Scanned Single-Electron Probe inside a Silicon Electronic Device.

Solid-state devices can be fabricated at the atomic scale, with applications ranging from classical logic to current standards and quantum technologies. Although it is very desirable to probe these devices and the quantum states they host at the atomic scale, typical methods rely on long-ranged capacitive interactions, making this difficult. Here, we probe a silicon electronic device at the atomic scale using a localized electronic quantum dot induced directly within the device at a desired location, using the biased tip of a low-temperature scanning tunneling microscope. We demonstrate control over short-ranged tunnel coupling interactions of the quantum dot with the device's source reservoir using sub-nanometer position control of the tip and the quantum dot energy level using a voltage applied to the device's gate reservoir. Despite the ∼1 nm proximity of the quantum dot to the metallic tip, we find that the gate provides sufficient capacitance to enable a high degree of electric control. Combined with atomic-scale imaging, we use the quantum dot to probe applied electric fields and charge in individual defects in the device. This capability is expected to aid in the understanding of atomic-scale devices and the quantum states realized in them.

Non-invasive ventilation versus high-flow nasal cannula oxygen therapy with apnoeic oxygenation for preoxygenation before intubation of patients with acute hypoxaemic respiratory failure: a randomised, multicentre, open-label trial.

BACKGROUND: Non-invasive ventilation has never been compared with high-flow oxygen to determine whether it reduces the risk of severe hypoxaemia during intubation. We aimed to determine if preoxygenation with non-invasive ventilation was more efficient than high-flow oxygen in reducing the risk of severe hypoxaemia during intubation. METHODS: The FLORALI-2 multicentre, open-label trial was done in 28 intensive care units in France. Adult patients undergoing tracheal intubation for acute hypoxaemic respiratory failure (a partial pressure of arterial oxygen [PaO2] to fraction of inspired oxygen [FiO2] ratio of ≤300 mm Hg) were randomly assigned (1:1; block size, four participants) to non-invasive ventilation or high-flow oxygen during preoxygenation, with stratification by PaO2/FiO2 ratio (≤200 mm Hg vs >200 mm Hg). Key exclusion criteria were intubation for cardiac arrest, altered consciousness (defined as a Glasgow coma score of less than eight points), other contraindications to non-invasive ventilation (recent laryngeal, oesophageal, or gastric surgery, and substantial facial fractures), pulse oximetry not available, pregnant or breastfeeding women, and refusal to participate. The primary outcome was the occurrence of severe hypoxaemia (pulse oximetry <80%) during the procedure, assessed in the intention-to-treat population. This trial is registered with ClinicalTrials.gov, number NCT02668458. FINDINGS: Between April 15, 2016, and Jan 8, 2017, 2079 patients were intubated in the 28 participating units, and 322 were enrolled. We excluded five patients with no recorded data, two who withdrew consent or were under legal protection, one who was not intubated, and one who had a cardiac arrest. Of the 313 patients included in the intention-to-treat analysis, 142 were assigned to non-invasive ventilation and 171 to high-flow oxygen therapy. Severe hypoxaemia occurred in 33 (23%) of 142 patients after preoxygenation with non-invasive ventilation and 47 (27%) of 171 with high-flow oxygen (absolute difference -4·2%, 95% CI -13·7 to 5·5; p=0·39). In the 242 patients with moderate-to-severe hypoxaemia (PaO2/FiO2 ≤200 mm Hg), severe hypoxaemia occurred less frequently after preoxygenation with non-invasive ventilation than with high-flow oxygen (28 [24%] of 117 patients vs 44 [35%] of 125; adjusted odds ratio 0·56, 0·32 to 0·99, p=0·0459). Serious adverse events did not differ between treatment groups, with the most common immediate complications being systolic arterial hypotension (70 [49%] patients in the non-invasive ventilation group vs 86 [50%] patients in the high-flow oxygen group) and chest infiltrate on x-ray (28 [20%] vs 33 [19%]), and the most common late complications being death at day 28 (53 [37%] vs 58 [34%]) and ventilator-associated pneumonia during ICU stay (31 [22%] vs 35 [20%]). INTERPRETATION: In patients with acute hypoxaemic respiratory failure, preoxygenation with non-invasive ventilation or high-flow oxygen therapy did not change the risk of severe hypoxaemia. Future research should explore the effect of preoxygenation method in patients with moderate-to-severe hypoxaemia at baseline. FUNDING: French Ministry of Health.

Relationship between digestive tract colonization and subsequent ventilator-associated pneumonia related to ESBL-producing Enterobacteriaceae.

BACKGROUND: Ventilator-associated pneumonia (VAP) is the most common ICU-acquired infection. Recently, the incidence of extended-spectrum beta-lactamase producing Enterobacteriaceae (ESBLE) has substantially increased in critically ill patients. Identifying patients at risk for VAP related to ESBLE could be helpful to improve the rate of appropriate initial antibiotic treatment, and to reduce unnecessary exposure to carbapenems. The primary objective was to identify risk factors for VAP related to ESBLE. Secondary objective was to determine the impact of ESBLE on outcome in VAP patients. METHODS: This retrospective study was conducted in a single mixed intensive care unit (ICU), during a 4-year period. All patients with confirmed VAP were included. VAP was defined using clinical, radiologic and quantitative microbiological data. VAP first episodes were prospectively identified using the continuous surveillance data. Exposure to different risk factors was taken into account until the diagnosis of ESBLE VAP or until ICU discharge, in patients with ESBLE VAP and VAP related to other bacteria, respectively. In all patients, routine screening for ESBLE (rectal swab) was performed at ICU admission and once a week. Patients with ESBLE VAP were compared with those with VAP related to other bacteria using univariate analysis. All significant factors were included in the multivariate logistic regression model. RESULTS: Among the 410 patients with VAP, 43 (10.5%) had ESBLE VAP, 76 (19%) patients had polymicrobial VAP and 189 (46%) had VAP related to multidrug resistant bacteria. Multivariate analysis identified prior ESBLE colonization of the digestive tract as the only independent risk factor for ESBLE VAP (OR [95% CI] = 23 [10-55], p < 0.001). Whilst the positive predictive value of ESBLE digestive colonization was low (43.6%), its negative predictive value was excellent (97.3%) in predicting ESBLE VAP. Duration of mechanical ventilation (median [IQR], 28 [18,42] vs 23 [15,42] d, p = 0.4), length of ICU stay (31 [19,53] vs 29 [18,46] d, p = 0.6), and mortality rates (55.8% vs 50%, p = 0.48) were similar in ESBLE VAP, compared with VAP related to other bacteria. CONCLUSION: Digestive tract colonization related to ESBLE is independently associated with ESBLE VAP. Its excellent negative predictive value suggests that patients without ESBLE colonization should not receive carbapenems as part of their initial empirical treatment to cover ESBLE.

Respiratory changes of the inferior vena cava diameter predict fluid responsiveness in spontaneously breathing patients with cardiac arrhythmias.

BACKGROUND: Whether the respiratory changes of the inferior vena cava diameter during a deep standardized inspiration can reliably predict fluid responsiveness in spontaneously breathing patients with cardiac arrhythmia is unknown. METHODS: This prospective two-center study included nonventilated arrhythmic patients with infection-induced acute circulatory failure. Hemodynamic status was assessed at baseline and after a volume expansion of 500 mL 4% gelatin. The inferior vena cava diameters were measured with transthoracic echocardiography using the bi-dimensional mode on a subcostal long-axis view. Standardized respiratory cycles consisted of a deep inspiration with concomitant control of buccal pressures and passive exhalation. The collapsibility index of the inferior vena cava was calculated as [(expiratory-inspiratory)/expiratory] diameters. RESULTS: Among the 55 patients included in the study, 29 (53%) were responders to volume expansion. The areas under the ROC curve for the collapsibility index and inspiratory diameter of the inferior vena cava were both of 0.93 [95% CI 0.86; 1]. A collapsibility index ≥ 39% predicted fluid responsiveness with a sensitivity of 93% and a specificity of 88%. An inspiratory diameter < 11 mm predicted fluid responsiveness with a sensitivity of 83% and a specificity of 88%. A correlation between the inspiratory effort and the inferior vena cava collapsibility was found in responders but was absent in nonresponder patients. CONCLUSIONS: In spontaneously breathing patients with cardiac arrhythmias, the collapsibility index and inspiratory diameter of the inferior vena cava assessed during a deep inspiration may be noninvasive bedside tools to predict fluid responsiveness in acute circulatory failure related to infection. These results, obtained in a small and selected population, need to be confirmed in a larger-scale study before considering any clinical application.

The next generation of rapid point-of-care testing identification tools for ventilator-associated pneumonia.

Ventilator-associated pneumonia (VAP) is a frequent issue in intensive care units (ICU), with a major impact on morbidity, mortality and cost of care. VAP diagnosis remains challenging: traditional culture-based microbiological techniques are still the gold-standard, but are too slow to enable clinicians to improve prognosis with timely antimicrobial therapy adjustment. Prolonged exposure to inappropriate antibiotics has also been shown to increase the incidence of multi-drug-resistant organisms (MDROs). Point-of-care testing (POCT) tools are diagnostic testing methods that can be used at or near the bedside, with delays ranging from a couple minutes to a few hours. The use of POCTs for VAP could allow for faster diagnosis and antimicrobial therapy adjustments. Despite uncertainty regarding their diagnostic value, C-reactive protein (CRP) and procalcitonin (PCT) can be detected using POCTs in few minutes. In VAP, CRP showed a sensitivity of 56% to 88% and specificity of 86% to 91%; PCT showed a sensitivity of 78% to 100% and a specificity between 75% and 97% using non-POCT methods. Automated microscopy could also be used in clinical ICU setting, with reported sensitivity of 100% and specificity of 97%, allowing for antibiotic susceptibility testing (AST) in less than 12 h. Multiplex polymerase chain reaction (MPCR) could allow for identification and AST approximation through the detection of drug-resistance genes in about 6 h, with reported sensitivity of 89.2% and specificity of 97.1%; although use as POCT was shown to result in test failure in about 40% of samples. Despite being at an early development stage, exhalome analysis, which allows for non-invasive fast identification, and chromogenic tests, more suited for the detection of drug-resistance enzymes, are also promising techniques for POCT diagnosis of VAP.

Towards visualisation of central-cell-effects in scanning tunnelling microscope images of subsurface dopant qubits in silicon.

Atomic-scale understanding of phosphorus donor wave functions underpins the design and optimisation of silicon based quantum devices. The accuracy of large-scale theoretical methods to compute donor wave functions is dependent on descriptions of central-cell corrections, which are empirically fitted to match experimental binding energies, or other quantities associated with the global properties of the wave function. Direct approaches to understanding such effects in donor wave functions are of great interest. Here, we apply a comprehensive atomistic theoretical framework to compute scanning tunnelling microscopy (STM) images of subsurface donor wave functions with two central-cell correction formalisms previously employed in the literature. The comparison between central-cell models based on real-space image features and the Fourier transform profiles indicates that the central-cell effects are visible in the simulated STM images up to ten monolayers below the silicon surface. Our study motivates a future experimental investigation of the central-cell effects via the STM imaging technique with potential of fine tuning theoretical models, which could play a vital role in the design of donor-based quantum systems in scalable quantum computer architectures.

Diagnostic Accuracy of the Inferior Vena Cava Collapsibility to Predict Fluid Responsiveness in Spontaneously Breathing Patients With Sepsis and Acute Circulatory Failure.

OBJECTIVE: To investigate whether the collapsibility index of the inferior vena cava recorded during a deep standardized inspiration predicts fluid responsiveness in nonintubated patients. DESIGN: Prospective, nonrandomized study. SETTING: ICUs at a general and a university hospital. PATIENTS: Nonintubated patients without mechanical ventilation (n = 90) presenting with sepsis-induced acute circulatory failure and considered for volume expansion. INTERVENTIONS: We assessed hemodynamic status at baseline and after a volume expansion induced by a 30-minute infusion of 500-mL gelatin 4%. MEASUREMENTS AND MAIN RESULTS: We measured stroke volume index and collapsibility index of the inferior vena cava under a deep standardized inspiration using transthoracic echocardiography. Vena cava pertinent diameters were measured 15-20 mm caudal to the hepatic vein junction and recorded by bidimensional imaging on a subcostal long-axis view. Standardized respiratory cycles consisted of a deep standardized inspiration followed by passive exhalation. The collapsibility index expressed in percentage equaled the ratio of the difference between end-expiratory and minimum-inspiratory diameter over the end-expiratory diameter. After volume expansion, a relevant (≥ 10%) stroke volume index increase was recorded in 56% patients. In receiver operating characteristic analysis, the area under curve for that collapsibility index was 0.89 (95% CI, 0.82-0.97). When such index is superior or equal to 48%, fluid responsiveness is predicted with a sensitivity of 84% and a specificity of 90%. CONCLUSIONS: The collapsibility index of the inferior vena cava during a deep standardized inspiration is a simple, noninvasive bedside predictor of fluid responsiveness in nonintubated patients with sepsis-related acute circulatory failure.

Efficiency of an electronic device in controlling tracheal cuff pressure in critically ill patients: a randomized controlled crossover study.

BACKGROUND: Despite intermittent control of tracheal cuff pressure (P cuff) using a manual manometer, cuff underinflation (<20 cmH2O) and overinflation (>30 cmH2O) frequently occur in intubated critically ill patients, resulting in increased risk of microaspiration and tracheal ischemic lesions. The primary objective of our study was to determine the efficiency of an electronic device in continuously controlling P cuff. The secondary objective was to determine the impact of this device on the occurrence of microaspiration of gastric or oropharyngeal secretions. METHODS: Eighteen patients requiring mechanical ventilation were included in this prospective randomized controlled crossover study. They randomly received either continuous control of P cuff with Mallinckrodt® device for 24 h, followed by discontinuous control with a manual manometer for 24 h, or the reverse sequence. During the 48 h after randomization, P cuff was continuously recorded, and pepsin and alpha amylase were quantitatively measured in tracheal aspirates. P cuff target was 25 cmH2O. RESULTS: Clinical characteristics were similar during the two study periods, as well as mean airway pressure. Percentage of time spent with cuff overinflation or underinflation was significantly lower during continuous control compared with routine care period [median (IQR) 0.8 (0.1, 2) vs 20.9 (3.1, 40.1), p = 0.0009]. No significant difference was found in pepsin [median (IQR) 230 (151, 300) vs 259 (134, 368), p = 0.95] or in alpha amylase level [median (IQR) 1475 (528, 10,333) vs 2400 (1342, 15,391), p = 0.19] between continuous control and routine care periods, respectively. CONCLUSIONS: The electronic device is efficient in controlling P cuff, compared with routine care using a manometer. Further studies are needed to evaluate the impact of this device on intubation-related complications. Trial registration ClinicalTrials.gov Identifier: NCT01965821.

The use of static and dynamic haemodynamic parameters before volume expansion: A prospective observational study in six French intensive care units.

OBJECTIVE: The aim of the present study was to determine the use of static and dynamic haemodynamic parameters for predicting fluid responsiveness prior to volume expansion (VE) in intensive care unit (ICU) patients with systemic inflammatory response syndrome (SIRS). METHODS: We conducted a prospective, multicentre, observational study in 6 French ICUs in 2012. ICU physicians were audited concerning their use of static and dynamic haemodynamic parameters before each VE performed in patients with SIRS for 6 consecutive weeks. RESULTS: The median volume of the 566 VEs administered to patients with SIRS was 1000mL [500-1000mL]. Although at least one static or dynamic haemodynamic parameter was measurable before 99% (95% CI, 99%-100%) of VEs, at least one them was used in only 38% (95% CI, 34%-42%) of cases: static parameters in 11% of cases (95% CI, 10%-12%) and dynamic parameters in 32% (95% CI, 30%-34%). Static parameters were never used when uninterpretable. For 15% of VEs (95% CI, 12%-18%), a dynamic parameter was measured in the presence of contraindications. Among dynamic parameters, respiratory variations in arterial pulse pressure (PPV) and passive leg raising (PLR) were measurable and interpretable before 17% and 90% of VEs, respectively. CONCLUSIONS: Haemodynamic parameters are underused for predicting fluid responsiveness in current practice. In contrast to static parameters, dynamic parameters are often incorrectly used in the presence of contraindications. PLR is more frequently valid than PPV for predicting fluid responsiveness in ICU patients.

Donor hyperfine Stark shift and the role of central-cell corrections in tight-binding theory.

Atomistic tight-binding (TB) simulations are performed to calculate the Stark shift of the hyperfine coupling for a single arsenic (As) donor in silicon (Si). The role of the central-cell correction is studied by implementing both the static and the non-static dielectric screenings of the donor potential, and by including the effect of the lattice strain close to the donor site. The dielectric screening of the donor potential tunes the value of the quadratic Stark shift parameter (η2) from -1.3 × 10(-3) µm(2) V(-2) for the static dielectric screening to -1.72 × 10(-3) µm(2) V(-2) for the non-static dielectric screening. The effect of lattice strain, implemented by a 3.2% change in the As-Si nearest-neighbour bond length, further shifts the value of η2 to -1.87 × 10(-3) µm(2) V(-2), resulting in an excellent agreement of theory with the experimentally measured value of -1.9 ± 0.2 × 10(-3) µm(2) V(-2). Based on our direct comparison of the calculations with the experiment, we conclude that the previously ignored non-static dielectric screening of the donor potential and the lattice strain significantly influence the donor wave function charge density and thereby leads to a better agreement with the available experimental data sets.

Few-electron edge-state quantum dots in a silicon nanowire field-effect transistor.

We investigate the gate-induced onset of few-electron regime through the undoped channel of a silicon nanowire field-effect transistor. By combining low-temperature transport measurements and self-consistent calculations, we reveal the formation of one-dimensional conduction modes localized at the two upper edges of the channel. Charge traps in the gate dielectric cause electron localization along these edge modes, creating elongated quantum dots with characteristic lengths of ∼10 nm. We observe single-electron tunneling across two such dots in parallel, specifically one in each channel edge. We identify the filling of these quantum dots with the first few electrons, measuring addition energies of a few tens of millielectron volts and level spacings of the order of 1 meV, which we ascribe to the valley orbit splitting. The total removal of valley degeneracy leaves only a 2-fold spin degeneracy, making edge quantum dots potentially promising candidates for silicon spin qubits.

Thermo-active elastomer composite for optical heating in microfluidic systems.

Single-walled carbon nanotubes are used as doping agents to form thermo-active composites with an elastomeric block-copolymer. Thermal imaging reveals that the temperature response upon irradiation with NIR laser light is dependent (among other things) on the mass fraction of the nanotubes in the polymer matrix.

Air stream-mediated vortex agitation of microlitre entities on a fluidic chip.

The method presented in this paper uses air flux to induce spiral motion in small-scale (e.g., microlitre) fluid entities in an efficient, technologically convenient manner. The set-up entails a manifold that modulates the air flux and projects it onto a liquid-containing reservoir. The flow behaviour of the liquid phase has been visualized through the dissolution of rhodamine B crystallites and the motion of fluorescent microbeads. In addition, the method proved effective to restoring a suspension of spherical particles upon sedimentation, promoting displacement and capture of the beads within a microfluidic system.

The conservative management of severe caustic gastric injuries.

OBJECTIVE: To determine the safety of a conservative approach to treating severe caustic injury in patients lacking clinical and biochemical signs of transmural necrosis. BACKGROUND: Esophagogastrectomy is thought to limit the progression of severe caustic injury in the upper gastrointestinal tract observed upon initial endoscopic examination. However, endoscopic evaluation of the depth and spread of necrosis is challenging and may lead to unnecessary gastrectomy. METHODS: From January 2002 to December 2008, 70 patients were classified as having stage III gastric injury in an initial digestive tract endoscopic examination. When patients had no signs of peritonitis, their treatment was determined by 6 clinical and biochemical factors of severity (abdominal rebound tenderness, neuropsychiatric troubles, cardiovascular shock, metabolic acidosis, disseminated intravascular coagulation, and kidney failure) in addition to endoscopic staging. If one of these clinical and biochemical factors was present, the patient underwent emergency laparotomy. Patients with isolated stage III gastric injury were kept under close observation. RESULTS: Twenty-four of the 70 endoscopic stage III patients required emergency surgery. Conservative treatment was initiated in the remaining 46. There were 4 postoperative deaths (5.7%). Fifteen patients required subsequent surgery: distal gastrectomy with Billroth I anastomosis (n = 7) for distal stricture and esophagoplasty for nondilatable esophageal stricture (n = 8). At the end of the follow-up period, total or partial gastric conservation was achieved in all 46 patients (65.7%) and the esophagus was conserved in 38 patients (54.3%). CONCLUSION: In the absence of clinical and biological signs of severity, conservative management of stage III gastric injury is clinically feasible, precludes gastrectomy and has a low mortality rate.