18,181 research outputs found
Cyber Security Awareness Among College Students
This study reports the early results of a study aimed to investigate student awareness and attitudes toward cyber security and the resulting risks in the most advanced technology environment: the Silicon Valley in California, USA. The composition of students in Silicon Valley is very ethnically diverse. The objective was to see how much the students in such a tech-savvy environment are aware of cyber-attacks and how they protect themselves against them. The early statistical analysis suggested that college students, despite their belief that they are observed when using the Internet and that their data is not secure even on university systems, are not very aware of how to protect their data. Also, it appears that educational institutions do not have an active approach to improve awareness among college students to increase their knowledge on these issues and how to protect themselves from potential cyber-attacks, such as identity theft or ransomware
On the Wake Structure in Streaming Complex Plasmas
The theoretical description of complex (dusty) plasmas requires multiscale
concepts that adequately incorporate the correlated interplay of streaming
electrons and ions, neutrals, and dust grains. Knowing the effective dust-dust
interaction, the multiscale problem can be effectively reduced to a
one-component plasma model of the dust subsystem. The goal of the present
publication is a systematic evaluation of the electrostatic potential
distribution around a dust grain in the presence of a streaming plasma
environment by means of two complementary approaches: (i) a high precision
computation of the dynamically screened Coulomb potential from the dynamic
dielectric function, and (ii) full 3D particle-in-cell simulations, which
self-consistently include dynamical grain charging and non-linear effects. The
applicability of these two approaches is addressed
A three-dimensional hydrodynamical line profile analysis of iron lines and barium isotopes in HD140283
Heavy-elements, i.e. those beyond the iron peak, mostly form via two neutron
capture processes: the s- and r-process. Metal-poor stars should contain fewer
isotopes that form via the s-process, according to currently accepted theory.
It has been shown in several investigations that theory and observation do not
agree well, raising questions on the validity of either the methodology or the
theory. We analyse the metal-poor star HD140283, for which we have a high
quality spectrum. We test whether a 3D LTE stellar atmosphere and spectrum
synthesis code permits a more reliable analysis of the iron abundance and
barium isotope ratio than a 1D LTE analysis. Using 3D model atmospheres, we
examine 91 iron lines of varying strength and formation depth. This provides us
with the star's rotational speed. With this, we model the barium isotope ratio
by exploiting the hyperfine structure of the singly ionised 4554 resonance
line, and study the impact of the uncertainties in the stellar parameters.
HD140283's vsini = 1.65 +/- 0.05 km/s. Barium isotopes under the 3D paradigm
show a dominant r-process signature as 77 +/- 6 +/- 17% of barium isotopes form
via the r-process, where errors represent the assigned random and systematic
errors, respectively. We find that 3D LTE fits reproduce iron line profiles
better than those in 1D, but do not provide a unique abundance (within the
uncertainties). However, we demonstrate that the isotopic ratio is robust
against this shortcoming. Our barium isotope result agrees well with currently
accepted theory regarding the formation of the heavy-elements during the early
Galaxy. The improved fit to the asymmetric iron line profiles suggests that the
current state of 3D LTE modelling provides excellent simulations of fluid
flows. However, the abundances they provide are not yet self-consistent. This
may improve with NLTE considerations and higher resolution models.Comment: 16 pages, 10 figures, 5 tables. Accepted for publication in A&
Quantum phase transition in Bose-Fermi mixtures
We study a quantum Bose-Fermi mixture near a broad Feshbach resonance at zero
temperature. Within a quantum field theoretical model a two-step Gaussian
approximation allows to capture the main features of the quantum phase diagram.
We show that a repulsive boson-boson interaction is necessary for thermodynamic
stability. The quantum phase diagram is mapped in chemical potential and
density space, and both first and second order quantum phase transitions are
found. We discuss typical characteristics of the first order transition, such
as hysteresis or a droplet formation of the condensate which may be searched
for experimentally.Comment: 16 pages, 17 figures; typos corrected, one figure adde
Chlorinated auxins–how does Arabidopsis thaliana deal with them?
Plant hormones have various functions in plants and play crucial roles in all developmental and differentiation stages. Auxins constitute one of the most important groups with the major representative indole-3-acetic acid (IAA). A halogenated derivate of IAA, 4-chloro-indole-3-acetic acid (4-Cl-IAA), has previously been identified in Pisum sativum and other legumes. While the enzymes responsible for the halogenation of compounds in bacteria and fungi are well studied, the metabolic pathways leading to the production of 4-Cl-IAA in plants, especially the halogenating reaction, are still unknown. Therefore, bacterial flavin-dependent tryptophan-halogenase genes were transformed into the model organism Arabidopsis thaliana. The type of chlorinated indole derivatives that could be expected was determined by incubating wild type A. thaliana with different Cl-tryptophan derivatives. We showed that, in addition to chlorinated IAA, chlorinated IAA conjugates were synthesized. Concomitantly, we found that an auxin conjugate synthetase (GH3.3 protein) from A. thaliana was able to convert chlorinated IAAs to amino acid conjugates in vitro. In addition, we showed that the production of halogenated tryptophan (Trp), indole-3-acetonitrile (IAN) and IAA is possible in transgenic A. thaliana in planta with the help of the bacterial halogenating enzymes. Furthermore, it was investigated if there is an effect (i) of exogenously applied Cl-IAA and Cl-Trp and (ii) of endogenously chlorinated substances on the growth phenotype of the plants
Optomechanical circuits for nanomechanical continuous variable quantum state processing
We propose and analyze a nanomechanical architecture where light is used to
perform linear quantum operations on a set of many vibrational modes. Suitable
amplitude modulation of a single laser beam is shown to generate squeezing,
entanglement, and state-transfer between modes that are selected according to
their mechanical oscillation frequency. Current optomechanical devices based on
photonic crystals may provide a platform for realizing this scheme.Comment: 11 pages, 5 figure
Intrinsically Legal-For-Trade Objects by Digital Signatures
The established techniques for legal-for-trade registration of weight values
meet the legal requirements, but in praxis they show serious disadvantages. We
report on the first implementation of intrinsically legal-for-trade objects,
namely weight values signed by the scale, that is accepted by the approval
authority. The strict requirements from both the approval- and the
verification-authority as well as the limitations due to the hardware of the
scale were a special challenge. The presented solution fulfills all legal
requirements and eliminates the existing practical disadvantages.Comment: 4 pages, 0 figure
Underground Gun Markets
This paper provides an economic analysis of underground gun markets drawing on interviews with gang members, gun dealers, professional thieves, prostitutes, police, public school security guards and teens in the city of Chicago, complemented by results from government surveys of recent arrestees in 22 cities plus administrative data for suicides, homicides, robberies, arrests and confiscated crime guns. We find evidence of considerable frictions in the underground market for guns in Chicago. We argue that these frictions are due primarily to the fact that the underground gun market is both illegal and %u201Cthin%u201D -- the number of buyers, sellers and total transactions is small and relevant information is scarce. Gangs can help overcome these market frictions, but the gang%u2019s economic interests cause gang leaders to limit supply primarily to gang members, and even then transactions are usually loans or rentals with strings attached.
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