Quantum Analogue Computing

We briefly review what a quantum computer is, what it promises to do for us, and why it is so hard to build one. Among the first applications anticipated to bear fruit is quantum simulation of quantum systems. While most quantum computation is an extension of classical digital computation, quantum simulation differs fundamentally in how the data is encoded in the quantum computer. To perform a quantum simulation, the Hilbert space of the system to be simulated is mapped directly onto the Hilbert space of the (logical) qubits in the quantum computer. This type of direct correspondence is how data is encoded in a classical analogue computer. There is no binary encoding, and increasing precision becomes exponentially costly: an extra bit of precision doubles the size of the computer. This has important consequences for both the precision and error correction requirements of quantum simulation, and significant open questions remain about its practicality. It also means that the quantum version of analogue computers, continuous variable quantum computers (CVQC) becomes an equally efficient architecture for quantum simulation. Lessons from past use of classical analogue computers can help us to build better quantum simulators in future.Comment: 10 pages, to appear in the Visions 2010 issue of Phil. Trans. Roy. Soc.

Firefighters: Hostility and world assumptions

The present project was intended to provide an initial exploratory investigation into the relationship between hostility and world assumptions for a firefighting sample. Specifically, we hypothesized that increased hostility would be associated with more negative assumptions with respect to world benevolence, world justness, and self-worth, and that these variables would also be related to years of service and self-reported mental health. The current study was part of a larger study with firefighters from British Columbia, Canada, and included 186 paid-professional firefighters who completed a series of questionnaires. We demonstrated that, for our firefighting sample, hostility was related to both world benevolence and self-worth across multiple measures, even while controlling for the individual characteristic neuroticism. We did not find any significant relationship with years of service, but world benevolence and self-worth were also important in the prediction of mental health outcomes. These findings may have clinical or occupational intervention implications in therapeutic relationships with firefighters, in that the present project demonstrated a first indication that reduced hostility in combination with increased positivity in world assumptions may help achieve good mental health

Diesel Exhaust Activates & Primes Microglia: Air Pollution, Neuroinflammation, & Regulation of Dopaminergic Neurotoxicity

BACKGROUND: Air pollution is linked to central nervous system disease, but the mechanisms responsible are poorly understood. OBJECTIVES: Here, we sought to address the brain-region-specific effects of diesel exhaust (DE) and key cellular mechanisms underlying DE-induced microglia activation, neuroinflammation, and dopaminergic (DA) neurotoxicity. METHODS: Rats were exposed to DE (2.0, 0.5, and 0 mg/m3) by inhalation over 4 weeks or as a single intratracheal administration of DE particles (DEP; 20 mg/kg). Primary neuron-glia cultures and the HAPI (highly aggressively proliferating immortalized) microglial cell line were used to explore cellular mechanisms. RESULTS: Rats exposed to DE by inhalation demonstrated elevated levels of whole-brain IL-6 (interleukin-6) protein, nitrated proteins, and IBA-1 (ionized calcium-binding adaptor molecule 1) protein (microglial marker), indicating generalized neuroinflammation. Analysis by brain region revealed that DE increased TNFα (tumor necrosis factor-α), IL-1β, IL-6, MIP-1α (macrophage inflammatory protein-1α) RAGE (receptor for advanced glycation end products), fractalkine, and the IBA-1 microglial marker in most regions tested, with the midbrain showing the greatest DE response. Intratracheal administration of DEP increased microglial IBA-1 staining in the substantia nigra and elevated both serum and whole-brain TNFα at 6 hr posttreatment. Although DEP alone failed to cause the production of cytokines and chemokines, DEP (5 μg/mL) pretreatment followed by lipopolysaccharide (2.5 ng/mL) in vitro synergistically amplified nitric oxide production, TNFα release, and DA neurotoxicity. Pretreatment with fractalkine (50 pg/mL) in vitro ameliorated DEP (50 μg/mL)-induced microglial hydrogen peroxide production and DA neurotoxicity. CONCLUSIONS: Together, these findings reveal complex, interacting mechanisms responsible for how air pollution may cause neuroinflammation and DA neurotoxicity

Diesel Exhaust Activates and Primes Microglia: Air Pollution, Neuroinflammation, and Regulation of Dopaminergic Neurotoxicity

Background: Air pollution is linked to central nervous system disease, but the mechanisms responsible are poorly understood

The Value of Information for Populations in Varying Environments

The notion of information pervades informal descriptions of biological systems, but formal treatments face the problem of defining a quantitative measure of information rooted in a concept of fitness, which is itself an elusive notion. Here, we present a model of population dynamics where this problem is amenable to a mathematical analysis. In the limit where any information about future environmental variations is common to the members of the population, our model is equivalent to known models of financial investment. In this case, the population can be interpreted as a portfolio of financial assets and previous analyses have shown that a key quantity of Shannon's communication theory, the mutual information, sets a fundamental limit on the value of information. We show that this bound can be violated when accounting for features that are irrelevant in finance but inherent to biological systems, such as the stochasticity present at the individual level. This leads us to generalize the measures of uncertainty and information usually encountered in information theory

Acute Trauma Factor Associations With Suicidality Across the First 5 Years After Traumatic Brain Injury

AbstractObjectiveTo determine whether severity of head and extracranial injuries (ECI) is associated with suicidal ideation (SI) or suicide attempt (SA) after traumatic brain injury (TBI).DesignFactors associated with SI and SA were assessed in this inception cohort study using data collected 1, 2, and 5 years post-TBI from the National Trauma Data Bank and Traumatic Brain Injury Model Systems (TBIMS) databases.SettingLevel I trauma centers, inpatient rehabilitation centers, and the community.ParticipantsParticipants with TBI from 15 TBIMS Centers with linked National Trauma Data Bank trauma data (N=3575).InterventionsNot applicable.Main Outcome MeasuresSI was measured via the Patient Health Questionnaire 9 (question 9). SA in the last year was assessed via interview. ECI was measured by the Injury Severity Scale (nonhead) and categorized as none, mild, moderate, or severe.ResultsThere were 293 (8.2%) participants who had SI without SA and 109 (3.0%) who had SA at least once in the first 5 years postinjury. Random effects logit modeling showed a higher likelihood of SI when ECI was severe (odds ratio=2.73; 95% confidence interval, 1.55–4.82; P=.001). Drug use at time of injury was also associated with SI (odds ratio=1.69; 95% confidence interval, 1.11–2.86; P=.015). Severity of ECI was not associated with SA.ConclusionsSevere ECI carried a nearly 3-fold increase in the odds of SI after TBI, but it was not related to SA. Head injury severity and less severe ECI were not associated with SI or SA. These findings warrant additional work to identify factors associated with severe ECI that make individuals more susceptible to SI after TBI

Soil organisms in organic and conventional cropping systems.

Apesar do crescente interesse pela agricultura orgânica, são poucas as informações de pesquisa disponíveis sobre o assunto. Assim, num Argissolo Vermelho-Amarelo distrófico foram comparados os efeitos de sistemas de cultivo orgânico e convencional, para as culturas do tomate (Lycopersicum esculentum) e do milho (Zea mays), sobre a comunidade de organismos do solo e suas atividades. As populações de fungos,bactérias e actinomicetos, determinadas pela contagem de colônias em meio de cultura, foram semelhantes para os dois sistemas de produção. A atividade microbiana, avaliada pela evolução de CO2, manteve-se superior no sistema orgânico, sendo que em determinadas avaliações foi o dobro da evolução verificada no sistema convencional. O número de espécimes de minhoca foi praticamente dez vezes maior no sistema orgânico. Não foi observada diferença na taxa de decomposição de matéria orgânica entre os dois sistemas. De modo geral, o número de indivíduos de microartrópodos foi superior no sistema orgânico do que no sistema convencional, refletindo no maior índice de diversidade de Shannon. As maiores populações de insetos foram as da ordem Collembola, enquanto para os ácaros a maior população foi a da superfamília Oribatuloidea. Indivíduos dos grupos Aranae, Chilopoda, Dyplopoda, Pauropoda, Protura e Symphyla foram ocasionalmente coletados e de forma similar entre os sistemas

Evidence for charge localization in the ferromagnetic phase of La_(1-x)Ca_(x)MnO_3 from High real-space-resolution x-ray diffraction

High real-space-resolution atomic pair distribution functions of La_(1-x)Ca_(x)MnO_3 (x=0.12, 0.25 and 0.33) have been measured using high-energy x-ray powder diffraction to study the size and shape of the MnO_6 octahedron as a function of temperature and doping. In the paramagnetic insulating phase we find evidence for three distinct bond-lengths (~ 1.88, 1.95 and 2.15A) which we ascribe to Mn^{4+}-O, Mn^{3+}-O short and Mn^{3+}-O long bonds respectively. In the ferromagnetic metallic (FM) phase, for x=0.33 and T=20K, we find a single Mn-O bond-length; however, as the metal-insulator transition is approached either by increasing T or decreasing x, intensity progressively appears around r=2.15 and in the region 1.8 - 1.9A suggesting the appearance of Mn^{3+}-O long bonds and short Mn^{4+}-O bonds. This is strong evidence that charge localized and delocalized phases coexist close to the metal-insulator transition in the FM phase.Comment: 8 pages, 8 postscript figures, submitted to Phys. Rev.

Sociological and Communication-Theoretical Perspectives on the Commercialization of the Sciences

Both self-organization and organization are important for the further development of the sciences: the two dynamics condition and enable each other. Commercial and public considerations can interact and "interpenetrate" in historical organization; different codes of communication are then "recombined." However, self-organization in the symbolically generalized codes of communication can be expected to operate at the global level. The Triple Helix model allows for both a neo-institutional appreciation in terms of historical networks of university-industry-government relations and a neo-evolutionary interpretation in terms of three functions: (i) novelty production, (i) wealth generation, and (iii) political control. Using this model, one can appreciate both subdynamics. The mutual information in three dimensions enables us to measure the trade-off between organization and self-organization as a possible synergy. The question of optimization between commercial and public interests in the different sciences can thus be made empirical.Comment: Science & Education (forthcoming

Deep structure of the Porcupine Basin from wide-angle seismic data

The Porcupine Basin, part of the frontier petroleum exploration province west of Ireland, has an extended history that commenced prior to the opening of the North Atlantic Ocean. Lithospheric stretching factors have previously been estimated to increase from 6 in the south of the basin. Thus, it is an ideal location to study the processes leading to hyper-extension on continental margins. The Porcupine Median Ridge (PMR) is located in the south of the basin and has been alternatively interpreted as a volcanic feature, a serpentinite mud diapir or a tilted block of continental crust. Each of these interpretations has different implications for the thermal history of the basin. We present results from travel-time tomographic modelling of two approximately 300 km-long wide-angle seismic profiles across the northern and southern parts of the basin. Our results show: (1) the geometry of the crust, with maximum crustal stretching factors of up to 6 and 10 along the northern and southern profiles, respectively; (2) asymmetry of the basin structures, suggesting some simple shear during extension; (3) low velocities beneath the Moho that could represent either partially serpentinized mantle or mafic under-plating; and (4) a possible igneous composition of the PMR