Two types of magnetic shape-memory effects from twinned microstructure and magneto-structural coupling in Fe1+y Te.

A detailed experimental investigation of Fe1+y Te (y = 0.11, 0.12) using pulsed magnetic fields up to 60 T confirms remarkable magnetic shape-memory (MSM) effects. These effects result from magnetoelastic transformation processes in the low-temperature antiferromagnetic state of these materials. The observation of modulated and finely twinned microstructure at the nanoscale through scanning tunneling microscopy establishes a behavior similar to that of thermoelastic martensite. We identified the observed, elegant hierarchical twinning pattern of monoclinic crystallographic domains as an ideal realization of crossing twin bands. The antiferromagnetism of the monoclinic ground state allows for a magnetic-field-induced reorientation of these twin variants by the motion of one type of twin boundaries. At sufficiently high magnetic fields, we observed a second isothermal transformation process with large hysteresis for different directions of applied field. This gives rise to a second MSM effect caused by a phase transition back to the field-polarized tetragonal lattice state.

Investigation of putative genes for the production of medium-chained acids and alcohols in autotrophic acetogenic bacteria.

Gas fermentation is a technology for producing platform chemicals as well as fuels and one of the most promising alternatives to petrochemicals. Medium-chained acids and alcohols such as hexanoate and hexanol are particularly interesting due to their versatile application. This study elucidated the pathway of chain elongation in native C6 compound-producing acetogens. Essential genes of Clostridium carboxidivorans for synthesis of medium-chained acids and alcohols were identified in order to demonstrate their catalytic activity in the acetogenic model organism Acetobacterium woodii. Two such gene clusters were identified, which are responsible for conversion of acetyl-CoA to butyryl-CoA by reverse ß-oxidation. Using RT-PCR it could be demonstrated that only genes of cluster 1 are expressed constitutively with simultaneous formation of C6 compounds. Based on genes from C. carboxidivorans, a modular hexanoyl-CoA synthesis (hcs) plasmid system was constructed and transferred into A. woodii. With the recombinant A. woodii strains AWO [pPta_hcs1], AWO [pPta_hcs2], AWO [pTet_hcs1], and AWO [pTet_hcs2] butyrate and hexanoate production under heterotrophic (1.22-4.15 mM hexanoate) and autotrophic conditions (0.48-1.56 mM hexanoate) with both hcs clusters could be detected. hcs Cluster 1 from C. carboxidivorans was transferred into the ABE-fermenting strain Clostridium saccharoperbutylacetonicum as well. For further analysis, genes were also cloned into the hcs plasmid system individually. The resulting recombinant C. saccharoperbutylacetonicum strains with just individual genes neither produced hexanoate nor hexanol, but the strains containing the entire gene cluster were capable of chain elongation. A production of 0.8 mM hexanoate and 5.2 mM hexanol in the fermentation with glucose could be observed.

Control of the expiratory flow in a lung model and in healthy volunteers with an adjustable flow regulator: a combined bench and randomized crossover study.

BACKGROUND: Pursed-lips breathing (PLB) is a technique to attenuate small airway collapse by regulating the expiratory flow. During mandatory ventilation, flow-controlled expiration (FLEX), which mimics the expiratory flow course of PLB utilizing a digital system for measurement and control, was shown to exert lung protective effects. However, PLB requires a patient's participation and coordinated muscular effort and FLEX requires a complex technical setup. Here, we present an adjustable flow regulator to mimic PLB and FLEX, respectively, without the need of a patient's participation, or a complex technical device. METHODS: Our study consisted of two parts: First, in a lung model which was ventilated with standard settings (tidal volume 500 ml, respiratory rate 12 min-1, positive end-expiratory pressure (PEEP) 5 cmH2O), the possible reduction of the maximal expiratory flow by utilizing the flow regulator was assessed. Second, with spontaneously breathing healthy volunteers, the short-term effects of medium and strong expiratory flow reduction on airway pressure, the change of end-expiratory lung volume (EELV), and breathing discomfort was investigated. RESULTS: In the lung model experiments, expiratory flow could be reduced from - 899 ± 9 ml·s-1 down to - 328 ± 25 ml·s-1. Thereby, inspiratory variables and PEEP were unaffected. In the volunteers, the maximal expiratory flow of - 574 ± 131 ml·s-1 under baseline conditions was reduced to - 395 ± 71 ml·s-1 for medium flow regulation and to - 266 ± 58 ml·s-1 for strong flow regulation, respectively (p < 0.001). Accordingly, mean airway pressure increased from 0.6 ± 0.1 cmH2O to 2.9 ± 0.4 cmH2O with medium flow regulation and to 5.4 ± 2.4 cmH2O with strong flow regulation, respectively (p < 0.001). The EELV increased from baseline by 31 ± 458 ml for medium flow regulation and 320 ± 681 ml for strong flow regulation (p = 0.033). The participants rated breathing with the flow regulator as moderately uncomfortable, but none rated breathing with the flow regulator as intolerable. CONCLUSIONS: The flow regulator represents an adjustable device for application of a self-regulated expiratory resistive load, representing an alternative for PLB and FLEX. Future applications in spontaneously breathing patients and patients with mandatory ventilation alike may reveal potential benefits. TRIAL REGISTRATION: DRKS00015296, registered on 20th August, 2018; URL: https://www.drks.de/drks_web/setLocale_EN.do .

Context-sensitive decrement times for inhaled anesthetics in obese patients explored with Gas Man®.

Anesthesia care providers and anesthesia decision support tools use mathematical pharmacokinetic models to control delivery and especially removal of anesthetics from the patient's body. However, these models are not able to reflect alterations in pharmacokinetics of volatile anesthetics caused by obesity. The primary aim of this study was to refine those models for obese patients. To investigate the effects of obesity on the elimination of desflurane, isoflurane and sevoflurane for various anesthesia durations, the Gas Man® computer simulation software was used. Four different models simulating patients with weights of 70 kg, 100 kg, 125 kg and 150 kg were constructed by increasing fat weight to the standard 70 kg model. For each modelled patient condition, the vaporizer was set to reach quickly and then maintain an alveolar concentration of 1.0 minimum alveolar concentration (MAC). Subsequently, the circuit was switched to an open (non-rebreathing) circuit model, the inspiratory anesthetic concentration was set to 0 and the time to the anesthetic decrements by 67% (awakening times), 90% (recovery times) and 95% (resolution times) in the vessel-rich tissue compartment including highly perfused tissue of the central nervous system were determined. Awakening times did not differ greatly between the simulation models. After volatile anesthesia with sevoflurane and isoflurane, awakening times were lower in the more obese simulation models. With increasing obesity, recovery and resolution times were higher. The additional adipose tissue in obese simulation models did not prolong awakening times and thus may act more like a sink for volatile anesthetics. The results of these simulations should be validated by comparing the elimination of volatile anesthetics in obese patients with data from our simulation models.

Flow-Controlled Ventilation Attenuates Lung Injury in a Porcine Model of Acute Respiratory Distress Syndrome: A Preclinical Randomized Controlled Study.

OBJECTIVES: Lung-protective ventilation for acute respiratory distress syndrome aims for providing sufficient oxygenation and carbon dioxide clearance, while limiting the harmful effects of mechanical ventilation. "Flow-controlled ventilation", providing a constant expiratory flow, has been suggested as a new lung-protective ventilation strategy. The aim of this study was to test whether flow-controlled ventilation attenuates lung injury in an animal model of acute respiratory distress syndrome. DESIGN: Preclinical, randomized controlled animal study. SETTING: Animal research facility. SUBJECTS: Nineteen German landrace hybrid pigs. INTERVENTION: Flow-controlled ventilation (intervention group) or volume-controlled ventilation (control group) with identical tidal volume (7 mL/kg) and positive end-expiratory pressure (9 cm H2O) after inducing acute respiratory distress syndrome with oleic acid. MEASUREMENTS AND MAIN RESULTS: PaO2 and PaCO2, minute volume, tracheal pressure, lung aeration measured via CT, alveolar wall thickness, cell infiltration, and surfactant protein A concentration in bronchoalveolar lavage fluid. Five pigs were excluded leaving n equals to 7 for each group. Compared with control, flow-controlled ventilation elevated PaO2 (154 ± 21 vs 105 ± 9 torr; 20.5 ± 2.8 vs 14.0 ± 1.2 kPa; p = 0.035) and achieved comparable PaCO2 (57 ± 3 vs 54 ± 1 torr; 7.6 ± 0.4 vs 7.1 ± 0.1 kPa; p = 0.37) with a lower minute volume (6.4 ± 0.5 vs 8.7 ± 0.4 L/min; p < 0.001). Inspiratory plateau pressure was comparable in both groups (31 ± 2 vs 34 ± 2 cm H2O; p = 0.16). Flow-controlled ventilation increased normally aerated (24% ± 4% vs 10% ± 2%; p = 0.004) and decreased nonaerated lung volume (23% ± 6% vs 38% ± 5%; p = 0.033) in the dependent lung region. Alveolar walls were thinner (5.5 ± 0.1 vs 7.8 ± 0.2 µm; p < 0.0001), cell infiltration was lower (20 ± 2 vs 32 ± 2 n/field; p < 0.0001), and normalized surfactant protein A concentration was higher with flow-controlled ventilation (1.1 ± 0.04 vs 1.0 ± 0.03; p = 0.039). CONCLUSIONS: Flow-controlled ventilation enhances lung aeration in the dependent lung region and consequently improves gas exchange and attenuates lung injury. Control of the expiratory flow may provide a novel option for lung-protective ventilation.

Flow-controlled ventilation improves gas exchange in lung-healthy patients- a randomized interventional cross-over study.

BACKGROUND: Flow-controlled ventilation (FCV) is a new ventilation mode that provides constant inspiratory and expiratory flow. FCV was shown to improve gas exchange and lung recruitment in porcine models of healthy and injured ventilated lungs. The primary aim of our study was to verify the influences of FCV on gas exchange, respiratory mechanics and haemodynamic variables in mechanically ventilated lung-healthy patients. METHODS: After obtaining ethical approval and informed consent, we measured arterial blood gases, respiratory and haemodynamic variables during volume-controlled ventilation (VCV) and FCV in 20 consecutive patients before they underwent abdominal surgery. After baseline (BL) ventilation, patients were randomly assigned to either BL-VCV-FCV or BL-FCV-VCV. Thereby, BL ventilation settings were kept, except for the ventilation mode-related differences (FCV is supposed to be used with an I:E ratio of 1:1). RESULTS: Compared to BL and VCV, PaO2 was higher [PaO2 : FCV: 38.2 (7.1), BL ventilation: 35.0 (5.8), VCV: 35.2 (7.0) kPa, P < .001] and PaCO2 lower [PaCO2 : FCV: 4.8 (0.5), BL ventilation: 5.1 (0.5), VCV: 5.1 (0.5) kPa, P < .001] during FCV. With comparable plateau pressure [BL: 14.9 (1.9), VCV: 15.3 (1.6), FCV: 15.2 (1.5) cm H2 O), P = .185], tracheal mean pressure was higher during FCV [BL: 10.2 (1.1), VCV: 10.4 (0.7), FCV: 11.5 (1.0) cm H2 O, P < .001]. Haemodynamic variables did not differ between ventilation phases. CONCLUSION: Flow-controlled ventilation improves oxygenation and carbon dioxide elimination within a short time, compared to VCV with identical tidal volume, inspiratory plateau pressure and end-expiratory pressure.

Flow-controlled ventilation (FCV) improves regional ventilation in obese patients - a randomized controlled crossover trial.

BACKGROUND: In obese patients, high closing capacity and low functional residual capacity increase the risk for expiratory alveolar collapse. Constant expiratory flow, as provided by the new flow-controlled ventilation (FCV) mode, was shown to improve lung recruitment. We hypothesized that lung aeration and respiratory mechanics improve in obese patients during FCV. METHODS: We compared FCV and volume-controlled (VCV) ventilation in 23 obese patients in a randomized crossover setting. Starting with baseline measurements, ventilation settings were kept identical except for the ventilation mode related differences (VCV: inspiration to expiration ratio 1:2 with passive expiration, FCV: inspiration to expiration ratio 1:1 with active, linearized expiration). Primary endpoint of the study was the change of end-expiratory lung volume compared to baseline ventilation. Secondary endpoints were the change of mean lung volume, respiratory mechanics and hemodynamic variables. RESULTS: The loss of end-expiratory lung volume and mean lung volume compared to baseline was lower during FCV compared to VCV (end-expiratory lung volume: FCV, - 126 ± 207 ml; VCV, - 316 ± 254 ml; p < 0.001, mean lung volume: FCV, - 108.2 ± 198.6 ml; VCV, - 315.8 ± 252.1 ml; p < 0.001) and at comparable plateau pressure (baseline, 19.6 ± 3.7; VCV, 20.2 ± 3.4; FCV, 20.2 ± 3.8 cmH2O; p = 0.441), mean tracheal pressure was higher (baseline, 13.1 ± 1.1; VCV, 12.9 ± 1.2; FCV, 14.8 ± 2.2 cmH2O; p < 0.001). All other respiratory and hemodynamic variables were comparable between the ventilation modes. CONCLUSIONS: This study demonstrates that, compared to VCV, FCV improves regional ventilation distribution of the lung at comparable PEEP, tidal volume, PPlat and ventilation frequency. The increase in end-expiratory lung volume during FCV was probably caused by the increased mean tracheal pressure which can be attributed to the linearized expiratory pressure decline. TRIAL REGISTRATION: German Clinical Trials Register: DRKS00014925. Registered 12 July 2018.

Effect of individualized PEEP titration guided by intratidal compliance profile analysis on regional ventilation assessed by electrical impedance tomography - a randomized controlled trial.

BACKGROUND: The application of positive end-expiratory pressure (PEEP) may reduce dynamic strain during mechanical ventilation. Although numerous approaches for PEEP titration have been proposed, there is no accepted strategy for titrating optimal PEEP. By analyzing intratidal compliance profiles, PEEP may be individually titrated for patients. METHODS: After obtaining informed consent, 60 consecutive patients undergoing general anesthesia were randomly allocated to mechanical ventilation with PEEP 5 cmH2O (control group) or PEEP individually titrated, guided by an analysis of the intratidal compliance profile (intervention group). The primary endpoint was the frequency of each nonlinear intratidal compliance (CRS) profile of the respiratory system (horizontal, increasing, decreasing, and mixed). The secondary endpoints measured were respiratory mechanics, hemodynamic variables, and regional ventilation, which was assessed via electrical impedance tomography. RESULTS: The frequencies of the CRS profiles were comparable between the groups. Besides PEEP [control: 5.0 (0.0), intervention: 5.8 (1.1) cmH2O, p < 0.001], the respiratory and hemodynamic variables were comparable between the two groups. The compliance profile analysis showed no significant differences between the two groups. The loss of ventral and dorsal regional ventilation was higher in the control [ventral: 41.0 (16.3)%; dorsal: 25.9 (13.8)%] than in the intervention group [ventral: 29.3 (17.6)%; dorsal: 16.4 (12.7)%; p (ventral) = 0.039, p (dorsal) = 0.028]. CONCLUSIONS: Unfavorable compliance profiles indicating tidal derecruitment were found less often than in earlier studies. Individualized PEEP titration resulted in slightly higher PEEP. A slight global increase in aeration associated with this was indicated by regional gain and loss analysis. Differences in dorsal to ventral ventilation distribution were not found. TRIAL REGISTRATION: This clinical trial was registered at the German Register for Clinical Trials (DRKS00008924) on August 10, 2015.

Dependency of respiratory system mechanics on positive end-expiratory pressure and recruitment maneuvers in lung healthy pediatric patients-A randomized crossover study.

BACKGROUND: The lungs of pediatric patients are subjected to tidal derecruitment during mechanical ventilation and in contrast to adult patients this unfavorable condition cannot be resolved with small c increases. This raises the question if higher end-expiratory pressure increases or recruitment maneuvers may resolve tidal derecruitment in pediatric patients. AIMS: We hypothesized that higher PEEP resolves tidal derecruitment in pediatric patients and that recruitment maneuvers between the pressure changes support the improvement of respiratory system mechanics. METHODS: The effects of end-expiratory pressure changes from 3 to 7 cmH2 O and vice versa without and with intermediate recruitment maneuvers on respiratory system mechanics and regional ventilation were investigated in 57 mechanically ventilated pediatric patients. The intratidal respiratory system compliance was determined from volume and pressure data before and after PEEP changes and categorized to indicate tidal derecruitment. RESULTS: Tidal derecruitment occurred comparably frequently at PEEP 3 cmH2 O without (13 out of 14 cases) and with recruitment maneuver (14 out of 14 cases) and at PEEP 7 cmH2 O without (13 out of 14 cases) and with recruitment maneuver (13 out of 15 cases). CONCLUSIONS: We conclude that contrary to our hypothesis, PEEP up to 7 cmH2 O is not sufficient to resolve tidal derecruitment and that recruitment maneuvers may be dispensable in mechanically ventilated pediatric patients.

Flow-controlled ventilation during ear, nose and throat surgery: A prospective observational study.

BACKGROUND: Flow-controlled ventilation (FCV) is a new mechanical ventilation mode that maintains constant flow during inspiration and expiration with standard tidal volumes via cuffed narrow-bore endotracheal tubes. Originating in manually operated 'expiratory ventilation assistance', FCV extends this technique by automatic control of airway flow, monitoring of intratracheal pressure and control of peak inspiratory pressure and end-expiratory pressure. FCV has not yet been described in a clinical study. OBJECTIVE: The aim of this study was to provide an initial assessment of FCV in mechanically ventilated patients undergoing ear, nose and throat surgery and evaluate its potential for future use. DESIGN: An observational study. SETTING: Two German academic medical centres from 24 November 2017 to 09 January 2018. PATIENTS: Consecutive patients (≥ 18 years) scheduled for elective ear, nose and throat surgery. Exclusion criteria were planned laser surgery, intended fibreoptic awake intubation, emergency procedures, increased risk of aspiration, American Society of Anesthesiologists (ASA) physical status more than III and chronic obstructive pulmonary disease classified as GOLD stage more than II. INTERVENTION: Peri-operative use of FCV provided by a new type of ventilator (Evone) via a narrow-bore endotracheal tube (Tritube). MAIN OUTCOME MEASURES: Minute volume, respiratory rate, intratidal tracheal pressure amplitude (Δp) and end-tidal CO2 (PetCO2) were recorded every 5 min. All adverse events were noted. Data are presented as median [IQR]. RESULTS: Sixteen patients provided 15 evaluable data sets. A minute volume of 5.0 [4.4 to 6.4] l min and a respiratory rate of 9 [8 to 11] min generated a PetCO2 of 4.9 [4.8 to 5.0] kPa. Δp was 10 [9 to 12] cmH2O. Five adverse events were recorded: a tube obstruction due to airway secretions and four tube dislocations (two attributed to coughing, two not study-related). CONCLUSION: FCV achieves adequate PetCO2 levels with minute volume and Δp in the normal range. Tritube's high flow resistance may increase the likelihood of tube dislocations if the patient coughs. Although further evaluation is necessary, FCV provides a new option for short-term mechanical ventilation. The successful operation of FCV with narrow-bore tubes contributes to the armamentarium for airway management. TRIAL REGISTRATION: DRKS00013312.

Glottic visibility for laryngeal surgery: Tritube vs. microlaryngeal tube: A randomised controlled trial.

BACKGROUND: Good visibility is essential for successful laryngeal surgery. A Tritube with outer diameter 4.4 mm, combined with flow-controlled ventilation (FCV), enables ventilation by active expiration with a sealed trachea and may improve laryngeal visibility. OBJECTIVES: We hypothesised that a Tritube with FCV would provide better laryngeal visibility and surgical conditions for laryngeal surgery than a conventional microlaryngeal tube (MLT) with volume-controlled ventilation (VCV). DESIGN: Randomised, controlled trial. SETTING: University Medical Centre. PATIENTS: A total of 55 consecutive patients (>18 years) undergoing elective laryngeal surgery were assessed for participation, providing 40 evaluable data sets with 20 per group. INTERVENTIONS: Random allocation to intubation with Tritube and ventilation with FCV (Tritube-FCV group) or intubation with MLT 6.0 and ventilation with VCV (MLT-VCV) as control. Tidal volumes of 7 ml kg predicted body weight, and positive end-expiratory pressure of 7 cmH2O were standardised between groups. MAIN OUTCOME MEASURES: Primary endpoint was the tube-related concealment of laryngeal structures, measured on videolaryngoscopic photographs by appropriate software. Secondary endpoints were surgical conditions (categorical four-point rating scale), respiratory variables and change of end-expiratory lung volume from atmospheric airway pressure to ventilation with positive end-expiratory pressure. Data are presented as median [IQR]. RESULTS: There was less concealment of laryngeal structures with the Tritube than with the MLT; 7 [6 to 9] vs. 22 [18 to 27] %, (P < 0.001). Surgical conditions were rated comparably (P = 0.06). A subgroup of residents in training perceived surgical conditions to be better with the Tritube compared with the MLT (P = 0.006). Respiratory system compliance with the Tritube was higher at 61 [52 to 71] vs. 46 [41 to 51] ml cmH2O (P < 0.001), plateau pressure was lower at 14 [13 to 15] vs. 17 [16 to 18] cmH2O (P < 0.001), and change of end-expiratory lung volume was higher at 681 [463 to 849] vs. 414 [194 to 604] ml, (P = 0.023) for Tritube-FCV compared with MLT-VCV. CONCLUSION: During laryngeal surgery a Tritube improves visibility of the surgical site but not surgical conditions when compared with a MLT 6.0. FCV improves lung aeration and respiratory system compliance compared with VCV. TRIAL REGISTRY NUMBER: DRKS00013097.

Peak airway pressure is lower during pressure-controlled than during manual facemask ventilation for induction of anesthesia in pediatric patients-a randomized, clinical crossover trial.

PURPOSE: Facemask ventilation during the induction of general anesthesia in paediatric patients remains a challenge as it may result in hypoxic conditions and gastric insufflation with subsequent regurgitation and aspiration. So far, it is unclear if pressure-controlled or manual facemask ventilation is preferable in children. We hypothesized that pressure-controlled ventilation in apnoeic children results in lower peak airway pressure and flow rates compared to manual ventilation at comparable respiratory rates and tidal volumes. METHODS: Sixty-two lung-healthy children undergoing scheduled ear-nose-throat surgery were included in the study. After the induction of anesthesia, the patient's lungs were consecutively ventilated via a facemask in either manual or pressure-controlled mode, in randomized order. The primary outcome measure was peak airway pressure. Secondary outcome measures included positive end-expiratory pressure, airway compliance, tidal volume and airway flow. RESULTS: Data of 52 patients could be analyzed. Pressure-controlled ventilation resulted in a lower mean and peak inspiratory pressure (both p < 0.001), airway pressure amplitude (p = 0.01) and inspiratory peak flow rate (p = 0.005) compared to manual ventilation. The ratio of inspiration to expiration time was lower in pressure-controlled ventilation compared to manual ventilation (p < 0.001). CONCLUSION: Pressure-controlled facemask ventilation during induction of anesthesia in pediatric patients results in lower airway pressure, and lower flow rates compared to manual ventilation, at comparable tidal and minute volumes.

Dirac Nodal Arc Semimetal PtSn4 : An Ideal Platform for Understanding Surface Properties and Catalysis for Hydrogen Evolution.

Conductivity, carrier mobility, and a suitable Gibbs free energy are important criteria that determine the performance of catalysts for a hydrogen evolution reaction (HER). However, it is a challenge to combine these factors into a single compound. Herein, we discover a superior electrocatalyst for a HER in the recently identified Dirac nodal arc semimetal PtSn4 . The determined turnover frequency (TOF) for each active site of PtSn4 is 1.54 H2 s-1 at 100 mV. This sets a benchmark for HER catalysis on Pt-based noble metals and earth-abundant metal catalysts. We make use of the robust surface states of PtSn4 as their electrons can be transferred to the adsorbed hydrogen atoms in the catalytic process more efficiently. In addition, PtSn4 displays excellent chemical and electrochemical stabilities after long-term exposure in air and long-time HER stability tests.

Evidence for Ferromagnetic Clusters in the Colossal-Magnetoresistance Material EuB_{6}.

We combined scanning tunneling microscopy and locally resolved magnetic stray field measurements on the ferromagnetic semimetal EuB_{6}, which exhibits a complex ferromagnetic order and a colossal magnetoresistance effect. In a zero magnetic field, scanning tunneling spectroscopy visualizes the existence of local inhomogeneities in the electronic density of states, which we interpret as the localization of charge carriers due to the formation of magnetic polarons. Micro-Hall magnetometry measurements of the total stray field emanating from the end of a rectangular-shaped platelike sample reveals evidence for magnetic clusters also in finite magnetic fields. In contrast, the signal detected below the faces of the magnetized sample measures a local stray field indicating the formation of pronounced magnetic inhomogeneities consistent with large clusters of percolated magnetic polarons.

Bacterial Anaerobic Synthesis Gas (Syngas) and CO2+H2 Fermentation.

Anaerobic bacterial gas fermentation gains broad interest in various scientific, social, and industrial fields. This microbial process is carried out by a specific group of bacterial strains called acetogens. All these strains employ the Wood-Ljungdahl pathway but they belong to different taxonomic groups. Here we provide an overview of the metabolism of acetogens and naturally occurring products. Characteristics of 61 strains were summarized and selected acetogens described in detail. Acetobacterium woodii, Clostridium ljungdahlii, and Moorella thermoacetica serve as model organisms. Results of approaches such as genome-scale modeling, proteomics, and transcriptomics are discussed. Metabolic engineering of acetogens can be used to expand the product portfolio to platform chemicals and to study different aspects of cell physiology. Moreover, the fermentation of gases requires specific reactor configurations and the development of the respective technology, which can be used for an industrial application. Even though the overall process will have a positive effect on climate, since waste and greenhouse gases could be converted into commodity chemicals, some legislative barriers exist, which hamper successful exploitation of this technology.

Thermal and electrical transport across a magnetic quantum critical point.

A quantum critical point (QCP) arises when a continuous transition between competing phases occurs at zero temperature. Collective excitations at magnetic QCPs give rise to metallic properties that strongly deviate from the expectations of Landau's Fermi-liquid description, which is the standard theory of electron correlations in metals. Central to this theory is the notion of quasiparticles, electronic excitations that possess the quantum numbers of the non-interacting electrons. Here we report measurements of thermal and electrical transport across the field-induced magnetic QCP in the heavy-fermion compound YbRh(2)Si(2) (refs 2, 3). We show that the ratio of the thermal to electrical conductivities at the zero-temperature limit obeys the Wiedemann-Franz law for magnetic fields above the critical field at which the QCP is attained. This is also expected for magnetic fields below the critical field, where weak antiferromagnetic order and a Fermi-liquid phase form below 0.07 K (at zero field). At the critical field, however, the low-temperature electrical conductivity exceeds the thermal conductivity by about 10 per cent, suggestive of a non-Fermi-liquid ground state. This apparent violation of the Wiedemann-Franz law provides evidence for an unconventional type of QCP at which the fundamental concept of Landau quasiparticles no longer holds. These results imply that Landau quasiparticles break up, and that the origin of this disintegration is inelastic scattering associated with electronic quantum critical fluctuations--these insights could be relevant to understanding other deviations from Fermi-liquid behaviour frequently observed in various classes of correlated materials.

Correlation between ground state and orbital anisotropy in heavy fermion materials.

The interplay of structural, orbital, charge, and spin degrees of freedom is at the heart of many emergent phenomena, including superconductivity. Unraveling the underlying forces of such novel phases is a great challenge because it not only requires understanding each of these degrees of freedom, it also involves accounting for the interplay between them. Cerium-based heavy fermion compounds are an ideal playground for investigating these interdependencies, and we present evidence for a correlation between orbital anisotropy and the ground states in a representative family of materials. We have measured the 4f crystal-electric field ground-state wave functions of the strongly correlated materials CeRh1-xIrxIn5 with great accuracy using linear polarization-dependent soft X-ray absorption spectroscopy. These measurements show that these wave functions correlate with the ground-state properties of the substitution series, which covers long-range antiferromagnetic order, unconventional superconductivity, and coexistence of these two states.

Improved lung recruitment and oxygenation during mandatory ventilation with a new expiratory ventilation assistance device: A controlled interventional trial in healthy pigs.

BACKGROUND: In contrast to conventional mandatory ventilation, a new ventilation mode, expiratory ventilation assistance (EVA), linearises the expiratory tracheal pressure decline. OBJECTIVE: We hypothesised that due to a recruiting effect, linearised expiration oxygenates better than volume controlled ventilation (VCV). We compared the EVA with VCV mode with regard to gas exchange, ventilation volumes and pressures and lung aeration in a model of peri-operative mandatory ventilation in healthy pigs. DESIGN: Controlled interventional trial. SETTING: Animal operating facility at a university medical centre. ANIMALS: A total of 16 German Landrace hybrid pigs. INTERVENTION: The lungs of anaesthetised pigs were ventilated with the EVA mode (n=9) or VCV (control, n=7) for 5 h with positive end-expiratory pressure of 5 cmH2O and tidal volume of 8 ml kg. The respiratory rate was adjusted for a target end-tidal CO2 of 4.7 to 6 kPa. MAIN OUTCOME MEASURES: Tracheal pressure, minute volume and arterial blood gases were recorded repeatedly. Computed thoracic tomography was performed to quantify the percentages of normally and poorly aerated lung tissue. RESULTS: Two animals in the EVA group were excluded due to unstable ventilation (n=1) or unstable FiO2 delivery (n=1). Mean tracheal pressure and PaO2 were higher in the EVA group compared with control (mean tracheal pressure: 11.6 ±â€Š0.4 versus 9.0 ±â€Š0.3 cmH2O, P < 0.001 and PaO2: 19.2 ±â€Š0.7 versus 17.5 ±â€Š0.4 kPa, P = 0.002) with comparable peak inspiratory tracheal pressure (18.3 ±â€Š0.9 versus 18.0 ±â€Š1.2 cmH2O, P > 0.99). Minute volume was lower in the EVA group compared with control (5.5 ±â€Š0.2 versus 7.0 ±â€Š1.0 l min, P = 0.02) with normoventilation in both groups (PaCO2 5.4 ±â€Š0.3 versus 5.5 ±â€Š0.3 kPa, P > 0.99). In the EVA group, the percentage of normally aerated lung tissue was higher (81.0 ±â€Š3.6 versus 75.8 ±â€Š3.0%, P = 0.017) and of poorly aerated lung tissue lower (9.5 ±â€Š3.3 versus 15.7 ±â€Š3.5%, P = 0.002) compared with control. CONCLUSION: EVA ventilation improves lung aeration via elevated mean tracheal pressure and consequently improves arterial oxygenation at unaltered positive end-expiratory pressure (PEEP) and peak inspiratory pressure (PIP). These findings suggest the EVA mode is a new approach for protective lung ventilation.

Pneumoperitoneum deteriorates intratidal respiratory system mechanics: an observational study in lung-healthy patients.

BACKGROUND: Pneumoperitoneum during laparoscopic surgery leads to atelectasis and impairment of oxygenation. Positive end-expiratory pressure (PEEP) is supposed to counteract atelectasis. We hypothesized that the derecruiting effects of pneumoperitoneum would deteriorate the intratidal compliance profile in patients undergoing laparoscopic surgery. METHODS: In 30 adult patients scheduled for surgery with pneumoperitoneum, respiratory variables were measured during mechanical ventilation. We calculated the dynamic compliance of the respiratory system (C RS) and the intratidal volume-dependent C RS curve using the gliding-SLICE method. The C RS curve was then classified in terms of indicating intratidal recruitment/derecruitment (increasing profile) and overdistension (decreasing profile). During the surgical interventions, the PEEP level was maintained nearly constant at 7 cm H2O. Data are expressed as mean [confidence interval]. RESULTS: Baseline C RS was 60 [54-67] mL cm H2O-1. Application of pneumoperitoneum decreased C RS to 40 [37-43] mL cm H2O-1 which partially recovered to 54 [50-59] mL cm H2O-1 (P < 0.001) after removal but remained below the value measured before pneumoperitoneum (P < 0.001). Baseline compliance profiles indicated intratidal recruitment/derecruitment in 48 % patients. After induction of pneumoperitoneum, intratidal recruitment/derecruitment was indicated in 93 % patients (P < 0.01), and after removal intratidal recruitment/derecruitment was indicated in 59 % patients. Compliance profiles showing overdistension were not observed. CONCLUSIONS: Analyses of the intratidal compliance profiles reveal that pneumoperitoneum during laparoscopic surgery causes intratidal recruitment/derecruitment which partly persists after its removal. The analysis of the intratidal volume-dependent C RS profiles could be used to guide intraoperative PEEP adjustments during elevated intraabdominal pressure.

Application of the Novel Ventilation Mode FLow-Controlled EXpiration (FLEX): A Crossover Proof-of-Principle Study in Lung-Healthy Patients.

BACKGROUND: Traditionally, mechanical ventilation is achieved via active lung inflation during inspiration and passive lung emptying during expiration. By contrast, the novel FLEX (FLow-controlled EXpiration) ventilator mode actively decreases the rate of lung emptying. We investigated whether FLEX can be used during intraoperative mechanical ventilation of lung-healthy patients. METHODS: In 30 adult patients scheduled for neurosurgical procedures, we studied respiratory system mechanics, regional ventilation, oxygenation, and hemodynamics during ventilation with and without FLEX at positive end-expiratory pressure (PEEP) of 5 and 7 cm H2O. The FLEX system was integrated into the expiratory limb and modified the expiratory flow profile by continuously changing expiratory resistance according to a computer-controlled algorithm. RESULTS: Mean airway pressure increased with PEEP by 1.9 cm H2O and with FLEX by 1 cm H2O (all P < .001). The expiratory peak flow was 42% lower with FLEX than without FLEX (P < .001). FLEX caused significant shifts in aeration from ventral to the dorsal lung regions. Respiratory mechanics, end-tidal carbon dioxide partial pressure, oxygenation, and hemodynamics were independent from FLEX and PEEP. We observed no critical incidents or FLEX malfunctions in any measurement that would have required an intervention or termination of the FLEX mode. CONCLUSIONS: FLEX can be used in lung-healthy patients who are mechanically ventilated during general anesthesia. FLEX improves the homogeneous distribution of ventilation in the lungs.