Design and implementation of fuzzy logic based automatic gain controller for EDFAs

In this study, the design and implementation of a fuzzy logic (FL) based automatic gain controller card (AGC) is performed in order to control the pump laser current with respect to signal power and signal wavelength. The FL-AGC card consists of an amplifier, an analogue to digital converter (ADC), a digital to analogue converter (DAC), and a FL based software that is embedded to a microcontroller. With this configuration, gain flattening at the output of the erbium doped fibre amplifier (EDFA) along C band is achieved. In this way, ergonomically designed FL-AGC card can be easily matched with EDFAs and can be applicable to optical system applications.     

Development of a rapid-scan fiber-integrated terahertz spectrometer

Scientists in terahertz (THz) wave technologies have benefited from the recent developments in ultrafast laser technologies and RF technologies and applied these new gained techniques into characterizing a wide variety of phenomena. Undoubtedly, the most successful of these applications has been in the development of time-domain terahertz spectroscopic and imaging systems which has been utilized in the characterization of dielectrics and semiconductors. This pulsed technique has allowed users to characterize dynamical behavior inside materials under illumination with picosecond resolution. Typically pump/probe or similar dynamical measurements require the use of amplified pulses derived from free-space solid state lasers in the $\upmu $ J–mJ range and since interferometric techniques are typically used in pulsed measurements the measurement time of a THz spectrum can last at least tens of minutes. Better systems can be realized based on fiber laser technologies. Here we discuss the advantages of a THz spectrometer driven by an ultrafast Ytterbium doped fiber laser whose repetition rate can be tuned rapidly allowing for rapid dynamical measurements. The efficient gain medium, robust operation and compact design of the system opens up the possibility of exploring rapid detection of various materials as well as studying dynamical behavior using the high brightness source.     

Lossless single-photon shaping via heralding

Using spontaneous optical parametric downconversion, we experimentally demonstrate heralded generation of shaped single photons, whose modes are tailored indirectly by applying amplitude modulation on the pump field that drives the downconversion process. Our experiment opens a door to creating high-quality, mode-shaped single photons at a substantially higher efficiency than is possible with the existing method of direct single-photon shaping.     

Hessenberg matrices and the Pell and Perrin numbers

In this paper, we investigate the Pell sequence and the Perrin sequence and we derive some relationships between these sequences and permanents and determinants of one type of Hessenberg matrices.     

Modeling of claim exceedances over random thresholds for related insurance portfolios

Large claims in an actuarial risk process are of special importance for the actuarial decision making about several issues like pricing of risks, determination of retention treaties and capital requirements for solvency. This paper presents a model about claim occurrences in an insurance portfolio that exceed the largest claim of another portfolio providing the same sort of insurance coverages. Two cases are taken into consideration: independent and identically distributed claims and exchangeable dependent claims in each of the portfolios. Copulas are used to model the dependence situations. Several theorems and examples are presented for the distributional properties and expected values of the critical quantities under concern.     

On the Quaternionic B 2-Slant Helices in the Euclidean Space E 4

In this paper we give a new definition of harmonic curvature functions in terms of B ₂ and we define a new kind of slant helix which we call quaternionic B ₂–slant helix in 4–dimensional Euclidean space E ⁴ by using the new harmonic curvature functions. Also we define a vector field D which we call Darboux quaternion of the real quaternionic B ₂–slant helix in 4–dimensional Euclidean space E ⁴ and we give a new characterization such as: "a: I ì \mathbb R ? E⁴{``\alpha : I \subset {\mathbb R} \rightarrow E^4} is a quaternionic B ₂–slant helix ${\Leftrightarrow H^\prime_2 -KH_{1} = 0"}${\Leftrightarrow H^\prime_2 -KH_{1} = 0"} where H ₂, H ₁ are harmonic curvature functions and K is the principal curvature function of the curve α.     

Differential separation of protein mixtures using convective assembly and label-free detection with surface enhanced Raman scattering

Differential separation and label-free detection of proteins using SERS from their mixtures after a convective assembly process is reported. Binary and ternary mixtures of proteins are mixed with AgNPs and assembled into ordered structures. The spectra acquired from the assembled area indicate that the proteins are differentially distributed.     

Experimental and theoretical study on the structure and vibrational spectra of β-2-aminopyridinium dihydrogenphosphate

Experimental and theoretical vibrational spectra of β-2-aminopyridinium dihydrogenphosphate (β-2APDP) have been investigated. The FT-IR spectrum of β-2APDP was recorded in the region 4000-400 cm(-1). The optimized molecular structure and theoretical vibrational frequencies of β-2APDP have been investigated using ab initio Hartree-Fock (HF) and density functional B3LYP method with 6-311++G(d,p) basis set. The optimized geometric parameters (bond lengths and bond angles) and theoretical frequencies have been compared with the corresponding experimental data and it is found that they agree well with each other. All the assignments of the theoretical frequencies were performed by potential energy distributions using VEDA 4 program. Furthermore, the used scale factors were obtained from the ratio of the frequency values of the strongest peaks in the experimental and theoretical IR spectra. From the results it was concluded that the B3LYP method is superior to the HF method for the vibrational frequencies.     

Characterisation of azo dye and carbon nanoparticle-doped guest–host liquid crystalline matrix

During the recent years, liquid crystals (LCs) have much attention owing to their wide range of possible application and structural properties in electronics and optics. In this study, two different azo structured dyes (Disperse Yellow 3 and 7) and their mixture were separately doped to each of two different nematic LCs (E8 and E63). Their solubilities (except dye mixture), order parameters, textures and phase transition temperatures were determined. Single-walled nanotubes and fullerene C60 in a small amount were separately added to each of these solutions, and the experiments were repeated at the final stage analogously except solubilities. The solubilities of dyes in the LC E63 were lower than those of E8. The highest order parameter value was attained with Yellow 7 dye in E63 nematic host.     

Towards single-microorganism detection using surface-enhanced Raman spectroscopy

The identification and discrimination of microorganisms is important not only for clinical reasons but also for pharmaceutical clean room production and food-processing technology. Vibrational spectroscopy such as IR, Raman, and surface-enhanced Raman scattering (SERS) can provide a rapid ‘fingerprint’ on the chemical structure of molecules and is used to obtain a ‘fingerprint’ from microorganisms as well. Because of the requirement that a single bacterium cell and noble metal nanoparticles must be in close contact and the lack of a significant physical support to hold nanoparticles around the single bacterium cell, the acquisition of SERS spectra for a single bacterium using colloidal nanoparticles could be a challenging task. The feasibility of SERS for identification down to a single bacterium is investigated. A Gram-negative bacterium, Escherichia coli, is chosen as a model for the investigation. Because the adsorption of silver nanoparticles onto the bacterial cell is an exclusive way for locating nanoparticles close to the bacterium cell, the absorption characteristics of silver nanoparticles with different surface charges are investigated. It is demonstrated that the citrate-reduced colloidal silver solution generates more reproducible SERS spectra. It is found that E. coli cells aggregate upon mixing with silver colloidal solution, and this may provide an additional benefit in locating the bacterial cell under a light microscope. It is also found that a laser wavelength in the UV region could be a better choice for the study due to the shallow penetration depth. It is finally shown that it is possible to obtain SERS spectra from a single cell down to a few bacterial cells, depending on the aggregation properties of bacterial cells for identification and discrimination.