Lateral Ge Diffusion During Oxidation of Si/SiGe Fins

This Letter reports on the unusual diffusion behavior of Ge during oxidation of a multilayer Si/SiGe fin. It is observed that oxidation surprisingly results in the formation of vertically stacked Si nanowires encapsulated in defect free epitaxial strained Si_xGe_1-x. High angle annular dark field scanning transmission electron microscopy (HAADF-STEM) shows that extremely enhanced diffusion of Ge occurs along the vertical Si/SiO₂ oxidizing interface and is responsible for the encapsulation process. Further oxidation fully encapsulates the Si layers in defect free single crystal Si_xGe_1-x (x up to 0.53), which results in Si nanowires with up to -2% strain. Atom probe tomography reconstructions demonstrate that the resultant nanowires run the length of the fin. We found that the oxidation temperature plays a significant role in the formation of the Si nanowires. In the process range of 800-900 °C, pure strained and rounded Si nanowires down to 2 nm in diameter can be fabricated. At lower temperatures, the Ge diffusion along the oxidizing Si/SiO₂ interface is slow, and rounding of the nanowire does not occur, while at higher temperatures, the diffusivity of Ge into Si is sufficient to result in dilution of the pure Si nanowire with Ge. The use of highly selective etchants to remove the SiGe could provide a new pathway for the creation of highly controlled vertically stacked nanowires for gate all around transistors.

Incidence and patterns of recurrence after resection for cure of colonic cancer in a well defined population

BACKGROUND

The aim of this study was to determine the incidence and patterns of failure following potentially curative surgery of colonic cancer.

METHODS

Data were obtained from the cancer registry of the Côte-d'Or (France). Data on 2657 patients who had resection for cure of colonic cancer between 1976 and 2000 were analysed. Local and distant failure rates were calculated using the actuarial method and multivariable analysis was performed using a Cox model.

RESULTS

The 5-year cumulative rate was 12.8 percent for local recurrence and 25.6 percent for distant metastases. Five-year cumulative local recurrence rates were 4.9 percent for stage I, 11.0 percent for stage II and 23.5 percent for stage III tumours (P<0.001). The corresponding rates for distant metastases were 6.4, 21.4 and 48.0 percent (P<0.001). The 5-year cumulative rates for distant metastases were 31.7 percent for the period 1976-1980 and 21.1 percent for 1996-2000, and the local recurrence rates were 17.6 and 9.0 percent respectively. The decreases in rates of local recurrence and distant metastases were significant in multivariable analysis. Cancer extension and presenting features were related to patterns of failure. Tumour location was significantly associated with risk of local recurrence, whereas age and gross features were associated with risk of distant metastasis.

CONCLUSION

Recurrence following resection of colonic cancer remains a substantial problem. Follow-up is of particular importance in the 3 years after surgery.

Is the management of hepatitis C patients appropriate? A population-based study

BACKGROUND

In order for hepatitis C patients to receive antiviral treatment, they must reach medical care.

AIM

To assess the proportion of patients reaching medical care after hepatitis C diagnosis in a general population (1 006 171 inhabitants) in France.

METHODS

Between 1994 and 1999, 1508 cases were diagnosed, of which 1251 were eligible for the study.

RESULTS

Two-hundred and two patients did not have any medical care; among them, 55.4% had normal alanine transferase, 58.4% had risk factors related to lifestyle and 22.8% were alcoholics. Amongst the 1049 other patients, 41.6% had a liver biopsy, 25.0% were treated. Treatment was more often carried out in males than in females (OR: 1.59; P = 0.001), and in patients under 65 than in older patients (OR: 2.22; P < 0.008). Among non-treatment reasons, alcoholism (P = 0.001), drug-addiction (P = 0.04) and escaping monitoring (P = 0.04) were more frequent in males than in females, whereas normal alanine transferase was more frequent in females than in males (P = 0.004). Amongst 278 patients with a Metavir score >A1F1, 71 (25.5%) did not undergo treatment.

CONCLUSION

In a general population, one patient in six did not receive on-going health care; a quarter of patients with a Metavir score >A1F1 did not receive any treatment. These results showed insufficient clinical management, which could compromise the effectiveness of treatment in general population.

Incidence and management of malignant digestive endocrine tumours in a well defined French population

BACKGROUND AND AIMS

Little is known about the epidemiology of malignant digestive endocrine tumours. The aim of this study was to report on their incidence and management in a well defined population.

METHODS

Data were obtained from the population based Digestive Cancer Registry of Burgundy (France) over a 24 year period. Incidence rates were calculated by sex, age groups, and period of diagnosis. Treatment and stage at diagnosis were also investigated. Prognosis was determined using crude and relative survival rates. A multivariate relative survival analysis was performed.

RESULTS

Between 1976 and 1999, 229 cases were recorded. Age standardised incidence rates were 0.76/100,000 for men and 0.50/100,000 for women. They increased over time in both sexes. The resectability rate was 74.1%. Among recorded cases, 26.6% did not extend beyond the organ, 20% had lymph node metastases, and 53.3% had visceral metastases or were unresectable. There was no improvement in the resection rate or in the stage at diagnosis over the study period. The overall relative survival rate was 66.9% at one year, 50.4% at five years, and 40.6% at 10 years. Stage at diagnosis, age at diagnosis, and subsite were independent significant prognostic factors.

CONCLUSIONS

Although their incidence is increasing, malignant digestive endocrine tumours remain a rare cancer, representing 1% of digestive cancers. Stage at diagnosis and prognosis at a population level are worse than those reported in hospital series. In the short term, new therapeutic possibilities represent the best way to improve their prognosis.

The use of inferior vena cava filter as a treatment modality for massive pulmonary embolism. A case series and review of pathophysiology

The use of inferior vena cava (IVC) filter for massive pulmonary emboli (PE) with cardiopulmonary instability has not been clinically studied. We present a case series of six such patients who received an IVC filter with anticoagulation rather than thrombolysis because of high risk of bleeding. Acute pulmonary embolectomy was considered, but was not possible for a variety of individual clinical situations. These six hospitalized patients prospectively followed during their admission. They were triaged to three medical intensive care units (ICUs) and one surgical ICU in three university teaching hospitals. One patient was transferred from another institution. All six patients had severe hypoxia and tenuous cardiopulmonary status. All required high inspiratory oxygen and hemodynamic support; two required mechanical ventilation and vasopressors. An IVC filter was placed emergently and anticoagulation was started immediately All six patients had resolution of pulmonary thromboemboli (PTE) on anticoagulation while the IVC filter prevented further PE. All six patients were discharged home in their pre-critical illness state. None ofthe patients suffered complications from this therapy and had excellent resolution ofcardiopulmonary collapse. The IVC filter placement prevented further major embolic events while the PTE resolved with anticoagulation. An IVC filter should be considered as an adjunct to anticoagulation therapy for those patients with massive PE and cardiopulmonary instability who are not candidates for thrombolysis, and acute pulmonary embolectomy is not readily available or is of very high risk.

Interaction of human immunodeficiency virus type I Rev protein with nuclear scaffold nucleoside triphosphatase activity

Human immunodeficiency virus type I encodes a regulatory protein, termed Rev, which is associated with the appearance of unspliced and partially spliced viral RNAs in the cytoplasm. Rev is believed to function via interaction with a sequence element in the env region of the viral RNA, termed the Rev-responsive element (RRE). In this study, we use a stably transfected, Rev-producing mouse cell line to show that low, functional levels of Rev are associated with the nuclear scaffold (NS). Immunohistochemical studies localize Rev to the NS. Furthermore, immunoblot analyses demonstrate the presence of Rev in NS preparations isolated from Rev-producing cells and document binding of purified Rev protein to isolated NS or to cloned lamin C in vitro. Results with an in vitro RNA transport assay suggest that Rev is associated with a significant defect in transport of RNAs which lack RRE, whereas transport of RRE-containing transcripts proceeds efficiently. This Rev-induced transport defect appears to be mediated via direct inhibition of NS nucleoside triphosphatase, an enzyme thought to be involved in the nucleocytoplasmic transport process. NS preparations isolated from Rev-producing cells show a significantly lower nucleoside triphosphatase activity than those from control preparations. Addition of Rev protein to isolated NS produces a significant inhibition of NS nucleoside triphosphatase activity, which is specifically reversed by addition of RRE transcripts. These data suggest that a major aspect of Rev function may involve selective modulation of host cell nucleocytoplasmic transport mechanisms via interaction with the NS.

Treatment of adenosine deaminase deficiency with polyethylene glycol-modified adenosine deaminase

We treated two children who had adenosine deaminase deficiency and severe combined immunodeficiency disease by injecting bovine adenosine deaminase modified by conjugation with polyethylene glycol. The modified enzyme was rapidly absorbed after intramuscular injection and had a half-life in plasma of 48 to 72 hours. Weekly doses of approximately 15 U per kilogram of body weight maintained plasma adenosine deaminase activity at two to three times the level of erythrocyte adenosine deaminase activity in normal subjects. The principal biochemical consequences of adenosine deaminase deficiency were almost completely reversed. In erythrocytes, adenosine nucleotides increased and deoxyadenosine nucleotides decreased to less than 0.5 percent of total adenine nucleotides. The activity of S-adenosylhomocysteine hydrolase, which is inactivated by deoxyadenosine, increased to normal in red cells and nucleated marrow cells. Neither toxic effects nor hypersensitivity reactions were observed. In vitro tests of the cellular immune function of each patient showed marked improvement, along with an increase in circulating T lymphocytes. Clinical improvement was indicated by absence of infection and resumption of weight gain. We conclude that from the standpoints of efficacy, convenience, and safety, polyethylene glycol-modified adenosine deaminase is preferable to red-cell transfusion as a treatment for adenosine deaminase deficiency. Patients with other inherited metabolic diseases in which accumulated metabolites equilibrate with plasma could benefit from treatment with the appropriate polyethylene glycol-modified enzyme.

Assessing clinical skills of residents with standardized patients

Current techniques do not provide a reproducible, reliable, or valid basis for assessing clinical skills. The need for large-scale direct observation and standardized assessment procedures has precluded development of better techniques. A project using standardized patients presenting with common clinical problems evaluated the skills of 336 internal medicine residents at 14 New England residency programs in 1289 standardized patient and resident encounters. Results indicated that reproducible assessment of the clinical skills could be achieved in approximately 1 day of testing time using standardized patients. Resident performance improved with years of training, and senior residents and those from programs with stronger reputations performed better and were more homogeneous in ability. Low correlations between standardized-patient-based measures of clinical skills and other evaluation techniques suggested that standardized patients provided unique information. Reactions of residents and faculty to standardized-patient-based evaluations were favorable.