Customizing MRI-Compatible Multifunctional Neural Interfaces through Fiber Drawing

Fiber drawing enables scalable fabrication of multifunctional flexible fibers that integrate electrical, optical, and microfluidic modalities to record and modulate neural activity. Constraints on thermomechanical properties of materials, however, have prevented integrated drawing of metal electrodes with low-loss polymer waveguides for concurrent electrical recording and optical neuromodulation. Here, two fabrication approaches are introduced: 1) an iterative thermal drawing with a soft, low melting temperature (T_m) metal indium, and 2) a metal convergence drawing with traditionally non-drawable high T_m metal tungsten. Both approaches deliver multifunctional flexible neural interfaces with low-impedance metallic electrodes and low-loss waveguides, capable of recording optically-evoked and spontaneous neural activity in mice over several weeks. These fibers are coupled with a light-weight mechanical microdrive (1 g) that enables depth-specific interrogation of neural circuits in mice following chronic implantation. Finally, the compatibility of these fibers with magnetic resonance imaging is demonstrated and they are applied to visualize the delivery of chemical payloads through the integrated channels in real time. Together, these advances expand the domains of application of the fiber-based neural probes in neuroscience and neuroengineering.     

A minisum location problem with regional demand considering farthest Euclidean distances

We consider a continuous multi-facility location-allocation problem that aims to minimize the sum of weighted farthest Euclidean distances between (closed convex) polygonal and/or circular demand regions, and facilities they are assigned to. We show that the single facility version of the problem has a straightforward second-order cone programming formulation and can therefore be efficiently solved to optimality. To solve large size instances, we adapt a multi-dimensional direct search descent algorithm to our problem which is not guaranteed to find the optimal solution. In a special case with circular and rectangular demand regions, this algorithm, if converges, finds the optimal solution. We also apply a simple subgradient method to the problem. Furthermore, we review the algorithms proposed for the problem in the literature and compare all these algorithms in terms of both solution quality and time. Finally, we consider the multi-facility version of the problem and model it as a mixed integer second-order cone programming problem. As this formulation is weak, we use the alternate location-allocation heuristic to solve large size instances.     

Quantitative HIV-1 RNA as a marker of clinical stability and survival in a cohort of 302 patients with a mean CD4 cell count of 300 x 10(6)/l

OBJECTIVE: To analyse plasma HIV-1 RNA levels as a marker of clinical stability and survival in a cohort of HIV-infected patients whose time of seroconversion is unknown. DESIGN: Retrospective cohort study. SETTING: Retrovirology laboratory and AIDS Unit in a teaching hospital. PATIENTS: A total of 916 samples from 302 patients, most on antiretroviral therapy, were analysed. Mean initial CD4 cell counts and HIV-1 RNA were 299 x 10(6)/l (range: 0-1600) and 134,261 copies/ml (range: < 200-4,300,000), respectively. Sixty-six cases had been diagnosed previously with AIDS. METHODS: Analysis of progression to AIDS and survival, according to initial and longitudinal viral load (VL) and CD4 cell count measurements was performed by Kaplan-Meier test. Relative risks were calculated by Cox's proportional hazards model. RESULTS: During a mean follow-up of 444 +/- 309 days, 29 patients developed AIDS and 21 died. Relative risk (RR) of progression related to the group with VL < 35,000 was: 10.4 when CD4 > or = 250 x 10(6)/l and VL > or = 35,000 (P = 0.001); and 45.3 when CD4 < 250 x 10(6)/l and VL > or = 35,000 (P < 0.0001). Cumulative probability of progression was: 0%, 0% and 12.3%, at the first, second and third year respectively, for patients with all their sequential VL determinations < 60,000; and 13.3%, 34.7% and 79.3% for patients who did not maintain VL values always < 60,000 (RR = 23; P < 0.0001). The minimum value of VL that reached statistical significance for the survival analysis was 100,000 copies/ml (P < 0.0001). CONCLUSIONS: VL > or = or < 35,000 is a better discriminant for progression than a CD4 cell count > or = or < 250 x 10(6)/l. Sequential VL determinations < 60,000 are associated with a better prognosis.     

Structural coloring in large scale core-shell nanowires

We demonstrated two complementary size-dependent structural coloring mechanisms, interference and scattering, in indefinitely long core-shell nanowire arrays. The unusual nanostructures are comprised of an amorphous semiconducting core and a polymer shell layer with disparate refractive indices but with similar thermomechanical properties. Core-shell nanowires are mass produced from a macroscopic semiconductor rod by using a new top-to-bottom fabrication approach based on thermal size reduction. Nanostructures with diameters from 30 to 200 nm result in coloration that spans the whole visible spectrum via resonant Mie scattering. Nanoshell coloration based on thin film interference is proposed as a structural coloration mechanism which becomes dominant for nanowires having 700-1200 nm diameter. Controlled color generation in any part of visible and infrared spectral regions can be achieved by the simple scaling down procedure. Spectral color generation in mass-produced uniform core-shell nanowire arrays paves the way for applications such as spectral authentication at nanoscale, light-scattering ingredients in paints and cosmetics, large-area devices, and infrared shielding.     

Effect of anchovy by-product protein coating incorporated with thyme essential oil on the shelf life of anchovy (<Emphasis Type="Italic">Engraulis encrasicolus</Emphasis> L.) fillets

The effects of anchovy by-product protein coatings incorporated with thyme essential oil (TEO) on the shelf life of anchovy (Engraulis encrasicolus L.) fillets stored at 4 ± 1 °C were investigated. We grouped fillets in three categories: untreated fillets, fillets treated in coating solution alone, and fillets treated in coating solution containing 1.5% TEO and analyzed on 0, 3, 6, and 9 days of storage. It was observed that the total volatile basic nitrogen (TVB-N) and pH of all the fillet groups increased under cold storage conditions; however, this increase was much slow in both the coated anchovy fillets. Both coating applications slowed down the lipid oxidation but the coating containing TEO exhibited better effect than coating alone. The coating application alone or with essential oil had limited effect on microbial growth but positively affected the sensory quality. These results revealed that anchovy by-product protein coating mixed with TEO may prolong anchovy fillets’ shelf life stored under cold condition.     

Analytical evaluation of charge carrier density of organic materials with Gauss density of states

We present analytical formulas for the calculation of the charge carrier density of organic materials with Gauss density of states. The charge carrier density is defined as the convolution of the Gauss density of states and Fermi–Dirac functions and is expressed in terms of Gauss–Fermi functions. The utility of the obtained series formulae is that they are built into standard computer mathematical packages so that neither approximations nor numerical integrations of Gauss–Fermi functions are necessary. The results of calculations are presented and compared with numerical procedure methods for the same problems.     

Features of technology of high-temperature superconductor films for microwave filters

The characteristics of fourth-order bandpass microwave filters based on high-temperature super-conductor (HTS) films have been numerically simulated and experimentally measured for the devices based on YBCO films purchased from Theva GmbH (Munich) and manufactured at the Institute for Physics of Microstructures (Nizhni Novgorod). Experimental data were used to determine the parameters of the surface impedance model for the HTS films. The results show that HTS-based filters with high performance characteristics can be obtained using HTS films manufactured by different technologies.     

Sub‐Micrometer Surface‐Patterned Ribbon Fibers and Textiles

The worldwide annual production volume of textiles is nearly one hundred million metric tons. Most of these undergo treatments to achieve specific properties, such as color, hydrophobicity, antimicrobial, or UV protection, using chemicals that lead to collateral environmental consequences. There is great interest in developing alternative and sustainable strategies to achieve textile functionality that do not involve chemical treatment. Here we present a thermal drawing approach to achieve fiber surface gratings on a rectangular cross‐section. We demonstrate directional wetting properties as well as structural coloration based on the gratings. Periods down to ≈ 600 nm were established on the surface of a fiber. Fabrics displaying higher‐order diffraction peaks in the visible regime were produced from surface‐patterned fibers using convetional weaving machinery.     

Microwave power amplifiers based on AlGaN/GaN transistors with a two-dimensional electron gas

A technique for synthesis of microwave power amplifiers based on transistors with a AlGaN/GaN heterojunction is discussed. Special focus is on the development of a technique for synthesis of transformation circuits of the power amplifier to increase efficiency with a retained high output power. The use of independent matching at the harmonic frequencies and fundamental frequency makes it possible to control the attainable efficiency in a wide frequency band along with the total suppression of harmonics beyond the operational band. Microwave power amplifiers for operation at 4 and 9 GHz have been developed and experimentally investigated.