Templated self-assembly of siloxane block copolymers for nanofabrication

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references.Monolayer patterns of block copolymer (BCP) microdomains have been pursued for applications in below sub-30 nm nanolithography. BCP selfassembly processing is scalable and low cost, and is well-suited for integration with existing semiconductor fabrication techniques. The two critical issues are how to obtain reliable long-range ordering of features with minimum defect densities and how to successfully transfer the patterns into other functional materials. Exceptionally well-ordered and robust nanoscale patterns can be made from poly(styrene-b-dimethylsiloxane) (PS-PDMS) BCPs, which have a very large Flory-Huggins interaction parameter between the blocks compared to other commonly used BCPs. Cylinder- or sphere-forming BCP films were spincoated over silicon substrates patterned with shallow steps using optical lithography or nanoscale posts made by electron-beam lithography, and solvent-annealed to induce ordering. This generates patterns with a correlation length of at least several micrometers. The annealed film was treated with plasma to obtain oxidized PDMS patterns with a lateral dimension of 14 - 18 nm. These can be used as an etch mask or an easily removable template for patterning functional materials. Solvent vapor treatments can tune the pattern dimension and morphology. Different degrees of solvent uptake in BCP films during solvent-annealing can manipulate the interfacial interaction between the two blocks, and a mixed solvent vapor can change the effective volume fraction of each block. The self-assembled patterns can be transferred into various kinds of functional materials.(cont.) For example, arrays of parallel lines were used as a mask to pattern poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) conducting polymer thin films. The resulting PEDOT:PSS nanowire array was used as an chemiresistive-type ethanol-sensing device. Metallic films such as Ti, Pt, Ta, W, and magnetic Co and Ni were structured using a pattern-reversal process. Coercivity enhancements were observed for the fabricated ferromagnetic nanostructures such as wires, rings, and antidots. These functional nanostructures can be utilized for a variety of devices such as high-density and high performance sensor or memory devices.by Yeon Sik Jung.Ph.D

The influence of chronic renal failure on the spectrum and antimicrobial susceptibility of uropathogens in community-acquired acute pyelonephritis presenting as a positive urine culture

<p>Abstract</p> <p>Background</p> <p>The role of chronic renal failure (CRF) in the antimicrobial resistance of uropathogens in patients with community-acquired acute pyelonephritis (APN) remains poorly understood.</p> <p>Method</p> <p>We performed a retrospective analysis of 502 adults (54 men, 448 women; mean age 61.7 ± 16.0 years, range 18-98 years) who were treated for community-acquired APN at Kosin University Gospel Hospital (Busan, Republic of Korea) during a ten-year period (January 2000 to December 2009). We evaluated the spectra and antimicrobial susceptibility profiles of uropathogens in CRF and non-CRF patients with community-acquired APN that presented as a positive urine culture.</p> <p>Results</p> <p>The 502 adult subjects were classified as either non-CRF APN patients (336 patients, 66.9%) or CRF APN patients (166 patients, 33.1%) according to their estimated glomerular filtration rate. No significant differences in the sensitivity of <it>E. coli </it>to a third cephalosporin, aminoglycoside (except gentamycin), or ciprofloxacin were observed between non-CRF and CRF patients.</p> <p>Conclusions</p> <p>In our series of patients with community-acquired APN that initially presented as a positive urine culture, CRF did not influence the isolation rates of different uropathogens or their patterns of susceptibility to antimicrobials.</p

Prevalence of Adrenal Insufficiency in Korean Patients undergoing Total Knee Arthroplasty

Background This study investigated the prevalence of adrenal insufficiency among patients admitted for total knee arthroplasty (TKA) due to osteoarthritis and identified factors contributing to adrenal insufficiency. Methods We divided the patients into two groups based on the results of preoperative standard-dose short synchronous stimulation tests: group 1 (adrenal insufficiency) and group 2 (normal adrenal function). We also assessed the prevalence of adrenal insufficiency and compared the numbers of patients who received oral steroids, the frequency of previous steroid injection use, and the frequency of systemic symptoms of steroid depletion such as fatigue and loss of appetite between the two groups. Multiple regression analysis was performed to identify factors related to adrenal insufficiency. Results The prevalence of adrenal insufficiency was 60.0% (120/200). Group 1 had higher numbers of previous steroid injections (12.8±10.2 vs. 6.8±7.9) and patients taking oral steroids (18/120 vs. 3/80) (p<0.001 and p=0.011, respectively). The frequency of systemic symptoms of steroid depletion, such as fatigue and loss of appetite, was also higher in group 1 (94/120 vs. 42/80, p<0.001). Recent steroid injections and loss of appetite were associated with adrenal insufficiency (p=0.002 and p=0.009, respectively). Conclusions The results of this study revealed a high prevalence of adrenal insufficiency in Korean patients hospitalized for TKA due to end-stage osteoarthritis. Recent steroid injections were causally related to the development of adrenal insufficiency. Therefore, adrenal function should be assessed preoperatively to prevent postoperative complications related to adrenal insufficiency

Wafer-scale fabrication of 2D nanostructures via thermomechanical nanomolding

With shrinking dimensions in integrated circuits, sensors, and functional devices, there is a pressing need to develop nanofabrication techniques with simultaneous control of morphology, microstructure, and material composition over wafer length scales. Current techniques are largely unable to meet all these conditions, suffering from poor control of morphology and defect structure or requiring extensive optimization or post-processing to achieve desired nanostructures. Recently, thermomechanical nanomolding (TMNM) has been shown to yield single-crystalline, high aspect ratio nanowires of metals, alloys, and intermetallics over wafer-scale distances. Here, we extend TMNM for wafer-scale fabrication of 2D nanostructures. Using Cu, we successfully nanomold Cu nanoribbons with widths < 50 nm, depths ~ 0.5-1 microns and lengths ~ 7 mm into Si trenches at conditions compatible with back end of line processing. Through SEM cross-section imaging and 4D-STEM grain orientation maps, we show that the grain size of the bulk feedstock is transferred to the nanomolded structures up to and including single crystal Cu. Based on the retained microstructures of molded 2D Cu, we discuss the deformation mechanism during molding for 2D TMNM.Comment: 4 figure

The susceptibility of Anopheles lesteri to infection with Korean strain of Plasmodium vivax

<p>Abstract</p> <p>Background</p> <p>Following its recent re-emergence, malaria has gained renewed attention as a serious infectious disease in Korea. Three species of the Hyrcanusgroup, <it>Anopheles lesteri, Anopheles sinensis </it>and <it>Anopheles pullus</it>, have long been suspected malaria vectors. However, opinions about their vector ability are controversial. The present study was designed with the aim of determining the susceptibility of these mosquitoes to a Korean isolate of <it>Plasmodium vivax</it>. Also, <it>An. sinensis </it>is primarily suspected to be vector of malaria in Korea, but in Thailand, the same species is described to have less medical importance. Therefore, comparative susceptibility of Thai and Korean strains of <it>An. sinensis </it>with Thai strain of <it>P. vivax </it>may be helpful to understand whether these geographically different strains exhibit differences in their susceptibility or not.</p> <p>Methods</p> <p>The comparative susceptibility of <it>An. lesteri</it>, <it>An. sinensis </it>and <it>An. pullus </it>was studied by feeding laboratory-reared mosquitoes on blood from patients carrying gametocytes from Korea and Thailand.</p> <p>Results</p> <p>In experimental feeding with Korean strain of <it>P. vivax</it>, oocysts developed in <it>An. lesteri</it>, <it>An. sinensis </it>and <it>An. pullus</it>. Salivary gland sporozoites were detected only in <it>An. lesteri </it>and <it>An. sinensis </it>but not in <it>An. pullus</it>. Large differences were found in the number of sporozoites in the salivary glands, with <it>An. lesteri </it>carrying much higher densities, up to 2,105 sporozoites in a single microscope field of 750 × 560 μM, whereas a maximum of 14 sporozoites were found in any individual salivary gland of <it>An. sinensis</it>. Similar results were obtained from a susceptibility test of two different strains of <it>An. sinensis </it>to Thai isolate of <it>P. vivax</it>, and differences in vector susceptibility according to geographical variation were not detected.</p> <p>Conclusion</p> <p>The high sporozoite rate and sporozoite loads of <it>An. lesteri </it>indicate that this species is highly susceptible to infection with <it>P. vivax</it>. <it>Anopheles sinensis </it>appears to have a markedly reduced ability to develop salivary gland infection, whilst in <it>An. pullus</it>, no sporozoites were found in the salivary glands. Provided that the survival rate of <it>An. lesteri </it>is sufficiently high in the field, it would be a highly competent vector of vivax malaria.</p

Design of the VISTA-ITL Test Facility for an Integral Type Reactor of SMART and a Post-Test Simulation of a SBLOCA Test

To validate the performance and safety of an integral type reactor of SMART, a thermal-hydraulic integral effect test facility, VISTA-ITL, is introduced with a discussion of its scientific design characteristics. The VISTA-ITL was used extensively to assess the safety and performance of the SMART design, especially for its passive safety system such as a passive residual heat removal system, and to validate various thermal-hydraulic analysis codes. The VISTA-ITL program includes several tests on the SBLOCA, CLOF, and PRHRS performances to support a verification of the SMART design and contribute to the SMART design licensing by providing proper test data for validating the system analysis codes. A typical scenario of SBLOCA was analyzed using the MARS-KS code to assess the thermal-hydraulic similarity between the SMART design and the VISTA-ITL facility, and a posttest simulation on a SBLOCA test for the shutdown cooling system line break has been performed with the MARS-KS code to assess its simulation capability for the SBLOCA scenario of the SMART design. The SBLOCA scenario in the SMART design was well reproduced using the VISTA-ITL facility, and the measured thermal-hydraulic data were properly simulated with the MARS-KS code

Effects of Hyul-Bu-Chuke-Tang on Erythrocyte Deformability and Cerebrovascular CO2 Reactivity in Normal Subjects

Aim. Hyul-bu-chuke-tang (HCEt) is a well-known traditional herbal medicine that is used for the treatment of ischemic cerebrovascular disorders. We investigated the acute effects of HCEt on erythrocyte deformability and cerebrovascular CO2 reactivity (CVR) in healthy male subjects. Materials and Methods. We examined erythrocyte deformability in an HCEt group (n = 14) and a control group (n = 10). CVR was measured using hyperventilation-induced CO2 reactivity of the middle cerebral artery and transcranial Doppler (TCD) in the HCEt group (n = 11). A historical control group (n = 10) of CVR measurements was also created from our previous study. All measurements were performed prior to and 1, 2, and 3 hours after HCEt administration. Results. HCEt significantly improved erythrocyte deformability 1 hour after administration compared to the control group (2.9 ± 1.1% versus −0.6 ± 1.0%, P = 0.034). HCEt significantly improved the CVR 2 hours after administration compared to the historical control group (9.1 ± 4.0% versus −8.1 ± 4.1%, P = 0.007). The mean blood pressure and pulse rate did not vary from baseline values in either group. Conclusions. We demonstrated that HCEt improved erythrocyte deformability and CVR. Our findings suggest that an improvement in erythrocyte deformability contributes to HCEt's effect on cerebral microcirculation

Transcatheter Arterial Embolization Using Ethanol in a Dialysis Patient for Contracting Enlarged Polycystic Kidneys

The mass effect of nephromegaly in patients with autosomal dominant polycystic kidney disease may cause pain and symptoms by compressing the alimentary tract, lungs, and heart. Conventional therapies exist to contract enlarged polycystic kidneys including surgical and interventional procedures. A surgical nephrectomy is often difficult to perform in dialysis patients due to the associated risks related to surgery. In contrast, renal transcatheter arterial embolization (TAE) with metallic coils, which is a less invasive interventional procedure, can also be utilized to contract enlarged kidneys in dialysis patients as an effective treatment. However, metallic coils present the possibility of recanalization and cost issues. Thus, we used ethanol instead of coils in renal TAE to resolve these issues. We report a dialysis patient with enlarged polycystic kidneys and poor oral intake due to abdominal distention that was successfully treated by TAE with absolute ethanol