Effective Work-Function Modulation by Aluminum-Ion Implantation for Metal-Gate Technology (Poly-Si/TiN/SiO2)

The impact of aluminum (Al) implantation into TiN/SiO₂ on the effective work function (EWF) of poly-Si/ TiN/SiO₂ is investigated. Al implanted at 5 keV with a dose of 5 times 10¹⁵ cm^-2 reduces the flatband voltage (V_FB) and the EWF of poly-Si/TiN/SiO₂ stack by ~150 mV compared with the unimplanted poly-Si/TiN/SiO₂ stack. This reduction of V_FB is found to be dose-dependent, which is correlated to the Al concentration at the TiN-SiO₂ interface as evidenced by secondary-ion-mass-spectrometry profiles. The interface dipole created due to the Al presence at the metal-dielectric interface is believed to contribute to the observed V_FB (or EWF) reduction (or increase). This technique for EWF modulation is promising for further threshold-voltage (V_t) tuning without any process complexities and is quite significant for planar and multiple gate field-effect transistors on fully depleted silicon on insulator.     

Accelerated Ionic Motion in Amorphous Memristor Oxides for Nonvolatile Memories and Neuromorphic Computing

Memristive devices based on mixed ionic–electronic resistive switches have an enormous potential to replace today's transistor‐based memories and Von Neumann computing architectures thanks to their ability for nonvolatile information storage and neuromorphic computing. It still remains unclear however how ionic carriers are propagated in amorphous oxide films at high local electric fields. By using memristive model devices based on LaFeO₃ with either amorphous or epitaxial nanostructures, we engineer the structural local bonding units and increase the oxygen‐ionic diffusion coefficient by one order of magnitude for the amorphous oxide, affecting the resistive switching operation. We show that only devices based on amorphous LaFeO₃ films reveal memristive behavior due to their increased oxygen vacancy concentration. We achieved stable resistive switching with switching times down to microseconds and confirm that it is predominantly the oxygen‐ionic diffusion character and not electronic defect state changes that modulate the resistive switching device response. Ultimately, these results show that the local arrangement of structural bonding units in amorphous perovskite films at room temperature can be used to largely tune the oxygen vacancy (defect) kinetics for resistive switches (memristors) that are both theoretically challenging to predict and promising for future memory and neuromorphic computing applications.     

Hypertensive cardiac hypertrophy--is genetic variance the missing link?

1. Hypertensive cardiac hypertrophy is a major independent predictor of adverse cardiovascular events. In man the cardiac response to increased afterload is very variable, even when ambulatory blood pressure monitoring is used. Analysis of breeding experiments using normotensive and hypertensive rat strains, human twin studies and other data indicate that genetic factors play a significant role in regulating cardiac mass; in other words, a large component of total variability is accounted for by genetic variance. 2. The observation that some patients with only mild-to-moderate hypertension exhibit gross left ventricular hypertrophy (LVH) similar to the inherited hypertrophic cardiomyopathies such as familial hypertrophic cardiomyopathy (FHC) and Friedreich's ataxia (FA) has prompted us to investigate the hypothesis that genetic factors associated with excessive myocardial hypertrophy, viz. mutations in FHC and FA genes alter the hypertrophic response of the heart to pressure overload. Here we review briefly three lines of study: (i) association analysis to test whether the allele frequencies differ in hypertensive patients with or without left ventricular hypertrophy; (ii) characterization of the cardiac manifestations of FA to understand the mechanism by which the heart is affected in a disease associated with pathology in a subgroup of neurons, and (iii) creation of transgenic models to facilitate the investigation of the interaction between hypertrophic stimuli and underlying genetic predisposition. 3. Information on the nature of the cardiac-mass-modifying genes involved may be useful not only for selecting high risk patients in strategies aimed at preventing the development of LVH, but also in opening new avenues of research on the reprogramming of cardiac myocytes to encourage them to hypertrophy in situations where cardiac muscle has been damaged or is hypoplastic.     

Development of a new method for the analysis of sphinganine and sphingosine in urine and tissues

The fumonisins are inhibitors of de novo sphingolipid biosynthesis in vitro and in vivo and thus possibly interfere with the regulation of cell growth, differentiation, and neoplastic transformation. In addition, the ratio of free sphinganine (Sa) to free sphingosine (So) has been proposed as a marker of exposure for animals or humans consuming feed or food contaminated by these toxins. A method to analyze these sphingolipid bases has been proposed [Merrill et al., 1988: Anal Biochem 171:373-381; Riley et al., 1994a: JAOAC 77:533-540] but involves numerous steps and consequently is not ideally suited to the analysis of large numbers of samples, as is often required in epidemiological studies. A new method was therefore developed for the analysis of the Sa/So ratio in tissues as well as human and rat urine. Briefly, the method involves isolation of exfoliated cells from as little as 0.5 ml of rat urine or 2 ml of human urine followed by a rapid and efficient extraction of sphingolipid bases in ethyl acetate, an optimized derivatization step with o-phthaldialdehyde and a high-pressure liquid chromatography separation on a 250 mm x 4.6 mm. 5 microns Kromasil C18 column, with a 4-step phosphate buffer/methanol gradient. Fluorescence was monitored at 340 nm excitation, 455 nm emission, and retention times for So, Sa, and C-20 Sa were about 11, 14, and 22 min, respectively. The method was adapted to tissue analysis by partially digesting approximately 30 mg tissue with trypsin to permit isolation of a cell pellet before extraction of the sphingolipids as described above. The method was applied to the analysis of So and Sa in urines and tissues of fumonisin B1 (FB1) treated and untreated male BDIV rats. The Sa/So ratio in urine of untreated rats varied from 0.1 to 0.7, and for treated rats (between 1-5 mg FB1/kg body weight daily by gavage), the ratio was between 1.2-10. In kidney, the ratio was 0.1 in control rats and varied from 4 to 10.3 in treated rats. In human urine, measurements could easily be made in 2 ml of urine in females, but in males much larger volumes were required due to the low levels of sphingolipid bases.     

Validation of the Applied Biosystems Prism 377 automated sequencer for the forensic short tandem repeat analysis

The Applied Biosystems (ABI) Prism 377 DNA sequencer has been evaluated in an attempt to increase the throughput of samples for short tandem repeat (STR) analysis, in both forensic casework and the UK National Criminal Intelligence DNA Database. The gel system assessed consisted of 0.2 mm, 4% acrylamide 6 M urea gels, with a well-to-read distance of 36 cm. Gels were run at a constant voltage of 3 kV and constant temperature of 51 degrees C. The run time of our second generation multiplex (SGM) STR system was achieved in less than 2 h. Rigorous validation has been performed on the instrument hardware and software. Complete resolution of 1 base differences was obtained, up to and beyond 350 bases; sizing precision across gels was more than 2-fold higher than the 373A and the sensitivity was increased by one third.     

Characterization of type I 5 alpha-reductase activity in DU145 human prostatic adenocarcinoma cells

Each amino acid is represented by a vector of numerical measurements for the attributes of volume, area, hydrophilicity, polarity, hydrogen bonding, shape, and charge. Inter-residue distances are then calculated according to common metrics, and we introduce a new clustering objective function derived from information-theoretic considerations. The arguments of the function are the inter-object distances of the things to be clustered: in this case the amino acids. By means of approximating the solution of an integer programming problem, then, the residues are partitioned into clusters. The clusters obtained are compared with groups obtained in substitution/mutation studies and found to be similar. Thus, probably the strongest and most objective evidence to date is supplied for believing that physico-chemical properties account for the viability of substitutions and that the important similarities/differences are explained by a relatively small and simple set of properties.     

A Ca2+-activated whole-cell Cl- conductance in human placental cytotrophoblast cells activated via a G protein

Evidence now suggests that some people can exert some degree of control over seizure initiation and inhibition. In order to explore this further, 79 young people with epilepsy, attending specialist residential schools, were interviewed regarding awareness of seizure precipitants; recognition of seizure warnings; attempts at seizure inhibition, and ways of self-inducing seizures. Questionnaires with the same content were completed by residential care staff. Results show that many subjects claimed to identify seizure precipitants (63.3%), experienced warnings (70.9%), and had developed means of trying to inhibit seizure occurrence (50.6%). However, in each instance, staff reports were much lower (56.9%, 47.2%, and 22.2%, respectively), and one-to-one concordance was poor. A larger than expected percentage of self-induction was reported for both subjects (8.9%) and staff (9.7%). The implication of these results for both the investigation and treatment of epilepsy are discussed further.     

Technology assessment methods for radiology systems

This article discusses the strengths and weaknesses of technology assessment methods for the evaluation of novel and complex radiology systems, including picture archiving and communication systems (PACS), computed radiography (CR), teleradiology, and other new models for the delivery of radiology services. Using examples from PACS and CR, we review early economic assessments of PACS from the radiology department. We then broaden our perspective to discuss the analytic criteria that can be used to evaluate economic analyses of PACS as the health care delivery system shifts toward managed care. We close with a proposal for optimizing the integration of information technology into the clinical environment through ongoing target data collection during the implementation of new radiology systems.     

Prognostic value of plasma fibrinogen concentration in patients with unstable angina and non-Q-wave myocardial infarction (TIMI IIIB Trial)

The records of 60 patients with gallbladder carcinoma (GBC) operatively treated between 1966 and 1993 at Belen Hospital, Trujillo, Perú, were retrospectively reviewed. The ratio of men to women was 1:7.5 and the average of age was 61 years. The accuracy of ultrasonography and oral cholecystograms for the specific diagnosis was 21% and 0% respectively. The surgical procedures employed were simple cholecystectomy (n = 56), right hepatectomy (n = 2). Whipple operation (n = 1) and extended cholecystectomy (n = 1), and our resectability rate for GBC is currently 50%. Simple cholecystectomy was a potentially curative surgical procedure in patients with in situ cancer (stage O) and early GBC (stage 1). In hospital mortality was 11.6% and 5-year survival rate for the total series was 15%. Gallstones were present in 95% of patients and most tumors (58%) had grown by diffuse infiltration or were associated with empyema (38%). Tumor stage, depth of invasion, tumor grade histologic type were all predictive of patient outcome. This report reinforces the difficulty in diagnosis and the poor prognosis for patients with GBC. We hold the view that more radical approaches for invasive cancers will enhance the operative results.