Bias and temperature dependence of homogeneous hot-electroninjection from silicon into silicon dioxide at low voltages

In this paper, new homogeneous hot-electron injection data at 300 K and 77 K is provided covering applied voltages from well below to well above the Si-SiO₂ barrier height, and a wide range of oxide fields. We found that, in contrast to the MOSFET case, homogeneous injection shows two different regimes for accelerating voltages below and above the barrier height. A simple interpretation of the data is proposed, and supported by Monte Carlo (MC) simulations of the injection experiment. Essentially, the two regimes are the signature of a marked transition between an electron population mostly heated by the electric field, and a tail population created by additional but less efficient energy gain mechanisms, leading to a sharp transition in the carrier distribution function. The details of the bias and temperature dependence of injection are then interpreted as the combined effect of tunneling and carrier distribution. Furthermore, possible implications on MOSFET gate currents are briefly discussed     

Contraindications to metformin therapy in patients with NIDDM

OBJECTIVE: Treatment with metformin is occasionally associated with the development of severe lactic acidosis. However, this is usually observed in patients with major contraindications to the drug. In this study, we aimed to determine the prevalence of conditions currently regarded as either contraindications or cautions to the use of metformin in patients with NIDDM. RESEARCH DESIGN AND METHODS: The case notes of metformin-treated NIDDM patients (mean age 62 years) attending a United Kingdom university hospital diabetes clinic over a 3-month period were reviewed according to criteria reflecting a pragmatic view of current prescribing recommendations. RESULTS: Of 89 consecutive patients whose notes could be evaluated in detail, only 41 (46%) had no contraindications or cautions to metformin whatsoever. Concomitant chronic disorders associated with a potentially increased risk of hyperlactatemia were renal impairment (n = 2; plasma creatinine concentrations 1.7 and 2.3 mg/dl, respectively), cardiac failure (n = 2), and chronic liver disease (n = 2). Other potentially relevant disorders included ischemic heart disease (n = 20), clinical proteinuria (n = 14), peripheral vascular disease (n = 22), and pulmonary disease (n = 7). Multiple conditions (i.e., two, three, or four) were present in eight, five, and one patient(s), respectively. CONCLUSIONS: More than half the patients in our series had concomitant conditions or complications conventionally regarded as cautions or contraindications to metformin; approximately 10% had a multiplicity of such conditions. Regular surveillance is necessary to detect the development of complications such as renal impairment. Vigilance is also required in view of the increased risk of major intercurrent illnesses, which may independently disturb lactate metabolism in patients with NIDDM. Metformin should be withdrawn promptly under such circumstances.     

Mapping a quantitative trait locus involved in melanotic encapsulation of foreign bodies in the malaria vector, Anopheles gambiae

A Plasmodium-refractory strain of Anopheles gambiae melanotically encapsulates many species of Plasmodium, whereas wild-type mosquitoes are usually susceptible. This encapsulation trait can also be observed by studying the response of refractory and susceptible strains to intrathoracically injected CM-Sephadex beads. We report the results of broad-scale quantitative trait locus (QTL) mapping of the encapsulation trait using the bead model system. Interval mapping using the method of maximum likelihood identified one major QTL, Pen1. The 13.7-cM interval containing Pen1 was defined by marker AGH157 at 8E and AGH46 at 7A on 2R. Pen1 was associated with a maximum LOD score of 9.0 and accounted for 44% of the phenotypic variance in the distribution of phenotypes in the backcross. To test if this QTL is important for encapsulation of Plasmodium berghei, F2 progeny were infected with P. berghei and evaluated for degree of parasite encapsulation. For each of the two markers that define the interval containing Pen1, a significant difference of encapsulation was seen in progeny with at least one refractory allele in contrast with homozygous susceptible progeny. These results suggest that Pen1 is important for melanotic encapsulation of Plasmodium as well as beads.     

Supramedullary modulation of sympathetic vasomotor function

1. Supramedullary structures including the ventral medial prefrontal cortex (MPFC) and the midbrain cuneiform nucleus (CnF) project directly and indirectly to premotor sympatho-excitatory neurons of the rostral ventrolateral medulla (RVLM) that are critically involved in the generation of sympathetic vasomotor tone. 2. Electrophysiological studies have demonstrated that activation of depressor sites within the MPFC is associated with splanchnic sympathetic vasomotor inhibition and inhibition of the activity of RVLM sympathoexcitatory neurons. 3. Antidromic mapping and anatomical studies support the notion that a relay in the nucleus tractus solitarius is involved in the cardiovascular response to MPFC stimulation. 4. The midbrain CnF, which lies adjacent to the midbrain periaqueductal grey, is a sympathoexcitatory region of the midbrain reticular formation. Sympathoexcitatory responses evoked from the CnF are associated with short-latency excitation of RVLM neurons. 5. Cuneiform nucleus stimulation induces the expression of mRNA for the immediate early genes c-fos and NGFI-A in mid-brain, pontine and hypothalamic structures. 6. The MPFC and CnF are supramedullary structures with opposing modulatory influences on sympathetic vasomotor drive, whose roles in cardiovascular control mechanisms warrant further investigation.     

Late rectal sequelae following definitive radiation therapy for carcinoma of the uterine cervix: a dosimetric analysis

OBJECTIVE: The structure of the collagen scar during healing of a myocardial infarction is a determinant of the function of the remodeled tissue. We hypothesize that the passive deformations of both scar and normal tissue are related to the underlying collagen uncoiling as the tissue stretches, and that the unloaded tortuosity of the collagen may be a determinant of tissue stiffness at low ventricular pressure. Hence collagen uncoiling and tissue strain were measured during passive loading in normal tissue, and in healing infarct tissue. METHODS: Left ventricles of rats were infarcted by ligation of the left anterior descending artery for 2 weeks. Surface strains were measured during passive inflation in the scar region in one set of excised hearts, and other arrested hearts were fixed at different ventricular pressures, after which collagen tortuosity was measured in the infarcted and normal tissue. RESULTS: Passive loading strains were smaller in the scar in both the fiber and cross-fiber directions. Tortuosity decreased with load in normal and infarcted tissue, with fibrils tending to straighten more in the scar tissue at higher pressures (1.056 +/- 0.009 vs. 1.024 +/- 0.009 at P = 20 mmHg) with similar tortuosities at zero pressure (1.110 +/- 0.012 vs. 1.098 +/- 0.019). The decrease in tortuosity with strain was greater for the infarcted tissue. CONCLUSIONS: The greater stiffness of infarcted tissue at low pressure is not due to 'straightened' collagen fibers, and there may be a different three-dimensional structure of infarct vs. normal coiled collagen fibers which can affect the material properties of these tissues.     

Laboratory studies in cross-species lung transplantation

The lack of sufficient suitable human donor lungs for the many patients requiring pulmonary transplantation as life-saving therapy for end-stage lung diseases has generated extensive interest in cross-species lung transplantation. Ethical concerns and those of animal rights advocates have prompted studies of nonprimate species as potential solid organ donors for humans. This paper provides an overview of some of the laboratory studies of cross-species pulmonary transplantation performed over the past 20 years and focuses, in particular, on more recent work (from our laboratory and others) in the area of porcine-to-primate pulmonary xenotransplantation.     

Oncological outcomes of operative treatment of subcutaneous soft-tissue sarcomas of the extremities

We reviewed the cases of sixty-two patients who had had a subcutaneous sarcoma to determine the effect of tumor and treatment-related variables on the rates of survival and local recurrence. Fifty-nine (95 per cent) of the patients had had an operation at another hospital before being referred to us. Twenty-nine (47 per cent) of the sixty-two tumors were high-grade, forty-two (68 per cent) were small (five centimeters or less), and thirty (48 per cent) were malignant fibrous histiocytomas. We followed a treatment strategy that consisted of repeat excision with the goal of obtaining wide margins. Excluding thirteen patients who had had a palpable local recurrence at the time of presentation, twenty (49 per cent) of forty-one patients who had had a marginal excision at another hospital had microscopic residual tumor on repeat excision. At a median of fifty-six months after the repeat excision, fifty (81 per cent) of the sixty-two patients had been continuously disease-free, one had no evidence of disease, eight had died of the disease, and three had died of other causes. The five-year rate of disease-free survival was 85 per cent (fifty-three of sixty-two patients). There were three local recurrences, all in patients who had had a marginal resection. No recurrences were noted in patients who had had a wide local excision of the tumor or of the previous operative field. Multivariate analysis revealed that a large tumor (greater than five centimeters), a marginal excision, and adjuvant radiation therapy were associated with a worse prognosis. Excellent rates of survival for patients who have a subcutaneous sarcoma, including those who have a large or high-grade tumor and those who have residual tumor following a previous operation, can be obtained with carefully planned operative treatment alone. We recommend operative excision or repeat excision with wide margins because of the high prevalence of residual tumor. Size is the most important tumor-related factor, and the operative margin is the most important treatment-related factor. The additional value of adjuvant radiation therapy remains unproved.     

Peripheral nerve stimulation by time-varying magnetic fields

PURPOSE: A study was performed to assess the stimulation threshold for healthy adults using sinusoidally oscillating gradients. METHOD: One hundred thirteen healthy adults were examined in the study. ECG and physiological parameters were measured. All measurements were performed of both the head and the abdomen. The subjects were measured in the supine position with the region of interest positioned in the center of the gradient coils. The measurement was performed for three orthogonal, four oblique, and double oblique orientations. RESULTS: No volunteer reported painful, severe stimulation. The mean thresholds for peripheral stimulation in head and body measurement were similar: 85.5% of stimulation during examination of the head and 87.6% during measurements of the abdomen were reported when the y-gradient was used. CONCLUSION: The greatest frequency of reported stimulations occurs when the y-gradient is used. This was confirmed by the results and supports the hypothesis that orthogonal to the y-axis the body has its largest conductive loop, resulting in the strongest peripheral stimulation.     

Initial experiences with the MR "magnitude contrast angiography of the lower extremities

45 patients with occlusive peripheral vascular disease were examined by MR angiography in a retrospective study. A FISP 3D sequence was used by acquiring a rephased and a dephased data set. The individual slices were post-processed by using a maximum-intensity-projection algorithm. The MRA results of the popliteal and tibioperoneal arteries were compared to conventional or digital angiography. In comparing these techniques MR angiography cannot be accepted for pre- and postoperative staging of patients with occlusive peripheral vascular disease. In future new MRA techniques may be useful in postoperative staging of patients with peripheral vascular stenosis.