Opening the system to the environment: new theories and tools in classical and quantum settings

The thesis is organized as follows. Section 2 is a first, unconventional, approach to the topic of EPs. Having grown interest in the topic of combinatorics and graph theory, I wanted to exploit its very abstract and mathematical tools to reinterpret something very physical, that is, the EPs in wave scattering. To do this, I build the interpretation of scattering events from a graph theory perspective and show how EPs can be understood within this interpretation. In Section 3, I move from a completely classical treatment to a purely quantum one. In this section, I consider two quantum resonators coupled to two baths and study their dynamics with local and global master equations. Here, the EPs are the key physical features used as a witness of validity of the master equation. Choosing the wrong master equation in the regime of interest can indeed mask physical and fundamental features of the system. In Section 4, there are no EPs. However I transition towards a classical/quantum framework via the topic of open systems. My main contribution in this work is the classical stochastic treatment and simulation of a spin coupled to a bath. In this work, I show how a natural quantum--to--classical transition occurs at all coupling strengths when certain limits of spin length are taken. As a key result, I also show how the coupling to the environment in this stochastic framework induces a classical counterpart to quantum coherences in equilibrium. After this last topic, in Section 5, I briefly present the key features of the code I built (and later extended) for the latter project. This, in the form of a Julia registry package named SpiDy.jl, has seen further applications in branching projects and allows for further exploration of the theoretical framework. Finally, I conclude with a discussion section (see Sec. 5) where I recap the different conclusions gathered in the previous sections and propose several possible directions.Engineering and Physical Sciences Research Council (EPSRC

Parental species and hybrid descendants of Bacillus (Insecta Phasmatodea) show different patterns of highly amplified, colocalized ribosomal and telomeric sequences

We investigated by dual-color fluorescence in situ hybridization (FISH) with 28S ribosomal and (TTAGG)n telomeric probes all species of the circum-Mediterranean genus Bacillus encompassing bisexual and parthenogenetic taxa, namely the three parental species (B. grandii, B. atticus, B. rossius) and the two derived hybrids (B. whitei, B. lynceorum). Specimens were collected in Italian mainland, Sardinia and Sicily. In all species the presence of colocalized, highly amplified ribosomal and telomeric sequences was demonstrated by the double labelling of the cytological satellites. These satellites varied in size, number and location both among and within species. In B. grandii and B. atticus a maximum of two FISH-labeled locations were observed, whereas in B. rossius and in the two hybrids up to 11 different positions were recorded. Moreover, our investigations showed a significant occurrence of chromosome breakages and rearrangements. The overall meaning of the ribosomal and telomeric sequence colocalization as well as the Nucleolar Organizer Region mobility and activity are discussed in both the ancestors and their hybrid descendants. It is noteworthy that the same trait has been shown in seven additional phasmid species belonging to distantly related genera. This trait could be a shared ancestral character in phasmids

Entanglement distance for arbitrary M -qudit hybrid systems

This is the final version. Available from the American Physical Society via the DOI in this recordThe achievement of quantum supremacy boosted the need for a robust medium of quantum information. In this task, higher-dimensional qudits show remarkable noise tolerance and enhanced security for quantum key distribution applications. However, to exploit the advantages of such states, we need a thorough characterisation of their entanglement. Here, we propose a measure of entanglement which can be computed either for pure and mixed states of a $M$-qudit hybrid system. The entanglement measure is based on a distance deriving from an adapted application of the Fubini-Study metric. This measure is invariant under local unitary transformations and has an explicit computable expression that we derive. In the specific case of $M$-qubit systems, the measure assumes the physical interpretation of an obstacle to the minimum distance between infinitesimally close states. Finally, we quantify the robustness of entanglement of a state through the eigenvalues analysis of the metric tensor associated with it.QuantERA ERA-NET Co-fundEngineering and Physical Sciences Research Council (EPSRC

Local master equations bypass the secular approximation

This is the author accepted manuscript. The final version is available on open access from Verein zur Förderung des Open Access Publizierens in den Quantenwissenschaften via the DOI in this recordMaster equations are a vital tool to model heat flow through nanoscale thermodynamic systems. Most practical devices are made up of interacting sub-system, and are often modelled using either local master equations (LMEs) or global master equations (GMEs). While the limiting cases in which either the LME or the GME breaks down are well understood, there exists a 'grey area' in which both equations capture steady-state heat currents reliably, but predict very different transient heat flows. In such cases, which one should we trust? Here, we show that, when it comes to dynamics, the local approach can be more reliable than the global one for weakly interacting open quantum systems. This is due to the fact that the secular approximation, which underpins the GME, can destroy key dynamical features. To illustrate this, we consider a minimal transport setup and show that its LME displays exceptional points (EPs). These singularities have been observed in a superconducting-circuit realisation of the model [1]. However, in stark contrast to experimental evidence, no EPs appear within the global approach. We then show that the EPs are a feature built into the Redfield equation, which is more accurate than the LME and the GME. Finally, we show that the local approach emerges as the weak-interaction limit of the Redfield equation, and that it entirely avoids the secular approximation.Engineering and Physical Sciences Research Council (EPSRC)Royal Societ

Mirrored images but not silicone models trigger aggressive responses in male common wall lizards

Disentangling the effects of single releasers in animal communication is a demanding task because a releaser often consists of a combination of different key stimuli. Territorial communication in reptiles usually depends on visual, chemical, and acoustic stimuli, but the role of each of them depends on phylogeny. Lacertids are modern lizards that rely mainly on chemical cues for their communication, but they also use aggressive displays based on visual recognition. We experimentally tested the visual stimuli that release an aggressive response in the males of a typical lacertid, the common wall lizard (Podarcis muralis), testing the effects of silicone models and mirrored images in captivity. The response to models and control (a blank sheet) was not significantly different and these stimuli did not release any aggressive behaviour. On the contrary, the reflected image in a mirror caused overt aggression (i.e., bites against it) in 63% of tested individuals. The results clearly demonstrate the role of visual stimuli in territorial communication, but only as a combined effect of shape and motion, differently from other lizard families for which shape is enough to stimulate aggre sive responses. Mirrors can be useful tools to investigate aggression related to physiological and morphological aspects in lacertid lizards

Fate of patients with spinal cord ischemia complicating thoracic endovascular aortic repair

ObjectiveSpinal cord ischemia (SCI) is a potentially devastating complication of thoracic endovascular aortic repair (TEVAR) that can result in varying degrees of short-term and permanent disability. This study was undertaken to describe the clinical outcomes, long-term functional impact, and influence on survival of SCI after TEVAR.MethodsA retrospective review of all TEVAR patients at the University of Florida from 2000 to 2011 was performed to identify individuals experiencing SCI, defined by any new lower extremity neurologic deficit not attributable to another cause. SCI was dichotomized into immediate or delayed onset, with immediate onset defined as SCI noted upon awakening from anesthesia, and delayed characterized as a period of normal function, followed by development of neurologic injury. Ambulatory status was determined using database query, record review, and phone interviews with patients and/or family. Mortality was estimated using life-table analysis.ResultsA total of 607 TEVARs were performed for various indications, with 57 patients (9.4%) noted to have postoperative SCI (4.3% permanent). SCI patients were more likely to be older (63.9 ± 15.6 vs 70.5 ± 11.2 years; P = .002) and have a number of comorbidities, including chronic obstructive pulmonary disease, hypertension, dyslipidemia, and cerebrovascular disease (P < .0001). At some point in their care, a cerebrospinal fluid drain was placed in 54 patients (95%), with 54% placed postoperatively. In-hospital mortality was 8.8% for the entire cohort (SCI vs no SCI; P = .45). SCI developed immediately in 12 patients, delayed onset in 40, and indeterminate in five patients due to indiscriminate timing from postoperative sedation. Three patients (25%) with immediate SCI had measurable functional improvement (FI), whereas 28 (70%) of the delayed-onset patients experienced some degree of neurologic recovery (P = .04). Of the 34 patients with complete data available, 26 (76%) reported quantifiable FI, but only 13 (38%) experienced return to their preoperative baseline. Estimated mean (± standard error) survival for patients with and without SCI was 37.2 ± 4.5 and 71.6 ± 3.9 months (P < .0006), respectively. Patients with FI had a mean survival of 53.9 ± 5.9 months compared with 9.6 ± 3.6 months for those without improvement (P < .0001). Survival and return of neurologic function were not significantly different when patients with preoperative and postoperative cerebrospinal fluid drains were compared.ConclusionsThe minority of patients experience complete return to baseline function after SCI with TEVAR, and outcomes in patients without early functional recovery are particularly dismal. Patients experiencing delayed SCI are more likely to have FI and may anticipate similar life-expectancy with neurologic recovery compared with patients without SCI. Timing of drain placement does not appear to have an impact on postdischarge FI or long-term mortality

Outcomes after redo aortobifemoral bypass for aortoiliac occlusive disease

ObjectivePatients presenting with occluded aortobifemoral (ABF) bypass grafts are managed with a variety of techniques. Redo ABF (rABF) bypass procedures are infrequently performed because of concerns about procedural complexity and morbidity. The purpose of this analysis was to compare midterm results of rABF bypass with those of primary ABF (pABF) bypass for aortoiliac occlusive disease to determine if there are significant differences in outcomes.MethodsA retrospective review was performed of all patients undergoing ABF bypass for occlusive disease between January 2002 and March 2012. A total of 19 patients underwent rABF bypass and 194 received pABF bypass during that period. Data for an indication- and comorbidity-matched case-control cohort of 19 elective pABF bypass patients were collected for comparison to the rABF bypass group. Primary end points included rate of major complications as well as 30-day and all-cause mortality. Secondary end points were amputation-free survival and freedom from major adverse limb events.ResultsThe rABF bypass patients more frequently underwent prior extra-anatomic or lower extremity bypass operations compared with pABF bypass patients (P = .02); however, no difference was found in the incidence of prior failed endovascular iliac intervention (P = .4). By design, indications for the rABF and pABF bypass groups were the same (claudication, n = 6/6 [31.6%]; P = 1; critical limb ischemia, n = 13/13 [78.4%]; P = 1). Aortic access was more frequently by retroperitoneal exposure in the rABF bypass group (n = 13 vs n = 1; P < .0001), and a significantly higher proportion of the rABF bypass patients required concomitant infrainguinal bypass or intraprocedural adjuncts such as profundaplasty (n = 14 vs n = 5; P = .01). The rABF bypass patients experienced greater blood loss (1097 ± 983 mL vs 580 ± 457 mL; P = .02), received more intraoperative fluids (3400 ± 1422 mL vs 2279 ± 993 mL; P = .01), and had longer overall procedure times (408 ± 102 minutes vs 270 ± 48 minutes; P < .0001). Length of stay (days ± standard deviation) was similar (pABF bypass, 11.2 ± 10.4; rABF bypass, 9.1 ± 4.5; P = .7), and no 30-day or in-hospital deaths occurred in either group. Similar rates of major complications occurred in the two groups (pABF bypass, n = 6 [31.6%]; rABF bypass, n = 4 [21.1%]; observed difference, 9.5%; 95% confidence interval, −17.6% to 36.7%; P = .7). Two-year freedom from major adverse limb events (±standard error mean) was 82% ± 9% vs 78% ± 10% for pABF and rABF bypass patients (log-rank, P = .6). Two-year amputation-free survival was 90 ± 9% vs 89 ± 8% between pABF and rABF bypass patients (P = .5). Two-year survival was 91% ± 9% and 90% ± 9% for pABF and rABF bypass patients (P = .8).ConclusionsPatients undergoing rABF bypass have higher procedural complexity compared with pABF bypass as evidenced by greater operative time, blood loss, and need for adjunctive procedures. However, similar perioperative morbidity, mortality, and midterm survival occurred in comparison to pABF bypass patients. These results support a role for rABF bypass in selected patients

Prediction of graft patency and mortality after distal revascularization and interval ligation for hemodialysis access-related hand ischemia

ObjectiveThe treatment goals of access-related hand ischemia (ARHI) are to reverse symptoms and salvage the access. Many procedures have been described, but the optimal treatment strategy remains unresolved. In an effort to guide clinical decision making, this study was undertaken to document our outcomes for distal revascularization and interval ligation (DRIL) and to identify predictors of bypass patency and patient mortality.MethodsA retrospective review was performed of all patients who underwent DRIL at the University of Florida from 2002 to 2011. Diagnosis of ARHI was based primarily upon clinical symptoms with noninvasive studies used to corroborate in equivocal cases. Patient demographics, procedure-outcome variables, and reinterventions were recorded. Bypass patency and mortality were estimated using cumulative incidence and Kaplan-Meier methodology, respectively. Cumulative incidence and Cox regression analysis were performed to determine predictors of bypass patency and mortality, respectively.ResultsA total of 134 DRILs were performed in 126 patients (mean [standard deviation] age, 57 [12] years) following brachial artery-based access. The postoperative complication rate was 27% (19% wound), and 30-day mortality was 2%. The wrist-brachial index and digital brachial index increased 0.31 (0.25) and 0.25 (0.29), respectively. Symptoms resolved in 82% of patients, and 85% continued to use their access. Cumulative incidences (± standard error of the mean) of loss of primary and primary-assisted patency rates were 5% ± 2% and 4% ± 2% at 1 year and 22% ± 5% and 18% ± 5% at 5 years, respectively, with mean follow-up of 14.8 months. Univariate predictors of primary patency failure were DRIL complications (odds ratio [OR], 3.3; 95% confidence interval [CI], 1.2-8.9; P = .02), configuration other than brachiobasilic/brachiocephalic autogenous access (OR, 3.4; 95% CI, 1.4-8.3; P = .009), and two or more prior access attempts (OR, 4.1; 95% CI, 1.6-10.4; P = .004). Brachiocephalic access configuration (OR, 0.2; 95% CI, 0.04-0.8; P = .02) and autogenous vein conduit (OR, 0.2; 95% CI, 0.06-0.58; P = .004) were predictors of improved bypass patency. All-cause mortality was 28% and 79% at 1 and 5 years, respectively. Multivariable predictors of mortality were age >40 (hazard ratio [HR], 8.3; 95% CI, 2.5-33.3; P = .0004), grade 3 ischemia (HR, 2.6; 95% CI, 1.5-4.6; P = .0008), complication from DRIL (HR, 2.4; 95% CI, 1.3-4.5; P = .004), and smoking history (HR, 2.2; 95% CI, 1.3-4; P = .007). Patients with no prior access attempts had lower predicted mortality (HR, 0.5; 95% CI, 0.3-0.9; P = .02).ConclusionsThe DRIL procedure effectively improves distal perfusion and reverses the symptoms of ARHI while salvaging the access, but the long-term survival of these patients is poor. Given the poor survival, preoperative risk stratification is critical. Patients at high risk for DRIL failure and mortality may be best served with alternate remedial procedures