Irreducible Representations of Diperiodic Groups

The irreducible representations of all of the 80 diperiodic groups, being the symmetries of the systems translationally periodical in two directions, are calculated. To this end, each of these groups is factorized as the product of a generalized translational group and an axial point group. The results are presented in the form of the tables, containing the matrices of the irreducible representations of the generators of the groups. General properties and some physical applications (degeneracy and topology of the energy bands, selection rules, etc.) are discussed.Comment: 30 pages, 5 figures, 28 tables, 18 refs, LaTex2.0

Leveraging Positive Psychological Capital (PsyCap) in Crisis: A Multiphase Framework

Despite recent advancements in understanding of leadership in context, there is surprisingly little insight into leadership in crisis. To provide insight into how leaders navigate crisis, we utilize historical sources of Sir Winston Churchill’s leadership during World War II to analyze which resources are used by leaders during a crisis and how they leverage these resources to lead through and out of the crisis. We discover that psychological capital (PsyCap) is a core individual resource that leaders leverage in crisis. Our findings suggest that leaders leverage PsyCap in varying ways based on the phase of the crisis. That is, different dimensions of PsyCap are used to lead ahead of, into, through, and out of the crisis. This study contributes to the strategic leadership and positive organizational behavior literatures by empirically illustrating the dynamic nature of PsyCap and how leaders leverage it to navigate crisis

Leveraging Positive Psychological Capital (PsyCap) in Crisis: A Multiphase Framework

Despite recent advancements in understanding of leadership in context, there is surprisingly little insight into leadership in crisis – a context that is both pervasive and particularly challenging. To provide insight into how leaders navigate crisis, we utilize historical sources of Sir Winston Churchill’s leadership during World War II (WWII) to analyze 1) which resources may leaders use in crisis and 2) how they leverage these resources to lead through and out of the crisis. We discover that positive psychological capital (PsyCap) is a core strategic resource that leaders leverage in crisis. Our findings suggest that leaders leverage PsyCap as a core resource to build second-order capabilities needed to 1) prepare in the anticipation of a crisis, 2) persevere in the face of obstacles during the crisis, and 3) lead out of the crisis. In addition, we show that leaders do not just leverage PsyCap in its entirety; rather depending on circumstances, different elements of the PsyCap become more prominent at different times. In doing so, this study contributes to positive organizational behavior and leadership literatures by empirically illustrating dynamic nature of PsyCap as well as how leaders leverage it to navigate crisis

Evolution of multi-gap superconductivity in the atomically thin limit: Strain-enhanced three-gap superconductivity in monolayer MgB2_2

Starting from first principles, we show the formation and evolution of superconducting gaps in MgB$_2$ at its ultrathin limit. Atomically thin MgB$_2$ is distinctly different from bulk MgB$_2$ in that surface states become comparable in electronic density to the bulk-like $\sigma$- and $\pi$-bands. Combining the ab initio electron-phonon coupling with the anisotropic Eliashberg equations, we show that monolayer MgB$_2$ develops three distinct superconducting gaps, on completely separate parts of the Fermi surface due to the emergent surface contribution. These gaps hybridize nontrivially with every extra monolayer added to the film, owing to the opening of additional coupling channels. Furthermore, we reveal that the three-gap superconductivity in monolayer MgB$_2$ is robust over the entire temperature range that stretches up to a considerably high critical temperature of 20 K. The latter can be boosted to $>$50 K under biaxial tensile strain of $\sim$ 4\%, which is an enhancement stronger than in any other graphene-related superconductor known to date.Comment: To appear in Phys. Re

Inelastic collisions of relativistic electrons with atomic targets assisted by a laser field

We consider inelastic collisions between relativistic electrons and atomic targets assisted by a low-frequency laser field in the case when this field is still much weaker than the typical internal fields in the target. Concentrating on target transitions we show that they can be substantially affected by the presence of the laser field. This may occur either via strong modifications in the motion of the relativistic electrons caused by the electron-laser interaction or via the Compton effect when the incident electrons convert laser photon(s) into photons with frequencies equal to target transition frequencies.Comment: 4 pages, 2 figure

Away from the Top: Exploring Strategic Leadership in an Emergent Strategic Initiative Process

Strategic leadership is essential to organizational viability and success. However, by looking only at the strategic leader of the organization, we may be missing important strategic leadership behaviors that are distributed throughout the organization. Using an in-depth instrumental case study of an emergent initiative in a healthcare institution, we find that strategic leadership behaviors permeate the organization in a dynamic manner. Our findings illustrate that in contrast to much of the extant literature, strategic leadership transpires much before individuals positioned at the apex of the organization formalize and implement the final initiative top- down. More specifically, we portray strategic leadership as a distributed phenomenon that occurs throughout the emergent initiative process. In doing so, our findings extend the current, predominately leader-centric, understanding of strategic leadership

Revisiting Weber’s charismatic leadership: Learning from the past and looking to the future

Purpose – Weber emphasized the informal structure, followers\u27 power, and time in charismatic leadership; yet the extant literature either overlooks or underplays the significance of each of these facets. The aim of this paper is to revisit Weber\u27s conceptualizations of charisma and illuminate these facets, thus creating new avenues for the contemporary charismatic leadership research. Design/methodology/approach – The focus of this research is on analysis of Weber\u27s conceptualization of charisma. The analysis of selected quotes is grounded within contemporary discourse in order to illustrate how three overlooked facets may propel future research on charismatic leadership. Findings – By revisiting Weber\u27s seminal work, the paper illustrates several historical findings and identifies research opportunities that are yet to be addressed by contemporary study in charismatic leadership. In doing so, the paper generates a set of propositions as an impetus for future exploration. Research limitations/implications – To address the three proposed questions, researchers should focus their attention on the exploration of charisma outside of the formal bureaucracy, the dynamic power relations between leaders and followers, and the temporally bound nature of charisma. Given the nature of these questions, researchers may also consider alternative research methods such as in-depth case studies and narratives in order to more fully capture the dynamic and unpredictable nature of charisma in complex contexts. Originality/value – Contemporary research largely overlooks or underplays the issues of time, the informal structure, and followers in the study of charisma. Through analysis of Weber\u27s writings, this paper brings to the forefront these issues, and thus provide rich opportunities for future research on charismatic leadership

Fine-tuning activity-dependent bulk endocytosis via kinases and phosphatases

The regulation of activity-dependent bulk endocytosis, the dominant mode of membrane retrieval in response to intense neuronal activity, is poorly understood. In this JCB issue, Peng et al. (2021. J. Cell. Biol.https://doi.org/10.1083/jcb.202011028) propose a novel molecular mechanism for the coordination of activity-dependent bulk endocytosis that builds on Minibrain kinase and its presynaptic substrate synaptojanin-1.I. Milosevic is supported by funding from the John Black Foundation, John Fell Fund (H5D00100), and Horizon 2020 (MIA-Portugal/857524), while M.A. Cousin is supported by The Wellcome Trust (204954/ Z/16/Z), Simons Foundation (529508), Epilepsy Research UK (P2003), and Cure Huntington’s Disease Initiative (A-11210)

Bleeding after dental extractions in patients taking warfarin.

ObjectiveTo assess the incidence of bleeding after dental extractions in subjects taking warfarin continuously before and after extractions whose International Normalised Ratio (INR) was below 4.0 at the time of extraction.MethodsThis was a case series study of 150 patients without controls who required extraction of at least one tooth under local anaesthetic. All sockets were subsequently packed with absorbable oxycellulose and sutured.ResultsA total of 58 women and 92 men were included (mean age 66 years); their ages were similar. The mean INR (S.D.) was 2.5 (0.56), although most patients had an INR less than 2.5 (n=101). Ten patients (7%) bled after extraction, enough to require a return to hospital. Five patients of 101 with an INR2.5 out of 49 bled after extraction (p=0.29). Bleeding after extraction was not associated with operative antibiotics. All patients who bled were managed conservatively and none was admitted to hospital.ConclusionPatients taking warfarin whose INR is up to 4.0 and who have dental extractions in hospital do not have clinically significant bleeds post-operatively