Generic Feasibility of Perfect Reconstruction with Short FIR Filters in Multi-channel Systems

We study the feasibility of short finite impulse response (FIR) synthesis for perfect reconstruction (PR) in generic FIR filter banks. Among all PR synthesis banks, we focus on the one with the minimum filter length. For filter banks with oversampling factors of at least two, we provide prescriptions for the shortest filter length of the synthesis bank that would guarantee PR almost surely. The prescribed length is as short or shorter than the analysis filters and has an approximate inverse relationship with the oversampling factor. Our results are in form of necessary and sufficient statements that hold generically, hence only fail for elaborately-designed nongeneric examples. We provide extensive numerical verification of the theoretical results and demonstrate that the gap between the derived filter length prescriptions and the true minimum is small. The results have potential applications in synthesis FB design problems, where the analysis bank is given, and for analysis of fundamental limitations in blind signals reconstruction from data collected by unknown subsampled multi-channel systems.Comment: Manuscript submitted to IEEE Transactions on Signal Processin

Percutaneous Absorption of Salicylic Acid after Administration of Trolamine Salicylate Cream in Rats with Transcutol® and Eucalyptus Oil Pre-Treated Skin

Purpose: This study was conducted to assess the effect of skin pre-treatment with Transcutol® and eucalyptus oil on systemic absorption of topical trolamine salicylate in rat. Methods: Pharmacokinetic parameters of salicylic acid following administration of trolamine salicylate on rat skin pre-treated with either Transcutol® or eucalyptus oil were determined using both non-compartmental and non-linear mixed effect modeling approaches and compared with those of control group. Results: Median (% of interquartile range/median) of salicylic acid AUC0-8hr (ng/mL/hr) values in Transcutol® or eucalyptus oil treated rats were 2522(139%) and 58976(141%), respectively as compared to the 3023(327%) of the control group. Skin pre-treatment with eucalyptus oil could significantly decrease extravascular volume of distribution (V/F) and elimination rate constant (k) of salicylic acid. Conclusion: Unlike Transcutol®, eucalyptus oil lead to enhanced transdermal absorption of trolamine salicylate through rat skin

Impact of incomplete ventricular coverage on diagnostic performance of myocardial perfusion imaging.

In the context of myocardial perfusion imaging (MPI) with cardiac magnetic resonance (CMR), there is ongoing debate on the merits of using technically complex acquisition methods to achieve whole-heart spatial coverage, rather than conventional 3-slice acquisition. An adequately powered comparative study is difficult to achieve given the requirement for two separate stress CMR studies in each patient. The aim of this work is to draw relevant conclusions from SPECT MPI by comparing whole-heart versus simulated 3-slice coverage in a large existing dataset. SPECT data from 651 patients with suspected coronary artery disease who underwent invasive angiography were analyzed. A computational approach was designed to model 3-slice MPI by retrospective subsampling of whole- heart data. For both whole-heart and 3-slice approaches, the diagnostic performance and the stress total perfusion deficit (TPD) score-a measure of ischemia extent/severity-were quantified and compared. Diagnostic accuracy for the 3-slice and whole-heart approaches were similar (area under the curve: 0.843 vs. 0.855, respectively; P = 0.07). The majority (54%) of cases missed by 3-slice imaging had primarily apical ischemia. Whole-heart and 3-slice TPD scores were strongly correlated (R2 = 0.93, P < 0.001) but 3-slice TPD showed a small yet significant bias compared to whole-heart TPD (- 1.19%; P < 0.0001) and the 95% limits of agreement were relatively wide (- 6.65% to 4.27%). Incomplete ventricular coverage typically acquired in 3-slice CMR MPI does not significantly affect the diagnostic accuracy. However, 3-slice MPI may fail to detect severe apical ischemia and underestimate the extent/severity of perfusion defects. Our results suggest that caution is required when comparing the ischemic burden between 3-slice and whole-heart datasets, and corroborate the need to establish prognostic thresholds specific to each approach

In vivo contrast free chronic myocardial infarction characterization using diffusion-weighted cardiovascular magnetic resonance.

BackgroundDespite the established role of late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) in characterizing chronic myocardial infarction (MI), a significant portion of chronic MI patients are contraindicative for the use of contrast agents. One promising alternative contrast free technique is diffusion weighted CMR (dwCMR), which has been shown ex vivo to be sensitive to myocardial fibrosis. We used a recently developed in vivo dwCMR in chronic MI pigs to compare apparent diffusion coefficient (ADC) maps with LGE imaging for infarct characterization.MethodsIn eleven mini pigs, chronic MI was induced by complete occlusion of the left anterior descending artery for 150 minutes. LGE, cine, and dwCMR imaging was performed 8 weeks post MI. ADC maps were derived from three orthogonal diffusion directions (b = 400 s/mm2) and one non-diffusion weighted image. Two semi-automatic infarct classification methods, threshold and full width half max (FWHM), were performed in both LGE and ADC maps. Regional wall motion (RWM) analysis was performed and compared to ADC maps to determine if any observed ADC change was significantly influenced by bulk motion.ResultsADC of chronic MI territories was significantly increased (threshold: 2.4 ± 0.3 μm2/ms, FWHM: 2.4 ± 0.2 μm2/ms) compared to remote myocardium (1.4 ± 0.3 μm2/ms). RWM was significantly reduced (threshold: 1.0 ± 0.4 mm, FWHM: 0.9 ± 0.4 mm) in infarcted regions delineated by ADC compared to remote myocardium (8.3 ± 0.1 mm). ADC-derived infarct volume and location had excellent agreement with LGE. Both LGE and ADC were in complete agreement when identifying transmural infarcts. Additionally, ADC was able to detect LGE-delineated infarcted segments with high sensitivity, specificity, PPV, and NPV. (threshold: 0.88, 0.93, 0.87, and 0.94, FWHM: 0.98, 0.97, 0.93, and 0.99, respectively).ConclusionsIn vivo diffusion weighted CMR has potential as a contrast free alternative for LGE in characterizing chronic MI

Root biomass in cereals, catch crops and weeds can be reliably estimated without considering aboveground biomass

Reliable information on belowground plant biomass is essential to estimate belowground carbon inputs to soils. Estimations of belowground plant biomass are often based on a fixed allometric relationship of plant biomass between aboveground and belowground parts. However, environmental and management factors may affect this allometric relationship making such estimates uncertain and biased. Therefore, we aimed to explore how root biomass for typical cereal crops, catch crops and weeds could most reliably be estimated. Published and unpublished data on aboveground and root biomass (corrected to 0–25 cm depth) of cereal crops (wheat and barley), catch crops and weeds were collected from studies in Denmark. Leave one out cross validation was used to determine the model that could best estimate root biomass. Root biomass varied with year, farming system (organic versus conventional) and cereal species. Shoot and root biomass of catch crops were higher than for weeds (sampled in late autumn), and farming system significantly affected root biomass of catch crops and weeds. The use of fixed root biomass based on the most influential factors (farming system and species) provided the lowest error of prediction for estimation of root biomass, compared with the use of fixed allometric relations, such as root/shoot ratio. For cereal crops, the average root dry matter in organic farming systems was 218 g m−2 (243 and 193 g m−2 for wheat and barley, respectively), but in conventional systems only 139 g m−2 (142 and 129 g m−2 for wheat and barley, respectively). For catch crops and weeds, the root dry matter in organic farming systems were around 127 and 35 g m−2, and in conventional farming systems 75 and 28 g m−2, respectively. In conclusion, the present analysis indicates that root biomass in cereals, catch crops and weeds can be reliably estimated without considering aboveground biomass, and it may be better estimated using fixed values based on species and farming systems than using fixed allometric ratios

Indomethacin electrospun nanofibers for colonic drug delivery: in vitro dissolution studies

Generally, although the conventional drug delivery systems, such as using only pHdependent polymers or time-dependent release systems are popular, the individuals’ variations of physiological conditions usually lead to premature or imperfect drug release from each of these systems. Therefore, a combination of pH- and time-dependent polymers could be more reliable for delivering drugs to the lower GI tract such as colon. To this end, electrospinning method was used as a fabrication approach for preparing electrospun nanofibers of indomethacin aimed for colon delivery. Formulations were prepared based on a 3 2 full factorial design. Independent variables were the drug:polymer ratio (with the levels of 3:5, 4.5:5 and 6:5 w/w) and Eudragit S:Eudragit RS w/w ratio (20:80, 60:40 and 100:0). The evaluated responses were drug release at pH 1.2, 6.4, 6.8 and 7.4. Combinations of Eudragit S (ES), Eudragit RS (ERS) and drug based on factorial design were loaded in 10 ml syringes. 3 Electrospinning method was used to prepare electrospun nanofibers from electrospinning solutions. Conductivity and the viscosity of the solutions were analyzed prior to electrospinning. After collection, the nanofibers were evaluated in terms of morphology and drug release. It was shown that the ratio of drug:polymer and polymer:polymer were pivotal factors to control the drug release from nanofibers. A formulation containing Eudragit S:Eudragit RS (60:40) and drug:polymer ratio of 3:5 exhibited the most appropriate drug release as a colon delivery system with a minor release at pH 1.2, 6.4 and 6.8 and major release at pH 7.4. Nanofibers resulted from this formulation were also more uniform and contained fewer amounts of beads. It was demonstrated that the electrospinning could be regarded as a modern approach for the preparation of colon drug delivery systems leading to marketable products

Inter-comparison of statistical models for projecting winter oilseed rape yield in Europe under climate change

While intercomparison of process-based crop models for projections under climate change is being intensively studied at European as well as at the global scale, little effort has been made for comparing statistical models. In this study, several regression techniques (ordinary least squares, stepwise, shrinkage methods, principle components and partial least squares) were combined with different types of climate input variables (with different temporal resolution) in order to define a large range of statistical models. Each model was fitted to winter oilseed rape data collected in 689, 325 and 173 field experiments carried out in Denmark, Germany, and Czech Republic, respectively. The fitted models were then used to predict yield of winter oilseed rape in the field experiments during more than 20 years, up to 2013.  Interpretability of the estimated climate variable effects and accuracy of yield predictions were both analysed. Results suggest that recent statistical methods (e.g., shrinkage methods) may have considerable capabilities to complement traditional statistical methods in yield prediction. The selection of the most influential variables was strongly influenced by the statistical method used to analyse the data. Among the most recent statistical methods, the uncertainties in projecting yield of winter oilseed rape under climate change were mainly due to residual errors and uncertainty in estimated parameter values, and not to model choice

Reducción de la absorción de yodo a través de la piel de ratas por micelas poliméricas en comparación con Povidona yodada: un estudio ex vivo

Background: topical antiseptic agents have been used widely in normal skin and wound which is associated with side effects such as systemic toxicity. Objective: Iodine is a non-metallic agent with an antimicrobial property that is used in the clinic as antiseptic. Iodophores such as Povidone-Iodine (PVP-I) introduced to improve the stability of the aqueous solution of iodine. Time taking and expensive procedures for producing complex between iodine and polyvinyl pyrolidine and systemic iodine absorption after topical PVP-I application are limitations on the application of this iodophore. The aim of this study was the design and evaluation of polymeric micelles for the overcoming of PVP-I limitations. Methods: Eight polymeric micelle formulations prepared by the thin-layer method based on full-factorial design. In an ex-vivo study permeability of iodine- loaded in polymeric micelles through rat skin was evaluated in comparison with PVP-I. Results: polymeric micelles demonstrated particle size between 14-153 nm that is affected by critical micelle concentration (CMC) and molecular weight of the polymer. Maximum % of drug released after 24 h was 62.3% that mainly controlled by the type of polymer. All polymeric micelles significantly decreased the percentage of drug permeated through rat skin and so decreased the risk of iodine toxicity. The minimum bactericidal concentration of polymeric micelles was comparable with PVP-I. Conclusion: Polymeric micelle demonstrated a perfect topical carrier for iodine loading and delivery through the skin by Iodine entrapment into the skin and sufficiently antimicrobial effect.Antecedentes: los agentes antisépticos tópicos se han utilizado ampliamente en la piel y heridas normales, lo que se asocia con efectos secundarios como la toxicidad sistémica. Objetivo: el yodo es un agente no metálico con propiedades antimicrobiana que se usa en la clínica como antiséptico. Los yodóforos como la povidona yodada (PVP-I) son introducidos para mejorar la estabilidad de la solución acuosa de yodo. El tiempo y el procedimiento costoso para producir complejos entre yodo y polivinilpirolidina y la absorción sistémica de yodo después de la aplicación tópica de PVP-I son limitaciones en la aplicación de este yodóforo. El objetivo de este estudio fue el diseño y la evaluación de micelas poliméricas para superar las limitaciones de PVP-I. Métodos: Ocho formulaciones de micelas poliméricas son preparadas por el método de capa delgada basado en un diseño factorial completo. En un estudio ex vivo, se evaluó la permeabilidad del yodo cargado en micelas poliméricas a través de la piel de rata en comparación con PVP-I. Resultados: las micelas poliméricas demostraron un tamaño de partícula entre 14-153 nm que se ve afectado por la concentración crítica de micelas (CMC) y el peso molecular del polímero. El porcentaje máximo de fármaco liberado después de 24 h fue del 62,3% que se controla principalmente por el tipo de polímero. Todas las micelas poliméricas disminuyeron significativamente el porcentaje de fármaco permeado a través de la piel de rata y, por lo tanto, disminuyeron el riesgo de toxicidad por yodo. La concentración bactericida mínima de micelas poliméricas fue comparable con PVP-I. Conclusión: la micela polimérica demostró ser un portador tópico perfecto para la carga y entrega de yodo a través de la piel mediante el atrapamiento de yodo en la piel y un efecto antimicrobiano suficiente