A remark on helical waveguides

Motivated by a proposal to create an optical helix-shaped waveguides for cold atoms and molecules, we discuss local perturbations which can create bound states in such a setting. This is known about a local slowdown of the twist; we show that a similar effect can result from a local tube protrusion or a change of the helix radius in correlation with its pitch angle.Comment: LaTeX, 12 page

ICU research: the impact of invasiveness on informed consent

Purpose: Studies into the preferences of patients and relatives regarding informed consent for intensive care unit (ICU) research are ongoing. We investigated the impact of a study's invasiveness on the choice of who should give consent and on the modalities of informed consent. Methods: At ICU discharge, randomized pairs of patients and relatives were asked to answer a questionnaire about informed consent for research. One group received a vignette of a noninvasive study; the other, of an invasive study. Each study comprised two scenarios, featuring either a conscious or unconscious patient. Multivariate models assessed independent factors related to their preferences. Results: A total of 185 patients (40%) and 125 relatives (68%) responded. The invasiveness of a study had no impact on which people were chosen to give consent. This increased the desire to get more than one person to give consent and decreased the acceptance of deferred or two-step consent. Up to 31% of both patients and relatives chose people other than the patient himself to give consent, even when the patient was conscious. A range of 3 to 17% of the respondents reported that they would accept a waiving of consent. Younger respondents and individuals feeling coerced into study participation wanted to be the decision makers. Conclusions: Study invasiveness had no impact on patients' and relatives' preferences about who should give consent. Many patients and relatives were reluctant to give consent alone. Deferred and two-step consent were less acceptable for the invasive study. Further work should investigate whether sharing the burden of informed consent with a second person facilitates participation in ICU researc

Informed consent for research in ICU obtained before ICU admission

Objective: To analyze the procedure of the informed consent for ICU research obtained before ICU admission. Design: Prospective, open, observational study. Setting: 20-bed surgical ICU of atertiary teaching university hospital and the ward before and after ICU. Patients: Patients, scheduled for elective cardiac surgery, who accepted to participate in acoagulation study. Interventions: Patients underwent the same informed consent procedure, including an oral presentation of the coagulation study and an informative leaflet the day before surgery on the ward. Measurements and results: Between January and August2001, we included 38patients; 36survived ICU. Ten to 12days after surgery, 8/36(22%) patients did not know they had participated in astudy, and 9/36(25%) could not recall the study purpose and the related risk. Patients with incomplete recall stayed longer in ICU [median (range): 4(3-6) vs3(1-5)days; p = 0.004]. None of these patients (0/9 vs10/27; p < 0.04) had read the informative leaflet AND asked at least one question during the informed consent procedure. Conclusions: Even when the informed consent is obtained in the most optimal conditions for ICU research, its ethical value remains questionable. Indeed, asubstantial number of patients were unaware of their study participation, or of the related purpose and risks. When the ICU stay is prolonged, we should at least repeatedly and actively (re)-inform patients about their study participatio

Spectrum of the Schr\"odinger operator in a perturbed periodically twisted tube

We study Dirichlet Laplacian in a screw-shaped region, i.e. a straight twisted tube of a non-circular cross section. It is shown that a local perturbation which consists of "slowing down" the twisting in the mean gives rise to a non-empty discrete spectrum.Comment: LaTeX2e, 10 page

Point of care management of heparin administration after heart surgery: A randomized, controlled trial

Objectives: Determination of activated partial thromboplastin time (aPTT) is used in coagulation management after heart surgery. Results from the central laboratory take long to be obtained. We sought to shorten the time to obtain coagulation results and the desired coagulation state and to reduce blood loss and transfusions using point of care (POC) aPTT determination. Design: Randomized, controlled trial. Setting: University-affiliated 20-bed surgical ICU. Patients and participants: Forty-two patients planned for valve surgery (Valves) and 84 for coronary artery bypass grafting (CABG) with cardiopulmonary bypass. Interventions: Valves and CABG were randomized to postoperative coagulation management monitored either by central laboratory aPTT (Lab group) or by POC aPTT (POC group). Heparin was administered according to guidelines. Measurements and results: POC aPTT results were available earlier than Lab aPTT after venipuncture in Valves (3 ± 2 vs. 125 ± 68 min) and in CABG (3 ± 4 vs. 114 ± 62 min). Heparin was introduced earlier in the POC group in Valves (7 ± 23 vs. 13 ± 78 h, p = 0.01). Valves of the POC group bled significantly less than Valves in the Lab group (647 ± 362 ml vs. 992 ± 647ml, p < 0.04), especially during the first 8 h after ICU admission. There was no difference in bleeding in CABG (1074 ± 869 ml vs. 1102 ± 620, p = NS). In Valves, fewer patients in the POC group than in the Lab group needed blood transfusions (1/21 vs. 8/21; p = 0.03). No difference was detected in CABG. Conclusions: In Valves in the POC group the time to the desired coagulation state was reduced, as was the thoracic blood loss, reducing the number of patients transfused. This improvement was not observed in CABG. Side effects were similar in the two group

A Hardy inequality in twisted waveguides

We show that twisting of an infinite straight three-dimensional tube with non-circular cross-section gives rise to a Hardy-type inequality for the associated Dirichlet Laplacian. As an application we prove certain stability of the spectrum of the Dirichlet Laplacian in locally and mildly bent tubes. Namely, it is known that any local bending, no matter how small, generates eigenvalues below the essential spectrum of the Laplacian in the tubes with arbitrary cross-sections rotated along a reference curve in an appropriate way. In the present paper we show that for any other rotation some critical strength of the bending is needed in order to induce a non-empty discrete spectrum.Comment: LaTeX, 20 page

Acoustic Phonon-Assisted Resonant Tunneling via Single Impurities

We perform the investigations of the resonant tunneling via impurities embedded in the AlAs barrier of a single GaAs/AlGaAs heterostructure. In the $I(V)$ characteristics measured at 30mK, the contribution of individual donors is resolved and the fingerprints of phonon assistance in the tunneling process are seen. The latter is confirmed by detailed analysis of the tunneling rates and the modeling of the resonant tunneling contribution to the current. Moreover, fluctuations of the local structure of the DOS (LDOS) and Fermi edge singularities are observed.Comment: accepted in Phys. Rev.

Research in critically ill patients: standards of informed consent

Patients in critical care lose their capability to make a judgement, and constitute a 'vulnerable population' needing special and reinforced protection. Even if the standard of informed consent is an essential way of demonstrating respect for the patient's autonomy, the usual informed-consent procedure is not as applicable as required or sufficient to warrant this ethical principle in critical care

Informed consent for research obtained during the intensive care unit stay

INTRODUCTION: Patients in the intensive care unit (ICU) may be in an inadequate condition to give their informed consent for research. The aim of this study was to analyse the ability to recall participation in a clinical trial for which ICU patients had given their consent. METHODS: The data presented are a two-step observational study: first, a protocolled informed consent procedure was conducted then the informed consent was given by the patient, and second, a patient interview was held 10 ± 2 days later by the same investigator. The primary endpoints were the ability to recall their participation in the clinical trial, as well as its purpose and related risks. As secondary endpoints, we investigated whether asking questions about the clinical trial or reading the informative leaflet was related to the recall. To be included in the study, the patient had to have a Glasgow Coma Scale score of 15, be fully oriented and free of mechanical ventilation, and be judged competent by both the investigator and the attending physician. Patients admitted to the ICU after major surgery or trauma were eligible. However, patients who refused to participate, or those whose next-of-kin gave consent, were excluded. RESULTS: Of the 44 patients, 35 (80%) recognized, 10 to 12 days after informed consent had been obtained, that they had participated in the clinical trial, but only 14 out of 44 (32%) could recall the clinical trial purpose and its related risks. More patients with complete recall had read the informative leaflet or asked at least one question before signing the informed consent. Asking at least one question was associated with complete recall. CONCLUSION: Our results confirm that obtaining informed consent for research during an ICU stay is associated with poor patient recall of participation in a clinical trial and its components (purpose and risk). Whether encouraging reading the informative leaflet and asking questions about the clinical trial improves the informed consent procedure remains to be fully investigated