Comparison of Semi-Analytical Formulations and Gaussian Quadrature Rules for Quasi-Static Double Surface Potential Integrals

This paper presents a comparison of a new semi-analytical expression with Gaussian-quadrature formulas for the quasi-static double-surface potential integrals arising in the boundary integral (BI) models of micron-size objects, such as RF-MEMS switches. The integrals considered are the quasi-static Green's functions for the scalar and vector potentials, with constant or linear basis functions over triangular subdomains. The examples given illustrate that the new semi-analytical formulations can achieve significantly higher solution accuracy and are more efficient when compared to the Gaussian-quadrature formulas.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87252/4/Saitou47.pd

Production of Genetically Engineered Golden Syrian Hamsters by Pronuclear Injection of the CRISPR/Cas9 Complex

The pronuclear (PN) injection technique was first established in mice to introduce foreign genetic materials into the pronuclei of one-cell stage embryos. The introduced genetic material may integrate into the embryonic genome and generate transgenic animals with foreign genetic information following transfer of the injected embryos to foster mothers. Following the success in mice, PN injection has been applied successfully in many other animal species. Recently, PN injection has been successfully employed to introduce reagents with gene-modifying activities, such as the CRISPR/Cas9 system, to achieve site-specific genetic modifications in several laboratory and farm animal species. In addition to mastering the special set of microinjection skills to produce genetically modified animals by PN injection, researchers must understand the reproduction physiology and behavior of the target species, because each species presents unique challenges. For example, golden Syrian hamster embryos have unique handling requirements in vitro such that PN injection techniques were not possible in this species until recent breakthroughs by our group. With our species-modified PN injection protocol, we have succeeded in producing several gene knockout (KO) and knockin (KI) hamsters, which have been used successfully to model human diseases. Here we describe the PN injection procedure for delivering the CRISPR/Cas9 complex to the zygotes of the hamster, the embryo handling conditions, embryo transfer procedures, and husbandry required to produce genetically modified hamsters

Assessment of genome integrity with array CGH in cattle transgenic cell lines produced by homologous recombination and somatic cell cloning

<p>Abstract</p> <p>Background</p> <p>Transgenic cattle carrying multiple genomic modifications have been produced by serial rounds of somatic cell chromatin transfer (cloning) of sequentially genetically targeted somatic cells. However, cloning efficiency tends to decline with the increase of rounds of cloning. It is possible that multiple rounds of cloning compromise the genome integrity or/and introduce epigenetic errors in the resulting cell lines, rendering a decline in cloning. To test these possibilities, we performed 9 high density array Comparative Genomic Hybridization (CGH) experiments to test the genome integrity in 3 independent bovine transgenic cell lineages generated from genetic modification and cloning. Our plan included the control hybridizations (self to self) of the 3 founder cell lines and 6 comparative hybridizations between these founders and their derived cell lines with either high or low cloning efficiencies.</p> <p>Results</p> <p>We detected similar amounts of differences between the control hybridizations (8, 13 and 39 differences) and the comparative analyses of both "high" and "low" cell lines (ranging from 7 to 57 with a mean of ~20). Almost 75% of the large differences (>10 kb) and about 45% of all differences shared the same type (loss or gain) and were located in nearby genomic regions across hybridizations. Therefore, it is likely that they were not true differences but caused by systematic factors associated with local genomic features (e.g. GC contents).</p> <p>Conclusions</p> <p>Our findings reveal that large copy number variations are less likely to arise during genetic targeting and serial rounds of cloning, fortifying the notion that epigenetic errors introduced from serial cloning may be responsible for the cloning efficiency decline.</p

Analysis of RF-MEMS Switches Using Finite Element-Boundary Integration with Moment Method

This paper presents a new hybrid methodology for modeling RF-MEMS switches. This method combines the usual finite element-boundary integration (FE-BI) method for the fixed section of the switch, and the method of moments for the movable beam. This approach is intended to address the large 100:1 scale variation within a single computational domain, which also spans a very small fraction of a wavelength.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87249/4/Saitou98.pd

Contact Physics Modeling and Optimization Design of RF-MEMS Cantilever Switches

RF MEMS direct-contact switches exhibit many advantages over the conventional semiconductor switches; however, existing drawbacks such as low power handling, high pull-in voltage and long switch opening time are most critical. This paper presents an optimization design for an RF-MEMS cantilever direct-contact switch to achieve maximum power handling capability, minimum pull-in voltage and switch opening time simultaneously. A 2-step optimization technique is proposed to achieve the optimal design to allow for a power handling capability of 130 mW, a pull-in voltage of 52 V, and a switch opening time 4.4 _s presented. The optimization results show that substantial room exists for improving the current designs of RF MEMS direct-contact switches.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87255/4/Saitou72.pd

Transcriptional reprogramming of gene expression in bovine somatic cell chromatin transfer embryos

<p>Abstract</p> <p>Background</p> <p>Successful reprogramming of a somatic genome to produce a healthy clone by somatic cells nuclear transfer (SCNT) is a rare event and the mechanisms involved in this process are poorly defined. When serial or successive rounds of cloning are performed, blastocyst and full term development rates decline even further with the increasing rounds of cloning. Identifying the "cumulative errors" could reveal the epigenetic reprogramming blocks in animal cloning.</p> <p>Results</p> <p>Bovine clones from up to four generations of successive cloning were produced by chromatin transfer (CT). Using Affymetrix bovine microarrays we determined that the transcriptomes of blastocysts derived from the first and the fourth rounds of cloning (CT1 and CT4 respectively) have undergone an extensive reprogramming and were more similar to blastocysts derived from <it>in vitro </it>fertilization (IVF) than to the donor cells used for the first and the fourth rounds of chromatin transfer (DC1 and DC4 respectively). However a set of transcripts in the cloned embryos showed a misregulated pattern when compared to IVF embryos. Among the genes consistently upregulated in both CT groups compared to the IVF embryos were genes involved in regulation of cytoskeleton and cell shape. Among the genes consistently upregulated in IVF embryos compared to both CT groups were genes involved in chromatin remodelling and stress coping.</p> <p>Conclusion</p> <p>The present study provides a data set that could contribute in our understanding of epigenetic errors in somatic cell chromatin transfer. Identifying "cumulative errors" after serial cloning could reveal some of the epigenetic reprogramming blocks shedding light on the reprogramming process, important for both basic and applied research.</p

A Preconditioner for Hybrid Matrices Arising in RF MEMS Switch Analysis

Despite the excellent characteristics of RF MEMS switches, they generally suffer from low power-handling capability. This limitation is due to the complex interactions among electromagnetic losses, heat transfer, and mechanical deformations associated with the switches. To understand these failure mechanisms, we proposed a multiphysics model (Jensen, B.D. et al., IEEE Microwave and Wireless Components Letters, vol.13, no.9, p.364-66, 2003). This model is based on an extended finite element-boundary integral (EFE-BI) model that allows efficient modeling of the boundary (MEMS beam for our case) exterior to the volumetric region modeled by the standard FE-BI method. The condition number of the resulting EFE-BI matrix system increases rapidly as the frequency decreases. The matrix condition number required at 2 GHz warrants computational accuracy beyond the capability of normal CPUs. For this reason, our EFE-BI analysis and validation of the code were limited to high frequency cases. We propose a preconditioning approach that lowers the condition number of the system. The proposed approach allows for fast, efficient analysis of RF MEMS switches at practical RF frequencies as low as 500 MHz, which will enable the desired multiphysics modeling.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87247/4/Saitou83.pd

Skin Effect Aggregated Heating in RF MEMS Suspended Structures

This paper presents experimental data together with 2 modeling approaches to demonstrate the increased heating of MEMS suspended structures at radio frequencies due to skin effects. Distinguishable average temperature rises are measured at 2, 13.5, and 18 GHz in a 616 _m _ 20 _m _ 2.7 _m suspended coplanar waveguide using 4-wire measurement configuration. Our measurements compare well with: (1) previous electromagnetic simulations and (2) a newly introduced analytical thermal model incorporating only skin effects. Buckling and plastic yielding have been observed during and after measurement. This study provides a simple and quantitative approach for the design of suspended structures such as low loss transmission lines, filters and switches with high power handling capability.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87275/4/Saitou79.pd

Skin-Effect Self-Heating in Air-Suspended RF MEMS Transmission-Line Structures

Air-suspension of transmission-line structures using microelectromechanical systems (MEMS) technology provides the effective means to suppress substrate losses for radio-frequency (RF) signals. However, heating of these lines augmented by skin effects can be a major concern for RF MEMS reliability. To understand this phenomenon, a thermal energy transport model is developed in a simple analytical form. The model accounts for skin effects that cause Joule heating to be localized near the surface of the RF transmission line. Here, the model is validated through experimental data by measuring the temperature rise in an air-suspended MEMS coplanar waveguide (CPW). For this measurement, a new experimental methodology is also developed allowing direct current (dc) electrical resistance thermometry to be adopted in an RF setup. The modeling and experimental work presented in this paper allow us to provide design rules for preventing thermal and structural failures unique to the RF operation of suspended MEMS transmission-line components. For example, increasing the thickness from 1 to 3 mum for a typical transmission line design enhances power handling from 5 to 125 W at 20 GHz, 3.3 to 80 W at 50 GHz, and 2.3 to 56 W at 100 GHz (a 25-fold increase in RF power handling)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87277/4/Saitou15.pd

Robust Design of RF-MEMS Cantilever Switches Using Contact Physics Modeling

This paper presents the robust design optimization of an RF-MEMS direct contact cantilever switch for minimum actuation voltage and opening time, and maximum power handling capability. The design variables are the length and thickness of the entire cantilever, the widths of the sections of the cantilever, and the dimple size. The actuation voltage is obtained using a 3-D structural-electrostatic finite-element method (FEM) model, and the opening time is obtained using the same FEM model and the experimental model of adhesion at the contact surfaces developed in our previous work. The model accounts for an unpredictable variance in the contact resistance resulting from the micromachining process for the estimation of the power handling. This is achieved by taking the ratio of the root mean square power of the RF current (signal") passing through the switch to the contact temperature ("noise") resulting from the possible range of the contact resistance. The resulting robust optimization problem is solved using a Strength Pareto Evolutionary Algorithm, to obtain design alternatives exhibiting different tradeoffs among the three objectives. The results show that there exists substantial room for improved designs of RF-MEMS direct-contact switches. It also provides a better understanding of the key factors contributing to the performances of RF-MEMS switches. Most importantly, it provides guidance for further improvements of RF-MEMS switches that exploit complex multiphysics phenomena.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87274/4/Saitou7.pd