Vapor Analysis of Fermented Spanish-type Green Olives by Gas Chromatography

SUMMARY: Five major components were detected gas chromatographically in the head-space vapor (HSV) of Spanish-type green olives fermented by pure cultures of Lactobacillus plantarum, Pediococcus cerevisiae and Leuconostoc mesenteroides. Three of these compounds were identified as acetaldehyde, methyl sulfide, and ethanol. The same compounds were present in unfermented olives but in different amounts. Olives that had undergone a natural fermentation contained the above five compounds, and, in addition, a varying number of other compounds. These results indicated that HSV analysis may be a rapid method for detecting volatile end products resulting from the metabolism of various microorganisms. A high ethanol content was found in olive brines that contained a predominance of yeasts. Abnormal fermentations gave unique HSV profiles, one of which indicated a high level of 2-butanol. Methyl sulfide was found to be a major odor component of fermented as well as unfermented olives. Acetaldehyde and ethanol contributed secondarily to the odor. Primary contributions of fermentation by the above lactic acid bacteria to the flavor of olives were: (1) production of a desirable level of acidity, and (2) utilization of fermentable sugars to the exclusion of microorganisms which produce metabolic end products with undesirable flavor characteristics.     

String-Pattern Matching in a Visual Programming Language

Determining whether or not a pattern of characters is present within a body of text is such a fundamental problem that it has led to a number of notations for the specification of patterns. These include regular expressions, and notations found within string processing and other application-specific languages. Too often, these approaches are either overly simplistic, offering little in the way of pattern-matching capabilities, or else they are extremely cryptic and terse.In the context of visual programming, the string- pattern-matching problem is largely unaddressed; yet the benefits ascribed to such languages offer the potential for extremely powerful and intuitively meaningful pattern notations. In the CALVIN language, designed for the creation of courseware, the authors have used purely visual constructs throughout. In particular, the content of strings may be analysed by using a graphical and augmented version of regular expressions to specify patterns. This notation, and its realization within CALVIN, is described in some detail, and comparisons are made with the more conventional textual form.     

The effect of specular reflectance on the relationship between reflectance and vegetation amount

Abstract

The specular reflectance of a leaf is unrelated to wavelength or leaf content. However, a vegetation canopy is not a large leaf and specular reflectance is likely to be related to wavelength and vegetation amount because of the correlation between canopy geometry and vegetation amount. It was hypothesised that if the specular component were removed from the total (specular and diffuse) reflectance of a canopy then the strength of the correlation between diffuse reflectance and vegetation amount would decrease in near-infrared wavelengths and increase in visible wavelengths.

Field based measurements of grassland using a polarising radiometer verified this hypothesis. It was recommended that where possible the specular component of the total reflectance be determined, at least in visible wavelengths, prior to the estimation of vegetation amount.     

Simple technique for high‐throughput marking of distinguishable micro‐areas for microscopy

Today's (nano)‐functional materials, usually exhibiting complex physical properties require local investigation with different microscopy techniques covering different physical aspects such as dipolar and magnetic structure. However, often these must be employed on the very same sample position to be able to truly correlate those different information and corresponding properties. This can be very challenging if not impossible especially when samples lack prominent features for orientation. Here, we present a simple but effective method to mark hundreds of approximately 15×15 μm sample areas at one time by using a commercial transmission electron microscopy grid as shadow mask in combination with thin‐film deposition. Areas can be easily distinguished when using a reference or finder grid structure as shadow mask. We show that the method is suitable to combine many techniques such as light microscopy, scanning probe microscopy and scanning electron microscopy. Furthermore, we find that best results are achieved when depositing aluminium on a flat sample surface using electron‐beam evaporation which ensures good line‐of‐sight deposition. This inexpensive high‐throughput method has several advantageous over other marking techniques such as focused ion‐beam processing especially when batch processing or marking of many areas is required. Nevertheless, the technique could be particularly valuable, when used in junction with, for example focused ion‐beam sectioning to obtain a thin lamellar of a particular pre‐selected area.     

A SPACE-TIME COUPLED p-VERSION LEAST SQUARES FINITE ELEMENT FORMULATION FOR UNSTEADY TWO-DIMENSIONAL NAVIER–STOKES EQUATIONS

This paper presents a p-version least squares finite element formulation for two-dimensional unsteady fluid flow described by Navier–Stokes equations where the effects of space and time are coupled. The dimensionless form of the Navier–Stokes equations are first cast into a set of first-order differential equations by introducing auxiliary variables. This permits the use of C⁰ element approximation. The element properties are derived by utilizing the p-version approximation functions in both space and time and then minimizing the error functional given by the space–time integral of the sum of squares of the errors resulting from the set of first-order differential equations. This results in a true space–time coupled least squares minimization procedure. The application of least squares minimization to the set of coupled first-order partial differential equations results in finding a solution vector {δ} which makes gradient of error functional with respect to {δ} a null vector. This is accomplished by using Newton's method with a line search. A time marching procedure is developed in which the solution for the current time step provides the initial conditions for the next time step. Equilibrium iterations are carried out for each time step until the error functional and each component of the gradient of the error functional with respect to nodal degrees of freedom are below a certain prespecified tolerance. The space–time coupled p-version approximation functions provide the ability to control truncation error which, in turn, permits very large time steps. What literally requires hundreds of time steps in uncoupled conventional time marching procedures can be accomplished in a single time step using the present space–time coupled approach. The generality, success and superiority of the present formulation procedure is demonstrated by presenting specific numerical examples for transient couette flow and transient lid driven cavity. The results are compared with the analytical solutions and those reported in the literature. The formulation presented here is ideally suited for space–time adaptive procedures. The element error functional values provide a mechanism for adaptive h, p or hp refinements.     

RHEOLOGICAL PROPERTIES OF CONCENTRATED YOGHURT (LABNEH)

The effect of six techniques for the elevation of the total solids on the rheological properties of labneh were investigated using controlled-stress dynamic rheometer. All samples exhibited a weak viscoelastic gel structure with the storage modulus (G') higher than the loss modulus (G") over all of the measured range. None of the experimental materials produced the same overall gel strength as the control made by draining with traditional cloth-bags. The changes in the storage modulus (G') as a function of amplitude sweep were mirrored by changes in the loss modulus (G"). Considerable differences in the loss tangent (G"/G') values of the various materials were observed at higher stress amplitudes. Rheological differences in the overall gel strength at low amplitude and frequency suggest that, although the type of protein interactions in each case may be similar, there are differences in the degree of interactions. Subsequent breakdown at higher amplitudes and frequencies suggests that the overall domains of the treated proteins may have been reduced, and that different methods of manufacture may be producing materials that have different space occupancy in the gel.     

Energy losses in colloidal metals

The nature of the energy loss from a charged particle passing close to the rough surface of some metallic material has posed a problem for some time. In this paper we show how to use our numerical technique, developed to study photons in complex dielectric structures, to explain the loss peaks from experimental studies on metallic colloids. We also show how the method may be used to explore the properties of the plasmons and induced electric fields in the colloidal system.     

A MODEL SYSTEM FOR DIFFERENTIATING BETWEEN WATER ACTIVITY AND GLASS TRANSITION EFFECTS ON SOLID STATE CHEMICAL REACTIONS

Recent debates have emerged on whether water activity (a_w) or the state of the system as dictated by the glass transition temperature (T_g) controls the rates of chemical reactions in reduced-moisture solid systems. Previously, model systems in which the effects of water activity and glass transition on chemical reactions could be evaluated independently did not exist. The use of polyvinyl-pyrrolidone (PVP) of different molecular weights allows the water activity and moisture content of the systems to be kept virtually constant while the glass transition temperature varies. At a given water activity and temperature, the equilibrium moisture content for any molecular weight of PVP differed by only 1–2%, while the T_g values differed by 20–30C. Using PVP of different molecular weights as a model system will allow the effects of water activity and glass transition on chemical reactions to be studied independently and at a constant temperature.