Metaheuristic hybridizations for the regenerator placement and dimensioning problem in sub-wavelength switching optical networks

Physical layer impairments severely limit the reach and capacity of optical systems, thereby hampering the deployment of transparent optical networks (i.e., no electrical signal regenerators are required). Besides, the high cost and power-consumption of regeneration devices makes it unaffordable for network operators to consider the opaque architecture (i.e., regeneration is available at every network node). In this context, translucent architectures (i.e., regeneration is only available at selected nodes) have emerged as the most promising short term solution to decrease costs and energy consumption in optical backbone networks. Concurrently, the coarse granularity and inflexibility of legacy optical technologies have re-fostered great interest in sub-wavelength switching optical networks, which introduce optical switching in the time domain so as to further improve resources utilization. In these networks, the complex regenerator placement and dimensioning problem emerges. In short, this problem aims at minimizing the number of electrical regenerators deployed in the network. To tackle it, in this paper both a greedy randomized adaptive search procedure and a biased random-key genetic algorithm are developed. Further, we enhance their performance by introducing both path-relinking and variable neighborhood descent as effective intensification procedures. The resulting hybridizations are compared among each other as well as against results from optimal and heuristic mixed integer linear programming formulations. Illustrative results over a broad range of network scenarios show that the biased random-key genetic algorithm working in conjunction with these two intensification mechanisms represents a compelling network planning algorithm for the design of future sub-wavelength optical networks.     

Molecular shift register and its utilization as an autonomous DNA synthesizer

A novel algorithmic approach to the synthesis of fairly long DNA molecules with nonrecurring sequences is demonstrated. The scheme exploits chemical embodiment of shift registers (SR) to execute algorithms similar to those used to generate pseudorandom numbers on a computer. Single stranded DNA molecules guide the synthesis of double stranded DNA according to the SR truth table. The SR logic facilitates an exponentially smaller synthesis effort compared with all other strategies. A redundancy based scheme, similar to those used in communication, is utilized to suppress synthesis errors.     

Common energy scale for magnetism and superconductivity in underdoped cuprates: a muon spin resonance investigation of (Ca(x)La(1-x)) (Ba(1.75-x)La(0.25+x))Cu3O(y)

We characterize the spontaneous magnetic field, and determine the associated temperature T(g), in the superconducting state of (Ca(x)La(1-x)) (Ba(1.75-x)La(0.25+x)) Cu(3)O(y) using zero and longitudinal field muon spin resonance measurements for various values of x and y. Our major findings are (i) T(g) and T(c) are controlled by the same energy scale, (ii) the phase separation between hole poor and hole rich regions is a microscopic one, and (iii) spontaneous magnetic fields appear gradually with no moment size evolution.     

Interrogation of fiber gratings by use of low-coherence spectral interferometry of noiselike pulses

We demonstrate an innovative method for a real-time interrogation of fiber Bragg gratings based on low-coherence spectral interferometry of noiselike pulses. By analyzing the spectral interference at the output of a Michelson interferometer we obtained the impulse response of the grating with a time resolution of ~350 fs . Using the Gabor transformation, we could directly detect nonuniform regions inside the grating and could measure the spatial dependence of the resonance wavelength along the grating.     

Experimental estimates of dephasing time in molecular magnets

Muon spin relaxation measurements in isotropic molecular magnets (MM) with a spin value S ranging from 7/2 to 27/2 are used to determine the magnitude and origin of dephasing time tau(phi) of molecular magnets. It is found that tau(phi) approximately 10 nsec with no S or ligand dependence. This indicates a nuclear origin for the stochastic field. Since tau(phi) is a property of the environment, we argue that it is a number common to similar types of MM. Therefore, tau(phi) is shorter than the Zener and tunneling times of anisotropic MM such as Fe(8) or Mn(4) for standard laboratory sweep rates. Our findings call for a stochastic Landau-Zener theory in this particular case.     

董务民先生二三事

传来《力学进展》创始人之一,原执行主编董务民先生于2007年1月1日去世的消息,很感突然,也很悲痛.两个多月前,我们还在一起讨论辞典翻译的事情,讨论发挥余热再作贡献的问题.他还露着慈祥的笑容,还很健谈,觉得马克思还没有向他招手,还想做不少事.     

A NISQ Method to Simulate Hermitian Matrix Evolution

As a universal quantum computer requires millions of error-corrected qubits, one of the current goals is to exploit the power of noisy intermediate-scale quantum (NISQ) devices. Based on a NISQ module–layered circuit, we propose a heuristic protocol to simulate Hermitian matrix evolution, which is widely applied as the core for many quantum algorithms. The two embedded methods, with their own advantages, only require shallow circuits and basic quantum gates. Capable to being deployed in near future quantum devices, we hope it provides an experiment-friendly way, contributing to the exploitation of power of current devices.     

Quadruple hydrogen bonding containing supramolecular thermoplastic elastomers: Mechanical and morphological correlations

We report the design of bioinspired, reversible supramolecular thermoplastic elastomers (TPEs) functionalized with ureido‐cytosine (UCyt) complementary quadruple hydrogen bonding (QHB) sites. The polymer contained a soft poly(n‐butyl acrylate) central block that imparted flexibility and two external, hard nucleobase‐containing blocks that contributed to structural integrity. In addition, the hard block with pendant QHB motifs served as efficient physical crosslinks to further enhance the thermomechanical performance, where the polymer service window extended up to 30 °C higher compared to the controls that bear dimeric hydrogen bonding units. The resulting UCyt copolymers also exhibited improved surface and bulk morphology, which self‐assembled into well‐ordered lamellar microstructures. Moreover, the polymer displayed an unexpected moisture‐resistant property with less than 1 wt % equilibrium moisture uptake even at 95% relatively humidity, which presumably correlated with its well‐ordered and densely‐packed morphology facilitated by strong hydrogen bonding. Variable temperature Fourier‐transform infrared spectroscopy experiments further confirmed the thermoreversibility of hydrogen bonding, indicating melt‐processablility and recyclability of the polymer. These physical properties verified quadruple bonding dominated behavior, and structure–property–morphology relationships suggest key design parameters for future TPEs. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 13–23     

1,1‐Diamino‐2,2‐dinitroethylenes are always zwitterions

The nitration of tetraiodoethylene (7) yields 1,1‐diiodo‐2,2‐dinitroethylene (8). The latter reacts with alkylamines 9 or alkyldiamines 11 to give the corresponding acyclic 1,1‐diamino‐2,2‐dinitroethylenes 10 or their cyclic analogs 12, respectively. On the basis of liquid and solid‐state ¹³C and ¹⁵N NMR data, x‐ray analysis and ab initio calculations, we suggest that the title compounds are always zwitterionic and that the C_A–C_N bond is not a true double bond. Copyright © 2012 John Wiley & Sons, Ltd.     

The protonated Schiff base of halorhodopsin from Natronobacterium pharaonis is hydrolyzed at elevated temperatures

Halorhodopsin from Natronobacterium pharaonis (pHR) is a light-driven chloride pump in which photoisomerzation of a retinal chromophore triggers a photocycle which leads to a chloride anion transport across the plasma membrane. Similarly to other retinal proteins the protonated Schiff base (PSB), which covalently links the retinal to the protein, does not experience hydrolysis reaction at room temperature even though several water molecules are located in the protonated Schiff base (PSB) vicinity. In the present studies we have revealed that in contrast to other studied archaeal rhodopsins, temperature increase to about 70 degrees C hydrolyses the PSB linkage of pHR. The rate of the reaction is affected by Cl-concentration and reveals an anion binding site (in addition to the Cl- in the SB vicinity) with a binding constant of 100mM (measured at 70 degrees C). We suggest that this binding site is located on the extracellular side and its possible role in the Cl-pumping mechanism is discussed. The rate of the hydrolysis reaction is affected by the nature of the anion bound to pHR. Substitution of the Cl- anion by Br-, I- and SCN- exhibits similar behavior to that of CI- in the region of 100mM but higher concentrations are needed for N3-, HCOO- and NO2-to achieve similar behavior. Steady state pigment illumination accelerates the reaction and reduces the energy of activation and the frequency factor. Adjusting the sample temperature to 25 degrees C following the hydrolysis reaction led to about 80% pigment recovery. However, the newly reformed pigment is different from the mother pigment and has different characteristics. It is concluded that the apo-membrane adopts a modified conformation and/or aggregated state which rebinds the retinal to give a new conformation of the pHR pigment.