation of data, they should be considered in any application. Therefore, we have outlined the principles and applications of each method, quantitatively evaluated their specificity,resolution and sensitivity, identified potential artifacts and suggested solutions, and discussed a paradox in the distribution of m5C in mammalian genomes that illustrates how methodological limitations can affect interpretation of data. Hopefully, the information and analysis provided here will guide new investigators entering this exciting field.     

A versatile Si-bipolar driver circuit with high output voltageswing for external and direct laser modulation in 10 Gb/s optical-fiberlinks

A monolithic integrated driver circuit developed for laser modulation in a 10 Gb/s optical-fiber link is presented. The IC was fabricated in a self-aligned double-polysilicon Si-bipolar production technology with f_T≈25 GHz. The circuit can be operated up to 14 Gb/s with a maximum output voltage swing as high as 3.6 V at 50 Ω load (corresponding to an internal current swing of 108 mA), which allows the circuit to drive external modulators. In addition, the circuit can be used for direct laser modulation at 10 Gb/s, since the output current swing can easily be controlled over a wide range (e.g., from 15 mA to 60 mA). Problems in the design of such driver circuits as well as their solutions are discussed in detail     

120-Gb/s VCSEL-based parallel-optical interconnect and custom 120-Gb/s testing station

A 120-Gb/s optical link (12 channels at 10 Gb/s/ch for both a transmitter and a receiver) has been demonstrated. The link operated at a bit-error rate of less than 10/sup -12/ with all channels operating and with a total fiber length of 316 m, which comprises 300 m of next-generation (OM-3) multimode fiber (MMF) plus 16 m of standard-grade MMF. This is the first time that a parallel link with this bandwidth at this per-channel rate has ever been demonstrated. For the transmitter, an SiGe laser driver was combined with a GaAs vertical-cavity surface-emitting laser (VCSEL) array. For the receiver, the signal from a GaAs photodiode array was amplified by a 12-channel SiGe receiver integrated circuit. Key to the demonstration were several custom testing tools, most notably a 12-channel pattern generator. The package is very similar to the commercial parallel modules that are available today, but the per-channel bit rate is three times higher than that for the commercial modules. The new modules demonstrate the possibility of extending the parallel-optical module technology that is available today into a distance-bandwidth product regime that is unattainable for copper cables.