Cat management in an unregulated shelter environment: Relationship between care provision and cat health in Hong Kong

Cat (Felis silvestris catus) shelter practices may have important implications for cats' health and well-being. This study explored the relationship between husbandry practices and cat health in Hong Kong's shelters which are unregulated. Cat health was measured via body condition score (BCS), coat condition and signs of oculo-nasal discharge. A total of 314 cats in 24 cat shelters were assessed. A satisfactory BCS was associated with regular veterinary input, more than once per day disinfection and more than once per day change of water. The presence of oculo-nasal discharge — as a marker for upper respiratory tract infection — was associated with a lack of regular veterinary input and less frequent change of water within the shelter. A lack of regular feeding was the only factor associated with a dull coat. In summary, this study showed that certain husbandry practices had important associations with different aspects of cats' health for cats housed in an unregulated shelter environment in Hong Kong. These findings provide evidence-based support for husbandry guidelines or regulations for cat shelters which could have a positive impact on shelter cats' health and welfare.

Molecular dynamics simulation of metallic Al-Ce liquids using a neural network machine learning interatomic potential

Al-rich Al-Ce alloys have the possibility of replacing heavier steel and cast irons for use in high-temperature applications. Knowledge about the structures and properties of Al-Ce alloys at the liquid state is vital for optimizing the manufacture process to produce desired alloys. However, reliable molecular dynamics simulation of Al-Ce alloy systems remains a great challenge due to the lack of accurate Al-Ce interatomic potential. Here, an artificial neural network (ANN) deep machine learning (ML) method is used to develop a reliable interatomic potential for Al-Ce alloys. Ab initio molecular dynamics simulation data on the Al-Ce liquid with a small unit cell (∼200 atoms) and on the known Al-Ce crystalline compounds are collected to train the interatomic potential using ANN-ML. The obtained ANN-ML model reproduces well the energies, forces, and atomic structure of the Al₉₀Ce₁₀ liquid and crystalline phases of Al-Ce compounds in comparison with the ab initio results. The developed ANN-ML potential is applied in molecular dynamics simulations to study the structures and properties of the metallic Al₉₀Ce₁₀ liquid, which would provide useful insight into the guiding experimental process to produce desired Al-Ce alloys.

A randomised controlled trial of succinylated gelatin (4%) fluid on urinary acute kidney injury biomarkers in cardiac surgical patients

Background

Fluid resuscitation is frequently required for cardiac surgical patients admitted to the intensive care unit. The ideal fluid of choice in regard to efficacy and safety remains uncertain. Compared with crystalloid fluid, colloid fluid may result in less positive fluid balance. However, some synthetic colloids are associated with increased risk of acute kidney injury (AKI). This study compared the effects of succinylated gelatin (4%) (GEL) with compound sodium lactate (CSL) on urinary AKI biomarkers in patients after cardiac surgery.

Methods

Cardiac surgical patients who required an intravenous fluid bolus of at least 500 mL postoperatively were randomly allocated to receive GEL or CSL as the resuscitation fluid of choice for the subsequent 24 h. Primary outcomes were serial urinary neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C concentrations measured at baseline, 1 h, 5 h and 24 h after enrolment, with higher concentrations indicating greater kidney injury. Secondary biomarker outcomes included urinary clusterin, α1-microglobulin and F₂-isoprostanes concentrations. Differences in change of biomarker concentration between the two groups over time were compared with mixed-effects regression models. Statistical significance was set at P < 0.05.

Results

Forty cardiac surgical patients (n = 20 per group) with similar baseline characteristics were included. There was no significant difference in the median volume of fluid boluses administered over 24 h between the GEL (1250 mL, Q1–Q3 500–1750) and CSL group (1000 mL, Q1–Q3 500–1375) (P = 0.42). There was a significantly greater increase in urinary cystatin C (P < 0.001), clusterin (P < 0.001), α1-microglobulin (P < 0.001) and F₂-isoprostanes (P = 0.020) concentrations over time in the GEL group, compared to the CSL group. Change in urinary NGAL concentration (P = 0.68) over time was not significantly different between the groups. The results were not modified by adjustment for either urinary osmolality or EuroSCORE II predicted risk of mortality.

Conclusions

This preliminary randomised controlled trial showed that use of succinylated gelatin (4%) for fluid resuscitation after cardiac surgery was associated with increased biomarker concentrations of renal tubular injury and dysfunction, compared to crystalloid fluid. These results generate concern that use of intravenous gelatin fluid may contribute to clinically relevant postoperative AKI.

Trial registration ANZCTR.org.au, ACTRN12617001461381. Registered on 16th October, 2017, http://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=373619&isReview=true.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40635-021-00412-9.

Localized electronic and vibrational states in amorphous diamond

Amorphous diamond structures are generated by quenching high-density high-temperature liquid carbon using tight-binding molecular-dynamics simulations. We show that the generated amorphous diamond structures are predominated by strong tetrahedral bonds with the sp3 bonding fraction as high as 97%, thus exhibit an ultra-high incompressibility and a wide band gap close to those of crystalline diamond. A small amount of sp2 bonding defects in the amorphous sample contributes to localized electronic states in the band gap while large local strain gives rise to localization of vibrational modes at both high and low frequency regimes.

Tailored Plasmons in Pentacene/Graphene Heterostructures with Interlayer Electron Transfer

van der Waals (vdW) heterostructures, which are produced by the precise assemblies of varieties of two-dimensional (2D) materials, have demonstrated many novel properties and functionalities. Here we report a nanoplasmonic study of vdW heterostructures that were produced by depositing ordered molecular layers of pentacene on top of graphene. We find through nanoinfrared (IR) imaging that surface plasmons formed due to the collective oscillations of Dirac Fermions in graphene are highly sensitive to the adjacent pentacene layers. In particular, the plasmon wavelength declines systematically but nonlinearly with increasing pentacene thickness. Further analysis and density functional theory (DFT) calculations indicate that the observed peculiar thickness dependence is mainly due to the tunneling-type electron transfer from pentacene to graphene. Our work unveils a new method for tailoring graphene plasmons and deepens our understanding of the intriguing nano-optical phenomena due to interlayer couplings in novel vdW heterostructures.

Observation of η-Al41Sm5 reveals motif-aware structural evolution in Al-Sm alloys

Using an effective genetic algorithm, we uncover the structure of a metastable Al41Sm5 phase that supplements its family sharing similar short-range orders. The phase evolves upon heating an amorphous Al-9.7 at.% Sm ribbon, produced by melt-spinning. The dynamical phase selection is discussed with respect to the structural connections between the short-range packing motifs in the amorphous precursor and those observed in the selected phases. The phase elucidated here is one of several newly discovered large-unit-cell phases found to form during devitrification from the glass in this binary system, further illustrating the power and efficiency of our approach, the important role of structural hierarchy in phase selection, and the richness of the metastable phase landscape accessible from the glassy structure.

Effects of Si solute on the glass formation and atomic structure of Pd liquid

Molecular dynamics simulations were performed to study the effects of Si solute on the glass formation and crystallization of Pd liquid. Pure Pd samples prepared by a quenching process with a cooling rate of 10¹³ K s^-1 can be in an amorphous state but the structural analysis indicates there is nearly no glass-forming motif in the sample. However, doping a small amount of Si (Si concentration ~4%) the sample can be vitrified at a cooling rate of 10¹² K s^-1. The glass-forming motifs such as Pd-centered Z13, Si-centered Z9-like and mixed-ICO-cube clusters with five-fold local symmetry are found to be the dominant short-range orders in the glassy samples. With the increasing of the Si-doping concentration, these glass-forming motifs tend to aggregate and connect with each other forming a network structure. Our calculated results revealed that Si solutes in liquid Pd can significantly enhance the glass-forming ability.

Novel superconducting structures of BH2 under high pressure

The crystal structures of boron hydrides in a pressure range of 50-400 GPa were studied using the genetic algorithm (GA) method combined with first-principles density functional theory calculations. BH4 and BH5 are predicted to be thermodynamically unstable. Two new BH2 structures with Cmcm and C2/c space group symmetries, respectively, were predicted, in which the B atoms tend to form two-dimensional sheets. The calculated band structures showed that in the pressure range of 50-150 GPa, the Cmcm-BH2 phase has very small gaps, while the C2/c-BH2 phase at 200-400 GPa is metallic. The superconductivity of the C2/c-BH2 structure was also investigated, and electron-phonon coupling calculations revealed that the estimated Tc values of C2/c-BH2 are about 28.18-37.31 K at 250 GPa.

Use of Intrathecal Neostigmine as an Adjunct to Other Spinal Medications in Perioperative and Peripartum Analgesia: A Meta-analysis

Intrathecal neostigmine has been used as an adjunct to intrathecal local anaesthetic or opioid to prolong regional analgesia and improve haemodynamic stability, with variable results. This meta-analysis aims to evaluate the effectiveness and side-effects of intrathecal neostigmine in the perioperative and peripartum settings. The literature search was based on Cochrane Controlled Trials Register, EMBASE and MEDLINE (from 1966 to 14 November 2003) databases. Volunteer and animal studies were excluded. We identified 26 studies and 19 were considered suitable for detailed data extraction. Intrathecal neostigmine increased the incidence of nausea and vomiting (OR 5.0, 95% CI: 3.4 to 7.3; P<0.00001), bradycardia requiring intravenous atropine (OR 2.7, 95% CI: 1.4 to 5.4; P=0.005), and anxiety, agitation, or restlessness (OR 10.3, 95% CI: 3.7 to 28.9; P=0.00001). It improved the overall 24 hour VAS score (–1.4 VAS pain score, 95% CI: -1.7 to -1.2, P<0.00001), delayed the time of first request for rescue analgesia (168 min, 95% CI: 125 to 211; P<0.00001), and reduced the total number of rescue injections of nonsteroidal anti-inflammatory drug within the first 24 hours (-0.8, 95% CI: -1.1 to -0.4; P=0.00001). It did not affect the duration of motor blockade (3.5 min, 95% CI: -1.5 to 8.6; P=0.17) or the total amount of ephedrine required (-0.4 mg, 95% CI: -1.5 to 0.7; P=0.5). Adding intrathecal neostigmine to other spinal medications improves perioperative and peripartum analgesia marginally when compared with placebo. It is associated with significant side-effects and the disadvantages outweigh the minor improvement in analgesia achieved.

Use of Intravenous Tranexamic Acid to Reduce Allogeneic Blood Transfusion in Total Hip and Knee Arthroplasty: A Meta-analysis

Total hip or knee arthroplasty is associated with significant blood loss. Techniques such as the use of antifibrinolytics or desmopressin, or normovolaemic haemodilution have been used to reduce the need for allogeneic blood transfusion. Tranexamic acid has been used to reduce blood loss and transfusion requirement for total hip and knee arthroplasty, with variable results. This meta-analysis aims to evaluate whether intravenous tranexamic acid, when compared with placebo, reduces blood loss and transfusion requirement in total hip and knee joint replacement surgery and whether it might increase the risk of thromboembolic complications. The literature search was based on MEDLINE, EMBASE, Cochrane Controlled Trials Register, and information from the pharmaceutical company that produces tranexamic acid (Pharmacia-Upjohn). We identified 15 clinical trials and 12 were considered suitable for detailed data extraction. Tranexamic acid reduces the proportion of patients requiring allogeneic blood transfusion (OR 0.16, 95% CI: 0.09–0.26), total amount of blood loss (WMD 460 ml, 95% CI: 274–626 ml), and the total number of units of allogeneic blood transfused (WMD 0.85 unit, 95% CI: 0.36–1.33). Tranexamic acid does not increase the risk of thromboemobolic complications such as deep vein thrombosis, pulmonary embolism, thrombotic cerebral vascular accident, or myocardial infarction (OR 0.98, 95% CI: 0.45–2.12). Intravenous tranexamic acid appears effective and safe in reducing allogeneic blood transfusion and blood loss in total hip and knee arthroplasty.

Withholding and Withdrawal of Therapy in New Zealand Intensive Care Units (ICUs): A Survey of Clinical Directors

Withdrawing and withholding life-support therapy in patients who are unlikely to survive despite treatment are common practices in intensive care units (ICUs). The literature suggests there is a large variation in practice between different ICUs in different parts of the world. We conducted a postal survey among all public ICUs in New Zealand to investigate the pattern of practice in withholding and withdrawal of therapy. Nineteen ICUs responded to this survey and they represented 74% of all the public ICU beds and 83% of the annual ICU admissions. The percentage of ICU admissions with therapy withdrawn or withheld was less than 10% in most ICUs. Only a small percentage (21%) of ICUs had a formal policy in withholding and withdrawal of therapy. The timing of making the decision to withhold or withdraw therapy was very variable. The patient and/or the family, the primary medical team consultant, two or more ICU consultants, and ICU nurses were usually involved in the decision making process. ICU nurses were more commonly involved in the decision making process in smaller ICUs (5 beds vs 10 beds, P=0.03). The patient's pre-ICU quality of life, medical comorbidities, predicted mortality, predicted post-ICU quality of life, and the family's wishes were important factors in deciding whether ICU therapy would be withheld or withdrawn. Hospice ward or the patient's home was the preferred place for palliative care in 32% of the responses.

Fundamental Link between β Relaxation, Excess Wings, and Cage-Breaking in Metallic Glasses

In glassy materials, the Johari-Goldstein secondary (β) relaxation is crucial to many properties as it is directly related to local atomic motions. However, a long-standing puzzle remains elusive: why some glasses exhibit β relaxations as pronounced peaks while others present as unobvious excess wings? Using microsecond atomistic simulation of two model metallic glasses (MGs), we demonstrate that such a difference is associated with the number of string-like collective atomic jumps. Relative to that of excess wings, we find that MGs having pronounced β relaxations contain larger numbers of such jumps. Structurally, they are promoted by the higher tendency of cage-breaking events of their neighbors. Our results provide atomistic insights for different signatures of the β relaxation that could be helpful for understanding the low-temperature dynamics and properties of MGs.

Intermittent pneumatic compression is a cost-effective method of orthopedic postsurgical venous thromboembolism prophylaxis

Background

Venous thromboembolism (VTE) is a major complication after lower-limb arthroplasty that increases costs and reduces patient’s quality of life. Using anticoagulants for 10–35 days following arthroplasty is the standard prophylaxis, but its cost-effectiveness after accounting for bleeding complications remains unproven.

Methods

A comprehensive, clinical model of VTE was created using the incidences, clinical effects (including bleeding), and costs of VTE and prophylaxis from randomized controlled trials, meta-analyses, and large observational studies. Over 50 years, the total health care costs and clinical impact of three prophylaxis strategies, that are as follows, were compared: low-molecular-weight heparin (LMWH) alone, intermittent pneumatic compression (IPC), and IPC with LMWH (IPC+LMWH). The cost per VTE event that was avoided and cost per quality-adjusted life year (QALY) gained in both the US and Australian health care settings were calculated.

Results

For every 2,000 patients, the expected number of VTE and major bleeding events with LMWH were 151 and 6 in the USA and 160 and 46 in Australia, resulting in a mean of 11.3 and 9.1 QALYs per patient, respectively. IPC reduced the expected VTE events by 11 and 8 in the USA and Australia, respectively, compared to using LMWH alone. IPC reduced major bleeding events compared to LMWH, preventing 1 event in the US and 7 in Australia. IPC+LMWH only reduced VTE events. Neither intervention substantially impacted QALYs but both increased QALYs versus LMWH. IPC was cost-effective followed by IPC+LMWH.

Conclusion

IPC and IPC+LMWH are cost-effective versus LMWH after lower-limb arthroplasty in the USA and Australia. The choice between IPC and IPC+LMWH depends on expected bleeding risks.

Adverse outcomes after planned surgery with anticipated intensive care admission in out-of-office-hours time periods: a multicentre cohort study

BACKGROUND

Increasing mortality for patients admitted to hospitals during the weekend is a contentious but well described phenomenon. However, it remains uncertain whether adverse outcomes, including prolonged hospital length-of-stay (LOS), may also occur after patients undergoing major planned surgery are admitted to an intensive care unit (ICU) out-of-office-hours, either during weeknights (after 18:00) or on weekends.

METHODS

All planned surgical admissions requiring admission to one of 183 ICUs across Australia and New Zealand between 2006 and 2016 were included in this retrospective population-based cohort study. Primary outcomes were hospital LOS and hospital mortality.

RESULTS

Of the total 504 713 planned postoperative ICU admissions, 33.6% occurred during out-of-office-hours. After adjusting for available risk factors, out-of-office-hours ICU admissions were associated with a significant increase in hospital LOS [+2.6 days, 95% confidence interval (CI) 2.5-2.6], mortality [odd ratio (OR) 1.5, 95%CI 1.4-1.6], and a reduced chance of being directly discharged home (OR 0.8, 95%CI 0.8-0.8). The strongest association for adverse outcomes occurred with weekend ICU admissions (hospital LOS: +3.0 days, 95%CI 3.2-3.6; hospital mortality: OR 1.7, 95%CI 1.6-1.8). Clustering of adverse outcomes by hospitals was not observed in the generalised estimating equation analyses.

CONCLUSIONS

Despite a greater clinical staff availability and higher monitoring levels, planned surgery requiring anticipated out-of-office-hours ICU admission was associated with a prolonged hospital LOS, reduced discharge directly home, and increased mortality compared with in-office-hours admissions. Our findings have potential clinical, economic and health policy implications on how complex planned surgery should be planned and managed.

Crystal genes in a marginal glass-forming system of Ni50Zr50

The marginal glass-forming ability (GFA) of a binary Ni-Zr system is an issue to be explained considering numerous bulk metallic glasses (BMGs) found in a Cu-Zr system. Using molecular dynamics, the structures and dynamics of Ni₅₀Zr₅₀ metallic liquid and glass are investigated at the atomistic level. To achieve a well-relaxed glassy sample, a sub-T_g annealing method is applied and the final sample is closer to the experiments than the models prepared by continuous cooling. With the state-of-the-art structural analysis tools such as cluster alignment and pair-wise alignment methods, two glass-forming motifs with some mixed traits of a metastable B2 crystalline phase and a crystalline Ni-centered B33 motif are found to be dominant in the undercooled liquid and glass samples. A new chemical order characterization on each short-range order (SRO) structure is accomplished based on the cluster alignment method. The significant amount of the crystalline motif and the few icosahedra in the glassy sample deteriorate the GFA.

Fe-Si networks in Na2FeSiO4 cathode materials

Using a combination of adaptive genetic algorithm search, motif-network search scheme and first-principles calculations, we have systematically studied the low-energy crystal structures of Na2FeSiO4. We show that the low-energy crystal structures with different space group symmetries can be classified into several families based on the topologies of their Fe-Si networks. In addition to the diamond-like network which is shared by most of the low-energy structures, another three robust Fe-Si networks are also found to be stable during the charge/discharge process. The electrochemical properties of representative structures from these four different Fe-Si networks in Na2FeSiO4 and Li2FeSiO4 are investigated and found to be strongly correlated with the Fe-Si network topologies. Our studies provide a new route to characterize the crystal structures of Na2FeSiO4 and Li2FeSiO4 and offer useful guidance for the design of promising cathodes for Na/Li ion batteries.

Novel penta-graphene nanotubes: strain-induced structural and semiconductor-metal transitions

Research into novel one-dimensional (1D) materials and associated structural transitions is of significant scientific interest. It is widely accepted that a 1D system with a short-range interaction cannot have 1D phase transition at finite temperature. Herein, we propose a series of new stable carbon nanotubes by rolling up penta-graphene sheets, which exhibit fascinating well-defined 1D phase transitions triggered by axial strain. Our first-principles calculations show that such penta-graphene nanotubes (PGNTs) are dynamically stable by phonon calculations, but transform from a tri-layer structure to a highly defective single-walled nanotube at low temperature in molecular dynamics simulations. We show that moderate compressive strains can drive structural transitions of (4,4), (5,5), and (6,6) PGNTs, during which the distances of neighboring carbon dimers in the inner shell have a sudden drop, corresponding to dimer-dimer nonbonding to bonding transitions. After such transition, the tubes become much more thermally stable and undergo semiconductor-metal transitions under increasing strain. The band gaps of PGNTs are not sensitive to chirality whereas they can be tuned effectively from visible to short-wavelength infrared by appropriate strain, making them appealing materials for flexible nano-optoelectronics. These findings provide useful insight into unusual phase transitions in low-dimensional systems.

Balancing the risks and benefits of using emergency diagnostic radiocontrast studies to diagnose life-threatening illness in critically ill patients: a decision analysis

Diagnosis of many life-threatening illnesses, including acute pulmonary embolism, aortic dissection, and ischaemic bowel disease, requires confirmatory radiological imaging with radiocontrast. It is well established that radiocontrast can induce acute kidney injury, especially in patients with pre-existing renal impairment. The decision to proceed with a radiological study with radiocontrast to confirm or exclude a life-threatening, but potentially reversible, illness in patients with renal impairment is difficult. Theoretically, a radiocontrast study will be justifiable provided its benefits outweigh its harms. Using published prognostic data of contrast-induced nephropathy (CIN), this decision analysis aimed to assess whether a certain threshold of pre-test probability of a life-threatening illness is needed before a radiocontrast study can be justified for patients with different levels of renal impairment. In critically ill patients presenting with a life-threatening illness with hypotension requiring vasopressors or inotropes, the risk of CIN (defined by an increment in plasma creatinine of 40 µmol/l) and the associated attributable mortality after using 50 to 100 ml of radiocontrast was about 30% and 4%, respectively, for patients with baseline plasma creatinine concentrations <400 µmol/l. The risk of CIN and its associated attributable mortality increased substantially and exceeded 80% and 10%, respectively, if patients also had diabetes mellitus and their baseline plasma creatinine concentrations were >400 µmol/l. In the latter high-risk patients, using a radiocontrast study to diagnose or exclude a life-threatening illness could only be justified if the life-threatening illness was readily treatable and the pre-test probability of having such disease was greater than 15%-20%.

Out-of-office hours' elective surgical intensive care admissions and their associated complications

BACKGROUND

The 'weekend' effect is a controversial theory that links reduced staffing levels, staffing seniority and supportive services at hospitals during 'out-of-office hours' time periods with worsening patient outcomes. It is uncertain whether admitting elective surgery patients to intensive care units (ICU) during 'out-of-office hours' time periods mitigates this affect through higher staffing ratios and seniority.

METHODS

Over a 3-year period in Western Australia's largest private hospital, this retrospective nested-cohort study compared all elective surgical patients admitted to the ICU based on whether their admission occurred 'in-office hours' (Monday-Friday 08.00-18.00 hours) or 'out-of-office hours' (all other times). The main outcomes were surgical complications using the Dindo-Clavien classification and length-of-stay data.

RESULTS

Of the total 4363 ICU admissions, 3584 ICU admissions were planned following elective surgery resulting in 2515 (70.2%) in-office hours and 1069 (29.8%) out-of-office hours elective ICU surgical admissions. Out-of-office hours ICU admissions following elective surgery were associated with an increased risk of infection (P = 0.029), blood transfusion (P = 0.020), total parental nutrition (P < 0.001) and unplanned re-operations (P = 0.027). Out-of-office hours ICU admissions were also associated with an increased hospital length-of-stay, with (1.74 days longer, P < 0.0001) and without (2.8 days longer, P < 0.001) adjusting for severity of acute and chronic illnesses and inter-hospital transfers (12.3 versus 9.8%, P = 0.024). Hospital mortality (1.2 versus 0.7%, P = 0.111) was low and similar between both groups.

CONCLUSION

Out-of-office hours ICU admissions following elective surgery is common and associated with serious post-operative complications culminating in significantly longer hospital length-of-stays and greater transfers with important patient and health economic implications.

Reconsidering the role of decompressive craniectomy for neurological emergencies

OBJECTIVE

There is little doubt that decompressive craniectomy can reduce mortality. However, there is concern that any reduction in mortality comes at an increase in the number of survivors with severe neurological disability.

METHOD

Over the past decade there have been several randomised controlled trials comparing surgical decompression with standard medical therapy in the context of ischaemic stroke and severe traumatic brain injury. The results of each trial are evaluated.

RESULTS

There is now unequivocal evidence that a decompressive craniectomy reduces mortality in the context of "malignant" middle infarction and following severe traumatic brain injury. However, it has only been possible to demonstrate an improvement in outcome by categorizing a mRS of 4 and upper severe disability as favourable outcome. This is contentious and an alternative interpretation is that surgical decompression reduces mortality but exposes a patient to a greater risk of survival with severe disability.

CONCLUSION

It would appear unlikely that further randomised controlled trials will be possible given the significant reduction in mortality achieved by surgical decompression. It may be that observational cohort studies and outcome prediction models may provide data to determine those patients most likely to benefit from surgical decompression.

Odd-Integer Quantum Hall States and Giant Spin Susceptibility in p-Type Few-Layer WSe_{2}

We fabricate high-mobility p-type few-layer WSe_{2} field-effect transistors and surprisingly observe a series of quantum Hall (QH) states following an unconventional sequence predominated by odd-integer states under a moderate strength magnetic field. By tilting the magnetic field, we discover Landau level crossing effects at ultralow coincident angles, revealing that the Zeeman energy is about 3 times as large as the cyclotron energy near the valence band top at the Γ valley. This result implies the significant roles played by the exchange interactions in p-type few-layer WSe_{2}, in which itinerant or QH ferromagnetism likely occurs. Evidently, the Γ valley of few-layer WSe_{2} offers a unique platform with unusually heavy hole carriers and a substantially enhanced g factor for exploring strongly correlated phenomena.

Association between functional iron deficiency and reactive thrombocytosis in hospitalised patients: a case-control study

The association of deficiency in total body iron with an increased risk of reactive thrombocytosis is well known, but whether 'functional iron deficiency' is also associated with reactive thrombocytosis is unknown. This retrospective case-control study assessed the relationships between functional iron deficiency, reactive thrombocytosis and risk of thromboembolism. A total of 150 patients with reactive thrombocytosis (platelet count >400 x 10⁹/l) and 343 controls (platelet count <400 x 10⁹/l) were selected from the hospital laboratory database system. Patients with haematological disease or recent chemotherapy were excluded. Reactive thrombocytosis, infection, and an elevated C-reactive protein (CRP) concentration were all significantly more common in patients with functional iron deficiency than in those without functional iron deficiency (all P <0.01). After adjusting for infection and CRP concentration, functional iron deficiency was the only marker of iron status significantly associated with reactive thrombocytosis (odds ratio 1.66, 95% confidence interval 1.10-2.75; P=0.048). Thromboembolic events occurred in 32 patients (6.6%). This was not significantly associated with functional iron deficiency. Our results suggest that in patients without haematological malignancy or recent chemotherapy there might be a link between functional iron deficiency and reactive thrombocytosis. Whether treating patients with functional iron deficiency with intravenous iron corrects reactive thrombocytosis without inducing infection remains uncertain, but merits further investigation.

Effects of Oxygen Impurities on Glass-Formation Ability in Zr2Cu Alloy

Using ab initio molecular dynamics simulations, we show that oxygen (O) impurities have a noticeable influence on the glass-formation ability (GFA) in Zr2Cu alloy. Cu-centered icosahedral clusters and Zr-centered Kasper polyhedra are the dominate short-range orders in undercooled Zr2Cu liquid which are most likely to be responsible for the glass formation in Zr2Cu systems. When O is introduced, a Zr octahedron is formed around the O impurity. Most of the Zr atoms in the octahedron also serve as the bridging atoms for cross-linked Kasper polyhedral network, resulting in an O-centered medium range order (MRO) structure. Meanwhile, Cu atoms are moved away from the first shell of O-centered octahedral clusters. With 1 at. % O impurities, the fractions of Zr-centered clusters are less affected, while the increase of ideal icosahedral order and decrease of distorted icosahedral order lead to a more stable atomic structure. This result suggests that a low concentration of O impurities would improve the GFA in Zr2Cu alloy. However, when ∼5 at. % O impurities are included, the ideal icosahedral clusters and Zr-centered Kasper polyhedra are seriously suppressed by the formation of O-centered MRO, which can lead to deterioration of GFA. Our analyses provide useful insight into glass formation behavior in O-doped metallic alloy systems.

Tight-binding calculation studies of vacancy and adatom defects in graphene

Computational studies of complex defects in graphene usually need to deal with a larger number of atoms than the current first-principles methods can handle. Here, we show that a recently developed three-center tight-binding potential for carbon is very efficient for large scale atomistic simulations and can accurately describe the structures and energies of various defects in graphene. Using the three-center tight-binding potential, we have systematically studied the stable structures and formation energies of vacancy and embedded-atom defects of various sizes up to four vacancies and four embedded atoms in graphene. Our calculations reveal low-energy defect structures and provide a more comprehensive understanding of the structures and stability of defects in graphene.

Ab initio molecular dynamics simulations of short-range order in Zr₅₀Cu₄₅Al₅ and Cu₅₀Zr₄₅Al₅ metallic glasses

Comparative analysis between Zr-rich Zr50Cu45Al5 and Cu-rich Cu50Zr45Al5 metallic glasses (MGs) is extensively performed to locate the key structural motifs accounting for their difference of glass forming ability. Here we adopt ab initio molecular dynamics simulations to investigate the local atomic structures of Zr50Cu45Al5 and Cu50Zr45Al5 MGs. A high content of icosahedral-related (full and distorted) orders was found in both samples, while in the Zr-rich MG full icosahedrons ⟨0, 0, 12, 0⟩ is dominant, and in the Cu-rich one the distorted icosahedral orders, especially ⟨0, 2, 8, 2⟩ and ⟨0, 2, 8, 1⟩, are prominent. And the ⟨0, 2, 8, 2⟩ polyhedra in Cu50Zr45Al5 MG mainly originate from Al-centered clusters, while the ⟨0, 0, 12, 0⟩ in Zr50Cu45Al5 derives from both Cu-centered clusters and Al-centered clusters. These difference may be ascribed to the atomic size difference and chemical property between Cu and Zr atoms. The relatively large size of Zr and large negative heat of mixing between Zr and Al atoms, enhancing the packing density and stability of metallic glass system, may be responsible for the higher glass forming ability of Zr50Cu45Al5.

Pitfalls in haemodynamic monitoring in the postoperative and critical care setting

Haemodynamic monitoring is a vital part of daily practice in anaesthesia and intensive care. Although there is evidence to suggest that goal-directed therapy may improve outcomes in the perioperative period, which haemodynamic targets we should aim at to optimise patient outcomes remain elusive and controversial. This review highlights the pitfalls in commonly used haemodynamic targets, including arterial blood pressure, central venous pressure, cardiac output, central venous oxygen saturation and dynamic haemodynamic indices. Evidence suggests that autoregulation in regional organ circulation may change either due to chronic hypertension or different disease processes such as traumatic brain injury, cerebrovascular ischaemia or haemorrhage; this will influence the preferred blood pressure target. Central venous pressure can be influenced by multiple pathophysiological factors and, unless central venous pressure is very low, it is rarely useful as a predictor for fluid responsiveness. Central venous oxygen saturation can be easily increased by a high arterial oxygen tension, making it useless as a surrogate marker of good cardiac output or systemic oxygen delivery in the presence of hyperoxaemia. Many dynamic haemodynamic indices have been reported to predict fluid responsiveness, but they all have their own limitations. There is also insufficient evidence to support that giving fluid until the patient is no longer fluid responsive can improve patient-centred outcomes. With the exception in the context of preventing contrast-induced nephropathy, large randomised controlled studies suggest that excessive fluid treatment may prolong duration of mechanical ventilation without preventing acute kidney injury in the critically ill.

Dynamics and Diffusion Mechanism of Low-Density Liquid Silicon

A first-order phase transition from a high-density liquid to a low-density liquid has been proposed to explain the various thermodynamic anomies of water. It also has been proposed that such liquid-liquid phase transition would exist in supercooled silicon. Computer simulation studies show that, across the transition, the diffusivity drops roughly 2 orders of magnitude, and the structures exhibit considerable tetrahedral ordering. The resulting phase is a highly viscous, low-density liquid silicon. Investigations on the atomic diffusion of such a novel form of liquid silicon are of high interest. Here we report such diffusion results from molecular dynamics simulations using the classical Stillinger-Weber (SW) potential of silicon. We show that the atomic diffusion of the low-density liquid is highly correlated with local tetrahedral geometries. We also show that atoms diffuse through hopping processes within short ranges, which gradually accumulate to an overall random motion for long ranges as in normal liquids. There is a close relationship between dynamical heterogeneity and hopping process. We point out that the above diffusion mechanism is closely related to the strong directional bonding nature of the distorted tetrahedral network. Our work offers new insights into the complex behavior of the highly viscous low density liquid silicon, suggesting similar diffusion behaviors in other tetrahedral coordinated liquids that exhibit liquid-liquid phase transition such as carbon and germanium.

Si78 double cage structure and special optical properties

We performed first-principles calculations to study the structural stability of Si78 clusters with or without hydrogen passivation. The calculations reveal that an endohedral double cage isomer is more stable than the diamond-like structure, whereas the opposite is found for the hydrogen passivated isomers. In particular, the hydrogenated double cage and diamond-like structure may display blue shifts to the visible and UV regions, respectively. The IR vibration spectra, ionization potential (IP) and electronic density-of-states of the clusters were calculated and discussed.

Theoretical study on the structures and optical absorption of Si₁₇₂ nanoclusters

The structures and optical properties of silicon nanoclusters (Si NCs) have attracted continuous interest in the last few decades. However, it is a great challenge to determine the structures of Si NCs for accurate property calculation due to the complication and competition of various structural motifs. In this work, a Si172 NC with a size of about 1.8 nm was investigated using a genetic algorithm combined with tight-binding and DFT calculations. We found that a diamond crystalline core with 50 atoms (1.2 nm) was formed in the Si172 NC. It can be expected that at a size of about 172 atoms, a diamond crystalline structure can nucleate from the center of the Si NCs. The optical properties of the pure and hydrogenated Si172 NC structures also have been studied using the TDDFT method. Compared with the pure Si172 NC, the absorption peaks of the hydrogenated Si172 NC are obviously blue-shifted.

van der Waals epitaxial growth of atomically thin Bi₂Se₃ and thickness-dependent topological phase transition

Two-dimensional (2D) atomic-layered heterostructures stacked by van der Waals interactions recently introduced new research fields, which revealed novel phenomena and provided promising applications for electronic, optical, and optoelectronic devices. In this study, we report the van der Waals epitaxial growth of high-quality atomically thin Bi2Se3 on single crystalline hexagonal boron nitride (h-BN) by chemical vapor deposition. Although the in-plane lattice mismatch between Bi2Se3 and h-BN is approximately 65%, our transmission electron microscopy analysis revealed that Bi2Se3 single crystals epitaxially grew on h-BN with two commensurate states; that is, the (1̅21̅0) plane of Bi2Se3 was preferably parallel to the (1̅100) or (1̅21̅0) plane of h-BN. In the case of the Bi2Se3 (2̅110) ∥ h-BN (11̅00) state, the Moiré pattern wavelength in the Bi2Se3/h-BN superlattice can reach 5.47 nm. These naturally formed thin crystals facilitated the direct assembly of h-BN/Bi2Se3/h-BN sandwiched heterostructures without introducing any impurity at the interfaces for electronic property characterization. Our quantum capacitance (QC) measurements showed a compelling phenomenon of thickness-dependent topological phase transition, which was attributed to the coupling effects of two surface states from Dirac Fermions at/or above six quintuple layers (QLs) to gapped Dirac Fermions below six QLs. Moreover, in ultrathin Bi2Se3 (e.g., 3 QLs), we observed the midgap states induced by intrinsic defects at cryogenic temperatures. Our results demonstrated that QC measurements based on h-BN/Bi2Se3/h-BN sandwiched structures provided rich information regarding the density of states of Bi2Se3, such as quantum well states and Landau quantization. Our approach in fabricating h-BN/Bi2Se3/h-BN sandwiched device structures through the combination of bottom-up growth and top-down dry transferring techniques can be extended to other two-dimensional layered heterostructures.

Nonclassical "explosive" nucleation in Pb/Si(111) at low temperatures

Classically, the onset of nucleation is defined in terms of a critical cluster of the condensed phase, which forms from the gradual aggregation of randomly diffusing adatoms. Experiments in Pb/Si(111) at low temperature have discovered a dramatically different type of nucleation, with perfect crystalline islands emerging "explosively" out of the compressed wetting layer after a critical coverage Θ_{c}=1.22  ML is reached. The unexpectedly high island growth rates, the directional correlations in the growth of neighboring islands and the persistence in time of where mass is added in individual islands, suggest that nucleation is a result of the highly coherent motion of the wetting layer, over mesoscopic distances.

A comparison of long-term outcomes after meticillin-resistant and meticillin-sensitive Staphylococcus aureus bacteraemia: an observational cohort study

BACKGROUND

Findings from previous studies have suggested that outcomes after meticillin-resistant Staphylococcus aureus (MRSA) bacteraemia are worse than after meticillin-sensitive S. aureus (MSSA) bacteraemia. We assessed whether patients who had MRSA bacteraemia had a higher risk of death and recurrent infections than those who had MSSA bacteraemia.

METHODS

For this observational cohort study, we assessed data from the microbiology laboratory database at the Royal Perth Hospital (WA, Australia). Data were for all patients who had an episode of MRSA bacteraemia between July 1, 1997, and June 30, 2007, and, by use of a computer-generated randomisation sequence, a randomly selected subgroup of patients who had an episode of MSSA bacteraemia (patients with one or more set of blood cultures positive for S. aureus). The primary outcomes were survival time and subsequent infection-related hospital readmissions, analysed by Cox proportional hazards regression with adjustment for important prognostic factors.

FINDINGS

Of the 583 patients who had an episode of MRSA or MSSA bacteraemia, we used data for the 582 who had complete data linkage: 185 patients who had MRSA bacteraemia and 397 patients who had MSSA bacteraemia. The crude survival time of patients after MRSA bacteraemia was shorter than it was for patients with MSSA bacteraemia (14 months [IQR 1-86] vs 54 months [3-105]; hazard ratio 1·46, 95% CI 1·18-1·79; p=0·01). The adverse association between MRSA and all-cause mortality (0·98, 0·77-1·30; p=0·87) or infection-related mortality (1·22, 0·89-1·69; p=0·22) were not statistically significant after adjustment for important prognostic factors including age, comorbidities, severity of acute illness, metastatic infections, and long-term care facility resident status. After adjustment for these confounding factors, we saw no difference in infection-related hospital readmissions between patients who had MRSA bacteraemia and those who had MSSA bacteraemia (odds ratio 0·95, 95% CI 0·59-1·53; p=0·83).

INTERPRETATION

Long-term outcomes after MRSA bacteraemia were worse than those after MSSA bacteraemia through its confounding associations with other prognostic factors. Our findings might have implications for management strategies to control MRSA colonisation.

FUNDING

The Medical Research Foundation of Royal Perth Hospital.

Patient factors associated with frequent clotting of dialysers during haemodiafiltration in critically ill patients: a post hoc analysis of a randomised controlled study

Continuous haemodiafiltration (CVVHDF) is the main form of renal replacement therapy in critically ill patients with severe acute kidney injury. Clotting of the dialysers during CVVHDF is frequent, because most patients with acute kidney injury have an increased risk of bleeding and cannot be systemically anticoagulated. Using data from a randomised controlled trial comparing the efficiency of CVVHDF by placing the dialysis catheter tip at the right atrium or superior vena cava, this study assessed the patient factors associated with an increased risk of frequent clotting of the dialysers-defined by >1 dialysers clotted per day of CVVHDF. Of the 94 patients included in this study, a higher body mass index, a higher platelet count and a lower International Normalized Ratio were associated with an increased risk of frequent clotting of dialysers in the univariate analyses. Use of aspirin or clopidogrel, causes of acute kidney injury and daily dose of unfractionated heparin used were not significantly associated with the risk of frequent clotting of dialysers. In the multivariate parsimony model, only a high body mass index (odds ratio 1.06 per point increment, 95% confidence interval 1.01 to 1.13; P=0.036) and a high platelet count (odds ratio 1.84 per 100x10(9)/l increment, 95% confidence interval 1.17 to 2.91; P=0.009), both in a relatively linear fashion, were independently associated with an increased risk of frequent clotting of dialysers. Optimising the position of the tip of the dialysis catheter may be particularly important for patients with a high body mass index and platelet count in order to reduce frequent clotting of dialysers during CVVHDF.

Exploring the structural complexity of intermetallic compounds by an adaptive genetic algorithm

Solving the crystal structures of novel phases with nanoscale dimensions resulting from rapid quenching is difficult due to disorder and competing polymorphic phases. Advances in computer speed and algorithm sophistication have now made it feasible to predict the crystal structure of an unknown phase without any assumptions on the Bravais lattice type, atom basis, or unit cell dimensions, providing a novel approach to aid experiments in exploring complex materials with nanoscale grains. This approach is demonstrated by solving a long-standing puzzle in the complex crystal structures of the orthorhombic, rhombohedral, and hexagonal polymorphs close to the Zr2Co11 intermetallic compound. From our calculations, we identified the hard magnetic phase and the origin of high coercivity in this compound, thus guiding further development of these materials for use as high performance permanent magnets without rare-earth elements.

An adaptive genetic algorithm for crystal structure prediction

We present a genetic algorithm (GA) for structural search that combines the speed of structure exploration by classical potentials with the accuracy of density functional theory (DFT) calculations in an adaptive and iterative way. This strategy increases the efficiency of the DFT-based GA by several orders of magnitude. This gain allows a considerable increase in the size and complexity of systems that can be studied by first principles. The performance of the method is illustrated by successful structure identifications of complex binary and ternary intermetallic compounds with 36 and 54 atoms per cell, respectively. The discovery of a multi-TPa Mg-silicate phase with unit cell containing up to 56 atoms is also reported. Such a phase is likely to be an essential component of terrestrial exoplanetary mantles.

Assessment of the plethysmographic variability index as a predictor of fluid responsiveness in critically ill patients: a pilot study

Optimising intravascular volume in patients with hypotension requiring vasopressor support is a key challenge of critical care medicine. The optimal haemodynamic parameter to assess fluid responsiveness in critically ill patients, particularly those requiring a noradrenaline infusion and mechanical ventilation, remains uncertain. This pilot study assessed the accuracy of the plethysmographic variability index (PVI), (Radical-7 pulse co-oximeter, Masimo®, Irvine, CA, USA) in predicting fluid responsiveness in 25 patients who required noradrenaline infusion to maintain mean arterial pressure over 65 mmHg and were mechanically ventilated with a 'lung-protective' strategy, and whether administering a fluid bolus was associated with a change in PVI (Δ PVI). In this study, fluid responsiveness was defined as an increase in stroke volume of greater than 15% after a 500 ml bolus of colloid infusion over 20 minutes. Of the 25 patients included in the study, only 12 (48%) were considered fluid responders. As static haemodynamic parameters, PVI, central venous pressure and inferior vena cava distensibility index were all inaccurate at predicting volume responsiveness with PVI being the least accurate (area under the receiver operating characteristic curve=0.41, 95% confidence interval 0.18 to 0.65). However, fluid responsiveness was associated with a change in PVI, but not a change in heart rate or central venous pressure. This association between Δ PVI and fluid responsiveness may be a surrogate marker of improved cardiac output following a fluid bolus and warrants further investigation.