A Variational Qubit-Efficient MaxCut Heuristic Algorithm

The resolution of hard combinatorial problems is essential in a wide range of industrial applications and theoretical fields. Quantum computers offer a unique platform for addressing such problems, with the Quantum Approximate Optimization Algorithm (QAOA) being a state-of-the-art example. However, due to high levels of noise and limited numbers of qubits in current quantum devices, only very small problem instances can be addressed on actual quantum hardware. Here we present a new variational Qubit-Efficient MaxCut (QEMC) algorithm that is specifically designed to find heuristic solutions for the MaxCut problem, a well-studied NP-hard combinatorial problem. The QEMC method introduces a unique information encoding scheme that requires $\log{N}$ qubits to address graphs with $N$ nodes, an exponential reduction in comparison to QAOA. Each node of the graph is assigned to a unique computational quantum state, and its logical state is depicted by the measurement probability of the corresponding state, using a probability-threshold encoding scheme. Consequently, each partition of the graph is associated with a volume of states, rather than with just a single state. We present noiseless QEMC simulations on regular graphs with up to 2048 nodes (11 qubits). These simulations achieved cut solutions that outperform those obtained by the best-known classical approximation algorithm of Goemans and Williamson (GW), by several percent. Moreover, executing the QEMC algorithm on actual IBM quantum devices achieved leading-edge results for graphs with up to 32 nodes (5 qubits), providing a challenging benchmark for the QAOA algorithm. We analyze the computational complexity of the QEMC algorithm and show that it can be simulated efficiently using classical methods, thereby constituting a new quantum-inspired classical MaxCut heuristic.Comment: 16 pages, 12 figure

FastML: a web server for probabilistic reconstruction of ancestral sequences

Ancestral sequence reconstruction is essential to a variety of evolutionary studies. Here, we present the FastML web server, a user-friendly tool for the reconstruction of ancestral sequences. FastML implements various novel features that differentiate it from existing tools: (i) FastML uses an indel-coding method, in which each gap, possibly spanning multiples sites, is coded as binary data. FastML then reconstructs ancestral indel states assuming a continuous time Markov process. FastML provides the most likely ancestral sequences, integrating both indels and characters; (ii) FastML accounts for uncertainty in ancestral states: it provides not only the posterior probabilities for each character and indel at each sequence position, but also a sample of ancestral sequences from this posterior distribution, and a list of the k-most likely ancestral sequences; (iii) FastML implements a large array of evolutionary models, which makes it generic and applicable for nucleotide, protein and codon sequences; and (iv) a graphical representation of the results is provided, including, for example, a graphical logo of the inferred ancestral sequences. The utility of FastML is demonstrated by reconstructing ancestral sequences of the Env protein from various HIV-1 subtypes. FastML is freely available for all academic users and is available online at http://fastml.tau.ac.i

The NEDD8 E3 ligase DCNL5 is phosphorylated by IKK alpha during Toll-like receptor activation

The activity of Cullin-RING ubiquitin E3 ligases (CRL) is regulated by NEDD8 modification. DCN-like proteins promote Cullin neddylation as scaffold-like E3s. One DCNL, DCNL5, is highly expressed in immune tissue. Here, we provide evidence that DCNL5 may be involved in innate immunity, as it is a direct substrate of the kinase IKKα during immune signalling. We find that upon activation of Toll-like receptors, DCNL5 gets rapidly and transiently phosphorylated on a specific N-terminal serine residue (S41). This phosphorylation event is specifically mediated by IKKα and not IKKβ. Our data for the first time provides evidence that DCNL proteins are post-translationally modified in an inducible manner. Our findings also provide the first example of a DCNL member as a kinase substrate in a signalling pathway, indicating that the activity of at least some DCNLs may be regulated

Bartonella henselae Endocarditis: An Usual Presentation of an Unusual Disease

Bartonella species are an emerging cause of culture-negative endocarditis with more cases being diagnosed now than 25 years ago when Bartonella quintana endocarditis was first described in a patient infected with human immunodeficiency virus (HIV). Despite the disease being increasingly reported, the exact epidemiological features are not clear, with prevalence rates ranging between 2% and 10% of all cases of culture-negative endocarditis. Moreover, the mortality rate is still high, presumably because of the subacute nature and relative rareness of the disease. Bartonella endocarditis occurs more often in men, and previous valvular surgery is a major risk factor. There is insufficient data to guide definitive treatment due to the paucity of literature. A previous study demonstrated that effective antibiotic therapy for Bartonella endocarditis should include an aminoglycoside prescribed for a minimum of 2 weeks. However, the treatment strategy is a matter of expert opinio

Interlayer Registry Determines the Sliding Potential of Layered Metal Dichalcogenides: The case of 2H-MoS2

We provide a simple and intuitive explanation for the interlayer sliding energy landscape of metal dichalcogenides. Based on the recently introduced registry index (RI) concept, we define a purely geometrical parameter which quantifies the degree of interlayer commensurability in the layered phase of molybdenum disulphide (2HMoS2). A direct relation between the sliding energy landscape and the corresponding interlayer registry surface of 2H-MoS2 is discovered thus marking the registry index as a computationally efficient means for studying the tribology of complex nanoscale material interfaces in the wearless friction regime.Comment: 13 pages, 7 figure

Burnout in Israeli medical students:a national survey

INTRODUCTION: Professional burnout is characterized by loss of enthusiasm for work, cynicism, and a low sense of personal efficacy. Burnout may adversely affect medical professionalism. Burnout is common in clinicians and varying rates have been reported in medical students. No data exist regarding the prevalence of burnout among Israeli medical students. The aims of this study were to assess the rate of burnout in Israeli medical students and to identify students who were particularly susceptible to burnout. METHODS: A cross-sectional questionnaire design was employed, gathering data from medical students in all years of study across three medical schools. Burnout was measured using the Maslach Burnout Inventory Student Survey (MBI-SS), translated into Hebrew. RESULTS: Of the 2160 students in the participating medical schools, 966 (44.7%) completed MBI-SS and demographic questionnaires. The overall burnout rate was 50.6%. Multivariate logistic regression analysis yielded that female gender, age under 25, advanced year of study, studying at a specific medical school and not being a parent are all significantly correlated with higher levels of burnout. CONCLUSIONS: A high rate of burnout was found. The identification of young women who are not parents during advanced years of studies as being at-risk is important, in order to guide the development of burnout prevention interventions

Distinct Contribution of the HtrA Protease and PDZ Domains to Its Function in Stress Resilience and Virulence of Bacillus anthracis

Anthrax is a lethal disease caused by the Gram-positive spore-producing bacterium Bacillus anthracis. We previously demonstrated that disruption of htrA gene, encoding the chaperone/protease HtrABA (High Temperature Requirement A of B. anthracis) results in significant virulence attenuation, despite unaffected ability of ΔhtrA strains (in which the htrA gene was deleted) to synthesize the key anthrax virulence factors: the exotoxins and capsule. B. anthracis ΔhtrA strains exhibited increased sensitivity to stress regimens as well as silencing of the secreted starvation-associated Neutral Protease A (NprA) and down-modulation of the bacterial S-layer. The virulence attenuation associated with disruption of the htrA gene was suggested to reflect the susceptibility of ΔhtrA mutated strains to stress insults encountered in the host indicating that HtrABA represents an important B. anthracis pathogenesis determinant. As all HtrA serine proteases, HtrABA exhibits a protease catalytic domain and a PDZ domain. In the present study we interrogated the relative impact of the proteolytic activity (mediated by the protease domain) and the PDZ domain (presumably necessary for the chaperone activity and/or interaction with substrates) on manifestation of phenotypic characteristics mediated by HtrABA. By inspecting the phenotype exhibited by ΔhtrA strains trans-complemented with either a wild-type, truncated (ΔPDZ), or non-proteolytic form (mutated in the catalytic serine residue) of HtrABA, as well as strains exhibiting modified chromosomal alleles, it is shown that (i) the proteolytic activity of HtrABA is essential for its N-terminal autolysis and subsequent release into the extracellular milieu, while the PDZ domain was dispensable for this process, (ii) the PDZ domain appeared to be dispensable for most of the functions related to stress resilience as well as involvement of HtrABA in assembly of the bacterial S-layer, (iii) conversely, the proteolytic activity but not the PDZ domain, appeared to be dispensable for the role of HtrABA in mediating up-regulation of the extracellular protease NprA under starvation stress, and finally (iv) in a murine model of anthrax, the HtrABA PDZ domain, was dispensable for manifestation of B. anthracis virulence. The unexpected dispensability of the PDZ domain may represent a unique characteristic of HtrABA amongst bacterial serine proteases of the HtrA family