ON THE SINGULAR INTEGRAL EQUATIONS WITH CARLEMAN SHIFT IN THE CASE OF THE VANISHING COEFFICIENT

Joint Research on Environmental Science and Technology for the Eart

Image processing for biological experiments on a mobile phone

Smartphone capabilities have been expanding rapidly since Apple Inc. introduced the iPhone in early 2007. Today’s smartphones offer decent computational power, good internet connectivity and high- pixel-count cameras. In this thesis, we leverage these resources in novel ways, using a smartphone CMOS camera as a sensing device and performing biological analyses immediately on the smartphone. We show two novel ways to exploit the capacities of the smartphone and discuss the challenges that we faced in the development of these applications. We first demonstrate a mobile system to identify counterfeit and substandard drug products effectively and inexpensively. Our system costs roughly 250 dollars, which is affordable in developing countries in Africa and Asia, where counterfeit and substandard drug products are flooding the markets. The system also enables analyses at the point of testing, which is particularly valuable when laboratory facilities are remote or unavailable. The system consists of a 3D-printed cradle, a cheap Android based smartphone and an UV lamp. The system is inspired by the use of the thin layer chromatography (TLC) method, which is known to be efficient in verifying the identity of drug products from unknown sources. The core analysis of a TLC plate is performed though a series of image processing algorithms on the Android smartphone. For drugs with a single active pharmaceutical ingredient (API) that absorbs ultraviolet (UV) light, the mobile phone-based detection system is able to discern 5% drug concentration differences, which is equivalent to a commercially available lab-based desktop TLC reader priced at roughly $40,000. We then demonstrate absorption-based biological assays by performing an enzyme-linked immunosorbent assay (ELISA) experiment. ELISA is an assay technique used to detect and quantify substances such as proteins, antibodies, hormones, etc. When combined with some simple optical components, the rear-facing CMOS camera in a smartphone can capture spectral data for biological samples. We developed image processing algorithms to calibrate and to analyze these spectra to match the results produced by conventional laboratory instruments. In order to enable unskilled users to perform ELISA experiment accurately, we integrated these techniques into an Android application with a simple user interface that walks users though assay steps. Finally, we generalize some of the lessons learned and challenges faced during development of the TLC and ELISA applications in order to provide a broader and more useful picture for developing smartphone bioassay applications in general

DESIGN OF A HIGH-SENSITIVITY DEVICE FOR DETECTING WEAK MAGNETIC FIELDS

An anti-serial fluxgate sensor configuration is proposed in this report. The design comprises two identical bilayer-rod fluxgate sensors connected anti-serially in a straight line. Each bilayer-rod sensor is constructed of an excitation coil and a pick-up coil wrapped around a core. The core material consists of Metglas ribbon, an amorphous alloy with high permeability, negligible hysteresis, and a high saturated magnetic field. The core is cut into a bar shape and uses double layers to enhance modulated flux density. A high sensitivity of 10 mV/Oe (with excitation of 45 kHz and 250 mA) is obtained experimentally with low noise of 1´10-5 Oe/Ö Hz at 1 Hz. In measurements of weak magnetic fields, the azimuth response indicates its vector feature. The proposed design is suitable for electronic compass and displacement applications

STUDY OF NEGATIVE REFRACTIVE INDEX IN Rb FOUR-LEVEL N-TYPE ATOMIC GAS MEDIUM

In this work, we study the generation of a negative refractive index based on electromagnetically induced transparency (EIT) in a Rb four-level N-type atomic gas medium. We derive analytic expressions for the relative permittivity and relative permeability of the medium according to the parameters of the probe, pump, and signal laser fields. We then investigate the variation of the real parts of the relative permittivity and relative permeability with respect to the intensity and frequency of the pump and signal laser fields. In the presence of the pump laser beam, the medium becomes transparent to the probe laser beam even in the resonant region. At the same time, the real parts of the relative permittivity and relative permeability are simultaneously negative (i.e., the medium exhibits a negative refractive index) in the EIT spectral domain. In the presence of the signal laser beam, the EIT effect occurs over two different frequency domains of the probe beam, so a negative refractive index is also generated in these two frequency domains. The investigation of the real parts of the relative permittivity and relative permeability with intensity and frequency of the pump and signal laser fields allowed us to find the laser parameters for the appearance of the negative refractive index, which can be useful for experimental observations

Asymptotic periodic solutions of differential equations with infinite delay

In this paper, by using the spectral theory of functions and properties of evolution semigroups, we establish conditions on the existence, and uniqueness of asymptotic 1-periodic solutions to a class of abstract differential equations with infinite delay of the form \begin{equation*} \frac{d u(t)}{d t}=A u(t)+L(u_t)+f(t) \end{equation*} where $A$ is the generator of a strongly continuous semigroup of linear operators, $L$ is a bounded linear operator from a phase space $\mathscr{B}$ to a Banach space $X$, $u_t$ is an element of $\mathscr{B}$ which is defined as $u_t(\theta)=u(t+\theta)$ for $\theta \leq 0$ and $f$ is asymptotic 1-periodic in the sense that $\lim\limits_{t \rightarrow \infty}(f(t+1)-$ $f(t))=0$. A Lotka-Volterra model with diffusion and infinite delay is considered to illustrate our results.Comment: 13 page