146 research outputs found
Improving the Quality of European Hard Cheese by controlling interactions between Lactic Acid Bacteria and Propionic Acid Bacteria (LAB/PAB) (Stimulation of Propionic Acid Bacteria by Lactic
End of Project ReportTeagasc acknowledges with gratitude grant aid under the EU Framework Programme (FAIR
96-CT-1024).In the manufacture of Swiss-type cheese two successive fermentations
occur. During manufacture, lactic acid bacteria (LAB), particularly
Streptococcus thermophilus, Lactobacillus helveticus and
Lb. delbrueckii subsp. lactis, convert lactose to lactate while,
during ripening, propionic acid bacteria (PAB) convert lactate to
propionic acid, acetic acid and carbon dioxide (CO2). CO2 is
responsible for eye formation and propionic acid results in the typical
nutty flavour of Swiss-type cheese. There have been a few reports of
interactions between a small number of LAB and PAB but the
compounds involved have not been identified. A better
understanding of this phenomenon is necessary to select strains of
PAB for cheesemaking and improve the quality of hard cheeses.
Cheese cannot be used for such a study because of its complexity and
the length of time it is ripened. Hence, a simple whey-based model
developed by Piveteau et al (1995) was successfully used to study the
interactions between LAB and PAB. In this procedure, the LAB were
grown overnight in milk and the whey was collected by centrifugation.
After neutralisation and filter-sterilisation, the growth of strains of PAB
in this whey and in a control whey produced from the same milk by
acidification with lactic acid were compared.
The objectives of this study were to refine the model of Piveteau et al
(1995) to study the interactions between LAB and PAB and to
determine the nature of the stimulant(s) produced by the LAB. * Thirty-two combinations of different commercial strains of PAB and
LAB were evaluated in a modified whey model. None showed any
inhibition and all showed some degree of stimulation but the extent of the stimulation depended on the particular pair of PAB and LAB
used.
* An inhibitor of PAB was found in milk, which prevented the growth
of PAB from low (105 cfu/ml) but not from high inocula (107 cfu/ml).
The inhibitor was heat stable (to autoclaving for 15 min), of low
molecular mass and could be removed by pre-growth of some but not
all starter LAB in milk.
* Growth of P. freudenreichii DPC 3801 in control whey was
stimulated by peptone, tryptone, casein hydrolysed by the crude
proteinase of Lb. helveticus DPC 4571 and by pre-growth of the
lactobacillus in milk, but not by vitamins (riboflavin, thiamine, PABA,
Ca panthothenate, biotin and nicotinic acid) or minerals (MgSO4,
MnCl2, CoCl2 and CuSO4).
* Growth of Lb. helveticus DPC 4571 in milk resulted in significant
increases in peptide and amino acid production but the amino acids
produced did not stimulate the growth of the PAB. Based on these
results it was concluded that the stimulation was due to production of
peptides by the LAB from casein.
* The whey model developed by Piveteau et al (1995) to study the
interactions between PAB and LAB was shown to be reproducible.
Adjustment of the pH of the whey to 5.4 rather than 6.0, incubation
at 24ºC rather than 30ºC and addition of 1% NaCl, to simulate
cheese ripening conditions allowed growth of all the PAB tested.
* Several chromatographic procedures, including ion-exchange, gel
permeation and reverse-phase, high-pressure liquid chromatography
failed to categorically identify the peptide(s) responsible for the
stimulation of the PAB. In some of these chromatographic systems,the stimulatory activity was shown to be present in several peaks
implying that different peptides were involved.European Unio
Quantum Hall effect anomaly and collective modes in the magnetic-field-induced spin-density-wave phases of quasi-one-dimensional conductors
We study the collective modes in the magnetic-field-induced spin-density-wave
(FISDW) phases experimentally observed in organic conductors of the Bechgaard
salts family. In phases that exhibit a sign reversal of the quantum Hall effect
(Ribault anomaly), the coexistence of two spin-density waves gives rise to
additional collective modes besides the Goldstone modes due to spontaneous
translation and rotation symmetry breaking. These modes strongly affect the
charge and spin response functions. We discuss some experimental consequences
for the Bechgaard salts.Comment: Final version (LaTex, 8 pages, no figure), to be published in
Europhys. Let
Thin films of calcium phosphate and titanium dioxide by a sol-gel route: a new method for coating medical implants
Titanium is a commonly used biomaterial for dental and orthopaedic applications. To increase its ability to bond with bone, some attempts were made to coat its surface with calcium phosphate (CaP). This paper describes a new type of coating. Instead of a pure CaP layer, a mixing of titanium dioxide (TiO2) and CaP is fabricated and deposited as a coating. These layers are deposited by a sol-gel route on pure titanium substrates using various pre-treatments. The method consists of mixing a solution of tetrabutyl ortho-titanate or a sol of titanium dioxide with a solution of calcium nitrate and phosphorous esters. This composite is deposited on to commercially pure titanium plates, mechanically polished or blasted with pure crystalline aluminum oxide, using the spin-coating technique. These coatings are then fired at 650 or 850°C for various times. The samples are characterized by X-ray diffraction for their crystallinity, X-ray photoelectron spectroscopy for their surface chemical composition and scanning electron microscopy for their topography. Samples treated at 850°C present a well-pronounced crystallinity, and a high chemical purity at the surface. The topography is strongly related to the viscosity of the precursor and the substrate pre-treatment. Possibilities to structure the outermost layer are presented. © 1999 Kluwer Academic Publisher
The Occipital Emissary Vein: A Possible Marker for Pseudotumor Cerebri
BACKGROUND AND PURPOSE: Transverse sinus stenosis can lead to pseudotumor cerebri syndrome by elevating the cerebral venous pressure. The occipital emissary vein is an inconstant emissary vein that connects the torcular herophili with the suboccipital veins of the external vertebral plexus. This retrospective study compares the prevalence and size of the occipital emissary vein in patients with pseudotumor cerebri syndrome with those in healthy control subjects to determine whether the occipital emissary vein could represent a marker of pseudotumor cerebri syndrome. MATERIALS AND METHODS: The cranial venous system of 46 adult patients with pseudotumor cerebri syndrome (group 1) was studied on CT venography images and compared with a group of 92 consecutive adult patients without pseudotumor cerebri syndrome who underwent venous assessment with gadolinium-enhanced 3D-T1 MPRAGE sequences (group 2). The presence of an occipital emissary vein was assessed, and its proximal (intraosseous) and distal (extracranial) maximum diameters were measured and compared between the 2 groups. Seventeen patients who underwent transverse sinus stent placement had their occipital emissary vein diameters measured before and after stent placement. RESULTS: Thirty of 46 (65%) patients in group 1 versus 29/92 (31.5%) patients in group 2 had an occipital emissary vein (P < .001). The average proximal and distal occipital emissary vein maximum diameters were significantly larger in group 1 (2.3 versus 1.6 mm, P <.005 and 3.3 versus 2.3 mm, P<.001). The average maximum diameters of the occipital emissary vein for patients who underwent transverse sinus stent placement were larger before stent placement than after stent placement: 2.6 versus 1.8 mm proximally (P<.06) and 3.7 versus 2.6 mm distally (P<.005). CONCLUSIONS: Occipital emissary veins are more frequent and larger in patients with pseudotumor cerebri syndrome than in healthy subjects, a finding consistent with their role as collateral venous pathway in transverse sinus stenosis. A prominent occipital emissary vein is an imaging sign that should raise the suspicion of pseudotumor cerebri syndrome.Fil: Hedjoudje, A.. Hospital Center University De Rouen; FranciaFil: Piveteau, A.. University Hospital of Geneva; SuizaFil: Gonzalez Campo, Cecilia. Sion Hospital; Suiza. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencias Cognitivas y Traslacional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva. Fundación Favaloro. Instituto de Neurociencia Cognitiva; ArgentinaFil: Moghekar, A.. The Johns Hopkins Hospital; Estados UnidosFil: Gailloud, P.. The Johns Hopkins Hospital; Estados UnidosFil: San Millán, D.. Sion Hospital; Suiz
Magneto-Roton Modes of the Ultra Quantum Crystal: Numerical Study
The Field Induced Spin Density Wave phases observed in quasi-one-dimensional
conductors of the Bechgaard salts family under magnetic field exhibit both Spin
Density Wave order and a Quantized Hall Effect, which may exhibit sign
reversals. The original nature of the condensed phases is evidenced by the
collective mode spectrum. Besides the Goldstone modes, a quasi periodic
structure of Magneto-Roton modes, predicted to exist for a monotonic sequence
of Hall Quantum numbers, is confirmed, and a second mode is shown to exist
within the single particle gap. We present numerical estimates of the
Magneto-Roton mode energies in a generic case of the monotonic sequence. The
mass anisotropy of the collective mode is calculated. We show how differently
the MR spectrum evolves with magnetic field at low and high fields. The
collective mode spectrum should have specific features, in the sign reversed
"Ribault Phase", as compared to modes of the majority sign phases. We
investigate numerically the collective mode in the Ribault Phase.Comment: this paper incorporates material contained in a previous cond-mat
preprint cond-mat/9709210, but cannot be described as a replaced version,
because it contains a significant amount of new material dealing with the
instability line and with the topic of Ribault Phases. It contains 13 figures
(.ps files
Influence of Enterococci and Thermophilic Starter Bacteria on Cheddar Cheese Flavour
End of Project ReportThis project set out to identify suitable enterococci and thermophilic starter strains which could be added to the cheese during manufacture (as starter adjuncts) with the specific aims of enhancing flavour during ripening as well as facilitating flavour diversity - a trait sought by many commercial Cheddar companies. This project confirmed the potential of thermophilic lactic acid strains to affect flavour when used as starter adjuncts in Cheddar cheese manufacture. Their use can also lead to the development of novel flavours. Many adjunct cultures proposed to-date to enhance Cheddar flavour are composed of strains of lactococcal starter, selected for their flavouring capacity. However, application of such strains in industry would lead to increased probability of phage attack on the primary starter. On the other hand, thermophilic lactic acid strains are phage unrelated to conventional starter and thus would not lead to the introduction of starter specific phage into the cheese plant.
A thermophilic strain from the Moorepark collection (DPC 4571) was shown to have major commercial potential as a flavour enhancer.Department of Agriculture, Food and the Marin
Safety, tolerability and efficacy of intradermal rabies immunization with DebioJect™.
In a single-center study, 66 healthy volunteers aged between 18 and 50years were randomized to be immunized against rabies with three different injection routes: intradermal with DebioJect™ (IDJ), standard intradermal with classical needle (IDS), also called Mantoux method, and intramuscular with classical needle (IM). "Vaccin rabique Pasteur®" and saline solution (NaCl 0.9%) were administered at D0, D7 and D28. Antigen doses for both intradermal routes were 1/5 of the dose for IM. Tolerability, safety and induced immunogenicity of IDJ were compared to IDS and IM routes. Pain was evaluated at needle insertion and at product injection for all vaccination visits. Solicited Adverse Event (SolAE) and local reactogenicity symptoms including pain, redness and pruritus were recorded daily following each vaccination visit. Adverse events (AE) were recorded over the whole duration of the study. Humoral immune response was measured by assessing the rabies virus neutralizing antibody (VNA) titers using Rapid Fluorescent Focus Inhibition Test (RFFIT). Results demonstrated that the DebioJect™ is a safe, reliable and efficient device. Significant decreases of pain at needle insertion and at vaccine injection were reported with IDJ compared to IDS and IM. All local reactogenicity symptoms (pain, redness and pruritus) after injection with either vaccine or saline solution, were similar for IDJ and IDS, except that IDJ injection induced more redness 30min after saline solution. No systemic SolAE was deemed related to DebioJect™ and classical needles. No AE was deemed related to DebioJect™. No Serious Adverse Event (SAE) was reported during the study. At the end of the study all participants were considered immunized against rabies and no significant difference in humoral response was observed between the 3 studied routes
Sign reversals of the Quantum Hall Effect in quasi-1D conductors
The sign reversals of the Quantum Hall Effect observed in
quasi-one-dimensional conductors of the Bechgaard salts family are explained
within the framework of the quantized nesting model. The sequence of reversals
is driven by slight modifications of the geometry of the Fermi surface. It is
explained why only even phases can have signign reversals and why negative
phases are less stable than positive ones.Comment: 4 LaTex pages, 3 Postscript figure
Sign reversals of the quantum Hall effect and helicoidal magnetic-field-induced spin-density waves in quasi-one-dimensional organic conductors
We study the effect of umklapp scattering on the magnetic-field-induced
spin-density-wave phases, which are experimentally observed in the
quasi-one-dimensional organic conductors of the Bechgaard salts family. Within
the framework of the quantized nesting model, we show that umklapp processes
may naturally explain sign reversals of the quantum Hall effect (QHE) observed
in these conductors. Moreover, umklapp scattering can change the polarization
of the spin-density wave (SDW) from linear (sinusoidal SDW) to circular
(helicoidal SDW). The QHE vanishes in the helicoidal phases, but a
magnetoelectric effect appears. These two characteristic properties may be
utilized to detect the magnetic-field-induced helicoidal SDW phases
experimentally.Comment: 4 pages, latex, 3 figure
Effect of umklapp scattering on the magnetic-field-induced spin-density waves in quasi-one-dimensional organic conductors
We study the effect of umklapp scattering on the magnetic-field-induced
spin-density-wave (FISDW) phases which are experimentally observed in the
quasi-one-dimensional organic conductors of the Bechgaard salts family. Within
the framework of the quantized nesting model, we show that the transition
temperature is determined by a modified Stoner criterion which includes the
effect of umklapp scattering. We determine the SDW polarization (linear or
circular) by analyzing the Ginzburg-Landau expansion of the free energy. We
also study how umklapp processes modify the quantum Hall effect (QHE) and the
spectrum of the FISDW phases. We find that umklapp scattering stabilizes phases
which exhibit a sign reversal of the QHE, as experimentally observed in the
Bechgaard salts. These ``negative'' phases are characterized by the
simultaneous existence of two SDWs with comparable amplitudes. As the umklapp
scattering strength increases, they may become helicoidal (circularly polarized
SDWs). The QHE vanishes in the helicoidal phases, but a magnetoelectric effect
appears. These two characteristic properties may be utilized to detect the
magnetic-field-induced helicoidal SDW phases experimentally.Comment: Revtex, 27 pages, 9 figure
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