The three-dimensional evolution of a plane mixing layer. Part 1: The Kelvin-Helmholtz roll-up

The Kelvin Helmholtz roll up of three dimensional, temporally evolving, plane mixing layers were simulated numerically. All simulations were begun from a few low wavenumber disturbances, usually derived from linear stability theory, in addition to the mean velocity profile. The spanwise disturbance wavelength was taken to be less than or equal to the streamwise wavelength associated with the Kelvin Helmholtz roll up. A standard set of clean structures develop in most of the simulations. The spanwise vorticity rolls up into a corrugated spanwise roller, with vortex stretching creating strong spanwise vorticity in a cup shaped region at the vends of the roller. Predominantly streamwise rib vortices develop in the braid region between the rollers. For sufficiently strong initial three dimensional disturbances, these ribs collapse into compact axisymmetric vortices. The rib vortex lines connect to neighboring ribs and are kinked in the opposite direction of the roller vortex lines. Because of this, these two sets of vortex lines remain distinct. For certain initial conditions, persistent ribs do not develop. In such cases the development of significant three dimensionality is delayed. When the initial three dimensional disturbance energy is about equal to, or less than, the two dimensional fundamental disturbance energy, the evolution of the three dimensional disturbance is nearly linear (with respect to the mean and the two dimensional disturbances), at least until the first Kelvin Helmholtz roll up is completed

Coherent structures in a simulated turbulent mixing layer

A direct numerical simulation of a plane turbulent mixing layer has been performed. The simulation was initialized using two turbulent velocity fields obtained from direct numerical simulation of a turbulent boundary layer at momentum thickness Reynolds number 300 (Spalart, 1988). The mixing layer is allowed to evolve long enough for self-similar linear growth to occur, with the visual thickness Reynolds number reaching 14,000. The simulated flow is examined for evidence of the coherent structures expected in a mixing layer (rollers and rib vortices). Before the onset of self-similar growth, such structures are present with properties similar to the corresponding laminar or transitional structures. In the self-similar growth regime, however, only the rollers are present with no indication of rib vortices and no indication of conventional pairing. This results in a reduction of mixing and layer growth

The three-dimensional evolution of a plane mixing layer. Part 2: Pairing and transition to turbulence

The evolution of three-dimensional temporally evolving plane mixing layers through as many as three pairings was simulated numerically. Initial conditions for all simulations consisted of a few low-wavenumber disturbances, usually derived from linear stability theory, in addition to the mean velocity. Three-dimensional perturbations were used with amplitudes ranging from infinitesimal to large enough to trigger a rapid transition to turbulence. Pairing is found both to inhibit the growth of infinitesimal three-dimensional disturbances and to trigger the transition to turbulence in highly three dimensional flows. The mechanisms responsible for the growth of three-dimensionality as well as the initial phases of the transition to turbulence are described. The transition to turbulence is accompanied by the formation of thin sheets of span wise vorticity, which undergo a secondary roll up. Transition also produces an increase in the degree of scalar mixing, in agreement with experimental observations of mixing transition. Simulations were also conducted to investigate changes in span wise length scale that may occur in response to the change in stream wise length scale during a pairing. The linear mechanism for this process was found to be very slow, requiring roughly three pairings to complete a doubling of the span wise scale. Stronger three-dimensionality can produce more rapid scale changes but is also likely to trigger transition to turbulence. No evidence was found for a change from an organized array of rib vortices at one span wise scale to a similar array at a larger span wise scale

Further studies are necessary in order to conclude a causal association between the consumption of monosodium L-glutamate (MSG) and the prevalence of metabolic syndrome in the rural Thai population

Please see related articles and author responses: http://www.nutritionandmetabolism.com/content/9/1/50 http://www.nutritionandmetabolism.com/content/10/1/10 http://www.nutritionandmetabolism.com/content/10/1/13 ABSTRACT: The article entitled “Monosodium glutamate (MSG) intake is associated with the prevalence of metabolic syndrome in a rural Thai population”, concluded that higher amounts of individual’s MSG consumption are associated with the risk of having the metabolic syndrome and being overweight independent of other major determinants. However, this epidemiological study is the only study indicating such a relationship between MSG intake and the prevalence of metabolic syndrome and there is no direct supporting evidence for a causal relationship between MSG intake and prevalence of metabolic syndrome. This study does not indicate that MSG causes metabolic syndrome. Furthermore, there are several questionable points concerning study methods. Further carefully designed studies taking into account all glutamate sources are necessary to demonstrate the relationship between overweight, metabolic syndrome, MSG intake and umami sensitivity

State Funded Marketing and Promotional Activities to Support a State's Winery Business; Are There Economic Returns?: A Case study using Texas Senate Bill 1370's support of the Texas Wine Industry

Texas wineries responded to a survey regarding their participation in wine marketing activities, annual changes in gross sales and level of sales growth they attribute to TDA’s support and if these funds create positive economic impacts to their winery. The response rate was 53 of the 93 registered wineries or a 57 percent response rate. Senate Bill 1370 funds allocate annually $725,000 to marketing and promotion of Texas wine. Combining the$725,000 and the normal funding of $250,000 identifies$975,000 in annual support to grow economic value. The most often utilized promotional activity is promotional materials and attending TDA supported wine events. Ninety-two percent of Texas wineries recognize an increase in awareness for the Texas wine industry and attribute 49 percent of the increase to state marketing efforts. A portion of TDA marketing funds were directed towards supporting wine events in Texas as they attract large numbers of consumers and allow promotional opportunities. One result found that 68 percent of consumers reported the event encouraged them to buy more Texas wine. Annual Economic Impact Results from supported marketing activities are estimated to create $8.42 per$1 of funding in direct sales increases, $15.33 per$1 of funding in economic impact of increases in sales and $1.54 per$1 of funding in value added impacts (based on IMPLAN Type II Economic Multiplier values). Annual Economic Impact Results from all funding activities are $2.16 per$1 of funding of total direct sales increases, $3.93 per$1 of funding in economic impacts of increases in sales and $.40 per$1 of funding in valued added impacts (based on IMPLAN Type II Economic Multiplier values). It is apparent that both direct and indirect economic results are positive returns to program funding and create economic growth in local economies.Texas Wine, Wine Economics, State Commodity Support, State Agricultural Marketing, State Commodity Marketing, Agribusiness, Agricultural and Food Policy, Marketing,

Branchinecta hiberna, a new species of fairy shrimp (Crustacea: Anostraca) from western North America

This is the published version. Copyright Brigham Young University, Monte L Bean Life Science MuseauBranchinecta hiberna, a new species of fairy shrimp, is described from temporary pools in the Great Basin region of south central Oregon, northeastern California, and adjacent Nevada. The new species shares several characters with Branchinecta cornigera Lynch, 1958: males bear a similar large patch of small spines on the basal segment of antenna 2, and females bear the similar robust antenna 2 with medial spur, brood pouch shape, and resting egg (cyst) morphology. The new species differs from B. cornigera in the shape of the distal segment of antenna 2 and the number and size of spines on the paired penis warts of males, and in the thoracic spine pattern and lack of dorsal cephalic projections in females. Observations on behavior and ecology of B. hiberna are discussed

Introductory Remarks

Introductory Remarks