Aeroelasticity-based fluid agitation for lab-on-chips.

In this study, we report a robust agitation method for small-volume liquids. It utilizes an elastic diaphragm as the bottom of a liquid chamber, upon which an initial tension is also applied to enhance the aeroelasticity effects at small/micro scales. As a result, spontaneous vibration of the diaphragm can be induced by an external air flow, which further provides fluid agitations. The device structure is simple and can be easily fabricated at low cost. More importantly, the vibration amplitude is controllable and varies widely from several tens to several hundred micrometers depending on the applied air pressure. The resulting agitation is effective and applicable at high viscosities of up to 900 cSt. The influences of air pressure and liquid viscosity on the vibration frequency are discussed. Potential applications of this technique for solid particle agitation, focusing and fluid mixing are also demonstrated.

Converting steady laminar flow to oscillatory flow through a hydroelasticity approach at microscales.

We report a hydroelasticity-based microfluidic oscillator that converts otherwise steady laminar flow to oscillatory flow. It incorporates an elastic diaphragm to enhance nonlinearity of the flow. Negative differential flow resistance is observed. High-frequency oscillatory flow is produced passively through interactions among hydrodynamic, elastic and inertial forces, without resorting to external actuators and control equipment. Driven by fluid flow and pressure, this device can operate in either steady laminar flow or oscillatory flow states, or work as a valve. Its applications for flow control and operation, and mixing enhancement are demonstrated.

Molecular characterization, technological properties and safety aspects of enterococci from 'Hussuwa', an African fermented sorghum product.

AIMS: To identify enterococci from Hussuwa, a Sudanese fermented sorghum product, and determine their technological properties and safety for possible inclusion in a starter culture preparation. METHODS AND RESULTS: Twenty-two Enterococcus isolates from Hussuwa were identified as Enterococcus faecium by using phenotypic and genotypic tests such as 16S rDNA gene sequencing, RAPD-PCR and restriction fragment length polymorphism of the 16S/23S intergenic spacer region fingerprinting. Genotyping revealed that strains were not clonally related and exhibited a considerable degree of genomic diversity. Some strains possessed useful technological properties such as production of bacteriocins and H2O2 or utilization of raffinose and stachyose. None produced alpha-amylase or tannase. A safety investigation revealed that all strains were susceptible to the antibiotics ampicillin, gentamicin, chloramphenicol, tetracycline and streptomycin, but some were resistant to ciprofloxacin, erythromycin, penicillin and vancomycin. Production of biogenic amines or presence of genes encoding virulence determinants occurred in some strains. CONCLUSIONS: Enterococcus faecium strains are associated with fermentation of Sudanese Hussuwa. Some strains exhibited useful technological properties such as production of antimicrobial agents and fermentation of indigestible sugars, which may aid in stabilizing and improving the digestibility of the product respectively. SIGNIFICANCE AND IMPACT OF THE STUDY: Enterococci were shown to play a role in the fermentation of African foods. While beneficial properties of these bacteria are indicated, their presence in this food may also imply a hygienic risk as a result of antimicrobial resistances or presence of virulence determinants.

Effect of clindamycin therapy on phagocytic and oxidative activity profiles of spleen mononuclear cells in Babesia rodhaini-infected mice.

Spleen weight, the number of spleen mononuclear cells, and their phagocytic activity in groups of Babesia rodhaini-infected mice treated with diminazene diaceturate and clindamycin increased significantly in the early stage of treatment, and then decreased in the final stage of treatment to approximately the pre-infection level. The number of F4/80-positive macrophages and their oxidative activity per mean whole-spleen weight also increased significantly during the course of treatment in comparison with the untreated group. The increases in the clindamycin-treated group were more prominent than those in the group treated with diminazene diaceturate, suggesting the effectiveness of clindamycin therapy for murine babesiosis.

Therapeutic effect of clindamycin and tetracycline on Babesia rodhaini infection in mouse model.

In order to identify the alternative effective chemotherapeutic agents for murine babesiosis, some selected drugs were examined for their efficacy against protozoan infection in the mouse-Babesia rodhaini (B. rodhaini) model. Clindamycin was not completely effective for elimination of parasites in a dose of 50 mg or 100 mg/kg BW/day b.i.d. but effective to prolong the life span of hosts, while it completely cured B. rodhaini infections in a dose of 200 mg. On the other hand, a double therapy consisting of 2 treatments with 100 mg clindamycin and 100 mg clindamycin and with 100 mg clindamycin and 100 mg tetracycline; respectively, and a single therapy with 100 mg tetracycline or 200 mg clindamycin, had a possibility to clear away B. rodhaini organisms from hosts. However, almost all the treatment groups, had a relapse of the infection within 10 days post treatment or re-treatment. Cured mice by treatment with clindamycin and clindamycin, or clindamycin and tetracycline showed complete resistance against challenge with B. rodhaini, while mice cured by administration of clindamycin at 200 mg or tetracycline at 100 mg showed incomplete resistance to challenge infection. The present data suggest that the two former chemotherapies can induce effective protective immunity (premunization), but the latter two chemotherapies induce incomplete premunization.