88 research outputs found
Complexity of the XY antiferromagnet at fixed magnetization
We prove that approximating the ground energy of the antiferromagnetic XY
model on a simple graph at fixed magnetization (given as part of the instance
specification) is QMA-complete. To show this, we strengthen a previous result
by establishing QMA-completeness for approximating the ground energy of the
Bose-Hubbard model on simple graphs. Using a connection between the XY and
Bose-Hubbard models that we exploited in previous work, this establishes
QMA-completeness of the XY model
Journal Club Review of Diabetic Foot Infections
The general purpose of this journal club is to review foundational articles in the diagnostic and surgical treatment of diabetic foot infections and osteomyelitis. These articles help form the basis for clinical decision making and best treatment practices involving outpatient and inpatient care for diabetic foot infections
Phylogenetic similarity and structure of Agaricomycotina communities across a forested landscape
The Agaricomycotina are a phylogenetically diverse group of fungi that includes both saprotrophic and mycorrhizal species, and that form species â rich communities in forest ecosystems. Most species are infrequently observed, and this hampers assessment of the role that environmental heterogeneity plays in determining local community composition and in driving ÎČ-diversity. We used a combination of phenetic (TRFLP) and phylogenetic approaches [Unifrac and Net Relatedness Index (NRI)] to examine the compositional and phylogenetic similarity of Agaricomycotina communities in forest floor and surface soil of three widely distributed temperate upland forest ecosystems (one, xeric oak â dominated and two, mesic sugar maple dominated). Generally, forest floor and soil communities had similar phylogenetic diversity, but there was little overlap of species or evolutionary lineages between these two horizons. Forest floor communities were dominated by saprotrophic species, and were compositionally and phylogenetically similar in all three ecosystems. Mycorrhizal species represented 30% to 90% of soil community diversity, and these communities differed compositionally and phylogenetically between ecosystems. Estimates of NRI revealed significant phylogenetic clustering in both the forest floor and soil communities of only the xeric oak-dominated forest ecosystem, and may indicate that this ecosystem acts as a habitat filter. Our results suggest that environmental heterogeneity strongly influences the phylogenetic ÎČ-diversity of soil inhabiting Agaricomycotina communities, but has only a small influence on forest floor ÎČ-diversity. Moreover, our results suggest that the strength of community assembly processes, such as habitat filtering, may differ between temperate forest ecosystems.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79172/1/j.1365-294X.2010.04566.x.pd
Atmospheric N deposition alters connectance, but not functional potential among saprotrophic bacterial communities
The use of coâoccurrence patterns to investigate interactions between microâorganisms has provided novel insight into organismal interactions within microbial communities. However, anthropogenic impacts on microbial coâoccurrence patterns and ecosystem function remain an important gap in our ecological knowledge. In a northern hardwood forest ecosystem located in Michigan, USA, 20Â years of experimentally increased atmospheric N deposition has reduced forest floor decay and increased soil C storage. This ecosystemâlevel response occurred concomitantly with compositional changes in saprophytic fungi and bacteria. Here, we investigated the influence of experimental N deposition on biotic interactions among forest floor bacterial assemblages by employing phylogenetic and molecular ecological network analysis. When compared to the ambient treatment, the forest floor bacterial community under experimental N deposition was less rich, more phylogenetically dispersed and exhibited a more clustered coâoccurrence network topology. Together, our observations reveal the presence of increased biotic interactions among saprotrophic bacterial assemblages under future rates of N deposition. Moreover, they support the hypothesis that nearly two decades of experimental N deposition can modify the organization of microbial communities and provide further insight into why anthropogenic N deposition has reduced decomposition, increased soil C storage and accelerated phenolic DOC production in our field experiment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111976/1/mec13224.pd
Quantum Transport in Semiconductor Nanostructures
I. Introduction (Preface, Nanostructures in Si Inversion Layers,
Nanostructures in GaAs-AlGaAs Heterostructures, Basic Properties).
II. Diffusive and Quasi-Ballistic Transport (Classical Size Effects, Weak
Localization, Conductance Fluctuations, Aharonov-Bohm Effect, Electron-Electron
Interactions, Quantum Size Effects, Periodic Potential).
III. Ballistic Transport (Conduction as a Transmission Problem, Quantum Point
Contacts, Coherent Electron Focusing, Collimation, Junction Scattering,
Tunneling).
IV. Adiabatic Transport (Edge Channels and the Quantum Hall Effect, Selective
Population and Detection of Edge Channels, Fractional Quantum Hall Effect,
Aharonov-Bohm Effect in Strong Magnetic Fields, Magnetically Induced Band
Structure).Comment: 111 pages including 109 figures; this review from 1991 has retained
much of its usefulness, but it was not yet available electronicall
Combination Therapy Is Superior to Sequential Monotherapy for the Initial Treatment of Hypertension:A Double-Blind Randomized Controlled Trial
Background: Guidelines for hypertension vary in their preference for initial combination therapy or initial monotherapy, stratified by patient profile; therefore, we compared the efficacy and tolerability of these approaches.
Methods and Results: We performed a 1âyear, doubleâblind, randomized controlled trial in 605 untreated patients aged 18 to 79 years with systolic blood pressure (BP) â„150 mm Hg or diastolic BP â„95 mm Hg. In phase 1 (weeks 0â16), patients were randomly assigned to initial monotherapy (losartan 50â100 mg or hydrochlorothiazide 12.5â25 mg crossing over at 8 weeks), or initial combination (losartan 50â100 mg plus hydrochlorothiazide 12.5â25 mg). In phase 2 (weeks 17â32), all patients received losartan 100 mg and hydrochlorothiazide 12.5 to 25 mg. In phase 3 (weeks 33â52), amlodipine with or without doxazosin could be added to achieve target BP. Hierarchical primary outcomes were the difference from baseline in home systolic BP, averaged over phases 1 and 2 and, if significant, at 32 weeks. Secondary outcomes included adverse events, and difference in home systolic BP responses between tertiles of plasma renin. Home systolic BP after initial monotherapy fell 4.9 mm Hg (range: 3.7â6.0 mm Hg) less over 32 weeks (P<0.001) than after initial combination but caught up at 32 weeks (difference 1.2 mm Hg [range: â0.4 to 2.8 mm Hg], P=0.13). In phase 1, home systolic BP response to each monotherapy differed substantially between renin tertiles, whereas response to combination therapy was uniform and at least 5 mm Hg more than to monotherapy. There were no differences in withdrawals due to adverse events.
Conclusions: Initial combination therapy can be recommended for patients with BP >150/95 mm Hg.
Clinical Trial Registration URL: http://www.ClinicalTrials.gov. Unique identifier: NCT00994617
Disturbance and the resilience of coupled carbon and nitrogen cycling in a north temperate forest
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96419/1/jgrg864.pd
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