Search

In order to solve overfitting of Convolutional Neural Network (CNN) in Synthetic Aperture Radar (SAR) image ground object recognition detection, in this paper CNN was optimized and improved for obtaining improved performance. Firstly, tanh function was selected as activation function to make CNN stably converge. Secondly, dropout was adopted in hidden layer of CNN to reduce overfitting. For the problem of CNN fell into local minimum value after adopting dropout, this paper proposed a weight update method of the ‘variable step size + gradient descent with momentum’, which could make CNN escape local minimum value and weaken oscillation. Finally, optimized and improved method of the ‘tanh + dropout + variable step size + gradient descent with momentum’ was proposed, which effectively reduced overfitting. Effectiveness and accuracy of proposed method are verified by experiments.

In the classification detection of Synthetic Aperture Radar (SAR) images, there are SAR images acquired from different radars. For the problem of ground objects classification detection of less-label heterogeneous SAR images, this paper uses the Convolutional Neural Network (CNN) based on transfer learning to train a pre-trained network with fewer labels. To fine-tune the network, we can realize the ground object classification detection of heterogeneous SAR images. The effectiveness of the proposed method is verified by experiments.

We recently defined a magnetic bead-based assay that exploited an agglutination-like response for DNA and applied it to DNA-containing cell enumeration using inexpensive benchtop hardware [ J. Am. Chem. Soc. 2012 , 134 ( 12 ), 5689 - 96 ]. Although cost-efficient, the open-well format assay required numerous manual steps, and the magnetic field actuation scheme was not readily adaptable for integration. Here, we demonstrate a low-cost ($2 in-lab), higher-throughput "pinwheel assay" platform that relies on a combination of a disposable rotation-driven microdisc (RDM), and a simple bidirectional rotating magnetic field (bi-RMF). The assay was transformed into an integrated microfluidic system using a multilayered polyester microfluidic disc created through laser print, cut and laminate fabrication, with fluid flow controlled by rotation speed without any mechanical valves. The RDM accepts four samples that undergo on-chip dilution to five different concentrations that cover the effective concentration range needed for downstream cell counting by pinwheel assay. We show that a bi-RMF is effective for the simultaneous actuation of pinwheel assays in 20 detection chambers. The optimization of the bi-RMF frequencies allows the RDM-based pinwheel assay detect human genomic DNA down to a mass of human genomic DNA (5.5 picograms) that is roughly equal to the mass in a single cell. For proof of principle, enumeration of the white blood cells in human blood samples on the RDM provided data correlating well (C.V. of 10%) with those obtained in a clinical lab. Fusing the cost-effective RDM with a simple bi-RMF provides a promising strategy for automation and multiplexing of magnetic particle-based agglutination assays.

This work describes the development of a novel microdevice for forensic DNA processing of reference swabs. This microdevice incorporates an enzyme-based assay for DNA preparation, which allows for faster processing times and reduced sample handling. Infrared-mediated PCR (IR-PCR) is used for STR amplification using a custom reaction mixture, allowing for amplification of STR loci in 45 min while circumventing the limitations of traditional block thermocyclers. Uniquely positioned valves coupled with a simple rotational platform are used to exert fluidic control, eliminating the need for bulky external equipment. All microdevices were fabricated using laser ablation and thermal bonding of PMMA layers. Using this microdevice, the enzyme-mediated DNA liberation module produced DNA yields similar to or higher than those produced using the traditional (tube-based) protocol. Initial microdevice IR-PCR experiments to test the amplification module and reaction (using Phusion Flash/SpeedSTAR) generated near-full profiles that suffered from interlocus peak imbalance and poor adenylation (significant -A). However, subsequent attempts using KAPA 2G and Pfu Ultra polymerases generated full STR profiles with improved interlocus balance and the expected adenylated product. A fully integrated run designed to test microfluidic control successfully generated CE-ready STR amplicons in less than 2 h (

This paper presents a simple and cost-effective polyester toner microchip fabricated with laser print and cut lithography (PCL) to use with a battery-powered centrifugal platform for fluid handling. The combination of the PCL microfluidic disc and centrifugal platform: (1) allows parallel aliquoting of two different reagents of four different volumes ranging from nL to μL with an accuracy comparable to a piston-driven air pipette; (2) incorporates a reciprocating mixing unit driven by a surface-tension pump for further dilution of reagents, and (3) is amenable to larger scale integration of assay multiplexing (including all valves and mixers) without substantially increasing fabrication cost and time. For a proof of principle, a 10 min colorimetric assay for the quantitation of the protein level in the human blood plasma samples is demonstrated on chip with a limit of detection of ∼5 mg mL(-1) and coefficient of variance of ∼7%.

This work describes the development of a novel microdevice for forensic DNA processing of reference swabs. This microdevice incorporates an enzyme-based assay for DNA preparation, which allows for faster processing times and reduced sample handling. Infrared-mediated PCR (IR-PCR) is used for STR amplification using a custom reaction mixture, allowing for amplification of STR loci in 45 min while circumventing the limitations of traditional block thermocyclers. Uniquely positioned valves coupled with a simple rotational platform are used to exert fluidic control, eliminating the need for bulky external equipment. All microdevices were fabricated using laser ablation and thermal bonding of PMMA layers. Using this microdevice, the enzyme-mediated DNA liberation module produced DNA yields similar to or higher than those produced using the traditional (tube-based) protocol. Initial microdevice IR-PCR experiments to test the amplification module and reaction (using Phusion Flash/SpeedSTAR) generated near-full profiles that suffered from interlocus peak imbalance and poor adenylation (significant -A). However, subsequent attempts using KAPA 2G and Pfu Ultra polymerases generated full STR profiles with improved interlocus balance and the expected adenylated product. A fully integrated run designed to test microfluidic control successfully generated CE-ready STR amplicons in less than 2 h (1 h of hands-on time). Using this approach, high-quality STR profiles were developed that were consistent with those produced using conventional DNA purification and STR amplification methods. This method is a smaller, more elegant solution than current microdevice methods and offers a cheaper, hands-free, closed-system alternative to traditional forensic methods.

We report on a novel and cost-effective microfluidic platform that integrates immunomagnetic separation and cell enumeration via DNA-induced bead aggregation. Using a two-stage immunocapture microdevice, 10 μL of whole blood was processed to isolate CD4+ T-cells. The first stage involved the immuno-subtraction of monocytes by anti-CD14 magnetic beads, followed by CD4+ T-cell capture with anti-CD4 magnetic beads. The super hydrophilic surface generated during polydimethylsiloxane (PDMS) plasma treatment allowed for accurate metering of the CD4+ T-cell lysate, which then interacted with silica-coated magnetic beads under chaotropic conditions to form aggregates. Images of the resulting aggregates were captured and processed to reveal the mass of DNA, which was used to back-calculate the CD4+ T-cell number. Studies with clinical samples revealed that the analysis of blood within 24 hours of phlebotomy yielded the best results. Under these conditions, an accurate cell count was achieved (R(2) = 0.98) when compared to cell enumeration via flow cytometry, and over a functional dynamic range from 106-2337 cells per μL.

We describe a technique for fabricating microfluidic devices with complex multilayer architectures using a laser printer, a CO2 laser cutter, an office laminator and common overhead transparencies as a printable substrate via a laser print, cut and laminate (PCL) methodology. The printer toner serves three functions: (i) it defines the microfluidic architecture, which is printed on the overhead transparencies; (ii) it acts as the adhesive agent for the bonding of multiple transparency layers; and (iii) it provides, in its unmodified state, printable, hydrophobic 'valves' for fluidic flow control. By using common graphics software, e.g., CorelDRAW or AutoCAD, the protocol produces microfluidic devices with a design-to-device time of ∼40 min. Devices of any shape can be generated for an array of multistep assays, with colorimetric detection of molecular species ranging from small molecules to proteins. Channels with varying depths can be formed using multiple transparency layers in which a CO2 laser is used to remove the polyester from the channel sections of the internal layers. The simplicity of the protocol, availability of the equipment and substrate and cost-effective nature of the process make microfluidic devices available to those who might benefit most from expedited, microscale chemistry.

Infrared (IR)-mediated thermal cycling system, a method proven to be a effective for sub-μL scale polymerase chain reaction (PCR) on microchips, has been integrated with DNA extraction and separation on a glass microchip in a fully integrated micro Total Analysis System by Easley et al., in 2006. IR-PCR has been demonstrated on both glass and PMMA microdevices where the fabrication (bonding) is not trivial. Polyester-toner (PeT) microfluidic devices have significant potential as cost-effective, disposable microdevices as a result of the ease of fabrication (∼$0.25 USD and

We recently defined a method for fabricating multilayer microdevices using poly(ethylene terephthalate) transparency film and printer toner, and showed these could be successfully applied to DNA extraction and amplification (Duarte et al., Anal. Chem. 2011, 83, 5182-5189). Here, we advance the functionality of these microdevices with flow control enabled by hydrophobic valves patterned using laser printer lithography. Laser printer patterning of toner within the microchannel induces a dramatic change in surface hydrophobicity (change in contact angle of DI water from 51° to 111°) with good reproducibility. Moreover, the hydrophobicity of the surface can be controlled by altering the density of the patterned toner via varying the gray-scale setting on the laser printer, which consequently tunes the valve's burst pressure. Toner density provided a larger burst pressure bandwidth (158 ± 18 Pa to 573 ± 16 Pa) than could be achieved by varying channel geometry (492 ± 18 Pa to 573 ± 16 Pa). Finally, we used a series of tuned toner valves (with varied gray-scale) for passive valve-based fluidic transfer in a predictable manner through the architecture of a rotating PeT microdevice. While an elementary demonstration, this presents the possibility for simplistic and cost-effective microdevices with valved fluid flow control to be fabricated using nothing more than a laser printer, a laser cutter and a laminator.