An 8-GHz f/sub t/ carbon nanotube field-effect transistor for gigahertz range applications

In this letter, the authors report on the high-frequency (HF) performance of self-assembled carbon nanotube field-effect transistors. HF device structures including a large number of single-wall carbon nanotubes have been designed and optimized in order to establish a new state of the art. The device exhibits a current gain (|H/sub 21/|/sup 2/) cutoff frequency (f/sub t/) of 8 GHz and a maximum stable gain value of 10 dB at 1 GHz, after de-embedding the access pads. Considering such results, nanotube-based circuits with gigahertz performance are now conceivable.     

Laparoscopic appendectomy in the adult

AIM OF THE STUDY: The benefits of laparoscopic appendectomy remain controversial. The aim of the study was to evaluate the advantages and disadvantages of this technique. MATERIAL AND METHODS: Four hundred and forty-eight patients operated on for suspected appendicitis during a 5-year period were analysed in a retrospective study. The preoperative diagnosis was corrected in 21.4% of the cases (8.1% for males and 28.7% for females) and the conversion rate was 9.7%. There were 17 patients with generalized peritonitis and 28 with localized peritonitis. During the past year, this surgical method was introduced in another hospital and a prospective study included 92 consecutive patients operated on for appendicitis. The operating time was 53 minutes and the conversion rate was 7.6%. There were five patients with generalized peritonitis and eight with localized peritonitis. RESULTS: There were no postoperative deaths. In the first period, the morbidity rate was 2.3% in the laparoscopic group without conversion. After pathological examination, there was a 14.2% rate of normal appendix. The mean hospital stay was 4.3 days. In the second period, there were only three minor complications and the mean hospital stay was 4.19 days. CONCLUSION: The choice of laparoscopic approach is associated with some advantages: corrections of the diagnosis (mainly in young women) and simplification of the postoperative course, provided that the surgeon has sufficient experience.     

Outcomes following physical restraint reduction programs in two acute care hospitals.

BACKGROUND: Physical restraint rates can be reduced safely in long term care settings, but the strategies used to prevent wandering, falls, and patient aggression have not been tested for their effectiveness in preventing therapy disruption. A restraint reduction program (RRP) consisting of four core components (administrative, educational, consultative, and feedback) was implemented in 1998-1999 in 14 units at two acute care hospitals in geographically distant cities. METHODS: The RRP was targeted at units with prevalence rates of > or = 4% for non-intensive care units (non-ICUs) and > or = 25% for ICUs, as well as two additional units. The RRP was implemented by an interdisciplinary team consisting of geriatricians and nurse specialists. RESULTS: Of the 16,605 admissions to the RRP units, 2,772 cases received RRP consultations. Only six units (four of seven general units and two of six ICUs) demonstrated a relative reduction of > or = 20% in the physical restraint use rate. No increase in secondary outcomes of patient falls and therapy disruptions (patient-initiated discontinuation or dislodgment of therapeutic devices) occurred, injury rates were low, and no deaths occurred as a direct result of either a fall or therapy disruption event. DISCUSSION: Given the minimal success in the ICU settings, further studies are needed to determine effective nonrestraint strategies for critical care patients. ICU clinicians need to be persuaded of the favorable risk-to-benefit ratio of alternatives to physical restraint before they will change their practice patterns. SUMMARY: Efforts to identify more effective interventions that match patient needs and to identify non-clinician factors that affect physical restraint use are needed.     

Active properties of carbon nanotube field-effect transistors deduced from S parameters measurements

AC performances of carbon nanotube field-effect transistors (CNT-FETs) are analyzed by means of scattering parameters measurements. The active ac properties of CNT-FETs are clearly demonstrated up to 80 MHz and indications of active behavior are obtained up to 1 GHz. From these measurements, a small signal equivalent circuit is proposed and validated up to 10 MHz. The extraction procedure and the determination of the intrinsic ac elements of CNT-FETs are pointed out.     

Nonlinear Characterization and Modeling of Carbon Nanotube Field-Effect Transistors

We report for the first time to our knowledge large-signal measurements performed at 600 MHz and in time domain on carbon nanotube field-effect transistors (CNFETs) using a large-signal network analyzer. To overcome the very high mismatch between the high CNFET impedance and the basic 50-$Omega$ configuration of the setup, the output impedance was matched with the help of an experimental active load–pull configuration. Hence, we were able to observe under large-signal conditions the nonlinear behavior of CNFETs. Static measurements and continuous-wave ${ S}_{ ij}$-parameter measurements were made for many different biases. They were used in order to determine a nonlinear electrical model that has been validated thanks to the nonlinear measurements. The developed model opens the way for electrical CNFET circuit simulation and nonlinear applications of these devices.