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Neither author has any conflicts of interest to disclose. A 40-year-old man was found unconscious in a poorly ventilated room with a coal heater. He reacted slowly to stimuli and had brainstem reflexes, followed by slow recovery. Brain MRI showed lesions consistent with carbon monoxide toxicity [1] . Anterograde amnesia remained after 6 months. Follow-up MRI revealed prominent bilateral hippocampal atrophy. Received: July 11, 2011 Accepted: September 5, 2011 Published online: November 11, 2011

The susceptibility vessel sign (SVS) on T2*-weighted gradient-echo imaging (T2*- GRE) is useful for detecting intra-arterial clots and monitoring the response to thrombolysis. SVS-GRE was observed in a 52-year-old man with acute occlusion of the posterior cerebral artery (PCA) before and after failed intra-arterial thrombolysis. One-week follow-up T2*-GRE revealed a hyperintensity within the SVS-GRE in the affected PCA. The right PCA remained occluded on time-of-flight (TOF) magnetic resonance angiography (MRA), but its P2 segment exhibited luminal patency on contrast-enhanced (CE) MRA. Black-blood MR imaging using a T1-weighted turbo- spin echo sequence revealed narrowing of the arterial lumen and thickening of the wall due to an atherosclerotic plaque. The observations from TOF-MRA, CE-MRA, and black-blood MR imaging suggest that a newly developed hyperintensity within the SVS-GRE seems to be associated with slow flow through a severe atherosclerotic stenosis or near-occlusion.

Purpose: We wanted to determine whether or not the “susceptibility asymmetry index” (SAI) of acute stroke on the T2*-weighted image is related with successful recanalization using multimodal intra-arterial thrombolysis (IAT). Materials and Methods: The 81 patients who underwent multimodal IAT for middle cerebral artery (MCA) territory acute stroke were included in this retrospective study. The multimodal IAT included intra-arterial urokinase infusion, clot disruption by a microwire, microcatheter and balloon manipulation, and balloon angioplasty and/or stenting for the flow-limiting stenosis. The diameter of the susceptibility vessel sign was measured on the T2*-weighted gradient echo imaging (GRE), and the diameter of the contralateral normal MCA at the corresponding level was measured on magnetic resonance angiography (MRA); the ratio between these two diameters was defined as the susceptibility asymmetry index. The relation between the TICI (Thrombolysis In Cerebral Infarction) score of 2-3 after multimodal IAT and the SAI was assessed. The receiver operating characteristic (ROC) curve analysis was performed on the SAI to predict a TICI score of 2-3 after multimodal IAT. Results: The mean SAI of 81 patients was 1.66 ± 0.66. Seventy nine percent of the patients had a TICI of 2-3 after multimodal IAT. According to the ROC curve analysis, an SAI less than 1.3 was optimal for predicting the presence of stenotic lesion after recanalization (area under the curve: 0.821, sensitivity: 88.2%, specificity: 69.8%, p=0.0001), and the SAI ≤1.61 (area under the curve: 0.652, sensitivity: 60.9%, specificity: 70.6%, p=0.0226) could predict a TICI score of 2-3. The TICI score of 2-3 after multimodal IAT was achieved in 88.6% of the cases with a SAI ≤ 1.61 and in 67.6% of the cases with a SAI >1.61 (p=0.028). Conclusion: The lower SAI on T2*-GRE could predict stenotic lesion and successful recanalization after performing IAT.

How to form a thin and uniform residual layer, which is difficult to be created for a feature with nonuniform pattern densities, is of critical importance in nanoimprint lithography since residual layer removal by a reactive ion etching process will result in poor pattern transfer fidelity for nonuniform residual layers. A capacity-equalized mold using complementary cavity patterns to balance the imprinted volume of the feature with pattern density variation was verified to be a good method against pattern density variation for producing a uniform residual layer. To obtain an insight into the validity of the capacity-equalized mold, the effects of the introduced complementary patterns for capacity equalization on the residual layer, at locations that were not only at a distance away from the introduced complementary patterns but also the ones that were very close to the introduced complementary patterns, were carefully studied. It was found that a capacity-equalized mold with even very coarse complementary patterns as large as 10 times the minimum width of original patterns could result in a good uniform residual layer. It showed that the residual layer thickness was mainly determined by the volume of the capacity of the pattern trench with varied depths per unit area, but not by the size of the complementary patterns. Furthermore, the local nonuniformity induced by the complementary patterns themselves was also studied. The authors found that this local nonuniformity had little influence on producing a uniform residual layer that contributed to the low viscosity of the UV-curable resin. The authors also found that the nonuniformity of the residual layer was produced even by using a capacity-equalized mold due to the presence of air bubbles.

Applicability of UV nanoimprint based on gas condensation to 45 nm line and space (L/S) patterning using a spin-coat UV curable resin was evaluated. Although high capillary pressure is generated in such fine L/S patterns when UV curable resin liquid comes in contact with the groove surface, the trapped air in those grooves is not completely compressed and results in the formation of bubble defects. Bubbles much larger than the pattern size were generated at the middle of the L/S patterns for a 108 nm thick, UV curable resin film, and incomplete filling may occur on a large area of the L/S patterns for a 19 nm thick film. Since nearly bubble-free L/S patterns have been fabricated for 48 nm thick, UV curable resin film, it might be possible to make bubble-free UV nanoimprint by prolonging the imprinting time. On the contrary, when UV nanoimprint was carried out in pentafluoropropane (PFP), no bubbles were created for all thicknesses of the UV curable resin films. Uniformity of residual layer looked quite good judging from the color uniformity of the area around the L/S patterns. It was found, from the residual layer measurement by a reflective thickness monitor, that bubble-free UV nanoimprint was carried out with a residual layer thickness of 15.2 nm. UV nanoimprinted samples were inspected with a scanning electron microscope and it was verified that UV nanoimprint using PFP is viable for the fabrication 45 nm L/S patterns.

UV nanoimprint in air and in pentafluoropropane (PFP) was carried out at imprint pressures ranging from 200 down to 10 kPa using a mold with fractal structure recesses with nominal sizes of 1.3, 3.9, 11.7, 35, 105, and 316 µm. While UV nanoimprint in air suffered severe bubble defect problems, UV nanoimprint in PFP was free from the bubble defect problem even at 10 kPa. From real-time monitoring of recesses being filled with resin for UV nanoimprint in PFP, it was found that the recesses are filled in the ascending order of sizes and filling is completed in 2–4 s. No imprint pressure by the imprint apparatus is needed for UV nanoimprint in PFP, and a full wetting can be spontaneously realized even at a concave area where a large amount of gas is liable to be trapped. This suggests that a capillary force must play an important role of filling at the initial stage of contact and filling between unparallel surfaces of the mold and wafer.

Rapid bubble elimination using pentafuoropropane (CFH2CH2CF3, HFC-245fa, CAS No. 460-3-1) condensing gas is one of the most promising methods to realize ultrahigh-speed ultraviolet nanoimprint lithography (UV-NIL). In this study, we investigated the shrinkage behaviors and elimination time of bubbles for different cavity sizes and resist thicknesses by employing a UV-NIL stepper with a real-time monitoring system. As predicted, a smaller cavity size resulted in a faster filling. Unlike the prediction from an analysis model based on Stefan's equation, a nonlinear decrease in bubble elimination time was observed in accordance with the decrease in cavity size (area). Instead, a linear relationship between bubble elimination time and cavity width was found for a certain range of cavity widths (W). In the cavity width, range from 25 to 340 µm, bubble elimination time was almost proportional to cavity width and could be defined as 0.00145×W(s). When the cavity width was 25 µm, the complete filling time was less than 0.033 s, indicating the potential to realize a ultrahigh-throughput nanopatterning process. Regarding the effect of initial resist thickness on a bubble shrinkage behavior, bubble elimination time tended to increase with the decrease in resist thickness.

The surface quality of a mold is one of the major factors in imprint lithography as it determines the final surface quality and the minimum size of the replicated patterns. This paper describes a process for O2-based reactive ion etching (RIE) of glassy carbon (GC) without encountering any micro masking effect. Glassy carbon, because of its attractive properties such as its surface inertness, thermal stability and extraordinary hardness, has drawn much interest as a mold material for high-temperature imprinting on glasses and metals. Etch profiles with highly smooth surfaces free of micro masking effects were achieved by adding SF6 to the etching gas. The fraction of SF6 in the gas mixture (ranging from 0.1 to 0.6) showed little change in the quality of the etched surface, but it did lead to a proportional decrease in the etch rate of GC. A reasonable GC etch rate (115?120 nm min?1) and a smooth etch surface were obtained using SF6 at a fraction 0.2 or below. Using electron beam lithography (EBL), and processing under the established SF6/O2 RIE conditions, GC molds were fabricated and successfully applied to thermal imprinting onto glass and metals.

In this study, we demonstrated a process for fabricating a dual damascene opening in a chemically amplified negative UV photoresist, such as SU-8. The process is based on a UV-assisted thermal-imprinting process, which involved UV pretreatment and thermal imprinting using a Ni mold. After establishing process parameters (e.g., adhesion enhancing, UV pre-treating, thermal imprinting, and etch back conditions) for the given geometry and dimensions of the mold pattern, we could successfully form 25-µm-deep trenches with a 10 µm line-and-space pattern and 45 µm-deep via holes in SU-8/Si samples by UV-assisted thermal imprinting, followed by O2/CHF3 reactive ion etching (RIE). Delamination defects could be avoided with the help of adhesion enhancement treatment. The process studied here showed great potential in reducing time and cost compared with the standard photolithographic dual damascene process.

In this study, we have explored the hot-embossing of polyimide films through dynamic mechanical thermal analysis (DMTA), forming and mold fabrication studies. First, the relationship between the formability and the temperature for the polyimide film was investigated by DMTA and hot-embossing tests. The DMA results represented that, as a polyimide goes through its glass transition, it exhibited dramatic decreases in storage elastic modulus, storage shear modulus and viscosity as well as the peak of tangent delta, and continued to show strong dependence on frequency and temperature. The filling characteristics of the polyimide film investigated by hot-embossing tests showed a sharp increase in the replicated depth near the glass transition temperature. Second, silicon microfluidic platforms and molds were prepared by electron beam lithography (EBL) combined with inductively coupled plasma (ICP). An ICP etching condition to prevent reverse taper of a microstructure was investigated, and Si microfluidic channels and high aspect-ratio microstructures with nearly vertical sidewall were structured. Finally, the channel structures could be successfully replicated on the polyimide surface by hot-embossing with the Si mold prepared by using EBL combined with ICP plasma etching.

Purpose: To assess the usefulness of intracellular pH (pHi), calculated by determining the shift of a high-energy metabolite such as inorganic phosphate (Pi) or γ-ATP after performing MRS with ECG-gated two-dimensional CSI (chemical shift imaging), as a parameter for the overall state of the intracellular milieu. Materials and Methods: Proton decoupled 31P CSI was performed on a 1.5-T scanner using a - dual-tuned surface coil. Cardiac MRS data were obtained from eight normal volunteers aged 24-32 years with no history of heart disease. From the spectra obtained from several regions of the heart, peak position and peak area were estimated. The metabolic ratios of -, -, γ-ATP, PCr, Pi, phosphodiester and diphosphoglycerate were calculated, and pHi was estimated from the chemical shift of Pi and γ-ATP resonance. We then compared the data for the anterior myocardium with those previously published. Results: The major phosphorous metabolites identified in these human hearts were as follows: PCr, at -0.1 to +0.1 ppm; three phosphate peaks from ATP, with a chemical shift centered at about -2.7 ppm (γ-ATP), -7.8 ppm (-ATP), and -16.3 ppm (-ATP); and phosphodiester (PDE) at 2-3 ppm, inorganic phosphate (Pi) at 4.5-5.4 ppm, and diphosphoglycerate (DPG) at 5.4-6.3 ppm. The PCr/-ATP ratio was 2.200.17 and the PDE/-ATP ratio, 1.040.09. pHi readings were 7.310.23 (calculated by the shift of Pi) and 6.810.20 (calculated by the shift of γ-ATP). Pi/PCR was 0.539, a ratio higher than that mentioned in previously published reports. Conclusion: The measurement of intracelluar metabolism was affected by vaious kinds of factors. We believe, however, that pHi readings indicate the overall state of the cardiac intracelluar milieu. An unexpected pHi readings, seen at MRS, may reflect errors in the MR procedure itself and, or in the alanytical method.

Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/handle/2042/5920); International audience; This study investigates the changes in the mechanical and morphological properties (hardness, elastic modulus, surface roughness and dimensions) of the FIB-milled GC sample heat-treated at 1400oC for different times (0, 10, 20 and 30 min) using nano/micro-indentation, optical microscope, optical interferometer, scanning electron microscope and atomic force microscope. The FIB milled structures had white surfaces, and they were surrounded by a faint circular area. As the temperature hold-time increased, their surfaces became dim as a result of both the diffusion of gallium into the surface and the evaporation of exhaustible gallium source. Additionally, FIB-milled depth was 25-30 nm increased after heat-treatment regardless of increasing the temperature hold time. The surface roughness for both milled and un-milled surfaces increased to less than Ra = 5 nm with the increase of the temperature hold time. Both the uniform distributions and the highest values of the hardness and elastic modulus for the GC mold were obtained after heat-treatment at 1400oC for 10-20 min.