Mustaherukan kukankehitys ja marjanmuodostus

Development of flower primordia in the areas north of the 60th latitude is scarcely known. The differentiation data on Lepaan musta (Lepaa black), Brödtorp, Wellington xxx and of Silvergieter (Silvergieters Zwarte) in Viik, close to Helsinki, are given (Tables 2 and 3). Table 4 gives the differentiation stages of Lepaan musta, Brödtorp, Wellington xxx and of Laxtons Tinker on four latitudes in Finland. It is clear that differentiation is delayed by the long day in the north (Table 5) and that a daylength of less than 13 hours favours the differentiation process. This was confirmed in tests with an artificial prolonging of the day (Table 6). The Finnish varieties Lepaan musta and Brödtorp seem to be more adapted to the long day conditions than Wellington xxx and Laxtons Tinker. Development of the primordia occurs during winter, despite the temperature remaining far below zero, until the fifth stage (9, 20), where overwintering occurs (Table 3). Flowering data are given in Table 7. In pollination tests in 1963 and 1964 it was shown that Lepaan musta belongs to the completely self-fertile varieties, Brödtorp to partially self-fertile ones (7, 8, 12). On Lepaan musta and Brödtorp the intrafloral self-pollination gave better berry formation than interfloral self-pollination. Of the pollinating varieties Wellington xxx was more vigorous than the domestic varieties Lepaan musta for Brödtorp and vice versa (Tables 8 and 9). »Running off» in the tests was stated to depend on a low number of seeds in the berries (Table 10). Close correlation existed between the size of berry and the number of seeds (Figures 2 and 3).Lepaan musta -lajikkeen kukanaiheiden erilaistuminen alkaa Viikissä heinäkuun 10. p:n, Rovaniemellä elokuun 10. p:n aikaan. Talvehtivan asteen kukanaiheet saavuttavat lokakuun loppuun mennessä. Brödtorpin kukanaiheiden erilaistuminen alkaa Viikissä kolmea viikkoa myöhemmin kuin Lepaan mustan kukanaiheiden, ja viimeiset kukanaiheet ovat talvehtimisasteella tammikuun puolivälissä. Ulkomaisista lajikkeista Wellington xxx:n kukanaiheiden erilaistuminen alkoi Viikissä elokuun puolivälissä, Silvergieterin ja Laxtons Tinkerin kukanaiheiden elokuun 20. p:n aikaan, Oulun seudulla vastaavasti syyskuun 5. p:n aikaan ja lokakuun alussa, Rovaniemen korkeudella syyskuun 20. p:n ja lokakuun 1. p:n aikaan. Mustaherukan kukanaiheiden erilaistuminen alkoi eri osissa maata vasta sen jälkeen kun luontainen päivä oli lyhennyt noin 13 tunnin pituiseksi. Tätä pitempi päivä viivyttää kukanaiheiden kehitystä, joten sanottu kehitys kasvissa on kvantitatiivisesti lyhyenpäivän reaktio. Kotimaiset lajikkeet Lepaan musta ja Brödtorp ovat tässä suhteessa paremmin sopeutuneet pitkänpäivän olosuhteisiin kuin ulkomaiset Wellington xxx ja Laxtons Tinker. Eri lajikkeiden kukinta alkoi Viikissä vuonna 1962 2—4 päivää myöhemmin ja kesti 2—3 viikkoa kauemmin kuin v. 1963. Syynä näytti olevan alhaisempi toukokuun ja kesäkuun lämpötila v. 1962. Lepaan musta kuuluu pölytyskokeiden perusteella täysin itsefertiileihin mustaherukkalajikkeisiin, Brödtorp osittain itsefertiileihin. Kumpaakin voidaan viljellä yksinomaisena lajikkeena, mutta Brödtorpin satoisuus on parempi, jos pölytys tapahtuu vieraan lajikkeen siitepölyllä. Kummallekin lajikkeelle aiheutti kukansisäinen pölytys paremman marjanmuodostuksen kuin lajikkeensisäinen kukkien välinen pölytys

Spacetime topology from the tomographic histories approach: Part II

As an inverse problem, we recover the topology of the effective spacetime that a system lies in, in an operational way. This means that from a series of experiments we get a set of points corresponding to events. This continues the previous work done by the authors. Here we use the existence of upper bound in the speed of transfer of matter and information to induce a partial order on the set of events. While the actual partial order is not known in our operational set up, the grouping of events to (unordered) subsets corresponding to possible histories, is given. From this we recover the partial order up to certain ambiguities that are then classified. Finally two different ways to recover the topology are sketched and their interpretation is discussed.Comment: 21 pages, slight change in title and certain minor corrections in this second version. To apear in IJT

Spacetime topology from the tomographic histories approach I: Non-relativistic Case

The tomographic histories approach is presented. As an inverse problem, we recover in an operational way the effective topology of the extended configuration space of a system. This means that from a series of experiments we get a set of points corresponding to events. The difference between effective and actual topology is drawn. We deduce the topology of the extended configuration space of a non-relativistic system, using certain concepts from the consistent histories approach to Quantum Mechanics, such as the notion of a record. A few remarks about the case of a relativistic system, preparing the ground for a forthcoming paper sequel to this, are made in the end.Comment: 19 pages, slight chang in title and corrected typos in second version. To appear to a special proceedings issue (Glafka 2004) of the International Journal of Theoretical Physic

Causal Sets: Quantum gravity from a fundamentally discrete spacetime

In order to construct a quantum theory of gravity, we may have to abandon certain assumptions we were making. In particular, the concept of spacetime as a continuum substratum is questioned. Causal Sets is an attempt to construct a quantum theory of gravity starting with a fundamentally discrete spacetime. In this contribution we review the whole approach, focusing on some recent developments in the kinematics and dynamics of the approach.Comment: 10 pages, review of causal sets based on talk given at the 1st MCCQG conferenc

Dynamics & Predictions in the Co-Event Interpretation

Sorkin has introduced a new, observer independent, interpretation of quantum mechanics that can give a successful realist account of the 'quantum microworld' as well as explaining how classicality emerges at the level of observable events for a range of systems including single time 'Copenhagen measurements'. This 'co-event interpretation' presents us with a new ontology, in which a single 'co-event' is real. A new ontology necessitates a review of the dynamical & predictive mechanism of a theory, and in this paper we begin the process by exploring means of expressing the dynamical and predictive content of histories theories in terms of co-events.Comment: 35 pages. Revised after refereein

Spacelike distance from discrete causal order

Any discrete approach to quantum gravity must provide some prescription as to how to deduce continuum properties from the discrete substructure. In the causal set approach it is straightforward to deduce timelike distances, but surprisingly difficult to extract spacelike distances, because of the unique combination of discreteness with local Lorentz invariance in that approach. We propose a number of methods to overcome this difficulty, one of which reproduces the spatial distance between two points in a finite region of Minkowski space. We provide numerical evidence that this definition can be used to define a `spatial nearest neighbor' relation on a causal set, and conjecture that this can be exploited to define the length of `continuous curves' in causal sets which are approximated by curved spacetime. This provides evidence in support of the ``Hauptvermutung'' of causal sets.Comment: 32 pages, 16 figures, revtex4; journal versio

Recent advances in the structural and molecular biology of type IV secretion systems

Bacteria use type IV secretion (T4S) systems to deliver DNA and protein substrates to a diverse range of prokaryotic and eukaryotic target cells. T4S systems have great impact on human health, as they are a major source of antibiotic resistance spread among bacteria and are central to infection processes of many pathogens. Therefore, deciphering the structure and underlying translocation mechanism of T4S systems is crucial to facilitate development of new drugs. The last five years have witnessed considerable progress in unraveling the structure of T4S system subassemblies, notably that of the T4S system core complex, a large 1 MegaDalton (MDa) structure embedded in the double membrane of Gram-negative bacteria and made of 3 of the 12 T4S system components. However, the recent determination of the structure of ∼3 MDa assembly of 8 of these components has revolutionized our views of T4S system architecture and opened up new avenues of research, which are discussed in this review

Realization of Quantum Digital Signatures without the Requirement of Quantum Memory

Digital signatures are widely used to provide security for electronic communications, for example in financial transactions and electronic mail. Currently used classical digital signature schemes, however, only offer security relying on unproven computational assumptions. In contrast, quantum digital signatures (QDS) offer information-theoretic security based on laws of quantum mechanics (e.g. Gottesman and Chuang 2001). Here, security against forging relies on the impossibility of perfectly distinguishing between non-orthogonal quantum states. A serious drawback of previous QDS schemes is however that they require long-term quantum memory, making them unfeasible in practice. We present the first realisation of a scheme (Dunjko et al 2013) that does not need quantum memory, and which also uses only standard linear optical components and photodetectors. To achieve this, the recipients measure the distributed quantum signature states using a new type of quantum measurement, quantum state elimination (e.g. Barnett 2009, Bandyopadhyay et al 2013). This significantly advances QDS as a quantum technology with potential for real applications.Comment: 18 pages, 4 figures. Vesrion accepted in PRL. In v3 small change of title and substancial rewriting of parts of the paper following suggestion of referee. Part of the security analysis included in the appendix (supplementary material) for completeness, is similar to the one in our earlier paper arXiv:1309.1375, since it uses similar methods applied to a different settin

The Generalized Second Law implies a Quantum Singularity Theorem

The generalized second law can be used to prove a singularity theorem, by generalizing the notion of a trapped surface to quantum situations. Like Penrose's original singularity theorem, it implies that spacetime is null geodesically incomplete inside black holes, and to the past of spatially infinite Friedmann--Robertson--Walker cosmologies. If space is finite instead, the generalized second law requires that there only be a finite amount of entropy producing processes in the past, unless there is a reversal of the arrow of time. In asymptotically flat spacetime, the generalized second law also rules out traversable wormholes, negative masses, and other forms of faster-than-light travel between asymptotic regions, as well as closed timelike curves. Furthermore it is impossible to form baby universes which eventually become independent of the mother universe, or to restart inflation. Since the semiclassical approximation is used only in regions with low curvature, it is argued that the results may hold in full quantum gravity. An introductory section describes the second law and its time-reverse, in ordinary and generalized thermodynamics, using either the fine-grained or the coarse-grained entropy. (The fine-grained version is used in all results except those relating to the arrow of time.) A proof of the coarse-grained ordinary second law is given.Comment: 46 pages, 8 figures. v2: discussion of global hyperbolicity revised (4.1, 5.2), more comments on AdS. v3: major revisions including change of title. v4: similar to published version, but with corrections to plan of paper (1) and definition of global hyperbolicity (3.2). v5: fixed proof of Thm. 1, changed wording of Thm. 3 & proof of Thm. 4, revised Sec. 5.2, new footnote