Effect of the surface treatment on the room-temperature bonding of Al to Si and SiO2

Bonding of polycrystalline Al to Si(1 0 0) and SiO2 (fused silica) was carried out at room temperature by means of surface-activated bonding method. In the present work, different means of surface activation such as irradiation of an argon fast atom beam (FAB) and a hydrogen radical beam (RB) were used. Influence of the exposure to a vacuum atmosphere of the activated surfaces by fast atom irradiation on the bonding behaviour was investigated. The strength of the Al–Si joints sputter cleaned by FAB before bonding reaches as much as 32 MPa. When the activated surfaces were exposed to 30 L (where L is the abbreviation for langmuir (1.33×10-4 Pa s)) in the residual gases (mainly vapour), the strength of the Al–Si joint decreased to 20 MPa and approached that of the Al–SiO2 joint. This indicates that the fracture strength of the joint of Al and Si with an intermediate layer of OH groups and oxide is close to that of Al and Si oxide. The adhesion between Al and Si deteriorated strongly because of hydrogen termination on the Si surface which had been irradiated by the hydrogen RB. On the contrary, bonding of Si with native oxides to Al was successful with the hydrogen RB irradiation.     

Photoaffinity labeling of peroxisome proliferator binding proteins in rat hepatocytes; dehydroepiandrosterone sulfate- and bezafibrate-binding proteins

Neuronal nitric oxide synthase produces nitric oxide, a radical involved in neurotransmission as well as in cytotoxicity during stroke and neurodegenerative diseases. In the adult Wistar rat neuronal nitric oxide synthase-positive neurons are inhomogenously distributed along defined cortical areas, with highest densities (18 cells/mm2) in cingular area 1, piriform cortex, frontal motor area Fr 2 and in the medial visual association area Oc 2MM. A medium packing density of neuronal nitric oxide synthase neurons (10/mm2) characterizes primary sensory areas, whereas retrosplenial cortices contain lowest cell numbers (3-5/mm2). The data suggest that functions of certain cortical areas are more dependent on intracortically produced nitric oxide than others, and that cortical injury may cause more severe nitric oxide related cytotoxicity in areas with higher numbers of neuronal nitric oxide synthase-positive neurons.     

Direct bonding of CMP-Cu films by surface activated bonding (SAB) method

The chemical mechanical polishing (CMP) process is indispensable to the fabrication of Cu wiring layers in the large-scale integration (LSI). Recently, a direct bonding method with low bonding temperature is required for the CMP-Cu surface in order to obtain a narrow bonding pitch. In this study, we realized a direct bonding between CMP-Cu films by means of the surface activated bonding (SAB) method at room temperature. The critical vacuum pressure to obtain large bonding strength was estimated at about 4×10⁻³ Pa from the growth rate of oxide on an active surface measured by the X-ray photoelectron spectroscope (XPS). The films were bonded successfully at the vacuum pressure better than around 3×10⁻³ Pa with the shear strength larger than 50 MPa. The transmission electron microscope (TEM) observation showed that the polycrystalline films with the mean surface roughness of 0.3 nm were bonded directly between Cu grains in atomic level. Moreover, the adhesion between the films was improved due to the stress relaxation at the interface during the thermal aging test conducted at 200 and 300^∘C in the vacuum condition.     

Surface activated bonding of LCP/Cu for electronic packaging

A lamination technique for liquid crystal polymer (LCP)/Cu was developed for high speed and high performance printed circuit boards (PCB). This approach was accomplished by using a modified surface activated bonding (SAB) process to achieve enhanced adhesion and a smooth interface. Systematic investigation of peel strength of four categories of samples, namely “as bonded”, “annealed”, “Cu-deposited”, and “Cu-deposited and annealed” showed highest peel strength in the “Cu-deposited and annealed” sample. Significant improvements in adhesion were observed in the samples cleaned with argon-radio frequency (Ar-rf) plasma (“as bonded” samples) followed by Cu deposition on LCP, which were heated after bonding in low vacuum pressure at 240∘C (about 70–75 times higher than that of “as bonded”). XPS analyses on peeled surfaces of the “Cu-deposited and annealed” sample reveal bulk fracture in the LCP. Threefold lower loss in conduction of SAB processed laminate than that of conventional heat laminate was most likely due to smooth interface of the SAB processed laminate (surface roughness was ninefold lower than that of conventional heat laminate). A plausible adhesion mechanism of Cu/LCP might be due to bonding of Cu adhesion sites to plasma induced dangling sites of LCP surface, and thermal reconstruction of Cu deposited layers.     

High speed data collection system for magnetic field imaging by CTtechnique

A method of high-speed data collection used in imaging the magnetic-field distribution leaking from magnetic devices along any plane is proposed. The method uses the computed tomography (CT) technique. A high-speed data collection system developed for demonstrating the method is described. An image of the magnetic field is reconstructed from projection data provided by the voltage induced in the sensors of a line conductor and a rectangular coil moving in the plane of observation. Rotational scanning of the sensors is used for collecting the projections so that data-acquisition time can be reduced. To demonstrate the performance of the system, the reconstructed images of the magnetic-field distributions made by some permanent magnets are shown     

Dynamic cardiac compression improves contractile efficiency of the heart

The effect of dynamic cardiac compression on left ventricular contractile efficiency was assessed in terms of the pressure-volume relationship and myocardial oxygen consumption. In 11 excised cross-circulated dog hearts, the ventricle was directly compressed during systole (dynamic cardiac compression). Measurements for pressure-volume area (a measure of total mechanical energy), external work, and myocardial oxygen consumption were done before and during dynamic cardiac compression. Dynamic cardiac compression increased pressure-volume area by 28% +/- 17% (mean plus or minus the standard deviation) and external work by 24% +/- 20% (p = 0.0000185 and 0.0000212, respectively) at given end-diastolic and stroke volumes without affecting myocardial oxygen consumption. As a result, the oxygen cost of pressure-volume area, that is, the slope of the myocardial oxygen consumption-pressure-volume area relationship, significantly decreased by 16% +/- 13% (p = 0.0000135) whereas the pressure-volume area-independent myocardial oxygen consumption was unchanged. Then, contractile efficiency, that is, the reciprocal of the slope of the myocardial oxygen consumption-pressure-volume area relationship in joules significantly improved from 45% +/- 8% to 53% +/- 13% (p = 0.0000437). When the native myocardial oxygen consumption-pressure-volume area relationship was assessed by subtracting the dynamic cardiac compression pressure applied to the heart, the slope of the myocardial oxygen comsumption-pressure-volume area relationship returned to the control level. This indicates that the contractile efficiency of the native heart was not affected by dynamic cardiac compression. We conclude that dynamic cardiac compression enhances left ventricular pump function by improving the contractile efficiency of the overall heart leaving the energetics of the native heart unchanged.     

Comparison of ciliary sulcus fixation techniques for posterior chamber intraocular lenses

OBJECTIVE: To anatomically and histologically evaluate suturing techniques for sulcus fixation of posterior chamber intraocular lenses. SETTING: Kitano Hospital, Osaka, Japan. METHODS: The reproducibility of three suturing techniques (perpendicular to the eye wall; parallel to the iris; midway between perpendicular to the eye wall and parallel to the iris) were evaluated in a postmortem eye. Histologic sections of another eye and ultrasound biomicroscopy (UBM) images of 21 normal eyes were evaluated to determine the safety zone for the needle to avoid damaging adjacent structures. RESULTS: The ciliary sulcus was completely penetrated in the three techniques in 100, 40, and 70% of cases, respectively. The histologic sections and the UBM images showed that when sutures were placed perpendicular to the eye wall, there was the possibility of postoperative angle closure and suturing parallel to the iris might damage adjacent structures because of a narrow safety zone. CONCLUSIONS: The needle should penetrate obliquely, as in the technique in which the suturing is midway between perpendicular to the eye wall and parallel to the iris. This technique provides better reproducibility and causes less damage to adjacent tissue.     

Endothelin-induced activation of mitogen-activated protein kinases in glomerular mesangial cells from normotensive and stroke-prone spontaneously hypertensive rats

1. Kinase assay in myelin basic protein (MBP) containing polyacrylamide gels revealed that endothelin-1 (ET-1) and ET-3 increased MBP kinase activities in glomerular mesangial cells (MC) from Wistar-Kyoto (WKY) rats and spontaneously hypertensive rat (SHRSP). ET-1 stimulated MBP kinase activities more potently than ET-3. 2. Immunoprecipitation with anti-41-kDa MAPK antiserum showed that the MBP kinases activated by ET-1 correspond to 43- and 41-kDa MAPK. 3. Since Phorbol 12-myristate 13-acetate, a direct activator of protein kinase C, also activated MAPK, protein kinase C was suggested to mediate ET-induced activation of MAPK. 4. These results suggest that MAPK may mediate the ET actions in glomerular mesangial cells from normotensive rats as well as spontaneously hypertensive rats. Since ET is produced by vascular endothelial cells of the kidney and glomerular mesangial cells, the ET signalling pathway may have some physiological and pathophysiological significance in vivo glomerulus.     

Four cases of human herpesvirus 6 variant B infection after pediatric liver transplantation

BACKGROUND: Little is known about human herpesvirus (HHV)-6 infection after liver transplantation. We present our experiences with four cases of HHV-6 infection after liver transplantation from living related donors. METHODS: Peripheral blood was collected from four donor and recipient pairs at the time of transplantation and biweekly from the recipients after transplantation. We attempted to isolate HHV-6 and measure antibody titers to HHV-6 and HHV-7. RESULTS: HHV-6 was isolated from four recipients approximately 2 weeks after transplantation. A significant rise in HHV-6 antibody titers was observed in four recipients at some point in their course, whereas HHV-7 antibody titers were increased in one recipient. Four isolates were variant B. When HHV-6 was isolated, all recipients had an unexplained fever. CONCLUSIONS: HHV-6 variant B infection after pediatric liver transplantation was confirmed. HHV-6 infection occurred approximately 2 weeks after transplantation. Moreover, there appears to be an association between HHV-6 infection and unexplained fever.     

Direct conversion mechanism of fluorine-GIC into poly(carbon monofluoride), (CF)n

The reaction mechanisms of a stage-1 fluorine-graphite intercalation compound (GIC), C_2.5F, with 0.10 MPa of fluorine gas have been studied at 573-773 K. The original stage-1 structure of C_2.5F with semi-ionic C-F bonds and planar sp² carbon sheets is maintained in most part of the compound after the reaction at 573 K, although a large number of covalent C-F bonds are formed on the surface. This compound is partially or completely converted to poly(carbon monofluoride), (CF)_n, with covalent C-F bonds and puckered sp³ carbon sheets at 673 or 773 K, respectively. Single-phase (CF)_n obtained at 773 K possesses remarkably small BET specific surface area, 61 m²/g carbon, almost unchanged from the value of the precursor C_2.5F (69 m²/g carbon). In this reaction, the accommodation of fluorine atoms supplied from the atmosphere into the galleries of C_2.5F is facilitated by the rearrangement of originally intercalated fluorine atoms in the GIC, forming (CF)_n with fewer defects compared to those by the conventional direct fluorination of graphite.