Geometry and the onset of rigidity in a disordered network

Disordered spring networks that are undercoordinated may abruptly rigidify when sufficient strain is applied. Since the deformation in response to applied strain does not change the generic quantifiers of network architecture - the number of nodes and the number of bonds between them - this rigidity transition must have a geometric origin. Naive, degree-of-freedom based mechanical analyses such as the Maxwell-Calladine count or the pebble game algorithm overlook such geometric rigidity transitions and offer no means of predicting or characterizing them. We apply tools that were developed for the topological analysis of zero modes and states of self-stress on regular lattices to two-dimensional random spring networks, and demonstrate that the onset of rigidity, at a finite simple shear strain $\gamma^\star$, coincides with the appearance of a single state of self stress, accompanied by a single floppy mode. The process conserves the topologically invariant difference between the number of zero modes and the number of states of self stress, but imparts a finite shear modulus to the spring network. Beyond the critical shear, we confirm previously reported critical scaling of the modulus. In the sub-critical regime, a singular value decomposition of the network's compatibility matrix foreshadows the onset of rigidity by way of a continuously vanishing singular value corresponding to nascent state of self stress.Comment: 6 pages, 6 figue

The impact of non-compliance to business processes : a case of a South African commercial bank

This paper investigates the non-compliance of most Business Processes in the implementation of the goals and targets of commercial Banks in Gauteng South Africa. The Banks lose millions of Rands, as a result of staff not adhering to the Business processes. The non-compliance has a major impact on the successful implementation of bank strategy. The study explores why staffs do not adhere to business processes and establishes their level of understanding and maturity in terms of business processes. The study was conducted in selected branches chosen randomly in Gauteng Province. The analysis done was on data obtained from audit reports, bank investigative reports and financial loss data reports provided by different branches. Questionnaires were also administered to staff in the different branches to understand their own perspective. It is evident from the research that non adherence to processes have a financial and reputational impact on the Banks. Non adherence also has detrimental and adverse impact on achieving overall objectives of the Banks. The most common areas not adhered to were notably; identification and verification of customers; transactions not authorised according to laid down procedures; customers cards not cancelled immediately when reported lost or stolen. The paper then concludes with several recommendations to Bank Management and Strategy implementers on how to use technological methods to check and monitor these processes

Deterministic delivery of remote entanglement on a quantum network

Large-scale quantum networks promise to enable secure communication, distributed quantum computing, enhanced sensing and fundamental tests of quantum mechanics through the distribution of entanglement across nodes. Moving beyond current two-node networks requires the rate of entanglement generation between nodes to exceed their decoherence rates. Beyond this critical threshold, intrinsically probabilistic entangling protocols can be subsumed into a powerful building block that deterministically provides remote entangled links at pre-specified times. Here we surpass this threshold using diamond spin qubit nodes separated by 2 metres. We realise a fully heralded single-photon entanglement protocol that achieves entangling rates up to 39 Hz, three orders of magnitude higher than previously demonstrated two-photon protocols on this platform. At the same time, we suppress the decoherence rate of remote entangled states to 5 Hz by dynamical decoupling. By combining these results with efficient charge-state control and mitigation of spectral diffusion, we are able to deterministically deliver a fresh remote state with average entanglement fidelity exceeding 0.5 at every clock cycle of $\sim$100 ms without any pre- or post-selection. These results demonstrate a key building block for extended quantum networks and open the door to entanglement distribution across multiple remote nodes.Comment: v2 - updated to include relevant citatio

Is politics for everyone? :A study on perceived representation, institutional trust, and political participation among individuals with a migration background.

Nederlanders met een migratieachtergrond hebben minder vertrouwen in de politiek en voelen zich vaker niet door de politiek vertegenwoordigd dan Nederlanders zonder een migratieachtergrond. Dat blijkt uit dit onderzoek van het Sociaal en Cultureel Planbureau (SCP). Mensen met een migratieachtergrond vinden vaak dat de politiek niet naar hen luistert en dat onderwerpen die zij belangrijk vinden worden gebagatelliseerd of aan de kant worden geschoven. Gevoelens van uitsluiting spelen hierbij een belangrijke rol: dat zij, en de politici in wie zij zich herkennen en met wie zij zich identificeren, politiek niet volwaardig meedoen en meetellen.Onze democratie functioneert optimaal als iedereen kan participeren, gehoord en vertegenwoordigd wordt en dit ook zo ervaart. Het is dus zorgelijk als een grote groep Nederlanders het idee heeft dat de politiek er niet is ‘voor mensen zoals zij’ en minder geneigd te zijn te gaan stemmen. Er kan op die manier een vicieuze cirkel ontstaan: problemen van kiezersgroepen die minder participeren krijgen minder aandacht, het gevoel er niet toe te doen wordt verder versterkt en dat leidt vervolgens tot een grotere ervaren kloof met de politiek en nog minder politieke aandacht. Om dit te veranderen, kan de politiek zelf een rol spelen

The Proper Motion of SgrA*: I. First VLBA Results

We observed Sgr A* and two extragalactic radio sources nearby in angle with the VLBA over a period of two years and measured relative positions with an accuracy approaching 0.1 mas. The apparent proper motion of Sgr A* relative to J1745-283 is 5.90 +/- 0.4 mas/yr, almost entirely in the plane of the Galaxy. The effects of the orbit of the Sun around the Galactic Center can account for this motion, and any residual proper motion of Sgr A*, with respect to extragalactic sources, is less than about 20 km/s. Assuming that Sgr A* is at rest at the center of the Galaxy, we estimate that the circular rotation speed in the Galaxy at the position of the Sun is 219 +/- 20 km/s, scaled by Ro/8.0 kpc. Current observations are consistent with Sgr A* containing all of the nearly 2.6 x 10^6 solar masses, deduced from stellar proper motions, in the form of a massive black hole. While the low luminosity of Sgr A*, for example, might possibly have come from a contact binary containing of order 10 solar masses, the lack of substantial motion rules out a "stellar" origin for Sgr A*. The very slow speed of Sgr A* yields a lower limit to the mass of Sgr A* of about 1,000 solar masses. Even for this mass, Sgr A* appears to be radiating at less than 0.1 percent of its Eddington limit

Self-stresses control stiffness and stability in overconstrained disordered networks

We investigate the interplay between pre-stress and mechanical properties in random elastic networks. To do this in a controlled fashion, we introduce an algorithm for creating random freestanding frames that support exactly one state of self stress. By multiplying all the bond tensions in this state of self stress by the same number---which with the appropriate normalization corresponds to the physical pre-stress inside the frame---we systematically evaluate the linear mechanical response of the frame as a function of pre-stress. After proving that the mechanical moduli of affinely deforming frames are rigourously independent of pre-stress, we turn to non-affinely deforming frames. In such frames, pre-stress has a profound effect on linear response: not only can it change the values of the linear modulus---an effect we demonstrate to be related to a suppressive effect of pre-stress on non-affinity---but pre-stresses also generically trigger bistable mechanical response. Thus, pre-stress can be leveraged to both augment the mechanical response of network architectures on the fly, and to actuate finite deformations. These control modalities may be of use in the design of both novel responsive materials and soft actuators.Comment: 13 pages, 9 figure