Xylan is the principal type of hemicellulose. It is a linear polymer of beta-D-xylopyranosyl units linked by (1-4) glycosidic bonds. In nature, the polysaccharide backbone may be added to ...4-O-methyl-alpha-D-glucuronopyranosyl units, acetyl groups, alpha-L-arabinofuranosyl, etc., in variable proportions. An enzymatic complex is responsible for the hydrolysis of xylan, but the main enzymes involved are endo-1,4-beta-xylanase and beta-xylosidase. These enzymes are produced by fungi, bacteria, yeast, marine algae, protozoans, snails, crustaceans, insect, seeds, etc., but the principal commercial source is filamentous fungi. Recently, there has been much industrial interest in xylan and its hydrolytic enzymatic complex, as a supplement in animal feed, for the manufacture of bread, food and drinks, textiles, bleaching of cellulose pulp, ethanol and xylitol production. This review describes some properties of xylan and its metabolism, as well as the biochemical properties of xylanases and their commercial applications.
Objectives
The aim of this study was to compare muscle quality (MQ) between octogenarians classified as non-fallers, fallers and recurrent fallers and identify confounding intrinsic and extrensic ...factors that impact likelihood for falls.
Design
This observational, descriptive, cross-sectional study included older adults (N=220) aged 80 years or older.
Measurements
The Short Physical Performance Battery (SPPB) was used to evaluate physical function and MQ was calculated using the ratio of grip strength to arm muscle mass (in kilograms) quantified by DXA. Variables related to sociodemographic, clinical, cognitive function, and falls were evaluated using a questionnaire and symptoms of depression were evaluated by the Geriatric Depression Scale (GDS). A Kruskal-Wallis H test was used to verify differences between groups. Binomial logistic regression was performed to determine the impact of age, depression, polypharmacy, balance, MQ, and sex on participants having more than four falls in their history.
Results
Increasing MQ was associated with reduced likelihood of more than four falls in their history. Non-fallers were statistically younger (p = 0.012) and took more medications (p = 0.023) than recurrent fallers. Recurrent fallers had lower MQ when compared with fallers (p = 0.007) and non-fallers (p = 0.001) and had a lower GDS score when compared with fallers (p = 0.022). Finally, fallers presented lower scores for balance when compared to non-fallers (p = 0.013).
Conclusion
A higher MQ is associated with a reduction in the likelihood falls in octogenarians. Therefore, it may be advantageous for clinicians to evaluate MQ when the screening of the risk of falls in older adults.
In many biomedical studies, the event of interest can occur more than once in a participant. These events are termed recurrent events. However, the majority of analyses focus only on time to the ...first event, ignoring the subsequent events. Several statistical models have been proposed for analysing multiple events. In this paper we explore and illustrate several modelling techniques for analysis of recurrent time-to-event data, including conditional models for multivariate survival data (AG, PWP-TT and PWP-GT), marginal means/rates models, frailty and multi-state models. We also provide a tutorial for analysing such type of data, with three widely used statistical software programmes. Different approaches and software are illustrated using data from a bladder cancer project and from a study on lower respiratory tract infection in children in Brazil. Finally, we make recommendations for modelling strategy selection for analysis of recurrent event data.
Laser-driven plasma accelerators provide tabletop sources of relativistic electron bunches and femtosecond x-ray pulses, but usually require petawatt-class solid-state-laser pulses of wavelength λ
~ ...1 μm. Longer-λ
lasers can potentially accelerate higher-quality bunches, since they require less power to drive larger wakes in less dense plasma. Here, we report on a self-injecting plasma accelerator driven by a long-wave-infrared laser: a chirped-pulse-amplified CO
laser (λ
≈ 10 μm). Through optical scattering experiments, we observed wakes that 4-ps CO
pulses with < 1/2 terawatt (TW) peak power drove in hydrogen plasma of electron density down to 4 × 10
cm
(1/100 atmospheric density) via a self-modulation (SM) instability. Shorter, more powerful CO
pulses drove wakes in plasma down to 3 × 10
cm
that captured and accelerated plasma electrons to relativistic energy. Collimated quasi-monoenergetic features in the electron output marked the onset of a transition from SM to bubble-regime acceleration, portending future higher-quality accelerators driven by yet shorter, more powerful pulses.
Bacterial cellulose (BC) is a versatile material produced by microorganisms in the form of a hydrogel film with high water retention capacity, porosity, and mechanical strength. BC can incorporate ...and release substances, making it an interesting polymer for use in the cosmetic and biomedical industries. The aim of the present study was to evaluate the use of a bacterium for the production of cellulose films in which propolis extract was added in situ and ex situ (during and after membrane production, respectively) with promising use as a skincare product. The bacterium Gluconacetobacter hansenii was grown in standard Hestrin–Schramm (HS) medium as well as HS medium with propolis extract for 7 days. A radiolytic process with 60Co was investigated as a safe sterilization method. The average yield was 120.55 ± 2.40 g of cellulose/L. The polymeric system exhibited antioxidant activity (15.16% inhibition of oxidant activity) and high water‐retention capacity (98.01 ± 0.17%). In conclusion, natural additives can provide the antioxidant characteristics of BC. Moreover, gamma irradiation proved to be an effective sterilization method, while maintaining the properties of the material.
Bacterial cellulose characteristics from Gluconacetobacter hansenii were investigated and propolis extract was added to the polymer via ex situ. The polymer blend was sterilized with 60Co irradiation. The obtained polymer blend showed an antioxidant activity content of 15.16%.
Abstract The interpretation of odds ratios (OR) as prevalence ratios (PR) in cross-sectional studies have been criticized since this equivalence is not true unless under specific circumstances. The ...logistic regression model is a very well known statistical tool for analysis of binary outcomes and frequently used to obtain adjusted OR. Here, we introduce the {\fontshape{it
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