Individual differences in extended practice functions and solution strategies for basic addition facts.

Practice on addition basic facts and changes in solution strategies were examined in 3rd- and 4th-grade students, practicing over 3 months. Response latencies decreased, indicating positive practice effects. Each of 3 student groups demonstrated different solution–strategy mixtures. Different mixtures led to different practice effects, indexed by shifts to more efficient counting strategies and more direct retrieval. Expectations about effects of practice and instructional strategies for optimizing practice must be sensitive to a child's actual strategy pattern. Most students had decreasing latency practice functions. However, quantitative functions fit to the practice session data indicated a high proportion of cases where the latency pattern over sessions was nonmonotonic. Trends over a small number of practice sessions may be inadequate for decisions about the utility of further practice, because such data may poorly represent long-term, cumulative effects on modifying strategy usage. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Measurement of pulmonary resistance and dynamic compliance with airway obstruction

We compared four algorithms by using least squares regression for determination of pulmonary resistance and dynamic elastance in subjects with emphysema, normal subjects, and subjects with asthma before and after bronchoconstriction. The four methods evaluated include 1) a single resistance and elastance, 2) separate resistances and elastances for each half breath, 3) separate inspiratory and expiratory resistances with a single elastance, and 4) separate inspiratory and expiratory resistances, an expiratory volume interaction term, and a single elastance. All methods gave comparable results in normal and asthmatic subjects. We found expiratory resistance was larger than inspiratory resistance in normal and asthmatic subjects during control conditions, but inspiratory resistance was higher than expiratory resistance in subjects who experienced severe bronchoconstriction in response to methacholine. In subjects who are flow limited, method 2 gives a higher inspiratory resistance than would be computed by assuming that the elastic pressure-volume curve passes through the zero-flow points. Methods 1 and 3 overestimate dynamic elastance and inspiratory resistance. Method 4 appears to identify flow limitation and dynamic hyperinflation and gives a good measure of inspiratory resistance and dynamic elastance.     

Quantitative molecular monitoring of HIV-1 RNA during antiretroviral therapy

Plasma HIV-1 RNA testing was used to monitor 43 HIV-1 infected patients newly placed on antiretroviral therapy or whose therapy had been recently changed. A polymerase chain reaction kit was used to measure HIV-1 RNA in clinical samples or frozen plasma. The cutoff of this test was 200 RNA copies/ml. The first group (11 patients) was stable on long-term zidovudine monotherapy when switched to stavudine. The HIV-1 RNA of three patients who had a regular decline in CD4+ T cell count did not change despite this switch, with a mean follow-up of 630 days. The HIV-1 RNA copy numbers of eight patients whose CD4+ T cell counts were stable declined an average of 0.53 log10 between days 90 and 650. The second group (14 patients) was on long-term zidovudine monotherapy and had declining CD4+ T cell counts over the past 6 months. Lamivudine was added to this regimen on day 0. HIV-1 RNA copy number decreased rapidly within 30 d, reaching -0.86 log10 on day 90, and this effect was maintained thereafter, with a mean follow-up of 161 days. There was a concomitant mean gain of +33 CD4+ T cells on day 90. The third group (nine patients) had never received anti-retroviral therapy and was given zidovudine+didanosine. HIV-1 RNA copy number decreased in all cases but one, reaching -1.31 log10 on day 150. This decrease was transient in three cases. The last group (nine patients) had also not had previous anti-retroviral therapy and was given zidovudine + didanosine + lamivudine in combination. HIV-1 RNA copy numbers declined rapidly in all cases, to below the cutoff in eight cases within a mean period of 50.5 days. The CD4+ cell counts increased by 164 cells/microliter on day 14 and by 201 cells/microliter on day 180. The response to therapy of the total population of 43 patients varied according to cases. The relative changes in p24 antigen compared to HIV-1 RNA also differed between patients. Measurement of HIV-1 viremia appears to be a valuable tool in current practice for individualizing therapy.     

Viscosity and Surface Tension of Saturated <Emphasis Type="Italic">n</Emphasis>-Pentane

Light scattering by thermally excited capillary waves on liquid surfaces or interfaces can be used for the investigation of viscoelastic properties of fluids. In this work, the simultaneous determination of surface tension and liquid kinematic viscosity of n-pentane by surface light scattering (SLS) on a gas–liquid interface was carried out. The experiments are based on a heterodyne detection scheme and signal analysis by photon correlation spectroscopy (PCS). Measurements were performed under saturation conditions over a wide temperature range from about 233 to 363 K. For the whole temperature range the total uncertainty of the liquid kinematic viscosity and surface tension is estimated to be better than 1.0 and 1.2, respectively. The results obtained corroborate the reliability of the SLS technique for the determination of thermophysical properties.     

Detection of DNA in virgin olive oils extracted from destoned fruits

Characterization of genetic identity using DNA extracted from olive oil has the potential to facilitate assessment of origin and varietal conformity. Such a prospect is particularly interesting in light of the increased regional spread of olive cultivars and their various contributions to olive oil mixtures for certification of denomination of origin. Towards this goal, we have devised a reliable method for extracting DNA from virgin olive oil that was utilized on monovariety oils from the single, self-sterile cultivar ‘Ogliarola salentina’. We show that DNA purified from oil can be used for microsatellite analysis and that the profile of DNA purified from a monovariety oil corresponds to the profile of DNA purified from the leaves of the same cultivar. While DNA from the pollinators present in the genome of the seed embryo, could potentially contain alleles not present in the genome fruit pulp, invalidating the molecular traceability of olive oil, we show for the first time that there is no contamination of seed embryo DNA in a monovariety oil. Thus, this molecular assay is applicable for monovariety olive oils.     

Regulatory Noncoding and Predicted Pathogenic Coding Variants of CCR5 Predispose to Severe COVID-19

Genome-wide association studies (GWAS) found locus 3p21.31 associated with severe COVID-19. CCR5 resides at the same locus and, given its known biological role in other infection diseases, we investigated if common noncoding and rare coding variants, affecting CCR5, can predispose to severe COVID-19. We combined single nucleotide polymorphisms (SNPs) that met the suggestive significance level (P ≤ 1 × 10⁻⁵) at the 3p21.31 locus in public GWAS datasets (6406 COVID-19 hospitalized patients and 902,088 controls) with gene expression data from 208 lung tissues, Hi-C, and Chip-seq data. Through whole exome sequencing (WES), we explored rare coding variants in 147 severe COVID-19 patients. We identified three SNPs (rs9845542, rs12639314, and rs35951367) associated with severe COVID-19 whose risk alleles correlated with low CCR5 expression in lung tissues. The rs35951367 resided in a CTFC binding site that interacts with CCR5 gene in lung tissues and was confirmed to be associated with severe COVID-19 in two independent datasets. We also identified a rare coding variant (rs34418657) associated with the risk of developing severe COVID-19. Our results suggest a biological role of CCR5 in the progression of COVID-19 as common and rare genetic variants can increase the risk of developing severe COVID-19 by affecting the functions of CCR5.     

Effect of the chemical structure of aromatic polyimides on their thermal aging,relaxation behavior and mechanical properties

This article examines the effects of structural changes and thermal aging treatments on the relaxation processes and mechanical properties of three polyimides differing for their molecular structure i.e. PMDA-ODA, 6FDA-ODA, and 6FDA-6FpDA. These polyimides were obtained by thermal imidization of their polyamic acid precursors, which were synthesized from the respective dianhydrides [pyromellitic anhydride (PMDA), hexahydrofluoroisopropylidene diphthalic anhydride (6FDA)], and diamines [4,4′-diaminodiphenyl ether (ODA), 4,4′-(hexafluoroisopropylidene) dianiline (6FpDA)]. After the curing process, the polyimides were thermally aged at a fixed temperature for various times Dynamic mechanical measurements performed in a multi-frequency mode, were used to determine the glass-rubber and sub-glass transitions, as well as the activation energy of the β transition. It was found that the T _g decreased in the order PMDA-ODA > 6FDA-6FpDA > 6FDA-ODA as a result of an increased chain rigidity and molecular packing induced by charge transfer interactions during the thermal imidization process. The β sub-glass transition showed two relaxation processes identified as β′ and β′′. The β′ process was attributed to the local motion of the diamine constituents while the β′′ process was caused by the local motion of the dianhydride moiety. The cooperativity of these molecular motions was also assessed via the Starkweather method. The thermal aging enhanced the state of aggregation of polyimide chains and thus the T _g and the sub-glass transition properties. This effect was particularly marked for the PMDA-ODA polyimide. Also the mechanical properties were significantly affected by chemical structure and aging treatments. For non-aged samples the more influenced parameter was the elongation at break, which decreased in the order PMDA-ODA > 6FDA-ODA > 6FDA-6FpDA. The aging enhanced the elastic modulus and the tensile strength and reduced the elongation at break.     

COVID-19 and Lung Mast Cells: The Kallikrein–Kinin Activation Pathway

Mast cells (MCs) have relevant participation in inflammatory and vascular hyperpermeability events, responsible for the action of the kallikrein–kinin system (KKS), that affect patients inflicted by the severe form of COVID-19. Given a higher number of activated MCs present in COVID-19 patients and their association with vascular hyperpermeability events, we investigated the factors that lead to the activation and degranulation of these cells and their harmful effects on the alveolar septum environment provided by the action of its mediators. Therefore, the pyroptotic processes throughout caspase-1 (CASP-1) and alarmin interleukin-33 (IL-33) secretion were investigated, along with the immunoexpression of angiotensin-converting enzyme 2 (ACE2), bradykinin receptor B1 (B1R) and bradykinin receptor B2 (B2R) on post-mortem lung samples from 24 patients affected by COVID-19. The results were compared to 10 patients affected by H1N1pdm09 and 11 control patients. As a result of the inflammatory processes induced by SARS-CoV-2, the activation by immunoglobulin E (IgE) and degranulation of tryptase, as well as Toluidine Blue metachromatic (TB)-stained MCs of the interstitial and perivascular regions of the same groups were also counted. An increased immunoexpression of the tissue biomarkers CASP-1, IL-33, ACE2, B1R and B2R was observed in the alveolar septum of the COVID-19 patients, associated with a higher density of IgE⁺ MCs, tryptase⁺ MCs and TB-stained MCs, in addition to the presence of intra-alveolar edema. These findings suggest the direct correlation of MCs with vascular hyperpermeability, edema and diffuse alveolar damage (DAD) events that affect patients with a severe form of this disease. The role of KKS activation in events involving the exacerbated increase in vascular permeability and its direct link with the conditions that precede intra-alveolar edema, and the consequent DAD, is evidenced. Therapy with drugs that inhibit the activation/degranulation of MCs can prevent the worsening of the prognosis and provide a better outcome for the patient.     

Understanding the Evolution of CdTe Buffer Layer Surfaces on ZnTe/Si(211) and GaAs(211)B During Cyclic Annealing

We present the results of a detailed study of the changes that occur on CdTe buffer layer surfaces grown on ZnTe/Si(211) and GaAs(211)B during the routine thermal cyclic annealing (TCA) process. Observations indicate that CdTe buffer layer surfaces are Te saturated when the TCA is performed under Te overpressure. In the absence of Te flux during the TCA step, the CdTe surface loses CdTe congruently and the typical CdTe nanowires show the presence of nodules on their surfaces. The observed changes in reflection high-energy electron diffraction patterns during TCA are explained in terms of surface chemistry and topography observations. Overall, the Te overpressure is necessary to maintain a smoother and pristine surface to continue the molecular beam epitaxy (MBE) growth.