DFT/NEGF study of discrete dopants in Si/III-V 3D FET.

In this work, electron densities around dopants in Si and GaAs have been calculated using density functional theory (DFT) calculations. These extracted densities have been used to describe dopants in an in-house non-equilibrium Green functions device simulator. The transfer characteristics of nanowire gate all around field effect transistor have been calculated using DFT electron densities. These transport calculations were compared with those using a point charge model of the dopant. The dopants are located in the middle of the channel of the device. Specifically, DFT calculations of a 512 atom Si supercell with a single impurity atom have been carried out, both phosphorous and boron atoms have been used as donor and acceptor impurities respectively. The calculations were repeated on a gallium arsenide supercell, where the silicon atom substituted gallium and arsenide to act as donor and acceptor respectively. We found that for donors and acceptors, the DFT charge distribution extends similarly in both materials. In addition, the relaxed structure produces a 50% larger spread of electronic charge as compared with unrelaxed Si and GaAs. The extracted current voltage characteristics of the devices are altered significantly using the charge density obtained by DFT. At 0.7 V the current in Si is 20% larger using the DFT charge density compared to the point charge model for donors. Whereas the current using the point charge model in GaAs is 2.5 times larger than the distributed charge. Devices exhibit substantial tunnelling currents for donors and acceptors irrespective of the model of the dopant considered. In GaAs, this was 76% using a point charge and 78% using the distributed charge when using a donor; 61% and 68% in Si respectively. The tunnelling current using acceptors for Si was 100% and 99% using GaAs for both models.

Multidrug resistance-1 gene expression does not increase during tumor progression in the MGH-OGS murine osteosarcoma tumor model.

In addition to its possible role in drug resistance, expression of the multidrug resistance-1 gene may also be associated with a more malignant phenotype and tumor progression. This study evaluated its expression during tumor progression in the MGH-OGS transplantable murine osteosarcoma tumor model. Three variables of tumor progression were analyzed: tumor size, local recurrence, and metastasis. With a highly sensitive reverse transcription-polymerase chain reaction method, mRNA levels of multidrug resistance-1 were compared in primary tumors of different sizes. In addition, the levels were compared in primary, locally recurrent, and metastatic tumors isolated from individual mice. No significant difference was found in the levels of expression with increasing primary tumor size. In addition, the levels in primary, locally recurrent, and metastatic tumors were not significantly different. Our results indicate that--at least in the MGH-OGS tumor model, which is analogous to the majority of spontaneously occurring human osteosarcomas in that it has low levels of multidrug resistance-1/P-glycoprotein and is sensitive to doxorubicin--there is no evidence of upregulation of multidrug resistance-1 expression during tumor progression.

Interstellar polycyclic aromatic hydrocarbons: the infrared emission bands, the excitation/emission mechanism, and the astrophysical implications.

This article presents a comprehensive treatment of the polycyclic aromatic hydrocarbon (PAH) hypothesis. The interstellar, infrared spectral features which have been attributed to emission from highly vibrationally excited PAHs are discussed in detail. These include major (most intense) bands at 3040, 1615, "1310," 1150, and 885 cm-1 (3.29, 6.2 "7.7," 8.7, and 11.3 micrometers), minor bands and broad features in the 3200-2700 cm-1 [correction of 3200-2700-1] (3.1-3.7 micrometers), 1600-1100 cm-1 (6.0-9 micrometers) and 910-770 cm-1 (11-13 micrometers) regions, as well as the vibrational quasi-continuum spanning the entire mid-IR and the electronic transitions which contribute to the high-frequency IR continuum. All the major and minor bands, as well as the quasi-continuum, can be attributed to vibrational transitions in molecular-sized PAHs. The latter two broad features probably arise from very large PAHs, PAH clusters, and amorphous carbon particles. A precise match of the interstellar spectra with laboratory spectra is not yet possible because laboratory spectra are not available of PAHs in the forms probably present in the interstellar medium (completely isolated, ionized, some completely dehydrogenated, and containing between about 20 and 40 carbon atoms). The method with which one can calculate the IR fluorescence spectrum from a vibrationally excited molecule is also described in detail. Fluorescence band intensities, relaxation rates, and dependence on molecule size and energy content are treated explicitly. Analysis of the interstellar spectra indicates that the PAHs which dominate the infrared spectra contain between about 20 and 40 carbon atoms. The results obtained with this method are compared with the results obtained using a thermal approximation. It is shown that for high levels of vibrational excitation and emission from low-frequency modes, the two methods give similar results. However, at low levels of vibrational excitation and for the high-frequency modes (for example, the 3040 cm-1, 3.3 micrometers band), the thermal approach overestimates the emission intensities. For calculations of molecular reactions (such as H-loss, deuterium enrichment, and carbon skeleton rearrangement) a thermal approximation is invalid. The relationship between PAH molecules and amorphous carbon particles is presented and their production in circumstellar shells is described. The most likely interstellar PAH molecular structures are discussed and the possibility of destructive reactions with interstellar oxygen and hydrogen atoms is considered in detailed and found to be unimportant. Interstellar PAH size and abundance estimates are made. On the order of a few percent of the available interstellar carbon is tied up in the small (20-40 carbon atom) PAHs which are responsible for the sharp features, and a similar amount is tied up in the larger (200-500 carbon atom) PAHs or PAH clusters and amorphous carbon particles which are responsible for the broad components underlying the 1600-1100 and 900-770 cm-1 (6-9 and 11-13 micrometers) regions. It is shown that the spectroscopic structure these PAHs and PAH-related materials produce in the UV portion of the interstellar extinction curve lie just below current detection limits but fall in the range detectable by the Hubble Space Telescope. Finally, the influence of PAH charge on the ultraviolet, visible, and infrared regions is described.

A system for customer feedback: the InterVention (IV) Line.

Healthcare organizations use a number of data collection methodologies to identify opportunities for improving customer satisfaction. One methodology used at the 665-bed University Hospitals and Clinics of the University of Mississippi Medical Center is a customer service telephone hotline. Patients, visitors, and staff members call in their compliments and concerns to the InterVention (IV) Line, which provides customized problem solving. This article provides an overview of the customer hotline and presents lessons learned from its implementation.

A mathematical model for a thermal clearance probe.

We introduce a new mathematical model for a thermal clearance probe for the measurement of skin blood flow. It is concluded that the technique is more sensitive to differences in the thermal conductivity of the skin than to differences in blood flow. The depth of measurement is also considered.

Management of imported fire ant allergy: results of a survey.

BACKGROUND: Fire ant allergy is a significant health problem in the southern United States. Management of fire ant allergy is less clearly defined than management of allergy to the winged Hymenoptera. OBJECTIVE: To determine how fire ant allergy is managed by practicing allergists. METHODS: A survey form was developed and distributed to American College of Allergy, Asthma & Immunology members practicing in fire ant endemic states. Completed forms were returned to the American College of Allergy, Asthma & Immunology central office and forwarded to the authors for analysis. RESULTS: Three hundred twenty-nine of 879 (37.4%) surveys were returned; 81% of respondents have evaluated patients with imported fire ant allergy. Immunotherapy is used by 96.7% of respondents to treat fire ant allergy. A wide range of maintenance dosages are prescribed. Skin testing is the most common diagnostic method. Systemic reactions to stings while on maintenance immunotherapy were reported by 19%. Allergists utilize different criteria in consideration for stopping immunotherapy; 19% continue it indefinitely. CONCLUSIONS: There are many areas of general uniformity and other areas of divergence in how allergists manage imported fire ant allergy. These findings suggest continued need for further investigation regarding the efficacy, dosage, and duration of immunotherapy, as well as further elucidation of the natural history of fire ant allergy.

Reengineering communication at the University of Mississippi Medical Center: the case for the campus dialogue.

One of the key concepts at the heart of the continuous improvement of processes and outcomes in health care is improved organizational communication. Complex organizations such as academic health centers often find that communication among internal customers is informal and ineffective. The article describes a successful effort for improving communication in an academic health center that was the product of reengineering a previous communication process. Implications of reengineering and lessons learned from implementation are presented. Reengineering is a beneficial concept for guiding some improvements in health care organizations.

Descriptive and graphical strategies for assessing change: a case study of functional status in stroke patients.

A primary focus in the current context of the health care industry is the measurement of outcomes. Outcomes research, although inclusive of the use of advanced statistical analyses, can often be conducted using more easily understood analytical techniques such as descriptive analysis and graphical display of data. The article addresses the description and analysis of patient change scores on the Functional Independence Measure (FIM) from 745 stroke rehabilitation inpatients. Display and discussion of percentiles, cross-tabulations, scatter plots, and side-by-side box plots are used in this case study of describing outcomes.

Improving clinical performance: a "how to" for procedures review.

As part of comprehensive performance improvement for accredited hospitals, the Joint Commission on Accreditation of Healthcare Organizations requires that institutional data collection include a review of "operative, other invasive, and noninvasive procedures that place patients at risk" (JCAHO, 1998b, p. 125). To meet the standard for comprehensive procedures review, the University Hospitals and Clinics at the University of Mississippi Medical Center developed an innovative methodology to ensure Joint Commission compliance. This article describes the processes used and the outcomes realized by the performance improvement team responsible for procedures review.

Intracavity dye laser spectroscopy studies of the Ba + N(2)O, Ca + N(2)O + CO, and Sr + N(2)O + CO reactions.

A search for gain or absorption on several candidate visible chemical laser transitions has been carried out using the intracavity dye laser probe technique. Absorption was found on the following v'' ? v' bands of the BaO(A(1)Sigma ? X(1)Sigma) bands in the Ba + N(2)O reaction: 0 ? 1; 0 ? 4; 1 ? 1; 1 ? 2, and 5 ? 1. No gain or absorption could be detected on the 7 ? 1, 6 ? 0, and 4 ? 0 bands (sensitivity ~10(-4)/cm). In Ca, Sr + N(2)O + CO flames, absorption was found in the green arc bands of CaO and the red arc bands of SrO. Several new bandhead wavelengths are reported. Our results support assignment of the arc bands to the diatomic metal oxides. Absorptions and enhancements were found on various Sr, Ba, and Ba(+) transitions.

Magnetic resonance imaging of severe frostbite injuries.

Frostbite injury causes damage by direct ice crystal formation at the cellular level with cellular dehydration and microvascular occlusion. Acute treatment is well defined with rapid tissue rewarming. Definitive surgical therapy is usually delayed until a clear level of demarcation is seen. Technium (Tc)-99 bone scanning has become the standard imaging study employed within the first several days to assess tissue perfusion and viability. We present 2 patients with severe frostbite injury in which magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) were compared to Tc-99 bone scans. MRI/MRA appears to be superior to bone scanning by allowing direct visualization of occluded vessels, imaging of surrounding tissues, and by showing a more clear-cut line of demarcation of ischemic tissue. MRI/MRA may also allow early intervention in cases of severe frostbite, thus preventing secondary infection and increased cost.