Browsing by Subject "Screening"

Now showing 1 - 8 of 8

Open Access
A confirmatory test for sperm in sexual assault samples using a microfluidic-integrated cell phone imaging system
(Elsevier, 2020) Deshmukh, S.; İnci, Fatih; Karaaslan, M. G.; Öğüt, M. G.; Duncan, D.; Klevan, L.; Duncan, G.; Demirci, U.
Rapid and efficient processing of sexual assault evidence to accelerate forensic investigation and decrease casework backlogs is urgently needed. Therefore, the standardized protocols currently used in forensic laboratories can benefit from continued innovation to handle the increasing number and complexity of samples being submitted to forensic labs. To our knowledge, there is currently no available rapid and portable forensic screening technology based on a confirmatory test for sperm identification in a sexual assault kit. Here, we present a novel forensic sample screening tool, i.e., a microchip integrated with a portable cell phone imaging platform that records and processes images for further investigation and storage. The platform (i) precisely and rapidly screens swab samples (<15 min after sample preparation on-chip); (ii) selectively captures sperm from mock sexual assault samples using a novel and previously published SLeX-based surface chemistry treatment (iii) separates non-sperm contents (epithelial cells and debris in this case) out of the channel by flow prior to imaging; (iv) captures cell phone images on a portable cellphone-integrated imaging platform, (v) quantitatively differentiates sperm cells from epithelial cells, using a morphology detection code that leverages Laplacian of Gaussian and Hough gradient transform methods; (vi) is sensitive within a forensic cut-off (>95% accuracy) compared to the manual counts; (vii) provides a cost-effective and timely solution to a problem which in the past has taken a great deal of time; and (viii) handles small volumes of sample (20 μL). This integration of the cellphone imaging platform and cell recognition algorithms with disposable microchips can be a new direction toward a direct visual test to screen and differentiate sperm from epithelial cell types in forensic samples for a crime laboratory scenario. With further development, this integrated platform could assist a sexual assault nurse examiner (SANE) in a hospital or sexual assault treatment center facility to flag sperm-containing samples prior to further downstream testing.
Open Access
Local current distribution at large quantum dots (QDs): A self-consistent screening model
(Elsevier B.V., 2008) Krishna, P. M.; Siddiki, A.; Güven, K.; Hakioǧlu T.
We report the implementation of the self-consistent Thomas-Fermi screening theory, together with the local Ohm's law to a quantum dot system in order to obtain local current distribution within the dot and at the leads. We consider a large dot (size > 700 nm) defined by split gates, and coupled to the leads. Numerical calculations show that the non-dissipative current is confined to the incompressible strips. Due to the non-linear screening properties of the 2DES at low temperatures, this distribution is highly sensitive to external magnetic field. Our findings support the phenomenological models provided by the experimental studies so far, where the formation of the (direct) edge channels dominate the transport.
Open Access
Robust screening under ambiguity
(Springer, 2017) Pınar, M. Ç.; Kızılkale, C.
We consider the problem of screening where a seller puts up for sale an indivisible good, and a buyer with a valuation unknown to the seller wishes to acquire the good. We assume that the buyer valuations are represented as discrete types drawn from some distribution, which is also unknown to the seller. The seller is averse to possible mis-specification of types distribution, and considers the unknown type density as member of an ambiguity set and seeks an optimal pricing mechanism in a worst case sense. We specify four choices for the ambiguity set and derive the optimal mechanism in each case.
Open Access
The self-consistent calculation of the edge states at quantum Hall effect (QHE) based Mach-Zehnder interferometers (MZI)
(Elsevier B.V., 2008) Siddiki, A.; Kavruk, A. E.; Öztürk, T.; Atav, U.; Şahin, M.; Hakioǧlu T.
The spatial distribution of the incompressible edge states (IES) is obtained for a geometry which is topologically equivalent to an electronic Mach-Zehnder interferometer, taking into account the electron-electron interactions within a Hartree type self-consistent model. The magnetic field dependence of these IES is investigated and it is found that an interference pattern may be observed if two IES merge or come very close, near the quantum point contacts. Our calculations demonstrate that, being in a quantized Hall plateau does not guarantee observing the interference behavior.
Open Access
A self-consistent microscopic model of Coulomb interaction in a bilayer system as an origin of Drag Effect Phenomenon
(Elsevier B.V., 2008) Güven, K.; Siddiki, A.; Krishna, P. M.; Hakioǧlu T.
In this work we implement the self-consistent Thomas-Fermi model that also incorporates a local conductivity model to an electron-electron bilayer system, in order to describe novel magneto-transport properties such as the Drag Phenomenon. The model can successfully account for the poor screening of the potential within the incompressible strips and its impact on the inter-layer Coulomb interaction. An externally applied current in the active layer results in the tilting of the Landau levels and built-up of a Hall potential across the layer, which, in turn, induces a tilted potential profile in the passive layer as well. We investigate the effect of the current intensity, temperature, magnetic field, and unequal density of layers on the self-consistent density and potential profiles of the bilayer system.
Open Access
The static and dynamic screening of power loss of a two-dimensional electron gas
(Academic Press, 1998) Bennett, C.; Balkan, N.; Tanatar, Bilal; Celik, H.; Cankurtaran, M.
Experimental results concerning the well-width dependence of the acoustic-phonon-assisted energy relaxation of a two-dimensional electron gas in GaAs/Ga1-xAlxAs quantum-well structures are compared with theoretical models that involve piezoelectric and deformation-potential scattering and the effects of static and dynamic screening of the electron-acoustic phonon interaction. It is shown that screening only slightly modifies the predictions of the approximate calculations. © 1998 Academic Press.
Open Access
To invest or screen efficiently: a potential conflict in relationships governed by incomplete contracts
(Elsevier BV, 2001) Bac, M.
We consider a dynamic trade relationship where quality is not contractible and potential sellers retain quality-relevant private information. We show that the presence of an investment technology to improve the incumbent seller's innate quality may impair the efficiency of the screening process. If the conflict is effective, the buyer has to induce an inefficient screening process or reduce the productivity of the investment technology. This conflict suggests that the hold-up problem may be more severe than predicted by models of incomplete contracts that assume complete information. © Elsevier Science B.V.
Open Access
Where are the edge-states near the quantum point contacts? A self-consistent approach
(Elsevier B.V., 2007) Siddiki, A.; Cicek, E.; Eksi, D.; Mese, A. I.; Aktas, S.; Hakioğlu, T.
Abstract In this work, we calculate the current distribution, in the close vicinity of the quantum point contacts (QPCs), taking into account the Coulomb interaction. In the first step, we calculate the bare confinement potential of a generic QPC and, in the presence of a perpendicular magnetic field, obtain the positions of the incompressible edge states (IES) taking into account electron–electron interaction within the Thomas–Fermi theory of screening. Using a local version of Ohm’s law, together with a relevant conductivity model, we also calculate the current distribution. We observe that, the imposed external current is confined locally into the incompressible strips. Our calculations demonstrate that, the inclusion of the electron–electron interaction, strongly changes the general picture of the transport through the QPCs.