Particle-hole symmetry protects spin-valley blockade in graphene quantum dots.

Particle-hole symmetry plays an important role in the characterization of topological phases in solid-state systems1. It is found, for example, in free-fermion systems at half filling and it is closely related to the notion of antiparticles in relativistic field theories2. In the low-energy limit, graphene is a prime example of a gapless particle-hole symmetric system described by an effective Dirac equation3,4 in which topological phases can be understood by studying ways to open a gap by preserving (or breaking) symmetries5,6. An important example is the intrinsic Kane-Mele spin-orbit gap of graphene, which leads to a lifting of the spin-valley degeneracy and renders graphene a topological insulator in a quantum spin Hall phase7 while preserving particle-hole symmetry. Here we show that bilayer graphene allows the realization of electron-hole double quantum dots that exhibit near-perfect particle-hole symmetry, in which transport occurs via the creation and annihilation of single electron-hole pairs with opposite quantum numbers. Moreover, we show that particle-hole symmetric spin and valley textures lead to a protected single-particle spin-valley blockade. The latter will allow robust spin-to-charge and valley-to-charge conversion, which are essential for the operation of spin and valley qubits.

Widening access to veterinary education: descriptive analysis of ethnicity, societal representation and educational background of applicants to veterinary education in Aotearoa New Zealand.

AIMS: To describe the ethnicity of domestic applicants for selection into the professional phase of veterinary education in Aotearoa New Zealand from 2003 to 2019, and to compare this with the ethnic composition of New Zealand society. This study also aims to explore whether there are differences in the demographic features and educational background of Maori applicants compared to non-Maori applicants that may be relevant to widening access to veterinary education. METHODS: This study was conducted with a Kaupapa Maori research methodology. Data for all applicants to the Bachelor of Veterinary Science programme at Massey University (Palmerston North, NZ) from 2003 to 2019 were retrieved from the university's Student Management System and the School of Veterinary Science selection application databases. Self-identified ethnicity was analysed in four time periods (2003-2006, 2007-2012, 2013-2016, 2017-2019) defined by factors that might influence whether an individual chose to apply for selection into the veterinary programme. Gender, age, previous university experience, decile and type of high school, and being first in family to attend university were compared between Maori and non-Maori. RESULTS: From 2003 to 2019, 3,819 individuals submitted 4,802 applications for selection into the veterinary programme. Across all time periods, applicants who identified as Maori (274/4,802; 5.7%) or Pacific (56/4,802; 1.2%) were underrepresented compared to the New Zealand population (Maori 16.5%; Pacific 8.1%), while applicants who identified as European (4,035/4,802; 84%) were over-represented (70.2% of the New Zealand population). The proportion of Maori (p = 0.82) and Pacific (p = 0.31) applicants did not change over time, while the proportion of European applicants decreased from 853/968 (88.1%) to 823/977 (84.2%; p < 0.001). Compared to non-Maori, Maori applicants were more likely to have attended a lower decile school (p < 0.001), have attended a state rather than private or overseas school (p = 0.003) and to have been the first in their family to attend university (p = 0.001). CONCLUSIONS: Maori are underrepresented in the veterinary applicant pool and veterinary profession in comparison to the New Zealand population. Additionally, Maori applicants differed from non-Maori applicants in pre-university factors that are barriers to university attendance. Implementing activities and processes aimed at widening veterinary programme access with the eventual goal of improving the ethnic representation of the veterinary workforce needs to be a priority for the university and profession.

[Pleural empyema - treatment strategies in light of etiology]. / Pleuraempyem - Behandlungsstrategien unter Berücksichtigung der Ätiologie.

The variety of strategies in the treatment of parapneumonic pleural empyema demonstrates the ambiguity for the method of choice. Parapneumonic pleural empyema has been classified into different stages and classes. While the American Thoracic Society (ATS) classification is based on the natural course of the disease, or according to the radiological, physical and biochemical characteristics respectively, the American College of Chest Physicians (ACCP) has categorized the patients with pleural empyema according to the risk of a poor outcome. The British Thoracic Society (BTS) developed a treatment algorithm based on a systematic review of peer-reviewed literature. With regard to this classification the management of parapneumonic and postoperative pleural empyema is based on the stage of the disease. Therapeutic strategies include chest tube alone, chest tube with fibrinolysis, thoracoscopic debridement and decortication in open or minimally invasive techniques, closed empyemectomy, or treatment with thoracomyoplasty, open window treatment or vacuum clothing with negative pressure. The different conservative and operative therapeutic possibilities determinate the central treatment function of thoracic surgery.

Coherent charge oscillations in a bilayer graphene double quantum dot.

The coherent dynamics of a quantum mechanical two-level system passing through an anti-crossing of two energy levels can give rise to Landau-Zener-Stückelberg-Majorana (LZSM) interference. LZSM interference spectroscopy has proven to be a fruitful tool to investigate charge noise and charge decoherence in semiconductor quantum dots (QDs). Recently, bilayer graphene has developed as a promising platform to host highly tunable QDs potentially useful for hosting spin and valley qubits. So far, in this system no coherent oscillations have been observed and little is known about charge noise in this material. Here, we report coherent charge oscillations and [Formula: see text] charge decoherence times in a bilayer graphene double QD. The charge decoherence times are measured independently using LZSM interference and photon assisted tunneling. Both techniques yield [Formula: see text] average values in the range of 400-500 ps. The observation of charge coherence allows to study the origin and spectral distribution of charge noise in future experiments.

Spin relaxation in a single-electron graphene quantum dot.

The relaxation time of a single-electron spin is an important parameter for solid-state spin qubits, as it directly limits the lifetime of the encoded information. Thanks to the low spin-orbit interaction and low hyperfine coupling, graphene and bilayer graphene (BLG) have long been considered promising platforms for spin qubits. Only recently, it has become possible to control single-electrons in BLG quantum dots (QDs) and to understand their spin-valley texture, while the relaxation dynamics have remained mostly unexplored. Here, we report spin relaxation times (T1) of single-electron states in BLG QDs. Using pulsed-gate spectroscopy, we extract relaxation times exceeding 200 µs at a magnetic field of 1.9 T. The T1 values show a strong dependence on the spin splitting, promising even longer T1 at lower magnetic fields, where our measurements are limited by the signal-to-noise ratio. The relaxation times are more than two orders of magnitude larger than those previously reported for carbon-based QDs, suggesting that graphene is a potentially promising host material for scalable spin qubits.

Xenon or propofol anaesthesia for patients at cardiovascular risk in non-cardiac surgery.

BACKGROUND: The results of two European multi-centre trials on xenon anaesthesia led to the hypothesis that a xenon-based anaesthetic would keep left ventricular (LV) and circulatory function more stable than a propofol-based anaesthetic, in patients with coronary artery disease (CAD). METHODS: In a prospective, randomized design, 40 patients of ASA classes III and IV with known CAD were anaesthetized for elective non-cardiac surgery with either xenon (n=20) or propofol (n=20), each combined with remifentanil. Target criteria were intraoperative LV function as evaluated by transoesophageal echocardiography (TOE: Tei index, circumferential fibre shortening), arterial pressure, and heart rate (HR). RESULTS: Mean arterial pressure was decreased with propofol but was stable at pre-anaesthetic level with xenon (P<0.02) and HR was lower with xenon (P<0.01). The Tei index (also known as myocardial performance index) improved from 0.53 (0.14) to 0.45 (0.10) after 1 h with xenon and changed from 0.50 (0.14) to 0.55 (0.20) with propofol anaesthesia [means (SD); P=0.01 between the groups]. Deviation of circumferential fibre shortening from expected value after 1 h was -2 (14)% with xenon and -14 (18)% with propofol [means (SD); P=0.03]. There were no perioperative signs of acute myocardial ischaemia (TOE, ECG, and troponin T release). CONCLUSIONS: Xenon anaesthesia provided a higher arterial pressure level than propofol, with no signs of cardiovascular compromise, in patients with CAD. Echocardiographic indices showed better LV function with xenon.

Effects of transcranial direct-current stimulation on laparoscopic surgical skill acquisition.

BACKGROUND: Changes in medical education may limit opportunities for trainees to gain proficiency in surgical skills. Transcranial direct-current stimulation (tDCS) can augment motor skill learning and may enhance surgical procedural skill acquisition. The aim of this study was to determine the effects of tDCS on simulation-based laparoscopic surgical skill acquisition. METHODS: In this double-blind, sham-controlled randomized trial, participants were randomized to receive 20 min of anodal tDCS or sham stimulation over the dominant primary motor cortex, concurrent with Fundamentals of Laparoscopic Surgery simulation-based training. Primary outcomes of laparoscopic pattern-cutting and peg transfer tasks were scored at baseline, during repeated performance over 1 h, and again at 6 weeks. Intent-to-treat analysis examined the effects of treatment group on skill acquisition and retention. RESULTS: Of 40 participants, those receiving tDCS achieved higher mean(s.d.) final pattern-cutting scores than participants in the sham group (207·6(30·0) versus 186·0(32·7) respectively; P = 0·022). Scores were unchanged at 6 weeks. Effects on peg transfer scores were not significantly different (210·2(23·5) in the tDCS group versus 201·7(18·1) in the sham group; P = 0·111); the proportion achieving predetermined proficiency levels was higher for tDCS than for sham stimulation. Procedures were well tolerated with no serious adverse events and no decreases in motor measures. CONCLUSION: The addition of tDCS to laparoscopic surgical training may enhance skill acquisition. Trials of additional skills and translation to non-simulated performance are required to determine the potential value in medical education and impact on patient outcomes. Registration number: NCT02756052 (https://clinicaltrials.gov/).

RNA analysis by ion-pair reversed-phase high performance liquid chromatography.

Ion-pair reversed-phase high performance liquid chromatography (IP RP HPLC) is presented as a new, superior method for the analysis of RNA. IP RP HPLC provides a fast and reliable alternative to classical methods of RNA analysis, including separation of different RNA species, quantification and purification. RNA is stable under the analysis conditions used; degradation of RNA during the analyses was not observed. The versatility of IP RP HPLC for RNA analysis is demonstrated. Components of an RNA ladder, ranging in size from 155 to 1770 nt, were resolved. RNA transcripts of up to 5219 nt were analyzed, their integrity determined and they were quantified and purified. Purification of mRNA from total RNA is described, separating mouse rRNA from poly(A)(+) mRNA. IP RP HPLC is also suitable for the separation and purification of DIG-labeled from unlabeled RNA. RNA purified by IP RP HPLC exhibits improved stability.

Development and validation of a feline abdominal palpation model and scoring rubric.

Simulation in veterinary education enables clinical skills practice without animal use. A feline abdominal palpation model was created that allows practice in this fractious species. This study assessed the model and rubric using a validation framework of content evidence, internal structure and relationship with level of training. Content Evidence: Veterinarians accepted this model as a helpful training tool for students (median=4 on five-point Likert scale). Internal Structure Evidence: G-coefficients were low for first- and second-year students (0.28 and 0.23), but were acceptable for veterinarians (0.61). Internal consistency values (0.24, 0.42 and 0.67) followed a similar pattern. Thus, scores were more reliable for veterinarians than for the students. Evidence of Relationship with Level of Training: Although level of training impacted reliability, its effect on performance scores was inconsistent. Analysis of variance (ANOVA) identified no differences among the groups of students and veterinarians. However, effect size between first- and third-year students was medium to large (0.62). Effect sizes between the veterinarians and student groups were small. Although the model and rubric appeared valid for experts, modifications would be necessary to generate reliable scores for students. These results allow greater understanding of the needs of students utilising a low-fidelity model.

High and low annealing temperatures increase both specificity and yield in touchdown and stepdown PCR.

Touchdown (TD) PCR represents a versatile one-step procedure for optimizing PCRs even if the degree of primer-template complementarity is not fully known. The protocol relies on incremental annealing temperature decreases in progressive cycles designed to bracket the melting temperature (Tm) of the reaction. Here we investigate the characteristics of TD PCR that serve to minimize the need to optimize annealing temperature or buffer conditions and yet produce single strong target amplicons. We demonstrate that priming initiates above the optimum annealing temperature; this helps to ensure a competitive advantage for the target amplicon. On the other hand, as the cycling program progresses, annealing temperatures well below the Tm can serve to significantly increase yields in reactions that would otherwise be marginal due to suboptimal buffer composition and yet do not promote spurious amplification. Modified forms of TD PCR, termed stepdown PCR, consisting of fewer but steeper incremental declines in annealing temperature, are also shown to be effective and can simplify thermal cycler programming.

Error analysis of chemically synthesized polynucleotides.

Two single-stranded polynucleotide constructs, 123 and 126 nucleotides in length, were chemically synthesized using standard phosphoramidite chemistry. Clonable, double-stranded DNA fragments about 100-bp long were prepared from the polynucleotides by primer extension with a DNA polymerase and end-trimming with two restriction endonucleases, then the fragments were ligated into separate plasmids. Errors in individual insert copies were determined by dideoxy sequencing after in vivo amplification of plasmids. Five of the ten inserts sequenced contained errors, including seven single-base-pair deletions, one four-base-pair deletion and one G-->C transversion. The origins of the latter two errors are unclear, but single-base deletions are inconsistent with errors of polymerases; thus, the most common sequence errors of chemical synthesis are deletion mutations. Deletions are most likely to result from incomplete capping or de-tritylation. The observed error rate can became a significant limiting factor in applications that depend on the correctness of a polynucleotide sequence in individual insert clones.

Mutation detection in the human HSP7OB' gene by denaturing high-performance liquid chromatography.

Variances, particularly single nucleotide polymorphisms (SNP), in the genomic sequence of individuals are the primary key to understanding gene function as it relates to differences in the susceptibility to disease, environmental influences, and therapy. In this report, the HSP70B' gene is the target sequence for mutation detection in biopsy samples from human prostate cancer patients undergoing combined hyperthermia and radiation therapy at the Dana-Farber Cancer Institute, using temperature-modulated heteroduplex analysis (TMHA). The underlying principles of TMHA for mutation detection using DHPLC technology are discussed. The procedures involved in amplicon design for mutation analysis by DHPLC are detailed. The melting behavior of the complete coding sequence of the target gene is characterized using WAVEMAKER software. Four overlapping amplicons, which span the complete coding region of the HSP70B' gene, amenable to mutation detection by DHPLC were identified based on the software-predicted melting profile of the target sequence. TMHA was performed on PCR products of individual amplicons of the HSP70B' gene on the WAVE Nucleic Acid Fragment Analysis System. The criteria for mutation calling by comparing wild-type and mutant chromatographic patterns are discussed.

Selective DNA binding of (N-alkylamine)-substituted naphthalene imides and diimides to G+C-rich DNA.

Alkylamine-substituted naphthalene imides and diimides bind DNA by intercalation and have applications as anticancer agents. The unique structures of these imides in which two adjacent carbonyl groups lie coplanar to an extended aromatic ring system allow the possibility of sequence-selective interactions between the intercalated chromophore and guanine amino groups situated in the DNA minor groove. The binding affinities of N-[3-(dimethylamino)propyl amine]-1,8-naphthalenedicarboxylic imide (N-DMPrNI) and N,N'-bis [3,3'-(dimethylamino)propylamine]-naphthalene-1,4,5,8-tetracarboxylic diimide (N-BDMPrNDI) for natural DNAs of differing base composition were determined spectroscopically and by equilibrium dialysis. In agreement with the above proposition, binding studies indicated that both the naphthalene imide and diimide strongly prefer to intercalate into steps containing at least one G:C base pair. The dependencies of association constants on DNA base composition are consistent with a requirement for one G:C pair in the binding site of the monomide, and two G:C pairs in binding sites of the diimide. These selectivities are comparable to or exceed that of actinomycin D, a classic G:C-selective drug. Protection footprinting with DNase I confirmed that the naphthalene monoiimide (N-DMPrNI) prefers to bind adjacent to G:C base pairs, with a most consistent preference for "mixed" steps containing both a G:C and an A:T pair, excepting GA:TC. Several 5'-CG-3' steps were also good binding sites as indicated by nuclease protection, but few GC:GC or GG:CC steps were protected. The naphthalene diimide inhibited DNase I digestion, but did not yield a footprint. The base recognition ability and versatile chemistry make naphthalene imides and diimides attractive building blocks for design of highly sequence-specific, DNA-directed drug candidates including conjugated oligonucleotides or oligopeptides.

Analysis and purification of nucleic acids by ion-pair reversed-phase high-performance liquid chromatography.

Sizing of DNA fragments is a routine analysis traditionally performed on agarose or polyacrylamide gels. Electrophoretic analysis is labor-intensive with only limited potential for automation. Recovery of DNA fragments from gels is cumbersome. We present data on automated, size-based separation of DNA fragments by ion-pair reversed-phase high performance liquid chromatography (IP RP HPLC) - DNA chromatography - on the WAVE DNA Fragment Analysis System with the DNASep cartridge. This system is suitable for accurate and rapid sizing of double-stranded (ds) DNA fragments from 50 to ca. 2000 base pairs (bp). Fluorescently labeled DNA fragments are compatible with the technology. Length-dependent separation of dsDNA fragments is sequence independent and retention times are highly reproducible. The resolving capabilities of DNA chromatography are illustrated by the analysis of multiple DNA size markers. Resolved dsDNA fragments are easily collected and are suitable for downstream applications such as sequencing and cloning. DNA chromatography under denaturing conditions with fluorescently labeled DNA fragments offers a means for the separation and purification of individual strands of dsDNA. Analysis of DNA fragments on the WAVE System is highly automated and requires minimal manual intervention. DNA chromatography offers a reliable and automated alternative to gel electrophoresis for the analysis of DNA fragments.

Hosts manipulated by one parasite incur additional costs from infection by another parasite.

Manipulation of host phenotype by parasites often serves to increase the predation rate of definitive hosts on intermediate hosts. For intermediate hosts, the indirect consequences of manipulation may extend beyond the direct increase in predation, however. Metacercariae of the trematode Curtuteria australis encyst in the foot of New Zealand cockles, Austrovenus stutchburyi, and stunt its growth, rendering cockles incapable of burrowing into the sediments. Here, we show that cockles manipulated by C. australis are 5 times more likely to be infected by the castrating sporocysts of another trematode than normal, nonmanipulated cockles. Our results indicate that the consequences for C. australis-manipulated cockles are far more important than a simple increase in the risk of predation and that indirect repercussions of manipulation can be as severe as direct ones.

Surgery for carcinoma of the gallbladder.

BACKGROUND/AIMS: Carcinoma of the gallbladder is one of the gastrointestinal malignancies with an extraordinarily poor prognosis. The 5-year survival rate amounts to less than 5 per cent in most series. Our aim was to analyze the experience of a single center with surgery for gallbladder carcinoma with special reference to liver wedge resection. MATERIALS AND METHODS: A retrospective analysis examined all patients of the Clinic of Surgery of the Humboldt University Medical School (Charité) with diagnosed gallbladder carcinoma operated on between January 1981 and August 1993. The analysis was based on patient documentation. Cumulative survival rates were calculated according to the method of Kaplan/Meier. Statistical significances were calculated using logrank and Wilcoxon's tests. RESULTS: Eighty one patients (61 female, 20 male) were included in the study. The preoperative diagnoses were confirmed in 33 patients (40.7%). The stage distribution according to the TNM-system revealed 6, 10, 12, and 53 patients at the stages I-IV, respectively. The curative resection rate was 22.2%. Stage-dependent surgical procedures resulted in cumulative survival rates of 33.3% for stages I and II, 8.3% for stage III and 1.9% for stage IV. The overall prognosis was significantly determined by metastatic spread to the lymph nodes. CONCLUSIONS: Diagnostic efforts should focus on detecting the low stages I and II of gallbladder carcinoma. Our results suggest that aggressive surgical management with second intervention and wedge resection or more extended liver resection is the method of choice for stage T1b or more advanced stages of gallbladder carcinoma.

Bronchial collapse during bronchoalveolar lavage in horses is an indicator of lung inflammation.

REASONS FOR PERFORMING STUDY: The bronchoalveolar lavage (BAL) procedure can return variable volumes of fluid, possibly depending on the presence of bronchial collapse during fluid aspiration and on the severity of lung inflammation. OBJECTIVES: We tested the hypothesis that horses with bronchial collapse during BAL are at higher risk of having severe lung inflammation. STUDY DESIGN: Prospective field study. METHODS: Bronchial collapse was graded using a new simple scoring method (0, 1 or 2) during a standardised BAL procedure in the field on 131 horses with normal, mild/moderate or severe lower airway inflammation on cytology of BAL fluid. RESULTS: Of the 131 horses, 37 (28%), 55 (42%) and 39 (30%) horses had bronchial collapse scores of 0, 1 and 2, respectively. There was a difference in collapse scores between all the BAL inflammation categories (P<0.001). Severe collapse had a positive predictive value of 0.95 for both mild/moderate and severe BAL inflammation, with a prevalence of 63% and 20%, respectively. The BAL fluid return volume in the horses with severe collapse scores was lower than volumes in the partial (score 1/2) and no collapse (score 0/2) groups (P<0.001). The BAL fluid volume was negatively correlated with BAL neutrophil percentage (P<0.001). CONCLUSIONS: Airway collapse during BAL is associated with airway inflammation and neutrophilia. POTENTIAL RELEVANCE: During a standardised BAL procedure, clinicians can expect lung inflammation in horses that have bronchial collapse and bronchial collapse in horses with lung inflammation. Lung inflammation may be a contributing factor in the mechanism of bronchial collapse during BAL in horses.

Standardised clients as assessors in a veterinary communication OSCE: a reliability and validity study.

In human medicine, standardised patients (SP) have been shown to reliably and accurately assess learners' communication performance in high-stakes certification Objective Structured Clinical Examinations (OSCE), offering a feasible way to reduce the need for recruitment, time commitment and coordination of faculty assessors. In this study, we evaluated the use of standardised clients (SC) as a viable option for assessing veterinary students' communication performance. We designed a four-station, two-track communication skills OSCE. SC assessors used an adapted nine-item Liverpool Undergraduate Communication Assessment Scale (LUCAS). Faculty used a 21-item checklist derived from the Calgary-Cambridge Guide (CCG) and a five-point global rating scale. Participants were second year veterinary students (n=96). For the four stations, intrastation reliability (α) ranged from 0.63 to 0.82 for the LUCAS, and 0.73 to 0.87 for the CCG. The interstation reliability coefficients were 0.85 for the LUCAS and 0.89 for the CGG. The calculated Generalisability (G) coefficients were 0.62 for the LUCAS and 0.60 for the CGG. Supporting construct validity, SC and faculty assessors showed a significant correlation between the LUCAS and CCG total percent scores (r=0.45, P<0.001), and likewise between the LUCAS and global rating scores (r=0.49, P<0.001).Study results support that SC assessors offer a reliable and valid approach for assessing veterinary communication OSCE.