Magnetic microparticle-polydimethylsiloxane composite for reversible microchannel bonding

In this study, an iron oxide magnetic microparticles and poly(dimethylsiloxane) (MMPs-PDMS) composite material was employed to demonstrate a simple high-strength reversible magnetic bonding method. This paper presents the casting of opaque-view (where optical inspection through the microchannels was impossible) and clear-view (where optical inspection through the microchannel was possible) MMPs-PDMS. The influence of the microchannel geometries on the casting of the opaque-view casting was limited, which is similar to standard PDMS casting. Clear-view casting performance was highly associated with the microchannel geometries. The effects of the microchannel layout and the gap between the PDMS cover layer and the micromold substrate were thoroughly investigated. Compared with the native PDMS bonding strength of 31 kPa, the MMPs-PDMS magnetic bonding experiments showed that the thin PDMS film with an MMPs-PDMS layer effectively reduced the surface roughness and enhanced MMPs-PDMS reversible magnetic bonding strength. A thin PDMS film-coated opaque-view MMPs-PDMS device exhibited the greatest bonding strength of 110 kPa, and a clear-view MMPs-PDMS device with a thin PDMS film attained a magnetic bonding strength of 81 kPa.     

Wirebond profiles characterized by a modified linkage-spring model which includes a looping speed factor

The linkage-spring model based on a quasi-static looping has been used to determine the design rules to reduce the loop heights and the sagging altitude of gold wire in the package. In order to further simulating the capillary trajectory which includes a looping speed factor from the first bond to the second bond stages, a linkage-spring model is modified in this study. The factors of the inertia mass and variations in material properties with different strain-rates need to be considered due to a high speed looping.It is found that the looping speed effects on the wirebond profiles due to the inertia mass can be neglected at a regular looping process of 3–5g acceleration even up to around 10g acceleration. However, variations in the material properties during deformation at different strain-rates could be an important factor on the wirebond profiles. Fortunately, a pure annealed state like pure gold wire would be little strain-rate sensitivity. The effects of the strain-rate in pure gold wire, therefore, can be excluded in analysis. Accordingly, a linkage-spring model based on the quasi-static looping is still applicable in analyzing the wirebond profiles.     

Enhanced intestinal adenomatous polyp formation in Pms2-/-;Min mice

Analysis of two human familial cancer syndromes, hereditary nonpolyposis colorectal cancer and familial adenomatous polyposis, indicates that mutations in either one of four DNA mismatch repair gene homologues or the adenomatous polyposis coli (APC) gene, respectively, are important for the development of colorectal cancer. To further investigate the role of DNA mismatch repair in intestinal tumorigenesis, we generated mice with mutations in both Apc and the DNA mismatch repair gene, Pms2. Whereas Pms2-deficient mice do not develop intestinal tumors, mice deficient in Pms2 and heterozygous for Min, an allele of Apc, develop approximately three times the number of small intestinal adenomas and four times the number of colon adenomas relative to Min and Pms2+/-;Min mice. Although Pms2 deficiency clearly increases adenoma formation in the Min background, histological analysis indicated no clear evidence for progression to carcinoma.     

Degradation of annexin I in bronchoalveolar lavage fluid from patients with cystic fibrosis

BACKGROUND/AIMS: The number of perisinusoidal myofibroblasts has been shown to be increased in hepatocellular carcinoma, as compared to cirrhosis. This increase might suggest a cooperative relationship between tumour cells and myofibroblasts. To assess this relationship, we undertook: (a) an immunohistochemical study to confirm the existence of an increased number of perisinusoidal myofibroblasts in human hepatocellular carcinoma, as compared to cirrhosis with or without liver cell dysplasia, (b) an in vitro study testing the role of normal or tumoral human hepatocytes in myofibroblast proliferation. METHODS: Forty explanted cirrhotic livers, including 14 with hepatocellular carcinoma and 24 with liver cell dysplasia, were studied. Myofibroblasts were detected by immunohistochemistry using an antibody directed against alpha-smooth muscle actin. Hepatic myofibroblasts in culture were obtained by outgrowth from human liver explants. RESULTS: There was a progressive increase in the number of perisinusoidal myofibroblasts, from cirrhotic nodules without dysplasia to liver cell dysplasia and hepatocellular carcinoma. Conditioned medium from isolated normal human hepatocytes had only minor mitogenic effects on myofibroblasts, as assessed by measuring DNA synthesis and cell growth. In contrast, conditioned medium from a human hepatoma cell line (HepG2 cells) markedly stimulated the proliferation of human myofibroblasts. This mitogenic activity was stored in HepG2 cells and secreted in the extracellular medium rather than being simply released following cell lysis. CONCLUSIONS: These results suggest that the increased number of myofibroblasts in hepatocellular carcinoma might be due to a paracrine mechanism involving soluble mitogenic factor(s) secreted by tumour cells.     

Rapid diagnosis of tuberculous meningitis by polymerase chain reaction assay of cerebrospinal fluid

A polymerase chain reaction (PCR) method for the rapid diagnosis of tuberculous meningitis (TBM) was used to study prospectively 47 cerebrospinal fluid (CSF) samples from 45 patients. Twenty CSF samples were from patients with clinically suspected TBM and another 27 samples came from patients without clinically suspected TBM. Mycobacterial DNA was detected in 15 CSF samples (14 from patients with clinically suspected TBM and 1 from a patient not suspected of having TBM). Of the PCR-positive samples, 4 were also positive for mycobacterial culture. However, 32 PCR-negative samples were all culture-negative. All samples were negative for the acid-fast bacillus by direct smear. The single PCR-positive patient in the clinically unsuspected TBM group was initially diagnosed as suffering from aseptic meningitis on the basis of his clinical features. The mycobacterial culture of his CSF specimen was also positive and a revised diagnosis of an aseptic type of TBM was made. The estimations of specificity and sensitivity in this study were 100% and 70% respectively. The results showed that using a PCR to detect mycobacterial DNA in CSF for the early diagnosis of TBM is not only a rapid but also an accurate method.     

Effects of exit back-up on delamination in drilling composite materials using a saw drill and a core drill

Machining of composites has caught greater attention in manufacturing of structural parts in aerospace, automobile and sporting goods. Composite materials have advantageous features in strength and stiffness coupled with lightweight compared to the conventional metallic materials. Amongst all machining operations, drilling is the most commonly applied method for generating holes for riveting and fastening the structural assembly. Delamination is one of the serious concerns in drilling holes in composite materials at the bottom surface of the workpiece (drill exit). Quite a few references of the drilling of fiber-reinforced plastics report that the quality of cut is strongly dependent on drilling parameter as well as the drill geometry. Saw drills and core drills produce less delamination than twist drills by distributing the drilling thrust toward the hole periphery. Delamination can be effectively reduced or eliminated by slowing down the feed rate when approaching the exit and by using back-up plates to support and counteract the deflection of the composite laminate leading to exit side delaminations. The use of the back-up does reduce the delamination in practice, which its effects have not been well explained in analytical fashion. This paper predicts the effects of backup plate on delamination in drilling composite materials using saw drill and core drill. The critical drilling thrust force at the onset of delamination is calculated and compared with that without backup. The well known advantage of industrial use of backup can be understood fundamentally by the fact that the threshold thrust force at the onset of delamination is increased making the delamination less induced.     

The optimization of spectrum analysis for digital signals

This paper provides a complete method to solve the defects of spectrum analysis for discrete signals. Many researches had issued to deal with the defects of fast Fourier transform (FFT). Those methods may cause the characteristics of original signal altered, or solve this problem in part only. The defects of spectrum analysis cannot be solved efficiently and completely by those methods. These defects result from that those frequency scales cannot match with signal characteristics. This paper is based on the concept to establish a complete solution, divided into three steps: First, this paper analyzes the signal characteristics to be the basis of spectrum adjustment. A simple and accurate algorithm is used to find the frequency and amplitude of each component. Next, this paper finds optimum spectrum parameters to make the new spectrum match with signal characteristics. Finally, this paper takes the parameters to reanalyze the original signal. The method will make spectrum analysis reach optimization. Every procedure in this paper compares with traditional ones to prove its benefits. Moreover, the authors verify the theory feasible by analyzing actual signals.     

Theorem and application of adjustable spectrum

This paper affords the theorem, procedures, and evaluation of ability of adjustable spectrum for signals. By mean of adjusting frequency resolution and frequency shift, we can adjust frequency scale. The paper evaluates every process of computation to verify accurate computation and fast response of adjustable spectrum. Since frequency scale of this spectrum is adjustable, it makes the spectrum analysis of signal reach optimization. The method eliminates the picket-fence effect and the leakage effect by fast Fourier transform (FFT). Since the procedures remain as the characteristic of fast computation that this method can be used for real-time analysis.