Preprint arXiv: 2106.05030 Submitted on 9 Jun 2021

Non-Hermitian Hamiltonians, which effectively describe dissipative systems, and analogue gravity models, which simulate properties of gravitational objects, comprise seemingly different areas of current research. Here, we investigate the interplay between the two by relating parity-time-symmetric dissipative Weyl-type Hamiltonians to analogue Schwarzschild black holes emitting Hawking radiation. We show that the exceptional points of these Hamiltonians form tilted cones mimicking the behavior of the light cone of a radially infalling observer approaching a black hole horizon. We further investigate the presence of tunneling processes, reminiscent of those happening in black holes, in a concrete example model. We interpret the non-trivial result as the purely thermal contribution to analogue Hawking radiation in a Schwarzschild black hole. Assuming that our particular Hamiltonian models a photonic crystal of experimental relevance, we argue that the loss from the latter in the form of thermal radiation can be interpreted as the blackbody contribution to analogue black hole radiation when measuring at the exceptional cone. As such, these systems are promising candidates for black hole analogue models

PT symmetry-protected exceptional cones and analogue Hawking radiation

We show that the exceptional surfaces of linear three-dimensional non-Hermitian parity-time-symmetric two-band models attain the form of topologically stable tilted exceptional cones. By relating the exceptional cones to energy cones of two-dimensional Hermitian parity-time-symmetric two-band models, we find a connection between the exceptional cone and the light cone of an observer in the vicinity of a Schwarzschild black hole. When the cone overtilts, light-like particle-antiparticle pairs are created resembling Hawking radiation. We also investigate dissipative features of the non-Hermitian Hamiltonian related to the latter and comment on potential realizations in laboratory setups

Functional Dissection of Streptococcus pyogenes M5 Protein: the Hypervariable Region is Essential for Virulence

The surface-localized M protein of Streptococcus pyogenes is a major virulence factor that inhibits phagocytosis, as determined ex vivo. Because little is known about the role of M protein in vivo we analyzed the contribution of different M protein regions to virulence, using the fibrinogen (Fg)-binding M5 protein and a mouse model of acute invasive infection. This model was suitable, because M5 is required for mouse virulence and binds mouse and human Fg equally well, as shown here. Mixed infection experiments with wild type bacteria demonstrated that mutants lacking the N-terminal hypervariable region (HVR) or the Fg-binding B-repeat region were strongly attenuated, while a mutant lacking the conserved C-repeats was only slightly attenuated. Because the HVR of M5 is not required for phagocytosis resistance, our data imply that this HVR plays a major but unknown role during acute infection. The B-repeat region is required for phagocytosis resistance and specifically binds Fg, suggesting that it promotes virulence by binding Fg. However, B-repeat mutants were attenuated even in Fg-deficient mice, implying that the B-repeats may have a second function, in addition to Fg-binding. These data demonstrate that two distinct M5 regions, including the HVR, are essential to virulence during the early stages of an infection. In particular, our data provide the first in vivo evidence that the HVR of an M protein plays a major role in virulence, focusing interest on the molecular role of this region

Protective Activity of Streptococcus pneumoniae Spr1875 Protein Fragments Identified Using a Phage Displayed Genomic Library

There is considerable interest in pneumococcal protein antigens capable of inducing serotype-independent immunoprotection and of improving, thereby, existing vaccines. We report here on the immunogenic properties of a novel surface antigen encoded by ORF spr1875 in the R6 strain genome. An antigenic fragment encoded by spr1875, designated R4, was identified using a Streptococcus pneumoniae phage displayed genomic library after selection with a human convalescent serum. Immunofluorescence analysis with anti-R4 antisera showed that Spr1875 was expressed on the surface of strains belonging to different serotypes. Moreover, the gene was present with little sequence variability in 27 different pneumococcal strains isolated worldwide. A mutant lacking Spr1875 was considerably less virulent than the wild type D39 strain in an intravenous mouse model of infection. Moreover, immunization with the R4 recombinant fragment, but not with the whole Spr1875 protein, induced significant protection against sepsis in mice. Lack of protection after immunization with the whole protein was related to the presence of immunodominant, non-protective epitopes located outside of the R4 fragment. In conclusion, our data indicate that Spr1875 has a role in pneumococcal virulence and is immunogenic. As the R4 fragment conferred immunoprotection from experimental sepsis, selected antigenic fragments of Spr1875 may be useful for the development of a pneumococcal protein-based vaccine

Symmetry-protected exceptional and nodal points in non-Hermitian systems

One of the unique features of non-Hermitian (NH) systems is the appearance of non-Hermitian degeneracies known as exceptional points~(EPs). The occurrence of EPs in NH systems requires satisfying constraints whose number can be reduced in the presence of some symmetries. This results in stabilizing the appearance of EPs. Even though two different types of EPs, namely defective and non-defective EPs, may emerge in NH systems, exploring the possibilities of stabilizing EPs has been only addressed for defective EPs, at which the Hamiltonian becomes non-diagonalizable. In this letter, we show that certain discrete symmetries, namely parity-time, parity-particle-hole, and pseudo-Hermitian symmetry, may guarantee the occurrence of both defective and non-defective EPs. We extend this list of symmetries by including the non-Hermitian time-reversal symmetry in the two-band systems. We further show that the non-defective EPs manifest themselves by i) the diagonalizability of non-Hermitian Hamiltonian at these points and ii) the non-diagonalizability of the Hamiltonian along certain intersections of non-defective EPs. Two-band and four-band models exemplify our findings. Through an example, we further reveal that ordinary (Hermitian) nodal points may coexist with defective EPs in non-Hermitian models when the above symmetries are relaxed

Bovine chromosomal regions affecting rheological traits in acid-induced skim milk gels.

The production of fermented milk products has increased worldwide during the last decade and is expected to continue to increase during the coming decade. The quality of these products may be optimized through breeding practices; however, the relations between cow genetics and technological properties of acid milk gels are not fully known. Therefore, the aim of this study was to identify chromosomal regions affecting acid-induced coagulation properties and possible candidate genes. Skim milk samples from 377 Swedish Red cows were rheologically analyzed for acid-induced coagulation properties using low-amplitude oscillation measurements. The resulting traits, including gel strength, coagulation time, and yield stress, were used to conduct a genome-wide association study. Single nucleotide polymorphisms (SNP) were identified using the BovineHD SNPChip (Illumina Inc., San Diego, CA), resulting in almost 621,000 segregating markers. The genome was scanned for putative quantitative trait loci (QTL) regions, haplotypes based on highly associated SNP were inferred, and the additive genetic effects of haplotypes within each QTL region were analyzed using mixed models. A total of 8 genomic regions were identified, with large effects of the significant haplotype explaining between 4.8 and 9.8% of the phenotypic variance of the studied traits. One major QTL was identified to overlap between gel strength and yield stress, the QTL identified with the most significant SNP closest to the gene coding for κ-casein (CSN3). In addition, a chromosome-wide significant region affecting yield stress on BTA 11 was identified to be colocated with PAEP, coding for β-lactoglobulin. Furthermore, the coagulation properties of the genetic variants within the 2 genes were compared with the coagulation properties identified by the patterns of the haplotypes within the regions, and it was discovered that the haplotypes were more diverse and in one case slightly better at explaining the phenotypic variance. Besides these significant QTL comprising the 2 milk proteins, 3 additional genes are proposed as possible candidates, namely RAB22A, CDH13, and STAT1, and all have previously been found to be expressed in the mammary gland. To our knowledge, this is the first attempt to map QTL regions for acid-induced coagulation properties

Environmental and climate policy integration: Targeted strategies for overcoming barriers to nature-based solutions and climate change adaptation

Nature-based adaptation planning is a challenging endeavor, not least because it requires transdisciplinary approaches to unite different actors' efforts and capacities. However, empirical knowledge on associated governance processes is scarce and fragmented. Against this background, this paper examines the integration of nature-based approaches for climate change adaptation into municipalities’ daily planning practices and associated governance. A city-to-city learning lab was established to systematically analyze selected urban development projects step-by-step, from the initial idea, to comprehensive and detailed planning, procurement, implementation, maintenance and follow-up. The results show the numerous constraints municipal staff face and how they use targeted strategies to overcome them and tap into existing drivers. We identify five, complementary strategies: i) targeted stakeholder collaboration; ii) strategic citizen involvement; iii) outsourcing; iv) the alteration of internal working structures; and v) concealed science–policy integration. Importantly, these strategies reveal an increasing need for relational approaches that, in turn, require individuals to develop the cognitive/emotional capacity to establish trust, communicate inclusively and promote social learning, while at the same time dealing with an increasingly complex and uncertain working environment. We conclude that tapping into the potential of nature-based solutions for climate adaptation governance requires more financial and human resources, and capacity development to support personal development, systematic mainstreaming and, ultimately, more sustainable development

Genetic parameters for rennet- and acid-induced coagulation properties in milk from Swedish Red dairy cows.

Milk coagulation is an important processing trait, being the basis for production of both cheese and fermented products. There is interest in including technological properties of these products in the breeding goal for dairy cattle. The aim of the present study was therefore to estimate genetic parameters for milk coagulation properties, including both rennet- and acid-induced coagulation, in Swedish Red dairy cattle using genomic relationships. Morning milk samples and blood samples were collected from 395 Swedish Red cows that were selected to be as genetically unrelated as possible. Using a rheometer, milk samples were analyzed for rennet- and acid-induced coagulation properties, including gel strength (G'), coagulation time, and yield stress (YS). In addition to the technological traits, milk composition was analyzed. A binary trait was created to reflect that milk samples that had not coagulated 40 min after rennet addition were considered noncoagulating milk. The cows were genotyped by using the Illumina BovineHD BeadChip (Illumina Inc., San Diego, CA). Almost 600,000 markers remained after quality control and were used to construct a matrix of genomic relationships among the cows. Multivariate models including fixed effects of herd, lactation stage, and parity were fitted using the ASReml software to obtain estimates of heritabilities and genetic and phenotypic correlations. Heritability estimates (h(2)) for G' and YS in rennet and acid gels were found to be high (h(2) = 0.38-0.62) and the genetic correlations between rennet-induced and acid-induced coagulation properties were weak but favorable, with the exception of YSrennet with G'acid and YSacid, both of which were strong. The high heritability (h(2) = 0.45) for milk coagulating ability expressed as a binary trait suggests that noncoagulation could be eliminated through breeding. Additionally, the results indicated that the current breeding objective could increase the frequency of noncoagulating milk and lead to deterioration of acid-induced coagulation through unfavorable genetic associations with protein content (0.38) and milk yield (-0.61 to -0.71), respectively. The outcome of this study suggests that by including more detailed compositional traits genetically associated with milk coagulation or by including milk coagulation properties directly within the breeding goal, it appears possible to breed cows that produce milk better suited for production of cheese and fermented products