Small-scale universality in fluid turbulence

Turbulent flows in nature and technology possess a range of scales. The largest scales carry the memory of the physical system in which a flow is embedded. One challenge is to unravel the universal statistical properties that all turbulent flows share despite their different large-scale driving mechanisms or their particular flow geometries. In the present work, we study three turbulent flows of systematically increasing complexity. These are homogeneous and isotropic turbulence in a periodic box, turbulent shear flow between two parallel walls, and thermal convection in a closed cylindrical container. They are computed by highly resolved direct numerical simulations of the governing dynamical equations. We use these simulation data to establish two fundamental results: (i) at Reynolds numbers Re ∼ 10² the fluctuations of the velocity derivatives pass through a transition from nearly Gaussian (or slightly sub-Gaussian) to intermittent behavior that is characteristic of fully developed high Reynolds number turbulence, and (ii) beyond the transition point, the statistics of the rate of energy dissipation in all three flows obey the same Reynolds number power laws derived for homogeneous turbulence. These results allow us to claim universality of small scales even at low Reynolds numbers. Our results shed new light on the notion of when the turbulence is fully developed at the small scales without relying on the existence of an extended inertial range.An enduring notion in the phenomenology of turbulence is the universality of small scales. It has been taken for granted in theoretical approaches (e.g., refs. 1–8) and analyzed in numerical simulations (9–11) as well as various laboratory experiments (e.g., refs. 5 and 12). The standard paradigm is that whereas the large scales are nonuniversal, reflecting the circumstances of their generation, an increasingly weaker degree of nonuniversality is imparted to small scales with increasing separation between the large and small scales. This scale separation is thought to increase with the flow Reynolds number, so a proper test of universality has been thought to require very high Reynolds numbers. Consequently, many substantial efforts have been made to produce such high-Reynolds-number flows (e.g., ref. 12).Here, we show evidence for an alternative point of view: If one resolves small scales accurately, one observes, even at low Reynolds numbers, universal scaling of velocity gradients that manifest primarily at small scales. We stress that small-scale dynamics are strongly nonlinear even in low-Reynolds-number flows driven by large-scale forcing. There is thus considerable merit in measuring or simulating low-Reynolds-number flows much more accurately than has been the practice and exploring the evidence for universality (or lack thereof), instead of advancing as inevitable the notion that useful lessons about universality are possible only at very high Reynolds numbers. Indeed, another result of this paper is that there exists a threshold Reynolds number above which Gaussian-like fluctuations tend to assume intermittent characteristics of fully developed flows and that these features can be extracted by accessing increasingly smaller scales even if the Reynolds numbers are quite moderate. The latter result is especially important for purposes of identifying a fixed point in certain renormalization group expansion procedures (8).     

Administration Time Between Seasonal Live-Attenuated Influenza Vaccine and Trivalent Influenza Vaccine During the “Stop Flu at School” Campaign— Hawaii, 2009

Objectives

We determined whether the administration time differed between seasonal intranasal live-attenuated influenza vaccine (LAIV) and seasonal injectable trivalent inactivated influenza vaccine (TIV) during Hawaii''s 2009 school-located influenza vaccination clinics. This information is useful for public health response and allows further investigation into possible differences between the two vaccines.

Methods

We conducted a prospective cohort study in 15 public schools to determine mean times to administer LAIV and TIV to students. We performed group analyses to control for various clinic characteristics and conducted a stratified, weighted analysis.

Results

A total of 4,701 students were enrolled in the study, and administration time was obtained for 3,869 (82%) students (1,492 [39%] LAIV and 2,377 [61%] TIV). The mean administration time for LAIV was 62 seconds and for TIV was 90 seconds, a difference of 28 seconds (p<0.01). This finding remained significant in the stratified analysis.

Conclusions

Although results indicated that both LAIV and TIV can be administered rapidly among school-aged populations, LAIV was faster to administer. This finding, in addition to the greater immunogenicity of LAIV compared with TIV among children, may be an important consideration for public health administrators in planning school-located mass vaccination clinics and encouraging patient acceptance of this vaccine.Depending on the severity of an influenza season, influenza has been reported to cause approximately 200,000 hospitalizations and up to 49,000 deaths annually.^1–3 School-aged children (those aged 5–18 years) account for approximately 40% of infections during a typical influenza season, the highest among any age group.^4–6 Additionally, children amplify transmission in a community; therefore, it is logical to focus influenza vaccination efforts on this age group.⁷ With this idea in mind, the Hawaii Department of Health (HDOH) implemented school-located influenza vaccination (SLIV) clinics throughout the state during 2007.¹ In February 2008, the Advisory Committee on Immunization Practices recommended that all children aged 6 months to 18 years receive annual influenza vaccination, thus offering support for providing alternatives to physician offices to accommodate the increased annual influenza vaccination target cohort.^8,9The HDOH “Stop Flu at School” (SFAS) campaign is a statewide program that attempts to provide students in kindergarten through eighth grade with an annual influenza vaccination. SFAS, a voluntary program, offers both seasonal intranasal live-attenuated influenza vaccine (LAIV) and injectable trivalent inactivated influenza vaccine (TIV) free to students and staff in participating schools. Vaccine doses for the period during this study were acquired by HDOH through a combination of federal programs (e.g., Vaccines for Children, Section 317) and state funds, while operational costs were secured through a combination of federal grant funds and private (e.g., vaccine manufacturers and foundations) grants and contributions.Intranasal LAIV was licensed in the United States in 2003 for use among healthy individuals aged 2–49 years.¹⁰ In comparison with TIV, LAIV is administered in two sites (i.e., the sprayer is inserted in one nostril, used, removed, and then reinserted into the second nostril), has a longer list of contraindications, and is a newer delivery system.¹¹ Recent studies suggest that LAIV can induce both mucosal and innate immunity; is more immunogenic than TIV, as it is effective after only one dose; and requires less time to elicit an antibody response.^12–15 Intramuscular TIV, in use for >30 years, has fewer contraindications, is injected in one site, and can be used in all people ≥6 months of age, including groups at high risk (e.g., those with asthma or other chronic underlying medical conditions) who cannot receive a live-virus vaccine.¹⁶During the fall of 2009, the second wave of pandemic influenza A (H1N1) was sweeping through the U.S. mainland. Hawaii state public health planners were tasked with rapidly implementing programs for H1N1 vaccine delivery, and SLIV clinics were considered an important venue to accomplish this goal.¹⁷ HDOH was in its third year of providing seasonal influenza vaccine through SFAS, and this program offered an opportunity to study logistical considerations for implementing SLIV clinics and enhance public health program planning. Additionally, given the distinctions between seasonal LAIV and seasonal TIV, we were interested in determining whether a substantial difference existed in the administration time of the two vaccines and what factors might influence a difference during the statewide 2009 SFAS campaign.     

Cerium oxide nanoparticles attenuate monocrotaline induced right ventricular hypertrophy following pulmonary arterial hypertension

Cerium oxide (CeO₂) nanoparticles have been posited to exhibit potent anti-oxidant activity which may allow for the use of these materials in biomedical applications. Herein, we investigate whether CeO₂ nanoparticle administration can diminish right ventricular (RV) hypertrophy following four weeks of monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH). Male Sprague Dawley rats were randomly divided into three groups: control, MCT only (60 mg/kg), or MCT + CeO₂ nanoparticle treatment (60 mg/kg; 0.1 mg/kg). Compared to the control group, the RV weight to body weight ratio was 45% and 22% higher in the MCT and MCT + CeO₂ groups, respectively (p < 0.05). Doppler echocardiography demonstrated that CeO₂ nanoparticle treatment attenuated monocrotaline-induced changes in pulmonary flow and RV wall thickness. Paralleling these changes in cardiac function, CeO₂ nanoparticle treatment also diminished MCT-induced increases in right ventricular (RV) cardiomyocyte cross sectional area, β-myosin heavy chain, fibronectin expression, protein nitrosylation, protein carbonylation and cardiac superoxide levels. These changes with treatment were accompanied by a decrease in the ratio of Bax/Bcl2, diminished caspase-3 activation and reduction in serum inflammatory markers. Taken together, these data suggest that CeO₂ nanoparticle administration may attenuate the hypertrophic response of the heart following PAH.     

Evaluation of Matrix-assisted laser desorption/ionization Time-of flight Mass spectrometry (MALDI TOF MS) and VITEK 2 in routine microbial identification

BacgroundMicrobial Identification was done by phenotypic methods. VITEK-2 and Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) are now being increasingly used in laboratories.ObjectivesTo compare and evaluate the usefulness of MALDI-TOF MS and VITEK-2 in routine microbial identification.MethodsThe performances of MALDI-TOF MS and VITEK 2 were compared for identifying microorganisms.ResultsMALDI- TOF MS and VITEK-2 correctly identified 96 % (96/100) and 97% (97/100) of the isolates upto the genus level.ConclusionMALDI TOF MS and VITEK -2 gave comparable identification and error rates. The rapid reduction in turnaround time with MALDI TOF is a significant game-changer in the field of clinical microbiology.FundingState Board of Medical Research (SBMR).     

Evidence for invasion of a human oral cell line by Actinobacillus actinomycetemcomitans.

Actinobacillus actinomycetemcomitans, an oral bacterial species associated with periodontal disease, was found to invade human cell lines. Invasion was demonstrated by recovery of viable organisms from gentamicin-treated KB cell monolayers and by light and electron microscopy. Internalization occurred through a cytochalasin D-sensitive process. Invasion efficiencies of some A. actinomycetemcomitans strains were comparable to those of invasive members of the family Enterobacteriaceae. Differences in invasiveness were correlated with bacterial colonial morphology. Smooth variants invaded more proficiently than rough variants. A. actinomycetemcomitans can undergo a smooth-to-rough colonial morphology shift which results in the loss of invasiveness. Coordinated regulation of genes involved in the rough-to-smooth phenotypic transitions may play a role in the episodic nature of periodontal disease.