Use of conductimetric technique for data capture in predictive microbiology

Conductimetry as an alternative data capture method for following microbial growth has a great potential as a research tool of predictive microbiology. In spite of this fact there is only a limited number of applications using conductimetric data for model generation. In this study the growth of single strains of Listeria monocytogenes and Lactococcus lactis was tested in 5 media using a RABITinstrument. The goal of the work was to find selective growth media for Listeria and Lactococcus, respectively, in order to study their interaction in mixed-culture using the conductimetric technique. Whitley Anaerobic broth, Whitley Impedance broth and modified Whitely Impedance broth (Whitley Impedance broth + Chloramphenicol 7 mg l Ś1) were not suitable for following selectively the growth of Lactococcus lactis or Listeria monocytogenes in a mixed culture of the two bacteria. BiMedia 630 A for Lactococcus lactis and Bimedia 403 A for Listeria monocytogenes satisfied the demands raised by conductance measurement. Linear correlations were established between the graphically estimated TTD values of the conductance curves and the logarithmic numbers of colony forming units (CFU). The correlations were very strong in each case (determination coefficients (R 2) of the linear regression were higher than 0.98 at both medium-strain combinations). However, in BiMedia 630 Listeria monocytogenes was capable of slow growth, therefore, this medium would be feasible for studying microbial interactions if only low concentrations of Listeria (less than 10 6 CFU ml Ś1) were present in the mixed culture

Interaction between Lactococcus lactis strains and Listeria monocytogenes in mixed cultures

Competition between a bacteriocinogenic and a non-bacteriocinogenic Lactococcus lactis strain, respectively, and a Listeria monocytogenes strain was studied in two semi-synthetic liquid media at various temperatures. The media used for the study were ST I and modified ST I broth (ST I broth + 1 g l-1 Tween 80). In both media, at 30 °C, a significant cell count reduction (5 log) of L. monocytogenes occurred only when the cell concentration of the bacteriocinogenic competitor reached the level of at least 107 CFU ml-1 required for the production of sufficient concentration of nisin-like bacteriocin. The same phenomenon was also observed when the initial level of the lactic acid bacteria (LAB) was one log higher or lower than that of the Listeria, however, the reduction of Listeria cell count occurred earlier with the higher initial concentration of the LAB. Incubation of the mixed cultures at 20 °C gave similar results but the bacteriocinogenic activity resulted in only a three log decline of the cell count of L. monocytogenes. At 10 °C Lactococcus lactis produced much less bacteriocin than at 30 °C, therefore, a drastic decrease of the Listeria cell count was not observed. Suppression of the Listeria growth was expressed in its decreased maximum population level (i.e. in an earlier appearance of the stationary phase). When the non-bacteriocinogenic Lac. lactis and Listeria were present at the same initial level (approx. 105 CFU ml-1), the Lactococcus did not affect the growth of L. monocytogenes at 30 °C in modified ST I broth

Precision atomic gravimeter based on Bragg diffraction

We present a precision gravimeter based on coherent Bragg diffraction of freely falling cold atoms. Traditionally, atomic gravimeters have used stimulated Raman transitions to separate clouds in momentum space by driving transitions between two internal atomic states. Bragg interferometers utilize only a single internal state, and can therefore be less susceptible to environmental perturbations. Here we show that atoms extracted from a magneto-optical trap using an accelerating optical lattice are a suitable source for a Bragg atom interferometer, allowing efficient beamsplitting and subsequent separation of momentum states for detection. Despite the inherently multi-state nature of atom diffraction, we are able to build a Mach-Zehnder interferometer using Bragg scattering which achieves a sensitivity to the gravitational acceleration of $\Delta g/g = 2.7\times10^{-9}$ with an integration time of 1000s. The device can also be converted to a gravity gradiometer by a simple modification of the light pulse sequence.Comment: 13 pages, 11 figure

Why momentum width matters for atom interferometry with Bragg pulses

We theoretically consider the effect of the atomic source's momentum width on the efficiency of Bragg mirrors and beamsplitters and, more generally, on the phase sensitivity of Bragg pulse atom interferometers. By numerical optimization, we show that an atomic cloud's momentum width places a fundamental upper bound on the maximum transfer efficiency of a Bragg mirror pulse, and furthermore limits the phase sensitivity of a Bragg pulse atom interferometer. We quantify these momentum width effects, and precisely compute how mirror efficiencies and interferometer phase sensitivities vary as functions of Bragg order and source type. Our results and methodology allow for an efficient optimization of Bragg pulses and the comparison of different atomic sources, and will help in the design of large momentum transfer Bragg mirrors and beamsplitters for use in atom-based inertial sensors.Comment: 25 pages, 11 figure

Heisenberg-limited metrology with a squeezed vacuum state, three-mode mixing, and information recycling

We have previously shown that quantum-enhanced atom interferometry can be achieved by mapping the quantum state of squeezed optical vacuum to one of the atomic inputs via a beamsplitter-like process [Phys. Rev. A 90, 063630 (2014)]. Here we ask the question: is a better phase sensitivity possible if the quantum state transfer (QST) is described by a three-mode-mixing model, rather than a beamsplitter? The answer is yes, but only if the portion of the optical state not transferred to the atoms is incorporated via information recycling. Surprisingly, our scheme gives a better sensitivity for lower QST efficiencies and with a sufficiently large degree of squeezing can attain near-Heisenberg-limited sensitivities for arbitrarily small QST efficiencies. Furthermore, we use the quantum Fisher information to demonstrate the near optimality of our scheme

Relationship of increase in body weight, fattened liver weight and liver quality in geese of different breeds, determined on the basis of force feeding methods

From the age of 9 weeks, 90-90 Kolos, Gourmaud and Babati goose breeds were force fed with 2 different types of technology and 3 types of feedstuff. Force feeding technologies were the traditional Hungarian and Israeli soft groats quick methods. In the case of the latter, feedstuff was fed both in a pre-fermented (Lactobacillus plantarumlactic acid bacteria) form and without fermentation. Frequency of daily force feeding was gradually increased from 2 to 6 until the 21st day of force feeding. Live weight before and after fattening and liver weight were measured in the case of each breed and treatment. Liver quality was also determined. On the basis of our results, differences in liver weight average were significantly influenced only by the genetic property of the breed. Liver quality was also influenced by the method of force feeding of one breed (Babati). Feedstuff tested did not result in significant differences in liver weight or in liver quality. Independently of the breed very close correlation was found between „fattening weight” and liver weight (r=0.98) and between „fattening weight” and liver quality grade (r=–0.97)