Efficacious symmetry-adapted atomic displacement method for lattice dynamical studies

Small displacement methods have been successfully used to calculate the lattice dynamical properties of crystals. It involves displacing atoms by a small amount in order to calculate the induced forces on all atoms in a supercell for the computation of force constants. Even though these methods are widely in use, to our knowledge, there is no systematic discussion of optimal displacement directions from the crystal's symmetry point of view nor a rigorous error analysis of such methods. Based on the group theory and point group symmetry of a crystal, we propose displacement directions, with an equivalent concept of the group of $k$, deduced directly in the Cartesian coordinates rather than the usual fractional coordinates, that maintain the theoretical maximum for the triple product $V$ spanned by the three displacements to avoid possible severe roundoff errors. The proposed displacement directions are generated from a minimal set of irreducible atomic displacements that keep the required independent force calculations to a minimum. We find the error in the calculated force constant explicitly depends on the inverse of $V$ and inaccuracy of the forces. Test systems such as Si, graphene, and orthorhombic Sb2S3 are used to illustrate the method. Our displacement method is shown to be very robust in treating low-symmetry cells with a large `aspect ratio' due to huge differences in lattice parameters, use of a large vacuum height, or a very oblique unit cell due to unconventional choice of primitive lattice vectors. It is expected that our displacement strategy can be used to address higher-order interatomic interactions to achieve good accuracy and efficiency

Control and Characterization of Individual Grains and Grain Boundaries in Graphene Grown by Chemical Vapor Deposition

The strong interest in graphene has motivated the scalable production of high quality graphene and graphene devices. Since large-scale graphene films synthesized to date are typically polycrystalline, it is important to characterize and control grain boundaries, generally believed to degrade graphene quality. Here we study single-crystal graphene grains synthesized by ambient CVD on polycrystalline Cu, and show how individual boundaries between coalescing grains affect graphene's electronic properties. The graphene grains show no definite epitaxial relationship with the Cu substrate, and can cross Cu grain boundaries. The edges of these grains are found to be predominantly parallel to zigzag directions. We show that grain boundaries give a significant Raman "D" peak, impede electrical transport, and induce prominent weak localization indicative of intervalley scattering in graphene. Finally, we demonstrate an approach using pre-patterned growth seeds to control graphene nucleation, opening a route towards scalable fabrication of single-crystal graphene devices without grain boundaries.Comment: New version with additional data. Accepted by Nature Material

Enhanced recovery in colorectal surgery: a multicentre study

<p>Abstract</p> <p>Background</p> <p>Major colorectal surgery usually requires a hospital stay of more than 12 days. Inadequate pain management, intestinal dysfunction and immobilisation are the main factors associated with delay in recovery. The present work assesses the short and medium term results achieved by an enhanced recovery program based on previously published protocols.</p> <p>Methods</p> <p>This prospective study, performed at 12 Spanish hospitals in 2008 and 2009, involved 300 patients. All patients underwent elective colorectal resection for cancer following an enhanced recovery program. The main elements of this program were: preoperative advice, no colon preparation, provision of carbohydrate-rich drinks one day prior and on the morning of surgery, goal directed fluid administration, body temperature control during surgery, avoiding drainages and nasogastric tubes, early mobilisation, and the taking of oral fluids in the early postoperative period. Perioperative morbidity and mortality data were collected and the length of hospital stay and protocol compliance recorded.</p> <p>Results</p> <p>The median age of the patients was 68 years. Fifty-two % of the patients were women. The distribution of patients by ASA class was: I 10%, II 50% and III 40%. Sixty-four % of interventions were laparoscopic; 15% required conversion to laparotomy. The majority of patients underwent sigmoidectomy or right hemicolectomy. The overall compliance to protocol was approximately 65%, but varied widely in its different components. The median length of postoperative hospital stay was 6 days. Some 3% of patients were readmitted to hospital after discharge; some 7% required repeat surgery during their initial hospitalisation or after readmission. The most common complications were surgical (24%), followed by septic (11%) or other medical complications (10%). Three patients (1%) died during follow-up. Some 31% of patients suffered symptoms that delayed their discharge, the most common being vomiting or nausea (12%), dyspnoea (7%) and fever (5%).</p> <p>Conclusion</p> <p>The following of this enhanced recovery program posed no risk to patients in terms of morbidity, mortality and shortened the length of their hospital stay. Overall compliance to protocol was 65%. The following of this program was of benefit to patients and reduces costs by shortening the length of hospital stay. The implantation of such programmes is therefore highly recommended.</p

Probing Specific Interaction Forces Between Human IgG and Rat Anti-Human IgG by Self-Assembled Monolayer and Atomic Force Microscopy

Interaction forces between biological molecules such as antigen and antibody play important roles in many biological processes, but probing these forces remains technically challenging. Here, we investigated the specific interaction and unbinding forces between human IgG and rat anti-human IgG using self assembled monolayer (SAM) method for sample preparation and atomic force microscopy (AFM) for interaction force measurement. The specific interaction force between human IgG and rat anti-human IgG was found to be 0.6–1.0 nN, and the force required for unbinding a single pair of human IgG and rat anti-human IgG was calculated to be 144 ± 11 pN. The results are consistent with those reported in the literatures. Therefore, SAM for sample preparation combined with AFM for interaction measurement is a relatively simple, sensitive and reliable technique to probe specific interactions between biological molecules such as antigen and antibody

Search for rare quark-annihilation decays, B --> Ds(*) Phi

We report on searches for B- --> Ds- Phi and B- --> Ds*- Phi. In the context of the Standard Model, these decays are expected to be highly suppressed since they proceed through annihilation of the b and u-bar quarks in the B- meson. Our results are based on 234 million Upsilon(4S) --> B Bbar decays collected with the BABAR detector at SLAC. We find no evidence for these decays, and we set Bayesian 90% confidence level upper limits on the branching fractions BF(B- --> Ds- Phi) Ds*- Phi)<1.2x10^(-5). These results are consistent with Standard Model expectations.Comment: 8 pages, 3 postscript figues, submitted to Phys. Rev. D (Rapid Communications

Functional Insight into the C-Terminal Extension of Halolysin SptA from Haloarchaeon Natrinema sp. J7

Halolysin SptA from haloarchaeon Natrinema sp. J7 consists of a subtilisin-like catalytic domain and a C-terminal extension (CTE) containing two cysteine residues. In this report, we have investigated the function of the CTE using recombinant enzymes expressed in Haloferax volcanii WFD11. Deletion of the CTE greatly reduced but did not abolish protease activity, which suggests that the CTE is not essential for enzyme folding. Mutational analysis suggests that residues Cys303 and Cys338 within the CTE form a disulfide bond that make this domain resistant to autocleavage and proteolysis under hypotonic conditions. Characterization of full-length and CTE-truncation enzymes indicates the CTE not only confers extra stability to the enzyme but also assists enzyme activity on protein substrates by facilitating binding at high salinities. Interestingly, homology modeling of the CTE yields a β-jelly roll-like structure similar to those seen in Claudin-binding domain of Clostridium perfringens enterotoxin (clostridial C-CPE) and collagen binding domain (CBD), and the CTE also possesses collagen-binding activity, making it a potential candidate as an anchoring unit in drug delivery systems

An empirical analysis of the determinants of mobile instant messaging appropriation in university learning

Published ArticleResearch on technology adoption often profiles device usability (such as perceived usefulness) and user dispositions (such as perceived ease of use) as the prime determinants of effective technology adoption. Since any process of technology adoption cannot be conceived out of its situated contexts, this paper argues that any pre-occupation with technology acceptance from the perspective of device usability and user dispositions potentially negates enabling contexts that make successful adoption a reality. Contributing to contemporary debates on technology adoption, this study presents flexible mobile learning contexts comprising cost (device cost and communication cost), device capabilities (portability, collaborative capabilities), and learner traits (learner control) as antecedents that enable the sustainable uptake of emerging technologies. To explore the acceptance and capacity of mobile instant messaging systems to improve student performance, the study draws on these antecedents, develops a factor model and empirically tests it on tertiary students at a South African University of Technology. The study involved 223 national diploma and bachelor’s degree students and employed partial least squares for statistical analysis. Overall, the proposed model displayed a good fit with the data and rendered satisfactory explanatory power for students’ acceptance of mobile learning. Findings suggest that device portability, communication cost, collaborative capabilities of device and learner control are the main drivers of flexible learning in mobile environments. Flexible learning context facilitated by learner control was found to have a positive influence on attitude towards mobile learning and exhibited the highest path coefficient of the overall model. The study implication is that educators need to create varied learning opportunities that leverage learner control of learning in mobile learning systems to enhance flexible mobile learning. The study also confirmed the statistical significance of the original Technology Acceptance Model constructs

A Randomised Experiment Evaluating the Mindful Raisin Practice as a Method of Reducing Chocolate Consumption During and After a Mindless Activity

The present study investigated the impact of the mindful raisin exercise on overeating during and after the experiment while controlling for wellbeing. One-hundred and twenty-eight participants were recruited and completed a questionnaire on wellbeing (i.e. depression, anxiety and stress) and state mindfulness. Participants were randomly allocated to either the mindful raisin exercise or a newspaper reading control condition. The State Mindfulness Scale was then completed again, and participants watched a neutral video while exposed to chocolate for 10 min. For those 10 min, results showed that the mindfulness condition translated into lower food consumption during the mindless activity when compared to the control condition. Post experiment, participants were asked to wait for 5 min, and any extra chocolate consumption during this time was recorded. Post-consumption was non-significantly different between the two groups, with those in the mindfulness condition consuming 1.3 g less than those in the control group. Controlling for wellbeing did not alter the impact of the mindfulness intervention on consumption. Implications for future work and practical applications for weight regulation are discussed

Scholarly publishing depends on peer reviewers

The peer-review crisis is posing a risk to the scholarly peer-reviewed journal system. Journals have to ask many potential peer reviewers to obtain a minimum acceptable number of peers accepting reviewing a manuscript. Several solutions have been suggested to overcome this shortage. From reimbursing for the job, to eliminating pre- publication reviews, one cannot predict which is more dangerous for the future of scholarly publishing. And, why not acknowledging their contribution to the final version of the article published? PubMed created two categories of contributors: authors [AU] and collaborators [IR]. Why not a third category for the peer-reviewer

Computational Identification of Phospho-Tyrosine Sub-Networks Related to Acanthocyte Generation in Neuroacanthocytosis

Acanthocytes, abnormal thorny red blood cells (RBC), are one of the biological hallmarks of neuroacanthocytosis syndromes (NA), a group of rare hereditary neurodegenerative disorders. Since RBCs are easily accessible, the study of acanthocytes in NA may provide insights into potential mechanisms of neurodegeneration. Previous studies have shown that changes in RBC membrane protein phosphorylation state affect RBC membrane mechanical stability and morphology. Here, we coupled tyrosine-phosphoproteomic analysis to topological network analysis. We aimed to predict signaling sub-networks possibly involved in the generation of acanthocytes in patients affected by the two core NA disorders, namely McLeod syndrome (MLS, XK-related, Xk protein) and chorea-acanthocytosis (ChAc, VPS13A-related, chorein protein). The experimentally determined phosphoproteomic data-sets allowed us to relate the subsequent network analysis to the pathogenetic background. To reduce the network complexity, we combined several algorithms of topological network analysis including cluster determination by shortest path analysis, protein categorization based on centrality indexes, along with annotation-based node filtering. We first identified XK- and VPS13A-related protein-protein interaction networks by identifying all the interactomic shortest paths linking Xk and chorein to the corresponding set of proteins whose tyrosine phosphorylation was altered in patients. These networks include the most likely paths of functional influence of Xk and chorein on phosphorylated proteins. We further refined the analysis by extracting restricted sets of highly interacting signaling proteins representing a common molecular background bridging the generation of acanthocytes in MLS and ChAc. The final analysis pointed to a novel, very restricted, signaling module of 14 highly interconnected kinases, whose alteration is possibly involved in generation of acanthocytes in MLS and ChAc