Extracting dynamical equations from experimental data is NP-hard

The behavior of any physical system is governed by its underlying dynamical equations. Much of physics is concerned with discovering these dynamical equations and understanding their consequences. In this work, we show that, remarkably, identifying the underlying dynamical equation from any amount of experimental data, however precise, is a provably computationally hard problem (it is NP-hard), both for classical and quantum mechanical systems. As a by-product of this work, we give complexity-theoretic answers to both the quantum and classical embedding problems, two long-standing open problems in mathematics (the classical problem, in particular, dating back over 70 years).Comment: For mathematical details, see arXiv:0908.2128[math-ph]. v2: final version, accepted in Phys. Rev. Let

Preasymptotic Convergence of Randomized Kaczmarz Method

Kaczmarz method is one popular iterative method for solving inverse problems, especially in computed tomography. Recently, it was established that a randomized version of the method enjoys an exponential convergence for well-posed problems, and the convergence rate is determined by a variant of the condition number. In this work, we analyze the preasymptotic convergence behavior of the randomized Kaczmarz method, and show that the low-frequency error (with respect to the right singular vectors) decays faster during first iterations than the high-frequency error. Under the assumption that the inverse solution is smooth (e.g., sourcewise representation), the result explains the fast empirical convergence behavior, thereby shedding new insights into the excellent performance of the randomized Kaczmarz method in practice. Further, we propose a simple strategy to stabilize the asymptotic convergence of the iteration by means of variance reduction. We provide extensive numerical experiments to confirm the analysis and to elucidate the behavior of the algorithms.Comment: 20 page

From a rare inhabitant into a potential pest - status of the nun moth in Finland based on pheromone trapping

Forests are affected by climate change in various ways. This includes abiotic factors such as droughts, but also biotic damage by pest insects. There are numerous examples from cases where pest insects have benefitted from longer growing seasons or from warmer summers. Similarly, new pest insects have been able to expand their range due to climatic conditions that have changed from hostile to tolerable. Such seems to be the case with the nun moth (Lymantria monacha), an important defoliator of coniferous trees in Europe. For centuries, the species has had massive outbreaks across Central-Europe, while it has been a rare inhabitant in Northern Europe. Recently, the nun moth population in Finland has not only expanded in range, but also grown more abundant. This research note describes the results from the first years (2018-2019) of a monitoring program that is being conducted with pheromone traps across central and southern Finland. So far, the northernmost individuals were trapped near the 64 N degrees. However, there were more southern locations where no moths were trapped. The species was present in every trapping site below the latitude of 62 N degrees. More importantly, at some sites the abundance of the nun moth suggested that local forest damage may already occur. Given the current climatic scenarios for Fennoscandia, it is likely that the nun moth populations will continue to grow. which is why systematic surveys on their abundance and range expansions will be topical

An insulin hypersecretion phenotype precedes pancreatic β cell failure in MODY3 patient-specific cells

MODY3 is a monogenic hereditary form of diabetes caused by mutations in the transcription factor HNF1A. The patients progressively develop hyperglycemia due to perturbed insulin secretion, but the pathogenesis is unknown. Using patient-specific hiPSCs, we recapitulate the insulin secretion sensitivity to the membrane depolarizing agent sulfonylurea commonly observed in MODY3 patients. Unexpectedly, MODY3 patient-specific HNF1A+/R272C β cells hypersecrete insulin both in vitro and in vivo after transplantation into mice. Consistently, we identified a trend of increased birth weight in human HNF1A mutation carriers compared with healthy siblings. Reduced expression of potassium channels, specifically the KATP channel, in MODY3 β cells, increased calcium signaling, and rescue of the insulin hypersecretion phenotype by pharmacological targeting ATP-sensitive potassium channels or low-voltage-activated calcium channels suggest that more efficient membrane depolarization underlies the hypersecretion of insulin in MODY3 β cells. Our findings identify a pathogenic mechanism leading to β cell failure in MODY3.Peer reviewe

The impact of an intervention to introduce malaria rapid diagnostic tests on fever case management in a high transmission setting in Uganda: A mixed-methods cluster-randomized trial (PRIME).

Rapid diagnostic tests for malaria (mRDTs) have been scaled-up widely across Africa. The PRIME study evaluated an intervention aiming to improve fever case management using mRDTs at public health centers in Uganda. A cluster-randomized trial was conducted from 2010-13 in Tororo, a high malaria transmission setting. Twenty public health centers were randomized in a 1:1 ratio to intervention or control. The intervention included training in health center management, fever case management with mRDTs, and patient-centered services; plus provision of mRDTs and artemether-lumefantrine (AL) when stocks ran low. Three rounds of Interviews were conducted with caregivers of children under five years of age as they exited health centers (N = 1400); reference mRDTs were done in children with fever (N = 1336). Health worker perspectives on mRDTs were elicited through semi-structured questionnaires (N = 49) and in-depth interviews (N = 10). The primary outcome was inappropriate treatment of malaria, defined as the proportion of febrile children who were not treated according to guidelines based on the reference mRDT. There was no difference in inappropriate treatment of malaria between the intervention and control arms (24.0% versus 29.7%, adjusted risk ratio 0.81 95\% CI: 0.56, 1.17 p = 0.24). Most children (76.0\%) tested positive by reference mRDT, but many were not prescribed AL (22.5\% intervention versus 25.9\% control, p = 0.53). Inappropriate treatment of children testing negative by reference mRDT with AL was also common (31.3\% invention vs 42.4\% control, p = 0.29). Health workers appreciated mRDTs but felt that integrating testing into practice was challenging given constraints on time and infrastructure. The PRIME intervention did not have the desired impact on inappropriate treatment of malaria for children under five. In this high transmission setting, use of mRDTs did not lead to the reductions in antimalarial prescribing seen elsewhere. Broader investment in health systems, including infrastructure and staffing, will be required to improve fever case management

High Effective Coverage of Vector Control Interventions in Children After Achieving Low Malaria Transmission in Zanzibar, Tanzania.

\ud \ud Formerly a high malaria transmission area, Zanzibar is now targeting malaria elimination. A major challenge is to avoid resurgence of malaria, the success of which includes maintaining high effective coverage of vector control interventions such as bed nets and indoor residual spraying (IRS). In this study, caretakers' continued use of preventive measures for their children is evaluated, following a sharp reduction in malaria transmission. A cross-sectional community-based survey was conducted in June 2009 in North A and Micheweni districts in Zanzibar. Households were randomly selected using two-stage cluster sampling. Interviews were conducted with 560 caretakers of under-five-year old children, who were asked about perceptions on the malaria situation, vector control, household assets, and intention for continued use of vector control as malaria burden further decreases. Effective coverage of vector control interventions for under-five children remains high, although most caretakers (65%; 363/560) did not perceive malaria as presently being a major health issue. Seventy percent (447/643) of the under-five children slept under a long-lasting insecticidal net (LLIN) and 94% (607/643) were living in houses targeted with IRS. In total, 98% (628/643) of the children were covered by at least one of the vector control interventions. Seasonal bed-net use for children was reported by 25% (125/508) of caretakers of children who used bed nets. A high proportion of caretakers (95%; 500/524) stated that they intended to continue using preventive measures for their under-five children as malaria burden further reduces. Malaria risk perceptions and different perceptions of vector control were not found to be significantly associated with LLIN effective coverage While the majority of caretakers felt that malaria had been reduced in Zanzibar, effective coverage of vector control interventions remained high. Caretakers appreciated the interventions and recognized the value of sustaining their use. Thus, sustaining high effective coverage of vector control interventions, which is crucial for reaching malaria elimination in Zanzibar, can be achieved by maintaining effective delivery of these interventions

Type-i Optical Emissions In Gesi Quantum Dots

The authors studied the optical emission of GeSi quantum dots under externally applied biaxial stress using samples grown with different temperatures varying from 430 to 700 °C. The optical emission energy of samples grown at low temperatures is rather insensitive to the applied external stress, consistent with the type-II band alignment. However, for samples grown at high temperatures we observed a large blueshift, which suggests type-I alignment. The result implies that recombination strength can be controlled by the growth temperature, which can be useful for optical device applications. © 2007 American Institute of Physics.915Brunner, K., (2002) Rep. Prog. Phys., 65, p. 27Medeiros-Ribeiro, G., Bratkovski, A.M., Kamins, T.I., Ohlbert, D.A.A., Williams, R.S., (1998) Science, 279, p. 353Wan, J., Jin, G.L., Jiang, Z.M., Luo, Y.H., Liu, J.L., Wang, K.L., (2001) Appl. Phys. Lett., 78, p. 1763El Kurdi, M., Sauvage, S., Fishman, G., Boucaud, P., (2006) Phys. Rev. B, 73, p. 195327Yakimov, A.I., Dvurechenskii, A.V., Nikiforov, A.I., Bloshkin, A.A., Nenashev, A.V., Volodin, V.A., (2006) Phys. Rev. B, 73, p. 115333Dashiell, M.W., Denker, U., Müller, C., Costantini, G., Manzano, C., Kern, K., Schmidt, O.G., (2002) Appl. Phys. Lett., 80, p. 1279Larsson, M., Elfving, A., Holtz, P.O., Hansson, G.V., Ni, W.-X., (2003) Appl. Phys. Lett., 82, p. 4785Thewalt, M.L.W., Harrison, D.A., Reinhart, C.F., Wolk, J.A., Lafontaine, H., (1997) Phys. Rev. Lett., 79, p. 269Larsson, M., Elfving, A., Ni, W.-X., Hansson, G.V., Holtz, P.O., (2006) Phys. Rev. B, 73, p. 195319Schmidt, O.G., Eberl, K., (2000) Phys. Rev. B, 62, p. 16715Tudury, H.A.P., Nakaema, M.K.K., Iikawa, F., Brum, J.A., Ribeiro, E., Carvalho Jr., W., Bernussi, A.A., Gobbi, A.L., (2001) Phys. Rev. B, 64, p. 153301Gomes, P.F., Godoy, M.P.F., Nakaema, M.K.K., Iikawa, F., Lamas, T.E., Quivy, A.A., Brum, J.A., (2004) Phys. Status Solidi C, 3, p. 547De Godoy, M.P.F., Nakaema, M.K.K., Iikawa, F., Carvalho Jr. Wilson, Evaldo, R., Gobbi, A.L., (2004) Rev. Sci. Instrum., 75, p. 194

A Nested Case-Control Study of Intrauterine Exposure to Persistent Organochlorine Pollutants in Relation to Risk of Type 1 Diabetes

BACKGROUND: The incidence of type 1 diabetes in Europe is increasing at a rate of about 3% per year and there is also an increasing incidence throughout the world. Type 1 diabetes is a complex disease caused by multiple genetic and environmental factors. Persistent organochlorine pollutants (POPs) have been suggested as a triggering factor for developing childhood type 1 diabetes. The aim of this case-control study was to assess possible impacts of in utero exposure to POPs on type 1 diabetes. METHODOLOGY/ PRINCIPAL FINDINGS: The study was performed as a case-control study within a biobank in Malmö, a city located in the Southern part of Sweden. The study included 150 cases (children who had their diagnosis mostly before 18 years of age) and 150 controls, matched for gender and day of birth. 2,2',4,4',5,5'-hexachlorobiphenyl (PCB-153) and the major DDT metabolite 1,1-dichloro-2,2-bis (p-chlorophenyl)-ethylene (p,p'-DDE) were used as a biomarkers for POP exposure. When comparing the quartile with the highest maternal serum concentrations of PCB-153 with the other quartiles, an odds ratio (OR) of 0.73 (95% confidence interval [CI] 0.42, 1.27) was obtained. Similar results was obtained for p,p'-DDE (OR 0.56, 95% CI 0.29, 1.08). CONCLUSIONS: The hypothesis that in utero exposure to POPs will trigger the risk for developing type 1 diabetes was not supported by the results. The risk estimates did, although not statistically significant, go in the opposite direction. However, it is not reasonable to believe that exposure to POPs should protect against type 1 diabetes