170 research outputs found
Seasonal and regional occurrence of heat-resistant spore-forming bacteria in the course of ultra-high temperature milk production in Tunisia
International audienceSpore-forming bacteria, principally Bacillus species, are important contaminants of milk. Because of their high heat resistance, Bacillus species spores are capable of surviving the heat treatment process of milk and lead to spoilage of the final product. To determine the factors influencing the contamination of milk, spore-forming bacteria occurrence throughout the UHT milk production line during winter, spring, and summer was studied. The obtained results confirm that the total viable rate decreases rapidly throughout the production line of UHT milk showing the efficiency of thermal treatments used. However, the persistent high rate of spore-forming bacteria indicates their high heat resistance , especially in spring and summer. In addition, a significant variation of the quality of raw milk according to the location of the collecting centers was revealed. The molecular identification showed a high degree of diversity of heat-resistant Bacillus species, which are isolated from different milk samples. The distribution of Bacillus species in raw milk, stored milk, bactofuged milk, pasteurized milk, and UHT milk were 28, 10, 16, 13, and 33%, respectively. Six Bacillus spp. including Bacillus licheniformis (52.38%), Bacillus pumilus (9.52%), Bacillus sp. (4.76%), Bacillus sporothermodurans (4.76%), Terribacillus aidingensis (4.76%), and Paenibacillus sp. (4.76%) were identified in different milk samples
Measuring the Boltzmann constant by mid-infrared laser spectroscopy of ammonia
We report on our ongoing effort to measure the Boltzmann constant,
using the Doppler broadening technique on ammonia. This paper presents some of
the improvements made to the mid-infrared spectrometer including the use of a
phase-stabilized quantum cascade laser, a lineshape analysis based on a refined
physical model and an improved fitting program 2 increasing the confidence in
our estimates of the relevant molecular parameters, and a first evaluation of
the saturation parameter and its impact on the measurement of k B. A summary of
the systematic effects contributing to the measurement is given and the optimal
experimental conditions for mitigating those effects in order to reach a
competitive measurement of at a part per million accuracy level are
outlined
Imidazolium-based ionic liquid type dependence of the bending response of polymer actuators
Actuators based on polymer blends of poly(vinylidene fluoride) (PVDF) with 40 % of
different ionic liquids (IL) are prepared by solvent casting. [C2mim][Cl], [C6mim][Cl],
[C10mim][Cl], [C2mim][NTf2], [C6mim][NTf2] and [C10mim][NTf2] were selected in
order to evaluate the effect of anion and cation sizes in the bending properties. The
microstructure, mechanical and electrical properties of the blend depend on the IL type,
which in turn leads to a different bending response. In particular, the mechanical
properties are independent on the IL type but the AC conductivity of the composites
depend more on the anion type than on the size of the alkyl chain connected to the
imidazolium based cation. Thus, the bending response of the IL/PVDF composites is
correlated with the anion and cation sizes and a maximum bending response of 0.3 % is
achieved for a 10 volts square signal in the IL/PVDF composite with 40 wt% content of
[C2mim][NTf2].The authors thank FEDER funds through the COMPETE 2020 Programme and National
Funds through FCT - Portuguese Foundation for Science and Technology under Strategic
Funding UID/FIS/04650/2013, UID/Multi/04551/2013, UID/QUI/50006/2013, project
PTDC/EEI-SII/5582/2014, a contract under Investigador FCT 2012 program
(J.M.S.S.E.), and grants SFRH/BD/90215/2012 (JCD) and SFRH/BPD/112547/2015
(CMC). Financial support from the Basque Government Industry Department under the
ELKARTEK Program is also acknowledged. The authors (R. M. and S. B. H.) would like
to thank the Tunisian Ministry of Higher Education and Research for its financial support.
The authors thank the support of M. S. Martins (U. Minho) for supporting the
electromechanical measurements
Hygrothermal aging effects on mechanical and fatigue behaviors of a short-natural-fiber-reinforced composite
A new natural fiber composite made of high density polyethylene (HDPE) and 40% wt of short birch fibers (SBF) was developed to replace polyamide (better known under its industrial name “Nylon”) in spur gear manufacturing. The effect of hygrothermal aging on quasi-static and fatigue bending behaviors of this new composite has been studied in this work. Once hygrothermal aging is completed, flexural quasi-static tests have been performed on aged specimens and results compared with those obtained from unaged specimens. It has been observed that hygrothermal aging has no significant effect on flexural mechanical properties of this composite. After characterization, bending fatigue tests have been conducted on aged specimens and results have been compared with those of unaged specimens. These fatigue tests show that hygrothermal aging decreases the high cycles fatigue strength (HCFS) of this composite. The cause of this fatigue durability decrease has been investigated using Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and a scanning electron microscope (SEM). These tests show that the chemical composition and thermal behavior of this composite are not affected by hygrothermal aging. On the contrary, these tests show that damage mechanisms of this composite (HDPE/40% wt of SBF) are directly affected by this type of aging
Fatigue life and residual strength of a short-natural-fiber-reinforced plastic vs Nylon
A new natural fiber composite made of high density polyethylene (HDPE) and short birch fibers (SBF) was developed to replace high-performance thermoplastics (Polyamide) commonly used in gears manufacturing. 3-point flexural quasi-static tests were achieved on bending specimens to assess mechanical properties. Comparison between these results and those of polyamide (PA) and neat polyethylene has showed that the polyethylene reinforced with 40%wt of SBF presents tensile and flexural mechanical properties that are higher than those of the PA11 or the neat polyethylene. After static characterisation, fatigue tests were performed to determine ε-N curves and the evolution of residual strength. Then, the fatigue behavior of the studied composite has been compared with that of PA66 and of ultra-high molecular weight polyethylene (UHMWPE). It has been noticed that polyethylene reinforced with 40%wt of SBF presents a high cycle fatigue strength (HCFS) that is more important than that of PA66 and UHMWPE. Consequently, the studied composite represents a good alternative to replace Nylon in spur gears manufacturing
Reliability and Validity of a New Taekwondo-Specific Change-of-Direction Speed Test With Striking Techniques in Elite Taekwondo Athletes:A Pilot Study
International audienceThe purpose of this study was to examine the test-retest reliability, and convergent and discriminative validity of a new taekwondo-specific change-of-direction (COD) speed test with striking techniques (TST) in elite taekwondo athletes. Twenty (10 males and 10 females) elite (athletes who compete at national level) and top-elite (athletes who compete at national and international level) taekwondo athletes with an average training background of 8.9 +/- 1.3 years of systematic taekwondo training participated in this study. During the two-week test-retest period, various generic performance tests measuring COD speed, balance, speed, and jump performance were carried out during the first week and as a retest during the second week. Three TST trials were conducted with each athlete and the best trial was used for further analyses. The relevant performance measure derived from the TST was the time with striking penalty (TST-TSP). TST-TSP performances amounted to 10.57 +/- 1.08 s for males and 11.74 +/- 1.34 s for females. The reliability analysis of the TST performance was conducted after logarithmic transformation, in order to address the problem of heteroscedasticity. In both groups, the TST demonstrated a high relative test-retest reliability (intraclass correlation coefficients and 90% compatibility limits were 0.80 and 0.47 to 0.93, respectively). For absolute reliability, the TST's typical error of measurement (TEM), 90% compatibility limits, and magnitudes were 4.6%, 3.4 to 7.7, for males, and 5.4%, 3.9 to 9.0, for females. The homogeneous sample of taekwondo athletes meant that the TST's TEM exceeded the usual smallest important change (SIC) with 0.2 effect size in the two groups. The new test showed mostly very large correlations with linear sprint speed (r = 0.71 to 0.85) and dynamic balance (r = -0.71 and -0.74), large correlations with COD speed (r = 0.57 to 0.60) and vertical jump performance (r = -0.50 to -0.65), and moderate correlations with horizontal jump performance (r = -0.34 to -0.45) and static balance (r = -0.39 to -0.44). Top-elite athletes showed better TST performances than elite counterparts. Receiver operating characteristic analysis indicated that the TST effectively discriminated between top-elite and elite taekwondo athletes. In conclusion, the TST is a valid, and sensitive test to evaluate the COD speed with taekwondo specific skills, and reliable when considering ICC and TEM. Although the usefulness of the TST is questioned to detect small performance changes in the present population, the TST can detect moderate changes in taekwondo-specific COD speed
s-ITSF: a service based intelligent transportation system framework for smart accident management
Environmental variables, habitat discontinuity and life history shaping the genetic structure of Pomatoschistus marmoratus
Coastal lagoons are semi-isolated ecosystems
exposed to wide fluctuations of environmental conditions
and showing habitat fragmentation. These features may
play an important role in separating species into different
populations, even at small spatial scales. In this study, we
evaluate the concordance between mitochondrial (previous
published data) and nuclear data analyzing the genetic
variability of Pomatoschistus marmoratus in five localities,
inside and outside the Mar Menor coastal lagoon (SE
Spain) using eight microsatellites. High genetic diversity
and similar levels of allele richness were observed across
all loci and localities, although significant genic and
genotypic differentiation was found between populations
inside and outside the lagoon. In contrast to the FST values
obtained from previous mitochondrial DNA analyses
(control region), the microsatellite data exhibited significant
differentiation among samples inside the Mar Menor
and between lagoonal and marine samples. This pattern
was corroborated using Cavalli-Sforza genetic distances.
The habitat fragmentation inside the coastal lagoon and
among lagoon and marine localities could be acting as a
barrier to gene flow and contributing to the observed
genetic structure. Our results from generalized additive
models point a significant link between extreme lagoonal
environmental conditions (mainly maximum salinity) and
P. marmoratus genetic composition. Thereby, these environmental
features could be also acting on genetic structure
of coastal lagoon populations of P. marmoratus favoring
their genetic divergence. The mating strategy of P. marmoratus
could be also influencing our results obtained from
mitochondrial and nuclear DNA. Therefore, a special
consideration must be done in the selection of the DNA
markers depending on the reproductive strategy of the
species
Laser locking to the 199Hg clock transition with 5.4x10^(-15)/sqrt(tau) fractional frequency instability
With Hg atoms confined in an optical lattice trap in the Lamb-Dicke regime,
we obtain a spectral line at 265.6 nm in which the full-width at half-maximum
is <15Hz. Here we lock an ultrastable laser to this ultranarrow clock
transition and achieve a fractional frequency stability of
5.4x10^(-15)/sqrt(tau) for tau<=400s. The highly stable laser light used for
the atom probing is derived from a 1062.6 nm fiber laser locked to an
ultrastable optical cavity that exhibits a mean drift rate of -6.0x10^(-17)
s^(-1) (or -16.9 mHz.s^(-1) at 282 THz) over a five month period. A comparison
between two such lasers locked to independent optical cavities shows a flicker
noise limited fractional frequency instability of 4x10^(-16) per cavity
Excretory/Secretory-Products of Echinococcus multilocularis Larvae Induce Apoptosis and Tolerogenic Properties in Dendritic Cells In Vitro
Parasitic helminths are inducers of chronic diseases and have evolved mechanisms to suppress the host immune response. Mostly from studies on roundworms, a picture is currently emerging that helminths secrete factors (E/S-products) that directly act on sentinels of the immune system, dendritic cells, in order to achieve an expansion of immunosuppressive, regulatory T cells (T-reg). Parasitic helminths are currently also intensely studied as therapeutic agents against autoimmune diseases and allergies, which is directly linked to their immunosuppressive activities. The immunomodulatory products of parasitic helminths are therefore of high interest for understanding immunopathology during infections and for the treatment of allergies. The present work was conducted on larvae of the tapeworm E. multilocularis, which grow like a tumor into surrounding host tissue and thus cause the lethal disease alveolar echinococcosis. The authors found that E/S-products from early infective larvae are strong inducers of tolerogenic DC in vitro and show that E/S-products of larvae of the chronic stage lead to an in vitro expansion of Foxp3+ T cells, suggesting that both the expansion of these T cells and poorly responsive DC are important for the establishment and persistence of E. multilocularis larvae within the host
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