bluuebunny/crossref_metadata_2025 huggingface dataset:
Becoming Transnational Through Assimilation: Emergence of National/Ethnic Identity Among Chinese Migrants in Late Nineteenth‐Century Chicago
Authors: Ooi Yuki
Published: December 2008

This paper explores the transnationalism seen among Chicago's Chinese migrants in tandem with their Americanization in the late 19th century. While migrants’ transnationalism has several dimensions, the focus of this paper has been placed on their political practices, so‐called “long‐distance nationalism.” Previous studies on migrants’ transnationalism tended to assume marginalization in and a failure to assimilate into a host society as a reason for migrants’ maintaining their ties to their countries of origin. A historical study of the migrants, however, showed another picture: transnationalism and assimilation processes could be reconciled. In order to explain how this is possible, this paper provides in the first part a background on the Chinese enclave in Chicago. Here the paper illustrates how seriously divided the Chinese community was over the difference of clan. The second part is divided into three sections and shows the process by which migrants became politically transnational. First, it deals with the emerging “Chinese” consciousness of migrants, elaborating on how such an inclusive awareness began to appear while they mobilized into a movement demanding naturalization and citizenship rights. In the course of such a movement, they promoted the Americanization of Chinese migrants. Second, how such processes, that is, the emergence of “Chinese” consciousness and assimilation proceeded at the same time is explained. Third, the paper shows how and when Chinese Chicagoans became politically involved in homeland politics. Throughout the paper, the idea of transnationalism is considered in relation to assimilation.
Partnership and Parenthood in Post‐transitional Societies: Will Specters Be Exorcised?
Authors: Fukuda Nobutaka
Published: December 2008

Abstract: The purpose of this article is to reconsider partnership and parenthood in post‐transitional societies from the viewpoint of sociology. As is well known, after the end of the Baby Boom, albeit with variations in the tempo and the level, a considerable decline in fertility has occurred in industrialized countries. Furthermore, this decline has occurred in tandem with the transformation of partnership such as an increase in the number of cohabited couples. The causes and effects of this decline in fertility have hitherto been studied by social scientists such as economists and demographers. Although the family has been one of the main research interests for sociologists for a long while, the changes in partnership and fertility behavior in developed countries have not been sufficiently argued from the perspective of sociological theory on family. In this article, we will initially compare and contrast two changes in fertility patterns: the first of these is the fertility decline that occurred around the latter half of the nineteenth century; the second is the change that has been observed in industrialized countries since the second half of the 1960s. We will then discuss the difference between economic and ideational approaches in the explanation of partnership and fertility changes. Finally, we will examine the convergence and the divergence theories on family change. This article will conclude with an emphasis on the importance of the middle‐range theories.
A novel hepatitis B virus surface antigen immunoassay as sensitive as hepatitis B virus nucleic acid testing in detecting early infection
Authors: Matsubara Naoko , Kusano Osamu , Sugamata Yasuhiro , Itoh Tetsuo , Mizuii Masaaki , Tanaka Junko , Yoshizawa Hiroshi
Published: December 2008

BACKGROUND: The aim was to considerably enhance the sensitivity of hepatitis B virus (HBV) surface antigen (HBsAg) detection and investigate whether the window period for HBV detection could be reduced.

STUDY DESIGN AND METHODS: A high‐sensitivity chemiluminescent enzyme immunoassay (CLEIA) was developed for quantitative HBsAg detection by a combination of monoclonal antibodies, each one for a specific epitope of HBsAg, and by improving the conjugation technique. The sensitivity of the assay was compared with that of the existing chemiluminescent immunoassay (CLIA). Commercially available seroconversion panels and samples of HBV‐infected chimpanzees were tested with the developed prototype to assess whether the window period for HBsAg detection could be reduced to that for DNA detection.

RESULTS: Compared to the existing CLIA, the CLEIA prototype detected HBsAg with approximately 230‐fold higher sensitivity and showed a reduced window period. HBsAg detection by the CLEIA prototype and HBV DNA detection by polymerase chain reaction (PCR) occurred simultaneously. The mean time for the CLEIA prototype to first detect HBsAg was approximately 17.4 days less than that for the existing systems. Further, CLEIA prototype enabled HBsAg detection even in anti‐HBs–positive seroconversion samples. In the inoculated chimpanzees the HBsAg and HBV DNA became detectable simultaneously and concentrations increased in parallel, whereas HBsAg remained detectable longer than HBV DNA in the declining phase of viremia.

CONCLUSION: The CLEIA prototype yielded results comparable with those of HBV DNA PCR. This novel high‐sensitivity assay may be useful for early detection of HBV infection and monitoring patients with a history of infection.
Positive direct and indirect antiglobulin tests associated with oxaliplatin can be due to drug antibody and/or drug‐induced nonimmunologic protein adsorption
Authors: Arndt Patricia , Garratty George , Isaak Edahn , Bolger Michael , Lu Qun
Published: December 2008

BACKGROUND: Two patients were suspected of having immune hemolytic anemia (IHA) due to oxaliplatin. A related drug, cisplatin, is known to cause nonimmunologic protein adsorption (NIPA). Studies were performed to determine the presence of oxaliplatin‐dependent antibodies in addition to oxaliplatin‐induced NIPA.

STUDY DESIGN AND METHODS: Sera and eluates from the two patients were tested against red blood cells (RBCs) treated with oxaliplatin, cisplatin, and carboplatin (another platinum drug). Sera were also tested against untreated RBCs in the presence of the same drugs. Testing with pooled normal sera and anti‐human albumin was used to demonstrate the presence of NIPA. Oxaliplatin‐treated RBCs sensitized with the patients' sera and pooled normal sera were tested by a monocyte monolayer assay (MMA) to determine potential clinical significance.

RESULTS: Both patients had high‐titer antibodies to oxaliplatin in their sera that reacted with oxaliplatin‐treated RBCs and with untreated RBCs in the presence of oxaliplatin. RBCs treated with oxaliplatin, cisplatin, and carboplatin all demonstrated NIPA (pooled normal sera and anti‐human albumin were reactive to low titers). NIPA was also detected in tests with untreated RBCs in the presence of oxaliplatin and cisplatin. Lower‐titer reactivity of both patients' sera with cisplatin may have been due to NIPA and/or cross‐reactivity of anti‐oxaliplatin with cisplatin. MMAs were weakly positive due to NIPA and more strongly positive due to oxaliplatin antibodies.

CONCLUSION: Two patients with IHA were demonstrated to have oxaliplatin‐dependent antibodies. Oxaliplatin was also shown to cause NIPA. The drug‐dependent antibody and/or the drug‐induced NIPA could have contributed to the patients' hemolytic anemia.
Downregulation ofCcnd1andHes6in rat hippocampus after chronic exposure to the antidepressant paroxetine
Authors: McHugh Patrick C. , Rogers Geraldine R. , Glubb Dylan M. , Allington Melanie D. , Hughes Mark , Joyce Peter R. , Kennedy Martin A.
Published: December 2008

Objective:

The mechanism of action of antidepressant drugs is not fully understood. Application of genomic methods enables the identification of biochemical pathways that are regulated by antidepressants, and this may provide novel clues to the molecular and cellular actions of these drugs. The present study examined gene expression profiles in the hippocampus of rats exposed to chronic antidepressant treatment.

Methods:

Animals were treated for 12 days with the selective serotonin reuptake inhibitor paroxetine; then, hippocampal ribonucleic acid was recovered, and changes in gene expression were assessed by microarray analysis.

Results:

A total of 160 genes that showed differential expression after paroxetine exposure were identified. Using functional relevance and observed fold change as selection criteria, the expression changes in a subset of these genes were confirmed by quantitative polymerase chain reaction.

Conclusion:

Of this subset, only two genes, cyclin D1 (Ccnd1) and hairy and enhancer of split 6 (Hes6), showed robust and consistent changes in expression. Both genes were downregulated by paroxetine, and both have been previously implicated in neurogenesis. Further investigation of these two genes may provide new insight into the mechanism of action of antidepressants.
Functional impairment and previous suicide attempts in bipolar disorder
Authors: Rosa Adriane R. , Franco Carolina , Martínez-Aran Anabel , Sánchez-Moreno Jose , Salamero Manel , Valenti M. , Tabarés-Seisdedos Rafael , González-Pinto Ana , Kapczinski Flávio , Vieta Eduard
Published: December 2008

Objective:

The aim of the present study was to assess the association between previous suicide attempts and functional impairment among euthymic patients with bipolar disorder (BD).

Methods:

Seventy-one Diagnostic Statistical Manual IV (DSM-IV) patients with BD and 61 healthy volunteers were recruited from the Bipolar Disorder Program at the Clinic Hospital of Barcelona. Patients with (n = 36, 50.7%) and without (n = 35, 49.3%) previous suicide attempts were assessed using the Structured Clinical Interview for DSM-IV-TR (SCID-P). Previous suicide attempts were carefully investigated by means of patient and caregiver interview and by a standard structured interview from the protocol of our BD Program. The Functioning Assessment Short Test (FAST) was employed to assess functional impairment.

Results:

Euthymic patients with previous suicide attempts showed functional impairment, particularly in occupational (F = 30.39; p = 0.001) and cognitive functioning (F = 18.43; p = 0.001). In addition, family history of psychiatric illness (χ2: 6.49; degrees of freedom (df) = 2;132; p = 0.010), family history of affective disorders (χ2 = 5.57; p = 0.017), psychotic symptoms (χ2 = 5.88; p = 0.014) and axis II comorbidity were associated with previous suicide attempts (χ2 = 5.16; p = 0.021).

Conclusion:

Bipolar patients with previous suicide attempts had lower overall functioning than patients who did not attempt suicide. Previous suicide attempts were particularly associated with the occupational and cognitive domains of functioning.
Shakespeare and Food: A Review Essay
Authors: Goldstein David B.
Published: December 2008

The study of food in Shakespeare does not constitute a coherent body of criticism; indeed, for some it barely counts as a legitimate one. As of this writing, only one book specifically devoted to the subject has been published; the most important work exists in scattered articles. Yet since at least 1935, authors have noted the ubiquity and power of food in Shakespeare's work. This article reviews the critical literature on the subject, emphasizing recent scholarship, and asks why interest in food as a topic of analysis is, and should be, increasing in Shakespeare studies.
Surveys of rodent‐borne disease in Thailand with a focus on scrub typhus assessment
Authors: Lerdthusnee Kriangkrai , Nigro Joseph , Monkanna Taweesak , Leepitakrat Warisa , Leepitakrat Surachai , Insuan Sucheera , Charoensongsermkit Weerayut , Khlaimanee Nittaya , Akkagraisee Wilasinee , Chayapum Kwanta , Jones James W.
Published: December 2008

The epidemiology of many rodent‐borne diseases in South‐East Asia remains ill‐defined. Scrub typhus and lep‐tospirosis are common and medically significant, while other zoonotic diseases, such as spotted fever group Rickettsiae have been identified, but their overall medical significance is unknown. Rodent surveillance was conducted from June 2002 to July 2004 in 18 provinces from Thailand. Traps were set up for one to three nights. Blood and serum samples and animal tissue samples (liver, spleen, kidney and urinary bladder) were collected. Chiggermites, ticks and fleas were removed from captured rodents. A total of 4536 wild‐caught rodents from 27 species were captured over two years of animal trapping. Rattus rattus was the dominant species, followed by Rattus exulans and Bandicota indica. Almost 43 000 ectoparasites were removed from the captured animals. Approximately 98% of the ectoparasites were chigger‐mites, of which 46% belonged to the genus Leptotrombidium (scrub typhus vector). Other genera included Schoengastia and Blankaartia. Tick and flea specimens together comprised less than 1% of the sample. Among the five species of ticks collected, Haemaphysalis bandicota was the predominant species caught, followed by Ixodes granulatus other Haemaphysalis spp., Rhipicephalus spp. and Dermacentor spp. Only two species of fleas were collected and Xenopsylla cheopis (rat flea) was the predominant species. Using both commercial diagnostic kits and in‐house molecular assays, animal tissue samples were examined and screened for zoonotic diseases. Seven zoonotic diseases were detected: scrub typhus, leptospirosis, murine typhus, tick typhus, bartonella, babesiosis and trypanosomiasis. Most samples were positive for scrub typhus. Other zoonotic diseases still under investigation include borrelosis, ehrlichiosis, the plague, and other rickettsial diseases. Using geographic information systems, global positioning systems and remote sensing technology, epidemiological and environmental data were combined to assess the relative risk in different biotopes within highly endemic areas of scrub typhus in Thailand.
Geographical patterns based on faunal types of breeding birds and mammals in China
Authors: XING Yajun , ZHOU Lizhi , ZHANG Youyu , WANG Xinjian
Published: December 2008

We collected available chorological data of birds and mammals in China and assigned faunal types. The 19 sub‐regions of the zoogeographical regions of China were used as operative geographical units. Matrices of the geographical units using the species number of each faunal type were then constructed. Based on the matrices we clustered the geographical units using a hierarchical cluster analysis The results of the faunal divisions according to the cluster analysis were illustrated in a geographic information system (GIS). When 19 geographical units were clustered into two clusters, the boundary of the two clusters corresponded to that of the Palearctic and Indomalayan (Oriental) realms in the recent division of Chinese fauna. When the geographical units were clustered into eight clusters, the sub‐region Southern Yunnan Hilly became an idiographic cluster. As a result, Southern Yunnan hilly should be regarded as a region rather than a sub‐region at the same level as Southwest region, Central China region and South China region. The differences in the distribution patterns of birds and mammals among the units in the Indomalayan (Oriental) realm were more complicated than those in Palearctic realm. A few differences of the cluster analysis results based on the faunal types were found between the bird and mammal species. These differences might result from the different ecological and geographical distribution patterns of these two animal categories.
Speech Development in Prelingually Deaf Children with Cochlear Implants
Authors: Bouchard Marie‐Eve , Ouellet Christine , Cohen Henri
Published: December 2008

Since the early 1980s, cochlear implantation has been an approved method for treating profound bilateral sensorineural hearing loss in children. It is widely believed that the use of this device would significantly benefit young deaf children's development of speech and ability to participate in aural–oral communication. However, whereas significant improvement in speech reception and perception skills following implantation has been widely documented, cochlear prostheses as speech production aids have been studied less extensively. The main objective of this article is to review the work conducted on speech produced by prelingually deaf children following cochlear implantation. Cochlear implants and their functioning are described, as are the cognitive, social and clinical factors known to play a role in successful implantation of children. It is concluded that cochlear implantation may speed up speech production to near normal rates, but initial delays are not totally reversible. In addition, the variability in all performance measures is high, and the reasons for good and poor outcomes are only partly understood.
Clinical epidemiology of fulminant hepatitis in Japan
Authors: Takikawa Yasuhiro , Suzuki Kazuyuki
Published: December 2008

The annual incidence of fulminant hepatitis (FH) in Japan has decreased from 3700 patients in 1972 to 1000 patients in 1989, 1050 patients in 1995 and 426 in 2004. The most frequent cause of FH in Japan is hepatitis B virus (HBV)‐related hepatitis, which accounts for around 40%, with hepatitis A accounting for around 10%; drug reaction accounts for around 10%; other hepatitis, including an unknown cause, accounts for around 40%. The acute type FH, which has a disease duration as 10 days or shorter before the development of encephalopathy (onset‐coma days [OCD]), mainly consists of hepatitis A and B and has relatively better prognosis, with an approximately 40% survival rate without transplantation. The subacute type FH, which has 11 to 56 days OCD, mainly consists of unknown hepatitis including acute‐onset autoimmune hepatitis and has poorer prognosis of about 20% survival. Approximately 25% of FH patients underwent liver transplantation and about 80% of them survived. High volume plasma exchange (PE) and hemodialysis filtration (HDF) have been the most common and principal therapies and they are administered to about 90% and 70% of patients, respectively. The progress of artificial liver support such as combination treatment of PE with HDF is considered to play a role in the slight improvement of the survival proportion of patients with acute type FH in recent years.
Living donor liver transplantation for patients with fulminant hepatic failure
Authors: Hashikura Yasuhiko
Published: December 2008

The prognosis for patients with fulminant hepatic failure has improved since the introduction of liver transplantation. However, the death rate of patients awaiting liver transplantation is high, possibly because of the difficulty in obtaining grafts in a timely manner, given the relative shortage of cadaveric donors. Under these circumstances, living donor liver transplantation is an alternative therapeutic option for patients with fulminant hepatic failure. The present review provides recent updates on the clinical and therapeutic aspects of living donor liver transplantation for fulminant hepatic failure.
Nutritional treatment of chronic liver failure
Authors: Bianchi Giampaolo , Marzocchi Rebecca , Lorusso Caterina , Ridolfi Valentina , Marchesini Giulio
Published: December 2008

The liver plays a central role in the regulation of nutrition by trafficking the metabolism of nutrients, their distribution and appropriate use. Accordingly, protein‐energy malnutrition is common in patients with advanced liver disease, and it is a significant prognostic factor, affecting survival, the success of liver transplantation and quality of life. Clinical guidelines for the assessment and treatment of malnutrition have been issued by International societies, suggesting that nutritional therapy should be instituted in all patients where requirements are not adequately met by diet. The supplementation of the diet with amino acids (mainly branched‐chain amino acids) and trace elements may improve nutritional status, liver function and hepatic encephalopathy. Nutritional issues should be carefully considered in Liver Units treating patients with advanced cirrhosis, and long‐term, carefully controlled studies are needed to better define the type of nutritional support and the amount and timing of administration.
Long‐term outcome of branched‐chain amino acid treatment in patients with liver cirrhosis
Authors: Moriwaki Hisataka , Shiraki Makoto , Fukushima Hideki , Shimizu Masahito , Iwasa Junpei , Naiki Takafumi , Nagaki Masahito
Published: December 2008

Clinical impact of protein‐energy malnutrition (PEM) on the outcome of liver cirrhosis is well documented. As a candidate interventional modality to improve PEM in cirrhosis, effects of branched‐chain amino acid (BCAA) supplementation on event‐free survival and quality of life (QOL) was first reported by Yoshida et al. in 1989. Although critical arguments still continue regarding the effects of BCAA, several randomized trials in the last 5 years have brought positive results, and seem to have settled the discussion in a favorable direction for the efficacy of BCAA in liver cirrhosis. Actually, The European Society for Clinical Nutrition and Metabolism (ESPEN) upgraded the recommendation of BCAA supplementation in decompensated liver cirrhosis in the latest revision of its guidelines in 2006, by referring to the literatures from Italy and Japan. Particularly in these two long‐term randomized studies with 1–2 years‐supplementation, event‐free survival was estimated by employing composite endpoints such as aggravation of hepatic failure (ascites, peripheral edema, hepatic encephalopathy, and jaundice), rupture of esophageal or gastric varices, development of liver cancer, and death from any cause. Both trials agreed on the effect of BCAA to reduce the incidence of hepatic failure, thus contributing to the rise in the event‐free survival. Quality of life is another essential marker of outcome survey. Marchesini, Muto, and Nakaya reported the improved QOL in cirrhotics with BCAA supplementation. In particular, quantitative analysis of QOL measured by Short Form 36 (SF‐36) questionnaire demonstrated a significant recovery of general heath perception score in BCAA supplemented patients in a randomized trial. In this article, the long‐term outcome of BCAA treatment in liver cirrhosis will be reviewed with its action mechanisms. In addition, the effects of BCAA treatment on the incidence of liver cancer in obese patients with type C liver cirrhosis, significance of obesity as a risk factor for type C liver cancer, and a possible role of Body Mass Index to estimate the histological grade of fat deposition in the liver will be briefly discussed.
Treatment of minimal hepatic encephalopathy
Authors: Kumashiro Ryukichi
Published: December 2008

Several reports, conducted as a placebo‐controlled, double‐blind study, presented a favorable result in treating MHE. They included branched chain aminoacid, fluzazenil‐a benzodiazepin receptor antagonist, lactulose, lactitol, and L‐ornithin‐L‐aspartate. Lactulose and lactitol have been shown to be effective in MHE. It improved psychomotor tests and lowered ammonia levels as well as quality of life. Branched chain amino acids (BCAAs) were reported to improve nitrogen metabolism, blood ammonia level, and psychomotor tests. Flumazenil, an antagonist of benzodiazepine receptor, has not been associated with established consensus on the effectiveness in MHE. L‐ornithine‐L‐aspartate (OA) exerts its ammonia‐lowering action in the kidney, skeletal muscles, brain, as well as in the liver. OA administered per orally improved number connection test, ammonia levels, and mental state. OA may be a promising therapy for patients with MHE. A shunt‐closure manipulation with balloon occluded retrograde transvenous obliteration (BRTO) has been shown to be effective for hepatic encephalopathy and its efficacy in MHE has not been elucidated. Synbiotic modulation of gut flora. was shown to increase fecal content of non‐urease‐producing Lactobacillus species and this change was associated with a reversal of MHE. In conclusion, there are no definitive conclusion on the treatment of MHE because of difficulties in diagnosis and evaluation. Therapeutic strategy should be planned specifically for each patient depending on the etiological factors.
ZnO nanostructures grown on zinc nanocones by thermal oxidation
Authors: Chao Liang-Chiun , Liau Chung-Chi , Lin Syuan-Jhih , Lee Jun-Wei
Published: December 2008

ZnO nanostructures were grown on metallic zinc nanocones by thermal oxidation. The metallic nanocones are prepared by argon ion beam sputtering utilizing a capillaritron ion source. The aspect ratios of zinc nanocones are found to be dependent on ion beam energy and substrate temperatures. By maintaining the substrate temperature to be less than 60°C, the aspect ratio of zinc nanocones increases from 1.2 to 2.7 as ion beam energy increases from 6to12keV. Zn nanocones with aspect ratio larger than 25 are obtained by utilizing a 12keV ion beam and allowing the substrate to increase to ∼180°C by in situ ion beam heating. Thermal oxidation of zinc nanocones results ZnO nanowires and nanoblades grown outwardly from the shank. This provides a convenient route for the fabrication of ZnO nanowires for field emission flat panel display and dye-sensitized solar cell applications.
Evaluation of electron energy spread in CsBr based photocathodes
Authors: Maldonado Juan R. , Sun Yun , Liu Zhi , Liu Xuefeng , Tanimoto Sayaka , Pianetta Piero , Pease Fabian
Published: December 2008

Photocathodes with relatively low energy spread (<0.5eV) are required for electron sources in several applications including single and multiple electron beam inspection and lithography tools and free electron lasers. CsBr based photocathodes have been shown to be very robust and capable of operation at high current density (>150A∕cm2) with very long lifetime (approximately hundreds of hours/spot). Experimental results of the photoelectron energy spread obtained in CsBr films deposited on both metal and InGaN substrates will be presented in this paper.
Patterning of polyfluorene based polymer light emitting diodes by reversal imprint lithography
Authors: Cardozo B. L. , Pang S. W.
Published: December 2008

The authors demonstrated the fabrication of patterned arrays of polymer light emitting diodes (PLEDs) with a polyfluorene based emissive layer using reversal imprint lithography. A stack of patterned metal and polymer films is transferred to a glass substrate in a single reversal imprint step. Two different techniques for coating the patterned Si mold are shown, one involving the spin coating of polymer layers directly onto the mold and one involving inking of the polymers onto the mold from a spin-coated PDMS inkpad. Using these techniques, PLED devices with a minimum feature sizes as small as 1μm and luminescence starting at 3.5V have been demonstrated.
Electron beams in individual column cells of multicolumn cell system
Authors: Yamada Akio , Yasuda Hiroshi , Yamabe Masaki
Published: December 2008

In the Mask D2I project at ASET, the authors designed a novel electron beam exposure system having the concepts of multicolumn cell (MCC), character projection, and variable shaped beam to improve the throughput of electron beam exposure systems. They presented the electron optical structure of an individual column cell in the MCC and have shown shaped beam performances in the column cell. They evaluated the impacts on beam position in one column cell caused by deflections of major and minor deflectors in other column cell, which were less than 2.5nm for both averaged and transitional impacts between +full and −full deflections. They will improve the evaluation accuracy to analyze the origin of the impacts and decrease the impacts from other column cell.
Resist charging effect in photomask: Its impact on pattern placement error and critical dimension
Authors: Choi Jin , Nam Dong Seok , Kim Byung Gook , Woo Sang-Gyun , Cho Han Ku
Published: December 2008

By the development of the double exposure technique or the double patterning technique, the pattern placement error of a photomask is interesting because of its impact on the size and position of wafer pattern. Among various sources to induce the pattern placement error, we have focused on the charging effect of the FEP-171 resist and have shown that the resist charging effect generates the pattern position error of a clear pattern and the critical dimension variation of a dark pattern. Based on experiment and simulation, we present quantitatively the dependence of position error on pattern density, pattern shape, and writing order. Furthermore, we have discussed the model to describe the charging effect and its agreement with experiment and the correction method to remove the resist charging effect.
Toward 1Tdot∕in.2 nanoimprint lithography for magnetic bit-patterned media: Opportunities and challenges
Authors: Yang XiaoMin , Xu Yuan , Seiler Carl , Wan Lei , Xiao Shuaigang
Published: December 2008

Nanoimprint lithography presents unique opportunities for patterned media applications due to its advantages of sub-10nm resolution capability, patterning of a whole disk in a single imprint step with reasonably high throughput, and the relatively low capital cost in comparison to other next generation lithography technologies. However, there are several critical issues that still remain very challenging. This article will briefly discuss these challenges in general and then focus on imprint lithography work including the fabrication of templates and demonstrate the imprinted results. In this work two types of polarities of high-density templates (pillar tone and hole tone) have been fabricated on fused silica substrates for the UV imprint process. The difficulties and limitations in each of the template fabrication processes will be discussed. The authors have successfully demonstrated template fabrication followed by imprinted results with a pitch of 24nm (1.1Tdots∕in.2) for both tones of templates. Initial imprinted results of dense dot patterns with a pitch as small as 18nm (2.0Tdots∕in.2) have been achieved. High-resolution scanning electron microscopy images are used as the primary metrology for both the dot size uniformity and the placement accuracy analysis. The difficulties and the limitations in template fabrication, the imprint process, and associated metrology will be discussed.
Si-containing block copolymers for self-assembled nanolithography
Authors: Ross C. A. , Jung Y. S. , Chuang V. P. , Ilievski F. , Yang J. K. W. , Bita I. , Thomas E. L. , Smith Henry I. , Berggren K. K. , Vancso G. J. , Cheng J. Y.
Published: December 2008

Block copolymers can self-assemble to generate patterns with nanoscale periodicity, which may be useful in lithographic applications. Block copolymers in which one block is organic and the other contains Si are appealing for self-assembled lithography because of the high etch contrast between the blocks, the high etch resistance of the Si-containing block, and the high Flory–Huggins interaction parameter, which is expected to minimize line edge roughness. The locations and long range order of the microdomains can be controlled using shallow topographical features. Pattern generation from poly(styrene)-poly(ferrocenyldimethylsilane) and poly(styrene)-poly(dimethylsiloxane) block copolymers, and the subsequent pattern transfer into metal, oxide, and polymer films, is described.
Optimization of electrostatic lens systems for low-energy scanning microcolumn applications
Authors: Oh Tae-Sik , Kim Dae-Wook , Ahn Seungjoon , Kim Young Chul , Kim Ho-Seob , Ahn Seong Joon
Published: December 2008

The optimization of a low-energy scanning microcolumn is proposed by adopting a modified Einzel lens sandwiched between an aligner and a deflector. The modified Einzel lens is composed of four electrodes, and the two center electrodes are specially designed quadrupole lenses having keyhole type rather than circular apertures. The outer electrodes of the Einzel lens having circular apertures are grounded, and the quadrupole lens is operated by applying the quadrupole voltages. The effects of the separated deflector system and the static quadrupole lens were investigated by analyzing the scanning electron beam spot at the target, and the results show that the proposed system can improve the performance of the scanning microcolumn.
Influence of hydrogen silsesquioxane resist exposure temperature on ultrahigh resolution electron beam lithography
Authors: Sidorkin Vadim , van der Drift Emile , Salemink Huub
Published: December 2008

Performance of hydrogen silsesquioxane (HSQ) resist material with respect to the temperature during electron beam exposure was investigated. Electron beam exposure at elevated temperatures up to 90 °C shows sensitivity rise and slight contrast (γ) degradation compared to lower temperature cases. Ultrahigh resolution structures formed at elevated temperatures manifest better uniformity together with aspect ratio improvement and less linewidth broadening with overdose. Potential mechanisms for observed phenomena are proposed.
Easy duplication of stamps using UV-cured fluoro-silsesquioxane for nanoimprint lithography
Authors: Pina-Hernandez Carlos , Fu Peng-Fei , Guo L. Jay
Published: December 2008

A simple procedure for duplicating original nanoimprint masters was developed by using a new fluorinated photocurable silsesquioxane (SSQ) resin cast on either hard or flexible substrates. With an appropriate viscosity, this resin can be spin coated on the substrate, and the original SiO2 masters easily replicated in this resin by using a low pressure nanoimprinting process. The resin has a sufficient modulus in its cured state, which makes it suitable for nanoimprinting other polymeric materials. Due to the high thermal stability and UV transparency of SSQ materials, such a stamp can be used for both UV and thermal nanoimprinting. Furthermore, the fluoroalkyl groups contained in the silsesquioxane resin provide the low surface energy necessary for easy demolding after nanoimprinting. These features combined make the material an excellent candidate to fabricate a multitude of duplicates from an original nanoimprint lithography master for mass fabrication.
Solid-phase growth mechanism of tungsten oxide nanowires synthesized on sputtered tungsten film
Authors: Kojima Y. , Kasuya K. , Nagato K. , Hamaguchi T. , Nakao M.
Published: December 2008

The authors have proposed a solid-phase growth mechanism of tungsten oxide nanowires synthesized on sputtered tungsten films. Transmission electron microscopy observation, x-ray diffraction analyses, and some ex situ experiments were performed to verify the growth model. The nanowire nuclei are generated at irregular points on the W surface. An amorphous oxidized layer is formed on the W surface by annealing, and tungsten oxide molecules migrate on the W surface into the nuclei, thus contributing to the nanowire growth.
Directed self-assembly of individual vertically aligned carbon nanotubes
Authors: Goyal Amit , Liu Sheng , Iqbal Zafar , Fetter Linus A. , Farrow Reginald C.
Published: December 2008

The deposition of high-aspect-ratio particles such as carbon nanotubes may be done in sub-100-nm windows in insulating thin films over metal using electrophoresis. Surface charge on the insulator causes the windows to become nanoscopic electrostatic lenses. Under certain conditions only one nanotube will be deposited at the base of a window. Finite element analysis shows that the number of deposited nanotubes is controlled by the electric field and the geometry of the windows and nanotubes. This discovery enables the process integration of carbon-based electronics with more traditional technologies such as complementary metal oxide semiconductor using the current generation of lithography and process technology. Devices such as vertical field effect transistors and interconnected nanoprobe arrays may now be fabricated in the metal levels to facilitate three-dimensional polylithic circuit architectures.
Scanning proximal probes for parallel imaging and lithography
Authors: Ivanova K. , Sarov Y. , Ivanov Tzv. , Frank A. , Zöllner J. , Bitterlich Ch. , Wenzel U. , Volland B. E. , Klett S. , Rangelow I. W. , Zawierucha P. , Zielony M. , Gotszalk T. , Dontzov D. , Schott W. , Nikolov N. , Zier M. , Schmidt B. , Engl Wolfgang , Sulzbach T. , Kostic I.
Published: December 2008

Scanning proximity probes are uniquely powerful tools for analysis, manipulation, and bottom-up synthesis. A massively parallel cantilever-probe platform is demonstrated. 128 self-sensing and self-actuated proximal probes are discussed. Readout based on piezoresistive sensors and bending control based on bimorph dc/ac actuations are described in detail.
Preparation and thermal desorption properties of dc sputtered zirconium-hydrogen-helium thin films
Authors: Wei Y. C. , Shi L. Q. , Zhang L. , He Z. J. , Zhang B. , Wang L. B.
Published: December 2008

We developed a new approach for preparing hydrogen and helium co-containing zirconium films (Zr–H–He) to simulate aging metal tritides. We also studied the effect of hydrogen on helium behavior, in which we applied direct current magnetron sputtering in a mixture of working gases (helium, argon, and hydrogen). The amount and depth profile of helium and hydrogen trapped in the films were determined using the elastic recoil detection analysis. The microstructure and surface morphology of the Zr–H–He films were studied by x-ray diffraction, transmission electron microscopy, and atomic force microscopy. To investigate the effect of hydrogen on the thermal release behavior of helium in the Zr film, thermal desorption spectrometry (TDS) was used, which revealed a similar desorption behavior to aged tritides. TDS experiments showed that the spectra were constituted by low-temperature peaks around 300°C and high temperature peaks above 750°C. Furthermore, the solid-phase α to δ transformation changed the shapes of the high-temperature peaks related to microstates of helium bubbles and caused the peak with a massive helium release shift toward lower temperature obviously.
In situ ultrahigh vacuum residual gas analyzer “calibration”
Authors: Malyshev O. B. , Middleman K. J.
Published: December 2008

Knowing the residual gas spectrum is essential for many applications and research in ultrahigh vacuum (UHV). Residual gas analyzers (RGAs) are used for both qualitative and quantitative gas analyses, where the quadrupole mass analyzers are now the most popular. It was found that RGAs supplied by different manufacturers are not necessarily well calibrated for quantitative gas analysis. A procedure applied for in situ RGA “calibration” against a calibrated UHV total pressure gauge is described in this article. It was found that special attention should be paid to H2 calibration, as RGAs are usually much more sensitive to H2 than ionization gauges. The calibration coefficients are quite reproducible in Faraday cup mode, however, using the secondary electron multiplier requires frequent checks of the calibration coefficients. The coefficients obtained for the RGA allow the use of the RGA as an accurate device for gas spectrum analysis.
In situ characterization of block copolymer ordering on chemically nanopatterned surfaces by time-resolved small angle x-ray scattering
Authors: Stuen K. O. , Liu C. , Welander A. M. , Liu G. , de Pablo J. J. , Nealey P. F. , Satapathy D. K. , Nygård K. , Bunk O. , Solak H. H. , van der Veen J. F.
Published: December 2008

The assembly of lamella-forming block copolymer blend thin films on chemically nanopatterned striped surfaces was monitored in real time with small angle x-ray scattering (SAXS) in transmission mode. The strongest diffraction from the assembled grating structure was detected after 4.5min of annealing as the temperature was ramped from 100to240°C at a rate of about 20°C∕min. Real-space images were also obtained from samples annealed for specific times using top-down scanning electron microscopy (SEM) and this identified structures formed during annealing that are unique to the block copolymer blends. The data are compared to previously reported SEM and molecular simulation studies with pure block copolymers. Because it can be used in real time and probes the entire film thickness, transmission SAXS proved to be a useful tool for better understanding the block copolymer annealing process.
Prospects of free electron analog to digital technology
Authors: Aldana Rafael , Pease R. Fabian
Published: December 2008

Free electron analog to digital conversion is accomplished by deflecting an electron beam bunch transversally by the voltage to be sampled and then quantizing the deflected angle in an array of electron detectors. Miniaturization of the whole system, especially the deflection plates, leads to an improved performance. A system restricted by the fundamental limit of diffraction could achieve a sampling rate of 1THz with 8bit resolution; the source requirements would be a brightness of 2×1013Acm−2∕sr at 5kV and a source jitter of 1fs. A more practical system using a negative electron affinity photocathode electron source with a brightness of 1×107Acm−2∕sr at 5kV will allow the system to sample 4bits at 750GHz or 6bits at 450GHz.
GaN nanowire and Ga2O3 nanowire and nanoribbon growth from ion implanted iron catalyst
Authors: Johnson Jason L. , Choi Yongho , Ural Ant
Published: December 2008

The authors experimentally demonstrate a simple and efficient approach for nucleating the catalytic chemical vapor deposition (CVD) growth of GaN nanowires, Ga2O3 nanowires, and Ga2O3 nanoribbons by using ion implantation of Fe+ into thermally grown SiO2 layers and subsequent annealing to form the catalyst nanoparticles. This work shows that ion implantation can be used as a versatile method to create catalyst nanoparticles for wide band gap nanowire/nanoribbon growth. They also demonstrate that ion implanted catalyst nanoparticles prepared under identical conditions can be used to grow different types of nanowires/nanoribbons containing Ga by simply changing the gas types and flow rates during CVD growth. Furthermore, they systematically characterize the structural properties of the as-grown nanomaterials, and find that the distance between the Ga source and the substrate, growth temperature, growth time, and flow rates are all critical parameters for nanowire growth. They explain the growth of single-crystal wurtzite GaN and monoclinic β-Ga2O3 nanowires by the vapor-liquid-solid (VLS) growth model, whereas the growth of monoclinic β-Ga2O3 nanoribbons by a combination of the VLS and vapor-solid (VS) mechanisms. This work opens up the possibility of controlling the origin of wide band gap nanowires/nanoribbons at the nanometer scale using the technique of catalyst ion implantation through a lithographically defined mask, of integrating nanowires/nanoribbons into nonplanar three-dimensional device structures, and of growing different Ga-based wide band gap semiconductor nanostructures on the same substrate by simply changing the gas types and flow rates.
Structure and interdiffusion of epitaxial ZnO∕ZnMgO nanolayered thin films
Authors: Stevens B. L. , Cohen D. J. , Barnett S. A.
Published: December 2008

Interdiffusion was studied in Zn1−xMgxO:Al∕ZnO expitaxial superlattices with periods of 15 and 25nm grown on basal-plane sapphire by dc reactive sputtering. Interdiffusion coefficients were determined by analyzing low angle x-ray reflectivity peak intensity decreases during isothermal annealing, using analytical interdiffusion expressions. The results were corroborated with diffusion data obtained from secondary ion mass spectrometry compositional depth profiles. An initial fast diffusion stage was observed for, e.g., the first few hours at 500°C, followed by slower diffusion at longer times.
Direct write electron beam patterning of DNA complex thin films
Authors: Jones R. A. , Li W. X. , Spaeth H. , Steckl A. J.
Published: December 2008

The authors report on the first use of direct write electron beam lithography (DW-EBL) patterning of DNA-based materials. Water insoluble and organic solvent soluble DNA:CTMA complexes were formed by reaction of DNA polymers with cationic surfactants and other molecular species. Thin films with thicknesses ranging from 85 to 300 nm were prepared by spin coating. DW-EBL was conducted using a Raith 150 system. The resulting exposed areas demonstrated either positive or negative resist properties depending on development solution. The characteristics of the DNA:CTMA material as a patternable electron sensitive resist medium are presented for different exposure conditions (10–30 kV), development conditions, structure sizes (100 nm to 20 μm), and structure complexities. Contrast values of ∼2 have been obtained in both positive and negative resist modes. Both simple (20 μm diameter circle and square) and complex (Fresnel lens) patterns with nanometer scale features (<100 nm) in DNA films are possible using this method.
Contributions of resist polymers to innate material roughness
Authors: Fedynyshyn Theodore H. , Astolfi David K. , Goodman Russell B. , Cann Susan , Roberts Jeanette
Published: December 2008

The authors have extended the atomic force microscopy-based technique to measure intrinsic material roughness after base development to evaluate a number of different polymer types in resist formulations. These polymers include environmentally stable chemical amplified photoresist type copolymers and terpolymers, methacrylate polymers, and fluoropolymers. The surface roughness of resists containing these polymers was measured along with the clearing dose with both extreme ultraviolet (EUV) and deep ultraviolet (DUV) exposures. Selected resists containing a representative sampling of different lithographic polymers were imaged with both EUV and DUV exposures. It has been suggested by many that there is a fundamental inverse relationship between resist sensitivity and LER that leads to a fundamental limit to resist performance. It was found that no simple relationship exists between intrinsic material roughness (IMR) and sensitivity and instead some other, more complex relationship between the material properties of the polymer and resist process that is determining both the IMR and sensitivity. It was also found that no simple relationship existed between resist sensitivity and LER. This suggests that resist performance is not innately limited by any fundamental law but is instead open to further improvements through the use of new materials or material combinations.
Projection maskless patterning for nanotechnology applications
Authors: Platzgummer Elmar , Loeschner Hans , Gross Gerhard
Published: December 2008

Projection maskless patterning (PMLP) is based on a programmable aperture plate system and on charged particle projection optics with 200× reduction, providing thousands of electron or ion (H+, He+, Ar+, Xe+, C60−) beams working in parallel on the substrate. As part of the European CHARPAN project a PMLP proof-of-concept tool has been realized. Using resolution templates, with 10keV H+ multibeams a resolution of 16nm lines and spaces was achieved in HSQ resist across the proof-of-concept tool 25×25μm2 exposure field at an exposure dose of 25μC∕cm2. Enhancing the dose by 10% there was <1nm increase in linewidth. With 10keV Ar+ multibeams resistless nanopatterning of various materials was accomplished. Inserting a wired programmable aperture plate system providing ∼4000 beams, first HSQ resist exposure and patterning results have been accomplished, implementing gray scale exposure techniques. The system is being upgraded to a PMLP engineering tool integrating an aperture plate system with complementary metal oxide semiconductor electronics providing ∼40000 programmable beams, a precursor gas injection system for in situ ion multibeam induced etching and deposition, and a laser-interferometer controlled high-precision vacuum stage. Industrial PMLP nanotechnology applications are discussed.