4,234 research outputs found

    Memory-Controlled Diffusion

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    Memory effects require for their incorporation into random-walk models an extension of the conventional equations. The linear Fokker-Planck equation for the probability density p(r,t)p(\vec r, t) is generalized to include non-linear and non-local spatial-temporal memory effects. The realization of the memory kernels are restricted due the conservation of the basic quantity pp. A general criteria is given for the existence of stationary solutions. In case the memory kernel depends on pp polynomially the transport is prevented. Owing to the delay effects a finite amount of particles remains localized and the further transport is terminated. For diffusion with non-linear memory effects we find an exact solution in the long-time limit. Although the mean square displacement shows diffusive behavior, higher order cumulants exhibits differences to diffusion and they depend on the memory strength

    Fermionic coherent states for pseudo-Hermitian two-level systems

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    We introduce creation and annihilation operators of pseudo-Hermitian fermions for two-level systems described by pseudo-Hermitian Hamiltonian with real eigenvalues. This allows the generalization of the fermionic coherent states approach to such systems. Pseudo-fermionic coherent states are constructed as eigenstates of two pseudo-fermion annihilation operators. These coherent states form a bi-normal and bi-overcomplete system, and their evolution governed by the pseudo-Hermitian Hamiltonian is temporally stable. In terms of the introduced pseudo-fermion operators the two-level system' Hamiltonian takes a factorized form similar to that of a harmonic oscillator.Comment: 13 pages (Latex, article class), no figures; v2: some amendments in section 2, seven new refs adde

    Differentially fed dual band directional monopole antenna array for wireless communication

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    A dual band 2 × 2 monopole antenna array is proposed. The antenna array elements are fed differentially to align the radiated electric fields so that vectorial addition can be maximized to yield a high gain. Differential feeding is implemented by a 180-degree phase inverter placed in the feeding network. To avoid backside radiation, a metal reflector is placed beneath the ground plane. The proposed antenna operates at 2.75 GHz and 4.7 GHz, yielding a peak gain of 10 dBi and 6.51 dBi respectively. The proposed antenna array exhibits a broadside radiation patterns at the operating frequencies

    Can Reproductive Health Voucher Programs Improve Quality of Postnatal Care? A Quasi-Experimental Evaluation of Kenya’s Safe Motherhood Voucher Scheme

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    This study tests the group-level causal relationship between the expansion of Kenya’s Safe Motherhood voucher program and changes in quality of postnatal care (PNC) provided at voucher-contracted facilities. We compare facilities accredited since program inception in 2006 (phase I) and facilities accredited since 2010-2011 (phase II) relative to comparable non-voucher facilities. PNC quality is assessed using observed clinical content processes, as well as client-reported outcome measures. Two-tailed unpaired t-tests are used to identify differences in mean process quality scores and client-reported outcome measures, comparing changes between intervention and comparison groups at the 2010 and 2012 data collection periods. Difference-in-differences analysis is used to estimate the reproductive health (RH) voucher program’s causal effect on quality of care by exploiting group-level differences between voucher-accredited and non-accredited facilities in 2010 and 2012. Participation in the voucher scheme since 2006 significantly improves overall quality of postnatal care by 39% (p=0.02), where quality is defined as the observable processes or components of service provision that occur during a PNC consultation. Program participation since phase I is estimated to improve the quality of observed maternal postnatal care by 86% (p=0.02), with the largest quality improvements in counselling on family planning methods (IRR 5.0; p=0.01) and return to fertility (IRR 2.6; p=0.01). Despite improvements in maternal aspects of PNC, we find a high proportion of mothers who seek PNC are not being checked by any provider after delivery. Additional strategies will be necessary to standardize provision of packaged postnatal interventions to both mother and new-born. This study addresses an important gap in the existing RH literature by using a strong evaluation design to assess RH voucher program effectiveness on quality improvement

    Pan-genomic Matching Statistics for Targeted Nanopore Sequencing

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    Nanopore sequencing is an increasingly powerful tool for genomics. Recently, computational advances have allowed nanopores to sequence in a targeted fashion; as the sequencer emits data, software can analyze the data in real time and signal the sequencer to eject “nontarget” DNA molecules. We present a novel method called SPUMONI, which enables rapid and accurate targeted sequencing using efficient pan-genome indexes. SPUMONI uses a compressed index to rapidly generate exact or approximate matching statistics in a streaming fashion. When used to target a specific strain in a mock community, SPUMONI has similar accuracy as minimap2 when both are run against an index containing many strains per species. However SPUMONI is 12 times faster than minimap2. SPUMONI's index and peak memory footprint are also 16 to 4 times smaller than those of minimap2, respectively. This could enable accurate targeted sequencing even when the targeted strains have not necessarily been sequenced or assembled previously

    Stereotactic body radiotherapy for Ultra-Central lung Tumors: A systematic review and Meta-Analysis and International Stereotactic Radiosurgery Society practice guidelines

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    BACKGROUND Stereotactic body radiotherapy (SBRT) is an effective and safe modality for early-stage lung cancer and lung metastases. However, tumors in an ultra-central location pose unique safety considerations. We performed a systematic review and meta-analysis to summarize the current safety and efficacy data and provide practice recommendations on behalf of the International Stereotactic Radiosurgery Society (ISRS). METHODS We performed a systematic review using PubMed and EMBASE databases of patients with ultra-central lung tumors treated with SBRT. Studies reporting local control (LC) and/or toxicity were included. Studies with <5 treated lesions, non-English language, re-irradiation, nodal tumors, or mixed outcomes in which ultra-central tumors could not be discerned were excluded. Random-effects meta-analysis was performed for studies reporting relevant endpoints. Meta-regression was conducted to determine the effect of various covariates on the primary outcomes. RESULTS 602 unique studies were identified of which 27 (one prospective observational, the remainder retrospective) were included, representing 1183 treated targets. All studies defined ultra-central as the planning target volume (PTV) overlapping the proximal bronchial tree (PBT). The most common dose fractionations were 50 Gy/5, 60 Gy/8, and 60 Gy/12 fractions. The pooled 1- and 2-year LC estimates were 92 % and 89 %, respectively. Meta-regression identified biological effective dose (BED10) as a significant predictor of 1-year LC. A total of 109 grade 3-4 toxicity events, with a pooled incidence of 6 %, were reported, most commonly pneumonitis. There were 73 treatment related deaths, with a pooled incidence of 4 %, with the most common being hemoptysis. Anticoagulation, interstitial lung disease, endobronchial tumor, and concomitant targeted therapies were observed risk factors for fatal toxicity events. CONCLUSION SBRT for ultra-central lung tumors results in acceptable rates of local control, albeit with risks of severe toxicity. Caution should be taken for appropriate patient selection, consideration of concomitant therapies, and radiotherapy plan design

    Extensive sampling sheds light on species-level diversity in Palearctic Placobdella (Annelida: Clitellata: Glossiphoniiformes)

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    The bloodfeeding leech genus Placobdella is dominated by North American diversity, with only a single nominal species known from Central America and one from the Palearctic region. This is likely due to considerable underestimation of Palearctic biodiversity, but investigations into potential hidden diversity are lacking. To shed light on this, the present study introduces new data for specimens initially identified as Placobdella costata from Ukraine (close to the type locality), Italy, Germany, Latvia, Montenegro, Bulgaria, Slovenia, Turkey, Azerbaijan, Tunisia, and Algeria, and uses both nuclear (Internal Transcribed Spacer [ITS] region) and mitochondrial (cytochrome c oxidase subunit I [COI]) sequence data in phylogenetic and DNA barcoding frameworks, in order to better understand species-level diversity. Seven independent lineages are present in the trees, five of which show adequate separation at the COI locus to suggest their unique species-level status (COI distances between these clades range from 4.86 to 8.10%). However, the ITS data suggest that speciation is recent or incipient in these clades, and that not enough time has passed for clear separation at this locus. We discuss the evolutionary and taxonomic implications of our findings and speculate on dispersal events that may have contributed to shaping this pattern of geographic distribution
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